JPH051714Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a crankshaft for an internal combustion engine, and more particularly to a crankshaft that reduces vibration and noise.

[Prior Art] FIG. 3 is a schematic perspective view of a conventional crankshaft and flywheel for an internal combustion engine.

In FIG. 3, 1 is a crankshaft, and 2 is a flywheel. Arrow F indicates the front of the internal combustion engine, and arrow A indicates the direction of rotation of the crankshaft 1. As can be seen from the figure, the internal combustion engine in FIG. 3 is an in-line four-cylinder, four-cycle internal combustion engine.

By the way, not only in-line 4-cylinder 4-cycle internal combustion engines, but in general internal combustion engines, during operation,
Crankshaft 1 causes bending vibration. This bending vibration occurs in the middle part of the crankshaft 1, for example, in a vertical plane containing the axis Z of the crankshaft, with the node marked with 3 being the node and the point where the flywheel 2 is attached, as shown by the arrow M. It happens in a mode like this. In internal combustion engines, there has been a problem in that noise is generated due to this bending vibration M.

The bending vibration of the crankshaft 1 as indicated by the arrow M is caused by the combustion pressure acting as an excitation force. That is, for example, when combustion pressure acts on the crank pin numbered 4 in FIG. It is vibrated as shown by arrow M around a horizontal axis (horizontal axis perpendicular to axis Z of crankshaft 1). This excitation force resonates with the natural frequency of the flywheel 2 around the Y axis, resulting in large vibrations and noise.

As mentioned above, the noise is based on the resonance of the two parts of the flywheel, and the noise can be reduced by preventing the two parts of the flywheel from resonating. In order to do this, the natural frequency of the flywheel 2 portion around the Y axis can be changed. For example, if the moment of inertia of the flywheel 2 around the Y-axis is reduced, the natural frequency of the flywheel 2 around the Y-axis will be increased, so resonance can be avoided.

In order to reduce the moment of inertia of the flywheel 2 around the Y axis, the thickness of the flywheel 2 can be made thinner to reduce the weight of the flywheel 2.
Because it has the role of smoothing the rotation of
A certain amount of weight is absolutely necessary, and there is a limit to reducing the weight of the flywheel 2.

A technique for solving this dilemma is disclosed in Japanese Patent Application Laid-open No. 128546/1983. Tokukai Akira
The technology proposed in Japanese Patent No. 58-128546 is to provide recesses and protrusions here and there in the circumferential direction of the flywheel 2, and to make the flywheel 2 as a whole the same weight as a conventional flywheel without unevenness. . Moreover, the installation position relationship (installation angle) between flywheel 2 and crankshaft 1
The moment of inertia of the flywheel 2 around the Y axis is made small only when the piston is at the top dead center. In other words, when the piston is at the top dead center, the concave portion is positioned in the vertical direction and the convex portion is positioned in the horizontal direction.

If you do this, the moment of inertia of the flywheel 2 around the Y axis will momentarily decrease only when the piston is at the top dead center, that is, when the excitation force is applied. The natural frequency around the Y axis becomes higher. Therefore, only then can the resonance point of vibration be shifted.
Therefore, since resonance can be prevented, noise can be reduced. Furthermore, since the weight of the flywheel 2 is the same as that of a conventional type without unevenness, the function of the flywheel 2 to smoothen the rotation of the crankshaft 1 is not impaired.

Another known technique is one in which the bending rigidity of the flywheel is made uneven and the resonance point is shifted (Japanese Utility Model Application Publication No. 62-27244), and the flywheel is of a split type and an elastic body is interposed between the two pieces. The one with reduced vibration level at the resonance point
181143) etc. are known.

However, although all of the above-mentioned known techniques aim to reduce bending vibration or prevent resonance when the piston is at top dead center, in an actual internal combustion engine, the greatest excitation force occurs when the crankshaft is applied. , in other words, the time when the combustion pressure is at its maximum is not when the piston is at top dead center;
It was about 20 to 30 degrees past top dead center. On the other hand, in the device disclosed in Japanese Patent Application Laid-Open No. 58-128546, the concave portion is positioned in the vertical direction when the piston is at the top dead center, so when the largest excitation force is applied, the flywheel 2 is not designed to minimize the moment of inertia around the Y axis. In other words, in the device disclosed in JP-A-58-128546, at the moment when the excitation force reaches its maximum, the natural frequency of the flywheel 2 around the Y axis becomes high enough to not resonate with the vibration caused by the excitation force. Because there was no noise, it was not possible to sufficiently reduce the noise.

