BUS WITH COOLED IN-WHEEL ELECTRIC ENGINES

An articulated, bus with at least two bodies or carts, adapted for carrying at least fifty or one hundred passengers in the passenger compartment. The articulated bus comprises several wheel housings, each with two longitudinally aligned wheels. Each wheel is disposed in the wheel housing and comprises an in-wheel electric engine in its rim. A cooling circuit is in communication with the in-wheel electric engine and comprises a heat exchanger outside the wheel housing in order to cool the wheels. The cooling circuit also cools the battery pack electrically connected to the electric engine. A cooling process for controlling the temperature in-wheel electric engine, and a use of a heat exchanger for heating a seat or a passenger compartment.

TECHNICAL FIELD

The invention lies in the field of engine cooling. More precisely, the invention proposes a bus with driving wheels which comprises cooled electric engines.

BACKGROUND OF THE INVENTION

Electric buses are provided with electric engines. During propulsion phases and regenerative phases, the electric machines heat. This temperature elevation reduces the efficiency since the permanent magnet properties decrease. In addition, a high temperature may irremediably damage the permanent magnets and other electric devices.

In order to preserve the yield, an electric engine is generally provided with a cooling device. A cooling flow prevents excessive heat peaks, and allows a temperature control. Yet, this temperature control may turn out cumbersome when the corresponding vehicle runs in cities where speed is limited by law or by traffic jam. Then, the potential cooling flow is limited. Uphill slopes require more electric power which heat even more the electric engines.

Moreover, the positioning of the heat exchanger must comply with several requirements, notably in mass transportation vehicles such as buses. Indeed, the available place is reduced. In addition, the cost, the weight and the passenger comfort must be considered as well. On top of this, servicing and collisions with other vehicles also affect the way the heat exchangers are arranged close to seating and standing passengers.

The document DE 197 32 637 A1 discloses an omnibus comprising an electric engine with a cooling pipe where cooling water flows.

The document JP 2009 227130 A discloses a wheel with an in-wheel engine lubricated by an oil circuit. The oil flows through an oil cooler in the middle of the oil path.

The document US 2019/068028 A1 discloses a four-wheel vehicle equipped with a cooling mechanism. Each wheel is dotted with an electric engine cooled by an oil cooler. The oil coolers compose heat exchangers coupled to the radiator.

Technical Problem to be Solved

It is an objective of the invention to present a bus, which overcomes at least some of the disadvantages of the prior art.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, it is provided a bus, notably an articulated bus with several units, the bus comprising: a passenger compartment adapted for at least fifty passengers, a wheel housing, a wheel disposed in the wheel housing and comprising an in-wheel electric engine, a cooling circuit in fluid flow communication with the in-wheel electric engine and comprising a heat exchanger outside the wheel housing.

Preferably, the cooling circuit comprises a first passage which is outside the in-wheel electric engine and which comprise a first inner width W1, the cooling circuit further comprising a second passage which is in the in-wheel electric engine and which comprise a second inner width W2, the first inner width W1representing at least 80% of the second inner width W2, optionally the first inner width W1is larger than the second inner width W2.

Preferably, the heat exchanger is transversally and/or vertically level with the wheel, respectively with the in-wheel electric engine, the bus further comprising a seat row above said heat exchanger, or a seat above the heat exchanger.

Preferably, the wheel housing comprises a tight wall and/or a protection bar between the wheel and the heat exchanger.

Preferably, the bus comprises an enclosure in which the heat exchanger is arranged, said enclosure being adjacent to the wheel housing and/or the passenger compartment, the bus is notably adapted such that the heat exchanger heats the passenger compartment.

Preferably, the wheel is a first wheel, the bus further comprising a second wheel identical to the first wheel and disposed in the wheel housing longitudinally at distance from the first wheel, the cooling medium being adapted for flowing through the in-wheel electric engine of said second wheel.

Preferably, the cooling circuit comprises a pump adapted for pressurizing a cooling liquid in the first wheel and in the second wheel, and/or a tank with a cooling liquid, such as a water glycol mix, the cooling liquid being intended to flow through the in-wheel electric engine in order to cool it.

Preferably, the bus comprises a suspension arm adapted to pivot with respect to the wheel housing and/or the passenger compartment, the cooling circuit comprising a tube, notably a resilient tube, joined to said suspension arm and being in fluid flow communication with the in-wheel electric engine.

Preferably, the suspension arm is an upper suspension arm, the cooling circuit comprising a pipe fixed to said tipper suspension arm, said pipe being stiffer than the resilient tube.

Preferably, the bus comprises a battery pack adapted for electrically powering the in-wheel electric engine, the cooling circuit comprising a cooling unit adapted fur cooling said battery pack, the wheel housing being disposed longitudinally between the battery pack and the heat exchanger.

Preferably, the in-wheel electric engine comprises a rotor and a stator, said stator comprising a diameter and a thickness TH along the rotation axis of the in-wheel electric engine.

Preferably, the stator is arranged in the rotor, the cooling circuit comprising an inner network through the stator in order to cool said stator.

Preferably, the wheel further comprises a disc brake with a brake disc, the distance D between the brake disc and the stator being larger than the width W of the stator.

Preferably, the bus comprises a frame and a movable wheel support on which the wheel is rotatably fixed, the wheel support is notably disposed between the brake disc and the in-wheel electric engine.

Preferably, transversally, the in-wheel electric engine comprises an inner face and an outer face, the cooling circuit comprising an inlet and an outlet on the inner face, the inlet and the outlet notably being arranged on the inner face, preferably in the upper half of the inner face.

