DESC:TECHNICAL FIELD
[0001] The present subject matter generally relates to an integrated starter generator for an internal combustion engine, and more particularly, relates to a cooling arrangement for such integrated starter generator.

BACKGROUND
[0002] Typically, a starter generator is mounted on a vehicle driven by an engine. The integrated starter generator (ISG) is a rotating electric machine which combines a starter motor which drives a crankshaft of the engine at the start of the engine. It also acts as a generator which provides electric power to various electric loads after the starting operation of the engine is completed.
[0003] Thus, the ISG replaces the conventional starter motor and the alternator (generator). Apart from serving its two basic functions of starting the engine and acting as a generator to provide electric power to various electric loads, it also acts as an automatic vehicle start-stop system.
[0004] The ISG consists of two parts, namely starter and generator. The starter part of the component is composed of a stator, windings, armature, and brushes. The armature is connected to wires wound in a circular motion making a field coil. Voltage is sent to the coil, then into the brushes and to the armature. As the voltage flows through a series field, a magnetic field is created. The voltage runs through different parts of the coil, changing the magnetic fields created. As the magnetic field rotates around the coil, the stator turns, engaging the engine.
[0005] The generator portion of the starter generator components provides voltage to all the electrical components of the vehicle. Each electric feature of a vehicle requires some amount of voltage to operate. The generator sends the correct amount of voltage to each component, while maintaining enough voltage to operate all the components simultaneously.
[0006] The electronic control system switches off the internal combustion engine at zero load (such as when standing at a traffic light) and automatically restarts it using the ISG very rapidly when the gas pedal is pressed. The internal combustion engine is accelerated to the required cranking speed (idle speed) and only then the combustion process for instant ignition is initiated. During braking, the ISG can convert the vehicle’s kinetic energy into electrical energy, and then feed this power back into the electrical system. As it fully supports the stop-and-start operation, electric drive-off and acceleration and recycling of braking energy the ISG helps to reduce both fuel consumption and emissions.

