JP2018002844A - Hydraulic oil for hydraulic systems, and hydraulic systems using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hydraulic oil for hydraulic systems with a small friction coefficient and a small change of the friction coefficient associated with temperature variation, and to provide hydraulic systems using the same.SOLUTION: This invention relates to a hydraulic oil for hydraulic systems, comprising: a base oil; at least one of a phosphorous ester compound and a phosphoric ester compound; and a secondary amide compound expressed by chemical formula 1. (Rand Rare each independently a 8-24C saturated/unsaturated alkyl group).SELECTED DRAWING: Figure 1

Description

  The present invention relates to hydraulic fluid for hydraulic devices and hydraulic devices using the hydraulic fluid.

  In a hydraulic device configured with a piston rod, an oil seal, and hydraulic fluid, the oil seal is arranged so as to always contact the piston rod, and serves to prevent hydraulic fluid from flowing out from the inside of the hydraulic device. I'm in charge.

  Generally, since the oil seal is made of a rubber-based material, the coefficient of friction with the surface of the piston rod made of metal is large, and this coefficient of friction varies with changes in temperature. Therefore, when the piston rod operates in the hydraulic device, a frictional force is generated between the oil seal and the piston rod, and the frictional force varies with a temperature change.

  If the frictional force generated between the oil seal and the piston rod changes, a desired damping force characteristic may not be obtained.

  Attempts have been made to reduce the frictional force between the oil seal and the piston rod by adding an additive to the hydraulic fluid of the hydraulic system so that the damping force characteristic of the hydraulic system does not change due to temperature changes.

  For example, Patent Document 1 discloses providing a lubricating oil composition that exhibits a friction reducing effect by blending a specific sulfur-containing compound and a specific polar group-containing compound with a base oil. As the polar group-containing compound, a compound having at least one polar group selected from an amino group, an amide group and a hydroxyl group and an alkyl group having 3 to 24 carbon atoms is disclosed. Patent Document 1 discloses that a substance containing a phosphite or a phosphate can be added as an antiwear or extreme pressure agent.

Republished WO2011-068137

  However, when the lubricating oil composition disclosed in Patent Document 1 is employed in a hydraulic device that uses a wide range of temperature conditions, the coefficient of friction between the oil seal and the piston rod still varies with temperature changes. For this reason, hydraulic oil that is used under a wide range of temperature conditions is desired to have a hydraulic fluid that has a small coefficient of friction between the oil seal and the piston rod and a small variation of the coefficient of friction with temperature. .

化学式１において、Ｒ_１およびＲ_２は共に、炭素数８以上２４以下の飽和または不飽和アルキル基を示す。なお、Ｒ_１およびＲ_２は共にアルキル基であることから極性基は含まない。 According to the first aspect of the present invention, the hydraulic device hydraulic fluid includes a base oil, at least one of a phosphite compound and a phosphate ester compound, a secondary amide compound represented by Chemical Formula 1, Containing.

In Chemical Formula 1, R ₁ and R ₂ both represent a saturated or unsaturated alkyl group having 8 to 24 carbon atoms. Since R ₁ and R ₂ are both alkyl groups, no polar group is contained.

  ADVANTAGE OF THE INVENTION According to this invention, the hydraulic fluid for hydraulic apparatuses with a small friction coefficient and the fluctuation | variation of the friction coefficient accompanying a temperature change can be provided, and the hydraulic apparatus using this hydraulic fluid.

FIG. 1 is an enlarged cross-sectional view of an automobile shock absorber according to an embodiment of the present invention. It is the schematic of the reciprocating friction test machine used in order to estimate the dynamic friction between an oil seal and a piston rod. It is a table | surface which shows the mixing | blending composition and test result of the hydraulic fluid for hydraulic apparatuses of the Example which concerns on this invention. It is a table | surface which shows the mixing | blending composition and test result of the hydraulic fluid for hydraulic apparatuses of a comparative example. It is a table | surface which shows the sensory test result of the riding comfort of the motor vehicle carrying the buffer for motor vehicles using the hydraulic fluid for hydraulic apparatuses of the Example which concerns on this invention, and a comparative example.

