Internal combustion engine with variable compression ratio

A coupler, such as a piston pin, is pivotally coupled to a piston such that the piston can pivot about a first axis relative to the coupler. A connecting rod is coupled to the coupler for pivoting about a second axis. The relative positions of the first and second axes can be shifted by pivoting an eccentric portion of the coupler to thereby vary the compression ratio of a piston cylinder within which the piston slides. The coupler comprises a pivot member engager portion that is selectively shifted from first to second positions to vary the compression rates in response to shifting of a pivot member. The pivot member engager is shifted from first to second positions as the piston approaches the bottom dead center position. The pivot member and pivot member engager disengage from one another as the piston travels away from the bottom dead center position.

FIELD

The technology disclosed herein relates to methods and apparatus for adjusting the compression ratio of an internal combustion engine, such as for gasoline and diesel fueled engines.

BACKGROUND

Gasoline engines are typically designed so that under full load (open throttle) no uncontrolled combustion (knocking) occurs which limits the combustion ratio. Under throttled conditions, the gasoline engine is under compressed which can reduce engine efficiency. Diesel engines are typically over compressed to enhance starting in cold conditions. Diesel engines that have warmed up would be more efficient if they had a lower compression ratio. Thus, a variable compression ratio engine can be operated under various operating conditions to vary the engine compression so as to, for example, increase engine efficiency. A need exists for an improved variable compression ratio engine and related methods.

SUMMARY

In accordance with aspect of one embodiment of internal combustion engine, a piston coupler is pivotable about a first axis and pivotally couples a piston to a connecting rod with the piston being slidable in an associated piston cylinder in response to rotation of a crank shaft coupled to the connecting rod. The piston is reciprocated between top dead center and bottom dead center positions. The piston coupler comprises a first coupling portion pivotally coupled to the piston such that the piston is pivotable about a first axis and a second coupler portion pivotally coupled to the connecting rod such that the connecting rod is pivotable about a second axis. One of the first and second coupler portions comprises an eccentric portion operable such that pivoting of the piston coupler about the first axis from a first coupler position to a second coupler position pivots the eccentric portion from a first eccentric position to a second eccentric position and shifts the second axis relative to the first axis to thereby vary the compression ratio of the associated piston cylinder. The piston coupler can also comprise a pivot member engager. As another aspect of the embodiment, a pivot member is provided and comprises a pivot coupler engager movable from a first pivot coupler engager position to a second pivot coupler engager position and positioned to engage the pivot member engager to pivot the piston coupler from the first coupler position to the second coupler position as the piston approaches the bottom dead center position and in response to such movement of the pivot coupler engager. As another aspect of this embodiment, the pivot coupler engager is disengaged from the pivot member engager as the piston travels away from bottom dead center position.

In accordance with another aspect of an embodiment, a pivot member can be pivotable about a pivot member axis for pivoting movement from first to second pivot member positions in response to movement of the pivot coupler engager from first to second positions so as to result in corresponding movement of the piston coupler from first to second coupler positions to thereby vary the compression of the engine.

As another aspect of an embodiment, the pivot member engager can comprise at least one pivot member engagement surface which, for example, can be flat or planar and the pivot member can comprise at least one pivot member engagement surface which can also be flat or planar.

In a more specific embodiment, the pivot member is pivotable about a pivot member axis and comprises two pivot member engagement surfaces respectively positioned at opposite sides of the pivot member axis and the first axis and wherein there is a first set of two pivot coupler engagement surfaces on opposite sides of the pivot member axis. In accordance with another aspect of an embodiment, a plurality of pistons are provided with a common pivot member being provided to engage the pivot member engagement surfaces of the couplers associated with the pistons in the respective first and second piston cylinders. A first bracket positioned at least in part in the first cylinder and a second bracket positioned at least in part within the second cylinder can be used to support respective ends of the common pivot member. A first set of two pivot coupler engagement surfaces can be provided at one end portion of the common pivot member and a second set of two pivot coupler engagement surfaces can be provided at the opposite end portion of the common pivot member.

In accordance with a further aspect of an embodiment, the piston coupler can comprise a piston pin pivotable about the first axis with exemplary forms of piston pins being described in greater detail below. In one specific embodiment, the piston pins include internal cavities. These internal cavities can include a first cavity at one end portion of the piston pin that can be at least in part conical, a second cavity at an opposite end portion of the pivot pin that can also be at least in part conical, and an internal passageway extending therebetween. These passageways can be dimensioned and positioned to provide a homogeneous bending line in response to the application of force by the piston to the piston pin and the counterforce applied by the connecting rod during operation of an engine.

In accordance with another aspect of an embodiment, the piston coupler comprises a piston pin. A piston associated with a cylinder can comprise a body having an upper cylindrical piston ring supporting portion of a first diameter and a lower body portion sized to create a pivot member engager receiving space between the lower body portion and the associated cylinder. One end portion of the piston pin can extend outwardly from the lower body portion into the pivot member engager receiving space, said one end portion of the piston pin can comprise a pivot member engager.

