JPH108981A - Engine for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To set the center of gravity of an engine to a high position without lengthening a wheel base, quickly perform a right/left bank turn of a car body so that a passing speed of a continuous curve can be improved. SOLUTION: An upper/lower side cylinder block 7, 9 arranged so as to form a V bank is provided, in the case of constituting a motorcycle engine 1 mounting the V bank in a car body toward the front of a vehicle, an arrangement position of the upper/lower side cylinder block 7, 9 and a crankshaft 5 is set so as to position a bisector B of the V bank in an upper side from a drive shaft 29 taking out drive force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a front opening V-type engine used for a motorcycle.

[0002]

2. Description of the Related Art As a motorcycle engine, there is a motorcycle engine in which an upper cylinder and a lower cylinder are arranged so as to form a V-bank, and the V-bank is mounted on a vehicle body facing forward of the vehicle body. Conventionally, in this type of motorcycle engine, the center of gravity of the engine is generally set as low as possible from the viewpoint of improving running stability. In this case, the height position of the drive shaft from which the engine power is taken out is necessarily determined to be a predetermined height that is related to the rear wheel shaft. , The lower cylinder is arranged lower.

As a result, in a conventional front-opening V-type engine for a motorcycle, a drive shaft for extracting engine power is located on a bisector of a bank angle formed by an upper cylinder shaft and a lower cylinder shaft (Japanese Patent Application Laid-Open No. H10-163840). 63-198725),
Or, the drive shaft is generally located above the bisector.

By the way, in recent motorcycles for road racing, for example, in order to improve the traveling speed when passing through an S-shaped curve, a so-called right and left bank switching which allows the vehicle body to be quickly and alternately turned left and right alternately. There is a demand for improved performance. To this end, it is desirable to set the center of gravity of the engine rather high so that the rotational moment of inertia around the axis in the vehicle longitudinal direction can be reduced. in this case,
Since the arrangement position of the drive shaft is set in relation to the rear wheel shaft as described above, in order to increase the center of gravity in the engine of the conventional structure, the entire engine is rotated upward around the drive shaft in order to increase the center of gravity. It will be mounted on the frame in a state where it is set.

[0005]

However, when the conventional engine is rotated around a drive shaft,
The cylinder head of the lower cylinder moves upward and at the same time also moves to the front side of the vehicle body, so that interference between the cylinder head and the front wheels becomes a problem, and in order to avoid this interference,
This will make the wheelbase longer. However, when the wheelbase is lengthened, there arises a problem that the maneuverability deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides an engine for a motorcycle in which the center of gravity of the engine can be set high without increasing the wheelbase, and the right and left bank switching performance can be improved and the S-curve passing speed can be improved. It is intended to provide.

[0007]

According to a first aspect of the present invention, there is provided a motorcycle including an upper cylinder and a lower cylinder arranged to form a V bank, the motorcycle being mounted on a vehicle body with the V bank facing forward of the vehicle. The engine is characterized in that the positions of the upper cylinder, the lower cylinder, and the crankshaft are set so that the bisector of the V bank is located above the drive shaft (axis) for extracting the driving force. .

A second aspect of the present invention is characterized in that, in the first aspect, the V-bank bisector is inclined forward and upward from the ground line.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 to 6 are views for explaining a motorcycle engine according to an embodiment of the present invention. FIGS. 1 to 4 are a left side view, a plan view, a rear view, and a right side of the engine of the embodiment, respectively. FIG. 5 is a configuration diagram showing an oil passage of a lubrication system, and FIG. 6 is a side view of a motorcycle on which the engine is mounted. Note that the terms front, rear, left, right, upper, and lower in this embodiment are those in a state of being seated on a seat, and are as shown in the drawings.

In FIG. 6, reference numeral 70 denotes a motorcycle on which the engine 1 is mounted. The motorcycle 70 has a head pipe 72a fixed to the front end of a vehicle body frame 71 to allow a front fork 74 supporting a front wheel 73 to be steerable left and right. While pivoting, the rear arm 7
5 is pivotally supported so as to be able to swing up and down,
A fuel tank 77 and a seat 78 are arranged above the vehicle body frame 71 and a side cover 79 is arranged. The engine 1 is suspended and supported in a cradle formed by the main frame 80 and the down tube 81 of the body frame 71.

