JPH05126647A - Temperature sensor unit - Google Patents

Abstract

PURPOSE:To invariably correctly measure the temperature by compensating the measurement error caused by the difference of the thermal time constant between two sensors with a simple structure in a temperature sensor unit constituted of an infrared sensor and a correcting temperature sensor detecting the temperature of the infrared sensor and correcting its output. CONSTITUTION:A member having a large heat capacity is provided on at least one sensor having a good heat following property within an infrared sensor 91 and a correcting temperature sensor 93 for correcting its temperature characteristic, the difference of the heat time constant between two sensors 91, 93 is apparently resolved, and the following properties of two sensors 91, 93 against the temperature change are made nearly equal. The temperature characteristic of the infrared sensor 91 can be invariably correctly corrected, and the correct temperature measurement is realized.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a temperature sensor unit for measuring the surface temperature of an object to be measured based on infrared rays emitted from the object to be measured.

[0002]

2. Description of the Related Art In an electrophotographic printer or the like, it is necessary to maintain the surface temperature of a heat fixing heat roller at an optimum value in order to fix a toner image well on a sheet. Therefore, in the thermal fixing device of this type, it is necessary to measure the surface temperature of the heat roller accurately and quickly, and to feedback-control the energization / disconnection of the heater according to the value. As a configuration for this, conventionally, for example,
As disclosed in Japanese Patent Application Laid-Open No. 58-160972, a non-contact type infrared sensor is installed in the vicinity of a heat roller, and the temperature is measured by receiving infrared rays emitted from the heat roller. Scheme schemes have been developed.

A temperature sensor using such an infrared sensor has the advantages that the temperature can be measured quickly without contacting the temperature-measured object and that the object is not damaged.
However, the output signal level of the infrared sensor has the property of being influenced by the ambient temperature. Therefore, in a temperature control circuit using this type of infrared sensor, a correction temperature sensor for detecting the temperature of the infrared sensor itself is provided, and the output of the correction temperature sensor is used to correct the output of the infrared sensor. By doing so, the surface temperature of the object to be measured is accurately detected.

[0004]

In the structure in which the infrared sensor and the correction temperature sensor are used in combination as described above, strictly speaking, the thermal time constants of both sensors should be taken into consideration. The "thermal time constant of the sensor" here means the good followability of the temperature change of the sensor itself when the ambient temperature of the sensor changes, and the initial temperature of the sensor and the final temperature The time required to change by a temperature corresponding to {1- (1 / e)} (about 63.2%) of the temperature difference from the reached temperature of.

Actually, for example, the thermal time constant of the thermistor varies depending on its size, the material of the package, etc., and it is generally in the range of 1 to 30 sec in air. On the other hand, the thermal time constant of the infrared sensor is different from that of the thermistor and is generally shorter than that of the thermistor. For example, assuming that the thermal time constant of the thermistor is 10 times that of the infrared sensor, and a trial calculation is made when the ambient temperature rises from 20 ° C to 60 ° C, when the infrared sensor reaches 45.3 ° C, the temperature of the thermistor is still 23.8 ° C. ℃, there is a temperature difference of 20 ℃ or more.

However, conventionally, even when the infrared sensor is provided with a correction temperature sensor for correcting its temperature characteristic, the difference between the thermal time constants of both sensors is hardly taken into consideration, and the infrared sensor is left as it is. It was the actual situation that had been done.
For this reason, when the power of the device is turned on and the ambient temperature of the sensor unit in which the infrared sensor is housed rises from a low temperature, the temperature of the correction sensor rises after this, which is caused by the temperature difference between the two. The measurement error caused by this is larger than when the power was turned on.

Therefore, if the temperature feedback control is performed based on each signal output from such a sensor, the temperature of the temperature-measuring object is measured lower than the actual temperature when the power is turned on. A large overshoot occurs, and it takes a long time to stabilize at the set temperature.

A technique for dealing with such an overshoot phenomenon is disclosed in Japanese Patent Laid-Open No. 62-102267.
Some are described in Japanese Patent Publication. This is intended to compensate for the time lag of the temperature signal of each sensor by software in the temperature control circuit without touching the structure of the sensor unit itself.

The present invention has been made in view of the above circumstances, and the temperature sensor unit can always accurately measure the temperature of an object to be measured in a non-contact manner and does not require any special device in the temperature control circuit. The purpose is to provide.

[0010]

A temperature sensor unit of the present invention is installed in the vicinity of an object to be measured whose temperature is to be measured, and an infrared sensor receives infrared rays radiated from the object to be measured. In a temperature sensor unit for measuring a body surface temperature, a temperature sensor for correction that outputs a temperature signal for correcting the temperature characteristic of the infrared sensor based on the temperature of the infrared sensor in the vicinity of the infrared sensor By providing a member having a large heat capacity to at least one of the correction temperature sensor and the infrared sensor, which has better followability to temperature change, the followability to temperature change of both sensors is made substantially equal. There is a feature in the place.

[0011]

[Operation] By attaching a member having a large heat capacity,
In order to make the two sensors have approximately the same trackability with respect to temperature changes, a member with a significantly larger heat capacity than both sensors should be attached to both sensors, and the difference in the thermal time constants of both sensors should appear apparently. There is a method to prevent it, and a method to match the thermal time constant of the sensor to the thermal time constant of the other sensor as much as possible by attaching a member having a large heat capacity only to the sensor having the better followability to the temperature change. ..

In any of the above methods, if the two sensors have substantially the same trackability with respect to temperature changes, the output of the infrared sensor can always be accurately corrected, so that the temperature of the temperature measurement object can be accurately measured. become able to. Further, the temperature control circuit that controls the temperature of the temperature measurement object based on the output of the sensor unit does not require any special device. Therefore, the so-called hardware or software configuration becomes simple.

[0013]

Embodiments of the present invention will be described below. [1] Configuration of a printer equipped with a temperature sensor unit according to the embodiment [2] Fixing temperature control device [3] Configuration of temperature sensor unit [4] Operation [Effect] 5] Another embodiment will be described in order.

[1] Configuration of Printer FIG. 1 is a diagram schematically showing a configuration of a main part of a printer in which a temperature sensor unit according to an embodiment is mounted. The illustrated printer is a device that forms an image by electrophotography, and is a photosensitive drum 1 that can be rotated at a constant speed in the arrow direction.
Members such as a charging charger 2, a writing head 3, a developing device 4, a transfer charger 8 and a cleaner 11 are arranged around the periphery of the device.

A charge latent image is written line by line by the writing head 3 on the surface of the photosensitive drum 1 which is sequentially charged by the charging charger 2. The charge latent image is toner-developed by the developing device 4 to be visualized, and then transferred onto the sheet 5 by the transfer charger 8. The write head 3 is an LED head provided with the LED array 3a here, but it may be an apparatus that forms a charge latent image by laser scanning.

The above-mentioned paper 5 is stored in a paper storage tray 7 and is sequentially drawn out by a paper feeding roller 6 and is transferred at a predetermined timing to a transfer position (photosensitive drums 1 to 1).
The paper is fed to the transfer charger (between 8) and subjected to the above-mentioned transfer processing. The paper 5 after the transfer processing is conveyed by the conveyor belt 13 and sent to the thermal fixing device 9, where it is subjected to image fixing processing by thermocompression bonding, and then discharged to the paper discharge tray 10 face up.

The heat fixing device 9 has a pressure roller 9b which is a driving roller and a heater roller 9a which is driven and rotated by the pressure roller 9b. Inside the controller 9a,
A heater lamp 9d, which is a heating means, is provided. Further, a sensor unit 9c which is a temperature detecting portion of the fixing temperature control device is disposed near the surface of the heater roller 9a, and a sensing portion 94 of the infrared sensor 91 which is a constituent member thereof.
(See FIG. 4) is parallel to the tangent plane of the facing surface of the heater roller 9a.

[2] Fixing Temperature Control Device FIG. 2 shows a schematic configuration of this control device, and FIG. 3 shows a circuit of a sensor unit and a sensor substrate. Fig. 4 shows the structure of this sensor unit.

* Processing of temperature detection signal The output of the infrared sensor 91 is affected by the ambient temperature.
That is, even if the amount of infrared rays incident from the heater 9a is constant, when the ambient temperature rises, the output voltage of the infrared sensor 91 decreases.

