DE102020211635A1 - Method for assembling a rotor of an electric machine on a transmission and an electric drive unit for a vehicle - Google Patents

Abstract

The invention relates to a method for mounting a rotor (12) of an electric machine on a transmission (11) of an electric drive unit (10) and an electric drive unit (10) for a vehicle, the rotor (12) having a rotor shaft (14). has a receiving section (16) for receiving an input pinion (18), comprising the steps of:- providing at least one sealing element (20) and at least one roller bearing (22);- passing the rotor shaft (14) through the sealing element (20) and through the roller bearing (22), so that the receiving section (16) protrudes into the gear (11);- mounting the input pinion (18) on the receiving section (16) of the rotor shaft (14) and- joining the input pinion (18) to the rotor shaft (14 ) by means of a welding process.

Description

State of the art

The invention relates to a method for mounting a rotor of an electric machine on a transmission of an electric drive unit for a vehicle with features of claim 1 and an electric drive unit with features of the independent claim.

Electric drive units usually include an electric machine and a transmission with one or more gear stages. The electric machine has a rotor with a rotor shaft, which engages in the transmission and represents the input shaft for the transmission. An input pinion is arranged on the end of the rotor shaft that engages in the gearbox, which pinion meshes with a gearwheel of a gear stage and thus transmits a torque from the rotor shaft to the gearbox. The rotor shaft is mounted using roller bearings and sealed off from the gearbox (housing) using sealing elements. To assemble the rotor shaft, it is pushed through the roller bearing and the sealing elements so that the end of the rotor shaft with the input pinion protrudes into the gearbox.

In order to transmit the currently required torques (especially in drive units of low power classes), rather small rotor shaft diameters are required. However, these cannot be dimensioned arbitrarily small, since the rotor shaft diameter must always be larger than the outer diameter of the input pinion. This is due to the fact that the rotor shaft usually has to be guided or joined through at least one sealing element and at least one roller bearing during the assembly or joining process. The outer diameter of the input pinion must be designed to be significantly smaller than the outer diameter of the rotor shaft, otherwise joining is not possible or the sealing elements or bearing seats may be damaged.

A rotor shaft designed in this way is, for example, in DE 10 2015 203 068 A1 shown.

In the case of rotor shafts that are made up of several parts, the input pinion is joined as a separate element to the rotor shaft by means of a welding process. Joining the input pinion to the rotor shaft by means of a welding process after the rotor shaft has been installed in the transmission is problematic because, for example, during capacitor discharge welding, the current flow could go through the bearings and damage could occur there. In addition, the heat generated during a welding process could damage the bearings and/or the sealing elements, which are usually made of rubber and/or plastic.

Disclosure of Invention

The problem underlying the invention is solved by a method for mounting a rotor of an electric machine on a transmission of an electric drive unit for a vehicle with the features of claim 1 and an electric drive unit with the features of the independent claim. Advantageous developments of the invention are specified in the dependent claims.

• Bereitstellen mindestens eines, insbesondere radialen, Dichtelements (z. B. Radialwellendichtring). Es sind auch mehrere zueinander entlang der Rotorwelle beabstandet angeordnete Dichtelemente denkbar. Bereitstellen mindestens eines Wälzlagers. Auch hier sind mehrere zueinander entlang der Rotorwelle beabstandet angeordnete Wälzlager denkbar.

According to the invention, a method for mounting a rotor of an electric machine on a transmission of an electric drive unit for a vehicle is proposed. The electric drive unit can, for example, be an electric drive axle (“E-axle”). The rotor has a rotor shaft with a receiving section. The receiving section serves to receive an input pinion. The rotor shaft and the input pinion are present as separate elements before assembly. The procedure includes the following steps:

• Providing at least one, in particular radial, sealing element (e.g. radial shaft sealing ring). Several sealing elements arranged spaced apart from one another along the rotor shaft are also conceivable. Providing at least one roller bearing. Here, too, a plurality of roller bearings arranged spaced apart from one another along the rotor shaft are conceivable.

The electric drive unit has a housing in which the electric machine (electric motor) and the transmission are arranged (possibly in different housing sections). The sealing element or the roller bearing can be provided, for example, by installing the sealing element and/or roller bearing in a passage of a housing wall. The housing wall, which has a passage in which the sealing element and the roller bearing can be arranged, can separate the two housing sections (electric motor and transmission) from one another. The housing wall is part of the housing of the drive unit.

Passing the rotor shaft through the sealing element and through the roller bearing. If there are several roller bearings and/or sealing elements, the rotor shaft is guided through the corresponding number of roller bearings and/or sealing elements. The roller bearings and sealing elements can be arranged alternately along the rotor shaft (e.g. sealing element-roller bearing-sealing element). The rotor shaft is so through the sealing element and through the roller bearing carried out that the receiving portion protrudes into the gear.

Installing the input pinion on the receiving portion of the rotor shaft.

Joining the input pinion to the rotor shaft by means of a welding process. This can be implemented in particular by means of a resistance welding process, in particular by means of capacitor discharge welding.

The method steps presented above can be carried out one after the other, as presented above.

This method makes it possible to dimension the input pinion in such a way that the input pinion has a significantly larger outer diameter than the outer diameter of the rotor shaft.

This allows an independent design of the minimum required outer diameter of the rotor shaft and an optimal design of the input pinion compared to a gear stage. In other words, a minimally dimensioned rotor shaft (motor shaft of the electric motor) can be used. Irrespective of this, the size of the input pinion can be optimally designed.

Due to the minimal design of the rotor shaft and optimal design of the input pinion, the required masses of the two components can be reduced.

According to a development, the welding process can be carried out by means of resistance welding, in particular by means of capacitor discharge welding. A first welding electrode makes contact with the input pinion. This means that the current during welding essentially flows through the input pinion.

According to one development, the first welding electrode can contact the input pinion on a side facing away from the rotor shaft and/or the electric machine (“from the transmission side”), in particular in a ring-shaped manner. For this purpose, the first welding electrode can be ring-shaped. It is also conceivable to design the first welding electrode or the contacting of the first welding electrode in a different shape, for example oval or (rectangular.

According to a further development, the diameter of the ring-shaped contact of the first welding electrode can be larger than the outer diameter of the rotor shaft at its transmission-side end. In particular, the diameter of the welding electrode is smaller than the outer diameter of the input pinion.

According to a further development, the rotor shaft can have an end face at its transmission-side end, with a second welding electrode making contact with the end face. The second welding electrode can make point contact with the end face (e.g. in the middle). It is also conceivable that the second welding electrode can be designed in a ring-shaped, oval or (rectangular) corner analogous to the first welding electrode.

According to a development, the receiving section can be at least partially hollow. In this case, a second welding electrode can contact the rotor shaft within the hollow receiving section. Here, too, it is conceivable for the contacting of the second welding electrode to be punctiform (e.g. in the middle), ring-shaped on the front side or on the radial surfaces (e.g. inner peripheral surface) of the hollow receiving section.

According to a development, the second welding electrode can contact the rotor shaft in an area between the receiving section and the roller bearing, in particular in an annular manner. It is also conceivable in this development that the receiving section can be hollow.

According to a further development, the rotor shaft can have a radially protruding collar (or collar sections) adjoining the receiving section. The second welding electrode can contact the rotor shaft at the collar or in a region between the collar and the roller bearing, in particular in an annular manner.

In all versions, the contacting of the first and second welding electrodes is chosen in such a way that the current flow that occurs during the welding process between the two welding electrodes does not run through the roller bearing and/or the sealing element, or only to a negligible extent. This enables damage-free resistance welding, in particular capacitor discharge welding, of the rotor shaft to the input pinion when it is mounted on the gearbox.

According to the invention, an electric drive unit for a vehicle (e.g. motor vehicle) is proposed with an electric machine and a transmission. The electrical machine has a rotor shaft and an input pinion. In addition, the assembly is carried out using a method according to the above statements. With regard to the advantages that can be achieved in this way, this is referred to referenced to the assembly process.

The electric drive unit is characterized by the fact that the outer diameter of the input pinion is larger than the outer diameter of the rotor shaft.

The rotor shaft and the input pinion are designed as separate elements that are joined together. Due to the outer diameter of the rotor shaft and the input pinion, the input pinion can only be joined to the rotor shaft after the rotor shaft has been mounted on the gearbox.

The electric drive unit can be designed, for example, as an electric drive axle (“E-axle”). The electric machine drives the transmission. The rotor shaft of the electrical machine thus serves as the input shaft of the transmission.

According to a development, an axial extent of the receiving section can be smaller than an axial extent of the input pinion. In other words, the input pinion can represent the end of the rotor shaft. As a result, a saving in material and thus weight can be effected.

The measures described in connection with the assembly method can serve to further refine the electric drive unit.

• 1 eine schematische Schnittdarstellung einer elektrischen Antriebseinheit;
• 2 eine perspektivische Darstellung des Rotors gemäß 1;
• 3 eine schematische Schnittdarstellung einer Kontaktierung eines Eingangsritzels und einer Rotorwelle bei einem Schweißvorgang;
• 4 eine schematische Schnittdarstellung einer weiteren Kontaktierung eines Eingangsritzels und einer Rotorwelle bei einem Schweißvorgang und
• 5 eine schematische Schnittdarstellung einer weiteren Kontaktierung eines Eingangsritzels und einer Rotorwelle bei einem Schweißvorgang.

Embodiments of the invention will be explained below with reference to the accompanying drawings. Show it:

• 1 a schematic sectional view of an electric drive unit;
• 2 a perspective view of the rotor according to FIG 1 ;
• 3 a schematic sectional view of contacting an input pinion and a rotor shaft during a welding process;
• 4 a schematic sectional view of a further contact of an input pinion and a rotor shaft during a welding process and
• 5 a schematic sectional view of a further contact of an input pinion and a rotor shaft during a welding process.

The drive unit carries in 1 overall reference numeral 10. The drive unit 10 can be designed, for example, as an E-axis or form part of an E-axis.

The drive unit 10 includes a rotor 12 of an electric machine (electric motor) and a gear 11. The rotor 12 includes a rotor shaft 14 which engages in the gear 11 with an end 28 of the rotor shaft 14 on the gear side. The rotor shaft 14 has a receiving section 16 which serves to receive an input pinion 18 . In the present case, the receiving section 16 is arranged on the transmission-side end 28 of the rotor shaft 14 . In the present case, the input pinion 18 is arranged on the receiving section 16 .

The input pinion 18 is non-rotatably joined to the rotor shaft 14 and meshes (in 1 only indicated) with a gear 13 of a gear stage. The gear stage is indicated only schematically by the gear wheel 13 . Thus, the gear 11 is driven by the rotor shaft 14 . The rotor shaft 14 represents the input shaft of the transmission 11.

In the present case, the transmission 11 and the electric machine are separated by a housing wall 15 (separate housing sections). The housing wall 15 can be formed, for example, as part of the transmission housing. The housing wall 15 has a passage 17 . A sealing element 20 and a roller bearing 22 are arranged in the passage 17 .

To mount the rotor 12 on the gear 11 , the rotor shaft 14 is inserted or guided through the sealing element 20 and the roller bearing 22 . The input pinion 18 is then mounted on the receiving section 16 .
The input pinion gear 18 is joined to the rotor shaft 14 by a capacitor discharge welding process, which is discussed in detail below.

The outside diameter of the input pinion 18 is indicated with a double arrow and the reference number 36 . The outside diameter of the rotor shaft 14 is indicated with a double arrow and the reference number 38 . How from the 1 (and the 3 until 5 ) can be clearly seen, the outside diameter 36 of the input pinion 18 is significantly larger than the outside diameter of the rotor shaft 14.

Because the input pinion 18 is only joined to the rotor shaft 14 after the rotor shaft 14 has been mounted on the transmission 11, the outer diameter 36 of the input pinion 18 is not a limited size for the design of the outer diameter 38 of the rotor shaft 14.

In the present case, an axial extension 40 of the receiving section 16 is smaller than an axial extension 42 of the input pinion 18. In other words, the thickness of the input pinion 18 is greater than the length of the receiving section 16. The receiving section 16 therefore does not completely penetrate the input pinion 18.

2 shows a perspective view of the rotor 12 according to 1 . The rotor shaft 14 is shown with the input pinion 18 on the transmission-side end 28 or the receiving section 16 of the rotor shaft 14 . In addition, the sealing element 20 and the roller bearing 22 are shown in the mounted or joined state of the rotor 12 .

3 shows a schematic sectional view of a contact between the input pinion 18 and the rotor shaft 14 during a welding process. In this case, a first welding electrode 24 is in contact with the input pinion 18 . In the present case, the first welding electrode 24 is ring-shaped and contacts the input pinion 18 on a side 26 facing away from the rotor shaft 14.

In the present case, the rotor shaft 14 has an end face 30 on its transmission-side end 28 . A second welding electrode 32 makes contact with the end face 30 in the middle.

The contacting of the two welding electrodes 24,32 in the 3 until 5 is indicated with black triangles.

Both welding electrodes 24, 32 are connected to capacitor plates 25, which serve as a current or voltage source for the welding process. During the welding process arises between the first welding electrode 24 and the second welding electrode 32, a current flow in the 3 until 5 is indicated by dashed lines and reference numeral 27.