As described above, the hydraulic fluid for a hydraulic device according to the present invention has (B) at least one of a phosphite compound and a phosphate ester compound, and (C) Chemical Formula 1 with respect to (A) the base oil. And a secondary amide compound represented. As described above, in Chemical Formula 1, both R ₁ and R ₂ represent a saturated or unsaturated alkyl group having 8 to 24 carbon atoms.

  The base oil of the above (A) is not particularly limited as long as it contains petroleum and / or synthetic hydrocarbon system, and is a mineral oil system and / or synthetic oil system conventionally used as hydraulic fluid for hydraulic equipment. Any material can be selected from these base oils. Examples of the mineral base oil include paraffin base mineral oil and naphthene base mineral oil.

  Synthetic oil base oils include, for example, polybutene, polypropylene, polyalphaolefin, polyol ester, fatty acid monoester, aromatic monoester, fatty acid diester, aliphatic polybasic acid ester, aromatic polybasic acid ester, polyol polyester And esters such as polyalkylene glycol, polyphenyl ether, polyglycol, polyphenyl ether, alkylbenzene, synthetic naphthene, and ionic liquid.

  Among these base oils, base oils used for hydraulic device hydraulic fluids include paraffin-based mineral oil, naphthene-based mineral oil, poly α-olefin, polyphenyl ether, alkylbenzene, synthetic naphthene, silicone, polyalkylene glycol, and the like. preferable. These base oils may be used alone or in combination of two or more.

The kinematic viscosity preferable as the base oil differs depending on the hydraulic device to which the hydraulic fluid is applied. For example, when the hydraulic device is a shock absorber for automobiles, the kinematic viscosity at 40 ° C. 8 mm ² / s (cSt) or more and 17 mm ² / s (cSt) or less.

  As the material (B), at least one of a phosphite compound and a phosphate compound is used. Both the phosphite compound and the phosphate compound release a proton by a catalytic action and are adsorbed on the surface of the piston rod to form a stable adsorbing film. This adsorption film is considered to reduce the coefficient of friction between the oil seal and the piston rod.

The phosphite compound used as the material of (B) preferably has a structure represented by the following chemical formula 2. In Chemical Formula 2, one of R ₃ and R ₄ is hydrogen or an alkyl group having 10 to 24 carbon atoms, and the other is an alkyl group having 10 to 24 carbon atoms. The number of carbon atoms is more preferably 12 or more and 18 or less. These alkyl groups may be saturated alkyl groups or unsaturated alkyl groups. One may be a saturated alkyl group and the other may be an unsaturated alkyl group. In either case saturated alkyl group or unsaturated alkyl group, from an alkyl group, R ₃ and R ₄ of the phosphite compound does not contain a polar group.

Moreover, it is preferable that the phosphate ester compound used as a material of said (B) has a structure shown to following Chemical formula 3. In Chemical Formula 3, one of R ₅ and R ₆ is hydrogen or an alkyl group having 10 to 24 carbon atoms, and the other is an alkyl group having 10 to 24 carbon atoms. The number of carbon atoms is more preferably 12 or more and 18 or less. These alkyl groups may be saturated alkyl groups or unsaturated alkyl groups. One may be a saturated alkyl group and the other may be an unsaturated alkyl group. In either case of a saturated alkyl group or an unsaturated alkyl group, since it is an alkyl group, R ₅ and R ₆ of the phosphite compound do not contain a polar group.

Examples of the saturated alkyl group include a lauryl group, a myristyl group, a cetyl group, and a stearyl group. Moreover, an oleyl group etc. are mentioned as an example of an unsaturated alkyl group. R ₃ , R ₄ , R ₅ and R ₆ may all be the same alkyl group or different alkyl groups. Alternatively, some of R ₃ , R ₄ , R ₅ and R ₆ may be composed of the same alkyl group, and the rest may be composed of different alkyl groups. As the phosphite compound and / or phosphate compound used as the material of (B), one type may be used, or a plurality of types of phosphite compounds and / or a plurality of phosphate compounds may be used. You may mix and use.

