Claims:We Claim;
1. A four-stroke liquid cooled power unit (125) for a vehicle (100), said power unit (125) comprising:
a crankcase (205) having a coolant pump (203);
a cylinder block (204);
said cylinder block (204) disposed above said crankcase (205);
a cylinder head (201) disposed above said cylinder block (204);
said cylinder head (201) being configured with a thermostat (202) wherein said thermostat (202) and said coolant pump (203) being disposed towards one side of a cylinder axis (C-C’) when seen from a direction orthogonal to a crankshaft axis CA.
2. The power unit (125) as claimed in claim 1, wherein a short bypass circuit (as shown by arrow) being formed between said thermostat (202) and said coolant pump (203) wherein said bypass circuit (as shown by arrow) being configured with one or more passage formed on same side of said cylinder head (201) as that of said thermostat (202).
3. The power unit (125) as claimed in claim 1, wherein cam chain window (213) being disposed on an opposite side with respect to said cylinder axis C-C’.
4. The power unit (125) as claimed in claim 1, wherein said thermostat (202) and said coolant pump (203) disposed substantially along a plane VP formed at a predetermined offset from a plane passing through the cylinder axis C-C’ and crankshaft axis CA.
5. The power unit (125) as claimed in claim 1, wherein said cylinder head (201) comprises a coolant jacket (207), wherein said thermostat (202) is located towards one end of said coolant jacket (207).
6. The power units (125) as claimed in claim 1 or claim 4, wherein said cylinder head (201) includes a coolant bypass inlet (208) and a coolant bypass pocket (209), forming said passage X of said bypass circuit in said cylinder head (201), where said coolant bypass inlet (208) receives coolant through said thermostat and said coolant bypass pocket (209) receives coolant through said coolant bypass inlet (208).
7. The power unit (125) as claimed in claim 1 or claim 2, wherein said cylinder block (204) includes a coolant passage (Y) of said bypass circuit which receives coolant from a coolant bypass pocket (209) of said cylinder head (201).
8. The power unit (125) as claimed in claim 1 or claim 7, wherein said crankcase (205) includes a passage (Z) of said bypass circuit for receiving coolant from said passage (Y) of said cylinder block (204) and wherein said coolant pump (203) receives coolant from said channel of said passage (Z) of said bypass circuit formed in said crankcase.
9. The power unit (125) as claimed in claim 1 or claim 2, wherein said coolant pump (203) being mounted on a balancer shaft (212) of said power unit (125).
10. The power units (125) as claimed in claim 1, wherein said cylinder head (201) includes a cam chain window (213) being disposed at another side of said cylinder head (201), wherein said cam chain window (213) disposed opposite to said thermostat (202).
11. A cylinder head (201) for a power unit (125), said cylinder head (201) comprising;
one or more intake valves;
one or more exhaust valves;
a thermostat (202) disposed in between said one or more intake valves and said one or more exhaust valves.
12. The cylinder head (201) as claimed in claim 11, wherein said thermostat (202) being disposed on one side of said cylinder head (201) and a cam chain window (213) being disposed on another side of said cylinder head (201). , Description:TECHNICAL FIELD
[0001] The present subject matter relates to a motor vehicle. More particularly, the present subject matter relates to of a power unit of the motor vehicle.
BACKGROUND
[0002] In a saddle ride type vehicle, a power unit either is mounted or is low slung to a frame assembly of the vehicle. Moreover, in a scooter type vehicle with a step through type portion, the power unit is swingably mounted to the frame assembly through damping members, which are typically suspensions. Generally, the power unit of the vehicle is operated in a high temperature state, in different conditions like cold condition, hot condition and normal condition. The high temperature state is caused due to generation of heat. The generation of heat happens or takes place because of friction of each moving part and combustion inside the power unit. In this regard, lubricating oil is used for lubricating the moving parts in the power unit. This results in low friction characteristics at high temperature, which enables higher fuel efficiency. Therefore it is required to maintain the optimal performance of the power unit, in all the conditions. Hence, there is a constant drive from manufacturers to maintain the optimal performance of the power unit in all the conditions.
BRIEF DESCRIPTION OF THE DRAWINGS

[0003] The detailed description is described with reference to an embodiment in a type step thru type two wheeled vehicle along with the accompanying figures. The same numbers are used throughout the drawings to reference like features and components.
[0004] Fig.1 is a side view of a saddle type vehicle as per one embodiment of the present invention.
[0005] Fig.2 is a perspective view of a power unit as per one embodiment of the present invention.
[0006] Fig.2a is a top view of a cylinder head of the power unit as per one embodiment of the present invention.
[0007] Fig. 2b is a sectional view of the power unit as per one embodiment of the present invention.
[0008] Fig. 2c is a graphical representation as per one embodiment of the resent invention.
DETAILED DESCRIPTION
[0009] Generally, temperature of the power unit increases with time and with operation of various components inside the power unit. In this regard, maintaining of temperature within a safe operating region or the predetermined temperature range is important as it increases the durability and efficiency of the components of the power unit. The overheating of the power unit happens because of factors like, issues with belts and hoses., which impacts efficiency of the components of the power unit and thus ultimately decreases the performance of the power unit. Hence, there is a need to regulate the heat of the power unit and to provide constant cooling to the components of the power unit.
[00010] In different vehicles like saddle type vehicle, straddle type vehicle, HEV, Step thru type vehicle, location of the power unit in the vehicle layout also plays an important role in heat dissipation from the respective vehicle to the atmosphere. For example, in a saddle type vehicle, the power unit is mounted in a space formed between a down frame and centre frame of a frame assembly of the vehicle. The power unit is attached with various attachment means to the frame assembly of the vehicle. In the saddle type vehicle, the location of the mounting of the power unit has access to atmospheric air which results in cooling of the power unit of the vehicle. In straddle type vehicle or in step thru type vehicle, the power unit is typically low slung and also covered with component like side panels in the vehicle. The side panels as disposed cover at least major regions of the power unit from all sides. Such layout configuration often leads to overheating of the power unit as insufficient atmospheric air is channelized near the power unit to cool it down. In vehicle like HEV, or vehicle with auxiliary driving source like an Integrated Starter Generator (ISG) etc. the vehicle consists of the power unit and an electric motor or ISG. In this type of vehicle, low speed acceleration may be achieved by a simple single speed transmission. The single speed transmission reduces complexity of gear box and CVT. Although the low speed acceleration can be achieved by this configuration, however, maximum speed of the vehicle is dependent only on the operation of the power unit. Hence, in order to achieve higher vehicle speed there is a need for the power unit to operate at higher speed proportionately. Higher operating speed of power unit leads to higher operating temperature of engine. Additionally, for HEV type vehicles or ISG based vehicles or auxiliary energy storage type vehicles, the packaging of surrounding components like energy storage device, wiring harness for the vehicle also restrict natural cooling air circulation in the vehicle. In this regard, higher operating speed along with lower circulation of natural cooling air leads to overheating of the power unit. This leads to increased lubricating oil temperature and faster wears out of parts potentially making customer uncomfortable while going for a long drive.
[00011] Also, when the power unit is heated up above a predetermined temperature due to overheating of the components of the power unit owing to prolonged working of the components, it increases risk of damaging of moving parts due to mechanical contact, surface wear and tear, etc. Thus, there is constant need to dissipate excess heat generated in the the power unit. Further, in the cold condition, the power unit does not generate excess heat, thus there is a need to restrict the dissipation of heat from the power unit.
[00012] For maintaining cooling efficiency of the overheated power unit in normal condition or hot condition, typically, the vehicles incorporate a cooling system to reduce overheating of the power unit because of multiple factors like faulty carburetor, coolant leaking, continuous operation of various components etc. Conventionally, a coolant is circulated through power unit block to remove heat from the overheated power unit, where the power unit is in active state for long duration. The cooling system may include various components like valves, thermostats, radiators etc. A coolant pump is assembled to the power unit for circulation of coolant in the power unit. More precisely, the coolant pump is connected to a crankshaft, or any other driven shaft. The coolant flows through the radiator to transfer the heat from the power unit to air, thereby maintaining the optimal performance of the power unit. Further, in cold condition, the power unit does not generate excess amount of heat, as a result there is no need of dissipation of heat from the power unit to the atmosphere. In this regard, conventionally, a bypass circuit is configured for coolant to bypass the radiator to avoid any excess heat loss in the air, thus, maintaining the optimal performance of the power unit in the cold condition as well.
[00013] Further, the coolant pump outlet has path along crankcase which is connected to a cylinder block of the power unit, to circulate the coolant to cylinder head of the power unit. The cylinder head in the power unit has an outlet which includes a thermostat. The thermostat has two ends for coolant to flow, where one end is connected to the bypass circuit and another end is connected to the radiator. The thermostat is placed to ensure that temperature of the power unit stays above a certain predetermined temperature. If the power unit temperature falls below predetermined temperature, the thermostat blocks the coolant flow to the radiator, forcing the coolant to channelize back to the coolant pump through the bypass circuit that mostly happens in cold condition. If the power unit temperature exceeds the predetermined temperature, the thermostat opens the valve and channelizes the coolant back through the radiator, in normal or hot condition. Typically, the bypass circuit is connected from an outlet of the thermostat to an inlet of the coolant pump through various connecting means like hose, combined hoses etc. This has disadvantages necessitating use of additional parts like hoses for formation of the bypass circuit. This also leads to challenging task to package the additional component in the conventional compact layout of the power unit and the vehicle.
[00014] As per known art, a bypass circuit is disclosed that is integrated to the cylinder head of the power unit. More particularly, part of the bypass circuit is provided in the cylinder head and is adjacent to one of inlet ports of the combustion chamber. The bypass circuit extends in a direction perpendicular to the adjacent inlet port. The bypass circuit also overlaps the inlet port when viewed in a direction along an axis line of the cylinder bore. The bypass circuit extends outside the power unit to connect a cylinder block to a coolant pump. This configuration leads to challenging task to package the components in a compact layout of the vehicle. Further, the bypass circuit as disclosed contains multiple machined holes on the cylinder head. Formation of such machined holes causes long lead timing in terms of manufacturers. It also increases cost involved in manufacturing. The joining regions of multiple machined holes creates formation of aluminium burrs. The aluminium burrs, as formed, leads to contamination of coolant and also leads to blockage of coolant passage in the power unit. The aluminium burrs, as formed, get stuck in thermostats sealing area, which disrupts sealing and functioning of the thermostat. Also, the coolant flow in the power unit covers longer path in the bypass circuit, which affects the efficiency of the coolant in the power unit and thus impacts the optimal performance of the power unit.
[00015] Hence, there exists a contradictory challenge of maintaining efficiency of coolant of the power unit while having a bypass circuit in a compact layout of the vehicle, while maintaining optimal performance of the power unit, achieving elimination of additional components required for forming the bypass circuit, and also retaining compact layout design of the power unit and manufacturing set up of the vehicle.
[00016] Therefore, there is a need to have an improved bypass circuit of the power unit which overcomes all of the above problems and other problems of known art.
[00017] The present invention provides a solution to the above problems while eliminating need for additional components from the vehicle, thereby also achieving low cost of the vehicle.
[00018] With the above objectives in view, the present invention is an improved bypass circuit of the power unit, ensuring efficient cooling of the power unit.
[00019] As per one aspect of the present invention, a vehicle includes a power unit. The power unit is located in a space formed between a down frame and a centre frame. The power unit includes a cylinder block, cylinder head etc.
[00020] As per one aspect of the present invention, one side of the cylinder head is configured with a passage. The passage is further configured to connect a thermostat and a passage in a crankcase of the power unit, which is further directly connected to an inlet of a coolant pump in the power unit. This configuration is termed as bypass circuit. The passage from the cylinder head is configured to connect with the passage of the crankcase of the power unit through a passage provided on a side of the cylinder block in the power unit. The thermostat is located towards one end of a coolant jacket of the cylinder head. The coolant pump is located on same side below the thermostat. This configuration ensures that the bypass circuit so formed has a shortest possible path from the thermostat to the coolant pump for channelizing coolant from the thermostat to the coolant pump.
[00021] As per one aspect of the present invention, the thermostat is disposed at the coolant jacket of the cylinder head, located at one side of the cylinder head. Further, the thermostat is located along a crankshaft axial direction and in between inlet valves and exhaust valves. As per one aspect of the present invention, the cylinder head is configured with a cam chain window which is disposed at another side with respect to a cylinder axis and the thermostat is disposed at the one side with respect to the cylinder axis. This configuration eliminates additional machined parts; hoses required to bypass the flow of coolant to the inlet of the coolant pump and achieves a simple and shorter path internally to bypass the flow of the coolant in the power unit. The shorter path as designed ensures the efficiency of the coolant in the power unit. This coolant is channelised directly from the thermostat to the coolant pump, thus restricting dissipation of required heat in the atmosphere. This ensures the optimal performance of the power unit in all the conditions, more particularly, in cold condition.
[00022] In the ensuing exemplary aspects, the vehicle is a saddle type vehicle. However, it is contemplated that the concepts of the present invention may be applied to any of the vehicles having four stroke liquid cool internal combustion engine without defeating the spirit of the invention.
[00023] Various other features of the invention are described in detail below with reference to the accompanying drawings. In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number. With reference to the accompanying drawings, wherein the same reference numerals will be used to identify the same or similar elements throughout the several views.
[00024] Further “front” and “rear”, and “left” and “right” referred to in the ensuring description of the illustrated embodiment refer to front and rear, and left and right directions as seen in a state of being seated on a seat of the vehicle. Furthermore, a longitudinal axis refers to a front to rear axis relative to the vehicle, while a lateral axis refers to a side to side, or left to right axis relative to the vehicle. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. Further, the present subject matter can also be used in any two-wheeler, but for reference, the present subject matter is explained with respect to the straddle type two wheeled vehicle.
[00025] Fig. 1 is a left side view of an exemplary saddle type vehicle as per one embodiment of present subject matter. The vehicle (100) has a frame assembly (not shown, which acts as the skeleton for bearing the loads. Instrument cluster (119) is mounted on handle bar assembly (126). The handle bar assembly (126) is disposed over a head tube (not shown) and it includes brake levers (not shown). The handle bar assembly (126) is connected to a front wheel (129) by one or more front suspension(s) (130). A front fender (131) is disposed above the front wheel (129) for covering at least a portion of the front wheel (129). A leg shield (112) is provided on the vehicle (100). A fuel tank (103) is mounted to a main frame (not shown) and it is disposed in the front portion F of the vehicle. The vehicle (100) having lighting means which includes Head lamp (127), Tail lamp (not shown), Turning indicators includes front side indicators (111) and rear side indicator (not shown) respectively. The rear fender (138) is projected outwardly of the vehicle systems and is intended to protect the pillion from mud splash as well as to protect the rear wheel (133) from external environmental impact. A power unit (125) is mounted to the lower portion of frame (200). In an embodiment, the power unit (125) is a four stroke liquid cooled IC engine. The fuel tank (103) is functionally connected to the power unit (125). The seat (132) is located at the back region of the fuel tank (103) and is extended in a longitudinal direction along the seat frames.
[00026] Fig. 2 is a perspective view of the power unit as per one embodiment of the present invention. As per embodiment of the present invention, the power unit (125) includes a cylinder portion defined by a cylinder block (204) and a cylinder head (201). The cylinder block (204 ) is mounted to a crankcase (205) of the power unit. The crankcase (205 ) is connected to a frame assembly of the vehicle (100).
