Pendulum crank cycloid insert for pendulum crankshaft having integral carrier

A pendulum crankshaft for an internal combustion engine includes a pendulum crankshaft having pendulum crank cycloid inserts. The inserts may be formed from high graded hardened steel while the crankshaft may be formed from conventional iron. The pendulum crankshaft includes a crankshaft having pendulum-holding ears. A cycloid insert-receiving aperture is formed in each of said ears for receiving a cycloid insert. Each of the cycloid inserts has a cycloid path formed therethrough. The pendulum is movably attached to the ears by a rolling pin fitted through the cycloid paths of the ears and captured between the cycloid paths formed in each half of the pendulum. Each half of the pendulum includes recessed areas on which the cycloid paths are formed. A pin is provided between each cycloid insert and the ear into which it is inserted to restrict rotation of the cycloid insert with respect to the ear.

TECHNICAL FIELD

The disclosed inventive concept relates generally to pendulum crankshafts for internal combustion engines. More particularly, the disclosed inventive concept relates to pendulum crank cycloid inserts for a pendulum crankshaft having an integral carrier.

BACKGROUND OF THE INVENTION

Internal combustion engines having a relatively small number of cylinders provide automobile makers with an attractive solution to the need for improved fuel economy. In order to compensate for reduction of cubic capacity, vehicle manufacturers developed technologies to improve engine power, such as direct fuel injection, turbocharging, and variable timing for inlet and exhaust camshafts. In this way six- and eight-cylinder engines can be scaled down without losing available horsepower.

An undesirable consequence of engines with a small number of cylinders is high crankshaft torsional vibration and high engine block vibration caused by forces, such as first and second order forces, that are not cancelled. Such vibrations are ultimately transmitted through the engine mounts and to the vehicle structure.

Engineers managed these vibrations to one extent or another through a variety of approaches, many of which increase the cost of construction and reduce fuel economy. One accepted solution to overcome excessive vibration is the provision of one or more pendulums on the crankshaft to lower the torsional vibration of the crankshaft and the consequent block vibration. Such crankshaft-mounted pendulums function as vibration absorbers as they are tuned to address and thus cancel out vibrations generated by crankshaft rotation, thus smoothing torque output of the crankshafts. This approach is taken as well by designers of some airplane piston engines where the pendulums smooth output torque and reduce stress within the crankshaft itself.

An example of a pendulum vibration absorber associated with an engine crankshaft is set forth in U.S. Pat. No. 4,739,679, assigned to the assignee of the instant application. According to the arrangement set forth in this patent, a pendulum includes an inner curved cam follower surface that is alternately engaged and disengaged from a pin type cam fixed on the pendulum carrier. The crankshaft pendulum is interconnected with the pendulum carrier by pairs of rollers that are movable on mating curved tracks. While there are a number of variations of the movable relationship between the pendulum and the cycloid surface of the crankshaft it is common to incorporate rolling pins as the points of contact between these two components.

While providing an effective solution to the problem of vibrations in smaller internal combustion engines the pendulum crankshaft requires high strength hardened steel on which the rollers can roll. To satisfy this requirement the entire crankshaft must be formed from high grade steel to meet the hardness requirements for the cycloid surfaces. Attempts to harden only the surface of the cycloid sometimes result in distortion of the crankshaft. Beyond the prohibitions created by material costs for an all-hardened steel crankshaft, the labor and tooling required to machine a cycloid into the crankshaft is also expensive.

Thus a new approach to the pendulum crankshafts is needed to address the problems associated with known arrangements.

SUMMARY OF THE INVENTION

The disclosed inventive concept overcomes the problems associated with known pendulum crankshafts for internal combustion engines by providing a pendulum crankshaft having pendulum crank cycloid inserts, thus requiring only the cycloid inserts to be formed from high graded hardened steel. The crankshaft itself may be formed from conventional iron.

The pendulum crankshaft for an internal combustion engine of the disclosed inventive concept includes a crankshaft having pendulum-holding ears. A cycloid insert-receiving aperture is formed in each of said ears for receiving a cycloid insert. Each of the cycloid inserts has a cycloid path formed therethrough. The pendulum is movably attached to the ears by a rolling pin fitted through the cycloid paths of the ears and captured between the cycloid paths formed in each half of the pendulum.

Each half of the pendulum includes recessed areas. The cycloid paths are formed on the recessed areas. A pin is provided between each cycloid insert and the ear into which it is inserted to restrict rotation of the cycloid insert with respect to the ear.

For base line testing purposes, it may be necessary to temporarily fix the pendulum relative to the crankshaft in what would likely be a non-production engine. To this end and for this purpose, a locking pin passing aperture is formed in each pendulum. The crankshaft includes a locking pin receiving aperture. A removable locking pin passes through said locking pin passing aperture and into the locking pin receiving aperture for locking movement of the pendulum with respect to the crankshaft. The locking pin deactivates the pendulum for base line testing. Under normal operations the locking pin is removed and is replaced with a balance pin. The locking pin and its associated components would be removed for operation in the non-production engine.

According to the disclosed inventive concept and as noted above, the crankshaft can be formed from conventional iron while the cycloid inserts themselves are formed from a high graded hardened steel then attached to the crankshaft. The cycloid inserts can be machined from a long, hardened bar with wire EDM and then sliced to the correct width.

As a variation of the disclosed inventive concept, the path of the insert is not limited to the cycloid path described above. Alternative path configurations could include, for example, epicycloid and circular.

As a further variation of the disclosed inventive concept, while the hardened inserts are described above as being inserted into the crankshaft it may also be possible to instead fit the hardened inserts to the pendulum. In addition, it is conceivable that a combination of inserts fitted to both the crankshaft and to one or more pendulums in the same engine is possible.

The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.

Referring toFIGS. 1 and 2, a crankshaft assembly for an internal combustion engine is illustrated.FIG. 3illustrates an end view of the pendulum crankshaft shown inFIG. 2without the cycloid inserts whileFIG. 4illustrates the same view asFIG. 3but with the cycloid inserts. It is to be understood that the overall configuration of the illustrated crankshaft assembly, generally illustrated as10inFIGS. 1 and 2, is set forth for suggestive purposes only as the overall configuration may be altered from that illustrated.

The crankshaft assembly10includes a crankshaft12. The crankshaft12has a rotational axis14. Rotation of the crankshaft12about its rotational axis14is made possible by the provision of main journals16,16′,16″ and16′″. The journals16,16′,16″ and16′″ are integrally formed as part of the crankshaft10and are restrained within the engine block (not shown) by crankshaft bearings (not shown).

The connecting rods (not shown) are attached as is known in the art to rod journals18,18′ and18″ by rod bearings. The rod journals18,18′ and18″ are integrally formed on the crankshaft12, again as is known in the art.

The crankshaft12includes a first end20and a second end22. Conventionally provided extending from one end, in this case the first end20, is a snout24. The snout24serves as a mount for any number of engine components, such as a damper, a fan belt pulley and a drive mechanism for a camshaft. None of these components is shown but these components and their methods of attachment are known to those skilled in the art.

Conventionally attached to the other end of the crankshaft12, in this case the second end22, is a flywheel (not shown). The flywheel, which assists in reducing torsional fluctuations in the crankshaft12, is in operative engagement with the drive shaft or transaxle of the vehicle.

Counterweights26and26′ are formed as integral components of the crankshaft12. It is understood that the conventional modern internal combustion engine includes one or more such counterweights to provide balance to the crankshaft12, the connecting rods, and their associated pistons.

To each side of the rod journal18is provided a spaced apart pair of crank webs28and28′. Extending from the crank web28is a pair of ears30and30″. Extending from the crank web28′ is a pair of ears32and32′.

To each side of the rod journal18″ is a spaced apart pair of crank webs34and34′. Extending from the crank web34is a pair of ears of which one ear36is illustrated. Extending from the crank web34′ is a pair of ears38and38′.

