JPH0890305A - Machine tool spindle device - Google Patents

Abstract

(57) [Summary] [Objective] An object of the present invention is to provide a new spindle device for a machine tool that employs a preload member system using a fluid pressure generator. [Structure] A spindle head 11 includes a plurality of bearings 1, 2, 3, 4, 5 including a tip 10A, a middle belly 10B, and a rear end 10C of the spindle 10.
In the double-row arrangement, the bearing member supporting the middle and rear ends of the main shaft is compensated for by the pressure detector P that detects the preload decrease due to the thermal expansion toward the rear end of the main shaft and the preload decrease. In addition to independently equipping the fluid pressure generator means 12 and 19, the main spindle device 10 for controlling the pressure of the preload applying means 20 and 30 so that the pressure detected by the pressure detector becomes a set pressure.
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Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle device for a machine tool, and more particularly to a spindle device having a preload member mounted on a bearing such as a middle portion or a rear portion of the spindle.

[0002]

2. Description of the Related Art Conventionally, in a spindle device of a machine tool,
The mainstream type is one in which only one set of preload members is installed on the rear bearing of the main shaft. This preload member is a necessary component because the main shaft is required to have high rigidity as the main shaft rotates at high speed, and because the main shaft is thermally expanded in the axial direction as the main shaft rotates at high speed. It is also a necessary part because the spindle has a long nose.

That is, the heat generation of the bearing increases as the speed of the main shaft increases. Due to this increase in heat generation, members such as the main shaft thermally expand, the preload of the bearing portion increases, and heat generation is further promoted. This repetition leads to damage such as seizure of the bearing member. On the contrary, if the preload of the bearing portion tends to decrease due to the thermal expansion of the main shaft or the like member, the bearing portion becomes loose. The preload member is adopted as a means for solving the problems that occur in these bearings.

[0004]

In the spindle device of the machine tool described above, since only one set of preload members is provided only on the rear bearing of the spindle, the axial direction due to the bearing heat generation due to the high speed rotation of the spindle and the like. Although it can cope with the thermal expansion of, it cannot cope with the run-out of the center abdomen of the spindle due to insufficient rigidity due to the high-speed rotation of the spindle. Further, in the case where the main shaft has a long nose, the runout of the abdomen of the main shaft is enlarged,
There is a problem that the processing accuracy is greatly adversely affected.

In view of the problems of the above-described conventional spindle device for machine tools, it is an object of the present invention to provide a novel spindle device for machine tools that employs a preload member system using a fluid pressure generator.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention uses a plurality of bearings in which the front end, middle side, rear end, etc. of the main spindle are arranged in a double row in the main spindle head. Also, the bearing member supporting the rear end is independently equipped with a pressure detector for detecting a preload decrease due to thermal expansion in the rear end direction of the main shaft and a preload applying means for the fluid pressure generator for correcting the preload decrease. In addition, the spindle device of the machine tool is characterized in that the preload applying means is pressure-controlled so that the detected pressure from the pressure detector becomes a set pressure.

[0007]

According to the present invention, when the main shaft is rotated at a high speed, the bearing part generates heat, and when the heat is generated, the main shaft is thermally expanded in the axial direction to form a gap in the ball of the bearing part. Is detected by the pressure detector, and the preload applying means is pressure-controlled so that the detected pressure from the pressure detector becomes the set pressure. Thus, it is possible to cope with runout of the main shaft abdomen due to insufficient rigidity due to high speed rotation of the main shaft. Further, even when the spindle has a long nose, the center runout of the abdominal portion of the spindle is suppressed, and the working accuracy is guaranteed to be constant.

In particular, the decrease in preload is directly detected by the detector,
Since the preload applying means is pressure-controlled so that this becomes a constant pressure, it responds quickly to the thermal expansion of the spindle in the axial direction, and the thermal expansion of the spindle is measured as in the conventional case, so that the elongation is canceled out. There is an effect that the problem of the indirect correction method for correcting the decrease in preload is solved.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments shown in the drawings will be described below. FIG. 1 is a front sectional view of a spindle device 100 of a machine tool according to the present invention, FIG. 2 is an enlarged sectional view of a spindle tip side, and FIG. 3 is an enlarged sectional view of a spindle rear end side. Further, FIG. 4 is a partial cross-sectional view showing the operation of the main part of FIG.

In the spindle device 100 of the machine tool,
The spindle device 100 shown in FIG. 1 is of a built-in motor type, and the spindle 10 has a built-in motor BM on the middle abdomen 10B.
Of the long nose main shaft 10A is supported by the front and rear two groups of bearings 1 and 2, and the middle abdomen 10B is supported by the first group of bearings 3 to prevent the main shaft from running out. ing. Further, the rear end 10C of the main shaft 10 is supported by the front and rear two groups of bearings 4 and 5 so as not to cause runout of the main shaft. As described above, the spindle 10 is the spindle head 11
In the inside, three places before and after that are highly rigidly supported by the bearing members of the second to third groups.

Since the rotor R of the built-in motor BM is fitted in the middle abdominal portion 10B of the main shaft 10, a large amount of thermal expansion occurs in the rear end direction (upward direction) of the axis, and each bearing A gap Z, Z'is created between 3 and 4, 5 and the main shaft,
This leads to a decrease in preload in the axial direction. However, the bearing member 3 of the middle portion 10B and the rear end 10C of the main shaft 10 is
And 4, 5 are independent preload applying means 20, 30 respectively.
Equipped. The detailed configuration is as shown in FIGS.

First, the preload applying means 20 provided on the bearing member 3 of the middle abdominal portion 10B of the main shaft 10 is as shown in FIG. The inner ring 3A is brought into contact with the step portion (a) which is the back of the main shaft of the three groups of bearings 1, 2 and 3 in the front and rear of the main shaft tip 10A, and the spacer 6, the bearing 2, the spacer 7 and the bearing are sequentially arranged from the back to the front end. 1, it is assembled like a tightening ring (nut) 8. The outer ring 3B side of the bearing 3 in which the inner ring 3A is brought into contact with the stepped portion (a) is slidably fitted into the enlarged space 11A of the spindle head 11, and the annular pressure detector P is attached to the outer ring 3B side. The piston type fluid pressure generator CP and the spacer 13 are interposed therebetween. Then, the pressure detector P (11
In A), the preload is detected, and the preload F is controlled by controlling the pressure applied to the piston type fluid pressure generator 12 so that the predetermined pressure is reached.
1 is given. With this preload F1, the abdomen 10B due to the axial expansion of the main shaft 10 (using the bearing 1 as a reference point).
It functions to cancel the gap Z between the main shafts of the bearing 3 of FIG.

The preload applying means 30 provided on the rear bearing members 4, 5 of the main shaft 10 is as shown in FIG. The front and rear two groups of bearings 4 and 5 at the rear end 10C of the main shaft are composed of a stepped portion (b) which is the back of the main shaft and a flange body 15 fixed to the main shaft 10.
Spacers 14 and 16 are interposed between the inner rings 4A and 5
A is incorporated and each outer ring 4B, 5B is held by the inner peripheral surface 17A of the pressure regulating cylinder 17. Outer ring 5B of the bearing 5
A pressure detector P is interposed between the inner ring 5A and the main shaft 1
Preload with 0 is detected. The pressure regulating tubular body 17 is a tubular body 18 in which a bolt 21 is fitted to the rear end narrowed portion 11B of the spindle head 11.
, The lower end flange 17B is locked to the outer ring side of the bearing members 4, 5, and the top end disc 17C is arranged on the circumference of the top surface of the cylindrical body 18. Pressure generator 19
As a result, the entire bearing members 4, 5 are levitated with a predetermined preload F2. The magnitude of this preload F2 depends on the pressure detector P
The pre-pressure is detected by and the applied pressure to the piston type fluid pressure generator 12 is controlled so as to become a predetermined pressure, and the pre-pressure F2 is applied. This functions to cancel the gap Z'between the main shafts that is applied to the bearings 4 and 5 due to the axial expansion of the main shaft 10.

Preload F of the bearings 1, 2, 3, 4, 5
1, F2 is controlled by the bearings 1, 2, 3, as shown in FIG.
Piston type fluid pressure generators 12 and 19 for applying preloads F1 and F2 to 4,5, a pressure detector P for detecting the preloads F1 and F2, an output value of the pressure detector and a preload setter 25. A control circuit 40 for controlling the pressure adjusting and supplying means 27 for adjusting and controlling the air pressure or the hydraulic pressure to the fluid pressure generators 12 and 19 is configured by the comparison calculation by the comparator 26 with the set value of. FIG. 6 shows the increasing / decreasing relationship of the pre-pressures F1 and F2 with respect to the fluctuation of the air or hydraulic fluid supply pressure to the fluid pressure generators 12 and 19.

According to the spindle device 100 of the present invention, the spindle 1
The preloads F1 and F2 are set to 0 in advance.
Has been granted by. In the main shaft 10, the rotor R of the built-in motor BM and the respective bearings 1, 2, 3, 4, 5 generate heat due to high-speed rotation and the like, and this heat generation causes the bearing 1 at the lower end of the main shaft 10 to serve as a reference point in the axial direction. Bearings 3 that have been thermally expanded to be installed at two locations on the mid-abdominal side and the rear-end side of the main shaft 10.
The gaps Z and Z'will be created in the balls 4 and 5.

However, the pressure drop due to the gaps Z and Z'is quickly detected by the pressure detector P of the preload applying means 20 and 30, and the output value e1 of the pressure detector and the preload setter 25.
The fluid pressure generator 1 is calculated by comparing the set value f1 (preloads F1 and F2 are set values) f1 with the comparator 26.
It is used as an adjusting control signal of the pressure adjusting and supplying means 27 for adjusting and controlling the pneumatic pressure or the hydraulic pressure to the pressure sensors 2 and 19. That is, the preload setting device 25
When the actual pre-pressures F1 and F2 fluctuate from the set values (pre-pressures F1 and F2) f1 in the above, the fluid pressure sent from the pressure adjusting and supplying means 27 to the fluid pressure generators 12 and 19 is controlled to correct them. To do. By controlling the preloads F1 and F2 to the set values, the bearings 3, 4, and 5 are moved to predetermined preloads F1 and F2.
Lift up with to cancel the gaps Z and Z '. Thus, it is possible to deal with the runout of the main shaft abdomen 10B due to insufficient rigidity due to the high speed rotation of the main shaft 10. Further, even if the main shaft 10 has a long nose, the main shaft middle abdomen 10B
The core runout is suppressed, and it acts so as to guarantee a constant processing accuracy.

The present invention is not limited to the above-described embodiments, and it is possible to change the design in details within the scope of the invention. For example, the machine tool may be a horizontal type, and the detailed configuration of each part may be appropriately changed in design. Further, the fluid pressure generator P for correcting the decrease in the preload and the preload applying means 20, 2 are provided.
At least 3 sets of 3 are enough on the main shaft.

[0018]

[Effects] According to the present invention, the effect of suppressing heat generation and suppressing shaft runout, which were not possible with the conventional single-row preloading member, is exerted. In addition, the bearing part generates heat as the main shaft rotates at high speed, and this heat causes the main shaft to thermally expand in the axial direction, creating gaps in the balls of the bearing part, and the pressure detector detects this gap as a decrease in preload. However, the preload applying means is pressure-controlled so that the detected pressure from the pressure detector becomes the set pressure, and the preload of the set value is continuously applied. It also has the effect of dealing with shakes.

[Brief description of drawings]

FIG. 1 is a front sectional view of a spindle device of a machine tool according to the present invention.

FIG. 2 is an enlarged cross-sectional view of a spindle tip side according to the present invention.

FIG. 3 is an enlarged cross-sectional view of a rear end side of a spindle.

FIG. 4 is a partial cross-sectional view showing an operation of a main part.

FIG. 5 is a block diagram of a control circuit for controlling the pneumatic pressure or hydraulic pressure to the fluid pressure generator.

FIG. 6 is a characteristic diagram showing the relationship between preload and supply fluid pressure.

[Explanation of symbols]

 1 to 5 bearing 10 main spindle 10A main spindle tip 10B main spindle abdomen 10C main spindle rear end 12,19 fluid pressure generator 20 preload applying means 30 preload applying means F1, F2 preload e1 output value f1 set value Z gap P pressure detector 25 preload Setting device 26 Comparator 27 Pressure adjusting and supplying means 40 Control circuit 100 Spindle device

Claims (1)

[Claims] 1. A bearing member supporting a middle and a rear end of a main shaft, wherein a front end, a middle part, a rear end, etc. of the main shaft are arranged in a plurality of rows in a main shaft head, and a rear end of the main shaft is provided. The pressure detector that detects the decrease in preload due to the thermal expansion in the direction and the preload applying means of the fluid pressure generator that corrects the decrease in preload are separately equipped, and the detected pressure from the pressure detector is the set pressure. A spindle device for a machine tool, characterized in that the pressure of the preload applying means is controlled so that.