CYLINDER UNIT FOR ELIMINATING SECONDARY FORCES IN INLINE INTERNAL COMBUSTION ENGINES

Abstract

A cylinder unit includes a piston disposed in the cylinder bore that is connected to a piston connecting frame member. The piston connecting frame member replaces a conventional connecting rod, and reciprocates exclusively along the bore axis. A crank connecting member has a linear rail at its top that is captured in a transverse gap along the bottom of the piston connecting frame member, and converts the circular movement of a crank throw to linear motion of the piston connecting frame member.

Claims

1. An internal combustion engine, comprising: a plurality of in-line cylinder units; each one of the cylinder units having: a bore having a bore axis; a piston disposed in the bore that reciprocates within the bore along the bore axis, the piston having a head and a connecting boss extending from a bottom of the head; a piston connecting frame member having a top boss that is centrally located on the piston connecting frame member and that is coupled to the connecting boss of the piston, the piston connecting frame member further having a pair of lateral portions extending outward in opposing direction, each lateral portion having a vertical end face with a respective vertical linear bearing mounted on the vertical end face, the piston connecting frame member further having a bottom on which a bottom linear bearing is mounted; a crank connecting member having a lateral rail at a top of the crank connecting member, wherein the lateral rail is captured at a bottom of the piston connecting frame member and reciprocates laterally along the bottom of the piston connecting frame member, the crank connecting member further having a crank throw opening to connect to a throw of a crankshaft.

2. The internal combustion engine of claim 1, wherein the piston of each cylinder unit is a skirtless piston.

3. The internal combustion engine of claim 1, wherein the piston connecting frame member includes a pair of vertical side extension, each one of the vertical side extensions mounted on a respective one of opposing sides of the piston connecting frame member, and having a lower portion that extends inward, under the bottom linear bearing, and wherein the lower portion of each vertical side extension include a linear bearing under the bottom linear bearing on the bottom of the piston connecting frame member, wherein the lateral rail of the crank connecting member is captured between the bottom linear bearing and the linear bearings on each of the vertical side extensions.

4. The internal combustion engine of claim 1, wherein the crank connecting member includes an oil groove formed in a crank journal, and further includes at least one oil passage to the lateral rail, and wherein the at least one oil passage to the lateral rail is open at the lateral rail.

5. The internal combustion engine of claim 4, wherein the lateral rail comprises oil passages that are open at a top, sides, and ends of the lateral rail.

6. The internal combustion engine of claim 1, wherein the connecting boss of the piston includes a threaded bore, the top boss of the piston connecting frame member includes a bore that corresponds to the bore in the connecting boss, the piston connecting frame member further having a port through the piston connecting frame member to which the bore in the top boss extends, a threaded rod is disposed in the bore of the connecting boss the bore through the top boss such that free end of the threaded rod is in the port, and a nut is threaded onto the free end to retain the piston to the piston connecting frame member.

7. The internal combustion engine of claim 6, further comprising an anti-rotation pin that extends from the top boss into a bottom of the connecting boss that prevents the piston from rotating with respect to the piston connecting frame member.

8. An inline four-cylinder engine, comprising: four piston assemblies arranged in a line and each connected to a crankshaft, each one of the piston assemblies including: a piston having a head and a connecting boss extending from a bottom of the head; a piston connecting frame member having a top boss that is centrally located on the piston connecting frame member and that is coupled to the connecting boss of the piston, the piston connecting frame member further having a pair of lateral portions extending outward in opposing directions, each lateral portion having a vertical end face with a respective vertical linear bearing mounted on the vertical end face, the piston connecting frame member further having a bottom on which a bottom linear bearing is mounted; a crank connecting member having a lateral rail at a top of the crank connecting member, and a journal opening configured to receive a crank throw therein, wherein the lateral rail is captured at a bottom of the piston connecting frame member and reciprocates laterally along the bottom of the piston connecting frame member, the crank connecting member further having a crank throw opening to connect to a throw of the crankshaft.

