US3728995A

US3728995A - Accessory arrangement for a reciprocating internal combustion engine

Info

Publication number: US3728995A
Application number: US00185519A
Authority: US
Inventors: G Schramm
Original assignee: Avco Corp
Current assignee: Avco Corp
Priority date: 1971-10-01
Filing date: 1971-10-01
Publication date: 1973-04-24
Anticipated expiration: 1990-04-24

Abstract

The disclosure illustrates a reciprocating internal combustion engine where the idler gear between the crankshaft and camshaft gears drives an oil pump. A magneto drive gear also meshes with the crankshaft gear. A fuel pump and propeller governor are driven from the forward end of the camshaft. This greatly reduces the number of gears required for the accessory drive train. A few simple modifications enable the oil pump to deliver oil to the engine for forward or reverse engine rotation.

Description

mired Sires mm 1 1 Schramm 1451 Apr. 24, 1973 1 ADCIESSORY ARRANGEMENT FOR A 3.094.190 6/1963 Conover el al. 123/1310. 6 RECIPRQCATHNG HNTERNAL 3.447393 6/1969 Wisemun et al. 123/195 A X QOMBUSTHON ENGINE FOREIGN PATENTS OR APPLICATIONS [75] Inventor: gorge Schramm wm'amspon 118,135 8/1918 Great Britain ..123 195 R 671,152 4/1952 Great Britain ..123/l19 C [73] Assignee: Avco Corporation, Williamsport, Pa.

Primary ExaminerCar1ton R. Croyle [22] Out. 1971 Assistant EraminerMichae1 Koczo, Jr. [21] Appl. No.: 185,519 Attorney-Charles M. Hogan et al.

52 U.S. c1. ..123/195 A, 123/193 R, 123/1310. 6, [57] ABSTRACT The disclosure illustrates a reciprocating internal com- Int. Cl. bustion engine where the idler gear between [he of Search l, 6, crankshaft and camshaft gears drives an A l23/DIG' 1 192 B, 195 9027, 198 R magneto drive gear also meshes with the crankshaft 90-31; 184/628; 417/364; 74/15-63 gear. A fuel pump and propeller governor are driven from the forward end of the camshaft. This greatly [56] References Clted reduces the number of gears required for the accesso- UNITED STATES PATENTS rv drive tram. few simple modif cations enable the 011 pump to deliver Oil to the engine for forward or 3,145,695 8/1964 Conover er a] ..123/l92 B X reverse engine rotation. 2,792,820 5/1957 Leach i v v ..I23/195 A 1,424,428 8/1922 Vincent ..l23/90.27 X 10 Claims, 9 Drawing Figures Pmgmmmmsm I 3.728.995

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I f NTOR. 'GEORGE R. RAMM ATTORNEYS ACCESSORY ARRANGEMENT FOR A RECIIROCATING INTERNAL COMBUSTION ENGINE The present invention relates to reciprocating internal combustion engines and more particularly to accessory drive systems for this type of engine.

Over the last thirty years the reciprocating internal combustion engine of the horizontally opposed type has been highly developed for aircraft use. While this high state of refinement provides an efficient engine capable of supplying power for a wide range of accessories, it also has produced a relatively high level of complexity and cost. Typical examples of accessories used with an engine are propeller governor drives, air conditioning units, vacuum drives and many other devices. In the past extensive modifications have been made to engines to accommodate this range of accessories. As a result, a basic engine type may have a number of substantially different models. The extensive modification and added complexity greatly increases the manufacturing costs of the engine.

Therefore it is an object of the present invention to provide an economical, simplified engine accessory drive arrangement that permits the use of a wide variety of accessories.

In the broader aspects of the present invention these ends are achieved in an engine of the above type which incorporates a gear type oil pump directly driven by an idler gear meshing with crankshaft and camshaft gears.

In a more specific aspect of the present invention these ends are achieved by an oil pump of the above type that is readily adaptable to deliver oil through a given lubrication system for forward or reverse engine rotation.

Other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawin g and the novelty thereof pointed out in the appended claims.

