JP2003239757A - Single cylinder four-cycle engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a balancer shaft and to improve its assembling property to a crankcase in a single cylinder four-cycle engine. <P>SOLUTION: A central weight part 78 positioned between webs 49, 49 of a crankshaft 41 is integratedly formed with a balancer shaft 50 at the central part of the shaft 50 in a shaft core direction, and side weight parts 79, 80 formed separately from the shaft 50 is removably fitted to the both end parts of the shaft 50 in the shaft core direction. At both sides of a crankcase 51 in the shaft core direction, cover chambers 58, 59 are formed via end walls 53, 54 of the crankcase, and the shaft 50 is supported to the end walls 53, 54 via bearings 65, 65. The central weight part 78 of the shaft 50 is housed in the crankcase 41, and right and left side weight parts 79, 80 are housed in the cover chambers 58, 59, respectively. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a single cylinder four-cycle engine, and more particularly to improvement of a balancer shaft.

[0002]

2. Description of the Related Art In a single-cylinder four-cycle engine, the weight of the balancer shaft is conventionally distributed to three parts, that is, the center part and both ends in the axial direction, to prevent the radial size of the balancer shaft from increasing. , Those that prevent the engine from increasing in size have been proposed. For example, the actual fair 7-
In the engine described in Japanese Patent No. 24566, as shown in FIG. 7, a balancer shaft 300 is arranged in parallel with the crankshaft 301, and a web 302 of the crankshaft 301 is provided at the center of the balancer shaft 300 in the axial direction. A central weight portion 305 located between them is formed, and side weight portions 306 and 307 are provided at both ends in the axial direction, respectively.

[0003]

However, in the balancer shaft 300 shown in FIG. 7, the central weight portion 305, both side weight portions 306 and 307, and the balancer gear 311 are integrally formed with the balancer shaft 300, and all of them are formed. The weight portions 305, 306, 307 and the balancer gear 311 are arranged between the bearing portions 315 and the crank chamber 316.
It is stored inside.

Therefore, the distance between the bearings of the balancer shaft 300 increases, and the distance between the bearings of the crank shaft 301 increases accordingly, and the balancer shaft 300 and the crank shaft 30 increase.
It is necessary to increase the rigidity of No. 1, which is an obstacle to making the engine lightweight and compact. Further, the overall shape of the balancer shaft becomes complicated, and it takes time and labor to process parts, and it also takes time and effort to assemble and maintain the balancer shaft.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to make a balancer shaft and an engine compact and to facilitate the assembly and maintenance of the balancer shaft.

[0006]

In order to solve the above-mentioned problems, the invention according to claim 1 of the present application provides a single-cylinder four-cycle engine equipped with a balancer shaft arranged in parallel with a crankshaft. The central weight part located between the webs of the crankshaft is integrally molded with the balancer shaft at the center part in the direction, and the side weight part formed separately from the balancer shaft is formed at both ends in the axial direction of the balancer shaft. It is detachably attached to the balancer shaft.

As a result, as compared with the conventional structure in which the three weight portions are formed integrally with the balancer shaft, the parts of the balancer shaft can be machined more easily, and the assembling work and the maintenance work of the balancer shaft to the crankcase are also performed. It will be easier.

According to a second aspect of the present invention, in a single-cylinder four-cycle engine equipped with a balancer shaft arranged in parallel with the crankshaft, the crankcase end wall is provided both in the crankshaft core direction of the crankcase. A cover chamber is formed, the balancer shaft is supported on the crankcase end wall via a bearing, and a central weight portion located between the crankshaft webs is provided at the central portion in the axial direction of the balancer shaft. Side weight portions housed in the cover chambers are provided at both ends in the axial direction.

As a result, the distance between the bearings of the balancer shaft can be shortened, so that the distance between the bearings of the crankshaft can be shortened, and the balancer shaft and the engine can be made compact.

