JPS59121062A - Method for compensating deviation in transfer position of image - Google Patents

Abstract

PURPOSE:To eliminate the positional deviation of a transferred image due to the kind or contamination of transfer paper by adjusting the point of the time when a start signal for scanning exposure in the upper part or a start signal for paper feed is generated according to the quantity of the light detected with a photoelectric sensor. CONSTITUTION:The 1st photoelectric sensor 10 which is a detector for transfer paper and the 2nd photoelectric sensor 20 which is a generator for data on the kind of the paper are provided on the way of a path for conveying the transfer paper from a paper feed part 8 to a transfer part T. When the output voltage E0 of a photodetector 10B of the detector for transfer paper exceeds a reference voltage Ef, an output E1 detecting the transfer paper is outputted and is used as a start signal for scanning the exposure. The output voltage E0 from the sensor 20 which is a generator for data on the kind of the paper latches the output voltage E0 of a phototransistor 20B at said point of time by a sampling pulse SP and converts the same to 4-bit b0, b1, b2 and b3. The binary data on the quantity of light is thus obtd. from an A/D converter 21 according to the kind of the paper (including the presence or absence of contamination). The start of the scanning for exposure is regulated with a microcomputer.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a transfer type electrophotographic recording device, such as a copying machine, a laser printer, etc., and more particularly to a method for compensating for transfer positional deviation of an image.

PRIOR ART Conventionally known transfer type electrophotographic recording devices generally have a reflective or transmissive type transfer paper detector in the middle of the transfer paper conveyance path from the paper feed section to the transfer section, and paper detection from the detector is provided. The output is used to start an exposure scan of a scanning type exposure device or to start feeding paper from a registration roller. However, in both reflective and transmissive types, the output of the photoelectric sensor does not rise sharply when the leading edge of the paper actually reaches the detection point, but rather rises around the detection point. Moreover, it was found that the vertical 142 curves differ depending on the type of paper. Therefore, if a photoelectric sensor is used as the above transfer paper detector and the threshold level for determining that the detector has detected paper is set to the value of the sensor output, the will give a correct response, but for other types of paper, such as translucent paper, the actual paper leading edge position will respond at a position shifted from the detection point. Therefore, an image shift corresponding to a detection error occurs between the image position of the original and the image position of the copy. Image shifts such as θ occur because the amount of reflected or transmitted light that enters the light-receiving element that makes up the sensor differs depending on the type of transfer paper, so even if the paper is of the same type, there may be dirt on the paper. In some cases, image shift also occurs.

OBJECTS The present invention provides a method for eliminating misalignment of transferred images caused by the type of transfer paper or dirt.

Configuration The configuration of the present invention will be described below based on (1) Examples.

In FIG. 1, 1 is a photoreceptor belt that runs in the direction of the arrow. After the photoreceptor belt 1 is charged by a charging charger 2, it is sent to an exposure section.

In this embodiment, the exposure optical system is composed of a convergent light transmitter 3-1 and an illumination device 3-2, and the original is sent along with the original platen 4 in the direction of the arrow based on an exposure scan start signal, which will be described later. The latent image formed by slit exposure is developed by five developing devices.
The image is visualized with retoner, and the toner image is sent to the transfer section T. On the other hand, one sheet of transfer paper 8-1 is sent out from the paper feed section 8 by a paper feed roller 8-2, and a double-feed prevention roller 8-3
The toner image is sent to the transfer section T via the transfer roller 8-4 and the conveyance roller 8-5, where it is superimposed on the above-mentioned toner image and passes through the transfer charger 6. Due to the function of this transfer charger 6,
The toner image is transferred to the transfer paper.

Thereafter, the transfer paper passes through the fixing roller 9 and is discharged from the conveyance path 20 to the outside of the machine. After the transfer, the remaining toner is removed from the photoreceptor belt 1 by a cleaning device and it can be reused.

In the middle of the transfer paper conveyance path from the paper feed section 8 to the transfer section T,
A first photoelectric sensor 10, which is a component of a transfer paper detector (FIG. 3), is provided, and a paper type data generator (a fourth A 20th photoelectric sensor 20, which is a component of FIG.

In this embodiment, both sensors 10 and 20 are
As shown in the figure, the sensor will be described as a reflective type sensor in which a light emitting element 10A (20A) and a light receiving element 10B (20B) are present on the same side with respect to the transfer paper S on the transport path. However, both sensors 1
0 and 20 may be transmission type sensors. An LED lamp or the like can be used as the light emitting element, and a phototransistor, a Cds cell or the like can be used as the trench light receiving element.

FIG. 3 is an example of a circuit of a transfer paper detector, and the above-mentioned sensor 1
0, a light emitting element 10A made of an LED and a light receiving element 10B made of a phototransistor are used. Voltage E obtained at the output terminal of the phototransistor. is input to one input terminal of the comparator 11 and compared with the reference voltage (threshold level) Ef, and Eo becomes Ef.
When the transfer paper detection output E is exceeded, the transfer paper detection output E is outputted, and becomes the above-mentioned exposure scan start signal.

