Vehicle panel actuation mechanism

Abstract

A vehicle panel actuation mechanism 200 has a slide block 206a, 206b, a non-straight (for example curved) rail 208a, 208b slidable relative to the slide block in a first rail direction, a yoke or hub

Description

TECHNICAL FIELD The present disclosure relates to a vehicle panel actuation mechanism. Aspects of the invention relate to a vehicle panel actuation mechanism, and to a vehicle. BACKGROUND It is known to provide vehicle panels that may be moved by an actuator. However, the range of different movement paths that a vehicle panel may take may be limited by the type of actuator used. Further, there may be desire to move a vehicle panel in a non-straight or curved path, which may require an expensive or complex actuator. 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 vehicle panel actuation mechanism, and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a vehicle panel actuation mechanism comprising: a rail coupleable to a vehicle panel and moveable from a first position to a second position, the rail being arranged to slide relative to a vehicle body in a first rail direction, the rail having a non-straight shape; a yoke arranged to move relative to the vehicle body in a second rail direction, the second rail direction being non-parallel to the first rail direction; and a linear actuator coupleable between the vehicle panel and the yoke and arranged to impart a force to the yoke in a first actuator direction to move the vehicle panel relative to the vehicle body; wherein the yoke is arranged to slide relative to the vehicle body in the second rail direction to allow the first actuator direction to vary dependent on the non-straight shape of the rail as the rail moves from the first position to the second position; and wherein the first actuator direction has a component in the first rail direction while the rail moves from the first position to the second position. The vehicle panel actuation mechanism may further comprise a slide block coupleable to the vehicle body, the yoke may be slidably coupled to the slide block to allow the yoke to move relative to the slide block in the second rail direction. The rail may have a curved shape. With such an arrangement, the linear actuator may exert a force in a constant direction relative to a vehicle panel to which it is coupled, while the vehicle panel may move relative to the vehicle body in a curve or other non-straight line. This may allow a greater range of movement for the vehicle panel while allowing a purely linear actuator to be used. The linear actuator may extend in a straight line that is generally in the same direction as the rail, with the slide block constraining movement of the rail to one degree of freedom, while the yoke may move relative to the slide block in a direction that may be perpendicular to the direction of movement of the rail to avoid stresses being generated on the linear actuator. The second rail direction may be perpendicular to the first rail direction, and generally the yoke may be arranged to allow a distance between the rail and the linear actuator to vary along the rail without requiring flexing of the components. It will be understood that the slide block may have a fixed orientation relative to the vehicle body, constraining the direction of movement of the rail relative to the slide block. Components fixed relative to the slide block may be described based on a reference frame that is fixed relative to the slide block. Other components may have a fixed orientation relative to the linear actuator and so may be best described using a reference frame of the linear actuator. The two reference frames will have different angles between them at different points along the rail, due to the non-straight nature of the rail. The yoke may be rotatable relative to the slide block. In this way, the slide block and rail may maintain a fixed orientation, allowing the slide block and rail to slide smoothly relative to each other, while the yoke may maintain a fixed orientation relative to the linear actuator. In this way, unnecessary stresses on the linear actuator may be reduced and the range of non-straight shapes the rail may take may be increased. The vehicle panel actuation mechanism may further comprise: a yoke housing fixed to the slide block, the yoke housing at least partially surrounding the yoke, and one or more sliding and / or pivotal joints between the yoke and the yoke housing. The yoke housing may provide a convenient coupling means for providing pivotal and / or sliding joints between the yoke and the slide block, allowing the degrees of freedom between the yoke and the slide block to be selected and tailored. The vehicle panel actuation mechanism may further comprise a lateral dowel extending from the yoke in a second actuator direction perpendicular to the first actuator direction, the lateral dowel being received in a lateral slot in the yoke housing and moveable along the lateral slot in a second rail direction, the lateral slot preventing relative movement between the lateral dowel and the yoke housing in the first rail direction. The arrangement of the lateral dowel and the lateral slot may provide a simple means to allow the yoke to move relative to the slide block in a direction non-parallel to the rail, accounting fora deviation from the path of the rail from the first direction. The lateral dowel may also transfer a force along the direction of the rail and / or along the direction of the linear actuator from the yoke to the slide block, allowing the linear actuator to move the vehicle panel relative to the vehicle body along the rail. It will be understood that the term “lateral” with reference to the lateral dowel and lateral slot is merely a label and is not intended to impart any particular limitation onto the dowel or slot. The vehicle panel actuation mechanism may further comprise a pitching dowel extending from the yoke in a third actuator direction, the third actuator