JPH027466B2 - - Google Patents

Abstract

PURPOSE:To prevent fog due to fluctuation of voltage of a photosensitive body by controlling intensity of laser beams so as to regulsate a fogging region between the first set level at the upper limit chargeable voltage of the body and second set level at a voltage slightly higher than this. CONSTITUTION:When the upper limit of fluctuation range of the chargeable voltage of a photosensitive body is about 150 deg.C higher than 800V standard, 950V is made the first set level, and voltage slightly higher than this, such as 970V is made the second set level. When a switch 32 is connected to the terminal A of the circuit 3 for the first set level, the body 1 is charged to the first set level, and when the switch 32 is connected to the terminal B of the circuit 34 for the second set level, the body 1 is charged to the second set level. Then, the border of the fogging region is adjusted so as to come between both levels by controlling laser intensity. As a result, fog due to fluctuation of the chargeable voltage of the photosensitive body can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION (A) Technical field of the invention The present invention relates to a printer exposure adjustment method and apparatus,
In particular, the present invention relates to a method and apparatus for adjusting the exposure amount of a printer, which makes it possible to easily and reliably adjust the optimum exposure amount in a printing device using a laser exposure method, for example.

(B) Prior art and problems Figure 1 is an example of a general laser printer, Figure 2 is an example of a general laser printer.
FIG. 3 is an explanatory diagram of electrostatic latent image formation, FIG. 3 is an explanatory diagram of laser sensitivity characteristics of a photosensitive drum, FIG. 4 is an explanatory diagram of temperature characteristics of a photosensitive drum, and FIG. 5 is an explanatory diagram of problems in the conventional method.

In FIG. 1, a high voltage power supply circuit 1 includes a charger 2
A high voltage on the order of several KV is supplied to the The photosensitive drum 3 is uniformly charged by the charger 2 so as to have a surface potential of usually about 800V. An optical section including a semiconductor laser 4 converts electrical information into optical information and irradiates the photosensitive drum 3 with laser light. The power of the laser beam is determined by the LD power adjustment circuit 5.
It is now adjustable. BEL part 6 is
The BEL eliminates electricity from the photosensitive drum 3 between the sheets of paper to prevent toner from being developed. The developing section 7 visualizes the electrostatic latent image on the photosensitive drum 3 that has not been neutralized by the laser beam. Then, the visible image on the photosensitive drum 3 is transferred by the transfer section 9 onto the printing paper fed from the paper feed section 8 . In the fixing unit 10, the toner transferred to the paper is fixed to form a permanent image on the paper.
The paper ejecting unit 11 neutralizes static electricity on the paper using a static elimination brush, and sends out the printed paper to the paper transport path. The static eliminating section 12 weakens the electrostatic attraction force on the photosensitive drum 3, and the cleaner section 13 collects residual toner on the photosensitive drum 3.

That is, as shown in FIG. 2, in an electrophotographic printing apparatus, the photoreceptor 20 is first uniformly charged, then light is irradiated to the area to be made white to reduce the potential of that area, and the photoreceptor 3, etc. An electrostatic latent image 21 is formed thereon.

By the way, the laser sensitivity characteristics of the photosensitive drum are as shown in FIG. 3, for example. If the surface potential of the photosensitive drum is above a certain value, the paper will be printed black, and if it is below about 100V, for example, no toner will adhere to it and the paper will remain white. As mentioned above, laser light is used to lower the surface potential of a photosensitive drum that has been uniformly charged with, for example, 800V, but the extent to which the surface potential is lowered depends on the irradiated laser beam, as shown in Figure 3. Depends on light energy. Therefore, when using a printing apparatus, it is necessary to adjust the optimum exposure amount by adjusting the power of the laser beam.

Conventionally, this optimal exposure adjustment was done using, for example, 800V.
This is done by adjusting the volume of the LD power adjustment circuit 5 shown in FIG. 1 under the photoreceptor standard voltage value of . However, even if the predetermined charge voltage supplied to the charger is constant, the surface potential of the photosensitive drum changes depending on the environmental temperature, as shown in FIG. 4, for example. If the initial surface potential of the photosensitive drum differs, of course the surface potential after laser beam irradiation will also be affected. Therefore, even if the optimum exposure amount is adjusted strictly under standard settings,
Variations in photoreceptor voltage often result in deviations from optimal conditions.

