JP2001132796A - Crank shaft for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a crank shaft for an internal combustion engine for suppressing the generation of engine noise for a long period by maintaining the effect to reduce the generation of vibration of the crank shaft, through simple constitution. SOLUTION: In this crank shaft for an internal combustion engine, a damper weight 43 is mounted on a crank web 11b via an elastic member 44, such tat the center of gravity of the damper weight 43 approximately coincides with the rotary center axis of the crank shaft 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a crankshaft for an internal combustion engine.

[0002]

2. Description of the Related Art Since a crankshaft is an elastic body,
Explosive load causes torsional vibration due to bending vibration and torque fluctuation. In particular, when a gear, clutch or other rotating body is provided at the end protruding outward from the bearing, the natural frequency of the crankshaft system and the frequency of torque fluctuation, including these, are supported by the crankshaft supported by the bearing. Resonance tends to increase the torsional vibration amplitude, and there is a problem of noise caused by torsional vibration.

An example in which a dynamic damper is provided on a crank web of a crankshaft (Japanese Utility Model Application Laid-Open No. 57-10
No. 4012). FIG. 6 shows an example described in the publication.

[0004] Crank pin in crankshaft 01
Each of the circular crank webs 02, 02 on both sides of 03 is provided with a notch in a substantially semicircular shape, and a substantially semicircular weight piece 06, 06 is attached to each notch via an elastic plate 05, 05. .

The weight pieces 06, 06 vibrate due to the deformation of the elastic plates 05, 05 so as to cancel the torsional vibration of the crankshaft 01, and the vibration energy is diffused as heat by the internal friction of the elastic plates 05, 05 to attenuate the torsional vibration. Let it.

[0006]

However, the weight pieces 06
Is attached to the semicircular portion of the circular crank web 02, and the center of gravity of the weight piece 06 is eccentric from the center axis of rotation of the crankshaft 01. The load due to this centrifugal force is always applied to the elastic plate 05, and the higher the rotation speed, the greater the load,
The durability of the elastic plate 05 is reduced, and the damping force of the torsional vibration is deteriorated, which may cause noise.

A crankshaft that is supported by at least one pair of crank bearings is apt to generate bending vibration, and a power transmission system on one side tends to generate torsional vibration. If the crank web is attached to both sides of the crank pin by press fitting, the bending vibration cannot be effectively reduced, and the noise caused by the bending vibration cannot be sufficiently suppressed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to maintain the effect of reducing the vibration of the crankshaft with a simple configuration and to suppress engine noise for a long period of time. In providing a crankshaft for an internal combustion engine.

[0009]

In order to achieve the above object, according to the first aspect of the present invention, the damper weight is elastically adjusted so that the center of gravity of the damper weight substantially coincides with the rotation center axis of the crankshaft. The crankshaft of the internal combustion engine was attached to the crank web via members.

[0010] Since the center of gravity of the damper weight attached to the crank web substantially coincides with the rotation center axis of the crankshaft, the centrifugal force accompanying the rotation of the damper weight does not act to displace the damper weight. Since no load due to centrifugal force is applied, the durability of the elastic member can be improved.

[0011] Since the damper weight is attached to the crank web via an elastic member having improved durability,
The effect of attenuating torsional vibration and bending vibration of the crankshaft can be maintained, and engine noise can be reduced over a long period of time.

According to a second aspect of the present invention, in a crankshaft that is supported by a crankcase by a pair of left and right crank bearings, the crank web on the opposite side of the crank web on both sides of the crank pin to the side on which power is transmitted is provided. 5 is a crankshaft of an internal combustion engine to which a damper weight is attached via an elastic member.

By attaching a damper weight via an elastic member to the crank web on the side opposite to the side where the power of the crankshaft is transmitted, torsional vibration and bending vibration amplitude under an explosion load with the power transmission system side as a fulcrum shaft. Will have a dynamic damper on the side where
Torsional vibration and bending vibration of the crankshaft can be reduced more effectively, and engine noise can be prevented.