9. The inline four-cylinder engine of claim 8, wherein the piston of each cylinder unit is a skirtless piston.

10. The inline four-cylinder engine of claim 8, wherein the piston connecting frame member includes a pair of vertical side extension, each one of the vertical side extensions mounted on a respective one of opposing sides of the piston connecting frame member, and having a lower portion that extends inward, under the bottom linear bearing, and wherein the lower portion of each vertical side extension include a linear bearing under the bottom linear bearing on the bottom of the piston connecting frame member, wherein the lateral rail of the crank connecting member is captured between the bottom linear bearing and the linear bearings on each of the vertical side extensions.

11. The inline four-cylinder engine of claim 8, wherein the crank connecting member includes an oil groove formed in a crank journal, and further includes at least one oil passage to the lateral rail, and wherein the at least one oil passage to the lateral rail is open at the lateral rail.

12. The inline four-cylinder engine of claim 11, wherein the lateral rail comprises oil passages that are open at a top, sides, and ends of the lateral rail.

13. The inline four-cylinder engine of claim 8, wherein the connecting boss of the piston includes a threaded bore, the top boss of the piston connecting frame member includes a bore that corresponds to the bore in the connecting boss, the piston connecting frame member further having a port through the piston connecting frame member to which the bore in the top boss extends, a threaded rod is disposed in the bore of the connecting boss the bore through the top boss such that free end of the threaded rod is in the port, and a nut is threaded onto the free end to retain the piston to the piston connecting frame member.

14. The inline four-cylinder engine of claim 13, further comprising an anti-rotation pin that extends from the top boss into a bottom of the connecting boss that prevents the piston from rotating with respect to the piston connecting frame member.

15. A cylinder unit for an internal combustion engine, comprising: a cylinder having a bore, the bore having a bore axis; a piston disposed in the bore; a piston connecting frame member connected to the piston, the piston connecting frame member having lateral portions extending in opposite directions and generally in a direction normal to the bore axis, each of the lateral portions having a vertical linear bearing that each face outward from the respective lateral portions and are each oriented to have an outer face that is parallel to the bore axis, a transverse gap formed at a bottom of the piston connecting frame member; a crankcase having vertical tracks on opposite sides of an interior of the crankcase, wherein the vertical linear bearings are each engaged in one of the vertical tracks; and a crank connecting member having a top portion, a linear rail formed at the top portion that is captured in the transverse gap, the crank connecting member further having a journal opening configured to receive a crank throw therein; wherein the crank connecting member translates a circular movement of the crank throw to a vertical linear movement of the piston connecting frame member and piston along the bore axis.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and explain various principles and advantages all in accordance with the present invention.

[0029] FIGS. 1A-1C show various views of a piston for an internal combustion engine, in accordance with some embodiments;

[0030] FIGS. 2A-2B show a piston connecting frame member in an assembly series, in accordance with some embodiments;

[0031] FIG. 3 shows an exploded view or a piston sub-assembly, in accordance with some embodiments;

[0032] FIGS. 4A-4D show a series of views for assembly of slide rails being assembled onto a piston connecting frame member, in accordance with some embodiments;

[0033] FIGS. 5A-5D show views of a crank connecting member, in accordance with some embodiments;

[0034] FIG. 6 shows a crank connecting member assembled to a piston connecting frame member, in accordance with some embodiments;

[0035] FIG. 7 shows a side cut-away view of a piston assembly connected to a crankshaft, in accordance with some embodiments;

[0036] FIGS. 8A-8D show a series of stroke positions of a piston assembly in an internal combustion engine, in accordance with some embodiments; and

[0037] FIG. 9 shows a side view of a four piston assemblies connected to a crankshaft for an inline four cylinder engine, in accordance with some embodiments.

DETAILED DESCRIPTION

[0038] While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the following description in conjunction with the drawing figures, in which like reference numerals are carried forward. It is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms.

