KR20130010282A - Assembly of the screw and ball screw having it - Google Patents

Abstract

PURPOSE: Screw assembly and ball screw including thereof are provided to compensate screw-rotation axis, using connection nut, by fitting at the center of circle which screw groove of the screw is forming, thereby implement precise operation. CONSTITUTION: Bearing shaft(1) is combined to bearing(30). The bearing shaft is rotated on the bearing. Connection nut(5) connects the end part of screw(4) and the bearing shaft. The connection nut goes in valley of the screw groove. The connection nut is combined with the end part of the screw by nut combining.

Description

Assembly of the screw and ball screw having it

The present invention relates to an assembly for rotatably securing a screw and a ball screw comprising such an assembly.

Ball screw (ball screw) is one of the devices for changing the direction of movement. In general, ball screws are used to convert the rotation of the motor into linear motion. The ball screw is largely divided into a long rod-shaped screw with a screw formed on the outer circumferential surface, and a ball nut coupled to the screw. As is well known, the ball nut is circulated with a plurality of steel balls in contact with the screw of the screw.

The ball nut is coupled to a mechanical device to be transferred. The screw is also rotatably coupled at both ends to the ground or another mechanism. One end of the screw is rotated as it is connected to the motor by a timing chain or the like, so that the ball nut moves smoothly along the length of the screw.

Generally the end of the screw is supported by a bearing. One end of the screw is a fixed end and the other end is a free end. Alternatively, both ends of the screw may be made of a fixed end.

In the prior art, as shown in Figure 1, the end of the screw 200 is processed to a smaller diameter to form a coupling end 210, the coupling end 210 is fitted to the inner ring of the bearing 220 (See Korean Unexamined Utility Model Publication No. 20-2011-5565 (2011.06.08), Japanese Unexamined Patent Application Publication No. 10-118876 (12 May 1998), and Japanese Unexamined Utility Model Publication No. 04-052647).

A fixing nut 230 fixed to the coupling end 210 is fastened to the other side of the coupling end 210 passing through the bearing 220, and thereafter, a timing chain is coupled to the coupling end 210. Is coupled to a timing pulley 240. At this time, the coupling end 210 may be processed into a plurality of stages.

On the other hand, the screw is divided into a screw manufactured by rolling and a screw manufactured by grinding according to the processing method.

The grinding process cuts the cylindrical base material and processes the screw and the mating end, thus enabling precise machining of the screw. However, grinding has the disadvantage of high manufacturing cost.

On the other hand, the rolling process has the advantage that it is suitable for mass production and inexpensive compared to the grinding process, but has a disadvantage that it is difficult to manage the tolerance of the outer diameter of the thread formed by the thread.

Referring to FIGS. 2 and 3, which exaggerated the threads for better understanding, the bone diameter A is easy to manufacture due to the low tolerance. However, since the base material protrudes and is formed in accordance with the depression of the valley, it is difficult to reduce the height tolerance of the thread. That is, it is very difficult to reduce the tolerance of the outer diameter B formed by the thread.

Therefore, as shown in FIG. 2, the central axis B1 of the screw based on the thread B2 farthest from the axis center and the central axis A1 of the screw based on the screw valleys A2 do not coincide with each other. easy.

In addition, since the coupling end 210 is machined in a state where the machine tool is fixed to the outer diameter of the base material, the shaft center of the coupling end 210 does not coincide with the center of the circle formed by the screw bone. That is, in the case of rolling, the center of the circle formed by the screw bone and the axis center of the coupling end are often inconsistent.

Since the diameter of the rotation axis of the screw (the center axis of the coupling end supported by the bearing) and the diameter of the bone diameter are inconsistent, there is a concern that vibration may occur in the ball screw during operation of the screw.

Therefore, in the field of high precision machinery, the screw manufactured by grinding is preferred to the screw manufactured by rolling. However, the screw manufactured by grinding is expensive and therefore economical.

The present invention has been made to solve the above-described problems, even if the center of the circle formed by the thread and the center of the circle formed by the valley does not coincide with the rotation axis of the screw and the center of the circle formed by the valley coincide The screw can be mounted on a bearing or the like.

