JP3180921B2 - Cylinder for internal combustion engine using alcohol fuel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the alcohol - related cylinder for inner combustion engine that uses <br/> Le-based fuel. This cylinder is applicable to, for example, an in-line four-cylinder type.

[0002]

2. Description of the Related Art In an internal combustion engine, high rotation and high compression are required.
Further, there is a demand for weight reduction and improved fuel efficiency. Conventionally, as one of such attempts, Japanese Unexamined Patent Publication No. 60-93162 discloses a sliding member that slides with respect to each other.
A combination of sliding members in which the sliding surface of the member is formed by a hard chromium plating surface and the sliding surface of the sliding second member is formed by a plasma sprayed layer of a high carbon Fe-Cr alloy is disclosed. .

[0003] In recent years, with the worsening of the gasoline fuel situation, use of alcohol-based fuel as a gasoline fuel alternative fuel has been studied. However, when an alcohol-based fuel is used, an acid such as formic acid is easily generated in the cylinder bore. Therefore, when the internal combustion engine is stopped, in a static state in which the piston is stopped, there is a problem that the inner wall surface portion of the cylinder bore in contact with the outer peripheral surface of the stopped piston is corroded by acid. The formation of a hard chromium plating layer or the formation of a sprayed layer as described above is not always sufficient as a measure against static corrosion at the piston stop position when alcohol fuel is used. Absent.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to secure the corrosion resistance of the sliding surface of a cylinder bore when using an alcohol-based fuel while maintaining the corrosion resistance. An object of the present invention is to provide a cylinder that can reduce wear of a piston ring as a material.

[0005]

SUMMARY OF THE INVENTION The present inventor has found that, when an alcohol-based fuel is used for the above purpose, the internal combustion engine is stopped and the piston is stopped, thereby causing corrosion of the cylinder bore and wear of the piston ring. Intensive research. The present inventor examined the oil film distribution of the lubricating oil on the outer peripheral surface of the top ring during the reciprocating drive of the piston and the wear of the piston ring. The oil film distribution on the cylinder bore surface is shown by a characteristic line h in FIG. This is shown by the characteristic line k in FIG. 4 (reference Piston Fric
Tion Force AndPistonRing
OiL Film Thickness, SAE845
067). Here, as shown by the characteristic line h in FIG. 4, the oil film of the lubricating oil on the cylinder bore surface is the thickest near the center of the cylinder bore surface (generally 5 mm).
The oil film near the top dead center is thinner than the oil film near the bottom dead center. Further, as shown by the characteristic line k in FIG. 4, the wear ratio of the outer peripheral surface of the top ring is small at the center of the cylinder bore surface, large near the top dead center and near the bottom dead center, and moreover, at the top dead center. Is larger than the bottom dead center. Therefore, the wear on the outer peripheral surface of the top ring almost corresponds to the oil film distribution on the bore surface, hardly occurs in the center area of the bore surface, occurs near the top and bottom dead center, and especially occurs near the top dead center. Is what you do.
In addition, when the internal combustion engine, especially the in-line four-cylinder internal combustion engine is stopped to stop the piston, the piston must always stop at approximately the center region between the top dead center and the bottom dead center due to the balance weight. It has been known.

The present inventor has paid attention to the points described above,
The distance from the top dead center position to the bottom dead center position on the Davos surface
When the separation is L, 1 / 3L ≦ A ≦ 5 / from the top dead center position
Corrosion resistance is given to the sliding surface of only part A within the range of 6L.
With the layer which hasFrom top dead center position to 1 / 3L
In the range from 5 / 6L to the bottom dead center position,
If the base material on the cylinder bore surface is exposed without the layer
For example, when using alcohol fuel, the piston stops
Resistance of sliding surface of cylinder bore in static state
In this case, and in this case, the thickness of the lubricating oil film
Because it is thin, it tends to wear the piston ring.
Since no corrosion resistant layer is formed in the cylinder bore,
Wear of the piston ring, which is the mating material, can be effectively reduced
I learned that The present invention has been completed based on these findings.
It was a thing.

That is, the alcohol fuel according to the present invention is
When the distance from the top dead center position to the bottom dead center position on the cylinder bore surface is L, the portion of A within the range of 1 / 3L ≦ A ≦ 5 / 6L from the top dead center position is used for the cylinder for the internal combustion engine to be used. Only a sliding surface is provided with a layer having corrosion resistance, and a range from the top dead center position to 1 / 3L, 5 / 6L
Of the cylinder bore surface in the range from
The material is exposed . This prevents static corrosion of the cylinder bore surface when the piston stops, and reduces wear of the mating material near the top and bottom dead centers, particularly near the top dead center.

