JP2001248415A - Oil return structure in engine - Google Patents

Abstract

(57) Abstract: A cylinder head having an exhaust port opened downward is connected to a cylinder block having a cylinder bore inclined with the cylinder head side as an upper position, and a valve operating chamber for accommodating a valve operating mechanism is provided. In an engine in which a head cover formed between the cylinder head and the cylinder head is coupled to the cylinder head, a simple structure capable of avoiding an increase in the size and weight of the engine can be used to quickly raise the temperature of the oil. Return oil from the valve chamber to the crankcase. An oil return passage for returning oil from a valve operating chamber to a crank chamber in a crankcase.
However, the cylinder head 39 surrounds a part of the exhaust port 71.
Is provided at the lower part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a valve operating system for accommodating a valve operating mechanism in which a cylinder head having an exhaust port opened downward is connected to a cylinder block having a cylinder bore inclined with the cylinder head side as an upper position. The present invention relates to an oil return structure for returning oil from a valve operating chamber to a crank chamber in an engine in which a head cover that forms a chamber between the cylinder head and the cylinder head is connected to the cylinder head.

[0002]

2. Description of the Related Art It is possible to shorten the warm-up time of an engine by rapidly raising the temperature of lubricating oil at the time of starting the engine. Japanese Patent Application Laid-Open No. 9-20973 discloses a method for shortening the warm-up time of
This is already known from Japanese Patent Publication No.

[0003]

However, in the case where the oil is heated by the heater as in the prior art, the size of the engine is increased due to the balance between the capacity of the generator for supplying power to the heater and the power consumption of the heater. This leads to an increase in weight.

The present invention has been made in view of the above circumstances, and provides an oil return structure in an engine capable of quickly raising the temperature of oil with a simple configuration capable of avoiding an increase in the size and weight of the engine. The purpose is to do.

[0005]

In order to achieve the above object, according to the present invention, a cylinder head having an exhaust port opened downward has a cylinder bore inclined with the cylinder head side as an upper position. A head cover coupled to the cylinder block and forming a valve train accommodating a valve mechanism between the cylinder head and the head cover is formed in a crankcase coupled to the cylinder block in an engine coupled to the cylinder head. An oil return passage for returning oil from the valve operating chamber to the crank chamber is provided below the cylinder head so as to surround a part of the exhaust port.

According to the first aspect of the present invention, heat from the exhaust gas is effectively transmitted to the oil returning from the valve operating chamber to the crank chamber via the wall constituting the exhaust port. You. Therefore, the temperature of the oil can be quickly raised by utilizing the heat of the exhaust port, the temperature of which rises most quickly at the time of cold start of the engine, and the warm-up performance of the engine can be improved. In addition, since the oil return passage is provided only at the lower part of the cylinder head so as to surround a part of the exhaust port, the structure for rapidly raising the temperature of the oil is extremely simple. In comparison, the size and weight of the engine can be reduced.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention described above, an on-off valve capable of opening and closing the oil return passage is provided in the cylinder head, and a passage that can return oil in the valve operating chamber to the crank chamber side in response to closing of the on-off valve. According to this configuration, the oil return passage is closed by an on-off valve, so that the oil is removed through another passage separated from the exhaust port. Returns to the crankcase side, so that the influence of heat from the exhaust port on the oil is reduced, and overheating of the oil can be prevented by opening and closing the on-off valve.

According to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the projection of the exhaust port on a plane perpendicular to the axis of the cylinder bore is provided.
The exhaust port is curved so that one side of a vertical line passing through the center of the combustion chamber facing the top of the piston slidably fitted to the cylinder bore has an arc shape bulging toward the vertical side. The oil return passage is formed and provided in the cylinder head so as to open below the exhaust port and below the valve chamber. According to such a configuration, the curvature of the exhaust port is utilized. Therefore, an oil return passage can be provided in the cylinder head without increasing the size of the cylinder head, and a relatively large area of the outer periphery of the wall of the exhaust port can be effectively used for raising the temperature of the oil. Even if the lean burn operation associated with swirling by bending the exhaust port is executed, it is possible to compensate for the decrease in warm-up property due to the lean burn.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on one embodiment of the present invention shown in the attached drawings.

