Electromotive drive unit with a seal and a shaft retaining ring

Abstract

An electric motor drive unit (1) comprising an electric machine (42), a gearbox (5, 43), and at least two machine elements (10, 20), as well as a component locking device (17, 24, 25) and a rotor shaft (4) of the electric machine (42), wherein the rotor shaft (4) is a first machine element (10) of the machine elements (10, 20), wherein the component locking device (17, 24, 25) is formed at least from a shaft retaining ring (11, 26) and from a locking element (16) for securing the shaft retaining ring (11, 26) on the rotor shaft (4), and wherein a second machine element (20) of the machine elements (10, 20) is an output shaft (6) of the gearbox (5, 43), wherein at least one first component (15) seated on the rotor shaft (4) is secured by means of the component locking device (17, 24,25) is secured axially to the rotor shaft (4) at least in an axial direction and wherein an annular gap (7) between the rotor shaft (4) and the output shaft (6) is sealed by means of at least one seal (19, 22, 23, 40) and wherein the component locking device (17, 24, 25) and the seal (19, 22, 23, 40) are operatively connected to each other to form a functional unit that seals the annular gap (7) and secures the shaft retaining ring (11, 26) against expansion due to centrifugal force.

Description

Field of invention

[0001] The invention relates to an electric motor drive unit comprising an electric machine, a gearbox, and at least one machine element, as well as a component locking device for securing at least one first machine element of the machine elements on a rotor shaft of a rotor of the electric machine, wherein the component locking device is formed at least from a shaft retaining ring and from a locking element for securing the shaft retaining ring on the rotor shaft, and wherein a second machine element of the machine elements comprises an output shaft of the gearbox, wherein at least one first component of the first machine element sitting on the rotor shaft is axially secured to the rotor shaft at least in an axial direction by means of the component locking device. Background of the invention

[0002] DE 2215 041 A1 describes a component retention device with at least two concentrically arranged machine elements, one of which is a shaft and the other a housing. The component is a rolling bearing that sits in a bore of the housing and with which the shaft is mounted so that it can rotate about its own axis of rotation relative to the housing. The rolling bearing is axially secured on the shaft and / or in the housing, either on one or both sides, by a component retention device. The component retention device is a shaft retaining ring. This shaft retaining ring has a dual function: it secures the rolling bearing axially on the shaft or in the housing and also serves as the seal carrier for a sealing lip of the seal.The description in DE 2215 041 A1 indicates that the shaft retaining ring is a single-slotted retaining ring which, when inserted into a groove in the shaft, must be bent open at its ends and pushed over the shaft until it reaches the groove. The seal is vulcanized to the retaining ring. The seal seals an annular gap between the shaft and the outer ring of the rolling bearing or the housing. The deformable sealing lip, made of an elastic material, rests, for example, in a sliding contact with the outer ring of the rolling bearing.

[0003] Due to its slot, the shaft retaining ring can deform and expand radially at high speeds and the resulting centrifugal forces and / or under the influence of axial loads. In these cases, a secure hold in the groove of the shaft retaining ring is not guaranteed. As a standard part, the shaft retaining ring's cross-sections are precisely adapted to the requirements of its assembly and holding capacity. The surface area available on the shaft retaining rings for a secure connection with elastomers may be insufficient for use in the functional units described in DE 2215 041 A1. A secure hold of the sealing lips on the shaft retaining ring is not guaranteed in every case – or the effort required to create a secure connection makes the seal too expensive. Alternatively, shaft retaining rings adapted to the manufacturing of the functional unit can be produced as a special part.However, the costs for these are significantly higher compared to standard parts. When manufacturing such a functional unit, it must also be taken into account that a shaft retaining ring must be radially expanded during assembly. The resulting deformation also affects the design of the sealing lip, at least to the extent that the sealing lip must follow this deformation without sustaining damage and that the retaining ring's mounting openings remain accessible. The effort required to manufacture such a functional unit can be relatively high, particularly with regard to the complexity of the molds for overmolding the retaining ring and the associated tooling costs.

