JPS62169180A - Laser beam printer - Google Patents

Abstract

PURPOSE:To easily correct printing deviation caused by the deviation of transfer paper from its carrying position, by providing a selecting means which selects the output of a beam position detecting means in accordance with the output of a positional deviation detecting means and picture formation controlling means which stops picture formation when the positional deviation of the paper carrying position in the main scanning direction detected by the detecting means exceeds a prescribed range. CONSTITUTION:A printer controller 11 inputs BD signals 61 from a beam detector 4, paper position information from a paper position detector 1, and picture information from an external host computer 15 and outputs a VDO signal to a laser unit 52. A BD signal selecting device 12 selects one out of the eight BD signals 61a-61h sent from the beam detector 4 in accordance with a BD selecting signal from a BD selecting signal generating device 13 and outputs the selected BD signal 61 to VDO signal generating device 14. The VDO signal generating device 14 sends a VDO signal 51 to the laser unit 52 in synchronism with the BD signal sent from the external host computer 15. A jam signal generating circuit 16 sends a jam signal when the deviation of the paper carrying position in the main scanning direction detected by the paper position detector 1 exceeds a prescribed range.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a laser beam printer that scans a laser beam to form a reproduced image.

[Conventional technology]

FIG. 6 is a diagram explaining the image forming operation of a conventional laser beam printer, in which 51 is an image signal (VDO signal);
It is input to the laser unit 52. 53 is a laser beam modulated on and off by the laser unit 52;
A motor 54 rotates a rotating polygon mirror 55 at a constant speed. 56 is an imaging lens that focuses the deflected laser beam 57 on the photosensitive drum 5841m.

Therefore, the laser beam 57 modulated by the VDO signal
is horizontally scanned (scanned in the main scanning direction) on the photosensitive drum 58. Reference numeral 59 denotes a beam detector, which has a photoelectric converter Hiroko 601, for example, a photodiode, and a horizontal synchronizing signal (hereinafter referred to as BD double signal) 6, which is the image + tf recording timing.
Outputs 1. 62 is a transfer paper, on which the latent image formed on the photosensitive drum 58 is visualized by a developing device (not shown);
The developer (toner) is transferred by a transfer device (not shown). Next, the operation of each part will be explained.

The laser unit 52 generates a laser beam 53 modulated based on the input VDO signal 51. The VDO signal 51 is generated from a control section (not shown) inside the laser beam printer. The modulated laser beam 53 is deflected by a polygon mirror 55 (rotating at a constant speed) having a plurality of mirror surfaces driven by a motor 54. The deflected laser beam 57 scans the photosensitive drum 58 at a constant speed. Further, the laser beam 57 is focused onto the photosensitive drum 58 by the imaging lens 56 . When the photosensitive drum 58 rotates at a constant speed and the laser beam 57 scans at a constant speed, a latent image based on the VDO signal 51 is formed on the photosensitive drum 58. At this time, a beam detector 59 is fixed near the scanning start position of the laser beam 57.
The light is incident on the photoelectric conversion element 6o, and a BD signal 61 is generated. The BD signal 61 is generated at regular intervals for each scan of the laser beam 57. The control device defines the image position on the photosensitive drum 58 in the main scanning direction by generating the VDO signal 51 for one scan in synchronization with the BD signal 61.

FIGS. 7(a) and 7(b) show the VDO signal 51 and the BD signal 61.
In this timing chart, the same parts as in FIG. 6 are given the same reference numerals.

Note that T indicates the time until the effective image area.

indicates the scanning interval of the BD signal 61.

As can be seen from this figure, after a certain period of time T has elapsed since the beam detector 59 detected the BD signal 61, the VD
Generates O signal 51 (side line part). In addition, in the figure, 3
It shows a scanning line segment.

As described above, the latent image formed on the photosensitive drum 58 is
After being developed by a known electrophotographic process, the transfer paper 6
2, and a note copy is obtained.

FIG. 8 is a plan view showing the relationship between the photosensitive drum 58 and the transfer paper 62 shown in FIG. 6, and the same parts as in FIG. 6 are given the same reference numerals.

In this figure, Ll indicates the left edge position of the image formed on the transfer paper 62, L2 indicates the left margin interval, and L
3 indicates the amount of positional shift, and L4 indicates the distance from the position where the photoelectric conversion element 6o is disposed to the left end position L1 of the image. L5 indicates the left end passing position of the transfer paper 62 to be set. Note that the solid line indicates the positional deviation Ffj (
A state in which the transfer paper 62 is conveyed at L3 is shown.

Conventionally, the beam detector 59 includes one photoelectric conversion element 6o, and the beam detector 59 has a fixed position with respect to the photosensitive drum 58. Therefore, Fig. 7(a),(b)
The left end position Ll of the image on the photosensitive drum 58 can be defined in the relationship between the BD signal 61° and the VDO signal 51 shown in FIG. Therefore, in order to set the left margin of the image transferred to the transfer paper 62 to the left margin interval L2, it is sufficient to set the transfer paper 62 being conveyed to pass the left end passing position L5.

