GB2541731A

GB2541731A - An inductive power transfer pad and method of operating an inductive power transfer pad

Info

Publication number: GB2541731A
Application number: GB1515336.4A
Authority: GB
Inventors: Wechsler Simon; Gunt Roman; Schuele Robert
Original assignee: Bombardier Transportation GmbH
Current assignee: Alstom Transportation Germany GmbH
Priority date: 2015-08-28
Filing date: 2015-08-28
Publication date: 2017-03-01
Also published as: WO2017036942A1; GB201515336D0

Abstract

An inductive power transfer pad, 1, in particular a transfer pad of a system for inductive power transfer to a vehicle. The pad (plate) comprises a stationary part, 2, and a movable part, 7, wherein the movable part comprises a primary winding structure (coil, transmitter), 8. The inductive power transfer pad comprises at least one actuating means to allow the movable part to move in at least one direction, z. The actuating means is provided by a shape memory alloy (SMA, smart alloy, memory alloy) actuator, 6. The pad may include four shape memory alloy actuators. The shape memory alloy actuator may comprise a metal sheet element, 11, connected to a current source, 10. The metal sheet may be designed as a corrugated strip. The pad may include a cooling unit thermally coupled to the shape memory alloy actuator. The pad may also include a scissor lift.

Description

AN INDUCTIVE POWER TRANSFER PAD AND METHOD OF OPERATING AN INDUCTIVE POWER TRANSFER PAD

An inductive power transfer pad and a method of operating an inductive power transfer pad

The invention relates to an inductive power transfer pad, in particular a transfer pad of a system for inductive power transfer to a vehicle, and a method of operating such an inductive power transfer pad.

Electric vehicles, in particular a track-bound vehicle, and/or a road automobile, can be operated by electric energy which is transferred by means of an inductive power transfer. Such a vehicle may comprise a circuit arrangement, which can be a traction system or a part of a traction system of the vehicle, comprising a receiving device adapted to receive an alternating electromagnetic field and to produce an alternating electric current by electromagnetic induction. Furthermore, such a vehicle can comprise a rectifier adapted to convert an alternating current (AC) to a direct current (DC). The DC can be used to charge a traction battery or to operate an electric machine. In the latter case, the DC can be converted into an AC by means of an inverter.

The inductive power transfer is performed using two sets of e.g. three-phase windings. A first set is installed on the ground (primary windings or primary winding structure) and can be fed by a wayside power converter (WPC). The second set of windings (secondary winding structure) is installed on the vehicle. For example, the second set of windings can be attached underneath the vehicle, in the case of trams under some of its wagons. For an automobile it can be attached to the vehicle chassis. The second set of windings or, generally, the secondary side is often referred to as pick-up-arrangement or receiver. The first set of windings and the second set of windings form a high frequency transformer to transfer electric energy to the vehicle. This can be done in a static state (when there is no movement of the vehicle) and in a dynamic state (when the vehicle moves).

In particular in the case of road automobiles, a stationary primary unit comprises a plurality of elements which are often arranged spatially separated. GB 1306403.5 (not yet published) discloses an inductive power transfer pad, in particular an inductive power transfer pad of a system for inductive power transfer to a vehicle, comprising a housing, a primary winding structure, a connecting terminal, wherein the inductive power transfer pad further comprises an inverter, wherein the inverter is arranged within the housing, wherein an input side of the inverter is electrically coupled to the connecting terminal and an output side of the inverter is electrically coupled to the primary winding structure.

Also known are inductive power transfer systems which comprise a movable primary element. US 5,654,621 A discloses an inductive transmitter having a primary element and a secondary element which is attached to the vehicle, wherein the primary element is power driven to move in all three spatial coordinates with a predetermined spatial area. DE 102010042395 A1 discloses a system for inductive charging of a battery of a vehicle, wherein a primary coil is automatically placeable. DE 102007033654 A1 discloses a base unit with a driving means to reduce a distance between a primary conductor and a secondary coil. US 2010/0235006 A1 discloses a movable automated charging apparatus comprising a base, a scissor lift, a pedestal, a joint and a charger. The charger is configured to mate with a vehicle receptacle physically or via proximity. PCT/EP2015/054106 (PCT application number, not yet published) discloses an inductive power transfer pad comprising a stationary part and a movable part, wherein the movable part comprises a primary winding structure, wherein the movable part is movable between a retracted state and an extended state. Further, the inductive power transfer pad is designed and/or controllable such that the movable part is only movable to a position from a set of predetermined positions, wherein the set of predetermined positions is a subset of all positions between the retracted and the extended state.

There is the technical problem of providing an inductive power transfer pad and a method of operating an inductive power transfer pad which provide a robust and accurate movement of a movable part of the inductive power transfer pad.

The solution to said technical problem is provided by the subject-matter with the features of claims 1 and 15. Further advantageous embodiments are provided by the subject-matter with the features of the sub claims.

An inductive power transfer pad, in particular a transfer pad of a system for inductive power transfer to a vehicle, is proposed.

An inductive power transfer pad, in particular a transfer pad of a system for inductive power transfer to a vehicle, is proposed. The inductive power transfer pad (IPT pad) can be part of a primary unit of a system for inductive power transfer. The power transfer pad comprises a stationary part and a movable part, wherein the movable part comprises a primary winding structure. The primary winding structure generates an alternating (electro-) magnetic field if the primary winding structure is energized or supplied with an operating current.

