JPH11218222A - Joining structure of die cast product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To adapt a device to whatever shaped flange joining parts, and hold sure air tightness by arranging, on either one side of joining surfaces, bolt hole projection parts for enclosing each circumference of a plurality of bolt holes and connecting projection parts for connecting to each other in a state in which the bolt hole projection parts are closed, and slightly projecting the bolt hole projection parts and the connecting projections from the joining surface, and forming the bolt hole projection parts and the connecting projections in a small projection shape having a narrow width and having a thin wall. SOLUTION: Projection parts 68 projected to a joining surface 678 of a crank case side of a cylinder 1, is formed in a closed plane surface shape, and is formed by coupling a circumferential part 68 for enclosing a plurality of bolt holes 69 concentrically with the bolt holes 69 and curve parts 68b, 68c with each other. A cross sectional shape of the projection parts 68 is thinned in a wideth direction, and is formed as a thin wall small projection whose height h is about 0.15 mm. A gascket 72 is laid on the joining surface 71 of the crank case 3, the projection parts 68 of the cylinder 1 is fitted to the upper surface of the gasket 72, and then, four fastening bolts 73 are fastened. Local high surface pressure is generated on upper and lower surfaces of the gasket 72, and thereby, the joining surfaces 67, 71 are air-tightly sealed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision die-cast member such as a cylinder of a general-purpose small internal combustion engine, a crankcase, an exhaust pipe, and an intake pipe including a carburetor. Related to the joint structure.

[0002]

2. Description of the Related Art In general-purpose small engines, members such as an intake pipe including a cylinder, a crankcase, and a carburetor case are manufactured by precision die casting.

FIG. 4 is a sectional view taken along a cylinder center line showing an example of a general-purpose small engine using such a precision die-cast product. FIG.
No. 757 and Japanese Utility Model Application Laid-Open No. 58-167756 show prior art. FIG. 5 is a plan view of a flange for joining a crankcase, FIG. 6 is a sectional view taken along the line ZZ of FIG. 5, and FIG. FIG. 8 is a plan view of the joining flange, FIG. 8 is a sectional view taken along line YY of FIG. 7, FIG. 9 is a plan view of the muffler joining flange, and FIG.
FIG. 3 is a sectional view taken along line XX of FIG.

In FIG. 4, reference numeral 1 denotes a cylinder, and 3 denotes a crankcase connected to a lower portion of the cylinder 1, both of which are manufactured by precision die casting. Reference numeral 5 denotes a piston fitted in the cylinder 1 so as to be slidable back and forth. 7
Is a connecting rod having one end pivotally connected to the piston 5 by a piston pin 9, and the other end of the connecting rod 7 is connected to the crankcase 3 via a main bearing (not shown).
Crank pin 15 fixed to one crank arm 13
It is supported rotatably. 17 is a carburetor connected and fixed to an intake port 19 opened to the cylinder 1;
Reference numeral 1 denotes an air cleaner fixed to the suction side flange of the carburetor 17. 23 is a muffler connected and fixed to an exhaust port 25 opened in the cylinder 1, and 27 is an ignition plug.

The lower opening 29 of the cylinder 1 is communicated with the inside of the crankcase 3, and around the opening 29,
A first flange portion 31 is provided on the cylinder 1 side.
As shown in FIGS. 5 and 6, a second flange portion 33 provided facing the crankcase 3 side is fixed to the flange portion 31 with a bolt 35 via a gasket 36. Reference numeral 37 denotes an annular projection provided on the flange surface of the second flange 33 on the inner peripheral side with respect to the bolt 35. As shown in FIGS. 7 and 8, a first intake flange portion 39 is provided around the intake port 19, and a second intake flange portion 41 provided opposite to the carburetor 17 side.
Are fixed via screws 43, 43 via a gasket 44. Reference numeral 45 denotes an annular protrusion provided on the flange surface of the first intake flange portion 39 on the inner peripheral side of the screw 43.

Further, a first exhaust flange portion 47 is provided around the exhaust port 25, and a second exhaust flange portion 49 provided on the muffler 23 side is provided with screws 51, 51.
Is fixed via a gasket 52. Reference numeral 53 denotes an annular projection provided on the flange surface of the first exhaust flange 47. When assembling such a general-purpose small engine, the annular projection 3 is formed on the flange surface of the second flange portion 33 at the opening 29 of the cylinder 1, that is, on the joint surface.
Since the gasket 36 is provided, the gasket 36 is partially pressed and compressed by the projection 37. This ensures that the joint between the cylinder 1 and the crankcase 3 is kept airtight.

