CA2972991A1 - Internal combustion engine - Google Patents

Abstract

An internal combustion engine has a crankcase, a cylinder block connected to the crankcase, the cylinder block defining at least one cylinder, at least one piston disposed in the at least one cylinder, a crankshaft disposed at least in part in the crankcase and operatively connected to the at least one piston, and a counterweight operatively connected to and driven by the crankshaft. The crankshaft rotates in a first direction about a crankshaft axis. The counterweight rotates in a second direction opposite the first direction about a counterweight axis. The counterweight axis and the crankshaft axis are coaxial. A marine outboard engine having the internal combustion engine assembly is also disclosed.

Description

INTERNAL COMBUSTION ENGINE
CROSS-REFERENCE
[0001] The present application claims priority to United States Provisional Patent Application =
No. 62/381,699, filed August 31, 2016.
FIELD OF TECHNOLOGY

[0002] The present technology relates to internal combustion engines, and more specifically to internal combustion engine balancing.
BACKGROUND

[0003] It is common to provide, for each cylinder of an internal combustion engine, a counterweight formed by the crankshaft opposite the crank pin in order to balance the translation of the piston and connecting rod. However, while the rotation of such a counterweight may balance at least a portion of the translation mass, it can create additional forces in a direction perpendicular to the direction of translation that result in noise, harshness and vibration (NVH).

[0004] It is also known to provide an internal combustion engine with one or more balance shafts typically include a shaft with one or more eccentric masses rotating within the crankcase about an axis parallel to the crankshaft axis. Some balance shafts rotate in the same direction as the crankshaft and others rotate in the opposite direction.

[0005] Although the use of a balance shaft helps in reducing some of the vibrations generated by the rotating and translating masses of the engine, the distance between the crankshaft axis and the axis of rotation of the balance shaft causes an imbalance.

[0006] There is therefore a desire for an internal combustion engine that addresses at least some of the above-mentioned disadvantages.
9884737.1 SUMMARY

[0007] It is an object of the present technology to ameliorate at least some of the inconveniences present in the prior art.

[0008] According to one aspect of the present technology, an internal combustion engine has a crankcase, a cylinder block connected to the crankcase, the cylinder block defining at least one cylinder, at least one piston disposed in the at least one cylinder, a crankshaft disposed at least in part in the crankcase and operatively connected to the at least one piston, and a counterweight operatively connected to and driven by the crankshaft. The crankshaft rotates in a first direction about a crankshaft axis. The counterweight rotates in a second direction opposite the first direction about a counterweight axis. The counterweight axis and the crankshaft axis are coaxial.

[0009] In some implementations of the present technology, the counterweight is disposed inside the crankcase.

[0010] In some implementations of the present technology, the counterweight forms part of body defining an aperture.

[0011] In some implementations of the present technology, the counterweight axis passes through a center of the aperture.

[0012] In some implementations of the present technology, the crankshaft extends through the aperture.

[0013] In some implementations of the present technology, a bearing is disposed radially between the body and the crankshaft and is at least in part in the aperture.

[0014] In some implementations of the present technology, the body is an annulus. The counterweight forms a sector of the annulus. The sector has a greater thickness than a remainder of the annulus.

[0015] In some implementations of the present technology, the counterweight and the crankshaft rotate at a same speed.
9884737.1

[0016] In some implementations of the present technology, the counterweight is operatively connected to and driven by the crankshaft.

[0017] In some implementations of the present technology, a first gear is mounted to the counterweight. A second gear is mounted to the crankshaft. An idler gear engages the first and second gears. The crankshaft rotates the second gear in the first direction.
The second gear rotates the idler gear. The idler gear rotates the first gear in the second direction. The first gear rotates the counterweight in the second direction.

[0018] In some implementations of the present technology, the first and second gears are bevel gears and the idler gear is a pinion.

[0019] In some implementations of the present technology, the first and second gears are annular bevel gears. The first gear rotates about the counterweight axis. The second gear rotates about the crankshaft axis. The pinion rotates about a pinion axis normal to the counterweight axis and to the crankshaft axis.

