JP2933115B2 - Engine oil for diesel engines with exhaust gas recirculation system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine oil for a diesel engine equipped with an exhaust gas recirculation device (hereinafter abbreviated as EGR).

[0002]

2. Description of the Related Art Generally, an engine oil mainly used for lubricating an engine uses a mineral oil or a synthetic oil as a base oil, and a detergent or other additive is added to improve the physical properties of the base oil.・ It is blended.

[0003] In an engine oil for a diesel engine, a main additive is required to improve performance such as cleanliness, abrasion resistance and friction reduction. Conventionally, several types of detergents such as metal sulfonates, metal phenates, and metal salicylates have been used. Among these engine oil detergents,
There is known a calcium alkalicylate represented by the following chemical formula 1 described in -35325.

[0004]

Embedded image In addition, zinc thiophosphate-based antioxidants and anti-wear agents and friction modifiers such as molybdenum dithiophosphate or borate esters are used, but primary alkyl zinc dithiophosphate represented by the following chemical formula 2 is used. And oil-soluble oxymolybdenum sulfide dialkyldithiophosphates represented by the following chemical formula 3 described in JP-B-51-5409 are known.

[0005]

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[0006]

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[0007]

In recent years, there has been a tendency to use EGR which recirculates exhaust gas of an engine into intake air for purifying exhaust gas of an internal combustion engine which is an engine of an automobile or the like.

[0008] All of the aforementioned additives are effective in themselves.
But nitrogen in diesel engine exhaust gas
Oxide (NO_xEGR is installed in order to reduce
The diesel engine
Sulfur dioxide changed during the combustion process of sulfur contained in gas
(SO_Two) (SO_Three) Reacts with condensed water to produce sulfuric acid (H
_TwoSO_Four).

As a result, corrosion wear of the piston ring, liner, valve, etc. increases, and the amount of soot mixed particularly as a cause of deterioration of the diesel engine oil increases, so that abrasive wear on the sliding surface inside the engine increases. As a result, the durability and reliability of the engine are reduced.

[0010] Therefore, as means for securing the life of the engine and the engine oil to the conventional level, it is conceivable to reduce the sulfur content of the fuel (light oil) or to change the material, on the one hand, but to improve the quality of the engine oil on the other. Improvement is required.

The present invention has been made in view of the above-mentioned circumstances, and is intended to reduce the influence of sulfuric acid (H ₂ SO ₄ ) generated in a combustion chamber of an engine and to prevent an increase in engine wear due to soot mixed therein. An object of the present invention is to provide an engine oil of a diesel engine with EGR (hereinafter, abbreviated as the present oil).

[0012]

SUMMARY OF THE INVENTION The present invention relates to a method in which a lubricating base oil (mineral oil / synthetic oil) has a total base number (T) as a detergent.
BN) 5.8-8.3% by mass of calcium axalicylate {calcium (Ca) content 6.0% by mass} having 165 mg KOH / g, primary alkyl type zinc as an antioxidant and antiwear agent 0.09 to 0.13 of dithiophosphate in mass% of zinc (Zn); oil-soluble oxymolybdenum as a friction modifier and wear inhibitor
The dialkyldithiophosphate is converted to molybdenum (Mo)
0.02 to 0.04 by mass%.

[0013]

The oil of the present invention is excellent in sulfuric acid neutralization rate, sulfuric acid neutralization ability, heat stability and high-temperature detergency by using calcium-alxalicylate having a Ca content of 6.0% by mass as a detergent. . Therefore, it is possible to obtain an engine oil that can be used for a long period of time due to the fact that thermal decomposition at a high temperature due to combustion of fuel is unlikely to occur.

Further, by using a primary alkyl type zinc dithiophosphate having a zinc content of 0.09 to 0.13 as a mass% of zinc as an antioxidant and an antiwear agent, a friction equivalent to that of DD1 standard oil of the Society of Automotive Engineers of Japan. The prevention performance is obtained.

Further, the content of molybdenum is 0.02 to
By using 0.04 oil-soluble oxymolybdenum dialkyldithiophosphate (a friction modifier and an antiwear agent), the combustion process and severe conditions such as an increase in the amount of soot mixed in with EGR were encountered. Even so, a sufficient anti-friction effect can be obtained due to the low adsorption and affinity of soot.

[0016]

Next, an embodiment of the present invention will be described below.
The oil of the present invention is mainly SAE standard 0W-40W.
(Kinematic viscosity at 100 ° C. is 3.8 to 16.3 mm ² /
This is applied to the refined base oil for lubricating oil of s), and the following additives are added and blended with this refined base oil for lubricating oil.

As a refined base oil for lubricating oil of the experimental material in this example, SAE30W (kinematic viscosity at 100 ° C. of 9.3 or more and 12.5 or less) was used. (1) 165 mg of total base number (TBN) having a mass concentration of calcium (Ca) element of 3500 to 5000 ppm (preferably 4300 ppm) as a detergent.
Calcium-alxalicylate having KOH / g is not less than 5.8 and not more than 8.3 in mass%. (2) As an antioxidant and antiwear agent, primary alkyl type zinc dithiophosphate may be zinc (Z
n) 900 to 1300 ppm (preferably 1000 ppm in mass) of the element by mass. (3) Oil-soluble oxymolybdenum sulfide / dialkyldithiophosphate is used as a friction modifier and an antiwear agent in a mass concentration of 200 to 400 ppm of molybdenum (Mo) element.
(Preferably 300 ppm).

The following Table 1 shows a comparison of the additives of the present invention obtained by adding these additives to the refined base oil for lubricating oils and the conventional oils.

[0019]

[Table 1] As is clear from the above table, in the present invention, the detergent, the antiwear agent and the antioxidant, and the friction modifier and the antiwear agent are different.

Among them, calcium (Ca) -alxalicylate having a calcium (Ca) content of 6.0% by mass used as a detergent is specified in the JASO M336 standard for a test method for cleanliness of automotive diesel engine lubricating oil. It was adopted as a standard oil to be obtained, which is equivalent to a standard oil DDI which is an engine oil having a good cleanability test result in a 100-hour test.

The mixing ratio of calcium (Ca) / alxalicylate to the lubricating base oil is 5.8 to 8.3% by mass with respect to the lubricating base oil. The concentration is slightly inferior at 2100 to 3000 ppm, and is equal to or more than 3000 to 5000 ppm.

The typical metal-based detergents which have been used in the past, the speed of neutralizing sulfuric acid and the ability of neutralizing sulfuric acid of the above-mentioned metal-based detergents used in the present invention. The following table shows the results of a comparison of height, heat stability, and cleanliness at high temperatures by laboratory tests.

In this table, ◎ indicates good, ○ indicates somewhat good, Δ
It shows a little bad.

[0024]

[Table 2] In the above table, ^{* 1} , ^{* 2} , ^{* 3} are based on the following experimental methods and criteria. * 1: A base oil (TBN) is adjusted to a constant value by adding / mixing only a detergent to the base oil to prepare a sample.

A solvent (toluene + isopropanol) is mixed with a fixed amount of a sample, and a sulfuric acid aqueous solution adjusted to a constant concentration is continuously dropped. Neutralization rate)
Total reaction consumption of sulfuric acid required for neutralization end point (sulfuric acid neutralization capacity)
Are tested using an automatic neutralization titrator specified in ISK2501.

The neutralization rate of sulfuric acid is evaluated in the form of a sulfuric acid reaction at the beginning of the titration.
The sample with the smallest value was marked with ◎. Sulfuric acid neutralization ability is the minimum consumption of sulfuric acid aqueous solution at the end of the reaction.
The sample with the largest consumption of sulfuric acid aqueous solution was marked with ◎, and the middle was marked with ○.

* 2: Only a detergent is added to the base oil, and the total base number (TBN) is adjusted to a constant value by mixing to prepare a sample. The sample was subjected to an oxidation stability test (165.5 ° C. × 8 hours and 1 hour) in accordance with a test device specified in JIS K2514.
80 ° C x 8 hours), and the total base number (T
BN) is measured according to the method specified in JIS K2501.

Samples with a sharp decrease in TBN value before and after the test were evaluated as Δ, samples with the smallest decrease in TBN value were evaluated as ◎, and the middle was evaluated as ○. * 3: Add only a detergent to the base oil and adjust it to a constant total base number (TBN) to prepare a sample.