  Specific examples of the phosphite compound used as the material of (B) include dilauryl hydrogen phosphite, distearyl hydrogen phosphite, dioleyl hydrogen phosphite and the like. Examples of the phosphoric acid ester compound used as the material (B) include lauryl acid phosphate and oleyl acid phosphate.

  The blending amount of (B) is preferably 0.01% by mass or more and 5.0% by mass or less, and more preferably 0.1% by mass or more and 5.0% by mass or less with respect to the mass of the base oil. In addition, (B) will exhibit an effect if 0.01 mass% is mix | blended, and will exhibit a sufficient effect by mix | blending 0.1 mass%. Further, even if the blending amount exceeds 5.0% by mass, the same effect is exhibited, but from the viewpoint of maintaining good solubility in the base oil, the blending amount is preferably 5.0% by mass or less. .

In the secondary amide compound represented by Chemical Formula 1 which is a material of (C), as described above, both R ₁ and R ₂ of Chemical Formula 1 represent a saturated or unsaturated alkyl group having 8 to 24 carbon atoms. Show. However, from the viewpoint of good solubility in base oil, the number of carbon atoms of these alkyl groups is more preferably 12 or more and 22 or less. Examples of such alkyl groups include lauryl group, myristyl group, cetyl group, stearyl group and the like. Examples of the alkenyl group include oleyl group and erucyl group. R ₁ and R ₂ may be the same alkyl group or different alkyl groups.

  Such a secondary amide compound promotes a reaction in which the phosphite ester or phosphate ester, which is the material of (B), releases protons (hydrogen). Thus, it is considered that the material (B) ionized by releasing protons is stably adsorbed on the surface of the piston rod to form an adsorption film. This adsorption film functions to reduce the coefficient of friction between the oil seal and the piston rod, and this function is considered to be maintained even when the temperature changes.

When a polar group is present in R ₁ or R ₂ of the secondary amide compound that is the material of (C), the material of (B) has no effect of accelerating the reaction of releasing protons. The material (B) is not ionized and the adsorption film is not stably formed. That is, it is a requirement that R ₁ and R ₂ of the secondary amide compound that is the material of (C) do not contain a polar group.

  Specific examples of the material (C) include N-lauryl lauric acid amide, N-lauryl stearic acid amide, N-lauryl oleic acid amide, N-lauryl erucic acid amide, N-stearyl lauric acid amide, N-stearyl. Examples include stearic acid amide, N-stearyl oleic acid amide, N-stearyl erucic acid amide, N-oleyl lauric acid amide, N-oleyl stearic acid amide, N-oleyl oleic acid amide, N-stearyl stearic acid amide and the like.

  The blending amount of (C) is preferably 0.01% by mass or more and 2.0% by mass or less, and more preferably 0.05% by mass or more and 0.1% by mass or less with respect to the mass of the base oil. preferable. In addition, (C) will exhibit an effect, if it mix | blends 0.01 mass%, and will exhibit a sufficient effect by mix | blending 0.05 mass%. Further, even if the blending amount exceeds 0.1% by mass, the same effect is exhibited, but from the viewpoint of maintaining good solubility in the base oil, the blending amount is preferably 0.2% by mass or less. .

  With respect to the hydraulic fluid for a hydraulic device according to the present invention, additives may be blended within a range that does not impair the effect. Specific additives include antiwear agents, oiliness improvers, antioxidants, ashless dispersants, metal dispersants, viscosity index improvers, pour point depressants, metal deactivators, and rust inhibitors. , And an antifoaming agent.