Preferably, the wheel comprises a radial space between the in-wheel electric engine and the rim of the wheel, said radial space being radially larger than the outer radius of the in-wheel electric engine, possibly at least two times larger than the outer radius.

Preferably, the cooling circuit is a first cooling circuit, the wheel housing is a first wheel housing, the bus farther comprising additional wheel housings and additional cooling circuits which are identical to the first cooling circuit and which are each associated with one of the additional wheel housings, the additional cooling circuits notably being independent from one another.

Preferably, the cooling circuit comprises a first passage which is outside the in-wheel electric engine and which comprise a first inner width W1, the cooling circuit further comprising a second passage which is in the in-wheel electric engine and which comprise a second inner width W2, the first inner width W1being larger than the second inner width W2.

Preferably, the second inner width W2represents at least 4% of the outer diameter of the in-wheel electric engine.

Preferably, the heat exchanger is longitudinally aligned with the wheel.

Preferably, the heat exchanger is vertically level with the passenger compartment.

Preferably, the heat exchanger comprises a heat dissipation device.

Preferably, the wheel extends over the whole height of the heat exchanger.

Preferably, the pump and/or the tank are arranged in the enclosure.

Preferably, the heat exchanger is intended to be cooled by the bus environment.

Preferably, the heat exchanger is adapted for cooling a cooling medium flowing through the cooling circuit.

Preferably, the wheel comprises a rim with an inner space, the in-wheel electric engine being at least partially disposed in said inner space.

Preferably, the inner space comprises a first outer diameter which is larger than a second outer diameter of the in-wheel electric engine, preferably at least two times larger.

Preferably, the additional cooling circuits are separate and distinct.

Preferably, the wheel comprises an outer half and an inner half in which the in-wheel electric engine is arranged, the in-wheel electric engine being at distance from said outer half.

Preferably, the wheel support is a steering knuckle which is adapted for moving vertically and/or for pivoting about a vertical pivot axis.

Preferably, the cooling circuit comprises water, and is notably adapted to keep the water temperature under 100° C.

Preferably, the second wheel and the heat exchanger are aligned, and/or transversally overlapping.

Preferably, the cooling fluid is isolated from the bus environment by the cooling circuit.

Preferably, the cooling circuit comprise a first portion fixed to a suspension arm, and a second portion of reduced stiffness which comprise a lower stiffness than the first portion.

Preferably, the second portion is between the first portion and the engine.

Preferably, the first portion is at distance from the engine.

It is another aspect of the invention to provide a bus, notably an articulated bus with several units, the bus comprising: a passenger compartment adapted for at least fifty passengers, a seat row, notably a longitudinal seat row; a wheel disposed under the seat row and comprising an in-wheel electric engine, a cooling circuit in fluid flow communication with the in-wheel electric engine and comprising a heat exchanger under the seat row.

The passenger compartment is not an essential aspect of the invention.

It is another aspect of the invention to provide a cooling process of an in-wheel electric engine for a bus, the bus comprising: a capacity of at least fifty passengers notably defined by a passenger compartment, a wheel housing, a wheel with an in-wheel electric engine, a cooling circuit with a cooling liquid, a heat exchanger at distance from the wheel, a connection between the heat exchanger and the in-wheel electric engine, the cooling process comprising the steps: heating the in-wheel electric engine, and cooling the in-wheel electric engine by means of the cooling liquid, wherein the speed of the cooling liquid in the connection is similar to the speed of the cooling liquid in the in-wheel electric engine, the bus notably being in accordance the invention, and the bus comprises a seat over the cooling circuit.

The cooling liquid may generally be a fluid such as a gas.

Preferably, the speed of the cooling liquid in the connection represents from 50% to 150%, or from 80% to 120%, of the speed of the cooling liquid in the in-wheel electric engine.

Preferably, during step cooling the in-wheel electric engine, the passenger compartment is heated, and the pressure of the cooling fluid in the connection is similar to the pressure of the cooling fluid in the in-wheel electric engine.

Preferably, the heat exchanger is at distance and: or outside the wheel housing.

Preferably, the wheel is inside the wheel housing.

It is another aspect of the invention to provide a cooling process of an in-wheel electric engine for a bus, the bus comprising: a passenger compartment adapted for receiving at least fifty passengers, a wheel housing, a wheel and comprising an in-wheel electric engine, a cooling circuit with a cooling liquid, a heat exchanger at distance from the wheel, a connection between the heat exchanger and the in-wheel electric engine, the cooling process comprising the steps: heating the in-wheel electric engine, and cooling the in-wheel electric engine by means of the cooling liquid, wherein the flow speed of the cooling liquid in the connection represents from 40% to 200%, or from 50% to 150%, or from 80% to 120%, of the flow speed of the cooling liquid in the in-wheel electric engine, the bus notably being in accordance with the invention.

The heat exchanger is not an essential feature of the invention. It is another aspect of the invention to provide a cooling process, notably a temperature management process, of an in-wheel electric engine for a bus, the bus comprising: a passenger compartment adapted for receiving at least fifty passengers, a wheel housing, a wheel and comprising an in-wheel electric engine, a cooling circuit with a cooling liquid, the cooling process comprising the steps: heating the in-wheel electric engine, and cooling the in-wheel electric engine by means of the cooling liquid which is cooled outside the wheel and notably outside the wheel housing, the bus notably being in accordance with the invention.

