JP2017153319A - Stepping motor driving device and image formation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and accurately determine time degradation of a component that is a driving object of a stepping motor.SOLUTION: In a stepping motor driving device 10, a first pulse signal generating part 40 generates a first pulse signal CS indicating a command value of a rotation angle of a stepping motor 14. A second pulse signal generating part 15 generates a second pulse signal ES corresponding to an actual rotation angle of the stepping motor. A first determination part 41 compares the first pulse signal CS with the second pulse signal ES to determine a degree of a load of the stepping motor 14. A second determination part 43 determines the presence or absence of degradation of a component 50 that may affect the load of the stepping motor 14 on the basis of the determined degree of the load.SELECTED DRAWING: Figure 12

Description

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

  In image forming apparatuses such as printers, facsimile machines, and copiers, it is desirable to be able to determine the part replacement time as accurately as possible in order to perform maintenance efficiently. For example, in the technique described in Japanese Patent Laid-Open No. 2002-290650 (Patent Document 1), the image forming apparatus determines whether or not each component is used when performing image formation. Then, the count value of the usage counter of the used component is increased. Then, the image forming apparatus predicts the time when each component reaches the number of useful life according to the usage status of each component over 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 or not an abnormality has occurred in each unit. In addition, a technique for easily grasping is disclosed. Specifically, an image forming apparatus disclosed in this document includes a DC (direct current) motor for driving a rotating body provided in the unit, a detection unit that detects the number of rotations of the DC motor, a difference calculation unit, a modulation pulse, and the like. A generating unit, a driving unit, and a determining unit are provided. The difference calculating means calculates the difference between the detected motor rotation speed and the target rotation speed. The modulation pulse generating means generates a pulse having a pulse width modulated based on the difference in rotation speed calculated by the difference calculating means. The driving means drives the DC motor based on the pulse generated by the modulation pulse generating means. The determination unit determines the state of the unit (necessity of replacement) by comparing the pulse width of the pulse generated by the modulation pulse generation unit with a threshold value.

JP 2002-290650 A JP 2007-114291 A

  Stepping motor control methods include open loop control and closed loop control. When the stepping motor is driven by 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, when a step-out occurs in the paper transport mechanism of the image forming apparatus, a paper jam occurs, which causes problems of downtime and wasteful paper consumption.

  On the other hand, in the 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 The motor rotates while correcting the error. According to closed loop control, even if the motor is subjected to an unexpected impact load, the motor current is instantaneously exceeded to increase the torque, and the motor will step out without consuming heat or excessive power. Can be avoided.

  However, if a load exceeding the expected load is continuously applied to the motor due to deterioration of parts over time, a motor current exceeding the rating is continuously supplied 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, which causes a problem that downtime occurs.

  In the case of the above-mentioned Japanese Patent Application Laid-Open No. 2002-290650 (Patent Document 1), the degree of deterioration with time (necessity of replacement) of each component is determined from the number of times of use, and therefore may differ from the actual degree of deterioration. For this reason, there may be a waste of replacing even a part that can be used continuously.

  The technique disclosed in JP 2007-114291 A (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 the input pulse does not change even when the load becomes heavy. In the current stepping motor drive device, there is no known device that detects and notifies a heavy load before the motor stops.

  The present disclosure has been made in consideration of the above-described problems, and a main purpose thereof is a stepping motor driving apparatus capable of easily and accurately determining deterioration with time of a part to be driven by the stepping motor. Is to provide.

  In one aspect, the present disclosure is a stepping motor drive 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 for the rotation angle of the stepping motor. The second pulse signal generation unit generates a second pulse signal corresponding to the actual rotation angle of the stepping motor. The first determination unit determines the degree of load of the stepping motor by comparing the first pulse signal and the second pulse signal. The second determination unit determines the presence or absence of component deterioration that may affect the load of the stepping motor based on the determined degree of load.

  Preferably, the first determination unit counts the number of pulses of the second pulse signal for each predetermined period of the first pulse signal, and determines the number of counted pulses and the number of pulses of the second pulse signal for each predetermined period. Calculates the difference value from the target value, calculates the accumulated value of the difference value calculated for each predetermined period from the start of the stepping motor, and determines the stepping motor load level based on the calculated accumulated value Configured to do.

  In a preferred embodiment, the second determination unit determines the load of the stepping motor based on whether the absolute value of the cumulative value exceeds the first threshold value or whether the first threshold value is exceeded a predetermined number of times. The presence or absence of deterioration of a part that may be affected is determined.

  More preferably, the second determination unit determines that the stepping motor is likely to step out when the absolute value of the cumulative value exceeds a second threshold value that is greater than the first threshold value.

  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 the degree of load of the stepping motor based on the calculated average value of the cumulative values Is configured to determine.

  More preferably, the second determination unit determines whether the load of the stepping motor is based on whether the absolute value of the average value of the cumulative values exceeds the third threshold or whether the third threshold is exceeded a predetermined number of times. The presence or absence of deterioration of parts that can affect the process is determined.

  More preferably, the second determination unit determines that the stepping motor is likely to step out when the absolute value of the average value of the cumulative values exceeds a fourth threshold value that is greater than the third threshold value. To do.

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

  Preferably, 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.

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

  Preferably, the second determination unit is configured to display on the display unit or to print on the printer in a state in which the determination result of the degree of load is compared with the operation state of the parts along a common time axis. The

  Preferably, the second determination unit determines that the component has deteriorated when the determination result of the degree of load is in phase with the operation state of the component.

  This disclosure is an image forming apparatus according to another aspect, and includes a sheet conveyance unit that conveys a sheet for printing an image. The paper transport unit includes the above stepping motor driving device.

  According to this disclosure, it is possible to easily and accurately determine the deterioration with time of a component that is a driving target of a stepping motor.

It is a hardware block diagram of the stepping motor drive device by 1st Embodiment. It is a block diagram which shows the structural example of the controller of FIG. It is a figure which shows typically the structural example of the rotor of a stepping motor, and a stator. It is a figure for demonstrating the positional relationship of a rotor and a stator. It is a figure shown about an example of an encoder signal. It is a figure which shows an example of the deviation | shift amount of the design value and measured value of the pulse number of an encoder signal in the case of a light load in a table format. It is a figure which shows the time change of the total value of the deviation | shift amount of the design value and measured value of the encoder pulse in FIG. It is a figure which shows an example of the deviation | shift amount of the design value and measured value of the pulse number of an encoder signal in the case of a heavy load in a table format. It is a figure which shows the time change of the accumulated value of the deviation | shift amount of the design value and measured value of the encoder pulse in FIG. FIG. 9 is a diagram showing an example different from the case of FIG. 8 in a table format in the case of heavy load. It is a figure which shows the time change of the total value of the deviation | shift amount of the design value and measured value of the encoder pulse in FIG. FIG. 3 is a functional block diagram of a portion related to load amount detection in the stepping motor driving device of FIGS. 1 and 2. It is a flowchart which shows the procedure for determining the grade of the load of a stepping motor. It is a flowchart of the modification of FIG. FIG. 3 is a schematic diagram illustrating a configuration of a paper transport system. FIG. 16 is a diagram illustrating a state in which the sheet has moved more than the case of FIG. It is a figure which shows the state which the paper moved further than the case of FIG. FIG. 6 is a timing diagram illustrating an example of an operation state of the paper transport system. 1 is an external view of an image forming apparatus 100 configured as an MFP (Multi-Functional Peripheral). 1 is a block diagram illustrating a configuration of an image forming apparatus 100. FIG.

  Hereinafter, embodiments will be described in detail with reference to the drawings. The same or corresponding parts are denoted by the same reference numerals, 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 driving apparatus according to the first embodiment. Referring to FIG. 1, a stepping motor driving apparatus 10 includes a stepping motor 14, a driver 13, an encoder 15, and a controller 12. Hereinafter, 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 the 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 of each pulse signal differs depending on the number of phases. The stepping motor 14 rotates in accordance with the drive pulse signal DS.

  The encoder 15 generates an encoder signal ES that is a pulse signal corresponding to the actual rotation angle of the rotor of the stepping motor 14. In general, the encoder signal ES includes two A-phase and B-phase pulse signals that are shifted from each other by ¼ period. Based on the A-phase and B-phase pulse signals, the rotational direction, rotational position, and rotational speed of the motor can be detected.

  The controller 12 controls the rotation angle and 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.