direction being perpendicular to the first and second actuator directions, the pitching dowel being received in a pitching slot in the yoke housing and moveable along the pitching slot in the first rail direction, the pitching slot preventing relative movement between the pitching dowel and the yoke housing in a third rail direction, the third rail direction being perpendicular to the first and second rail directions. The pitching dowel and pitching slot may prevent rotation of the yoke relative to the yoke housing. This may improve stability of the vehicle panel. Further, where the linear actuator is a screw-drive, the torque of the screw-drive may be resisted by engagement between the pitching dowel and the pitching slot. By allowing the pitching dowel to move along the pitching slot in the first rail direction, rotation of the yoke about an axis in the second actuator direction may be permitted. This may be seen as pitching of the yoke as the rail moves. In this way, the yoke may be maintained at a fixed orientation relative to the linear actuator, reducing the generation of stresses on the linear actuator and increasing the range of linear actuators that may be used. It will be understood that the term “pitching” with reference to the pitching dowel and pitching slot is merely a label and is not intended to impart any particular limitation onto the dowel or slot. The lateral dowel may be a first lateral dowel and the lateral slot may be a first lateral slot, the actuation mechanism may further comprise: a second lateral dowel extending from the yoke in a direction opposite to the second actuator direction, and a second lateral slot in the yoke housing, wherein the second lateral dowel is received in the second lateral slot and moveable along the second lateral slot in the second rail direction, the second lateral slot preventing relative movement between the second lateral dowel and the yoke housing in the first rail direction, and the first lateral dowel and the second lateral dowel may be coaxial. By providing two lateral dowels and two lateral slots, the relative change in orientation between the yoke and the yoke housing may be constrained to pitching in the direction of the rail by the dowels alone. This may reduce any bending moment being exerted on the linear actuator. The rail may extend in a single plane and the linear actuator may extend parallel to the single plane. In this case, the required degrees of freedom of the yoke may be reduced, allowing a simpler and lighter mechanism to be used. In this case, the third actuator direction and the third rail direction may both be normal to the single plane and so may be parallel. The rail may be curved or non-straight and may be curved or bent in a single plane, such that any curves or bends in the rail may all be in the same direction, i.e. curved about parallel axes normal to the plane in which the rail lies. The rail may be a first rail and the slide block may be a first slide block, the vehicle panel actuation mechanism may further comprise: a second rail coupled to the vehicle panel; and a second slide block coupled to the vehicle, the linear actuator and the yoke may be arranged between the first and second rails. In this way, the vehicle panel may be better supported. The yoke housing may be arranged between the first and second slide blocks and the first and second slide blocks may be rigidly coupled via the yoke housing. The two rails may be parallel. The rails and the slide blocks may be arranged symmetrically about a centreline of the vehicle panel or the vehicle. The slide block may be coupled to the vehicle body via at least one arm, the at least one arm being arranged to move the slide bock relative to the vehicle body in a direction away from the vehicle body. The at least one arm may be pivotally coupled to the vehicle body. The at least one arm may move the slide block and the vehicle panel away from the vehicle body, allowing the vehicle panel to sit flush with surrounding vehicle panels in a closed position, and to move away from the vehicle as it transitions to an open position, allowing the vehicle panel to move closely around the vehicle by actuation of the linear actuator. The vehicle panel actuation mechanism may further comprise a further actuator arranged to move the at least one arm relative to the vehicle body to move the slide block relative to the vehicle body. The further actuator may be arranged in the vehicle body. This may allow the vehicle panel to be made smaller. Further, the further actuator may be operated separately from the linear actuator, allowing a greater level of customisation of the motion of the vehicle panel. The linear actuator may be a screw drive and the yoke may comprise a nut arranged on the screw drive. A screw drive may provide a high range of movement relative to the length of the actuator. This may allow the vehicle panel to be moved along substantially its entire length by the linear actuator. This may improve access to a compartment covered by the vehicle panel. The screw drive may be arranged on a centre line of the vehicle panel or of the vehicle. The screw drive may be equidistant from the two rails. The linear actuator may be arranged within the vehicle panel. By arranging the linear actuator within the vehicle panel, the number of mechanical connections between the vehicle body and the vehicle panel may be reduced. This may allow improved access to a compartment covered by the vehicle panel. According to another aspect of the invention, there is provided a vehicle comprising: a vehicle body; a vehicle panel moveable relative to the vehicle body; and the vehicle panel actuation mechanism of the first-mentioned aspect. The vehicle panel may be a tailgate. In this case, the vehicle panel may cover a boot or trunk space. The tailgate may be arranged to move above a roof of the vehicle. Overall, the mechanism may allow a tailgate to remain close to a vehicle body as it opens. This may allow easier access to the boot space, such as in cases where the vehicle is parked under a low ceiling. 