US1871899A - Balancing device - Google Patents

Description

1932- c. o. MARSHALL 1,871,899

BALANCING DEVICE Filed Dec. 15, 1,924

Patented Aug. 16, 1932 UNITED STATES PATENT OFFHCE CHARLES ORR MARSHALL, OF TOLEDO, OHIO, ASSIGNOR TO THE WILLYS-OVERLAND COMPANY, OF TOLEDO, OHIO, A CORPORATION OF OHIO BALANCING DEVICE Application filed December 13, 1924. Serial No. 755,638.

This invention relates to engines having pistons connected to crank shafts by means of angularly movable connecting rods, and particularly to high speed multi-cylinder engines such as are used in automobiles, airplanes and motor trucks.

In engines of this type the upward movement of one or more of the pistons is approximately balanced by the downward movement of other pistons, so that the cen-i ter of the combined mass of the pistons and their connecting rods remains in nearly the same position throughout their cycle of movement. Owing, however, to the angularp'osition assumed by the connecting rods as the crank arms swing about the crank shaft axis, the pistons are pulled inwardly toward the crank shaft during the quarter revolution of the crank shaft moving them from the outer ends of their strokes, to positions in which their centers of mass are slightly nearer the crank shaft than their centers of stroke. During the same period the pistons moving outwardly from the inner ends of their strokes do not reach their centers of stroke. Because of this unequal opposite movement of the pistons the center of the combined mass of the reciprocating parts moves slightly toward and away from the crank shaft twice during each crank shaft revolution. This unbalanced movement of the reciprocating parts is the cause of the so-called secondary vibration of high speed multi-cylinder engines.

The principal object of this invention is to provide simple and effective means for counter'ba-lancing the unbalanced movement of the reciprocating parts and thereby preventing the so-called secondary vibration. I

Another object is to provide a counterbalance, the center of which moves so as to neutralize the movement of the combined center of mass of the parts.

Another object is to provide a counterbalance, the inertia of which acts upon the crank shaft to counteract the hammering efiect on the main bearings due to the unbalanced movement of the center of the combined mass of the pistons and connecting links.

Another object is to provide a counterbalance carried by the crank shaft and having a center movable to balance the movement of the center of mass of the reciprocating parts.

Another object is to provide a counterbalance and means connected to the moving parts of an engine to so move the counterbalance as to neutralize the movement of the combined center of mass of the pistons without the use of intermediate gearing or linkage.

Another object is the provision of a counterbalance revoluble with the crankshaft and means to move the counterbalance to neutralize the movement of the center of mass of the pistons.

Another object is the provision of a slidable weight and means on the crank shaft for. imparting to the weight two outward and inward radial movements during each revolution of the crank shaft.

Another object is the provision of a single weight with means on the crank shaft for moving the weight to counterbalance the movement of the combined center of mass of the reciprocating parts of the engine.

Another object is the provision of angularly movable members and means connecting them to the crank shaft to so move them 7 as to counterbalance the movement of the combined center of mass of the other parts of the engine.

Another object is the provision of angularly movable members connected to the crank shaft and means for so moving them as to counteract the vibratory effect resulting from the angular movement of the connecting rods. j Y 7 Another object is the provision of angularly movable members and means connecting them to the connecting rods for movement to counteract the vibratory effect of the angular movement of the connecting rods.

Another object is the provision of means for giving to an engine having four cylinders in line a dynamic balance similar to that of a double opposed. engine.

Another object is the provision of means for giving to an engine having four cylinders in line a dynamic balance similar to that of an engine having eight cylinders in line.

Other objects and advantages will be apparent from the following description, in which reference is had to the accompanying drawing illustrating preferred embodiments of my invention.

In the drawing Figure I is a front elevational view of a four cylinder engine embodying my invention, parts being broken away and parts shown in section;

Figure II is an enlarged fragmentary side elevational view showing part of the engine illustrated in Figure I, some of the parts being shown in vertical section on a plane through the axis of the crank shaft;

Figure III is an enlarged detail view of a counterbalancing weight showing the means by which the weight is connected to the crank shaft, the crank shaft being shown in section;

Figure IV is a similar view showing the position of the weight after the crank shaft has moved through a quarter revolution;

Referring to the drawing indetail, the engine illustrated is of the well known type commonly used in automobiles, having a frame 1 and a plurality of cylinders 2, the axes of which are vertical and parallel. Located beneath the cylinders 2 in a crank .1 case 3 and journaled in bearings 4; is a longitudinally extending crank shaft 5 having a plurality of cranks 6, one for each cylinder. In an engine of the type illustrated, in which the number of cylinders is four, the cranks co-operating with the two end cylinders extend from the crank shaft in one direction, while the cranks co-operating with the two middle cylinders extend from the crank shaft in the opposite direction. The pistons in the two end cylinders, therefore, move together in one direction, while the pistons in the two middle cylinders move together in the opposite direction. When the cranks are vertical, one pair extending upwardly and the other downwardly, the pistons connected respectively to the upwardly and downwardly ex tending cranks are at the ends of their strokes, one pair being at the upper end of the stroke, the other pair being at the lower end of the stroke. During the succeeding quarter revolution of the crank shaft the crank arms swing: to horizontal position and one pair of pistons moves downwardly while the other moves upwardly. Owing to the angular position assumed by the connecting rods when the cranks are horizontal, the pistons are not, however, at their centers of stroke when the crank arms are horizontal, but are all slightly below their centers of stroke, so that the center of the combined mass of the pistons and tion of the crank shaft the center of mass moves upwardly to its original position and as the crank shaft swings through another 180 of its movement the center of mass again moves downwardly and upwardly. There are thus two down and up movements of the center of the combined mass of the pistons and connecting links for each revolution of the crank shaft. The distance which the center of the combined mass of the pistons and connecting links moves depends on the length of the connecting links and the length of the cranks and upon the distribution of the mass of the piston-connecting link assemblies, but in most engines it is a very small fraction of an inch.

In order to neutralize-the vibratory effect produced by this rapid upward and downward movement of the center of the combined mass of the pistons. and connecting links, I have provided a counterbalance, the center of which moves oppositely, so that the center of the combined mass of the reciprocating parts and the counterbalance remains substantially stationary.

As illustrated in Figures I to IV, the oppositely moving counterbalance consists of a weight 7, the center of mass of which is located substantially in the axis of a pin' 8 mounted by means of a block 9 and groove 10 for vertical reciprocation beneath thecenter main bearing 4. of the crank shaft 5.

Formed upon or otherwise fixed to the center main bearing-4 is an eccentric boss 12, the axis of'which lies above the axis of the. crank shaft,and rotatably mounted upon the boss 12 is a bearing member in the form of a split ring 13 having two straight external sides 14. Slidably mounted upon the straight sides 14 and adapted to turn with the ring 13 upon the boss 12 is a member 15, the outer periphery of which is circular in form so that the member 15 may be rotatably journaled within a bearing ring 16 formed in the upper end of the counterbalance 7 The member 15 is also provided with a pair of bearings 17 which slidably receive pins 18 that are fixed to the crank shaft 5 and extend therefrom at right angles to the crank arms, so that when the crank arms are horizontal the pins18 are vertical. The member 15 is thus so mounted that it revolves with the crank shaft and'also moves radially thereto. By reference to Figure III it will be observed that when the pins 18 are vertical the center of curvature of the outer surface of the member 15, and hence the center of the bearing ring 16, is coincident with the axis of the stationary boss 12. In this position of the crank shaft the weight 7 is at its highest pointand' the center of mass of the combined pistons and connecting links is at its lowest point.

Figure IV shows the position of the coimterbalance and counterbalancing operating parts when the crank shaft has turned through a quarter revolution. It will be observed that the center of the bearing ring 16 has moved downwardly so that it lies in the axis of the crank shaft, which is below the axis of the boss 12. This downward movement is brought about by the turning of the pins 18 to horizontal position and is permitted by reason of the fact that the member 15 is slidably mounted on the ring 13. When the counterbalance 7 is in its lowermost position (the position in which it is shown in Figure IV), the center of the combined mass of the pistons and connecting links is in its uppermost position. The counterbalance 7 moves upwardly and downwardly twice during each revolution of the crank shaft, and the product of its mass by the extent of its vertical movement may be made equal to the product of the combined mass of the pistons and connecting links by the extent of movement of the center of the combined mass. Since the movement of the counterbalance 7 is opposite to that of the center of the combined mass of the pistons and connecting links, the center of the combined mass of the pistons and connecting links and the counterbalance remains substantially stationary.

During the vertical movement of the member 15 it also swings laterally, but this lateral movement of the upper end of the weight is counteracted by the opposite lateral movement of the lower end of the weight and the center of mass of the weight which lies in the axis of the pin 8 moves vertically only.

The embodiments of my invention herein shown and described are to be regarded as illustrative only, and it is to be understood that the invention is susceptible to variation, modification and change within the spirit and scope of the subjoined claim.

Having described my invention, I claim:

In an engine, in combination, a plurality of cylinders, pistons reciprocally mounted in said cylinders, a crank shaft, connecting links connected to said pistons and said crank shaft, the arrangement being such that the center of the combined mass of the pistons and connecting links has a vibratory movement, a weight, a bearing boss surrounding said crank shaft and having its axis parallel to the axis of said crank shaft and lying in the same vertical plane, a ring surrounding said boss and rotatable thereon, and a member slidably mounted on said ring and having a radially slidable connection with said crank shaft for moving said weight to neutralize the movement of the combined center of mass of said pistons and connecting links.

CHARLES ORR MARSHALL.

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