GB2441655A

GB2441655A - Articulated bus

Info

Publication number: GB2441655A
Application number: GB0717349A
Authority: GB
Inventors: Alex Naef
Original assignee: Carrosserie Hess AG
Current assignee: Carrosserie Hess AG
Priority date: 2006-09-07
Filing date: 2007-09-06
Publication date: 2008-03-12
Anticipated expiration: 2027-09-06
Also published as: AT12822U1; GB2441655B; FR2905663B1; GB0717349D0; CH698437B1; FR2905663A1; AU2007100849A4; DE202007012413U1

Abstract

The invention relates to an articulated bus 1 having at least three vehicle parts 2-4 which are connected to one another in an articulated fashion, wherein a frontmost vehicle part 2 of the vehicle 1 has two axles 5, 6. Each of a central vehicle part 3 and a rear vehicle part 4 has one axle 13, 17. The rearmost axle 17 and the frontmost axle 5 of the bus are articulated and two successive axles of the bus 1 are each driven by an associated drive assembly 30, 40. The drive assemblies 30, 40 are arranged under the floor 27. The bus 1 has a continuous low floor design and thus permits easy, comfortable and in particular stepless access to the entire passenger compartment.

Description

Articulated bus

Technical field

The invention relates to an articulated bus having at least three vehicle parts which are connected to one another in an articulated fashion, wherein a frontmost vehicle part which is arranged at a front end with respect to a longitudinal direction of the vehicle has two axles and a rearmost vehicle part which is arranged at the rear with respect to a longitudinal direction of the vehicle has a single axle, and there is at least one further single-axle vehicle part arranged between them, wherein the frontmost axle and the rearmost axle of the bus are articulated, and at least two of the remaining axles are power axles which are driven by in each case one associated drive assembly, by means of their drive axles, wherein the drive assemblies are arranged in each case in an underfloor design on the vehicle parts with the power axles.

Prior art

Modern buses, in particular also articulated buses, have a low floor design which permits the bus to be entered easily. Typical heights of the vehicle floors in the passenger compartment above an underlying travel surface are 30-35 cm here. The low floor technology requires the use of drive assemblies which are as compact as possible or else at least requires different arrangements of the drive technology and secondary assemblies, for example the bus motor has to be located to the side at the rear instead of at the rear. Such an embodiment is however virtually impossible in an articulated bus with three vehicle parts since a single power axle is not sufficient to be able to move the bus reliably. Owing to the articulations of the bus it is virtually impossible to transmit the drive force from the rearmost vehicle part in which the motor is arranged to axles of further vehicle parts which are also to have power axles.

DE 40 02 890 (MAN Nutzfahrzeuge AG) describes an articulated bus with four axles and three vehicle parts which are connected to one another by means of two articulations, in which the frontmost axle and at least one of the rear axles and at least two successive axles are power axles. Each of the power axles has an associated drive assembly in the corresponding vehicle part which is arranged in an underfloor design. Owing to the installation and the size of the drive assemblies, the bus has a vehicle floor in the passenger compartment which is at a higher position above an underlying travel surface than are the wheel hubs of the wheels of the bus. As a result, in order to enter the passenger compartment a passenger must ascend to the height of the vehicle floor by means of steps in the entry areas. This is both uncomfortable and forms an obstacle which cannot be overcome independently by elderly people or people with walking difficulties, in particular people in wheelchairs.

DE 40 05 686 (MAN Nutzfahrzeuge AG) likewise describes a three-part articulated bus which has two articulations and four axles and is of a low floor design at least in an area of the front two vehicle parts. However, in the rear vehicle part the vehicle floor of the passenger compartment is raised owing to the insertion under the floor of a drive assembly and two drive shafts for the two rearmost axles of the bus.

As a result, when the rear vehicle part is entered, it is necessary to climb steps, and the advantages of the low floor design are limited to the front two vehicle parts.

Summary of the invention

The object of the invention is to provide an -3-.

articulated bus which is associated with the technical

field mentioned at the beginning and which has

comfortable and disabled-friendly accessibility to the entire passenger compartment through all the access possibilities of the articulated bus.

The means of achieving the object is defined by the features of Claim 1. According to the invention, an articulated bus comprises at least three vehicle parts which are connected to one another in an articulated fashion: a frontmost, two-axle vehicle part which is arranged at a front end with respect to a longitudinal direction of the vehicle, a rearmost, single-axle vehicle part which is arranged at the rear with respect to a longitudinal direction of the vehicle, and at least one further single-axle vehicle part arranged between them.

In this context, the frontrnost and rearmost axles of the bus with respect to the longitudinal direction of the vehicle are articulated, and at least two successive axles are power axles. The power axles are driven here by in each case one associated drive assembly, by means of their drive axles. The drive assemblies are arranged here in each case in an underfloor design on the vehicle parts with the power axles. The articulated bus is distinguished by a low floor area which is continuous over the entire length of the vehicle.

A continuous low floor design of an articulated bus according to the invention permits certain areas of the vehicle floor in the interior of the passenger compartment to be embodied as a continuous, flat, i.e. in particular stepless, floor which is oriented essentially parallel to an underlying surface on which the bus is travelling.