The engine 1 is a water-cooled V-type two-cylinder two-stroke engine. A crankcase 2 of the engine 1 is divided into a front case 3 and a rear case 4, and a crankshaft 5 includes a front and rear case. 3 and 4 are supported via a bearing 6 at a mating surface A portion.

An upper cylinder block 7 is fixed to the upper part of the front wall of the front case 3 by bolts, and an upper cylinder head 8 is fixed to the upper surface of the cylinder block 7 by bolts. A lower cylinder block 9 and a lower cylinder head 10 are laminated and fixed to a lower portion of the front case 3, and the upper and lower cylinder blocks 7,
The nine cylinder shafts C, C are arranged so as to form a V-shaped so-called V bank when viewed in the crankshaft direction, and the V bank forms 90 degrees and opens toward the front of the vehicle.

Pistons 11, 11 are slidably inserted into cylinder bores 7a, 9a of the cylinder blocks 7, 9, respectively.
To the crankshaft 5. A plurality of scavenging ports 15 communicating with the crank chamber and the inside of the cylinder bores 7a, 9a are formed in the cylinder blocks 7, 9 at intervals in the circumferential direction.

Exhaust ports 16, 16 are formed on the lower wall of each of the cylinder blocks 7, 9, and exhaust pipes 17, 17 are connected to each of the exhaust ports 16. A variable exhaust valve 18 is inserted into each of the exhaust ports 16. The variable exhaust valve 18 has a fully closed position where the valve portion 18a advances to retard the exhaust timing, and retreats to advance the exhaust timing. It is configured to move forward and backward between the fully open position to be angled. The exhaust variable valve 18 is controlled in accordance with an operating state such as an engine speed. For example, the exhaust timing is controlled such that the exhaust timing is delayed by driving to a fully-closed position in a low-speed rotation region and is fully opened in a high-speed rotation region to accelerate the exhaust timing. Is done.

A balancer shaft 20 is disposed in the rear upper portion of the rear case 4 behind the crankshaft 5 in parallel with the crankshaft 5. A weight 20 is provided at the left end of the balancer shaft 20.
a, a balancer gear 20b integrated with a balancer weight is mounted at the right end thereof.
Ob meshes with a balancer drive gear 21 mounted on the right end of the crankshaft 5.

At the rear of the rear case 4, a cassette type speed change mechanism 25 is provided. The transmission mechanism 25 has a main shaft 27 having a transmission gear group 26 mounted on a lower rear portion of the crankshaft 5, and a counter gear group 28 meshing with the transmission gear group 26 mounted on an upper rear portion of the main shaft 27. Drive shafts 29 are arranged in parallel with the crankshaft 5, and the right ends of the main shaft 27 and the drive shaft 29 are supported by a cassette base 30 separate from the crankcase 2.
4a, and the other end is supported by a boss of the rear case 4 via a bearing 34b. The cassette base 30 is a boss (not shown) formed in the rear case 4. It is bolted and fixed detachably. The speed change mechanism 25 is configured to switch between a minimum speed and a highest speed by rotating the change shaft 31.

The left end of the drive shaft 29 is the rear case 4
The drive sprocket 32 is mounted on the protrusion, and the sprocket 32 is connected to a rear wheel sprocket 75a via a chain 83 (see FIG. 6).

The right end of the main shaft 27 projects outward from the case cover 33, and a dry clutch 35 is mounted on the projection. This clutch 35 has a large number of clutch plates 35 between an outer drum 35a connected to the crankshaft 5 via a crank gear 36 and a reduction gear 37, and an inner drum 35b connected to the main shaft 27.
c. A push rod 40 connected to the inner drum 35b is inserted into the axis of the main shaft 27 so as to be able to advance and retreat.
The cam portion 41a of the push lever 41 is engaged with the left end of the “0”. By rotating the push lever 41, the engine power is disconnected.

A drive shaft 4 of an oil pump 42 constituting a lubrication system is provided below the main shaft 27 of the cassette base 30.
2a is pivotally supported. Further, a rotation shaft 43a of a cooling water pump 43 constituting a cooling system is coaxially connected to the drive shaft 42a, and the cooling water pump 43 is disposed on the left side wall of the rear case 4.

