Engine assembly for a motor vehicle

Abstract

The present invention relates to an engine assembly (100) for a motor vehicle. The assembly has a crankshaft (110) housed in a crankcase (120), a cam chain window (130) through which an oil path passes from a cylinder head to an oil sump in the crankcase (120), and an integrated starter generator (ISG) (200) having a rotor (210) rotatably mounted on one end of the crankshaft (110), the rotor having a plurality of protrusions (212) on a circumferential surface; wherein the circumferential surface of the rotor (210) receives oil from the cylinder head through the cam chain window (130) and the plurality of protrusions (212) splash the oil towards an inner wall (122A) of a crankcase cover (122) proximate to the ISG (200), thereby cooling the oil.

Description

TECHNICAL FIELD

[0001] The present invention relates to an engine assembly for a motor vehicle. BACKGROUND

[0002] In conventional motor vehicles, magneto (also known as ignition magneto) provides current to the ignition system of a spark ignition engine. Magneto is a rotating auxiliary device with generator properties, having a permanent magnet that generates a periodic pulse of alternating current. In a spark ignition engine, magneto provides a high voltage pulse to the spark plug.

[0003] In these conventional motor vehicles including magneto, a starter motor is also required for starting of the engine. For starting the engine, the starter motor is connected to a ring gear mounted on the crankshaft for multiplication of torque input and to an adjacent starter drive one-way clutch to transmit torque from the starter motor to the ring gear. The requirement of accommodating the ring gear and the starter drive one-way clutch in addition to the magneto and the starter motor results in an extension of the length of the crankshaft and a wider crankcase, especially on the magneto side.

[0004] In such conventional motor vehicles, the return path of the engine oil starts from the cylinder head of the engine where the engine oil provides lubrication to the pistons (and in some cases to the air and fuel valves) and ends at an oil sump provided in the crankcase and passes through a window provided for the cam chain. Although the outgoing path of the oil from the oil sump to the cylinder head is established by an oil pump, the return path is largely gravity assisted. The engine oil in the return path is cooled by the ambient air flowing through the crankcase.

[0005] However, the oil return path in conventional motor vehicles does not enable efficient cooling of the oil as the ambient air comes in contact with the outer surface of the crankcase and in the conventional oil return path, the oil path is away from the outer surface of the crankcase while returning from the cylinder head to the oil sump.

[0006] This not only affects the oil temperature but also the engine performance as oil operating at higher temperatures loses its lubricity over time and is unable to provide the necessary heat exchange and lubrication at the cylinder head.

[0007] Such conventional design also has a higher number of mechanical components (such as the ring gear and the starter drive one-way clutch) resulting in a more height overhang of the crankshaft, which results in more end flex and noise.

[0008] Further, the heat issues arising from such conventional design can result in the engine oil operating beyond the Toxic Air Pollutant (TACS) limit.

[0009] Thus, there is a need in the art for an engine assembly that addresses at least the above-mentioned problems. SUMMARY

[0010] In one aspect of the present application, the present application relates to an engine assembly for a motor vehicle. The assembly has a crankshaft housed in a crankcase, a cam chain window through which an oil path passes from a cylinder head to an oil sump in the crankcase, and an integrated starter generator (ISG). The ISG has a rotor rotatably mounted on one end of the crankshaft, wherein the rotor has a plurality of protrusions on a circumferential surface thereof. The circumferential surface of the rotor receives oil from the cylinder head through the cam chain window, and the plurality of protrusions splashes the oil towards an inner wall of a cover crankcase proximate to the ISG, thereby cooling the oil.

[0011] In one embodiment of the present application, the rotor of the ISG is vertically aligned with the cam chain window.

[0012] In another embodiment of the present application, the engine assembly has a deflector positioned below the cam chain window to direct oil onto the circumferential surface of the rotor of the ISG.

[0013] In another embodiment of the present application, the engine assembly includes a bearing mounted on the crankshaft, and a cam chain sprocket sandwiched between the bearing and the ISG along the length of the crankshaft. In one embodiment of the present application, the crankcase is reduced in size in the vehicle width direction.

[0014] In another aspect of the present application, the present application relates to an integrated starter generator for a motor vehicle. The ISG has a rotor having a plurality of protrusions on a circumferential surface thereof, and is configured to be mounted on one end of a crankshaft.

