CN110821593A

CN110821593A - Gear train for internal combustion engine system

Info

Publication number: CN110821593A
Application number: CN201810906017.1A
Authority: CN
Inventors: 孙兵
Original assignee: Cummins Inc
Current assignee: Cummins Inc
Priority date: 2018-08-10
Filing date: 2018-08-10
Publication date: 2020-02-21
Anticipated expiration: 2038-08-10
Also published as: CN110821593B

Abstract

The present application relates to gear trains for internal combustion engine systems. The gear train includes a plurality of gears to transmit rotational power from a crankshaft of the engine assembly to the camshaft. The plurality of gears includes a crank gear coupled to the crankshaft and a cam gear coupled to the camshaft. The gear ratio between the cam gear and the crank gear is configured to be 2: 1. The center distance between the longitudinal axis of the crank gear and the longitudinal axis of the cam gear is about 563 mm. One of the plurality of gears is a compound cam idler gear to allow a particular fractional gear ratio. The plurality of gears are high contact ratio spur gears to increase gear life. None of the gears has a number of teeth that is a multiple of the number of cylinders in the engine assembly.

Description

Gear train for internal combustion engine system

Technical Field

The present application relates generally to gear trains for use with internal combustion engines.

Background

Internal combustion engines, such as diesel or gasoline engines, typically include one or more cylinders that receive fuel in an operating cycle (e.g., a four-stroke cycle) of the engine, compress the fuel or air/fuel mixture via a piston that reciprocates in the cylinder, combust the fuel, and expel exhaust gases out of the cylinder. Traditionally, the operating cycle is advanced by the cylinder valves opening and closing at exactly the right moment in synchronism with the movement of the piston. For example, in a four-stroke cycle engine, a camshaft is used to open and close the cylinder valves. The camshaft may include a series of cams configured to open and close the cylinder valves during rotation of the camshaft. For optimum functioning of the internal combustion engine, the camshaft may rotate once per two revolutions of the crankshaft. One common way to synchronize the crankshaft and camshaft is to rotate the camshaft by using a transmission (i.e., a pulley (pulley), belt, gear, sprocket, chain, etc.).

The vertical distance between the crankshaft and the camshaft may be unique for each engine. Certain center-to-center distances, either larger or smaller than usual, may present challenges to the manufacturer, increase the weight, cost, or both of the engine assembly.

Disclosure of Invention

Embodiments described herein relate generally to gear trains for engine assemblies, and in particular, to gear trains configured to transmit rotary power from a crankshaft to a camshaft of an engine such that a speed ratio between the crankshaft and the camshaft is 2: 1.

In a first set of embodiments, a gear train for transmitting rotary power from a crankshaft to a camshaft of an engine assembly includes a plurality of gears. The plurality of gears includes a crank idler gear. The plurality of gears further includes a crank gear configured to mesh with the crank idler gear. The crank gear is configured to be coupled to a crankshaft. The intermediate idler gear is meshed with the crank idler gear. A cam gear (cam gear) is configured to be coupled to the camshaft. The plurality of gears further includes a compound cam idler gear (compound cam idler gear) including a first cam idler gear meshing with the intermediate idler gear and a second cam idler gear meshing with the cam gear.

In another set of embodiments, a gear train for transmitting rotational power from a crankshaft to a camshaft of an engine includes a plurality of gears. The plurality of gears includes a crank idler gear. The plurality of gears further includes a crank gear configured to mesh with the crank idler gear. The crank gear is configured to be coupled to a crankshaft. The intermediate idler gear is meshed with the crank idler gear. The cam gear is configured to be coupled to a camshaft. The plurality of gears further includes a compound cam idler gear including a first cam idler gear in meshing engagement with the intermediate idler gear and a second cam idler gear in meshing engagement with the cam gear. Each of the plurality of gears has a normal module of 3.0 and a normal pressure angle of 17.5 °.

In another set of embodiments, a gear train for transmitting rotary power from a crankshaft to a camshaft of an engine assembly includes:

a plurality of gears, the plurality of gears comprising:

a crank idler gear;

a crank gear configured to mesh with the crank idler gear, the crank gear configured to be coupled to the crankshaft;

an intermediate idler gear that meshes with the crank idler gear;

a cam gear configured to be coupled to the camshaft; and

a compound cam idler gear, the compound cam idler gear comprising:

a first cam idler gear that meshes with the intermediate idler gear; and

a second cam idler gear that meshes with the cam gear.

In some embodiments, the gear ratios of the plurality of gears are configured such that the ratio of crankshaft speed to camshaft speed is 2: 1.

In some embodiments, the vertical distance between the longitudinal axis of the crank gear and the longitudinal axis of the cam gear is configured to be in the range of 560 and 565 millimeters.

In some embodiments, the vertical distance between the longitudinal axis of the crank gear and the longitudinal axis of the cam gear is configured to 563 millimeters.

In some embodiments, the number of gear teeth of each of the plurality of gears is not a multiple of the number of cylinders included in the engine assembly.

In some embodiments, the plurality of gears further includes a fuel pump gear in meshing engagement with the crank idler gear, the fuel pump gear configured to be coupled to a fuel pump of the engine assembly.

In some embodiments, the gear ratio between the crank gear and the fuel pump gear is 1: 1.696.

In some embodiments, the plurality of gears further comprises an air compressor gear in meshing engagement with the crank idler gear, the air compressor gear configured to be coupled to an air compressor of the engine assembly.

In some embodiments, the gear ratio between the crank gear and the air compressor gear is configured to be 1: 1.182.

In some embodiments, the diameter of the first cam idler gear is configured to be larger than the diameter of the second cam idler gear.

In some embodiments, the gear ratio between the crank gear and the first cam idler gear is configured to be 4: 3.

In some embodiments, the gear ratio between the second cam idler gear and the cam gear is configured to be 2: 3.

In some embodiments, the gear train further comprises: a Rear Engine Power Take Off (REPTO) gear; and a REPTO idler gear configured to mesh with the REPTO gear and the crank idler gear.

In some embodiments, the REPTO idler gear and the REPTO gear are positioned out of plane relative to the crank gear and the intermediate idler gear.

In some embodiments, each of the plurality of gears is configured to have a normal module of 3.00 and a normal pressure angle of 17.5 °.

In some embodiments, each of the plurality of gears is configured to have an addendum coefficient ranging from 1.0 to 1.4 and a dedendum coefficient ranging from 1.2 to 1.8.

In some embodiments, the plurality of gears are configured as high contact ratio spur gears.

In yet another set of embodiments, a gear train for transmitting rotary power from a crankshaft to a camshaft of an engine assembly includes:

a plurality of gears, the plurality of gears comprising:

a crank idler gear;

a crank gear configured to mesh with the crank idler gear, and the crank gear is configured to be coupled to the crankshaft;

an intermediate idler gear configured to mesh with the crank idler gear;

a cam gear configured to be coupled to the camshaft; and

a compound cam idler gear, the compound cam idler gear comprising:

a first cam idler gear configured to mesh with the intermediate idler gear; and

a second cam idler gear configured to mesh with the cam gear;

wherein each of the plurality of gears is configured to have a normal module of 3.00 and a normal pressure angle of 17.5 °.

In some embodiments, the vertical distance is configured to 563 mm.

In some embodiments, the number of gear teeth of each of the plurality of gears is configured to be not a multiple of the number of cylinders included in the engine assembly.

In some embodiments, the plurality of gears further includes a fuel pump gear configured to engage the crank idler gear, the fuel pump gear configured to be coupled to a fuel pump of the engine assembly.

In some embodiments, the gear ratio between the crank gear and the fuel pump gear is configured to be 1: 1.696.

In some embodiments, the plurality of gears further comprises an air compressor gear configured to mesh with the crank idler gear, the air compressor gear configured to be coupled to an air compressor of the engine assembly.

In some embodiments, the diameter of the first cam idler gear is greater than the diameter of the second cam idler gear.

In some embodiments, each gear of the plurality of gears has an addendum coefficient ranging from 1.0 to 1.4 and a dedendum coefficient ranging from 1.2 to 1.8.

It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (so long as the concepts are not mutually inconsistent) are contemplated as being part of the subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the subject matter disclosed herein.

Drawings

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope, the disclosure will be described with additional specificity and detail through use of the accompanying drawings.

Fig. 1 is a rear side perspective view of an engine assembly including a gear train according to an embodiment.

Fig. 2 is a rear view of a gear train included in the engine of fig. 1.

FIG. 3 is a rear side perspective view of an engine including a gear train according to another embodiment.

Fig. 4 is a rear view of a gear train included in the engine of fig. 3.

FIG. 5 is a view of a portion of a gear to show gear teeth thereof, according to one embodiment.

Throughout the following detailed description, reference is made to the accompanying drawings. In the drawings, like reference numerals generally refer to like parts throughout the various views unless the context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented herein. It will be readily understood that the aspects of the present disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Detailed Description

Various engine components may include a crankshaft and a camshaft. For some internal combustion engines, it may be desirable for the camshaft to rotate exactly once every two revolutions of the crankshaft. To configure the camshaft and the crankshaft in this way, a drive train including at least one of gears, pulleys and belts, or chains and sprockets is typically used between the crankshaft and the camshaft.

The crankshaft and camshaft in an engine assembly are typically located on opposite sides of the engine. A crankshaft rotated by the piston may be mounted near the bottom of the engine. The camshaft, which opens and closes the cylinder valves to facilitate movement of air through the cylinders, is typically mounted near the top of the engine (e.g., in the cylinder head). The distance between the crankshaft and the camshaft may present significant challenges in transferring rotational power from the crankshaft to the camshaft.

In addition to operating the camshaft, the crankshaft may also be responsible for providing rotational power to a fuel pump of the engine assembly, an air compressor of the engine assembly, and, in some cases, a Rear Engine Power Take Off (REPTO). Each of these devices may operate using a particular gear ratio. Furthermore, the fuel pump cannot be loaded with axial forces.

Another challenge associated with transferring rotational power from a crankshaft to a camshaft of an engine assembly is the center distance between the middle of the crankshaft and the middle of the camshaft. The center distance may be changed according to the user's needs. A smaller center distance may be required if the engine assembly is designed to be compact or designed to reduce weight. Alternatively, the center distance may be large to accommodate larger cylinder displacements or longer crank arms. Additionally, the center distance may be any distance therebetween for any number of reasons, such as the size, height, weight, or shape of the engine or related components.

Gears have proven to be a reliable and adjustable way of transmitting rotational power from the crankshaft to the camshaft, fuel pump, air compressor and REPTO. The gear comprises a plurality of gear teeth that can be manufactured and adjusted according to the needs of the user. Each tooth of the plurality of gear teeth is configured to have a profile (e.g., shape, geometry, contour, etc.) and a contact surface (e.g., tooth face, pressure face, tooth surface, etc.). Each tooth is also configured to have a pressure angle and a normal modulus, both of which are a result of the changes made to the profile and the contact surface. Furthermore, the same type of gears (e.g., spur, helical, spiral bevel, etc.) having the same normal modulus and the same normal pressure angle can be meshed together and operate without problems.