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

  FIG. 2 is a block diagram illustrating a configuration example of the controller of 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 as an example. The CPU 20, RAM 21, and ROM 22 are connected to each other via a bus 26. The driver 13 and the encoder 15 in 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 drive device 10 and its drive target 50. The display unit 120 is used to display information such as characters and images to the user, and the operation unit 121 is used for user input operations.

  Note that, unlike 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 (drive control unit 11 in FIG. 1) may be configured as one circuit unit.

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

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

  In the following, the configuration of the stepping motor shown in FIG. 3 will be described as an example, but the example of this figure is only 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 may be a micro-step mode. .

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

  As shown in FIG. 4A, when the load is light with respect to the motor torque, the magnetic pole of the rotor 30 and the magnetic pole of the stator 31 of the excitation phase are sequentially engaged with each other at the center position (ideal position). It rotates. On the other hand, as shown in FIG. 4B, when the load is increased with respect to the motor torque, a deviation occurs between the center position of the magnetic poles of the rotor 30 and the center position of the magnetic poles 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 poles of the rotor 30 and the center position of the magnetic poles of the excitation phase stator 31 is a measure of the load applied to the rotor 30 of the stepping motor 14. This deviation amount can be detected by an encoder signal ES as shown 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 of FIG. In the example of this figure, it is assumed that the rotor 30 rotates by one step angle (1.8 °) in one cycle of the control pulse signal CS (from time t1 to time t2).

  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 at a light load. In terms of design, it is assumed that 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 heavy load. When the load applied to the rotor is relatively large, the amount of rotation of the rotor is insufficient, so the number of pulses corresponding to one cycle of the control pulse signal CS may be less than the ideal number of pulses (80 pulses). Arise. 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 decreased to 70 pulses.

  In this way, by detecting a 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 table showing an example of a deviation amount between the designed value and the actually measured value of the number of pulses of the encoder signal in the case of a light load. In the table of FIG. 6, starting from the leftmost column, the number of input pulses of the driver 13 of FIG. 1 (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 measurement 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 poles of the rotor 30 and the center position of the magnetic poles of the stator 31 of the excitation phase coincide. The deviation amount between the design value and the actual measurement value of the encoder pulse in this initial state is zero. Whether or not the stepping motor steps out 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 (ie, 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 actually measured value of the encoder pulse for each step angle.

  FIG. 7 is a diagram showing a change over time in the cumulative value of the deviation amount between the design value and the actual measurement 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 cumulative value of the deviation (difference) between the design value of the encoder pulse number and the actual measurement value.

  In terms of design, it is assumed that the rotor rotates 1.8 ° per input pulse, and the number of encoder pulses counted at this time is 80. Step-out occurs when the angle deviation between the rotor and the stator becomes 0.9 °. The accumulated value of the deviation amount between the designed value of the encoder pulse and the actual measurement value when this step-out occurs is ± 40. Corresponds to the count.

  Therefore, the stepping motor drive device of the present embodiment provides a threshold value before the accumulated value of the deviation amount reaches ± 40 counts in order to prevent step-out, and when this threshold value is exceeded. Notify users. Specifically, when the cumulative value of the deviation amount between the design value and the actual measurement value exceeds ± 20 counts (first threshold value: ± TH1), it is determined that there is an overload. When the cumulative value of the deviation amount between the design value and the actual measurement value exceeds ± 35 counts (second threshold: ± TH2), it is determined that there is a risk of step-out.

  In the example of FIG. 7, the accumulated value of the deviation amount between the design value and the actual measurement value of the encoder pulse in the initial state is 0 count. That is, in the initial state, the center position of the magnetic poles of the rotor 30 and the center position of the magnetic poles of the stator 31 in the excitation phase coincide. In the initial state, the motor is driven in a state in which the motor current is increased during the predetermined time after the start of the stepping motor so that the deviation amount between the magnetic pole centers of the rotor and the stator is zero. . 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 rotor position oscillates based on the ideal position. In a normal state where the load is relatively light, the cumulative value (absolute value) of the deviation amount between the design value and the actual measurement 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 cumulative value of this deviation amount is within ± 10 counts.

[Specific example of load detection: under heavy load]
FIG. 8 is a table showing an example of a deviation amount between the designed value and the actually measured value of the number of pulses of the encoder signal in the case of heavy load. FIG. 9 is a diagram showing a change over time in the cumulative value of the deviation amount between the design value and the actual measurement value of the encoder pulse in FIG. The table of FIG. 8 and the graph of FIG. 9 correspond to the table of FIG. 6 and the graph of FIG.

  As shown in FIG. 8 and FIG. 9, when the number of input pulses reaches 5 counts, the cumulative value of the deviation amount between the design value of the encoder pulse and the actual measurement value becomes −22, which is ± 20 which is the first threshold value. Over. Thereby, the controller 12 of FIG. 1 detects that the load applied to the rotor of the stepping motor 14 is increasing. The cause of such an increase in load may be due to deterioration over time of a component that is the driving target 50 of the stepping motor 14 or 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.

  In addition, when the use of deteriorated parts that need replacement is temporary, the increase in load is also temporary. Therefore, as shown in FIG. 8, even if the cumulative value of the deviation amount between the encoder pulse design value and the actual measurement value exceeds the first threshold value (± TH1 = ± 20) and then returns to the first threshold value or less. The user is informed of the need for parts replacement. Note that the stepping motor operation is continued as it is because the possibility of step-out is low only by exceeding the first threshold value (± TH1). Or you may make it restrict | limit some operations, such as limiting the continuous operation time of a stepping motor.

  In the above, when the cumulative value of the deviation amount between the design value and the actual measurement value of the encoder pulse exceeds the first threshold value even once, the user is notified that the parts need to be replaced. Alternatively, the user may be notified that component replacement is required when the number of times that the cumulative value of the deviation amount exceeds the first threshold reaches a predetermined number.

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

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

[Stepping motor load detection procedure]
The procedure to detect the degree of load applied to the rotor of the stepping motor will be described by summarizing the description so far.

  FIG. 12 is a functional block diagram of a part related to detection of the load amount in the stepping motor driving apparatus of FIGS. 1 and 2. Referring to FIG. 12, the stepping motor driving apparatus 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. Including.

  In the case of this embodiment, the control pulse signal generation unit 40 and the load determination unit 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 of FIG.

  Specifically, the control pulse signal generation unit 40 (first pulse signal generation unit) 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 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 determination unit 41 (first determination unit) determines the degree of load on the stepping motor 14 by comparing the control pulse signal CS and the encoder signal ES. Specifically, the load determination unit 41 counts the number of pulses of the encoder signal ES for each predetermined period (usually one period) of the control pulse signal CS, and the number of counted pulses and the number of pulses of the encoder signal ES for each predetermined period. The difference value (deviation amount) from the target value is calculated. The load determination unit 41 calculates a total value by adding the difference values calculated every predetermined period from the time of starting the stepping motor, and determines the degree of load of the stepping motor based on the calculated total value.

  For example, when the absolute value of the cumulative value of the encoder signal deviation amount exceeds the first threshold value TH1 or exceeds the first threshold value TH1 a predetermined number of times, the load determination unit 41 is heavier than normal. It is determined that The load determination unit 41 further determines that there is a risk of step-out when the second threshold value TH2 (TH2> TH1) is exceeded. 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. Also good.

  The component deterioration determination unit 43 (second determination unit) determines the presence or absence of deterioration of the component that is the driving target 50 of the stepping motor 14 based on the degree of load determined by the load determination unit 41. For example, when the absolute value of the calculated cumulative value of encoder signal deviations exceeds the first threshold value TH1, the component deterioration determination unit 43 notifies that the component that is the drive target 50 has deteriorated (for example, A warning is displayed on the display unit 120).

  FIG. 13 is a flowchart showing a procedure for determining the degree of load of the stepping motor. Referring to FIGS. 12 and 13, when the initial operation is started (YES in step S <b> 100), controller 12 starts from stepping motor 14 to stepping motor 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 is made to coincide with the center position of the magnetic pole of the stator of the excited phase.

  While the stepping motor 14 is in operation (that is, until a motor stop command is received from the control device 110), the load determination unit 41 sets the number of pulses of the encoder signal ES for each predetermined period with reference to the edge of the control pulse signal CS. Counting is performed (step S110), and the difference between the counted number of pulses and the target value is calculated (step S115). Further, the load determination unit 41 calculates a cumulative value from the initial state of the calculated difference value (step S120).

  When 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 the normal state. (Step S135). Alternatively, the load determination unit 41 may determine that the load amount of the stepping motor 14 is a heavy load when the absolute value of the calculated cumulative value exceeds the first threshold value TH1 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 the step-out does not occur due to an increase in the load.

  When a plurality of parts can affect the load of the stepping motor 14, the part deterioration determination unit 43 determines that the part has deteriorated if there is a difference between the operation state of a certain part and the determination result of the heavy load. To do. This is because a component that is not in an operating state when it is determined to be a heavy load is not necessarily deteriorated (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 (where TH2> TH1) (YES in step S145), the load determination unit 41 determines that the stepping motor 14 has a risk of stepping out. It is determined that there is (step S150). In this case, the controller 12 stops the operation of the stepping motor 14 (step S160). Note that it is also possible to notify only the necessity of component replacement without stopping the operation. Furthermore, in order to prevent step-out, the motor current may be temporarily increased from the normal time.

[Modified example of load detection procedure]
FIG. 14 is a flowchart of a modification of FIG. The flowchart in FIG. 14 is different 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 an average value of the cumulative value per one rotation of the rotor, based on the calculated cumulative value of the deviation amount of the encoder pulse.

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

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

[effect]
According to the first embodiment, the stepping motor drive apparatus 10 determines that the load applied to the rotor of the stepping motor 14 has fluctuated from the initial state based on the encoder signal from the encoder 15 attached to the motor. If it is determined that the load is heavy, the stepping motor drive device 10 indicates that the part to be driven by the stepping motor 14 (part that can affect the load) has deteriorated over time (that is, the replacement time). To the user. As a result, it is possible to accurately and easily determine whether or not the component has deteriorated with 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 example, for transporting paper or a document in a printer or a scanner.

  FIG. 15 is a schematic diagram showing the 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 showing a state in which the sheet has moved further than in the case of FIG.

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

  The unit UA includes a sensor 70 for detecting paper 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 where the member 61 is moved by the operation of the motor 60, that is, a state where the unit UB is operating. FIG. 17 shows a state where the leading edge of the paper 52 is detected by the sensor 70, that is, a state where the unit UA is operating.

  The units UA and UB are parts used for printing the paper 52, for example. When these parts are operating, a load is applied to the rotor on 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 with time, it is detected as an increase in the load on the stepping motor 14.

  FIG. 18 is a timing diagram illustrating an example of an operation state of the paper transport system. In FIG. 17, the operating state of the stepping motor 14, the operating state of the motor 60, the operating state of the sensor 70, the determination result of the degree of load of the motor 14, the determination result of the possibility of step-out of the motor 14, and the encoder signal deviation The cumulative value of the quantity is shown in a state of comparison along a common time axis.

  Referring to FIGS. 12, 15, and 18, it is assumed that the accumulated value of the deviation amount of the encoder signal exceeds the first threshold value ± TH1 at the time of operation of unit UB (motor 60) (time t3). As a result, the load determination unit 41 determines that the load of the stepping motor 14 has increased from the normal time (the determination result changes to H level). The component deterioration determination unit 43 notifies the user that the unit UB that is operating at time t2 has deteriorated with time. For example, the display unit 120 displays that the unit UB needs to be replaced. Furthermore, in order to prevent a step-out due to an increase in load, the number of continuous sheets conveyed may be limited (thus, 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 deviation 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 of the stepping motor 14 compared with the normal time (the determination result changes to H level). The component deterioration determination unit 43 notifies the user that the unit UA that is operating at time t4 has deteriorated over time. For example, the display unit 120 displays that the unit UB needs to be replaced. In this case, in order to prevent a step-out due to an increase in load, the motor current may be temporarily increased as compared with the normal time, or the conveyance of a new sheet may be stopped.

  Note that the paper transport system is preferably configured such that the timing diagram 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 during maintenance.

<Third Embodiment>
In the third embodiment, an example in which the paper conveyance 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.

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

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

  The printer 140 prints an image such as a document read by the scanner 130 or print data transmitted from an external device on a sheet by, for example, an electrophotographic method. The printer 140 includes a 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 an image has been 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 a storage medium such as a hard disk and / or an external storage device. The storage device 122 stores a control program for causing the CPU 111 of the control device 110 to operate.

  An antenna (not shown) or the like is connected to the network interface 123. The image forming apparatus 100 exchanges data with other communication devices 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 to download a control program operated by the control device 110 from a server via an antenna.

