JPH0329969B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an in-line four-cylinder engine for a motorcycle, and particularly to the structure of a power transmission path from its crankshaft to a transmission shaft.

[Prior Art] This type of parallel four-cylinder engine is mounted horizontally along the width direction of the motorcycle body, but because it is a four-cylinder engine, the crankshaft is long, and the crankcase is mounted on the left and right sides of the motorcycle body. It tends to stick out on both sides.

In other words, the crankshaft for an in-line four-cylinder engine has a long shaft length because it has crank pins connected to piston connecting rods equal to the number of cylinders, and a pair of crank arms connected on both sides of these crank pins. Therefore, in order to reduce the width of the crankcase, it is necessary to keep the overall length of the crankshaft as short as possible.

Incidentally, in an engine for a motorcycle, a transmission case is continuously provided at the rear of a crankcase, and a gear transmission is integrally built into this transmission case. This gear transmission includes two shift shafts, a first and a second shift shaft, and a plurality of shift gears that mesh with each other are provided on each shift shaft. These speed change shafts are parallel to the crankshaft and are arranged behind the crankshaft on the same straight line in the front and back direction passing through the center of the crankshaft, and the first speed change shaft is located on the side of the crankshaft. A clutch is provided at one end.

In this engine, in order to transmit the power of the crankshaft to the gear transmission, a separate primary reduction gear is attached to the crankshaft, and this primary reduction gear is meshed with the primary reduction gear of the clutch. The power extracted from the crankshaft is transmitted to the transmission shaft via the clutch.

However, when a separate primary reduction pinion gear is attached to the crankshaft, the total length of the crankshaft increases by the thickness of the primary reduction pinion gear, which causes the problem that the width of the crankcase becomes wider.

Therefore, conventionally, among the crank arms of the first cylinder located at the end of the above-mentioned crankshaft, a driving tooth portion that meshes with the primary reduction gear was integrally carved on the outer peripheral surface of the inner crank arm adjacent to the second cylinder. The installed engine is known.

This configuration has the advantage that the above-mentioned special primary reduction gear is not required, and the overall length of the crankshaft can be shortened by the amount of this gear.

[Problems to be Solved by the Invention] However, with this configuration, the position of the clutch is naturally determined by the position of the crank arm having the drive teeth, so it is not possible to use the drive teeth as in the conventional case. If the clutch is provided on the crank arm of the first cylinder at one end of the crankshaft, the clutch will be largely biased toward one end of the crankshaft.

For this reason, the amount of lateral protrusion of the clutch increases, and if the center of gravity of the engine is made to coincide with the center of the vehicle body, the center of the engine and the center of the vehicle body will shift by the amount that the clutch is biased, and This causes the engine or transmission case to become biased to either the left or right. Then, since the shift pedal for changing the meshing of the transmission gears is placed on the outside of the transmission case on the side opposite to the clutch, this shift pedal also shifts in the above direction, causing the shift pedal to shift in the direction described above. , it becomes impossible to arrange the shift pedal and clutch in a well-balanced manner on the left and right sides.

Moreover, if the driving teeth are provided on the crank arm on the innermost side of the cylinder as described above, this crank arm becomes perfectly circular and cannot function as a counterweight (balance weight). It becomes necessary to increase the counterweight of the outer crank arm that pairs with the crank arm. In this case, if mass is ensured by increasing the thickness of the counterweight, the overall length of the crankshaft increases by the increased thickness, causing the crankcase to protrude laterally.

On the other hand, if mass is secured by increasing the outer diameter of the counterweight, the side portions of the crankcase will swell significantly in the vertical direction.

Therefore, the advantage of eliminating the need for the driving tooth portion is lost, and there is also the problem that a sufficient bank angle cannot be secured.

Furthermore, if the drive teeth are carved directly on the outer circumferential surface of the crank arm, this crank arm will have a larger diameter than the reduction pinion, so although the overall length of the crankshaft can be shortened, the The distance between the shafts and the first speed change shaft tends to increase. For this reason, if the first speed change shaft and the second speed change shaft are arranged side by side on the longitudinal center line passing through the center of the crankshaft as described above, the gear transmission will protrude significantly behind the crankshaft. As the overall length of the engine becomes longer, it causes other problems.

The present invention has been made based on the above circumstances, and allows the clutch and the gear shift operation member of the gear transmission to be arranged behind the crankshaft in a well-balanced manner on the left and right sides, and the width from the clutch to the shift operation member is as narrow as possible. In addition, the crank arm at the end of the crankshaft has been made smaller to ensure a sufficient bank angle, and the overall length of the case has been kept short, resulting in a parallel four-cylinder engine for motorcycles that is compact in both length and width. The purpose is to provide.

