JPS59131059A - Ball screw with angular contact ball bearing - Google Patents

Abstract

PURPOSE:To enable steel balls of circulating smoothly and noiselessly by providing a nut which is screwed on the external periphery of a screw shaft, with a deflector which has on the internal periphery thereof a concaved part transversely running the screw thread which is formed on the nut to connect both the adjacent screws. CONSTITUTION:A nut 4 which is screwingly engaged via steel balls 5 on a screw shaft 2 on which a screw thread 3 is formed at a specified pitch has the screw thread 6 shaped on the internal periphery thereof, the pitches P1 and P2 between the bottoms of the screw thread 6, 6 on the middle side of the nut being longer than the other pitches P3 and P4. The nut has ellipsoidal through-holes 7 and 8 which are axially deviated at the top part and the bottom part of the internal periphery thereof and a deflector 9 is engaged and settled in each of the holes 7 and 8. This deflector 9 has a concaved part 9b having the curved bottom part 9a and the depth of the concaved part 9b is greater than the diameter of each of the steel balls 5. An angular contact ball bearing 12 which bears the axial and the radial loading is mounted on the external peripheral face of the nut 4.

Description

Detailed Description of the Invention The present invention provides an angular contact ball bearing in which a steel ball is inserted between a screw shaft and a nut to enable relative rotational movement or axial movement, and the nut is installed on its outer periphery. This invention relates to an angular contact ball bearing pole screw that also serves as an inner ring.

Conventionally, feeding devices such as cutting tools and work tables have a series of steel balls interposed between the screw shaft and the thread groove of the nut to allow the steel balls to be moved freely, unlike the conventional feeding operation based on sliding friction. Instead of those that do this, there are pole screws that can perform very light feeding motions due to rolling friction.

However, in such a pole screw, after the steel ball rotates around the screw shaft and the thread groove of the nut once to three times, it is scooped up into the pole tube, which has a smaller radius of curvature than the nut, and rotates around the outside of the nut. Because it was designed to return to its original position after almost one revolution, the smooth movement of the steel ball rolling inside the pole tube was not hindered, and this allowed smooth, high-speed movement of the nut or screw shaft. Not only was this impossible, but it also caused noise problems.

1. With such conventional pole screws, dust is drawn into the interior from the nut end side through the thread groove of the screw shaft, and the dust prevents the smooth rotation of the steel ball, making the relative movement of the screw shaft and nut heavy. There was a problem that

In addition, in conventional ball screws, there is an axial clearance between the steel balls fitted between the thread grooves of the screw shaft and the nut, so when either the screw shaft or the nut moves in the axial direction, the steel balls There is a problem that not only uneven wear and noise occur due to the axial clearance between the screw shaft and the screw groove, but also the responsiveness of the screw shaft or nut is poor. To counter this, proposed countermeasures include installing a spacer to apply preload (pre-compression) between the left and right pairs of nuts, and forcibly shifting the nuts in the compression direction or expansion direction to eliminate the axial clearance. However, since unnecessary stress is applied to the nut, it becomes necessary to provide sufficient mechanical reinforcement, and the time-consuming assembly process becomes inefficient.

Furthermore, in the above-mentioned pole screw, the screw shaft or the nut can be rotated relative to each other or moved in the axial direction, and in particular, the screw shaft and the nut can be freely rotated with respect to a fixed member such as a frame or a housing that supports the nut. It may be necessary to support the In such a case, a ball bearing is interposed between the fixing member and the nut, with steel balls interposed between the inner ring and the outer ring. However, by installing such a dζ-ru pair cylinder) l/-
There is a problem in that the overall outer diameter of the screw is large, making it unsuitable for applications such as transmission devices where precision and miniaturization are desired.

The present invention has been developed by paying attention to such conventional problems, and an object of the present invention is to recover the ridge that scoops up the steel ball that has rolled through the thread groove formed on the screw shaft. By removing the nut outer periphery node yt'-retug that returns the nut to the thread groove, it is possible to make smooth and high-speed movement of the screw shaft or (t) nut, and eliminate the problem of noise when the steel ball returns. Furthermore, by using the nut screwed onto the outer periphery of the screw shaft as the inner ring of the angular contact ball bearing, the number of parts and radial dimensions are reduced as much as possible, making it more compact. At the same time, by providing a pitch difference in the thread groove of a single nut fitted to the screw shaft, a preload (preliminary compression) can be applied to the steel ball by one nut,
An object of the present invention is to provide an angular contact ball bearing with a higher screw thread, which can further reduce the number of parts and manufacturing costs by omitting preload applying members such as spacers.