Ferral T. M. STD. No.
791a. According to Method 3462, a sample is intermittently sprayed on a metal test piece (aluminum plate) heated to a high temperature (280 ° C. and 300 ° C.) for a certain time (2 hours), and solid decomposition generated in the test piece is performed. Stuff (Coke D
The total amount of epoxides is compared and evaluated.

The sample having the maximum coke amount was indicated by Δ, the sample having the minimum coke amount was indicated by ◎, and the middle thereof was indicated by ○. Thus, C
The use of calcium axalicylate having an a content of 6.0% by mass as a detergent results in excellent sulfuric acid neutralization rate, sulfuric acid neutralization ability, heat stability and high-temperature detergency. The properties are significantly improved.

Next, zinc dithiophosphates as antioxidants and antiwear agents include (A) secondary (active), (B) short chain primary alkyl, and (C) long chain primary alkyl. Type, (D) allyl type (heat stable type) and the like are known.

With respect to the wear of the valve train of the engine, (D) is the highest in a gasoline engine, and the wear resistance decreases as (D) is reached. It is known that the wear resistance is improved in the order of (D).

As the antioxidant and antiwear agent, a primary alkyl type zinc dithiophosphate capable of obtaining the same antiwear performance as that of the above-mentioned DD1 standard oil can be obtained by adding 0% by mass of zinc (Zn) to the lubricating base oil. 0.09 to 0.
13 or less.

The primary alkyl type zinc dithiophosphate is deteriorated and consumed at the same level as the conventional level, such as the metal reaction under boundary lubrication and the adsorption / affinity to soot. As a corresponding means, an oil-soluble oxymolybdenum sulfide dialkyldithiophosphate, which is a friction modifier and an antiwear agent, is used.

The oil-soluble oxymolybdenum sulfide / dialkyldithiophosphate, which is a friction modifier and an antiwear agent, has a molybdenum mass concentration of 200 p
In the range of pm to 400 ppm, a molybdenum extreme pressure film is formed in a region under boundary lubrication and the like, and is excellent in abrasion and seizure prevention.

Also, soot dispersed in oil contains soot in oil that has low adsorption and low affinity as compared with, for example, the above-mentioned zinc dithiophosphate. Element analysis.

Although the reason for this has not been elucidated, it is presumed to be related to the difference in polarity of the additive itself. The test for antiwear properties described above with reference to FIG.
In accordance with the high-speed shell four-ball wear test specified in MD2273, the test was performed by changing the mass concentration of molybdenum and measuring the diameter of the wear scar formed on the test piece under a constant load. (Test conditions: 1/2 inch steel ball, rotation speed 1800
In FIG. 1, the abscissa indicates the molybdenum mass concentration (ppm) and the ordinate indicates the wear scar diameter, and the molybdenum mass concentration used in the present invention is in the range of 200 to 400 ppm. It has been shown that the amount of wear is significantly reduced.

This phenomenon is presumed to be due to the fact that the additive forms sulfide (MoSx) on the friction surface due to thermal decomposition, and the sulfide film exerts an anti-friction effect. In order to confirm the practical performance of the oil of the present invention, a bench test was conducted using a large diesel EGR engine compared with a conventional diesel engine oil (hereinafter abbreviated as a conventional oil), and the deterioration analysis of the used oil was performed as shown in FIG. Is shown in

The sulfur content in the fuel (light oil) used in this test was unified to 0.05% by mass. Therefore, the effect of sulfuric acid (H ₂ SO ₄ ), which is a combustion product on the oil, was affected by Are equivalent.

In FIG. 2, the horizontal axis indicates the operating time of the engine, and the vertical axis indicates the total base number (TBN). The total base number is measured mainly to check the remaining amount of the metal detergent. This measurement is performed according to JIS K2501 method or ASTM D664.
Based on the above, neutralization measurement is performed by adding a standard solution of hydrochloric acid / alcohol to a fixed sample, and is calculated based on the consumption of the standard solution required at the end point of the neutralization.

A degraded oil that has already reached the neutralization point has a total base number (TBN) of zero, and is considered to have completely lost cleanliness and acid neutralization. In this figure, A shows the characteristics of the conventional oil without EGR, B shows the characteristics of the conventional oil with EGR, and C shows the characteristics of the diesel engine oil for an EGR-equipped engine of the present invention.