As yet another aspect of an embodiment, the pivot members can be selectively driven to cause pivoting of the pivot members to thereby vary the compression ratio of the engine. In a specific example, a motor can be coupled to a worm gear which operably engages a pivot member to pivot the pivot member between various positions to adjust the compression ratio to a plurality of values depending upon the position to which the pivot member has been pivoted. A single motor can be coupled to a plurality of pivot member drivers, such as to plural worm gears, such as a respective worm gear for driving each pivot member. As another aspect of an embodiment, a worm gear associated with a pivot member can engage a pivot member to restrict movement of a pivot member in either direction along a pivot member axis about which the pivot member can be pivoted. In a more specific aspect, the pivot member can define a recess extending in a direction perpendicular to the pivot member axis with the worm gear being positioned at least partially in the recess and engaging the pivot member to restrict movement of the pivot member in either direction along the pivot member axis.

Pivoting of the pivot member can be limited to be within predetermined limits such as by configuring a worm gear drive for the pivot member. In addition, a mechanism can be provided for limiting the extent of pivoting of the pivot coupler about the first axis to be within a predetermined limit.

In accordance with yet another aspect of an embodiment, a piston coupler retainer can be coupled to the piston coupler to apply a retention force to resist pivoting of the piston coupler. The piston coupler retainer can also limit pivoting of the pivot coupler about the first axis to be within a predetermined limit. The piston coupler retainer can comprise a friction brake having a braking surface received within a braking surface defining cavity of the piston coupler.

As a still further aspect of an embodiment, an internal combustion engine is provided wherein a piston cylinder has a longitudinal centerline and wherein the maximum eccentricity is defined as E and corresponds to the maximum offset between the first and second axes, wherein an origin of a reference coordinate system is at the intersection of the longitudinal centerline of the at least one piston cylinder and a bottom dead centerline corresponding the second axis when the second axis is in the bottom dead center position, wherein the Z dimension is along the longitudinal center line of the piston cylinder from the origin and the X dimension is along the bottom dead centerline from the origin, wherein the pivot member axis is parallel to the first axis and, wherein the pivot member axis intersects an area wherein X is from −0.5 E to −0.8 E and Z is from −0.25 E to 0.25 E.

As yet another aspect of an embodiment, an internal combustion engine comprises at least one piston cylinder with a longitudinal centerline, wherein the longitudinal centerline is positioned between a first line parallel to the longitudinal centerline that intersects the first axis and a second line parallel to the longitudinal centerline that intersects the second axis when the eccentric portion is pivoted to the maximum allowed extent.

As a further aspect of an embodiment, an internal combustion engine is provided wherein the maximum eccentricity is defined as E and corresponds to the maximum offset between the first and second axes arising from pivoting the eccentric portion, wherein the piston coupler comprises a piston pin comprising first and third portions and a second portion intermediate the first and third portions, the first and third portions having longitudinal centerlines that are aligned with the first axis, the second portion comprising the eccentric portion and having a longitudinal center line that is aligned with the second axis, the first, second and third portions comprising right cylindrical surfaces, the second portion having a right cylindrical surface of a first diameter defined as RCR, one of the first and third portions having a right cylindrical surface of a diameter R1, wherein R1≧(RCR+E), and the other of the first and third portions having a right cylindrical surface of a diameter R2, wherein R2≦(RCR−E).

As a still a further specific aspect of an embodiment, an internal combustion engine is provided wherein there are first and second of said piston cylinders, a respective associated first piston slidably received by the first of said piston cylinders, a respective associated second piston slidably received by the second of said piston cylinders, a respective connecting rod and piston coupler associated with and coupled to said first piston, a respective connecting rod and piston coupler associated with and coupled to the second piston, and wherein there is a common pivot member for engaging the piston couplers associated with the first and second pistons. The common pivot member can comprise a first set of two pivot coupler engagement surfaces for engaging two pivot member engagement surfaces of the piston coupler associated with the first piston and a second set of two pivot coupler engagement surfaces for engaging two pivot member engagement surfaces of the piston coupler associated with the second piston. The common pivot member can comprise a first pivot member end portion extending into a first region defined by the first cylinder and a second pivot member end portion extending into a second region defined by the second cylinder. A first bracket can be coupled to the first cylinder in a position to pivotally support the first pivot member end portion and a second bracket can be coupled to the second cylinder in a position to pivotally support the second pivot member end portion. The first and second brackets can be fastened together with a portion of the first cylinder and a portion of the second cylinder positioned between the first and second brackets. The first and second brackets are configured to provide clearance for the respective pivot member engagement surfaces and pivot coupler engagement surface to engage one another.

As yet another aspect of an embodiment, the piston coupler can define a piston coupler braking surface. A spring biased friction brake can be coupled to the at least one piston and can comprise a friction brake with a braking surface positioned to frictionally engage the piston coupler braking surface. As a more specific aspect of an embodiment, each of the piston coupler braking surface and friction brake braking surface can be at least partially conical. The piston coupler can comprise a piston pin with a first end portion comprising a brake receiving cavity defining the piston coupler braking surface with the friction brake being inserted at least partially into the brake receiving cavity. The piston pin can comprise a second end portion that defines a cavity that is at least partially conical with the pivot member engager comprising an outwardly projecting portion of the second end portion. An internal cavity can be provided that interconnects the second end portion cavity and the brake receiving cavity. The internal cavity, the second end portion cavity and the brake receiving cavity can be shaped and dimensioned to achieve a homogenous bending line in response to the application of force by the piston to the piston pin and the counterforce applied by the connecting rod during operation of the engine. As yet another aspect of an embodiment, the friction brake can comprise a stop portion positioned to engage the piston coupler to limit the extent of pivoting of the piston coupler to within a predetermined limit.

The invention encompasses all novel and non-obvious assemblies, sub-assemblies and individual elements, as well as method acts, that are novel and non-obvious and that are disclosed herein. The embodiments described below to illustrate the invention are examples only as the invention is defined by the claims set forth below. In this disclosure, the term “coupled” and “coupling” encompasses both a direct connection of elements as well as the indirect connection of elements through one or more other elements. Also, the terms “a” and “an” encompass both the singular and the plural. For example, if an element or a element is referred to, this includes one or more of such elements. For example, if a plurality of specific elements of one type present, there is also an element of the type described. The invention is also not limited to a construction which contains all of the features described herein.

Adjustable compression ratio engines can be operated to improve the efficiency of the engine by varying the compression ratio appropriately.

DETAILED DESCRIPTION

FIG. 1illustrates a vertical sectional view through a portion of an internal combustion engine, in this case a six cylinder engine. Various dimensions of an exemplary engine are set forth in Table 1 below. It is to be understood that these dimensions are for example only and do not limit the scope of this disclosure.

The engine10ofFIG. 1comprises a portion of an engine block12having respective end walls14,16that pivotally support a crank shaft20for rotation about an axis24. Respective bearings26,28(or bushings) pivotally couple the crank shaft to the respective housing walls. Additional support bearings or bushings30,32couple the crank shaft to the engine housing at locations intermediate the ends of the crank shaft for further support.

For purposes of clarity only, portions of three pistons40,42and44are shown inFIG. 1, the other three pistons of this illustrative engine are not shown. The technological developments disclosed herein are not limited to six cylinder engine applications as engines with any number of cylinders can utilize the technology.

InFIG. 1, the piston40is shown in a top dead center position, the piston42is shown in a bottom dead center position and the piston44is shown in an intermediate position. Since each of the pistons and the associated coupling elements can be identical, like numbers are assigned to like components for the various pistons and will be discussed in connection with piston40. Thus, a piston or connecting rod60is coupled by bearings or bushings62at a lower end portion64of the connecting rod to a connecting rod mounting location66of the crank shaft20. The upper end portion70of connecting rod60is provided with an opening72extending therethrough, the opening having a longitudinal axis74that is parallel to the longitudinal axis24of the crank shaft. In the example shown inFIG. 1, opening72is of a right cylindrical shape. A piston coupling bushing or bearing76can be positioned within opening72. Bushing76has a centrally extending coupler receiving opening78extending therethrough. Opening78is of a right cylindrical configuration in this example and has a longitudinal axis concentric with the axis74. A coupler such as a coupling or piston pin80extends through the opening78and couples the piston40to the connecting rod60.

The piston40comprises a body having an upper cylindrical piston ring supporting portion81of a first diameter and a lower body portion sized to create a pivot member engager receiving space between the lower body portion83. One end portion of the piston pin40extends outwardly from the lower body portion83and into a pivot member engager receiving space85, said one end portion of the piston pin can comprise a pivot member engager (e.g., including engagement surface170′) as explained below.

Thus, in one embodiment, a pivot member engager comprises an outwardly projecting portion of a pivot coupler.

Coupler80in this configuration comprises an eccentric that can be pivoted to cause relative motion of the piston40relative to the connecting rod60to thereby vary the combustion chamber volume and thereby the compression ratio of the cylinder. Suitable couplers can assume shapes other than the shape of an elongated pin and comprise an eccentric operable to selectively shift the pivot axis of the connecting rod where it is coupled to the piston relative to the pivot axis about which the piston and pivot pin pivots. Exemplary constructions of an eccentric coupler80in the form of piston pins are described below. A coupler retaining mechanism, for example a friction brake82, an example of which is explained below, can be used to retain the coupler80in, or resist the motion of the coupler88from, a desired position to which it has been pivoted. Given the small eccentricity that can be employed in certain embodiments of this technology, the piston coupler, such as the pin, can interfit tightly enough with the piston to resist motion from a desired position to which it has been pivoted until such time as the resistance is overcome by engaging a pivot member that has been shifted to a different position. A cavity84is provided in the head of piston40to accommodate the relative movement of the piston and connecting rod. A pivot mechanism is utilized to pivot the coupler80to a desired position of eccentricity to adjust the combustion ratio. An exemplary form of pivot member90is shown inFIG. 1and is described in more detail below. A modified form of pivot member90ais shown for selective coupling to the couplers for pistons42and44and is also described below. The pivot member90ais an example of, a single or common pivot member for engaging the piston couplers80associated with first and second pistons (e.g., pistons42,44), the pivot member90acomprising a first set of two pivot coupler engagement surfaces (e.g.,210a′,210a″ ofFIG. 9) for engaging the two pivot member engagement surfaces (e.g.,170′,170″ ofFIG. 5B) of the piston coupler80associated with the piston42and a second set of two pivot coupler engagement surfaces (e.g.,210b′,210b″ ofFIG. 9) for engaging the two pivot member engagement surfaces (e.g.,170′,170″) of the piston coupler80associated with the piston44.

Thus, in this example, there is at least one pivot member operable to pivot the pivot coupler of more than one piston.

In general, in the illustrated embodiment, as a piston approaches the bottom dead center position, the piston coupler80engages the pivot member90and, if the pivot member90has been pivoted to adjust the eccentricity of the associated coupler, the coupler engages the pivot member and is pivoted to the desired eccentricity position. During pivoting of coupler80, the friction applied by friction brake82, if included, is overcome to allow such pivoting. Following pivoting, the friction brake82retains the coupler80in position relative the connecting rod60until further adjustment of the pivot member to adjust the eccentricity position. If during a stroke the coupler80happens to pivot slightly in an undesired manner, upon return to the bottom dead center position, the coupler80is again adjusted to the desired position of eccentricity by engagement of the pivot engager portion of the coupler with the pivot member90. The pivot members90,90acan be pivoted together so that their positions are maintained at the same rotational position. As each cylinder reaches its bottom dead center position, the eccentricity of the cylinder is adjusted if the pivot member has been turned. For example, inFIG. 1, piston42is at the bottom dead center position with surface170″ of piston coupler80shown engaging a surface210a″ of pivot member90a. If pivot member90ahas been turned to adjust the eccentricity of the associated coupler80, upon such engagement of surfaces210a″ and170″, the coupler80for piston42turns to adjust the relative position of piston42to its associated connecting rod60. Similarly, as each of the other pistons40,44reach their bottom dead center positions, they would likewise be adjusted to the desired compression ratio by pivoting their associated couplers80.

Thus, an exemplary internal combustion engine comprises a rotatable crank shaft24; at least one piston cylinder (e.g., in one example, six cylinders including cylinders receiving pistons40,42and44) with each piston being slidably received by its associated cylinder so as to reciprocate between top dead center and bottom dead center positions within the receiving cylinder. The piston comprises a first piston coupler portion receiving bore defining a first axis (e.g., axis74explained below) (see e.g.,FIG. 7). The connecting rod60comprises a first crank coupling end portion64pivotally coupled to the crank shaft such that rotation of the crank shaft causes the connecting rod to reciprocate. The connecting rod60also comprises a second piston coupling end portion70comprising a second piston coupler receiving bore defining a second axis160. A piston coupler (e.g., a piston pin80) comprises a piston coupler portion pivotally received by the piston coupler receiving bore (e.g., the ends of piston pin80can comprise the piston coupler portion) so as to be pivotable about the first axis. The piston coupler comprises a connecting rod coupler portion (e.g.78) pivotally received by the second piston coupler receiving bore to couple the connecting rod60to the piston (e.g.,40). One of the piston coupler portion and connecting rod coupler portion comprises an eccentric portion such that reciprocation of the connecting rod causes the piston to reciprocate between the top dead center and bottom dead center positions. Also, pivoting of the piston coupler about the first axis from a first coupler position to a second coupler position pivots the eccentric portion from a first eccentric position to a second eccentric position and shifts the second axis relative to the first axis to thereby vary the compression ratio of the associated cylinder. For purposes of an example, the portion78of pin80C an be considered an eccentric portion. Alternatively, the piston coupler portion can be the eccentric portion. The piston coupler also comprises a pivot member engager that can comprise an end portion of a piston pin (e.g., surfaces170′,170″) and a pivot member (e.g.,90,90a) comprising a pivot coupler engager (e.g., surfaces210′,210″;210a′,210a″;210b′,210b″) movable from a first pivot coupler engager position to a second pivot coupler engager position and positioned to engage the pivot member engager to pivot the piston coupler from the first coupler position to the second coupler position as the piston approaches the bottom dead center position and in response to such movement of the pivot coupler engager from the first pivot coupler engager position to the second pivot coupler engager position. The pivot coupler engager is also operable in one embodiment to disengage the pivot member engager as the piston travels away from the bottom dead center position.

The pivot member can be pivotable about a pivot member axis. In such a case, the pivot member can be pivotable about the pivot member axis from a first pivot member position to a second pivot member position to pivot the pivot coupler engager from the first pivot couple engager position to the second pivot coupler engager position. The piston coupler is pivoted from a first coupler position to a second coupler position as the piston approaches the bottom dead center position in response to the pivoting of the pivot coupler engager from the first pivot coupler engager position to the second pivot coupler engager position.

The pivot member engager can comprise at least one pivot member engagement surface (e.g., surface170′) and the pivot coupler engager can comprise at least one pivot coupler engagement surface (e.g. surface210′). In this example, the at least one pivot coupler engagement surface can be pivoted from a first position to a second position in response to pivoting of the pivot member from the first pivot member position to the second pivot member position. The at least one pivot member engagement surface and at least one pivot coupler engagement surface are desirably positioned to engage one another as the piston approaches the bottom dead center position to pivot the piston coupler from the first coupler position to the second coupler position in response to the pivoting of the at least one pivot coupler engagement surface from the pivot coupler engager first position to the pivot coupler engager second position. The at least one pivot coupler engagement surface and the at least one pivot member engagement surface can each be a flat surface and such surfaces can be planar. In a specific embodiment, there are two of said pivot member engagement surfaces (e.g.,170′,170″) positioned on opposite sides of the first axis. In an alternative embodiment, there can be a first set of two pivot coupler engagement surfaces on opposite sides of the pivot member axis (see surfaces210′,210″ of pivot member90and either surfaces210a′,210a″ or210b′,210b″ of pivot member90a). In a specific form, the pivot member engager comprises downwardly facing first and second pivot member engagement surfaces of one end portion of a piston pin.

In the example ofFIG. 1, the couplers80can, for example, have an eccentricity of 1.8 mm. In addition, the turning angle of the pivot member90,90acan be limited to a predetermined amount or extent. In a specific example, the turning angle can be limited to 110 degrees to thereby provide a maximum 3 mm piston movement. With the exemplary dimensions shown in Table 1, a variable combustion chamber volume is provided and a variable combustion ratio of from 10-16 results. These dimensions can be varied.

FIG. 2illustrates the piston40without the coupler80and without the connecting rod60coupled thereto. The piston40comprises a first bore section110of circular cross-section and having a longitudinal axis aligned with the longitudinal axis74in this example. Friction brake engagers are provided adjacent to the bore110. These engagers can take numerous forms and are designed to engage a friction brake in the illustrated example to prevent rotation of the friction brake relative to the piston. Although recesses and other interfitting arrangements can be used, inFIG. 2a plurality of projections, in this case radially extending projections114,116and118are provided. These projections extend in an outward direction from the edge of bore110at locations spaced 120 degrees about the center of the bore110. These projections extend outwardly away from a surface112of the piston.

InFIG. 3, a vertical sectional view through piston40ofFIG. 2, the bore110is shown along with the projections114and118. A second bore124, having a longitudinal axis corresponding to the axis74in this example, is also shown. The bores110and124are co-axial and are of right cylindrical shape.

FIGS. 4,4B,5,5A and5B illustrate an exemplary eccentric piston coupler80in the form of a piston pin for coupling the piston40to the associated connecting rod60. Coupler80comprises a first end portion130, a second end portion140and a central section150intermediate the first and second end portions130,140. End portion130comprises an exterior right cylindrical surface152. End section140comprises a right cylindrical surface154. In addition, the central portion150comprises a right cylindrical surface156. The axis of cylindrical surface156is centered on the axis160. In contrast, the surfaces152,154are eccentrically located relative to axis160as these surfaces have a longitudinal axis centered on an axis74with the spacing between axes74and160indicating the eccentric offset (see, e.g., offset E2inFIG. 2).FIG. 4aillustrates an end view of the coupler80ofFIG. 4. Thus, at least one portion of the piston coupler of this example can comprise an eccentric portion that is eccentric relative to at least one other portion of the piston coupler.

With reference toFIG. 4B, the maximum eccentricity of this form of coupler can be defined as E and corresponds to the maximum offset between the first and second axes74,160arising from pivoting the eccentric portion150. The piston coupler80comprises a piston pin comprising first and third portions130,140and a second portion150intermediate the first and third portions, the first and third portions have longitudinal centerlines that are aligned with the first axis160. In addition, the second portion150comprises the eccentric portion and has a longitudinal center line that is aligned with the second axis160. In this example, the first, second and third portions comprise right cylindrical surfaces152,154. Also, the second portion comprises a right cylindrical surface156of a first radius defined as RCR, one of the first and third portions (e.g., portion140) has a right cylindrical surface of a radius R1, wherein R1≧(RCR+E), and the other of the first and third portions (e.g., portion130) has a right cylindrical surface of a radius R2, wherein R2≦(RCR−E).

In an embodiment shown inFIG. 5C, a second end portion140bof the piston pin defines a second cavity193that is at least partially conical. In this example, a pivot member engager comprises (e.g., including surface170b″) an outwardly projecting portion of the second end portion of the piston pin. Also, a first end portion130bof this form of pivot pin also defines a first cavity195that is at least partially conical with a surface213b″ operable as explained below in connection with surface213ofFIG. 7.

An internal cavity182binterconnects the first and second cavities193,195. The internal cavity and the first and second cavities can be shaped and dimensioned to achieve a homogenous bending line201(FIG. 5D) in response to the application of force by the piston to the piston pin (forces Fp, Fpapplied to end portions of the piston pin) and the counterforce applied by the connecting rod during operation of the engine.

The piston coupler can comprise a first end portion130(FIG. 7) comprising a piston coupler braking surface and a second end portion140, the pivot member engager can comprise an outwardly projecting portion of the second end portion.FIG. 7illustrates the coupler80installed in place. With this exemplary construction, turning of the coupler80shifts the piston relative to the piston rod to thereby vary the combustion ratio.

FIGS. 4C and 7Billustrate an alternative form of coupler80a. In this form, first and third portions130a,140ahave respective first and third diameters that are equal. Also, portion150ahas a second diameter that is greater than the first and third diameters. In this example, the piston coupler receiving bore comprises right cylindrical first and second piston bore portions110a,124ahaving a diameter that is greater than the second diameter such that the piston pin is insertable in one direction through one of the first and second piston bore portions and the connecting rod bore. A first bushing171is mounted to the first piston pin portion130aand positioned within the first piston bore portion110aand second bushing173is mounted to the third piston pin portion140aand is positioned within the second piston bore portion124a. One or both of the bushings171,173are desirably mounted in place after the piston pin has been inserted into the piston and through the connecting rod. The first and second bushings171,173restrict the piston pin against motion along the axis74.

With reference toFIG. 5B, an exemplary pivot member engager can comprise at least one pivot member engagement surface (e.g., two surfaces170′ and170″). The pivot coupler engager can comprise at least one pivot coupler engagement surface (seeFIG. 9). The at least one pivot coupler engagement surface can be pivoted from a first position to a second position in response to pivoting of the pivot member from the first pivot member position to the second pivot member position. The at least one pivot member engagement surface and at least one pivot coupler engagement surface are desirably positioned to engage one another as the piston approaches the bottom dead center position to pivot the piston coupler from the first coupler position to the second coupler position in response to the pivoting of the at least one pivot coupler engagement surface from the pivot coupler engager first position to the pivot coupler engager second position.

Again,FIG. 5illustrates a vertical sectional view through the exemplary coupler80.FIGS. 5aand5bare respective end views of the coupler.FIG. 5also illustrates a pivot member engaging element, in this case a surface170″ positioned to engage the pivot member90to turn the coupler80to adjust the eccentricity of the coupler and thereby the compression ratio as explained below.

The internal combustion engine can also comprise a piston coupler retainer coupled to the piston coupler to apply a retention force to resist pivoting of the piston coupler. The piston coupler retainer can also limit the pivoting of the pivot coupler about the first axis (e.g., axis74) to be within a predetermined limit. One specific example of a mechanism for retaining the piston coupler in a location to which it has been pivoted or turned, comprises a friction brake. The illustrated coupler comprises a brake engaging surface, such as a partially conical or frusto conical recess180extending inwardly into the end portion130of coupler80. An internal bore182is provided at the base of recess180. An exemplary friction brake184is shown inFIGS. 6 and 6a. The illustrated friction brake comprises a body185with a generally conical braking component186having an external braking surface186ashaped to engage the braking surface180of the coupler80. The body185can comprise a generally triangular base portion187from which the braking portion186projects. The base185can also be provided with interfitting members that mate with or interfit with corresponding interfitting members of the piston. Thus, for example, the base can comprise plural indentations or recesses190,192,194for engaging the respective projections118,114and116of the piston (seeFIG. 2). When engaged in this manner, relative rotation between the brake184and the piston42is prevented. As can be seen inFIG. 7, a biasing spring196can be positioned within the conical portion186of the break184. A braking force adjustment screw198having a head197threadedly received and captured in a threaded bore182of coupler80is provided. A nut199coupled to screw198can be rotated to adjust the braking force by changing the axial position of the screw in bore182to thereby change the compression of the spring196. The nut199can be fastened to or otherwise mounted so as to be retained on the screw so as not to be dislodged during operation of the engine. Surfaces213,215(FIG. 4A) of the piston pin cooperate with the friction brake to limit the extent of pivoting of the piston pin to within a predetermined angular limit, such as 110 degrees. Other mechanisms can be used to limit such pivoting.

