JP2012195984A - Controller of stepping motor and control method of stepping motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption by monitoring a load of a stepping motor at all times and setting a driving current optimum for the load of the moment without causing step-out of the motor.SOLUTION: A controller of a stepping motor includes: a driving current setting unit 121 for setting a driving current for driving a stepping motor 100; a load detection unit 124 for detecting the load from a driving waveform of the stepping motor 100; a step-out sign determination unit 125 for determining that there is a sign of step-out when the detected load exceeds a certain threshold; and a driving current optimization control unit 130 for varying the driving current and setting the minimum driving current which is needed for the load without causing the step-out. The driving current optimization control unit 130 variably controls the driving current according to presence/absence information on a step-out sign by the step-out sign determination unit 125 every time the variably controlled prescribed time elapses.

Description

  The present invention relates to a stepping motor control device and a stepping motor control method.

  Conventionally, a drive source that requires driving / stopping, forward rotation / reverse rotation, acceleration / deceleration, etc., on a driven object, such as a document conveyance mechanism of a document reading scanner, a carriage scanning mechanism, or a conveyance mechanism such as a copying machine. A stepping motor is used. When mounting this stepping motor, it is necessary to select a motor of a scale that takes into account the load of the driven object, that is, the output energy for driving the driven object. For this reason, as a method for determining the driving current value of the stepping motor, the load torque is obtained in advance by calculation or actual measurement, and a margin for allowing variation in the load torque of the stepping motor, the environment, assembly, etc. is added. Determined above. For this reason, since the current value in consideration of various variation conditions is set, a value larger than the current value that covers the actual load torque is often set. Further, the load driven by the stepping motor is not necessarily constant, and there are drive points where the load increases and drive points where the load decreases, but the drive current for driving the stepping motor is set to a current value that can drive the maximum load.

  In an apparatus using such a stepping motor as a drive source, the stepping motor is driven while gradually reducing the drive current for the purpose of reducing the power consumption of the stepping motor, and based on the drive current value when the step-out is detected. A technique for optimizing the drive current is disclosed (for example, see Patent Document 1). Also, a change in the current flowing through the stepping motor is detected, and based on the detected waveform, it is determined whether the motor output at the currently set drive current value is appropriate for the required load torque, and the result is A technique for changing the drive current value accordingly is disclosed (for example, see Patent Document 2).

  Note that step-out is caused by the stepping motor overloading or sudden speed change, etc., and the synchronization between the input pulse signal and the motor rotation is lost. A phenomenon that does not match.

Japanese Patent Laid-Open No. 11-215890 JP 2008-236940 A

  However, in the apparatus for reducing the power consumption of the stepping motor as shown above, the load of the stepping motor is constantly monitored, and the drive current value is not optimized for the load at that time. Since the drive current value is optimized only at the maximum load, the drive current values other than the maximum load cannot be optimized. In addition, since the stepping motor is stepped out when performing the optimization process of the drive current value, if the home position is not detected at the next start-up, the position information cannot be grasped and the non-driven object There was also a possibility that the device might be damaged by the runaway or lock of the machine. In addition, when the home position is detected, there is a problem that downtime occurs because it takes time to detect.

  In the technique of Patent Document 1, although the actual load torque is obtained while gradually reducing the drive current value and the optimum drive current value is determined for the actual load torque, the drive current at times other than the maximum load is determined. It cannot be optimized. In addition, since the stepping motor is stepped out in performing the optimization process, there is a problem in that the machine is damaged or downtime due to the inability to grasp the position information.

  In the technique of Patent Document 2, the threshold for determining that the drive current is optimal is a preset value, and therefore a margin is set in consideration of changes in the drive environment, load variations between machines, and the like. There is a need. In addition, the threshold value may be changed from the operation panel, but in that case, it is necessary for the user or service person to set the current value so that an output close to the required torque can be automatically obtained. Cannot be set. In addition, when the variation is large, there is a possibility of stepping out.

  The present invention has been made in view of the above, and by constantly monitoring the load of the stepping motor, it is possible to set the optimum drive current for the load at that time without stepping the motor, The purpose is to reduce electric power.

  In order to solve the above-described problems and achieve the object, the present invention detects a load of the stepping motor from drive current setting means for setting a drive current for driving the stepping motor and a drive waveform of the stepping motor. A load detecting means, a step-out predicting judging means for judging that there is a sign of step-out when the load detected by the load detecting means exceeds a certain threshold, and a variable driving current required for the load. Drive current optimization control means for setting to the minimum drive current that does not step out, and the drive current optimization control means performs the step-out predictive judgment means by the step-out predictor judgment means every time a predetermined variable control time elapses. The drive current is variably controlled in accordance with the presence / absence information of the adjustment sign.

