JPH0369973A - Image forming device - Google Patents

Abstract

PURPOSE:To detect the home position and step-out of a moving table by the use of one sensor by counting level changes by a detecting means for detecting a 1st or a 2nd member to be detected and deciding the developing position, etc., of each developing device when the moving table moves from the home position. CONSTITUTION:The device is provided with plural 1st members to be detected 2M, 2C, 2Y and 2BK corresponding to positions where respective developing devices 1M, 1C, 1Y and 1BK are mounted, the 2nd member 3 to be detected which is fixed at the home position of a moving body distant from the developing positions by the developing devices 1M, 1C, 1Y and 1BK, and the detecting means 2. When the moving table 1 moves from the home position, the number of the level changes and the changing time of the detection signal of the detecting means 2 which detects the 1st members to be detected 2M, 2C, 2Y and 2BK or the 2nd member 3 to be detected are counted to decide the developing position and the home position of the respective developing devices 1M, 1C, 1Y and 1BK. Thus, the home position and the step-out of the moving table 1 are detected by the use of one position sensor 2.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus that develops a latent image formed on a photoreceptor using a plurality of developing devices, and particularly relates to an image forming apparatus that develops a latent image formed on a photoconductor using a plurality of developing devices, and in particular, an image forming device that develops a latent image formed on a photoconductor using a plurality of developing devices. The present invention relates to an image forming apparatus that moves to a developing position.

[Conventional technology]

An electrophotographic color printer will be described as an example of a conventional image forming apparatus. This color printer is usually equipped with developing units for four colors: magenta, cyan, yellow, and black. These developing units are placed on a moving table, and the required color can be developed by moving the moving table. The latent image formed on the photosensitive drum is developed by bringing the device close to the photosensitive drum.

FIG. 11 shows a cross-sectional structure of a conventional image forming apparatus of this type.

In FIG. 11, the developing devices of each color are arranged at equal intervals on the moving stage L, Ic, IY, and IB, and the moving motor 12
The movable base is moved from side to side in the figure via a gear mechanism (not shown). When a developing device of a required color comes directly under the photosensitive drum 5, development of that color is performed according to instructions from the control circuit. Also, developing devices for each color IM, IC, IY,
A pulse motor is used as a moving motor to accurately and quickly move the IBK directly below the photoreceptor drum. Furthermore, in order to accurately move the position of each color developer to just below the photosensitive drum, a reference position is required, so a home position sensor 2 is provided around the moving table 1, and the home position A flag 3, such as a light shielding plate, for changing the output of the position sensor 2 is attached to the movable base 1. Each color developer IM uses this home position as a reference point.

The positioning of the moving table 1 is controlled by driving the moving motor at a rotational speed corresponding to the distance required to move the IC, IY, and IBK directly below the photosensitive drum.

Pulse motors used in moving motors have the characteristic that if a load greater than the specified drive load is applied, they will lose synchronization and will no longer rotate normally. From this,
If an obstacle such as something getting caught or caught in the moving platform 1 occurs and a load exceeding a specified value is applied to the moving motor, it is possible that step-out may occur.

If the moving operation of the moving table 1 continues in this state, accurate positioning control will not be possible, and not only will development not occur normally, but there is also the risk of damaging the developing device, etc. As shown in FIG. 11, a step-out detection sensor 1001 is arranged around the movable stage 1 to detect whether or not a step-out detection sensor 1001 is present, and a plurality of flags (shading plates) 10 are associated with each developing device.
02 is installed on the moving base 1, and by monitoring the cycle of the output of the step-out detection sensor 1001, which changes as the flag 1002 passes, it is confirmed that the moving motor 12 is rotating normally, for example.

(Problem to be solved by the invention) However, in the conventional device, the home position sensor 2
Since the system has two sensors, the step-out sensor 1001 and the out-of-step sensor 1001, the installation space for the two sensors is required, which increases the size of the device, increases manufacturing costs, and requires time and effort to adjust the position of the sensor. was there.

Furthermore, when the sensor, motor, etc. fails, there is a problem in that it is difficult to identify the location of the failure from the output f error of the sensor.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an image forming apparatus that can detect the home position and out-of-step of a movable base with a single sensor.

