JP6911547B2 - Super finishing method for grooves and manufacturing method for bearings - Google Patents

Description

The present invention relates to a method for superfinishing a groove formed by combining a plurality of curved surfaces each having an arcuate cross-sectional shape, and a method for manufacturing a bearing.

In a general deep groove ball bearing, the raceway groove existing on the peripheral surface of the raceway ring has a single arcuate cross-sectional shape. When superfinishing the surface of such a raceway groove at the final stage of processing, in the conventional general superfinishing method, a grindstone is applied to the surface of the raceway groove while rotating the raceway ring around its own central axis. The grindstone is oscillated with the center of curvature of the cross-sectional shape of the raceway groove as the oscillating center. As a result, the surface of the track groove is polished to improve the surface roughness of the track groove.

On the other hand, in the four-point contact ball bearing, the raceway groove existing on the peripheral surface of the raceway ring has a Gothic arc-shaped cross-sectional shape formed by combining two arcs having different centers of curvature. That is, the raceway grooves of the four-point contact ball bearings are formed by combining two curved surface portions, each of which has an arc-shaped cross-sectional shape and whose center of curvature of each cross-sectional shape exists at a different position. Has a surface. When superfinishing the surface of such a raceway groove at the final stage of processing, the conventional general superfinishing method is the same as the case of a raceway groove of a general deep groove ball bearing for each of two curved surfaces. It was super-finished by the method of. That is, in the conventional general super-finishing method, the super-finishing applied to one curved surface portion and the super-finishing applied to the other curved surface portion are performed in separate steps.

For this reason, the processing line for the raceway groove of the four-point contact ball bearing requires equipment for super-finishing one curved surface portion and equipment for super-finishing the other curved surface portion, respectively. The equipment cost was higher than that of a general deep groove ball bearing raceway groove processing line.

As an invention capable of eliminating such inconvenience, Japanese Patent Application Laid-Open No. 2003-260650 describes a method of superfinishing two curved surfaces constituting the surface of a raceway groove of a four-point contact ball bearing in one step. ing. The super-finishing method described in Japanese Patent Application Laid-Open No. 2003-260650 uses one grindstone having two grindstone portions, and rocks the grindstone around a swing axis inclined with respect to the circumferential direction of the raceway groove. While moving, one grindstone portion gives a super finish to one curved surface portion, and the other grindstone portion gives a super finish to the other curved surface portion.

Japanese Unexamined Patent Publication No. 2003-260650

In the superfinishing method described in JP-A-2003-260650, the swing loci of the two grindstone portions are similar to the cross-sectional shapes of the two curved surface portions, but are not the same as the cross-sectional shapes of the two curved surface portions. Therefore, it is difficult to apply a highly accurate super finish to the two curved surfaces.

The present invention has been made in view of the above circumstances, and an object of the present invention is to cover the surface of a groove formed by combining a plurality of curved surface portions each having an arcuate cross-sectional shape in one step. It is to provide a method capable of applying a highly accurate super finish.

The groove superfinishing method of the present invention comprises a work having a peripheral surface and a groove having a surface formed on the peripheral surface and formed by combining a plurality of curved surfaces each having an arcuate cross-sectional shape. While rotating around the central axis of the work, the tip surface of the grindstone having a width dimension smaller than the width dimension of any of the curved surface portions of the plurality of curved surface portions is pressed against the surface of the groove. By swinging the grindstone around the swing axis of the grindstone, the tip surface of the grindstone is reciprocated between one side end portion and the other side end portion of the surface of the groove with respect to the axial direction of the work. The swing axis is moved when the tip surface of the grindstone is moved from one of the two curved surfaces adjacent to each other to the other curved surface of the plurality of curved surfaces. Is moved from the position of the center of curvature of the cross-sectional shape of one of the curved surfaces to the position of the center of curvature of the cross-sectional shape of the other curved surface.

In the groove superfinishing method of the present invention, when the tip surface of the grindstone is moved from one of the curved surface portions to the other curved surface portion, the tip surface of the grindstone is connected at the connecting portion of these two curved surface portions. The movement of the swing axis is changed from the position of the center of curvature of the cross-sectional shape of one of the curved surfaces to the cross-sectional shape of the other curved surface without stopping or once stopped. It can be moved to the position of the center of curvature.

In the groove super-finishing method of the present invention, the grindstone is oscillated at a constant oscillating frequency around the oscillating axis, and the oscillating axis is oscillated by the cross-sectional shape of one of the curved surfaces. It is possible to move from the position of the center of curvature of the above to the position of the center of curvature of the cross-sectional shape of the other curved surface portion.