According to a third aspect of the present invention, there is provided a crankshaft which is supported on a crankcase by a pair of left and right crank bearings, the pair of crank bearings having different rigidities, and the crank webs on both sides of the crankpin are used. The crankshaft of the internal combustion engine has a damper weight attached to a low rigidity crank bearing side crank web via an elastic member.

By supporting the crankshaft with a pair of left and right crank bearings having different rigidities, the low-rigidity crank bearing side receives an explosive load with the high-rigidity crank bearing as a fulcrum shaft, and the bending vibration amplitude increases. By attaching a damper weight to the low rigidity crank bearing side crank web via an elastic member, bending vibration of the crankshaft can be reduced more effectively, and engine noise can be prevented.

According to a fourth aspect of the present invention, in the crankshaft for an internal combustion engine according to the second or third aspect, the damper weight is provided via an elastic member such that a center of gravity substantially coincides with a rotation center axis of the crankshaft. , Attached to the crank web.

The bending vibration of the crankshaft can be reduced, and the load of the elastic member due to centrifugal force is not applied, so that the durability of the elastic member can be improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment according to the present invention will be described below with reference to FIGS. The internal combustion engine 1 according to the present embodiment is a water-cooled, single-cylinder, four-cycle internal combustion engine mounted on a motorcycle.

The internal combustion engine 1 has a large crankcase 2,
Cylinder 3, cylinder head 4, cylinder head cover 5
, And are superimposed and assembled substantially forward in this order.

Left and right horizontal crankshafts
10 is the left crankshaft 11 and the right crankshaft
The crankshafts 13 and 12 are integrally formed by connecting a crankpin 13 to each other.
Both ends of the crank pin 13 are press-fitted into eccentric circular holes of the thick disk-shaped crank webs 11b and 12b, respectively, and are connected to each other.

The crankcase 2 is of a left-right split type, and reinforcing rings are provided in corresponding circular holes of the left and right crankcases 2a and 2b.
The right and left reinforcing rings 14 and 15 are fitted.
The left and right crank webs 11 of the crankshaft 10 are provided with ball bearings 8 and roller bearings 9, respectively.
The root portions of the outer crank journals 11a and 12a of the outer crankshafts b and 12b are supported, respectively, so that the entire crankshaft
10 is rotatably supported by left and right ball bearings 8 and roller bearings 9.

The inner race of the left ball bearing 8 is press-fitted into the crank journal 11a and fixed, while the outer race is press-fitted into the inner periphery of the reinforcing ring 14 integrated with the crankcase 2. The retaining plate for preventing the ball bearing 8 from coming off because the press-in allowance is loosened due to thermal expansion at the time of heating.
16 is fixed to the left crankcase 2a by bolts 17. The retaining plate 16 partially presses the reinforcing ring 14, and an end of the retaining ring 16 is fitted and fixed in a cut of the outer race of the ball bearing 8.

A transmission chamber is formed behind the crankshaft 10, and a main shaft 20 is provided with a starting clutch 21,
The gears 22 and 23 are arranged so as to be able to transmit power via a gearshift clutch 24, and a counter shaft 25 is disposed behind the main shaft 20 so as to be able to transmit power via a gear group 26.

On the other hand, in the cylinder 3, a piston 18 reciprocates in a cylinder bore, and a connecting rod is provided between the piston 18 and the crankpin 13 of the crankshaft 10.
19 are linked.

The cylinder head 4 has an intake passage extending upward from the combustion chamber facing the cylinder bore, an exhaust passage extending downward, and a spark plug 27 fitted into the combustion chamber from the right side.

The cylinder head 4 is provided with a valve operating mechanism, a camshaft 31 for swinging a rocker arm is mounted on the upper part of the cylinder head 4, and a driven sprocket 32 is coaxially fixed to the left end of the camshaft 31. Water pump driven via the driven sprocket 32
36 is provided on the left side of the cylinder head 4.