[effect]
In the paper transport units 131 and 141 described above, the stepping motor driving device 10 described in the first embodiment can be applied as a drive function for paper transport. As a result, as described in the first embodiment, whether or not a part has deteriorated with time is determined accurately and easily based on the detection result of the actual load applied to the rotor of the stepping motor 14. be able to. As a result, the part replacement display to the user can be extended to the actual life of the part instead of being predicted based on the frequency of use, so that the service cost can be reduced. In addition, even when parts need to be replaced, parts can be urged to be replaced before a paper jam (JAM) due to step-out or machine stoppage due to overload detection, leading to downtime and wasted paper consumption. Can be suppressed.

  It should be thought that embodiment disclosed this time is an illustration and restrictive at no points. 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.

  DESCRIPTION OF SYMBOLS 10 Stepping motor drive device, 11 Drive control part, 12 Controller, 13 Driver, 14 Stepping motor, 15 Encoder, 20, 111 CPU, 30 rotor, 31 Stator, 40 Control pulse signal generation part, 41 Load judgment part, 43 Parts deterioration Determination unit, 50 Drive target (component), 52 paper, 100 image forming device, 110 control device, 120 display unit, 121 operation unit, 130 scanner, 131, 141 paper transport unit, 140 printer, CS control pulse signal, DS drive Pulse signal, ES encoder signal, TH1-TH4 threshold, UA, UB unit (parts).

Claims (14)

Stepper motor,
A first pulse signal generator for generating a first pulse signal representing a command value of the rotation angle of the stepping motor;
A second pulse signal generator for generating a second pulse signal corresponding to the actual rotation angle of the stepping motor;
A first determination unit that determines the degree of load of the stepping motor by comparing the first pulse signal and the second pulse signal;
A stepping motor drive apparatus comprising: a second determination unit that determines whether there is any deterioration of a component that may affect the load of the stepping motor based on the determined load level. The first determination unit includes:
Counting the number of pulses of the second pulse signal for each predetermined period 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 predetermined period;
Calculate a cumulative value obtained by accumulating the difference value calculated every predetermined cycle from the time of starting the stepping motor,
The stepping motor driving device according to claim 1, wherein the stepping motor driving device is configured to determine a degree of load of the stepping motor based on the calculated cumulative value.   The second determination unit affects the load on the stepping motor based on whether the absolute value of the cumulative value exceeds a first threshold or whether the first threshold is exceeded a predetermined number of times. The stepping motor drive device according to claim 2, wherein presence or absence of deterioration of a component that can be applied is determined.   The second determination unit determines that the stepping motor is likely to step out when an absolute value of the cumulative value exceeds a second threshold value that is greater than the first threshold value. Item 4. A stepping motor driving device according to Item 3. 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 drive device according to claim 2, wherein the stepping motor driving device is configured to determine a degree of load of the stepping motor based on an average value of the calculated cumulative values.   The second determination unit determines whether the load of the stepping motor is based on whether the absolute value of the average value of the cumulative values exceeds a third threshold or whether the third threshold is exceeded a predetermined number of times. The stepping motor driving device according to claim 5, wherein presence or absence of deterioration of a component that can affect the step is determined.   The second determination unit determines that the stepping motor is likely to step out when the absolute value of the average value of the cumulative values exceeds a fourth threshold value that is greater than the third threshold value. The stepping motor driving device according to claim 6.   The stepping motor drive device according to any one of claims 1 to 7, wherein a motor current higher than that after the elapse of the predetermined period is supplied to the stepping motor during a predetermined period from the start of the stepping motor. .   The stepping motor driving device according to claim 8, wherein a magnitude of a motor current supplied to the stepping motor is a maximum value that can be supplied during a predetermined period from the startup.   The stepping motor driving apparatus according to claim 1, wherein the stepping motor is open-loop controlled.   The stepping motor drive device according to any one of claims 1 to 10, wherein when the second determination unit determines that the component is deteriorated, a continuous operation time of the stepping motor is limited. .   The second determination unit is configured to display on the display unit or to print on the printer in a state where the determination result of the degree of 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 11.   The said 2nd determination part determines with the said component having deteriorated, when the determination result of the grade of the said load and the operation state of the said component are in phase. The stepping motor drive device according to item. A paper transport unit for transporting paper for printing images;
The image forming apparatus including the stepping motor driving device according to any one of claims 1 to 13.

Images