JP6642107B2 - Stepping motor drive device and image forming apparatus - Google Patents

Description

  The present disclosure relates to a stepping motor driving device and an image forming apparatus including a sheet transport unit driven by the stepping motor.

  2. Description of the Related Art In an image forming apparatus such as a printer, a facsimile machine, and a copier, it is desirable that a component replacement time can be determined as accurately as possible in order to perform maintenance efficiently. For example, in the technique described in Japanese Patent Application Laid-Open No. 2002-290650 (Patent Document 1), the image forming apparatus determines whether or not each component has been used when forming an image, and when the component is used, Then, the count value of the usage counter of the used component is increased. Then, the image forming apparatus predicts a time when each component reaches the endurance count based on the usage status of each component during a certain period in the past.

  Japanese Patent Application Laid-Open No. 2007-114291 (Patent Document 2) discloses an early state of each unit such as whether each unit attached to the image forming apparatus has reached the end of its life or whether any abnormality has occurred in each unit. In addition, a technique for easily grasping is disclosed. Specifically, the image forming apparatus disclosed in this document includes a DC (direct current) motor for driving a rotating body provided in the unit, a detecting unit for detecting the number of rotations of the DC motor, a difference calculating unit, and a modulation pulse. The apparatus includes a generating unit, a driving unit, and a determining unit. The difference calculating means calculates a difference between the detected rotation speed of the motor and the target rotation speed. The modulation pulse generation means generates a pulse having a pulse width modulated based on the difference between the number of revolutions calculated by the difference calculation means. The driving unit drives the DC motor based on the pulse generated by the modulated pulse generation unit. The determining means determines the state of the unit (whether replacement is necessary) by comparing the pulse width of the pulse generated by the modulated pulse generating means with a threshold.

JP 2002-290650 A JP 2007-114291 A

  As a control method of the stepping motor, there are open loop control and closed loop control. When the stepping motor is driven by the normal open loop control, a step-out occurs when the rotation of the stepping motor cannot follow the input pulse signal due to an increase in load. For example, if a step-out occurs in a sheet transport mechanism of an image forming apparatus, a paper jam occurs, which causes a problem of downtime and wasteful consumption of paper.

  On the other hand, in a method of controlling a stepping motor by closed loop control, position and speed information is fed back from a high-resolution encoder mounted on the stepping motor, and the detected position and speed information and an operation command (for example, a clock signal) are transmitted. The motor rotates while correcting the error. According to the closed loop control, even if an unexpected impact load is applied to the motor, the motor will instantaneously flow the motor current exceeding the rating to increase the torque and step out without consuming heat or excessive power of the motor. Can be avoided.

  However, if a load exceeding the expectation is continuously applied to the motor due to deterioration of components over time or the like, a motor current exceeding the rating will flow continuously for a long time. In such a case, the motor control unit finally determines that the motor is in an abnormal state and stops the motor, so that there is a problem that downtime occurs.

  In the case of Japanese Patent Application Laid-Open No. 2002-290650 (patent document 1), the degree of deterioration over time (necessity of replacement) of each component is determined from the number of times of use, and thus may differ from the actual degree of deterioration. For this reason, there is a case where wasteful replacement of parts that can be used continuously occurs.

  The technique disclosed in Japanese Patent Application Laid-Open No. 2007-114291 (Patent Document 2) is limited to feedback control of a DC motor. Therefore, the technique of this document cannot be applied to a stepping motor in which the pulse width of an input pulse does not change even when the load increases. There is no known stepping motor drive device that detects and notifies a heavy load before the motor stops.

  The present disclosure has been made in consideration of the above problems, and a main object of the disclosure is to provide a stepping motor driving device capable of easily and accurately determining deterioration with time of a component to be driven by the stepping motor. It is to provide.

One aspect of the present disclosure is a stepping motor driving device, which includes a stepping motor, a first pulse signal generation unit, a second pulse signal generation unit, a first determination unit, and a second determination unit. Is provided. The first pulse signal generation unit generates a first pulse signal representing a command value of a rotation angle of the stepping motor. The second pulse signal generator generates a second pulse signal corresponding to the actual rotation angle of the stepping motor. The first determination unit determines the degree of the load on the stepping motor by comparing the first pulse signal with the second pulse signal. The second determination unit determines, based on the determined degree of the load, whether or not there is any deterioration of a component that can affect the load on the stepping motor. The first determination unit counts the number of pulses of the second pulse signal for each predetermined cycle of the first pulse signal when determining the degree of load on the stepping motor, and determines the number of pulses counted and the number of pulses for each predetermined cycle. A difference value between the number of pulses of the second pulse signal and a target value is calculated, a difference value calculated for each predetermined cycle is calculated as a cumulative value from the start of the stepping motor, and based on the calculated cumulative value. To determine the degree of load on the stepping motor.

  In a preferred embodiment, the second determination unit determines whether or not the absolute value of the cumulative value has exceeded the first threshold or whether or not the first threshold has exceeded the predetermined number of times. It is determined whether or not there is any deterioration of a component that may have an effect.