On the left side of the cylinder 3, a chain chamber 3a is formed. On the left side of the left crankcase 2a, a large concave portion 2ay which is bordered on the front side by a peripheral wall 2ax and opened to the left.
Is formed, and the recess 2ay is formed in the chain chamber 3a.
And the left crankshaft 11 in the recess 2ay.
A drive sprocket 33 is fitted to the crank journal 11a.

A timing chain 34 extends between the drive sprocket 33 and the driven sprocket 32 through the chain chamber 3a.
The ten rotations drive the valve train via the timing chain.

As described above, the left and right sides of the crank webs 11b and 12b are supported by the crankcase 2 by the ball bearings 8 and the roller bearings 9, and the crank journal 11a protrudes leftward from the left ball bearing 8. An AC generator 35 is provided at an end of the drive sprocket 33, and the drive sprocket 33 is fitted between the AC generator 35 and the ball bearing 8. A
The left side of the C generator 40 is covered with the case cover 6.

On the other hand, the starting clutch 21 and the centrifugal oil strainer 28 are provided at the end of the crank journal 12a of the crankshaft 10 projecting rightward from the right roller bearing 9. Centrifugal oil strainer
The right side of the clutch 28 and the clutch 24 are covered by the clutch cover 7.

The oil sucked up by the oil pump disposed below the crankshaft 10 passes through an oil passage 7a formed in the wall of the clutch cover 7 to pass through a communication passage 12c at the end of the right crankshaft 12. The oil enters the strainer chamber 28a of the centrifugal oil strainer 28 through the centrifugal force, and foreign matter is removed by centrifugal force.
Enter 12d, crank pin 13 and connecting rod 19
Is supplied to the connecting portion of the.

The internal combustion engine 1 has a structure as roughly described above, and includes a crankshaft 10 oriented horizontally in the left-right direction.
The AC generator 35 is provided at the end of the crank journal 11a which is supported on the crankcase 2 by ball bearings 8 and roller bearings 9 on the left and right sides of the crank webs 11b and 12b, and protrudes leftward from the left ball bearing 8. A start clutch 21 is provided at an end of the crank journal 12a projecting rightward from the roller bearing 9 on the right side.

In this crankshaft system, a dynamic damper 40 is provided on the crank web 11b of the left crankshaft 11 opposite to the right crankshaft 12 constituting the power transmission system such as the starting clutch 21.

That is, a thick disk-shaped crank web 11b
As shown in FIG. 3, a concave portion 41 is formed in a bold U-shape so as to go around a central circle portion where the crank journal 11a projects, as shown in FIG.

A circular hole 42 into which the crankpin 13 is press-fitted is formed in a portion where the concave portion 41 between both ends of the U-shape is not formed. Rigidity and strength are secured.

Both ends of the U-shape of the concave portion 41 are slightly bulged outward, and the generally U-shaped concave portion 41 is provided with the same concave portion.
A damper weight 43, which is a metal plate of the same shape slightly smaller than 41, is inserted with a margin and is elastically supported via an elastic rubber member 44.

The elastic rubber member 44 is interposed between the inner surface of the concave portion 41 and the corresponding surface of the damper weight 43 and is baked on the both surfaces. It is elastically supported by the elastic rubber member 44 in such a form that it is loosely fitted with a gap so as to be trimmed. The elastic rubber member 44 is interposed in the outer gap of the outer edge of the damper weight 43, but merely forms the air gap 45 without intervening in the inner gap (see FIG. 3).

The U-shaped ends of the damper weight 43 are also recessed 41.
The bulges at both ends eliminate the unbalance around the center of the rotation axis due to the U-shaped notch.

As described above, the shape and thickness of the damper weight 43 are determined so that the center of gravity of the damper weight 43 loosely fitted to the left side surface of the crank web 11b is located on the rotation center axis of the crankshaft 10.

Therefore, the damper weight 43 does not displace in the centrifugal direction due to the centrifugal force even if it rotates with the rotation of the crankshaft 10, so that the elastic rubber member 44
The centrifugal force is not applied to the plate.

As described above, since the load due to the centrifugal force is not applied to the elastic rubber member 44, the durability of the elastic rubber member 44 is improved. Elastic rubber member applies centrifugal force load especially at high speed rotation
If it is applied to the elastic member 44, the load of the elastic rubber member 44 is large, but since the centrifugal force is not applied to the elastic rubber member 44, the load on the elastic member 44 is greatly reduced regardless of the rotation speed, and The durability of the rubber member 44 is improved.

Further, since the damper weight 43 is not displaced by centrifugal force, the damper weight 43 can be attached with a simple structure by baking the elastic rubber member 44, and a separate member is required to increase the attachment strength. It does not increase or increase in size, but further damper weight
Reference numeral 43 is attached so as to be embedded in the crank web 11b, thereby reducing the size and weight.

Further, the damper weight 43 is embedded in the crank web 11b. An elastic rubber member 44 is interposed in the outer gap of the outer edge of the damper weight 43, and the movement of the damper weight 43 is guided by the inner peripheral surface of the concave portion 41. Therefore, the durability of the elastic rubber member 44 is higher than when the damper weight is externally attached.

The damper weight 43 and the elastic rubber member 44
Except that the damper weight 43 is not displaced by centrifugal force, it acts as a dynamic damper, and since the elastic rubber member 44 has high durability, the effect of reducing torsional vibration and bending vibration of the crankshaft 10 is maintained for a long time. You.

Since the dynamic damper 40 is provided on the crank web 11b of the left crankshaft 11 opposite to the right crankshaft 12 constituting the power transmission system, the explosion load is generated using the power transmission system as a fulcrum shaft. The dynamic damper 40 is provided on the side where the amplitude of the bending and torsional vibration on the side of the crank pin 13 is increased, so that the bending and torsional vibration of the crankshaft 10 can be reduced more effectively.

The dynamic damper 40 is provided on the crank web 11b on the side of the pair of left and right ball bearings 8 and roller bearings 9 on which the low rigidity ball bearings 8 are interposed. The dynamic damper 40 is provided on the side where the explosion load is applied and the bending vibration amplitude increases with the fulcrum as the fulcrum axis, and the bending vibration of the crankshaft 10 can be reduced even more effectively.

As described above, the bending and torsional vibration of the crankshaft 10 is greatly reduced, and the engine noise caused by the vibration of the crankshaft 10 is reliably prevented. Particularly, even at the time of high rotation, the bending and torsional vibration of the crankshaft 10 can be sufficiently attenuated, and the engine noise can be significantly reduced.

Since the bending and torsional vibration of the crankshaft 10 is reduced, the load on the press-fitted portion of the crankpin 13 on the crank webs 11b and 12b is greatly reduced.

Next, another embodiment will be described with reference to FIGS. Internal combustion engine 50 according to the present embodiment
Has substantially the same structure as the internal combustion engine 1, and the same members have the same reference numerals. The crankshaft 51 is configured by integrally connecting a left crankshaft 52 and a right crankshaft 53 with a crankpin 54.

Crank web of left crankshaft 52
52b is not formed with a recess for embedding a damper weight, and the left crankcase 2a and the crank web are not formed.
The interval from the internal combustion engine 52b is somewhat wider than that of the internal combustion engine 1. The dynamic damper 60 is attached to the crank web 52b using this gap.

The dynamic damper 60 is configured such that a damper weight 62 is elastically supported via an elastic rubber member 63 on a mounting plate 61 for mounting on the crank web 52b.

The mounting plate 61 has a peripheral wall portion 61b with the outer peripheral edge of a hollow disk portion 61a slightly extending in the axial direction, and the inner diameter of the peripheral wall portion 61b is a thick disk-shaped crank web 52.
The diameter of the hollow circle of the disc portion 61a is substantially equal to the outer diameter of the disk portion 61b, and has a diameter that allows the crank journal 52a to be inserted with a margin.

