GB2455097A

GB2455097A - A transmission unit for use in ancillary devices of an engine

Info

Publication number: GB2455097A
Application number: GB0723268A
Authority: GB
Inventors: John Westwood Moore; Didier Brun
Original assignee: Antonov Automotive Technologies BV; Antonov Automotive Europe BV
Current assignee: Antonov Automotive Technologies BV; Antonov Automotive Europe BV
Priority date: 2007-11-27
Filing date: 2007-11-27
Publication date: 2009-06-03
Anticipated expiration: 2027-11-27
Also published as: GB0723268D0; WO2009068882A2; WO2009068882A3; GB2455097B

Abstract

A transmission unit for use in ancillary devices of an engine comprises an input pulley 108 mounted on an input shaft 49, an output pulley 100 mounted on an output shaft 4, an epicyclic arrangement gears 51, 58, 54, a brake assembly 60,70,71,78 operable to brake a sun gear 51 of the epicyclic arrangement and a one-way clutch 53 which acts between the input shaft 49 and the output shaft 4 to allow relative rotation in only one direction. The brake assembly 60,70,71,78 comprises a plurality of flyweights 60 which when rotating apply a force acting to disengage the brake and a biasing spring 78 that applies a force acting to engage the brake. When torque is reacted by the sun gear 51 the reacted torque results in an axial force which acts to engage the brake. For a first range of low rotational speeds of the input shaft the output shaft 4 rotates at a rotational speed greater than the input shaft 49 and for a second range of high rotational speeds the one-way clutch locks the output shaft 4 to the input shaft 49 to rotate therewith. The ancillary device may be a supercharger or a turbocharger or a pump etc.

Description

A TRANSMISSION UNIT

The present invention relates to a transmission unit suitable for use in driving ancillary devices of an internal combustion engine, such as an alternator, a supercharger, power steering pump, a water pump and an oil pump.

It is typical for internal combustion engines to be provided with a pulley mounted to the crankshaft which rotates at a crankshaft speed. This pulley is then connected by a belt or by belts to various devices driven by the internal combustion engine which are ancillary to the internal combustion engine itself (or, in certain applications, ancillary to the vehicle in which the internal combustion engine is provided). To date, the ratio of the speed of rotation of the crankshaft to the speed of rotation of the ancillary devices is typically fixed for all engine speeds. However, this is disadvantageous. For instance, it is advantageous for a supercharger at low engine speeds to run at a speed which is a first higher multiple of crankshaft speed whilst at higher engine speeds the supercharger runs at second lower multiple of crankshaft speed. Traditional drive arrangements for superchargers do not permit this. The same logic also applies to the operation of alternators, power-assisted steering pumps, air-conditioning pumps etc. The present invention provides a transmission unit comprising: an input pulley mounted on an input shaft for rotation therewith; an output pulley mounted on an output shaft for rotation therewith; an epicyclic arrangement of a helical sun gear, helical planet gears and a helical annulus gear, the helical planet gears being supported by a planet carrier; brake assembly operable to brake the sun gear; and a one-way clutch which acts between the input shaft and the output shaft to allow relative rotation therebetween in only one direction; wherein: the planet carrier is attached to the input shaft for rotation therewith; the annulus gear is attached to the output shaft for rotation therewith; the brake assembly comprises a plurality of flyweights driven to rotate by the input shaft which when rotating apply a force acting to disengage the brake and a biasing spring which applies a force acting to engage the brake; the sun gear is mounted to slide axially within the epicyclic arrangement and is connected to the braking assembly in such a way that when torque is reacted by the sun gear then the reacted torque results in an axial force on the sun gear which is relayed to the braking assembly and acts to engage the brake and when the flyweights are driven to rotate then the force applied by the flyweights gives rise to an axial force on the sun gear opposed to the axial force resulting from the reacted torque; in a first range of low rotational speeds of the input shaft the spring force and the axial force resulting from the reacted torque together exceed the force applied by the flyweights and together engage the brake and thereby prevent the sun gear from rotating; in a second range of high rotational speeds of the input shaft, greater than the rotational speeds of the first range, the force applied by the flyweights exceeds the sum of the spring force and the axial force resulting from the reacted torque and disengages the brake and thereby allow the sun gear to rotate; for the first range of low rotational speeds rotation is relayed from the input shaft via the planet carrier and the planet gears carried thereby to the output shaft and the output shaft rotates at a rotational speed greater than the rotational speed of the input shaft; and for the second range of high rotational speeds the sun gear is free to rotate and the one-way clutch locks the output shaft to the input shaft to rotate therewith.

A preferred embodiment of the present invention will now be described with reference to the accompanying drawings in which: Figure 1 is a cross-section through a two-speed transmission according to the present invention; Figure 2 is a representation of a meshing sun gear and planet gear of the transmission unit of Figure 1; Figure 3 is a schematic representation of the Figure 1 transmission unit operating with a first transmission ratio; Figure 4 is a schematic representation of the Figure 1 transmission unit, operating with a second transmission ratio; and Figure 5 is a schematic drawing showing the front of an engine with the two- speed transmission unit of Figure 1 and also auxiliary devices driven by the transmission unit.

In Figure 1. a two-speed transmission unit can be seen.

It comprises an input pulley 108 which receives drive from an internal combustion engine via a belt, as will be described later. The input pulley 108 is mounted on an input shaft 49 for rotation therewith. The input shaft 49 is secured in a housing which comprises a central housing section 2, an end cover 80 and an end cover 95. The input shaft 49 is mounted for rotation in a bearing 90 and by needle bearings arranged in a cage, shown as 104, which act between the input shaft 49 and an output shaft 4. The output shaft 4 is coaxial with the input shaft 49 and is formed as a sleeve having a central aperture through which the input shaft 49 passes. The output shaft 4 is itself mounted in the housing 2, 80, 95 by a bearing 96 and by a bearing 7. An output pulley 100 is mounted on the output shaft 4 for rotation with the output shaft 4.

A one-way sprag clutch 53 acts between the input shaft 49 and the outer shaft 4, the one-way sprag clutch allowing the output shaft 4 to rotate quicker than the input shaft 49, but preventing the output shaft 4 from rotating slower than the input shaft 49 by locking them to rotate together (i.e. the one-way clutch permits relative rotation in only one sense).

Drive from the input pulley 108 is transmitted via the input shaft 49 and via a planet gear carrier 50 to planet gears such as 58. The planet gear 58 is rotatably mounted on the planet carrier 50 by a needle roller bearing 57 interposed between the planet gear 58 and a satellite axle 55. A steel washer 56 holds the planet gear 58 in place on -5-.

the axle 55. A low friction plate 54 is provided to act between the washer 56 and a planet carrier cover 51.

The planet gear 58 meshes with a sun gear 64 which is mounted coaxially around the input shaft 49, separated from the input shaft 49 by a plane bearing 66. The planet gear 58 also meshes with an annulus gear 5 which is mounted on the output shaft 4 for rotation therewith. A snap ring 6 holds the annulus gear 5 in place on the output shaft 4.

The sun gear 64 is attached to a friction disk carrier which rotates with the sun gear. The friction disk carrier 65 carries a plurality of friction disks 70 which are held in splined engagement with the carrier 65 by splines on the exterior of the carrier 65. The splined engagement allows the friction disks 70 to move axially along the carrier 65, but prevents the friction disks 70 rotating relative to the carrier 65 and hence rotating relative to the sun gear 64.

A pusher plate 61 is provided to act between the planet carrier cover 51 and the friction disk carrier 65 (via a thrust washer 62 and an adjusting washer 72)and the operation of this will be described later.

A plurality of steel disks 69, 71 sandwich the friction disks 70. They are slidable on splines provided on an internal surface of the housing 2 and are slidable axially along the housing while being constrained from rotation relative to the housing. The friction disks 80 and steel disks 69,71 are kept in place by a retaining ring 68.

The friction disks 70 and the steel disks 69, 71 act to provide a braking assembly which can either brake rotation of the sun gear 51 to hold the sun gear 51 stationary or, alternatively, allow the sun gear 51 to rotate freely. In operation of the transmission unit the sun gear 51 is allowed to rotate freely when the input shaft 49 is rotated in a high rotational speed range and the sun gear 64 is braked and held stationary while the input shaft 49 is rotated in a low rotational speed range. How this is achieved will be explained later.

The components within the transmission unit are lubricated by action of components within the unit. A pump body 83 is illustrated alongside a pump rotor 84, a pump stator 82, and a pump cover 86 containing the previously-mentioned components. An 0-ring seal 87 acts between the pump cover 86 and the surrounding housing cover 80. The pump rotor 84 rotates with rotation of the shaft 49, the pump rotor being mounted on a pump sleeve 75 which in turn is mounted on the input shaft 49 for rotation with the input shaft. The pump rotor 84 acts with the pump stator 82 to pump lubricant around the transmission unit. Also in the unit there is an oil deflector ring 67 which rotates with the input shaft 49 and helps to circulate lubricant oil around the unit. A spacer washer 105 and an 0-ring seal 106 placed around the ends of the shafts 49 and 4 keep lubricant oil within the unit. An inner ring seal 109 and a lip seal 102 are also provided for this purpose. A further lip seal 98 also prevents the escape of lubricant oil around the output pulley 100.

The operation of the previously described brake assembly is controlled by a spring washer 78 which acts between the casing cover 80 and a pressure plate 42. The friction disks 70 and the steel disks 71 are sandwiched between the pressure plate 42 and the retaining ring 68.

An assembly comprising the pressure plate 42, the washers 62, adjusting washer 72, the friction disk carrier and the sun gear 51 is slidable axially along the input shaft 49.

As seen in Figure 2, the sun gear 64 is a helical gear, meshing with helical planet gears of the planet carrier, such as the planet 58. As torque is transmitted between the sun gear 64 and the planet gears (e.g.58) then the sun gear 51 is slid to the right, as shown in the figures 3 and 4 where the arrows 300 show the action of the force, so that the bearing 61 is pushed up against the pusher plate 61, with the force then reacted by the planet carrier cover 51.

The force acts in the same direction as the spring force, which is indicated by arrows 301. These forces, at low rotational speeds of the input shaft 49, acting via the pressure plate 42 together push the friction plates 70 into frictional engagement with the friction plates 69,71 and this brakes the sun gear 64 and holds the sun gear 64 stationary. The planet gears rotate around the stationary sun gear 64 and transmit motion from the input shaft 49 to the output shaft 4 via the annulus gear 5. The output shaft 4 is thus in geared connection with the input shaft 49 and rotates at a higher rotational speed than the input shaft 49. This is permitted by the one-way clutch 53.

At higher speeds, free ends of flyweights such as 60 are forced radially outwardly by the rotation of the planet carrier 50. This causes the L-shaped flyweights such as 60 to rotate about their elbows. This in turn causes the flyweights 60 to apply pressure on the pusher plate 61 which then moves axially to the left (as shown in the figures) the assembly comprising the sun gear 64, the bearing 61, the spacer 72 and the pressure plate 42. In other words, the separation between the planet carrier cover 51 and the pressure plate 62 is increased. The assembly is moved against the biasing action of the spring 78 and the force applied by the flyweights indicated by arrows 302. This movement releases the brake and therefore allows the sun gear 64 to rotate freely. The one-way clutch 53 then locks the output shaft 4 to rotate with the input shaft 49. With the sun gear 64 rotating freely, rio torque is reacted by the sun gear 64 and thus no axial loading on the sun gear 64 is occasioned by the interaction of the gears.

The balance of forces between, on the one hand, the forces applied by the flyweights such as 60, on the other hand, and the forces applied by the spring 78 and by the axial loading on the sun gear 64, sets the point at which the brake is engaged and disengaged. The operation of the brake enables the transmission unit to provide two different gear ratios and enables the unit to switch between these two different gear ratios without the need for any external control and without the need for supply of hydraulic fluid or for electronics to control the switchover. The switchover happens purely mechanically. On a shift from braked to non-braked condition, the torque reacted by the sun gear 64 decreases as the braking force decreases and this speeds the transmission ratio change since the axial force on sun gear 64 decreases with decrease in reacted torque. On a shift from unbraked to braked condition, the braking of the sun gear increases the axial force on the sun gear 64 (indicated by arrows 300) which acts against the flyweight generated forces 302 in addition to spring force 301 to fully brake the sun gear 64 quickly. In both cases, the duration of frictional slipping of the plates is limited.

The two-speed transmission unit 1 is shown in use in Figure 5. Figure 5 shows an internal combustion engine having a two-speed transmission unit 201 of the type described above. This has an input pulley 202 and an output pulley 203. The input pulley 202 is driven to rotate by a belt 204 which is driven by a pulley 205 mounted on and rotating with a crankshaft of the engine 200. The output pulley 203 drives a belt 206. The belt 206 in turn drives a pulley 207 which is connected to a supercharger which pressurises intake air of the engine 200. The belt 206 is also arranged to drive a pulley 208 which is connected to an alternator of the engine. At low engine speeds the transmission unit 201 operates (as described above) so that the output pulley 203 rotates at a rotational speed higher to the input pulley 202 and therefore the supercharger attached to pulley 207 and the alternator attached to pulley 208 are advantageously driven at rotational speeds in excess of crankshaft rotational speeds, with the ratio of rotational speed of pulley 207 to speed of rotation of pulley 205 having a first value and the ratio of the rotational speed of pulley 208 to the rotational speed of pulley 205 having a second value (which may be the same as -10 -the first value). Then at higher rotational speeds of the pulley 205 the transmission unit 201 changes the transmission ratio so that the output pulley 203 has the same rotational speed as the input pulley 202. Then the ratio of speed of rotation of pulley 207 to pulley 205 is a third ratio lower than the first ratio, e.g. the pulley 207 and the pulley 205 could be rotated with the same rotational speed. Also, the ratio of the rotational speed of pulley 208 to the rotational speed of pulley 205 is a fourth ratio different to the second ratio mentioned previously, e.g. the pulley 208 could rotate at the same rotational speed as the pulley 205. Operation of the ancillaries is thereby improved with the supercharger giving a greater boost at low engine speeds than it would otherwise and with the alternator generating more electrical power at lower engine speeds than it would otherwise. Smaller-sized alternators and superchargers can be used than in comparable engines with fixed transmission ratios.

Although the two-speed transmission unit has been described above in its use in connection with an internal combustion engine and in use driving engine ancillaries, it is not limited to such use and could be used in any application where a two-speed drive is needed with the speed change occurring mechanically without the need for supply of hydraulic pressure to the transmission unit or electrical/electronic control. Nevertheless, the unit is of particular advantage in its use with an internal combustion engine since a plurality of different ancillaries of the engine can be driven from a single transmission unit which requires no connection to the hydraulic circuits of the engine, nor any electronic or electrical control by the -11 -engine management system. The transmission unit can easily be fitted with existing engine designs without requiring substantial modifications of the existing engine designs.

Whilst above the input pulley 108 and output pulley 100 are both provided side-by-side on one side of the transmission unit, the input pulley could easily be relocated to the opposite side of the transmission unit, which may be of use in certain applications. In such a case the output shaft need not overlie the input shaft and the two shafts could be arranged end-to-end with a one-way clutch arranged between facing ends of the shafts.

Claims

-12 - CLAIMS

1. A transmission unit comprising: an input pulley mounted on an input shaft for rotation therewith; an output pulley mounted on an output shaft for rotation therewith; an epicyclic arrangement of a helical sun gear, helical planet gears and a helical annulus gear, the helical planet gears being supported by a planet carrier; a brake assembly operable to brake the sun gear; and a one-way clutch which acts between the input shaft and the output shaft to allow relative rotation therebetween in only one direction; wherein: the planet carrier is attached to the input shaft for rotation therewith; the annulus gear is attached to the output shaft for rotation therewith; the brake assembly comprises a plurality of flyweights driven to rotate by the input shaft which when rotating apply a force acting to disengage the brake and a biasing spring which applies a force acting to engage the brake; the sun gear is mounted to slide axially within the epicyclic arrangement and is connected to the braking assembly in such a way that when torque is reacted by the sun gear then the reacted torque results in an axial force on the sun gear which is relayed to the braking assembly and acts to engage the brake and when the flyweights are driven to rotate then the force applied by the flyweights gives rise to an axial force on the sun gear opposed to the axial force resulting from the reacted torque; in a first range of low rotational speeds of the input shaft the spring force and the axial force resulting from -13 -the reacted torque together exceed the force applied by the flyweights and together engage the brake and thereby prevent the sun gear from rotating; in a second range of high rotational speeds of the input shaft, greater than the rotational speeds of the first range, the force applied by the flyweights exceeds the sum of the spring force and the axial force resulting from the reacted torque and disengages the brake and thereby allow the sun gear to rotate; for the first range of low rotational speeds rotation is relayed from the input shaft via the planet carrier and the planet gears carried thereby to the output shaft and the output shaft rotates at a rotational speed greater than the rotational speed of the input shaft; and for the second range of high rotational speeds the sun gear is free to rotate and the one-way clutch locks the output shaft to the input shaft to rotate therewith.

2. A transmission unit as claimed in claim 1, wherein: the output shaft and the input shaft are co-axial and the output shaft is a sleeve and the input shaft extends through the output shaft; the sun gear is co-axial with the input shaft and is mounted external to the input shaft for free rotation relative to the input shaft and for axial movement along the input shaft; the sun gear is attached to a friction disk carrier which has a splined portion on which are mounted one or more sun gear friction disk(s) which can slide along the splines and which are prevented from rotating relative to the friction disk carrier by the spines, the friction disk carrier sliding axially with and rotating with the sun gear; -14 -one or more non-rotating friction disk(s) are mounted on a splined static support and can slide along the splined static support and are prevented from rotation by the splines; and the sun gear friction disk(s) and the non-rotation friction disk(s) are forced into frictional engagement with each other by the force applied by the biasing spring and the force resulting from the reacted torque.

3. A transmission unit as claimed in claim 2 wherein: the flyweights are each L-shaped and pivot about their elbows; and the flyweights are located between the planet carrier and a push plate via which the flyweights apply force on the friction disk carrier, the flyweights acting to increase separation between the planet carrier and the friction disk carrier as their rotational speed increases.

4. A transmission unit as claimed in claim 3 wherein: the'biasing spring acts on a pressure plate via which the spring applies pressure to the sun gear friction disk(s) and the non-rotating friction disk(s) to force them together; and the pressure plate, the friction disk carrier and the sun gear together form an assembly which slides axially under the action of the forces applied thereto, namely the spring force, the axial force resulting from reacted torque and the force applied by the rotating flyweights.

5. A transmission unit as claimed in any one of the preceding claims wherein the input pulley and the output pulley are located side-by-side on one side of the -15 -transmission unit, the input pulley having a first radius and the output pulley having a second larger radius.

6. An internal combustion engine having a crankshaft; a crankshaft pulley mounted on the crankshaft for rotation therewith; a transmission unit as claimed in any one of the preceding claims; an input belt connecting the crankshaft pulley to the input pulley of the transmission unit; an engine-driven ancillary having an ancillary pulley via which drive is relayed to the ancillary; and an output belt connecting the output pulley of the transmission unit to the ancillary pulley.

7. An internal combustion engine as claimed in claim 6 which comprises a plurality of engine-driven ancillaries, each of which has an ancillary pulley and wherein the output belt connects the output pulley of the transmission unit to all of the ancillary pulleys of the engine- driven ancillaries.

8. An internal combustion engine as claimed in claim 6 or claim 7 wherein the engine-driven ancillaries comprise one or more of: a supercharger; an alternator; an oil pump; a water pump; power-assisted steering pump and/or an air conditioning pump.

9. A transmission unit as hereinbefore described with reference to and as shown in the accompanying figures.

867563; AWP; CTF