Electric drive unit with assembly having multi-disc brakes and method for heating an electric drive unit

Abstract

The invention relates to an electric drive unit having an electric machine (EM) with a transmission, which electric machine can be connected to an assembly (300) via a connection (401), wherein the assembly (300) comprises at least one multi-disc brake (303) in each case, which multi-disk brake is arranged concentrically about axle side shafts (301), in a housing (25), wherein at least one brake piston (3) can be actuated hydraulically or electrically and moves axially parallel to the axle side shafts (301) in a part of the housing (25) against movable discs (12), and wherein cooling oil of the electric machine (EM) is applied to the housing (25) and the multi-disc brakes (303).

Description

[0001] Electric drive unit with assembly with multi-disk brakes and method for heating an electric drive unit

[0002] The invention relates to an electric drive unit with an electric machine with a transmission, which can be connected to an assembly via a connection, wherein the assembly comprises at least one multi-disk brake in a housing, which are arranged concentrically around axle side shafts.

[0003] The invention further relates to a method for heating an electric drive unit.

[0004] State of the art

[0005] A wheel brake integrated into the transmission requires an actuation mechanism. A wheel brake consisting of a multi-disk, oil-cooled disc pack is known.

[0006] The motivation for integrating the wheel brake into the transmission is, among other things, to avoid fine dust, which is typically and inevitably present with open wheel brakes (drum or disc). Other reasons include maintenance-free operation and weight savings in the unsprung masses, which are relevant to driving dynamics.

[0007] DE 102020 211 442 A1 discloses a braking system for a vehicle comprising an electric machine with a stator, a rotor, and a rotor shaft connected to the rotor. The electric machine is configured to provide torque to the rotor shaft. The braking system comprises a first drive shaft kinematically coupled to the rotor shaft such that the torque can be transmitted from the rotor shaft to the first drive shaft.Furthermore, a first multi-disk brake arranged on the first drive shaft has a first multi-disk brake housing and multi-disk discs arranged in the first multi-disk brake housing, wherein at least one multi-disk disc is fixedly connected to the first drive shaft and at least two multi-disk discs are fixedly connected to the first multi-disk brake housing, and wherein the multi-disk discs can be pressed axially against one another such that a braking force for braking the first drive shaft can be generated. According to one embodiment, it can be provided that the braking system additionally has a first differential gear kinematically coupled to the rotor shaft and having a first differential housing, wherein the first drive shaft is coupled to the first differential gear.Furthermore, the braking system can additionally comprise a second drive shaft, which is kinematically coupled to the rotor shaft such that the torque from the rotor shaft can be transmitted to the second drive shaft and which is coupled to the first differential gear. Furthermore, the braking system can comprise a second multi-disk brake arranged on the second drive shaft with a second multi-disk brake housing and multi-disk discs arranged in the second multi-disk brake housing. The multi-disk brakes can be arranged in the differential housing and can be actuated electrically, electromechanically, or hydraulically.

[0008] Anti-lock braking systems and electronic stability programs are state-of-the-art. Robust, proven, and cost-optimized control units with appropriate hydraulics are available.

[0009] The object of the invention is to design an electric drive with a single assembly, wherein the assembly contains independent multi-disk brakes with actuators and can be flexibly installed with different electric machines and brake control systems. Description of the invention

[0010] The object is achieved with an electric drive unit with an electric machine with a gearbox, which can be connected to an assembly via a connection, wherein the assembly comprises at least one multi-disk brake in a housing, which are arranged concentrically around axle side shafts, wherein at least one brake piston is hydraulically or electrically actuated and moves axially parallel to the axle side shafts in a part of the housing against movable discs and wherein the housing and the multi-disk brakes are supplied with cooling oil from the electric machines and the cooling circuit is sealed and separated from the brake circuit.

[0011] The brake pistons are sealed against cooling oil by piston seals or a metal bellows.

[0012] The assembly is connected to hydraulic brake components via brake lines via a further connection.

[0013] The assembly includes a quick-fill device.

[0014] The quick-filling device connected to the brake components comprises at least one electric motor, a movement spindle, an axial piston and a reservoir.

[0015] The quick-filling device comprises two electric motors, two movement spindles, one axial piston each with a smaller and a larger piston area, and a reservoir, whereby the quick-filling device is not connected to brake components.

[0016] The quick-fill device alternatively comprises at least one electric motor, a motion spindle, an axial piston, and a reservoir. The proposed electric drive unit enables the integration of existing brake control systems with anti-lock braking systems and electronic stability programs into a single brake component unit and also utilizes the oil cooling of the electric motor to cool the integrated brake disc pack as needed. In the terminology of the application, the term "electric motor" is always used to include a reduction gear.

[0017] The proposed piston and brake disc design represents a pre-assembled and tested brake unit. This assembly can enhance the functionality of an electric machine and also be marketed as a basic drive without the brake functionality.

[0018] The actuation with sealed brake pistons and potential connection to the brake components is quite small due to the high pressures and offers the usual ratio of maximum braking torque to maximum braking pressure.

[0019] Existing software structures within the anti-lock braking systems and electronic stability programs only need to be adapted and, if necessary, optimized.

[0020] The electric drive system with the assembly provides a neutral pressure interface to the brake components, so that brake control systems from a wide variety of manufacturers can be connected.

[0021] The actuation can also be carried out by a simplified high-pressure actuator, thus realizing a “brake-by-wire” system predicted for the future.

[0022] The task is also fulfilled with an electric drive unit, whereby at least one brake piston can be operated electrically.

[0023] The task is also fulfilled by the method for heating an electric drive unit, wherein a control of the electric drive unit in a time window predetermined by the outside temperature, recuperation during

[0024] brakes and uses only the disc brakes.

[0025] Description of the characters

[0026] Figure 1 shows a first embodiment of a transmission-internal brake, Figure 2 shows a second embodiment with metal bellows,

[0027] Figure 3 shows a hydraulic concept for operating the brakes

[0028] Figure 4 shows the hydraulic concept of Figure 3 with a quick filling, Figure 5 shows another embodiment of the hydraulically operated quick filling,

[0029] Figure 6 shows a diagram of the integration of the brake hydraulics, Figure 7 shows an actuation with a ring piston,

[0030] Figure 8 shows an electromechanical actuation of the brake.

[0031] Figure 1 shows an assembly 300 for an electric drive with an electric motor EM that drives two axle shafts 301, each for a wheel of a vehicle. The drive is provided via the output shaft 302 of the electric motor EM via a differential gear.

[0032] A multi-disk brake 303 is arranged concentrically around the axle side shaft 301. The multi-disk brake 303 consists of a piston carrier plate 1, in which the bearings 2, which are arranged in the direction of the output shaft 302, the associated shaft seals, the individual brake pistons 3, and a distributor device 4 are arranged, which directs the brake fluid to the brake pistons 3. The inlet 5 and a vent device 6 are integrated into the distributor device 4. Ideally, the piston carrier plate 1 also represents a guide 7 for guiding the outer discs 8, which is designed as a yoke and is firmly connected to a housing 25.

[0033] For this purpose, an end plate 9 is also inserted into the guide 7 and axially fixed by a retaining ring 10. The end plate 9 can be designed with a step 13, which serves as a stop for an inner disk carrier 11. The inner disk carrier 11 of the disk pack 12, which is connected to the axle side shaft, is axially movable, but cannot be removed from the assembly 300 once assembled. This creates a self-contained, pre-assembled assembly. Ideally, the end plate 9 also serves an oil-conducting function by forming a catch edge 14.

[0034] Together with an oil guide pot 15 mounted on the output shaft side, an oil channel 16 is formed that directs cooling oil beneath the plate pack 12. This eliminates the need for oil guide structures in the housing 25 of the assembly 300 and simplifies the housing machining.

[0035] The multi-disk brakes run together with the electric motor EM and a gearbox in the transmission oil and use the oil cooling to cool the integrated disc pack 12 as needed.

[0036] However, for the brakes to function, the brake circuit must be clearly sealed against the oil cooling.

[0037] Brake pistons 3 are arranged coaxially to the axle side shaft 301 in a brake piston bore 304 in the piston carrier plate 1. The number of brake pistons 3 is selected so that the axial force can be distributed as evenly as possible on the disk pack 12. An annular piston 3a, which is arranged coaxially to the output shaft 302, can also be used in an embodiment according to Figure 7. The brake pistons 3 are designed with a piston seal 17 suitable for brake fluid. On the brake side, a wiper seal 18 is provided on the brake piston bore 304, which in turn shields the piston seal 17 from contact with the transmission oil. Any leaks that arise can be diverted into a vented reservoir 19. In one embodiment, the filling of the reservoir 19 is monitored by a sensor 20.

[0038] Figure 2 shows an embodiment for optimal sealing.

[0039] On the brake fluid side of the brake piston bore 304, a metal bellows 21 is installed, which hermetically and completely seals off the brake fluid from the transmission oil. During braking, the metal bellows 21 expands and transmits the axial force via the brake piston 3 to the first pressure plate 12a of the disc pack 12. In one embodiment, the brake piston 3 can partially have an internal bore 22 for weight savings and improved cooling.

[0040] A further alternative embodiment designs the brake piston 3 on the metal bellows side with a thermally insulating material 23.

[0041] A piston support plate 1 closes the housing 25 of the assembly on both sides 24 facing the wheels and is designed symmetrically for dual use. The piston support plate 1 can also be designed asymmetrically if required.

[0042] Figure 3 shows the integration of assembly 300 into the hydraulic braking system.

[0043] An oil pump 100, which typically cools the electric motor EM with transmission oil, also cools the clutch disc packs 12. During braking, the oil flow is diverted from the electric motor EM to the brake discs of the clutch disc packs 12 using a switching valve 103. The switching valve 103 can be controlled electrically or, alternatively, switched by oil pressure. The oil pressure required for switching can be generated by the cooling oil itself or provided by the brake pressure.

[0044] The electric switching valve 103 is designed so that, in the de-energized valve basic position, the plate pack 12 is supplied with the volume flow of the oil pump 100. The plate pack 12 is supplied with a minimum cooling oil volume flow via a base orifice 106 when the switching valve 103 is in cooling mode for the electric machine EM. In the opposite case, the electric machine EM is again supplied with a minimum amount via the base orifice 106. However, in combination with a check valve 107, one of the flow directions can be stopped and blocked.

[0045] Since the brake pressure is generated by on-board brake components 104, such as an electric brake pedal, an anti-lock braking system, and electronic stability programs, their performance should be adapted to the requirements of the transmission-integrated brake system. The filling time of the brake pistons 3 is particularly important here. The brake circuit with the brake components 104 is connected to the brake piston 3 via brake lines 102. The dashed lines indicate the component areas that can be interconnected via connectors 400, 401. Thus, the brake components 104 and / or the electric motor EM can be interchangeable.

[0046] As an alternative to the hydraulic actuation of the disk pack 12, an electromechanical actuation according to Figure 8 is also possible, as is used in an implementation with “brake-by-wire”.

[0047] For this purpose, a smaller electric drive 402 is installed on each side of the disc packs 12. The output of the small electric drive 402 is connected to a spindle 404 via a suitable reduction gear. In this embodiment, the reduction gear is a planetary gear 403. With the help of the spindle 404, the brake piston 3 is moved toward and away from the discs.

[0048] In this embodiment, brake fluid is no longer required.

[0049] If the filling volume flow of the external unit of the brake components 104 is too small, it may be useful to integrate a quick filling device 105 on the side of the brake components 104 for both brake sides.

[0050] Figure 4 shows such an embodiment with a quick-fill device 105. This is implemented by a motor 305 and an axial piston 110 driven by a spindle 306. Two isolating valves 111 close the connection to the brake pistons 3 as soon as the brake pressure rises above a threshold value limited by the drive motor 305 of the axial piston 110.

[0051] In this variant, the drive motor 305 of the axial pump can be designed to be relatively weak, since it only has to operate at low oil pressure levels.

[0052] Alternatively, the axial piston 110 can, as shown in Figure 5, also follow a master piston 112 actuated by cooling oil pressure. In this case, the axial piston 110 is subjected to cooling oil pressure on the large piston surface 113, which is generated by a back pressure valve 117 during braking. On the smaller piston side 114, the brake pressure of the brake fluid prevails until the isolation valves 115 close. In the diagram shown, the isolation valves are shown as shuttle valves 115. These close the connection to the axial piston 110 as soon as the brake pressure of the external brake components 104 is greater than the pressure in the axial piston 110. The pressure in the axial piston 110 is in turn limited by a pressure relief valve 116. This makes it possible to design the axial piston 110 for the low-pressure range, e.g. 2 bar, with thin walls and also from plastic.

[0053] The shuttle valves 115 are also applicable to the electric axial piston drive of the embodiment shown in Figure 4. Another variant of the hydraulic actuation of the disc packs 12 according to Figure 6 involves placing the necessary hydraulic power supply close to the transmission or even integrating it into the transmission. This eliminates the need for the brake line 102 from the master brake cylinder of the external brake components 104 to the wheel brakes, the disc packs 12. This design enables the implementation of a "brake-by-wire" system.

[0054] The hydraulic system of this embodiment is characterized in that the brake pressure is applied separately for each vehicle side by an axial piston drive 200. The axial piston drive 200 consists of a drive motor 201, a motion spindle 202, a hydraulic piston with integrated spindle nut 203, a pair of seals 204, and a piston spring 205. Both piston sides are connected to a reservoir 207 via check valves 206. The reservoir has a vent port 208, and a diaphragm 209 slightly preloads the oil volume in the reservoir.

[0055] Brake pressure is only built up by moving the piston, thus avoiding permanent leaks such as those that occur during storage charging, which provides an energy advantage.

[0056] A special feature of this hydraulic concept, however, is that a hydraulic cylinder with uneven surfaces is used on both sides. The larger piston surface 210 is always used to fill the connected brake pistons 3, while the smaller piston surface 211 is used to apply and regulate the high brake pressures. The special use of the piston surfaces allows the drive motor 201 of the motion spindle 202 to be designed to be small at maximum speed and maximum torque, because the required torque is defined by the smaller piston surface 211 and the pressure.

[0057] During filling, a large volume and low pressure are required, whereas during pressure control, the volume requirement is low and the pressure very high. After filling, the direction of rotation of the drive motor 201 of the spindle drive is reversed. Shuttle valve 212 and check valves 206 enable this reversal.

[0058] The non-self-locking axial piston drive 200 can be preloaded with the piston spring 205 in the direction of the smaller piston surface 211, so that the spindle nut 203 runs on the movement spindle 202 without play and the movement spindle 202 is brought into the basic filling position even without a motor drive.

[0059] The pressure reduction is dynamically controlled by the switching valves 213. This is useful, for example, when rapid control interventions must be carried out by the brake components 104.

[0060] The large and small pressure chambers of the brake pressure actuator are separated from each other by suitable seals. Any leakage is drained through a drainage hole 214 located centrally between the seals and is guided via the movement spindle 203 toward the motor via lines 215, from where it is returned to the reservoir 207.

[0061] The described electric drive unit with internal wheel brake is particularly well suited for use in a thermal optimization process.

[0062] With this method, especially in cold temperatures, any recuperation by the electric motor is omitted during a time window after starting or during a further, to-be-defined time window. Especially immediately after setting off, the transmission oil is cold at low temperatures and must be warmed up, as does the battery of the electric vehicle.

[0063] Any braking deceleration of the vehicle during this time window is applied solely by the brake friction clutch within the transmission. This is achieved by controlling the electric drive unit and / or the thermal system.

[0064] This leads to several advantages. On the one hand, the vehicle's battery is not yet capable of recovering large amounts of energy through recuperation in cold temperatures, and this is even more true when the battery is high or fully charged.

[0065] It is more efficient for the entire vehicle system if recuperation energy is deliberately omitted in cold weather and instead the transmission oil is first heated via the friction in the brake clutches in order to bring it into the correct viscosity range and improve lubrication, etc. This heated transmission oil can then be used directly to heat the cooling water so that it can be used for other purposes, such as heating the vehicle battery, driver's cab, etc.

[0066] Reference symbol

[0067] 1 piston carrier plate

[0068] 2 camps

[0069] 3 brake pistons

[0070] 3a Ring piston

[0071] 4 Distribution device

[0072] 5 Inlet

[0073] 6 venting device

[0074] 7 Guide

[0075] 8 outer slats

[0076] 9 End plate

[0077] 10 Retaining ring

[0078] 11 inner disc carrier

[0079] 12 slat pack

[0080] 12a printing plate

[0081] 13th level

[0082] 14 catch edge

[0083] 15 Oil guide pot

[0084] 16 Oil channel

[0085] 17 Piston seal

[0086] 18 Wiper seal

[0087] 19 Reservoir

[0088] 20 sensors

[0089] 21 Metal bellows inner bore thermally insulating material side housing oil pump cooling line brake line changeover valve brake components quick-fill device base plate check valve axial piston isolating valves master piston piston area smaller piston side shuttle valves pressure relief valve back pressure valve 0 axial piston drive 1 drive motor 2 movement spindle 3 spindle nut 04 seal pair 05 piston spring 06 check valve 07 reservoir 08 vent connection 09 diaphragm 10 larger piston area 11 smaller piston area 12 shuttle valve 13 switching valve 14 drainage hole 15 line 00 assembly 01 axle side shaft 02 output shaft 03 multi-disk brake 04 brake piston bore

[0090] 305 drive motor

[0091] 306 spindle

[0092] 400, 401 connection connections

[0093] 402 electric drive

[0094] 403 planetary gear

[0095] 404 spindle

[0096] EM electric machine

Claims

Claims 1. Electric drive unit with an electric machine (EM) with a gearbox, which can be connected to an assembly (300) via a connection (401), wherein the assembly (300) comprises at least one multi-disk brake (303) each, which are arranged concentrically around axle side shafts (301), in a housing (25), wherein at least one brake piston (3) is hydraulically actuated and moves axially parallel to the axle side shafts (301) in a part of the housing (25) against movable discs and wherein the housing (25) and the multi-disk brakes (303) are supplied with cooling oil from the electric machine (EM) and the cooling circuit is sealed off from the brake circuit.

2. Electric drive unit according to claim 1, characterized in that the brake pistons (3) or a single annular piston are sealed against cooling oil via piston seals (17).

3. Electric drive unit according to claim 1, characterized in that the brake pistons (3) are sealed against cooling oil by a metal bellows (21).

4. Electric drive unit according to one of the preceding claims, characterized in that the assembly (300) is connected to hydraulic brake components (104) via brake lines (102) via a further connection (400).

5. Electric drive unit according to one of the preceding claims, characterized in that the assembly (300) comprises a quick-filling device (105).

6. Electric drive unit according to claim 5, characterized in that the quick-filling device (105) connected to the brake components (104) comprises at least one drive motor (305), a movement spindle (306), an axial piston (110) and a reservoir (207).

7. Electric drive unit according to claim 5, characterized in that the quick-filling device (105) generates the brake pressure with an axial piston drive (200), wherein the axial piston drive (200) consists of a drive motor (201), a movement spindle (202), a hydraulic piston with integrated spindle nut (203), a pair of seals (204) and a piston spring (205).

8. Electric drive unit according to claim 7, characterized in that the quick-filling device (105) comprises two electric motors (201), two movement spindles (202), one axial piston each (203) with a smaller and a larger piston surface (210, 211) and a reservoir (207), wherein the quick-filling device (105) is not connected to brake components (104).

9. Electric drive unit with an electric machine (EM) with a gearbox, which can be connected to an assembly (300) via a connection (401), wherein the assembly (300) comprises at least one multi-disk brake (303) each, which are arranged concentrically around axle side shafts (301), in a housing (25), wherein at least one brake piston (3) is electrically actuated and moves axially parallel to the axle side shafts (301) in a part of the housing (25) against movable discs (12) and wherein the housing (25) and the multi-disk brakes (303) are supplied with cooling oil from the electric machine (EM).

10. Method for heating an electric drive unit according to one of claims 1 to 9, wherein a control of the electric drive unit suspends recuperation during braking in a time window predetermined by the outside temperature and uses exclusively the multi-disk brakes (303) for braking.

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