JPH0734962A - Cylinder block made of light alloy and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a linerless plated cylinder block made of a light alloy which is manufactured through die casting and has a plated layer of high quality and to provide the manufacture thereof CONSTITUTION:The manufacture of a cylinder block made of a light alloy comprises a process wherein a chiller 4 is installed at a part where the inner surface of a cylinder 2 is formed and a cylinder block 1 is die-cast through internal chill of the chiller 4; a process wherein a cutting work C is applied so that a sound layer 2a of a die cast material formed at a part making contact with the chiller 4 is exposed to a surface; and a process wherein a plated layer 5 is formed on the surface of the sound layer 2a of a die cast material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light alloy cylinder block, and more particularly to a linerless plated cylinder block and a manufacturing method thereof.

[0002]

2. Description of the Related Art A liner made of cast iron has conventionally been provided on the inner surface of a cylinder block made of an aluminum alloy, but in order to reduce the weight and improve the cooling efficiency, plating is applied instead of the liner. Cylinder blocks are being developed. This linerless plated cylinder block is generally manufactured by a low pressure casting method. In other words, when trying to manufacture a linerless plated cylinder block by die casting, the general layer of die casting material must be exposed on the surface by cutting after casting, so it is difficult to apply high quality plating to the surface. Was thought to be.

[0003]

However, the low-pressure casting method is generally low in productivity because of a long casting cycle time.
Therefore, the present invention provides a light alloy linerless plated cylinder block that can be manufactured by die casting that has a significantly shorter casting cycle time than the low pressure casting method, and has a high quality plating layer, and a manufacturing method thereof. With the goal.

[0004]

The present invention has been made to achieve the above object, that is, the first invention is to install a chiller on a portion forming an inner surface of a cylinder,
A step of die-casting a cylinder block around the chiller, a step of cutting so that a sound layer of a die-cast material formed in a portion abutting the chiller is exposed on the surface, and a sound layer of the die-cast material And a step of forming a plating layer on the surface of the cylinder, and a method of manufacturing a light alloy cylinder block. According to a second aspect of the present invention, the draft of a bore mold for casting the inner surface of the cylinder is less than or equal to the ratio of the thickness of the sound layer of the die casting material formed on the inner surface of the cylinder to the depth of the portion of the inner surface of the cylinder where the piston ring slides. Formed into a die block, a step of die casting a cylinder block, a step of releasing the die cast before shrinkage resistance of the cast die cast, and a step of cutting so that the sound layer of the die cast material surface remains on the surface. And a step of forming a plating layer on the surface of the sound layer of the die-cast material, the method comprising the steps of: A third aspect of the invention is to reduce the draft of a bore mold for casting the inner surface of a cylinder.
It is formed below the ratio of the thickness of the sound layer of the die-cast material formed on the inner surface of the cylinder to the depth of the portion on the inner surface of the cylinder where the piston ring slides, and a combustible sheet is wound around the bore mold to die-cast the cylinder block. And a step of performing a cutting process so that the sound layer on the surface of the die casting material remains on the surface after releasing, and a step of forming a plating layer on the surface of the sound layer of the die casting material, It is a method of manufacturing a cylinder block. A fourth invention is that a die-cast material general layer made of an Al-Si eutectic alloy is formed on the inner surface of the cylinder, a sound layer having a crystal grain size of 10 µ or less formed on the surface of the general layer, and a surface of the sound layer. And a plating layer formed on the cylinder block.

[0005]

The present invention will be described with reference to the drawings. 1 to 4 show a first embodiment of the present invention. A plurality of cylinders 2 are formed in a cylinder block 1 of this embodiment, and each cylinder 2 shares an adjacent portion with an adjacent cylinder. It is shaped like a cyramise. The outer peripheral surface of each cylinder 2 is surrounded by a water jacket 3. The cylinder block 1 is manufactured as follows. First, as shown in FIGS. 1 and 2,
A cylindrical chiller 4 made of an aluminum alloy is installed in a portion forming an inner surface of each cylinder 2, that is, a portion forming a sliding surface that slides with a piston (not shown).
The cylinder block 1 is cast by die casting. As a result, as shown in FIG. 3, a sound layer 2a of die-cast material is formed on the portion of the cylinder 2 that contacts the chiller 4. Next, a cutting process is performed along the line C-C in FIG. 3, that is, so as to cut the sound layer 2a of the die-cast material. As a result, the chiller 4 is completely cut off, and a part of the sound layer 2a is also cut off, so that the rest of the sound layer 2a is exposed on the inner surface of the cylinder 2. Then in FIG.
The plating layer 5 is formed on the surface of the sound layer 2a of the die-cast material exposed as shown in FIG.

