阅读说明：本技术 内燃发动机 (Internal combustion engine ) 是由 V·I·拉克什米纳拉西姆汉 T·L·巴拉苏布拉曼尼亚 K·维蒂林格 于 2020-02-14 设计创作，主要内容包括：本发明主题涉及一种用于内燃发动机的用于提供机械式可变阀定时的凸轮轴组件。凸轮轴组件(200)包括被设置为邻近至少一个进气凸缘(220)和至少一个排气凸缘(225)中的一者的机械定相组件(230)。至少一个径向预加载的质量构件(235)能够根据凸轮轴组件(200)的旋转速度执行进气凸缘(220)和排气凸缘(225)中的至少一者相对于从动链轮(205)的相移。将沿轴向方向预加载的轴向载荷构件(245)设置为邻近质量构件(235),以对其施加轴向载荷。本发明主题改善了阀的打开和关闭时间的变化,从而满足发动机在所有运行速度下的进气和排气要求。(The present subject matter relates to a camshaft assembly for an internal combustion engine for providing mechanically variable valve timing. The camshaft assembly (200) includes a mechanical phasing assembly (230) disposed adjacent one of the at least one intake flange (220) and the at least one exhaust flange (225). The at least one radially preloaded mass member (235) is configured to perform a phase shift of at least one of the intake flange (220) and the exhaust flange (225) relative to the driven sprocket (205) as a function of a rotational speed of the camshaft assembly (200). An axial load member (245) preloaded in an axial direction is disposed adjacent the mass member (235) to apply an axial load thereto. The present subject matter improves the variation in valve opening and closing times to meet the intake and exhaust requirements of the engine at all operating speeds.)

1. An internal combustion engine (100), the internal combustion engine (100) comprising:

a cylinder block (102);

at least one piston slidably movable within a cylinder portion defined by the cylinder block (102);

a cylinder head (103) forming one end of the cylinder portion, the cylinder head (103) supporting one or more intake valves and one or more exhaust valves;

a crankshaft (110) connected to the piston by a connecting rod, the crankshaft (110) being rotatably supported by a crankcase (101) of the engine (100); and

a camshaft assembly (200) rotatably supported by the cylinder head (103), the camshaft assembly (200) including a driven sprocket (205), and the camshaft assembly (200) being connected to the crankshaft (110) by the driven sprocket (205), the camshaft assembly (200) comprising:

a first cam portion (201) and a second cam portion (202);

at least one intake flange (220) and at least one exhaust flange (225), the at least one intake flange (220) being connected to one of the first cam portion (201) and the second cam portion (202), and the at least one exhaust flange (225) being connected to the other of the first cam portion (201) and the second cam portion (202);

a mechanical phasing assembly (230), the mechanical phasing assembly (230) disposed adjacent to one of the at least one intake flange (220) and the at least one exhaust flange (225), the mechanical phasing assembly (230) comprising at least one radially preloaded mass member (235), the mass member (235) being configured to perform a phase shift of at least one of the at least one intake flange (220) and the at least one exhaust flange (225) relative to the driven sprocket (205) as a function of a rotational speed of the camshaft assembly (200), and

an axial load member (245) preloaded in an axial direction is provided for applying an axial load.

2. The internal combustion engine (100) of claim 1, wherein the axial load member (245) preloaded in an axial direction is disposed adjacent the mass member (235) to apply an axial load to the mass member (235).

3. The internal combustion engine (100) of claim 1, wherein the stationary plate (240) is disposed at an axial end of the camshaft assembly (200) and adjacent the driven sprocket (205), and one or more axial force resilient members (242) configured to apply a force to the axial load member (245) are disposed between the axial load member (245) and the stationary plate (240) through one or more apertures (206) of the driven sprocket (205).

4. The internal combustion engine (100) of claim 1, wherein the driven sprocket (205) is fixed to one of the at least one intake flange (220) and at least one exhaust flange (225).

5. The internal combustion engine (100) of claim 1, wherein the camshaft assembly (200) includes at least one intake lobe (210) connected to a corresponding at least one intake flange (220) and at least one exhaust lobe (211) connected to a corresponding at least one exhaust flange (225), and the intake lobe (210) and the exhaust lobe (211) are adapted to control opening and closing of the valve, and the lobes (210, 215) are disposed on one side of the axial load member (245) and the fixed plate (240) is disposed on the other side of the axial load member (245).

6. The internal combustion engine (100) of claim 1, wherein the axial load member (245) is a disc-shaped member disposed adjacent the driven sprocket (205), and wherein the driven sprocket (205) is provided with a disc-shaped recess configured to receive the axial load member (245) therein.