As is apparent from FIG. 5, in the conventional oil, the total base number is greatly reduced by adding EGR as compared with the case where there is no EGR. On the other hand, it can be seen that the oil of the present invention has a remarkably improved total base number of about 1/2 compared to the case where the conventional oil is used for EGR, and prevents oil deterioration.

As a cause of the decrease in the total base number, nitrate ions (NO ₃ ^-1 ) and nitrite ions (NO ₂ ^-1 ), as well as sulfate ions (SO ₄ ^-2 ) as combustion products, Further, it has been found that the oil has a wide variety of complexities such as organic oxidation products of the oil itself and thermal degradation of the additive itself.

The reason why the property C of the oil of the present invention was improved was that the thermal decomposition temperature of the detergent, ie, calcium alkalicylate, was higher than that of the others, and this difference was apparent. It can be inferred.

FIG. 3 shows the experimental results of the wear scar diameter and the insoluble content in oil in the high-speed shell four-ball wear test described above. From this figure, the characteristic D of the conventional oil
On the other hand, it can be seen that the characteristic E of the oil of the present invention is remarkably improved to about 1/3.

As a result, the conventional oil for the rings of the piston is on the left, and the oil of the present invention is on the right.
FIG. 4 shows the results of a comparative experiment on the wear (expressed in terms of lost weight) of the top ring R1, the second ring R2, and the oil ring R3.
Shown in

FIG. 5 shows the wear of the liner (comparison of bore polish) on the left side of the conventional oil and the oil of the present invention on the right side. FIG. 6 shows the comparison of the wear (nose) of the cam on the left side of the conventional oil and the oil of the present invention on the left. Indicates the right side.

As is apparent from the above, it is clear that the oil of the present invention is effectively improved in any wear of the top ring R1, the second ring R2, the oil ring R3, the cylinder liner, and the cam nose.

The above test was conducted on a refined base oil for lubricating oil having a kinematic viscosity of SAE30W. However, even when the kinematic viscosity of the refined base oil for lubricating oil was changed, the same effect was obtained. Is no different.

[0050]

As described above, the oil of the present invention is E
In a GR-equipped diesel engine, deterioration of characteristics as an engine oil is prevented by adding and blending the above-mentioned additives, particularly oil-soluble oxymolybdenum dialkyldithiophosphate having a molybdenum mass concentration of 200 to 400 ppm as an additive. In addition, the internal wear of the engine can be reduced.

[Brief description of the drawings]

FIG. 1 is a characteristic diagram showing a relationship between a molybdenum mass concentration and a wear scar diameter.

FIG. 2 is a graph showing a change in total base number (TBN) according to operation time.

FIG. 3 is a correlation diagram between the concentration of insoluble components in oil and the diameter of wear marks.

FIG. 4 is a relative wear diagram of a piston ring.

FIG. 5 is a relative wear diagram of the liner.

FIG. 6 is a relative wear diagram of a cam.

[Explanation of symbols]

 A Conventional oil without EGR B Conventional oil with EGR C Inventive oil with EGR D Wear scar diameter of conventional oil E Wear scar diameter of present oil R1 Top ring R2 Second ring R3 Oil ring

Continuation of the front page (51) Int.Cl. ⁶ Identification code FI C10M 137: 10) C10N 10:04 10:12 30:04 30:06 30:08 30:10 40:25 (58) Field surveyed (Int. .Cl. ⁶ , DB name) C10M 163/00 C10M 159/22 C10M 139/00 C10M 137/10 C10N 10:04 C10N 10:12 C10N 40:25 WPI / L (QUESTEL)

Claims (1)

(57) [Claims] 1. A lubricating base oil (mineral oil / synthetic oil)
165mgKOH / g total base number (TBN) as detergent
Alkali citrate (calcium (Ca) content 6.0% by mass) having 5.8 to 8.% by mass%.
3. The primary alkyl type zinc dithiophosphate is used as an antioxidant and an antiwear agent by mass% of zinc (Zn).
Oil-soluble oxymolybdenum dialkyldithiophosphate as a friction modifier and an antiwear agent, and 0.02 to 0.03 by mass% of molybdenum (Mo).
4. A diesel engine oil for an engine with an exhaust gas recirculation device, characterized by containing 4 in the composition.