In the drawings:

FIG. 1 is a longitudinal side view partially broken away of a reciprocating internal combustion engine embodying the present invention;

FIG. 2 is a cross-sectional view of the engine of FIG. ll taken on line 22 of FIG. 1;

FIG. 3 is an enlarged aft view of the engine of FIG. 1, partially broken away, showing the oil pump arrangement for forward rotation of the engine;

FIGS. 4 and 5 are sectional views of FIG. 3 taken on lines 4- 3 and 5-5, respectively, of FIG. 3;

FIG. 6 is an aft view of the engine of FIG. 1, partially broken away, showing the oil pump arranged for reverse rotation of the engine;

FIGS. 7 and 8 are sectional views of FIG. 6 taken on lines 77 and 8-8, respectively, of FIG. 6; and

FIG. 9 is a sectional view of FIG. 1 taken on line 9---9 of FIG. ll.

Referring to FIGS. 1 and 2 there is shown a reciprocating internal combustion engine comprising a pair of

crankcase halves

110 and 112 in which a crankshaft I4 is joumaled by means of bearing assemblies 16. The crankshaft 14 has a plurality of throws 13 (only one of which is shown) which connect with pistons reciprocable in cylinders extending from the engine in a horizontally opposed arrangement. The cylinders through a suitable valve arrangement admit a combustible mixture which is ignited to reciprocate the pistons and rotate crankshaft M which provides a rotatable output through shaft 20 extending from its forward end. The details of this aspect of the engine design are omitted to simplify the description of the present invention. It should be readily apparent to those skilled in the art that many different specific engine arrangements may be utilized with the accessory arrangement described below.

The aft end of crankshaft I4 incorporates a gear 22 meshing with an idler gear 24 that engages a camshaft drive gear 26. There is a 21 speed reduction between the camshaft gear 26 and the crankshaft gear 22, as is the usual practice. The camshaft gear 26 is attached to an aft flange 28 of a camshaft assembly 30 by means of bolts 32. Camshaft 30 is joumaled in bearings 34 and has a series of lobes 36 to actuate the valving arrangement in the cylinder heads of the engine.

The idler gear 24 is telescoped over and fixed on a shaft 38 joumaled in engine crankcase half 12 by means of a nut 40. Shaft 38 provides a drive input for an oil pump assembly, generally indicated by reference character 42, which will be discussed in detail below. As herein shown, the end of shaft 33 may extend into bore 43 in the oil pump assembly. An internal spline 45 provides a connection to the input shaft 47 of a vacuum pump, generally indicated by reference character 49. Vacuum pump 49 is removably secured to the oil pump assembly 42 by screws 51. The aft crankshaft gear 22 also meshes with a magneto drive gear 44 connected to an input shaft 46 of a dual magneto assembly 48. Many types of magneto assemblies may be used for this purpose, for example, a Scintilla D4RN-2000 series magneto.

The drive for a flexible engine tachometer drive shaft 52 is derived from shaft 50 connected to the aft end of camshaft 30 and joumaled in housing 54. The drive for a fuel pump and propeller governor drive are taken from the forward end of camshaft 30 by means of a cam lobe 56 and bevel gear 58, respectively. The details of these units will be discussed below.

Referring now to FIGS. 3 and 4 the oil pump assembly 42 comprises a housing 60 secured to the aft end of crankcase half 12 by means of bolts 62. The oil pump housing 60 is keyed to the crankcase half 12 by a hollow dowel 104 received in bores 1106 and 108, respectively, formed in housing 60 and crankcase half 12.

First and second generally

circular chambers

64 and 66 house intermeshing spur gears 68 and 7t respectively. Gear 70 is joumaled by means of shaft 38 and gear 68 is joumaled on a shaft 72 received in crankcase half I2 and pump housing 60, respectively.

A first pump housing chamber '78 connects with a first crankcase chamber 80. A second pump housing chamber 32 connects with a second crankcase chamber As shown in FIGS. 3, 4 and 5, chambers '78 and form an inlet for oil which comes from oil inlet passage 83 extending to an oil sump (not shown) underneath the engine crankcase halves. Chamber 84 connects with

transfer passages

86 and 88 interconnected by a hollow dowel 90 spanning the junction between the crankcase halves l2 and 10. Sleeve 9% is held in place by

shoulders

92 and 94, respectively, formed in

passages

86 and 88 and has an inside diameter that presents an unobstructed flow path for the oil through

passages

86 and 88. As shown particularly in FIG. 5, passage 88 may connect to an optional oil filter mounting housing 98 which supports an automotive type full flow oil filter. From there the oil travels through a main galley supply passage 96 to supply oil to the rotating components of the engine in the usual fashion.

For engine crankshaft rotation in a clockwise fashion when viewing FIG. 3, the

gears

68 and 70 rotate in the direction indicated by arrows F. During this

condition chambers

78 and 80 serve as the low pressure inlet and

chambers

82 and 84 serve as the high pressure outlet.

It is seen in FIGS. 6, 7 and 8 that gears 68 and 70 rotate in the direction indicated by arrows R. In this configuration a tube 110 is fitted into the end of inlet 83' and extends through an opening 112 in crankcase half 12' to directly connect chamber 84 with inlet 83', thus making chamber 84 a low pressure inlet chamber.

.A bore 1 11 in chamber 84 enables the end of tube 110 to be flared out at 1 13 to hold it in place.

Chamber 78 now serves as the high pressure output chamber. A tube 114 extends through an opening 116 in pump housing 60' to connect with bore 106' in housing 60'. Hollow dowel 104 provides a passage to bore 108. The hollow dowel 90, shown in FIG. 3, is replaced by an elongated tubular element 118 which extends from shoulder 94' across the junction between the crankcase halves 10' and 12', through passage 86 which has had shoulder 92 removed and across chamber 84 to connect with bore 108'.

Thus a flow path is established from chamber 78' which now functions as the high pressure output chamber through to the pressurized oil output passage 88'. As shown particularly in FIG. 8, passageway 88 may extend to a simple oil pressure screen housing 120 which incorporates an oil pressure screen 122 across which oil passes before discharge through an outlet passage 124 connecting with the main oil galley passage 96'. It should be apparent to those skilled in the art that the full flow oil filter arrangement of FIG. or the oil pressure screen of FIG. 8 may be used alternately with the forward or reverse oil pump configurations.

Referring now to FIGS. 9 and 1, there is shown the details of the drive for the fuel pump and propeller governor drive referred to above. The lobe 56 on the forward end of camshaft 30 is a simple eccentric circular shape adapted to reciprocate a rock shaft 128 of a typical automotive fuel pump assembly 130 secured to crankcase half 12 by screws 132.

Bevel gear 58 has internal splines 134 which telescope over external splines 136 on the end portion 138 of camshaft 30. Bevel gear 58 meshes with a bevel gear 140 integral with a shaft 142 joumaled in bore 144 in crankcase 10. The axis of shaft 142 is at right angles to the axis of rotation of camshaft 30 and generally in line with the fuel pump 130. Shaft 142 has an internally splined end 146 receiving an externally splined drive shaft 148 of a propeller governor drive, generally indicated by reference character 150. The bevel gear 58 is free to slide axially relative to camshaft 30 and has a thrust face 152 adapted to abut a thrust washer 154 received in a suitable groove in the crankcase halves and 12.

During engine operation the accessories are driven in the following fashion:

The crankshaft gear 22 drives idler gear 24 which in turn drives camshaft gear 26 to rotate camshaft 30. The crankshaft gear 22 also drives the dual magneto unit through gear 44. Idler gear 24 provides a drive for the oil pump 42 through shaft 38. In addition to driving oil pump 42, shaft 38 may provide a drive for a vacuum pump unit 49.

Camshaft 30 provides, from its aft end, a drive for a tachometer through flexible cable 52. In addition, the forward end of camshaft 30 provides a drive for fuel pump through cam lobe 56 and a propeller governor unit 150 through bevel gear 58.

It is apparent from the above that the number of accessory gears required for the engine has been greatly reduced by utilizing the gears or their shafts in a dual capacity. In addition to reducing the gears, this dual capacity permits a high degree of flexibility in the addition or deletion of accessory units without eliminating the function of the gear or shaft. For example, the vacuum drive 49 may be eliminated simply by providing a cover over oil pump housing 60. The shaft 38 still functions as a drive for the oil pump 42. Another example is the propeller governor drive 150 which may be eliminated and by providing a cover and eliminating the bevel gears 58 and 140. In this case the forward end of the camshaft 30 is still used to drive the fuel pump 130.

When the engine is designed for forward rotation, that is, rotation of the crankshaft in a clockwise direction when viewing the aft end of the engine, the oil pump arrangement of FIGS. 3-5 is used. In this arrangement oil is supplied through inlet passage 83 through

low pressure chambers

78 and 80 and through two

high pressure chambers

82 and 84. The oil is then transferred through

passages

86 and 88 to the main galley oil supply passage 96.

In certain applications it is necessary to have an engine which provides reverse rotation or, in other words, rotation of the crankshaft in a counterclockwise direction when viewing the aft end of the engine. This situation arises when the engines are used in a twin engine aircraft where the torque reaction of the propellers is sought to be balanced. The modifications to the oil pump system shown in FIGS. 6-8 enable the engine to be manufactured in a reverse configuration at a minimum cost. This is achieved by the provision of

tubes

110, 114 and 118 to cross over the passages so that chambers 82 and 84' act as the low pressure inlet chamber and chambers 78 and 80' act as the high pressure outlet chambers. The tubes enable the same supply and delivery passages to be used. The remaining components of the engine are readily purchased in forward and reverse configurations from suppliers, for example, the magneto assembly and the camshaft.

Since the bevel gear 58 is positioned at the forward end of camshaft 30 which is axially restrained at its aft end, there is a possibility for thermal growth differential between the crankcase halves l0 and 12 and the camshaft 30. This is eliminated by

splines

134, 136 which permit the bevel gear 58 to be axially positioned irrespective of the thermal differential by the thrust washer 154. This permits set up of the bevel gears 58 and and permits smoother operation.

It will be apparent from the above that the engine described utilizes a minimum number of gears to drive the usual complement of accessories found in reciprocating engines of this type. The oil pump arrangement described above, with the simple addition of a few tubular elements, permits rotation of the engine in reverse direction as contrasted to prior art units which require reverse gears to achieve this end.

The above engine provides a highly economical package that is readily adaptable to a wide variety of accessories from a stripped engine, including the bare essentials, to an engine incorporating all of the accessories normally required for a highly sophisticated twin engine aircraft.

While the preferred embodiment of the present invention has been described, it should be apparent to those skilled in the art that modifications may be made without departing from the spirit and scope thereof.

Having thus described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:

1. In a reciprocating internal combustion engine, the combination comprising:

a crankcase;

a crankshaft and camshaft journaled in said crankcase for rotation on parallel axes;

a first gear secured to one end of said crankshaft;

a second gear mounted on the end of the camshaft and defining a 2:1 speed reducing ratio relative to the first gear;

an idler gear meshing with the first and second gears;

and

an oil pump comprising:

a housing secured to said crankcase;

a pair of intermeshing gears journaled for rotation in said housing;

a shaft connecting said idler gear and one of said intermeshing gears;

said crankcase having first and second chambers positioned relative to said intermeshing gear housing to form inlet and outlet chambers for said oil pump.

2. Apparatus as in claim 1 wherein said oil pump further comprises:

an internally splined accessory driving connection on said shaft; and

means for removably mounting an accessory on said oil pump housing to be driven thereby.

3. Apparatus as in claim 1 wherein:

said crankcase has an inlet supply line extending from an oil supply and into one of said chambers;

the other of said chambers being positioned so that it is intercepted by an extension of the longitudinal axis of said inlet supply line;

said crankcase has a passageway extending from the other of said chambers for distribution to the engine components;

whereby said pump pressurizes lubricant for supply to said engine components when said crankshaft is rotating in a first direction.

4. Apparatus as in claim 3 further comprising:

means for forming a passageway from said inlet passage through said first chamber and into said second chamber whereby said second chamber forms the inlet for said pump; means for forming a passageway from said first chamber and through said second chamber to said outlet passage;

whereby said oil pump pressurizes lubricant for delivery to said engine in an opposite direction.

5. Apparatus as in claim 4 wherein said means for forming said passageways comprise tubes received in openings formed in said crankcase and said oil pump housing.

6. Apparatus as in claim 3 wherein:

said crankcase has first and second halves;

said output passageway extends from one crankcase half to the other and across the joint therebetween and said apparatus further comprises a tubular element sealingly received in said passageway and extending across the junction between said crankcase halves.

7. Apparatus as in claim 5 wherein:

said crankcase comprises first and second halves;

said output passageway extends from one crankcase half to the other and through the junction therebetween;

the means forming a passageway through said second chamber comprises a tubular element extending through said second chamber and across the junction between said crankcase halves thereby forming a pilot for the alignment of said halves.

8. Apparatus as in claim 1 further comprising:

a drive gear meshing with the crankshaft gear; and

a magneto assembly bolted to said crankcase and driven by said accessory drive gear.

9. Apparatus as in claim 1 further comprising:

a cam lobe secured to the end of said camshaft opposite said second gear; and

a fuel pump assembly having a reciprocable input lever secured to said crankcase so that the reciprocable lever is actuated by said cam lobe.

10. Apparatus as in claim 9 further comprising a splined output shaft journaled for rotation in said crankcase about an axis normal to the axis of rotation of said camshaft;

a bevel gear mounted on said output shaft;

a bevel gear coaxial with and splined to said camshaft and meshing with the bevel gear on said output shaft, said last-mentioned bevel gear abutting an axial thrust face for positioning relative to said first-mentioned bevel gear, said last-mentioned bevel gear being slidably mounted relative to said camshaft whereby the thermal expansion of said camshaft is compensated for.

Claims

1. In a reciprocating internal combustion engine, the combination comprising: a crankcase; a crankshaft and camshaft journaled in said crankcase for rotation on parallel axes; a first gear secured to one end of said crankshaft; a second gear mounted on the end of the camshaft and defining a 2:1 speed reducing ratio relative to the first gear; an idler gear meshing witH the first and second gears; and an oil pump comprising: a housing secured to said crankcase; a pair of intermeshing gears journaled for rotation in said housing; a shaft connecting said idler gear and one of said intermeshing gears; said crankcase having first and second chambers positioned relative to said intermeshing gear housing to form inlet and outlet chambers for said oil pump.

2. Apparatus as in claim 1 wherein said oil pump further comprises: an internally splined accessory driving connection on said shaft; and means for removably mounting an accessory on said oil pump housing to be driven thereby.

3. Apparatus as in claim 1 wherein: said crankcase has an inlet supply line extending from an oil supply and into one of said chambers; the other of said chambers being positioned so that it is intercepted by an extension of the longitudinal axis of said inlet supply line; said crankcase has a passageway extending from the other of said chambers for distribution to the engine components; whereby said pump pressurizes lubricant for supply to said engine components when said crankshaft is rotating in a first direction.

4. Apparatus as in claim 3 further comprising: means for forming a passageway from said inlet passage through said first chamber and into said second chamber whereby said second chamber forms the inlet for said pump; means for forming a passageway from said first chamber and through said second chamber to said outlet passage; whereby said oil pump pressurizes lubricant for delivery to said engine in an opposite direction.

6. Apparatus as in claim 3 wherein: said crankcase has first and second halves; said output passageway extends from one crankcase half to the other and across the joint therebetween and said apparatus further comprises a tubular element sealingly received in said passageway and extending across the junction between said crankcase halves.

7. Apparatus as in claim 5 wherein: said crankcase comprises first and second halves; said output passageway extends from one crankcase half to the other and through the junction therebetween; the means forming a passageway through said second chamber comprises a tubular element extending through said second chamber and across the junction between said crankcase halves thereby forming a pilot for the alignment of said halves.

8. Apparatus as in claim 1 further comprising: a drive gear meshing with the crankshaft gear; and a magneto assembly bolted to said crankcase and driven by said accessory drive gear.

9. Apparatus as in claim 1 further comprising: a cam lobe secured to the end of said camshaft opposite said second gear; and a fuel pump assembly having a reciprocable input lever secured to said crankcase so that the reciprocable lever is actuated by said cam lobe.

10. Apparatus as in claim 9 further comprising a splined output shaft journaled for rotation in said crankcase about an axis normal to the axis of rotation of said camshaft; a bevel gear mounted on said output shaft; a bevel gear coaxial with and splined to said camshaft and meshing with the bevel gear on said output shaft, said last-mentioned bevel gear abutting an axial thrust face for positioning relative to said first-mentioned bevel gear, said last-mentioned bevel gear being slidably mounted relative to said camshaft whereby the thermal expansion of said camshaft is compensated for.