In addition, a concave annular portion can be provided in place of the projecting portion 37. In this case, the gasket is partially pressed and compressed by the edge of the concave annular portion. The airtightness at the joint between the motor and the crankcase 3 is maintained. Also, since the projections 45 and the projections 53 are provided at the intake port 19 and the exhaust port 25, respectively, airtightness can be reliably maintained in the same manner as when the cylinder 1 and the crankcase 3 are joined. .

In Japanese Patent Application Laid-Open No. 56-47463, two thin, small, annular, thin projections are provided on the lower surface of the cylinder head at the joint between the cylinder head and the cylinder. This locally presses the gasket to ensure a gas seal between the cylinder head and the cylinder.

[0009]

In the general-purpose small-sized engine shown in FIGS. 4 to 10, the main outer shell parts such as the cylinder 1, the crankcase 3, and the carburetor 17 as described above. Is made of a precision die-cast product, but there is a problem of elimination of secondary machining of the die-cast product from the viewpoint of engine processing and reduction of the number of assembly steps.

In particular, in such an engine, secondary machining is omitted from the joining flange portions 31 and 33 between the cylinder 1 and the crankcase 3 shown in FIGS. 4 to 6 and sufficient airtightness is maintained at the joining surface. Is strongly required.
In order to respond to such a demand, the Japanese Utility Model Showa 5 shown in FIGS.
In the technique proposed in Japanese Patent Application Laid-Open No. 8-167775 and Japanese Utility Model Application Laid-Open No. 58-167756, annular projections 3 are provided on joining flanges 31 and 33 between cylinder 1 and crankcase 3.
7 is provided, and the flange surface of the other side is pressed by the projection 37, so that the secondary machining of the flange surface is omitted.

However, when such an annular projection 37 is provided, the processing is simple, but the application site is limited. Further, in the conventional technology,
The flange portion 31,
Since the bolts 35, 35 for tightening 33 are on the outer peripheral side, the flange on the side of the previously tightened bolt 35 is inclined so as to be lower, and then, when the bolt on the opposite side is tightened, the side of the previously tightened bolt 35 becomes strong. The problem that the protrusion 37 is damaged due to excessive tightening or excessive tightening will be seen.

Further, in the technique proposed in Japanese Patent Application Laid-Open No. 56-47463, the sealing performance with the gasket is improved by the annular thin projections. Since it is on the circumferential side, it has the same drawbacks as the above-mentioned prior art shown in FIGS.

In view of the problems of the prior art, the present invention is applicable to a die-cast product which can be applied to a flange joint having any shape, can omit secondary machining, and can maintain reliable airtightness at the flange joint surface. It is intended to provide a joint structure.

[0014]

According to the present invention, as a first invention, two members manufactured by die casting are formed on a joint surface formed on a joint flange portion of both members. A joining structure for a die-cast product formed by fastening with bolts inserted into a plurality of bolt holes in a flange portion, wherein one of the joining surfaces has an annular bolt hole surrounding a periphery of the plurality of bolt holes. A projection and a coupling projection for coupling the bolt hole projections to each other in a closed form on a plane, wherein the bolt hole projection and the coupling projection project slightly from the joint surface and have a small thickness; A joint structure for a die-cast product characterized by being formed on a small projection is proposed.

In a second aspect of the present invention, in the first aspect,
The thin small protrusion is a joint surface of a flange portion joining a cylinder and a crankcase of an internal combustion engine, a joint surface of a flange portion of an exhaust pipe including a muffler, or a joint surface of a flange portion of an intake pipe including a carburetor. It is provided in any one or all.

According to this invention, the periphery of the tightening bolt hole is surrounded by the bolt hole protrusion formed of an annular thin small protrusion, so that the inside of the crankcase is completely covered by the protrusion with respect to the bolt hole. The inside of the crankcase is completely airtightly sealed to the outside because the bolt hole projections are connected to each other in a closed form on a plane by the connection projections.

[0017] Further, the generation of an excessive pressing force in the vicinity of the tightening bolt is reduced by the annular bolt hole projection, and even if some of the tightening bolts are partially tightened, the tightening bolts previously tightened are tightened. The inclination of the joint surface with respect to the mating joint surface due to this is mitigated by the annular bolt hole projections provided for each tightening bolt.

Further, according to this embodiment, since the annular bolt hole projections surrounding the plurality of tightening bolt holes are connected to each other in a form closed to the connection projection, the form of the flange portion is formed. The present invention can be applied to any type of flange portion without being affected by the above.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described in detail with reference to the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the components described in this embodiment are not intended to limit the scope of the present invention unless otherwise specified, and are merely illustrative examples. Only.

FIG. 4 is a sectional view taken along a cylinder center line of a general-purpose small engine to which the present invention is applied. In FIG. 4, reference numeral 1 denotes a cylinder, and 3 denotes a crankcase, both of which are manufactured by precision die casting. 5 is the cylinder 1
The piston is reciprocally slidably fitted therein. A connecting rod 7 has one end pivotally connected to the piston 5 by a piston pin 9, and the other end of the connecting rod 7 is connected to a crankshaft 11 which is supported by the crankcase 3 via a main bearing (not shown). It is rotatably supported by a crank pin 15 fixed to the crank arm 13. Reference numeral 17 denotes a carburetor connected to and fixed to an intake port 19 opened in the cylinder 1, and reference numeral 21 denotes an air cleaner fixed to a suction side flange of the carburetor 17. 23 is a muffler connected and fixed to an exhaust port 25 opened in the cylinder 1, and 27 is an ignition plug.

In the embodiment of the present invention, the joint flange portion between the cylinder 1 and the crankcase 3 is improved, and details thereof are shown in FIGS.

1 to 3, reference numeral 1 denotes a cylinder;
Is the inner diameter of the cylinder in which the piston 5 slides back and forth, 65
Is an ignition plug mounting hole in which the ignition plug 27 is mounted, 19 is an intake port connected to the carburetor 17, and 25 is the muffler 2
3 is an exhaust port connected to. Reference numeral 31 denotes a first flange portion formed at a lower portion of the cylinder 1.
The second flange portion 3 of the crankcase 3
3 is formed. An inner diameter portion 62 of the cylinder 1 extends from the first flange portion 31 to a cylindrical portion 66 formed to protrude into the crankcase 3 and opens into the crankcase 3. And the cylindrical portion 66
The outer peripheral surface of the is fitted into the fitting hole 3a of the crankcase 3.

Reference numeral 72 denotes the first flange 3 of the cylinder 1.
1 is a gasket interposed between the first joint surface 67 and the joint surface 71 of the second flange portion 33 of the crankcase 3. Reference numeral 73 denotes a tightening bolt for tightening the cylinder 1 and the crankcase 3, which is inserted into four (as long as a plurality of) bolt holes 69 are formed in the cylinder 1 as shown in FIG. 3 is screwed into a screw hole (not shown) formed in the crankcase 3 or tightened by a nut (not shown) through a bolt hole (not shown) of the crankcase 3.

The cylinder 1 is manufactured by precision die casting as described above, and includes a secondary machine including an inner diameter portion 62, a joint surface 67, a projection 68 (68a, 68b, 68c) described later, and other joint surfaces. It is designed to be used as it is without casting. The crankcase 3 is also used as it is with the cast surface without secondary machining similarly to the cylinder 1.

Reference numeral 68 denotes the crankcase 3 of the cylinder 1
It is a projection projecting from the joint surface 67 to the side. As shown in FIG. 2, the protrusion 68 includes a plurality of circumferential portions 68a concentrically surrounding the plurality of bolt holes 69, and a plurality of circumferential portions 6a.
8a is formed into a closed planar shape connected by curved portions 68b and 68c. As shown in FIGS. 3A and 3B, the cross-sectional shape of the protrusion 68 is a thin small protrusion having a thickness h in the width direction and a height h of about 0.15 mm. 3 (a) having a trapezoidal cross section,
A cross section having a semicircular shape as shown in FIG. 3B is used. Further, the projection 68 may be provided on the joint surface 71 of the crankcase 3 without being provided on the cylinder 1.

When tightening the cylinder 1 and the crankcase 3 having such a configuration, a gasket 72 is spread on the joint surface 71 of the crankcase 3 and
The protrusion 68 of the cylinder 1 is applied to the upper surface of the cylinder 1 and four tightening bolts 73 are tightened. As a result of the tightening, the protrusion 68 bites into the gasket 72 and is locally pushed. Thereby, even if the joint surfaces 67 and 71 of the cylinder 1 and the crankcase 3 remain as cast surfaces, the upper and lower surfaces of the gasket 72 are localized along the protrusions 68 (68a, 68b, 68c). A high surface pressure is generated and the joint surfaces 67 and 71 are hermetically sealed.