  More preferably, the second determination unit determines that the stepping motor has a possibility of step-out when the absolute value of the accumulated value exceeds a second threshold larger than the first threshold.

  In another preferred embodiment, the first determination unit calculates an average value of a plurality of cumulative values per predetermined rotation angle of the stepping motor, and determines a degree of load of the stepping motor based on the calculated average value of the cumulative values. Is determined.

  More preferably, the second determination unit is configured to determine whether or not the absolute value of the average value of the accumulated value has exceeded a third threshold value or whether or not the third threshold value has exceeded a predetermined number of times. It is determined whether or not there is any deterioration of a component that can affect the condition.

  More preferably, the second determination unit determines that the stepping motor has a possibility of step-out when the absolute value of the average value of the cumulative value exceeds a fourth threshold value larger than the third threshold value. I do.

  In the above-described embodiment and other embodiments, preferably, a higher motor current is supplied to the stepping motor during a predetermined period from the start of the stepping motor than after the predetermined period has elapsed.

  Preferably, during a predetermined period from the start, the magnitude of the motor current supplied to the stepping motor is the maximum value that can be supplied.

Preferably, the stepper motor is open-loop controlled.
Preferably, when the second determination unit determines that the component is deteriorated, the continuous operation time of the stepping motor is limited.

  Preferably, the second determination unit is configured to be displayed on the display unit or printable by a printer in a state where the determination result of the degree of the load and the operation state of the component are compared along a common time axis. You.

Preferably, it is determined that the second determination unit, when the operating state of the determination results and part of the degree of load is correlation, parts is deteriorated.

  Another embodiment of the present disclosure is an image forming apparatus that includes a sheet transport unit that transports a sheet for printing an image. The paper transport unit includes the above-described stepping motor driving device.

  According to this disclosure, it is possible to easily and accurately determine deterioration with time of a component to be driven by a stepping motor.

FIG. 2 is a hardware configuration diagram of the stepping motor drive device according to the first embodiment. FIG. 2 is a block diagram illustrating a configuration example of a controller in FIG. 1. It is a figure which shows typically the structural example of the rotor and stator of a stepping motor. FIG. 4 is a diagram for explaining a positional relationship between a rotor and a stator. FIG. 3 is a diagram illustrating an example of an encoder signal. FIG. 9 is a diagram illustrating, in a table form, an example of a shift amount between a design value and an actually measured value of the number of pulses of the encoder signal at the time of light load. FIG. 7 is a diagram showing a time change of a cumulative value of a deviation amount between a design value and an actual measurement value of an encoder pulse in FIG. 6. FIG. 10 is a diagram illustrating, in a table form, an example of a deviation amount between a design value and an actually measured value of the number of pulses of the encoder signal in the case of a heavy load. FIG. 9 is a diagram showing a time change of a cumulative value of a deviation amount between a design value and an actually measured value of the encoder pulse in FIG. 8. FIG. 9 is a diagram illustrating, in a table form, an example different from the case of FIG. 8 in the case of a heavy load. FIG. 11 is a diagram showing a time change of a cumulative value of a deviation amount between a design value and an actually measured value of the encoder pulse in FIG. 10. FIG. 3 is a functional block diagram of a portion related to detection of a load amount in the stepping motor driving device of FIGS. 1 and 2. 6 is a flowchart illustrating a procedure for determining a degree of a load on a stepping motor. It is a flowchart of the modification of FIG. FIG. 2 is a schematic diagram illustrating a configuration of a sheet transport system. FIG. 16 is a diagram illustrating a state in which the sheet has moved more than in the case of FIG. 15. FIG. 17 is a diagram illustrating a state in which the sheet has moved further than in the case of FIG. 16. FIG. 4 is a timing chart illustrating an example of an operation state of the sheet transport system. FIG. 1 is a diagram illustrating an appearance of an image forming apparatus 100 configured as an MFP (Multi-Functional Peripheral). FIG. 2 is a block diagram illustrating a configuration of the image forming apparatus.

  Hereinafter, embodiments will be described in detail with reference to the drawings. The same or corresponding parts have the same reference characters allotted, and description thereof will not be repeated.

<First embodiment>
[Configuration of stepping motor drive device]
FIG. 1 is a hardware configuration diagram of the stepping motor drive device according to the first embodiment. Referring to FIG. 1, a stepping motor driving device 10 includes a stepping motor 14, a driver 13, an encoder 15, and a controller 12. In the following, the controller 12 and the driver 13 may be collectively referred to as a drive control unit 11.

  The driver 13 generates a drive pulse signal DS to be supplied to the stator of the stepping motor based on a control pulse signal CS (for example, a clock signal) input from the controller 12. The drive pulse signal DS is composed of a plurality of pulse signals corresponding to the number of phases of the stepping motor 14. The phase difference between the pulse signals differs according to the number of phases. The stepping motor 14 rotates according to the drive pulse signal DS.

