JPH0549110B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Technical Field> The present invention relates to a device that controls the position of transferring a toner image formed on a photoreceptor onto a sheet of paper based on the sheet feeding timing.

<Prior Art and Its Disadvantages> FIG. 3 shows a schematic structure of a general copying machine.
A photosensitive drum 1 is installed approximately at the center inside the main body of the copying machine, and around this, a charging charger 2, a developing device 3, a transfer charger 4, a cleaner 5, a static elimination charger 6, and a static elimination lamp 7 are arranged in the order of the copying process. ing. A glass plate document table 8 on which a document is placed is installed on the top surface of the copying machine body, and an optical system 9 is installed below the document table 8 to transmit reflected light from the document to the photosensitive drum 1. . The reflected light of the image enters between the charger 2 and the developing device 3.

A paper cassette 10 is inserted into the lower right part of the main body of the copying machine, and a paper feed roller 11 is installed above the leading end of the paper cassette 10. A paper conveyance path is provided at the bottom of the copying machine main body, and sheets are fed into this paper conveyance path from the tip of the paper cassette. This paper conveyance path includes a PS roller 12, a paper guide 14, a conveyor belt 15, etc., and the conveyor belt 1
A fixing device 16 is installed on the left side of 5. P.S.
The roller 12 temporarily stops the leading edge of the paper fed from the paper cassette 10. Fixing device 16
A paper discharge roller 17 for discharging the paper discharged from the fixing device 16 to a paper discharge tray 18 is installed on the left side. A paper sensor 13 is installed in front of the PS roller 12 on the paper transport path to detect when the paper has been transported to this position.

In the copying machine configured as described above, when the copying process is started, scanning of the document table 8 and rotation of the photosensitive drum 1 are started, and at the same time, one of the uppermost sheets of paper stored in the paper cassette 10 is fed. roller 1
1 onto the conveyance path, and PS roller 1
It is transported to the second position (point P). The optical system 9
By scanning the original and rotating the photoreceptor drum 1, an image of the original on the original platen 8 is exposed on the surface of the photoreceptor drum 1 at a point Q. The photoreceptor moving to the position of point Q is uniformly charged by the charger 2 immediately before it, and the charge is removed in accordance with the amount of exposure to form an electrostatic latent image. Become. As the photosensitive drum 1 rotates, this electrostatic latent image is developed into a toner image by the developing device 3. This toner image is transferred to the copy paper at a position (point R) opposite to the transfer charger 4 by corona discharge of opposite polarity of the transfer charger.

Here, in order to copy the position accurately, the leading edge of the original image and the leading edge of the paper must be fed to point R at the same time, but if the paper fed from the paper cassette 10 onto the conveyance path is If paper is directly fed to point R without stopping once, the toner image will reach point R after a considerable amount of time has passed after the paper reaches point R. Therefore, an image is transferred to the paper with a very delayed image in the copying direction. The start of rotation (paper feeding) of the PS roller 12 must be delayed until exposure has progressed to some extent.

In order to correct this misalignment, typical copying machines make the paper wait at the position of the PS roller 12 until the copying process has progressed to a point where it is acceptable to start copying the paper, so that the leading edge of the copied image is aligned with the leading edge of the paper. A method is adopted in which paper feeding is started when the paper has moved to a position where matching can be achieved. The time during which the paper is kept waiting at point P as described above is called the delay time. There are approximate values for this delay time depending on the model of the copying machine, but the PS roller 12
The optimum value varies depending on the model due to variations in the operation of the machine, etc., and the optimum value for the model is stored in the control section at the time of adjustment. The optimum value is called the inherent delay time of the copying machine.

In order to perform the above paper feeding timing control, the copying machine is equipped with a control section as shown in FIG. This control unit has a CPU 20, a ROM 21 connected to the CPU 20 for storing programs, etc., and a RAM 22 for storing specific delay time, mode setting data, etc., and the PS roller 12 and paper sensor 13 are connected to the CPU 20. . The RAM 22 is backed up by a battery 23 so that the memory is not lost even when the power is turned off. Further, a photo sensor 24 is connected to the interrupt terminal INT of the CPU 20. This photo sensor 24
outputs "H" every time it detects a slit in the rotary plate 25, causing the CPU 20 to perform an interrupt routine. This rotating plate 25 has slits at equal intervals and is configured to rotate in synchronization with the rotation of the photosensitive drum 1.

The interval between the slits is equal to the photo sensor 24 passing period T when the photosensitive drum 1 is rotating at a constant speed.
The pulse period T is determined by, for example, the process speed (the speed at which the surface of the photoreceptor drum 1 is exposed).
If it is 100mm/s and the resolution of tip adjustment is 0.5mm, then the setting should be T=0.5/100=5ms.

Therefore, the inherent delay time stored in the RAM 22 is not stored in seconds, but when the allowable signal is
The pulse count is stored as the number of pulses from when it is input to the CPU 20 until the PS roller 12 is turned on (after the paper is conveyed to point P and the paper sensor 13 is turned on). For example, a specific delay time such as turning on the PS roller 12 250 ms after inputting the permission signal is stored as the number of pulses "50". Further, this data is stored as 1-byte data in which the 10th digit of the decimal number is stored in the above 4 bits and the 1st digit is stored in the lower 4 bits. Therefore, there are 100 memory contents from 00 to 99,
When converted to time, the unique delay time is stored in 0.005 second increments from 0s to 0.495s.

FIG. 2 shows an interrupt routine for controlling the feeding timing of the leading edge of paper during the copying process in the copying machine. This operation is performed every time the photo sensor 24 outputs "H" to the interrupt terminal INT of the CPU 20. When the copying process is started and the photosensitive drum 1 begins to rotate, the rotary plate 25 also begins to rotate in synchronization with the rotation, and the slits begin to cross the photo sensor 24. When the photo sensor 24 detects the slit and outputs "H"
The CPU 20 jumps to step n10 (hereinafter, step ni will be simply referred to as ni). At n10, the paper is conveyed to point P and it is determined whether or not the paper sensor 13 is on (permission signal on). If it is not turned on, it is assumed that the delay time has not yet begun, and the control delay time C (inherent delay time) is set in the subtraction count register D, and the process returns to the main routine. If the paper sensor 13 is on, the paper is
Since the PS roller 12 is transported to the position (point P) and enters a standby state (delay time) for synchronization with the image on the photosensitive drum 1, the delay time is measured by subtracting 1 from the subtraction counter D. (n11).
When the subtraction counter D becomes "0" as a result of the operation in n11, the PS roller 12 is turned on and feeding of the paper to the transfer position starts (n14), and if it does not become "0", it is still within the delay time. Therefore, the process returns to the main routine.

In this way, the paper feeding timing is controlled to be optimal, but if the inherent delay time changes to an incorrect value due to static electricity, etc. (so-called memory corruption), or if the value changes during transfer to the CPU. If the image changes, the image on the copied paper will be completely shifted. That is, if a value smaller than the specific delay time is transferred to the CPU, the paper will be fed too quickly and the image transfer position will be delayed, whereas a value larger than the specific delay time will be transferred to the CPU. In this case, there is a disadvantage that the paper feed is too slow and the image transfer position is advanced. For example, JP-A-58-122568
Like the image forming apparatus disclosed in the publication,
Even if the adjustment data from the outside is added to the reference data stored internally, and this added data is used to control the conveyance timing so that the leading edge of the transfer paper matches the leading edge of the image on the photoreceptor, incorrect data may be used. A similar problem occurs when data is imported (so-called garbled data). Conventional copying machines cannot cope with such data abnormalities, and once a data abnormality occurs, no further copying work can be performed.

<Object of the Invention> In view of the above-mentioned drawbacks, it is an object of the present invention to provide a paper feed timing control device for a copying machine that can copy at a substantially accurate position even if an incorrect inherent delay time is transferred to the CPU.

<Structure and Effects of the Invention> The present invention sets the paper feeding timing for aligning the leading edge of the original image formed on the photoconductor with the leading edge of the copy paper in the transfer unit from the time when scanning of the original is started to the time when the copying paper is transferred. The copying machine is controlled by the delay time until the start of paper feeding to the copying machine, and has a storage means for storing a unique delay time which is an optimum delay time unique to the copying machine, In a copying machine that reads a specific delay time and sets it as a control delay time, means for determining whether the read specific delay time is accurate based on whether it is within a predetermined range;
The present invention is characterized by comprising means for setting a pre-stored fixed time as the control delay time when it is determined that the read specific delay time is inaccurate.