A continuous low floor design, which extends in particular as far as the accesses of the bus, serves to permit a passenger to get in and out easily and comfortably without steps at all access possibilities.

This also eliminates the need, for example, for the installation *of elevated platform entries, which are difficult to integrate into a town environment, especially given lengths of an articulated bus according to the invention of up to 25 m or more. In addition, elevated platform entries for people with walking difficulties often do not provide the desired simplification of access to the means of public transportation. If the low floor design according to the invention is used in conjunction with a possibility of lowering the bus, which can be achieved for example by pneumatically lowering the entry side of the bus, the possibility of accessing a passenger compartment of the bus virtually at the same level as the ground is provided. Buses with such access possibilities can be used relatively easily and independently by, for example, people with walking difficulties and even by people in wheelchairs. However, in known buses only some of the accesses to the passenger compartment often have corresponding low floor measures, as a result of which the passenger in question is directed to the corresponding accesses when getting in or out of the vehicle. An articulated bus according to the invention can have five or more doors. By virtue of the continuous low floor design according to the invention, the same comfortable access is obtained at all the access possibilities and the particular entry through which the passenger enters or leaves the bus is irrelevant in terms of his comfort.

Additional measures can also be provided on the bus which further simplify entry in particular for people in wheelchairs. It is possible, for example, for additional ramps which permit complete threshold-free or step-free entry to be provided at various doors. The ramps can be configured here for example in an extendable or temporarily mountable fashion. As a result of the continuous low floor concept it is possible for such additional means to be present at only one door of the bus without the stepless access being consequently restricted to selected areas of the passenger compartment. Disabled-friendly mobility without steps is ensured in the entire passenger compartment in the bus. However, an embodiment which provides the same level of comfort at every access possibility to the passenger compartment is preferred.

In addition to simplifying the possibilities of accessing the passenger compartment, an articulated bus according to the invention also provides simplified access possibilities to seats and standing facilities within the passenger compartment of the bus. In a relatively small means of public transportation the necessity for comfortable and easy mobility for the passengers within the interior of the passenger compartment either does not occur owing to the small size or a corresponding low floor design is comparatively easy to implement (for example in the case of buses with only two axles) . In an articulated bus according to the invention with a typical length of m or more, it is, however, often necessary to move relatively large distances within the passenger compartment in order, for example, to move from the point of entry to free sitting places or standing places which are located in a different vehicle part.

The continuous low floor according to the invention means that all the seating facilities and standing facilities are connected to one another in an easily manageable way. It is not necessary to deal with any steps in order to move from one location in the passenger compartment to any other location.

One area of the floor of the passenger compartment is embodied as a continuous low floor which connects the entire accessible interior of the bus and all the access possibilities to one another. An articulated bus according to the invention therefore in the first instance provides consistent implementation of the low floor concept and makes available a disabled-friendly solution which promotes independent mobility.

The drive assemblies are preferably arranged offset laterally with respect to a longitudinal centre axis of the respective vehicle part, towards a side wall. As a result of the laterally offset arrangement of the drive assemblies it is possible for a central area of a vehicle floor to be formed at a height above an underlying travel surface which is closer to the underlying travel surface than the highest point of the drive assemblies. In particular, a central area of the vehicle floor can be formed at the same height as an entry threshold at the doors of the bus. A continuous low floor is thus made possible in a central area of the vehicle floor by virtue of the fact that any elevations and/or platforms which are caused by the underfloor installation of the drive assemblies are offset towards a side wall where, for example under seats, they do not adversely affect the accessibility and ease of movement within the passenger compartment.

Alternatively, the assemblies can also be arranged centrally in an underfloor design, in which case, however, only small assemblies can specifically be used so that a continuous low floor design is made possible.

The drive axles of the drive assemblies are preferably arranged obliquely with respect to a longitudinal centre axis of the corresponding vehicle part. In particular, a drive axle of a drive assembly is arranged inclined with respect to the vehicle floor of the corresponding vehicle part in such a way that the distance between a virtual extension of the drive axle from the vehicle floor on a side of the drive assembly facing away from the driven axle becomes larger as the distance from the assembly increases. The drive axle is preferably also arranged obliquely with respect to a plane which is perpendicular to the low floor area of the vehicle floor and in which the longitudinal centre axis of the corresponding vehicle part is located. In this context, the distance of the drive axle from this plane decreases as the distance from the driven axle decreases. In particular, the drive axle is inclined with respect to the longitudinal centre axis by an angle of approximately 10 degrees in a plane parallel to the low floor area of the vehicle floor or to an underlying surface on which it is travelled and by an angle of approximately 9 degrees in a plane perpendicular to said low floor area of the vehicle floor or the surface on which it is travelling.

Such an oblique installation of the drive assembly has the advantage that a force-transmitting or torque-transmitting coupling between the drive axle of the drive assembly and the power axle can be correspondingly adapted to the requirements. In buses of a low floor design, what are referred to as portal axles can be used as power axles, in which portal axles the axle area is closer to an underlying travel surface than the wheel hubs of the wheels, i.e. lower than the geometric axle of the wheels. This ensures that even a vehicle floor which is arranged above the lower lying axle area can be closer to an underlying travel surface than the geometric axles of the wheels, or as close to said surface as the geometric axles of the wheels.

