Drive device with an electric motor and a gearbox

Abstract

Drive device (1) with an electric motor (2) and a gearbox (3), wherein an output shaft (4) of the electric motor (2) is connected in a rotationally fixed manner to an input shaft (5) of the gearbox (3) via a toothing (6), and the output shaft (4) is mounted in a housing (11, 12) via a fixed bearing (14) and a loose bearing (13), and the input shaft (5) is mounted in the housing (11, 12) in the region of an end facing away from the output shaft (4), and is mounted in the output shaft (4) in the region of the end facing the output shaft (4), wherein the input shaft (5) is designed as a hollow shaft on the output shaft side and is mounted in a shaft journal (17) of the output shaft (4), and wherein the drive device (1) has a bearing area adjacent to the toothing (6) for mounting the input shaft (5) in the shaft journal (17), characterized in that the bearing area for Bearing the input shaft (5) in the shaft journal (17) has a plain bearing (28).

Description

[0001] The invention relates to a drive device with an electric motor and a transmission according to the preamble of claim 1.

[0002] US 2015 / 0 038 277 A1 discloses a drive device according to the preamble of claim 1.

[0003] US 6 952 061 B2 discloses a drive device. In this device, the output shaft, which is a rotor shaft, is designed as a hollow shaft starting from the input shaft over a large part of its length. The input shaft is inserted into the rotor shaft in the area of its end facing the rotor shaft and is connected in a rotationally fixed manner via a spline between the input shaft and the rotor shaft. In the area of the overlapping spline connection, the rotor shaft is mounted in the housing via a fixed bearing, which is designed as a rolling bearing. The gear teeth of the input shaft are located in the area of the input shaft bearing in the housing. The housing has several housing parts and, moreover, the design of the rotor shaft and input shaft means that the drive device is relatively complex.Apart from this, the support of the gearing forces is not optimal due to the bearing of the rotor shaft in the area of its end facing the input shaft in the housing, the plug connection between the input shaft and the rotor shaft in the area of this bearing and, moreover, the relatively large distance between the plug connection and the gear teeth of the input shaft.

[0004] Similar drive devices are described in JP 2015 - 216 819 A and JP 2015 - 216 820 A.

[0005] DE 26 16 310 A1 discloses a drive device with an electric motor and a transmission. A transmission output shaft is supported by an axial bearing and a radial bearing, and a rotor shaft of the electric motor is supported by a journal in the transmission output shaft.

[0006] A drive train for a vehicle is known from DE 10 2011 010 204 A1. A drive shaft driven by an internal combustion engine is mounted in a fixed bearing and a floating bearing. An electric motor is arranged in an area of the drive shaft that is centrally located between its bearings. A rotor hub of the electric motor is arranged concentrically to the drive shaft and mounted radially outwardly in a housing via a fixed bearing. At a distance from this fixed bearing, the rotor hub has internal gearing, which together with gearing on the shaft side of the drive shaft forms a spline. The spline forms a rotationally fixed connection between the electric motor and the drive shaft and serves both as a second bearing point for the rotor hub and for power transmission between the electric motor and the drive shaft.

[0007] WO 2017 / 145 653 A1, DE 10 2012 008 652 A1, DE 19 72 103 U, DE 10 2012 205 318 B3, DE 10 2009 027 198 A1, EP 3 421 842 A1, DE 10 2014 218 453 A1, DE 10 2017 123 586 A1, DE 10 2017 123 620 A1, DE 10 2017 131 232 B3 and DE 10 2015 223 669 B4 disclose further prior art.

[0008] The object of the invention is to further develop a drive device of the type mentioned at the outset in such a way that a favorable support of the gearing forces is ensured with a structurally particularly simple mounting of the output shaft of the electric motor and the input shaft of the transmission.

[0009] The object is achieved by a drive device which is designed according to the features of patent claim 1.

[0010] In this drive device, the input shaft is designed as a hollow shaft on the output shaft side and is mounted in a shaft journal of the output shaft.

[0011] Since the shaft journal supports the input shaft, and the output shaft is also supported in the housing via both the fixed bearing and the floating bearing, the gearing, relative to the axial extent of the output shaft and input shaft, is located at an axial distance from the bearing plane of the output shaft bearing facing the gearbox. This provides favorable support for the gearing forces, also because the gearing of the input shaft and output shaft is, or can be, arranged closer to the gearing of the input shaft.

[0012] This basic design of the drive device makes it possible to optimize the drive device from a wide variety of perspectives, be it from the perspective of optimized bearings of the output shaft and / or input shaft in the housing, bearings of the output shaft and input shaft in each other and / or assembly sequence of the drive device and / or optimized cooling of components of the drive device.

[0013] According to a particularly preferred development of the invention, it is provided that the output shaft of the electric motor is a rotor shaft of the electric motor.

[0014] Preferably, the fixed bearing of the output shaft is arranged on the output side of the output shaft. The fixed bearing of the output shaft is thus located in the area of the output shaft that is assigned to the input shaft of the transmission. Accordingly, the floating bearing of the output shaft is located in the area facing away from the input shaft. It is advantageous if the output shaft is axially preloaded, e.g., by means of a tensioning element designed as a wave spring, particularly on the bearing of the output shaft that faces away from the transmission.

[0015] It is considered particularly advantageous if the output shaft is mounted in the housing via its shaft journal. This provides a favorable location for the transmission of the output shaft's reaction forces into the housing and also allows for particularly simple positioning and mounting of the output shaft due to the diameter changes caused by the shaft journal.

[0016] According to a preferred development, the fixed bearing is designed as a rolling bearing with an inner ring on the output shaft side, an outer ring on the housing side, and rolling elements arranged between them. From this aspect, it is considered advantageous if the inner ring of the rolling bearing rests against a shaft extension of the output shaft on its side facing away from the input shaft, and this inner ring is axially secured on its side facing away from the shaft extension by means of a retaining ring, in particular a snap ring. The retaining ring is preferably inserted into an outer annular groove of the output shaft. In this way, the fixed bearing of the output shaft can be axially secured with respect to the output shaft in a particularly simple construction.

[0017] According to a preferred development, the input shaft radially engages the retaining ring in an outer region of the retaining ring. This ensures that the retaining ring or snap ring is secured against centrifugal force by the input shaft of the transmission.

[0018] It is also considered preferable if the input shaft has an axial contact surface that rests against the inner ring of the rolling bearing. This provides a particularly simple structural means for axial support of the input shaft on the inner ring of the rolling bearing.

[0019] A structurally simple bearing and assembly of the input shaft results if the input shaft is mounted axially and radially in the housing in the area of its end facing away from the output shaft. This bearing is preferably designed such that the input shaft is mounted in the housing in the area of its end facing away from the output shaft via at least one rolling bearing. Two rolling bearings are preferably used there. In particular, the input shaft is mounted radially in the housing in this area via a cylindrical roller bearing and axially via a needle bearing. The proposed bearing with cylindrical roller bearing and needle bearing enables uncomplicated adjustment of the input shaft of the gearbox in its axial direction. In particular, axially acting adjusting shims are arranged between the needle bearing and the housing of the drive device.In principle, any means between the housing and the end of the input shaft facing away from the output shaft are suitable for adjusting the axial preload of the input shaft within the drive device.

[0020] It is considered particularly advantageous if the shaft journal has a cylindrical or spherical outer geometry in the area of its output shaft side bearing for centering the input shaft. It is also considered particularly advantageous if the shaft journal has a shaft area with the gearing designed as a spline for centering the input shaft under load. In particular, the shaft journal is provided with two functional areas: in the functional area of the centering journal with a cylindrical or spherical outer geometry for centering the input shaft, in this case in the load-free state or under low loads, and furthermore the shaft area with spline, e.g. according to DIN 5480, flank-centered. This optimises centering under load, torque is transmitted by means of positive locking.

[0021] In particular, the input shaft has a gear toothing in an area of the input shaft adjacent to the bearing of the input shaft in the housing.

[0022] Due to the favorable distances (leverage ratios) between the gear teeth / running teeth and the rolling bearings and between the gear teeth / running teeth and the shaft / shaft bearings, the additional radial play of the shaft / shaft bearings has only a minimal effect on the position of the gear teeth / running teeth. Gear forces are partially absorbed by the electric motor's output shaft bearings. This avoids undefined load conditions or the undershooting of the minimum bearing loads of the output shaft bearings due to the application of gear forces.

[0023] According to the invention, the drive device has a bearing area adjacent to the gearing for supporting the input shaft in the shaft journal. The gearing and the bearing area are arranged adjacently.

[0024] The bearing area for supporting the input shaft in the shaft journal can be arranged on the side of the gearing facing the input shaft bearing in the housing or on the side facing away from it. The advantage of arranging the bearing area for supporting the input shaft in the shaft journal on the side of the gearing facing the input shaft bearing in the housing is that a gearing with a larger diameter, and thus a higher torque capacity, can be realized with the same overall length. Furthermore, load centering of the gearing is observed under load, with force support (radial support) via the gearing and force introduction near the bearing. This results in a reduced influence on the output shaft.

[0025] According to the invention, the bearing area for supporting the input shaft in the shaft journal comprises a plain bearing, in particular a plain bearing bush. This plain bearing is provided between the output shaft and the input shaft to prevent fretting corrosion in the area of the shaft journal. This allows for sliding movements in the circumferential direction due to a clearance in the gearing and / or sliding movements in the axial direction, e.g., due to bearing clearances and alternating loads, thermal expansion, etc.

[0026] According to a preferred development of the invention, the input shaft has an axial passage. This extends, in particular, over the entire length of the input shaft. The passage makes it possible, in particular, to supply and / or drain oil for the purpose of lubrication and / or cooling of relevant components of the drive device. In particular, an oil lance is arranged within the passage of the input shaft, with outlets for the axial and / or radial supply of oil to the output shaft and / or to the rotor and / or to bearings and / or to the gearbox for the purpose of lubrication and / or cooling. According to another development, the output shaft has, at least over a partial axial length, a passage for supplying oil by means of the oil lance into this passage for the purpose of further conveying it for the lubrication and / or cooling of components of the electric motor, in particular for rotor cooling.

[0027] Preferably, the input shaft is arranged in a different housing section than the output shaft. This division of the housing into at least two housing sections makes it possible to achieve an advantageous assembly sequence for the drive device. The electric motor is thus completely assembled, allowing commissioning and acceptance of the electric motor without the gearbox. The gearbox is then installed, thus assembling the gearbox and electric motor.

[0028] Further features of the invention will become apparent from the dependent claims, the accompanying drawings, and the description of the exemplary embodiments shown in the drawings. It shows: Fig. 1 a drive device according to the prior art known from practice, illustrated in a longitudinal center section for the area of the electric motor and the area relevant to the invention of the bearing of an input shaft of the transmission in an output shaft / rotor shaft of the electric motor and in the housing, Fig. 2 a first embodiment of the drive device according to the invention, illustrated in a longitudinal center section for the area of the connection of the input shaft of the gearbox to the rotor shaft of the electric motor as well as the bearing of the rotor shaft and input shaft in this area, Fig. 3 in a longitudinal center section a compared to the embodiment according to Fig. 2 modified drive device, Fig. 4 a compared to the embodiment according to Fig. 2 modified drive device with additional oil guide for internal rotor cooling, bearing lubrication, etc.

[0029] The state of the art according to the Fig. 1 shows a drive device 1 with an electric motor 2 and a gearbox 3. An output shaft 4 of the electric motor 2, which is a rotor shaft, is connected in a rotationally fixed manner to an input shaft 5 of the gearbox 3 via a toothing 6.

[0030] Reference numeral 7 designates a rotor of the electric motor 2, which rotates during operation of the electric motor 2 according to the speed of the rotor shaft 4. The input shaft 5 of the gearbox 3 is formed integrally with a pinion 8, which meshes with a gear wheel 9. The axis of rotation of the rotor shaft 4 and input shaft 5 is designated by reference numeral 10. A housing of the drive device 1 is formed in several parts and divided into planes perpendicular to the axis of rotation 10. More specifically, a housing part 11 of the electric motor 2 and a housing part 12 of the gearbox 3 are designated. A loose bearing 13 and a fixed bearing 14 for the rotor shaft 4 are mounted in the housing part 11, these being roller bearings. Furthermore, a fixed bearing 15 for the input shaft 5 of the gearbox 3 is mounted in the housing part 11, and a loose bearing for the input shaft 5 is mounted in the housing part 12.The torque interface between the rotor shaft 4 and the input shaft 5 is the toothing 6, which is designed as a spline.

[0031] The input shaft 5 is designed as a hollow shaft on the rotor shaft side and a shaft journal 17 of the rotor shaft 4 has the toothing 6.

