JPS61272811A - Temperature controller - Google Patents

Abstract

PURPOSE:To control the temperature with high accuracy in a simple constitution by arranging a sensor, which detects the temperature around an object to be controlled and a sensor, which detects the temperature of a heater for heating the object to be controlled, in series and controlling the temperature of their resultant resistance value. CONSTITUTION:Since a certain current from a variable constant current source 11 driven by a constant voltage source 10 is given to the series connection between a temperature sensor 18 which detects the ambient temperature of an ink jet head part and a temperature sensor 19 which detects the temperature of the heater, the change of the resultant resistance value due to temperatures of both sensors is converted to a voltage and is inputted to one input of a shift amplifier 14. The detected voltage shifted by the voltge from a shift voltage generator 12 is compared with the reference voltage from a reference voltage generator 15 by an error amplifier 15. The output is power-amplified by a power amplifier 16 to control the ink temperature of an ink jet printer as a driving power of a heater 17.

Description

[Detailed description of the invention] Limb five stand! The present invention relates to a temperature control device, and more particularly, to a temperature control device suitable for use in an inkjet printer or the like to maintain a constant temperature of ink.

Figure 7 is a main part configuration diagram for explaining an example of ink temperature control in a charge control type inkjet printer.
In the figure, 1 is an ink tank, 2 is an ink supply pump, 3 is a filter/heater, 4 is an inkjet head, 5 is a charging electrode, 6 is a deflection electrode, 7 is a gutter, and 8 is an ink recovery pump, as is well known. The ink droplets ejected from the inkjet head 4 are charged at the charging electrode 5 according to the printing information signal, and the deflection electrode 6 gives a deflection according to the amount of charge to print information on a recording paper (not shown). Ink droplets that are not used for this purpose are not charged or deflected and travel straight and are captured by the gutter 7, collected by the pump 8 into the ink tank 1, and reused. Therefore, in the above-mentioned inkjet printer, it is important to form ink droplets into particles with a constant diameter, but this particle formation varies greatly depending on the environment in which the printer is used. Assuming that the temperature is 5° C. to 35° C. and the particulate region is 27° C. to 40° C., at low temperatures, the ink used must be heated up to raise the ink temperature to the desired temperature. Various types of temperature control have been proposed in the past, such as heating the ink supplied to the inkjet head by providing a heater in a part of the filter at the front of the inkjet head, as shown in the illustrated example, or
Although attempts have been made to heat the inkjet head to heat the ink within the inkjet head, it has been difficult to maintain the ink temperature at a desired constant value.

This invention was made in view of the above-mentioned circumstances,
In particular, the purpose of this invention is to provide a temperature control device that can accurately control temperature with a simple configuration.

In order to achieve the above object, the present invention includes a first temperature sensor that detects the temperature around a controlled object, a heater that heats up the controlled object, and a second temperature sensor that detects the temperature of this heater. and a temperature controller for controlling these, the first temperature sensor and the second temperature sensor are arranged in series with a constant current generator in the temperature controller, and the first temperature sensor and the second temperature sensor are arranged in series with a constant current generator in the temperature controller, Performing temperature control using a combined resistance value of the temperature sensor and the second temperature sensor, or
A temperature sensor that detects the temperature of the controlled object, a constant current generator that detects changes in the resistance of this temperature sensor, and a sensor voltage that is generated by the constant current from this constant current generator and the resistance of the temperature sensor. , a reference voltage generator that generates a reference voltage for temperature control, an error amplifier that amplifies the error voltage between this reference voltage and the sensor voltage, and a voltage amplifier that controls the heater with the output of this error amplifier. A temperature control device comprising: a shift voltage generator for amplifying a change in resistance value temperature change of the temperature sensor; The sensor voltage is obtained by amplifying only the change in temperature, or a temperature sensor that detects the temperature of the controlled object, a constant current generator that detects changes in the resistance of this temperature sensor, and a constant current generator that detects changes in the resistance of this temperature sensor. A reference voltage generator that generates a sensor voltage generated by a constant current from a generator and a temperature sensor resistance, a reference voltage for temperature control, and an error amplifier that amplifies an error voltage between this reference voltage and the sensor voltage. In a temperature control device comprising a voltage amplifier for controlling the output of the error amplifier with a heater, the resistance value deviation of the temperature sensor is adjusted to a reference resistance value with respect to the temperature at room temperature by varying the constant current generator. or a temperature sensor Ta for detecting the temperature around the controlled object, a heater for heating up the controlled object, and a temperature sensor TH for detecting the temperature of the heater; In a temperature control device having a temperature controller that controls these in combination, thermistor sensors having different resistance values are used for the one-degree sensors Ta and TH, and the resistance value of the temperature sensor Ta is changed at the control temperature point. RATC,
When the resistance value of the temperature sensor TH is R8TC, and the resistance value of the temperature sensor Ta at the lower limit of the temperature control range is RATL, RATL < RATC + R6tc, or a temperature sensor that detects the temperature around the controlled object. In a temperature control device that includes Ta, a heater for heating up the controlled object, a temperature sensor that detects the temperature of this heater, and a temperature controller that controls these in combination, a resistor is connected to both temperature sensors. Using a sensor whose value changes linearly with temperature, the temperature coefficient of the temperature sensor Ta is KA, the resistance value at the control temperature is RATC, and the temperature sensor T? + temperature coefficient in KB
+The resistance value at the controlled temperature is R87C). Hereinafter, the present invention will be explained based on examples.

FIG. 1 is an electrical block diagram for explaining one embodiment of the temperature control device according to the present invention, in which lO is a constant voltage source, 11 is a variable constant current generator, and 12 is a shift voltage generator. , 13 is a reference voltage generator, 14 is a shift amplifier, 15 is an error amplifier, 16 is a power amplifier, 17 is a heater, 18 is a temperature sensor (Ta sensor) that detects the ambient temperature of the inkjet head, and 19 is a heater temperature sensor. The constant voltage source 10 is a temperature sensor (TH sensor) to detect, and the constant voltage source 10 is connected to each control element variable constant current power source 11. Shift voltage generator 12. The voltage applied to the reference voltage generator 13 is kept constant, and each control element voltage is kept constant. Further, the variable constant current generator 11 converts changes in the resistance of the sensor into changes in voltage. Temperature sensor 1
8 and 19 are placed in series with the output of the variable constant current generator, and these sensors have resistance values of IKΩ,
It is provided on the assumption that a temperature-sensitive resistor with a deviation of ±2%, a temperature coefficient of 3900 ppm/'c, and a temperature coefficient deviation of ±10% is used. This sensor has a small temperature coefficient with respect to resistance deviation. To explain clearly, if the temperature changes by 10℃, the resistance value is 3900X10-'Xl0-3.9X10-
2 (3,9%) change. That is, a resistance value deviation of ±2% corresponds to a temperature of about 5°C. For this reason, in the illustrated apparatus, the sensor voltage is adjusted in a constant temperature state in which the heater does not work to correct for variations. However, since the environmental temperature at the time of adjustment also changes, the correction value is changed depending on the room temperature at the time of measurement using the temperature coefficient of the sensor. The shift amplifier 14 is used to increase the amount of change since the sensor voltage changes little with respect to temperature, and the shift voltage generator 12 generates the voltage of the portion that does not change, thereby reducing this voltage. It shifts and amplifies it. Reference voltage generator 13
generates a control reference voltage for the sensor voltage amplified by the shift amplifier 14, and defines a reference point for applying power to the heater 17. Error amplifier 15 is shift amplifier 14
The error voltage between the amplified sensor voltage and the reference voltage is amplified.

Figure 2 is a detailed diagram of the electric circuit shown in Figure 1.
Parts having the same functions as in FIG. 1 are given the same reference numerals as in FIG. 1.

In the embodiment shown in FIGS. 1 and 2, temperature sensors 19 (Ta) and 19 (TH) whose resistance value changes linearly with temperature are used, and these are connected in series. Temperature control is performed using this composite resistance value, and the resistance value of the temperature sensor is selected for the heat transfer coefficient, and the ink temperature Ti is selected as T i = (THTa) TE + Ta, so that the control range is constant. The temperature is set to the ink temperature.