Therefore, in order to measure the surface temperature of the heater 9a, it is necessary to detect the temperature of the infrared sensor 91. Therefore, a thermistor 93, which is a temperature sensor for correction, is provided integrally with the sensor unit 9c as shown in FIG. 4, and its output voltage is the infrared sensor 91c as shown in the circuit of FIG. Is superimposed on the output voltage of. The configuration of the sensor unit 9c will be described in detail later.

That is, the output voltage SG01 (Fig.
2) is the resistance after being amplified by the operational amplifier 21.
It is input to the inverting input terminal of the operational amplifier 22 via R3. On the other hand, the detection voltage SG02 (see FIG. 2) of the thermistor 93 obtained by resistance-dividing the constant voltage V1 by the resistor R6 and the thermistor 93 having the negative resistance temperature characteristic is amplified by the operational amplifier 23 and then amplified. It is input to the inverting input terminal of the operational amplifier 22 via the resistor R4.

Thus, the operational amplifier 22 as a buffer
The voltage signal in which the output voltages of the two sensors 91 and 93 are superimposed is input to the inverting input terminal of the
The signal SG10 corresponding to the surface temperature of the controller 9a is input to the microcomputer 12 (see FIG. 2).

* Outline of fixing temperature control In the temperature control of the heater 9a, the surface temperature of the heater 9a is set to a predetermined set temperature (= maintenance temperature during operation, temperature control temperature, maintenance temperature during standby, etc.). Value) so that the temperature signal SG10
It is executed based on. In order to realize this function, a required program is stored in the microcomputer 12, and the microcomputer 12 is operated according to the program.

That is, from the microcomputer 12, the temperature signal SG
A control signal SG20 is output based on 10 and is sent to the SSR 13 inserted in the power supply circuit from the power supply 14 to the heater lamp 9d. The control method is basically feedback control, and the SSR 13 is on / off controlled so that the temperature of the heat roller 9a reaches a predetermined set temperature.

[3] Structure of Temperature Sensor Unit In the sensor unit 9c, as shown in FIG. 4, an infrared sensor 91 and a thermistor 93, which is a temperature sensor for correction, are housed together in a case 92. , Inside the case 92,
It is filled with a resin material having a low thermal conductivity, for example, amorphous polyether sulfone (PES). The thermal conductivity of PES, which is the filling resin material, is 190 Kcal / aluminum.
mh ℃, iron is 50Kcal / mh ℃, only 0.15Kcal / m
Very low at h ℃.

Therefore, both of the sensors 91 and 93 housed in the case 92 are in a state of being provided with a filling resin material having a thermal time constant sufficiently larger than their own thermal time constants. The trackability of 91, 93 with respect to temperature change is
Both are greatly reduced by the resin material. As a result, the difference between the thermal time constants of the two sensors does not substantially appear on the surface, and the followability with respect to the temperature change is almost the same.

In the case 92, the thermistor 93
Is provided at a position where it comes into contact with the metal package of the infrared sensor 91, and this also ensures uniform followability with respect to temperature changes of both sensors 91, 93. Also,
In front of the sensing section 94 of the infrared sensor 91, the viewing angle of 10
In order to make 0% the surface of the heat roller 9a, a cylindrical window portion 95 whose diameter increases toward the outside is opened.
Moreover, the inner peripheral surface of the window 95 is black so as not to affect the emissivity.

[4] Operation According to the embodiment having the above-described structure, when the heater lamp 9d is energized to heat the heat roller 9a, a part of infrared rays radiated from the surface of the heat roller 9a is an infrared sensor of the sensor unit 9c.
Upon entering 91, the infrared sensor 91 outputs a voltage corresponding to the amount of infrared rays. This output signal has a temperature characteristic that when the amount of incident infrared rays is constant, the higher the ambient temperature of the infrared sensor 91, the lower it becomes.

On the other hand, a thermistor which is a temperature sensor for correction.
93 outputs a voltage according to the ambient temperature of the infrared sensor 91, which is amplified by the operational amplifier 23. This amplified signal has a temperature characteristic opposite to that of the output signal from the operational amplifier 21, and both signals are superposed by the operational amplifier 22.
Therefore, the temperature signal SG10 output from the operational amplifier 22 has a flat temperature characteristic.

