WO2008132575A1

WO2008132575A1 - Propulsion system for a vehicle, in particular a bus

Info

Publication number: WO2008132575A1
Application number: PCT/IB2008/000986
Authority: WO
Inventors: Mauro Palitto
Original assignee: Prototipo S.P.A.
Priority date: 2007-04-27
Filing date: 2008-04-22
Publication date: 2008-11-06
Also published as: ITTO20070284A1

Abstract

The present invention relates to a propulsion system (1) for a vehicle, in particular a bus, comprising a first power unit (10) for the drive of a vehicle, said first power unit (10) comprising: a first transversally mounted thermal engine (11); - a first clutch (12), in particular a servocontrolled one, connected to an output shaft of the first engine (11); a first gearbox (13), in particular a servocontrolled one, connected to said first clutch (12) in order to be coupled to said first engine (11); first connecting means (3, 4, 14, 15) adapted to connect said first gearbox (13) to an axle (2) of the vehicle. The invention is characterized in that said propulsion system (1) comprises a second power unit (20) comprising: a second transversally mounted thermal engine (21); a second clutch (22), in particular a servocontrolled one; - a second gearbox (23), in particular a servocontrolled one, connected to said second clutch (22) in order to be coupled to said second engine (21); second connecting means (24, 25) adapted to provide a connection between the first power unit (10) and the second power unit (20) downstream of said first gearbox (13) and second gearbox (23).

Description

PROPULSION SYSTEM FOR A VEHICLE, IN PARTICULAR A BUS

DESCRIPTION

The present invention relates to a propulsion system for a vehicle, in particular a bus, according to the preamble of claim 1.

In the art, the term "bus" designates vehicles adapted to transport a plurality of people; in particular, most buses used at present consist of big road vehicles capable of transporting dozens of people at a time, such as those used for local public transportation services, which can generally carry a hundred people or so.

Most buses known in the art have a propulsion system comprising a power unit with the associated gearbox connected to the rear axle, the power unit being arranged in a rear compartment of the vehicle. Propulsion systems for vehicles, in particular buses, are known in the art which comprise a power unit featuring a transversally mounted thermal engine connected to a rear axle of the vehicle. In particular, said rear axle is of the type comprising a differential gear mounted close to a rear wheel of the vehicle. Generally, said differential gear drives the rear wheel which is closer to it through a first axle shaft, and the rear wheel farther from it through a second axle shaft. Also, said first and second axle shafts are aligned horizontally with each other.

However, propulsion systems for vehicles, in particular buses, of the above-described type lack of efficiency at partial loads and heavy loads.

In this frame, it is the main object of the present invention to overcome the above-mentioned drawbacks by providing a propulsion system for a vehicle, in particular a bus, which reduces both the fuel consumption and the weight of the vehicle.

In order to achieve these objects, the present invention provides a propulsion system for a vehicle, in particular a bus, incorporating the features set out in the appended claims, which are intended as an integral part of the present description.

Further objects, features and advantages of the present invention will become apparent from the following detailed description and from the annexed drawings, which are supplied by way of non-limiting example, wherein:

Fig. 1 is a schematic view of a first embodiment of a propulsion system for a vehicle, in particular a bus, according to the present invention;

Fig. 2 is a schematic view of a second embodiment of a propulsion system for a vehicle, in particular a bus, according to the present invention. Referring now to the drawings, reference numeral 1 designates as a whole a propulsion system for a vehicle, in particular a bus, according to the present invention.

Propulsion system 1 comprises a first power unit 10 for the drive of a vehicle, said first power unit 10 comprising: - a first transversally mounted thermal engine 11 ; a first clutch 12, in particular a servocontrolled one, connected to an output shaft (not shown) of first engine 11 ; a first gearbox 13, in particular a servocontrolled one, connected to said first clutch 12 in order to be coupled to said first engine 11 ; - first connecting means 3, 4, 14, 15 adapted to connect said first gearbox 13 to an axle

2 of the vehicle. hi accordance with the present invention, said propulsion system 1 comprises a second power unit 20 comprising: a second transversally mounted thermal engine 21 ; - a second clutch 22, in particular a servocontrolled one; a second gearbox 23, in particular a servocontrolled one, connected to said second clutch 22 in order to be coupled to said second engine 21.

