JPH0521183B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to an evaluation method for evaluating the static oil film retention ability of a lubricant (lubricating oil, paste grease, etc.) and an apparatus for implementing the evaluation method. [Background Art] Various methods have been known to evaluate the performance of lubricants, such as a load-bearing capacity test, an oxidation stability test, and a viscosity test. In some cases, it was not possible to evaluate the performance of a lubricant that was suitable for the intended use. For example, when automatic control machine tools, which have been used in a wide variety of fields in recent years, are stopped for a long period of time (several hours or more) and then restarted, the lubricant used in the moving parts is This caused some moving parts to become thinner and unable to perform the desired movements, causing major problems in the entire manufacturing process. This is because the lubricant used in the moving parts of automatic control machine tools lacks the ability to maintain a static oil film (ability to maintain oil film adhesion in a stationary state). There is no evaluation method that allows for quantitative evaluation based on standards, and it has not been possible to obtain useful data when selecting lubricants for use in the moving parts of automatically controlled machine tools. Furthermore, it was not possible to obtain useful data for improving and developing lubricants. Furthermore, there are cases where it is necessary to quantitatively evaluate the ability of a lubricant to maintain a static oil film not only for lubricants used in movable parts of automatically controlled machine tools but also for other uses. [Object of the Invention] An object of the present invention is to provide an evaluation method and apparatus for quantitatively evaluating the static oil film retention ability of a lubricant. Note that the term "lubricant" as used herein includes all types of lubricants whose ability to retain an oil film is a problem, including lubricating oils, paste-like greases, and the like. [Structure of the Invention] Therefore, the evaluation method according to the present invention forms a thin film layer of lubricant between two sliding surfaces that are in an inclined state (in other words, a state in which the lubricant can flow down),
The objective is to be achieved by measuring the change over time in the thickness of the thin film layer when a predetermined load is applied between the two sliding surfaces. Further, the evaluation device according to the present invention includes a movable body having a conical first sliding surface with the apex side facing vertically downward, and a second sliding surface that is in close contact with the first sliding surface. a holder for holding the movable body, a thin film layer of lubricant is formed between the first and second sliding surfaces, and the vertical direction of the movable body when a predetermined load is applied to the movable body. detecting the displacement of the lubricant by a displacement detector, thereby making it possible to measure the change over time in the thickness of the thin film layer of lubricant formed between the first and second sliding surfaces; It is an attempt to achieve a goal. [Description of Examples] Examples of the present invention will be described below based on the drawings. FIG. 1 shows the overall configuration of an embodiment of a lubricant evaluation device according to the present invention. In the figure, a table 2 is fixed to a base 1 at a predetermined height position via legs 3, and a cylindrical holder 4 is erected on the table 2 with its central axis oriented vertically. A moving body 5 in the form of a shaft member is removably fitted into the holding body 4 and held therein. The movable body 5 is, for example, a plug gauge such as a Morse taper gauge, and a conical first sliding surface 6 whose apex side is directed vertically downward is formed around the movable body 5 . On the other hand, the cylindrical holder 4 is a ring gauge such as a Morse taper gauge, and its inner peripheral surface is a conical second sliding surface 7, and this second sliding surface 7 is a ring gauge of a Morse taper gauge. A thin film layer 8 of lubricant is formed between these sliding surfaces 6 and 7. Here, if the surface roughness of the sliding surfaces 6 and 7 is excessive, it becomes impossible to slide between the sliding surfaces 6 and 7, making it impossible to evaluate. From this point of view, the surface roughness is preferably 1 micron or less,
Furthermore, it is particularly preferable that the particle size is 0.5 micron or less. Further, the taper angle (apex angle) of the conical sliding surfaces 6 and 7 is preferably about 0.5 to 10 degrees, and particularly preferably 1 to 5 degrees. Further, a rod 9 of a predetermined length is fixed to the lower end of the movable body 5 along the virtual central axis of the movable body 5. The distal end of the rod 9 is loosely inserted into an insertion hole 11 made in the table 2, and a saucer 12 is attached to the distal end, and a weight 13 as a loading means is placed replaceably on the saucer 12. It is becoming more and more common. A probe 17 at the tip of a spindle 16 of a dial gauge 15 as a displacement detector is brought into contact with the upper end of the movable body 5, so that the displacement amount of the movable body 5 along the vertical direction is measured by the dial gauge 15. It's getting old. The dial gauge 15 is held via an arm 18 and a column 19 so that its height from the base 1 can be adjusted and can be attached and detached. Next, the operation of this embodiment will be explained. First, as a preliminary preparation, the movable body 5 is removed from the holder 4, and the first and second sliding surfaces 6, 7 are washed with a solvent and then dried. After drying, the moving body 5 is attached to the holding body 4.
gently insert the slider to bring the first sliding surface 6 into close contact with the second sliding surface 7, measure the position along the vertical direction of the moving body 5 at the time of close contact with the dial gauge 15, and use this as a reference point. I'll leave it as that. Next, the movable body 5 is removed from the holder 4 again, and lubricant is applied to each of the first sliding surface 6 and the second sliding surface 7 with a brush or the like, and the same procedure as in the case of determining the reference point is carried out. Then, the first sliding surface 6 is brought into close contact with the second sliding surface 7. Through such an operation, a thin film layer 8 of lubricant is formed between the first sliding surface 6 and the second sliding surface 7, and a receiving plate is further applied to apply a predetermined load to this thin film layer 8 of lubricant. A weight 13 is placed on 12. When the vertical displacement of the movable body 5 is measured over time using the dial gauge 15 while applying a predetermined load to the lubricant thin film layer 8, the displacement stops after approximately 30 minutes to 2 hours. Thereafter, there will be no displacement. FIG. 2 shows the change over time in the thickness t of the lubricant thin film layer 8 obtained by the above operations. Here, when the displacement amount of the movable body 5 along the vertical direction in the measurement stage when the reference position is 0 is 1, and the vertex angle of the first and second sliding surfaces 6 and 7 is 2θ. , the thickness t of the lubricant thin film layer 8, the displacement 1, and the apex angle 2θ have a relationship of t=1·sinθ, and the vertical axis in FIG. 2 is the displacement 1 using this equation. is converted into thickness t. Further, the following table shows a specific example of evaluation results obtained by such operations.

