COMBUSTION ENGINE

BACKGROUND

[0001] The present invention relates generally to the field of internal combustion engines. In particular, the present invention relates to compression release systems of internal combustion engines.

SUMMARY

[0002] One embodiment of the invention relates to an internal combustion engine including an engine block including a first cylinder and a second cylinder arranged in a V- twin configuration. The first cylinder includes a first cylinder head including a first intake valve and a first exhaust valve. The second cylinder includes a second cylinder head including a second intake valve and a second exhaust valve. A first piston is positioned within the first cylinder and configured to reciprocate within the first cylinder. A second piston is positioned within the second cylinder and configured to reciprocate with the second cylinder. The engine includes a crankshaft driven by the first piston and the second piston and configured to rotate about a crankshaft axis, a first intake pushrod, a first exhaust pushrod, a second intake pushrod, a second exhaust pushrod, and a camshaft driven by the crankshaft via a timing gear. The camshaft includes a first intake cam configured to engage the first intake pushrod to open and close the first intake valve, a second intake cam configured to engage the second intake pushrod to open and close the second intake valve, a first exhaust cam configured to engage the first exhaust pushrod to open and close the first exhaust valve, a second exhaust cam configured to engage the second exhaust pushrod to open and close the second exhaust valve, a movable first compression release member comprising a first tab, and a movable second compression release member comprising a second tab. In a first position, the first tab is adjacent the first intake cam to engage the first intake pushrod and the second tab is adjacent the second exhaust cam to engage the second exhaust pushrod. In a second position, the first tab is spaced apart from the first intake cam to not engage the first intake pushrod and the second tab is spaced apart from the second exhaust cam to not engage the second exhaust pushrod. [0003] Another embodiment of the invention relates to a mechanical compression release system including a cylinder head including an intake valve and an exhaust valve and a camshaft. The camshaft includes an intake cam configured to engage with an intake pushrod to open and close the intake valve, an exhaust cam configured to engage with an exhaust pushrod to open and close the exhaust valve, and a movable compression release member comprising a tab. In a first position, the tab is adjacent to the intake cam to engage the intake pushrod and in a second position the tab is rotated away from the intake cam to disengage the intake pushrod.

[0004] Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The disclosure will become more fully understood from the following detailed description, taken in conjunction with the accompanying figures.

[0006] FIG. 1 is a perspective view of an internal combustion engine, according to an exemplary embodiment.

[0007] FIG. 2 is a perspective view from below of the engine of FIG. 1, according to an exemplary embodiment.

[0008] FIG. 3 is a schematic view of an internal combustion engine, according to an exemplary embodiment.

[0009] FIG. 4 is a perspective view of a mechanical compression release system of the engine of FIG. 1, according to an exemplary embodiment.

[0010] FIG. 5 is a side view of the mechanical compression release system of FIG. 4 in an engaged position, according to an exemplary embodiment.

[0011] FIG. 5 A is a side view of the mechanical compression release system of FIG. 4 in an engaged position with the first cylinder tappets shown, according to an exemplary embodiment. [0012] FIG. 5B is a side view of the mechanical compression release system of FIG. 4 in an engaged position with the second cylinder tappets shown, according to an exemplary embodiment.

[0013] FIG. 6 is a side view of the mechanical compression release system of FIG. 5 in a disengaged position, according to an exemplary embodiment.

[0014] FIG. 6A is a side view of the mechanical compression release system of FIG. 5 in a disengaged position with the first cylinder tappets shown, according to an exemplary embodiment.

[0015] FIG. 6B is a side view of the mechanical compression release system of FIG. 5 in a disengaged position with the second cylinder tappets shown, according to an exemplary embodiment.

[0016] FIG. 7 is a detailed view of the mechanical compression release system in the engaged position with a first cylinder tappet shown, according to an exemplary

embodiment.

DETAILED DESCRIPTION

[0017] Before turning to the figures, which illustrate the exemplary embodiments in detail, it should be understood that the application is not limited to the details or

methodology set forth in the description or illustrated in the figures. It should also be understood that the terminology is for the purpose of description only and should not be regarded as limiting.

