JPH0214826Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a core sand removal device for cast products, and is applicable to hollow castings having a core sand removal hole, such as cylinder blocks, cylinder heads, and intake manifolds of internal combustion engines. It can be applied to all products.

[Background of the idea]

As a conventional core sand extraction device, for example,
There is something like the one shown in Figure 4.

Fig. 2 is a side sectional view of the conventional example (Utility Model No. 57-193937), Fig. 3 is a cutaway plan view taken along line A-A in Fig. 2, and Fig. 4 is an enlarged view of section B in Fig. 3. The outer wall 1a of the cylinder block 1, which is a hollow casting, is provided with a boss portion 4 having a core sand extraction hole 3 communicating with the cooling water passage 2 in order to remove core sand from the cooling water passage 2. The two-dot chain line 3a in FIG. 4 shows the shape of the material before forming the core sand removal hole 3. When processing the cylinder block 1, the core sand removal hole 3 is processed, and an appropriate interference is applied to the machined surface 3b. A Welch plug 5 is press-fitted to close the core sand removal hole 3.

However, in the conventional core sand extraction device shown in Figs. 2 to 4, the thickness H of the boss portion 4 and the depth of the core sand extraction hole 3 are
Since the rear opening end of the core sand removal hole 3 (point C in Figure 4) had a right-angled edge, stress was applied to point C when the welch plug 5 was press-fitted. There was a problem in which it was easy to concentrate and cracks easily occurred in this area.

[Purpose of invention]

An object of the present invention is to provide a core sand removal device for a cast product that alleviates stress concentration on the rear opening end of the core sand removal hole during press-fitting of a Welch plug and prevents the occurrence of cracks.

[Structure of the idea]

According to the present invention, in the hollow casting product, in which a boss portion is provided on the outer wall of the hollow casting product, and a core sand removal hole having a machined surface for press-fitting a plug (welch plug) into the boss portion is provided, the boss portion In this method, the thickness of the boss part is made larger than the depth of the core sand removal hole, and the inner diameter of the boss part is made to approximately match the machined surface of the core sand removal hole, and the rear protruding end of this boss part is provided with the core sand removal hole. Provided is a device for removing core sand from a cast product, characterized in that a curved surface that intersects the machined surface at an obtuse angle is formed as the casting surface.

[Example of idea]

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing one embodiment of the present invention, and is a partially enlarged view corresponding to FIG. 4 of the conventional example.

In this embodiment, a boss portion 4 is provided on the outer wall 1a of a hollow cast product, for example, a cylinder block 1, and a machined surface 3 is provided for press-fitting a Welch plug 5 into the boss portion 4.
No. 2 to 4 in that the core sand extraction hole 3 having b is provided.
Although it is similar to the conventional example shown in the figure, the shape of the material on the side of the cooling water passage 2 is changed from the conventional example, and the thickness H of the boss portion 4 is adjusted in advance by using core sand as shown by the two-dot chain line 3a in FIG. While making the depth of hole 3 larger than H″,
A curved surface 4a is formed at the rear protruding end of the boss portion 4 so that the thickness of the boss portion 4 gradually increases from the inside to the outside in the radial direction, and a core is formed so that the processed surface 3b penetrates this curved surface 4a. By processing the sand removal hole 3, the thickness H of the boss portion 4 is made larger than the depth H' of the core sand removal hole 3 after processing, and the inner diameter of the boss portion 4 is made larger than the thickness H' of the core sand removal hole 3 after processing. Make the core sand removal hole 3 approximately coincident with the surface 3b.
The processed surface 3b and the curved surface 4a of the rear protruding end of the boss portion 4
and intersect at an obtuse angle.

By doing this, unlike the conventional example, a sharp edge is not formed at the rear opening end of the core sand removal hole 3 (point C in Figure 1), so stress concentration at point C when press-fitting the Welch plug is alleviated. Stress in this part can be reduced.

To show the effect of this invention numerically, for example, a hole diameter of 30 mmφ is machined in a cylinder block (material: gray cast iron).
When providing a core sand removal hole, in the configuration shown in Figure 4 where H = H' = 8.5 mm, the stress measured at point D near the rear opening end of the core sand removal hole when press-fitting the welch plug is 10.2Kg. /mm ² , whereas H = 9.5mm,
In the configuration shown in Figure 1 with H' = 8.5 mm, the stress measured at point D near the rear opening end of the core sand removal hole when press-fitting the Welch plug was 5.2 Kg/mm ² , which has a large stress reduction effect. This was confirmed.

[Effect of idea]

According to the present invention, the thickness of the boss part is made larger than the depth of the core sand extraction hole, and the inner diameter of the boss part is made approximately equal to the machined surface of the core sand extraction hole. Since the curved surface formed on the rear protruding end of the boss part intersects at an obtuse angle, the stress concentration on the rear opening end of the core sand removal hole when press-fitting the Welch plug is alleviated, and the cracks that occur in the conventional example are avoided. The occurrence of defects can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a partially enlarged sectional view showing an embodiment of the present invention, Fig. 2 is a side sectional view of a conventional example applied to a cylinder block, and Fig. 3 is a cutting plane taken along line A-A in Fig. 2. 4 is an enlarged view of part B in FIG. 3. 1...Hollow casting product (cylinder block), 1a
... External wall, 3 ... Core sand extraction hole, 3a ... Material shape, 3b ... Processed surface, 4 ... Boss part, 4a ... Curved surface of rear protruding end, 5 ... Welch plug, H ...
Thickness of the boss part, H′...Depth of the core sand removal hole after processing.

Claims (1)

[Scope of utility model registration request] In a hollow casting product having a boss part on the outer wall and a core sand extraction hole having a machined surface for press-fitting a plug into the boss part, the boss part has a thickness of the core sand part. The inner diameter of the boss is made to be larger than the depth of the punched hole, and the inner diameter of the boss is made to approximately match the machined surface of the core sand punched hole.
A core sand extraction device for a cast product, characterized in that a curved surface that intersects at an obtuse angle with the processed surface of the core sand extraction hole is formed as a casting surface at the rear projecting end of the boss portion.