The contacting is selected in such a way that current flow 27 flows in a targeted manner through input pinion 18 and receiving section 16 and not through roller bearing 22 and/or sealing element 20. This prevents damage to sealing element 20 or roller bearing 22 by current flow 27 or The associated heat generation is avoided.

4 shows a schematic sectional view of a further contact of the input pinion 18 and the rotor shaft 14 during a welding process. The illustrated embodiment differs from that in 3 shown embodiment characterized in that the receiving portion 16 of the rotor shaft 14 is hollow. The second welding electrode 32 makes annular contact with the rotor shaft 14 inside the hollow receiving section 16 . In addition, the rotor shaft 14 has a collar 34 . The collar 34 protrudes radially from the rotor shaft 14 and can have interruptions. In other words, the collar 14 can be designed to run completely radially around the rotor shaft 14 or consist of collar sections.

The collar 34 borders on the receiving section 16 of the rotor shaft 14 . The collar 34 can facilitate the mounting of the input pinion 18 on the rotor shaft 14 or the receiving section 16 by serving as a stop for the input pinion 18, for example.

The current flow 27 is conducted through the input pinion 18 , the collar 34 and at least partially through the receiving section 16 as a result of the contacting of the two welding electrodes 24 , 32 shown. Here, too, is analogous to the embodiment 3 damage to the sealing element 20 and/or the roller bearing 22 by the current flow 27 and the heat generation associated therewith is avoided.

5 shows a schematic sectional view of a further contact of the input pinion 18 and the rotor shaft 14 during a welding process. The illustrated embodiment differs from that in 4 embodiment shown in that the second welding electrode 32 contacts the collar 34 in a ring shape. In this exemplary embodiment, the flow of current 27 is conducted through the collar 34 and the input pinion 18 . Here, too, the damage to the sealing element 22 or the roller bearing 22 by the current flow 27 or the heat development associated therewith is avoided analogously to the preceding exemplary embodiments.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102015203068 A1 [0004]

Claims (10)

Method for mounting a rotor (12) of an electric machine on a transmission (11) of an electric drive unit (10) for a vehicle, the rotor (12) having a rotor shaft (14) with a receiving section (16) for receiving an input pinion (18 ) comprising the steps: - Providing at least one sealing element (20) and at least one roller bearing (22); - Passing through the rotor shaft (14) through the sealing element (20) and through the roller bearing (22) so that the receiving section (16) projects into the transmission (11); - Assembling the input pinion (18) on the receiving section (16) of the rotor shaft (14) and - Joining the input pinion (18) with the rotor shaft (14) by means of a welding process. procedure after claim 1 , characterized in that the welding process is carried out by means of resistance welding, in particular by means of capacitor discharge welding, with a first welding electrode (24) making contact with the input pinion (18). procedure after claim 2 , characterized in that the first welding electrode (24) contacts the input pinion (18) on a side (26) facing away from the rotor shaft (14) and/or from the electric machine, in particular in an annular manner. Method according to the preceding claim, characterized in that the diameter of the ring-shaped contact of the first welding electrode (24) is greater than the outside diameter of the rotor shaft (14) at its transmission-side end (28). Procedure according to one of claims 2 until 4 , characterized in that the rotor shaft (14) has an end face (30) at its transmission-side end (28), a second welding electrode (32) making contact with the end face (30). Procedure according to one of claims 2 until 4 , characterized in that the receiving section (16) is at least partially hollow, wherein a second welding electrode (32) contacts the rotor shaft (14) inside the hollow receiving section (16). Procedure according to one of claims 2 until 4 , characterized in that a second welding electrode (32) contacts the rotor shaft (14) in an area between the receiving section (16) and the roller bearing (22), in particular in an annular manner. Procedure according to one of claims 2 until 4 , characterized in that the rotor shaft (14) has a radially projecting collar (34) adjoining the receiving section (16), a second welding electrode (32) welding the rotor shaft (14) to the collar (34) or in an area between the Collar (34) and the roller bearing (22), in particular ring-shaped contacted. Electrical drive unit (10) for a vehicle, with an electrical machine and a transmission (11), the electrical machine having a rotor shaft (14) and an input pinion (18), the assembly using a method according to one of Claims 1 until 8th is carried out, characterized in that the outside diameter (36) of the input pinion (18) is larger than the outside diameter (38) of the rotor shaft (14). Electric drive unit (10) after claim 9 , characterized in that an axial extent (40) of the receiving portion (16) is smaller than an axial extent (42) of the input pinion (18).

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