The cooling liquid flow speed(s) may he an average flow speed, or a maximum flow speed.

It is another aspect of the invention to provide a use of a heat exchanger for heating the passenger compartment of a bus, wherein the bus comprises:a wheel housing,a wheel disposed in the wheel housing and comprising an in-wheel electric engine,a cooling circuit for with the in-wheel electric engine and comprising a heat exchanger;an enclosure in heat exchange with the passenger compartment and in which the heat exchanger is disposed, the bus notably being in accordance with the invention,

It is another aspect of the invention to provide a use of a heat exchanger for heating a passenger compartment of a bus, wherein the bus comprises a wheel housing, a wheel in said wheel housing, an electric in-wheel engine in said wheel, a cooling circuit through the electric in-wheel engine, the heat exchanger being part of said cooling circuit, the bus notably being in accordance with the invention.

It is another aspect of the invention to provide a use of a heat exchanger for heating the passenger compartment of a bus, wherein the bus comprises:a wheel housing,a wheel disposed in the wheel housing and comprising an in-wheel electric engine,a cooling circuit thermally cooperating with the in-wheel electric engine and comprising a heat exchanger; and optionallyan enclosure in thermal communication with the passenger compartment and in which the heat exchanger is disposed, the bus notably being in accordance with the invention.

It is another aspect of the invention to provide a use of a heat exchanger for heating seat of a bus, wherein the bus comprises:a wheel housing,a wheel disposed in the wheel housing and comprising an in-wheel electric engine,a cooling circuit thermally cooperating with the in-wheel electric engine and comprising a heat exchanger thermally coupled to the seat;the bus notably being in accordance with the invention.

Preferably, the bus further comprises an enclosure in which the heat exchanger is disposed and the set being above said enclosure.

Preferably the seat comprises a seat place row thermally coupled to the heat exchanger and/or above said enclosure.

The different aspects of the invention may be combined to each other. In addition, the preferable features of each aspect of the invention may be combined with the other aspects of the invention, unless the contrary is explicitly mentioned.

Technical Advantages of the Invention

The invention improves the flow control through the cooling circuit. It provides a position for the heat exchanger which is sufficiently remote from the hot source for a better cooling, but sufficiently close in order to shorten the lines so as to lower the pressure losses.

In addition, the pressure losses are further managed by specific diameter or width choices. These dimensions foster smooth flow in spite of the connection deformation, and of the vibrations generated by the contact between the wheel and the ground unevenness.

The invention addresses the technical problem of cooling a substantially small size in-wheel electric engine equipping a steering and driving wheel, where said wheel drives a bus which keeps a spacious passenger compartment with seat rows. Thus, the passenger capacity is preserved, and the ratio between seat places and standing places is optimized.

DETAILED DESCRIPTION OF THE INVENTION

This section describes the invention in further detail based on preferred embodiments and on the figures. Similar reference numbers will be used to describe similar or the same concepts throughout different embodiments of the invention.

It should be noted that features described for a specific embodiment described herein may be combined with the features of other embodiments unless the contrary is explicitly mentioned. Features commonly known in the art will not he explicitly mentioned for the sake of focusing on the features that are specific to the invention. For example, the bus in accordance with the invention is evidently controlled by a computer, even though such a computer is not explicitly referenced on the figures nor referenced in the description.

By way of convention, it may be defined that the word “longitudinal” refers to the longitudinal direction and may correspond to the main driving direction of the bus. It may be along the main central axis of the vehicle. The word “transversal” refers to the transversal direction and may be perpendicular to the longitudinal direction. It may be understood that the directions are not used in a strict meaning. Indeed, each direction used below may include a variation of at most 5°, or 2°, or 1°, with respect to a strict meaning. The skilled in the art will understood that a longitudinal pivot axis may be inclined with respect to the longitudinal direction of the bus and/or the horizontal direction.

In the following description and claims, the mentioned length(s), width(s), and thickness(es) may be average ones.

The radial direction is understood as perpendicularly to an associated wheel rotation axis. The radial direction is along the radius of a wheel.

The term “similar” used in relation with a value such as a size or flow, is understood as implying a variation of at most 50%; preferably 20%, more preferably 10%.

It should be noticed that the present drawings generally provide configurations where wheels are substantially parallel to the longitudinal direction. The steering angle is of 0°. The vehicle may drive along a straight trajectory. However, the skilled in the art will be able to adapt the following teaching to situations where the steering angle of the bus is changed.

FIG. 1shows a vehicle for mass transportation in accordance with a preferred embodiment of the invention. The vehicle is partially represented.

The vehicle is adapted for transportation of passengers in cities and may transport about fifty, or one hundred passengers, for instance one hundred and twenty passengers. The vehicle may be a bus2, notably an electric bus2. The bus2may include electric driving engines and electric batteries (not represented) powering the electric driving engines. The bus2may be purely electric, in the meaning that it is only driven by electric power. The bus2may be combustion engine free.

The bus2may be an articulated bus. It may comprise a first unit4and a second unit4(partially represented). Each unit4, may form a body, and/or may form a rigid cart. Each unit4may be a trailer and/or a tractor. The units4may be similar or identical. These units4may be joined by a joint, for instance a hinged joint6enabling the units4to swivel with respect to each other.

In the current embodiment, only two units4are represented, however it is contemplated in the current invention that the electric bus2includes three, four, or more units4; which are articulated. with respect to one another by hinged joint(s)6. Then, the passenger capacity may be of more than two hundred. Each unit4may be self-supporting. Thus, each unit4may move without the hinged joint6.

A bus formed of a single unit is also considered in the invention.

Each unit4may include several wheels8engaging the ground G. Pairs of symmetric wheels8may form axles, for instance four axles for each unit4. The axles and thus the wheels8may be distributed along the length of the bus2. At least one pair of wheels is formed of steered wheels. Optionally, each wheel8of the bus2or of at least one unit4are steered wheels and/or driving wheels.

The bus2may include a bus structure. The bus structure may distribute and/or support the weight of the bus, and load therein. The bus structure may include a roof10, and/or a passenger platform12, and/or side walls14. The side walls14may be outer walls. Two transversally opposite side walls14may go down from the roof10to the passenger platform12. They may form the bodywork of the bus2. They may mask the wheels8. The bodywork may be part of the bus structure. The side walls14may receive windows16and doors17for passengers. Optionally, doors17are arranged in one of the two side walls14, notably between windows16.

For instance; the side walls14may close the wheel housings18. Optionally, at least one or each wheel housing18may receive two longitudinally spaced wheels8. The wheel housings18may form downwardly open boxes. The wheel housings18may exhibit four faces in front of the wheels8. At least one or each wheel housing18may be adapted for blocking front, rear and top projections from the associated wheel. The wheel housings18may be longitudinally at distance from the ends of the units4. The wheel housings18may be arranged below the windows16. The door17may be disposed between two wheel housings18of the corresponding unit4.

Generally, the or each wheel housing18may be understood a space in which at least one wheel is arranged. The or each wheel housing18may be a wheel cavity. The or each wheel housing18may be a wheel guard.

Equipment may be provided on the roof10. For instance, the bus may comprise an air conditioning device20. The air conditioning device20may be adapted to cool air in the passenger compartment (behind the door17). It may be adapted for keeping the temperature between 18° C. and 25° C. for the passenger comfort. This air conditioning device20may be reversible and may heat the passenger compartment during winter. It may comprise a compressible gas.

The bus2may comprise at least one battery pack22. The battery packs22may power electric engines driving the bus2. The battery packs22may power electric engines (not represented) which activate the wheels8. The electric engines may be in-wheel electric engines. For instance, each wheel housing18is associated with a battery pack22. The battery packs22may be independent. In the current example, each unit4may comprise four battery packs22. By way of illustration, the bus2includes eight battery packs22and eight wheel housings18. There may be sixteen wheels8, for instance each with an electric engine. The battery packs22may power other equipment of the bus2.

In order to cool the electric engines, notably the in-wheel electric engines, the bus2may comprise at least one cooling circuit24. The bus2may comprise one cooling circuit24for each of the wheel housings18, and thus for each of the wheel pairs. Each battery pack22may be associated with a cooling circuit24, Each cooling circuit24may be associated with one wheel housing18, and/or with at least one wheel8. Each cooling circuit24may cool one or two electric engines. At least one door17may be between two adjacent cooling circuit24. The cooling circuits24may be independent from each other. They may be separate and distinct. They may be at distance from each other in order to reduce the length of required pipes when considering the whole vehicle.

The current configuration reduces the thermal stress of the cooling circuits24, and improves the general reliability. The cost and the weight are considered as well. The or each cooling circuit24may comprise a closed loop, and/or vanes which arc easier to control.

The or each cooling circuit24may comprise a tank26. Each tank26may be a closed and tight vessel. Each tank26may be adapted for containing a cooling fluid, notably a cooling liquid. The cooling liquid may comprise water and glycol. The tank26may be adapted for resisting to the cooling fluid pressure. The cooling circuit may be adapted for avoiding contact between the cooling fluid and the bus environment.

The or each cooling circuit24may comprise a pump28. The pumps28may be adapted for sucking up the cooling fluid, and for injecting it through the corresponding, circuit24. The pumps28may inject the cooling fluid in the hydraulically connected electric engines in order to cool them. The cooling fluid pressure in the electric engines may be comprised between 0.5 bar and 2 bars.

The or each cooling circuit24may comprise a heat exchanger30. The heat exchanger(s)30may be heat dissipator(s). Each heat exchanger30may be adapted to cool down the cooling fluid flowing therethrough by means of the pump28. The heat exchangers30may be in thermal contact of the bus environment. The or each heat exchanger30may be separate and distinct from the air conditioning device20. The heat exchangers30may be adapted to cool the battery packs22, the tanks26and the electric engines.

The heat exchangers30may be vertically level with the passenger compartment. The heat exchangers30may be above the platform12. They may heat the passenger compartment.

At least one or each heat exchanger30may be at distance from the wheels8. They may be outside the wheel housings18. Thus, the heat exchangers30may be physically protected from projections propelled by the wheels8.

At least one or each heat exchanger30may be arranged in an enclosure. The enclosure may receive the connected pump28and the connected tank26. At least one or each enclosure may be adjacent to the corresponding wheel housing18. The enclosure and the associated wheel housing18may be in contact of each other. Thus, the length of pipe is reduced such that the pressure loss, the cost and the weight are optimized. The cooling circuits24are more reliable. The length of the pipes becomes important when their diameter increases.

FIG. 2provides an aerial illustration of the frame32of a bus2, notably from a unit4, in accordance with a preferred embodiment of the invention. The longitudinal central axis L and the transversal direction T are represented. The longitudinal central axis L may correspond to the longitudinal direction L, and may be horizontal.

The bus2and/or the unit4may correspond to those as described in relation withFIG. 1. Two pairs or wheels8are disposed in the respective wheel housings18. The rotations axes9of the wheels8are represented. The wheel rotations axes9may correspond to the axles when the wheels8are aligned at each side. It may be understood that the wheels8comprise toe-in or toe-out. Thus, the term “aligned” may be understood in the meaning of the environment of the invention.

In each wheel housing18, the wheels8may form pairs. The wheel gap8G between the wheels8in the same wheel housing may be smaller than the transversal width8W of at least one wheel8or of each wheel8. The wheels8of each pair are adapted to run on the same wheel path. These wheels8may be transversally aligned. In each pair, the wheels8are longitudinally offset. The wheel gap8G may separate them longitudinally. The wheels8of each pair may be identical.

At least one or each wheel8may be a driving wheel. At least one or each wheel8, respectively driving wheel, may comprise an electric engine42. The electric engines42may generally be electric machines. The electric engines42may be in-wheel electric engines, or more generally in-wheel engines. The electric engines42, notably the in-wheel electric engines42, may be powered by the battery pack22. The cooling circuit24may comprising a cooling unit22C in at least one of the battery packs22. Each cooling unit22C may be adapted for cooling the corresponding battery pack22. The cooling units22C may be in thermal contact of the corresponding battery pack22, notably of the contained battery cells.

In the current example two battery packs22are represented, namely a left battery pack22and a right battery pack22. The combination of the battery packs22and of the electric engines42, notably the in-wheel electric engines42, allows to drive the bus2. These electric components may be adapted for driving the bus2at least at: 50 km/h or 100 km/h. These speeds may be reached with one hundred passengers in the passenger compartment2P of the bus.

At least one or each wheel2may be joined to the frame32by a suspension system44. At least one or each wheel is joined to the frame32by a dedicated suspension system44. The suspension systems44may be separate and distinct from each other. At least one or each suspension system44may comprise a steering module (not represented).

At least one or each suspension system44may comprise suspension arms46. The suspension arms may be designated as pivoting arms. The suspension arms46may be pivotably fixed to the frame32, for instance to longitudinal beams40. The suspension arms46may be pivoting links, notably swinging arms. The suspension arms46may pivot about horizontal pivot axis. At least one or each suspension arm46may pivot about longitudinal pivot axis48. The longitudinal pivot axes48may be parallel.

The wheel housings18may comprise plates50. The plates52may be vertical. They may be tight. They may be fixed to the transversal bars38. The plates50may close tightly the wheel housings18. They may form longitudinal end walls thereon.

The frame32may exhibit enclosures52. The plates50may be at the interface between the wheel housings18and the enclosures52. The enclosures52may be adjacent to the wheel housings18. At least one or each enclosure52may be adjacent to the passenger compartment2P. The enclosures52may be above the platform12. The position of the enclosures52with respect to the wheel housings18allows thermal cooperation. The enclosures52, more precisely the heat exchangers disposed therein, are cooled by the wheel housings18which raises when the bus drives due to the air flow forced by the wheels.

The current portion of the bus2, respectively of the unit4, exhibit two cooling circuits24, namely a left cooling circuit24and a right cooling circuit24. The left and the right cooling circuits24may be separated by the passenger compartment2P. They may be transversally distant. They may be hydraulically and/or thermally independent.

At least one cooling circuit24may comprise a tank26in the corresponding enclosure52, and/or a pump28in the corresponding enclosure52. At least one or each cooling circuit24may comprise a heat exchanger30in the enclosure52. As an option, the enclosure52may allow an air flow with the passenger compartment2P and/or with the bus environment. Thus, at least one or each heat exchanger30may provide calories to the bus environment and/or the passenger compartment2P. Thus, the passenger compartment2P may benefit from the calories generated by the electric engines42. A kind of synergy is achieved.

As apparent from the current figure, each wheel housings18separates the associated battery pack22and the associated enclosure52. It may increase heat exchange while allowing a height and a transversal width reduction of the enclosures52.

The integration of the cooling circuits24is performed in a narrow area. Indeed, the cooling circuits24may be below seats56. The seats56may form longitudinal rows. The seats56may be above the cooling circuits24. For instance, the tanks26, the pumps28and the heat exchangers30may be under the seats56.

Thus, the cooling circuits24may be disposed between the seats56and the platform12. Then the cooling system54and its cooling circuits24only require a reduced place in the bus since it is divided in smaller units which are individually easier to arrange in the bus2. At least one or the cooling circuits24are adapted for heating the seat(s)56. Then, the thermal management of the vehicle is improved. The thermal comfort of the seat(s) increases.

The cooling circuits24may comprise connections58, or lines. The connections58may form loops, notably closed loops. The pumps28may force the cooling liquid circulation in the associated loops. The cooling liquid may flow through the connections58in order to meet the battery packs22, the engines42, the heat exchangers30; and thereby achieving temperature control. In addition, the connections58and the engines42may be configured such that the flow speeds in the connections58and the engines42are similar, and notably reduced. The differences of speeds may be of at most: 30%, or 20% or 10%. The considered speed may be average speeds. Accordingly, the cooling fluid speed remains homogeneous. Accelerations and slowdowns are controlled, notably at the interfaces of the engines42. The pressures losses are limited. In addition, the liquid speed in the connections58may he limited in order to limit the pressure tosses therein.

FIG. 3provides a schematic illustration of a longitudinal view of a cooling system24, and of a suspension system44in a wheel housing18. The transversal direction T, the longitudinal direction L and the vertical direction V are provided. These directions (T, L, V) may be perpendicular to each other.

The bus2may correspond to those as described in relation with any one ofFIGS. 1 and 2.

The suspension system44may be provided with a gas actuator60and a damper62. In addition or as an alternative, the gas actuator60forms a gas spring. Varying the gas pressure therein may allow to set its stiffness. This may be useful when the number of passengers varies in the passenger compartment2P. The damper62, also designated as shock absorber, may be adapted to absorb and dissipate energy when the wheel8meets a protrusion or a recess on/in the ground G, namely the road on which the bus2drives.

The suspension system44may comprise arms46or links. The suspension system44may comprise pivoting arms46also designated as pivoting links. The pivoting arms46may comprise an upper pivoting arm64and a lower pivoting arm66. The upper pivoting arm64and the lower pivoting arm66may pivot about longitudinal pivot axes48. Pivot joints48J may allow the pivoting motions of the pivoting arms (64;66) about the longitudinal pivot axes48. These pivoting motions allow the wheel8to move between an upper position and a lower position.

The gas actuator60may be joined to the upper pivoting arm64whereas the damper62may be joined to the lower pivoting arm66. The damper62and the gas actuator60may be separate and distinct. They may be at distance from each other.

The lower pivoting arm66may be joined to the longitudinal beam34by means of the lower pivot joint48J. A transversal beam36is apparent. The rotation axis9of the wheel8may extend through the longitudinal beam34. The ground clearance GC between the platform12and the ground G is represented. An upper longitudinal beam40of the frame32may form an upper and outer end of the wheel housing18.

A wheel support68receives the wheel8. The wheel support68may comprise bearing about which the wheel8turns around its rotation axis8. The wheel support68may be joined to the upper pivoting arm64and the lower pivoting arm66. Thus, the outboard ends of these pivoting arms may be maintained at a fixed distance. joints, such as pivot joints or ball joints68J may attach the wheel support68to the upper pivoting arm64and to the lower pivoting arm66. The ball joints may allow rotation with respect to three directions. Then, the wheel support68may swivel about a vertical pivot axis68P in any angular orientation of the arms with respect to the frame32.

Accordingly, the wheel support68may be a steering knuckle. A steering actuator (not represented) may control the orientation of the steering knuckle about the vertical pivot axis68P.

A connection68of the cooling system24is apparent. The connection68may comprise a deformable portion. The connection68may comprise a tube70. The tube70may be a resilient tube70and/or an arcuate tube70. The tube70may form an arcuate line with curves in the cooling system24. The tube70may project from the electric engine42. The tube70may extend toward a pivoting arm, for instance the upper pivoting arm64. The tube70may extend along the upper ball joint68J attaching the upper pivoting arm64to the wheel support68. The tube70may be deformed in order to accommodate the motion of the engine42about the ball joints68J.

The connection58may comprise a pipe72, notably a stiff pipe. The pipe72may project from the tube70. The pipe72may be essentially straight. It may be rigidly fixed to the upper pivoting arm64. It may extend toward the pivot joint48J attaching the upper pivoting arm64to the wheel housing18. The pipe72may he stiffer than the rube70. The tube70may be more resilient than the pipe72.

As an option, the connection58may comprise an additional resilient tube70A joining the pipe72to the frame32.

As an option, the connection68comprise a single resilient tube projecting from the electric engine42to the pivot joint48J attaching the upper pivoting arm64to the wheel housing18.

The electric engine42may be an in-wheel electric engine42. The in-wheel electric engine42may be in the rim8R of the wheel8. The in-wheel electric engine42may be encircled by the tire8T received by the rim8R. The in-wheel electric engine42may comprise a portion outside the wheel8. It may comprise an inner face outside the wheel8, and notably outside the rim8R.

A heat exchanger30is represented with a dotted line. The eight of the heat exchanger30is smaller than that of the wheel housing18. The wheel housing18extends on the whole height and/or the whole width of the heat exchanger30. The wheel8may extends on the whole height of the heat exchanger30. Thus, the heat exchanger30is disposed in a narrow space. Its integration in the frame32requires a small place. The cooling system24is therefore compact.

The bus2comprises at least one seat56, for instance several seats forming one row. Each seat56may comprise a seat base56B and a back rest56R. The seat(s)56, notably the seat base(s)56B, may be above the cooling system24. The seat(s)56, notably the seat base(s)56B, may be above the connection58. The seat(s)56, notably the seat base(s)56B, may be above the tube(s)70and/or the pipe72. Accordingly, the available space for the connection68and its portion is delimited by the seat(s)56. Such an arrangement optimises the bus2compacity and respect a specific seat arrangement allowing to increase the number of seats56in the bus. Hence, the invention improves compacity.

The current figure only describes the cooling system24in relation with one wheel8. However, the wheel housing18may further receive another wheel8. Thus, the above description may be duplicated for said another wheel8.

In addition, the bus2may comprise another wheel housing which is symmetric to the above described one. A symmetric cooling system may be associated to the symmetric wheel housing18As an alternative, the ball joints68J may be replaced by pivot joints.

FIG. 4provides a schematic illustration of a cut out of a wheel where a cooling system24according to the invention, spans. The bus2may correspond to those as described in relation with any one ofFIGS. 1 to 3.

The transversal direction T, the longitudinal direction L and the vertical direction V are provided. These directions (T, L, V) may be perpendicular to each other. The rotation axis9of the wheel8may be along the transversal direction T, notably depending on the steering angle of the wheel support68, and of the configuration of the suspension system44. The position of the vertical pivot axis68P is provided. A longitudinal beam34is represented, whereas the pivoting arms are omitted for the sake of clarity.

The wheel support68may comprise a main body68M also designated as central body. The main body68M may be disposed in the wheel8, notably in the radial space8C delimited by the rim8R. The radial space8C may form an inner cavity in the rim8R. The radial space8C may have an annular shape. It may have a toroidal shape encircling the rotation axis9. In addition, the wheel support68may comprise an inner plate74to which the electric engine42is fixed. The inner plate74may be fixed to the main body68M by fixation means74F such as screws. The fixation means74F may project along, and notably over the electric engine42.

The electric engine42may comprise a rotor42R and a stator42S. The rotor42R may comprise permanent magnets (not represented). The stator42S may comprise magnetic coils. The electric engine42may be of radial type, with a radial magnetic air gap. Alternatively, it may be an axial one.

The rotor42R may be outside the stator42S. The rotor42R may encircle, and possibly encapsulate the stator42S. As an option, the stator42S may be fixed to the inner plate74at a location outside the rim8R, and more generally the wheel8. Fittings58F (only one represented) of the connection58, may form the inlet and the outlet of the electric engine42, and may cross the inner plate74. As an example, the fittings58F may be connected to the tube70.

The cooling circuit24may comprise an inner network76through the electric engine42. The cooling circuit24, respectively the inner network76, may comprise at least one loop in the electric engine42, notably in the stator42S. The inner network76may form a serpentine. The inner network76may allow a cooling fluid flow adapted for cooling the electric engine42. The inner network76may be formed in, and in thermal contact of the stator42S. The inner network76may be at distance from the rotor42R. The inner network76may be, at least partially in the radial space8C; and more generally in the wheel8. Thus, the inner network76may directly cool the stator42S, and may cool the magnetic coils heated by the electric power. Then, the temperature may be reduced during drive, and the maximum torque may be delivered continuously.

The wheel8may comprise a disc brake with a brake calliper and a brake disc78. The disc brake may be an emergency brake, or a safety brake. It may be activated mechanically. It may assist the electric engine42when it is used a power generator during braking. The brake disc78may be at distance from the electric engine42. The main body58M of the wheel support58may be arranged between them. The brake disc78may be in the wheel8. The thickness TH of the stator42S may be smaller than the distance D between the brake disc78and the stator42S. The thickness TH and the distance D may be measured transversally and/or along the rotation axis9or the wheel8.

Optionally, the thickness of the electric engine42is as thick or smaller than the distance D between the brake disc78and the electric engine42.

The arrangement of the brake disc78with respect to the electric engine42, respectively the stator42S, reduce the thermal effect of the brake disc78on the magnetic parts. Accordingly, the performances of the electric engine42are preserved. Its physical properties too.

The tube70may define a first passage with a first inner width in the cooling circuit24. The inner network76may define a second passage with a second inner width in the cooling circuit24. The first passage may be outside the in-wheel electric engine42. The first inner width may represent at least 80% of the second inner width. As an option, the first inner width is larger than the second inner width. The widths may be measured perpendicularly to the cooling flow through the corresponding segment.

The heat exchanger30is represented. Along the longitudinal direction, the heat exchanger30may be aligned with the wheel8. In addition, the heat exchanger30may be outside the wheel housing in which the wheel is arranged.

FIG. 5provides a schematic illustration of a wheel8combined with a cooling system24of a bus2according to the invention. The bus2may correspond to those as described in relation with any one ofFIGS. 1 to 4.

The transversal direction T, the longitudinal direction L and the vertical direction V are provided. These directions (T, L, V) may be perpendicular to each other,

The suspension system44is represented with the upper pivoting arm64and the lower pivoting arm66. The upper pivoting arm64and the lower pivoting arm66are joined by the wheel support68. The ball joints68J and the pivot joints48J at their transversal ends are represented. The later allows oscillations about the longitudinal pivot axis48. The fixation means74F of the wheel support68are represented. The fixation means74F may project from the main body68M winch is represented behind the engine42.

The rim8R of the wheel8defines a radial space8C in which the engine42is disposed. The radial space8C may have an annular shape around the rotation axis9. The engine42may be an in-wheel electric engine42. The in-wheel electric engine42, notably its rotor42R, may rotate about the rotation axis9of the wheel8.

The heat exchanger30may be at distance from the in-wheel electric engine42. The heat exchanger30may be at distance from the wheel8. The heat exchanger30may be outside the wheel housing18. The heat exchanger30may be in fluid flow communication with the in-wheel electric engine42by means of the connections58. The represented position of the heat exchanger30with respect to the wheel8may be purely illustrative in the current figure.

The connections58may comprise several lines entering or going out of the heat exchanger30. The connections58may comprise lines attached to the pivoting arms, for instance the upper pivoting arm64. As apparent from the current figure, the wheel8may transversally comprise an outer half, and an inner half in which the in-wheel electric engine42is arranged. The in-wheel electric engine42may be at distance from said outer half.

The cooling circuit24may comprise an inlet24I and an outlet24O in the in-wheel electric engine42. The inlet24I and an outlet24O may be at the interface between the connections58and the in-wheel electric engine42. They may be at the interface between the tube70and the inner network76. The inlet24I and an outlet24O may be disposed on the upper half of the engine42. They may be above the rotation axis9. Thereby, they are more protected against stone projections lifted from the ground G.

The inner network76may comprise passageways arranged radially. A radial passageway extends perpendicularly to the rotation axis9. The inner network76may comprise circular passageways, for instance around the rotation axis9of the wheel8. These passageways, and thus the inner network76, increase the contact surface between the stator42S and the cooling fluid. This surface increase allows a cooling fluid flow speed reduction in order to avoid pressure losses in the cooling circuit. Thus, the associated pump requires less energy.

The wheel8may comprise a radial space8C between the in-wheel electric engine42and the rim8R. The radial space8C may be radially larger than the outer radius42O of the in-wheel electric engine42, possibly at least two times larger than the outer radius42O. For instance, the radial thickness8TH of the radial space8C may be radially larger than the outer radius42O of the in-wheel electric engine42, possibly at least two times larger than the outer radius42O.

The cooling circuit24may comprise several tubes70. The tubes70may be arcuate tubes. They may have elbow portions. The tubes70may extend from the inlet24I and the outlet24O connected to the in-wheel electric engine42. The cooling circuit24may comprise pipes72. The pipes may be in contact of the tubes70. They may be one after the other. The pipes72may be fixed and secured to at least one pivoting arm (64;66), notably the upper pivoting arm64. The tubes70may be more resilient than the pipes72in order to allow wheel motions about the vertical pivot axis68P.

FIG. 6provides a schematic illustration of the interface between an engine42, notably an in-wheel electric engine42, and connections58of a cooling circuit24. The engine42, notably an in-wheel electric engine42, may correspond to those as described in relation with anyone ofFIGS. 1. to5. The cooling circuit24may correspond to anyone of those as described in relation withFIGS. 1 to 5.

The, cooling circuit24may comprises a first passage80outside the in-wheel electric engine42. The first passage $0may comprise a first inner width W1. The inner width W1may be an inner diameter. The cooling circuit23may further comprise a second passage82in the in-wheel electric engine42. The second passage82may comprise a second inner width W2, which may correspond to an inner diameter. The second passage82may correspond to the passageway. The second passage82may be in fluid flow communication with the inner network76.

The first passage80and the second passage82may have similar cross sections. The first inner width W1may represent at least 80% of the second inner width W2. As an option, the first inner width W1is larger than the second inner width W2. The ratio W1/W2may range from 0.8 to 1.50. Optionally the ratio W1/W2is equal to 1. These inner widths (W1; W2) may be similar. The first inner width W1and the second inner width W2may be measured at distance from the fitting58F. They may be measured where they are constant. They may be measured at the inlet24I or at the outlet24O of the cooling circuit24.

By way of an example, the first inner width W1measures about: 8 mm, or 10 mm, or 12 mm. The second inner width W2may represents at least; 2%, or 4%, or 6%, of the outer diameter of the in-wheel electric engine42. The outer diameter may he deduced from the outer radius42O as defined inFIG. 5. The outer diameter of the engine42may be at most: 30 cm, or 25 cm. Thus, the engine is substantially small in order to reduce unbalanced weight, and to increase track control and road holding.

The first passage80may be formed in a connection58, notably in a tube70. The tube70may be arcuate. Its centreline may draw a curve. The second passage82may be formed in the engine42, notably an in-wheel electric engine42. It may be formed in the stator42S. It may be at distance from the inner plate74of the wheel support.

The current arrangement ensures a smooth transition for the cooling fluid. In addition, it avoids pressure losses which negatively affects the engine temperature control. The size of the required pump may be reduced, and the pumping energy as well.

The invention considers an embodiment with the combination of the teachings ofFIGS. 1 to 6.

FIG. 7provides a schematic illustration of a cooling process of an in-wheel electric engine by means of a cooling circuit for a bus in accordance with a preferred embodiment of the invention. The bus, and notably the cooling circuit, may correspond to anyone of those as described in relation withFIGS. 1 to 6, or more generally above.

The cooling process may comprise the steps:

standby100,
heating102the in-wheel electric engine, and
cooling104the in-wheel electric engine by means of the cooling liquid.

During step standby100, the in-wheel electric engine may he free of electric power. It may be electrically disconnected from the battery pack. Similarly, the pump may be free of electric power, The cooling fluid may he stopped therein,

Steps heating102and cooling104may be performed simultaneously. After them, the bus, notably the electric engine and the battery pack may return to step standby100.

During step heating102and/or during step cooling104, the flow speed of the cooling fluid in the connection may be similar to the flow speed of the cooling fluid in the in-wheel electric engine.

During step heating102and/or during step cooling104, the flow speed of the cooling fluid in the connection may represent: from 50% to 150%, or from 80% to 120%, of the flow speed of the cooling fluid in the in-wheel electric engine.

The cooling fluid may be a cooling liquid. Its temperature may be kept below 100° C.

During step cooling104the in-wheel electric engine, the passenger compartment is heated, and the pressure of the cooling fluid in the connection may be similar to the pressure of the cooling fluid in the in-wheel electric engine.
During step heating102and/or during step cooling104, the pressure of the cooling liquid in the connection may represent: from 50% to 150%, or from 80% to 120%, of the pressure of the cooling liquid in the in-wheel electric engine. The pressure may be the static or the dynamic pressure.

It should be understood that the detailed description of specific preferred embodiments is given by way of illustration only, since various changes and modifications within the scope of the invention will be apparent to the person skilled in the art. The scope of protection is defined by the following set of claims.