EP0235230A1 - An oscillatory drive arrangement - Google Patents

Abstract

An oscillating drive arrangement includes a camshaft (12) rotatable about its axis. Two intermediate shafts (6) and (15) are carried by a support (7) so as to be able to rotate about their respective axes, parallel to the axis of rotation of the camshaft, each intermediate shaft carrying a cam ( 21, 22) in contact with a drive lever (10) fixed on the camshaft. A toothed wheel (2) drives a main gear (13) engaged with planetary gears (13a) and (13b) freely mounted on the intermediate shafts (6) and (15), the two planetary gears being engaged with a gear annular toothed inside (5b), the rotation of the main gear (13) causing the advance of the two planetary gears (13a) and (13b) around the annular gear (5b), driving with them the intermediate shafts (6) and (15) as well as the support (7). A second planetary gear (8, 18) is mounted so as to be able to rotate with each of the intermediate shafts (6) and (15), each of these planetary gears being engaged with a second annular gear toothed inside rotating under the effect of the movement of the intermediate shaft, so as to rotate the cams (8) and (18) and to apply pulses to the movement of the drive lever (10).

Description

Description of Invention

"An oscillatory drive arrangement"

THIS INVENTION relates to an oscillatory drive arrangement for use in situations where it is considered desirable or necessary for oscillatory motion to be introduced between a driving member and a driven member. The oscillatory drive arrangement of the present invention finds particular application, however, in the provision of variable valve timing in internal combustion engines.

According to the present invention, there is provided an oscillatory drive arrangement, comprising: a driven member which is rotatable about a first axis; a drive element which is rotatable about a second axis parallel to the first, which is drivingly engaged with the driven member at a location spaced on the first axis and is constrained to move along a circular path around the first axis while rotating about the second axis; a driving member which is rotatable to drive the element around its circular path and thus rotate the driven member; and means carried by the drive element eccentrically of the second axis for superimposing periodic oscillations on the rotary motion of the driven member as a result of the rotation of the drive element about its axis.

The advantages of being able to achieve variable valve timing in internal combustion engines are, of course, well known and the present invention enables variable valve timing to be achieved without the need for complete re-designing of existing camshafts and their associated equipment. In this context, the benefits of being able to impart regulated and fully variable oscillatory motion to a camshaft are considerable.

In order that the invention may be readily understood, an embodiment thereof will now be described, by way of example, with reference to the accompanying drawings, in which: Flgure 1 is on axial cros-sec tion through a first oscillatory camshaft drive arrangement embodying the Invention;

Figure 2 is a diogrammatic view of part of the assembly as seen from the left in Figure 1;

Figure 3 is an axial cross-sectional view of a second camshaft drive arrangement embodying the invention;

Figure 4 illustrates schematically a drive lever of the Figure 3 camshaft drive arrangement;

Figures 5 and 6 diagrammatically illustrate a third embodiment of camshaft drive arrangement in accordance with the invention;

Figures 7, 8 and 9 illustrate a fourth embodiment of oscillatory camshaft drive arrangement suitable for incorporation between two adjacent portions of a camshaft; and

Figure 10 illustrates a fifth embodiment of an oscillatory camshaft drive arrangement in accordance with the present invention, which arrangement is also suitable for incorporation in a divided camshaft.

Figures 1 and 2 illustrate a first embodiment of oscillatory drive arrangement which may be installed between a main camshaft drive sprocket wheel 2 and a main camshaft 12. This "nose" mounted device is capable of both varying the timing of the camshaft 12 relative to the sprocket wheel 2 and imposing oscillatory pulses on the rotary motion of the camshaft, the sequence and timing of the pulses being independent of the relative timing of the camshaft and sprocket wheel.

In the embodiment shown in Figures 1 and 2, the sprocket wheel 2 is fixed to, or forms part of, a carrier 3 which is fashioned so as to form both a backing plate for the sprocket 2 and also a concentric sleeve-shaft mounting for a sun gear 13. The assembly 2, 3, 13 is bearing located upon the pilot shaft 1 and extension shaft 20 and is also supported by bearings placed concentrically arount it and located in an outer casing 1 1 of the arrangement. AM solid black areas represent bearing devices and/or bearing surfaces.