According to a third aspect of the present invention, in the dry sump type four-cycle engine according to the first or second aspect, the central weight portion has a larger radial dimension than the side weight portion.

This makes it possible to effectively use the space between the webs of the crankshaft to secure a large eccentric weight for balancing. Especially, in the case of a dry sump type engine, since the crank chamber is in a dry state, the oil It is possible to increase the central weight portion up to the inner wall of the crankcase without taking into account the resistance.

According to a fourth aspect of the invention, in the first to third aspects of the invention, a balancer gear is detachably provided at an end portion of the balancer shaft in the axial direction, and a side weight portion is integrally formed with the balancer gear. is there.

As a result, the number of parts for the balancer can be reduced.

According to a fifth aspect of the present invention, in the dry sump type four-cycle engine according to the fourth aspect, the balancer gear is a scissors gear.

Further, if a scissor gear is adopted as the side gear integrally formed with the side weight portion, the backlash of the balancer shaft, which is apt to vary in rotation, can be eliminated and the gear noise can be reduced.

According to a sixth aspect of the present invention, in the dry sump type four-cycle engine according to the second aspect, one of the left and right cover chambers is a clutch chamber for accommodating a clutch, and the oil in the crank chamber is drained. It is a dry sump type engine that pumps out into a clutch chamber by a scavenging pump, and a balancer gear is provided in the clutch chamber where oil is stored.

As a result, for example, the space on the outer peripheral side of the crank gear can be effectively used as a space for disposing the side weight portion, and the engine can be made compact. Also, by immersing the balancer gear in the oil in the clutch chamber,
The balancer gear itself can lubricate the surface of the balancer gear.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION [Vehicle on which Engine is Mounted] FIG. 1 shows a four-wheeled vehicle for riding on rough terrain equipped with a dry sump type single cylinder four-cycle engine to which the present invention is applied. A pair of left and right front wheels 2 at the front of 1
And a pair of left and right rear wheels 5 via a swing arm 4, and the swing arm 4 is elastically supported by a shock absorber 3. An engine 7, a radiator 8 and the like are mounted in the body frame 1, and a riding type seat 10, a fuel tank 11, a bar-shaped handle 12 and the like are provided on an upper portion of the body frame 1.

In the engine 7, a cylinder 21, a cylinder head 22 and a head cover 23 are sequentially fastened on a crankcase 20, an exhaust pipe 24 is connected to a front exhaust port of the cylinder head 22, and the exhaust pipe 24 is connected to the exhaust pipe 24. It curves to the right, extends rearward, and is connected to the muffler 25. An intake pipe 26 is connected to a rear intake port of the cylinder head 21, and the intake pipe 26 includes a carburetor 27, an intake duct 28, and an element 29 in a rear air cleaner box 30.
Connected to.

The vehicle employs a chain drive system, and a drive chain 34 is wound between an output sprocket 31 of the engine 7 and a sprocket 33 of a rear axle 32.
The rear chain 5 is driven by the drive chain 34. In FIG. 1, reference numerals O1, O2, O3 and O5 respectively represent a crank shaft core of the engine 7, a shift input shaft core, a shift output shaft core and a balancer shaft core.

[Outline of Engine] FIG. 2 is an enlarged sectional view taken along the line II-II of FIG. 1, showing an engine in a plane passing through a cylinder center line C, a crank shaft core O1, a shift input shaft O2 and a shift output shaft O3. It is the figure which cut | disconnected 7 and developed. In FIG. 2, the crankcase 20 is divided into two left and right crankcase members 20a and 20b, and both crankcase members 20a and 20b have a mating surface that is orthogonal to the crankshaft axis O1 and passes through the cylinder center line C. Are combined as. In the crankcase 20, the front part is a crank chamber 51 for housing the crankshaft 41, and the rear part is a mission chamber 52 for housing the mission M.

Left and right end walls 53, 54 of the crankcase 20
Crankcase covers 56 and 57 are fastened to the respective crankcases, and a generator 60 is housed in a cover chamber 58 covered by the left crankcase cover 56, and a generator chamber 60 is housed in a cover chamber 59 covered by the right crankcase cover 57. Contains a multi-plate friction clutch 61.

Left and right crankcase covers 56, 57
In order to clearly distinguish the cover chambers 58 and 59 from each other, the left side crankcase cover 56 and the cover chamber 58 are referred to as a generator cover and a generator chamber, and the right side crankcase cover 57 is named according to the names of the devices to be housed therein.
The cover chamber 59 and the cover chamber 59 are referred to as a clutch cover and a clutch chamber, and will be described below.

[Power transmission system] The crankshaft 41 is rotatably supported by the left and right end walls 53 and 54 of the crankcase 20 via bearings 65 and 65, and has a left and right divided structure. The left and right crankshaft parts are connected. The left end portion of the crankshaft 41 projects into the generator chamber 58 to form a cam chain sprocket 68, and a starting gear 84 and a rotor (flyhole) 70 of the generator 60 are attached. The cam chain 71 wound around the cam chain sprocket 68 is a cam chain tunnel 62 formed in the cylinder 21 and the cylinder head 22.
Passes through the inside of the head cover 23 and is wound around the sprocket 72 of the cam shaft 48.

The right end of the crankshaft 41 is a clutch chamber 59.
A balancer drive gear 83 and a crank gear 82 are arranged side by side from the bearing 65 side (left side) in this order at the right end portion that projects inward and projects into the clutch chamber 59.
Meshes with the clutch gear 81 of the clutch 61.

The mission M in the mission chamber 52 is composed of a speed-changing shaft such as the speed-changing input shaft 42 and the speed-changing output shaft 43, a speed-changing gear group, and the like. The right end portion of the speed-changing input shaft 42 is inside the clutch chamber 59. The clutch 61 is attached to the right end protruding portion. The left end of the variable speed output shaft 43 projects outside the crankcase, and the output sprocket 31 is fixed to the left end projection.

[Structure of Balancer Shaft] FIG. 4 shows IV-IV of FIG.
The cross section is shown, and the balancer shaft 50 is the crankshaft 41.
Is arranged in parallel with the crankshaft 41 and is rotatably supported by the left and right end walls 53, 54 of the crankcase 20 via bearings 75, 75. An oil seal is provided outside the bearing 75 on the right side of the balancer shaft 50. The left and right ends of the balancer shaft 50 project from the crank chamber 51 into the generator chamber 58 and the clutch chamber 59, respectively. The center weight portion 78 and the left and right side weight portions 79 are provided at the center and left and right ends of the balancer shaft center. , 80 are provided respectively.

The central weight portion 78 is formed in a semicircular shape and is integrally formed with the balancer shaft 50, and is arranged between the webs 49 of the crankshaft 41.

The left side weight portion 79 is the balancer shaft 50.
It is formed separately from and is detachably fixed to the left end of the balancer shaft 50 in the axial direction. Specifically, the left side weight portion 79 is spline-fitted to a spline tooth formed at the left end portion of the balancer shaft 50 in the axial center direction, and is axially locked by a locking ring 73. It is housed in the chamber 58 and faces the cam chain sprocket 68 from the front.

The right side weight portion 80 is the balancer gear 9
The balancer gear 91 is formed integrally with the balancer gear 91 on the right side surface of the No. 1 and is housed in the clutch chamber 59 together with the balancer gear 91. The balancer gear 91 meshes with the balancer drive gear 83 of the crankshaft 41. Since the balancer gear 91 meshes with the balancer drive gear 83 as described above, the right side weight portion 80 faces the crank gear 82 adjacent to the balancer drive gear 83 from the front. That is, the right side weight portion 80 is arranged by effectively utilizing the outer peripheral side space of the clutch gear 82.

