JPH08308293A - Stepping motor driver and image reader using the driver - Google Patents

Abstract

PURPOSE: To prevent the step-out of a stepping motor and the vibration of an object at the time of accelerating and decelerating an object. CONSTITUTION: A carriage controller 21 outputs a drive pulse for controlling the rotational speed of a stepping motor 7 and a threshold value signal for controlling the current value of a driving current suppled to the motor 7. A motor driver 22 sequentially switches the exciting phase of the motor 7 at the timing to be specified by the drive pulse, and supplies the drive current of the current value specified by the threshold value signal to the motor 7. The controller 21 outputs the threshold value signal for supplying the drive current having small current value to the motor with respect to the drive current supplied for an ordinary period for maintaining the motor 7 at a target rotating speed during the accelerating period from the start of the rotation of the motor 7 to the arrival at the target speed set by a main controller 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stepping motor driving device for driving and controlling a stepping motor, and driving control of a stepping motor of a carriage driving mechanism using the stepping motor driving device to drive a carriage by the carriage driving mechanism. The present invention relates to an image reading device to be moved.

[0002]

2. Description of the Related Art FIGS. 5 and 6 are a plan view and a side view showing a schematic configuration of an image reading apparatus having a carriage driving mechanism, respectively. Reference numeral 1 is a contact glass on which a document D is placed, 2 is a carriage provided with a bearing portion 2a and a guide roller 2b. The carriage 2 has a light source unit 3 for illuminating the document on the contact glass 1 and a multi-phototransistor. And a sensor unit 4 in which a double image forming element such as a rod lens array is integrated. Reference numeral 5 is a support shaft extending along the contact glass 1 in the directions of arrows A1 and A2, 6 is a guide rail arranged so as to be parallel to the support shaft 5, and the carriage 2 has the bearing portion 2a with the support shaft. 5, and the guide roller 2b is rotatably supported on the guide rail 6.

Reference numeral 7 is a stepping motor, 8 is a drive-side belt pulley fixed to the drive shaft of the stepping motor 7,
Reference numeral 9 denotes a driven-side belt pulley arranged near one end of the support shaft 5, and a driving belt 11 tensioned by a tension roller 10 to a predetermined tension is wound around the driving-side belt pulley 8 and the driven-side belt pulley 9. It is hung. 12
Is a drive side wire pulley fixed coaxially with the driven side belt pulley 9, 13 is a driven side wire pulley arranged near the other end of the support shaft 5, and the drive side wire pulley 12 and the driven side wire pulley 13 are not shown in the figure. A synchromesh wire 14 connected to the carriage 2 is wound around the omitted wire tension.

When reading an image of a document placed on the contact glass 1, the stepping motor 7 rotates a drive shaft in a predetermined direction by supplying an electric pulse from a motor driver (not shown). The rotational force of the stepping motor 7 is transmitted from the driving side belt pulley 8 to the driven side belt pulley 9 by the driving belt 11, and rotates the driving side wire pulley 12 fixed coaxially with the driven side belt pulley 9. The rotational force of the drive side wire pulley 12 is
An arrow A1 is formed by the synchromesh wire 14 wound around the drive-side wire pulley 12 and the driven-side wire pulley 13.
Direction or the force in the direction of arrow A2 is converted to the carriage 2
Are moved along the support shaft 5. That is, when the stepping motor 7 is considered as the drive source in the illustrated image reading apparatus, the carriage driving means is a driving force transmission member including belt pulleys 8 and 9, driving belt 11, wire pulleys 12 and 13, and synchromesh wire 14. When,
It is configured by a support shaft 5 that supports or guides the carriage 2 and a support member including a guide rail 6.

When reading an original, the stepping motor 7 starts moving the carriage 2 at the position shown in the direction of arrow A1, for example. At this time, the stepping motor 7 moves the carriage 2 moving in the direction of arrow A1. The carriage 2 is accelerated to a predetermined reading speed, and the carriage 2 is maintained at the reading speed in the reading section facing the document, and after the carriage 2 is deviated from the reading section, the carriage 2 is moved.
Decelerates and stops. In the reading section, the light source unit 3 irradiates the image surface of the document with light, and the reflected light from the document enters the sensor unit 4 and is converted into an electric signal by the linear image sensor.

In such an image reading apparatus, the speed fluctuation of the carriage 2 in the reading section deteriorates the reproducibility of the image, so that the moving speed of the carriage 2 must be controlled to a predetermined reading speed with high accuracy in the reading section. I have to. Further, when the movement resistance when moving the carriage 2 in the directions of the arrows A1 and A2 is large, a large torque must be generated by the stepping motor 7, so that a large stepping motor 7 is required and power consumption is high. Will also increase. Therefore, in the above-described image reading device, the bearing portion 2 of the carriage 2 is
By engaging a with the support shaft 5, the frictional resistance between the carriage 2 and the support shaft 5 is suppressed, and the carriage 2 can be smoothly moved in the arrow A1 direction and the arrow A2 direction with a small force. I am trying.

