EP3315738A1

EP3315738A1 - Engine

Info

Publication number: EP3315738A1
Application number: EP17196287.1A
Authority: EP
Inventors: Yasushi Matsushita
Original assignee: Yamaha Motor Co Ltd
Current assignee: Yamaha Motor Co Ltd
Priority date: 2016-10-18
Filing date: 2017-10-13
Publication date: 2018-05-02
Anticipated expiration: 2037-10-13
Also published as: EP3315738B1; JP2018066294A

Abstract

An oil tank (5) includes a first oil compartment (5A,5B) and a second oil compartment (5A,5B). A cylinder head (2) is supplied with a lubricating oil from the first oil compartment (5A,5B) when the lubricating oil has a temperature of less than a predetermined value. The cylinder head (2) is supplied with the lubricating oil at least from the second oil compartment (5A,5B) when the lubricating oil has a temperature of greater than or equal to the predetermined value. An outer surface of the first oil compartment (5A,5B) and an outer surface of the second oil
compartment (5A,5B) are exposed outside an engine (1). A sum of a surface area of an inner surface and a surface area of the outer surface of the first oil compartment (5Am5B) is smaller than a sum of a surface area of an inner surface and a surface area of the outer surface of the second oil compartment (5A,5B).

Description

The present invention relates to an engine and a method for supplying lubricating oil to a cylinder head of an engine.
It is preferred to warm lubricating oil quickly when the lubricating oil has a low temperature in such a condition as engine starting. Friction loss due to the lubricating oil is quickly reduced by quickly warming the lubricating oil, whereby enhancement in fuel consumption or reduction in exhaust gas can be achieved.
Because of the above, it has been proposed to use a double sump oil pan in the field of automobiles. For example, an engine described in JP 2006-77697 A includes an oil pan divided into a main compartment located on a lower side and a sub compartment located on an upper side. A thermostat valve is provided between the main compartment and the sub compartment.
When the lubricating oil has a temperature of less than or equal to a predetermined value, the thermostat valve is closed. With this configuration, the lubricating oil flows only from the sub compartment and circulates through the interior of the engine. Accordingly, the lubricating oil can be warmed quickly. On the other hand, when the lubricating oil has a temperature of greater than the predetermined value, the thermostat valve is opened. With this configuration, the lubricating oil flows from the main compartment as well as the sub compartment and circulates through the interior of the engine. Accordingly, excessive increase in temperature of the lubricating oil can be inhibited.
However, when the oil pan has a structure divided up and down as described above, increase in up-and-down directional dimension of the engine is inevitable. It is true of straddled vehicles, but is not the case for automobiles, that the up-and-down directional dimension of the engine affects the vehicle lowest height from the ground. Therefore, increase in up-and-down directional dimension of the engine is not preferred.
It is an object of the present invention to provide engine and a method for supplying lubricating oil to a cylinder head of an engine which can achieve quick warming of lubricating oil and inhibition of excessive increase in temperature of the lubricating oil with a compact structure. According to the present invention said object is solved by engine having the features of independent claim 1. Moreover, said object is also solved by method for supplying lubricating oil to a cylinder head of an engine having the features of independent claim 15. Preferred embodiments are laid down in the dependent claims. With said teaching applied to an engine in a straddled vehicle, inhibition of increase in up-and-down directional dimension of the engine, and besides, quick warming of lubricating oil and inhibition of excessive increase in temperature of the lubricating oil can be achieved.
An engine according to an aspect includes a cylinder head, a cylinder, a crankcase and an oil tank. The cylinder is connected to the cylinder head. The crankcase is connected to the cylinder. The oil tank includes a first oil compartment and a second oil compartment, and is disposed below the crankcase.
The cylinder head is supplied with a lubricating oil from the first oil compartment when the lubricating oil has a temperature of less than a predetermined value. The cylinder head is supplied with the lubricating oil at least from the second oil compartment when the lubricating oil has a temperature of greater than or equal to the predetermined value.
An outer surface of the first oil compartment is exposed outside the engine. An outer surface of the second oil compartment is exposed outside the engine. A sum of a surface area of an inner surface and a surface area of the outer surface of the first oil compartment is less than a sum of a surface area of an inner surface and a surface area of the outer surface of the second oil compartment.
In the engine according to the present aspect, the first oil compartment and the second oil compartment are disposed such that the outer surface of the first oil compartment and that of the second oil compartment are exposed outside the engine. Therefore, increase in up-and-down directional dimension of the engine can be inhibited compared to a configuration that the first and second compartments are disposed up and down to overlap one another.
