US3633429A - Piston stroke control mechanism - Google Patents

Abstract

Connections between a reciprocating piston and a cooperating crankshaft for providing a substantial dwell period for the piston at opposite ends of each stroke of reciprocatory movement of the piston. The connections include a connecting rod comprising a pair of pivotally connected rod sections between the piston and crankshaft, a control shaft, crank means on the control shaft, a control rod connected to the crank means and the connecting rod, and connections between the crankshaft and control shaft for imparting rotation to the control shaft at a predetermined speed relative to that of the crankshaft.

Description

United States Patent Thorvald N. Olson Ormsby, Minn. 56162 [21] Appl. No. 44,102

[22] Filed June 8, 1970 [45] Patented Jan. 11, 1972 [72] lnventor [54] PISTON STROKE CONTROL MECHANISM 123/48 B, 78 E, 197 AB, 197 AC [5 6] References Cited UNITED STATES PATENTS 2,314,789 3/1943 Jacobsen 74/44 X 1,873,908 8/1932 Schinke 123/197 AB 6 ill. Ill

VIII'IZIIIIWII Primary Examiner-William F. ODea Assistant Examiner-P. O. Ferguson Attorney--Merchant & Gould ABSTRACT: Connections betweena reciprocating piston and a cooperating crankshaft for providing a substantial dwell period for the piston at opposite ends of each stroke of reciprocatory movement of the piston. The connections include a connecting rod comprising a pair of pivotally connected rod sections between the piston and crankshaft, a control shaft, crank means on the control shaft, a control rod connected to the crank means and the connecting rod, and connections between the crankshaft and control shaft for imparting rotation to the control shaft at a predetermined speed relative to that of the crankshaft.

PATENTEU JAN] 1 m2 INVENTOR. THORVA 1.0 N OLSON ATTOFPN E Y5 PISTON STROKE CONTROL MECHANISM BACKGROUND OF THE INVENTION the crankshafts. Examples of these are disclosed in US. Pat.

Nos. 1,107,529; 1,128,885; 1,786,423; 3,l76,67l;and others. These various mechanisms utilize two-part connecting rods between the pistons and their respective crankshafts, as well as control rods extending between the connecting rods and cranks of laterally displaced control shafts often used as cam shafts for valve operation. In these prior art devices, some control shafts are connected to their respective primary or crankshafts to be rotated at the same speed as the crankshafts, others being rotated at one-half the speed of the crankshafts. With such arrangements, the length of piston stroke or travel may be controlled to provide relatively shorter compression, power, and exhaust strokes as well as relatively longer intake strokes. However, stroke control devices heretofore produced do not affect the direction reversing operation of a reciprocatory piston, the reversal of movement thereof being instantaneous as in conventional engines having one-piece rigid connecting rods between the pistons and crankshafts thereof. It is well-known that such instant reversal of piston movement causes a loss of efficiency in internal combustion engine operation due to the difficulty of obtaining proper value timing to effectively scavenge exhaust gases and introduce fresh gases. This applies to two-stroke engines as well as to fourstroke engines.

SUMMARY OF THE INVENTION The primary object of this invention is the provision of piston control mechanism which provides for a substantial dwell or stationary period in the movement of a piston at each end of its reciprocatory stroke during uninterrupted rotary movement of its cooperating crankshaft. To this end, I provide a reciprocatory piston, a primary shaft or crankshaft joumaled on an axis extending transversely of the direction of reciprocatory movement of the piston and disposed substantially in the extended path of said movement and having a crank thereon, a connecting rod including a pair of rod sections having adjacent inner ends pivotally secured together and outer ends operatively pivotally secured one to the piston and the other to the crank, all on axes parallel to the primary shaft axis. A control shaft, joumaled on an axis in laterally spaced parallel relation to the primary shaft axis, has crank means thereon pivotally connected to one end of a control rod having an opposite end pivotally connected to the connecting rod. The control rod is responsive to rotation of the control shaft to angularly displace the connecting rod sections relative to each other during reciprocatory movements of the piston to control the movement of the piston. The control shaft is connected to the primary shaft by gears which are responsive to rotation of the primary shaft to impart rotation to the control shaft at a speed three times that of the primary shaft. By so driving the control shaft at such speed relative to that of the primary shaft, the piston is caused to dwell or pause at each end of its reciprocatory stroke for an interval of appreciably greater duration than is achieved with the presently used one-piece piston rod between the piston and crankshaft. Not only does such a dwell provide for mechanical advantage in devices such as internal combustion engines, but it also enables more efficient transfer of gases in such engines, both of the four-stroke and two-stroke variety. Further, in heat engines, such as the Stirling thermal engine, causing the pistons to pause or dwell for a greater length of time at each end of their stroke, more effective heat transfer and greater operating efficiency is achieved.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a more or less diagrammatic view in cross section of an internal combustion engine including the piston stroke control mechanism of this invention;

FIG. 2 is an enlarged fragmentary view partly in side elevation and partly in section, taken on line 2-2 of FIG. 1; and

FIGS. 3-6 are diagrammatic views showing different relative positions of the piston and crankshaft or primary shaft crank.

DETAILED DESCRIPTION An internal combustion engine, indicated generally at l, is shown as comprising a block portion 2 defining a cylinder 3 and a cylinder head portion 4, a crankcase 5, an oil pan 6 and a side cover 7 bolted or otherwise rigidly secured to the crankcase 5. As shown in FIG. 1, the crankcase 5 is bolted to the cylinder block 2, the oil pan 6 being bolted or screwed to the bottom portion of the crankcase 5. A primary shaft or crankshaft 8 is joumaled in suitable bearings 9, one of which is shown in FIG. 1, in underlying spaced relationship to the cylinder 3, and a control shaft 10 is suitably journaled in the crankcase 5 in laterally spaced parallel relationship to the primary shaft 8. As shown, the primary shaft 8 is provided with a relatively long crank 11 having a crankpin 12, the control shaft 10 being provided with a relatively shorter crank 13 having a crankpin l4 thereon. The shafts 8 and 10 are connected by a relatively large gear 15 on the shaft 8 and a relatively small gear or pinion 16 mounted fast on the control shaft 10 and having meshing engagement with the gear 15. The pinion 16 has a pitch diameter that is one-third as great as the pitch diameter of the gear 15, so that the shaft 10 will rotate at a speed greater than that of the primary shaft 8. Specifically, the shaft 10 will rotate three times as fast as the primary shaft 8 when rotation is imparted to either thereof.

A piston 17 is connected to the crank 11 by a connecting rod 18 which comprises a pair of connecting rod sections 19 and 20, having adjacent bifurcated inner ends 21 and 22 respectively, pivotally secured together by a pin or shaft 23 disposed on an axis parallel to the axis of the primary shaft 8. The opposite or outer end of the connecting rod section 19 is pivotally connected to the piston 17 by a wristpin 24, and the outer end of the connecting rod section 20 is provided with a split bearing 25 whereby the connecting rod section 20 is journaled on the crankpin 12. A rigid control rod 26 has one end 27 joumaled on the pin or shaft 23, and at its opposite end in provided with a split bearing 28 that is journaled on the crankpin 14. Thus, as the shafts 8 and 10 rotate during reciprocatory movement of the piston 17, movement of the control rod 26 controls the angular displacement of the connecting rod sections 19 and 20 relative to each other.

In the arrangement illustrated, the crank 11 has a crank length substantially 4% times that of the crank 13 and, for the purpose of the present example, the primary shaft or crankshaft 8 is rotated in a counterclockwise direction with respect to FIGS. 1 and 3-6, the control shaft 10 rotating in a clockwise direction. When the crank 11 is disposed at top dead center, as shown in FIG. I, the top surface of the piston 17 is disposed at its upper limit of travel, indicated by the horizontal broken line UL in FIGS. 1, 3 and 4. In this position of the crank 11 and piston 17, the control crank am 13 is disposed at 143 circular degrees past top dead center. As the primary shaft crank 11 rotates in a counterclockwise direction to its position of FIG. 4 where it is disposed at 30 degrees past top dead center, the crank 13 is rotated to a position 127 degrees before top dead center, the top surface of the piston 17 being disposed at a level very slightly below that of the line UL and indicated by a broken line A. The line A further indicates the level of the,top surface of the piston 17 with the crank 11 disposed 30 beyond top dead center if the crank 11 were connected to the piston 17 by a one-piece rigid connecting rod, not shown, having a length equal to the distance between the crankpin l2 and wristpin 24 disposed as in FIG.

I. It will be here noted that, with such a one-piece rigid connecting rod, not shown, having a length equal to the distance between the crankpin I2 and wristpin 24 disposed as in FIG. 1. It will be here noted that, which such a one-piece rigid connecting rod, not shown, and without the control rod 26, when the crank 11 is rotated to its bottom dead center position, the top surface of the piston 17 would be disposed at a lower limit indicated in FIGS. 5 and 6 by a broken line LR.

As the primary shaft- 8 rotates, the crank 11 moves to its position of FIG. 5 wherein it is disposed at 110 beyond top dead center, the crank 13 moving to a position 113 degrees beyond its top dead center position, the piston 17 being disposed close to its limit of downward movement. From this position, the piston 17 moves very slowly downwardly to the lower limit of its downward movement wherein the top surface of the piston 17 would be v disposed on a broken line LL, slightly above the line LR. At the 1 10 position of the crank 13, should the crank 11 and piston 17 be connected with the above-mentioned one-piece connecting rod, and without the control rod 26, the top of the piston 17 would be disposed on a level with a line C in FIG. 5 which, it will be noted, is substantially upwardly spaced from its lower limit line LR. As the shaft 8 continues to rotate, the crank 11 reaches its' position shown in FIG. 6 at 160' before top dead center, the crank 13 on the control shaft 10 moving around to a position 23 beyond top dead center. At this point, the top surface of the piston 17 is still very closely spaced from the lower limit line LL. With the use of the above-mentioned one-piece rigid connecting rod, and without the control rod 26, the top surface of the piston 17 would be disposed substantially at the level indicated by the line LR.

From its position of FIG. 6, the piston 17 moves upwardly to its position of FIG. 3 wherein the crank 13 is disposed at 40 before top dead center, the crank 13 being disposed 23 beyond top dead center. At this point, it will be noted that the top surface of the piston 17 would be disposed substantially at the level indicated by the line LR.

From its position of FIG. 6, the piston 17 moves upwardly to its position of FIG. 3 wherein the crank 11 is disposed at 40 before top dead center, the crank 13 being disposed 23 beyond top dead center. At this point, it will be noted that the top surface of the piston 17 is disposed in very closely spaced relationship to the upper limit line UL. It will be further noted, that with the above-mentioned rigid one-piece connecting rod, and without the use of the control rod 26, the top surface of the piston 17 would be disposed on a level with a broken line D in FIG. 3, this line being disposed in substantial downwardly spaced relation to the upper limit line UL.

From the above, and with reference particularly to FIGS. 3-6, it will be seen that the piston 17 pauses or dwells for a substantially greater time interval at both its upper and lower ends of its reciprocatory movement, that when the conventional one-piece rigid connecting rod is used.

The piston stroke control mechanism of this invention may be used to advantage, not only in internal combustion engines, but also in external combustion heat engines of single or double action, open or closed cycle, and simple or compound engines; as well as with heat pumps used in heating and refrigeration, for more efficient valve timing. Further, and as abovementioned, greater operating efficiency may be obtained when the stroke control mechanism of this invention is used in connection with hot air engines or heat engines of the type exemplified by the well-known Stirling thermal engine, wherein the pistons are alternately cooled and heated at opposite ends of their stroke.

While I. have shown and described a preferred embodiment of my piston stroke control'mechanism, it will be understood that the same is capable of modification without departure from the spirit and scope of the invention, as defined in the claims.

What is claimed is:

I. In combination:

a. a reciprocatin piston; b. a primary sh mounted for rotation on an axis normal to the direction of reciprocatory movement of the piston and substantially in the extended path of said reciprocatory movement;

c. a control shaft mounted for rotation on an axis in laterally spaced parallel relation to said primary shaft axis;

d. a crank arm on said primary shaft;

e. crank means on said control shaft;

f. a connecting rod comprising a pair of rod sections having adjacent inner ends pivotally connected together and outer ends one pivotally connected to said crank arm and the other operatively pivotally connected to said piston, all on axes parallel to said primary shaft axis;

g. a control rod pivotally connected at one end to said crank means and operatively pivotally connected at its opposite end to said rod sections; and

h. means responsive to rotation of said primary shaft for imparting rotation to said control shaft at a speed greater than that of said primary shaft whereby said piston is caused to dwell at each end of its reciprocatory stroke.

2. The combination according to claim 1 in which said lastmentioned means comprises connected gearing on said primary and control shaft arranged to impart three revolutions to said control shaft for each revolution of said primary shaft.

3. The combination according to claim 2 in which said gearing is arranged to rotate said control shaft in a direction opposite the direction of rotation of said primary shaft.

4. The combination according to claim 3 in which said gearing comprises a gear on said primary shaft and a pinion on said control shaft in meshing engagement with said gear, said pinion having a pitch diameter one-third that of said gear.

5. The combination according to claim 1 in which said crank arm on the primary shaft has a longer radial length than said crank means on the control shaft.

Claims (5)

1. In combination: a. a reciprocating piston; b. a primary shaft mounted for rotation on an axis normal to the direction of reciprocatory movement of the piston and substantially in the extended path of said reciprocatory movement; c. a control shaft mounted for rotation on an axis in laterally spaced parallel relation to said primary shaft axis; d. a crank arm on said primary shaft; e. crank means on said control shaft; f. a connecting rod comprising a pair of rod sections having adjacent inner ends pivotally connected together and outer ends one pivotally connected to said crank arm and the other operatively pivotally connected to said piston, all on axes parallel to said primary shaft axis; g. a control rod pivotally connected at one end to said crank means and operatively pivotally connected at its opposite end to said rod sections; and h. means responsive to rotation of said primary shaft for imparting rotation to said control shaft at a speed greater than that of said primary shaft whereby said piston is caused to dwell at each end of its reciprocatory stroke.

2. The combination according to claim 1 in which said last-mentioned means comprises connected gearing on said primary and control shaft arranged to impart three revolutions to said control shaft for each revolution of said primary shaft.

3. The combination according to claim 2 in which said gearing is arranged to rotate said control shaft in a direction opposite the direction of rotation of said primary shaft.

4. The combination according to claim 3 in which said gearing comprises a gear on said primary shaft and a pinion on said control shaft in meshing engagement with said gear, said pinion having a pitch diameter one-third that of said gear.

5. The combination according to claim 1 in which said crank arm on the primary shaft has a longer radial length than said crank means on the control shaft.

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