JPS6124820A - Rolling bearing - Google Patents

Abstract

PURPOSE:To reduce the friction torque by lowering the ratio h/delta to 1 or less, where h is the thickness of oil film and delta at least one of the surface roughnesses, among those of the orbital surface of inner or outer ring or rolling surface of rolling body, which is made to be 0.3-0.5mum rms. CONSTITUTION:In this rolling bearing, taking notice of the tendency that the rolling friction becomes less in proportion to the increase of the value representing the surface roughness of rolling contact surface, the following means is taken. At least one of three surface roughnesses delta, that is, the roughness of orbital surface of inner or outer ring of rolling bearing or that of rolling surface of rolling body, is made to be 0.3-0.5mum rms, and the ratio of the thickness h of intervening oil film to the said roughness delta, h/delta, is made to be 1 or less.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to rolling bearings, particularly tapered roller bearings, self-aligning roller bearings, etc., which have low frictional torque and little temperature rise.

Long life, low friction torque, low noise in rolling bearings,
Low temperature rise, etc. are always a development goal, and among the above goals, low friction torque and low temperature rise are
Conventionally, improving the roughness of the raceway surfaces of the inner and outer rings of rolling bearings, as well as improving the roughness of the rolling surfaces of rolling elements, reduces the chance of metal contact between the two opposing surfaces and reduces dry friction. ,
It was believed that the above objectives could be achieved. Therefore, efforts in processing have been focused on how to improve the roughness.

However, while attempting various experimental analyses, the inventor began to think that the conventional wisdom that improving roughness would reduce friction torque and temperature rise was not necessarily correct. The purpose of this invention is to obtain rolling bearings such as tapered roller bearings, self-aligning roller bearings, and ball bearings that have low friction torque and low temperature rise. roughness,
Or, the roughness of at least one of the kings of roughness on the rolling surface of the rolling element is set to 0.3 to 0.511 mrmS,
This is a rolling bearing in which the ratio h/a of the thickness h of the intervening oil film to the roughness C is 1 or less.

The present invention will be described below with reference to graphs based on actually measured values, existing graphs, and the like.

Mechanisms of friction generation in rolling bearings include (1) rolling friction (including rolling resistance), (2) micro-friction within the rolling contact surface (friction of the contact area), and (4) lubricant. Among the above items, (3)
3. (Regarding item 41, the rotation is not very fast,
Under normal conditions where the food load is not large, the influence on friction is considered to be smaller than in terms (1) and (2), and the inventors believe that (Kyusuiji rolling friction in term 11) The friction moment (torque) T of a tapered roller bearing focusing on the slight rolling friction within the rolling contact surface in item (2) is given by MR, the rolling friction of the raceway, and MS, the friction of the second part, as follows: T=MR+Ms Therefore, the friction MS of the collar during rolling bearing rotation has been measured by Korean, 1);]1maz, etc., and as shown in Figure 1, J- It is known that it becomes weaker.

On the other hand, according to the inventor's research, it was found that the dynamic friction torque tends to increase as the rotation speed increases, except at low speeds, as shown in Fig. 2 (measurement bearing 32307C). However, by examining this Figure 2 and also considering the above-mentioned Figure 1, we have come to the conclusion that the dynamic friction torque is extremely influenced by the rolling friction MR.

Therefore, we decided to focus our research and development on how to reduce the rolling friction r-R, and first focused on two cylindrical bodies that made simple rolling contact. In this study, cylindrical bodies with contact surfaces of various roughness were prepared, and a pair of cylindrical bodies formed with the same phase was heated at a rate of 500 per minute using a two-cylinder testing machine.
The friction torque when rotating was measured. FIG. 3 is a graph of the measurement results, that is, a relationship diagram between the roughness of the rolling contact surface and the frictional torque.

According to FIG. 3, it is clear that rolling friction tends to decrease as the roughness value increases.

