JPH1182154A - Aluminum alloy cylinder block and method of manufacturing the same - Google Patents

Abstract

(57) [Abstract] [Problem] To improve the adhesion of plating, stably retain the plating on the inner peripheral surface of the sleeve, and prevent the plating from adhering to the casting surface of the crank chamber wall surface where the plating is easily peeled off. An alloy cylinder block is provided. SOLUTION: A base material 6 made of an aluminum alloy casting
In the cylinder block 2 in which the sleeve 40 made of an aluminum alloy is mounted in the cylinder bore 12 of
A plated layer was formed on the inner circumferential surface 37 of the sleeve, and a non-plated layer having a plated layer supporting portion exposed at an end of the inner circumferential surface of the sleeve on the side of the crankcase was provided in an annular shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine cylinder block, and more particularly to an aluminum alloy cylinder block in which a separate sleeve is mounted on a cylinder bore and an inner peripheral surface of the sleeve is plated.

[0002]

2. Description of the Related Art A vehicle engine, a marine engine or a general-purpose engine is generally constituted by a cylinder block made of an aluminum alloy casting, and the inner wall surface of the cylinder bore has improved wear resistance and lubricity against piston sliding. For this reason, plating is applied. In this case, if the casting is directly plated, the plating peels off during operation of the engine due to poor adhesion of the plating, which affects the engine performance and the like. A method of manufacturing a cylinder block in which a sleeve is cast in a cylinder bore and plating is performed on the sleeve in order to prevent such peeling of plating has been disclosed (JP-A-3-90594).

In the method of manufacturing a cylinder block described in this publication, a sleeve is formed from an extruded material or a drawn material of aluminum, and a molten raw material such as AC4C is poured in a state where the sleeve is placed in a mold in advance, and a cylinder is formed. The cylinder block is manufactured by machining the material of a cylinder block in which a sleeve is cast on the inner wall surface, further applying a composite plating to the inner peripheral surface of the sleeve, and performing a honing process on the composite plating. By using an aluminum sleeve in this manner, plating can be performed while preventing an increase in weight, and wear resistance and lubricity of a cylinder bore against sliding of a piston are ensured.

[0004] On the other hand, the inventor of the present application has proposed, in addition to the method of mounting the sleeve in the cylinder bore by such casting, press-fitting the sleeve into the base material of the cast cylinder block, and thereafter plating the inner surface of the sleeve. Alternatively, a method of manufacturing a cylinder block by plating and then press-fitting a sleeve was also examined.

[0005] In either case of casting or press-fitting, unless the plating applied to the inner peripheral surface of the sleeve maintains the wear resistance and lubricity against the sliding of the piston, a stable engine output cannot be obtained. No. For this reason, sufficient adhesion of plating must be ensured.

[0006]

However, in the plating process, when plating is performed on a cylinder block in which a sleeve has already been mounted by press-fitting or casting, the plating layer on the sleeve side is gradually moved from the plating support portion from the end of the crankcase side. When peeling and peeling progress to the piston sliding range, part of the plating layer separates and enters the crankcase, enters the sliding lubrication part in the engine such as the crank bearing, and damages that part, The durability of the engine 1 may be reduced.

[0007] This is because if the rate of thermal expansion and contraction is slightly different between the sleeve and the cylinder block base material, the engine starts and stops when a plating layer is formed from the cylinder bore end of the sleeve to the side of the crank chamber wall. This is because, as is repeated, the plating layer on the base material side is pushed up by the plating supporting portion and acts to peel off the plating layer on the sleeve side. Furthermore, when the sleeve vibrates during the operation of the engine, the amplitude increases because the sleeve end is not only an antinode of the vibration but also a free end, and the sleeve end of the plating layer has a larger distortion than other parts. This also occurs because the plating layer is peeled off from the plating support part due to long-term use of the engine.

After plating the sleeve alone,
When press-fitting into the cylinder block base material, if the plating layer is formed up to the end of the sleeve in the plating process, the plating layer is plated by the vibration of the sleeve during the operation of the engine during the long-term use of the engine as described above. There is a possibility that it will come off from the support. In this case, the sliding lubrication portion in the engine may be similarly damaged, and the durability of the engine may be reduced.

The present invention has been made in consideration of the above points, and improves the adhesion of the plating, stably holds the plating on the inner peripheral surface of the sleeve, and improves the slidability of the piston. An object of the present invention is to provide a cylinder block made of aluminum alloy, in which a plating is hardly peeled off and the durability of the engine is not reduced, and an aluminum alloy sleeve is provided in a cylinder bore portion to reduce the weight.

[0010]

According to the present invention, there is provided a cylinder block in which a sleeve made of an aluminum alloy is mounted in a cylinder bore of a base material made of an aluminum alloy casting. A cylinder block made of an aluminum alloy, wherein a non-plated layer exposing a plated layer support portion is provided in an annular shape at an end of the inner peripheral surface of the sleeve on the crankcase side, wherein the plated layer is formed. I will provide a.

According to this configuration, the portion from the crank chamber side end of the inner peripheral surface of the sleeve to the base material of the cylinder block where the plating layer may be peeled off from the plating support portion due to thermal expansion and thermal contraction due to engine stoppage. No plating layer is formed on the crank chamber side end of the inner peripheral surface of the sleeve, which may be peeled off from the plating supporting portion by the vibration of the sleeve during operation of the engine. Therefore, there is no problem caused by peeling of the plating.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional view of a cylinder block made of an aluminum alloy containing a sleeve according to an embodiment of the present invention. In the figure, reference numeral 1 denotes a four-cycle internal combustion engine using gasoline as fuel, and the internal combustion engine 1 has a cylinder block 2. A crankshaft 4 is accommodated in a crank chamber 3 formed by a skirt portion 6 at a lower portion of the cylinder block 2 and a crankcase 7, and the crankshaft 4 is rotatable around its axis 5. It is supported by part 6. The skirt 6 and the crankcase 7 are detachably fastened to each other by fasteners 8.

