Method for determining a contact quality, computer program, computer program product, system, and electric vehicle

Abstract

The invention relates to a method for determining the contact quality between at least one sliding brush (4, 6) of a brush adjuster (2) and an associated rotor shaft slip ring (8, 10), against which the sliding brush (4, 6) is pressed, in order to externally excite an electric motor rotor provided on the rotor shaft, in accordance with the contact quality such that the slip ring (8, 10) is sufficiently contacted by the sliding brushes (4, 6) for a given excitation current and when the smallest possible contact pressure is applied. In the process, electromagnetic radiation emitted by the assembly consisting of the at least one sliding brush (4, 6) and the associated slip ring (8, 10), said electromagnetic radiation arising as a result of the sliding brush (4, 6) being lifted off the slip ring (8, 10) during an operation of the electric motor, is detected by means of an electrical component with a sufficient inductance in a region of the assembly and used to determine the contact quality. The invention additionally relates to a computer program, to a computer program product, to a system, and to an electric vehicle.

Description

[0001] Description

[0002] Method for determining contact quality, computer program, computer program product, system and electric vehicle

[0003] The invention relates to a method for determining a contact quality between at least one grinding brush of a brush holder and an associated slip ring of a rotor shaft, against which the grinding brush is pressed in a quality-based manner to externally excite a rotor of an electric motor arranged on the rotor shaft.

[0004] The invention further relates to a computer program and a computer program product, each of which depicts this method, a system with a brush holder and a control unit for actuating the brush holder, wherein the control unit comprises such a computer program or computer program product, and an electric vehicle with such a computer program or computer program product or such a system.

[0005] One of the problems underlying the invention is to ensure reliable external excitation of an electric motor rotor. A further problem underlying the invention is to ensure this external excitation in an energy-efficient manner.

[0006] The present invention is intended to enable a dynamically adaptive and quality-based control of brush force, with which an arrangement of grinding brushes is pressed against associated slip rings of a rotor shaft in a quality-based manner. Such a control system is implemented in a control unit of an electric vehicle, which embodies this control.

[0007] Reference is made here, for example, to the German patent application with file number 10 2023 211 551 .4 filed by the applicant, which describes such a dynamically adaptive and quality-based control of brush force. These problems are solved by a proposed method with the features of claim 1. The dependent claims relate to advantageous embodiments.

[0008] Quality-based – or a quality-based contact or pressing of at least one grinding brush against the associated slip ring – means that, in order to achieve sufficient contact of the slip ring by the grinding brush via the brush holder, no more pressure is applied to the grinding brush than is necessary.

[0009] With such a contact pressure, one can therefore speak – from an energy perspective – of the best possible or optimal contact, in which – for a given load-dependent excitation current – ​​a minimum of wear on the grinding brushes is achieved. This wear consists of a superposition of mechanically abrasive and electrically erosive wear and is a function of the contact pressure on the grinding brushes.

[0010] Such quality-based pressure reduces the wear of grinding brushes to a minimum.

[0011] This also advantageously minimizes the friction of an electric motor and thus also the friction of a drivetrain of an electric vehicle, against which the electric motor works as the drive unit of the electric vehicle.

[0012] The proposed method enables robust, quality-based control of a brush force of the type described above.

[0013] The proposed method also enables reliable current transmission for torque generation. Sufficient contact between slip rings and associated brushes can be detected and monitored using various physical quantities, such as: the ripple current (also called hum current) that occurs shortly before contact is interrupted; a developing contact resistance resulting from a voltage drop and a flowing or monitorable excitation current; and / or broadband electromagnetic radiation emitted by the arrangement consisting of at least one brush and the associated slip ring, the frequency and amplitude of which can be detected and monitored.

[0014] The present invention relates to utilizing or exploiting this last-mentioned electromagnetic radiation to determine a contact quality between at least one grinding brush of a brush holder and an associated slip ring of a rotor shaft, in order to enable a quality-based control of a brush force of the type described above.

[0015] This broadband emitted electromagnetic radiation arises during the non-stationary operation of an electric motor - with such a brush holder - due to the lifting of at least one grinding brush from the associated slip ring by reducing the contact pressure of the grinding brush and / or increasing the shaft speed.

[0016] In one embodiment, it is proposed that an electrical component in the form of a coil – with sufficient inductance – be used to detect the electromagnetic radiation emitted by the arrangement consisting of the at least one grinding brush and the associated slip ring. In another embodiment, it is additionally or alternatively proposed that an electrical component in the form of an SMD component – ​​with sufficient inductance – on a printed circuit board be used to detect this electromagnetic radiation.

[0017] In a further embodiment, it is proposed that an electrical component in the form of a coil of an inductive signal transmitter and / or an SMD component of a printed circuit board of a speed sensor of the electric motor can advantageously be used to detect this electromagnetic radiation, in order to save additional electrical components and thus costs.