Thus, in this example, each of the piston coupler braking surface and friction brake braking surface is at least partially conical. The piston coupler, in this example, comprises a piston pin with first and second end portions, the first end portion comprising a brake receiving first cavity defining the piston coupler braking surface. Also, a friction brake being inserted at least partially into the brake receiving cavity in this example.

FIGS. 8 and 8aillustrate an exemplary pivot member90. The illustrated pivot member comprises a body202having an outer surface204which can be of a right cylindrical shape for insertion into a bore206in the end wall16of the engine housing12(FIG. 13). A recess209can be provided in the body202. In theFIGS. 8 and 8aform, recess209is an arcuate recess having a radius and centered about the axis24. A worm gear200is positioned and captured or formed within recess209. As can be seen inFIG. 8a, the illustrated recess209does not extend entirely around the circumference of the body202. Instead, the recess209and worm gear is of a limited length, in this example, although this can be varied, the length is limited to “θ”+“Δ”, such as 110 degrees (e.g., in the example where “θ” is equal to “Δ” and equal to 55 degrees, 55 degrees either side of vertical). This limits the extent to which the pivot member90can be turned during operation of the engine. The pivot member also comprises first and second eccentric coupler engaging surfaces210′,210″ (only one, namely210″, of which is shown inFIG. 8, and with both of these surfaces being shown inFIG. 13). The operation of these surfaces to engage and pivot the eccentric coupler will be understood from the description below.

In this example, the worm gear drivenly is coupled to the pivot member. A motor can be coupled to the worm gear and is operable to pivot the pivot member from plural first positions to plural second positions to adjust the compression ratio to a plurality of values. Also, as a specific example, the pivot member can define a recess extending in a direction perpendicular to the pivot member axis, the worm gear being positioned at least partially in the recess. The worm gear engages the pivot member to restrict movement of the pivot member in either direction along the pivot member axis. Also, as explained above, the worm gear can be configured to restrict pivoting of the pivot member to be within a predetermined limit. Thus, the predetermined limit can be, in one example, approximately one hundred and ten degrees. The center position of the limit can correspond to the pivot coupler being pivoted to a position that aligns the first axis74and the second axis160.

FIGS. 9,9A and9B illustrate another exemplary form of pivot member90a. Components of theFIG. 90aexample of pivot member in common with those of pivot member90are assigned the same numbers as inFIGS. 8 and 8awith the letter “a” following the number. When mounted in place, the illustrated form of pivot member90aprovides two coupler engaging surfaces210a′,210a″ in position to engage the piston coupler80that couples piston42to its associated piston rod60and two coupler engaging surfaces210b′ and210b″ in position to engage the coupler80that couples piston44to its piston rod60. These engaging surfaces are also shown inFIG. 13. Pivot member supports220,222shown inFIGS. 10,10a,11,11aand12can be mounted to engine block12as shown inFIG. 13to support and retain the pivot member90ain position. In this example, pivot member90acomprises one form of a common pivot member comprising a first pivot member end portion extending into a first region defined by the first cylinder and a second pivot member end portion extending into a second region defined by the second cylinder. A first bracket can be coupled to the first cylinder in a position to pivotally support the first pivot member end portion. A second bracket can be coupled to the second cylinder in a position to pivotally support the second pivot member end portion. The first and second brackets can be fastened together (e.g., using bolts227,229) with a portion of the first cylinder and a portion of the second cylinder positioned between the first and second brackets. The first and second bracket can be shaped to provide clearance for the respective pivot member engagement surfaces and pivot coupler engagement surface to engage one another.

With reference toFIG. 13, a shaft300having a distal end portion with a worm gear drive portion302engages the worm gear200of pivot member90such that rotation of the shaft300in respective opposite directions pivots the pivot member90in respective opposite directions within the limits of the worm gear200. A similar shaft (not shown) can be used to drive the worm gear209aof pivot member90a. These shafts300are respectfully driven by worm gears304,306coupled thereto. A rotatable shaft308having worm gear drive elements coupled thereto and in engagement with worm gears304,306is rotated in respective opposite directions to drive the worm gears304,306and the associated shafts300and pivot members90and90ain the desired direction for adjusting the position of the respective pivot members90,90atogether.FIGS. 14A,14B, and14C illustrate exemplary positions of the pivot member driven by the associated worm gear. A motor360controlled by control signals via a connector362(or wireless coupling or other coupling) can be controlled to drive the shaft308and thereby the mechanism as explained above. Motor360can be any suitable motor, such as a stepper motor. Control signals for motor360can come from, for example, a microprocessor or electronic control module via an electrical signal carrying bus of a vehicle. The interaction of these components will be more apparent fromFIG. 14wherein corresponding elements are given corresponding numbers.

The operation of these exemplary components will also be better understood with reference toFIGS. 15A-15D.

InFIG. 15A, assume that coupler90has been turned counterclockwise (in this example, in the direction of arrow370) a certain amount to adjust the compression ratio. The amount of turning has been exaggerated in these figures for purposes of illustration. As the piston coupler80moves downwardly, as indicated by arrow350, eventually (as shown inFIG. 15B), a portion of one of the coupler surfaces, in this example surface170″ engages a portion of one of the pivot member turning surfaces in this example surface210″. Continued downward movement of the piston results in rotation (pivoting) of the coupler (in this example in the direction of arrow372). When in the bottom dead center position shown inFIG. 15C, the surfaces170′,170″ of the coupler have been rotated to a position that matches the position of the surfaces210′,210″ of the pivot member90. As the piston moves upwardly, as indicated by arrow352, and away from the bottom dead center position, the coupler80has been adjusted to vary the compression rate (note the position of surfaces170′,170″) and can be retained in adjustment by the friction brake as previously explained.

With reference toFIGS. 16A and 16B, a piston cylinder shown with a longitudinal centerline400. The longitudinal centerline is desirably positioned between a first line parallel to the longitudinal centerline that intersects the first axis and a second line parallel to the longitudinal centerline that intersects the second axis when the eccentric portion is pivoted to the maximum allowed extent.

With reference toFIG. 17, a piston cylinder is illustrated with a longitudinal centerline and wherein the maximum eccentricity is defined as E and corresponds to the maximum offset between the first and second axes, wherein an origin of a reference coordinate system430is at the intersection of the longitudinal centerline of the at least one piston cylinder and a bottom dead centerline432corresponding the second axis when the second axis is in the bottom dead center position, wherein the Z dimension is along the longitudinal center line of the piston cylinder from the origin and the X dimension is along the bottom dead centerline from the origin, wherein the pivot member axis is parallel to the first axis and, wherein the pivot member axis (into the page and intersecting point433) intersects an area434wherein X is from −0.5 E to −0.8 E and Z is from −0.25 E to 0.25 E.

With reference toFIG. 18, an exemplary motor360is shown for driving worm gear shaft308to pivot the pivot members and adjust the compression ratio of the engine such as previously described. Motor360can be a stepper motor or other form of motor and can provide feedback to an engine controller370which provides drive signals to the motor. Motor360is simply one example of a mechanism for driving a worm gear or other pivot member drive mechanism. Engine controller370can be a conventional engine controller, such as programmable controller, used in a vehicle which captures various vehicle parameter signals on a system bus utilized in the vehicle. These parameter signals can be used by the engine controller to generate motor control signals should conditions exist where it is desirable to selectively adjust the pivot members to vary the stroke of the piston cylinders. These control signals can be responsive to one or more engine operating parameters. Exemplary parameters are indicated within block372, together with schematic illustrations of sensors for measuring the parameters. For example, a throttle angle sensor374can be used to deliver a throttle angle signal via a data bus to the engine controller. The motor360can drive worm gear308in clockwise or counterclockwise directions in response to control signals from the engine controller370in response to the throttle angle sensor signals. For example, under open throttle (full load) conditions, the compression ratio would typically be reduced. Under closed throttle (idle) conditions, the compression ratio would typically be increased. As another example, the combustion air temperature can be sensed by temperature sensor376. In general, higher combustion air temperatures can be used to lower thresholds of alternatively used signals to control the motor to reduce the compression ratio. In contrast, lower temperature sensed signals can be used to increase the threshold to increase the compression ratio. As yet another example, a pressure sensor377can be used to sense the cylinder head pressure. Above a pre-defined pressure level at a certain crank shaft position, for example the top dead center position, the compression ratio would typically be decreased. Below this pre-determined pressure level, the compression ratio can be increased. The crank shaft position can be sensed by a crank shaft position sensor379. As a further example, an ionization sensor, typically integrated into an ignition plug, senses in the moment of ignition the grade of the ionization of the air/fuel mixture of the internal combustion engine. Above a pre-determined threshold, the compression ratio is typically decreased. Below the pre-determined threshold, the compression ratio is typically increased. An ignition plug with an ionization sensor is indicated at378inFIG. 18. As another alternative, a knocking sensor indicated schematically at380, typically mounted to a cylinder block, senses vibration spikes caused by uncontrolled ignition of the combustion mix, corresponding to the engine knocking. In response to such signals, the engine controller370can control motor360to decrease the compression ratio. Control signals derived from combinations of sensed engine parameter conditions can also be used.

Having illustrated and described the principles of my invention with reference to exemplary embodiments, it should be apparent to those of ordinary skill in the art that these elements can be modified in arrangement and detail without departing from the inventive principles disclosed herein. I claim all such modifications.