Induction system for a four cycle engine Number:7,152,706 from the United States Patent and Trademark Office (PTO) owispatent

Title: Induction system for a four cycle engine

Abstract: A four cycle engine having at least one cylinder unit is disclosed. The engine includes a continuously variable transmission (CVT) connected to the engine on one side of the engine. An air box is also provided that is located on the same side of the engine as the CVT. The engine further includes an intake manifold operatively connected to the air box for connecting the air box to each cylinder unit and a throttle assembly operatively connected to air box and the intake manifold. The intake manifold may have a generally Y-shaped manifold having a connector leg connected to the throttle assembly and a pair of branches. One branch is operatively connected to one of the cylinder units and another branch is connected to another of the cylinder units. The connector leg is generally parallel to the axis of the crankshaft. The intake manifold may further include a baffle assembly, which directs gas flow within the intake manifold.

Patent Number: 7,152,706 Issued on 12/26/2006 to Pichler,   et al.

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Inventors:	Pichler; Anton (Steyr, AT), Kusel; Rudolf (Thalheim bei Weis, AT), Matte; Sylvain (St-Denis de Brompton, CA), Winter; Andreas (St. Polton, AT), Haydl; Andreas (Wels, AT)
Assignee:	BRP-Rotax GmbH & Co. KG (Gunskirchen, AT)
Appl. No.:	10/230,408
Filed:	August 29, 2002

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Current U.S. Class:	180/68.3 ; 123/52.3; 180/182; 180/292
Current International Class:	B60K 5/02 (20060101)
Field of Search:	180/68.3,291,182 114/55.5 440/88,89 123/561,563,564,559.1,52.3

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References Cited [Referenced By]

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Other References

European Search Report dated Nov. 17, 2003, for European Patent Application No. 03018378, which is the European Counterpart of the above-captioned U.S. application. cited by other . European Search Report, issued by the European Patent Office, dated Feb. 16, 2004. cited by other.

Primary Examiner: Restifo; Jeff
Attorney, Agent or Firm: Osler, Hoskin & Harcourt LLP

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Parent Case Text

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CROSS REFERENCE TO RELATED APPLICATIONS

This application is related to and claims priority to U.S. Provisional Patent Application Ser. No. 60/402,709, which was filed on Aug. 13, 2002.

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Claims

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What is claimed is:

1. A vehicle, comprising: a frame having a longitudinal axis, wherein the vehicle has a from end and a rear end; and a four cycle engine secured to die frame, comprising: a crankcase having a crankshaft extending therethrough, wherein the crankshaft has a crankshaft axis, wherein the crankshaft axis is transverse to the longitudinal axis; at least one cylinder unit connected to the crankcase, wherein each cylinder unit includes a cylinder and a cylinder head; a continuously variable transmission including a drive pulley connected to the crankshaft and a driven pulley operatively connected to the drive pulley via a drive belt, the drive and the driven pulleys being situated on one side of the longitudinal axis of the vehicle; an air box located on the same side of the longitudinal axis as the continuously variable transmission, the air box being arranged laterally of the at least one cylinder unit with respect to the longitudinal axis of the vehicle; an intake manifold operatively connected to the air box for connecting the air box to each of the at least one cylinder unit; a throttle assembly operatively connected to the air box and the intake manifold.

2. The vehicle according to claim 1, wherein the engine has a single cylinder unit.

3. The vehicle according to claim 1, wherein the at least one cylinder unit includes a pair of cylinder units located on opposite sides of the crankshaft axis.

4. The vehicle according to claim 3, wherein the pair of cylinder units are arranged at an angle with respect to each other, wherein a space is formed between the pair of cylinder units.

5. The vehicle according to claim 4, wherein the intake manifold is located in the space between the pair of cylinder units.

6. The vehicle according to claim 5, wherein the intake manifold is generally Y-shaped, wherein the intake manifold comprises: a connector leg connected to the throttle assembly; and a pair of branches, wherein one branch is operatively connected to one of the cylinder units and another branch is connected to another of the cylinder units.

7. The vehicle according to claim 6, wherein die connector leg is generally parallel to the axis of the crankshaft.

8. The vehicle according to claim 6, wherein the intake manifold further includes a battle assembly located within the intake manifold, wherein the baffle assembly is oriented in a direction of gas flow within the intake manifold.

9. The vehicle according to claim 8, wherein the baffle assembly divides each of the branches into two separate flow paths at approximately equal size.

10. The vehicle according to claim 9, wherein each cylinder unit has a cylinder axis, wherein the baffle assembly extends substantially parallel to the cylinder axis in an area of the branches adjacent the cylinder unit.

11. The vehicle according to claim 4, further comprising: a surge tank located within the space between the pair of cylinder units, wherein the surge tank is operatively coupled to the throttle assembly and the intake manifold.

12. The vehicle according to claim 11, wherein the intake manifold includes a pair of rising manifold branches connected at one end to the surge tank and the cylinder units at another end.

13. The vehicle according to claim 1, wherein the air box is positioned above the continuously variable transmission.

14. The vehicle according to claim 1, further comprising a charger assembly for compressing gas supplied to the at least one cylinder unit, wherein the charger assembly is located on a side opposite the continuously variable transmission relative to the longitudinal axis.

15. The vehicle according to claim 14, wherein the air box includes at least two chambers, wherein a first chamber being connected through at least one opening to the atmosphere, wherein the first chamber being further operatively connected to the charger, wherein a second chamber being operatively connected to the charger and the throttle assembly.

16. The vehicle according to claim 14, wherein the engine has a front side located on one side of the crankshaft and a rear side located on opposite side of the crankshaft, wherein die charger assembly having a center of gravity, wherein the center of gravity or the charger assembly is located on the rear side of the engine.

17. The vehicle according to claim 14, wherein the charger assembly is a supercharger, wherein the supercharger is connected to die crankcase and operatively driven by the crankshaft.

18. The vehicle according to claim 17, wherein the supercharger is positioned adjacent one cylinder unit.

19. The vehicle according to claim 17, wherein the supercharger includes a centrifugal blower.

20. The vehicle according to claim 17, wherein the engine further comprising an exhaust system for exhausting exhaust gas from the at least one cylinder unit, wherein the charger assembly is a turbocharger, wherein the turbocharger is connected to the exhaust system.

21. The vehicle according to claim 20, wherein the turbocharger having an axis, wherein the axis is essentially parallel to die crankshaft axis.

22. The vehicle according to claim 20, further comprising a deflector assembly connected to an intake side of the turbocharger, wherein the deflector assembly redirects a flow of air into the turbocharger.

23. The vehicle according to claim 20, further comprising a muffler system for exhausting exhaust gases to the environment from the exhaust system.

24. The vehicle according to claim 23, wherein the turbocharger having a turbine, wherein the turbine is driven by the exhaust gases.

25. The vehicle according to claim 23, wherein the muffler system and the turbocharger being located on the same side of the longitudinal axis of the vehicle.

26. The vehicle according to claim 25, wherein the muffler system being spaced further from the longitudinal axis of the vehicle than the turbocharger.

27. The vehicle according to claim 17, further comprising a charge-air cooler, wherein the charge-air cooler is operatively connected to the air box and the charger.

28. The vehicle according to claim 27, wherein the charge-air cooler is located on the front side of the engine.

29. The vehicle according to claim 1, wherein the air box includes at least two chambers, wherein a first chamber being connected through at least one opening to the atmosphere, a second chamber being connected to the throttle assembly.

30. The vehicle according to claim 29, wherein the first chamber is operatively connected to the second chamber through at least one opening.

31. The vehicle according to claim 30, wherein the at least one opening is a venturi pipe.

32. The vehicle according to claim 1, wherein the throttle assembly is located in a recess within the air box.

33. The vehicle according to claim 32, further comprising a removable lid covering the recess.

34. The vehicle according to claim 1, further comprising: at least one injection nozzle connected to the intake manifold for each of the at least one cylinder unit.

35. The vehicle according to claim 34, wherein the at least one injection nozzle comprises a pair of injection nozzles associated with each of the at least one cylinder unit, wherein a first injection nozzle is operatively connected to the intake manifold adjacent the cylinder head unit, wherein a second injection nozzle is operatively connected to the intake manifold upstream of and spaced apart from the first injection nozzle.

36. The vehicle according to claim 35, wherein the first injection nozzle operates under all engine loads, wherein the second injection nozzle operates only during predetermined engine loads.

37. The vehicle according to claim 36, wherein the predetermined engine load is a full engine load.

38. A snowmobile, comprising: a snowmobile having a longitudinal axis, wherein the snowmobile has a front end and a rear end; a snowmobile track for propelling the snowmobile, wherein the track is secured to the frame; and a four cycle engine secured to the frame, comprising: a crankcase having a crankshaft extending therethrough, wherein the crankshaft has a crankshaft axis, wherein the crankshaft axis is transverse to the longitudinal axis; at least one cylinder unit connected to the crankcase, wherein each cylinder unit includes a cylinder and a cylinder head; a continuously variable transmission including a drive pulley connected to the crankshaft, and a driven pulley operatively connected to the drive pulley via a drive belt, the drive and driven pulleys being situated on one side of the longitudinal axis of the vehicle; an air box located on the same side of the longitudinal axis as the continuously variable transmission, the air box being arranged laterally of the at least one cylinder unit with respect to the longitudinal axis of the vehicle; an intake manifold operatively connected to the air box for connecting the air box to each of the at least one cylinder unit; a throttle assembly operatively connected to the air box and the intake manifold, wherein the engine drives the track.

39. The snowmobile according to claim 38, wherein the engine has a single cylinder unit.

40. The snowmobile according to claim 38, wherein the at least one cylinder unit includes a pair of cylinder units located on opposite sides of the crankshaft axis.

41. The snowmobile according to claim 40, wherein the pair of cylinder units are arranged at an angle with respect to each other, wherein a space is formed between the pair of cylinder units.

42. The snowmobile according to claim 41, wherein the intake manifold is located in the space between the pair of cylinder units.

43. The snowmobile according to claim 42, wherein the intake manifold is generally Y-shaped, wherein the intake manifold comprises: a connector leg connected to the throttle assembly; and a pair or branches, wherein one branch is operatively connected to one of the cylinder units and another branch is connected to another of the cylinder units.

44. The snowmobile according to claim 43, wherein the connector leg is generally parallel to the axis of the crankshaft.

45. The snowmobile according to claim 43, wherein the intake manifold further includes a baffle assembly located within the intake manifold, wherein the baffle assembly is oriented in a direction of gas flow within the intake manifold.

46. The snowmobile according to claim 45, wherein the baffle assembly divides each of the branches into two separate how paths of approximately equal size.

47. The snowmobile according to claim 46, wherein each cylinder unit has a cylinder axis, wherein the baffle assembly extends substantially parallel to the cylinder axis in an area of the branches adjacent the cylinder unit.

48. The snowmobile according to claim 41, further comprising: a surge tank located within the space between the pair of cylinder units, wherein the surge tank is operatively coupled to the throttle assembly and the intake manifold.

49. The snowmobile according to claim 48, wherein the intake manifold include a pair of rising manifold branches connected at one end to the surge tank and the cylinder units at another end.

50. The snowmobile according to claim 38, wherein the air box is positioned above the continuously variable transmission.

51. The snowmobile according to claim 38, further comprising a charger assembly for compressing gas supplied to the at least one cylinder unit, wherein the charger assembly is located on a side opposite the continuously variable transmission relative to the longitudinal axis.

52. The snowmobile according to claim 51, wherein the air box includes at least two chambers, wherein a first chamber being connected through at least one opening to the atmosphere, wherein the first chamber being further operatively connected to the charger, wherein a second chamber being operatively connected to the charger and the throttle assembly.

53. The snowmobile according to claim 51, wherein the engine has a front side located on one side of the crankshaft and a rear side located on opposite side of the crankshaft, wherein the charger assembly having a center or gravity, wherein the center of gravity of the charger assembly is located on the rear side of the engine.

54. The snowmobile according to claim 51, wherein the charger assembly is a supercharger, wherein the supercharger is connected to the crankcase and operatively driven by the crankshaft.

55. The snowmobile according to claim 54, wherein the supercharger is positioned adjacent one cylinder unit.

56. The snowmobile according to claim 54, wherein the supercharger includes a centrifugal blower.

57. The snowmobile according to claim 51, wherein the engine further comprising an exhaust system for exhausting exhaust gas from the at least one cylinder unit, wherein the charger assembly is a turbocharger, wherein the turbocharger is connected to the exhaust system.

58. The snowmobile according to claim 57, wherein the turbocharger having an axis, wherein the axis is essentially parallel to the crankshaft axis.

59. The snowmobile according to claim 57, further comprising a deflector assembly connected to an intake side of the turbocharger, wherein the deflector assembly redirects a flow of air into the turbocharger.

60. The snowmobile according to claim 57, further comprising a muffler system for exhausting exhaust gases to the environment from the exhaust system.

61. The snowmobile according to claim 60, wherein the turbocharger having a turbine, wherein the turbine is driven by the exhaust gases.

62. The snowmobile according to claim 60, wherein the muffler system and the turbocharger being located on the same side of the longitudinal axis of the vehicle.

63. The snowmobile according to claim 62, wherein the muffler system being spaced further from the longitudinal axis of the vehicle than the turbocharger.

64. The snowmobile according to claim 51, further comprising a charge-air cooler, wherein the charge-air cooler is operatively connected to the air box and the charger.

65. The snowmobile according to claim 64, wherein the charge-air cooler is located on the front side of the engine.

66. The snowmobile according to claim 38, wherein the air box includes at least two chambers, wherein a first chamber being connected through at least one opening to the atmosphere, a second chamber being connected to the throttle assembly.

67. The snowmobile according to claim 66, wherein the first chamber is operatively connected to the second chamber through at least one opening.

68. The snowmobile according to claim 67, wherein the at least one opening is a venturi pipe.

69. The snowmobile according to claim 38, wherein the throttle assembly is located in a recess within the air box.

70. The snowmobile according to claim 69, further comprising a removable lid covering the recess.

71. The snowmobile according to claim 38, further comprising: at least one injection nozzle connected to the intake manifold for each of the at least one cylinder unit.

72. The snowmobile according to claim 71, wherein the at least one injection nozzle comprises a pair or injection nozzles associated with each of the at least one cylinder unit, wherein a first injection nozzle is operatively connected to the intake manifold adjacent the cylinder head unit, wherein a second injection nozzle is operatively connected to the intake manifold upstream of and spaced apart from the first injection nozzle.

73. The snowmobile according to claim 72, wherein the first injection nozzle operates under all engine loads, wherein the second injection nozzle operates only during predetermined engine loads.

74. The snowmobile according to claim 73, wherein the predetermined engine load is a full engine load.

75. A four cycle engine, comprising: a crankcase; a crankshaft rotatably mounted in the crankcase, wherein the crankshaft having a crankshaft axis; at least two cylinder units, wherein each cylinder unit includes a cylinder head secured to the crankcase, wherein each cylinder unit further includes at least two inlet valves; a throttle assembly; and an intake manifold operatively connected to the throttle assembly and each of the cylinder units, wherein the intake manifold includes a main intake pipe that is connected to the throttle assembly, wherein the intake manifold further includes at least two secondary intake pipes extending from the main intake pipe, wherein each of the at least two secondary intake pipes is operatively connected to the cylinder head of its corresponding cylinder unit; and the intake manifold further including baffle assemblies located within each of the secondary intake pipes, the baffle assemblies being oriented in a direction of gas flow within their secondary intake pipes and wherein each baffle assembly divides its intake pipe into separate flow paths of approximately equal size, wherein separate flow paths are directed to each of the at least two inlet valves.

76. The engine according to claim 75, wherein each cylinder unit has a cylinder axis, wherein each baffle assembly extends substantially parallel to the cylinder axis of its corresponding cylinder in an area of the intake pipes adjacent the cylinder head.

77. The engine according to claim 75, wherein the throttle assembly includes a fluid path for circulating engine coolant for warming the throttle assembly in severe operating conditions.

