JP2008086151A - Motor controller, original reading apparatus, and motor control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller, an original reading apparatus, and a motor control method that can prevent the deterioration of the throughput of original reading even when a motor is driven at an extremely low speed. <P>SOLUTION: This motor controller comprises a signal output means 124, which outputs interrupt signals according to the revolutions of a motor 50; a power addition control means 112, which performs control to increase electric power supplied to the motor 50 from the power range not to rotate the motor with the lapse of time; and a determination means 111, which receives the interrupt signals, compares with a specified reference value a measured value corresponding to a time interval from the previous interrupt signal every time the interrupt signals are inputted, determines whether or not a measurement period exceeds a reference period as a comparison result, instructs the power addition control means 112 to reduce electric power supplied to the motor 50 to stand-by power when it is determined that the measurement period does not exceed the reference period, and allows the power addition control means 112 to continue the power increase, when the determination means 111 determines that the measurement period exceeds the reference period. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a motor control device, a document reading device, and a motor control method.

  Conventionally, various motors such as a DC (direct current) motor and a stepping motor are used in apparatuses such as a scanner and a printer. For example, a printer is provided with a paper feed motor, a motor that transports a carriage on which a print head is mounted, and the like (see, for example, Patent Document 1). In addition, for example, a scanner is provided with a motor that transports a carriage on which an image sensor is mounted (see, for example, Patent Document 2).

JP 2001-219613 A JP 2005-184390 A

  In the above-described devices, there is a demand for rotating the motor at an extremely low speed. For example, in a scanner, the reading resolution can be increased by rotating the carriage transport motor at an extremely low speed (very low speed) and moving the reading position of the image sensor mounted on the carriage at an extremely low speed. Because.

  In order to realize the driving of the motor at such an extremely low speed, the adoption of a method of driving in a state in which the voltage applied to the motor is reduced at every predetermined timing has been studied. However, when the motor is rotated at an extremely low speed by such a method, the motor may rotate at a rotational speed lower than the expected rotational speed. At this time, if the voltage applied to the motor is reduced at a predetermined timing, the moving speed of the carriage and the image sensor becomes very slow. As a result, there arises a problem that the throughput of document reading is significantly reduced.

  Here, the purpose of driving the motor at an extremely low speed and the improvement of the document reading throughput are contradictory, but the motor drive device and the document reading capable of satisfying both of these purposes Realization of the device is desired.

  The present invention has been made based on the above circumstances, and its object is to provide a motor control device capable of preventing a reduction in document reading throughput even when the motor is driven at an extremely low speed, An original reading device and a motor control method are to be provided.

  In order to solve the above-mentioned problems, the present invention provides a signal output means for outputting an interrupt signal based on rotation of a motor that provides a driving force for transporting an object to be transported, and electric power applied to the motor over time. A time interval between the power addition control means for performing control to increase from the electric power range in which the motor does not rotate, and the interrupt signal is input every time this interrupt signal is input. The measured value is compared with the specified reference value, and as a result of the comparison, it is determined whether or not the motor rotational speed exceeds the target rotational speed, and the motor rotational speed is set to the target rotational speed. If it is determined that the motor power exceeds the power addition control means, a command to reduce the power applied to the motor to a power range where the motor does not rotate is given to the motor rotation speed as a target speed. If it is determined not to exceed the speed, in which includes a determination unit configured to continue the increase in power, the.

  In such a configuration, each time the interrupt signal is input from the signal output unit, the determination unit compares the measured value corresponding to the time interval between the previous interrupt signal and the reference value. Then, as a result of the comparison, it is determined whether or not the rotational speed of the motor exceeds the target rotational speed. When it is determined that the rotational speed of the motor exceeds the target rotational speed, the motor is driven at a sufficient average rotational speed between the two interrupt signals. Is accelerated, it becomes difficult to rotate the motor at an extremely low speed. Therefore, in this case, the electric power applied to the motor is reduced to a range of electric power at which the motor does not rotate. If it is determined by comparison between the measured value and the reference value that the motor rotation speed exceeds the target rotation speed, the motor drives between the two interrupt signals at a sufficient average rotation speed. Even in extremely low speed driving, it is in a very slow state. In this case, the increase in power in the power addition control means is continued.

  By doing so, when the motor is driven at a very low speed, the duty ratio applied to the motor is increased when the motor is in a very slow state. Throughput can be improved. In addition, it is possible to satisfy both conflicting purposes of driving the motor at an extremely low speed and improving the throughput in transporting the object to be transported.

  In another invention, in addition to the above-described invention, the power addition control means further increases the duty ratio applied to the motor step by step when a predetermined interrupt time arrives, and copes with this duty ratio. Current to be applied to the motor.

  In such a configuration, when a predetermined interruption time arrives, the duty ratio applied to the motor is increased stepwise, so that the motor can be accelerated stepwise.

  Further, according to another invention, in addition to each of the above-described inventions, the power addition control means returns the power to a range where the motor does not rotate after a predetermined acceleration region has elapsed, and then stepwise sets the duty ratio applied to the motor. The current corresponding to the duty ratio is applied to the motor.

  In such a configuration, a predetermined acceleration region exists, and the motor is accelerated until this acceleration region elapses. For this reason, the power addition control means can accelerate the motor by an amount corresponding to driving the motor at an extremely low speed. Further, the presence of the acceleration region can improve the throughput in transporting the object to be transported, and can shorten the entire processing time when the motor is driven at an extremely low speed.

  In another invention, in addition to the above-described inventions, the signal output means detects an interrupt signal every time an edge between a high level and a low level is detected in an output signal output according to the rotation of the motor. Is output.

  With this configuration, an interrupt signal is output each time an edge between the high level and low level in the output signal is detected, so the period between adjacent edges (motor rotation speed) is highly accurate. Can be calculated.

  Furthermore, in another invention, in addition to the above-described invention, the motor is a DC motor. In the case of such a configuration, it is possible to reduce the generation of noise compared to the case where a stepping motor is used.

  Another invention includes a motor control device related to each of the above-described inventions, and includes a motor controlled by the motor control device, and an object to be conveyed whose document reading position is moved by the motor. .

  In such a configuration, when the motor is driven at an extremely low speed in the document reading apparatus, when the rotation speed of the motor is slower than the specified rotation speed (when the measured value exceeds the reference value). Even in such a case, it is possible to improve the throughput of document reading.

  Furthermore, in another invention, the motor outputs a signal output step for outputting an interrupt signal based on the rotation of the motor that provides a driving force for conveying the object to be conveyed, and the electric power applied to the motor as time passes. A power addition control step for performing control to increase from the range of power that does not rotate, and an interrupt signal is input, and a measurement value and a specification in a time interval between the interrupt signal immediately before each input of the interrupt signal The reference speed value of the motor is compared, and as a result of the comparison, a speed determination step for determining whether or not the motor rotation speed exceeds the target rotation speed, and the motor rotation speed at the speed determination step When it is determined that the speed is exceeded, the power applied to the motor is reduced to a range of power that the motor does not rotate, and the target rotational speed of the motor is reduced. If it is determined that e not, are those comprising a selecting step to continue the increase in power, the.

  When configured in this manner, in the speed determination step, each time an interrupt signal is input from the signal output means, the measured value corresponding to the time interval between the previous interrupt signal and the reference value are compared, and the comparison is made. As a result, it is determined whether or not the rotational speed of the motor exceeds the target rotational speed. When it is determined that the rotational speed of the motor exceeds the target rotational speed, the motor is driven at a sufficient average rotational speed between the two interrupt signals. Is accelerated, it becomes difficult to rotate the motor at an extremely low speed. Therefore, in this case, the electric power applied to the motor is reduced to a range of electric power at which the motor does not rotate. If it is determined by comparison between the measured value and the reference value that the motor rotation speed exceeds the target rotation speed, the motor drives between the two interrupt signals at a sufficient average rotation speed. Even in extremely low speed driving, it is in a very slow state. In this case, the increase in power is continued in the selection step.

