JPH11279580A - Fluid composition for power steering - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fluid composition capable of inhibiting dissolution of copper in a working fluid by blending a base oil selected from among mineral oils and synthetic oils other than silicone oil with a phosphate-based compound and a 2-alkyldithio-5-mercapto-1,3,4-thiadiazole compound. SOLUTION: At least one compound (A) selected from among an alkyl or alkyl-substituted or unsubstituted phenyl phosphate compounds, alkyl or alkyl- substituted or unsubstituted phenyl thiophosphate compounds and alkyl or alkyl- substituted or unsubstituted phenyl dithiophosphate compounds other than metal salts is blended with at least one of 2-alkyldithio-5-mercapto-1,3,4-thiadiazoles (B) of the formula (wherein R<1> is a 1-12C linear or branched chain alkyl). The amount of the component A blended is about 0.005-0.5 mass % in terms of phosphor and the component B, about 0.02-1 mass%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a fluid composition for power steering, and more particularly, to a fluid composition for power steering.
An oil pump is driven by an engine or an electric motor, and the driver operates a steering wheel to operate a control valve and a power cylinder as an actuator, and a fluid used in a hydraulic system for boosting the steering output. Composition.

[0002]

2. Description of the Related Art A power steering device is a mechanism for reducing the operation of a steering wheel and facilitating driving, and includes an oil tank, an oil pump, a control valve, a steering gear box, and the like. The working fluid for power steering is used there. In order to operate the power steering device smoothly for a long period of time, various kinds of anti-wear, low temperature fluidity, thermal oxidation stability, low friction characteristics, seal compatibility, etc. are used. Performance is required. In order to satisfy these performances, various additives such as an antioxidant, a viscosity index improver, an antiwear agent, a friction modifier and the like are blended with the selected base oil and provided as a fluid composition for power steering. .

[0003]

An inherent problem with fluid compositions for power steering is the dissolution of copper in oil. An oil tank that constitutes a power steering device,
The oil pump and the steering gear box are connected by a rubber hose and a copper pipe, respectively. As a result, the fillers and the like in the rubber hose elute into the oil, which tends to attack the copper piping and increase the copper concentration in the oil, and this copper in the oil deteriorates the oil seal made of the rubber material, and the strength is reduced. Or oil leaks. To cope with this problem, a method of suppressing the elution of copper into oil by combining a thiadiazole derivative and a phosphoric acid compound has already been proposed (Japanese Patent Publication No. 6-99701). However, since this thiadiazole derivative is expensive, a fluid composition for power steering in which an additive which is inexpensive and in a small amount is effective in preventing copper elution is blended has been desired. In particular, the structure of recent automobile engines and peripheral equipment has become more complicated, the length of rubber hoses used in power steering devices has become longer, and the amount of copper-dissolving components from rubber has increased. There is a need for the development of additives that can provide sufficient copper elution prevention properties even when used in small amounts.

In the hydraulic system of power steering, there is a power cylinder which slides at a high pressure, and its lip seal has to be repeatedly and frequently slid under a high pressure against the cylinder wall. But,
The power steering fluid must be capable of providing good lubrication between the flexible lip member and the cylinder wall and must have a low coefficient of friction.

[0005]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result,
Specific phosphoric acid compound and specific 2-alkyldithio-5
It has been found that by adding a mercapto-1,3,4-thiadiazole compound, the dissolution of copper in a working fluid can be suppressed more than in a conventional thiazole compound, and the present invention has been completed.

That is, the gist of the present invention is to provide (a) an alkyl- or alkyl-substituted or unsubstituted phenylphosphoric acid-based compound, an alkyl- or alkyl-substituted or unsubstituted phenylthiophosphate-based compound and an alkyl- or alkyl-substituted or unsubstituted phenylthiophosphate-based compound other than a metal salt. At least one member selected from the group consisting of substituted phenyldithiophosphate compounds;
Seed, (b) following formula