Driven portal axles have a power divider by means of which the drive power of a drive assembly is fed in and distributed among the wheels. The feed is carried out here in the low lying axle area of the portal axles.

Standardized power dividers on portal axles often have a feed which occurs obliquely with respect to the geometric axle of the low lying axle area. In particular, the feed can be provided, for example, via a shaft which is inclined, for example, by an angle of approximately 10 degrees with respect to the longitudinal centre axis, in a plane parallel to an underlying travel surface and to the vehicle floor, and by an angle of approximately 9 degrees in a plane perpendicular to an underlying travel surface and to the vehicle floor. In order to be able to use cost effective, standardized components, it is highly advantageous if the arrangement of the drive assemblies can be selected such that the oblique feeding of the drive torques into the power axles does not result in any disadvantages for the transmission of the drive torques.

A drive torque of a drive assembly has to be transmitted from the drive axle to the power divider of the portal axle. Given a laterally offset installation of the drive assemblies, it is, however, necessary to allow not only for oblique feeding into the portal axle but also above all a lateral offset of the assemblies with respect to the longitudinal centre axis of the vehicle part also has to be coped with. In an embodiment with a cardan shaft, this means that when the drive axles of the drive assemblies are arranged in parallel with respect to the longitudinal axis of the vehicle part, such as is known for example from DE 40 02 890, relatively large angles occur at the joints of the shaft when the lateral offset is overcome if the installation length of the system comprising the power axle and assembly is to be kept as short as possible. In addition, when standard power dividers are used the drive shafts and output shafts are not aligned in parallel and it is necessary to use special power dividers with a feed which is also parallel to the longitudinal axis in order to bring about parallel alignment of the drive shafts and output shafts.

However, as a result the torques which can be transmitted by the cardan shaft are very limited since the torques or forces which can be transmitted when there are relatively large angles at the joints of a cardan shaft are reduced. An oblique installation of the assemblies allows the angles occurring at the joints of the shaft to be minimized or optimized. This is advantageous in particular if electric motors which have a significantly higher torque than, for example, corresponding diesel assemblies are used as the drive assemblies. Attempts have shown that in an arrangement of electric motors with drive axles which are parallel to the longitudinal centre axis and conventional cardan shafts the torques which occur cannot be transmitted, which can lead to severe damage to the components.

In one preferred embodiment, a drive force or a drive torque of the drive assemblies is transmitted to the associated power axle by means of a cardan shaft with a drive shaft and an output shaft. The drive shaft is coupled here to a drive axle of the respective drive assembly, and the output shaft is coupled to a power divider of the corresponding power axle. By transmitting the drive torques via a cardan shaft it is possible for the drive torque of the drive axle to be tapped coaxially with any desired orientation of the drive axle and transmitted easily to the power axle even when there is an oblique feed into the power divider. Alternatively, the drive torque can also be transmitted by means of a gear mechanism.

In one preferred embodiment, the drive shaft and the output shaft of one cardan shaft interact via two double cardan joints. Each of the two double cardan joints comprises here two cardan joints. As a result, on the one hand the angles occurring at each individual cardan joint are reduced further and, on the other hand, the oscillating transmission which occurs with single cardan joints in the rotation of a drive shaft to an output shaft is compensated by an embodiment as a double cardan joint. Alternatively, it is also conceivable for just one double cardan joint to be present, but this embodiment is less preferred.

The power dividers of the power axles are preferably arranged offset laterally on the power axles with respect to a longitudinal centre axis of the -10 -corresponding vehicle part. The drive shaft and the output shaft of, in each case, one cardan shaft are aligned parallel to one another and lie in a plane which is perpendicular to the vehicle floor of the respective vehicle part. In this context, the drive shafts are arranged coaxially with respect to the drive axles of the corresponding drive assemblies, and the output shafts lie coaxially with the shafts of the feed in the power dividers of the portal axles. A parallel arrangement of the drive shafts and output shafts of a cardan shaft is necessary in order to avoid undesired oscillations of the shaft occurring during operation.

Furthermore, an arrangement in a plane perpendicular to the vehicle floor or to an underlying travel surface reduces the angles which occur at the joints of the cardan shaft.

The two drive assemblies of the at least two power axles are preferably identical in design and arranged in the same way on the vehicle parts with the power axles. Identity of design of the drive assemblies provides the advantage of simplified maintenance and existing spare parts can be used for all the assemblies. The drive assemblies are arranged here in front of the associated power axle with respect to the longitudinal direction of a vehicle part, i.e. on a side of the respective power axle facing the front longitudinal end of the vehicle. This provides the advantage that there is no need for a space to be present between the power axle and a rear end of a vehicle part with respect to the longitudinal direction of the vehicle in order to provide space for the drive assembly in the longitudinal direction. As a result, the axle can be positioned closer to a rear end of the respective vehicle parts. In particular in the case of a driven axle in the frontmost vehicle part it is a great advantage for reasons of driving stability if the (rear) power axle can be arranged as close as possible to the rear end of the vehicle part, or as far as -11 -possible away from the front steered axle.

In one preferred embodiment, the at least two power axles are arranged in successive vehicle parts. An embodiment with power axles in successive vehicle parts is preferred since in a vehicle concept with two power axles high thrust loading and tensile loading occurs between driven vehicle parts. In the case of power axles which are not successive, a nondriven vehicle part which is arranged between the vehicle parts with the power axles is difficult to stabilize since the vehicle part has a tendency to veer off as a result of the thrust loading which occurs in the longitudinal direction of the vehicle.

The drive assemblies are preferably electric motors. It is possible here, for example, for electric motors to be used such as are known from tramways. However, it is also possible to use other electric motors such as, for example, also those in other electric vehicles. The motors are preferably distinguished by high power (for example 160 kW) and comparatively high torques. The motors here are preferably three-phase-current asynchronous motors with external ventilation.

Alternatively, all other drive assemblies which appear suitable can also be applied, however electric motors are preferred owing to their small size and the high power levels and torques.

In one preferred embodiment, an articulated bus according to the invention has an exchangeable power supply unit which supplies the electric motors with electrical energy. The power supply unit is preferably embodied as a module which can be present in an exchangeable form in a corresponding module bay in the bus. This ensures that different embodiments of the power supply units can be used on the same bus. It is, for example, conceivable for the same bus to be supplied by a fuel cell or via a contact wire. The -12 -various operating modes can then be implemented, for example, by exchanging the power supply unit. Other embodiments of the power supply unit are also conceivable here. The modular design of the power supply unit in a bus according to the invention allows the power supply of the motors to be configured in a flexible way and adapted to the requirements.

Alternatively it is also possible to install the power supply unit fixedly in the bus so that it cannot be exchanged.

In one preferred embodiment, the exchangeable power supply unit is embodied as a hybrid unit. The hybrid unit then comprises, in particular, a power storage unit and a power feed unit. For example batteries and accumulators which store electrical energy can be used as power storage units. However, mechanical or chemical power storage units such as, for example, flywheels or fuel tanks, are also conceivable. Generally, all suitable storage means for usable energies can be applied alone or in combination in a power supply unit.

The power feed unit refers here to devices which can feed energy in any form to the electric motors, to the power storage unit or to other parts of the bus. In one preferred embodiment, the power feed unit comprises current collectors which draw the energy externally in the form of electrical current from a contact wire such as, for example, an overhead line (trolley bus) . The power feed unit can however also comprise a power generating unit which generates electrical energy which is then passed on, for example, to the electric motors or the power storage unit. The power generating unit can comprise, for example, a fuel cell which generates the electrical current directly from a fuel. The electrical energy which is generated by the fuel cell is then fed for example to an energy store in the form of a battery and stored. The electrical energy can then be extracted from the battery by the electric motors.

However, in a further possible embodiment, diesel -13 -assemblies are also used which drive electrical power generators and thus generate the necessary electrical energy. In fact all assemblies or devices are conceivable, alone and in combination with one another, as a power generating unit which can supply electric motors or a power storage unit with electrical energy or electric current.

In one preferred embodiment of an articulated bus according to the invention, the steered rearmost axle is controlled by means of a mechanical steering gear.

In this context, the steering gear translates a rotational angle between the longitudinal centre axis of the rearmost vehicle part and the longitudinal centre axis of the vehicle part which adjoins it in the direction of the front into a steering angle of wheels of the steered axle. The translation of the rotational angle into the steering angle takes place here in accordance with an exponential function. The steering angle of the steered wheels therefore depends exponentially on the rotational angle between the rearmost vehicle part and the adjoining vehicle part.

Alternatively, the dependence of the steering angle of the wheels on the rotational angle can also be linear.

Such an embodiment is however less preferred since comparatively severe swerving out of the rearmost vehicle part occurs as a result.

The steering gear is preferably embodied as a compact unit which reads the instantaneous rotational angle mechanically by means of a first transmission arm and passes on the steering angle mechanically to the steered axle by means of a second transmission arm. The steering gear is preferably present here at the rearmost vehicle part. The steering gear is connected via the first transmission arm to the vehicle part which adjoins it at the rearmost vehicle part. The first transmission arm acts on the steering gear which transmits the effect of the first transmission arm to -14 -the second transmission arm using mechanical speed changing transmitting means comprising, for example, rollers, reels and cam elements. The second transmission arm then acts, for example, via a control device on the steerable wheels of the steered axle. If the rearmost vehicle part then swerves compared to the adjoining vehicle part, the rotational angle is transmitted into a steering angle of the steerable wheels of the steered axle in accordance with the transmission ratio of the steering gear. Alternatively, the steering gear can also be formed directly on the steered wheels so that, for example, only one transmission arm is present and said transmission arm reads the rotational angle. However, as a result, a less advantageous large length of the transmission arm results and there is less freedom in the embodiment and positioning of the steering gear.

Further advantageous embodiments and feature combinations of the invention can be found in the following detailed description and the totality of the claims.