[0004] An electric motor drive unit of this type is described in DE 198 41 159 A1. The drive unit is a compact unit mounted transversely in the vehicle, comprising an electric motor drive and a gearbox. Within the drive unit, power from the motor is transmitted via the gearbox to two output shafts of the drive unit. The gearbox of the drive unit consists of two sub-gearboxes. One sub-gearbox is a speed reduction stage, which is a planetary gear set. The second sub-gearbox is a differential. The input shaft of the planetary gear set is a planet carrier, which is connected in the same direction as the rotor shaft of the electric motor drive. The axis of rotation of the rotor shaft lies on the central axis of the drive unit. The sun gear of the planetary gear set is fixed to the housing of the drive unit. A set of planet gears meshes with the sun gear and with a ring gear.The ring gear is the output shaft of the speed reduction stage and is rigidly connected to the differential housing. The housing and the ring gear are rotatable around the central axis of the drive unit. The speed reduction stage reduces the rotational speed of the drive's rotor shaft to a lower rotational speed at the output shaft.

[0005] The differential is equipped on the input side with the differential carrier and on the output side with the output shafts, which rotate relative to the rotor shaft. One of the drive shafts passes coaxially through the hollow rotor shaft. The drive unit housing is divided into two chambers, one of which houses the electric motor drive and the other the gearbox.

[0006] Typically, gaps and other passages are formed between the various interconnected or rotating machine parts, and these must be sealed against the ingress of lubricating oil. Therefore, a radial shaft seal is installed in the drive unit within an annular gap located between the rotor shaft and the output shaft. The radial shaft seal prevents lubricating oil from the gearbox chamber from entering the annular gap. Otherwise, the lubricating oil could coke up in the annular gap between the rotor shaft and the output shaft due to the heat generated by the electric motor and its transfer to the rotor shaft, with detrimental consequences.

[0007] The drive units described above often employ a radial shaft seal, which sits in the rotor shaft and runs with its sealing lip on the surface of the output shaft. During operation of the drive unit, the seal rotates at the speed of the rotor shaft. The sealing lip of the seal, however, slides on the output shaft at a relative speed resulting from the speed difference between the rotor and output shafts. Since the rotational speeds of electric motor rotor shafts are usually very high, the sealing lip is subjected to high circumferential speeds. Furthermore, the sealing lip is sometimes subjected to such high centrifugal forces that it lifts off the sealing surface, negating the sealing effect of a sliding seal at high speeds. A radial shaft seal is thus subjected to high loads and wear. The high speeds limit the suitability of radial shaft seals in certain applications.In some cases, the use of radial shaft seals at this location is ruled out for functional reasons. In these cases, complex seals have previously been used, which are correspondingly elaborate in design or made of expensive materials.

[0008] DE 10 2016 222 452 A1 discloses an electromechanical drive device with an electric motor and a gearbox arranged axially adjacent to it, wherein the gearbox comprises a gear stage designed as a planetary gear drive with a sun gear driven by a hollow shaft of the electric motor. An output shaft is guided through the hollow shaft, and the sun gear carries a sealing device for sealing between the hollow shaft and the output shaft, wherein the sealing device has a sealing lip structure that can make sealing contact with an end face of the hollow shaft. Description of the invention

[0009] The purpose of the invention is to create an improved drive unit that is easy and inexpensive to manufacture and easy to assemble.

[0010] The problem is solved according to the subject matter of claim 1.

[0011] The electric motor drive unit according to the invention comprises an electric machine, a gearbox, and at least one machine element, as well as a component locking device for securing at least one first machine element of the machine elements to a rotor shaft of a rotor of the electric machine. The electric machine is an electric motor, which may also have generator functions. The gearbox is preferably a planetary gearbox and preferably comprises a differential or transfer gearbox with two output shafts. The component locking device consists of at least one shaft retaining ring and a locking element for securing the shaft retaining ring to the rotor shaft. A second machine element is an output shaft of the gearbox. At least one first component of the first machine element, mounted on the rotor shaft, is axially secured to the rotor shaft by means of the component locking device, at least in one axial direction.An annular gap between the rotor shaft and the second machine element is sealed by means of at least one seal. The component retainer and the seal are operatively connected to each other to form a functional unit that seals the annular gap and secures the shaft retaining ring against centrifugal force-induced expansion.

