JPS6325359A - Machining method for crankcase - Google Patents

Abstract

PURPOSE:To prevent decentering of a bolt enlargement of the diameter of a bolt hole, by forming a hollow part at a portion where a cylinder block attaching bolt crosses a side cover attaching bolt, in a crankcase. CONSTITUTION:A hollow part 11 is formed in a fitting surface 10a for the cylinder block of a crank case 10. From the bottom surface 13 of the hollow part 11, a prepared hole 15 for a stud bolt 12 is drilled to work a tapped hole. After that, a prepared hole 17 for a side cover fitting bolt 16 is drilled from a fitting surface 10b for a side cover to a side wall 14 to work tapped hole. According to this, even if the prepared hole 15 for the stud bolt 12 and the prepared hole 17 for the side cover fitting bolt 16 are in a mutually crossing possision, it can be prevented that a burr is made in the prepared hole 15 by the prepared hole 17 or decentering of the prepared hole 17 occurs.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for processing a crankcase.

[Prior art]

BACKGROUND OF THE INVENTION A crankcase in a motorcycle has a cylinder block attached to its top surface and side covers attached to both sides of the crankcase. The cylinder block is attached by stud bolts (cylinder block mounting bolts) screwed into the four corners of each cylinder of the crankcase, and the side cover is attached by threading multiple side cover mounting bolts around its outer periphery. It is being

FIG. 4 shows the hole positions of the respective bolts in the crankcase, and 1 is the crankcase. If the pilot hole of the stud bolt 2 and the pilot hole 3 of the side cover mounting bolt are formed at a position where they intersect, the cross sections shown in FIGS. 5(a) and (b) will be As shown in the figure, the hole A that is drilled earlier is affected by the hole B that is drilled later, resulting in a burr 4 at the meeting point of hole A and hole B.

Additionally, if hole B is drilled later, it will not only be affected by the hole A that is placed earlier, causing the center of hole B to be misaligned or the diameter of hole B to expand, but there is also the risk of breaking the drill bit used for drilling the hole. there were.

Therefore, conventionally, as shown in FIG. 3, the pilot holes 3 of the side cover mounting bolts were formed by being shifted to 3' so as not to intersect the pilot holes of the stud bolts 2.

However, when the positions of the side cover mounting bolts are shifted as described above, the distance between the side cover mounting bolts increases, and there is a risk that the sealing effect may become insufficient.

[Purpose of the invention]

In view of the above-mentioned problems, an object of the present invention is to prevent burrs, misalignment, and enlargement of the hole diameter even if the position of the pilot hole of the side cover mounting bolt intersects the position of the pilot hole of the stud bolt. The purpose of this invention is to provide a processing method for a rank case.

[Structure of the invention]

In the crankcase processing method according to the present invention, a recess is formed in advance at a vertical position of a cylinder block mounting bolt on a cylinder block mounting surface of the crankcase, and a screw hole for the cylinder block mounting bolt is formed in the bottom surface of the recess. In addition, the above object is achieved by providing a pilot hole for a side cover mounting bolt through the recess from the side surface of the crankcase, and forming a threaded hole for the side cover mounting bolt therein.

That is, by forming the recessed portion, the pilot holes of the respective bolts are prevented from directly meeting each other.

〔Example〕

The present invention will be described below with reference to embodiments shown in the drawings.

FIGS. 1 to 3 show an embodiment of the method of machining a rotary crankcase according to the present invention. Reference numeral 10 denotes a crankcase, which is made of aluminum alloy casting or the like, and has a cylinder block mounting surface 10a on its top surface and a side cover mounting surface 10b on its side surface. A recess 11 is formed in the cylinder block mounting surface 10a.
is located at the upright position of the stud bolt 12 and is cast out when the crankcase 10 is molded.

Further, the recess 11 has a bottom surface 13 and a side wall 14.
3 is parallel to the cylinder block mounting surface 10a, and is parallel to the side wall 14
is parallel to the side cover mounting surface 10b.

In the crankcase 10 thus formed, a pilot hole 15 for the stand bolt 12 is bored from the bottom surface 13 as shown in FIG. 2, and a screw hole is machined. Next, as shown in FIG. 3, a pilot hole 17 for the side cover mounting bolt 16 is drilled from the side cover mounting surface 10b to the side wall 14, and a screw hole is machined.

If the above processing method is used, the stud bolt 12
Pilot hole 15 and pilot hole 17 of side cover mounting bolt 16
Even if they intersect, the lower holes 15 and 17 do not meet directly because the recess 11 is formed. Therefore, the bulge generated by the pilot hole 17 remains within the plane of the side wall 140 and does not affect the pilot hole 15 in any way.

In addition, since the side wall 14 is parallel to the side cover mounting surface 10b, the pilot hole 17 can be machined in the correct position and according to the dimensions.In the above embodiment, the recess 11 was formed by casting, but the recess 11 is formed by cutting, etc. I don't mind if you do.

Further, in the above embodiment, the recess 11 has a bottom surface 13 parallel to the cylinder block mounting surface 10a and a side cover mounting surface 1.
Although it has a side wall 14 parallel to 0b, in the present invention,
These are not necessarily required.

〔Effect of the invention〕

As described above, according to the crankcase processing method according to the present invention, the lower holes of the side cover mounting bolts can be positioned to intersect with the lower holes of the stud bolts, increasing the degree of freedom in design.

This makes it possible to prevent oil leakage caused by, for example, the spacing between the side cover mounting bolts.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional perspective view of a conceptual main part of a crankcase showing the crankcase processing method according to the present invention, Fig. 2 is a partial sectional view showing the side surface, and Fig. 3 is a view from the top of the crankcase. 4 is a side view of a main part showing the hole positions of a conventional crankcase, and FIGS. 5(a) and 5(b) are sectional views taken from the top thereof. 10... Crank case, 10a... Cylinder block mounting surface, 10b... Side cover mounting surface, 11.
... Recessed portion, 12 ... Stud bolt, 13 ... Bottom surface, 14 ... Side wall, 16 ... Side cover mounting bolt, 17 ... Pilot hole for side cover mounting bolt. Applicant Suzuki Motor Co., Ltd. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A recess is formed in advance on the cylinder block mounting surface of the crankcase at the upright position of the cylinder block mounting bolt, and a screw hole for the cylinder block mounting bolt is formed in the bottom of the recess, and A method for machining a crankcase, comprising: penetrating a pilot hole for a side cover mounting bolt into the recess from a side surface, and forming a threaded hole for the side cover mounting bolt therein. (2) The shape of the recess is such that the bottom surface of the recess is parallel to the cylinder block mounting surface, and the surface of the recess through which the side cover mounting bolt hole is inserted is parallel to the side surface of the crankcase. A crankcase processing method according to claim (1), characterized in that: