Differential carrier temperature sensing method

Abstract

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.sub.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.sub.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.sub.PCB. The second temperature sensor senses an internal package temperature T.sub.PCB within the package. Consequently, an internal temperature of the differential is calculated from the equation:
T.sub.INT=T.sub.SNS(1+R.sub.ENC/R.sub.PCB)T.sub.PCB(R.sub.ENC/R.sub.PCB).

Claims

1. A method of determining an internal differential carrier temperature T.sub.INT, comprising: measuring a temperature T.sub.SNS of a fluid within a differential carrier; measuring an internal temperature T.sub.PCB of an electronic circuit board disposed within a package housing of a temperature sensing package; utilizing a known housing plus thermal conductor thermal resistance R.sub.ENC of a thermal conductor disposed within the package housing; and utilizing a known thermal conductor resistance of the package housing at the electronic circuit board R.sub.PCB disposed within the package housing of the temperature sensing package, wherein an internal differential carrier temperature T.sub.INT is calculated by way of the equation: T.sub.INT=T.sub.SNS(1+R.sub.ENC/R.sub.PCB)T.sub.PCB(R.sub.ENC/R.sub.PCB) wherein the internal differential carrier temperature Tint is to be used to monitor and control a vehicle within which the differential carrier resides.

2. The method of determining an internal differential carrier temperature of claim 1, wherein thermal energy is conducted from the interior of the differential carrier to the electronic circuit board of the temperature sensing package when the temperature inside the differential carrier is higher than the temperature outside the differential carrier.

3. The method of determining an internal differential carrier temperature of claim 1, wherein thermal energy is conducted from the electronic circuit board of the temperature sensing package to the interior of the differential carrier when the temperature outside the differential carrier is higher than the temperature inside the differential carrier.

4. A method of determining an internal differential carrier temperature, comprising: providing a package housing comprising an upper portion and a lower portion connected together to form a sealed package housing, wherein the upper portion and the lower portion are in thermally conductive contact with an environment external to a differential carrier housing, wherein the lower portion is in thermally conductive contact with an outer surface of the differential carrier housing, wherein the lower portion of the package housing extends through an opening in the differential carrier housing, and wherein the lower portion of the package housing is in thermally conductive contact with a fluid within the differential carrier housing; providing an electronic circuit attached to the upper portion within the package housing, and wherein the electronic circuit is in thermally conductive contact with the upper portion of the package housing; providing a first temperature sensor disposed on the electronic circuit and in thermally conductive contact with a thermal conductor imbedded in and in thermally conductive contact with the lower portion of the package housing, wherein the lower portion of the package housing is in thermally conductive contact with the fluid within the differential carrier housing; providing a second temperature sensor disposed on the electronic circuit; measuring a temperature T.sub.SNS of the fluid within the differential carrier and an internal temperature T.sub.PCB of the electronic circuit board disposed within the package housing; and utilizing a known package housing plus thermal conductor thermal resistance R.sub.ENC of the thermal conductor disposed within the package housing, and a known thermal conductor resistance of the package housing at the electronic circuit board R.sub.PCB, wherein an internal differential carrier temperature T.sub.INT is determined by way of the equation T.sub.INT=T.sub.SNS(1R.sub.ENC/R.sub.PCB)T.sub.PCB (R.sub.ENC/R.sub.PCB) wherein the internal differential carrier temperature Tint is to be used to monitor and control a vehicle within which the differential carrier resides.

