GB2512435A

GB2512435A - Three Wheeler Drive Train

Info

Publication number: GB2512435A
Application number: GB1323020.6A
Authority: GB
Inventors: Mark Ashley Reeves; Matthew Welch
Original assignee: MORGAN MOTOR Co Ltd
Current assignee: MORGAN MOTOR Co Ltd
Priority date: 2012-12-27
Filing date: 2013-12-24
Publication date: 2014-10-01
Anticipated expiration: 2033-12-24
Also published as: GB201323020D0; GB2512435B; GB201223448D0

Abstract

A drive train for a rear wheel driven three wheel motor vehicle (100 see fig 1) comprises, a front mounted V-configuration engine 130, a gearbox (120 see fig 1) behind the engine 130 having an input connected to the crankshaft through a torque damper 300, and a driveshaft (140 see fig 1) connected to an output of the gearbox (120). The torque damper 300 comprises an inner member 320 having an outward facing surface, and a cup-like outer member which has an inward facing surface 315 defining a cavity, the inner member 320 being located partially within the cavity. Each member includes a plurality of pockets 330, 395 arranged as opposing pocket pairs, and a resilient barrel-like connector 400 is located in each pocket pair, deforming as torque is applied and restricting rotational movement of the outer member relative to the inner member 320. The invention copes with torque spikes which occur for instance with high output v twin engines.

Description

Rear Wheel Driven Three Wheel Vehicle This invention relates to rear wheel driven three wheel motorised vehicles.

S The concept of a three wheel vehicle is weD known. Many configurations are possibk but one well known configuration has two steered wheels at the front of the vehicle, spaced either side of the centre line of the vehicle, and a single driven rear wheel which is usually aligned on, or close to, the centre line. The engine is mounted at the front of the vehicle with space for a passenger cockpit between the engine and rear wheels.

Traditionally, internal combustion engines used to drive these vehicles relied on air cooling and mounting the engine at the front was a convenient way to ensure the engine was kept cooled. Mounting it at the very front ahead of the front wheels ensured that the weight distribution of the vehicle was favourable.

In recent times, most development of the vehides has been concerned with four wheel vehicles. Providing four wheels allows a larger cockpit to be provided, and increasing stability of the vehicle. Over time vehicles have become larger and more luxurious, the emphasis being on making the cockpit quieter at speed and increasing safety.

The applicant has appreciated that a modern interpretation of a traditional three wheeled vehicle would provide an exciting alternative to a four wheeled vehicle. With advances in engines, a larger more powerful engine could be used, and by using a lightweight chassis the weight saving benefit of having one less wheel could be exploited.

Accordingly the applicant has developed a new vehicle which makes use of modern components and which also includes some features that drivers have become accustomed to in conventional four svhee vehicles, This meant providing a more powerful engine, an ability to drive in both forward and reverse gears and a level of refinement and reliability that meets the expectation of the modern driver.

According to a first aspect the invention provides a drive train for a rear wheel driven three wheel motor vehicle comprises: an engine mounted at a front part of the vehicle, the engine having a crankshaft that is inline with the vehicle chassis and a pair of cylinders arranged in a V configuration, each cylinder containing a piston which is coupled to the crankshaft, a gearbox located behind the engine and having an input and an output, the input S being operatively connected to the crankshaft engine through a torque damper, and a driveshaft connected to the output of the gearbox and extending towards the rear of the chassis, characterised in that the torque damper comprises a first member having an axis and an outward facing surface, and a second member which has an axis and an inward facing surface defining a cavity, the axis of the second member being aligned with the axis of the first member so that the first member is located partially within the cavity with the outward facing surface facing the inward facing surface, the first and second members being supported so that they are free to rotate around the common axis, the first member and the second member each including a plurality of pockets defined by their respective outwards and inward facing surfaces which are arranged as opposing pocket pairs, and a resilient connector located in each pockets pair that restricts rotationa' movement of the outer member relative to the inner member about the common axis to tral1sfer drive between the first member and the second member, the connector deforming within the pocket as torque is applied across the damper The applicant has appreciated that high output v twin engines present a unique challenge when used in a three wheel vehicle. Such engines heretofore have only been used in motorbikes, where the engine is typically arranged in a transverse configuration and the output of the motor is connected directly to a gear wheel which drives a drivebelt coupled to the rear wheel, Having only two cylinders means that there are very high torque spikes during operation, which will be absorbed by the drive belt. However, if the motor is instead used in an inline configuration and connected directly to a gearbox the torque spikes will be passed to the gearbox. This will p'ace a huge strain on the components and may lead to failure. This is exacerbated where there is a large distance between the engine and the gearbox.

Providing a damper between the motor and gearbox helps reduce the strain by smoothing out the torque spikes.

The damper may comprise four pockets spaced equally around the first member and second members. The equal spacing helps ensure that the torque is transferred evenly from the inner to outer members. Each pocket may contain one roller.

S The second (outer) member may be fixed to the crankshaft and the first (inner) member fixed to the input of the gearbox. By fixed in this context we mean fastened together in such a way that the member cannot rotate relative to the part (crankshaft or gearbox) to which it is connected.

Each resilient connector may comprise a cylindrical roller, the axis of the cylinder being parallel to but offset from the common axis of the inner and outer members.

The rollers may comprise rubber barrels. The barrels may be cylindrical in cross section at any point along their length but are of smaller cross section towards the ends than at the centre, allowing them to self align in the pockets.

Each pocket may include a ramp portion whereby upon relative rotation of the first member and second members one side of the roller is squashed by the ramp in a controlled manner, the rate at which the damper is squashed and the properties of the damper providing a controlled absorption of energy.

The second member may comprise a hollow cylindrical cup with a base and a cylindrical side wall defining the inward facing surface and an axis of rotation passing through the base. The inward facing wall may be generally uniform in cross section along its length. The cylindrical side wall may be located concentrically around this axis. The cup preferably has four pockets spaced around the inner wall of the cup, formed by recesses in the wall where the radius is increased.

The first member may be located partially within the cup. It may comprise a top plate, preferably circular in outline, that may secured to a flywheel by a splined shaft which engages a splined hole which may be provided in the top plate.

The inner member may comprise a body defining a plurality, preferably four, outwardly extending ribs which depend from the top plate, a pocket being defined between adjacent pairs of these ribs, the ribs and pockets defining the outward facing surface. The first member has an axis of rotation that passes through the top plate and along a centre of the body, the four ribs projecting away from the axis. This axis may be aligned with the axis of the second member and the first member may be located so that the ribs are within the cup, with each pocket facing a corresponding pocket of the cup.

The pockets may be shaped so that upon relative rotation of the inner and outer mcmbcrs thc barrcls roll ovcr thc surfaccs of thc pockets. dcformation of thc barrels being mainly due to compressive forces acting on the barr&s orthogonal to the surface of the barrel. Because the barrels roll over the surfaces, shear forces are minimised and hence wear of thc barrels is minimised, To achieve the rolling motion the pockets may have a teardrop cross section that defines a ramp along which the barrel rolls.

The first member, second member and barrels may form a self contained torque dampcr.

The torque damper may include a guide pin or spindle which acts between the first member and second member to ensure they remain axially aligned. The pin may be secured to a cylindrical plate that fits into the bottom of the cup, the pin engaging an elongate hole in the first member which is aligned on the axis of the second member.

The drivetrain may include a clutch between the gearbox and the damper so that the input of the gearbox is not directly connected to the output of the damper. The clutch may be located in a bell housing.

The output of the damper may be connected to a flywheel.

The drivetrain may also include: a bevel gearbox connecting the driveshaft to an intermediate pufley. the axis of rotation of the pufley being orthogona' to the driveshaft.

a drive pulley connected to the rear wheel, and a drive belt connecting the intermediate pulley to the drive pulley.

The belt drive may engage a drive wheel secured to the rear wheel. Tension of the belt may be adjusted by movement of the rear wheel backwards and forwards relative to the chassis.

The engine may comprise a v-twin engine with a capacity of at least 2 litres. It may be of a design that does not include a balanced shaft, and may be arranged so as to produce torque pulses of up to 15001b/ft or up to 18001b/ft or more in use.

According to a second aspect the invention provides a three wheeled vehicle comprising a tubular frame forming a chassis to which the drivetrain of the first aspect of the invention is mounted and a cockpit provided within the tubular frame.

The vehicle may include a pair of front wheels spaced on respective sides of a centre line of the vehicle and a single rear wheel driven by the drivetrain. This may be located on the centre line of the vehicle.

The cockpit may be located at a position along the length of the vehicle between the engine and the rear wheels.

The engine may be mounted at the front of the vehicle ahead of the front wheels.

The rear wheel may be secured to a swing arm which is secured to the tubular chassis.

According to a third aspect the invention provides a torque damper for connecting the output of a high capacity high tune two stroke v-twin engine to an input shaft of a gearbox, the torque damper comprising: a first member having an axis and an outward facing surface, and a second member which has an axis and an inward facing surface defining a cavity, the axis of the second member being aligned with the axis of the first member so that the first member is located partially within the cavity with the outward facing surface facing the inward facing surface, the first and second members being supported so that they are free to rotate around the common axis, the first member and the second member each including a plurality of pockets defined by their respective outwards and inward facing surfaces which are arranged as opposing pocket pairs, and a resilient connector located in each pockets pair that restricts rotational movement of the outer member relative to the inner member about the common axis to transfer drive between the first member and the second r member, the connector deforniing within the pocket as torque is applied across the damper S The use of a torque damper of this kind in an automotive application to coupk a high torque transient internal combustion engine to a gearbox has not been considered before. Previously a traditional rotoflex type coupling has always been used. The applicant has appreciated for the first time that rotoflex couplings may not be suitable unless high'y specified and has proposed a novel, simple. torque damper for an automotive application.

Four resilient connectors may be provided, spaced evenly around an axis of the torque damper, Each one may be ocated in a complimentary pocket which is half formed by a recess in the outer member and half by a recess in the inner member.

Each resilient connector may comprise a rubber barrel. It may be a solid rubber barrel.

The torque damper may comprise four pockets spaced equally around the first and second members and arranged as pocket pairs. The equal spacing helps ensure that the torque is transferred evenly from tile first member to the second members without any inbalance of forces. Each pocket may contain one resilient connector.

Each resilient connector may comprise a cylindrical roller or barrel, the axis of the barr& being parafle to but offset from the common axis of the inner and outer members, the diameter of the cylinder being greater at the centre than at each end.

Each pocket may include a ramp portion whereby upon relative rotation of the first and second members one side of the barrel is squashed by the ramp in a controlled manner, the rate at which the damper is squashed and the properties of the damper providing a controfled absorption of energy.

There will now be described by way of example only one embodiment of the present invention with reference to and as illustrated in the accompanying drawings of which: Figure 1 is a cutaway view of a three wheeled vehicle without its bodywork and interior fitting. showing the chassis and drivetrain of a three wheeled vehicle; Figure 2 is a schematic of the drivetrain of the vehicle of Figure I with the engine, S damper, dutch and gearbox of the drivetrain of the vehide of Figure I; Figure 3 is an exploded view of the components connecting the motor to the gearbox including a torque damper; Figure 4 is a similar drawing of the bevel box of the drivetrain; and Figure 5(a) is a view from the end of the torque damper under no torsional load, and (b) the same damper under a high torsional toad, A three wheeled vehicle 100 is shown in Figure 1. The bodywork and interior fixings (such as seats, carpet and dashboard) have been removed to show the chassis and drivetrain more dearly.

The vehicle 100 comprises a tubular spaeeframe chassis 110. At the front of the chassis is a space into which a gearbox 120 and engine 130 are located. A driveshaft projecting from the back of the gearbox runs down the length of the chassis towards a bevel box 150 at the rear. As shown in Figure 2, the output of the bevel box is connected to an intermediate drivewheel 160. The engine 130 is located at the very front of the vehide. with the gearbox 120 located at the front of the passenger cell defined by the chassis.

On each side of the engine 130 a pair of double wishbone suspension arms 160 are secured to the spaceframe chassis 110 (only the passenger side arms are visible in Figure I). Each pair of arms ocates a wheel carrier 170 onto which a front wheel 190 (not shown in Figure I but visible in Figure 2) of the vehicle is attached. The tower wishbone 160 on each side is also connected to the chassis 110 by a spring and damper assembly 180 which controls movement of the wheel.

At the rear of the vehicle, attached to each side of the chassis 110, is a pair of swing arms 200, The free end of each swing arm 200 is connected through a spring and damper assembly 210 to a respective upper point on the rear of the tubular chassis.

The free end of each swing arm 200 is a'so provided with a rear facing drop out (not shown) into which a single rear wheel 220 is attached. Secured to the rear wheel (between the wheel 220 and one swing arm 200) is a drive pulley 230, and this is connected to the intermediate pulley 160 of the bevel box by a toothed drive beft 240.

The belt 240 is tensioned by adjusting the location of the wheel within the drop outs, and the swing axis of the swing arms 200 is arranged so that the tension on the belt remains constant as the wheel is deflected.

The drivetrain is shown schematically in Figure 2 of the drawings. The engine 130 comprises a highly tuned large capacity 2 litre V-twin engine, more typically associated with large motorbikes than with three wheel vehicles. It is arranged in an inline fashion, by which we mean that the output of the engine crankshaft from which drive is taken off is inline with the front-back axis of the chassis X-X', The two cylinders of the engine 130 turn a crankshaft and the output of the engine crankshaft is connected directly to a torque damper (not visible in Figure 2 but clearly shown in Figure 3) which is located in a bell housing 135 connecting the gearbox to the engine. The output of the damper is connected to a flywheel(also not shown) that is protected within the bell housing, and this in turn is connected through a clutch to the input shaft of the gearbox. In this example the gearbox is of the kind originally designed for a MXS motorcar built by Mazda Motorcars Ltd. The clutch is also protected within the bell housing. The bell housing is a bespoke casting which couples the gearbox housing to the crankcase of the engine. It holds the gearbox far enough away from the engine to accommodate a starter motor working from the flywheel conneted to the gearbox, which would otherwise foul the engine casing.

The gearbox output is connected to the driveshaft 140 which runs under the centre of the passenger cdl towards the bevel gearbox 150 at the rear of the vehide, This gearbox turns the output through 90 degrees to the intennediate pulley 160. Finally the drive pulley drives the rear wheel through the toothed belt.

The applicant has found that the use of a high capacity and high'y tuned V-twin engine generates very large instantaneous torque spike throughout its ignition cycle.

This is shown in Figure 4 of the drawings. The torque spikes can be as high as 18001b/ft. In use these spikes are so large that they could shear the output shaft of the motor or input of the gearbox if left undamped.

In a typical installation of a v-twin in a motorbike, the output of the crankshaft will S drive a belt rather than a gearbox and the belt will help absorb the spikes. Even so it is commonplace to use a form of complex rotoflex coupling to help absorb the spikcs, The applicant has found that such as coupling can be made to work with a direct drive to a gearbox but rcquires expensive modification and rcinforcement and may have a limited lifespan.

To this end. the three wheel vehicle shown in Figures 1 and 2 includes a novel torque damper as shown in Figures 3 and 5 of the drawings.

The torque damper 300 is located within the bell housing but is a self contained unit.

It comprises an outer member 310 that is fixed to the output shaft of the motor. This comprises a hollow cylindrical cup with a base and a cylindrical side wall that defines an inward facing surface 315 and an axis of rotation 340 passing through the base. The cylindrical wall is located concentrically around this axis and has a uniform cross section along its length. The cup 310 has four pockets 330 spaced around the inward facing surface, formed by recesses in the wall where the radius is increased.

Located with the outer member is an inner member 320 that is free to rotate within the cup. This has a circular top plate 360 that is secured to a flywheel 370 by a splined shaft 380 which engages a splined hole 390 in the top plate. The inner member includes a body defining four outwardly extending ribs 391 which depend from the top plate, a 395 pocket being defined between adjacent pairs of these ribs, The ribs/pockets define an outwardly facing surface. The inner member 320 has an axis of rotation that passes through the top plate and along a centre of the body, the four ribs projecting away from the axis 320, Notably this axis is aligned with the axis of rotation of the outer member 310. The inner member 320 is located so that the ribs are within the cup. with each pocket facing a corresponding pocket of the cup.

The torque damper also includes four elongate rubber barrels 400. Each barrel 400 is located partially within a pocket of the outer member and partially in a pocket of the inner member, the two pockets facing each other forming a pocket pair. The four barrels 400 therefore couple the inner member to the outer member, thereby coupling the output shaft of the motor 130 to the flywhed 370, The barrels 400 are cylindrical in cross section at any point along their length but are of smaller cross section towards the ends than at the centre, allowing them to self align in the pockets.

In use, the barrels 400 normally rest in an uncompressed state in the pocket pairs as shown in Figure 5(a). When a torque is generated by the motor at the crankshaft, the outer member 310 tries to twist relative to the inner member 320 around the shared axis. This is shown by the arrows in Figure 5(b). This re'ative motion disp'aces the outer pocket relative to the inner pocket of each pocket pair and this deforms the rubber barrels 400 so they are no longer cylindrical in cross section which absorbs some of the torque spikes from the motor. The deformation of the rubber barrels can be seen in Figure 5(b).

The input side of the gearbox carries a flywhee' which has a ring gear to which a starter motor is attached, This is held clear of the engine casing by the beD housing, which in use means a distance of about 300mm between the flywheel and the take off from the engine crankshaft, Without the torque damper the high torque spikes would tend to cause the shaft connecting the engine to the flywheel to snap. but with the torque damper this problem can be totafly ameliorated,

Claims

CLAIMS1 A drive train for a rear wheel driven three wheel motor vehicle comprises: an engine mounted at a front part of the s'ehide, the engine having a crankshaft that is inline with the vehicle chassis and a pair of cylinders arranged in a V configuration, each cylinder containing a piston which is coupled to the crankshaft, a gearbox located behind the engine and having an input and an output the input being operatively connected to the crankshaft of the engine through a torque damper, and a driveshaft connected to the output of the gearbox and extending towards the rear of the chassis, characterised in that the torque damper comprises a first member having an axis and an outward facing surface, and a second member which has an axis and an inward facing surface defining a cavity, the axis of the second member being aligned with the axis of the first member so that the first member is located partially within the cavity with the outward facing surface facing the inward facing surface, the first and second members being supported so that they are free to rotate around the common axis, the first member and the second member eac11 including a plurality of pockets defined by their respective outwards and inward facing surfaces which arc arranged as opposing pocket pairs, and a resilient connector located in each pockets pair that restricts rotationa' movement of the outer member relative to the inner member about the common axis to transfer drive between the first member and the second member, the connector deforming within the pocket as torque is applied across the damper.
2, A drivctrain according to claim 1 in which the damper comprises four pockets spaced equally around the first member and second members.
3. A drivetrain according to claim 1 or 2 in which the second member is fixed to the crankshaft and the second first member fixed to the input of the gearbox.
4, A drivetrain according to any one of claims 1 to 3 in which each resilient connector is generally cylindrical, the axis of the cylinder being parallel to but offset from the common axis of the first and second members.
5. A drivetrain according to claim 4 in which the resilient members comprise rubber barrels.
6. A drivetrain according to any preceding claim in which each pocket includes a ramp portion whereby upon relative rotation of the first member and second members one sidc of the resilicnt mcmbcr is squashed by the ramp in a controlled manner, thc rate at which the resilient member is squashed providing a controlled absorption of cncrgy.
7. A drivetrain according to any preceding claim in which the second member comprises a hollow cylindrical cup with a base and a cylindrical side wall defining the inward facing surface and an axis of rotation passing through the base.
8. A drivetrain according to claim 7 in which the inner member comprises a body defining a plurality, prcfcrably four, outwardly cxtcnding ribs which dcpcnd from the top plate, a pocket being defined between adjacent pairs of these ribs, the ribs and pockets defining the outward facing surface.
9. A drivetrain according to any preceding claim in which the output of the damper is connected to a flywheel.
10. A three wheeled vehicle comprising a tubular frame forming a chassis to which the drivetrain of any one of claims 1 to 9 is mounted and a cockpit provided within the tubular frame.
11. A torque damper for connecting the output of a high capacity high tune two stroke v-twin engine to an input shaft of a gearbox, the torque damper comprising: a first member having an axis and an outward facing surface, and a second member which has an axis and an inward facing surface defining a cavity, the axis of the second member being aligned with the axis of the first member so that the first member is located partially within the cavity with the outward facing surface facing the inward facing surface, the first and second members being supported so that they are free to rotate around the common axis, the first member and the second member each including a plurality of pockets defined by their respective outwards and inward facing surfaces which are arranged as opposing pocket pairs, and a resilicnt connector located in each pockets pair that restricts rotational movement of the outer member relative to the inner member about the common axis to transfer drive between the first member and the second r member, the connector deforming within the pocket as torque is applied across the damper 12, A torque damper according to claim 11 in which the damper comprises four pockets spaced equally around the first member and second members. The equal spacing helps ensure that the torque is transferred evenly from the inner to outer members, Each pocket may contain one rofler.13. A torque damper according to claim 11 or 12 in which the second member is fixed to the crankshaft and the second first member fixed to the input of the gearbox.14, A torque damper according to any one of claims 11 to 13 in which each resilient connector is generally cylindrical, the axis of the cylinder being parallel to but offset from the common axis of the first and second members.15. A torque damper according to claim 14 in which the resilient members comprise rubber barrels.16, A torque damper according to one of claims 11 to IS in which each pocket includes a ramp portion whereby upon relative rotation of the first member and second members one side of the resilient member is squashed by the ramp in a controlled manner, the rate at which the resilient member is squashed providing a controfled absorption of energy.17. A torque damper according to any one of claims 11 to 16 in which the second member comprises a hollow cylindrical cup with a base and a cylindrical side wall defining the inward facing surface and an axis of rotation passing through the base.18. A torque damper according to claim 17 in which the inner member comprises a body defining a plurality, preferably four. outwardly extending ribs which depend from the top plate, a pocket being defined between adjacent pairs of these ribs, the ribs and pockets defining the outward facing surface 19. A torque damper according to claim 18 in which four resilient connectors are provided, spaced evenly around an axis of the torque damper. each one ocated in a complimentary pocket which is half formed by a recess in the outer member and half by a recess in the inner member, 20, A drivetrain for a three wheeled vehicle substantially as described herein with reference to and as illustrated in the accompanying drawings.