JP2008202629A - Balance shaft for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a balance shaft for an internal combustion engine having improved durability by preventing bearings from reaching a high temperature as well as suppressing rotational resistance while dipped in a lubricating oil. <P>SOLUTION: The balance shaft has shaft parts 10A, 10B rotatably supported by the bearings 100A, 100B, a first and a second eccentric mass parts 20, 30 of which center of gravity is eccentric to the axis J of the shaft parts 10A, 10B and an auxiliary part 50 consisting of a foam metal structuring a cylinder body of which center is the axis J shared with the first and the second eccentric mass parts 20, 30. The auxiliary part 50 is molded integrally with the shaft parts 10A, 10B and the first and the second eccentric mass parts 20, 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a balance shaft for an internal combustion engine.

In an internal combustion engine, a balance shaft having an eccentric weight is used in order to suppress vibration generated by a member such as a reciprocating piston. The balance shaft is rotated by transmission of rotation from the crankshaft. However, since the balance shaft is relatively heavy, from the viewpoint of the stability of the internal combustion engine, the balance shaft is immersed in the lubricating oil stored in the oil pan. It is used in a state (see, for example, Patent Document 1).
When the balance shaft is rotated in the lubricating oil, the lubricating oil is agitated by the eccentric weight, so that there is a problem that the power of the internal combustion engine is lost and the deterioration of the lubricating oil is accelerated.
For this reason, Patent Document 1 discloses a technique for suppressing the stirring of the lubricating oil while maintaining the function of the eccentric weight by surrounding the eccentric weight with a cylindrical member concentric with the balance shaft.

Japanese Patent Laid-Open No. 5-92465

  By the way, the balance shaft rotates at high speed. For this reason, there is a problem that heat generation is large in the bearing that rotatably supports the balance shaft, and the bearing is easily deteriorated by heat.

  The present invention has been made in view of the above circumstances, and the object of the present invention is to prevent the bearing from becoming high temperature while suppressing rotational resistance in a state immersed in the lubricating oil. An object of the present invention is to provide a balance shaft for an internal combustion engine with improved durability.

A balance shaft for an internal combustion engine according to the present invention includes a shaft portion rotatably supported by a bearing, an eccentric mass portion whose center of gravity is decentered with respect to the axis line of the shaft portion, and the axis line together with the eccentric mass portion. And an auxiliary portion made of a foam metal constituting the rotating body, and the auxiliary portion is integrally formed with the shaft portion and the eccentric mass portion.
According to this configuration, the power loss due to the stirring of the lubricating oil can be suppressed by configuring the rotating body as a whole by the auxiliary portion made of the foam metal. In addition, by integrally molding the auxiliary part to the shaft part and the eccentric mass part, the auxiliary part, the shaft part and the eccentric mass part are in close contact with each other, and the heat generated in the bearing is transferred to the auxiliary part made of foam metal through the shaft part. Directly transmitted, heat is efficiently released from the auxiliary portion to the lubricating oil, and damage due to heat generation of the bearing can be suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the balance shaft for internal combustion engines which improved the durability with respect to a heat | fever is suppressed, suppressing the power loss by stirring of lubricating oil.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
1 to 3 are views showing an embodiment of a balance shaft according to the present invention. FIG. 1 is a view as seen from the axial direction, FIG. 2 is a view as seen from a direction perpendicular to the axial line, and FIG. It is sectional drawing of the AA line direction of 1. FIG.

The balance shaft includes shaft portions 10A and 10B, a first eccentric mass portion 20 and a second eccentric mass portion 30 as eccentric mass portions, a drive gear portion 40, an auxiliary portion 50, and the like.
The shaft portions 10A, 10B, the first eccentric mass portion 20, the second eccentric mass portion 30, and the drive gear portion 40 are integrally formed, for example, by performing predetermined machining on a material made of cast iron, carbon steel, or the like. It is formed by.
Moreover, this balance shaft is used in the state immersed in the lubricating oil stored in the oil pan which is not shown in figure located in the lower part of an internal combustion engine from a stability viewpoint of an internal combustion engine, for example.

  The shaft portions 10A and 10B have a common axis J, and these shaft portions 10A and 10B are rotatably supported by bearings 100A and 100B such as ball bearings as shown in FIG. The bearings 100A and 100B generate heat due to the rotation of the balance shaft.

The first eccentric mass portion 20 is formed so as to define a disk-shaped outer shape, and a part thereof is cut out in a substantially semicircular shape, whereby the center of gravity is eccentric from the axis J. The first eccentric mass portion 20 is integrally formed with a drive gear portion 40 on the outer peripheral portion thereof.
The drive gear portion 40 is formed to transmit rotation from a crankshaft (not shown) to a balance shaft that is rotatably supported by bearings 100A and 100B.

  The second eccentric mass portion 30 has a substantially semi-cylindrical shape, and the center of gravity is eccentric in the same direction as the first eccentric mass portion 20. Thereby, as for the balance shaft, the center of gravity is eccentric from the axis line J as a whole.

  The auxiliary portion 50 constitutes a cylindrical body (rotary body) centering on the axis J together with the first eccentric mass portion 20 and the second eccentric mass portion 30. Thereby, stirring of lubricating oil can be suppressed when a balance shaft is rotated centering around the axis line J in lubricating oil.

The auxiliary portion 50 is formed of a foam metal, and is integrally formed with the shaft portions 10 </ b> A and 10 </ b> B, the first eccentric mass portion 20, and the second eccentric mass portion 30. As the foam metal, for example, a powder metal such as an aluminum alloy, a copper alloy, or a nickel alloy foamed with a foaming agent can be used.
The reason why the auxiliary portion 50 is formed of the foam metal is that the foam metal is lighter than the first eccentric mass portion 20 and the second eccentric mass portion 30, and the foam metal has a property of high thermal conductivity. It is.

  In order to integrally form the auxiliary portion 50 into the shaft portions 10A and 10B, the first eccentric mass portion 20 and the second eccentric mass portion 30, the balance shaft in a state where the auxiliary portion 50 is not attached is accommodated in a mold having a predetermined shape. At the same time, a portion corresponding to the auxiliary portion 50 in the mold is filled with a metal material containing a foaming agent. In this state, when the mold is heated to foam the foaming agent, an auxiliary portion 50 made of foam metal is formed, and the auxiliary portion 50 includes the shaft portions 10A and 10B, the first eccentric mass portion 20 and the second eccentric portion. Coupled to the mass portion 30. Thereby, the foam metal is in close contact with the shaft portions 10A and 10B, the first eccentric mass portion 20 and the second eccentric mass portion 30, and heat is more easily transmitted.

  In the balance shaft having the above configuration, as shown in FIG. 3, the heat HT generated in the bearings 100 </ b> A and 100 </ b> B (not shown) is mainly conducted to the auxiliary portion 50 through the shaft portions 10 </ b> A and 10 </ b> B and lubricated from the surface layer of the auxiliary portion 50. Released into oil. Thereby, it can suppress that bearing 100A, 100B becomes high temperature.

As the foam metal constituting the auxiliary portion 50, either a so-called skin layer having a dense surface layer or one without this skin layer can be used.
When the skin layer is present, since the surface layer has less irregularities than when the skin layer is present, bubbles are not easily generated in the lubricating oil, and deterioration of the lubricating oil can be suppressed.
On the other hand, when the skin layer is not present, the surface area is enlarged due to the fine pores in the surface layer, compared with the case where the skin layer is present, so that the heat dissipation to the lubricating oil is enhanced.

  In the above embodiment, the case where the shaft portions 10A and 10B, the first eccentric mass portion 20, the second eccentric mass portion 30, and the drive gear portion 40 are integrally formed has been described. It is also possible to configure with members. Moreover, it is also possible to comprise shaft part 10A, 10B with a common shaft member.

  In the above embodiment, the case where the balance shaft is used in a state of being immersed in the lubricating oil has been described. However, even when the balance shaft is not immersed in the lubricating oil, the heat generated in the bearing is efficiently transmitted to the outside through the shaft portion and the auxiliary portion. Can be released.

  In the said embodiment, although the case where the cylindrical body was comprised by the 1st eccentric mass part 20, the 2nd eccentric mass part 30, and the auxiliary | assistant part 50 was demonstrated, it is not limited to this, The stirring of lubricating oil can be suppressed, Other rotating bodies such as a sphere and a cone may be used.

It is the figure seen from the axial direction of one Embodiment of the balance shaft which concerns on this invention. It is the figure seen from the direction orthogonal to the axial direction of one Embodiment of the balance shaft which concerns on this invention. It is sectional drawing of the AA line direction of FIG.

Explanation of symbols

10A, 10B ... shaft portion 20 ... first eccentric mass portion (eccentric mass portion)
30 ... 2nd eccentric mass part (eccentric mass part)
40 ... Drive gear 50 ... Auxiliary parts 100A, 100B ... Bearing HT ... Heat

Claims (1)

A shaft portion rotatably supported by a bearing;
An eccentric mass portion whose center of gravity is eccentric with respect to the axis of the shaft portion;
An auxiliary portion made of a metal foam that constitutes a rotating body centered on the axis along with the eccentric mass portion;
The auxiliary portion is integrally formed with the shaft portion and the eccentric mass portion.
A balance shaft for an internal combustion engine.

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