Additionally, the sum of the surface areas of the inner and outer surfaces of the first oil compartment is smaller than that of the second oil compartment. Therefore, when the lubricating oil has a low temperature, the lubricating oil is circulated from the first oil compartment, whereby the amount of heat released from the outer surface of the first oil compartment can be reduced low. Accordingly, the lubricating oil can be warmed quickly. On the other hand, when the lubricating oil has a high temperature, the lubricating oil is circulated from the second oil compartment, whereby the heat release amount can be increased. Accordingly, excessive increase in temperature of the lubricating oil can be inhibited.
The lubricating oil from the cylinder head may return to the first oil compartment.
The cylinder head, the cylinder and the crankcase may be provided with a cam chain compartment inside thereof. The first oil compartment may be disposed adjacently to the cam chain compartment. The lubricating oil from the cylinder head may return to the first oil compartment through the cam chain compartment.
The lubricating oil from the cylinder and/or the crankcase may return to the first oil compartment.
It should be noted that in returning to the first oil compartment, the lubricating oil may return to the first oil compartment via the second oil compartment. Alternatively, the lubricating oil may return to the first oil compartment without via the second oil compartment.
The engine may further include an oil guide pathway. The oil guide pathway may lead the lubricating oil from the cylinder and/or the crankcase to flow to the first oil compartment.
The first oil compartment may have a smaller capacity than the second oil compartment.
The outer surface of the first oil compartment may have a smaller area than the outer surface of the second oil compartment.
The inner surface of the first oil compartment may have a smaller area than the inner surface of the second oil compartment.
The second oil compartment may include a fin protruding from the inner surface or the outer surface of the second oil compartment.
The first oil compartment and the second oil compartment may be provided adjacently to each other. The engine may further include a partition and a switch valve. The partition may be disposed between the first oil compartment and the second oil compartment, and may divide the first oil compartment and the second oil compartment. The switch valve may be provided in the partition, and may allow or block communication between the first oil compartment and the second oil compartment. The switch valve may block the communication between the first oil compartment and the second oil compartment when the lubricating oil supplied to the cylinder head has the temperature of less than the predetermined value. The switch valve may allow the communication between the first oil compartment and the second oil compartment when the lubricating oil supplied to the cylinder head has the temperature of greater than or equal to the predetermined value. A suction port of a supply pathway for supplying the lubricating oil to the cylinder head from the oil tank may be opened inside the first oil compartment.
The switch may be a thermostat that is closed when the lubricating oil has the temperature of less than the predetermined value and is opened when the lubricating oil has the temperature of greater than or equal to the predetermined value.
The engine may further include a cover attached to the crankcase. The partition may be integrated with the crankcase or the cover.
At least portion of the oil tank may be integrated with the crankcase.
The cylinder may be disposed in front of the crankcase. The cylinder head may be disposed in front of the cylinder. The cylinder may have a cylinder axis extending forward and obliquely upward. The first oil compartment may be disposed in front of the second oil compartment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a configuration of an engine according to a preferred embodiment.
FIG. 2 is a cross-sectional view of a structure of a switch valve.
FIG. 3 is a schematic diagram showing a top view layout of a first oil compartment and a second oil compartment.
FIG. 4 is a schematic diagram showing another exemplary top view layout of the first oil compartment and the second oil compartment.
FIG. 5 is a cross-sectional view of an engine according to a first practical example.
FIG. 6 is a cross-sectional view of the engine according to the first practical example.
FIG. 7 is a cross-sectional view of an engine according to a second practical example.
FIG. 8 is a cross-sectional view of an engine according to a third practical example.
FIG. 9 is a cross-sectional view of the engine according to the third practical example.
FIG. 10 is a cross-sectional view of an engine according to a fourth practical example.
FIG. 11 is a cross-sectional view of the engine according to the fourth practical example.
FIG. 12 is a cross-sectional view of an engine according to a fifth practical example.
FIG. 13 is a side view of an exemplary straddled vehicle in which the engine according to the preferred embodiment is installed.
FIG. 14 is a side view of another exemplary straddled vehicle in which the engine according to the preferred embodiment is installed.
FIG. 15 is a schematic diagram of an engine according to a first modification.
FIG. 16 is a schematic diagram of an engine according to a second modification.
FIG. 17 is a schematic diagram of an engine according to a third modification.
FIG. 18 is a schematic diagram of an engine according to a fourth modification.
FIG. 19 is a cross-sectional view of a switch valve according to a modification.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment will be hereinafter explained with reference to drawings. FIG. 1 is a schematic diagram of a configuration of an engine 1 according to the preferred embodiment. It should be noted that in the following explanation, front, rear, left, right, up and down directions are defined as meaning the front, rear, left, right, up and down directions, respectively, based on a condition that the engine 1 is installed in a straddled vehicle to be described.
As shown in FIG. 1, the engine 1 includes a cylinder head 2, a cylinder 3, a crankcase 4 and an oil tank 5. The cylinder head 2 is disposed in front of the cylinder 3. A cylinder axis Ax1 of the cylinder 3 extends forward and obliquely upward. The cylinder 3 is connected to the cylinder head 2. The cylinder 3 is disposed in front of the crankcase 4. The crankcase 4 is connected to the cylinder 3.
The oil tank 5 is disposed below the crankcase 4. The oil tank 5 stores lubricating oil. The oil tank 5 includes a first oil compartment 5a and a second oil compartment 5b. The outer surface of the first oil compartment 5a and that of the second oil compartment 5b are exposed outside the engine 1. Each of the first and second oil compartments 5a and 5b is opened upward.
The first and second oil compartments 5a and 5b are provided adjacently to each other. A partition 6 is disposed between the first oil compartment 5a and the second oil compartment 5b, whereby the first and second oil compartment 5a and 5b are divided through the partition 6. The partition 6 includes a communication hole 7. The first and second oil compartments 5a and 5b are communicated through the communication hole 7.
The engine 1 includes a supply pathway 8 for the lubricating oil, and is switchable between a first state and a second state. In the first state of the engine 1, the cylinder head 2 is supplied with the lubricating oil from the first oil compartment 5a through the supply pathway 8. In the second state of the engine 1, the cylinder head 2 is supplied with the lubricating oil from the second oil compartment 5b through the supply pathway 8. The lubricating oil supplied to the cylinder head 2 returns therefrom to the first oil compartment 5a through, for instance, a cam chain compartment to be described. Additionally, the lubricating oil supplied to the cylinder 3 and the crankcase 4 also returns therefrom to the first oil compartment 5a.
The supply pathway 8 includes a first suction port 11 and a second suction port 12. The first suction port 11 is opened in the first oil compartment 5a. The second suction port 12 is opened in the second oil compartment 5b. The engine 1 includes an oil pump 13 and a switch valve 14. FIG. 2 is a cross-sectional view of a structure of the switch valve 14.
The switch valve 14 is a thermostat that is switched in accordance with the temperature of the lubricating oil to be supplied to the cylinder head 2, and includes a thermo-element 15 and an urging member 16. When the lubricating oil to be supplied to the cylinder head 2 has a temperature of less than the predetermined value, the thermo-element 15 is held in a position shown in diagram (A) of FIG. 2 by the urging force of the urging member 16. In this state, the switch valve 14 connects the first suction port 11 and a connecting port 17 leading to the oil pump 13. Accordingly, the lubricating oil is sucked from the first oil compartment 5a through the first suction port 11 by the oil pump 13, and is supplied to the cylinder head 2 through the supply pathway 8.
When the lubricating oil has a temperature of greater than or equal to the predetermined value, the thermo-element 15 displaces against the urging force of the urging member 16 and moves to a position shown in diagram (B) of FIG. 2. In this state, the switch valve 14 connects the second suction port 12 and the connecting port 17 leading to the oil pump 13. Accordingly, the lubricating oil is sucked from the second oil compartment 5b through the second suction port 12 by the oil pump 13, and is supplied to the cylinder head 2 through the supply pathway 8.
FIG. 3 is a schematic diagram showing a top view layout of the first and second oil compartments 5a and 5b. As shown in FIG. 3, the first and second oil compartments 5a and 5b are disposed back and forth (this layout will be hereinafter referred to as "a first exemplary layout"). The capacity of the first oil compartment 5a is smaller than that of the second oil compartment 5b. It should be noted that the capacity of each oil compartment is defined as meaning the volume of the lubricating oil stored in each oil compartment when the engine 1 in an idling state.
