JPH04189239A - Offset and skew correcting system in printer device - Google Patents

Abstract

PURPOSE:To correct a skew without moving a sheet by providing a control means for outputting the control signal of an optical system and the drive signal of an optical system regulating motor after receiving the detection signal from a detecting means followed by correction. CONSTITUTION:A detecting means 5 for detecting the state of a carried sheet and a control means 4 for receiving the detection signal from the detecting means 5 and outputting the control signal CS of an optical system and the drive signal MS of an optical system regulating motor CM are provided between a waiting roller for carrying a sheet P and a sensitizing drum 2. An offset amount X is detected from the detection signal by the detecting means 5 to correct printing start position and printing start timing, the skew angle G of the sheet is also calculated from the detection signal, and the position of an optical system 3 is regulated by this drive signal MS to correct the skew angle.

Description

[Detailed Description of the Invention] [Summary] Regarding offset and skew correction methods in printing devices, especially laser printers, the purpose of this invention is to reduce offset and skew errors of paper as much as possible. The method includes a detection means for detecting the state of the paper carried in between a standby roller that carries the paper and a photosensitive drum, and a detection signal from the detection means and outputs a control signal for the optical system. The control means detects the offset amount using the detection signal from the detection means to correct the print start position and print start timing, and the optical system calculates the skew angle of the paper from the detection signal and corrects the skew angle. configured to adjust the position of the system;

[Industrial application field]

The present invention relates to an offset and skew correction method in a printing device, particularly a laser printer.

[Conventional technology]

FIG. 8 is a diagram showing the configuration of a conventional main part. 1 is a standby roller for carrying in the paper P; 2 is a photosensitive drum that performs exposure, development, transfer, etc. around it; 3 is an optical system consisting of a laser emitting source, a polygon mirror, etc.; 4 is a control system for the optical system 3; Motor M
This is a control/circuit that performs control, etc.

When the paper P is carried in in the direction of the arrow (sub-scanning direction), it is temporarily stopped by the standby roller 1, and the paper is started to be carried in in synchronization with the laser emission timing to adjust the printing start position.

In this case, the direction perpendicular to the paper conveyance direction (main scanning direction) is not particularly adjusted and depends on the accuracy of the mechanical parts.

[Problem to be solved by the invention]

Such a conventional configuration has the following problems. That is, (1) When the paper is temporarily stopped by the standby roller, it is difficult to stop the paper accurately, which tends to cause errors in the printing start position.

(2) On the other hand, since the main scanning direction depends on the precision of the mechanical parts, variations in precision directly appear as variations in the printing area.

Next, the problem of paper skew will be explained.

A conventional skew correction mechanism uses a sensor to determine the skew state and corrects the skew based on the detected value.

FIG. 9 is an explanatory diagram of an example of conventional skew correction. As shown in the figure, there are rollers R for skew correction on both sides of the paper P.
1 and R2, and by adjusting the rotation of these rollers, the inclination of the paper is mechanically corrected.

FIG. 10 is an explanatory diagram of another example of conventional skew correction. The tilted paper P is scanned with the laser beam LB as shown in the figure, but in this case, the read data is rotated by predetermined image processing.

However, the above two methods have the following problems. That is, in the method of FIG. 9, roller R1 and roller R2
Since the skew is corrected by the difference in rotation between the two, it is not always possible to completely correct the skew due to roller slips, etc. Further, the correction may cause wrinkles on the paper, and furthermore, the paper may be tilted before it reaches the photosensitive drum.

In addition, in FIG. 10, in order to correct the video map data, jagged lines are created in the character lines as shown in FIG. 11.

It is an object of the present invention to reduce as much as possible the offsets and skews suffered by printing devices, especially laser printers.

[Means to solve the problem]

The present invention is an offset and skew correction method for a printing device, and a detection means 5 is provided between a standby roller for carrying paper and a photosensitive drum to detect the state of paper carried in.
and a control means 4 that receives a detection signal from the detection means and outputs an optical system control signal C5 and an optical system adjustment motor drive signal MS, and detects the offset amount X based on the detection signal from the detection means. The present invention is characterized in that the print start position and print start timing are corrected using the detection signal, and the skew angle θ of the paper is calculated from the detection signal, and the position of the optical system is adjusted using the drive signal to correct the skew angle.

[Effect]

In the present invention, a linear scale sensor such as a CCD is provided as paper detection means between the standby roller and the photosensitive drum, and the offset amount is detected by this and the printing start position is adjusted using this data. In the present invention, both the stop timing of the standby roller and the print start timing can be adjusted particularly for offsets in the sub-scanning direction.

Furthermore, in the present invention, a skew angle is calculated from the detection signal of the sensor, and the position of the optical system is adjusted and corrected based on this skew angle.

〔Example〕

FIG. 1 is a block diagram of the main parts of the present invention. As shown in the figure, a sensor 5 is provided as paper detection means on the drum side between the standby roller 1 and the photosensitive drum 2. During printing, first, the standby roller 1 transports the paper P at the same timing, and then the sensor 5 The amount of offset is detected and a detection signal S is sent to the control circuit 4, and if there is an error, the print start timing and print start position are adjusted.

FIG. 2 is a block diagram of the main parts of the control circuit of the present invention.

The control circuit 4 mainly includes a BD value correction circuit 41, a video data transmission circuit 42, and an optical system adjustment motor drive signal generation circuit 43. The detection signal S from the sensor 5 and the BD multiplied signal are input to the BD value correction circuit 41. Here, the BD (beam detect) signal is a signal that detects the scanning of the laser beam, and a sensor (not shown) for this purpose is provided on the laser beam scanning start side, that is, on the left side of the paper in the paper conveyance direction. ing. Therefore, the offset amount X determined by the sensor 5 is corrected by adding the BD multiplied signal, and a correction signal AS is sent to the video data transmission circuit 42.

