Vehicle braking system

Abstract

The invention relates to a vehicle braking system with a multi-disc brake (7) by means of which a rotating transmission component, in particular an output shaft (17), can be braked during driving operation, wherein the multi-disc brake (7) is connected to a cooling / lubricating fluid circuit in which a cooling / lubricating fluid is circulated by a circulation pump (41) to cool the multi-disc brake (7). According to the invention, the braking system has a mechanical switching unit (51) which activates the circulation pump (41) when the brake is applied and deactivates the circulation pump (41) when the multi-disc brake (7) is not applied.

Description

[0001] The invention relates to a vehicle braking system with a multi-disc brake according to the preamble of claim 1.

[0002] A vehicle braking system of this type features multi-disc brakes instead of conventional wheel disc brakes, enabling vehicle braking. Each multi-disc brake is connected to a cooling / lubricating fluid circuit in which a pump circulates the fluid to cool the brake.

[0003] In the current state of the art, the circulation pump is activated not only when the multi-disc brake is applied, but also when the multi-disc brake is not applied. The coolant / lubricant pumped by the inactive multi-disc brake creates a drag torque. Furthermore, controlling the circulation pump's motor results in additional control and / or software complexity.

[0004] DE 10 2024 101 021 A1 discloses a vehicle braking system with a brake or clutch device. DE 10 2022 131 384 A1 discloses a vehicle braking system in which the inner or outer plates of a multi-disc brake are connected to the rotor of an electric machine in a torque-transmitting manner. DE 10 2020 214 433 A1 discloses a vehicle drive unit that has a cooling circuit in which a brake unit is integrated.

[0005] The object of the invention is to provide a vehicle braking system with a multi-disc brake in which, compared to the prior art, drag losses are avoided in a simple manner and / or the control or software effort in controlling the circulation pump is reduced.

[0006] The problem is solved by the features of claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.

[0007] The invention relates to a vehicle braking system with a multi-disc brake, by means of which a rotating transmission component, in particular an output shaft, can be braked during driving. The multi-disc brake is connected to a cooling / lubricating fluid circuit in which a cooling / lubricating fluid is circulated by a pump to cool the multi-disc brake. According to the invention, the following measures are taken to avoid drag losses and to reduce the control and software effort required for controlling the pump: The braking system has a mechanical switching unit that activates the pump when the brake is applied and deactivates it when the multi-disc brake is not applied.

[0008] To activate the circulation pump, the switching unit establishes a drive connection between the still-rotating transmission component to be braked and a pump drive shaft of the circulation pump. In this case, the still-rotating transmission component is also braked as a result of the activation of the mechanical circulation pump. Furthermore, no external energy is required to drive the circulation pump.

[0009] The multi-plate brake consists of the following components: an inner plate carrier fixed to the transmission component, an outer plate carrier fixed to a transmission housing, a plate pack arranged between the inner and outer plate carriers, and an actuator that applies pressure to the plate pack for brake actuation.

[0010] During vehicle braking, the actuator builds up contact pressure in the clutch pack, increasing the frictional engagement between the inner and outer clutch plates, while the inner clutch plate carrier continues to rotate due to slippage. When the vehicle is stationary, the contact pressure is sufficient to create a complete frictional engagement within the clutch pack.

[0011] In a specific embodiment, the invention utilizes the fact that the inner lamella carrier continues to rotate during vehicle deceleration: Accordingly, the slip-induced rotation of the inner lamellae occurring during the friction build-up phase can be transferred to the pump drive shaft via the drive connection established by the mechanical switching unit in order to activate the circulation pump.

[0012] To provide this drive connection, the switching unit has a drive plate arranged between two inner plates. The inner plates are axially adjustable on the inner plate carrier, but are guided against rotation. In contrast, the drive plate is not in a positive-locking connection with either the inner or outer plate carrier; that is, the drive plate can rotate freely with respect to both the inner and outer plate carriers.

[0013] During vehicle deceleration, a synchronization process occurs in which the drive plate is clamped between the two inner plates, i.e., synchronized with them. The inner plate carrier drives the pump drive shaft via this clamping connection. To create a structurally simple drive connection, the drive plate can be designed as a gear connected to the pump drive shaft via a gear stage.

[0014] In the coolant / lubricant circuit, a pressure line from the circulation pump can lead into a distribution chamber, which is radially bounded to the outside by the inner fin carrier. The coolant / lubricant can be injected into the distribution chamber. From there, the coolant / lubricant flows, driven by centrifugal force, through openings in the inner fin carrier into the fin pack. After passing through the fin pack, the coolant / lubricant is collected radially on the outside and returned to a pump sump, which is in flow connection with a suction line of the circulation pump.

[0015] An exemplary embodiment is described below with reference to the attached figures.

[0016] They show: Fig. 1 and Fig. 2 views each, illustrating the vehicle braking system according to the invention.

[0017] In the Fig. Figure 1 shows an electrified vehicle axle with an electric motor EM and a gearbox 3. The electric motor EM is connected to a high-voltage battery (not shown). Conventional wheel disc brakes are omitted from the vehicle axle. Instead, the vehicle axle has a braking system with multi-disc brakes 7, by means of which vehicle braking can be performed.

[0018] The electric machine EM is connected via its rotor shaft 9, through an intermediate reduction stage 11, to the input side of an axle differential 15. The output sides of the differential are driven via output shafts 17 to vehicle wheels (not shown). Fig. 1 The electric motor EM is installed transversely in the vehicle axle. Accordingly, the rotor shaft 9 and the output shafts 17 are parallel to each other along the axis. Likewise, the multi-disc brakes 7 installed in the rear axle are aligned parallel to each other along the transverse direction y of the vehicle.

[0019] Viewed in the transverse direction y of the vehicle, the axle has one of the multi-disc brakes 7 on each side of the vehicle. These can be controlled by an electronic control unit for uniform or uneven braking of the vehicle at both wheels.

[0020] The reduction gear 11 is driven in conjunction with an input-side axle differential gear 21. The axle differential gear 21 is rotationally fixed to a rotating differential housing 25. According to the Fig. 1 drives the axle differential 15 with the multi-plate brakes 7 open in the transverse direction y of the vehicle in a 50 / 50 distribution on both sides to the two output shafts 17 leading to the vehicle wheels.

[0021] In the Fig. 1. The two multi-disc brakes 7 each act directly on the output shafts 17. This means that each of the multi-disc brakes 7 is rotationally fixed to the respective output shaft 17 via its inner disc carrier 27, while the outer disc carrier 29 is rotationally fixed to a gearbox housing wall 31. The disc pack located between the outer disc carrier 29 and the inner disc carrier 27 is connected via a Fig. 2 indicated actuator 33 pressure-sensitive.

[0022] As from the Fig. As further shown in Figure 2, the lamellar pack of the lamellar brake 7 consists of a number of inner lamellae 35 and a number of outer lamellae 37, which are stacked alternately one behind the other in the axial direction. The inner lamellae 35 are axially displaceable but rotationally fixed on the inner lamella carrier 27, while the outer lamellae 37 are axially displaceable but rotationally fixed on the outer lamella carrier 29.

[0023] The actuator 33 consists of the Fig. 2 consists of a pair of discs with a rotationally fixed disc 39 and a rotatable loose disc 40, which are arranged axially to the multi-disc brake 7 and to the output shaft 17, respectively. A ball-ramp unit 43 acts between the fixed disc 39 and the loose disc 40. When the loose disc 40 is rotated (for example, by means of a spindle drive not shown), the pair of discs expands in the axial direction to apply the contact pressure to the multi-disc pack.

[0024] The multi-plate brake 7 is also integrated into a cooling / lubricating circuit in which a pressure line 42 of a circulation pump 41 opens into a distribution chamber 44, which is radially bounded to the outside by the inner plate carrier 27. The cooling / lubricant is injected from the pressure line 42 into the distribution chamber 44. From there, the cooling / lubricant flows into the plate pack through openings in the inner plate carrier due to centrifugal force. After passing through the plate pack, the cooling / lubricant is collected radially on the outside and returned to a pump sump 47. This sump is in flow connection with a suction line 49 of the circulation pump 41.

[0025] A key aspect of the invention is that the vehicle braking system has a mechanical switching unit 51 which activates the circulation pump 41 when the brake is applied and deactivates the circulation pump 41 when the multi-disc brake 7 is not applied. A particular aspect of the invention is that, to activate the circulation pump 41, the switching unit 51 establishes a drive connection between the output shaft 17 to be braked and a pump drive shaft 61 of the circulation pump 41.

[0026] The following describes the brake actuation of the multi-disc brake 7: The braking process begins with a building-up contact pressure, which is generated by the actuator 33 and acts on the multi-disc pack. The multi-disc pack is in the Fig. 2 is pressed by the actuator 33 against an axially opposite movement stop 55. As the contact pressure increases, a friction build-up phase occurs, resulting in vehicle deceleration or braking. During this phase, the frictional force between the inner and outer lamellae 35, 37 increases steadily. Due to slippage, the inner lamella carrier 27 still exhibits relative movement to the outer lamella carrier 29. Kinetic energy is converted into heat as the lamellae 35, 37 rub against each other due to the increasing contact pressure. Once the contact pressure is sufficiently high, the vehicle comes to a standstill, at which point complete frictional engagement is established within the lamella assembly.

[0027] According to the invention, the fact that the inner lamella carrier 27 continues to rotate during vehicle deceleration is utilized as follows: The mechanical switching unit 51 has a drive plate 57, which is arranged between two inner lamellae 35 at the end of the lamella pack facing the movement stop 55. The drive plate 57 is not positively engaged with either the inner lamella carrier 27 or the outer lamella carrier 29. Furthermore, the drive plate 57 is designed as a gear which is driven via a gear stage 59 into a pump drive shaft 61 of the circulation pump 41. The gear stage 59 consists of the Fig. 2 from the drive plate 57 and a fixed gear 63 arranged on the pump drive shaft 61.

