Braking system for a vehicle and wheel brake device

Abstract

The invention relates to a braking system for a vehicle, preferably an electrically driven vehicle, comprising a brake (5) for at least one vehicle wheel (13). In a braking system, which forgoes an additional braking hydraulics system, the brake (5) is filled with a viscous fluid (9), bringing about friction in the brake, in order to generate a braking force, and the brake (5) filled with the viscous fluid (9) is arranged in an encapsulated container (3).

Description

[0001] Braking system for a vehicle and wheel braking device

[0002] The invention relates to a braking system for a vehicle, preferably an electrically driven vehicle, comprising a brake for at least one vehicle wheel and a wheel braking device.

[0003] DE-AS 1 215 013 describes a continuous brake for motor vehicles, particularly heavy trucks. A continuous brake uses a hydrodynamic brake mounted on a differential gear of a vehicle axle. A gear drive with high-speed transmission is located at the rim of the differential gear, which drives a rotor of the hydrodynamic brake to pump brake fluid. To regulate the braking power, an adjustable pumping tube pumps the brake fluid to a desired diameter. The braking effect is adjusted by the pressure of the brake fluid in the brake.

[0004] The object of the invention is to provide a braking system for a vehicle and a wheel braking device which do not require additional brake hydraulics.

[0005] The invention is based on the features of the independent claims. Advantageous developments and refinements are the subject of the dependent claims. Further features, possible applications, and advantages of the invention will become apparent from the following description and the explanation of exemplary embodiments of the invention, which are illustrated in the figure.

[0006] The problem is solved by the subject matter of patent claim 1.

[0007] The braking system explained above comprises a brake for at least one vehicle wheel to generate braking force. The brake is filled with a viscous fluid that creates friction in the brake, and the brake filled with the viscous fluid is arranged in an encapsulated container. By arranging the fluid in a completely sealed container, additional brake hydraulics are omitted, thereby reducing the overall volume and weight of the braking system. Since the brake acts by filling the brake with the viscous fluid due to the inertia occurring when the fluid moves, via fluid friction on its walls, the brake operates wear-free and does not release any particles into the environment. Replacing the viscous fluid is therefore not necessary.

[0008] Advantageously, the brake has a plurality of interlocking partition walls, wherein the viscosity of the fluid spreading between the partition walls is selected depending on the distance between the opposing partition walls.

[0009] The distance between the partition walls determines the fluid friction and thus the braking torque of the brake.

[0010] In one embodiment, the brake is arranged close to an electric drive unit of the wheel and is preferably an integral part of the drive unit. This allows for the production of a compact drive / brake unit that requires little installation space. Furthermore, positioning the brake close to the drive unit reduces the unsprung mass on the wheel side, which increases the vehicle's ride comfort.

[0011] In one variant, a gear is mounted on the drive unit, which is coupled to the electric drive unit and an auxiliary drive to trigger the braking effect. The auxiliary drive is responsible for initiating or preventing the braking effect.

[0012] A further aspect of the invention relates to a wheel brake device for a vehicle, comprising a brake arranged in a housing and filled with a viscous fluid, wherein the housing is connected in a rotationally fixed manner to a wheel shaft and the wheel shaft is drivable by a hollow shaft that is coupled to an electric drive unit. Such a wheel brake device does not require additional brake hydraulics, which reduces manufacturing costs. Since the housing, drive shaft, and output shaft rotate at the same speed during operation, there is zero braking torque when the brake is released, as no fluid friction occurs. The fluid friction, which is caused by the shearing effect in the viscous fluid, results in a speed difference between the wheel shaft and the hollow shaft, which triggers a braking effect on the wheel.

[0013] It is advantageous if a gear is located in the housing containing the brake, which is connected to an auxiliary drive via an auxiliary hollow shaft extending partially outside the hollow shaft to apply a deceleration force. Thus, the braking effect can be triggered by a simple design measure.

[0014] In one embodiment, the transmission is designed as a planetary gear transmission, the sun gear of which is coupled to the hollow shaft connected to the electric drive unit, while the housing carries the ring gear, and the planetary gear carrier is connected to the auxiliary hollow shaft actuated by the auxiliary drive. Planetary gear transmissions are well-known and are mass-produced in large quantities. This makes them particularly cost-effective, which reduces the manufacturing costs of the wheel brake device.

[0015] In one variant, the brake has several interlocking partition walls, with the viscosity of the fluid spreading between the partition walls being selected depending on the distance between the opposing partition walls. The interlocking partition walls increase the effective surface area for fluid friction in a small installation space, thereby increasing the performance of the wheel brake device.

[0016] In one embodiment, the coaxially arranged shafts are rotatably supported relative to each other and / or the housing. This allows all shafts and the housing to be rotated relative to each other as desired, which supports the functionality of the wheel brake device in a small installation space.

[0017] Advantageously, the planetary gear is mounted on the housing in a rotationally fixed manner via a clutch coupled to the auxiliary hollow shaft. This allows electrically powered vehicles to operate in unbraked cruising mode, with the vehicle's high-voltage electric drive in recuperation mode. This is particularly important when driving downhill. Advantageously, the driven wheel is aerodynamically designed. This is possible because there is no need to cool the wheel brakes. The vehicle thus has a longer range and better efficiency.

[0018] Further advantages, features, and details will become apparent from the following description, in which at least one exemplary embodiment is described in detail—possibly with reference to the drawings. Described and / or illustrated features may form the subject matter of the invention alone or in any meaningful combination, possibly independently of the claims, and may, in particular, also be the subject of one or more separate applications. Identical, similar, and / or functionally equivalent parts are provided with the same reference numerals.

[0019] It shows:

[0020] Fig. 1 shows an embodiment of the braking system according to the invention with a wheel braking device.

[0021] Fig. 1 shows an embodiment of a vehicle braking system in the form of a wheel brake device. The wheel brake device 1 comprises a housing 3 in which the brake 5 and a gear 7 are arranged. The housing 3 is completely filled with a viscous fluid 9 and completely sealed from the environment, so that the viscous fluid 9 cannot escape. The brake 5 consists of several interlocking lamellae 11, forming comb-like partition walls, between which the viscous fluid 9 expands.

[0022] The brake 5 is connected in a rotationally fixed manner to a solid wheel shaft 15 driving a wheel 13 of the vehicle. The housing 3 is rotatably mounted on the solid wheel shaft 15 by means of a rolling bearing. A hollow shaft 19, which is driven by an electric drive unit 17, extends around the solid wheel shaft 15. The hollow shaft 19 is coupled to the sun gear 21 of a planetary gear train 23, the ring gear 25 of which is carried by the housing 3. The planet gear carrier 27 of the planetary gear train 23 is connected to an auxiliary hollow shaft 29, which in turn surrounds the hollow shaft 19 and can be driven in a braking manner by an electromechanically actuated auxiliary brake 31. The solid wheel shaft 15, the hollow shaft 19, and the auxiliary hollow shaft 29 are supported against each other and against the housing 3 by the rolling bearings 33 and form a coaxial system.When the vehicle is in operation, a torque generated by the electric drive unit 17 is transmitted from the hollow shaft 19, designed as an output shaft, to the solid wheel shaft 15, thereby driving a wheel 13. The solid wheel shaft 15 rotates at the speed of the hollow shaft 19. The speed difference is zero. When braking, which is triggered by the driver of the vehicle pressing a brake pedal or by a signal automatically generated by the braking system, the planet gear carrier 27 is decelerated by means of the auxiliary brake 31. Deceleration occurs when the auxiliary brake 31 is activated by the brake signal. The deceleration torque is transmitted via the auxiliary hollow shaft 29 to the planet gear carrier 27 of the planetary gear train 23. The viscous fluid expanding between the plates 11 creates fluid friction on the plates, which slows down the rotational movement of the wheel shaft 15.This creates a differential speed between the wheel shaft 15 and the housing 3, which leads to the formation of a braking torque between the hollow shaft 19 and the solid wheel shaft 15, whereby the wheel 13 is braked.

[0023] By means of a clutch 35 arranged within the housing 3, the first clutch disc 37 of which is connected to the auxiliary hollow shaft 29 and the second clutch disc 39 of which is connected in a rotationally fixed manner to the housing 3, the planetary gear carrier 15 is firmly coupled to the housing 3 during driving operation of the electric-driven vehicle. Thus, the vehicle can continue to roll without being decelerated.

Claims

Braking system for a vehicle, preferably an electrically powered vehicle, comprising a brake (5) for at least one vehicle wheel (13), characterized in that the brake (5) is filled with a viscous fluid (9) that creates friction in the brake (5) to generate a braking force, and the brake (5) filled with the viscous fluid (9) is arranged in an encapsulated container (3). Braking system according to claim 1, characterized in that the brake (5) has several interlocking partition walls (11), the viscosity of the fluid (9) spreading between the partition walls (11) being selected depending on the distance between the opposing partition walls (11). Braking system according to claim 1 or 2, characterized in that the brake (9) is arranged close to an electric drive unit (17), preferably being an integral part of the drive unit (17).Braking system according to at least one of the preceding claims, characterized in that a gear (23) is arranged on the drive unit (17), which is coupled to the electric drive unit (17) and an auxiliary drive (31) to trigger the braking effect. Wheel brake device for a vehicle, comprising a brake (5) arranged in a housing (3) and filled with a viscous fluid (9), wherein the housing (3) is connected in a rotationally fixed manner to a wheel shaft (15), wherein the wheel shaft (15) is drivable by a hollow shaft (19) coupled to an electric drive unit (17). Wheel brake device according to claim 5, characterized in that a gear (23) is positioned in the housing (3) enclosing the brake (5), which gear is connected to an auxiliary drive (31) via an auxiliary hollow shaft (29) extending partially outside the hollow shaft (19) for applying a deceleration force.Wheel brake device according to claim 5 or 6, characterized in that the transmission is designed as a planetary gear transmission (23), the sun gear (21) of which is coupled to the hollow shaft (19) connected to the electric drive unit (17), while the housing (3) carries its hollow gear (25), and the planetary gear carrier (27) is connected to the auxiliary hollow shaft (29) actuated by the auxiliary drive (31). Wheel brake device according to claim 5, 6, or 7, characterized in that the brake (5) has a plurality of intermeshing intermediate walls (11) in a comb-like manner, wherein the viscosity of the fluid (9) spreading between the intermediate walls (11) is selected depending on the distance between the opposing intermediate walls (11). Wheel brake device according to at least one of the preceding claims 5 to 8, characterized in that the coaxially extending shafts (15, 19, 29) are rotatably supported relative to one another and / or relative to the housing (3). Wheel brake device according to at least one of the preceding claims 5 to 9, characterized in that the planetary gear (23) is mounted in a rotationally fixed manner on the housing (3) in drive-free driving operation via a state of the clutch (35) coupled to the auxiliary hollow shaft (29).

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