Method for Determining the Temperature in an Electronic Controller of a Motor Vehicle

Abstract

The invention relates to a method for determining the temperature in an electronic controller of a motor vehicle, the controller having at least one electrical winding, characterized in that the electrical resistance of the winding is determined in a defined operating state and based thereon the temperature is determined.

Claims

1.-6. (canceled)

7. A method for determining temperature within an electronic control device of a motor vehicle, the electronic control device comprising at least one electrical winding, the method comprising: determining an electrical resistance of the at least one electrical winding in a defined operating state; and determining the temperature based on the electrical resistance of the at least one electrical winding in the defined operating state.

8. The method as claimed in claim 7, wherein the electrical resistance of the at least one electrical winding is determined by applying an electrical impulse with a constant current amplitude and measuring a voltage on the at least one electrical winding.

9. The method as claimed in claim 7, wherein the electrical resistance of the at least one electrical winding is determined by applying an electrical impulse with a constant voltage amplitude and measuring current in the at least one electrical winding.

10. The method as claimed in claim 7, wherein a temperature coefficient of a specific resistance of material of the at least one electrical winding is utilized to determine the temperature of the at least one electrical winding.

11. The method as claimed in claim 7, wherein ambient temperature is determined and a calibration process of temperature determination is performed with this known temperature during an idle state of the electrical device in which an internal temperature of the electrical device corresponds to the ambient temperature.

12. The method as claimed in claim 7, wherein the at least one electrical winding of an electric motor is utilized for temperature determination.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The invention is explained in more detail with reference to figures, in which:

[0017] FIG. 1 is a schematic illustration of an exemplary control device for a motor vehicle;

[0018] FIG. 2 is an exemplary graphical plot of a temperature-resistance characteristic;

[0019] FIG. 3 is an exemplary illustration of a typical measurement setup for the case of a brushless DC motor with delta connection; and

[0020] FIG. 4 is a flowchart of the method in accordance with the invention.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

[0021] The exemplary control device shown in FIG. 1 comprises an electronic circuit 1 on a circuit board 2, an electric motor 3 with a shaft 4, where the shaft is connected to an actuator (not shown) for converting the rotational movement into a linear movement.

[0022] The electric motor 3 is preferably formed as a brushless DC motor (BLDC motor) with three-phase winding and excitation by permanent magnets 5 that are particularly suitable as servomotors.

[0023] The permanent magnets 5 are often the most thermally sensitive elements of the arrangement, their maximum operating temperature, i.e., the Curie temperature, is between 100 and 460? Celsius for hard magnetic ferrites.

[0024] In order to prevent demagnetization, the temperature in the device must therefore be monitored and, if necessary, countermeasures taken in good time.

[0025] In accordance with the invention, the electrical resistance 7 of a winding 6 of the electric motor is therefore determined in the exemplary embodiment in a standstill phase of the electric motor. This results in a very simple measurement setup as shown in FIG. 3.

[0026] However, under certain circumstances it may also be advantageous to determine the resistance during the movement of the electric motor 3 in a quasi-stationary state and to determine the temperature therefrom.

[0027] This temperature also corresponds to a good/optimal approximation of the temperature of the environment in the motor and thus also of the permanent magnets.

[0028] For this purpose, a defined current pulse is applied by the electronic circuit 1 of the selected winding 6, i.e., an electrical impulse with a constant current amplitude and a duration that corresponds approximately to twice the impulse response determined by the inductance of the winding 6.

[0029] Thus, on the one hand, a stable output voltage is obtained at the end of the impulse and, on the other hand, the time is too short for the current in the winding to cause significant self-heating.

[0030] It can also be advantageous to provide as high a current amplitude as possible to keep inaccuracies of current amplifiers of the electronic control system low and thus increase the accuracy of the temperature determination.

[0031] By measuring the motor voltage, with knowledge of the current amplitude, the current resistance of the motor winding 6 can be determined in a conventional manner in accordance with the relationship R=U/I.

[0032] The voltage can either be measured directly on the motor or alternatively via the very accurate measurement of the input voltage on the control device divided by the current pulse width modulation of the output stage.

[0033] As shown in a diagrammatic view in FIG. 3, for this purpose, in the case of a brushless DC motor (BLDC motor) with delta connection of the windings 6, which is driven by switches SL . . . S6, the winding voltages V1, V2, V3 are measured via high-resistance voltage dividers R1/R2, R3/R4 and R5/R6, and the currents I1, I2 are measured by two windings 6 via current shunts, and the current through the third winding results from this in accordance with the Kirchhoff rule I3=I1+I2. From these values, the current resistance of the windings 6 and, in turn, the temperature can be determined.

[0034] With the specific temperature coefficient ? of the winding material, in the exemplary embodiment copper (?=0.00393 per K), and the winding resistance of the motor (42.2 m?+/?7%) at 23.5? C., according to

[00001]$?R=???T?R_k$$R_w=R_k+?R$

[0035] the current temperature can now be determined.

[0036] In order to further increase the accuracy of the temperature determination, the ambient temperature can be determined in an idle state of the electrical device, in which the internal temperature of the device corresponds to the ambient temperature, and a calibration process of temperature determination can be performed with this known temperature.

[0037] This can occur, for example, in a motor vehicle on a factory floor both during the assembly of the vehicle or after a prolonged standstill, for example, during a maintenance operation.

[0038] If the temperature on this factory floor is 23.5? C., for example, then the result of the temperature determination must also have this value.

[0039] It may also be advantageous to perform the calibration process during the assembly of the control device before installation in the vehicle.

[0040] If the vehicle has a way to measure the ambient temperature, then it may be expedient to use this information to calibrate the temperature determination in the electrical device and to regularly perform the calibration process automatically after a prolonged standstill, including outdoors.

[0041] With this calibration, all initial errors of temperature determination are eliminated and, if performed regularly, ageing-related changes are also detected.

[0042] To further illustrate the method in accordance with the disclosed embodiments of the invention, FIG. 2 shows, by way of example, the dependence of the winding resistance 7 and the motor voltage 8 on the temperature.

[0043] FIG. 4 is a flowchart of the method for determining temperature within an electronic control device of a motor vehicle, where the electronic control device comprising at least one electrical winding 6.

[0044] The method comprises determining an electrical resistance 7 of the at least one electrical winding 6 in a defined operating state, as indicated in step 410.

[0045] Next, the temperature is determined based on the electrical resistance 7 of the at least one electrical winding 6 in the defined operating state, as indicated in step 420.

[0046] Thus, while there have been shown, described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the methods described and the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.

LIST OF REFERENCE CHARACTERS

[0047] 1 Electronic circuit [0048] 2 Circuit board [0049] 3 Electric motor [0050] 4 Shaft [0051] Permanent magnet [0052] 6 Winding [0053] 7 Winding resistance [0054] 8 Motor voltage [0055] S1 . . . S6 Switch [0056] V1, V2, V3 Winding voltages [0057] R1/R2, R3/R4, R5/R6 Voltage divider