  The encoder 15 generates an encoder signal ES which is a pulse signal according to the actual rotation angle of the rotor of the stepping motor 14. Generally, the encoder signal ES includes two A-phase and B-phase pulse signals that are shifted from each other by １ ／ cycle. The rotation direction, the rotation position, and the rotation speed of the motor can be detected based on the A-phase and B-phase pulse signals.

  The controller 12 controls the rotation angle and the rotation speed of the stepping motor 14 by generating and outputting the control pulse signal CS. The control method of the stepping motor 14 by the controller 12 is open loop control.

  The controller 12 further determines the magnitude of the load applied to the stepping motor 14 by comparing the encoder signal ES received from the encoder 15 with the control pulse signal CS. Based on the result of this determination, the degree of deterioration over time of the driven object 50 of the stepping motor 14 (necessity of component replacement) is determined. Here, the drive target 50 includes not only components directly driven by the stepping motor 14 but also all components that can affect the load of the stepping motor 14. The details of the method of determining the magnitude of the load and the method of determining the deterioration state of the driven object 50 will be described later.

  FIG. 2 is a block diagram illustrating a configuration example of the controller in FIG. FIG. 2 also shows other blocks connected to the controller 12.

  Referring to FIG. 2, the controller 12 is configured based on a microcomputer including a CPU (Central Processing Unit) 20, a RAM (Random Access Memory) 21, and a ROM (Read Only Memory) 22, for example. The CPU 20, the RAM 21, and the ROM 22 are mutually connected via a bus 26. The driver 13 and the encoder 15 of FIG. 1 are connected to a bus 26 via interface (I / F) circuits 23 and 24, respectively.

  Further, the controller 12 is connected to the control device 110, the display unit 120, the operation unit 121, and the like via the interface circuit 25. The control device 110 controls the entire device including the stepping motor driving device 10 and its driving target 50. The display unit 120 is used for displaying information such as characters and images to the user, and the operation unit 121 is used for input operation by the user.

  Note that, although different from the case of FIG. 2, the controller 12 can be configured by a logic circuit such as an FPGA (Field Programmable Gate Array). The entire controller 12 and driver 13 (the drive control unit 11 in FIG. 1) may be configured as one circuit unit.

[Example of rotor and stator configuration]
FIG. 3 is a diagram schematically illustrating a configuration example of a rotor and a stator of the stepping motor. In FIG. 3, the number of magnetic poles of the north pole teeth 33 of the rotor 30 is 50, the number of magnetic poles of the south pole teeth 34 (hatched in the drawing) is 50, and the number of phases is 2 (A phase). , B-phase). Further, the case where the excitation mode is the full step mode is shown. In this case, the step angle (the rotation angle for each step) is 1.8 °, and the number of steps (the number of divisions for one rotation of the motor) is 200.

  Further, FIG. 3 shows a state in which the A-phase stator teeth 31A and the N-pole teeth 33 mesh with each other when the A-phase coil 32A is excited. Next, when the B-phase coil 32B is excited, the rotor 30 rotates by 1.8 °, and the B-phase stator teeth 31B and the S-pole teeth 34 mesh.

  Hereinafter, the configuration of the stepping motor shown in FIG. 3 will be described as an example, but the example in FIG. 3 is merely an example. For example, the number of magnetic poles and the number of phases of the stepping motor may be different from those in FIG. 3, and the excitation mode may be a half step mode instead of the full step mode or a micro step mode. .

[How to detect the size of load]
FIG. 4 is a diagram for explaining the positional relationship between the rotor and the stator. FIG. 4A shows a case of light load, and FIG. 4B shows a case of heavy load. The arrows in the figure represent the magnetic force acting between the magnetic pole of the rotor 30 and the magnetic pole of the stator 31.

  As shown in FIG. 4A, when the load is light relative to the motor torque, the magnetic poles of the rotor 30 and the magnetic poles of the stator 31 in the excitation phase are sequentially engaged with each other at the center position (ideal position) of each other. It rotates. On the other hand, as shown in FIG. 4B, when the load becomes heavier than the motor torque, a deviation occurs between the center position of the magnetic pole of the rotor 30 and the center position of the magnetic pole of the stator 31 in the excitation phase. For example, in the case of a stepping motor having a step angle of 1.8 °, a step out occurs when a deviation of 0.9 ° or more occurs. Therefore, the amount of deviation between the center position of the magnetic pole of the rotor 30 and the center position of the magnetic pole of the stator 31 in the excitation phase is a measure of the magnitude of the load applied to the rotor 30 of the stepping motor 14. This shift amount can be detected by the encoder signal ES as described below.

  FIG. 5 is a diagram illustrating an example of an encoder signal. FIG. 5A shows an example of the waveform of the control pulse signal CS output from the controller 12 in FIG. In the example of this figure, it is assumed that the rotor 30 rotates one step angle (1.8 °) in one cycle of the control pulse signal CS (from time t1 to time t2).