The sun gear 13 is engaged with two planet gears 13a and 13b mounted in free-running communication upon the extended Jay-shafts 6 and

15. The two planet gears 13a and 13b are, in turn, engaged with an annular gear 5b, with the ratio of the sun gear to the annular gear being 2: 1. For example, if the sun gear has 20 teeth, then the annular gear has 40 teeth.

The annular gear 5b is fixed to, or part of, an annular carrier 5 which is also formed externally as a worm-wheel 5a. Carrier 5 is mounted in free- running communication within an annular bearing device to enable it to be freely rotated concentrically of the axis of rotation of the camshaft. These annular bearings are mounted in the casing 1 1 which may be any convenient type of frame device, or structure or, if required, may form part of the cylinder-head casting of an engine.

The annular carrier 5 is prevented from turning in an uncontrolled manner by a worm 17 engaged with the worm-wheel 5a, the lead angle of the worm being approximately 10º, this representing a locking angle which allows the worm 17 to drive the worm wheel 5a but prevents the worm-wheel from driving the worm 17. By coupling a drive shaft 16 of the worm to suitable drive means, such as electric or other motor, the rotational position of the annular carrier can be accurately set and, once adjusted, can be locked in position simply by providing a negative drive to the worm. Such a mechanism can provide extremely fine adjustment, in that it is not unusual for a 200 : I worm to worm-wheel ratio to be provided, so that the size of electric motor required is very small, and the degree of adjustment is both considerable (up to 360 ) but fine.

With the annular carrier 5 locked in place, rotation of the sun gear 13 by the sprocket 2 causes the two planet gears 13a and 13b to progress or "walk" around the inner annular gear 5b, taking with them the lay-shafts 6 and 15 together with a carrier 7 on which they are mounted in a similar rotational direction at a reduction of 2 : 1. The carrier 7 is a free-running device which is bearing mounted upon the extension shaft 20. The lay-shafts 6 and 15 are provided with end plates 4 and 14 in order to retain the planet gears driven by the sun gear 13. These planet gears 8 and 18 are totally idle upon the respective lay-shafts 6 and 15.

By driving the worm 17, the carrier 7 can be advanced or retarded, according to the direction of rotation of the worm, in relation to the rotation of the sprocket wheel 2.

The planet drive gears 8 and 18 are fixed to, or part of, the respective lay-shafts 6 and 15 and are engaged with a second annular carrier 9 which is bearing mounted in the same way as annular carrier 5 and is provided with an internal annular gear 9b and an external worm-wheel 9a. The worm-wheel 9a is engaged with a worm 19 and is controlled, in the same way as worm-wheel 5a, by a worm drive shaft 23.

If the annular gears 5b and 9b have 40 teeth each, as suggested, and the sun gear 13 has 20 teeth, then the four planet gears will have ten teeth each. These values are given, however, by way of example only and any suitable ratios may be used. Assuming the planet drive gears 8 and 18 have ten teeth each and their respective annular gear 9b has 40 teeth, then a single rotation of the carrier 7 with she annular carrier 9 fixed in annular position will cause the planet gears 8 and 18 to rotate four times. As the planet gears 8 and 18 are fixed to the lay-shafts 6 and 15 respectively, these lay-shafts will also rotate four times for each revolution of the carrier 7, provided the annular carrier 9 is locked in position.

