JPS59195701A - Controlling method of liquid temperature - Google Patents

Abstract

PURPOSE:To control a liquid temperature most suitably by giving power to a heater until the rise becomes the first set value and adding outputs of an air temperature sensing element and a heater temperature sensing element with weights inversely proportional to respective coefficients of temperature in a normal proportional control to obtain a differential output between this added value and the second set value. CONSTITUTION:Resistances 11, 12, a resistance 13, a temperature sensing element 14 which detects the temperature of the heater, a resistance 15, and a temperature sensing element 16 which detects the air temperature are connected in series to a power source +V, and one ends of the resistance 12 and elements 14 and 16 are grounded. The coefficient of temperature of the element 16 is set to a value higher than that of the element 14, and outputs of elements 16 and 14 are added with the same weights. Then, power is supplied to the heater until the addition output becomes a prescribed first set value, and the rise temperature of a liquid is controlled. When the addition output exceeds the set value, outputs of elements 16 and 14 are added with weights inversely proportional to respective coefficients of temperature, and power is given to the heater on a basis of the differential output between the added value and the second set value to control the temperature of the liquid.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a liquid temperature control method for an inkjet recording apparatus, and particularly to a liquid temperature control method for speeding up temperature heating at the time of startup.

Conventional Art 1-1 In a conventional inkjet recording apparatus, a circuit for implementing a liquid temperature control method in which ink temperature and air temperature are detected and the ink temperature is controlled is configured as shown in FIG. In Fig. 1, l is a constant current circuit, 2 is a temperature sensing element that detects the heater temperature, 3 is a temperature sensing element that detects the air temperature, 4 is an error amplifier, 5 is a comparator, 6.7 is a diode, and 8 is a heater, and the temperature sensing element 2.3 is composed of a thermistor or a temperature sensing resistor and has positive temperature characteristics. The reference voltage Vrθf1 of the comparator 5 is to provide the temperature necessary for rising, and here it is assumed to be 60°C.
shall be. Therefore, the comparator 5 not only determines whether the liquid temperature has reached 60° C., but also has the role of supplying the power necessary for starting up the heater 8. Further, the reference voltage Vref2 of the error amplifier 4 is a voltage for bringing the liquid temperature to a predetermined temperature, and the temperature of the heater 8 is controlled in a normal proportional manner based on the temperature difference between the temperature sensing elements 2.3.

The operation of the conventional circuit configured in this way will be explained with reference to FIG. First, the temperature of the heater 8 in steady state is 20℃,
The temperature is set to 5℃. At this time, in order to quickly raise the liquid temperature, we assume that the sum of the heater temperature and the air temperature must be 60°C, as shown by the straight line in Figure 2. When the temperature is 20°C, the optimum temperature of the heater is controlled to be 40°C, and when the air temperature is 40°C, the optimum temperature of the heater is controlled to be 20°C. However, with inkjet recording devices,
As shown in Figure 3, the installation position of the heater 8 is at the head 9.
The temperature is set high to account for the drop in the ink temperature sent to the head 9, but as the temperature rises, the drop in the ink temperature decreases, so the temperature control circuit If the temperature of the heater 8 is controlled as described above in step 10, an overshoot will occur at the time of startup.

In addition, if the reference voltage Vrefl is set so that it has an optimal rise without overshoot at an air temperature of 10°C, when the urine temperature is 5°C, there will be a large drop in ink temperature, resulting in undershoot, and the rise in ink temperature will increase. The drawback was that time could not be made much faster.

Here, as shown by the straight line a in FIG. 2, the reference voltage Vre
If f4 is set so that the ink temperature is 40℃,
Although no overshoot occurs, the initial objective of fast rise time cannot be achieved.

The present invention has been made in consideration of the above-mentioned drawbacks, and its purpose is to make the temperature coefficient of the urine temperature sensor larger than the temperature coefficient of the heater temperature sensor, so that the output of the air temperature sensor and the heater The outputs of the temperature detectors are added with the same weighting, and until this added output reaches the predetermined first set value, the power required for the rise is given to the heater to control the rise temperature of the liquid, and the normal rise temperature is controlled. In proportional control,
By adding the output of the air temperature sensor and the 3-output of the heater temperature sensor with weighting inversely proportional to each temperature coefficient, we have created a liquid that can be expected to perform optimally at any temperature. A temperature control method is provided.

-I Kuichi The structure of the present invention will be described below based on (1) Examples.

FIG. 4 shows a circuit diagram for carrying out the liquid temperature control method according to one embodiment of the present invention, in which a resistor 11 and a resistor 1
2. Resistor 13 and temperature sensing element 14 that detects the temperature of the heater
A resistor 15 and a temperature sensing element 16 for detecting the temperature are connected in series, and one ends of the resistor 12 and the temperature sensing elements 14 and 16 are each grounded. The connection point between the resistors 11 and 12 is connected to one terminal side of the differential amplifier 18 via a resistor 17, and the connection point between the resistor 13 and the temperature sensing element 14 is connected to the + side of the differential amplifier 18 via a resistor 19. terminal, and is also connected to one side terminal of the error amplifier 21 via a resistor 20, and the connection point between the resistor 15 and the temperature sensing element 16 is connected to the resistor 22.
It is connected to the + side terminal of the differential amplifier 14-8 through the resistor 23, and to the one side terminal of the error amplifier 21 through the resistor 23.

The output of the differential amplifier 18 is connected to one side terminal of the comparator 24, and the + side terminal of the comparator 24 is connected to the reference voltage V.
refl is input, and the reference voltage Vref2 is input to the + side terminal of the error amplifier 21.