7. The internal combustion engine (100) of claim 1, wherein the axial load member (245) has a first axially inner surface (246) and the driven sprocket (205) has a second axially inner surface (207), and the first axially inner surface (246) and the second axially inner surface (207) are disposed along a plane (P) taken orthogonal to an axis (a- Α') of the camshaft assembly (200).

8. The internal combustion engine (1000) of claim 1, wherein the phasing assembly (230) comprises one or more pins (255), the one or more pins (255) extending in an axial direction disposed through one or more elongated slots (260, 261, 262, 263) disposed on the driven sprocket (205), on the intake flange (220), on the exhaust flange (225), and on the axial load member (245), wherein the one or more elongated slots (260, 261, 262, 263) comprise an angled elongated slot (261).

9. The internal combustion engine (100) of claim 5, wherein the mass member (235) is formed of two or more arc-like members (236, 237) connected to each other by one or more tension elastic members (238), and the arc-like members (236, 237) are in frictional contact with the axial load member (245), and a spacer (275) is provided between the driven sprocket (205) and at least one flange (261, 262) to maintain a predetermined spacing.

10. The internal combustion engine of claim 1, wherein the mass member (235) is formed of first and second arc-like members (236, 237) forming two or more arc-like members (236, 337), the arc-like members (236, 237) being provided with one or more apertures (270) for receiving at least one pin (255) therethrough, the pin (255) passing through a plurality of elongated slots (261, 262) provided on at least one intake flange (220) and at least one exhaust flange (225) to create a phase shift between the at least one intake flange and the at least one exhaust flange resulting in variable valve timing control.

11. The internal combustion engine according to claim 7, wherein the plurality of elongated slots (261, 262) includes a first elongated slot (261) and a second elongated slot (262), the first elongated slot (261) disposed on one of the at least one intake flange (220) and the at least one exhaust flange (225) extending in an axial direction in an arcuate manner, the second elongated slot (262) disposed on the other of the at least one intake flange (220) and the at least one exhaust flange (225) extending substantially in a linear-axial direction.

12. A motor vehicle comprising an internal combustion engine (100) according to any one of the preceding claims.

13. A camshaft assembly (200), the camshaft assembly (200) being rotatably supported on a cylinder head (103) of an internal combustion engine (100), the camshaft assembly (200) comprising:

a driven sprocket (205);

two or more cam portions (201, 202);

at least one intake flange (220), the at least one intake flange (220) connected to at least one of the two or more cam portions (201, 202); and

at least one exhaust flange (225), the at least one exhaust flange (225) connected to at least another one of the two or more cam portions (202);

a mechanical phasing assembly (230) configured to perform a phase shift of at least one flange (220, 225) relative to the driven sprocket (205) as a function of a rotational speed of the camshaft assembly (200); and

an axial load member (245) preloaded in an axial direction for applying an axial load.

14. A method of operating a mechanical phasing assembly (230) for a camshaft assembly (200) of an internal combustion engine (100), the method comprising the steps of:

checking a Centrifugal Force (CF) acting on a mass member (235) of the camshaft assembly (200);

comparing the Centrifugal Force (CF) with a cumulative force comprising a stiff force (FF) exerted by a tension elastic member () and a frictional force (μ (FF)) exerted by an axial load member (245); and

mechanically phased by the mechanical phasing assembly (230) when the Centrifugal Force (CF) exceeds the cumulative force.

Technical Field

The present subject matter relates generally to an Internal Combustion (IC) engine for a motor vehicle. More specifically, the present subject matter relates to a camshaft assembly for an internal combustion engine that provides mechanically variable valve timing.

Background

Internal Combustion (IC) engines are used to convert chemical energy into mechanical energy through the combustion of an air-fuel mixture. The thermal energy generated as a result of the combustion of the air-fuel mixture is used to provide motion to one or more reciprocating pistons within the cylinder. One or more reciprocating pistons transmit this reciprocating motion, resulting in rotational motion of one or more crankshafts connected thereto by a crank-slider mechanism through connecting rods. The cylinder head typically includes at least one air inlet port and at least one air outlet port that respectively allow the air-fuel mixture to enter and the combustion gases to exit the combustion chamber. In this operation, the precise movement and timing of the opening and closing of the inlet and outlet orifices of the combustion chamber is critical to the accurate performance of the IC engine.

Typically, such opening and closing of the intake/exhaust ports is controlled by various components present on the cylinder head and cylinder bore, and the opening and closing of the valves is driven by one or more camshafts driven by one or more crankshafts through a camshaft transmission system. The camshaft includes cam lobes that control the orifice opening and the duration of the orifice opening. One of the biggest drawbacks of many commuter motor vehicle engines is the use of fixed timing to close and open the orifices (via valves), so these engines operate in a sub-optimal manner. For example, a fixed timing of the valve at higher speeds sets the open time to an optimal setting, while a higher valve opening is desired. The intake valve may close late using the inertia of the incoming air. However, such later opening of the valve at lower engine speeds may affect the volumetric efficiency of the engine. Thus, even if set to an optimal setting, the fixed timing of valve opening can affect engine performance within a particular speed range. Various electrical, electromechanical, mechanical and hydraulic devices are known in the art to achieve cam phasing (cam phasing). For example, cam phasing, cam variation, etc. are some of the techniques used in the prior art. For example, cam phasing is one of the techniques that provides a phase difference of one cam lobe from another to achieve variable valve opening.

Drawings

The detailed description is described with reference to the accompanying drawings.

Fig. 1 illustrates a side view of an exemplary Internal Combustion (IC) engine, according to an embodiment of the present subject matter.

FIG. 2 illustrates an exemplary cross-sectional view of an IC engine, the cross-sectional view being taken along axis W-W'.

Fig. 3(a) shows a perspective view of a camshaft assembly according to an embodiment of the present subject matter.

FIG. 3(b) shows another perspective view of a camshaft assembly with selected features thereon according to the embodiment of FIG. 3 (a).

FIG. 3(c) shows a radial cross-sectional view of camshaft assembly 200 taken along axis U-U'.

Fig. 4 depicts the mass member in a first state and a second state according to the embodiment of fig. 3.

Fig. 5(a) illustrates a cross-sectional view of a camshaft assembly according to an embodiment of the present subject matter.

Fig. 5(b) illustrates another cross-sectional view of a camshaft assembly according to an embodiment of the present subject matter.

Fig. 6 illustrates an exploded view of a camshaft assembly according to an embodiment of the present subject matter.

FIG. 7 illustrates a detailed cross-sectional view of a camshaft assembly according to an embodiment of the present subject matter.

Detailed Description

Typically, cam phasing/altering enables the engine to operate beyond its next best performance. For example, if the intake valve is advanced during lower RPM, the intake valve experiences early closing, thereby minimizing backflow during the compression stroke, thereby improving volumetric efficiency and torque at lower RPM. Further, at higher RPMs, phasing of the intake valves may be performed, which results in late/late closing of the intake valves, thereby utilizing the momentum of air entering the intake manifold at high speed for scavenging. Similarly, the opening and closing of the exhaust valve may be advanced or retarded by cam phasing. Also, cam phasing may be accomplished on both the intake and exhaust valves.

Typically, to perform cam phasing/altering, various electrical, electromechanical and hydraulic devices are used, such devices being complex and not cost-effective. For example, solenoids or sliding pins or the like are required, which are accommodated near a camshaft portion that requires a large space on an already compact cylinder head area. Furthermore, for two-or three-wheeled straddle vehicles, it is important that the power system be as compact as possible to enable packaging in a small space, and that it allow easy access to the various parts of the power system for timely maintenance and repair with simple tools, without the need to remove the power system from the vehicle. Furthermore, such electric/electromechanical or hydraulic systems comprise an electric or hydraulic drive which is powered by an on-board battery and controlled by a control unit. Furthermore, the addition of a control module like a controller increases the cost of the system and the motor, for example resulting in phased stepper motors making the engine bulky, especially in the cylinder head part. In some other solutions known in the art, sliding mechanisms are proposed for engaging and disengaging the various rocker arms according to the speed. Even in such systems, an externally controlled slide is required, and a motor or the like is used to control the slide movement, making the system more expensive and bulky. Therefore, additional systems are required and those systems also consume battery power. Furthermore, the functional characteristics of the electrical and mechanical systems are affected by variations in engine temperature, for example during cold starts or at high temperatures.

