JP2003139135A - Linear bush and raceway shaft for linear bush - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear bush to increase an allowable load in a radial direction in a state where the characteristics of a linear bush to obtain light movement is maintained, and besides to be manufactured at a low cost and easily. SOLUTION: The linear bush is provided with a raceway shaft 1; an outer cylinder 2 mounted relatively movably on the raceway shaft; and a plurality of balls 5 movably in a rolling state situated between the raceway shaft 1 and the outer cylinder 2. Ball rolling grooves 3 approximately in a circular arc shape in cross section making one-point-contact with the ball 5 and formed in the raceway shaft 1, and the depth of the ball rolling groove 3 are set to approximate 1/50 of the diameter of the ball 5. The linear bush does not need transmit torque like a ball spline and may be loaded in a radial direction to some extent. The depth of the ball rolling groove 3 is prevented from increasing more than necessary to receive a load in a radial direction by setting the depth of the ball rolling groove to approximately 1/50 of a ball diameter and in turn grinding process is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear bush in which an outer cylinder is attached to a raceway shaft and a raceway shaft for a linear bush.

[0002]

2. Description of the Related Art In a linear bush, an outer cylinder is fitted on a raceway shaft having a circular cross section, and the outer cylinder moves linearly along the raceway axis. A plurality of balls are provided between the raceway shaft and the outer cylinder so as to be capable of rolling motion. A plurality of rows of ball rolling grooves extending in the axial direction, which are the orbits for a plurality of balls, are formed in the outer cylinder. A plurality of balls roll along the ball rolling groove in the axial direction of the outer cylinder along with the relative movement of the outer cylinder with respect to the track axis. The ball that has rolled to one end of the outer cylinder is scooped up by a retainer that is integrated into the outer cylinder, returned to the other end of the outer cylinder, and rolls again between the outer cylinder and the raceway shaft.

In the linear bush, the surface of the raceway shaft is formed into a perfect circle, so that the ball and the raceway shaft are in complete point contact at one point on the surface of the raceway shaft. Since the ball rolls on the track axis with the minimum frictional resistance, a light-moving linear bush can be obtained.

[0004]

However, in the conventional linear bushing, the ball and the raceway shaft are in complete point contact with each other at one point. Therefore, while light movement is obtained, the allowable load in the radial direction is increased. There is a problem that you can not. Further, if the outer cylinder is forced to rotate with respect to the track axis, the outer tube will rotate, which may damage the surface of the track axis and hinder the linear guide.

On the other hand, the use is different from the linear bush,
Ball splines capable of transmitting torque are known.
In the ball spline, ball rolling grooves extending in the axial direction are formed on both the raceway shaft and the outer cylinder, and a plurality of balls roll on the ball rolling grooves of the raceway shaft and the outer cylinder, respectively.

In this ball spline, since the ball rolling groove is also formed on the raceway shaft, the ball and the raceway shaft contact each other with a certain contact area. Therefore, there is an advantage that the allowable load in the radial direction can be increased as compared with the linear bush. However, since the function of transmitting torque is required, the rolling groove formed on the raceway axis of the ball spline is formed relatively deep with respect to the ball diameter.
In general, carbon steel having high strength is used for the ball and the raceway shaft, and the surface of the ball rolling groove, which becomes the raceway when the ball rolls, needs to be smoothly ground. It has been difficult to grind a deep groove having a smooth surface on a raceway shaft having high strength, which has been a factor of increasing costs.

Therefore, an object of the present invention is to provide a linear bush capable of increasing the allowable load in the radial direction while maintaining the characteristics of the linear bush capable of obtaining a light movement and being inexpensive and easy to manufacture. And

[0008]

The present invention will be described below. In addition, in order to facilitate understanding of the present invention, reference numerals in the accompanying drawings are added in parentheses, but the present invention is not limited to the illustrated forms.

According to the invention of claim 1, the orbital shaft (1), the outer cylinder (2) assembled so as to be movable relative to the orbital shaft (1), the orbital shaft (1) and the A linear bush including a plurality of balls (5) provided so as to be capable of rolling movement between the outer cylinder (2) and the raceway shaft (1) having a substantially arcuate cross-section that makes one point contact with the balls (5). Ball rolling groove (3) is formed, and the depth of the ball rolling groove (3) is about 1/50 or less of the diameter of the ball (5). Solved the problem.