BRIEF DESCRIPTION OF DRAWINGS
[0007] The detailed description is described with reference to the accompanying figures, which is related to a two-wheeled vehicle being one embodiment of the present subject matter. However, the present subject matter is not limited to the depicted embodiment(s). In the figures, the same or similar numbers are used throughout to reference features and components.
[0008] Fig. 1 depicts a left-side view of an exemplary scooter-type vehicle in accordance with an embodiment of the present subject matter.
[0009] Fig. 2 illustrates an exploded side view of the arrangement of integrated starter generator with the cover magneto and crankcase LH within an internal combustion engine in accordance with an embodiment of the present subject matter.
[00010] Fig. 3 illustrates an engine cross-sectional view defining the first vent hole in crankcase LH and the second vent hole in cover magneto showing the cooling passage inside internal combustion engine in accordance with an embodiment of the present subject matter.
[00011] Fig. 4 illustrates another engine cross sectional view defining the entire oil lubrication path in accordance with an embodiment of the present subject matter.
[00012] Fig. 5(a) illustrates an outer portion of crankcase LH in accordance with an embodiment of the present subject matter.
[00013] Fig. 5(b) shows a cross sectional view (F-F’) of the crankcase LH defining the first vent hole in accordance with an embodiment of the present subject matter.
[00014] Fig. 6(a) illustrates an outer surface of cover magneto in accordance with an embodiment of the present subject matter.
[00015] Fig. 6(b) illustrates a cross sectional view (G-G’) of the cover magneto defining the second vent hole and mounting boss portion in accordance with an embodiment of the present subject matter.
[00016] Fig. 7 depicts a graph showing the difference in stator temperature and lubricating oil temperature vis-à-vis existing internal combustion engine vs present subject matter.
DETAILED DESCRIPTION
[00017] Various features and embodiments of the present subject matter here will be discernible from the following further description thereof, set out hereunder. It is contemplated that the concepts of the present subject matter may be applied to any kind of vehicle within the spirit and scope of this subject matter. The detailed explanation of the constitution of parts other than the present subject matter which constitutes an essential part has been omitted at suitable places.
[00018] Typically, the stator of the ISG is used to assembled with a magneto cover which made up of aluminium material which good in thermal conductivity. Also, rotor of ISG unit is assembled with a crankshaft of the internal combustion engine through a taper lock along with woodruff key which ensures the orientation of rotor to control the ignition. If the integrated starter generator (ISG) operates under continuously high loading conditions, the system’s performance and durability will decrease and the heat dissipation requirements will increase. It is a necessity for the ISG unit to generate high torque as a motor at the start of the engine to generate a high output. Even after the ISG acts as a generator after the starting operation of the engine is completed, a large amount of heat keeps getting generated from the armature coil, which causes a rise in temperature of the armature. Finally, this heat deteriorates the magneto/ISG unit efficiency which leads to create a drop in engine critical function like start ability. Further, due to the ISG and engine components being continuously exposed to such excessive heat, results in reduced durability of the engine. Moreover, such excessive heat from the ISG and thus the engine, is transmitted to the leg of the rider sitting on the vehicle, which is undesirable. Therefore, cooling arrangements to effectively cool the ISG is the need of the hour.
[00019] Conventionally, throughout the engine, splash lubrication takes place for cooling the stator and rotor of the conventional magneto assembly, however there is no specific lubrication path or arrangement for magneto which directly cools the stator and rotor. Such splash lubrication fails to efficiently cool the ISG since the splashed cooling water or oil is ineffectively splashed throughout the engine and is not directed towards the stator and rotor specifically.
[00020] Attempts have been made to perform cooling of the ISG through external cooling arrangements such as fans. A plurality of fans is placed on an outer surface of a portion close to the outer periphery of the bottom wall portion of the rotor yoke. The fans are arranged to be arranged in circumferential direction of the rotor yoke. Each vent hole which penetrates the bottom wall portion is formed at a position adjacent to a fan. Herein, the plurality of fans constitutes a centrifugal fan for leading air inside of the rotor yoke out through the vent holes to send the air to the outer peripheral side of the rotor yoke when the rotor rotates. Also, it is provided a guide surface on the stator bracket, which guides, into the inside of the rotor yoke, the air sent to the outer peripheral side of the rotor yoke by the centrifugal fan and flowed to the stator bracket side through a gap between the side wall portion of the protective cover and the peripheral wall portion of the rotor yoke.
[00021] However, the above arrangement for providing cooled air to stator and rotor is expensive due to utilisation of several fans. Moreover, it is not desirable since the arrangement becomes bulky and occupies more space in the vehicle due to mounting of several fans.
[00022] Another attempt has been made to provide a cooling water circulating passage formed inside of a side wall portion of a cover magneto and a stator of the generator. The cooling water circulating passage is arranged so that an outer peripheral surface of the armature core of the stator contacts with an inner surface of the side wall portion of the cover magneto. With such a construction, since heat being generated on the armature coil can be transferred to the side wall portion of the cover magneto, which is cooled by the cooling water, the armature coil can be cooled.
[00023] However, in the afore-mentioned arrangement, the cooling of the armature coil cannot be performed efficiently even if a cooling water circulating passage is formed inside of a side wall portion of a cover magneto, since an outer surface of an armature core cannot be contacted with the side wall of the cover magneto. Moreover, it requires space inside the internal combustion engine for the cooling water circulating passage, thereby increasing the size of the internal combustion engine.
[00024] Thus, there arises a need for an internal combustion engine with an efficient cooling arrangement directed towards ISG that does not require major constructional changes in the existing internal combustion engine, and effectively cools the stator and rotor part of the ISG, that further addresses the other afore-mentioned problems of the prior art.
[00025] The present subject matter along with all the accompanying embodiments and their other advantages would be described in greater detail in conjunction with the figures in the following paragraphs.
[00026] The present subject matter aims to provide an internal combustion engine with an inbuilt-cooling passage directed towards ISG to cool the stator and rotor of the ISG, with minimal constructional changes to the existing internal combustion engine.
[00027] The present subject matter discloses an internal combustion engine for a vehicle comprising a crankcase rotatably supporting a crankshaft, an integrated starter generator including a rotor having a plurality of permanent magnet poles, and a stator having a plurality of phase windings disposed the stator, with each of the phase winding including a plurality of coils, a cover magneto enclosing the integrated starter generator from a first side and the integrated starter generator being disposed with the crankcase with a second side of the integrated starter generator facing toward the crankcase and a cooling passage being formed between the crankcase and the cover magneto for directing lubricating oil towards the integrated starter generator for cooling of the stator and the rotor of the integrated starter generator.
[00028] In another embodiment, the crankcase includes a crankcase LH and a crankcase RH.
[00029] In yet another embodiment, the crankcase LH includes one or more first vent holes formed on an inner portion of crankcase LH.
[00030] In another aspect of the invention, the cover magneto includes one or more second vent holes formed on an inner portion of the cover magneto.
[00031] In yet another embodiment, the one or more second vent holes are in proximity to the integrated starter generator.
[00032] In another embodiment, the cover magneto includes a mounting boss portion which connects the one or more first vent holes and one or more second vent hole to allow passage of lubricating oil from said one or more first vent hole of the crankcase and the one or more second vent hole of the cover magneto towards the stator and the rotor of the integrated stator generator.
[00033] In yet another embodiment, the one or more first vent hole of the crankcase is connected to a gear transmission oil passage to allow passage of lubricating oil through said gear transmission oil passage to the cooling passage of the internal combustion engine.
[00034] In another embodiment, the lubricating oil is pumped into the gear transmission oil passage from an oil cooler through an oil pump.
[00035] The present subject matter is further described with reference to accompanying figures. It should be noted that the description and figures merely illustrate principles of the present subject matter. Various arrangements may be devised that, although not explicitly described or shown herein, encompass the principles of the present subject matter. Moreover, all statements herein reciting principles, aspects, and examples of the present subject matter, as well as specific examples thereof, are intended to encompass equivalents thereof.
[00036] The present subject matter may be implemented in any two-wheeled vehicle. However, for the purpose of explanation and by no limitation, the present invention, and corresponding additional advantages and features are described through the following embodiments depicting a scooter-type vehicle. Arrows wherever provided on top right corner of the figure represent direction with respect to vehicle. Arrow F represents forward direction, arrow R represents rearward direction, arrow UW represents upward direction and arrow DW represents downward direction.