[0012] The invention provides in detail that the shaft retaining ring is held against centrifugal force-induced expansion on a rotatable machine element by means of the retaining element. Furthermore, the functional unit sealing the annular gap is formed between this retaining element and the seal.

[0013] Machine elements within the meaning of the invention are assemblies composed of components or individual components. Machine elements are components that are contained in the same or at least similar form in technical structures, in this case in the drive unit. The term "element" in this sense does not refer to the smallest possible element, but rather to the smallest possible meaningful unit that is suitable for the function or the manufacturing requirements of technical structures. Thus, in this case, a machine element would be, for example, a gear, a shaft of the drive unit's transmission, or a rolling bearing. It is irrelevant whether the shaft or gear is composed of several components or is manufactured as a single piece. Rolling bearings, on the other hand, are composed of several components such as rings, balls, and cages.

[0014] Shaft retaining rings are used to secure components or machine elements to shafts, at least axially. A functional connection between the shaft and the retaining ring is established when the retaining ring is radially or circumferentially compressed into a groove on the shaft, forming an axial stop for the machine part. A shaft retaining ring is, for example, a standard part with a single slot according to DIN 471. During installation on the shaft, this retaining ring must be spread circumferentially, placed axially onto the shaft, and radially compressed into a groove.

[0015] The term "locking elements" refers to all elements that provide a secure hold for at least one sealing lip, as well as preventing the shaft retaining ring from expanding due to centrifugal forces. For this purpose, the shaft retaining ring is engaged radially on its outer side by a locking element, so that it is supported against radial outward expansion due to centrifugal force, and the seal is held by a seal carrier.

[0016] The shaft retaining ring is surrounded on the outside by a hollow cylindrical section of the retaining element, wherein the radial distance of the retaining element in the radial direction to the shaft retaining ring is less than the radial depth of the circumferential groove in the same radial direction. The radial distance preferably corresponds to a value of zero, particularly if the retaining ring is elastic.

[0017] The rotor shafts of electric motor drives rotate at very high speeds, so that the securing of machine elements is generally subject to the problems described in the chapter "Background of the Invention". The electric motor can be coupled to a gearbox via the rotor shaft, as is the case in vehicle drive units. The machine elements to be secured by means of the component securing device are preferably rolling bearings or gears. The component securing device in the electric motor drive unit according to the invention advantageously provides a cost-effective and reliable solution to the problem and simultaneously solves several tasks.

[0018] The functional units according to the invention, consisting of a sealing lip and a retaining element for the shaft retaining ring, as well as stabilization of the seal against opening at high speeds, can be optimally designed to meet all requirements. This applies in particular to their shape and surfaces, which can be specifically adapted to the requirements of a secure bond between the metal material and the elastomer on the one hand, and the requirements for securing the retaining ring on the other. According to the invention, the slotted shaft retaining rings are secured to shafts by means of a retaining element, preferably a retaining ring, when very high shaft speeds occur during operation and / or high axial forces act on the retaining ring. A retaining ring provides a secure hold all around, acting as both a retainer and a seal carrier.The advantage of the invention lies in the fact that, on the one hand, a standard part can still be used cost-effectively as a retaining ring, as in the prior art, and on the other hand, the manufacturing effort for producing the retaining element does not exceed the manufacturing effort for producing arrangements of the prior art. However, according to the invention, in addition to the sealing unit, the shaft retaining ring is secured against expansion by its support (reinforcement) and axial displacement within the functional unit.

[0019] State-of-the-art seals are typically equipped with a carrier element, usually a ring made of sheet metal or plastic. Modern injection molding technologies, commonly referred to as vulcanization, fuse various materials with the carrier to create a metal-plastic bond. Such carriers can be manufactured cost-effectively from sheet steel, particularly in mass production. These carriers, preferably cup-shaped, form a reinforcement that simultaneously ensures a secure fit of the seal on the rotor shaft, holds the shaft retaining ring in position, and supports, protects, and reinforces the sealing lip against expansion caused by centrifugal force.

[0020] Previously, the carriers and the elastomer seals were largely manufactured separately and then joined, for example, by vulcanization. With a modern manufacturing process, also known as a two-component (2K) process, the seals can be produced in the same mold in which the plastic carrier is injection-molded. The component securing device according to the invention, or its functional unit, can thus be manufactured more advantageously and cost-effectively than arrangements known in the prior art.

[0021] As mentioned above, the slotted rings known as shaft retaining rings, with mounting holes at the ends, can be used as retaining rings, but alternatively, any other type of slotted ring can also be used. Alternatively, the ring can be split and formed from at least two segments, i.e., slotted twice around its circumference. A double-slotted shaft retaining ring, for example, is formed from two arc-shaped, tire-like half-rings or half-perforated discs that can be inserted radially into the circumferential groove.

[0022] In one embodiment of the invention, the retaining ring has a first ring section (retaining element) that axially overlaps the shaft retaining ring and radially engages behind it. "Axial" refers to the direction of rotation aligned with the shaft's axis of rotation, and "radial" refers to the direction perpendicular to the shaft's axis of rotation. Accordingly, the retaining ring is provided with a hollow cylindrical ring section that radially engages behind the shaft retaining ring in directions perpendicular to the axis of rotation, viewed from the shaft's axis of rotation, and circumferentially surrounds it. Furthermore, the retaining ring has a second ring section with an outer or inner cylindrical surface, which is connected to the first ring section.The retaining ring's externally or internally cylindrical surface allows for a secure fit on the shaft / housing by means of an interference fit with one of the machine elements. This force-fit connection of the retaining ring is achieved by pressing the retaining ring onto the shaft, with the retaining ring being supported on the shaft via its internal cylindrical surface. Description of the drawings

[0023] The invention is explained in more detail below using exemplary embodiments.

[0024] Fig. Figure 4 schematically shows an electric motor drive unit 1. The drive unit 1 comprises an electric motor 42, a gearbox 43, and a differential 44 within a housing 9. The motor 42 is operatively connected to the gearbox 43 via a rotor shaft 4. A further operative connection 46 exists between the gearbox 43 and the differential 44. Output shafts 6 and 45 are connected to the differential 44. The output shaft 6 passes concentrically through the rotor shaft 4, which is designed as a hollow shaft.

[0025] Fig. Figure 1 shows a detail of the electromechanical drive unit 1 in a longitudinal section. A component 15, designed as a sun gear / gear 2, of a planetary gear 5 comprising planet gears 3 of the in Fig. The gearbox 43 shown in 1 sits on a rotor shaft 4 which is otherwise in Fig. 1. Electrical machine 42 (not shown further). The rotor shaft 4 is one of the machine elements 10, between which and another machine element 20 an annular gap 7 is formed. The first machine element 10 is hollow cylindrical, and an output shaft 6, designated as the second machine element 20, passes concentrically through the rotor shaft 4. The annular gap 7 is formed between the rotor shaft 4 and the output shaft 6. The rotor shaft 4 is rotatably mounted in a housing 9 by means of a rolling bearing 8. The sun gear 2, located on the rotor shaft 4, is torsionally fixed to the rotor shaft 4 and axially secured to the rotor shaft 4 in one of its longitudinal directions by means of a component locking device 17.

[0026] The component locking device 17 comprises a shaft retaining ring 11 and a locking element 16. The shaft retaining ring 11 sits in a circumferential groove 12 of the rotor shaft 4. The locking element 16 is a retaining ring 13. The retaining ring 13 is optionally made of plastic or steel, or formed from another metal, and sits with a seat 18 in a bore 14 of the component 15. The shaft retaining ring 11 is circumferentially surrounded by the retaining ring 13, radially engaged by the retaining ring 13 on the outside, and thus potentially radially supported by the retaining ring 13. The retaining ring 13, in turn, is radially supported on the outside in the bore 14. A radial distance A of the locking element 16 in the radial direction to the shaft retaining ring 11 is less than the radial depth T of the circumferential groove in the same radial direction.

[0027] A functional unit sealing the annular gap 7 is formed by the retaining ring 13 with the locking element 16 and by a seal 19, which seals the annular gap 7 between the rotor shaft 4 and the output shaft 6. The functional unit between the locking element 16 and the seal 19 is thus formed by the fact that the locking element 16 and at least one rubber-elastic sealing lip 21 of the seal 19 are connected to each other, the retaining ring 13 having a seal carrier 28 for the sealing lip 21. Furthermore, the retaining ring 13 has the external cylindrical seat 18 for an interference fit in the gear 2.

[0028] The Fig. 2 and Fig. 3 each show an alternative to the execution variant according to Fig. Figure 1 shows a detail of an embodiment of a drive unit according to the invention, comprising at least two concentrically arranged machine elements 10 and 20, each with at least one component 15, at least one axial component retaining ring 24 or 25, and at least one seal 22 or 23 operatively connected to the component retaining ring 24 or 25. Each of the component retaining rings 24 or 25 has at least one shaft retaining ring 26 slotted at least once in its circumferential direction and a retaining element 16 of a retaining ring 30. In addition to the retaining element 16, the retaining ring 30 is also provided with a seat 39 for an interference fit in the component 15. The respective component 15, which is designed as a gear 32, sits on the machine element 10 of the machine elements 10, 20, which is designed as a rotor shaft 4 and is rotatable about a rotation axis 27, and is axially secured on the rotatable machine element 10 by the shaft retaining ring 26.By means of the seal 22 or 23, an annular gap 7 in the respective drive unit is sealed.

[0029] The in Fig. The seal 22 shown in Figure 2 has a seal carrier 28, a sealing lip 33, and a sealing surface 29. The component retainer 24 and the seal 22 form a functional unit that seals the annular gap 7, such that the retaining ring 30 is the seal carrier 28 for the sealing lip 33, a carrier for a retaining element 16 in the form of the hollow cylindrical section 34, and the seat 39 of the component retainer 24 on the rotor shaft. The sealing lip 33 bridges the annular gap 7 and seals against the sealing surface 29.

[0030] The retaining ring 30 is supported on the machine element 10 by the material of the seal 22 and is preferably made of a plastic. The shaft retaining ring 26 is surrounded radially outside the hollow cylindrical section 34 when viewed from the axis of rotation 27. The hollow cylindrical section 34 is formed as a retaining element 16 by the elastic material of the sealing lip 33. Since the retaining element 16 is made of plastic / elastomer, it can / must be reinforced circumferentially on its outer surface with a wire ring 35. The radial distance A of the retaining element 16 in the radial direction to the shaft retaining ring 26 is zero and therefore less than the radial depth T of the circumferential groove 12 in the same radial direction.

[0031] The in Fig. The seal 23 shown in Figure 3 has a seal carrier 36, a sealing lip 33, and a sealing surface 29. The component retention 25 is formed by the retaining element 16, the shaft retaining ring 26, and the seat 39. The component retention 25 and the seal 23 form a functional unit sealing the annular gap 7, such that the retaining ring 31 has a retaining element 16 in the form of an extension 37 made of the elastic material of the sealing lip 33 and the elastic sealing lip 33. Viewed from the axis of rotation 27, the shaft retaining ring 26 is engaged and surrounded radially outside by the hollow cylindrical section of the extension 37 of the retaining ring 30. The extension 37 is reinforced circumferentially with a wire ring 35. A radial distance A of the retaining element 16 in the radial direction to the shaft retaining ring 26 is less than the radial depth T of the circumferential groove in the same radial direction.

[0032] The seal carrier 36 is a sheet metal ring that secures the retaining ring 31 and the sealing lip 33 to the shaft via the seat 39 and simultaneously provides reinforcement for the seal 23. The sealing lip 33 rests against the sealing surface 29 to create a seal.

[0033] Fig.Figure 3a shows a section of a seal 40, which consists of a seal carrier 36, a sealing lip 33, and the sealing surface 29. The seal carrier 36 is a sheet metal cup 38 and is press-fitted 39 onto the machine element 10, which is designed as a rotor shaft 4. A peripheral extension 41 of the sheet metal cup 38 forms a hollow cylindrical section 34, which constitutes the locking element 16 and circumferentially encompasses the shaft retaining ring 26. A radial distance A of the locking element 16 in the radial direction to the shaft retaining ring 26 is less than the radial depth T of the circumferential groove in the same radial direction. The component locking element 25 and the seal 40 form a functional unit such that the sheet metal cup 38 provides not only the locking element 16 but also the seal carrier 36 for the sealing lip 33. The sealing lip 33 bridges the annular gap 7 and elastically seals against the sealing surface 29 of the output shaft 6.The sheet metal cup 38 is therefore simultaneously reinforcement of the seal 40, component securing 25 and seat 39 on the rotor shaft 4. Reference sign 1 drive unit 2 sun wheel 3 planetary gear 4 Rotor shaft 5 planetary gears 6 Output shaft 7 annular gap 8 rolling bearings 9 cases 10 Machine element 11 Shaft retaining ring 12 circumferential groove 13. Retaining ring 14 bore 15 components 16 safety element 17 Component protection 18 seats 19 Seal 20 Machine element 21 Sealing lip 22 Seal 23 Seal 24 Component protection 25 Component securing 26 Shaft retaining ring 27 Rotation axis 28 sealing carriers 29 Sealing surface 30 retaining ring 31 retaining ring 32 gear 33 Sealing lip 34 hollow cylindrical section 35 wire ring 36 sealing carriers 37 Extension 38 tin bowls 39 seats 40 Seal 41 Extension 42 electric machine 43 gearboxes 44 Differential 45 Output shaft 46 Functional connection

Claims

An electric motor drive unit (1) comprising an electric machine (42), a gearbox (5, 43), and at least two machine elements (10, 20), as well as a component locking device (17, 24, 25) and a rotor shaft (4) of the electric machine (42), wherein the rotor shaft (4) is a first machine element (10) of the machine elements (10, 20), wherein the component locking device (17, 24, 25) is formed at least from a shaft retaining ring (11, 26) and from a locking element (16) for securing the shaft retaining ring (11, 26) on the rotor shaft (4), and wherein a second machine element (20) of the machine elements (10, 20) is an output shaft (6) of the gearbox (5, 43), wherein at least one first component (15) seated on the rotor shaft (4) is secured by means of the component locking device (17, 24,25) is secured axially to the rotor shaft (4) at least in an axial direction and wherein an annular gap (7) between the rotor shaft (4) and the output shaft (6) is sealed by means of at least one seal (19, 22, 23, 40) and wherein the component locking device (17, 24, 25) and the seal (19, 22, 23, 40) are operatively connected to each other to form a functional unit that seals the annular gap (7) and secures the shaft retaining ring (11, 26) against expansion due to centrifugal force. Electromotive drive unit (1) according to claim 1, in which the component locking device (17, 24, 25) has a sealing carrier (28, 36) for at least one sealing lip (21, 33) of the seal (19, 22, 23, 40). Electromotive drive unit (1) according to claim 1 or 2, in which the locking element (16) is located on the rotor shaft (4) and circumferentially surrounds the shaft retaining ring (11, 26) located in a circumferential groove of the rotor shaft (4), wherein a radial distance (A) of the locking element (16) in the radial direction to the shaft retaining ring (11, 26) is smaller than the radial depth (T) of the circumferential groove in the same radial direction. Electromotive drive unit (1) according to claim 1, 2 or 3, in which the component (15) is a gear (2, 32) mounted on the rotor shaft (4), wherein the gear (2, 32) is secured to the rotor shaft (4) by means of the shaft retaining ring (26). Electromotive drive unit (1) according to claim 4, in which the gear (2, 32) is a component (15) of the transmission (43). Electromotive drive unit (1) according to claim 1, in which the machine elements (10, 20) are arranged concentrically to each other, wherein the locking element (16) and the seal (19, 22, 23, 40) are connected to each other in such a way that a radial annular gap (7) formed between the machine elements (10, 20) is sealed by means of the seal (19, 22, 23). Electromotive drive unit (1) according to claim 1 or 6, characterized in that the locking element (16) is made of sheet metal, wherein the shaft retaining ring (26) is surrounded by a hollow cylindrical section (34) of the locking element (16) and wherein a sealing lip (33) of the seal (40) formed from a plastic is connected to the locking element (16). Device according to claim 1 or 7, characterized in that the locking element (16) and at least one sealing lip (21, 33) of the seal (19, 22) are connected to each other, wherein the functional unit is formed by the component locking (24, 25) having a sealing carrier (28, 36), wherein the locking element (16), the sealing carrier (28, 36) and the sealing lip (21, 33) are connected to each other, wherein the sealing lip (21, 33) is in contact with a sealing surface (29) of the second machine element (20).

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