FIGS. 1 to 10 show one embodiment of the present invention. FIG. 1 is a side view of a motorcycle, and FIG.
FIG. 3 is an enlarged view of a main part of FIG. 2, FIG. 4 is an enlarged view of the power unit taken along a line 4-4 in FIG. 3, with a head cover removed, and FIG. 6 is an enlarged view of a main part of FIG. 3, FIG. 7 is an enlarged vertical sectional view of a thermostat in a cold state of the engine, and FIG.
8 is a cross-sectional view corresponding to FIG. 7 in a state where engine warm-up is completed, FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 8, and FIG.
It is a line sectional view.

Referring to FIG. 1, a motorcycle body frame 15 has a front pipe W provided at a front end thereof with a front wheel W.
A front fork 17 that supports F is pivotally supported so as to be steerable. A bar-shaped steering handle 18 is connected to an upper end of the front fork 17, and a front fender 19 that covers an upper part of the front wheel WF is supported by the front fork 17. A rear fork 20 that supports the rear wheel WR is pivotally supported at an intermediate portion of the body frame 15, and a rear cushion 21 is provided between the rear portion of the body frame 15 and the rear fork 20.

A power unit P comprising a water-cooled engine E and a transmission M is supported at an intermediate portion of the body frame 15, and the output of the transmission M is transmitted to the rear wheels WR via a chain (not shown). , The chain is covered with a chain cover 22.

The air cleaner 23 and the radiator 24 disposed above the engine E are connected to the body frame 1.
5, a fuel tank 25 disposed above the transmission M, and a storage box 26 disposed above the fuel tank 25 so that electrical components can be stored are supported by the vehicle body frame 15.

An exhaust pipe 27 for guiding exhaust gas from the engine E is connected to an exhaust muffler 28 disposed between the power unit P and the rear wheels WR.

The front portion of the vehicle body frame 15, the engine E, the air cleaner 23, and the radiator 24 are covered with a leg shield 29 made of synthetic resin and attached to the vehicle body frame 15. The rear part of the body frame 15, the fuel tank 25 and the storage box 26
A rear fender 31 is provided on the rear cover 30 to cover an upper rear portion of the rear wheel WR. On the rear cover 30,
A seat 32 is provided so that the upper end opening of the storage box 26 can be opened and closed, and a driver can sit on the seat 32.

In front of the driver sitting on the seat 32, a windscreen 33 having a light-transmitting property for protecting the driver from wind, rain and the like is arranged. The base end of a pair of left and right stays 34 extending upward in a rod shape is attached to the rod-like steering handle 18. Shafts extending downward from the upper ends of the stays 34 and the left and right mirrors 35. The lower ends of the parts 36 are fastened with the wind screen 33 interposed therebetween. That is, the left and right mirrors 35 are attached to the steering handle 18 and the wind screen 33 is attached to the steering handle 18.

2 to 5, the engine body 37 of the water-cooled engine E has a cylinder block 38 having a cylinder bore 44 into which a piston 43 is slidably fitted.
And a cylinder head 39 connected to a cylinder block 38 by forming a combustion chamber 45 between the top of the piston 43 and a crankshaft 47 connected to the piston 43 via a connecting rod 46. And a crankcase 40 coupled to the cylinder block 38. The cylinder block 38, the cylinder head 39 and the crankcase 40 are fastened by a plurality of, for example, four through bolts 41. Further, the crankcase 40 is configured such that the right crankcase half 40a and the left crankcase half 40b are connected to each other with a plane including the operating axis of the piston 43 as a mating surface. A crank chamber 42 is formed. Further, the engine body 37 is supported by the vehicle body frame 15 with the cylinder head 39 disposed immediately after the front wheel WF being in the upper position and the axis of the cylinder bore 44 being inclined forward and upward.

