JP2009014101A - Bearing device and machine tool provided with the same - Google Patents

Abstract

A bearing device capable of individually adjusting a preload applied to a rolling bearing and suppressing occurrence of resonance and a machine tool including the same are provided.
A bearing device includes a main shaft, an inner ring provided on the outer periphery of the main shaft, a ball disposed on the outer periphery of the inner ring, and an outer ring that sandwiches the ball with the inner ring. It is characterized by comprising a rolling bearing 20 having an electromagnet 40 disposed to face at least a part of the outer ring 23 (flange portion 23c).
[Selection] Figure 1

Description

  The present invention relates to a bearing device including a rolling bearing that supports a main shaft, and a machine tool including the same.

  In general, for example, in a machine tool, it is known to use a bearing device provided with a rolling bearing in order to rotatably support a main shaft (spindle). In general, a rolling bearing of such a bearing device is preliminarily provided with a preload for increasing rigidity from the viewpoint of suppressing vibrations of the rolling bearing and the main shaft supported by the rolling bearing.

  Here, even if the above-described preload is conventionally applied to the rolling bearing, the main shaft supported by the rolling bearing vibrates (rotates) at the same frequency as its natural frequency. There was a problem that resonance (so-called chatter vibration) occurred. In particular, when resonance occurs in a bearing device used in a machine tool for processing a workpiece (processing object), the workpiece cannot be processed accurately, and thus it is necessary to reduce the rotation speed of the spindle. . As a result, there is a problem that the machining efficiency of the workpiece is lowered.

In order to suppress resonance in the bearing device, it is known to adjust the preload applied to the rolling bearing. That is, by adjusting the preload applied to the rolling bearing, the rigidity of the rolling bearing is changed, and the natural frequency of the main shaft supported by the rolling bearing is made different from the rotational speed of the main shaft. It is possible to suppress the occurrence of resonance. As such a bearing device for adjusting the preload, a magnetic force generated by excitation of an electromagnet is applied to a thrust disk formed integrally with the main shaft, and the main shaft is moved in the axial direction to be applied to the rolling bearing. A bearing device that adjusts the preload (that is, adjusts the preload by moving the main shaft in the axial direction) is disclosed (for example, see Patent Document 1).
Japanese Patent No. 2759232

  However, in the above prior art, in order to adjust the preload applied to the rolling bearing by moving the main shaft, when the bearing device includes a plurality of rolling bearings, the preload applied to the rolling bearing is individually set. It cannot be adjusted. As a result, since the preload of the rolling bearing cannot be individually adjusted, there is a problem that the natural frequency of the main shaft supported by the rolling bearing cannot be freely adjusted.

  Therefore, the present invention has been made in view of the above-described problems, and can individually adjust the preload applied to the rolling bearing and can freely adjust the natural frequency of the main shaft. And it aims at providing a machine tool provided with the same.

  The invention according to claim 1 is a rolling bearing having a main shaft, an inner ring provided on the outer periphery of the main shaft, a rolling element disposed on the outer periphery of the inner ring, an outer ring sandwiching the rolling element with the inner ring, and an outer ring An electromagnet disposed opposite to at least a part of the electromagnet.

  According to this configuration, since the bearing device includes the electromagnet disposed so as to face at least a part of the outer ring, the rolling bearing is applied to the rolling bearing by the magnetic force (magnetic attraction force) generated by supplying current to the electromagnet. The applied preload changes. Therefore, for example, even when a plurality of rolling bearings are provided, the preload applied to the rolling bearing can be individually adjusted, and the natural frequency of the main shaft supported by the rolling bearing can be freely adjusted. As a result, the occurrence of resonance can be suppressed by making the natural frequency of the main shaft different from the number of rotations of the main shaft.

  The invention according to claim 2 is the bearing device according to claim 1, wherein the outer ring is formed by a main body portion having a raceway surface of the rolling element and a flange portion provided in the main body portion, and the electromagnet is a flange. It is characterized by facing the part.

  According to this configuration, since the electromagnet faces the flange portion, the magnetic force generated by supplying current to the electromagnet facing the flange portion can be effectively applied to the outer ring, and the rolling bearing The preload applied to can be effectively adjusted.

  The invention according to claim 3 is the bearing device according to claim 2, wherein the flange portion is extended outward from the main body portion, the electromagnet is opposed to the flange portion in the axial direction, and It faces the main body in the radial direction.

  According to this configuration, the space in which the electromagnet is disposed in the axial direction (that is, the direction parallel to the rotation axis of the main shaft) can be reduced. The axial direction is a direction parallel to the rotation axis of the main shaft, and the radial direction is a direction perpendicular to the axial direction.

According to a fourth aspect of the present invention, the bearing device according to any one of the first to third aspects is provided.
According to this configuration, since the bearing device according to any one of claims 1 to 3 is provided, the same effect as the invention according to any one of claims 1 to 3 can be obtained. In addition, since the occurrence of resonance can be suppressed, for example, it is not necessary to reduce the rotational speed of the main shaft, and the machining efficiency of the workpiece can be maintained.

  According to the present invention, the preload applied to the rolling bearing can be individually adjusted, and the natural frequency of the main shaft supported by the rolling bearing can be freely adjusted, thereby suppressing the occurrence of resonance. can do.

  Hereinafter, a specific embodiment of the present invention will be described with reference to FIG. In the present embodiment, a machine tool that includes the bearing device of the present invention and processes a workpiece will be described as an example.

  As shown in FIG. 1, a bearing device 1 included in a machine tool includes a main shaft 10, a pair of rolling bearings 20 and 30 that support the main shaft 10, and rolling bearings 20 in the axial direction (the direction of arrow A in the drawing). 30 and electromagnets 40 and 50 disposed to face each other.

  As shown in FIG. 1, the main shaft 10 protrudes in the axial direction A from the large diameter portion 11, a pair of medium diameter portions 12 and 13 sandwiching the large diameter portion 11 in the axial direction A, and one intermediate diameter portion 12. A small diameter portion 14 is provided. A laminated silicon steel plate 11 a is provided on the outer periphery of the large-diameter portion 11, and a grinding or cutting tool 14 a is attached to the tip of the small-diameter portion 14.

  As shown in FIG. 1, the rolling bearing 20 includes an inner ring 21 provided on the outer periphery of the main shaft 10, a ball 22 as a rolling element disposed on the outer periphery of the inner ring 21, and an outer ring that sandwiches the ball 22 with the inner ring 21. 23. Since the rolling bearing 20 is an angular bearing in which the inner ring 21 and the outer ring 23 and the ball 22 have contact angles, the rolling bearing 20 receives not only a load in the radial direction (that is, the direction of arrow R in the figure) but also a load in the axial direction A. Similarly to the rolling bearing 20, the rolling bearing 30 also has an inner ring 31 fixed to the main shaft 10, a ball 32 as a rolling element disposed on the outer periphery of the inner ring 31, and an outer ring 33 that holds the ball 32 with the inner ring 31. And an angular bearing. Each of the rolling bearings 20 and 30 which are angular bearings supports loads in the axial direction A and the radial direction R by the raceway surfaces 21a and 31a of the inner rings 21 and 31 and the raceway surfaces 23a and 33a of the outer rings 23 and 33. In the present embodiment, the rolling elements are balls 22 and 32, but they may be cylindrical or conical rollers.

  Further, as shown in FIG. 1, the outer ring 23 of the rolling bearing 20 is formed by a main body portion 23b having a raceway surface 23a of a ball 22 and a disk-shaped flange portion 23c provided integrally with the main body portion 23b. . As shown in FIG. 1, the flange portion 23 c protrudes in the direction of the arrow D <b> 1 and further extends outward (in the direction of the arrow G in the drawing). Similarly, the outer ring 33 is formed by a main body portion 33b having a raceway surface 33a of the ball 32 and a disk-shaped flange portion 33c provided integrally with the main body portion 33b. As shown in FIG. 1, the flange portion 33 c protrudes in the direction of the arrow D <b> 2 and further extends outward G. These flange portions 23c and 33c are made of a magnetic material. In the present embodiment, each of the flange portions 23c and 33c is integrally formed with the outer rings 23 and 33, but may not be formed integrally, and at least the flange portions 23c and 33c are made of a magnetic material. It only has to be formed.

  The electromagnets 40 and 50 are composed of a magnetic body (not shown) and a coil (not shown) formed by winding a conducting wire around the magnetic body. Each of the electromagnets 40 and 50 is accommodated in the yoke members 41 and 51, and is arranged at a predetermined interval so as to face at least a part of the outer rings 23 and 33 (that is, the flange portions 23c and 33c) in the axial direction A. It is installed.

  The machine tool including the bearing device 1 having the above configuration includes, in addition to the bearing device 1, a stator (stator) 60 that generates a rotating magnetic field for rotating the main shaft 10 as a rotor (rotor), and rolling bearings 20 and 30. And a housing 70 for protecting the stator 60. That is, the main shaft 10 that is a rotor and the stator 60 constitute an electric motor.

  The stator 60 includes a cylindrical stator core 61 and a coil 62 made of a conductive wire wound around the stator core 61. Since the stator core 61 is made of a soft magnetic material, a rotating magnetic field can be generated by supplying a current to the coil 62.

  The housing 70 is formed in a cylindrical shape, and the yoke members 41 and 51 and the stator 60 are fixed to the inner periphery of the housing 70, and the movement of the main shaft 10 in the axial direction A is restricted by holding the rolling bearings 20 and 30. is doing.

Next, operation | movement of the machine tool provided with the bearing apparatus 1 is demonstrated.
Torque is generated in the silicon steel plate 11a, which is a magnetic material, by the rotating magnetic field generated by the stator 60, and the main shaft 10 supported by the rolling bearings 20 and 30 rotates. As the main shaft 10 rotates, the tool 14a attached to the tip of the main shaft 10 also rotates. By pressing the rotating tool 14a against a workpiece (not shown), the machine tool can process the workpiece by grinding or cutting.

  Here, the present embodiment is characterized in that the bearing device 1 includes the electromagnet 40 disposed to face at least a part of the outer ring 23 as described above. That is, the outer ring 23 is attracted in the direction of the arrow D1 in the figure by the magnetic attraction force generated by supplying current to the electromagnet 40. In this case, since the inner ring 21 is fixed to the main shaft 10, the entire rolling bearing 20 does not move in the direction of the arrow D1 in the figure, and the preload applied to the rolling bearing 20 changes. Similarly, the bearing device 1 includes an electromagnet 50 disposed so as to face at least a part of the outer ring 33, and the outer ring 33 is illustrated in FIG. Suction in the direction of arrow D2. As a result, the preload applied to the rolling bearing 30 changes. Since changes in the preload applied to the rolling bearings 20 and 30 corresponding to the amount of current supplied to the electromagnets 40 and 50 can be known in advance, control of the current supplied to each of the electromagnets 40 and 50 is possible. Is easy.

  Further, as described above, the outer rings 23 and 33 are attracted by the magnetic attraction force generated by the electromagnets 40 and 50 so that the preload applied to the rolling bearings 20 and 30 is increased. That is, the outer races 23 and 33 are applied to the rolling bearings 20 and 30 in order to move the outer races 23 and 33 in the direction in which the raceways 23a and 33a of the outer races 23 and 33 approach the raceway surfaces 21a and 31a of the inner races 21 and 31, respectively. The preload that is being increased. Therefore, the electromagnets 40 and 50 generate a magnetic force (that is, a magnetic attractive force) so as to increase the rigidity of the rolling bearings 20 and 30.

  In the present embodiment, as described above, the outer rings 23 and 33 include the main body portions 23b and 33b having the raceway surfaces 23a and 33a of the balls 22 and 32 and the flange portions 23c and 33b provided on the main body portions 23b and 33b. 33c, and the electromagnets 40 and 50 are opposed to the flange portions 23c and 33c.

According to the bearing device 1 of the above embodiment, the following effects can be obtained.
(1) The preload applied to the rolling bearing 20 is changed by the magnetic force generated by supplying current to the electromagnet 40 disposed opposite to at least a part of the outer ring 23 (that is, magnetic attraction force). Can be made. Further, the preload applied to the rolling bearing 30 is changed by the magnetic force (that is, magnetic attraction force) generated by supplying a current to the electromagnet 50 disposed to face at least a part of the outer ring 33. be able to. Accordingly, even when a plurality of rolling bearings 20 and 30 are provided, the preload applied to the rolling bearing 20 or the rolling bearing 30 can be individually adjusted and supported by the rolling bearing 20 and the rolling bearing 30. The natural frequency of the main shaft 10 can be freely adjusted. As a result, the occurrence of resonance can be suppressed by making the natural frequency of the main shaft 10 different from the number of rotations of the main shaft 10.

  (2) Each of the electromagnets 40 and 50 generates a magnetic force (that is, a magnetic attractive force) so as to increase the rigidity of the rolling bearings 20 and 30. Therefore, by increasing the rigidity of the rolling bearings 20 and 30, the rolling bearings The natural frequency of the main shaft 10 supported by 20 and 30 increases. Therefore, resonance can be suppressed and the main shaft 10 can be rotated at a higher speed.

  (3) Since each of the electromagnets 40 and 50 is opposed to the flange portions 23c and 33c, the magnetic force generated by supplying a current to the electromagnets 40 and 50 opposed to the flange portions 23c and 33c is generated by the outer rings 23 and 33. Therefore, the preload applied to the rolling bearings 20 and 30 can be adjusted effectively.

  Moreover, in the said embodiment, since the machine tool is provided with the bearing apparatus 1, it can acquire the same effect as the effect as described in said (1) thru | or (3), and suppresses generating a resonance. Therefore, it is not necessary to reduce the rotational speed of the main spindle 10, and the machining efficiency of the workpiece can be maintained.

  In addition, this invention is not limited to the said embodiment, A various design change is possible based on the meaning of this invention, and they are not excluded from the scope of the present invention. For example, the above embodiment may be modified as follows.

  In the above-described embodiment, each of the flange portions 23c and 33c protrudes in the direction of the arrow D1 or the arrow D2 and further extends outward G. However, as shown in FIG. You may be extended toward the outward G from the parts 23b and 33b. In this case, as shown in FIG. 2, the electromagnets 40 and 50 are preferably opposed to the flange portions 23c and 33c in the axial direction A, and are further opposed to the main body portions 23b and 33b in the radial direction R. If it does in this way, the effect of said (1) thru | or (3) can be acquired, and also the space where the electromagnets 40 and 50 are arrange | positioned in the axial direction A can be made small.

  In the above embodiment, each of the flange portions 23c and 33c extends outward G, but as shown in FIG. 3, it may extend inward (that is, in the direction of arrow N in the figure). Good. Even in this case, the effects (1) to (3) can be obtained.

  In the above embodiment, the bearing device 1 includes a pair (two) of rolling bearings 20 and 30, but one of them may be another bearing (for example, a sliding bearing). May have three or more rolling bearings. That is, the number of rolling bearings provided in the bearing device 1 can be changed as appropriate, and even in this case, the effect (1) can be obtained.

Sectional drawing which shows the machine tool provided with the bearing apparatus which concerns on embodiment of this invention. Sectional drawing which shows the modification of the machine tool provided with the bearing apparatus which concerns on embodiment of this invention. Sectional drawing which shows the modification of the machine tool provided with the bearing apparatus which concerns on embodiment of this invention.

Explanation of symbols

  A ... Axial direction, G ... Outward, R ... Radial direction, 1 ... Bearing device, 10 ... Main shaft, 20,30 ... Rolling bearing, 21,31 ... Inner ring, 22,32 ... Ball (rolling element), 23,33 ... outer ring, 23a, 33a ... raceway surface, 23b, 33b ... main body, 23c, 33c ... flange, 40, 50 ... electromagnet, 60 ... stator, 70 ... housing.

Claims (4)

The spindle,
A rolling bearing having an inner ring provided on the outer periphery of the main shaft, a rolling element disposed on the outer periphery of the inner ring, and an outer ring sandwiching the rolling element with the inner ring;
An electromagnet disposed opposite to at least a part of the outer ring. The outer ring is formed by a main body portion having a raceway surface of the rolling element, and a flange portion provided in the main body portion,
The bearing device according to claim 1, wherein the electromagnet faces the flange portion. The flange portion extends outward from the main body portion,
The bearing device according to claim 2, wherein the electromagnet is opposed to the flange portion in the axial direction, and is further opposed to the main body portion in the radial direction.   A machine tool comprising the bearing device according to any one of claims 1 to 3.

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