[0039] A cylinder unit and an inline engine using the disclosed cylinder unit uses a connecting rod assembly that moves vertically, or along the axis of movement of the piston, exclusively. That is, no portion of the connecting rod assembly moves in a direction other than vertically. As a result, the connecting rod does not swing with the crank. Instead, a crank connecting member is connected to the bottom of the connecting rod assembly and reciprocates laterally and vertically with the crank throw. The crank connecting member slides along a rail on the bottom of the connecting rod frame. As a result, the connecting rod moves at a uniform speed, vertically, through its cycle, for a given cycle rate, and avoids the creation of secondary forces that are created by conventional connecting rods due to following the crank throw.

[0040] FIGS. 1A-1C show various views of a piston 100 for an internal combustion engine, in accordance with some embodiments. FIG. 1A shows a top and side perspective view of the piston 100, FIG. 1B shows a side elevational view of the piston 100, and FIG. 1C shows a side cut-away view of the piston 100 where the piston 100 has been cut vertically through the center of the piston 100. The piston 100 uses an unconventional configuration that is facilitated by the structures connecting the piston 100 to the crankshaft. In many conventional internal combustion engines, the piston has a skirt, and a wrist pin that connect to a connecting rod which is also connected to a throw (crank throw) on a crankshaft. That conventional arrangement is what produces the well-known secondary forces in inline engines, particularly inline four-cylinder (I4) engines. The piston 100 includes a head 102 having a crown 104 or top. A plurality of ring grooves 106 are formed in the side of the head 102. The grooves 106 can include oil and compression ring groove and receive oil and compression rings accordingly. A connecting boss 108 extends downward from the bottom of the head 102. The connecting boss 108 is generally a columnar structure that is centrally located, and includes a bore 110 along the axis of the connecting boss 108 that is open at the bottom 114 of the connecting boss 108. The bore 110 can be threaded to receive a threaded connecting member. In some embodiments a hole 112 is formed in the bottom 114 adjacent the opening of the bore 110 to receive an anti-rotation pin that prevents the piston 100 from rotating once assembled to the connecting member as the pin will seat in both the piston in hole 112 and in a corresponding hole in the connecting member.

[0041] In general, the bottom 114 of the connecting boss 108 is flat along a plane that is parallel to the plane of the crown 104. The underside of the head 102 can be recessed to lighten the piston 100. The recesses can be formed between the side of the piston the connecting boss 108, having, for example, a toroidal shape around the connecting boss 108. In general, the piston 100 lacks a skirt portion, which on conventional pistons extends substantially below the ring groves 106 to reduce a tendency of the piston to turn in the cylinder bore due to the horizontal force component created by the connecting rods. However, in the inventive piston assembly and engine, only a vertical force component acts on the pistons, thus there is no need for a conventional skirt, which allow for the pistons to have lower mass over that of conventional engines. In some embodiments the piston can have a minimal skirt in order to add support when the bore of the cylinder is not vertical so as to cause the piston to rest on the cylinder wall. A small skirt portion can then add support for the weight of the piston and provide enough surface area to create the necessary oil film barrier needed to support the piston weight. In some embodiments, the minimal skirt can extend about one half inch below the ring groove section 106, but overall, the larger skirt needed for pistons using conventional connecting rods is not necessary using the inventive cylinder unit arrangement.

[0042] FIGS. 2A-2B show a piston connecting frame member 200 in an assembly series, in accordance with some embodiments. The piston connecting frame member 200 is shown in FIG. 2A in an unassembled state, and in FIG. 2B in a partially assembled state, where linear bearing elements are attached to the piston connecting frame member 200. The piston connecting frame member 200 connects to the piston 100 at a centrally located top boss 202, at the top surface of the top boss 202. The top boss 202 is sized and shaped to mate with connecting boss 108 of the piston 100 at the bottom 114 of the connecting boss 108. A bore 208 passes through the center of the top boss 202 and aligns with the bore 110 in the connecting boss 108 of the piston 100. While the top boss 202 is generally cylindrical at its uppermost portion (i.e., where it meets the bottom 114 of the connecting boss 108), the piston connecting frame member 200 transitions from the cylindrical shape at the top boss 202 to a generally planar shape toward the bottom 222 of the piston connecting frame member 200. Side portions 206 extend outward from the top boss 202 to opposite sides at about a forty-five-degree angle to lateral portions 210, 212 on opposing sides of the top boss 202, which also extend laterally from the central region of the piston connecting frame member 200. In general, lateral portion 210, 212 extend laterally on opposite sides of the axis of the bore 208 such that between vertical end faces 218, 220 there is a straight line through the axis of the bore 208.

[0043] A port 204 passes through the middle of the piston connecting frame member 200 under the bore 208, and the bottom of the bore 208 opens to the port 204. The lateral portions 210, 212 extend outward, to the sides, and have vertical end faces 218, 220, respectively. The end faces 218, 220 provide surfaces on which vertical linear bearings 224, 226 are mounted, and which can be held in place by bolts 232 that thread into support portions such as 214, 216. The vertical linear bearings 224, 226 each face outward and have a face that is oriented parallel to the axis of the bore. Each of the vertical bearings 224, 226 slide along respective vertical tracks in the crankcase wall of the engine that are parallel to the axis of the bore, ensuring that the movement of the piston connecting frame member 200 is strictly vertical (up/down), meaning in a direction along the cylinder bore axis. As a result, the vertical linear bearing 224, 226 also move or reciprocate in a direction parallel to the axis of the cylinder bore. Along the bottom portion of the piston connecting frame member 200 are a plurality of holes 230 that pass through the piston connecting frame member 200 from side to side, in a horizontal direction perpendicular to the direction from one end face 218 to the opposite end face 220, as with port 204. The holes 230 are used to connect extension members to the sides of the piston connecting frame member 200. A horizontal linear bearing 228 is attached to the flat bottom 222 of the piston connecting frame member 200.

[0044] FIG. 3 shows an exploded view of a piston sub-assembly 300, in accordance with some embodiments. The piston 100 is shown as it would be assembled to an assembled piston connecting frame member 200. The piston 100 is as shown in FIGS. 1A-1C and the piston connecting frame member 200 is as shown in FIG. 2B. A threaded rod 302 is placed into the bore 110 in the connecting boss 108 of the piston 100. The bore 110 can be threaded to receive the threaded rod 302. A portion of the threaded rod 302 will extend through the bore 208 in the top boss 202, and into the port 204, where fastening nut 310 is placed on the lower end of the threaded rod 302 to hold the piston 100 to the piston connecting frame member 200. To prevent the piston 100 from rotating, an anti-rotation pin 304 can be placed such that an upper end of the pin 304 is in a vertical alignment bore 306 in the bottom 114 of the connecting boss 108 of the piston, and the lower end of the pin 304 can be in a corresponding alignment bore 308 in the top of the top boss 202 of the piston connecting frame member 200. The pin 304 prevents the piston 100 from rotating and loosening the connection between the piston 100 and the piston connecting frame member 200. Other structures for connecting the piston 100 to the piston connecting frame member 200 can be used equivalently. For example, the port 204 can extend through the bottom of the piston connecting frame member 200 to allow a bolt to be inserted into the bores 208, 110.

[0045] FIGS. 4A-4D show a series of views for assembly of slide rails being assembled onto a piston connecting frame member, in accordance with some embodiments. FIGS. 4A and 4B show an end view of a piston connecting frame member 200 looking at the end having vertical linear bearing 226 in which vertical side extensions 402, 404 are being attached. FIG. 4A shows the exploded view and FIG. 4B shows the assembled view. FIGS. 4C and 4D show a similar series but from the side view as shown in FIGS. 2A-2B. In FIG. 4C a vertical extension 402 is shown separated from the piston connecting frame member 200, and in FIG. 4D the vertical side extension 402 is shown assembled onto the piston connecting frame member 200.