The disclosed inventive concept provides a cycloid insert formed from high grade hardened steel that is fitted into insert-receiving holes formed in the ears of the crankshaft which may be formed of conventional iron due to the provision of the hardened steel inserts.

The ear36includes a cycloid insert-receiving hole44and the other ear formed on the web34includes a cycloid insert-receiving hole (not shown). The ear38includes a cycloid insert-receiving hole46and the ear38′ includes a cycloid insert-receiving hole (not shown).

Cycloid inserts are fitted into the insert-receiving holes formed in the ears. Specifically, a cycloid insert48is fitted into the cycloid insert-receiving hole40and a cycloid insert48′ is fitted into the cycloid insert-receiving hole40′. A cycloid insert50is fitted into the cycloid insert-receiving hole42and a cycloid insert (not shown) is fitted into the cycloid insert-receiving hole42′.

A cycloid insert52is fitted into the cycloid insert-receiving hole44and a cycloid insert (not shown) is fitted into the cycloid insert-receiving hole (not shown) formed in the other ear of the web34. A cycloid insert54is fitted into the cycloid insert-receiving hole46and a cycloid insert54′ is fitted into the cycloid insert-receiving hole (not shown) formed in the ear38′.

To prevent rotation of the cycloid inserts within their respective holes, anti-rotation pins are provided. A pin56is provided to interlock the cycloid insert48with respect to the ear30while a pin (not shown) is provided to interlock the cycloid insert48′ with respect to the ear30′. A pin58is provided to interlock the cycloid insert50with respect to the ear32while a pin (not shown) is provided to interlock the cycloid insert (not shown) with respect to the ear32′.

A pin60is provided to interlock the cycloid insert52with respect to the ear36while a pin (not shown) is provided to interlock the cycloid insert (not shown) with respect to the other ear formed on the web34. A pin62is provided to interlock the cycloid insert54with respect to the ear38while a pin62′ is provided to interlock the cycloid insert54′ with respect to the ear38′.

Each cycloid insert includes a cycloid path formed therein. Some of these are illustrated inFIG. 1in which a cycloid path64is shown formed in the cycloid insert48, a cycloid path66is formed in the cycloid insert50, a cycloid path68is formed in the cycloid insert52, a cycloid path70is formed in the cycloid insert54, and a cycloid path70′ is formed in the cycloid insert54′. Cycloid paths are also formed in the inserts not shown inFIG. 1but understood to be provided as set forth above.FIG. 4illustrates the cycloid insert54fitted into the cycloid insert-receiving hole46and the cycloid insert54′ fitted into the cycloid insert-receiving hole46′. As also illustrated inFIG. 4, the pin62is fitted into the groove72(shown inFIG. 3) to interlock the cycloid insert54in relation to the ear38and the pin62′ is fitted into the groove72′ (also shown inFIG. 3) to interlock the cycloid insert54′ in relation to the ear38′.

Referring toFIGS. 5 and 6, an exemplary pendulum74for use with the disclosed inventive concept is illustrated.FIG. 5shows the pendulum separated into two halves, a first pendulum half76and a pendulum second half76′.FIG. 6shows the two pendulum halves76and76′ assembled to form the pendulum74.

As shown inFIG. 5, and referring to the first pendulum half76, a cycloid path78is formed in a recessed surface80and a cycloid path78′ is formed in a recessed surface80′. In the same manner and with respect to the second pendulum half76′ a cycloid path82is formed in a recessed surface84and a cycloid path82′ is formed in a recessed surface84′.

FIG. 7illustrates a close-up side view of a pendulum86attached to the ear30and a pendulum88attached to the ear32. It is to be understood that pendulums are attached to each of the ears of the crankshaft12.

To allow for restricted movement of the pendulums of the disclosed inventive concept relative to their associated ears, rolling pins are provided that extend between the cycloid paths formed in opposing pendulum halves and through the cycloid paths formed in the cycloid inserts.