[00037] Fig. 1 illustrates a left-side view of an exemplary vehicle (100), in accordance with an embodiment of the present subject matter. The vehicle (100) comprises a main frame (101) having a head tube (102). Towards front side, the vehicle (100) has one or more front suspensions (104) connected to a front wheel (106) which is further connected to a handlebar assembly (108), which forms a steering assembly of the vehicle (100). The steering assembly has a pair of rear-view mirrors (112a, 112b). The steering assembly is rotatably disposed about the head tube (102). The main frame (101) extends rearwardly downward from the head tube (102) and has a bent portion thereafter extending substantially in a longitudinal direction.
[00038] The vehicle (100) further has an internal combustion (IC) engine (120). In the present embodiment, the internal combustion engine (120) is swingably connected to the main frame (101). Towards rear side, the vehicle (100) has a rear wheel assembly (124) connected to one or more rear suspensions (122). The rear wheel assembly (124) has a rear wheel (110) mounted on a wheel rim (126). The vehicle (100) also has an exhaust system (130) extending rearwards from the internal combustion engine (120). In addition, the vehicle (100) has a rear fender (132) covering at least a portion of the rear wheel (110) and is positioned upwardly of the rear wheel (110).
[00039] Further, the vehicle (100) has a seat assembly (135) supported by the main frame (101). The seat assembly (135) is hingedly openable. The vehicle 100 has a floorboard (137) wherein a rider can operate the vehicle 100 in a seated position by resting feet on the floorboard (137). Further, the floorboard (137) can carry loads. In addition, a utility box is disposed below the seat assembly (135) and is supported by the main frame (101). A fuel tank (not shown) is disposed adjacent to the utility box. Furthermore, the vehicle (100) comprises of plurality of electrical and electronic components including a headlight assembly (not shown), a taillight assembly (not shown), a transistor-controlled ignition (TCI) unit (not shown). The vehicle (100) is thus made to stay in a riding ready position over a center stand (not shown).
[00040] Fig. 2 illustrates an exploded side view of the arrangement of integrated starter generator with the cover magneto and crankcase LH within an internal combustion engine in accordance with an embodiment of the present subject matter. Herein, an integrated starter generator (230) including a stator (235) and a rotor (237) is disposed within the crankcase (210). The crankcase (210) is rotatably supporting a crankshaft (shown in Fig. 4). The rotor (237) has a plurality of permanent magnet poles (not shown) and the stator (235) has plurality of phase windings (not shown) disposed on the stator (235). Each of the phase windings (not shown) has a plurality of coils. The integrated starter generator (230) is further enclosed with a cover magneto (220) from a first side. A second side of the integrated starter generator (230) is facing the crankcase (210). For starting the internal combustion engine (120), one or modes may be selected by manual method or depending the driver requirements (throttle demand), in either case when starting engine from cold can result significantly higher emissions, in order to increase temperature & reduce emissions engine is driven by starter motor /ISG for few cycles without ignition & fuelling. This facilitates scavenging of cold gases inside engine & heating of engine is achieved by compression of air for few cycles. This can be optimised with use of decompression system tuning & selecting suitable engine operating points/conditions. Engine with decomp in intake sends a significant amount of charge back to intake which is at higher temperature, this helps in enhancing charge temperature faster. Engine is also motored at optimum speed to achieve desired engine wall temperature.
[00041] For brevity purposes, Fig.3 and Fig. 4 have been explained together. Fig. 3 and Fig. 4 illustrates the internal combustion engine cross-sectional view depicting the cooling passage and path of lubricating oil. The internal combustion engine (200) has a gear transmission passage (not shown) in crankcase (210) for transmission parts especially gear box (not shown) which is directly connected with an oil pump (420). The lubricating oil is pumped from the oil pump (420). Such lubricating oil travels along an oil cooler inlet pipe (430) and reaches to an external oil cooler (410). The cooled lubricating oil is then transferred from the oil cooler (410) through an oil cooler outlet pipe (440) to an oil filter (450). Once the cooled lubricating oil is filtered through the oil filter (450), it is then transferred to the gear transmission oil passage. Herein, a cooling passage (400) is created that supplies cooled lubricating oil from the gear transmission passage directly towards the integrated starter generator (230). The stator (235) of the integrated starter generator (230) is mounted on the cover magneto (220) which is longitudinally connected with the crankcase (210). An inner portion of the crankcase (210) namely the crankcase LH includes one or more first vent holes (310) to connect to the gear transmission oil passage which is receiving the cooled lubricating oil from the external oil cooler (410).
[00042] Once, the cooled lubricating oil is received in the cooling passage (400) from the gear transmission oil passage (not shown) through the one or more first vent holes (210), it then travels toward a mounting boss portion (330) of the cover magneto (220). Such mounting boss portion (330) is configured to connect said one or more first vent hole (310) to one or more second vent hole (320) formed in an inner portion of the cover magneto (220). The mounting boss portion (320) thus allows passage of cooled lubricating oil from said one or more first vent holed (310) to the one or more second vent hole (320). The second vent hole (320) is in proximity to the stator (235) and the rotor (237) of the integrated starter generator (230). Thus, the second vent hole (320) directs the cooled lubricating oil directly towards the stator (235) and the rotor (237) of the integrated starter generator (230). A plurality of mounting fasteners (not shown) is used between the crankcase (210) and the cover magneto (220) for assembling purposes.
[00043] Referring to Fig. 5(a) and Fig. 5 (b), the crankcase (210) is shown with a cross-sectional view taken along an axis F-F’. The crankcase (210) includes the one or more first vent hole (310) on an inner portion of the crankcase (210) being connected to the gear transmission oil passage (not shown). The first vent hole (310) facilitates the passage of cooled lubricating oil from the gear transmission oil passage (not shown) from the external oil cooler (410) (shown in Fig. 4).
[00044] Referring to Fig. 6(a) and Fig. 6(b), the cover magneto (220) is shown with a cross-sectional view taken along an axis G-G’. The cover magneto (220) includes the one or more second vent hole (320) on an inner portion of the cover magneto (220). The inner portion of the cover magneto (320) further includes the mounting boss portion (330) which connects the one or more first vent hole (310) (shown in Fig. 3) to the one or more second vent hole (320). The second vent hole (320) is in proximity to the integrated starter generator (230). The cooled lubricating oil is thereby directly transferred from the first vent hole (310) to the mounting boss portion (330) and then to the second vent hole (320), after which it is directed towards the stator (235) and the rotor (237) of the integrated starter generator (230).
[00045] Referring to Fig. 7, which depicts a graph showing the difference in stator temperature and lubricating oil temperature vis-à-vis existing internal combustion engine vs present subject matter. Herein, in the existing prior art that utilizes either a cooling fan or an external oil cooler only, the temperature of the stator (235) coil is depicted as t1 which is ~160 degree Celsius. The temperature of the cooled lubricating oil is depicted as t3 which is ~118 degree Celsius. However, due to cooling passage created between the crankcase (210) and the cover magneto (220), the temperature of the stator (235) coil is estimated to be t2 which is ~140 degree Celsius. Moreover, the temperature of the cooled lubricating oil directed towards the integrated starter generator (230) is estimated to be ~115 degrees Celsius. Thus, it is clearly established that t1>t2 and t3>t4. Therefore, the present subject matter creates a cooling passage (400), thereby targeting the cooled lubricating oil directly towards the integrated starter generator (230), thus resulting in enhanced cooling efficiency of the internal combustion engine (120). The cooled lubricating oil temperature is also lower as compared to the existing prior art since the cooling passage makes the cooled lubricating oil a longer distance, thereby cooling down the temperature of the cooled lubricating oil.
[00046] Therefore, the present subject matter discloses a cooling oil passage which is directly connected with oil pump and feeding the oil to gear box. Since the transmission oil is routed through the oil cooler, the temperature of cooled lubricating oil is better than the splash type oil cooling. Hence, this cooled lubricating oil will carries the heat which is generated in the stator due to armature coil temperature rise. Such cooled lubricating oil which is directed towards the integrated starter generator carries the heat from the stator unit. Also, the cooled lubricating oil creates splash lubrication on rotor as well. Hence, the present subject matter discloses a cost-effective internal combustion engine providing increased cooling efficiency of the integrated starter generator with minimal constructional changes to the existing design of the internal combustion engine, with no additional parts such a fan or external cooling passage as disclosed in the prior art. The disclosed internal combustion engine is easy to manufacture and does not require extensive constructional changes to the existing internal combustion engine. Moreover, since the cooled lubricating oil is directed towards the integrated starter generator, the efficiency of the rotor also increases, and the copper winding resistance also comes down which further increases the current flow. Since this increased current flow is directly proportional to the torque, the integrated starter generator can generate desired torque output to crank the internal combustion engine, thereby eliminating the problem of start ability due to low torque output. The rider of the vehicle also feels less heat emitted from the internal combustion engine due to the cooling arrangement. Since, the internal combustion engine is cooled in a better manner, the durability of the engine components is also increased.
[00047] While certain features of the claimed subject matter have been illustrated and described herein, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes that fall within the true spirit of the claimed subject matter.