The balancer gear 91 is formed separately from the balancer shaft 50, is fitted to the right end of the balancer shaft 50 in the axial direction, is fixed in the rotational direction by the key 74, and is immovable in the axial direction by the nut 85. It is fixed.

Since the balancer shaft 50 is a uniaxial primary balancer for a single cylinder four-cycle engine, the weight portions 78, 79, 80 are in opposite phases to the crank pin 37 at the top dead center of the crank web 49 and piston. It is located (see Figure 3).

The balancer gear 91 is formed to have the same diameter as the balancer drive gear 83 of the crankshaft 41, so that the balancer shaft 50 rotates synchronously in the opposite direction to the crankshaft 41. The radial dimension (radius) R1 of the central weight portion 78 is set to be substantially the same as the radius of the balancer gear 91, and the radial dimension R2 of the right side weight portion 80 is smaller than the radial dimension R1 of the central weight portion 78. Is set to be smaller, the radial dimension R3 of the left side weight portion 79 is set to be smaller than the radial dimension R2 of the right side weight portion 80, and the left side weight portion 79 in the generator chamber 58 is arranged in the cam chain 71. It doesn't get in the way.

As the balancer gear 91, a scissors gear is used so as to absorb backlash. That is, the sub gear 86 is provided so as to be relatively rotatable with respect to the gear body of the balancer gear 91 within a certain range, the circumferentially compressible coil spring 87 is contracted between the gear body and the sub gear 86, and the elasticity of the coil spring 87 is reduced. The force causes the teeth of the gear body and the teeth of the sub-gear 86 to deviate at a predetermined angle.

At the right end edge of the balancer shaft 50, the water pump 9
8 pump shafts 99 are interlockingly connected via a joint.

FIG. 3 shows the inner surface (right side surface) of the left crankcase member 20a, and clearly shows the positional relationship between the balancer shaft 50 and the crankshaft 41 in the front-rear direction.

[Oil Storage Structure in Crank Case] Referring to FIG. 3, the engine of this embodiment is of the dry sump type as described above, but instead of installing an oil tank outside the engine, the crank chamber 51 and rear The mission chamber 52 and the mission chamber 52 are partitioned by a partition wall 55 having a constant height, whereby the crank chamber 51 is kept in a dry state and the lower portion of the mission chamber 52 is used as an oil tank chamber 64. The partition wall 55 is formed at substantially the same height as the crank shaft core O1, extends forward and downward along the outer shape of the crank web 49, and is connected to the partition wall 101 extending downward at a position substantially directly below the crank shaft core O1. As a result, the oil tank chamber 64 is expanded to a position below the crank chamber 51. The crank chamber 51 has the partition wall 55.
Is surrounded by a bottom wall 102 connected to the front from the front lower end (intersection point with the partition wall 101). The bottom wall 102 reaches a position below the front balancer shaft 50, and further, a central weight portion 78 of the balancer shaft 50. Extends to the front upper end of the crank chamber 51 along the outer periphery of the crank chamber 51.

In FIG. 5, the left end wall (crank case left end wall) 53 of the crank chamber 51 is formed with an oil escape passage 125 substantially flush with the bottom of the crank chamber 51.
The oil escape passage 125 is opened to the generator chamber 58 with a step D. Below the bottom wall 102 of the crank chamber 51, a pair of oil passages 130 and 131 parallel to the crankshaft axis O1 are provided in parallel with the crankcase 20, and the left end of one of the oil passages 130 is the generator chamber. 58, the right end is closed, the left end of the other oil passage 131 is closed, and the right end is below the oil level L1.
It opens towards. A left half of the oil passages 130 and 131 is separated by a partition wall 133, and a right half of the oil passages 130 and 131 communicate with each other through a plate-shaped tertiary filter 135.

