JP3515091B2 - Cylinder for internal combustion engine - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cylinder for an internal combustion engine made of an aluminum alloy having an inner peripheral surface plated, and a method for treating the inner peripheral surface thereof, and more particularly to a portable power work such as a brush cutter or a chain saw. Small air cooling used in the machine 2
The present invention relates to a cylinder suitable for a cycle gasoline engine.

[0002]

2. Description of the Related Art A typical example of a cylinder for a small air-cooled two-cycle gasoline engine used in a conventional portable power working machine is shown in FIG. The cylinder 1 of the illustrated example is made of an aluminum alloy, and has a body portion 2 provided with a pair of left and right columnar swelled portions 2a.
And a head portion 3 provided with a combustion chamber 4 called a squish dome shape are integrally formed, and a large number of cooling fins 19 are formed on the outer peripheral portion thereof, and the head portion 3 is ignited. A female screw portion 18 for mounting the plug is formed.

An inner peripheral surface (cylinder bore surface) 9 of the body portion 2
The exhaust port 5 which is opened and closed by the piston (20)
Also, the intake port 6 is opened so as to face each other in an up and down direction, and the ports 5 and 6 are displaced from each other by 90 ° in the circumferential direction to form the columnar bulging portion 2
A hollow scavenging passage 7, 7 with an inner wall 7a, 7a having a predetermined thickness is provided inside a, 2a.
A pair of left and right scavenging ports 8 which are opened and closed by the piston 20 are formed at a downstream end (upper end) of the cylinder 7 so as to be slightly upward in a direction opposite to the exhaust port 5 of the cylinder bore 9. There is.

The cylinder 1 is a so-called Schneule two-flow scavenging type cylinder in which a pair of scavenging ports 8, 8 are provided symmetrically across a longitudinal section FF that divides the exhaust port 5 in two. However, a so-called four-flow scavenging type in which two pairs of scavenging ports are additionally provided is also known. Further, as a form of the scavenging passage, the inner wall 7 as shown in the drawing is used.
In addition to the hollow type with a and 7a and the type without the inner walls 7a and 7a (the inner peripheral surface 9 side is open), the air-fuel mixture introduced from the crank chamber through the scavenging passage to the scavenging port is introduced into the skirt of the piston. In some cases, a half wall having a predetermined thickness is left in the upper portion of the scavenging passage to make contact with the scavenging passage, and a notch opening is formed in the lower portion along the height direction.

The cylinder 1 for a two-cycle internal combustion engine made of an aluminum alloy as described above is usually cast by a high pressure die casting method or the like, and then the inner peripheral surface 9 on which the piston is slid is resistant to wear. In order to increase the temperature, plating treatment (plating film 10) is performed.

[0006]

Conventionally, the cylinder 1 is used.
The inner peripheral surface 9 is plated with nickel (Ni),
Alternatively, hard chrome (Cr) plating is used. In recent years, nickel (N
i) In many cases, plating (electrolytic Ni-SiC, electroless Ni-B plating, etc.) is adopted. This is because the toxicity of the plating bath is low with respect to chromium (Cr) plating, which uses harmful hexavalent chromium, and it is possible to have performance comparable to that of chromium plating by adding additives. It is thought to be because. In the future, it is expected that chromium plating, which has a large environmental impact, will be in the direction of reduction, and there is a strong demand for the development of cylinder plating as an alternative to chromium plating. In particular, for nickel plating, the Vickers hardness of the plating film is 350 (H
It is as low as v [50gf]), and the issue is how to make it hard.

In addition, the conventional plating process has a low accuracy,
The film thickness of the plating film on each part of the inner peripheral surface, which is the sliding surface of the piston, was uneven, and finishing processing such as honing processing was required after plating. The present invention has been made in view of such circumstances, and an object thereof is to provide an inner peripheral surface, which is a piston sliding surface, with a small environmental load and a hardness that can be practically used. An object of the present invention is to provide a cylinder for an internal combustion engine, which has a plating treatment that does not require finishing work such as honing work, and an inner peripheral surface treatment method that can obtain such a cylinder.