The bearing to be the target of the manufacturing method of the present invention has a peripheral surface and a raceway groove having a surface formed by combining a plurality of curved surfaces formed on the peripheral surface and each having an arcuate cross-sectional shape. It is configured to include a raceway ring that is provided and the raceway groove is super-finished.
In particular, in the bearing manufacturing method of the present invention, the raceway groove is super-finished by the groove super-finishing method of the present invention.

According to the groove super-finishing method and the bearing manufacturing method of the present invention, the surface of the groove formed by combining a plurality of curved surface portions each having an arc-shaped cross-sectional shape is super-finished with high accuracy in one step. Can be applied.

FIG. 1 is a half cross-sectional view of an inner ring constituting a four-point contact ball bearing according to the first example of the embodiment. FIG. 2 is an enlarged view showing an intermediate portion in the left-right direction of the upper end portion of FIG. FIG. 3 is a schematic perspective view of the super finishing device of the first example of the embodiment. FIG. 4 is a cross-sectional view showing a state in which the grindstone held by the grindstone holder constituting the superfinishing apparatus of the first example of the embodiment is pressed against the surface of the raceway groove of the inner ring. FIG. 5 is an enlarged cross-sectional view showing a tip portion of a grindstone constituting the superfinishing apparatus of the first example of the embodiment. FIG. 6 is a cross-sectional view for explaining the movement of the grindstone when carrying out the superfinishing method of the first example of the embodiment. FIG. 7 is a cross-sectional view for explaining the moving conditions of the grindstone constituting the superfinishing apparatus of the first example of the embodiment. FIG. 8 (A) is a diagram showing a temporal change in the swing angle of the grindstone when the superfinishing method of the first example of the embodiment is carried out, and FIG. 8 (B) is a diagram showing FIG. 8 (A). ) Is a diagram showing the temporal change of the swing center position of the grindstone, and FIG. 8 (C) is a diagram showing the temporal change of the moving speed of the swing center position of the grindstone of FIG. 8 (A). be. FIG. 9 is a partial cross-sectional view of the inner ring constituting the angular contact ball bearing according to the second example of the embodiment. FIG. 10 is a diagram showing a temporal change in the swing angle of the grindstone when the superfinishing method of the third example of the embodiment is carried out.

[First Example of Embodiment]
A first example of the embodiment will be described with reference to FIGS. 1 to 8.
This example relates to a method for manufacturing a four-point contact ball bearing, and is characterized by a method of superfinishing the raceway groove (inner ring raceway) 2 of the inner ring 1 which is a raceway ring constituting the four-point contact ball bearing. Therefore, this feature portion will be mainly described below.

First, the configuration of the inner ring 1 will be described with reference to FIGS. 1 and 2. The inner ring 1 is made of a hard metal such as bearing steel and is formed in a cylindrical shape as a whole, and includes an outer peripheral surface and an annular raceway groove 2 formed on the outer peripheral surface. The cross-sectional shape of the raceway groove 2 is a Gothic arc shape formed by combining two arcs having different centers of curvature. That is, each of the raceway grooves 2 has an arcuate cross-sectional shape, and the curvature centers O _a and _Ob (see FIG. 2) of the respective cross-sectional shapes are present at different positions. It has a surface composed of a combination of 3b and 3b.

Perpendicular to the center axis C ₁ of the inner ring 1, and, when a virtual plane passing through the axial center portion of the track groove 2 is set to S _1, 2 two curved portions 3a, connections 3b, the virtual plane S ₁ above Exists in. Further, the two curved portions 3a, 3b of the cross-sectional shape is adapted to mirror symmetrical with respect to the imaginary plane S _1. That is, the center of curvature O _a cross-sectional shape of one of the curved surface portion 3a located also one side than the virtual plane S ₁ with respect to the axial direction of the inner ring 1 is located on the other side of the imaginary plane S ₁ with respect to the axial direction of the inner ring 1 and is, the center of curvature O _b of the cross-sectional shape of the other of the curved portion 3b positioned on the other side of the imaginary plane S ₁ with respect to the axial direction of the inner ring 1, one side than the virtual plane S ₁ with respect to the axial direction of the inner ring 1 Is located in. Further, a curvature center O _a cross-sectional shape of one of the curved surface portion 3a, and the center of curvature O _b of the cross-sectional shape of the other of the curved portion 3b, equal radial distance from the central axis C ₁ of the inner ring 1, and, The axial distances from the virtual plane S ₁ are all equal at L / 2. Further, the curvature radius R _a of the cross-sectional shape of one of the curved surface portion 3a, and the radius of curvature R _b of the cross-sectional shape of the other of the curved portion 3b, are equal to each other (R _a = R _b). The one side in the axial direction of the inner ring 1 is the left side in FIGS. 1, 2, 4, 6, and 7, and the other side in the axial direction of the inner ring 1 is FIG. 1, FIG. 2, FIG. 4, the right side in FIGS. 6 and 7. Further, the surface of the track groove 2 is super-finished by the super-finishing method of this example described later.

The four-point contact ball bearing to be manufactured in this example includes an inner ring 1, an outer ring which is a raceway ring, and a plurality of balls. The outer ring has an inner peripheral surface and an annular raceway groove (outer ring raceway) having a Gothic arc-shaped cross-sectional shape formed on the inner peripheral surface. The plurality of balls are rotatably arranged between the raceway groove 2 of the inner ring 1 and the raceway groove 2 of the outer ring.

Next, a super-finishing device for super-finishing the surface of the track groove 2 will be described with reference to FIGS. 3 to 5. The super-finishing device includes a base 5, an X stage 6, a support 7, a Z stage 8, a swing shaft 9, a grindstone holder 10, a grindstone 11, and a spindle device, which are fixed to the floor of a factory. 12 and a control device 13.

The X stage 6 is supported on the upper surface of the base 5 so as to be able to move in the X direction, which is one direction in the horizontal plane. The movement of the X stage 6 with respect to the base 5 in the X direction can be performed with high accuracy by using the servomotor 14 as a drive source.

The columns 7 are arranged so as to extend upward from the upper surface of the X stage 6, and are fixed to the X stage 6 in this state.

The Z stage 8 is supported with respect to the support column 7 so as to be able to move in the Z direction, which is the vertical direction. The movement of the Z stage 8 with respect to the support column 7 in the Z direction can be performed with high accuracy by using the servomotor 15 as a drive source.

_{The swing shaft 9} is supported with respect to the Z stage 8 so as to be able to rotate, that is, swing around the swing axis C 9, which is its own central axis. The direction of the swing axis C ₉ of the swing shaft 9 coincides with the Y direction, which is a direction perpendicular to the X direction in the horizontal plane. _{The swing around the swing axis C 9} of the swing shaft 9 with respect to the Z stage 8 is driven by a servomotor 16 directly connected to the swing shaft 9 or via an endless belt, a gear mechanism, or the like. As a result, it can be performed with high accuracy.

The grindstone holder 10 is fixed to the tip of the swing shaft 9 and has a spring-type, pneumatic-type or other cylinder 17. Center axis C ₁₇ of the cylinder 17 is perpendicular to the pivot axis C ₉ of the rocking shaft 9.

The grindstone 11 is a vitrified grindstone using vitrified as a binder, and is assembled to the cylinder 17 of the grindstone holder 10. In this state, the grindstone 11 is capable of being displaced in the direction of _{the central axis C 17 of the cylinder 17. The width dimension W 18} of the tip surface 18 of the grindstone 11 in the virtual plane orthogonal to the swing axis C 9 of the swing shaft ₉ , that is, in the XZ plane is a curved surface forming the surface of the raceway groove 2 of the inner ring 1. It is smaller than _{the width dimensions W 3a} and W _{3b of the} portions 3a and 3b, respectively. Further, the cross-sectional shape of the tip surface 18 of the grindstone 11 in the XZ plane is an arc shape in which the tip side of the grindstone 11 is convex. Further, the radius of curvature R ₁₈ of the arc is smaller than the _{radius of curvature R a} and R _b of the cross-sectional shape of the curved surface portions 3a and 3b forming the surface of the raceway groove 2. When carrying out the present invention, as the grindstone 11, a grindstone using another type of binder, such as a resin bond grindstone which is an elastic grindstone using a resin bond as a binder, can also be adopted.

The spindle device 12 is supported by the base 5 and has a drive shaft 19. The drive shaft 19 can be rotationally driven around the _{drive shaft center C 19} , which is the center line of the drive shaft 19. The direction of the drive axis C ₁₉ of the drive shaft 19 coincides with the X direction. The drive axis C 19 of the drive shaft ₁₉ and the central axis C ₁₇ of the cylinder 17 exist in a common virtual plane orthogonal to the Y direction.

The control device 13 controls the positions and movements of the grindstone 11 and the swing shaft 9 by controlling the drive of the spindle device 12 and the servomotors 14 to 16 when the surface of the raceway groove 2 is superfinished. It is for.

Specifically, the control device 13 is mounted on the tip of the drive shaft 19 by controlling the drive of the spindle device 12, that is, by controlling the rotation of the drive shaft 19 about the drive shaft center _{C 19.} It is possible to control the rotation of the inner ring 1.
Further, the control device 13 controls the drive of the servomotor 14, that is, by controlling the position and movement of the X stage 6 in the X direction, the position and movement of the grindstone 11 and the swing shaft 9 in the X direction. It is controllable.
In addition, the control device 13 controls the drive of the servomotor 15, that is, by controlling the position and movement of the Z stage 8 in the Z direction, the position and movement of the grindstone 11 and the swing shaft 9 in the Z direction. Can be controlled.
Further, the control device 13 controls the drive of the servomotor 16, that is, controls the position and movement of the swing shaft 9 about the swing axis _{C 9 in the swing direction.} The position and movement of the grindstone 11 around the center C _{9 in the swing direction can be controlled.}

In particular, in this example, the control device 13 controls the driving of the servomotors 14 to 16 in synchronization with the swing axis C ₉ while swinging the grindstone 11 around the swing axis C _9. It is possible to move the position of in the XZ plane.

