Spring loaded brush carrier

A charging station for an electric vehicle may include a charge head configured to engage with the charging blade of the vehicle to transfer power. The charge head may include a housing with a central cavity extending along its longitudinal axis and a plurality of electrode holders. Each electrode holder may include an electrode configured to transform from an extended configuration when the charging blade is not positioned in the central cavity to a retracted configuration when the charging blade is positioned in the central cavity. In its extended configuration, the electrode may extend into the central cavity from a side wall of the housing, and in the retracted configuration, at least a portion of the electrode may retract into the housing. Each electrode may also include a plurality of springs configured to bias the electrode in the extended configuration.

TECHNICAL FIELD

The current disclosure relates to a spring loaded brush carrier of an electric vehicle charging station.

BACKGROUND

Electric vehicles, such as transit buses, are charged at charging stations. The charging station includes a charge head that automatically engages with a charging interface of the bus to direct electric current to the bus for charging. When the bus is positioned proximate the charging station, the charge head engages with the charging interface of the bus. The charge head includes electrodes that contact with electrodes of the charging interface for current transfer. In some applications, the charge head electrodes are pneumatically actuated to transform from a retracted configuration to an extended configuration to make contact with the bus electrodes. After charging, the charge head electrodes are retracted into the charge head, and the bus is allowed to proceed on its route. Pneumatically activated electrodes on the charge head may increase cost and complexity of the system.

Embodiments of the current disclosure may alleviate some of the problems discussed above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.

SUMMARY

Embodiments of the present disclosure relate to spring loaded electrodes of a charging station. Each of the embodiments disclosed herein may include one or more of the features described in connection with any of the other disclosed embodiments.

In one embodiment, a charging station for an electric vehicle, is disclosed. The electric vehicle may include a charging blade configured to receive power from the charging station. The charging station may include a charge head configured to engage with the charging blade and transfer electric power to the vehicle. The charge head may include a housing having a longitudinal axis, and a central cavity extending along the longitudinal axis of the housing. The central cavity may be configured to receive the charging blade of the vehicle therein. The charge head may also include a plurality of electrode holders positioned in the housing. Each electrode holder of the plurality of electrode holders may include an electrode configured to transform from an extended configuration when the charging blade is not in the central cavity to a retracted configuration when the charging blade is positioned in the central cavity. In its extended configuration, the electrode may extend into the central cavity from a side wall of the housing, and in the retracted configuration, at least a portion of the electrode in the central cavity may retract into the housing. Each electrode may also include a plurality of springs configured to bias the electrode in the extended configuration.

In another embodiment, a method of charging an electric vehicle at a charging station is disclosed. The electric vehicle may include a charging blade on an external surface, and the charging station may include a charge head with a central cavity extending along a longitudinal axis of the charge head and a plurality of spring-loaded electrodes positioned in the central cavity. The method may include moving the charge head into contact with the external surface of the vehicle, and moving the vehicle with the charge head in contact with the external surface such that the charging blade of the vehicle slides into the central cavity of the charge head. The method may also include sliding at least one electrode of the plurality of electrodes of the charge head against the charging blade, and rotating the at least one electrode about a first axis perpendicular to the longitudinal axis while the electrode is sliding against the charging blade.

In yet another embodiment, a charging system for an electric vehicle is disclosed. The charging system may include an electric vehicle with a charging blade that extends along a longitudinal axis of the vehicle positioned on a roof of the vehicle. The charging system may also include a charging station having a charge head positioned over the roof of the vehicle. The charge head may be configured to automatically descend to contact the charging blade. The charge head may include a housing that extends along the longitudinal axis, and a central cavity that extends through the housing along the longitudinal axis. The central cavity may be configured to receive the charging blade of the vehicle therein. The charge head may also include a plurality of electrode holders positioned in the housing. Each electrode holder of the plurality of electrode holders may include a spring-loaded electrode configured to slide against the sliding blade and rotate about an axis perpendicular to the longitudinal axis while sliding against the charging blade, and a plurality of links rotatably coupled to each other. Each electrode holder may also include a plurality of springs coupled to the plurality of links and the electrode. The plurality of springs may be arranged parallel to each other and each spring of the plurality of springs may be inclined with respect to a second axis perpendicular to the longitudinal axis and the first axis.

DETAILED DESCRIPTION

The present disclosure describes charging brushes of an electric vehicle charging system. While principles of the current disclosure are described with reference to the charging system of an electric bus, it should be understood that the disclosure is not limited thereto. Rather, the systems and methods of the present disclosure may be used in charging systems of any vehicle.

FIG. 1illustrates an electric vehicle in the form of an electric transit bus10. Electric bus10may include a body12enclosing a space for passengers. In some embodiments, some (or all) parts of body12may be fabricated using composite materials to reduce the weight of the bus10. Without limitation, body12of bus10may have any size, shape, and configuration. In some embodiments, bus10may be a low-floor electric bus. As is known in the art, in a low-floor bus, there are no steps at the front and/or the back doors of the bus. In such a bus, the floor of the bus10is positioned close to the road surface to ease entry and exit into the bus10. In some embodiments, the floor height of the low-floor bus may be about 12-16 inches (30.5-40.6 cm) from the road surface. In this disclosure, relative terms, such as, “about,” “approximately,” “substantially,” etc. are used to indicate a possible variation of ±10% in a stated value.

Bus10may be propelled by an electric motor. A battery system14may store electrical energy to power the motor. In some embodiments, the battery system14may be positioned under the floor of the bus10, and may be configured as a plurality of batteries configured as battery packs. These battery packs may be positioned in cavities (not shown) located under the floor of the bus10, and may be accessible from below the bus10. The batteries of battery system14may have any chemistry and construction. In some embodiments, the chemistry of the batteries may include lithium titanate oxide (LTO) or nickel manganese cobalt (NMC). In some embodiments, the layout and design of the battery system14may enable fast charging of the batteries. By fast charging, the battery system14may be recharged (to greater than about 95% state of charge) in less than or equal to about 10 minutes.

A charging interface16may be provided on the roof18of the bus10to charge the battery system14.FIG. 2Aillustrates an exemplary charging interface16of the bus10. The charging interface16may include components that interface with a charge head assembly120of an external charging station110(seeFIG. 1) to charge the battery system14. These components may include a funnel-shaped alignment scoop30comprising a pair of spaced apart rails (wall or other features) extending along a portion of the length of the bus10. The pair of rails may be positioned in a mirror symmetric manner about a longitudinal axis100of the bus10, and arranged such that the gap between the rails decreases towards the rear of the bus. A charging blade20may be positioned between the pair of rails of the alignment scoop30in a region where the pair of rails are the closest to each other.

FIG. 2Billustrates an exemplary charging blade20of bus10. The charging blade20may protrude vertically upwards from the roof18of the bus10, and include a plurality of electrodes separated from each other by an electrically insulating material. These electrodes may include positive and negative electrodes22,24connected to opposite poles of the batteries of battery system14, a pilot electrode26, and a ground electrode28. The positive and negative electrode22,24may be positioned on opposite side surfaces of the blade20, and the pilot and ground electrodes26,28may be positioned on the top surface of the blade20. When the charge head (shown inFIG. 3) of charge head assembly120properly engages with charging blade20, electrical contact between the pilot electrode26and a mating electrode on the charge head may trigger a signal (pilot signal) that initiates charging. In some embodiments, charging of the bus10may not be initiated unless the pilot signal is detected. The ground electrode28of blade20may be connected to a common ground of the bus10.