Brief description of the drawings

The drawings which are used to explain the exemplary embodiment are as follows: Figure 1 shows an external view of a bus according to the invention from an entry side; Figure 2 shows a plan view of a bus according to the invention without a roof; Figure 3 shows a schematic side view of an arrangement of a drive assembly with respect to a power axle; Figure 4 is a schematic plan view of an arrangement of -15 -a drive assembly with respect to a power axle; and Figure 5 is a schematic view of a bus according to the invention when cornering.

All parts which are identical in the figures are provided with the same reference symbols in all cases.

Ways of implementing the invention Figure 1 shows an articulated bus 1 according to the invention with three elongate vehicle parts 2, 3 and 4 in an external view from an entry side 64, which has doors 21 to 25. Figure 2 shows a plan view of the bus 1 without a* roof 53. In the text which follows, reference is made to both figures together. The first vehicle part 2 has two axles and has a steered axle 5' and an unsteered axle 6. With respect to a longitudinal axis A of the vehicle the first vehicle part 2 is arranged at a longitudinal end 7 of the bus 1 in such a way that a longitudinal axis B of the first vehicle part 2 is located coaxially with respect to the longitudinal axis A of the vehicle. A direction pointing to the longitudinal end 7 is referred to as at the front in the text which follows, while an end 8 of the bus 1 which lies longitudinally opposite the longitudinal end 7 is referred to as a rear end 8.

The first vehicle part 2 has a front end 9 and a rear end 10, with the steered axle 5 being closer to the front end 9 of the vehicle part 2, and the unsteered axle 6 being arranged closer to the rear end 10. The axle 5 forms a frontrnost axle of the bus 1. The rear end 10 of the first vehicle part 2 is adjoined by the vehicle part 3 with a front end 12 by means of a pivoting point 11. The vehicle part 3 has an unsteered axle 13 which is located closer to a rear end 14 than to the front end 12 of the vehicle part 3. A longitudinal axis C of the vehicle part 3 is arranged coaxially with respect to the axis A. The rear end 14 of the vehicle part 3 is adjoined by the third vehicle part 4 by means of a further pivoting point 15 with a front end 16. A longitudinal axis D of the vehicle part 4 is likewise arranged coaxially with respect to the axis A here. The third vehicle part 4 has a steered axle 17 which is arranged closer to a rearend 18 than to a front end 16 of the vehicle part 4. The rear end 18 forms here the rear end 8 of the bus 1. The axle 17 therefore forms a rearmost axle of the bus 1.

The pivoting points 11 and 15 are essentially conventional and known live ring joint connections such as are used in known articulated buses. The pivoting points 11 and 15 can be allocated, inter alia, bending protection devices (not illustrated) here which prevent the vehicle parts veering off or swerving out when there are thrust loads between two vehicle parts, for example. The pivoting points 11 and 15 are not described in more detail here and reference is made in this regard to the statements relating to known buses.

The first vehicle part 2 has the first door 21 in the longitudinal direction A between the front end 9 and the axle 5. The second door 22 is present between the axles 5 and 6. The third door 23 is formed in the second vehicle part 3, and the fourth door 24 is formed between the front end 16 and the axle 17 in the third vehicle part 4. The third vehicle part 4 has the fifth door 25 which is arranged between the axle 17 and the rear end 18. The first door 21 is embodied as a double-wing, pivoting-in door, while the doors 22 to 25 are embodied as pivoting-out sliding doors. In the illustration in Figure 1, the doors 21 to 25 are illustrated in the closed state. In the illustration in Figure 2, the doors 21 to 25 are open, with door wings of the doors 21 to 25 being either pivoted inwards (door 21) or outwards and slid (doors 22 to 25) -17 -depending on the design of the door.

Interior spaces of the vehicle parts 2, 3 and 4 form together a passenger compartment 56 in which seats 57 and standing places 58 for passengers are arranged. The floors of the interior spaces form together a floor 27 of the passenger compartment 56. The floor 27 has a stepless and essentially level low floor area 59 which lies in the centre with respect to the width of the bus 1 and forms a continuous floor over the entire length of the passenger compartment 56. The low floor area 59 has, in the perpendicular direction with respect to the axis A, a width which corresponds approximately to a quarter of a width of the passenger compartment 56. In the areas 60 and 61 of the pivoting points 11 and 15 the low floor area 59 extends as far as the side walls 19 of the bus 1. Likewise, in areas 62 at the doors 21 to 25 the low floor area 59 extends respectively as far as door thresholds 63. The door thresholds 63 here are essentially at the same height above an underlying travel surface 29 as the low floor area 59 of the floor 27.

According to the invention, the low floor area 59 is embodied in the bus 1 in such a way that when the bus 1 is ready to travel it is arranged at a height above the underlying travel surface 29 of the bus 1 which corresponds approximately to the height of wheel hubs 51 of the axles above the underlying travel surface 29.

This height is preferably approximately 32 cm, but it can also be greater or smaller. In particular, the bus 1 can be moved, for example by pneumatic lowering, at the entry side 64 into a position in which the door thresholds 63 are at a significantly lower height above the underlying travel surface 29 than in the ready-to-travel state.