78. The vehicle according to claim 1, wherein the throttle assembly includes a fluid path for circulating engine coolant for warming the throttle assembly in severe operating conditions.

79. The snowmobile according to claim 38, wherein the throttle assembly includes a fluid path for circulating engine coolant for warming the throttle assembly in severe operating conditions.

80. The engine according to claim 75, wherein the main intake pipe extends substantially parallel to the crankshaft axis.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a four-cycle engine that is intended for use in a vehicle, such as for example a snowmobile or a three-wheeled vehicle. More particularly, the present invention relates to a four-cycle engine having an improved induction system that complies with the strict emission control regulations currently developed in the United States without having a negative effect on the balance of the vehicle. The engines disclosed herein are described in connection with a snowmobile. The present invention, however, is not intended to be so limited; rather, it is contemplated that the engines described herein may be used in motorcycles, all-terrain vehicles, and various watercraft.

2. Description of Related Art

Snowmobiles are used for cross-country travel, during which it is frequently necessary to negotiate steep ascending and descending gradients, which requires powerful engines. Snowmobiles are used for both leisure-time pursuits as well as in a work environment. With this in mind, various demands are placed on the engine characteristics with respect to engine speed and torque. Known snowmobiles include a frame. Two steerable spring-mounted skis are installed on the front of the frame. A track driven by the engine is located on the lower rearward end of the frame. The track serves to propel the snowmobile over snow or ice covered ground. The engine and the track are usually connected by way of a continuously variable transmission (CVT), and a positive connection between the engine and the CVT. The positive connection is typically a centrifugal clutch that is integrated into the CVT.

At present, two-cycle engines are typically used to drive snowmobiles because these engines are capable of delivering a relatively large power output for a small installed size and low weight. Two-cycle engines, however, emit a considerable quantity of unburned hydrocarbons and other pollutants into the environment in the form of exhaust gas. The hydrocarbons and other pollutants are formed within the engine cylinders during the combustion process when the cylinder is inadequately flushed, and as a result of the lubricating oil that is added to the fuel.

Considerable structural and design modifications must be incorporated into the two-cycle engine to comply with current and ever more rigorous emission control regulations, which results in higher production costs. These modifications may include fuel injection and the use of catalysts. Furthermore, costly design features must be incorporated when the engines are used in snowmobiles to ensure that noise emissions are comparable to those of four-cycle engines.

One known snowmobile having a four-cycle engine is manufactured by Redline. The engine is a single overhead cam (SOHC), V-twin internal combustion engine that develops approximately 90 kW of power. The engine was originally designed for use in a motorcycle. These snowmobiles, which are up-market vehicles that are marketed under the brand name "954 Revolution," are sport machines having a tubular frame. As such, these vehicles are only suitable for small-scale production. Due to predetermined minimum track width, the CVT is always remote from the longitudinal axis of the snowmobile. This arrangement is problematic especially for V-twin designs. If the center of gravity of the engine and the center of gravity of the CVT are on the same side of the vehicle, this would have a negative impact on the balance of the snowmobile and handling is made more difficult.

If the center of gravity of the engine (without auxiliary units) is arranged on the longitudinal axis of the snowmobile or on the opposite side of the vehicle relative to the center of gravity of the CVT, such an arrangement would require a relatively long drive shaft between the engine and the CVT. This arrangement, however, would generate undesirable oscillations within the drive train, which could result in a reduction of the service life or the destruction of the drive train. Furthermore, an engine in a snowmobile should be located to the rear as far as possible in order to locate its center of gravity as close possible to the track, which enhances the snowmobile handling and improves driving dynamics. This arrangement is not possible in the Redline design because the engine would collide with the steering rod.

Maximumsled also produces a snowmobile under the brand name "Venom" that is also based on a motorcycle engine. This snowmobile suffers from many of the same problems discussed above.

Large-scale production snowmobiles are typically manufactured from a sheet metal profile frame that is preferably of aluminum. A snowmobile of this kind is sold, for example, by Yamaha under the brand name "RX-1" and "RX-1 ER." This snowmobile is powered by a four-cycle, four-cylinder, in-line, carburetor-type motorcycle engine that is installed transversely to the longitudinal axis of the vehicle. The engine has a dry-sump lubrication system, and develops approximately 107 kW of power. This engine has a relatively high nominal engine speed. As a result, additional reduction gearing has to be installed between the crankshaft and the drive pulley of the CVT. This engine has numerous drawbacks including a greater installed length and a greater weight. Furthermore, the exhaust runs beneath the tank and beneath the seat to the rear of the snowmobile. This produces a significant buildup of heat beneath the tank and the seat.

Published U.S. patent application Ser. No. 09/925,522 to Yatagai et al. discloses a snowmobile four-cycle engine arrangement. Yatagai discloses a four-cycle engine arranged in an engine compartment formed in the front body of a snowmobile. The crankshaft of the engine is laid substantially parallel to the body width of the snowmobile. The engine has a cylinder case inclined in a forward direction. The engine has a dry sump oil supplying system and an oil tank separate from the engine. This engine arrangement has several drawbacks. First, the cylinders are inclined in the forward direction. The turbocharger and oil tank are located in front of the engine. With this arrangement, the center of gravity of the engine is positioned relatively far away from a center point of the vehicle and the track. This adversely impacts the handling and maneuverability of the snowmobile. Second, the snowmobile is typically operated in severe working conditions (temperature changes between +15.degree. C. to -40.degree. C., ice formation, etc.). The water pump and alternator are belt driven. The belt is prone to failure.

OBJECTS OF THE INVENTION

It is an object of the present invention to provide a four cycle engine for use in a vehicle.

It is another object of the present invention to provide a four cycle engine having a low center of gravity for improved vehicle handling and maneuvering.

It is another object of the present invention to provide a four cycle engine overcoming the drawbacks of the prior art.

It is another object of the present invention to provide a four cycle engine having a single cylinder.

It is another object of the present invention to provide a four cycle engine having a pair of cylinder arranged in a V-shaped orientation.

It is another object of the present invention to provide a four cycle engine having a small installed size and low weight with a high a level of performance relative to the volumetric displacement of the engine.

It is another object of the present invention to locate and orient the four cycle engine in accordance with the present invention in a vehicle such that vehicle has a relatively low center of gravity.

It is another object of the present invention to provide a four cycle engine that has a longitudinal axis that is transverse to the longitudinal axis of the vehicle, wherein the center of gravity of the four cycle engine is located as close to the longitudinal axis of the vehicle as possible.

It is another object of the present invention to provide a four cycle engine having specific components that are located on opposing sides of the longitudinal axis of the vehicle to balance the engine with respect to the vehicle and locate the center of gravity of the engine as close to the longitudinal axis of the vehicle as possible.

It is another object of the present invention to arrange the induction system and the exhaust system on opposite sides of the engine, such that the combustion air is not heated to improve cylinder charging.

It is another object of the present invention to provide an engine that enhances the manner in which a snowmobile handles, whereby the resulting center of gravity that is determined by the vehicle frame and the engine is located as close as possible to the center of the vehicle in order to reduce the inertia of the snowmobile about its vertical axis.

It is another object of the present invention to provide an engine for use in a snowmobile having engine components and auxiliary units arranged as close as possible to the track of the snowmobile.

It is another object of the present invention to provide an engine having the cylinders rotated as far as possible to the rear, whereby the rear cylinder crankcase is located to one side of the steering rod.

SUMMARY OF THE INVENTION

To overcome the deficiencies of the prior art and achieve the above described objectives, applicants have developed a four cycle engine for use in a vehicle. The four cycle engine includes a crankcase having a crankshaft extending therethrough. The crankshaft has a crankshaft axis that is transverse to the longitudinal axis of the vehicle. The engine further includes at least one cylinder unit connected to the crankcase. Each cylinder unit includes a cylinder and a cylinder head. It is contemplated that a single cylinder unit may provided. It is also contemplated that two or more cylinder units may be provided. In such a configuration, the cylinder units are arranged at an angle with respect to each other. The engine in accordance with the present invention further includes a continuously variable transmission (CVT) connected to the crankcase on one side of the longitudinal axis of the vehicle. The CVT is driven by the crankshaft. An air box is also provided that is located on the same side of the longitudinal axis as the CVT. The engine further includes an intake manifold operatively connected to the air box for connecting the air box to each cylinder unit and a throttle assembly operatively connected to the air box and the intake manifold.

When two or more cylinder units are present, the cylinder units are arranged at an angle with respect to each other, wherein a space is formed between the cylinder units. With such an arrangement, the intake manifold is located in the space.

When a pair of cylinder units are provided, the intake manifold may have a generally Y-shaped manifold having a connector leg connected to the throttle assembly and a pair of branches. One branch is operatively connected to one of the cylinder units and another branch is connected to another of the cylinder units. The connector leg is generally parallel to the axis of the crankshaft. The intake manifold may further include a baffle assembly, which directs gas flow within the intake manifold. The baffle assembly divides each of the branches into two separate flow paths of approximately equal size.

When additional intake capacity is desired, a surge tank located within the space between the cylinder units may be provided. The surge tank is operatively coupled to the throttle assembly and the intake manifold. In such an arrangement, the intake manifold includes rising manifold branches connected at one end to the surge tank and the cylinder units at another end.

When the engine is a naturally aspirated engine, the air box also includes at least two chambers. A first chamber is connected through at least one opening to the atmosphere. A second chamber is connected to the throttle assembly. The first and second chambers are also operatively connected to each other.

In accordance with the present invention, the engine may further include a charger assembly for compressing gas before it is supplied to the at least one cylinder unit. The charger assembly is located on a side opposite the CVT. This arrangement balances the weight of the CVT. When a charger is provided, the air box includes at least two chambers. A first chamber is connected through at least one opening to the atmosphere and is operatively connected to the charger. The second chamber is operatively connected to the charger and the throttle assembly. The center of gravity of the charger assembly is located on the rear side of the engine. The charger may be either a supercharger, which is driven by the crankshaft of the engine and attached to the crankcase, or a turbocharger, which is driven by exhaust gases.

It is preferable that the engine in accordance with the present invention include fuel injection. At least one injection nozzle is associated with each cylinder unit. It is preferable that a pair of injection nozzles are associated with each cylinder unit. A first injection nozzle is operatively connected to the intake manifold adjacent the cylinder head unit. A second injection nozzle is operatively connected to the intake manifold upstream of and spaced apart from the first injection nozzle. The first injection nozzle operates under all engine loads. The second injection nozzle operates only during predetermined engine loads (e.g., full open throttle).

The present invention is also directed to a vehicle containing a four cycle engine. The combination of the vehicle and the engine produces a vehicle having improved handling and maneuverability and lower emissions when compared to prior art vehicles.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following description and claims, the references to front and rear relate to the direction of travel of the vehicle. The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

FIG. 1 is a top view of a four-cycle engine according to an embodiment of the present invention with an air box and the throttle assembly being omitted, wherein the four-cycle engine is illustrated within a snowmobile;

FIG. 2 is an end view of an output side of the engine of FIG. 1;

FIG. 3 is an end view of the output side shown in FIG. 2, wherein the continuously variable transmission (CVT) and the air box are omitted;

FIG. 4 is an end view of the engine of FIG. 1 opposite the output side, as shown in FIG. 2;

FIG. 5 is a perspective view from the right rear side of the engine of FIG. 1;

FIG. 6 is a front view of the engine, in partial cross section;

FIG. 7 is an end view of the engine shown in FIG. 4 having a secondary housing omitted;

FIG. 8 is an end view of the engine illustrated in FIG. 4 having the water pump housing omitted;

FIG. 9 is a top view of a single-cylinder engine in partial cross-section according to another embodiment of the present invention;

FIG. 10 is an end view of the engine of FIG. 9;

FIG. 11 is an end view of the engine illustrated in FIG. 3 having the oil tank and throttle assembly omitted, wherein chamber 24 and the oil filter 41 are shown in partial cross section;

FIG. 12 is a cross sectional view of the engine of FIG. 1 through the crankcase, transverse to the crankshaft;

FIG. 13 is a cross sectional view of the lubricating-oil tank of the engine illustrated in FIG. 1;

FIG. 14 is a schematic view of the oil pickup assembly;

FIG. 15 is a cross sectional view of the oil pick up assembly of FIG. 14 along the main axis of the oil pickup assembly located within the engine of FIG. 1;

FIG. 16 is a cross sectional view of a non-return valve within the crankcase of the engine illustrated in FIG. 1;

FIG. 17 is a top view of a turbocharged version of the engine illustrated in FIG. 1 illustrating the induction and exhaust systems;

FIG. 18 is an end view of the supercharged version of engine of FIG. 1 illustrating a centrifugal blower;

FIG. 19 is the end view shown in FIG. 18 illustrating the induction system ducts;

FIG. 20 is a partial cross sectional view of the air box according to the present invention;

FIG. 21 is a cross sectional view of the air box along section lines XXI--XXI in FIG. 20;

FIG. 22 is bottom schematic view of a Y-manifold used in the engine of FIG. 1 according to the present invention;

FIG. 23 is an end schematic view of the Y-manifold of FIG. 22;

FIG. 24 is a partial cross sectional view of one of the secondary branches of the Y-manifold of FIG. 22; and

FIG. 25 is a partial end view of a variation of the engine of FIG. 1 having increased capacity.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

A four-cycle engine having one or more cylinders 4 will now be described in greater detail. A two cylinder engine 1 in accordance with the present invention is illustrated in FIG. 1. A single cylinder engine 100 in accordance with the present invention is illustrated in FIG. 9. As shown in FIG. 1, the engine 1 is mounted to a chassis of a snowmobile 90. The engine 100 may be similarly mounted in the chassis of the snowmobile 90. The present invention is not limited to four-cycle engines used in snowmobiles; rather, it is intended that the engines 1 and 100 disclosed herein and any variations thereof may be used in multiple vehicles including but not limited to three-wheeled vehicles, ATVs, motorcycles, and watercraft.

The four-cycle engine 1 having a pair of cylinders 4A and 4B will now be described in greater detail. Although a pair of cylinders 4A and 4B are disclosed, the present invention is not limited to a pair of cylinders; rather, it is contemplated that a single cylinder 4 may be provided, as described below in connection with FIGS. 9 and 10. It is further contemplated that more than two cylinders maybe provided (e.g. V-four cylinder engine). As shown in FIGS. 2 and 3, the engine 1 includes a crankcase 2 having a crankshaft 3 rotatably supported therein. The engine 1 further includes a pair of cylinders 4A and 4B that are arranged in a V configuration, as shown in FIGS. 3, 4, 5 and 8. The angle between the cylinders 4A and 4B is approximately 80.degree.. Angles greater than 80.degree. and less than 80.degree. are considered to be well within the scope of the present invention. In order to locate the center of gravity of the engine 1 as close as possible to the middle of the snowmobile 90 or the track 96 and the same time to provide space for the steering rod 51, the cylinder axis 70 of the front cylinder 4B should be closer to the longitudinal axis 9 of the snowmobile 90 and the cylinder axis 70 of the rear cylinder 4A, so that the center of gravity of the engine 1 is moved as close as possible towards the longitudinal axis of the snowmobile 90.

Each of the cylinders 4A and 4B includes at least one inlet valve and at least one exhaust valve, which are located within the cylinder heads 8A and 8B, respectively. A pair of inlet valves and a pair of exhaust valves associated with each cylinder 4A and 4B is preferred.

The crankcase 2 includes a drive-side or output side section 34 and a second side section 33, as shown in FIG. 4. The sections 33 and 34 together form a crankshaft chamber 5 that encloses the crankshaft 3. The crankshaft 3 extends from opposite ends of the crankshaft chamber 5. Each of the cylinders 4A and 4B includes a piston 6 movably mounted therein. The piston 6 is operatively connected to the crankshaft 3 by a connecting rod 7, as shown in FIG. 12. The reciprocating movement of the pistons 6 is converted into a rotary movement at the crankshaft 3.

The intake and exhaust valves of each cylinder are actuated by a single overhead camshaft (SOHC) (not shown) located within the cylinder heads 8A and 8B. The cams on the camshaft may directly operate the valves or indirectly operate the valves through rocker arms. The camshaft is operatively connected to the crankshaft 3 by way of a chain-drive system. The present invention, however, is not limited to the use of a single camshaft and rocker arms to operate the valves. It is, of course, understood that any other type of valve operating system such as DOHC and/or a camshaft driven by way of a notched belt could be used, without departing from the underlying concept of the present invention.

The arrangement of the engine 1 will now be described. As shown in FIG. 1, the four-cycle engine 1 may be installed in a snowmobile adjacent to a steering rod 51. The engine 1 is arranged such that the axis 10 of the crankshaft 3 is transverse to the longitudinal axis 9 of the snowmobile. The rear cylinder 4A is located adjacent the steering rod 51. The cylinder axis of the front cylinder 4B is located closer to the longitudinal axis 9 of the snowmobile than the cylinder axis of the rear cylinder 4A.

A CVT 11 is supported on the engine 1, as shown in FIG. 2, on one side of the longitudinal axis 9. The CVT 11 is driven by the crankshaft 3. A plurality of auxiliary units, shown in FIGS. 1 and 4 and described below, are supported on an opposite side of the engine 1 on an opposite side of the longitudinal axis 9. Relative to the CVT 11, the auxiliary units are located on the opposite side of the longitudinal axis 9 of the snowmobile 90. As shown in FIGS. 8, 17 and 18, the auxiliary units include but are not limited to an alternator or generator 12, a starter motor 13, a water pump 14, at least two oil pumps including a suction pump 15 and a force pump 16, and an optional charger. The charger may either be a mechanical supercharger 17 or a turbocharger 22. The alternator 12, the starter motor 13 and the optional supercharger 17 or turbocharger 22 are arranged with their centers of gravity on the same side of the axis 10 of the crankshaft 3 on the rear engine side. The auxiliary units (except the turbocharger 22) are driven by a common drive unit operatively connected to the crankshaft 3. It is preferable that the common drive unit is a toothed wheel gearing 18, as shown in FIG. 7. The use of common drive unit produces a particularly compact construction for the engine 1. It is advantageous to have the starter motor 13 arranged to the rear of the axis 10 of the crankshaft 3, which locates the resultant center of gravity of the engine even further towards the rear of the snowmobile. The CVT 11 and the auxiliary units will now be described in greater detail.

The toothed-wheel gearing 18 is accommodated in a secondary housing 20 that is located on the end of the second section 33 of the crankcase 2 to protect the gearing 18 from the external environment. As illustrated in FIGS. 4 6, the secondary housing 20 protects the toothed-wheel gearing 18 from environmental influences. The water pump 14 and the generator 12 are mounted on the exterior of the secondary housing 20. Their respective drive shafts pass through the secondary housing 20 and mesh with the toothed-wheel gearing 18. The suction pump 15 and the force pump 16 are located within the secondary housing 20. All of these components are located on a side of the engine opposite the CVT 11.

The generator 12 is preferably connected to the toothed-wheel gearing 18 through a dynamic damper to damp out excessive oscillations associated with the great inertial moment of the generator 12. The generator 12 is driven by a gear wheel 18A of the toothed-wheel gearing 18 that is arranged on the crankshaft 3 in the secondary housing 20, as shown in FIG. 7. The drives for the water pump 14 and for the starter motor 13 also mesh with the same gear wheel 18A. The starter motor 13 is coupled to the driving gear wheel 18A and thus to the crankshaft 10 through a plurality of intermediate gear wheels in order to arrive at the required transmission ratio. The starter motor 13 is connected through a slip clutch 21 to the crankshaft to compensate for torque peaks. The suction pump 15 and the force pump 16, are driven through the driving gear wheel 18B of the toothed-wheel gearing 18.

The water pump 14 delivers engine coolant through the coolant channels 81 within the engine 1, shown in FIGS. 7 and 8. The water pump 14 includes a spiral housing 82, shown in FIG. 8 and an outer housing 83, shown in FIG. 4. The housing 83 forms connecting pieces for coolant feed and return lines and incorporates a thermostat 84, which is shown in FIG. 4. The thermostat 84 controls the flow of coolant.

A heat exchanger (not shown) is preferably arranged between the engine 1 and the track 96 in such a manner that when the snowmobile 90 is operated, snow or ice crystals are continuously thrown against the heat exchanger when the snowmobile track 96 is moving. This provides a simple yet highly effective means for cooling the engine without the need for any costly components.

As shown in FIG. 2, the CVT 11 comprises, amongst other things, a drive pulley 91 and driven pulley 92. The drive pulley 91 is secured to the crankshaft 3. The driven pulley 92 is secured to one end of an output shaft 94 that is supported by the chassis 90 of the vehicle. The drive pulley 91 and driven pulley 92 are operatively connected by a belt 93. The transmission ratio between drive pulley 91 and driven pulley 92 is variable as a function of the load on the engine and engine speed. A reduction gear assembly 95 is connected to an opposite end of the output shaft 94, as shown in FIG. 1. The reduction gearing 95 drives the track 96 of the snowmobile.