[0008] The cylinder can be formed of iron or aluminum alloy. The layer having corrosion resistance preferably contains chromium and nickel. This takes into account the corrosion resistance and wear resistance of the base material of the cylinder. The layer having corrosion resistance can usually be formed by a thermal spray layer or a plating layer. Further, it can also be formed by a permeation plating layer such as chromizing, or a vapor phase plating layer constituted by a vapor deposition layer, sputtering or the like. The thermal spray layer can be formed of an alloy thermal spray layer or a ceramic thermal spray layer. When the cylinder is iron-based, Cr: 55 to 70 wt%
%, C: 1.8 to 8.4 wt%, inevitable impurities, and the balance can be formed of a Fe-Cr alloy substantially consisting of iron. In this case, if the Cr content is less than 55 wt%, C
Since r does not play a sufficient role, corrosion of the bore surface may occur. When Cr exceeds 70 wt%, the aggressive material becomes more aggressive, and the abrasion of the other material increases. In addition, C is 1.8 wt%
If the amount is less than the above, sufficient hardness of the thermal sprayed layer cannot be obtained and the wear resistance is also lacking. If C exceeds 8.4 wt%, the wear of the mating material increases, and the toughness of the thermal sprayed layer also decreases. Further, the above-mentioned plating layer can be formed of, for example, a hard chrome plating layer, a porous chrome plating layer, or a nickel plating layer. Prior to forming the layer, pretreatments such as cleaning and surface roughening can be performed on the bore surface. After the formation of the layer, a post-treatment such as honing can be performed.

The thickness of the layer having corrosion resistance is 80 to 200 μm.
Is preferred. If the thickness is less than 80 μm, the base material of the base material will be formed early due to insufficient life of the layer. On the other hand, if the thickness exceeds 200 μm, the adhesiveness of the layer becomes poor due to thermal stress, and N
Since expensive elements such as i and Cr are used, the cost increases. In addition, dimensional accuracy defects at the time of finishing the layer are likely to occur. Regarding the surface roughness of the layer, 1.6 to 3.2 μm
Rz is preferred. If the surface roughness is less than 1.6 μmRz, the oil holding power is small, and seizure with the partner material is likely to occur. If the surface roughness exceeds 3.2 μmRz, the wear amount of the layer itself is large, and the opposing aggressiveness is also large. The hardness of the layer having corrosion resistance depends on the mating material, but can generally be Hv 400 to 800.

[0010] The mating material is generally a piston ring, and can be formed of a stainless steel or a steel based on nitriding. In this case, the thickness of the nitrided layer is preferably 70 to 150 μm. If the thickness is 70 μm, the life is insufficient, and the base material of the mating material is easily exposed. If the thickness exceeds 150 μm, the nitride layer may be peeled off due to thermal stress.

[0011]

In an internal combustion engine, in particular, an in-line four-cylinder internal combustion engine, when the internal combustion engine is stopped and the piston is stopped, the piston is located at approximately the center region between the top dead center and the bottom dead center due to the balance weight. It will stop. In the present invention, since the layer having corrosion resistance is provided within the range of 1 / 3L ≦ A ≦ 5 / 6L from the position of the top dead center, the layer stops almost at the center area between the top dead center and the bottom dead center. The portion of the cylinder bore surface facing the outer peripheral surface of the piston is covered with a layer having corrosion resistance. Therefore, the corrosion resistance of the sliding surface of the cylinder bore when the piston is stopped when alcohol fuel is used is ensured.
Moreover, in the present invention, in the cylinder bore near the top dead center and near the bottom dead center where the lubricating oil film tends to be thinned during the reciprocating operation of the piston, the corrosion resistant layer having the aggressive material aggression is not formed, so Wear of the piston ring is reduced.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be specifically described below. First, gray cast iron (JIS standard: FC2) as shown in FIG.
5) Made with a bore diameter of 81 mm and a stroke of 77 mm
Was manufactured.
Next, as shown in FIGS. 2A to 2D, on the inner peripheral surface of the cylinder bore 2, the top dead center position (T.D.C.) and the bottom dead center position (B.D.C. ) Is L, 1 / 3L ≦ A ≦ 5 / from the top dead center position
Boring was performed using only a cutting tool on the portion A of 6 L, and a groove 2 a having a maximum depth of 100 μm was formed in a ring shape so as to be continuous in the circumferential direction of the cylinder bore 2. As for the shape of the edge of the groove 2a, an undercut of 45 degrees is formed in order to form a uniform sprayed layer on the edge. Thereafter, using a thermal spray gun, the thermal spray gun was disposed in the cylinder bore 2 and covered the thermal spray layer 3 without masking. In this case, low-carbon Fe-Cr alloy powder (Cr: 56 wt%, C: 0.02 wt%, Si: 0.
8%, Fe: balance) and 70% by weight of high carbon Fe-Cr
Alloy powder (Cr: 62 wt%, C: 8 wt%, Si:
Fe-C mixed with 1.3%, Fe: balance) at 30 wt%
r alloy powder (Cr: 60 wt%, C: 2.2 wt%, S
i: 1 wt%, Fe: balance), and spraying the powder by plasma spraying to form a sprayed layer 3A of a Fe-Cr alloy having a thickness of 150 µm, and then performing rough honing and finish honing on the sprayed layer 3A. Thus, a sprayed layer 3 was formed as shown in FIG. Here, the sprayed layer 3 has a thickness of 80 μm.
m, sprayed layer hardness HV430, and surface roughness 2 μmRz. The low carbon Fe-Cr alloy powder used in the thermal spraying process has an average particle size of 10 to 75 m. High carbon Fe-C
The average particle size of the r alloy powder is 10 to 63 μm.