Embodiments of the gear trains described herein may provide benefits including, for example: (1) providing a predetermined speed ratio between a crankshaft and a camshaft of the engine; (2) providing rotational power to the fuel pump, air compressor, and/or REPTO in addition to the camshaft; (3) preventing torsional vibrations (e.g., third order torsional vibrations) by including a gear with teeth that are not a multiple of the number of cylinders of the engine, thereby increasing robustness, reducing tooth pass frequency and reducing harmonics, which reduces gear noise; (4) providing a multi-layer gear arrangement to save space; and (5) allows the use of smaller gears to further save space and weight.

Furthermore, the described gear trains provide advantages over other forms of power transmissions, including, but not limited to, higher torque density (e.g., more torque can be transmitted while the transmission takes up less space) and increased system life.

As described herein, the term "pressure angle," when referring to a gear arrangement, refers to the angle between the gear contact surface and a tangent to the gear pitch circle (e.g., an imaginary line having an intersection with the gear pitch diameter).

As described herein, the term "normal module" of a gear is the module of the gear (e.g., a selected gear diameter) divided by the number of gear teeth on the gear measured using a pitch diameter (e.g., the diameter of a pitch circle of the gear). The pitch circle of the gear is an imaginary circle formed around the gear at a position between the outer diameter of the gear and the diameter of the root of the gear. When a gear is meshed with another gear, the pitch circle of each gear is tangent to the other such that the linear velocity of the pitch circle of each gear is the same. The normal modulus is a number used to classify gears that can mesh together without requiring advanced mathematical operations.

FIG. 1 is a rear side perspective view of an engine assembly 10 according to one embodiment. The engine assembly may be included in various systems, such as passenger vehicles, excavators, fire trucks, cement trucks, fluid pumping stations, and the like. The engine assembly 10 includes an engine block 12, the engine block 12 containing an engine. The engine may include, for example, a diesel engine, a gasoline engine, a natural gas engine, an ethanol engine, a biodiesel engine, an E85 engine, any other suitable fuel-powered engine, or a combination thereof. The engine assembly 10 may also include an air compressor 14, a camshaft 16, and a fuel pump. The engine assembly 10 may also include a coolant reservoir or oil reservoir 18. The internal workings (workings) of the engine assembly 10 are within the engine block 12, but are not shown in fig. 1. These internal workings may include camshafts, a plurality of pistons positioned within respective cylinders 13 and configured to reciprocate therein, and crankshafts (not shown) operably coupled to the pistons and configured to rotate in response to the reciprocating motion of the pistons. In some embodiments, the camshaft 16 may be housed in a cylinder head (not shown).

The engine assembly 10 also includes a gear train 100. Fig. 2 shows a rear view of the gear train 100. The gear train 100 is configured to transmit rotational power from the crankshaft to the camshaft 16. The gear train 100 includes a crank idler gear 110, a crank gear 112, a fuel pump gear 114, an air compressor gear 116, an intermediate idler gear 120, a compound cam idler gear 130, and a cam gear 140.

The crank gear 112 is configured to be coupled to a crankshaft. The crank gear 112 is coupled to the crankshaft such that rotation of the crankshaft causes the crank gear 112 to simultaneously rotate radially about the same axis of rotation, but does not allow the crank gear 112 to move translationally or axially relative to the crankshaft. The crank gear 112 is configured with a plurality of gear teeth configured with a normal pressure angle (e.g., a normal pressure angle of 17.5 °) and a normal module (e.g., a normal module of 3.0). The crank gear 112 may comprise, for example, a high contact ratio spur gear.

The crank gear 112 meshes with the crank idler gear 110 (e.g., by leaving an optimal center point distance for the gear teeth to interlock). The crank idler gear 110 is rotatably coupled to the engine block 12 such that the crank idler gear 110 is free to rotate radially about its central axis, but such that the crank idler gear 110 is not movable translationally or axially relative to the engine block 12. The crank idler gear 110 includes a plurality of gear teeth and may be configured to have the same normal pressure angle and the same normal module as the crank gear 112. In certain embodiments, the crank idler gear 110 may also include the same type of gear as the crank gear 112, such as a high contact ratio spur gear.

In some embodiments, the crank idler gear 110 may be in mesh with a plurality of gears in addition to the crank gear 112. For example, as shown in fig. 1 and 2, the crank idler gear 110 is meshed with the fuel pump gear. The fuel pump gear 114 may be coupled to a fuel pump of the engine assembly 10, for example, to drive the fuel pump of the engine assembly 10. In some embodiments, the fuel pump gear 114 may have a plurality of gear teeth and have the same normal pressure angle and the same normal module as the crank gear 112. In certain embodiments, the fuel pump gear 114 is also configured as the same type of gear as the crank gear 112, such as a high contact ratio spur gear. In certain embodiments, the gear ratio between the crank gear and the fuel pump gear is 1: 1.696.

In some embodiments, the crank idler gear 110 may also be in meshing engagement with the air compressor gear 116. The air compressor gear 116 may be coupled to the air compressor 14, for example, to drive the air compressor 14. The air compressor gear 116 may be coupled to the air compressor 14 (e.g., via a shaft) such that the air compressor gear 116 is radially rotatable about its central axis, but is not translationally or axially movable relative to the air compressor 14. The air compressor gear 116 includes a plurality of gear teeth that may have the same normal pressure angle and the same normal modulus as the crank gear 112. The air compressor gear 116 may also be the same type of gear as the crank gear 112, for example, a high contact ratio spur gear. In some embodiments, the gear ratio between the crank gear and the air compressor gear is 1: 1.182.

