JPH01108562A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent the generation of an image misalignment by controlling the output start time of an optical information output means and the driving start time of a resist means, based on information of a tip position of transfer paper. CONSTITUTION:A tip position of transfer paper G which is carried by a resist means F is detected by a transfer paper tip position detecting means I which is placed between a transfer means D and the resist means F. Based on such detected position information, the output start time by an optical information output means B to an image carrying means and the driving start time of the resist means F are controlled by a start time control means J. In such a way, since the timings of both of them are allowed to coincide, a copy or a print being free from the image misalignment is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an image forming apparatus, particularly to an image forming apparatus such as an electronic copying machine, a printing press, or a laser beam printer.

[Prior Art] Conventionally, in image forming apparatuses such as copying machines and laser beam printers, optical signals such as light emitted from a document table or a laser beam are transmitted to a photoreceptor that is an image carrier, and an electrostatic latent image is formed. Ru.

A well-known electrophotographic process is widely used in which this latent image is developed with a developer, the developer is transferred to the transferred transfer material at the same time, and the developer is fixed on the transfer material. There is.

Here, as a method of matching the image on the photoreceptor with the transfer material, a method using a pair of registration rollers and a method using a mechanical shutter are widely used.

[Problems to be Solved by the Invention] However, in all of the above methods, after the transfer material is once brought into contact with the roller nip section or the shutter section to form a loop and correct the inclination of the paper, that is, the skew correction is performed. It starts driving the registration roller pair and shutter.

At this time, since such driving is performed through an electromagnetic clutch or the like, it takes time to reach a predetermined transmission torque after the electric signal to start driving is turned on, resulting in variations in driving.

In addition, there are many types of paper used as transfer materials, and there are variations in stiffness, so it may not be able to fully hit the registration roller pair or the shutter part. etc. may occur. Furthermore, the strength of the hips may also change due to changes in the environment such as temperature and humidity.

Therefore, the leading edge registration position is not constant, resulting in misalignment between the image on the photoreceptor and the paper.

Particularly recently, the functions have been expanded through the systemization of devices, and devices equipped with automatic duplex and automatic multiple copying mechanisms have been developed. Therefore, if the above-mentioned deviation occurs, in the case of multiple copying, the problem of image deviation becomes noticeable, especially since the dihedral opening is superimposed on the negative side.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the disadvantages of such conventional devices and to provide an image forming device that does not cause image shift.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an optical information outputting means for outputting optical information to an image carrier to form a latent image;
an image forming section comprising a developing means for developing a latent image formed on the image bearing member; a transfer means for transferring the image on the image bearing member developed by the developing means onto transfer paper; In an image forming apparatus having a paper conveyance means including a registration means for conveying the transfer paper to an image forming section at a timing, a transfer paper leading edge position detection device is disposed between the transfer means and the registration means and detects the leading edge position of the transfer paper. and a start time control means for controlling the output start time of the optical information output means and the drive start time of the registration means based on the transfer paper leading edge position information obtained by the transfer paper leading edge position detection means.

[Function] According to the present invention, the leading edge position of the transfer paper conveyed by the registration means is detected by the transcription paper leading edge position detection means disposed between the transfer means and the registration means.

Then, based on the detected position information, the start timing control means controls the start timing of output by the optical information output means to the image holding means and the drive start timing of the registration means.

Therefore, since the timings of both are matched, copies or prints without image shift can be obtained.

〔Example) Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, A is a photosensitive drum that is an image carrier on which an electrostatic latent image is formed, and B is an optical drum that outputs optical information such as irradiated light from a document table or a laser beam to photosensitive drum A to form a latent image. Information output means, C is a developing means for developing the latent image formed on the photosensitive drum A with toner or the like, and D is a transfer means for transferring the image developed on the photosensitive drum A by the developing means C onto a transfer paper. , The image forming section E is configured with the above.

F is a registration roller, which constitutes a part of paper conveyance means H that sends the transfer paper G to the image forming section E.

(3) is a transfer paper leading edge position detecting means which is arranged between the transfer means and the registration roller F and detects the leading edge position of the transfer paper G;
J is a start timing control means for controlling the timing at which the optical information input means B starts applying manual force to the photosensitive drum A and the timing at which driving of the registration roller F starts, based on the transfer paper leading edge position information detected by the transfer paper leading edge position detection means. It is.

Next, an example of a copying apparatus to which the present invention is applied will be explained based on the drawings.

