JPS58139163A - Original scanner - Google Patents

Abstract

PURPOSE:To improve the rise characteritics and the inversion characteristic of an original scanner, by turning off a clutch when a DC motor rises or is switched to normal rotation and reverse rotation and turning on the clutch after the DC motor reaches a set rotation number. CONSTITUTION:When a copy switch is turned on, a DC motor 1 starts normal rotation. When it is detected by an encoder 1-1 that the rotation number of the motor 1 reaches the first set rotation number alpha, a signal to turn on a clutch 2 is outputted from a controlling part 3, and the driving force of the motor 1 is transmitted to a reading part 5 through a driving pulley 4a and a wire 4b, and the reading part 5 starts to go forward in the direction of an arrow A. When scanning of an original 6 is completed by movement of the reading part 5, a signal to turn off the clutch 2 is outputted from the controlling part 3 by turning-on of a limit switch 8, and a reverse rotation command signal for the motor 1 is outputted simultaneously or after a certain delay time.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a document scanning device such as a copying machine or a facsimile transmitter.

Conventionally, induction motors and pulse motors have been used as drive sources for reciprocating document scanning means such as optical systems that move relative to a fixed document table or document tables that move relative to a fixed optical system. One way to solve this problem is to attach an encoder to a DC motor and use it to control it.

When used in the low speed range, it follows load fluctuations well and provides a somewhat satisfactory drive performance, but
When the required rotational speed ranges from a low speed range to a high speed range, or when scanning a document at a high speed is required, the start-up time of the motor becomes a problem. In other words, the movement of the document scanning device during the time until the motor connected to the document scanning device reaches a constant rotation speed and becomes stable cannot be used for scanning the document and becomes a run-up. There is a problem in that the faster the scanning speed is, the more the number of scans per unit time increases. Furthermore, since the run-up distance is large, the machine dimensions also become correspondingly large.

In addition, since the load fluctuation when reversing the document scanning means is a large load on the motor shaft, the gear head must also be large and have sufficient strength.Furthermore, in order to shorten the run-up distance, the motor However, all drive power supplies had to be of large capacity, resulting in an increase in cost.

The present invention has been made in view of the above points, and an object thereof is to provide a document scanning device using a DC motor with a simple structure that improves the rise characteristics and reversal characteristics of the document scanning device.

An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a schematic explanatory diagram of an embodiment of the document scanning device according to the present invention, and FIG. 2 shows the motor and clutch of the device shown in FIG. 1, with the vertical axis representing the number of revolutions per unit time and the horizontal axis representing time. This is a timing chart.

In Fig. 1r, a clutch 2 is connected to the output shaft of a driving DC motor, and a DC motor/4CH encoder/
-/ is installed. The output side of the control section 3 is electrically connected to the input side of the DC motor and the clutch 2, and the output side of the h1 encoder /-/ is connected to the input side of the control section 3. Clutch control output side Kl
d For example, Boo IJ p a is connected.

A wire 4b is wound around the pulley paK, and this wire tI-b is connected to a document reading section j that slides on a sliding section (not shown) via an idler pulley 4'c@1l-d*4''. Therefore, the driving force of the DC motor l is transmitted to the drive boolean IJpa via the clutch 2, and is transmitted from the drive pulley≠a to the reading section j via the wire 4b. The reading section j is moved back and forth in the direction indicated by A'.
/, Syrah! -2, lens j-3. Solid-state image sensor
(CCD), etc. A document table 7 on which a document B is placed is fixedly arranged above the moving path of the reading section j. A sensor and a limit switch are arranged at the starting point and end point of the forward movement (movement in the A direction) of the reading section j, respectively, and the output side of each is connected to the input side of the control section 3.

In the configuration as described above, the first point is to explain its operation.
This will be explained with reference to the figure and the first episode. 1 First,
When a signal to start reading the original is input by turning on a switch (not shown) for single-sheet copying or continuous copying, a predetermined voltage set by the control unit 3 is applied to the first
The rotational speed α, r, p, m.

The DC motor begins to rotate forward. The rotation speed of the DC motor / is determined by the encoder /-/ to the first set rotation speed α,
When it is detected that r and p0m have been reached, the signal from this encoder /-l is input to the control unit 3.
A signal is output from which the clutch 2 is engaged. As a result, the driving force of the motor l is transmitted to the reading section j via the drive pulley lla and the wire tb, and the reading section! starts forward movement in the direction of arrow A shown in FIG. Further, as soon as the clutch is connected, the rotation speed of the DC motor is set to a second set rotation speed β, r, p8m, which is set without changing the input voltage to the motor according to a signal output from the control unit 3.

(β is smaller than α). Therefore, the load on the motor shaft is reduced, and the forward movement of the reading section j is rapid and smooth.

