Lubrication system for an electromotive unit with a magnet and a calibrated passage between oil reserves

Abstract

An electromotive unit for a vehicle, comprising an electric machine (1) and a transmission (TR) with a differential (DIF) with a ring gear (3) providing a lube-oil pickup function, the electric machine compartment comprising a first oil reserve (VM) and the transmission compartment comprising a second oil reserve (VT), the casing having a wall passage (6), connecting the second oil reserve to the first oil reserve, the electromotive unit comprising an oil pump (5), supplying a lubrication circuit, a multifunctional insert (7) closing off the wall passage and comprising a calibrated passage hole (8), defining a predefined flow cross section between the second oil reserve and the first oil reserve, a magnet (2) received and held between shapes formed by the casing and by the elements that hold the multifunctional insert.

Description

[0001] DESCRIPTION

[0002] TITLE OF THE INVENTION: Lubrication system for electric motor set with magnet and calibrated passage between oil reservoirs

[0003] The present invention relates to an electric motor unit for a motor vehicle and its lubrication system. The electric motor unit comprises an electric machine and a differential transmission. The electric motor unit includes, on the one hand, an electrically driven oil pump and, on the other hand, an oil lifting function achieved by the rotation of the differential input wheel, also referred to as the ring gear in this document.

[0004] The electric motor is cooled when necessary by circulating pressurized oil supplied by the pump. This same oil lubricates all the transmission components: the gears, bevel gears, bearings, bushings, etc.

[0005] An interior space is planned to house the electric machine and another interior space is planned to house the transmission, separated by a casing wall.

[0006] [0 II A first oil reservoir is planned on the electrical machine side and a second oil reservoir on the transmission side. The first oil reservoir is connected to the second oil reservoir by a passage which will be the focus of the discussion here.

[0007] For the oil lifting function, the differential ring lifts oil from the second oil reservoir. Regarding the pressurized oil circuit, the strainer connected to the electric oil pump draws oil from the first oil reservoir.

[0008] The electric motor unit is arranged transversely in the front or rear engine compartment of the vehicle, and it drives one of the vehicle's axles.

[0009]

[0007] There are dynamic situations where a centrifugal force tends to move the oil to the right, i.e., towards the electric motor, or conversely, other situations where the centrifugal force tends to move the oil to the left, i.e., towards the transmission. Of course, left and right can be reversed depending on the arrangement of the electromotor unit along the transverse Y-axis.

[0010] It is common practice to place a magnet on the oil circuit to trap and collect residues / waste from the manufacturing process, as well as particles that are released during operation, and even metallic pollutants introduced into the oil.

[0011] [0 Furthermore, there are life situations where the electric oil pump is not in operation while the transmission is turning, and conversely there are also life situations where the electric oil pump is working while the transmission is not turning.

[0012]

[0010] It is in this context that the inventors sought to propose a solution which allows relevant management of oil volumes in static and dynamic conditions, according to different life situations, paying particular attention to the cost of the solution and also to the weight.

[0011] To this end, an electric motor unit is proposed comprising an electric machine and a transmission, the transmission comprising at least one differential with a ring geared and providing a lubricating oil lifting function, the electric motor unit comprising a casing separating an electric machine compartment from a transmission compartment, the electric machine compartment comprising a first oil reservoir and the transmission compartment comprising a second oil reservoir, the casing having a wall passage, obtained by casting, connecting the second oil reservoir to the first oil reservoir, the electric motor unit comprising:.

[0013] - an oil pump, configured to supply a high-pressure lubrication circuit, capable of at least cooling the electrical machine and delivering pressurized oil to the transmission components,

[0014] - a multi-function insert generally used to seal the wall opening and comprising a calibrated passage hole and receiving elements configured to receive a magnet, the calibrated passage hole defining a predefined passage section between the second oil reservoir and the first oil reservoir,

[0015] - a magnet housed and held between shapes from the casing and the receiving elements of the multifunction insert.

[0016] Thanks to the provisions promoted above, the multi-function insert cleverly combines a calibrated section communication function between the first oil reservoir and the second oil reservoir as well as a function for maintaining the particle trapping magnet.

[0017] Under the term "obtained from casting" with respect to the low wall passage, it should be understood that there is no machining rework at this location.