A rotor 44 is connected to the inside of the cassette base 30 of the drive shaft 42a, and a driven gear 45 driven by the main shaft 27 is connected to the outside thereof.
A strainer housing 30a communicating with a suction port of the oil pump 42 is provided at a lower edge of the cassette base 30.
Are integrally formed, and a mesh 46 is bolted and fixed to the lower surface opening of the housing 30a.

The strainer housing 30a is formed so as to protrude outward from the cassette base 30, and an oil reservoir 4c is formed in a portion of the rear case 4 located below the strainer housing 30a. As described above, in the present embodiment, since the strainer housing 30a is formed outside the cassette base 30, the oil reservoir 4c can be arranged on the right edge of the rear case 4, and the lower exhaust pipe 17 passing below the rear case 4 can be arranged. Can be avoided.

That is, the exhaust pipe 17 from the lower cylinder block 9 is disposed below the rear case 4 in a rear-down state. For this reason, if the strainer housing is formed inside the cassette base as in the prior art, the oil sump is located as shown by the two-dot chain line in FIG. 3, and interference between the oil sump and the exhaust pipe 17 is avoided. Therefore, the exhaust pipe 17 must be disposed so as to pass further downward, and a problem arises in that a minimum ground clearance cannot be secured.

When the strainer housing is formed inside the cassette base, the clutch, the case cover, and the cassette transmission must be removed when performing maintenance and inspection of the suction port. On the other hand, in the present embodiment, workability can be improved because it is only necessary to remove the clutch 35 and the case cover 33.

A first oil passage 50 communicating with a discharge port of an oil pump 42 is formed in the cassette base 30 in a front-rear direction (see FIG. 4). Case 4 after the above
A second oil passage 51 communicating with the downstream end of the first oil passage 50 is formed in the crankshaft direction.
The downstream end of the oil passage 51 extends close to the cooling water discharge passage 48 of the cooling water pump 43 (see FIG. 1).

The rear case 4 has a second oil passage 5.
A third oil passage 52 extending upward from the downstream end of the first case 1 is formed. The third oil passage 52 is formed obliquely inward from the upper wall of the rear case 4 toward the front and inside.
The downstream end of the third oil passage 52 is connected to a passage (not shown) communicating with the axis of the main shaft 27 through the cam portion 41a of the push lever 41 from here. Further, lubricating oil is supplied from the first oil passage 50 to the drive shaft 29 via the oil passages 53 and 54. An oil pipe 55 is provided in parallel with the main shaft 27 above the main shaft 27, and an oil passage 53 communicates with the oil pipe 55.

In the lubricating oil of the engine 1, the oil sump 4
c through the first to third oil passages 50 to 50
52, the gear shaft 26 is supplied from the main shaft 27 to the transmission gear group 26, and is also supplied from the drive shaft 29 to the counter gear group 28.
Supplied in the state of oil shower.

In the present embodiment, since the third oil passage 52 is formed obliquely inward from the upper wall of the rear case 4, as shown in FIG. The cooling water discharge passage 48 can be arranged outside the above. As a result, the cooling water pump 43 can be disposed on the front side of the main shaft 27, the cassette base 30 can be reduced in size, the transmission mechanism can be made compact accordingly, and the engine as a whole can be reduced in size. This can improve the degree of freedom in layout when mounted on the vehicle body. In addition,
Conventionally, since the third oil passage was formed vertically in the vertical direction, a cooling water pump was arranged behind the main shaft to avoid interference with the oil passage, and the cassette base was large. There was a problem of becoming.

Next, the intake system of the engine 1 will be described. A lower intake passage 60 communicating with the crank chamber of the lower cylinder block 9 is provided at a front wall in the V bank of the front case 3.
The lower reed valve 61 is inserted and arranged in the intake passage 60. The reed valve 61 has a mounting seat surface 62 formed on the opening edge of the intake passage 60.
The mounting seat surface 62 is formed so as to be substantially parallel to the split surface A of the crankcase 2.

