JPH1182459A - Split nut and manufacture of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce high quality split nuts inexpensively. SOLUTION: Split nuts 11a and 11b constituting parts of a nut 11 are made of sintered metallic materials, the split nuts 11a and 11b are formed easily and efficiently, the outer surface shaped of the split nuts 11a and 11b are formed so as to have roughly uniform distances from a female screw part 11c in the circumferential direction and, thus, a compressing force is applied to metallic powders nearly uniformly in the circumferential direction during compression molding, and a complex shape of a screw part or the like is formed well at a uniform density.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a split nut in which a nut is constituted by a plurality of split nut members and a method of manufacturing the split nut.

[0002]

2. Description of the Related Art Conventionally, split nuts, such as half-split nuts, in which a plurality of split nut members forming a part of a nut are assembled, have been used in various devices. Such a divided nut member is usually formed by dividing a nut manufactured using a steel material into a plurality of pieces along an axis by cutting or the like.

[0003]

However, such a conventional split nut is expensive due to poor productivity. On the other hand, when trying to mold such a divided nut from metal powder, the compression force of the punch of the die device is not uniform due to the complicated shape of the divided nut, and the molding density of the surface portion close to the punch is increased. There is a problem that the density of the central portion becomes low and a uniform molding state cannot be obtained. In particular, the variation in the molding density is large in the thread portion, and a molded product having good quality cannot be obtained.

Accordingly, an object of the present invention is to provide a split nut which is inexpensive and can obtain good productivity and quality, and a method of manufacturing the split nut.

In order to achieve the above object, according to the first aspect of the present invention, a nut having an internal thread on an inner peripheral portion is formed by assembling a plurality of divided nut members forming a part of the nut. The split nut member is made of a sintered metal material, and the outer surface shape of the split nut member is substantially uniform in the circumferential direction in a radial distance from the female screw portion to the outer surface. Is formed.

In the invention according to claim 2, the outer surface of the split nut member according to claim 1 is formed into a shape chamfered by a plane extending substantially parallel to the axial direction.

Further, according to the third aspect of the invention, the outer surface of the split nut member according to the first aspect is formed by an arc-shaped surface corresponding to the female screw portion of the nut.

Further, in the invention according to the fourth aspect, the sintered metal material constituting the split nut member according to the first aspect is provided with porous open pores, and lubricating oil is filled in the open pores. Is filled.

According to a fifth aspect of the present invention, there is provided a method of manufacturing the split nut member according to the first aspect,
A predetermined metal powder is compression-molded into a predetermined shape by a press, and the split nut member is manufactured by sintering.

Further, in the invention described in claim 6, the press described in claim 5 is performed by using a molding die that opens and closes and moves substantially perpendicularly to the axial direction of the split nut member.

According to the first or fifth aspect of the present invention, the split nut member is easily and efficiently formed by compressing and sintering the metal powder using the mold. That is, since the outer surface shape of the split nut member is set to be substantially uniform in the circumferential direction between the split nut member and the female screw portion, the compression force on the metal powder is reduced when performing compression molding. It acts almost uniformly in the direction, and in particular, the female screw portion is favorably formed with a uniform density.

Such an operation can be realized by a simple chamfered shape as in the second aspect of the present invention, but is extremely enhanced by forming an arc shape along the thread as in the third aspect of the present invention. Realized in a good homogeneous state.

According to the fourth aspect of the invention, good lubricity is maintained by the lubricating oil contained in the sintered metal material of the split nut member.

Further, according to the present invention, the split nut member is easily and accurately formed in a state where the divided nut member is stably held horizontally by the forming die which opens and closes substantially perpendicularly to the axial direction. It is supposed to be.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which a split nut according to the present invention is applied to a screw feeder will be described below in detail with reference to the drawings. In the screw feeder according to the embodiment shown in FIGS. 1 and 2, one end portion in the longitudinal direction of the main body frame 1 (the left end in the figure) is provided in the box-shaped main body frame 1 extending in a hollow elongated shape. A motor housing box 2 is provided in (part), and a drive motor 3 composed of a stepping motor or the like is fixed in the motor housing box 2.

