JPH05255683A - Hydraulic oil composition for bumper - Google Patents

Abstract

PURPOSE:To provide the subject hydraulic oil composition for a bumper, exhibiting excellent friction properties under a condition where fine vibrations or fine oscillations are applied to the bumper and sufficiently excellent in abrasion resistance and friction properties even in the case of a bumper made of a polytetrafluoroethylene resin member. CONSTITUTION:The hydraulic oil composition for a bumper characteristically contains a base oil, one or more kinds of compounds selected from a phosphate, a phosphite and an amine salt of a phosphate and an alkanolamine.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydraulic fluid composition for shock absorbers, and more particularly to a hydraulic fluid composition for shock absorbers having good wear resistance and a low coefficient of friction. The hydraulic fluid composition for shock absorbers of the present invention is particularly suitable as a hydraulic fluid for shock absorbers used in suspensions of automobile bodies.

[0002]

2. Description of the Related Art A hydraulic shock absorber (damper) for absorbing vibrations is used in a vehicle body suspension (suspension device) in an automobile. Its structure is a tubular shape utilizing the flow resistance of oil. The structure is the basis. Specifically, a hydraulic piston with a small hole is used. The oil passes through the hole depending on the position of the piston, and the resistance at that time is proportional to the speed of the piston. A bush that also serves as a guide is inserted in the sliding portion between the cylinder and the piston rod to prevent mutual wear, and is sealed to prevent oil leakage. And
Various shock absorbers such as double pipe type and gas filled type are known.

In the shock absorber having such a structure, there are many combinations of friction such as between the piston rod and the bush, between the piston rod and the seal, between the piston and the cylinder. Moreover, in order to secure the ride comfort and driving stability by reducing the vibration to the vehicle under the severe driving condition of the vehicle,
With respect to the hydraulic fluid (buffer fluid) used for the shock absorber, it is required to have good wear resistance and durability as well as good friction characteristics.

In addition to the above, similar shock absorbers are also used in automobiles for supporting devices for engines, shock absorbing devices for bumpers, door checkers and the like. In addition, a hydraulic shock absorber is arranged on the aircraft to absorb impact during takeoff and landing. The hydraulic oil used in these shock absorbers is required to have the same performance as described above.

Conventionally, a hydraulic fluid composition for a shock absorber, in which zinc dithiophosphate (Zn-DTP) is added to a lubricating base oil together with an oiliness agent such as a long-chain fatty acid or a detergent dispersant (Japanese Patent Laid-Open Publication No. 5 (1999) -58242).
No. 5-165996), or a fluid composition for a buffer containing a boron-containing detergent-dispersant and a phosphoric acid ester (Japanese Patent Publication No. 2-44879).

However, although the hydraulic fluid containing Zn-DTP has good wear resistance, it has the drawback of having a high friction coefficient. Therefore, Zn-DTP
Are usually used in combination with other additives to reduce the coefficient of friction, but the oily agents such as long-chain fatty acids used together, for example, corrode the bearing material of the shock absorber and accelerate the wear. have. Furthermore, conventional Zn-DTP
The hydraulic fluid containing phosphoric acid ester does not have sufficient friction characteristics with respect to slight vibration and minute amplitude applied to the shock absorber.

That is, the operating conditions of the shock absorber vary depending on the running state of the automobile and the presence or absence of pavement on the road, and the performance required for the hydraulic fluid also varies. Due to the recent development of automobile-related technologies and improvement of road pavement, the traveling condition of automobiles has been improved, and in particular, automobiles traveling on paved roads are often subjected to slight vibration and slight amplitude. However, it has been found that when minute vibrations and minute amplitudes are applied to an automobile for a long time, the frictional characteristics of conventional hydraulic oils for shock absorbers containing Zn-DTP and phosphoric acid ester deteriorate, and the frictional force sharply increases. Therefore, the hydraulic oil for shock absorbers is required to have low friction and low wear in the minute vibration and minute amplitude of the shock absorber.

In a hydraulic shock absorber such as a shock absorber, a sliding member such as a bush is made of polytetrafluoroethylene resin (hereinafter abbreviated as PTFE resin).
Is being used. Therefore, the combination of friction is also PTFE resin / steel. By the way, lubricating oil additives such as antiwear agents and oiliness agents play a role of reacting on the friction surface to form a film with a low melting point to prevent wear, or to form an oil film on the friction surface to reduce friction and wear. However, it is difficult to form such a film on the surface of the PTFE resin member. Moreover, even if a film or oil film is formed on the surface of the steel member, which is the other friction surface, there is a problem that it is scraped off by sliding with the PTFE resin member.

However, in the conventional hydraulic fluid for shock absorbers, when used in a shock absorber using a PTFE resin member,
It cannot show sufficient wear resistance and friction characteristics.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to provide a hydraulic fluid composition for shock absorbers, which exhibits good friction characteristics even when slight vibrations and slight amplitudes are applied to the shock absorber. Another object of the present invention is to provide a hydraulic fluid composition for shock absorbers that exhibits sufficient wear resistance and friction characteristics when used in a shock absorber using a PTFE resin member.

The present inventor has conducted intensive studies to overcome the above-mentioned problems of the prior art and found that the above object can be achieved by using a phosphoric acid ester compound and an alkanolamine together as a lubricating oil additive. The present invention has been completed based on the findings.

[0012]

Thus, according to the present invention, at least one selected from the group consisting of (a) base oil, (b) phosphoric acid ester, phosphorous acid ester and phosphoric acid ester amine salt. A hydraulic fluid composition for a shock absorber, which comprises a compound and (c) an alkanolamine.

The present invention will be described in detail below. (Base oil) The base oil used in the present invention is not particularly limited, and various conventionally known mineral oils and synthetic oils can be used. Examples of the mineral oil include light neutral oil, medium neutral oil, heavy neutral oil, and bright stock. Examples of synthetic oils include poly-α-olefins, polybutenes, alkylbenzenes, polyol esters, dibasic acid esters, silicone oils, and the like. These base oils may be used alone or in admixture of two or more, and mineral oil and synthetic oil may be mixed and used.

The base oil usually has a viscosity at 100 ° C. of 1.5-.
It is preferably in the range of 3.0 cSt.

(Phosphate Compound) In the present invention,
At least one compound selected from the group consisting of phosphoric acid ester, phosphorous acid ester and phosphoric acid ester amine salt is used.

Examples of the phosphoric acid ester and phosphorous acid ester include those represented by the following general formula. O = P (OR ¹ ) (OR ² ) (OR ³ ) O = P (OH) (OR ¹ ) (OR ² ) O = P (OH) ₂ (OR ¹ ) P (OR ¹ ) (OR ² ) ( OR ³ ) P (OH) (OR ¹ ) (OR ² ) P (OH) ₂ (OR ¹ ) (wherein R ¹ , R ² and R ³ have 4 or more carbon atoms, preferably 4 to 20 saturated or Unsaturated alkyl group, aryl group or alkyl-substituted aryl group, which may be the same or different.)

Specific examples of the phosphoric acid ester and the phosphorous acid ester include dibutyl acid phosphate and 2-
Ethylhexyl acid phosphate, lauryl acid phosphate, oleyl acid phosphate, dioleyl acid phosphate, dibutyl hydrogen phosphite, dilauryl hydrogen phosphite,
Examples thereof include distearyl hydrogen phosphite, dioleyl hydrogen phosphite, and diphenyl hydrogen phosphite.

The phosphoric acid ester amine salt used in the present invention is a reaction product of a phosphoric acid ester or phosphorous acid ester and an amine compound. Examples of the amine compound include primary or secondary amines having a saturated or unsaturated alkyl group having 10 to 20 carbon atoms. Specific examples, diisooctyl acid phosphate amine salt _{[(i-C 8 H 17 O} ) 2 P (OH) O and (C
₁₈ H ₃₅ ) NH ₂ reaction product], oleyl acid phosphate amine salt, and the like.

These phosphoric acid ester compounds can be used alone or in combination of two or more kinds. The mixing ratio of the phosphate ester compound is
The total amount of the composition is usually 0.1 to 5.0% by weight, preferably 0.2 to 3.0% by weight, more preferably 0.3 to
It is 2.0% by weight. Within the range of this mixing ratio,
When used in combination with an alkanolamine, it can exhibit good wear resistance and friction characteristics.

