JPH04276776A - Printer - Google Patents

Abstract

PURPOSE:To prevent the deterioration of a photosensitive drum by preventing the photosensitive body from being irradiated with natural emitted light generated from a laser unit in a standby state. CONSTITUTION:The natural emitted light generated in the standby state is previously detected by an identification part 11 provided on an optical path which is scanned by a polygon mirror 4, and a polygon motor stopping position control circuit 19 controls so that the identification part 11 may be always irradiated with the natural emitted light in the standby state, thereby preventing the photosensitive drum 1 from being irradiated with the natural emitted light.

Description

[Detailed description of the invention]

0001

FIELD OF THE INVENTION This invention relates to printers, and more particularly to electrophotographic printers using laser beams.

0002

[Prior Art] Figure 5 shows an example of a conventional electrophotographic printer (hereinafter referred to as a laser printer) using a laser beam.
Shown below. In this laser printer, the external device 7
The video signal sent from the main controller 10
is sent to the laser driver circuit 8 via. The laser driver circuit 8 forms a signal for driving the laser unit 6 (hereinafter referred to as a laser drive signal) and sends it to the laser unit 6 according to instructions from the main controller 10 . The laser unit 6 generates a laser beam modulated by a laser drive signal. The modulated laser beam is reflected by a polygon mirror 4 rotating at a constant rotation speed, and is directed to a photosensitive drum 1 by an imaging lens 3.
Focus in a spot on the top. The photosensitive drum 1 rotates at a constant rotation speed, and the surface of the photosensitive drum 1 is uniformly charged by corona discharge generated by the primary charger 15.

When a laser beam scans the charged surface of the photosensitive drum 1 at a constant speed, an electrostatic latent image is formed on the photosensitive drum 1. Next, the electrostatic latent image on the surface of the photosensitive drum 1 is developed with toner in the developing device 12 to make it a visible image. Next, a negative charge is applied by a transfer charger 13 provided on the back side of the printing paper 18 to transfer the toner on the surface of the photosensitive drum 1 to the printing paper 18. Thereafter, the transferred printing paper 18 is sandwiched between a plurality of fixing rollers 14, and the toner image is fixed.

[0004] Also, in preparation for the next print, the cleaner 17
The residual toner on the surface of the photosensitive drum 1 is removed so that the surface of the photosensitive drum 1 can be cleaned and a clear image can be produced again. Next, the exposure unit 16 erases residual charges on the surface of the photosensitive drum 1 to prevent uneven print density. The above is an overview of the operation of a conventional laser printer.

Next, the operation sequence of a conventional laser printer will be explained using FIG. 6. The main controller 10 counts clock pulses based on the number of rotations of the photosensitive drum 1, and controls the execution of each sequence and the operation of electrical components based on the counted value. When the power is turned on, the device enters a wait state, the fixing roller heater lights up, and temperature control of the fixing roller 14 is started. When the temperature of the fixing roller 14 reaches the specified temperature, the wait time ends and the standby state is entered. The time when the wait time ends and the printer is waiting for a print command from the external device 7, and the time when printing ends and the printer waits for the next print command are called standby states. Further, the time during which the polygon motor 5, photosensitive drum 1, and developing device 12 are activated in response to a print command from the external device 7 is referred to as print time. A latent image is formed on the photosensitive drum 1 by a laser beam oscillated by a laser drive signal within the printing time, and the above-described series of printing operations are performed to output a printing result.

Further, a conventional laser printer uses a laser unit 6 having characteristics as shown in FIG. 4, and is used at an operating point as shown in FIG.