An annular damper weight 62 is provided on the outer surface of the disk portion 61a of the mounting plate 61 via an elastic rubber member 63.
Is attached. Annular damper weight 62
Is further adhered by baking to an elastic rubber member 63 burned around the outer circumference of the hollow circle of the disk portion 61a and is elastically supported.

The mounting plate 61 on which the damper weight 62 is supported via the elastic rubber member 63 is press-fitted into the crank web 52b of the left crankshaft 52 and mounted. The center of gravity of the damper weight 62 is on the rotation center axis of the crankshaft 51.

Therefore, the damper weight 62 does not displace in the centrifugal direction due to centrifugal force even if it rotates with the rotation of the crankshaft 51.
Since no load due to centrifugal force is applied to the elastic rubber member 63
Durability is improved.

In addition, the dynamic damper 60 can effectively reduce torsional vibration and bending vibration of the crankshaft 51 similarly to the dynamic damper 40.
Engine noise can be prevented.

The dynamic damper 60 is attached to the mounting plate 61.
If it is manufactured separately from the crankshaft 51 including
The rest can be assembled simply by press-fitting into the crankshaft 51, so that productivity can be improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of an internal combustion engine according to one embodiment of the present invention.

FIG. 2 is a side view of the internal combustion engine partially omitted.

FIG. 3 is a side view of a crankshaft and a connecting rod.

FIG. 4 is a longitudinal sectional view of a main part of an internal combustion engine according to another embodiment.

FIG. 5 is a side view of a crankshaft and a connecting rod of the internal combustion engine.

FIG. 6 is a plan view of a main part of a conventional crankshaft.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Crank case, 3 ... Cylinder, 4
... cylinder head, 5 ... cylinder head cover, 6 ... case cover, 7 ... clutch cover, 8 ... ball bearing, 9 ... roller bearing, 10 ... crankshaft, 11
… Left crankshaft, 12… right crankshaft,
13 ... crank pin, 14, 15 ... reinforcement ring, 16 ... retaining plate, 17 ... bolt, 18 ... piston, 19 ... connecting rod, 20 ... main shaft, 21 ... starting clutch,
22, 23 gear, 24 gearshift clutch, 25 counter shaft, 26 gear group, 27 spark plug, 28 centrifugal oil strainer, 31 camshaft, 32 driven sprocket, 33 drive sprocket, 34 Timing chain, 35… AC generator, 36… Water pump, 40…
Dynamic damper, 41 recess, 42 hole, 43 damper weight, 44 elastic rubber member, 45 gap, 50 internal combustion engine, 51 crankshaft, 52 left crankshaft, 53 right crankshaft, 54 ... crank pin, 60
... Dynamic damper, 61 ... Mounting plate, 62 ... Damper weight, 63 ... Elastic rubber member.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Satoshi Shimizu 1-4-1 Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 3J033 AA02 BA13 CA03

Claims (4)

[Claims] 1. A crankshaft for an internal combustion engine, wherein the damper weight is attached to the crank web via an elastic member such that the center of gravity of the damper weight substantially coincides with the rotation center axis of the crankshaft. 2. A crankshaft which is supported by a crankcase by a pair of left and right crank bearings, wherein a damper is provided on an opposite one of the crank webs on both sides of the crank pin to a side opposite to a side to which power is transmitted via an elastic member. A crankshaft for an internal combustion engine, wherein a weight is attached. 3. A crankshaft which is supported on a crankcase by a pair of left and right crank bearings, wherein said pair of crank bearings have different stiffness, and said low rigidity crank out of crank webs on both sides of a crank pin. A crankshaft for an internal combustion engine, wherein a damper weight is attached to a bearing-side crank web via an elastic member. 4. The internal combustion engine according to claim 2, wherein the damper weight is attached to the crank web via an elastic member such that a center of gravity substantially coincides with a rotation center axis of the crankshaft. Engine crankshaft.