US20100077980A1 - Compression release mechanism - Google Patents
Compression release mechanism Download PDFInfo
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- US20100077980A1 US20100077980A1 US12/285,084 US28508408A US2010077980A1 US 20100077980 A1 US20100077980 A1 US 20100077980A1 US 28508408 A US28508408 A US 28508408A US 2010077980 A1 US2010077980 A1 US 2010077980A1
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- Prior art keywords
- trigger
- camshaft
- axis
- lobe
- compression release
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- 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.)
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Classifications
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- 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
- F01L13/08—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for decompression, e.g. during starting; for changing compression ratio
- F01L13/085—Modifications of valve-gear to facilitate reversing, braking, starting, changing compression ratio, or other specific operations for decompression, e.g. during starting; for changing compression ratio the valve-gear having an auxiliary cam protruding from the main cam profile
-
- 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
- F01L1/14—Tappets; Push rods
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T74/00—Machine element or mechanism
- Y10T74/21—Elements
- Y10T74/2101—Cams
- Y10T74/2102—Adjustable
Definitions
- This invention relates generally to compression release mechanisms and more particularly to compression release mechanisms preferably used in motorcycle engines.
- Compression release mechanisms have been used to reduce undesirable forces associated with the operation of an engine, such as forces resisting the starting of an internal combustion engine.
- Exemplary compression release mechanisms are described, for example, in U.S. Pat. Nos. 4,790,271; 4,615,312; and 4,453,507, which are incorporated by reference herein in their entirety.
- Known compression release mechanisms suffer from various problems.
- a loosely fitting ring is utilized with a decompression lobe mounted on the camshaft.
- the ring is held from rotating by two pins and a spring mounted on the camshaft.
- the ring will partially rotate until it is lifted onto one of the pins on the camshaft.
- the cam follower will ride up the decompression lobe, causing a valve to open and partially relieve cranking compression.
- the ring gets pulled out by rotational forces for normal engine operation.
- Another problem with the above referenced design relates to the robustness of the assembly.
- the design relies on the use of small pins to hold it in place during the decompression mode.
- One of skill in the art would appreciate that, at least with respect to internal combustion engines with high valve spring forces, the use of small pins would not be robust enough to handle the high spring force.
- FIG. 1 is an exploded assembly view of a compression release mechanism according to an embodiment of the present invention.
- FIG. 2 is a side view of the compression release mechanism of FIG. 1 according to an embodiment of the present invention.
- FIG. 3 is a side view of the compression release mechanism of FIG. 1 according to another embodiment of the present invention.
- FIG. 4 is a side view of the compression release mechanism of FIG. 1 according to another embodiment of the present invention.
- FIG. 5 is a side view of the compression release mechanism of FIG. 1 according to another embodiment of the present invention.
- FIG. 6 is a side view of a camshaft with the compression release mechanism of FIG. 1 in a disengagement position according to an embodiment of the present invention.
- FIG. 7 is a side view of the camshaft and compression release mechanism of FIG. 6 with the compression release mechanism in an engagement position according to an embodiment of the present invention.
- FIG. 8 is an exploded assembly view of a compression release mechanism usable with a front exhaust camshaft according to another embodiment of the present invention.
- FIG. 9 is an exploded assembly view of a compression release mechanism usable with a rear exhaust camshaft according to another embodiment of the present invention.
- FIG. 10 is a cross sectional view of a rear exhaust camshaft and a front exhaust camshaft with associated lifter assemblies and associated triggers according to an embodiment of the present invention.
- FIG. 11 is a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a front exhaust camshaft according to an embodiment of the present invention.
- FIG. 12 is a cross sectional view of the camshaft of FIG. 11 with the trigger of FIG. 11 in a disengagement position according to an embodiment of the present invention.
- FIG. 13 is a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a rear exhaust camshaft according to an embodiment of the present invention.
- FIG. 14 is a cross sectional view of the camshaft of FIG. 13 with the trigger of FIG. 13 in a disengagement position according to an embodiment of the present invention.
- FIG. 15 is a cross sectional view of the camshaft of FIG. 13 from the opposite side, including a cross sectional view of the trigger shown in FIG. 13 .
- FIG. 16 is a cross sectional view of the camshaft of FIG. 13 from the opposite side.
- FIG. 17 depicts the cross sectional view of FIG. 15 rotated partially about a spring axis.
- FIG. 18 depicts the cross sectional view of FIG. 16 rotated partially about a spring axis.
- FIG. 19 depicts the cross sectional view of FIG. 16 rotated partially about a spring axis.
- FIG. 20 depicts the cross sectional view of FIG. 16 rotated partially about a spring axis.
- FIG. 21 depicts the cross sectional view of FIG. 16 rotated partially about a spring axis and partially about a camshaft axis.
- FIG. 22 depicts a perspective view of a camshaft, a compression release mechanism, and a lifter assembly according to an embodiment of the present invention.
- FIG. 23 depicts the camshaft, compression release mechanism, and lifter assembly of FIG. 22 rotated partially about a spring axis and partially about a camshaft axis.
- FIG. 24 depicts a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a rear exhaust camshaft according to an embodiment of the present invention.
- FIG. 25 is a perspective view of the trigger shown in FIG. 24 .
- FIG. 26 is another perspective view of the trigger shown in FIG. 24 .
- FIG. 27 is a front end view of the trigger shown in FIG. 24 .
- FIG. 28 is a top view of the trigger shown in FIG. 24 .
- FIG. 29 is a top view of the trigger shown in FIG. 24 .
- FIG. 30 is a close up view of contact between the trigger shown in FIG. 24 and a lifter assembly, and depicts an optional cut out/recessed portion of a camshaft lobe proximate to a compression release lobe.
- FIG. 31 is a cross sectional view of a compression release mechanism according to another embodiment of the present invention.
- FIG. 32 is a perspective view of the compression release mechanism of FIG. 31 , with the trigger in a disengagement position according to an embodiment of the present invention.
- FIG. 33 is a side view of the trigger of the embodiment shown in FIG. 31 .
- FIG. 34 is a perspective view of the trigger shown in FIG. 33 .
- FIG. 35 is a side by side comparison of the trigger from the embodiment of FIG. 33 with the trigger from the embodiment of FIG. 24 .
- FIGS. 36 and 37 show the camshaft form the embodiment of FIG. 33 , with FIG. 37 being a cross section of FIG. 36 along line A-A.
- FIGS. 38 and 39 show the camshaft from the embodiment of FIG. 24 , with FIG. 39 being the cross section of FIG. 38 along line F-F.
- FIG. 40 depicts a side view of a compression release mechanism with a trigger in an engagement position according to an embodiment of the present invention.
- FIG. 41 depicts a side view of the compression release mechanism of FIG. 40 with the trigger in a disengagement position according to an embodiment of the present invention.
- FIG. 42 is a perspective view of the embodiment shown in FIG. 40 .
- FIG. 43 is a flowchart of a method of selectably releasing compression in an engine according to an embodiment of the present invention.
- various embodiments of the present invention are directed at a compression release mechanism for use in an internal combustion engine such as a V-twin motorcycle engine.
- Examples include original equipment manufacturer (OEM) applications and retrofit applications, such as use with Twin Cam® and Sportster® style engines.
- OEM original equipment manufacturer
- retrofit applications such as use with Twin Cam® and Sportster® style engines.
- One exemplary motorcycle engine is described in WO 2006/083350 (Aug. 10, 2006), which is incorporated by reference herein in its entirety. It should be appreciated, however, that one or more of these embodiments may also be used in other applications, such as automotive engines, all terrain vehicle (ATV) engines, personal watercraft and boat engines, snowmobile engines, commercial equipment engines, lawn and garden equipment engines, etc.
- ATV all terrain vehicle
- snowmobile engines commercial equipment engines
- lawn and garden equipment engines etc.
- the disclosed embodiments should not be construed as being limited solely to motorcycle engine applications.
- materials and manufacturing processes can be used for one or more components of the disclosed embodiments. Exemplar
- the compression release mechanisms shown include a ring 110 detachably positioned on a camshaft 210 .
- the ring 110 includes a counterweight 125 , an engagement surface 120 , and a compression release lobe 115 .
- the camshaft 210 preferably includes a flat 215 on which the ring 110 is slidably engaged, an engagement surface 220 which engages engagement surface 120 of ring 110 , and a pocket 225 which receives a spring 340 .
- a removable retaining collar 300 may be provided with or without a set screw for easy assembly/disassembly.
- the ring 110 is positioned on a camshaft 210 such that the ring 110 is held from rotating (relative to the camshaft 210 ) by preferably two flats 215 (though one flat, or more than two flats could be used) on the camshaft 210 .
- two positions will be discussed in detail below: (i) an “engagement position” in which a compression release lobe 115 is positioned so as to engage a valve assembly (e.g., by way of direct contact with a lifter assembly); and (ii) a “disengagement position” in which a compression release lobe 115 is positioned so as to avoid engagement with the valve assembly.
- the engagement position is shown, for example, in FIG. 7 .
- the disengagement position is shown, for example, in FIG. 6 .
- the ring 110 of the present embodiment is selectively slid (relative to the camshaft 210 ) between the engagement position and the disengagement position as discussed in greater detail below.
- Selective sliding of the ring 110 can be achieved by way of interplay between centripetal forces operating on counterweight 125 (when rotating) and spring forces operating on spring engagement surfaces of ring 110 /camshaft 210 (at all times).
- the spring 340 provides a relative force between the ring 110 and the camshaft 210 tending to cause sliding of the ring 110 into the engaged position and to hold the ring 110 therein.
- the centripetal forces acting on counterweight 125 similarly gradually increase. These centripetal forces tend to cause a sliding of ring 110 opposite the sliding caused by spring 340 .
- the force on ring 110 caused by centripetal forces acting on counterweight 125 exceeds the force caused by spring 340 .
- the ring 110 slides from the engagement position toward the disengagement position.
- the force caused by spring 340 again exceeds the forces caused by centripetal forces acting on counterweight 125 , and the ring 110 slides back toward the engagement position from the disengagement position. In this manner, the ring 110 is selectively slid between the engagement position and the disengagement position.
- ring 110 The operation of ring 110 relative to camshaft 210 can also be observed by reference to FIGS. 3-5 .
- the lifter follows the base circle, it catches a lobe 115 protruding from the ring 110 . This slides the ring 110 along the flat 215 on the cam lobe.
- the camshaft 210 continues to rotate, the lifter rides along the lobe 115 and pushes the spring loaded ring 110 down such that an engagement surface 120 of the ring 110 engages a corresponding engagement surface 220 of camshaft 210 . See, for example, contact point 310 in FIG. 5 where the lifter assembly contacts the lobe 115 .
- the lobe 115 forces the lifter up slightly at the lobe 115 , causing the exhaust valve to crack open during the compression stroke, relieving a certain amount of cylinder pressure. The exhaust valve then returns closed, allowing the engine to start with much less cranking compression.
- increased rotational speed generates enough rotational force to cause a counterweight 125 on the ring 110 to act against a spring 340 in a pocket 225 of camshaft 210 and stay in the disengaged position for normal engine operation.
- the compression release mechanisms shown include a camshaft 1060 rotatable about a camshaft axis 1065 , a trigger 1000 rotatable about a trigger axis 1015 that is substantially perpendicular to camshaft axis 1065 , and a spring 1040 positioned between the camshaft 1060 and the trigger 1000 (the spring preferably being aligned along a spring axis 1045 shown best in FIGS. 11 and 12 ).
- the axes 1015 and 1065 intersect.
- axes 1015 and 1065 may be offset in some applications.
- the camshaft 1060 includes a camshaft lobe 1070 with an obround shape relative to the camshaft axis 1065 , and a first spring engagement surface for engaging spring 1040 .
- the trigger 1000 preferably includes a compression release lobe 1030 formed at a first distal end of the trigger 1000 proximate to the camshaft lobe 1070 , a counterweight 1020 formed at a second distal end of the trigger 1000 , and a second spring engagement surface for engaging spring 1040 .
- the trigger 1000 may be rotatably coupled to the camshaft 1060 by a pin 1010 and associated nut 1050 or by other suitable fastener techniques.
- the compression release mechanism can be used in a variety of applications. Shown on the left of FIG. 10 is a trigger 1000 positioned with an associated a rear exhaust camshaft 1061 (a cross section thereof is depicted) that actuates a lifter assembly 1080 for the rear exhaust valve of a twin cylinder motorcycle engine. Shown on the right of FIG. 10 is a trigger 1000 positioned with an associated front exhaust camshaft 1062 (a cross section thereof is depicted) that actuates a lifter assembly 1090 for the front exhaust valve of the twin cylinder motorcycle engine.
- the camshafts 1061 , 1062 shown rotate in a clockwise direction about associated camshaft axes.
- the triggers 1000 rotate about trigger axes 1015 substantially perpendicular to the associated camshaft axes 1065 , and as part of the complete compression release mechanisms that rotate about the camshaft axes 1065 in response to rotation of the associated camshafts 1061 , 1062 .
- the compression release mechanism described above is configured to selectively contact a lifter assembly 1080 , 1090 with a compression release lobe 1030 of trigger 1000 .
- the compression release lobe 1030 of a given trigger 1000 is selectively rotated into and out of a lifter roller path of travel so as to selectively contact an associated lifter assembly 1080 , 1090 .
- FIGS. 11 and 13 show an exemplary trigger 1000 and camshaft 1060 with a trigger 1000 oriented in an engagement position.
- FIGS. 12 and 14 show the same exemplary trigger 1000 and camshaft 1060 of FIGS. 11 and 13 respectively with the trigger 1000 oriented in a disengagement position.
- the trigger 1000 selectively rotates between the engagement position of FIGS. 11 and 13 and the disengagement position of FIGS. 12 and 14 so as to selectively engage the associated lifter assembly 1080 , 1090 .
- Selective rotation of the trigger 1000 can be achieved by way of interplay between centripetal forces operating on counterweight 1020 (when rotating) and spring forces operating on spring engagement surfaces of trigger 1000 /camshaft 1060 (at all times).
- the spring 1040 provides a relative force between the trigger 1000 and the camshaft 1060 tending to cause rotation of the trigger 1000 into the engaged position and to hold the trigger 1000 therein.
- the spring 1040 tends to cause clockwise rotation of trigger 1000 about pin 1010 based on the spring 1040 's application of a relative force between camshaft 1060 and trigger 1000 .
- centripetal forces acting on counterweight 1020 similarly gradually increase. These centripetal forces tend to cause a rotation of trigger 1000 opposite the rotation caused by spring 1040 (and, in some applications, opposite the rotation caused by gravity with or without assistance by spring 1040 ). Referring again to FIG. 15 , the centripetal forces acting on counterweight 1020 will tend to cause counterclockwise rotation of trigger 1000 about pin 1010 . At some known rotational velocity (and at rotational velocities above this known value) that depends on spring 140 parameters and trigger 1000 parameters, the torque on trigger 1000 caused by centripetal forces acting on counterweight 1020 exceeds the torque caused by spring forces from spring 1040 .
- the trigger 1000 rotates from the engagement position toward the disengagement position (i.e., from the orientation shown in FIG. 11 to the orientation shown in FIG. 12 ).
- the rotational velocity falls below the known value (e.g., when the engine is turned off)
- the torque caused by spring forces from spring 1040 again exceeds the torque caused by centripetal forces acting on counterweight 1020 , and the trigger 1000 rotates back toward the engagement position from the disengagement position (i.e., from the orientation shown in FIG. 12 to the orientation shown in FIG. 11 ).
- the trigger 1000 is selectively rotated between the engagement position and the disengagement position.
- the compression release lobe 1030 of trigger 1000 and/or the camshaft lobe 1070 of camshaft 1060 are configured to have peripheries that enhance operation of the compression release mechanism.
- the compression release lobe 1030 may include a lifter roller engagement surface (i.e., the surface that comes into contact with lifter assembly 1080 , 1090 ) arced between a first end and a second end, both the first end and the second end being at about a same fixed distance from the trigger axis 1015 .
- the lifter roller engagement surface arcs about the camshaft axis 1065 . See, for example, FIG. 24 .
- the compression release lobe 1030 of trigger 1000 may also include beveled edges extending along at least a portion of the lifter roller engagement surface.
- the compression release lobe 1030 of trigger 1000 at least includes beveled edges on those edges extending between the first end and the second end of the engagement surface described above.
- the camshaft lobe 1070 includes a recess that receives the compression release lobe 1030 when the trigger 1000 is in the engagement position.
- the recess may have a sufficient volume to permit direct contact between the roller of the lifter assembly 1080 and the lifter roller engagement surface of compression release lobe 1030 .
- the recess may have a volume that only allows for part of the roller of the lifter assembly 1080 to directly contact the lifter roller engagement surface of compression release lobe 1030 .
- the compression release lobe 1030 of trigger 1000 protrudes from the camshaft base circle when in the engaged position, the compression release lobe 1030 contacts the lifter assembly 1080 , 1090 traveling the camshaft base circle.
- Contact between the compression release lobe 1030 and the lifter assembly 1080 , 1090 causes the lifter assembly 1080 , 1090 to crack the associated valve open.
- a lifter assembly 1080 , 1090 for an exhaust valve may be contacted during the compression stroke to relieve a certain amount of cranking compression and thereby allow the engine to start easier.
- the trigger 1000 is held in the engaged position at RPMs below a known value due to the use of a spring 1040 positioned between the trigger 1000 and the camshaft 1060 (or due to the presence of gravity, with or without assistance by spring 1040 ).
- a compression spring 1040 is utilized with a known spring constant. Certain parameters of the compression spring 1040 , such as the spring constant, can be adjusted for a given application at hand so as to correspondingly adjust the RPM at which a given trigger 1000 will rotate from an engaged position to a disengagement position and vice versa.
- certain parameters of the trigger 1000 can be adjusted for a given application at hand so as to correspondingly adjust the RPM at which the trigger 1000 will rotate from an engaged position to a disengagement position and vice versa.
- an optional through hole 1025 may be provided in counterweight 1020 to reduce the associated mass or the center of gravity thereof. Through hole 1025 may also be used for manufacturing purposes.
- a compression release mechanism may be provided in camshaft 10600 (which includes camshaft lobe 10700 ) which actuates a lifter assembly 10800 .
- the compression release mechanism shown includes a trigger 10000 with compression release lobe 10300 and counterweight 10200 , a pin 10100 about which the trigger 10000 rotates, and a spring 10400 positioned between the camshaft 10600 and the trigger 10000 .
- Operation of the compression release mechanism shown in FIGS. 31-34 is substantially similar to operation of the compression release mechanism(s) shown in FIGS. 8-30 .
- the compression release mechanism of FIGS. 31-34 differs from the compression release mechanism(s) of FIGS. 8-30 , however, in several respects.
- the compression release mechanism of FIGS. 31-34 has been modified to accommodate a different engine family. As shown, for example, by comparing the camshaft 10600 of FIGS. 36 & 37 with the camshaft 1060 of FIGS. 38 , 39 , different lifter assembly orientations are accommodated by the profiles of the camshafts 1060 and 10600 .
- Camshaft differences include, for example, a change in diameter of about 0.150′′, shallower counterweight pockets in camshaft 10600 due to smaller trigger counterweight 10200 , simplification and enlargement of the angled pockets in camshaft 10600 to speed machining processes, and reorientation of the trigger counterweight 10200 to between camshaft lobes.
- the trigger 10000 includes a shorter nose part than trigger 1000 to accommodate the smaller camshaft diameter.
- counterweight 10200 is shortened and given a modified shape to provide for lifter clearance due to the presence of two lifter assemblies operating on the same camshaft 10600 .
- the counterweight through hole in trigger 10000 is decreased in diameter and moved so as to maximize the mass and movement of the counterweight 10200 .
- machining around the nose of lobe 10300 was simplified and/or eliminated to reduce machining time. Other variations may also exist as would be readily understood by those of skill in the art after reading this disclosure.
- FIGS. 40-42 A compression release mechanism and associated camshaft 20600 according to yet another embodiment of the present invention is shown in FIGS. 40-42 .
- the compression release mechanism includes a ring 20000 which rotates about a pin 20100 operably connected to camshaft 20600 .
- the ring 20000 includes a decompression lobe 20300 and a counterweight 20200 .
- a spring 20400 such as a coil spring, is operably attached to pin 20100 and counterweight 20200 .
- Operation of the compression release mechanism shown in FIGS. 40-42 is analogous in at least some respects to operation of the compression release mechanisms shown in FIGS. 8-39 .
- the spring 20400 applies a relative force between ring 20000 and camshaft 20600 so as to hold the release in an engagement position ( FIG. 40 ).
- centripetal forces acting on counterweight 20200 overcome the force of the spring 20400 thereby causing ring 20000 to rotate from the engagement position shown in FIGS. 40 and 42 to the disengagement position shown in FIG. 41 .
- a lifter assembly (not shown) traveling along camshaft lobe 20700 will thus contact lobe 20300 when ring 20000 is in the engagement position, and will avoid contact with lobe 20300 when ring 20000 is in the disengagement position.
- camshaft lobe 20700 of camshaft 20600 may include a periphery so as to accommodate lobe 20300 of ring 20000 .
- a region 2 of the camshaft lobe periphery is recessed relative to region 1 of the camshaft lobe periphery.
- Region 1 includes a width corresponding to the engagement portion of lobe 20300 as shown, for example, in FIGS. 40 and 42 .
- Other configurations are also contemplated.
- step 5000 a compression release mechanism is provided with an internal combustion engine.
- step 5000 may comprise providing the compression release mechanism of the embodiments shown in FIGS. 8-30 with an OEM twin cylinder motorcycle engine or retrofitting a twin cylinder motorcycle engine to include such a compression release mechanism.
- a trigger of the compression release mechanism is held in an engagement position, e.g., by way of a spring.
- step 5010 is performed at least while the engine is turned off and while the engine is operating at RPMs below a known value.
- step 5020 the trigger is rotated about a camshaft axis at a rotational velocity.
- Step 5020 may be initiated, for example, by a starter motor or kick starter of a motorcycle engine which causes the engine to turn over at a relatively low RPM. While operating at the relatively low RPM (e.g., at camshaft RPMs below about three hundred and fifty RPMs or crankshaft RPMs below about seven hundred RPMs), the trigger remains held in the engagement position and a lifter assembly in the engine comes into contact in step 5030 with a compression release lobe of the trigger.
- “contact” in step 5030 refers to the periodic contact once per revolution of the compression release lobe with the lifter assembly. Contact in step 5030 with the lifter assembly causes an associated valve to open slightly, thereby releasing pressure in cylinder and allowing the engine to start more easily.
- step 5040 can be performed by rotating a trigger from the orientation shown in FIG. 11 to the orientation shown in FIG. 12 , or from the orientation shown in FIG. 13 to the orientation shown in FIG. 14 .
- a profile of the trigger e.g., of the compression release lobe 1030 shown in FIGS. 25-30
- the lifter assembly preferably contacts in step 5050 only the camshaft lobe and not any portion of the trigger.
- the trigger may be positioned within the camshaft in the disengagement position such that a leading surface is at or below a leading surface of an associated camshaft lobe.
- a leading surface of the trigger may project beyond a leading surface of an associated camshaft lobe provided the trigger be positioned wholly outside the lifter assembly path of travel.
- step 5060 When the rotational velocity of the camshaft falls below the known value, such as during engine shutdown, the trigger is rotated in step 5060 from the disengagement position toward the engagement position.
- step 5060 can be performed by rotating a trigger from the orientation shown in FIG. 12 to the orientation shown in FIG. 11 , or from the orientation shown in FIG. 14 to the orientation shown in FIG. 13 .
- the present invention can be used in a wide variety of applications. It should be appreciated that various parameters, such as spring constants, counterweight mass, counterweight center of mass, etc. may be adjusted for a particular application at hand.
- one or more of the aforementioned embodiments can be used so as to operate in an engagement position at RPMs below an RPM in a range of about six hundred and twenty five crankshaft RPMs to about seven hundred and twenty five crankshaft RPMs, or about half that for camshaft RPMs. More preferably, one or more of the aforementioned embodiments can be used so as to operate in an engagement position at RPMs below about seven hundred crankshaft RPMs or about three hundred and fifty camshaft RPMs. Other possibilities are also contemplated.
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Abstract
Description
- This invention relates generally to compression release mechanisms and more particularly to compression release mechanisms preferably used in motorcycle engines.
- Compression release mechanisms have been used to reduce undesirable forces associated with the operation of an engine, such as forces resisting the starting of an internal combustion engine. Exemplary compression release mechanisms are described, for example, in U.S. Pat. Nos. 4,790,271; 4,615,312; and 4,453,507, which are incorporated by reference herein in their entirety. Known compression release mechanisms, however, suffer from various problems.
- In one exemplary design, a loosely fitting ring is utilized with a decompression lobe mounted on the camshaft. The ring is held from rotating by two pins and a spring mounted on the camshaft. At starting speeds, the ring will partially rotate until it is lifted onto one of the pins on the camshaft. At this point, the cam follower will ride up the decompression lobe, causing a valve to open and partially relieve cranking compression. After startup the ring gets pulled out by rotational forces for normal engine operation.
- One problem with the above referenced design relates to the loose fit of the ring. In particular, because the ring fits loosely on the camshaft, the ring tends to be very unsteady at low and rough idling speeds of some internal combustion engines. The unsteadiness, in turn, can cause erratic engagement in a running internal combustion engine. One of skill in the art would appreciate the undesirableness of such erratic engagement.
- Another problem with the above referenced design relates to the robustness of the assembly. In particular, the design relies on the use of small pins to hold it in place during the decompression mode. One of skill in the art would appreciate that, at least with respect to internal combustion engines with high valve spring forces, the use of small pins would not be robust enough to handle the high spring force.
- A need thus exists for an improved compression release mechanism that addresses one or more of the above referenced problems, or other problems relating to known compression release mechanisms.
-
FIG. 1 is an exploded assembly view of a compression release mechanism according to an embodiment of the present invention. -
FIG. 2 is a side view of the compression release mechanism ofFIG. 1 according to an embodiment of the present invention. -
FIG. 3 is a side view of the compression release mechanism ofFIG. 1 according to another embodiment of the present invention. -
FIG. 4 is a side view of the compression release mechanism ofFIG. 1 according to another embodiment of the present invention. -
FIG. 5 is a side view of the compression release mechanism ofFIG. 1 according to another embodiment of the present invention. -
FIG. 6 is a side view of a camshaft with the compression release mechanism ofFIG. 1 in a disengagement position according to an embodiment of the present invention. -
FIG. 7 is a side view of the camshaft and compression release mechanism ofFIG. 6 with the compression release mechanism in an engagement position according to an embodiment of the present invention. -
FIG. 8 is an exploded assembly view of a compression release mechanism usable with a front exhaust camshaft according to another embodiment of the present invention. -
FIG. 9 is an exploded assembly view of a compression release mechanism usable with a rear exhaust camshaft according to another embodiment of the present invention. -
FIG. 10 is a cross sectional view of a rear exhaust camshaft and a front exhaust camshaft with associated lifter assemblies and associated triggers according to an embodiment of the present invention. -
FIG. 11 is a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a front exhaust camshaft according to an embodiment of the present invention. -
FIG. 12 is a cross sectional view of the camshaft ofFIG. 11 with the trigger ofFIG. 11 in a disengagement position according to an embodiment of the present invention. -
FIG. 13 is a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a rear exhaust camshaft according to an embodiment of the present invention. -
FIG. 14 is a cross sectional view of the camshaft ofFIG. 13 with the trigger ofFIG. 13 in a disengagement position according to an embodiment of the present invention. -
FIG. 15 is a cross sectional view of the camshaft ofFIG. 13 from the opposite side, including a cross sectional view of the trigger shown inFIG. 13 . -
FIG. 16 is a cross sectional view of the camshaft ofFIG. 13 from the opposite side. -
FIG. 17 depicts the cross sectional view ofFIG. 15 rotated partially about a spring axis. -
FIG. 18 depicts the cross sectional view ofFIG. 16 rotated partially about a spring axis. -
FIG. 19 depicts the cross sectional view ofFIG. 16 rotated partially about a spring axis. -
FIG. 20 depicts the cross sectional view ofFIG. 16 rotated partially about a spring axis. -
FIG. 21 depicts the cross sectional view ofFIG. 16 rotated partially about a spring axis and partially about a camshaft axis. -
FIG. 22 depicts a perspective view of a camshaft, a compression release mechanism, and a lifter assembly according to an embodiment of the present invention. -
FIG. 23 depicts the camshaft, compression release mechanism, and lifter assembly ofFIG. 22 rotated partially about a spring axis and partially about a camshaft axis. -
FIG. 24 depicts a cross sectional view of a camshaft with a trigger in an engagement position as may be used with a rear exhaust camshaft according to an embodiment of the present invention. -
FIG. 25 is a perspective view of the trigger shown inFIG. 24 . -
FIG. 26 is another perspective view of the trigger shown inFIG. 24 . -
FIG. 27 is a front end view of the trigger shown inFIG. 24 . -
FIG. 28 is a top view of the trigger shown inFIG. 24 . -
FIG. 29 is a top view of the trigger shown inFIG. 24 . -
FIG. 30 is a close up view of contact between the trigger shown inFIG. 24 and a lifter assembly, and depicts an optional cut out/recessed portion of a camshaft lobe proximate to a compression release lobe. -
FIG. 31 is a cross sectional view of a compression release mechanism according to another embodiment of the present invention. -
FIG. 32 is a perspective view of the compression release mechanism ofFIG. 31 , with the trigger in a disengagement position according to an embodiment of the present invention. -
FIG. 33 is a side view of the trigger of the embodiment shown inFIG. 31 . -
FIG. 34 is a perspective view of the trigger shown inFIG. 33 . -
FIG. 35 is a side by side comparison of the trigger from the embodiment ofFIG. 33 with the trigger from the embodiment ofFIG. 24 . -
FIGS. 36 and 37 show the camshaft form the embodiment ofFIG. 33 , withFIG. 37 being a cross section ofFIG. 36 along line A-A. -
FIGS. 38 and 39 show the camshaft from the embodiment ofFIG. 24 , withFIG. 39 being the cross section ofFIG. 38 along line F-F. -
FIG. 40 depicts a side view of a compression release mechanism with a trigger in an engagement position according to an embodiment of the present invention. -
FIG. 41 depicts a side view of the compression release mechanism ofFIG. 40 with the trigger in a disengagement position according to an embodiment of the present invention. -
FIG. 42 is a perspective view of the embodiment shown inFIG. 40 . -
FIG. 43 is a flowchart of a method of selectably releasing compression in an engine according to an embodiment of the present invention. - As illustrated in the discussion below, various embodiments of the present invention are directed at a compression release mechanism for use in an internal combustion engine such as a V-twin motorcycle engine. Examples include original equipment manufacturer (OEM) applications and retrofit applications, such as use with Twin Cam® and Sportster® style engines. One exemplary motorcycle engine is described in WO 2006/083350 (Aug. 10, 2006), which is incorporated by reference herein in its entirety. It should be appreciated, however, that one or more of these embodiments may also be used in other applications, such as automotive engines, all terrain vehicle (ATV) engines, personal watercraft and boat engines, snowmobile engines, commercial equipment engines, lawn and garden equipment engines, etc. Thus, the disclosed embodiments should not be construed as being limited solely to motorcycle engine applications. Moreover, one of skill in the art would appreciate that various materials and manufacturing processes can be used for one or more components of the disclosed embodiments. Exemplary materials include billet aluminum and steel (e.g., stainless steel).
- Turning now to the embodiments of
FIGS. 1-7 , the compression release mechanisms shown include aring 110 detachably positioned on acamshaft 210. Thering 110 includes acounterweight 125, anengagement surface 120, and acompression release lobe 115. Thecamshaft 210 preferably includes a flat 215 on which thering 110 is slidably engaged, anengagement surface 220 which engagesengagement surface 120 ofring 110, and apocket 225 which receives aspring 340. In some applications, aremovable retaining collar 300 may be provided with or without a set screw for easy assembly/disassembly. - In at least one mode of operation, the
ring 110 is positioned on acamshaft 210 such that thering 110 is held from rotating (relative to the camshaft 210) by preferably two flats 215 (though one flat, or more than two flats could be used) on thecamshaft 210. For discussion purposes, two positions will be discussed in detail below: (i) an “engagement position” in which acompression release lobe 115 is positioned so as to engage a valve assembly (e.g., by way of direct contact with a lifter assembly); and (ii) a “disengagement position” in which acompression release lobe 115 is positioned so as to avoid engagement with the valve assembly. The engagement position is shown, for example, inFIG. 7 . The disengagement position is shown, for example, inFIG. 6 . Thering 110 of the present embodiment is selectively slid (relative to the camshaft 210) between the engagement position and the disengagement position as discussed in greater detail below. - Selective sliding of the
ring 110 can be achieved by way of interplay between centripetal forces operating on counterweight 125 (when rotating) and spring forces operating on spring engagement surfaces ofring 110/camshaft 210 (at all times). In particular, at all RPMs thespring 340 provides a relative force between thering 110 and thecamshaft 210 tending to cause sliding of thering 110 into the engaged position and to hold thering 110 therein. However, as the rotational velocity of thecamshaft 210 gradually increases, the centripetal forces acting oncounterweight 125 similarly gradually increase. These centripetal forces tend to cause a sliding ofring 110 opposite the sliding caused byspring 340. At some known rotational velocity (and at rotational velocities above this known value) that depends onspring 340 parameters and ring 110 parameters, the force onring 110 caused by centripetal forces acting oncounterweight 125 exceeds the force caused byspring 340. Thus, thering 110 slides from the engagement position toward the disengagement position. When the rotational velocity falls below the known value (e.g., when the engine is turned off), the force caused byspring 340 again exceeds the forces caused by centripetal forces acting oncounterweight 125, and thering 110 slides back toward the engagement position from the disengagement position. In this manner, thering 110 is selectively slid between the engagement position and the disengagement position. - The operation of
ring 110 relative to camshaft 210 can also be observed by reference toFIGS. 3-5 . As the lifter follows the base circle, it catches alobe 115 protruding from thering 110. This slides thering 110 along the flat 215 on the cam lobe. As thecamshaft 210 continues to rotate, the lifter rides along thelobe 115 and pushes the spring loadedring 110 down such that anengagement surface 120 of thering 110 engages acorresponding engagement surface 220 ofcamshaft 210. See, for example,contact point 310 inFIG. 5 where the lifter assembly contacts thelobe 115. Now locked in place, thelobe 115 forces the lifter up slightly at thelobe 115, causing the exhaust valve to crack open during the compression stroke, relieving a certain amount of cylinder pressure. The exhaust valve then returns closed, allowing the engine to start with much less cranking compression. When the engine starts, increased rotational speed generates enough rotational force to cause acounterweight 125 on thering 110 to act against aspring 340 in apocket 225 ofcamshaft 210 and stay in the disengaged position for normal engine operation. - Turning next to the embodiments of
FIGS. 8-30 , the compression release mechanisms shown include acamshaft 1060 rotatable about acamshaft axis 1065, atrigger 1000 rotatable about atrigger axis 1015 that is substantially perpendicular tocamshaft axis 1065, and aspring 1040 positioned between thecamshaft 1060 and the trigger 1000 (the spring preferably being aligned along aspring axis 1045 shown best inFIGS. 11 and 12 ). In the embodiment shown inFIGS. 11 and 12 , theaxes axes camshaft 1060 includes acamshaft lobe 1070 with an obround shape relative to thecamshaft axis 1065, and a first spring engagement surface for engagingspring 1040. Thetrigger 1000 preferably includes acompression release lobe 1030 formed at a first distal end of thetrigger 1000 proximate to thecamshaft lobe 1070, acounterweight 1020 formed at a second distal end of thetrigger 1000, and a second spring engagement surface for engagingspring 1040. Thetrigger 1000 may be rotatably coupled to thecamshaft 1060 by apin 1010 and associatednut 1050 or by other suitable fastener techniques. - As shown for example in
FIG. 10 , the compression release mechanism can be used in a variety of applications. Shown on the left ofFIG. 10 is atrigger 1000 positioned with an associated a rear exhaust camshaft 1061 (a cross section thereof is depicted) that actuates alifter assembly 1080 for the rear exhaust valve of a twin cylinder motorcycle engine. Shown on the right ofFIG. 10 is atrigger 1000 positioned with an associated front exhaust camshaft 1062 (a cross section thereof is depicted) that actuates alifter assembly 1090 for the front exhaust valve of the twin cylinder motorcycle engine. Thecamshafts triggers 1000 rotate abouttrigger axes 1015 substantially perpendicular to the associatedcamshaft axes 1065, and as part of the complete compression release mechanisms that rotate about thecamshaft axes 1065 in response to rotation of the associatedcamshafts - In at least one mode of operation, the compression release mechanism described above is configured to selectively contact a
lifter assembly compression release lobe 1030 oftrigger 1000. Namely, thecompression release lobe 1030 of a giventrigger 1000 is selectively rotated into and out of a lifter roller path of travel so as to selectively contact an associatedlifter assembly compression release lobe 1030 is positioned so as to engage a valve assembly (e.g., by way of direct contact with alifter assembly 1080, 1090); and (ii) a “disengagement position” in which acompression release lobe 1030 is positioned so as to avoid engagement with the valve assembly.FIGS. 11 and 13 show anexemplary trigger 1000 andcamshaft 1060 with atrigger 1000 oriented in an engagement position.FIGS. 12 and 14 show the sameexemplary trigger 1000 andcamshaft 1060 ofFIGS. 11 and 13 respectively with thetrigger 1000 oriented in a disengagement position. Thetrigger 1000 selectively rotates between the engagement position ofFIGS. 11 and 13 and the disengagement position ofFIGS. 12 and 14 so as to selectively engage the associatedlifter assembly - Selective rotation of the
trigger 1000 can be achieved by way of interplay between centripetal forces operating on counterweight 1020 (when rotating) and spring forces operating on spring engagement surfaces oftrigger 1000/camshaft 1060 (at all times). In particular, at all RPMs thespring 1040 provides a relative force between thetrigger 1000 and thecamshaft 1060 tending to cause rotation of thetrigger 1000 into the engaged position and to hold thetrigger 1000 therein. For example, referring toFIG. 15 , thespring 1040 tends to cause clockwise rotation oftrigger 1000 aboutpin 1010 based on thespring 1040's application of a relative force betweencamshaft 1060 andtrigger 1000. However, as the rotational velocity of thecamshaft 1060 gradually increases, the centripetal forces acting oncounterweight 1020 similarly gradually increase. These centripetal forces tend to cause a rotation oftrigger 1000 opposite the rotation caused by spring 1040 (and, in some applications, opposite the rotation caused by gravity with or without assistance by spring 1040). Referring again toFIG. 15 , the centripetal forces acting oncounterweight 1020 will tend to cause counterclockwise rotation oftrigger 1000 aboutpin 1010. At some known rotational velocity (and at rotational velocities above this known value) that depends on spring 140 parameters and trigger 1000 parameters, the torque ontrigger 1000 caused by centripetal forces acting oncounterweight 1020 exceeds the torque caused by spring forces fromspring 1040. Thus, thetrigger 1000 rotates from the engagement position toward the disengagement position (i.e., from the orientation shown inFIG. 11 to the orientation shown inFIG. 12 ). When the rotational velocity falls below the known value (e.g., when the engine is turned off), the torque caused by spring forces fromspring 1040 again exceeds the torque caused by centripetal forces acting oncounterweight 1020, and thetrigger 1000 rotates back toward the engagement position from the disengagement position (i.e., from the orientation shown inFIG. 12 to the orientation shown inFIG. 11 ). In this manner, thetrigger 1000 is selectively rotated between the engagement position and the disengagement position. - Preferably, the
compression release lobe 1030 oftrigger 1000 and/or thecamshaft lobe 1070 ofcamshaft 1060 are configured to have peripheries that enhance operation of the compression release mechanism. For example, as shown inFIGS. 25-30 , thecompression release lobe 1030 may include a lifter roller engagement surface (i.e., the surface that comes into contact withlifter assembly 1080, 1090) arced between a first end and a second end, both the first end and the second end being at about a same fixed distance from thetrigger axis 1015. Preferably, when thetrigger 1000 is positioned in the engagement position, the lifter roller engagement surface arcs about thecamshaft axis 1065. See, for example,FIG. 24 . Such an orientation allows thelifter assembly FIG. 30 Thecompression release lobe 1030 oftrigger 1000 may also include beveled edges extending along at least a portion of the lifter roller engagement surface. Preferably, thecompression release lobe 1030 oftrigger 1000 at least includes beveled edges on those edges extending between the first end and the second end of the engagement surface described above. - According to an embodiment of the present invention, the
camshaft lobe 1070 includes a recess that receives thecompression release lobe 1030 when thetrigger 1000 is in the engagement position. As shown, for example, inFIG. 30 , the recess may have a sufficient volume to permit direct contact between the roller of thelifter assembly 1080 and the lifter roller engagement surface ofcompression release lobe 1030. As shown inFIGS. 16 and 30 , however, the recess may have a volume that only allows for part of the roller of thelifter assembly 1080 to directly contact the lifter roller engagement surface ofcompression release lobe 1030. Stated another way, when thelifter assembly 1080 is in contact with thetrigger 1000, part of the lifter roller surface is in contact with the lifter roller engagement surface and another part of the lifter roller surface is free floating. This configuration allows the base circle to remain intact for normal engine operation, and thetrigger 1000 to contact the lifter assembly during low engine speeds as described in greater detail below. - Because the
compression release lobe 1030 oftrigger 1000 protrudes from the camshaft base circle when in the engaged position, thecompression release lobe 1030 contacts thelifter assembly compression release lobe 1030 and thelifter assembly lifter assembly lifter assembly compression release lobe 1030 and thelifter assembly lifter assembly camshaft lobe 1070. - It should be appreciated that the
trigger 1000 is held in the engaged position at RPMs below a known value due to the use of aspring 1040 positioned between thetrigger 1000 and the camshaft 1060 (or due to the presence of gravity, with or without assistance by spring 1040). Preferably, acompression spring 1040 is utilized with a known spring constant. Certain parameters of thecompression spring 1040, such as the spring constant, can be adjusted for a given application at hand so as to correspondingly adjust the RPM at which a giventrigger 1000 will rotate from an engaged position to a disengagement position and vice versa. Similarly, certain parameters of the trigger 1000 (e.g., the amount of mass and distribution thereof in counterweight 1020) can be adjusted for a given application at hand so as to correspondingly adjust the RPM at which thetrigger 1000 will rotate from an engaged position to a disengagement position and vice versa. By way of example, an optional throughhole 1025 may be provided incounterweight 1020 to reduce the associated mass or the center of gravity thereof. Throughhole 1025 may also be used for manufacturing purposes. - The modifiability of the compression release mechanism (and/or parameters thereof) described above is exemplified by the embodiments shown in
FIGS. 31-34 , comparisonFIG. 35 , and/or camshaftFIGS. 36-39 . As shown, for example, inFIGS. 31-34 , a compression release mechanism may be provided in camshaft 10600 (which includes camshaft lobe 10700) which actuates alifter assembly 10800. The compression release mechanism shown includes atrigger 10000 withcompression release lobe 10300 andcounterweight 10200, apin 10100 about which thetrigger 10000 rotates, and aspring 10400 positioned between thecamshaft 10600 and thetrigger 10000. Operation of the compression release mechanism shown inFIGS. 31-34 is substantially similar to operation of the compression release mechanism(s) shown inFIGS. 8-30 . - The compression release mechanism of
FIGS. 31-34 differs from the compression release mechanism(s) ofFIGS. 8-30 , however, in several respects. In particular, the compression release mechanism ofFIGS. 31-34 has been modified to accommodate a different engine family. As shown, for example, by comparing thecamshaft 10600 ofFIGS. 36 & 37 with thecamshaft 1060 ofFIGS. 38 , 39, different lifter assembly orientations are accommodated by the profiles of thecamshafts camshaft 10600 due tosmaller trigger counterweight 10200, simplification and enlargement of the angled pockets incamshaft 10600 to speed machining processes, and reorientation of thetrigger counterweight 10200 to between camshaft lobes. -
Corresponding trigger FIG. 35 . As shown, thetrigger 10000 includes a shorter nose part thantrigger 1000 to accommodate the smaller camshaft diameter. Further,counterweight 10200 is shortened and given a modified shape to provide for lifter clearance due to the presence of two lifter assemblies operating on thesame camshaft 10600. Further, the counterweight through hole intrigger 10000 is decreased in diameter and moved so as to maximize the mass and movement of thecounterweight 10200. As shown inFIGS. 33 and 34 , machining around the nose oflobe 10300 was simplified and/or eliminated to reduce machining time. Other variations may also exist as would be readily understood by those of skill in the art after reading this disclosure. - A compression release mechanism and associated
camshaft 20600 according to yet another embodiment of the present invention is shown inFIGS. 40-42 . The compression release mechanism includes aring 20000 which rotates about apin 20100 operably connected tocamshaft 20600. Thering 20000 includes adecompression lobe 20300 and acounterweight 20200. Aspring 20400, such as a coil spring, is operably attached to pin 20100 andcounterweight 20200. - Operation of the compression release mechanism shown in
FIGS. 40-42 is analogous in at least some respects to operation of the compression release mechanisms shown inFIGS. 8-39 . In particular, at low RPMs (e.g., during engine cranking), thespring 20400 applies a relative force betweenring 20000 andcamshaft 20600 so as to hold the release in an engagement position (FIG. 40 ). Once thecamshaft 20600 achieves or exceeds a certain rotational velocity, centripetal forces acting oncounterweight 20200 overcome the force of thespring 20400 thereby causingring 20000 to rotate from the engagement position shown inFIGS. 40 and 42 to the disengagement position shown inFIG. 41 . A lifter assembly (not shown) traveling alongcamshaft lobe 20700 will thus contactlobe 20300 whenring 20000 is in the engagement position, and will avoid contact withlobe 20300 whenring 20000 is in the disengagement position. - It should be appreciated that
camshaft lobe 20700 ofcamshaft 20600 may include a periphery so as to accommodatelobe 20300 ofring 20000. As shown, for example, inFIG. 41 , a region 2 of the camshaft lobe periphery is recessed relative to region 1 of the camshaft lobe periphery. Region 1 includes a width corresponding to the engagement portion oflobe 20300 as shown, for example, inFIGS. 40 and 42 . Other configurations are also contemplated. - Referring now to the flowchart of
FIG. 43 , a method of selectably releasing compression in an engine is shown. Instep 5000, a compression release mechanism is provided with an internal combustion engine. For example,step 5000 may comprise providing the compression release mechanism of the embodiments shown inFIGS. 8-30 with an OEM twin cylinder motorcycle engine or retrofitting a twin cylinder motorcycle engine to include such a compression release mechanism. Instep 5010, a trigger of the compression release mechanism is held in an engagement position, e.g., by way of a spring. Preferably step 5010 is performed at least while the engine is turned off and while the engine is operating at RPMs below a known value. - In
step 5020, the trigger is rotated about a camshaft axis at a rotational velocity.Step 5020 may be initiated, for example, by a starter motor or kick starter of a motorcycle engine which causes the engine to turn over at a relatively low RPM. While operating at the relatively low RPM (e.g., at camshaft RPMs below about three hundred and fifty RPMs or crankshaft RPMs below about seven hundred RPMs), the trigger remains held in the engagement position and a lifter assembly in the engine comes into contact instep 5030 with a compression release lobe of the trigger. It should be appreciated that “contact” instep 5030 refers to the periodic contact once per revolution of the compression release lobe with the lifter assembly. Contact instep 5030 with the lifter assembly causes an associated valve to open slightly, thereby releasing pressure in cylinder and allowing the engine to start more easily. - Once the rotational velocity of the crankshaft achieves a known value (e.g., at about engine idle or slightly below engine idle), the trigger is rotated about a trigger axis in
step 5040 from the engagement position toward a disengagement position. By way of example,step 5040 can be performed by rotating a trigger from the orientation shown inFIG. 11 to the orientation shown inFIG. 12 , or from the orientation shown inFIG. 13 to the orientation shown inFIG. 14 . In order to reduce the possibility of the trigger being partially engaged when the trigger is in transition (e.g., from an engagement position to a disengagement position or vice versa), a profile of the trigger (e.g., of thecompression release lobe 1030 shown inFIGS. 25-30 ) can be designed to include an arced surface and/or beveled edges. - While the trigger is oriented in the disengagement position, the lifter assembly preferably contacts in
step 5050 only the camshaft lobe and not any portion of the trigger. To facilitate this functionality, the trigger may be positioned within the camshaft in the disengagement position such that a leading surface is at or below a leading surface of an associated camshaft lobe. Alternatively, a leading surface of the trigger may project beyond a leading surface of an associated camshaft lobe provided the trigger be positioned wholly outside the lifter assembly path of travel. - When the rotational velocity of the camshaft falls below the known value, such as during engine shutdown, the trigger is rotated in
step 5060 from the disengagement position toward the engagement position. By way of example,step 5060 can be performed by rotating a trigger from the orientation shown inFIG. 12 to the orientation shown inFIG. 11 , or from the orientation shown inFIG. 14 to the orientation shown inFIG. 13 . - As illustrated by the embodiments above, the present invention can be used in a wide variety of applications. It should be appreciated that various parameters, such as spring constants, counterweight mass, counterweight center of mass, etc. may be adjusted for a particular application at hand. By way of example, one or more of the aforementioned embodiments can be used so as to operate in an engagement position at RPMs below an RPM in a range of about six hundred and twenty five crankshaft RPMs to about seven hundred and twenty five crankshaft RPMs, or about half that for camshaft RPMs. More preferably, one or more of the aforementioned embodiments can be used so as to operate in an engagement position at RPMs below about seven hundred crankshaft RPMs or about three hundred and fifty camshaft RPMs. Other possibilities are also contemplated.
- The foregoing description of various embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated.
Claims (23)
Priority Applications (3)
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US12/285,084 US7699035B1 (en) | 2008-09-29 | 2008-09-29 | Compression release mechanism |
PCT/US2009/058577 WO2010037010A2 (en) | 2008-09-29 | 2009-09-28 | Compression release mechanism |
EP09816980.8A EP2331793B1 (en) | 2008-09-29 | 2009-09-28 | Compression release mechanism |
Applications Claiming Priority (1)
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US12/285,084 US7699035B1 (en) | 2008-09-29 | 2008-09-29 | Compression release mechanism |
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US20100077980A1 true US20100077980A1 (en) | 2010-04-01 |
US7699035B1 US7699035B1 (en) | 2010-04-20 |
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US12/285,084 Active US7699035B1 (en) | 2008-09-29 | 2008-09-29 | Compression release mechanism |
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US (1) | US7699035B1 (en) |
EP (1) | EP2331793B1 (en) |
WO (1) | WO2010037010A2 (en) |
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JP2015148156A (en) * | 2014-02-05 | 2015-08-20 | スズキ株式会社 | Decompression device for outboard engine |
CN105673215A (en) * | 2016-03-02 | 2016-06-15 | 重庆亘富软件开发有限公司 | Stopping method for engine reverse positioning pressure reduction |
USD885439S1 (en) * | 2017-02-17 | 2020-05-26 | Eaton Corporation | Engine valve lifter having anti-rotation plug |
WO2022118287A1 (en) * | 2020-12-03 | 2022-06-09 | Jacobs Vehicle Systems, Inc. | Rotating actuator system for controlling valve actuation in an internal combustion engine |
US11591939B2 (en) | 2021-02-24 | 2023-02-28 | Yamaha Hatsudoki Kabushiki Kaisha | Compression release mechanism and internal combustion engine including the same |
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JP5027739B2 (en) * | 2008-06-10 | 2012-09-19 | 川崎重工業株式会社 | Decompression mechanism |
JP6226787B2 (en) * | 2014-03-19 | 2017-11-08 | 本田技研工業株式会社 | Internal combustion engine with decompression mechanism |
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Also Published As
Publication number | Publication date |
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US7699035B1 (en) | 2010-04-20 |
EP2331793A2 (en) | 2011-06-15 |
WO2010037010A3 (en) | 2010-07-01 |
WO2010037010A4 (en) | 2010-08-19 |
WO2010037010A2 (en) | 2010-04-01 |
EP2331793B1 (en) | 2015-08-26 |
EP2331793A4 (en) | 2012-10-03 |
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