EP0739444B1 - Variable valve timing mechanism - Google Patents
Variable valve timing mechanism Download PDFInfo
- Publication number
- EP0739444B1 EP0739444B1 EP95905179A EP95905179A EP0739444B1 EP 0739444 B1 EP0739444 B1 EP 0739444B1 EP 95905179 A EP95905179 A EP 95905179A EP 95905179 A EP95905179 A EP 95905179A EP 0739444 B1 EP0739444 B1 EP 0739444B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- drive
- camshaft
- valve
- drive mechanism
- lever
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01L—CYCLICALLY OPERATING VALVES FOR MACHINES OR ENGINES
- F01L13/00—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations
- F01L13/0015—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque
- F01L13/0057—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for optimising engine performances by modifying valve lift according to various working parameters, e.g. rotational speed, load, torque by splittable or deformable cams
Definitions
- the present invention relates to a variable valve timing mechanism for an internal combustion engine.
- WO 92/04532 uses a coil spring as the coupling member that jams against a pad when it is unwound and takes up the lost motion by winding up. Though this construction reduced the noise problem significantly, impact shock was still excessive causing the spring to fracture.
- the present invention seeks to provide a variable valve timing mechanism which introduces lost motion into the valve train but which mitigates noise and wear problems.
- a drive mechanism for transmitting driving torque from the crankshaft to a camshaft of an internal combustion engine comprising concentric drive and driven members connectable respectively to the crankshaft and the camshaft, and a spring biased lost motion coupling acting between the drive and the drive members to permit a limited degree of change in the phase of the driven member relative to the drive member, the lost motion coupling acting when in use in such a manner that during the opening of each engine valve by the camshaft, the driven member rotates at substantially the same speed as the drive member and during the closing of each engine valve the driven member may be accelerated by the valve spring to lead the drive member and thereby reduce the duration of each engine valve event by altering the closing timing of each valve, characterised in that the lost motion coupling comprises a lever pivotably supported on one of the members and having a force transmitting surface that is biased by a spring to remain in contact at all times with a reaction surface on the other member, the position of the point of contact between the two surfaces being dependent upon the relative angular position
- the surface of the lever and the reaction surface with which it makes contact are profiled in such a manner that the surface of the lever rolls without slipping on the reaction surface. This avoids wear due to friction and reduces the lubrication requirements of the mechanism.
- the strength of the valve springs and the friction on the valve train determine the applied torque to effect the phase change and the rate of change of the phase during such torque reversal will also depend upon the moment of inertia of the drive mechanism.
- the amplitude of the phase change i.e. the extent to which the duration of the valve event is reduced, further depends on the time that the torque acts, in other words upon the engine speed.
- the valve springs and the moment of inertia are constant and the extent of variation will vary only and automatically with engine speed, assuming no change in friction. It is possible to apply a variable drag between the drive and driven members, for example by the use of a magnetic clutch, to reduce the phase change occurring at any given engine speed.
- a drive mechanism comprises a driven member 10 connected to the camshaft 12 of an engine and a drive member 14 driven through a belt 16 by the engine crankshaft.
- the drive member 14 is journalled about the camshaft 12 and can rotate relative to it.
- the coupling between the drive and driven members 14 and 10 is effected by means of pins 18 in the driven member 10 about which there are pivoted two levers 20 that are both biased to rotate in a clockwise direction as viewed in Figure 1 by helical springs 22.
- the pins 18 and levers 20 are located within a deep recess in the drive member 14 bounded by reaction surfaces 24 against which the levers 20 are urged by the springs 22.
- An electromagnetic clutch 30 is included to apply a controllable drag between the drive and driven members 14 and 10.
- a disk 32 is formed in close proximity to the drive member 14 and fixed for rotation with the camshaft 12 and an electromagnet 34 powered by a suitable control circuit 36 can apply a variable magnetic field to a thin film of magnetic fluid 38 disposed between the disk 32 and the drive member 14.
- the purpose of the clutch 30 is to apply a variable drag between the drive and driven members 14 and 10 to moderate the extent of phase change at any given engine speed.
- the illustrated embodiment incorporates a position sensor 40 that provides a position feedback signal to the control circuit 36 so that the phase change can be accurately closed loop controlled.
- both surface may be curved or the reaction surfaces alone may be curved.
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve Device For Special Equipments (AREA)
- Valve-Gear Or Valve Arrangements (AREA)
Description
Claims (5)
- A drive mechanism for transmitting driving torque from the crankshaft to a camshaft (12) of an internal combustion engine, comprising concentric drive and driven members (14,10) connectable respectively to the crankshaft and the camshaft (12), and a spring biased lost motion coupling acting between the drive and the driven members (14,10) to permit a limited degree of change in the phase of the driven member (10) relative to the drive member (14), the lost motion coupling acting when in use in such a manner that during the opening of each engine valve by the camshaft, the driven member (10) rotates at substantially the same speed as the drive member (14) and during the closing of each engine valve the driven member (10) may be accelerated by the valve spring to lead the drive member (14) and thereby reduce the duration of each engine valve event by altering the closing timing of each valve, characterised in that the lost motion coupling comprises a lever (20) pivotably supported on one of the members (14, 10) and having a force transmitting surface that is biased by a spring (22) to remain in contact at all times with a reaction surface (24) on the other member, the position of the point of contact between the two surfaces being dependent upon the relative angular position of the drive and driven members (14,10) and being operative to move progressively to vary the mechanical advantage of the lever (20) as the members rotate relative to one another under the action of the torque reversals on the camshaft.
- A drive mechanism as claimed in claim 1, wherein two levers (20) acting against two opposed reaction surfaces (24) are provided symmetrically about the axis of rotation of the drive mechanism.
- A drive mechanism as claimed in claim 1 or 2, wherein the surface of the, or each, lever (20) and the reaction surface (24) with which it makes contact are profiled in such a manner that the lever surface rolls without slipping on the reaction surface (24).
- A drive mechanism as claimed in any preceding claim, further comprising means (30) for applying a variable drag between the drive and driven members to moderate the extent of the phase change during torque reversal at any given engine speed.
- A drive mechanism as claimed in claim 4, wherein the means for applying a drag (30) includes a position sensor (40) for detecting the extent of phase change during torque reversal, to permit closed loop control of the drag.
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9400748A GB2285671A (en) | 1994-01-15 | 1994-01-15 | Variable valve timing mechanism |
GB9400748 | 1994-01-15 | ||
PCT/GB1994/002797 WO1995019493A1 (en) | 1994-01-15 | 1994-12-15 | Variable valve timing mechanism |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0739444A1 EP0739444A1 (en) | 1996-10-30 |
EP0739444B1 true EP0739444B1 (en) | 1998-06-17 |
Family
ID=10748875
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP95905179A Expired - Lifetime EP0739444B1 (en) | 1994-01-15 | 1994-12-15 | Variable valve timing mechanism |
Country Status (4)
Country | Link |
---|---|
EP (1) | EP0739444B1 (en) |
DE (1) | DE69411193T2 (en) |
GB (1) | GB2285671A (en) |
WO (1) | WO1995019493A1 (en) |
Families Citing this family (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102005024485A1 (en) * | 2005-05-27 | 2006-11-30 | Daimlerchrysler Ag | camshaft unit |
Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1992004532A1 (en) * | 1990-09-12 | 1992-03-19 | Ford Motor Company Limited | Internal combustion engine having variable event valve timing |
Family Cites Families (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB884434A (en) * | 1958-11-29 | 1961-12-13 | Bosch Gmbh Robert | Improvements in or relating to hydraulically adjustable rotary couplings |
DE3234640A1 (en) * | 1982-09-18 | 1984-03-22 | Volkswagenwerk Ag, 3180 Wolfsburg | Valve gear, in particular for an internal combustion engine |
DE4026480C2 (en) * | 1989-08-31 | 1998-07-23 | Volkswagen Ag | Camshaft, in particular for charge exchange valves of an internal combustion engine, with at least one swivel cam |
-
1994
- 1994-01-15 GB GB9400748A patent/GB2285671A/en not_active Withdrawn
- 1994-12-15 DE DE69411193T patent/DE69411193T2/en not_active Expired - Fee Related
- 1994-12-15 EP EP95905179A patent/EP0739444B1/en not_active Expired - Lifetime
- 1994-12-15 WO PCT/GB1994/002797 patent/WO1995019493A1/en active IP Right Grant
Patent Citations (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO1992004532A1 (en) * | 1990-09-12 | 1992-03-19 | Ford Motor Company Limited | Internal combustion engine having variable event valve timing |
Also Published As
Publication number | Publication date |
---|---|
GB2285671A (en) | 1995-07-19 |
EP0739444A1 (en) | 1996-10-30 |
DE69411193T2 (en) | 1999-03-11 |
GB9400748D0 (en) | 1994-03-16 |
DE69411193D1 (en) | 1998-07-23 |
WO1995019493A1 (en) | 1995-07-20 |
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