[0007]

However, the arrow A
When the movement resistance of the carriage 2 in the 1 and A2 directions is very small, the influence of the inertial force generated by the carriage 2 during acceleration and deceleration increases. That is, during acceleration and deceleration, the inertial force of the carriage 2 corresponding to the acceleration and mass of the carriage 2 is applied to the stepping motor 7, and this inertial force causes the stepping motor 7 to lose synchronization. When such a step-out occurs during acceleration, a deviation is generated between the actual position and the control position in the position control of the carriage 2, and when the step-out occurs during deceleration, the carriage 2 is moved. It becomes difficult to stop at a predetermined stop position. further,
When the acceleration changes, the tension of the synchromesh wire 14 changes for a short time due to the inertial force of the carriage 2. As described above, the tension of the synchromesh wire 14 changes for a short time, which causes a pulsating phenomenon in the driving force transmitted to the carriage 2 by the synchromesh wire 14 and causes the carriage 2 to vibrate.

The stepping of the stepping motor 7 and the vibration of the carriage 2 during the acceleration of the carriage 2 are likely to occur when the torque generated by the stepping motor 7 is excessive. Here, FIG. 7 is a measurement diagram showing the relationship between the rotation speed of the stepping motor and the generated torque. Generally, the stepping motor 7 is driven by being supplied with a drive current having a constant current value. At this time, the torque generated by the stepping motor 7 is large at a low speed as shown in FIG.
Decreases with increasing speed. Therefore, when the stepping motor 7 is drive-controlled with a constant drive current, the torque generated from the stepping motor 7 becomes too low at a low speed to increase the absolute value of the acceleration of the carriage 2 and at a low speed. Since the change in the tension of the synchromesh wire 14 is increased, the stepping motor 7 is out of step and the carriage 2 is easily vibrated. Further, when the stepping motor 7 is rotated near the resonance rotation speed in the reading section, hunting is likely to occur in the rotation speed of the stepping motor 7 due to the influence of vibration until the carriage 2 is accelerated to the reading speed. Since it takes a long time for the hunting to converge, it becomes difficult to accurately read the carriage 2 immediately after the start of reading.

When decelerating the carriage 2,
The inertial force of the carriage 2 easily causes the stepping motor 7 to lose synchronization. That is, the carriage 2 receives the braking force generated by the holding torque of the stepping motor 7.
When the inertial force becomes larger, step-out occurs in the stepping motor, and this step-out also causes vibration of the carriage 2.

The above-mentioned step-out and vibration are phenomena which can occur in common in an apparatus for moving an object such as the carriage 2 which generates an inertial force by using the stepping motor 7 as a driving source, and it is not always necessary to read an original. The device is not the only problem.

The present invention relates to an apparatus for moving an object which generates an inertial force by using a stepping motor as a drive source,
To provide a stepping motor drive device capable of preventing stepping of a stepping motor and vibration of an object at the time of accelerating and decelerating the object, and an image reading device for moving the carriage by using the stepping motor as a drive source. It is an object of the present invention to provide an image reading apparatus in which stepping of a stepping motor and vibration of a carriage are prevented during acceleration and deceleration.

[0012]

In order to solve the above-mentioned problems, a stepping motor drive device according to claim 1 of the present invention comprises a drive pulse for controlling the rotation speed of the stepping motor and a drive current supplied to the stepping motor. Control means for outputting a threshold value signal for controlling the current value of
The stepping motor is sequentially switched at a timing defined by the drive pulse from the control means, and a motor driver that supplies a driving current having a current value defined by the threshold signal to the stepping motor is provided. In the stepping motor drive device, the control means, during the acceleration period from the start of rotation of the stepping motor until reaching a preset predetermined steady rotation speed, during the steady period during which the stepping motor is rotated at the steady rotation speed. It is characterized in that the threshold signal for outputting a drive current having a smaller current value to the supplied drive current is output to the stepping motor.

Further, a stepping motor drive device according to a second aspect of the present invention includes setting means for setting the target value of the steady rotation speed to the control means, and the control means controls the stepping motor of the stepping motor by the setting means. It is characterized in that the drive current in the acceleration period is decreased with respect to the steady period only when a target value near the resonance speed is set.

Further, a stepping motor drive device according to a third aspect of the present invention comprises setting means for setting the target value of the steady rotational speed to the control means, and the control means,
It is characterized in that the amount of decrease in the drive current to be reduced in the acceleration period with respect to the steady period is set in correspondence with the target value.

