JPS6261083A - Color printing density controller - Google Patents

Abstract

PURPOSE:To realize a printed density control ensuring a quick response and stability even if different colors are used and to maintain the constantly printed quality by permitting a table converting circuit to correct a sensor spectral sensitivity characteristic for colors used with the aid of a signal which identifies colors used and is transmitted from an electrophotographic developing part. CONSTITUTION:A target value generating circuit 1 generates the target value of the color printed density, an adder 2 outputs the difference between the target value and an output from the table converting circuit 9, and a PID control circuit 3 drives a toner supply part 4 by the quantity in proportion to the difference and supplies color toner to the electrophotographic developing part 5. The table converting circuit 9 has plural tables on printed densities with respect to the output of an AD converter 8 at every color. Namely, conversion characteristics between the output level of a sensor 7 at every color and the printed densities are previously stored. With the aid of the signal of the color used from the electrophotographic developing part 5, which conversion characteristic on the table in used is decided, and the output of the AD converter 8 is converted into a table and outputted to the adder 2.

Description

TECHNICAL FIELD The present invention relates to an electrophotographic printing apparatus, and more particularly to a print density control device for a printing apparatus capable of color printing.

BACKGROUND ART Conventionally, this type of concentration control device has a target value generating circuit 1, an adder 2 whose output is inputted, as shown in FIG.
A PID i11 control circuit 3 which receives the output of this adding device 2 as an input, a toner supply section 4 which receives the output thereof as an input, and an electrophotographic developing section 5 which receives the output of this toner supply section 4 as an input. , a color toner mark 6 on the paper output from this electrophotographic developing section 5, a sensor 7 that detects this toner mark, and an AD whose output is connected to the σ accelerator 2 with the output of the sensor 7 as input. It is composed of a converter 8.

Next, its operation will be explained. A target value generation circuit 1 generates a target value for printing S degrees, and an adder 2 outputs the deviation between the target value and the output from the AD converter 8. The PAD control circuit 3 drives the toner supply section 4 by an amount proportional to the amount of deviation to supply 1 to toner to the electrophotographic developing section 5.

As described above, the circuit shown in FIG. 2 has a configuration and operation well known as feedback control, and has a function of detecting the amount of reflected light from the toner mark 6 and matching the print density with the target value. ing.

In the conventional print density control circuit described above, the sensor 7, which is a component thereof, generally has a spectral sensitivity as shown in FIG. When this is done, the ratio of the output of the sensor 7 to the print density differs depending on the color, as shown in FIG. For this reason, the open loop gain of the circuit varies depending on the color, and as a result, the system's connectivity and stability vary depending on the color to be printed, resulting in a disadvantage that printing quality cannot be made constant.

OBJECTS OF THE INVENTION An object of the present invention is to provide a color print density control device that can maintain constant connectivity and stability of a print density control system even when different colors are used, and that can improve print quality.

Structure of the Invention According to the present invention, there is provided a color print density control device which detects print 11 [II by a sensor and controls the print density according to the deviation between this print density and a preset target print density. Therefore, a table is provided in which the conversion characteristics of printing density for the detection output of the sensor are stored in advance for each color, and the conversion characteristics in the table are specified corresponding to the colors to be printed, and based on the specified conversion characteristics. A color print density control device is obtained, characterized in that the obtained print 111 degrees is compared with the target print density.

Example Next, the present invention will be explained with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In this example, the eye Wf
an iI generation circuit 1, an adder 2 whose output is input,
a PID control circuit 3 whose input is the output of the adder 2;
This PIDυII! 11 A toner supply section 4 which receives the output of the circuit 3 as an input, an electrophotographic developing section 5 which receives the output of the toner supply section 4 as an input, and a toner mark 6 on the paper output from the electrophotographic developing section 5. , a sensor 7 that detects this mark 6, an AD converter 8 that receives the output of the sensor 7, an electrophotographic developing section 5, and an output of the AD converter 8 and an output of the electrophotographic developing section 5. As a human power, it includes a table conversion circuit 9 whose output is connected to the adder 2.

Next, its operation will be explained. The target value generation circuit 1 generates a target value for color printing density, the adder 2 outputs the deviation between the target value and the output from the table conversion circuit 9, and the PID control circuit 3 outputs the deviation amount. The toner supply section 4 is driven by a proportional amount to supply color toner to the electrophotographic development section 5.

The electrophotographic developing section 5 prints printed information and toner marks 6 on the paper.
Print. The sensor 7 detects the amount of light reflected from the toner mark 6 and outputs an analog value proportional to the print density, and the AD converter 8 converts the analog value into a table conversion circuit 9.
is conveyed in digital value. The electrophotographic developing section 5 transmits a signal to the table converter 9 that distinguishes the color of the toner stored therein.

The table converter 9 is a ΔD converter 8 as shown in FIG.
It has a plurality of tables of print m degree values for each color. That is, it is assumed that conversion characteristics between the output level of the sensor 7 and print density for each print color are stored in advance. Based on the signal of the color to be used from the electrophotographic developing section 5, which conversion characteristic in the table 9 is to be used is determined, and the output of the AD converter 8 is converted into the table and output to the adder 2.

DETAILED DESCRIPTION OF THE INVENTION As described in detail, according to the present invention, the spectral sensitivity characteristics of the sensor for the color to be used are corrected by the table conversion circuit using the CM bow that distinguishes the color to be used from the electrophotographic developing section. Even when different colors are used, print density control with constant continuity and stability can be realized, and the print quality can be kept constant.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram showing an example of the prior art, Fig. 3 is a spectral sensitivity characteristic diagram of the sensor, and Fig. 4 is an output characteristic diagram of the sensor with respect to print density. , FIG. 5 is a diagram showing an example of print density conversion characteristics for each color that the table conversion circuit has. Explanation of symbols of main parts 1...Target value generation circuit 3...PAD control circuit 6...Toner mark 7...Sensor

Claims (1)

[Claims] A color print density control device that detects print density using a sensor and controls the print density according to a deviation between this print density and a preset target print density, the print density being controlled according to the deviation between the print density and a preset target print density. A table is provided in which conversion characteristics are stored in advance for each color, the conversion characteristics in the table are specified corresponding to the colors to be printed, and the print density obtained by the specified conversion characteristics is set as the target print density. A color printing density control device characterized by being designed for comparison.