Next, a method of superfinishing the surface of the track groove 2 by the above superfinishing device will be described with reference to FIGS. 6 to 8 in addition to FIGS. 3 to 5.

First, as a preparatory process, the inner ring 1 to be a work is set in the super finishing device. That is, as the central axis C ₁ of the drive axis C ₁₉ and the inner ring 1 of the drive shaft 19 of the spindle device 12 is coaxial, mounting the inner ring 1 to the distal end of the drive shaft 19.

After setting the inner ring 1 in the superfinishing device, the drive shaft 19 of the spindle device 12 is rotated to rotate the inner ring 1 about the central axis C ₁ of the inner ring 1. _{Further, while rotating the inner ring 1 in this way, as shown in FIGS. 4 and 6, the swing axis C 9} is pressed in a state where the tip surface 18 of the grindstone 11 is pressed against the surface of the raceway groove 2 of the inner ring 1. The grindstone 11 is swung as a center. As a result, the tip surface 18 of the grindstone 11 is repeatedly reciprocated between one side end portion and the other side end portion of the surface of the raceway groove 2 with respect to the X direction which is the axial direction of the inner ring 1, thereby causing the raceway groove. Super finish the surface of 2.

Specifically, when moving the tip surface 18 of the grindstone 11 from one side end to the other side of the surface of the raceway groove 2 in the X direction, first, FIG. 6A → FIG. 6 (B) → as shown in the order of FIG. 6 (C), the the pivot axis C ₉ in a state that is aligned with the center of curvature O _a, swinging the grindstone 11 around the rocking Dojikukokoro C ₉ As a result, the tip surface 18 of the grindstone 11 is extended in the X direction from one side end portion of one curved surface portion 3a to the other side end portion, that is, to the connecting portion between one curved surface portion 3a and the other curved surface portion 3b. Move. Then, as shown in the order of FIG. 6 (C) → FIG. 6 (D) → FIG. 6 (E), the tip surface 18 of the grindstone 11 is moved at the connecting portion between one curved surface portion 3a and the other curved surface portion 3b. once in a state of stopping, the pivot axis C _9, it is moved from the position of the center of curvature O _a to the position of the center of curvature O _b, i.e., to match the pivot axis C ₉ to the center of curvature O _b. Then, in this state, as shown in the order of FIG. 6 (E) → FIG. 6 (F) → FIG. 6 (G), the _{grindstone 11 is swung around the swing axis C 9} to cause the grindstone 11 to swing. The tip surface 18 is moved from one end of the other curved surface 3b toward the other end in the X direction.

On the contrary, when the tip surface 18 of the grindstone 11 is moved from the other side end portion of the surface of the raceway groove 2 toward the one side end portion in the X direction, FIG. 6 (G) → FIG. 6 (F). → as shown in the order of FIG. 6 (E), the state in which the oscillation axis C ₉ to coincide with the center of curvature O _b, by swinging the grindstone 11 around the rocking Dojikukokoro C _9, grindstone The tip surface 18 of 11 is moved in the X direction from the other side end portion to the one side end portion of the other curved surface portion 3b, that is, to the connecting portion between the other curved surface portion 3b and the one curved surface portion 3a. Then, as shown in the order of FIG. 6 (E) → FIG. 6 (D) → FIG. 6 (C), the tip surface 18 of the grindstone 11 is moved at the connection portion between the other curved surface portion 3b and the one curved surface portion 3a. once in a state of stopping, the pivot axis C _9, is moved from the position of the center of curvature O _b to the position of the center of curvature O _a, i.e., to match the pivot axis C ₉ to the center of curvature O _a. Then, in this state, as shown in the order of FIG. 6 (C) → FIG. 6 (B) → FIG. 6 (A), the _{grindstone 11 is swung around the swing axis C 9} to cause the grindstone 11 to swing. The tip surface 18 is moved from the other side end portion of one curved surface portion 3a toward the one side end portion in the X direction.

In this example, as described above, the operation of moving the tip surface 18 of the grindstone 11 from one side end to the other end of the surface of the raceway groove 2 in the X direction, and the tip surface 18 of the grindstone 11. Is repeatedly and alternately moved from the other side end portion of the surface of the raceway groove 2 toward the one side end portion in the X direction to superfinish the surface of the raceway groove 2. At this time, the pressing force (contact pressure) of the tip surface 18 of the grindstone 11 against the surface of the raceway groove 2 is substantially constant (predetermined) by a force such as a spring type or a pneumatic type applied to the grindstone 11 from the cylinder 17. The size of the range of) is maintained.

Further, in this example, the super-finishing of the surface of the raceway groove 2 as described above is _{performed while swinging the grindstone 11 around the swing axis C 9} at a constant swing frequency. That is, in this example, as shown in FIGS. 6 (A) to 6 (C), or as shown in FIGS. 6 (E) to 6 (G), the tip surface 18 of the grindstone 11 is used. Not only the operation of moving the curved surfaces 3a and 3b, but also as shown in the order of FIG. 6 (C) → FIG. 6 (D) → FIG. 6 (E), or FIG. 6 (E) → FIG. 6 (D) → as shown in the order of FIG. 6 (C), the the pivot axis C ₉ 2 single curvature center O _a, O _b operation of moving between also the constant grindstone 11 around the oscillation axis C ₉ swings Perform while swinging at the frequency. Therefore, in this example, when the tip surface 18 of the grindstone 11 is transferred from one curved surface portion 3a to the other curved surface portion 3b, or when the tip surface 18 of the grindstone 11 is transferred from the other curved surface portion 3b to one curved surface portion 3a. At a speed at which the movement of the tip surface 18 of the grindstone 11 temporarily stops at the connection portion between the curved surface portion 3a on one side and the curved surface portion 3b on the other side, the swing axis C _{9 is set} to the two centers of curvature O _a . moving between O _b.

Here, various conditions for realizing the movement of the grindstone 11 as shown in FIG. 6 will be specifically described with reference to FIG. 7. In FIG. 7, in order to generalize the model, with different two curved portions 3a constituting the surface of the raceway groove 2, the center of curvature O _a and 3b of the cross-sectional shape, the radial position of the O _b to each other and _{The radii of curvature R a} and R _b of the cross-sectional shapes of the two curved surfaces 3a and 3b are different from each other.

First, the preconditions are as follows.
<Prerequisites>
Swing frequency of grindstone 11: f [Hz]
Range of change in the swing angle of the grindstone 11: + α to −α [rad]
Swing angular velocity of grindstone 11 ω: ω = 4 · α · f [rad / sec]
Center of curvature O _a, the distance between O _b: L [mm]
Curved surface portion 3a, the center of curvature O _a as viewed from the connection portion of 3b with each other, the angle between O _b: θ [rad]

Center of curvature O _a, movement conditions of pivot axis C ₉ between O _b is as follows.
<Movement conditions>
Movement time of the swing axis C ₉ between the centers of curvature O _a and Ob _b : t = θ / ω [sec]
Center of curvature O _a, the moving speed of the pivot axis C ₉ between _{O b v: v = L /} t [mm / sec]
Incidentally, the grindstone 11, because it is biased to the surface of the raceway groove 2 by the cylinder 17, with the possible pivot axis C ₉ moves between the center of curvature O _a, O _b, the swing of the grinding 11 Even if the radius changes, the pressing state of the tip surface 18 of the grindstone 11 against the surface of the raceway groove 2 is always maintained.

Therefore, if the control device 13 executes the control based on the above <preconditions> and <movement conditions>, the movement of the grindstone 11 as shown in FIG. 6 can be realized. Note that FIG. 8 shows a “temporal change in the swing angle” of the grindstone 11 and a temporal change in the position of _{the swing axis C 9 of the grindstone 11 when the superfinishing method of this example is carried out.} The relationship between "the temporal change of the swing center position" and "the temporal change of the swing center position movement speed" which is the temporal change of the movement speed v of the swing axis C _{9 of the grindstone 11 is shown.}

In this example, the two curved portions 3a, and 3b of the cross-sectional shape curvature center O _a, the radial position of the O _b are equal to each other, and two curved portions 3a, and 3b cross section curvature radius R _a, R _b are equal to each other. Therefore, when the pivot axis C ₉ moves between the center of curvature O _a, O _b, the moving velocity v of the pivot axis C ₉ is a grinding wheel 11 about the pivot axis C ₉ It is almost equal to the circumferential speed of the tip surface 18.

As described above, according to the superfinishing process of the grooves of this embodiment, each having an arcuate cross-sectional shape, and the curvature center O _a of the respective cross-sectional shape, present in the O _b are different positions, The surface of the track groove 2 formed by combining the two curved surface portions 3a and 3b can be super-finished with high accuracy in one step.