A feed pump 106 is provided in the clutch chamber 59.
And a scavenging pump 107 are arranged, and the feed pump 106 sucks the oil in the oil tank chamber 64 shown in FIG. 6 and sends the oil under pressure to each lubrication point of the engine. The suction portion 159 of the scavenging pump 107 of FIG. 5 is connected to the oil passage 131 via the O-ring 161.
The oil sucked from the generator chamber 58 is directly connected to the right end opening of the clutch chamber 59 by the hose 163.
It is designed to discharge above the oil level.

The clutch chamber 59 communicates with the oil tank chamber 64 through the communication hole 105 at the lower end as shown in FIG.
Further, the same level L1 of oil as the oil tank chamber 64 is stored in the clutch chamber 59. In the clutch chamber 59 containing such oil, the lower end of the balancer gear 91 is immersed in the oil in the clutch chamber 59, and the rotation of the balancer gear 91 can lubricate the balancer gear surface. On the other hand, as shown in FIG. 6, the clutch 61 is located at a height that does not allow it to be immersed in oil.

[0041]

[Assembly of Balancer Shaft] In FIG. 4, when the left and right crankcase members 20a and 20b are fastened, the balancer shaft 50 is detached from the left and right side weight portions 78 and 79 and the balancer gear 91, and the central weight. The portion 78 is inserted between the crank webs 49, and the left and right ends of the balancer shaft 50 are projected into the generator chamber 58 and the clutch chamber 59 via the bearings 75.

After fastening both crankcase members 20a, 20b, the left side weight portion 79 is spline-fitted to the left end portion of the balancer shaft 50 at a predetermined phase and locked by the locking ring 73. On the other hand, the balancer gear 91 is fitted to the right end portion and positioned and fixed by the key 74 at a predetermined phase,
Fasten with the nut 85.

As is well known, during operation of the engine, the balancer shaft 50 rotates synchronously in the opposite direction to the crankshaft 41 and balances with the crankshaft 41. The radial dimension R1 of the central weight portion 78 is set large enough to approach the front end wall of the crank chamber as shown in FIG. 3, but since the inside of the crank chamber 51 is in a dry state, the central weight portion 78 has a resistance to oil. I will not receive it.

On the other hand, as shown in FIG. 5, the balancer gear 91 is submerged in the oil in the clutch chamber 59, and therefore the surface of the balancer gear 91 and the balancer drive gear 83 is lubricated by the oil that is lifted up by itself.

Further, since the scissors gear is used as the balancer gear 91, even the balancer gear 91 in which the right side weight portion 80 is integrally formed absorbs the backlash in the meshing portion of the balancer drive gear 83 and the balancer gear 91, and thus the balancer. The smooth rotation of the shaft 50 can be maintained, and gear noise can be prevented.

[0046]

Other Embodiments of the Invention (1) It is also possible to apply the present invention to a dry sump type single cylinder four-cycle engine in which an oil tank is installed outside the engine or an engine other than the dry sump type.

(2) Gears other than the scissors gear can be used as the balancer gear.

[0048]

As described above, the present invention has the following advantages. (1) The central weight portion located between the webs of the crankshaft is integrally molded with the balancer shaft at the center portion of the balancer shaft in the axial direction, and is formed separately from the balancer shaft at both ends of the balancer shaft. Since the side weights are detachably attached to the balancer shaft, the balancer shaft parts are easier to machine and the balancer shaft crank is easier than the conventional structure in which three weights are integrally formed on the balancer shaft. Assembly work and maintenance work on the case are also easy.

(2) A cover chamber is formed in each of the crank chamber axial directions through the crankcase end wall, and the balancer shaft is supported by the crankcase end wall through a bearing. When the central weight portion located between the webs of the crankshaft is provided at the central portion in the axial direction, and the side weight portions accommodated in the cover chambers are provided at both ends in the axial direction of the balancer shaft, the balancer is provided. It is possible to reduce the distance between the shaft bearings, which can shorten the distance between the crankshaft bearings, and to achieve compactness of the balancer shaft and the engine.