The present invention will be explained below based on illustrated embodiments. In FIGS. 1 to 6, 1 indicates the entire ball screw;
2 is a screw shaft having a spiral thread groove 3 formed at a predetermined pitch on the outer periphery of the shaft, and a cylindrical screw shaft which is movable in the axial direction or rotational direction and is screwed onto the screw shaft 2 through a steel ball 5. This nut 4 is also provided with a spiral thread groove 6 on its inner periphery for rolling a steel ball 5, and the spiral thread groove 6 is mutually connected to the thread groove 3 on the screw shaft side. We are being made to respond.

Here, the thread groove 6 of the nut 4 has a pitch P between the thread grooves 6°6 on the center side of the nut, as shown in FIG.
+, Pz ((assuming that there is a condition of fj and P+ = Pz) is the pitch P3. P4 (P
It is assumed that there is a condition of a=P4), larger than R, P
2=P3+α and R, Pz=P4+α. Therefore, the load steel ball 51 located on the left side of the nut 4 center shaft is preloaded to the left, while the load steel ball 52 located on the fabric side is preloaded to the right, respectively, in the axial direction outward of the nut 4. It becomes. In addition, on the contrary, pitch P+
, Pz is made smaller than the pitches Ps and P4 on both sides,
Pl, Pz = P3-α and Pt, Pz =
By establishing the relationship P4-α, a preload can be applied to the left load steel ball 51 and the right load steel ball 52 in the compression direction axially inward of the j-nut 4, respectively.

Reference numeral 7.8 denotes an oblong through hole that is bored in the top and bottom of the inner periphery of the nut 4 so as to be offset in the axial direction. It is provided across a thread groove 6 that is continuously formed in a spiral shape with a predetermined pitch. Reference numeral 9 denotes a deflector that is fitted into the through holes 7 and 8 of the nut from the outside of the nut and fixed to the nut with an adhesive or the like.As shown in FIG. A recess 9b with a curved bottom 9a is formed in a cylindrical body having an outer peripheral shape that matches the shape of the holes 7 and 8, and a semicircular shape offset in the longitudinal direction near the ends of both side walls 9c and 9c. An inlet 9d and an outlet 9e are provided. The curved bottom surfaces of the inlet 9d and the outlet 9e are threaded grooves 61+62.
The deflector is aligned at the same height as the curved bottom surface of the deflector.
When the steel balls 5 flow into the recess 9b or flow out from the recess 9b, smooth transfer of the steel balls is ensured. The depth of the recess 9b is set such that when the steel ball 5 passes through the deflector 9, the steel ball comes into contact with the screw thread on the screw shaft 2 side and the smooth movement of the steel ball is hindered. l! i
i! , 9 can be set freely.

Next, as shown in FIGS. 4 and 5, the deflector 9
is the rolling starting end position A of the steel ball 5 when the steel ball 5 crosses the thread M formed between the adjacent thread grooves 61 + 62 and makes one round in each thread groove that continues in a spiral shape. In other words, the adjacent screw groove 6. , 62. Now, to explain the movement of the steel ball 5 rolling in the thread grooves 61+62 of the - thread with reference to FIGS. 7 and 8, it starts rolling from the rolling start position A in the thread groove 6I inside the nut. When the steel ball 5 has made approximately half a turn around the inner circumference of the nut, it moves to the adjacent thread groove 62 side on the outside of the nut, and eventually reaches the rolling end position B.
reach. Then, from the rolling end position B, avoid contact with the thread on the screw shaft 2 side, take a slight detour radially outward from the central axis O of the nut, and enter both thread grooves 61 on the nut side.
+ 62, and then returns to the transfer start position A provided in the original thread groove 61 on the inner side of the nut. After that, one thread groove 61 is removed in the same cycle as the above-mentioned operation.
This is a transfer within +62.

In the illustrated embodiment, a deflector having the above configuration is used.
Although two 9s are installed at the top and bottom of the inner circumference of the nut 4, three, four, etc. may be installed in multiple numbers as necessary.
In either case, they are arranged at equal intervals in the circumferential direction so as to equally divide the circumference.

10.11 is an annular nut whose outer circumferential portion is integrally attached to the inner circumferential surface of both ends of the nut 4, and has a thread N formed on the inner circumferential portion of the opposite side to fit into the thread groove 3 of the screw shaft 2 all around. This wiper 10.degree. 11 is used to isolate the interior space of the nut 4 from the outside.

Reference numeral 12 denotes an angular contact ball bearing that is attached to the outer circumferential surface of a nut 4 screwed onto the screw shaft 2 and supports the axial and radial loads applied to the nut 4. (Fig. 12) or back-to-back combination (Fig. 2).

(Fig. 4). In the present invention, the nut on the curl thread side of the inner ring of the angular contact ball bearing also serves as the nut. The angular contact ball bearing according to the present invention will be described in detail with reference to the drawings below. Inward goal grooves 13 and 14 are provided on both sides of the outer peripheral surface of the nut 4, which serves as an inner ring screwed onto the screw shaft 2. On the other hand, the outer rings are of a split type, and each pair of annular outer rings 15, 16 has an outward facing pole corresponding to the above-mentioned Nara (all pawl grooves 13, 14) on the inner peripheral surface. Groove 171
8 is formed. By inserting a split spacer S into the middle of the pair of outer rings 15 and 16, which presses each outer ring in opposite directions, each outer ring side and the nut side have more irradiation between the grooves. - A preload can be applied to the pole in the direction of expansion (the direction in which the poles move away from each other), and this preload is adjusted by adjusting the thickness of the spacer S.

Furthermore, on one side 16 of the outer ring, a fixing means to be fixed to a frame such as a work table, that is, a fixing flange 19 having a mounting hole H is provided, and a nut 4 used as the inner ring of the angular contact ball bearing is provided. A gear 20 for transmitting rotational torque to the nut from an external drive means is formed on the outer periphery of one end of the nut. Of course, the member that transmits rotational torque to the inner ring nut is not limited to the front HI'' gear, and other transmission means such as a timing belt (not shown) may be used.

The operation of the pole screw for infinite sliding with an angular contact ball bearing of the present invention having the above configuration will be explained based on the usage state diagram in Fig. 9. Two parallel rows of track bases G are installed on the fixed side plate P. A linear sliding pair cylinder 22 fixed to the bottom surface of the work table 21 is placed on the track G so that the work table 21 can freely move in the axial direction on the track G. - Blade fixation (i11 The fixing flange 19 of the blade side outer ring 16 is fixed to the support stand 23 erected on the plate P by screwing a bolt into the mounting hole H, and the angular contact ball bearing 12 Of the components, the outer ring 15 and 16 sides are fixed in both the axial and rotational directions, while the nut 4 side, which serves as the inner ring, is fixed in the axial direction but movable in the rotational direction. In this state, when a rotational torque is transmitted to the nut 4 from an external drive means such as a stepper motor 24 via the gear 20, the nut rotates in the forward or reverse direction and the work table 21 It is fixed in the axial direction via the bracket 25; since feed is applied to the female threaded shaft 2, the threaded shaft 2 makes a relative W-line movement to the left or right in the drawing. As a result, the work table 21 holding the screw shaft 2 fixedly moves in the axial direction together with the screw shaft 2 which is moved in the axial direction with respect to the nut 4.

10 to 12 show another embodiment of the infinite sliding ball screw with angular contact ball bearings according to the present invention, and in this second embodiment, the annular wiper 10a on the -blade side is The other annular wiper 11a, which is fixed to the outer end surface of the cylindrical pole screw side nut 4 via the fixture 26 and fixed to the inner periphery of the nut 4, is attached to the other outer end surface of the nut 4. Gear body 2 delt-fastened to
The wiper 10a of the nut 4 is held by the nut 4.

The degree of fixation to 11a is increased. In addition, outward ball grooves 13a and 14a, opposite to those in the first embodiment, are provided on both sides of the outer peripheral surface of the cylindrical nut 4, which serves as the inner ring of the angular contact ball bearing 12a. Inward ball grooves 17a, 18a corresponding to the nut-side pawl grooves 13a, 14a are formed on the inner circumferential surface of the annular outer rings 15a, 1.6a of the 11 type. By inserting a halved annular spacer S into the middle of the pair of outer rings 15a and 16a, and pulling the outer rings 15a and 16a toward each other, the distance between each outer ring side and the nut side is further increased. The compression direction (yR-
A preload can be applied in the direction in which the wheels approach each other.

The rest of the structure of the second embodiment is the same as that of the first embodiment, so the same reference numerals as in the first embodiment will be given and the explanation thereof will be omitted.