[0008]

[Means for Solving the Problems] To achieve the above object,
A cylinder for an internal combustion engine according to the present invention is made of aluminum.
Made of an alloy, the inner surface of the piston that slides
Addition of trimethylamine borane to the Kell plating solution
Electrolytic plating is applied in a bath and the inner surface is covered
The coating has a Vickers hardness of 650 to 750 (H v [ 50 g
f ]), and the plating skin on each part of the inner peripheral surface
The film thickness difference is 15 μm or less, and the inner peripheral surface is
The feature is that it is a finished surface without being subjected to finishing such as honing.

Further, the cylinder for an internal combustion engine according to the present invention is used in a portable power working machine or the like in which a head portion in which a combustion chamber is formed and a body portion in which a piston is slidably inserted are integrated. It is a small air-cooled 2-cycle gasoline engine cylinder that is used.

On the other hand, the method for treating the inner peripheral surface of a cylinder for an internal combustion engine according to the present invention uses a plating bath in which a boron compound such as trimethylamine borane or dimethylamine borane is added to a nickel plating solution to form a piston sliding surface. Electrolytic plating is applied to the inner peripheral surface. In this way, the hardness of the plating film is improved by performing electrolytic plating on the inner peripheral surface, which is the piston sliding surface, with a plating bath in which a boron compound such as trimethylamine borane or dimethylamine borane is added to a nickel plating solution. Was confirmed to be significantly improved. Specifically, the Vickers hardness of the nickel plating film to which the borane is not added is 350 (Hv [5
0 gf]), whereas the nickel plating film containing borane has a Vickers hardness of 700 (Hv [50 g
f]), and doubled.

It was also confirmed that the difference in the film thickness of the nickel plating film on each part of the inner peripheral surface was 15 μm or less, and the nickel plating film was adhered with high accuracy according to the cutting dimension. Therefore, according to the present invention, the inner peripheral surface, which is the piston sliding surface, has a low environmental load, has a hardness that can be practically used, and is a plating process that does not require finishing such as honing. It is possible to provide a cylinder for an internal combustion engine which has been subjected to the above, and an inner peripheral surface treatment method capable of obtaining the cylinder.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. One embodiment of the cylinder for an internal combustion engine according to the present invention is a small air-cooled two-cycle gasoline made of aluminum alloy, which is used in a portable power working machine such as a brush cutter or a chainsaw, as in the case shown in FIG. A cylinder for an engine (displacement of about 20 to 150 mL). However, in the structure shown in FIG. 2, the scavenging passage 7 has an inner wall 7a,
7a is hollow, but in the present embodiment, the inner wall 7a,
Without 7a (open on the inner peripheral surface 9 side)
Has become. Other than that, the configuration is almost the same, and hence the following description will be given with reference to the cylinder 1 shown in FIG.

In the cylinder of this embodiment, after the cylinder material is cast from an aluminum alloy by a high pressure die casting method or the like, the inner peripheral surface 9 cut to a predetermined dimension to allow the piston to slide is wear-resistant. In order to increase the above, a plating bath in which trimethylamine borane (TMAB) is added to a nickel plating solution is used to perform electrolytic plating (nickel plating coating 1
0) is applied. The trimethylamine borane was added using a chemical and used at a rate of 0.5 g / L.

As described above, in the cylinder for internal combustion engine made of an aluminum alloy, in which the inner peripheral surface 9 serving as the piston sliding surface is electrolytically plated with a plating bath in which trimethylamine borane is added to a nickel plating solution, To check the characteristics and properties of the plating film 10 part, T
A comparative test was conducted by preparing a nickel-plated sample without adding MAB. The nickel plating conditions are shown in [Table 1] below, and the results are described below.

[0015]

[Table 1]

(I) The hardness of the plating film 10 is AKA
As a result of measurement with a SHI-made Micro Vickers hardness meter MVK-H1, the nickel plating film without the addition of TMAB had a Vickers hardness of about 350 (Hv [50 gf]), whereas the present embodiment with the addition of TMAB The Vickers hardness of the nickel plating film of the form is 700 (Hv [5
0gf]) has been reached.

(II) Further, the nickel plating film 1
The graph of FIG. 1 shows the result of measuring the film thickness of 0 and examining the distribution thereof. In the graph shown, the vertical axis represents the film thickness (μm),
The distance (mm) from the combustion chamber machining clearance groove 12 (see FIG. 2) is taken on the horizontal axis, and each part of the inner peripheral surface (9), that is, the exhaust port 5 side (A) and the intake port 6 side are (B), the one scavenging passage 7 (scavenging port 8) side is represented by each line of (D). In each of the lines (A), (B), and (D), the exhaust port 5, the intake port 6, and the scavenging passage 7 (opening) are naturally not plated, so that part is blank. There is. As can be seen from the graph shown in the figure, the film thickness of each part of the plating film 10 of the present embodiment is 28 to 40 μm, and the difference in film thickness between them is 15 μm or less. As a result, the cylinders of this embodiment do not require finishing such as honing.

(III) As a result of observing the plating surface condition using an optical microscope, the boundary of the plating particles was not clear in the nickel plating to which TMAB was not added.
The surface condition also looks rough. On the other hand, in the nickel-plated coating 10 containing TMAB of the present embodiment, the boundaries of the plated particles were clearly visible, and the surface state was similar to that of conventional high-speed chrome plating and iron plating.

(IV) As a result of observing the plating cross section using a scanning electron microscope, in the nickel plating to which TMAB was not added, the plating particles grew vertically only from the material part, and the new particles in the plating layer were observed. No generation of large plating particles was observed. On the other hand, the TM of the present embodiment
In the case where AB was added, fine scale-like plated particles were observed, and new plated particles were generated while the plating layer was being formed in addition to the material portion.
Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the invention described in the claims. It is possible. For example, trimethylamine borane was used in the above-mentioned embodiment, but other boron compounds such as dimethylamine borane can also be used.

[0020]

As can be understood from the above description, according to the present invention, the inner peripheral surface, which is the sliding surface of the piston, has a small environmental load and a hardness that can be practically used. It is possible to provide a cylinder for an internal combustion engine that has been subjected to a plating treatment that can eliminate the need for finishing such as honing, and an inner peripheral surface treatment method that can obtain such a cylinder.

[Brief description of drawings]

FIG. 1 is a graph showing a result of measuring a film thickness of a plating film and examining a distribution state thereof in an embodiment of a cylinder for an internal combustion engine according to the present invention.

FIG. 2 is a vertical cross-sectional view showing an example of a cylinder for an internal combustion engine.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Compact air-cooled 2-cycle gasoline engine cylinder (cylinder for internal combustion engine) 2 ... Body 3 ... Head 4 ... Combustion chamber 9 ... Inner peripheral surface 10 ... Plating coating 20 ... Piston

Front page continuation (72) Inventor Shinji Tsuchiya 1-7 Suehiro-cho, Ome-shi, Tokyo Kyoritsuuchi Co., Ltd. (56) References JP-A-6-159131 (JP, A) JP-A-5-59582 ( JP, A) JP 8-218179 (JP, A) JP 63-157896 (JP, A) JP 62-96692 (JP, A) JP 50-60436 (JP, A) JP SHO 55-40341 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) C25D 7/00 F02F 1/00

Claims (2)

(57) [Claims] 1. An inner peripheral surface (9) which is a sliding surface of a piston,
Internal-combustion engine made of aluminum alloy electrolytically plated in a plating bath in which a boron compound such as trimethylamine borane or dimethylamine borane is added to a nickel plating solution
The plating film (10) applied to the inner peripheral surface (9) is
Vickers hardness is 650~750 (H v [50gf]) Der
The plating film on each part of the inner peripheral surface (9)
The difference in the film thickness of (10) is 15 μm or less, and the inner circumference is
Surface (9) is subjected to finishing such as honing
It is characterized as being a finished surface as it is
An internal combustion engine cylinder that. 2. A portable power working machine in which a head portion (3) in which a combustion chamber (4) is formed and a body portion (2) into which a piston (20) is slidably inserted are integrated. The cylinder for an internal combustion engine according to claim 1 , which is a cylinder (1) for a small air-cooled two-cycle gasoline engine used in.