Lay-shaft 6 is provided with a cam 22 and lay-shaft 15 is provided with a cam 21 , which cams are shown, in Figure 2, as being in contact with a follower 10 which is fixed to, or part of, camshaft 12. Bearing in mind that the camshaft 12 is loaded, and that is there is the usual rotational resistance imposed inter alia by the valves and their springs, any clockwise rotation of carrier 7 will result in the cams 21 and 22 being forced against the follower 10. This contact will drive the camshaft in the same direction as its sprocket 2 but at a 2 : 1 reduction as a result of the 2 : 1 gearing included in the epicyclic arrangement of gears 13, 13a, 13b and 5b. Furthermore, remembering the four revolutions per rotation of carrier 7, and thus of cams

21 and 22, any surface undulations on the profiles of the cams will be reproduced by a follower 10. The cams 22 and 21 have lobes which, in the present example, provide four pulses per revolution of the carrier 7. The duration of the pulses is determined by the particular shape or profile cams.

By selecting the rotational position of the annular carrier 5, the entire camshaft 12 and carrier 7 can be advanced and/or retarded relative to the sprocket wheel 2 and by repositioning the annular carrier 9 the pulses can be advanced and/or retarded in relation to the rotational position of carrier 7. The pulses applied to follower 10 can thus be advanced and/or retarded in relation to single valve events, to the extent of being relocated to any part of the event cylce and/or to any area of negative valve operation, i.e. the pulses can be created at a time when there is no valve profile engagement of an actuating nature. This means, that the oscillatory motion can be completely negated as far as the valves operated by the camshaft are concerned.

The basic advance and retard capabilities of the described arrangement, regardless of the oscillatory characteristics, can provide complete control of the overlap between the inlet valve and exhaust valve operation, e.g. by fitting an arrangement as described above to either, or both, of the inlet valve camshaft and exhaust valve camshaft. The overlap between the two operations can thus be eliminated or promoted to almost any extent and, in particular, low speed negative overlap can be realised with significant savings in emissions without requiring any compromise at the higher speed end of the operating range. As much overlap as required can be realised at high speed, again without compromising the negative lowspeed requirement, so that optimum timing can be achieved throughout the operating range.

The arrangement shown in Figures 3 and 4 is a simpler embodiment of the invention which is capable of providing oscillatory pulses but without an advanced/retard capability. In this second embodiment, the cams 22 and 21 are replaced by eccentrics 4 and 14 located in radial slots 5 and 19 as particularly shown in Figure 4 which illustrates the crank assembly 13.

The two eccentrics 4 and 14 are fixed to, or part of, respective layshafts 6 and 9, these being bearing located within housings formed within the general sprocket 10 unit. Lay-shaft 6 is provided with a drive planet wheel 2 ond loy-shoft 9 is provided with α drive planet wheel 16. The sprocket 10 octs as a carrier for the two lay-shaft assemblies 6, 2, 3, 4 and 9, 16, 15, 14, small cranks 2 and 15 being fixed to, or part of, lay-shafts 6 and 9.

Gears 2 and 16 are engaged with a fixed (non-rotatable) annular gear 1, at a ratio suitable to the requirement; e.g. if three pulses per single camshaft revolution are required, then a ratio of 3 : 1 between the planets 2 and 16 and annular gear 1, i.e. planets with 20 teeth each and an annular gear of 60 teeth, will be used.

In the example shown, a 4 : 1 engagement is indicated.

By rotating the sprocket in either direction, the eccentrics 4 and 14 will be forced to rotate, causing an oscillatory drive to be experienced by the camshaft 12 as a result of the eccentrics running up and down the length of the radial slots. This has the effect of slowing down, and speeding up (accelerating and decelerating) the camshaft. The number of oscillations is determined by the number of revolutions made by the planets. The extent of the degree range covered can be altered, in fixed design, by the shape, slope, and/or general characteristics of the radial, or semi-radial slots which can be of any acceptable contour.

If annular-gear 1 is given rotational repositioning capability, as in Figure 1, then the pulse sequence could again be advanced/retarded.

This eccentric coupling of Figures 3 and 4 could, if required, be used in a device such as described by Figure 1, in replacement for the cam type coupling.

As the direction of rotation of the drive planets, in both the above embodiments determines the retard/advance, or advance/retard characteristic, the annular gears could, if required, be replaced by sun gears in the pulse generating mechanisms. These could again be fixed or adjustable.

Figures 5 and 6 depict a variation of the idea shown in Figure 1. It will be seen, that follower 10 in Figure 2 is replaced by follower 2 In Figure 5. However, instead of cam 22 being the only drive device engaged with follower 10 (aside from 21 working in unison) follower 2 is shown to be in contact with a second cam device 3 which is a negative profile of cam 8. This positive/negative arrangement allows for the sprocket feed to be rotated in either direction without contact being lost with the camshaft 12. Furthermore, depending upon which of the two cams 8 or 3 is deemed to be the "driving" cam, depends the advance or retard characteristic of the device.

These "negative" profile cams could, of course, be used in replacement for the "positive" types used in Figure 2.

Circular follower 2 is a non rotating "solid" follower, contacted by both the positive cam 8 and the negative counterpart cam 3, both being driven by their respective lay-shafts 10 and 4, and these are in turn, driven by their respective planet gears 9 and 5. However, in this suggested arrangement gears 9 and 5 share a common annular gear 1 1 , and, as a result, any adjustment in the position of annular gear 1 1, will automatically advance and/or retard the positive and negative elements in concert.

A second follower 13 could be included.

If roller contacts were required, then Figure 6 shows a plan view of a typical assembly, with the negative cam 3 in contact with roller 2a and positive cam 8 in contact with roller 2, these being free-running upon the eccentric.

Depending upon which of the cams is indeed driving (the other being used if a reverse of input is experienced), the clearance between the "out of use" cam and the follower would probably allow for a single roller to be used between the two, i.e. both sharing a common roller, with contact just lost by the redundant cam.

Six cylinder in-line engines pose problems to the "nose" located variable timing profile device in that the disposition of the cylinders causes an overlapping of events along the camshaft (inlet or exhaust), which would result in a pulse suitable for one cylinder overlapping, or Interrupting with the event required by another. Therefore, by splitting the camshaft (inlet or exhaust) into two, or more shafts, and then by coupling those shafts by way of oscillatory pulse generator, with the second (and further) shafts, or sub-shafts, being driven off the previous shaft, the intermediate generators could be made to (a) negate the first pulse and (b) instigate a second (or third) set of pulses suitable to the rest of the valves. In this way, an in-line six cylinder engine can take advantage of this type of device without major redesign of the existing hardware.

The devices described herein can be added to existing engines by way of "off the shelf" or after-market components.

While it has been suggested that these generators can be used in conjunction with groups of valves, it is of course, a realistic possibility to consider using a generator with each valve, or double valve assembly, thereby making control of the cylinders independent of one another.

The profile of the cams used to generate the oscillatory pulses can be of any profile, thereby making it possible to "design" the shape of each pulse.

In Figure 3 the eccentrics were mounted upon the lay-shafts, with the slots fashioned in the cranked assembly. It should be noted that the cranked assembly could, if desired, be provided with a drive planet lay-shafts and eccentric, working in slots in the sprocket, or sprocket carrier.

The above described devices are simple, cost-effective and could be used in conjunction with any engine layout. They represent an easy means of providing an engine manufacturer with a solution to the major part of pollutive emission elimination without power-loss, indeed, they offer considerably increased power output capability, thereby again offering a further means of sustaining present power outputs for less fuel consumption, thereby again decreasing emissions.

Although worm and worm-wheel gearing is indicated as being the basic repositioning mechanism in respect of the two annular assemblies, any suitable means of creating rotation and locking of these units may be used, such as screw-threoded devices or levers, and the mechanisms may be controlled by electrical, and/or other means, e.g. mechanical linkage or hydraulic coupling.

A second positive/negative cam mechanism can be included, in order to provide a balanced drive to the camshaft and this can be achieved in many ways. Furthermore, it is possible for the negative cam to be located, in a free-running lay-shaft carrier (not shown) diametrically opposed, in a positional sense, to the positive cam, and, in this case, a second follower pin would be required and the resultant follower configuration would be a "V".

The variation indicated by Figures 5 and 6 provides the possibility of using oscillatory cam techniques with full reversibility; i.e. continuous contact, thus allowing for any slight reversal of input drive.

In Figure 3 the sprocket 10 is shown as performing two roles and serves as both the input drive component and lay-shaft carrier. However, these functions can be separated. Furthermore, the lay-shafts 6 and 9 can be replaced with stub-axles, giving further simplification.

A further variation of the Figure 3 embodiment would be to replace the two end plates (indicated at the ends of the two lay-shafts 6 and 9) with two planet gears. These would then engage an annular gear fixed to or part of the internal surface of the sprocket 10 which is free-running. The carrier for the lay-shafts would also be free-running. The presently indicated planets would be idle upon the lay-shafts (and not fixed to them as indicated). The annular gear 1 would be adjustable. This variation offers extreme rotational and pulse sequence possibilities, and is included in order to illustrate the scope offered by the present invention.

Figures 7 to 10 illustrate two examples of "mid-shaft" embodiments, these being suitable for engine applications, wherein it is considered necessary to divide the camshaft into two or more sub-shafts; e.g. as in the suggested installation of the invention into an in-line six cylinder engine.

It will be seen that Figure 7 is, in fact, a variation of the device shown in Figure 1. However, the feed to the sun gear 13 is now provided by quill shaft 27 insteod of the direct attachment via carrier 3. Quill shaft 27 is concentrically mounted, In free-running bearing location, within camshaft 12a, this being "half (or a portion) of the overall camshaft. The other section is indicated at 12.

Figures 8 and 9 show the two sets of driving cams 22 and 21 and 22a and 21a, together with the two cranked followers 10 and 10a.

Planet gears 25 and 26 are responsible for driving carrier 7, and therefore the ratio between the sun gear 13 and its respective annular gear

5b is important in determining the rate of rotation of the camshaft 12, or camshafts 12 and 12a in respect of the sprocket 2 or, as in this example, the quill-shaft 27.

The fact that this arrangement can allow for a reduction between the quill-shaft and the annular gear of, say 2 : 1 or more (e.g. 4 : 1 ) means that the sprocket, assumed to be fitted to the input end of quillr-shaft 27, can be reduced in size without causing complications in arriving at the desired 2 : 1 between crankshaft and the camshaft; i.e. an increased ratio between the crankshaft and the sprocket (say 1 : 2) can be accepted, providing the ratio between sun gear 13 and annular gear 5b has sufficient scope to enable eventual drive to carrier 7 to resolve at 2 : 1.

This aspect is extremely important, as it enables the "top sprocket" to be reduced in size, thereby enabling the important front face of the engine to be reduced in height. This has considerable styling implications in regard to overall vehicle shape etc., therefore, this critical dimension is extremely pertinent.

Lay-shaft 6 is now provided with one drive gear 8 and two cams 22 and 22a, these being fixed to, or part of said shaft.

Figures 8 and 9 are merely hypothetical representations, and the various components are only suggested designs. However, the disposition of the cams is sufficient to demonstrate the wide differences made possible between the two camshaft feeds; i.e. the attachment of the two sets of cams to lay shafts 6 and 15 is accomplished by way of a 90º difference; i.e. the "peaks" of corns 22a and 21 a are 90° out of alignment with those of cams 22 and 21. This is a very considerable difference, however, it will appreciated that these items can be anything between zero degrees difference, up to 360 degrees of difference, therefore, the oscillatory pulses generated to the two "half" camshafts can be out of phase by any required amount, thereby allowing the events created by each "half" camshaft to be independent of each other, thus preventing the pulses generated for one set of valves to impinge upon those created for the remaining valves.

The basic advance/retard functions as already described for both the overall camshaft timing and the pulse sequence remain as for Figure 1.

A further variation of the device, would be to engage sun gear 13 directly with planets 8 and 18, thereby eliminating the annular assembly 5, 5a, 5b and the input planets 25 and 26. However, the rotational station variation provided for assembly 9, 9a, 9b would then be responsible for both advance/retard of the camshaft and, at the same time, adjust the pulse sequence.

Figure 10 shows a further variation based upon Figure 3, in that, the quill shaft 10a drives directly from the sprocket not shown to a carrier 10. Therefore an advance/retard of the overall camshaft would be provided elsewhere. However, the double crank arrangement shown by Figure 10 wHl allow a very simple oscillatory mid-shaft device to be realised.

The two "half" camshafts 10a and 12 are driven by their respective radial slot carriers 13 and 13a, and the engaged eccentrics 4a, 14a and 4, 14 are, in this example, 180º apart, in that, they can cause oscillatory pulse generation 180 º out-of phase.

This 180º difference can be, of course, anything from zero difference up to 360º of difference.

Eccentrics 4a and 4 together with planet gear 2 are fixed to, or part of, lay-shaft 6. Eccentrics 14a and 14, together with planet gear 16 are fixed to, or part of, lay-shaft 9. Radial slot carrier 13a is fixed to, or part of sleeve-camshaft 12a, and radial slots carrier 13 is fixed to, or part of, camshaft 12.

Claims

CLAIMS:

1. An osciallαtory drive arrangement, comprising a driven member which is rotatable about a first axis; a drive element which is rotatable about a second axis parallel to the first, which is drivingly engaged with the driven member at a location spaced on the first axis and is constrained to move along a circular path around the first axis while rotating about the second axis; a driving member which is rotatable to drive the element around its circular path and thus rotate the. driven member; and means carried by the drive element eccentrically of the second axis for superimposing periodic oscillations on the rotary motion of the driven member as a result of the rotation of the drive element about its axis.

2. A drive arrangement according to claim I , wherein the drive element comprises a rotatable shaft carrying eccentric means engaging the driven member.

3. A drive arrangement according to claim 2, wherein the eccentric means is a cam having a surface which engages a surface of the driven member extending transversely of the first axis.

4. A drive arrangement according to claim 2, wherein the eccentric means comprises a pin carried eccentrically by the shaft and engaged in a slot of the driven member.

5. A drive arrangement according to any one of claims 2 to 4, wherein the shaft is rotatable with a planet gear wheel engaged with a stationary internally toothed ring around which the planet travels as a result of rotation of the driving member.

6. A drive arrangement according to claim 5, wherein the toothed ring is angularly adjustable about the first axis to vary the timing relationship between the rotation of the drive element and the driven member.

7. A drive arrangement according to claim 6, wherein the internally toothed ring is formed externally as a worm-wheel which is engaged with a worm by which the angular position of the worm-wheel can be odjυsted.

8. A drive arrangement according to any one of claims 2 to 7, wherein the shaft is journalled in the driving member.

9. A drive arrangement according to any one of claims 2 to 8, wherein the shaft has a freely rotatable planet wheel thereon which is engaged with a second stationary internally toothed ring and with a sun wheel rotatable with the driving memebr, so that upon rotation of the driving member the planet wheel travels around the second ring together with the shaft.

10. A drive arrangement according to claim 9, wherein the angular position of the second toothed ring is adjustable about the first axis to adjust the timing of the rotation of the shaft relative to the rotation of the driving member.

I f. A drive arrangement according to claim 10, wherein the second toothed ring is formed externally as a worm-wheel engaged with a worm by which the angular position of the second toothed ring is adjustable.

12. A drive arrangement according to any preceding claim, wherein a plurality of drive elements are provided.

13. A drive arrangement according to claim 12, wherein two drive elements are provided diametrically opposite one another with respect to the first axis.

14. A drive arrangement according to claim 12, wherein a portion of the driven member extending transversely of the first axis is captively positioned between a pair of drive elements presenting complementary cam surfaces.

15. A drive arrangement substantially as hereinbefore described with reference to the accompanying drawings.

16. Any novel feature or combination of features described herein.