Further, each temperature sensor 9 of the sensor unit 9c
Since the trackability of 1 and 93 with respect to temperature is almost the same, as shown in Fig. 5, both sensors 91 and 93 rise in temperature at the same speed, and as in the conventional case (see Fig. 8), the temperature sensor for correction 93
However, there is no delay in raising the temperature. As a result, the time lag of the temperature correction of the infrared sensor 91 is eliminated. Therefore, the temperature control of the heater lamp 9d can be appropriately performed without taking special measures on the temperature control circuit side.

[5] Other Embodiments FIGS. 6 and 7 show a second embodiment of the present invention. In this embodiment, only the infrared sensor 91, which is a sensor having good followability with respect to temperature, is housed in the case 92, and a material having a large heat capacity is filled in the case 92, which is attached to the infrared sensor 91. The thermistor 93, which is a correction temperature sensor having a poorer followability with respect to temperature, is provided in contact with the outer surface of the case 92.

In the structure of the second embodiment, since the thermal time constant on the infrared sensor 91 side is lengthened by the filler having a large heat capacity, as shown in FIG. Can be equivalent. That is, the first
It is possible to obtain the same effect as that of the embodiment.

As the "material having a large thermal time constant" necessary for carrying out the present invention, various materials can be selected according to the magnitude of each thermal time constant of the two sensors. In the case of the combination of the infrared sensor 91 and the thermistor 93 as in the example, in addition to the materials already exemplified, in the resin material,
For example, crystalline polyphenylene sulfide (PP
S) is preferred.

Further, the material is not necessarily limited to the resin material, and as the ceramic material, silicon nitride (Si3N4) (for example, FFX-600 manufactured by Toshiba Ceramics Co., Ltd.), or
Steatite (SS-2 manufactured by Tokyo Gaishi Co., Ltd.) is preferable. The thermal conductivity of the silicon nitride is 0.01 cal / cm s
ec ℃, specific heat is 0.18. The thermal conductivity of the above steatite is 0.008 cal / cm sec ° C.

[0035]

As described above, according to the temperature sensor unit of the present invention, the two sensors have substantially the same followability with respect to the temperature change. Therefore, the temperature of the temperature measurement object can be accurately measured even when the device is started up. Further, there is an effect that the so-called hardware or software configuration of the temperature control circuit that controls the temperature of the temperature measurement object based on the output of the temperature sensor unit can be simplified.

[Brief description of drawings]

FIG. 1 is an explanatory diagram schematically showing a main part of a printer equipped with a temperature sensor unit according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a fixing temperature control circuit.

FIG. 3 is a circuit diagram showing a sensor unit and a circuit board.

FIG. 4 is a cross-sectional view showing a schematic configuration of a sensor unit.

5 is a graph showing a control result when the sensor unit of FIG. 4 is used.

FIG. 6 is a sectional view showing a sensor unit according to a second embodiment of the present invention.

7 is a graph showing a control result when the sensor unit of FIG. 6 is used.

FIG. 8 is a graph showing a control result using a conventional sensor unit.

[Explanation of symbols]

9a heat roller, 9d heater lamp (heating means), 12 microcomputer, 91 infrared sensor, 93 thermistor (correction temperature sensor),

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideyuki Uebayashi, Inventor 2-13-3 Azuchi-cho, Chuo-ku, Osaka, Osaka International Building Minolta Camera Co., Ltd. (72) Eiichi Yoshida, Azuchi-cho, Chuo-ku, Osaka 3-13-3 Osaka International Building Minolta Camera Co., Ltd. (72) Inventor Hiroki Kinoshita 2-33-1 Azuchi-cho, Chuo-ku, Osaka City Osaka International Building Minolta Camera Co., Ltd.

Claims (1)

[Claims] 1. A temperature sensor unit which is installed in the vicinity of an object to be measured whose temperature is to be measured, and which receives an infrared ray radiated from the object to be measured by an infrared sensor to measure the surface temperature of the object to be measured. In the vicinity of the infrared sensor, a correction temperature sensor that outputs a temperature signal for correcting the temperature characteristic of the infrared sensor based on the temperature of the infrared sensor is provided, and the correction temperature sensor and the infrared sensor A temperature sensor unit in which at least the one having the better followability to the temperature change is provided with a member having a large heat capacity so that the two sensors have substantially the same followability to the temperature change.