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 is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, 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: Figure 1 shows a side view of a vehicle in accordance with the invention with a tailgate in a closed position; Figure 2 shows a rearview of the vehicle of Figure 1 with the tailgate in the closed position; Figure 3 shows a side view of the vehicle of Figure 1 with the tailgate in an open position; Figure 4 shows a rearview of the vehicle of Figure 1 with the tailgate in the open position; Figures 5a to 5c show a vehicle panel opening mechanism; Figure 6a, 6b and 6c show schematic drawings of a vehicle panel opening mechanism in accordance with the invention; Figure 7a and 7b show schematic drawings of a vehicle panel actuation mechanism in accordance with the invention; Figure 8a and 8b show schematic drawings of a further vehicle panel actuation mechanism in accordance with the invention; Figure 9 shows a yoke arrangement for use with a vehicle panel actuation mechanism in accordance with the invention; Figure 10 shows a further yoke arrangement for use with a vehicle panel actuation mechanism in accordance with the invention; and Figures 11 a and 11 b show a still further yoke arrangement for use with a vehicle panel actuation mechanism in accordance with the invention. DETAILED DESCRIPTION A vehicle in accordance with an embodiment of the present invention is described herein with reference to the accompanying Figures 1 to 4. As shown in Figures 6a to 8c, there is also provided a vehicle panel opening mechanism according to the present invention. Figures 1 to 4 show a vehicle 10 having a vehicle body 25. The vehicle 10 has a number of vehicle panels that are arranged to allow access into the vehicle. For example, the vehicle 10 has a front door 14, which may be referred to as a driver door or a passenger door, which allows access to a passenger compartment of the vehicle 10. The vehicle 10 also has a rear passenger door 16, to allow access to a rear portion of a passenger compartment. The vehicle 10 also has a bonnet or hood 20 at the front of the vehicle 10, which may allow access to an engine compartment or a front storage compartment, which may be referred to as a trunk. The vehicle 10 has a rear storage compartment 12, which may be referred to as a boot or trunk 12. The rear storage compartment 12 is accessible via a movable tailgate 18. The tailgate 18 may be moved into a closed position, which is shown in Figures 1 and 2, where the rear storage compartment 12 is relatively isolated from the external environment and inaccessible to a person outside the vehicle. The tailgate 18 may be moved to an open position, shown in Figures 3 and 4, where the rear storage compartment 12 may be accessible to a person outside the vehicle 10. It will be understood that any of the vehicle panels may be opened using a vehicle panel opening mechanism described herein, and that any of the vehicle panels, such as the bonnet or the doors, may be omitted, may be maintained substantially closed or immovable, or may be opened using a different vehicle panel opening mechanism. As can be seen from Figures 3 and 4, the tailgate 18 may be positioned over the roof 15 of the vehicle when the tailgate 18 is in the open position. This may allow the tailgate to be opened when the vehicle 10 is in a confined area, such as an area with a low ceiling. This may also allow improved access to the rear storage compartment 12 from above, due to the tailgate 18 not being situated above the rear storage compartment 12 when in the open position. Figures 5a to 5c show a vehicle panel opening mechanism 100 for moving a vehicle panel from a closed position shown in Figure 5a to an open position shown in Figure 5c via a partially open position shown in Figure 5b, and in the opposite direction. It will be understood that the vehicle panel opening mechanism 100 may be used for opening any vehicle panel, including vehicle doors or a vehicle bonnet or hood, as well as being used to open a vehicle tailgate in the manner shown in Figures 1 to 4. The vehicle panel opening mechanism 100 comprises a first lifting member 104 and a second lifting member 105. The first lifting member 104 has a first end 104a that is pivotally coupled to a base 102 and the second lifting member 105 has a first end 105a that is pivotally coupled to the base 102. The base 102 may comprise one or more lugs fixed to a plate that in turn is arranged to be coupled to a vehicle body, or may be any other coupling arrangement that may be fixed to, or a portion of, a vehicle body. A second end 104b of the first lifting member 104 is pivotally coupled to a carriage 106 and a second end 105b of the second lifting member 105 is also pivotally coupled to the carriage 106. The carriage 106, which may also be referred to as a slide block 106, is slidably engaged with a rail 108. The rail 108 is in turn fixed to the moveable vehicle panel 110, which may be a tailgate. The carriage 106 may have a fixed orientation relative to the base 102 and so may move relative to the base 102 in a pure translation. The orientation of the carriage 106 may alternatively vary controllably relative to the base 102 as carriage 106 is moved. In some cases, the second lifting member 105 may be omitted and the orientation of the carriage 106 may be determined by an actuator or gear arrangement arranged between the carriage 106 and the first lifting member 104. As can be seen by comparing Figures 5a and 5b, the base 102, first lifting member 104, carriage 106 and second lifting member 105 form a four-bar mechanism which constrains the orientation of the carriage 106 as it is moved from the closed position to the partially open position. In this way, the carriage 106 may have an orientation that is constrained relative to the base 102 without any gearing mechanism or further actuators being required. The provision of the second lifting member 105 may therefore have the benefit of providing a lightweight means of constraining the orientation of the carriage 106. It will be understood that both lifting members 104,105 may be omitted some cases, and that the carnage 106 may be moved relative to the base 102 via an hydraulic actuator or other lifting means. The carriage 106 and the rail 108 may be arranged to slide relative to one another, and may have rolling elements or rotatable discs arranged between them, which may move within a groove of the rail 108. In the closed position, as shown in Figure 5a, the carriage 106 may be at an end of the rail 108 that is proximal the base 102. As the lifting member 104 moves the vehicle panel 110 toward a partially open position, which is shown in Figure 5b, the vehicle panel 110 may move in a direction parallel to the vehicle opening toward the base 102, as well as being moved out of the opening in which the vehicle panel 110 may sit. This may reduce a required length of the rail 108. Together, the lifting members 104,105 and the pivotal ends 104a, b, 105a, b thereof define a lifting mechanism which is arranged to move the vehicle panel 110 outwardly relative to a vehicle body, such that the vehicle panel 110 may attain the position shown in Figure 5b, where the vehicle panel may substantially overlap an opening in the vehicle body while being spaced from the vehicle body. Put another way, the vehicle panel may be moved in a direction normal to a plane of the opening, so that the vehicle panel 110 is free to slide relative to the vehicle body, which may be sliding in a direction along a contour of the vehicle body. As shown in Figure 5c, the rail 108 may slide relative to carriage 106 to move from the partially open position shown in Figure 5b into the open position shown in Figure 5c. In this way, the vehicle panel 110 may be moved away from the opening in the vehicle body, to allow access to the interior of the vehicle body, such as to a rear storage compartment of the vehicle. The rail 108 and the vehicle panel 110 may be curved. It will be understood that in some cases the vehicle panel 110 may be substantially flat and the rail 108 may be curved or that the vehicle panel 110 may be curved and the rail 108 straight. The rail 108 and / or the vehicle panel 110 may slide in a curve between the partially open position shown in Figure 5b and the fully open position shown in Figure 5c. By being curved, the vehicle panel 110 may lie flush with surrounding surfaces of a vehicle when in the closed position. By providing a curved rail 108, the vehicle panel 110 may remain close to the vehicle body when moving to the open position, further improving accessibility of the interior space of the vehicle when the vehicle is in a confined space. While Figures 5a to 5c show the lifting mechanism comprised of the lifting members being moved through its entire range of motion before sliding of the rail relative to the carriage commences, the rail may begin to slide relative to the carriage before the lifting members have moved through their entire range of motion. In this way, when an instruction is received to open the vehicle panel, an actuator may begin to move the lifting members in order to move the carriage relative to the base, and subsequently a further actuator may be actuated to move the rail relative to the carriage, the further actuator being actuated before the first actuator has moved the lifting members through their complete range of movement. In this way, a smooth transition from a fully closed state to a fully open state may be achieved without jerking or juddering of the vehicle panel. Figures 6a to 6c show a further vehicle panel opening mechanism 200. In Figure 6a to 6c, the vehicle panel has been omitted in order to show underlying details of the vehicle panel lifting mechanism more clearly. However, it will be understood that the vehicle panel may be fixed to the rails 208a, 208b that are part of the vehicle panel lifting mechanism 200. The vehicle panel opening mechanism 200 comprises a base 202, which may be a coupling plate that is formed as a single piece to support the vehicle panel opening mechanism and the vehicle panel. The vehicle panel opening mechanism base 202 may include lugs for coupling to a vehicle panel lifting mechanism and may support the lifting mechanism and one or more actuators arranged to move the lifting mechanism. A plurality of lugs 203 extend upwardly from the plate 202, the lugs 203 being pivotally coupled to lifting members 204a, 204b, 205a, 205b of a lifting mechanism. The lifting mechanism may comprise two first lifting members 204a, 204b, which may be coupled together or fixed together via a shaft 224. By coupling the first lifting members 204a, b together via the shaft 224, the lifting members may move in tandem, allowing even lifting of the vehicle panel. Further, torque may be applied to the shaft 224 in order to move the lifting mechanism and so torque may be applied at a single point and distributed by the shaft 224. This may allow a single actuator to operate the lifting mechanism. To this end, an actuator 220, which may be lifting actuator and may include an electric motor and / or a gearbox, may be coupled to the shaft 224 via a linkage 222. The linkage 222 may allow the lifting actuator 220 to be situated a distance from the shaft 224, allowing the actuator 220 to be situated under an adjacent panel of the vehicle, such as a roof of the vehicle. This may improve access to the opening covered by the vehicle panel. The lifting mechanism actuator 220 may be arranged on and / or fixed to the vehicle coupling plate 202 in order to allow the lifting mechanism to be installed more easily, as the entire lifting mechanism may be coupled to the vehicle body via the vehicle coupling plate 202. The second lifting members 205b, 205a may be freely movable and pivotable relative to lugs 203 extending from the coupling plate 202 such