The stepping motor drive device according to a fourth aspect of the present invention includes control means for outputting a drive pulse for controlling the rotation speed of the stepping motor and a switching signal for controlling the voltage value of the drive voltage applied to the stepping motor, and the control means. A power supply unit that generates a drive voltage having a voltage value defined by the switching signal from the control unit and the excitation phase of the stepping motor are sequentially switched at the timing defined by the drive pulse, and the drive voltage from the power supply unit is set to the above-mentioned value. In a stepping motor drive device including a motor driver for applying to an excitation phase, the control means comprises:
During the deceleration period until the stepping motor rotating at a predetermined steady rotation speed is stopped, a reverse drive pulse that sequentially moves the excitation phase in the direction opposite to the rotation direction of the stepping motor, and the stepping motor is set to the steady state. The switching signal that causes the power supply unit to generate a drive voltage having a large voltage value with respect to the drive voltage applied during the stationary period of rotating at the rotation speed is characterized by being output.

Further, a stepping motor drive device according to a fifth aspect of the present invention comprises a setting means for setting the target value of the steady rotation speed to the control means, and the control means,
Only when the target value matches a preset rotation speed, the reverse rotation drive pulse during the deceleration period and the switching signal for generating a drive voltage having a large voltage value during the steady period are output. Characterize.

Further, a stepping motor drive device according to a sixth aspect of the present invention comprises setting means for setting the target value of the steady rotational speed to the control means, and the control means,
The output number of the reverse rotation drive pulse in the deceleration period and the increase amount of the drive voltage to be increased in the deceleration period with respect to the steady period are set in correspondence with the target value.

Further, in the image reading apparatus according to the present invention, at least a carriage on which a linear image sensor for reading the reflected light from the original is mounted, and a driving force from a stepping motor is transmitted to the carriage to make the original on the original. An image reading apparatus comprising: a carriage driving unit that reciprocates along a stepping motor; and a stepping motor driving device that drives and controls the stepping motor.
The stepping motor driving device described in 2 or 3 is used.

Further, in the image reading apparatus according to the present invention, at least a carriage on which a linear image sensor for reading the reflected light from the original document is mounted, and a driving force from a stepping motor is transmitted to the carriage to make the original document. 5. An image reading apparatus including a carriage driving unit that reciprocates along the path, and a stepping motor driving device that drives and controls the stepping motor, wherein the stepping motor driving device is the image reading device.
It is characterized in that the stepping motor driving device described in 5 or 6 is used.

[0020]

According to the present invention, in order to solve the above problems, according to the stepping motor drive device of the first aspect, the control means starts the rotation of the stepping motor, and then the preset constant rotation speed is set. Outputting the threshold value signal that causes the stepping motor to be supplied with a drive current having a smaller current value than the drive current supplied in the steady period during which the stepping motor is rotated at the steady rotation speed during the acceleration period until reaching As a result, the current value of the drive current supplied to the stepping motor by the motor driver becomes small during the acceleration period, and it is possible to prevent the stepping motor from generating an excessive torque more than necessary.

Further, according to the stepping motor driving device of the present invention, the control means sets the acceleration period to the steady period only when the setting means sets the target value near the resonance speed of the stepping motor. By reducing the drive current in the stepping motor, it is possible to prevent excessive torque from being generated from the stepping motor during the acceleration period only when the vicinity of the resonance speed is set as the target value of the steady rotation speed of the stepping motor. It

Further, according to the stepping motor drive device of the third aspect, the control means makes the drive current decrease corresponding to the target value set by the setting means in the acceleration period with respect to the steady period. By setting the reduction amount, the target value of the steady rotation speed changes, even if the length of the acceleration period until reaching the steady rotation speed or the acceleration of the stepping motor during the acceleration period changes.
It becomes possible to generate optimum torque from the stepping motor during the acceleration period.

Further, according to the stepping motor drive device of the fourth aspect, the rotation direction of the stepping motor is defined as the deceleration period until the control means stops the stepping motor rotating at a predetermined steady rotation speed. A reverse drive pulse for sequentially moving the excitation phase in the opposite direction,
And driving the stepping motor during the deceleration period by outputting a switching signal for causing the power supply means to generate a drive voltage having a large voltage value with respect to the drive voltage applied during the steady period in which the stepping motor is rotated at the steady rotation speed. Reverse torque in the direction opposite to the rotation direction acts on the shaft, and the voltage value of the drive voltage applied to the stepping motor increases, and the holding torque of the stepping motor during the deceleration period increases with respect to the steady period. .

Further, according to the stepping motor drive device of the fifth aspect, the control means drives the reverse drive pulse during the deceleration period only when the target value set by the setting means matches the preset rotation speed. , And by outputting a switching signal that generates a drive voltage having a large voltage value for a steady period, the stepping motor is stopped in a short time, and the object to be moved by using the stepping motor as a drive source is accurately predetermined. The reverse torque can be applied to the drive shaft of the stepping motor and the holding torque of the stepping motor can be increased during the deceleration period only under the condition that it is necessary to stop at the stopped position.