[0020] In some implementations of the present technology, the crankshaft extends through the first and second gears.

[0021] In some implementations of the present technology, the at least one cylinder is a single cylinder. The at least one piston is a single piston. The crankshaft defines a single crankpin.
The engine also has a single connecting rod connecting the piston to the crankpin. The first and second gears are disposed on opposite sides of the connecting rod.

[0022] In some implementations of the present technology, the first gear is disposed between the counterweight and the connecting rod.

[0023] In some implementations of the present technology, the at least one cylinder is a single cylinder. The at least one piston is a single piston. The crankshaft defines a single crankpin.
The counterweight is a first counterweight. The engine also has a second counterweight rotating in the first direction about the crankshaft axis.

[0024] In some implementations of the present technology, the second counterweight is integrally formed with the crankshaft.
9884737.1

[0025] In some implementations of the present technology, the first counterweight has a first moment of inertia. The second counterweight has a second moment of inertial.
The second moment of inertia is equal to or greater than the first moment of inertia.

[0026] In some implementations of the present technology, a third counterweight rotates in the first direction about the crankshaft axis.

[0027] In some implementations of the present technology, a single connecting rod connects the piston to the crankpin. The first and second counterweights are disposed on a first side of the connecting rod and the third counterweight is disposed on a second side of the connecting rod.

[0028] In some implementations of the present technology, a first gear is connected to the first counterweight, a second gear connected to the third counterweight, and a pinion engages the first and second gears. The third counterweight rotates the second gear in the first direction. The second gear rotates the pinion. The pinion rotates the first gear in the second direction. The first gear rotates the first counterweight in the second direction.

[0029] In some implementations of the present technology, the crankshaft includes a first output shaft, a second output shaft, the crankpin, the second counterweight and the third counterweight. The crankpin extends between the second and third counterweights. The second counterweight is disposed between the first output shaft and the crankpin. The third counterweight is disposed between the second output shaft and the crankpin.
The crankshaft axis extends through centers of the first output shaft and of the second output shaft.

[0030] In some implementations of the present technology, the first output shaft and the second counterweight are integrally formed and form a first crankshaft portion. The third counterweight and the second output shaft are integrally formed and form a second crankshaft portion. The crankpin connects the second crankshaft portion to the first crankshaft portion.

[0031] In some implementations of the present technology, the first counterweight forms part of a body haying an eccentric mass distribution. The body defines an aperture.
The crankshaft axis extends through the aperture. The third counterweight forms part of a crank disk haying an eccentric mass distribution.
9884737.1

[0032] In some implementations of the present technology, the first, second and third counterweights are aligned when the piston is at a top dead center (TDC) and at a bottom dead center (BDC).

[0033] In some implementations of the present technology, when the piston is at the TDC: the first, second and third counterweights are intersected by a plane containing a cylinder axis and the crankshaft axis, the piston is disposed on a first side of the crankshaft axis, and the first, second and third counterweights are disposed on a second side of the crankshaft axis. When the piston is at the BDC: the first, second and third counterweights are intersected by the plane, the piston is disposed on the first side of the crankshaft axis, and the first, second and third counterweights are disposed on the first side of the crankshaft axis.

[0034] According to another aspect of the present technology, there is provided a marine outboard engine having a cowling, the internal combustion engine according to any one of the above aspect and implementations disposed at least in part in the cowling, a driveshaft operatively connected to and driven by the crankshaft, a propeller shaft operatively connected to and driven by the driveshaft, and a propeller connected to and driven by the propeller shaft.

[0035] In some implementations of the present technology, a marine outboard engine has a cowling, the internal combustions according to any one of the above aspect and implementations disposed at least in part in the cowling, a driveshaft operatively connected to and driven by the crankshaft, a propeller shaft operatively connected to and driven by the driveshaft, and a propeller connected to and driven by the propeller shaft.

[0036] Implementations of the present technology each have at least one of the above-mentioned object and/or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and/or may satisfy other objects not specifically recited herein.

[0037] Additional and/or alternative features, aspects and advantages of implementations of the present technology will become apparent from the following description, the accompanying drawings and the appended claims.
9884737.1 BRIEF DESCRIPTION OF THE DRAWINGS

[0038] For a better understanding of the present technology, as well as other aspects and further features thereof, reference is made to the following description which is to be used in conjunction with the accompanying drawings, where:

[0039] Figure 1 is a left side elevation view of a marine outboard engine shown in an upright position;

[0040] Figure 2 is a perspective view, taken from a front, left side of an internal combustion engine assembly of the marine outboard engine of Fig. 1;

[0041] Figure 3 is a partially exploded perspective view, taken from a front, right side of an engine of the engine assembly of Fig. 2;

[0042] Figure 4 is a perspective view taken from a lower, front, left side of a cross-section of a portion of the engine of Fig. 3 taken through a plane passing through a crankshaft and a pinion of the engine;

[0043] Figure 5 is a perspective view taken from a rear, right side of internal components of the engine of Fig. 3;

[0044] Figure 6 is a left side elevation view of the internal components of Fig. 5;

[0045] Figure 7 is an exploded perspective view, take from a lower, rear, right side of the internal components of Fig. 5;

[0046] Figure 8 is a schematic illustration of the crankshaft, the connection rod, the piston and the counterweights of the engine of Fig. 3 with the piston in a top dead center position; and

[0047] Figure 9 is a schematic illustration of the crankshaft, the connection rod, the piston and the counterweights of the engine of Fig. 3 with the piston in a bottom dead center position.
DETAILED DESCRIPTION
9884737.1

[0048] An internal combustion engine assembly 100 having an engine 102 will be described herein as being provided in a marine outboard engine 10 used to propel a watercraft. It is contemplated that the internal combustion engine assembly 100 and the engine 102 alone could be used in other vehicles such as, but not limited to, snowmobiles, all-terrain vehicles (ATVs), and scooters, and in other applications such as, but not limited to, electric generators, lawnmowers and other small engine applications.

[0049] With reference to Fig. 1, the marine outboard engine 10 has a cowling 12. The marine outboard engine 10 includes a top portion 14 and a bottom portion 16. The bottom portion 16 includes a mid-section 18, a gear case assembly 20, a skeg portion 22 and a propeller 24.

[0050] The cowling 12 surrounds and protects the engine assembly 100 housed within the cowling 12. The engine assembly 100 will be described in greater detail below.
The engine assembly 100 is operatively connected to a vertically oriented driveshaft 26 disposed in the cowling 12. The driveshaft 26 is coupled to a drive mechanism 28, which includes a transmission 30, a propeller shaft 32 and the propeller 24. The propeller 24 is mounted on the propeller shaft 32 which is driven by the transmission 30. The propeller shaft 32 is disposed in part in the gear case assembly 20 and is generally perpendicular to the driveshaft 26. The driveshaft 26 and the drive mechanism 28 are housed in part within the gear case assembly 20 of the bottom portion 16, and transfer power from the engine 102 to the propeller 24 mounted on the rear side of the gear case assembly 20 of the outboard engine 10. The propulsion system of the outboard engine 10 could also include a jet propulsion device, turbine or other known propelling device.

[0051] A stern bracket 34 and a swivel bracket 36 are used to mount the outboard engine 10 to a watercraft. The stern bracket 34 is attached to the watercraft and can take various forms, the details of which are conventionally known. The swivel bracket 36 is pivotally connected to the stern bracket 34 such that the angle of outboard engine 10 relative to the watercraft may be changed in order to steer the watercraft.

[0052] In the implementation shown in Fig. 1, a tiller 38 is operatively connected to the swivel bracket 36 and extends forward of the cowling 12 to provide a lever used for manually steering of the outboard engine 10. The tiller 38 is rotatably fastened to the swivel bracket 36 such that it can be raised for ease of handling and transportation. The tiller 38 includes a handle 9884737.1 40 in the form of a twist grip used as throttle control as in most conventional small marine outboard engines. The tiller 38 also includes a shift lever 42 for selecting a forward, neutral or reverse gear of the transmission 30. It is contemplated that the tiller 38 could be omitted and that the outboard engine 10 could be steered using a steering wheel connected to a hydraulic or electric steering system and that the throttle of the engine 102 and the position of the transmission 30 could be controlled by one or more levers disposed near the steering wheel.

