Locking pawl arrangement for an electromechanical parking brake

Abstract

The invention relates to a pawl assembly (1) for a parking brake of a motor vehicle. The pawl assembly comprises a ratchet wheel (2) rotatable about a pivot axis (D), which has a locking toothing (3) with a plurality of pawl teeth (4). Furthermore, the pawl assembly comprises a pawl (5) which is adjustable between a locking position, in which it engages the locking toothing (3) of the ratchet wheel (2) and thereby blocks rotation of the ratchet wheel (2), and a release position, in which it is arranged at a distance from the locking toothing (3) and thereby releases the rotation of the ratchet wheel (2). The pawl (2) and the locking toothing (3) are designed and aligned such that, in the locking position, the pawl (5) blocks the movement of the ratchet wheel (2) under compressive load.

Description

[0001] The present invention relates to a pawl arrangement for an electromechanical parking brake and to an electromechanical parking brake with such a pawl arrangement.

[0002] Electromechanical parking brakes for motor vehicles typically employ a pawl mechanism. To block the movement of a wheel connected to the parking brake, a pawl engages with a locking toothed gear, which in turn is mounted on a ratchet wheel that is fixed to the wheel. This prevents the wheel from rotating and eliminates any unwanted movement of the vehicle.

[0003] If the locking of the wheel and, accordingly, the blocking of the ratchet wheel are to be released again when the motor vehicle is to be moved, the locking pawl is disengaged from the locking teeth for this purpose.

[0004] The adjustment of the pawl required for locking and unlocking can be achieved, for example, by means of an electric actuator connected to the drive of the pawl.

[0005] The pawl in question is often designed in the form of a hook, which is subjected to tensile stress by the ratchet wheel when it is locked. This results in a considerable mechanical load on the pawl, which can negatively impact its lifespan. To prevent premature, wear-related breakage of the pawl, it is therefore necessary to equip the hook-shaped, tensile-loaded pawl with increased robustness. However, this requires the use of larger and mechanically stronger components for the pawl. This, in turn, leads to undesirable cost increases.

[0006] It is therefore an object of the present invention to demonstrate new approaches in the development of pawl arrangements for electromechanical parking brakes. In particular, an improved embodiment of such a pawl arrangement is to be created in which the aforementioned disadvantages are at least partially, and ideally completely, eliminated.

[0007] This problem is solved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent patent claims.

[0008] The basic idea of ​​the invention is therefore to design the pawl and locking teeth of a pawl assembly mentioned above in such a way that, in a locking position in which the pawl blocks the movement of the ratchet wheel as explained above, the pawl is not subjected to tensile stress, but is subjected exclusively to compressive stress.

[0009] In the solution proposed here, the pawl engaging with the ratchet wheel presses against the locking teeth, thus blocking any rotational movement of the ratchet wheel. An externally imposed, attempted rotation of the ratchet wheel—typically triggered by the rotation of a motor vehicle wheel that is rigidly connected to the ratchet wheel—results, in the pawl arrangement presented here according to the invention, in an increase in the compressive load on the pawl, without the ratchet wheel subsequently moving.

[0010] It is therefore a self-locking arrangement consisting of a pawl and locking teeth, in which, with increasing pressure on the pawl, the counterforce exerted by the pawl to block the ratchet wheel also increases.

[0011] This self-locking arrangement of pawl and locking teeth allows the components involved, especially the pawl, to be made comparatively small and therefore cost-effective, without compromising the robustness and thus the service life of the entire pawl assembly. This, in turn, leads to the desired cost advantages in manufacturing.

[0012] Following the above inventive concept, a pawl assembly according to the invention comprises a ratchet wheel rotatable about an axis of rotation, which has a ratchet toothing with a plurality of pawl teeth. The pawl assembly according to the invention also comprises a pawl which is adjustable between a locking position and a release position. In the locking position, the pawl engages in the ratchet toothing of the ratchet wheel and thereby blocks rotation of the ratchet wheel about the axis of rotation. In the release position, the pawl is arranged at a distance from the ratchet toothing and thereby releases the rotation of the ratchet wheel.

