JPH06136382A - Low-temperature hydraulic oil - Google Patents

Abstract

PURPOSE:To obtain a low-temperature hydraulic oil which consists mainly of an ultra-low-temp. hydraulic oil of the grade MIL H-5606E and is reduced in oiliness change (becoming tacky) during use and in adverse influence during use on the properties of a rubber seal. CONSTITUTION:The oil comprises an ultra-low-temp. hydraulic oil of the grade MIL H-5606E and a wear resistant hydraulic oil having a viscosity not lower than ISO VG 32.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a low temperature hydraulic oil.
More specifically, it relates to a low temperature hydraulic oil that can operate hydraulic equipment without trouble even at an extremely low temperature of -40 ° C or lower.

[0002]

2. Description of the Related Art For hydraulic equipment used in an extremely low temperature environment of -40 ° C or lower, a hydraulic oil of a type that has a small increase in oil viscosity even at an extremely low temperature is used in order to avoid equipment loss due to an increase in oil viscosity. Has been done. As a guideline, H5606E (U.S. military standard for mineral oil hydraulic oil for aircraft,
In most cases, equipment manufacturers select oil that has been used in aircraft, industrial machinery, ships, construction equipment, freezer, etc. and has the maximum feature of withstanding -60 ° C or less). .

As a result, in a device such as a hydraulic cylinder rod part in which the state of being immersed in oil and the state of being exposed to the atmosphere alternate, the exposure of the oil to the adhered oil causes Of the components, volatile components will be evaporated. When oil is exposed to the atmosphere, evaporation phenomenon is observed for any type of oil, but evaporation is more severe for oils of lower viscosity type, and as a result, the degree of change in the properties of oil increases.

When the oil equivalent to MIL H5606E is used in a hydraulic cylinder, it is exposed to the atmosphere with an oil film having a thickness of about 10 μm adhered to the hydraulic cylinder rod portion, so that the oil film dries and evaporates, resulting in a paste-like adhesion. It changes into a sexually charged state. As a result, the sliding resistance of the hydraulic cylinder increases significantly, and the energy loss of the hydraulic cylinder increases. In addition, the increased sliding resistance causes an increased load on the rubber seal, which causes wear and damage to the seal.

Further, MIL H5606E equivalent oil has a very large degree of swelling and softening a rubber seal, generally a nitrile rubber seal having an excellent low temperature property. In the case of a nitrile rubber seal, the use limit level is 15%. The above volume expansion is observed, which leads to a reduction in the strength of the rubber seal. As a result, not only the pressure resistance and durability of the rubber seal are lowered, but also the behavior of the rubber seal exceeds the prediction at the time of design due to swelling and softening, which often leads to oil leakage.

[0006]

The object of the present invention is to provide a MIL
To provide a low-temperature hydraulic oil whose main component is a cryogenic hydraulic oil equivalent to H5606E, which alleviates oil property changes (adhesion development) and deterioration of rubber seal physical properties during use. is there.

[0007]

The object of the present invention is as follows.
Achieved by a low temperature hydraulic oil consisting of a cryogenic hydraulic oil equivalent to MIL H5606E and an abrasion resistant hydraulic oil having a viscosity equal to or higher than ISO VG32 equivalent oil.

As the wear resistant hydraulic fluid having a viscosity equal to or higher than ISO VG32 equivalent oil, ISO VG32, ISO VG46, ISO VG56
Equivalent oil is used. These can be commercially available MIL H5606E equivalent oils, and the mixing ratio depends on the viscosity of the wear-resistant hydraulic fluid used.For example, in the case of ISO VG32, the volume ratio is about 4 to 6 times. Used in combination with MIL H5606E equivalent oil. If the volume ratio of the oil equivalent to MIL H5606E is increased more than this, the reforming effect aimed at by the present invention cannot be obtained. On the other hand, if the volume ratio is less than this, the original characteristics of the cryogenic hydraulic oil become difficult to be exhibited.

[0009]

[Effect of the invention] Cryogenic oil equivalent to MIL H5606E
The following effects can be achieved by mixing and using a wear resistant hydraulic fluid that is equivalent to ISO VG32 or higher. (1) Prevent alteration of MIL H5606E equivalent oil into a pasty state due to drying and evaporation of oil film (2) Reduce the increase in resistance of hydraulic equipment (3) Reduce deterioration of physical properties of rubber seal

[0010]

EXAMPLES Next, the effects of the present invention will be described with reference to examples.

