JPH04216260A - Motor controller - Google Patents

Abstract

PURPOSE:To obtain a satisfactory starting characteristic without enlarging the device by disconnecting a position loop corresponding to control velocity or a monochromatic mode. CONSTITUTION:This device is composed of a first mirror 103, second mirror 104, third mirror 105 and lens 106 or the like, and when exposing an original image onto a photosensitive object 110 by moving a scanner while providing a velocity loop and the position loop at a servo motor for the drive, the position loop is disconnected from a control system corresponding to the control velocity so as to improve the starting characteristic without changing an approach run position. This control is enabled even in the monochromatic mode as well.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device for controlling a scanner motor used to drive a scanner of a color copying machine.

0002

2. Description of the Related Art Generally, in an electrophotographic copying machine, the document side is fixed, and a scanner consisting of a lamp and an optical system is moved back and forth along the document to read the document. The scanner is returned to its home position after each reciprocation and always moves from the home position to the starting position. By the way, the run-up distance from the scanner's home position (stop position) to the leading edge of the document is as shown in FIG.
In the full color mode, the length is, for example, 41 mm, and in the black and white mode, the length is set to increase as the magnification is changed toward the reduction side where the scanning speed becomes faster. This is because a normal black and white copying machine scans by speed control using only a speed loop as shown in Figure 8, whereas a copying machine with a full color mode superimposes toner.
This is because positioning control with a minor velocity loop is required, and as shown in FIG. 9, responsiveness such as rising is poor. Generally, it is said that a rise time of 4 to 6 times is required compared to the case of only a velocity loop. Therefore, with a prescan length similar to that of a black-and-white copying machine, "image distortion" occurs at the leading edge of the image, as shown in Figure 10.
or "magnification error" (in the example of FIG. 10, the perfect circle is an ellipse). Therefore, JP-A-61-1455
As shown in Japanese Patent Application No. 40 and Japanese Patent Application Laid-Open No. 62-192735, the scanner start position is moved after changing the positions of the mirror and lens. Also, Unexamined Japanese Patent Publication No. 6
No. 0-8813 deals with this problem by performing servo control at the time of startup.

0003

However, in the above-mentioned prior art, since the scanner start position is moved, there is a problem that the size of the machine in the left-right direction varies greatly. For example, in the example in Figure 7, the starting position is extended by 46 mm, so the 46/
The machine becomes larger by 2=23mm. Also, JP-A-60
In Publication No. 8813, since servo control is performed during scanner scanning, it tends to become unstable due to chattering, variations in switching time, etc.

The present invention has been made in view of the above, and an object of the present invention is to obtain good start-up characteristics without increasing the size of the device.

[0005]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a motor control system that controls a servo motor for driving a document scanner used in an image forming apparatus by a control system having a speed loop and a position loop. In the apparatus, there is provided a motor control device provided with a control means for separating the position loop from the control system according to the control speed of the document scanning member.

[0006] Furthermore, a servo motor used in an image forming apparatus having a color mode and a black-and-white mode, and which drives a document scanner with different scanning speeds in the color mode and the black-and-white mode at the same magnification, has a speed loop and a position loop. The present invention provides a motor control device which is controlled by a control system provided with the present invention, and is provided with a control means for separating the position loop from the control system when in the monochrome mode.

[0007]

[Operation] In the motor control device according to the present invention, the position loop is cut off at the start of scanning of the document scanner, and only the velocity loop is left, thereby improving the responsiveness and securing the start-up time. This eliminates the need to change the run-up position as in the past, making it possible to reduce the size and weight of the device.

Furthermore, by separating the position loop from the control system in the monochrome mode, position alignment control becomes unnecessary. As a result, image quality deterioration is eliminated, and since the separation operation can be performed while the scanner is stopped, control instability is not caused.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a sectional view showing a reading section of a color copying machine to which a motor control device according to the present invention is applied. As shown in FIG. 1, the reading section includes a contact glass 101 on which an original is placed, an exposure lamp 102 that illuminates the reading area of the supplied original, and a first mirror 103 that reflects the reflected light from the reading section in the horizontal direction. , a second mirror 104 that reflects the light from the first mirror 103 downward;
A third mirror 105 that reflects the light from the mirror 104 in a direction opposite to the light emitted from the first mirror 103; this third mirror 1;
A lens 106 that is movably disposed in the output optical path of the lens 105 and focuses the optical image on the surface of the photoreceptor 110;
4th mirror 1 that reflects the light from 06 to the photoreceptor 110
07. A color separation filter 108 is disposed in the output optical path of the fourth mirror 107 and inserts a filter color (blue, green, red) corresponding to the developed color, separating the space between the reading system and the color copying mechanism. However, each of the reading systems includes a dustproof glass 109 that prevents dust from entering the reading system. The exposure lamp 102, the first mirror 103, the second mirror 104, and the third mirror 105 constitute a scanner, and integrally move back and forth in the horizontal direction as shown in the figure in response to scanning. Further, the lens 106 moves in the left-right direction depending on the magnification ratio.

