JP2785362B2 - Bearing structure of cylinder body - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a bearing structure of a cylinder body that rotatably supports a crank journal.

[Prior art] In conventional aluminum cylinder bodies, in order to increase the rigidity around the crank journal as a measure against vibration noise, and to reduce the change in clearance due to temperature change due to the large coefficient of thermal expansion of aluminum. The bearing gap is made of cast iron, and the bearing gap is bolted to the cylinder body.

That is, as shown in FIG. 4, a bearing surface d for engaging the upper half of the crank journal c is formed in a partition wall b of an aluminum cylinder body a, and the partition wall b is formed.
, A bearing cap e that engages with the lower half of the crank journal (crank bearing) is attached, and two bolts f that are screwed to the partition wall b are provided on both sides of the bearing cap e. That the bearing cap e is firmly fixed to the partition wall b with the axial force of "(the bearing cap mounting structure of the internal combustion engine)"
(JP-A-59-119047) and the like have been developed. However, even if the rigidity of the bearing cap e itself and the mounting strength of the bearing cap e are increased, the rigidity of the partition b around the bearing cap e is low. However, the processing time and accuracy are problematic. Therefore, recently, a ladder frame on which the cylinder body is mounted is formed by the side member and the cross member, and a bearing surface for rotatingly supporting the crank journal is formed on the cross member so as to improve the overall rigidity. The proposed proposal has been made.

[Problems to be Solved by the Invention] However, as shown in FIGS. 5 and 6, when the ladder frame g is formed of aluminum, the clearance of the bearing surface i with respect to the crank journal c due to the thermal expansion and contraction of the cross member h. And the crank journal c causes eccentric rotation and the rotation resistance of the crank journal c increases with the change.

An object of the present invention is to make a clearance between a bearing surface of a ladder frame and a crank journal constant.

Means for Solving the Problems In order to achieve the above object, the present invention provides a ladder frame having a bearing surface for rotatingly supporting a crank journal, and a ladder frame formed of a metal material having a higher rigidity than the ladder frame. The reinforcing plate to be joined is bolted to the cylinder body with bolts, and the frame and the reinforcing plate are bolted to each other below the bearing surface.

[Operation] When heat from the crank journal and the cylinder body is transmitted to the ladder frame, the ladder frame expands and contracts according to the degree of the heat. However, since the reinforcing plate joined to the lower surface of the ladder frame, that is, the surface on the oil pan side, is formed of a metal material having higher rigidity than the ladder frame, thermal expansion of the ladder frame is forcibly prevented. When the frame and the reinforcing plate at the center of the bearing portion are bolted, even if the ladder frame is contracted, the contraction is prevented by the reinforcing plate. As a result, the clearance between the crank journal and the bearing surface can be set to an appropriate minimum clearance.

Hereinafter, a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows a schematic cross section of a cylinder body of a V-shaped multi-cylinder engine formed with a fixed bank angle.

As shown in FIG. 1, a partition wall 3 for separating between adjacent cylinders 2 is formed integrally with the cylinder body 1, and a semi-circular bearing surface which is engaged with an upper half of a crank journal is formed below the partition wall. 4 are formed. The lower surface of the cylinder body 1, that is, the side surface of the oil pan, is formed as a horizontal surface that is continuous with both ends of the bearing surface 4. A rudder frame 6 made of aluminum is mounted on the lower surface 5 of the horizontal cylinder body 1. The ladder frame 6 includes two side members 7 on which the cylinder body 1 is mounted along the longitudinal direction of the cylinder body 1 (the row direction of the cylinders 2).
And a plurality of cross members 8 for connecting the side members 7, 7 to each other in the width direction of the cylinder body 1 and abutting against the partition walls 3 to mount the partition walls 3. A semicircular bearing surface 10 that engages with the lower half of the crank journal 9 is formed on the side surface of the partition wall 3 of the cross member 8. That is, the bearing surface 10 is the bearing surface 4 of the partition wall 3.
And a bearing portion for rotatingly supporting the crank journal 9. The side member 7 and the cross member 8 form a part of a crankcase that houses the crank journal 9. And the cross member 8
Bolt insertion holes 11 are formed on both sides of the bearing surface 10 of the cross member 8 on the radial outer side at predetermined intervals outward in the radial direction. 12 is formed.

The purpose of the present invention is to provide a bearing surface 10 of the ladder frame 6 associated with thermal expansion and contraction of the ladder frame 6.
The object of the present invention is to suppress the thermal expansion and contraction of the crank journal 9 and to keep the clearance with respect to the crank journal 9 constant to suppress the eccentric rotation of the crank journal 9 and the increase in the rotational resistance.

Therefore, in this embodiment, the reinforcing plate 14 is integrally attached to the lower surface of the ladder frame 6, that is, to the side member 7 and the oil pan side surface 13 of the cross member 8. The reinforcing plate 14 is formed of a metal material having higher rigidity than the metal material forming the ladder frame 6, for example, iron, cast iron, or the like.

A bolt hole 15 is formed in the reinforcing plate 14 at a position corresponding to the screw hole 12 of the partition wall 3, and another bolt hole 16 is formed in the middle of the bolt holes 15, 15 located inward in the radial direction. Be composed. A screw hole 17 is formed on the lower surface of the cross member 8 so as to correspond to the other bolt hole 16.