[Table] The measurement conditions are as follows. Moving body 5...Morse taper gauge No.3JIS-B-
3301, material is alloy tool steel SKS-3 Load amount...500g Surface roughness of first and second sliding surfaces 6, 7...0.2 microns Vertical angle 2θ of first and second sliding surfaces 6, 7... 2゜52′32″ Thin film layer of lubricant 8…Two types of lubricant A and lubricant B (both have viscosity at 40℃)
45cst) Room temperature...25℃ Note that the time it takes for the lubricant to reach the thin film layer 8 at equilibrium shown in the table (T _A , T _B ) is 2
It was hot around the hour. This embodiment has the following effects. None of the conventional evaluation methods were able to evaluate the static oil film retention ability of the lubricant, but in this example, the thickness (t _A , t _B ) of the thin film layer 8 of the lubricant at equilibrium is determined. By this, the ability of the lubricant to maintain a static oil film can be quantitatively evaluated. Therefore, for example, it is possible to select a lubricant suitable for controlled machine tools that have been used in a wide range of fields in recent years, and also to obtain useful data for the development of lubricants. Also, the time required to obtain evaluation results (T _A , T _B )
The evaluation time is usually about 30 minutes to 2 hours, which has the effect of shortening the evaluation time. Further, in the above embodiment, a Morse taper gauge specified by JIS (Japanese Industrial Standards) is used as the first sliding surface 6, and a ring gauge is also used as the holder 4.
Since the holding body 4 and the movable body 5 are extremely easy to obtain, it is easy to obtain quantitative values under certain standards. Furthermore, since a normal dial gauge 15 is used as a displacement detecting device, the structure is simple from this point of view as well, and there is no need for large-scale equipment, and the economic burden is small. In addition, in carrying out the evaluation, the evaluation is not limited to the thickness (t _A , t _B ) of the thin film layer 8 at the time of equilibrium (T _A , T _B ), but also the time taken to reach the equilibrium state (T _A , T B ).
T _B ) or the diagram shape shown in FIG. 2 may be used for evaluation. Further, the first sliding surface 6 and the second sliding surface 7 are not limited to conical shapes, but may be pyramidal shapes, or may be mere inclined surfaces, but may have a conical shape. If so, processing, handling, etc. are extremely easy, and furthermore, it is convenient because a Morse taper gauge or the like can be used as is. Further, the loading means is not limited to the weight 13, and a spring biasing means may be used, but the use of the weight 13 has the advantage that the load amount is stable and the structure is simple. Further, it is not always necessary to provide the weight 13 as a loading means in addition to the movable body 5, and the load may be applied using the own weight of the movable body 5. Furthermore, the displacement detector is the dial gauge 1.
5, a displacement detector that detects the amount of displacement using an electric or magnetic encoder may be used.
In such a case, the output signal may be used to cause an XY recorder or the like to directly draw a line diagram corresponding to the above-mentioned FIG. 2. [Effects of the Invention] As described above, according to the present invention, it is possible to provide a lubricant evaluation method and an evaluation device that can quantitatively evaluate the holding ability of a static oil film lubricant.

[Brief explanation of the drawing]

FIG. 1 is a partially cutaway front view showing the overall configuration of an embodiment of a lubricant evaluation device according to the present invention, and FIG. 2 is a diagram showing an example of the evaluation results according to the embodiment. 4... Holding body, 5... Moving body, 6, 7... First and second sliding surfaces, 8... Thin film layer of lubricant, 13
...Weight as a loading means, 15...Dial gauge as a displacement detector.

Claims (1)

[Claims] 1. Slanted so that lubricant can flow down 2.
forming a thin film layer of lubricant between the two sliding surfaces;
A method for evaluating a lubricant, the method comprising: measuring a change over time in the thickness of the thin film layer when a predetermined load is applied between two sliding surfaces. 2. A movable body having a conical first sliding surface with the apex side facing vertically downward, and a holder that holds the movable body by a second sliding surface that is in close contact with the first sliding surface. , a displacement detector that detects vertical displacement of the moving body when a predetermined load is applied to the moving body by forming a thin film layer of lubricant between the first and second sliding surfaces. A lubricant evaluation device characterized by: