JPS63230218A - Working device for groove for generating dynamic pressure - Google Patents

Abstract

PURPOSE:To provide the title device suitable for working the sleeve having very small inner diameter with simple driving mechanism made by composing of a circular columnar shaft providing the through hole with the direction intersecting at right angles with a shaft core as the axial line and of plural balls inserted freely coming in and out and rolling along the axial line direction of said through hole. CONSTITUTION:Specific rotary speed W3 and feeding speed V3 are given to a shaft 12 to insert into the inner diameter face of a sleeve 15 to be worked. Accordingly, the ball 14 in two pieces at the outside press-welded to said inner diameter face advances by performing spiral movement to subject the spiral groove 16 for generating dynamic pressure to plastic work on the inner diameter face of the sleeve 15 by said ball 14. With this invention, the conventional work head cage can be omitted and even in the case of using it as for grooving of the sleeve having very small inner diameter, the external shape of the shaft 12 can be formed larger compared with the conventional one. Consequently the necessary stiffness for the shaft 12 can be secured, hence the forming becomes easy as well besides the problems on strength being solved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a device for plastically forming a groove for generating dynamic pressure on the inner diameter surface of a sleeve of a hydrodynamic bearing device for a video tape recorder, a digital audio tape recorder, etc. Regarding.

[Conventional technology]

Conventionally, as shown in FIG. 5, for example, as shown in FIG. 5, a core shaft is placed in a cage 1 in which a plurality of holes 2 are provided in the radial direction at equal intervals in the circumferential direction. 4
A processing head is used in which a hard ball 5 having a diameter larger than the wall thickness of the cage 1 is inserted into the hole 2 of the cage 1 so as to be freely removable and rotatable.

This machining head has a rotational speed of W and a rotation speed of the core shaft 4 relative to the sleeve 7 to be processed. and the feed rate of
The ball 5 is rolled between the core shaft 4 and the sleeve 7 to be processed to perform a spiral motion, and the cage 1 is set at the rotational speed of the W machining and the feed rate of the VK so as to follow the spiral motion of the ball 5. The groove 8 for generating dynamic pressure is created by the ball 5 pressed against the inner diameter surface of the sleeve 7 to be processed.
It is used for plastic processing.

[Problem that the invention seeks to solve]

In the conventional processing head as described above, the core shaft 4 and the cage 1 are given different rotational speeds W, , WK and feed speeds V, , VK to perform the rolling and spiral motion of the balls 5. Therefore, it is necessary to provide a separate rotation drive mechanism and a separate feed drive mechanism, which not only complicates the attached equipment but also increases the equipment cost.

In addition, if the inner diameter of the sleeve 7 to be processed is extremely small, such as 3 dragons or less, it is necessary to reduce the diameter of each component of the processing head, but the outer diameter of the core shaft of the processing head must be reduced. Then, there is a problem in that the rigidity when given a predetermined rotational speed and feed rate decreases, which is not desirable in terms of strength, and it is extremely difficult to mold small-diameter components with high precision.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a processing device that has a simple drive mechanism and is suitable for processing a dynamic pressure generating groove of a sleeve having an extremely small inner diameter.

[Means for solving problems]

The apparatus for processing a dynamic pressure generating groove of the present invention includes a cylindrical shaft provided with a through hole passing through the shaft center and having an axis extending in a direction perpendicular to the shaft center; It is composed of a plurality of balls inserted so as to be freely removable and rotatable.

The plurality of balls are harder than the sleeve to be processed, and the diameter of the circumscribed circle containing the plurality of balls that contacts the workpiece is set larger than the inner diameter of the sleeve to be processed.

[Operation] The dynamic pressure generating groove machining device of the present invention applies a rotational speed and a feed rate to the shaft to cause the ball to perform a spiral motion while rolling with respect to the sleeve to be processed.

As a result, a groove for generating dynamic pressure is machined via the ball pressed against the inner diameter surface of the sleeve to be machined.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention in a state during groove machining, and FIG. 2 is a sectional view taken along the line X--X in FIG. 1.

In the figure, reference numeral 10 indicates a processing device, and 15 indicates a sleeve to be processed.

The shaft 12 of the processing device 10 is a cylindrical body, and a through hole 13 is provided at one end of the shaft in a direction perpendicular to the shaft.

The inner peripheral surface of this through hole 13 is a cylindrical surface, and its axis passes through the axis of the shaft 12 and is perpendicular to the longitudinal center line.

In the through hole 13 of the shaft 12, three balls 14 having approximately the same diameter are arranged in a row on the same center line along the axial direction of the through hole 13, and are fitted between the balls 14 and the inner peripheral surface of the through hole 13. They are inserted with a suitable gap A between them, so that they can move in and out of the through hole 13 and can roll between them.

These balls 14 are harder than the sleeve 15 to be processed, and are configured such that the diameter of the circumscribed circle containing the plurality of balls that contacts the workpiece is larger than the inner diameter of the sleeve 15 to be processed. ing.

When performing groove machining using the machining device having the above configuration, the shaft 12 is given a predetermined rotational speed W and feed rate V, and is inserted into the inner diameter surface of the stationary sleeve 15 to be processed.

As a result, the two outer balls 14 pressed against the inner diameter surface of the sleeve 15 to be processed move forward by performing a spiral motion.
The ball 14 plastically forms a spiral groove 16 for generating dynamic pressure on the inner diameter surface of the sleeve 15 to be processed.