[Means for Solving the Problems] Therefore, in the present invention, four cylinders are arranged in parallel at intervals in the axial direction of the crankshaft, and a transmission case is provided at the rear of the crankcase that accommodates the crankshaft. A first speed change shaft and a second speed change shaft constituting a gear transmission are arranged in series and parallel to the crankshaft within this transmission case, and of these two speed change shafts, the crankshaft side A clutch is provided at one end of the first speed change shaft located at the crankshaft for intermittent transmission of power from the crankshaft to the first speed change shaft,
In a parallel four-cylinder engine for a motorcycle, in which a shift operation member for shifting the gear transmission is arranged on the outside of the transmission case opposite to the clutch, the crankshaft is connected to the pistons of each cylinder. It is equipped with four connected crank pins and a pair of crank arms connected to both ends of each crank pin, and among the crank arms of the other cylinders adjacent to the cylinder at the extreme end on the clutch side, the cylinder at the extreme end A drive tooth section for power extraction is provided on the outer circumferential surface of one of the crank arms located on the side, and this drive tooth section is engaged with the reduction gear at the input end of the clutch. The second speed change shaft is located at a position shifted downward from the first speed change shaft, and is located within a range surrounded by the outer peripheral edge of the reduction gear.

[Function] According to this configuration, the position of the drive teeth is moved inward in the axial direction of the crankshaft by one cylinder compared to the conventional structure, so the clutch driven by the drive teeth is moved to the innermost position of the crankshaft. It can be moved closer to the center of the engine than the cylinders at the ends. Therefore, since the clutch does not need to protrude to the side, the gear shift operating member on the opposite side of the clutch can be arranged in a well-balanced manner on the left and right sides of the crankshaft. By keeping the length equal to or less than the length of the transmission case, the area around the transmission case can be made narrow and compact.

In addition, since a counterweight can be provided on each of the pair of crank arms located at the extreme end of the crankshaft, it is possible to increase the size of the counterweight of one of the crank arms located on the axially inner side of the crankshaft. If this is ensured, both the diameter and wall thickness of the outer counterweight at the end of the crankshaft can be reduced. Therefore,
At the same time as the crankshaft is shortened, the shape of its end can also be made smaller, and a sufficient bank angle can be secured.

Furthermore, since the first and second transmission shafts are not located on the same straight line passing through the center of the crankshaft in the front-rear direction, but are vertically offset from each other, The distance between the axes can be shortened. Therefore, even if the distance between the crankshaft and the first transmission shaft increases due to the provision of the drive teeth directly on the outer circumferential surface of the crank arm, this increase will be absorbed by the two transmission shafts. The rearward protrusion ratio of the gear transmission can be suppressed to a small extent, and the overall length of the engine can be shortened.

[Example] The present invention will be described below based on an example shown in the drawings.

Figures 1 and 2 show a 4-stroke, 4-cylinder engine that is mounted horizontally along the left-right direction on the body of a motorcycle, where 1 is a power unit case, 2 is a cylinder block, and 3 is a cylinder block. It is a cylinder head. In the cylinder block 2, four cylinders 4a, 4b, 4c, and 4d are arranged in parallel at intervals in the left-right direction of the vehicle body, and each cylinder 4a, 4b, 4c, and 4d has a piston 5.
is accommodated.

The power unit case 1 is composed of a crankcase 6 and a transmission case 7 that is integrally provided at the rear of the crankcase 6. An oil pan 8 is attached to the lower part of both cases 6 and 7. There is. A crankshaft 9 is housed horizontally in the crankcase 6 along the width direction of the vehicle body, that is, along the left-right direction, and the four cylinders 4a, 4b, 4c, 4d
are lined up. Inside the transmission case 7, a gear transmission 10 is housed behind the crankshaft 9. This gear transmission 10 is located behind the middle two cylinders, that is, the second cylinder 4b and the third cylinder 4c, among the four cylinders 4a, 4b, 4c, and 4d.

The gear transmission 10 also includes a first speed change shaft 11 and a second speed change shaft 12 that are parallel to the crankshaft 9 and extend in the left-right direction.

A clutch 29 is located at the right end of the first speed change shaft 11.
is provided. This clutch 29 is for disconnecting power transmission from the crankshaft 9 to the first transmission shaft 11, and a reduction gear 32 is provided in a clutch housing 31 located on the input side thereof.

When the engine is viewed from the axial direction of the transmission shafts 11 and 12 as shown in FIG.
It is located below and within a range surrounded by the outer peripheral edge of the reduction gear 32. Therefore, the two speed change shafts 11 and 12 are not located on the same straight line in the longitudinal direction passing through the center of the crankshaft 9, but are arranged vertically shifted from each other.

A plurality of speed change gears 13 and 14 are provided on the first speed change shaft 11 and the second speed change shaft 12. These speed change gears 13 and 14 selectively change the combination of meshing gears by operating a shift pedal 15 as a speed change operation member, and change the rotation of the first speed change shaft 11 into multiple stages to change the rotation of the first speed change shaft 11 into a plurality of stages. The transmission is transmitted to the speed change shaft 12 of.

Incidentally, since the gear transmission 10 is arranged behind the second cylinder 4b and the third cylinder 4c, the side surface of the transmission case 7 opposite to the clutch 29 has a crankshaft as shown in FIG. The shift pedal 15 is recessed one step further than the side surface of the case 6, and the shift pedal 15 is housed in a space created between the continuous parts of the cases 6 and 7. For this reason, the shift pedal 15 is
It is arranged on the outer side of the transmission case 7 opposite to the clutch 29.

A drive shaft 16 is rotatably supported at the rear end of the transmission case 7 , and this drive shaft 16 is interlocked with the second speed change shaft 12 via an interlocking gear 17 . Further, an output shaft 18 that extends in the front-back direction perpendicular to the drive shaft 16 is rotatably supported at the rear end of the transmission case 7, and the front end of the output shaft 18 and the left end of the drive shaft 16 are interlocked via bevel gears 19 and 20 that mesh with each other. The rear end portion of the output shaft 18 passes through the transmission case 7 and is led out rearward, and this lead-out end includes:
A flange joint 21 for connecting a drive shaft (not shown) is attached.

By the way, the crankshaft 9 has each cylinder 4a,
Four crank pins 2 to which connecting rods 22 of pistons 4b, 4c, and 4d are connected.
3, and four pairs of crank arms 24a, 24 located on both sides of these crank pins 23.
b, 25a, 25b, 26a, 26b and 27
a, 27b and a journal portion 28 rotatably supported by the crankcase 6. These journal parts 28 and crank pins 23 have
It is induction hardened. Of the crank arms 25a, 25b of the second cylinder 4b adjacent to the first cylinder 4a closest to the clutch 29, the crank arm 25a is located closest to the cylinder 4a.
As shown in FIG. 4, the crank arm 25a has a perfect circular shape and is provided coaxially with the journal portion 28, and a drive tooth portion 30 for power transmission is integrally carved on the outer peripheral surface of the crank arm 25a. It is set up. The drive teeth 30 mesh with the reduction gear 32 of the clutch 29, and when the clutch 29 is engaged, the rotation of the crankshaft 9 is transmitted to the first speed change shaft 11 of the gear transmission 10.

Note that the other crank arms 24a, 24 except for the crank arm 25a on which the drive tooth portion 30 is carved
b, 25b, 26a, 26b, 27a, 27b
are each equipped with a counterweight 38, and the outer periphery of these counterweights 38 is connected to the driving tooth portion 3.
0 protrudes radially outward.

Also, inside the crankcase 6, there is an oil intake port 33 for sucking oil in the oil pan 8.
An oil pump 34 connected thereto is housed. As shown by the chain line in FIG. 2, the oil sucked up by the oil pump 34 passes through the oil filter 35 to the oil passages 36 in the transmission gears 13, 14, the crankshaft 9, and the cylinders 4a, 4.
It is designed to be pumped to various parts of the engine such as b, 4c, and 4d. The oil passage 36 of the crankshaft 9 is connected to the crank pin 23 and the journal portion 2.
The oil passage 36 is connected to an oil hole 37 that opens on the circumferential surface of the oil passage 36, and the oil sent to the oil passage 36 is guided to the sliding portion of the crank pin 23 and the journal portion 28.

According to such a configuration, the drive tooth portion 30 with which the reduction gear 32 of the clutch 29 meshes is connected to the second cylinder 4.
Since it is engraved on the outer crank arm 15a of the crankshaft 9, the position of the drive tooth portion 30 on the crankshaft 9 is located further inward in the axial direction of the crankshaft 9 than the first cylinder 4a at the end. , the clutch 29 can be moved closer to the center of the engine than the end of the crankshaft 9.

For this reason, even though the crankshaft 9 directly drives the reduction gear 32 of the clutch housing 31, the clutch 29 does not protrude significantly to the side of the transmission case 7;
The shift pedal 15 on the opposite side can be arranged behind the crankshaft 9 with good left-right balance.

Therefore, it is possible to suppress the width from the clutch 29 to the shift pedal 15 to be equal to or less than the length of the crankshaft 9, and the rear part of the transmission case 7 can be suppressed to be narrow and compact.

Further, the drive tooth portion 30 is connected to the crank arm 25a of the second cylinder 4b located in the middle of the crankshaft 9.
By providing these counterweights 38, the counterweights 38 can be provided on the crank arms 24a, 24b at the ends of the crankshaft 9, respectively. In this case, the inner crank arm 24b adjacent to the second cylinder 4b
If the mass of the counterweight 38 of the outer crank arm 24a is ensured by increasing its size, both the diameter and wall thickness of the counterweight 38 of the outer crank arm 24a can be reduced.

Therefore, the shape of the end of the crankshaft 9 can be made small, the overall length of the crankshaft 9 can be shortened, and a sufficient bank angle can be ensured.

At the same time, the first speed change shaft 11 and the second speed change shaft 12 are not located on the same straight line passing through the center of the crankshaft 9 in the front and rear direction, but are vertically shifted. transmission shafts 11, 12
The inter-axle distance from the crankshaft 9 to the second speed change shaft 12 can be made shorter than when the two are arranged on the same straight line.

For this reason, even if the distance between the crankshaft 9 and the first transmission shaft 11 becomes large due to the provision of the drive tooth portion 30 directly on the outer peripheral surface of the large-diameter crank arm 25a, this distance between the shafts This increase can be offset between the first speed change shaft 11 and the second speed change shaft 12.

As a result, the proportion of rearward protrusion of the gear transmission 10 can be suppressed to a small extent, and the total length of the power unit case 1 can be kept short, and the width of the transmission case 7 can be narrowed.
Both the overall length can be shortened and the engine can be made more compact.

Note that the present invention is not limited to the above embodiments.
For example, in the above embodiment, the engine is equipped with a shaft drive type power transmission means, but a chain drive type engine may also be used.

[Effects of the Invention] According to the present invention described in detail above, although the crankshaft directly drives the reduction gear of the clutch, the clutch does not protrude significantly to the side of the transmission case. This clutch and the speed change operating member located on the opposite side thereof can be arranged with good left-right balance behind the crankshaft.

Therefore, it is possible to suppress the width from the clutch to the speed change operating member to be equal to or less than the length of the crankshaft, and the transmission case can be formed narrow and compact.

In addition, the counterweight of the crank arm located at the extreme end of the crankshaft can be made smaller.
The shape of the end portion of the crankshaft can be made small, and together with the shortening of the axial length of the crankshaft, a sufficient bank angle can be ensured.

Moreover, the two transmission shafts are not located on the same straight line in the front and rear direction passing through the center of the crankshaft.
Since they are vertically shifted from each other, the distance between the crankshaft and the second transmission shaft can be made shorter than when the transmission shafts are arranged on the same straight line.

Therefore, even if the distance between the crankshaft and the first gear shift shaft increases due to the provision of the drive teeth directly on the outer circumferential surface of the large-diameter crank arm, the increased distance between the crankshaft and the first gear shift shaft increases. can be offset between the two transmission shafts, the ratio of rearward protrusion of the gear transmission can be suppressed, and the overall length of the transmission case can be shortened.

Therefore, in addition to being able to form the area around the clutch to be narrow, both the overall width and overall length of the engine can be shortened, making it possible to make the engine more compact.

[Brief explanation of drawings]

The drawings show an embodiment of the invention, FIG.
Figure 2 is a cross-sectional view taken along the line in Figure 2, Figure 2 is a partially sectional side view of the engine, Figure 3 is a front view of the crankshaft, and Figure 4 is a cross-section taken along the line in Figure 3. It is a diagram. 1...Power unit case, 4a, 4b, 4
c, 4d...Cylinder, 6...Crankcase, 7...
...Transmission case, 9...Crankshaft, 10...Gear transmission, 11...First speed change shaft, 12...Second
Shift shaft, 15...Shift operation member (shift pedal), 23...Crank pin, 24a, 24b,
25a, 25b, 26a, 26b, 27a, 27
b...Crank arm, 29...Clutch, 30
... Drive tooth section, 32 ... Reduction gear.

Claims (1)

[Claims] 1. Four cylinders are arranged in parallel at intervals in the axial direction of the crankshaft, and a transmission case is connected to the rear of the crankcase that accommodates the crankshaft, and the transmission case is A first speed change shaft and a second speed change shaft constituting a gear transmission are arranged parallel to the crankshaft, and of these two speed change shafts, the first speed change shaft located on the crankshaft side is A clutch is provided at one end of the transmission case for intermittent transmission of power from the crankshaft to the first transmission shaft, and a transmission for operating the gear transmission is provided on the outside of the transmission case on the opposite side from the clutch. In a parallel four-cylinder engine for a motorcycle in which an operating member is arranged, the crankshaft has four crank pins connected to the pistons of each cylinder and a pair of crank arms connected to both ends of each crank pin, Among the crank arms of other cylinders adjacent to the cylinder at the end, one of the crank arms located on the side of the cylinder at the end is provided with a drive tooth for power extraction on the outer circumferential surface of the crank arm, and this drive tooth is engaged with the reduction gear at the input end of the clutch, and the second transmission shaft of the two transmission shafts is shifted downward from the first transmission shaft, and A parallel four-cylinder engine for a motorcycle, characterized in that it is disposed within an area surrounded by an outer periphery.