(Actual machine test) Next, using the cylinder 1 on which the above-mentioned sprayed layer 3 was formed, the cylinder 1 of the first embodiment was set on a cassette bench using an alcohol fuel of 85% methanol, and was placed on a table. A corrosion test was performed. Here, the test conditions are as follows: engine speed 2000 rpm, water temperature 40 ° C., 1
After running for 1 minute, the engine was stopped and allowed to stand for 14 days. At that time, the occurrence of static corrosion on the inner wall surface of the cylinder bore 2 was visually inspected. The engine oil used was a durability deterioration oil.

Table 1 shows the results of the bench corrosion test. As shown in Table 1, in Example 1, the occurrence of corrosion in the cylinder bore 2 was not observed, which was a good result. Comparative Example 1
As Nos. To 3, cylinders of the same type in which a sprayed layer was formed in the cylinder bore in the range shown in Table 1 were manufactured. The thickness and surface roughness of the sprayed layer were 80 μm each as in Example 1.
m, 2 μm Rz. As Comparative Example 4, a cylinder having no sprayed layer was also manufactured.

[0015]

[Table 1] The bench corrosion test was similarly performed for Comparative Examples 1 to 4.
Table 1 also shows the test results of Comparative Examples 1 to 4. Comparative Example 1
No corrosion was observed on the cylinder bore surface on the top dead center side as in Example 1, but on the bottom dead center side, the formation range of the corrosion-resistant sprayed layer was small. Minor corrosion was observed at the boundary.
Also, in Comparative Example 2, corrosion occurred on the cylinder bore surface as in Comparative Example 1, and slight corrosion was observed at the boundary at the top dead center side and about 5 mm from the boundary at the bottom dead center side. Corrosion occurred in the unsprayed part at the location. In Comparative Example 4 in which the thermal sprayed layer was not formed, a large amount of corrosion was observed over a wide area near the center of the cylinder bore surface such that the base material of the bore eluted. In Comparative Example 3, no corrosion was observed. From the above test results, Example 1 in which the sprayed layer was formed at 1 / 3L ≦ A ≦ 5 / 6L from the top dead center position on the bore surface, 1 / 6L ≦ A ≦ from the top dead center position
It can be seen that Comparative Example 3, in which the sprayed layer was formed in 5/6 L, had high resistance to static corrosion when the piston was stopped when alcohol fuel was used.

Further, in Example 1 in which good results were obtained in the bench corrosion test, the engine speed was 6,000 rpm, 300 rpm using alcohol fuel of 85% methanol.
A continuous high-speed endurance test for hours was performed. The piston ring, which is a sliding partner, is made of stainless steel (JIS: S)
No. 440B), and has a 100 μm-thick nitriding layer subjected to gas nitriding at a nitriding temperature of 450 ° C. for a nitriding time of 50 hours.

Further, Comparative Examples 5 to 9 were similarly tested. Here, in Comparative Example 5, similarly to Comparative Example 3, the processing range of the sprayed layer is in the range of 1 / 6L ≦ A ≦ 5 / 6L. In Comparative Examples 6 to 9, the processing range of the thermal sprayed layer was 1 / the same as in Example 1.
3L ≦ A ≦ 5 / 6L, provided that the thickness of the sprayed layer and the surface roughness of the sprayed layer were changed as shown in Table 2.

[0018]

[Table 2] The results of the bench durability test are shown in FIG. 5 as the sprayed layer wear amount and the piston ring wear amount. Here, the wear amount of the sprayed layer is measured by a surface roughness meter and is an average value of four pieces, and the piston ring wear amount is measured by a surface roughness meter and is an average value of four pieces. As shown in FIG. 5, in Example 1, the wear amount of the thermal sprayed layer itself was extremely small at about 5 μm as compared with Comparative Examples 5 to 9, and the wear amount of the piston ring as a mating material was also extremely small at about 10 μm. Therefore, the aggressiveness to the opponent material is extremely small, and it is understood that the cylinder is a good cylinder. On the other hand, the sprayed layer is 1 / 6L ≦ A ≦ 5 /
In Comparative Example 5 formed in the range of 6 L, the sprayed layer is applied to the cylinder bore near the top dead center position where the lubricating oil film becomes thin and the aggressive material aggression increases. The aggressiveness of the material is increased, and accordingly, the wear amount of the piston ring, which is the mating material, is increased to nearly 20 μm. Further, the wear amount of the sprayed layer itself is large. Further, in Comparative Example 7 in which the surface roughness of the thermal sprayed layer was as large as 5.0 μmRz, not only the piston ring, which is the mating material, was worn a lot, but also the cylinder bore itself was also abraded. The effect on abrasion resistance is remarkably observed. Also,
In Comparative Example 8 in which the thickness of the thermal spray layer is 50 μm, the durability and the life of the thermal spray layer are short because the thermal spray layer is thin.
In Comparative Example 9 in which the thickness of the sprayed layer was 250 μm, the thickness of the sprayed layer was thick, contrary to Comparative Example 8, and there was no problem with the durability life. However, the adhesion of the sprayed layer was significantly reduced. Part of the sprayed layer at the boundary with the base metal was observed.

As described above, the thickness of the oil film on the cylinder bore surface is generally smaller near the top dead center than near the bottom dead center, as indicated by the characteristic line h in FIG. Example 1 in which the sprayed layer was formed in the range of 1 / 3L ≦ A ≦ 5 / 6L from the top dead center position, and 1 / 6L ≦ A ≦ 5 from the top dead center position
The difference in the amount of wear between the mating material and the sprayed layer between Comparative Example 5 formed in the range of / 6 L was presumed to be due to the large effect of the oil film.

That is, in the first embodiment, the corrosion-resistant treatment is performed by the sprayed layer on the sliding surface of the cylinder bore surface in the range corresponding to the oil film distribution and the range corresponding to the piston stop position when the engine is stopped. In addition to preventing static corrosion of the bore surface when the piston is stopped, wear of the bore surface itself, and further, wear of the piston ring as a mating material can be suppressed. However, in Comparative Example 5, the thermal spray layer is formed up to the vicinity of the top dead center where the lubricating oil film becomes thin, so that the opposing material aggressiveness is high.

Next, the relationship between the thickness of the sprayed layer and the durable life of the sprayed layer was examined. In this case, a 1600 cc, cylinder bore of an in-line four-cylinder internal combustion engine is used, a nitriding-processed piston ring is used, and methanol-85% alcohol fuel is used.
An actual machine durability test (300 hr) was performed at 000 rpm.
The durability life of the sprayed layer was measured by the time until the thickness of the sprayed layer reached 30 μm. The test results are shown in FIG. As shown by the characteristic line S1 in FIG. 6, in order to ensure the durability life of the sprayed layer, the thickness of the sprayed layer needs to be 80 μm. In addition, the relationship between the thickness of the sprayed layer and the adhesion was examined by a similar actual machine durability test. The adhesion was measured by a shear test. The test results are shown in FIG. As indicated by the characteristic line S2 in FIG. 7, when the thickness of the sprayed layer exceeds about 200 μm, the adhesion of the sprayed layer is reduced and the sprayed layer may be peeled off. Therefore, in order to obtain an adhesion of 4 kg / mm ² or more while securing the thickness of the sprayed layer, the thickness of the sprayed layer is desirably 80 to 200 μmRz.

(Model Test) Next, the relationship between the surface roughness of the sprayed layer and the wear amount of the sprayed layer was examined. In this case, a reciprocating sliding type friction and wear test was performed. In this reciprocating sliding friction and wear test, specifically, using a cut piece of a piston ring as a mating material, a pin test piece was pressed with a pressing force of 15 kgf while a flat plate test piece having a sprayed layer was reciprocated at 5 Hz. A wear test was performed at a sliding distance of 50 mm for 20 hours. The lubricating condition was an oil bath using diesel degraded oil. The test result is shown by a characteristic line T1 in FIG. As shown by the characteristic line T1 in FIG. 8, the surface roughness of the sprayed layer of the flat plate specimen was 1.6 to 3.2 μm Rz.
At that time, it was found that the wear amount of the sprayed layer was reduced. When the surface roughness of the sprayed layer was 0.6 μmRz, seizure occurred. It is presumed that the oil holding power was small. Further, the relationship between the surface roughness of the sprayed layer and the width per nitrided material was examined. Also in this case, a reciprocating sliding type friction and wear test was performed. The test result is shown by a characteristic line T2 in FIG. As shown by the characteristic line T2 in FIG. 8, when the surface roughness of the thermal sprayed layer is smaller than 1.6 μmRz, seizure occurs between the flat specimen having the thermal sprayed layer and the nitrided pin specimen. Was found. It is presumed that the oil holding power was small. It has also been found that when the surface roughness of the sprayed layer is larger than 3.2 μmRz, the wear amount of the pin test piece, that is, the width per nitrided material increases. Therefore, the surface roughness of the sprayed layer is 1.6 to 3.2 μmR.
z is desirable.

[0023]

According to the cylinder for an internal combustion engine of the present invention, the layer having corrosion resistance is 1 / 3L≤A≤5 from the top dead center position.
Since it is provided only in the portion A within the range of / 6 L, the cylinder bore portion facing the outer peripheral surface of the piston stopped at a substantially central area between the top dead center and the bottom dead center is a layer having corrosion resistance. Coated. Therefore, when the alcohol-based fuel is used, the corrosion resistance of the sliding surface of the cylinder bore in the piston stopped state is ensured. In addition, a corrosion-resistant layer is not formed near the top dead center and the bottom dead center of the cylinder bore surface near the top dead center and the bottom dead center where the lubricating oil film is thin and the opponent material aggressiveness tends to increase when the piston reciprocates. Wear of the piston ring, which is a material, is reduced. In particular, in the vicinity of the top dead center where the oil film of the lubricating oil is thin, in the range of 1 / 3L from the top dead center position, since the corrosion resistant layer is not formed, abrasion of the mating material can be effectively reduced.

[Brief description of the drawings]

FIG. 1 is a perspective view of a cylinder.

FIG. 2 is a view showing a step of forming a sprayed layer in a cylinder bore.

FIG. 3 is a schematic sectional view of a cylinder bore.

FIG. 4 is a graph showing an oil film thickness of a top ring, an outer peripheral surface wear ratio of the top ring, and a positional relationship of a cylinder bore.

FIG. 5 is a graph showing a sprayed layer wear amount and a piston ring wear amount.

FIG. 6 is a graph showing a relationship between a sprayed layer thickness and a durable life of the sprayed layer.

FIG. 7 is a graph showing the relationship between the thickness of a sprayed layer and the adhesion of the sprayed layer.

FIG. 8 is a graph showing the relationship between the sprayed layer wear amount, the width per nitrided material, and the surface roughness of the sprayed layer.

[Explanation of symbols]

 1 indicates a cylinder, 2 indicates a cylinder bore, and 3 indicates a sprayed layer.

Continuation of the front page (56) References JP-A-4-221100 (JP, A) JP-A-61-175253 (JP, A) JP-A-59-90744 (JP, A) JP-A-4-175442 (JP) , A) JP-A-61-231154 (JP, A) JP-A-61-144469 (JP, A) JP-A-60-93162 (JP, A) Fully open Showa 63-21748 (JP, U) Really open 59-123641 (JP, U) Fully open sho 60-88049 (JP, U) Fully open sho 59-182645 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F02F 1/00 -7/00 C23C 4/00 F16J 10/04

Claims (2)

(57) [Claims] When the distance from the top dead center position to the bottom dead center position on the cylinder bore surface is L, the distance from the top dead center position is 1 /.
3L ≦ A ≦ 5 / 6L provided with a layer having corrosion resistance to the sliding surface of only the portion A in the range of Rutotomoni, ranging from the top dead center position to the 1 / 3L, bottom dead from 5 / 6L
The base material of the cylinder bore surface is exposed up to the point position
<br/> cylinder for an internal combustion engine that uses alcohol fuel, characterized in that it is. 2. The layer having corrosion resistance has a thickness of 80 to 200 μm.
The cylinder for an internal combustion engine according to claim 1, wherein the cylinder is a thermal sprayed layer or a plated layer containing at least chromium and nickel and having a surface roughness of 1.6 to 3.2 mRz.