To explain in more detail, when the temperature before control is below the control temperature and the temperatures of both sensors are equal (Ta=TH), the resistance value of temperature sensor 18 is RAya, and the resistance of temperature sensor 19 is Rev H.
and the resistance value at the control temperature Tc is R^TCIR
If it is 87C, RATC+R8TC>RAra+R
8TH-(1), and after control, the resistance of temperature sensor 18 and the resistance of temperature sensor 19 are different ('l'a#TH), and at this time, the resistance value of each sensor is RATC+Revc =RAva +R8TH1...
2). Here, let K^ be the temperature coefficient of R^, and if this temperature coefficient KA is linear with respect to temperature, then from equation (2) above, RATC+Revc =RATC(1+KA (Ta
-Tc ) )+Revc (1+ to 8 (TH-
Tc ) ) - (3) holds, and KARATCTa -Tc +KB RIITC(TH
TC)) From 1000, KB Revc TH=Ka R8TCTC-KARA
TC (Ta - Tc), TH=Tc - Ct (Ta - Tc) - (4)
is established, and the ink temperature Ti becomes Ti = (THTa)TE + Ta - (5).

According to the above equations (4) and (5), the ink temperature Ti is: Ti = (Tc - ex (Ta - Tc) - T
a) TE +Ta = Tc TE (1+α) −
Ta(αTε+TE-1)...(6)
becomes.

In Equation (6), the ink temperature is the head peripheral temperature Ta
In order to control it so that it is constant regardless of , αTε+Tε−1−〇 must be satisfied, which results in the following.

Table 1 is a diagram showing the temperature state when Ta sensor IKΩ and TH sensor IKΩ. In Table 1, when TH=0.5,
α=1.

Table 1 Table 2 is a diagram showing the temperature situation when Ta sensor IKΩ and TM sensor 2 are Ω. In Table 2, Tε=0.
When it is 33, it is α-double 2.

Table 2 FIG. 3 shows another embodiment of the present invention, namely the temperature sensor 1.
8.19 is a diagram showing an example using a high-precision thermistor with a resistance value deviation of ±1% and a temperature coefficient of ±1%. Figure 4 is a detailed diagram of the circuit in Figure 3. Parts having the same function as in FIGS. 1 and 2 are provided with the same reference numerals as in FIGS. 1 and 2. In this embodiment, the thermistor sensor has a large temperature coefficient (approximately 35.000 ppm/''C at 10°C), so compared to the embodiments shown in FIGS. 1 and 2, The configuration of a shift voltage generator and shift amplifier is not required.

In FIGS. 3 and 4, Ω is used for 2 and Ω is used for 5 for the Ta sensor. This means that if two Ω wires are used for 2 as shown in the figure, the control point cannot be reached at temperatures below 10°C no matter how much the TH sensor is heated up. This is because the temperature coefficient in the low temperature range is larger than that in the high temperature range. For this reason,
It is necessary to use a thermistor with a higher resistance value than the Ta sensor for the 78 sensor whose temperature changes with the heater. Figure 6 shows when the ink temperature is set to 30°C or higher, 2 shows the combined resistance value at 30°C when there are two Ω wires, and 3.4 shows the combined resistance value at 30°C when the ink temperature is set to 30°C or higher. It is the value of the hour. This shows that it is uncontrollable below 11°C. When using Ω for Ta sensor 2 and Ω for 5 for TH sensor, the combined resistance value at 30℃ is 5.9 and Ω, and the temperature indicated by 1 Ω for Ta sensor 2 or 5.9 for Ω is -3. ℃ or less, and the operating temperature of the machine is 5.
Since the temperature is above ℃, it can be sufficiently controlled. Ω to 2, Ω to 5
With the combination of , the combined resistance value is 5.9Ω at 30℃
To become, when Ta-Q℃, TH-88℃, Ta-5
℃ when T H-56℃, Ta=10℃ T)l! 47
℃, Ta - 15℃ TH = 39℃, Ta = 20
When the temperature is 35°C, the temperature is controlled at TH-35°C. If the transfer coefficient is 0.6, the ink temperature Ti at this time is when Ta=5℃.
When T H=35.6℃, Ta=10℃, T H=
When 32.2℃, Ta=15℃, TH=30℃, Ta=
At 20℃, TH= 29.6℃.

When Ta=25°C, TH is controlled to 29.5°C.

To explain in more detail, if the temperature of each sensor before control is below the control temperature Tc (Ta=T+<Tc), then between the temperature sensors 18 and 19, RATC+R8TC≦R
ATC+RevM...(7) is established, and after control, Ta < Tc < TH, and RATC+R8TC=
RAva +R11TH...(8) holds true.