(Alkanolamine) The alkanolamine used in the present invention includes those known as amine oily agents. Among them, the compounds represented by the following general formulas can be preferably used. R—N (C _n H _2n OH) ₂ (wherein R is a saturated or unsaturated alkyl group having 4 to 18 carbon atoms, and n is an integer of 1 to 6). _{C 12 H 25 -N (CH 2} CH 2 O
H) ₂ and other diethanolamine compounds can be mentioned.

The blending ratio of the alkanolamine is usually 0.1 to 5.0% by weight, preferably 0.2 to 3.0% by weight, more preferably 0.3 to 2.0, based on the total amount of the composition.
% By weight.

(Other Additives) In the hydraulic fluid composition of the present invention, other additives such as antiwear agents, ashless detergent dispersants, and the like may be added, if necessary, so long as the object of the present invention is not impaired. An antioxidant, a metal detergent, a metal activator, a viscosity index improver, a pour point depressant, a rust preventive, a defoaming agent, a corrosion inhibitor and the like can be appropriately added.

Examples of antiwear agents include metal salts of dithiophosphoric acid (Zn, Pb, Sb, Mo, etc.), metal salts of dithiocarbamic acid (Zn, etc.), sulfur compounds, etc. It is used in a proportion of 0.05 to 3.0% by weight.

Examples of ashless detergent dispersants include succinimide-based, succinamide-based, benzylamine-based and ester-based ones, and a boron-containing ashless detergent-dispersant can also be used. These are usually used in a proportion of 0.5 to 7.0% by weight.

Examples of the antioxidant include amine-based antioxidants such as alkylated diphenylamine, phenyl-α-naphthylamine and alkylated-α-naphthylamine, 2,6-di-t-butylphenol, 4,4'- Mention may be made of phenolic antioxidants such as methylenebis- (2,6-ditertiarybutylphenol), which are usually used in a proportion of 0.05 to 2.0% by weight.

Examples of the metal detergent include Ca-sulfonate, Mg-sulfonate, Ba-sulfonate,
There are Ca-phenate, Ba-phenate and the like, and these are usually used in a proportion of 0.1 to 5.0% by weight.

Examples of the metal activator include benzotriazole, benzotriazole derivative, benzothiazole, benzothiazole derivative, triazole, triazole derivative, dithiocarbamate, dithiocarbamate derivative, indazole and indazole derivative. Is usually used in a proportion of 0.005 to 0.3% by weight.

Examples of the viscosity index improver include polymethylmethacrylate type, polyisobutylene type, ethylene-propylene copolymer type, styrene-butadiene hydrogenated copolymer type, etc., and usually 0.5 to 35% by weight. Used in proportion.

Examples of the rust preventive agent include alkenyl succinic acid and its partial ester and the like, which can be appropriately added.

Examples of the defoaming agent include dimethylpolysiloxane, polyacrylate and the like, which can be appropriately added.

(Hydraulic fluid composition for shock absorber) The hydraulic fluid for shock absorber of the present invention uses a combination of a phosphoric acid ester compound and an alkanolamine as an essential additive component to allow the shock absorber to vibrate slightly. And exhibits excellent friction characteristics even under conditions where a slight amplitude is applied.
Even when it is used in a shock absorber using a sliding member made of TFE resin, it has good wear resistance and friction characteristics.

Therefore, the hydraulic oil for shock absorbers of the present invention can be used for various shock absorbers, but is particularly suitable as a hydraulic oil for shock absorbers of automobiles.

[0033]

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. The methods for measuring various physical properties are as follows.

(1) Method of measuring frictional force The time-dependent change of frictional force was measured by a bench test. Specifically, a monotube shock absorber for automobiles was used, and the piston rod was moved up and down at high speed, and the force required for moving the rod up and down was measured and used as the frictional force (kgf). In this case, the lateral load, stroke, frequency and the like were set to the following test conditions in order to match the running condition of slight vibration and slight amplitude.

