JPH0615873A - Image forming device - Google Patents

Abstract

PURPOSE:To ensure that the adjustment of print density and the display of adjustment status can be performed on a panel. CONSTITUTION:If a density change-over switch 15 is pressed, D-FF17Q output changes from logic L to H through an inverter 16, and a transistor 18 turns ON. A reference voltage VREF depends upon the split ratio between a resistor R1 and the composite resistance of R2 and R3, and the voltage is lower than that when the transistor 18 is turned OFF. A D/A converter 11 converts a digital signal from an output port of CPU 8 from a digital to an analogic phase. Further, the converter analogic signal is fed back to a light-emitting current control circuit 6. Consequently, the current to drive a laser becomes less and thereby the amount of toner sticking to a photosensitive drum reduces, thus lowering a print density level.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer capable of controlling print density.

[0002]

2. Description of the Related Art Conventionally, as an image forming apparatus of this type, for example, as shown in FIG. 5, a photosensitive drum 31, which is electrostatically latent imaged by a laser beam, a developing cylinder 32 coated with toner, and a cylinder 32 are mounted. Blade 3 to evenly apply the toner
3. AC bias power supply 3 applied to the developing cylinder 32
4, a DC bias power source 35.

[0003]

However, in the above-mentioned conventional image forming apparatus, the output voltage of the DC power source is changed to adjust the density, and the volume for adjusting the output voltage is located inside the printer. In order to change the amount of toner, it is necessary to open the outer cover of the apparatus to adjust the density, which causes a problem that the adjustment itself becomes complicated.

Further, since the DC voltage used is a high voltage, it is dangerous to provide the adjusting volume outside the printer, so that it is provided inside the apparatus.

[0005]

The present invention has been made for the purpose of solving the above-mentioned problems, and has the following structure as one means for solving the above-mentioned problems. That is, according to the first aspect of the invention, in an image forming apparatus that performs printing using a laser beam, an adjusting unit that adjusts the laser light amount of the laser beam, and a display that displays the state of the print density according to the laser light amount. And adjusting means and display means are provided on the operation panel of the apparatus.

According to the second aspect of the invention, in an image forming apparatus for printing using a laser beam, an adjusting means for adjusting a DC voltage applied to the developing cylinder, and a print density by the DC voltage. And a display means for displaying the above state, and the adjusting means and the display means are provided on the operation panel of the apparatus.

[0007]

In the above structure, the function of adjusting the print density and displaying the state on the panel can be achieved.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 1 is a block diagram showing the configuration of a laser beam printer according to an embodiment of the present invention. In the figure, 1 is a laser diode, 2 is a photodiode for detecting the amount of laser light, 3 is a light emitting current switching circuit for driving the laser diode 1, 4 is video data (hereinafter,
A buffer for sending VDO (abbreviated as VDO), 5 is a light emission constant current circuit for driving the laser diode 1 with a constant current, and 6 is a light emission current control circuit for converting a voltage into a current.

Reference numeral 7 is an amplifier for converting the current flowing in the photodiode 2 into a voltage and amplifying it. Reference numeral 8 is a CPU for controlling the amount of laser light. Inside, a differential amplifier 9 and an A / D are provided. There is a converter 10, which converts a difference voltage between an output voltage from the amplifier 7 and a reference voltage (hereinafter abbreviated as V _REF ) into a digital value and outputs the digital value to an output port. The D / A converter 11 outputs the digital signal from the output port of the CPU 8 to D
/ A conversion, and feeds it back to the emission current control circuit 6.

Here, the reference voltage V _REF is the resistance R1 and R
2 has a voltage value determined by the division ratio of the power supply voltage Vcc1. However, when the density changeover switch 15 is pressed, a clock pulse is applied to the D-type flip-flop (hereinafter abbreviated as D-FF) 17 through the inverter 16,
The Q output of the D-FF changes from logic L to H, and the transistors 18 and 19 are turned on. As a result, V _{REF changes} from the voltage value determined by the division ratio of the resistors R1 and R2 to that of the resistor R1.
The voltage value is determined by the division ratio of the combined resistance of R2 and R3, and the voltage is lower than that when the transistor 18 is OFF. Therefore, the current that drives the laser is reduced,
The amount of toner attached to the photosensitive drum is reduced, and as a result, the print density can be reduced. At this time, since the transistor 19 is turned on, the LED 20 is also turned on.

In the laser beam printer according to the present embodiment, the switch 15 and the LED 20 are on a panel (not shown), and density adjustment and print density display are performed on the panel. As described above, according to this embodiment, the current for driving the laser diode or the voltage applied to the developing cylinder is indicated on the panel, and the state of the print density is displayed on the panel. It is possible to improve the operability and the visibility of the print density.

In addition, when formal printing is not required, such as during trial printing, it is possible to easily select and print a thin mode as the print density, and it is possible to reduce the amount of toner used and save energy. Hereinafter, modified examples of the above embodiment will be described. [Modification 1] FIG. 2 is a block diagram showing the arrangement of a laser beam printer according to Modification 1 of the above embodiment.

In the case of this modification, the resistor R in the preceding stage of the amplifier 7
4, a resistor R5 and a transistor 18 are provided in series, and DF
The inverted output of the Q output of F17 is controlled by the transistor 18
It is pressure. Normally, this inverted output is at logic H level
Then, the transistor 18 turns on, so the input of the amplifier 7
The voltage is I_PD× R4 (I_PDFlows to the photodiode 2.
Current), the transistor 18 is turned off, and amplified
Input voltage to the device 7 is I _PDWhen it becomes × (R3 + R4)
It takes a smaller value. Therefore, the output of the differential amplifier 9 is
And the current that drives the laser diode 1 is also large.
Yes.

However, when the switch 15 is pressed, the inverted output of the Q output becomes the L level, and the transistor 18 turns off.
F, and the input voltage to the amplifier 7 becomes I _PD as described above.
X (R3 + R4), which results in a smaller current for driving the laser diode 1 and a lower print density. It should be noted that in the above embodiment and the first modification, C
Inside the PU, the output of the differential amplifier is converted into a digital value by using the A / D converter, then converted into an analog value again by the D / A converter, and input to the light emission current control circuit 6. CP
It goes without saying that a differential amplifier may be provided outside U and the output thereof may be directly input to the light emission current control circuit. [Modification 2] FIG. 3 is a block diagram showing a configuration of a laser beam printer according to Modification 2. In this modification, the differential amplifier 9 in the above embodiment is digitized and replaced by the subtractor 24. Here, as the signal corresponding to V _REF in the above embodiment, the density data small 21
Alternatively, the setting information of large density data 22 is set to the selector 2
Select at 3, and input it to the subtractor 24. As a result, in the same operation as the above-mentioned embodiment or the first modification,
The density of print density can be adjusted. [Modification 3] As a modification 3, a high voltage DC power supply 3 is shown in FIG.
The case where the voltage V _CONT input to 6 is switched to change the high-voltage DC output voltage to control the print density is shown.

Here, as in the above embodiment, the switch 1 is also used.
When 5 is pressed, the D-FF 17 is passed through the inverter 16.
A clock pulse is added to the D-FF Q output
→ Transits to H and transistor 18 turns on. As a result, V _CONT changes from a voltage value determined by the division ratio of the resistors R1 and R2 to a voltage value determined by the division ratio of the resistor R1 and the combined resistance of R2 and R3, and the voltage lower than that when the transistor 18 is OFF. Become. Therefore, the amount of toner attached to the photosensitive drum is reduced, and the print density can be reduced.
The present invention may be applied to a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0016]

As described above, according to the present invention,
By switching the print density and displaying the print density on the panel of the apparatus, the operability and the visibility of the print density can be improved.

[Brief description of drawings]

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

FIG. 2 is a block diagram showing a configuration of a laser beam printer according to a modified example 1.

FIG. 3 is a block diagram showing a configuration of a laser beam printer according to Modification 2.

FIG. 4 is a block diagram showing a configuration of a laser beam printer according to Modification 3.

FIG. 5 is a diagram showing a configuration of a conventional image forming apparatus.

[Explanation of symbols]

 1 Laser diode 2 Photodiode 3 Light emission current switching circuit 4 Buffer 5 Light emission constant current circuit 6 Light emission current control circuit 7 Amplifier 8 CPU 9 Differential amplifier 10 A / D converter 11 D / A converter 15 Density switching switch 16 Inverter 17 D-type flip-flop 18, 19 Transistor 20 LED 21, 22 Density data 23 Selector 24 Subtractor 31 Photosensitive drum 32 Developing cylinder 33 Blade 34 AC bias power supply 35 High-voltage DC power supply

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G03G 15/06 101

Claims (2)

[Claims] 1. An image forming apparatus for performing printing using a laser beam, comprising: adjusting means for adjusting a laser light amount of the laser beam; and display means for displaying a state of print density according to the laser light amount, the adjusting means. An image forming apparatus, characterized in that the display means is provided on an operation panel of the apparatus. 2. An image forming apparatus for printing using a laser beam, comprising: adjusting means for adjusting a DC voltage applied to a developing cylinder; and display means for displaying a print density state by the DC voltage. An image forming apparatus, wherein the adjusting means and the display means are provided on an operation panel of the apparatus.