The crank idler gear 110 is also meshed with an intermediate idler gear 120. The intermediate idler gear 120 is rotatably coupled to the engine block 12 (e.g., via a shaft) such that the intermediate idler gear 120 is radially rotatable about its central axis, but is not translationally or axially movable relative to the engine block 12. The intermediate idler gear 120 includes a plurality of gear teeth and may be configured to have the same normal pressure angle and the same normal module as the crank gear 112. The intermediate idler gear 120 may also be the same type of gear as the crank gear 112, for example, a high coincidence spur gear.

The intermediate idler gear 120 is engaged with a compound cam idler gear 130. The compound cam idler gear 130 is configured to be rotatably coupled to the engine block 12 (e.g., a cylinder head of the engine block 12) such that the compound cam idler gear 130 is free to rotate radially about its central axis, but is not translatable or axially moveable relative to the engine block 12. The compound cam idler gear 130 includes a first cam idler gear 132 and a second cam idler gear 134 coupled to each other along their rotational axes. In some embodiments, the first cam idler gear 132 may be larger than the second cam idler gear 134.

The first cam idler gear 132 is engaged with the intermediate idler gear 120. The first cam idler gear 132 also includes a plurality of gear teeth and can have the same normal pressure angle and the same normal module as the crank gear 112. The first cam idler gear 132 and the second cam idler gear 134 may be the same type of gear as the crank gear 112, for example, high coincidence spur gears. In some embodiments, the gear ratio between the crank gear 112 and the first cam idler gear 132 may be 4: 3.

The second cam idler gear 134 is engaged with a cam gear 140 coupled to the cam shaft 16. The second cam idler gear 134 includes a plurality of gear teeth and may have the same normal pressure angle and the same normal module as the crank gear 112. The first cam idler gear 132 and the second cam idler gear 134 may have the same or different normal pressure angles and the same normal module. The compound cam idler gear 130 is rotatably coupled to the engine block 12 such that the compound cam idler gear is rotatable about the central axis of both the first cam idler gear 132 and the second cam idler gear 134, but the first cam idler gear 132 is not rotatable relative to the second cam idler gear 134. In other words, the first cam idler gear 132 and the second cam idler gear 134 rotate together at the same speed. In certain embodiments, the gear ratio between the second cam idler gear 134 and the cam gear 140 can be 2: 3. Because the second cam idler gear 134 rotates with the first cam idler gear 132, the second cam idler gear 134 and the first cam idler gear 132 can have the same rotational speed. In some embodiments, the gear ratio between the first cam idler gear 132 and the second cam idler gear 134 can be 2: 1.

The cam gear 140 is configured to be coupled to the camshaft 16 such that rotation of the cam gear 140 causes the camshaft 16 to simultaneously rotate radially about a central axis of the camshaft 16, but the cam gear 140 cannot move translationally or axially relative to the camshaft 16. The camshaft 16 may be housed within a cylinder head. The camshaft 16 is configured to control the flow of air into and out of the cylinders 13, for example, by cooperating with a plurality of cylinder valves (not shown) to open and close the cylinder valves in response to rotation of the crankshaft.

The gear ratio between the crank gear 112 and the cam gear 140 may be configured to synchronize rotation of the camshaft 16 with rotation of the crankshaft in a manner optimized for operation of the engine assembly 10, for example, based on the phase of the engine cycle corresponding to a particular piston position. The gear ratio may vary depending on the number of cylinders 13 included in the engine assembly 10, the number of cylinder valves within the engine block 12, and/or the number of cylinders 13, among other things.

The vertical distance D between the rotational axes of the crank gear 112 and the cam gear 140 may be configured to optimize the engine assembly 10 to provide, for example, cost reduction, weight reduction, or space usage reduction. The center vertical distance D may change if the size of any of the gears within the gear train 100 changes. For example, the vertical distance D may change if at least one of the normal pitch angle, normal module, or number of teeth of any one of the gears within the gear train 100 changes. In other arrangements, the vertical distance D may vary if the relative spacing between the crankshaft and the camshaft 16 varies due to a function of the engine assembly 10, such as an increase in piston displacement or an increase in crank arm length. In some embodiments, the vertical distance D can be in the range of 560 and 565mm (e.g., 560mm, 561mm, 562mm, 563mm, 564mm, or 565mm, including all ranges and values therebetween). In a particular embodiment, the vertical distance may be 563 mm.

As previously described herein, one or more gears included in the gear train 100 may include a high contact ratio spur gear. During power transfer, the high overlap spur gear shares the load between more than one gear tooth. This load sharing may reduce wear on the gear teeth and allow for longer gear life during operation of the engine assembly 10. High coincidence spur gears may be used in the gear train 100 to achieve stable transmission between gears and to reduce sound (e.g., gear whine) during operation of the engine assembly 10.

