JP2020132763A - Hydraulic pressure working fluid for work machine and work machine using same - Google Patents

Abstract

To provide a hydraulic pressure working fluid for a work machine which, even when working at a low-temperature environment using a working fluid filter, can suppress damage of a working fluid filter due to electric discharge, and work machine using the same.SOLUTION: The hydraulic pressure working fluid for a work machine contains a base oil and at least one compound selected from a compound represented by the formula (1), other ether, and an ester compound (in the formula (1), Ris an acyl group bearing an alkyl group or an alkene group having a carbon number of 8-18; one of the two Ris an acyl group bearing an alkyl group or an alkene group having a carbon number of 8-18, or hydrogen atom; the other Ris hydrogen atom).SELECTED DRAWING: None

Description

The present invention relates to a hydraulic fluid for a work machine and a work machine using the same.

In work machines such as hydraulic excavators and wheel loaders, hydraulic pressure is used as a power source when performing work, and hydraulic fluid is used to transmit pressure. The hydraulic fluid is pressurized by a hydraulic pump, the pressure and flow rate are adjusted by a hydraulic valve, and then sent to a hydraulic actuator that drives a part to perform work to transmit power. The hydraulic fluid that has completed power transmission is cooled by an oil cooler, impurities are filtered by a hydraulic oil filter, and then returned to the hydraulic oil tank.

As described above, the hydraulic fluid used for power transmission is composed of a base oil obtained by refining crude oil and a plurality of additives added to the base oil. Base oils are roughly classified into mineral oils and synthetic oils, and mineral oils are mainly used as hydraulic fluids for working machines. Additives include detergent dispersants, antioxidants, weight-resistant additives, rust inhibitors, corrosion inhibitors, metal deactivators, viscosity index improvers, pour point depressants, emulsifiers, anti-emulsifiers, and antifungal agents. , Solid lubricants, etc. are used for the purpose of improving the function.

When the hydraulic fluid is based on mineral oil, the electric conductivity is generally as low as several pS / m to several tens of pS / m at an oil temperature of 25 ° C. That is, hydraulic fluids based on mineral oil generally have insulating properties. Further, as the hydraulic oil filter, a filtration member formed of an organic material such as cellulose or an insulating material such as glass fiber may be used. Therefore, the filtration member of the hydraulic fluid and the hydraulic oil filter is charged by the flow resistance (friction) when the hydraulic fluid passes through the hydraulic oil filter.

In recent years, in work machines, the rated pressure of hydraulic pumps has been increased and the hydraulic oil tank has been downsized. Due to the high pressure of hydraulic pressure, there is a concern that foreign matter mixed in hydraulic fluid may cause equipment malfunction. Therefore, by making the filtration member of the hydraulic fluid filter finer, it is possible to further suppress the mixing of foreign matter into the hydraulic fluid. However, as the mesh of the filtration member is made finer, the flow resistance of the hydraulic fluid when passing through the hydraulic oil filter increases, and the charge amount of the hydraulic oil and the filtration member of the hydraulic oil filter increases. Further, as the hydraulic fluid tank is downsized, the amount of hydraulic fluid stored is reduced, and the circulation of hydraulic fluid tends to be accelerated accordingly. Therefore, the amount of charge per unit amount of hydraulic fluid tends to increase.

As described above, the amount of charge generated when the hydraulic fluid passes through the filtration member of the hydraulic oil filter tends to increase. When the filter members of the hydraulic fluid and the hydraulic oil filter are charged and the amount of accumulated charge increases, there is a concern that an electric discharge may occur in the hydraulic fluid filter.

In particular, when the work machine is used in a low temperature environment, there is a concern that an electric discharge may occur in the hydraulic oil filter. It is known that the kinematic viscosity of mineral oil increases as the temperature decreases. When the hydraulic fluid containing mineral oil is used in a low temperature environment, the kinematic viscosity of the hydraulic fluid is higher than that when it is used in a normal environment, so that the flow resistance of the hydraulic fluid is also increased accordingly. Therefore, the charge amount of the hydraulic oil and the filter member of the hydraulic oil filter tends to increase further, and there is a greater concern about the occurrence of electric discharge in the hydraulic oil filter. When an electric discharge occurs in the hydraulic oil filter, the hydraulic oil filter may be locally damaged due to its impact or heat generation.

As a means for suppressing damage to the hydraulic oil filter due to electric discharge, for example, there is a technique described in Patent Document 1. In the filter described in Patent Document 1, among a plurality of layers constituting a filter medium (filter member) for treating hydraulic oil, the first layer on the upstream side is composed of a material having a positive or negative potential with respect to the hydraulic oil. On the other hand, when the second layer on the downstream side is made of a material having a negative or positive potential opposite to that of the first layer with respect to the hydraulic oil, it flows through the first layer and the second layer of the filter medium. It is intended to reduce the charge of the hydraulic oil by at least partially neutralizing the charge generated in the hydraulic oil. Further, the filter is provided in the filter medium by providing a charge compensation layer that returns a part of the electric charge generated in the hydraulic oil to the filter medium on the downstream side of the filter medium, or by forming the filter medium with a conductive material. It is intended to reduce electric charge.