The charging blade20may extend along the longitudinal axis100of bus10, and may include a cuboid section32at the middle flanked by triangular prismatic sections34at either end. As illustrated inFIG. 2B, the side surfaces36of the blade20at the cuboid section32may extend parallel to each other, and the side surfaces38at the prismatic sections34may converge towards each other to form tips39at the front and rear ends of the blade20. In some embodiments, these tips39may be rounded to avoid a sharp tip. The positive and negative electrodes22,24of blade20may be positioned on the side surfaces36of the cuboid section32of the blade20. The converging side surfaces38at either end of the blade20may form guiding features that serve to guide the charge head of the charge head assembly120into engagement with the blade20.

To charge the bus, when bus10is positioned under the charge head assembly120of charging station110, a charge head of the charge head assembly120may descend to land on a landing zone32(seeFIG. 2A) of the charging interface16.FIG. 3schematically illustrates the top view of an exemplary charge head130resting on the landing zone32of the charging interface16. Commonly-assigned U.S. patent application Ser. No. 14/442,200 (National Stage Application of PCT/US2013/069953 (International Publication No. WO/2014/078456)) filed May 12, 2015, which is incorporated by reference in their entirety herein, describes an exemplary process of lowering the charge head to engage with the charging blade of a bus10. InFIG. 3, only the outline of the charge head assembly120is depicted (using dashed lines) to show the charge head130. The charge head130includes a boat-shaped housing132(called boat) that extends along the direction of bus travel (see arrow). The housing132includes a central channel135extending from one end of the housing132to its opposite end. A plurality of electrodes (called brushes134) may extend into the central channel135from the side walls of the housing132. In general, charge head130may include any number of brushes134. In some embodiments, the charge head130may include a total of four brushes134, with two of these brushes extending from each side of the channel135. The brushes134may have any size and shape. In general, the size and number of brushes134may be dictated by their current carrying requirement. In some embodiments, the brushes134may be sized such that two of the brushes134(e.g., one on each side) are capable of carrying the entire current needed to charge the bus10. In such an embodiment, the remaining two brushes134(of the four total brushes) may provide redundancy to the system. In some embodiments, brushes134may be formed with fibers or wires.

To engage the charge head130with the charging blade20, with the charge head130resting on the landing zone32(as depicted inFIG. 3), the bus10is moved forward (in the direction of arrow). As the bus10moves forward, the charge head130slides on the charging interface16towards the charging blade20. The rails of the alignment scoop30on either side of the charge head130aligns and directs the charge head130towards the blade20. When the charge head130reaches the blade20, the blade20enters the central channel135of the charge head130.FIG. 4is an illustration of the charge head130with the blade20in its central channel135. The rounded tip39formed at the end of the blade20, and the wider opening of the channel135at its leading end assists in directing the blade20into the channel135. As the external surfaces of the blade20interact with (or pushes against) the side walls of the central channel135, the charge head130may be rotate slightly (about a vertical axis through the plane of the paper), such that the central channel135is aligned with the longitudinal axis100, so that the blade20can enter the central channel135. As the bus10continues to move forward, the brushes134of the charge head130make contact with the positive and negative electrodes22,24of the charging blade20. The charge head130may also include electrodes (not shown) that make contract with the pilot electrode26and ground electrode28of blade20. Signals (e.g., pilot signal) between the charging station110and the bus10indicate when suitable contact between the brushes134and the bus electrodes (22,24,26, and28) is achieved. When the pilot signal is received, the bus10may be stopped and charging initiated.

The conductive brushes134of the charge head130may be spring-loaded electrodes that are biased to remain in an extended configuration. When the blade20squeezes through the gap between the brushes134(in the central channel135), the brushes134are pushed into the housing132against the force of the springs to apply contact force on the electrodes22,24of the blade20. This contact force improves electrical contact between the bus10and the charge head130and reduces contact resistance. Reducing contact resistance improves current transfer and reduces heating. The charge head housing132may house spring-loaded brush carriers150that support the brushes134. As the blade20first makes contact with the brushes134and slides against the brushes134(as the bus10continues to move forward), the tip39and the inclined side surfaces38of the blade20, in turn, make contact with the brushes134. The brush carriers150may minimize point loading of the brush surface as the blade20engages and disengages with the brushes134by rotating the brushes134to remain parallel to the blade surface, that is in contact with the brushes134, as the blade20is dragged against the brushes134. Keeping the brushes134parallel to the blade surface during contact makes the force across the brush surface relatively uniform and assists in even brush wear.