[0046] As can be seen in FIGS. 4A-4B, looking at the end of the piston connecting frame member 200, it can be seen that the top boss 202 is round or cylindrical at the top portion of the top boss 202, which matches the cylindrical shape of the connecting boss 108 of the piston 100. The top boss 202 then flattens/narrows farther down the piston connecting frame member 200, and below the port 206 the piston connecting frame member 200 is generally flat along the bottom of the piston connecting frame member 200 from end to end (e.g., from end face 218 to end face 220) in the vertical direction. On each side 234, 236 of the piston connecting frame member 200, along the bottom, and vertical side extension 402, 404 is respectively attached. Each of the vertical side extension 402, 404 are “L” or “J” shaped, having a vertical portion that extends downward along the side 234, 236 of the piston connecting frame member 200, and has a lower horizontal portion that turns inward to extend under the bottom 222 of the piston connecting frame member 200 and under the bottom linear bearing 228, leaving a gap between the horizontal portions of the two vertical side extensions 402, 404. On the top 416, 418 of each horizontal portion of the vertical side extensions 402, 404 is a linear bearing 406, 408 that each have a length equal to bottom linear bearing 228 on the bottom 222 of the piston connecting frame member 200. The linear bearings 406, 408 are positioned by the vertical side extensions 402, 404 so as to be spaced apart from the bottom linear bearing 228, leaving a gap between the bottom linear bearing 228 and the linear bearing 406, 408.

[0047] The vertical side extensions 402, 404 each have a plurality of holes 414 along their horizontal length that correspond with the holes 230 near the bottom of the piston connecting frame member 200. Alternating along the holes 414, every other hole 414 has an enlarged recess 412. Bolts 410 pass through the holes 414 on each vertical side extension 402, 404, and through holes 230 in the piston connecting frame member 200, to hold the vertical side extension 402, 404 to the piston connecting frame member 200. The heads of the bolts 410 fit into the recesses 412. In some embodiments rivets can be used in place of the bolts 410. Once the vertical side extension 402, 404 are connected to the sides of the piston connecting frame member 200, the crank connecting member 500 can be attached to the assembled piston connecting frame member 200. Thus, the vertical side extensions 402, 404 server to form a lateral gap along the bottom of the piston connecting frame member, and further to provide support for linear bearings along the bottom of that gap. The gap is used to capture the lateral rail 506 of the upper portion 502 of the crank connecting member 500 and allow lateral rail 506 to reciprocate within the gap in the linear bearings 228, 406, 408.

[0048] FIGS. 5A-5D show views of the crank connecting member 500, in accordance with some embodiments. The crank connecting member 500 connects the piston connecting frame member 200 to a throw of the crankshaft, and translates the rotational motion of the crank throw to a strictly vertical motion of the piston connecting frame member 200 and piston 100 by reciprocating laterally on the linear bearings 228, 406, 408. The crank connecting member 500 is comprised of an upper portion 502 and a lower portion 514 which each have a semicircular journal bearing 504, 516, respectively, that are sized to interface with half of the bearing surface of the circular crank throw journal. The upper and lower portions 502, 514 can be joined together by bolts 518 that extend vertically through the opposing ends 520, 522 of the lower and upper portions 514, 502, with the circular journal opening formed by the semicircular journals 504, 516 between the ends 520, 522 where the bolts 518 pass.

[0049] At the top of upper portion 502 is a lateral rail 506 that extends laterally from end to end, and has a flat top surface 508, and flat bottom surfaces 510 on each side of a vertical support section 512. The vertical support section 512 is narrower than a width of the lateral rail 506, and the length of the lateral rail 506 can be longer than the diameter of the circular journal opening formed by the semicircular journals 504, 516. The length of the lateral rail 506 is oriented in a direction that is normal to the axis of the journal opening, and the crank throw, and the width of the lateral rail 506 is in the direction of the journal opening (i.e., normal to the length). Furthermore, an oil groove 524 can be formed in the semicircular journals 504, 516 which encircles the journal opening and is connected to oil passages 526, 528, 530 on the lateral rail 506. One or more oil channels 702 (as shown in FIG. 7) can be formed through the upper portion 502, and through the support section 512 that joins to passages 526, 528, 530. Oil, under pressure, passes through the crankshaft and the crank throw, as is conventional, into the oil groove 524, and the pressure forces oil from the oil groove 524 into the channel(s) and out of passages 526, 528, 530. Passages 526 provide oil to the top of the lateral rail 506, passages 528 provide oil at the ends of the lateral rail 506 (and are provided on both ends of the lateral rail 506), and passages 530 are provided on both sides of the lateral rail to provide oil on the sides of the lateral rail 506 which lubricates the linear bearings 406, 408. The lateral rail 506 is assembled into the gap at the bottom of the piston connecting frame member 200, between linear bearing 228 and linear bearings 406, 408, and reciprocates laterally along that gap as the crank throw in journal opening turns circularly around the crankshaft and within the journal opening on journal bearings 504, 516.

