JPS59219738A - Variable power device for optical system of copying machine - Google Patents

Abstract

PURPOSE:To make highly accurate positioning of the carriage of a roof-mirror to a reference position, by setting the rotation of a worm wheel which is necessary for moving the roof-mirror to make variable power to <=1 revolution and detecting the reference position of the worm wheel for starting the revolution with a sensor fixed to a machine frame. CONSTITUTION:A lens bracket 1a carrying an image forming lens 1 can be displaced in the direction of the optical axis of the lens by means of a feed screw 3 which is rotated by a drive motor 2 through a gear. A feeler 1b fitted to the lens bracket 1a is highly accurately detected by an optical sensor 4 when the feeler 1b is at the position of variable power. A stepping motor is used as the drive motor 2 and the motor 2 is rotated by a preset pulse number by means of a variable power signal so that the lens is displaced rightward in the case of enlargement and leftward at the time of reduction. When the motor 2 is rotated, the feed screw 3 is rotated in a prescribed direction by a prescribed quantity and the lens 1 is positioned to a prescribed position corresponding to the variable power ratio.

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a variable magnification type copying system in which a lens of an imaging optical system and a roof mirror are moved in relation to predetermined positions by separate motors, thereby enabling multi-stage variable magnification copying. This article relates to the optical system variable magnification device of the machine.

As shown in FIG. 1, the exposure system of the prior art electrophotographic copying machine includes f7. A document 22 placed on the upper surface of a contact glass 21 is illuminated with a gold light source lamp 23, and the reflected light is reflected onto a first mirror 24, and second and third mirrors 25 and 26 which are orthogonal to each other and form a roof mirror.
, the imaging lens 11 is imaged at a fixed position on the photoreceptor 28 via the fourth mirror 27, and the light source lamp 23 and the first
An optical system is widely used in which a scanner 6 that integrally carries a mirror 24 and a carriage 5 that carries the second and third mirrors 25 and 26 ff are synchronized and moved at a speed of l:H to perform scanning. There is.

K, which enables variable magnification copying in this optical system, is carried out by displacing the lens l and the carriage 5 in the direction of the optical path in relation to each other. Conventionally, these displacements were performed by a variable magnification motor. The carriage 5 is moved by the cam according to the movement of the lens.
ff: No method was used to move it. However, in recent years, the variable magnification range has become wider as the magnification ratio has become more multi-stage, and as the variable magnification range has expanded, the amount of carriage movement has increased, and positioning with a cam has become a complete waste of space.
In addition, since the accuracy deteriorates, a system in which the lens and carriage are driven by separate motors has gradually been adopted.

In that case, the method of positioning the roof mirror carriage at the position corresponding to each magnification is generally to position the carriage by installing a sensor at the position of the carriage at constant magnification, +e, and each magnification change. However, the amount of displacement of the carriage is not very large, and it is not used in the transmission mechanism between the drive motor and the carriage.1.
It was difficult to obtain high accuracy due to the backlash of the gears.

Purpose: As described above, the present invention provides a method for highly accurate positioning of a roof mirror in an optical magnification device of an electrophotographic copying machine, which performs magnification-variable copying by displacing the lens, roof mirror, and the entire sky by separate motors. Figures 2 and 3 are top views of an embodiment in which the present invention is applied to the optical system explained in Figure 1. They are a figure and a front view.

Imaging lens 1'ff: A lens bracket la supported by a feed screw 3 rotated by a drive motor 2 via a gear
The filler lb attached to the lens bracket 1aK is detected with high precision by the optical sensor 4 at the same magnification position. A step motor is used as the drive motor.The feed screw 3 is rotated by the preset f and number of pulses so that the lens moves to the right in the figure when enlarging and to the left when reducing. By rotating the lens l by a predetermined amount in a predetermined direction, the lens l is positioned at a predetermined position according to the magnification ratio.'1. Ru. In this case, enlargement 1111 and reduction 1
111, it is expected that a feed error will occur due to the bank rack of the screw, so in order to completely prevent this,
It is best to always feed from one direction when stopped.

Original exposure scanning is performed by the scanner drive motor 20, which rotates the scanner drive pulley 13i, the turn pulley 12, the end fixed pulley (left) +O, the movable pulley 5' pivotally supported by the roof mirror carriage 5, and the variable magnification. Pulley 7,
The scanner 6 is fixed to the wire that forms a closed loop that returns to the original position via the turn pulley 14, the wire drive pulley 15 for variable magnification, the wire tension pulley 8, the moving pulley 5', and the end fixed pulley (right) ll. By driving the scanner 6 at the moving speed of the wire, the moving pulley 5
' Toko 21. This is done by simultaneously moving the K-coupled carriage 5 at a speed equal to that percentage. In addition, the code 9 is
It is a wire tension spring. During scanning, the wire drive boolean IJ15U for variable magnification is fixed and the wire does not move between the variable magnification pulleys 7 and 8.

The wire drive pulley 15 for variable magnification is fixed to the shaft of a worm wheel 18 driven by a stepping motor 19 for moving the carriage via a worm gear 17i. The wire drive boolean IJ 15 is integrally equipped with a tween 15a, which is detected by an optical sensor 16 at a reference position.

The displacement of the roof mirror carriage 5 for changing the magnification is achieved through the worm gear 17 and the worm wheel 18 by rotating the stepping motor 19'i5 in predetermined steps according to the magnification ratio while the motor 20 is stopped at the reference position. This is done by rotating the boot IJ15'z and moving the wire between the pulleys 7.8 to displace the movable pulley 5'. The circumferential length of the worm wheel 18 is set to be larger than the maximum displacement amount of the roof mirror carriage 5 from the reference position. Therefore, when the sensor 16 detects the tween 15a'jz, the carriage 5 is always at the reference position.

The circumferential speed of the wire drive pulley 15 is twice the amount of movement of the carriage 5, and the tween 15a is the wire drive pulley I.
Since it protrudes beyond the outer periphery of J15, the amount of movement in the circumferential direction of the end portion is more than twice the amount of movement of the carriage 5. Therefore, the accuracy of detecting the reference position of the carriage 5 is extremely high. In addition, since the variable magnification position is controlled by the number of steps of the stepping motor rather than by the sensor, there is no need to increase the number of sensors even when changing the magnification in multiple stages, and by decelerating with a worm gear, it takes up a small amount of space. The carriage can be positioned at multiple magnification positions with high precision.

The transmission device V (worm gear 17 toe worm wheel 18'ff) from the carriage moving stepping motor 19 to the wire drive boob IJI5 is used, so it is necessary to accurately position the stopper etc. using the sensor 16 and the number of steps of the motor. Scanner drive motor 2
This prevents the wire from becoming loose due to tension during scanning drive at zero.

In addition, as in the case of lens displacement described above, the positioning of the carriage when changing magnification from one magnification to another must be done in such a way that the direction of the force applied to the worm wheel from the scanner drive motor via the wire during document scanning coincides with the direction of the force applied to the worm wheel. By doing this from the same direction, it is possible to eliminate the decrease in accuracy due to worm gear backlash. This eliminates the need to return to the reference position each time the magnification is changed, and the carriage can be moved from one magnification changing position to another with extremely high precision.

Effects As described above, according to the present invention, it is possible to position the carriage of the roof mirror at the reference position and the variable magnification position with high precision.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an optical system of a copying machine to which the present invention is applied, FIG. 2 is a top view showing an embodiment of the invention, and FIG. 3 is a front view thereof. l゛... Lens 5... Roof mirror carriage 6... Original height scanner 15... Wire drive pulley for variable magnification 15tr=-Tween I6... Sensor 17°
°・Worm gear 18... Worm wheel 19
... Carriage movement motor 20 ... Scanner, drive motor 25, 26 ... 21st g3 mirror (roof mirror) 2
8...Photoreceptor

Claims (3)

[Claims] (1) The above-mentioned lens and roof mirror of the copying machine optical system which senses the light reflected from the original document illuminated by a light source through a YC system including a roof mirror and lens and forms an image on the body are separated, respectively. Move it in relation to a predetermined position with a motor! I
TJ, +l, a variable-magnification copying machine capable of variable-magnification copying)
Y: In a scientific magnification device that uses a worm gear and a worm wheel to move the roof mirror, the rotation f of the worm wheel required for the movement of the roof mirror to change the magnification is 1 rotation. 6. A variable magnification device as follows, characterized in that the rotation start reference position of the worm wheel can be detected and set by a tween rotating integrally with the worm wheel and a sensor fixed to the machine frame.6. . (2) The magnification drive motor of the roof mirror described above is a stepping motor, and the roof mirror is positioned by rotating the number of steps corresponding to the moving distance according to each magnification from the reference position t14-above. A variable power device according to claim 1. (3) The above-mentioned roof mirror positioning is always performed by rotation of the drive motor from one direction, and the direction is the same as the direction of the force applied to the worm wheel via the wire from the scanner 1 drive motor during document scanning. 2. A variable magnification device according to claim 2, characterized in that: