JPH0370785B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a lubricant evaluation device, and more specifically, four steel balls are stacked in a so-called pyramid shape, and the bottom three steel balls and the top steel ball make frictional contact while rotating relative to each other. This paper relates to an improvement of a four-ball type evaluation device. Fatigue damage (pitting,
Various methods are known for evaluating the performance of lubricants used to prevent or reduce flaking, spalling, etc., but the four-ball test is the most common. For the four-ball test, the bottom three of four steel balls stacked in a pyramid shape are used.
The so-called normal four-ball test (JIS K-2519), in which two steel balls are brought into sliding friction contact with one steel ball above.
and the rolling four-ball test, in which one steel ball is rolled against three steel balls in frictional contact. All of these four-ball tests are relatively simple methods, but they have the drawback of requiring a long time to obtain evaluation results. This is thought to be due to the fact that conventionally all four steel balls had mirror surfaces, but in order to ensure correlation with the actual machine, all steel balls had surfaces with mirror surfaces. It was believed that the surface should be mirrored. However, as a result of extensive research by the present inventors, we have found that even if the surface of the steel ball is roughened, the correlation with the actual machine is not lost. The present invention has been made based on this knowledge. An object of the present invention is to provide a lubricant evaluation device that can ensure correlation with actual equipment and complete evaluation within a short time. Therefore, in the present invention, at least one of the four steel balls in the four-ball test device has a rough surface, without impairing the correlation with the actual machine. The objective is to be achieved by shortening the time required for damage to occur on the surface of the steel ball. Embodiments of the present invention will be described below based on the drawings. FIG. 1 shows a first embodiment of a lubricant evaluation apparatus according to the present invention. In the figure, a sample container 1 having a substantially cylindrical shape with a bottom is rotatably supported on a support base 3 via a rolling ball bearing 2, and a pressure mechanism 4 such as a hydraulic system is connected to the support base 3. There is. A seat plate 5 whose surface is polished with high precision is embedded in the bottom surface 1A of the sample container 1, and first to third steel balls 6 to 8 are arranged on the bottom surface 1A via the seat plate 5. There is. The first to third steel balls 6 to 8 are arranged in a substantially equilateral triangular shape within a substantially ring-shaped outer ring 9, and the outer ring 9 maintains the substantially equilateral triangular state while the bottom surface 1
It is possible to roll on A. Further, the outer ring 9 is fixed to the sample container 1 by an outer ring holder 11 which is fixed to the sample container 1 via a bolt (not shown). A fourth steel ball 12 is placed in the center of the steel balls 6 to 8 arranged in a substantially equilateral triangle shape.
8 and 12 are stacked in a pyramid shape.
The fourth steel ball 12 is fixed to the tip of the drive shaft 13 by a fixing ring 14. In addition, drive shaft 1
3 is connected to a rotational drive mechanism 15 such as a motor, and this rotational drive mechanism 15 drives the fourth steel ball 12.
is configured to rotate together with the drive shaft 13 while contacting each of the first to third steel balls 6 to 8. A predetermined amount of lubricant 16 is contained in the sample container 1, and the fourth steel ball 12 is in the first position in the lubricant 16.
- It is designed to come into contact with the third steel balls 6-8. Further, the lubricant 16 is supplied into the container 1 from the lubricant supply source 19 via the supply pipe 17 and the filter 18, and is discharged from the container 1 from the discharge pipe 20 and then returned to the lubricant supply source 19. It is beginning to be reverted to An acceleration detector 21 is provided at a predetermined position on the outer periphery of the sample container 1, and this acceleration detector 21 detects the magnitude of the rotational runout occurring in the rotating sample container 1, which is calculated by measuring the vibration acceleration along the radial direction of the container 1. It is configured so that it can be detected as a size. This acceleration detector 21 is connected to a recorder 23 and the rotation drive mechanism 15 via an amplifier 22, and the magnitude of the vibration acceleration is sequentially recorded on the recorder 23, and the magnitude of the vibration acceleration is set in advance. When the predetermined value is reached, the rotation of the rotary drive mechanism 15 is automatically stopped, and the time required at this time is recorded by a recorder 23. Here, to explain the surfaces of the steel balls 6 to 8 and 12, it is sufficient that at least one of the steel balls 6 to 8 and 12 has a rough surface. , 12 combinations of surface states are specifically listed as shown in Table 1.

[Table] Any combination shown in Table 1 may be used, but if you want to particularly shorten the time required to obtain an evaluation result, use the combinations 1 to 5 in the table above. Preferably, the first one,
Particularly preferred is the fourth and fifth combination. In addition, the degree of roughness on the rough surface is preferably 0.1 μm or more when expressed in root mean square roughness (Rrms), and among them, 0.1 to
A range of 0.5 μm is particularly preferred. Also, when expressed in maximum height (Rmax), it is 0.4μ
m or more, preferably 0.4
It is particularly preferable that the thickness is within the range of 2.0 μm. In addition, a mirror surface is 0.025μm or less in Rrms,
Rmax is usually 0.1 μm or less. Next, the evaluation method and effects of this example will be specifically explained using the following example. Experimental Examples 1 to 3 and Comparative Example The conditions common to Experimental Examples 1 to 3 and the comparative example are as follows. Sample container 1...Capacity 0.1. Steel balls 6 to 8, 12...Ball diameter 19.1mm (3/4in), hardness Rc
(Rockwell hardness C scale) 62, material SUJ
-2 (JIS G 4805 high carbon chromium bearing steel) is common. Rough surface Rrms0.3μm, Rmax1.5μ
m, mirror surface Rrms 0.025μm or less. Outer ring 9...Taper roller bearing outer ring lubricant 16...Mineral oil-based lubricating oil, oil temperature 56℃, viscosity
46cst, supply rate 200ml/min The above conditions are common to Examples 1 to 3 and Comparative Examples, but each Example 1 to 3 and Comparative Example differ in the combination of the rough surface and the mirror surface. Second
The combinations of Examples 1 to 3 in the table are shown in the first example above.
According to the indications in the table, the comparative example is a case in which all four steel balls have a mirror surface, and in other words, it is the same as the conventional rolling four-ball test. The evaluation method is to use the acceleration detector 21 to detect the vibrational acceleration (rotational vibration) in the radial direction of the sample container 1 due to pitting occurring on the contact surface of the steel ball 12, and when the acceleration level reaches 0.4G. The rotation drive mechanism 15 was automatically stopped and the time required from the start of the experiment was recorded, and this time was taken as the life time. The evaluation results thus obtained are shown in Table 2.

[Table] From the above results, it can be seen that according to this example, the time required to obtain evaluation results can be significantly shortened. Experimental Examples 4 to 6 Experimental Examples 4 to 6 were the same as Experimental Example 1 except that oil A, oil B, and oil C, which had different properties from the lubricating oil used in Example 1, were used as lubricants. I did it under the following conditions. The purpose of these Experimental Examples 4 to 6 is to confirm the correlation with the actual machine, and the evaluation test of the lubricant on the actual machine conducted here complies with the following conditions. Testing using an actual machine...This is an engine bench test. The surface fatigue damage of the tappet that transmits the cam motion to the valve train was evaluated. The engine used is a 6-cylinder overhead valve type, with a total displacement of 6000 c.c., and a rotation speed of
Full load operation was performed continuously for 100 hours at 3000 rpm. Also, the oil temperature is 110°C. The results thus obtained are shown in Table 3.

