Vehicle brake system

Abstract

The invention relates to a vehicle brake system for a vehicle axle of a two-track vehicle, which vehicle brake system comprises, for each vehicle side, a multi-disc brake or multi-disc clutch (3) which has an electrically controllable actuator (21) and by means of which a braking function for braking the vehicle during driving operation or a parking function when the vehicle is stationary can be engaged / disengaged in the multi-disc brake or multi-disc clutch (3). According to the invention, the vehicle brake system additionally comprises a parking lock (41), the locking pawl (43) of which can be brought into locking engagement with a locking gear (45). Each of the two actuators (21) is drivingly connected (50) to the locking pawl (43) such that, when the parking function is engaged by at least one of the actuators (21), the locking pawl (43) can be moved into locking engagement.

Description

[0001] AUDI AG

[0002] Vehicle braking system

[0003] DESCRIPTION:

[0004] The invention relates to a vehicle braking system according to the preamble of claim 1.

[0005] A vehicle braking system of this type features, instead of conventional disc or drum brakes, at least one multi-disc brake acting on the vehicle axle. This brake allows for the activation or deactivation of a braking function for vehicle braking during ferry operations or a parking function when the vehicle is parked. For this purpose, the multi-disc brake has two independently operating actuators: a brake actuator and a parking actuator. These are controlled by a control unit via electrical or hydraulic signals. For safety reasons, the brake actuator can be designed to be normally open (non-self-locking), while the parking actuator can be normally closed (self-locking). Integrating these two actuators into the multi-disc brake requires installation space and involves additional design effort.

[0006] DE 10 2014 102 831 A1 discloses a parking lock arrangement with a pawl and a cooperating locking gear. When the parking function is engaged, the pawl can be brought into locking engagement with the locking gear. EP 3 428 021 A1 discloses another parking lock arrangement that can be actuated by an electric motor.

[0007] The object of the invention is to provide a vehicle braking system that, compared to the prior art, can be implemented with reduced installation space and reduced design effort. This object is achieved by the features of claim 1. Preferred embodiments of the invention are disclosed in the dependent claims.

[0008] The invention relates to a vehicle braking system that has a multi-disc brake or clutch acting on a vehicle axle for each side of the vehicle. This clutch allows for the engagement / disengagement of a braking function for vehicle braking during operation and a parking function when the vehicle is parked. Each multi-disc brake or clutch is assigned exactly one electrically controlled actuator. The actuator can be used to engage or disengage either the braking function or, alternatively, the parking function. This results in a simplified braking concept compared to the prior art, with regard to cost, installation space, and component weight. For safety reasons, the electrically controlled actuator is normally open (i.e., not self-locking) when the braking function is engaged, while it is normally closed (i.e., self-locking) when the parking function is engaged.

[0009] According to the characterizing part of claim 1, the vehicle braking system additionally comprises exactly one parking lock, the pawl of which can be brought into locking engagement with a locking gear. The pawl is in drive connection with each of the two actuators, so that when the parking function is engaged by at least one of the actuators, the pawl can be adjusted into locking engagement.

[0010] The drive connection between the two actuators and the locking pawl is designed in such a way that the parking lock is only engaged, i.e., the locking pawl is returned from its locked position to its released position, if both actuators are engaged in the parking function.

[0011] Conversely, each actuator can engage the multi-plate clutch or brake and also actuate the pawl towards its locked position when the parking function is engaged. The parking lock can support the parking function engaged by the electrically controlled actuator. According to the invention, the parking function is therefore implemented not only by the electrically controlled actuator but also by the parking lock. The requirements for the electrically controlled actuator regarding holding torque are therefore reduced compared to a vehicle braking system without a parking lock. Alternatively, the parking function can also be implemented solely by means of the pawl.

[0012] In a technical implementation, the actuator can include at least one ball ramp unit. This unit allows the multi-disc brake or clutch to be subjected to contact pressure when the braking or parking function is engaged. Conversely, the multi-disc brake or clutch can be relieved of pressure when the braking or parking function is disengaged. The ball ramp unit consists of a pair of discs: one stationary and one rotatable coaxially. The ball can roll between the discs' inclined, facing brake ball tracks.

[0013] The braking function can be engaged as follows: An electric rotary drive (i.e., a spindle drive) of the actuator adjusts the rotatable disc from a neutral position in a braking direction by a braking angle into a braking range. This causes the ball to roll along the brake ball tracks, with axial spreading of the disc pair over a specific axial spreading path. In this way, the multi-disc brake / clutch is subjected to a contact pressure. This pressure varies depending on the size of the braking angle.

[0014] When the braking function is engaged, rolling resistance acts between the ball and the brake ball tracks of the disc pair. The low rolling resistance compared to a sliding system means that the ball-ramp unit is not self-locking, i.e., it remains open when de-energized. Therefore, in the event of a power failure, the actuator's braking effect automatically cancels out, thus fulfilling safety requirements.

[0015] Conversely, the clamping mechanism according to the invention is designed such that when the parking function is engaged, the actuator is self-locking, i.e., closed when de-energized. Therefore, in the event of a power failure, the parking function – unlike the braking function – is permanently maintained, so that the parking function also meets safety requirements.

[0016] The braking and parking functions can be implemented as follows: The ball-ramp unit can have corresponding, inclined sliding ramps. These are formed on both discs and can be brought into sliding contact with each other. To engage the parking function, the electric rotary drive (i.e., the spindle drive) of the actuator moves the rotatable disc from its neutral position in a parking direction opposite to the braking direction, over a parking rotation angle into a parking position. In the parking position, the sliding ramps of the two discs come into sliding contact, with the disc pair being axially spread by the axial spreading distance, thereby exerting a contact pressure on the multi-disc brake / clutch.

[0017] When the parking function is engaged, a sliding resistance acts between the corresponding sliding ramps of the discs. This is significantly greater than the rolling resistance between the ball and the brake ball tracks of the disc pair. Therefore, when the parking function is engaged, the ball-ramp unit is self-locking (unlike in the braking function), meaning it remains closed when de-energized. Thus, when the parking function is engaged, the braking effect can be maintained even in the event of a power failure.

[0018] To ensure reliable engagement of the parking function, the following measure is preferred: The parking position can be divided into a first section and a second section following the direction of rotation in the parking direction. In the first section, the ball can roll between the opposing parking ball tracks of the disc pair. In contrast, in the second section, the ball is out of contact with the disc pair. To engage the parking function, the rotating disc is moved from its neutral position in the direction of rotation by a parking angle into the first section until a transition point is reached. During this movement in the first section, the ball rolls on the parking ball tracks of the disc pair. This occurs with axial spreading of the disc pair over an axial spreading path. In this way, any play in the multi-disc brake / clutch is eliminated.Once the transfer point is exceeded, the rotating disc is adjusted in the second section with a continuously increasing parking rotation angle until the parking function is engaged.

[0019] During the adjustment process in the first section, the sliding surfaces of the two discs remain outside the sliding contact area. Only when the transition point is exceeded do the two sliding surfaces come into sliding contact with each other, while at the same time the ball comes out of rolling contact with the pair of discs.

[0020] The inclination angle of the two sliding ramps is preferably greater than the inclination angle of the parking ball tracks. This ensures that when the ball passes the transfer point, it reliably lifts off the parking ball tracks of the disc pair, meaning the ball is no longer in contact with the parking ball tracks. With the parking function engaged, this ensures that only the sliding resistance of the corresponding sliding ramps acts between the discs.

[0021] The parking ball tracks and the braking ball tracks can transition into each other in the circumferential direction of the disc at a ramp recess. This defines the zero rotation position. The parking ball tracks can be designed to be mirror-symmetrical to the braking ball tracks with respect to the symmetry provided by the ramp recess. Starting from the zero rotation position, as the braking or parking rotation angle increases, the clearance of the multi-disc brake / clutch is first eliminated. Subsequently, a kiss point is reached at which the multi-disc brake / Z-clutch transmits a measurable or predefined torque. For reliable engagement of the parking function, it is preferred if the transition point is crossed shortly before reaching the kiss point in the parking range.

[0022] Operational reliability is further increased if, when the parking function is engaged, the ball (after lifting off the two parking ball tracks) remains in a predefined ball-freewheel position. In this ball-freewheel position, the ball can roll freely between the parking ball tracks of the disc pair, without any rolling contact.

