Temperature measurement system and method of calibration thereof

Abstract

A temperature measurement system of a vehicle includes a controller, a first temperature sensor associated with a first location, and a second temperature sensor associated with a second location. The temperature measurement system is calibratable based upon a comparison of a temperature of the first location and a temperature of the second location, wherein the temperature of at least one of the first location and the second location is determined after a predetermined time from an end of operation of the vehicle.

Claims

1. A temperature measurement system of a vehicle, comprising: a controller in electrical communication with a memory for storing data; a first temperature sensor in electrical communication with the controller, wherein the first temperature sensor is configured to transmit a measured voltage difference representative of a temperature of a first location to the controller; and a second temperature sensor in electrical communication with the controller, wherein the second temperature sensor is configured to transmit a temperature of a second location to the controller, wherein the controller is configured to determine the temperature of the first location from the measured voltage difference using a determination method which is calibratable based upon a comparison of the temperature of the first location to the temperature of the second location.

2. The temperature measurement system according to claim 1, wherein the first temperature sensor is a thermistor.

3. The temperature measurement system according to claim 1, wherein the first location is one of a component and fluid of the vehicle of which a direct temperature measurement is unobtainable by the first temperature sensor.

4. The temperature measurement system according to claim 1, wherein the second location is one of a component and fluid of the vehicle of which a direct temperature measurement is obtainable by the second temperature sensor.

5. The temperature measurement system according to claim 1, wherein the determination method of the temperature measurement system determines the temperature of the first location based upon at least one of a tolerance band and a function stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor.

6. The temperature measurement system according to claim 1, wherein the determination method of the temperature measurement system determines the temperature of the first location based upon a look-up table stored in the memory for storing data and the measured voltage difference transmitted by the first temperature sensor.

7. The temperature measurement system according to claim 1, wherein the temperature of at least one of the first location and the second location is at least one of measured and estimated after a predetermined time from an end of operation of the vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The above, as well as other advantages of the present embodiments, will become readily apparent to those skilled in the art from the following detailed description when considered in the light of the accompanying drawings in which:

(2) FIG. 1 is a graphical representation of a vehicle including a temperature measurement system according to an embodiment of the present subject matter; and

(3) FIG. 2 is a schematic flow diagram of a method for calibration of the temperature measurement system shown in FIG. 1 according to an embodiment of the subject disclosure.

DETAILED DESCRIPTION

(4) It is to be understood that the preferred embodiments 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 herein. Hence, specific dimensions, directions or other physical characteristics relating to the embodiments disclosed are not to be considered as limiting.

(5) FIG. 1 depicts a vehicle 10 according to an embodiment of the present subject matter. The vehicle 10 may be any vehicle type as desired such as a conventional fuel-powered vehicle, an electric vehicle, and an electric-hybrid vehicle, for example. The vehicle 10 includes a temperature measurement system 12. In certain embodiments, the temperature measurement system 12 includes a controller or microcontroller 14, a first temperature sensor 16 for measuring and/or estimating a temperature T.sub.1 of a desired location 18 (e.g. a component or fluid of the vehicle 10 which is impossible or impracticable to obtain a direct temperature measurement), a memory 20 for storing data, and a second temperature sensor 24 for measuring a temperature T.sub.2 of an input location 26 (e.g. a component or fluid of the vehicle 10). It is understood that additional temperature sensors 24 may be employed for measuring temperatures at a plurality of input locations 26. More particularly, the desired location 18 may be a clutch assembly of a rear drive unit, differential gear assembly, and the like, for example. Further, the input location 26 may be a vehicle engine, an engine fluid, a vehicle transmission, a transmission fluid, ambient air, and the like, for example.

(6) The temperature measurement system 12 is configured to allow various components, modules, systems, and applications of the vehicle 10 to communicate with each other. Various types of controllers or microcontrollers 14 may be employed in the vehicle 10 such as a controller area network (CAN) system, for example. In the embodiment shown, the controller 14 is electrically connected to at least one of the first temperature sensor 16, the memory 20, and the second temperature sensor 24 of the temperature measurement system 12 to allow communication thereamong.

