JPS5984127A - Thermocouple type temperature detector - Google Patents

Abstract

PURPOSE:To eliminate the need for a temperature compensating circuit and a compensating conductor by correcting temperature variation at a reference contact part according to the elapsed time from a power-on point or the detected temperature of a temperature sensor used for another part to be measured, and detecting the temperature of the part to be measured. CONSTITUTION:A heat contact part 13a of a thermocouple 13 is disposed on the exhaust passage 12 in an engine room 11 to be measured, and a reference contact part 13b is positioned in the engine room 11. This reference contact part 13b and input terminals of the A/D conversion part 15 of a controller 14 as a temperature deciding circuit are connected together by conductors 16 and the electromotive force of the thermocouple generated according to exhaust gas temperature is applied to the input terminals of the A/D converter 15. This A/D converter 15 outputs a digital signal corresponding to the electromotive force to a microcomputer 17, which decides the exhuast gas temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a temperature detection device equipped with a thermocouple used in internal combustion engines for automobiles, etc., and particularly relates to a temperature detection device equipped with a thermocouple attached to a part to be measured, and a temperature detection device that inputs the electromotive force of the thermocouple to detect the temperature detected by the thermocouple. The present invention relates to a thermocouple-type temperature detection device that includes a temperature determination circuit that determines the temperature of a measuring section, and a temperature determination circuit that is connected by a conductive wire.

A conventional device of this type is shown in FIG. That is, the temperature at which the temperature of the part to be measured 1 is determined by inputting the electromotive force from the thermocouple 2 and the thermal junction part 2a of the thermocouple 2 attached to the part to be measured 1 such as the exhaust pipe of an automobile internal combustion engine. The thermocouple 2 and the temperature determination circuit 3 are connected to each other by a compensating conductor 4 made of an alloy mainly composed of nickel, and the reference junction of the thermocouple 2 is connected to the determination circuit 3 at a separate location. 2b
is set on the temperature determination circuit 3 side. Then, the thermocouple 2 is caused to generate an electromotive force according to the temperature difference between the thermal contact portion 2a and the reference contact portion 2b. E, here, temperature judgment circuit 3
In order to accurately determine the temperature of the measured part 1 by the temperature determination circuit 3, even if the electromotive force of the thermocouple changes due to a change in the temperature of the reference junction part 2b, the temperature inside the temperature determination circuit 3 is adjusted. A temperature sensor 5 for detecting , and a temperature compensation circuit 6 comprising, for example, a thermistor with a negative characteristic, for correcting the changed electromotive force upon receiving the signal from the temperature sensor 5 are provided.

Then, the electromotive force corrected by the temperature compensation circuit 6 is input to the A/D converter 7, and the A/D converter 7 outputs a digital signal corresponding to the electromotive force to the microcomputer 8. The microcomputer 8 that receives this digital signal determines the temperature of the part to be measured 1 based on the digital signal.

However, such a conventional temperature detection device uses a temperature compensation circuit 6 or an expensive compensation lead wire 4, which increases the manufacturing cost of the device.

In the present invention, even if the temperature of the reference junction of a thermocouple changes, the temperature of this reference junction is indirectly determined by the elapsed time from power-on or the temperature detected by a temperature sensor used in another part to be measured. This was done with a focus on the fact that it can be predicted. For this purpose, the thermocouple and the temperature judgment circuit installed at a remote location are connected by a conductive wire, and the elapsed time from the power-on time or the detected temperature of the temperature sensor used for other measured parts and the reference junction are connected. A reference junction temperature corresponding to the elapsed time or the detected temperature is read from a memory in which a correlation with the part is stored in advance, and the temperature of the measured part determined by the electromotive force is determined based on this reference junction temperature. It is an object of the present invention to provide a low-cost temperature detection device that has a configuration that performs correction and eliminates the need for a temperature compensation circuit and compensation conductor.

Hereinafter, an explanation will be given based on an embodiment shown in FIG. 2 of the present invention. In this embodiment, an example in which the present invention is applied to measurement of exhaust gas temperature of an internal combustion engine for an automobile will be described.

In the figure, the hot junction part 13a of the thermocouple 13 faces the exhaust passage 12 in the engine room 11, which is the part to be measured, and the reference junction part 13b for the hot junction part 13B is located in the engine room 11. It is. This reference junction part 1
3b and the input terminal of an A/D converter 15 of a control device 14 as a temperature determination circuit provided in the vehicle interior are connected by a conductor (for example, copper m) 16), and the thermocouple generated depending on the exhaust temperature is connected. An electromotive force is applied to the input terminal of the A/D converter 15.

Then, the A/D converter 15 outputs a digital signal corresponding to the electromotive force to the microcomputer 17, and the exhaust temperature is determined in the microcomputer 1T based on the digital signal.

Further, the input terminal of the A/D converter 15 is connected to the output terminal of a water temperature sensor 1B for detecting the groove depth of the cooling water, which is used for correcting the water temperature of the fuel injection amount in the electronically controlled fuel injection device. The cooling water temperature is input to the microcomputer 17 via the A/D converter 15.

The memory 17a of the microcomputer 17 stores the reference junction portion 1 of the thermocouple 13 corresponding to the temperature change of the water temperature sensor 18.
The correlation between the temperature change of 3fL and the correlation between the electromotive force change with respect to the temperature change of the reference junction part 13b and the temperature of the measured part are stored.

Then, in the central processing unit 17b of the microcomputer 17 as a correction means, the temperature of the reference junction part 13b is determined based on the temperature detected by the water temperature sensor 1B, and the electromotive force input from the thermocouple 13 is calculated based on this temperature. Determine the exhaust temperature.

According to the temperature detection device having such a configuration, the temperature of the exhaust passage 12 can be accurately detected based on the electromotive force input from the thermocouple 13 based on the temperature detected by the water temperature sensor 18, and a temperature compensation circuit and compensation conductor are not required. It is possible to reduce the manufacturing cost of the device without having to do so.

As explained above, the present invention corrects the temperature change at the reference junction of a thermocouple based on the elapsed time since the power is turned on or the detected temperature of a temperature sensor used in another measured part to determine the temperature of the measured part. can be detected accurately, thereby eliminating the need for a temperature compensation circuit and compensation conductor, and reducing the cost of the temperature detection device.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a conventional temperature measuring device, and FIG. 2 is a schematic diagram showing an embodiment of the present invention.

Claims (1)

[Claims] A thermoelectric device that has a thermal junction facing the part to be measured and a reference junction that has a reference temperature for the temperature of the thermal junction, and generates an electromotive force according to the temperature difference between the thermal junction and the reference junction. vs.
A thermocouple temperature detection device comprising a temperature determination circuit that inputs the electromotive force of the thermocouple and determines the temperature of the part to be measured based on the electromotive force, and is connected by a conductive wire, the temperature determination circuit comprising: A memory that stores the correlation between the elapsed time since power-on or the temperature detected by a temperature sensor used in another measured part and the reference junction temperature, and a memory that stores the correlation between the elapsed time or the detected temperature from this memory 1. A thermocouple temperature detection device comprising: means for reading a reference junction temperature and correcting the temperature of the measured part determined by the electromotive force based on the reference junction temperature.