[0015] In one embodiment of the present application, the plurality of protrusions on the rotor of the integrated starter generator functions as a crank position sensing device. BRIEF DESCRIPTION OF DRAWINGS

[0016] Reference will be made to embodiments of the application, examples of which are illustrated in the accompanying drawings. These drawings are intended to be illustrative and not restrictive. Although the application will be described generally in the context of these embodiments, it should be understood that the application is not intended to be limited to these specific embodiments.

[0017] Figure 1 An exemplary motor vehicle according to one embodiment of the present application is shown.

[0018] Figure 2 is a cross-sectional view of an engine assembly for a motor vehicle according to one embodiment of the present application.

[0019] Figure 3 An integrated starter generator according to one embodiment of the present application is shown.

[0020] Figure 4 An integrated starter generator is shown in accordance with one embodiment of the present application.

[0021] Figure 5 is a cross-sectional view of a portion of an engine assembly for a motor vehicle in accordance with one embodiment of the present application.

[0022] Figure 6 A comparison of engine operating temperatures in a conventional configuration and in a current configuration in accordance with one embodiment of the present application is shown. DETAILED DESCRIPTION

[0023] The present application relates to an engine assembly for a motor vehicle. More particularly, the present application relates to an engine assembly for a motor vehicle to provide efficient cooling of oil.

[0024] Figure 1 An exemplary motor vehicle 10 is shown in accordance with one embodiment of the present application. The motor vehicle 10 includes a vertically arranged IC engine 12. Preferably, the IC engine 12 is a single cylinder IC engine. The motor vehicle 10 includes front wheels 14, rear wheels 16, frame members, a seat assembly 18, and a fuel tank 20. The frame members include a head tube 22, a main tube 24, a down tube (not shown), and seat rails (not shown). The head tube 22 supports a steering shaft (not shown) and two telescoping front suspensions 26 (only one is shown) attached to the steering shaft by lower brackets (not shown). The two telescoping front suspensions 26 support the front wheels 14. An upper portion of the front wheels 14 is covered by a front fender 28 mounted to a lower portion of the telescoping front suspensions 26 at an end of the steering shaft. A handlebar 30 is fixed to the upper brackets (not shown) and is rotatable to both sides. A headlight 32, a windshield (not shown), and an instrument panel (not shown) are provided on an upper portion of the head tube 22. The frame members include a down tube that can be located in front of the IC engine 12 and extends downwardly and obliquely from the head tube 22. The main tube 24 of the frame members is located above the IC engine 12 and extends rearwardly from the head tube 22. The IC engine 12 is mounted in front of the down tube, and a rear portion of the IC engine 12 is mounted at a rear portion of the main tube 24. In one embodiment, the IC engine 12 is mounted vertically with the cylinder extending vertically above the crankcase. In an alternative embodiment, the IC engine 12 is mounted horizontally (not shown) with the cylinder extending horizontally forwardly from the crankcase. In one embodiment, the cylinder is arranged behind the down tube.

[0025] A fuel tank 20 is mounted on the horizontal portion of the main tube 24. Seat rails are joined to the main tube 24 and extend rearward to support the seat assembly 18. Rear swing arms 34 are connected to the frame members to swing vertically, and rear wheels 16 are connected to the rear ends of the rear swing arms 34. Generally, the rear swing arms 34 are supported by a single rear suspension 36, as shown in this embodiment, or by two suspensions on both sides of the motor vehicle 10. Tail light units (not shown) are arranged at the end portions of the motor vehicle 10 and at the rear of the seat assembly 18. Armrests (not shown) are also provided on the rear of the seat rails. The rear wheels 16 provided below the seat 18 are rotated by the driving force of the IC engine 12 transmitted through a chain transmission mechanism (not shown) from the IC engine 12. A rear fender 38 is arranged above the rear wheels 16.

[0026] Further, an exhaust pipe 40 of the vehicle extends vertically downward from the IC engine 12 until a certain point before terminating at a muffler 42, and thereafter extends longitudinally along the length of the vehicle below the IC engine 12. The muffler 42 is generally arranged adjacent to the rear wheels 16.

