JPH0517539B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention provides a method for scanning to prevent deterioration in the image quality of a copied image due to incomplete synchronization between the scanning of the document surface by a scanning system and the movement of the surface of a photoreceptor. Even if the scanning system and photoreceptor are driven by separate motors and the rotations of these motors are synchronized using closed-loop control, any deviation in the relative position of the scanning system and photoreceptor will cause the optical path of the reflected light from the document surface to change. Adjusting the inclination angle of the transparent plate placed inside according to the amount of deviation,
The present invention relates to an exposure position control device for a copying machine that corrects deviations in the exposure position.

[Prior art]

In a copying machine that obtains a copy through each process of scanning the original surface, exposing, developing, transferring, and fixing, it is necessary to completely synchronize both the scanning of the original surface and the movement of the photosensitive surface to obtain a good copy image. This is particularly important in multi-transfer type copying machines for color copying.

Conventionally, as a means of synchronizing the scanning of the document surface by the scanning system (consisting of a light source, reflector, mirror, etc.) and the movement of the photoreceptor (in most cases, the rotation of the photoreceptor drum), there has been a method of driving both systems. It is known that the power source (motor) is shared and the power transmission mechanism is provided separately. However, in this method, the structure is complicated, the loss within the power transmission mechanism cannot be ignored, and it is difficult to always maintain a specified accuracy due to mechanical play, etc. In the case of variable size copying, there are disadvantages such as the speed switching mechanism becoming more complicated.

In addition, the drive sources for both are independent, and each PPL
There is a method to synchronize these rotations using closed-loop control, but the response characteristics are generally slow due to the large mass of the scanning system and photoreceptor, and to improve this, it is necessary to increase the motor speed. There are problems such as an increase in size, an increase in the price of the product, and an increase in power consumption.

[Object and structure of the invention]

The present invention has been made in view of the above, and provides quick response characteristics without making the device larger or less economical, and also allows for a rational response even when the amount of deviation of the exposure position is large. To be able to compensate for this, the scanning system and photoreceptor are driven by separate motors, and the rotation of these motors is synchronized by closed-loop control, yet still introduces an excursion in the relative position of the scanning system and photoreceptor. When this occurs, the amount of deviation is detected as the difference between the moving speed of the scanning system and the moving speed of the photoreceptor, and the inclination angle of a transparent plate placed in the optical path of the light reflected from the document surface is adjusted to the amount of deviation. It is an object of the present invention to provide an exposure position control device for a copying machine which adjusts accordingly and thereby corrects the deviation of the exposure position.

Hereinafter, the exposure position control device for a copying machine according to the present invention will be explained in detail.

〔Example〕

Figures 1, 2 and 3 illustrate one embodiment of the invention.
In these figures, reference numeral 1 denotes a scanning system that scans the surface of a document (not shown) while irradiating it; a lamp (illumination light source) 2; a reflector 3 that focuses the light and illuminates the surface of the document; It is composed of a first mirror 4 that guides reflected light from the mirror toward a moving mirror system 5, which will be described later. Reference numeral 5 denotes a movable mirror system that guides the reflected light from the document surface guided by the first mirror 4 to the lens 23, and is composed of a second mirror 6, a third mirror 7, and pulleys 8a and 8b. Move in the same direction as this at 1/2 the speed.
Reference numeral 24 denotes a fourth mirror that guides the reflected light from the document surface, which is focused by the lens 23, to the surface of the photosensitive drum 14 and forms an image thereon.

The photosensitive drum 14 is a drive motor (not shown).
The scanning system 1 and the moving mirror system 5 are both driven by a motor 13a,
Controlled to repeat scan and return.
The driving force of the motor 13a is transmitted to the drive shaft 9 by the pulley 12, belt 25, and pulley 26. Also, pulleys 10a and 10b are fixed to the drive shaft 9, and extend wires 21a and 21b together with pulleys 20a and 20b fixed to the device body, respectively, and the scanning body 1 is transmitted via these wires. It moves along a guide rail (not shown) by the driving force. Note that here, the drive motor 13b (FIG. 3) of the photosensitive drum 14 and the motor 13a that drives the scanning system are controlled in a closed loop so that their rotations are synchronized, but the details will be described later.

15 is a transparent plate (consisting of a transparent flat member) that controls the exposure position (position of the original image) on the photoreceptor drum surface 14; one end of the plate is connected to a drive pulley 16; (not shown), and its rotation angle is controlled by a step motor 18 via a belt 26 and a pulley 17. The control of the step motor 18 will be described later.

19a and 19b are pulleys 10a and 19b, respectively.
The encoders are directly connected to the rotating shafts 9 of 10b and 11 and the rotating shafts of the photoreceptor drums 14, and play the role of detecting the respective scanning speeds and rotational speeds, and as described later, by integrating these speeds, the respective The moving distance of the scanning system 1 and the surface of the photoreceptor drum 14 can be known.