Further, the movable part can be movable between a retracted state and an extended state. The power transfer pad can comprise at least one actuating means, wherein the movable part is movable by the at least one actuating means. In the context of this invention, the term "actuating means" can denote an entity of all components or elements by which the movement of the movable part is generated. The term "actuating means" can thus comprise at least one actuator and/or at least one lifting mechanism. Further, the actuating means can comprise coupling means for mechanically coupling the actuator and the lifting means and/or at least one guiding means for guiding the movement of the movable part.

The actuating means can be coupled to the movable part. It is possible that the actuating means is directly coupled to the movable part, wherein a driving force generated by the actuating means can directly be exerted onto the movable part. Alternatively, the actuating means can be coupled to the movable part via the scissor lift means. In this case, the driving force generated by the actuating means can be exerted onto the scissor lift means and thus be transferred to the movable part.

The movable part can be movable at least in the first direction by the at least one actuating means. Further, the movable part can be movable against the first direction, e. g. also by the at least one actuating means. A movement in the first direction can also be referred to as upward movement or lifting movement. A movement against the first direction can also be referred to as downward or lowering movement. The first direction can be oriented parallel to a main propagation direction of the electromagnetic field generated by the primary winding structure. In particular, the first direction can be oriented perpendicular to the bottom surface of the power transfer pad or a surface of the ground on which the power transfer pad is mounted, wherein the first direction is directed away from the ground. In the retracted state, an upper surface of the movable part can be arranged within the same plane as an upper surface of the stationary part.

In the context of this invention, the first direction can also be defined as a vertical direction. In the following, terms as “upper”, “lower”, “above”, “under”, “lowest”, “highest”, “bottom” refer to the vertical direction.

In the retracted state, the movable part, in particular an upper surface of the movable part, can be positioned at a retracted position, in particular with respect to the first direction, e.g. a predetermined lowest vertical position. In the retracted state, a height of the power transfer pad, i.e. a distance of the highest portion of the power transfer pad, e.g. the upper surface of the movable part, from a mounting portion of the power transfer pad along the first direction can be minimal. Correspondingly, in an extended state, the movable part, in particular an upper surface of the movable part, can be positioned at an extended position, e.g. a predetermined heighest vertical position. In the extended state, the height of the power transfer pad can be maximal. The mounting portion can correspond to a bottom surface of the power transfer pad. The mounting portion can be used to mount the power transfer pad to a mounting structure, in particular to a surface of a route. The retracted state and the extended state can be defined by mechanical elements, e.g. stop elements, and/or by the design of the actuating means.

The height in the retracted state can be chosen from an interval from 50mm to 110mm, in particular from an interval from 70mm to 90mm. Preferably, the height in the retracted state can be equal to 65 mm. The height in the extended state can e.g. be chosen from an interval of 95mm to 280 mm. Preferably, the height in the extended state can be equal to 230 mm.

Further, the power transfer pad can be designed and/or controllable such that the movable part is only movable (or movable only) to a position from a set of predetermined positions, wherein the set of predetermined positions is a subset of the set of all positions between the retracted and the extended state. In other words, the movable part can preferably be only movable to a set of selected discrete positions along the range of all theoretically possible positions between the retracted state and the extended state. The set of predetermined positions can comprise at least the position of the movable part in the retracted state and the position of the movable part in the extended state. In addition, the set of predetermined positions can comprise one or more, but not all, positions between the position of the movable part in the retracted state and the position of the movable part in the extended state.

The positions can denote positions along a trajectory of the movable part, wherein the movable part is moved along said trajectory from the retracted state to the extended state and vice versa. Also, the positions can denote positions with respect to the aforementioned first direction, e.g. vertical positions.

The power transfer pad can e.g. comprise at least one position sensing means for determining the position of the movable part. Depending on the sensed position of the movable part, the movement can be controlled, e.g. by a control unit, such that the movable part is moved to a selected position from a set of predetermined positions.

Alternatively or in addition, the power transfer pad, in particular the movable part, more particular at least one lifting or guiding means or mechanism for guiding the movement of the movable part, can comprise at least one, preferably multiple, stop element(s), wherein the at least one stop element is designed and/or arranged such that the movement of the movable part is restricted to a movement into the positions of the set from predetermined positions. The at least one stop element can e.g. be a mechanical element.

This advantageously allows a simple design of the power transfer pad and/or implementation of the motion control.

Further, the movable part can only be movable to the retracted state or to the extended state. In other words, the movable part is only movable to the position of the movable part in the retracted state, i.e. the retracted position, and to the position of the movable part in the extended state, i.e. the extended position. This means that the set of predetermined positions comprises only two positions.

This advantageously further simplifies the design of the power transfer pad and/or implementation of the motion control.

Further, the movable part can be, in particular only, movable in steps. The movement of the movable part can e.g. be a one-step movement, e.g. a movement between the retracted state and the extended state and vice versa, or a multiple-step movement. If the movement is a multiple-step movement, the steps can have equal length or can have different lengths.

