GB2401163A

GB2401163A - Variable phase mechanism

Info

Publication number: GB2401163A
Application number: GB0309711A
Authority: GB
Inventors: Timothy Mark Lancefield
Original assignee: Mechadyne PLC
Current assignee: Mechadyne PLC
Priority date: 2003-04-29
Filing date: 2003-04-29
Publication date: 2004-11-03
Also published as: DE102004019733A1

Abstract

A variable phase mechanism comprises a shaft 16, first 10 and second 14 members rotatable about the shaft 16 and a yoke 20 coupling the first member 10 for rotation with the second member 14. The rotation of the first member 10 relative to the shaft 16 causes the outer surface of the shaft 16 to interact with the inner surface of the yoke 20 through meshing teeth 182, 184, causing the angular position of the second member 14 to be varied in relation to the first member 10. Also disclosed are arrangements comprising a hollow shaft 16 and first 18 and second 20 yokes. The first yoke 18 couples the first member 10 with the hollow shaft 16. An actuating rod 31 is slidably received in the hollow shaft 16, and has cam surfaces 36, 38 which act axially on a first yoke 18, causing it to move radially, varying the angular position of the first member 10 in relation to the hollow shaft 16. Again this causes the outer surface of the shaft 16 to interact with the inner surface of the yoke 20 through meshing teeth 182,184, causing the angular position of the second member 14 to be varied in relation to the first member 10.

Description

24011 63 - 1 Variable Phase Mechanism

Field of the invention

The present invention relate to a variable phase mechanism for use in a valve train of an internal combustion engine to permit the crank angles at which the valves open and close to be varied.

lo Background of the invention

As is well known, valve timing has a significant effect on engine performance and the optimum setting varies with engine operating conditions. To optimise performance under is different operating conditions, it is necessary to be able to vary the valve timing.

Various variable valve timing mechanisms have been proposed in the past that achieve a variable phase relationship between the crank shaft and the camshaft of an engine. These mechanisms have suffered from various problems. Some, though feasible, have been costly to implement and some have developed excessive friction or not proved to be reliable. Furthermore, many could not be fitted as a modification to existing engines and required much of the valve train and cylinder head to be redesigned.

The most relevant prior art is believed to be the

Applicants' own earlier proposal in EP 1030035. This discloses a variable phase mechanism comprising a hollow shaft, first and second members rotatable about the hollow shaft, two yokes surrounding the hollow shaft, one yoke coupling the hollow shaft for rotation with first member and the other coupling the second member for rotation with the first member, an actuating rod slidably received in the hollow shaft, a cam surface on the actuating rod acting on the first yoke by way of a plunger passing through a - 2 - generally radial bore in the hollow shaft to cause the first yoke to move radially in response to axial movement of the actuating rod so as to vary the angular position of the first member relative to the hollow shaft, rotation of the hollow shaft relative to the first member causing the outer surface of the hollow shaft to interact with the inner surface of the second yoke to cause the angular position of the second member to be varied in relation to the first member.

Figures 6 and 7 of the invention referred to, show the method in which the hollow shaft shift phase with respect to the second member which is intended to drive another camshaft or increase the degree of phase difference between the input pulley and on camshaft. As a result of the contouring of the inner surface of the second yoke, it moves from side to side as the hollow shaft rotates. This requires the use of part cylindrical shoes 50 which are seated in pockets. These components are difficult to machine since their shape is specifically chosen to impart lateral movement when engaged with the profiled inner surface of the second yoke.

Object of the invention The present invention seeks to improve over the different embodiments of the prior art by providing a different interaction between the hollow shaft and the secondary yoke.

Summary of the Invention

According to one aspect of the present invention, there is provided a variable phase mechanism comprising a shaft, first and second members rotatable about the shaft and a yoke coupling the first member for rotation with the second member wherein rotation of the first member relative to the - 3 - shaft causes the outer surface of the shaft to interact with the inner surface of the yoke so as to cause the angular position of the second member to be varied in relation to the first member, characterized in that the outer surface of the shaft and inner surface of the yoke are provided with intermeshing teeth.

Second, third and fourth aspects of the present inventions are set forth in claims 3, 6 and 8 respectively, lo of the appended claims.