In particular, said axle 2 of the vehicle is a rear axle 2 and the propulsion system according to the present invention provides a rear wheel drive. By fitting propulsion system 1 with a first power unit 10 and a second power unit 20, it is possible to obtain lower fuel consumption as well as a reduction in the weight of the propulsion system installed in a bus. hi particular, said reduction in the weight of the propulsion system of the vehicle is also due to the fact that first power unit 10 and second power unit 20 do not comprise a differential gear nor any of those typical accessories (e.g. air conditioner compressor, alternator, power steering pump, starter motor, etc.) which are normally associated with a known power unit.

Said first engine 11 and second engine 12 may even have different displacements; they preferably share at least a portion of the same fuel system and/or intake system.

Preferably, said first engine 11 and second engine 12 share at least a portion of the same exhaust system and cooling system, so that both the coolant and a catalyst used in propulsion system 1 are always at an appropriate temperature, in particular for engine 11, 21 which is restarted during a mission.

Said exhaust system, said cooling system and said catalyst are not shown in the annexed B2008/000986

drawings.

According to the present invention, second power unit 20 comprises second connecting means 24, 25 adapted to provide a connection between first power unit 10 and second power unit 20 downstream of said first gearbox 13 and second gearbox 23. Consequently, said second connecting means 24, 25 also allow said second gearbox 23 to be connected to axle 2 of the vehicle.

As shown in the annexed drawings, said first connecting means comprise a first reduction gear 14 of the first gearbox 13 which is connected to an intermediate gear 3, said intermediate gear 3 being connected to axle 2 through a third drive shaft 4. Furthermore, said second connecting means comprise a second reduction gear 24 of the second gearbox 23 which is connected to said first reduction gear 14 and/or to said intermediate gear 3 through a main drive shaft 25. hi particular, in Fig. 1 said main drive shaft 25 is connected directly to intermediate gear 3, since first reduction gear 14 is located on the opposite side of intermediate gear 3 with respect to second reduction gear 24. As an alternative, it is apparent that main drive shaft 25 may engage first reduction gear 14 directly, e.g. through a constant- velocity joint; in this case, the positioning of intermediate gear 3 and first reduction gear 14 will be reversed compared to Fig. 1.

Fig. 2 is a schematic view of a second embodiment of a propulsion system 1 for a vehicle, in particular a bus, according to the present invention. In this drawing, first reduction gear 14 of first gearbox 13 is connected to intermediate gear 3 through a second drive shaft 15, whereas third drive shaft 4 is obliquely connected to axle 2 of the vehicle. As a consequence, this embodiment is particularly suitable for use in known buses, wherein intermediate gear 3 is positioned on one side of the engine compartment of the vehicle. It should be noted that in both the embodiment of Fig. 1 and the embodiment of Fig. 2 the connection between first power unit 10 and second power unit 20 is made downstream of said first gearbox 13 and second gearbox 23.

Advantageously, the special connection between said first power unit 10 and second power unit 20 according to the present invention allows to fully exploit the potentiality of said first engine 11 and second engine 21. hi fact, when the power output of first engine 11 is sufficient to provide the performance level required, that engine is turned on and brought to a power level which is appropriate to the user's requests or to the requirements of the mission under way, and all that is needed is that the first gearbox 13 is in gear and first clutch 12 is engaged, while second engine 21 is off and disconnected because second clutch 22 is disengaged. The same applies to the case wherein second engine 12 alone can provide the performance level required. If the performance level required can only be provided by the power output of both engines 11, 12, the latter are connected together to axle 2 by engaging both first clutch 12 and second clutch 22. The two engines can also be managed in a fully independent way, and it is sufficient that the appropriate gear is selected in first gearbox 13 and in second gearbox 23 and that first clutch 12 and second clutch 22 are engaged.

It is also apparent that said first gearbox 13 and second gearbox 23 comprise discrete gear ratios, which are suitably conceived in accordance with the characteristics of first engine 11 and second engine 21 , respectively.

Said first transversally mounted thermal engine 11 also comprises an output shaft (not shown) which is revolving about a first axis A.