Embedded image (Wherein, R ¹ represents a linear or branched alkyl group having 1 to 12 carbon atoms).
It is characterized by containing one or more of 5-mercapto-1,3,4-thiadiazole and (c) at least one base oil selected from the group consisting of mineral oils and synthetic oils other than silicones. Power steering fluid composition.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The component (A) used in the present invention is an alkyl- or alkyl-substituted or unsubstituted phenylphosphoric acid compound, an alkyl- or alkyl-substituted or unsubstituted phenyldithiophosphorus compound, and an alkyl- or alkyl-substituted or unsubstituted phenyldithiophosphorus compound other than a metal salt. The alkyl group is a linear or branched alkyl group having 1 to 18 carbon atoms. Specific examples are methyl, ethyl, propyl, butyl, hexyl, octyl,
Nonyl, hexadecyl, octadecyl groups and the like can be mentioned. The same applies to the alkyl group of the alkyl-substituted phenyl group. Preferred as the alkyl group of the component (a) or the alkyl group of the alkyl-substituted phenyl group is an alkyl group having 4 to 18 carbon atoms.

Examples of the alkyl- or alkyl-substituted or unsubstituted phenyl phosphate compounds include phosphites, phosphonates, orthophosphates, pyrophosphates, acid phosphates, and acid phosphate amine salts. Can be mentioned.

Examples of the alkyl- or alkyl-substituted or unsubstituted phenylthiophosphate compounds include thiophosphate compounds such as thiophosphates and acid thiophosphates, and fully neutralized or partially neutralized salts of these acid thiophosphates with alkylamines. Can be mentioned.

Examples of the alkyl- or alkyl-substituted or unsubstituted phenyldithiophosphate compounds include dithiophosphate compounds such as dithiophosphate and acidic dithiophosphate, and fully neutralized or partially neutralized salts of these acidic dithiophosphates with alkylamines. And the like. In the present invention, the metal salts are excluded from the alkyl or alkyl-substituted or unsubstituted phenyldithiophosphate-based compounds because these metal salts,
This is because zinc salts usually have a disadvantage of promoting copper elution.

These phosphate compounds may be used alone or in combination of two or more.

The amount of the component (A) is about 0.005% by mass to about 0.5% by mass, preferably about 0.02% by mass to about 0.07% by mass in terms of phosphorus. If the amount is too large, the effect is not so high and the cost increases. On the other hand, if the amount is too small, the wear prevention performance tends to decrease, which is not preferable.

The component (b) used in the present invention has the following formula

Embedded image (Wherein, R ¹ represents a linear or branched alkyl group having 1 to 12 carbon atoms).
5-mercapto-1,3,4-thiadiazole.

2-alkyldithio-5-mercapto-
The alkyl group (R ¹ in the formula) of 1,3,4-thiadiazole is preferably a linear or branched alkyl group having 1 to 10 carbon atoms, and more preferably a linear alkyl group. A particularly preferred alkyl group is an alkyl group having 6 to 10 carbon atoms, and specific examples thereof include an n-nonyl group and an n-octyl group. If the number of carbon atoms exceeds 12, a sufficient copper elution suppressing effect cannot be obtained.

The amount of the component (b) is about 0.02% by mass.
１1% by mass, preferably about 0.05-0.5% by mass. If the amount is less than 0.02% by mass, a sufficient effect of suppressing copper elution cannot be obtained. If the amount exceeds 1% by mass, the abrasion prevention performance tends to decrease, which is not preferable.

The base oil used as the component (c) in the present invention may be a mineral oil which has been refined by solvent refining or hydrotreating or a synthetic oil described below and which has an appropriate viscosity. I just need. For example, synthetic oils include poly-α-olefins, polybutenes, diesters, polyethylene propylenes, polyglycols, and hindered esters, but considering the solubility of additives, preferably mineral oil. Similar poly-α-
Examples include olefins, polybutenes, and polyethylene propylene. Incidentally, even in the case of synthetic oil, silicone has a high volume compressibility and poor lubricating property, so that it is not suitable as a base oil of the fluid for power steering of the present invention.

These base oils may be used alone,
Further, two or more kinds may be used in combination.

Generally, in the fluid for power steering, the appropriate viscosity for the vane pump or gear pump used is such that the viscosity at 100 ° C. is about 5 to 10 mm ² / s, preferably about 6 to 10 in consideration of fluidity at low temperatures. 8m
m ² / s, viscosity at -30 ° C is about 50,000 mPa · s
Or less, preferably about 5,000 mPa · s or less, so that the viscosity at 100 ° C. is usually about ^{2 to} 7 mm ² / s,
Preferably, a base oil of about 3 to 4.5 mm ² / s is used, and a polymethacrylate polymer or a polymer of polyethylene propylene or polybutene is used to obtain a thickening effect and a pour point depressing effect as required. And a polymethacrylate-based polymer compound are used in combination to make the viscosity range appropriate.

The fluid composition for power steering according to the present invention may further contain known additives such as a rust preventive, a metal deactivator, an antioxidant, a viscosity index improver, a detergent / dispersant, a friction modifier and an erasing agent. It may contain a foaming agent and the like. Specifically, examples of the rust preventive include amines, alkenyl succinimides and alkenyl succinates. Examples of the metal deactivator include thiadiazole derivatives such as 2,5-bis (alkyldithio) -1,3,4-thiadiazole and benzotriazole. Examples of the antioxidant include amine-based and phenol-based antioxidants. Examples of the viscosity index improver include polymethacrylate and olefin copolymer. Examples of the metal-type detergent / dispersant include alkaline earth metal sulfonates, alkaline earth metal phenates, and alkaline earth metal salicylates. Examples of the ashless detergent and dispersant include alkenyl succinimide, alkenyl succinate, amide of long chain fatty acid and polyamine (aminoamide type), and the like. Examples of the friction modifier include a fatty acid and an organic molybdenum compound. Examples of the antifoaming agent include a silicon compound and an ester compound.

The amount of each of these additives is about 20% by mass or less, preferably about 10% by mass or less. In the composition of the present invention, the total amount of additives is about 20% by mass or less,
In particular, about 15% by mass or less is preferable.

[0021]

Next, the present invention will be described more specifically with reference to examples and comparative examples. The present invention is not limited by these examples.

(A), (B), (C) used in the examples
The components are shown below. Component (a) As alkyl or alkyl-substituted or unsubstituted phenylphosphate compounds, tricresyl phosphate,
Triisodecyl phosphite was used.

As alkyl or alkyl-substituted or unsubstituted phenylthiophosphate compounds, trialkylthiophosphates (alkyl groups C ₁₂ : C ₁₃ = 1: 1)
Was used.

As the alkyl or alkyl-substituted or unsubstituted phenyldithiophosphate compound other than the metal salt, 2-ethylhexyldithiophosphate was used.

(B) Component As the 2-alkyldithio-5-mercapto-1,3,4-thiadiazole, 2-nonyldithio-5-mercapto-1,3,4-thiadiazole having 9 carbon atoms of R ¹ is used. Was.

(C) Component As the base oil, a highly refined paraffinic mineral oil having a viscosity of 4.0 mm ² / s at 100 ° C. was used.

The following additives were used as other additives. Ashless detergent dispersant; succinimide dispersant Metal detergent dispersant; Ca salicylate viscosity index improver; polymethacrylate antioxidant; alkyldiphenylamine defoamer; dimethylpolysiloxane metal deactivator; -Bis (octyldithio)-
1,3,4-thiadiazole

In Examples and Comparative Examples, copper elution prevention performance evaluation and friction characteristics were evaluated. The evaluation method is described below.

Copper Leaching Prevention Performance Evaluation Test Copper leachability test was conducted under the following test conditions. This test was performed using an apparatus and a sample container specified in Section 4 of JIS K2514. After this test, the Cu concentration in the sample oil was measured to evaluate the copper elution prevention performance of the composition.

Sample oil amount: 250 ml Temperature: 110 ° C. Gum plate: Low-pressure rubber hose (acrylonitrile butadiene rubber) cut into 3 mm × 3 mm × 2 mm 20 g Copper plate: 75 mm × 180 mm × 0.8 mm Time: 96 h

Friction Characteristics Test The evaluation of the friction characteristics of the fluid composition for power steering was carried out as follows.
The test was performed using the apparatus shown in FIGS.

FIG. 1 is a front view of the friction test tool main body used, FIG. 2 is a cross-sectional view taken along the line II of FIG. 1, and FIG. 3 is a view of a grip portion for gripping a rubber plate as a test material. . Acrylonitrile butadiene rubber plate (hereinafter simply referred to as rubber plate)
10 is gripped by the gripper 12 of the gripper 11 shown in FIG.
Then, as shown in FIG. 2, the axis 13 of the gripper 11
Is inserted into the slit portion 3 of the test apparatus main body 1 and is fixed with the nut 14 so that one surface of the rubber plate 10 is in contact with the fixing means 2 at a position where the rubber plate 10 has an elongation of 100%.