A cylinder body 10 protrudes from the upper part of the cylinder block 2. The skirt portion 6 and the cylinder body 10 are made of an aluminum alloy and are integrally formed with each other.

The integral casting comprising the aluminum alloy skirt 6 and the cylinder body 10 constitutes the base material 60 of the cylinder block according to the present invention. The cylinder block 2 is constituted by the base material 60 and a sleeve 40 described later.

A cylinder bore 12 having a circular section is formed in the cylinder body 10 with an axis 11 oriented vertically.

A sleeve 40 according to the present invention is mounted in the cylinder bore 12 by casting or press fitting as described later. As described later, the inner peripheral surface 37 of the sleeve 40 is subjected to a plating process for enhancing abrasion resistance and lubricity.

The lower end of the cylinder bore 12 communicates with the crank chamber 3, and the upper end of the cylinder bore 12 is closed by a cylinder head 13. The cylinder head 13 is detachably fastened to the upper end of the cylinder body 10.

Cylinder bore 1 in cylinder body 10
2, a piston 15 is slidably fitted in the axial direction.
Further, a connecting rod 17 having one end connected to the crankshaft 4 and the other end connected to the piston 15 by a piston pin 16 is provided.
And the piston 15 are connected. A piston ring 15a is mounted on the piston 15 and slides on the inner surface of the cylinder bore. P indicates the sliding range of the piston 15.

A space surrounded by the cylinder head 13 and the piston 15 in the cylinder bore 12 is a combustion chamber 1.
9. An intake port 20 and an exhaust port 21 for communicating the combustion chamber 19 with the outside of the cylinder head 13 are formed in the cylinder head 13, and an intake valve 22 and an exhaust valve 23 for opening and closing the ports 20 and 21 are formed. Is provided. Further, an ignition plug facing the discharge unit is provided in the combustion chamber 19.

When the piston 15 is lowered and the intake valve 22 is opened, the air-fuel mixture 26 is sucked into the cylinder bore 12 through the intake port 20 and is compressed by the rise of the piston 15 to be ignited and burned by the spark plug. . Thus, the internal combustion engine 1 is driven and output via the crankshaft 4. The exhaust gas 27 generated by the combustion is discharged through the exhaust port 21 by opening the exhaust valve 23.

Further, a cooling water jacket 28 is formed in the cylinder body 10 to suppress the temperature of the cylinder body 10 from becoming high due to combustion heat.

(Example) Examples of the aluminum alloy forming the cylinder block base material 60 of the present invention comprising the skirt portion 6 of the cylinder block 2 and the cylinder body 10 are JIS shown in Tables 1 and 2 below. Standard aluminum alloys can be used.

[0023]

[Table 1]

[0024]

[Table 2]

Further, as an example of the aluminum alloy of the sleeve 40 constituting the inner peripheral surface of the cylinder bore 12, alloys shown in Table 3 below can be used.

[0026]

[Table 3]

As shown in Tables 1 to 3, the base aluminum alloy contains 5 to 20% (% by weight) of Si.
As the aluminum alloy of the sleeve, (S
An aluminum alloy having a Si content that satisfies 50 <α <150, where α is the content of (i weight content / Si weight content of base material) × 100.
By forming each of the base material and the sleeve using the aluminum alloy having such a configuration, the difference in the coefficient of thermal expansion between the base material and the sleeve is reduced, and a heat spot is generated between the base material and the sleeve, and the inner circumference of the sleeve is reduced. Thermal deformation of the surface is reduced, and peeling of plating applied to the inner peripheral surface of the sleeve is suppressed.

When the cylinder block base material 60 is formed by AC4C in Table 2, the Si content by weight of the base material 60 is 6.5 to 7.5%. 2, the Si content is, for example, 3.75 to
An alloy changed to 9.75% by weight is used to satisfy the condition of Si content by weight of the sleeve / Si content by weight of the base material. Similarly, when the cylinder block base material 60 is formed by the ADC 10,
Since the weight content is 7.5 to 9.5%, in the alloy 1 or the alloy 2 in Table 3, the Si content is set to, for example, 4.7.
An alloy changed to 5 to 15% by weight is used so as to satisfy the condition of Si weight content of the sleeve / Si weight content of the base material.

Further, as shown in Table 3, the aluminum alloy of the sleeve has a C content of at least 0.2 to 10 each.
Contains both u and Mg. Thereby, the hardness can be easily increased to HB 70 or more by performing the T6 treatment as described below. Even when only one of Cu and Mg is contained, the hardness can be easily increased to HB 70 or more by T6 treatment. Further, as shown in Tables 1 and 2, the base aluminum alloy contains one or both of Cu and Mg. This makes it possible to easily increase the hardness by performing T6 treatment on the base material together with the sleeve as described below, and to increase the rigidity of the entire cylinder block while improving the plating holding ability of the plating layer support portion of the sleeve. And the durability of the engine can be improved.

FIG. 2 is a flowchart for explaining a process of manufacturing a cylinder block by casting a sleeve according to the present invention. In this flow, the T6 treatment (steps S2, S4, S6) is performed in accordance with JIS standard H in order to increase the surface hardness of the inner peripheral surface serving as the plated layer support of the sleeve.
According to 5202, the sleeve alone or the entire block into which the sleeve is cast is solution-aged at a predetermined temperature and then age-hardened, and may be performed once in S2, S4, or S6, or may be omitted. It is desirable that the surface hardness of the sleeve be HB 70 or more (70 to 150) by such T6 treatment. When the surface hardness of the inner peripheral surface is made HB 70 or more by extrusion or drawing of the sleeve, the subsequent surface hardening treatment by T6 treatment can be omitted.

In addition, according to the T6 process of S2 or S4, the hardness of only the sleeve can be increased. At the time of casting, the hardness of the sleeve slightly decreases due to the heat of the base material in the molten state, but the casting time itself is shorter than that of the T6 treatment, and the hardness of the inner peripheral side of the sleeve can be maintained at HB 70 or more. Further, according to the T6 process in S6, the hardness of the base material of the cylinder block can be increased in addition to the increase in the hardness of the sleeve, the rigidity of the entire cylinder block can be increased, and the sliding portion of each part can be increased by engine vibration. Of the engine can be prevented from being reduced due to, for example, an increase in sliding wear due to a decrease in clearance or the like.

Outer peripheral shot blast (step S3)
Is for forming fine irregularities on the outer peripheral surface of the sleeve to improve the bonding property with the base material. By forming the irregularities on the outer peripheral surface of the sleeve before casting the sleeve, the sleeve can be reliably prevented from coming off even if the tension force is reduced due to the difference in the coefficient of thermal expansion between the base material and the sleeve during operation. Such irregularities on the outer peripheral surface of the sleeve can be formed by other mechanical processing other than shot blasting, or by pickling (etching) the entire sleeve. Note that the shot blast processing (step S3) may be omitted. Further, instead of a method of forming irregularities on the outer periphery of the sleeve by shot blasting or the like to enhance the bonding property with the base material, the sleeve and the base material may be bonded by using low melting point solder to prevent the sleeve from coming off. .

Here, shot blasting refers to steel balls, carbide beads, stainless steel balls, zinc beads, glass beads having a particle size of 50 to 150 μm, river sand containing a lot of quartz having a slightly larger particle size, and the like. With a projector, for example, 40-8
It refers to what is projected onto a work at a projection speed of 0 m / s.

(Embodiment) As shown in FIG. 3, the embodiment of the manufacturing method using the sleeve casting is a T6 treatment (S2, S6).
4, S6) and the flow A in which the outer peripheral shot blast (S3) is omitted become a flow including the minimum necessary steps (however, it is necessary that the hardness of the sleeve is previously set to HB 70 or more by extrusion or drawing). ). The flow B and the flow C are also similar to those obtained by omitting the outer peripheral shot blast (S3). Among them, the flow B is a T6 before the sleeve casting step (step S5).
This is the flow after the processing, and the flow C is the flow after the T6 processing after the sleeve casting step (Step S5).

Flows D to G are for performing the outer peripheral shot blasting step (step S3). Among them, the flow D is a flow in which the T6 treatment is omitted (however, the hardness of the sleeve must be set to HB 70 or more by extrusion or drawing in advance), and the flow E is a T6 treatment before the shot blasting treatment (S3). The flow subjected to the treatment (S2), the flow F is the flow subjected to the T6 treatment (S4) after the shot blast (S3) and before the sleeve casting (S5), and the flow G is the T after the sleeve casting (S5).
6 is a flow that has been subjected to the processing 6 (S6).

Steps S7 to S10 are similarly performed for each of the flows A to E. That is, in step S7, the shapes of the cast sleeve and other parts of the cylinder block are adjusted by machining. Subsequently, in step S8, plating is performed on the inner surface of the sleeve in order to improve the wear resistance and lubricity of the inner surface of the sleeve (described later). Next, in step S9, the inner surface of the cylinder bore (sleeve) is honed. Finally, the entire cylinder block is cleaned, and the flow ends (step S10).

FIG. 4 shows the plating process (step S).
8) is a detailed flowchart, and FIG. 5 is a block diagram of a plating apparatus for performing this plating process. FIG.
FIG. 4 is a cross-sectional view of a sleeve processing surface in a main step of the plating process.

In the flowchart of FIG. 4, the plating of the inner surface of the sleeve is basically performed by a degreasing process (step S11) and an alkali etching process (step S1).
3), five processes of mixed acid etching process (step S15), alumite process (step S17), and composite plating process (step S19), and after each process, washing process (steps S12, 14, 16, 18, and 20). Is applied.

In this water washing process, two separate water tanks (a total of ten tanks) are used for each step, and the entire cylinder block is sequentially immersed in the two water tanks and moved up and down to remove the processing liquid in the previous step. Things. The water in the aquarium is regularly replaced with fresh clean water. It is desirable to move to the next step as soon as possible after completion of each water washing treatment, and to carry out the next treatment with a water film on the surface. Accordingly, it is possible to prevent dust or the like from adhering to the processing unit and to prevent oxygen in the air from directly touching, thereby preventing formation of an oxide film and the like, and improving reliability of processing in a later step. This is particularly effective in the case of plating.

As shown in FIG. 5, the sleeve 40 is
The cylinder block 2 cast into the cylinder body 0 has a cylinder body 10 on the lower side and a sealing gasket 41 on a dedicated apparatus body 44 in each step in order to perform various processes on the inner peripheral surface 37 of the sleeve 40. Mounted. In each process, the processing liquid 47 in the processing liquid tank 48 dedicated to each is supplied to the inside of the apparatus main body 44 by the dedicated pump 49, and the sleeve 4
0, and returns to the processing liquid tank 48 through the inner cylinder 46.