[0053] The cowling 12 includes an upper motor cover assembly 44 with a top cap 46, and a lower motor cover 48. The upper motor cover assembly 44 encloses a top portion of the engine assembly 100. The lower motor cover 48 surrounds the remainder of the engine assembly 100 and the exhaust system (not shown). The mid-section 18 extends from the lower motor cover 48 to the gear case assembly 20 and includes the lower half of the lower motor cover 48. The gear case assembly 20 encloses the transmission 30 and supports the drive mechanism 28 in a known manner.

[0054] The upper motor cover assembly 44 and the lower motor cover 48 are made of sheet material, such as plastic, but could also be made of metal, composite or the like. The lower motor cover 48 and/or other components of the cowling 12 can be formed as a single piece or as several pieces. For example, the lower motor cover 48 can be formed as two lateral pieces mating along a vertical joint. The lower motor cover 48, which is also made of sheet material, such as plastic, but could also be made of metal, composites or the likes. One suitable composite is a sheet molding compound (SMC) which is typically a fibreglass reinforced sheet molded to shape.

[0055] A lower edge 50 of the upper motor cover assembly 44 mates in a sealing relationship with an upper edge 42 of the lower motor cover 48. A seal is disposed between the lower edge 50 of the upper motor cover assembly 44 and the upper edge 52 of the lower motor cover 48 to form a watertight connection. One or more locking mechanisms (not shown) are provided on at least one of the sides and/or at the front and/or back of the cowling 12 to lock the upper motor cover assembly 44 onto the lower motor cover 48.

[0056] The upper motor cover assembly 44 is formed in two parts, but could also be a single part. The upper motor cover assembly 44 includes an air intake portion 54 formed as a recessed portion on the rear of the cowling 12. The air intake portion 54 is configured to allow the entry of 9884737.1 air but prevent the entry water into the interior of the cowling 12 and then into the engine assembly 100. Such a configuration can include a tortuous path for example.
The top cap 46 defines a portion of the air intake portion 54. It is contemplated that the air intake portion could be defined elsewhere on the cowling 12. The top cap 46 also defines a recess 56 in which a handle 104 of a manual start assembly (not shown) is received.

[0057] As can be seen in Fig. 2, the engine assembly 100 includes the internal combustion engine 102 and a housing 106 mounted to the engine 102. The housing 106 houses a magneto (not shown) and the manual start assembly. It is contemplated that the upper motor cover assembly 44 and the lower motor cover 48 could be omitted such that the housing 106 is exposed.

[0058] Turning now to Figs. 3 to 9, the engine 102 will be described in more detail. The engine 102 is a two-stroke, direct injected internal combustion engine. It is contemplated that other types of engines, such as engines operating on the four-stroke principle or carbureted engines for example, could be used.

[0059] As can be seen in Fig. 3, the engine 102 has a crankcase 108, a cylinder block 110 and a cylinder head 112. One portion 114 of the crankcase 108 is integrally formed with the cylinder block 110. Another portion 116 of the crankcase 108 is formed separately from the cylinder block 110 and is fastened to the portion 114 of the crankcase 108. The cylinder block 110 defines a single cylinder 118 (shown in dotted lines in Fig. 3). A single piston 120 is disposed in the cylinder 118. It is contemplated that the cylinder block 110 could define more than one cylinder 118 in which case a corresponding number of pistons 120 would be provided. The cylinder block 110 and the portions 114, 116 are made by a metal casting process, but other processes are contemplated. The cylinder head 112 is fastened to the end of the cylinder block 110.

[0060] A crankshaft 122 is housed in part in the crankcase 114. With reference to Figs. 4 and 7, the crankshaft 122 is made in two portions 124, 126 connected together by a crankpin 134.
The portion 124 of the crankshaft 122 includes an output shaft 128, a counterweight 130 and a web 132, which are integrally formed. The portion 126 of the crankshaft 122 includes a crank disk 136 and an output shaft 138 which are integrally formed. The piston 120 is connected to the crankshaft 122 by a connecting rod 140. The crankpin 134 is inserted though an aperture 142 in the connecting rod 140. A bearing 144 is disposed radially between the crankpin 134 and the connecting rod 140. The crank disk 136 defines an aperture 146 through which the crankpin 134 is inserted to engage the crank disk 136. The web 132 defines an aperture 147 (Fig. 4) through which the crankpin 134 is inserted to engage the web 132. As such, the crankpin 134 extends between the web 132, and therefore the counterweight 130, and the crank disk 136. The counterweight 130 and the web 132 are disposed between the output shaft 128 and the crankpin 134. The crank disk 136 is disposed between the crankpin 134 and the output shaft 138. It is contemplated that the crankpin 134 could be integrally formed with the portion 124 or the portion 126 of the crankshaft 122. It is also contemplated that the crankpin 134 could be integrally formed with both portions 124, 126 in order to have a unitary crankshaft 122, in which case the connecting rod 140 would be split in two parts through the center of the aperture 142 to permit attachment to the crankpin 134.

[0061] A counterweight 148 is integrally formed with the crank disk 126.
The counterweight 148 forms a sector of the crank disk 136. The sector formed by the counterweight 148 has a greater thickness than a remainder of the crank disk 136 which causes the crank disk 136 to have an eccentric mass distribution. It is contemplated that the sector formed by the counterweight 148 could alternatively or additionally have a greater radius than the remainder of the crank disk 136. The counterweight 148 and the counterweight 130 are always aligned with each other. As can be seen in Fig. 6, the counterweight 130 and the crank disk 136 are located on opposite sides of the connecting rod 140. It is contemplated that the counterweight 148 could be fastened to the crank disk 136. It is also contemplated that the counterweight 148 and the crank disk 136 could be replaced by a counterweight and web like the counterweight 130 and web 132.

[0062] As can be seen in Fig. 4, the output shaft 128 of the crankshaft 122 protrudes from the crankcase 108 and passes through a disk 150 provided in the bottom of the housing 106. The output shaft 128 is rotationally supported in the disk 150 by a bearing 152.
The bearing 152 is disposed radially between the output shaft 128 and a flange 153 formed by the disk 150. The output shaft 138 is rotationally supported by a bearing 154 in an aperture formed between the portions 114, 116 of the crankcase 108. As a result, reciprocation of the piston 120 along a central axis of the cylinder 118, referred to herein as the cylinder axis 156 (Fig. 6), causes all the 9884737.1 parts of the crankshaft 122 to rotate about a crankshaft axis 158 (Fig. 6) in the direction indicated by the arrow 160 in Fig. 5. The crankshaft axis 158 extends through the centers of the output shafts 128, 138.

[0063] The output shaft 128 of the crankshaft 122 is connected to a rotor (not shown) of the magneto that is disposed in the housing 106 in order to drive the rotor. The output shaft 138 of the crankshaft 122 is connected to a splined shaft 162 that is coaxial with the crankshaft axis 158.
The splined shaft 162 is connected to the driveshaft 26 such that the engine 102 can drive the driveshaft 26. It is contemplated that the driveshaft 26 could be connected to the crankshaft 122 in a manner other than the one described above.

[0064] The engine 102 has another counterweight 170. The counterweight 170 is integrally formed with a body, which in the present implementation is an annulus 172 defining a central aperture 173 (Fig. 7). It is contemplated that the body could have a shape other than that of an annulus. The counterweight 170 forms a sector of the annulus 172. The sector formed by the counterweight 170 has a greater thickness than a remainder of the annulus 172 which causes the annulus 172 to have an eccentric mass distribution. It is contemplated that the sector formed by the counterweight 170 could alternatively or additionally have a greater radius than the remainder of the annulus 172. The annulus 172 is located inside the crankcase 108. The annulus 172 is positioned such that the counterweight 130 and the web 132 are disposed between the annulus 172 and the connecting rod 140, as can be seen in Fig. 6. The output shaft 128 of the crankshaft 122 extends through the aperture 173 of the annulus 172.