that the first and second lifting members 204a, 204b, 205a, 205b may, together with the coupling plate 202 and the carriages 206a, 206b, form a four bar mechanisms to constrain the orientation of the carriages 206a, b as the carriages are moved by the lifting mechanism. The carriages 206a, 206b may therefore be moved into a partially open arrangement shown in Figure 6b, such as by the actuator 220. The rails 208a, 208b, to which the panel may be fixed, may then be moved relative to the carriages 206a, b by actuation of a second actuator 212. The second actuator 212 may also be referred to as a sliding actuator 212 and may be a screw drive that is arranged to rotate a threaded shaft, the threaded shaft being received in a nut or hub 214, which may also be referred to as a yoke 214 that is coupled to the carriages 206a, 206b. By rotation of the threaded shaft by the sliding actuator 212, the rails 208a, 208b may be arranged to slide relative to the carriages 206a, b in order to move the vehicle panel along the vehicle body in order to allow access to the interior of the vehicle. The sliding actuator 212 may be fixed to and moveable with the rails 208a, 208b and the vehicle panel, such that the nut 214 remains in a substantially constant position relative to the carriages 206a, b as the vehicle panel is moved by the sliding actuator 212. The vehicle panel may therefore be moved into the fully open position shown in Figure 8c. It will be understood that some relative movement between the nut 214 and carriages 206a, b may be allowed in order to compensate for the curvature of the rails 208a, b as explained below. This may be provided by a yoke arrangement. The second actuator 212 may alternatively be a linear or telescoping actuator, and the nut 214 may be a hub or yoke that is coupled to the second actuator 212. Power may be supplied to the sliding actuator 212 and any other actuators within the vehicle panel, via a wire or cable which may pass along one of the lifting members. The wire or cable may also transfer data to and from the sliding actuator 212. Figures 7a and 7b show a vehicle actuation mechanism in accordance with the present invention. It will be understood that elements of the vehicle actuation mechanism shown in Figures 7a and 7b may be accentuated in order to display the underlying principles of the invention and that features such as the curvature of the rail and the length of the slot may be reduced in reality. The vehicle panel actuation mechanism 300 comprises a rail 308, which is non-straight and may be described as curved. The rail 308 is arranged to be fixed to a vehicle panel in order to move with the vehicle panel. The vehicle panel actuation mechanism 300 also comprises a slide block or carriage 306. The rail 308 may be slidably coupled to the slide block 306, and the rail 308 may have one or more grooves, the slide block 306 may have one or more rolling or rotatable elements received within the grooves of the rail 308. As the rail slides, the slide block 306 may be considered to be substantially stationary and the rail 308 may translate and rotate as it slides through the slide block 306. The panel actuation mechanism 300 also comprises an actuator 302, which is arranged to move the rail 308 relative to the slide block 306, the actuator 302 may be a linear actuator, such as a telescoping linear actuator or may be a screw drive. The actuator 302 is fixed at a first end 302a to the rail 308 such that the first end 302a of the actuator 302 translates and rotates with the rail 308. At an opposite end, or at a second point, of the actuator 302, the actuator 302 is coupled to a yoke mechanism 310. The yoke mechanism 310 is arranged to allow the point at which the actuator 302 is coupled to the slide block 306 to slide and rotate relative to the slide block 306. The yoke mechanism 310 may be formed of a dowel 314, which may be a substantially cylindrical piece of material, and a slot 312, in which the dowel 314 may be received. The slot 312 may be fixed to the slide block 306, such that slot 312 extends perpendicularly to the direction the rail 308 passes through the slide block 306. The slot 312 may be formed in an extension of the slide block 306 or may be formed in a separate part that is fixed to the slide block 306. In an alternative yoke mechanism, the dowel may be replaced by a rotatable extension from the actuator 302, the rotatable extension having a channel for receiving a rod extending from the slide block 306. Generally, any slidable and rotatable coupling mechanism between the slide block 306 and the actuator 302 may be provided. In order to understand the principles of the invention, since the actuator 302 and rail 308 may rotate relative to the slide block 306, the actuator may be described with reference to a reference frame which has a first actuator direction A1, a second actuator direction A2, which is perpendicular to the page, and a third actuator direction A3. The actuator 302 may be arranged to extend and to retract in the first actuator direction A1. The slide block 306, and the portion of the rail 308 that is situated in slide block, which will naturally be aligned with the slide block, may be described using a rail reference frame, which includes a first rail direction R1, which is the direction that the rail 308 is constrained to slide through the slide block 306, and a second direction R2, which is non-parallel to the first rail direction R1. The slot 312 may therefore extend in the second rail direction R2, which that is not parallel to the first rail direction R1, so as to constrain the position of the rail 308 relative to the slide block to be dependent on the extension of the actuator. The second rail direction R2, and the direction of extension of the slot 312, may be perpendicular to the first rail direction R1 in order to reduce play in the system and to better constrain the position of the rail 308. Figure 7b shows the vehicle panel actuation mechanism 300 in a second