FIGS. 5A and 5Billustrate an exemplary brush carrier150that supports a brush134.FIG. 5Ais an illustration of the brush carrier150when the brush134is in contact with an inclined side surface38of the prismatic section34of the blade20, andFIG. 5Billustrates the brush carrier150when the brush134interfaces with a side surface36of the cuboidal section32of the blade20. In the discussion that follows, reference will be made to bothFIGS. 5A and 5B. Brush holder150includes a four link assembly made up of a leading link154, a trailing link156, a first link158, and a second link162(seeFIG. 5B). First and second links158and162may be used to constrain brush rotation about a virtual pivot. The leading link154and the trailing link156each include a plurality of openings170spaced apart along their lengths. As illustrated inFIG. 5A, springs160are connected between the openings170of the leading link154and the openings170of the trailing link156. The springs160are not shown inFIG. 5Bfor clarity.

The leading link154and the trailing link156are pivoted at a first end (left end inFIGS. 5A and 5B) at a fixed leading link pivot172and a fixed trailing link pivot174respectively. Fixed leading and trailing link pivots172,174are fixed locations that allow the first end of the leading link154and the trailing link156to rotate about these pivots without translation. The opposite second end (right end inFIGS. 5A and 5B) of the leading link154and the trailing link156are pivoted to a T-shaped brush carrier plate168at a moving leading link pivot166and a moving trailing link pivot164respectively. The brush carrier plate168is configured to translate towards and away from the blade20(i.e., along the y-axis inFIGS. 5A and 5B) without rotating. Moving leading and trailing link pivots166,164allow the second end of the leading and the trailing link154,156to rotate about these pivot points while translating with the brush carrier plate168. One end (top end inFIGS. 5A and 5B) of the first and second links158,162are pivoted on the brush carrier plate168and their opposite ends (bottom end inFIGS. 5A and 5B) are pivoted on a brush mount152which supports the brush134. A conductor shoe assembly176, connected to the brush mount152, provides electric power to the brush134.

As the brush134is pushed inwards (into housing132) by the blade20, the leading and trailing links154,156and the first and second links158,162rotate about their respective pivots, and the brush carrier plate168translates (in the y direction) to load the springs160and provide a net outward force that is applied by the brush134on the side surface of the blade20. When the inclined side surface38of the blade20contacts an end of the brush134, that end of the brush134is pushed into the housing132, causing the links to rotate the brush mount152to keep the brush surface flush against the inclined side surface38. Since the openings170in the leading and trailing links158,156that support each spring160are spaced apart in the x-direction (direction of bus travel as shown by the arrow), a component of the spring force (marked FyinFIG. 5A) creates a moment which helps to rotate the brush134to be substantially flush (or parallel to) against the inclines side surface38, and thereby apply a substantially even force over the entire inclined side surface38.

As the brush134slides across the side surface38of the prismatic section34(or the blade20) to contact the side surface36of the cuboid section32(seeFIG. 5B), the links of the brush carrier150and the moments created by the spring force rotate the brush134to be substantially parallel to the side surface36and apply a substantially even contact force against the blade20. Rotating the brush134surface to be substantially parallel to the blade surface reduces point loads on the brush134and assists making brush wear uniform.

While the current disclosure describes using a spring loaded brush carrier in the charging station of a bus, it should be understood that the disclosure is not limited thereto. Rather, the principles of the systems and methods described herein may be employed in any charging system. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, embodiments, and substitution of equivalents all fall within the scope of the embodiments described herein. Accordingly, the invention is not to be considered as limited by the foregoing description. For example, while certain features have been described in connection with various embodiments, it is to be understood that any feature described in conjunction with any embodiment disclosed herein may be used with any other embodiment disclosed herein.