[Means to solve the problem]

In order to achieve such an object, the present invention provides a photoreceptor that moves in a fixed direction at a predetermined speed, a plurality of developing devices for developing a latent image on the photoreceptor, and a plurality of developing devices. a moving body that is mounted and moves relative to the photoreceptor; a plurality of first detected members corresponding to the mounting positions of the respective developing units; and a home position of the moving body that is distant from the developing position of the developing unit; a second detected member fixed to the movable body; a single detection means for detecting the first detected member and the second detected member when the movable body moves; The present invention is characterized by comprising a detection means for detecting the movement position and home position of each of the developing devices and detecting an abnormality in the drive source of the movable body. Further, the first detected member and the second detected member are light shielding plates having different widths in the moving direction of the moving body, and the detection means is a light sensor that detects passage of the light shielding plate. Features.

(Function) In the present invention, when the movable base moves from the home position, the number of times the level of the detection signal of the detection means that detects the first detected member or the second detected member changes and the time of the change are counted. It is possible to determine the developing position, home position, and position of each developing unit, and the normality of the drive source can be confirmed by changing the level of the detection signal. Further, when the movable body is to be moved from the developing position, the level change does not appear in the detection signal in the case of an abnormality in the drive source, so it is possible to specify the abnormality in the drive source and its occurrence position M. Furthermore, if there is no output of the detection signal at all, this indicates an abnormality in the detection means, so it is also possible to detect an abnormality in the detection means. In addition, by making the widths of the first detected member and the second detected member different, a difference occurs in the level change time of the detection signal, so that the first detection member and the second detection member can be distinguished from each other based on this level change time.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 shows the overall configuration of an electrophotographic image forming apparatus to which the present invention is applied.

In FIG. 2, reference numeral 1 denotes a movable stage of a horizontally movable developing device.
8 is installed. Further, a position sensor 2 is provided around the periphery of the moving table 1, and step-out detection flags 2M, 2G, and 2Y are provided for detecting step-out of the moving motor 12 at the developing position C6 on the back side of the moving table 1.

28K, home position flag for detecting the home position position3. A limit flag 4 is attached to detect the end of the moving table 1.

Next, what is the sequence of the entire image forming device, taking as an example the case of full color mode? Explain to JIL.

A photoreceptor formed on the surface of a photoreceptor drum 5 rotating in the direction of the arrow in the figure is uniformly charged by a charger 6. Next, under the control of the printer control circuit 28, a document (not shown) is scanned while being irradiated with the document illumination lamp 7. The light reflected from the document at that time passes through the lens system IO using the first mirror 8 and the folding mirror 9, and is imaged on the color image sensor 11.

Image exposure is performed on the photosensitive drum 5 by the laser beam E modulated by the magenta image signal color-separated by the color image sensor 11, and an electrostatic latent image is formed on the photosensitive drum 5. Thereafter, development is performed by the magenta developing device 1M, which has been fixed in advance at the developing position by the moving motor 12&:.

On the other hand, the paper feed guide 13. The transfer paper that has passed through the registration rollers 14 is transferred to an adsorption charger 15 in synchronization with a predetermined timing. Electrostatically by the contact roller 16,
It is wound around the transfer drum 17. The transfer drum 17 rotates in the direction of the arrow shown in the figure in synchronization with the photosensitive drum 5, and the developed image developed by the magenta developer 1M is transferred by the transfer charger 18. The transfer drum 17 continues to rotate and prepares for transfer of the next color (cyan in FIG. 1).

After the photosensitive drum 5 is neutralized by the charger 19 and cleaned by the cleaning member 20, it is charged again by the charger 6, and is then charged by the next cyan image signal.
Exposure is performed using the procedure described above. During this time, the printer control circuit 28 outputs a movement start signal to the movement control circuit 27, and the movement control circuit 27 rotates the movement motor 12 based on this signal to horizontally move the developing device in the direction of the arrow in the figure. Predetermined cyan development is performed when the image forming apparatus is placed at a predetermined development position.

Subsequently, the above processing steps are performed for yellow and black, respectively, and when the transfer of the four color images is completed, each charger 21
．． The static electricity is removed by 22. The image on the transfer paper is created by a charger 23.
After being recharged by the transfer drum 17, the transfer paper is separated from the transfer drum 17 by the separation claw 24, and transferred to the fixing device 2 by the conveyor belt 25.
Sent to 6. As a result, a series of full-color print sequences are completed, and a desired full-color print image is formed on the transfer paper.