Further, mechanical phasing systems are known in the art that are capable of performing cam phasing based on changes in engine speed/RPM. Typically, the mechanical phasing system can be used in a compact vehicle (like a two-wheel or three-wheel vehicle with a compact engine layout). Moreover, such mechanical phasing systems offer cost benefits due to their ability to operate without any electrical/hydraulic controls. However, such systems are not foolproof and tend to fail as the phase angle increases. For example, in a mechanical system using centrifugal force for cam phasing, cam phasing occurs abruptly even before the desired speed is reached due to a force component acting on the phasing means, e.g. centrifugal force component/inertial component. Such problems are prominent in vehicles that use a single camshaft to control both intake and exhaust valves because the torque of the camshaft is higher and the operating speed of the camshaft is also higher. Considering the case of a sudden acceleration of the user, a sudden increase in the rotation rate/speed of the camshaft may occur, which results in a sudden increase in the centrifugal force, resulting in an increase in the centrifugal component, and thus in slippage. Furthermore, even in systems using roller bearings, such premature phenomena may occur due to the effect of centrifugal forces. Thus, in such systems, cam phasing occurs at an undesirable rate, affecting the performance of the system due to the opening/closing of the valve under undesirable conditions, and this may also lead to poor emissions. For example, the occurrence of cam phasing during mid range may affect engine performance when intake time or undesirable scavenging occurs, thereby affecting engine performance. Furthermore, even if pre-loaded in the radial direction, systems known in the art may cause vibrations due to the presence of the movable parts, which may cause unnecessary noise.

Accordingly, there is a need for a mechanical cam phasing system that can be implemented even in compact IC engines, and that should be capable of performing its function only at a desired engine speed and that should overcome the above-mentioned and other problems of the prior art.

The present subject matter thus provides an internal combustion engine provided with a mechanical phasing system/assembly that uses mechanical components and does not require external control depending on the speed/RPM of the engine.

The present subject matter provides a camshaft assembly including a mechanical phasing assembly capable of performing a phase shift of one of the intake lobes or the exhaust lobes relative to each other, thereby advancing/retarding valve opening/closing.

The camshaft assembly of the present subject matter is capable of opening/closing intake and exhaust valves by providing phase-shifted integrated components.

In one embodiment, a camshaft assembly includes a first cam portion and a second cam portion, wherein one or more bearings rotatably support the first cam portion and the second cam portion. Further, in one embodiment, another bearing (e.g., a roller bearing) is disposed between the first cam portion and the second portion to enable relative rotation thereof.

The intake flange is connected to one of the first cam portion and the second cam portion, and the exhaust flange is connected to the other of the first cam portion and the second cam portion. The terms "intake flange" and "exhaust flange" are not limited to a single member and may include more than one flange. The camshaft assembly includes one or more cam lobes corresponding to each of the flanges, wherein the cam lobes are selected to perform valve lift according to engine requirements. Similarly, the term cam lobe refers to any geometry of the profile of the component performing valve actuation.

The camshaft assembly includes a driven sprocket supported on one of the cam portions. In other words, the driven sprocket is fixed to one of the cam portions. The mechanical phasing assembly includes a mass member that is capable of changing position in a radial direction based on a rotational speed of the camshaft assembly. The mass member is disposed adjacent to one of the intake flange or the exhaust flange.

In one embodiment, the mass member may be formed of two or more arc-like members that are split in the circumferential direction and held close to the axis by a tensile elastic member. Such two or more arc-shaped members are capable of moving in a radial direction due to centrifugal force.

In one embodiment, the two or more arc-shaped members are provided with one or more apertures and one or more pins are configured to pass through the apertures, wherein the one or more pins are movable with the arc-shaped members.

According to one embodiment, the intake flange, the exhaust flange and the driven sprocket are provided with elongated slots. According to one embodiment, one of the intake flange and the exhaust flange is fixed to the driven sprocket. One of the flange and the driven sprocket is each provided with an elongated slot thereon having a phase angle or arc. The other of the intake and exhaust flanges has an elongated slot extending in a substantially radial direction. Thus, as the pin moves along the angled elongated slot of the driven sprocket and one flange connected to the driven sprocket, the pin tends to phase shift the other flange due to the angular movement of the pin.

For example, in order to phase shift the intake flange (change the intake valve opening/closing depending on the speed), the driven sprocket and the exhaust flange are provided with arc-shaped elongated grooves, and the intake flange is provided with elongated grooves extending substantially radially. Thus, as the mass member expands in the radial direction, the pins moving with the mass member move along the arcuate elongated slots that phase shift the inlet flanges.

The phase shift assembly includes an axial load member disposed substantially adjacent to one of the flanges. The axial load member is preloaded in an axial direction to apply a frictional force to the mass member.

In one embodiment, a driven sprocket driven by the crankshaft is connected to one of the flanges, while the other flange is adapted to perform a phase shift relative to the orientation of the driven sprocket. In another embodiment, both flanges are adapted to experience a phase shift (advance or retard) relative to the driven sprocket one at a time or two at a time.