[0027] Figure 2 A cross-sectional view of an engine assembly 100 for a motor vehicle 10 according to one embodiment of the present application is shown. As shown, the engine assembly 100 has a crankshaft 110 housed in a crankcase 120. The crankshaft 110 is driven by a crank mechanism comprising a series of crank pins to which connecting rods are attached to pistons to convert the reciprocating motion of the pistons into rotational motion. The crankshaft 110 has a linear axis 112 about which the crankshaft 110 rotates. In this embodiment, the IC engine 12 is a single cylinder engine, one connecting rod being connected to one crank pin of the crankshaft 110.

[0028] As further shown in the figure, the engine assembly 100 further has a cam chain window 130. The cam chain window 130 is an aperture in the crankcase 120 provided to allow the crankshaft 110 to be connected to a camshaft via a cam chain. The camshaft, driven by the crankshaft 110, operates the intake and exhaust valves in the IC engine 12 via a plurality of cam pins. In the present application, the return path of oil from the cylinder head of the IC engine 12 to an oil sump in the crankcase 120 is directed through the cam chain window 130. The oil reaches the cylinder head from the oil sump in its outgoing path with the aid of an oil pump, and after lubricating the exhaust and intake valves and the reciprocating piston in the cylinder head, returns to the oil sump through the cam chain window 130.

[0029] As further shown in the figure, the engine assembly 100 further has an integrated starter generator (ISG) 200 mounted on one end of the crankshaft 110. As Figure 3 and Figure 4As shown in the figure, the ISG 200 has a rotor 210 with a plurality of protrusions 212 on its circumferential surface, which rotates on the same axis 112 as the crankshaft 110. In one embodiment of the present invention, the protrusions 212 on the rotor 210 are used as a crank position sensing device, wherein a crank position angle sensor (not shown) detects the position of the crankshaft 110 based on the rotation of the protrusions 212. The ISG is configured to provide torque to the engine 12 during start-up and to utilize energy from the crankshaft 110 as a generator when the engine 12 is running. The ISG 200 is also configured to provide a pulsed signal to the spark plug for ignition, thereby replacing the conventional magneto and starter motor configuration. The replacement of the magneto and starter motor configuration by the ISG 200 also eliminates the need for mechanical components such as a ring gear and a starter drive one-way clutch, which allows for a reduction in the length of the crankshaft 110. In one embodiment of the present invention, the length of the crankshaft 110 is reduced by up to 15-20 mm with respect to the conventional configuration. The reduction in the length of the crankshaft 110 results in a reduction in the width of the crankcase 120 and thereby the engine assembly 100.

[0030] Reference is made to Figure 2 wherein the reduction in the length of the crankshaft 110 in the present application allows the oil to fall on the circumferential surface of the rotor 210 from the cam chain window 130 with the aid of gravity in its return path. When the oil falls on the circumferential surface of the rotor 210, the impact of the oil on the rotating protrusions 212 creates a splashing effect due to the interruption of the flow of the oil by the protrusions 212 and the centrifugal force imparted by the rotation of the rotor 210.

[0031] The splashing effect causes the oil to splash outwardly with respect to the axis of rotation 112 of the crankshaft 110 and onto the inner surface 122A of the crankcase cover 122 proximate to the ISG 200. The falling of the oil on the circumferential surface of the rotor 210 and the subsequent splashing effect has been depicted by the arrows as shown in the figure. The outer surface 122B of the crankcase cover 122 is exposed to the ambient air, and the ambient air passes over the outer surface 122B of the crankcase cover 122 when the vehicle is running. The passing air encounters the outer surface of the crankcase cover 122, thereby cooling the crankcase cover 122 and consequently the oil in contact with the inner surface 122A of the crankcase cover 122. In one embodiment of the present invention, the crankcase cover 122 is made of aluminum, which provides effective cooling of the crankcase cover 122 by the passing ambient air.

[0032] The oil splashed onto the inner surface 122A of the crankcase cover 122, which is cooled, flows to the oil sump in the crankcase 120 with the aid of gravity, thereby completing its return path, which can be pumped again from the return path by the oil pump towards the cylinder head.

[0033] In one embodiment of the present application, the rotor 210 of the ISG 200 is vertically aligned with the cam chain window 130, thereby causing the oil in its return path to fall directly onto the circumferential surface of the rotor 210 aided by gravity from the cam chain window 130.