Further, according to the stepping motor drive device of the sixth aspect, the control means corresponds to the target value set by the setting means with respect to the output number of the reverse drive pulse in the deceleration period and the steady period. By setting the amount of increase of the drive voltage to be increased during the deceleration period, even if the external inertial force acting on the stepping motor changes, the reverse torque generation time and the holding time are kept in correspondence with the change of the inertial force. The amount of torque increase can be set.

Further, according to the image reading apparatus of the seventh aspect, the stepping motor driving apparatus is the first aspect.
By using the stepping motor driving device described in 2 or 3, it is possible to prevent the stepping motor from generating an excessive torque when the carriage is accelerated.

Further, according to the image reading apparatus of the eighth aspect, the stepping motor driving apparatus can be used as the stepping motor driving apparatus.
By using the stepping motor driving device described in 5 or 6, it is possible to increase the braking force generated by the stepping motor when decelerating the carriage, and the stepping motor is out of step due to the inertial force from the outside. Is prevented.

[0028]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of a stepping motor drive device of a first embodiment of the present invention. The stepping motor drive device of the first embodiment is a stepping motor 7 in the image reading device shown in FIGS. 5 and 6. Drive control. Reference numeral 20 is a main control unit that controls the entire image reading apparatus, 21 is a carriage control unit that controls the position and speed of the carriage 2, and 22 is a motor driver that outputs an electric pulse to the stepping motor 7.

The main controller 20, which is a setting means for setting the target rotation speed of the stepping motor 7, reads the carriage 2 in the reading section according to the pixel density of the reading before starting the reading of the document. A speed setting signal for setting a speed target value is output to the carriage control unit 21. The carriage controller 21
The reading speed of the carriage 2 and control conditions for accelerating the stationary carriage 2 to the reading speed are determined according to the speed setting signal. Specifically, the carriage control unit 21 outputs a drive pulse and a threshold signal to the motor driver 22 in order to define control conditions for accelerating the carriage 2 to the reading speed and further maintaining the reading speed. The motor driver 22 switches the excitation phase in the stepping motor 7 in synchronism with the frequency of the drive pulse, so that the stepping motor 7
Is rotated at a target rotation speed corresponding to the drive pulse, and the chopping condition is changed by the threshold signal, so that a drive current having a current value corresponding to the threshold signal is supplied to the stepping motor 7.

FIG. 2 is a flow chart showing the control during the acceleration of the carriage by the stepping motor driving device of the first embodiment. First, when the reading start signal and the speed setting signal from the main control unit 20 are input (S1-1), the carriage control unit 21 presets the target rotation speed set by the speed setting signal in the carriage control unit 21 in advance. It is determined whether or not it belongs to the resonance range (S1-2). Here, the resonance range set in the carriage control unit 21 is a range of rotation speed obtained by increasing or decreasing a predetermined value with respect to the resonance rotation speed specific to the stepping motor 7.

When the target transfer rate belongs to the resonance range (S
If the answer is 1-2), the carriage controller 21
The drive current I supplied to the stepping motor 7 is set during the acceleration period from the start of rotation of the stepping motor 7 until the rotation speed reaches the target rotation speed set by the main controller 20 (S1-3). . In step S1-3, the carriage control unit 21 selects the reduced current _ID corresponding to the target rotation speed set by the main control unit 20 from the data table, and maintains the stepping motor 7 at the target rotation speed. A threshold value signal that defines a drive current I smaller than the steady drive current I _S supplied to the stepping motor 7 during the period by the reduction current I _D is output to the motor driver 22.

Thereafter, the carriage controller 21 outputs an acceleration driving pulse to the motor driver 22 to start driving the stepping motor 7 (S1-4). The acceleration drive pulse is a drive pulse whose frequency increases at a predetermined increase rate, and the motor driver 22 switches the excitation phase of the stepping motor 7 in synchronization with this acceleration drive pulse, so that the stepping motor 7 accelerates. The rotation speed is increased with an acceleration proportional to the frequency increase rate of the drive pulse. If the carriage control unit 21 determines that the rotation speed of the stepping motor 7 has reached the target rotation speed set by the main control unit 20 (S1-
If YES in 6), the frequency of the drive pulse is fixed, and the signal level of the threshold signal is changed to increase the drive current I supplied to the stepping motor 7 to the steady drive current I _S (S1-7). ).

When it is determined in S1-2 that the target transfer rate set by the main control unit 20 does not belong to the resonance range, steady drive is performed as the drive current I supplied to the stepping motor 7 even during the acceleration period. When the current I _S is set (S1-5) and it is determined that the rotation speed of the stepping motor 7 has reached the target rotation speed set by the main control unit 20 (Yes in S1-6), the drive pulse The frequency is fixed and the drive current I is maintained at the steady drive current I _S (S1-7).