The cylinder block 38 and the cylinder head 39 of the engine body 37 are provided with a jacket 48 for flowing cooling water. The cylinder head 39 has a pair of spark plugs having different ignition timings. 49 and 50 are attached so as to face the combustion chamber 45.

The transmission M has a main shaft 51 and a countershaft 52 having an axis parallel to the crankshaft 47 and rotatably supported by the crankcase 40.
And a plurality of gear trains 53 provided between the main shaft 51 and the counter shaft 52 to enable selective establishment.
Shift drum 54 that rotates to selectively establish 3
Is rotatably supported.

One end of a crankshaft 47 projecting from the right crankcase half 40a is connected to a drive gear 56 via a centrifugal clutch 55.
The driven gear 57 meshing with the right crankcase half 40
and is rotatably supported on one end side of a main shaft 51 protruding from a. The driven gear 57 is connected to a clutch outer 60 of a clutch 59 via a damper 58. The clutch 59 is a multi-plate clutch that disconnects and connects between the clutch inner 62 connected to the main shaft 51 and the clutch outer 60 by the action of the release cam mechanism 61 in response to the driver's operation. In this state, the gear train 53 can be selectively established. The centrifugal clutch 55 and the clutch 59 are covered with a right cover 63 connected to the right crankcase half 40a.

A driving sprocket 64 covered with the chain cover 22 is fixed to an end of the counter shaft 52 protruding from the left crankcase half 40b, and a rear wheel WR is connected via a chain wound around the driving sprocket 64. Power is transmitted to.

A rotor 66 of a generator 65 is fixed to the other end of the crankshaft 47 protruding from the left crankcase half 40b, and is connected to the left crankcase half 40b so as to cover the generator 65. Left cover 68
, The stator 67 of the generator 65 is fixed.

With particular attention to FIG.
An intake port 70 for supplying an air-fuel mixture to the combustion chamber 45 is provided so as to open upward above the cylinder head 39, and an exhaust port 71 for discharging exhaust gas from the combustion chamber 45 is provided. Is the cylinder head 3
9 is provided so as to open downward at the lower part. The air cleaner 23 is connected to the intake port 70 via a carburetor (not shown), and the exhaust pipe 27 is connected to the exhaust port 71.

Moreover, the intake port 70 and the exhaust port 7
1 is curved so as to open into the combustion chamber 45 at a position deviated from the center line of the combustion chamber 45, that is, the axis of the cylinder bore 44, so as to generate swirl in the combustion chamber 45. A projection (projection indicated by a dotted line in FIG. 4) onto a plane orthogonal to the axis of the cylinder bore 44 is shown in FIG.
One side (left side in FIG. 4) of the vertical line 73 that takes the center 72 of the combustion chamber 45 is curved so as to form an arc bulging toward the vertical line 73.

An intake valve 74 for switching the communication between the intake port 70 and the combustion chamber 45, and an exhaust port 71
Exhaust valve 75 for switching between communication and shutoff between the combustion chamber 45
Is provided on the cylinder head 39 so as to be capable of opening and closing, and the intake valve 74 and the exhaust valve 75 are spring-biased in the valve closing direction.

The intake valve 74 and the exhaust valve 75 are opened and closed by a valve operating mechanism 76. The valve operating mechanism 76 includes a cylinder head 39 and the cylinder head 3.
9 is housed in a valve operating chamber 79 formed between the head cover 78 and a plurality of bolts 77.

The valve operating mechanism 76 includes a crankshaft 4
7, which is rotatably supported by the cylinder head 39 with an axis parallel to that of the cam 7, and on the intake side and exhaust side cams 81, 8.
And a camshaft 80 provided with the camshaft 8
The intake-side and exhaust-side rocker shafts 83 and 84 supported by the cylinder head 39 and having an axis parallel to 0, and the intake-side rocker shaft 83 driven by the intake-side cam 81 to open and close the intake valve 74. An exhaust-side rocker arm 85 is swingably supported, and an exhaust-side rocker arm 86 is swingably supported by an exhaust-side rocker shaft 84 to open and close the exhaust valve 75 following the exhaust-side cam 82.

Referring to FIG. 2, a driving sprocket 87 is fixed to the crankshaft 47 between the left crankcase half 40b of the crankcase 40 and the generator 65, and corresponds to the driving sprocket 87. A chain passage 88 connecting the crank chamber 42 in the crankcase 40 and the valve operating chamber 79 at a portion thereof is provided in the exhaust port 7.
Left crankcase half 40 at a position relatively distant from 1
b, provided between the cylinder block 38 and the cylinder head 39.

On the other hand, a driven sprocket 89 is provided at an end of the camshaft 80 at a portion corresponding to the chain passage 88.
Is fixed, and an endless chain 90 that can run in a chain passage 88 is wound around the driven sprocket 89 and the driving sprocket 87.

The chain 90 between the driving sprocket 87 and the driven sprocket 89 is connected to the cylinder block 3.
8 around the idle sprocket 91 and the chain 90 between the idle sprocket 91 and the driving sprocket 87.
A tension is applied by a tensioner 92 disposed at 0b.

With particular attention to FIGS. 2 and 5, an oil pump 95 is provided on the outer side of the right crankcase half 40a.
Is mounted, and the rotary shaft 9 of the oil pump 95 is mounted.
The driven gear 97 provided on the crankshaft 47
The drive gear 98 rotates integrally with the drive gear 98.

The oil pump 95 is for pumping oil from a lower portion in the crank chamber 42, and the oil discharged from the oil pump 95 is used for the right crankcase half 4
Piston jet 99 mounted on the inner side of
And is supplied to the crankshaft 47 through the passage 100 provided in the right crankcase half 40a and the right cover 63 as indicated by the arrow.

Incidentally, of the plurality of through bolts 41 for fastening the cylinder block 38, the cylinder head 39 and the crankcase 40, the through bolts 41 arranged below the cylinder head 39 and adjacent to the exhaust port 71 The inner diameters of the insertion holes provided in the cylinder block 38 and the cylinder head 39 so that the
An annular passage 102 is formed around the through bolt 41, and a part of oil discharged from an oil pump 95 is supplied to the passage 102 through an orifice 101. The cylinder head 39 is provided with a passage 104 for communicating the passage 102 with a passage 103 in the camshaft 80.
Each of the cams 81, 82 is provided with oil supply holes 105, 106 for guiding oil from the passage 104 to a sliding portion between the cams 81, 82 and the rocker arms 85, 86.

In this manner, each of the oil supply holes 105, 10
6 supplies oil to the valve operating mechanism 76, and the oil after lubricating the valve operating mechanism 76 is guided to the lower part in the valve operating chamber 79.

The cylinder head 39 is provided with an oil return passage 107 for returning oil in the valve operating chamber 79 to the crank chamber 42 side. Passage 10
8 communicates with the crank chamber 42.

Further, the oil return passage 107 of the cylinder head 39 is located below the exhaust port 71 on the opposite side of the passage 102 surrounding the through bolt 41, and
1 is provided at the lower portion of the cylinder head 39 so as to surround a part of the oil return passage 107.
The opening to 9 is set at a position lower than the opening to the valve chamber 79 of the chain passage 88.

The valve operating chamber 7 of the oil return passage 107
An opening / closing valve 109 capable of opening and closing a portion closer to 9 is provided in the cylinder head 39. The opening / closing valve 109 includes, for example, a valve body 110 capable of opening and closing the oil return passage 107, and a driving unit for driving the valve body 110 When the temperature of the oil flowing through the oil return passage 107 becomes equal to or higher than the set temperature, the driving unit 111
11 is driven to close the valve.

The oil that has accumulated in the lower portion of the valve operating chamber 79 when the on-off valve 109 is closed is reduced as the liquid level of the oil reaches the opening of the chain passage 88 to the valve operating chamber 79. It is returned from the chain passage 88 to the crank chamber 42 side.

In FIG. 6, the water pump 11 having a rotation axis coaxial with the camshaft 80 of the valve mechanism 76 is attached to the cylinder head 39. The pump housing 116 of the water pump 115 has a housing main body 117 opened on the side opposite to the camshaft 80, a mounting cylinder 118 engaged with the outer periphery of the open end of the housing main body 117, and an open end of the housing main body 117 closed. The partition 119 is fitted to the inner periphery of the open end of the housing main body 117 as described above, and the pump cover 120 sandwiches the open end of the housing main body 117 and the partition plate 119 between the mounting cylinder 118. The mounting cylinder 118 is fastened to the cylinder head 39.

The housing main body 117 includes the camshaft 8.
The dish-shaped part 11 is attached to the open end of the bottomed cylindrical part 117a with the zero side closed.
7b are integrally connected to each other.
17 a is coaxially inserted into a driven gear 89 formed in a cylindrical shape and fixed to the camshaft 80.

At the center of the closed end of the bottomed cylindrical portion 117a and at the center of the partition plate 119, both ends of a rotary shaft 121 are rotatably supported. A plurality of magnets 123, 123 are provided on the outer surface of the rotor 122 inserted in the cylindrical portion 117a.
... is fixed. On the other hand, a plurality of magnets 124 are fixed to the inner periphery of the driven gear 89, and the driven gear 89 is driven by the camshaft 8 to drive the valve mechanism 76.
The rotor 122 rotates together with the rotating shaft 121 in accordance with the rotation with the rotation shaft 121.

The dish-shaped portion 117 of the housing main body 117
A swirl chamber 125 partitioned from the pump cover 120 by a partition plate 119 is formed in b. An impeller 126 housed in the swirl chamber 125 is provided on the rotor 122.

At a plurality of locations surrounding the rotary shaft 121 at the center of the partition plate 119, there are provided suction ports 127 communicating with the center of the vortex chamber 125. The suction ports 127 are sucked into the vortex chamber 125 from the suction ports 127. The cooling water is pressurized by the rotation of the impeller 126. The cooling water discharged from the water pump 115 is supplied to the jacket 4 as shown in FIG.
The jacket 48 is connected to the inlet 24 a of the radiator 24.

A thermostat 128 is provided on the pump cover 120 of the pump housing 116. The thermostat 128 determines whether or not the suction ports 127 are connected to the outlet 24b of the radiator 24 according to the temperature of the cooling water. It works to switch. That is, the cooling water from the jacket 48 is cooled by the thermostat 12 when the temperature of the cooling water is low, that is, when the engine E is in a cold state.
8 and the water pump 115, the cooling water is returned to the jacket 48 via the radiator 24, the thermostat 128 and the water pump 115 when the temperature of the cooling water is high, that is, when the warming-up of the engine E is completed. The cooling water is cooled by the heat radiation in the cooling device.

7 and 8, the thermostat housing 129 of the thermostat 128 is formed in a cylindrical shape, and is fitted into a bottomed mounting hole 130 provided in the pump cover 120. 130
Is closed by the lid member 131, and is fixed to the pump cover 120 so as to be sandwiched between the closed end of the mounting hole 130 and the lid member 131.

Moreover, the mounting hole 130 is provided in the pump cover 120 so as to have a rotation axis of the impeller 126 of the water pump 115, that is, an axis orthogonal to the axis of the rotation shaft 121.
Thermostat housing 1 fitted and fixed in
29 will be arranged to have an axis orthogonal to the axis of rotation of the impeller 126.

At one end of the thermostat housing 129, a bottomed cylindrical sealing member 132 made of an elastic material is mounted so as to cover one end of the thermostat housing 129. One end of the thermostat housing 129 is exposed as a tip reinforcing portion 133. The other end of the opened thermostat housing 129 is in contact with the lid member 131, and a retaining ring 134 is mounted on the inner surface of the other end of the thermostat housing 129.

In the thermostat housing 129,
The wax case 135 is slidably fitted. The wax case 135 is provided in the thermostat housing 12.
9, a case main body 136 that directly contacts the outer surface to the inner surface of
And a cover 137 coupled to the case main body 136.
The peripheral edge of the diaphragm 138 is sandwiched between the seven. A cylindrical guide tube 139 that is slidably fitted in the seal member 132 is integrally connected to the case main body 136.

A wax 140 is built in the wax case 135 so as to be filled between the diaphragm 138 and the cover 137.
Is deformed. On the other hand, in the guide cylinder 139, a rod-shaped piston 1 is sequentially arranged from the side opposite to the diaphragm 138.
41, disc-shaped plate 142 and rubber piston 1
43 is slidably fitted to the rubber piston 14
3 and the wax case 135 between the diaphragm 138
Is filled with a medium 144 for transmitting the deformation of the diaphragm 138 to the rubber piston 143.

The wax case 135 and the retaining ring 1
34, a wax case 135 is attached to the sealing member 132.
A spring 145 is provided to urge the sealing member 132 when the temperature of the cooling water is low and the wax 140 is in a contracted state, as shown in FIG. . When the temperature of the cooling water rises and the wax 140 expands, the diaphragm 1
38 is deformed to bend to the left in FIG.
As is pushed out of the guide cylinder 139, the wax case 135 slides to the side away from the seal member 132 while compressing the spring 145, as shown in FIG.

Referring to FIG. 9 as well, an inlet hole 146 and an outlet hole 147 opposed to the inlet hole 146 are provided on the side wall of the thermostat housing 129 so as to be arranged on one diameter line of the thermostat housing 129. It is provided in. On the other hand, the radiator 2
4 is provided with a cooling water passage 151 communicating with the outlet 24b. The thermostat housing 129 allows the cooling water passage 151 to communicate with the inlet hole 146 and the outlet hole 147 with the suction holes 127. Into the pump cover 120 and fixed. In order to achieve such positioning around the axis of the thermostat housing 129, the thermostat housing 129 is required.
A pair of protrusions 129a, 129a are integrally formed so as to extend in the axial direction of the thermostat housing 129, and the inner surface of the mounting hole 130 has the protrusions 129a.
Grooves (not shown) for fitting the first and second grooves 29a and 129a are provided.

The inlet hole 146 and the outlet hole 147
The thermostat housing 12 is connected to the seal member 132 side, that is, one end of the thermostat housing 129.
9 and is slidably fitted in the thermostat housing 129.
Is the inlet hole 1 as shown in FIG.
The slide between the position where the space between the inlet hole 146 and the outlet hole 147 is interrupted and the position where the space between the inlet hole 146 and the outlet hole 147 is communicated as shown in FIG.

A water chamber 148 is formed between the other end of the thermostat housing 129 and the wax case 135 and the lid member 131, and the wax case 135 is located at a position where the wax case 135 blocks between the inlet hole 146 and the outlet hole 147. Sometimes, a bypass hole 149 is formed in the side wall of the thermostat housing 129 at a position adjacent to the outlet hole 147 to allow the suction ports 127 to communicate with the water chamber 148. Moreover, the bypass hole 149 is located at a position communicating with the inlet hole 146 and the outlet hole 147.
When 5 moves, it is closed by the wax case 135.

A connection pipe 150 communicating with the water chamber 148 is attached to the lid member 131, and this connection pipe 150 is connected to the jacket 48.

Next, the operation of this embodiment will be described. An oil return passage 107 for returning oil from the valve operating chamber 79 to the crank chamber 42 is provided in the cylinder head 39 so as to surround a part of the exhaust port 71. The heat from the exhaust gas is effectively transmitted to the oil flowing through the oil return passage 107 via the wall constituting the exhaust port 71. Therefore, the oil can be quickly heated by utilizing the heat of the exhaust port 71 whose temperature rises most quickly at the time of the cold start of the engine E, and the warm-up performance of the engine E can be improved. Moreover, the oil return passage 107
Is provided only at the lower part of the cylinder head 39 so as to surround a part of the exhaust port 71, the structure for rapidly raising the temperature of the oil is extremely simple, and compared with the conventional one in which the temperature is raised by a heater. In addition, the size and weight of the engine E can be reduced. Further, since the cylinder head 39 is disposed directly behind the front wheel WF, it is possible to avoid cooling the vicinity of the exhaust port 71 by the traveling wind of the motorcycle as much as possible, and to avoid the influence of the traveling wind. The temperature of the oil can be raised quickly.