[0018] For the purposes of this description, the term "oil reservoir" refers to a hollow area in the lower part of the crankcase designed to receive oil by gravity; it designates the oil receptacle. In practice, before the power unit is filled with oil, the first and second oil reservoirs are empty. During operation, the oil reservoirs are replenished by oil runoff that naturally returns to the lower part of the crankcase by gravity. The current oil level in the reservoirs depends on the operating lubrication conditions.

[0019]

[0015] The wall passage is a through passage in the lower part which connects the electrical machine compartment with the transmission compartment for the lubrication system as will be seen later.

[0020]

[0016] The oil pump is an electrically driven oil pump, meaning that it is equipped with an electric motor that drives the oil pump impeller / turbine. This motor is selectively controlled by a control unit, for example, according to the cooling requirement.

[0021]

[0017] It is noted that the lubricating oil lifting function is carried out where there is a small radial gap left free between the differential ring and the differential housing; there is no pump element here as such.

[0022] The use of the multi-functional insert with its calibrated bore allows for a reduction in stress on the shape and cross-section of the cast wall opening, resulting in a larger cross-section and contributing to the overall weight reduction of the electro-motor unit. The magnet's function is to trap metallic particles carried by the circulating oil flow. The housing is made of aluminum and does not interfere with the effectiveness of the magnetic field created by the magnet.

[0023] According to one embodiment, when the electric oil pump is in operation, a first oil circuit C1 is established in which the magnet is positioned upstream of the calibrated passage hole, and when the electric pump is not in operation and the differential ring is rotating, a second oil circuit C2 is established in which the magnet is positioned upstream of the lifting zone provided by the ring.

[0024]

[0021] The filtering and trapping effect provided by the magnetic field of the magnet thus makes it possible to treat the entire hydraulic flow which will be sent back upwards and in particular towards the elements to be lubricated, whatever the operating conditions.

[0025] Furthermore, in a static situation—that is, when the electric oil pump and differential ring gear are not rotating, with the vehicle essentially parked on a level surface—the axis of the calibrated through-hole is below the overall oil level. The two oil reservoirs then share the same oil level, thanks to the communicating vessel function of the calibrated through-hole.

[0026] [0 It is noted that during operation, the levels decrease and can be different between the first reserve and the second reserve.

[0027] [0 According to one embodiment, the multi-function insert comprises on the one hand an insert body which rests at least in part on the edge of the wall passage and on the other hand one or more retaining elements.

[0028] The body of the insert is typically plate-shaped.

[0029] The calibrated through hole is made in the insert body.

[0030] According to one embodiment, the retaining elements include at least one fixing tab bearing on an edge of the wall passage and / or at least one S-shaped tab bearing on an edge of the wall passage.

[0031] The tabs and / or S-shaped brackets are designed to position and securely hold the multi-function insert in place at the wall penetration. On one side, the body of the multi-function insert rests against the edge of the wall penetration, and on the other side, the ends of the tabs and / or S-shaped brackets hook onto the wall penetration.

[0032] According to a preferred embodiment, 2 fixing tabs and two S-shaped tabs are provided. One or more positioning locating points may also be provided.

[0033]

[0030] According to one embodiment, the multi-function insert is inserted into the wall penetration by a translation along the transverse Y direction. The tabs and / or S-shaped lugs flex during the passage and return at the end of the translation to their rest position, thus achieving the desired anchoring. The multi-function insert is removable.

[0034]

[0031] It is noted that the multifunction insert is inserted from the transmission compartment, which offers good access when the transmission-side crankcase cover is not in place.

[0035] According to one design, the multi-functional insert is made of plastic, preferably polyamide reinforced with fibers. For example, PA66 with GF35 fiber reinforcement could be chosen. [0] Complex shapes can be obtained by molding, including retaining elements such as tabs of varying complexity and hooks, as well as magnet holders.

[0036] Advantageously, the multi-function insert is made from a single piece of material.

[0037] According to an alternative embodiment, the multi-function insert can be made of metal, for example by cutting and bending a sheet metal blank.

[0038] In one embodiment, the calibrated passage hole is circular with a diameter D8 between 4 mm and 8 mm. The inventors conducted simulations and tests to verify the damping effect of such a passage cross-section, which limits the flow rate from one oil reservoir to the other in the presence of centrifugal force. However, this hole allows sufficient flow for the first lubrication circuit when the pump is running and supplying the transmission compartment, as the oil return passes through the calibrated passage hole in this case.

