Electromechanical brake force booster

Abstract

The invention relates to an electromechanical brake booster (1) for a vehicle, having a spindle nut (22) which is in operative engagement with an axially displaceable spindle (21), having an actuator (4) for rotational driving of the spindle nut (22) for displacing the spindle (21) in a control direction, having a pressure piston (9) which can be displaced in the control direction through the spindle (21), the brake booster being couplable at one end to a master brake cylinder (2) and being operatively connected at the other end via a coupling device (14) to the spindle (21) and to a coupling lever (6) which can be connected to a brake pedal, having at least one pretensioned return spring (26) which acts against the control direction, having a housing (11) which contains at least the pressure piston (9), the coupling device (14) and the return spring (26), in particular in multiple parts, having at least one tie rod (12, 13) which is fixed to the housing (11) and extends through the housing (11) parallel to the spindle (21), and having an anti-twist device (27) for the spindle (21). It is provided that the anti-twist device (27) has at least one rotational stop (34) which is fixed to the spindle (21) and at least one rotational backstop (35) which is formed by the housing (11) and which limits at least the twisting of the spindle (21) in the housing (11).

Description

Technical Field

[0001] This invention relates to an electromechanical brake force amplifier for a vehicle, comprising a main shaft nut operatively engaged with an axially movably supported main shaft, an electric motor for rotatably driving the main shaft nut to move the main shaft in the operating direction, a pressure piston movable in the operating direction via the main shaft, one end of the pressure piston being coupled to a master brake cylinder and the other end being operatively connected via a coupling device to the main shaft and a coupling rod connectable to a brake pedal, at least one preloadable or preloaded return spring acting against the operating direction, particularly on the pressure piston, a housing comprising at least the pressure piston, the coupling device, and at least one return spring, particularly a multi-component housing, at least one tie rod fixed to the housing and extending through the housing parallel to the main shaft, and an anti-torsion device for the main shaft. Background Technology

[0002] Electromechanical brake force amplifiers of the above type are known from the prior art. For example, publication DE10 2015 217 528 A1 discloses a general electromechanical brake force amplifier. When the driver of a motor vehicle operates the brake pedal during operation, the pressure piston moves axially relative to the main shaft, causing the master brake cylinder to be directly mechanically operated by the driver. To amplify the braking force, an electric motor is operated (the motor drives the main shaft nut as a result of the operation), through which the main shaft also moves axially in the direction of the master brake cylinder, thereby applying an additional operating force to the master brake cylinder. To prevent the main shaft from being twisted instead of moving axially due to the rotation of the main shaft nut, an anti-torsion device is provided for the main shaft. Here, the main shaft is guided by a bracket extending transversely to the main shaft at a tie rod extending parallel to the main shaft through the housing. For this purpose, the bracket has radially projecting tabs, through which one of the tie rods is guided, and wherein an elastomeric element is provided between the respective tie rod and the tab for a substantially clearance-free sliding support. The bracket is torsionally connected to the spindle, so that when the motor applies torque to the spindle nut, the spindle is supported on the tie rod in the direction of rotation and thus prevents rotational movement, so that the force applied by the motor is converted into thrust movement of the spindle in the direction of operation or the direction of the main brake cylinder. Summary of the Invention

[0003] The advantage of the braking amplifier according to the invention is that the anti-torsion device is separated from the pull rod, which in particular simplifies assembly and reduces the number of individual components. According to the invention, the anti-torsion device has at least one rotation stop fixed to the main shaft and at least one rotational reverse stop constructed from the housing, by which the rotation stop and the rotational reverse stop at least limit, and preferably prevent, the torsion of the main shaft within the housing. Therefore, the anti-torsion device now acts not between the pull rod and the main shaft, but directly between the housing and the rotation stop or the main shaft. This ensures that the anti-torsion device operates independently of the pull rod and avoids engagement between the pull rod and the anti-torsion device during assembly. This also eliminates the need for a sliding element that improves the guidance of the current support on the pull rod. Thus, the position of the anti-torsion device, or the position of action of the anti-torsion device, is also independent of one or more pull rods, thus increasing design freedom in designing the braking amplifier and, in particular, improving the utilization of structural space. The rotational reverse stop is formed, for example, by molding the housing, such as a recess in the housing or an inwardly projecting section of the casing. Thus, the rotational reverse stop is integrally constructed with the housing, ensuring the aforementioned advantages.

[0004] According to a preferred embodiment of the invention, the anti-torsion device has at least one lateral protrusion forming a rotation stop. The protrusion is particularly directly arranged or fixed to the spindle or coupling device. Particularly preferred is that the lateral protrusion is arranged at the end of the spindle facing the master brake cylinder, and it protrudes axially from the spindle nut, at least under normal conditions. This ensures that the protrusion can also protrude radially beyond the spindle nut to reliably cooperate with the rotational backstop of the housing.

[0005] Furthermore, it is preferably specified that the rotational backstop, viewed in the rotational direction of the main shaft nut, is spaced apart from at least one tie rod such that, in the rotational direction of the main shaft nut, the rotational backstop is positioned between the tie rod and the rotational stop of the anti-torsion device for operating the main brake cylinder. This ensures that the rotational stop of the anti-torsion device does not contact the tie rod itself. Preferably, the rotational backstop of the housing extends longitudinally along the housing parallel to the tie rod and extends at least along the maximum possible displacement of the main shaft within the housing, so as to ensure anti-torsion regardless of the axial position of the main shaft or the carrying device.

[0006] According to an advantageous improvement of the invention, the protrusion has an opening through which the pull rod extends spaced apart from the protrusion. In this case, the protrusion of the anti-torsion device is pushed onto the pull rod, thereby creating an anti-torsion device with a pull rod independent of the rotation direction of the spindle. The opening is preferably constructed with closed edges such that the protrusion completely surrounds the pull rod. In particular, the opening and the pull rod are constructed such that a gap exists between them in the rotational direction, allowing the rotation stop to reach the rotational reverse stop without the protrusion encountering the pull rod.

[0007] Furthermore, it is preferably specified that the rotational backstop of the housing is formed by the contour of the housing wall, as mentioned above. This ensures that the rotational backstop is easily integrated into the housing.

[0008] Furthermore, it is preferably specified that the coupling device has a bracket, particularly a metal bracket, fixed to the spindle, which extends substantially transversely to the longitudinal extension of the spindle and has a protrusion at at least one end. The bracket is preferably welded to the spindle to ensure a robust connection between the spindle and the bracket, which reliably transmits the torque applied to the spindle to the bracket. Because the bracket extends transversely to the longitudinal extension of the spindle, the protrusion at one end of the bracket is constructed to face the housing so that it advantageously acts as both a rotation stop and a rotation backstop.

[0009] Preferably, the anti-torsion device has at least two rotation stops and at least two rotation reverse stops, which are arranged opposite each other. For this purpose, the bracket preferably has one of the protrusions at each of its two ends, each protrusion forming one of the rotation stops.

[0010] According to a preferred embodiment of the invention, two tie rods extending through the housing are arranged on the housing. The presence of the two tie rods optimizes the load-bearing capacity of the housing and its connection with the main brake cylinder.

[0011] Furthermore, it is preferably specified that the corresponding pull rod is screwed to the master brake cylinder at one end, thereby ensuring favorable integration of the pull rod or connection and force transmission from the brake force amplifier to the master brake cylinder.

[0012] According to a preferred embodiment of the invention, the corresponding rotary stop has a wear-resistant protective layer, particularly a plastic coating or sleeve associated with the rotary backstop. If the rotary stop abuts against the rotary backstop and the main shaft moves axially, the wear-resistant protective layer ensures low friction between the rotary stop and the rotary backstop, thereby reducing power loss. Furthermore, the wear-resistant protective layer ensures low wear on the anti-torsion device, and thus ensures a long service life for the entire braking amplifier. Attached Figure Description

[0013] In the following description, the invention will be explained in more detail with reference to the accompanying drawings.