[0007]

[Problems to be Solved by the Invention] Generally, as shown in FIG. 4, the characteristics of a laser unit are that laser light is generated when the threshold current is 23 or more, but when the threshold current is 23 or less, spontaneous emission occurs. It is well known that light is generated. Standby operating point 2 as shown in Figure 4
1 is used in the spontaneous emission light range 24, so spontaneous emission light is generated in the standby state. Photosensitive drum 1
When a latent image is formed, the laser is driven with a laser drive current 20 that is a latent image operating point 22 that is a laser beam oscillation range 25 . Therefore, in a conventional laser printer, in the standby state, the photosensitive drum 1 and the polygon motor 5 are stopped, so one point on the photosensitive drum 1 is irradiated with the above-mentioned spontaneous emission light, causing the one point on the photosensitive drum 1 to deteriorate. There was a problem in that it had a serious effect on printing results.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a printer in which spontaneously emitted light is not irradiated onto a photosensitive drum in a standby state.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the printer of the present invention includes a laser unit that generates a laser beam, and a polygon mirror that rotates and reflects the laser beam from the laser unit and irradiates it onto a photosensitive drum. In a printer equipped with a motor that is in an operating state in which a polygon mirror is rotated and in a standby state in which the rotation is stopped, the printer is provided with an irradiation blocking means that prevents reflected light from the polygon mirror from irradiating a photosensitive drum during a standby state. It is as follows.

[0010] If necessary, the irradiation blocking means includes an identification unit that is provided on an optical path other than the optical path from the polygon mirror to the photosensitive drum and detects reflected light from the polygon mirror;
The configuration includes a motor stop position control circuit that positions the polygon mirror at a position where the identification section performs the above detection in a standby state and stops the motor.

[0011]

According to the printer constructed as described above, in the operating state, the laser beam from the laser unit is reflected by the polygon mirror and irradiated onto the photosensitive drum. In the standby state, laser beam irradiation is not performed, and even if spontaneously emitted light is reflected by the polygon mirror, this reflected light is blocked by the irradiation blocking means, and the photosensitive drum is no longer irradiated.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the printer according to the embodiment shown in FIGS. 1 and 2, a laser unit 6 converts a video signal from an external device 7 into a predetermined laser beam via a main controller 10 and a laser driver circuit 8. . 4 is a polygon mirror that reflects the laser beam from the laser unit 6 while rotating, and passes it through the imaging lens 3 and mirror 2 to the photosensitive drum 1.
It irradiates the area. Reference numeral 5 denotes a polygon motor, which operates to rotate the polygon mirror 4 and to a standby state to stop the rotation. 9 is a polygon motor 5 based on a command from the main controller 10.
This is a polygon motor driver circuit that drives the.

Further, the printer according to the embodiment is provided with an irradiation blocking means for preventing the reflected light from the polygon mirror 4 from irradiating the photosensitive drum 1 during the standby state. This irradiation blocking means includes an identification section 11 that is provided on an optical path other than the optical path from the polygon mirror 4 to the photosensitive drum 1 and detects the reflected light of the polygon mirror 4, and a position where the identification section 11 performs the above detection in the standby state. A motor stop position control circuit for positioning the polygon mirror 4 and stopping the polygon motor 5 is provided.

[0014] The other configurations are the same as those described above, so their explanation will be omitted.

Therefore, this printer operates as follows. A video signal sent from the external device 7 is sent to the laser driver circuit 8 via the main controller 10. The laser driver circuit 8 forms a signal for driving the laser unit 6 (hereinafter referred to as a laser drive signal) and sends it to the laser unit 6 in accordance with the command from the main controller 10 . The laser unit 6 generates a laser beam modulated by a laser drive signal. The modulated laser beam is reflected by a polygon mirror 4 rotating at a constant rotation speed, and is focused into a spot on the photosensitive drum 1 by an imaging lens 3. The photosensitive drum 1 rotates at a constant rotation speed, and the primary charger 1
The surface of the photosensitive drum 1 is uniformly charged by the corona discharge generated in step 5.

When a laser beam scans the charged surface of the photosensitive drum 1 at a constant speed, an electrostatic latent image is formed on the photosensitive drum 1. Next, the electrostatic latent image on the surface of the photosensitive drum 1 is developed with toner in the developing device 12 to make it a visible image. Next, a negative charge is applied by a transfer charger 13 provided on the back side of the printing paper 18 to transfer the toner on the surface of the photosensitive drum 1 to the printing paper 18.

Thereafter, the transferred printing paper 18 is sandwiched between a plurality of fixing rollers 14, and the toner image is fixed. Further, in preparation for the next printing, the surface of the photosensitive drum 1 is cleaned by the cleaner 17, and residual toner on the surface of the photosensitive drum 1 is removed so that a clear image can be produced again. Next, the exposure unit 16 erases residual charges on the surface of the photosensitive drum 1 to prevent uneven print density. The above is an overview of the operation of a laser printer.

Next, the operation sequence of the laser printer will be explained using FIG. 3. Main controller 1
At 0, clock pulses are counted based on the number of rotations of the photosensitive drum 1, and the execution of each sequence and the operation of electrical parts are controlled based on the count value. When you turn on the power,
It enters a wait state, the fixing roller 14 lights up, and temperature control starts. When the temperature of the fixing roller 14 reaches the specified temperature, the wait time ends and the standby state is entered. The time when the wait time ends and the printer is waiting for a print command from the external device 7, and the time when printing ends and the printer waits for the next print command are called standby states. Furthermore, the time during which the polygon motor 5, photosensitive drum 1, and developing device 12 are activated in response to a print command from the external device 7 is referred to as print time. A latent image is formed on the photosensitive drum 1 by a laser beam oscillated by a laser drive signal within the printing time, and the above-described series of printing operations are performed to output a printing result.

During the time when the polygon motor 5 is stopped, the identification section 11 is always detected by the identification section 11 provided in advance on the scanning optical path of the polygon motor 5 and the stop position control circuit 19.
It is stopped at a position where it is illuminated with spontaneous emission light. This prevents the photosensitive drum 1 from deteriorating.

[0020]

Effects of the Invention As explained above, according to the printer of the present invention, it is possible to prevent spontaneous emission light generated during standby from being irradiated onto the photosensitive drum, thereby preventing deterioration of the photosensitive drum during standby. It has the effect of being able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a printer according to an embodiment of the present invention.

FIG. 2 is a diagram of main parts of the printer according to the embodiment.

FIG. 3 is a timing diagram showing the operation sequence of the printer according to the embodiment.

FIG. 4 is a characteristic diagram of the laser unit shown in FIGS. 1 and 5. FIG.

FIG. 5 is a block diagram showing an example of a conventional printer.

FIG. 6 is a timing diagram showing the operation sequence of a printer of a conventional device.

[Explanation of symbols]

1 Photosensitive drum 2 Mirror 3 Imaging lens 4 Polygon mirror 5 Polygon motor 6 Laser unit 7 External device 8 Laser driver circuit 9 Polygon motor driver circuit 10 Main controller 11 Identification unit 12 Phenomenon 13 Transfer charger 14 Fixing roller 15 Primary charger 16 Exposure device 17 Cleaner 18 Printing paper 19 Polygon motor stop position control circuit 20
Laser drive current 21 Operating point during standby 22 Operating point during laser latent image 23 Threshold current 24 Spontaneous emission light generation range 25 Laser light generation range

Claims (2)

[Claims] 1. A laser unit that generates a laser beam, a polygon mirror that rotates and reflects the laser beam from the laser unit and irradiates it onto a photosensitive drum, an operating state in which the polygon mirror is rotated, and a standby state in which the rotation is stopped. What is claimed is: 1. A printer comprising a motor for controlling a photosensitive drum, characterized in that the printer is provided with an irradiation blocking means for preventing reflected light from a polygon mirror from irradiating a photosensitive drum during a standby state. 2. The irradiation blocking means includes an identification section that is provided on an optical path other than the optical path from the polygon mirror to the photosensitive drum and detects reflected light from the polygon mirror, and a position where the identification section performs the above detection in a standby state. 2. The printer according to claim 1, further comprising a motor stop position control circuit that positions the polygon mirror and stops the motor.