JPH10323088A - Scanner device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To read high quality images by stabilizing a stepping motor. SOLUTION: When driving a stepping motor, the CPU drives the stepping motor with a large exciting current II for starting for a certain time during slow-up operation and a certain time period after entering steady-state drive; when a certain time has elapsed after entering steady-state drive, the stepping motor is driven with an exciting current I2 lower than the exciting current I1 of starting time, thereby preventing a drop in the torque of stepping motor when entering from the start operation to steady drive.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanner device for reading image information of an original in an image forming apparatus such as a facsimile machine, and more particularly to a drive stabilization.

[0002]

2. Description of the Related Art A facsimile apparatus often performs an intermittent drive, and a stepping motor is often used as a drive source of a scanner apparatus because of its easy handling and cost advantages. When this stepping motor is driven, a slow-down operation is often performed at the time of startup in order to prevent loss of synchronism and to ensure the stability of operation. As a method of supplying a current to the stepping motor at the time of the slow-up, for example, as shown in Japanese Patent Application Laid-Open No. 3-65096, an exciting pulse closer to the starting time has a larger current value.

Further, in an image forming apparatus such as a facsimile apparatus, it is necessary to perform shading correction before starting reading of a document by a scanner apparatus. In this case, if the stepping motor is excited using the constant current driving method, correct shading correction may not be performed due to noise generated during chopping. To prevent this, the excitation of the stepping motor is turned off during the shading correction.

In a scanner device, a stepping mode is used.
In order to reduce the vibration component in the rotation direction of the motor, a microstep drive system in which the exciting current between the two phases is proportionally distributed to control the relative position (stable point) between the stator and the rotor finely has been developed in recent years. Used. In this case, starting is performed by a two-phase excitation method that can obtain a large starting torque.

[0005]

As for the stepping motor, the output torque tends to decrease at the time of high rotation for both the starting torque and the escape torque. However, as shown in Japanese Patent Application Laid-Open No. 3-65096, the stepping motor has a disadvantage. Slow at startup
If the current value of the excitation pulse is increased only during the up period and the current value applied to the stepping motor during the transition from the starting operation to the steady driving is reduced, the torque of the stepping motor is reduced at the transition point where a large acceleration torque is required. It is necessary to drive the motor while suppressing it, which may cause loss of synchronism, and it is difficult to obtain sufficient starting stability. Further, at the time of transition from the starting operation to the steady driving, it is difficult to ensure the driving stability only after sufficiently removing the rotational unevenness which is the initial hunting generated at the time of the starting operation.

Further, the stepping motor may rotate unexpectedly when an external force is applied in a non-excited state,
When performing the shading correction before the reading of the original is started by the scanner device, it is desirable that the excitation of the stepping motor is not cut off but is continuously applied.

Further, in order to reduce the vibration component in the rotation direction of the stepping motor, the scanner device is started up by the two-phase excitation method, and when the steady drive is performed by the micro step drive method, a large rotation vibration component is placed. When the micro-step drive is started, the step-out easily occurs due to the influence of the phase shift.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanner device capable of stably driving a stepping motor and reading a high-quality image.

[0009]

According to the present invention, there is provided a scanner apparatus using a stepping motor as a driving source, wherein the stepping motor is used during a slow-up period at the time of startup and within a predetermined time period immediately after steady driving. And driving the motor with a larger current value than in the steady driving.

A second scanner device according to the present invention is a scanner device using a stepping motor driven by a constant current excitation method as a driving source, wherein a current limiting resistor is connected in series with coils of each phase of the stepping motor. The current is supplied to the coil of each phase without passing the current limiting resistor at the time of driving below the time of shading correction, and the current is supplied to the coil of each phase via the current limiting resistor at the time of shading correction. And

A third scanner device according to the present invention is a scanner device using a stepping motor driven by a micro-step driving method as a driving source.
The stepping motor is driven by a two-phase excitation method during a predetermined period immediately after the up period and immediately after the steady driving, and then driven by a micro step driving method.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A drive control section of a stepping motor for driving a scanner device according to the present invention has a CPU, a memory storing preset drive sequence data, and a motor driver. The drive sequence data stored in the memory includes a fixed time from when the stepping motor starts driving and a slow-down operation has elapsed and a steady drive is started, and an excitation current and a steady drive at the time of startup. When the excitation current is set.

When driving the stepping motor, C
The PU drives the stepping motor with a large exciting current at the time of start-up during the slow-up operation and for a certain period of time after entering the steady driving stored in the memory, and is started after a certain period of time has elapsed after the steady driving is started. The stepping motor is driven by an exciting current smaller than the exciting current at the time, and the torque of the stepping motor is prevented from being reduced when the steady operation is started from the starting operation.

When performing shading correction by pre-feeding the stepping motor with the scanner device,
In a normal constant current drive circuit, a current limiting resistor connected in series with the coil of each phase of the stepping motor and a switch for supplying current to the coil of each phase without passing through the current limiting resistor are provided. In driving other than the above, a current is supplied to the coil of each phase without passing through the current limiting resistor, and when shading correction is performed, a switch is switched to supply a current to the coil of each phase via the current limiting resistor. In this manner, when performing the shading correction before starting the reading of the document, the stepping motor is stopped in a state where the stepping motor is continuously excited and the chopping is not started, and even when a certain external force is applied. Ensure that the stator does not deviate from the stable excitation point.

Further, two-phase excitation driving is performed only at the time of starting,
In the case of employing a control method in which the steady driving is performed by the micro-step driving, a predetermined time determined by the system is stored in a memory. Then, two-phase excitation drive is performed from the slow-up operation at the time of starting the stepping motor until a certain time has elapsed since the start of steady driving, and microstep drive is started after a certain time has elapsed since the start of the steady drive.
In this way, after the initial hunting is converged, micro-step driving having a vibration damping effect is performed to prevent a step-out immediately after steady driving.

[0016]

FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. A drive control unit of a stepping motor 1 for driving a scanner device for reading an original by a facsimile device has a same size operation as a central processing unit (CPU) 2 and an enlarging operation.
It has a speed command unit 3 for outputting a speed diagram determined in accordance with the reduction operation, a memory 4 storing drive sequence data set in advance, a generator 5 and a motor driver 6. The driving sequence data stored in the memory 4
As shown in the time chart of FIG. 2, the time T1 during the slow-up operation from the start of the driving of the stepping motor 1 has elapsed and the fixed time T2 from the start of the steady driving. The exciting current I1 of the stepping motor 1 and the exciting current I2 after the lapse of the fixed time T2 are set in the form of a table during the slow-up operation and until the lapse of the fixed time T2 from the start of the steady driving. I have. The fixed time T2 is determined by setting in advance a time from when the stepping motor 1 starts driving until the initial hunting during the slow-down operation stops, and the exciting current I1 is set to be larger than the exciting current I2. The CPU 1 controls the driving of the stepping motor 1 based on the driving sequence stored in the memory 2 and information from the encoder 7. Generator 5 is CPU
Stepping motor 1 based on the driving data received from
A timing signal serving as an excitation control signal for each phase is generated, and the generated timing signal and the excitation current sent from the CPU 1 are transmitted to the motor driver 6. The motor driver 6 determines the stepping motor based on the transmitted timing signal.
An excitation signal for each phase of the motor 1 is generated, and the stepping motor 1 is driven with a predetermined excitation current.

The stepping mode configured as described above
As shown in a time chart in FIG. 2, the CPU 2 of the drive control unit of the motor 1 performs a slow-up operation from the start of the driving of the stepping motor 1 until the speed reaches a predetermined speed. When it reaches, steady drive is performed. When the stepping motor 1 is driven in this manner, the CPU 2 supplies the exciting current I during the slow-up period T1 and a certain time T2 after the steady driving stored in the memory 4 in advance.
In step 1, the stepping motor 1 is driven. After a lapse of a predetermined time T2 from the start of the steady driving, the stepping motor 1 is driven with the exciting current I2 smaller than the exciting current I1.

As described above, when the stationary drive is started and the predetermined time T2
The stepping motor 1 is driven by the large excitation current I1 at the time of starting until the time elapses, so that the stepping motor 1 is driven without a decrease in the torque of the stepping motor 1 when starting the steady driving from the starting operation. And step-out can be prevented. Further, after the initial hunting is sufficiently removed, the steady exciting current I2
, The stepping motor 1 can be driven stably.

In the scanner device for reading an original by a facsimile apparatus, as described above, the stepping motor 1 is driven by a large excitation current I1 at the time of starting until the fixed time T2 elapses after the steady driving, and before the original is read. To
The reading section is pre-read to perform shading correction.
It is desirable to keep exciting the stepping motor 1 when performing this shading correction. Therefore, as shown in the circuit diagram of FIG. 3, the motor driver 6 is provided with a current limiting resistor Ra and a current limiting resistor Ra connected in series with the coil L of each phase of the stepping motor 1 in an ordinary constant current drive circuit. A switch Sw composed of a transistor or the like that supplies a current to the coil L of each phase without passing through is connected. The CPU 2 controls the current limiting resistor R during driving other than during shading correction.
The current is supplied to the coil L of each phase without passing through a, and when the shading correction is performed, the switch Sw is switched to supply the current to the coil L of each phase via the current limiting resistor Ra. FIG. 3 shows a drive unit for only one phase of the stepping motor 1.