  The present invention sets the drive current at every elapse of a predetermined time, and controls the drive current to be constant during the predetermined time, thereby stabilizing the rotation of the stepping motor and driving at a predetermined time without stepping out. Since the current can be optimized, the power consumption can be reduced.

FIG. 1 is a block diagram showing a system configuration in which a stepping motor control device according to this embodiment is mounted. FIG. 2 is a block diagram showing a functional configuration example (1) of the stepping motor control device according to this embodiment. FIG. 3 is a flowchart showing an overall control operation example (1) of the stepping motor control apparatus according to this embodiment. FIG. 4A is a flowchart of a current optimization sequence operation example (1-1) of the stepping motor control device according to this embodiment. FIG. 4B is a flowchart of a current optimization sequence operation example (1-2) of the stepping motor control device according to this embodiment. FIG. 5 is a timing chart showing an example of drive current control. FIG. 6 is a graph showing a set range of t1 during the slow-up control of the stepping motor. FIG. 7: is a block diagram which shows the function structural example (2) of the stepping motor control apparatus concerning this embodiment. FIG. 8A is a flowchart of a current optimization sequence operation example (2-1) of the stepping motor control device according to the present embodiment. FIG. 8-2 is a flowchart of a current optimization sequence operation example (2-2) of the stepping motor control device according to this embodiment. FIG. 9A is a flowchart of a current optimization sequence operation example (3-1) of the stepping motor control device according to this embodiment. FIG. 9-2 is a flowchart of a current optimization sequence operation example (3-2) of the stepping motor control device according to this embodiment. FIG. 10 is a timing chart showing an example of rotation speed control according to this embodiment. FIG. 11: is a block diagram which shows the function structural example (3) of the stepping motor control apparatus concerning this embodiment. FIG. 12 is a flowchart showing an overall control operation example (2) of the stepping motor control apparatus according to this embodiment. FIG. 13 is an explanatory diagram showing a configuration example of the automatic document feeder according to this embodiment.

  Exemplary embodiments of a stepping motor control device and a stepping motor control method according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment)
The present invention constantly monitors the load of the stepping motor, feeds back an optimum drive current to the monitored load at the time, and further optimizes the drive current based on the step-out predictive signal, thereby stepping. The power consumption of the motor is reduced. This will be specifically described below.

  FIG. 1 is a block diagram showing a system configuration in which a stepping motor control device according to this embodiment is mounted. In FIG. 1, reference numeral 100 is a stepping motor, reference numeral 110 is a system control unit, reference numeral 111 is a motor driver, reference numeral 112 is a motor control unit, reference numeral 113 is a storage unit, reference numeral 114 is a temperature detection element, reference numeral 115 is a notification unit, Reference numeral 120 denotes a driven part.

  The stepping motor 100 is used as a driving source of the driven unit 120 such as a paper feeding and conveying mechanism of an automatic document reading apparatus such as a copying machine, a carriage scanning mechanism, and various conveying and driving mechanisms such as a copying machine. The system control unit 110 includes a motor driver 111, a motor control unit 112, a storage unit 113, and the like, and controls the entire apparatus. The motor driver 111 drives the stepping motor 100. The motor control unit 112 exchanges control signals such as the motor rotation direction, the excitation pattern, and the drive frequency with the motor driver 111 that drives the stepping motor 100. The storage unit 113 stores the drive current value of the stepping motor 100, the optimum time condition, and the like. As the temperature detection element 114, a known temperature detection element that is disposed in the vicinity of the stepping motor 100 and can detect the temperature at the time of driving is used. The notification unit 115 is connected to a display unit of a device on which the stepping motor 100 is mounted, or a device such as a service center, and is used to perform a warning processing operation described later. Each of the above control units is constituted by a microcomputer system having a CPU, a ROM, a RAM, a timer, an I / O port, and the like, and the CPU executes a control operation described later according to a control program stored in the ROM. .

  FIG. 2 is a block diagram showing a functional configuration example (1) of the stepping motor control device according to this embodiment. In FIG. 2, reference numeral 121 denotes a drive current setting unit, reference numeral 122 denotes an output control unit, reference numeral 123 denotes a drive waveform output unit, reference numeral 124 denotes a load detection unit, reference numeral 125 denotes a step-out sign determination unit, and reference numeral 126 denotes a step-out sign. It is a flag generator. In addition, the motor control unit 112 includes a drive current optimization control unit 130.