As is clear from the above description, according to the present invention, the nut screwed onto the outer periphery of the screw shaft has four internal parts that cross the thread formed on the nut and communicate between both adjacent thread grooves. Since we have provided a deflection mechanism around the periphery, we have installed a pole tube that scoops up the steel balls that have rolled through the thread groove formed on the screw shaft, then wraps them around the outside of the nut and returns them to the thread groove again. There is no need to use it, and since the depth of the recess formed on the inner periphery of the deflector is larger than the diameter of the steel ball, when the steel ball enters and exits from the thread groove on the outer periphery of the screw shaft to the recess on the inner periphery of the deflector, When passing through the recess, even if the direction of movement changes suddenly, the steel ball will not receive an excessive load from the screw shaft and the thread groove of the nut. As a result, the steel balls can be circulated smoothly and without making noise, thereby ensuring quiet and smooth movement of the screw shaft or nut. Also, as mentioned above, the moving direction kK of the steel ball
There is no excessive load generated between the steel ball and the helical thread groove formed on the screw shaft and nut.
It is possible to improve their durability and significantly extend their lifespan.

Furthermore, an angular contact ball bearing was provided on the outer periphery of the nut, and the angular contact ball bearing was composed of an inner ring made of the nut, and an outer ring that was fitted to the inner and outer radial peripheries of the inner ring via a ring. Therefore, the thrust load in the axial direction and the radial load in the radial direction that are applied to the nut when the screw shaft rotates can be supported by the angular contact ball bearing. It is possible to reduce the radial dimension of the entire device and make it compact. Therefore, it is suitable for use in the sliding parts of recent miniaturized fc industrial ferrules, etc. suitable for

Well, we created a pitch difference in the spiral thread groove formed on the inner periphery of the nut, so there is no need to use a spacer or the like to insert between the two halves of the nut as in the past. It is possible to apply preload to the steel balls interposed in between,
Therefore, the threading operation of the nut onto the threaded shaft can be carried out very efficiently, and the production efficiency of the entire apparatus can be greatly improved. In addition, since a separate pressurizing member such as a spacer for applying pressurization to the steel balls is omitted, the number of parts can be reduced and the configuration can be simplified.

[Brief explanation of drawings]

The drawings show an actual example of the angular contact ball bearing pole screw according to the present invention.
The figures are Fig. 1 n-ng vertical sectional front view, Fig. 3 is a cross-sectional bottom view taken along the line m-■ in Fig. 1 showing the pitch of the thread groove on the nut side, and Fig. 5 is a plane projection of the deflector installation part on the inner periphery of the nut. Fig. 6 is a perspective view of the main part of the deflector, Fig. 7 and Fig. 8 are perspective views showing the trajectory of the steel ball rolling between the thread groove between the screw shaft and the nut. 9 is a longitudinal sectional front view showing how the pole screw is used, FIG. 10 is a side view showing another embodiment of the pole screw, and FIG. 11 is a 10th M-M@I
＠：Correct 'W Figure, No. 121
Fig. 0 is a cross-sectional bottom view of Figure 0. Code fraud 1...Pole screw 2...Screw shaft 3+6
+ 61+62...Thread groove 4...Nut 5 +
51.52...Steel ball 7,8...Through hole 9...
・Deflector 9a...bottom 9b...recess 9C...side wall 9d...
Entrance 9e...Exit 10.10a, 11.
lla...wiper 12.12a...angular contact ball bearings 13.13a, 14, 14a, 17.1
8--Pole groove 15, l5a, 16
, l 6 a --・Outer ring 19...Fixing flange 20...Gear 21...Work table 22...@ Line drawing bearing 23...Support stand 24...Stepping motor 25... Bracket 26...Mounting tool 2
7... Gear body A... Rolling start position B... Rolling end position H.
...Mounting holes M, N...Thread 0...Central axis Pl, P2, Ps, P4...
...Hitsuchi S...Maza-"--41 Fig. 2 Fig. 1 ■ J M JP-A-59-131059 (7) Fig. 11 Fig. 10

Claims (1)

[Claims] A screw shaft having a spiral thread groove formed therein, a nut having a spiral thread groove corresponding to the thread groove of the screw shaft formed on the inner periphery, and both screws provided on the nut and adjacent to each other across the thread threads. Deflector with four parts on the inner periphery that connect the grooves
a plurality of steel balls that are fitted between corresponding thread grooves of the screw shaft and the nut and roll between the screw shaft and the nut; and an angular contact ball bearing provided on the outer periphery of the nut. , the depth of the recess of the deflector is larger than the diameter of the steel ball, and the angular contact ball bearing is fitted with an inner ring made of the nut and a radial outer circumference of the inner ring via a pole. 1. An angular contact ball bearing pole screw, characterized in that the nut has a pitch difference in the spiral thread groove formed on the inner periphery of the nut.