According to the invention, the at least one actuating means is provided by a shape memory alloy actor (SMA actor). The shape memory alloy actor can be provided by a structure or an alloy which can adopt or take at least two shapes, preferably more than two or a variety of shapes. In particular, the memory shape alloy actor can have at least one defined shape, wherein SMA actor returns from a deformed shape to the defined shape if thermal energy is transferred to the SMA actor or drawn from the SMA actor. A first defined shape can e. g. be an extended shape, e. g. a shape in which the SMA actor has a maximal height. A further defined shape can e. g. be a retracted shape, e. g. a shape in which the SMA actor has a minimal height.

It is thus possible that the movable part is in the extended state if the at least one SMA actor takes or adopts the first defined shape. An upward movement of the movable part can e. g. be generated if thermal energy is transferred to the SMA actor. It is further possible that the movable part is in the retracted state if the SMA actor takes or adopts the further defined shape. A downward movement of the movable part can e. g. be generated if thermal energy is drawn from the SMA actor.

The first defined shape can also be referred to as high-temperature shape, wherein the further defined shape can be referred to as low-temperature shape. If thermal energy is transferred to the SMA actor, the SMA actor is heated and adopts or takes the first defined shape. If thermal energy is drawn from the SMA actor, the SMA actor is cooled and adopts or takes the second defined shape. Thus, the SMA actor can provide a so-called two-way shape memory effect.

Alternatively, the movable part can be in the extended state if the SMA actor is in the second defined shape, wherein the movable part is in the retracted state if the SMA actor is in the first defined shape.

It is also possible that the SMA actor can take more than two, in particular, multiple shapes, wherein each shape provides a different position along the first direction. Especially in this case, the movable part can be movable in steps.

The at least one SMA actor can be designed and/or arranged such that a driving force for generating an upward and/or a downward movement of the movable part can be directly exerted on the movable part. Alternatively, the driving force can be exerted on the movable part by at least one coupling means.

The movable part can be moved to a desired position by providing a temperature which corresponds to that position. To keep the position, it is desirable to keep the temperature.

It is also possible that the inductive power transfer means comprises at least one position fixing means, e.g. a braking means, wherein a position of the movable part can be fixed by the braking means. It is e.g. possible that a position or shape of the at least one SMA actor is fixable by the at least one position fixing means. Alternatively or in addition, a position or shape of at least one scissor lift means (which will be explained later) is fixable by the at least one position fixing means. Fixing the movable part in a desired position advantageously allows to reduce the power consumption of the SMA actors.

Further, the inductive power transfer pad can comprise at least one thermal insulation means for insulating the at least one SMA actor. This means that the at least one thermal insulation means can be designed and/or arranged that a transfer of thermal energy from or to a predetermined volume comprising at least a part of the SMA actor is minimized. This advantageously reduces the energy to operate the SMA actor. Further, environmental influences on the SMA actor are reduced.

The usage of a SMA actor advantageously allows a reliable and precise movement of the movable part.

In another embodiment, the inductive power transfer pad comprises four SMA actors. It is, of course, possible that the inductive power transfer pad comprises two, three or more than four SMA actors. Providing more than two, in particular three or four, SMA actors advantageously allows providing a statically determinated bearing of the movable part.

In another embodiment, the SMA actor comprises at least one metal sheet element, wherein the metal sheet element is electrically connected to a current source. In this embodiment, the inductive power transfer pad can additionally comprise the current source. An operating current can be provided or supplied to the at least one metal sheet element by the current source. Due to a resistance of the metal sheet element, the metal sheet element will be heated if the operating current flows through the metal sheet element. Thus, thermal energy is transferred to the SMA actor.

In particular, the at least one metal sheet element can be a strip-like element. The metal sheet element can e.g. consist of CuZn, CuZnAI, CuAINi, FeNiAI.

This advantageously provides an easy-to-implement way of transferring thermal energy to the SMA actor.

In another embodiment, a metal sheet element is designed as a corrugated strip. A corrugated strip can have a wave-like form, a sinusoidal form, a zig-zag form or any other form which provides projections and recesses relative to an uncorrugated center line of the strip. It is further possible that the corrugated strip is curved. This can mean that the corrugated strip extends along an uncorrugated curved center line, in particular along a part-circle-shaped line, wherein the corrugation is provided relative to the curved center line. The metal sheet element can e.g. be designed as a corrugated strip which provides a ring. This advantageously reduces a manufacturing effort with only a few components.

In another embodiment, the SMA actor comprises multiple metal sheet elements, wherein the multiple metal sheet elements are arranged one above the other, wherein two adjacent metal sheet elements are directly connected or wherein two adjacent metal sheet elements are coupled by at least one coupling element.

In the case of a direct connection, two adjacent metal sheet elements can be arranged one above the other, wherein a mechanical contact is provided between the two metal sheet elements. The mechanical contact can be provided by welding, soldering or glueing the metal sheet elements. Advantageously, no additional coupling element is required while maintaining a firm connection with a fixed relative position between two metal sheet elements. Further, the whole SMA actor can be made from a single piece of the shape memory alloy.

Alternatively, two adjacent metal sheet elements can be arranged one above the other, wherein no mechanical contact is provided between the two metal sheet elements. A coupling element can e.g. be a coupling block. The coupling element can e.g. be made of the same material like the metal sheet elements.

In particular, two adjacent metal sheet elements can be arranged one above the other such that a recess of one metal sheet element with respect to its center line faces a projection of the other metal sheet element with respect to its center line. Projections and recesses can be defined, as explained before, relative to an uncorrugated centre line of the metal sheet element. Further, recesses and projections can be defined with respect to the first direction.