[0065] The annulus 172, and therefore the counterweight 170, rotates about a counterweight axis 174 that is coaxial with the crankshaft axis 158. The counterweight axis 174 passes through a center of the aperture 173 of the annulus 172. The annulus 172 is rotationally connected to the flange 153 of the disk 150 by a bearing 176 disposed partially in the aperture 173 of the annulaus 172 and radially between the flange 153 and the annulus 172 as can be seen in Fig. 4. As can also be seen in Fig. 4, a thrust bearing 178 is disposed between the inner side of the upper wall of the crankcase 108 and the upper side of the annulus 172. It is contemplated that the annulus could alternatively be rotationally connected on the output shaft 128 of the crankshaft 122 by a bearing disposed radially between the output shaft 128 and the annulus 172.
9884737.1

[0066] As will be described in more detail below, the annulus 172 is driven by the crankshaft 122 to rotate at the same speed as the crankshaft 122 but in the direction indicated by arrow 180 in Fig. 5 about the counterweight axis 174. As such, the annulus 172 rotates in the direction opposite to the crankshaft 122. Therefore, the counterweight 170 rotates in the direction opposite to the counterweights 130, 148.

[0067] With reference to Figs. 8 and 9, the relative position of the counterweights 130, 148, 170 and the piston 120 will be described. The mass of each counterweight 130, 148, 170 is selected such that the combined mass of the counterweights 130, 148, 170 at least partly counterbalances the forces generated by the reciprocating and rotating masses of the engine 102.
The reciprocating masses include the mass of the piston 130 and part of the mass of the connecting rod 140. The rotating masses include part of the mass of the connecting rod 140, the mass of the web 132 and the mass of the crankpin 134. The masses of the counterweights 130, 148, 170 are also distributed along the crankshaft axis 158 so that the resultant force for balancing the reciprocating masses is centered about the cylinder axis 156.
Also, in the present implementation, the counterweight 148 has a moment of inertia that is equal to or greater than a moment of inertia of the counterweight 170. The piston 120 moves between a top dead center position (TDC), shown in Fig. 8, where it is furthest from the crankshaft axis 158, and a bottom dead center (BDC), shown in Fig. 9, where it is closest to the crankshaft axis 158. It should be understood that the top and bottom referred to in TDC and BDC do not refer to the top and bottom of the engine 102 when in use, but they are rather in reference to the standard naming convention used for these positions of pistons in the art of internal combustion engines. For ease of understanding and consistency with respect to the standard naming convention, the orientation of the crankshaft 122 in Figs. 8 and 9 has been changed compared to the other figures. As such, in Figs. 8 and 9, the rear of the engine 102 corresponds to the top of these figures and the front of the engine 102 corresponds to the bottom of the figures. The crankshaft portion 128, the crank disk 136 and the annulus 172 are mounted in the crankcase 108 such that the counterweights 130, 148, 170 are aligned with each other when the piston 130 is at the TDC
and at the BDC, as can be seen in Figs. 8 and 9. When the piston 130 is at the TDC and at the BDC, the counterweights 130, 148, 170 are intersected by a plane containing the cylinder axis 156 and the crankshaft axis 158. As can be seen in Fig. 8, when the piston 130 is at the TDC, the counterweights 130, 148, 170 and the piston 130 are disposed on opposite sides of the crankshaft 9884737.1 axis 158. When the piston 130 is at the BDC, the counterweights 130, 148, 170 and the piston 130 are disposed on the same side of the crankshaft axis 158. As a result, the counterweights 130, 148, 170 help to counterbalance the vibrations generated by the piston 130 and the connecting rod 140 as they translate along the cylinder axis 156 and the vibrations generated by the connecting rod 140, the web 132 and the crankpin 134 as they rotate about the crankshaft axis 158. Also, since the counterweight 170 rotates about the counterweight axis 177, coaxially with the crankshaft axis 158, at the same speed as the counterweights 130, 148, but in the opposite direction, the counterweight 170 helps to counterbalance the lateral vibrations generated by a portion of the mass of the counterweights 130, 148 (i.e. in a direction normal to the axes 156 and 174).