The distance between the forward movement starting point position and the reading start position of the leading edge of the document 1 can be reduced. Incidentally, before the reading section j reaches the reading position of the leading edge of the document I, the number of revolutions of the motor is β.

When the limit switch comes into contact with the limit switch and the limit switch is turned on, an ON signal is input to the control section 3, and this signal causes the control section 3 to output a signal to disengage the clutch 2. Then, the clutch 2 is disengaged, and after a certain delay time or at the same time that the signal for disengaging the clutch 2 is output, the control unit 3 outputs a reverse rotation command signal for the DC motor 2, and the direction of the input voltage to the motor 2 is changed. changes, the DC motor is reversed, a predetermined voltage set by the control unit 3 is applied, and the third rotational speed is r, r, p, m.

(r is larger than α and β). The DC motor l is rotated at this third set rotation speed 1. r, p, m.

When the encoder /-/ detects that the
A signal is input from the encoder /-/ to the control unit 3, and the control unit 3 outputs a signal to close the clutch 2, which closes the clutch 2, and the reading unit moves in the AI direction at a higher speed than the forward speed. Start to retreat.

At this time as well, when clutch 2 is connected, the motor Q
The number of revolutions per hour for j time is δ r, pom, (γ〉δ〉
It is also possible to change the input voltage to the motor by giving a signal β). In either case, the load on the motor shaft is reduced.

Then, when the sensor detects that the reading section j has reached the forward movement starting point position, a signal from the sensor is input to the control section 3. A signal for disengaging clutch 2 is output, and clutch 2 is disengaged. At this time, in the case of single-sheet copying, since the switch for single-sheet copying is turned on in advance, a stop command signal is simultaneously output from the control unit 3 to the DC motor l based on the on signal of this switch and the signal from the sensor. , stop the DC motor. In the case of continuous copying, the switch for continuous copying is turned on in advance, so clutch! At the same time or after a certain delay time, when the switch is turned off, the controller 3 turns on the DC motor/
A normal rotation command signal is outputted to , and the DC motor l rotates in the normal direction again at the first set rotation speed set by the control unit 3. Then, when the encoder /-/ detects that the DC motor l has reached the first set rotation speed, the clutch 2 is connected as described above, and the reading unit jk'i is started again for scanning and reading the original. Commencement of forward movement. In addition, when the reading section j moves forward, the document B is illuminated with the lamp 3-1, and the Schiller j-, 2,
A document image is formed on a solid-state image sensor t-<z by a lens j-3, photoelectrically converted by a solid-state image sensor j-1, and visualized by a printer (not shown). Although the present invention has been described with the beamer section and part of the printer separated, the present invention can also be applied to a method in which each section is dividedly driven by several DC motors even in a normal copying machine. It can be applied as is. moreover,
It is effective to arrange mechanical dampers at the start and end points of the movement path of the reading section j to dampen shocks when the reading section j is stopped or reversed. □ In addition, the present invention fixes the reading section 5 and both ends of the wire 4b.
The present invention can also be applied to an apparatus that scans and reads a document by connecting the document table 1 to the document table 7 and moving the document table back and forth. It can also be used in ordinary copying machines that use an electrophotographic photoreceptor instead of a CCI as a photoreceptor.As described above, according to the present invention, the rise characteristics at high speeds and the impact during forward/reverse switching can be improved. Problems that would be difficult to control using a DC motor alone can be solved, and stable optical scanning becomes possible. Furthermore, the motor, gear head, drive power source, etc. can be made smaller because the impact caused by the reversal of the moving direction of the scanning means, etc., is alleviated on the motor. Furthermore, since the run-up distance can be reduced, the number of scans per unit time can be increased, and the machine body can also be downsized, resulting in lower costs and higher reliability.

[Brief explanation of the drawing]

FIG. 1 is a schematic explanatory diagram of an embodiment according to the present invention, and FIG. 2 is a timing chart of the motor and clutch of the device shown in FIG. 1. 0/...DC motor, 2...Clutch, 3...Control unit, j...Optical system reading unit, g...Limit switch% (position detection means)...
・Sensor, (position detection means) /-/...Encoder (rotation speed detection means), patent applicant Canon Co., Ltd.

Claims (1)

[Claims] A DC motor that rotates in forward and reverse directions to reciprocate the movable original scanning means along a predetermined path, a clutch that connects and disconnects the output of the DC motor to the movable original scanning means, and a clutch that connects and disconnects the output of the DC motor to and from the movable original scanning means. a control section that controls the rotation speed of a DC motor to a set rotation speed, the control section transmitting a signal to disengage the clutch at startup of the DC motor and switching between forward and reverse directions; Document scanning device 0, characterized in that it outputs a signal to close a clutch after the number of rotations per unit time of a DC motor reaches a set number of rotations.