Each gear included in the gear train 100 is also configured to have a plurality of gear teeth. For example, fig. 5 shows a portion of an exemplary gear that includes gear teeth 300. The gear teeth of each gear in gear train 100 are defined by contact surfaces, i.e., surfaces of the gear teeth that transmit force (e.g., contact surfaces 305 shown in FIG. 5). The gear teeth are also defined by a node (shown as node 307) (e.g., the point at which force is transmitted from the contact surface 305 to another contact surface of another gear, the point at which effective torque is measured). The pitch circle (e.g., an imaginary circle formed around the gear somewhere in the middle of the gear teeth; when the gear meshes with another gear, the pitch circle of each gear is tangent to the other such that the linear velocity of the pitch circle of each gear is the same) is created by the circle formed around each node 307 of the gear, shown as pitch circle 309. The gear also includes a profile (e.g., geometry, shape, contour, etc.), such as profile 310. The addendum factor is a factor that defines a profile (shown as profile 310) of the gear tooth (e.g., geometry, shape, profile, etc.). An addendum coefficient above zero means that the tooth thickness (shown as tooth thickness 315) increases and the addendum (shown as addendum 320) (e.g., the tooth height above the pitch circle 309) increases. The root height factor is a factor that further defines the profile 310 of the gear tooth. The root height factor is a measure of the tooth root height (shown as root height 330) of the gear tooth (e.g., the distance between the root circle and the pitch circle 309).

In various embodiments, each gear included in gear train 100 may have an addendum coefficient in a range of 1.0 to 1.4. Further, each gear included in the gear train 100 may have a dedendum height factor in a range of 1.2 to 1.8. The root height coefficient and the addendum height coefficient may be varied with respect to each other to obtain strong and reliable gear teeth, resulting in a strong and reliable gear.

Each gear included in gear train 100 may have the same normal pressure angle, for example, a normal pressure angle of 17.5 °. As shown in FIG. 5, the normal pressure angle 340 is the angle between the contact surface of the gear tooth 300 and the tangent of the pitch circle 309. Further, each gear in gear train 100 may have the same normal module, e.g., a normal module of 3.00 (e.g., the diameter of pitch circle 309 divided by the number of gear teeth, as shown in fig. 5). Such a normal modulus and normal pressure angle may increase the overall strength of the gear train 100 and/or reduce the manufacturing cost of the gear train 100.

In some embodiments, the crank idler gear 110, the crank gear 112, the fuel pump gear 114, the air compressor gear 116, the intermediate idler gear 120, and the first cam idler gear 132 all lie in a first plane such that the gears can mesh with other gears that lie in the first plane. Further, the second cam idler gear 134 and the cam gear 140 may be located in a second plane that is offset from the first plane.

In some embodiments, the gear ratios of the plurality of gears included in the gear train 100 may be configured such that the ratio of crankshaft speed to camshaft speed is 2: 1. The crank gear 112 is coupled to one end of the crankshaft along a central axis of the crankshaft such that rotation of the crankshaft causes the crank gear 112 to rotate about the central axis of the crankshaft and in the same direction as the crankshaft. In some embodiments, the crank gear 112 may have 39 gear teeth. In some embodiments, the first cam idler gear 132 has 52 gear teeth and the second cam idler gear 134 has 34 gear teeth. In some embodiments, the cam gear 140 has 51 gear teeth.

In some embodiments, the number of teeth of each of the plurality of gears included in the gear train 100 may not be a multiple of the number of cylinders 13 of the engine assembly 10. For example, as shown in FIG. 1, the engine assembly 10 includes six cylinders 13. Operation of the engine assembly 10 may produce natural third order torsional vibrations. Natural order torsional vibrations can damage gear train 100 through cyclic loads and unbalanced tooth wear. All gears included in the gear train 100, including the fuel pump gear 114 and the air compressor gear 116, may be configured to have a number of gear teeth that is not a multiple of six. This arrangement may spread wear out on the gear teeth and increase the life of the engine assembly 10. While the number of teeth on the gears in the gear train 100 does not prevent the occurrence of natural third-order torsional vibrations, it spreads the wear evenly across the gear teeth, thereby improving the overall life of the gear train 100.

In addition, the compound cam idler gear 130 may advantageously allow a smaller gear to be used to transmit torque within the gear train 100 at a particular gear ratio. The compound cam idler gear 130 may also advantageously reduce the overall weight of the gear train 100, as well as reduce the space occupied within the housing in which the gear train 100 is positioned.

In some embodiments, crank gear 112 may be removably coupled to the crankshaft to allow crank gear 112 to be removed for repair or replacement. In other embodiments, the crank idler gear 110 and the intermediate idler gear 120 may be removably coupled to the engine block 12 such that the crank idler gear 110 and the intermediate idler gear 120 may be removed for repair or replacement.

In other embodiments, the compound cam idler gear 130 may be flipped 180 degrees such that the first cam idler gear 132 still lies in the first plane, but the cam shaft 16 no longer extends through the first plane. In such embodiments, the cam gear 140 and the second cam idler gear 134 may be located in a third plane offset from the first plane, but located on an opposite side of the first plane relative to the second plane, as previously described herein.

In some embodiments, all gears in the gear train 100 may have at least one of a different normal pressure angle, a different normal modulus, or a different number of gear teeth such that the same gear ratio is achieved. In other embodiments, all of the gears in gear train 100 may include helical gears, herringbone gears, bevel gears, or any other suitable gears. In still other embodiments, the gear may not be a high overlap ratio gear. In other embodiments, the gears in the gear train 100 may have different addendum coefficients and dedendum coefficients.

In other embodiments, the gears included in the gear train 100 may be heat treated, cold worked, hobbed, ground, or milled. In other embodiments, the gears included in the gear train 100 may be coupled to the shaft using keyways, cotter pins, set screws, press fits, threaded fits, welding, or any other method for attaching the gears to the shaft.