  The drive current setting unit 121 sets a drive current for driving the stepping motor 100. The output control unit 122 controls a drive waveform output unit 123 to be described later based on command information such as the rotation direction, excitation pattern, and drive frequency received from the motor control unit 112. The drive waveform output unit 123 drives the stepping motor 100 according to a command signal from the output control unit 122. The load detection unit 124 monitors the drive waveform of the stepping motor 100 and detects load information applied to the stepping motor 100. The step-out predictor determination unit 125 determines a sign of whether or not step-out is being performed when the load information of the stepping motor 100 obtained by detection by the load detection unit 124 exceeds a predetermined threshold. The out-of-step sign flag generation unit 126 generates a flag when the out-of-step sign determination unit 125 determines that there is a out-of-step sign.

  The drive current optimization control unit 130 performs control to optimize the drive current of the stepping motor 100 based on information stored in the step-out predictor flag generation unit 126 and the storage unit 113. Note that. The optimization refers to a process of setting (controlling) the drive current value to a minimum current value that does not step out and is necessary for the load.

  FIG. 3 is a flowchart showing an overall control operation example (1) of the stepping motor control apparatus according to this embodiment. This control operation is executed by a stepping motor control device configured as shown in FIG. When the control operation is started, first, the motor control unit 112 reads the driving current value of the driving stepping motor 100 stored in the storage unit 113 (step S101), and the read driving current value is read into the driving current setting unit 121. Set (step S102). Subsequently, a current optimization sequence to be described later is executed (step S103), and it is determined whether or not the operation for this one mode is completed (step S104). Note that one mode means a series of operations designated by the user, for example, operations from the start to completion of 20-sheet copying when 20-sheet copying is designated.

  When the current optimization sequence is completed and one mode is completed in step S104 (determination Yes), the drive current value is reset (step S105). On the other hand, when one mode is not completed (determination No), the process returns to step S101, and the drive current value stored immediately before is read from the storage unit 113. Then, by repeatedly executing steps S101 to S104 until one mode is completed, the drive current value for driving the stepping motor 100 during the first mode is optimized.

  The reason why the drive current value is reset in step S105 is that, when one mode is completed and another mode is started again, the conditions are not always the same as before. For example, in a document feeder of a copying machine, the motor load varies depending on the type of paper, specifically the thickness of the paper. In addition, it is also affected by the ambient temperature during driving. For this reason, in the control operation of FIG. 3, the data in the storage unit 113 is reset when one mode is completed. However, in the example of the document feeder of the copying machine, the data is combined with the drive current value optimized during the first mode. When the thickness sensor is provided and the paper thickness information and the temperature sensor (FIG. 1: temperature detection element 114) are provided and the ambient temperature information is stored in the storage unit 113, it is not necessary to reset the drive current value. By utilizing this information, the time for optimizing the current can be shortened.

  Next, the current optimization sequence will be described with reference to FIGS. FIGS. 4-1 and 4-2 are flowcharts showing a current optimization sequence operation example (1) of the stepping motor control device according to this embodiment. FIG. 5 is a timing chart showing an example of drive current control. In FIG. 5, (A) is an example of rotational speed control, (B) and (C) are examples of conventional drive current control (1), (2), and (D) are examples of drive current control according to this embodiment. Show. FIG. 6 is a graph showing a setting range of t1 during the slow-up control of the stepping motor 100.

4A and 4B, first, it is determined whether or not the stepping motor 100 is starting or being excited (step S201). Here, when excitation is starting or during excitation (determination Yes), it is further determined whether or not the rotation speed of the stepping motor 100 is controlled at a constant speed (step S202). Here, if the rotational speed for controlling the stepping motor 100 is constant control simultaneously with the start of excitation (determination Yes), an optimization cycle (T for controlling the drive current value to a minimum current value that does not step out) _SE ) is set to t0 (step S203). Here, t0 may be selected by the stepping motor 100 to be driven. For example, t0 is increased for a stepping motor whose load fluctuation is known to be relatively small, or t0 is stored as a small initial value in the storage unit 113 for a stepping motor 100 whose load fluctuation is known to be large. .

  On the other hand, when the rotational speed is not constant control in Step S202 (determination No), the following control is executed. Specifically, when the stepping motor 100 is used in a high-speed region that is higher than the self-starting region, slow-up control (excitation is started from the rotational speed having a torque margin in the self-starting region and the target rotation is performed). Control that gradually increases the number of revolutions to the number: T1 range in Fig. 5 (A)) or slowdown control (opposite to slowup control, when position control is performed to prevent step-out when operation stops) In the case of the control for gradually decreasing the rotational speed to the target rotational speed: the range of T3 in FIG. 5A), the cycle is set to t1 (step S204). That is, while the rotational speed is variably controlled, the drive current is optimized at the cycle t1.