In other words, according to the conventional method, when the photoconductor voltage is in the standard setting state, the laser light intensity is adjusted to a level that is strong enough to eliminate so-called fog, and as a result, the photoconductor voltage increases while the printing device is in use. As can be seen from FIG. 5, when the color changes to 100%, fogging occurs and areas that should originally be white become smeared. In the conventional method, even if an attempt is made to make adjustments so that fog does not occur even when the photoreceptor voltage fluctuates, there is no standard for making adjustments, and maintenance personnel must rely on their intuition to make adjustments. In some cases, the amount of laser light was increased too much, leading to overexposure and resulting in thin prints.

(C) Object and Structure of the Invention The present invention aims to solve the above-mentioned problems, and when adjusting the laser beam power, the optimum exposure amount is set in the voltage condition including the voltage fluctuation of the photoreceptor, and then the photoreceptor is adjusted. It is an object of the present invention to provide a method and apparatus for adjusting the exposure amount of a printer, which makes it possible to obtain stable printing results even with fluctuations in the voltage of the photoreceptor by returning the voltage to the standard voltage. Therefore, the exposure amount adjustment method for a printer according to the present invention is applicable to a printer that forms an electrostatic latent image and prints by irradiating light by optical means onto a photoreceptor that has been charged in advance by a charger. A first step of adjusting the amount of light of the optical means so as not to cause background smear on the printed result while the charging voltage of the body is set to the charging voltage equal to the photoreceptor standard voltage value plus approximately the photoreceptor voltage fluctuation amount; ,
a second step of checking whether background smear occurs in the print result with the charged voltage of the photoconductor set to a value higher than the set voltage; If no background smear occurs, the light intensity of the optical means is changed to perform the first and second steps.
It is characterized by repeating the process.

Further, the printer exposure adjustment device of the present invention includes:
An exposure amount adjustment device for a printer that forms and prints an electrostatic latent image by irradiating light by optical means onto a photoconductor that has been charged in advance by a charger, and the device controls the charging voltage of the photoconductor by adjusting the charging voltage of the photoconductor. a first setting means for setting a voltage value that is approximately the sum of a photoreceptor voltage fluctuation amount to a body standard voltage value; and setting the charged voltage of the photoreceptor to a value larger than the voltage value set by the first setting means. a light amount adjustment circuit that adjusts the amount of light of the optical means in a state where at least the charging voltage set by the charge adjustment circuit is supplied to the charger; It is characterized by having the following.

(D) Embodiment of the Invention FIG. 6 is an explanatory diagram of the principle of the present invention, and FIG. 7 shows the configuration of a main part of an embodiment of the present invention.

The charging voltage of the photoreceptor is set as standard, for example,
Although it is determined to be 800V, as shown in FIG. 4, the photoreceptor voltage varies depending on the environmental temperature. It is also affected by the repetition characteristics of the photoreceptor related to the repetition period of charging and neutralization. The variation range of the photoreceptor voltage due to the temperature characteristics, repetition characteristics, etc. of the photoreceptor can be ascertained from statistical data based on experiments and usage results. For example, if the upper limit of the fluctuation range is about 150V above 800V, as shown in Figure 6,
950V is the first setting level. Further, a voltage slightly higher than 950V, for example 970V, is set as the second setting level.

In the case of the present invention, the photoconductor voltage is set to the standard setting state.
It can be easily switched to 800V, a first setting level of 950V, or a second setting level of 970V, for example, by a switch. Conventionally, when adjusting the laser exposure amount, the standard setting condition is
Conventionally, the photoreceptor voltage was fixed at 800V and adjusted, but in the case of the present invention, the photoreceptor voltage is first set to a first setting level of 950V. In this state, adjust the laser light intensity to a level that does not cause fogging. You can easily check whether fog appears or not by actually printing, but just because fog does not appear, it cannot be said that the condition is the optimum exposure condition. . If the amount of laser light is too strong, overexposure may occur and fine lines may not be printed.

However, checking the printing condition of fine lines and the like is not as easy as checking whether fogging occurs or not. Therefore, after adjustment at the first set level, the photoreceptor voltage is set to the second set level of 970V using a switch. Confirm that fogging occurs at this second setting level. That is, as shown in FIG. 6, the amount of laser light is adjusted so that the boundary of the so-called fog area is between the first setting level of 950V and the second setting level of 970V. This adjustment has two setting levels:
Since it is only necessary to check the presence or absence of fog in each case, it is easy to perform the adjustment, and there is no possibility of variations in adjustment depending on the adjuster. After adjusting the laser light intensity, return the charging voltage of the photoreceptor to the standard setting of 800V and use it. By doing the above, fogging will not occur even if the photoreceptor voltage fluctuates, and clear printing results can be obtained.