That is, in this example, when superfinishing one curved surface portion 3a, that is, when moving the tip surface 18 of the grindstone 11 by one curved surface portion 3a, the center of curvature of the cross-sectional shape of one curved surface portion 3a. O _a a pivot axis C ₉ in a state of being matched to, swinging the grindstone 11 around the rocking Dojikukokoro C _9. Further, when performing a super-finish on the other of the curved portion 3b, i.e., when moving the distal end surface 18 of the grinding 11 at the other of the curved portion 3b, rocking the center of curvature O _b of the cross-sectional shape of the other of the curved portion 3b With the center of motion C ₉ aligned, the grindstone 11 is swung around the center. Therefore, when superfinishing one curved surface portion 3a, the swing locus of the tip surface 18 of the grindstone 11 becomes the same as the cross-sectional shape of one curved surface portion 3a, and the other curved surface portion 3b is superfinished. At the time of application, the swing locus of the tip surface 18 of the grindstone 11 becomes the same as the cross-sectional shape of the other curved surface portion 3b. Therefore, the two curved surface portions 3a and 3b can be subjected to high-precision super-finishing.

Further, in this example, the tip surface 18 of the grindstone 11 pressed against the surface of the track groove 2 passes through the connecting portions of the two curved surface portions 3a and 3b in the axial direction as the grindstone 11 swings. High-precision super-finishing can also be applied to the connection part.

In the case of a four-point contact ball bearing, the balls do not roll and contact the connecting portions of the two curved surface portions 3a and 3b. However, if the connecting portions of the two curved surface portions 3a and 3b are subjected to high-precision super-finishing to improve the surface roughness of the connecting portions, even if stress acts on the connecting portions during use, this connection portion can be used. It is possible to reduce the possibility of damage such as cracks starting from the surface of the connecting portion.

On the other hand, when the super-finishing applied to one curved surface portion 3a and the super-finishing applied to the other curved surface portion 3b are performed in different steps as in the conventional super-finishing method, they are pressed against the surface of the raceway groove 2. The tip surface 18 of the grindstone 11 does not pass through the connecting portions of the two curved surface portions 3a and 3b in the axial direction as the grindstone 11 swings. Therefore, the connection portion cannot be super-finished, and the surface roughness of the connection portion cannot be improved.

Further, in this example, as the grindstone 11, a vitrified grindstone that hardly elastically deforms when the surface of the track groove 2 is superfinished is used. Therefore, even if the surface of the raceway groove 2 has a mottled surface roughness called chatter due to the grinding process performed in the previous step, this surface roughness is significantly improved by super-finishing with a vitrified grindstone. be able to.

When carrying out the present invention, as a modification of the first example of the above-described embodiment, the movement of the grindstone 11 is controlled as follows when the surface of the track groove 2 is superfinished. You can also do it.

That is, in the first example of the embodiment, the tip surface 18 of the grindstone 11 is directed from one side end portion to the other side end portion of the surface of the raceway groove 2 (from the other side end portion to the one side end portion). ) When moving, with the movement of the tip surface 18 of the grindstone 11 temporarily stopped at the connecting portion between the curved surface portion 3a on one side and the curved surface portion 3b on the other side, the swing axis C ₉ is moved to the center of curvature O _a . control is performed to move from the position (the position of the O _b) to the position of the center of curvature O _b (position of O _a). However, when practicing the present invention, in this case, moving the pivot axis C ₉ from the position of the center of curvature O _a (position of the O _b) to the position of the center of curvature O _b (position of O _a) The operation starts shortly before the tip surface 18 of the grindstone 11 reaches the connection portion between the one curved surface portion 3a and the other curved surface portion 3b, and ends when the tip surface 18 of the grindstone 11 reaches the connection portion. It is also possible to control the operation. That is, when the tip surface 18 of the grindstone 11 passes through the connection portion without temporarily stopping the movement of the tip surface 18 of the grindstone 11 at the connection portion, the moving speed of the tip surface 18 of the grindstone 11 (curved surface portion). It is also possible to control so that the speed of movement in the width direction) does not substantially change.

Usually, the shape of the surface of the track groove 2 is determined by cutting and grinding, and the super-finishing process performed thereafter is performed to adjust the surface roughness of the surface of the track groove 2. In the super-finishing process performed properly, the cutting allowance is extremely small, and the shape of the surface of the track groove 2 is not changed. _{Regarding this point, in the above-described modified example, the swing axis C 9} is moved while the tip surface 18 of the grindstone 11 is moving on one curved surface portion 3a (the other curved surface portion 3b) in the width direction. Will be done. However, even while the swing axis C ₉ is moving, the contact pressure of the tip surface 18 of the grindstone 11 with respect to one curved surface portion 3a (the other curved surface portion 3b) is appropriate due to the urging of the grindstone 11 by the cylinder 17. It is regulated by size (size within a predetermined range). Therefore, even while the swing axis C ₉ is moving, it is possible to appropriately perform superfinishing on one curved surface portion 3a (the other curved surface portion 3b).