Fig. 3 is a rear side perspective view of the engine assembly 20 including a gear train 200 according to another embodiment. Fig. 4 is a rear view of the gear train 200. As described with respect to the engine assembly 10, the engine assembly 20 includes an engine block 12, the engine block 12 including a plurality of cylinders 13, a crankshaft (not shown) disposed therein, an air compressor 14, and a camshaft 16.

Similar to the gear train 100, the gear train 200 includes a crank idler gear 210, a crank gear 212, a fuel pump gear 214, an air compressor gear 216, an intermediate idler gear 220, a compound gear 230, a cam gear 240. However, gear train 200 also includes REPTO idler gear 250 and REPTO gear 252. The compound cam idler gear 230 includes a first cam idler gear 232 and a second cam idler gear 234, the first cam idler gear 232 and the second cam idler gear 234 being coupled together such that the first cam idler gear 232 and the second cam idler gear 234 rotate simultaneously along the same central axis at the same speed.

In some embodiments, each gear included in the gear train 200 may include a high overlap spur gear, for example, to achieve stable transmission between the gears and to generate a low sound (e.g., a gear whine) during operation of the engine assembly 20.

In some embodiments, each gear included in gear train 200 may have an addendum coefficient in a range of 1.0 to 1.4 and a dedendum coefficient in a range of 1.2 to 1.8. The dedendum coefficient and the addendum coefficient may be varied relative to each other to obtain strong and reliable gear teeth, resulting in a strong and reliable gear.

In some embodiments, each gear included in gear train 200 may have the same normal module, e.g., a normal module of 3.00, and/or have the same normal pressure angle, e.g., a normal pressure angle of 17.5 °. Further, the number of teeth of each of the gears may not be a multiple of the number of cylinders 13 of the engine assembly 20 (e.g., not a multiple of 6), for example, to avoid natural third order torsional vibrations, as previously described herein.

The crank gear 212, the crank idler gear 210, the fuel pump gear 214, the air compressor gear 216, the intermediate idler gear 220, and the first cam idler gear 232 all lie in a first plane such that the gears can mesh with one another. The crank gear 212 is coupled to the crankshaft along a central axis of the crankshaft such that rotation of the crankshaft causes the crank gear 212 to rotate about the central axis of the crankshaft and in the same direction as the crankshaft. The crank gear 212 is coupled to the crankshaft such that the crank gear 212 may not move translationally or axially relative to the crankshaft. In some embodiments, the crank gear 212 includes 39 gear teeth. The crank gear 212 is configured to mesh with the crank idler gear 210 such that rotation of the crank gear 212 causes the crank idler gear 210 to simultaneously rotate in opposite rotational directions.

The crank idler gear 210 is configured to mesh with the crank gear 212, the fuel pump gear 214, the air compressor gear 216, the intermediate idler gear 220, and the REPTO idler gear 250. In some embodiments, the crank idler gear 210 may have 74 gear teeth. The crank idler gear 210 may be rotatably coupled to the engine block 12 such that the crank idler gear 210 may rotate radially about its central axis, but the crank idler gear 210 cannot move translationally or axially relative to the engine block 12.

The REPTO idler gear 250 and REPTO gear 252 lie in a third plane parallel to the first and second planes. The crank idler gear 210 is configured to extend through a third plane such that the crank idler gear 210 lies in both the first plane and the third plane. The crank idler gear 210 is configured to mesh with the REPTO idler gear 250 in a third plane in addition to the gears with which the crank idler gear 210 meshes in the first plane. The REPTO idler gear 250 is configured to be rotatably coupled to the engine block 12 such that the REPTO idler gear 250 is permitted to rotate radially about its central axis, but the REPTO idler gear 250 is not permitted to move translationally or axially relative to the engine block 12. In some embodiments, the REPTO idler gear 250 may include 56 gear teeth. The REPTO idler gear 250 is engaged with the REPTO gear 252 and the crank idler gear 210 so that the rotation of the REPTO idler gear 250 is performed simultaneously with the rotation of the crank idler gear 210 and the REPTO gear 252.

The REPTO gear 252 also meshes with the REPTO idler gear 250 such that rotation of the REPTO idler gear 250 causes simultaneous rotation of the REPTO gear 252. REPTO gear 252 may include 29 gear teeth. REPTO gear 252 may transmit rotational power to a unit included in the system housing engine assembly 20. These units may include, for example, fire hose pumps included in fire fighting vehicles, excavating equipment included in excavators, cement tumbling units, and the like.

The fuel pump gear 214 is configured to mesh with the crank idler gear 210. The fuel pump gear 214 is configured to apply no axial load to the fuel pump. In some embodiments, the fuel pump gear 214 includes 23 gear teeth. The air compressor gear 216 is configured to be coupled to the air compressor 14 within the engine assembly 20 such that rotation of the air compressor gear 216 causes simultaneous operation of the air compressors 14. The air compressor gear 216 is also configured to move non-translationally or axially relative to the engine block 12. In some embodiments, the air compressor gear 216 may have 33 gear teeth.

The intermediate idler gear 220 is engaged with the compound cam idler gear 230 and the crank idler gear 210. In some embodiments, the intermediate idler gear 220 includes 64 gear teeth. The intermediate idler gear is configured to be rotatably coupled to the engine block 12 such that it is possible for the intermediate idler gear 220 to rotate radially about a central axis of the intermediate idler gear 220, but the intermediate idler gear 220 cannot move translationally or axially relative to the engine block 12.