JP-A-2016-5836

However, in the filter described in Patent Document 1, when the hydraulic oil used in various work machines is different, it is necessary to select the materials for the first layer and the second layer of the filter medium according to the characteristics of the different hydraulic oil. There is. That is, different filter media are required depending on different hydraulic fluids, and it is difficult to apply the same filter medium for general purposes.

Further, the filter described in Patent Document 1 is intended to reduce the charge of the filter medium by installing a charge compensation layer or using a conductive filter medium. In this case, the charge of the filter medium is dissipated to the ground point through the filter housing containing the filter. That is, the filter housing is provided with a structure that dissipates the electric charge to the grounding point. On the other hand, the filter housing of the conventional hydraulic oil filter generally does not have such a structure. Therefore, in a conventional work machine equipped with a hydraulic oil filter, in order to prevent damage to the hydraulic oil filter due to electric discharge, the existing filter housing is modified by providing a structure for dissipating electric charges to the grounding point. , It is necessary to replace the existing filter housing with a filter housing having the structure.

In this way, when trying to suppress damage to the hydraulic oil filter due to electric discharge by the structure and structure of the hydraulic oil filter, it is necessary to complicate the structure and structure of the filter or to repair or replace the existing hydraulic oil filter. It happens. Therefore, as a method of suppressing damage to the hydraulic oil filter due to electric discharge, means from different viewpoints are required.

The present invention has been made based on the above matters, and an object of the present invention is to suppress damage to the hydraulic oil filter due to electric discharge even when working in a low temperature environment using an existing hydraulic oil filter. The purpose is to provide hydraulic hydraulic oil for work machines and work machines.

The present application includes a plurality of means for solving the above problems, and to give an example thereof, a base oil and a compound represented by the following general formula (1) and a compound represented by the general formula (2). It is characterized by containing at least one of these compounds.

In the formula (1), R ¹ is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms. One of the ^two R2s is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms, or a hydrogen atom. The other of the ^two R 2s is a hydrogen atom.

In the formula (2), one of the two R ^3, an acyl group having an alkyl group or alkene group having 8 to 18 carbon atoms. The other of the two R ³ is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms, or a hydrogen atom.

According to the present invention, the hydraulic fluid contains at least one compound of the compound represented by the general formula (1) and the compound represented by the general formula (2). The electrical conductivity is higher than when the above compound is not added. As a result, the amount of charge in the hydraulic fluid is reduced, so even when working in a low temperature environment using an existing hydraulic fluid filter, discharge from the hydraulic fluid filter is suppressed and damage to the hydraulic fluid filter is suppressed. Can be done.
Issues, configurations and effects other than those described above will be clarified by the description of the following embodiments.

It is the schematic which shows the structure of one Embodiment of the work machine provided with the hydraulic fluid for work machine of this invention. It is sectional drawing which shows the structure of the hydraulic oil filter which constitutes a part of one Embodiment of the work machine of this invention shown in FIG.

Hereinafter, a hydraulic fluid for a work machine and an embodiment of the work machine of the present invention will be described with reference to the drawings. In the present embodiment, a hydraulic excavator will be described as an example of a working machine.

[One Embodiment]
First, the configuration of an embodiment of the work machine of the present invention will be described with reference to FIG. FIG. 1 is a schematic view showing a configuration of an embodiment of a work machine provided with the hydraulic fluid for the work machine of the present invention. In FIG. 1, thick arrows indicate the flow direction of hydraulic fluid.

In FIG. 1, the hydraulic excavator 1 as a work machine is mounted on a self-propelled lower traveling body 2, an upper rotating body 3 rotatably mounted on the lower traveling body 2, and a front end portion of the upper rotating body 3. It is equipped with a work front 4 that is movably attached. The upper swing body 3 is swiveled by a swivel hydraulic motor 6 as a hydraulic actuator.

The lower traveling body 2 has crawler-type traveling devices 8 (only the left side is shown in FIG. 1) on both left and right sides. The left and right traveling devices 8 are each operated by a traveling hydraulic motor 9 as a hydraulic actuator.

The work front 4 is an articulated work device for performing work such as excavation work, and is composed of, for example, a boom 11, an arm 12, and a bucket 13 as a work tool. The base end side of the boom 11 is rotatably attached to the front end portion of the upper swing body 3. A base end portion of the arm 12 is rotatably attached to the tip end portion of the boom 11. A base end portion of the bucket 13 is rotatably attached to the tip end side of the arm 12. The boom 11, arm 12, and bucket 13 are operated by the boom cylinder 15, arm cylinder 16, and bucket cylinder 17 as hydraulic actuators, respectively.