  FIGS. 5B and 5C show examples of the waveform of the encoder signal ES output from the encoder 15 of FIG. FIG. 5B shows an example of the waveform of the encoder signal ES in an ideal case under a light load. In design, the encoder 15 outputs 80 pulses per cycle of the control pulse signal CS (from time t1 to time t2).

  On the other hand, FIG. 5C shows an example of the waveform of the encoder signal ES in the case of a heavy load. When the load on the rotor is relatively large, the amount of rotation of the rotor is insufficient, so that the number of pulses corresponding to one cycle of the control pulse signal CS may be smaller than the ideal number of pulses (80 pulses). Occurs. For example, in the case of FIG. 5C, the number of pulses corresponding to one cycle of the control pulse signal CS from time t1 to time t2 has been reduced to 70 pulses.

  As described above, by detecting the deviation between the design value (target value) of the number of pulses of the encoder signal ES and the actually measured number of pulses of the encoder signal ES for each predetermined period (for example, one period) of the control pulse signal CS. , The magnitude of the load can be estimated. Hereinafter, a specific example will be described.

[Example of load detection: light load]
FIG. 6 is a diagram illustrating, in a table form, an example of a shift amount between a design value and an actually measured value of the number of pulses of the encoder signal at the time of light load. In the table of FIG. 6, in order from the leftmost column, the number of input pulses (the cumulative value of the number of pulses of the control pulse signal CS), the design value (ideal value) of the encoder pulse signal for each input pulse, and The actual measured value, the deviation amount (difference) between the design value and the actual measurement value, and the cumulative value of the deviation amount are shown. As described with reference to FIGS. 3 to 5, it is assumed that 80 encoder pulses are ideally generated for one input pulse (corresponding to a rotation angle of 1.8 °).

  Here, in the initial state, it is assumed that the center position of the magnetic pole of the rotor 30 matches the center position of the magnetic pole of the stator 31 in the excitation phase. In this initial state, the amount of deviation between the design value and the measured value of the encoder pulse is zero. Whether the stepping motor loses synchronism when the stepping motor rotates depends on the amount of deviation between the center position of the rotor and the center position of the stator (that is, the amount of deviation from the initial state). The amount of deviation from the initial state is obtained by accumulating the amount of deviation between the designed value and the measured value of the encoder pulse for each step angle.

  FIG. 7 is a diagram showing a time change of the cumulative value of the deviation amount between the design value and the actually measured value of the encoder pulse in FIG. The horizontal axis in FIG. 7 represents the number of input pulses corresponding to the elapsed time. The vertical axis in FIG. 7 represents the accumulated value of the amount of deviation (difference) between the design value of the encoder pulse number and the actually measured value.

  By design, it is assumed that the rotor rotates 1.8 ° per input pulse, and the number of encoder pulse counts at this time is 80. Step-out occurs when the angle difference between the rotor and the stator becomes 0.9 °. When the step-out occurs, the accumulated value of the difference between the designed value and the measured value of the encoder pulse is ± 40. Equivalent to counting.

  Therefore, the stepping motor drive device according to the present embodiment sets a threshold value before the accumulated value of the deviation amount reaches ± 40 counts in order to prevent the step-out from occurring. Notify users. Specifically, when the cumulative value of the deviation between the design value and the actually measured value exceeds ± 20 counts (first threshold value: ± TH1), it is determined that an overload has occurred. If the accumulated value of the deviation between the design value and the measured value exceeds ± 35 counts (second threshold value: ± TH2), it is determined that there is a risk of step-out.

  In the example of FIG. 7, in the initial state, the accumulated value of the deviation amount between the designed value and the measured value of the encoder pulse is 0 count. That is, in the initial state, the center position of the magnetic pole of the rotor 30 matches the center position of the magnetic pole of the stator 31 in the excitation phase. Note that the motor is driven with the motor current increased within a predetermined time after the start of the stepping motor so that the displacement between the center of the magnetic pole of the rotor and the stator is set to 0 in the initial state. . Preferably, the maximum current value that can be supplied is supplied to the stator.

  On the other hand, during the rotation of the stepping motor, the position of the rotor vibrates based on the ideal position. When the load is normal and the load is relatively light, the accumulated value (absolute value) of the deviation amount between the designed value and the measured value of the encoder pulse is sufficiently smaller than the set first threshold value TH1. In the case of FIG. 6 and FIG. 7, the total value of the shift amount is within ± 10 counts.

[Example of load detection: heavy load]
FIG. 8 is a diagram illustrating, in a table form, an example of a deviation amount between the design value and the measured value of the number of pulses of the encoder signal in the case of a heavy load. FIG. 9 is a diagram showing a temporal change in the cumulative value of the amount of deviation between the design value of the encoder pulse and the actually measured value in FIG. The table in FIG. 8 and the graph in FIG. 9 correspond to the table in FIG. 6 and the graph in FIG. 7, respectively.