  After executing steps S203 and S204, the Ts timer starts from 0 (step S205). In addition, in order to consider the influence of vibration described later, after the slow-up control is started ([1] in FIG. 5A), after switching from the slow-up control to the constant speed control ([ 2]), after slow-down control is activated ([3] in FIG. 5A), and after switching from slow-down control to constant speed control ([4] in FIG. 5A), Tα In the meantime, the drive current may be optimized at a predetermined time t1. This Tα is determined from vibration data acquired by a design test, and is stored in the storage unit 113 as an initial value.

  Subsequently, the step-out prediction signal is monitored until t0 or t1 elapses (step S206). Until t0 or t1 elapses, driving is performed with the drive current value acquired before executing this sequence. If there is a step-out sign signal between t0 or t1, it is determined that there is a step-out sign (determination Yes), stored in the storage unit 113 (step S207), and steps S206 to S208 are repeated and executed until t0 or t1 elapses.

On the other hand, in step S206, if there is no out-of-step sign signal between t0 or t1, it is determined that there is no out-of-step sign (judgment No) and the process proceeds to step S208. Step S208 In either passed Ts _{= T SE,} i.e., determines whether the elapsed t0 or t1. Here, after the lapse of t0 or t1 (determination Yes), the Ts timer is reset (step S209). Then, the motor control unit 112 checks the information in step _S207, it is determined whether there is a step-out sign between _{T SE} (step S210). Here, when there is a step-out sign (determination Yes), the predetermined value Ax is added to the drive current value An (step S211). On the other hand, if there is no sign of step-out (determination No), the predetermined value Ay is subtracted from the drive current value An (step S212).

  In the above, the relationship between Ax and Ay is Ax> Ay. Here, An is a drive current set for every elapse of a predetermined time, A1 means a current value in the first excitation start section, and A2 means a current value in the second excitation start section. The initial value may be set to a value larger than the optimum current value (FIG. 5D), for example, as shown in FIG.

  Subsequently, after any one of steps S211 and S212, the drive current value An is stored in the storage unit 113 (step S213). Then, it is determined whether or not excitation is completed (step S214). If excitation is not completed (determination No), the process proceeds to step S201, and steps S201 to S214 are repeated and executed. On the other hand, if excitation has been completed (determination Yes), this series of operations is terminated.

  In the above description, the current optimization is performed with a step-out sign (step S211) or without a step-out sign (step S212). However, the step-out sign (step S211) is repeated twice in the same section, for example, twice. If this occurs and the drive current value An is the same, the drive current value is close to the optimum value (there is a possibility of stepping out when the drive current value falls below the drive current value). If the value An = An × 1.1 is fixed and a step-out sign is generated again, the process of step S211 may be performed.

  Here, the setting of t1 will be described. As described above, in the slow-up control, when the stepping motor 100 is used in a high speed region that is higher than the self-starting region, the frequency is varied from low speed to high speed in order to prevent step-out. At that time, at low speed, the pulse interval is large and vibration is generated. As the speed increases, the vibration gradually converges (see FIG. 6).

Since it is known from experiments that the rotation period affects the rotational speed (r0 [pps] in the example of FIG. 5A) for controlling the stepping motor 100 at the start of the slow-up control, The period tf is obtained by the following formula.
tf [ms] = 1000 ÷ r0

Further, since the load torque of the stepping motor 100 changes due to a change in vibration, the period t1 for optimizing the drive current value is preferably as follows.
0 <t1 ≦ tf <t0

  In the case of controlling at the rotational speed shown in FIG. 5A, conventionally, constant control is performed with a necessary current obtained from the load condition during excitation and the worst condition of the ambient temperature as shown in FIG. 5B. In another example, as shown in FIG. 5 (C), constant control is performed with necessary currents obtained under worst-case conditions during slow-up control, slow-down control, and other portions. FIG. 5D is an example of current control according to this embodiment, and the current optimization sequence of FIGS. 4-1 and 4-2 is executed (between [1]-[2], [3]-[4 ] Is a period t1, and a period between [2] and [3] is a period t0).

  FIG. 7: is a block diagram which shows the function structural example (2) of the stepping motor control apparatus concerning this embodiment. In this configuration, a margin setting unit 127 is added to the motor driver 111 in the configuration of FIG. Since other configurations are the same as those in FIG. 2, the same reference numerals are given here, and redundant descriptions are omitted.

  In the stepping motor control device configured as shown in FIG. 7, the margin setting unit 127 has a margin for providing a predetermined torque margin for variations that cannot be compensated for by load feedback control (for example, sudden load fluctuations). Set the value.