A hydraulic oil tank 21, a hydraulic pump 22, a prime mover 23, a hydraulic valve 24, an oil cooler 25, a hydraulic oil filter 30, and the like are arranged inside the upper swing body 3. The hydraulic oil tank 21 is arranged on the suction side of the hydraulic pump 22, and the hydraulic valve 24 is arranged on the discharge side of the hydraulic pump 22. The hydraulic oil filter 30 is arranged on the upstream side of the hydraulic oil tank 21, and the oil cooler 25 is arranged on the upstream side of the hydraulic oil filter 30. The hydraulic circuit is composed of a hydraulic oil tank 21, a hydraulic pump 22, a hydraulic valve 24, a hydraulic actuator, an oil cooler 25, a hydraulic oil filter 30, and the like.

The hydraulic oil tank 21 stores hydraulic fluid, and an oil level gauge, an air breather, or the like can be attached to the hydraulic oil tank 21. The hydraulic fluid is supplied to the hydraulic actuator as pressure oil to transmit power. The hydraulic actuator is driven by the supply of pressure oil. As the hydraulic actuator, as described above, the boom cylinder 15 for operating the work elements 11, 12, and 13 of the work front 4, the arm cylinder 16, the hydraulic cylinder of the bucket cylinder 17, and the swivel hydraulic motor for swiveling the upper swivel body 3. 6. There is a traveling hydraulic motor 9 for traveling the hydraulic excavator 1.

The hydraulic pump 22 is a mechanism that applies pressure to hydraulic fluid and discharges it as pressure oil. As the hydraulic pump 22, a piston pump, a gear pump, a vane pump, a screw pump, a swash plate type axial piston pump, a sloping shaft type axial piston pump, a radial piston pump, or the like can be used. The prime mover 23 is a power source for the hydraulic pump 22, and is composed of an engine, an electric motor, and the like. The hydraulic valve 24 controls the direction and flow rate of the pressure oil supplied from the hydraulic pump 22 to the hydraulic actuator. The hydraulic valve 24 can be configured by combining a hydraulic control valve, a flow rate control valve, a directional control valve, and the like.

The oil cooler 25 cools the hydraulic fluid. The oil cooler 25 has an air-cooled type and a water-cooled type. For example, the oil cooler 25 is configured to exchange heat via a tube or fin made of a metal such as copper or aluminum. The hydraulic fluid filter 30 is a mechanism for ensuring cleanliness by filtering impurities contained in hydraulic fluid. A suitable hydraulic fluid filter can be selected according to the amount of hydraulic fluid used and the value of hydraulic pressure.

Next, the structure of the hydraulic oil filter according to the embodiment of the working machine of the present invention will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view showing the structure of a hydraulic oil filter that constitutes a part of an embodiment of the working machine of the present invention shown in FIG. In FIG. 2, the thick arrow indicates the flow direction of the hydraulic fluid.

In FIG. 2, the hydraulic fluid filter 30 includes a filter element 31 that filters hydraulic fluid. As the material of the filter element 31, an organic substance such as cellulose is generally used. The filter element 31 is, for example, a tubular one having a large number of folds formed by bending a cellulose filter paper. The filtration performance of the filter element 31 can be changed by selecting the density and roughness of the filter paper.

The hydraulic oil filter 30 is, for example, a cartridge type. Specifically, the filter element 31 is held by the element case 32 and the element case lid 33 provided on one side and the other side of the element case 32, and is a structure integrated with the element case 32 and the element case lid 33. Is forming. The filter element 31, the element case 32, and the element case lid 33 as an integral structure are housed in the filter case 34. The filter case 34 is, for example, a bottomed tubular container that opens on one side, and the opening is closed by the filter case lid 35. The filter case 34 forms a flow path through which hydraulic fluid flows. The filter case 34 is provided with an inflow port 36 into which hydraulic fluid flows in. The filter case lid 35 is provided with an outflow port 37 through which the cleaned hydraulic fluid flows out through the filter element 31.

The filter element 31 can be replaced by taking out the element case 32 from the filter case 34. The hydraulic oil filter 30 does not have a structure for grounding the filter case 34, for example.

Next, the flow of the hydraulic fluid according to the embodiment of the working machine of the present invention will be described with reference to FIGS. 1 and 2.

The hydraulic fluid in the hydraulic oil tank 21 shown in FIG. 1 is sucked and pressurized by the hydraulic pump 22 driven by the prime mover 23. The hydraulic hydraulic oil as the pressure oil discharged from the hydraulic pump 22 is controlled by the hydraulic valve 24 in the direction and flow rate, and then the boom cylinder 15, arm cylinder 16, bucket cylinder 17, swivel hydraulic motor 6, and so on. It is supplied to the traveling hydraulic motor 9 and the like. When the pressure oil (hydraulic hydraulic fluid) is supplied, the hydraulic actuator is driven to perform various operations of the hydraulic excavator 1.

For example, the work front 4 operates by supplying pressure oil to three hydraulic cylinders, a boom cylinder 15, an arm cylinder 16, and a bucket cylinder 17. Further, by supplying pressure oil to the swivel hydraulic motor 6, the upper swivel body 3 swivels in the left-right direction. Further, the hydraulic excavator 1 travels by supplying pressure oil to the traveling hydraulic motor 9.