According to this invention, since the ball rolling groove having an arcuate cross section is formed on the raceway shaft, the contact surface between the ball and the rolling groove is made larger than in the case where the rolling groove is not formed on the raceway shaft. be able to. Therefore, the allowable load in the radial direction can be increased. Further, by forming the groove, it is possible to prevent the outer cylinder from rotating with respect to the track axis (that is, prevent rotation) even if the outer tube is forced to rotate with respect to the track axis.

Unlike the ball spline, the linear bush of the present invention does not need to transmit torque, and it is sufficient that a load in the radial direction can be applied to some extent. As will be described in detail later, by setting the depth of the ball rolling groove to about 1/50 or less of the ball diameter, the depth of the ball rolling groove becomes deeper than necessary to receive the load in the radial direction. Can be prevented. Since this makes it possible to make the depth of the ball rolling groove extremely shallow, grinding of the ball rolling groove becomes easy, and furthermore, the existing outer cylinder and ball used for the linear bush with a perfect raceway axis are used. Since it can be diverted as it is, the linear bush can be easily manufactured at low cost.

According to a second aspect of the present invention, in the first aspect, the depth of the ball rolling groove (3) is about 0.05 mm or less.

The ball rolling groove is a rolling surface on which the ball rolls, and is therefore ground. This grinding process is performed, for example, by pressing the outer peripheral surface of the grinding wheel that has been rotated at a high speed against the track axis and moving the track axis in the axial direction. According to the present invention, since the cutting depth of the grinding process is set to be 0.05 mm or less, the ball rolling groove can be used for one pass (one time without reciprocating the table on which the raceway shaft is attached) even under normal grinding conditions. It is possible to produce by processing. Therefore, the ball rolling groove can be manufactured easily and quickly.

According to a third aspect of the present invention, in the linear bush according to the first or second aspect, the center (P1) of the ball (5) and the ball (5) are in contact with the ball rolling groove. The contact angle line (L) connecting the point (P2) is characterized by passing substantially through the center of the orbital axis (1).

The linear bush of the present invention does not have to have the function of transmitting torque as described above, and it is sufficient that a slight radial load can be applied. For this reason, it is most desirable that the contact angle line connecting the center of the ball and the point where the ball contacts the rolling groove substantially passes through the center of the raceway axis.

The present invention also provides, as described in claim 4,
A raceway shaft (1) for a linear bush, in which an outer cylinder (2) of the linear bush is assembled so as to be relatively movable via a plurality of balls (5) capable of rolling, the raceway shaft (1)
A ball rolling groove (3) having a substantially arcuate cross section is formed in the ball rolling point (3) so as to make a single point contact with the ball (5).
The depth may be about 1/50 or less of the diameter of the ball, and the raceway shaft (1) for a linear bush can be configured.

Further, according to the present invention, as described in claim 5, a linear bush raceway shaft to which the outer cylinder (2) of the linear bush is assembled so as to be relatively movable through a plurality of balls (5) capable of rolling motion. (1) A ball rolling groove (3) having a substantially arcuate cross section is formed on the raceway shaft (1) at one point contact with the ball, and the ball rolling groove (3) is formed.
The depth can be about 0.05 mm or less, and the raceway shaft (1) for a linear bush can be configured.

[0018]

1 and 2 show a linear bush according to an embodiment of the present invention. The linear bush includes, as a raceway shaft, a raceway shaft 1 having a substantially circular cross section and elongated in the axial direction, and an outer cylinder 2 fitted into the raceway shaft 1. The linear bush is one of the mechanical parts and is used to guide the linear motion part of the mechanism. It is used not only in the mechanical industry but also in almost all industrial fields such as electronics, electricity, medicine, civil engineering, chemistry, and automobiles.

The raceway shaft 1 has a substantially circular cross section, and is made of bearing steel, stainless steel or the like having a high rigidity. On the surface of the orbital axis 1, a ball 5 ...
A plurality of rows of ball rolling grooves 3 extending in the axial direction of the raceway shaft 1 are formed. For example, the ball rolling groove 3 is divided into four in the circumferential direction and formed into four threads. The ball rolling groove 3 has a circular arc shape whose cross section is a single arc, and the depth h thereof is about 1/50 or less of the diameter of the balls 5, preferably about 1 /.
It is set to 60 or more and 1/50 or less (see FIG. 5). The radius of curvature of the ball rolling groove 3 is slightly larger than the radius of curvature of the balls 5, ... And is set to, for example, 0.52D (D; diameter of ball). Therefore, the ball rolling groove 3 and the ball 5 are in contact with each other at one point with a certain contact area. The reason why the depth of the ball rolling groove 3 is extremely shallow will be described later.

Since the balls 5 ... Roll, the surface of the raceway shaft 1 is hardened by quenching or the like. The ball rolling groove 3 is formed by grinding the surface of the track shaft 1 using a grindstone. During the grinding process, the depth of the ball rolling groove is about 0.05 mm or less, preferably about 0.01 mm or more.
It is set to 05 mm or less. The reason why the depth of the ball rolling groove is set to about 0.05 mm or less will be described later.

The track shaft 1 may be formed with a tap, a flattening with a milling cutter, a screw, a key groove, or the like so as to be attached to an object to be linearly guided, and a hollow shaft is used to reduce the weight. In some cases.

As shown in FIGS. 2 and 3, the outer cylinder 2 fitted in the raceway shaft 1 is an outer cylinder 2 loosely fitted in the raceway shaft 1, and
A plurality of balls 5 that roll in accordance with the relative linear movement of the outer cylinder 2 with respect to the raceway shaft 1, and a plurality of balls 5 that are integrally incorporated in the outer cylinder 2 and are aligned in the axial direction of the raceway shaft 1. And a holder 6 for holding.

The outer cylinder 2 is made of strong bearing steel or the like, and is formed into a substantially cylindrical shape so that the raceway shaft 1 can penetrate therethrough. On the inner peripheral surface of the outer cylinder 2, as shown in FIG.
And the four ball rolling grooves 7 extending in the axial direction are formed corresponding to the ball rolling grooves 3 of the track shaft 1. The ball rolling groove 7 is formed in a V-shaped cross section, and the opening angle θ of both wall surfaces thereof is set to, for example, approximately 120 ° to 160 °. .. and the ball rolling groove 7 of the outer cylinder make point contact at two points.

In this embodiment, the ball rolling groove 7 has a V-shaped cross section, but it may have a Gothic arch groove having two arcs. Also in the case of this Gothic arch groove, the opening angle θ which is the intersection angle of the tangents at the contact point between the ball 5 ... And the ball rolling groove 7 is, for example, 120 °.
It is desirable to set it to ˜160 °.

In this embodiment, the balls 5 ...
Since the ball rolling groove 7 has a certain width and is in contact with the ball rolling groove 7 of the outer cylinder 2 at a single point with a certain width, the ball 5 is also in contact with the ball rolling groove 7 of the outer tube 2 at a two point with a total width. The balls 5 are in contact with the outer cylinder 2 and the raceway shaft 1 at three points. In the present invention, it is also possible to adopt a configuration in which the balls 5 ... Contact the ball rolling groove 7 of the outer cylinder 2 at one point.

As shown in FIG. 3, the outer cylinder 2 has balls 5 ...
A substantially cylindrical holder 6 in which a circuit-shaped circulation path for circulating the is formed is integrally incorporated. The circulation path will be described. Ball rolling groove 7 formed on the outer cylinder 2
And the ball rolling groove 3 formed on the raceway shaft 1 constitutes a load rolling path A. Next to the loaded rolling passage A, an unloaded return passage B in which the balls 5 released from the load roll is formed. Linear load rolling path A and unloaded return path B
A curved return passage C that connects the load rolling passage A and the unloaded return passage B is formed at both ends of the.

This retainer 6 holds balls 5 rolling between the outer cylinder 2 and the raceway shaft 1 from both sides in the load rolling passage A, and even between the outer cylinder 2 and the retainer 6 in the unloaded return passage B. Holds the ball 5. Therefore, the cage 6 prevents the balls 5 from falling off the outer cylinder 2 when the outer cylinder 2 is pulled out from the raceway shaft 1. The cage 6 is made of synthetic resin, stainless steel, or the like.

As shown in FIG. 3, retaining rings 9 for integrally assembling the retainer 6 to the outer cylinder 2 are provided at both ends of the outer cylinder 2 in the axial direction. Further, on the outer peripheral surface of the outer cylinder 2, an outer peripheral groove 2a for a snap ring for attaching the outer cylinder 2 to an object for linearly guiding the outer cylinder 2 is formed. A seal member may be attached to the outer cylinder 2 as required for dustproof measures.

When the outer cylinder 2 is linearly moved relative to the track axis 1, the balls 5 roll in the axial direction while receiving a load on the load rolling path A. The balls 5 rolling on the load rolling passage A are scooped up by the ship bottom type lip 12 formed on the cage 6 (see FIG. 3), and gradually gradually returned to one return passage C provided at both ends of the load rolling passage A. You can change the direction. Then, it moves to the unloaded return passage B. In the unloaded return path B, the balls 5 move in the opposite direction to the loaded rolling path A. The balls 5 moving in the unloaded return passage B are redirected again in the other return passage C, and are returned from the lip 12 into the loaded rolling passage A again.

FIGS. 4 and 5 show the contact state between the raceway shaft and the balls in the linear bushing of this embodiment in comparison with the contact state between the raceway shaft balls in the ball spline. In the figure, (A) shows the contact state between the raceway shaft 1 and the ball 5 in the ball spline, and (B) in the figure shows the contact state between the raceway shaft 1 and the ball 5 in the linear bush. Since the ball spline requires a function of receiving a radial load and a function of transmitting torque, the ball rolling groove 3 formed on the raceway shaft 1 of the ball spline 3
Are formed in a relatively deep groove with respect to the ball diameter. Further, the contact angle line L connecting the center point P1 of the ball 5 and the contact point P2 where the ball 5 contacts the ball rolling groove 3 does not pass through the center of the track axis 1.

On the other hand, the linear bush of this embodiment requires a function of receiving a slight radial load, but does not require a function of transmitting torque. Therefore, the ball rolling groove 3 is formed extremely shallow with respect to the ball diameter. Moreover, the contact angle line L connecting the center point P1 of the ball 5 and the contact point P2 where the ball 5 contacts the ball rolling groove 3 substantially passes through the center of the raceway axis 1.

FIG. 5 compares the depth SH of the ball rolling groove in the ball spline with the depth h of the ball rolling groove in the linear bush of this embodiment. The left half of the center line shows the depth SH of the ball rolling groove in the ball spline, and the right half of the center line shows the depth of the ball rolling groove h in the linear bush of the present embodiment. As shown in this figure, it can be seen that when the depth h of the ball rolling groove 3 is set to about 1/60 or more and about 1/50 or less of the diameter of the ball 5, the groove is extremely shallow. Here, the depth of the ball rolling groove 3 refers to the distance from the assumed perfect circular raceway axis 1 to the deepest part of the ball rolling groove 3.

The reason why the depth of the ball rolling groove 3 of the raceway shaft 1 is set to about 1/50 or less of the ball diameter will be described. The ball rolling groove 3 of the raceway shaft 1 is a surface that comes into contact with the rolling balls 5, and thus is ground so that the surface becomes smooth. This grinding process becomes easier as the rolling groove 3 has a smaller depth. In the present invention, the depth of the ball rolling groove 3 is set to about 1/50 or less of the ball diameter to prevent the ball rolling groove from becoming deeper than necessary to receive the load in the radial direction. As a result, it prevents the grinding process from becoming difficult.

FIG. 6 shows a state in which the ball 5 and the ball rolling groove 3 are in contact with each other under a load (as viewed from the direction orthogonal to the track axis 1 in this figure). The diameter of the ball is D and the ball rolling groove 3 has a radius of curvature of about 0.52D. When a load is applied to the ball 5, elastic deformation occurs at the contact portion between the ball 5 and the raceway groove 1, and a contact ellipse having a major axis radius a and a minor axis radius b is formed. As a result, the mutual approaching amount of the ball 5 and the ball rolling groove 3 becomes δ. When the load applied to the ball increases, the contact surface and mutual approaching amount δ
Also grows.

FIG. 7 is a graph showing the relationship between the load Q applied to each ball and the mutual approach amount δ. In this graph, the mutual approach amount δ is calculated from the applied load using a theoretical formula derived from the HERTZ contact theory. In this calculation, carbon steel generally used for bearings is used for the ball 5 and the raceway shaft 1, and the radius of curvature of the rolling groove is set to 52% of the diameter of the ball. Among the balls commonly used for linear bushing, the ball diameter is
Relatively small diameter (φ0.8mm-φ2.381mm)
Is used.

When the mutual approaching amount δ becomes larger than the depth of the ball rolling groove 3 as shown in FIG. 6, the ball 5 rides on the edges 3a, 3a of the ball rolling groove 3. When riding on the edge, the ball 5 moves to the edge 3 of the ball rolling groove 3.
Since the two points a and 3a are contacted, a local edge load acts on the ball 5. This edge load causes local plastic deformation of the ball 5 and the ball rolling groove 3. Therefore, the depth of the ball rolling groove 3 is preferably set to a depth such that the ball 5 does not ride on the edges 3a, 3a of the ball rolling groove 3 even if a load is applied.

By the way, in a linear system such as a linear bushing, a basic static load rating Co is specified in order to represent the static load capacity of the system. The basic static load rating Co will be described. When the linear system receives an excessive load or a large impact load in a stationary or moving state, a local permanent deformation occurs between the ball rolling groove and the ball. If this amount of permanent deformation exceeds a certain limit, smooth movement of the linear system will be impeded.
For this reason, a load at which the sum of the amount of permanent deformation of the ball and the amount of permanent deformation of the raceway becomes 1/10000 times the diameter of the ball at the contact portion under maximum stress is the basic static load rating Co.
The basic load rating C is the load applied to the linear system.
The linear system is selected so that o or less.

The table below shows the values obtained by calculating the basic static load rating Co per ball under the above conditions using the formula for calculating the basic static load rating Co.

[0039]

[Table 1]

For comparison, Table 2 below shows the basic static load rating of a conventional linear bush with a perfect circular orbital axis.
It can be seen that the basic static load rating is extremely small in the conventional linear bushing in which the ball rolling groove is not formed, because the ball makes one point contact with the outer surface of the raceway shaft.

[0041]

[Table 2]

The basic static load rating obtained in Table 1 is plotted as ● on the graph of FIG. 7, and the mutual approach amount δ and the mutual approach amount δ / ball diameter D when the basic static load rating is applied for each ball diameter. Table 3 below is obtained.

[0043]

[Table 3]

It can be seen from Table 3 that the value of mutual approach amount / ball diameter is about 1/50 regardless of the ball diameter.

The maximum load applied to the ball 5 is the basic static load rating Co. Considering that no load is applied to the ball 5 beyond the basic static load rating Co,
If the depth of the ball rolling groove 3 is set to be the mutual approach amount δ when the basic static load rating Co is applied even at the maximum, the groove depth will not be set deeper than necessary. That is, in this embodiment, the depth of the ball rolling groove does not have to be larger than about 1/50 of the ball diameter regardless of the ball diameter. In actuality, the load applied to the ball 5 is set to about 1/10 of the basic static load rating in consideration of the safety factor, so under normal use conditions, it is unlikely that a load greater than the basic static load rating will be applied. Impossible.

Further, the depth of the ball rolling groove 3 is set to 1 of the ball diameter.
When set to / 50 or more, the scooping distance for returning the ball rolling on the loaded rolling path to the unloaded return path becomes extremely short. For this reason, the existing outer cylinder and ball used for the raceway shaft of a perfect circle having no ball rolling groove can be diverted as they are.

Next, the grinding depth of the ball rolling groove 3 is set to 0.05.
The reason why it is set to mm or less will be described. FIG. 8 shows an example in which the surface of the track shaft 1 is ground by the grinding wheel 13.
The grinding of the ball rolling groove is performed, for example, by so-called surface grinding in which the outer peripheral surface of the grinding wheel 3 rotated at a high speed is pressed against the raceway shaft and the raceway shaft 3 is moved in the axial direction. In the linear bushing of the present embodiment, the depth of cut and the feed rate are set to predetermined values, and surface grinding is performed in one pass (that is, machining that requires only one feed without reciprocating the table on which the track axis is attached). Is done.

FIG. 9 shows types of surface grinding (source: precision work handbook). For surface grinding, the depth of cut is set to be relatively large (depth of cut; for example, 0.1 to 0.5 mm), heavy grinding is performed to set the feed speed to be relatively small, and the depth of cut is set to relatively small (depth of cut; 0.001-0.005m
m), speed stroke grinding in which the feed rate is set relatively large, and the depth of cut and feed rate are between heavy grinding and speed stroke grinding (depth of cut; for example, 0.01 mm to
It is classified as normal grinding set to 0.05 mm, feed rate). Recently, creep feed grinding is also known, in which the cutting depth of the grindstone is set large (for example, 1.0 mm to 5.0 mm), the feed speed is set small, and grinding is performed by table feed once or several times.

In this embodiment, by setting the cutting depth of the grinding process to 0.05 mm or less, the ball rolling groove can be processed in one pass even in normal grinding (without reciprocating the table with the track axis attached, It is possible to manufacture it by processing that only needs to be fed once. Therefore, the ball rolling groove can be manufactured easily and quickly.

[0050]

EXAMPLES Table 4 below shows the diameters of balls actually manufactured,
The relationship between the shaft diameter of the raceway shaft, the depth of the ball rolling groove, and the groove depth / ball diameter is shown.

[0051]

[Table 4]

By setting the ball diameter and the depth of the ball rolling groove as shown in this table, it is possible to obtain a linear bush that can obtain the same light movement as the existing linear bush and can also receive a radial load. . Further, it is possible to apply the existing perfect circular linear bush in which the ball rolling groove is not formed as it is to the linear bush of the present invention.

[0053]

As described above, according to the present invention, since the ball rolling groove having an arcuate cross section is formed on the raceway shaft, the rolling groove is formed on the contact surface between the ball and the rolling groove on the raceway shaft. It can be made larger than when not. Therefore, the allowable load in the radial direction can be increased. Further, by forming the groove, it is possible to prevent the outer cylinder from rotating (that is, prevent rotation) even if the outer cylinder is forced to rotate with respect to the track axis.

The linear bush of the present invention does not need to transmit torque unlike a ball spline, and it is sufficient that a load in the radial direction can be applied to some extent. By setting the depth of the ball rolling groove to about 1/50 or less of the diameter of the ball, it is possible to prevent the depth of the ball rolling groove from becoming unnecessarily large to receive the load in the radial direction. And by doing this, the depth of the ball rolling groove can be made extremely shallow,
The ball rolling groove can be ground easily, and the existing outer cylinder and ball used for the linear bush with a perfect raceway axis can be diverted as they are, so the linear bush can be manufactured easily at low cost. be able to.

[Brief description of drawings]

FIG. 1 is a perspective view showing a linear bush according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view in a direction orthogonal to the axis of the linear bush.

FIG. 3 is a perspective view (including a partial cross section) showing an outer cylinder and a retainer of the linear bush.

FIG. 4 is a diagram comparing the contact angle lines of the spline shaft and the linear bush of the present embodiment.

FIG. 5 is a diagram comparing the depths of ball rolling grooves of the spline shaft and the linear bushing of the present embodiment.

FIG. 6 is a view showing a contact state between a ball and a ball rolling groove.

FIG. 7 is a graph showing the relationship between the load Q per ball and the mutual approaching amount.

FIG. 8 is a schematic view showing surface grinding.

FIG. 9 is a graph showing various aspects of surface grinding.

[Explanation of symbols]

1 ... Orbital axis 2 ... Outer cylinder 3 ... Ball rolling groove 5 ... ball P1 ... Center of the ball P2: Point where the ball contacts the ball rolling groove L: contact angle line

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Claims (5)

[Claims] 1. An orbital shaft, an outer cylinder mounted so as to be movable relative to the orbital shaft, and a plurality of balls rotatably provided between the orbital shaft and the outer cylinder. ,
In the linear bush provided with, a ball rolling groove having a substantially arcuate cross section which is in point contact with the ball is formed on the raceway shaft, and the depth of the ball rolling groove is about ⅕ of the diameter of the ball.
A linear bush characterized by being 0 or less. 2. The depth of the ball rolling groove is about 0.05 m.
The linear bushing according to claim 1, wherein the linear bushing is less than or equal to m. 3. A contact angle line connecting a center of the ball and a point where the ball comes into contact with the ball rolling groove substantially passes through a center of the raceway axis. The linear bush described in either 1 or 2. 4. A raceway shaft for a linear bush, in which an outer cylinder of a linear bush is movably mounted via a plurality of balls capable of rolling motion, wherein the raceway shaft has a substantially circular cross section which makes one point contact with the ball. An arc-shaped ball rolling groove is formed, and the depth of the ball rolling groove is about 1/50 of the ball diameter.
A raceway shaft for a linear bush characterized in that: 5. A raceway shaft for a linear bush, in which an outer cylinder of the linear bush is movably assembled through a plurality of balls capable of rolling, wherein the raceway shaft has a substantially circular cross section which makes one point contact with the ball. A raceway shaft for a linear bush, wherein an arc-shaped ball rolling groove is formed, and the depth of the ball rolling groove is about 0.05 mm or less.