JPS61127922A - Automatic preload regulating method for rolling bearing and device thereof - Google Patents

Abstract

PURPOSE:To make proper preload securable as well as to make a bearing usable extending over a wide range, by giving such a function that varies the preload according to revolving speed in a rotary shaft or bearing temperature, to a preload member of a rolling bearing. CONSTITUTION:Outer rings 2b and 3b of a rolling bearing are locked to a bearing housing 7 fitly attached to a headstock 6 via a distance collar 5 formed with a piezo-element. Temperature in a bearing 3 is detected by a thermistor 9 embedded in the headstock and the bearing housing, while impressing voltage corresponding to this temperature detection signal is given to the piezo-element via a lead wire 8. Therefore, according to the bearing temperature, proper preload is given to the bearing so that the bearing is usable extending over a wide range.

Description

[Detailed description of the invention] Fields of use of M Tojo The present invention relates to a main shaft of a machine tool, such as an internal grinding shaft of a grinding machine.

The present invention relates to a preload adjustment method and device for a bearing of a main shaft of a machining center or a lathe.

In the conventional machine tools, the speed of the main spindle has been increased due to improvements in motors, cutting tools, and spouts 3 of attached parts, resulting in increased productivity and improved surface finish accuracy. However, it was difficult to set the amount of preload on the bearing, which caused problems such as seizure due to the heat generated by the bearing at daytime speeds, or lack of rigidity in the low-body range due to the design of the bearing as a high-speed type. To solve this problem, a preload mW device using hydraulic pressure or spring pressure has been adopted.

Problems to be Solved by the Invention However, this method using hydraulic pressure has drawbacks such as securing space in the hydraulic chamber, sealing against oil leaks, and automatic control.

Furthermore, the constant pressure preloading method using spring pressure was incapable of control.

Means for solving the problem Actively causes dimensional changes in the preload member 50 in response to changes in the rotational speed of the rotating shaft 1 or the temperature of the bearings 2.3 that require preload, so that the preload can be adjusted to the appropriate level over a wide range. This is a method to ensure that the Furthermore, due to bearing 2゜3 and bearing temperature change, l0i
l[Bearing 2. It consists of a preload means 5 which maintains the preload of B at an appropriate pressure over a wide range. Furthermore, it consists of the bearings 2 and 6, the preload means 5, and the input means 9 for giving an input to cause the preload means 5 to actively change its dimensions in response to a change in the temperature of the bearings, a change in the rotational speed, or a rotational speed command. It is something.

EXAMPLES Below, examples of the present invention will be described based on the drawings, first of all a first example. Main spindle 1 of machining centers, lathes, grinders, etc.
The inner rings 2a of the bearings 2 and 3 bear the bearings.

5& are fixed to the spindle 1 at regular intervals via distance collars 4, and outer rings 2b and 5'b are bearings fitted to the headstock 1 via distance collars 5 formed of electrostrictive elements such as piezo elements. A voltage is applied to the piezo element by a lead wire 8 fixed to the housing 7 and passed inside the housing Z, detected by a thermistor 9, for example, and sent to a control device (not shown). Or, based on the actual rotation speed of the rotation speed detection device (not shown), a corresponding voltage is detected at the lead mound 8.
given to. In addition, if necessary, in the case of control based on the rotational speed, a means for giving a time lag to the voltage supply is provided. The piezo element of the distance collar 5 is manufactured so that the dimension in the width direction, that is, the axial direction, becomes longer by increasing the applied voltage. A voltage is applied so that .

This voltage is calculated by determining the relationship between thermal expansion due to temperature rise as the rotational speed of the main shaft 1 increases, and also by determining the mark 7J of the distance collar 5 made with this piezo element.
Experimentally find the relationship between IJ voltage and dimensional change, and then
When N buds are required, it is determined based on experimental values obtained by calculating the dimensional change considering both the expansion due to temperature of the piezo element and the applied voltage by 7 JD, and the rotation speed command of the control device (not shown) is determined so that the bearing preload is at an appropriate value. Alternatively, the applied voltage is controlled based on the value of a thermistor 9 provided near each main shaft bearing. As shown in Figure 2, as the rotational speed of the main shaft 1 increases, the entire bearing group including the collar expands thermally and the actual preload increases, so the voltage applied to the piezo element is gradually lowered and the collar width dimension is reduced. It's something that will happen. This prevents the preload from increasing during high speed rotation and adjusts it to an appropriate preload.

The second embodiment is applied to an internal grinding wheel shaft, and a stator frame 12 having an H circumferential groove 12& formed on the outer periphery for passing cooling water is fitted into the frame 11, and a stator filter 1 is fitted inside the frame 12.
6 is wrapped. The rotor 14 is located at the center of the stator coil 16, and the grindstone shaft 15 of the rotor shaft is supported by the front bearing 17 of the lid 16 of the frame 11, and by the inner wall 1 of the frame 11.
1 & a bearing housing 18 slidably fitted in the axial direction.
It is rotatably supported by a rear bearing 19.

In this front bearing 17, the inner ring 17 & is fixed to the grindstone shaft 15, and the outer ring 417b is fixed to the lid 16.