(7) In one embodiment, the first temperature sensor 16 is thermistor. Various types of thermistors may be employed as the first temperature sensor 16 such as a negative temperature coefficient (NTC) thermistor and a positive temperature coefficient (PTC) thermistor, for example. With an NTC thermistor, when the temperature increases, resistance of the NTC thermistor decreases. Conversely, when temperature decreases, resistance of the NTC thermistor increases. On the other hand with a PTC thermistor, when temperature increases, the resistance of the PTC thermistor increases, and when temperature decreases, resistance of the PTC thermistor decreases.

(8) Unlike other temperature sensors, the first temperature sensor 16 is a nonlinear thermistor, meaning a relationship between a resistance and a temperature is not a 1:1 ratio. As such, the temperature to resistance values plotted on a graph representing such relationship form a curve rather than a straight line. It is understood that the first temperature sensor 16 may have a variety of shapes and sizes such as a disk, chip, bead, rod, surface-mounted, for example. The first temperature sensor 16 can also be encapsulated in epoxy resin, glass, baked-on phenolic, and painted, if desired.

(9) In the embodiment shown, the first temperature sensor 16 is employed to at least one of measure and estimate the temperature T.sub.1 of the desired location 18. The first temperature sensor 16 has a minimal amount of electrical current 25 (also commonly referred to as a bias current) flowing therethrough. The controller 14 is configured to cause an electrical source 27 to transmit the electrical current 25 to the first temperature sensor 16. The first temperature sensor 16 has a resistance R.sub.1 associated with the temperature T.sub.1 of the desired location 18. The electrical current 25 flowing through the first temperature sensor 16 converts the resistance R.sub.1 of the first temperature sensor 16 to a measured voltage difference V.sub.1 across terminals of the first temperature sensor 16. The measured voltage difference V.sub.1 is then transmitted from the first temperature sensor 16 to the controller 14. In certain embodiments, the controller 14 determines a temperature T.sub.1 of the desired location 18 based upon at least one determination method such as using the measured voltage difference V.sub.1 and a tolerance band or function of the first temperature sensor 16 stored within the memory 20 of the temperature measurement system 12, for example. The first temperature sensor 16 is initially configured to operate within a certain tolerance band or function. A relationship between voltage and resistance is known, and may be calculated by utilizing a look-up table 28, or other mathematical relationship therebetween. As such, in certain other embodiments, the determination method of the controller 14 utilizes the look-up table 28 stored in the memory 20 to determine the temperature T.sub.1 of the desired location 18 based upon the measured voltage difference V.sub.1 of the first temperature sensor 16.

(10) To improve accuracy of measuring or estimating the temperature T.sub.1 of the desired location, the determination method of the temperature measurement system 12, from which the temperature T.sub.1 is determined, is calibratable. In certain embodiments, the determination method, using the tolerance band or function of the first temperature sensor 16 stored within the memory 20 of the temperature measurement system 12 or look-up table 28, is calibratable based upon thermal dynamics of the vehicle 10.

(11) Referring now to FIG. 2, a flow diagram showing a method of calibration 100 for the temperature measurement system 12. At step 102, the temperature measurement system 12, during an operation of the vehicle 10, causes the electrical source 27 to transmit the electrical current 25 to the first temperature sensor 16 and flow therethrough, which generates the resistance R.sub.1. At step 104, the resistance R.sub.1 of the first temperature sensor 16 is then converted to the measured voltage difference V.sub.1 across the terminals of the first temperature sensor 16 representative of the temperature T.sub.1 of the desired location 18. At step 106, the measured voltage difference V.sub.1 is then transmitted to the controller 14 of the temperature measurement system 12. At step 108, the controller 14, using the determination method, determines the temperature T.sub.1 of the desired location 18. In one embodiment, the temperature T.sub.1 of the desired location 18 is based upon the tolerance band or function of the measured voltage difference V.sub.1 of the first temperature sensor 16. In certain other embodiments, the temperature measurement system 12 utilizes the lookup table 28 stored in the memory 20 to determine the temperature T.sub.1 of the desired location 18 based upon the measured voltage difference V.sub.1 of the first temperature sensor 16. At step 110, the temperature T.sub.1 of the desired location 18 is stored in the memory 20 of the temperature measurement system 12.

