JPH05100324A - Method for controlling driving motor for optical system traveling body - Google Patents

Abstract

PURPOSE:To provide a method for controlling the driving motor of an optical system traveling body that the rise of the temperature of the driving motor of the optical system traveling body can be suppressed to be low and the driving motor of the optical system traveling body is not stepped out at the accelerated traveling time and the decelerated traveling time thereof. CONSTITUTION:In an image reader where a stepping motor 14 is used as the driving motor of the optical system traveling body for reciprocatingly moving the optical traveling body provided with an optical system for exposing and scanning the image of an original, the driving current of the motor 14 when the optical traveling body is accelerated and made to travel and when the optical traveling body is decelerated and made to travel is larger than that when the optical traveling body is made to travel at a fixed speed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling an optical system running body drive motor used in an image reading apparatus such as a copying machine.

[0002]

2. Description of the Related Art Generally, a copying machine is provided with an optical traveling member having an optical system for exposing and scanning an original image and an optical traveling member drive motor for reciprocating the optical traveling member. There is. In recent copying machines, a stepping motor is used as an optical system running body drive motor, and the stepping motor is driven by a constant current drive system.

FIG. 3 shows the moving speed of the optical system running body with respect to time during exposure. The optical system traveling body starts in the forward movement direction at a predetermined timing (time point t0) from the traveling start position, and moves in the forward movement direction while being gradually accelerated. Then, when the set speed for forward movement VO1 is reached (time point t1), the vehicle moves to constant speed traveling, deceleration is started before the return position (time point t2), and the vehicle reaches the return position and stops (time point t3). When the vehicle reaches the return position, it is started in the backward movement direction and gradually accelerates to move in the backward movement direction. Then, when the set speed VO2 for backward movement is reached (time point t4), the vehicle moves to constant speed travel, deceleration is started before the travel start position (time point t5), and the travel start position is reached and stopped (time point t6). In the process of the optical system traveling body moving forward, the original image is exposed and scanned, and the original image is projected on the photosensitive drum.

[0004]

The conventional copying machine has the following problems because the drive current of the stepping motor is always constant. That is, if the set value of the drive current of the stepping motor is too large, the temperature rise of the stepping motor becomes large and the stepping motor is burned out. On the other hand, if the set value of the drive current of the stepping motor is too small, the drive torque of the stepping motor decreases, and the stepping motor loses step during acceleration traveling and deceleration traveling with a large required torque (load torque + acceleration torque).

Therefore, the temperature rise of the stepping motor is suppressed to a low level, and the stepping motor is not out of step during the acceleration traveling and the deceleration traveling of the optical system traveling body.
Although it is necessary to set the drive current value, it has not been easy to determine such a drive current value.

According to the present invention, the temperature rise of the optical system traveling body drive motor can be suppressed to a low level, and the optical system traveling body drive motor is not out of step during acceleration traveling and deceleration traveling. It aims at providing the control method of.

[0007]

A method of controlling an optical system running body drive motor according to the present invention is an optical system running body drive motor for reciprocating an optical running body having an optical system for exposing and scanning a document image. In an image reading apparatus in which a stepping motor is used as the stepping motor, the drive current of the stepping motor when the optical traveling body is accelerated and decelerated is set to the stepping motor when the optical traveling body is driven at a constant speed. It is characterized in that it is made larger than the drive current of.

As a method of switching the drive current of the stepping motor, for example, the switching timing of the drive current of the stepping motor is stored in advance in the storage means, and the stepping motor is driven at the switching timing stored in the storage means. A method of switching the current, a method of switching the driving current of the stepping motor by detecting a speed change of the stepping motor, and the like are used.

[0009]

The driving current of the stepping motor for accelerating the optical traveling body and for decelerating the optical traveling body is made larger than the driving current of the stepping motor for traveling the optical traveling body at a constant speed.

[0010]

Embodiments of the present invention will be described below with reference to FIGS.

FIG. 1 shows the electrical construction of the copying machine.

The copying machine is controlled by the CPU 10. The CPU 10 is a ROM that stores the program and the like.
11 and a RAM 12 for storing necessary data. From the CPU 10, the speed command signal Sv, the rotation direction command signal Sd, and the drive current designation signal S are sent to the drive circuit 13 of the stepping motor 14 as the optical system drive motor.
s and are sent. The drive circuit 13 has a drive current designation signal S.
When s is sent, the drive current of the stepping motor 14 is set to the drive current IL for constant speed travel and the drive current I for constant speed travel.
Drive current IH for acceleration / deceleration larger than L (IH> I
L) and the specified current value is controlled.

The speed program of the stepping motor 14, that is, the data regarding the rotation speed with respect to time is stored in the ROM 11 in advance. In addition, data regarding the timing of outputting the drive current designating signal Ss for switching between the constant speed traveling drive current IL and the acceleration / deceleration traveling drive current IH is also stored in the ROM 11 in advance.

FIG. 2 shows the moving speed of the optical system traveling body with respect to the time during exposure and the drive current of the stepping motor with respect to time. At the time of exposure, at a predetermined timing (time t0), the CPU 10 causes the drive circuit 13 to
A speed command signal Sv for gradually accelerating the speed of the optical system traveling body to the set speed VO1 for forward movement, and a rotation direction command signal Sd indicating the forward rotation direction, here, the forward rotation direction. , The drive current designating signal Ss designating the drive current IH for acceleration / deceleration travel is sent, and the stepping motor 14 is driven. As a result, the optical system traveling body is gradually accelerated and moves in the forward movement direction from the traveling start position. At this time, the drive current of the stepping motor 14 is set to the acceleration / deceleration travel drive current IH.

When the traveling body of the optical system reaches the set speed VO1 for forward movement (time t1), the speed command signal Sv changes to the set speed V
It becomes a value corresponding to O1. Further, the CPU 10 sends a drive current designating signal Ss designating the drive current IL for constant speed traveling to the drive circuit 13. As a result, the drive current of the stepping motor 14 is switched to the constant-speed traveling drive current IL.

When the optical system traveling body moves at the set speed VO1 for forward movement and approaches the return position, the speed of the optical system traveling body is gradually increased from the CPU 10 to the drive circuit 13 at a predetermined timing (time t2). A speed command signal Sv for decelerating and a drive current designating signal Ss designating a drive current IH for acceleration / deceleration traveling are sent. This causes the stepping motor 14 to start decelerating. Further, the drive current of the stepping motor 14 is switched to the drive current IH for acceleration / deceleration running.

When the optical system traveling body reaches the return position while decelerating (time point t3), the CPU 10 causes the drive circuit 13 to gradually accelerate the speed of the optical system traveling body to the set speed VO2 for backward movement. Speed command signal S for going
v and the rotation direction command signal Sd indicating the reverse rotation direction, which is the rotation direction corresponding to the backward movement direction, are sent, and the stepping motor 14 is driven in reverse. In this case, the drive current of the stepping motor 14 maintains the acceleration / deceleration travel drive current IH.

When the traveling body of the optical system is gradually accelerated in the backward direction and reaches the set speed VO2 for backward movement (time t4),
The speed command signal Sv has a value corresponding to the set speed VO2. Further, the CPU 10 sends a drive current designating signal Ss designating the drive current IL for constant speed traveling to the drive circuit 13. As a result, the drive current of the stepping motor 14 is switched to the constant-speed traveling drive current IL.

When the optical system traveling body moves at the set speed VO2 for backward movement and approaches the traveling start position, the CPU 10 causes the drive circuit 13 to gradually increase the speed of the optical system traveling body at a predetermined timing (time t5). A speed command signal Sv for decelerating and a drive current designating signal Ss designating a drive current IH for acceleration / deceleration travel are sent. As a result, the stepping motor 14 starts decelerating. Further, the drive current of the stepping motor 14 is switched to the drive current IH for acceleration / deceleration running. Then, the optical system traveling body moves while being decelerated, reaches the traveling start position, and stops (time point t6).

According to this embodiment, during acceleration and deceleration traveling with a large required torque, the driving current is set to a relatively large acceleration / deceleration driving current IH so that the driving torque of the stepping motor 14 becomes large, and the required torque is reduced. When the vehicle is traveling at a small constant speed, the drive current is set to a relatively small constant-speed traveling drive current IL so that the temperature rise of the stepping motor 14 becomes small. Therefore, it is possible to prevent the stepping motor 14 from going out of step during acceleration and deceleration running, and to suppress the temperature rise of the stepping motor 14 to a low level.

In the above embodiment, the stepping motor 14
The drive current is switched based on the switching timing data stored in the ROM 11 in advance. However, even if the drive current of the stepping motor 14 is switched by detecting the speed change of the stepping motor 14. Good.

Further, the drive current for constant speed travel during forward rotation and the drive current for constant speed travel during reverse rotation may be controlled to different values. Similarly, the drive current for acceleration / deceleration travel during forward rotation and the drive current for acceleration / deceleration travel during reverse rotation may be controlled to different values. For example, the drive current for constant speed travel during forward rotation should be smaller than the drive current for constant speed travel during reverse rotation, and the drive current for acceleration / deceleration travel during forward rotation should be smaller than the drive current for acceleration / deceleration travel during reverse rotation. Can be considered. Even in this case, the drive current for constant speed traveling is made smaller than the drive current for acceleration / deceleration traveling.

[0023]

According to the present invention, the temperature rise of the optical system traveling body drive motor can be suppressed to a low level, and it is possible to avoid the stepping out of the optical system traveling body drive motor during acceleration traveling and deceleration traveling. ..

[Brief description of drawings]

FIG. 1 is an electrical block diagram showing a configuration of a copying machine.

FIG. 2 is a time chart showing a moving speed of an optical traveling body with respect to time during exposure and a drive current of a stepping motor with respect to time.

FIG. 3 is a time chart showing the moving speed of the optical traveling body with respect to the time during exposure.

[Explanation of Codes] 10 CPU 11 ROM 12 RAM 13 Drive Circuit 14 Stepping Motor

Claims (3)

[Claims] 1. An image reading apparatus using a stepping motor as an optical system running body drive motor for reciprocally moving an optical running body having an optical system for exposing and scanning a document image. The drive current of the stepping motor when traveling and when the optical traveling body is decelerated is made larger than the drive current of the stepping motor when traveling the optical traveling body at a constant speed. Control method. 2. The stepping motor drive current switching timing is stored in advance in the storage means, and the stepping motor driving current is switched at the switching timing stored in the storage means. A method for controlling an optical system traveling body drive motor as described. 3. The method for controlling an optical system running body drive motor according to claim 1, wherein the drive current of the stepping motor is switched by detecting a speed change of the stepping motor.