There is. Further, the inner ring 19a of the rear bearing 19 is fixed to the grindstone @15, and the outer ring 19b is fixed to the bearing housing 18. And the rear end of the bearing housing 18 has 7 lunges 18
a is formed, and these 7 rungs 18 & and the frame 11
An annular piezo element 21 whose dimensions change in the axial direction according to changes in applied voltage is interposed between the cooling water circulation cylinder 20 fixed on the back of the inner wall 11a, and its lead wire 21 and stator The lead wire 22 of the coil 16 is connected to the frame 11
It is connected to a connector 24 installed on the rear measuring cover 23, and receives the human power of an external human power device zp. Then, in the convenient rotation Ii of the grinding wheel shaft 15, the size and the magnitude of the applied voltage are determined so that the parent-child pressure becomes a predetermined appropriate pressure. In this case, as the rotational speed increases, the capacity 11 pressure is further reduced to increase the size of the piezo element.

That is, when the bearing temperature rises due to the rotation of the grindstone shaft, the stator frame 12, which is cooled by cooling water 6. Cooling water circulation 2J! 1*
Since the grinding wheel shaft 15 extends longer than the piezo element 21
By gradually increasing the voltage applied to the piezo element 21, the rotation of the piezo element 21 is increased, and the necessary bearing preload is applied. Although the piezo elements are annular, it is also possible to arrange rod-shaped elements parallel to the axis at equal angular positions on the circumference.

In the sixth embodiment, a circular piezo element is used instead of an annular piezo element for the same inner grinding wheel shaft, and the thread part will be explained in particular. Outer #M52a of rear bearing 62 of grindstone shaft 61
A preload member 65, which is a rod-shaped piezo element whose axial dimension changes with changes in applied voltage, is interposed between the back side of the center of the wall of the bearing housing 63 into which the bearing housing 63 is fitted, and the frame 64.
Appropriate preload is applied to the bearing over the range of use of the grindstone shaft.

That is, when the grindstone shaft is rotated by M Pi at a high rotational speed, the grindstone shaft is extended, so that the bearing preload tends to decrease. Therefore, the marks on the preload member 65 of the four piezo elements, IJ'', Ji,'
j Lower the pressure and deform the element to shorten it, +,:
+? This is to maintain a constant and appropriate preload.

Next, a case will be described in which a fourth embodiment using a shape memory alloy instead of the '4 strain element is used for the main shaft of a lathe or the like.

The four piezo elements of the distance collar 5 of the first embodiment are changed to a shape memory alloy 51, and a description of the parts that are not changed will be omitted. Shape memory alloys take on the memorized shape when they reach the reversal zone, and the width in the axial direction decreases dramatically.
By sequentially combining ml of 4&
As the height increases, the thickness of the distance collar 5 decreases. If the shape memory alloy has a shape that increases in diameter and decreases in width at the transformation temperature, it is necessary to provide a gap around the outer periphery of the distance collar 5. It is also possible to provide waviness in the circumferential direction so that the amount of waviness changes slightly depending on the transformation temperature.

As explained in detail above, Motoaki is il! By using a 'Biao strain element or a shape-described alloy for the member that applies preload to the III support, the shape changes as the spindle rotational speed or bearing temperature increases, so that the The preload of the bearing can be maintained at a predetermined appropriate level, and the fineness of the bearing can be improved at both low and high speeds, and a smooth finished surface can be obtained. Furthermore, it is possible to suppress the temperature rise in the heat transfer region and prevent troubles that tend to occur due to thermal expansion due to heat generation. It also has the effect of allowing use in a wider range of speed changes.

[Brief explanation of drawings]

Figure 1 is a vertical cross section of the lathe main shaft support, Figure 2 is the relationship between the four pressures applied to the piezo element and the rotational speed, Figure 6 is a top view of the ridge of the inner grinding wheel shaft, Figure 4 Figure 5 shows the vertical curve of another example of ζξ7-ki main gear, and Figure 6 shows the temperature change of LC-shaped memory alloy. In contrast, it is a diagram showing a change in distance color ■t. 1... Main shaft 2.6, 17, 19.32... Bearing 5.5... Distance collar 9... Thermistor 7.18.35... Bearing/X-Using 15.31...
・Uchiken whetstone i! 4121,65...Piezo element patent appearance person

Claims (5)

[Claims] (1) When it is necessary to apply preload to a rolling bearing that supports a rotating shaft, the dimensions of the preload member can be actively changed in response to changes in the rotational speed of the rotating shaft or the temperature of the bearing, etc. Automatic preload adjustment method for rolling bearings that maintains the appropriate preload over a wide range. (2) The rolling bearing that supports the rotating shaft actively and step-by-step changes in dimensions due to temperature changes in the bearing, etc., and the preload is adjusted to the appropriate pressure over a wide range through the outer ring or inner ring of the bearing. Automatic preload adjustment device for rolling bearings consisting of preload means. (3) The automatic preload adjustment device for a rolling bearing according to claim 2, wherein the preload means is a combination and arrangement of a plurality of shape memory alloys having different transformation temperatures. (4) A rolling bearing that supports a rotating shaft, a preload means that acts on an outer ring or an inner ring of the bearing to apply a preload, and detects a change in temperature of the bearing, etc. or detects a change in the rotational speed of the rotating shaft, or rotates the bearing. An automatic preload adjustment device for a rolling bearing, comprising an input means for applying an input that causes the preload means to actively cause continuous dimensional changes in accordance with a number of commands, and adjusting the preload to an appropriate pressure over a wide range. (5) The automatic preload adjustment device for a rolling bearing according to claim 4, wherein the preload means is an electrostrictive element.