5. A method of determining an internal differential carrier temperature, comprising: providing a package housing comprising an upper portion and a lower portion connected together to form a sealed package housing, wherein the upper portion and the lower portion are in thermally conductive contact with an environment external to a differential carrier housing, wherein the lower portion of the package housing is in thermally conductive contact with an outer surface of the differential carrier housing, wherein the lower portion of the package housing is extends through an opening in the differential carrier housing, and wherein the lower portion of the package housing is in thermally conductive contact with a fluid within the differential carrier housing; providing an electronic circuit attached to the upper portion of the package housing within the package housing, and wherein the electronic circuit is in thermally conductive contact with the upper portion of the package housing; providing a thermal conductor imbedded in and in thermally conductive contact with the lower portion of the package housing, and wherein the lower portion of the package housing is in thermally conductive contact with the fluid within the differential carrier housing; measuring a temperature T.sub.SNS of the fluid within the differential carrier and an internal temperature T.sub.PCB of an electronic circuit board disposed within the package housing; and utilizing a known package housing plus thermal conductor thermal resistance R.sub.ENC of the thermal conductor disposed within the package housing, and a known thermal conductor resistance of the package housing at the electronic circuit board R.sub.PCB, wherein an internal differential carrier temperature T.sub.INT is determined by way of the equation T.sub.INT=T.sub.SNS(1+R.sub.ENC/R.sub.PCB)T.sub.PCB (R.sub.ENC/R.sub.PCB) wherein the internal differential carrier temperature Tint is to be used to monitor and control a vehicle within which the differential carrier resides.

6. The method of determining an internal differential carrier temperature of claim 5, wherein thermal energy is conducted from the interior of the differential carrier to the electronic circuit board of the temperature sensing package when the temperature inside the differential carrier is higher than the temperature outside the differential carrier.

7. The method of determining an internal differential carrier temperature of claim 5, wherein thermal energy is conducted from the electronic circuit board of the temperature sensing package to the interior of the differential carrier when the temperature outside the differential carrier is higher than the temperature inside the differential carrier.

8. A method of determining an internal differential carrier temperature T.sub.INT, comprising: measuring a temperature T.sub.SNS of a fluid within a differential carrier; measuring an internal temperature T.sub.PCB of an electronic circuit board disposed within a package housing of a temperature sensing package; utilizing a known housing plus thermal conductor thermal resistance R.sub.ENC of a thermal conductor disposed within the package housing; utilizing a known thermal conductor resistance of the package housing at an electronic circuit board R.sub.PCB disposed within the package housing of the temperature sensing package; and utilizing a known series dynamic thermal capacitance C.sub.PCB1 and dynamic thermal resistance R.sub.PCB1 of the package housing at an electronic circuit board disposed within the package housing of the temperature sensing package, wherein the electronic circuit board is in parallel with the base R.sub.PCB, wherein an internal differential carrier temperature T.sub.INT is calculated by way of the equation: T.sub.INT=T.sub.SNS(1+R.sub.ENC/R.sub.PCB)T.sub.PCB(R.sub.ENC/R.sub.PCB), wherein R.sub.PCB=(R.sub.PCB(sR.sub.PCB1.Math.C.sub.PCB1+1))/(sC.sub.PCB1(R.sub.PCB+R.sub.PCB1+1)) wherein the internal differential carrier temperature Tint is to be used to monitor and control a vehicle within which the differential carrier resides.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a first thermal circuit schematic diagram in accordance with the present invention;

(2) FIG. 2 is a second thermal circuit schematic diagram in accordance with the present invention;

(3) FIG. 3 is a cross sectional view of a first differential carrier temperature sensing package in accordance with the present invention; and

(4) FIG. 4 is a cross sectional view of a second differential carrier temperature sensing package in accordance with the present invention.

DESCRIPTION OF THE INVENTION

(5) It is to be understood that the invention may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting, unless the claims expressly state otherwise.

(6) FIG. 1 illustrates a simplified thermal circuit schematic diagram of an internal differential carrier temperature T.sub.INT that is determined by utilizing a measured differential carrier fluid temperature T.sub.SNS and an internal housing package temperature T.sub.PCB, in combination with a given known thermally conductive resistance R.sub.ENC of a housing and a thermal conductor, and a given known thermal resistance R.sub.PCB of the housing at an electronic circuit board.