In order to solve the above problems, an embodiment of the present invention provides a rotatable connection of an end of a screw having a screw groove formed on an outer circumferential surface thereof to a bearing for supporting a bearing shaft, the bearing shaft being rotatably coupled to the bearing, and an end of the screw. And a connection nut connecting the bearing shaft, wherein the connection nut is provided with a screw assembly engaged with the end of the screw by screwing engagement with the valley of the screw groove.

Here, the coupling nut is formed with a coupling groove formed on the inner peripheral surface of the female thread bited by the screw groove, the curvature of the thread of the female screw may be smaller than the curvature of the valley of the screw groove.

On the other hand, the bearing is fixed to the mechanism for supporting the screw, the bearing shaft rotatably coupled to the bearing, one end is coupled to the rotating shaft of the bearing shaft, the other end is formed with a coupling groove having a female screw on the inner peripheral surface A threaded groove is formed in the connection nut and the outer circumferential surface to contact the steel balls, and includes a screw inserted into the coupling groove and screwed into the coupling groove. A screw assembly is provided at a point corresponding to a point of contact in contact with the field.

In addition, one of the bearing shaft and the connecting nut is formed with a protrusion having a non-circular cross section, and the other is formed with a receiving portion to which the protrusion is coupled, so that the connecting nut can be rotated by the rotation of the bearing shaft. have.

In addition, one end of the bearing shaft is formed with a supporting jaw portion in contact with one side of the bearing inner ring, the other side of the bearing inner ring may be touched by the connecting nut.

Furthermore, a timing pulley may be further formed at the support jaw, and the timing pulley, the support jaw and the bearing shaft may be integrally formed.

In addition, the end portion penetrating the bearing shaft may further include a fixing bolt coupled to the end of the screw. In addition, the screw direction of the fixing bolt may be opposite to the screw direction of the screw.

Meanwhile, in a ball screw including a ball nut having a plurality of steel balls circulated, and a screw groove formed on an outer circumferential surface of the steel ball, the ball screw is provided at a point parallel to the contact points of the steel ball and the screw groove. A ball screw comprising a connection nut screwed to the screw and a bearing shaft connected to the connection nut is provided.

According to the embodiment of the present invention, as the connection nut is provided, the rotational axis of the screw is compensated for the center of the circle formed by the screw valley of the screw, which has the advantage of enabling precise operation. As a result of the compensation of the screw rotation axis, even when using a screw by rolling, it brings about the same high precision as using a ground screw, thereby producing a ball screw which is economical and has high operational reliability.

1 is an exploded plan view of a screw assembly according to the prior art.
FIG. 2 is a schematic cross-sectional view of the screw shown in FIG. 1. FIG.
3 is a side view of the screw shown in FIG.
4 is an exploded plan view of a screw assembly according to an embodiment of the present invention.
5 is a perspective view showing a connection nut and a bearing shaft employed in the embodiment shown in FIG. 4.
6 is a cross-sectional view of the embodiment shown in FIG. 4 assembled.
7 is a cross-sectional view showing the coupling of the screw and the connection nut shown in FIG.

According to the present invention, the screw assembly is for rotatably mounting the screw to a bearing installed in a mechanical device or the like, and includes a bearing shaft and a connection nut.

The bearing shaft is coupled to the bearing while the outer circumferential surface is in contact with the inner ring of the bearing. The bearing shaft is cylindrical in shape and can be changed in length corresponding to the number of bearings.

The connecting nut is a member connecting the bearing shaft and the screw. At this time, the connection nut is screwed to the end of the screw threaded groove formed on the outer peripheral surface. The connection nut may be provided with a receiving groove formed with a female thread for screwing with the screw.

The female thread of the connection nut comes into contact with the valley of the screw thread groove.

Preferably, according to the design of the ball screw, the female nut of the connection nut is brought into contact with the side of the threaded groove formed in the screw and the point where the balls of steel balls of the ball nut contact each other (generally, two points symmetrical at the lowest point of the valley).

The radius of curvature of the female thread of the connection nut may be smaller than the radius of curvature of the thread of the screw groove so that the female thread engages with the thread of the screw groove.

Alternatively, the female thread may have a larger radius of curvature at that point than other portions of the female thread such that the female thread contacts the screw of the screw at the point where the steel balls contact the screw groove. Alternatively, a protrusion protruding around the thread of the female thread may be further formed corresponding to the points of the screw groove in contact with the steel ball.