The pressure oil (hydraulic hydraulic oil) discharged from the hydraulic actuator by driving the hydraulic actuator is cooled by the oil cooler 25 and then cleaned by the hydraulic oil filter 30. Specifically, the hydraulic hydraulic fluid flows into the filter case 34 through the inflow port 36 of the hydraulic oil filter 30 shown in FIG. 2, and is secondary from the primary side of the filter element 31 arranged in the filter case 34. Pass to the side. As a result, impurities such as sludge contained in the hydraulic fluid are removed. The hydraulic fluid that has passed through the filter element 31 flows out from the outlet 37 of the hydraulic oil filter 30, returns to the hydraulic oil tank 21 shown in FIG. 1, and is sucked into the hydraulic pump 22 again.

In this way, the hydraulic fluid circulates in the hydraulic circuit of the hydraulic excavator 1 and transmits power to the hydraulic actuator. The hydraulic fluid also functions as a lubricating oil for lubricating sliding points in the hydraulic pump 22 and the hydraulic actuator.

When the hydraulic fluid passes through the filter element 31 of the hydraulic oil filter 30, both the hydraulic fluid and the filter element 31 are charged by the flow resistance (friction).

In recent years, in work machines, the rated pressure of the hydraulic pump 22 has been increased and the hydraulic oil tank 21 has been downsized. Due to the increase in hydraulic pressure, there is a concern that the hydraulic pump 22, the hydraulic valve 24, the hydraulic actuator, and other devices may malfunction due to foreign matter mixed in the hydraulic fluid. Therefore, by making the mesh of the filter element 31 of the hydraulic fluid filter 30 finer, it is possible to further suppress the mixing of foreign matter into the hydraulic fluid. However, as the mesh of the filter element 31 is made finer, the flow resistance (friction) of the hydraulic fluid when passing through the filter element 31 increases, and the charge amount of the hydraulic fluid and the filter element 31 increases. Further, as the hydraulic fluid tank 21 is downsized, the amount of hydraulic fluid stored is reduced, so that the circulation of hydraulic fluid tends to be accelerated. Therefore, the amount of charge per unit amount of hydraulic fluid tends to increase.

In this way, the hydraulic fluid and the charge amount of the filter element 31 tend to increase. When the hydraulic fluid and the filter element 31 are charged and the amount of accumulated charge increases, there is a concern that an electric discharge may occur in the hydraulic fluid filter 30.

In particular, when the hydraulic excavator 1 is used in a low temperature environment, there is a concern that an electric discharge may occur in the hydraulic oil filter 30. The hydraulic fluid used in the hydraulic excavator 1 generally increases in its kinematic viscosity as the temperature decreases. When the hydraulic fluid is used in a low temperature environment, the kinematic viscosity of the hydraulic fluid increases as compared with the case of using it in a normal environment, so that the flow resistance of the hydraulic fluid also increases accordingly. Therefore, the charge amounts of the hydraulic fluid and the filter element 31 tend to increase further, and there is a greater concern about the occurrence of electric discharge in the hydraulic fluid filter 30. When an electric discharge occurs in the hydraulic oil filter 30, the hydraulic oil filter 30 may be locally damaged due to its impact or heat generation.

Therefore, the hydraulic fluid according to the present embodiment is configured to contain a compound different from the conventional hydraulic fluid in order to suppress damage to the hydraulic fluid filter 30 due to electric discharge.

Next, the composition of one embodiment of the hydraulic fluid for work machines of the present invention will be described. The hydraulic fluid for work machines (hereinafter referred to as hydraulic fluid) contains a base oil and an additive.

As the base oil, mineral oil obtained by refining crude oil and synthetic oil synthesized from crude oil or the like as a raw material can be used. Generally, mineral oil is used from the viewpoint of cost and the like. Mineral oils are classified into Group I to Group III (classified by the American Petroleum Institute (API)) according to the refining method from crude oil, the amount of residual sulfur, the ratio of saturated hydrocarbons, and the like. Mineral oil has low electrical conductivity and has insulating properties.

The hydraulic fluid according to the present embodiment contains at least one compound represented by the following general formula (1) and the compound represented by the general formula (2) as an additive to the base oil. It is a thing.

In the formula (1), R ¹ is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms. One of the ^two R2s is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms, or a hydrogen atom. The other of the ^two R 2s is a hydrogen atom.

In the formula (2), one of the two R ^3, an acyl group having an alkyl group or alkene group having 8 to 18 carbon atoms. The other of the two R ³ is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms, or a hydrogen atom.

The compounds represented by the general formulas (1) and (2) are organic substances. This is intended to be free of metallic components that are the source of sludge. Further, the acyl group contained in the general formula (1) and the general formula (2) functions as a parent oil group that enhances the solubility in the base oil. The hydroxyl groups contained in the general formula (1) and the general formula (2) function as hydrophilic groups that adsorb water.

In the present embodiment, the hydraulic fluid contains at least one compound of the compound represented by the general formula (1) and the compound represented by the general formula (2). The electrical conductivity of is larger than that in the case where the above compound is not added. As a result, the amount of charge in the hydraulic fluid is reduced, so that even when working in a low temperature environment using the existing hydraulic fluid filter, the discharge in the hydraulic fluid filter 30 (see FIG. 2) is suppressed and the operation is performed. Damage to the oil filter 30 can be suppressed.