Providing more than one metal sheet element which is arranged one above the other advantageously allows increasing a maximum displacement of the movable part.

In another embodiment, the inductive power transfer pad comprises at least one cooling unit, wherein the cooling unit is thermally coupled to the at least one SMA actor. The inductive power transfer pad can also comprise means for transferring thermal energy from the cooling unit to the SMA actor. If the cooling unit is operated, thermal energy can be drawn from the SMA actor. In particular, the SMA actor can be cooled down.

This advantageously allows a fast and precise movement of the movable part, in particular if the SMA actor has a high-temperature shape at a high temperature and a low-temperature shape at a low temperature, i.e. a lower temperature than the high temperature. Preferably, the low temperature is the temperature of the environment at the site at which the pad is employed. This can be the room temperature. It is also possible to define a stable intermediate holding position by heating the SMA actor or the metal sheets elements to an intermediate temperature which is a temperature between the high temperature and the low temperature. Moreover, the inductive power transfer pad can comprise a holding mechanism, e.g. arranged inside the inductive power transfer pad, to hold the SMA actor in the high, low or intermediate position.

In another embodiment, a first end of the SMA actor is connected to the stationary part. In particular, the first end can be connected to a base plate of the stationary part e. g. to an upper surface of said base plate. Further, a further end of the SMA actor is connected to the movable part. In particular, the further can be connected to a base plate of the movable part, more particular to a lower surface of said base plate. The first and the further end of the SMA actor can denote sections of the SMA actor which are moved relative to each other if the SMA actor changes its shape.

This advantageously allows directly exerting a driving force onto the movable part.

In another embodiment, the inductive power transfer pad comprises a scissor lift means, wherein the movable part and the stationary part are coupled by the scissor lift means. The scissor lift means can be used for guiding the upward and downward movement of the movable part.

In particular, the movable part and the stationary part are movably coupled by the scissor lift means. In the context of this invention, the term “coupling” can refer to a mechanical coupling or mechanical connection.

The scissor lift means can comprise one, preferably two, scissor arrangement/s. Preferably, the scissor lift means can comprise one scissor arrangement per longitudinal side of the movable part. Each scissor arrangement can comprise two scissor leg elements. The two scissor leg elements of one scissor arrangement can be movably connected or coupled. Preferably, all scissor leg elements of the scissor lift means are provided as common parts. This means that all scissor leg elements are designed similar.

The scissor lift means can be used to guide the movement between the retracted and the extended state. A driving force for the execution of said movement can be exerted onto the scissor lift means or directly onto the movable part.

As explained before, the scissor lift means can comprise a position fixing means for fixing a position of the movable part, e.g. a braking means.

In another embodiment, the first end of the SMA actor is connected to the stationary part. In particular, the first end can be connected to a base plate, in particular an upper surface of the base plate, of the stationary part. Further, a further end of the shape memory alloy actor is connected to the scissor lift means. In this case, a driving force is exerted onto the movable part via the scissor lift means, wherein the scissor lift means provides a coupling means for coupling the SMA actor and the movable part.

As will be explained in the following, a further end of the SMA actor can be connected to a central connecting element of the scissor lift means. It is, however, also possible to connect the further end of the SMA actor to any other movable part of the scissor lift means.

Connecting further end of the SMA actor to the scissor lift means advantageously allows using less SMA actors, e.g only one SMA actor. Further, no balancing between the multiple SMA actors is required. Further, an inherent stability is provided by the combination of the SMA actor and the scissor lift.

In another embodiment, a scissor arrangement of the scissor lift means is coupled to the stationary part by fixed bearings, wherein the scissor arrangement is coupled to the movable part by floating bearings. Thus, a scissor arrangement can be connected to the stationary part via fixed bearings and to the movable part via floating bearings. A fixed bearing can denote a bearing which does not allow a translational movement of the born or mounted part of the scissor arrangement, e. g. of a scissor leg element. However, a rotational movement of the born or mounted part can be allowed by the fixed bearing. For example, a scissor leg element can be pivotally coupled to the fixed bearing. A floating bearing can allow a translational movement of the born or mounted part of the scissor arrangement along one or more spatial direction(s). Further, the floating bearing can also allow a rotational movement of the born part. For example, the scissor leg element can also be pivotally coupled to the floating bearing

Preferably, a floating bearing is partially provided by an elongated hole within the movable part, wherein a guided element of a scissor leg element or connected to the scissor leg element is movably arranged within the elongated hole. The elongated hole provides a guiding slot for the guided element in and against one or more spatial direction(s).

Providing the connection to the movable part via floating bearings advantageously allows to prevent dirt accumulation at the floating bearings since they are not arranged in the vicinity of the stationary part where dirt can accumulate easier. Additionally it allows a horizontal movement of the movable part, e.g. due to a manual operation or due to an exposure to an external load. Thus, the risk of damage to the lifting mechanism can be reduced.

Further, a floating bearing can be at least partially provided by elongated guiding holes within the movable part. The elongated guiding holes are used for guiding a movement of an upper end section of a scissor leg element. It is for instance possible that a guided element is movably, in particular pivotally, coupled to the upper end section of the scissor leg element. The guided element can be movably arranged within the elongated guiding hole. In particular, the elongated guiding holes can provide a linear guiding for the upper end section of the scissor leg element.

This advantageously provides a design which can easily be constructed and thus reduces a construction effort and building costs.

Further, an upper end section of at least one scissor leg element can be in a stop position if the movable part is in the extended state. The stop position can denote a position of the movement guided by the elongated hole. A stop position can denote a position in which a further upward movement is mechanically blocked, e.g. because the upper end section or the aforementioned guided element contacts an edge of the elongated guiding hole, in particular a front-sided or rear-sided edge. In the stop position, a further movement of the upper end section in one direction of the linear movement is prevented or blocked. In particular, a further movement of the upper end section which would provide a further upward movement of the movable part is prevented or blocked.

This advantageously provides a reliable and easy-to-construct limitation of the upward movement of the movable part.

Further, an upper end section of at least one scissor leg element can be in an intermediate position if the movable part is in the retracted state. The intermediate position can denote a position of the movement guided by the elongated hole. Within the intermediate position, the movement of the upper end section in and against the direction of the linear movement is unblocked. This can mean that the upper end section can be moved such that the movable part is moved upwards. Further, the upper end section could theoretically be moved such that the movable part is moved downwards in the retracted state. This further downward movement, however, can be blocked, e.g. by other stop elements. In the intermediate position, the upper end section does not contact a front-sided or a rear-sided edge of the elongated guiding hole.

This advantageously allows a shearing movement of the movable part, in particular if an ice layer covers the movable part in the retracted state. In other words, it is possible that one portion of the movable part, e.g. a right or a left half of the movable part executes a limited upward movement, wherein the remaining part remains in the retracted state. This, in turn, advantageously simplifies to clear the mechanical blockage of the movable part due to icing and/or soiling.

In another embodiment, a central connecting element connects a first and a further scissor arrangement. The SMA actor, in particular a further end of the SMA actor, can be connected to said central connecting element.

The central connecting element can e.g. be designed as a connecting rod. Scissor leg elements of each of the scissor arrangements can be movably coupled to the central connecting element. Providing a central connecting element advantageously stabilizes the scissor lift mechanism.

In another embodiment, each of the first and the further scissor arrangement comprises scissor leg elements, wherein the central connecting element and each scissor leg element of one of the scissor arrangements is connected via a sliding block connection.

It is possible that the central connecting element provides at least one sliding element, e.g. at each end of the connecting element. The sliding element can be provided by the central connecting element itself or by an element connected to the central connecting element. Further, the sliding block connection can comprise a guiding means, wherein a movement of the sliding element is guided by said guiding means. The guiding means can e.g. be provided by a recess or opening in a scissor leg element. Via the sliding block connection, the central connecting element is movably connected or coupled to each scissor leg element. This advantageously provides a mechanically stable scissor lift means which is connected to the movable part via floating bearings and which reliably guides the movement of the movable part.

Further, each scissor leg element of a scissor arrangement can have a guiding slot for guiding an end section of the central connecting element. The guiding slot can be part of the sliding block connection. The guiding slot allows relative movement between the scissor leg elements and the central connecting element which occurs during the movement of the movable part as the movable part is connected to the scissor leg elements by floating bearings. Thus, the guiding slot advantageously provides a stable scissor lift means and allows the movement of the movable part in case of the floating connection of the scissor leg elements to the movable part.

Further, the guiding slot can be a curved slot. In particular, the guiding slot can be a part-circle-shaped slot.

The part-circle-shaped slot can have a predetermined radius. The curved slot advantageously ensures that a torque or force generated by the driving unit for the upward and downward movement does not vary more than a predetermined amount during the upward or downward movement of the movable part.

In another embodiment, the central connecting element is connected to the movable part by at least one spring element.

This can mean that one end of the spring element, e.g. a spiral spring, is attached to the central connecting element, wherein another end of the spring element is attached to the movable part. The ends of the spring element can be pivotally connected to the central connecting element and to the movable part.

The spring element can be designed and/or arranged such that the spring element relaxes if the movable part is moved upwards, wherein the spring element tenses if the movable part is moved downwards. A spring force generated by the spring element can be a centering force, wherein the centering force is generated such that the movable part is centered with respect to the central connecting element. In particular, the spring element can be designed and/or arranged such that the central connecting element is centered in the guiding slots of the scissor leg elements during the upward and downward movement of the movable part.

Further, the spring element can be designed and/or arranged such that a smooth and uniform lifting movement of the movable part is provided.

Further, each end section of the central connecting element can be connected to the movable part by two spring elements, e.g. two spiral springs. Further, one of the spring elements is connected to a first half of the movable part, wherein the remaining spring element is connected to the remaining half of the movable part. In particular, each spring element can be connected to the movable part in the area or vicinity of another floating bearing. A half of the movable part can denote a portion of the movable part which comprises one floating bearing for one of the scissor leg elements of a scissor arrangement, wherein the remaining part comprises the remaining floating bearing for the remaining scissor leg element of said scissor arrangement. Both halves can have the same size.

This advantageously improves the aforementioned centering of the movable part relative to the central connecting element during an upward and downward movement.

