JPS6145096B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, a ball that fits between both helical grooves of a screw shaft and a ball nut, and that rolls and moves along the helical groove during relative helical movement between the screw shaft and the ball nut, is attached to the ridge of the screw shaft. The present invention relates to a method for manufacturing a ball circulation groove of a ball nut in an internal circulation type ball screw, in which the ball can be circulated by going over the ridge along the ridge and returning to the adjacent spiral groove.

In general, such internal circulation type ball screws have a piece with a ball circulation groove attached to the ball nut in order to roll the balls over the peak of the screw shaft, and the ball circulation is carried out by the spiral groove of the ball nut and this ball circulation groove. It is designed to form a groove.

In this type of ball screw, the shape of the ball guide groove formed in the piece is not simple, so it is difficult to accurately machine the ball circulation groove, and the piece, which is machined separately from the ball nut, has dimensional errors during machining. Because of this, when the piece is attached to a ball nut, it is inevitable that a step will be created at the connection between the spiral groove of the ball nut and the ball circulation groove.

For this reason, the balls passing through the connection between the helical groove and the ball circulation groove hit this step, which hindered the smooth rolling movement of the balls, and this ball screw had the drawback of causing small torque fluctuations.

Particularly in the case of a ball screw mechanism that requires precision, there is a problem in that smooth operation cannot be obtained even with slight torque fluctuations because the force handled is generally small.

In order to avoid such steps, it has been proposed that the ball circulation groove and the spiral groove are integrally molded without using a piece, but conventionally this type of groove is made by casting,
It could only be manufactured by a manufacturing method such as hydraulic molding using a mold, and it was not possible to precisely manufacture the spiral groove that is the rolling surface of the ball. That is, since the spiral groove and the ball circulation groove twisted in the opposite direction are connected to each other, it is impossible to thread-grind such a groove, making it impossible to obtain a precise ball screw.

The present invention has been made in view of the above-mentioned drawbacks, and its object is to provide a method for manufacturing a ball circulation groove of a ball nut of an internal circulation type ball screw that is easy to manufacture and operates smoothly.

To achieve this objective, the present invention provides a screw shaft with a diameter slightly larger than the ball diameter on the outer surface of the screw shaft in order to prevent a step from forming at the connection between the ball circulation groove and the precisely thread-ground helical groove of the ball nut. Using a mold made from a bent wire rod as a matrix, the ball circulation groove is filled into the hole formed in the ball nut with the molded material and solidified to form an integral mold. By engaging the mold with the helical groove of the ball nut from the inside, a ball circulation groove with no level difference formed at the connection between the helical groove and the ball guide groove can be manufactured.

Next, embodiments of the invention will be described with reference to the drawings.

The screw shaft 1 is a shaft having a spiral groove 2 having an arcuate cross section on its outer peripheral surface.

The ball nut 3 has an inner circumferential surface that loosely fits onto the screw shaft 1, and a helical groove 4 corresponding to the helical groove 2 of the screw shaft 1 is formed on this inner circumferential surface.

A large number of balls 5 are disposed in both the helical grooves 2 and 4 of the screw shaft 1 and the ball nut 3, and the balls 5 are movable along the helical grooves 2 and 4 during the relative helical movement of the screw shaft 1 and the ball nut 3. ing. As the balls 5 roll along the helical grooves 2 and 4, the screw shaft 1 is caused to make a helical movement relative to the ball nut 3. Also, ball nut 3
On the inner circumferential surface of the ball nut, an elongated S-shaped ball circulation groove 6 having a deeper portion than the helical groove 4 of the ball nut is connected to the helical groove 4 to form a one-turn ball guide groove 7. The balls 5 rolling along the helical grooves 2 of the screw shaft move along the ridges 8 that separate the adjacent helical grooves 2 of the screw shaft by the ball circulation groove 6, and climb over the ridges 8 to reach the adjacent helical grooves 2. It is returned to the spiral groove 2 and can be circulated.

This ball guide groove 6 reaches the inner surface from the outer circumferential surface of the ball nut 3, extends over the two adjacent spiral grooves 4 of the ball nut, and closes the circular hole 9 cut out from the inner surface with a mold 10 using epoxy or the like. It is molded by filling and solidifying plastics. The shape of the hole 9 may be circular or oval.

The mold 10 has an outer surface 11 that coincides with the inner circumferential surface of the ball nut 3 and closes the hole 9, and an end 12 that engages with the spiral groove 4 communicating with the side surface of the hole 9 and closes the spiral groove. a protrusion 13 for forming a ball circulation groove 6 that guides the ball 5 to roll over the peak 8 of the screw shaft 1; and a spiral that communicates with the side surface of the hole 9 and does not form the ball guide groove 7. It has a protrusion 14 that closes the groove.

