JP2005308141A - Ball screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a piece type ball screw, in particular, one for tightening and fixing a piece member in which corrosion resistance of the piece member and the workability for fixing the piece member are excellent by selecting a material, and the cost can be reduced. <P>SOLUTION: The ball screw 1 comprises a screw shaft 2 and a nut 3, and balls 6 interposed between screw grooves 4, 5. The nut 3 has a piece member 7 as a component for circulating the balls 6. The piece member 7 is fitted to a fitting opening 8 formed in the nut 3 through outer and inner faces. The piece member 7 has a pair of wing parts 10 to be engaged with the screw groove 5 of the nut 3, and a pair of tightening parts 11 fixed to an outside diameter part of the nut 3. The piece member 7 is a sintered product manufactured by the metal injection molding method. The material of the piece member 7 mainly consists of iron with 6.5-8.5 wt.% nickel. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a piece-type ball screw used in various actuators, machine tools, industrial machines and the like in automobiles.

There are various ball screw circulation types such as a piece type, a return tube type, a guide plate type, and an end cap type. A piece-type ball screw has a piece member provided on a nut as a circulating member, and the piece member is provided with a connecting groove for connecting the screw grooves of the nut to circulate the ball. The piece-type ball screw is excellent in compactness, and the circulation part can be equally distributed in the circumferential direction, and since it has a good dynamic balance when used in nut rotation, it is often used for nut rotation. Further, in the case of the piece type, the interval between the circulating portions is freely arranged, and a high degree of freedom can be obtained in designing the interval between the ball rows corresponding to the load capacity and the like.
In automotive applications, there are many space restrictions and compactness is strongly required, so the piece type is often used.
In a piece-type ball screw, the piece member is often processed by cold forging (for example, Patent Document 1).

Conventionally, in a piece-type ball screw, a plurality of connecting grooves are provided in one piece member, the lead of the screw groove is reduced, and the load capacity is increased by increasing the number of balls circulating in the nut. Has been proposed (Patent Document 2). In this proposed example, it is proposed that the piece member having a plurality of connecting grooves is made of a sintered alloy (made by MIM) using an injection molding technique. In the proposed example, it is also proposed to fix the piece member by plastic deformation, and to provide a wing portion to be engaged with the thread groove of the nut on the piece member. If the wing portion is provided, the piece member can be reliably prevented from coming off. In addition, when the wing portion is provided and the crimping portion is provided, the piece member is securely fixed, and the piece member is prevented from dropping off unexpectedly.
It is disclosed that the material of the piece member in the case of being made of MIM is preferably a material that can be subsequently carburized and quenched, with 0.3% carbon, 1-2% nickel, and the remainder made of iron. ing.
JP-A-10-82458 JP 2001-289301 A

  When processing by cold forging like a conventional general piece member, if the piece member has a complicated shape having the wing part or the like, there is a possibility that cracking or the like may occur due to a high degree of processing. It is expensive to process so as not to break. As shown in Patent Document 2, when the piece member is made of a sintered alloy (made by MIM) using an injection molding technique, it has excellent formability even if the piece member has a complicated shape. .

However, the conventional piece-type ball screw has insufficient corrosion resistance due to the characteristics of the material of the piece member, and has insufficient workability for fixing by plastic working. If the corrosion resistance is insufficient, it is necessary to avoid shortening the service life in severe use environments such as automobiles where salt mud water is applied. As for workability, when fixing by caulking or the like, the material is hard, and there is a risk that problems such as cracking may occur in the caulking part.
The piece member is usually hardened by carburizing and quenching in order to prevent indentation due to the ball hitting, but in such a case, the toughness is insufficient and the workability is low. Deteriorate. In particular, when the piece member has a caulking portion, if the bending angle of the caulking portion is deepened, there is a risk of bending, and if the bending angle is small, stable caulking cannot be performed. There is a problem that it is difficult to design.

An object of the present invention is to provide a ball screw which can be made excellent in corrosion resistance and workability for fixing it by selecting a material in a piece type ball screw, and can be reduced in cost. .
Another object of the present invention is to obtain the stability of the caulking particularly when the piece member is caulked and fixed.

The ball screw according to the present invention includes a screw shaft and a nut formed with opposing screw grooves for rolling the ball, a plurality of balls interposed between the opposing screw grooves, and a fitting opening formed in the nut. And a piece member having a ball circulation connecting groove for connecting the screw grooves of the nut, and the material of the piece member is composed mainly of iron and nickel of 3.0. It is characterized by containing ˜10.0 wt%. More preferably, the nickel content in the piece member is in the range of 6.5 to 8.5 wt%. The piece member is manufactured by, for example, a metal injection molding method.
The said piece member is good also as what has a wing part which engages with the thread groove of the said nut and prevents this piece member from dropping out to the nut outer diameter side. Further, the piece member may have a caulking portion fixed to the outer diameter portion of the nut. The ball screw of the present invention may be used for an automobile actuator.

According to this structure, since the material of the piece member contains a large amount of nickel of 3.0 wt% or more, it becomes excellent in workability and corrosion resistance, and the processing cost can be reduced. When the nickel content is increased from 3.0 wt%, the workability and corrosion resistance are improved as the nickel content is increased. However, even if it exceeds about 8.0 wt%, the workability and corrosion resistance accompanying the increase cannot be obtained. It is useless to increase the content of nickel, which is an expensive material compared to iron, more than necessary, and the upper limit of the nickel content is preferably set to 10% or less.
In particular, when the nickel content in the piece member is set to 6.5 to 8.5 wt%, no bending occurs even if the bending angle is increased when the piece member is provided with a caulking portion for caulking and fixing. . Therefore, the material is optimal for caulking, and there is no problem such as cracking in the caulking portion, and stable production is possible. If the nickel content is less than 6.5, the caulking process becomes difficult due to insufficient toughness.

  When the piece member is manufactured by the metal injection molding method, even if the piece member has a complicated shape having a connecting groove, a wing part, a caulking part, etc., it should be manufactured easily and accurately. Can do. In the case of producing by the metal injection molding method, it is effective to make the nickel content 3.0 to 10.0 wt%, particularly 6.5 to 8.5 wt%.

  When the piece member has a wing portion that engages with the thread groove of the nut, the piece member is reliably prevented from falling to the nut outer diameter side. When the wing part is fitted into the screw groove of the nut, the dimensional variation is directly connected to the step accuracy between the connecting groove of the piece member and the nut screw groove. It is easy to manage the level difference between the ball rake face at the end of the circulation groove and the thread groove inner face of the nut, and smooth ball circulation can be performed. Therefore, the reliability of fixing the piece member is high, and the cost is reduced and the mass productivity is excellent.

  When the piece member has a caulking portion that is fixed to the outer diameter portion of the nut, the piece member can be fixed by a simple process by a cold caulking process, and workability and mass productivity are also improved. It will be excellent. In particular, when both the wing portion and the caulking portion are provided, the piece member is prevented from coming off to the outer diameter side of the nut by the wing portion, and the caulking portion is prevented from coming off to the inner diameter side. Thereby, prevention of the fall of the piece member at the time of an assembly and stabilization of the mounting state with respect to the nut of the piece member after crimping are achieved, and reliability improves further.

  Thus, when the piece member is provided with a wing portion or a caulking portion, the shape becomes complicated. However, by adopting a metal injection molding method, the piece member can be accurately manufactured and assembled to the nut. In that case, if the material of the piece member contains 6.5 to 8.5 wt% of nickel, it will be the most suitable material for caulking, and will not cause any problems such as cracks in the caulking part, and will be stable. Production is possible.

  The ball screw of the present invention may be used for an automobile actuator. Automotive parts are strongly required to be compact, and there is a strong demand for improved productivity and lower costs. In response to these demands, the ball screw of the present invention can meet the above-described effects. As an automobile actuator using this ball screw, there are, for example, an automatic manual transmission (AMT) shift actuator, a select actuator, a power steering device, an actuator of a rear wheel steering device, and the like.

The ball screw according to the present invention includes a screw shaft and a nut formed with opposing screw grooves for rolling the ball, a plurality of balls interposed between the opposing screw grooves, and a fitting opening formed in the nut. And a piece member having a ball circulation connecting groove for connecting the screw grooves of the nut, and the material of the piece member is composed mainly of iron and nickel of 3.0. Since the content is ˜10.0 wt%, the corrosion resistance of the piece member and the workability for fixing the piece member can be excellent, and the cost can be reduced.
In particular, when a wing part or a caulking part is provided on the piece member, the piece member is manufactured by a metal injection molding method, and when the nickel content is 6.5 to 8.5 wt%, The piece can be assembled reliably and accurately without fear of dropping off, and it is the most suitable material for caulking, and there is no risk of cracks and other problems in the caulking part, allowing stable production. become.

  A first embodiment of the present invention will be described with reference to FIGS. This ball screw 1 is a piece type ball screw used for an actuator for an automobile, and includes a screw shaft 2 and a nut 3, and screw grooves 4 and 5 formed on opposing surfaces of the screw shaft 2 and the nut 3. It consists of balls 6 interposed therebetween. The screw grooves 4 and 5 are spiral grooves that roll on the ball 6. The automotive actuator using the automotive ball screw 1 of this embodiment is used for an automatic manual transmission (AMT) of an automobile, but is also used for a power steering, a rear wheel steering device, and the like. It can be a thing.

  The nut 3 is provided with a piece member 7 as a part for circulating the ball 6. The piece member 7 is fitted into a fitting opening 8 formed in the nut 3 so as to penetrate the inner and outer surfaces, and one piece of connection for connecting adjacent circumferential portions of the helical thread groove 5 of the nut 3. It is a member in which the groove 9 is formed on the inner surface. By this connecting groove 9, a spiral ball rolling path formed between the screw shaft 2 and the threaded grooves 4 and 5 of the nut 3 becomes a circular path, and the ball 6 circulates and moves along this circular path. When the ball 6 passes through the connecting groove 9, the ball 6 gets over the thread of the screw groove 4 of the screw shaft 2.

  In such a piece-type ball screw 1, in this embodiment, the piece member 7 has a pair of wing portions 10 that engage with the screw grooves 5 of the nut 3 and is fixed to the outer diameter portion of the nut 3. A pair of crimping portions 11. Further, the piece member 7 is made of a sintered alloy manufactured by a metal injection molding method. A schematic shape of the piece member 7 is shown in FIG. FIG. 1C is a cross-sectional view taken along the line CC in FIG.

As shown in FIG. 1B, the piece member 7 extends so that the connecting groove 9 inclines in a direction intersecting the inclined direction of the screw groove 5 with respect to the nut axis O, and the extending direction of the connecting groove 9 is This is the longitudinal direction of the piece member 7. The planar shape of the connecting groove 9 is substantially S-shaped so that both ends smoothly follow the screw groove 5.
The wing part 10 is a part which prevents the piece member 7 from dropping off to the nut outer diameter side. The wing portion 10 protrudes along the extending direction of the nut screw groove 5 on both side surfaces along the longitudinal direction of the piece member 7, and is fitted into the nut screw groove 5. The piece member 7 is inserted into the fitting opening 8 from the inside of the nut 3 in a fitted state, and the wing portions 10 on both sides are fitted into the nut screw grooves 5.

The caulking portions 11 are provided at both ends of the piece member 7 in the longitudinal direction as protruding pieces that protrude toward the nut outer diameter side. These caulking portions 11 are formed in an upright state as shown in FIG. 5 (A) when the piece member 7 is manufactured, and are bent in the longitudinal direction of the piece member so as to bend at the root portion as shown in FIG. 5 (B). Tighten it so that it tilts outward. Thereby, the crimping part 11 engages with the expansion part 8a provided in the opening edge by the side of the nut outer diameter of the opening 8 for fitting of the nut 3 like FIG.1 (C).
As shown in FIGS. 3A and 3B, the planar shape of the fitting opening 8 is a track shape in which both ends are semicircular. The widened portion 8a is formed in a semicircular portion at both ends of the fitting opening 8 as a countersink-shaped portion having a tapered cross section that gradually widens on the outer diameter side. The caulking portion 11 is pressed against the expanding portion 8a having a tapered shape by caulking.

  Thus, the piece member 7 is fixed to the nut 3 by the wing portion 10 engaging with the inner diameter side of the nut 3 and the crimping portion 11 engaging with the outer diameter side.

  The shape of the piece member 7 will be described with reference to FIG. As for the piece member 7, the center of the longitudinal direction in the surface on the nut outer diameter side is a flat surface portion 7a, and projecting pieces that serve as the caulking portion 11 are provided on both sides of the flat surface portion 7a via notched portions 7b. . The flat surface portion 7a is a surface that is placed on a table (not shown) during firing in the manufacturing process of the piece member 7, and is a flat surface portion. The projecting pieces to be the caulking portions 11 on both sides have the same length as that of the flat surface portion 7a or a length at which the protruding portions are retracted from the flat surface portion 7a. The length La of the flat surface portion 7a is 50% or more of the full length L in the longitudinal direction of the piece member 7. For example, when the total width L is 11 mm, the length La of the flat surface portion 7a is 5.6 mm. The gate 19 at the time of injection molding of the piece member 7 is preferably provided on the tip surface of the wing portion 10.

  Details and materials of the screw shaft 2, the nut 3, and the piece member 7 in FIG. 1 will be described. As shown in FIG. 2, the formation range of the screw groove 4 of the screw shaft 2 is a portion excluding both ends, and a coupling fitting portion 13 is provided at one end. The screw shaft 2 is made of a steel material, the screw groove 4 is rolled, and the screw groove 4 and the coupling fitting portion 13 are heat-treated by induction hardening or the like, or the whole is subjected to heat treatment such as carburizing and quenching.