[0018] In another version, this circuit board is also used to control the brush actuator, thus saving on components and costs.

[0019] Furthermore, a computer program for carrying out the procedure of the type described above is proposed.

[0020] Furthermore, a computer program product comprising program code means stored on a computer-readable data carrier is proposed to carry out the procedure of the type described above when the program code means are executed on a computer.

[0021] Furthermore, a system comprising a brush holder and a control unit for actuating the brush holder is proposed, wherein the control unit comprises a computer program product of the type described above.

[0022] Furthermore, an electric vehicle is proposed that incorporates a computer program product of the type described above and / or a system of the type described above. Further advantages and features will become apparent from the dependent claims and the exemplary embodiments. These are illustrated by:

[0023] Fig. 1 shows a proposed brush holder in a sectional view,

[0024] Fig. 2 shows the brush holder shown in Fig. 1 in a perspective view.

[0025] Opinion,

[0026] Fig. 3 shows a first embodiment of a printed circuit board and Fig. 4 shows a second embodiment of a printed circuit board.

[0027] The bidirectional brush actuator 2, also called active brush module 2, illustrated in Figures 1 and 2, serves to externally excite a rotor (not shown) of an electric motor in the form of a synchronous machine for driving an electric vehicle. The rotor is arranged on a rotor shaft RW. The electric motor is combined with a reduction gearbox, which is oil-lubricated and oil-cooled. The gearbox oil also lubricates and cools the electric motor and is circulated within an oil cooling circuit that includes the gearbox and the electric motor.

[0028] This brush holder 2 is wet-running in the area of ​​an oil-lubricated bearing point of the rotor shaft RW (not shown here) and is arranged radially to the rotor shaft RW and stationary relative to a housing of the electric motor. An oil seal is omitted at this bearing point to avoid the friction associated with an oil seal. As a result, during operation of the electric vehicle, gear oil from inside the housing of the electric motor escapes through the bearing point and reaches the brush holder 2. The arrangement of the brush holder 2, illustrated in Figures 1 and 2, is sealed off from the surrounding area of ​​the electric motor by a housing cover (not shown here).

[0029] The brush holder 2 has a first and second grinding brush 4, 6, each of which can be variably pressed against an associated slip ring 8, 10 of the rotor shaft RW. These two grinding brushes 4, 6 are movably arranged within a brush holder and brush guide element 7 and radially to the rotor shaft RW. The grinding brush 4 is, for example, negatively polarized and the grinding brush 6 is therefore positively polarized.

[0030] The two slip rings 8, 10 are inserted into a so-called rotor shaft attachment RWA made of plastic, whereby this rotor shaft attachment RWA is pushed or attached to one end of the rotor shaft RW.

[0031] The grinding brushes 4, 6 are at least passively spring-loaded against the slip rings s, 10 by a helical spring inside the electromagnet EM – also called a solenoid. In the unenergized state of the brush holder 2, these grinding brushes 4, 6 thus experience only a passive spring preload against the associated slip rings 8, 10.

[0032] By applying a suitable current to the electromagnet EM, this spring preload can be increased or decreased as required by imposing an electromagnetic force on the armature of the electromagnet EM, acting in the direction of the spring preload or in the opposite direction. This is referred to as actively pressing the grinding brushes 4, 6 against the slip rings 8, 10.

[0033] The brush force with which the two grinding brushes 4, 6 are pressed against the associated slip rings 8, 10 of the rotor shaft RW - actively - based on quality is the subject of a so-called quality-based control of the brush force, which as such is implemented in a control unit of the electric vehicle.

[0034] The brush holder 2 and this control unit belong to a system of the electric vehicle, or the system has these two components.

[0035] Such a quality-based control of the brush force is described, for example, in the German patent application with file number 10 2023 211 551 .4, already mentioned at the beginning, to which express reference is hereby made. In Figures 1 and 2, a circuit board L is shown to the left of this grinding brush arrangement, via which the brush adjuster 2 is contacted and controlled.

[0036] In Fig. 2, an arrangement consisting of a coil S and a encoder wheel GR is shown schematically to the right of the brush holder 2. These work together inductively and thereby form a speed sensor or sensor arrangement SA, which serves to commutation the said electric motor for driving the electric vehicle.

[0037] This coil S is integrated into the circuit board L or is part of this circuit board L. The encoder wheel GR, on the other hand, is integrated into the rotor shaft RW or the rotor shaft attachment RWA, specifically in the form of the slip ring 8 shown in Fig. 1, and is thus part of the rotor shaft attachment RWA.

[0038] It is proposed that this coil S of the speed sensor of the electric motor be advantageously used to detect the broadband electromagnetic radiation emitted by the arrangement of the grinding brushes 4, 6 and the associated slip rings 8, 10, which arises as a result of the grinding brushes 4, 6 lifting off the associated slip rings 8, 10 during operation of the electric motor.

