GB2202584A - Adjustable valve gear - Google Patents
Adjustable valve gear Download PDFInfo
- Publication number
- GB2202584A GB2202584A GB08806331A GB8806331A GB2202584A GB 2202584 A GB2202584 A GB 2202584A GB 08806331 A GB08806331 A GB 08806331A GB 8806331 A GB8806331 A GB 8806331A GB 2202584 A GB2202584 A GB 2202584A
- Authority
- GB
- United Kingdom
- Prior art keywords
- fulcrum
- valve
- transmission lever
- cams
- valve arrangement
- 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.)
- Granted
Links
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
- F01L13/0036—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 the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction
- F01L13/0047—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 the valves being driven by two or more cams with different shape, size or timing or a single cam profiled in axial and radial direction the movement of the valves resulting from the sum of the simultaneous actions of at least two cams, the cams being independently variable in phase in respect of each other
-
- 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
- F01L1/00—Valve-gear or valve arrangements, e.g. lift-valve gear
- F01L1/12—Transmitting gear between valve drive and valve
Landscapes
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Valve Device For Special Equipments (AREA)
Abstract
The valve 1 is operated by two cams 10,11 acting via a lever 21 having a fulcrum 23. Adjustment of the position of the fulcrum or the cams varies the lift and/or timing of the valve. The specification discloses many constructional variations of the lever and fulcrum arrangement. <IMAGE>
Description
Description of Invention "Improvements in or relating to valve arrangements"
THIS INVENTION relates to a valve arrangement and, more particularly, to the control of poppet valves as found in internal combustion engines.
The present invention aims to provide a valve arrangement which offers a means of achieving variation in lift, dwell and timing, together with the ability to extend the event of a valve in either direction or, if required, in both directions at the same time.
According to the invention, there is provided a valve arrangement comprising a linearly movable valve member, a pair of rotatable cams and means for converting rotary motion of both cams into linear movement of the valve member, the converting means comprising transmission lever means which extends transversely of the direction of movement of the valve member and through which the cams act on the valve member with both cams being permanently engaged with the transmission lever means and means for varying a fulcrum of the transmission lever means so as to adjust the relative effectiveness of the cams in order to vary a characteristic of the movement of the valve member.
In one form of the invention, the fulcrum adjusting means comprises a carrier which is interposed between the transmission lever means and the valve element and which carries fulcrum means, the carrier being movable transversely of the direction of movement of the valve member to position the fulcrum relative to the transmission lever means.
In the one form of the invention, the fulcrum means may be a roller extending transversely of the length of the transmission lever means or may be formed by a fulcrum lever means extending parallel to the transmission lever means and formed with a transverse projection engaging the transmission lever to define the fulcrum or may be constituted by a transversely extending integrally formed portion of the carrier.
The transmission lever means may comprise a single transmission lever upon which the two cams act at spaced apart locations along the length of the lever and, preferably, the transmission lever is pivotable about a fixed pivot, the fulcrum adjusting means defining a variable fulcrum at a variable distance from the fixed pivot.
The transmission lever means may alternatively comprise first and second transmission levers each pivotable about a respective fixed pivot point and acted upon by a respective one of the cams, the fulcrum adjusting means comprising means for defining respective variable fulcrums for the first and second levers at a fixed distance apart.
In another form of the invention, the fulcrum adjusting means comprises means for longitudinally shifting the transmission lever means relative to fixed fulcrum means.
The cams may act on the transmission lever means via respective reciprocable profile adjusting members held in contact with the cam profiles and constrained reciprocate parallel to the direction of movement of the valve member.