  Among these, the hydraulic fluid for a hydraulic device according to the present invention is one or more kinds selected from an antioxidant, an ashless dispersant, a metal dispersant, a viscosity index improver, a rust inhibitor, and an antifoaming agent. It is preferable to include an additive.

  Examples of the antiwear agent include zinc dithiophosphate and derivatives thereof, sulfur compounds and derivatives thereof, molybdenum disulfide and derivatives thereof, and the like.

  Examples of oiliness improvers include aliphatic alcohols and derivatives thereof, fatty acid esters and derivatives thereof, fatty acids and derivatives thereof, amine compounds and derivatives thereof, and the like.

  Examples of the antioxidant include amine antioxidants and derivatives thereof, phenol antioxidants and derivatives thereof, sulfur antioxidants and derivatives thereof, carbamate antioxidants and derivatives thereof.

  Examples of the ashless dispersant include succinimide and derivatives thereof, benzylamine and derivatives thereof, esters and derivatives thereof, and the like.

  Examples of the metal dispersant include calcium salicylate and derivatives thereof, calcium phenate and derivatives thereof, calcium sulfonate and derivatives thereof, potassium borate and derivatives thereof, and the like.

  Examples of the viscosity index improver include polymethacrylate and derivatives thereof, polyisobutylene and derivatives thereof, olefin copolymers and derivatives thereof, and the like.

  Examples of the pour point depressant include polymethacrylate and derivatives thereof, polybutene and derivatives thereof, polyalkylstyrene and derivatives thereof.

  Examples of metal deactivators include benzotriazole and its derivatives, thiadiazole and its derivatives.

  As the rust inhibitor, imidazole and its derivatives, benzotriazole and its derivatives, thiadiazole and its derivatives, etc. are used.

  Examples of the antifoaming agent include silicone antifoaming agents and derivatives thereof, polyacrylate antifoaming agents and derivatives thereof, and the like.

  Next, a configuration of a hydraulic device using hydraulic fluid for a hydraulic device according to the present invention will be described with reference to the drawings. Here, a multi-cylinder automobile hydraulic shock absorber will be described as an example of the hydraulic device.

  FIG. 1 shows a cross-sectional view of an automobile hydraulic shock absorber 100 as an embodiment of the present invention as an embodiment of the present invention. The automobile hydraulic shock absorber 100 is a double cylinder type, and includes a cylinder 1 including a cylindrical outer cylinder 11 having a bottom portion, an inner cylinder 12 provided coaxially with the outer cylinder 11 inside the outer cylinder 11, and a cylinder. 1 and a piston rod 2 that is movable relative to 1. Hydraulic oil 3 for hydraulic device and gas for volume compensation are injected into the inside of the inner cylinder 12 and the reservoir chamber C between the inner cylinder 12 and the outer cylinder 11.

  With respect to the piston rod 2, the piston 4 is fixed to one end side inserted into the inner cylinder 12, and the other end is disposed so as to protrude from the cylinder 1. The outer peripheral portion of the piston 4 is slidably fitted to the inner surface of the inner cylinder 12. A bottom valve 5 is fixed to the lower end of the inner cylinder 12, and a rod guide 6 that slidably guides the piston rod 2 is fixed to the upper end of the inner cylinder 12. A through hole is provided in the center of the rod guide 6, and the piston rod 2 is inserted into the through hole. An oil seal 7 is fixed to the upper part of the outer cylinder 11, and the inside of the outer cylinder 11 is sealed through the oil seal 7. The oil seal 7 and the piston rod 2 are fitted together, whereby the oil seal 7 prevents the hydraulic device hydraulic oil 3 from leaking out of the cylinder 1 through the gap between the piston rod 2 and the rod guide 6. .

  As can be seen from FIG. 1, in the hydraulic shock absorber 100 for an automobile, the piston 4 separates the inside of the inner cylinder 12 into an oil chamber A and an oil chamber B. Further, the bottom valve 5 separates the reservoir chamber C and the oil chamber A between the inner cylinder 12 and the outer cylinder 11. The piston 4 is provided with a damping force generating mechanism 8 having a valve. The damping force generation mechanism 8 has a small cross-sectional area between the oil chamber A and the oil chamber B when the piston rod 2 moves to the extension side (the piston rod 2 moves upward in FIG. 1) and the valve opens. A predetermined damping force is generated by forming a flow path and restricting the flow of the hydraulic fluid 3 for the hydraulic device. The bottom valve 5 is provided with a damping force generation mechanism 9. The damping force generation mechanism 9 is configured by a small cross-sectional flow path formed in the bottom valve 5. When the piston rod 2 moves to the contraction side (the piston rod 2 moves downward in FIG. 1), the hydraulic device hydraulic oil 3 in the oil chamber A flows into the reservoir chamber C through the small cross-sectional area flow path. By doing so, a damping force is generated.

Next, examples according to the present invention will be specifically described.
(1) Reciprocating friction test In order to estimate the frictional force generated between the oil seal 7 and the piston rod in a hydraulic system, tests were performed on hydraulic system hydraulic fluids of various blend compositions using a reciprocating friction tester. It was. As a reciprocating friction tester, a Bauden tester HEIDON-14D type manufactured by Shinto Kagaku Co., Ltd. was used. FIG. 2 shows an outline of a test method using the reciprocating friction tester 200. The reciprocating friction test machine 200 is arranged so as to be movable relative to the first test tool on the first test tool and the table 21 that reciprocates, the first test tool placed on the table 21. And a load applying unit 22 for applying a load to the first test tool via the second test tool. A first test tool is fixed to the table 21, and a second test tool is fixed to the load application unit 22.

  The first test tool was made of a chrome-plated carbon steel plate, which is the same material as the piston rod, and the second test tool was made of nitrile butadiene rubber, which is the same material as the oil seal. The hydraulic fluid for hydraulic device is interposed between the first test tool and the second test tool, and the table 21 is reciprocated in this state to measure the dynamic friction between the first test tool and the second test tool. did. As hydraulic oil for hydraulic equipment, the various frictional compositions shown in FIG. 3 are used in sequence, and the dynamic friction between the first test tool and the second test tool when the hydraulic oil for hydraulic equipment is used. The coefficient was measured. The hydraulic fluid for hydraulic devices having the above-mentioned various blending compositions was evaluated by regarding the above test results as corresponding to the frictional force between the piston rod and the oil seal.

The conditions of the reciprocating friction test are as follows.
Test machine name: Bowden test machine HEIDON-14D type 1st test tool material: Chromium-plated carbon steel plate 2nd test tool material: nitrile butadiene rubber [Test conditions]
Test temperature: 20 ° C and 60 ° C
Applied load of load application part: 20N
Table operating amplitude: 10 mm
Table speed: 2 mm / sec

  FIG. 3 shows the value of the dynamic friction coefficient measured under each condition and the ratio of the dynamic friction coefficient at the test temperature of 20 ° C. to the dynamic friction coefficient at the test temperature of 60 ° C. As can be seen from the test results for Examples 1 to 16 shown in FIG. 3, the dynamic friction coefficient measured by the reciprocating friction test was small for any hydraulic fluid. That is, the measured value of the dynamic friction coefficient at the test temperature of 20 ° C. is in the range of about 0.11 to 0.3, and the measured value of the dynamic friction coefficient at the test temperature of 60 ° C. is in the range of about 0.11 to 0.28. Met. Further, the ratio (dynamic friction coefficient ratio) between the measured value of the dynamic friction coefficient at the test temperature of 20 ° C. and the measured value of the dynamic friction coefficient at the test temperature of 60 ° C. is a value close to 1 (0.93 to 1. 16 range). That is, the difference between the dynamic friction coefficient at the test temperature of 20 ° C. and the dynamic friction coefficient at the test temperature of 60 ° C. is extremely small. From these results, in the hydraulic devices using the hydraulic fluid for hydraulic devices of Examples 1 to 16, the frictional force acting between the piston rod and the oil seal is small, and the fluctuation of the frictional force due to the temperature change is I understand that it is small.

  The hydraulic fluid for hydraulic device of Comparative Example 1 has a composition of only the base oil of (A), and none of the materials of (B) and (C) is blended. The test results for Comparative Example 1 were 0.894 at a test temperature of 20 ° C. and 0.414 at a test temperature of 60 ° C., showing a large value at any test temperature. The value of the dynamic friction coefficient ratio was 2.16, which was significantly different from 1.

  In the hydraulic fluid for hydraulic device of Comparative Example 2, the phosphite compound that is the material of (B) is blended with the base oil of (A), but the secondary amide compound that is the material of (C) is Not blended. The test results for Comparative Example 2 showed that the dynamic friction coefficient at a test temperature of 20 ° C. was 0.447, the dynamic friction coefficient at a test temperature of 60 ° C. was 0.152, and a relatively small dynamic friction coefficient at 60 ° C. The coefficient of dynamic friction at ℃ was large. As a result, the dynamic friction coefficient ratio was 2.94, which was significantly different from 1.

  In the hydraulic fluid for hydraulic device of Comparative Example 3, the secondary amide compound that is the material of (C) is blended with the base oil of (A), but the phosphite compound that is the material of (B) and None of the phosphate ester compound is blended. The test results for Comparative Example 3 were 0.863 at the test temperature of 20 ° C. and 0.443 at the test temperature of 60 ° C., showing a large value at any test temperature. The value of the dynamic friction coefficient ratio was 1.95, which was significantly different from 1.

  In the hydraulic fluid for hydraulic devices of Comparative Examples 4 to 6, although the phosphite compound which is the material of (B) is blended with the base oil of (A), the material of (C) is grade 2 Other amide compounds are blended. Test results for Comparative Examples 4 to 6 show that the dynamic friction coefficient at a temperature of 20 ° C. is about 0.43 to 0.46, the dynamic friction coefficient at a test temperature of 60 ° C. is about 0.13 to about 0.15, and at 60 ° C. Showed a small coefficient of dynamic friction, but the coefficient of dynamic friction at 20 ° C. was large. As a result, the dynamic friction coefficient ratio was 3 or more and 3.5 or less, which was significantly different from 1.

  As described above, when the hydraulic fluid for a hydraulic device according to the embodiment of the present invention is used in a hydraulic device, the dynamic friction coefficient between the oil seal and the piston rod shows a small value in a predetermined temperature range, and It can be seen that the variation of the dynamic friction coefficient with the temperature change is small.

(2) Sensory test by automobile equipped with automobile shock absorber Automotive shock absorber using hydraulic oil for hydraulic equipment having two blending compositions shown in Example 1 shown in FIG. 3 and Comparative Example 1 shown in FIG. The car that actually mounted the vehicle was moved and a sensory test was conducted on its ride comfort. Specifically, two testers who perform a sensory test board a vehicle equipped with an automobile shock absorber using hydraulic fluid for hydraulic equipment having the composition of Example 1, and vibrations caused by road surface unevenness. The degree of transmission was evaluated on a 5-point scale. Similarly, the vehicle was mounted on a vehicle equipped with a shock absorber for hydraulic equipment having the composition of Comparative Example 1, and an evaluation score of a maximum of 5 points was determined for the degree of transmission of vibration caused by road surface unevenness. . The higher the evaluation score (the higher the numerical value), the better the ride comfort. The average score of two testers was used as the final score. The result is shown in FIG.

  As shown in FIG. 5, the automobile equipped with the hydraulic shock absorber for hydraulic equipment shown in Example 1 is equipped with the automobile shock absorber filled with the hydraulic equipment hydraulic oil shown in Comparative Example 1. It is clear that the ride is superior to

  In addition, the same result as in the case of using the hydraulic fluid for hydraulic equipment of Example 1 is obtained also in the automobile equipped with the automotive shock absorber using the hydraulic fluid for hydraulic equipment of Examples other than Example 1. In addition, the same result as in the case of using the hydraulic fluid for hydraulic equipment of Comparative Example 1 can be obtained in the automobile equipped with the shock absorber for hydraulic equipment using the hydraulic fluid for hydraulic equipment of Comparative Examples other than Comparative Example 1.