In the case of carrying out the above-mentioned modification _{, when the swing radius becomes small while the swing axis C 9} is moving, the swing speed (swing frequency) of the grindstone 11 is controlled by controlling the servomotor 16. Is preferably reduced so that the moving speed of the tip surface 18 of the grindstone 11 does not substantially change.

In any case, in the above-described modification, the tip surface 18 of the grindstone 11 is reciprocated between one side end portion and the other side end portion of the surface of the raceway groove 2 as in the case of the first example of the embodiment. _{During the moving operation, basically, the swing axis C 9} is aligned with the center of curvature of the cross-sectional shape of the curved surface portion on which the tip surface 18 of the grindstone 11 is pressed, and one of the curved surface portions is used. Only when the tip surface 18 of the grindstone 11 is moved from the to the other curved surface portion, the swing axis C ₉ is moved from the position of the center of curvature of the cross-sectional shape of the other curved surface portion to the cross-sectional shape of the other curved surface portion. Controls the movement to the position of the center of curvature of.

[Second Example of Embodiment]
A second example of the embodiment will be described with reference to FIG.
This example relates to a method for manufacturing an angular contact ball bearing, and is characterized by a method of superfinishing the raceway groove (inner ring raceway) 2a of the inner ring 4 which is a raceway ring constituting the angular contact ball bearing. Therefore, this feature portion will be mainly described below.

The inner ring 4 is made of a hard metal such as bearing steel and is formed in a cylindrical shape as a whole, and includes an outer peripheral surface and an annular raceway groove 2a formed on the outer peripheral surface. The cross-sectional shape of the raceway groove 2a is a composite curved shape formed by combining three arcs having different centers of curvature. That is, the raceway grooves 2a, each having an arc cross-sectional shape, and the curvature center O _c of the respective cross-sectional shape, O _d, O _e is in different positions, three curved portions 3c, 3d It has a surface composed of a combination of 3e and 3e. Further, in this example, in the connecting portions of the two curved surface portions 3c and 3d adjacent to each other, the end portions of the cross-sectional shapes of the curved surface portions 3c and 3d have a common tangent line to each other. Therefore, these curved surface portions 3c and 3d are smoothly connected to each other. Further, even in the connecting portions of the two curved surface portions 3d and 3e adjacent to each other, the end portions of the cross-sectional shapes of the curved surface portions 3d and 3e have a common tangent line to each other. Therefore, these curved surface portions 3d and 3e are also smoothly connected to each other. The surface of the track groove 2a is super-finished by a method described later.

The angular contact ball bearing to be manufactured in this example includes an inner ring 4, an outer ring which is a raceway ring, and a plurality of balls. The outer ring has an inner peripheral surface and an angular type raceway groove (outer ring raceway) formed on the inner peripheral surface. The plurality of balls are rotatably arranged between the raceway groove 2a of the inner ring 4 and the raceway groove of the outer ring.

Also in this example, when manufacturing such an angular contact ball bearing, the surface of the raceway groove 2a of the inner ring 4 is super-finished by the same method as in the case of the modified example of the first example of the above-described embodiment. To give. Therefore, the entire surface of the track groove 2a, that is, the three curved surface portions 3c, 3d, 3e, the connecting portions of the two curved surface portions 3c, 3d adjacent to each other, and the two curved surface portions 3d, 3e adjacent to each other are connected. High-precision super-finishing can be applied to each part in one process.

In the angular contact ball bearing including the inner ring 4, the rolling contact portion of the ball with respect to the surface of the raceway groove 2a moves in the axial direction as the axial load applied changes. Therefore, on the surface of the track groove 2a, there is a possibility that the ball may roll and contact the connecting portions of the two curved surface portions 3c and 3d adjacent to each other and the connecting portions of the two curved surface portions 3d and 3e adjacent to each other. be. Therefore, in this example, the surface roughness of these connecting portions can be improved, and the rolling fatigue life of the surface of the raceway groove 2a can be extended.
Other configurations and operations are the same as in the case of the modified example of the first example of the embodiment.

[Third example of the embodiment]
A third example of the embodiment will be described with reference to FIG.
In this example, the method of swinging the grindstone 11 (see FIG. 2) centered on _{the swinging axis C 9} when superfinishing the surface of the track groove 2 is the first example of the embodiment. Slightly different from the case.

That is, in the first example of the embodiment, when the surface of the track groove 2 is super-finished, the grindstone 11 is constant _{about the swing axis C 9 as shown by the alternate long and short dash line P in FIG.} It was oscillated at the oscillating frequency f of. On the other hand, in this example, when the surface of the track groove 2 is super-finished, the grindstone 11 is subjected to the swing direction centered _{on the swing axis C 9 as shown by the solid line Q in FIG.} While vibrating finely, it is oscillated at a constant oscillating frequency f around _{the oscillating axis C 9.}

Therefore, in this example, the amount of polishing per unit time can be increased as compared with the case of the first example of the embodiment. Therefore, even if the swing frequency f cannot be increased due to the mechanical responsiveness and the electrical responsiveness of the superfinishing device, the time for superfinishing the surface of the raceway groove 2 can be shortened.
Other configurations and operations are the same as in the case of the first example of the above-described embodiment.

In addition, the present invention can be carried out by appropriately combining the above-described embodiments as long as they do not cause mutual contradiction.

The method for superfinishing a groove of the present invention is a ball such as a four-point contact ball bearing or an angular contact ball bearing as long as the groove has a surface formed by combining a plurality of curved surface portions each having an arc-shaped cross-sectional shape. This can be applied not only to the raceway grooves formed on the outer peripheral surface of the inner ring constituting the bearing, but also to the grooves formed on the peripheral surface of various workpieces.
For example, the groove superfinishing method of the present invention includes a raceway groove existing on the inner peripheral surface of an outer ring constituting a ball bearing such as a four-point contact ball bearing and an angular ball bearing, and a ball screw shaft constituting a ball screw device. It can also be applied to a ball screw groove formed on the outer peripheral surface or a ball nut groove formed on the inner peripheral surface of the ball nut constituting the ball screw device.
When the method for superfinishing a groove of the present invention is applied to a ball screw groove or a ball nut groove, the ball screw shaft or ball nut, which is a work piece, is rotated about its own central shaft, and a grindstone is used. While moving in the axial direction with respect to the ball, the grindstone is swung in a state where the grindstone is pressed against the surface of the ball screw groove or the ball nut groove.
Further, according to the present invention, when there are three or more curved surface portions constituting the surface of the groove, the centers of curvature of the cross-sectional shapes of these curved surface portions do not have to all exist at different positions, and they do not have to exist at different positions. It suffices that the centers of curvature of the cross-sectional shapes of the adjacent curved surfaces exist at different positions.

1 Inner ring 2, 2a Track groove 3a to 3e Curved surface part 4 Inner ring 5 Base 6 X stage 7 Strut 8 Z stage 9 Swing shaft 10 Grindstone holder 11 Grindstone 12 Spindle device 13 Control device 14 Servo motor 15 Servo motor 16 Servo motor 17 Cylinder 18 Tip surface 19 Drive shaft

Claims (5)

A work having a peripheral surface and a groove having a surface formed by combining a plurality of curved surfaces formed on the peripheral surface and each having an arcuate cross-sectional shape is rotated about the central axis of the work. While pressing the tip surface of the grindstone having a width dimension smaller than the width dimension of any of the curved surface portions among the plurality of curved surface portions against the surface of the groove, the grindstone is moved to the swing axis of the grindstone. By swinging around the center, the tip surface of the grindstone is reciprocated between one side end portion and the other side end portion of the surface of the groove with respect to the axial direction of the work, and the plurality of curved surface portions. When the tip surface of the grindstone is moved from one of the two curved surfaces adjacent to each other to the other curved surface, the swing axis is set to the cross section of the one of the curved surfaces. A method for superfinishing a groove, in which the position of the center of curvature of the shape is moved to the position of the center of curvature of the cross-sectional shape of the other curved surface portion. When the tip surface of the grindstone is moved from one of the curved surfaces to the other curved surface, the movement of the tip surface of the grindstone is not temporarily stopped at the connecting portion of these two curved surfaces. The method for superfinishing a groove according to claim 1, wherein the swing axis is moved from the position of the center of curvature of the cross-sectional shape of one of the curved surfaces to the position of the center of curvature of the cross-sectional shape of the other curved surface. When the tip surface of the grindstone is moved from one of the curved surfaces to the other curved surface, the movement of the tip surface of the grindstone is temporarily stopped at the connecting portion of these two curved surfaces. The method for superfinishing a groove according to claim 1, wherein the swing axis is moved from the position of the center of curvature of the cross-sectional shape of one of the curved surfaces to the position of the center of curvature of the cross-sectional shape of the other curved surface. .. While swinging the grindstone around the swing axis at a constant swing frequency, the swing axis is moved from the position of the center of curvature of the cross-sectional shape of one of the curved surfaces to the other curved surface. The method for superfinishing a groove according to any one of claims 1 to 3, wherein the groove is moved to the position of the center of curvature of the cross-sectional shape. The raceway groove is provided with a peripheral surface and a raceway groove having a surface formed by combining a plurality of curved surface portions each having an arc-shaped cross-sectional shape, and the raceway groove is super-finished. This is a method for manufacturing a bearing including a raceway ring, wherein the raceway groove is superfinished by the groove superfinishing method according to any one of claims 1 to 4. Manufacturing method.

Images