[0039]

[0037] According to one embodiment, the wall passage obtained from casting has a passage section at least 3 times greater than the passage section provided by the calibrated passage hole.

[0040] It should be noted that if the tests lead to the need to modify the cross-section of the calibrated hole, this does not compromise the casting of the housing, which would have been the case if the hole had been made directly in the housing casting. It is easier and more practical to modify the multi-function insert than to modify the generator housing.

[0041] In one embodiment, the electromotor unit further comprises a housing cover, and the magnet is held in place by at least one rib formed in the housing cover. Closing the cover immobilizes the magnet along the transverse Y-direction.

[0042]

[0040] According to one embodiment, the receiving elements are L-shaped, U-shaped, or wedge-shaped walls. These receiving elements, in combination with those present on the housing casting, make it possible to visibly and intuitively delimit the housing for the magnet and frame the magnet. Thanks to these receiving elements, the magnet mounting is intuitive, and they provide a pre-retaining function for the magnet before the transmission housing cover is closed.

[0043] In one design, at least one guide rib is provided at the bottom of the housing, facilitating the installation of the insert. A corresponding notch is provided in the bottom of the multifunction insert. The rib under construction provides visual and physical guidance for mounting the insert in the wall opening.

[0044] The present invention also relates to an electric or hybrid vehicle, comprising at least one electromotor unit as described above.

[0045] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which:

[0046] - [Fig.1] schematically illustrates an electric vehicle in top view with the electromotor unit mounted transversely;

[0047] - [Fig.2] illustrates a schematic cross-section of the electromotor unit, generally vertical, with the electrical machine compartment shown on the right and the transmission compartment shown on the left; - [Fig.3] illustrates a schematic detail view of the wall passage between the transmission compartment and the electrical machine compartment, with the multifunction insert not yet installed, the view taken along the arrow lll-lll visible in figure 2;

[0048] - [Fig.4] shows a perspective view of an example of a multifunctional insert according to the present invention;

[0049] - [Fig.5] is analogous to figure 3 and illustrates the area of ​​the wall passage equipped with the multifunction insert and the magnet;

[0050] - [Fig.6] is analogous to figure 3 and illustrates the area of ​​the wall passage equipped with the multifunction insert, the magnet being removed with the oil circulations around the magnet;

[0051] - [Fig.7] illustrates a schematic vertical cross-section of the multifunction insert area, the differential ring not being shown and the transmission side cover of the housing not being closed;

[0052] - [Fig.8] illustrates a schematic cross-section of the multifunction insert area, along the section line VIII-VIII visible in figure 5;

[0053] - [Fig.9] illustrates a front view of the multifunction insert from the side facing the electrical machine compartment.

[0054] In the various figures, the same references designate identical or similar elements. For the sake of clarity, some elements are not necessarily shown to scale, particularly gaps and intervals.

[0055]

[0045] Figure 1 shows a top view of a vehicle VH. In the illustrated example, this vehicle includes an electric motor unit located in the front engine compartment, with an electric traction machine 1 located on the right side of the electric motor unit and a transmission TR located on the left side of the electric motor unit.

[0056]

[0046] Of course, the arrangement could be reversed, with the machine on the left and the transmission on the right. Alternatively, the electric motor unit could interact with the rear axle of the vehicle. The electric motor unit can be installed in conjunction with a steering or non-steering axle.

[0057]

[0047] In the figures, the vehicle and its electromotor unit are located with respect to an orthogonal frame of reference as follows: the vertical direction is noted Z, the horizontal direction called longitudinal is noted X, the horizontal direction called transverse is noted Y.

[0058] The TR transmission includes a RED reduction gear and a DIF differential. The lubrication system equipping the electric motor unit will be discussed in the following paragraphs.

[0059] In the illustrated example, the electric motor 1 provides torque which enters the transmission, to be distributed to the two wheels of the axle via the differential DIF. At the output of the transmission TR, there are two wheel shafts, one connected to the left wheel and the other connected to the right wheel of the vehicle (not shown).

[0060] Regarding the reduction gear, as known per se and not described in detail, an intermediate double pinion 61 is provided, which is driven by an output pinion of the electric machine and which in turn drives the ring gear 3 of the differential.

[0051] As can be seen in Figure 2, this intermediate gear 61 comprises a first pinion of large diameter and a second pinion of small diameter fixed to the first pinion. The second pinion is permanently engaged with the teeth 31 of the ring gear 3 of the differential.

[0061] The differential DIF comprises a ring gear 3 and a gear housing 32 containing the planetary and satellite gears, as is known per se. The ring gear 3 forms the input wheel of the differential. Note that the ring gear's contact is parallel; it is not a bevel gear. The ring gear 3 has teeth 31. In the illustrated example, the teeth are helical; they are not parallel to the axis.

[0062] The rotor of the electric motor rotates around the axis A1. The rotor of the electric motor is rotationally fixed to a primary pinion permanently engaged with the large pinion of the intermediate gear 61.

[0063] The crown gear 3 rotates around an axis labeled A3. The intermediate gear 61 rotates around an axis labeled A2. Axes A1, A2, and A3 are parallel.

[0064] The electromotor unit includes a main casing 4.

[0065] The casing 4 delimits an internal space 4M which houses the electric machine and another internal space 4T which houses the transmission.

[0066] In other words, the casing 4 delimits an electrical machine compartment from the transmission compartment; the two compartments are generally separated by a casing wall.

[0067] The housing 4 is made of aluminum and does not interfere with the effectiveness of the magnetic field created by the magnet. It is provided with a cover 42 on the machine side and a cover 41 on the transmission side. The housing 4 can be made in one piece or in several pieces assembled together.

[0068] The electric motor unit includes an oil pump 5, which is the driving element of a first lubrication circuit, labeled C1. The oil pump is electrically driven. The oil pump supplies pressurized oil to the core of the electric machine; circuit C1 is shown schematically in Figure 2. Furthermore, a heat exchanger, not shown in the figures, is included on the first oil circuit, C1.

[0069] Furthermore, an oil lifting function is provided, obtained through the rotation of the teeth 31 of the ring 3. The oil lifting function is part of a second lubrication circuit labeled C2, circuit C2 being schematically represented in figure 2.

[0070] Furthermore, the second lubrication circuit includes a trough 9, also known as a multi-function reservoir trough. This trough acts as a buffer oil reservoir; during lubrication operation, trough 9 is continuously supplied by the hydraulic lift or electric oil pump and simultaneously dispenses oil onto the relevant parts through orifices.

[0071] In the second lubrication circuit C2, there is no specific filter per se, but a magnet 2 is provided to trap any metallic particles that might circulate in the oil. The position of this magnet 2 will be discussed later. A first oil reservoir VM is located on the electric motor side, and a second oil reservoir VT is located on the transmission side. The first oil reservoir is connected to the second oil reservoir by a passage that will be discussed below. Regarding the pressurized oil circuit, the strainer connected to the electric oil pump draws oil from the first oil reservoir. An oil filter is located near the strainer or the pump to supplement the filtering effect provided by the magnet 2. The housing includes a wall passage 6, cast in place, connecting the second oil reservoir VT to the first oil reservoir VM.

[0072] There are dynamic situations where a centrifugal force FC1 (see figures 1 and 2) tends to move the oil to the right, i.e. towards the electric machine, or conversely other situations where the centrifugal force FC2 tends to move the oil to the left, i.e. towards the transmission.

[0073] Under the effect of inertial forces, the oil moves from one reservoir to another through a communicating passage.

[0074] According to an advantageous feature of the present invention, the electromotor unit includes a multi-function insert 7 which generally closes the wall passage 6. This part is called an 'insert' because it is inserted in a position provided for this purpose in the wall passage 6; it can be removed if necessary and is therefore removable.

[0075] This part is described as multifunctional because on the one hand it defines the passage of oil between the two oil reservoirs and on the other hand it contributes to housing and maintaining the particle trapping magnet.

[0076] The multi-function insert 7 includes a calibrated through hole 8.

[0077] The calibrated passage hole defines a predefined passage section between the second VT oil reservoir and the first VM oil reservoir.

[0078]

[0071] According to one option, the calibrated through hole is circular. According to one embodiment, the diameter D8 is between 4 mm and 8 mm.

[0079] We note that the shape of the passage hole could be something other than circular, for example a roughly rectangular window.