Generally, according to die casting, the crystal grain size is 10 at a depth of about 1 mm from the surface of the die casting.
A sound layer 2a having a thickness of about μ or less is formed, and a general layer 2b of a die-cast material having a rougher cloth is formed at a position deeper than the sound layer 2a. When the die casting is plated, the sound layer 2a on the surface of the die casting must be plated without fail, and the general layer 2b cannot be plated with sufficient quality because the material is rough. On the other hand, the mold needs to be provided with a draft for releasing the mold, and the inner surface of the cylinder 2 needs to be formed in a cylindrical shape for sliding the piston. Therefore, if the chiller 4 is cast before it is cast, the inner surface of the cylinder after casting must have a truncated cone shape with the diameter decreasing downward, and the sound layer 2a formed on the inner surface of the cylinder also has a truncated cone shape. Inevitably. Therefore, if this is cut and processed into a cylindrical shape, the general layer 2b of the die-cast material is exposed at the bottom of the cylinder, and plating of sufficient quality cannot be applied.

However, since the chiller 4 is cast around in this embodiment, the draft can be formed on the inner surface of the chiller, and the interface between the chiller and die casting can be formed in a cylindrical shape. Therefore, a healthy layer 2a of die casting material
Since it is also formed into a cylindrical shape, even if a cutting process is performed so as to cut the inside of the sound layer 2a, all the exposed layers become the sound layer 2a, so that the surface can be plated with high quality. Thus, according to this embodiment, the linerless plated cylinder block can be obtained by die casting with a short casting cycle time. In addition, since the chiller is used in this embodiment, the structure of the sound layer 2a can be densified, so that a high quality cylinder block can be obtained. Since a chill layer having a finer metal structure is formed in the surface layer portion of the sound layer 2a, it is more preferable to perform cutting so as to cut the inside of the chill layer. Further, in this embodiment, since the inner surface of the cylinder is plated, it is not necessary to use a hypereutectic alloy as a die casting material, and Al-Si which is easy to process
A eutectic alloy can be used. Regarding the type of plating, considering the matching with the piston ring, Ni
Plating, Cr plating, Fe plating or the like can be used.

Next, FIG. 5 shows a second embodiment. The gradient α of the inner surface of the cylinder 2 after die casting in this embodiment is determined by the thickness t of the sound layer 2a of the die casting material formed on the inner surface of the cylinder and the piston ring (not shown) on the inner surface of the cylinder 2.
Is formed at a ratio of not more than t / L with the depth L of the sliding portion, that is, α ≦ t / L. Conversely, the draft of the bore die 6 forming the inner surface of the cylinder is α, and this α is formed so that α ≦ t / L.
For example, if t = 1 mm and L = 100 mm, α ≦ 0.
01 (radian), that is, the draft α of the bore die 6 is formed to be α ≦ 34 ′. In this way, after the cylinder block 1 is die cast, the cylinder block 1 is released before contraction resistance of the cast die cast occurs. Then, in FIG.
A cutting process is performed on the C line, that is, on any of the sliding surfaces of the cylinder 2 so that the sound layer 2a of the die casting material is cut, and a plating layer is formed on the exposed surface of the sound layer 2a of the die casting material.

Generally, in die casting, the draft angle α of the die is at least α = 1.5 ° to 3 °, that is, α = 0.026, so that the die can be released even after the die casting solidifies and contracts. .About.0.052 (radian). As a result, the depth L of the cylinder sliding surface is, for example, L =
When it is 100 mm, the radius at the bottom of the cylinder sliding surface is Lα = 2.6 mm to 5.2 than the radius at the cylinder upper surface.
It is cast narrowly by mm. Therefore, in order to process the cylinder sliding surface into a cylindrical shape thereafter, at least 2.6 mm to 5.2 mm must be cut at the bottom of the cylinder sliding surface, and the general layer 2b of the die-cast material must be exposed. ,
High quality plating cannot be applied. However, in this embodiment, the general layer 2 of the die-cast material is used even if it is cut.
This is a solution to the problem of die casting by die casting using a bore die 6 having a shallow draft so that b is not exposed, and releasing the die casting before the shrinkage resistance of the die casting occurs. The solidified die casting is released from the mold considerably early after solidification. Therefore, it is preferable to adjust the temperature of the bore mold 6 in order to prevent deformation of the die casting.

Next, FIG. 6 shows a third embodiment. The draft α of the bore mold 6 of this embodiment is also determined by the thickness t of the sound layer 2a of die-cast material formed on the inner surface of the cylinder and the cylinder 2
The piston ring (not shown) on the inner surface is formed to have a ratio of not more than t / L with the depth L of the sliding portion, that is, α ≦ t / L. Further, in this embodiment, the bore mold 6
A cylinder block 1 is die-cast by winding a combustible sheet 7 around the cylinder block 1. As a result, the combustible sheet 7 functions to maintain a constant gap between the bore die 6 and the die casting, and at the same time, the combustible sheet 7 burns to become mainly carbon in the casting process, so that lubrication at the time of demolding is performed. It also functions as a material. That is, in the present embodiment, die casting is performed by the bore die 6 having a shallow draft so that the general layer 2b of the die casting material is not exposed even if the cutting process is performed. This is solved by winding the combustible sheet 7 in advance.

[0011]

Industrial Applicability According to the present invention, since it can be produced by the die casting method, the casting cycle time is short, and since the sound layer of the die casting material can be plated, a high quality plated layer can be formed. A light alloy linerless plated cylinder block and a method for manufacturing the same.

[Brief description of drawings]

FIG. 1 is a plan view showing the first embodiment of the present invention after casting.

FIG. 2 is a sectional view taken along line AA in FIG.

FIG. 3 is an enlarged view of part B in FIG.

FIG. 4 is a view corresponding to FIG. 3 showing a state after plating.

FIG. 5 is a longitudinal sectional view of a main part showing a second embodiment.

FIG. 6 is a vertical cross-sectional view of a main part showing a third embodiment.

[Explanation of symbols]

1 ... Cylinder block 2 ... Cylinder
2a ... Healthy layer 2b ... General layer 3 ... Water jacket
4 ... Chiller 5 ... Plating layer 6 ... Bore mold
7 ... Combustible sheet t ... Healthy layer thickness L ... Piston ring bottom dead center depth α ... Draft slope C ... Cutting position

Claims (4)

[Claims] 1. A step of installing a chiller on a portion forming an inner surface of a cylinder, die-casting a cylinder block around the chiller, and a sound layer of a die-cast material formed on a portion abutting the chiller on the surface. A method of manufacturing a light alloy cylinder block, comprising: a step of performing a cutting process so as to be exposed at a surface; and a step of forming a plating layer on the surface of the sound layer of the die-cast material. 2. The draft of a bore mold for casting the inner surface of the cylinder is set to be less than or equal to the ratio of the thickness of the sound layer of the die casting material formed on the inner surface of the cylinder to the depth of the portion of the inner surface of the cylinder where the piston ring slides. Forming and die casting the cylinder block, releasing the die cast before shrinkage resistance of the cast die casting, and performing a cutting process so that the sound layer of the die casting material surface remains on the surface, A method of manufacturing a light alloy cylinder block, comprising a step of forming a plating layer on the surface of the sound layer of the die-cast material. 3. The draft of a bore mold for casting the inner surface of the cylinder is set to be less than or equal to the ratio of the thickness of the sound layer of the die casting material formed on the inner surface of the cylinder to the depth of the portion of the inner surface of the cylinder where the piston ring slides. Forming, winding a combustible sheet around the bore mold, and die-casting the cylinder block; cutting the die block so that the sound layer on the surface of the die-cast material remains on the surface; and the die-cast material. And a step of forming a plating layer on the surface of the sound layer, and a method of manufacturing a light alloy cylinder block. 4. A die-cast material general layer made of an Al-Si eutectic alloy on the inner surface of the cylinder, a sound layer having a crystal grain size of 10 μm or less formed on the surface of the general layer, and a surface of the sound layer. A cylinder block having a formed plating layer.