Therefore, when the bolt 18 inserted into the bolt hole 15 of the reinforcing plate 14 is inserted into the bolt insertion hole 11 of the cross member 8 and screwed into the screw hole 12 of the partition wall 3, the ladder frame 6 and the reinforcing plate 14 It is fastened to the body together. When another bolt 19 inserted into the another bolt hole 16 is screwed into the screw hole 17 of the cross member 8, the ladder frame is positioned at a position below the bearing surface 10 of the cross member 8 at the minimum height. 6 and the reinforcing plate 14 are bolted to each other.

By the way, since the height of the cross member 8 is smaller than other parts below the bearing surface 10, in this embodiment, the height of the reinforcing plate 14 between the bolt holes 18, 18 (see FIG. The wall thickness is made larger than other portions to further increase the rigidity.

 Next, the operation will be described.

When heat from the crank journal 9 and the cylinder body 1 is conducted to the cross member 8, the cross member 8
It expands and contracts according to the degree of the heat. However, the reinforcing plate 14 joined to the oil pan side surface of the cross member 8 is formed of a metal material having higher rigidity than the cross member 8,
Moreover, since the portion having the bearing surface 10 is formed thicker than the other portions, the thermal expansion of the cross member 8 is forcibly prevented. When the cross member 8 and the reinforcing plate 14 at the center of the bearing surface 10 are fixed by bolts, the fixing plate prevents the cross member 8 from being thermally contracted.

That is, in the case where the reinforcing member 14 is not provided in the ladder frame structure, D ₀ is the inner diameter of the bearing portion at normal temperature, t is the temperature difference from normal temperature,
When considering the expansion and contraction of α as the coefficient of linear expansion, high temperature at the time of the bearing portion as indicated by a dotted line in FIG. 6 expands, the _{D / 2 = D 0/2} × (1 + αt).

Also at low temperatures as shown in Figure 5 decreases the _{D / 2 = D 0/2} × (1-αt) and vice versa.

On the other hand, when the reinforcing plate 14 is provided and the height of the cross member 8 is H, H−D _0/2 = A, β is the linear expansion coefficient of the bolt 19, As shown by the dotted line in the figure, D / 2 = H (1 + βt) −A (1 + αt). When this is formulated, D / 2 = D0 / 2 + Hβt−Aαt.

Then, when material selection and dimensions are set to α ≒ 2β, H ≧ 2A,
Hβt ≒ Aαt, and the result is D / 2 ≒ D0 / 2.

The low temperature, the D / 2 ≒ D _0/2 and polynomial similarly becomes _{D / 2 = D 0/2} -Hβt + Aαt as shown in Figure 3.

As described above, by selecting and dimensioning the material such that α ≒ 2β, H ≧ 2A in the thermal expansion and thermal contraction, the clearance of the bearing portion does not change.

Therefore, the clearance between the crank journal 9 and the bearing surfaces 4 and 10 can be set to an appropriate minimum clearance, and the rotation of the crank journal 9 becomes appropriate. By properly maintaining the clearance, it is possible to secure high-temperature hydraulic pressure on the bearing surfaces 4 and 10 and reduce low-temperature friction. In addition, the reinforcing plate 14 is joined to the lower surface of the cross member 8 and fastened together with bolts 18 and further fastened to the cross member 8 with bolts 19, so that the structure and assembly are simple, and the existing engine can be used. Addition is possible.

In the embodiment, the cylinder body 1 has been described as a cylinder body 1 for a V-type engine. However, the present invention is not limited to this. is there. The material of the reinforcing member 14 is, of course, formed of a rigid metal material, but is naturally formed of a metal material having a lower coefficient of thermal expansion than the ladder frame 6.

[Effects of the Invention] As is clear from the above description, according to the present invention, the following excellent effects are exhibited.

The rigidity of the ladder frame against thermal expansion and contraction can be increased, and the clearance between the bearing surface of the ladder frame and the crank journal can be made constant.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a preferred embodiment of the present invention, FIG. 2 and FIG. 3 are explanatory views showing a change in clearance of a bearing surface, FIG. 4 is a partial sectional view showing a conventional example, FIG. FIG. 5 and FIG. 6 are explanatory diagrams showing a change in clearance with respect to thermal expansion and thermal contraction of a bearing surface in a conventional ladder frame structure. In the figure, 1 is a cylinder body, 6 is a ladder frame, 4 is a bearing surface, 9 is a crank journal, and 14 is a reinforcing plate.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-127915 (JP, A) JP-T-62-501094 (JP, A) Fully open sho. 59-553 (JP, U) Really open sho. 61- 131516 (JP, U) JP-A 1-71159 (JP, U) JP-A 61-200443 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) F02F 7/00 301 F16C 9/02

Claims (1)

(57) [Claims] A ladder frame having a bearing surface for rotatably supporting a crank journal, and a reinforcing plate formed of a metal material having higher rigidity and joined to a lower surface of the frame are jointly fastened to a cylinder body by bolts. A bearing structure for a cylinder body, wherein the frame and the reinforcing plate are bolted to each other below the bearing surface.