Friction braking system for vehicles

Abstract

This application relates to a friction braking system for a vehicle. The proposed friction braking system includes a first gear unit having a first component and a second component. The first gear unit is configured to convert rotational motion of the first component into braking motion of the second component. Furthermore, the first component is configured such that the rotational motion can be driven by an electric motor. The braking system also includes a second gear unit having a spindle and a nut for converting the rotational motion into linear motion for brake pad wear compensation. The spindle can be connected to a brake pad. The second component of the first gear unit and the nut of the second gear unit are or can be mechanically connected such that during braking motion, the second component of the first gear unit pushes against the nut of the second gear unit to press the brake pad against a friction surface. Furthermore, the first gear unit and the second gear unit are or can be arranged such that the second gear unit at least partially penetrates the first gear unit.

Description

Technical Field

[0001] This application relates to a friction braking system for a vehicle. Specifically, this application relates to a friction braking system having a gear unit for converting rotational motion into braking motion and a gear unit for converting rotational motion into linear motion for liner wear compensation. Background Technology

[0002] Various friction braking systems for vehicles are known. For example, a motor vehicle braking system (such as a brake-by-wire system) may include a master cylinder and piston arrangement that can be actuated by a brake pedal to compress hydraulic fluid. A pedal travel sensor may be coupled to the brake pedal to detect the amount of brake pedal travel. A corresponding signal may be sent to a controller that can control a pressure supply device based on the amount of brake pedal travel. The pressure supply device is hydraulically coupled to the wheel brakes. Furthermore, a pedal feel simulator coupled to the output of one of the master cylinders can be provided to mimic the feel of the hydraulic connection between the brake pedal and the wheel brakes. Additionally, as a backup mode, the master cylinder can communicate directly with the wheel brakes in the event of a failure, such that actuation of the brake pedal directly causes braking. For example, related prior art is described in document US2014 / 0159473A1. Other friction braking systems may include an electric motor for actuating the wheel brakes during normal operation. These systems may have a gear unit for converting the rotational motion generated by the electric motor into braking motion, in which brake pads are pushed against the brake disc. Furthermore, friction braking systems may include mechanisms for compensating for pad wear. However, the encapsulation of brake calipers can be more challenging than that of rear wheels, especially for the front wheels which are typically used to steer the vehicle, because interference with other components is more difficult to avoid. Summary of the Invention

[0003] In view of the foregoing, one object of this application is to provide an improved friction braking system for vehicles. The proposed friction braking system is designed to ensure reliable operation and is particularly suitable for installation in challenging spaces, especially when used with the front wheels of a vehicle.

[0004] The stated objective is achieved through a friction braking system having the features of the first aspect. Further optional features and further developments will become apparent from the other aspects and the detailed description in conjunction with the accompanying drawings.

[0005] The proposed friction braking system for a vehicle includes a first gear unit having a first component and a second component. The first gear unit is configured to convert rotational motion of the first component into braking motion of the second component. Furthermore, the first component is configured such that the rotational motion can be driven by an electric motor. The braking system also includes a second gear unit having a spindle and a nut for converting the rotational motion into linear motion for brake pad wear compensation. The spindle can be connected to the brake pad. The second component of the first gear unit and the nut of the second gear unit are or can be mechanically connected such that during braking motion, the second component of the first gear unit pushes against the nut of the second gear unit to press the brake pad against a friction surface. Furthermore, the first and second gear units are or can be arranged such that the second gear unit at least partially penetrates the first gear unit.

[0006] The proposed friction braking system allows for reliable braking operation while being particularly robust and very compact. Therefore, it is particularly suitable for installation in challenging spaces where undesirable interference with other vehicle components (e.g., with the vehicle's drive shaft) is possible. A particularly suitable application for the proposed friction braking system is for the front wheels of a vehicle, as the space available for installation can be particularly limited due to the steering mechanism coupled to the front wheels. Therefore, electromagnetic braking systems coupled to the front wheels typically require short actuators, making the proposed friction braking system particularly suitable.

[0007] The braking motion of the second component of the first gear unit is typically linear. The braking motion can be the motion that achieves braking during normal operation (e.g., in online control braking mode). The first gear unit is typically configured to perform normal braking, while the second gear unit is configured for liner wear compensation. The proposed friction braking system enables separate braking and liner wear compensation operations with independent stroke lengths. Typically, the stroke achieved by the first gear unit is less than the stroke achieved by the second gear unit. For example, the stroke achieved by the first gear unit can be at least 1 mm and / or at most 4 mm, such as 2 mm. The stroke achieved by the second gear unit can be at least 10 mm and / or at most 40 mm, such as 20 mm. Typically, the nut and spindle of the second gear unit are coaxially arranged relative to the first gear unit.

[0008] Typically, a very compact arrangement is achieved when the nut of the second gear unit axially overlaps with the first gear unit (especially with the first and / or second components of the first gear unit). In a typical embodiment, the nut of the second gear unit is connected to the spindle of the second gear unit via the threaded surface of the nut. For a particularly compact arrangement, the threaded surface of the nut may have axial overlap with the first gear unit. The axial direction typically corresponds to the direction of braking motion of the second component and / or the direction of linear motion for liner wear compensation.

[0009] The second component of the first gear unit and the nut of the second gear unit can be rotatably connected, specifically allowing the nut of the second gear unit to rotate relative to the second component of the first gear unit during liner wear compensation. In this way, the compact arrangement of the proposed friction braking system enables efficient and reliable liner wear compensation.

[0010] The first gear unit may include at least one ball disposed and held between a first member and a second member of the first gear unit. The ball may be configured to convert rotational motion of the first member into braking motion of the second member. In this way, the first gear unit constitutes a highly efficient linear gear. Most embodiments include more than one ball disposed and held between the first member and the second member of the first gear unit to convert rotational motion of the first member into braking motion of the second member. For example, the first gear unit may include at least three (particularly at least four or more) balls for efficient conversion and a stable and robust arrangement.

[0011] For a particularly compact and robust arrangement, the balls (especially all balls) of the first gear unit may have axial overlap with the threaded surface of the nut of the second gear unit. Typically, the second gear unit has a longer axial extension than the first gear unit. In most embodiments, all components of the first gear unit axially overlap with the second gear unit. Typically, the second gear unit extends beyond the first gear unit at a first axial end and / or at a second axial end opposite to the first axial end.

[0012] In some particularly robust embodiments, the first and second components of the first gear unit may be axially spaced apart from each other, specifically such that the first and second components do not have axial overlap. Typically, at least one ball of the first gear unit (specifically each ball) has radial overlap, i.e., the components are arranged at a common radial position at a different axial position from the first and second components.

[0013] For example, the first gear unit can be a ball sprocket gear. In this embodiment, the first component can be a first plate having at least one groove. The second component is a second plate having at least one groove facing the first plate. The at least one ball can be arranged between the first plate and the second plate. The ball can be held by the grooves of the first plate and the second plate. The ball sprocket gear can be configured to convert the rotational motion of the first plate into the translational motion of the second plate relative to the first plate. In this way, braking motion can be achieved. The implementation of the ball sprocket gear has the advantages of robustness and relatively low cost.

[0014] In some embodiments, the first gear unit has a travel-dependent transmission ratio such that, for a given rotational angle of rotational motion, the travel distance corresponding to the braking motion when the brake pad is away from the friction surface is longer than when the brake pad is in contact with the friction surface. Typically, after the brake pad has traveled a certain distance, particularly after the brake pad has contacted the friction surface, a certain angular momentum is converted into a smaller relative travel distance for the brake pad. If the first gear unit is a ball-bearing ramp gear, this can be achieved, for example, by selecting the non-linear profile of the grooves of the first and second plates. In this way, a low transmission ratio during ramp start can be achieved with the proposed friction braking system. Furthermore, sufficiently high clamping force can be obtained for a short time with lower motor power. Therefore, this embodiment enables cost reduction because a smaller electric actuator may be required.

[0015] In some particularly compact embodiments, the first component and the second component of the first gear unit have axial overlap. Typically, at least one ball (particularly each ball) of the first gear unit has axial overlap, meaning the components are arranged at a common axial position at a different radial position from the first and second components. For example, the first gear unit can be a ball screw. In this case, the first component can be a ball screw nut. Furthermore, the second component can be a ball screw shaft. The ball screw can be surrounded by the ball screw nut. The ball screw shaft can surround the nut of the second gear unit. Additionally, the nut of the second gear unit can surround the spindle of the second gear unit. Typically, the ball screw nut, ball screw shaft, nut of the second gear unit, and spindle of the second gear unit are arranged coaxially.

[0016] Friction braking systems may include brake caliper assemblies. The brake caliper assemblies may be configured to press another brake pad against a surface opposite the friction surface during braking motion. Typically, the friction surface is the surface of the brake disc. When braking motion is performed (e.g., due to a braking signal sent to an electric motor causing the electric motor to rotate a first component of a first gear unit), the caliper assemblies are typically able to apply forces to the brake disc from both sides.

[0017] The friction braking system may also include a hydraulic chamber. Furthermore, the friction braking system may include a piston disposed between the hydraulic chamber and a first gear unit and / or a second gear unit. The piston may be configured to push the first gear unit and / or the second gear unit against the friction surface when the hydraulic chamber is pressurized, to press the brake pads against the friction surface in a hydraulic standby mode. The hydraulic chamber typically has a direct or indirect fluid connection to the brake cylinder. In the event of electromagnetic brake failure or malfunction, fluid pressure can be generated in the brake cylinder using the brake pedal. This fluid pressure can be transmitted to the hydraulic chamber of the friction braking system to activate emergency braking in standby mode. Typically, the piston and the first and / or second gear units move axially as the piston pushes the first gear unit and / or the second gear unit against the friction surface. In most embodiments, the piston is configured to actuate against, for example, a nut of the second gear unit directly or indirectly via the first gear unit. In particular, the piston may be configured to actuate against a first member of the first gear unit. In some embodiments, when the rotational movement of the first component is driven by an electric motor, bearings, particularly roller bearings, are arranged between the piston and the first component of the first gear unit so that the first component can rotate relative to the piston.

[0018] To achieve a more compact arrangement, the first gear unit can be arranged such that the second member is closer to the brake pad than the first member, especially when the electric motor applies braking motion.

[0019] The proposed friction braking system may further include the electric motor. The electric motor may be mechanically coupled to a first component of the first gear unit to drive the rotational movement of the first component of the first gear unit. Specifically, the electric motor may be mechanically coupled to the first component of the first gear unit via a driver.

[0020] In a typical implementation, the nut of the first component and / or the second component and / or the spindle of the second gear unit are formed as a single part to achieve a robust arrangement and easy assembly. Typically, the spindle of the second gear unit and / or the second component of the first gear unit are non-rotatable. Attached Figure Description

[0021] Exemplary embodiments will be described in conjunction with the following figures.

[0022] Figure 1 A perspective view of a friction braking system for a vehicle is shown;

[0023] Figure 2 A side view of the friction braking system is shown;

[0024] Figure 3 An exploded view of the components of a friction braking system is shown, which includes a ball-bearing ramp gear.

[0025] Figure 4 A cross-sectional view of the first gear unit and the second gear unit of the friction braking system is shown.

[0026] Figure 5 A cross-sectional view of the friction gear unit is shown; and

[0027] Figure 6 A schematic diagram of a first gear unit and a second gear unit according to another embodiment is shown. Detailed Implementation

[0028] Figure 1 A friction braking system 1 for a vehicle is shown. The friction braking system 1 includes a brake caliper assembly 2 having two brake pads configured to press against the brake discs of the vehicle's wheels for braking. System 1 also includes a housing 3. The portion of housing 3 used to cover the electric motor of system 1 is not shown in the figure to allow for observation of the motor shaft 4. The electric motor forms part of an electromechanical actuator that can press the brake pads against and release them from the brake discs. The motor shaft 4 is connected to a belt 5 for driving the rotation of a rotary connector 6. As explained below, the rotary connector 6 is connected to a first gear unit, or more precisely, to a first component of the first gear unit, for converting the rotational motion generated by the electric motor into linear braking motion, causing the brake pads to press against the brake discs of the wheels from opposite sides.

[0029] Figure 2 The friction braking system 1 is shown in a side view. Corresponding and recurring features shown in different figures are indicated by the same reference numerals. The portion 7 covering the electric motor and belt 5 is shown in this figure. Additionally, a connector 8 for electrically connecting system 1 to the vehicle control unit and power supply is shown. Lines with reference numeral 9 indicate the following... Figure 4 , Figure 5 and Figure 6 The cross-sectional plane.

[0030] Figure 3An exploded view of the components of a friction braking system 1 is shown. According to the illustrated embodiment, the friction braking system 1 includes a ball helical gear 10 as a first gear unit. The first gear unit has a first plate 11 as a first component, a second plate 12 as a second component, and a set of balls 13, 13', 13'” disposed between the first plate 11 and the second plate 12. The balls 13, 13', 13'” are held by a pair of grooves in the inner surfaces of the first plate 11 and the second plate 12, respectively. Although grooves 14, 14' of the second plate 12 are shown, the first plate 11 includes corresponding grooves not visible in the figure. The balls and the corresponding grooves are shaped such that the ball helical gear 10 converts the rotational motion of the first plate 11 driven by the electric motor into the translational motion of the second plate 12 to press the brake pad against the brake disc. In some embodiments, the grooves 14, 14' are shaped such that the first gear unit 10 has a stroke-dependent transmission ratio, such that when the plates 11, 12 are brought close together, the travel distance is longer for a given rotational angle of the motor shaft 4. To allow smooth rotation of the first plate 11, the first plate 11 abuts against the piston 18 via a roller bearing 19. A component 17 of the rotary connector 6 transmits rotational motion from the motor shaft 4 to the first plate 11 of the first gear unit. Plates 11, 12 and balls 13, 13', 13" in the ball helical gear 10 surround the second gear unit 15 for shim wear compensation. The second gear unit 15 has a nut 16. Compared to the first gear unit 10, the second gear unit 15 is arranged radially closer to the main shaft of the system 1. A spring may be arranged between the first plate 11 and the second plate 12 to ensure rapid release of the caliper device 2 in case of failure. The first and second gear units may be arranged in parallel and may have a common main axis.

[0031] Figure 4 This is a detailed cross-sectional view showing the first gear unit 10 and the second gear unit 15. As shown, the second gear unit 15 is disposed within the first gear unit 10 such that the second gear unit 15 penetrates the first gear unit 10. The second gear unit 15 includes a nut 16 and a spindle 20. The nut 16 and the spindle 20 include complementary threaded surfaces 21, allowing the spindle 20 to rotate relative to the nut 16 to compensate for liner wear. The spindle 20 has a threaded portion 22 received within the nut 16, and the widened portion is arranged close to the brake disc. A brake liner is attached to the widened portion 23 such that the brake liner is arranged between the spindle 20 and the brake disc.

[0032] When braking is applied using an electric motor, rotation of the first plate 11 causes the second plate 12 to translate to the left. The second plate 12 is fixed about rotational motion and movable about linear motion. As the second plate 12 moves to the left, it pushes the nut 16 of the second gear unit 15 to the left, causing the main shaft 20 to move to the left along with the brake pads to perform the braking motion. The nut 16 of the second gear unit 15 is rotatable relative to the second plate 12 to allow for pad wear adjustment. To compensate for pad wear, the nut 16 can rotate, causing the main shaft 20 to move to the left. The nut 16 can be connected to the second plate 12, for example, via a ratchet mechanism.

[0033] System 1 also has a small hydraulic chamber 24 disposed between the piston 18 and the end face portion 25 of the housing. When the hydraulic chamber is not pressurized, as shown, the piston 18 can contact the end face portion 25 of the housing. The hydraulic chamber 24 is fluidly connected to the brake cylinder and can be pressurized by actuating the brake pedal in a standby operating mode. When the hydraulic chamber 24 is pressurized, the hydraulic fluid inside forces the roller bearing 19, the component 17 of the rotary connector 6, the first gear unit 10, and the second gear unit 15 to the left, causing the brake pads to be pushed against the brake disc. A spring may be provided to push the piston back directly or indirectly after a hydraulic braking operation has been performed.

[0034] Figure 5 The friction braking system 1 is shown in limited detail. As can be seen, the brake caliper assembly 2 includes a set of brake pad holders 26, 26' configured to hold the brake pads. During braking, the brake pad holders 26, 26' move inward together with the brake pads, causing force to be applied to the brake disc (not shown) from opposite sides. As can be seen, the arrangement shown is particularly compact because the second gear unit 15 is received within the first gear unit 10.

[0035] Figure 6 A detailed view of system 1' according to another embodiment is shown. System 1' includes all the features of system 1 described above. However, according to... Figure 6The first gear unit 10 of the illustrated embodiment is a ball screw. The ball screw 10 includes a ball screw nut 27 as a first component and a ball screw shaft 28 as a second component. Furthermore, a set of balls 13, 13' are arranged between the ball screw shaft 28 and the ball screw nut 27 to convert the rotational motion of the ball screw nut 27 into the translational motion of the ball screw shaft 28. The ball screw nut 27 and the ball screw shaft 28 are substantially tubular in shape and are arranged so that they are concentric. The ball screw nut 27 is rotated around the ball screw shaft 28 and can be rotated using a motor and a rotary connector 6. When braking is applied, the rotation of the ball screw nut 27 causes the ball screw shaft 28 to translate to the left, thereby pushing the ball screw shaft closer to the brake disc. In this case, the ball screw shaft 28 is pushed against the nut 16 of the second gear unit 15, causing the second gear unit 15 to move to the left and the brake pad to press against the brake disc.

[0036] Features of the different embodiments disclosed by way of example only can be combined with each other, and can also be claimed individually.

Claims

1. A friction braking system (1) for a vehicle, the friction braking system comprising: A first gear unit (10) having a first component (11) and a second component (12), wherein the first gear unit (10) is configured to convert the rotational motion of the first component (11) into the braking motion of the second component (12), wherein the first component (11) is configured such that the rotational motion can be driven by an electric motor; as well as A second gear unit (15) having a main shaft (20) and a nut (16), the second gear unit being used to convert rotary motion into linear motion for liner wear compensation, wherein the main shaft (20) is capable of being connected to the brake liner, Its features are: The second member (12) of the first gear unit (10) and the nut (16) of the second gear unit (15) are mechanically connected such that during the braking motion, the second member (12) of the first gear unit (10) pushes against the nut (16) of the second gear unit (15) to press the brake pad against the friction surface. The first gear unit (10) and the second gear unit (15) are arranged such that the second gear unit (15) at least partially penetrates the first gear unit (10), and The friction braking system includes a hydraulic chamber (24) and a piston (18) disposed between the hydraulic chamber (24) and the first gear unit (10) and / or the second gear unit (15). The piston (18) is configured to push the first gear unit (10) and / or the second gear unit (15) toward the friction surface when the hydraulic chamber (24) is pressurized in a hydraulic standby mode, so that the brake pad presses against the friction surface.

2. The friction braking system (1) according to claim 1, characterized in that, The nut of the second gear unit (15) is connected to the spindle (20) of the second gear unit (15) via the threaded surface of the nut (16), wherein the threaded surface of the nut (16) has axial overlap with the first gear unit (10).

3. The friction braking system (1) according to claim 1, characterized in that, The second member (12) of the first gear unit (10) and the nut (16) of the second gear unit (15) are rotatably connected, such that the nut (16) of the second gear unit (15) is allowed to rotate relative to the second member (12) of the first gear unit (10) during liner wear compensation.

4. The friction braking system (1) according to claim 1, characterized in that, The first gear unit (10) includes at least one ball (13, 13') arranged and held between the first member (11) of the first gear unit (10) and the second member (12) of the first gear unit (10) to convert the rotational motion of the first member (11) into the braking motion of the second member (12).

5. The friction braking system (1) according to claim 4, characterized in that, The balls (13, 13') of the first gear unit (10) have axial overlap with the second gear unit (15).

6. The friction braking system (1) according to claim 4, characterized in that, The first gear unit (10) is a ball helical gear, wherein the first member (11) is a first plate having at least one groove, and the second member (12) is a second plate having at least one groove (14, 14') facing the groove of the first plate, wherein at least one ball (13, 13') is arranged between the first plate and the second plate, wherein the ball (13, 13') is held by the groove of the first plate and the groove (14, 14') of the second plate, wherein the ball helical gear is configured to convert the rotational motion of the first plate into the translational motion of the second plate relative to the first plate.

7. The friction braking system (1) according to claim 4, characterized in that, The first gear unit (10) is a ball screw, wherein the first component is a ball screw nut (27) and the second component is a ball screw shaft (28) surrounded by the ball screw nut (27).

8. The friction braking system (1) according to claim 1, characterized in that, The first gear unit (10) has a stroke-dependent transmission ratio such that, for a given rotation angle of the rotational motion, the travel distance corresponding to the braking motion is longer when the brake pad is away from the friction surface compared to when the brake pad is in contact with the friction surface.

9. The friction braking system (1) according to claim 1, characterized in that, The first gear unit (10) is arranged such that the second member (12) is closer to the brake pad than the first member (11).

10. The friction braking system (1) according to claim 1, wherein the friction braking system includes the electric motor, wherein, The electric motor is mechanically connected to the first component (11) of the first gear unit (10) to drive the rotational movement of the first component (11) of the first gear unit (10).

11. The friction braking system (1) according to claim 1, characterized in that, The brake caliper assembly (2) is configured to press another brake pad against the surface opposite the friction surface during the braking motion.

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