[Problem that the invention seeks to solve]

However, when the positional deviation of the transfer paper 62 in the main scanning direction X becomes L3 as shown by the solid line, the left margin after transfer becomes L2-L3, and the printing deviation in the main scanning direction X also becomes L2-L3. , there were problems such as image deletion and alteration.

This invention was made to solve the above-mentioned problems, and it is possible to prevent image loss and alteration even if the transferred transfer paper is misaligned in the main scanning direction, and also to prevent the transferred transfer paper from being misaligned in the main scanning direction. It is an object of the present invention to provide a laser beam printer that can prevent inputted image information from disappearing by stopping the formation of one image when the image is transported beyond a range that can prevent deletion and alteration of the image.

[Means for Solving the Problems] The laser beam printer according to the present invention includes a positional deviation detection means for detecting paper conveyance positional deviation in the main scanning direction, and a position of a laser beam horizontally scanned in the main scanning direction. and a beam position detection means that generates a plurality of outputs;
Selection means for selecting the output of the beam position detection means in accordance with the output of the positional deviation detection means, and an image for stopping image formation when the paper conveyance position deviation in the main scanning direction detected by the detection means exceeds a predetermined range. A formation control means is provided.

[Effect]

In this invention, when the positional deviation detection means detects a positional deviation of the conveyed transfer paper, the selection means selects one output from the plurality of outputs of the beam position detection means. When the paper conveyance positional deviation in the main scanning direction detected by the positional deviation detection means exceeds a predetermined range, the image formation control means stops image formation.

〔Example〕

FIG. 1 is a schematic perspective view of a laser beam printer showing an embodiment of the present invention, and the same parts as in FIG. 6 are given the same reference numerals.

In this figure, reference numeral 1 denotes a paper position detector which constitutes a positional deviation detection means of the present invention, and an eight-row LED array 2 arranged at a predetermined position on the left end of the transfer paper 62 on the paper transport path and It is composed of eight phototransistor arrays 3 arranged vertically symmetrically with respect to the transfer paper 62.

Reference numeral 4 denotes a beam detector forming a p-stage beam position detection according to the present invention, which is composed of eight photodiode arrays 5, detects a laser beam 57, and outputs BD signals 61a to 61, which will be described later.
Output h. BD signals 61a to 61d are BD signals to be described later.
One is selected by the signal selection device (selection means) 12.

FIG. 2 is a block diagram illustrating the control operation of the laser beam printer shown in FIG. 1, and the same parts as in FIGS. 1 and 6 are given the same reference numerals.

In this figure, reference numeral 11 denotes a printer control device, which inputs a BD signal 61 from the beam detector 4, paper position information from the paper position detector 1, and image information from an external host computer 15, which will be described later, to the laser unit 52. A VDO signal 51 is output.

12 is a BD signal selection device; a BD selection signal generation device 13;
Among the eight BD signals 61a to 81h sent out from the beam detector 4 in response to the BD selection signal from the VDO signal generator V! 114. The VDO signal generator 14 generates a VDO signal 51 in synchronization with the BD double signal sent from the external host computer 15.
is sent to the laser unit 52. Reference numeral 16 denotes a jam signal generation circuit, which performs image formation (not shown) in response to a command sent from the BD signal selection device 12 when the paper conveyance position deviation in the main scanning direction detected by the paper position detector 1 exceeds a predetermined range. Sends a jam signal that stops the drive of the unit.

When the laser beam 57 scans the photosensitive drum 58 once, eight photodiode arrays 5 provided in the beam detector 4
The laser beam 57 successively irradiates the BD signals 61a to 61h from the beam detector 4, and input them to the BD signal selection device 12 in the printer control device 11. On the other hand, in the paper position detector 1, eight LEDs
The array 2 and eight phototransistor arrays 3 are paired, and when the light from the LEDs of the LED array 2 enters each of the seven phototransistor arrays 3, the phototransistor is ONL, and the light from the LEDs is directed to the transfer paper 62 being conveyed. The phototransistor blocked by is turned off. Therefore, due to the ON10FF state of the phototransistor array 3,
It is possible to detect the position of paper during transport. The paper position information obtained in this manner is sent from the paper position detector 1 to the BD selection signal generator 13. The BD selection signal generating device 13 generates BD signals 61a to 61 according to the paper position information S2.
A signal instructing which BD multiplied signal of 1h should be selected, that is, a BD selection signal S1, is sent to the BD signal selection device 12. However, the BD selection signal St is outputted immediately before the latent image for a certain paper that is the object of paper position information is formed on the photosensitive drum 58, and the BD selection signal S% Sl for the next paper is output. It is held until the timing to output. Note that the paper position detector 1 is installed at a position where the paper position of a certain paper can be detected before outputting the BD selection signal S1 for that paper.

The BD signal selection device 12 selects an appropriate signal from among the eight signals 61a to 61h based on the BD selection signal S1, and sends it to the VDO signal generator 14 as a BD signal 61.VDO The signal generator 14 sends the VDO signal 51 to the laser unit 52 in synchronization with the input BD signal 61.The content of the VDO signal 57 is based on the image information S3 output from the external host computer 15. be.