Brief description of the drawings

The invention will be described further by way of example, with reference to the accompanying drawings, in which figures 1 to 9 represent the prior art and figures 10 and 11 show the embodiments of the present invention. In particular: Figure 1 is an axial section through a variable phase

mechanism of a first prior art embodiment,

Figure 2 is an axial section through the variable phase mechanism of Figure 1 taken through the plane normal to the section plane in Figure 1, 2s Figure 3 is a partly cut-away perspective view of the variable phase mechanism of Figures 1 and 2, Figures 4 and 5 are sections in a plane normal to the rotational axis passing through the first yoke and the plungers, Figures 6 and 7 are sections in a plane normal to the rotational axis passing through the second yoke, Figure 8 is an axial section similar to that of Figure 1 showing a second embodiment of the prior art, Figure 9 is a similar view to figure 8 but shows a 3s differing embodiment provided for in the prior art document, and - 4 Figures 10 and 11 each represent the same view as figures 6 and 7 in different stages of phase shifting (A, B and C) but using the improvement provided by two embodiments of the present invention, respectively.

Detailed description of the preferred embodiments

Figures 1 to 7 show a prior art variable phase

mechanism that has a drive pulley 10 connected to be driven lo by the engine crankshaft, a camshaft 12 that is rotatable with variable phase in relation to the drive pulley 10 and a driven pulley 14 that can itself be used to drive a second camshaft and that is also rotatable with variable phase in relation to the drive pulley 10. The end of the camshaft 12 is formed as a hollow shaft 16 on which the two pulleys 10 and 14 are rotatably mounted. The coupling between the hollow shaft 16 and the two pulleys is effected by two yokes 18 and 20 that are better shown in Figures 4 and 5 and Figures 6 and 7, respectively.

The yoke 18 is a ring having a contoured inner surface that surrounds the hollow shaft 16 with clearance. To one side of the hollow shaft 16, the yoke 18 is connected by a pivot pin 22 to the drive pulley 10. To the other side of the hollow shaft 16, the yoke 18 is connected by means of a pin 24 and a slide block 26 to an annular disk 28 that is fast in rotation with the hollow shaft 16 and secured to the hollow shaft 16 by means of a nut 30. As the yoke 18 rocks from about the pin 22 (compare Figures 4 and 5), the pin 24 moves from side to side and rotates the disk 28 and the hollow shaft 16 relative to the drive pulley 10, the slide block 26 permitting the necessary simultaneous radial movement of the pin 24. In this way, the angular position of the hollow shaft 16 is varied in relation to the drive pulley 10, that is to say their relative phase is changed when they rotate at the same speed. - 5

The mechanism for moving of the yoke 18 from side to side is best illustrated by Figures 2, 4 and 5. An actuating rod 32 movable by a piston 34 is axially slidable within the hollow shaft 16. The actuating rod 32 has two cam surfaces in the form of oppositely sloping ramps 36, 38 that act on the inner surface of the yoke 18 by way of two plungers 40, 42. Each of the plungers 40, 42 is formed at one end with a part spherical shoe 44 and with a part cylindrical shoe 45 at its other end so that the plungers at 0 all times make surface contact with the actuating rod 32 and the contoured inner surface of the yoke 18. As the yoke 18 pivots about the pin 22, the hollow shaft 16 and the plungers 40, 42 also rotate under the action of the pin 24.

In order to avoid backlash, it is important to ensure that the shoes 44 on the ends of the plungers 40, 42 remain in contact with the cam surfaces 36, 38 and with the inner surface of the yoke 18 at all times. This is achieved in that one of the cam surfaces 38 is defined by a slidable wedge 48 that is biased by a resilient member 49 in a direction to widen the distance between the two cam surfaces 36, 38.

The piston 34 connected to the actuating rod 32 is reciprocable in a double skinned cylinder 60. Oil can be pumped into the working chamber to the left of the piston 34, as viewed, through a central opening 62 to chamber on the opposite side of the piston 34 through the annular gap 64 between the two skins of the cylinder 60 and through an annular recess 66 machined into the front face of the disk 28.

Referring now to Figures 6 and 7, it will be seen that the hollow shaft 16 has two further part-cylindrical shoes 50 that are received directly in part-cylindrical recesses in the surface of the hollow shaft 16. These shoes 50 make contact with the contoured inner surface of the second yoke - 6 - which is pivoted on one side by means of the pin 22 to the drive pulley 10 and is coupled on the other side by means of a pin 52 and a slide block 54 to the second pulley 14. Because of the contouring of the inner surface 56 of the yoke 20, it moves from side to side as the hollow shaft 16 rotates and this in turn causes the pulley 14 to rotate in the opposite sense relative to the drive pulley 10. In this case, backlash can be avoided by the resilience of the yoke or by resiliently biasing the shoes 50 towards the yoke lo surface 56.

