DRIVE UNIT FOR AN ELECTRIC VEHICLE AND METHOD FOR DETECTING FAULTS IN A DRIVE UNIT

Abstract

The invention relates to a drive unit (10) for an electric vehicle, said drive unit comprising an electric motor (20), a transmission (30), a power electronics unit (40) for controlling the electric motor (20), and an acceleration sensor (50). The acceleration sensor (50) is located in a housing (42) of the power electronics unit (40), and the housing (42) of the power electronics units (40) is mechanically coupled to the electric motor (20) and/or to the transmission (30) such that vibrations generated by the electric motor (20) and/or by the transmission (30) are transmitted to the acceleration sensor (50) located in the housing (42) of the power electronics unit (40), said acceleration sensor being designed to pick up the transmitted vibrations and convert said vibrations into a measurement signal. The drive unit (10) comprises a signal processing unit which is designed to generate an order spectrogram from the measurement signal and from the speed of the electric motor (20). The invention also relates to a method for detecting faults in a drive unit (10) according to the invention, wherein vibrations which are generated by the electric motor (20) and/or by the transmission (30) are picked up by the acceleration sensor (50) and converted into a measurement signal, an order spectrogram is generated from the measurement signal and from the speed of the electric motor (20) using a signal processing unit, at least one level of the order spectrogram for at least one order is compared using a comparison unit with a threshold value assigned to said order, and a fault in the drive unit (10) is detected if the at least one level of the order spectrogram exceeds the threshold value assigned to said order.

Claims

1. A drive unit (10) for an electric vehicle, said drive unit comprising an electric motor (20), a transmission (30), a power electronics unit (40) for controlling the electric motor (20), and an acceleration sensor (50), wherein the acceleration sensor (50) is arranged in a housing (42) of the power electronics unit (40) and the housing (42) of the power electronics unit (40) is mechanically coupled to the electric motor (20) and/or to the transmission (30) in such a manner that vibrations that are generated by the electric motor (20) and/or by the transmission (30) are transmitted to the acceleration sensor (50) that is arranged in the housing (42) of the power electronics unit (40), said acceleration sensor being configured so as to receive the transmitted vibrations and to convert them into a measurement signal, and the drive unit (10) comprises a signal processing unit (60) that is configured to create an order spectrogram from the measurement signal and from a rotational speed of the electric motor (20).

2. The drive unit (10) as claimed in claim 1, wherein the signal processing unit (60) comprises a comparison unit that is configured so as to compare at least one level of the order spectrogram in the case of at least one order with a threshold value that is allocated to the order.

3. The drive unit (10) as claimed in claim 1, wherein the signal processing unit (60) comprises a scanning unit for scanning the measurement signal and for generating discrete-time and discrete-value measurement values.

4. The drive unit (10) as claimed in claim 1, wherein the signal processing unit (60) comprises a scanning unit for scanning the measurement signal and for generating discrete-angle and discrete-value measurement values.

5. The drive unit (10) as claimed in claim 3, wherein the signal processing unit (60) comprises a digital signal processor that is configured so as to perform a Fourier transformation or an almost Fourier transformation of the measurement values.

6. The drive unit (10) as claimed in claim 1, wherein the acceleration sensor (50) is embodied as an MEMS sensor.

7. A method for detecting faults in a drive unit (10) having an electric motor (20), a transmission (30), a power electronics unit (40) for controlling the electric motor (20), and an acceleration sensor (50), the method comprising: receiving, via the acceleration sensor (50), vibrations that are generated by the electric motor (20) and/or by the transmission (30) and converting the same into a measurement signal, creating an order spectrogram via the signal processing unit (60) from the measurement signal and from a rotational speed of the electric motor (20), comparing at least one level of the order spectrogram via a comparison unit with a threshold value that is allocated to the at least one order, and detecting a fault in the drive unit (10) when the at least one level of the order spectrogram exceeds the threshold value that is allocated to the order.

8. The method as claimed in claim 7, wherein the measurement signal is scanned by a scanning unit, whereby discrete-time and discrete-value measurement values are generated.

9. The method as claimed in claim 7, wherein the measurement signal is scanned by a scanning unit, whereby discrete-angle and discrete-value measurement values are generated.

10. The method as claimed in claim 8, wherein a Fourier transformation or an almost Fourier transformation of the measurement values is performed by a digital signal processor.

11. An electric vehicle comprising a drive unit (10), the driving unit having an electric motor (20), a transmission (30), a power electronics unit (40) for controlling the electric motor (20), and an acceleration sensor (50), wherein the acceleration sensor (50) is arranged in a housing (42) of the power electronics unit (40) and the housing (42) of the power electronics unit (40) is mechanically coupled to the electric motor (20) and/or to the transmission (30) in such a manner that vibrations that are generated by the electric motor (20) and/or by the transmission (30) are transmitted to the acceleration sensor (50) that is arranged in the housing (42) of the power electronics unit (40), said acceleration sensor being configured so as to receive the transmitted vibrations and to convert them into a measurement signal, and the drive unit (10) comprises a signal processing unit (60) that is configured to create an order spectrogram from the measurement signal and from a rotational speed of the electric motor (20).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Embodiments of the invention are further explained with the aid of the drawings and the description below.

[0029] In the drawings:

[0030] FIG. 1 illustrates a schematic view of a drive unit for an electric vehicle,

[0031] FIG. 2 illustrates a schematic circuit diagram of the drive unit shown in FIG. 1 and

[0032] FIG. 3 illustrates a graphic view of a created order spectrogram of the drive unit.

DETAILED DESCRIPTION

[0033] In the description below of the embodiments of the invention, like or similar elements are described by like reference numerals, wherein a description of these elements is not repeated in individual cases. The figures are only a schematic representation of the subject matter of the invention.

[0034] FIG. 1 illustrates a schematic view of a drive unit 10 for an electric vehicle. The drive unit 10 comprises an electric motor 20 having a housing 22. The drive unit 10 also comprises a transmission 30 having a housing 32. Moreover, the drive unit 10 comprises a power electronics unit 40 having a housing 42.

[0035] The housing 22 of the electric motor 20, the housing 32 of the transmission 30 and the housing 42 of the power electronics unit 40 are mechanically connected to one another in particular by means of screws (not illustrated in the figure).

[0036] Vibrations that are generated by or in one of the housings 22, 32, 42 are transmitted to the other housings 22, 32, 42. During the operation of the drive unit 10, vibrations are generated in particular by the electric motor 20 and by the transmission 30.

[0037] The drive unit 10 also comprises an acceleration sensor 50. The acceleration sensor 50 is arranged in this case in the housing 42 of the power electronics unit 40. The housing 42 of the power electronics unit 40 is, as already mentioned, mechanically coupled to the electric motor 20 and to the transmission 30 in such a manner that vibrations that are generated by the electric motor 20 and by the transmission 30 are transmitted to the acceleration sensor 50 that is arranged in the housing 42 of the power electronics unit 40.

[0038] The acceleration sensor 50 of the drive unit 10 is configured so as to receive the vibrations that are transmitted to it and to convert these vibrations into a measurement signal. The acceleration sensor 50 is embodied in the present case as an MEMS sensor, in other words as a microelectromechanical system sensor. The acceleration sensor 50 is consequently relatively cost-efficient and comprises a compact structure.

[0039] FIG. 2 illustrates a schematic circuit diagram of the drive unit 10 that is illustrated in FIG. 1 for an electric vehicle. The power electronics unit 40 serves to control the electric motor 20 and supplies an electrical current for driving the electric motor 20. The electric motor 20 is embodied in the present case as three-phase. The power electronics unit 40 is electrically connected by means of three-phase conductors to the electric motor 20.

[0040] The power electronics unit 40 of the drive unit 10 is electrically connected to a traction battery 15 of the electric vehicle. The traction battery 15 supplies in particular electrical energy for driving the electric vehicle. The power electronics unit 40 comprises a three-phase power inverter or inverter that from the DC voltage that is supplied by the traction battery 15 generates a three-phase AC voltage for controlling the three-phase electric motor 20.

[0041] The power electronics unit 40 of the drive unit 10 also comprises a signal processing unit 60 that is connected to the acceleration sensor 50. The signal processing unit 60 serves in particular so as to create an order spectrogram from the measurement signal of the acceleration sensor 50 and from a rotational speed of the electric motor 20.

[0042] The signal processing unit 60 of the power electronics unit 40 comprises a comparison unit. The comparison unit serves in particular so as to compare the level of the order spectrogram in the case of multiple orders with in each case a threshold value that is allocated to the order.

[0043] The signal processing unit 60 of the power electronics unit 40 also comprises a scanning unit. The scanning unit serves in particular to scan the measurement signal of the acceleration sensor 50 and to generate discrete-value measurement values. Depending upon the functioning principle of the scanning unit, the discrete-value measurement values can be discrete-time measurement values as well as discrete-angle measurement values.

[0044] For example, the scanning unit can scan the measurement signal in periodic time intervals. As a consequence, discrete-time measurement values are generated. In this case, the scanning frequency also remains constant in the case of a changing rotational speed of the electric motor 20. The scanning unit can also scan the measurement signal in the case of specific angles of rotation of the electric motor 20. As a consequence, discrete-angle measurement values are generated. In this case, the same number of measurement values are always generated during one rotation of the electric motor 20. In this case, the scanning frequency is proportional to the changing rotational speed of the electric motor 20.

[0045] The signal processing unit 60 of the power electronics unit 40 also comprises a digital signal processor. The digital signal processor serves in particular so as to perform a Fourier transformation or an almost Fourier transformation of the discrete-value measurement values. The discrete-value measurement values that are to be transformed can be discrete-time measurement values as well as discrete-angle measurement values.

[0046] FIG. 3 illustrates a graphic illustration of an order spectrogram of the drive unit 10, said order spectrogram being created by the signal processing unit 60 that is illustrated in FIG. 2. In this case, the frequency of the measurement signal that is received by the acceleration sensor 50 is plotted in the unit “Hz” on the x-axis. The rotational speed of the electric motor 20 is plotted in the unit “rotations per minute” on the y-axis. An order in the present case is a ratio of the frequency of the measurement signal to the rotational speed of the electric motor 20. It is to be noted that in order to calculate the said ratio the rotational speed of the electric motor 20 must first be converted into the unit “Hz”.

[0047] In this case, only one order is illustrated in the order spectrogram, the level of said order having exceeded an allocated threshold value. As is apparent from the graphic illustration in FIG. 3, the ratio of the frequency of the received measurement signal to the rotational speed of the electric motor 20 in the case of the illustrated order is equal to 27. The level of the 27.sup.th order of the order spectrogram therefore exceeds the allocated threshold value. A fault in the drive unit 10 is consequently detected.

[0048] The invention is not limited to the exemplary embodiments described here and the aspects mentioned in said exemplary embodiments. On the contrary, a multiplicity of variants that lie within the scope of professional expertise is possible within the range that is disclosed by the claims.