[0080] When the vehicle travels on a curved road and a rightward centrifugal force FC1 prevails, the transfer of oil through the calibrated hole 8 is limited in flow and prevents the second oil reservoir VT from drying out quickly.

[0081] Similarly, in the other direction, when a left-hand centrifugal force FC2 prevails, the transfer of oil through the calibrated hole 8 is limited in flow and prevents the first oil reservoir VM from drying out quickly.

[0082] There is no other passage for the oil between the two reservoirs at the bottom of the crankcase than the calibrated hole 8.

[0083] Furthermore, the multi-function insert 7 also includes 24 reception elements configured to receive a 2-magnet.

[0084] The multi-function insert comprises an insert body 70. The insert body rests at least partially on the edge 47 of the wall opening (see Figure 8). The insert body 70 closes the wall opening except for the calibrated hole 8. The thickness E7 of the insert body 70, for example from 1.5 to 3 mm, is less than the thickness L1 of the housing wall.

[0085] The multi-function insert includes retaining elements for holding said insert in the wall passage area 6.

[0086] In the example shown in Figure 4, the retaining elements include two fixing tabs 71, 72 bearing on an edge 49 of the wall passage and two S-shaped tabs 73, 74 bearing on an edge 49 of the wall passage.

[0087] The number of tabs and / or S-shaped tabs or equivalent may of course be different.

[0088] It should be noted that any other means of clipping and / or retaining the multi-function insert 7 in the wall passage 6 could be used within the scope of the present invention. [0 For the function of housing and retaining the magnet 2, the multi-function insert 7 includes retaining elements. In the illustrated example, these are L-shaped, U-shaped, or wedge-shaped walls 24. The walls 24 protrude from the body of the plate 70.

[0089] The multi-function insert 7 is made of plastic. In the example shown, a polyamide reinforced with reinforcing fibers, for example PA6-6 grade GF35, is preferred.

[0090] All the necessary shapes can be derived directly from the mold that forms the multi-function insert part, including the retaining elements on the housing and also the receiving elements that allow the magnet 2 to be housed.

[0091] However, it is not out of the question to form the multifunctional insert out of metal. According to one option, the maximum dimension of the insert is 25 mm, the thickness of the body 70 is 3 to 4 mm, and it is understood that the dimensions mentioned are not limiting.

[0092] In the lower wall of the housing, two ribs 45 and 46 are provided against which the magnet rests. These ribs act as spacers to keep the magnet away from the bottom wall of the housing. These ribs are cast and do not require any further machining.

[0093] It is noted that opposite rib 46, a notch 78 is provided in the insert body, which allows for guidance during insertion. A locating 79, with a recessed shape in the housing, is also provided in the insert body for positioning.

[0094] [0 As can be seen in Figure 5, the housing also includes side walls 64 which complement the reception elements provided on the multifunction insert. Preferably, these side walls 64 are cast without further machining.

[0095]

[0090] Figure 9 illustrates another example in its multifunctional form with three similar tabs 71, 72, 77 extending perpendicularly from the body of the inserts (two at the bottom and one at the top) and bearing against the edge 49 of the wall passage. The multifunctional insert 7 can thus be an inexpensive part.

[0096]

[0091] As illustrated in figures 7 and 8, the housing cover 41 includes a rib 41a provided which locks the position of the magnet when the cover is placed in its position.

[0097] Magnet 2 is made of a material known per se, so it is not detailed here. The magnet is prismatic in shape, preferably with a general parallelepiped shape. Its dimensions L2 and W2 can be from a few tens to thirty millimeters. The thickness can be less than 10 millimeters.

[0098] Functioning Figure 6 shows the passage of oil which is drawn in either by the lift provided by the rotation of the ring or by the operation of the electric oil pump. The oil passage F1 above the magnet has a height E3. The oil passage F2 below the magnet has a maximum height E4 and passes through a path delimited by the walls 45, 46 and 41a.

[0099] The oil passage F3 illustrates the suction provided by the lifting effect of the rotation of the ring 3.

[0100] When the electric oil pump 5 is in operation, the oil level in the first oil reservoir VM drops. The portion of oil delivered to the 4T transmission compartment trickles into the transmission compartment, passes near the magnet (F1, F2) where particles are trapped, then passes through the calibrated hole 8 and returns to the first oil reservoir to be drawn back into the pump.

