JPH01251060A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the blurring of an image without decreasing the number of image formed sheets per unit time by altering a scanning starting position by a scanning means according to an image forming magnification. CONSTITUTION:In a device where the scanning means is moved at different speed corresponding to the image forming magnification, the scanning starting position by the scanning means is altered according to the image forming magnification. Namely, the starting position of a carriage 411 can be altered according to a copying magnification. In case of enlargement, the carriage 411 is made to start from a position close to the leading edge of an original and in case of reduction, it is made to start from a position far from the leading edge of the original. Thus, the step-out of a pulse motor 43 and the blurring of the image caused by the vibration of the carriages 411 and 412 in case of reduction can be prevented without decreasing the number of copied sheets per unit time.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to an image forming apparatus applied to, for example, an electronic copying machine.

(Prior Art) As is well known, a copying machine has a function of copying an original image directly onto a sheet of paper, or enlarging or reducing the original image to make a copy. Such enlargement and reduction copying of an original image is performed by changing the speed of a carriage that moves an optical system that exposes and scans the original.

That is, the moving speed of the carriage increases in the order of enlarged copying, same-size copying, and reduced copying.

In addition, the acceleration of the carriage is as shown in FIG.
It is the same regardless of the copying magnification, and the starting position of the carriage is also the same regardless of the copying magnification.

However, in such a device, if the start position of the carriage is moved closer to the starting point of reading the original in order to increase the number of copies per unit time at the same magnification, that is, the copying speed, the acceleration of the carriage will not be able to keep up in time when reducing the size. Scanning of the original begins before the vibrations due to acceleration have subsided, causing blur in the scanned image.To avoid this, if you accelerate suddenly, the motor that drives the carriage may step out or the carriage may vibrate. The image may become blurred if the image is not completely corrected.

On the other hand, if the starting position of the carriage is moved away from the original reading starting point, the above drawbacks can be avoided, but the copying speed becomes slower.

Therefore, there has been a need for something that eliminates image blurring caused by motor adjustment and carriage vibration during reduction without reducing the number of copies per unit time.

(Problems to be Solved by the Invention) As mentioned above, there is a need for something that eliminates image blurring without reducing the number of images formed per unit time, and reduces the number of images formed per unit time. An object of the present invention is to provide an image forming apparatus that can eliminate image blur without causing blurring.

[Structure of the Invention] (Means for Solving the Problems) The image forming apparatus of the present invention optically scans a document placed on a document table, and charges an optical image obtained by this scanning. A scanning means for forming an image on the applied image carrier, a moving means for moving this scanning means, an instruction means for instructing an image formation magnification, and scanning by the scanning means according to the image formation magnification instructed by this instruction means. A changing means for changing the starting position, a control means for moving the moving means at a speed corresponding to the image formation magnification instructed by the indicating means, a developing means for developing the image formed on the image carrier, and the developing means. The image forming apparatus is provided with a transfer means for transferring the image onto a material to be transferred.

(Function) In the present invention, the scanning means is moved at different speeds in accordance with the image forming magnification, and the scanning start position of the scanning means is changed in accordance with the image forming magnification.

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

FIGS. 2 and 3 schematically show an image forming apparatus of the present invention, such as a copying machine. That is, 1 is a main body of a copying machine, and a document table (transparent glass) 2 is fixed to the upper surface of the main body 1 to support a document. Fixed scales 21 are provided at both ends of the document table 2 to serve as a reference for setting the document. Further, near the document table 2, a document cover 11 and a work table 12, which can be opened and closed, are provided.

The original placed on the original table 2 is moved back and forth by an optical system consisting of an exposure lamp 4 and a mirror 5, 6, 7 along the lower surface of the original table 2 in the direction of arrow aSb. It is designed to be exposed and scanned. The light reflected from the original by the scanning of the optical system, that is, the light reflected from the original by the light irradiation of the exposure lamp 4 is reflected by the mirror 5.6.7.
After being reflected by mirrors 91.9□, 93
The light is reflected by the photoreceptor drum (image carrier) 10 and an image of the document is formed on the surface of the photoreceptor drum 10 .

The photoreceptor drum 10 rotates in the direction of arrow C in the figure, and the surface is first charged by the charger 11, and then an electrostatic latent image is formed on the surface by slit exposure of the image. This electrostatic latent image is made visible by adhering toner to it by a developing device (developing means) 121% 122 in which toner is stored.

On the other hand, the paper (transferring material) P is delivered from the selected upper paper feed cassette 131, middle paper feed cassette 132, or lower paper feed cassette 133 to the feed rollers 141, 142, 14.
3 and roller pairs 151, 152, and 153, the paper guide paths 11Ez and 162, 163 take out the sheets one by one.
The image is guided through the image to a pair of registration rollers 17, and guided to a transfer section by the pair of registration rollers 17. Here, the paper feed cassettes 131, 132, 1
33 is removably provided at the lower right end of the main body 1, and either one can be selected on the operation panel described later. In addition, each of the above paper feed cassettes 131
．． The cassette sizes are detected by cassette size detection switches 607, 602, and 603, respectively. The cassette size detection switches 6011602 and 603 are composed of a plurality of microswitches that are turned on and off according to the insertion of cassettes of different sizes.

The paper P sent to the transfer section comes into close contact with the surface of the photoreceptor drum 10 at the transfer charger (transfer means) 18, so that the toner image on the photoreceptor drum 10 is generated by the action of the charger 18. is transcribed.

The transferred paper P is electrostatically peeled off from the photoreceptor drum 10 by the action of the peeling charger 19 and placed on the conveyor belt 20.
The transferred image is conveyed by a fixing roller 21, which serves as a fixing device, provided at the end thereof, and the transferred image is fixed by passing therethrough. After fixing, the paper P is discharged to a tray 25 outside the main body 1 by a pair of delivery rollers 22, a sorting gate 23 operated as shown by the solid line, and a pair of paper discharge rollers 24. In addition, the photosensitive drum 1 after transfer
0, the residual toner on the surface is removed by the cleaner 26, and the residual image is erased by the static elimination lamp 27, so that the initial state is restored. Note that 29 is a cooling fan for preventing the temperature inside the main body 1 from rising.

FIG. 4 shows an operation panel (operation section) 30 provided on the main body 1.
This shows that. This operation panel 30 includes a copy key 31 for instructing to start copying, a liquid crystal display section 36 for displaying the number of copies, copy magnification, scanning guide, etc., a numeric keypad 32 for setting the number of copies, etc., and a same-size key for instructing to make a same-size copy. 33. A magnification change key 44 for changing the copy magnification displayed on the display section 36 in 1% increments in the reduction direction, and a magnification change key 44 for changing the copy magnification displayed on the display section 36 in 1% increments in the enlargement direction. It is constituted by a key 45. The copying magnification can be set between 65% and 154%.

FIG. 5 shows a drive mechanism for reciprocating the optical system. That is, the mirror 5 and the exposure lamp 4 are supported by the first carriage 411, and the mirror 6.7 is supported by the second carriage 41□.
The carriages 411 and 412 are guided by guide rails (not shown) and are movable in parallel in the direction of arrow aSb.

That is, the four-phase pulse motor 43 drives a pulley (not shown) via the shaft 44. This boo and the mirror 5 above
An endless belt 46 is stretched between the first carriage 411 that supports the mirror 6.7 and an idle pulley 45 fixed to the idler pulley 45, and one end of the second carriage 412 that supports the mirror 6. Fixed. Therefore, by rotating the pulse motor 43, the belt 4
6 rotates and the first and second carriages 411 and 412 move. Note that the moving directions of the first and second carriages 411 and 412 are controlled by switching the rotation direction of the pulse motor 43.