Figure 4 is a graph showing the measurement results of the rolling friction of a cylindrical body using two cylindrical measuring machines.
Select turbine oil (viscosity 55 cst) and 60 spindle oil (viscosity 15 c'st), measure the magnitude of friction of various phases, take the ratio of oil film thickness to roughness, and calculate the difference between this and rolling friction. It shows a relationship. It can be seen from FIG. 4 that as the ratio of oil film thickness to roughness decreases, rolling friction decreases.

By the way, according to 1.1i(L (elastic fluid vortex?l theory), rolling friction (viscous resistance) is expressed as l': f'(L
(13) This is caused by the viscous fluid (oil) present at the inlet of the part, and if the load and speed conditions are the same, the viscosity of the oil and the chaotic membrane pressure at the inlet of the contact part (as the pressure increases, the viscosity generally increases). It is determined by 4-ru).
If the conditions are the same, the oil film thickness h is constant. At this time, if the phase difference σ of the contact surfaces is small (approximately h/σ - 3), metal-to-metal contact will not occur, so the entire load will be supported by the oil film as shown in Figure 5a. c Fluid pressure is generated.

The diagram in Figure 5 shows the viscosity of 15 between the cylinders in rolling contact.
When the roughness of the contact surface of the cylindrical body is ff = 0.1-10.4.0.9 sm rms with the presence of spindle oil of cst, the maximum contact pressure Pmax = 40Kgf/fnr
The gHL contact contact day inlet side force P and oil film thickness h are calculated and illustrated when the rotational speed of the cylindrical body is given as n = 720°820 and 11080 rpm under a pressure such that n'. be.

Figures 5A and 5C are cases in which the roughness is larger than that in Figure 5A, and metal contact occurs, and a portion of the load is supported by the portion where the roughness peaks contact each other. These contact points are actually dispersed, but when averaged, it becomes as shown in the figure, and the fluid pressure is the total pressure minus the pressure in the shaded area. When this fluid pressure is Pf, the half width of the Ruth contact is b, the distance from the center of contact is X, and the thickness of the oil film is 11, the rolling friction Fr is expressed as:

As mentioned above, when the roughness increases, the fluid pressure Pf decreases, and if the fluid pressure Pf decreases, the rolling friction
It can be expected that F'% Fr will decrease.As mentioned above, it has been found through actual measurements and calculations that, contrary to common sense, if the roughness of the rolling contact surface is made rougher, the friction torque tends to decrease. So, we conducted an experiment to see if a similar phenomenon would occur in the case of a hollow bearing.

Figure 6 shows an example of the experimental results.
, the roughness of the raceway surfaces of the inner and outer rings and the rolling surface of the rollers of a tapered roller bearing with an outer diameter of 189 mm and an assembled width of 40 mm was set to 0.
．． Processed to have 15μm r+ns and 0.5μmrmS, and thrust load of 400kgf for each bearing.
Change the rotation speed under load to increase the friction torque.
This is a graphical representation of the results.

In addition, Fig. 7 shows an inner diameter of 50 mm, an outer diameter of 110 m+n,
Roughness of raceway surface and roller rolling surface of 40 mm wide spherical roller bearing: 0.14 μm rms and 0.33 μm r
Prepare ms and apply radial load of 1200k to each bearing.
gf was applied, the friction torque was measured by changing the rotation speed, and the results are illustrated. As can be seen from the graphs in Figures 6 and 7, in both H tapered roller bearings and spherical roller bearings, as in the case of contact rotation of a simple cylindrical body, the force with a large roughness value is The value of friction torque is small.

There is a concern that choosing a value may lead to other problems.

Calculating the oil film thickness of bearings that are actually used shows that the oil film thickness depends on the viscosity of the oil, but using oil with a high viscosity will generate more heat, while using a low viscosity oil will cause wear and galling. In many cases, the oil film thickness h = 0.2 to 0.4 μm, and the oil film thickness h = 0.2 to 0.4 μm. Fourth
According to Fig. 5, the rolling friction begins to decrease at h/
Although σ ranks second, b/e is considered to be l or less in order to actively reduce friction.