[0023] The predefined ball freewheel position can be achieved, for example, as follows: Each of the parking ball tracks of the two discs, viewed in the direction of parking rotation, can end at a ball track outlet that forms a ball movement stop. When the parking function is engaged, the two ball track outlets, viewed in the circumferential direction of the disc, can be spaced apart by a ball freewheel, which defines the ball freewheel position. When the parking function is disengaged, the rotating disc is moved against the direction of parking rotation until it reaches the zero rotation position.

[0024] By providing the ball freewheel position, it is ensured that the ball comes into rolling contact with the parking ball tracks at least approximately at the transfer point and that the ball is in the ramp recess when the rotational zero position is reached.

[0025] A key feature of the invention is that the electrically controlled actuator not only controls the pressure mechanism acting on the multi-plate brake or clutch, but also additionally controls the pawl of the parking lock between a locking position, in which the pawl can be brought into locking engagement with the locking gear, and a release position, in which the pawl is out of locking engagement with the locking gear.

[0026] For simple pawl actuation, the rotatable discs of the two actuators are mechanically connected to the pawl. This connection is designed so that when at least one of the rotatable discs rotates into the park position, the pawl automatically engages. Conversely, when both rotatable discs rotate from the park position into the brake position, the pawl automatically engages.

[0027] In one specific embodiment, the vehicle axle can have an axle differential. Its output sides drive to the vehicle wheels via output shafts. A multi-plate brake or clutch is arranged on each output side, acting on the respective output shaft. The locking gear of the parking lock can, for example, be fixed to a differential housing of the axle differential. In this configuration, the parking lock is positioned at an axial distance from the respective multi-plate brake or clutch.

[0028] The mechanical connection formed between the respective rotating disc and the pawl can be realized in a structurally simple manner as follows: The pawl can be part of a two-armed lever arm that pivots about a pawl axis. This lever arm sits on a central lever arm shaft that rotates about a pawl axis and is aligned coaxially with the two parking lock shafts. The lever arm has a first lever arm, which forms the pawl, and a second lever arm opposite the pawl axis, whose end face furthest from the axis is coupled to a rocker element at a force application point.

[0029] On either side of the pawl, one of the parking lock shafts is arranged axially, aligned coaxially with the central pawl axis of rotation. The spatial position of the axes of rotation of the parking lock shafts and the pawl axis of rotation remains unchanged in all operating states of the parking lock. A control lever and an axially spaced drive lever are fixedly connected to each of the parking lock shafts. Each of the two control levers is in sliding contact with a control contour formed on the rotatable disc under spring preload. The two drive levers are each connected to a coupling point on the rocker element. Each of the two coupling points is spaced a distance of one lever arm length from the central force application point of the rocker element.

[0030] The point of force application of the rocker element can be implemented as a pivot point, around which the rocker element can rotate about a rocker axis oriented perpendicular to the pawl axis. Furthermore, the pawl is pre-tensioned towards the locking engagement by a spring element, which in turn pre-tensions both control levers towards the control contour by means of the spring element action.

[0031] An embodiment of the invention is described below with reference to the accompanying figures.

[0032] They show:

[0033] Figs. 1 to 14 show different views, which describe the structure and function of the vehicle braking system according to the invention.

[0034] Figure 1 shows an electrified vehicle axle with an electric motor EM and a gearbox. The electric motor EM is connected to a high-voltage battery (not shown). Conventional wheel disc or drum brakes are omitted from the vehicle axle. Instead, the vehicle axle has a multi-disc brake 3 on each side, by means of which vehicle braking can be performed. The vehicle axle also has a parking lock 41 (not shown in Figure 1 or 2), the construction and function of which will be described later with reference to Figures 9 to 14.

[0035] The electric motor EM is connected via its rotor shaft 5 and a reduction gear 7 to the input side of an axle differential 9. The output sides of the differential are connected to the vehicle wheels via output shafts 11. In Figure 1, the electric motor EM is mounted transversely in the vehicle axle. Accordingly, the rotor shaft 5 and the output shafts 11 are parallel to each other. Likewise, the multi-disc brakes 3 mounted in the vehicle axle are aligned parallel to each other in the transverse direction y of the vehicle.

[0036] Viewed in the transverse direction y of the vehicle, the axle has one of the multi-disc brakes 3 on each side of the vehicle. These can be controlled by an electronic control unit (not shown) to perform uniform or uneven braking at both vehicle wheels.

[0037] The reduction gear 7 is in close connection with an input-side axle differential gear 13. The axle differential gear 13 is fixedly connected to a rotating differential housing 15. As shown in Figure 1, with the multi-disc brakes 3 open, the axle differential 9 drives in the transverse direction y of the vehicle in a 50 / 50 distribution to both output shafts 11 leading to the vehicle wheels.

[0038] In Figure 1, the two multi-disc brakes 3 act directly on the output shafts 11. This means that the inner disc carrier 18 of the multi-disc brake 3 is connected to the respective output shaft 11, while the outer disc carrier 17 is fixed to a gearbox housing wall 19. The disc assembly located between the outer disc carrier 17 and the inner disc carrier 18 can be subjected to contact pressure via an actuator 21. The two actuators 21 can be controlled by the control unit using electrical signals.

[0039] One of the actuators 21 is shown in Figures 2 to 3c. This actuator consists of a spindle drive (not shown) with an electric motor, which is connected to a toothed section 31 of a rotatable disc 27. The rotatable disc 27, together with a non-rotating disc 25, forms part of a clamping mechanism. The non-rotating disc 25 can be supported circumferentially by an indicated torque support 14. The non-rotating disc 25 is also supported axially on a counter support 12. The clamping mechanism has a total of four circumferentially distributed ball-ramp units 23, as shown in Figures 3a to 3b. Each ball-ramp unit 23 has a ball 29 that rolls between the two discs 25 and 27.

[0040] The lamella assembly located between the outer lamella carrier 39 and the inner lamella carrier can be subjected to contact pressure by means of the actuator 21. Depending on the control of the actuator 21, a braking function for vehicle braking during ferry operation, or alternatively a parking function when the vehicle is parked, can be engaged or disengaged. A key aspect of the invention is that both the braking function and the parking function can be engaged / disengaged by means of the actuator 21. For safety reasons, the electrically controlled actuator 21 is normally open (i.e., not self-locking) when the braking function is engaged. In contrast, the electrically controlled actuator 21 is normally closed (i.e., self-locking) when the parking function is engaged.

[0041] As can be seen from Figures 3a to 3c, each of the ball-ramp units 23 has ball ramps 34 and spaced-apart sliding ramps 38 that act between the disks 25, 27. The balls 29 of the four ball-ramp units 23 are guided in a cage 30, as shown in Figure 3b. In Figures 4a and 4b, one of the ball-ramp units 23 is shown in its developed form. Figure 4a shows two corresponding sliding ramps 38 of the disk pair, while Figure 4b shows two corresponding ball ramps 34 of the disk pair with an intermediate ball 29. Each of the ball ramps 34 consists of a braking ball track 35 and a parking ball track 37, which merge into one another at a ramp recess 39. In Figure 4a, the ball 29 is located in the ramp recess 39. The ramp recess 39 defines a rotation zero position 0, in which the disc pair exerts no contact pressure on the lamella pack.The ball ramps 34 of the two discs 25, 27 are point-symmetrical to each other with respect to the ball 29. Furthermore, the parking ball track 37 and the braking ball track 35 of each ball ramp 34 are symmetrical to each other with equal inclination angles with respect to an axis of symmetry passing through the ramp recess 39.

[0042] A key feature of the invention is that, depending on the direction of rotation DB, DP of the rotatable disc 27, either a braking function for vehicle braking during ferry operation or, alternatively, a parking function when the vehicle is parked can be engaged or disengaged. An important aspect of the invention is that the disc pair of the actuator 21 is open when de-energized, i.e., not self-locking, when the braking function is engaged. In contrast, the disc pair of the actuator 21 is closed when de-energized, i.e., self-locking, when the parking function is engaged.

[0043] Figures 4a and 4b show the pair of disks in their zero-rotation position 0. In the zero-rotation position 0, the two sliding ramps 38 are out of contact (unlike in Figure 4a). According to Figure 4b, the ball 29 is located in the ramp recesses 39 of the ball ramps 34 of the two disks 25, 27.

[0044] The engagement of the brake function is described below with reference to Figures 5a to 6b. Starting from the zero position 0 shown in Figures 4a and 4b, the rotatable disc 27 is moved to the left in a braking direction DB via a braking rotation angle into a braking adjustment range SB. This causes the ball 29 to roll on the two brake ball tracks 35 of the disc pair, with axial spreading of the disc pair via an axial spreading path s. In this way, the disc pack of the multi-disc brake 3 is subjected to contact pressure. The contact pressure varies depending on the size of the braking rotation angle. Immediately after leaving the zero position 0, the rotatable disc 27 is moved by an axial spreading path s, thereby eliminating any play in the disc pack.Further rotation of the rotatable disc 27 within the brake adjustment range SB results in a kiss point KP (Figure 5b) at which the multi-disc brake 3 transmits a measurable, predefined torque. At the kiss point KP, the rotatable disc 27 (starting from the zero rotation position 0) is rotated by a first axial displacement Asi. In Figures 6a and 6b, the rotatable disc 27 is adjusted to an end position in which it is rotated by a second axial displacement AS2.

[0045] When the braking function is engaged, a comparatively low rolling resistance acts between the ball 29 and the brake ball tracks 35 of the disc pair. This low rolling resistance means that the ball-ramp units 23 are not self-locking, i.e., they remain open when de-energized. Accordingly, in the event of a power failure, the braking effect of the actuated actuator 21 would decrease, thus fulfilling safety requirements.

[0046] To activate the brake function, the rotatable disc 27 (starting from its end position (Figures 6a and 6b) is moved back to the zero position 0 (Figures 4a and 4b) in the opposite direction to the brake rotation DB.

[0047] During the adjustment movement in the brake adjustment range SB, the corresponding, inclined sliding ramps 38 remain out of contact with each other, so that smooth rotary adjustment of the rotatable disc 27 is ensured.

[0048] The engagement of the parking function is described below with reference to Figures 7a to 8b. Starting from the zero position 0 shown in Figures 4a and 4b, the rotatable disc 27 is rotated to the right in a parking direction Dp, opposite to the brake direction DB, via a parking angle into a parking position SP.

[0049] According to Figure 7b, the parking area SP is divided into a first sub-area SPI and a second sub-area SP2. In the first sub-area SPI, the ball 29 rolls between the facing parking ball tracks 37 of the disc pair, while the corresponding sliding ramps 38 are still out of sliding contact. In contrast, in the second sub-area SP2, the sliding ramps 38 are in sliding contact with each other, while the ball 29 is out of rolling contact with the disc pair. To engage the parking function, the rotatable disc 27 is moved from the zero rotation position 0 in the parking rotation direction Dp by a parking rotation angle into the first sub-area SPI until a transfer point U is reached, as indicated in Figures 7a and 7b. According to Figures 7a and 7b, the disc pair generates a third axial spreading path Ass. at the transfer point U.

[0050] During the adjustment movement in the first section SPI, the ball 29 rolls on the parking ball tracks 37 of the disc pair, with axial spreading of the disc pair, thus eliminating any play in the lamellar brake 3. Upon passing the transfer point U, the rotatable disc 27 is rotated into the second section SP2 with a further increasing parking rotation angle until the parking function is engaged.

[0051] To ensure reliable engagement of the parking function, the transfer point U located in the parking position SP is positioned between the rotational zero position 0 and the kiss point KP. When engaging the parking function, the transfer point U is therefore passed shortly before reaching the kiss point KP. Upon reaching the kiss point KP, the two corresponding sliding ramps 38 are already in sliding contact with each other, while the ball 29 is out of rolling contact with the two parking ball tracks 37.

[0052] In Figures 8a and 8b, the rotatable disc 27 is rotated to its parked end position, in which the parking function is fully engaged. With the parking function engaged, the ball 29 is in a predefined ball-freewheel position P (Figure 8b). The ball-freewheel position P is defined in Figure 8b by means of ball track exits 41 of the parking ball tracks 37. With the parking function engaged, the ball track exits 41 are spaced apart in the disc's circumferential direction by a ball-freewheel f, in which the ball 29 rolls with play, i.e., without rolling contact, between the parking ball tracks 37 of the disc pair. The contact pressure of the disc pair is therefore generated exclusively by means of the sliding ramps 38 in sliding contact. To engage the parking function, the rotatable disc 27 is turned back in the opposite direction of rotation Dp to the zero rotation position 0.The ball 29 remaining in the ball-freewheel position P ensures that the ball 29 comes into rolling contact with the parking ball track 37 at least approximately at the transfer point U and is again in the ramp recess 39 when the rotation zero position 0 is reached.

[0053] A key aspect of the invention is that the vehicle braking system, as shown in Figures 9 to 14, additionally includes a parking lock 41, which consists of a pawl 43 and a cooperating locking gear 45, which, as shown in Figure 9, is connected to the differential housing 15. When the parking function is engaged, the pawl 43 can be brought into locking engagement with the locking gear 45, whereby the parking lock 41 assists the electrically controlled actuators 21 when the parking function is engaged.

[0054] The pawl 43 and the actuator 21 are motionally coupled to each other via a drive connection 50. They are constructed as follows: The pawl 43 is part of a two-armed lever arm 61 (Figure 10) that pivots about a pawl axis of rotation A1. The lever arm 61 is mounted on a central lever arm shaft that rotates about the pawl axis of rotation A1 and is aligned coaxially with the two parking lock shafts 47. The lever arm 61 has a first lever arm, which forms the pawl 43, and a second lever arm 63 opposite the pawl axis of rotation A1. The second lever arm 63 is coupled at its end face furthest from the axis to a rocker element 67 at a force application point 65.

[0055] On either side of the pawl 43, one of the parking lock shafts 47 is arranged axially, aligned coaxially with the central pawl pivot axis A1. The spatial position of the pivot axes of the parking lock shafts and the pawl pivot axis A1 remains unchanged in all operating states of the parking lock 41. A control lever 49 and an axially spaced drive lever 69 are fixedly connected to each of the parking lock shafts 47. Each of the two control levers 49 is in sliding contact with a control contour 53 formed on the rotatable disk 27 under spring preload. The two drive levers 69 are each connected to a coupling point 71 on the rocker element 67. As shown in Figure 9, each of the two coupling points 71 is spaced from the central force application point 65 of the rocker element 67 by a lever arm length h, I2.

[0056] The force application point 65 is realized in Figure 10 as a pivot point at which the rocker element 67 can rotate about a rocker pivot axis A2 (Figure 10), which is aligned perpendicular to the pawl pivot axis A1. Furthermore, the pawl 43 is biased towards the locking engagement by a spring element 51 (indicated only by an arrow in Figure 10), whereby the two control levers 49 are biased towards the control contour 53 by means of the spring element action.

[0057] In Figures 10 and 11, the control contour 53 has a recess or a small-diameter contour section 55, which transitions at a transition flank 57 into a larger-diameter contour section 59. In Figure 11, the control lever 49 is in sliding contact with the larger-diameter contour section 59, directly adjacent to the transition flank 57. As can be seen in Figure 11, each of the balls 29 is in its zero-rotation position 0. When the rotatable disc 27 rotates into the brake adjustment range SB (a counterclockwise rotation according to Figure 11), the control lever 49 remains in sliding contact with the larger-diameter contour section 59. Accordingly, the pawl 43 also remains disengaged from the pawl gear 45.

[0058] Figures 12 to 14 show the drive connection 50 in different operating states from a viewing direction B indicated in Figure 10. In Figure 12, the parking lock 41 is shown. When the parking function is engaged correctly, the two control levers 49 move synchronously, as indicated in Figure 14. In this case, the two pivot levers 49 are pivoted into the small-diameter contour sections 55 of the control contour 53 of the rotatable disks 27. The force application point 65 is therefore shifted upwards by a full pivot travel hvoii due to the lever arm ratios h, I2 (Figure 9). Accordingly, the pawl 43 comes into full tooth engagement Zvoii with the locking gear 45.

[0059] Figure 13 illustrates an incorrect engagement of the parking function, in which only the left control lever 49 pivots into the smaller diameter contour section 55 of the control contour 53 of the rotatable disc 27, while the right control lever 49 incorrectly remains in contact with the larger diameter contour section 59 of the control contour 53 of the rotatable disc 27. In this case, the force application point 65 (starting from the designed state according to Figure 12) is only shifted upwards by a reduced pivot travel hred due to the lever arm ratios h, l2. However, the reduced pivot travel hred is still large enough that the pawl 43 comes into partial tooth overlap Zred with the locking gear 45. The parking lock function can therefore be engaged even with only one functioning control lever 49.

[0060] When the parking function is correctly engaged, the two control levers 49 move synchronously. The force application point 65 is therefore moved back by the full pivot travel hvoii. This completely disengages the pawl 43 from the locking gear 45. If the parking function is incorrectly engaged, the movement occurs only in one of the two control levers 49. In this case, due to the lever arm ratios h, I2, the force application point 65 is only moved by the reduced pivot travel hred. However, the reduced pivot travel hred is insufficient to disengage the pawl 43 from the locking gear 45. Instead, the pawl 43 and the locking gear 45 remain in reduced tooth engagement Zred. Therefore, the parking function remains engaged in the event of a fault. Only when both pivot levers 49 are moved can the tooth overlap between the pawl 43 and the locking gear 45 be removed.Furthermore, during a rotational movement of the rotatable disc 27 from the zero rotation position 0 shown in Figure 11 to the park position SP (a clockwise rotation according to Figure 11), the following two cases can occur: In the first case, the control lever 49 slides from the larger diameter contour section 59 into the transition flank 57, causing the pawl 43 to come into tooth-to-tooth contact with the locking gear 45. Therefore, during a further rotation of the rotatable disc 27, the control lever 49 no longer slides along the transition flank 57 to the smaller diameter contour section 55, but instead lifts off the control contour 53. Only when the vehicle continues to roll does the pawl 43 engage with the locking gear 45, so that the parking lock 41 is engaged and the control lever 49 comes back into contact with the small diameter contour section 55.In the second case, the pawl 43 comes into contact with the pawl gear 45 immediately after the rotation of the rotatable disk 27 begins. The pawl 43 is therefore engaged immediately, while the control lever 49 slides along the transition flank 57 to the small-diameter contour section 55.

[0061] REFERENCE MARK LIST:

[0062] 3-disc brake

[0063] 5 Rotor shaft

[0064] 7 reduction gears

[0065] 9 axle differential

[0066] 11 Output shaft

[0067] 12 Counterholds

[0068] 13 Axle differential gear

[0069] 14 Torque support

[0070] 15 Differential housings

[0071] 17 outer slat carriers

[0072] 18 internal slat carriers

[0073] 19 Gearbox housings

[0074] 21 Actuator

[0075] 23 Ball Ramp Unit

[0076] 25 fixed disc

[0077] 27 rotating disc

[0078] 29 balls

[0079] 30 cage

[0080] 31 Gearing

[0081] 34 Ball Ramp

[0082] 35 Brake ball track

[0083] 37 Park Ball Track

[0084] 38 sliding ramps

[0085] 39 Ramp pen recess

[0086] 41 Parking restrictions

[0087] 43 Locking pawl

[0088] 45 Locking gear

[0089] 47th wave of parking restrictions

[0090] 49 Control levers

[0091] 50 instinctual connection

[0092] 51 spring

[0093] 53 Control contour 55 Diameter smaller contour section

[0094] 57 Transition flank

[0095] 59 diameter contour section

[0096] 61 two-armed lever arm

[0097] 63 second lever arm

[0098] 65 Force application point

[0099] 67 rocker element

[0100] 69 Drive lever

[0101] 71 coupling point

[0102] A1 pawl pivot axis

[0103] A2 rocker element pivot axis

[0104] B Viewing direction h, I2 Lever arm lengths hi full swivel range hred reduced swivel range

[0105] Zvoii complete tooth coverage

[0106] Zred reduced tooth coverage

[0107] 0 Rotation zero position

[0108] U handover point

[0109] KP Kisspoint

[0110] P Ball freewheel position

[0111] I1, I2 Lever arms s Axial spreading path

[0112] SB brake adjustment range

[0113] SP Park parking area

[0114] SRI, SP2 sub-areas

[0115] DB Brake Direction of Rotation

[0116] Dp Park direction of rotation f ball freewheel

Claims

PATENT CLAIMS:

1. Vehicle braking system for a vehicle axle of a two-track vehicle, which has a multi-disc brake or clutch (3) for each side of the vehicle with an electrically controllable actuator (21) with which a braking function for vehicle braking during ferry operation or a parking function when the vehicle is parked can be engaged / disengaged in the multi-disc brake or clutch (3), characterized in that the vehicle braking system additionally has a parking lock (41) whose pawl (43) can be brought into locking engagement with a locking gear (45), and that each of the two actuators (21) is in drive connection (50) with the pawl (43), so that when the parking function is engaged by at least one of the actuators (21), the pawl (43) can be adjusted into locking engagement.

2. Vehicle braking system according to claim 1, characterized in that the drive connection (50) between the two actuators (21 ) and the pawl (43) is designed such that the release of the parking lock (41), i.e., the return of the pawl (43) from its locking position to its release position, only occurs under the condition that both actuators (21 ) are in the parking function.

3. Vehicle according to claim 1 or 2, characterized in that each of the actuators (21 ) engages the multi-plate clutch or brake (3) and also moves the pawl (43) towards its locking position when the parking function is engaged, or that each of the actuators (21 ) disengages the multi-plate clutch or brake (3) and also moves the pawl (43) towards its release position when the parking function is disengaged.

4. Vehicle according to claim 1, 2 or 3, characterized in that Each of the actuators (21) has a pressure mechanism acting on the multi-disc brake or clutch (3), and in particular the pressure mechanism consists of a pair of discs comprising a stationary disc (25) and a disc (27) rotatable coaxially thereto, and in particular for engaging the brake function an electric rotary drive of the actuator (21) adjusts the rotatable disc (27) from a zero rotation position (0) in a brake rotation direction (DB) via a brake rotation angle into a brake setting range (SB), and in particular for engaging the park function the rotatable disc (27) is adjustable from the zero rotation position (0) in a park rotation direction (Dp) opposite to the brake rotation direction (DB) into a park setting range (SP).

5. Vehicle according to claim 4, characterized in that for a pawl actuation the rotatable disc (27) of each of the two actuators (21) is in drive connection (50) with the pawl (43), so that when at least one of the rotatable discs (27) is rotated into the park position (SP) the pawl (43) can be automatically brought into the locked position, and that when the two rotatable discs (27) are rotated from the park position (SP) into the brake position (SB) the pawl (43) can be automatically brought into the release position.

6. Vehicle according to one of the preceding claims, characterized in that the vehicle axle has an axle differential (9) whose output sides drive to the vehicle wheels via output shafts (11), and that a multi-plate brake or clutch (3) acts on the respective output shaft (11) on each output side, and / or that the locking gear (45) of the parking lock (41) is rotationally fixed to an axle differential housing (15), and / or that the parking lock (41) is arranged at an axial distance to the respective multi-plate brake or clutch (3).

7. Vehicle according to claim 5 or 6, characterized in that the drive connection (50) formed between the rotatable disc (27) and the pawl (43) has a parking lock shaft (47) to which a control lever (49) and the pawl (43) axially spaced therefrom are rotatably connected, and that the control lever (49), in particular under spring preload, is in sliding contact with a control contour (53) formed on the rotatable disc (27).

8. Vehicle according to one of claims 4 to 7, characterized in that the pressure mechanism acting on the multi-disc brake or clutch (3) has at least one ball-ramp unit (23) with which the multi-disc brake or clutch (3) can be subjected to pressure when the brake function or parking function is engaged and can be pressure-relieved when the brake or parking function is disengaged, and in particular that the ball-ramp unit (23) has a ball (29) which rolls between mutually facing, inclined ball tracks (35, 37) of the disc pair, and in particular that when the brake function is engaged the ball (29) rolls on brake ball tracks (35), whereby the disc pair is axially spread over an axial spreading path (s) in order to subject the multi-disc brake / clutch (3) to pressure which varies depending on the size of the brake rotation angle.

9. Vehicle according to claim 8, characterized in that when the braking function is engaged, a rolling resistance acts between the ball (29) and the brake ball tracks (35) of the disc pair, and in particular the rolling resistance causes the ball-ramp unit (23) to not be self-locking, i.e. it is open when de-energized, so that in particular the braking effect of the actuator (21) is cancelled in the event of a power failure.

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