JPS6188015A - Pre-load controlling spindle unit - Google Patents

Abstract

PURPOSE:To make the value of pre-loading always optimum by detecting temperature, vibration, number of revolution, initial pre-load, actual pre-load, etc. inside a spindle including a rotating part,and controlling a means of giving pre-load depending on the detected value. CONSTITUTION:An FM telemeter transmitter 63 is installed on the outer peripheral part of a rotary shaft 10, and and FM telemeter receiver 64 is installed on the inside part of a housing 30, close to the transmitter 63, in a spindle unit. A hole 65 which is opened radially through the peripheral part of the rotary shaft 10 in a position in contact with, or close to, a bearing inner race 21. And, a temperature sensor 61 is installed in this hole 65 and a pre-load sensor 62 is provided in a notch part formed on a part of the bearing inner race 21. Besides, a bearing outer race sensor 57 and a rotation sensor 59 for the rotary shaft 10 are provided and the signals of these sensors are inputted in a microcomputer 54, to control the oil pressure of a hydraulic pump 56.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a spindle unit mainly used in machine tools, etc., and more particularly to a positioning t&preload control spindle unit IC that maintains an appropriate preload force applied to an angular contact ball bearing.

In recent years, the speed of spindles in machine tools such as machining centers has increased significantly, and the dm-n value (dm; average value of bearings) has increased significantly.
1111) In some cases, a fixed position preload type with a rotation speed (rpm) exceeding 1 million is required. On the other hand, spindles for machine tools are required to meet such high-speed rotation requirements and at the same time have high cutting rigidity at low rotation speeds of about 200,000 to 400,000 dm-n1.

In general, in the case of fixed position preload type spindles for machine tools, when rotating at high speeds of DM-N of 1 million or more, it is necessary to use VC light pressure in order to prevent heat generation holes, seizure, and shortened life due to increased IJE moment. However, with this light preload, the rigidity is low when rotating at a low speed, chatter and the like occur, and machining accuracy is also reduced, making it impossible to obtain a satisfactory cutting effect. Ideally, it would be good to have preload and high rigidity at low speed rotation, and light preload and stiffness for light cutting at high speed rotation, but the fixed position preload type spindles actually used are Although the preload is appropriate,
When rotating at high speeds, the preload becomes even higher due to centrifugal force, which causes a problem with current maintenance.

A system has been proposed in which the outer ring of the angular contact ball 111 bearing is pressed to change the preload depending on the rotation speed, so that the preload is high at low speed rotation and light at high speed rotation, but the preload during use of the spindle is It must be determined appropriately according to not only the rotation speed but also temperature, vibration, initial preload, etc. In this case, in this type of spindle, it is optimal to detect the temperature and preload load from the rotating part, and it is important for signal transmission to output this detection signal to the outside and control the pressurizing device of the angular ball bearing. However, there were some difficulties, and as mentioned above, only the rotational speed had to be detected.

The present invention detects the temperature inside the spindle including the rotating part, the imaging speed, the rotational speed, the initial preload load, and the real load during rotation, and adjusts the preload so that the preload is always optimal according to these values. It is an object of the present invention to provide a spindle unit in which a applying means is controlled.

The gist of the present invention is to detect temperature, imaging, rotation speed, preload load, etc. during rotation in an angular contact ball bearing fixed position preload spindle unit, and to detect the detection signal of the rotating part by an FM installed inside the spindle unit. The optimum preload is calculated in real time according to the detected values by a telemeter transmitter/receiver via wireless transmission, and the outer ring of the angular contact ball bearing is pressurized using hydraulic pressure to control the preload.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a partial longitudinal sectional view of a spindle unit according to an embodiment of the present invention. On the rotating shaft 10, the left inner ring 15 of the two angular contact ball bearings 14 on the tip side is in contact with the stepped portion 12, and the inner ring spacer 16 and the outer ring P4! ! 18
The two angular contact ball bearings 2'0 on the rear end side are fitted with the spacer 2 between them, and the spacer 2 is in contact with the inner ring 21 of the right sleeve holder.
2 and nuts 24. The outer ring 341-t of the left bearing 14 is pressed by the cover 37. The bearings 14 and 20 are arranged in parallel on the back. The width of the outer ring spacer 18 is made larger than the width of the inner ring spacer 16, thereby applying a predetermined preload to the bearing 14°20.

In this case, as the rotating shaft 10 and the inner rings 15 and 21 rotate, the balls (rolling elements) between the inner and outer rings rotate and revolve, and try to move outward in the radial direction due to the centrifugal force generated by the revolution. At this time, the balls are pressed by the shoulder of the raceway groove of the outer ring 34.26 of the angular contact ball bearing 14.20,
Due to the partial pressure, the inner rings 15 and 21 along with the balls try to move in the 1 oil direction (the inner ring 15Fi is to the left and the inner ring 21 is to the right VC). However, the inner ring has a stepped portion 12 and an inner ring spacer 16.
Since the movement rate in the axial direction is set to t1 by the spacer 22, the state is substantially the same as when a preload is applied.

In a conventional fixed position preload spindle, the magnitude of the internal thrust load increases as the orbital speed of the balls increases and the radius increases.
0+u! , outer diameter 180 mm, soil scraping 19, 05 dragon, contact angle 40°). RPM 50 with 9t preload
When used at 00 times/min, the preload is approximately 520kl.
? f (increase of 320 to 9 f).Therefore, with a fixed position preload, a heavy preload would be produced contrary to the requirement for a light preload during high-speed rotation, and there was a risk of seizure of the bearing due to temperature rise.

In the present invention, in addition to the above-described configuration, a groove 52 is formed on the inner circumferential surface of the outer ring spacer 18, thereby increasing the deformability against compressive force in the axial direction. An oil chamber 58 is formed in the housing 30 on the side of the bearing 20, and a hydraulic piston 60 is slidably fitted in the oil chamber 58. The hydraulic piston 60 is movable in parallel to the axial direction of the rotating shaft 10, and its tip can come into contact with the end surface of the outer ring 26 of the right bearing 20.

Various sensors are built into the spindle unit to detect rotational speed, vibration, temperature, and even preload.

These sensors are attached at different locations depending on their type, but the temperature sensor 61 and preload load sensor are attached to rotating parts such as the rotor 10 or the inner shoulder 21, as will be described later.

An FM telemeter transmission rock 63 is attached to the outer periphery of the rotating shaft 10 within the unit.
An FM telemeter receiver 64 is mounted on the inside of the nousing 30 in close proximity to the FM telemeter receiver 64 . Temperature sensor 61
For installation details such as K 60, please refer to the illustrated examples.
L <To explain, the circumferential portion of the rotating shaft 10 at the contacting portion of the bearing inner ring 21'/c or in the vicinity thereof in the radial direction iC)
(A hole 65 is made through the hole 65, and the temperature sensor 61 is installed inside this hole 65, and the number 1g d61a is 1!2
The above-mentioned F provided with the shaft outer circumference 7c passing through the hollow part of the one-turn shaft 10
It is connected to the terminal of the M telemeter transmitter 63. In this embodiment, a strain gauge 62 is used as the preload load sensor.

The strain gauge 62 is attached to a notch formed in a part of the bearing inner ring 21, and its signal line 62a transmits a 1 cFM telemeter like the temperature sensor through a hole 66 penetrated in the radial direction around the rotating shaft. It is connected to machine 63. Note that 57 is a temperature sensor that detects the temperature of the outer ring of the bearing, and 59 is a rotation sensor for rotation @10.

FIG. 2 is a diagram showing a preload control system for a spindle unit according to the present invention. A detection signal whose detection point is a rotating part, such as the above-mentioned rotating shaft temperature signal, the initial preload of the bearing 14°20 given by tightening the nut 24,
A preload signal detected by the strain gauge 62, such as the actual pressure load during rotation, is transmitted by FM radio oscillation from the FM telemeter transmitter 63 to the FM telemeter receiver 64, and is input to the microcomputer 54 via the interface 68. . Since the rotating shaft rotates 100 times, ejection signals such as vibration values and bearing outer ring temperature are directly input to the microcomputer 54 via the interface 68. The ROM 67 stores an optimal preload pattern for external factors such as rotational speed and external loads, and the microcomputer uses the aforementioned detection signal and the ROM
67, and based on the difference signal, calculate the amount of deformation of the outer ring spacer 18 that will give the optimum preload, and the hydraulic pressure of the hydraulic pump 56 that brings about this amount of deformation.
A pump drive signal is applied to the hydraulic pump 56 via the interface 69 to drive the pump 56.

To give a concrete example of applying such a preload control spindle unit to the main spindle of a machine tool, a strain gauge 6
When the microcomputer 54 determines that the preload load detected in step 2 is in the optimum state, no signal is output from the microcomputer 54 to the hydraulic pump 56. Therefore, the hydraulic piston 60
is in contact with the outer ring 26 of the right bearing 20, but does not substantially deform the outer ring spacer 18. Therefore, bearing 1
4.20 has a heavy preload of the originally set size (for example, 200 kgf) applied.