A first drive assembly 30 is arranged in an area 28 of the first vehicle part 2 which lies between the second -18 -door 22 and the axle 6 in the longitudinal direction of the bus 1 at the height of the vehicle floor 27 above the underlying travel surface 29. When viewed from the outside, the drive assembly 30 can be seen only underneath an underbody 26 of the bus 1. The position of the drive assembly 30 is shown in Figures 1 and 2 for the purpose of illustration. A geometric longitudinal axis E of the drive assembly 30 which lies coaxially with respect to a drive axle 36 (see Figure 3) of the drive assembly 30 is inclined here by an angle a with respect to the low floor area 59 of the vehicle floor 27. The angle a is preferably approximately 9 degrees. The axis E is inclined with respect to the low floor area 59 and the vehicle floor 27 in such a way that a front end 31 of the drive assembly 30 is higher above the underlying travel surface 29 than a rear end 32 (see Figure 3 for a schematic illustration of the position). The axis E of the drive assembly 30 is inclined by an angle 13 with respect to a plane F, with the plane F being perpendicular to the low floor area 59 of the vehicle floor 27 and including the axis A. The angle 13 of inclination with respect to the plane F preferably has an angle of approximately 10 degrees. Of course, larger or smaller values can also be selected for both angles a and J3 of inclination, depending on the arrangement of the power axle 6 and/or of the drive assembly 30.

A second drive assembly 40, which is of identical design to the first drive assembly 30, is present on the second vehicle part 3, in an area 33 which lies above the underlying travel surface 29 in the longitudinal direction of the bus 1 between the third door 23 and the axle 13 at the height of the vehicle floor 27. The arrangement of the drive assembly 40 in the area 33 on the vehicle part 3 corresponds to the arrangement of the assembly 30 in the area 28 on the vehicle part 2. A detailed illustration of the arrangement of a drive assembly with respect to an axle -19 -can be found in Figures 3 and 4.

In the areas 28 and 33, the vehicle floor 27 is raised and forms platforms 34 and 35 in the vehicle parts 2 and 3. The platforms 34 and 35 accommodate here parts of the drive assemblies 30 and 40 which lie above the low floor area 59 with respect to the underlying travel surface. The platforms are formed near to the side walls 50 here and do not extend into the low floor area 59.

In Figure 1, current collectors 50 are present on a roof 73 of the bus 1 and they can be placed in contact with a current-conducting contact wire (not shown) . The current collectors 50 are provided on the rearmost vehicle part 4 and correspond in their design to conventional current collectors of previously known trolley buses. In the illustration in Figure 1, the current collectors 50 are illustrated in a position of rest and are lowered onto the roof 73. A drive current controller 74 is also formed on the roof 73 at the frontmost vehicle part 2. The drive current controller 74 conditions the current, which will be tapped by means of the current collectors 50, in accordance with the requirements. The drive current controller.74 can, however, also be formed at other locations in the bus 1, however it is advantageous to use the roof surface 73 which is otherwise unused.

Figures 3 and 4 show a schematic view of the arrangement of the drive assembly 30 with respect to a power axle 6. Figure 3 shows a side view, while Figure 4 shows a plan view. In the text which follows, both figures are described together. The drive assembly 30 is arranged here, as in Figures 1 and 2, in front of the power axle 6 with respect to the longitudinal centre axis A of the vehicle. The arrangement of the second drive assembly 40 corresponds to the arrangement of the illustrated first assembly 30, and the -20 -

description below as well as the illustrations in

Figures 3 and 4 apply correspondingly to the drive assembly 40.

The assembly 30 is arranged inclined at an angle a with respect to a plane G which is parallel to the low floor area 59 of the vehicle floor 27 and at a height of a wheel hub 51.1 of a wheel 39 above the underlying travel surface 29. In particular, the drive axle 36 which is coaxial with respect to the geometric axis E here is inclined by the angle a in such a way that the front end 31 of the drive assembly 30 is above the plane G with respect to the underlying travel surface 29 and the rear end 32 of the assembly 30 is below G. The axle 6 is illustrated in one embodiment as a portal axle 37. The portal axle 37 has an axle area 38 with a geometric axle H which is parallel to the plane G and perpendicular to the plane F. The axle area 38 is closer here to the underlying travel surface 29, i.e. below the plane G, than the wheel hubs 51.1 of the wheel 39. In the axle area 38, a power divider 41 is formed on the portal axle 37 which is offset towards the wheel 39 in the perpendicular direction with respect to the plane F. The power divider 41 has a feed axle 42 which is oriented at an angle a with respect to the plane G, and at an angle 13 with respect to the plane F. The angle 13 is selected here in such a way that the front end 31 of the assembly 30 is at a greater distance from the plane F than the rear end 32.

The point at which the drive axle 36 emerges from the assembly 30 is arranged here approximately at the same distance from the plane G as an exit point of the feed axle 42 from the power divider 41. Since the assembly is spaced apart from the axle 37, the axles 36 and 42 are thus arranged offset with respect to one another in parallel in a projection onto the plane F (Figure 3) . Furthermore, the assembly 30 is oriented in such a -21 -way that the drive axle 36 is located coaxially with respect to the feed axle 42 in a projection onto the plane G (Figure 4). The drive axle 36 and the feed axle 42 are therefore arranged spatially parallel to one another.