This mold 10 has balls 5 on the outer surface of the screw shaft 1.
A wire rod with a diameter slightly larger than the diameter of the ball is bent to follow the shape of the desired ball passage, and is used as a master mold, and is manufactured by three-dimensional profiling or the like. This mold 1
The shape of ball nut 0 is almost the same as the mother die, but if the spiral groove 4 of the ball nut has a gossic arch cross section, the end 12 that engages with the spiral groove 4 is modified to have a gossic arch shape, and the ball 5 At the part where the ball 5 leaves the helical groove 2 of the screw shaft and climbs over the ridge 8, the ball guide groove 6 moves the ball 5 rolling on the screw shaft 1.
The protrusion 13 is slightly modified so that there is a slight gap. At this time, the amount of application of the mold release agent, shrinkage of the molding material during molding, etc. are also taken into consideration.

The wire rod to be bent along the screw shaft 1 is made of copper, aluminum, or the like that can be easily bent. Needless to say, the shape of the convex portion 14 of the mold 10 matches the shape of the spiral groove.

The mold 10 can be mounted with good workability by engaging a telescopic rod 15 as shown in FIG. 5 with the inner surface of the ball nut 3. 16 is a sleeve provided on the back side of the mold 10, and the rod 15
It is used to expand and contract the . 17 is bar 1
This is a spring that biases 5.

When forming this ball guide groove 6, by making the convex part 14 of the mold 10 slightly retracted from the hole 9, the ball 5 can be formed at the same time to prevent it from falling out against the force exerted on the ball guide groove 6 from the inside. things are possible. Furthermore, by providing a notch on the side or top surface of the hole 9, it is possible to more reliably hold the molded ball circulation groove member.

Next, another embodiment of the present invention will be described with reference to FIG. FIG. 6 shows the mold 10' mounted on the ball nut 3'. An auxiliary member 18 is loosely fitted into the hole 9', and the ball circulation groove 6'
are integrally molded, and projections 19 are placed at appropriate locations to prevent uneven thickness of the molded material. 20 is an air vent hole provided in the auxiliary member 18 during molding.

The ball screw of this invention configured as described above is
The end 12 of the mold 10 is connected to the spiral groove 4 of the ball nut.
The ball circulation groove 6 is molded integrally with the ball nut by filling and solidifying the molded member in close contact with the ball nut.
The spiral groove 4 can be precision thread-ground before forming the ball guide groove 6, and there is no difference in level between the spiral groove 4 and the ball circulation groove 6, resulting in an extremely smooth ball 5. This has the effect that it is possible to easily obtain an internal circulation type ball nut that provides circulation.

In addition, since the ball circulation groove 6 can be formed using a mold 10 made of a wire rod having a diameter approximately equal to the diameter of the ball 5 bent along the helical groove 2 of the screw shaft, the ball circulation groove 6 can be formed separately from the ball nut. It is easier to manufacture a ball guide path that is more accurate than the ball circulation groove provided in the conventional piece.

Furthermore, in the case where the ball guide groove 6' is formed by inserting the auxiliary member 18 into the hole 9 of the ball nut when forming the ball guide groove 6, less molding material is required, and the molded part shrinks. Therefore, it is possible to obtain a ball screw with a strong ball circulation groove portion without deformation caused by this.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view showing a ball screw to which the present invention is applied, Fig. 2 is a cross-sectional view of Fig. 1, Fig. 3 is a top view of Fig. 1, and Fig. 4 is a molded ball screw. FIG. 5 is a perspective view of the mold, and FIG. 5 is an explanatory view showing the mold mounted on a ball nut. FIG. 6 is a sectional view of a main part of another embodiment. 1... Screw shaft, 2... Spiral groove, 3, 3'... Ball nut, 4... Spiral groove, 5... Ball, 6,
6'...Ball circulation groove, 8...Peak, 9,9'...
Hole, 10, 10'...Mold, 12...End,
13...Protrusion, 14...Convex part, 18...Auxiliary member, 19...Protrusion.

Claims (1)

[Claims] 1 A screw shaft 1 having a helical groove 2 on its outer circumferential surface, a ball nut 3 having a helical groove 4 corresponding to the helical groove 2 on its inner circumferential surface, and a ball nut 3 that fits into both of the helical grooves 2 and 4 and rotates. The ball nut is provided with a large number of freely movable balls 5, and the ball nut has a long S-shaped ball circulation groove 6 that is provided between adjacent spiral grooves 4 and has a deeper part than the spiral groove 4 of the ball nut, The balls 5 rolling along the spiral grooves 2 of the screw shaft 1 are guided by the ball circulation grooves along the ridges 8 formed between the adjacent spiral grooves 2 of the screw shaft 1, and the balls 5 are guided along the ridges 8 formed between the adjacent spiral grooves 2 of the screw shaft 1. In the method for manufacturing a ball circulation groove of an internal circulation type ball nut which is passed over and returned to the spiral groove 2 of the screw shaft for circulation, a matrix is prepared by bending a wire rod along the screw shaft 1 in the shape of a desired ball passage. A mold 10 manufactured as a ball nut is brought into contact with the hole 9 of the ball nut in which the two spiral grooves 4 are cut out, and a molding material such as plastic is filled into the hole 9 of the ball nut and solidified to form the ball nut. A method of manufacturing a ball circulation groove of a ball nut, the method comprising forming a ball circulation groove.