The video data transmission circuit 42 generates an optical system control signal C8 based on the correction signal AS from the BD value correction circuit 41.

The optical system adjustment motor drive generation circuit 43 calculates the skew amount θ based on the detection signal S from the sensor 5, and generates a drive signal MS for the optical system adjustment motor based on the calculation result.

In this way, offsets in the paper conveyance direction are corrected in a double manner: after the paper is fed with the standby roller at the same printing start timing, it is detected by the sensor 5, and if there is an error, the laser emission timing is changed. ing. Further, since offset in the direction perpendicular to the paper conveyance direction can be corrected by changing the print start position, accuracy can be obtained without depending on the accuracy of the mechanical parts.

FIG. 3 is an explanatory diagram of the relationship between the sensor and paper.

The sensor 5 has a plurality of detection elements arranged at the detection position X in the main scanning direction (that is, in the direction perpendicular to the paper conveyance direction). Then, when the paper reaches the detection position X, the sensor detects it and sends it to the control circuit 4, which causes the laser to emit light after a predetermined period of time. Note that X is the offset amount in the lateral direction of the paper.

FIG. 4.5 is an explanatory diagram of skew correction according to the present invention. When the sensor 5 detects one end of the paper at the detection position y1, it is determined to which side the paper is skewed depending on whether it is detected at one end A or the other end B. Next, the sensor on the right side is looked at and the point yb where the paper width is detected most often in the X-axis direction is identified.

Then, the distance C between yl and yb and the area of this region.

and calculate the distance between A and B. Therefore, the skew angle θ can be expressed by the following formula.

5=C(Ctanθ 10)+2,', tanθ=(2S/C-D)+
Since the skew angle θ is determined as shown in the figure, the drive signal MS for the optical system adjustment motor is generated based on this skew angle, and the optical system adjustment motor is thereby rotated.By rotating the optical system, the position of the optical system can be determined. Adjust. However, if this continues, as shown in FIG. 6, the printing will be shifted and the printing start position will be shifted. Therefore, as shown in Fig. 7, at a place Yl away from the first row, Yl sin
Accurate printing can be achieved by delaying the printing start position by θ.

As described above, according to the present invention, since the skew is corrected without moving the paper, paper clogging, wrinkles, paper angle correction errors, etc. are reduced, and the paper does not become skewed again before reaching the drum after skew correction. and,
The text lines do not become jagged, as they do when video map data is corrected.

〔Effect of the invention〕

As explained above, according to the present invention, offsets in the sub-scanning direction are handled by adjusting the print start timing with the standby roller, detecting with a sensor, and changing the laser emission timing if there is an error. Further, offset in the main scanning direction can be corrected by changing the printing start position, so accuracy can be obtained without depending on the accuracy of the mechanical part.

Furthermore, since the skew can be corrected without moving the paper, paper jams, wrinkles, paper angle correction errors, etc. are reduced, and the paper does not become skewed again before it reaches the drum after skew correction. Furthermore, the character lines do not become jagged, which is the case when conventional video map data is corrected.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of the present invention, Fig. 2 is a block diagram of the control circuit of the present invention, Fig. 3 is an explanatory diagram of the sensor section of the present invention, and Figs. 4 to 7 are diagrams of the skew correction of the present invention. An explanatory diagram, FIG. 8 is a conventional main part configuration diagram, and FIGS. 9 to 11 are explanatory diagrams of problems in conventional skew correction. (Explanation of symbols) 1... Standby roller, 2... Photosensitive drum, 3... Optical system, 4... Control circuit, 5... Sensor, 41... BD value correction circuit, 42 ...Video data transmission circuit, 43...Drive signal generation circuit, M...Motor, S...Detection signal, As...Correction signal, CS...Optical system control signal, P... Paper, MS...adjustment motor drive signal, C8...optical system adjustment motor. Main part configuration diagram of the present invention 1 h 151 large 1 Figure 2 Explanatory diagram of the sensor section of the present invention No. 30 Explanatory diagram of the skew correction of the present invention (Part 1) Explanatory diagram of the skew correction of the present invention (Part 2) Part 5 Explanatory diagram of the skew correction of the present invention (part 3) Explanatory diagram of the skew correction of the present invention (part 4) Figure 7 Diagram 8 An explanatory diagram of the conventional skew correction Section 9 An explanatory diagram of the problems of the conventional skew correction Conventional Explanatory diagram of problems with skew correction Part 11

Claims (1)

[Scope of Claims] 1. An offset and skew correction method in a printing device, which includes: a detection means (5) for detecting the state of paper carried in between a standby roller that carries paper and a photosensitive drum; After receiving and correcting the detection signal from the detection means, the optical system control signal (CS) and the optical system adjustment motor drive signal (MS
), the offset amount (X) is detected by the detection signal from the detection means to correct the print start position and print start timing, and the paper skew angle ( An offset and skew correction method in a printing apparatus, characterized in that the position of the optical system (3) is adjusted by the drive signal to calculate the skew angle (θ) and correct the skew angle. 2. The control means controls the detection signal and the BD (beamde).
tect) signal and the correction signal (AS
), a video data transmission circuit (42) that receives the correction signal and outputs an optical system control signal (CS) to the optical system, and generates a drive signal for the optical system adjustment motor. 2. The offset and skew correction method according to claim 1, further comprising a drive signal generation circuit (43).