Further, the first and second carriages 411 and 412 are moved to predetermined positions (start positions according to the magnification) by driving a pulse motor 43 according to the copy magnification. When the copy key 31 is pressed, the lamp 4 is turned on, and the first and second carriages 411 and 412 are moved from the start position in the direction of arrow a (forward movement). When scanning of the original is completed, the lamp 4 is turned off, and the first and second carriages 411 s 412 move in the direction of the arrow (
(backward movement) and then returned to the starting position.

Further, a home position switch 54 is provided, which is a microswitch that is turned on by the second carriage 412 when the first and second carriages 410, 41□ move to the leftmost end (home position).

FIG. 6 shows the overall control circuit.

The main control unit 71 includes an operation panel 30 and various switches and sensors, such as the cassette size detection switch 601.
, 602, 603, or a high-voltage transformer 76 that detects input from an input device 75 such as the home position switch 54 and drives each of the chargers, the static elimination lamp 27, and the blade solenoid 26a1 of the cleaner 26.
The heater 23a1 of the pair of fixing rollers 23, the exposure lamp 4, the motor 43, etc. are controlled to perform the above-described copying operation.

The exposure lamp 4 is controlled by the main control section 71 via the lamp regulator 81, and the heater 23a is controlled by the heater control section 8.
The motor 43 is controlled by the main controller 71 via a motor driver 83.

The motor driver 83 is connected to the A phase, B phase, A phase, and B phase of each winding of the pulse motor 43, and controls the speed of the pulse motor 43 by switching the phases. As shown, the motor drive signal (A.

B, ASB) pull-up block resistor RB2
, RB3, amplifiers D1, ~D4, NPN transistors Q23, ~Q26 that switch the excitation phase of the pulse motor 43 according to the motor drive signal, and a resistor RB4 that limits the base current of the transistors Q2B, ~Q26. , and the transistors 02B, ~Q26
It is composed of Zener diodes ZD5 to ZD8 for protection.

As shown in FIG. 8, the motor drive signals outputted from the main control section 71 differ in phase shift between normal rotation and reverse rotation.

As a result, when a normal rotation signal is input, the pulse motor 4
The excitation phase of No. 3 switches in the order of AB→BA→AB-4BA, the pulse motor 43 rotates forward, and the first and second carriages 411 and 412 move forward (in the direction of arrow a). . Furthermore, when a reverse rotation signal is input, the excitation phase of the pulse motor 43 is switched in the order of AB-AB-BA→AB, the pulse motor 43 rotates forward, and the first and second carriages 411 and 412 move backward. It is designed to move (in the direction of the arrow).

Also, the number of rotations of the pulse motor 43 and the first and second
The moving speed of the carriages 411, 412 is proportional to the high frequency of the motor drive signal, and the first and second carriages 411, 412 move by rO, 25 mmJ per step.

Next, the copying operation of the present invention in the above configuration will be explained with reference to the flowchart shown in FIG. For example, when the power switch (not shown) is turned on now, the main control section 71 outputs 500 outputs to the motor driver 83.
Outputs pps motor drive signal (reverse rotation). As a result, the motor driver 83 drives the pulse motor 33 in the reverse direction to drive the first and second carriages 411 and 412.
Move in the direction indicated by the arrow (backward movement). Due to this movement, the second carriage 412 causes the home position switch 5 to
4 is turned on, the main control section 71 turns off the output of the motor drive signal (reverse rotation). Two seconds after the motor drive signal (reverse rotation) is turned off, the main control section 71 outputs a 500 pps motor drive signal (normal rotation) for 20 steps to the motor driver 83. As a result, the pulse motor 33
The first and second carriages 411.41
2 moves in the direction of arrow a (forward movement) by 20 steps and becomes ready. In this case, the first and second carriages 41
1.412 is 5mm (20 steps XO, 25mm)
It is moving in the direction of arrow a (forward movement).

In this state, the operator inputs the copying magnification using the same magnification key 33 and magnification change keys 34 and 35 on the operation panel 30. This selected magnification is input to the main control section 71. As a result, when the copy magnification is less than 100% (reduction), the main control section 71 outputs a motor drive signal (reverse rotation) of 500 pp8 for 10 steps to the motor driver 83. As a result, the pulse motor 33 is reversed by 21 steps, and the first and second carriages 4111412 are rotated by 1
It moves in the direction of the arrow (backward movement) by 0 steps and becomes ready. In this case, the first and second carriages 411%4
12 is moving 2.5 mm (10 steps x Q, 25 mm) in the direction of the arrow (backward movement). As a result, the starting position of the first carriage 411 becomes point A.

Furthermore, when the copy magnification is 101% or more (enlargement), the main control unit 71 outputs a 500 pps motor drive signal (normal rotation) to 1%.
Outputs 0 steps to the motor driver 83. As a result, the pulse motor 33 rotates forward by 10 steps, and the first
, the second carriages 411 and 412 move 10 steps in the direction of arrow a (forward movement) and become ready. In this case, the first and second carriages 411 and 412 have a diameter of 2.5 mm.
(10 steps xQ, 25 mm) Moving in the direction of arrow a (backward movement). As a result, the starting position of the first carriage 411 becomes 0 point.

In addition, when the copy magnification is 100% (same size), the main control unit 7
1 remains in the ready state. As a result, the starting position of the first carriage 411 becomes point B.

After setting the copy magnification as described above,
The operator inserts the copy key 31. Then, the main control section 7
1 outputs a motor drive signal according to the copying magnification to the motor driver 83.

For example, when the copy magnification is 65% (reduction), a motor drive signal such as rdJ shown in FIG. 9 is sent to the motor driver 8.
Output to 3. As a result, the first carriage 411 starts moving from the state where it is stopped at the start position A, accelerates from 0 pps to 3000 pps in 50 steps, and then accelerates to 800 pps at the moving speed r3000 ppsJ.
Drives in forward rotation at constant step speed. During this time, the original is exposed and scanned. After that, it decelerates in 50 steps and stops. When this forward movement is completed, the main control section 71 outputs a motor drive signal (reverse rotation) such as "d'" shown in FIG. 10 to the motor driver 83. As a result, the first
The movement of the second carriage 4111412 is started and 0p
After accelerating from ps to 5000pps, its moving speed r
It is driven in reverse at 5000 ppsJ, then decelerated and stopped. At this time, the first carriage 41. returns to starting position A. This backward movement has a total of 900 steps. Furthermore, during continuous copying, the above operation is repeated.

Furthermore, when the copy magnification is 154% (enlargement), a motor drive signal such as reJ shown in FIG. 9 is sent to the motor driver 83.
Output to. As a result, the first carriage 411 starts moving from the state where it is stopped at the start position C, accelerates from 0 pps to 1300 pps in 50 steps, and then drives forward at a constant speed of 780 steps at the moving speed r1300 ppsJ. do. During this time, the original is exposed and scanned. After that, it decelerates in 50 steps and stops. When this forward movement is completed, the main control section 71 outputs a motor drive signal (reverse rotation) such as "e'' shown in FIG. 10 to the motor driver 83. As a result, the movement of the first and second carriages 411 and 412 is started, and the 0pp
After accelerating from s to 5000pps, its moving speed r5
It is driven in reverse at 000 ppsJ, then decelerates and stops. At this time, the first carriage 41 is at the starting position C.
Return to This backward movement has a total of 880 steps.

Furthermore, when the copy magnification is 100% (equal magnification), a motor drive signal such as rfJ shown in FIG. 9 is sent to the motor driver 83.
Output to. As a result, the first carriage 411 starts moving from the state where it is stopped at the start position 8, accelerates from 0 pps to 2000 pps in 50 steps, and then drives forward at a constant speed of 790 steps at the moving speed r2000 ppsJ. do. During this time, the original is exposed and scanned. After that, it decelerates in 50 steps and stops. When this forward movement is completed, the main control section 71 outputs a motor drive signal (reverse rotation) such as "f'' shown in FIG. 10 to the motor driver 83. As a result, the movement of the first and second carriages 411 and 412 is started, and the 0pp
After accelerating from s to 5000pps, its moving speed r5
It is driven in reverse at 000 ppsJ, then decelerates and stops. At this time, the first carriage 411 is at the starting position B.
Return to This backward movement has a total of 890 steps.

A normal copying operation is performed in response to the exposure scan as described above.

Furthermore, when the magnification is changed from enlargement to reduction, the main control section 71 outputs a 5.0 Opps motor drive signal (reverse rotation) to the motor driver 83 for 20 steps, thereby moving the first carriage 411 to the starting position. is changed (moved) from rCJ to rAJ. Furthermore, when the magnification is changed from enlargement to normal magnification, the main control unit 71
ps motor drive signal (reverse rotation) for 10 steps to the motor driver 83, the first carriage 41. The start position of is changed (moved) from "C" to rBJ.

In addition, when the magnification is changed from reduction to enlargement, the main control unit 71 outputs a 500pps motor drive signal (normal rotation) to 2
By outputting 0 steps to the motor driver 83, the starting position of the first carriage 411 is changed (moved) from rAJ to "C". Furthermore, when the magnification is changed from reduced to equal magnification, the main control unit 71
By outputting the motor drive signal (normal rotation) of s to the motor driver 83 for 10 steps, the first carriage 4
11 start position changed (moved) from rAJ to rBJ
be done.

As described above, the starting position of the carriage is changed depending on the copying magnification. That is,
The carriage is started from a position close to the leading edge of the original when enlarging, and from a position far from the leading edge of the original when reducing. As a result, it is possible to eliminate blurring of images due to pulse motor adjustment and carriage vibration during reduction without reducing the number of copies per unit time.

In addition, although the case where a pulse motor was used as a scan motor was explained in the said Example, it is not limited to this.
Other motors may also be used.

[Effects of the Invention] As detailed above, according to the present invention, it is possible to provide an image forming apparatus that can eliminate image blurring without reducing the number of images formed per unit time.

[Brief explanation of the drawing]

1 to 10 show an embodiment of the present invention, in which FIG. 1 is a flowchart for explaining the main parts of the operation, FIG. 2 is an external perspective view of the image forming apparatus, and FIG. 4 is a plan view showing the configuration of the operation panel; FIG. 5 is a perspective view schematically showing the driving mechanism of the optical system; and FIG. 6 is the overall control circuit. 7 is a diagram showing the configuration of the motor driver, FIG. 8 is a timing chart for explaining the motor drive signal, and FIG. 9 is for explaining the start position and moving speed when the carriage moves forward. , and FIG. 10 are diagrams for explaining the moving speed and number of steps during the backward movement of the carriage,
FIG. 11 is a diagram for explaining the start position and moving speed of a conventional carriage during forward movement. DESCRIPTION OF SYMBOLS 1...Main body, 2...Document stand, 10...Photosensitive drum, 11...Charging device, 12...Developing device, 30
. . . Operation panel, 31 . . . Copy key, 32 . . . Display unit, 33 . ...First carriage, 412...Second carriage, 43...Pulse motor, 54...Home position switch, 71...
Main control unit, 83...motor driver. Applicant's agent Patent attorney Takehiko Suzue Figure 2 Figure 4

Claims (1)

[Scope of Claims] A scanning means that optically scans a document placed on a document table and forms an optical image obtained by this scanning on an image carrier to which a charge is applied; a moving means for moving the means; an instructing means for instructing an image formation magnification; a changing means for changing a scanning start position by the scanning means in accordance with the image forming magnification instructed by the instructing means; a control means for moving the moving means at a speed corresponding to an instructed image formation magnification; a developing means for developing the image formed on the image carrier; and a transfer means for transferring the developed image onto a transfer material. An image forming apparatus comprising: means;