[0013] According to the invention, the pawl and the locking teeth are designed and aligned such that, in the locked position, the pawl blocks the movement of the ratchet wheel under compressive stress. In this way, a self-locking arrangement of pawl and locking teeth is achieved.

[0014] In a preferred embodiment, the pawl, when in the locked position, blocks the rotational movement of the ratchet wheel without tensile stress. This reduces the mechanical stress on the pawl and thus protects it mechanically. This results in a significant extension of the service life of the pawl and therefore of the entire pawl assembly.

[0015] To achieve the self-locking effect of the arrangement, it is proposed that at least one pawl tooth has the geometry of a sawtooth. Such a sawtooth allows the pawl to be geometrically designed in such a way that, when engaging the locking teeth as proposed according to the invention, it is only subjected to compressive stress. It is therefore particularly preferable that all pawl teeth are each provided with the geometry of a sawtooth.

[0016] Preferably, at least one saw tooth or pawl tooth can have a first tooth flank extending along one circumferential direction of the ratchet wheel, which transitions into a second tooth flank extending along the same circumferential direction. In this variant, the first flank pitch of the first tooth flank is greater than the second flank pitch of the second tooth flank. Particularly preferably, all saw teeth or pawl teeth can be configured as described above. By means of such an asymmetrical configuration of the two tooth flanks of the saw tooth or pawl tooth, a particularly stable fixation of the pawl – exclusively under compressive load – can be achieved in the ratchet mechanism.

[0017] Therefore, the pawl is particularly preferably supported in the locking position at least on the first tooth flank of the saw tooth or pawl tooth under pressure, i.e. under compressive load.

[0018] The contour of the first and / or second tooth flank may be particularly favorably curved.

[0019] Since the pawl in the pawl assembly according to the invention does not have to be subjected to tensile stress, the hook design can be omitted. Preferably, the pawl can therefore be provided with a hook-free pawl geometry. This simplifies the construction of the pawl and thus of the entire pawl assembly.

[0020] A particularly advantageous design for the pawl is the geometry of an elongated bolt that tapers towards the ratchet wheel. This type of pawl requires very little installation space.

[0021] The pawl, in the locked position, engages particularly favorably in a recess formed between two adjacent pawl teeth. This ensures a particularly stable fixation of the pawl within the locking teeth.

[0022] In another preferred embodiment, the pawl has an end section designed as an engagement section. Preferably, this engagement section can be designed to complement the said recess(s) between two pawl teeth or the pawl. Particularly preferably, the engagement section can have a curved contact surface which, in the locked position, rests against a similarly curved boundary surface of the recess. This measure also promotes a particularly stable fixation of the pawl in the locking teeth.

[0023] The intervention section can also expediently have a round surface contour.

[0024] According to an advantageous embodiment of the pawl arrangement according to the invention, it can have an electric actuator for adjusting the pawl at least from the release position to the locking position and, moreover, particularly preferably, a preloading device by means of which the pawl is preloaded into the release position.

[0025] The invention further relates to an electromechanical parking brake with a pawl arrangement according to the invention as described above. The advantages of the pawl arrangement according to the invention, as explained above, are therefore transferred to the electromechanical parking brake according to the invention.

[0026] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0027] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0028] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0029] They show, schematically: Fig. 1 an example of a pawl arrangement according to the invention, Fig. 2 a detailed representation of the locking pawl arrangement of the Fig. 1 in the area around the pawl and locking teeth.

[0030] The Fig. Figure 1 illustrates an exemplary pawl arrangement 1 according to the invention. The pawl arrangement 1 comprises a ratchet wheel 2 rotatable along a direction of rotation X about an axis of rotation D, which has a ratchet toothing 3 with a plurality of pawl teeth 4. The direction of rotation X corresponds to a circumferential direction U of the ratchet wheel 2.

[0031] The pawl arrangement according to the invention also comprises a pawl 5 which is rotatable along a direction of rotation G about an axis of rotation F and is thereby adjustable between a locking position and a release position.

[0032] To adjust the pawl 5, the pawl assembly 1 can include an electric actuator 12 and also a pre-tensioning device (not shown in the figures). Advantageously, the pawl 5 is pre-tensioned into the release position by means of the pre-tensioning device. The actuator 12, in turn, can have a spindle drive.

[0033] The Fig. Figure 1 shows the pawl 5 in the release position, in which it allows rotation of the ratchet wheel 2 along the direction of rotation X. For this purpose, the pawl 5 is arranged at a distance from the locking teeth 3 and thus also from the ratchet wheel 2, as shown, thereby releasing the rotation of the ratchet wheel 2.

[0034] In the Fig. In the locking position not shown, the pawl 5 engages in the locking teeth 3 of the ratchet wheel 2 and thereby blocks the rotational movement of the ratchet wheel 2 about the axis of rotation D.

[0035] The Fig. Figure 2 shows a detailed representation of the locking pawl arrangement of the Fig. 1 in the area around pawl 5 and locking teeth 3. Accordingly, the pawl 5 and the locking teeth 3 are designed and coordinated in such a way that in the (not shown) locking position, the pawl 5 blocks the movement of the ratchet wheel 2 exclusively under pressure load on the pawl 5.

[0036] This creates a self-locking arrangement consisting of pawl 5 and locking teeth 3, in which the pawl 5 blocks any rotational movement of the ratchet wheel 2 in the locking position without the occurrence of a tensile load.

[0037] For self-locking operation, the pawl 5 can, as shown, have the geometry of an elongated bolt 8 that tapers towards the ratchet wheel 2. In this case in particular, the pawl 5 has a hook-free pawl geometry.

[0038] The latch teeth 4 also contribute to the formation of said self-locking arrangement, as shown in the illustration. Fig. 1 and in particular the Fig. 2 each removable the geometric shape of a saw tooth 6.

[0039] According to the Fig. 1 and Fig. 2. Between two adjacent pawl teeth 4 or saw teeth 6 along the circumferential direction U, a recess 9 is formed. Thus, the pawl teeth 4 or saw teeth 6 and the recesses 9 alternate along the circumferential direction U. In the locked position, the locking pawl 5 engages in a recess 9 formed between two adjacent pawl teeth 4.

[0040] Each of the saw teeth 6 or ratchet teeth 4 can have a first tooth flank 7a extending along a circumferential direction U of the ratchet wheel 2. The first tooth flank 7a transitions along the direction of rotation X or along the circumferential direction U into a second tooth flank 7b, which also extends along the circumferential direction U.

[0041] The recesses 9 are therefore at least partially bounded by a respective first tooth flank 7a of a respective pawl tooth 4 or saw tooth 6 and by a second tooth flank 7b of the pawl tooth 4 or saw tooth 6 adjacent in the circumferential direction U.

[0042] The tooth contours of the first and second tooth flanks 7a, 7b can be curved as shown. Furthermore, the first flank pitch S1 of the first tooth flank 7a is preferably greater than the second flank steepness S2 of the second tooth flank 7b. In the ratchet wheel 2 shown in the figures, all saw teeth 6 and ratchet teeth 4 of the economy toothing 3 are designed as described above.

[0043] In the (not shown) locking position, the pawl 5 is supported during engagement in the recess 9 at least on the first tooth flank 7a of a specific saw tooth 6.

[0044] How Fig.As can be further seen in Figure 2, the locking pawl 5 can have an end section 11 designed as an engagement section 10. The engagement section 10 can be provided with a round surface contour as shown.

[0045] The intervention section 10 can optionally also be designed as a complement to the aforementioned recesses 9 or between two latch teeth 4 or saw teeth 6.

[0046] In the example scenario, the engagement section 10 has a curved contact surface 13 which, in the locking position, rests against a curved boundary surface 14 of the recess 9.

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