(This value of 1 or less assumes the presence of an oil film, so it does not include zero.) The roughness equivalent to this is σ of 0.3 μm rms or more based on the median value of the oil film thickness h. Select.

The raceway surfaces of the inner and outer rings and the rolling surfaces of the rollers in rolling bearings appear to be ground or superfinished, but as the roughness is increased, the average spacing of the peaks is one of the parameters related to surface roughness. , the average tip radius of the mountain, the average slope of the mountain, etc. also change.

The influence of these parameters on Junpo has also been studied, but it is undesirable for the average slope of the mountain to become too large. Usually, the angle is 1 to 2 degrees, but the limit is considered to be 3 to 4 degrees if vibrations during rotation of the bearing are also considered. 0.6μm
When the average slope of the ridges is measured on a ground surface with a roughness of rms, it exceeds 56-, which is inappropriate as a wet surface.

The roughness of the rolling surface of the body is considered to be 0.3 to 0.5 μm [ln3].

In the above embodiments, tapered roller bearings and spherical roller bearings have been described, but the present invention is applicable to other rolling bearings, such as cylindrical roller bearings and ball bearings.In particular, radial balls used in places where the thrust load is small and spin does not occur. Of course, this invention can also be applied to bearings.As mentioned above, this invention limits the roughness of the raceway surface of the raceway of the roller bearing and the rolling surface of the rollers,
As a result of reviewing the relationship with oil film thickness, the friction torque is reduced compared to conventional bearings, and as a result, the temperature rise can be kept low, so when used on a machine tool, there is less thermal deformation, and therefore the machine tool is more stable. By maintaining the high precision of the machine, saddle workpieces can be processed with high precision.

[Brief explanation of drawings]

tU is a diagram of the relationship between dynamic friction torque and rotational speed of a tapered roller bearing, Figure 2 is a diagram of the relationship between dynamic friction torque and rotational speed of tapered roller bearing 32307C, and Figure 3 is a diagram of the relationship between rolling cylindrical body 1.
A diagram showing the relationship between g1i'% and the roughness of the cylinder. Figure 4 is a diagram showing the relationship between the rolling friction of the cylinder and the ratio of oil film to roughness. Figure 5 is a diagram showing the relationship between the rolling friction of the cylinder and the ratio of oil film to roughness. Figure 5 shows two cylinders with various roughness. Figure 6 is a diagram showing the relationship between roughness and friction torque at various rotational speeds for tapered roller bearings. Figure 7 is a diagram showing the pressure distribution of moist oil and calculated values for oil film shape during busy periods. Figure 7 is a diagram showing the relationship between roughness and friction torque at various rotation speeds of tapered roller bearings. FIG. 3 is a diagram showing the relationship between roughness and friction torque at various rotational speeds of a roller bearing. Explanation of symbols: MR is rolling friction, Ms is friction at the part shown, T is friction moment, σ is resistance, Fr is rolling friction, h is oil film thickness, Pf is fluid pressure, b is half width of Hertzian contact, X is Distance from the center of contact θ θ20.4 θ2 θDO AIQ;” yutr=r匍5 bud 3 times Q Yukai Sushi Yu (decisive calculation 41 ￥l Fuyu 51 Sword Kessaku 5 Tsuwa pole IΔ C

Claims (1)

[Claims] In a rolling bearing having an inner ring, an outer ring, and a plurality of rollers interposed between the inner ring and the outer ring, at least one member has roughness on the raceway surface of the inner ring or outer ring or roughness on the rolling surface of the rolling elements. Roughness σ of 0.3 to 0.5
μmrms, and the ratio h of the oil film thickness h to the roughness σ
Rolling bearing with /σ less than 1.