In the hydraulic hydraulic oil, at least one of R ¹ and R ^{2 in} the general formula (1) is an oleoyl group (acyl group having an alkene group having 18 carbon atoms) or a stearoyl group (alkyl having 18 carbon atoms). compounds represented by the general formula is an acyl group) having a group (1), and the general formula is a two at least one oleoyl group or a stearoyl group of R ³ in the general formula (2) (2 ), It is preferable that at least one of the compounds is added. Acyl groups having 18 carbon atoms tend to have higher electrical conductivity of hydraulic fluids than acyl groups having less than 18 carbon atoms.

As the acyl group of R ¹ and R ^{2 in} the general formula (1), an octanoyl group (acyl group having an alkyl group having 8 carbon atoms), a lauroyl group (acyl group having an alkyl group having 12 carbon atoms), and the like. A myritoyl group (acyl group having an alkyl group having 14 carbon atoms), a palmitoyl group (acyl group having an alkyl group having 16 carbon atoms) and the like are possible. Further, a palmitre oil group (acyl group having an alkene group having 16 carbon atoms) and the like are also possible. Acyl group R ³ in the general formula (2) is similar.

Also, the hydraulic fluid is a compound in which two R ² is represented by the general formula (1) is a hydrogen atom in the general formula (1), and the two R in the general formula (2) It is preferable to add at least one of the compounds represented by the general formula (2) in which one of ³ is a hydrogen atom. Since a large number of hydroxyl groups as hydrophilic groups are present, the rate of increase in electrical conductivity with respect to hydraulic fluid to which the compound is not added tends to increase.

The hydraulic fluid described above includes a compound represented by the general formula (1) in which one of the ^two R2s in the general formula (1) is an acyl group, and two Rs in the general formula (2). It is possible to add at least one of the compounds represented by the general formula (2) in which ³ is an acyl group.

The blending amount of the compound represented by the general formula (1) and the compound represented by the general formula (2) is 0.2% by mass or more and 0.4% by mass or less with respect to the mass of the base oil. Is preferable. Since the above compound is an additive, it is required to improve the electric conductivity by adding a small amount.

Further, the hydraulic fluid is electrically conducted at an oil temperature of 25 ° C. by adding at least one compound of the compound represented by the general formula (1) and the compound represented by the general formula (2). The rate is preferably 400 pS / m or more. A hydraulic fluid having an electric conductivity of 400 pS / m or more at an oil temperature of 25 ° C. can prevent damage to the hydraulic fluid filter due to electric discharge during operation of a work machine in a low temperature environment.

By the way, the hydraulic fluid used in the hydraulic excavator 1 is repeatedly heated by pressurization by the hydraulic pump 22, flow rate control by the hydraulic valve 24, and cooling by the oil cooler 25. In a hydraulic fluid containing at least one of the compound represented by the general formula (1) and the compound represented by the general formula (2), the electrical conductivity is significantly reduced due to repeated heating and cooling. It has been confirmed that there is no such thing.

In the hydraulic fluid according to the present embodiment, additives that supplement various functions that are insufficient only with the base oil can be blended within a range that does not impair the above effects. Typical examples are cleaning dispersants, antioxidants, load-bearing additives, rust inhibitors, corrosion inhibitors, metal deactivators, viscosity index improvers, pour point depressants, emulsifiers, defoamers, anti-virus. Examples include emulsifiers, anticorrosive agents, solid lubricants and the like.

Use an organic acid metal compound, a neutral / hyperbasic metal, a perbasic metal sulfonate, a perbasic metal phenate, a perbasic metal sulfonate, a succinimide, a succinate, a benzylamine, etc. Can be done.

As the antioxidant, zinc dithiophosphate, an organic sulfur compound, hindered phenol, aromatic amine and the like can be used.

As the load-bearing additive, long-chain fatty acids, fatty acid esters, higher alcohols, alkylamines, phosphate esters, zinc dithiophosphates, organic sulfurs, phosphorus compounds, organic halogen compounds and the like can be used.

As the rust preventive, carboxylic acid, sulfonate, phosphate, alcohol, ester and the like can be used.

As a corrosion inhibitor, a nitrogen-containing compound, zinc dithiophosphate, or the like can be used.

A nitrogen-containing compound can be used as the metal inactivating agent.

As the viscosity index improver, polymethacrylate, olefin copolymer, styrene-olefin copolymer, polyisobutylene and the like can be used.

As the pour point lowering agent, polymethacrylate, an alkylated aromatic compound, a fumarate / vinyl acetate copolymer, an ethylene / vinyl acetate copolymer and the like can be used.

As the emulsifier, ethylene oxide adducts, esters, carboxylates, sulfate esters, sulfonates, phosphate esters, amine derivatives, quaternary ammonium salts and the like can be used.