The outputs of the comparator 24 and the error amplifier 21 are input to the heater 27 via diodes 25 and 26, respectively. Further, it is assumed that the temperature sensing elements 14 and 16 have the same value at the measurement reference temperature, for example, 25°C. Also resistance 11
．． 12, 13, and 15 all have equal resistance values, and furthermore, resistors 19.20-22 all have equal resistance values.

Note that the temperature sensing element 14 is a temperature sensor for detecting the temperature TH of the heater 27, and the temperature sensing element 16 is a temperature sensor for detecting the air temperature Ta. Further, if the temperature coefficient of the temperature sensing element 14 is "1", the temperature coefficient of the temperature sensing element 16 is set to be larger than "1", but here it is assumed to be "2".

The resistance value of the resistor 20.23 is made to correspond to the temperature coefficient of the temperature sensing element 14.16;
If the resistance values of 23 are R2o and R23, then R20/R
23=172. In other words, the configuration is such that the temperature coefficients of the detection voltages of the temperature sensing elements 14 and 16 to the error amplifier 21 are made equal. The differential amplifier 18 also has a temperature sensing element 14.1.
It operates as an adder that inputs the detected voltage of No. 6 with a weight of "1" and adds both outputs.

Vref4 of the comparator 24 is a reference voltage that gives the maximum temperature required when the liquid temperature rises, and the comparator 24 supplies the power necessary for rising the heater 27 until the temperature detection power VO reaches vrefl, and Vref4
When the voltage exceeds , the output voltage of the comparator 24 becomes zero. The input to one side terminal of the error amplifier 21 is an input indicating the true heater temperature TH+air temperature Ta, and Vref2 is a reference voltage that provides the control target temperature. Further, the diodes 25 and 26 are provided to prevent the rising voltage and steady-state control voltage of the heater 27 from flowing backwards.

Next, the operation of this embodiment will be explained with reference to the operation diagram shown in FIG. In FIG. 5, Tal is the temperature when the temperature coefficient of the temperature sensing element 16 is "1", T a 2 is the temperature when the temperature coefficient of the temperature sensing element 16 is "2", and THl is the temperature when the temperature coefficient of the temperature sensing element 16 is "2". 1 temperature and TI2 respectively indicate the heater temperature of the present invention.

Note that although it should originally be shown in terms of voltage, the explanation is complicated and difficult to understand, so it is shown in terms of temperature.

Furthermore, since the temperature T a 2 is assumed to be twice the temperature coefficient that gives the true relative temperature, it is an apparent value that does not exist.

In the circuit of this embodiment configured in this manner, as is clear from FIG. 5, when the temperature is 20°C, the temperature coefficient of the temperature sensing element 16 is twice that of the temperature sensing element 14. ,
T a 2 appears to be 40°C, and TI2 is 20°C. Therefore, no overshoot occurs. Furthermore, when the air temperature is 5°C, the heater temperature TH is 5°C compared to the conventional example.
The temperature is only 50°C, but in this case, the reference voltage V
This can be solved by adding 5℃ to raf1. At this time,
When the air temperature is 20°C, the maximum temperature at the start is 25°C, but as shown in FIG. 6, the temperature of the outflowing ink is hardly affected by the heat capacity of the head. That is, in FIG. 6, TI (L is the heater 2 when the temperature is low)
7, TiL is the ink outflow temperature when the air temperature is low, THH is the rise temperature of the heater 27 when the air temperature is high, TiH is the ink outflow temperature when the air temperature is high, and Tloss is shown in Figure 3. Heater 2 as shown
This is a temperature loss due to the distance between 7 and the head.

When the rising operation is completed in this way, the error amplifier 2
1, it becomes a steady control state.

Current is supplied to the heater 27 through the diode 26, but the resistance values R2, R2s of the resistor 20.23 are R2
Since o/R23==1/2, the temperature coefficient of the temperature sensing element 16 is isometrically equal to rlJ, resulting in normal proportional control.

Essentially, it is better to strictly match the temperature coefficient of the temperature sensing element 16 that detects the temperature by, for example, twice, and change the reference voltage Vref2, but it is very difficult to match the temperature coefficients. Moreover, the cost also increases.

8-111- As is clear from the above description, the present invention makes the temperature coefficient of the air temperature sensor larger than the temperature coefficient of the heater temperature sensor, so that the output of the air temperature sensor and the heater temperature detection The outputs of each device are added with the same weighting, and the power required for the rise is given to the heater to control the rise temperature of the liquid until the added output reaches a predetermined set value, so it can be used at any temperature. The advantage is that an optimal start-up operation can be expected even when

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional liquid temperature control method, FIG. 2 is an explanatory diagram of the operation of the circuit in FIG. FIG. 5 is an explanatory diagram of the operation of the circuit of FIG. 4, and FIG. 6 is a diagram showing the temporal relationship between heater temperature and ink temperature at startup. It is. 11.12.13.15.17.19.20.23...
- Resistor, 14.16... Temperature sensing element, 18... Differential amplifier, 20... Error amplifier, 24... Comparator, 25.26... Diode, 27... Heater. Patent applicant Ricoh Co., Ltd. 11- Figure 1 Figure 2 Ta -〉('C) Figure 3 4-

Claims (1)

[Claims] The temperature coefficient of the temperature sensor for air temperature is made larger than the temperature coefficient of the temperature sensor for the heater, and the output of the temperature sensor for air temperature and the output of the temperature sensor for the heater are added with the same weighting, and the added output is The rising temperature of the liquid is controlled by supplying the electric power required to start up the heater until it reaches a predetermined first set value, and when the added output exceeds the first set value, the temperature of the air temperature increases. The output of the detector and the output of the temperature sensor of the heater are added with weighting inversely proportional to the temperature coefficient, and power is applied to the heater by the output of the difference between the added value and a predetermined second set value. A liquid temperature control method characterized by controlling the liquid temperature by giving