FIG. 2 shows the structure of the developing device shown in FIG. 1 in an enlarged cross section.

In Fig. 2, when the moving motor 12 rotates CCW (clockwise) when viewed from the output shaft side, the developing device mounted on the movable table 1 moves in the direction of the arrow ■, and when it rotates CCW (counterclockwise). It will move in the direction of the arrow ■.

In addition, step-out detection flags 2BK, 2Y, 2G, 2M
The home position flag 3 and the home position flag 3 use light shielding plates of the same width, and the limit flag 4 that detects the end of the moving platform is
A light shielding plate having a width larger than the flag is used.

In this embodiment, the light blocking time of the flag is counted in the movement control circuit 27, and in the counting result, the limit flag 4
and other flags.

In addition, the second flag position to the left from the rightmost limit flag 4 is the installation position of the home position flag 3, and the home position flag 3 is identified by counting the number of days the flag has been detected after the limit flag 4 is detected. do.

FIG. 3 shows the circuit configuration of a movement control circuit 27 that performs home position detection and step-out detection as well as movement control of the developing device.

In FIG. 3, 301 is a central processing unit (CPII).
) This is a motor driver that generates two drive pulses based on the instruction signal from 302 and rotates the moving motor 12. 2 is an optical sensor that detects the home position and a step-out of the moving motor 12. When a flag attached to the moving base 1 blocks the detection surface of the sensor 2, the inverter 3
The voltage of the signal input from the sensor via 03 becomes high level. The output signal of sensor 2 is inverted by inverter 303 and input to CPII 302 .

Next, the home position detection operation after the power is turned on will be explained with reference to the flowchart of FIG.

First, when the printer is powered on (step S1), the CPU 302 in the movement control circuit identifies the output level of the position sensor 2 (step S2).

When the human power signal from the position sensor 2 is at a high level, the detection surface of the position sensor 2 is set to the step-out detection flag 2 shown in FIG.
M, 2C, 2Y, 28, home position flag 3. Determining that one of the limit flags 4 is blocking the CPII 302, the CPII 302 outputs an instruction signal to the driver 301 to rotate the moving motor 12 clockwise in the CW direction, and rotates the motor 12 at a constant low speed in the direction of the arrow ■ in FIG. The developing device is moved at the same speed (step 53).

Next, a built-in timer is activated in the CPLI 302 (step 514). When the rotation of the moving motor 12 is normal, the output level of the position sensor 2 changes from "high" to "
This change in output level is detected, and the built-in timer is stopped and reset (step 51).
7). Even if a certain period of time Tx has elapsed, the movement motor 12
When the CP does not rotate, the sensor output is always at a low level, so when the built-in timer counts the predetermined time, the CP
U 302 uses warning lamps, buzzers, indicators, etc.
An error message is displayed and the developing operation is stopped (steps 54 to 515→51B).

When it is detected in step S4 that the flag has come off the detection surface of the sensor, the movement motor 12 is rotated counterclockwise.
Rotate in the CW direction to move the developing device in the direction of the arrow ■ in FIG. If you did not interrupt (
519) It is determined that the developing device has not moved normally, that is, it is out of step, and an error message is displayed on a display section (not shown), and the developing operation is stopped (516).

The output of position sensor 2 becomes high level and rotates counterclockwise C.
When no operational abnormality is detected in the rotation of the CW, the built-in timer is reset to detect the type of flag currently passing through the position sensor 2, the built-in timer is started again, and the output of the position sensor 2 is set to high level. Count the time during which When this counting result exceeds TL for a certain period of time,
It is determined that the flag currently being passed is limit flag 4, and the moving motor 12 is reversed in the clockwise CW force direction (step S8→510→Sll).

Hereinafter, the number of flags passing through the position sensor 2 is counted by the number of level reversals, and when it is detected that the counting result is "2" (the number of level reversals is "4"), at that time the flags pass through the position sensor 2. The flag inside is identified as the home position sensor 3, the moving motor 12 is stopped, and the developing device is positioned at the home position (steps 512→513).

On the other hand, when it is determined from the count result of the built-in timer that the flag currently passing through the position sensor 2 is not the limit flag 4 (step 510), until the flag finishes passing through the position sensor 2, Step 58~
The SlO procedure is repeated. After passing the flag, the output of the position sensor 2 becomes low level, so the procedure progresses from step S8 → S9 → S5, the moving table 1 is moved in the direction ■ in FIG. 2, and the sensor position of the limit flag 4 is passed. The above procedure is repeated until .

The above operation can be expressed in a timing chart as shown in FIG.

In FIG. 5, symbol TD indicates step-out detection flag 2M, 2
It shows the time that C, 2Y, and 28K block the position sensor 2. The code TL indicates that the limit flag 4 is the position sensor 2.
Indicates the amount of time that is being blocked. The relationship between T and TL is To
<Becomes TL. Also, since the moving motor 12 uses a 5-phase pulse motor, there are 5 signal lines, but for the sake of clarity, in this diagram, it is shown whether it rotates CW (clockwise) or CCW (counterclockwise). ).

In Figure 5, after immersing the power supply in Taiku Fugu Tl, CPI
The movement motor 12 moves clockwise CW according to the instruction from I 302.
The rotation direction is reversed at timing T2 in response to detection of any step-out flag.

Therefore, the movable table 1 moves in the direction {circle around (2)} in FIG. 2, and each time the flag passes the position sensor 2, the built-in timer of the CPU 302 counts the time taken for the flag to pass. When this passing time exceeds a certain time TL (timing T5)
, the flag currently being passed is identified as limit flag 4 by the CPU 302 &:.

Next, the rotational direction of the moving motor 12 is reversed, and thereafter, the CPU 302 identifies the flags in the order of the step-out detection flag 2M and the home position flag 3 based on the change in the output of the position sensor 2. At the time when the home position flag 3 is detected (timing T7), the moving motor 12 is stopped, and the moving table 1 is located at the home position.

Next, step-out detection during a full-color printing operation will be explained with reference to the flowchart of FIG.

After the home position detection operation is completed (step 5101)
First, the moving motor 12 is rotated in the CCW direction until the magenta developing device 1M is located directly below the photosensitive drum 5, and the developing device is moved at high speed (Stella 5102).

The CPU 302 detects a change in the output level of the position sensor 2 (from low level to high level) (step 5103).
), confirm the normality of the moving motor 12. If the output of the position sensor 2 remains at a low level at this point, it is determined that the moving motor 12 is out of step, an error message is displayed on the display section (not shown), and the printing operation is stopped (step 5104).

When the rotation is normal, the step-out detection flag 2M stops at a position that blocks the detection surface of the position sensor 2, and the output of the position sensor 2 becomes high level. Next, a well-known control procedure for development is executed to start the development process (step 5105).

After magenta development is completed, the moving motor 12 is then rotated in the CW force direction to move the developing device until the cyan developing device ICh is located below the photosensitive drum 5 (step 51).
06).

Next, the output level of the position sensor 2 is checked to detect whether the moving motor 12 has stepped out of step (step 5107).
If the moving motor 12 is not out of step and the developing device moves normally, development is started (step 5108).

Thereafter, the yellow developing device IY and the black developing device IB)t are moved in the same manner as described above in step 5109.
5112), after detecting the presence or absence of step-out (step 51
10.5113), perform development (step 5ill,
5114). When the development with the black developer IBK is completed, move the developing device to the home position.Step 5
115), the developing operation is ended.

In this embodiment, the home position flag 3 and the step-out detection flags 2M, 2C, 2Y, and 28K have the same width, so no matter where the developing device is located, the limit flag 4, which has a width different from the above flag, is always used as the position sensor. The developing device is moved until it obstructs 2, the position of the developing device is confirmed, and then the developing device is moved to the home position.

However, as a second embodiment, as shown in FIG. 7, the width of the home position flag 3 is changed to a step-out detection flag 2M,
2[:, 2Y, 28 may be made wider and the developing device may be positioned at the home position using the home position flag. In this case, the step-out detection flag 2M,
The time T) IP during which the home position flag 3 is blocking the position sensor 2 is longer than the time To during which the position sensor 2 is blocked by 2G, 2Y, and 28K.

As a result, the home position flag 3 is set to the position sensor 2.
limit flag 4 is on the right side of position sensor 2.
Rather than moving the developing device until the home position flag 3 blocks the position sensor 2, the moving motor 12 is stopped when the home position flag 3 blocks the position sensor 2.

FIG. 8 shows a control procedure for determining the home position in the second embodiment.

Now, when the home position flag 3 is on the right side of the position sensor 2, the moving motor 12 is rotated in the CCw direction to move the developing device in the direction of the arrow ■ in FIG. 7 (step 5205), and the flag is on the right side of the position sensor. 2 is blocked (step S2G?).

If this count value is the specified value THP, this flag is determined to be the home position flag 3, and step 52
21) To stop/reset the timer count, step 5222) Rotate the moving motor 12 in the CW direction to move the developing device in the direction of the arrow ■ in FIG. Afterwards (step 5224), the moving motor is stopped (step 5213), and the home position detection operation ends. The drive timing of the moving motor 12 in the above operation is expressed in a timing chart as shown in FIG. 9.

Further, in the above embodiment, the position sensor 2 is fixed to the bottom plate of the printer body, and the step-out detection flag 2M is set.

2G, 2Y, 2BK, home position flag 3.
The limit flags 4 are each fixed to a moving table 1 and can move to the right or left with the moving table 1, but as shown in FIG. 10, each flag is fixed to the bottom plate and the position sensor 2 is attached to the moving table. Needless to say, it's a good thing.

〔Effect of the invention〕

In the present invention, the developing position of each developing unit is determined by counting the number of times the level of the detection signal of the detection means that detects the first detected member or the second detected member changes when the movable table moves from the home position. The home position can be determined, and the normality of the drive source can be confirmed by changing the level of the detection signal. Also,
When it is desired to move the movable body from the development position, if there is an abnormality in the drive source, no level change will appear in the detection signal, so the abnormality in the drive source and its occurrence position can be identified.

Furthermore, if there is no output of the detection signal at all, this indicates an abnormality in the detection means, so it is also possible to detect an abnormality in the detection means. In addition, by making the widths of the first detected member and the second detected member different, a difference occurs in the level change time of the detection signal, so that the first detection member and the second detection member can be distinguished from each other based on this level change time.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the overall structure of a color printer according to an embodiment of the present invention, FIG. 2 is a cross-sectional view showing the device structure according to an embodiment of the present invention, and FIG. 3 is a circuit configuration of a movement control circuit according to an embodiment of the present invention. 4 is a flowchart showing the control procedure for detecting the home position according to the embodiment of the present invention. FIG. 5 is a timing chart showing the home position detection timing according to the embodiment of the present invention. A flowchart showing a control procedure for detecting synchronization according to the embodiment, FIG. 7 is a sectional view showing the structure of the developing device according to the second embodiment of the present invention, and FIG. FIG. 9 is a timing chart showing the home position detection timing of the second embodiment of the present invention, FIG. 1O is a sectional view showing the structure of the third embodiment of the present invention, and FIG. 11 is a conventional FIG. 3 is a cross-sectional view showing an example configuration. 1...Moving table, 2...Position sensor, 3...Home position flag, 4...Limit flag, 1M...Magenta developer, LC...Cyan developer, IY...Yellow Developer, IBK...Black developer, 2M, 2C, 2Y, 28K...Out-of-step detection flag,
5... Photosensitive drum, 12... Movement motor, 27... Movement control circuit. 5 Shiko drum f This book shows a large cross-section of the actual device of the I row. (The circuit configuration of the wholesale circuit is shown in Figure 3. Figure 1. Figure 10

Claims (1)

[Scope of Claims] 1) a photoconductor that moves in a fixed direction at a predetermined speed; a plurality of developing devices for developing latent images on the photoconductor; a plurality of first detected members corresponding to the mounting positions of the respective developing units; and a second member fixed at a home position of the moving unit remote from the developing position of the developing unit. a member to be detected; a single detection means for detecting the first member to be detected and the second member to be detected during movement of the movable body; An image forming apparatus comprising: a detection means for detecting a moving position and a home position of the moving body and detecting an abnormality in a drive source of the moving body. 2) The first detected member and the second detected member are light shielding plates having different widths with respect to the moving direction of the moving body,
The image forming apparatus according to claim 1, wherein the detection means is an optical sensor that detects passage through the light shielding plate.