An opening / closing valve 109 capable of opening and closing the oil return passage 107 is provided in the cylinder head 39. When the opening / closing valve 109 is closed, the oil in the valve operating chamber 79 is separated from the exhaust port 71. Chain passage 88
Can be returned to the side of the crank chamber 42 through the valve. Therefore, when the on-off valve 109 is closed, the influence of heat from the exhaust port 71 on the oil can be reduced. Overheating can be prevented.

Further, the projection of the exhaust port 71 on a plane perpendicular to the axis of the cylinder bore 44 corresponds to the center 7 of the combustion chamber 45.
The exhaust port 71 is formed so as to be curved on one side of the vertical line 73 passing through the exhaust port 71 so as to form an arc bulging toward the vertical line 73, and the oil return passage 107 is provided below the exhaust port 71 in the valve operating chamber. 79 is provided in the cylinder head 39 so as to open at the lower part. Therefore, it is possible to provide the oil return passage 107 in the cylinder head 39 without increasing the size of the cylinder head 39 by using the curvature of the exhaust port 71, and to reduce the relatively large area of the outer periphery of the wall of the exhaust port 71. Since it can be effectively used for raising the temperature of the oil, even if the lean burn operation associated with the swirl is performed by curving the exhaust port 71, the deterioration of the warm-up property due to the lean burn can be compensated.

The thermostat 128 provided on the pump cover 120 which is a part of the pump housing 116 of the water pump 115
5, a cylindrical thermostat housing 129 having an axis perpendicular to the rotation axis of the impeller 126 and attached to the pump cover 120, and a wax 140 built therein, and a sliding operation according to expansion and contraction of the wax 140 is enabled. Thermostat housing 12
9, a wax case 135 which is slidably fitted to the water pump 115, an outlet hole 147 which communicates with suction ports 127 provided in the pump housing 116 so as to communicate with the vortex chamber 125 of the water pump 115, and a radiator. 2
4 and the wax case 135
An inlet hole 146 for switching the communication with the outlet hole 147 in accordance with the slide of the thermostat housing 129 is provided on the side wall of the thermostat housing 129 so as to face each other on one diameter line of the thermostat housing 129.

Therefore, the pressure fluctuation of the vortex chamber 125 in the water pump 115 acts on the wax case 135 via the suction ports 127 and the outlet holes 147 in a direction orthogonal to the sliding direction thereof, and the sliding of the wax case 135 is performed. The effect of the pressure fluctuation on the operation is small, and it is possible to arrange the thermostat 128 as close to the vortex chamber 125 as possible, thereby contributing to downsizing of the pump cover 120.

Further, by bringing the thermostat 128 as close to the vortex chamber 125 of the water pump 115 as possible, the suction pressure of the suction ports 127.. Can be improved.

The wax 140 contained in the wax case 135 has a thermostat housing 129.
Since heat conduction is performed via the wax case 135, it is not necessary to secure a large space for flowing cooling water around the wax case 135. Therefore, it is possible to reduce the size of the thermostat 128 itself, so that the pump cover 120 can be further reduced in size.

The water pump 11 has a side wall of the thermostat housing 129 in a state where the space between the inlet hole 146 and the outlet hole 147 is blocked by the wax case 135.
5 is provided adjacent to the outlet hole 147 so as to communicate with the jacket 48, so that the bypass water 149 bypasses the radiator 24 and allows cooling water to flow when the engine E is cold. And the inlet 1
27, the suction pressure of 27... Is applied directly, and even if the opening area of the bypass hole 147 is set to be small, the required circulation amount of the cooling water when the engine E is cold is ensured. The size of the pump cover 120 can be further reduced.

Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible.