The surface area of the outer surface of the first oil compartment 5a is smaller than that of the second oil compartment 5b. The surface area of the inner surface of the first oil compartment 5a is smaller than that of the second oil compartment 5b. Therefore, the sum of the surface areas of the inner and outer surfaces of the first oil compartment 5a is smaller than that of the second oil compartment 5b. It should be noted that the surface area of each oil compartment is defined as meaning the surface area of a spatial region in which the lubricating oil is stored when the engine 1 is in the idling state.
In the engine 1 according to the present preferred embodiment, the first and second oil compartments 5a and 5b are disposed such that the outer surface of the first oil compartment 5a and that of the second oil compartment 5b are exposed outside the engine 1. Therefore, increase in up-and-down directional dimension of the engine 1 can be herein inhibited compared to a configuration that the first and second oil compartments 5a and 5b are disposed up and down to overlap one another.
Additionally, the sum of the surface areas of the inner and outer surfaces of the first oil compartment 5a is smaller than that of the second oil compartment 5b. Therefore, when the lubricating oil to be supplied to the cylinder head 2 has a temperature of less than the predetermined value, the lubricating oil is circulated from the first oil compartment 5a, whereby the amount of heat released from the outer wall surface of the first oil compartment 5a can be reduced low. Accordingly, the lubricating oil can be warmed quickly.
Especially in traveling of the vehicle, the amount of discharge from the oil pump 13 is increased when engine rotational velocity becomes greater than or equal to idling rotational velocity. Because of this, the volume of the lubricating oil is reduced more in the first oil compartment 5a. Hence, the lubricating oil is unlikely to be cooled by the outside air. As a result, the lubricating oil can be warmed quickly.
On the other hand, when the lubricating oil has a temperature of greater than or equal to the predetermined value, the lubricating oil is circulated from the second oil compartment 5b, whereby the heat release amount can be increased. Accordingly, excessive increase in temperature of the lubricating oil can be inhibited.
In the aforementioned preferred embodiment, the first and second oil compartments 5a and 5b are disposed back and forth as shown in the first exemplary layout of FIG. 3. However, the layout of the first and second oil compartments 5a and 5b is not limited to the first exemplary layout and may be changed.
Diagram (A) of FIG. 4 shows a second exemplary layout. Diagram (B) of FIG. 4 shows a third exemplary layout. As shown in diagrams (A) and (B) of FIG. 4, the first and second oil compartments 5a and 5b may be disposed right and left. As shown in diagram (A) of FIG. 4, the first oil compartment 5a may be disposed on the left side, whereas the second oil compartment 5b may be disposed on the right side. Alternatively, as shown in diagram (B) of FIG. 4, the first oil compartment 5a may be disposed on the right side, whereas the second oil compartment 5b may be disposed on the left side.
Diagram (C) of FIG. 4 show a fourth exemplary layout. Diagram (D) of FIG. 4 shows a fifth exemplary layout. As shown in diagrams (C) and (D) of FIG. 4, the second oil compartment 5b may be continuously provided to be disposed behind and lateral to the first oil compartment 5a. As shown in diagram (C) of FIG. 4, the second oil compartment 5b may be continuously provided to be disposed behind and on the right of the first oil compartment 5a. Alternatively, as shown in diagram (D) of FIG. 4, the second oil compartment 5b may be continuously provided to be disposed behind and on the left of the first oil compartment 5a.
FIGS. 5 and 6 are cross-sectional views of an engine 1a according to a first practical example. In the engine 1a according to the first practical example, similarly to the first exemplary layout described above, the first oil compartment 5a is disposed in front of the second oil compartment 5b. The partition 6 extends in the right-and-left direction on the bottom portion of the crankcase 4, and divides the first and second oil compartments 5a and 5b back and forth. The first and second oil compartments 5a and 5b are integrated with the crankcase 4.
As shown in FIG. 6, the engine 1a according to the first practical example includes a cam chain compartment 22 in which a cam chain 21 is disposed. The cam chain compartment 22 is provided inside the cylinder head 2, the cylinder 3 and the crankcase 4. The lubricating oil supplied to the cylinder head 2 flows therefrom through the cam chain compartment 22 and then returns to the first oil compartment 5a.
As shown in FIG. 5, the engine 1a according to the first practical example includes an oil guide pathway 23. The oil guide pathway 23 leads the lubricating oil from the cylinder 3 and the crankcase 4 to the first oil compartment 5a. Part of the partition 6 composes the oil guide pathway 23. The partition 6 divides the first and second oil compartments 5a and 5b, and extends to a position between the second oil compartment 5b and a crankshaft 18 disposed inside the crankcase 4. Accordingly, the lubricating oil dripping from the crankshaft 18 flows along the partition 6 and is lead to the first oil compartment 5a. The partition 6 is integrated with the crankcase 4. It should be noted that the partition 6 may be provided separately from the crankcase 4.
FIG. 7 is a cross-sectional view of an engine 1b according to a second practical example. In the engine 1 b according to the second practical example, similarly to the second exemplary layout described above, the first and second oil compartments 5a and 5b are disposed right and left. The partition 6 extends in the back-and-forth direction on the bottom portion of the crankcase 4, and divides the first and second oil compartments 5a and 5b right and left.
Similarly to the engine 1a according to the first practical example, the engine 1b according to the second practical example includes the cam chain compartment 22. The first oil compartment 5a is disposed adjacently to the cam chain compartment 22, and the lubricating oil supplied to the cylinder head 2 flows through the cam chain compartment 22 and then returns to the first oil compartment 5a.
In the engine 1 b according to the second practical example, the crankcase 4 has a structure divided right and left. In this case, it is difficult to integrally form the partition 6 and the crankcase 4 by casting. Therefore, it is preferred that the partition 6 is provided separately from the crankcase 4 as a member made of sheet metal or so forth. In this case, it is preferred that the partition 6 is fixed to the crankcase 4 by fastening means such as bolts.
It should be noted that in the engine 1 b according to the second practical example, the first and second oil compartments 5a and 5b may be disposed in the fourth exemplary layout described above.
FIGS. 8 and 9 are cross-sectional views of an engine 1c according to a third practical example. In the engine 1c according to the third practical example, similarly to the third exemplary layout described above, the first and second oil compartments 5a and 5b are disposed right and left. In the engine 1c according to the third practical example, a cover 24, provided separately from the crankcase 4, is attached to the crankcase 4. The engine 1 c according to the third practical example includes an electric power generator 25, and the electric power generator 25 is covered with the cover 24. The first oil compartment 5a is disposed adjacently to a space in which the electric power generator 25 is disposed.
portion of the first oil compartment 5a is integrated with the cover 24. The first oil compartment 5a is provided in the crankcase 4 as well as in the cover 24. It should be noted that portion of the second oil compartment 5b may be integrated with the cover 24.
It should be noted that in the engine 1c according to the third practical example, the first and second oil compartments 5a and 5b may be disposed in the fifth exemplary layout described above.
FIGS. 10 and 11 are cross-sectional views of an engine 1d according to a fourth practical example. In the engine 1d according to the fourth practical example, similarly to the third exemplary layout described above, the first and second oil compartments 5a and 5b are disposed right and left. The engine 1d according to the fourth practical example is a single-cylinder engine including a manual transmission 26. As shown in FIG. 10, the manual transmission 26 includes a plurality of shift gears 27 and a clutch 28. The clutch 28 is covered with the cover 24. It should be noted that in the drawings, reference sign 27 is assigned to only part of the plural shift gears 27.
In the engine 1d according to the fourth practical example, the first oil compartment 5a is disposed adjacently to a space in which the clutch 28 is disposed. The second oil compartment 5b is disposed adjacently to a space in which the shift gears 27 are disposed. The first oil compartment 5a is provided in the cover 24 as well as in the crankcase 4. The second oil compartment 5b is integrated with the crankcase 4.
The oil guide pathway 23 is disposed between the second oil compartment 5b and the space in which the shift gears 27 are disposed. The lubricating oil dripping from the shift gears 27 flows along the oil guide pathway 23, and is thus led to the first oil compartment 5a.
It should be noted that in the engine 1d according to the fourth practical example, the first and second oil compartments 5a and 5b may be disposed in the fifth exemplary layout described above.
FIG. 12 is a cross-sectional view of an engine 1e according to a fifth practical example. In the engine 1e according to the fifth practical example, similarly to the third exemplary layout described above, the first and second oil compartments 5a and 5b are disposed right and left. The engine 1e according to the fifth practical example is a multicylinder engine including the manual transmission 26.
In the engine 1e according to the fifth practical example, an oil pan 29, provided separately from the crankcase 4, is attached to the crankcase 4. The first and second oil compartments 5a and 5b are integrated with the oil pan 29. The partition 6 is integrated with the oil pan 29. Alternatively, the partition 6 may be provided separately from the oil pan 29.
In the engine 1 e according to the fifth practical example, similarly to the engine 1d according to the fourth practical example, the first oil compartment 5a is disposed adjacently to a space in which the clutch 28 is disposed. The second oil compartment 5b is disposed adjacently to a space in which the plural shift gears 27 of the manual transmission 26 are disposed. Additionally, the oil guide pathway 23 is disposed between the second oil compartment 5b and the space in which the plural shift gears 27 are disposed, and leads the lubricating oil dripping from the plural shift gears 27 to the first oil compartment 5a.
It should be noted that in the engine 1 e according to the fifth practical example, the first and second oil compartments 5a and 5b may be disposed in the fifth exemplary layout described above. Alternatively, in the engine 1e according to the fifth practical example, the first and second oil compartments 5a and 5b may be disposed in the first exemplary layout described above.
Next, a straddled vehicle, in which the engine 1 according to the aforementioned preferred embodiment is installed, will be explained. FIG. 13 is a side view of a straddled vehicle 100 that is an exemplary straddled vehicle in which the engine 1 is installed. The straddled vehicle 100 is a motorcycle of a scooter type. The straddled vehicle 100 includes a steering device 101, a vehicle body 102, a power unit 103, a front wheel 104, a rear wheel 105 and a seat 106.
The steering device 101 includes a front fork 107. The front fork 107 supports the front wheel 104 such that the front wheel 104 is rotatable. A handle 108 is provided on the upper portion of the steering device 101.
The vehicle body 102 includes a front cover 131, a rear cover 133 and a lower cover 134. The front cover 131 covers the steering device 101 from the front and the back. The rear cover 133 is disposed below the seat 106. The lower cover 134 is disposed between the front cover 131 and the rear cover 133. The upper surface of the lower cover 134 includes a footboard 135. The footboard 135 is disposed such that the legs of a rider are put thereon. The footboard 135 has a flat shape. The footboard 135 may be entirely flat in a vehicle width direction. Alternatively, the footboard 135 may have an upwardly protruding shape in the vehicle width directional middle portion thereof.
The power unit 103 is disposed below the seat 106. The power unit 103 is pivotably supported by the vehicle body 102. The power unit 103 supports the rear wheel 105 such that the rear wheel 105 is rotatable. The power unit 103 includes the engine 1. The engine 1 is disposed below the seat 106. The cylinder axis Ax1 of the engine 1 tilts forward and upward.
FIG. 14 is a side view of a straddled vehicle 200 that is another exemplary straddled vehicle in which the engine 1 according to the aforementioned preferred embodiment is installed. The straddled vehicle 200 is a motorcycle of a so-called sport type. The straddled vehicle 200 includes a fuel tank 201, a seat 202 and a vehicle body frame 203.
The fuel tank 201, the seat 202 and the engine 1 are supported by the vehicle body frame 203. The fuel tank 201 is disposed in front of the seat 202. The engine 1 is disposed below the fuel tank 2.
The straddled vehicle 200 includes a steering device 204, a front wheel 205, a handle 206 and a headlight unit 207. The steering device 204 includes a front fork 209. The front fork 209 supports the front wheel 205 such that the front wheel 205 is rotatable. The handle 206 is provided on the upper portion of the steering device 204. The headlight unit 207 is disposed in front of the fuel tank 201.
The straddled vehicle 200 includes a swing arm 211 and a rear wheel 212. The swing arm 211 backwardly extends from the vehicle body frame 203. The swing arm 211 is connected to the vehicle body frame 203 while being pivotable up and down. The rear wheel 212 is rotatably supported by the rear portion of the swing arm 211.
One preferred embodiment has been explained above. However, the present teaching is not limited to the aforementioned preferred embodiment, and a variety of changes can be made without departing from the gist of the present teaching.
The switch valve 14 is not limited to the thermostat, and alternatively, may be an electrically actuated valve or a hydraulically actuated valve. The oil guide pathway 23 may lead the lubricating oil to the first oil compartment 5a only when the lubricating oil flows thereto from the cylinder 3. Alternatively, the oil guide pathway 23 may lead the lubricating oil to the first oil compartment 5a only when the lubricating oil flows thereto from the crankcase 4.
In the aforementioned preferred embodiment, when the lubricating oil to be supplied to the cylinder head 2 has a temperature of greater than or equal to the predetermined value, the lubricating oil is supplied from the second oil compartment 5b. However, when the lubricating oil to be supplied to the cylinder head 2 has a temperature of greater than or equal to the predetermined value, the lubricating oil may be supplied from both the first oil compartment 5a and the second oil compartment 5b. FIG. 15 is a schematic diagram of the engine 1 according to a first modification.
As shown in FIG. 15, the engine 1 according to the first modification includes the switch valve 14 provided in the partition 6. The switch valve 14 allows or blocks communication between the first oil compartment 5a and the second oil compartment 5b. The switch valve 14 is a thermostat that is closed when the lubricating oil has a temperature of less than a predetermined value and is opened when the lubricating oil has a temperature of greater than or equal to the predetermined value.
A suction port 31 of the supply pathway 8 for supplying the lubricating oil from the oil tank 5 to the cylinder head 2 is opened inside the first oil compartment 5a. When the lubricating oil to be supplied to the cylinder head 2 has a temperature of less than the predetermined value, the switch valve 14 blocks communication between the first oil compartment 5a and the second oil compartment 5b. Accordingly, the oil pump 13 supplies the lubricating oil to the cylinder head 2 from the first oil compartment 5a. The lubricating oil is thus circulated from the first oil compartment 5a, whereby the lubricating oil can be warmed quickly.
When the lubricating oil to be supplied to the cylinder head 2 has a temperature of greater than or equal to the predetermined value, the switch valve 14 allows communication between the first oil compartment 5a and the second oil compartment 5b. Accordingly, the oil pump 13 supplies the lubricating oil to the cylinder head 2 from both the first oil compartment 5a and the second oil compartment 5b. The lubricating oil is thus circulated from both the first oil compartment 5a and the second oil compartment 5b, whereby excessive increase in temperature of the lubricating oil can be inhibited.
In the aforementioned preferred embodiment, supplying the lubricating oil in the engine 1 is switched by the switch valve 14, but may be switched by means other than the switch valve 14. For example, FIG. 16 is a schematic diagram of the engine 1 according to a second modification.
In the engine 1 according to the second modification, oil pumps 13a and 13b, which are independent from each other, are provided in the first and second oil compartments 5a and 5b, respectively. In other words, the engine 1 according to the second modification includes a first oil pump 13a and a second oil pump 13b. The first oil pump 13a sucks the lubricating oil from the first oil compartment 5a through the first suction port 11. The second oil pump 13b sucks the lubricating oil from the second oil compartment 5b through the second suction port 12.
When the lubricating oil to be supplied to the cylinder head 2 has a temperature of less than a predetermined value, the first oil pump 13a is driven. Accordingly, the lubricating oil is supplied to the cylinder head 2 from the first oil compartment 5a. When the lubricating oil to be supplied to the cylinder head 2 has a temperature of greater than or equal to the predetermined value, the first and second oil pumps 13a and 13b are driven. Accordingly, the lubricating oil is supplied to the cylinder head 2 from the first oil compartment 5a and the second oil compartment 5b.
It should be noted that when the lubricating oil to be supplied to the cylinder head 2 has a temperature of greater than or equal to the predetermined value, only the second oil pump 13b may be driven without driving of the first oil pump 13a.
In the aforementioned preferred embodiment, the first oil compartment 5a is disposed in front of the second oil compartment 5b. However, the first oil compartment 5a may be disposed behind the second oil compartment 5b. For example, FIG. 17 is a schematic diagram of the engine 1 according to a third modification.
As shown in FIG. 17, in the engine 1 according to the third modification, the first oil compartment 5a is disposed behind the second oil compartment 5b. Additionally, an oil guide pathway 32 is disposed above the second oil compartment 5b. The oil guide pathway 32 leads the lubricating oil from the cylinder head 2, the cylinder 3 or the crankcase 4 to the first oil compartment 5a.
The surface area of the second oil compartment 5b may be expanded by providing the second oil compartment 5b with fins. For example, FIG. 18 is a schematic diagram of the engine 1 according to a fourth modification. As shown in FIG. 18, the second oil compartment 5b is provided with a plurality of fins 33 protruding from the inner surface of the second oil compartment 5b. The surface area of the inner surface of the second oil compartment 5b is expanded by providing the second oil compartment 5b with the fins 33. Accordingly, the amount of heat released in the second oil compartment 5b can be increased.
It should be noted that the fins 33 may protrude from the outer surface of the second oil compartment 5b. Accordingly, the surface area of the outer surface of the second oil compartment 5b can be expanded. Alternatively, the fins 33 may be provided to protrude from both the outer surface and the inner surface of the second oil compartment 5b.
The structure of the switch valve 14 may be changed. For example, the switch valve 14 may be switched to a state in which the thermo-element 15 is set in an intermediate position so as to suck the lubricating oil from both the first oil compartment 5a and the second oil compartment 5b. Specifically, when the thermo-element 15 is set in the intermediate position shown in FIG. 19, the switch valve 14 connects the first suction port 11 and the connecting port 17, and simultaneously, connects the second suction port 12 and the connecting port 17. Accordingly, the lubricating oil is sucked from the first oil compartment 5a and the second oil compartment 5b by the oil pump 13, and is supplied to the cylinder head 2 through the supply pathway 8.
In the aforementioned preferred embodiments, the crankcase and the oil tank are configured as one unit. However, within an alternative embodiment, crankcase and the oil tank are configured separately.