FIG. 2 is a drawing explaining the function of the transparent plate 15.
Here, the straight line shown by the two-dot chain line is the path of light passing through the light-transmitting plate 15, and the one-dot chain line is the normal to the surface of the light-transmitting plate 15 at the point of incidence of the light, and n ₀ and n ₁ are The refractive index of air and the material of the light transmitting plate, t, means the thickness of the light transmitting plate 15, respectively. θ is the angle of incidence of light (from a different perspective, it is the rotation angle of the transparent plate 15), and θ' is the angle of refraction. When θ = o (normal incidence), the light travels straight as shown in Figure 2 A, but when θ'≠o, the transmitted light is refracted as shown in Figure 2 B, and therefore Later, a lateral deviation x (perpendicular to the direction of incidence) is generated in the optical path. To express this quantitatively, it becomes x=sin(θ−θ′)/cosθ′t θ′=sin ⁻¹ (n ₀ /n ₁ sinθ). Here, when θ, θ'<1, xt(1-n ₀ /n ₁ )θ, and x is proportional to θ. As is clear from the above ideas, the exposure position on the surface of the photoreceptor drum 14 can be controlled by controlling the rotation angle θ of the light-transmitting plate 15, and conversely, if the amount of deviation of the exposure position is known, the light-transmitting This can be corrected by adjusting the rotation angle θ of the plate 15.

Next, FIG. 3 shows the configuration of the control section of this apparatus, including the rotation angle control section of the transparent plate 15 and the drive motors of the scanning system 1 and photoreceptor drum 14 (each with one
3a and 13b). Of these, the rotation angle control section of the transparent plate 15 detects the moving speed of the scanning system 1 and the photosensitive drum 14 using encoders 19a and 19b, and based on this detects the exposure position due to incomplete synchronization between the two. A calculation unit 2 that calculates the amount of deviation, further calculates the rotation angle of the transparent plate 15 suitable for compensating this, and outputs this as a command value to the next process.
7. Consists of a transparent plate drive motor drive circuit 28 which outputs an appropriate number of pulses to the slap motor 18 based on the command value. The calculation unit 27 also includes a speed difference comparator 27a that compares the outputs of the encoders 9a and 19b to detect a difference in moving speed between the scanning system 1 and the surface of the photoreceptor drum 14, and a speed difference comparator 27a that compares the outputs of the encoders 9a and 19b to detect a difference in moving speed between the surfaces of the scanning system 1 and the photoreceptor drum 14; The speed difference for calculating the displacement amount - the deviation amount for calculating the rotation angle of the transparent plate 15 necessary to correct the deviation amount based on the value of the deviation amount of the exposure position - - Consisting of a rotation angle conversion circuit 27c.

The details of the closed loop control circuit 30 will be explained with reference to FIG.
and 13b), encoders 31a and 31b, respectively, which are directly connected to these rotating shafts and output frequencies according to their rotational speeds, and waveform shaping circuits 32a, which shape these into pulse signals with predetermined waveforms. and 32b, phase comparators 33a and 33b, respectively, which compare the phases of these outputs and a reference phase signal to be described later and output a DC value (positive or negative) proportional to the phase difference, and a triangular wave generator 37.
a and 37b, comparators 38a and 38b, respectively, which compare the above-mentioned respective phase difference signals with these triangular waves and convert both phase difference signals into control voltages of constant polarity that increase or decrease around a reference value; and both drive motors 13a and 13b
The drive circuits 39a and 39b respectively drive the oscilloscopes, a reference frequency generator 34, a multiplier 35, and a frequency divider 36. The output of the reference frequency generator 34 becomes a reference phase signal for the phase comparators 33a and 33b, and the output is directly sent to the phase comparator 33b, and the output of the reference frequency generator 34 is sent to the multiplier 35 and the frequency divider 3 to the phase comparator 33b.
Input after going through step 6. The multiplier 35 and the frequency divider 36 serve to maintain the moving speed ratio of the scanning system 1 and the surface of the photosensitive drum 14 at a predetermined value. In addition, the third
The drive motor 13b of the photosensitive drum 14 shown in the figure and the encoders 31a and 31b built in the two drive motors 13a and 13b, respectively, are not shown in FIG.

In the above configuration, when an original is placed on the platen glass and the start key is operated, the moving system 1 starts scanning while irradiating the original surface (not shown), and at the same time, the reflected light from the original surface is It is reflected by the first mirror 4 on the scanning system, then reflected again by the second and third mirrors (6 and 7, respectively) of the moving mirror system 5, and guided to the lens 23. The reflected light from the document surface is collected here, reflected by the fourth mirror 24, and after passing through the transparent plate 15, is imaged on the surface of the photoreceptor drum 14, forming an electrostatic latent image there. do. The electrostatic latent image is then subjected to development, transfer, and fixation steps (none of which are shown) (in a multi-transfer copying machine, after these steps are repeated multiple times), it is copied. The remaining paper is ejected to the outside of the machine.

Next, closed loop control of the rotational synchronization of the drive motors 13a and 13b of the scanning system 1 and the photosensitive drum 14, respectively, will be described with reference to FIGS. 3 and 4. The rotation speed and rotation angle of both drive motors 13a and 13b are detected through the frequency and phase of the outputs of encoders 31a and 31b directly connected to these rotation axes, and these outputs are converted into predetermined waveforms ( The output pulses are shaped into a rectangular waveform pulse train and input to phase comparators 33a and 33b, respectively. First, control of the drive motor 13b of the photoreceptor drum 14 will be explained. A highly stabilized pulse train of constant frequency is output from the reference frequency generator 34 and input to the phase comparator 33b, where the phase is compared with the output of the waveform shaper 32b.
When the drive motor 13b is rotating at a predetermined rotation speed and rotation angle, the output of the phase comparator 33b is zero, so the comparator 38b outputs the value of the half cycle of the output of the triangular wave generator 37b. In response, the drive circuit 39b outputs a reference voltage, and the drive motor 13b continues to rotate at a predetermined speed. Furthermore, when the drive motor 13b rotates at a predetermined speed or below with a lag behind the predetermined phase, the output of the waveform shaper 32b (that is, the encoder 31b) is out of phase with respect to the reference phase signal (output of the reference frequency generator 34). Due to the delay, the phase comparator 33b
outputs a negative DC value proportional to the amount of phase delay.
Therefore, the output of the comparator 37b increases, and the drive circuit 39b outputs a value equal to or higher than the reference value, so that the drive motor 13b speeds up and its rotation speed or rotation angle reaches a predetermined value. pulled back. Conversely, when the rotation speed of the drive motor 13b becomes excessive or the rotation angle advances too much, the phase comparator 33b outputs a positive DC value, so the output of the comparator 39b also decreases and the output of the drive circuit 39b decreases. Therefore, the drive motor 13b is decelerated and the rotation speed or rotation angle is returned to a predetermined value. That is, the rotation speed and rotation angle of the drive motor 13b are locked based on the output of the reference frequency generator 34. The rotation of the drive motor 13a of the scanning system 1 is similarly locked to the output of the reference frequency generator 34, but it is possible to copy at variable magnification (0.71, 0.82, 1.41 times, etc.).
In such cases, it is necessary to maintain the moving speed ratio of the scanning system 1 and the surface of the photosensitive drum 14 at a predetermined value,
This can be dealt with by appropriately selecting the multiplication rate (xn) of 5 and the frequency division rate (x1/m) of the frequency divider 36.

The rotations of the two drive motors 13a and 13b are synchronized by the closed-loop control described above, but since the masses of the scanning system 1 and the photoreceptor drum 14 are quite large, when these motors are started or their rotations are In the event of a disturbance, it is inevitable that there will be some time delay before complete synchronization is restored. In this way, the deviation of the exposure position caused by the remaining incomplete synchronization can be corrected by adjusting the rotation angle of the transparent plate 15, which will be described below. In the configuration shown in FIG. 3, the moving speeds of the scanning system 1 and the surface of the photosensitive drum 14 are detected by encoders 19a and 19b, respectively, and the instantaneous value of the speed difference between the two is detected by a speed comparator 27a in the calculation section 27. Detected. The amount of deviation of the exposure position based on this speed difference, in other words, the difference in the moving distance between the two is obtained by integrating the speed difference with respect to time, and this calculation is performed by the speed difference-deviation amount converter 27c.
Processed by Next, the deviation amount-rotation angle converter 27c calculates the rotation angle of the transparent plate 15 necessary to correct this based on the deviation amount (output value of 27c), and commands this value. It is output as a value to the transparent plate drive motor drive circuit 28. The transparent plate drive motor drive circuit 8 sends a number of rotation pulses to the step motor 18 according to the amount of rotation angle.
The step motor 18 rotates by a predetermined amount in a predetermined rotation direction. Step motor 18
The rotational force is transmitted to the drive pulley 16 through the drive pulley 17 and belt 26 shown in FIG. The amount of deviation of the image exposure position is corrected. Thereafter, the above-mentioned operation is repeated at regular time intervals, and each time the transparent plate 15 changes its posture, the deviation of the exposure position on the photoreceptor drum 14 is corrected, and good copy image quality is always maintained. In addition, since the transparent plate 15 is extremely lightweight, its response characteristics are quick.

Considering the cooperative relationship between the closed loop control of the scanning system drive motor and photoreceptor drive motor and the transparent plate rotation angle control in the exposure position deviation correction operation in the frequency domain, we can see that Closed loop control will be in charge of control in a relatively low frequency range, and rotation angle control of the transparent plate, which has an extremely small mass to be controlled, will be in charge of high frequency range.

That is, when starting up or when rotation is disturbed, each closed loop of the scanning system and photoreceptor independently performs control to approach the reference speed. This is a control that follows at a relatively low frequency.

At this time, the amount of deviation between the scanning system and the photoreceptor is
It is extremely small compared to the low frequency component (error) in the speed control, so the adjustment range of the rotation angle of the transparent plate is small, and the mass is also small, so the drive frequency of the step motor can be made extremely high. It is possible to constantly and rationally correct the amount of positional deviation at high speed.

Incidentally, if an encoder is attached to the rotating shaft of the step motor 18 that rotationally drives the transparent plate 15 and feedback control is performed, the response accuracy of the step motor 18 to the command value can be further improved.

〔effect〕

As explained above, according to the exposure position control device for a copying machine of the present invention, each of the scanning system and the photoreceptor is driven by a separate drive motor, and their rotations are synchronized by closed loop control, and even then, scanning When a deviation occurs in the relative position of the system and the photoconductor, the inclination angle of the transparent plate placed in the optical path of the light reflected from the document surface is adjusted according to the amount of deviation, thereby increasing exposure. Since the positional deviation is corrected, quick response characteristics can be obtained without increasing the size of the device or increasing the product price, and even when the deviation of the exposure position is large, it can be rationally corrected. This has made it possible to obtain good quality copied images.

[Brief explanation of the drawing]

FIG. 1: An embodiment of the present invention. FIG. 2: An explanatory diagram of the structure and function of the transparent plate. FIG. 3: An explanatory diagram showing the configuration of a control section in one embodiment of the present invention. Figure 4...
FIG. 2 is an explanatory diagram showing the configuration of a closed-loop control circuit for a scanning system and a drive motor for a photosensitive drum. Explanation of symbols: 1... Scanning system, 2... Lamp, 3... Reflector, 4... First mirror, 5... Moving mirror system, 6... Third mirror, 7... Seventh mirror, 8a, 8
b...Pulley, 9...Drive shaft, 10a, 10
b... Kifpustan, 11, 12... Drive pulley,
13a...Scanning system drive motor, 13b...Photoconductor drive motor, 14...Photoconductor drum, 15...Transparent plate, 16, 17...Drive pulley, 18...Step motor, 19a, 19b...Encoder, 20
a, 20b...Pulley, 21a, 21b, 22
a, 22b...drive wire, 23...lens, 24...
4th mirror, 25, 26...belt, 27...calculating section, 27a...same speed comparator, 27b...same speed difference -
Deflection amount converter, 27c... Deflection amount-rotation angle converter,
28...Transparent plate drive motor drive circuit, 30...Closed loop control circuit, 31a, 31b...Encoder, 32
a, 32b... Waveform shaping circuit, 33a, 33b... Phase comparator, 34... Reference frequency generator, 35... Multiplier, 36... Frequency divider, 37a, 37b... Triangular wave generator, 38a, 38b... Comparator, 39a ,39b...
drive circuit.

Claims (1)

[Scope of Claims] 1. A scanning system, a photoconductor, a motor that drives the scanning system, a motor that drives the photoconductor, a means for detecting the rotational speed of the motor that drives the scanning system, and a device that drives the photoconductor. means for detecting the rotational speed of the motor;
Comparing a reference frequency generating means for generating a signal with a frequency corresponding to the reference speed of the motor, and a reference speed of the scanning system drive motor based on the rotational speed of the motor that drives the scanning system and the frequency from the reference frequency generating means. a closed loop control circuit for a scanning system drive motor that controls the rotational speed of the motor based on the difference between the two; and a reference for the photoconductor drive motor based on the rotational speed of the motor that drives the photoconductor and the frequency from the frequency generating means. An exposure position control circuit for a copying machine comprising a closed loop control circuit for a photoconductor drive motor that compares the speeds and controls the rotational speed of the motor based on the difference, the exposure position control circuit being arranged in the optical path of the scanning light reflected from the document surface;
A light transmitting plate that adjusts the exposure position of the photoreceptor based on the refractive index and the arrangement angle, a detection means that detects the moving speed of the scanning system, a detection means that detects the moving speed of the photoreceptor, and the moving speed of the scanning system. a calculation unit that compares the moving speed of the photoreceptor with the scanning system, converts the speed difference into a deviation amount of the movement of the scanning system and the photoreceptor, and converts the obtained deviation amount into a rotation angle of the transparent plate; 1. An exposure position control device for a copying machine, comprising means for controlling an arrangement angle of a light-transmitting plate based on a rotation angle signal of the light-transmitting plate output from the light-transmitting plate.