[0050] FIG. 6 shows an end view piston assembly 600 including a crank connecting member 500 assembled to a piston connecting frame member 200, which is connection to a piston 100, in accordance with some embodiments. A detail view 602 shows the lateral rail 506 of the crank connecting member 500 positioned in the gap between linear bearing 228 and linear bearings 406, 408. FIG. 7 shows a side cut-away view of a piston assembly 700 as otherwise assembled as shown in FIG. 6, and including the elements shown in the exploded view of FIG. 3.

[0051] The lateral rail 506 slides laterally in the gap, against the linear bearing 228 on the upstroke, and against linear bearings 406, 408 on the downstroke, as the crank connecting member 500 moves with the crank throw 808, with the vertical support section 512 reciprocating between the vertical downward extensions 402, 404. Oil can be pumped through the crankshaft and crank throw through oil passage 706 in the crank throw into groove 528 of the crank journals 504, 516, and through one or more channels or passages 702 in the upper portion 502 of the crank connecting member 500. From the oil passages 702 the oil is distributed to passages 526, 528, 530 and oil exiting these passages lubricate the linear bearings 228, 406, 408. It will be understood by those skilled in the art that the term “passage” as used here refers to a void of material that allows oil to pass through the structure. The passages are generally internal to a structure, with openings on different sides of or other parts of the structure so that oil under pressure can be fed into one opening, through the passage, and out the opening at the other end(s) of the passage. One of the crank counterweights 704 is also shown in FIG. 7. As the crank throw 808 revolves around the axis of the crank shaft, the crank connecting member likewise moves in a circular path, therefore having both vertical and horizontal motion. Accordingly, as the piston connecting frame member 200 is constrained by the vertical linear bearings 224, 226 bearing against vertical tracks or guides in the crank case, the piston connecting frame member 200 can only move vertically, up and down. The lateral rail 506 both pushes the piston connecting frame member 200 up, and pulls it down, as it slides laterally relative to the piston connecting frame member 200, as captured between the bottom linear bearing 228, and the linear bearings 406, 408.

[0052] FIGS. 8A-8D show a series of stroke positions of a piston assembly in an internal combustion engine, in accordance with some embodiments. In all of FIGS. 8A-8D, there is shown a piston assembly (e.g., 600) in an internal combustion engine having a head 802 and a crankcase 804. The piston 100 reciprocates vertically in a cylinder bore 806 in the head, along the axis of the cylinder bore. Valves for intake and exhaust (not shown) can be provided at the top of the head in a conventional manner.

[0053] In FIG. 8A the piston 100 is shown at the top of its stroke (“top dead center”). The crank throw 808 is elevated higher than the crank bearing 810 which is on the crank axis about which the crankshaft revolves. The crank throw counterweight 812 is at the bottom of its path. The vertical linear bearings 224, 226 on the opposing ends of the piston connecting frame member 200 slide vertically (up and down) in respective tracks 814, 816 in the vertical wall of the crankcase.

[0054] In FIG. 8B the piston have moved downward, as indicated by arrow 820, as would happen on either an intake stroke or a combustion stroke. The position shown could be at ninety degrees of a stroke crankshaft revolution. Likewise, the piston connecting frame member 200 has moved downward as indicated by arrow 822. As a result, the crank connecting member 500 has move downward, but also to the side, as indicated by arrow 824. The lateral rail 506 will bear against the bottom linear bearing 228 on a combustion downstroke, and against linear bearings 406, 408 on an intake downstroke. The counterweight 812 has also rotated a quarter of a revolution as indicated by arrow 826.

