JPH05209628A - Bearing lubricator and control method therefor - Google Patents

Abstract

PURPOSE:To independently control each temperature of an inner race and an outer race and apply an optimum pre-load by forming a scoop and axial through holes in the inner race, and independently connecting supply oil passages, between which a hot water temperature controller is interposed, to injection holes for supplying oil to the inner race and the outer race. CONSTITUTION:In an angular ball bearing 10, an annular scoop 26 projected in the axial direction is formed at one end of an inner race 18 fixed to a rotary shaft 16. Numerous through holes 28 communicated with an inside space of the scoop 26 are formed under a raceway surface 30 of the inner race 18 in the axial direction. The through hole 28 is branched on the way and extends toward the approximately radial direction, to thus serve as a supply oil hole 31 reaching the raceway surface 30 of a steel ball 22. A first injection hole 12 and a second injection hole 14 are formed in an outer race spacer 32 in contact with the side surface of the outer race 20 fixed to a housing 19, where the injection holes 12, 14 are directed toward the inside space of the scoop 26 and the raceway surface 30 of the inner race 18. Furthermore, the injection holes 12. 14 are connected to supply oil passages 38, 42 independent of each other so as to supply oil, a temperature of which is adjusted by a mixture valve.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to the lubrication of bearings used at high speeds, such as bearings for machine tool spindles.

[0002]

2. Description of the Related Art Angular ball bearings and the like are often used for high-speed rotating shafts of machine tools such as main shafts. In recent years, various methods for adjusting the preload of such ball bearings have been proposed. That is, it is necessary to increase the rigidity of the bearing when the bearing is subjected to heavy cutting at low speed rotation, and conversely, it is necessary to reduce the bearing rigidity to suppress heat generation and expansion of the bearing when rotating at high speed with low load. Because there is.

[0003]

DISCLOSURE OF THE INVENTION The present invention proposes a new method of preload adjustment, and its purpose is to control the temperature of the inner ring and the outer ring independently to thereby adjust the preload load or the bearing rigidity of the bearing. Controllability.

[0004]

In order to solve the above-mentioned problems, a lubrication device for a bearing according to the present invention connects two independent injection holes for supplying lubricating oil to the inner and outer races with independent oil supply passages. An oil temperature control means is provided in each of the oil supply passages. Further, the method of controlling the bearing lubrication device of the present invention makes the inner ring temperature relatively higher than that of the outer ring when the bearing rotates at a low speed, and conversely lowers the inner ring temperature when the bearing rotates at a high speed. I am trying to do it.

[0005]

The temperature of the inner and outer rings is arbitrarily adjusted because the temperature of the oil injected into them can be controlled by the oil temperature control means. Therefore, for example, it is possible to set the optimum preload or select the bearing rigidity according to the type of cutting of the machine tool. In particular, when the inner ring temperature is relatively higher than that of the outer ring during low speed rotation, the bearing rigidity is increased, and conditions suitable for low speed heavy cutting can be obtained. Further, when the inner ring temperature is relatively lowered at the time of high speed rotation, the preload is reduced and the repeated heat amplification and expansion of the bearing are effectively suppressed.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of the present invention will be described below.

FIG. 1 shows an angular ball bearing 10 used in the lubricating device of the present invention. The ball bearing 10 is lubricated with oil from the first and second injection holes 12 and 14. Specifically, the ball bearing 10 includes an inner ring 18 fixed to the rotating shaft 16, an outer ring 20 fixed to a housing 19, and
A plurality of steel balls 2 rotatably interposed between the inner and outer rings 18, 20
2 and a cage 24 that keeps the steel balls 22 at equal intervals in the circumferential direction.

One end of the inner ring 18 projects in the axial direction to form an annular scoop 26, and a large number of through holes 28 (only one is shown in FIG. 1) communicating with the inner space of the scoop 26 are formed in the inner ring 18. It extends in the axial direction below the orbital surface 30. However, the axial direction here is not strict meaning, and in order to improve the fluidity of the oil in the through hole 28 in implementation, the inlet end (the left end in FIG. 1) of the through hole 28 is set to the inner ring 1
It is normal to make it slightly inclined with respect to the rotation direction of 8.
The through hole 28 is branched in the middle, and extends substantially in the radial direction to form an oil supply hole 31 reaching the raceway surface 30 of the steel ball 22.

The outer ring spacer 3 which is in contact with the side surface of the outer ring 20.
2 has the first and second injection holes 12 and 14, and the first injection hole 12 supplies oil toward the inner space of the scoop,
The second injection hole 14 is configured to supply oil toward the raceway surface 30 of the inner ring 18. That is, the first injection hole 12
Serves to cool the inner ring 18, and the second injection hole 14 serves to lubricate the bearing and cool the outer ring.

The ball bearings 10 are employed as a pair of left and right in the lubricating device 34 for a bearing for machine tools shown in FIG. However, this drawing is a conceptual illustration, and it is needless to say that two or more ball bearings 10 may be adopted in the implementation. In the first injection holes 12 of the pair of ball bearings 10,
One end of an oil supply passage 38 is connected via a passage 36 in the outer ring spacer 32. Similarly, one end of an oil supply passage 42 is connected to the second injection hole 14 via another passage 40 in the outer ring spacer 32. Mixing valves 44 and 46, which can freely adjust the mixing ratio, are connected to the other ends of the oil supply passages 38 and 42, respectively. The oil supply passages 38, 4
Pumps 66 and 68 are provided in the middle of 2.

The mixing valves 44 and 46 have three ports, one port is connected to the oil supply passages 38 and 42, and the remaining two ports are high temperature oils via the oil supply passages 48, 50, 52 and 54, respectively. It is connected to the tank 56 and the low temperature oil tank 58. The temperature of the high temperature oil tank 56 is t1
Oil is stored in the low-temperature oil tank 58, and oil having a temperature t2 lower than that of t1 is stored in the low-temperature oil tank 58. These temperatures t1 and t2 are constantly maintained by heating means (not shown). After the oils having different temperatures from both tanks 56 and 58 are mixed by the mixing valves 44 and 46, the oil supply passage 38 is provided. , 42 through the first and second injection holes 12, 1
4 is supplied. The temperature difference between t1 and t2 is
At least the temperature difference to be applied to the inner and outer rings 18, 20 is required. The oil discharged from the housing 19 of the bearing is returned to the high temperature oil tank 56 and the low temperature oil tank 58 via the reflux passage 64.

The mixing ratio of the mixing valves 44 and 46 is controlled by a signal from the control device 62 based on a feedback signal from the rotation speed sensor 60 of the bearing. Various control methods can be considered depending on the operating state or cutting conditions of the machine tool, and for example, the following control method is proposed.

That is, when performing low-speed heavy cutting with a machine tool, it is necessary to increase the bearing rigidity, but on the other hand, the circulation of the inner ring expansion due to the frictional heat of the bearing → the increase of the preload → the generation of larger frictional heat is the number of revolutions. It is relatively unlikely to occur because of low. Therefore, in the case of this low speed heavy cutting, the first injection hole 12
The relatively high temperature oil is supplied to the inner ring 18 by the above, and the relatively low temperature oil is supplied to the outer ring 20 by the second injection hole 14. By thus making the inner ring 18 higher in temperature than the outer ring 20, the preload load or the bearing rigidity of the bearing 10 can be increased, and low-speed heavy cutting can be stably performed.

Further, when performing medium-speed cutting to high-speed cutting, especially ultra-high-speed cutting with a machine tool, it is very important to suppress the frictional heat of the bearing, so the inner ring 18 is oiled at a relatively low temperature. To supply the outer ring 20 with oil having a relatively high temperature. As a result, the preload of the bearing 10 can be reduced and ultra-high speed cutting due to low heat generation becomes possible.

Further, it is necessary to warm up the machine tool at the time of starting the machine tool to stabilize the machine, but it is desirable that the time for that is short. Therefore, the preload of the bearing 10 may be temporarily increased more positively than in the low speed heavy cutting, thereby increasing the heat generation amount of the bearing 10 and shortening the time until the completion of warming up.

Next, the operation of this embodiment will be described.

The oil pressurized by the pump 66 is injected from the first injection hole 12 into the scoop 26 through the oil supply passage 38 and the passage 36. This oil is through hole 2
The inner ring 18 is cooled in the process of passing through the
Go to 4. At this time, since the scoop 26 protrudes relatively long, the cooling area of the inner ring 18 increases and effective cooling is performed. A part of the oil flowing through the through hole 28 is jetted onto the raceway surface 30 by the centrifugal force through the oil supply hole 31 to lubricate the same surface.