Second engine 21 of second power unit 20 is preferably so positioned as to have an output shaft (not shown) which is substantially coaxial to said first axis A. In the event that first power unit 10 and second power unit 20 are too large for the transversal dimension of the vehicle, it is also conceivable that first power unit 10 and second power unit 20 are not coaxial to each other and that said second power unit 20 is mounted in an offset position relative to first axis A. To accomplish this, intermediate gear 3 may be fitted with a transmission means, e.g. a set of gears in cascade in mesh with said main drive shaft 25. According to the present invention, propulsion system 1 comprises first transmission means 16, 17, 18, 19 connecting first power unit 10 to an accessory assembly 30. Said accessory assembly 30 comprises: a motor-generator 31 ; a compressor for an air conditioning system or kinetic energy recovery means 32; - other accessories 36, 37.

Said motor-generator 31 and compressor or kinetic energy recovery means 32 are positioned on a second axis B, said axis B being preferably substantially parallel to first axis A. Said other accessories 36, 37 are positioned on at least one additional axis C, a single axis C being shown in the annexed drawings. In a preferred embodiment of propulsion system 1 according to the present invention, said first transmission means comprise: a third clutch 16 mounted to an extension 13 A of an input shaft (not shown) of first gearbox 13; a first pulley 17 mounted downstream of third clutch 16; a first belt 18 to connect said first pulley 17 to a second pulley 19 connected to second axis B.

Said third clutch 16 is preferably of the dry single-plate type. In addition, propulsion system 1 according to the present invention comprises second gearbox means 26, 27, 28, 29 connecting second axis B to second engine 21. Said second transmission means comprise: an electromagnetic joint 26 mounted to a front portion 21 A of the shaft (not shown) of second engine 21; - a third pulley 27 mounted downstream of electromagnetic j oint 26 ; a second belt 28 adapted to connect said third pulley 27 to a fourth pulley 29 connected to second axis B.

From the above description it is apparent that motor-generator 31 may be used as both an alternator and a starter motor. In this particular case, it may be used in order to start: - first engine 11, in particular when first clutch 12 and third clutch 16 are engaged, first gearbox 13 is in neutral and electromagnetic joint 26 is disengaged; second engine 21, in particular when second clutch 22 is disengaged, electromagnetic joint 26 is engaged and third clutch 16 is disengaged.

According to the present invention, propulsion system 1 additionally comprises third transmission means 33, 34, 35 adapted to connect second axis B to third axis C. Said third transmission means comprise: a fifth pulley 33 connected to second axis B; a third belt 34 to connect said fifth pulley 33 to a sixth pulley 35 connected to third axis C. Preferably, said third axis C is substantially parallel to second axis B and comprises additional accessories 36, 37 which may include energy recovery means.

Depending on type, the accessories 31, 32, 36, 37 may be connected to said second axis B and third axis C either directly or through a respective electromagnetic joint (not shown). In accordance with the present invention, motor-generator 31 and accessories 32, 36, 37 can be activated in the following ways: by the vehicle wheels while first engine 11 and second engine 12 are off and disconnected from vehicle axle 2. This situation occurs when first clutch 12, second clutch 22 and electromagnetic joint 26 are disengaged, first gearbox 13 is in gear and third clutch 16 is engaged; by first engine 11 only, whether it is transmitting power (i.e. when first gearbox 13 is in gear, first clutch 12 and third clutch 16 are engaged, and electromagnetic joint 26 and second clutch 22 are disengaged) or the vehicle is stationary (i.e. when first gearbox 13 is in neutral, first clutch 12 and third clutch 16 are engaged, and electromagnetic joint 26 and second clutch 22 are disengaged); by second engine 21 only, whether it is transmitting power (i.e. when second gearbox 23 is in gear, second clutch 22 and electromagnetic joint 26 are engaged, and first clutch 12 and third clutch 16 are disengaged) or the vehicle is stationary (i.e. when first gearbox 13 and second gearbox 23 are in neutral, second clutch 22 is either engaged or disengaged, electromagnetic joint 26 is engaged and third clutch 16 is disengaged); by both first engine 11 and second engine 21, when they are co-operating to vehicle drive (i.e. when first gearbox 13 and second gearbox 23 are both in gear, clutches 12, 16 and 22 are engaged, and electromagnetic joint 26 is either engaged or disengaged). Advantageously, propulsion system 1 according to the present invention comprises an electronic control unit (not shown) which controls the operation of said propulsion system 1. In particular, said electronic control unit selects which of said first engine 11 and second engine 21 must be activated, determines the power to be delivered by first engine 11 and second engine 21, determines which gears must be engaged in the first gearbox 13 and second gearbox 23, and selects the appropriate combination of clutches 12, 16, 22 to be disengaged or engaged. In short, said electronic control unit allows to obtain the maximum level of efficiency from propulsion system 1 as a function of the performance requested by the user. The advantages of a propulsion system for a vehicle, in particular a bus, according to the present invention are apparent from the above description. In particular, said advantages are due to the fact that propulsion system 1 so conceived as to comprise a first power unit 10 and a second power unit 20 allows to obtain a considerable reduction in fuel consumption and weight.