One end of a long feed screw 4 is connected to the output shaft of the drive motor 3. The feed screw 4 is disposed so as to extend substantially horizontally from the partition wall 5 of the motor housing box 2 along the longitudinal direction of the main body frame 1. )
Is rotatably supported by a ball bearing 7 embedded in a terminal wall 6 on the opposite side of the main body frame 1.
Reference numerals 1a and 3a in FIG. 1 indicate encoders for detecting a rotational position.

Further, a partition wall 5 of the motor housing box 2 and
A pair of guide shafts 8, 8 extending along the longitudinal direction of the main body frame 1 is substantially horizontal between the partition wall 5 and the end wall 6 of the main body frame 1 facing the longitudinal direction. It is fixed to. The pair of guide shafts 8, 8 are
The nut holding frame 10 is mounted on the pair of guide shafts 8 so as to be reciprocally movable with respect to the pair of guide shafts 8.

As shown in FIGS. 3 to 6, the nut holding frame 10 is formed of a substantially rectangular parallelepiped block. The width direction of the nut holding frame 10 (FIG. 3)
A pair of guide holes 10 is provided on both sides in the vertical direction).
a, 10a are drilled substantially in parallel, and the pair of guide shafts 8, 8 penetrate through these guide holes 10a, 10a in a loosely fitted state. The main body frame 1 is configured to reciprocate along the longitudinal direction.

A screw mounting hole 10b is formed through a substantially central portion in the width direction of the nut holding frame 10 so as to extend substantially parallel to the pair of guide holes 8,8. The above-mentioned feed screw 4 is rotatably penetrated through the screw mounting hole 10b in a loosely fitted state.

Furthermore, as shown in particular in FIG.
The nut holding frame 10 is provided with a nut receiving hole 10c at an intermediate portion in the axial direction of the screw mounting hole 10b. The nut receiving hole 10c is for holding the divided nut 11 screwed to the feed screw 4 passing through the screw mounting hole 10b, and has a substantially rectangular central portion of the upper surface of the nut holding frame 10. It is recessed so as to be dug to a predetermined depth, and has a function of holding a pair of half-split split nut members 11a and 11b constituting each half of the split nut 11 at a predetermined position.

The pair of half-split split nut members 11a,
11b has a shape divided in half by a plane including the center axis of the nut, and a female screw portion of the nut 11 is formed on the inner peripheral surfaces of the divided nut members 11a and 11b. The concave and convex portions 11c having a divided shape are formed so as to be arranged in the axial direction. That is, the nut 11 having the female screw portion 11c on the inner peripheral portion is formed by symmetrically assembling the two half-split split nut members 11a and 11b.
The inner female screw portion 11c of the nut 11 thus formed is screwed to the feed screw 4 described above.

Each of the half-split split nut members 11a, 11
b includes body portions 11a1 and 11b1 each having a chamfered outer peripheral corner of a rectangular parallelepiped, as shown in FIG.
Each of the body portions 11a1 and 11b1 is chamfered by a plane extending substantially parallel to the axial direction.
That is, the width direction of the body portions 11a1 and 11b1 (FIG. 6)
The chamfered planes 11a2 and 11b2 formed of inclined surfaces are formed on both side edges, and the outer surface of the split nut members 11a and 11b extends from the female screw portion 11c to the outer surface. The radial distance is substantially uniform in the circumferential direction.

At this time, each of the half-split split nut members 1
1a and 11b are made of a sintered metal material formed by mixing metal powders such as iron powder and copper powder. The sintered metal material forming the split nut members 11a and 11b has porous open pores, and the open pores are filled with a predetermined lubricating oil.

Further, the nut receiving hole 10c of the nut holding frame 10 has a first hole portion 10c1 on the lower side in FIG. 3 for receiving and holding one half split nut member 11a, and the other half split nut. The second hole 10c2 on the upper side in FIG. 3 for housing and holding the member 11b. These first
Each of the hole portion 10c1 and the second hole portion 10c2 has a common mounting reference end surface S on the right side in FIG. 3, and the left end surface in FIG. It is formed on a flank T having a step.

That is, the mounting reference end face S is formed so as to form a plane in the direction perpendicular to the axis, and the leaf spring member 12 is mounted so as to be pressed against the mounting reference end face S.
The half-split split nut members 11a and 11b housed in the first hole portion 10c1 and the second hole portion 10c2 respectively move in the axial direction (left side in FIG. 1) by the urging force in the axial direction (left side in FIG. 1). Direction).

The half-split nut members 11a and 11b are urged by the pressing force of the leaf spring member 12.
Is applied to the feed screw 4 in the axial direction as described above, and the screwing is performed in a state where backlash does not occur due to the pressurization.

On the other hand, the step flank T in each of the first hole 10c1 and the second hole 10c2 has a flank whose axial position is different from each other. Specifically, FIG.
The flank of the lower first hole 10c1 is
3 is arranged at a position substantially coinciding with the end face of the half-split split nut member 11a housed in c1.
The flank of the upper second hole 11c2 is
It is formed so as to be separated from the end face of the half-split split nut member 11b accommodated in c2 by a predetermined distance.

Then, the half-split split nut member 11b accommodated in the second hole 10c2 is allowed to move in the axial direction by an amount corresponding to such a large interval.
As a result, the axial preload on the feed screw 4 is favorably applied. In particular, when the thread of the female thread portion of each half-split split nut member 11b has a gap with the thread of the feed screw 4, the female thread of the half-split split nut member 11b The part is axially moved until it comes into close contact with the male screw of the feed screw 4, and a good screwed state is obtained.

In such an apparatus, the influence of backlash is removed by pressurizing the half-split split nut members 11a and 11b, and a highly accurate feeding operation can be obtained. That is, a good feeding operation can be obtained without using expensive parts such as a ball screw used in a general screw feeder, even when using ordinary inexpensive screws.

On the other hand, each of the half-split nut members 11a and 11b in the above-described apparatus is made of a sintered metal material, and is divided into the half-split split nut members 11a and 11b.
Since the lubricating oil is filled in the sintered metal material constituting 11b, good lubricity can be obtained for a long time.

Such a split nut member 11a,
11b is easily formed by a compression and sintering process using a predetermined mold. That is, in forming the half-split split nut members 11a and 11b, first, metal powders such as iron powder and copper powder which are main components are mixed, and the mixed metal powder is shown in FIG. A predetermined amount is filled in a cavity of a molding die apparatus (die apparatus) 20 as described above, and press-molded into a predetermined shape.

The above-mentioned molding die apparatus (die apparatus) 20 is half-cut with respect to a lower punch 22 for forming the female screw uneven portion 11c on the inner peripheral surface of the above-mentioned half-split split nut members 11a and 11b. Outer peripheral surface 1 of nuts 11a and 11b
The upper punch 23 for forming 1a1 and 11a2 is configured to move vertically, and the upper punch 23 is opened and closed in a direction substantially perpendicular to the axial direction of the split nut members 11a and 11b. Configuration.

The upper punch 23 is pressed at a predetermined pressure from the upper side toward the lower punch 22 to compress the metal powder therein, so that the split nut members 11a and 11b having the above-described shape are formed. Material is formed.
If such a molding die device (die device) 20 that opens and closes approximately vertically is used, the half-split split nut members 11a, 1
Press forming can be performed in a state where 1b is stably held in a horizontal position, and the molding is easily and accurately performed.

At this time, the compression surfaces of the upper and lower punches 22 and 23 correspond to the outer surface 11a of the half-split split nut member 11a.
1, 11a2 and the female screw uneven portion 11c, respectively, but the radial distance from the female screw uneven portion 11c of the half-split split nut member 11a to the outer surfaces 11a1 and 11a2 is: As described above, since it is formed in a shape that is substantially uniform in the circumferential direction, when performing compression molding, the compressive force on the metal powder acts substantially uniformly in the circumferential direction. In particular, the female screw concavo-convex portion 11c having a complicated shape is favorably formed with a uniform density.

Next, the material of the press-formed half-split split nut members 11a and 11b is passed through a sintering furnace for a certain period of time to perform sintering. When the sintering is completed, the adhered powder and the like are removed by a washing treatment, and a rust-preventive treatment is performed on the iron component. Then, re-pressing is performed by sizing, and the external dimensions changed by the sintering are accurately determined.

Further, after a predetermined lubricating oil is filled into the porous open pores of the sintered metal constituting the half-split split nut members 11a and 11b by vacuum impregnation,
The surplus oil on the surface is washed and removed, followed by drying, and the entire process is completed.

