JPH051013U - Multi-cylinder internal combustion engine crankshaft - Google Patents

Abstract

(57) [Summary] [Purpose] To reduce the vibration of the flywheel and improve its durability. [Structure] Crankshaft 1 of multi-cylinder internal combustion engine
The crank arm 3h arranged at a position closest to the mounting end 4b of the flywheel 6 is formed to have a larger wall thickness than the other crank arms 3a to 3g.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 This invention relates to crankshafts of internal combustion engines, especially multi-cylinder internal combustion engines.

[0002]

[Prior Art]

 As an example of a crankshaft of a conventional multi-cylinder internal combustion engine, FIG. 3 shows a crankshaft 10 of a four-cylinder internal combustion engine. In this crankshaft 10, crank journals 11a to 11e forming an axis of the crankshaft 10 and crank pins 12a to 12d to which connecting rods are connected are integrally connected by crank arms 13a to 13h.

Further, a pulley 5 for driving a timing belt or a fan belt is fixed to a front end portion 14a of the crankshaft 10, while a rear end portion 14b of the crankshaft 10, that is, a power output end, is provided with an engine. A flywheel 6 is fixed to average the shaft torque and smooth the rotation. The flywheel 6 is formed as a large disc to have a large moment of inertia, and is usually also used as a friction surface of a clutch.

In the conventional crank arms 13a to 13h, the stresses applied to the respective crank arms 13a to 13h have been theoretically equal. Therefore, all of them have the same shape, that is, the same thickness. Has been formed. This is also effective in suppressing the imbalance during rotation of the crankshaft 10 to the minimum.

[0005]

[Problems to be solved by the device]

 However, in the conventional crankshaft 10, when the rigidity of the crankshaft 10 is insufficient, the flywheel 6 vibrates, and the crank arm 13h arranged closest to the mounting end of the flywheel 6 is located in front of the crank arm 13h. It was empirically recognized that strong vibrational stress was sequentially applied from the flywheel 6 to 13 g to 13 a. Therefore, in the crankshaft 10 of the conventional multi-cylinder internal combustion engine, the crank arm portion near the mounting end of the flywheel 6 has a problem of poor durability due to insufficient rigidity.

In order to solve such a problem, it is possible to uniformly increase the wall thickness of the crank arms 13a to 13h as in the conventional case to increase the strength, that is, the rigidity, but the strength is relatively large. The thickness of the crank arms 13a to 13f at a certain front portion is also increased, which causes adverse effects such as a significant increase in the overall length, weight, and cost of the engine.

The present invention has been made to solve such a problem, and reduces the vibration and durability of the crankshaft while minimizing the adverse effects such as increase in the total length, weight and cost of the engine. It is an object of the present invention to provide a crankshaft for a multi-cylinder internal combustion engine, which has been improved.

[0008]

[Means for Solving the Problems]

 In order to achieve the above-mentioned object, the crankshaft of the multi-cylinder internal combustion engine of the present invention has a crankshaft of a multi-cylinder internal combustion engine in which a flywheel is mounted on the shaft end, at least at a position closest to the flywheel mounting end. It is characterized in that the wall thickness of the crank arm arranged in the above is larger than that of the other crank arms.

[0009]

[Action]

 In the crankshaft of the above-mentioned multi-cylinder internal combustion engine, the wall thickness of at least the crank arm located closest to the flywheel mounting end is larger than the wall thickness of other crank arms. The strength of the crank arm, which receives the strongest vibration stress, is much higher than the strength of other crank arms.

[0010]

【Example】

 Hereinafter, an embodiment of a crankshaft of a multi-cylinder internal combustion engine of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a crankshaft 1 of a 4-cylinder engine as an example of a concrete structure of the crankshaft of the multi-cylinder internal combustion engine of the present invention.

The crankshaft 1 is composed of crank journals 1a to 1e, crank pins 2a to 2d, and crank arms 3a to 3h, and is integrally forged. The crank journals 1a to 1e are formed to have the same axial length and diameter. The crank journals 1a to 1e are rotatably supported by bearings of a crankcase (not shown), and rotatably support the crankshaft 1.

The crank pins 2a to 2d described above are also formed to have the same axial length and diameter. A large end of a connecting rod (not shown) is rotatably connected to the crank pins 2a to 2d to transmit the output of the piston. Next, the crank journals 1a to 1e and the crank pins 2a to 2d described above are alternately arranged and integrally connected by the crank arms 3a to 3h.

The conventional pulley 5 described above is fixed to the front end 4a (left end in the drawing) of the crankshaft 1, and the conventional flywheel described above is attached to the rear end 4b (right end in the drawing). The wheel 6 is fixed. By the way, the crank arms 3a to 3h described above are respectively composed of arm portions 3a 'to 3h' and weight portions 3a "to 3h", as shown in FIG. The arm portions 3a 'to 3h' correspond to actual connecting portions between the crank journals 1a to 1e and the crank pins 2a to 2d, and are generally subjected to strong stress. However, the tip end portions on the side of the crank pins 2a to 2d are tapered to correspond to the stress distribution in order to reduce the weight. On the other hand, each of the weight portions 3a "-3h" is formed in a fan shape and acts as a counter weight for imbalance correction.

Among these crank arms 3a to 3h, the front crank arms 3a to 3f are all of the same axial length, that is, the thickness T.₁2 and the same cross-sectional shape as shown in FIG. 2, that is, the same arm width W.₁Is formed in. That is, the crank arms 3a to 3f have the same thickness. Next, the crank arm 3g located at the seventh position from the front has the same thickness T as the crank arms 3a to 3f.₁Although it is formed on the₁Wider W ₂ Is enlarged and formed. That is, the wall thickness of the crank arm 3g is formed to be larger than the wall thickness of the crank arms 3a to 3f, and the strength thereof is increased. However, the cross-sectional shape of the weight portion 3g ″ is the same as that of the weight portions 3a ″ to 3f ″.

Next, the crank arm 3h arranged at the rearmost position, that is, the position closest to the flywheel mounting end, is enlarged and formed to have a thickness T ₂ which is thicker than the thickness T ₁ of the crank arms 3a to 3f as a whole. with the arm width is enlarged further formed on the wider W ₃ than the arm width W ₂ of the crank arm 3g. That is, the thickness of the crank arm 3h is made larger than that of the crank arm 3g, and the strength thereof is maximized as compared with the other crank arms 3a to 3g.

However, the cross-sectional shape of the weight portion 3h ″ is the same as that of the weight portions 3a ″ to 3g ″. Thus, in the present crankshaft 1, the front crank arms 3a to 3f to the rear crank arm 3g. , 3h, the wall thickness is increased and the strength is increased in response to the vibration stress input from the flywheel 6, so that the durability of the crankshaft 1 is effectively improved. By increasing only the wall thickness of the three crank arms 3g and 3h, the weight increase of the crankshaft 1 is minimized and the durability thereof is improved. since the is increased to W _2, the arrangement interval in the axial direction of the crank journal 1a~1e the crank journal 1d, only between 1e is increased from L ₁ to L ₂ Is extended. Thus, the overall length increase of the engine also stopped only increase the thickness of the crank arm 3h, the weight gain and cost increase of the entire engine is greatly reduced.

By increasing the strength of the crankshaft 1, that is, the rigidity, the strain of the crankshaft 1 during operation is reduced. As a result, the vibration of the flywheel 6 is suppressed, and the vibration stress input to the crankshaft 1 is consequently reduced. This leads to a more effective and significantly improved durability of the crankshaft 1.

In addition, as the vibration of the flywheel 6 is suppressed as described above, vibration of the cylinder block due to vibration resonance with the flywheel 6 is suppressed, engine noise is reduced, and the flywheel is also reduced. Since No. 6 is also used as the clutch friction surface as described above, it is possible to improve the clutch disengagement failure at high rotation speed. By increasing the rigidity of the crankshaft 1 in this manner, various secondary effects are produced.

Further, in the present crankshaft 1, the thickness of the rearmost crank arm 3h is increased as a whole from T ₁ to T ₂ . This means that the mass of the weight portion 3h ″ is increased, and the increase in the imbalance of the crankshaft 1 due to the expansion of the arm widths of the crank arms 3g and 3h to W ₂ and W ₃ , respectively, is effectively offset. Therefore, it is possible to eliminate the need to newly add a required mass to another portion of the crankshaft 1, for example, the frontmost crank arm 3a for the purpose of correcting the imbalance.

In the present crankshaft 1, the thickness of the weight portion 3h ″ of the crank arm 3h is uniformly enlarged to T ₂ , but the weight portion 3h ″ has an imbalance correction of the crankshaft 1. It may be formed by appropriately changing its shape according to the required mass. For example, the tip of the weight portion 3h ″ may be tapered or thickened.

The present crankshaft 1 is for a four-cylinder engine, but the present invention is not limited to this, and it goes without saying that the present invention can be applied to crankshafts of all multi-cylinder engines.

[0022]

[Effect of the device]

 As described in detail above, in the crankshaft of the multi-cylinder internal combustion engine of the present invention, the wall thickness of the crank arm arranged at least in the position closest to the flywheel mounting end is larger than that of the other crank arms. The strength of the formed crank arm, which receives the strongest vibration stress from the flywheel, is further increased than the strength of other crank arms.

Therefore, the durability of the crankshaft is effectively and remarkably improved while the adverse effects such as the increase in the total length, the weight and the cost of the engine are minimized.

[Brief description of drawings]

FIG. 1 is a side view showing a specific configuration of a crank shut of a multi-cylinder internal combustion engine of the present invention.

FIG. 2 is a front view showing a cross-sectional shape of crank arms 3a to 3h in FIG.

FIG. 3 is a side view showing a configuration of a crankshaft of a conventional multi-cylinder internal combustion engine.

[Explanation of symbols]

 1 Crank Shaft 1a-1e Crank Journal 2a-2d Crank Pin 3a-3h Crank Arm 5 Pulley 6 Flywheel

Claims (1)

[Claim 1] In a crankshaft of a multi-cylinder internal combustion engine in which a flywheel is mounted on a shaft end, at least a crank arm arranged at a position closest to a flywheel mounting end has a wall thickness of , A crankshaft of a multi-cylinder internal combustion engine, which is formed to be thicker than other crank arms.