Electrical drive with integrated brake

Abstract

The invention relates to an electric drive (1) for a vehicle, in which at least one electric machine (20), one differential (21) and two brakes (22) are mounted in a common housing (6), the brakes (22) being a multi-plate brake having a first and a second plate pack (15, 16), the brake housing (9) and the differential (21) are rotatably arranged together on a side output shaft (8) of the differential (21), and the side output shaft (8) is connected to the brake housing (9) in an operating condition in order to apply a braking torque to the vehicle.

Description

Technical Field

[0001] The present invention relates to an electric drive for a vehicle, in which at least one electric motor, a differential, and two brakes are mounted in a common housing, wherein the brakes are multi-disc brakes.

[0002] The present invention also relates to a method for operating the brakes of an electric drive of a vehicle. Background Art

[0003] Particulate matter is one of the greatest health risks posed by air pollution. Assessments of multiple studies have shown that particulate matter is responsible for the deaths of millions of people each year. In particular, ultrafine particles such as soot particles are classified as carcinogens.

[0004] The engine is only one cause of the problem, because a large part of the measurable particulate matter in cities comes from wear particles. In addition to tires, the main sources of these particulate matters are especially brake discs and brake linings.

[0005] Replacing with electric vehicles does not change anything about the problem, because electric vehicles are usually also implemented with disc brakes or drum brakes.

[0006] Therefore, even a large-scale replacement with electric vehicles cannot change anything about the pollution by these harmful substances.

[0007] Heavy electric vehicles with long ranges even exacerbate the wear problems of brakes, tires, and roads.

[0008] Therefore, countermeasures to reduce brake wear and tire wear must be found. Emissions generated during the combustion process have been analyzed in depth, while the research on so-called non-exhaust emissions, i.e., non-exhaust particulate matter emissions, is still in its infancy. This especially involves the simulation of particulate matter emissions and microplastic emissions. So far, there is no fixed unified test method for non-exhaust particulate matter emissions from vehicles.

[0009] In addition, there is no legislation to limit or reduce non-exhaust particulate matter emissions so far. However, legal regulations on limit values have been published for particulate matter generation caused by braking.

[0010] Manufacturers and suppliers are currently seeking methods and technical solutions to reduce brake wear and tire wear. By means of hard material cladding of brake discs via diode lasers, a method that can achieve a reduction in brake-related particulate matter emissions can be provided in the future. Although the cladded brakes still generate particulate matter, the particulate matter they generate is much less than that of uncladded brake discs. The advantages of gray cast iron brake discs still exist here.

[0011] In electric vehicles, the brakes are mostly implemented as disc brakes or drum brakes and are placed in the wheel housings.

[0012] It is known from the project ZEDU1 (Zero Emission Drive Unit) of the German Aerospace Center (DLR). Among them, the braking system is moved from the wheel carrier to the drive unit and integrated there. Combined with specially adjusted high-performance electronics, power batteries and a BBW (Break by Wire) system, the braking energy can be almost completely recovered, that is, reused, so that the mechanical braking share can be minimized. This enables a very compact construction of the drive unit, integrates it into the transmission-brake unit and completely eliminates brake wear emissions. In ZEDU-1, the multi-disc brake is directly integrated into the electric motor. The multi-disc brake and the high-performance electronics together ensure almost complete recovery of the drive energy. Here, the brake wear debris falls into the oil sump, and the contents of the oil sump are continuously pumped through the filter and cleaned. Summary of the Invention

[0013] The object of the present invention is to provide an improved electric axle for a vehicle with an integrated brake, where the brake is integrated into the electric drive unit, and the problems known from the prior art are largely avoided.

[0014] The object is achieved by an electric drive for a vehicle, wherein at least one electric motor, a differential and two brakes are mounted in a common housing, wherein the brakes are multi-disc brakes, and the brakes are rotatably arranged together on the side driven shafts of the differential, and the side driven shafts are connected to the brake housing in operation so as to apply a braking torque to the vehicle.

[0015] When the brake is open, the brake rotates completely at the output shaft speed of the side driven shaft (rotation of the entire brake), so that almost no drag loss is generated compared with the traditional braking system. This situation corresponds to the neutral position.

[0016] The brake advantageously includes a synchronizing unit. The synchronizing unit is used in various variants in a motor vehicle, for example in a transmission, and is generally known to those skilled in the art. The synchronizing unit is used for speed matching between the elements to be coupled, so as to reduce the shifting force and wear. A known variant here is the conical friction clutch. Depending on the torque to be synchronized, one or more friction cones may be present. Depending on the number of the friction cones, a distinction can be made between single-cone synchronization and multi-cone synchronization.

[0017] In a preferred embodiment of the brake, the synchronizing unit is implemented as a single-cone synchronizer. The conical friction clutch of the synchronizing unit is formed between a first synchronizing ring and a second synchronizing body.

[0018] The operating piston applies a force to a hub that is axially movable but torsionally fixed on a side driven shaft. The hub is supported at a first leaf carrier via an axial bearing. The first leaf carrier is coupled to a synchronizing ring such that its axial displacement causes it to form a frictionally engaging connection with a synchronizing body fixed to the housing and to establish a frictionally engaging connection with the brake housing. The first leaf carrier can be fastened in a housing-fixed manner in the operating position via a synchronizing unit.

[0019] The second leaf group can be connected to the first leaf group and the side driven shaft via an operating piston.

[0020] The object is also achieved by a method for braking an electric drive, in which an open brake is rotated together with a side driven shaft by two leaf groups and the leaf groups are connected to the brake housing in two successive movement steps when operating the brake.

[0021] In a first step of the method, first, by operating a hub that is torsionally fixed but axially movable on the side driven shaft, synchronization of the first leaf carrier that rotates together with the first leaf group is caused, starting from the output speed of the driven shaft of the differential 21 to a speed of 0. After synchronization, the first leaf carrier is frictionally fixed to a synchronizing body connected to the housing 6 via a synchronizing ring.

[0022] In a subsequent second method step, the axially alternatingly arranged leaves of the first and second leaf groups are axially moved and brought into frictional contact with each other by further operation.

[0023] A corresponding braking torque is generated in relation to a further operating force.

[0024] No oil supply is provided in the neutral position when the brake is open, but oil supply is carried out through an oil hole along the side driven shaft and a hole in the movable hub when the brake is closed. Description of the Drawings

[0025] The drawings show:

[0026] Figure 1 A brake at the side driven shaft of an electric drive;

[0027] Figure 2 Schematically shows the construction of an electric drive;

[0028] Figure 3 A schematic axial sectional view of an unoperated brake (neutral position);

[0029] Figure 4 A simplified schematic view of an operated brake in a first operating state; and

[0030] Figure 5 A simplified schematic view of an operated brake in a second operating state. Detailed implementation mode

[0031] Figure 2 The electric drive unit 1 is shown, which includes an electric motor 20. The electric motor 20 is effectively connected and coupled to a reducer (not shown), and the reducer has a speed-changing stage. The transmission output shaft 20a drives a differential 21. The driven shafts 21a, 21b of the differential 21 are connected to the side driven shafts 8. As can be seen from the Figure 2 schematic diagram, brakes 22 are arranged symmetrically on both sides of the differential 21. When the brakes are operated correspondingly, the braking torque is transmitted to the side driven shafts 8. The side driven shafts 8 drive the vehicle wheels 23.

[0032] Components, namely the electric motor 20 with a reducer, the differential 21 and the brakes 22, are installed in a common housing 6 and form a module.

[0033] Figure 1 The brake 22 on one side of the electric drive unit 1 in the open state is shown in an axial sectional schematic diagram. The open state in which the braking torque is not transmitted corresponds to the neutral position.

[0034] Below, only the brake 22 on one side of the differential 21 will be described. The brakes on the opposite side of the differential on the side driven shaft 8 are correspondingly symmetrically constructed.

[0035] Figure 3 A highly simplified schematic diagram of the brake 22 in the open state / neutral position is also shown. The diagram only shows a partial part of the brake. The rotational axis D of the side driven shaft 8 is shown in the figure.

[0036] Below, the direction along the rotational axis D will be referred to as the axial direction.

[0037] The brake 22 has a first plate carrier 13 with a first plate group 13a and a second plate carrier 17 with a second plate group 17a. The first and second plate groups 13a, 17a are arranged in an engaged manner such that the plates of the first plate group 13a and the second plates of the second plate group 17a are adjacent to each other and arranged alternately when viewed in the axial direction. In the neutral position, there is a gap between the first and second plates when viewed in the axial direction. In the operating position, a friction fit is formed between the alternately arranged plates of the first and second plate groups by axially moving the plates. The basic structure and arrangement of the plate groups and plate carriers are known from the prior art and will not be elaborated here.

[0038] The first plate carrier 13 is preferably the outer plate carrier when viewed in the radial direction. The second plate carrier 17 is then correspondingly the inner plate carrier. The first plate carrier 13 is supported on the second plate carrier 17 via a radial support 18.

[0039] The second carrier 17 is fixed to the hub 5. In Figures 3 to 5 In an alternative embodiment schematically shown in

[0040] The hub 5 is torsionally rigidly arranged on the side driven shaft 8 for torque transmission. In the axial direction, the hub 5 is movably supported on the side driven shaft 8. A known embodiment of such a hub 5 is a splined hub 5a which is form-fittingly arranged on the side driven shaft 8 via spline engagement and is axially movable on the side driven shaft 8 due to the form-fitting engagement between the splined hub 5a and the side driven shaft 8. The axial movability of the hub 5 is indicated by a double arrow.

[0041] Radial oil holes 11 are introduced into the hub 5 as through holes, which extend from the outer surface of the hub 5 to the radially inner surface of the hub 5.

[0042] The side driven shaft 8 also includes oil holes 12. The oil holes 12 are first implemented to extend in the axial direction starting from one end side of the side driven shaft 8 and then branch into a plurality of radial holes 12a. The radial holes 12a extend from the axial oil hole 12 to the surface of the side driven shaft 8, so as to supply oil towards the outer surface of the side driven shaft 8 in the region of the discharge openings of the radial holes 12a. In Figure 3 In the neutral position of the brake 22 shown in

[0043] The brake 22 also has a synchronizing unit 7, which is implemented as a single-cone synchronizer. A conical friction clutch with friction linings of the synchronizing unit is formed between the synchronizing ring 14 and the synchronizing body 24. Such synchronization is known from the prior art and will not be described in detail herein.

[0044] The synchronizing body 24 is fixedly arranged in the housing. The synchronizing ring 14 is directly or indirectly coupled to the first carrier 13.

[0045] In the neutral position of the brake 22, the synchronizing ring 14 has a spacing Δd relative to the synchronizing body fixedly arranged in the housing when observed in the axial direction.

[0046] The first carrier 13 is supported on both sides via axial supports 3a, 3b. Under the condition of the intermediate connecting spring 26, the axial support 3a supports the first carrier 13 at the brake housing 9. The second axial support 3b supports the first carrier 13 on the second carrier 17 or on the first piece fixedly arranged in the second piece group 17a when observed in the axial direction.

[0047] The brake 22 further includes an operating piston 2 which is preferably hydraulically actuated. The actuating device is not shown and described in detail in the figures. The operating piston 2 has a radial section 2a and an operating section 2b which extends axially at the upper end section of the radial section 2a. The operating section 2b extends in the direction of the first and second sets of plates 13a and 13b which are nested with each other. In the neutral position, there is a gap with a spacing S1 between the operating section 13a of the operating piston 2 and the first set of plates 13a or the first plate located on the outside when viewed in the axial direction.

[0048] With the intermediate connecting spring 4, the operating piston 2 is supported at the end side of the hub 4 via the axial support 3c. The operating piston 2 is axially movable by introducing an operating force shown by the arrow F0.

[0049] The spring constant of the spring 4 is greater than the spring constant of the spring 26.

[0050] If the brake 22 is opened in the neutral position, the sets of plates of the brake 22 are not supplied with oil through the covered oil holes 12 / radial holes 12a. However, the oil supply can also be achieved via external supply and control.

[0051] When operating the brake, the operating piston 2 is loaded with the force F0 such that the operating piston 2 moves axially. In the first step, first, when axially moving and loading the force in the direction of the arrow F0, the force is transmitted to the hub 5 via the axial support 3c. The first method step is shown in Figure 4 . In this case, the hub 5 moves axially as can be seen from the figures and the radial hole 11 overlaps with the radial hole 12a, so that it is ensured that oil is input to the set of plates. The hub 5 abuts against the side driven shaft 8 in an axially supported manner at the axial stop 10 and does not continue to move axially.

[0052] A further force flow is transmitted via the axial support 3b to the first plate carrier 13 and to the synchronizing ring 14 of the synchronizing unit 7. The axial movement of the hub 5 causes the synchronizing ring 14 to move axially against the spring force of the spring 26. The synchronizing ring 14 forms a frictionally engaging effective connection with the synchronizing body 24. After synchronization is completed in the first working step shown, the first plate carrier 13 is fixedly connected to the housing 9 via the synchronizing unit 7 to brake to zero speed. The axial movement in the first method step corresponds to the displacement Δd.

[0053] In this case, after the first method step (the first plate carrier 13 is fixedly coupled to the housing 6), the operating piston 2 or the axial operating section 13a is also spaced apart from the first set of plates of the first plate carrier 13 via the gap S1.

[0054] In Figure 5In the second method step shown in [description], by further moving the operating piston 2 after moving an axial distance +, the operating section 13a abuts against the outer sheet of the first sheet group 13a, so that an operating force is applied to the first sheet group 13a. Thereby, the gap between the alternately arranged sheets of the first and second sheet groups 13 and 17 is closed, and thus a braking torque can be generated by the frictional engagement connection between the two sheet groups.

[0055] By "closing" the brake 22 in the second method step as described above, the spring 4 is compressed and the hub 5 is supported at the stop 10 in a spring-loaded manner. Since the hub 5 is torsionally arranged on the side driven shaft 8 and the frictionally engaged sheet groups are fixedly supported via the first sheet carrier 13 and the housing of the synchronizing unit 7, a braking torque is applied to the side driven shaft 8.

[0056] Figure 5 The brake 22 shown in [description] is in the closed state.

[0057] When the brake 22 is opened, the braking force first decreases, and then the synchronizing unit 7 is opened by the spring force of the spring 26. After the first sheet carrier 13 is decoupled from the brake housing 9, due to the existing drag torque and the radial support on the second sheet carrier 17, the first sheet carrier 13 can rotate freely again together.

[0058] The oil is pumped to the filter by means of a pump in order to filter out friction particles if necessary. Thereby, oxidative particulate matter in the environment is avoided.

[0059] List of reference numerals

[0060] 1 Tram bridge drive

[0061] 2 Operating piston

[0062] 2a Radial section of the operating piston

[0063] 2b Axial section / operating section

[0064] 3a - 3c Axial supports

[0065] 4 Spring

[0066] 5 Hub

[0067] 5a Splined hub

[0068] 6 Housing

[0069] 7 Synchronizing unit

[0070] 8 Side driven shaft

[0071] 9 Brake housing

[0072] 10 Stop

[0073] 11 holes

[0074] 12 oil holes

[0075] 12a radial holes

[0076] 13 first carrier

[0077] 13a first group

[0078] 14 synchronizing ring

[0079] 17 second carrier

[0080] 18 radial support

[0081] 17a second group

[0082] 20 motor with gear stage

[0083] 21 differential

[0084] 22 brake

[0085] 23 wheel

[0086] 24 synchronizing body

[0087] 26 spring

Claims

1. An electric drive (1) for a vehicle, in which at least one electric motor (20), a differential (21), and two brakes (22) are mounted in a common housing (6), wherein the brakes (22) are multi-disc brakes, the multi-disc brakes having first and second disc carriers (13, 17) together with associated first and second disc packs (13a, 17a), and wherein the brakes (22) include a brake housing (9), wherein the first and second disc carriers (13, 17) are rotatably arranged together on a side output shaft (8) of the differential (21) and the side output shaft (8) is connected to the brake housing (9) in an operating situation in order to apply a braking torque to the vehicle.

2. An electric drive (1) for a vehicle, in which in an operating situation, an operating force can be applied to the first disc pack (13, 17) via an axially displaceably supported operating piston (2), and wherein the operating piston (2) is supported directly or indirectly at the second disc carrier via an axial support with an intermediate connecting spring (4).

3. The electric drive (1) according to claim 1 or 2, wherein each brake (22) includes a synchronizing unit (7), wherein the second disc carrier (17) is axially displaceably but torsionally rigidly arranged directly or indirectly on the side output shaft, and wherein the first disc carrier is supported by means of a radial support (18) on the second disc carrier (17) or on a component connected to the disc carrier.

4. The electric drive (1) according to any one of the preceding claims, wherein the second disc carrier (17) is fixedly connected to or configured as a hub (5), and the hub (5) is a hub (5) that is axially displaceably but torsionally rigidly arranged on the side output shaft (8).

5. The electric drive (1) according to any one of the preceding claims, wherein the brake includes a synchronizing unit (7) having a synchronizing ring (14) and a synchronizing body (24), wherein the synchronizing body (24) is fixedly connected to the brake housing (9) and the synchronizing ring (14) is connected to the first disc carrier (13), and wherein a frictionally engaged connection can be established between the synchronizing ring (14) and the synchronizing body (24) when an operating force is applied to the hub (4) via the operating piston (2) for effecting a housing-fixed fastening of the first disc carrier (13).

6. The electric drive (1) according to claim 1, wherein the second disc pack (17a) can be connected to the first disc pack (13a) and the corresponding side output shaft (8) via the operating piston (2).

7. The electric drive (1) according to any one of the preceding claims, wherein the synchronizing unit (7) is a single-cone synchronizer.

8. A method for braking an electric drive (1) according to any one of claims 1 to 7, wherein an open brake (22) is rotated together with the associated blade groups (13a, 17a) by means of the first and second blade carriers (13, 17) in a neutral position along with the side driven shaft (8), and the blade groups (13a, 17a) are connected to the brake housing (9) in two successive movement steps when operating the brake (22).

9. The method according to claim 8, wherein in a first method step, the first blade carrier (13) and the first blade group (13a) are first fixed to the brake housing (9) via the synchronization unit (7), and in another method step, the alternately arranged blades of the two blade groups (13a, 17a) are brought into frictional contact with each other.

10. The method according to claim 8 or 9, wherein in the case of the brake (22) being open, the blade groups (13a, 17a) are not supplied with oil in the neutral position, but in the case of the brake (22) being closed, the blade groups (13a, 17a) are supplied with oil through the oil holes (12) and radial holes (12a) along the side driven shaft (8) and the radial holes (11) in the axially movable hub (5).

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