JP2009250248A - Bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing device moving an inner ring of a bearing in an axial direction by thermal displacement of seats between inner rings with a simple structure and inhibiting change of preload due to the thermal displacement. <P>SOLUTION: The seat 8 between the inner rings is composed of material having larger thermal expansion coefficient than thermal expansion coefficient of a rotary shaft 5, a spacer 7 is composed of material having smaller thermal expansion coefficient than thermal expansion coefficient of the rotary shaft 5. Difference ΔL1 of displacement between the seat 8 between the inner ring thermally displaced by heat generated at bearings 3, 4 by rotation of the rotary shaft 5 and the rotary shaft 5 near the seat between the inner ring are offset by difference ΔL2 of displacement of the space 7 thermally displaced by the heat and the rotary shaft 5 near the spacer 7. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  According to the present invention, inner and outer ring spacers are provided between the bearings that support the rotating shaft, and a preload is applied to each bearing via the spacer and the inner ring spacer by tightening a nut provided on the rotating shaft. The present invention relates to a bearing device.

Conventionally, a rotary shaft is rotatably supported by a bearing fitted with a gap in the axial direction in the housing, and an inner ring spacer and an outer ring spacer are provided between the bearing and the bearing, respectively. In a bearing device in which a spacer is provided between the nut provided on the rear end side and the rear bearing, and a preload is applied to each bearing through the spacer and the inner ring spacer by tightening the nut, the rotating shaft rotates. The inner ring and the rolling element of the bearing are pressed against the outer ring by centrifugal force, and heat is generated by friction between the inner and outer rings and the rolling element. As shown in Patent Documents 1 and 2, the inner ring spacer is made of a material having a large coefficient of thermal expansion, and the inner ring spacer is thermally displaced in the axial direction by the heat to change the inner ring of the bearing. It is known to be displaced in the axial direction. Patent Document 3 describes a structure in which a spacer is formed so as to have elasticity by providing a concave groove.
Japanese Utility Model Publication No. 61-114121 Japanese Utility Model Publication No. 2-127817 Japanese Unexamined Patent Publication No. 9-19805

However, the inner ring spacer is thermally displaced by the heat generated in the bearing, and the rotating shaft and the spacer are also thermally displaced in the axial direction. Therefore, in Patent Documents 1 and 2, the rotation of the inner ring spacer that is thermally displaced and the vicinity of the inner ring spacer are performed. Because the difference in displacement from the shaft cannot be offset by the difference in displacement between the spacer that is thermally displaced and the rotating shaft near the spacer, the thermal displacement of the inner ring spacer and the thermal displacement of the spacer rotate. Since the inner ring of the bearing does not move in the axial direction because it is larger than the thermal displacement of the shaft, the preload applied to the bearing in advance may be different from the preload applied to the bearing during rotation of the rotating shaft. Therefore, it has been considered that the inner ring of the bearing is moved in the axial direction by the thermal displacement of the inner ring spacer by the expansion and contraction of the spacer even if the spacer and the rotating shaft are thermally displaced as in Patent Document 3. However, the rotation of the rotating shaft may cause a centrifugal force in the deflection of the spacer, which may adversely affect the rotation of the rotating shaft.
In view of the above problems, an object of the present invention is to provide a bearing device in which the inner ring of the bearing is moved in the axial direction by the thermal displacement of the inner ring spacer with a simple configuration, and the change in the preload due to the thermal displacement is suppressed. For the purpose.

  The present invention rotatably supports a rotating shaft by a bearing fitted with an interval in the axial direction in the housing, and an inner ring spacer and an outer ring spacer are provided between the bearing and the bearing, respectively. In a bearing device in which a spacer is provided between the nut provided on the rear end side of the shaft and the rear bearing, and a preload is applied to each bearing through the spacer and the inner ring spacer by tightening the nut. The seat is made of a material with a coefficient of thermal expansion larger than that of the rotating shaft, the spacer is made of a material with a coefficient of thermal expansion smaller than the coefficient of thermal expansion of the rotating shaft, and thermal displacement is caused by the heat generated in the bearing by the rotation of the rotating shaft. The difference in displacement between the inner ring spacer and the rotating shaft in the vicinity of the inner ring spacer is offset by the difference in displacement between the spacer thermally displaced by the heat and the rotating shaft in the vicinity of the spacer. To do.

  In the present invention, the inner ring spacer is made of a material having a thermal expansion coefficient larger than the thermal expansion coefficient of the rotary shaft, the spacer is made of a material having a thermal expansion coefficient smaller than the thermal expansion coefficient of the rotary shaft, and the bearing is driven by the rotation of the rotary shaft. The difference in displacement between the inner ring spacer that is thermally displaced by the heat generated in the inner ring and the rotating shaft in the vicinity of the inner ring spacer is offset by the difference in displacement between the spacer that is thermally displaced by the heat and the rotating shaft in the vicinity of the spacer. Therefore, even if the rotation shaft, the inner ring spacer and the spacer are thermally displaced due to the rotation of the rotation shaft, the total amount of thermal displacement of the inner ring spacer and the spacer is substantially the same as the heat displacement amount of the rotation shaft. During the rotation, it is possible to continue to apply the same preload as that previously applied to the bearing. In addition, the spacer can be made of a material having a small coefficient of thermal expansion and can be made with a simple structure by simply adjusting the length.

In a bearing device 1 shown in FIG. 1, a rotating shaft 5 (for example, a main shaft of a machine tool) is rotatably supported by bearings 3 and 4 which are fitted with a space in an axial direction inside a housing 2. The outer ring 3a and the inner ring 3b of the front bearing 3 are brought into contact with the head cap 6 attached to the housing 2 and the step portion 5a of the rotary shaft 5, respectively. The outer ring 4a and the inner ring 4b of the rear bearing 4 are brought into contact with the stepped portion 2a of the housing 2 and the spacer 7 fitted into the rotary shaft 5, respectively. An inner ring spacer 8 and an outer ring spacer 9 are provided between the front bearing 3 and the rear bearing 4, respectively. A nut 10 provided on the rear end side of the rotary shaft 5 is brought into contact with the spacer 7. By tightening the nut 10, a preload is applied to the bearings 3 and 4 via the spacer 7 and the inner ring spacer 8.
In this embodiment, when the rotating shaft 5 is made of steel, the inner ring spacer 8 is made of a material having a thermal expansion coefficient larger than that of the steel having a thermal expansion coefficient A of 11 to 12 × 10 ⁻⁶ / ° C., for example, thermal expansion coefficient B. : 19-23 × 10 ⁻⁶ / ° C. aluminum material. The spacer 7 is made of a material having a thermal expansion coefficient smaller than that of a steel material having a thermal expansion coefficient A of 11 to 12 × 10 ⁻⁶ / ° C., for example, novinite cast iron having a thermal expansion coefficient C of 1 to 2 × 10 ⁻⁶ / ° C. Name).

In the bearing device 1 configured as described above, heat is generated in the bearings 3 and 4 by the rotation of the rotating shaft 5, and the heat is transmitted to the rotating shaft 5, the inner ring spacer 8 and the spacer 7, and is thermally displaced. Since the amount of thermal displacement is length × thermal expansion coefficient, when the lengths of the inner ring spacer 8 and the spacer 7 are L1 and L2, the amount of displacement between the inner ring spacer 8 and the rotating shaft 5 near the inner ring spacer 8 is The difference ΔL1 is L1 × (19-23) × 10 ⁻⁶ −L1 × (11-12) × 10 ⁻⁶ , and the difference ΔL2 in the displacement amount between the spacer 7 and the rotating shaft 5 near the spacer 7 is L2 × (1 ˜2) × 10 ⁻⁶ −L2 × (11 to 12) × 10 ⁻⁶ . Therefore, the inner ring spacer 8 is thermally displaced by ΔL1 more than the rotating shaft 5 near the inner ring spacer 8, and the rotating shaft 5 near the spacer 7 is thermally displaced by ΔL2 more than the spacer 7. Therefore, L2 is set so that L1 × (8 to 11) = L2 × 10, and the difference ΔL1 in the displacement amount is canceled by the difference ΔL2 in the displacement amount. Even if the inner ring spacer 8 and the spacer 7 are thermally displaced, the total amount of thermal displacement of the inner ring spacer 8 and the spacer 7 becomes substantially the same as the amount of thermal displacement of the rotary shaft 5, and the bearing 3 is preliminarily used during the rotation of the rotary shaft 5. , 4 can be continuously applied with the same preload as that applied to. Further, the spacer 7 is made of a material having a small thermal expansion coefficient and is simply configured to adjust the length, and it is not necessary to perform groove processing for expanding and contracting the spacer 7 as in the prior art. Even if the inner ring spacer 8 and the spacer 7 are made of materials other than those described above, the inner ring spacer 8 is made of a material having a large thermal expansion coefficient, such as magnesium or stainless steel, and the spacer 7 has a coefficient of thermal expansion. A small material may be used, such as a ceramic material or an Invar material, and the displacement amount difference ΔL1 may be selected to be offset by the displacement amount difference ΔL2.

It is a figure which shows the bearing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bearing apparatus 2 Housing 3 Bearing 4 Bearing 5 Rotating shaft 7 Spacer 8 Inner ring spacer 9 Outer ring spacer 10 Nut ΔL1 Difference in displacement ΔL2 Difference in displacement

Claims (1)

A rotating shaft is rotatably supported by a bearing fitted with an interval in the axial direction in the housing, and an inner ring spacer and an outer ring spacer are provided between the bearing and the bearing, respectively, and a rear end of the rotating shaft. In a bearing device in which a spacer is provided between a nut provided on the side and a rear bearing, and a preload is applied to each bearing via the spacer and the inner ring spacer by tightening the nut, the inner ring spacer is a rotating shaft. The inner ring spacer is made of a material having a coefficient of thermal expansion larger than that of the shaft, the spacer is made of a material having a coefficient of thermal expansion smaller than that of the rotating shaft, and is thermally displaced by the heat generated in the bearing by the rotation of the rotating shaft. The bearing device is characterized in that the difference in displacement between the inner ring spacer and the rotating shaft in the vicinity of the inner ring spacer is canceled out by the difference in displacement between the spacer thermally displaced by the heat and the rotating shaft in the vicinity of the spacer.

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