These advantages derive from the fact that propulsion system 1 according to the present invention provides a connection between first power unit 10 and second power unit 20 downstream of said first gearbox 13 and second gearbox 23. This allows to fully exploit in a particularly advantageous way the potentiality of said first engine 11 and second engine 21 ; as a matter of fact, each of said first engine 11 and second engine 21, whether used alone or combined together, can be used within a particularly suitable and appropriate power range, 6

thus fully complying with the user's requests and/or mission requirements and offering improved efficiency.

Another advantage offered by propulsion system 1 according to the present invention is that said first engine 11 and second engine 12 share the same exhaust system and cooling system; this advantageously ensures that both the coolant and the catalyst used in propulsion system 1 are always at an adequate temperature, in particular for engine 11, 12 which is re-started during a mission.

Furthermore, the presence of an electronic control unit adapted to control the operation of the various components of propulsion system 1 according to the present invention allows to obtain the highest efficiency from propulsion system 1 as a function of the performance level requested by the user.

The embodiments of the propulsion system described herein by way of example may be subject to many possible variations without departing from the novelty spirit of the inventive idea; it is also clear that in the practical implementation of the invention the illustrated details may have different shapes or be replaced with other technically equivalent elements.

For example, among many variations, electromagnetic joint 26 may be mounted to second axis B of propulsion system 1, so that third pulley 27 can either be connected to second axis B or be disconnected from said second axis B. According to another variation, propulsion system 1 may comprise a start-stop control (not shown in the drawings) which allows to turn off said propulsion system 1 not only when the bus stops in traffic, but also in deceleration, in which condition the accessories keep operating since they are driven by the vehicle wheels.

It can therefore be easily understood that the present invention is not limited to the above- described propulsion system, but may be subject to many modifications, improvements or replacements of equivalent parts and elements without departing from the inventive idea, as clearly specified in the following claims.

A A & A -k &

Claims

1. Propulsion system (1) for a vehicle, in particular a bus, comprising a first power unit (10) for the drive of a vehicle, said first power unit (10) comprising: a first trans versally mounted thermal engine (11); a first clutch (12), in particular a servocontrolled one, connected to an output shaft of the first engine (11); a first gearbox (13), in particular a servocontrolled one, connected to said first clutch (12) in order to be coupled to said first engine (11); first connecting means (3, 4, 14, 15) adapted to connect said first gearbox (13) to an axle (2) of the vehicle, characterized in that said propulsion system (1) comprises a second power unit (20) comprising: a second transversally mounted thermal engine (21); a second clutch (22), in particular a servocontrolled one; a second gearbox (23) connected to said second clutch (22) in order to be coupled to said second engine (21); second connecting means (24, 25) adapted to provide a connection between the first power unit (10) and the second power unit (20) downstream of said first gearbox (13) and second gearbox (23).

2. Propulsion system (1) according to claim 1, characterized in that said second connecting means (24, 25) allow said second gearbox (23) to be connected to the axle (2) of the vehicle.

3. Propulsion system (1) according to claim 1, characterized in that said first connecting means comprise a first reduction gear (14) of the first gearbox (13) which is connected to an intermediate gear (3).

4. Propulsion system (1) according to claim 3, characterized in that said first reduction gear (14) is connected to the intermediate gear (3) through a second drive shaft (15).

