Rotor of a separately excited synchronous machine

Abstract

The invention relates to a rotor (10) of a separately excited synchronous machine, particularly in a motor vehicle. The rotor (10) according to the invention has a rotor core (11) with rotor teeth (12) arranged star-shaped around a rotor axis (R) on the rotor core (11), wherein at least one winding (14) is provided for each rotor tooth (12), which is wound around the corresponding rotor tooth (12). Furthermore, at least one displacer body (16) is arranged in a groove (15) formed between the windings (14) of adjacent rotor teeth (12), which extends in the axial direction of the rotor (10).Furthermore, at least one cooling channel (17) is provided, which is arranged in the at least one displacer body (16) and through which coolant flows, and has a coolant inlet (171) on an axial end face of the displacer body (16), configured to introduce coolant into the cooling channel (17), and a coolant outlet (172) on the opposite axial end face of the displacer body (16), configured to discharge coolant from the cooling channel (17). According to the invention, a slope in the radial direction of the rotor (10), i.e., perpendicular to the rotor axis (R), is provided between the coolant inlet (171) and the coolant outlet (172), wherein the radial distance from the coolant inlet (171) to the rotor axis (R) is less than the radial distance from the coolant outlet (172) to the rotor axis (R), so that a radial offset (a) is formed between the coolant inlet (171) and the coolant outlet (172).

Description

[0001] The invention relates to a rotor of a separately excited synchronous machine, in particular in a motor vehicle.

[0002] Externally excited synchronous motors (FSMs) do not have permanent magnets in the rotor, unlike permanent magnet synchronous motors (PSMs). The magnetic field in the rotor is generated by electromagnets formed by windings around rotor teeth. During operation, externally excited synchronous motors can generate high temperatures in both the rotor and stator due to friction and the currents required to maintain the magnetic fields. These high temperatures negatively impact both the efficiency and lifespan of the electric motors. Consequently, FSM rotors are typically cooled.

[0003] For this purpose, cooling channels are provided at various points in the rotor, extending axially, i.e., parallel to the axis of rotation (also called rotor axis) of the electric motor, and transporting coolant. A sufficient flow rate of coolant must be provided for this, which requires an oil pump, which, however, incurs additional power consumption.

[0004] To reduce this, the prior art documents DE 10 2014 009 926 A1, EP 4 142 121 A1 and EP 2 110 926 A1 disclose cooling channels introduced axially in the rotor, which have a slope in the radial direction, i.e. perpendicular to the rotor axis, whereby the coolant flows through the coolant channel due to the centrifugal force present when the rotor rotates.

[0005] Patent document US 2018 375 395 A1 discloses a rotor with a meandering coolant channel, wherein a coolant flows radially from an inlet channel extending through a rotor shaft into the coolant channel provided on a rotor base body and flows out of the coolant channel via the two end faces of the rotor base body. The inlet of the coolant channel is radially spaced from the outlet of the coolant channel.

[0006] Document EP 2 490 322 A1 describes a rotor with a cooling channel extending between the two end faces, the cross-section of which increases from the inlet to the outlet.

[0007] Document DE 10 2019 216 982 A1 discloses a rotor with a rotor body, wherein the rotor body has several coolant channels. Each coolant channel has two coolant sections radially offset from each other.

[0008] In light of the aforementioned prior art, the object of the present invention is to further reduce the power consumption of the oil pump and thus improve the overall efficiency of the electric motor, as well as to provide a separately excited synchronous machine with a rotor according to the invention and a corresponding motor vehicle with a separately excited synchronous machine according to the invention.

[0009] The problem is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are contained in the dependent claims.

[0010] The rotor of a separately excited synchronous machine according to the invention has a rotor core with rotor teeth arranged star-shaped around a rotor axis on the rotor core, wherein at least one winding is provided for each rotor tooth, which is wound around the corresponding rotor tooth. The rotor core and rotor teeth are preferably formed from a laminated core with laminations arranged perpendicular to the rotor axis. Furthermore, at least one displacer body is arranged in a groove formed between the windings of adjacent rotor teeth, which extends in the axial direction of the rotor, i.e., parallel to the axis of rotation.Furthermore, at least one cooling channel is provided, which is arranged in the at least one displacer body and through which coolant flows, and has a coolant inlet on an axial end face of the displacer body, configured to introduce coolant into the cooling channel, and a coolant outlet on the opposite axial end face of the displacer body, configured to discharge coolant from the cooling channel. According to the invention, a slope in the radial direction of the rotor, i.e., perpendicular to the rotor axis, is provided between the coolant inlet and the coolant outlet, wherein the distance from the coolant inlet to the rotor axis in the radial direction is less than the distance from the coolant outlet to the rotor axis in the radial direction, so that an offset is formed between the coolant inlet and the coolant outlet in the radial direction.

[0011] Due to the radial offset between the coolant inlet and outlet, and the resulting radial slope, the centrifugal force of the rotor pushes the coolant in the displacer body against the outer wall of the cooling channel, thus automatically accelerating it axially towards the coolant outlet. This axial acceleration no longer needs to be provided by the pump to maintain the coolant flow rate, allowing for a reduction in pump power and an increase in the overall efficiency of the electric motor.

[0012] In an advantageous embodiment of the invention, the cooling channel is formed by a bore oriented essentially in the axial direction. This means that, apart from the radial offset, the bore is only oriented in the axial direction. Such an embodiment allows for a particularly simple cooling channel geometry, which offers many advantages, especially with regard to manufacturing effort. Furthermore, the cooling channels can be selectively positioned at the required locations depending on the temperature distribution within the displacer body.

[0013] In an alternative embodiment of the invention, the at least one cooling channel is formed by a radially extending slot. The slot is preferably designed such that it extends continuously from radially inside to radially outside and does not form any points that are closer to the axis of rotation than a previous point, thus ensuring a continuous increase in distance to the axis of rotation. In other words, when mentally tracing the contour of the slot from radially inside to radially outside, there is no reversal point that would cause the radial distance of the slot's contour to the rotor axis to decrease. A particularly preferred embodiment is one in which the slot has a wave-like shape in the radial direction. The wave-like shape of the slot allows the coolant to be distributed evenly within the displacer body, thereby increasing the cooling capacity.

[0014] Preferably, the displacer body is designed to substantially fill the groove between two rotor teeth. The phrase "substantially fill" means that the displacer body is in contact with the adjacent windings and completely fills the groove except for the cavities created by the curvature of the winding wire. Such displacers can further increase efficiency because they are particularly well cooled by the cooling channels, thus maximizing the volume cooled by the cooling channels within the rotor, especially due to direct contact with the windings.

[0015] A further advantageous embodiment of the invention is one in which at least one cooling channel, in addition to the radial slope between the coolant inlet and outlet, has a tangential slope (i.e., in the circumferential direction) of the rotor, such that a second tangential offset is formed between the coolant inlet and outlet, and the coolant outlet is located downstream of the coolant inlet in the direction of rotation of the rotor. With such an embodiment, the coolant in the cooling channel can be further accelerated when the rotor rotates, thereby further reducing the pumping power and increasing the efficiency.

[0016] In a further preferred embodiment of the rotor according to the invention, the slope between the coolant inlet and coolant outlet in the radial and tangential directions of the rotor is not linear, but rather quadratic. By means of specifically shaped cooling channels with, for example, a quadratically increasing slope, a suction effect can be generated in the cooling channel, which enhances the axial acceleration of the coolant. It is also conceivable that the cooling channel is designed in sections, with different sections having different slopes. This allows the acceleration of the coolant within the cooling channel to be controlled, thus further enhancing the advantageous effect of the invention.

[0017] The separately excited synchronous machine according to the invention has a rotor according to the invention, while a motor vehicle according to the invention has a separately excited synchronous machine according to the invention.

[0018] Advantageous aspects and embodiments of the invention are explained in more detail below with reference to the accompanying figures. They show: Fig. Figure 1a shows a section of a top view parallel to the rotor axis R of a rotor 10 according to the invention in a first embodiment. Fig. Figure 1b shows a detailed view of a displacement body 16 according to the embodiment shown. Fig. 1a Fig. Figure 2a shows a section of a top view parallel to the rotor axis R of a rotor 10 according to the invention in a second embodiment. Fig. Figure 2b shows a detailed view of a displacement body 16 according to the embodiment shown. Fig. 2a

[0019] Fig. Figure 1a shows a section of a top view parallel to a rotor axis R (axis of rotation) of a rotor 10 according to the invention in a first embodiment. The rotor 10 has a rotor core 11 on which rotor teeth 12 are arranged radially outwards around the axis of rotation R. The rotor core 11 and the rotor teeth 12 are formed from a laminated core of individual laminated sheets, which are arranged perpendicular to the rotor axis R. A rotor bandage 13 is arranged around the circumference of the rotor 10. Windings 14 are arranged around each of the rotor teeth 12 to generate the magnetic field of the rotor 10. A groove 15 is arranged between each adjacent rotor teeth 12, which is filled by a displacer body 16 extending in the axial direction. The displacer body 16 is clamped by the windings 14 around the rotor teeth 12 and the bandage 13 and is thus fixed in its position.The displacement body 16 has cooling channels 17 which extend axially through the displacement body 16.

[0020] Fig. 1b shows the one in Fig. Figure 1a shows a detailed side view of the displacer body 16, excluding the windings 14 that define it, the rotor core 12, and the rotor teeth 13. The rotor axis R, which serves as the axis of rotation for the rotor 10, is shown as a dashed line. The four cooling channels 17 shown extend axially along the displacer body 16 and each has a coolant inlet 171 and a coolant outlet 172, located on the axially opposite end faces of the displacer body 16. Each coolant outlet 172 is always offset a further radially from the rotor axis R than its corresponding coolant inlet 171. This creates a slope in the radial direction between the coolant inlet 171 and the corresponding coolant outlet 172.