In order that the present invention may be more readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a diagrammatic, partly sectioned, front view of a first valve arrangement embodying the invention;
Figure 2 is a side view, partly in section, of the valve arrangement of Figure 1;
Figure 3 is a fragmentary plan view of a sliding lever forming part of a transmission lever assembly of the Figure 1 valve arrangement;
Figure 4 is a front view, partly in section, of a second valve arrangement embodying the present invention;
Figure 5 is a side view, partly in section, of the
Figure 4 valve arrangement;
Figure 6 is a partly sectioned side view of the
Figure 4 arrangement with parts omitted to illsutrate the mounting of a transmission lever assembly;;
Figure 7 is a diagrammatic front view, partly in section, of a third arrangement embodying the present invention;
Figure 8 is a side view, partly in section, of the
Figure 7 arrangement;
Figure 9 is a plan view of a floating lever of a transmission lever assembly of the Figure 7 embodiment;
Figure 10 is a diagrammatic front view, partly in section, of a fourth valve arrangment embodying the present invention;
Figure 11 is a side view, partly sectioned, of the
Figure 10 valve arrangement;
Figure 12 is a diagrammtic front view of a fifth valve arrangement embodying the present invention; and
Figure 13 is a side view of the Figure 12 embodiment.
Referring initially to Figures 1 to 3 of the accompanying drawings, a first valve arrangement embodying the present invention comprises a conventional poppet valve 1 having a head 2 and an elongate stem 3.
The poppet valve is of the type which is conventional as found in an internal combustion engine. The head of the poppet valve is intended to cooperate with the valve seat (not shown). The elongate stem 3 of the valve passes through a conventional valve guide 4 and the upper end of the stem 3 is received within a recess formed in the underside of a bucket 5. The bucket is slidably received within aperture 6 formed in part of a conventional cylinder head 7. The upper surface of the bucket 5 is provided with a surface plate 8.
A camshaft 9 for controlling the operation of the valve 1 comprises a pair of cams 10 and 11 rotatable with the camshaft. The cams have respective lobes 12 and 13 of different angular extent and are received in respective profile adjusters 14 and 15 constrained to reciprocate parallel to the stem 3 of the valve 1 upon rotation of the cams 10 and 11 with the camshaft 9. The profile adjusters have respective cylindrical heads 16 and 17 and pairs of bifurcated arms 18a, 18b and 19a, 19b forming a yoke in which the camshaft 9 is rotatable.
Disposed between the reciprocal profile adjusters 16 and 17, is a transmission lever assembly 20 composed of a transmission lever 21 and a slide bar 22 carrying a roller 23 extending transversely of the direction of movement of the slide bar.
The transmission lever 21 has a pair of cylindrical depressions in which the heads 16 and 17 of the profile adjusters 14 and 15 are respectively received and located. The roller 23 carried by the slide bar 22 defines a variable fulcrum for the transmission lever 21 which is shown in full lines in a central position and in phantom lines in two possible off-centre positions.
A valve spring (not shown) 'biasses the valve member 1 upwardly in Figure 1, so that the contact plate 8 on the valve bucket 5 engages the roller 23 and presses this upwardly into engagement with the underneath of trans, mission lever 21 which is thereby held in engagement with the profile adjusters 14 and 15.
As shown in Figure 3 the roller 23 is mounted on the slide bar 22 extending transversely across a slot 24 formed in the slide bar.
In operation of the described valve arrangement, the position of slide bar 22 may be adjusted by suitable means (not shown) to position the roller 23 at any desired location along the transmission lever 21, so as to vary the relative effectiveness of the cams 10 and 11 in transmitting movement to the valve member 1.
With the roller 23 in its illustrated central position, both cams 10 and 11 have equal effect upon the valve 1. If the roller 23 is re-positioned by moving slide bar 22 to the left, the effect of cam 11 will be progressively reduced until it disappears completley when roller 23 is positioned at its left hand limiting position 23a. At this point, the movement of the valve 1 is determined only by the cam 10. Similarly movement of the roller 23 into the right hand postion 23b progressively negates the effect of cam 10 until finally the movement of the valve 1 is determined only by a cam 11.
If the cams 10 and 11 are in phase but have different profiles as shown in Figure 2, then the effective cam profile acting on valve 1 can be varied between the extreme values represented by the profile of cam 10 and the profile of cam 11.
If cams 10 and 11 were of similar profile, but out of phase with one another, then adjusting the position of roller 23 enables the phase or timing of the valve to be advanced or retarded depending upon the direction of movement of the reciprocal bar 22.
If valve 1 is an inlet valve operated by cams 10 and 11, then a corresponding pair of exhaust cams may be mounted upon the same camshaft 9 and the single camshaft will be able to provide both inlet and outlet valve events without difficulty and can, moreover, apply a variable profile to either or both the inlet and exahust valves.
The lateral positioning of fulcrum roller 23 enables a stepless variation between one cam profile and the other, so that, if cam 1 were profiled in accordance with low speed engine demands and cam 2 profiled in accordance with high speed engine demands, suitable control of the slide bar 22 would enable optimum operation of the valve 1 at both low and high engine speeds and, indeed, at any intermediate engine speed.
Figures 4 to 6 illustrate a second valve arrangement embodying the present invention. The second embodiment is similar to the first embodiment in many respects and corresponding parts have the same reference numerals in the drawings.
In the second embodiment of the invention, the two cams 10 and 11 act on the valve 1 via a transmission lever assembly consisting of a pair of pivotally mounted transmission levers 30 and 31 pivotable about respective fixed pivot point 32 and 33 and engage respectively by the cams 10 and 11. The transmission lever assembly further comprises a fulcrum lever 34 mounted in a slot 35 of a slide bar 36 reciprocal transversely of the direction of movement of the valve 1. The fulcrum lever 34 has two upstanding lobes 37 and 38 which are engaged by the levers 30 and 31. and which define respective variable fulcrums for the two transmission levers. The fulcrum lever 34 is engaged with the valve bucket by way of a cylindrical rib 39 provided on the upper surface of the bucket 5.
Figure 6 illustrates upstanding flanges 40 and 41 on the cylinder head 7, which flanges are provided for mounting the transmission lever assembly.
In operation of the valve arrangement shown in
Figures 4 to 6, slide bar 36 is movable by suitable means (not shown) to adjust the fulcrums of the two transmission levers 30 and 31 to vary the effectiveness of the two cams 10 and 11 on the valve 1. With the fulcrum lever 34 in the position illustrated in Figure 4, the transmission lever 31 is free to pivot about its fixed pivot point 33 and therefore applies no force to the fulcrum lever 34 and hence has no action on the valve 1. On the other hand, the transmission lever 30 is received between the head 16 of the profile adjuster and the lobe 37 of the lever 34 and thus applies a force to the lever 34 in the direction of movement of the valve 1 and the eccentricity of cam 10 is converted into reciprocal movement of the valve 1.
By moving the slide bar 36 to the left in Figure 4, the cam 11 will progressively come into effect, while the effect of cam 10 will progressively decrease until in an extreme left hand position with the fulcrum defined by lobe 37 positioned beneath the axis of pivot 32, only the cam 11 will be effective in operating the valve 1.
It is noted that the lever 34 applies actuating force to the valve 1 along the axis of the valve stem 3, unlike the embodiment of Figures 1 to 3, where the line of application of the force to the valve 1 is displaced from the axis of the stem 3 as the slide bar 22 is displaced from the position shown in Figure 1.
As illustrated in Figure 5, the lobe of cam 11 extends through an angle of 1540, while the lobe of cam 0 10 has an angular extent of 110 Figures 7 to 9 illsutrate a third embodiment of the present invention, in which parts corresponding to parts in the first two embodiments are indicated by the same reference numerals.
In the third embodiment, the camshaft 9 carries a first cam 10 associated with a profile adjsuter 14 which has a head formed with a contact bar 45. The second cam 11 is of smaller extent axially of the camshaft 9 and is hollow ground to form a concave peripheral surface 46 in which is engaged a profile adjuster 47 having a semicircular cross-section with a flat base in contact with the upper surface of a transmission lever 48 which is pivotable about a fixed pivot 49.
The transmission lever assembly further comprises a fulcrum lever 50 which is movable transversely of the direction of movement of valve 1 and is positioned between the contact plate 45 and lever 48 on the one hand and a guide structure 51 on the valve bucket 5 on the other hand. The fulcrum lever 50 comprises a pair of rollers 52 and 53 defining respective fulcrums for the contact plate 45 and the transmission lever 48 and interconnected by a pair of side plates 54 and 55. The guide structure on the valve bucket comprises a pair of spaced apart rails 56 and 57 on which the fulcrum lever is slidably supported by horizontal flanges 58 and 59 of the side plates 54 and 55. An aperture 60 in the fulcrum lever provides clearance for movement of the transmission lever 48.
Figure 7 illustrates the fulcrum lever 50 in a position in which only cam 10 has any effect upon valve 1, since rollers 52 and 53 of lever 50 are in an extreme right hand position in which the movable fulcrum of transmission lever 48 as defined by roller 53 is substantially in line with the fixed pivot axis 49 and the lever 48 is thus free to move around the pivot 49, whereas the reciprocal movement of profile adjuster 14 is transmitted to the valve 1 through the roller 52 of lever 50.
Movement of the lever 50 to the left by suitable means (not shown) to the position indicated in phantom brings the cam 11 into effect in addition to cam 10 which is permanently effective via profile adjuster 14 and roller 52.
The fourth embodiment of the invention illustrated in Figures 10 and 11 of the drawings has components correspond to those of the earlier embodiments and these are indicated by the same reference numerals.
In the embodiment of Figures 10 and 11, the two cams 10 and 11 on camshaft 9 have different degrees of lift with the cam 11 having a greater lift than the cam 1. Each of the cam is associated with a corresponding reciprocable profile adjuster 60, 61, the profile adjuster 60 having a head 62 with a flat contact surface and the profile adjuster 61 having a head 63 with a cylindrical contact surface.
A transmission lever 64 is movable transversely of the direction of movement of the valve 1 and carries a roller 65 defining an adjustable fulcrum. The lever 64 is disposed between a rounded contact projection 66 on the upper surface of the valve bucket 5 and the heads of the two profile adjusters 60 and 61.
With the lever 64 in th eposition illustrated in
Figure 10, the lever 64 is free to pivot about the roller 65, so that cam 11 has no effect on valve 1. However, cam 1 acts on valve 1 via its head 62 which transmits movement through the roller 62 to the valve bucket. Arrow 67 indicates the line of action of a spring which may be provided to retain the lever 64 in contact with the profile adjuster 61.
As the lever 64 is moved to the left as indicated by the phantom position 65a of the roller 65, the effectiveness of cam 11 is progressively increased and added to the effect of cam 10, which is constant, to vary the operation of the valve 1.
Figures 12 and 13 illustrate a fifth embodiment of the invention, in which the cams 10 and 11 act on the valve 1 via respective profile adjusters 14 and 15.
In this embodiment, a transmission lever 70 is pivotally mounted at 71 on head 17 of profile adjuster 15 and a slide bar 72 having a roller 73 mounted in an aperture 74 of the slide bar 72 is positioned between the lever 70 and a contact projection 75 on the valve bucket 5. The slide bar 72 is movable transversely of the direction of movement of valve 1 to adjust the position of roller 73 which defines a variable fulcrum for the lever 70.
With the slide bar 72 in the position illustrated in Figure 12, both cams 10 and 11 are equally effective.
Movement of roller 73 to the right hand position shown in phantom allows the lever 70 to pivot about the pivot 71 and negates the action of cam 10. Movement of the roller 73 to the left hand position shown in phantom in Figure 12 negates the action of cam 11.
The above described embodiments of the invention do not require longitudinal movement of the camshaft 9.
However, it is envisaged that the camshaft 9 could be longitudinally movable in order to vary the fulcrum of the transmission lever assembly, thus obviating the need for the slide bar mechanism described in connection with the above embodiments.
The lateral repositioning of the variable fulcrum of the transmission lever assembly enables a stepless variation to be achieved between two extreme cam profiles, thus enabling the timing, duration, lift and dwell of the valve movement to be varied without undue complication or cost.
The mechanism to control the movement of the slide bar or the longitudinal movement of the camshaft 2 effect adjustment of the variable fulcrum of the trasnsmission lever means may be any suitable mechanical, hydraulic or electrical arrangement. For example, if one cam is associated with low speed and the other cam with high speed, the adjustment of the variable fulcrum could be effected by a simple direct mechanical link to the throttle actuating system.
Claims (14)
1. A valve arrangement comprising a linearly movable valve member, a pair of rotatable cams and means for converting rotary motion of both cams into linear movement of the valve member, the converting means comprising transmission lever means which extends transversely of the direction of movement of the valve member and through which the cams act on the valve member and means for varying a fulcrum of the transmission lever means so as to adjust the relative effectiveness of the cams in order to vary a characteristic of the movement of the valve member.
2. A valve arrangement according to claim 1, wherein the fulcrum adjusting means comprises a carrier which is interposed between the transmission lever means and the valve element and which carries fulcrum means, the carrier being movable transversely of the direction of movement of the valve member to position the fulcrum relative to the transmission lever means.
3. A valve arrangement according to claim 2, wherein the fulcrum means is a roller extending transversely of the length of the transmission lever means.
4. A valve arrangement according to claim 2, wherein the fulcrum means is formed by a fulcrum lever means extending parallel to the transmission lever means and formed with a transverse projection engaging the transmission lever to define the fulcrum.
5. A valve arrangement according to claim 2, wherein the fulcrum means is constitute by a transversely extending integrally formed portion of the carrier.
6. A valve arrangement according to any preceding claim, wherein the transmission lever means comprises a single transmission lever upon which the two cams act at spaced apart locations along the length of the lever.
7. A valve arrangement according to claim 6, wherein the transmission lever is pivotable about a fixed pivot, the fulcrum adjusting means defining a variable fulcrum at a variable distance from the fixed pivot.
8. A valve arrangement according to any one of calims 1 to 5, wherein the transmission lever means comprises first and second transmission levers each pivotable about a respective fixed pivot point and acted upon by a respective one of the cams, the fulcrum adjusting means comprising means for defining respective variable fulcrums for the first and second levers at a fixed distance apart.
9. A valve arrangement according to claim 1, wherein the fulcrum adjusting means comprises means for longitudinally shifting the transmission lever means relative to fixed fulcrum means.
10. A valve arrangement according to any preceding claim, wherein the cams act on the transmission lever means via respective reciprocable profile adjusting members held in contact with the cam profiles and constrained to reciprocate parallel to the direction of movement of the valve member.
11. A valve arrangement according to any preceding claim, wherein the cams have similar profiles which are displaced in phase from one another.
12. A valve arrangement according to any preceding claim, wherein the cams have a different profiles.
13. A valve arrangement substantially as hereinbefore described with reference to the accompanying drawings.
14. Any novel feature or combination of features described herein.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB878706331A GB8706331D0 (en) | 1987-03-17 | 1987-03-17 | Valves |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8806331D0 GB8806331D0 (en) | 1988-04-13 |
| GB2202584A true GB2202584A (en) | 1988-09-28 |
| GB2202584B GB2202584B (en) | 1991-04-03 |
Family
ID=10614101
Family Applications (2)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB878706331A Pending GB8706331D0 (en) | 1987-03-17 | 1987-03-17 | Valves |
| GB8806331A Expired - Fee Related GB2202584B (en) | 1987-03-17 | 1988-03-17 | Improvements in or relating to valve arrangements |
Family Applications Before (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB878706331A Pending GB8706331D0 (en) | 1987-03-17 | 1987-03-17 | Valves |
Country Status (1)
| Country | Link |
|---|---|
| GB (2) | GB8706331D0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5052350A (en) * | 1990-11-02 | 1991-10-01 | King Brian T | Device to combine the motions of two camlobes differentially phased |
-
1987
- 1987-03-17 GB GB878706331A patent/GB8706331D0/en active Pending
-
1988
- 1988-03-17 GB GB8806331A patent/GB2202584B/en not_active Expired - Fee Related
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5052350A (en) * | 1990-11-02 | 1991-10-01 | King Brian T | Device to combine the motions of two camlobes differentially phased |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8806331D0 (en) | 1988-04-13 |
| GB8706331D0 (en) | 1987-04-23 |
| GB2202584B (en) | 1991-04-03 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19930317 |