  By doing so, when the motor is driven at a very low speed, the duty ratio applied to the motor is increased when the motor is in a very slow state. Throughput can be improved. In addition, it is possible to satisfy both conflicting purposes of driving the motor at an extremely low speed and improving the throughput in transporting the object to be transported.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS.

<Overall schematic configuration>
FIG. 1 is a diagram showing a configuration of a document reading apparatus 10 according to an embodiment of the present invention. An original reading apparatus 10 shown in FIG. 1 is a flatbed scanner that reads an original placed on a transparent contact glass 11 by scanning the image sensor 20 through the contact glass 11.

  An image sensor 20 shown in FIG. 1 is a CIS (Contact Image Sensor) type image sensor, and includes a light receiving element (CCD: Charge Coupled Device) arranged at a predetermined pixel density in a main scanning direction which is a longitudinal direction, A lens corresponding to the light receiving element and an exposure lamp for irradiating the original with RGB light of three colors are provided. Each light receiving element receives the reflected light from the document every predetermined period, generates and accumulates electric charge according to the amount of received light, and outputs it as an electrical signal.

  In addition, the image sensor 20 is fixed to the carriage 30 as the object to be conveyed, and can be moved along the guide rail 31 in the sub-scanning direction perpendicular to the main scanning direction. Fixed.

  The motor 50 moves the image sensor 20 along the sub-scanning direction. In the present embodiment, the motor 50 is a DC motor. The worm gear 60 is fixed to the shaft 51 of the motor 50, and the spur gear 70 is engaged with the worm gear 60. Further, the pulley 71 is fixed to the same shaft as the spur gear 70 and rotates with the same rotation amount as the spur gear 70. The pulley 72 is rotatably installed, and the timing belt 40 is disposed outside the pulley 71 and the pulley 72 so as to generate an appropriate tensile force. With such a drive system configuration, the motor 50 applies a rotational force to the timing belt 40 via the worm gear 60, the spur gear 70 and the pulley 71, and rotates the timing belt 40 around the pulley 71 and the pulley 72. Thus, the carriage 30 is conveyed in the sub-scanning direction.

  On the other hand, the disk 52 has a predetermined number of slits formed along the radial direction at predetermined angular intervals in the circumferential direction, and is fixed to the shaft 51 perpendicular to the shaft 51 of the motor 50 and at the center. And rotates as the shaft 51 rotates.

  The photo interrupter 80 includes a light emitting diode 81 and a photodiode 82, and among the light emitted from the light emitting diode 81, the light passing through the slit of the disk 52 is received by the photodiode 82, and according to the amount of light received. Outputs electrical signals. That is, the output signal (ENC signal) of the photo interrupter 80 is at a high level only when light passes through the slit of the disk 52, and is at a low level when light is blocked at a portion other than the slit of the disk 52. Therefore, when the motor 50 rotates, the ENC signal is pulsed and has a number of pulses proportional to the rotation angle or the number of rotations of the motor 50. For this reason, the rotation amount of the motor 50 can be obtained by measuring the number of pulses of the output signal of the photo interrupter 80.

  In the present embodiment, the photo interrupter 80 has two sets of light emitting diodes 81 and photodiodes 82, and corresponds to a part of the signal output means. The two photodiodes 82 are arranged such that the phase difference between the ENC signals is a predetermined angle (for example, 90 degrees). The disk 52 and the photo interrupter 80 constitute a rotary encoder.

