US 3656408 A
A variable displacement mechanism for use as a prime mover, pump or compressor having a frame supporting a pair of cylinder barrels for rotation about their common respective axes which can be varied from 90 DEG to 180 DEG with respect to each other, each cylinder barrel including a plurality of equally angularly and radially spaced cylinders having pistons therein which are interconnected through pivotal connectors with corresponding pistons of the other cylinder barrel to permit reciprocating motion of the pistons and transfer or torque between these pistons and the rotatable cylinder barrels during rotation and between the rotating cylinder barrels and a shaft fixed to one of the cylinder barrels.
Claims available in
Description (OCR text may contain errors)
United States Patent Fox  VARIABLE DISPLACEMENT MECHANISM  Inventor: Robert M. Fox, Warren, Mich.
 Assignee: General Motors Corporation, Detroit,
 Filed: Nov. 9, 1970  Appl.No.: 88,062
 U.S.Cl ..9l/500,91/504,91/505  lnt.Cl ..F0lb 13/04  Field olSearch ..91/500,504,505;92/60.5; 417/274  I References Cited UNITED STATES PATENTS 1,943,664 1/1934 Fear ..91/500 1,986,584 1/1935 Koplar.....
MacNeil is] 3,656,408 [451 Apr. 18, 1972 2,967,395 1/1961 Foerster ..60/53 A 2,971,498 2/1961 Bloch ..417/222 3,142,963 8/ 1964 Thoma ..60/52 Primary Examiner-William L. Freeh Attorney-Jean L. Carpenter and Arthur N. Krein [5 7] ABSTRACT A variable displacement mechanism for use as a prime mover, pump or compressor having a frame supporting a pair of cylinder barrels for rotation about their common respective axes which can be varied from 90 to 180 with respect to each other, each cylinder barrel including a plurality of equally an 8 Claims, 8 Drawing Figures FATE NTEDAPR 18 1972 SHEET 1 BF 3 INVEN'I 1R, BY fider/Wfi v ATTORNEY PATENTEDAPR 18 I972 3,656,408 sum 2 or s ATTORNEY RATIO COMPRESSION PATENTEIJIPII 18 I972 v 3,656,408 SHEET 30F 3 STROKE P3 (O=I.5c)
| l l O I l I I l 2 3 4 STROKE INCHES I I l I l I O l I I I I I 5 IO 2o so 4o ROTATION ANGLE o OEOREEs COMPRESSION RATIO CHARACTERISTICS INVENIOR.
ATTORNEY 1: LE DISPLACEMENT MECHANISM This invention relates to a variable displacement mechanism for use as a prime mover, pump or compressor and, in particular, to a variable displacement harmonic mechanism wherein displacement can be varied while the mechanism is in operation and in the case of a prime mover, a constant compression ratio can be maintained while varying the displacement of the mechanism.
Various arrangements have been used in the prior art to utilize, as prime movers, pumps or compressors, structures in which one or more cylinder barrels are interconnected to rotate about their respective axes of rotation and are provided with a plurality of cylinders arranged in each cylinder barrel concentrically about and parallel to its axis of rotation. However, none of the known prior art structures were capable of operation as variable displacement mechanisms operable, if
desired, at a constant compression ratio as its displacement could be varied.
Accordingly, it is the principal object of this invention to improve a reciprocating type mechanism for use as a variable displacement harmonic mechanism in which a pair of rotatable cylinder barrels having pistons operating in cylinders arranged concentrically about and parallel to the axis of rotation of their respective cylinder barrels are pivotally connected together so that as the bank angle between cylinder barrels is varied, the output of the mechanism is varied while maintaining constant or varied compression ratios in the cylinders, as desired. 7
Another object of this invention is to provide a compact, lightweight, low cost, variable displacement mechanism of simplified design.
These and other objects of the invention are obtained by means of a variable displacement mechanism having a frame supporting a pair of rotatable cylinder barrels on axes intersecting each other at angles varying from 90 to 180 with respect to each other. Each cylinder barrel includes annularly spaced cylinders having pistons which are interconnected through pivotal connecting pins with corresponding pistons of the other cylinder barrel. This provides for reciprocating motion of the pistons and the transfer of torque from the rotatable barrels and from a drive shaft connected to the inner end of one of the cylinder barrels. Each cylinder barrel cooperates with a nonrotatable head fixed to the frame of the mechanism adjacent to the cylinder barrel with which it cooperates with intake and discharge ports therein placed sequentially into communication with the spaced cylinders as the cylinder barrel rotates relative to the nonrotatable head.
For a better understanding of the invention, as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:
FIG. 1 is a perspective view of the variable displacement mechanism of the invention;
FIG. 2 is a sectional view of one of the cylinder barrels of the mechanism of FIG. 1;
FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;
FIG. 4 is a sectional view taken along line 4-4 of FIG. 2;
FIG. 5 is a sectional view of the variable displacement mechanism of FIG. 1 with the axes of rotation of the cylinder barrels normal to each other;
FIG. 6 is a view similar to FIG. 5 but with the axes of rotation of the cylinder barrels positioned at an angle greater than 90 but less than 180 with respect to each other;
FIG. 7 is a view illustrating how the pivotal axis between the two cylinder barrels can be varied relative to the axis of rotation of the cylinder barrels; and,
FIG. 8 is a plot of compression ratio versus stroke and angle setting for different placements of the pivotal axis between the cylinder barrels illustrating how a constant compression ratio or variable compression ratios can be obtained by varying the location of the pivotal axis.
For purposes of this disclosure, the invention is illustrated and described as it relates to a compressor. However, it should be realized that the structure and principles discussed herein are equally applicable for use in a pump or prime mover and, specifically, the disclosure relating to compression ratios is especially applicable to a prime mover.
Referring now to FIGS. 1, 2, 5 and 6, there is shown a variable displacement compressor having a pair of cylinder barrels 10 and 11 joumaled in cylinder support frames 12 and 13, respectively, for rotation with their axes of rotation in a common plane, the cylinder support frames being pivotally connected together with one of the cylinder support frames movable with respect to the other for varying the angle of intersection of the axes of rotation of the two cylinder barrels.
As shown in FIG. 1, each of the support frames 12 and 13 is substantially U-shaped with one leg 14 thereof supporting a cylinder head 15 fixed thereto in a suitable manner and the other leg 16, in the form of a ring, having a bearing 17 mounted therein to rotatably support one end of a cylinder barrel. Support frames 12 and 13 are provided with apertured flanges l8 and 19, respectively, to receive the pivot member 21 whereby the support frames, and therefore the cylinder barrels, can be pivoted with respect to each other about the axis of the pivot member. A displacement actuating mechanism 22, which may be a double acting hydraulic cylinder or the like, is operatively connected by conduits 23 to a source of pressurized operating fluid, not shown, and is pivotally connected at opposite ends by a clevice 24 and pin 25 arrangement to flanges 26 on each of the support frames 12 and 13. In addition, one of the support frames, support frame 12 in the embodiment shown, is provided with depending brackets 27 whereby it can be mounted to a suitable mounting platform which may, for example, also carry the drive motor, not shown, to drive the compressor.
Cylinder barrel 10 is supported in support frame 12 for rotation by means of the bearing 17 and by a shaft 31 which is joumaled in bearing 32 positioned in the cylinder head 15 associated with this cylinder barrel. As shown, shaft 31 extends through a central counterbore 33 in the cylinder barrel 10 and is fixed for rotation therewith by means of a key 34. Shaft 31 is held axially with respect to the cylinder head 15 by a shoulder 31a on the shaft and by means of a retaining ring 35 positioned in a suitable groove formed for this purpose in the shaft 31, with the free end of the shaft extending through a suitable aperture in leg 14 and having a pulley 36 fixed thereto whereby this shaft can be coupled by a belt 37 to a suitable drive motor, not shown. Cylinder barrel 10 is biased into sliding sealing engagement with its associated cylinder head 15 by means of a coiled spring 38 encircling shaft 31 with one end thereof abutting against the cylinder barrel 10 and the other end abutting against a spring retainer collar 41 held in place by a retaining ring 42 positioned in a suitable groove in the shaft 31.