  As shown in FIGS. 8 and 9, when the number of input pulses reaches 5 counts, the accumulated value of the deviation between the design value and the actually measured value of the encoder pulse becomes −22, and the first threshold value ± 20. Exceeds. Thereby, the controller 12 in FIG. 1 detects that the load on the rotor of the stepping motor 14 is increasing. The cause of such an increase in the load is considered to be the deterioration over time of the component to be driven by the stepping motor 14 or the failure of the component. Therefore, the controller 12 in FIG. 1 or the control device 110 in FIG. 2 notifies the user that the parts need to be replaced.

  When the deteriorated parts that need to be replaced are temporarily used, the load increases temporarily. Therefore, as shown in FIG. 8, even if the accumulated value of the deviation amount between the design value of the encoder pulse and the measured value exceeds the first threshold value (± TH1 = ± 20), and returns to the first threshold value or less. The notification of the necessity of parts replacement to the user is continued. It is to be noted that the stepping motor operation is continued as it is unlikely that the step-out will occur if the value exceeds the first threshold value (± TH1) alone. Alternatively, some operations may be limited, such as limiting the continuous operation time of the stepping motor.

  In the above description, the user is notified that component replacement is required when the cumulative value of the deviation between the design value of the encoder pulse and the actually measured value exceeds the first threshold even once. Alternatively, the user may be notified that component replacement is necessary when the number of times the accumulated value of the deviation exceeds the first threshold reaches a predetermined number.

[Specific example of load detection: heavy load (other examples)]
FIG. 10 is a diagram showing, in the form of a table, an example different from the case of FIG. 8 in the case of a heavy load. The table in FIG. 10 corresponds to the tables in FIGS. 6 and 8, and shows an example of the amount of deviation between the design value and the measured value of the number of pulses of the encoder signal. FIG. 11 is a diagram showing a time change of the cumulative value of the deviation amount between the design value and the actually measured value of the encoder pulse in FIG. The graph of FIG. 11 corresponds to the graphs of FIGS. 7 and 9.

  In the examples shown in FIGS. 10 and 11, the accumulated value of the deviation amount between the design value and the measured value of the encoder pulse does not exceed the first threshold value (± TH1 = ± 20). However, the absolute value of the average of the accumulated values is larger than that in the normal case shown in FIGS. Therefore, the average value of the accumulated values of the deviation amounts between the design value of the encoder pulse and the measured value for each predetermined rotation angle (for example, one rotation) is calculated, and when the calculated average value exceeds the threshold value, Alternatively, it may be determined that the load is increasing.

[Step detection procedure for stepping motor load]
The procedure for detecting the degree of the load applied to the rotor of the stepping motor will be described generally.

  FIG. 12 is a functional block diagram of a portion related to detection of a load amount in the stepping motor driving device of FIGS. 1 and 2. Referring to FIG. 12, the stepping motor driving device 10 functionally includes a control pulse signal generation unit 40, a load determination unit 41, a component deterioration determination unit 43, a driver 13, a stepping motor 14, and an encoder 15 And

  In the case of the present embodiment, the control pulse signal generator 40 and the load determiner 41 correspond to the controller 12 (CPU 20) in FIGS. 1 and 2, and these functions are realized by the CPU 20 operating according to a program. The function of the component deterioration determination unit 43 is realized by the control device 110 in FIG.

  Specifically, the control pulse signal generator 40 (first pulse signal generator) generates a control pulse signal CS (first pulse signal) representing a command value of the rotation angle of the stepping motor 14. Typically, the stepping motor 14 rotates one step at a time for each pulse of the control pulse signal CS. The encoder 15 (second pulse signal generation unit) generates an encoder signal ES (second pulse signal) corresponding to the actual rotation angle of the stepping motor 14.

  The load determining unit 41 (first determining unit) determines the degree of the load on the stepping motor 14 by comparing the control pulse signal CS with the encoder signal ES. Specifically, the load determination unit 41 counts the number of pulses of the encoder signal ES at each predetermined cycle (usually one cycle) of the control pulse signal CS, and counts the number of pulses and the number of pulses of the encoder signal ES at each predetermined cycle. The difference value (deviation amount) from the target value is calculated. The load determination unit 41 calculates a cumulative value by accumulating the difference values calculated for each predetermined cycle from the start of the stepping motor, and determines the degree of the load on the stepping motor based on the calculated cumulative value.

  For example, when the absolute value of the accumulated value of the amount of shift of the encoder signal exceeds the first threshold value TH1 or exceeds the first threshold value TH1 by a predetermined number of times, the load determination unit 41 loads heavier than normal. Is determined. The load determination unit 41 further determines that there is a risk of step-out when the load exceeds a second threshold value TH2 (where TH2> TH1). When the load determination unit 41 determines that there is a risk of step-out, the control pulse signal generation unit 40 controls the stepping motor 14 to stop by stopping the output of the control pulse signal CS. Is also good.