The compound cam idler gear 230 includes a first cam idler gear 232 and a second cam idler gear 234, the first cam idler gear 232 and the second cam idler gear 234 being coupled together (e.g., mounted on the same shaft) such that both the first cam idler gear 232 and the second cam idler gear 234 rotate simultaneously about the same central axis at the same speed. In some embodiments, the first cam idler gear 232 includes 52 gear teeth and the second cam idler gear 234 includes 34 gear teeth. The compound cam idler gear 230 is configured to be rotatably coupled to the cylinder head such that rotational movement about a central axis of the compound cam idler gear 230 is permitted, but the compound cam idler gear 230 cannot move translationally or axially relative to the cylinder head.

The cam gear 240 is configured to be coupled to the camshaft 16 such that rotation of the camshaft 16 causes the cam gear 240 to simultaneously rotate along a central axis of the camshaft 16, but such that the cam gear 240 is not permitted to move translationally or axially relative to the camshaft 16. In some embodiments, cam gear 240 includes 51 gear teeth.

The second cam idler gear 234 and the cam gear 240 are located in a second plane such that the second cam idler gear 234 and the cam gear 240 can mesh. The second plane is parallel to and sufficiently offset from the first plane such that gears located in the first plane do not interfere or intersect gears located in the second plane. In some embodiments, the gear ratio between the crank gear 212 and the fuel pump gear 214 is 1: 1.696. In other embodiments, the gear ratio between the crank gear 212 and the air compressor gear 116 is 1: 1.182.

In some embodiments, the gear ratio between the crank gear 212 and the cam gear 240 may be 2: 1. This may correspond to a 2: 1 speed ratio between the crankshaft and the camshaft 16. In some embodiments, the vertical distance between the longitudinal axis of the center of the crank gear 212 and the longitudinal axis of the center of the cam gear 240 may be in the range of 560 and 565 mm. The vertical distance D may be based on the desired size of the engine assembly 20. In a particular implementation, the vertical distance D may be 563 millimeters.

In various embodiments, each of the gears included in gear train 200, including REPTO idler gear 250 and REPTO gear 252, is configured to have a number of gear teeth that is not a multiple of the number of cylinders 13, e.g., not a multiple of 6. This may reduce the natural third order torsional vibrations, as previously described herein. The gears are configured such that wear is distributed over the gear teeth and increases the life of the engine assembly 20. While the number of teeth on the gears in the gear train 200 may not completely prevent the occurrence of natural third-order torsional vibrations, it spreads the wear evenly across the gear teeth, thereby improving the overall life of the gear train 200.

The compound cam idler gear 230 may allow a smaller gear to be used to transmit torque within the gear train 200 at a particular gear ratio and may also occupy less space than having two gears, thus reducing space requirements and/or reducing the weight of the gear train 200.

In some embodiments, crank gear 212 may be removably coupled to the crankshaft to allow for gear removal for repair or replacement. In other embodiments, the crank idler gear 210 and the intermediate idler gear 220 may be removably coupled to the engine block 12 to allow removal for repair or replacement purposes.

In still other embodiments, the compound cam idler gear 230 may be flipped 180 degrees such that the first cam idler gear 232 still lies in the first plane, but the camshaft 16 will no longer extend through the first plane. In this embodiment, the cam gear 240 will still be in the second plane, but the second plane will move to the opposite side of the first plane, as described herein.

In some embodiments, all gears included in the gear train 200 may have at least one of a different normal pressure angle, a different normal module, or a different number of gear teeth to achieve the same gear ratio. In other embodiments, all of the gears in the gear train 200 may include helical gears, herringbone gears, bevel gears, or any other suitable gears. In other embodiments, the gear may not be a high overlap gear. In still other embodiments, the gears in the gear train 200 may have different addendum coefficients and dedendum coefficients.

In some embodiments, the gear train 200 may not include the air compressor gear 216 or the fuel pump gear 214. In other embodiments, the gear train may include another gear, such as a second air compressor gear or a second fuel pump gear. In still other embodiments, the fuel pump gear 214 may mesh with a gear that is not the crank idler gear 210. In yet another embodiment, the air compressor gear 216 may mesh with a gear that is not the crank idler gear 210.

In other embodiments, the gears included in the gear train 200 may be heat treated, cold worked, hobbed, ground, or milled. In other embodiments, the gears included in the gear train 200 may be coupled to the shaft using keyways, cotter pins, set screws, press fits, threaded fits, welding, or any other method for attaching the gears to the shaft. In other embodiments, REPTO idler gear 250 and REPTO gear 252 can be coupled to an accessory that is not REPTO, such as a supercharger or alternator.

It should be noted that the term "exemplary" as used herein to describe various embodiments is intended to mean that such embodiments are possible examples, representations, and/or illustrations of possible embodiments (and such terms are not intended to imply that such embodiments must be specific or best examples).

As used herein, the terms "coupled," "connected," and the like are intended to mean that two members are directly or indirectly joined to one another. Such engagement may be fixed (e.g., permanent) or movable (e.g., removable or releasable). Such joining may be achieved by the two members or the two members and any additional intermediate members being integrally formed as a single unitary body with one another or by the two members or the two members and any additional intermediate members being attached to one another.

It is important to note that the construction and arrangement of the various exemplary embodiments are illustrative only. Although only a few embodiments have been described in detail in this disclosure, those skilled in the art who review this disclosure will readily appreciate that many modifications are possible (e.g., variations in sizes, dimensions, structures, shapes and proportions of the various elements, values of parameters, mounting arrangements, use of materials, colors, orientations, etc.) without materially departing from the novel teachings and advantages of the subject matter recited herein. Other substitutions, modifications, changes and omissions may also be made in the design, operating conditions and arrangement of the various exemplary embodiments without departing from the scope of the embodiments described herein.