The gasket 41 is a sealing material for preventing a processing liquid from leaking in each processing step.
In the alumite treatment step (step S17) and the composite plating step (step S19), which will be described later, it functions as an insulating material for electrolytic action. In the alumite treatment step and the composite plating step, for example, a DC voltage is applied between the cylinder body 10 and the inner cylinder 46d (46e) from the AC power supply 63 via the rectifier 64 and the control circuit 65, and the DC Flow. In the other steps, no DC current is passed through the processing solution.

First, the degreasing process of FIG. 4 (step S11)
At this time, dirt such as processing oil adhering to the inner peripheral surface 37 (FIG. 5) of the sleeve 40 is removed. As shown in FIG. 5, this degreasing treatment is performed by supplying a degreasing liquid 47a in a processing liquid tank 48a into an apparatus main body 44a by a pump 49a. The degreasing liquid 47a rises while being in contact with the inner peripheral surface of the sleeve 40, returns to the processing liquid tank 48a through the inner cylinder 46a, circulates, and degreases the inner peripheral surface 37 of the sleeve.

By this degreasing process, as shown in FIG. 6A, the sleeve surface 53 (the inner peripheral surface 37 of the sleeve 40)
Is cleaned. In the figure, reference numeral 51 denotes an aluminum alloy material, and 52 denotes primary crystal Si particles.

Thereafter, as described above, using the two water tanks, the cylinder block 61 is sequentially immersed in the water tank and moved up and down to wash and remove the degreasing liquid in the previous step (step S12).

Next, an alkali etching step (Step S)
13), the alkaline solution 4 in another processing solution tank 48b
7b is supplied into the apparatus main body 44b by the pump 49b, and rises while being in contact with the inner surface of the sleeve 40 and rises in the inner cylinder 46b.
And returns to the processing liquid tank 48b. The oxide film on the inner peripheral surface 37 of the sleeve is removed by this alkali etching treatment. In this state, as shown in FIG. 6B, the aluminum alloy base 51 on the sleeve surface 53 is further dissolved and removed to some extent by etching. Next, as described above, the alkaline solution is washed and removed by the water washing process (Step S1).
4).

Next, a mixed acid etching process for removing primary crystal Si particles in the aluminum alloy is performed (step S15). In this step S15, the mixed acid solution 47c in the dedicated treatment liquid tank 48c is supplied into the apparatus main body 44c by the pump 49c, and the inner peripheral surface 3
7 and returns to the processing liquid tank 48c through the inner cylinder 46c.
By the circulation of the mixed acid solution 47c, as shown in FIG. 6C, the Si particles 52 exposed on the inner peripheral surface of the sleeve are dissolved and removed, and a dent is formed in the trace.

Here, the mixed acid solution may be a mixture of hydrofluoric acid and nitric acid in a volume ratio of 1: 2, or a mixture of hydrofluoric acid, nitric acid and acetic acid in a volume ratio of 1: 2: 1. Use things. In addition, what added a small amount of surfactant further to these may be used. This mixed acid etching dissolves and removes Si to form a recess for plating anchor, and improves the plating holding ability by changing the particle size and dispersion state of Si particles in the aluminum alloy constituting the sleeve. it can.

Due to the depression of the Si particle trace, the inner periphery of the sleeve becomes an uneven surface, and the adhesion effect of the plating in the subsequent step is improved by the anchor effect of the depression, and the plating is hardly peeled off.

In order to form fine recesses on the inner surface of the sleeve, shot blasting may be performed on the inner surface of the sleeve, in addition to the above-described method of removing Si particles by mixed acid etching.

When the recesses are formed on the inner surface of the sleeve by removing the Si particles by mixed acid etching, it is desirable that the primary crystal Si particles are uniformly distributed in a fine state in the aluminum alloy. Further, in order to reduce variation in the size of a hole (dent) formed by removing Si by etching, S
It is desirable that the i-particles have a uniform size. As a result, the anchor effect is increased, the distribution of this effect is made uniform, and the distribution of plating adhesion is made uniform. In addition, the Si crystal grains may be miniaturized by forming the sleeve with an extruded or drawn material of an aluminum alloy.

In the present embodiment, the diameter of the spherical Si particles is 1 μm to 100 μm.
High plating adhesion due to anchor effect. In addition, Si
In order to increase the number of particles distributed, the weight content of Si is set to 1
It is often 0-14. In addition, in order to make the distribution of Si particles uniform and to prevent a portion having low adhesion of plating from being formed, a long pipe material is cut into a sleeve material by extrusion or drawing under stable conditions. Furthermore, the average converted diameter of each Si particle is 20 to 3
Desirably, it is 0 μm. Further, it is desirable that the variation of the converted diameter is also about ± 10 to 15 μm.

Next, as described above, the mixed acid solution is washed and removed by the water washing process (step S16). Next, in step S17, an anodizing treatment (alumite treatment) of aluminum is performed. In this alumite treatment, a positive voltage of a DC power supply is applied to the cylinder body 10, the inner cylinder 46d is grounded, and the alumite liquid (electrolyte) 47d in a dedicated treatment liquid tank 48d is pumped by the pump 4.
9d into the apparatus main body 44d,
Of the processing liquid tank 48 through the inner cylinder 46d.
Return to d.

Due to the high-speed circulation of the alumite liquid 47d, as shown in FIG. 6 (d), the aluminum surface of the sleeve is exposed together with the inner surface where the concave aluminum surface formed at the mark where the Si particles 52 have been removed is exposed. To the entire inner peripheral surface.
An alumite layer 54 having a thickness of 1 to 1 μm is formed. If the film thickness does not reach this value, increase the current value to increase the current density, or increase the circulation speed of the processing solution,
Alternatively, the processing time is lengthened.

In the part where the Si particles cannot be completely removed and a dent is formed but the Si particles slightly remain on the inner surface, even though the Si is an electric conductor, the alumite solution 47
d is circulated at a high speed, whereby an alumite layer formed by oxidizing the aluminum surrounding the residual Si particles is
It adheres and adheres to the part where the particles remain. Since the alumite layer has a very small thickness of 0.1 to 1 μm and conducts electricity, it is possible to form a plating layer on the alumite layer by reducing metal ions in the plating solution at the time of composite plating in the next step.

That is, in addition to the flat surface and the dent where the aluminum ground is exposed, the plating layer is formed also in the portion where the Si particles remain. Then, a thin (0.1-1 μm) alumite layer is formed inside the recess formed at the mark where the Si particles 52 have been removed, and the plating layer is formed so as to bite into the still remaining recess. The alumite layer 54 is a columnar oxide film layer, and the pinholes extending from the surface of the alumite layer 54 to the aluminum ground become porous in which countless microholes are formed. The alumite layer 54 is easy to conduct electricity and can be plated on the surface of the alumite layer, and the plating layer is also formed in the pinhole, so that the anchor effect is large and the adhesion of plating is further enhanced. On the other hand, the thickness of the alumite layer is 20 to 30 μm
In the hard alumite treatment, the alumite layer becomes difficult to conduct electricity, and it becomes difficult to apply plating to the alumite layer. Similarly, an oxide film is formed on the surface that has been extruded or drawn out or on the processed surface from which the oxide film has been removed by processing, and the surface is naturally oxidized by being left in the air, and an oxide film is formed. It is difficult to conduct electricity and plating is difficult, and even if a plating layer is formed, an anchor effect as in the case of an oxide film formed by alumite treatment in which pinholes are formed cannot be obtained. For this reason, the natural oxide film of aluminum on the surface of the sleeve is removed in step S13, and instead, an alumite layer 54 having a large anchor effect is formed in step S17.

In the alumite processing step S17, since the processing liquid 47d is circulated at a high speed and the amount of the circulating liquid is large, the upper part (crank) of the cylinder bore (sleeve) is prevented in order to prevent the processing liquid 47d from spouting to the crank chamber side. The cover 45d is attached to the (room side). This cover 45d
Seals the upper end of the sleeve 40 with the O-ring 62. The degreasing process (S11), the alkali etching process (S13), and the mixed acid etching process (S1)
In 5), since the processing liquids 47a, 47b, and 47c are low in speed and the amount of circulating liquid is small, the cover 45d is unnecessary.

After the alumite treatment, the electrolytic solution of the alumite treatment is removed by the water washing treatment (step S18) as described above.

The above pretreatment process (steps S11 to S1)
8) After that, in step S19, a composite plating process is performed on the inner peripheral surface of the sleeve. This composite plating process is a high-speed plating process. Under a plating condition described later, a plating solution 47e in a dedicated processing solution tank 48e is supplied into the apparatus main body 44e by a pump 49e, and the processing solution tank 4e is passed through the inner cylinder 46e.
8e, the inner surface of the sleeve 40 is plated while circulating at a high speed.

In this high-speed plating step, the inner cylinder 46
e to the (+) side of the power supply circuit and the cylinder body 10 to the (-) side.
Side, and direct current is passed through the plating solution. As a result, Ni ⁺ and P ^{+ in} a plating solution having a composition described later adhere to the inner peripheral surface of the sleeve, and accordingly, SiC particles serving as a dispersant are caught in the plating layer.

Thus, as shown in FIG. 6E, the inner peripheral surface of the sleeve on which the alumite layer 54 has been formed
Plating layer 3 containing SiC and having excellent wear resistance and lubricity
8 are formed. The sleeve 40 is made of an aluminum alloy material containing Si in order to match or approximate the thermal expansion coefficient of the aluminum alloy base material 60 containing Si for improving castability. By performing the etching process as a pre-process of the plating process, a concave portion can be formed on the surface. For this reason, the plating layer 38 is made of the Si in step S15.
Due to the anchor effect due to the surface irregularities due to the removal of the particles and the anchor effect due to the minute pinholes of the alumite layer in step S17, the adhesion is greatly improved, and the adhesive adheres firmly to the inner peripheral surface of the sleeve.

In the high-speed plating process in step S19, the cover 45e is attached to the upper end of the sleeve 40. The cover 45e is provided with a plating solution 47 circulating at a high speed.
In addition to preventing the scattered ejection of e, the range of plating corresponding to the sliding range of the piston on the inner surface of the sleeve 40 is restricted.

That is, the plating range is the gasket 4 which is the inner peripheral surface of the sleeve 40 and is the boundary with the cylinder head.
1 to the O-ring 62 of the cover 45e.
That is, in FIG. 5, plating does not adhere to the inner surface of the sleeve above the O-ring 62 and the inner wall surface 6a of the skirt portion 6 that forms the crank chamber 3 further above the O-ring 62. Therefore, by making the position of the O-ring 62 correspond to the position of the lower end of the piston at the bottom dead center of the piston, plating can be applied only to the inner surface of the cylinder bore (sleeve) in the piston sliding range P (see FIG. 1). it can.

Accordingly, as shown in FIG. 9, for example, when plating is performed on the cylinder block 2 in which the sleeve 40 has already been mounted by press-fitting or casting, the plating layer 38A on the sleeve 40 side is gradually peeled off from the crank chamber side end 40a. However, when the peeling proceeds to the piston sliding range, a part of the plating layer separates and enters the crank chamber 3, enters a sliding lubrication part in the engine such as a crank bearing, and damages the part. The durability of the engine 1 may be reduced.

If the rate of thermal expansion and contraction is slightly different between the sleeve 40 and the cylinder block base material 60, the plating layer 38 extends from the end 40 a of the cylinder bore of the sleeve 40 on the crank chamber 3 side to the inner wall side of the crank chamber 3. Is formed, as the operation and stop of the engine 1 are repeated, the plating layer 38B on the base material 60 side is pushed up by the plating support portion 60a, and acts to peel off the plating layer 38A on the sleeve 40 side. is there. Further, when the sleeve 40 vibrates during the operation of the engine 1, the amplitude is increased because the sleeve end is not only an antinode of vibration but also a free end, and the sleeve end portion of the plating layer is larger than other portions. This is because distortion occurs, and this also causes the plating layer 38 to peel off from the plating supporting portion due to long-term use of the engine 1.

However, as in this embodiment, the plating layer 38 is formed on the inner peripheral surface of the sleeve 40, and the plating layer supporting portion is exposed at the end of the inner peripheral surface of the sleeve on the crank chamber side. Annular non-plated inner peripheral surface 37A
This eliminates the problem that the plating is peeled off during operation and invades and adheres to the crankshaft and the bearing portion to affect the durability.

As shown in FIG. 10, since the casting surface of the aluminum alloy containing Si, especially in contact with the mold, is cooled in a short time during casting, chill casting in which large Si particles are exposed on the casting surface. Because it is skin, Si is difficult to conduct electricity, that part is hard to be anodized and plated,
Peeling of the plating occurs from the missing hole 38C of the plating. Further, even if Si is dissolved and removed by mixed acid etching described below, since the Si particles are large, the plating layer 38
The plating layer 3 does not fill the particle removal holes 60b.
8 is bent and formed in the Si particle removal hole 60b.
When vibration is applied to the base material 60, the base material 60 may peel off from the bent portion 38D of the plating layer 38. However, as in this embodiment, the plating is prevented from adhering to the wall surface of the crank chamber from the beginning, and similarly, the plating is peeled off during operation and enters and adheres to the crankshaft and bearings, thereby affecting the durability of the engine. Disappears.

As described above, when the sand blasting process for forming the uneven surface for the anchor effect on the inner surface of the sleeve is performed, the sand blasting process is performed not only on the inner surface of the sleeve but also on the inner wall of the crank chamber of the cylinder block. The plating adhesion may be enhanced. When the plating adhesion of the inner wall of the crank chamber is thus enhanced, the cover 45e may be omitted in the plating process of step S19, and the plating may adhere to the inner wall of the crank chamber. Alternatively, in this case, without using the plating apparatus of FIG.
The plating process may be performed by immersing the cylinder block in a stationary plating tank.

The plating conditions in step S19 are as follows. Plating solution: sulfamic acid solution or sulfuric acid solution Plating condition: PH 3.0-4.5 Bath temperature 65-80 ° C. Flow rate between electrodes: 1.0-3.0 m / sec Current density: 20-200 A / dm ² Treatment method: Workpiece and electrode fixation, plating solution flow Deposition rate (when SiC eutectoid amount is 2.5% by weight): 20 to 30μ / m
An example of the in composite plating solution is as follows.

Here, the interelectrode flow velocity is the flow velocity of the composite plating solution flowing between the inner peripheral surface of the sleeve 40 and the inner cylinder 46e.

(Example 1) Nickel sulfamate plating solution Nickel sulfamate Ni (SO ₃ .NH ₂ ) ₂ : 270 to 330 g / l Nickel chloride NiCl ₂ : 10 to 30 g / l Boric acid H ₃ BO ₃ : 30 g / l phosphorus P: 0.1 to 0.3 g / l sodium Na: 1.0~3.5g / l silicon carbide (dispersing agent) SiC: 1.5 to 3.5 wt% water H ₂ O: balance the plating solution PH3.0~4.5 Desirably PH4.
The plating is performed while controlling the temperature at 0 to 4.5 and the bath temperature at 65 to 80 ° C.

[0071] (Example 2) of nickel sulfate plating solution nickel sulfate _{NiSO 4 · 6H 2 O: 450g} / l nickel chloride _{NiCl 2 · 6H 2 O: 60g} / l boric acid H ₃ BO _3: 30g / l phosphorus P: 0.1 to 0.3 g / l sodium Na: 1.0~3.5g / l silicon carbide (dispersing agent) SiC: 1.5 to 3.5 wt% water H ₂ O: balance the plating solution PH3.0~4.5 preferably PH4.
The plating is performed while controlling the temperature at 0 to 4.5 and the bath temperature at 65 to 80 ° C.

By using these plating solutions,
50 μm or more on the alumite layer on the inner peripheral surface of the sleeve 40
A Ni—P—SiC plating layer having a thickness of 150 μm can be formed. If the film thickness is not reached, the current value is increased to increase the current density, the circulation speed of the processing liquid is increased, or the processing time is lengthened. This plating layer allows the piston 15 and the piston ring 15
The coefficient of friction at the time of sliding a can be reduced, and the abrasion resistance and lubricity of the inner peripheral surface of the sleeve 40 against sliding of the piston 15 and the piston ring 15a can be improved.

It should be noted that phosphorus (P) was removed from the nickel sulfamate plating solution of Example 1 or phosphorus (P) was removed from the nickel sulfate plating solution of Example 2 to carry out the plating treatment in step S19. If implemented, the sleeve 40
50 μm to 150 μm on the alumite layer on the inner peripheral surface of
A Ni—SiC plating layer having a thickness of 2 μm can be formed. This plating layer also makes it possible to reduce the coefficient of friction when the piston 15 and the piston ring 15a slide, and to reduce the wear resistance and lubricity of the inner peripheral surface of the sleeve 40 against the sliding of the piston 15 and the piston ring 15a. Can be improved.

After the composite plating process in step S19, the washing process is again performed in step S20 to remove the plating solution, and the water adhering to the cylinder block 2 is removed by air blowing in step S21.

After the above plating step S8, the honing is performed on the plating layer on the inner peripheral surface of the sleeve 40 in the honing step S9. Thereby, the thickness of the plating layer is desirably about 50 μm, and in some cases, 20 μm to 1 μm.
The plating layer is scraped off to a thickness of 00 μm, and the surface roughness of the plating layer is reduced to 1.0 μmRz or less. As a result, the surface of the plating layer can be surely smoothed, the coefficient of friction at the time of sliding of the piston 15 and the piston ring 15a can be reduced, and the retention of engine oil is improved and lubricity is improved. be able to. Note that Rz is defined in JIS B0601.

FIG. 7 is a flowchart of a cylinder block manufacturing method according to another embodiment of the present invention. In this embodiment, a sleeve is pressed into a cylinder bore.

On the base material side, first, a cylinder block base material including the cylinder body is cast from the above-described aluminum alloy (step S31). Next, the various parts including the cylinder bores of the casting are trimmed by machining (step S3).
2).

On the other hand, the sleeve side comprises steps from step S33 to step S36. First, a pipe material made of the above-mentioned aluminum alloy for a sleeve is formed by extrusion or drawing, and cut into a predetermined length (step S33). ). Thereafter, a sleeve is formed by machining finish, cleaning process, and the like (step S35). This sleeve formation flow includes (1) steps S34 and S3
6 omitting both T6 processes (S33 → S3
5), (2) T6 processing in step S34 before sleeve processing, and omitting T6 processing in step S36 after processing (S33 → S34 → S35); (3) T6 processing in step S34 before sleeve processing Is omitted and T6 processing is performed in step S36 after processing (S33 → S35 → S
36).

In this case, by forming the sleeve by extrusion or drawing, the surface hardness can be set to 70 to 150 HB by utilizing the work hardening during the plastic working of the aluminum alloy. In this case, the surface hardening treatment by the T6 treatment is unnecessary, and the above-mentioned (1) step S33 → S
The flow of 35 may be sufficient. If the surface hardness of the sleeve formed by extrusion or drawing is HB 70 or less, the surface hardness of the sleeve is HB 70 or more (70 to 150) by the T6 treatment in step S34 or S36.

The sleeve thus formed is pressed into the cylinder bore of the base material of the cylinder block (step S37). After that, against the inner peripheral surface of the press-fitted sleeve,
Steps S8, S9, S of the flow in the case of the above-mentioned casting
Similarly to 10, a high-speed plating process (Step S38), a honing process (Step S39), and a cleaning process (Step S40) are performed. After the sleeve is press-fitted, a T6 processing step of Y is provided between step S37 and step S38, and the entire cylinder block is subjected to T6 processing, so that at least the surface hardness of the sleeve is Hb7.
It can be 0 or more.

Further, step S31 and step S31 in FIG.
At X in the middle of 32, the base material may be subjected to T6 processing, and the sleeve may be subjected to T6 processing in step S34 or step S38.

In the cylinder block manufacturing method shown in FIG. 7, the plating step S38 is performed before the sleeve press-fitting step S37 and the T6 processing step S36.
Or if there is no step S36, the step may be performed after the processing (sleeve manufacturing) step S35, and then the sleeve press-fitting step S37 and then the honing step S35. In this case, the plating time is lengthened so that the thickness of the plating layer is about 500 μm, and in the honing step S35, a removal allowance in centering boring is secured prior to honing with a grindstone to remove misalignment due to press-fitting. I do. Thereby, even if there is misalignment, the minimum thickness of plating can be secured to 20 μm or more, and lubricity can be improved.

Further, the sleeve press-fitting step S3
7 before plating step S38 with the sleeve 40 alone
Then, the honing process step S35 is performed,
Thereafter, the sleeve press-fitting step S37 and the cleaning step S40 may be performed. In these cases,
In FIG. 5, the main body 44 of the apparatus
(44a-44e) Each step of the plating step S38 is performed so as to be placed and held on the upper surface via the gasket 41.

In this plating step S38, plating is performed in a state where the crank chamber 3 side of the sleeve 40 is faced up and the cover 45e in which the O-ring 62 is fitted is attached to the end of the cylinder bore surface 37 of the sleeve 40 on the crank chamber 3 side. The plating is performed by circulating the solution. As a result, a plating layer can be formed on the cylinder bore surface 37, and a non-plating portion having a plating support portion exposed at the end on the crank chamber side can be provided in an annular shape.

Thus, when the sleeve 40 alone is plated and then press-fitted into the cylinder block base material, if the plating layer is formed up to the end of the sleeve in the plating process, the engine may be used for a long period of time. During the operation of the engine, the plating layer may be peeled off from the plating supporting portion due to the vibration of the sleeve during operation of the engine, which may damage the sliding lubrication portion in the engine and reduce the durability of the engine. In this case, the peeling that causes such a problem can be suppressed.

FIG. 8 is a graph showing the relationship between the weight percent of Si in the aluminum alloy and the coefficient of thermal expansion. As shown in the figure, the coefficient of thermal expansion changes largely corresponding to the Si content.
In each of the above-described embodiments, an appropriate amount of Si is contained in consideration of castability and distribution of Si particles for forming an uneven surface in consideration of a difference in coefficient of thermal expansion between the base material and the sleeve. Thereby, castability of the base material can be improved and peeling of plating can be suppressed.

[0087]

As described above, according to the present invention,
The plating layer is not formed on the part from the crank chamber side end of the inner peripheral surface of the sleeve to the base material of the cylinder block, where the plating layer may be peeled off from the plating support part due to thermal expansion and thermal contraction due to engine stoppage. Not
Moreover, the plating layer may not be formed at the crank chamber side end of the inner circumferential surface of the sleeve due to the vibration of the sleeve during the operation of the sleeve, and the plating layer may be peeled off from the wall surface of the crank chamber. There is no problem, and the durability of the engine can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part of a four-cycle engine to which the present invention is applied.

FIG. 2 is a flowchart of a method of manufacturing a cylinder block by casting a sleeve according to the present invention.

FIG. 3 is an explanatory diagram of an embodiment of the flowchart of FIG. 2;

FIG. 4 is a detailed flowchart of a plating process according to the present invention.

FIG. 5 is a configuration diagram of a processing apparatus for performing the flow of FIG. 4;

FIG. 6 is a sectional view of a processing unit in a main step of the flow in FIG. 4;

FIG. 7 is a flowchart of a method for manufacturing a cylinder block by press-fitting a sleeve according to the present invention.

FIG. 8 is a graph showing the relationship between the Si% of an aluminum alloy and the coefficient of thermal expansion.

FIG. 9 is a cross-sectional view of a plating layer when a plating layer is formed from a sleeve end to a base material.

FIG. 10 is a sectional view of a plating layer showing a plating state of a large surface of Si particles.

[Explanation of symbols]

1: internal combustion engine, 2: cylinder block, 3: crankcase, 6: skirt, 7: crankcase, 10: cylinder body, 12: cylinder bore, 13: cylinder head, 37: inner peripheral surface, 38: plating layer, 40: Sleeve,
41: Gasket, 44: Device body, 45d, 45e:
Cover, 46: inner cylinder, 47: processing liquid, 48: processing liquid tank,
49: pump, 51: aluminum alloy ground, 52: Si particles,
53: sleeve surface, 54: alumite layer, 60: base material of cylinder block.

Claims (7)

[Claims] 1. A cylinder block in which a sleeve made of an aluminum alloy is mounted in a cylinder bore of a base material made of an aluminum alloy casting, wherein a plating layer is formed on an inner peripheral surface of the sleeve, and a plating layer is formed on the inner peripheral surface of the sleeve. A cylinder block made of an aluminum alloy, wherein a non-plated layer exposing a plated layer support portion is provided in an annular shape at an end portion on a crankcase side. 2. A concave part in which the sleeve is made of an aluminum alloy containing a Si component, the center part of the sleeve contains Si particles, and the circumferential surface of the sleeve serving as a support part of the plating layer has the Si particles missing. 2. The aluminum alloy cylinder block according to claim 1, wherein a plating layer is formed on the circumferential surface of the sleeve including the inside of the recess. 3. The aluminum-aluminum alloy cylinder block according to claim 1, wherein a porous alumite layer of 5 μm or less is formed as a plating base layer on a circumferential surface of the sleeve. 4. A method of manufacturing a cylinder block in which a sleeve made of an aluminum alloy is mounted in a cylinder bore of a base material made of an aluminum alloy casting, wherein the sleeve is mounted in a cylinder bore of the base material, A seal material is provided on the inner peripheral surface of the sleeve at the side end to block the combustion chamber side and the crank chamber side, and plating is performed on the combustion chamber side of the inner peripheral surface of the sleeve with the seal material as a boundary. Of manufacturing aluminum alloy cylinder blocks. 5. A method for manufacturing a cylinder block in which a sleeve made of an aluminum alloy is mounted in a cylinder bore of a base material made of an aluminum alloy casting, wherein the sleeve of the cylinder bore is cranked before mounting the sleeve in the cylinder bore of the base material. On the inner peripheral surface of the sleeve at the chamber side end, a seal material for shutting off the combustion chamber side and the crank chamber side is provided, and after plating the inner peripheral surface of the sleeve on the combustion chamber side with the seal material as a boundary, A method for manufacturing a cylinder block made of an aluminum alloy, wherein the sleeve is mounted in a cylinder bore of a base material by press fitting. 6. The aluminum alloy according to claim 4, wherein before the plating process, a shot peening or a sand blasting process is performed on an inner peripheral surface of the sleeve to form a concave portion for anchoring the plating. Method of manufacturing cylinder block. 7. The sleeve according to claim 1, wherein the sleeve is made of an aluminum alloy containing Si particles. Prior to the plating process, a concave portion for anchoring plating is formed. The method for manufacturing an aluminum alloy cylinder block according to claim 4 or 5, wherein an etching process is performed.