JP2008240857A - Angular contact ball bearing for machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angular contact ball bearing for a machine tool, which prevents an impression from being generated on a rolling body when changing tools. <P>SOLUTION: In the angular contact ball bearing 10, a plurality of balls 3 retained to a retainer 4 are interposed between traveling surfaces 1a, 2a of an inner ring 1 and an outer ring 2, and the traveling surface 1a of the inner ring 1 is formed to a groove-like shape that both sides of the minimum diameter portion 1aa become a large diameter. An outer ring inner peripheral surface portion 2b continued from the maximum diameter portion 2aa in the traveling surface 2a of the outer ring 2 to a bearing front surface side, is made to a shape that a cylinder surface part 2ba having the same diameter as the maximum diameter and a taper surface part 2bb diameter-enlarged from an end of the cylinder portion 2ba to an outer ring end surface side, are successively continued. Alternatively, it is made to a taper surface part 2bb that the whole of the outer ring inner peripheral surface portion 2b is diameter-enlarged to the outer ring end surface side. The outer ring inner peripheral surface portion 2b is made to a flat cross section shape with no recession/projection. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an angular ball bearing for a machine tool used for supporting a spindle of a machine tool such as a machining center or a multi-task machine.

When the spindle of a machine tool is supported by a ball bearing, a support bearing having a structure capable of absorbing thermal expansion of the spindle is used for supporting the spindle rear side. As the support bearing that supports the rear side of the main shaft, the inner ring or the outer ring on which the ball rolls has a linear raceway, which allows the main shaft to move in the axial direction and absorbs the thermal expansion of the main shaft. Have been proposed (for example, Patent Document 1).
Since the above-mentioned support bearing cannot support an axial load, this bearing cannot be applied to support on the front side of the main shaft to which the axial load is applied. An angular ball bearing 40 as shown in FIG. 5A is used for supporting the spindle front side. In this angular ball bearing 40, a counter projection 44 for preventing the ball 43 from moving in the axial direction is formed immediately on the rolling surface of the outer ring 42.
JP 2000-120703 A

  By the way, in a machining center or a multi-task machine, a relative displacement occurs between the main shaft and the housing when changing tools. In this case, the angular ball bearing 40 of FIG. 5A is used as a bearing for supporting the front side of the main shaft between the main shaft and the housing, but the allowable axial displacement δ between the inner and outer rings 41 and 42 is as shown in FIG. As shown in (B), it is slight. Therefore, there is a problem that the ball 43 comes into contact with the counter projection 44 and an indentation is generated in the ball 43, resulting in a decrease in rotational accuracy.

  An object of the present invention is to provide an angular ball bearing for a machine tool that can prevent indentation from occurring on a rolling element during tool change.

An angular contact ball bearing for machine tools according to a first aspect of the present invention includes a plurality of balls held by a cage between rolling surfaces of an inner ring and an outer ring, and the rolling surface of the inner ring is a minimum diameter portion. In the angular ball bearing formed in a groove shape with both sides having a large diameter, a cylindrical surface portion having the same diameter as the maximum diameter is formed from the maximum diameter portion on the rolling surface of the outer ring to the inner peripheral surface portion of the outer ring continuing from the bearing front side. And a tapered surface portion that expands in order from the end of the cylindrical portion toward the outer ring end surface side, or a tapered surface portion that expands the entire outer ring inner peripheral surface portion toward the outer ring end surface, and the outer ring inner peripheral surface portion. It is characterized by having a flat cross-sectional shape without unevenness.
According to this configuration, since the inner and outer rings are separated from each other, when used for supporting the front side of the main spindle of the machine tool, the inner ring has an inner ring with respect to the outer ring according to the relative displacement generated between the main spindle and the housing during tool change. The relative displacement can be absorbed by freely moving relative to the front side of the bearing. For this reason, it can prevent that a ball | bowl contacts with the counter protrusion part of the internal peripheral surface of an outer ring | wheel with the said relative displacement, and an indentation arises in a ball | bowl, and the fall of the rotation precision resulting from an indentation can be avoided.

An angular contact ball bearing for a machine tool according to a second aspect of the present invention includes a plurality of balls held by a cage between the rolling surfaces of the inner ring and the outer ring, and the rolling surface of the outer ring has a maximum diameter portion. In the angular contact ball bearing formed in a groove shape having a small diameter on both sides of the inner ring, the inner ring inner peripheral surface portion continuing from the minimum diameter portion on the rolling surface of the inner ring to the bearing back side is a cylindrical surface portion having the same diameter as the minimum diameter, And a tapered surface portion that decreases in diameter from the end of the cylindrical portion to the inner ring end face side in order, or a tapered surface portion that reduces the diameter of the entire inner ring outer peripheral surface portion toward the inner ring end surface, and the inner ring outer peripheral surface portion is uneven. It is characterized by having no flat cross-sectional shape.
According to this configuration, since the inner and outer rings are separated, when used for supporting the spindle front side of the machine tool, the inner ring is in front of the bearing with respect to the outer ring according to the relative displacement generated between the spindle and the housing during tool change. The relative displacement can be absorbed by freely moving relative to the side. For this reason, it can prevent that a ball | bowl contacts with the counter protrusion part of the outer peripheral surface of an inner ring | wheel with the said relative displacement, and an indentation arises in a ball | bowl, and the fall of the rotation precision resulting from an indentation can be avoided.

  An angular contact ball bearing for machine tools according to a first aspect of the present invention includes a plurality of balls held by a cage between rolling surfaces of an inner ring and an outer ring, and the rolling surface of the inner ring is a minimum diameter portion. In the angular ball bearing formed in a groove shape with both sides having a large diameter, a cylindrical surface portion having the same diameter as the maximum diameter is formed from the maximum diameter portion on the rolling surface of the outer ring to the inner peripheral surface portion of the outer ring continuing from the bearing front side. And a tapered surface portion that expands in order from the end of the cylindrical portion toward the outer ring end surface side, or a tapered surface portion that expands the entire outer ring inner peripheral surface portion toward the outer ring end surface, and the outer ring inner peripheral surface portion. Because of the flat cross-sectional shape without unevenness, it is possible to prevent indentation from occurring on the ball when changing the tool. An angular contact ball bearing for a machine tool according to a second aspect of the present invention includes a plurality of balls held by a cage between the rolling surfaces of the inner ring and the outer ring, and the rolling surface of the outer ring has a maximum diameter portion. In the angular contact ball bearing formed in a groove shape having a small diameter on both sides of the inner ring, the inner ring inner peripheral surface portion continuing from the minimum diameter portion on the rolling surface of the inner ring to the bearing back side is a cylindrical surface portion having the same diameter as the minimum diameter, And a tapered surface portion that decreases in diameter from the end of the cylindrical portion to the inner ring end surface side sequentially, or a tapered surface portion that reduces the diameter of the entire inner ring outer peripheral surface portion toward the inner ring end surface, and the inner ring outer peripheral surface portion is uneven. Due to the flat cross-sectional shape, the ball can be prevented from being indented when changing the tool.

  An embodiment of the present invention will be described with reference to FIGS. In FIG. 1 (A), this angular contact ball bearing 10 for machine tools has an inner ring 1, an outer ring 2, and a plurality of balls 3 interposed between the rolling surfaces 1a, 2a of the inner and outer rings 1, 2. The plurality of balls 3 are held by the cage 4. The inner ring 1 is fitted to a main shaft (not shown) so as to be rotatable, and the outer ring 2 is fixedly supported in a fitted state on the inner periphery of a housing (not shown).

  As shown in an enlarged cross-sectional view in FIG. 1B, the outer ring inner peripheral surface portion 2b continuing from the maximum diameter portion 2aa on the rolling surface 2a of the outer ring 2 to the bearing front side is flat without unevenness such as a counter projection. The cross-sectional shape is a shape in which a cylindrical surface portion 2ba having the same diameter as the maximum diameter, and a tapered surface portion 2bb whose diameter increases from the end of the cylindrical surface portion 2ba toward the outer ring end surface side are successively provided. The rolling surface 1a of the inner ring 1 is formed in a groove shape in which both sides of the minimum diameter portion 1aa have a large diameter. Thereby, this angular ball bearing 10 for machine tools becomes a separated inner and outer ring type in which the inner ring 1 can move relative to the outer ring 2 toward the front side of the bearing.

  Since this angular contact ball bearing 10 for machine tools is of the inner and outer ring separation type having the above-described structure, when used for supporting the front side of the spindle of the machine tool, the relative displacement that occurs between the spindle and the housing during tool change is detected. Accordingly, as shown in FIG. 2, the inner ring 1 can move relative to the outer ring 2 relative to the bearing front side to absorb the relative displacement. For this reason, it is possible to prevent the ball 3 from coming into contact with the counter projections or the like on the inner peripheral surface of the outer ring 2 along with the relative displacement, thereby preventing the ball 3 from being indented, and avoiding a decrease in rotational accuracy due to the indentation.

  In the above-described embodiment, the outer ring inner peripheral surface portion 2b includes the cylindrical surface portion 2ba having the same diameter as the maximum diameter of the outer ring rolling surface 2a, and the tapered surface portion 2bb that expands from the end of the cylindrical surface portion 2ba toward the outer ring end surface side. However, the present invention is not limited to this, and the entire outer ring inner peripheral surface portion 2b may be a tapered surface portion 2bb whose diameter is expanded toward the outer ring end surface. In this case, the angular ball bearing 10 for machine tools is used as the inner and outer rings. Can be separated.

  FIG. 3 shows another embodiment of the present invention. In the angular contact ball bearing 10A for machine tools of this embodiment, in the embodiment shown in FIG. 1, as shown in an enlarged sectional view in FIG. 3 (B), from the smallest diameter portion 1aa in the rolling surface 1a of the inner ring 1, the bearing back surface is provided. The inner ring inner peripheral surface portion 1b following the side has a flat cross-sectional shape with no irregularities, and has a cylindrical surface portion 1ba having the same diameter as the minimum diameter, and a tapered surface portion 1bb whose diameter is reduced from the end of the cylindrical surface portion 1ba to the inner ring end surface side. The shape continues in order. As shown in FIG. 3A, the rolling surface 2a of the outer ring 2 is formed in a groove shape in which both sides of the maximum diameter portion 2aa have a small diameter. Other configurations are the same as those in the embodiment of FIG. Thereby, this angular contact ball bearing 10A for machine tools becomes an inner and outer ring separation type in which the inner ring 1 can move relative to the outer ring 2 relative to the bearing front side.

  This angular contact ball bearing for machine tool 10A is also of the inner and outer ring separation type having the above-described structure. Therefore, when used for supporting the front side of the main spindle of the machine tool, the relative displacement generated between the main spindle and the housing in the tool change is reduced. Accordingly, the inner ring 1 can move relative to the outer ring 2 to the bearing front side to absorb the relative displacement. For this reason, it is possible to prevent the ball 3 from coming into contact with the counter projections on the outer peripheral surface of the inner ring 1 in accordance with the relative displacement, and to prevent the ball 3 from being indented, thereby avoiding a decrease in rotational accuracy due to the indentation.

  In the above-described embodiment, the inner ring inner peripheral surface portion 1b includes the cylindrical surface portion 1ba having the same diameter as the minimum diameter of the inner ring rolling surface 1a, and the tapered surface portion 1bb whose diameter is reduced from the end of the cylindrical surface portion 1ba toward the inner ring end surface. However, the present invention is not limited to this, and the entire inner ring inner peripheral surface portion 1b may be a tapered surface portion 1bb whose diameter is reduced toward the inner ring end surface. In this case, the angular ball bearing 10A for machine tools is used as the inner and outer rings. Can be separated.

  FIG. 4 shows an example of a machine tool spindle device using the machine tool angular ball bearing 10 of the embodiment shown in FIGS. 1 and 2. In the spindle device 24 for machine tools, a tool or workpiece chuck is attached to the front side end portion (left side in the figure) of the main shaft 25. The front side of the main shaft 25 is supported by two angular ball bearings 10 for a machine tool that are combined in the back side. The rear side of the main shaft is supported by two support bearings 11. The rear-side support bearing 11 uses an angular ball bearing in the illustrated example, but may be a cylindrical roller bearing. A bearing lubrication spacer 12 is interposed between the angular ball bearings 10 on the front side of the spindle.

  The inner ring 1 of both the angular ball bearings 10 is fitted to the outer diameter surface of the main shaft 25, and the outer ring 2 is fitted to the inner diameter surface of the housing 26. The inner ring 13 of the support bearing 11 that supports the rear side of the main shaft is also fitted to the outer diameter surface of the main shaft 25, and the outer ring 14 is also fitted to the inner diameter surface of the housing 26. A motor 30 for driving the main shaft 25 is disposed at an intermediate position in the axial direction in the housing 26, a motor rotor 31 is fixed to the main shaft 25, and a motor stator 32 is fixed to the housing 26.