According to the image reading apparatus using the stepping motor driving device of the first embodiment described above, when the carriage control unit 21 determines that the target rotation speed belongs to the resonance range, the stepping motor 7 is turned on. During the acceleration period from the start of rotation until the target rotation speed set by the main control unit 20 is reached, the stepping motor 7
By outputting to the motor driver 22 a threshold value signal that defines a small drive current I, with respect to the steady drive current I _S that is supplied in the steady period for maintaining the target rotation speed,
The drive current I supplied to the stepping motor 7 by the motor driver 22 during the acceleration period is prevented from being reduced, and the stepping motor 7 is prevented from generating excessive torque more than necessary. Therefore, the absolute value of the acceleration of the carriage 2 is suppressed. And the change in tension of the synchromesh wire 14 during the acceleration period can be reduced. As a result, even when an object, such as the carriage 2, that generates a large inertial force during movement is moved by using the stepping motor 7 as a drive source, step-out of the stepping motor 7 and vibration of the carriage 2 during the acceleration period are suppressed. You can

Further, the carriage control unit 21 reduces the drive current I in the acceleration period with respect to the steady period only when the target control speed of the resonance range of the stepping motor 7 is set by the main control unit 20. Since an excessive torque is prevented from being generated from the stepping motor 7 during the acceleration period, when the target rotation speed outside the resonance range is set, the steady driving current I _S is applied to the stepping motor 7 even during the acceleration period. Is supplied, the stepping motor 7 generates normal torque.
Therefore, due to the influence of the vibration until the carriage 2 is accelerated to the reading speed, hunting is likely to occur in the rotation speed of the stepping motor 7 immediately after reaching the target rotation speed, and the hunting converges after the steady period. When the target rotation speed that requires a long time is set, the stepping motor 7 loses step and the carriage 2 vibrates during the acceleration period due to the decrease in the drive current. The reading speed can be controlled. Further, when the target rotation speed that is less affected by the resonance of the stepping motor 7 is set, the carriage 2 can be accelerated with a large acceleration during the acceleration period, and the reading speed is reduced after the steady period. Hunting converges in a short time.

Further, the carriage control unit 21 sets the decreasing current I _D corresponding to the target rotation speed set by the main control unit 20, so that the target rotation speed in the steady period changes and the acceleration period Even if the length or the acceleration of the stepping motor 7 changes during the acceleration period, an optimum torque can be generated from the stepping motor 7 during the acceleration period. Therefore, step-out of the stepping motor 7 and vibration of the carriage 2 during the acceleration period can be prevented. It can be surely suppressed.

FIG. 3 is a block diagram showing the essential parts of a second embodiment of the stepping motor driving device of the present invention.
The stepping motor driving device of the second embodiment drives and controls the stepping motor 7 in the image reading device shown in FIGS. Reference numeral 30 is a main control unit that controls the entire image reading apparatus, 31 is a carriage control unit that controls the position and speed of the carriage 2, 32 is a power supply unit that applies a drive voltage to the stepping motor 7 via a motor driver 33, and 33 is It is a motor driver that outputs electric pulses to the stepping motor 7.

The main control section 30, which is a setting means for setting the target rotation speed of the stepping motor 7, reads the carriage 2 in the reading section in correspondence with the reading pixel density before starting the reading of the original. A speed setting signal for setting a target speed value is output to the carriage control unit 31. The carriage controller 31
A reading speed of the carriage 2 and a control condition for stopping the carriage 2 moving at the reading speed are determined according to the speed setting signal. Specifically, the carriage control unit 31 outputs a drive pulse having a frequency corresponding to the reading speed to the motor driver 33 in order to define the reading speed of the carriage 2. The motor driver 33 rotates the stepping motor 7 at a rotation speed corresponding to the frequency of the drive pulse by switching the excitation phase in the stepping motor 7 in synchronization with the drive pulse. Then, the carriage control unit 31 outputs a drive pulse having a constant frequency that sets the rotation speed of the stepping motor 7 to the target rotation speed set by the main control unit 30 in the steady period, and sets the carriage 2 to the reading speed in the reading section. maintain.

FIG. 4 is a flow chart showing the control during deceleration of the carriage by the stepping motor driving device of the second embodiment. First, the carriage control unit 31 receives a reading completion signal from the main control unit 30 (S2-1),
It is determined whether or not the target rotation speed during the stationary period matches the set rotation speed set in the memory of the carriage control unit 31 in advance (S2-2).

If the target transfer rate matches the set rotational speed (YES in S2-2), the carriage control unit 31
Is the stepping motor 7 rotating at the target rotation speed.
During the deceleration period until the stepping motor 7 is stopped
The drive voltage V to be applied to is set (S2-3). In step S2-3, the carriage control unit 31 selects the increased voltage V _I corresponding to the target rotation speed set by the main control unit 30 from the data table, and maintains the stepping motor 7 at the target rotation speed during the steady period. against the constant drive voltage V _S applied to, and outputs a switching signal for specifying said increased voltage V _I only large driving voltage V to the power supply unit 32. Here, for example, assuming that the steady drive voltage V _S is 12 V, in this embodiment, the increased voltage V _S is made to correspond to the inertial force of the carriage 2.
It is possible to set the drive voltage V to 24V or 36V by setting _I or 12V or 24V, and under the condition that the inertial force of the carriage 2 is small, set 0V as the increase voltage V _I and set the drive voltage V May be maintained at 12V.

After that, when the carriage 2 reaches the deceleration start position where the reading section ends (Yes in S2-4), the carriage control unit 31 outputs the deceleration drive pulse P _D to the motor driver 33. By outputting to
The deceleration of the stepping motor 7 is started (S2-5). The deceleration drive pulse P _D is a drive pulse obtained by decreasing the frequency at a predetermined reduction rate with the drive pulse defined by the speed setting signal as a starting point, and is synchronized with the deceleration drive pulse P _D. By the motor driver 33 switching the excitation phase of the stepping motor 7, the stepping motor 7 reduces the rotational speed from the target rotational speed with a negative acceleration proportional to the frequency reduction rate of the deceleration drive pulse P _D.

Then, if the count number N of the output deceleration drive pulse P _D reaches the preset set pulse number N _j (Yes in S2-6), the carriage control section 31 determines that the stepping motor is The reverse drive pulse P _R for sequentially moving the excitation phase of the stepping motor 7 in the direction opposite to the rotation direction of 7 is output as k pulses (S2-7).
Here, the set pulse number N _j in S2-6 is a pulse number obtained by dividing the total set pulse number N _T corresponding to the distance from the deceleration start position to the predetermined stop position. Further, in step S2-7, the carriage control unit 31 selects the output number k of the reverse drive pulse P _R corresponding to the target rotation speed set by the main control unit 30 from the data table. The reverse rotation drive pulse P _R set in this way causes the motor driver 33 to switch the excitation phase of the stepping motor 7, so that a force in the direction opposite to the inertial force acts on the drive shaft of the stepping motor 7 to cause stepping. A large braking force can be generated by the motor 7.

The carriage controller 31 controls the reverse drive pulse P
After the output of _R , when the count number N of the deceleration drive pulse P _D matches the total set pulse number N _T (Yes in S2-8), the output of the deceleration drive pulse P _D is stopped and the stepping motor 7 is stopped. When stopped and the count number N of deceleration drive pulses P _D does not reach the total set pulse number N _T
(No in S2-8), the process returns to step S2-5.

Further, in step S2-2, when the target rotation speed in the steady period does not match the set rotation speed set in the memory of the carriage control unit 31 in advance, the carriage control unit 31 determines the drive voltage V for deceleration. Steady state drive voltage V
_{When S} is set (S2-9) and the carriage 2 reaches the deceleration start position (Yes in S2-10), the deceleration drive pulse P _D is output to the motor driver 33 to drive the stepping motor 7. Start deceleration (S2-11). Then, the carriage control unit 31 outputs the output deceleration drive pulse P
_If the count number N of _D matches the preset total pulse number N _T (Yes in S2-12),
When the output of the deceleration driving pulse P _D is stopped to stop the stepping motor 7 and the count number N of the deceleration driving pulse P _D is less than the total set pulse number N _T (S2-12
(No in step S11), the process returns to step S2-11.

According to the image reading apparatus using the stepping motor driving device of the second embodiment described above, the carriage control unit 31 performs the deceleration period until the stepping motor 7 rotating at the target rotation speed is stopped. , The reverse drive pulse P _R for sequentially moving the excitation phase in the direction opposite to the rotation direction of the stepping motor 7 is output, and the increase voltage V _{I is} larger than the steady drive voltage V _S applied in the steady period. By applying the voltage V to the stepping motor 7 by the power supply unit 32, a reverse torque in a direction opposite to the rotation direction is applied to the drive shaft of the stepping motor 7 in the deceleration period, and a steady torque is generated in the deceleration period. Since the holding torque for the drive shaft of the stepping motor 7 increases, a large braking force is applied by the stepping motor 7. The carriage 2 can be generated and stopped in a short time, and can be accurately stopped at a predetermined stop position.

Further, the carriage control unit 31 outputs the reverse rotation drive pulse P _R during the deceleration period only when the target rotation speed set by the main control unit 30 matches the preset rotation speed. By increasing the drive voltage V in the deceleration period with respect to the steady period,
Reverse torque is applied to the drive shaft of the stepping motor 7 during the deceleration period only when it is necessary to stop the carriage 2 in a short time and highly accurately stop it at a predetermined stop position, and Since the holding torque of the stepping motor 7 can be increased, in such a case, the carriage 2 can be stopped in a short time and accurately stopped at a predetermined stop position, and in other cases, deceleration can be performed. Control over the period can be simplified.