Since the balls 14 that are in direct pressure contact with the sleeve 15 to be processed during groove machining are the two outer ones, these two balls 14
shaft 1 due to the force received from the workpiece sleeve 15
However, in order to prevent the eccentricity of the shaft 12, the radial clearance A between the through hole 13 of the shaft 12 and the ball 14 should be set as small as possible, and the outer diameter of the shaft 12 should be It is effective to set the radial clearance B between the shaft 12 and the sleeve 15 to be processed small by using a diameter as close as possible to the inner diameter of the sleeve 15 to be processed.・I
4. It is possible to process i:416 for dynamic pressure generation with a constant depth.

In the above embodiment, all three balls 14 have the same diameter, but the two outer balls have the same diameter, and the middle ball held between them is different from the outer ball. It is also possible to use different diameters. When using such balls of different diameters, it is preferable to form a convex portion on the inner peripheral surface of the through hole 13 of the shaft 12 where the small diameter ball is arranged.

Furthermore, the number of balls 14 is not limited to three, but may be two, and four or more balls may be used if necessary.

Next, the rolling state when the ball makes a spiral motion during groove machining will be described for the case where an odd number of balls are used and the case where an even number of balls are used.

Figure 3 shows the case where three balls are used, and Figure 4 shows the case where two balls are used. The rolling states of the ball due to rotation around the axis are shown respectively.

When three balls are used, the axial feed given to the shaft 12 causes the outer two balls 14a,
1 and 1b receive a reaction force from the sleeve 15 to be processed, and the third
The ball rotates in the direction of the arrow shown in Figure a, but since this rotation direction is the opposite direction, slippage occurs at the contact point between the outer balls 14a, 14b and the intermediate ball 14C that contacts them. Further, due to the rotation around the axis given to the shaft 12, the two outer balls 1.4a and 14b receive a reaction force from the sleeve 15 to be processed and rotate in the direction of the arrow shown in FIG. , since this rotation direction is the same direction,
Since the middle ball 14c rotates in the opposite direction to the outer balls 14a, 14b due to the friction between the middle ball 14c and the outer balls 14a, 14b, no slippage occurs at the contact points.

When two balls are used, each ball 14a is moved by the axial feed given to the shaft 12.

14b receives a reaction force from the sleeve 15 to be processed, and as shown in FIG.
The balls 14a and 14b rotate in the direction of the arrow shown in FIG. 1, but since this direction of rotation is in the opposite direction, no slippage occurs at the contact points of the balls 14a and 14b. Further, due to the rotation around the axis given to the shaft 12, each ball 14a, 14b receives a reaction force from the sleeve 15 to be processed and rotates in the direction of the arrow shown in FIG. 4, but the rotation direction is the same. Because of the direction, slippage occurs at the contact point of each ball 14a, 14b.

As mentioned above, whether the number of balls used is an odd number or an even number, the balls not only rotate but also roll with slippage at the contact points. The ratio of the rotational speed applied to the shaft and the feed rate varies depending on the desired pattern of grooves for generating dynamic pressure, so if the feed rate is relatively slow, for example When machining grooves close to When machining a groove nearly parallel to the axis of the sleeve to be machined, by using two, ie, an even number of balls, it is possible to prevent the resistance force against rolling of the balls from becoming excessive.

In this way, by selecting the number of balls to be used according to the pattern of the grooves for generating dynamic pressure, it is possible to machine grooves with high shape accuracy, with less wear on the balls 14, and with fewer cracks and cracks at the groove bottom. can do.

〔Effect of the invention〕

As explained above, the dynamic pressure generating groove machining device of the present invention inserts a plurality of balls in the axial direction of a through hole provided in a shaft, and applies rotational speed and feed rate to the shaft. Since the groove for generating dynamic pressure is formed in the inner diameter surface of the sleeve to be processed, the drive mechanism is extremely simple, and a processing device with low equipment cost can be obtained. In addition, according to the present invention, the gutter cage can be omitted from conventional processing, so even when used for grooving a sleeve with an extremely small inner diameter, the outer diameter of the shaft can be reduced compared to the conventional method. This not only solves the problem of strength because it can be formed into a large size and ensure the necessary resistance, but also makes it easier to form, so the outer diameter of the shaft can be reduced to an extremely small diameter. A processing device suitable for grooving a sleeve to be processed having an inner diameter of .

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view showing the main part of the embodiment of the present invention during groove machining, FIG. 2 is a sectional view taken along the line X--X of FIG. 1, and FIG. FIG. 3 is a cross-sectional view taken along the line X-X of FIG. FIG. 5 is a longitudinal sectional view showing a conventional processing head. In the figure, 10 is a processing head, 12 is a shaft, 13 is a through hole, 14 is a ball, 15 is a sleeve to be processed, Dl is the diameter of a circumscribed circle containing a plurality of balls in contact with the workpiece, D
is the inner diameter of the sleeve to be processed. Porridge 1 Figure 16 ``Figure 2 (o) = A3 figure 4''

Claims (2)

[Claims] (1) A cylindrical shaft with a through hole whose axis is perpendicular to the axial center through the axial center, and a cylindrical shaft inserted so that it can move in and out and roll freely along the axial direction of the through hole of the shaft. The plurality of balls are harder than the sleeve to be processed, and the diameter of the circumscribed circle containing the plurality of balls that contacts the workpiece is set larger than the inner diameter of the sleeve to be processed. A processing device for a groove for generating dynamic pressure, characterized in that: (2) The dynamic pressure generating groove machining device according to claim 1, wherein a minute radial clearance is maintained between the through hole of the shaft and the ball.