  FIGS. 8A and 8B are flowcharts illustrating the current optimization sequence operation example (2) of the stepping motor control device according to this embodiment. This operation is obtained by adding steps S311 to S314 to FIGS. 4-1 and 4-2 described above, and other operations are the same as those in FIGS. 4-1 and 4-2. Will be omitted and a description of this additional part will be given.

8A and 8B, when the rotation speed of the stepping motor 100 is constant control (determination Yes in step S302), T _SE = t0 is set (step S303). The motor control unit 112 confirms the information stored in the storage unit 113 in step S307. If there is a step-out sign (determination Yes in step S310), T _SE = t0 (determination Yes in step S311). A predetermined value Ax is added to the value An. An = An + Ax is set (step S312).

On the other hand, when the rotation speed of the stepping motor 100 is not constant control, that is, in the case of variable control (determination No in step S302), T _SE = t1 is set (step S304). The motor control unit 112 confirms the information stored in the storage unit 113 in step S307, and when there is a step-out sign (determination Yes in step S310), T _SE = t1 (determination No in step S311). A predetermined value Ax and a margin value Az are added to the value An (An = An + Ax + Az), and this value is set (step S313). Here, the relationship between Ax, Ay, and Az is Az ≧ Ax> Ay.

In the above, the predetermined value Ax and the margin value Az are added, but the following calculation may be performed. That is,
An = An + Ax × n times In another example,
An = An + margin value Azz (predetermined value Ax <margin value Azz)
It is good.

  In the above control operation, the margin value Az is added only when the rotational speed is not constant control, that is, when a step-out sign is detected during variable control, but this is not restrictive. For example, even when the rotation speed is under constant control (determination Yes in step S302), when a sign of step-out is detected a plurality of times during a predetermined time (counted in steps S305 to S307 and stored in the storage unit 113) The margin value may be added because the possibility of step-out is high.

  FIGS. 9-1 and 9-2 are flowcharts showing a current optimization sequence operation example (3) of the stepping motor control device according to this embodiment. This operation is different from the above-described FIGS. 8-1 and 8-2 in steps S411 and subsequent steps, and the other operations are the same as those in FIGS. 8-1 and 8-2. The part will be described.

  In this figure, when the rotation speed of the stepping motor 100 is not constant control, that is, in the case of variable control (determination No in step S402), the operations after step S404 are executed. The motor control unit 112 confirms the information stored in the storage unit 113 in step S407, and if there is a step-out sign (determination Yes in step S410), calculates the rotational speed gradient kn.

For example, as shown in FIG.
In the range of T1, k1 = | (r1-r0) | ÷ T1
In the range of T2, k2 = | (r2-r1) | ÷ T2
In the range of T3, k3 = | (r0−r2) | ÷ T3
It becomes.

  After calculating the rotational speed gradient kn in step S413, compared with a predetermined gradient k0 (step S414), if kn <k0, a margin value 1 (Az1) is added (step S415), and kn ≧ k0 In this case, the margin value 2 (Az2) is added (step S416). The relationship between Ax, Ay, Az1, and Az2 is Az2> Az1 ≧ Ax> Ay. That is, when the inclination is small, the power consumption is reduced by suppressing the margin value as much as possible, and when the rotation speed inclination kn is large, the margin value is increased to reliably prevent step-out.

  In FIGS. 9A and 9B, the predetermined inclination k0 is one, but it may be two or more. Further, the margin value may be changed during the slow-up control (the range of T1 and T2 in FIG. 10) and during the slow-down control (the range of T3 in FIG. 10).

  As described with reference to FIG. 5, the setting of t1 is 0 <t1 ≦ tf <t0. Further, at T1, tf [ms] = 1000 ÷ r0, at T2, tf [ms] = 1000 ÷ r1, and at T3, tf [ms] = 1000 ÷ r0.

  FIG. 11: is a block diagram which shows the function structural example (3) of the stepping motor control apparatus concerning this embodiment. This configuration is obtained by adding optimization prohibiting means 140 to the configuration of FIG. 2 described above. Since other configurations are the same as those in FIG. 2, the same reference numerals are given here, and redundant descriptions are omitted. The optimization prohibiting means 140 outputs an optimization prohibiting signal, and prohibits optimization of the drive current when the optimization prohibiting signal is output.

  The operation of the stepping motor control device configured as shown in FIG. 11 will be described. FIG. 12 is a flowchart showing an overall control operation example (2) of the stepping motor control apparatus according to this embodiment. This control operation is executed by a stepping motor control device configured as shown in FIG. When the control operation is started, first, the motor control unit 112 reads the driving current value of the driving stepping motor 100 stored in the storage unit 113 (step S501), and the read driving current value is read into the driving current setting unit 121. Setting is performed (step S502).