It is suitable for heavy cutting due to its high rigidity.

On the other hand, if the rotational speed, temperature, or vibration of the rotating shaft 100 exceeds a predetermined value and the detected preload deviates from the optimum turn, a new corrected hydraulic pressure signal is output from the microcomputer 54 to the hydraulic pump 56. As the hydraulic piston 60 moves forward, the outer ring 26 of the bearing 20 is deflected in the axial direction, and as a result, the difference in width between the spacers 16 and 18 becomes smaller, so that the preload that was previously applied to the bearing 14° 201C is reduced. Therefore, even if an internal thrust load is generated due to the centrifugal force acting on the ball during high-speed rotation of the shaft 10 of one rotation, this internal thrust load and the decrease in the preload described above are offset, and the bearings 14, 2
This means that the preload acting on zero does not increase compared to when rotating at low speed. How does the preload at high speed rotation compare to the preload at low speed rotation?

Although it depends on the output of the hydraulic pump 56 and the deformability of the outer ring spacer 18, the important thing is that the former is not significantly larger than the latter, and it is desirable that the former be approximately equal to the latter. It is even more desirable if the former's 10,000 is smaller than the latter. In any case, according to this embodiment, the preload of the bearings 14, 20 during high-speed rotation can be lowered compared to the conventional case, and cutting work can be performed at low and high-speed rotations under optimal conditions.

It should be noted that what has been described above is merely one embodiment of the present invention, and it goes without saying that the present invention should not be interpreted as being limited thereto. for example.

In FIG. 1, the outer ring 34 of the bearing 14 on the cover 37 side can be pressed by a hydraulic piston.

The shapes of the hydraulic piston 60 and the oil chamber 58 are not limited to those of the above embodiment. Further, the means for adjusting the preload of the bearings 14, 20 may be of the one-machine S' activation type rather than the hydraulic drive type. In order to further improve the deformability of the outer ring spacer 18, the recess 1';/
The thickness of the spacer instead of forming #52? All you have to do is reduce the amount and change the material. The type of bearing may be a conical roller bearing in addition to an angular contact ball bearing, and 'f111
The way the receivers are assembled can be changed as appropriate, such as a single row back-to-back combination. ! (It is not necessary to complete all of the above items for Departure and East. In some cases, for example, the sensor may be only a rotation sensor, and the optimum preload value can be determined by calculating the rotation speed.)
It may also be calculated.

As described above, according to the present invention, although it is a fixed position preload type spindle unit, it detects the rotation speed, vibration, temperature, preload load, etc. during actual use, and comprehensively judges the rubbing L etc. Specifically calculate the most restrictive preload value under the usage conditions at that time 1-1 The preload applying means is actively controlled so that this preload is 1 direct yc, so it can be used under any conditions. Also, a proper preload condition can be brought about at normal Tt(-).

[Brief explanation of the drawing]

FIG. 1 is a partial vertical sectional view of a spindle unit according to an embodiment of the present invention, and FIG. 2 is a diagram showing a preload control system in an actual example of the present invention. 10... Rotation/oil, 14.20... Angular contact ball bearing. 15.21...Inner ring, 16...Inner ring spacer, 18
... Outer ring spacer, 26, 34... Outer ring, 30.
...Housing, 54...Full controller, 56...Hydraulic pump, 60...Hydraulic piston, 61...Temperature sensor, 62...Strain gauge. 63...fi'M telemeter transmitter, 64...FM
Telemeter receiver. Agent Patent attorney Rikichi Someyo (and 1 other person) Figure 2

Claims (1)

[Claims] In a spindle unit that supports a rotating shaft by arranging angular ball bearings at both ends of the inner ring spacer and outer ring spacer,
A sensor that detects temperature, vibration, preload, etc. occurring inside the unit, an FM telemeter transmitter attached to the rotating shaft and connected to the sensor, and an FM telemeter receiver attached to a fixed part outside the rotating shaft. and a pressurizing force applying means for pressurizing the outer ring of the angular contact ball bearing to deform the outer ring spacer, and a control device for calculating and controlling the pressurizing force of the pressurizing force applying means based on the detection signal of the sensor. . A spindle unit, wherein a detection signal from a sensor attached to a rotating part inside the unit is applied from the FM telemeter transmitter to the FM telemeter receiver to the control device.