JPS6051709B2 - light beam printer - Google Patents

Description

Detailed Description of the Invention The present invention modulates a light beam with pattern signals such as letters, numbers, symbols, etc., forms an electrostatic latent image on a photoreceptor, develops it, and transfers it to paper. The present invention relates to a light beam printer that performs printing.

The above-mentioned light beam printer is generally shown in Figures 1 and 2.
The configuration is as shown in the figure.

In FIGS. 1 and 2, a light beam from a light beam oscillator 1 is guided to a modulator 3 via a reflecting mirror 2. In FIG. The light beam is modulated in intensity depending on the input signal to the modulator 3, and is further guided to a beam expander 4, where the beam diameter is expanded while remaining parallel, and is incident on a polyhedral rotating mirror 5. A light beam swept horizontally by a polyhedral rotating mirror 5 rotated at a constant speed by a servo motor 6 is imaged as a spot on a photosensitive drum 8 by an f-θ lens 7 . Photosensitive drum 8
has a photosensitive plate Ba consisting of a conductive support, a photoconductive layer and an insulating layer, and the surface of the insulating layer of the photosensitive plate Ba is uniformly positive or negative in advance by a first corona charger 9. is charged with electricity. When the surface of this insulating layer to be charged is irradiated with a light beam and also subjected to alternating current corona discharge from the alternating current corona discharger 10, a pattern is obtained due to the difference in surface potential that occurs depending on the brightness of the light beam, and furthermore, a pattern is obtained on the surface of the insulating layer. When the entire surface is exposed to light by the light source 11, an electrostatic latent image with high contrast is formed. The electrostatic latent image is developed in a developing device 12, visualized, and then transferred to a printing paper 13 using a transfer charger 14. - The transferred image is fixed by a heat fixing means 15 such as a heat drum, and characters, numbers,
An electrophotographic print image of a symbol or the like can be obtained. The light beam printer configured as described above employs a corona discharge transfer method in which the printing paper 13 is charged by the transfer charger 14 and then transferred.

Therefore, the printing paper 13 comes into close contact with the photosensitive drum 8 which is charged with the opposite polarity. Although the feeding speed of the printing paper 13 and the rotation of the photosensitive drum 88 are designed to be synchronized, it is difficult to achieve complete synchronization due to manufacturing problems, and a slight error usually occurs. Due to this error, when continuous printing paper is used, for example, if the rotation of the photosensitive drum 8 is slightly fast, the printing paper 13 will jam, and conversely, if the rotation of the photosensitive drum 8 is slightly slow, the sprocket hole of the printing paper 13 will be damaged. do.
These accidents can be prevented if there is some degree of slippage between the printing paper 13 and the photosensitive drum 8, but as mentioned above, the printing paper 13 is in close contact with the photosensitive drum 8 due to electrostatic force, so the transfer area In this case, a braking force or a feeding force is applied to the printing paper 13 depending on the rotational speed of the drum 8. The present invention aims to solve the above-mentioned problems in light beam printers, and a shield plate is positioned between a transfer charger and the printing paper only while an image is not transferred to the printing paper, so that the printing paper is not charged. In this way, the paper is released from close contact with the photosensitive drum and the feed amount of the paper is adjusted. The present invention will be described in detail below with reference to the illustrated embodiments. FIG. 3 shows an example of an image transfer section of a light beam printer according to the present invention. A grounded shield plate 16 is positioned between the transfer charger 14 and the printing paper 13. The shield plate 16
is movable to the position shown by the dotted line by the plunger magnet 17, and remains at the position shown by the solid line only during the time when no image is transferred. In the illustrated state, the shield plate 16 is charged by the transfer charger 14, but the charge disappears by grounding. Therefore, in this state, printing paper 1
3 is not charged, so it is separated from the photosensitive drum 8. The feed amount of the separated printing paper 13 is controlled only by a paper feeding device such as a pin tractor, so that there is no slack in the paper or excessive paper! The tension is corrected. When the printing paper 13 is fed by a predetermined number of lines, the plunger magnet 17 is activated to move the shield plate 16 from the position shown by the solid line to the position shown by the dotted line, so that the transfer charger 14 directly faces the printing paper 13. The transfer becomes possible again. Next, FIG. 4 is a block diagram showing an example of the operating circuit of the shield plate 16.

Character information and control information from an external device such as a computer are sent to the character buffer 1 via the interface 18.
94 and command register 20, respectively. The sequence control circuit 21 controls the operation of the light beam printer according to the received control information, and sequentially extracts character information from the character buffer 19 and supplies it to the character generator 22 to generate a print pattern signal for the character information. . This print pattern signal is sent to the print control circuit 23 for each scan line under the control of the sequence control circuit 21, and a bright and dark pattern is formed on the photosensitive drum 8 by the modulator 3 shown in FIG. On the other hand, command register 20
The control information set in includes a start/stop command for basic operations such as starting and stopping, as well as a skip command for leaving a desired number of lines blank. The skip command may be used, for example, to leave several lines blank to avoid printing near perforation lines on the printing paper 13, or to make the boundary between a series of print data and the next print data clear. Used when leaving a line blank. The skip code detection circuit 24 counts up the skip counter 25 every time a skip code is detected from the control information set in the command register 20. The skip counter 25 is reset when a skip code is not detected. When the count value of the skip counter 25 exceeds a certain value, the one-shot pulse generator 26 generates a pulse width corresponding to the count value. It generates pulses and is composed of, for example, a D-A converter and a Schmitt trigger circuit that inputs this output voltage.The pulses from the one-shot pulse generator 26 are passed through a delay circuit 27 for a predetermined period of time. This delay time is set to the time required for the last printed line on the photosensitive drum 8 to pass through the transfer area.The pulse passing through the delay circuit 27 is flipped.
Set flop 28. Said flip●flop 2
A driver 29 for causing current to flow through the coil 17a of the plunger magnet 17 shown in FIG. 3 is connected to the output on the reset side of the plunger magnet 8. This driver 29 has an input Rl
J, the current flows through the coil 17a, but when the flip-flop 28 is set as described above and its input becomes ROJ, the current in the coil 17a is cut off. For this reason, the plunger magnet 17 shown in FIG. 3 is deenergized,
The shield plate 16 is positioned in front of the transfer charger 14.
This condition continues until the flip-flop 28 is reset again, at which time the flip-flop 28
Depends on the above pulses input to. The time during which the pulse continues is proportional to the number of rows skipped, and corresponds to the time required for an area on the photosensitive drum 8 without a transferred image to pass in front of the transfer charger 14. Thus the third
The shield plate 16 shown in the figure is located between the transfer charger 14 and the printing paper 13 while no image is transferred to the printing paper 13.

Note that the above operation control is only an example and is not limited to this.As described above, according to the present invention, when printing on continuous paper with a light beam printer, the action of the shield plate Since the time period during which the paper can be separated from the photosensitive drum is selectively provided, it is possible to prevent the paper from being bent or the sprocket holes from being damaged due to the difference between the paper feeding speed and the rotational speed of the photosensitive drum. can.

[Brief explanation of the drawing]

1 and 2 are diagrams each showing a schematic configuration of a light beam printer, FIG. 3 is a diagram showing a transfer section of a light beam printer according to the present invention, and FIG. 4 is a circuit diagram of a light beam printer according to the present invention. FIG. 2 is a block diagram simply showing the configuration. 1... Light beam oscillator, 3... Modulator, 4... Beam expander, 5... Polyhedral rotating mirror, 7... f
-θ lens, 8... Photosensitive drum, 13... Print paper, 14... Transfer charger, 16... Shield plate, 17
...Plunger magnet.

Claims (1)

[Claims] 1 A light beam modulated by the pattern signal to be printed scans the photoreceptor to form an electrostatic latent image, which is developed and transferred to continuous paper, and then thermally fixed to print. In optical printers that charge continuous paper and perform transfer by bringing it into close contact with the photoreceptor, a movable shield plate is installed between the transfer charger fixed at a predetermined position and the continuous paper, A light beam printer characterized in that the shield plate is positioned between a transfer charger and a continuous sheet of paper to shield the photoreceptor side of the transfer charger only while an image is not transferred.