The copying apparatus 1 that performs automatic double-sided copying and automatic multiple copying has a second
It has a configuration as schematically shown in the figure, and when a document is placed on the document table 2 and a copy start button (not shown) is operated, the image written on the document is transferred to the scanning system 3 as appropriate.
The toner image is developed as a toner image on a rotating photoreceptor 6 in the copying section 5 via the toner image. Then, a sheet supply section 1 such as a sheet cassette 7.9 or a manual feed table 10 is provided.
The blank sheet from 1 to paper feed roller 12.13.15
, conveyance roller pair 16.17, registration roller pair 19a,
19b and is conveyed synchronously to the copying section 5, the toner image described above is transferred onto the upper surface of the sheet at the transfer section 20, and the thus copied sheet is fixed at the fixing section 22 via the conveyance belt 21. , and then transported to various subsequent mechanisms. If only one side of the sheet needs to be copied, the sheet is guided by the first switching guide 23, which is in the switching state shown by the dotted line in the figure, and passes through the pair of transport rollers 25, which is provided outside the copying machine. They are sequentially accumulated on the tray 26. When double-sided copying or multiple copying is required, the sheet is directed to the second switching guide 29 via the transport roller pair 27 by the guiding action of the first switching guide 23 in the switching state shown by the solid line in the figure. transported. Here, when double-sided copying is performed, the second switching guide 29, which is switched to the solid line state in the figure, transports the sheet to the reversing section 30, where the sheet is subjected to a reversing action by the reversing roller 31 that rotates forward and backward. In the case of large sheets, they are sequentially stacked on the intermediate tray device 36 via the conveying roller pair 32 and under the guide 33 by the guiding action of the third switching guide 33 shown in the solid line state. In this case, the sheets pass through a pair of conveying rollers 32, are guided on the upper surface of the third switching guide 33 (shown by the dotted line in the figure), and are sequentially stacked on an intermediate tray device 36 via a pair of conveying rollers 35. and,
In the case of multiple copying, the second switching guide 29, which has been switched to the dotted line state in the figure, passes directly through the conveying roller pair 32, etc., in the same manner as in the case of double-sided copying described above.
They are sequentially accumulated on the intermediate tray device 36. In this way, after a predetermined number of single-sided copied sheets are accumulated on the intermediate tray device 36, the second side of the previous original is placed on the original platen 2, or the original to be subjected to multiple copying is placed. When the double-sided copy start button is operated, the paper refeed roller 37 and separation roller 38 in the intermediate tray device 36 are driven,
The sheets stacked on the intermediate tray device 36 are sequentially conveyed from the bottom via the conveyance roller pair 39, the conveyance roller pair 17, etc. to the copying section 5, and the sheets that have been copied as described above are now conveyed to the tray 26. It is transported to be collected on top.

Further, FIG. 3 shows details of the parts according to the present invention.

A CCD 41 for detecting the leading edge position of a sheet (transfer paper) 40 and a light source 42 are arranged between the registration roller pair 19a, 19b and the transfer section 20 near the photoreceptor 6. Here, the light source 42 is for ensuring the detection of the leading edge of the sheet by the CCD 41, and is unnecessary if external light can be used. Furthermore, a registration roller driving means 43 is connected to one of the pair of registration rollers 19a, and this may be a combination of a motor and an electromagnetic clutch, or a direct step motor. On the other hand, photoreceptor 6
An optical signal 44 is irradiated onto the optical system 3, and information by the optical system 3 is written therein.

In the case of a laser beam printer, this optical signal 44 is
Needless to say, it corresponds to the irradiation light of a laser beam.

Note that FIG. 4 shows a control block diagram.

The control unit 50 includes a microprocessor (CPU) 51 that performs calculations and logical judgments for image formation and transport processing.
, a read-only fixed memory (ROM) 52, a writable memory (RAM) 53, etc., and the ROM 52 stores a control program for the CPU 51 and control procedures shown in FIG. 5 or 7, which will be described later. There is.

The control section 50 receives an output signal from the CCD 41 as a transfer sheet leading edge position detection means, an image tip signal, and a laser writing signal 54, and controls the registration roller driving means 43, the image forming means 55, and the like.

Hereinafter, an example of a control procedure of an embodiment of the present invention having the above configuration will be explained using a flowchart shown in FIG.

First, when a copy key (not shown) is pressed, a drive system (not shown) operates (step si), and a timer t for giving a predetermined feed amount to form a loop on the sheet 40 is set. Among them, paper feed rollers 12, 13.
One of the 15 paper feed clutches selected is turned on (step S3). Here, the paper feed roller 12,
13 and 15 are respectively connected to a motor as a paper feed driving means via a paper feed Clara. In step S4, a timer t is counted up, and the paper feed roller continues to rotate until a time T1 corresponding to a predetermined feed amount necessary to form a loop is reached (step S5). FIG. 6(1) shows the state immediately after the sheet feeding roller starts rotating and the sheet 40 is fed. At this time, all the elements of the output signal (binarized output signal) of the [:CD 41 are in the on state as shown in the figure. When the paper feed roller is rotated for a predetermined time T, sheet 4
The tip of 0 is a pair of registration rollers 19a.

It is inserted into the nip portion of 19b, and a loop is formed as shown in FIG. 6(2). In this case as well, since the sheet 40 is not fed out from the pair of registration rollers 19a and 19b, C
The output signal of CD41 remains unchanged. Therefore, step S
After turning off the paper feed clutch in step S6, the process returns to step S7.
Then, the registration roller pair 19a is installed on the sheet 40.

A timer t for giving a predetermined amount of output from 19b is set. Then, in step S8, the registration roller pair 1 is
The clutch of the registration roller drive means 43 connected to the rollers 9a and 19b is turned on. In step S9, a timer t is counted up, and a time T corresponding to a predetermined sending amount is counted up.
The registration roller driving means 43 is driven until the number reaches 2 (step 510). When the predetermined time T2 is reached, the clutch of the registration roller drive means 43 is turned off in step Sll. The state at this time is shown in FIG. 6 (3). At this time, the tip of the sheet 40 covers a part of the CCD 41. Therefore, the output signal of C1l:041 is
As shown in the figure, the signal level changes from 1 to 0 at the a-th bit (arrow).

Here, the output signal of the CCD 41 is binarized so that each bit is 1 in the light receiving state and each bit is 0 in the non-light receiving state.

Therefore, in step S12, the output signal of the CCD 41 is read, and in step 513, from the relationship with the mounting position of the CCD 41, as shown in FIG.
The distance 1jtj2 from the tip of is calculated. Next step 51
4, the timing time T3 for starting to drive the registration roller pair 19a, 19b again is calculated.

Here, the timing time T3 is calculated as follows. That is, as shown in FIG. 3, the distance from the writing point of the optical signal 44 to the transfer unit 20 is L, and the process speed (peripheral speed of the photoreceptor and sheet feeding speed) is V, so that the relationship LEA is established. A CCD 41 and a pair of registration rollers 19a and 19b are arranged. Therefore, from the start of writing the optical signal 44, the registration roller driving means 4
3 is turned on and T is the timing time from when the pair of registration rollers 19a and 19b starts driving, it can be calculated as T3=□■.

Next, in step 515, the optical/drum motor for driving the photoreceptor 6 is rotated, and in step 516, the image tip is detected.

The image tip signal can be detected by a sensor (not shown), which is installed at a location corresponding to the image tip position during scanning by the scanning optical system 3. Further, in the case of a laser beam printer or the like, the image tip signal corresponds to a laser writing signal.

If the tip of the image is detected, a timer t is set and started in step 517. Then, in step 518, the timer t is counted, and writing using the optical signal 44 is continued. In step 519, it is determined whether or not the time T3 calculated in step 514 has been reached, and writing using the optical signal 44 is performed while the register roller driving means 43 is in the OFF state. Step 520 when time T3 is reached
Then, the clutch of the registration roller drive means 43 is turned on and sheet feeding is started.

By turning on the clutch of the registration roller driving means 43, the sheet 40 is sent to the transfer section 20 with the relationship L=42, and is transferred with the leading edge of the image and the leading edge of the sheet aligned with high accuracy. A copy is obtained by passing through the so-called image forming process of transfer and fixation (step 5).
21).

Next, another embodiment of the present invention will be described. In this example, compared to the previous example, due to variations in clutch start-up time and slippage between the transfer paper and the registration roller, the predetermined process speed was set immediately after the registration roller started rotating.
This allows for more accurate tip alignment by taking into consideration the possibility that there may be a short period of time in which the tip is not reached. That is, the rising speed of the leading edge of the transfer paper is detected using CC[), and the optical signal for writing is controlled based on the positional information when a predetermined speed is reached. This is suitable for use in devices with a high process speed V, such as a high-speed copying machine.

In this example, a case of a laser beam printer will be explained. Therefore, the optical signal 44 in FIG. 3 becomes a laser beam writing signal. Note that the other arrangement relationships are the same.

An example of the control procedure of another embodiment of the present invention having the above configuration will be explained using the flowchart of FIG. 7.

Steps Sl' to Sll' are the same sequence as steps S51 to Sll in the previous embodiment, so redundant explanation will be avoided. That is, feeding of the transfer paper (sheet)→forming a loop by abutting against the pair of registration rollers 19a, 19b→rotating the pair of registration rollers 19a, 19b by a predetermined amount→stopping. Therefore, in step 512', the clutch of the registration roller drive means 43 is turned on again, and the sheet 40
At the same time, a memory address counter i is set in step 513'. In step 514', the memory address counter i is incremented, and then in step 515
In step 516', the output signal CCD0UT of the CCD 41 is input, and in step 516', the distance ill between the leading edge of the sheet 40 and the transfer unit 20 at that time is calculated. Next, in step S17', the distance of the tip position is stored in the memory 42 (
i) and store it. The state shown in FIG. 8(1) shows the state immediately after the registration roller pair 19a, 19b starts rotating again. Then, in step 518', the sheet 40 is advanced by a predetermined time Δt through a timer routine to obtain the state shown in FIG. 8(2). In order to calculate the distance @fl of the tip position after the lapse of time, Δ is [
:The output signal CCD0UT of the CD 41 is input, and l is calculated in step 520'. Then, in step 521', this calculated distance A is input and stored in the memory fl(i+1). Further, in step 822', the advance amount δ(i) of the sheet 40 is calculated as δ(i) = 11 (j+
Calculated by 1)-1(i).

In step 523', it is checked whether the advance amount δ(i) is equal to a predetermined advance amount δ. Here, the predetermined advance amount δ is the above-mentioned timer predetermined time Δt.

If the process speed is V, it can be calculated as δ=V·Δt. That is, the feeding speed of the sheet 40 is detected by measuring the advance amount δ per hit for a predetermined time Δ.

If the predetermined advance amount δ has not been reached in step 523', the process returns to step 514' and the above steps are repeated. In FIG. 8, each time ti (however, till
-tf=Δt), and shows the state of the sheet 40 at 1
Repeat until (i+1)-u (i) becomes δ. For example, if the predetermined feed amount δ is reached at time t5, the laser writing timing time T3' is calculated in step 524' based on the tip position C (5) at that time.

The timing time T31 is calculated by 1, u(5)-LT3-□■. While the sheets 40 are being conveyed sequentially,
At step 825', timer t is set and started again. Next, in step 526', the timer t is counted up, and the sheets 40 are successively fed until the timer t reaches t=T3' (step S27').
, T3', the process proceeds to step 528' to start writing using the optical signal 44, that is, laser writing. In this way, the leading edge of the sheet 40 and the leading edge of the image are transferred with high accuracy and are further fixed, passing through a so-called image forming process and obtaining a copy (step 529').

[Effects] As is clear from the above description, according to the present invention, the leading edge of the image and the leading edge of the transfer paper can be matched with high accuracy,
In particular, it is possible to eliminate the problem of image shift during multiple printing and obtain clear copies.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention; FIG. 2 is a schematic diagram showing an example of a copying apparatus to which the present invention is applied; FIG. 3 is an explanatory diagram showing details of parts according to the present invention. , FIG. 4 is a block diagram showing the configuration of the control section, FIG. 5 is a flowchart showing an example of the control procedure of an embodiment of the present invention, FIG. 6 is an explanatory diagram showing the feeding state of the transfer paper, and FIG. 7 FIG. 8 is a flowchart showing an example of a control procedure of another embodiment of the present invention, and FIG. 8 is an explanatory diagram showing the feeding state of transfer paper. A: Photosensitive drum, B: Optical information manual means, C: Developing means, D: Transfer means, E: Image forming section, F, 19a, 19b: Registration roller pair ,G
, 40...Transfer paper (sheet), H...Paper conveyance means, ■...Transfer paper leading edge position detection means, J...Start timing control means, 41...CCD. 43... Registration roller drive means. Actual trip of the present invention - Shape of the prisoner Pro 1, 77 Figure 1 , shows the power of prayer↑Pro, ・7F Figure 4

Claims (1)

[Scope of Claims] 1) Optical information output means for outputting optical information to an image carrier to form a latent image; developing means for developing the latent image formed on the image carrier; and the developing device. an image forming unit configured to transfer the image on the image carrier developed by the unit to a transfer paper; and a paper sheet including a resist unit that conveys the transfer paper to the image forming unit at a predetermined timing. an image forming apparatus comprising: a transfer paper leading edge position detection unit disposed between the transfer unit and the registration unit and detecting the leading edge position of the transfer paper; An image forming apparatus comprising: a start time control means for controlling an output start time of the optical information output means and a drive start time of the registration means based on position information. 2) The image forming apparatus according to claim 1, wherein the transfer paper leading edge position detection means includes a plurality of detection units arranged side by side in the conveyance direction of the transfer paper. 3) The image forming apparatus according to claim 1 or 2, wherein the transfer paper leading edge position detection means is a CCD. 4) The transfer paper leading edge position information obtained by the transfer paper leading edge position detecting means uses information obtained at the time when the transport speed of the transfer paper reaches a predetermined value. The image forming apparatus according to any one of .