[0034] In one embodiment of the present application, the engine assembly 100 further has a deflector (not shown) positioned below the cam chain window 130 to direct the oil towards the circumferential surface of the rotor 210, which has higher effectiveness for further enhancing the splashing effect.

[0035] Figure 5 An engine assembly 100 is shown in accordance with one embodiment of the present application. As shown, the engine assembly 100 further has a bearing 140 which supports the crankshaft 110 and allows the crankshaft 110 to rotate during operation of the engine 12. The engine assembly 100 further has a cam chain sprocket 150 which is a profiled wheel having teeth / teeth meshing with the cam chain. The cam chain sprocket 150 is coupled to the crankshaft 110, thereby causing it to rotate with the crankshaft 110 and thereby rotate the camshaft. In the present configuration, the cam chain sprocket 150 is sandwiched between the bearing 140 and the ISG 200 along the length of the crankshaft 110.

[0036] The crankshaft overhang 160 is defined by the length of the crankshaft 110 between the cam chain sprocket 150 and the ISG 200. As Figure 5 shown in the present configuration, the crankshaft overhang 160 is minimized, which further reduces crankshaft 110 end deflection and thereby reduces noise, vibration and harshness during engine operation.

[0037] The smaller crankshaft overhang 160 also allows the crankcase 120 to be reduced in size in the vehicle width direction, meaning the rider's feet are further away from the crankcase 120, which creates a better airflow path for the ambient air of the environment and thereby makes cooling more effective.

[0038] As Figure 6 shown in the present configuration, the engine 12 operating temperature is significantly reduced compared to the engine operating temperature in the conventional configuration. Up to 3 degrees Celsius temperature difference can be achieved with the present application, reducing the average engine 12 operating temperature from 110 degrees Celsius to 107 degrees Celsius.

[0039] Advantageously, the present application provides an engine assembly which allows reduction in the crankshaft length, which allows the rotor of the ISG to be aligned with the cam chain window and thereby allows more effective cooling of the oil in its return path. This effective cooling of the oil extends the life cycle of the oil and improves engine performance by maintaining the engine operating temperature at a lower level, while also keeping the oil within the TACS limit.

[0040] Further, the present configuration eliminates the need for additional mechanical elements (e.g., magneto, ring gear, and one-way clutch), reduces crankshaft overhang, and reduces noise, vibration, and harshness during engine operation.

[0041] The crankcase cover in the present configuration is reduced in size compared to a conventional crankcase cover that covers a magneto, and thus the present configuration allows a more compact engine to be achieved and a better air flow path for air traveling, thereby providing more effective cooling.

[0042] While the application has been described with respect to specific embodiments thereof, various changes and modifications can be suggested to one skilled in the art, and it is intended to encompass such changes and modifications as fall within the scope of the application defined by the appended claims.

Claims

1. An engine assembly (100) for a motor vehicle, the engine assembly (100) comprising: a crankshaft (110) housed in a crankcase (120); a cam chain window (130) through which an oil path passes from a cylinder head to an oil sump in the crankcase (120); and an integrated starter generator (ISG) (200) having a rotor (210) rotatably mounted on one end of the crankshaft (110), the rotor having a plurality of protrusions (212) on a circumferential surface; wherein the circumferential surface of the rotor (210) receives oil from the cylinder head through the cam chain window (130) and the plurality of protrusions (212) splash the oil towards an inner wall (122A) of a crankcase cover (122) proximate to the ISG (200), thereby cooling the oil.

2. The engine assembly (100) as claimed in claim 1, wherein the rotor (210) is aligned with the cam chain window (130).

3. The engine assembly (100) as claimed in claim 1, comprising a deflector positioned below the cam chain window (130) to direct the oil onto the circumferential surface of the rotor (210) of the ISG.

4. The engine assembly (100) as claimed in claim 1, comprising a bearing (140) mounted on the crankshaft (110) and a cam chain sprocket (150) sandwiched along the length of the crankshaft (110) between the bearing (140) and the ISG (200).

5. The engine assembly (100) as claimed in claim 1, wherein the crankcase (120) is reduced in size in a vehicle width direction.

6. The engine assembly (100) as claimed in claim 1, wherein the plurality of protrusions (212) on the rotor (210) function as a crank position sensing device. ​

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