List of reference signs:
100 vehicle 460 crankshaft
101 main frame F-F’ cross section of crankcase
102 head tube G-G’ cross section of cover magneto
104 front suspensions
106 front wheel
108 handlebar assembly
110 rear wheel
112a, 112b rear view mirrors
120 internal combustion engine
122 rear suspensions
124 rear wheel assembly
126 wheel rim
130 exhaust system
132 rear fender
135 seat assembly
137 floorboard
210 crankcase
220 cover magneto
230 integrated starter generator
235 stator
237 rotor
310 first vent hole
320 second vent hole
330 mounting boss portion
400 cooling passage
410 oil cooler
420 oil pump
430 oil cooler inlet pipe
440 oil cooler outlet pipe
450 oil filter
,CLAIMS:We claim:
1. An internal combustion engine (120) for a vehicle (100) comprising:
a crankcase (210), said crankcase (210) rotatably supporting a crankshaft (460);
an integrated starter generator (230) including a rotor (237) having a plurality of permanent magnet poles, and a stator (235) having a plurality of phase windings disposed on said stator (235), said phase winding including a plurality of coils;
a cover magneto (220), said cover magneto (220) being configured to enclose said integrated starter generator (230) from a first side and said integrated starter generator (230) being disposed within said crankcase (210) with a second side of said integrated starter generator (230) facing towards said crankcase (210); and
a cooling passage (400) being formed between said crankcase (210) and said cover magneto (220),
wherein said cooling passage (400) being configured for directing cooled lubricating oil towards said integrated starter generator (230) for cooling of said stator (235) and said rotor (237) of said integrated starter generator (230).