[0055] In FIG. 8C the piston assembly is at the bottom of the stroke cycle, or one hundred eighty degrees of the stroke cycle, therefore the piston 100, and piston connecting frame member 200 are at the lowest point in the stroke cycle, and have moved farther downward from that of FIG. 8B, as indicated by arrows 828, 830, respectively. The crank connecting member 500 is also at the bottom of its rotation about the crank bearing 810 but has moved laterally in the opposite direction from that of FIG. 8B, as indicated by arrow 832, and the counterweight 812 is at the top of its rotation as indicated by arrow 834.

[0056] In FIG. 8D the piston 100 and piston connecting frame member 200 are on the upstroke, as indicated, respectively, by arrows 836, 838, either compressing fuel prior to combustion or pushing burnt fuel vapors out of the exhaust port (not shown) in the head 802. This position is about two hundred seventy degrees of a crank rotation. the crank connecting member 500 is now at the extreme right side of its movement relative to the piston connecting frame member 200 as indicated by arrow 842, and the counterweight 812 in in a downward portion of its rotation as indicated by arrow 840.

[0057] After FIG. 8D the cycle repeats for a second half of the process. As can be seen, while the piston 100 and piston connecting frame member 200 travel exclusively in the vertical direction, the crank connecting member 500 slides laterally with respect to the piston connecting frame member 200, but also rotationally around the crank bearing 810. The motion of the piston 100 and piston connecting frame member 200 are both purely vertical, and follow a sinusoidal reciprocation, slowing equally at the top and bottom, and having their fastest travel at mid-stroke. The crank connecting member 500 follows a perfectly circular motion is it travels around the axis of the crank shaft on the crank throw 808, and imparts motion to the piston connecting frame member 200 and piston by exerting force on the linear bearings 228, 406, 408 at alternating times of the stroke cycle. Thus, there are no secondary forces resulting from a velocity differential at the lower end of the connecting rod, as in a conventional piston assembly.

[0058] FIG. 9 shows a side view 900 of four piston assemblies 902, 904, 906, 908 connected to a crankshaft 909 for an inline four-cylinder (I4) engine, in accordance with some embodiments. The head and crankcase have been removed, but the piston assemblies 902-908 are otherwise each as shown in FIGS. 8A-8D, and each have a piston 100, a piston connecting frame member 200, a crank connecting member 500. The center two piston assemblies 904, 906 are one hundred eighty degrees out of phase with the outer two piston assemblies 902, 908 to balance forces exerted on the crankshaft 909. Since the inventive 14 engine does not experience the secondary forces that are present in a conventional 14 engine using connecting rods to connect the crank throw directly to the piston, the inventive 14 engine disclosed here can achieve engine speeds (revolutions per minute) and high-power output over the a conventional 14 engine of the same displacement and general configuration (e.g. valve size and number, compression ratio, etc.). Each piston assembly is separated from adjacent piston assembly/assemblies by a main bearing crankshaft journal 912. Each piston assembly 902-908 is connected to a respective crank throw 808 that passes through the crack connecting member 500 of each piston assembly 902-908. The crank throws 808 are joined with counterweights 812 that extend across the opposite side of the axis of the crankshaft from the crank throws 808, and as the crank throw 808 and counterweights 812 rotate about the axis of the crankshaft, the crank connecting member 500 will pass between the counterweights 812 as shown in piston assemblies 902, 908.

[0059] A cylinder unit and engine using the cylinder unit has been disclosed that eliminates the secondary forces that occur in conventional inline four-cylinder engines by use of a piston connecting frame member that reciprocates exclusively in a direction parallel to that of the piston. A crank connecting member connects the piston connecting member to the crank throw and translates the circular motion of the crank throw to a linear motion of the piston and piston connecting frame member. The crankcase walls are used to stabilize the piston connecting frame member and constrain the motion of the piston connecting frame member along the direction of the axis of the cylinder bore. The crank connecting member, as it is moved circularly by the crank throw, reciprocates laterally with respect to the piston connecting frame member, as it reciprocates vertically.

[0060] The claims appended hereto are meant to cover all modifications and changes within the scope and spirit of the present invention.