The inner and outer rings 1 and 2 of the bearing 10 positioned on the main shaft end side of the angular ball bearings 10 and the inner and outer rings 13 and 14 of the bearing 11 positioned on the main shaft end side of the both support bearings 11 are respectively an inner ring retainer 27 and The outer ring presser 28 is fixed in the housing 26. The housing 26 has a double structure including an inner peripheral housing 26A and an outer peripheral housing 26B.
A bearing fixing nut 33 that presses against the inner ring retainer 27 and fixes the angular ball bearing 10 is screwed to the front side of the main shaft. The inner peripheral housing 26A is provided with oil supply passages 34A and 34B communicating with the oil supply passage of the bearing lubrication spacer 12, and a drain oil recovery passage 35 communicating with the lubricant discharge passage of the bearing lubrication spacer 12. . Lubricating oil supplied from the outside of the spindle device through the oil supply passages 34A and 34B is discharged from the nozzle of the bearing lubrication spacer 12 toward the inner ring rolling surface 1a of each angular ball bearing 10, These angular ball bearings 10 are lubricated. Of the lubricating oil discharged from the nozzle of the bearing lubrication spacer 12, the lubricating oil supplied to the inner ring rolling surface 1 a passes from the lubrication discharge path of the bearing lubrication spacer 12 through the drain oil recovery path 35. The oil is collected in an oil collection tank (not shown) outside the spindle device.

  According to the spindle device 24 having this configuration, even when the relative displacement between the main shaft 25 and the housing 26 occurs when the tool is changed on the front side of the main shaft, the angular contact ball bearing 10 allows the inner ring relative to the outer ring 2 so as to allow the displacement. Since 1 can be moved relatively, no indentation is generated in the ball 3 of the angular ball bearing 10, and it is possible to prevent the rotation accuracy from being reduced due to the indentation.

(A) is sectional drawing of a part of angular ball bearing for machine tools concerning one Embodiment of this invention, (B) is a partial expanded sectional view of (A). It is explanatory drawing of the relative movement of the inner and outer ring | wheels in the angular ball bearing. (A) is sectional drawing of a part of angular ball bearing for machine tools concerning other embodiment of this invention, (B) is a partial expanded sectional view of (A). It is sectional drawing of the spindle apparatus using the angular ball bearing of the said embodiment. (A) is a partial cross-sectional view of a conventional example, and (B) is an explanatory view of the relative movement of the inner and outer rings.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Inner ring 2 ... Outer ring 1a, 2a ... Rolling surface 1aa ... Minimum diameter part 1b of inner ring rolling surface ... Inner ring outer peripheral surface part 1ba ... Cylindrical surface part 1bb of inner ring outer peripheral surface part ... Tapered surface part 2aa of inner ring outer peripheral surface part ... Outer Maximum diameter portion 2b of the raceway surface ... Outer ring inner peripheral surface portion 2ba ... Cylindrical surface portion 2bb of outer ring inner peripheral surface portion ... Tapered surface portion 3 of outer ring inner peripheral surface portion ... Ball 4 ... Cage 10, 10A ... Angular ball for machine tool bearing

Claims (2)

  In the angular ball bearing in which a plurality of balls held by a cage are interposed between the rolling surfaces of the inner ring and the outer ring, and the rolling surface of the inner ring is formed in a groove shape with both sides of the smallest diameter portion having a large diameter, A cylindrical surface portion having the same diameter as the maximum diameter from the maximum diameter portion on the rolling surface of the outer ring to the bearing front side, and a tapered surface portion that expands from the end of the cylindrical portion toward the outer ring end surface side. In which the outer ring inner peripheral surface portion is tapered toward the outer ring end surface, and the outer ring inner peripheral surface portion has a flat cross-sectional shape without irregularities. Angular contact ball bearings.   In the angular contact ball bearing in which a plurality of balls held by a cage are interposed between the rolling surfaces of the inner ring and the outer ring, and the rolling surface of the outer ring is formed in a groove shape in which both sides of the maximum diameter portion have a small diameter, A cylindrical surface portion having the same diameter as the minimum diameter, and a tapered surface portion that reduces the diameter from the end of the cylindrical portion toward the inner ring end surface side from the minimum diameter portion on the rolling surface of the inner ring to the bearing back side. Angular balls for machine tools characterized by having a shape that continues in order, or a tapered surface portion that reduces the diameter of the entire outer peripheral surface portion of the inner ring toward the end surface of the inner ring, and that the outer peripheral surface portion of the inner ring has a flat cross-sectional shape without irregularities. bearing.

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