In the case of a thermistor, the temperature coefficient of resistance is not a linear equation, so it will be explained with reference to FIG. In FIG. 6, curve A is the resistance value vs. temperature characteristic of a thermistor sensor having a resistance value of 2Ω at 25°C. When a Ta sensor and a 78 sensor are serially connected as in the configuration of this example, the resistance value vs. temperature characteristic is curved with curve B.0 curve B uses an Ω thermistor for both the Ta sensor and Ta sensor 2. The curve is such that Ω is used for the Ta sensor 2 and Ω is used for the TH sensor 5.

If the control temperature (the point at which the temperature control circuit operates) is 30°C, when the Ta sensor 2 is Ω and the TH sensor 2 is Ω, the 6th
In the figure, when the intersection point X is Ω and the Ta sensor 2 is Ω, and the 78 sensor 5 is Ω, the intersection Y is the control point. That is, in the circuit of this embodiment, Ta is connected to sensor 2, Ω is connected to sensor 2, and 78 sensors are connected to sensor 2.
When the temperature is 2Ω, the combined resistance of the sensor is 30°C, and the sum of the resistance values when the temperature is 2Ω is controlled to be 3.4Ω. but,
What must be noted here is that the thermistor resistance value has a large temperature change rate (as in this example, when Ta is constant and Tel
It is necessary to check the following points to see if it can be used for circuits that only change.

That is, R2a +RTH=R2c (9) R2a<R
It becomes 2c.

Here, the operating environment temperature of the inkjet printer is 5℃.
-35°C, equation (9) must hold at Ta=5°C.

Here, in the currently used thermistor sensor, the temperature characteristic B constant corresponding to the temperature coefficient is resistance value at temperature T1, R2; resistance value at absolute temperature T2), and the plot of this characteristic is the sixth
It is a diagram. In the figure, the B constants of the 2Ω and 5Ω thermistors used are 3182 and 3324, respectively.

In FIG. 6, at point XA, Rva=RTC. That is, at a temperature below the XA point, no matter how much temperature control is performed on TH, it becomes uncontrollable. That is, it becomes unusable at temperatures below 12°C. To solve this problem, it may be possible to leave the Ta sensor as is and increase the resistance value of the T8 sensor.

When 5 and Ω are used for the TH sensor, the combined resistance value at 30°C is 5.9 and Ω. In this case, the point where Rva=Rvc is -3.5°C, which is sufficient for use. Ω at Ta=2.

Table 3 shows the ink temperature when the Ω sensor is used for TH=5.

Table 3 From the above explanation, it can be understood that in order to accurately control the ink temperature to a desired temperature, it is possible to change the resistance value balance of the Ta sensor and TH sensor in terms of the transfer coefficient TE.

In FIG. 6, the curve is a temperature curve based on the combined resistance value of the sensors of Ω for Ta2 and Ω for 7M5.

The arrow from the curve means the change in resistance value when temperature is controlled.

...As is clear from the above description, according to the present invention, the resistance value deviation of the temperature sensor is adjusted to the reference resistance value for the temperature at room temperature by changing the constant current generator.
Variations caused by the temperature sensor can be corrected using a variable constant current circuit. In addition, the sensor Ta that detects the temperature around the controlled object and the sensor TH that detects the temperature of the heater have different resistance values, and the sensor T , the temperature coefficient of a is KA, the resistance value at the control temperature is RATC,
The temperature coefficient of the sensor TH is KB, the resistance value at the control temperature is RIITC, the resistance value is the heat transfer coefficient (transfer coefficient), and the ink temperature can be kept constant in the control range. In addition, a high precision thermistor is used as the temperature detection sensor, and the resistance value of the temperature sensor Ta that detects the temperature around the controlled object and the resistance value of the temperature sensor TH that detects the temperature of the heater are set to R^ at the control temperature point, respectively. τc, R6vc
When the resistance value of temperature sensor Ta is RATL at the lower limit of the temperature control range, RATL < RATC+
Reyc, it is possible to perform temperature control without adjustment.

To explain in more detail, according to the embodiment shown in FIGS. 1 and 2, it is possible to control the temperature of an inkjet printer using a sensor with a resistance value that changes linearly with temperature changes. By clarifying the relationship between the sensor resistance value and the heat transfer coefficient, constant control is possible, and more accurate control can be achieved by correcting small resistance changes due to sensor temperature changes using the shift voltage. becomes possible. Furthermore, according to the embodiments shown in FIGS. 3 and 4, it is possible to control the temperature of an inkjet printer using a high-precision thermistor, and it is possible to cover uncontrollable areas by combining the resistance values of the thermistor sensors. Also, since a high-precision thermistor with large temperature changes is used, the control circuit is simple. Furthermore, as an advantage common to the above two embodiments, Ta sensor and TH
The control circuit is simple because the sensors are arranged in series and the temperature is controlled by their combined resistance value. Furthermore, since the composite resistance value is corrected by a variable constant current circuit to correct for room temperature variations in these resistance values, there are advantages such as high precision control is possible even if the sensor is not very precise. There is.