As the defoaming agent, polymethylsiloxane, silicate, organic fluorine compound, metal soap, fatty acid ester, phosphoric acid ester, higher alcohol, polyalkylene glycol and the like can be used.

As the anti-emulsifier, ethylene oxide adduct, ethylene oxide / propylene oxide block polymer, quaternary ammonium salt and the like can be used.

As the antifungal agent, a phenol compound, a formaldehyde donor compound, a salicyrianilide compound and the like can be used.

As the solid lubricant, molybdenum disulfide, tungsten disulfide, graphite, boron nitride, tetrafluoroethylene polymer, graphite fluoride, fullerene and the like can be used.

Next, the compositions of Examples 1 to 10 and the effects thereof of the hydraulic fluid for work machines of the present invention will be described with reference to Table 1 while comparing with Comparative Examples 1 and 2. Table 1 shows the composition, the measurement result of the electric conductivity, and the result of the damage test of the hydraulic fluid filter in Examples 1 to 10 of the hydraulic fluid for work machinery of the present invention and Comparative Examples 1 and 2 with respect to the example. Is.

The electric conductivity of the hydraulic fluids of Comparative Examples 1 and 2 and Examples 1 to 10 below was measured. The specific measurement method is as follows. The volume resistivity of the hydraulic fluid was measured by a method based on the electrically insulating oil test method described in JIS C2101. However, the measurement temperature was 25 ° C. instead of 80 ° C. The electrical conductivity of the hydraulic fluid was determined from the reciprocal of the volume resistivity of the measurement results.

In addition, a damage test of the hydraulic fluid filter due to the operation of the work machine was performed using the hydraulic fluids of Comparative Examples 1 and 2 and Examples 1 to 10 below. When the outside air temperature is low and the temperature of the hydraulic fluid is low, there is a concern that the hydraulic fluid filter may be damaged by electric discharge. Therefore, as a test condition, the work machine was started (starting the hydraulic pump) five times from a state where the temperature of the hydraulic fluid was low in a low temperature environment where the outside air temperature was 0 ° C. or less. After starting 5 times, it was confirmed whether or not the hydraulic oil filter was damaged. Damage testing of hydraulic fluid filters is by the same work machine. That is, the test was conducted under the same conditions as the rated pressure of the hydraulic pump, the capacity of the hydraulic oil tank, the configuration and structure of the hydraulic oil filter, and the configuration of the hydraulic circuit.

[Comparative Example 1]
In the hydraulic fluid of Comparative Example 1, as shown in Table 1, a group III mineral oil was used as the base oil. A cleaning dispersant, an antioxidant, a load-bearing additive, a viscosity index improver, an antifoaming agent, and an anti-emulsifier were used as additives for the base oil.

The measurement result of the electric conductivity of the hydraulic fluid of Comparative Example 1 was 90 pS / m (25 ° C.). Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Comparative Example 1, the hydraulic fluid filter was damaged.

[Comparative Example 2]
In the hydraulic fluid of Comparative Example 2, as shown in Table 1, a group II mineral oil was used as the base oil. The same type of additives as in Comparative Example 1 (cleaning dispersant, antioxidant, load-bearing additive, viscosity index improver, defoaming agent, and anti-emulsifier) were used as additives for the base oil. ..

The measurement result of the electric conductivity of the hydraulic fluid of Comparative Example 2 was 110 pS / m (25 ° C.). Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Comparative Example 2, the hydraulic fluid filter was damaged.

[Example 1]
In the hydraulic fluid of Example 1, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 (cleaning dispersant, antioxidant, load-bearing additive, viscosity index improver, defoaming agent, and anti-emulsifier) were added to the base oil. Further, as a further additive, sorbitan monooleate of the chemical formula (3) was added to the base oil at a concentration of 0.2% by mass. Sorbitan monooleate is a compound represented by the above general formula (1) in which R ¹ is an oleic acid group and two R ² are both hydrogen atoms.

The measurement result of the electric conductivity of the hydraulic fluid of Example 1 was 550 pS / m (25 ° C.). That is, the hydraulic fluid of Example 1 to which sorbitan monooleate was added had about 6.1 times the electric conductivity as that of the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Example 1, no damage occurred in the hydraulic fluid filter.

Based on the above results, by adding sorbitan monooleate to the base oil (mineral oil) of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the work machine operates in a low temperature environment. It was found that damage to the oil filter can be suppressed.

[Example 2]
In the hydraulic fluid of Example 2, as shown in Table 1, a group II mineral oil was used as the base oil. The same additives as in Comparative Example 2 (cleaning dispersant, antioxidant, load-bearing additive, viscosity index improver, defoaming agent, and anti-emulsifier) were added to the base oil. Further, sorbitan sesquioleate was added to the base oil at a concentration of 0.3% by mass as a further additive.

The measurement result of the electric conductivity of the hydraulic fluid of Example 2 was 460 pS / m (25 ° C.). That is, the hydraulic fluid of Example 2 to which sorbitan sesquioleate was added had about 4.2 times the electric conductivity as that of the hydraulic fluid of Comparative Example 2 to which the compound was not added. Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Example 2, no damage occurred in the hydraulic fluid filter.

