JPH1113750A - Three-point contact ball bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a three-point contact ball bearing to provide an increased life in relation to precision. SOLUTION: A radial ball bearing consists of a three-point contact ball bearing 10, and the radial ball bearing is provided with a steel ball 1 held between outer and inner rings 2 and 3. An orbit groove 2a formed in an arcuate shape with a radius r0 in cross section is formed in the outer ring 2, and an orbit groove 3a formed in the shape of a Gothic arc in cross section is formed in the inner ring 3. The steel ball 1 is held between the outer and inner rings 2 and 3 such that the steel ball makes contact with the orbit groove 2a of the outer ring 2 at one point Po and with the orbit groove 3a of the inner ring at two points Pi1 and Pi2 . The contact angle of the steel ball 1 with the outer ring 2 is an angle α. One of the contact angles of the inner ring 3 of the steel ball 1 with two points Pi1 and Pi2 is an angle α-β obtained by subtracting a given angle β from a contact angle α. The other contact angle is an angle α+β obtained by adding the given angle β to the contact angle α.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel ball having an outer ring and an inner ring which are in contact with one of the races at one point and with the other at two points. The present invention relates to a three-point contact ball shaft held between races.

[0002]

2. Description of the Related Art In general, a ball bearing comprises an outer ring, an inner ring, and steel balls held between them.
As an example of this ball bearing, there is a radial ball bearing. In a radial ball bearing, usually, a steel ball rotates (revolution, rotation) while contacting each of an outer ring and an inner ring at one point, thereby forming an outer ring and an inner ring. Are configured to relatively rotate.

FIG. 11 shows the configuration of this radial ball bearing.
This will be described with reference to FIG. 11 is a diagram showing a configuration of a conventional ball bearing, FIG. 12 is a diagram showing a contact state between a steel ball, an outer ring, and an inner ring when the radial ball bearing in FIG. 11 is in a regular positional relationship, and FIG. FIG. 12 is a diagram for explaining a shift of a contact angle α due to a frictional force acting between a steel ball and an outer ring and an inner ring in the radial ball bearing of FIG. 11.

As shown in FIG. 11, the radial ball bearing 100 includes an outer ring 101, an inner ring 102, and a steel ball 1 held between the outer ring 101 and the inner ring 102.
Reference numeral 01 is fixed to the support 103. In contrast,
The inner ring 102 is fixed to a rotating shaft 104, and a load Q including a preload and its own weight is applied to the inner ring 102 by the rotating shaft 104 rotating around the X axis.

As shown in FIG. 12, a raceway groove 101a having an arc-shaped cross section with a radius ro is formed in the outer race 101, and the diameter of the raceway groove 101a is set to a diameter Do. A raceway groove 102a having an arc-shaped cross section with a radius ri is formed in the inner ring 102. The raceway groove 102a
Is set to the diameter Di. The steel ball 1 is composed of a sphere having a diameter d.
a, is held between the outer ring 101 and the inner ring 102 so as to contact each of the raceway grooves 102a of the inner ring 102 at one point.

The contact angle of the steel ball 1 with the outer ring 101 and the inner ring 102 is an angle α, and the contact angle α is a straight line connecting the contact point Po between the steel ball 1 and the outer ring 101 and the center point Os of the steel ball 1. And the Y axis passing through the center point Os of the steel ball 1 and orthogonal to the X axis. Similarly, the angle between the point Pi and the Y axis at the point of contact between the steel ball 1 and the inner ring 102 is the contact angle α. The contact angle α is determined by the diameter Do of the raceway groove 101a of the outer ring 101 and the diameter Di of the raceway groove 102a of the inner race 102. As can be seen from this figure, the raceway groove 1 of the outer race 101
A straight line l connecting the contact point Pi with the raceway groove 102a of the inner ring 102 from the contact point Po with the center ball Os of the steel ball 1 to the contact point Pi with the inner ring 102.
The center of the cross section of each of the track grooves 101a and 102a is located above, and such a positional relationship is called a normal positional relationship.

However, actually, as shown in FIG.
The contact angle α is shifted by an angle Δα due to the frictional force acting between the steel ball 1 and the outer ring 101 and the inner ring 102. That is, the points of contact Po and Pi move to the points Po 'and Pi'. The shift of the contact angle α by the angle Δα means that the contact angle α is shifted by a distance Δ in a direction perpendicular to the contact angle α, and the positional relationship between the contact points Po ′ and Pi ′ in the state shifted by the distance Δ While holding, the steel ball 1 is stably held between the outer ring 101 and the inner ring 102. This corresponds to the apparently larger diameter d of the steel ball 1, and the difference Δd is represented by the following equation (1).

Δd = dd ′ = {r− (d / 2)} μ ² (1) where μ is the steel ball 1, the outer ring 101, and the inner ring 10.
2 and r indicates the radius of the raceway groove.

For example, if the radius r of the raceway groove is 1.06 mm,
The diameter d of the steel ball 1 is 2.0 mm, and the friction coefficient μ is 0.01 to
Assuming a value between 0.02, the difference Δ
d is 6 nm to 2 when the friction coefficient μ is between 0.01 and 0.02.
4 nm. The value of the difference Δd within such a range does not cause a problem when used in a general device, but when used in a hard disk device or a precision machine tool, the required accuracy of the device is nm. Since it is on the order, it is difficult to secure an accuracy on the order of several tens of nm using the above-described radial ball bearing.

Therefore, as an alternative to the above-described radial ball bearing, a three-point contact ball bearing can be considered. This three-point contact ball bearing is configured, for example, to hold a steel ball between an outer ring and an inner ring so as to contact the outer ring at one point and to contact the inner ring at two points.

The structure of the three-point contact ball bearing will be described with reference to the drawings. FIG. 14 is a view showing a configuration of a conventional three-point contact ball bearing, and FIG. 15 is a view for explaining a method of machining a raceway groove of an inner race of the three-point contact ball bearing of FIG.

As shown in FIG. 14, a three-point contact ball bearing 200 includes an outer ring 201 fixed to a support table 103,
The inner ring 202 fixed to the rotating shaft 104 and the outer ring 20
1 and a steel ball 1 held between the inner ring 202. A raceway groove 201a having an arc-shaped cross section with a radius ro is formed on the outer ring 201, and a raceway groove 202a having a cross section of a Gothic arc is formed on the inner ring 102. The steel ball 1 is made up of a sphere having a diameter d. The sphere has an outer race 201 and an inner race 202 so as to contact the raceway groove 201a of the outer race 201 at one point and to contact the raceway groove 202a of the inner race 202 at two points. And is held between.

The contact angle of the steel ball 1 with the outer ring 201 is an angle α, and the contact point is a point Po. On the other hand, one of the contact angles of the steel ball 1 with respect to the two points of the inner ring 202 is the angle γ.
1 and the contact point Pi1. Inner ring 20 of steel ball 1
The other of the contact angles with respect to two points is an angle γ2, and the contact point is a point Pi2.

A method of determining the cross-sectional shape of the raceway groove 202a of the inner ring 202 will be described with reference to FIG.

First, as shown in FIG. 15A, an inner ring member is formed by combining two ring-shaped components 202b more integrally with each other, such as an arbor, and the outer peripheral surface of the inner ring member is positioned on the Y axis. A point O which is ΔY away from the center position Os of the steel ball 1
An arc-shaped orbit groove 202c having a radius ri centered on i is formed. After the formation of the raceway groove 202c, the inner race member is separated into the constituent members 202b, and the mating surfaces of the constituent members 202b are cut by the width ΔXc. After this cut,
As shown in FIG. 15 (b), the respective constituent members 202b are again united together. Each component 2 after this cut
The inner race 202 having the raceway groove 202a having the cross-sectional shape of the Gothic arc is obtained by integrally combining 02b.

As described above, in the three-point contact ball bearing, the steel ball 1
Is held between the outer ring 201 and the inner ring 202 so that the steel ball 1 contacts the raceway groove 201a of the outer ring 201 at one point and the raceway groove 202a of the inner ring 202 at two points. The positional relationship between the outer ring 201 and the inner ring 202 is kept constant irrespective of friction, and required accuracy, for example, accuracy on the order of nm can be easily secured.

[0017]

However, in the above-mentioned conventional three-point contact ball bearing, as shown in FIG.
The tangent line lo at o (the center point Os of the steel ball 1 and the contact point Po
), The steel ball 1 and the inner ring 20.
Assuming that the point of intersection with the straight line li passing through each of the contact points Pi1 and Pi2 between the two track grooves 202a is Poi, the point of intersection Poi is not located on the X axis (rotation axis) which is the center of rotation, and this point of intersection Poi
The distance in the direction along the Y axis between the X axis and the X axis is large. Assuming that the tangents at the contact points Pi1 and Pi2 are li1 and li2, the angle between the tangent li1 and the straight line li becomes the contact angle γ1 and the tangent l
The angle formed by i2 and the straight line li is equal to the contact angle γ2, and the angle formed by the tangent line li1 and the straight line li and the tangent line l
The angle formed by i2 and the straight line li increases. Therefore, the slip at each of the contact points Pi1 and Pi2, that is, the slip within the contact ellipse becomes large, causing problems such as a short bearing life. In particular, when used in a hard disk drive, a precision machine tool, or the like, it takes a short time. There is a problem that rotation accuracy, vibration accuracy and the like are reduced.

An object of the present invention is to provide a three-point contact ball bearing capable of extending the life with respect to accuracy.

[0019]

According to the first aspect of the present invention,
A steel ball is held between each of the outer and inner races so as to contact one of the races at one point and the other at two points. In the point contact ball bearing, assuming that the contact angle of the steel ball with respect to one point of the one orbital ring is α, one of two contact angles of the steel ball with respect to the other orbital ring is set as the contact angle α. The contact angle of the two points is defined as an angle obtained by adding the predetermined angle β, and the other of the two contact angles is defined as the angle obtained by subtracting the predetermined angle β from the contact angle α.