The drive axle 36 is adjoined coaxially by a drive shaft 43 of a cardan shaft 44. An output shaft 45 of the cardan shaft 44 likewise adjoins the feed axle 42 coaxially. The drive shaft 43 and output shaft 45 are thus also aligned parallel to one another. Furthermore, the cardan shaft 44 comprises a connecting shaft 65 which is arranged between the drive shaft 36 and output shaft 45. The drive shaft 36 is adjoined by a first double cardan joint 46 which connects the drive shaft 36 to the connecting shaft 65. The double cardan joint 46 has here a cardan joint 47 on the drive axle side and a cardan joint 48 on the connecting shaft side as well as an articulated axle body 49 lying between them.

A further double cardan joint 52 which connects the output shaft 45 to the connecting shaft 65 also adjoins the output shaft 45. The double cardan joint 52 has here a cardan joint 53 on the output shaft side and a cardan joint 55 on the connecting shaft side as well as an articulated axle body 55 lying between them. The drive shaft 36 and the output shaft 45 enclose an angle x or ö in each case with the connecting shaft 65 in a projection onto the plane F. Owing to the parallel alignment of axles 36 and 45, the angles x and ó are of equal size. Both angles are preferably approximately 14 degrees. It is to be noted here that as a result of the embodiment as double cardan joints 46 and 52, the angles x and are respectively distributed half and half between the individual cardan joints 47 and 48, and 53 and 54 respectively. As a result, the cardan shaft 44 does not have an angle greater than 05x or 0.5ó at any point. When x ö=14 degrees it follows that no angle of the cardan shaft is greater than 7 degrees.

The oblique or inclined arrangement of the drive -22 -assembly 30 thus ensures that the cardan shaft 44 has only relatively small angles at the joints and thus large torques such as can occur in an embodiment of the assembly 30 as an electric motor can be transmitted.

Figure 5 shows the bus 1 according to the invention when cornering in a schematic plan view. In this context, the longitudinal axis B of the first vehicle part 2 and the longitudinal axis C of the second vehicle part 3 enclose an angle c. The axes B and C intersect here at a centre of rotation 11.1 of the first pivoting point 11. The axis C and the longitudinal axis D of the third vehicle part 4 enclose an angle 4) with one another in the same way as axes B and C. The axes C and D intersect here at a centre of rotation 15.1 of the second pivoting point 15.

A wheel 5.1 which is on the inside of the bend on the front-most axle 5 is deflected here by an angle y in the same way as the angles and 4). The rotational angle 4' is transmitted by a steering gear (not illustrated) into a steering angle q of the wheel 17.1 which is on the inside of the bend on the rearmost axle 17. According to the invention, this transmission is distinguished by an exponential dependence of the steering angle ri on the rotational angle 4). The wheels 5.2 and 17.2 which are on the outside of the bend have here the corresponding steering angles which correspond to the larger bend radius of the outer wheels. A wheel 13.1 which is on the inside of the bend on the unsteered axle 13 then describes, in the case of constant cornering with a side 71 on the inside of the bend, a virtual circle 67 with a radius Ri. A corner 68 of the bus 1 which is on the outside of the bend at the front end 7 then describes a virtual circle 69 with a radius R2. The exponential translation of the rotational angle 4' into the steering angle ri by the steering gear ensures that an outer side 70 which is on the inside of the bend of the rearmost vehicle part 4 -23 -abuts tangentially against the virtual circle 67 during cornering. When the bus 1 corners it thus traverses a circular ring 72 which is bounded by the circles 67 and 69 and would also be traversed by a bus with only the first two vehicle parts 2 and 3. This results in cornering behaviour to which a driver is accustomed from a bus with only two vehicle parts.

To summarize it is to be noted that the invention makes available an articulated bus which has comfortable and disabled-friendly accessibility to the entire passenger compartment through all the accesses of the articulated bus. In addition, an articulated bus according to the invention also has a driving behaviour which hardly differs in terms of cornering from a conventional articulated bus with two articulations. The third and last vehicle part is steered in such a way that the area traversed by the last vehicle part does not extend over the area traversed by the second vehicle part. It is to be noted here that the possibility that in addition to the frontmost and rearmost axles further axles of the bus are also steered is not ruled out here. In particular in one possible embodiment with more than three vehicle parts it may be advantageous if, for example, the frontmost and the two rearmost axles are steered.