As the connection nut is coupled to the end of the screw, the cross-sectional center of the connection nut may match the bone diameter of the screw. As the bearing shaft is coupled to the center of the connecting nut, the center of the bearing shaft coincides with the center of the screw valley of the screw.

As a result, the bearing shaft, the connecting nut and the screw coupled to the bearing are rotated around the center of the circle formed by the screw bone of the screw, so that the quiet operation of the ball nut having the rolling balls in contact with the screw bone of the screw and around the screw bone is prevented. It becomes possible.

Hereinafter, with reference to the accompanying drawings will be described the configuration, function and operation of the screw assembly and the ball screw including the same according to an embodiment of the present invention. However, the expression of the screw in Figure 7 is exaggerated to help understanding.

4 to 6, there is shown a screw assembly according to an embodiment of the invention.

The screw assembly 10 includes a bearing shaft 1 rotatably coupled to the bearing 30, and a connecting nut 5 connecting the screw 4 and the bearing shaft 1. At this time, the connection nut 5 may transmit the rotational force to the screw 4 when the bearing shaft 1 rotates.

One end of the bearing shaft 1 is further formed with a supporting jaw portion 2 in contact with one side of the inner ring of the bearing 30. On the other hand, the other side of the inner ring of the bearing 30 is in contact with the connecting nut (5).

A plurality of bearings 30 can be used. The number of bearings 30 may vary with the length of the screw. One side of the inner ring of the bearing 30 is passed by the supporting jaw portion 2, and the other side is held by the connecting nut 5. The supporting jaw portion 2 and the connection nut 5 are fixed ends.

The support jaw portion 2 has a larger outer diameter than the bearing shaft 1 in order to contact one side of the inner ring of the bearing 30. In this case, the bearing shaft and the support jaw may be integrally formed, or may be separately formed and assembled together by a key to form a single body.

In addition, the connection nut 5 may also have the same outer diameter as the support jaw portion 2 to contact the other side of the inner ring.

A timing pulley 3 is further formed at the support jaw 2. The timing pulley 3 is formed with a gear for connecting with a timing belt (not shown) on the outer circumferential surface.

In this case, the timing pulley and the support jaw may be made of a separate article from each other and assembled by a key or a set screw. However, the timing pulley and the support jaw may be integrally formed.

Preferably, the bearing shaft 1, the supporting jaw portion 2 and the timing pulley 3 are integrally manufactured. The timing pulley, support jaw, and bearing shaft (hereinafter, referred to as 'shaft member 10a'), which are integrally manufactured, improve the reliability of the operation.

When the timing pulley 240, which is manufactured separately as in the related art, is coupled to the coupling end 210 (see FIG. 1), even if a key or a set screw is used, precise operation control is difficult due to assembly error, wear due to use, and the like. do. In particular, the driving force of the motor is difficult to be accurately transmitted to the bearing shaft due to the assembly error, which is often caused in the coupling between the timing pulley and the screw.

However, the driving force transmitted to the timing pulley 3 is immediately transmitted to the bearing shaft 1 by making the shaft member 10a integrally as in the embodiment of the present invention, thereby solving the problems according to the related art. Will be.

The bearing shaft 1 of the shaft member 10a is coupled to the connecting nut 5 after passing through the bearing 30.

The bearing shaft 1 and the connecting nut 5 are formed by the protrusion 11 and the receiving portion 52. At this time, any one of the bearing shaft and the connection nut is formed with a projection having a non-circular cross section, the other one is formed with a receiving portion coupled to the projection.

In the drawing, the protrusion 11 is formed at one end of the bearing shaft 1, and the receiving portion 52 is formed at the connecting nut 5.

The cross-sectional shape of the protrusion 11 is approximately square, and the cross-sectional shape of the accommodating portion 52 is also rectangular. Since the protruding portion 11 and the receiving portion 52 have a non-circular cross section, the rotational force of the shaft member 10a is directly transmitted to the connecting nut 5.

Unlike shown, the coupling structure of the bearing shaft and the connection nut for completely transmitting the rotational force can be variously changed. Although not shown, the outer circumferential surface of the bearing shaft has a plurality of insertion grooves formed therein, and each insertion groove may be screwed with a bolt to pass through the connection nut.