[0064]

As described above, according to the first aspect of the present invention, the oil returning from the valve operating chamber to the crank chamber is utilized by utilizing the heat of the exhaust port whose temperature rises most quickly during cold start of the engine. The temperature can be raised quickly, and the warm-up performance of the engine can be improved. Moreover, the structure for rapidly raising the temperature of the oil is extremely simple, and it is possible to avoid an increase in the size and weight of the engine.

According to the second aspect of the present invention, overheating of the oil can be prevented by opening and closing the on-off valve.

Further, according to the third aspect of the present invention, an oil return passage can be provided in the cylinder head without increasing the size of the cylinder head, and a relatively large area of the outer circumference of the wall of the exhaust port can be reduced. Therefore, even if the lean burn operation associated with the swirl is performed, it is possible to compensate for the decrease in the warm-up property due to the lean burn.

[Brief description of the drawings]

FIG. 1 is a side view of a motorcycle.

FIG. 2 is a sectional view of the power unit taken along line 2-2 of FIG.

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is an enlarged view taken along line 4-4 in FIG. 3 with a head cover removed.

FIG. 5 is a vertical sectional view of the engine taken along line 5-5 in FIG. 4;

FIG. 6 is an enlarged view of a main part of FIG. 3;

FIG. 7 is an enlarged vertical sectional view of the thermostat in a cold state of the engine.

FIG. 8 is a cross-sectional view corresponding to FIG. 7 in a state where engine warm-up is completed.

FIG. 9 is a sectional view taken along line 9-9 of FIG. 8;

FIG. 10 is a sectional view taken along line 10-10 of FIG. 8;

[Explanation of symbols]

 39 ... cylinder head 38 ... cylinder block 40 ... crankcase 42 ... crankcase 43 ... piston 44 ... cylinder bore 45 ... combustion chamber 71 ... exhaust port 72 ... Center of combustion chamber 73 Vertical line 76 Valve operating mechanism 78 Head cover 79 Valve operating chamber 88 Chain passage 107 Oil return passage 109 On-off valve E ··engine

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F02F 1/24 F02F 1/24 G F-term (Reference) 3G013 AA02 AB02 BC11 BD11 BD47 DA14 3G015 AA05 AB02 BA14 BF03 BF04 BF06 CA04 CA06 DA10 FA01 FB05 FB09 FC05 FD01 3G024 AA01 AA06 AA12 AA44 BA23 DA08 EA04 FA07

Claims (3)

[Claims] A cylinder head (39) having an exhaust port (71) having a downward opening is connected to the cylinder head (3).
9) Cylinder bore (44) inclined with side facing upward
A head cover (78) coupled to the cylinder head (39), which is connected to the cylinder block (38) having the valve head (39) and accommodates the valve mechanism (76), and forms a valve operating chamber (79) between the cylinder head (39) and the cylinder head (39). A crankcase (42) formed in a crankcase (40) connected to the cylinder block (38).
An oil return passage (107) for returning oil from the valve train chamber (79) to a portion below the exhaust port (71) and provided below the cylinder head (39). Oil return structure in 2. An on-off valve (109) capable of opening and closing the oil return passage (107) is provided in the cylinder head (39), and the valve operating chamber (79) is opened in response to closing of the on-off valve (109). The cylinder head (39) according to claim 1, characterized in that a passage (88) capable of returning oil in the cylinder chamber (42) to the side of the crank chamber (42) is provided at a position separated from the exhaust port (71). Oil return structure in the engine. 3. The projection of said exhaust port (71) onto a plane perpendicular to the axis of said cylinder bore (44) faces the top of a piston (43) slidably fitted in said cylinder bore (44). The center (7) of the combustion chamber (45)
The exhaust port (7) is formed so that one side of the vertical line (73) passing through 2) forms an arc bulging toward the vertical line (73).
1) is formed to be curved, and the oil return passage (10) is formed.
7) is located below the exhaust port (71) below the valve operating chamber (7).
The oil return structure for an engine according to claim 1 or 2, wherein the oil return structure is provided on the cylinder head (39) so as to open to a lower portion of (9).