The embodiments of the present invention shown in figures 10 and 11 provide an alternative to the above coupling between the second yoke 20 and the hollow shaft 16.

This is achieved by means of intermeshing teeth 182, 184 located on the outer circumference of the hollow shaft 16 and the inner surface of the second yoke. An embodiment of the invention is shown in figure 10 A, B and C. When the hollow shaft is rotated by means of the first yoke, teeth 182 on the hollow shaft 16 mesh with teeth 184 on the second yoke 20 causing it to move from side to side, and in so doing impart a torque to pin 24 and hence pulley 14. This is analogous with the situation as described in the prior art invention in figures 6 and 7, except that the meshing teeth are cheaper and more simple to manufacture. The embodiments of figures 10 and 11 differ from one another in that the position of the teeth 182 and 184 is such that rotation in the same direction of the hollow shaft 16 causes the second yoke 30 to shift sideways in relation to pin 22. This is useful depending on the desired output of the second yoke.

The embodiment of Figures 1 to 7 has two phase changers constituted by the two yokes 18 and 20 that are connected effectively in parallel with one another to transmit torque from the drive pulley 10 to two separate elements, namely the camshaft 12 and the pulley 14. The embodiments of Figures 8 and 9 differ in that they have two phase changers - 7 connected in series with one another to double the maximum angular displacement of a camshaft 112 relative to its drive pulley 110.

In Figure 8, the drive pulley 110 is freely rotatable on the hollow shaft 116. The first yoke 118 is pivoted on the hollow shaft 116 by means of a fixed pin 124, the second yoke 120 is pivoted on the drive pulley 110 by a second fixed pin 122. The two yokes 118 and 120 are connected to lo one another on the opposite side of the hollow shaft 116 from the pins 122 and 124 by a pin 126 located in sliders 127,129 in the two yokes 118,120. The pin 126 passes through a thin separator 125 that is rotatable about the hollow shaft 116. The other components including the actuating rod, the plungers and the hydraulic system for displacing the actuating rod are all as previously described.

Figure 8 also shows an engine front cover 180 that is stationarily mounted in relation to the engine block that fits over the end of the double-skinned cylinder 160 through appropriate rotary seals to supply oil to the working chambers of the hydraulic piston 134.

In this embodiment, movement of the actuating rod causes the yoke 118 to swing from side to side by the action of its cam surfaces and the plungers. This causes a rotation of the separator 125 and the pin 126 about the pin 124 in the hollow shaft 116. The side to side movement of the pin 126 causes the second yoke 120 to rotate about the hollow shaft 116 which interacts with the inner surface of the second yoke 120 to cause a further rotation of the drive pulley 110 relative to the hollow shaft 116.

The purpose of the separator 125 in the embodiment of Figure 8 is to maintain the radius of the pin 126 constant in relation to the axis of rotation of the hollow shaft 116.

This is necessary because the pin 126 is held in slide 8 - blocks 127, 129 in both yokes and in the absence of the separator 125 it would be able to move indiscriminately in a radial direction.

The alternative to the provision of a separator 125 is shown in Figure 9. This embodiment of the invention is essentially the same as that of Figure 8 except that the pin 126 is fixed in relation to the yoke 118 and is only held in a slide block 127 in the yoke 120. The slide block 129 has lo been omitted which also allows the omission of the separator 125.

It will be clear that the modified coupling between the hollow shaft 16 and the second yoke 20 as shown in figures IS 10 and 11 can equally be applied to the coupling in figures 8 and 9 between the second yoke 120 and the hollow shaft 116.

It should mentioned that the slide block 54 has been omitted from figures 10 and 11, but it or an equivalent is still required to permit radial movement of the second yoke relative to the axis of the hollow shaft 16. Of course the slide block need not be provided within the yoke as it may be fitted to the opposite end of pin 52. - 9 -

Claims

1. A variable phase mechanism comprising a shaft, first and second members rotatable about the shaft and a yoke coupling the first member for rotation with the second member wherein rotation of the first member relative to the shaft causes the outer surface of the shaft to interact with the inner surface of the yoke so as to cause the angular position of the second member to be varied in relation to lo the first member, characterized in that the outer surface of the shaft and inner surface of the yoke are provided with intermeshing teeth.

2. A variable phase mechanism as claimed in claim 1, wherein the shaft is fast in rotation with a first camshaft of a dual camshaft engine, the first member is a drive sprocket to be driven in use by the engine crankshaft and serving to drive the first camshaft by way of means for varying the phase of the first member in relation to the first camshaft, and the second member is a drive sprocket for connecting the first camshaft of the engine to a second camshaft of the engine.

3. A variable phase mechanism comprising a hollow shaft, first and second members rotatable about the hollow shaft, two yokes surrounding the hollow shaft, one yoke coupling the hollow shaft for rotation with first member and the other coupling the second member for rotation with the first member, an actuating rod slidably received in the hollow shaft, a cam surface on the actuating rod acting on the first yoke by way of a plunger passing through a generally radial bore in the hollow shaft to cause the first yoke to move radially in response to axial movement of the actuating rod so as to vary the angular position of the first member relative to the hollow shaft, rotation of the hollow shaft relative to the first member causing the outer surface of the hollow shaft to interact with the inner 10 surface of the second yoke to cause the angular position of the second member to be varied in relation to the first member, characterized in that the outer surface of the hollow shaft and inner surface of the second yoke are provided with intermeshing teeth.

4. A variable phase mechanism as claimed in claim 3, wherein the hollow shaft is fast in rotation with a first camshaft of a dual camshaft engine, the first member is a lo drive sprocket connecting the engine crankshaft to the first camshaft, and the second member rotatable on the hollow shaft is a drive sprocket serving to transmit drive torque to the second camshaft.

5. A variable phase mechanism as claimed in Claim 4, wherein partcylindrical shoes are provided on the ends of the plungers acting on the inner surface of the first yoke.

6. A variable phase mechanism comprising a hollow shaft, first and second members rotatable about the hollow shaft, two yokes surrounding the hollow shaft, one yoke coupling the hollow shaft for rotation with the first member and the other coupling the first member for rotation with the second member, an actuating rod slidably received in the hollow shaft, a cam surface on the actuating rod acting on the first yoke by way of a plunger passing through a generally radial bore in the hollow shaft to cause the first yoke to move radially in response to axial movement of the actuating rod so as to vary the angular position of the first member relative to the hollow shaft, the resultant rotation of the first member about the hollow shaft causing the outer surface of the hollow shaft to interact with the inner surface of the second yoke to cause the angular position of the second member to be further varied in relation to the hollow shaft, characterized in that the outer surface of the hollow shaft and inner surface of the second yoke are provided with intermeshing teeth.

7. A variable phase mechanism as claimed in Claim 6, wherein partcylindrical shoes are provided on the ends of the plungers acting on the inner surface of the first yoke.

8. A variable phase mechanism comprising a hollow shaft, a member rotatable about the hollow shaft, two yokes surrounding the hollow shaft, the first yoke coupling the hollow shaft for rotation with the second yoke and the second yoke coupling the first yoke for rotation with the lo rotatable member, an actuating rod slidably received in the hollow shaft, a cam surface on the actuating rod acting on the first yoke by way of a plunger passing through a generally radial bore in the hollow shaft to cause the first yoke to move radially in response to axial movement of the actuating rod so as to vary the angular position of the second yoke relative to the hollow shaft, the resultant rotation of the second yoke about the hollow shaft causing the outer surface of the hollow shaft to interact with the inner surface of the second yoke to cause the angular position of the rotatable member to be further varied in relation to the hollow shaft, characterized in that the outer surface of the hollow shaft and inner surface of the second yoke are provided with intermeshing teeth.

9. A variable phase mechanism as claimed in Claim 8, wherein partcylindrical shoes are provided on the ends of the plungers acting on the inner surface of the first yoke.

10. A variable phase mechanism as claimed in any preceding claim, wherein the actuating rod is connected to a hydraulic piston.

11. A variable phase mechanism as claimed in claim 10, wherein the piston is a double acting piston reciprocable within a cylinder having a double skinned wall, pressure medium being supplied to the working chamber on one side of the piston through the gap in the double skinned wall.

12. A variable phase mechanism as claimed in Claim 10 or 11, wherein the actuating rod has opposed ramp surfaces of which one is defined by a wedge movable relative to the body of the actuating rod and resiliently biased in a direction to increase the distance between the two ramp surfaces.

13. A variable phase mechanism as claimed in any lo preceding claim, wherein the position of the intermeshing teeth relative to the pivot point of the yoke is operative to determine the direction of movement of the yoke relative to the shaft.