[0068] As previously mentioned, the annulus 172, and therefore the counterweight 170, is driven by the crankshaft 122 to rotate at the same speed as the crankshaft 122 but in the opposite direction. In the present implementation, this is achieved by gears 200, 202, 204. It is contemplated that the annulus 172 could be driven by the crankshaft 122 via other mechanisms such as, but not limited to, friction wheels and bets and pulleys.

[0069] The gear 200 is an annular bevel gear. The gear 200 is mounted to an upper face of the crank disk 136 coaxially with the crankshaft axis 158, and therefore with the counterweight axis 174. As a result, the crankshaft 122 (i.e. the crank disk 136) rotates the gear 200 about the crankshaft axis 158 in the direction indicated by arrow 160 (Fig. 5). As can be seen in Fig. 6, the gear 200 is disposed between the crank disk 136 and the connecting rod 140.

[0070] The gear 202 is an idler gear, and more specifically a pinion 202.
The pinion 202 is engages the gears 202 and 204. As best seen in Fig. 4, the pinion 202 is mounted to a shaft 206 that is rotationally supported inside a recess 208 in the crankcase 108 by a needle bearing 210 and a thrust bearing 212. The pinion 202 rotates about a pinion axis 214 (Fig.
6) that is normal to the counterweight and crankshaft axes 174, 158 and angled relative to the plane containing the cylinder axis 156 and the crankshaft axis 158. The gear 200 rotates the pinion 202, which in turn rotates the gear 204 in the direction opposite to the gear 202 (i.e. the direction indicated by arrow 180 in Fig. 5). It is contemplated that more than one idler gear could be provided between the gears 202 and 204.
9884737.1

[0071] The gear 204 is an annular bevel gear. The gear 204 is mounted to a lower face of the annulus 172 coaxially with the crankshaft and counterweight axes 158, 174. As can be seen in Fig. 6, the gear 204 is disposed between the annulus 172 having the counterweight 170 and the connecting rod 140. As described above, the gear 204 is engaged by the pinion 202. As the gear 204 has the same diameter and the same number of teeth as the gear 200, the gear 204 rotates about the counterweight axis 158 at the same speed as the gear 200 rotates about the crankshaft axis 158, but in the direction opposite to the gear 200 due to the manner in which the gears 200, 202, 204 engage each other. The gear 204 rotates the annulus 172, and therefore the counterweight 170, at the same speed as the gear 200, and therefore the crankshaft 122, but in the opposite direction.

[0072] Modifications and improvements to the above-described implementations of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims.
9884737.1

Claims (25)

What is claimed is:

1. An internal combustion engine comprising:
a crankcase;
a cylinder block connected to the crankcase, the cylinder block defining at least one cylinder;
at least one piston disposed in the at least one cylinder;
a crankshaft disposed at least in part in the crankcase and operatively connected to the at least one piston, the crankshaft rotating in a first direction about a crankshaft axis; and a counterweight operatively connected to and driven by the crankshaft, the counterweight rotating in a second direction opposite the first direction about a counterweight axis, the counterweight axis and the crankshaft axis being coaxial.

2. The engine of claim 1, wherein the counterweight is disposed inside the crankcase.

3. The engine of claim 1, wherein the counterweight forms part of body defining an aperture.

4. The engine of claim 3, wherein the counterweight axis passes through a center of the aperture.

5. The engine of claim 4, wherein the crankshaft extends through the aperture.
6. The engine of claim 5, further comprising a bearing disposed radially between the body and the crankshaft and at least in part in the aperture.
7. The engine of claim 3, wherein:
the body is an annulus; and the counterweight forms a sector of the annulus, the sector having a greater thickness than a remainder of the annulus.

6. The engine of claim 1, wherein the counterweight and the crankshaft rotate at a same speed.

7. The engine of claim 1, wherein the counterweight is operatively connected to and driven by the crankshaft.

8. The engine of claim 7, further comprising:
a first gear mounted to the counterweight;
a second gear mounted to the crankshaft; and an idler gear engaging the first and second gears;
wherein:
the crankshaft rotates the second gear in the first direction;
the second gear rotates the idler gear;
the idler gear rotates the first gear in the second direction; and the first gear rotates the counterweight in the second direction.