Here, the precision die-cast cylinder 1
According to experiments performed by the inventors when the flatness of the joint surfaces 67 and 71 of the crankcase 3 is about 0.05,
If the protrusion 68 is not provided, even if the pressing force near the tightening bolt 73 is excessively strengthened, the tightening bolt 73
In the middle part of the figure, a shortage of the pressing force occurs, but if the protrusion 68 is provided as in this embodiment, a sufficiently large pressing force is evenly applied to each bolt over the entire area of the protrusion 68. It was confirmed that airtightness was maintained.

Further, since the projection 68 has a circumferential portion (annular portion) 68a concentrically surrounding the bolt hole 69, the inside of the crankcase 3 is completely formed with respect to the bolt hole 69. Airtight, and alleviates the generation of an excessive pressing force in the vicinity of the tightening bolt 73.
In the case where 3 is partially tightened, the circumferential portion 68a functions to alleviate the inclination of the joint surface 67 with respect to the mating joint surface 71 by the tightening bolt previously tightened.

As described above, according to this embodiment,
Joint surfaces 67 and 71 of cylinder 1 and crankcase 3
Even if the casting surface remains as it is, due to the sealing action of the projection 68, the joint surfaces 67 and 71 are uniformly airtightly sealed via the gasket 72.

The first flange portion 4 of the exhaust pipe to be joined to either the joining surface of the first flange portion 39 or the second flange portion 41 of the intake pipe including the carburetor 17 or the muffler 23.
The protrusion 68 described above can be provided on any of the joining surfaces of the seventh and second flange portions 49.

Further, the present invention can be applied not only to the general-purpose small-sized engine but also to a general die-cast product in which two flange joint surfaces are connected to each other while maintaining airtightness via a gasket.

[0032]

As described above, according to the present invention, the following remarkable effects are obtained.

(1) The joining surfaces of precision die-cast products can be completely airtightly fastened via gaskets without performing secondary machining. Thereby, the production cost of the product can be significantly reduced.

(2) Since the bolt hole projection formed near the tightening bolt hole is formed in a concentric annular shape around the tightening bolt, an excessive pressing force is generated and the joint surface at the time of single tightening. Can be reduced.

(3) Since the annular bolt hole projections provided for each of the plurality of tightening bolts are configured to be coupled in a closed form on a plane by the coupling projections, any form of flange can be used. Widely applicable.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along a center line of a cylinder in a general-purpose small engine according to an embodiment of the present invention.

FIG. 2 is a view taken in the direction of the arrow A in FIG. 1;

FIG. 3 is an enlarged sectional view of a protrusion in the embodiment.

FIG. 4 is a sectional view taken along a cylinder center line of a general-purpose small engine to which the present invention is applied.

FIG. 5 is a plan view of a joint flange portion between a cylinder and a crankcase according to the related art in the general-purpose small engine.

FIG. 6 is a sectional view taken along line ZZ of FIG. 5;

FIG. 7 is a plan view of a carburetor joint flange according to the related art.

FIG. 8 is a sectional view taken along line YY of FIG. 7;

FIG. 9 is a plan view of a muffler joining flange according to the related art.

FIG. 10 is a sectional view taken along line XX of FIG. 9;

[Explanation of symbols]

 Reference Signs List 1 cylinder 2 crankcase 5 piston 17 carburetor 19 intake port 21 air cleaner 23 muffler 25 exhaust port 31 first flange portion (cylinder) 33 second flange portion (crankcase) 66 cylindrical portion 67 joint surface (cylinder) 68 projection 68a Circumference part (protrusion part) 68b, 68c Curved part 69 Bolt hole 71 Joint surface (crankcase) 72 Gasket 73 Tightening bolt

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI // F02F 11/00 F02F 11/00 D

Claims (2)

[Claims] 1. A die formed by fastening two members manufactured by die-casting with bolts inserted into a plurality of bolt holes of a flange portion at a joint surface formed on a joint flange portion of the two members. A joint structure for a cast product, wherein one of the joint surfaces is joined to an annular bolt hole protrusion surrounding the plurality of bolt holes, and the bolt hole protrusions are closed in a plane. A joining projection which is provided on the die casting product, wherein the bolt hole projection and the joining projection are formed as thin, small projections slightly protruding from the joining surface and having a small width. 2. The thin projection is a joint surface of a flange portion that joins a cylinder and a crankcase of an internal combustion engine, a joint surface of a flange portion of an exhaust pipe including a muffler, or a flange of an intake pipe including a carburetor. The joining structure for a die-cast product according to claim 1, wherein the joining structure is provided on any one or all of the joining surfaces of the portions.