In one embodiment, the axial load member is disposed on one axial side of the driven sprocket, and the axial load member is provided with a preload in the axial direction to apply a force to the mass member. In one embodiment, a fixed member is disposed on the other side of the driven sprocket, and the fixed plate supports one end of the preload member, which is the other side adjacent the axial load member.

An axial load member that applies a force in an axial direction causes a frictional force to act on the mass member from either side. The friction forces balance the force components acting on the mass member in the direction of movement of the pin along the elongated slot. This force component, which would otherwise tend to move the pin in a radially outward direction, is balanced by the frictional force exerted by the axial load member.

Therefore, even when the phase angle is increased to about 20 degrees, the pin tends not to slip due to the frictional force (even if the tangential velocity component acts on the pin). It is a feature of the present subject matter that the camshaft assembly may be adapted to be phased in the range of about 5-25 degrees by merely adjusting the preload on the axial load member. For example, the assembly may remain unchanged and only the spring-like preload member may be replaced.

Preferably, at least two apertures on the mass member, at least two elongated slots on the flange and the driven sprocket are provided, and correspondingly, two pins are used to evenly transfer rotational force from one component to the other. In addition, the use of elongated slots reduces the weight of the system and maintains the structural integrity of the components.

Further, the present subject matter is compactly housed in the axial direction. For example, in one embodiment, the driven sprocket is provided with a disc-shaped recess, and the axial load member is compactly housed at the recess. Thus, there is no need to modify the layout, especially with reference to the cam lobes and the driven sprocket.

Furthermore, the axial load member dampens any vibrations that may occur due to the mass member being formed of subcomponents connected by tension springs.

In another embodiment, the mass member may be a collection of annularly arranged roller bearings, and the roller bearings are movable in the radial direction due to the application of centrifugal force thereto. Movement of the roller bearing in the radial direction (along a path angularly disposed on one of the contact portions) enables a phase shift. The axial load member is arranged to apply an axial load to the mass member that introduces a frictional force.

Various features and embodiments of the inventive subject matter will become apparent from the following further description of the inventive subject matter set forth below. According to one embodiment, the internal combustion engine (IC) described herein is one or the only prime mover of the prime movers of the motor vehicle. The IC engine may be of a forward tilting type or a substantially horizontal type, fixedly mounted or swingably connected to the motor vehicle. An IC engine contains at least two valves per cylinder head, one intake valve and one exhaust valve.

The subject matter and all of the attendant embodiments and other advantages thereof will be described in more detail using embodiments of a single cylinder IC engine in conjunction with the drawings in the following paragraphs.

Fig. 1 illustrates a side view of an IC engine 100 according to an embodiment of the present subject matter. The IC engine 100 includes a cylinder block 102 supported by a crankcase 101 of the IC engine. The cylinder block 102 defines a cylinder portion at which the piston can perform a reciprocating motion. The cylinder head 103 is mounted to the cylinder block 102, and the cylinder head 103 serves as one end of the cylinder portion. The cylinder block 102 is provided with fins 106, and the cylinder head 103 may be provided with fins. The IC engine 100 includes a piston (not shown) that performs a reciprocating motion in a cylinder portion due to a force imparted thereto by combustion of an air-fuel mixture. This reciprocating motion is converted to and transmitted to the rotational motion of the crankshaft 110 by a connecting rod (not shown). Further, a cylinder head-cover 104 is mounted to the cylinder head 103. The crankcase 101 is composed of a left-side crankcase and a right-side crankcase. The crankcase 101 rotatably supports a crankshaft 110. Further, a motor, such as a magneto assembly 111 or an integrated starter generator, is mounted to crankshaft 110. Magneto assembly 111 is used to charge a battery (not shown) during operation. The cylinder head 103 includes intake ports 105 and exhaust ports (not shown) disposed on first and second faces of the cylinder head 103. In this embodiment, the first face is the upwardly facing side and the second face is the downwardly facing side thereof. In addition, the cylinder head 103 supports a camshaft assembly 200 (partially shown in fig. 2) that is configured to operate the intake and exhaust valves of the IC engine 100. Fig. 2 illustrates a cross-sectional view of IC engine 100 taken along line W-W' in accordance with an embodiment of the present subject matter.