[0018] Typical compression release systems use a compression release mechanism on only the exhaust side of the engine. It is desirable to provide a cost-effective way of accomplishing a user-friendly engine starting process and restricting the compression release mechanism to only the exhaust side can cause the machine, manufacture, and assembly of the mechanism to be costly. In particular, with engines of two or more cylinders, it may be beneficial to provide a compression release mechanism that is amenable to use with both the exhaust and intake tappets and valves to save a manufacturer assembly time and money. [0019] Referring to FIGS. 1-2, an internal combustion engine 100 is shown according to an exemplary embodiment. The internal combustion engine 100 includes an engine block 105 having two cylinders 110 and 112, two cylinder heads 125 and 127, two pistons, and a crankshaft 104. Each piston reciprocates in a cylinder along a cylinder axis to drive the crankshaft 104. The crankshaft 104 rotates about a crankshaft axis 107. The crankshaft 104 is positioned in part within a sump or crankcase cover 116. The engine 100 also includes a fuel system for supplying an air-fuel mixture to the cylinder (e.g., a carburetor, an electronic fuel injection system, a fuel direct injection system, etc.), a camshaft 130 for actuating intake and exhaust valves in the cylinder heads, a muffler, a flywheel, and a blower fan. The engine 100 includes a blower housing 113 configured to direct cooling air over the engine block 105 and other components of the engine. The blower fan pulls air into the blower housing 113 through an air inlet 111. The cylinder and cylinder axis may be oriented horizontally (i.e., a horizontal cylinder engine), vertically (i.e., a vertical cylinder engine), or at an angle (i.e., a slanted engine). The engine may include one cylinder or two or more cylinders. The internal combustion engine 100 may be used in outdoor power equipment, standby generators, portable jobsite equipment, or other appropriate uses.

Outdoor power equipment includes lawn mowers, riding tractors, snow throwers, pressure washers, portable generators, tillers, log splitters, zero-turn radius mowers, walk-behind mowers, riding mowers, industrial vehicles such as forklifts, utility vehicles, etc. Outdoor power equipment may, for example, use an internal combustion engine to drive an implement, such as a rotary blade of a lawn mower, a pump of a pressure washer, the auger a snow thrower, the alternator of a generator, and/or a drivetrain of the outdoor power equipment. Portable jobsite equipment includes portable light towers, mobile industrial heaters, and portable light stands.

[0020] Referring to FIG. 3, an internal combustion engine 100 including a mechanical compression release system 102 is shown according to an exemplary embodiment. The engine 100 is shown to include an engine block 105 having a first cylinder 110, a piston 115, a cylinder head 125, a camshaft 130, and a crankshaft 104. The piston 115

reciprocates in the first cylinder 110 to drive the crankshaft 104. As illustrated in FIG. 3, the engine 100 includes two cylinders arranged in a V-twin configuration. In other embodiments, the engine includes a single cylinder. In other embodiments, the engine includes two or more cylinders that can be arranged in different configurations (e.g., inline, horizontally opposed, etc.). In some embodiments, the engine 100 is vertically shafted, while in other embodiments, the engine is horizontally shafted.

[0021] The piston 115 is coupled to a crankshaft 104 with a connecting rod 135 to convert translation of the piston 115 to rotation of the crankshaft 104. The engine 100 includes a camshaft 130 driven by a geared connection between a cam gear 145 and a timing gear coupled to the crankshaft 104. The camshaft 130 rotates about a camshaft axis 132 (shown in FIG. 4). The engine 100 includes pushrods 140 including tappets or cam followers 155 configured to engage the cams 150 as the camshaft 130 rotates. In some embodiments, the pushrods 140 can engage the cams 150 without use of the tappets 155. The cams 150 are positioned at varying angular positions on the camshaft 130 such that the tappets 155 engaged with the cams 150 are varying distances away from the camshaft 130 at a singular point in time. The cams 150 rotate with the rotation of the camshaft 130 such that the tappets 155 move between relatively nearer and further distances from the camshaft 130 during the combustion processes. The tappets 155 drive push rods 140 to rotate

corresponding rocker arms to, in turn, operate intake and exhaust valves that direct fuel and air flow through the combustion chamber, where combustion processes interact with the piston 115. The first cylinder 110 includes a first intake port 165 in which the first intake valve 160 is positioned and a first exhaust port 175 in which the first exhaust valve 170 is positioned. Valve seats 142, 144 are press fit to the first cylinder 110 around an aperture (e.g., opening) to each of the first intake port 165 and the first exhaust port 175.

[0022] As shown in FIG. 3, a second cylinder 112 is included. The second cylinder 112 includes a second intake port 195 in which a second intake valve 190 is positioned and a second exhaust port 185 in which a second exhaust valve 180 is positioned. Valve seats 122, 124 are press fit to the cylinder 112 around an aperture (e.g., opening) to each of the second intake port 195 and the second exhaust port 185.

[0023] Referring now to FIGS. 4-5B, the cams 150 include a first intake cam 152, a second intake cam 154, a first exhaust cam 156, and a second exhaust cam 158. The tappets 155 include a first intake tappet 162 engaging with the first intake cam 152, a second intake tappet 164 engaging with the second intake cam 154, a first exhaust tappet 166 engaging with the first exhaust cam 156, and a second exhaust tappet 168 engaging with the second exhaust cam 158. The tappets 155 engage the corresponding cams 150 to open and close corresponding intake and exhaust valves on each of the cylinders 110, 112.

[0024] Each of the tappets 155 moves between an open position and a closed position. In an open position, each of the tappets 155 are configured to rotate individual rocker arms to open valves in each cylinder 110, 112. In a closed position, each of the tappets 155 are configured to rotate individual rocker arms to allow valves to close in each cylinder 110, 112.

[0025] Accordingly, the first intake tappet 162 is configured to rotate the first intake rocker arm 182 to open and close the first intake valve 160. The second intake tappet 164 is configured to rotate the second intake rocker arm 194 to open and close the second intake valve 190. The first exhaust tappet 166 is configured to rotate the first exhaust rocker arm 184 to open and close the first exhaust valve 170. Finally, the second exhaust tappet 168 is configured to rotate the second exhaust rocker arm 192 to open and close the second exhaust valve 180.

[0026] As shown in FIG. 4, a mechanical compression release system 102 is included with the engine 100. According to an exemplary embodiment, the mechanical compression release system 102 includes a camshaft 130 with cams 150, tappets 155, a first compression release member 104, and a second compression release member 106. The first and second compression release members 104, 106 are configured to allow a release of pressure within the respective cylinders 110, 112 during a starting process of the engine 100. This release of pressure allows a user to more easily start the engine 100.

[0027] The first and second compression release members 104, 106 move between an engaged position and a disengaged position. In the engaged position, the first and second compression release members 104, 106 are configured to each lift one of the tappets 155 slightly to, in turn, open either an intake or exhaust valve in each of the cylinders 110, 112 to release pressure within the cylinders 110, 112. In an exemplary embodiment, the engaged position is achieved during engine starting speeds (approximately 0 RPM-800

RPM). As the engine speed increases, the centrifugal force of the camshaft 130 increases and forces the first and second compression release members 104, 106 to rotate away from the engaged position and into the disengaged position. In the disengaged position, the first and second compression release members 104, 106 do not lift the tappets 155. As such, in the disengaged position, the tappets 155 engage with the cams 150 as during normal combustion processes of the engine 100.

[0028] When the engine 100 is slowed or stopped, the centrifugal forces of the camshaft 130 decrease and the first and second compression release members 104, 106 are configured to return to the engaged position, as shown in FIG. 3. As such, the first and second compression release members 104, 106 are each biased to the engaged position by a biasing member 138 (e.g., torsion spring, clock spring, clip). The biasing member 138 is attached (e.g., linked, coupled, fastened) to a pin 139 (e.g., rod, fastener) attached and extending through the cam shaft 130 and through aperture 137 of the first compression release member 104 on each side of the cam shaft 130. The pin 139 maintains the position of the aperture 137 of member 104 in substantially the same position along the cam shaft 130 during engine operation, while the first compression release member 104 rotates about the pin 139 moving the first tab 1 14 away from the first intake cam 152 when above engine starting speeds. As such, the spring constant of the biasing member 138 can be selected so as to achieve a rotation of the first compression release member 104 at an optimal time during the engine operation (e.g., approximately above 800 RPM). In other embodiments, the first compression release member 104 is otherwise biased to the engaged position. In some embodiments, the second compression release member 106 additionally uses the biasing member 138 and pin 139 arrangement. In other embodiments, the second compression release member 106 is biased using other types of biasing members (e.g., torsion spring, clock spring, clip).

[0029] Referring to FIGS. 5-5B, the first and second compression release members 104, 106 are shown in the engaged position. As illustrated, the first compression release member 104 is positioned proximate the first intake cam 152. In other embodiments, the first compression release member 104 can be positioned proximate any other cam so as to engage a tappet to open a corresponding valve for compression release.

[0030] The first compression release member 104 includes a first tab 114 configured to extend above the first intake cam 152 by a first distance 134 in the engaged position.

Referring to FIG. 7, the first compressions release member 104 further includes a base 131 (e.g., counterweight) and one or more legs 133 (e.g., side walls). The base 131 and legs 133 form a rectangular shape surrounding the camshaft 130. In other embodiments, the member 104 is otherwise shaped. The first tab 114 is positioned on the opposite side of the camshaft 130 from the base 131. As such, the first tab 114 is positioned such that during a starting process of the engine 100 (e.g., engine speeds up to 800 revolutions per minute (RPM)), the first tab 114 contacts the first intake tappet 162 as shown in FIG. 5A. The base 131 is configured to act as a counterweight such that when the engine 100 exceeds engine starting speeds (e.g., greater than 800 RPM), the tab 1 14 is rotated away from the first intake cam 152, while the base 131 rotates toward the first intake cam 152 as shown in FIGS. 6-6B.

[0031] The second compression release member 106 includes a second tab 116 extending above the second exhaust cam 158 by a second distance 136 in the engaged position. The second compression release member 106 is positioned proximate the second exhaust cam 158. In other embodiments, the second compression release member 106 can be positioned proximate any other cam so as to engage a tappet to open a corresponding valve for compression release. The tappets 155 are not shown in FIG. 5 for purposes of clarity.

[0032] Referring to FIG. 5 A, the first intake tappet 162 and first exhaust tappet 166 are shown, while the second intake tappet 164 and the second exhaust tappet 168 are omitted for sake of clarity. According to an exemplary embodiment and as shown in more detail in FIG. 7, in the engaged position, the first tab 114 of the first compression release member 104 lifts the first intake tappet 162 away from the first intake cam 152 by the first distance 134 to open the first intake valve 160. Referring back to FIG. 5 A, the first exhaust tappet 166 is engaged with the first exhaust cam 156, while the first intake tappet 162 is engaged with the first tab 114. When engine speeds exceed engine starting speeds, the first tab 114 is configured to rotate away from the first intake tappet 162 and the first intake tappet 162 will engage with the first intake cam 152 at that moment to proceed with normal operation of the first intake valve 160 during the combustion processes of the engine 100.

[0033] Referring to FIG. 5B, the second intake tappet 164 and the second exhaust tappet 168 are shown, while the first intake tappet 162 and the first exhaust tappet 166 are omitted for sake of clarity. According to an exemplary embodiment, in the engaged position, the second compression release member 106 lifts the second exhaust tappet 168 away from the second exhaust cam 158 by a second distance 136 to open the second exhaust valve 180. As is shown, the second intake tappet 164 is engaged with the second intake cam 154, while the second exhaust tappet 168 is engaged with the second tab 116. When engine speeds exceed engine starting speeds, the second tab 116 is configured to rotate away from the second exhaust tappet 168 and the second exhaust tappet 168 will engage with the second exhaust cam 158 at that moment to proceed with normal operation of the second exhaust valve 180 during the combustion processes of the engine 100.

[0034] Referring to FIGS. 6-6B, the first and second compression release members 104, 106 are shown in the disengaged position. The first tab 114 of the first compression release member 104 rotates away from the first intake cam 152 and the second tab 116 of the second compression release member 106 rotates away from the second exhaust cam 158. As the first and second tabs 114, 116 move away from the respective cams 152, 158, the first and second compression release members 104, 106 move into a disengaged position.

[0035] Referring to FIG. 6 A, the first intake tappet 162 and the first exhaust tappet 166 are shown, while the second intake tappet 164 and the second exhaust tappet 168 are omitted for sake of clarity. According to an exemplary embodiment, the first compression release member 104 is rotated to a disengaged position such that the first tab 114 is not contacting (e.g., lifting) the first intake tappet 162 away from the first intake cam 152. The first intake tappet 162 contacts the first intake cam 152 and normal operation of the first intake valve 160 occurs with the combustion processes of the engine 100.

[0036] Referring to FIG. 6B, the second intake tappet 164 and the second exhaust tappet 168 are shown, while the first intake tappet 162 and the first exhaust tappet 166 are omitted for sake of clarity. According to an exemplary embodiment, the second compression release member 106 is rotated to a disengaged position such that the second tab 116 is not contacting (e.g., lifting) the second exhaust tappet 168 away from the second exhaust cam 158. The second exhaust tappet 168 contacts the second exhaust cam 158 and normal operation of the second exhaust valve 180 occurs with the combustion processes of the engine 100.

[0037] In other contemplated embodiments, the engine 100 includes only a single cylinder (e.g., first cylinder 110) and a single compression release member (e.g., the first

compression release member 104). In this embodiment, the first compression release member 104 is positioned proximate the first intake cam 152. In other contemplated embodiments, the first compression release member 104 can be otherwise positioned, such as proximate the first exhaust cam 154. [0038] The construction and arrangement of the apparatus, systems and methods as shown in the various exemplary embodiments are illustrative only. Although only a few

embodiments have been described in detail in this disclosure, many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.). For example, some elements shown as integrally formed may be constructed from multiple parts or elements, the position of elements may be reversed or otherwise varied and the nature or number of discrete elements or positions may be altered or varied. Accordingly, all such modifications are intended to be included within the scope of the present disclosure. The order or sequence of any process or method steps may be varied or re-sequenced according to alternative embodiments. Other substitutions, modifications, changes, and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present disclosure.

[0039] Although the figures may show or the description may provide a specific order of method steps, the order of the steps may differ from what is depicted. Also two or more steps may be performed concurrently or with partial concurrence. Such variation will depend on various factors, including software and hardware systems chosen and on designer choice. All such variations are within the scope of the disclosure. Likewise, software implementations could be accomplished with standard programming techniques with rule based logic and other logic to accomplish the various connection steps, processing steps, comparison steps and decision steps.