position. It can be seen that the actuator 302 is retracted in order to move the rail 308 through the slide block 306. In this position, the dowel 314 is moved closer to the first end 302a of the actuator 302. Due to the curvature of the rail, the actuator 302 has also rotated relative to the slide block 306, such that the first actuator direction A1 is rotated relative to the first rail direction R1. The dowel 314 has also moved along the slot 312, in order to account for the change in position of the rail 308 and actuator 302 relative to the slide block 306 in the second rail direction R2 as the rail 308 moves through the slide block 306. In this way, it can be understood that the slot 312 may allow the actuator 302 to move relative to the slide block 306 in a direction perpendicular to the first rail direction R1. Figure 8a and 8b show a further vehicle panel actuation mechanism 400. The further vehicle panel actuation mechanism 400 comprises a rail 408, and a slide block 406 substantially similar to those described above with reference to Figures 7a and 7b. The vehicle panel actuation mechanism 400 also comprises an actuator 402, which similarly to the actuator of Figures 7a and 7b, may be a linear telescoping actuator or may be a screw drive. The actuator 402 is fixed to the rail 408 at a first end 402a and at a second end, or a second point spaced from the first end, is coupled to a yoke mechanism 410, the yoke mechanism 410 being slidably and pivotally coupled to the slide block 406. The yoke mechanism 410 comprises a rod 412, which is rigidly coupled to the actuator 402, to rotate with the actuator 412, i.e. to remain fixed in the actuator reference frame. The rod 412 is arranged to move relative to the rail 408 as the actuator extends and contracts. The rod 412 is pivotally coupled and slidably coupled to the slide block 406 at a coupling point 414. The coupling point 414 may comprise an extension from the slide block extending out of the page (i.e. in the second actuator direction or the third rail direction) that is received in a slot within the rod 412. Alternatively, the coupling point 414 may comprise a rotatable channel in the slide block 406 arranged to receive the rod 412. As can be seen by comparing Figures 8a and 8b, the rod 412 may be fixed relative to the actuator reference frame and may be substantially aligned with the third actuator direction A3, which is non-parallel to the first actuator direction A3. In particular, the rod 412 and the third actuator direction A3 may be perpendicular to the 10 first actuator direction A1. Therefore, as the actuator 402 contracts, the rod 412 may rotate due to the curvature of the rail 408 as the rail 408 passes through the slide block 406, and the rod 412 may slide relative to the slide block 406 in the third actuator direction A3 due to the coupling mechanism at coupling point 414. With reference to Figures 7a to 8b, it will be understood that, in cases where the real may exhibit a small degree of curvature, the actuator 402 may be slidably coupled to the slide block 406 and not pivotally coupled or may be rotatably coupled and not slidably coupled. Such an arrangement may require a small degree of play between the slide block and the actuator or a degree of flexibility of the actuator, but may allow a simpler coupling mechanism to be provided between the actuator and the slide block. Figures 9 to 11b shows yoke mechanisms for use in a vehicle panel actuation mechanism, in particular, the vehicle panel actuation mechanisms disclosed above with reference to Figures 5a to 6c. The yoke arrangement 500 is arranged on an actuator 502, which may be the actuator of any above-described arrangement. An actuator coupling member 504, which may be referred to as a yoke 504, is coupled to the actuator 502. Where the actuator 502 is a screw drive, the actuator coupling mechanism 504 may be a nut, which may be arranged around a threaded shaft of the actuator 502. Where the actuator 502 is an extendable linear actuator, the actuator coupling member 504 may be a straightforward coupling arrangement. The yoke arrangement 500 is coupled to carriage portions 506a, 506b, which are each arranged to be coupled to or fixed to a respective slide block, in particular, the slide blocks 206a, 206b disclosed with reference to Figures 6a to 6c. It will be understood that, in some cases, only a single carriage portion 506 a, b may be provided, but that provision of two separate carriage portions 506 a, b may reduce a bending moment on the actuator 502 due to resistance of the rail and slide block arrangement. The yoke arrangement 500 comprises two dowels 508a, 508b, each extending in a second actuator direction A2, which may be perpendicular to an extension direction of the actuator 502, which is a first actuator direction A1. The dowels 508a, 508b are each received in a respective slot 510a, 510b formed in a respective carriage portion 506a, 506B. The slots 510a, 510b extend in a second rail direction R2, which is non-parallel to the first rail direction and optionally may be perpendicular to the first rail direction R1. The dowels 508a, 508b are therefore free to move relative to the slots 510a, 510b in the second rail direction R2 as the carriage portions 506a, b will remain fixed relative to the slide blocks. Further, the dowels 508a, 508b may be coaxial and may be free to rotate in the slots 510a, b. In this way, the actuator 502, and the actuator nut 504 may be free to rotate in the slots 510a, 510b about an axis in the second actuator direction A2, i.e. about an axis along the direction of extension of the dowels 508a, b. In order to improve rotational freedom of the actuator 402 relative to the carriage portions 506a, b, the dowels may be cylindrical. The actuator 502 may also slide relative to the carriage portions 506a, 506b, as the dowels 508a, b may slide along the slots 510a, b in the second direction R2. When the actuator 502 is extended or retracted, the dowels 508a, b may engage and