[Brief explanation of the drawing]

FIG. 1 is an electrical block diagram for explaining one embodiment of the present invention, FIG. 2 is a detailed electrical circuit diagram of FIG. 1, and FIG.
4 is a detailed electrical circuit diagram of FIG. 3, and FIG. 5 is a temperature characteristic diagram of a temperature-sensitive resistance sensor. FIG. 6 is a temperature characteristic diagram of a thermistor, and FIG. 7 is a diagram showing an example of ink temperature control in a conventional inkjet recording apparatus. 10... Constant voltage source, 11... Variable constant current generator, 1
2... Shift voltage generator, 13... Reference voltage generator, 14... Shift amplifier, 15... Error amplifier, 1
6...Power amplifier, 17...Heater, 18...T
a sensor. 19...TH sensor.

Claims (5)

[Claims] (1) A first temperature sensor that detects the temperature around the controlled object, a heater that heats up the controlled object, a second temperature sensor that detects the temperature of this heater, and a temperature controller that controls these. In a temperature control device having
The first temperature sensor and the second temperature sensor are arranged in series with a constant current generator in the temperature controller, and temperature control is performed using a combined resistance value of the first temperature sensor and the second temperature sensor. A temperature control device characterized by: (2) A temperature sensor that detects the temperature of the controlled object, a constant current generator that detects changes in the resistance value of this temperature sensor, and a constant current from this constant current generator and the resistance of the temperature sensor. A reference voltage generator that generates the generated sensor voltage and a reference voltage for temperature control, an error amplifier that amplifies the error voltage between this reference voltage and the sensor voltage, and a heater that is controlled by the output of this error amplifier. The temperature control device includes a shift voltage generator for amplifying a change in resistance value of the temperature sensor by a change in temperature, and a shift voltage generator for amplifying a change in resistance value of the temperature sensor by a voltage that does not cause a change in temperature of the temperature sensor. A temperature control device characterized in that the sensor voltage is obtained by amplifying only the change amount using a shift amplifier. (3) A temperature sensor that detects the temperature of the controlled object, a constant current generator that detects changes in the resistance of this temperature sensor, and a constant current generated from this constant current generator and the temperature sensor resistance. A reference voltage generator that generates a sensor voltage and a reference voltage for temperature control, an error amplifier that amplifies the error voltage between this reference voltage and the sensor voltage, and a voltage that controls the output of this error amplifier to the heater. The temperature control device comprising an amplifier includes a variable constant current generator that varies the constant current generator to adjust the resistance value deviation of the temperature sensor to a reference resistance value for the temperature at room temperature. Temperature control device. (4) Temperature sensor Ta that detects the temperature around the controlled object
In a temperature control device having a heater for heating up a controlled object, a temperature sensor T_H for detecting the temperature of this heater, and a temperature controller for controlling these in combination, the temperature sensors Ta and T_H are connected to each other. When using thermistor sensors with different resistance values, and at the control temperature point, the resistance value of the temperature sensor Ta is R_A_T_C,
Let the resistance value of the temperature sensor T_H be R_B_T_C,
The resistance value of the temperature sensor Ta at the lower limit of the temperature control range is R_
When A_T_L, R_A_T_L<R_A_T_C
A temperature control device characterized in that +R_B_T_C. (5) Temperature sensor Ta that detects the temperature around the controlled object
In a temperature control device that has a heater for heating up a controlled object, a temperature sensor T_H that detects the temperature of this heater, and a temperature controller that controls these in combination, a resistance value is set for both temperature sensors. The temperature coefficient of the temperature sensor Ta is K_A, and the resistance value at the control temperature is R_A_T.
_C, and the temperature coefficient of the temperature sensor T_H is K_B,
The resistance value at the control temperature is R_B_T_C, and when K_AR_A_T_C/K_BR_B_T_C=α, α=(1-T_E)/T_E (where, T_E is the heat transfer coefficient). Temperature control device.