  The component deterioration determining unit 43 (second determining unit) determines whether or not the component that is the driving target 50 of the stepping motor 14 has deteriorated based on the degree of the load determined by the load determining unit 41. For example, when the absolute value of the calculated sum of the deviations of the encoder signal exceeds the first threshold value TH1, the component deterioration determination unit 43 reports that the component to be driven 50 has deteriorated (for example, Is displayed on the display unit 120).

  FIG. 13 is a flowchart illustrating a procedure for determining the degree of the load on the stepping motor. Referring to FIGS. 12 and 13, when the initial operation has been started (YES in step S100), controller 12 transmits a command from driver 13 to stepping motor 14 until a predetermined period elapses after starting stepping motor 14. The motor current supplied to 14 is set to the maximum value that can be supplied (step S105). Thus, in the initial state, the center position of the magnetic pole of the rotor and the center position of the magnetic pole of the stator in the excited phase are made to match.

  While the stepping motor 14 is operating (that is, until the motor stop command is received from the control device 110), the load determination unit 41 determines the number of pulses of the encoder signal ES at predetermined intervals based on the edge of the control pulse signal CS. It counts (step S110), and calculates the difference between the counted number of pulses and the target value (step S115). Further, the load determining unit 41 calculates a total value of the calculated difference values from the initial state (Step S120).

  If the absolute value of the calculated cumulative value exceeds the first threshold value TH1 (YES in step S130), the load determination unit 41 determines that the load amount of the stepping motor 14 is heavier than in the normal state. (Step S135). Alternatively, the load determining unit 41 may determine that the load amount of the stepping motor 14 is heavy when the absolute value of the calculated cumulative value exceeds the first threshold value TH1 by a predetermined number of times.

  In response to the determination result of the heavy load, the component deterioration determination unit 43 notifies that the component to be driven by the stepping motor 14 has deteriorated (Step S140). If the controller 12 determines that the load is heavy, the controller 12 may limit the continuous operation time of the stepping motor so that step-out does not occur due to an increase in the load.

When a plurality of components can affect the load of the stepping motor 14 is component degradation determining unit 43, if there is correlation to the determination result of the operating state of certain parts heavy load, and the component is degraded judge. The reason for this is that a component that is not in an operating state when it is determined to be a heavy load is not necessarily degraded (a specific example will be described in the second embodiment).

  When the absolute value of the calculated cumulative value exceeds the second threshold value TH2 (though TH2> TH1) (YES in step S145), the load determination unit 41 determines that the risk of the stepping motor 14 losing step is determined. It is determined that there is (Step S150). In this case, the controller 12 stops the operation of the stepping motor 14 (Step S160). It is also possible to notify only the necessity of component replacement without stopping the operation. Further, the motor current may be temporarily increased from a normal time to prevent the step-out.

[Modification of load detection procedure]
FIG. 14 is a flowchart of a modified example of FIG. The flowchart in FIG. 14 differs from the flowchart in FIG. 13 in that step S125 is included after step S120 in FIG. In step S125, the load determination unit 41 calculates the average value of the cumulative value per one rotation of the rotor based on the calculated cumulative value of the shift amount of the encoder pulse.

  Further, in the procedure of FIG. 14, the load determination unit 41 determines that the absolute value of the average value of the cumulative value calculated in step S125 exceeds the third threshold value TH3, or that the load determination unit 41 exceeds the third threshold value TH3 by a predetermined number of times. If it has (YES in step S130A), it is determined that the load on the stepping motor 14 is heavier than in the normal state (step S135). When the absolute value of the average value of the cumulative value calculated in step S125 exceeds the fourth threshold value TH4 (though TH4> TH3) (YES in step S145A), the load determination unit 41 determines whether the stepping motor 14 determines that there is a risk of step-out (step S150).

  Since the other steps in FIG. 14 are the same as those in FIG. 13, the same or corresponding steps are denoted by the same reference characters and description thereof will not be repeated.

[effect]
According to the first embodiment, the stepping motor driving device 10 determines that the load on the rotor of the stepping motor 14 has changed from the initial state based on an encoder signal from an encoder 15 attached to the motor. When it is determined that the load is heavy, the stepping motor driving device 10 determines that the component (the component that can affect the load) driven by the stepping motor 14 has deteriorated with time (that is, the replacement time). ) To the user. This makes it possible to accurately and easily determine whether or not the component has deteriorated over time based on the detection result of the actual load applied to the rotor of the stepping motor 14.

<Second embodiment>
In the second embodiment, an example in which the stepping motor driving device 10 of the first embodiment is applied to a paper transport system will be described. The paper transport system is used for transporting paper or a document in a printer or a scanner, for example.

  FIG. 15 is a schematic diagram illustrating a configuration of the paper transport system. FIG. 16 is a diagram illustrating a state in which the sheet has moved more than in the case of FIG. FIG. 17 is a diagram illustrating a state in which the sheet has moved further than in the case of FIG. 16.

  Referring to FIGS. 15 to 17, the paper transport system includes the stepping motor driving device 10 described in the first embodiment, transport rollers 51A to 51F for transporting paper 52, and units UA and UB. Including. The transport rollers 51A to 51F are driven by the stepping motor driving device 10.

  Unit UA includes a sensor 70 for detecting a sheet, and members 71 and 72. The unit UA operates when a sheet is detected by the sensor 70. The unit UB includes a motor 60, a drive control unit 62 thereof, and a member 61 driven by the motor 60. FIG. 16 shows a state in which the member 61 has moved by the operation of the motor 60, that is, a state in which the unit UB is operating. FIG. 17 illustrates a state in which the leading end of the sheet 52 is detected by the sensor 70, that is, a state in which the unit UA is operating.

  The units UA and UB are, for example, components used for printing the paper 52. When these components are in operation, a load is applied to the rotor by the stepping motor 14 via the paper 52 and the transport rollers 51A to 51F. Will be given. Therefore, when the units UA and UB deteriorate over time, it is detected as an increase in the load on the stepping motor 14.

  FIG. 18 is a timing chart showing an example of the operation state of the paper transport system. In FIG. 17, the operation state of the stepping motor 14, the operation state of the motor 60, the operation state of the sensor 70, the determination result of the degree of the load of the motor 14, the determination result of the possibility of the step-out of the motor 14, and the deviation of the encoder signal The cumulative values of the quantities are shown contrasted along a common time axis.

  Referring to FIG. 12, FIG. 15, and FIG. 18, it is assumed that the accumulated value of the shift amount of the encoder signal exceeds first threshold value ± TH1 at the time of operation of unit UB (motor 60) (time t3). As a result, the load determining unit 41 determines that the load on the stepping motor 14 has increased from the normal state (the determination result changes to the H level). The component deterioration determining unit 43 notifies the user that the unit UB operating at the time t2 has deteriorated with time. For example, the display unit 120 indicates that the unit UB needs to be replaced. Further, in order to prevent loss of synchronism due to an increase in the load, the number of conveyed sheets may be limited (the continuous operation time of the stepping motor 14 is limited).

  Next, at time t4, it is assumed that the sensor 70 of the unit UA detects the leading edge of the sheet, and at this time, the accumulated value of the shift amount of the encoder signal exceeds the second threshold value ± TH2. As a result, the load determination unit 41 determines that there is a risk of step-out due to an increase in the load on the stepping motor 14 from a normal state (the determination result changes to the H level). The component deterioration determination unit 43 notifies the user that the unit UA that is operating at time t4 has deteriorated with time. For example, the display unit 120 indicates that the unit UB needs to be replaced. In this case, in order to prevent loss of synchronism due to an increase in the load, the motor current may be temporarily increased from the normal time, or the conveyance of a new sheet may be stopped.

  It is preferable that the paper transport system is configured so that the timing chart as shown in FIG. 17 can be displayed on the display unit 120 or printed by the printer 140. The display result of the display unit 120 or the output result of the printer 140 is used at the time of maintenance.

<Third embodiment>
In the third embodiment, an example in which the paper transport system of the second embodiment is applied to an image forming apparatus will be described.

[Configuration of Image Forming Apparatus]
FIG. 19 is a diagram illustrating an appearance of the image forming apparatus 100 configured as an MFP (Multi-Functional Peripheral). FIG. 20 is a block diagram illustrating a configuration of the image forming apparatus 100.

  Referring to FIGS. 19 and 20, image forming apparatus 100 includes a display unit 120, an operation unit 121, a scanner 130, a printer 140, a control device 110, a storage device 122, and a network interface 123. .

  The display unit 120 is configured as, for example, a liquid crystal panel, and the operation unit 121 is configured as a touch pad (both are referred to as a touch panel) mounted on the liquid crystal panel.

  The scanner 130 detects an image by reading reflected light when the document is irradiated with light. The scanner 130 includes the paper transport unit 131 as described in the second embodiment. The paper transport unit 131 takes in the documents placed on the document tray 132 one by one, and discharges the document after reading the image to the document discharge tray 133.

  The printer 140 prints an image of a document or the like read by the scanner 130 or print data transmitted from an external device on paper by, for example, an electrophotographic method. The printer 140 includes the paper transport unit 141 as described in the second embodiment. The paper transport unit 141 takes in the paper stored in the paper tray 142 one by one, and discharges the paper on which the image is printed to the paper discharge tray 143.

  The control device 110 is configured based on a microcomputer including a CPU 111, a RAM 112, a ROM 113, and the like. The control device 110 controls the operation of the entire image forming apparatus 100 and operates as the component deterioration determination unit 43 described in the first and second embodiments.

  The storage device 122 is, for example, a storage medium such as a hard disk and / or an external storage device. The storage device 122 stores a control program and the like for causing the CPU 111 of the control device 110 to operate.