(7) Specifically in FIG. 1, the thermal energy Q flows through circuit 5 in a direction that is determined by the temperatures of the inside and outside of a differential carrier. When the inside temperature is higher than the outside temperature, thermal energy flows from T.sub.INT to T.sub.PCB, because the temperature at the point of the T.sub.PCB is close to that on the outside of the differential carrier. However, when the outside temperature is higher than the inside temperature, thermal energy flows from the outside temperature point T.sub.PCB to T.sub.INT within the differential carrier. The following equation 1 expresses the circuit thermal flow.
Q=(T.sub.INTT.sub.SNS)/R.sub.ENC=(T.sub.SNST.sub.PCB)/R.sub.PCB(eq. 1)

(8) Consequently, solving for T.sub.INT within equation 1 results in equation 2 for determining the internal carrier temperature.
T.sub.INT=T.sub.SNS(1+R.sub.ENC/R.sub.PCB)T.sub.PCB(R.sub.ENC/R.sub.PCB)(eq. 2)

(9) FIG. 3 illustrates a first embodiment of a differential carrier temperature sensing package 10 having a package housing 12 that comprises an upper portion 14 and a lower portion 16 that are sealed together. The two package portions 14, 16 may be unitary. The upper portion 14 comprises very conductive thermal material, for example, a thermally conductive metal like aluminum. The lower portion 16 comprises a significantly less thermally conductive material than that of the upper portion 14, for example, a high temperature plastic. Both portions 14, 16 are in thermally conductive contact with an environment E.sub.1 that is external to a differential carrier housing 18. The lower portion 16 is also in thermally conductive contact with an outer surface 20 of the differential housing 18, where the lower portion 16 of the package housing 12 extends through an opening 22 in the differential housing 18, thereby allowing the lower portion 16 to be in thermally conductive contact with a fluid F.sub.1 within the differential housing 18. The fluid F.sub.1 may be in a form of a liquid and/or vapor.

(10) The package housing 12 further comprises an electronic circuit 24 with first and second temperature sensors 26, 30 disposed thereon. The electronic circuit 24 is in close thermally conductive contact with the first and second temperature sensors 26, 30 that preferably are common negative temperature coefficient (NTC) thermistors. The electronic circuit 24 is also in thermally conductive contact with and attached to the upper portion 14 within the package housing 12.

(11) The first temperature sensor 26 is also in close thermally conductive contact with a thermal conductor 28, which may be a simple aluminum rod that is disposed within the package housing 12. The thermal conductor 28 is imbedded in and consequently in thermally conductive contact with the lower portion 16 but not in contact with the outer surface 17 of the lower portion 16. The lower portion 16 is in thermally conductive contact with the fluid F.sub.1 within the differential housing 18. The differential fluid temperature T.sub.SNS is determined by way the thermal conduction between the electronic circuit 24, the first sensor 26, the thermal conductor 28, and the lower portion 16 of the package housing 12.

(12) The second temperature sensor 30 is disposed on the electronic circuit 24. The temperature T.sub.PCB at the electronic circuit 24 is determined by the electronic circuit 24 sensing the second sensor 30. Hence, with a given known thermal resistance R.sub.ENC of the combination of the package housing 12 and the thermal conductor 28, along with a given known thermal resistance R.sub.PCB of the electronic circuit board PCB, the electronic circuit 24, wherein the electronic circuit 24 is disposed on the electronic circuit board PCB, can determine an internal carrier temperature T.sub.INT. Then, the temperature T.sub.INT can be communicated outside of the package housing 12 for monitoring and controlling a vehicle within which the differential carrier sensing package 10 is installed.

(13) In a second embodiment, which is depicted in FIG. 4, a differential carrier temperature sensing package 50 comprises a package housing 52 that comprises an upper portion 54 and a lower portion 56 that are sealed together. The two package housing portions 54, 56 may be unitary. The upper portion 54 and the lower portion 56 are in thermally conductive contact with an environment E.sub.2 that is external to a differential carrier housing 58. The lower portion 56 is also in thermally conductive contact with an outer surface 60 of the differential housing 58, where the lower portion 56 of the package housing 52 extends through an opening 62 in the differential housing 58, thereby being in thermally conductive contact with a fluid F.sub.2 within the differential housing 58. The fluid F.sub.2 may be in a form of a liquid and/or vapor.