[0032] In the embodiment of the present invention as shown in Fig. 2, the input shaft 5 of the gearbox 3 is mounted in the housing exclusively in the region of that end of the input shaft 5 which faces away from the rotor shaft 4. The end of the input shaft facing the rotor shaft 4, however, is mounted in the shaft journal 17 of the rotor shaft 4. The shaft journal 17 is inserted into the input shaft 5, which is designed as a hollow shaft at least in the region of this end. The fixed bearing 14 of the rotor shaft 4 is arranged on the output side of the rotor shaft 4. The fixed bearing 14, which is designed as a rolling bearing, has an inner ring 18 on the rotor shaft side, an outer ring 19 on the housing side and rolling elements 20 arranged between them. The inner ring 18 rests on its side facing the motor 7 against a shaft extension 21 of the rotor shaft 4 and this inner ring 18 is axially fixed on its side facing away from the shaft extension 21 by means of a retaining ring 22 which is designed as a snap ring.The retaining ring 22 is inserted into an outer annular groove 23 of the rotor shaft 4. The input shaft 5 has an axial contact surface 24 that rests against the inner ring 18.

[0033] The input shaft 5 is mounted axially and radially in the housing, specifically in the housing part 12, in the area of its end facing away from the rotor shaft 4. The bearings are provided radially in the housing via a cylindrical roller bearing 25 and axially in the housing via a needle bearing 26. Adjusting discs 27 between the housing part 12 and the end of the input shaft 5 facing away from the rotor shaft 4 are provided for adjusting the axial preload of the input shaft 5 within the drive device 1.

[0034] The shaft journal 17 has a cylindrical or spherical outer geometry in the area of its rotor shaft-side bearing for input shaft centering. Furthermore, the shaft journal 17 has a shaft area with the spline 6 designed as a spline for input shaft centering under load.

[0035] The bearing area for supporting the input shaft 5 in the shaft journal 17 is arranged adjacent to the toothing 6. This bearing area has a plain bearing 28, in particular a plain bearing bush. In the embodiment according to the Fig. 2, the toothing 6 is arranged adjacent to the rotor 7 and the plain bearing 28 is arranged adjacent to the toothing 6, but on its side facing away from the rotor 7.

[0036] The rotor shaft 4 is axially preloaded in the direction of the input shaft 5, in particular by means of a tensioning element which is designed, for example, as a wave spring and is arranged on the bearing of the rotor shaft 4 which faces away from the gearbox 3.

[0037] Since the input shaft 5 is arranged in a different housing part 12 than the rotor shaft 4, which is arranged in the housing part 11, an advantageous assembly sequence of the drive device is possible. First, the electric motor 3 is mounted and put into operation, which is possible without the gearbox 3 attached. The drive device 1 is then completed with the gearbox 3.

[0038] Due to the arrangement of the gearing 6 on the larger diameter of the shaft journal 17, a high torque capacity is possible with the same overall length. Under load, the spline is centered, thus optimizing force support (radially) via the spline. Force is introduced close to the bearing, thus reducing the influence on the rotor shaft 4.

[0039] The embodiment of the invention as shown in Fig. 3 differs from that according to the Fig. 2 only because the arrangement of toothing 6 and plain bearing 28 is reversed, thus in the embodiment according to Fig. 3 the plain bearing 8 is adjacent to the retaining ring 22, while the toothing 6 is arranged on the side of the plain bearing 28 facing away from the rotor 7, adjacent to the plain bearing 28. In the Fig. 4 is concerning the invention and the embodiment according to the Fig.2 shows a modification of the drive device 1 in that an oil guide is additionally provided for internal rotor cooling, bearing lubrication, etc. The input shaft 5 has an axial passage 29, which thus extends over the entire length of the input shaft 5. Arranged within the passage 29 is an oil lance 30 designed as a tube, with outlets 31 for the axial and radial supply of oil to the rotor shaft 4 and from there to the rotor 7 and to bearings, in particular the bearings 25 and 26, for the purpose of lubrication and / or cooling. A volume flow thus flows for bearing lubrication or cooling, further for the lubrication of the centering seat and spline, and also for rotor cooling. The oil is supplied to the oil lance 30 via a bore 32 in the housing part 12.