[00027] Further, the cylinder block (204) supports the cylinder head (201) that includes multiple valves (not shown). The valves enable entry of air-fuel mixture into the cylinder portion, where combustion of air-fuel mixture takes place. Subsequently, the valves enable dissipation of the burnt gases from the cylinder portion. A cylinder axis (C-C’) is drawn with respect to the cylinder bore. A thermostat (202) is disposed on the cylinder head (201) and at one side of the cylinder axis (C-C’). The thermostat (202) is located at one side of the cylinder head (201) along crankshaft axial direction and in between exhaust valves and inlet valves. Further, as per embodiment of the present invention, the cylinder head (201) includes a cam chain window (213) (as shown in fig. 2a) which is disposed at another side of the cylinder head and the thermostat (202) is disposed at the one side of the cylinder head (as shown in fig. 2a). Thus, the layout of the thermostat mounting configured as per this invention being disposed on the cylinder head and opposite to the side of the cam chain window helps in achieving reduction in a passage area of the coolant, which in turn helps in increasing the coolant efficiency. Also, the number of components required to configure the thermostat system is less while providing the shortest path of transfer of the coolant. This enables ease of serviceability and ease of assembly of the components in the power unit.
[00028] Fig. 2b is a sectional view of the power unit with as per one embodiment of the present invention. As per one embodiment of the present invention, the thermostat (202) is located towards one end of a coolant jacket (207) of the cylinder head (201). The coolant pump (203) is located on the same side, as that of the thermostat (202) and configured below the thermostat (202), that is, towards one side of the cylinder axis (C-C’) (as show in fig. 2) when seen from a direction orthogonal to a crankshaft axis CA (shown in Fig 2), forming a shortest path, termed as bypass circuit (as shown by arrow). More precisely, the thermostat and coolant pump are disposed substantially along a common plane VP which is parallel to a plane (not shown) passing through the cylinder axis CC’ and the crankshaft axis CA. The thermostat has two ends for coolant flow, where one end (202a) is connected to a radiator (not shown), which dissipates extra heat as generated in the power unit, when the power unit is overheated. Another end of the thermostat is connected the cylinder head (201). The bypass circuit connects the thermostat to a cooling pump in the power unit. The bypass circuit includes passage X, passage Y and passage Z. The passage (X) originates from the one side of the cylinder head (201) connects with the passage (Z) in the crankcase (205) of the power unit through the passage (Y) provided in the cylinder block (204) of the power unit. The coolant in the power unit flows from the thermostat to the passage of the bypass circuit formed in the cylinder head. From the passage X in the cylinder head, the coolant is further channelized to the passage Z of the bypass circuit formed in the crankcase through the passage Y of the bypass circuit formed in the cylinder block. The coolant ultimately reaches the coolant pump through the passage Z of the bypass circuit formed in the crankcase in the power unit, forming a shortest path for channelizing the coolant from thermostat to the coolant pump. The cylinder head (201) includes a coolant bypass inlet (208) and a coolant bypass pocket (209) forming the passage X. The coolant bypass inlet (208), which is formed by machined hole, present in the cylinder head (201) is connected to another end of the thermostat for receiving the coolant from the thermostat. The coolant bypass pocket receives coolant from the coolant bypass inlet (208), in the passage X of the bypass circuit in the cylinder head. The coolant bypass pocket (209) is formed by casting process and no separate machining is required. The thermostat (202) is covered with a thermally insulating cover (206) which also protects the thermostat from external disturbances. The s configuration disclosed as per present invention ensures that the coolant takes the shortest possible path (bypass circuit) from the thermostat to the coolant pump (203), thereby maintaining the coolant efficiency in the power unit.
[00029] The coolant pump (203) having a cover (211) is mounted over a driven shaft (212) (e.g. a balancer shaft) to provide constant coolant flow to the cylinder head of the power unit. The coolant pump includes plurality of pump inlet. An inlet (not shown) of the coolant pump (203) is connected to the coolant outlet of the radiator (not shown). The outlet of the coolant pump channelizes coolant inside the power unit to connect a plurality of cooling jacket (210a, 210b) of the cylinder block. When the power unit is in active state for a prolonged duration, the coolant flows from the coolant pump which is further channelized to the cylinder head of the power unit to remove extra heat generated in the power unit through the thermostat and the radiator, thereby maintaining the optimal performance of the power unit. However, in cold condition, when the temperature of the power unit is below predetermined temperature, the thermostat allows the coolant carrying heat of the components of the power unit to bypass the radiator and directly channelizes it to the another inlet of coolant pump through internally formed shortest path termed as the bypass circuit. This eliminates the additional heat loss from the power unit, hence maintains the optimal performance of the power unit while achieving a compact layout of the power unit. This configuration also eliminates additional machined parts; hoses required to pass the flow of coolant through the bypass circuit to the another inlet of the coolant pump, thereby reduce the overall weight of the power unit. This configuration provides a simple and shorter path internally to channelize the coolant from the components of the power unit to the coolant pump by bypassing the radiator, thereby eliminating packaging constraints in the power unit. Thus, the layout configuration of the thermostat being mounted and located on the cylinder head and the design of the bypass circuit being directly above the coolant pump provided on the crankcase helps in achieving reduction in the passage area of the coolant provided on the bypass circuit, which in turn helps in increasing the coolant efficiency in the power unit as well as compact power unit layout while overcoming all problems cited earlier. This provides optimal temperature for warming up the power unit faster in cold condition or while starting the power unit and thus maintains the overall performance of the power unit.
[00030] Fig, 2c is a graphical representation of the performance of the coolant in terms of its temperature on Y axis versus the time on X axis with and without the simple shortest path of the bypass circuit as per one embodiment of the present invention. The simple shortest path (curve denoted by E) termed here as bypass circuit channelizes the coolant carrying heat generated inside the power unit to the coolant pump by bypassing the radiator. This provides optimal temperature for warming up of the engine is shorter duration of time, in a situation like cold condition or when the power unit is just activated, ensuring optimal performance of the power unit, unlike as the path (denoted by curve F) disclosed in the state of art, where the path disclosed is an external path having longer length. The known art creates adverse impact on the performance of the power unit.
[00031] The invention helps in overcoming the problem related to coolant efficiency in the power unit having bypass circuit, while maintaining the overall weight and width of the power unit and additionally makes it cost effective.
[00032] Advantageously, the embodiments of the present invention, describes the potential modifications in the bypass circuit of the power unit, where bypass circuit is internally provided by mounting the thermostat and the coolant pump is same side of the cylinder axis, ensuring efficiency of the coolant in the power unit.
[00033] Many other improvements and modifications may be incorporated herein without deviating from the scope of the invention.
List of reference symbol:
Fig. 1:
100: Saddle type Vehicle
126: Handle Bar Assembly
119: Instrument Cluster
127: Head Lamp
111: Front Side Indicator
112: Leg shield
131: Front Fender
129: Front Wheel
130: Front Suspension
125: Engine
103: Fuel Tank Assembly
101: Frame member
132: Seat
138: Rear Fender
133: Rear Wheel
Fig. 2:
201: Cylinder Head
202: Thermostat
203: Coolant Pump
204: Cylinder Block
205: Crankcase
C-C’: Cylinder Axis
AA’: Section
Fig. 2a
213: cam chain window
Fig. 2b:
207: coolant jacket, cylinder head
208: coolant bypass inlet
209: coolant bypass pocket
210a, 210b; coolant jacket, cylinder block.
212: Balancer Shaft
202a; Outlet of thermostat
206: cover thermostat
211:Cover, coolant pump
X, Y, Z: passage of bypass circuit