This application relates to Provisional Application No. 62/230,277 having a filing date of June 1, 2015, Provisional Application No. 62/386,903 having a filing date of December 14, 2015, and Provisional Application No. 62/388,596 having a filing date of February 1 , 2016

BACKGROUND OF THE INVENTION

Prior art variable compression ratio engines having a flexible gasket for sealing between the crankcase and a movable cylinder head or cylinder jug have been made by SAAB, and are described in US Patent Number 5,611,301. These engines have an elastic seal (34) which extends around the whole cylinder jug or section (11). Seal (34) provides a seal between cylinder jug (11) and lateral walls (21 and 22) for containing crankcase splash oil inside the engine. Seal (34) has a bellows cross sectional shape. A problem with the bellows shape of seal (34) is that of vibration and wear because of the large pressure pulsations within the crankcase caused by the underside of the reciprocating pistons (15). The pressure differential between the inside and outside of the engine will at times cause seal (34) to bend excessively outward, and at times excessively inward. The vibrating seal (34) also fails to contain noise inside the crankcase, resulting in a noisy engine. Another problem with the seal (34) is that cylinder head (26) must be removed for replacement of seal (34). Removal of the cylinder head is a relatively expensive procedure. Seal (34) is clamped between cylinder head (26) and cylinder jug (11).

Accordingly, an objective of the present invention is to provide a seal for a variable compression ratio engine that does not vibrate or wear excessively when exposed to large fluctuating internal crankcase gas pressures. Another objective is to minimize engine noise. Another objective is for the seal to be easily replaceable in order to minimize maintenance costs.

SUMMARY OF THE INVENTION

According to the present invention the crankcase of a variable compression ratio engine is sealed with a gasket having a U shape. The U is turned sideways, with the legs of the U pointing outward, and the curved middle of the U facing inward. The inside of the U has the shortest perimeter length around the engine, and this short perimeter length serves to keep the gasket from bowing out or inverting. The short perimeter length acts like a belt for holding the gasket in place. In the preferred embodiment of the present invention, the outer legs of the gasket have clasps for replacing the gasket without removing the cylinder head of the engine. The clasps enable the gasket to be easily replaceable for minimized maintenance costs. The flexible portion of the gasket is short and well supported for minimizing vibration, wear and noise.

BRIEF DESCRIPTION OF THE FIGURES

Fig. 1 is intended to schematically illustrate a variable compression ratio engine having a flexible gasket according to the present invention.

Fig. 2 is a detailed view of the flexible gasket assembly.

Fig. 3 is a detailed view of the gasket.

Fig. 4 is a detailed view of a gasket retainer.

Fig. 5 is similar to Fig. 2 but shows a gasket bonded to the housings.

Fig. 6 is similar to Fig. 2 but shows an L shaped retaining bracket.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Figs. 1 and 2 are intended to illustrate a variable compression ratio engine 2 having a flexible gasket assembly 4 according to the present invention. Variable compression ratio engine 2 includes a crankcase 6 and a cylinder jug 8 and a cylinder head 10. Variable compression ratio engine 2 further includes a crankshaft 12 having a crankshaft axis of rotation 14. Cylinder jug 8 has a deck surface 16 for mounting cylinder head 10. Variable compression ratio engine 2 has a variable distance between crankshaft axis of rotation 14 and deck surface 16 for varying the compression ratio of the engine.

Flexible gasket assembly 4 is intended to seal the interior of crankcase 6 for containing engine oil inside of the crankcase. Flexible gasket assembly 4 includes a flexible gasket 18, a first housing 20, a second housing 22, and a variable separation distance 24 between first housing 20 and second housing 24.

Variable compression ratio engine 2 further includes an interior space 26 contained inside of flexible gasket assembly 4, and an exterior space 28 outside of interior space 26. Flexible gasket 18 further has a first contact surface 30 in sealing contact with first housing 20, and a second contact surface 32 in sealing contact with second housing 22, and a flexible middle curtain wall 34 spanning from first contact surface 30 to second contact surface 32. According to the present invention, flexible middle curtain wall 34 extends inwardly into interior space 26 for providing a stable gasket that does not flutter or invert with changing gas pressures within crankcase 6. In the preferred embodiment of the present invention, flexible gasket 18 has a U cross sectional shape, where first and second contact surfaces 30 and 32 forming the outer portions of the U cross sectional shape, and flexible middle curtain wall 34 forms the curved middle portion of the U cross sectional shape. According to the present invention the middle portion of the U cross sectional shape extends inwardly into interior space 26. First and second contract surfaces 30 and 32 are referred to generally as the outer legs of the U cross sectional shape. Optionally the U can face outward, but an inward facing U is more compact and less expensive to manufacture. The inward facing U also provides access from outside of the engine to retaining clasps for securing gasket 18 in place. Cross sectional shapes other than a U may be used according to the present invention, however, the preferred embodiment of the present invention has a generally U shaped cross section. The flexible gasket 18 and flexible middle curtain wall 34 may be made out of rubber, Nitrile, Viton, a Florosilicon or other functional material.

Referring now to Figs. 1 and 2, preferably flexible gasket 18 is an endless band 36 for sealing the entire perimeter around cylinder jug 8.

Flexible gasket 18 has an innermost perimeter length 38 and a first outermost perimeter length 40 for first contract surface 30 and a second outermost perimeter length 42 for second contract surface 32. According to the present invention innermost perimeter length 38 is shorter than first and second outermost perimeter lengths 40 and 42, thereby preventing interior gas pressures from inverting flexible gasket 18.

Referring now to Fig. 5, optionally first contract surface 30 is bonded or has a bond 44 to first housing 20. Bond 44 may be formed with an adhesive or chemical process, or by other functional means for securing first contract surface 30 to first housing 20 such as micro grooves. Similarly, second contact surface 32 optionally is bonded or has a bond 44 to second housing 22.

Referring now to Figs. 1 and 2, optionally first housing 20 is a bracket 45 and fastened to cylinder jug 8 with upper bracket fasteners 46.

Referring now to Fig. 5, optionally first housing 20 is a bracket clamped between cylinder head 10 and cylinder jug 16. A head gasket 48 is customarily used between cylinder head 10 and cylinder jug 16.

Referring now to Figs. 1 and 2, optionally flexible gasket assembly 4 includes a first gasket retainer 50 for securing first contact surface 30 to first housing 20. Similarly, flexible gasket assembly 4 may include a second gasket retainer 52 for securing second gasket surface 32 to second housing 22. First and said second gasket retainers 50 and 52 are removable, thereby enabling removal and replacement of flexible gasket 18 with a minimum disassembly of variable compression ratio engine 2. Referring now to Fig. 4, first gasket retainer 50 preferably has a plurality of sections 50a and 50b, thereby enabling removal and replacement of flexible gasket 18 with a minimum disassembly of variable compression ratio engine 2. Optionally, mounting rail 56 may have a plurality of sections to aid in removal and replacement of flexible gasket. 18.

Similarly, second gasket retainer 52 may have a plurality of sections, thereby enabling removal and replacement of flexible gasket 18 with a minimum disassembly of variable compression ratio engine 2.

Referring now to Fig. 6, first retainer 50 may be fastened to cylinder head 10 (not shown) or cylinder jug 8.

Referring now to Figs. 1 , 2 and 6, flexible gasket assembly 4 further includes lower bracket fasteners 54 for fastening second gasket retainer 52 to crankcase 6.

Referring now to Figs. 2 and 6, first and second housing 20 and 22 may include a mounting rail 56, where the first and second contact surfaces 30 and 32 are in sealing contact with mounting rail 56.

Optionally mounting rail 56 includes thermal insulation 58. First housing 20 may be formed in cylinder head 10 or cylinder jug 8, or be a separate part, and first housing 20 may optionally be an assembly of parts. Similarly, second housing 22 may be formed in crankcase 6 or be a separate part or an assembly of parts.

Referring now to Figs. 1 and 4, first and second gasket retainers 50 and 52 are generally flat for clasping flexible gasket 18. Referring now to Fig. 6, retainers 50 and 52 may optionally include a gland 70 for receiving a sealing bead 68.

Referring now to Fig. 6, optionally first or second gasket retainer 50 or 52 has an L shaped cross sectional area, thereby providing easier access to lower bracket retaining fasteners 54.

Referring now to Figs. 1, 2 and 3, preferably gasket assembly 4 includes washer inserts or compression washers 60 for controlling the clamping force applied to flexible gasket 18 by upper gasket fasteners 64.

Preferably first gasket retainer 50 includes threaded fastener holes 62 for receiving upper gasket fasteners 64 for clamping flexible gasket 18 to first housing 20.

Referring now to Fig. 3, preferably flexible middle curtain wall 34 preferably has ribbing 66, thereby providing greater flexibility in multiple directions for flexible gasket 18. Referring now to Figs. 1, 2, 3, and 6 preferably flexible gasket 18 includes a retaining or sealing bead 68 for retaining flexible gasket 18 in place or providing seal. Sealing bead 68 may be located outside of housings 20 and 22 as shown in Fig. 2, or located in a gland 70 as shown in Fig. 6.