2. The internal combustion engine (120) as claimed in Claim 1, wherein said crankcase (210) includes a crankcase LH and a crankcase RH.

3. The internal combustion engine (120) as claimed in Claim 1, wherein said crankcase LH includes one or more first vent hole (310) being formed on an inner portion of said crankcase LH.

4. The internal combustion engine (120) as claimed in Claim 1, wherein said cover magneto (220) includes one or more second vent hole (320) being formed on an inner portion of said cover magneto (220).

5. The internal combustion engine (120) as claimed in Claim 5, wherein said one or more second vent hole (320) being in proximity to an integrated starter generator (230).

6. The internal combustion engine (120) as claimed in Claim 1, wherein said cover magneto (220) includes a mounting boss portion (330) being configured to connect said one or more first vent hole (310) and said one or more second vent hole (320) to allow passage of cooled lubricating oil from said one or more first vent hole (310) of said crankcase (210) and said one or more second vent hole (320) of said cover magneto (220) towards said stator (235) and said rotor (237) of said integrated starter generator (230).

7. The internal combustion engine (120) as claimed in Claim 1, wherein said one or more first vent hole (310) of said crankcase (210) being connected to a gear transmission oil passage (not labelled) to allow passage of cooled lubricating oil through said gear transmission oil passage to said cooling passage (400) of said internal combustion engine (120).

8. The internal combustion engine (120) as claimed in Claim 7, wherein said cooled lubricating oil being pumped into said gear transmission oil passage from an oil cooler (410) through an oil pump (420).