In a similar manner, cylinder barrel 11 is rotatably supported in the support frame 13 by means of a bearing 17 and by a stub shaft 43 joumaled in a bearing 32 positioned in the cylinder head 15 associated with this cylinder barrel. Cylinder barrel 11 is biased into sliding sealing engagement with its associated cylinder head 15 in the same manner as described above with respect to cylinder barrel 10.
Radially spaced outward from the central axis of the cylinder barrels 10 and 11 are a plurality of cylinders 44, six in the embodiment shown, equallyspaced apart circumferentially one from the other, with the axes of the cylinders in a cylinder barrel being parallel with the central axis of that cylinder barrel. The cylinders 44 of cylinder barrel l0 slidably receive pistons 45 while the cylinders 44 of cylinder barrel 11 slidably receive pistons 46. The number one piston 45 in cylinder barrel 10 is connected by a pivot pin 47 to the number one piston 46 in cylinder barrel 11. The remaining pistons 45 in cylinder barrel 10 are similarly connected to the remaining pistons 46 in cylinder barrel 11. The connecting piston pivot pins 47 rotate with the cylinder barrels, but travel in an elliptical path.
As previously described, cylinder support frame 12 rotatably supporting cylinder barrel 10 is fixed while the cylinder support frame 13 rotatably supporting cylinder barrel 11 can be rotated so that the angle of intersection between the axes of the two cylinder barrels can be varied from 90 to 180. Full piston stroke is obtained at the 90 angle and zero piston stroke at I80". This arrangement provides a variable displacement mechanism so that the desired displacement of the pistons within the cylinders can be obtained by adjusting the angle between the two cylinder barrels to meet the desired output requirement.
The cylinder heads 15 also serve as valve plates controlling the ingress and egress of fluid into and from the cylinders through the arcuate openings 48 provided in the ends of the cylinder barrels in communication with the cylinders. As shown in FIGS. 3 and 4, each cylinder head is provided with an inlet 51 and an outlet 52 in the form of an elongated arcuate slot and a shorter arcuate slot, respectively, extending through the walls of the cylinder head 15. The inlet 51 is suffrciently long to permit communication of a cylinder therewith during the entire stroke of the piston within that cylinder, with a number of cylinders thus being in overlapping communication with the inlet 51. The outlet 52 is short enough so that at any given time, only one cylinder is fully in communication with the outlet during the final portion of the compression stroke of a piston within that cylinder.
In the embodiment disclosed, inlet and discharge from the two cylinder barrels is readily provided for by common manifolds conveniently formed as part of the pivot member 21. As shown, the bottom of the pivot member is provided with an inlet passage 53 in communication with arcuate radial passages 54. A pair of pivotal ring members 55, positioned between a shoulder provided near the bottom of the pivot member, and a snap ring 56 each have a radial passage 57 therein and are connected by flanged conduits 61 and 62 to the cylinder heads for the cylinder barrels and 11, respectively.
In similar manner, outlets 52 in the cylinder heads for the cylinder barrels 10 and 11 are connected by flanged discharge conduits 63 and 64, respectively, to the radial passages 57 and ring members 55 pivotally mounted with discharge ring 65 near the top of the pivot member 21 between a shoulder provided thereon and a snap ring 56 positioned within a suitable groove formed for this purpose in the pivot member 21. The radial passages 54 in these ring members 55 are in communication via arcuate radial passages 66 with an axial passage 67 with discharge therefrom through a radial passage 68 in communication with a radial passage 71 in the ring member 65.
In the subject de ice, variable displacement is obtained by changing the piston stroke which can be done while the device is operating. As described, cylinder barrel 10 and cylinder barrel ll rotate about the axis of shafts 31 and 43, respectively, which, as shown in FIG. 5, normally intersect at a 90 angle to each other. This angular position of the axes of rotation of the two cylinder barrels is controlled in a suitable manner through the displacement actuating mechanism 22. When the intersecting angle is 90, a piston travels through a full stroke which, in the embodiment disclosed, is equal to S, the distance between diametrically opposite cylinders as shown in FIG. 5.
Since the compression ratio of a reciprocating piston-type device is established by the design clearance between the cylinder head and the top of the piston with the piston located at top dead center (TDC) of a stroke, the following equation applies:
CR (S C)/C wherein: CR Compression Ratio S Stroke ck fs 1 and the same device could be designed for an 8:1 compression ratio by decreasing the TDC clearance to C m m 0.57 "Hill.
A constant compression ratio can be maintained in the subject device throughout all angular positions of the two cylinder barrels with respect to each other by proper positioning of the axis P of pivot member 21 with respect to the pivotal axis of a piston 46 positioned adjacent to the pivot member 21 with its pivotal axis parallel to the axis P of the pivot member and on the bank angle bisector line L. When the distance D, as shown in FIG. 7, between these axes equals the top dead center clearance C, as measured with the cylinder barrels intersecting at a 90 angle, then the clearance C will decrease to zero when the cylinder barrels are positioned at 180 with respect to each other and a constant compression ratio will be maintained for all intermediate angles. The following relationship illustrates that for this value of D, compression ratio is independent of bank angle.
Sm Maximum piston stroke D Offset distance between frame pivot axis and piston pivot axis or /2 180 bank angle between cylinder barrels).
The graph in FIG. 8 shows the plot of compression ratio versus stroke and a for a device with a pivot point P1 a distance D of 0.8 inch with D being equal to clearance C. In this case the compression ratio remains constant for all bank angles from to In the above arrangement when the bank angle between cylinder barrels is increased to l26.87, as shown in FIG. 6, the stroke of the pistons is reduced to one-half full piston stroke, or in this example 2.0 inches. When the bank angle is increased to 180, the piston stroke becomes zero.
To yield a variable compression ratio with varying bank angles, the pivot point can be moved along the bank angle bisector to a point on either side of pivot point P1. For example, pivot point P2 is located on the bisector at a distance D= 0.5 C above pivot point P] as seen in FIG. 7.
Apply the following relationship again, wherein the clearance at a bank angle of 180 will equal 056 and the compression ratio will decrease with increasing bank angles as shown by the graph of FIG. 3.
As another example, a pivot point P3 is located on the bank angle bisector at a distance D= 1.56, a point below Pl as seen in FIG. 7. The compression ratio equation described above again applies, however, a bank angle of 180 cannot be reached since top dead center interference will occur. In this example, the compression ratio will increase with increasing bank angles as shown in the graph of FIG. 3.
As shown in FIG. 8, at a bank angle of 90 (1: 45), the compression ratio is the same for both the variable and the constant compression ratio conditions. From the above description and the curves plotted in FIG. 8, it can readily be seen that a complete family of compression ratio curves can be established and any decreasing or increasing compression ratios can be obtained.
With this arrangement when used in an internal combustion engine, the output of the engine can be varied by changing the bank angle between cylinder barrels while maintaining a constant compression ratio during all operating conditions of the engine.
When used as a pump or as a compressor, as described, the advantage of variable displacement in these devices is that pumping capacity can be changed to meet the output demand requirements. Thus, if the subject variable displacement mechanism is used as an automotive air conditioning compressor, its output can be varied to meet varied load requirements for climatic demand and drive speed fluctuations. in addition, if the subject mechanism were used for this last mentioned purpose, it would not require the use of a magietic drive clutch as conventionally used on such automotive air conditioning compressors, since its displacement and therefore its output, becomes zero when the bank angle becomes 180. In addition, the straight line motion of the pistons and their interconnection between the cylinder barrels produce simple harmonic motion of the pistons, thereby reducing piston ac celeration and allowing higher operating speeds.
What is claimed is:
1. A variable displacement mechanism including a pair of frame means, a cylinder barrel mounted in each of said frame means for rotation about an axis, a drive shaft connected to one of said cylinder barrels for rotation therewith about said axis of said cylinder barrel, each of said cylinder barrels having a plurality of cylinders therein equally spaced concentrically about and parallel to the axis of rotation of said cylinder barrel, pistons slidably mounted in said cylinders in said cylinder barrels with corresponding sets of pistons in said cylinder barrels being pivotally connected at one end toeach other, said frame means being pivotally connected together about a pivotal axis with the said axis of one of said cylinder barrels intersecting the said axis of the other of said cylinder barrels in a common plane, and means operatively connected to said frame means for varying the angle of intersection of said axes of said cylinder barrels from 90 to 180 with respect to each other.
2. A variable displacement mechanism according to claim ll wherein the pair of said frame means each includes a frame and a cylinder head fixed thereto, one end of said cylinder barrel supported thereby being positioned in sliding engagement with said cylinder head on said frame means, each'of said cylinder heads having a fluid inlet and a fluid outlet for communication with said cylinders of said cylinder barrel with which it cooperates.
3. A variable displacement mechanism according to claim 11 wherein said pivotal axis of said pivotal connection of said frame means is positioned with respect to the rotational axes of said cylinder barrels to effect a constant compression ratio of said pistons operating in said barrels as the angle of intersection of said axes is varied from 90 to 180.
4. A variable displacement mechanism including a frame means, a first barrel mounted for rotation about an axis in said frame means, said first barrel having a plurality of cylinders therein equally spaced concentrically around the axis of rotation of said first barrel, 3 piston in each of said cylinders, a second barrel rotatably mounted in said frame means about an axis normally normal to the axis of rotation of said first barrel, said second barrel having a plurality of cylinders equal in number to the number of cylinders in said first barrel, said cylinders of said second barrel being equally spaced concentrically around the axis of rotation of said second barrel,
means interconnecting each of said pistons in said first barrel to a corresponding piston in said second barrel, a shaft journaled in said frame means and connected to said first barrel for rotation concentrically therewith, and means operatively associated with said barrels for varying the angle of intersection of the axes of rotation of said barrel from said normal angle to an obtuse angle.
5. A variable displacement mechanism according to claim 4 wherein said frame means includes a first cylinder head and a second cylinder head fixed relative to and positioned in sliding engagement with said first barrel and said second barrel, respectively, said first cylinder head and said second cylinder head each having a fluid inlet and a fluid outlet positioned for sequential communication with said cylinders of the barrel with which it cooperates.
A variable displacement mechanism including a first frame means and a second frame means, a first barrel including a drive shaft fixed thereto mounted in said first frame means for rotation about an axis, said first barrel having a plurality of cylinders therein with parallel axes centered on a common circle about the axis of rotation of said first barrel, a piston in each of said cylinders, a second barrel mounted in said second frame means for rotation about an axis, said second barrel having a plurality of cylinders therein positioned and equal in number to that of the said cylinders in said first barrel, a piston in each of said cylinders in said second barrel, means interconnecting each of said pistons in said first barrel to a respective piston in said second barrel, said first frame means and said second frame means being connected together for pivotal movement about a common axis with the axes of rotation of said first barrel and said second barrel intersecting each other in a common plane and, a displacement actuator mechanism operatively connected to said first frame means and said second frame means for changing the angle of intersection of the axes of rotation of said first barrel and said second barrel from an angle normal with respect to each other to an obtuse angle.
7. A variable displacement mechanism according to claim 6 wherein said first frame means and said second frame means are connected together for pivotal movement about a common axis positioned with respect to the axes of rotation of said first barrel and said second barrel to permit the angle of intersection of said axes of rotation to be varied between and while permitting a constant compression ratio to be maintained with the stroke of said pistons being reduced to zero when the intersection of said axes of rotation is 180 with respect to each other.
d. A variable displacement mechanism according to claim 6 wherein said first frame means includes a first cylinder head fixed relative to said first barrel and in sliding engagement with one end thereof, saidsecond frame means includes a second cylinder head fixed relative to said second barrel in sliding engagement with one end thereof, said first cylinder head and said second cylinder head each having a fluid inlet and a fluid outlet positioned to be sequentially in communication with said cylinders of said first barrel and said second barrel, respectively.