[0028] During vehicle braking, a synchronization process occurs in which the drive plate 57 is positively clamped between the two inner plates 35 due to the increasing contact pressure, i.e., synchronized with the inner plates 35. As a result of this positive clamping connection, the inner plate carrier 27 drives the pump drive shaft 61. The mechanical switching unit 51 thus provides a drive connection between the still-rotating output shaft 17, which is being braked, and the pump drive shaft 61, specifically during vehicle deceleration. Accordingly, the circulation pump 41 is activated during vehicle deceleration to dissipate the generated waste heat. When the multi-plate brake is not applied or when the vehicle is stationary, the circulation pump 41 remains deactivated. REFERENCE MARK LIST: 3 gearboxes 7-disc brake 9 Rotor shaft 11th gear stage 15 axle differential 17 Output shaft 21 Axle differential gear 25 Differential housings 27 inner slat carriers 29 outer slat carriers 31 Gearbox housing wall 33 Actuator 35 inner slat 37 Outer slat 39 Fixed disk 40 Lottery wheel 41 Circulation pump 42 Pressure line 43 Ball Ramp Unit 44 Distribution room 45 passage 47 Pump sump 49 Suction line 51 mechanical switching unit 55 Movement stop 57 Drive plate 59 gear stage 61 Pump drive shaft 63 Fixed gear 65 heat exchangers EM electric machine H Heating circuit

Claims

Vehicle braking system with a multi-disc brake (7) by means of which a rotating transmission component (17) can be braked during driving operation, wherein the multi-disc brake (7) is connected to a cooling / lubricating medium circuit in which a cooling / lubricating medium is circulated by a circulating pump (41) for cooling the multi-disc brake (7), wherein the braking system has a mechanical switching unit (51) which activates the circulating pump (41) when the multi-disc brake (7) is applied and deactivates the circulating pump (41) when the multi-disc brake (7) is not applied, characterized in that, for the purpose of activating the circulating pump (41), the switching unit (51) establishes a drive connection between the still rotating transmission component (17) to be braked and a pump drive shaft (61) of the circulating pump (41). Vehicle braking system according to claim 1, characterized in that the multi-plate brake (7) comprises: - an inner plate carrier (27) fixed to the transmission component (17), - an outer plate carrier (29) fixed to a transmission housing (31), - a plate pack arranged between the inner and outer plate carriers (27, 29), and - an actuator (33) which applies contact pressure to the plate pack for brake actuation. Vehicle braking system according to claim 2, characterized in that during vehicle braking or vehicle deceleration, the contact pressure acts on the lamellar package while the inner lamellar carrier (27) is still rotating due to slippage, and that the slippage-induced inner lamellar rotation occurring during vehicle deceleration is transmitted to the circulation pump (41) via the drive connection established by the mechanical switching unit (51) in order to activate it. Vehicle braking system according to one of the preceding claims, characterized in that the switching unit (51) has a drive plate (57) which is arranged between two inner plates (35) which are axially adjustable but rotationally fixed on the inner plate carrier (27). Vehicle braking system according to claim 4, characterized in that the drive plate (57) is in addition to a positive locking connection with the inner plate carrier (27) and in addition to a positive locking connection with the outer plate carrier (29). Vehicle braking system according to claim 5, characterized in that a synchronization process takes place during vehicle braking, in which the drive plate (57) is synchronized with the inner plates (35) with increasing contact pressure, i.e. the drive plate (57) is clamped between the two inner plates (35) in a force-fit manner, so that the inner plate carrier (27) drives the circulation pump (41) via this force-fit clamping connection. Vehicle braking system according to claim 5 or 6, characterized in that during vehicle braking there is slip between the inner plates (35) and the outer plates (37) until the vehicle comes to a standstill, and that the synchronization process between the drive plate (57) and the inner plates (35) is completed at a significantly earlier time due to the low power consumption of the circulation pump (41). Vehicle braking system according to claim 5, 6 or 7, characterized in that the drive plate (57) is an integral part of the circulation pump (41), or that the drive plate (57) is designed as a gear which is connected to the pump drive shaft (61) via a gear stage (59). Vehicle braking system according to one of the preceding claims, characterized in that a pressure line (42) of the circulation pump (41) opens into a distribution chamber (44) in the coolant / lubricant circuit, which is radially bounded to the outside by the inner lamella carrier (27), and that the coolant / lubricant can be injected into the distribution chamber (44), and from there flows into the lamella pack through passages (45) in the inner lamella carrier (27) due to centrifugal force, and after flowing through the lamella pack is collected radially outside and returned to a pump sump (47) which is in flow connection with a suction line (49) of the circulation pump (41), and / or that a heat exchanger (65) is connected in the coolant / lubricant circuit, which can be thermally coupled to a heating circuit (H), and that waste heat generated by the multi-plate brake is transferred via the heat exchanger (65). is purulent.

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