FIG. 5 shows the output value E of the phototransistor when the transfer paper S enters the sensor 10. This is an example of measurement. As shown in FIG. 2, the degree of penetration into the sensor 1o is determined by the light emitting element 10
A and the position where the optical axes of the light-receiving elements 10B intersect are expressed as 10, the position before the approach is expressed as (-), and the position after the approach is expressed as (+). As is clear from this measurement result, the threshold level Ef is kept constant, for example 2 [
■] For plain paper: -1,5 For translucent paper: -0,4M For Mylar paper: +0.1□ position The transfer paper will be detected respectively.

If the image position, in this example, the exposure start time, is determined based on the output signal E1 of the transfer paper detector as it is, the image transfer position will shift depending on the type of transfer paper.

For example, if plain paper is used as a reference, an image position shift of 1°61 width will occur with respect to Mylar paper.

Therefore, in the present invention, attention is paid to the fact that the distance deviation of the detected position with respect to each transfer paper substantially corresponds to the magnitude of the sensor output, and the deviation of the detected position is corrected using this deviation value. To achieve this purpose, the second photoelectric sensor 2o described above includes the same pair of light emitting and receiving elements 2OA and 20B as the first photoelectric sensor 10 for detecting the transfer paper, in this example, an LED and a phototransistor. It is used. At the output terminal of this phototransistor, as shown in FIG.
/D converter 21 is connected to constitute a paper type data generator. Output voltage E of sensor 20 of this paper type data generator. draws the curve shown in FIG. 5 on the transfer paper in the same way as the sensor lO. The A/D converter 21 uses the sampling pulse SP generated when the transfer paper fully enters the sensor 20 to adjust the output voltage E of the phototransistor 20B at that time. is latched, and this can be obtained as a binary number in this example.

In FIG. 6, 22 is a microcomputer;
Output B1 from the above-mentioned transfer paper detector and light amount data b from the paper type data generator. b, b2 b3, and a timing pulse T generated in synchronization with the running of the photoreceptor belt 1.
P is input. PF turns on the paper feed roller 8-2.
A paper feed clutch signal to the electromagnetic clutch (not shown) for turning off, SP is a sampling signal to the A/D converter, and ES is an exposure scan start to start exposure scan by the document table 4 and illumination device 3-2. signal, and C8
is an output signal for controlling other recording devices.

How to adjust the exposure scan start will be explained with reference to the timing chart of FIG. 7 and the drift figure of FIG.

From point A to point B in the flowchart in Figure 8, the program turns the clutch OFF at the timing when the paper feed clutch is ON.
N (point ■ in Figure 7). The transfer paper is fed and first passes the sensor 20. The output of the sensor 20 rises depending on the amount of light received, and eventually settles down to a value depending on the type of paper. If the transfer paper is plain paper, the voltage will settle to about 13V as shown on the left side of FIG. 7, and if the transfer paper is Mylar paper, the voltage will settle to about 6V as shown on the right side of FIG. The timing at which such a predetermined time has elapsed is the timing at which the sampling pulse is turned ON. The microcomputer 22 generates a sampling pulse SP between points B and C in the flowchart (point ■ in FIG. 7).

In response to this sampling pulse, the A/D converter 21
The 21 base power changes from the state of 0000 to the 2 base power according to the amount of light. In this example, for plain paper with no stains, 1
1φ1 (Eo-13 [V]), and in the case of clean Mylar paper, the value is φ11φ (EO=6 [V:]). When the transfer paper is further conveyed and reaches the sensor 10, the output E of the transfer paper detector, rises to the level of 1 paper cloth 1 (point ■ in Figure 7).The program starts from point C to point D in the flowchart by calculating the product of the light amount detection output E. (11φ1 or φ11φ) of the sensor 20 and the constant α. is created and temporarily stored in the memory P. This "constant a" is used to convert the light amount detection output E. into data P. corresponding to the positional deviation distance.

E for plain paper. -13, so Po-aEo-2×13-26, which is E in the case of Mylar paper. -6, so Po=a
Bo=2x6=12.

1. The transfer paper conveyance speed is 100□/see, the interval of timing pulses TP for recording device sequence control is lm5ec, and P. Let Po-26 and P be the number of counts due to timing pulses. =12
are 2 and 6 respectively. , and corresponds to a positional movement of 1°2.

Then, the program runs from point D to point E in the flowchart.
When the count number of timing pulses after the rise of the transfer paper detection output E1 (point 2 in FIG. 7) matches the value of Po, an exposure scan start signal BS is generated. In other words, the exposure scan takes 26 pulses (2.6 tns) for plain paper compared to the transfer paper detection output of CEF 4S10.
In the case of Mylar paper, the start time is delayed by 12 pulses (
The game will start with a delay of 1-2 matches). This means that the detection error of the photoelectric sensor 10 for each transfer sheet has been corrected by adjusting the exposure scan start timing.

The program causes the exposure scan start signal to disappear when the trailing edge of the transfer paper finishes passing the sensor 10 from point E to point F in the flowchart.

As described above, by shifting the exposure scan start timing with respect to the transfer paper detection output, it is possible to correct the transfer position shift of the image for various transfer papers. Although the document scanning method has been described in which the document table is moved, it is clear that the document document may be scanned in a manner in which the document table is fixed and the exposure optical system is moved. Further, lasers, polygons, θ lenses, etc. in laser printers are also scanning type exposure means to which the present invention can be applied. The photoreceptor may be drum-shaped.

To give a supplementary explanation about stains on the transfer paper, if the threshold level is constant when ordinary light is detected using a type sensor, any stains will cause a decrease in the overall level of the amount of light emitted and the amount of light received. As can be inferred, the transfer paper detection position moves in the (+) direction (delay direction). When looking only at the signal level of the sensor, this phenomenon is equivalent to a difference in the type of transfer paper, and the deviation in the detection position can be corrected for the reasons described above.

Therefore, in this specification, "one type of transfer paper" includes paper with or without stains.

The above is an example of a method of compensating for a shift in the transferred image position by adjusting the exposure scan start timing in accordance with the passing position of the transfer paper. However, the present invention is not limited to this, and the shift in the transferred image position can be similarly compensated for by adjusting the feeding timing of the transfer paper in accordance with the position IC of the image formed on the photoreceptor. be able to.

This latter method can be implemented, for example, in a type of copying machine that uses registration rollers instead of the conveyance roller 8-5 shown in FIG. In this type of copying machine, the transfer paper 8-1 in the paper feed section 8 is once fed out from the paper feed roller 8-2-, and the leading edge of the transfer paper is held in the pair of registration rollers (8-5). be temporarily suspended. This is done by disengaging the electromagnetic clutch of the registration roller pair (8-5) when the transfer paper sensor 10 located between the transfer section T and the registration roller pair 8-5 detects the transfer paper. Registration roller pair (8
The transfer paper that has been waiting at -5) is sent out at a good timing so that the toner image on the photoreceptor 1 coincides with the transfer portion T. The time point when the clutch of this pair of registration rollers (8-5) is engaged, that is, the time point when the sheet feeding start signal to the transfer section T is generated, is determined by the above-mentioned P. By delaying by the value of , there will be no shift in the transferred image position even if the type of transfer paper changes.

Therefore, in the timing chart of FIG. 7, it is sufficient to set the counting start point of Po to the clutch engagement point of the pair of registration rollers (8-5) instead of the transfer paper detection output E1.

Similarly, in the above example, the sensor 20 of the paper type data generator is provided separately from the sensor 10 of the transfer paper detector, but the sensor 20 can be used in common with the sensor 10.

Copies identical to the original can be obtained regardless of the effect or paper type.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a transfer type electrophotographic recording apparatus to which the transfer position shift compensation method of the present invention can be applied; FIG. 2 is a diagram showing the relationship between a photoelectric sensor for detecting transfer paper and the transfer paper; Figure 3 shows a circuit example of a transfer paper detector, Figure 4 shows a circuit example of a JD paper type data generator, and Figure 5 shows an example of measuring the output value of a phototransistor when a transfer paper enters a reflective sensor. , FIG. 6 is a diagram showing the input/output of the It microcomputer, FIG. 7 is a timing chart for explaining the compensation method of the present invention, and FIG. 8 is a flow diagram of the compensation method of the present invention. ■...Photoreceptor belt 2...Charging charger 3
-1...Focusing light transmission body 3-2...Illuminating device 4...Document table 5...Developing device 6...Transfer charger 8...Paper feed section 10...Transfer paper Photoelectric sensor 11 for detection...Comparator 20...Photoelectric sensor 21 for generating paper type data...A
/D converter 22...Microcomputer T...Transfer section 15- Fig. 1 Fig. 8 C No. of output of guo shouzai output Rise Is it atsushi of saiyo output? ES Light amount liquid discharge; E. and the constant, the talent of a: ρoL: Ioritsu I: 1) = αXE. NO Kikinidege 1's Nomarus; PL ma-une c! "2111') R1-ρ ES Riehi fish climbing power ON No Okende, output P fist zr!
J&J? 1 \ /

Claims (1)

[Claims] An electrophotographic recording device that exposes a charged photoreceptor to light using a scanning exposure device, develops it with toner, and then transfers it onto transfer paper fed from a paper feeder, and includes a transport path from the paper feeder to the transfer unit. In a device that has a photoelectric sensor for detecting transfer paper in the middle of the transfer paper, and uses the transfer paper detection output of the sensor as an exposure scan start signal or as a paper feed start signal to the transfer section, the photoelectric sensor or the individual A photoelectric sensor installed on the conveyance path detects the amount of reflected light or transmitted light of the transfer paper, and adjusts the generation point of the upper exposure scan start signal or the paper feed start signal according to the value of the detected light amount. A method for compensating for an image transfer position shift, comprising compensating for a detection error of the photoelectric sensor for detecting the transfer paper.