GB2428451A

GB2428451A - I.c. engine variable valve actuation system

Info

Publication number: GB2428451A
Application number: GB0514666A
Authority: GB
Inventors: Jean-Pierre Pirault; Samuel Lesley; Martin Love; Riccardo Meldolesi
Original assignee: Powertrain Technology Ltd
Current assignee: Powertrain Technology Ltd
Priority date: 2005-07-16
Filing date: 2005-07-16
Publication date: 2007-01-31
Anticipated expiration: 2025-07-16
Also published as: GB2428451B; GB0514666D0

Abstract

A variable valve actuation system in an i.c. engine having more than on cylinder comprises a control link 40,fig.2 which is caused to oscillate by means of a connecting rod 20,fig.2 driven by a crankshaft 18,fig.2. The control link 40,fig.2 oscillates about a control pin 38,fig.2 preferably at one end of the control link and the valve actuation means, eg cam link 56,fig.2, is connected preferably at the other end of the control link. The control pin 38,fig.2 is mounted adjustably on all cylinders so that fine corrections can be made to the valve timing from cylinder to cylinder to take account of any production variations in the valve actuation components. The control pin 106,fig.1 may be carried by a member 112,fig.1 attached by a leaf spring 110,fig.1 to the control link 102,fig.1 so that rotation of the adjustment screw 100,fig.1 moves the control pin 106 relative to the control link 102.

Description

Improvements to the Adjustment of Variable Valve Timing mechanisms of

Internal Combustion Engines

Field of the invention

The present invention relates to a variable valve timing mechanism of an internal combustion engine.

Background

In an internal combustion engine the valve timings i.e. the points at which the valve starts to open and close are traditionally fixed in relation to the instantaneous positions of the crankshaft. It is increasingly desirable and common to be able to provide valve timings that can be varied according to engine conditions. In multi- cylinder engines with variable valve timing, production tolerances create variations in valve timing from cylinder to cylinder. The invention described below is a means of making fine adjustments to the valve timing of each individual cylinder and applies particularly to timing mechanisms with oscillating motion, such as those described in the following section.

Prior Art

Patent application GB0413944.O discloses an oscillating valve-actuation mechanism using a link (one per valve) which oscillates about a control point at one of its ends.

The valve is actuated via a mechanism at the other end of the link. The oscillation is driven by a crank and connecting rod mechanism which is rotatably attached to the link. Variation in timing and lift are provided by movement of the control point. In multi-cylinder engines the movement is replicated between cylinders. The invention described below provides an additional enhancement to this system in which fine mechanical adjustments can be made to the angular positions of the control links.

These adjustments (small movements of the control point) take into account any production tolerance variations between the valve operating systems associated with each cylinder.

Summary of the invention

The broadest aspect of the invention comprises a variable valve-actuation mechanism including a cam lobe, cam link and control link in which a first pin on the control link is rotatably connected to the cam link, a second pin provides a centre of oscillation of said control link and a third pin on the control link is rotatably connected to a reciprocating connecting rod which in turn is connected to a crankshaft and the centres of either the first pin, the second pin or the third pin are adjustable in relation to the said control link.

Specific embodiments of the invention will now be described with reference to the accompanying figures.

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Brief Description of the Figures

Figure 1 - orthogonal views of the adjustable control link with leaf spring.

Figure 2- view of a control link as part of a vanable valve actuation system.

Figure 3 - orthogonal views of the adjustable control link with adjustable pin carrier.

Figure 4 - orthogonal views of the adjustable control link with eccentric pin.

Figure 5 - isometric views of the adjustable control link and slotted saddle.

Detailed Description of the Preferred Embodiments

Figure 1 shows a control link 102 with a widened end 114 around control pin 106.

Inside this widened end is an adjustable member 112 with a long protrusion 110.

Protrusion 110 is attached to control link 102 with two rivets 108. Control pin 106 projects beyond member 112 and runs in slots 104 in control link 102 and is retained by a circlip 105 at each end (only one of which is shown). Adjusting screw 100 acts on member 112 and is opposed by protrusion 110 acting as a leaf spring. The control link 102 forms a part of a variable valve actuation mechanism such that hole 118 is connected by means of a pin (not shown) to a link (not shown) which operates an oscillating camshaft (not shown). Hole 116 is connected by means of a pin (not shown) to a reciprocating connecting rod (not shown) which creates the oscillating motion of the control link 102 about the centre of pin 106. Rotating screw 100 in one direction moves pin 106 upwards (as shown) in relation to control link 102 under the influence of the leaf spring (protrusion 110) and thereby retards the timing of the start of valve lift; rotating screw 100 in the other direction lowers pin 106 in relation to control link 102 against the influence of the leaf spring (protrusion 110) and thereby advances the timing of the start of valve lift. Although in Figure 1 member 112 is attached to control link 102 by means of two rivets, other means of attachment are possible e.g. spot welding or threaded fasteners.

In Figure 2, crankshaft 18 rotates about axis 16 and has an eccentric 14. Crankshaft 18 is driven synchronously by the main engine crankshaft (not shown). Connecting rod 20 has one end mounted on eccentric 14, and the other end mounted on third pin 42 of control link 40. Second pin 38 of control link 40 is mounted at the control point 66 about which control link 40 oscillates as crankshaft 18 rotates. Cam link 56 has one end mounted on first pin 52 and the other end mounted on cam pin 10, which is mounted on cam lever 12. Camshaft 46 oscillates about camshaft axis 48 when cam lever 12 is oscillated by cam link 56. In this view, anticlockwise movement of camshaft 46 causes cam 54 to move anticlockwise, and, because cam 54 is in contact with roller 4 of roller follower 8, it makes roller follower 8 move clockwise about spherical end 58 of hydraulic backlash adjuster 60 thereby making valve 2 move along its axis to the open position (as shown).

With reference to Figure 3, control pin 170 is carried in stirrup 168 which is connected to control link 152 via threaded shaft 162. Shaft 162 is rotatable within stirrup 168 and has a threaded engagement with stirrup 168 such that as shaft 162 rotates stirrup 168 moves up or down along the threaded engagement. This movement is small and may be less than 1 mm. Shaft 162 is located in its vertical position by flange 163. The bottom face of flange 163 engages with the base of cup 2 of 6 166, which is permanently attached to control link 152, and the top face of flange 163 is engaged with the bottom surface of locking ring 164. Locking ring 164 is located in cup 166 with a threaded engagement such that as locking ring 164 is rotated flange 163 is gnpped or released allowing the location of stirrup 168 to be fixed or adjusted as required. Shaft 162 has slot 160 at its top end so that it can be rotated by a screw driver (not shown) or similar tool. Locking ring 164 has flats on its upper section such that it can be rotated by a spanner (not shown) or similar tool. The ends of control pin 170 are restrained by circlips (only one, 172, is shown) or similar mechanical fixings. Control pin 170 engages in control link 152 by means of slotted holes 158 allowing for the vertical movement of control pin 170.

With reference to Figure 4, control pin 136 is made with two different diameters on two different centres or axes. The smaller diameter is preferably in the centre section and the larger diameter is preferably in the two end sections engaging with holes 137 in control link 134. One end of control pin 136 has slot 138 so that it can be rotated by a screw driver (not shown) or similar tool. Other means of facilitating turning of control pin 136 are possible. Rotation of control pin 136 thus causes the axis of the central section, which is eccentric to the end sections, to move in relation to control link 134. When control pin 136 is in the desired position it can be locked in place by turning locking nuts 140. Other locking means are possible such as one or more grub screws. With a grub screw arrangement, the ends of the control pin would be restrained by circlips or similar means.

With reference to Figure 5 the control pin (not shown) engages with slots in both control link 200 and saddle 201. Slots 202 in control link 200 are orientated in a different direction to slots 203 in saddle 201. In the preferred embodiment the two sets of slots are orientated substantially at right angles to each other but other included angles are possible. Saddle 201 fits over the end section of control link 200 such that the ends of the control pin (not shown) can protrude through both pairs of slots. The ends of the control pin are restrained by circlips as in the previous embodiment but other mechanical means of restraint are possible. The axis of the control pin can be moved in relation to control link 200 by sliding saddle 201 in an axial direction along control link 200. When it is in the desired position, it can be locked in place by turning a grub screw (not shown) which is fitted in threaded hole 204. Other mechanical locking means are also possible and mechanical means for moving saddle 201 in a controlled manner may be applied. These may include a threaded shaft running substantially along or parallel to the axis of control link 200 such that turning a nut or turning the shaft causes saddle 200 to move.

Although the above preferred embodiments are applied to the pin at the control point (the control pin), they may equally be applied to other pins within the system such as the pin connecting the control link to the reciprocating connecting rod, the pin connecting the control link to the cam link or to the pin connecting the cam link to the oscillating cam.

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Claims

Claims 1. A variable valve-actuation mechanism including a cam lobe, cam

link and control link in which a first pin on the control link is rotatably connected to the cam link, a second pin provides a centre of oscillation of said control link and a third pin on the control link is rotatably connected to a reciprocating connecting rod which in turn is connected to a crankshaft and the centres of either the first pin, the second pin or the third pin are adjustable in relation to the said control link.
2. A variable valve-actuation mechanism as claimed in claim I in which the adjustable pin is the second or third pin in the control link.
3. A variable valve-actuation mechanism as claimed in claim 2 in which the adjustable pin is the second pin.
4. A variable valve-actuation mechanism as claimed in claim I in which either the first pin, the second pin or the third pin is additionally mounted in an adjustable member with a protrusion acting as a leaf spring by which the said adjustable member is attached to the control link.
5. A variable valve-actuation mechanism as claimed in claim 4 in which the adjustable member is moveable in relation to the control link by means of the rotation of a threaded fastener which bears on the said adjustable member.
6. A variable valve-actuation mechanism as claimed in any previous claim in which either the first pin, the second pin or the third pin is mounted in a slot in the control link allowing the centre of the said pin to move in relation to the said control link.
7. A variable valve-actuation mechanism as claimed in claim 4 in which the centre line of the slot forms an arc substantially about the attachment point of the leaf spring.
8. A variable valve-actuation mechanism as claimed in claim 1 in which the adjustable pin is mounted on or is integral with eccentric bearings such that rotation of the bearings causes displacement of the centre of the said adjustable pin.
9. A variable valve-actuation mechanism as claimed in claim 8 in which the eccentric bearings are lockable.
1O.A variable valve-actuation mechanism as claimed in claim 9 in which the eccentric bearings are lockable by means of a lock nut or a grub screw.
11.A variable valve-actuation mechanism as claimed in claim I in which the ends of the adjustable pin protrude through a first pair of slots in a first carrier member and through a second pair of slots in a second carrier member in which the slots in the first carrier member have a different orientation to the slots in the second carrier member.
12. A variable valve-actuation mechanism as claimed in claim 11 in which the second pair of slots is substantially at right angles to the first pair of slots.
13. A variable valve-actuation mechanism as claimed in claim 11 or 12 in which the second carrier member is adjustable in relation to the first carrier member and can be locked in position using a grub screw or other mechanical device.

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14.A variable valve-actuation mechanism as claimed in claim I in which the adjustable pin is mounted in a stirrup attached to the control link by means of a threaded fastener rotatable in the said stirrup and engaging with a threaded hole in the stirrup such that rotation of the threaded fastener causes the said stirrup to move in relation to the control link.
I 5.A means of adjusting an oscillating control link comprising: an oscillating control link, an input pin, an output pin, a pivot pin, a housing for the pivot pin, a spring, and an adjusting means; the input pin which drives the oscillating motion, and the output pin which is used to drive other devices, are fixed within the control link; the pivot pin is housed in and projects beyond an adjustable member which is movable within the control link with the pivot pin constrained to slide within a slot in the control link; the adjustable member is biased to move in one direction along the slot by means of the spring, and the adjusting means is used to force the adjustable member in the opposite direction along the slot.
16. A means of adjusting an oscillating control link as described in any of the above claims in which the adjusting means is a screw housed within the control link and acting upon the adjustable member.
17.A means of adjusting an oscillating control link as described in claim 15, in which the spring is an extension of the adjustable member in the form of a leaf spring which is attached to the control link.
18.A means of adjusting an oscillating control link as described in claims 15, 16 or 17 in which the slot forms an arc about the attachment point of the leaf spring.
19.A means of adjusting an oscillating control link as described in any of claims 17 or 18 in which the leaf spring is attached to the control link by means of one or more rivets.
20.A means of adjusting an oscillating control link as described in any of claims 17 or 18 in which the leaf spring is attached to the control link by means of welding.
21.A means of adjusting an oscillating control link as described in any of claims 17 or 18 in which the leaf spring is attached to the control link by means of one or more threaded fasteners.
22.An adjustable control link substantially as herein described, with reference to Figure 1.
23.An adjustable control link substantially as herein described, with reference to Figure 2.
24.An adjustable control link substantially as herein described, with reference to Figure 3.
25.An adjustable control link substantially as herein described, with reference to Figure 5. of 6

25.An adjustable control link substantially as herein described, with reference to Figure 4.