Based on the above results, by adding sorbitan sesquioleate to the base oil (mineral oil) of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the working machine operates in a low temperature environment. It was found that damage to the oil filter can be suppressed.

[Example 3]
In the hydraulic fluid of Example 3, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 were added to the base oil. Further, sorbitan dioleate was added to the base oil at a concentration of 0.4% by mass as a further additive. Sorbitan dioleate is a compound in which R ¹ is an oleoil group and one of the two R ² is an oleoil group and the other is a water atom among the compounds represented by the above general formula (1).

The measurement result of the electric conductivity of the hydraulic fluid of Example 3 was 400 pS / m (25 ° C.). That is, the hydraulic fluid of Example 3 to which sorbitan dioleate was added had about 4.4 times the electric conductivity as that of the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 3, no damage was caused to the hydraulic oil filter.

Based on the above results, by adding sorbitan dioleate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can be suppressed.

[Example 4]
In the hydraulic fluid of Example 4, as shown in Table 1, a group II mineral oil was used as the base oil. The same additives as in Comparative Example 2 were added to the base oil. Further, as a further additive, the monooleic acid glyceride of the chemical formula (4) was added to the base oil at a concentration of 0.3% by mass. Glycerides monooleate, among the compounds represented by the above general formula (2), two one oleoyl group R ^3, a compound other is hydrogen atom.

The measurement result of the electric conductivity of the hydraulic fluid of Example 4 was 480 pS / m (25 ° C.). That is, the hydraulic fluid of Example 4 to which the monooleic acid glyceride was added had about 4.4 times the electric conductivity as that of the hydraulic fluid of Comparative Example 2 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 4, no damage occurred in the hydraulic fluid filter.

Based on the above results, by adding monooleic acid glyceride to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can suppress.

[Example 5]
In the hydraulic fluid of Example 5, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 were added to the base oil. Further, as a further additive, sorbitan monostearate of the chemical formula (5) was added to the base oil at a concentration of 0.2% by mass. Sorbitan monostearate is a compound represented by the above general formula (1) in which R ¹ is a stearoyl group and both R ² are hydrogen atoms.

The measurement result of the electric conductivity of the hydraulic fluid of Example 5 was 540 pS / m (25 ° C.). That is, the hydraulic fluid of Example 5 to which sorbitan monostearate was added had an electric conductivity about 6.0 times that of the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 5, no damage was caused to the hydraulic oil filter.

Based on the above results, by adding sorbitan monostearate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can suppress.

[Example 6]
In the hydraulic fluid of Example 6, as shown in Table 1, a group II mineral oil was used as the base oil. The same additives as in Comparative Example 2 were added to the base oil. Further, sorbitan sesquistearate was added to the base oil at a concentration of 0.3% by mass as a further additive.

The measurement result of the electric conductivity of the hydraulic fluid of Example 6 was 450 pS / m (25 ° C.). That is, the hydraulic fluid of Example 6 to which sorbitan sesquistearate was added had about 4.1 times higher electrical conductivity than the hydraulic fluid of Comparative Example 2 to which the compound was not added. Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Example 6, no damage occurred in the hydraulic fluid filter.

Based on the above results, by adding sorbitan sesquistearate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can suppress.

[Example 7]
In the hydraulic fluid of Example 7, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 were added to the base oil. Further, sorbitan distearate was added to the base oil at a concentration of 0.4% by mass as a further additive. Sorbitan distearate is a compound in which R ¹ is a stearoyl group and one of the two R ² is a stearoyl group and the other is a hydrogen atom among the compounds represented by the above general formula (1).

The measurement result of the electric conductivity of the hydraulic fluid of Example 7 was 410 pS / m (25 ° C.). That is, the hydraulic fluid of Example 7 to which sorbitan distearate was added had an electric conductivity about 4.6 times that of the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 7, no damage was caused to the hydraulic oil filter.

Based on the above results, by adding sorbitan distearate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can be suppressed.

[Example 8]
In the hydraulic fluid of Example 8, as shown in Table 1, a group II mineral oil was used as the base oil. The same additives as in Comparative Example 2 were added to the base oil. Further, monostearic acid glyceride was added to the base oil at a concentration of 0.3% by mass as a further additive. Monostearate glyceride, among the compounds represented by the above general formula (2), two one stearoyl group R ^3, a compound other is hydrogen atom.

The measurement result of the electric conductivity of the hydraulic fluid of Example 8 was 470 pS / m (25 ° C.). That is, the hydraulic fluid of Example 8 to which the monostearic acid glyceride was added had about 4.3 times the electric conductivity as that of the hydraulic fluid of Comparative Example 2 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 8, no damage was caused to the hydraulic fluid filter.

Based on the above results, by adding monostearic glyceride to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can suppress.

[Example 9]
In the hydraulic fluid of Example 9, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 were added to the base oil. Further, sorbitan monolaurate was added to the base oil at a concentration of 0.2% by mass as a further additive. Sorbitan monolaurate is a compound represented by the above general formula (1) in which R ¹ is an acyl group having an alkyl group having 12 carbon atoms and two R ² are both hydrogen atoms.

