WO2015097631A1

WO2015097631A1 - Portal axle arrangement

Info

Publication number: WO2015097631A1
Application number: PCT/IB2014/067195
Authority: WO
Inventors: Márk LELKES; Patrik PATAI
Original assignee: Rába Futómü Kft.
Priority date: 2013-12-23
Filing date: 2014-12-21
Publication date: 2015-07-02
Also published as: HUP1300754A2; HU230843B1

Abstract

A portal axle arrangement, comprising an input axle shaft (22), an input spiral bevel gear (23), in connection with a differential drive (24), output transverse shafts (25) in connection with said differential drive (24), for each output transverse shaft (25), a gear unit having a transmission gear ratio, a wheel axle formed by a half shaft (33) having a longitudinal axis positioned higher than the longitudinal axis of the transverse shaft (25) associated with the gear unit, wherein a further gear (30) is formed at the inner end of each of the output half shafts (33), each gear unit is equipped with a further transmission gear (27) having internal toothing (28) in geared connection with the relating transverse shaft (25). The transmission gear (27) is associated with a gear (26) formed at the end of the transverse shaft (25) through its internal toothing (28), and the gear (30) formed at the end of the output half shaft (33) is connected to the gear (27) outside of a plane (P1) defined by the longitudinal axes of the transverse shaft (25) output half shaft (33) and the output half shaft (33).

Description

Portal axle arrangement

The invention relates to a portal axle arrangement, comprising an input axle shaft, an input spiral bevel gear, a differential drive in connection with said input spiral bevel gear, output transverse shafts in connection with said differential drive, for each output transverse shaft, a gear unit having a transmission gear ratio and associated with the transverse shaft, a wheel axle formed by a half shaft having a longitudinal axis positioned higher than the longitudinal axis of the transverse shaft associated with the gear unit.

It is necessary for the driven axles of low-floor vehicles (buses, trolley buses) to have a portal axle arrangement. Due to highly different gear ratio requirements of the driven- gear transmission of drive trains of vehicles with internal combustion (Diesel, CNG etc.) engines or electric drive (trolley-buses) - most often a gear ratio of 1:5 for internal combustion engines and a gear ratio of 1: 10 for electrically driven ones -, the design of the respective running gears is completely different, and the various build-ups have few common components. In electric drives, due to their increased space requirement, only the drum brake design is feasible, instead of that of the up-to-date disc brake.

US 20110259657 Al discloses several hybrid vehicle drive trains that have the common feature of applying one or several electric motors essentially assigned to various components of the drive chain, but no specific designs, structural considerations are dis- closed that would make the feasibility of the proposed solution likely and that would provide those skilled in the art adequate guidance for its implementation and further development.

Considering the above, there is a strong need for a portal axle arrangement that makes a hybrid drive feasible without the need to fully redesign the running gears of the various transport devices and/or makes it economical to convert the existing vehicle pool into one with a hybrid drive without the need for any special tools, knowledge and personnel requirements.

The object of the present invention is to disclose a solution that is suitable for being integrated into vehicles driven by an internal combustion engine or an electric drive due to its modular structure. Our object is, moreover, to make the up-to-date disc-brake design feasible in both cases. The task set has been solved by a portal axle arrangement comprising an input axle shaft, an input spiral bevel gear, a differential drive in connection with said input spiral bevel gear, output transverse shafts in connection with said differential drive, for each output transverse shaft, a gear unit having a transmission gear ratio and associated with the transverse shaft, a wheel axle formed by a half shaft having a longitudinal axis positioned higher than the longitudinal axis of the transverse shaft associated with the gear unit. A further gear is formed at the inner end of each of the output half shafts, the gear units are equipped with a further transmission gear having internal toothing in geared connection with the transverse shaft, said further transmission gear is associated with a gear formed at the end of the transverse shaft through its internal toothing, wherein the gear formed at the end of the output half shaft is connected to the gear having internal toothing outside of a plane defined by the longitudinal axes of the transverse shaft and the output half shaft.

In a preferred embodiment of the portal axle arrangement according to the invention the gear unit is associated with an electric motor.

In a further preferred embodiment the gear provided with internal toothing is associated with the electric motor.

In a further preferred embodiment of the portal axle arrangement according to the invention the rotor of the electric motor is formed on the outer mantle of the gear having internal toothing.

In a further preferred embodiment the rotor of the electric motor is formed uniaxially with the mantle of the gear having internal toothing, as a projection in a direction along the longitudinal axis of said gear.

In a further preferred embodiment electric motors are associated with the gears of the gear unit connected to the output half shaft.

The electric motors are preferably connected to a common electric control unit.

The characteristics and advantages of the present invention will be more apparent from the following description given by way of example of the new portal-type design and with reference to the appended figures, where: show schematically currently known hybrid drive train variants, illustrates an entire drive train of the portal axle arrangement according to the invention, illustrates schematically a possible embodiment of the portal axle arrangement according to the invention integrated into a vehicle having a so called mild hybrid drive system, illustrates unvarying and vehicle- specific parts of the drive train of the portal axle arrangement according to the invention, illustrates the implementation of a possible modification of the revolution number and the torque in several discrete stages, illustrates a possible embodiment of the first gear ratio stage of the gearing drive train responsible for the modification of the rotational speed and the driving torque according to Figure 5, illustrates a possible embodiment of the second gear ratio stage of the gearing drive train responsible for the modification of the rotational speed and the driving torque according to Figure 5, illustrates a possible embodiment of the arrangement of the elements constituting the second gear ratio stage shown in Fig. 7, illustrates a possible embodiment of the third gear ratio stage of the gearing drive train responsible for the modification of the rotational speed and the driving torque according to Figure 5, illustrates a possible embodiment of the third gear ratio stage of the gearing drive train responsible for the modification of the rotational speed and the driving torque in a diesel driven motor vehicle, illustrates a possible embodiment of the third gear ratio stage of the gearing drive train responsible for the modification of the rotational speed and the driving torque in an electrically driven motor vehicle, and Figure 12 illustrates schematically a possible embodiment of the portal axle arrangement according to the invention integrated into a low-floor vehicle having a hybrid drive system.

The most widespread hybrid drive types are serial drive (i.e. both the internal combus- tion engine and the electrical motor take part in the drive that is inserted directly into the drive train) and the parallel drive (an internal combustion engine drives a generator only, and the drive is provided exclusively by an electric motor), of which examples are shown in Figures 1A to 1C. In Fig. 1A illustrating a series hybrid drive, an internal combustion engine (ICE) 1 operates a generator 2 and the generator 2 in turn charges a battery 3. An electric motor 4, powered by the battery 3, drives the wheels 5 over a running gear 6. Serial hybrid drive trains principally do not approach the construction of the system from the side of the running gear, so the latter remains unchanged. The torque generated by the ICE 1 always undergoes two transmissions before reaching the running gear 6 of the vehicle, and each transformation results in some losses. The sys- tern is inflexible and does not make a posteriori integration into an existing vehicle structure possible.

In Fig. IB illustrating a parallel hybrid drive, an internal combustion engine (ICE) 7 operates over a clutch 8 a combined electric motor-generator 9, which in turn charges a battery 10 and drives the wheels 11 over a mechanical change-speed box 12 and a run- ning gear 13. When the battery 10 is empty, only the ICE 7 turns the electric motor- generator 9.

In Fig. 1C, an internal combustion engine (ICE) 14 operates over a power distributor 15 a generator 16 on the one hand and drives over a cardan shaft a power aggregator 17 on the other hand, which, in turn, is in driving connection with an electric motor 18 pow- ered by a battery 19 charged by said generator 16 as well as with a running gear 20 which is in connection with wheels 21. The ICE 14 can both drive the wheels 21 directly as in the parallel drive train and be effectively disconnected from the wheels 21 so that only the electric motor 18 drives the wheels 21 as in the series drive train.

In the Figures 1A to 1C mechanical connections are indicated by solid lines and electri- cal connections are indicated by dotted lines. Since the efficiency and emission characteristics of the serial internal combustion engine - mild hybrid - are better in the more elevated vehicle speed ranges exceeding 15- 20 km/h, an object of the present invention is to reconsider that design. Could the running gear constitute the hybrid component of the drive train, then the problem of insert- ing into existing vehicle structures could be solved.

One novelty of the portal axle arrangement according to the present invention is a hybrid drive train integrated into the portal driven bus running gear, and the other novelty is that three drive types can be fitted into the same structure, a diesel drive train with a lower gearing ratio, an electric drive train (trolley bus) with a higher gearing ratio and, moreover, an electric drive assigned and adjusted to the drive required for an internal combustion engine, of which the hybrid drive train described above can be formed.

The most important and most decisive features of the running gear according to the present invention are the following: portal design,

- modular structure,

three-stage drive train,

feasibility of a broad gear ratio range

pinion-gearbox (modular and vehicle-specific),

small-size differential gear,

- aisle that can be used in its entire width,

optional hybrid mode of operation.