(12) At step 112, an operation of the vehicle 10 is ended. At step 114, the temperature measurement system 12, after a first predetermined time from an end of the operation of the vehicle 10, causes the second temperature sensor 24 to measure a control temperature T.sub.c of the input location 26. At step 116, the control temperature T.sub.c of the input location 26 is stored in the memory 20 of the temperature measurement system 12. At step 118, the temperature measurement system 12, after a second predetermined time from the end of the operation of the vehicle 10, causes the electrical source 27 to transmit the electrical current 25 to the first temperature sensor 16 and flow therethrough. It should be appreciated that the steps to measure the control temperature T.sub.c of the input location 26 and the steps to determine the temperature T.sub.2 of the desired location 18 may be conducted substantially simultaneously, chronologically, or vice versa, by the temperature measurement system 12, as desired. In one example, each of the first and second predetermined times from the end of the operation of the vehicle 10 is of such a length of time to allow convergence of temperatures over an entirety of the vehicle 10, in other words, to allow the vehicle 10 to reach a steady state. In another example, at least one of the first and second predetermined times from the end of the operation of the vehicle 10 is longer than 4-5× a longest time constant of the vehicle 10. It is understood, however, that each of the first and second predetermined times can be any length of time, as desired. It is further understood that the first and second predetermined times may be substantially the same, the first predetermined time may be shorter than the second predetermined time, or the first predetermined time may be longer than the second predetermined time.

(13) The first temperature sensor 16 has a resistance R.sub.2 associated with a temperature T.sub.2 of the desired location 18. At step 120, the resistance R.sub.2 is then converted to a measured voltage difference V.sub.2 across the terminals of the first temperature sensor 16 representative of the temperature T.sub.2 of the desired location 18. At step 122, the measured voltage difference V.sub.2 is then transmitted to the controller 14 of the temperature measurement system 12. At step 124, the controller 14, using the determination method, determines the temperature T.sub.2 of the desired location 18 based upon the tolerance band and/or function of the measured voltage difference V.sub.2 of the first temperature sensor 16, or by utilizing the look-up table 28, or other mathematical relationship therebetween.

(14) At step 126, the temperature T.sub.2 of the desired location 18 is then compared to the control temperature T.sub.c of the input location 26. When the temperature T.sub.2 of the desired location 18 is not substantially equal to the control temperature T.sub.c of the input location 26, the determination method of the temperature measurement system 12 is calibrated at step 128. It should be appreciated that the temperature T.sub.2 of the desired location 18 may be permitted to differ from the control temperature T.sub.c of the input location 26 by a certain amount or percentage without requiring a calibration of the temperature measurement system 12.

(15) More particularly, at step 128, the determination method using the tolerance band and/or function of the measured voltage difference V.sub.1, or look-up table 28, or other mathematical relationship therebetween, is calibrated so that the temperature T.sub.2 of the desired location 18 determined therefrom would be substantially equal to the control temperature T.sub.c of the input location 26. In one embodiment, the controller 14, based upon the difference between T.sub.2 and T.sub.c, updates which tolerance band or function of the first temperature sensor 16 is utilized by the determination method to determine or calculate the temperature T.sub.2 of the desired location 18 when the measured voltage difference is received from the first temperature sensor 16. In another embodiment, the controller 14, based upon the difference between T.sub.2 and T.sub.c, updates which look-up table 28 is utilized by the determination method to determine or calculate the temperature T.sub.2 of the desired location 18 when the measured voltage difference is received from the first temperature sensor 16. Accordingly, the control temperature T.sub.c of the input location 26 when the vehicle 10 has reached steady state is a baseline utilized to adjust and calibrate the determination method from which the temperature T.sub.2 of the desired location 18 is determined, thereby minimizing error and improving an accuracy of the temperature measurement system 12.

(16) It should be appreciated that any number of tolerance bands, functions and look-up tables may be employed and stored within the memory 20 of the temperature measurement system 12. It should also be appreciated that the temperature measurement system 12 may only employ a single tolerance band, function, or look-up table, which is continuously calibrated and stored within the memory 20.

(17) In accordance with the provisions of the patent statutes, the present subject matter has been described in what is considered to represent its preferred embodiments. However, it should be noted that the subject matter can be practiced otherwise than as specifically illustrated and described without departing from its spirit or scope.