As described above, the current limiting resistor Ra and the switch S
When the original is read by driving the stepping motor 1 by the motor driver 6 provided with w, when the reading of the original is started as shown in a time chart of FIG. The excitation current I3 is connected to the coil L of each phase of the
The pre-feed is performed by driving the motor 1. Thereafter, the switch Sw is switched to the current limiting resistor Ra to change the stepping mode.
An exciting current I4 smaller than the exciting current I3 is supplied to the coil L of each phase of the motor 1, and the stepping motor 1 is excited by the exciting current I4. In this state, shading correction is performed. The resistance value of the current limiting resistor Ra is determined so that a voltage equal to or lower than the operation threshold of the comparator VC is applied to the resistor Rr by the exciting current I4. After the shading correction is performed, the starting operation is performed by supplying the exciting current I1 at the time of starting reading, and after a predetermined time T2 has elapsed since the start of the operation, the stepping motor is driven with the exciting current I2 smaller than the exciting current I1. 1 is driven.

As described above, when performing the shading correction before the reading of the original is started, the excitation of the stepping motor 1 is continuously performed, so that the stepping motor 1 can be stopped without starting the chopping. Even if an external force is applied, the stator does not deviate from the stable excitation point. Therefore, the stability of startup can be ensured.

In the scanner device, a stepping mode is used.
In recent years, in order to reduce the vibration component in the rotation direction of the motor 1, it has been frequently performed in the recent years to start up by the two-phase excitation method and to perform the steady drive by the micro step drive method. In this case, if the micro-step drive is started in a state where a large rotational vibration component is mounted, the step-out due to the influence of the phase shift is likely to occur. Therefore, when adopting a control method in which two-phase excitation drive is performed only at the time of start-up and steady drive is performed by microstep drive, a predetermined time T3 determined by the system is stored in the memory 4 in advance, and the time chart shown in FIG. As shown in the figure, the CPU 2 performs the two-phase excitation drive from the slow-up operation at the time of starting the stepping motor 1 to the steady drive until a predetermined time T3 elapses, and the fixed time T3 elapses after the steady drive is started. Then, the micro step drive is started.

As described above, when the stationary driving is started and the predetermined time T3 is reached.
By performing the two-phase excitation drive until the time elapses and performing the micro-step drive after a lapse of a predetermined time T3 after entering the steady drive, the micro-step drive having the vibration damping effect can be performed after the initial hunting is converged. Step-out can be prevented from occurring immediately after the steady driving, and the stepping motor 1 can be driven stably.

[0024]

As described above, according to the present invention, when the stepping motor is driven, the excitation during the start-up is large during the slow-down operation at the start of the start and for a certain time after the start of the steady drive. Driving the stepping motor with current,
Since the stepping motor is driven with the excitation current smaller than the excitation current at the start after a certain period of time from the start of the steady driving, the torque of the stepping motor decreases when the steady operation is started from the start operation. Can be prevented, and step-out can be prevented. Also,
Since the steady exciting current flows after the initial hunting is sufficiently removed, the stepping motor can be driven stably.

Further, when the shading correction is performed by pre-feeding the stepping motor by the scanner device,
Since the stepping motor is excited with a smaller current than during the steady driving to stop the chopping motor without starting the chopping, even if a certain amount of external force is applied, the stepper motor may be out of the stable excitation point. As a result, the stability of startup can be ensured.

Further, the two-phase excitation drive is performed only at the time of starting,
In the case of adopting a control method in which the steady driving is performed by the micro-step driving, it is necessary to take two steps from the slow-up operation at the time of starting the stepping motor to the elapse of a fixed time after entering the steady driving.
By performing phase excitation drive and starting microstep drive after a certain period of time after entering steady drive, microstep drive with a vibration damping effect can be performed after the initial hunting has converged, and immediately after steady drive The stepping motor can be driven stably by preventing step-out.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a time chart showing the operation of the embodiment.

FIG. 3 is a circuit diagram of a motor driver according to a second embodiment.

FIG. 4 is a time chart showing the operation of the second embodiment.

FIG. 5 is a time chart showing the operation of the third embodiment.

[Explanation of symbols]

 1 stepping motor 2 CPU 4 memory 6 motor driver

Claims (3)

[Claims] In a scanner device using a stepping motor as a drive source, the stepping motor is driven with a larger current value than during the steady driving during a slow-up period at the time of starting and within a predetermined time immediately after the steady driving. A scanner device. 2. A scanner device using a stepping motor driven by a constant current excitation method as a driving source, wherein a current limiting resistor is connected in series with coils of each phase of the stepping motor, and driving is not performed during shading correction. A scanner device characterized in that current is supplied to each phase coil without passing through a current limiting resistor, and current is supplied to each phase coil via a current limiting resistor at the time of shading correction. 3. A scanner apparatus using a stepping motor driven by a micro-step driving method as a driving source, wherein a stepping motor is used for two hours during a slow-up period at the time of start-up and a predetermined fixed time immediately after steady driving.
A scanner device driven by a phase excitation method and thereafter driven by a micro step driving method.