While this specification contains many specific implementation details, these should not be construed as limitations on the scope of any implementations or of what may be claimed, but rather as descriptions of features specific to particular implementations of particular implementations. Certain features that are described in this specification in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.

Claims

1. A gear train for transmitting rotary power from a crankshaft to a camshaft of an engine assembly, comprising:

a plurality of gears, the plurality of gears comprising:

a crank idler gear;

an intermediate idler gear that meshes with the crank idler gear;

a cam gear configured to be coupled to the camshaft; and

a compound cam idler gear, the compound cam idler gear comprising:

a first cam idler gear that meshes with the intermediate idler gear; and

a second cam idler gear that meshes with the cam gear.

2. The gear train of claim 1 wherein the gear ratios of the plurality of gears are configured such that the ratio of crankshaft speed to camshaft speed is 2: 1.

3. The gear train of claim 1 wherein the vertical distance between the longitudinal axis of the crank gear and the longitudinal axis of the cam gear is configured to be in the range of 560 and 565 millimeters.

4. The gear train of claim 1, wherein a vertical distance between a longitudinal axis of the crank gear and a longitudinal axis of the cam gear is configured to 563 millimeters.

5. The gear train of claim 1 wherein a number of gear teeth of each of the plurality of gears is not a multiple of a number of cylinders included in the engine assembly.

6. The gear train of claim 1 wherein the plurality of gears further comprises a fuel pump gear in mesh with the crank idler gear, the fuel pump gear configured to be coupled to a fuel pump of the engine assembly.

7. The gear train of claim 6 wherein the gear ratio between the crank gear and the fuel pump gear is 1: 1.696.

8. The gear train of claim 1 wherein the plurality of gears further comprises an air compressor gear in mesh with the crank idler gear, the air compressor gear configured to be coupled to an air compressor of the engine assembly.

9. The gear train of claim 8 wherein a gear ratio between the crank gear and the air compressor gear is configured to be 1: 1.182.

10. The gear train of claim 1 wherein the diameter of the first cam idler gear is configured to be larger than the diameter of the second cam idler gear.

11. The gear train of claim 10 wherein a gear ratio between the crank gear and the first cam idler gear is configured as 4: 3.

12. The gear train of claim 10, wherein a gear ratio between the second cam idler gear and the cam gear is configured to be 2: 3.

13. The gear train of any of claims 1-12, further comprising:

a Rear Engine Power Take Off (REPTO) gear; and

a REPTO idler gear configured to mesh with the REPTO gear and the crank idler gear.

14. The gear train of claim 13 wherein the REPTO idler gear and the REPTO gear are positioned out of plane relative to the crank gear and the intermediate idler gear.

15. The gear train of claim 2 wherein each of the plurality of gears is configured to have a normal module of 3.00 and a normal pressure angle of 17.5 °.

16. The gear train of any of claims 1-12 wherein each of the plurality of gears is configured to have an addendum coefficient ranging from 1.0 to 1.4 and a dedendum coefficient ranging from 1.2 to 1.8.

17. The gear train of any of claims 1-12, wherein the plurality of gears are configured as high contact ratio spur gears.

18. A gear train for transmitting rotary power from a crankshaft to a camshaft of an engine assembly, comprising:

a plurality of gears, the plurality of gears comprising:

a crank idler gear;

an intermediate idler gear configured to mesh with the crank idler gear;

a cam gear configured to be coupled to the camshaft; and

a compound cam idler gear, the compound cam idler gear comprising:

a first cam idler gear configured to mesh with the intermediate idler gear; and

a second cam idler gear configured to mesh with the cam gear;

19. The gear train of claim 18 wherein a vertical distance between the longitudinal axis of the crank gear and the longitudinal axis of the cam gear is configured to be in the range of 560 and 565 millimeters.

20. The gear train of claim 19, wherein the vertical distance is configured to 563 mm.

21. The gear train of claim 18 wherein the number of gear teeth of each of the plurality of gears is configured to be not a multiple of the number of cylinders included in the engine assembly.

22. The gear train of claim 18 wherein the plurality of gears further comprises a fuel pump gear configured to engage the crank idler gear, the fuel pump gear configured to be coupled to a fuel pump of the engine assembly.

23. The gear train of claim 22 wherein a gear ratio between the crank gear and the fuel pump gear is configured to be 1: 1.696.

24. The gear train of claim 18, wherein the plurality of gears further comprises an air compressor gear configured to mesh with the crank idler gear, the air compressor gear configured to be coupled to an air compressor of the engine assembly.

25. The gear train of claim 24 wherein a gear ratio between the crank gear and the air compressor gear is configured to be 1: 1.182.

26. The gear train of claim 18 wherein the diameter of the first cam idler gear is greater than the diameter of the second cam idler gear.

27. The gear train of claim 26 wherein a gear ratio between the crank gear and the first cam idler gear is configured as 4: 3.

28. The gear train of claim 26 wherein a gear ratio between the second cam idler gear and the cam gear is configured as 2: 3.

29. The gear train of claim 18, further comprising:

a Rear Engine Power Take Off (REPTO) gear; and

30. The gear train of claim 29 wherein the REPTO idler gear and the REPTO gear are positioned out of plane relative to the crank gear and the intermediate idler gear.

31. The gear train of any of claims 18-30 wherein each of the plurality of gears has an addendum coefficient ranging from 1.0 to 1.4 and a dedendum coefficient ranging from 1.2 to 1.8.

32. The gear train of any of claims 18-30, wherein the plurality of gears are configured as high contact ratio spur gears.