In the three-point contact ball bearing according to the first aspect of the present invention, when the contact angle of one of the steel balls with respect to one of the races is α, one of the contact angles of the steel ball with the other race is defined as one of the two contact angles. The contact angle α is obtained by adding the predetermined angle β to the contact angle α, and the other of the two contact angles is set to the angle obtained by subtracting the predetermined angle β from the contact angle α. The angles formed by the respective tangent lines at the points and the straight lines connecting the respective contact points become smaller, and the slip at the respective contact points between the steel ball and the other race, that is, the slip within the contact ellipse, becomes smaller. Therefore, the life with respect to accuracy can be extended as compared with the conventional three-point contact ball bearing.

[0021]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a structural view showing a main part of a three-point contact ball bearing according to a first embodiment of the present invention.

As shown in FIG. 1, the three-point contact ball bearing 10 forms a radial ball bearing, which is held between the outer ring 2, the inner ring 3, and the outer ring 2 and the inner ring 3. Steel ball 1 having The outer race 2 has a raceway groove 2a having an arc-shaped cross section with a radius ro, and the inner race 3 has a raceway groove 3a having a Gothic arc cross-section. The steel ball 1 is made up of a sphere having a diameter d. The sphere has an outer ring 2 and an inner ring 3 which contact the raceway groove 2a of the outer ring 2 at one point and the raceway groove 3a of the inner ring 3 at two points. And is held between. The contact angle of the steel ball 1 with the outer ring 2 is an angle α, and the contact point is a point Po. The contact angle α is set to the same angle as that of the above-described conventional radial ball bearing. On the other hand, one of the contact angles of the steel ball 1 with respect to the two points of the inner ring 3 is an angle α-β obtained by subtracting a predetermined angle β from the contact angle α, and the contact point is a point Pi1. The other of the contact angles of the steel ball 1 with respect to the two points of the inner ring 3 is an angle α + β obtained by adding a predetermined angle β to the contact angle α, and the contact point is a point Pi2.

Next, a method of setting the predetermined angle β will be described with reference to FIG.
This will be described with reference to FIG. FIG. 2 is a diagram for explaining a method of setting the predetermined angle β in the three-point contact ball bearing of FIG.

The predetermined angle β is determined by the position of the outer race 2 of the steel ball 1 due to the displacement between the outer race 2 and the steel ball 1 caused by the fall of the outer race 2.
The angle of deviation from the contact angle α with respect to
Assuming that the deviation angle of the steel ball 1 from the contact angle α of the steel ball 1 with the outer ring 2 due to the positional deviation of the steel ball 1 caused by the friction between the steel ball 1 and the outer ring 2 is Δα, the angle obtained by adding the deviation angle Δα ′ and the deviation angle Δα The angle is set to be large and as small as possible.

More specifically, as shown in FIG. 2, when the outer ring 2 falls down, a positional shift occurs between the outer ring 2 and the steel ball 1, and the contact angle causes the contact angle to deviate from the contact angle α. Δα
'It's off. Assuming that the inclination of the outer ring 2 is Δθ, the pitch diameter of the steel ball 1 is Dp, the diameter of the steel ball 1 is d, and the radius of the raceway groove 2a of the outer ring 2 is ro, Δα ′ is given by the following equation (2). Is calculated by

Δα ′ = [Dp / ｛2 (ro−d / 2) cos α｝ −1] Δθ (2) where Δθ = ΔH / Dp, and ΔH indicates the amount of inclination of the outer ring 2.

Further, similarly to the above-described conventional radial ball bearing, the friction between the steel ball 1 and the outer ring 2 causes a displacement of the steel ball 1, and the displacement causes the contact angle of the steel ball 1 with the outer ring 2. Is shifted from the contact angle α by an angle Δα. Between this deviation angle Δα and the friction coefficient μ between the steel ball 1 and the outer ring 2,
By satisfying the following relational expressions (3) and (4), the shift angle Δα is obtained by the expression (5).

Tan Δα = μ (3) Δα << 1 (4) Δα ≒ μ (5) Therefore, the predetermined angle β is as small as possible while satisfying the condition of the following equation (6). Is set to be

Β> Δα ′ + Δα (6) For example, the pitch diameter Dp of the steel ball 1 is set to 9.0 mm, the diameter d of the steel ball 1 is set to 2.0 mm, and the radius ro of the raceway groove 2 a of the outer ring 2 is set to 1 0.06 mm, the contact angle α is 20 degrees, and the inclination amount of the outer ring 2 is 25 μm (estimated value), the deviation angle Δα ′ is 12.6 degrees according to the above equation (2). If the friction coefficient μ is 0.1, the deviation angle Δα is 6 degrees according to the above equation (5). Therefore, the predetermined angle β is set to 19 degrees so as to satisfy the condition that the angle is larger than 18.6 degrees (12.6 degrees + 6 degrees) and is as small as possible from the above equation (6).

Next, a method of calculating an offset amount for determining the sectional shape of the raceway groove 3a of the inner race 3 will be described with reference to FIG. FIG. 3 is a diagram for explaining a method of calculating an offset amount for determining the cross-sectional shape of the raceway groove of the inner ring in the three-point contact ball bearing of FIG.

As described above, the raceway groove 3a of the inner race 3
Each contact angle of the steel ball 1 with respect to the raceway groove 3a of the inner ring 3 (α-
β, α + β) so as to obtain a Gothic arc sectional shape. The cross-sectional shape of this Gothic arc is shown in FIG.
As shown in FIG. 5, the center positions Oi1 and Oi2 of the arcs are offset from a straight line ls passing through the center position Os of the steel ball 1 and forming a contact angle α with the Y axis. . The offset amounts of the center positions Oi1 and Oi2 of the arc with respect to the straight line ls are an offset amount ΔX indicating a distance in a right angle direction and an offset amount ΔY indicating a distance from the center position Os of the steel ball 1 in a direction along the straight line ls. And represented by
The offset amounts ΔX and ΔY are calculated by the following equations (7) and (8).

ΔX = (ri−d / 2) sin β (7) ΔY = (ri−d / 2) cos β (8) For example, when the diameter d of the steel ball 1 is 2.0 mm, Assuming that the radius ri of the raceway groove 3a is 1.06 mm and the predetermined angle β is 20 degrees, the offset amount ΔX is obtained by the above equation (7).
Is 21 μm, and the offset Δ
Y becomes 56 μm.

As described above, by calculating the offset amounts ΔX and ΔY, the center position O of two arcs having a radius ri that defines the cross-sectional shape of the Gothic arc in the track groove 3a is obtained.
i1 and Oi2 are obtained, and it becomes possible to form a raceway groove 3a having a cross-sectional shape of a Gothic arc in which each contact angle (α-β, α + β) with respect to the raceway groove 3a of the inner ring 3 of the steel ball 1 is obtained.

As described above, in the present embodiment, the outer race 2 and the inner race 2 are so arranged that the steel ball 1 contacts the raceway groove 2a of the outer race 2 at one point and the raceway groove 3a of the inner race 3 at two points. 3, the positional relationship between the steel ball 1 and the outer ring 2 and the inner ring 3 is kept constant irrespective of friction, and it is possible to easily secure required accuracy, for example, accuracy on the order of nm. Can be.

One of the contact angles of the steel ball 1 with respect to the two points of the inner ring 3 is defined as an angle obtained by adding a predetermined angle β to the contact angle α, and the other of the contact angles of the steel ball 1 with the inner ring 3 is defined as the contact angle α. Is the angle obtained by subtracting the predetermined angle β from the angle 、, the angle formed by the tangent lines li1 and li2 at the contact points Pi1 and Pi2 between the steel ball 1 and the inner ring 3 and the straight line li connecting the contact points Pi1 and Pi2. γ1 becomes smaller, and the slip at the contact points Pi1 and Pi2 between the steel ball 1 and the inner ring 3, that is, the slip within the contact ellipse becomes smaller. Therefore, the life with respect to accuracy can be extended as compared with the conventional three-point contact ball bearing.

Further, the predetermined angle β is set such that the outer ring 2 of the steel ball 1
Is added to the contact angle α of the steel ball 1 with respect to the outer ring 2 due to the displacement of the steel ball 1 caused by the friction between the steel ball 1 and the outer ring 2. Are set so as to be larger than the set angle and as small as possible, so that the respective tangent lines li1, l at the respective contact points Pi1, Pi2 between the steel ball 1 and the inner ring 3 are set.
The angle γ formed between i2 and a straight line l i connecting the contact points Pi1 and Pi2.
1 is further reduced, and the slip at the contact points Pi1 and Pi2 between the steel ball 1 and the inner ring 3, that is, the slip within the contact ellipse, is further reduced.

In the present embodiment, the steel ball 1 is used as the outer ring 2
Outer race 2 and inner race 3 so as to make contact with raceway groove 2a at one point and to raceway groove 3a of inner race 3 at two points.
However, the outer ring 2 is held so that the steel ball 1 contacts the raceway groove 2a of the outer race 2 at two points and the raceway groove 3a of the inner race 3 at one point. In the configuration held between the steel ball 1 and the inner ring 3, one of the contact angles of the steel ball 1 with respect to the two points of the outer ring 2 is in contact with the contact angle α of the steel ball 1 with respect to one point of the inner ring 3. A similar effect can be obtained by setting the angle obtained by adding the predetermined angle β to the angle α and setting the other of the contact angles of the steel ball 1 and the outer ring 2 to the angle obtained by subtracting the predetermined angle β from the contact angle α.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a configuration diagram showing a main part of a three-point contact ball bearing according to a second embodiment of the present invention.

The three-point contact ball bearing 20 according to the present embodiment
Constitutes a radial ball bearing as shown in FIG. 4, in which the contact angle α of the steel ball 1 with respect to two points of the inner ring 3 of the steel ball 1 with respect to the contact angle α of the steel ball 1 with respect to one point of the outer ring 2. Is an angle obtained by adding a predetermined angle β1 to the contact angle α,
The other contact angle of the steel ball 1 with the inner ring 3 is defined as an angle obtained by subtracting the predetermined angle β2 from the contact angle α, and the tangent line lo to the contact angle α at the contact point Po between the steel ball 1 and the outer ring 2 and the steel ball 1 and the inner ring 3 The predetermined angle β1 and the predetermined angle β2 are set such that the straight lines li passing through the respective contact points Pi1 and Pi2 intersect at the same point on the X-axis.

In setting the predetermined angles β1 and β2, first, the tangent line lo to the contact angle α at the contact point Po between the steel ball 1 and the outer ring 2 is represented by a function of the coordinate system of the X and Y axes in the drawing. This tangent line lo is expressed by the following equation (9).

Y = aX + b (9) where a = − {Dp / 2 + d / (2 cos α)} / [{Dp / (2 cos α) + d / 2} / sin α−Dp tan α / 2] b = Dp / 2 + d / (2cos α) The point Poi at which the tangent line lo intersects the X axis is expressed by Y in the above equation (9).
= 0, and Poi = (xp, 0) xp = [{Dp / (2 cos α) + d / 2} / sin α−Dp tan α / 2].

Next, each contact point Pi between the steel ball 1 and the inner ring 3
1, Pi2 is represented by the coordinates of the coordinate system of the X and Y axes, and is defined as follows.

Pi1 = (x1, y1) Pi2 = (x2, y2) where x1 = −dsin (α−β1) / 2 y1 = Dp / 2−dcos (α−β1) / 2 x2 = −dsin ( α + β2) / 2 y2 = Dp / 2−dcos (α + β2) / 2 A straight line li passing through the contact points Pi1 and Pi2 is expressed by the following equation (10).

Y = {(y1-y2) / (x1-x2)} (X-x1) + y1 (10) A condition for the straight line li to intersect with the straight line lo at the same point on the X axis, that is, a straight line li is the intersection P between the straight line lo and the X axis
The condition passing through oi is represented by a conditional expression obtained by substituting the intersection Poi into the above expression (10), and this conditional expression is the following expression (11).

{Dp−dcos (α−β1)} {sin (α−β1) −sin (α + β2)} d = {cos (α + β2) −cos (α−β1)} d × [Dp {1 / (cos α sin α) −tan α} + {sin (α−β1) −1 / sin α} d] (11) In the above equation (11), the diameter d of the steel ball 1, the pitch diameter Dp of the steel ball 1, the contact If the angle α is a constant, the equation (11) is
This is a conditional expression for obtaining the relationship between the predetermined angle β1 and the predetermined angle β2. Further, a relationship of β1> β2 is established between the predetermined angle β1 and the predetermined angle β2. Therefore, the predetermined angle β
To determine 1, β2, the predetermined angle β2 is first determined by using the method of setting the predetermined angle β in the above-described second embodiment, and the determined predetermined angle β2 is determined by the above (11).
A method of determining a predetermined angle β1 that satisfies the relationship β1> β2 by substituting into the equation is used.

When the predetermined angles β1 and β2 are determined in this manner, the contact angles (α-β1, α + β2) of the steel ball 1 with respect to the raceway groove of the inner ring 3 are obtained from the determined predetermined angles β1 and β2. Thus, the cross-sectional shape of the gothic arc in the raceway groove of the inner ring 3 is defined.

As described above, in the present embodiment, one of the contact angles of the steel ball 1 with respect to the two points of the inner ring 2 is set to the contact angle α with respect to the contact angle α of the outer ring 2 with respect to one point. β
1 is the angle obtained by subtracting 1 and the other of the three contact angles of the steel ball 1 with the inner ring is the angle obtained by adding the predetermined angle β2 from the contact angle α, and the tangent to the contact angle α at the contact point Po between the steel ball 1 and the outer ring 2 lo, each contact point Pi1, P between steel ball 1 and inner ring 3
Since the predetermined angle β1 and the predetermined angle β2 are set so that the straight line li passing through i2 intersects at the same point on the X axis, each contact point Pi1 between the steel ball 1 and the inner ring 3 is set. , Pi2
, I.e., the slip within the contact ellipse, becomes smaller, and the life with respect to accuracy can be extended as compared with the conventional three-point contact ball bearing.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a configuration diagram showing a main part of a three-point contact ball bearing according to a second embodiment of the present invention.

The three-point contact ball bearing 30 in the present embodiment
Constitutes a radial ball bearing as shown in FIG. 5, in which the contact angle α of the steel ball 1 with respect to two points of the outer ring 2 with respect to the contact angle α of the steel ball 1 with respect to one point of the inner ring 3. Is an angle obtained by adding a predetermined angle β1 to the contact angle α,
The other contact angle of the steel ball 1 with the outer ring 2 is defined as the angle obtained by subtracting the predetermined angle β2 from the contact angle α, and the tangent line i to the contact angle α at the contact point Pi between the steel ball 1 and the inner ring 3 and the steel ball 1 and the outer ring 3 The predetermined angle β1 and the predetermined angle β2 are set so that the straight line lo passing through each of the contact points Po1 and Po2 intersects at the same point Poi on the X-axis.

In the case of the present embodiment, the same effects as those of the above-described second embodiment can be obtained.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 6 is a configuration diagram showing a main part of a three-point contact ball bearing according to a fourth embodiment of the present invention.

The three-point contact ball bearing 40 in the present embodiment
Constitutes a thrust ball bearing as shown in FIG. 6, in which the contact angle α of the steel ball 1 with respect to two points of the inner ring 42 with respect to the contact angle α of the steel ball 1 with respect to one point of the outer ring 41. One of the contact angles is set to the angle obtained by adding the predetermined angle β to the contact angle α, and the other of the contact angles of the steel ball 1 to the inner ring 42 is set to the angle obtained by subtracting the predetermined angle β from the contact angle α. ing.

As described above, according to the present embodiment, a thrust ball bearing can be obtained in which the life with respect to accuracy can be lengthened.

Further, in the present embodiment, similarly to the first embodiment described above, the predetermined angle β is set with respect to the outer ring 41 of the steel ball 1 due to the displacement between the outer ring 41 and the steel ball 1 caused by the fall of the outer ring 41. The deviation angle Δα ′ from the contact angle α and the deviation angle Δα from the contact angle α of the steel ball 1 with respect to the outer ring 41 due to the positional deviation of the steel ball 1 caused by friction between the steel ball 1 and the outer ring 41 are added. By setting the angle larger than the angle and as small as possible, the steel ball 1
Slip at the contact points Pi1 and Pi2 between the and the inner ring 42, that is, the slip within the contact ellipse, can be further reduced.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to FIG. FIG. 7 is a configuration diagram showing a main part of a three-point contact ball bearing according to a fifth embodiment of the present invention.

In this embodiment, as shown in FIG. 7, the ball screw 50 is applied by applying the principle of the three-point contact ball bearing of the present invention.
The ball screw 50 has a screw shaft 51, a nut 52, and a plurality of steel balls 1 held between the screw shaft 51 and the nut 52. The screw shaft 51 has a shaft groove 51a having an arc-shaped cross section with a predetermined radius, and the nut 52 has a nut groove 52a having a Gothic arc cross section. The steel ball 1 is brought into contact with the shaft groove 51a of the screw shaft 51 at one point Po and the nut 5
It is held between the nut 52 and the screw shaft 51 so as to contact the two nut grooves 52a at two points Pi1 and Pi2.
The contact angle of the shaft groove 51a of the screw shaft 51 of the steel ball 1 with respect to the point Po is an angle α, and the nut groove 52 of the nut 52 of the steel ball 1 is formed.
The other of the contact angles of the steel ball 1 with respect to the axial groove 51a is a predetermined angle from the contact angle α so that one of the contact angles with respect to the two points Pi1 and Pi2 is the angle obtained by adding the predetermined angle β to the contact angle α. Each angle is set so that the angle is obtained by subtracting β.

Thus, the ball screw 50 capable of extending the life with respect to accuracy can be obtained.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to FIG. FIG. 8 is a configuration diagram showing a main part in a sixth embodiment of the three-point contact ball bearing according to the present invention.

In the present embodiment, as shown in FIG. 8, the ball guide 6 is applied by applying the principle of the three-point contact ball bearing of the present invention.
0, the ball guide 60 has a track 61, a moving body 62, and a plurality of steel balls 1 for guiding the moving body 62 along the track 61. A rail groove 61a having a Gothic arc cross-sectional shape is formed in the way 61, and a bearing groove 62a having an arc-shaped cross-sectional shape is formed in the moving body 62. The steel ball 1 circulates between the bearing groove 62 a of the moving body 62 and the rail groove 61 a of the track base 61 in accordance with the movement of the moving body 62.
Rotate while circulating through 2b.

The steel ball 1 is provided in the bearing groove 62 of the moving body 62.
a and the rail groove 61a of the rail 61 at two points Pi1 and Pi2. The contact angle of the rail groove 62a of the moving body 62 of the steel ball 1 with respect to the point Po is an angle α, and the rail groove 61 of the rail 61 of the steel ball 1 is
The other of the contact angles of the steel ball 1 with respect to the rail groove 61a is a predetermined angle from the contact angle α so that one of the contact angles with respect to the two points Pi1 and Pi2 is an angle obtained by adding the predetermined angle β to the contact angle α. Each angle is set so that the angle is obtained by subtracting β.

Accordingly, the ball guide 60 capable of extending the life with respect to accuracy can be obtained.

It should be noted that two-point contact may be made with the bearing groove 62a of the moving body 62 and that the rail groove 61a of the track base 61 may be contacted at one point.

(Seventh Embodiment) Next, a seventh embodiment of the present invention will be described with reference to FIG. FIG. 9 is a configuration diagram illustrating a main part of a three-point contact ball bearing according to a seventh embodiment of the present invention.

In the present embodiment, as shown in FIG. 9, the ball guide 7 is applied by applying the principle of the three-point contact ball bearing of the present invention.
0, the ball guide 70 has a track 71, a moving body 72, and a plurality of circulation rows of steel balls 1 for guiding the moving body 72 along the track 71. The rail 71 has a rail groove 71a having a Gothic arc cross-sectional shape.
71b is formed for each circulating train of the steel balls 1, and the moving body 72 has bearing grooves 72a, 72 having an arc-shaped cross section.
b is formed for each circulating train of the steel balls 1.

A rail groove 71a and a bearing groove 72a are combined with the circulating train of the steel balls 1 located at the upper stage, and the steel balls 1 in this circulating train move in accordance with the movement of the moving body 72. Between the bearing groove 72a and the rail groove 71a of the rail 71 while circulating through the circulation hole 72c in the moving body 72. Steel ball 1 located at the bottom
The rail groove 71b and the bearing groove 7
2b, and the steel balls 1 in the circulation train are provided with a bearing groove 72b of the moving body 72 and a rail groove 71 of the track base 71.
b) and makes a rotational movement while circulating through a circulation hole 72d in the moving body 72.

The steel ball 1 is provided in the bearing groove 72 of the moving body 72.
It rotates while contacting at one point Po with respect to a and 72b and at two points Pi1 and Pi2 with the rail grooves 71a and 71b of the way 71. Rail grooves 72a, 7 of moving body 72 of steel ball 1
The contact angle of the point 2b with respect to the point Po is an angle α, and the two points Pi1 and Pi2 of the rail grooves 71a and 71b of the rail 71 of the steel ball 1 are shown.
One of the contact angles with respect to the rail groove 71a, 7
The other of the contact angles with respect to 1b is set to an angle obtained by subtracting a predetermined angle β from the contact angle α.

The contact point Po in the circulating train of the steel balls 1 located at the upper stage is located diagonally upward, and the contact points Pi1 and Pi2 are located diagonally downward. On the other hand, the contact point Po in the circulating train of the steel balls 1 located at the lower stage is located diagonally below, and the contact points Pi1 and Pi2 are located diagonally above.
As described above, the contact points Po and Pi1, Pi2 in the circulation train of the steel balls 1 located in the upper stage and the contact points Po, Pi1, Pi2 in the circulation train of the steel balls 1 located in the lower stage.
Is symmetric with respect to a horizontal axis orthogonal to the moving direction of the moving body 72 (the direction perpendicular to the plane of the paper). Therefore, although the rigidity against the moment is small, the interference between the moving body 72 and the track 71 is very small.

As described above, it is possible to obtain the ball guides 70 in a plurality of circulation rows to which the principle of the three-point contact ball bearing of the present invention is applied.

In the present embodiment, the steel ball 1 is located at one point Po with respect to the bearing grooves 72a and 72b of the moving body 72 and at two points Pi with respect to the rail grooves 71a and 71b of the track base 71.
1 and Pi2, but the steel ball 1 contacts the rail grooves 71a and 71b of the rail 71 at one point and the bearing grooves 72a and 72b of the moving body 72 at two points. You can also.

(Eighth Embodiment) Next, an eighth embodiment of the present invention will be described with reference to FIG. FIG.
0 is a configuration diagram showing a main part of an eight embodiment of a three-point contact ball bearing according to the present invention.

In the present embodiment, as shown in FIG.
The ball guide 80 is configured by applying the principle of the three-point contact ball bearing of the present invention, and the ball guide 80 includes a raceway 81 and
It has a moving body 82 and a plurality of circulation rows of steel balls 1 for guiding the moving body 82 along the track 81. Railway 81
Has a rail groove 81 having a Gothic arc cross-sectional shape.
a, 81b are formed for each circulating train of the steel ball 1, and the moving body 8
2, a bearing groove 82a having an arc-shaped cross section is provided.
82b is formed for each circulating train of steel balls 1.

A rail groove 81a and a bearing groove 82a are combined with the circulating train of the steel balls 1 located in the upper stage, and the steel balls 1 in this circulating train move in accordance with the movement of the moving body 82. Between the bearing groove 82a and the rail groove 81a of the rail 81 while circulating through the circulation hole 82c in the moving body 82. Steel ball 1 located at the bottom
The rail groove 81b and the bearing groove 8
2b, and the steel balls 1 of this circulation train are provided with a bearing groove 82b of the moving body 82 and a rail groove 81 of the track base 81.
b) and makes a rotational movement while circulating through a circulation hole 82d in the moving body 82.

The steel ball 1 is mounted on the bearing groove 82 of the moving body 82.
a, 82b and the rail groove 81a, 81b of the track base 81 at two points Pi1, Pi2 while rotating. Rail grooves 82a, 8 of moving body 82 of steel ball 1
The contact angle of the point 2b with respect to the point Po is an angle α, and the two points Pi1 and Pi2 of the rail grooves 81a and 81b of the rail 81 of the steel ball 1 are shown.
One of the contact angles with respect to the rail groove 81a, 8 of the steel ball 1 is set to an angle obtained by adding a predetermined angle β to the contact angle α.
The other of the contact angles with respect to 1b is set to an angle obtained by subtracting a predetermined angle β from the contact angle α.

The contact point Po in the circulating train of the steel balls 1 located at the upper stage is at the obliquely lower position, and the contact points Pi1 and Pi2 are at the obliquely upper position. On the other hand, the contact point Po in the circulating train of the steel balls 1 located at the lower stage is at an obliquely upper position, and the contact points Pi1 and Pi2 are at obliquely lower positions.
As described above, the contact points Po and Pi1, Pi2 in the circulation train of the steel balls 1 located in the upper stage and the contact points Po, Pi1, Pi2 in the circulation train of the steel balls 1 located in the lower stage.
Is symmetric with respect to a horizontal axis orthogonal to the moving direction of the moving body 82 (the direction perpendicular to the plane of the paper).

Thus, a plurality of circulation rows of ball guides 80 having high rigidity against moment can be obtained.

In this embodiment, the steel ball 1 is located at one point Po with respect to the bearing grooves 82a and 82b of the moving body 82 and at two points Pi with respect to the rail grooves 81a and 81b of the rail 81.
1 and Pi2, but the steel ball 1 is configured to contact the rail grooves 81a and 81b of the rail 81 at one point and the bearing grooves 82a and 82b of the moving body 82 at two points. You can also.

[0078]

As described above, according to the three-point contact ball bearing of the first aspect, if the contact angle of one ball of the steel ball with respect to one point is α, the steel ball contacts the other ball of the other race. Since one of the two contact angles is an angle obtained by adding the predetermined angle β to the contact angle α, and the other of the two contact angles is an angle obtained by subtracting the predetermined angle β from the contact angle α, The angles formed by the respective tangent lines at the respective contact points with the other bearing ring and the straight lines connecting the respective contact points become smaller, and the slip at the respective contact points between the steel ball and the other bearing ring, that is, the contact ellipse Slip inside is reduced. Therefore, the life with respect to accuracy can be extended as compared with the conventional three-point contact ball bearing.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a main part in a first embodiment of a three-point contact ball bearing according to the present invention.

FIG. 2 is a diagram for explaining a method of setting a predetermined angle β in the three-point contact ball bearing of FIG.

3 is a diagram for explaining a method of calculating an offset amount for determining a cross-sectional shape of a raceway groove of an inner ring in the three-point contact ball bearing of FIG. 1;

FIG. 4 is a configuration diagram illustrating a main part of a three-point contact ball bearing according to a second embodiment of the present invention.

FIG. 5 is a configuration diagram showing a main part of a three-point contact ball bearing according to a second embodiment of the present invention.

FIG. 6 is a configuration diagram illustrating a main part of a three-point contact ball bearing according to a fourth embodiment of the present invention.

FIG. 7 is a configuration diagram showing a main part of a three-point contact ball bearing according to a fifth embodiment of the present invention.

FIG. 8 is a configuration diagram illustrating a main part of a three-point contact ball bearing according to a sixth embodiment of the present invention.

FIG. 9 is a configuration diagram showing a main part of a three-point contact ball bearing according to a seventh embodiment of the present invention.

FIG. 10 is a configuration diagram showing a main part of a three-point contact ball bearing according to an eighth embodiment of the present invention.

FIG. 11 is a view showing a configuration of a conventional ball bearing.

12 is a diagram showing a contact state between a steel ball and an outer ring and an inner ring when the radial ball bearing in FIG. 11 is in a regular positional relationship.

13 is a view for explaining a shift of a contact angle α due to a frictional force acting between a steel ball and an outer ring or an inner ring in the radial ball bearing of FIG. 11;

FIG. 14 is a view showing a configuration of a conventional three-point contact ball bearing.

FIG. 15 is a view for explaining a method of processing a raceway groove of an inner race of the three-point contact ball bearing of FIG. 14;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Steel ball 2,41 Outer ring 2a, 3a Raceway groove 3,52 Inner race 10,20,30,40 Three-point contact ball bearing 50 Ball screw 60,70,80 Ball guide 51 Screw shaft 52 Nut 61,71,81 Way base 62, 72, 82 Moving object

Claims (1)

[Claims] A steel ball is provided between each of the outer and inner races so that the steel ball contacts one of the races at one point and the other race at two points. In the held three-point contact ball bearing, assuming that the contact angle of the steel ball with respect to one point of the one orbital ring is α, one of two contact angles of the steel ball with respect to the other orbital ring is defined as α. A three-point contact ball bearing, wherein the contact angle α is obtained by adding a predetermined angle β, and the other of the two contact angles is obtained by subtracting the predetermined angle β from the contact angle α.