[0039] Fig. 3 illustrates another possible embodiment of a printed circuit board L with such an integrated coil S as part of a speed sensor of an electric motor, wherein this coil S is also used on the one hand for commutating the electric motor and on the other hand for detecting such - broadband - electromagnetic radiation.

[0040] Investigations show that such shared use of the speed sensor's coil S is possible, because the voltage signals inductively generated by this coil S in conjunction with the encoder wheel GR are in the MHz range, whereas the broadband electromagnetic radiation emitted by the arrangement of the brushes 4, 6 and the associated slip rings 8, 10 induces or generates voltage signals in this coil S that are in the range below 1 kHz. Therefore, these signals can be very well separated and distinguished from each other across the frequency range.

[0041] The arcs generated during the lifting of the grinding brushes 4, 6 from the associated grinding rings 8, 10 represent the spectrum of emitted electromagnetic radiation visible to the human eye.

[0042] Fig. 4, however, illustrates a possible embodiment of a printed circuit board L with an SMD component arranged on it - in the sense of an alternative - with sufficient inductance to detect such broadband emitted electromagnetic radiation.

[0043] In another embodiment – ​​not shown here – both a coil and an SMD component of such a circuit board can be provided or used in a redundant arrangement of electrical components, each with sufficient inductance to detect such broadband emitted electromagnetic radiation.

[0044] The control unit described above comprises a digital microprocessor unit (CPU) connected to a memory system and a bus system, a working memory (RAM), and a storage medium. The CPU is configured to execute instructions stored as a program in the memory system, to acquire input signals from the data bus, and to output signals to the data bus. The memory system can utilize various storage media, including magnetic, solid-state, and other non-volatile media, on which a corresponding computer program for carrying out the method and its advantageous embodiments is stored. The program can be designed to embody or execute the process aspects described herein, enabling the CPU to perform the steps of such processes and thus control both the electric vehicle and the proposed brush actuator.A computer program (product) suitable for carrying out the proposed method is one which has program code means to perform all steps of any one of the claims or method claims when the program is executed in the CPU.

[0045] The computer program or computer program product can be easily integrated into existing control electronics and used to control and / or regulate both the electric vehicle and the proposed brush controller.

[0046] This includes a computer program product with program code stored on a computer-readable data carrier to perform the method according to any one of the claims when the computer program product is executed in the CPU. The computer program product can also be integrated into the control electronics as a retrofit option.

[0047] Although the preceding description explains exemplary embodiments, it should be noted that a multitude of variations are possible. Furthermore, it should be emphasized that the exemplary embodiments are merely examples and are not intended to restrict the scope of protection, applications, or structure in any way. Rather, the preceding description provides the skilled person with a guideline for implementing at least one exemplary embodiment, whereby various modifications, particularly with regard to the function and arrangement of the described components, can be made without departing from the scope of protection as defined by the claims and these equivalent combinations of features.

Claims

Patent claims 1. Method for determining the contact quality between at least one grinding brush (4, 6) of a brush holder (2) and an associated slip ring (8, 10) of a rotor shaft, against which the grinding brush (4, 6) is pressed in such a quality-based manner to externally excite a rotor of an electric motor arranged on the rotor shaft, such that sufficient contact of the slip ring (8, 10) by the grinding brushes (4, 6) is achieved at a given excitation current and with the application of the smallest possible contact pressure, wherein electromagnetic radiation emitted from this arrangement from the at least one grinding brush (4, 6) and the associated slip ring (8, 10), which arises as a result of the grinding brush (4, 6) lifting off the slip ring (8, 10) during operation of the electric motor,is detected by means of an electrical component with sufficient inductance in a region of this arrangement and used to determine the contact quality.

2. The method according to claim 1, wherein an electrical component in the form of a coil (S) is used to detect this electromagnetic radiation.

3. Method according to claim 1 or 2, wherein an electrical component in the form of an SMD component (SMD) of a printed circuit board is used to detect this electromagnetic radiation.

4. Method according to one of the preceding claims, wherein an electrical component in the form of a coil of an inductive signal transmitter (S) and / or an SMD component (SMD) of a printed circuit board (L) of a speed sensor of the electric motor is used to detect this electromagnetic radiation.

5. Method according to claim 3 or 4, wherein the circuit board (L) is also used to control the brush actuator (2).

6. Computer program for carrying out a method according to one of the preceding claims.

7. Computer program product comprising program code means stored on a computer-readable data carrier for carrying out the method according to any one of the preceding claims 1 to 5 when the program code means are executed on a computer.

8. System comprising a brush holder (2) and a control unit for actuating the brush holder (2), wherein the control unit comprises a computer program product according to claim 7.

9. Electric vehicle with a computer program product according to claim 7.

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