In another embodiment, the inductive power transfer pad comprises a movement supporting spring element, wherein a first end of the movement supporting spring element is connected to the stationary part, wherein the movement supporting spring element is pre-tensioned if the movable part is in a retracted state, wherein the movement supporting spring element relaxes if the movable part is moved to an extended state.

This advantageously supports the upward movement, as the movement supporting spring element can exert a supporting spring force which is directed at least partially in the first direction, wherein said force can support the upward movement. Additionally, the downward movement can be slowed down by the increasing spring force during the downward movement.

Further, the movement supporting spring element can be provided by a yoke spring. An axis of rotation of the yoke spring can be arranged on or within the stationary part.

Further, the axis of rotation can be oriented parallel to the central connecting element. Using a yoke spring advantageously provides a non-uniform supporting spring force during the upward movement. As the maximum force for driving the scissor lift means or the movable part can be needed in the retracted state and can decrease during the upward movement, the supporting force or supporting spring force provided by the yoke spring is advantageously adapted to such a force profile.

Further, the stationary part can have at least one element of a form-fit connection with the movable part, wherein the form-fit connection is provided if the movable part is in the retracted state. This advantageously reduces the probability of an undesired relative movement between the stationary and the movable part in the retracted state.

Further, the movable part can have at least one element of a form-fit connection with the stationary part, wherein the form-fit connection is provided if the movable part is in the retracted state. The at least one element of the form-fit connection can be called a corresponding element of the element providing the form-fit connection of the stationary part.

Further, the at least one form-fit element of the stationary part can be provided by a recess within or by a projection on an upper surface of a base plate of the stationary part, wherein the corresponding form-fit element of the movable part is provided by a projection on or by a recess within a lower surface of the movable part. This advantageously provides a simple design of the form-fit elements.

Further, inner scissor leg elements of two scissor arrangements can be connected by a stiffening rod. This advantageously increases a stability of the scissor lift means.

Further proposed is a method of operating an inductive power transfer pad according to one of the embodiments described in this disclosure. The movable part is moved at least in a first direction. Further, the movable part can be moved against the first direction.

In particular, a thermal energy can be transferred to the at least one SMA actor of the inductive power transfer pad. Upon reception of the thermal energy, e.g. upon heating, the SMA actor can vary its shape. In particular, the SMA actor can adopt a high-temperature shape. The high-temperature shape can e. g. be an extended shape, i. e. a shape with a maximum height.

Alternatively, thermal energy can be drawn from the SMA actor. During the drawing, e.g. during the cooling, of the SMA actor, the SMA actor can vary its shape. In particular, the SMA actor can adopt a low-temperature shape. The low-temperature shape can e. g. be a retracted shape, i. e. a shape with a minimum height. Although it is preferable that the low-temperature state of the SMA actor resembles the retracted state of the inductive power transfer pad, it is alternatively possible that the inductive power transfer pad is in the retracted state while the SMA actor is in the high-temperature state.

It is possible that thermal energy is transferred to the SMA actor by supplying an operating current to the SMA actor, in particular to a metal sheet element of the SMA actor.

It is further possible to draw thermal energy from the SMA actor by operating a cooling device, wherein the cooling device is thermally coupled to the SMA actor.

The invention will be described with reference to the attached figures. The figures show:

Fig. 1 a schematic side view of an inductive power transfer pad in an extended state.

Fig. 2 a schematic side view of the inductive power transfer pad shown in Fig. 1 in a retracted state,

Fig. 3 schematic side view of an inductive power transfer pad according to another embodiment in an extended state and

Fig. 4 the inductive power transfer pad shown in Fig. 3 in a retracted state.

In the following, the same reference numerals denote elements with the same or similar technical features.

Fig. 1 shows a schematic side view of an inductive power transfer pad 1. The inductive power transfer pad 1 comprises a stationary part 2 with a base plate 3 and side walls 4. The base plate 3 and the side walls 4 enclose a recess 5 for receiving lower end sections of shape memory alloy actors 6 (SMA actors 6).

Further, the inductive power transfer pad 1 comprises a movable part 7. The movable part 7 can be designed as a plate. Further, the movable part 7 can comprise a primary winding structure 8.

Further shown is a vertical direction z, wherein an arrow head of the vertical direction z is oriented upwards. Further shown is a bellow 9 of the inductive power transfer pad 1 which is attached to side walls 4 of the stationary part 2 and side walls of the movable part 7.

The movable part 7, in particular a lower surface of the movable part 7 is coupled or connected to the stationary part 2, in particular an upper surface of the base plate 3, by the SMA actors 6. The SMA actors 6 provide actuating means for moving the movable part 7 in and against the vertical direction z.

Fig. 1 shows that a lower end section of the SMA actors 6 is attached to the stationary part 2, in particular the upper surface of the base plate 3. An upper end section of the SMA actors 6 is attached to the movable part 7, in particular to a lower surface of the movable part 7.

The SMA actors 6 can take a variety of shapes. In particular, the SMA actors 6 can take a high-temperature shape, wherein a height of the SMA actors 6 along the vertical direction z is maximal in the high-temperature shape. To take the high-temperature shape, thermal energy has to be transferred to the SMA actor 6. In particular, the amount of thermal energy has to be chosen such that the SMA actor is heated to a temperature which is higher than or equal to a predetermined first temperature.