【table】

[Table] FIG. 2 shows the relationship between the average life (minutes) of each of Experimental Examples 4 to 6 and the overall score in an actual machine using the same lubricant. It can be seen from FIG. 2 and Table 3 above that this example has excellent correlation with the actual machine. Next, a second embodiment of the evaluation device according to the present invention will be described. Parts that are the same as or similar to those in the first embodiment will be denoted by the same reference numerals, and a description thereof will be omitted or simplified. FIG. 3 shows a second embodiment, and also in this second embodiment, the first to third steel balls 6 to 8 are connected to the drive shaft 1.
3 rotates, the bottom surface 1A passes through the fourth steel ball 12.
It is designed to roll on top. Further, a safety pin 31 is interposed between the sample container 1 and the container stand 30, and the safety pin 31 normally causes the sample container 1 and the container stand 30 to rotate synchronously.
At the center of the lower end of the container stand 30 is a torsion rod 3 that applies a predetermined rotational torque to the container stand 30 and therefore to the sample container 1 when the safety pin 31 is not broken.
2 is attached via a spline bearing 33, and the container stand 30 is rotatably supported on a pressurizing mechanism 34. When the drive shaft 13 is rotated, a rotation torque corresponding to the frictional force generated between the steel balls 6 to 8 and the steel ball 12 is transmitted to the sample container 1, and this rotation torque and the rotation torque generated by the torsion rod 32 in the opposite direction are transmitted to the sample container 1. The rotation of the sample container 1 stops at a position where the rotational torque of the sample container 1 is balanced.
The rotational torque at this time is detected by measuring the rotational displacement of the torsion rod 32 using a displacement meter 36 provided on the container stand 30. The lubricant 16 is evaluated based on the magnitude of the frictional force (ie, rotational torque), the tendency of the frictional force to change over time, or the time required to reach a predetermined frictional force. In this second embodiment, the rolling of the lubricant 16 -
The sliding friction characteristics and the like will be evaluated, and as in the first embodiment, the time required to obtain the evaluation results will be shortened and the correlation with the actual machine will be excellent. In addition, when evaluating the lubricant in practice, it is not limited to measuring the rotational runout and rotational torque of the sample container 1 as described above.
Measure the size of pitting marks and friction marks that occur on steel balls 6 to 8, 12, observe the surface conditions of steel balls 6 to 8, and 12, and determine the maximum (critical) load value without pitting, etc. ) Measuring the number of rotations, or measuring changes over time in the electric resistance value of the lubricant, etc. may be used, and various performances (characteristics) of the lubricant may be selected depending on the desired performance. In addition, the first to third steel balls 6 to 8 are placed in the sample container 1.
Alternatively, the fourth steel ball 12 may be fixed to and brought into sliding frictional contact with these, and in such a case, the sliding friction characteristics etc. will be evaluated. As described above, according to the present invention, it is possible to provide a lubricant evaluation device that can ensure correlation with actual equipment and complete evaluation within a short time.

[Brief explanation of drawings]

FIG. 1 shows a first diagram of a lubricant evaluation device according to the present invention.
FIG. 2 is a cross-sectional view showing the configuration of the embodiment; FIG. 2 is a diagram showing the correlation between the evaluation results of the embodiment and test results on an actual machine; and FIG. 3 is a cross-sectional view showing the configuration of the second embodiment. . 1... Sample container, 4, 34... Pressure mechanism, 6,
7, 8, 12... steel ball, 9... outer ring, 15... rotary drive mechanism, 16... lubricant, 21... acceleration detector, 30... container stand, 32... torsion rod, 36
...Displacement meter.

Claims (1)

[Scope of Claims] 1. A fourth steel that comes into frictional contact under a predetermined load in the lubricant with the first to third steel balls arranged in a substantially equilateral triangle shape in a sample container containing a lubricant. 1. A lubricant evaluation device equipped with balls, wherein at least one of the first to fourth steel balls has a rough surface. 2 In claim 1, the first to
A lubricant evaluation device characterized in that all of the third steel balls and at least one of the fourth steel balls have a rough surface. 3. In claim 1 or 2, the roughness of the rough surface is 0.1 μm or more when expressed as root mean square roughness, and 0.4 μm or more when expressed as maximum height. A lubricant evaluation device featuring: