JPS6239835A - Zoom lens system driving device for copying machine - Google Patents

Abstract

PURPOSE:To execute a lens movement smoothly and with a high accuracy by containing a linear pulse motor in a frame for holding a zoom lens system, sending a pulse to its coil, and driving directly the frame for holding the zoom lens system. CONSTITUTION:The titled device is provided with a scale 1 which has cut a groove in parallel to the optical axis direction of a zoom lens system, and a linear pulse motor is contained in a part P corresponding to the scale 1 of a frame 2 for holding the zoom lens system. A pulse is sent to a coil A4 and a coil B6 from a linear pulse motor use driving device by a control use controller, and the linear pulse motor is moved to the prescribed direction and position. In this way, the frame 2 for holding the zoom lens system is driven directly without passing through a transfer mechanism by a chain, a wire, etc., moved to a necessary position with a precise accuracy and can be stopped.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a drive device for moving a zoom lens system of a variable magnification copying machine capable of enlarging and reducing in the optical axis direction.

(Prior Art) A drive device for moving a zoom lens system of a conventional variable magnification copying machine in the optical axis direction is disclosed in Japanese Patent Publication No. 1983-133.
No. 756, ``Variable Magnification Copying Optical Apparatus Capable of Enlarging and Reducing'' The invention will be explained based on the detailed description and drawings disclosed in No. 756.

As shown in FIG. 4, the zoom lens system includes a front group lens system 22 with negative refractive power, a front frame 24 that holds the front group lens system 22, and a rear group lens system with positive refractive power. 23, and a rear frame 25 that holds the lens group 23. To move the zoom lens system in the optical axis direction, the stepping motor 34 is used as a driving source to rotate the feed screw 35 and move the rear frame 25, thereby stopping the rear group lens system 23 at a designated magnification position. A device for moving the rear group lens system 23 to a designated magnification position will be described.

The rear frame 25 is provided with a feed screw 3 which is rotatable by being passed to the front plate 26 and the rear plate 27 as a driving source for a stepping motor 341.
5 and a nut 36 fitted into the feed screw 35 and fixed to the rear frame 25.

It moves as the feed screw 35 rotates. Then, by sending the number of pulses and the direction corresponding to the amount of movement of the rear group lens system 23 to the steering motor 34, the rear group lens system 23 moves to the specified magnification position and stops.

By the way, in a zoom type copying machine, vertical enlargement and reduction are usually performed by controlling the speed of lamp and mirror systems, and horizontal direction enlargement and reduction are performed using a front panel with negative refractive power, as described above. A group lens system 22 and a rear group lens system 2302 type zoom lens system having positive refractive power perform an imaging function as two groups.

By moving both in the optical axis direction according to the magnification ratio such as enlargement or reduction, a variable magnification image of the original is projected onto the photosensitive drum while keeping the distance from the original surface to the imaging surface constant. At this time, as a means for moving the zoom lens system in the optical axis direction, the conventional device that uses the output of the stepping motor 34 using a timing belt to rotate the feed screw 35 to move the zoom lens system has been described above.

(Problems to be Solved by the Invention) Conventional zoom lens system drive devices for copying machines have a structure in which the driving force of a drive motor is transmitted by a feed screw or a wire passed around multiple pulleys, so one mechanism is difficult to solve. It's complicated and expensive.

Backlash of gears and screws, which are components that are damaged.

Adjustment was necessary because the smoothness of power transmission was hindered by the magnitude of the tension in the wire. In other words, there was a first-order drawback.

(1) Since gears, feed screws, chains, wires, etc. are used as power transmission parts, the two mechanisms become complicated.

(2) Power transmission becomes unstable due to backlash caused by gears, chains, feed screws, etc., and the magnitude of wire tension.

SUMMARY OF THE INVENTION An object of the present invention is to provide a zoom lens system driving device for a copying machine that can move smoothly and with high precision without requiring mechanical mechanisms.

(Means for solving the problem) The movement of the zoom lens system in the optical axis direction is replaced with a scale with a groove in place of the feed screw or wire, and the frame that holds the zoom lens system is made to correspond to the above scale. Built-in linear pulse motor.

Drive directly. The positioning of the front group lens and the rear group lens is conventionally performed using a cam mechanism or the like as in the invention described in Japanese Patent Application Laid-Open No. 56-133756.

(Function) First, the principle of a linear pulse motor will be explained based on FIG. 3 in the case of a two-phase excitation method. In the same figure, S
is a slider, a yoke C around which coil A is wound forms poles 1 and 2, a yoke D around which coil B is wound forms poles 3 and 4, and a permanent magnet PM is installed between yoke C and yaw 20. is intervening.

The slider S is a movable part incorporating coils A and B and a permanent magnet PM. L is a scale with comb teeth 1, 2.
3,4. . . . is a fixed portion formed with a pitch P.

(1) First, (a) As shown in the figure, coil A.

When a current is passed through B as shown by the arrow, PM magnetic flux - coil magnetic flux = 00 magnetic flux is generated at poles 1 and 4, PM magnetic flux - coil magnetic flux = 00, and magnetic flux is generated at poles 1 and 4, PM magnetic flux - coil magnetic flux = 00. An attractive force occurs between the pole 4 and the teeth 6.

(2) Next, the drive device sends a pulse, and as shown in (B), current flows through the coil in the opposite direction to that shown in (B). At pole 2.4, PM magnetic flux + coil magnetic flux pole 1.3, PM magnetic flux - coil magnetic flux = 00 magnetic flux is generated, and pole 2 and comb teeth 3. A suction force is generated between the pole 4 and the comb teeth 6, and the slider S moves to the right by 1/4P of the comb teeth.

(3) Next, the drive device sends a pulse, and as shown in the figure (C), when a current is passed through the coil B in the opposite direction to the figure (B), the PM magnetic flux and the coil magnetic flux poles at poles 2 and 3. 1.4, PM1M flux - coil magnetic flux = 00 magnetic flux is generated, and pole 2 and <L12. A suction force is generated between the pole 3 and the comb teeth 5, and the slider S moves to the right by 174P of the comb teeth.

(4) Next, the drive device sends a υ pulse, and as shown in (d) the coil, (c) current flows through the coil in the opposite direction to that shown in the figure. At poles 1 and 3, PM magnetic flux + coil magnetic flux pole A magnetic flux of PM magnetic flux - coil magnetic flux = 0 is generated at pole 1 and comb teeth 2 and 4. A suction force is generated between the pole 3 and the comb teeth 5, and the slider S moves to the right by 1/4P of the comb teeth.

(5) Next, the drive device sends a pulse to coil B (
d) When a current is passed in the opposite direction to that shown in the figure, the current flow is the same as shown in the figure (a), and poles 1 and 4 have PM magnetic flux, 0 coil magnetic flux, and poles 2 and 3 have PM magnetic flux - coil magnetic flux = 00 magnetic flux. generated, pole 1 and comb teeth 2. A suction force is generated between the pole 4 and the comb teeth 7, and the slider S moves to the right by 1/4P of the comb teeth.

As described above, four pulses move the slider S by one pitch P of the scale L to the right.

In the present invention, a linear pulse motor that operates as described above is built into a frame that holds a zoom lens system, a scale with grooves is provided parallel to the optical axis direction of the zoom lens system, and the linear pulse motor is controlled by a controller. The pulse motor drive device (driver) moves the linear pulse motor to nine positions in a predetermined direction, thereby directly driving the zoom lens system.

(Example) As shown in Fig. 1, a scale 1 is provided parallel to the optical axis direction of the zoom lens system, and a linear pulse motor as shown in Fig. 2 is installed in the P section of the frame 2 that holds the zoom lens system. Built-in. In the same figure.

1 is a scale fixed in the optical axis direction. 3 is yoke A, 4
is coil A, 5 is yoke B, and 6 is coil B.

7.8 is an oil-impregnated metal, and 9 is a permanent magnet. Coil A3
．． Coil B6. Then, the controller sends pulses from the linear pulse motor drive device (driver), moves the linear pulse motor to one position in a predetermined direction, and directly drives the frame holding the zoom lens system to achieve the required precision with precision. Move to the position and stop.

(Effects of the Invention) (1) Since the zoom lens system of the present invention is directly driven by a linear pulse motor, transmission mechanisms such as gears, feed screws, chains, wires, etc. can be omitted, and the two mechanisms can be simplified. Increased reliability.

(2) Since it is driven by a linear pulse motor, the controller that controls the linear pulse motor instructs the linear pulse motor drive device (driver) to set the number of pulses and pulse rate according to the required distance and speed. Distance and speed can be set.

(3) Since the motor can be stopped at any position according to the groove pitch provided on the scale, it is possible to maintain high precision and high stopping precision whether moving forward or backward.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a front cross-sectional view of a linear pulse motor built in section P in Fig. 1, Fig. 3 is an explanatory diagram showing the principle of the linear pulse motor, FIG. 4 is a perspective view showing a zoom lens system driving device of a conventional copying machine. 1 scale 2: frame.

Claims (1)

[Claims] 1. In a variable magnification copying machine capable of enlarging and reducing, a scale (1) with grooves cut in parallel to the direction of optical axis movement of the zoom lens system is provided, and a frame (2) for holding the zoom lens system is provided.
1. A zoom lens system drive device for a copying machine, characterized in that a linear pulse motor corresponding to the above scale (1) is built into the drive device.