abut the sides of the slots 510a, b and in this way a normal reaction force may be generated between the carriage portions 506a, b 11 and the actuator 502. Since the actuator 502 may be fixed one or more rails, and the carriage portions 506a, b may be fixed to one or more slide blocks, this may result in the rails moving through the slide blocks. Figure 10 shows a further yoke arrangement 600, comprising an actuator 602, an actuator hub or yoke 604, carriage portions 606a, 606b, and dowels 608a, 608b, which may be substantially similar to the similarly named parts described above reference to Figure 9. In the yoke arrangement 600, slots 610a, 610b formed in the carriage portions 606a, 606b comprise sides extending in a second rail direction R2, i.e. perpendicular to the sliding direction of slide blocks fixed to the carriage portions, which is the first rail direction R1. This may increase a range of movement of the dowels 608A, 608b within the slots 610a, 610b. Accordingly, a more curved rail may be used with such an arrangement, while the dowels may remain in their respective slots. A still further yoke arrangement 700 is shown in Figures 11 a and 11 b. Figures 11 a and 11 b show the same yoke arrangement 700 from the same angle, with hidden features not being shown in Figure 11b for clarity, while hidden features are shown in Figure 11a for completeness. The yoke arrangement 700 of Figure 11a is coupled to an actuator 702, which may in particular be a screw drive comprising a motor unit fixed to a rail and a threaded shaft rotatable by the motor unit. Actuator 702 is coupled to an actuator hub or yoke 704, which may be a nut that is threaded onto a threaded shaft of the actuator 702. The actuator hub 704 may form part of a yoke assembly, which may also be referred to as a floating yoke due to the freedom of movement of the actuator hub 704 relative to the carriage portions 706a, 706b. The actuator hub 704 has first dowels 708a, 708b, which may be referred to as lateral dowels 708a, 708b, extending from the actuator hub 704 in a direction that is non-parallel to the direction of extension of the threaded rod of the actuator 702, which may be referred to as a second actuator direction A2. In some cases, as described above, the dowels 708A, 708B may extend in a direction that is perpendicular to the direction of the threaded rod. The actuator hub 704, also includes further dowels, which may be referred to as pitching dowels 712a, 712b. The pitching dowels 712a, 712b extend in a third actuator direction A3, which may be perpendicular to the direction of extension of the lateral dowels 708 a, b (i.e. the second actuator direction A2) and perpendicular to the direction of extension of the threaded rod 702 (i.e. the first actuator direction A1). The pitching dowels 712a, b are each received in a respective pitching slot 714a, 714b. The pitching slots 714a, 714b extend in the first rail direction R1. A single pitching dowel 712a in a single pitching slot may serve the same purpose as the two pitching dowels 712a, 712b and two pitching slots 714a, b. Therefore, one of the pitching dowels and one of the pitching slots may be omitted. However, provision of two such dowels and slots may allow improved stability of the yoke arrangement and reduced stress on the components. The yoke arrangement 700 further comprises a yoke housing 709, which is fixed to the carriage portions 706 a, 706b and extends between the carriage portions 706a, 706b. The yoke housing 709 is arranged to surround the actuator hub 704 and includes slots for receiving dowels of the actuator hub 704. In this way, the yoke housing 709 may improve the strength of the carriage arrangement and may support the actuator hub 704 in a plurality of directions. The yoke housing 709 is formed from two side portions 709a, 709b and a top portion 709c. The top portion 709c is fixed to the side portions 709a, b and extends between the side portions 709a, b. The top portion 709c may alternatively be replaced with a bottom portion or may be formed of two separate portions, each separate portion being fixed to a respective side portion 709a, b. The yoke housing 709 has lateral slots 710 a, 710b arranged in the side portions 709a, 709b of the yoke housing 709, the side portions 709a, 709b of the yoke housing 709 being fixed to the carriage portions 706a, 706b. The side portions 709a, 709b may extend from the carriage portions along the second rail direction R2. The yoke housing 709 has pitching slots 714a, 714b arranged to receive respective pitching dowels 712a, 712b. the pitching dowels 712a, 712b are movable along the pitching slots 714a, 714b in a direction parallel to the path of a rail through a slide block, i.e. the first rail direction R1. The interaction between the pitching dowels 712a, 712b and the pitching slots 714a, 714b may allow the actuator hub 704 to rotate about an axis through the lateral dowels 708a, 708b and may prevent rotation of the actuator hub 704 about an axis along an extension direction of the actuator 702, i.e. the first actuator direction A1. In this way, where the actuator hub 704 is a nut and the actuator 702 comprises a threaded rod, rotation of the nut 704 may be resisted by engagement of the pitching dowels 712a, b with the sides of the pitching slots 714a, b, such that the nut is movable along the threaded rod by rotation of the threaded rod. Overall, the arrangement 700 may allow the actuator 702 to pitch about an axis through the lateral dowels 708a, 708b, and to slide along a direction perpendicular to the rail, which is along the lateral slots 710a, 710b. Rotation of the actuator hub 704 about the threaded rod may be resisted by the pitching dowels 712a, b in the pitching slots 712b. A force may be transmitted along the direction of the actuator 702 between the lateral dowels 708a, b and the lateral slots 708b, to cause a rail to move through the slide blocks as shown in Figures 5a to 8b. 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.