Owing to the portal system design, the differential drive and half shafts and the entire axle, resp. are positioned lower than usual, below the wheel axle, opening up the opportunity for a low-floor superstructure design. The flexibility due to its extensive coverage of the gear ratio and drive torque range makes it potentially suitable for diesel driven low-floor urban and suburban buses, electrically driven trolley-buses and vehicles having a hybrid drive system, of a structure and operation similar to the former, according to the theoretical schema shown in Figure 2. Figure 2 shows an exemplary complete drive train comprising several stages dis- closed in the following detailed description. A driven input shaft 22, e.g. a cardan shaft is connected via a conical gear 23 to a differential gear 24 from which two transverse shafts 25 extend. On the outer end of each transverse shaft 25 a further gear 26 is formed, being in driving connection with a transmission gear 27 provided with internal toothing 28. On the end of a rotational axis 29 of said transmission gear 27 a further gear 30 is formed, being in driving connection with two idlers 31, which in turn are in connection with an output gear 32, the rotational axis of which forms a half shaft 33 of the running gear bearing a wheel - not shown - mounted on it.

In a preferred embodiment the running gear of Fig. 2 is arranged in a low-floor vehicle body 34 shown in Figures 3 and 4 in a general and symbolic manner and has a modular structure. This means, there is no difference between the overall and the fitting dimensions, respectively, of the specific variants. The presence or absence of the devices making the optionally equipped hybrid operation possible does not influence the installation dimensions. Consequently, the axle has some invariable components as well as some changing, i.e. vehicle-specific, components. As a result, the differences of the versions are limited to the vehicle- specific modules.

In the presented embodiment, modifications of rotational speed and drive torque is realised through a gearing drive train with three stages of different gear ratios; cf. Figure 5.

The first stage, that is, the main drive unit is a small spiral bevel with the conical gear 23 and a crown-wheel 35 of the differential gear 24 with a gear ratio i of almost 1.0 as shown in Figure 6. Exemplary values of the gear ratio i in this first stage are: i 1.00

number of teeth zl 15

number of teeth z2 15

angle of action (mm) 25°

central normal modulus (mm) 7.689

width of teeth (mm) 45

tooth angle 30.0°

The second stage is constituted by a helical gear pair 26, 27 with external/internal tooth- ing 28 in the way shown in Figure 7. The second stage has a constant reducing gear ra- tio of around 3.3. This stage belongs to the invariable drive train part of the axle according to the invention. Exemplary values of the gear ratio i in this second stage are: i 3.333

number of teeth zl 12

number of teeth z2 -40

angle of action (mm) 20°

normal modulus (mm) 6.200

width of teeth (mm) 81

tooth angle 11.5° It is a novelty of the proposed portal axle arrangement that the rolling circles of the gear 26 with external teeth and the transmission gear 27 with internal toothing 28 touch instead of a vertical plane PI comprising the rotational axis 28 of the transmission wheel 27, in a plane P2 that is shifted with a distance D in course (forward) direction or in the opposite direction relative to this plane P2. Consequently, higher gear ratio is possible in the given second stage, and the gear ratio can be chosen more flexibly at same vertical wheelbase and crown wheel dimensions. This is illustrated in Figure 8.

In order to produce a hybrid drive, it is possible and preferred to mount an electrical drive, i.e. electric motor 36 on the outer cylindrical surface of the transmission wheel 27 with internal toothing 28 in the second stage of the axle. The third stage is a four-element gearing set, realising the transmission by the aid of two idlers 31 arranged symmetrically between the input and output gears 30, 32. This is illustrated in Figure 9.

The third stage already belongs to the variable drive train part of the axle, so the total gear ratio of the axle meeting the various requirements is preferably set by the aid of this third stage. Exemplary values of the gear ratio i in this third stage are: i 1.47

number of teeth zl 17

number of teeth z2 25

number of teeth zk 35

angle of action (mm) 20° normal modulus (mm) 7.00

width of teeth (mm) 75 (80) tooth angle 10.0°

The two versions presented so far cover the requirements of a typical ICE (Diesel, CNG, etc.) driven vehicle or a typical electrically driven public transport vehicle.

For a diesel driven vehicle, the gear ratio of the third stage is around 1.5 - see Figure 10 -, whereas for an electrically driven vehicle, it is around 2.9 - see Figure 11.

The total gear ratio of the presented axle arrangement is thus around 5 for a diesel drive and around 10 for an electric one. The arrangements realising the two different transmissions differ in terms of the diameter of the input, output and idler gears, respectively, and the position of the idlers 31. The position of the input and output gears 30, 32 (half axles 33) is constant in both variants.