Claims

An engine (1) comprising:
a cylinder head (2);

a cylinder (3) connected to the cylinder head (2);

a crankcase (4) connected to the cylinder (3); and

an oil tank (5) including a first oil compartment (5a) and a second oil compartment (5b), the oil tank (5) being disposed below the crankcase (4), wherein

the engine comprises means (14) configured to supply the cylinder head (2) with a lubricating oil from the first oil compartment (5a) when the lubricating oil has a temperature of less than a predetermined value,

the engine comprises means (14) configured to supply the cylinder head (2) with the lubricating oil at least from the second oil compartment (5b) when the lubricating oil has a temperature of greater than or equal to the predetermined value,

an outer surface of the first oil compartment (5a) is exposed outside the engine (1), an outer surface of the second oil compartment (5b) is exposed outside the engine (1), and

a sum of a surface area of an inner surface and a surface area of the outer surface of the first oil compartment (5a) is less than a sum of a surface area of an inner surface and a surface area of the outer surface of the second oil compartment (5b).
An engine (1) according to claim 1, wherein the engine comprises means configured to return the lubricating oil from the cylinder head (2) to the first oil compartment (5a).
An engine (1) according to claim 1 or 2, wherein the cylinder head (2), the cylinder (3) and the crankcase (4) are provided with a cam chain compartment (22) inside thereof, the first oil compartment (5a) is disposed adjacently to the cam chain compartment (22), and the engine comprises means configured to return the lubricating oil from the cylinder head (2) returns to the first oil compartment (5a) through the cam chain compartment (22).
An engine (1) according to any of claims 1 to 3, wherein the engine comprises means (14) configured to return the lubricating oil from the cylinder (3) and/or the crankcase (4) to the first oil compartment (5a).
An engine (1) according to any of claims 1 to 4, further comprising an oil guide pathway (23) configured to lead the lubricating oil from the cylinder (3) and/or the crankcase (4) to flow to the first oil compartment (5a).
An engine (1) according to any of claims 1 to 5, wherein the first oil compartment (5a) has a smaller capacity than the second oil compartment (5b).
An engine (1) according to any of claims 1 to 6, wherein the outer surface of the first oil compartment (5a) has a smaller area than the outer surface of the second oil compartment (5b).
An engine (1) according to any of claims 1 to 7, wherein the inner surface of the first oil compartment (5a) has a smaller area than the inner surface of the second oil compartment (5b).
An engine (1) according to any of claims 1 to 8, wherein the second oil compartment (5b) includes at least one fin (33) protruding from the inner surface or the outer surface of the second oil compartment (5b).
An engine (1) according to any of claims 1 to 9, wherein the first oil compartment (5a) and the second oil compartment (5b) are provided adjacently to each other,
the engine (1) further comprises
a partition (6) disposed between the first oil compartment (5a) and the second oil compartment (5b), the partition (6) dividing the first oil compartment (5a) and the second oil compartment (5b), and
a switch valve (14) provided in the partition (6), the switch valve (14) is configured to allow or block communication between the first oil compartment (5a) and the second oil compartment (5b),
the switch valve (14) is configured to block the communication between the first oil compartment (5a) and the second oil compartment (5b) when the lubricating oil supplied to the cylinder head (2) has the temperature of less than the predetermined value,
the switch valve (14) is configured to allow the communication between the first oil compartment (5a) and the second oil compartment (5b) when the lubricating oil supplied to the cylinder head (2) has the temperature of greater than or equal to the predetermined value, and
a suction port (11) of a supply pathway (8) for supplying the lubricating oil to the cylinder head (2) from the oil tank (5) is opened inside the first oil compartment (5a).
An engine (1) according to claim 10, wherein the switch valve (14) is a thermostat, the thermostat is configured to be closed when the lubricating oil has the temperature of less than the predetermined value, the thermostat is configured to be opened when the lubricating oil has the temperature of greater than or equal to the predetermined value.
An engine (1) according to claim 10 or 11, further comprising a cover (24) attached to the crankcase (4), wherein the partition (6) is integrated with the crankcase (4) or the cover (24).
An engine (1) according to any of claims 1 to 11, wherein at least portion of the oil tank (5) is integrated with the crankcase (4).
A vehicle provided with an engine (1) according to any of claims 1 to 13, wherein the cylinder (3) is disposed in front of the crankcase (4),
the cylinder head (2) is disposed in front of the cylinder (3),
the cylinder (3) has a cylinder (3) axis extending forward and obliquely upward, and
the first oil compartment (5a) is disposed in front of the second oil compartment (5b).
A method for supplying lubricating oil to a cylinder head (2) of an engine (1) with a cylinder (3) connected to the cylinder head (2), a crankcase (4) connected to the cylinder (3), and an oil tank (5) including a first oil compartment (5a) and a second oil compartment (5b), preferably the oil tank (5) being disposed below the crankcase (4), an outer surface of the first oil compartment (5a) is exposed outside the engine (1), and an outer surface of the second oil compartment (5b) is exposed outside the engine (1), and a sum of a surface area of an inner surface and a surface area of the outer surface of the first oil compartment (5a) is less than a sum of a surface area of an inner surface and a surface area of the outer surface of the second oil compartment (5b), according to the method the cylinder head (2) is supplied with a lubricating oil from the first oil compartment (5a) when the lubricating oil has a temperature of less than a predetermined value, and the cylinder head (2) is supplied with the lubricating oil at least from the second oil compartment (5b) when the lubricating oil has a temperature of greater than or equal to the predetermined value.