ENGINE MOUNTING ASSEMBLY AND DRIVETRAIN PACKAGING OF A LOW FLOOR FRONT ENGINE BUS

FIELD OF THE INVENTION

The invention generally relates to low floor front engine buses. In particular, the invention relates to engine mounting assembly and drivetrain packaging of a low floor front-engine buses.

BACKGROUND OF THE INVENTION

In most of the front engine buses, the engine assembly is generally mounted at such a height on the frame rail that most of the engine height lies below the top surface of the frame rail. Such buses mostly have a relatively higher floor height.

On the contrary, all the low floor buses with floor height of 650 mm and below are with rear engines. In rear engine low floor buses the engine mounting and associated drivetrain packaging are much simpler, as the engine assembly is placed high above compromising on the low floor area above the engine compartment.

However, the same arrangement cannot be implemented in the front engine low floor buses. For front engine buses, the conventional design would decrease the ground clearance and the approach angle considerably.

Further, in the front engine buses providing sufficient space for the gangway at the front door is difficult to achieve and it is a critical design criterion to meet the legal requirements.

Therefore, in light of the above discussion there is a need to provide an improved design for mounting the engine assembly and packaging the associated drivetrain assembly of a low floor front engine bus to achieve the required ground clearance, increased approach angle and adequate gangway.

SUMMARY OF THE INVENTION

The main object of the present invention is to design mounting of the engine assembly of a low floor front engine bus to achieve the required ground clearance and increased approach angle.

Another object of the present invention is to design mounting of the engine assembly of a low floor front engine bus, which achieves adequate gangway at the front door (door which will be ahead of the Front LH wheel for RH drive bus and vice versa).

Yet another object of the present invention is to package the drive-train components in a low floor front engine bus to maintain sufficient low floor area on saloon.

In order to achieve the above mentioned objects, the invention discloses low- floor vehicle which includes an engine assembly disposed at the front on a pair of parallelly spaced frame rails at a significantly higher position with a mounting bracket unit, a gearbox assembly along with the engine assembly inclined with the horizontal plane by a predefined power angle, a propeller-shaft configured in four pieces and positioned within a top flange and a bottom flange of the frame rails substantially parallel to them, a rear axle adapted to include a smaller crown wheel casing and configured to drive the low-floor vehicle, wherein, the configuration of the engine assembly, the gearbox assembly, the propeller-shaft, and the rear axle in combination enables to achieve sufficient ground clearance and higher low floor area on saloon of the vehicle. A hub reduction type rear axle with the smaller crown wheel casing is provided to avoid transverse step in the gangway of the low floor vehicle.

In another embodiment, the engine assembly is placed in an offset location with respect to vehicle centre line for providing an increased space for gangway, which enables the passengers to enter from left front entry. The left front entry is placed ahead of the front wheel.

In another embodiment, the mounting bracket unit further includes a pair of unsymmetrical rear mounting brackets directly mounted on the vertical sides of the frame rails, and a pair of symmetrical front mounting brackets mounted on a first cross member, the first cross member attached to the frame rails by a pair of end gussets, wherein, an engine mounting surface is raised above the top flange with the mounting bracket unit in order to achieve required approach angle.

In another embodiment, the propeller-shaft further includes a first propeller-shaft inclined at a steep angle and mounted on top of a second cross member, a second propeller-shaft and a third propeller-shaft inclined at low angle and routed below third, fourth and fifth cross members, and a fourth propeller-shaft positioned substantially parallel to the horizontal axis and inclined with the vertical axis.
In another embodiment, the engine assembly is mounted ahead of a front axle. Further, the front axle includes a double drop type front axle.

In yet another embodiment, the gearbox assembly along with the engine assembly is inclined with the horizontal plane by a power angle of four degrees (4°).

It is to be understood that both the foregoing general description and the following detailed description of the present embodiments of the invention are intended to provide an overview or framework for understanding the nature and character of the invention as it is claimed. The accompanying drawings are included to provide a further understanding of the invention and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments of the invention and together with the description serve to explain the principles and operation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and other advantages of the invention will be better understood and will become more apparent by referring to the exemplary embodiments of the invention, as illustrated in the accompanying drawings, wherein

FIG. 1 illustrates an isometric view of position of mounting brackets on a pair of frame rails for mounting an engine in a low floor front engine bus according to one embodiment of the present invention;

FIG. 2 illustrates an isometric view of mounting brackets for mounting the engine in a low floor front engine bus according to one embodiment of the present invention;

FIG. 3 illustrates an isometric view of position of an engine assembly mounted on a pair of frame rails in a low floor front engine bus according to one embodiment of the present invention;

FIG. 4a illustrates top view of floor layout with conventional engine packaging without offset.

FIG. 4b illustrates top view of floor layout of engine packaging with offset according to one embodiment of
the present invention;

FIG. 4c illustrates a cross sectional view at the centerline of the front axle according to one embodiment of the present invention;

FIG. 5 illustrates a top view of position of an engine assembly mounted on a pair of frame rails with offset in a low floor front engine bus according to one embodiment of the present invention;

FIG. 6 illustrates top view of overall engine and gearbox assembly with respect to a pair of frame rails in a low floor front engine bus according to one embodiment of the present invention;

FIG. 7 illustrates a top view of a drive shaft layout showing packaging of drivetrain components in a low floor front engine bus according to one embodiment of the present invention;

FIG. 8 illustrates a side view of inclined installation of engine and gearbox assembly in a low floor front engine bus according to one embodiment of the present invention;

FIG. 9 illustrates a side view of engine and gearbox assembly installation with respect to front axle in a low floor front engine bus according to one embodiment of the present invention; and

FIG. 10 illustrates a side view of a floor along with first propeller shaft installation according to one embodiment of the present invention.

DEATAILED DESCRIPTION OF THE INVENTION

Reference will now be made to the exemplary embodiments of the invention, as illustrated in the accompanying drawings. Where ever possible same numerals will be used to refer to the same or like parts.

Disclosed herein is an improved design for mounting of an engine assembly and packaging of drivetrain in a low floor front engine vehicle such as a bus. The engine may be mounted on an engine mounting assembly on a pair of frame rails. Such engine mounting assembly may include plurality of mounting brackets. FIG. 1 illustrates an isometric view of such an engine mounting assembly 100 according to one embodiment of the present invention. The engine mounting assembly 100 includes a pair of frame rails 102 and 104, two rear engine mounting brackets 106 and 108, a cross member 110, a pair of front engine mounting brackets 112, and an end gussets 114. In order to raise the height of engine of such low floor bus, the mounting brackets are attached at higher position of the frame rails 102, 104.

The cross member 110 connects the left frame rail 102 and the right frame rail 104 for providing support to the engine assembly at the front.

The front mounting brackets 112 are mounted on the cross member 110. The front mounting brackets 112 are structurally smaller compared to two rear engine mounting brackets 106 and 108. This is because the front mounting brackets 112 take only one fourth of the total engine and gearbox assembly. The remaining three fourth of the weight is supported by the rear mounting brackets 106 and 108. The left and right rear mounting brackets 106 and 108 are directly attached with the left and right frame rails 102, and 104 respectively.

In conventional vehicle mostly the engine is mounted in line with the centerline of the vehicle. In such cases the engine is packaged in between the side of frame rails. Therefore, depending on locations of the mounting hole in the bracket the rear and front mounting brackets are symmetrical. However, in the present embodiment the engine is mounted in an offset location with respect to the centerline of the vehicle. In the offset position of the engine, the mounting points in the engine goes away from the left frame rail 102 and it is closer to right frame rail 104. In order to accommodate the offset, the rear mounting brackets 106, and 108 are designed in unsymmetrical manner.

FIG. 2 illustrates an isometric view of mounting brackets for mounting the engine in a low floor front engine bus according to one embodiment of the present invention. The left rear mounting bracket 106 is attached to the inner surface of the left frame rail 102. However the right rear mounting bracket 108 is attached on the outer side of the right frame rail 104.

The left rear mounting bracket 106 is designed in a manner that it is attached to the inner side of the web portion 118 of the left frame rail 102 and extends towards right frame rail 104. It has two surfaces extending towards right hand side till the end of the frame flange 116 and then extends upward and ends in a flat portion for the seating of the mounts. In this way the left rear mounting bracket 106 is inside the frame width and the right rear mounting bracket 108 is attached to the outer side of the frame width.
The right rear mounting bracket 108 includes a vertical C channel abutting on the outer surface of the left frame rail 102 and on top of it is another inverted C channel placed horizontally over it. The horizontal C channel forms a flat portion for the engine mounting.

As described above, in the front two mounting brackets 112 are mounted on the cross member 110 connecting left frame rail 102 and right frame rail 104. The cross member 110 includes a C channel beam which is welded with two closing C channel as the end gussets 114 abutting with the inner web portion 118 of frame rails 102 and 104. The C channel centre beam 110 has a U profile including clearance at the centre. This is to match clearance with the damper pulley of the engine. The front mounting brackets 112 are a simple L profiled plate and supported by two stiffeners 202.

In the front, the offset is accommodated by shift in the mounting location of the front mounting brackets 112 on the cross member 110. Thus the front engine mounting bracket 112 remains symmetrical unlike the rear engine mounting brackets 106 and 108.

FIG. 3 illustrates an isometric view of position of an engine assembly 304 mounted on the pair of frame rails 102, 104 in a low floor front engine bus according to one embodiment of the present invention. As the engine 304 is to be packaged for a front engine low floor bus, enough clearance is to be maintained between the engine components and ground. In order to have enough ground clearance, the whole engine (304) and gearbox assemblies has been raised well above the frame rail top flange 120 level. The engine assembly 304 is mounted on the mounting brackets by means of leg portions 302 of the engine 304. Normally for the buses with high floor level with high frame height, the engine will be positioned in such a way that at least one third of its height will be below the frame bottom flange level 116.

Because of the low floor / frame height, the engine 304 is mounted at a higher level than the conventional mounting height. It is mounted at a high position in such a way that no part of the engine 304 is below the bottom flange of the framel 16 rails. This results in higher position of the engine mounting brackets as well. In conventional vehicle where the frame rail is at a higher level, the engine mounting bracket will be mounted between the height the frame side rail, i.e. between the top 120 and bottom flange 116.

But in this case, all the four mounting brackets 106, 108, and 112 are well above the top flange 120 of the frame side rail. The mounting brackets 106, 108, and 112 are designed in such a way that they are mounted on the web portion 118 of the frame side rails 102 and 104 but the engine mount seating flat portion is projecting well above the frame rail top flange 120.

FIG. 4 schematically illustrates floor layout of the engine packaging of a low floor front engine bus with offset compared to floor layout of conventional engine packaging according to one embodiment of the present invention. The chassis for this front engine bus is designed to have door 406 options in all the sections i.e. ahead of front axle, wheel base location and in ROH. So in order to have the door ahead of front axle with engine 304 packaged in the front overhang with low floor condition, the required gangway 408 for the movement of the passengers will not be available. The required space for gangway is also necessary to meet the legal requirements. FIG. 4a shows the floor layout of the buses with the conventional engine packaging in centerline with the vehicle and the proposed engine packaging which will be offset from the centerline of the vehicle is illustrated in FIG. 4b.

The main intent is to create enough space between the engine tunnel 402 and the wheel hump 404 portion. In order to achieve that, the engine 304 is positioned well ahead of the front axle wheel ends and also it is offset towards the right hand side of the vehicle.

Apart from the engine and gearbox assembly packaging, integration of the front axle 412 also plays a major role in the low floor area without any need of transverse step in the saloon. For this purpose, double drop (410) front axle 412 is used. In this type of axle the distance 410 between the wheel centerline and the beam top surface is almost twice that of the ordinary single drop axle. This allows enough space between the frame bottom and the axle beam, which is necessary to enable the axle travel during bumps. Also the wider spring track on a double drop axle beam helps in packaging of the suspension components so that none of the suspension components project above the frame top flange thereby avoiding the necessity of transverse steps in the gangway.

FIG. 5 illustrates a top view of position of the engine assembly 304 mounted on the pair of frame rails 102, 104 with offset in a low floor front engine bus according to one embodiment of the present invention. It also shows the structure of the engine mounting bracket 106, 108, 112 and their mounting arrangement. Normally when the engine's centerline is in line with the centre line of the vehicle, the drive output shaft from the gearbox and hence the propeller shaft will also be in line with the vehicle centre line. Now in this case, as the engine is offset, the gearbox output shaft and the three pieces of the four propeller shafts will be in offset condition. The distance through which the engine is offset towards the right hand side is also controlled by the fact that enough space is required for driver compartment beside the engine 304.

FIG. 6 illustrates top view of overall engine and gearbox assembly with respect to the pair of frame rails 102, 104 in a low floor front engine bus according to one embodiment of the present invention. FIG. 6 shows engine assembly 304 and gearbox assembly 602, front axle 412, and driveshaft 606 with respect to frame rails102, 104.

From the FIG. 6 it can be observed that the space between the engine tunnel 402 and the wheel hump 404 (explained in FIG. 4) is dependent on the packaging of engine 304 with respect to the front axle 412 and tires 604. So the whole engine 304 with gearbox assembly 602 is moved towards the front of the vehicle and towards right hand side by a certain distance in order to have door 406 and gangway 408 on the left hand side. In another embodiment, this will be done vice versa if door 406 and gangway 408 is needed on the right hand side in a left hand drive vehicle.

Further another aspect of the present invention is to package the entire drivetrain components in the front engine bus without compromising on the low floor area as well as achieving the required agility in terms of approach angle 902 (shown in FIG. 9) and ramp over angles. In order to achieve that, most of the drivetrain components are either modified or integrated in such a way that it is completely different from conventional system.

FIG. 7 illustrates a top view of a drive shaft layout showing packaging of drivetrain components in a low floor front engine bus according to one embodiment of the present invention. The main components of a drivetrain in a bus include engine 304, gearbox 602, drive shaft 606, and the rear axle 712.

The engine 304 and gearbox assembly 602 is placed well ahead of the front axle 412. Due to this the front overhang of the vehicle is on a higher side. The power angle 806, in the present embodiment, is kept at 4 deg as shown in FIG. 8. The power angle is the inclination 802 of the engine 304 and gear box assembly 602 with respect to the horizontal plane 804. As a result of this scheme, the engine is with a front well sump in order to have maximum ground clearance when compared with rear well sump as the power angle is high.

The high power angle 806 is also required to lay the propeller shaft 606 below the floor 1002 as shown in FIG. 10. Otherwise it may affect the low floor area on the saloon.

The drive shaft or propeller shaft 606 is a four piece member which runs almost parallel to the frame rails 102, 104 and lies within the top 120 and bottom 116 flange of the side frame rails 102, 104. The first propeller shaft 702 comes down at a steep angle and it is mounted on top of a cross member 710. The second 704 and third propeller shafts 706 are at low angles and it is routed below the cross member 710.

The fourth propeller shaft 708 is almost parallel to the ground but it is inclined with the vertical axis.
The rear axle 712 used in this arrangement is a hub reduction or double reduction axle with smaller crown wheel casing. This helps in maintaining the floor height at a lower level above the rear axle 712 with enough clearance for the rear axle 712 in bump condition. Rear axle with the smaller crown wheel casing is also a must to avoid transverse step in the gangway, which are common in rear engine buses.
In the present invention there are no auxiliary gearboxes or any transfer case in between the gearbox 602 and propeller shaft 606.

It is to be understood by a person of ordinary skill in the art that various modifications and variations may be made without departing from the scope and spirit of the present invention. Therefore, it is intended that the present invention covers such modifications and variations provided they come within the ambit of the appended claims and their equivalents.

We claim:

1. A low-floor vehicle comprising:

an engine assembly disposed at the front on a pair of parallelly spaced frame rails at a significantly higher position with a mounting bracket unit;

a gearbox assembly along with the engine assembly inclined with the horizontal plane by a predefined power angle;

a propeller-shaft configured in four pieces and positioned within a top flange and a bottom flange of the frame rails substantially parallel thereto; and

a rear axle adapted to include a smaller crown wheel casing and configured to drive the low-floor vehicle,

wherein, the configuration of the engine assembly, the gearbox assembly, the propeller-shaft, and the rear axle in combination enables to achieve sufficient ground clearanoe and higher low floor area on the saloon, without any transverse steps in the gangway.

2. The low-floor vehicle according to claim 1, wherein the engine assembly is placed in an offset location with respect to vehicle centre line for providing an increased space for gangway at left front entry.

3. The low-floor vehicle according to claim 1, wherein the mounting bracket unit further comprises:

a pair of unsymmetrical rear mounting brackets directly mounted on the vertical sides of the frame rails; and

a pair of symmetrical front mounting brackets mounted on a first cross member, the cross member attached to the frame rails by a pair of end gussets,

wherein, an engine mounting surface is raised above the top flange with the mounting bracket unit in order to achieve required approach angle and ground clearance.

4. The low-floor vehicle according to claim 1, wherein the propeller-shaft further comprising:

a first propeller-shaft inclined at a steep angle and mounted on top of a second cross member;

a second propeller-shaft and a third propeller-shaft inclined at low angle and routed below third, fourth and fifth cross members; and

a fourth propeller-shaft positioned substantially parallel to the horizontal axis and inclined with the vertical axis.

5. The low-floor vehicle according to claim 1, wherein the rear axle comprises a hub reduction type rear axle.

6. The low-floor vehicle according to claim 1, wherein the engine assembly is mounted ahead of a front axle.

7. The low-floor vehicle according to claim 6, wherein the front axle comprises a double drop type front axle.

8. The low-floor vehicle according to claim 1, wherein the gearbox assembly along with the engine assembly are inclined with the horizontal plane at a power angle of four degrees (4°).