On the other hand, the oil pressurized by the pump 68 is injected from the second injection hole 14 toward the raceway surface 30 of the inner ring 18 through the oil supply passage 42 and the passage 40. This oil lubricates the raceway surface 30 and cools the inner ring 18 and the outer ring 20, and then merges with the oil coming out from the oil supply hole 31 and goes out to the return passage 64. The oil returned to the high temperature oil tank 56 and the low temperature oil tank 58 through the reflux passage 64 is heated or cooled to have temperatures t1 and t2.

(Low-speed heavy cutting) When the machine tool is performing low-speed heavy cutting, the rotational speed sensor 60 detects the rotational speed value and inputs it to the control device 62. Controller 62 provides valve control signals to mixing valves 44 and 46 according to a pre-installed program. In the case of the present embodiment, a control signal is given to the mixing valve 44 so as to send the oil of relatively high temperature to the pump 66. Also the mixing valve 46
To the pump 68, a control signal is sent so that relatively low temperature oil is sent to the pump 68. As a result, both refueling passages 38, 42
When the temperature difference is + 5 ° C on the inner ring side, for example, the preload becomes about 160 kgf at 5000 rpm as shown by the broken line in FIG. 3, and the preload becomes significantly larger than when the temperature difference is zero. Such an increase in bearing rigidity is very advantageous in stably performing heavy cutting.

(Medium-speed to high-speed cutting) When the machine tool is performing medium-speed cutting to high-speed cutting, the rotational speed value is input to the control device 62 by the rotational speed sensor 60, and relatively to the mixing valve 44. A control signal is provided to pump cold oil into pump 66. Further, a control signal is given to the mixing valve 46 so as to send the oil of relatively high temperature to the pump 68. As a result, when the temperature difference between the two oil supply passages 38 and 42 becomes, for example, −5 ° C. on the inner ring side, it becomes about 140 kgf at 15000 rpm as shown by the alternate long and short dash line in FIG. It is almost halved. The reduction of the preload is very advantageous in suppressing heat generation of the bearing in high speed cutting, especially in ultra high speed cutting.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, the temperature control means may be of any type as long as it can stably supply the oil of the desired temperature. Further, the present invention is applicable not only to angular ball bearings, but also to cylindrical roller bearings, tapered roller bearings and the like.

[0022]

As described above, according to the first aspect of the invention, independent oil supply passages are connected to the first and second injection holes for supplying oil to the inner ring and the outer ring, and oil temperature control is provided in each of the oil supply passages. Since the means is provided, the temperatures of the inner ring and the outer ring can be independently controlled, and a desired preload can be freely added to the bearing. Therefore, if the lubrication apparatus of the present invention is applied to lubrication of the spindle of a machine tool, for example, the optimum preload can be selected according to the rotational speed of the shaft, the type of machining, and the like.

In the invention described in claim 2, since relatively high temperature oil is supplied to the inner ring when the bearing rotates at a low speed, a large preload is applied when high bearing rigidity such as low speed heavy cutting is required. The cutting can be stabilized, and when the bearing is rotating at a high speed, relatively low temperature oil is supplied to the inner ring, so that the preload can be reduced and the heat generation of the bearing can be suppressed.

[Brief description of drawings]

FIG. 1 is a sectional view of an angular ball bearing showing an embodiment of the present invention.

FIG. 2 is a block diagram showing a lubricating device for a bearing.

FIG. 3 is a graph showing the relationship between the rotational speed of the bearing and the preload.

[Explanation of symbols]

 10 Angular Ball Bearing 12 First Injection Hole 14 Second Injection Hole 16 Rotating Shaft 18 Inner Ring 20 Outer Ring 26 Scoop 28 Through Hole 30 Raceway Surface 32 Outer Ring Spacer 38,42 Oil Supply Passage 44,46 Mixing Valve 56 High Temperature Oil Tank 58 Low temperature oil tank 60 Rotation speed sensor 62 Control device 66, 68 Pump

Claims (2)

[Claims] 1. A scoop and an axial through hole communicating with the scoop are provided in the inner ring, and a first injection hole is provided to face the scoop of the inner ring for oil supply and a second oil supply is provided for the bearing raceway surface.
And a second lubrication passage which is independent of each other, and an oil temperature control means is disposed in each of the first lubrication passage. 2. When the bearing is rotating at a low speed, oil having a temperature higher than that of the oil in the second injection hole is supplied to the first injection hole, and when the bearing is rotating at a high speed, the oil is supplied to the first injection hole to the first injection hole. 2. The method for controlling a lubrication device for a bearing according to claim 1, wherein the oil having a temperature lower than that of the oil in the second injection hole is supplied.