The inductive power transfer pad 1 further comprises current sources 10, wherein each current source 10 is electrically connected to one SMA actor 6, respectively. The current sources 10 can generate an operating current which is supplied to a SMA actor 6. The current flow through the SMA actor 6 generates thermal energy, e.g. due a resistance of the SMA actor 6. This thermal energy heats up the SMA actor 6. By adjusting a current strength, a temperature of the SMA actor 6 can be adjusted.

The SMA actor 6 comprises multiple metal sheet elements 11, wherein only one metal sheet element 11 is referenced by a reference numeral for illustration purposes. It is shown that a metal sheet element 11 is designed as a corrugated strip, wherein each corrugated strip extends along an uncorrugated center line, wherein the strip oscillates about the center line in and against the z-direction. The uncorrugated center line, however can be curved, in particular be a circle line.

Multiple metal sheet elements, i.e. multiple corrugated strips, are arranged one above the other, wherein two adjacent metal sheet elements are coupled by at least one coupling element 12. In Fig. 1, only one exemplary coupling element 12 is referenced by a reference numeral for illustration purposes. The coupling element 12 can be made of an electrically conductive material. The coupling elements 12 can also be made of the same material as the metal sheet elements 13.

It is shown that two adjacent metal sheet elements are arranged one above the other such that a recess of the lower metal sheet element 11 (with respect to its uncorrugated center line and the vertical direction z) faces a projection of the upper metal sheet element 11 (with respect to its uncorrugated center line and the vertical direction z). Thus, the metal sheet elements 11 and the coupling elements 12 provide a honeycomb-like structure, in particular a cylindrical structure, thus forming a cylindrical column. Each of multiple columns can be spaced apart from the other columns.

Not shown in Fig. 1 is a cooling unit, wherein the cooling unit is thermally coupled to the SMA actors 6.

Further not shown are a thermal insulation elements of the SMA actors 6, e.g. one or more thermal insulation elements per SMA actor 6. One or more thermal insulation element can e.g. enclose one SMA actor 6.

Fig. 2 shows the inductive power transfer pad 1 shown in Fig. 1, wherein the movable part 7 is in a retracted state. The SMA actors 6 are only schematically indicated. They are, however, designed as the SMA actors 6 shown in Fig. 1. In Fig. 2, the SMA actors 6 have a low-temperature shape. The low-temperature shape can e.g. be taken if the temperature of the SMA actor 6 is lower than or equal to a second predefined temperature which is lower than the aforementioned first predefined temperature. It is, for instance, possible that one or multiple cooling unit/s (not shown) are operated such that thermal energy is drawn from the SMA actors 6. Due to the cooling, the temperature of the SMA actors 6 decreases, wherein the SMA actors 6 vary the shape such that the low-temperature shape is adopted.

By varying the temperature of the SMA actors 6, the movable part 7 can be moved upwards or downwards. If, for instance, the temperature of the SMA actors 6 is increased, the movable part 7 moves upwards. The upward movement, however, is limited. In particular, the movable part 7 is moved upwards until the SMA actors 6 take the high-temperature shape. If the temperature of the SMA actors 6 is decreased, the movable part 7 is moved downwards. The downward movement, however, is also limited. In particular. the movable part 7 can be moved downwards until the SMA actors take the low-temperature shape.

Fig. 3 shows an inductive power transfer pad 1 in another embodiment, wherein a movable part 7 of the inductive power transfer pad 1 is in an extended state. The inductive power transfer pad 1 comprises a scissor lift means 13. The scissor lift means 13 comprises two scissor arrangements 14, wherein only one scissor arrangement 14 is shown in Fig. 3. A scissor arrangement 14 comprises a first scissor leg 15a and a second scissor leg 15b. Further, the scissor lift means 13 comprises a central connecting rod 16, wherein the central connecting rod 16 connects the two scissor arrangements 14 of the scissor lift means 13.

It is shown that each scissor leg 15a, 15b has an elongated hole 17, wherein an end section of the central connecting rod 16 is movably or slidably arranged within the elongated hole 17 of the scissor leg 15a, 15b. The end section of the central connecting rod 16 is thus slidably born by the scissor legs 15a, 15b. In particular, the end section can execute a sliding motion within the elongated holes 17.

Further shown is that lower end sections of the scissor legs 15a, 15b are coupled to the stationary part 2, in particular to a base plate 3 by fixed bearings 18. The fixed bearings 18 prevent a translational movement of the lower end sections of the scissor legs 15a, 15b. The lower end sections of the scissor legs 15a, 15b are, however, pivotally connected to the fixed bearings 18. This means, that the lower end sections of the scissor legs 15a, 15b can execute a rotational movement.

Further shown is that upper end sections of the scissor legs 15a, 15b are coupled to the movable part by floating bearings 19. A sliding element 20 can e.g. be connected to the upper end section of a scissor leg 15a, 15b, in particular pivotally connected. The sliding element 20 is arranged within an elongated guiding hole 21 provided by the movable part 7. The floating bearing 19 allows a translational movement of the sliding element 20 (and thus the upper end section of the corresponding scissor leg 15a, 15b) in and against a longitudinal axis x.

In the extended state of the movable part 7, the sliding elements 20 are in a stop position in the elongated holes 21. This means that the sliding elements 20 mechanically contact front-sided and rear-sided edge sections of the elongated holes 21 with respect to the longitudinal direction x. Thus, a further upward movement of the movable part 7 is prevented mechanically.