  Subsequently, it is determined whether or not the current optimization flag F = 0 (step S503). Here, when the current optimization flag F = 0 (determination Yes), the current optimization sequence is executed (step S504), and it is determined whether or not this one mode is completed (step S507). On the other hand, if the current optimization F = 1 in step S503 (determination No), it is further determined whether or not An = A0 is set (step S505). If An = A0 is not set here. (Decision Yes), An = A0 is set (step S506), and the process proceeds to step S507. On the other hand, if the drive current value An = A0 has been set in step S506 (determination No), the process proceeds to step S507.

  When the current optimization sequence is completed and one mode is completed in step S507 (determination Yes), the drive current value is reset (step S508). On the other hand, when one mode is not completed (determination No), the process returns to step S501, and the current value stored immediately before is read from the storage unit 113. Then, by repeatedly executing steps S501 to S507 until one mode is completed, the drive current value is optimized during the first mode.

  That is, in the operation of FIG. 12 described above, when the signal from the optimization prohibiting unit 140 is detected asynchronously with the drive current optimization sequence of FIGS. F = 1 (step S503, judgment No), and the optimization prohibition process of prohibiting the optimization of the drive current is executed. Further, while the current optimization flag is F = 1 (step S503, determination No), a predetermined drive current value (An = A0) is set (steps S505 and S506). On the other hand, when the current optimization flag is F = 0 (step S503, determination Yes), the current optimization sequence is executed (step S504).

  The predetermined current value is set in advance as a current value A0 in consideration of the maximum load during the prohibited period. More specifically, an automatic document feeder of a copying machine will be described as an example with reference to FIG.

  FIG. 13 is an explanatory diagram showing a configuration example of the automatic document feeder according to this embodiment. As shown in FIG. 13, an automatic document feeder (ADF) 200 is mounted on the apparatus main body 150.

  In FIG. 13, the paper feed / separation unit for sequentially transporting the originals 1 stacked and placed on the original table 2 one by one from the top is rotatable to a position in contact with the original feed side on the original table 2. A call roller 4, a paper feed member 5 that rotates in the paper feed direction and takes in the original document 1 that is called up in the call roller 4, and an uppermost position of the original document 1 that is rotated in the direction opposite to the paper feed direction. It is comprised from the separation member 6 etc. which isolate | separate only one of these. The calling roller 4 is a solenoid (not shown), and the paper feeding member 5 and the separating member 6 are driven by a driving motor (not shown) (for example, the stepping motor 100 described above).

  Further, the original 1 is abutted against the abutting roller pair 7, 7a downstream of the paper feeding / separating unit, whereby the inclination of the original 1 is corrected and conveyed to the inlet roller pair 8, 8a. The transport unit for transporting the transported document 1 to the reading position on the contact glass 102 includes an entrance roller pair 8 and 8a, an exit roller pair 10 and 10a, and the like. It is driven by a motor (for example, the aforementioned stepping motor 100). A paper discharge unit for discharging the document 1 after reading to the discharge tray 14 or the downstream of the switching claw 13 is a paper discharge sensor that detects the document 1 conveyed through the pair of exit rollers 10 and 10a. For example, an optical reflection type sensor) 23, a switching claw 13 for changing the conveyance direction at the time of paper discharge or reversal, a paper discharge roller 11 and a reverse roller 15 driven by a drive motor (not shown), and the like. .

  In FIG. 13, reference numeral 3 is a stop claw, reference numeral 9 is a guide plate, reference numeral 11 is a paper discharge roller, reference numeral 11a is a lower discharge roller, reference numeral 12 is an upper discharge guide plate, reference numeral 15 is a reverse roller, reference numeral 15a. Is a reverse driven roller, numeral 21 is an inlet sensor, numeral 22 is a registration sensor, numeral 101 is a reading unit, numeral 103a is a front reading reference plate, numeral 103b is a rear reading reference plate, numeral R1 is a first conveying path, numeral R2 Is a second transport path, symbol R3 is a third transport path, and symbol R4 is a fourth transport path.

  Next, a basic paper feed / separation operation of the automatic document feeder 200 shown in FIG. 13 will be described. The document 1 stacked with the first image surface facing upward on the document table 2 is sent a start signal to the automatic document feeder 200 by pressing a start button (not shown) in an operation unit (not shown) of the apparatus body 150. By being sent, the sheets are fed one by one from the top. The operation procedure is described below. When the document 1 is stacked and placed on the document table 2, the leading end of the document is positioned by abutting against the stop claw 3. When the original 1 is set in this way, the calling roller 4 is rotated in the direction of arrow A by a solenoid (not shown) in response to the start signal, and is lowered to a position where the original 1 is in contact with the calling roller 4. The document 1 pressed by the calling roller 4 is conveyed to a separation unit including a sheet feeding member 5 and a separation member 6 by the calling roller 4 rotating in the sheet feeding direction, and is separated one by one from the top.

  The originals 1 separated one by one are conveyed to the first conveyance path R1 in which the inlet roller pairs 8 and 8a are arranged by the abutting roller pairs 7 and 7a. The detection signal from the registration sensor 22 arranged in the vicinity of the entrance roller pair 8 and 8a is used to detect the leading edge of the document and to synchronize the passage of the leading edge of the document to the reading unit 101 and the start of image reading.

  Further, the reading operation is started in accordance with the setting of the single side / double side mode in the operation unit. When only the first image surface is read in the single-side mode, the document 1 is read by the reading unit 101 as described above, and then the exit roller pair 10 and 10a and the discharge roller 11 are read. , And the second transport path R2 where the discharge lower driven roller 11a is disposed, and is discharged to the discharge tray 14. On the other hand, when reading the first image surface and the second image surface in the duplex mode, the document 1 passes through the second conveyance path R2 after the first image surface is read as described above, and the reversing roller 15 and The paper is discharged downstream of the switching claw 13 through the third conveyance path R3 where the reverse driven roller 15a is disposed. At this time, the switching claw 13 is moved to the B position (home) by a solenoid (not shown) at a predetermined timing after the leading edge of the document is detected by the paper discharge sensor 23 or the document 1 is detected by the registration sensor 22. The document 1 is lowered from the position) to the B ′ position, and the document 1 nipped and conveyed by the sheet discharge roller 11 and the sheet discharge lower driven roller 11 a is guided downstream of the switching claw 13.

  The switching claw 13 lowered to the B ′ position is a predetermined time after the leading edge of the document has passed through the paper discharge sensor 23 (the time until the trailing edge of the document passes through the paper discharge roller pair 11, 11 a and reaches the switching claw 13. ) After a lapse, the solenoid is released to return to the B position (home position). After the switching claw 13 returns, the reverse roller 15 rotates in the reverse direction, and the leading edge of the document enters the nip portion of the paper discharge roller 11 and the paper discharge upper driven roller 11b. The document 1 is transported through the fourth transport path R4, is abutted against the temporarily stopped butting roller pairs 7 and 7a, corrects the inclination, and is transported to the reading position through the first transport path R1. At 101, the second image plane is read. After the second image plane is read in this way, the switching claw 13 moves to the B ′ position so that the first image plane is stacked downward in order to arrange the page order of the document 1. As a result, the document 1 after reading through the second transport path R2 passes through the third transport path R3 and is temporarily held downstream of the switching claw 13 with the second image surface facing downward. Thereafter, the switching claw 13 returns to the B position (home position), and the document 1 once held downstream of the switching claw 13 passes through the fourth conveyance path R4, the first conveyance path R1, and the second conveyance path R2. As described above, the first image surface is discharged downward to the paper discharge tray 14.

  Next, a current optimization prohibiting sequence of the automatic document feeder 200 configured as shown in FIG. 13 will be described. In the configuration and operation as shown in FIG. 13, it is preferable to fix the drive current value during image reading in order to stabilize the rotation of the stepping motor 100. In order not to optimize the driving current of the stepping motor 100 during that time, a prohibition flag is set with a signal when the leading edge of the sheet passes the registration sensor 22 as a current optimization prohibiting signal, and the trailing edge of the sheet is discharged. The prohibition flag is reset by a signal when passing through the sensor 23.

  For example, after the second image surface in the duplex mode is read, the first image surface passes through the fourth transport path R4, the first transport path R1, and the second transport path R2 in order to arrange the page order of the document 1. Although the paper is discharged to the paper discharge tray 14 in the downward direction, since reading is not performed at this time, the current for driving the stepping motor 100 may be optimized as usual.

  During the prohibition of the optimization of the driving current of the stepping motor 100, since the driving is performed with the current value considering the maximum load, it is preferable to shorten the prohibition time. For this purpose, a method is conceivable in which the leading edge of the sheet is prohibited only immediately before the reading section (near reference numeral 103a in FIG. 13) and the trailing edge of the sheet is immediately after the reading section (near reference numeral 103b in FIG. 13). For example, a prohibition time may be determined in accordance with the paper size after a delay of a predetermined time from passing through the registration sensor 22. The delay time is determined by the linear velocity (paper conveyance speed) and the conveyance distance between the registration sensor 22 and the portion immediately before reading. In addition, the prohibition time for the optimization of the current for driving the stepping motor 100 is determined by the linear velocity and the paper size.

  Therefore, according to the embodiment described above, the drive current setting unit 121 that sets the current for driving the stepping motor 100 and the load detection unit 124 that detects the load of the stepping motor 100 from the drive waveform of the stepping motor 100. When the load detected by the load detection unit 124 exceeds a certain threshold value, the step-out predictor determining unit 125 determines that there is a step-out predictor, and every time a predetermined time for variable control elapses. And a drive current optimization control unit 130 that variably controls the drive current based on the presence / absence information of the out-of-step predictor by the adjustment sign determination unit 125, so that the drive current is set every predetermined time, and the predetermined time During this time, the drive current is controlled to be constant, so that the rotation of the stepping motor 100 can be stabilized, and the drive at every predetermined time without step-out. Hakare optimization of current, it is possible to reduce power consumption.

  Further, in the above configuration, since the predetermined time is variably controlled, for example, when the rotation speed is controlled from a low speed to a high speed in order to prevent a step-out at the time of starting the stepping motor 100, the load is reduced by optimizing at a short interval. Even when there is a variation, the drive current can be optimized every predetermined time without stepping out, and the power consumption can be reduced.

  Further, the stepping motor control device configured as described above includes a margin setting unit 127 for giving a predetermined torque margin to the load, and the margin value set by the margin setting unit 127 for the drive current is set. By setting each time the specified time elapses, while controlling the rotation speed from low speed to high speed to prevent step-out at motor start-up, increasing the margin value allows step-out even if there is initial variation in the load or deterioration with time. The drive current can be optimized every predetermined time without doing so. In addition, since the margin value is set every elapse of a predetermined time, the control load is not increased.

  Further, in the stepping motor control apparatus configured as described above, the stepping motor 100 has various inclinations by changing the margin level in accordance with the inclination of the rotational speed (ratio between the rotational speed change and the time required for the change). However, by changing the margin level according to the inclination, the drive current can be optimized every predetermined time without stepping out.

  Further, the stepping motor control apparatus configured as described above includes the drive current optimization prohibiting unit 140, and during the detection of the optimization prohibition signal output from the optimization prohibiting unit 140, the drive current of the stepping motor 100 is detected. Since the optimization of the drive current is prohibited, the optimization of the drive current is prohibited. Therefore, the drive current is kept constant for a desired period, so that the rotation of the stepping motor 100 can be stabilized.

DESCRIPTION OF SYMBOLS 100 Stepping motor 110 System control part 111 Motor driver 112 Motor control part 113 Memory | storage part 114 Temperature detection element 115 Notification part 121 Drive current setting part 122 Output control part 123 Drive waveform output part 124 Load detection part 125 Out-of-step sign determination part 126 Removal Predictive flag generation unit 127 margin setting unit 130 drive current optimization control unit 140 optimization prohibition means

Claims (6)

Drive current setting means for setting a drive current for driving the stepping motor;
Load detection means for detecting a load of the stepping motor from a driving waveform of the stepping motor;
A step-out sign determination unit that determines that there is a step-out sign when the load detected by the load detection unit exceeds a certain threshold;
Drive current optimization control means for setting the drive current to a minimum drive current that does not step out and is required for the load;
With
The stepping motor characterized in that the drive current optimization control means variably controls the drive current according to information on presence / absence of a step-out sign by the step-out sign determination means every time a predetermined variable time is elapsed. Control device.   And a margin setting means for giving a predetermined torque margin to the load, wherein the margin value set by the margin setting means for the drive current is set every time the predetermined time elapses. The stepping motor control device according to claim 1.   3. The margin setting unit changes the margin level according to a rotation speed gradient represented by a ratio between a change in the rotation speed of the stepping motor and a time required for the change. Stepping motor control device.   Further, an optimization prohibiting unit that prohibits the optimization process of the drive current is provided, and the optimization process of the drive current is prohibited while the optimization prohibition signal is output from the optimization prohibition unit. The stepping motor control device according to claim 1, 2, or 3.   5. The stepping motor control device according to claim 4, wherein the optimization prohibiting unit outputs the optimization prohibiting signal while a driven body driven by the stepping motor performs a predetermined operation. A drive current setting step in which the drive current setting means sets a drive current for driving the stepping motor; and
A load detecting step for detecting a load of the stepping motor from a driving waveform of the stepping motor;
A step-out precursor determination step for determining that there is a step-out precursor when the step-out precursor determination means exceeds a certain threshold value in the load detected in the load detection step;
A drive current optimization control step in which the drive current optimization control means sets the drive current to a minimum drive current that does not step out and is required for the load;
Including
The driving current optimization control step variably controls the driving current according to information on presence / absence of a step-out predictor in the step-out predictor determination step every time a predetermined variable control time elapses. Control method.

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