Particularly, and with respect toFIGS. 8 and 9, the pendulum74is shown attached to the ears38and38′.FIG. 8illustrates an end view of the pendulum74showing the second pendulum half76′ in place whileFIG. 9illustrates the same view asFIG. 8but without the second pendulum half76′.

As shown inFIG. 9, a rolling pin90is positioned through the cycloid path70formed in the cycloid insert54and into the cycloid path78′ formed in the recessed surface80′ of the first pendulum half76. In the same manner a rolling pin90′ is positioned through the cycloid path70′ formed in the cycloid insert54′ and into the cycloid path78formed in the recessed surface80of the first pendulum half76.

The first pendulum half76is attached to the second pendulum half76′ by mechanical fasteners such as bolts92and92′. Other methods of fastening may be employed.

Side-to-side movement of the pendulum relative to the ears of the crankshaft is restricted to a predetermined degree of movement. To reduce metal-to-metal impact of the pendulum against the ears, bumpers94and94′ are provided in stops96and96′ formed on opposing surfaces of the ears38and38′.

The pendulum stops96and96′ may be adjusted to allow for different angles of swing. For example, and preferably, the pendulum stops96and96′ allow +/−49.4° of travel. If the swing angle is larger the system must be detuned.

As noted above, or purposes of beta testing it may be necessary to temporarily fix the pendulum relative to the crankshaft. Such testing would ordinarily be performed on a pre-production or a non-production engine. Accordingly, an alternate embodiment of the pendulum crankshaft of the disclosed inventive concept is provided and is illustrated inFIGS. 10 through 13.

Referring toFIGS. 10 and 11, a pendulum100for use with the locking version of the disclosed inventive concept is illustrated.FIG. 10shows the pendulum separated into two halves, a first pendulum half102and a pendulum second half102′.FIG. 11shows the two pendulum halves102and102′ assembled to form the pendulum100.

As shown inFIG. 10, and referring to the first pendulum half102, a cycloid path104is formed in a recessed surface106and a cycloid path104′ is formed in a recessed surface106′. In the same manner and with respect to the second pendulum half102′ a cycloid path108is formed in a recessed surface110and a cycloid path108′ is formed in a recessed surface110′.

Also formed in the first pendulum half102is a balance pin groove112while formed in the second pendulum half102′ is a balance pin groove112′.

FIGS. 12 and 13illustrate the attachment of the pendulum100to the ears38and38′.FIG. 12illustrates an end view of the pendulum100showing the second pendulum half102′ in place over the first pendulum half102whileFIG. 13illustrates the same view asFIG. 12but without the second pendulum half102′ in place over the first pendulum half102.

A rolling pin90is positioned through the cycloid path70formed in the cycloid insert54and into the cycloid path104′ formed in the recessed surface106′ of the first pendulum half102. In the same manner a rolling pin90′ is positioned through the cycloid path70′ formed in the cycloid insert54′ and into the cycloid path104formed in the recessed surface106of the first pendulum half102.

A removable locking pin114is provided to lock the pendulum100with respect to the crankshaft12for base line testing as set forth above. The locking pin114is removably provided through the balance pin groove112formed in the first pendulum half102and the balance pin groove112′ formed in the second pendulum half102′. InFIGS. 12 and 13, the locking pin114is shown in its locked position extending from the pendulum100into a locking pin receiving aperture116formed in the crankshaft12.

When the locking pin114is in use a threaded plug118is provided to hold it in place. A snap ring120is fitted to hold the set screw118in place. Between the locking pin114and the set screw118is a nylon spacer122.

When not being tested, the threaded plug118, the nylon spacer122and the locking pin114are all removed. In such a case a solid balance pin (not shown) having a threaded upper portion is used. The snap ring120is fitted with the balance pin to prevent the balance pin from backing out.

The disclosed inventive concept as set forth above overcomes the challenges faced by known pendulum crankshaft arrangements for internal combustion engines by providing pendulum crank cycloid inserts for a pendulum crankshaft having an integral carrier. For example, the pendulum crankshaft of the disclosed inventive concept allows the lugging limit of an engine to be reduced to a relatively low RPM rate. However, one skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.