Further shown are spiral springs 22, wherein a first spiral spring 22a connects the central connecting rod 16 and a first half the movable part 7, wherein a second spiral spring 22b connects the central connecting rod 16 and another half of the movable part 7. The first half comprises the elongated hole 21 for guiding the sliding element 20 of the first scissor leg 15a, wherein the other half comprises the elongated hole 21 for guiding the sliding element 20 of the second scissor leg 15b.

In particular, the first spiral spring 22a is connected to the central connecting rod 16 and the movable part 7 in the vicinity of a first elongated hole 21. The second spiral spring 22b is connected to the central connecting rod 16 and to the movable part 7 in the vicinity of the remaining elongated guiding slot 21. The spiral springs 22 relax if the movable part 7 is moved upwards and tense if the movable part 7 is moved downwards. The spiral springs 22 generate a spring force which centers the movable part 7 with respect to the central connecting rod 16.

Further shown is a SMA actor 6, wherein a lower end section of the SMA actor 6 is attached to the stationary part 2, in particular to the upper surface of the base plate 3. An upper end section of the SMA actor 6 is attached to the central connecting rod 16. By varying the shape of the SMA actor 6, the central connecting rod 16 can be moved upwards or downwards. The upward or downward movement of the central connecting rod 16 will then generate an upward or downward movement of the movable part 7 via the scissor lift means.

Fig. 4 shows the inductive power transfer pad 1 shown in Fig. 3, wherein the movable part 7 is in a retracted state. In this state, the SMA actor 6 can take the aforementioned low-temperature shape. It is shown that the sliding element 20 is in an intermediate position within the elongated holes 21 of the movable part 7 in the retracted state. This means that the sliding elements 20 do not contact any of the front-sided or rear-sided edge sections of the elongated holes 21.

Claims

1. An inductive power transfer pad, in particular a transfer pad of a system for inductive power transfer to a vehicle, comprising a stationary part (2) and a movable part (7), wherein the movable part (7) comprises a primary winding structure (8), wherein the inductive power transfer pad (1) comprises at least one actuating means, wherein the movable part (7) is movable at least in a first direction (z) by the at least one actuating means, characterized in that the at least one actuating means is provided by a shape memory alloy actor (6).

2. The power transfer pad according to claim 1, characterized in that the inductive power transfer pad (1) comprises four shape memory alloy actors (6).

3. The power transfer pad according to claim 1 or 2, characterized in that the shape memory alloy actor (6) comprises at least one metal sheet element (11), wherein the metal sheet element (11) is electrically connected to a current source (10).

4. The power transfer pad according to claim 3, characterized in that a metal sheet element (11) is designed as a corrugated strip.

5. The power transfer pad according to claim 3 or 4, characterized in that the shape memory alloy actor (6) comprises multiple metal sheet elements (11), wherein the multiple metal sheet elements (11) are arranged one above the other, wherein two adjacent metal sheet elements (11) are directly connected or wherein two adjacent metal sheet elements (11) are coupled by at least one coupling element (12).

6. The power transfer pad according to one of the claims 1 to 5, characterized in that the inductive power transfer pad (1) comprises at least one cooling unit, wherein the cooling unit is thermally coupled to the at least one shape memory alloy actor (6).

7. The power transfer pad according to one of the claims 1 to 6, characterized in that a first end of the shape memory alloy actor (6) is connected to the stationary part (2), wherein a further end of the shape memory alloy actor (6) is connected to the movable part (7).

8. The power transfer pad according to one of the claims 1 to 7, characterized in that the inductive power transfer pad (1) comprises a scissor lift means (13), wherein the movable part (7) and the stationary part (2) are coupled by the scissor lift means (13).

9. The power transfer pad according to claim 8, characterized in that a first end of the shape memory alloy actor (6) is connected to the stationary part (2), wherein a further end of the shape memory alloy actor (6) is connected to the scissor lift means (13).

10. The power transfer pad according to one of the claims 8 to 9, characterized in that a scissor arrangement (14) of the scissor lift means (13) is coupled to the stationary part (2) by fixed bearings (18), wherein the scissor arrangement (14) is coupled to the movable part (7) by floating bearings (19).

11. The power transfer pad according to one of the claims 8 to 10, characterized in that a central connecting element (16) connects a first and a further scissor arrangement (14).

12. The power transfer pad according to claim 11, characterized in that each of the first and the further scissor arrangement (14) comprises scissor leg elements, wherein the central connecting element (16) and each scissor leg element (15a, 15b) of one of the scissor arrangements (14) is connected via a sliding block connection.

13. The power transfer pad according to one of the claims 8 to 12, characterized in that the central connecting element (16) is connected to the movable part (7) by at least one spring element (22, 22a, 22b).

14. The power transfer pad according to one of the claims 1 to 13, characterized in that the inductive power transfer pad (1) comprises a movement supporting spring element, wherein a first end of the movement supporting spring element is connected to the stationary part (2), wherein the movement supporting spring element is pretensioned if the movable part (7) is in a retracted state, wherein the movement supporting spring element relaxes if the movable part (7) is moved to an extended state.

15. A method of operating an inductive power transfer pad (1) according to one of the claims 1 to 14, wherein the movable part (7) is moved at least in a first direction (z).