  An antenna (not shown) and the like are connected to the network interface 123. The image forming apparatus 100 exchanges data with another communication device via the antenna. Other communication devices include, for example, a mobile communication terminal such as a smartphone, a server, and the like. The image forming apparatus 100 may be configured so that a control program operated by the control device 110 can be downloaded from a server via an antenna.

[effect]
In the above-described paper transport units 131 and 141, the stepping motor drive device 10 described in the first embodiment can be applied as a drive function for transporting paper. Thus, as described in the first embodiment, whether or not the component has deteriorated with time is accurately and easily determined based on the detection result of the actual load applied to the rotor of the stepping motor 14. be able to. As a result, it is possible to extend the life of the actual component to the user, instead of performing the component replacement display based on the prediction based on the frequency of use, thereby reducing the service cost. Furthermore, when parts need to be replaced, parts replacement can be prompted before a paper jam (JAM) due to step-out or a machine stoppage due to overload detection, resulting in downtime and wasted paper consumption. Can be suppressed.

  The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Reference Signs List 10 stepping motor drive device, 11 drive control unit, 12 controller, 13 driver, 14 stepping motor, 15 encoder, 20, 111 CPU, 30 rotor, 31 stator, 40 control pulse signal generation unit, 41 load judgment unit, 43 parts deterioration Judgment unit, 50 drive target (parts), 52 sheets, 100 image forming apparatus, 110 control unit, 120 display unit, 121 operation unit, 130 scanner, 131, 141 sheet transport unit, 140 printer, CS control pulse signal, DS drive Pulse signal, ES encoder signal, TH1 to TH4 threshold, UA, UB unit (parts).

Claims (13)

A stepper motor,
A first pulse signal generation unit that generates a first pulse signal representing a command value of a rotation angle of the stepping motor;
A second pulse signal generation unit that generates a second pulse signal corresponding to an actual rotation angle of the stepping motor;
A first determination unit that determines a degree of a load on the stepping motor by comparing the first pulse signal and the second pulse signal;
A second determination unit that determines whether or not there is any deterioration of a component that can affect the load on the stepping motor based on the degree of the determined load ,
The first determination unit is configured to determine a degree of a load on the stepping motor,
Counting the number of pulses of the second pulse signal for each predetermined cycle of the first pulse signal;
Calculating a difference value between the counted number of pulses and a target value of the number of pulses of the second pulse signal for each of the predetermined periods;
The difference value calculated for each of the predetermined periods is calculated as a cumulative value that is cumulative from the start of the stepping motor,
A stepping motor driving device configured to determine a degree of load of the stepping motor based on the calculated cumulative value . The second determination unit is configured to determine whether the absolute value of the cumulative value has exceeded a first threshold or whether the absolute value of the cumulative value has exceeded the first threshold a predetermined number of times. The stepping motor drive device according to claim 1, wherein it is determined whether or not there is any deterioration of the component that can be given. The second determination unit is configured to determine that the stepping motor has a possibility of step-out when an absolute value of the cumulative value exceeds a second threshold larger than the first threshold. Item 3. A stepping motor driving device according to item 2 . The first determination unit includes:
Calculating an average value of the plurality of cumulative values per predetermined rotation angle of the stepping motor,
The stepping motor driving device according to claim 1 , wherein the degree of load of the stepping motor is determined based on an average value of the calculated accumulated values. The second determination unit is configured to determine whether the absolute value of the average value of the cumulative value has exceeded a third threshold or whether the absolute value of the average has exceeded the third threshold a predetermined number of times. The stepping motor drive device according to claim 4, wherein it is determined whether or not there is any deterioration of a component that may affect the stepping motor. The second determination unit determines that the stepping motor has a possibility of step-out when the absolute value of the average value of the accumulated values exceeds a fourth threshold value larger than the third threshold value. The stepping motor driving device according to claim 5 , wherein The stepping motor driving device according to any one of claims 1 to 6 , wherein a higher motor current is supplied to the stepping motor during a predetermined period from the start of the stepping motor than after the predetermined period has elapsed. . The stepping motor driving device according to claim 7 , wherein the magnitude of the motor current supplied to the stepping motor is a maximum value that can be supplied during a predetermined period from the start. The stepping motor drive device according to any one of claims 1 to 8 , wherein the stepping motor is controlled by open loop. The stepping motor drive device according to any one of claims 1 to 9 , wherein when the second determination unit determines that the component is deteriorated, the continuous operation time of the stepping motor is limited. . The second determination unit is configured to be displayed on a display unit or printable by a printer in a state where the determination result of the degree of the load and the operation state of the component are compared along a common time axis. The stepping motor drive device according to any one of claims 1 to 10 , wherein: The second determination unit, when the degree of load judgment result and the operating state of the component is correlation determines that the component is deteriorated, any claim 1 to 1 1 2. The stepping motor driving device according to claim 1. A paper transport unit that transports paper for printing images is provided,
The paper conveyance unit includes a stepping motor driving apparatus according to any one of claims 1 to 1 2, the image forming apparatus.

Images