Temperature Measuring Resistor Probe

1. Field of the Invention

The invention lies in the field of temperature measuring probes, particularly probes for measuring temperatures in the exhaust of an internal combustion engine.

2. Prior Art

Thermistors are universally known. The term "thermistor" has reference to a temperature-dependent resistor comprised of semiconductor material having a relatively high negative temperature coefficient. Thermistors are also referred to as NTC (negative temperature coefficient) resistors. While silicon, germanium, or Groups III-V compounds in mono-crystalline form, are predominantly employed as base materials in electronic semiconductor elements, NTC resistors as discrete components are fabricated almost exclusively of poly-crystalline oxide ceramic. The NTC resistor bodies sintered and pressed into formed bodies yield considerable advantages over other semiconductor materials. Above all, they offer the possibility of being able to vary specific resistance and temperature coefficients over wide limits with relatively simple means.

More particularly, this invention is directed to a temperature measuring probe for measuring temperatures in the exhaust gas of an internal combustion engine. The probe incorporates a NTC resistor within a gas-tight metal housing.

A primary object of the present invention is to create a temperature sensor in a vacuum-tight, impact-proof and vibration-proof form (10 g RMS, 0 through 500 Hz) which is suitable for use at temperatures up to about 700.degree. C.

Other and further objects, aims, purposes, features, advantages, embodiments, and the like will be apparent to those skilled in the art from the present specification taken with the accompanying drawing.

The appended FIGURE is a side elevational view of one embodiment of the present invention with some parts thereof broken away and some parts thereof shown in section.

The invention is explained in greater detail with reference to a preferred exemplary embodiment. The temperature measuring probe shown appended in the FIGURE utilizes a temperature sensing NTC resistor 10, which is mounted axially in, and in radially spaced relationship to circumferential side wall portions of, a crimped metal tube or housing 1 consisting of a melt-down alloy (Vacon) containing NiFe or NiFeCo. The tube 1 is sealed at the bottom with a closure cover 2. After the NTC resistor 10 has been inserted into the tube 1 so that its lower end engages into the depression 3 formed in the cover 2, it is clamped about its upper end with centrally apertured circumferentially flanged sleeve 4, which is nestably received within the cross-sectionally circular walls of tube 1. Flanged portions of sleeve 4 are spot-welded to the adjacent walls of tube 1 by spot-welding apparatus (not shown). Within the top end of the tube 1 a ceramic wafer 5 is nestably received and wafer 5 is soldered to tube 1 in gas-tight relationship. Two small tubes 6, which each consist of the same material as the tube 1, are soldered to and carried by the ceramic wafer 5 and extend outwardly from one face of wafer 5. The NTC resistor leads 11 are conducted through these small tubes 6. After an evacuation and aeration process, finally, the leads 11 and small tubes 6 are soldered to one another. This is accomplished, for example, by means of an argon arc, solder ring process, or the like. This method step is conditioned by the fact that the NTC resistor may not come into contact with CO or CO.sub.2 but requires some O.sub.2 for re-oxidation. The crimped metal bead 7 formed in tube 1 allows for easy mounting of the temperature probe to the exhaust manifold of an internal combustion engine by means of a spigot nut 8. The arrow referenced 9 indicates the direction of flow of the exhaust gases in manifold 12.

The temperature measuring probe shown in the FIGURE is thus seen to comprise a combination of tube 1 and NTC resistor 10 together with the coacting components including flanged plate member 4, ceramic wafer 5, leads 11, and crimped bead 7.

Those skilled in the art will appreciate that variations and changes in the present invention can be made without departing from the spirit and scope thereof.