FIG. 7 illustrates an embodiment of the configuration of the charge control circuit portion of the printing apparatus of the present invention. In the figure, numerals 1 and 2 correspond to those in FIG.
0 is a reference voltage control circuit, 31 is a charging adjustment circuit, 3
2 is a switch, 33 is a first setting level circuit, 3
4 is the circuit for the second setting level, 35 is the OP amplifier,
36 represents a constant voltage diode.

The reference voltage control circuit 30 controls the photoreceptor voltage, for example.
This circuit supplies the high voltage power supply circuit 1 with a control voltage that is set to the standard setting state of 800V. It also has a temperature compensation circuit, etc. The charge adjustment circuit 31 increases the output voltage of the reference voltage control circuit 30 to adjust the photoreceptor voltage to a first set level of, for example, 950V or 970V.
This is a circuit for setting the second setting level. When switch 32 is located at terminal O,
Since the first setting level circuit 33 and the second setting level circuit 34 are not used, the photoreceptor voltage is in the standard setting state. When the switch 32 is connected to the terminal A of the first setting level circuit 33, the output voltage of the first setting level circuit 33 becomes the output voltage of the reference voltage control circuit 30, and the OP amplifier 35
and is supplied to the high voltage power supply circuit 1. The charger 2 is powered by the output of the high voltage power supply circuit 1.
The photoreceptor is charged to the first set level of 950V. When the switch 32 is connected to the terminal B of the second setting level circuit 34, the output voltage of the second setting level circuit 34 is similarly added to the output voltage of the reference voltage control circuit 30. , the photoreceptor is charged to a second set level of 970V. Note that the resistance R ₂ of the second setting level circuit 34
is selected to be smaller than the resistance R ₁ of the first setting level circuit 33. As described above, the set voltage of the photoreceptor can be made variable using a simple short circuit.

(E) Effects of the Invention As explained above, according to the present invention, it becomes possible to easily and reliably adjust the laser exposure amount, and even if the photoreceptor voltage fluctuates, clear images can be obtained without fogging. Print results can be obtained.
This also prevents variations in adjustment depending on the adjuster.

[Brief explanation of drawings]

Fig. 1 is an example of a general laser printer, Fig. 2 is an explanatory diagram of electrostatic latent image formation, Fig. 3 is an explanatory diagram of laser sensitivity characteristics of a photosensitive drum, and Fig. 4 is an explanatory diagram of temperature characteristics of a photosensitive drum. FIG. 5 is a diagram illustrating the problems of the conventional method, FIG. 6 is a diagram illustrating the principle of the present invention, and FIG. 7 is a diagram showing the main structure of an embodiment of the present invention. In the figure, 1 is a high-voltage power supply circuit, 2 is a charger, 30 is a reference voltage control circuit, 31 is a charge adjustment circuit, 33 is a first setting level circuit, and 34 is a second setting level circuit.

Claims (1)

[Scope of Claims] 1. In a printer that prints by forming an electrostatic latent image by irradiating light by optical means onto a photoconductor that has been charged in advance by a charger, a first step of adjusting the light intensity of the optical means so as not to cause background smear on the printing result, with the charging voltage set to a charging voltage that is approximately the photoconductor voltage fluctuation amount added to the standard voltage value of the photoconductor, and charging the photoconductor; and a second step of checking whether or not background smear occurs in the print result while the voltage is set to a value greater than the set voltage, and in this second step, background smear occurs in the print result. A method for adjusting the exposure amount of a printer, characterized in that if there is no exposure, the amount of light from the optical means is changed and the first step and the second step are repeated. 2. An exposure amount adjustment device for a printer that forms and prints an electrostatic latent image by irradiating light by optical means onto a photoreceptor that has been charged in advance by a charger, which adjusts the charging voltage of the photoreceptor. The first voltage value is set to the photoconductor standard voltage value plus approximately the photoconductor voltage fluctuation amount.
setting means for setting the charging voltage of the photoreceptor to the first setting means;
a charge adjustment circuit comprising at least a second setting means for setting the voltage to a value larger than the voltage set by the setting means; and a charging voltage set by at least the charge adjustment circuit is supplied to the charger. 1. An exposure amount adjustment device for a printer, comprising a light amount adjustment circuit that adjusts the amount of light of the optical means in the state.