A supercharger or turbocharger can be used to compress the intake air and increase the cylinder charge. As shown in FIGS. 18 and 19, the supercharger 17 is preferably a centrifugal blower. The supercharger 17 is driven by the crankshaft 3 through the gearing 18. The supercharger 17 is located on a side of the engine 1 that is opposite the CVT 11. The supercharger 17 is located adjacent the rear cylinder 4A. The axis 72 of the supercharger 17 is located parallel to and behind the axis. 10 of the crankshaft 3. Since the supercharger 17 is relatively heavy, it advantageously serves as a counterweight to the CVT. This arrangement improves both the handling and balance of the snowmobile 90. This location of the supercharger 17 requires relatively short ducts for connection to the induction system.

Alternatively, a turbocharger 22 can be provided to improve the power output of the engine 1 instead of the mechanically driven supercharger described above. The turbocharger 22 is connected to the exhaust system. Like the supercharger 17, the turbocharger 22 is mounted on the opposite side of the longitudinal axis 9 of the snowmobile 90 relative to the CVT 11. With this arrangement, the axis 72 of the turbocharger impeller is behind the axis 10 of the crankshaft 3, adjacent to the cylinder 4A. The turbocharger 22 acts as a counterweight to the CVT 11.

The induction system for the engine 1 will now be described. To configure the exchange of gases for the V-twin four cycle engine 1 in as simple a manner as possible, the inlet ports into the cylinder heads 8A and 8B are arranged on opposing sides of the cylinder heads 8A and 8B such that the inlet ports on cylinder head 8A face the inlet ports on cylinder head 8B, as shown in FIG. 8. The exhaust manifolds associated with each cylinder 4A and 4B are arranged on the opposing sides of the cylinders such that the exhaust ports on cylinder head 8A face away from the exhaust ports on cylinder head 8B.

Air and blow-by gas is drawn in through an air box or plenum 52, which is advantageously arranged on the same side of the engine 1 as the CVT 11, as shown in FIGS. 2, 5 and 6. The air box 52 is illustrated in greater detail in FIGS. 20 and 21. The air box 52 serves to equalize pressure waves and attenuate sound waves. A throttle assembly 55 is installed in a recess 53 that is formed in the air box 52, as shown in FIG. 20. The throttle assembly 55 is operatively connected to an intake manifold 54. The air and unburned gas mixture is supplied to the cylinder heads 8A and 8B and subsequently to the cylinders 4A and 4B by way of the intake manifold 54. To protect the throttle assembly 55 against dirt, the recess 53 in the air box 52 is covered from above by a removable cover 56, shown in FIG. 21.

As discussed above, the snowmobile 90 is typically operated in severe working conditions (e.g., as low as -40.degree. C.). Under such conditions, icing around the throttle assembly 55 can occur, which could have an adverse impact on engine performance. Furthermore, at full loads, the velocity of air around the throttle assembly can also increase ice build up. In accordance with the present invention, a portion of the engine coolant is directed through a portion of the throttle assembly 55. The coolant is fed through an inlet opening 551 through a passageway (not shown) to an outlet opening 552, as shown in FIG. 20. Although the passageway typically only extends through a small portion of the throttle assembly 55, the heat transfer properties of the material forming the throttle assembly are sufficient such that the coolant warms substantially the entire throttle assembly to prevent ice formation.

The air box 52 is arranged above the CVT 11 and incorporates at least two separate chambers 57 and 58. The first chamber 57 of the air box 52 communicates with the atmosphere through openings 59 formed therein through which air is drawn into the induction system.

In the event that the engine 1 is a naturally aspirating engine (i.e., no turbocharger or supercharger), the first chamber 57 is connected to the chamber 58 through venturi tubes 60, which attenuate induction noise. Air is first drawn into the first chamber 57 and then through the venturi tubes 60 into the second chamber 58. The air is then routed through the throttle assembly 55 into the intake manifold 54 to the cylinder heads 8A and 8B into the cylinders 4A and 4B.

In the event that the engine 1 is a charged engine (i.e., turbocharged or supercharged), air is drawn into the first chamber 57 through the openings 59. There are no venturi tubes 60 in the air box 52. Unlike the naturally aspirating engine, the two chambers 57 and 58 are no longer connected directly to each other. The turbocharger or supercharger draws air from the first chamber 57 by way of a suction line 110, as shown in FIGS. 17 and 19. The charger then compresses the air and returns the air to the second chamber 58 through a pressure line 111, as shown in FIGS. 17 and 19. The second chamber 58 acts as an equalizer tank. The pressure in the chamber 58 is higher than the pressure in the chamber 57 and corresponds to the charge pressure. The compressed air then passes through the second chamber 58 into the throttle assembly 55 to the intake manifold 54 where it is delivered to the cylinders 4A and 4B. The same air box 52 can be used in either the aspirated version of the engine or the charged version of the engine with only minor modification.

It is preferable that the suction line 110 is routed around the rear cylinder 4A and the cylinder head 8A. It is preferable that the pressure line 111 is routed around the front cylinder 4B and the cylinder head 8B of the engine. The suction line 110 and the pressure line 111 are preferably formed as flexible hoses and/or rigid pipes. The present invention, however, is not limited to the use of hoses and/or pipes; rather, it is contemplated that the lines 110 and 111 may be at least partially integrated into the crankcase 2 or air box 52. A charge-air cooler or intercooler 62 may be integrated into the pressure line 111 to cool the charge air. The cooler 62 has a relatively low weight and is preferably located in front of the axis 10 without adversely impacting the center of gravity. Furthermore, this location aids in cooling the air because it is exposed to wind du