List of reference symbols A Longitudinal centre axis of bus B Longitudinal centre axis of vehicle part 2 C Longitudinal centre axis of vehicle part 3 D Longitudinal centre axis of vehicle part 4 E Geometric longitudinal axis of drive __________ assembly 30 F Plane perpendicular to low floor area, __________ including A G Plane parallel to low floor area, passing __________ through wheel hubs 51 H Axis of low lying area 38 of the portal axle ___________ 37 a Angle of assembly to plane G __________ Angle of assembly to plane F x Angle of cardan shaft to double cardan joint ___________ 46 Angle of cardan shaft to double cardan joint ___________ 52 __________ Cornering angles B, C __________ Cornering angles C, D y Angle wheel 5.1 _________ Angle wheel 17.1 1 Articulated bus 2 First vehicle part 3 Second vehicle part 4 Third vehicle part Steered axle (frontmost) 5.1 Wheel on inside of bends 5.2 Wheel on outside of bends 6 Unsteered axle 7 Front longitudinal end of bus 8 Rear longitudinal end of bus 9 Front end of vehicle part 2 Rear end of vehicle part 2 11 Pivoting point 11.1 Centre of rotation of pivoting point 11 12 Front end of vehicle part 3 13 Unsteered axle 13.1 Wheel on inside of bends 14 Rear end of vehicle part 3 Pivoting point 15.1 Centre of rotation of pivoting point 15 16 Front end of vehicle part 4 17 Steered axle (rear) 17.1 Wheel on inside of bends 17.2 Wheel on outside of bends 18 Rear end of vehicle part 4 19 Side walls Door wing 21 First door 22 Second door 23 Third door 24 Fourth door Fifth door 26 Underbody 27 Vehicle floor 28 Area in vehicle part 2 29 Underlying travel surface First drive assembly 31 Front end of drive assembly 30 32 Rear end of drive assembly 30 33 Area in vehicle part 3 34 Platform in vehicle part 2 Platform in vehicle part 3 36 Drive axle of assembly 30 37 Portal axle 38 Low lying axle area 39 Wheel Second drive assembly 41 Power divider 42 Feed axle 43 Drive shaft 44 Cardan shaft Output shaft 46 Double cardan joint 47 First cardan joint 48 Second cardan joint 49 Articulated axle body Current collector 51 Wheel hubs 52 Second double cardan joint 53 First cardan joint 54 Second cardan joint Articulated axle body 56 Passenger compartment 57 Seat places 58 Standing places 59 Low floor area Area of pivoting point 11 61 Area of pivoting point 15 62 Area at doors 63 Door thresholds 64 Entry side Connecting shaft 66 _______________________________________________________ 67 Virtual circle radius Ri 68 Corner on outside of bends 69 Virtual circle radius R2 Outer side on inside of bends 71 Side of wheel 13.1 on inside of bends 72 Circular ring 73 Roof 74 Drive current controller

Claims

Patent claims 1. Articulated bus having at least three vehicle parts

which are connected to one another in an articulated fashion, wherein a frontmost vehicle part which is arranged at a front end with respect to a longitudinal direction of the vehicle has two axles and a rearmost vehicle part which is arranged at the rear with respect to a longitudinal direction of the vehicle has a single axle, and there is at least one further single-axle vehicle part arranged between them, wherein the frontmost axle and the rearmost axle of the bus are articulated, and at least two successive axles are power axles which are driven by in each case one associated drive assembly, by means of their drive axles, wherein the drive assemblies are arranged in each case in an underfloor design on the vehicle parts with the power axles, characterized in that the articulated bus has a continuous low floor area over the entire length of the vehicle.
2. Articulated bus according to Claim 1, characterized in that the drive assemblies of the respective vehicle parts are arranged offset laterally with respect to a longitudinal centre axis of the vehicle part and the drive axles of the drive assemblies in particular are arranged, on the one hand, obliquely with respect to the vehicle floor of the corresponding vehicle part and, on the other hand, obliquely with respect to a plane which is perpendicular to the vehicle floor and which is parallel to the longitudinal axis of the corresponding vehicle part.
3. Articulated bus according to one of Claims 1 to 2, characterized in that the drive shaft and the output shaft of, in each case, one cardan shaft interact via two double cardan joints and the drive shaft and the output shaft of, in each case, one cardan shaft are preferably arranged parallel to one another and lie in a plane which is perpendicular to the vehicle floor of the respective vehicle part, wherein the drive shafts are arranged coaxially with respect to the drive axles of the corresponding drive assemblies, and the drive assemblies are in particular identical in design and are arranged in the same way on the corresponding vehicle part, preferably in front of the power axle with respect to the longitudinal direction of a vehicle part, and the at least two power axles are preferably arranged on successive vehicle parts.
4. Articulated bus according to one of Claims 1 to 3, characterized in that the drive assemblies each comprise an electric motor which are preferentially supplied with electrical energy from an exchangeable power supply unit which, in particular, is embodied as a hybrid unit which preferably comprises a power storage unit and a power feed unit, and the power feed unit preferentially is connected to a power conducting contact wire via an overhead line system.
5. Articulated bus according to one of Claims 1 to 4, characterized in that the steered rearmost axle is controlled by means of a mechanical steering gear which translates a rotational angle between the longitudinal centre axis of the rearmost vehicle part and the longitudinal centre axis of the vehicle part which adjoins it in the direction of the front into a steering angle of wheels of the steered axle in such a way that the steering angle depends on the rotational angle in accordance with an exponential function and the steering gear is preferably embodied as a compact unit which reads the instantaneous rotational angle mechanically by means of a first transmission arm and passes on the steering angle mechanically to the steered axle by means of a second transmission arm.