Test conditions (A) Lateral load: 60 kgf Temperature: 60 ° C Stroke: ± 2 mm Vibration frequency: 15 Hz (continuous operation) Test conditions (B) Lateral load: 60 kgf Temperature: 60 ° C Stroke: ± 10 mm Vibration Number: 1 Hz (Operating with a superimposed wave for 300 seconds every 15 minutes for test condition A)

Example A highly refined mineral oil having a viscosity of 2.5 cSt at 100 ° C. was used as a base oil, and the respective components shown in Table 1 were added to prepare respective test oils. The components used are as follows. (1) Phosphate ester: dioleyl phosphate (2) Phosphite ester: dioleyl hydrogen phosphite (3) Phosphate ester amine salt: oleyl acid phosphate amine salt (4) Zinc dithiophosphate: di-n-butyldithio Zinc phosphate (5) C ₁₂ diethanolamine: C ₁₂ H ₂₅ —N (CH ₂
CH ₂ OH) ₂ (6) Viscosity index improver: polymethacrylate (7) Antioxidant: phenolic antioxidant (8) Metal deactivator: benzotriazole (9) Antifoaming agent: Silicon oil Table 1 The blending ratio of each additive component is 1% by weight based on the total amount of the composition, and the balance is base oil (total 100% by weight).

<Frictional Force> Table 1 shows the results of the frictional force test by the bench test for each test oil. The test conditions are
Under the test conditions (A) and (B), the frictional force after 400 hours of operation was measured, and the degree of increase was evaluated according to the following criteria. ◯: Increase in frictional force is less than 20 kgf ×: Increase in frictional force is 20 kgf or more

[0038]

[Table 1]

From Table 1, it is clear that the combined use of the phosphoric acid ester compound and the dialkanolamine (test oils 5 to 9; Examples) improves the friction characteristics. On the contrary,
When the phosphate ester compound alone or the zinc dithiophosphate alone was used (Experimental oils 1 to 4; Comparative example), the frictional force increased greatly, and the frictional characteristics at minute vibration and minute amplitude were poor.

<Change in Friction Force with Time> Test Oil 1 in Table 1
(Phosphate ester) and test oil 5 (phosphate ester + lauryl diethanolamine) were continuously operated under test condition A, and the change with time in frictional force in the bench test was measured. The results are shown in Figure 1.

In FIG. 1, A (□) is test oil 5 (Example)
B (∘) indicates test oil 1 (comparative example). As is clear from FIG. 1, in the combined use system (A) of the phosphate compound and the dialkanolamine, the change in frictional force with time is small. On the other hand, with the phosphate ester alone (B),
The frictional force increases remarkably with the passage of time.

<Evaluation of Abrasion Resistance and Friction Properties for PTFE Resin Sliding Member> For test oils 1 and 5, a polytetrafluoroethylene (PTFE) plate and a steel ball were used by a Bowden tester shown in FIG. The friction coefficient and the amount of wear (PTFE content in oil) were measured.

Test conditions Temperature: 60 ° C. Load: 15 Kgf Amplitude: 50 Hz Time: 120 min The results are shown in Table 2.

[0044]

[Table 2]

[0045]

According to the present invention, by adding a phosphate ester compound and an alkanolamine in combination to a base oil, excellent friction characteristics can be obtained even under conditions where slight vibration and slight amplitude are applied to the shock absorber. Demonstrate and also PTFE
Even when used in a shock absorber using a sliding member made of a resin, a shock absorber hydraulic oil exhibiting excellent wear resistance and friction characteristics is provided.

[Brief description of drawings]

FIG. 1 is a graph showing changes over time in frictional force in a bench test.

FIG. 2 is a schematic sectional view of a Bowden tester.

[Explanation of symbols]

 A (□): Test oil 5 (Example) B (○): Test oil 1 (Comparative example)

Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C10M 137: 08 133: 08) C10N 30:06 40:08

Claims (1)

[Claims] 1. At least one compound selected from the group consisting of (a) base oil, (b) phosphoric acid ester, phosphorous acid ester and phosphoric acid ester amine salt, and (c).
A hydraulic fluid composition for a shock absorber, which comprises an alkanolamine.