[0101] In this configuration, the first lubrication circuit C1 prevails, the lifting function may be disengaged, but there is no adverse consequence, the delivery of oil being ensured by the first lubrication circuit C1 which supplies the reservoir chute 9 with oil dispensing and distribution orifices at the appropriate locations.

[0102] When the electric oil pump 5 is not in operation, the oil lift function is operational, the oil level in the second VT reservoir on the transmission side may drop, but is partially replenished via the calibrated hole 8 from the first VM oil reservoir which is not being drawn by the pump.

[0103] It is therefore understood that the passage provided by the calibrated hole 8 in both directions must be sufficient to ensure the correct operation of the two lubrication configurations described above.

[0104]

[0100] Furthermore, we have seen that an excessively large cross-section promotes rapid oil transfer under the effect of inertial forces directed along the transverse axis. The cross-section of the calibrated orifice is therefore crucial.

[0105] The configuration shown therefore offers a compromise to ensure proper lubrication operation, whether or not the electric oil pump is running, and on the other hand to protect these two modes from undesired priming in the event of transverse centrifugal force applied for a certain time.

[0106] The trick of forming the calibrated hole in a small part, i.e. here the multi-function insert 7, allows a late adjustment of the passage section in the development of the electromotor group, after simulations and tests.

[0107] In addition, the multi-functional insert offered allows the magnet to be ideally placed in the oil path in order to maximize the trapping effect.

[0108] This allows for a reasonable oil quantity and limits the splashing of the crown in both lubrication configurations. For example, the total oil quantity can be between 500 ml and 1 liter.

Claims

DEMANDS 1. Motor vehicle power unit comprising an electric machine (1) and a transmission (TR), the transmission comprising at least one differential (DIF) with a ring gear (3) having teeth (31) and providing a lubricating oil lifting function, the power unit comprising a housing (4) separating an electric machine compartment (4M) from a transmission compartment (4T), the electric machine compartment comprising a first oil reservoir (VM) and the transmission compartment comprising a second oil reservoir (VT), the housing having a wall penetration (6), obtained by casting, connecting the second oil reservoir to the first oil reservoir, the power unit comprising: - an oil pump (5), configured to supply a high-pressure lubrication circuit, suitable at least for cooling the electrical machine and for delivering pressurized oil to the transmission components, - a multi-function insert (7) generally used to seal the wall opening and comprising a calibrated passage hole (8) and receiving elements configured to receive a magnet, the calibrated passage hole defining a predefined passage section between the second oil reservoir and the first oil reservoir, - a magnet (2) housed and held between shapes originating (45) from the housing and the receiving elements (24) of the multifunction insert.

2. Electric motor unit according to claim 1, characterized in that when the electric oil pump is in operation, a first oil circuit (C1) is established in which the magnet is positioned upstream of the calibrated passage hole (8), and when the electric pump is not in operation and the differential ring is rotating, a second oil circuit (C2) is established in which the magnet is positioned upstream of the lifting zone.

3. Electromotor unit according to any one of claims 1 to 2, wherein the multifunction insert (7) comprises on the one hand an insert body (70) which bears at least in part on the edge of the wall passage and on the other hand one or more retaining elements.

4. Electromotor unit according to claim 3, wherein the retaining elements comprise at least one fixing tab (71) bearing on an edge of the wall passage and / or at least one S-shaped tab (73) bearing on an edge of the wall passage.

5. Power unit according to any one of claims 1 to 4, wherein the multifunction insert (7) is made of plastic material, preferably of polyamide loaded with reinforcing fibers.

6. Electromotor unit according to any one of claims 1 to 5, wherein the calibrated through hole (8) is circular in shape and has a diameter (D8) between 4 mm and 8 mm.

7. A motor-driven unit according to any one of claims 1 to 6, further comprising a housing cover (41) and the magnet is further held by at least one rib (41a) formed in the housing cover.

8. A motor-driven unit according to any one of claims 1 to 7, wherein the receiving elements are L-shaped, U-shaped, or wedge-shaped walls.

9. Electromotor unit according to any one of claims 1 to 8, wherein at least one guide rib (46) is provided at the bottom of the housing, facilitating the installation of the insert.

10. Electric or hybrid vehicle, comprising at least one electric motor unit according to any one of claims 1 to 9.

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