As described above, according to the sintering manufacturing method of the present embodiment, the split nut members 11a, 1
1b can be easily and efficiently formed by a metal mold, and a female screw uneven portion having a complicated shape can be satisfactorily formed at a uniform density.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

In particular, in the above-described embodiment, uniform compression molding is enabled by the simple chamfered shape 11a2. However, as shown in FIG.
If the outer surface of 1a is formed as an arc-shaped surface 31a1 and a helical projection 31a2 corresponding to the thread of the female screw portion 31c is formed on the arc-shaped surface 31a1, extremely good uniform molding is achieved. A state will be obtained.

Further, in the above embodiment, a half split nut has been described. However, the present invention can be similarly applied to a split nut having three or more split nuts.

[0041]

As described above, according to the first or fifth aspect of the present invention, the split nut member forming a part of the nut is formed of a sintered metal material to easily and efficiently form the split nut member. The compression force on the metal powder in the compression molding can be reduced in the circumferential direction by forming the outer surface shape of the split nut member so as to have a substantially uniform circumferential distance between the split nut member and the female screw portion. And a complicated shape such as a female screw portion can be formed satisfactorily at a uniform density, so that the split nut member can be produced at low cost and with good quality.

Such an effect can be easily realized by a simple chamfered shape as in the second aspect of the present invention. By doing so, an extremely good homogeneously formed state can be obtained, and the above-described effects can be further improved.

Further, in the invention according to the fourth aspect, the lubricating oil is filled into the porous open pores of the sintered metal material constituting the split nut member, so that good lubricity can be maintained for a long time. And the usefulness of the split nut can be enhanced.

Further, according to the present invention, it is possible to easily and accurately mold the divided nut member in a state where the divided nut member is stably held horizontally by a molding die which is opened and closed substantially perpendicularly to the axial direction. Therefore, the above-described effects can be further improved.

[Brief description of the drawings]

FIG. 1 is an explanatory plan view showing a structure of a screw feeder using a split nut according to the present invention.

FIG. 2 is an explanatory side view of the screw feeder shown in FIG. 1;

FIG. 3 is an explanatory plan view of a nut holding frame used in the screw feeder shown in FIG. 1;

FIG. 4 is an explanatory longitudinal sectional view of a nut holding frame used in the screw feeder shown in FIG. 1;

5 is an explanatory cross-sectional view of a nut holding frame used in the screw feeder shown in FIG. 1;

6 is a schematic perspective explanatory view showing a mounting relationship between a nut holding frame and a split nut used in the screw feeder shown in FIG. 1;

FIG. 7 is an explanatory sectional view showing a mold apparatus for molding the split nut shown in FIG. 1;

FIG. 8 is a schematic perspective explanatory view showing another embodiment of the split nut.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Nut holding frame 10c Nut accommodation hole 10c1 1st hole 10c2 2nd hole 11, 31 Split nut 11a, 11b Half-split split nut member 11a1, 11b2 Chamfer plane 20 Molding apparatus (die apparatus) 22 Lower punch 23 Upper punch

Claims (6)

[Claims] 1. A nut having an internal thread portion on an inner peripheral portion, wherein a plurality of divided nut members forming a part of the nut are assembled, and the divided nut member is made of a sintered metal material. And the outer surface shape of the split nut member is formed in a shape that makes the radial distance from the female screw portion to the outer surface substantially uniform in the circumferential direction. nut. 2. The split nut according to claim 1, wherein the outer surface of the split nut member is formed into a shape chamfered by a plane extending substantially parallel to the axial direction. 3. The split nut according to claim 1, wherein the outer surface of the split nut member is formed from an arcuate surface corresponding to the female screw portion of the nut. 4. The divided metal member constituting the divided nut member according to claim 1, wherein porous open pores are provided, and the open pores are filled with lubricating oil. nut. 5. The method for manufacturing a split nut member according to claim 1, wherein a predetermined metal powder is compression-molded into a predetermined shape by a press, and the split nut member is manufactured by sintering. A method for producing a split nut, characterized by the following. 6. A method for manufacturing a split nut, wherein the press according to claim 5 is performed by using a molding die that opens and closes in a direction substantially perpendicular to the axial direction of the split nut member.