Further, the carriage control unit 31 makes the target rotation speed set by the main control unit 30 correspond to
By setting the output number k of the reverse drive pulse P _{R in} the deceleration period and the increase voltage V _I of the drive voltage V to be increased in the deceleration period for the steady period, the carriage 2 acting on the stepping motor 7 is set. Even when the inertial force changes, the reverse torque generation time and the increase amount of the holding torque can be set in accordance with the change in the inertial force, so that the carriage 2 is reliably stopped at the predetermined stop position. be able to.

[0048]

As described above, according to the stepping motor driving device of the present invention, the stepping motor driving device reduces the current value of the driving current supplied to the stepping motor during the acceleration period. By preventing excessive torque from being generated from the motor, the absolute value of the acceleration of the object moving with the stepping motor as the drive source is suppressed, and elastic deformation of the drive mechanism during the acceleration period is suppressed. Since the size can be reduced, even when an object that generates a large inertial force during movement is moved by using the stepping motor as a drive source, it is possible to suppress step-out of the stepping motor and vibration of the object during the acceleration period.

Further, according to the stepping motor drive device of the second aspect, only when the vicinity of the resonance rotation speed is set as the target value of the steady rotation speed of the stepping motor, the stepping motor excessively exceeds the necessary value during the acceleration period. By preventing the occurrence of various torques, hunting is likely to occur in the rotation speed of the stepping motor immediately after the steady rotation speed reaches the target value, and it takes a long time until the hunting converges after the steady period. When a target value that requires time is set, stepping motor step-out during the acceleration period and vibration of an object moving by the stepping motor are suppressed due to a decrease in drive current, and the object is accurately controlled to a target speed. It is possible to set a target value that is less affected by the resonance of the stepping motor. If, in the acceleration period becomes possible to accelerate the object with a large acceleration, and after a steady period hunting of the rotational speed converges in a short time.

Further, according to the stepping motor driving device of the third aspect, the length of the acceleration period until the target value of the steady rotation speed changes to reach the steady rotation speed or the acceleration of the stepping motor during the acceleration period. Even if the change occurs, it becomes possible to generate optimal torque from the stepping motor during the acceleration period, so that it is possible to reliably suppress step-out of the stepping motor and vibration of an object moved by the stepping motor during the acceleration period. it can.

According to another aspect of the present invention, the stepping motor drive device applies a reverse torque to the drive shaft of the stepping motor in the direction opposite to the rotational direction during the deceleration period, and the drive torque is applied to the stepping motor. By increasing the voltage value of the voltage and increasing the holding torque for the drive shaft of the stepping motor during the deceleration period with respect to the steady period, a large braking force is generated by the stepping motor and the object moved by the stepping motor is moved for a short time. It is possible to stop at, and accurately stop at a predetermined stop position. Further, since it is possible to prevent the stepping motor from being out of step, it is possible to improve the accuracy of the position control for the object that is moved by the stepping motor.

Further, according to the stepping motor drive device of the fifth aspect, the stepping motor is stopped in a short time, and the object to be moved by using the stepping motor as a drive source is accurately stopped at a predetermined stop position. The reverse torque can be applied to the drive shaft of the stepping motor and the holding torque of the stepping motor can be increased only during the deceleration period, so that the stepping motor moves in such a case. The object can be stopped in a short time and accurately stopped at a predetermined stop position, and in other cases, control during the deceleration period can be simplified.

Further, according to the stepping motor drive device of the sixth aspect, even when the external inertial force acting on the stepping motor is changed, the reverse torque generation time and the reverse torque are generated in accordance with the change of the inertial force. By setting the increase amount of the holding torque, the object moving by the stepping motor can be reliably stopped at the predetermined stop position.

According to the image reading device of the seventh aspect, the stepping motor driving device is the first or second aspect.
By using the stepping motor driving device described in 2 or 3, it is possible to prevent an excessive torque from being generated from the stepping motor when the carriage is accelerated. Even when it is moved as a drive source, it is possible to suppress the stepping of the stepping motor and the vibration of the carriage during the acceleration period.

According to the image reading apparatus of the eighth aspect, the stepping motor drive apparatus is provided as the fourth step.
By using the stepping motor driving device described in 5 or 6, it is possible to increase the braking force generated by the stepping motor when decelerating the carriage, and the stepping motor is out of step due to the inertial force from the outside. Since it is prevented, the stepping motor can generate a large braking force to stop the carriage in a short time and accurately stop the carriage at a predetermined stop position.

[Brief description of drawings]

FIG. 1 is a block diagram showing a main part in a first embodiment of a stepping motor drive device of the present invention.

FIG. 2 is a flowchart showing a control during acceleration of the carriage by the stepping motor driving device of the first embodiment of the stepping motor driving device of the present invention.

FIG. 3 is a block diagram showing a main part in a second embodiment of a stepping motor drive device of the present invention.

FIG. 4 is a flow chart showing control at the time of deceleration of the carriage by the stepping motor driving device of the second embodiment of the stepping motor driving device of the present invention.

FIG. 5 is a plan view showing a schematic configuration of an image reading apparatus including a carriage driving mechanism.

FIG. 6 is a side view showing a schematic configuration of an image reading apparatus including a carriage driving mechanism.

FIG. 7 is a measurement diagram showing the relationship between the rotation speed of the stepping motor and the generated torque.

[Explanation of symbols]

2 ... Carriage, 4 ... Sensor unit, 7 ... Stepping motor, 8 ... Drive side belt pulley, 9 ... Driven side belt pulley, 11 ... Drive belt, 12 ... Drive side wire pulley, 13 ... Driven side belt pulley, 14 ... Synchromesh Wires, 20, 30 ... Main control unit, 21,31 ... Carriage control unit, 22,33 ... Motor driver, 32 ... Power supply unit.

Claims (8)

[Claims] 1. A control means for outputting a drive pulse for controlling a rotation speed of a stepping motor and a threshold value signal for controlling a current value of a drive current supplied to the stepping motor, and the drive pulse from the control means. In the stepping motor drive device, which sequentially switches the excitation phase of the stepping motor at a specified timing, and a motor driver which supplies a driving current having a current value specified by the threshold value signal to the stepping motor, the control means. However, during the acceleration period from the start of rotation of the stepping motor to the reaching of a predetermined preset steady rotation speed, a current is supplied with respect to the drive current supplied in the steady period in which the stepping motor is rotated at the steady rotation speed. The drive current with a small value is supplied to the stepping motor. A stepping motor drive device characterized by outputting a threshold signal. 2. The setting means for setting the target value of the steady rotational speed to the control means, respectively, the control means sets the target value near the resonance speed of the stepping motor by the setting means. 2. The stepping motor drive device according to claim 1, wherein the drive current in the acceleration period is decreased with respect to the steady period only in the case. 3. A setting means for setting a target value of the steady rotation speed to the control means, the control means comprising:
2. The stepping motor drive device according to claim 1, wherein a reduction amount of a drive current to be reduced in the acceleration period with respect to the steady period is set in correspondence with the target value. 4. A control means for outputting a drive pulse for controlling a rotation speed of the stepping motor and a switching signal for controlling a voltage value of a drive voltage applied to the stepping motor,
The excitation means of the stepping motor is sequentially switched at the timing defined by the drive pulse and the power supply means for generating the drive voltage having the voltage value defined by the switching signal from the control means, and the drive voltage from the power supply means is supplied. In a stepping motor drive device including a motor driver for applying to the excitation phase, the control means changes the rotation direction of the stepping motor during a deceleration period until the stepping motor rotating at a predetermined steady rotation speed is stopped. Is a reverse drive pulse for sequentially moving the excitation phase in the opposite direction, and a drive voltage having a large voltage value with respect to the drive voltage applied in the steady period for rotating the stepping motor at the steady rotation speed by the power supply means. A stepping model characterized by outputting the switching signal to be generated. Motor drive unit. 5. A setting means for setting a target value of the steady rotation speed to the control means, the control means comprising:
Only when the target value matches a preset rotation speed, the reverse rotation drive pulse during the deceleration period and the switching signal for generating a drive voltage having a large voltage value during the steady period are output. The stepping motor drive device according to claim 4, which is characterized in that. 6. A setting means for setting a target value of the steady rotation speed to the control means, the control means comprising:
5. The stepping according to claim 4, wherein the output number of the reverse drive pulse in the deceleration period and the increase amount of the drive voltage to be increased in the deceleration period with respect to the steady period are set in correspondence with the target value. Motor drive device. 7. A carriage on which a linear image sensor for reading reflected light from at least a document is mounted, a carriage driving unit for transmitting a driving force from a stepping motor to the carriage to move the carriage along the document, An image reading device comprising a stepping motor drive device for driving and controlling a stepping motor, wherein the stepping motor drive device according to claim 1, 2 or 3 is used as the stepping motor drive device. 8. A carriage on which a linear image sensor for reading reflected light from at least an original is mounted, a carriage driving unit for transmitting a driving force from a stepping motor to the carriage to move the carriage along the original, An image reading apparatus comprising a stepping motor driving device for driving and controlling a stepping motor, wherein the stepping motor driving device according to claim 4, 5 or 6 is used as the stepping motor driving device.