Park lock system

Abstract

A park lock system 100 for a vehicle (1 fig. 1) comprising: a lead screw 102, a flange 104 extending radially outwardly from the lead screw, an actuation device 106 in threaded engagement with the lea

Description

TECHNICAL FIELD The present disclosure relates to a park lock system. In particular, but not exclusively, it relates to a park lock system for a vehicle. BACKGROUND Park lock systems are used in automatic and electric vehicles to prevent undesired movement of the vehicle. A gear wheel of the park lock system is connected to a transmission shaft of the vehicle. Preventing rotation of the gear wheel prevents rotation of the transmission shaft and thus prevents movement of the vehicle. A park lock system is typically provided as a secondary means of preventing movement of the vehicle, in addition to the vehicle’s parking brake. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a park lock system for a vehicle. According to an aspect of the invention there is provided a park lock system for a vehicle, the park lock system having an engaged configuration for preventing movement of a vehicle and a disengaged configuration for enabling movement of the vehicle, the park lock system comprising: a lead screw configured to rotate about a central longitudinal axis; a flange extending radially outward from the lead screw; an actuation device comprising at least a portion in threaded engagement with the lead screw such that rotation of the lead screw about the central longitudinal axis causes axial translation of the actuation device with respect to the lead screw; a pawl comprising a pivot portion, an engagement portion configured to contact the actuation device and a park lock gear wheel, and a middle portion connecting the pivot portion and the engagement portion, wherein the pawl is configured to be moved by the actuation device to transition the park lock system between the engaged configuration, in which the pawl is in a locking position to prevent rotation of the park lock gear wheel, and the disengaged configuration, in which rotation of the park lock gear wheel is enabled, wherein the pawl is positioned with respect to the actuation device such that: when the park lock system is in the disengaged configuration, a lower contact corner of the actuation device abuts a first contact face of the pawl; upon axial translation of the actuation device towards the flange, an upper contact corner of the actuation device contacts a contact corner of the pawl to move the pawl into the locking position, wherein the upper contact corner of the actuation device and the contact corner of the pawl are shaped to minimize a frictional force between the upper contact corner of the actuation device and the contact corner of the pawl; when the park lock system is in the engaged configuration, the lower contact corner of the actuation device abuts the contact corner of the pawl, and wherein an upper face of the middle portion of the pawl is angled relative to the first contact face of the pawl such that there is a consistent vertical distance between the upper face of the middle portion of the pawl and the contact corner of the pawl; a spacer positioned on the lead screw axially between the actuation device and the flange, the spacer comprising a first end face and a second end face; and a spring washer positioned on the lead screw axially between the spacer and the flange, wherein the second end face of the spacer faces the spring washer, wherein a diameter of the spring washer is less than or equal to a diameter of the second end face of the spacer and less than or equal to a diameter of the flange, such that the spring washer provides a cushioning effect between the spacer and the flange in both a first orientation, in which a first end of the spring washer contacts the second end face of the spacer, and a second orientation, in which the first end of the spring washer contacts the flange. The park lock system has reduced wear, providing improved durability and robustness, and thus reducing the likelihood of early lifetime failure of the system. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination that falls within the scope of the appended claims. That is, all embodiments and / or features of any embodiment can be combined in any way and / or combination that falls within the scope of the appended claims, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 illustrates an example of a vehicle; FIGs. 2A and 2B illustrate an example of a park lock system for a vehicle; FIG. 3 illustrates a detail view of an example of a park lock system for a vehicle; FIG. 4 illustrates an example method for manufacturing a park lock system for a vehicle; FIG. 5 illustrates a further example method for manufacturing a park lock system for a vehicle; FIG. 6 illustrates an example pawl for a park lock system for a vehicle; and FIG. 7 illustrates an example actuation device for a park lock system for a vehicle. DETAILED DESCRIPTION FIG. 1 illustrates an example of a vehicle 1 in which embodiments of the invention can be implemented. In some, but not necessarily all examples, the vehicle 1 is a passenger vehicle, also referred to as a passenger car or as an automobile. In other examples, embodiments of the invention can be implemented for other applications, such as commercial vehicles. Embodiments of the present invention, as shown in FIGs 2A and 2B, provide a park lock system 100 for a vehicle 1. As shown in FIG. 2A, the park lock system 100 has an engaged configuration for preventing movement of the vehicle 1. As shown in FIG. 2B, the park system has a disengaged configuration for enabling movement of the vehicle 1. The park lock system 100 comprises a lead screw 102 which an electric machine (not shown) or mechanism is configured to rotate about a central longitudinal axis. The park lock system 100 comprises a flange 104, which extends radially outwards from the lead screw 102. The flange 104 functions as a stopper to limit axial movement of components of the park lock system 100. The flange 104 may be provided as a separate part to the lead screw 102. Alternatively, the flange 104 may be formed with the lead screw 102 as a single part. Forming the flange 104 and the lead screw 102 as a single part provides an assembly with a reduced number of components and reduces assembly time. The park lock system 100 comprises an actuation device 106 in the form of a linear cam actuator which is positioned on the lead screw 102. At least a portion of the actuation device 106 is in threaded engagement with the lead screw 102 such that rotation of the lead screw 102 about the central longitudinal axis causes axial translation of the actuation device 106 with respect to the lead screw 102. The actuation device 106 may comprise a nut 106a and a shaped portion 106b which is provided separately to the nut 106a. In such examples, at least the nut 106a is in threaded engagement with the lead screw 102. Alternatively, the actuation device 106 may be formed as a single part. The actuation device and / or the shaped portion 106b may be a part of nonconstant cross section and may comprise a tapering portion. Movement of the actuation device along the lead screw is guided by a guide sleeve 122. FIG. 7 illustrates a detail view of the actuation device. As illustrated in FIG. 7, the shaped portion 106b of the actuation device 106 comprises a lower contact corner 1061, a contact face 1062, and an upper contact corner 1063. Referring back to FIG. 2A, the park lock system 100 comprises a pawl 108 and a park lock gear wheel 110. The park lock gear wheel 110 is connected to a transmission shaft of the vehicle 1 such that rotation of the transmission shaft about a central axis causes rotation of the park lock gear wheel 110 about the central axis. Thus, preventing rotation of the park lock gear wheel 110 about the central axis prevents rotation of the transmission shaft about the central axis. The transmission shaft may be a transmission intermediate shaft or a transmission input shaft. FIG. 6 illustrates a detail view of the pawl. As illustrated in FIG. 6, the pawl 108 comprises a pivot portion 108a, an engagement portion 108c configured to contact the actuation device and a park lock gearwheel, and a middle portion 108b connecting the pivot portion and the engagement portion. The middle portion has an upper face 1081; and the engagement portion has a first contact face 1082; a contact corner 1083; and a second contact face 1084. In the engaged configuration of the park lock system 100, shown in FIG. 2A, the pawl 108 is in a locking position and prevents rotation of the park lock gear wheel 110. In the locking position, the pawl 108 may be positioned such that a portion of the pawl 108 sits within awheel tooth gap of the gear wheel. In the disengaged configuration of the park lock system 100, shown in FIG. 2B, the pawl 108 is not in a locking position and rotation of the park lock gear wheel 110 is enabled. When the park lock system is in the disengaged configuration, the lower contact corner of the actuation device abuts the first contact face of the pawl. The actuation device 106 is configured to contact the pawl 108 and move the pawl by linear camming to transition the park lock system 100 between the engaged configuration and the disengaged configuration. Axial translation of the actuation device 106 towards the flange 104 causes the actuation device 106 to contact the pawl 108 such that the pawl 108 is moved into the locking position. The actuation device 106 may push the pawl 108 towards the locking position as the actuation device 106 moves towards the flange 104 and hold the pawl 108 in the locking position when the actuation device 106 reaches a limit of its axial translation. Upon axial translation of the actuation device 106 towards the flange 104, the upper contact corner of the actuation device 106 contacts the contact corner of the pawl 108 to move the pawl 108 into the locking position, wherein the upper contact corner of the actuation device and the contact corner of the pawl are shaped to minimize a frictional force between the upper contact corner of the actuation device and the contact corner of the pawl. The contact comer of the pawl has a radius of between 650mm and 1000mm and the upper contact corner of the actuation device has a radius of between 650mm and 1000mm. The contact corner of the pawl has a radius of between 700mm and 860mm and the upper contact corner of the actuation device has a radius of between 700mm and 860mm. The contact corner of the pawl has an R2 radius and the upper contact corner of the actuation device has an R2 radius. The radiuses of the contact corner of the pawl and the upper contact corner of the actuation device provide a shallower contact between the two features. This decreases wear on the pawl and on the actuation device. When the park lock system is in the engaged configuration, the lower contact corner of the actuation device abuts the contact corner of the pawl. An upper face of the middle portion of the pawl is angled relative to the first contact face of the pawl such that there is a consistent vertical distance between the upper face of the middle portion of the pawl and the contact corner of the pawl. Thus, the position at which the actuation device contacts the pawl does not affect the vertical position of the pawl. In particular, the upper face of the middle portion is angled relative to the pivot portion and the first contact face such that a lateral position of the lower contact corner on the first contact face in the disengaged position does not affect a vertical position of the contact corner of the pawl in the disengaged position. The angle of the upper face of the middle portion thus ensures consistent pawl position, compensating for system tolerances. In some, but not necessarily all, examples, the second contact face of the pawl has an angle, relative to the upper face of the middle portion, of between 1.5° and 4°. In some examples, the second contact face of the pawl has an angle, relative to the upper face of the middle portion, of between 1.5° and 2.5°. The angle of the second contact face is thus at least partially matched to the gradient of the upper contact corner of the actuation device, providing a shallower contact between the two features. This decreases wear on the pawl and on the actuation device. Axial translation of the actuation device 106 away from the flange 104 enables the pawl 108 to be moved away from the locking position, for example by a pawl return spring 120. The park lock system 100 comprises a spacer 112, positioned on the lead screw 102 axially between the actuation device 106 and the flange 104 as shown in the detail view of FIG.3. The spacer 112 comprises a first end face 114 and a second end face 116. The spacer 112 may also comprise a central portion, which separates the first end face 114 of the spacer 112 and the second end face 116 of the spacer 112. The first end face 114 of the spacer 112 may act as a stopper to provide the limit of axial translation of the actuation device 106 by preventing axial movement of the actuation device 106 along the lead screw 102 beyond the first end face of the spacer 112. A length of the spacer 112 thus determines the position of the actuation device 106 in the engaged position. In examples, a diameter of the first end face 114 of the spacer 112 is equal to the diameter of the second end face 116 of the spacer 112. FIG. 3 illustrates an example embodiment in which the central portion of the spacer 112 has a diameter less than the diameter of the first end face 114 of the spacer 112 and less than the diameter of the second end face 116 of the spacer 112. In such an example, the spacer 112 has a “bobbin” shape. The “bobbin” shape of the spacer 112 enables the spacer 112 to be positioned on the lead screw 102 in either direction, i.e., an end face of the spacer 112 may function as either the first end face 114 or the second end face; the spacer 112 is reversible. It will be appreciated that the spacer 112 is not limited to the bobbin shape shown. The park lock system 100 comprises a spring washer 118, positioned on the lead screw 102 axially between the spacer 112 and the flange 104 such that the second end face 116 of the spacer 112 faces the spring washer 118. In the engaged configuration of the park lock system 100, the actuation device 106 may be axially positioned with respect to the flange 104 such that the actuation device 106 applies a compressive force against the spacer 112, the spring washer 118 and the flange 104. The spring washer 118 provides a cushioning effect between the spacer 112 and the flange 104 and reduces an impact noise when the components of the park lock system 100 are brought into contact. This provides a bump stop for the park lock system 100 when it moves into the engaged configuration. As shown, the actuation device 106, spacer 112, spring washer 118, and flange 104 may be coaxial with each other along the lead screw 102. In the disengaged configuration of the park lock system 100, the actuation device 106 may be axially positioned with respect to the flange 104 such that there is axial separation between at least two adjacent components selected from: the actuation device 106, the spacer 112, the spring washer 118, and the flange 104. A diameter of the spring washer 118 is less than or equal to the diameter of the second end face 116 of the spacer 112 and less than or equal to a diameter of the flange 104. The diameter of the spring washer 118 may be a diameter of any cross-section of the spring washer 118. In particular, the diameter of the spring washer 118 may be the maximum diameter of the spring washer 118. Because the maximum diameter of the spring washer 118 is less than or equal to the diameter of the second end face 116 of the spacer 112 and less than or equal to the diameter of the flange 104, the spring washer 118 provides the cushioning effect between the spacer 112 and the flange 104 regardless of whether the assembler inserts the spring washer onto the lead screw in a first orientation such that a first end 119 of the spring washer 118 contacts the second end face 116 of the spacer 112, or in a second orientation such that the first end 119 of the spring washer 118 contacts the flange 104. The first end 119 of the spring washer 118 may be the widest point of the spring washer 118. The first orientation and the second orientation are different insertion orientations of the spring washer 118 on the lead screw 102. This enables the spring washer 118 to provide the cushioning effect between the spacer 112 and the flange 104 regardless of whether the first end 119 of the spring washer 118 faces the spacer 112 or faces the flange 104. This provides mistake-proofing for assembly of the park lock system 100 since the spring washer 118 will function regardless of orientation. The spring washer 118 may be a handed washer such that a geometric property of the first end 119 of the spring washer 118 is different to a geometric property of a second end of the spring washer 118. The geometric property of the first end 119 of the spring washer 118 may be a diameter of the first end 119 of the spring washer 118 and the geometric property of the second end of the spring washer 118 may be a diameter of the second end of the spring washer 118. The spring washer 118 may have a tapering cross section. The outer diameter of the first end 119 of the spring washer 118 may be smaller than the diameter of the flange. In examples, the outer diameter of the first end 119 of the spring washer 118 is approximately 0.7mm smaller than the diameter of the flange. An inner diameter of the first end 119 of the spring washer 118 may be larger than an outer diameter of the lead screw. In examples, the inner diameter of the first end 119 of the spring washer may be approximately 0.37mm larger than an outer diameter of the lead screw. Optionally, the spring washer 118 is a Belleville washer or another type of conical spring washer 118. Optionally, the same spring washer 118 may be arranged to contact both the flange 104 and the spacer 112 when the park lock system 100 is in the engaged configuration. This means that only one spring washer 118 is required to provide the bump stop for the park lock system 100. This provides an assembly with a reduced number of components. Further, the spring washer 118 may be arranged to contact both the flange 104 and the spacer 112 when the park lock system 100 is in the disengaged configuration. FIG. 4 illustrates a method 200 of manufacturing a park lock system for a vehicle. The park lock system may be a park lock system as described above. The method of FIG. 4 comprises: At block 202, providing a lead screw configured to rotate about a central longitudinal axis; At block 204, providing a flange such that the flange extends radially outward from the lead screw; At block 206, providing an actuation device such that at least a portion of the actuation device is in threaded engagement with the lead screw, such that rotation of the lead screw about the central longitudinal axis causes axial translation of the actuation device with respect to the lead screw; At block 208, providing a pawl such that the pawl is configured to be moved by the actuation device to transition the park lock system between the engaged configuration, in which the pawl is in a locking position to prevent rotation of a park lock gear wheel, and the disengaged configuration, in which rotation of the park lock gear wheel is enabled, and wherein the pawl is positioned with respect to the actuation device such that upon axial translation of the actuation device towards the flange, the actuation device contacts the pawl to move the pawl into the locking position; At block 210, providing a spacer, positioned on the lead screw axially between the actuation device and the flange, the spacer comprising a first end face and a second end face; and At block 212, providing a spring washer, positioned on the lead screw axially between the spacer and the flange, wherein the second end face of the spacer faces the spring washer, and wherein a diameter of the spring washer is less than or equal to a diameter of the second end face of the spacer and less than or equal to a diameter of the flange, such that the spring washer provides a cushioning effect between the spacer and the flange in both a first orientation, in which a first end of the spring washer contacts the second end face of the spacer, and a second orientation, in which the first end of the spring washer contacts the flange. A further example method 300 of manufacturing a park lock system for a vehicle, shown in FIG. 5 comprises inserting (302) a spring washer onto a park lock system for a vehicle, the park lock system having an engaged configuration for preventing movement of a vehicle and a disengaged configuration for enabling movement of the vehicle, the park lock system comprising a lead screw configured to rotate about a central longitudinal axis; a flange extending radially outwards from the lead screw; an actuation device comprising at least a portion in threaded engagement with the lead screw such that rotation of the lead screw about the central longitudinal axis causes axial translation of the actuation device with respect to the lead screw; a pawl configured to be moved by the actuation device to transition the park lock system between the engaged configuration, in which the pawl is in a locking position to prevent rotation of a park lock gear wheel, and the disengaged configuration, in which rotation of the park lock gear wheel is enabled, wherein the pawl is positioned with respect to the actuation device such that upon axial translation of the actuation device towards the flange, the actuation device contacts the pawl to move the pawl into the locking position; a spacer positioned on the lead screw axially between the actuation device and the flange, and the spacer comprising a first end face and a second end face, wherein inserting the spring washer comprises positioning the spring washer on the lead screw axially between the spacer and the flange, wherein the second end face of the spacer faces the spring washer, and wherein a diameter of the spring washer is less than or equal to a diameter of the second end face of the spacer and less than or equal to a diameter of the flange, such that the spring washer provides a cushioning effect between the spacer and the flange in both a first orientation, in which a first end of the spring washer contacts the second end face of the spacer, and a second orientation, in which the first end of the spring washer contacts the flange. Providing a component of the park lock system may comprise any one or more of affixing the component to a vehicle component external to the park lock system; attaching the component to the lead screw; placing the component on the lead screw; or any other appropriate method of incorporating the component into the park lock system. A component of the park lock system refers to any one or more of the lead screw; the flange; the actuation device; the pawl; the spacer; the spring washer; and any other components of the park lock system. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application. The blocks illustrated in FIG. 4 and FIG. 5 represent steps in a method. The illustration of a particular order to the blocks does not necessarily imply that there is a required or preferred order for the blocks and the order and arrangement of the blocks may be varied. Furthermore, it may be possible for some steps to be omitted. Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed. Features described in the preceding description may be used in combinations other than the combinations explicitly described. Although functions have been described with reference to certain features, those functions may be performable by other features whether described or not. Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not. Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and / or shown in the drawings whether or not particular emphasis has been placed 5 thereon.

Claims

1. A park lock system for a vehicle, the park lock system having an engaged configuration for preventing movement of a vehicle and a disengaged configuration for enabling movement of the vehicle, the park lock system comprising:a lead screw configured to rotate about a central longitudinal axis;a flange extending radially outward from the lead screw;an actuation device comprising at least a portion in threaded engagement with the lead screw such that rotation of the lead screw about the central longitudinal axis causes axial translation of the actuation device with respect to the lead screw;a pawl comprising a pivot portion, an engagement portion configured to contact the actuation device and a park lock gearwheel, and a middle portion connecting the pivot portion and the engagement portion,wherein the pawl is configured to be moved by the actuation device to transition the park lock system between the engaged configuration, in which the pawl is in a locking position to prevent rotation of the park lock gear wheel, and the disengaged configuration, in which rotation of the park lock gear wheel is enabled, wherein the pawl is positioned with respect to the actuation device such that:when the park lock system is in the disengaged configuration, a lower contact corner of the actuation device abuts a first contact face of the pawl;upon axial translation of the actuation device towards the flange, an upper contact corner of the actuation device contacts a contact corner of the pawl to move the pawl into the locking position, wherein the upper contact corner of the actuation device and the contact corner of the pawl are shaped to minimize a frictional force between the upper contact corner of the actuation device and the contact corner of the pawl;when the park lock system is in the engaged configuration, the lower contact corner of the actuation device abuts the contact corner of the pawl, andwherein an upper face of the middle portion of the pawl is angled relative to the first contact face of the pawl such that there is a consistent vertical distance between the upper face of the middle portion of the pawl and the contact corner of the pawl;a spacer positioned on the lead screw axially between the actuation device and the flange, the spacer comprising a first end face and a second end face; anda spring washer positioned on the lead screw axially between the spacer and the flange, wherein the second end face of the spacer faces the spring washer,wherein a diameter of the spring washer is less than or equal to a diameter of the second end face of the spacer and less than or equal to a diameter of the flange, such that the spring washer provides a cushioning effect between the spacer and the flange in both a first orientation, in which a first end of the spring washer contacts the second end face of the5 spacer, and a second orientation, in which the first end of the spring washer contacts the flange.15

Images