(3) The radial dimension of the central weight is
If it is larger than the side weight part, the space between the webs of the crankshaft can be effectively used to secure a large eccentric weight for balance. Especially in the case of a dry sump engine, the crank chamber is in a dry state. It is possible to increase the central weight portion up to the inner wall of the crankcase without considering the oil resistance.

(4) If the balancer gear is detachably provided at the end of the balancer shaft in the direction of the crankshaft center and the side weight part is integrally formed with the balancer gear, the number of parts for the balancer can be reduced.

(5) When a scissor gear is used as the balancer gear in which the side weight portions are integrally formed, backlash of the balancer shaft, which is apt to vary in rotation, is eliminated, and gear noise can be reduced.

(6) One cover chamber is a clutch chamber for accommodating a clutch, and is a dry sump type engine in which oil in the crank chamber is pumped out to the clutch chamber by a scavenging pump, and oil is accumulated. If the balancer gear is provided in the clutch chamber, for example, the space on the outer peripheral side of the crank gear can be effectively used as a space for disposing the right side weight portion, and the engine can be made compact. Further, by immersing the balancer gear in the oil in the clutch chamber, the balancer gear itself can lubricate the surface of the balancer gear.

[Brief description of drawings]

FIG. 1 is a side view of a riding type all-terrain vehicle for four-wheeled vehicle equipped with a dry sump type four-cycle engine according to the present invention.

FIG. 2 is a II-II cross sectional enlarged development view of the engine shown in FIG.

FIG. 3 is an inside view (right side view) inside the left crankcase member.

4 is a cross-sectional view taken along the line IV-IV of FIG.

5 is a sectional view taken along line VV of FIG.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a vertical sectional view of a conventional example.

[Explanation of symbols]

20 crank case 41 crank shaft 49 crank web 50 balancer shaft 51 crank chamber 52 mission chamber 53, 54 crank case end wall 56 generator cover (an example of crank case cover) 57 clutch cover (an example of crank case cover) 58 generator chamber (cover Chamber example) 59 clutch chamber (an example of cover chamber) 60 generator 61 clutch 64 oil tank chamber 73 locking ring 75 balancer shaft bearing 78 center weight portion 79 left side weight portion 80 right side weight portion 81 clutch gear 82 crank gear 83 Balancer Drive Gear 91 Balancer Gear (Scissors Gear) 107 Scavenging Pump

Claims (6)

[Claims] 1. A single-cylinder four-cycle engine having a balancer shaft arranged parallel to a crankshaft, wherein a central weight part located between webs of the crankshaft is provided at a central part of the balancer shaft in the axial center direction. A single-cylinder 4 cycle characterized by being integrally molded with the balancer shaft, and at both ends in the axial direction of the balancer shaft, side weights formed separately from the balancer shaft are detachably attached to the balancer shaft. engine. 2. A single-cylinder four-cycle engine having a balancer shaft arranged in parallel with a crankshaft, wherein a cover chamber is formed in both crankshaft core directions of the crankcase via a crankcase end wall. A balancer shaft is supported on the crankcase end wall via bearings, and a central weight portion located between the webs of the crankshaft is provided at the central portion of the balancer shaft in the axial center direction. The single-cylinder 4-cycle engine is characterized in that side weights are provided in the respective cover chambers. 3. The single-cylinder four-cycle engine according to claim 1, wherein the central weight portion has a larger radial dimension than the side weight portion. 4. A balancer gear is detachably provided at an end portion of the balancer shaft in the axial center direction, and a side weight portion is integrally formed with the balancer gear.
The single-cylinder 4-cycle engine described in 3. 5. The single-cylinder four-cycle engine according to claim 4, wherein the balancer gear is a scissors gear. 6. A dry sump type engine in which one of the left and right cover chambers is a clutch chamber for housing a clutch, and the oil in the crank chamber is pumped out to the clutch chamber by a scavenging pump. The single-cylinder four-cycle engine according to claim 2, wherein a balancer gear is provided in the clutch chamber in which is stored.