Claims

[1] Drive device (1) with an electric motor (2) and a transmission (3), wherein an output shaft (4) of the electric motor (2) is connected in a rotationally fixed manner to an input shaft (5) of the transmission (3) via a toothing (6), and the output shaft (4) is mounted in a housing (11, 12) via a fixed bearing (14) and a loose bearing (13), and the input shaft (5) is mounted in the housing (11, 12) in the region of an end facing away from the output shaft (4), and is mounted in the output shaft (4) in the region of the end facing the output shaft (4), wherein the input shaft (5) is designed as a hollow shaft on the output shaft side and is mounted in a shaft journal (17) of the output shaft (4), and wherein the drive device (1) has a bearing region adjacent to the toothing (6) for mounting the input shaft (5) in the shaft journal (17), characterized by that the bearing area for supporting the input shaft (5) in the shaft journal (17) has a plain bearing (28). [2] Drive device according to claim 1, characterized by that the output shaft (4) of the electric motor (2) is a rotor shaft (4) of the electric motor (2). [3] Drive device according to claim 1 or 2, characterized by that the fixed bearing (14) of the output shaft (4) is arranged on the output side of the output shaft (4). [4] Drive device according to claim 3, characterized by that the output shaft (4) is mounted in the housing (11, 12) via its shaft journal (17). [5] Drive device according to claim 4, characterized by that the fixed bearing (14) is designed as a rolling bearing with an inner ring (18) on the output shaft side, an outer ring (19) on the housing side and rolling elements (20) arranged between them. [6] Drive device according to claim 5, characterized bythat the inner ring (18) of the rolling bearing rests on its side facing away from the input shaft (5) against a shaft extension (21) of the output shaft (4) and its inner ring (18) is axially fixed on its side facing away from the shaft extension (21) by means of a retaining ring (22), in particular a snap ring, wherein the retaining ring (22) is inserted into an outer annular groove (23) of the output shaft (4). [7] Drive device according to claim 6, characterized by that the input shaft (5) radially engages around the retaining ring (22) in an outer region of the retaining ring (22). [8] Drive device according to one of claims 5 to 7, characterized by that the input shaft (5) has an axial contact surface (24) which bears against the inner ring (18) of the rolling bearing. [9] Drive device according to one of claims 1 to 8, characterized bythat the input shaft (5) is mounted axially and radially in the housing (11, 12) in the region of its end facing away from the output shaft (4). [10] Drive device according to claim 9, characterized by that the input shaft (5) is mounted in the housing (11, 12) in the region of its end facing away from the output shaft (4) via at least one rolling bearing (25, 26). [11] Drive device according to claim 10, characterized by that the input shaft (5) is mounted radially in the housing (11, 12) in the region of its end facing away from the output shaft (4) via a cylindrical roller bearing (25) and axially via a needle bearing (26). [12] Drive device according to one of claims 9 to 11, characterized by Means (27) between the housing (11, 12) and the end of the input shaft (5) facing away from the output shaft (4), for adjusting an axial preload of the input shaft (5) within the drive device (1). [13] Drive device according to one of claims 1 to 12, characterized by that the shaft journal (17) has a cylindrical or spherical outer geometry for input shaft centering in the region of its output shaft-side bearing. [14] Drive device according to one of claims 1 to 13, characterized by that the shaft journal (17) has a shaft area with the toothing (6) designed as a spline, for input shaft centering under load. [15] Drive device according to one of claims 1 to 14, characterized by that the bearing area for supporting the input shaft (5) in the shaft journal (17) is arranged on the side of the toothing (6) facing or facing away from the bearing of the input shaft (5) in the housing (11, 12). [16] Drive device according to one of claims 1 to 15, characterized by that the plain bearing (28) of the bearing area for supporting the input shaft (5) in the shaft journal (17) is a plain bearing bush. [17] Drive device according to one of claims 1 to 16, characterized by that the input shaft (5) has a gear toothing (8) in a region of the input shaft (5) adjacent to the bearing of the input shaft (5) in the housing (11, 12). [18] Drive device according to one of claims 1 to 17, characterized by that the input shaft (5) has an axial passage (29). [19] Drive device according to claim 18, characterized by that an oil lance (30) is arranged within the passage (29), with outlets for the axial and / or radial supply of oil to the output shaft (4) and / or to the rotor (7) and / or to bearings (25, 26, 28) and / or to the gearbox (3) for the purpose of lubrication and / or cooling. [20] Drive device according to claim 19, characterized bythat the output shaft (4) has, at least over a partial axial length, a passage for supplying oil by means of the oil lance (30) into this passage for the purpose of further conveyance for lubricating and / or cooling components of the electric motor (2), in particular for rotor cooling. [21] Drive device according to one of claims 1 to 20, characterized by that the output shaft (4) is axially preloaded, in particular by means of a clamping element on the bearing (13) of the output shaft (4), which is remote from the gearbox (3). [22] Drive device according to one of claims 1 to 21, characterized by that the input shaft (5) is mounted in a different housing part (12) than the output shaft (4).

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