[0014] Figure 1 A simplified longitudinal section diagram illustrates the advantageous electromechanical braking force amplifier, and Figure 2 An enlarged detailed view of the braking force amplifier is shown in an enlarged cross-sectional diagram. Detailed Implementation

[0015] Figure 1A simplified longitudinal section diagram illustrates an advantageous brake force amplifier 1. One end of the brake force amplifier 1 can be coupled to the master brake cylinder 2, and the other end can be coupled to a brake pedal 3 (not shown) of the vehicle. The brake force amplifier 1 is used to regulate the hydraulic pressure in the master brake cylinder 2 according to brake pedal operation. For this purpose, the brake force amplifier 1 has an actuator 4 with an electric motor (not shown) and a spindle drive mechanism 5, through which the torque of the electric motor can be applied as thrust to the connection between the brake pedal 3 and the master brake cylinder 2.

[0016] The brake amplifier 1 has a pressure piston 6, one end of which is attached to the master brake cylinder 2, and the other end is mechanically connected to a coupling rod 7 via a coupling device 14. The coupling rod is connected to the brake pedal 3 and moves by the operation of the brake pedal 3. One end of the pressure piston 6 is attached to a resiliently deformable coupling disc 8, which connects the pressure piston 6 and another pressure piston 9 acting on the master brake cylinder 2. The coupling disc 8 is located on the end face of the bracket 10, which is longitudinally supported in the housing 11 of the brake amplifier 1 and faces the master brake cylinder 2. Two pull rods 12 and 13 are fixed in the housing 11 and extend parallel to the longitudinal central axis M of the pressure piston 6 and the master brake cylinder 2. The brake amplifier 1 is connected to the master brake cylinder 2 via the pull rods 12 and 13. For this purpose, threads are constructed on the end sides of the pull rods 12 and 13, which pass through the fixing flange of the master brake cylinder 2 so that a fixing nut can be tightened on the side away from the brake amplifier 1. Figure 1 As shown in the diagram. During operation of the brake force amplifier 1, the operating force generated by the brake force amplifier 1 is reliably transmitted via levers 12 and 13 to the master brake piston or hydraulic pistons 16 and 17, which are currently movably supported in the master brake cylinder 2. In the direction of operation, the hydraulic pistons 16 and 17 are arranged sequentially in the master brake cylinder 2, thus forming a so-called tandem master brake cylinder.

[0017] The bracket 10 and the coupling disk 8 are components of the advantageous coupling device 14. The coupling device 14 also has a transmission element 15 located between the pressure piston 6 and the coupling element 8 and configured in a substantially U-shape (in longitudinal section), such that it surrounds the end section of the pressure piston 6 on the edge side with a cover wall.

[0018] The bracket is generally constructed in a V or U shape, wherein the transmission element 15 supporting the coupling disc 8 protrudes axially from the bottom section 19 of the bracket 10 toward the master brake cylinder 2. Preferably, the transmission element 15 is formed from a separate element from the bracket 10, which is fixed to the bracket 10 or to the V or U-shaped bracket base of the bracket 10, particularly clamped to the bracket base. Alternatively, the transmission element 15 is integrally constructed with the bracket 10 or its base. The pressure piston 6 passes through the opening 20 of the transmission element 15, particularly at the intermediate connection such as... Figure 1In the case of the other impact element shown, the pressure of the pressure piston 6 can be manually applied to the coupling element 8, the other pressure piston 9 and the master brake cylinder 7 when the brake pedal 3 is operated.

[0019] The actuator 4's main shaft 21 is coaxially arranged with the pressure piston 6, wherein the pressure piston 6 is longitudinally or axially movable within the sleeve-shaped main shaft 21. The main shaft 21 is effectively engaged with the main shaft nut 22. The main shaft 21 is torsionally arranged within the housing 11, but the main shaft nut 22 is torsionally and therefore axially fixed within the housing. A motor is connected to the main shaft nut 22 to drive the main shaft nut, so that the main shaft 21 moves axially only when the main shaft nut 22 rotates.

[0020] The main shaft nut 22 has a radially projecting flange 23 at its free end facing the master brake cylinder 2, the end face of which mates with the bottom section 19 of the bracket 10. If the motor is operated and the main shaft 21 is moved, the bracket 10, which is fixedly connected to the main shaft 21, particularly welded to it, moves toward the master brake cylinder 2, provided that the bracket 10 and the main shaft 21 are axially abutting each other. Thus, braking force can also be generated independently of brake pedal operation, for example, by a braking force request made by the vehicle's driving system rather than by the driver.

[0021] A carrying element 24 is fixed to the pressure piston 6 at the end facing the master brake cylinder 2 or at the end facing the coupling disc 8. According to this embodiment, the carrying element 24 is constructed as a carrying disc, which is mounted to and specifically fixed to the end of the pressure piston 6. The carrying element 24 supports two, three, or more spacers 25 extending toward the flange 23 of the main shaft nut 22. The bottom section 19 of the bracket 10 fixed to the main shaft 21 has a clearance for each spacer 25. Figure 1 The rest position shown passes through the gap, so that the spacer 25 is placed on the end face of the radial protrusion 23, wherein the carrying element 24 is axially spaced from the bottom section 19 of the bracket 10.

[0022] The transmission element 15 (which forms section 18 of the support 10 and the coupling disk 8 rests against the transmission element) is axially spaced from the bottom section 19 of the support 10 such that the carrying element 24 has an axial gap between the two sections 18 and 19.

[0023] When the brake pedal is actuated, the coupling disc 8 and the other pressure piston 9 are axially moved by the pressure piston 6. If the brake amplification actuator 4 is actuated, the bracket 10 moves accordingly, especially in the case of a time delay, and is displaced by the main shaft 21 against the force of the return spring 41. Thus, the spacer 25, which carries the movement of the carrying element 24, is axially spaced from the end face of the radial protrusion 23. If the driver removes his foot from the brake pedal, it is pushed back by the return spring 26, causing the carrying element 24 to move toward the bottom section 19 of the bracket 10.

[0024] To prevent the spindle 21 from rotating and not moving axially when torque is applied to the spindle nut 23, an anti-torsion device 27 is provided for the spindle. In conventional brake force amplifiers, the anti-torsion device 27 is thus formed such that the bracket 10 is radially and axially movable on the tie rods 12 and 13 without radial clearance at its free end, so that torque is introduced into the tie rods 12 and 13, thereby preventing the spindle 21 from twisting.

[0025] However, according to the current advantageous construction of the braking force amplifier 1, the anti-torsion device 27 is formed directly between the bracket 10 and the housing 11 or housing portion 11. For this purpose, the housing 11 has two lateral recesses 39, 40, which thus protrude into the interior space of the housing 11 toward the pull rods 12, 13. In this respect, the recesses 39, 40 are constructed opposite each other in the housing 11.

[0026] The bracket 10 has lateral protrusions 30 and 31 on its free ends 28 and 29, respectively, which are in the form of tabs. The protrusions 30 and 31 have openings 32 and 33, respectively, and the corresponding pull rods 12 and 13 are guided through the openings 32 and 33.

[0027] Figure 2 In response, along Figure 1 A simplified cross-sectional view of line AA shows an enlarged detail of the brake amplifier 1 within the region of the pull rod 12 and the protrusion 30. The opening 32 has a cross-section that ensures a relatively large radial clearance (relative to the pull rod 12) between the protrusion 30 and the pull rod 12, allowing the protrusion 30 to pivot partially independently of the pull rod 12 about the central axis M. The protrusion 30 forms a rotation stop 34 at its free outer end, corresponding to a notch 39 in the housing 11. The notch 39 protrudes into the path of motion of the protrusion 30 during the drive of the spindle for operating the master brake cylinder 2, causing the protrusion 30 to encounter the wall of the housing 11 within the region of the notch 39. The notch 39 thus forms a rotational reverse stop 35 for the rotation stop 34. Now, if the actuator 4 is actuated to operate the master brake cylinder 2, the rotation stop 34 strikes the rotational reverse stop 35 of the housing 11, thereby form-lockingly preventing rotation of the bracket 10.

[0028] The protrusion 31 is constructed according to the protrusion 30 so as to form a rotation stop 34 that works in conjunction with the rotational backstop 35 formed by the recess 17.

[0029] This ensures a reliable and robust anti-torsion device for the brake amplifier 1 or the spindle 21 of the brake amplifier 1.

[0030] According to another embodiment, protrusions 30 and 31 are offset from pull rods 12 and 13 when viewed in the rotational direction, thereby eliminating the need for the construction of openings 32 and 33 in protrusions 30 and 31. More precisely, protrusions 30 and 31 are generally spaced apart from pull rods 12 or 13. Therefore, in Figure 2 The area of ​​the protrusion 30 is illustrated by the dashed line 36. This area is set as an alternative construction scheme for the protrusion 30 and is particularly capable of being arranged in an angular position further separated from the tie rod 12 so as to cooperate there with the corresponding recesses 16, 17 or corresponding rotational backstops 35 also constructed in that position.

[0031] By separating the positions of protrusions 30 and 31 from the positions of pull rods 12 and 13, greater design freedom is achieved in designing the braking force amplifier 1, resulting in improved structural space utilization.

[0032] To reduce wear when the bracket 10 is axially displaced and thus the rotation stop 34 moves axially along the rotation counter 35, the bracket 10 has a wear-resistant protective layer 37 at the protrusions 30, 31, particularly at least in the area of ​​the corresponding rotation stop 34, which is constructed, for example, as a plastic sheath 38 that at least partially, optionally completely, surrounds the protrusion 30 to form a contact surface with the housing 11.

Claims

1. An electromechanical brake amplifier (1) for a vehicle, having a main shaft nut (22) operatively engaged with a main shaft (21) axially movably supported, having an actuator (4) for rotatably driving the main shaft nut (22) to move the main shaft (21) in an operating direction, having a pressure piston (9) movable in the operating direction via the main shaft (21), one end of the pressure piston being coupled to a master brake cylinder (2) and the other end being operatively connected via a coupling device (14) to the main shaft (21) and a coupling rod (6) connectable to a brake pedal, having at least one preloaded return spring (26) acting against the operating direction, having a housing (11) comprising at least the pressure piston (9), the coupling device (14) and the return spring (26), having at least one pull rod (12, 13) fixed to the housing (11) and extending through the housing (11) parallel to the main shaft (21), and having an anti-torsion device (27) for the main shaft (21), characterized in that, The anti-torsion device (27) has at least one rotation stop (34) fixedly connected to the main shaft (21) and at least one rotation reverse stop (35) formed by the housing (11), by which the rotation stop and the rotation reverse stop at least restrict the torsion of the main shaft (21) in the housing (11), wherein the coupling device (14) or the main shaft (21) has at least one lateral protrusion (30, 31) forming the rotation stop (34), wherein the protrusion (30, 31) has an opening (32, 33), through which the pull rod (12, 13) extends spaced apart from the protrusion (30, 31).

2. The braking force amplifier according to claim 1, characterized in that, The rotational reverse stop (35) is located between the pull rod (12, 13) and the rotational stop (34) in the rotational direction.

3. The braking force amplifier according to claim 1 or 2, characterized in that, The rotational reverse stop (35) of the housing is formed by the contour of the cover wall of the housing (11).

4. The braking force amplifier according to claim 1 or 2, characterized in that, The coupling device (14) has a bracket (10) fixed on the main shaft (21), which extends substantially transversely to the longitudinal extension of the main shaft (21) and has a protrusion (30, 31) at at least one end.

5. The braking force amplifier according to claim 1 or 2, characterized in that, The anti-torsion device (27) has at least two rotation stops (34) and two rotation reverse stops (35), which are arranged opposite to each other.

6. The braking force amplifier according to claim 1 or 2, characterized in that, Two tie rods (12, 13) are arranged on the housing (11), and the tie rods extend through the housing (11).

7. The braking force amplifier according to claim 1 or 2, characterized in that, The corresponding levers (12, 13) are screwed to the main brake cylinder (2) at one end.

8. The braking force amplifier according to claim 1 or 2, characterized in that, The rotation stop (34) has a wear-resistant protective layer.

9. The braking force amplifier according to claim 1, characterized in that, The housing (11) is constructed as a multi-part structure.

10. The braking force amplifier according to claim 4, characterized in that, The bracket (10) is a metal bracket.

11. The braking force amplifier according to claim 5, characterized in that, The anti-torsion device (27) has at least two rotation stops (34) and two rotation reverse stops (35), which are arranged opposite each other.

12. The braking force amplifier according to claim 8, characterized in that, The rotation stop (34) has a plastic coating or a sheath (38).

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