Given that the second and third stages are capable of producing the required reducing gear ratio, the gear ratio of the spiral bevel gear of the first stage may remain low, so much so that no real gear ratio with a value other than 1 may be needed. Here the main drive does not modify the torque at all, it only transmits the rotational movement from the cardan shaft to the half axles 33.

This solution results, on the one hand, in a low load differential drive and, on the other, due to the low gear ratio the crown wheel can also remain one with a small diameter. The crown wheel having a smaller diameter fits into the usually cast axle housing without the need to create a special hunched protrusion S for it. Consequently, the entire aisle width can be used even in low-floor vehicles with a standard height h, as shown in Figure 12. With the optional installed electric motor 36 the vehicle can operate also in hybrid mode.

In existing vehicles, the axle is suitable for converting a diesel driven vehicle - following an axle replacement - into hybrid ones, and to exploit the relevant benefits, especially in urban or city traffic. Given the tightness of the space to be built in, an electric motor 36 with moderate performance can be installed around the crown (so called "mild" hybrid), that may be an efficient component of the bus drive in the following modes of operation:

Dense traffic, crawling on highways or in the city at a velocity v<20 km/h, in self- drive mode;

Overtaking and ascent: acceleration boosting;

Progress at constant speed: boosting, fuel efficiency;

Braking, engine brake: recuperation of energy.

Owing to the modular structure of the portal axle arrangement according to the present invention the drive type shown in the description shares the highest possible number of identical parts, which represents a further advantage in the field of manufacture and maintenance.

Mention could be made among the further advantages of the running gear portal axle arrangement according to the invention of the fact that a whole portal axle family that can be formed out of it can cover an extensive range of the gear transmission ratio and drive torque requirements of the various types of passenger transport and utility vehicles.

List of reference signs

1 internal combustion engine (ICE)

2 generator

3 battery

4 electric motor

5 wheel

6 running gear

7 internal combustion engine (ICE)

8 clutch

9 combined electric motor-generator

10 battery

11 wheel

12 change- speed box

13 running gear

14 internal combustion engine (ICE) 15 power distributor

16 generator

17 power aggregator

18 electric motor

19 battery

0 running gear 1 wheel

2 input shaft 3 conical gear 4 differential gear 5 transverse shaft

26 gear

27 transmission gear

28 internal toothing

29 rotational axis

30 gear

31 idler

32 gear

33 half shaft

34 pinion

35 crown-wheel

36 electric motor PI plane

P2 plane

D distance

S space

h height

Claims

1. A portal axle arrangement, comprising

an input axle shaft (22),

an input spiral bevel gear (23),

- a differential drive (24) in connection with said input spiral bevel gear (23),

output transverse shafts (25) in connection with said differential drive (24), for each output transverse shaft (25), a gear unit having a transmission gear ratio and associated with the transverse shaft (25),

a wheel axle formed by a half shaft (33) having a longitudinal axis positioned higher than the longitudinal axis of the transverse shaft (25) associated with the gear unit, characterised in that

a further gear (30) is formed at the inner end of each of the output half shafts (33), the gear units are equipped with a further transmission gear (27) having internal toothing (28) in geared connection with the transverse shaft (25),

said further transmission gear (27) is associated with a gear (26) formed at the end of the transverse shaft (25) through its internal toothing (28),

wherein the gear (30) formed at the end of the output half shaft (33) is connected to the gear (27) having internal toothing (28) outside of a plane (PI) defined by the longitudinal axes of the transverse shaft (25) and the output half shaft (33).

2. The portal axle arrangement according to claim 1, characterised in that the gear unit is associated with an electric motor (36).

3. The portal axle arrangement according to claim 2, characterised in that the gear (27) having internal toothing (28) is associated with the electric motor (36).

4. The portal axle arrangement according to claim 3, characterised in that the rotor of the electric motor (36) is formed on the outer mantle of the gear (27) having internal toothing (28).

5. The portal axle arrangement according to claim 3, characterised in that the rotor of the electric motor (36) is formed uniaxially with the mantle of the gear (27) having internal toothing (28), as a projection in a direction along the longitudinal axis of said gear (27).

6. The portal axle arrangement according to claim 1, characterised in that electric motors (36) are associated with the gears of the gear unit connected to the output half shaft (33).

7. The portal axle arrangement according to claim 6, characterised in that the electric motors (36) are connected to a common electric control unit.