The IC engine 100 includes a drive gear 113 connected to the crankshaft 110 and rotates integrally therewith. The drive gear 113 acts as a main drive and is capable of transmitting rotational force to the main drive 112. The primary driven gear 112 is thus operatively connected to the crankshaft 110. The cylinder head 103 includes a valve mechanism arrangement for controlling the opening and closing of intake and exhaust valves, thereby controlling the air-fuel mixture and the out-gassing of intake and exhaust gases. A camshaft assembly 200 (partially shown) rotatably mounts the cylinder head 103. The cam chain 114 operatively connects the crankshaft 110 and the camshaft assembly 200. Driven sprocket 205 of camshaft assembly 200 is configured to mesh with drive gear 113, and driven sprocket 205 transmits the rotational motion of crankshaft 110 to camshaft assembly 200. In one embodiment, the ratio of driven sprocket 205 to drive gear 113 is 2, whereby camshaft assembly 200 will rotate once for every two revolutions of crankshaft 110. The IC engine 100 is provided with one or more chain tighteners 115 capable of adjusting the tension of the cam chain 114 by an adjusting member 116.

Fig. 3(a) illustrates an isometric view of a camshaft assembly according to an embodiment of the present subject matter. FIG. 3(b) shows another perspective view of a camshaft assembly with selected features thereon according to the embodiment of FIG. 3 (a). FIG. 3(c) shows a radial cross-sectional view of camshaft assembly 200 taken along axis U-U'. The camshaft assembly 200 includes at least one intake lobe 210 and at least one exhaust lobe 211. The cam chain 114 is loaded around the drive gear 113 and the driven sprocket 205. The camshaft assembly 200 is rotatably supported by one or more bearings 215, 216. In the present embodiment, the camshaft assembly 200 includes a first cam portion 201 and a second cam portion 202. Further, the driven sprocket 205 is provided to surround the rotation axis of the aforementioned components. The camshaft assembly 200 includes a mechanical phasing assembly 230. The camshaft assembly 200 includes at least one intake flange 220 corresponding to the at least one intake lobe 210 and at least one exhaust flange 225 corresponding to the at least one exhaust lobe 211. In the present embodiment, the intake flange 220 is disposed between the mass member 235 and the exhaust flange 225.

In one embodiment, the camshaft assembly 200 is also provided with a pressure relief system 280. The pressure relief system 280 includes a pressure relief arm that pivots at one end and has a movable end. The pressure relief arm is supported on the vent flange 225 by a preloaded resilient member. The decompression system 280 enables the exhaust valve to have additional lift during the compression stroke during engine start-up, and the additional lift is reduced once the engine speed exceeds a predefined value.

Fig. 4 shows a mass member according to the embodiment of fig. 3. FIG. 5(a) shows a cross-sectional view of the exhaust cam assembly 200 taken along axis X-X' according to the embodiment as depicted in FIG. 3 (a). FIG. 5(b) shows another cross-sectional view of the exhaust cam assembly 200 taken along axis V-V' according to the embodiment as depicted in FIG. 3 (b). Fig. 6 depicts an exploded view of a camshaft assembly according to an embodiment of the present subject matter. The first cam portion 201 is rotatably supported by a first bearing 215 and has an integrally formed intake lobe 210. The first cam portion 201 extends substantially along the axis of the camshaft assembly 200 and is connected to the intake flange 220. Similarly, the second cam portion 202 has an integrally formed exhaust lobe 211 and is rotatably supported by a second bearing 216. The second cam portion 202 is at least partially coaxially arranged around the first cam portion 201. In one embodiment, a roller bearing 214 is disposed between the first cam portion 201 and the second cam portion 202. The exhaust flange 225 is supported by the second cam portion 202. The camshaft assembly 200 is rotatably supported on the cylinder head 103 (shown in fig. 1).

In the present embodiment, the driven sprocket 205 is supported on the first cam portion 201. The driven sprocket 205 is fixed to the first cam portion 201 by a fastener 243. In addition, locking fasteners 241 (shown in FIG. 6) are provided to secure the fixed plate 240, the driven sprocket 205, and the flange 225 together. Mechanical phasing assembly 230 includes an axial load member 245. The mass member 235 is supported on the intake flange 220. Further, according to the present embodiment, the axial load member 245 is provided adjacent to the intake flange 220. The mass member 235 may be disposed adjacent to at least one of the flanges. Further, the camshaft assembly 200 includes an axial load member 245, wherein the mass member 235 is sandwiched between the axial load member 245 and the intake flange 220.

The axial load member 245 is disposed substantially on one side of the driven sprocket 205 and the fixed plate 240 is disposed on the other side of the driven sprocket 205. The driven sprocket 205 includes one or more through holes 206 and one or more axial force resilient members 242 are disposed between the axial load member 245 and the fixed plate 240 through the through holes 206 to provide a preload on the axial load member 245.

The driven sprocket 205 provides rotational force received from the crankshaft 110 through one or more pins 255 (as shown in fig. 3 (b)). Such one or more pins form part of the mechanical phasing assembly 230. Each of the driven sprocket 205, the intake flange 220, and the exhaust flange 225 is provided with an elongated slot 260, 261, 262, and one or more pins 255 are disposed about the elongated slots 260, 261, 262, whereby rotational force from the driven sprocket 205 is transmitted to the flanges 220, 225, enabling the lobes 210, 211 to rotate. In addition, the axial load member 245 is also provided with an elongated slot 263.

The mass member 235 is formed of a first arc member 236 and a second arc member 237 that are connected to each other by a tension elastic member 238 (as shown in fig. 4). When the centrifugal force exceeds the stiffness (k), the mass members 235 tend to expand in a radially outward direction due to the centrifugal force during rotation of the camshaft assembly 200. The resilient member 238 is selected such that after a predetermined RPM of the camshaft assembly 200, the stiffness (k) will be exceeded by centrifugal force. One of the flanges 220, 225 is provided with an angled elongate portion 261 as an arcuate portion.

The first arc member 236 and the second arc member 237 are provided with one or more apertures 270 through which the pins 255 pass. The movement of the arc members 236, 237 is guided by an elongated slot 260 provided on the driven sprocket 205. Movement of the arc-like members 236, 337 in the radial direction enables the pin 255 to move with the arc-like members 236, 237 due to centrifugal force, and the pin 255 can slide through the elongated slots 260, 262, 263. However, the first elongated slot 261 is an arcuate elongated slot disposed on at least one of the flanges 225, causing the flanges 225 to be phase shifted due to the movement of the pins 255, thereby causing a phase shift at a desired speed/RPM relative to a second elongated slot 262 disposed on another one of the flanges 220, the second elongated slot extending substantially linearly in a radial direction.

In the present embodiment, the exhaust flange 225 is fixed to the driven sprocket 205 with the spacer 275 disposed therebetween. The spacer 275 can maintain a predetermined spacing between the driven sprocket 205 and the flange, thereby allowing the axial load member 245 and the mass member 235 to operate without any additional axial load from other elements. The rotation of the driven sprocket 205 rotates the exhaust flange 261, thereby maintaining the same phase. Furthermore, the exhaust flange 225 is provided with an angled elongated slot 261 that has some degree of movement (angular rotation) as the pins 255 slide in a radially outward direction, thereby causing the intake flange 220 to experience a phase shift. Thus, the intake lobe 210 also experiences a phase shift that causes a change in the intake valve opening/closing timing. According to one embodiment, the angled elongated slots provide a phase shift in the range of 5-25 degrees. The axial load plate 245 applies an axial force to the mass member 235, whereby the sliding of the arc-shaped members 236, 237 in the radial direction is reduced.

Fig. 7 illustrates an enlarged/detailed view of a cross-section of a camshaft assembly 200 according to an embodiment of the present subject matter. When the camshaft assembly 200 is subjected to rotation, the arc-like members 236, 237 of the mass member 235 are subjected to centrifugal forces CF that tend to pull the arc-like members in a radially outward direction. The arc-like members 236, 237 are connected to one another by a resilient member 238 having a stiffness k that tends to pull the arc-like members 236, 237 in a radially inward direction with a force KF. Further, the axial load member 245 applies an axial force to the arc-like members 236, 237 due to a preload acting thereon. Thus, the arc-like members 236, 237 interposed between the flange 220 and the axial load member 245 receive the frictional force FF on the mass member 235 and control premature phasing due to the stiffness/tension of the resilient member 238.

Pin 255, which is one of the main components of mechanical phasing assembly 230 that passes through aperture 270, is also subject to forces acting on mass member 235. Due to the torque experienced by the camshaft assembly 200, i.e., the valve mechanism torque, this torque has a force component that acts in the direction of movement of the pin 255 in the radial direction along the elongated slot. This force component, which would otherwise tend to move the pin 255 in a radially outward direction, is balanced 245 by the frictional force exerted by the axial load member. Only when the speed/RPM of the engine 100 (which is similar to the speed of the camshaft assembly 200) is high, the centrifugal force CF replaces the force KF exerted by the elastic member 238 and the frictional force FF acting on the arc-shaped members 236, 237, whereby the arc-shaped members 236, 237 move in the radially outward direction. Thus, movement of the pin 255 changes the orientation of the flange 220, resulting in a phase shift. Further, the roller bearing 214 provided between the inner periphery of the second cam portion 202 and the outer periphery of the first cam portion 201 facilitates relative rotation between the cam portions 201, 202 during phase shifting. Accordingly, the mechanical phasing assembly 230 according to the inventive subject matter occurs according to the method defined by equation (1) below. The method of performing mechanical phasing as detailed in fig. 8 according to the subject of the invention is detailed below:

CF＝KF+μ(FF)………………(1)

according to one embodiment, an axial load member 245 preloaded in the axial direction configured to apply an axial load in the camshaft assembly 200 applies a resistive/frictional force FF to a side surface of the mass member 235. The axial load member 245 provides a friction force FF (which is the inherent surface friction of the material or the coefficient of friction due to the surface coating provided on the axial load member 245) that is dependent on the coefficient of friction μ of the axial load member 245 to counter any excessive centrifugal force acting on the mass member 235 during certain operating conditions (like sudden acceleration, etc.).

The method provides that at step S301, a system operating without any external control, as a mechanical phasing system, requires the IC engine 100 to be in an operating state whereby the crankshaft rotates the camshaft assembly 200. Due to the rotation of the camshaft assembly 200, centrifugal force acts on the mass member 235, which is preloaded in the radial direction. Further, at step S302, the centrifugal force CF acting on the mass member 235 is checked. The term "inspection" as used herein is meant only to explain the method and does not require actual inspection, as the mechanical phasing assembly 230 occurs automatically. Further, the centrifugal force CF acting on the mass member 235 is compared with the force KF exerted by the elastic member and the friction force FF according to the friction coefficient. If the centrifugal force CF is less than the cumulative force of the stiffness force KF and the friction force (i.e., μ time FF), the system returns to step S302 to continue checking the centrifugal force CF. At step S303, if the centrifugal force CF exceeds the sum of the force KF and the friction force μ time FF, then at step S304, the system performs mechanical phasing, which is performed without any external control. This results in a variation in the opening and closing times of the valves to meet the intake and exhaust requirements of the engine at all operating speeds.

Further, according to the present embodiment, the axial load member 245 is a disc-shaped member disposed adjacent to the driven sprocket 205. Further, the axial face of the driven sprocket 205 is provided with a disc-shaped recess capable of receiving the axial load member 245 at the recess. Thus, the axial load member 245 has a first axially inner surface 246 and the driven sprocket 205 has a second axially inner surface 207, and the first and second axially inner surfaces 246 and 207 are disposed along a plane P taken orthogonally to the axis A-A' of the camshaft assembly 200. Thus, the axial load member 245 is accommodated in the same amount of space required to accommodate the driven sprocket 205. This eliminates the need for additional mounting space on the camshaft assembly 200, particularly the space between the driven sprocket and the cam lobes 210, 211. Because the location of the cam chain 114 connected to the crankshaft, the receiving space of the cam chain 114, and the location of the valves interacting with the cam lobes 210, 211 need not be changed in accordance with the inventive subject matter, thereby maintaining a useable layout of the IC engine, particularly the cylinder head. Thus, the present subject matter provides an improved valve timing assembly/mechanical phasing assembly that does not require any layout modifications.

In one embodiment, the axial face of the axial load member 245 facing the mass member 235 and the axial face of the flange 220 facing the mass member are machined or provided with a surface coating to achieve a desired coefficient of friction.

Many modifications and variations of the present subject matter are possible in light of the above disclosure. Therefore, within the scope of the claims of the inventive subject matter, the disclosure may be practiced other than as specifically described.

List of reference numerals

100 engine 240 fixed plate

101 crankcase 241 locking fastener

102 cylinder block 242 axial force elastic member

103 cylinder head 243 fastener

104 cylinder head-cover 245 axial load member

105 air inlet 246 first axial inner surface

110 crankshaft 255 pin

111 magneto assembly 260-

113 pinion 261-

114 cam chain 262

115 chain tightener 263 elongated slot

116 adjustment member 270 aperture

200 camshaft assembly 275 spacer

201 first cam portion 280 relief system

202 second cam portion

205 driven gear/cam sprocket

206 holes

207 second axial inner surface

210 intake lobe

211 exhaust lobe

214

215/

216/bearing

220 air inlet flange

225 exhaust flange

230 phasing assembly

235 mass component

236 first arc shaped member

237 second arc shaped member

238 tension elastic member