[0021] The arrows shown at the coolant inlets 171 and coolant outlets 172 indicate the direction of coolant entry and thus the coolant flow, whereby the coolant is pumped through the displacer body 16 by a pump (not shown). During operation, the rotation of the rotor 10 forces the coolant radially outwards in the cooling channels 17 due to centrifugal force. Because of the offset 'a', the coolant experiences a force in the plane of the drawing due to the slope in the cooling channels 17, in addition to the purely radial force component of the centrifugal force. Fig. 1b downwards, i.e., in the axial direction of rotor 10. Thus, the coolant is accelerated in the axial direction, which is why the pump does not need to provide this axial acceleration component to deliver the required coolant flow rate. Consequently, the pump power and therefore the electricity consumption can be reduced, and the overall efficiency of the separately excited synchronous machine can be improved.

[0022] In the illustrated embodiment, the radial slope between coolant inlet 171 and coolant outlet 172 is linear. However, embodiments of the invention are also conceivable in which the slope of the cooling channel 17 is not linear, but rather quadratic. In particular, an axially extending cooling channel 17 can initially be provided, which only later acquires a slope. Thus, differently shaped cooling channels 17 are also conceivable in sections in order to influence the axial acceleration on the coolant within the cooling channel 17.

[0023] Furthermore, embodiments are also conceivable in which, in addition to the radially extending slope between coolant inlet 171 and coolant outlet 172, a slope in the tangential direction, i.e. in the circumferential direction of the rotor 10, is provided, which can further enhance the advantageous effect achieved by the invention.

[0024] The Fig. 2a and Fig. Figure 2b shows a second embodiment according to the invention, which largely corresponds to the one described in the Fig. 1a and Fig. The first embodiment of the invention shown in 1b corresponds to this, which is why only the differences between the embodiments will be discussed here. In contrast to the embodiments according to the Fig. 1a and Fig.In Figure 1b, instead of individual cooling channels 17 designed as bores, only a slot-shaped cooling channel 17 is provided. This channel extends radially outwards in a wave-like pattern or is formed with a short radial wave-like shape. Combinations of differently shaped cooling channels 17 in a rotor 10 or in a displacer body 16 are also conceivable. Due to the wave-like cross-sectional shape, a large area of ​​the displacer body 16 can be cooled. Other radially outward-extending slot shapes as cooling channels 17 and other cross-sectional geometries for a cooling channel 17 are also conceivable. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2014 009 926 A1

[0004] EP 4 142 121 A1

[0004] EP 2 110 926 A1

[0004] US 2018 375 395 A1

[0005] EP 2 490 322 A1

[0006] DE 10 2019 216 982 A1

[0007]

Claims

[1] Rotor (10) of a separately excited synchronous machine, comprising a rotor core (11) with rotor teeth (12) arranged in a star shape around a rotor axis (R) on the rotor core (11), at least one winding (14) per rotor tooth (12) which is wound around the corresponding rotor tooth (12), at least one displacement body (16) which is arranged in a groove (15) between the windings (14) of adjacent rotor teeth (12) and extends in an axial direction of the rotor (10), at least one cooling channel (17) which is arranged in the at least one displacement body (16) and through which coolant flows, comprising a coolant inlet (171) on an axial end face of the displacement body (16), designed to introduce coolant into the cooling channel (17), and a coolant outlet (172) on the opposite axial end axis of the displacement body (16), designed to discharge coolant from the cooling channel (17), wherein a gradient in the radial direction of the rotor (10) is provided between the coolant inlet (171) and the coolant outlet (172), and the distance in the radial direction from the coolant inlet (171) to the rotor axis (R) is smaller than the distance in the radial direction from the coolant outlet (172) to the rotor axis (R), so that an offset (a) is formed in the radial direction between the coolant inlet (171) and the coolant outlet (172). [2] Rotor (10) according to the preceding claim, wherein at least one cooling channel (17) is formed by a bore oriented substantially in the axial direction. [3] Rotor (10) according to one of the preceding claims, wherein at least one cooling channel (17) is formed by a slot extending in the radial direction. [4] Rotor (10) according to the preceding claim, wherein the slot is wave-shaped in the radial direction. [5] Rotor (10) according to one of the preceding claims, wherein the displacement body (16) is designed to substantially completely fill the groove between two rotor teeth (12). [6] Rotor (10) according to one of the preceding claims, wherein at least one cooling channel (17) has, in addition to the gradient in the radial direction between the coolant inlet (171) and the coolant outlet (172), a gradient in the tangential direction of the rotor (10), so that a second offset in the tangential direction is formed between the coolant inlet (171) and the coolant outlet (172) and the coolant outlet (172) is arranged behind the coolant inlet in the direction of rotation of the rotor (10). [7] Rotor (10) according to one of the preceding claims, wherein the gradient between the coolant inlet (171) and the coolant outlet (172) is non-linear in the radial direction or tangential direction of the rotor (10). [8] Separately excited synchronous machine comprising a rotor (10) according to one of the preceding claims. [9] Motor vehicle comprising at least one separately excited synchronous machine according to the preceding claim.

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