  The control circuit 100 is a circuit that controls the operations of the image sensor 20 and the motor 50 based on a signal from the photo interrupter 80 to execute a reading operation and outputs image data obtained by the reading operation. The control circuit 100 outputs the image data to an external device such as a personal computer and a storage device (memory card, hard disk drive, etc.) provided inside and outside the device. The control circuit 100 corresponds to a part of the signal output means (mainly the ENC interrupt signal output unit 124), the power addition control means (mainly the duty calculation unit 112), and the determination unit (mainly the determination unit 111).

  FIG. 2 is a block diagram showing the configuration of the control circuit 100 in FIG. The control circuit 100 includes a central processing unit (CPU) 101, a memory 102, an interface 103, an application specific integrated circuit (ASIC) 104, a bus 105, a timer 106, an RC circuit 107, and a motor driver 108.

  The CPU 101 operates according to a control program stored in the memory 102. The memory 102 has a RAM and a ROM, and a control program is stored in advance in the ROM. When the CPU 101 executes the control program, the scanner control unit 110, the determination unit 111, and the duty calculation unit 112 are realized.

  Among these, the scanner control unit 110 performs communication with an external apparatus, start of a document reading operation, control according to a user operation on an operation unit (not shown), and the like.

  In addition, the determination unit 111 receives a signal related to position information (position detection signal) from the position calculation unit 122, a signal related to period information (period detection signal) from the period calculation unit 123, and an ENC interrupt signal (from the ENC interrupt signal output unit 124). Corresponding to the interrupt signal). Then, the determination unit 111 compares the period T related to the period information (corresponding to the measurement value) and the target period To (corresponding to the reference value) in the extremely low speed control (BS control) described later based on the ENC interrupt signal. To do. Then, when the period T is smaller than the target period To, the determination unit 111 performs a process of reducing the duty ratio to a hold current value (corresponding to a range of electric power at which the motor does not rotate). The determination unit 111 compares the cycle T corresponding to the measurement value with the target cycle To corresponding to the reference value, so that the rotation speed of the motor 50 exceeds the rotation speed targeted by the motor 50. Determine whether or not.

  The hold current is calculated by multiplying the duty ratio at the time when the ENC interrupt signal is input by a predetermined magnification (coefficient of 0 to 1). Since the duty ratio at the time when the ENC interrupt signal is input is the duty ratio at which the motor starts to exceed the limit torque at that time, the duty ratio is decreased by multiplying by a predetermined magnification, and the limit torque at that time is slightly decreased. By setting a lower value, it is possible to perform extremely low speed control without reducing the throughput.

  In the present embodiment, the hold current is reduced by multiplying the duty at the time when the ENC interrupt signal is input by a predetermined magnification. However, the hold current may be calculated by subtracting a predetermined decrease amount from the duty ratio at the time when the ENC interrupt signal is input, or a fixed value (fixed value) may be used.

  When a hold current value that is a fixed value (fixed value) is used, the hold current is driven when the motor 50 is driven, for example, at startup or at other predetermined timing, and at that time, the duty becomes a predetermined rotation speed. Is calculated based on measuring (performing measurement). When performing such a measurement, not only the duty at a predetermined rotational speed is measured, but also the rotational speed when the motor 50 is driven at the predetermined duty may be measured.

  Further, when the scanner control unit 110 instructs execution of extremely low speed control (BS control) described later, the duty calculation unit 112 performs calculation for extremely low speed control (BS control). Note that, in extremely low speed control (BS control), the duty calculation unit 112 adds a fixed duty ratio each time a timer interrupt signal is received from the timer 106. Thereby, in the extremely low speed control in the present embodiment, a current profile as shown in FIG. 6 is obtained.

  The interface 103 includes an interface circuit such as a USB (Universal Serial Bus) that performs data communication with an external device, and an interface circuit that performs data communication with a memory card slot or the like provided in the device. The ASIC 104 includes an image sensor control unit 121, a position calculation unit 122, a cycle calculation unit 123, an ENC interrupt signal output unit 124, and a motor control unit 125.