  As described above, it is possible to provide a hydraulic fluid for a hydraulic device that has a small friction coefficient between the oil seal and the piston rod and that has a small temperature dependency, and further, the hydraulic fluid for the hydraulic device was used. A hydraulic device can be provided. An automobile equipped with a shock absorber for an automobile using hydraulic fluid according to the present invention has a desired damping force by the piston and the bottom valve because the friction coefficient between the piston rod and the oil seal is less likely to fluctuate due to temperature change. be able to. Therefore, the degree of transmission of vibrations due to road surface unevenness to the occupant is reduced, and good riding comfort is exhibited.

  The present invention is not limited to the embodiment described above. Specific constituent materials, parts, and the like may be changed without departing from the scope of the present invention. In addition, if the constituent elements of the present invention are included, a known technique can be added or replaced with a known technique. Furthermore, the hydraulic device is not limited to a shock absorber for an automobile, and may be used for a cylinder device adopted for a motorcycle or industrial equipment. Moreover, in embodiment, although the twin tube type which consists of an outer cylinder and an inner cylinder was shown, you may apply to a monotube type.

DESCRIPTION OF SYMBOLS 1 Cylinder 2 Piston rod 3 Hydraulic oil hydraulic oil 4 Piston 5 Bottom valve 6 Rod guide 7 Oil seal 8, 9 Damping force generation mechanism

Claims (10)

Base oil,
At least one of a phosphite compound and a phosphate compound,
A hydraulic fluid for hydraulic devices, comprising a secondary amide compound represented by Chemical Formula 1.

The hydraulic fluid for a hydraulic device according to claim 1,
The hydraulic fluid for hydraulic devices, wherein the saturated or unsaturated alkyl group of the secondary amide compound has 10 to 24 carbon atoms. The hydraulic fluid for a hydraulic device according to claim 1 or 2,
The hydraulic device hydraulic fluid, wherein the phosphite compound is represented by Formula 2, and the phosphate compound is represented by Formula 3.

The hydraulic fluid for a hydraulic device according to claim 3,
The hydraulic fluid for hydraulic devices, wherein the phosphite compound and the alkyl group in the phosphate compound have 12 to 18 carbon atoms. The hydraulic fluid for a hydraulic device according to claim 3 or 4,
The phosphite compound and the phosphoric acid ester compound are included in a total amount of 0.01% by mass or more and 5.0% by mass or less with respect to the base oil,
The secondary amide compound is a hydraulic fluid for a hydraulic device included in a range of 0.01% by mass to 2.0% by mass with respect to the base oil. The hydraulic fluid for a hydraulic device according to claim 5,
The phosphorous acid ester compound and the phosphoric acid ester compound are included in a total amount of 0.1% by mass or more and 5.0% by mass or less with respect to the base oil,
The secondary amide compound is a hydraulic fluid for a hydraulic device that is included in the range of 0.05% by mass to 0.1% by mass with respect to the base oil. A hydraulic device,
A hydraulic apparatus provided with the hydraulic fluid for hydraulic apparatuses as described in any one of Claims 1-6. The hydraulic device according to claim 7,
The hydraulic device includes a cylinder, a piston rod movable in the cylinder, and an oil seal fixed to the cylinder and sliding with the piston rod,
A hydraulic apparatus comprising the hydraulic apparatus hydraulic oil in the cylinder. The hydraulic device according to claim 8,
A hydraulic device, wherein at least part of the surface of the piston rod is plated with chromium. The hydraulic device according to claim 8 or 9, wherein
The hydraulic device is a shock absorber for an automobile.

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