To solve this problem, the present applicant previously made the position of the recess provided in the flywheel coincide with the piston movement direction at the time of maximum combustion pressure, so that when the excitation force is at the maximum, the inertia around the Y axis is A structure has been proposed in which the moment is maximized, the natural frequency is raised at that time, and the resonance point is shifted (Utility Application No. 37831, No. 37831, No. 61).
No. 188041).

In this proposed structure, a non-uniform flywheel 5 as shown in FIGS. 4 and 5 is attached to a conventional crankshaft 6 as shown in FIGS. 6 and 7. In other words, the flywheel 5 is provided with a thickened portion (recess) 7 and a normally thick portion 8, and the pistons 9 of the adjacent cylinders of the flywheel 5 are deviated from the top dead center by △θ degrees (crank angle). When the piston moves (advances), the recess arrangement direction 10 coincides with the piston movement direction. When the engine moves △θ degrees from top dead center, the cylinder closest to the flywheel 2 has the maximum combustion pressure. In this proposal, it is the combustion pressure acting on the piston closest to the flywheel that has the greatest effect on the bending vibration of the crankshaft, and the combustion pressure acting on other pistons has little to do with it. This characteristic is also used.

[Problems to be solved by the invention] However, the structure using the non-uniform flywheel as described above may cause the following problems.

That is, in a flywheel with non-uniform wall thickness as shown in FIG. 5, the wall thickness of the flywheel changes alternately, for example, by 90 degrees between thick and thin. Therefore, thermal stress is generated due to the difference in wall thickness during manufacturing, and this residual stress may reduce the durability of the flywheel.

Also, if the wall thickness is different, the flow of heat generated by contact with the clutch when the engine is rotating will not be uniform.
An uneven temperature distribution occurs inside the flywheel,
The flywheel may become deformed due to thermal stress.

The present invention focuses on the above-mentioned problems caused by the flywheel having a structure with uneven wall thickness, and aims to improve the flywheel and crankshaft while making the flywheel's wall thickness uniform, rather than improving the flywheel itself. The purpose is to obtain the same vibration and noise reduction effect as the above-mentioned non-uniform flywheel by improving the coupling part of the flywheel.

[Means for Solving the Problems] A crankshaft for vibration and noise reduction of the present invention that meets this purpose is a crankshaft for an internal combustion engine that has a flywheel mounting portion at the rear end, in which the flywheel mounting portion is shaped like an ellipse. The elliptical long axis direction is located closest to the flywheel mounting portion by forming the ellipse so as to increase the joint rigidity between the flywheel mounting portion and the flywheel in the long axis direction of the ellipse than the joint rigidity in other directions. The direction coincides with the direction of piston movement in the cylinder at the moment when the combustion pressure in the cylinder reaches its maximum.

[Operation] In such a crankshaft, the joint rigidity between the crankshaft and the flywheel can be changed around the crankshaft (flywheel axis) while the wall thickness of the flywheel remains uniform. When the joint rigidity between the flywheel mounting part and the flywheel is increased, the bending rigidity at the rear end of the crankshaft is increased and the natural frequency is increased, but the direction in which this joint rigidity is increased is at the maximum combustion pressure. It is determined to match the direction of piston movement. Therefore, the bending resonance frequency of the crankshaft-flywheel system at the moment when the rearmost cylinder reaches the maximum combustion pressure is increased, and resonance with the excitation force applied from the piston is avoided. Since there is no need to make the wall thickness of the flywheel non-uniform, the above-mentioned avoidance can be achieved without problems such as decreased durability and thermal deformation of the flywheel.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

1 and 2 show a crankshaft for reducing vibration and noise according to an embodiment of the present invention. This embodiment shows a crankshaft for a four-cylinder engine, with reference numeral 11 indicating the crankshaft and reference numeral 12 indicating the flywheel. A disk-shaped flywheel mounting portion 13 is provided at the rear end of the crankshaft 11, and the flywheel 12 is attached to the flywheel mounting portion 13 by bolts 1.
Attached via 4. The flywheel 12 is formed to have a uniform thickness.

As shown in FIG. 2, the flywheel mounting portion 13 is formed in an elliptical shape (including an ellipse), and the flywheel mounting portion 13 is formed in an elliptical shape (including an ellipse).
The joint rigidity between the flywheel 12 and the flywheel 12 is higher than the joint rigidity in other directions. More specifically, the flywheel mounting portion 13 and the flywheel 1 are connected by four bolts 14 along the long axis 15.
2, and the joint rigidity is significantly increased compared to other directions.

The direction of the long axis 15 of the ellipse is such that the piston 17 of the cylinder 16 closest to the flywheel mounting portion 13 reaches its maximum combustion pressure.
is set in a direction that coincides with the direction of movement of. As mentioned above, the maximum combustion pressure is 20 to 30 degrees (crank angle) from the piston top dead center, so the crank angle from the piston top dead center to the maximum combustion pressure is △θ degrees. Then, the positional relationship will be as shown in Fig. 2. FIG. 2 shows the state when the piston 17 is at the top dead center (corresponding to the line 18 in terms of crank angle), and at this time, the elliptical long axis 15 of the flywheel mounting portion 13 is away from the line of the top dead center 18. It is tilted by △θ degrees. Note that ω indicates the rotation direction of the crankshaft 11.

In such an embodiment device, the length of the connection between the flywheel mounting portion 13 and the flywheel 12 is long in the direction of the elliptical long axis 15 of the flywheel mounting portion 13, and the fastening bolt 14 along this direction is long.
, the joint stiffness in this direction is higher than in other directions. Therefore, the bending rigidity of the crankshaft-flywheel system is higher in the long axis 15 direction than in other directions, and the bending natural frequency in the long axis 15 direction is higher. In other words, the bending resonance frequency becomes higher.

Since the direction of the long axis 15 is set to match the direction of movement of the piston 17 when the maximum combustion pressure is applied in the cylinder 16, the bending resonance frequency is increased at this time, and the combustion pressure applied via the piston 17 Resonance with the excitation force caused by this is avoided.

As a result, vibrations are prevented from increasing,
Noise generation due to vibration is prevented.

[Effects of the invention] As explained above, when using the crankshaft for vibration and noise reduction of the invention, by making the joint rigidity of the flywheel attachment part of the crankshaft with the flywheel non-uniform in a specific direction, While maintaining a uniform flywheel wall thickness, we have increased the natural bending frequency of the crankshaft-flywheel system when the excitation force is at its maximum, thereby reducing flywheel durability and thermal deformation. It is possible to prevent resonance with the excitation force applied from the piston without causing any problems, and it is possible to keep vibrations low and prevent the generation of noise.

[Brief explanation of the drawing]

Fig. 1 is a side view of a crankshaft for vibration and noise reduction according to an embodiment of the present invention, Fig. 2 is a side view of the device shown in Fig. 1 in the direction of arrows, and Fig. 3 is a conventional crankshaft-flywheel. Schematic perspective view of the system,
4 and 5 are a schematic side view and a schematic front view of the device proposed in Utility Application No. 61-188041, FIG. 6 is a side view of a conventional general crankshaft, and FIG.
FIG. 3 is a side view of the crankshaft shown in FIG. 11...Crankshaft, 12...Flywheel, 13...Flywheel mounting portion, 14...
...Bolt, 15... Long shaft, 16... Cylinder, 17...
...Piston, 18... Line equivalent to top dead center.

Claims (1)

[Scope of utility model registration request] In a crankshaft for an internal combustion engine having a flywheel mounting portion at the rear end, the flywheel mounting portion is formed into an elliptical shape, and the joint rigidity between the flywheel mounting portion and the flywheel in the long axis direction of the ellipse is The joint rigidity is higher than that in the direction, and the long axis direction of the ellipse is made to coincide with the piston movement direction of the cylinder located at the moment when the combustion pressure of the cylinder closest to the flywheel attachment portion reaches its maximum. Crankshaft for vibration and noise reduction.