By configuring as described above, according to the present invention, even when the inherent delay time causes memory corruption or data transfer is not performed correctly and data corruption occurs, the preset value ( The delay time is controlled by a certain period of time).
By setting this certain time to an appropriate value that does not cause abnormal operation, for example, the average delay time for copying machines of the same model as the copying machine, the copying position can be maintained even when the data is defective. There is no extreme deviation, and the copy is made in approximately the correct position.
In this way, even when data is abnormal, a suboptimal response is taken, which has the advantage of increasing the reliability of the copying machine.

<Embodiment> FIG. 1 is a flowchart showing the operation of a control section of a copying machine to which a paper feed timing control device according to an embodiment of the present invention is applied. The configuration of each part of the copying machine is similar to that shown in FIGS. 3 and 4. Step n1 (hereinafter referred to as step ni) is executed when the copier is turned on.
simply say ni. ), the inherent delay time is input into the register A from the battery-backed-up RAM 22, which is the storage means of the present invention. If this value is "00H" or not, it is determined by n2 that the data transfer was not performed (it was defective) and the process proceeds to n3 for a preset period of time. Input (50H) to register A, convert this value to a hexadecimal value (n8), and return to the main routine. In this embodiment, (50H) is a value corresponding to the average delay time in copying machines of the same model.

If the value of register A is not "00H" at n2, go to n4, input only the first digit (lower 4 bits) to register B, and check whether this number is between 0 and 9 at n5. Judge by. As mentioned above, the specific delay time is stored in decimal numbers, so the number of each digit must be between 0 and 9. However, if the transfer is not successful or if the memory is corrupted, It may be a different number (A, B, C, D, E, or F in 4-bit hexadecimal). When it is determined at n5 that such a value exists, it is determined that the data is abnormal and the process proceeds to n3. At n6, only the 10th digit value (higher 4 bits) is input into register B, and at n7 it is determined whether the value is a number from 0 to 9 or not, similar to the operation at n4. If this digit is also normal, it goes directly to n8 and converts the value (inherent delay time) transferred from the RAM 22 into a hexadecimal number, which is used as a value for delay time control. If the 10th digit is a number other than decimal, it is considered a data error and the process goes to n3, enters a certain amount of time, and goes to n8.

Note that among the above operations, n2, n5, and n7 correspond to means for determining whether or not the inherent delay time is accurate in the present invention, and n3 corresponds to means for setting a constant time as a control delay means.

By the above-described operation, according to this embodiment, if the inherent delay time setting is not performed correctly when the copying machine is powered on, or the inherent delay time data stored in the RAM 22 becomes inaccurate. Even if there is an error in the copying machine, the average delay time is automatically set in the copying machine of that model, and the paper is fed and the copying process is performed based on that value. The influence on work can be kept to a minimum, and it can contribute to improving the reliability of the copying machine.

In addition to battery backed-up RAM, known storage methods include non-volatile memory and
ROM can also be used.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing the operation of the control unit when the power is turned on in a copying machine to which a paper feed timing control device according to an embodiment of the present invention is applied. FIG. 2 is a diagram showing an interrupt routine for paper feed timing control during the copying process in a general copying machine, and FIGS. 3 and 4 are a schematic structural diagram and a schematic block diagram of the general copying machine.

Claims (1)

[Scope of Claims] 1. The paper feeding timing for aligning the leading edge of the original image formed on the photoreceptor with the leading edge of the copy paper in the transfer unit is set such that the paper feeding timing to the copying unit is adjusted after scanning of the original is started. A copying machine that is controlled by a delay time until it starts printing paper, and has a storage means for storing a unique delay time that is an optimal delay time unique to the copying machine, and reads the unique delay time at the start of operation. In a copying machine that sets a delay time for control in a copying machine, there is a means for determining whether the read inherent delay time is accurate based on whether or not it is within a predetermined range, and a means for determining whether the read inherent delay time is inaccurate or not. A paper feed timing control device for a copying machine, comprising: means for setting a pre-stored fixed time as the control delay time when it is determined that there is a delay time. 2. The paper feed timing control device for a copying machine according to claim 1, wherein the certain time is an average delay time for copying machines of the same type.