4 and 6 again, the shaft member 3 has a bolt hole 101a having a stepped portion formed through the center of the cross section of the shaft member 10a. This bolt hole 101a is formed even in the protrusion part 11. In addition, the end of the screw 4 is formed with a fastening groove 42, the screw is formed on the inner peripheral surface.

The fixing bolt 6 is fastened to the fastening groove 42 of the screw 4 via the bolt hole 101a of the shaft member 10a and the receiving portion 52 of the connecting nut 5. The fixing bolt 6 prevents the shaft member from being pulled out of the bearing 30 by binding the shaft member 10a, the connection nut 5 and the screw 4 to each other.

In addition, the length of the bearing shaft 1 protruding from the support jaw 2 can be made shorter than the length of the bearings. When the fixing bolt 6 is tightened, the bearing shaft 1 and the screw 4 of the shaft member 10a are pulled closer to each other, so that the support jaw 2 and the connecting nut 5 are both sides of the inner ring of the bearing 30. Will be more firmly supported. In FIG. 4, reference numeral 20 denotes a set screw.

In addition, the screw direction of the fixing bolt 6 and the screw groove direction of the screw 4 are formed in opposite directions to each other. That is, when the screw groove 41 of the screw 4 is the right screw, the fixing bolt 6 is made of the left screw. Thereby, the fixing bolt is not released by the torque transmitted to the screw by the ball nut (not shown) at the time of rotation of the screw 4 by the timing pulley 3. Therefore, there is no fall in fastening force of the fixing bolt even by repeated use for a long time.

The coupling nut 5 has a coupling groove 53 in which a female thread 51 is formed. The inner side surface of the engaging groove 53 is in communication with the receiving portion 52. The connecting nut 5 may be manufactured by cutting, and the center of the circle formed by the thread of the female thread 51 coincides with the center of the receiving portion 52.

In the embodiment of the present invention, the center of the connection nut 5 substantially coincides with the center of the shaft member 10a. Compared with the error between the outer diameter center and the bone diameter center of the screw manufactured by the rolling method as described above, the error of the rotary shaft of the cutting shaft member 10a and the rotary shaft of the connecting nut 5 is very small.

Figure 7 shows an exaggerated portion of the screw connection of the connection nut and the screw. In FIG. 7, the thread of the female thread 51 of the connection nut 5 is screwed in contact with the valley of the threaded groove 41 of the screw 4.

In rolling the cylindrical base material, the grooves of the thread grooves are directly pressed by the rolling machine, so that the screw valleys are formed at a constant position with low tolerance. On the other hand, the screw thread has a relatively large height difference because the base material is pushed out and protruded during the process of forming the screw groove.

Since the female thread 51 of the connection nut 5 is screwed in contact with the threaded portion of the threaded groove 41 of the screw 4, the center of the connection nut 5 is the center of the threaded groove 41 of the screw 4. The screwing position determines the engagement position. That is, the center C of the connection nut 5 is not aligned with the center d1 according to the outer diameter of the screw 4 but with the center d2 of the circle formed by the screw bone.

Therefore, even if the outer diameter of the screw 4 is somewhat changed in the longitudinal direction, it is possible to rotate the screw 4 along the axis of rotation passing through the center of the circle formed by the screw bone. This prevents the ball nut screwed onto the screw from moving in a plane perpendicular to the axis of rotation of the screw, thereby ensuring a stable ball nut operation.

8, which is exaggerated for clarity, shows various examples of contact between a screw groove formed in the screw and a female screw formed in the connection nut. First, FIG. 8A illustrates an example in which the thread 511 of the female thread 51 contacts the screw bone 411 of the screw groove 41. To this end, the radius of curvature of the thread 511 of the female thread 51 is formed smaller than the radius of curvature of the threaded bone 411 of the threaded groove 41.

Meanwhile, in FIG. 8B, the screw grooves 41 are symmetrically spaced apart from each other at the center of the screw bone, and a contact protrusion 412 protruding further from the inner wall surface of the screw groove 41 is formed. The protrusion 412 may be intentionally shaped when the screw groove 41 is formed as a site where steel balls provided in the ball nut contact each other. In this case, the female screw 51 comes into contact with the protrusions 412.