Example A: Cryogenic oil (equivalent to MIL H5606E) Mobile Aero HFE B: Abrasion resistant hydraulic oil (equivalent to ISO VG32) Daphne Super Hydro # 32 Above A and B oils in various volume ratios After mixing, the following items were tested.

[Mixability (compatibility)] The mixed oil mixed at room temperature (21 ° C) is used at low temperature (-60 ° C) or high temperature.
The separation and dispersion state at (80 ℃) can be visually checked by putting it in a petri dish. AB (5: 1) mixed oil, AB (2: 1) mixed oil: normal temperature, low temperature,
Good at all high temperatures (no separation or dispersion) Regarding the fluidity at low temperatures, the AB (5: 1) blended oil is slightly lower than the A oil alone, but it has fluidity, and AB (2:
1) The mixed oil has no fluidity and becomes a solid grease.

[Amount of Evaporated Oil] Measure volume loss when left in a constant temperature bath of 80 ° C. for 24 hours. When the petri dish was open, both A oil and AB (5: 1) mixed oil were 50% petri dishes. A oil alone when the lid is covered with aluminum foil
10%, AB (5: 1) mixed oil 8%

[0014] [tackiness of the coating oil film in the axial] The oil film is applied by wiping the Hcr plated axis mixed oil absorption Wes, ambient temperature, elevated temperature, after each 12-hour standing at low temperature, check the adhesion at finger touch room temperature hot Low temperature A oil single substance Large stickiness Large stickiness (Medium stickiness) AB (5: 1) mixed oil Small stickiness Small stickiness (Medium stickiness) AB (10: 1) Mixed oil Small stickiness Small sticky Possibility (medium tackiness) Note) At low temperature, when the lid of the constant temperature bath is opened, frost is immediately formed on the shaft surface, so a clear difference cannot be judged with the fingers, but the oil film dries at a room temperature or higher. The oiliness change can be confirmed by the evaluation at normal temperature and high temperature.

[Sliding resistance] Using a packing sliding resistance measuring device, the test housing was filled with the test oil, the rod was stroked several times, and then the rod portion having the oil film adhered was left in the atmosphere by the stroke. After a certain period of time, measure the sliding resistance when the rod is stroked in the sliding resistance measurement direction (test conditions) Temperature: Room temperature (22 ° C) Pressure: Atmospheric pressure Speed: 25 mm / sec Stroke: 50 mm Leaving time: 0 , 12, 48, 72 (, 96) hours The measurement results are shown in the graph of FIG. from this result,
The sliding resistance of A oil increases almost as compared with the standing time, while the sliding resistance change of mixed oil containing 1/5 volume of B oil is slight and stable. I understand.

[Dip Test] A test O-ring packing (made of nitrile rubber for low temperature) having a cross-sectional shape shown in FIG.
Freely, in oil at 80 ° C in an open container without a lid
It was immersed for 96 hours, and the change in rubber hardness (JIS A) and the rate of change in volume before and after the immersion were measured. The results obtained are shown in the following table. Rubber hardness change (point) Volume change rate (%) [A oil] -9 +27.0 [AB (5: 1) mixed oil] -4 +9.4

[Brief description of drawings]

FIG. 1 is a graph showing measurement results of sliding resistance.

FIG. 2 is an end view showing the dimensions of the packing used in the immersion test.

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[Procedure amendment]

[Submission date] April 22, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0015

[Correction method] Change

[Correction content]

[Sliding resistance] Using a packing sliding resistance measuring device, the test housing was filled with the test oil, the rod was stroked several times, and then the rod portion with the oil film was left in the atmosphere by the stroke. After a certain period of time, measure the sliding resistance when the rod is stroked in the sliding resistance measurement direction (test conditions) Temperature: Room temperature (22 ° C) Pressure: Atmospheric pressure Speed: 25 mm / sec Stroke: 50 mm Leaving time: 0 , 12, 48, 72 (, 96) hours The measurement results are shown in the graph of FIG. from this result,
Sliding resistance of A oil increases almost in proportion to the standing time, while sliding resistance change of mixed oil containing 1/5 volume of B oil is slight and stable. I understand.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Figure 2

[Correction method] Change

[Correction content]

FIG. 2 shows the shape of the packing used in the immersion test.
FIG .

[Procedure 3]

[Document name to be corrected] Drawing

[Correction target item name] All drawings

[Correction method] Change

[Correction content]

[Figure 1]

[Fig. 2]

Claims (1)

[Claims] 1. A low temperature hydraulic oil comprising a cryogenic hydraulic oil equivalent to MIL H5606E and an abrasion resistant hydraulic oil having a viscosity equal to or higher than ISO VG32 equivalent oil.