5. Propulsion system (1) according to claims 1 to 4, characterized in that said second connecting means comprise a second reduction gear (24) of the second gearbox (23) which is connected to said first reduction gear (14) and/or said intermediate gear (3) through a main drive shaft (25).

6. Propulsion system (1) according to claims 2 to 5, characterized in that said intermediate gear (3) is connected to the axle (2) of the vehicle through a third drive shaft (4).

7. Propulsion system (1) according to claim 1, characterized in that said first engine (11) comprises an output shaft which is revolvingabout a first axis (A).

8. Propulsion system (1) according to claim 7, characterized in that the second engine (21) is so positioned as to have an output shaft which is substantially coaxial to said first axis (A).

9. Propulsion system (1) according to claims 3 and 7, characterized in that said second power unit (20) is mounted in a shifted position relative to the first axis (A), and that the intermediate gear (3) is fitted with a transmission means, in particular a set of gears in cascade, in mesh with said main drive shaft (25).

10. Propulsion system (1) according to claim 1, characterized by comprising first transmission means (16, 17, 18, 19) connecting the first power unit (10) to an accessory assembly (30).

11. Propulsion system (1) according to claim 9, characterized in that said accessory assembly (30) comprises: - a motor-generator (31); a compressor for an air conditioning system or kinetic energy recovery means (32); other accessories (36, 37).

12. Propulsion system (1) according to claims 7 and 11, characterized in that said motor- generator (31) and compressor or kinetic energy recovery means (32) are positioned on a second axis (B) which is substantially parallel to said first axis (A), and that said other accessories (36, 37) are positioned on at least one additional axis (C).

13. Propulsion system (1) according to claim 10, characterized in that said first transmission means comprise: a third clutch (16) mounted to an extension (13A) of an input shaft of the first gearbox (13); a first pulley (17) mounted downstream of the third clutch (16); a first belt (18) to connect said first pulley (17) to a second pulley (19) connected to the second axis (B).

14. Propulsion system (1) according to claim 13, characterized in that said third clutch (16) is of the dry single-plate type.

15. Propulsion system (1) according to one or more of claims 12 to 13, characterized by comprising second transmission means (26, 27, 28, 29) connecting the second axis (B) to the second engine (21). 0986

16. Propulsion system (1) according to claim 15, characterized in that said second transmission means comprise: an electromagnetic joint (26) mounted to a front portion (21A) of a shaft of the second engine (21); - a third pulley (27) mounted downstream of the electromagnetic joint (26); a second belt (28) adapted to connect said third pulley (27) to a fourth pulley (29) connected to the second axis (B).

17. Propulsion system (1) according to claim 12, characterized by comprising third transmission means (33, 34, 35) adapted to connect the second axis (B) to said third axis (C).

18. Propulsion system (1) according to claim 17, characterized in that said third transmission means comprise: a fifth pulley (33) connected to the second axis (B); a third belt (34) to connect said fifth pulley (33) to a sixth pulley (35) connected to the third axis (C).

19. Propulsion system (1) according to claim 12, characterized in that said third axis (C) is substantially parallel to the second axis (B), and that said other accessories (36, 37) comprise energy recovery means.

20. Propulsion system (1) according to one or more of the preceding claims, characterized by comprising an electronic control unit adapted to control the operation of said propulsion system (1).

21. Propulsion system (1) according to one or more of the preceding claims, characterized by comprising a start-stop control which allows said propulsion system (1) to be turned off not only when the bus stops in traffic, but also in deceleration, in which condition the accessories (30) keep operating since they are driven by the vehicle wheels.

22. Propulsion system (1) according to claim 1, characterized in that said axle (2) is a rear axle (2) of the vehicle and the propulsion system (1) provides a rear wheel drive.

23. Propulsion system (1) according to claim 1, characterized in that said first engine (11) and second engine (12) have different displacements.

24. Propulsion system (1) according to claim 1, characterized in that said first engine (11) and second engine (12) share at least a portion of the same fuel system and/or intake system.

25. Propulsion system (1) according to claim 1, characterized in that said first engine (11) and second engine (12) share at least a portion of a same exhaust and cooling systems.