JPS6274113A - Pi control circuit - Google Patents

Abstract

PURPOSE:To suppress a temperature drop caused by a variation of a heat load, and to prevent deterioration of the quality by increasing an output of an I circuit, only when a form of fixing roller is running. CONSTITUTION:A PI control circuit is constituted of a target value circuit 1, a temperature detecting circuit 2, an adder 3, a P circuit 4 and an I circuit 5, and a heater driving circuit 6 and a fixing roller 7, and the fixing roller 7 is held at a prescribed temperature so that a toner 9 on a form 8 is fixed thermally. In this case, a form running circuit 11 for informing a fact that the form is running, and a correcting value circuit 10 which has stored a correcting value are provided, and an output of the form running circuit 11 and an output of the correcting value circuit 10 are inputted to the I circuit 5. In this state, when a signal for informing a fact that the form is running is received from the form running circuit 11, the I circuit 5 adds an output of the correcting value circuit 10 only during that time and outputs it to the header driving circuit 6, and heats the fixing roller 7.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to electrophotographic printing devices.

[Conventional technology]

Conventionally, this type of PI control circuit has a target value circuit 1, a temperature detection circuit 2, and an adder 3 whose two inputs are the output of the target value circuit 1 and the output of the temperature detection circuit 2, as shown in FIG. , a P circuit 4 whose input is the output of the adder 3, a circuit 5, a heater drive circuit 6 whose two inputs are the output of the P circuit 4 and the output of the circuit 15, and the output of the heater drive circuit as its input. It had a fixing roll 7.

Next, its operation will be explained.

In an electrophotographic printing apparatus, a fixing roller 7 is maintained at a predetermined temperature in order to thermally fix toner 9 on paper 8.

A target value circuit 1 generates the value of the target temperature, and a temperature detection circuit 2 detects the actual temperature of the fuser roll 7. Adder 3
outputs the difference between the target temperature and the actual temperature.

The P circuit 4 and ■circuit 5 have the characteristics of a proportional element and an integral element of a control method well known as PID control, and the P circuit 4 controls a value P proportional to the difference between the target temperature and the actual temperature to the heater. Output to the drive circuit 6.

The I circuit 5 outputs a time-integrated value of the difference between the target temperature and the actual temperature to the drive circuit 6.

The heater drive circuit 6 adds the outputs of the two circuits 4 and the main circuit 5, and heats the fixing roll 7 for a time proportional to the sum.

At this time, each output is as shown in Fig. 3. A steady deviation occurs due to a change in load due to the start of the paper 80 running, and one circuit corrects this and increases the output by ΔI.
match the target temperature.

[Problem that the invention seeks to solve]

In the conventional PI control circuit described above, the temperature of the fixing roll 7 temporarily decreases due to load fluctuations due to paper running, and it takes more than a certain amount of time for the temperature to be corrected. For this reason, there is a disadvantage in that fixing failure occurs in the first half of the paper 8, leading to deterioration in print quality.

The present invention solves the above-mentioned problems and improves print quality using PI.
It provides a control circuit.

[Means for Solving the Problems] The present invention has two inputs: a temperature detector connected to a heating element in contact with a heated medium, a target temperature generating circuit, and the outputs of the target temperature generating circuit and the temperature detector. On the adder, there is a paper running circuit, a correction value circuit, the output of the paper running circuit, the output of the correction value circuit, and an integral control circuit whose three inputs are the output of the adder, and the output of the adder as input. A PI control circuit characterized by having a proportional control circuit, an integral control circuit, a heater drive circuit which takes the output of the proportional control circuit as two inputs, and a heating element which uses the output of the heater drive circuit as human power. It is.

〔Example〕

Next, an embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the present invention has a paper running circuit H that informs that the paper is running, and a correction value circuit 10 in which a correction value is stored. The output is connected to the input of one circuit 5 (1-). The rest of the configuration is the same as the conventional configuration shown in FIG.

The 6° paper running circuit 11, whose operation 1 will be explained next, outputs a signal indicating that the paper 8 is running. Correction circuit] 0 outputs a correction value corresponding to .DELTA. in the graph showing the output of one circuit in FIG.

1 circuit 5 receives a signal indicating that the paper is running, adds the output of the correction value circuit 10 only while the paper is running, and outputs the result to the heater drive circuit 6.

The heater drive circuit 6 adds the outputs of the two circuits 4 and the power circuit 5, and heats the fixing roll 7 for a time proportional to the added value.

〔Effect of the invention〕

As explained above, the present invention increases the output of one circuit only while the paper is running, thereby suppressing the drop in temperature of the fixing roll due to fluctuations in heat load as the paper runs, thereby reducing print quality due to poor fixing. It has the effect of preventing

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an embodiment of the present invention, Fig. 2 is a block diagram showing an embodiment of the prior art, and Fig. 3 is a characteristic diagram showing the relationship between the fixing roll, P, and the output of one circuit. It is. ]... Target value circuit, 2... Temperature detection circuit, 3... Adder, 4... 2 circuit, 5... Engineering circuit, 6... Heater drive circuit, 7... Fixing roll , 8...Paper, 9.
. . . Toner, ]O . . . Correction value circuit, 11 . . . Paper travel circuit.

Claims (1)

[Claims] (1) A temperature detector connected to a heating element in contact with a heated medium, a target temperature generation circuit, an adder having two inputs of the outputs of the target temperature generation circuit and the temperature detector, and a paper running circuit; a correction value circuit, an integral control circuit that receives three inputs of the output of the paper travel circuit, the output of the correction value circuit, and the output of the adder; a proportional control circuit that receives the output of the adder; an integral control circuit; 1. A PI control circuit comprising: a heater drive circuit whose two inputs are the outputs of the control circuit; and a heating element whose inputs are the outputs of the heater drive circuit.