JPH0412341A - Optical scanning device - Google Patents

Abstract

PURPOSE:To smoothly perform buffering operation at the time of braking in return motion and a startup in forward motion and to increase the scanning speed by supplying an electromagnet with different currents at the time of the forward motion startup and return motion braking of an optical moving body. CONSTITUTION:The electromagnet 13 is arranged nearby the stationary end of the optical moving body 3 and opposite it in its travel direction and a permanent magnet 12 is arranged opposite the electromagnet 13 of the optical moving body 3. For the purpose, the electromagnet 13 is supplied with the current at the time of the startup of the forward movement from the stationary end of the optical moving body 3 to accelerate the optical moving body 3 with the resiliency with the permanent magnet 12 on the side of the optical moving body 3 and then the optical moving body 3 can be accelerated to a scanning speed in a short time without making the initial driving torque of a driving means excessive, so the startup can be stabilized. Further, the electromagnet 13 is supplied with the current corresponding to the inertial force of the optical moving body 3 even in the braking in return motion to provide an effective buffering function even if the optical scanning body 3 is in fast scanning motion. Consequently, the startup operation is made smooth and an increase in the scanning speed can be handled effectively.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an optical scanning device for scanning a document in a copying machine, an image scanner, or the like.

(Prior Art) Conventionally, in optical scanning devices for copying machines, etc., as disclosed in Japanese Patent Application Laid-Open No. 57-13460, etc.,
The scanning carriage is movably supported by the moving guide shaft,
A buffering function is achieved by interposing an elastic member between the bearing portion of the scanning carriage and the side plate of the main body of the apparatus.

(Problem to be solved by the invention) However, in a shock absorber using such an elastic member,
In order to perform the shock absorbing function accurately, there are many disadvantages such as complicated positional accuracy management of the shock absorber, and it is difficult to respond to faster scanning speeds. Due to these changes, vibrations are generated during the reciprocating motion, resulting in a problem of deterioration of image quality. In addition, in order to increase the scanning speed, it is necessary to generate excessive torque in the scan motor that drives the optical moving body at the start of forward movement, which tends to cause overshoot in the scanning speed and impair scanning stability. There was a problem in that the image quality deteriorated.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, an object of the present invention is to provide an optical scanning device that can smoothly buffer during backward braking and rise during forward motion, cope with increased scanning speeds, and has a simple configuration. do.

(Means for Solving the Problems) In order to achieve the above object, an optical scanning device of the present invention is an optical scanning device that scans a document by reciprocating an optical movable body interposed in an optical system. , an electromagnet is disposed near the stationary end of the optical movable body at a position opposite to the running direction, and a permanent magnet is disposed at a position facing the electromagnet of the optical movable body, so that when the optical movable body starts forward movement and The present invention is characterized in that means is provided for supplying different currents to the electromagnets during double braking.

(Function) According to the above configuration of the present invention, when the optical movable body starts forward movement from the stationary end, current is applied to the electromagnet and the optical movable body is accelerated by the repulsive force with the permanent magnet on the optical movable body side. , the optical movable body can be accelerated to the scanning speed in a short time without increasing the initial drive torque of the drive means, making it possible to stabilize the start-up and prevent the occurrence of vibration. By passing a current corresponding to the inertial force of the moving object through the electromagnet, it can effectively act as a buffer even when scanning an optically moving object at high speed, preventing the occurrence of vibration. Since the current flowing during braking is different, by flowing a smaller current during start-up than during braking, it is possible to moderately accelerate so that no more external force is applied to the scanning moving object, smoothing the start-up operation and increasing the scanning speed. be able to respond effectively.

(Example) Hereinafter, an example of the present invention will be described with reference to FIGS. 1 to 5.

In FIG. 1, reference numeral 1 denotes an original platen glass on which an original is placed, and a first scanning carriage 2 is placed below the original platen glass 1.
A second scanning carriage 3 is disposed so as to be able to reciprocate along a predetermined path by a guide member (not shown). 1st
The scanning carriage 2 includes a main reflector 4, a lamp 5, a sub-reflector 6, a slit 7, and a first mirror 8.
The second scanning carriage 3 is equipped with a second mirror 9 and a third mirror 1°. Further, the first scanning carriage 2 and the second scanning carriage 3 are driven in conjunction with each other by a wire rope or the like (not shown) so that the moving speed is 2:1.

Incidentally, as shown in FIG. 2, the scanned image of the document by the first and second scanning carriages 2.3 is transmitted to the photosensitive drum 22 via the imaging lens 20 and the fourth mirror 21 that constitute the imaging system.
exposed to light.

Such scanning devices are required to repeatedly move back and forth when scanning documents, but vibrations occur due to rapid changes in acceleration that occur when switching directions of movement. The larger the change, the larger the change. Therefore, unless some kind of buffering means is provided, the scanning carry nozzle 2.3 will move back and forth without being able to stop its vibrations, and this vibration of the scanning system is very undesirable for the imaging system. If such vibration of the scanning system occurs during the second or subsequent forward movement during continuous scanning, uneven scanning speed and changes in the imaging position will occur, resulting in image deterioration.

Therefore, in this embodiment, in order to eliminate such inconvenience, an electromagnet 13 is fixedly provided on the side surface of the optical frame 11 facing the resting position of the scanning carriage 2. A permanent magnet 12 is provided on the end face. Then, the winding direction of the coil of the electromagnet I3 and the direction of current flow are set by the second scanning carriage 3.
The permanent magnet 12 provided in the permanent magnet 12 and the same pole are set to face each other, so that a repulsive force due to magnetic force is generated.

Further, as shown in FIG. 3, current control for the electromagnet 13 is performed by the current control circuit 1 by the CPU 6 that controls the entire device.
This is done through 7. Detection signals from the home switch 14, which detects the first scanning carriage 2 in the stationary position, and the brake switch 15, which detects the position before which braking should be started, are input to the CPU 16. Also, based on these detection signals, other detection signals, and command signals, the CP
At U16, the first and second
Scan motor 1 for moving and driving the scanning carriage 2.3
9 is controlled.

Next, the operation of the optical scanning device described above will be explained with reference to the timing chart shown in FIG.

When the scan carriage 2.3 starts its forward movement based on the scan start signal, a starting current is applied to the scan motor 19 to drive it, and a current having a current value of 11 is applied to the electromagnet 13 during acceleration by this starting current. Normally, at startup, the scan motor 19 moves the scan carriage 2.
The starting current is applied to give an acceleration that causes the speed in step 3 to overshoot, and after starting, the speed is feedback-controlled to reach a predetermined scanning speed. This results in the disadvantage that the amount of shoot tends to increase, and the stability of the scanning speed at the initial stage of scanning becomes worse. On this point, in this embodiment, by energizing the electromagnet 13 at the start of the forward motion, acceleration is applied by the repulsive force of the magnetic force only at the initial stage of the movement of the scanning carriage 2.3, and the initial velocity is smoothly provided. It is possible to accelerate to the scanning speed in a short time while flowing a starting current that does not increase the speed. In this way, by assisting the acceleration of the scanning carriage 2.3 with the repulsive force of the magnet, the amount of overshoot due to acceleration by the scan motor 19 can be suppressed to a small level.
The start-up of the scan is smooth, and the transition to the constant speed range can be performed smoothly and in a short time.

Thereafter, the scanning carriage 2.3 is moved forward at a constant speed by the scan motor 19 to perform scanning, and when the scanning area is exceeded, the scan motor 19 is driven in reverse, and the scanning carriage 2.3 moves backward at a higher speed than when moving forward. do.

The scanning carriage 2.3 returns to the scanning start side by backward movement,
When a detection signal is output from the brake switch 15, a current having a current value I2 is applied to the electromagnet 13. When the scanning carriage 3 approaches a distance such that the repulsive force caused by the magnetic forces of the permanent magnet 12 and the electromagnet 13 of the scanning carriage 3 affects the inertia of the scanning carriage 2.3, the braking of the scanning carriage 2.3 is promoted and deceleration is smoothed. It will be held in Moreover, as shown in Fig. 4, the repulsive force due to magnetic force is generated in inverse proportion to the square of the distance between magnetic objects, which limits the moving distance of the scanning carriage 2.3 and makes it difficult to decelerate efficiently. It's convenient. Furthermore, since there is no mechanical contact, no change in performance occurs.

When the scanning carriage 2.3 reaches the rest position, it is detected by the home switch 15, and the scanning motor 19 is stopped and stands still. In this stationary position, a current of a small current value 3 is applied to prevent the permanent magnet 12 from being attracted to the iron core of the electromagnet 13.

By the way, during double braking, the current value I given to the electromagnet 13
It is preferable to shorten the braking distance by increasing the value of 2, but if the current value I applied to the electromagnet 13 is increased at the start of forward motion and an excessively large repulsive force is generated, vibrations may be caused to the scanning carriage 2.3. Invite or scan motor 19
Therefore, it is desirable to generate a repulsive force that is consistent with the speed control system of the scan motor 19. Therefore, as mentioned above, the current value 11 applied to the electromagnet 13 at the time of forward movement rising is set to be smaller than the current value 2 applied at the time of backward movement braking, so that the scanning carriage 2.3
We are making the start-up smooth. Furthermore, if the torque of the scan motor 19 is sufficiently large, it will overcome the static frictional resistance of the scan carriage 2.3 and cause the scan carriage 2.3 to
It suffices to apply a current value that can slightly move the .

However, if the current value is completely set to O, the permanent magnet 12
is attracted to the iron core of the electromagnet 13 and the scanning carriage 2.3
This is not preferable because it causes an increase in the initial drive torque for moving the .

In the above embodiment, the permanent magnet 12 is attached to the second scanning carriage 3.
Although an example is shown in which it is provided only on the first scanning carriage 2, it may also be provided on both scanning carriages 2.3.

In addition, in the above embodiment, the brake switch 1 is
Although an example has been shown in which current is caused to flow through the electromagnet 13 based on the detection signal from the scan motor 19, based on the detection signal of the movement position of the scanning carriage 2.3 detected by the encoder provided in the scan motor 19 etc. The electromagnet 13 may be controlled to be energized at the time of forward motion start-up and backward motion braking, or may be temporally controlled using a timer.

(Effects of the Invention) As is clear from the above explanation, according to the optical scanning device of the present invention, when the optical movable body starts forward movement, a current is passed through the electromagnet and the repulsive force with the permanent magnet on the optical movable body side is used. By accelerating the optical movable body, sufficient acceleration can be achieved without increasing the initial drive torque of the drive means of the optical movable body;
It is possible to stabilize the start-up by reducing the overshoot of the speed at the time of start-up, and to effectively fulfill the buffering function by passing a current corresponding to the inertial force of the optical moving body to the electromagnet during backward braking. Furthermore, since the current that flows during startup and braking is different, by flowing less current during startup than during braking, it is possible to moderately accelerate the scanning moving object so that no more external force is applied than necessary, and the startup operation is smooth. Therefore, the scanning speed can be increased with a simple configuration without generating vibration.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a schematic configuration of essential parts of an embodiment of an optical scanning device of the present invention, FIG. 2 is a schematic overall configuration diagram of an optical scanning system, FIG. 3 is a block diagram of a control device, and FIG. The figure shows the relationship between distance and repulsive force due to magnetic force, and FIG. 5 is a timing chart of rotation speed control of the scan motor and energization control for the electromagnet. 2, 3

Claims (1)

[Claims] (1) In an optical scanning device that scans a document by reciprocating an optical movable body installed in an optical system, an electromagnet is arranged near a stationary end of the optical movable body and at a position opposite to the traveling direction. At the same time, a permanent magnet is arranged at a position facing the electromagnet of the optical moving body, and a means is provided to supply different currents to the electromagnet when the optical moving body starts moving forward and when braking in the backward movement. Characteristic optical scanning device.