The reed valve 61 has a structure in which a vent 61b is formed in a slope portion of a valve body 61a having a triangular cross section, and the vent 61b is opened and closed by a valve plate 61c. The reed valve 61 automatically opens and introduces air into the crank chamber when the pressure in the crank chamber becomes negative due to the rise of the piston 11, and closes when the pressure becomes positive to prevent the air from returning when the piston descends. In addition, 61d is a stopper for regulating the opening of the valve plate 61c.

An upper intake passage 65 communicating with the crank chamber of the upper cylinder block 7 is formed in the upper wall 4a of the rear case 4. An upper reed valve 66 having the same structure as described above is formed in the intake passage 65. It is inserted and arranged so as to extend toward the crank chamber beyond the division surface A. An upper mounting seat surface 67 is formed at an opening edge of the intake passage 66, and the upper reed valve 6 is mounted on the mounting seat surface 67.
The carburetor 70 and the cab joint 70a are bolted and fixed using the bolt holes 67a, and the carburetor 70 is bolted and fixed via the cab joint 70a. The mounting seat surface 67 is formed rearward so as to be substantially parallel to the division surface A, and is provided with the balancer shaft 20.
Is formed near the center in the axial direction (see FIG. 3) and forward of the balancer shaft 20.

Here, since the mounting seat surface 67 protrudes upward from the upper wall surface of the crankcase 2, the split surface A
In order to ensure the sealing performance of the front portion of the mounting seat surface 67 of the mounting surface 67, the front portion of the mounting seat surface 67 of the divided surface A is fastened and fixed by three bolts 67b and 67c. In this case, the upper bolt 67b is screwed from the front case 3 side to the rear case 4 side. This facilitates bolting work in a narrow place.

In the engine 1, the positions of the upper and lower cylinder blocks 7, 9 and the crankshaft 5 are determined by dividing the bank angle between the cylinder axes C, C of the upper and lower cylinder blocks 7, 9 by two. The line B is set so as to be located above the axis of the drive shaft 29. That is, as compared with the conventional engine in which the bank angle bisector is located below the drive shaft, the upper and lower cylinder blocks 7, 9 and the crankshaft 5 are moved upward along the dividing plane A. This has the same configuration as the one translated in parallel. The engine 1 is mounted on the vehicle body frame 71 such that the V-bank bisector B is inclined slightly upward with respect to the ground line G.

Next, the operation and effect of this embodiment will be described. In the present embodiment, the upper and lower cylinder blocks 7, 9 and the crankshaft 5 are moved upward along the division plane A such that the V bank bisector B is located above the drive shaft 29. The center of gravity of the engine can be set at a higher position, the rotational moment of inertia about the vehicle's longitudinal axis is reduced, and the rider's body is moved to the left and right while reducing the amount of left and right movement of the entire body of the rider. The ability to switch right and left banks alternately and quickly can be improved, and the passing speed of the S-shaped curve can be improved.

If the upper and lower cylinder blocks 7, 9 and the crankshaft 5 are moved upward along the dividing plane A, the exhaust pipe 17 easily interferes with the bottom surface of the rear case 4. In the present embodiment, as described above, since the oil reservoir 4c can be arranged on the right side edge, interference with the bottom surface of the rear case 4 of the exhaust pipe 17 can be avoided.

The position of the center of gravity is increased by moving the cylinder blocks 7, 9 and the crankshaft 5 upward in parallel, so that the lower portion of the engine can be rotated, as in the case of rotating the entire engine around the conventional drive shaft. Since the cylinder head does not move forward, it is possible to avoid interference with the front wheels 73 and to avoid a decrease in maneuverability due to an increase in the wheelbase. In the present embodiment, the case of a two-cycle engine has been described. However, the configuration for increasing the center of gravity of the present invention can of course be applied to a four-cycle engine.

According to the present embodiment, the mounting seat surface 67 is constituted only by the upper wall 4a of the rear case 4, and the upper reed valve 66 is mounted on the mounting seat surface 67.
Can be secured when the reed valve 67 is mounted, as compared with the case where the lead valve 67 is formed over the front and rear cases.