The friction test device main body 1 in this state is attached to a friction test device (not shown) at the attachment portion 1a, and a steel plate (J
IS-G-3141SPCC) 20. Next, 50 mg of the composition obtained in the example or the comparative example is applied between the rubber plate 10 and the steel plate 20. Then, a load of 500 g is applied between the rubber plate 10 and the steel plate 20 by a load applying means (not shown), and a relative speed of 1.3 mm / sec is applied between the rubber plate 10 and the steel plate 20 by an electric motor (not shown). give. The frictional force between the two plates 10 and 20 is detected by measuring the strain of a leaf spring (spring constant: 40 ± 1 g / mm, spring frequency: 15 ± 1 cycle / sec) with a strain gauge and recording it by an electromagnetic oscillograph. Then, the friction coefficient was calculated based on the detection result of the frictional force. The above measurements were performed at 80 ° C.

The details of the apparatus used here are disclosed in
1, FIG. 2, FIG. 3, and FIG. 3 used herein correspond to FIG. 3A, FIG. 3B, and FIG. 2, respectively. If so, see the above publication.

Examples 1 to 10 Power steering fluid compositions were prepared at the mixing ratios shown in Tables 1 and 2. The properties of the obtained composition are shown in the middle row of the table, and the above-described copper elution prevention performance evaluation and friction property test were performed. The results are shown in the lower row of the table.

[0036]

[Table 1]

[0037]

[Table 2]

Comparative Examples 1-4 Fluid compositions for power steering were prepared in the proportions shown in Table 3. The properties of the obtained composition are shown in the middle row of the table, and the above-described copper elution prevention performance evaluation and friction property test were performed. The results are shown in the lower row of the table.

[0039]

[Table 3]

[0040]

The fluid composition for power steering of the present invention comprises a specific phosphoric acid compound and 2-alkyldithio-5.
-By containing mercapto-1,3,4-thiadiazole, it is more effective in suppressing copper elution than before, without impairing other performances as a working fluid for conventional power steering. Damage due to corrosion can be suppressed, and long-term stable use of the power steering device can be ensured.

The working fluid composition for power steering of the present invention can be used as an automotive or industrial hydraulic working fluid such as an automatic transmission oil, a shock absorber oil and an active suspension fluid. It is suitable as a fluid composition for use.

[Brief description of the drawings]

FIG. 1 is a front view of a friction test device main body used in the present invention.

FIG. 2 is a cross-sectional view taken along line II of FIG.

FIG. 3 is a diagram of a gripping portion that grips a rubber plate as a material to be tested.

[Description of Signs] 1 : Friction test tool main body 2: Fixing means 3: Slit portion 10: Rubber plate 11 : Gripping tool 12: Gripping section 13: Shaft (shaft of gripping tool 11) 14: Nut 20: Steel plate

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification symbol FI C10M 137/04 C10M 137/04 137/10 137/10 Z // C10N 30:12 40:08 (72) Inventor Toshio Isao Saito Saitama 1134-2 Gongendo, Satte-shi

Claims (2)

[Claims] 1. A) alkyl or alkyl-substituted or unsubstituted phenylphosphoric acid compounds, alkyl or alkyl-substituted or unsubstituted phenylthiophosphoric acid compounds, and alkyl or alkyl-substituted or unsubstituted phenyldithiophosphate compounds other than metal salts At least one member selected from the group consisting of: (b) the following formula: (Wherein, R ¹ represents a linear or branched alkyl group having 1 to 12 carbon atoms).
It is characterized by containing one or more of 5-mercapto-1,3,4-thiadiazole and (c) at least one base oil selected from the group consisting of mineral oils and synthetic oils other than silicones. Fluid composition for power steering. 2. The compounding amount of the component (a) is 0.005% by mass to 0.5% by mass in terms of phosphorus content, and
The fluid composition for power steering according to claim 1, wherein the amount of the component is 0.02% by mass to 1% by mass.