In the above configuration, when a document is automatically carried onto the contact glass 101 by the ADF (automatic document feeder) 111 and set in a fixed position, the scanner starts moving and feeds the document from one end to the other. Scanning starts toward the end, and the accompanying reading light passes through the photoreceptor 11 along the path of first mirror 103 → second mirror 104 → third mirror 105 → lens 106 → fourth mirror 107 → color separation filter 108.
0, and exposure (formation of an electrostatic latent image) is performed. At this time, first, the first color filter is inserted into the optical path by the color separation filter 108. The color separation filter 108 is 1
The filter color is switched each time exposure is performed.

[0011] Through this exposure, an electrostatic latent image is formed on the photoreceptor 110, and the image is developed using a first color in a developing device (not shown). At the same time that the developed toner image (visible image) reaches the transfer position, recording paper of a specified size is sent out from a paper feed cassette (not shown) and rotated adjacent to the photoreceptor 110. It is wrapped around a transfer drum (not shown) that is attached to the transfer drum. The rotation of the photoreceptor 110 causes the first color toner image on the photoreceptor 110 to reach the transfer position, and the photoreceptor 110 rotates at the same time that the leading edge of the recording paper reaches the transfer position. The toner image on the transfer drum is transferred onto the recording paper by the electrostatic attraction force of a transfer charger (not shown), and the toner image is rotated while being attracted to the transfer drum.

On the other hand, exposure corresponding to the second color is started,
An electrostatic latent image is formed on the photoreceptor 110 through the second color filter of the color separation filter 108 . This electrostatic latent image is developed with a second toner color by a developing device, and the transfer drum rotates while adsorbing the recording paper at the same timing as this toner image reaches the transfer position. , the second color toner image reaches the transfer position in synchronization with the timing when the leading end reaches the transfer position, and the toner image is transferred onto the recording paper onto which the first color has been transferred.

Thereafter, the third color and then the fourth color are transferred as described above, resulting in full color transfer. Once all colors have been transferred, a separate charger (not shown)
By driving, the recording paper is peeled off from the surface of the transfer drum and conveyed to a fixing device (not shown). The fixing device fixes the multi-transferred toner image of a plurality of colors onto the paper using heating and pressure means. The recording paper that has been fixed is discharged to a paper discharge tray (not shown).

Here, the original scanning body 111 is driven by a servo motor having a minor loop of speed as shown in FIG. 2, and a control circuit that performs positioning by position feedback. That is, the control system includes an adder 2 that adds and subtracts the position command and the position feedback value.
01, element 202, adder 203 that adds and subtracts its output value and speed feedback value, servo driver 204 that performs control according to this addition output, this driver 204
A servo motor 205 is driven by a timing pulse generator 206 that is attached to the rotating shaft of the servo motor 205 and generates an electric signal (pulse) at every fixed angle of rotation, and a resistance value is determined according to the rotation of the servo motor 205. The position sensor 207 changes and outputs a voltage corresponding to the change as position feedback. Then, the function of the system in FIG. 2 becomes a three-dimensional transfer function as shown in FIG. Furthermore, the rise characteristics in this case are as shown in FIG. 4 or 5. In Figure 4, characteristic A shows the rise when the color mode is the same magnification, characteristic B when the color mode is changed to 50% magnification, and characteristic C is the rise when there is a loop at each position when the magnification is changed to 50% in the black and white mode. . Further, characteristic D shows the rise when the magnification is changed to 50% in the color mode, and characteristic E shows the rise when there is no position loop at the time when the magnification is changed to 50% in the monochrome mode. In the present invention, the position loop in the block diagram of FIG. 3 (or FIG. 2) is broken when black and white mode is selected. As the simplest example, this can be achieved by setting the feedback gain in FIG. 3 to zero.

FIG. 6 shows an example of a position loop disconnection circuit, which is mainly composed of an operational amplifier 601, with a resistor 602 for setting the gain and a capacitor 603 connected in parallel and inserted between the negative phase input terminal and the output terminal. has been done. Furthermore, a switch 604 for disconnecting the position loop is connected between the negative phase input terminal and the input line. Note that the resistor 605 is an input resistor that is involved in setting the gain. The feedback gain of this circuit is R2/
It is represented by R1. Setting this to 0 can be achieved by changing R1 → ∞ or by turning off a switch mechanism such as a relay or analog switch when switching modes. By this, two speed loops only as shown in FIG.
It becomes equivalent to the next control system. Although the positioning accuracy (steady deviation) decreases, the responsiveness is greatly improved, resulting in rising characteristics like characteristics D and E in FIG. 4. Here, an example is shown in which the line speed in color mode and black and white mode is approximately doubled, and the effect is tremendous.
There is no need to change the run-up distance to secure the start-up time as shown in Japanese Patent No. 45540. For this reason,
Good characteristics can be obtained without increasing the size of the machine. Furthermore, in the case of black and white mode, good image quality can be obtained without performing alignment control. Furthermore, since the switching is performed while the scanner is stopped, there is no need to switch during scanning as in Japanese Patent Application Laid-Open No. 60-8813, and control instability does not occur.

[00016] In the above explanation, the feedback gain is set to 0, but it is not necessary to completely set it to 0, and the ratio of R2 and R1 may be changed depending on the mode. Furthermore, in a drive system that is discretely controlled by software processing, such as software servo, the same effect can be obtained by separating the position feedback loop using software. For example, avoid using the encoder pulse count used in position control in calculation processing (soft routine)
It is possible to achieve this by

00017

[Effects of the Invention] Since the present invention is constructed as described above, it achieves the following effects. In the motor control device according to claim 1, the motor control device controls a servo motor for driving an original scanning member used in an image forming apparatus by a control system having a speed loop and a position loop, wherein the control speed of the original scanning member is Since a control means is provided to separate the position loop from the control system in accordance with the above, it is possible to reduce the size and weight of the apparatus without changing the run-up position.

[0018] In the motor control device according to the second aspect, the servo is used in an image forming apparatus having a color mode and a black-and-white mode, and drives a document scanner with different scanning speeds in the color mode and the black-and-white mode at the same magnification. In a motor control device that controls a motor by a control system having a speed loop and a position loop, a control means is provided for separating the position loop from the control system in the monochrome mode, so image quality deterioration can be eliminated, and control It does not cause instability.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a reading section of a color copying machine to which a motor control device of the present invention is applied.

FIG. 2 is a characteristic diagram showing a speed loop included in the motor control device for the document scanner shown in FIG. 1;

FIG. 3 is a control block diagram of a tertiary system corresponding to the velocity loop of FIG. 2;

FIG. 4 is a characteristic diagram showing the rise characteristics of the three-dimensional transfer function in FIG. 3;

FIG. 5 is a step response characteristic diagram of the positioning control circuit.

FIG. 6 is a circuit diagram showing a position loop disconnection circuit according to the present invention.

FIG. 7 is an explanatory diagram showing the distance relationship of movement of the scanner.

FIG. 8 is a control block diagram of a secondary system included in a normal black-and-white copying machine.

FIG. 9 is a step response characteristic diagram of a secondary system corresponding to FIG. 8;

FIG. 10 is an explanatory diagram showing image distortion caused by a delay in the rise time of the tertiary control system.

[Explanation of symbols]

103 1st mirror 104 Second mirror 105 Third mirror 106 Lens 107 4th mirror 108 Color separation filter 110 Photoreceptor 111 Automatic document feeder 204 Servo driver 205 Servo motor 601 Operational amplifier 602 Resistance 603 Capacitor 604 Switch 605 Resistance

Claims (2)

[Claims] 1. A motor control device for controlling a servo motor for driving a document scanning member used in an image forming apparatus by a control system having a speed loop and a position loop, comprising:
A motor control device comprising: a control means for separating the position loop from a control system according to a control speed of the document scanning member. 2. A servo motor used in an image forming apparatus having a color mode and a black-and-white mode, and which drives a document scanner with different scanning speeds in the color mode and the black-and-white mode at the same magnification, is provided with a speed loop and a position loop. What is claimed is: 1. A motor control device controlled by a control system comprising a control system, further comprising a control means for separating the position loop from the control system when in the monochrome mode.