(14) The package housing 52 further comprises an electronic circuit 64, and first and second temperature sensors 66, 70. The electronic circuit 64 is attached to the upper portion 54 within the package housing 52 and is in thermally conductive contact therewith. The first temperature sensor 66 is disposed on the electronic circuit 64 and is in thermally conductive contact with an outward projection 74 of the lower portion 56, which in turn is in thermally conductive contact with a thermal conductor 68. In contrast to the thermal conductor 28 of the first embodiment, the thermal conductor 68 is disposed in the fluid F.sub.2 that is within the differential housing 58, with the outward projection 74 surrounding the thermal conductor 68 and with fluid F.sub.2 therebetween. Further, the thermal conductor 68 may have an inward thermal conductor portion 72 that has a larger surface area than the upper thermal conductor 68, so as to make it more capable of quickly responding to thermal changes within the fluid F.sub.2. Hence, the differential fluid temperature T.sub.SNS is determined by way of thermal conduction between the electronic circuit 64, the first sensor 66, outward projection 74 of the lower portion 56, thermal conductor 68, and possibly the inward thermal conductor portion 72.

(15) The second temperature sensor 70 is disposed on the electronic circuit 64 for sensing the temperature within the package housing 52. The temperature at the electronic board T.sub.PCB is determined by way of the electronic circuit 64 and the second sensor 70. Hence, with a known thermal resistance R.sub.ENC of the combination of the package housing 52, the thermal conductor 68 with possibly the inward thermal conductor 72, and a known thermal resistance R.sub.PCB of the electronic circuit board 64, then the electronic circuit 64 can determine an internal carrier temperature T.sub.INT. Thus, T.sub.INT can be communicated outside of the package housing 52 for monitoring and controlling a vehicle within which the differential carrier 50 resides, by the electronic control circuit 64.

(16) Hence, the internal carrier temperature T.sub.INT can be determined based on the above-stated equation (eq. 2), while using the above-found temperatures T.sub.SNS and T.sub.PCB, for this embodiment, along with the known R.sub.ENC and R.sub.PCB.

(17) The above-stated models that are described by equations (1) and (2), and illustrated in FIGS. 1, 3, and 4, result in accurate determinations of live temperature conditions within the differential carriers 10 and 50. These models are significantly faster at determining temperatures within a differential carrier than prior art systems. Consequently, the above-stated embodiments are significantly better than prior art at monitoring internal differential temperatures. In turn, these beneficial means should result in a better operation of a vehicle and a better quality differential carrier that is more reliable.

(18) Further, FIG. 2 illustrates a more accurate thermal schematic diagram for deriving an internal differential carrier temperature. This model provides for an expression of the dynamic behavior of the thermal circuit 8, which modifies FIG. 1 by adding the components C.sub.PCB1, R.sub.PCB1 in parallel with R.sub.PCB so as to result in a base R.sub.PCB that more closely matches the thermal operation of the differential carriers 10, 60. This model results in the following equation 3:
Q=(T.sub.INTT.sub.SNS)/R.sub.ENC=(T.sub.SNST.sub.PCB)/R.sub.PCB(eq. 3)

(19) where R.sub.PCB is equal to:

(20) $\begin{array}{cc}{R}_{\mathrm{PCB}}^{}=\frac{R_{\mathrm{PCB}}\left({\mathrm{sR}}_{\mathrm{PCB}1}{C}_{\mathrm{PCB}1}+1\right)}{{\mathrm{sC}}_{\mathrm{PCB}1}(R_{\mathrm{PCB}}+R_{\mathrm{PCB}1}+1}& \left(\mathrm{eq}.4\right)\end{array}$

(21) The factor s is defined to be a Laplace complex argument. The capacitance C.sub.PCB1 in this dynamic model equation provides for the description of the rate of thermal flow in the assembly. This rate can be used to provide predictive information thereby functioning to effectively increase the response time of an internal differential carrier temperature measurement.

(22) In accordance with the provisions of the patent statutes, the principles and modes of operation of this invention have been described and illustrated in its preferred embodiments. However, it must be understood that the invention may be practiced otherwise than specifically explained and illustrated without departing from its spirit or scope.