3(a) to 3(f) are timing charts illustrating the operation of each part in FIG.
lb, 61c, and 61d, and (e) in the same figure shows the selected BD signal 61, in which, for example, the BD signal 61b is selected in accordance with the BD selection signal S1. (f) in the figure shows a case where the VDO signal generator 14 outputs the image information S3 sent from the external host computer 15 using the VDO signal 51 in synchronization with the BD signal 61 shown in (d) in the figure. .

As can be seen from these figures, the BD signals 61a to 61d
By arbitrarily selecting , the output timing of the VDO signal 51 can be adjusted in eight steps within the range of 67W, that is, the image area of the photosensitive drum 58 can be adjusted in eight steps in the main scanning direction. Therefore, if the output timing of the VDO signal 51 is adjusted based on the paper position on the conveyance path, printing deviation in the main scanning direction X can be prevented. Also in the L composition.

By varying the number of photodiodes in the beam detector 4, the adjustment of the image area and the number of stages can be varied.

Next, the jam signal sending operation by the jam signal generating device 16 shown in FIG. 2 will be explained.

In the paper position detector 1, when the light from the LEDs of the LED array 2, which is a pair of 8 LED arrays 2 and 8 phototransistor arrays 3, enters each phototransistor, the phototransistor turns on. , the phototransistor whose LED light is blocked by the transfer paper 62 being conveyed is O.
Although the transfer paper 6 is configured to be FF, it is
2 is in the main scanning direction X than the 8 LED array 2
If the phototransistor array 3 is shifted, all eight phototransistor arrays 3 are turned on or off. At this time, the BD signal selection device 12 recognizes that a jam has occurred and sends a command to the jam signal generation circuit 16. In response to this, the jam signal generation circuit 16 sends a jam signal to an image forming section (not shown) to stop image formation, thereby preventing the input image information from disappearing.

4 and 5 are perspective views schematically showing a laser beam printer according to another embodiment of the present invention. In FIG. 4, 21 is a beam detector, which is composed of a photoelectric conversion element 21a such as a COD. and generates several BD signals 61 depending on the incident position of the laser beam 57.

In FIG. 5, 22 is a beam detector, and the optical fiber/<
71/22a, and is used when there is no installation space for the beam detector 22.

〔Effect of the invention〕

As explained above, the present invention includes a positional deviation detection means for detecting paper conveyance positional deviation in the main scanning direction, a position of a laser beam horizontally scanned in the main scanning direction, and a
A beam position detection means that generates a plurality of outputs, a selection means that selects the output of the beam position detection means according to the output of the position deviation detection P stage, and a paper conveyance position deviation in the main scanning direction detected by the detection means. Since an image formation control means is provided that stops the formation of one image when a predetermined range is exceeded, it is possible to easily correct printing deviation in the main scanning direction due to deviation in the paper conveyance position of the laser beam printer, and the transfer paper being conveyed can be easily corrected. Even if a positional shift occurs in the main scanning direction, image deletion and alteration can be prevented. In addition, if the transferred transfer paper is misaligned in the main scanning direction beyond a predetermined range, image formation will be stopped.
Loss of image information can be prevented. Furthermore, since the number of paper sensing elements can be minimized, the total cost of the device can be significantly reduced, and has many excellent advantages. Note that this invention is particularly effective when performing double-sided copying.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of a laser beam printer showing an embodiment of the present invention, FIG. 2 is a block diagram explaining the control operation of the laser beam printer shown in FIG. 1, and FIG.
) to (f) are timing charts explaining the operation of each part in FIG. 2, FIGS. 4 and 5 are perspective views schematically showing a laser beam printer showing other embodiments of the present invention, and FIG.
The figure is a diagram explaining the image forming operation of a conventional laser beam printer, Figures 7(a) and (b) are timing charts showing the relationship between the VDO signal and the BD double signal, and Figure 8 is the photosensitive image shown in Figure 6. FIG. 3 is a plan view showing the relationship between a drum and transfer paper. In the figure, 1 is a paper position detector, 2 is an LED array, 3 is a phototransistor array, 4, 21, 22 are beam detectors, 11 is a printer control device, 12 is a BD signal selection device,
13 is a BD selection signal generator, 14 is a VDO signal generator, 16 is a jam signal generator, 51 is a VDO signal, 6
1 has a BD double signal. Fig. 1 61a to 61h: so double signal 2 Fig. 3 T ΔTw-1 Fig. 4 Fig. 5 Fig. 6 Fig. 7 Fig. 8 Fig. 62 bl

Claims (1)

[Claims] In a laser beam printer that scans a recording medium with a beam in the main scanning direction to form a latent image, and records the image by transferring the latent image onto a transferred transfer paper after development, the paper is transported in the main scanning direction. positional deviation detection means for detecting positional deviation; beam position detection means for detecting the position of the laser beam horizontally scanned in the main scanning direction and generating a plurality of outputs; a selection means for selecting an output of the beam position detection means in accordance with the output of the beam position detection means; and an image formation control means for stopping image formation when the paper conveyance position deviation in the main scanning direction detected by the detection means exceeds a predetermined range. A laser beam printer characterized by: