Differential carrier temperature sensing method
A method of sensing an internal temperature of a differential carrier includes providing a differential carrier temperature sensing package with an electronic circuit board having a first temperature sensor that is in thermally conductive contact with a thermal conductor, where the thermal resistance of the package and thermal conductor is given and known as R ENC . The package is extended through an opening in a differential carrier that has a fluid in it. The first temperature sensor senses a differential fluid temperature T SNS . The electronic circuit board further has a second temperature sensor, whereby the thermal resistance of the circuit board is a given known resistance R PCB . The second temperature sensor senses an internal package temperature T PCB within the package. Consequently, an internal temperature of the differential is calculated from the equation: T INT =T SNS (1+R ENC /R PCB )−T PCB (R ENC /R PCB ).
1. A differential carrier temperature sensing package comprising:
a package housing comprising an upper portion and a lower portion connected together to form a sealed package housing, the upper portion and the lower portion in thermally conductive contact with an environment external to a differential carrier housing, the lower portion in thermally conductive contact with an outer surface of the differential carrier housing, and the lower portion extended through an opening in the differential carrier housing, wherein the lower portion is in thermally conductive contact with fluid within the differential housing;
an electronic circuit attached to the upper portion within the package housing and in thermally conductive contact with the upper portion of the package housing;
a first temperature sensor disposed on and in thermally conductive contact with the electronic circuit and in thermally conductive contact with a thermal conductor imbedded in and in thermally conductive contact with the lower portion, the lower portion in thermally conductive contact with fluid within the differential housing; and
a second temperature sensor disposed on the electronic circuit, wherein a measured differential carrier fluid temperature T SNS , a measured internal package housing temperature T PCB , a known housing plus thermal conductor thermal resistance R ENC , and a known thermal conductor resistance of the housing at the electronic circuit board R PCB are utilized to determine an internal differential carrier temperature T INT , by way of the equation T INT =T SNS (1+R ENC /R PCB )−T PCB (R ENC /R PCB ).
2. The differential carrier temperature sensing package of claim 1 , wherein the upper and lower portions of the package housing are sealed together.
3. The differential carrier temperature sensing package of claim 1 , wherein the upper and lower portions of the package housing are unitary.
4. The differential carrier temperature sensing package of claim 1 , wherein the upper portion comprises a thermally conductive metal.
5. The differential carrier temperature sensing package of claim 1 , wherein the first and second temperature sensors comprise negative temperature coefficient thermistors.
6. The differential carrier temperature sensing package of claim 1 , wherein the thermal conductor comprises an aluminum rod separated from mechanical contact with an outer surface of the lower portion of the package housing, wherein a thermally conductive contact path from fluid within the differential carrier to the environment external to the differential carrier housing is by way of the lower portion of the package housing, thermal conductor, first temperature sensor, electronic circuit, and upper portion of the package housing.
7. The differential carrier temperature sensing package of claim 1 , wherein the internal housing package temperature T PCB is by way of the electronic circuit and the second temperature sensor;
the differential carrier fluid temperature T SNS is by way of the lower portion of the package housing, thermal conductor, first temperature sensor, and electronic circuit; and
the internal differential carrier temperature T INT is by way of the differential carrier fluid temperature T SNS , known thermal resistance of housing and thermal conductor R ENC , known thermal resistance of housing at electronic circuit board R PCB , and internal housing package temperature T PCB .
8. The differential carrier temperature sensing package of claim 1 , wherein the differential carrier fluid is selected from a group consisting of a mineral—standard base lubricant and a synthetic—premium lubricant.
9. The differential carrier temperature sensing package of claim 1 , wherein the differential carrier fluid is certified from a group consisting of an API GL5 classification oil and SAE J2360 standard oil.
10. A differential carrier temperature sensing package, comprising:
a package housing comprising an upper portion and a lower portion connected together to form a sealed package housing, the upper portion and lower portion of the package housing in thermally conductive contact with an environment external to a differential carrier housing, the lower portion of the package housing also in thermally conductive contact with an outer surface of the differential housing, and the lower portion of the package housing extends through an opening in the differential housing, wherein the lower portion is in thermally conductive contact with a fluid within the differential housing;
an electronic circuit attached to the upper portion within the package housing and in thermally conductive contact therewith;
a first temperature sensor disposed on the electronic circuit and in thermally conductive contact with an outward projection of the lower portion of the package housing, the lower portion of the package housing in thermally conductive contact with a thermal conductor disposed in the fluid within the differential housing; and
a second temperature sensor disposed on the electronic circuit, wherein a measured differential carrier fluid temperature T SNS , a measured internal package temperature T PCB , a known housing plus thermal conductor thermal resistance R ENC , and a known thermal conductor resistance of the housing at the electronic circuit board R PCB are utilized to determine an internal differential carrier temperature T INT , by way of the equation T INT =T SNS (1+R ENC /R PCB )−T PCB (R ENC /R PCB ).
11. The differential carrier temperature sensing package of claim 10 , wherein the thermal conductor has an inward thermal conductor portion disposed thereon, the inward thermal conductor portion disposed within the fluid on an inward end of the thermal conductor.
12. The differential carrier temperature sensing package of claim 10 , wherein the upper and lower portions of the package housing are sealed together.
13. The differential carrier temperature sensing package of claim 10 , wherein the upper and lower portions of the package housing are unitary.
14. The differential carrier temperature sensing package of claim 10 , wherein the upper portion comprises aluminum and the lower portion comprises a high temperature plastic.
15. The differential carrier temperature sensing package of claim 10 , wherein the first and second temperature sensors comprise negative temperature coefficient thermistors.
16. The differential carrier temperature sensing package of claim 10 , wherein the thermal conductor comprises an aluminum rod that is in mechanical contact with an outer surface of the lower portion of the package housing, wherein thermally conductive contact from fluid within the differential carrier to the environment external to the differential carrier housing is by way of the thermal conductor, lower portion of the package housing, first temperature sensor, electronic circuit, and upper portion of the package housing.