  In the ASIC 104, the image sensor control unit 121 controls the image sensor 20 to perform a reading operation for each color of RGB, and acquires image data read for each color. The position calculation unit 122 calculates the current position of the carriage 30 by counting the number of pulses of the ENC signal output from the photodiode 82. The period calculation unit 123 measures the period between the edges of the ENC signal, and calculates the current speed of the carriage 30 based on the period measurement.

  Further, when receiving the ENC signal from the photodiode 82, the ENC interrupt signal output unit 124 outputs an ENC interrupt signal based on the ENC signal to the CPU 101. When the ENC interrupt signal is received, the determination unit 111 implemented in the CPU 101 performs processing such as comparing the cycle T and the target cycle To as described above. The ENC interrupt signal output unit 124 outputs an ENC interrupt signal at every edge output from the photodiode 82. That is, the ENC interrupt signal output unit 124 outputs an ENC interrupt signal every time it detects a rising edge and a rising edge of the A-phase ENC signal and a rising edge and a rising edge of the B-phase ENC signal.

  The motor control unit 125 outputs a control signal for controlling the motor 50 in synchronization with a timing pulse output from the image sensor control unit 121 based on a control command from the CPU 101 (Duty calculation unit 112). To do. In the present embodiment, the motor control unit 125 outputs a PWM (Pulse Width Modulation) signal having a duty ratio corresponding to the rotation amount of the motor 50.

  The timer 106 measures time by counting clock signals (not shown). When a preset time is reached by this count, a timer interrupt signal is output to the CPU 101.

  The RC circuit 107 is a low-pass filter circuit that changes the output voltage to a DC voltage corresponding to the duty ratio of the input PWM signal. FIG. 3 is a circuit diagram showing an example of the RC circuit 107 in FIG. As shown in FIG. 3, the RC circuit 107 is a circuit that is divided by the resistors R1 and R2 and smoothed by the capacitor C. In the present embodiment, the output voltage of the RC circuit 107 has a voltage value proportional to the duty ratio of the input PWM signal.

  The motor driver 108 is a driver circuit that causes the motor 50 to conduct a current corresponding to the value of the current value command voltage Vref applied from the motor control unit 125 via the RC circuit 107. In the present embodiment, a current proportional to the value of the current value command voltage Vref is conducted to the motor 50.

  FIG. 4 is a diagram illustrating an example of the motor driver 108 in FIG. The switching elements Q1 to Q4 are bridge-connected, and are switching transistors. The diodes D1 to D4 are provided between the collector and emitter (between the gate and drain) of the switching elements Q1 to Q4, respectively. This is a regenerative diode that conducts current in the opposite direction to the current that conducts Q1 to Q4. The resistor Rd is a minute resistor that detects the value of the current flowing through the motor 50 as a voltage at both ends. The gate circuit 131 is a circuit that performs on / off control of the switching elements Q1 to Q4 based on the value of the current value command voltage Vref and the value of the driving current of the motor 50 obtained from the voltage across the resistor Rd. In the present embodiment, each of switching elements Q1 to Q4 is a P-type transistor, but an N-type transistor may be used. In that case, the resistor Rd is provided on the power supply VBB side.

  For example, when the switching elements Q1, Q4 are on and the switching elements Q2, Q3 are off, the power supply voltage VBB is applied to the motor 50 (and the small resistor Rd for current detection), and the motor 50 rotates in the forward direction. . When switching elements Q2 and Q3 are on and switching elements Q1 and Q4 are off, power supply voltage VBB is inverted and applied to motor 50 (and minute resistor Rd for current detection), and motor 50 is reversed. Rotates. When the switching elements Q1 and Q4 are on and the switching elements Q2 and Q3 are off, the gate circuit 131 is switched when the driving current of the motor 50 becomes equal to or greater than the value specified by the current value command voltage Vref. Q1 is turned off for a certain period to cause the motor driver 108 to perform a regenerative operation, and then the switching element Q1 is turned on.

  By repeating this operation, the drive current of the motor 50 is substantially maintained at the value specified by the current value command voltage Vref. In that case, the switching elements Q2 and Q3 remain off continuously. Similarly, when the switching elements Q2 and Q3 are on and the switching elements Q1 and Q4 are off, the gate circuit 131 is when the driving current of the motor 50 becomes equal to or greater than the value specified by the current value command voltage Vref. Then, the switching element Q2 is turned off for a certain period to cause the motor driver 108 to perform a regenerative operation, and then the switching element Q2 is turned on. By repeating this operation, the drive current of the motor 50 is substantially maintained at the value specified by the current value command voltage Vref. In that case, the switching elements Q2 and Q3 remain off continuously.

<About motor drive control>
A case where motor control is performed in the document reading apparatus 10 having the above configuration will be described below based on the operation flow of FIG. 5 and FIG.

  When a user sets a document to be read on the contact glass 11 and a reading mode at a high resolution is set by, for example, an operation on the operation panel of the document reading device 10, the document reading device 10 The very low speed control corresponding to the reading mode is started. At this time, the document reading apparatus 10 performs a predetermined preliminary operation such as moving the carriage 30 to a predetermined reference position or applying a hold current to the motor 50 (S10).

  When the preliminary operation ends, the determination unit 111 implemented in the CPU 101 instructs the duty calculation unit 112 to start calculating the duty ratio. In accordance with this instruction, the duty calculation unit 112 calculates a duty ratio corresponding to extremely low speed control (BS control). Here, the relationship between current and time in extremely low speed control (BS control) is shown in FIG. In FIG. 6, after starting the motor 50 and detecting the rising edge of the A phase (at this time, the ENC interrupt signal is input to the CPU 101), until the same falling edge of the A phase is detected. A current for accelerating the motor 50 is energized (S11). When this acceleration is performed, a current corresponding to the acceleration is supplied to the motor 50, but the duty ratio at this time is constant.

  Subsequently, it is determined whether or not the current position of the carriage 30 exists in the acceleration region (S12). This determination is made based on whether or not a predetermined number of edges are detected. If it is determined in S12 that the current position of the carriage 30 does not exist in the acceleration region (No), the current is reduced to the hold current (S13). Further, after the reduction to the hold current, the determination unit 111 determines whether or not the next ENC interrupt signal has been received (S14). When the speed is reduced in S14, the extremely low speed control (BS control) shown in FIG. 6 is started thereafter.

  If it is determined in S14 that an ENC interrupt signal is not received (in the case of No), the determination unit 111 determines whether a timer interrupt signal is received from the timer 106 (S15). If it is determined that the timer interrupt signal is not received in this determination (in the case of No), the process returns to S14 described above.

  If it is determined in S15 that the timer interrupt signal has been received (Yes), the duty calculation unit 112 adds a certain duty (S16). Here, as shown in FIG. 6, the constant duty to be added is a duty ratio that is added in stages with respect to the hold current, and the duty ratio that is added in each stage is equal. Yes.

  Note that the voltage corresponding to the duty ratio is actually converted into a current (direct current) that has been subjected to predetermined voltage division and smoothing through the RC circuit 107 shown in FIG. At this time, when the duty ratio is added stepwise, the current is also added stepwise. The timer interrupt signal issued from the timer 106 is in a state that is issued at a smaller time interval than the ENC interrupt signal issued from the ENC interrupt signal output unit 124.

  If it is determined in step S14 that the ENC interrupt signal has been received (Yes), whether the carriage 30 has moved to the target position (the count number of the ENC signal becomes the target). It is determined whether or not the count number has been reached (S17). If it is determined in S17 that the carriage 30 has reached the target position (Yes), then a process for stopping the motor 50 is performed (S18), and the process ends.

  In S17 described above, when it is determined that the carriage 30 has not moved to the target position (in the case of No), it is necessary to further move the carriage 30 toward the target position. Therefore, in this case, extremely low speed control is continued. As specific processing after S17, it is determined whether or not the current period T is smaller than the target period To (S19). Since the period is the reciprocal of the speed, the current speed and the target speed may be compared in this determination.

  In S19, when it is determined that the period T is smaller than the target speed To (determined as Yes), the speed of the carriage 30 between the two nearby edges is higher than the target speed. Therefore, in this case, the duty calculation unit 112 performs processing (calculation) for reducing the duty ratio to the duty ratio corresponding to the hold current (S20). Then, after the process of S20 ends, the process returns to S14 again.

  If it is determined in S19 that the period T is larger than the target speed To (determined No), the speed of the carriage 30 between the two adjacent edges is lower than the target speed. It becomes. In this slow state, if the duty ratio is lowered to the duty ratio corresponding to the hold current as in S20, the document reading throughput is reduced. Therefore, in this case (when it is determined No in S19), the process returns to S14 again without performing the process of S20 (without reducing the current to the hold current), and whether or not the next ENC interrupt signal has been received. Determine whether. As described above, extremely low speed control of the motor 50 is performed.

<Effects of the present invention>
According to the document reading apparatus 10 having the above-described configuration, when the ENC interrupt signal is input, the determination unit 111 compares the cycle T with the target cycle To. Then, when the period T is smaller than the target period To (when it is faster than the target speed), the duty ratio is reduced to the hold current value. Further, when the period T is larger than the target period To (when it is slower than the target speed), the duty ratio is continuously increased from the middle stage. For this reason, it is possible to improve the throughput when the carriage 30 is conveyed. In addition, it is possible to satisfy both the conflicting purposes of driving the motor 50 at an extremely low speed and improving the throughput in the conveyance of the carriage 30.

  Further, in the present embodiment, when the predetermined interruption time comes, the determination unit 111 increases the duty ratio applied to the motor 50 in stages, so that the motor 50 can be accelerated in stages. Become. Further, the motor 50 can be surely moved by increasing the duty ratio in stages.

  Furthermore, in the present embodiment, after a predetermined acceleration region as shown in FIG. 6 has elapsed, the current is reduced to the hold current, and then the duty ratio applied to the motor 50 is increased stepwise, and this duty ratio is increased. A corresponding current is applied to the motor 50. For this reason, the presence of this acceleration region enables acceleration corresponding to driving the motor 50 at an extremely low speed. Further, the presence of this acceleration region can improve the throughput in transporting the carriage 30 and can shorten the overall processing time when the motor 50 is driven at an extremely low speed.

  The ENC interrupt signal output unit 124 outputs an ENC interrupt signal every time an edge between a high level and a low level in the ENC signal output according to the rotation of the motor 50 is detected. For this reason, the ENC interrupt signal is output every time the edge of the ENC signal is detected, so that the period between the adjacent edges (the rotational speed of the motor 50) can be calculated with high accuracy.

  In the present embodiment, the motor 50 is a DC motor. For this reason, it becomes possible to reduce generation | occurrence | production of noise rather than the case where a stepping motor is used.

  In the document reading apparatus 10 of the present invention, it is possible to improve the document reading throughput.

  Although one embodiment of the present invention has been described above, the present invention can be variously modified. This will be described below.

  In the above-described embodiment, the case where a DC motor is used as the motor 50 has been described. However, the motor is not limited to a DC motor. For example, when the noise of the motor does not matter so much, a stepping motor may be used. Also, an AC (alternating current) motor such as a synchronous motor may be used.

  In the above-described embodiment, the control circuit 100 includes the CPU 101 and the ASIC 104. However, the control circuit 100 may be configured to control the motor 50 only with the ASIC, and in addition to these, the control circuit 100 may be combined with a one-chip microcomputer incorporating various peripheral devices. You may make it comprise.

  In the above-described embodiment, the case where the carriage 30 is used as the transported object is described. However, for example, in a document reading apparatus that directly feeds a document, the transported object may be a document such as a sheet. . In the above-described embodiment, the CIS type image sensor is used. However, as another method, an optical reduction type image sensor may be used.

  Further, in the above-described embodiment, in order to drive the motor 50 at an extremely low speed, the duty ratio is increased stepwise by a constant increase amount. However, the duty ratio is not limited to increasing by a constant increase amount. For example, the increase pitch in the case of a current in the vicinity of the hold current is made larger than that of the portion separated from the hold current, so that the increase amount is changed. Anyway.

1 is a diagram showing a schematic configuration of a document reading apparatus according to an embodiment of the present invention. It is a block diagram which shows the structure of a control circuit. FIG. 3 is a circuit diagram illustrating an example of an RC circuit in FIG. 2. It is a figure which shows an example of the motor driver in FIG. It is a figure which shows the operation | movement flow at the time of a motor drive start. It is a figure which shows the relationship between an electric current and an ENC signal.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Document reading apparatus, 20 ... Image sensor, 30 ... Carriage (corresponding to a conveyed object), 50 ... Motor, 80 ... Photo interrupter (corresponding to a part of signal output means), 100 ... Control circuit (of signal output means) 101 ... CPU, 104 ... ASIC, 106 ... Timer, 111 ... Determination unit, 112 ... Duty calculation unit (power addition control unit), 121 ... Image sensor control unit, 122 ... Position calculation unit, 123 ... Period calculation unit, 124 ... ENC interrupt signal output unit (signal output means), 125 ... Motor control unit

Claims (7)

A signal output means for outputting an interrupt signal based on rotation of a motor for applying a driving force for conveying the object to be conveyed;
Power addition control means for performing control to increase the power applied to the motor from the range of power that the motor does not rotate over time;
When the interrupt signal is input, each time this interrupt signal is input, the measured value in the time interval between the previous interrupt signal and the specified reference value are compared. As a result of the comparison, the rotation speed of the motor is determined. Determines whether the motor exceeds the target rotational speed, and if it is determined that the motor rotational speed exceeds the target rotational speed, the motor rotates the electric power applied to the motor. A command for lowering the power range to be not applied to the power addition control means, and when it is determined that the rotation speed of the motor does not exceed the target rotation speed, ,
A motor control device comprising:   The power addition control means increases the duty ratio applied to the motor stepwise when a predetermined interruption time arrives, and applies a current corresponding to the duty ratio to the motor. The motor control device according to claim 1.   The power addition control means returns the electric power to a range where the motor does not rotate after a predetermined acceleration region has elapsed, and then gradually increases the duty ratio applied to the motor, and generates a current corresponding to the duty ratio. The motor control device according to claim 2, wherein the motor control device is applied to the motor.   4. The signal output means outputs the interrupt signal every time an edge between a high level and a low level in an output signal output in accordance with rotation of the motor is detected. The motor control device according to any one of the above.   The motor control apparatus according to claim 1, wherein the motor is a DC motor. The motor control device according to any one of claims 1 to 5,
A motor controlled by the motor control device;
A conveyed object whose original reading position is moved by the motor;
An original reading apparatus comprising: A signal output step for outputting an interrupt signal based on rotation of a motor that provides a driving force for transporting the object to be transported;
A power addition control step for performing control to increase the power applied to the motor from a range of power in which the motor does not rotate over time;
When the interrupt signal is input, each time this interrupt signal is input, the measured value in the time interval between the previous interrupt signal and the specified reference value are compared. As a result of the comparison, the rotation speed of the motor is determined. A speed determination step for determining whether or not the motor exceeds a target rotational speed;
When it is determined in the speed determination step that the rotation speed of the motor exceeds the target rotation speed, the power applied to the motor is reduced to a range of power that the motor does not rotate, and the rotation of the motor A selection step of continuing to increase the power when it is determined that the speed does not exceed the target rotational speed;
A motor control method comprising:

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