9. The engine of claim 8, wherein the first and second gears are bevel gears and the idler gear is a pinion.

10. The engine of claim 9, wherein:
the first and second gears are annular bevel gears;
the first gear rotates about the counterweight axis;
the second gear rotates about the crankshaft axis; and the pinion rotates about a pinion axis normal to the counterweight axis and to the crankshaft axis.

11. The engine of claim 10, wherein the crankshaft extends through the first and second gears.

12. The engine of claim 11, wherein:
the at least one cylinder is a single cylinder;

the at least one piston is a single piston; and the crankshaft defines a single crankpin;
the engine further comprising a single connecting rod connecting the piston to the crankpin; and wherein the first and second gears are disposed on opposite sides of the connecting rod.

13. The engine of claim 12, wherein the first gear is disposed between the counterweight and the connecting rod.

14. The engine of claim 1, wherein:
the at least one cylinder is a single cylinder;
the at least one piston is a single piston;
the crankshaft defines a single crankpin; and the counterweight is a first counterweight;
the engine further comprising a second counterweight rotating in the first direction about the crankshaft axis.

15. The engine of claim 14, wherein the second counterweight is integrally formed with the crankshaft.

16. The engine of claim 14, wherein:
the first counterweight has a first moment of inertia;
the second counterweight has a second moment of inertial; and the second moment of inertia is equal to or greater than the first moment of inertia.

17. The engine of claim 14, further comprising a third counterweight rotating in the first direction about the crankshaft axis.

18. The engine of claim 17, further comprising a single connecting rod connecting the piston to the crankpin;

wherein the first and second counterweights are disposed on a first side of the connecting rod and the third counterweight is disposed on a second side of the connecting rod.

19. The engine of claim 18, further comprising:
a first gear connected to the first counterweight;
a second gear connected to the third counterweight; and a pinion engaging the first and second gears;
wherein:
the third counterweight rotates the second gear in the first direction;
the second gear rotates the pinion;
the pinion rotates the first gear in the second direction; and the first gear rotates the first counterweight in the second direction.

20. The engine of claim 18, wherein:
the crankshaft includes a first output shaft, a second output shaft, the crankpin, the second counterweight and the third counterweight;
the crankpin extends between the second and third counterweights;
the second counterweight is disposed between the first output shaft and the crankpin;
the third counterweight is disposed between the second output shaft and the crankpin;
the crankshaft axis extends through centers of the first output shaft and of the second output shaft.

21. The engine of claim 20, wherein:
the first output shaft and the second counterweight are integrally formed and form a first crankshaft portion;
the third counterweight and the second output shaft are integrally formed and form a second crankshaft portion; and the crankpin connects the second crankshaft portion to the first crankshaft portion.

22. The engine of claim 17, wherein:

the first counterweight forms part of a body having an eccentric mass distribution, the body defining an aperture;
the crankshaft axis extends through the aperture; and the third counterweight forms part of a crank disk having an eccentric mass distribution.

23. The engine of claim 17, wherein the first, second and third counterweights are aligned when the piston is at a top dead center (TDC) and at a bottom dead center (BDC).

24. The engine of claim 23, wherein:
when the piston is at the TDC:
the first, second and third counterweights are intersected by a plane containing a cylinder axis and the crankshaft axis;
the piston is disposed on a first side of the crankshaft axis; and the first, second and third counterweights are disposed on a second side of the crankshaft axis; and when the piston is at the BDC:
the first, second and third counterweights are intersected by the plane;
the piston is disposed on the first side of the crankshaft axis; and the first, second and third counterweights are disposed on the first side of the crankshaft axis.

25. A marine outboard engine comprising:
a cowling;
the internal combustion engine according to any one of claims 1 to 24 disposed at least in part in the cowling;
a driveshaft operatively connected to and driven by the crankshaft;
a propeller shaft operatively connected to and driven by the driveshaft; and a propeller connected to and driven by the propeller shaft.