Claims

1. A vehicle panel actuation mechanism comprising:a slide block coupleable to a vehicle body;a rail coupleable to a vehicle panel and moveable from a first position to a second position, the rail being arranged to slide relative to the slide block in a first rail direction, the rail having a non-straight shape;a yoke slidably coupled to the slide block such that the yoke is arranged to move relative to the slide block in a second rail direction, the second rail direction being non-parallel to the first rail direction; anda linear actuator coupleable between the vehicle panel and the yoke and arranged to impart a force to the yoke in a first actuator direction to move the vehicle panel relative to the vehicle body;wherein the yoke is arranged to slide relative to the slide block in the second rail direction to allow the first actuator direction to vary dependent on the non-straight shape of the rail as the rail moves from the first position to the second position; andwherein the first actuator direction has a component in the first rail direction while the rail moves from the first position to the second position.

2. The vehicle panel actuation mechanism of claim 1, wherein the yoke is rotatable relative to the slide block.

3. The vehicle panel actuation mechanism of claim 1 or 2, further comprising:a yoke housing fixed to the slide block, the yoke housing at least partially surrounding the yoke, and one or more sliding and / or pivotal joints between the yoke and the yoke housing.

4. The vehicle panel actuation mechanism of claim 3, further comprising a lateral dowel extending from the yoke in a second actuator direction perpendicularto the first actuator direction, the lateral dowel being received in a lateral slot in the yoke housing and moveable along the lateral slot in a second rail direction, the lateral slot preventing relative movement between the lateral dowel and the yoke housing in the first rail direction.

5. The vehicle panel actuation mechanism of claim 4, further comprising a pitching dowel extending from the yoke in a third actuatordirection, the third actuator direction being perpendicularto the first and second actuator directions, the pitching dowel being received in a pitching slot in the yoke housing and moveable along the pitching slot in the first rail direction, the pitching slot preventing relative movement between the pitching dowel and the yoke housing in a third rail direction, the third rail direction being perpendicularto the first and second rail directions.

6. The vehicle panel actuation mechanism of claim 5, wherein the lateral dowel is a first lateral dowel and the lateral slot is a first lateral slot, the actuation mechanism further comprising:a second lateral dowel extending from the yoke in a direction opposite to the second actuator direction, anda second lateral slot in the yoke housing,wherein the second lateral dowel is received in the second lateral slot and moveable along the second lateral slot in the second rail direction, the second lateral slot preventing relative movement between the second lateral dowel and the yoke housing in the first rail direction, andwherein the first lateral dowel and the second lateral dowel are coaxial.

7. The vehicle panel actuation mechanism of any preceding claim, wherein the rail extends in a single plane and wherein the linear actuator extends parallel to the single plane.

8. The vehicle panel actuation mechanism of any preceding claim, wherein the rail is a first rail and the slide block is a first slide block, the vehicle panel actuation mechanism further comprising:a second rail coupled to the vehicle panel; anda second slide block coupled to the vehicle, wherein the linear actuator and the yoke being arranged between the first and second rails.

9. The vehicle panel actuation mechanism of any preceding claim, wherein the slide block is coupled to the vehicle body via at least one arm, the at least one arm being arranged to move the slide bock relative to the vehicle body in a direction away from the vehicle body.

10. The vehicle panel actuation mechanism of claim 9, further comprising a further actuator arranged to move the at least one arm relative to the vehicle body to move the slide block relative to the vehicle body.

11. The vehicle panel actuation mechanism of any preceding claim, wherein the linear actuator is a screw drive and wherein the yoke comprises a nut arranged on the screw drive.

12. The vehicle panel actuation mechanism of any preceding claim, wherein the linear actuator is arranged within the vehicle panel.

13. A vehicle comprising:a vehicle body;a vehicle panel moveable relative to the vehicle body; and the vehicle panel actuation mechanism of any preceding claim.

14. The vehicle of claim 13, wherein the vehicle panel is a tailgate.

15. The vehicle of claim 14, wherein the tailgate is arranged to move above a roof of the vehicle.

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