Further, since the mounting seat surface 67 is constituted only by the upper wall 4a of the rear case 4, the seat surface 67 can be formed so as to be substantially parallel to the dividing surface A, and the intake passage can be made substantially linear. The angle θ between the axis D and the cylinder axis C can be made obtuse, thereby reducing the passage resistance and directing the intake air flow to the vicinity of the skirt of the piston 11 located near bottom dead center. Can be improved.

Incidentally, in order to improve the intake efficiency, the intake passage resistance is reduced and the source of the intake negative pressure,
That is, it is effective to direct the axis D of the intake passage near the skirt portion of the piston located near the bottom dead center. In the present embodiment, since the mounting seat surface 67 is constituted only by the rear case 4 as described above, linearization of the intake passage and directing to the intake negative pressure generation source can be realized. Further, in this embodiment, since the drive shaft 29 is located below the bisector B of the bank angle, the position of the vaporizer 70 can be lowered by lowering the upper wall 4a of the rear case 4 accordingly. The point also contributes to the linearization of the intake passage and the pointing of the negative pressure source.

Further, since the reed valve 66 is inserted so as to extend toward the crank chamber beyond the dividing plane A, the length of the intake passage 65 communicating with the crank chamber can be shortened, and the volume of the crank chamber is reduced. The compression ratio can be increased.

The mounting seat surface 67 is connected to the balancer shaft 20.
Are formed near the center in the axial direction, so that the intake passage 65 and the carburetor 70 can be prevented from interfering with the weight 20a and the balancer gear 20b, and the balancer shaft 20 can be brought close to the crankshaft 5; Also the intake passage 65
Can be shortened, and the compression ratio can be further improved.

That is, in a couple balancer having a larger balancer effect as the balancer weight interval is wider, the weight 2
Since the balancer gear 0a and the balancer gear 20b are arranged far apart to the left and right, the weight 20a and the balancer gear 20b can be reduced in diameter when the necessary balancer effect is the same, so that the balancer shaft 20 can be brought closer to the crankshaft 5. It is a thing.

By the way, in the prior art, the carburetor and, consequently, the mounting seat surface need to be arranged away from the balancer shaft in a direction perpendicular to the shaft in order to avoid interference with the balancer weight of the balancer shaft. From the air intake path, and there is a problem that the intake passage becomes long after all.

Further, in this embodiment, the carburetor 70 can be connected to the intake passage 65 so that the intake passage axis D forms a substantially straight line, so that the passage resistance can be reduced and the air flow can be directed to the negative pressure generating source. Yes, the intake efficiency can be improved accordingly.

[0044]

As described above, according to the motorcycle engine of the first aspect, the upper cylinder, the lower cylinder, and the crankshaft such that the V-bank bisector is located above the drive shaft. The position of the center of gravity has been set, so the center of gravity of the engine can be set at a higher position without lengthening the wheelbase, improving the left and right bank switching performance of the vehicle and improving the passing speed of continuous curves. .

According to the second aspect of the present invention, since the V-bank bisector is inclined slightly upward from the ground line, the center of gravity can be further increased, and the effect of further improving the left and right bank switching performance can be obtained. is there.

[Brief description of the drawings]

FIG. 1 is a left side view illustrating a front-opening V-type two-stroke engine according to an embodiment of the present invention.

FIG. 2 is a plan view of the engine.

FIG. 3 is a rear view of the engine.

FIG. 4 is a right side view of the engine.

FIG. 5 is a configuration diagram showing an oil passage of the engine.

FIG. 6 is a side view of a motorcycle on which the engine is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Front opening V type 2 cycle engine 5 Crankshaft 7 Upper cylinder block (upper cylinder) 9 Lower cylinder block (lower cylinder) 29 Drive shaft B V bank bisector

Claims (2)

[Claims] 1. A motorcycle engine, comprising an upper cylinder and a lower cylinder arranged to form a V bank and mounted on a vehicle body with the V bank facing forward of the vehicle, comprising: an upper cylinder, a lower cylinder, A motorcycle engine, wherein the position of the crankshaft is set such that the bisector of the V bank is located above the drive shaft for extracting the driving force. 2. The motorcycle engine according to claim 1, wherein a bisector of the V bank is inclined forward and upward from a ground line.