Meanwhile, in FIG. 8C, the screw groove 41 is formed in a continuous curved surface as in FIG. 8A. The contact portion 512 protrudes from the surface of the female screw 51 corresponding to the portion where the steel ball contacts the female screw 51.

(A), (b) and (c) of FIG. 8 are examples of a form for allowing the female thread to contact the periphery of the screw bone of the screw groove, and in addition to the bar point, the lowest point or the contact point at which the steel ball and the screw groove contact each other. Various modifications are possible to make contact with the female thread at.

The ball screw according to the embodiment of the present invention includes a ball nut having a plurality of steel balls circulated, and a screw groove 41 formed by rolling the steel balls on an outer circumferential surface thereof. The connection nut 5 is screwed with the screw 4 at points parallel to the contact points that make contact.

The ball screw according to the embodiment of the present invention includes the screw assembly described above. At this time, the configuration of the ball nut and the steel ball may be the same as the well-known configuration.

According to the embodiment of the present invention, the connecting nut 5 and the bearing shaft 1 are manufactured separately from the screw 4 to facilitate the manufacture of the screw 4 according to the rolling process. Specifically, the length of the screw 4 used for the ball screw may be several meters. When the base material is bitten by the tool post and sag occurs according to the length of the base material, it is difficult to manufacture the coupling end, and furthermore, the machining precision of the screw groove is deteriorated at both ends of the screw.

According to the present invention, there is no need to form a coupling end at the end of the screw, thereby improving the convenience of processing, and it is possible to process the screw groove of the screw end with high precision. Therefore, the operation of the ball nut near both ends of the screw can also be achieved with high accuracy.

10: assembly
10a: shaft member 101a: bolt hole
1: bearing shaft 11: protrusion
2: support jaw 3: timing pulley
4 screw 41 screw groove 411 screw bone 412 protrusion 42 fastening groove
5 Connecting Nut 51 Female Thread 511 Thread 512 Contact 52 Receptacle
53: coupling groove 6: fixing bolt
20: set screw 30: bearing

Claims (10)

By connecting the end of the screw with a screw groove formed on the outer peripheral surface rotatably to the support bearing,
A bearing shaft rotatably coupled to the bearing;
A connection nut connecting the end of the screw and the bearing shaft,
The connecting nut is screw assembly that is coupled to the end of the screw by screwing engagement with the groove of the screw groove. In claim 1,
The connecting nut
And a coupling groove formed on an inner circumferential surface of the female screw bited by the screw groove, and the curvature of the thread of the female screw is smaller than the curvature of the valley of the screw groove. Bearing support,
A bearing shaft rotatably coupled to the bearing,
One end is coupled to the rotating shaft of the bearing shaft, the other end of the coupling nut is formed with a coupling groove having a female thread on the inner peripheral surface and
A screw groove is formed on the outer circumferential surface to contact the steel balls, and includes a screw inserted into the coupling groove and screwed to the coupling groove.
The contact between the female thread and the screw groove,
And a screw groove corresponding to the point of contact with the steel balls. 4. The method of claim 3,
One of the bearing shaft and the connecting nut is formed with a protrusion having a non-circular cross section,
The other one is formed with a receiving portion is coupled to the protrusion, the screw assembly is rotated by the rotation of the bearing shaft screw assembly. 4. The method of claim 3,
One end of the bearing shaft is formed with a supporting jaw portion in contact with one side of the bearing inner ring,
The other side of the bearing inner ring is a screw assembly that is opposed by the connecting nut. The method of claim 5,
The timing pulley is further formed in the support jaw,
The timing pulley, the support jaw portion and the bearing shaft are integrally formed screw assembly. 4. The method of claim 3,
A screw assembly further comprises a fixing bolt end portion penetrating the bearing shaft is coupled to the end portion of the screw. In claim 7,
The screw direction of the fixing bolt is opposite to the screw direction of the screw screw assembly. A ball screw comprising a ball nut having a plurality of steel balls circulated, and a screw groove formed by the steel ball rolling on an outer circumferential surface thereof,
A connection nut screwed to the screw at points corresponding to the contact points of the steel ball and the screw groove;
Ball screw comprising a bearing shaft connected to the connecting nut. A ball screw provided with the screw assembly according to any one of claims 1 to 8.

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