JP2600160B2 - Image output device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image output apparatus that forms a plurality of images on the same sheet while the sheet is conveyed by a sheet conveyance path.

[Conventional technology]

FIG. 5 is a view showing the configuration of the entire image output apparatus, and FIG. 6 is a view for explaining the mechanism of the paper transport unit. 11 is a laser optical system, 12 is a photoconductor, 13 is a developing device, and 14 is Cleaner, 15 is a fixing unit, 16 is a paper transport unit, 17 is a cassette tray, 18 is a chain, 19 is a gear, 20 is a motor, 21 is a gripper, 22 is a gripper position detection piece, 23 is a position sensor, and 24 is a home position. Show the sensor.

In the image output device shown in FIG. 5, the photosensitive member 12 is charged in advance, and then exposed by the laser optical system 11 to form an electrostatic latent image, and the developing device 13 develops the electrostatic latent image. The paper transport section 16 includes a gripper 21, a chain 18, and a motor 20 for driving the gripper 21, as shown in FIG. The paper is
The paper is sent out one by one from the cassette tray 17 to the paper transport unit 16 by a rubber roller or the like (not shown), and is gripped by the gripper 21. Then, when the gripped sheet passes below the photoconductor 12, an image developed on the photoconductor 12 is transferred to the sheet. Since the motor 20 of the paper transport unit 16 rotates at a constant speed, the paper is fed at a substantially constant speed and the images are sequentially transferred by the respective photoconductors 12. When four images are formed on one sheet of paper, the paper separates from the gripper 21 and the toner on the paper is fixed by the fixing device 15.
Since the surface speed of the photoconductor 12 and the transport speed of the paper transport unit 16 are controlled to be constant, when an image is formed at a fixed paper position, the position sensor 23 is used as shown in FIG.
It is necessary to detect the position of the sheet by detecting the gripper position detecting piece 22 attached to the gripper 21 to start the exposure of the laser optical system 11 at a certain timing.

[Problems to be solved by the invention]

By the way, in the image output device as shown in FIG. 5, when the paper is gripped and transported by the clipper 21 and the images on the respective photosensitive drums are transferred, the chain 18 supporting the gripper 21 and Low frequency vibration is generated by the gear 19, the motor 20, and the like. That is, in the case of the image output device as shown in FIG. 5, the motor 20 is rotating at a constant speed, but the chain 18 has a circumference of 2 m or more, and the chain 18 has a gripper made of metal. Although a plurality of 21s are provided, when they are driven, a mechanically low-frequency speed fluctuation occurs, and the low-frequency speed fluctuation propagates also to the paper gripped by the gripper 21. In this case, the vibration frequency is often 1 Hz or less, and if the timing is controlled for a certain period of time, the initial position of the developed image on the photoconductor transferred to the paper is shifted. This frequency and the magnitude of the displacement are It is represented by Here, Δx represents the amount of displacement, f represents the vibration frequency, and Δv represents the magnitude of the vibration. The frequency and magnitude of the vibration differ depending on the type of the paper transport unit 16, and the same type of the paper transport unit 16 also has a difference due to a difference in chain tension or friction. Therefore, even if an image is to be placed on the same point on the paper, there is a disadvantage that the low frequency vibration causes a shift. Further, when there are a plurality of grippers, there is a drawback that each sensor varies, and there is a problem in that an image is shifted by controlling for a certain period of time.

SUMMARY OF THE INVENTION The present invention is directed to an image output apparatus which eliminates the above-mentioned disadvantages and reduces the deviation of an image on a sheet.

[Means for solving the problem]

For this purpose, the present invention provides an image output for forming a plurality of images on a same sheet conveyed by a common sheet conveyance path by a plurality of image forming apparatuses each having a photoconductor and an optical system for writing an image on the photoconductor. In the apparatus, a plurality of paper gripping means for gripping and transporting the paper to the common paper transport path,
A plurality of sensors provided upstream of the image forming apparatus in the paper transport direction to detect the passage of the plurality of paper gripping means, and between the sensors for each of the paper gripping means from detection signals of the sensors. A timing control device for calculating and accumulating a transit time characteristic, and determining a timing of writing an image on a photosensitive member of the optical system of each of the image forming apparatuses based on the transit time characteristic. .

[Action]

In the image output apparatus of the present invention, the time characteristic of the paper transport unit moving for a predetermined distance when the paper transport unit is operating is measured by the measuring unit, and the timing from the paper position detection to the start of image formation is controlled using the measured data. Therefore, the timing is controlled by the measurement data including the low frequency vibration. Therefore, when a plurality of images are formed on the same sheet while the sheet is conveyed by the sheet conveying unit, the deviation of the images is reduced.

〔Example〕

 Hereinafter, embodiments will be described with reference to the drawings.

FIG. 1 is a diagram for explaining an embodiment of an image output device according to the present invention, FIG. 2 is a diagram for explaining a time measurement process, and FIGS. 3 and 4 are image outputs according to the present invention. It is a figure for explaining other examples of a device. In the figure, 1 is a home position sensor, 2 is a machine controller, 3 is a motor, 4 is a speed measurement circuit, 5 is a laser timing circuit, 6 is a position sensor, 7 is a cleaner, 8 is a photoconductor,
Reference numeral 9 denotes a developing device.

In FIG. 1, a machine controller 2 controls the entire image output apparatus.
The motor 3, the speed measuring circuit 4, and the laser timing circuit 5 are controlled while the home position sensor 1 detects the specified position of the sheet transport unit. The speed measurement circuit 4
As shown in FIG. 2, a signal from each position sensor 6 is detected, and data on the time when the same gripper passes through the same position sensor is obtained and averaged. The laser timing circuit 5 controls the start timing of the exposure of the laser optical system. The laser timing circuit 5 is operated after a time calculated in advance from the time when the gripper position detecting piece has passed the position sensor 6 according to each gripper. The system is controlled to start exposure. The position sensor 6, the cleaner 7, the photoconductor 8, and the developing unit 9 are respectively a position sensor 23, a cleaner 14, a photoconductor 12,
The image forming apparatus is the same as the developing device 13, and includes the cleaner 7, the photoconductor 8, and the developing device 9.

Next, the operation will be described. First, when the image output device is turned on, the machine controller 2 rotates the motor 3. Then, while the home position sensor 4 detects the specified position of the paper transport unit, the speed measurement circuit 2 uses the gripper position detection pieces (the gripper position detection pieces 22 shown in FIG. 6B) attached to the plurality of grippers. ) Is detected by the position sensor 6, and the time required to pass between the two position sensors is measured. This resolution is, for example, about 10 μm in terms of distance, depending on the paper transport speed. In this way, the paper transport unit is rotated several times or more, and the data of the time when the same gripper has passed the same position sensor is obtained by the speed measurement circuit 2, averaged, and the data is sent to the laser timing circuit 3, where it is stored. Keep it. After storing the time data in the laser timing circuit 3 in this way,
When the image output device is activated, the laser timing circuit 3 starts the exposure of the laser optical system after a lapse of a pre-calculated time from the time when the sensor position detecting piece passes the position sensor 6 according to each gripper. Control.

As described above, in the image output apparatus according to the present invention, the gripper of the member that grasps and conveys the sheet is between two position sensors corresponding to a plurality of marking units (laser optical system, photoconductor, developing device, cleaner, etc.). Is measured in advance, and the time data is processed to control the exposure start timing of the laser optical system, thereby reducing the deviation of the leading edge of the image when a plurality of images are transferred onto paper. .

It should be noted that the present invention is not limited to the above embodiment, and various modifications are possible. For example, in the above embodiment, the speed of the paper transport unit is measured by the elapsed time between two points. However, in order to obtain more accurate dynamic characteristics, a plurality of position sensors 6 are attached as shown in FIG. You need to take the time to travel between short distances. For example, when seven position sensors 6 are arranged at equal intervals as shown in FIG. 4,
The time to pass through the position sensor 6 can be measured from t ₁ to t _6. In the example of FIG. 3, a plurality of the position sensors shown in FIG. 5 are installed. However, as the position sensor, an optical system or a magnetic linear position sensor used for linear motion positioning is used. May be used.

〔The invention's effect〕

As is apparent from the above description, according to the present invention, when a plurality of images are formed by a plurality of image forming apparatuses on the same sheet conveyed by the common sheet conveying path, a plurality of sheet speeds upstream of each image forming apparatus are used. Since the image writing timing of the optical system is determined based on the section passing time obtained by the detection sensor, the image writing of the optical system is performed during the section passing time in which the speed fluctuation of the sheet conveying path is absorbed and the speed fluctuation of the sheet conveying path is not easily affected. The timing can be determined for each image forming apparatus, and it is possible to reduce the deviation of the leading end portions of the images when a plurality of images are transferred onto the same sheet. In addition, even if there are a plurality of grippers and each position sensor varies, it is possible to minimize the image deviation by using the averaged data.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining an embodiment of an image output device according to the present invention, FIG. 2 is a diagram for explaining a time measurement process, and FIGS. 3 and 4 are image outputs according to the present invention. FIG. 5 is a diagram for explaining another embodiment of the apparatus, FIG. 5 is a diagram showing a configuration of the entire image output device, and FIG. 6 is a diagram for explaining a mechanism of a sheet transport unit. 1 ... Home position sensor, 2 ... Machine controller, 3 ... Motor, 4 ... Speed measurement circuit, 5 ...
Laser timing circuit, 6 Position sensor, 7
Cleaner 8, photoreceptor 9, developing device.

Claims (1)

(57) [Claims] An image output apparatus for forming a plurality of images on a same sheet conveyed by a common sheet conveyance path by a plurality of image forming apparatuses each having a photoconductor and an optical system for writing the photoconductor image. In the above, a plurality of paper gripping means for gripping and transporting the paper to the common paper transport path, and detecting passage of the plurality of paper gripping means provided upstream of the image forming apparatus in the paper transport direction. A plurality of sensors, calculating and accumulating a transit time characteristic between the sensors for each gripping means of the paper from the detection signals of the sensors, and accumulating the transit time characteristics based on the transit time characteristics; An image output device, comprising: a timing control device for determining a timing of writing an image on a photoconductor.