The measurement result of the electric conductivity of the hydraulic fluid of Example 9 was 530 pS / m (25 ° C.). That is, the hydraulic fluid of Example 9 to which sorbitan monolaurate was added had about 5.9 times higher electrical conductivity than the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic oil filter using the hydraulic hydraulic fluid of Example 9, no damage was caused to the hydraulic oil filter.

Based on the above results, by adding sorbitan monolaurate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can be suppressed.

[Example 10]
In the hydraulic fluid of Example 10, as shown in Table 1, a group III mineral oil was used as the base oil. The same additives as in Comparative Example 1 were added to the base oil. Further, sorbitan monooctanoate was added to the base oil at a concentration of 0.2% by mass as a further additive. Sorbitan monooctanoate is a compound represented by the above general formula (1) in which R ¹ is an acyl group having an alkyl group having 8 carbon atoms and two R ² are both hydrogen atoms.

The measurement result of the electric conductivity of the hydraulic fluid of Example 10 was 530 pS / m (25 ° C.). That is, the hydraulic fluid of Example 10 to which sorbitan monooctanoate was added had an electric conductivity about 5.9 times that of the hydraulic fluid of Comparative Example 1 to which the compound was not added. Further, in the damage test of the hydraulic fluid filter using the hydraulic hydraulic fluid of Example 10, no damage occurred in the hydraulic fluid filter.

Based on the above results, by adding sorbitan monooctanoate to the base oil of the hydraulic fluid, the electrical conductivity of the hydraulic fluid is increased, and the hydraulic fluid filter is damaged during operation of the work machine in a low temperature environment. It turned out that it can suppress.

[Other Embodiments]
The present invention is not limited to the present embodiment, and includes various modifications. The above-described embodiments have been described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the described configurations. It is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. It is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

For example, although an example in which the present invention is applied to a hydraulic excavator has been shown, the present invention can be widely applied to various work machines such as a hydraulic crane and a wheel loader in which a hydraulic actuator is driven by hydraulic fluid.

Further, in the above-described embodiment, an example of the configuration in which the filter element 31 of the hydraulic oil filter 30 is formed in a cylindrical shape is shown, but a hydraulic oil filter having a configuration including a plate-shaped filter element is also possible. Further, although an example in which cellulose is used as the material of the filter element 31 is shown, various materials such as glass fiber can also be used.

1 ... hydraulic excavator (working machine), 6 ... swivel hydraulic motor (hydraulic actuator), 9 ... traveling hydraulic motor (hydraulic actuator), 15 ... boom cylinder (hydraulic actuator), 16 ... arm cylinder (hydraulic actuator), 17 ... bucket Cylinder (hydraulic actuator), 30 ... Hydraulic oil filter

Claims (7)

Base oil and
A hydraulic hydraulic oil for a working machine, which comprises a compound represented by the following general formula (1) and at least one of the compounds represented by the general formula (2).

(In the formula (1), R ¹ is an acyl group having an alkyl group or an alkene group having 8 to 18 carbon atoms. One of the two R ² has an alkyl group or an alkene group having 8 to 18 carbon atoms. acyl groups having, or other of the .2 one R ² is a hydrogen atom, a hydrogen atom.)

(In the formula (2), one of the two ^{R 3,} the other is alkyl of 8-18 carbon atoms of .2 one ^{R 3} is an acyl group having an alkyl group or alkene group having 8 to 18 carbon atoms An acyl group having a group or an alkene group, or a hydrogen atom.) In the hydraulic fluid for work machines according to claim 1,
In the compound represented by the general formula (1), at least one of R ¹ and R ^{2 in} the general formula (1) is an oleoil group or a stearoyl group.
The compound represented by the general formula (2), the general formula (2) at least one work machine hydraulic working oil, which is a oleoyl group or a stearoyl group of the two R ³ in. In the hydraulic fluid for work machines according to claim 1,
Compound represented by the general formula (1), the two both R ² in the general formula (1) is a hydrogen atom,
The compound represented by the general formula (2), the general formula (2) one of the working machine hydraulic working oil, which is a hydrogen atom of the two R ³ in. In the hydraulic fluid for work machines according to claim 1,
Compound represented by the general formula (1) are two one acyl group R ² of the general formula (1),
The compound represented by the general formula (2), the general formula (2) two working machine hydraulic working fluid, wherein R ³ is an acyl group in. In the hydraulic fluid for work machines according to claim 1,
A hydraulic fluid for a work machine characterized by having an electric conductivity of 400 pS / m or more at an oil temperature of 25 ° C. In the hydraulic fluid for work machines according to claim 1,
The base oil is a hydraulic fluid for work machines, characterized in that it is a mineral oil. Hydraulic actuator and
The hydraulic fluid supplied to the hydraulic actuator to transmit power and
In a work machine provided with a hydraulic fluid filter for purifying the hydraulic fluid.
A work machine characterized in that the hydraulic fluid is the hydraulic fluid for a work machine according to claim 1.

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