  As shown in FIG. 3, the nut 3 has a pair of trunnion shaft portions 14 on the outer peripheral surface. As shown in FIG. 4, the nut 4 is provided with a plurality of fitting openings 8 (four places in the illustrated example), and the piece member 7 is fixed to each fitting opening 8. The nut 4 is made of a steel material, and the thread groove 5 is processed by cutting such as tapping, and then heat-treated. For the heat treatment, carburizing and quenching under vacuum is employed.

The piece member 7 is manufactured by the metal injection molding method (hereinafter abbreviated as “MIM”) as described above, and is made of sintered metal. MIM is a method in which a metal powder is adjusted to a plastic shape, molded with an injection molding machine, and then fired. Specifically, for example, metal powder and a binder made of plastic and wax are kneaded with a kneader, and the kneaded product is granulated into pellets. The pellets granulated as described above are supplied to a hopper of an injection molding machine (not shown) and molded by being injected into a mold in a heated and melted state. The injection molding machine may be the same as that for plastic. The green body of the formed piece member 7 is subjected to a heat treatment such as a carburizing process in a vacuum furnace or the like and fired.
The fired piece member 7 may be used as it is, but after firing, it is quenched by carburizing quenching or induction quenching to obtain a finished product.

  The material of the piece member 7 is a material mainly containing iron and containing 3.0 to 10.0 wt% of nickel. The nickel content is more preferably 6.5 to 8.5 wt%. It can also contain trace amounts of carbon. As such a material, for example, FEN8 of Japanese powder metallurgy industry standard is preferable, and stainless steel SUS316L or SUS630 may also be used. “FEN8” is C: 0.1 wt% or less and Ni: 6.5-8.5 wt% according to Japanese Powder Metallurgy Industry Standard. The metal powder of such a material is used for the metal powder in the MIM.

According to the ball screw 1 having this configuration, the piece member 7 has a structure in which the wing portion 10 fitted into the nut screw groove 5 is projected from the inner diameter portion and is fixed by the crimping portion 11 on the outer diameter side. 7 can be firmly fixed. Moreover, the fixing work is easy. That is, the fall prevention of the piece member 7 at the time of an assembly and the stabilization of mounting | wearing of the piece member 7 after crimping are achieved.
When the wing portion 10 is configured to be fitted into the nut screw groove 5, the dimensional variation is directly connected to the level difference between the rake face of the connecting groove 9 of the piece member 7 and the nut screw groove 5. Therefore, this fitting structure cannot be established unless the accuracy of the wing portion 10 is stable. However, since the piece member 7 is made of MIM, it can be fixed with high accuracy. In the case of a general sintered part, a tolerance of ± 0.1 to 0.2 mm is required, but in the case of MIM, it is possible to finish within a tolerance of ± 0.05 mm. Therefore, the step accuracy can be ensured and the balls 6 can be smoothly circulated. Since actuators for automobiles, particularly actuators for transmissions, affect the feeling of driver's operation, smooth operation is desired.

  Since the material of the piece member 7 is mainly composed of iron and contains 6.5 to 8.5 wt% of nickel, it becomes an optimum material for caulking, and the caulking portion 11 has problems such as cracking. And stable production is possible. When the material of the piece member contains a large amount of nickel of 3.0 wt% or more, it becomes excellent in workability and corrosion resistance, and the processing cost can be reduced. When the nickel content is increased from 3.0 wt%, the workability and corrosion resistance are improved as the nickel content is increased. However, even if it exceeds about 8.0 wt%, the workability and corrosion resistance accompanying the increase cannot be obtained. It is useless to increase the content of nickel, which is an expensive material compared to iron, more than necessary, and the upper limit of the nickel content is preferably set to 10% or less. In particular, the range is preferably 6.5 to 8.5 wt%.

Although it is possible to make nickel less than 6.5 wt% as the material of the piece member 7, according to Japanese Powder Metallurgy Industry Standard, only “FEN2” is the same material as FEN8 as the MIM material. FEN2 is defined as C: 0.1 wt% or less and Ni: 1.50-2.50 wt%, which has a low nickel (Ni) content and exhibits properties almost similar to pure iron. In the case of FEN2, it has almost no corrosion resistance, and the mechanical strength as the piece member 7 is insufficient before caulking. Further, the surface hardness of FEN8 is HV170, but FEN is only about half of HV90, so it is not suitable for use as a piece member 7 which is a machine structural component.
Moreover, even if the nickel amount exceeding 8.0 wt% is added as described above, the strength and the surface hardness hardly change. Therefore, adding the nickel amount exceeding 8.5 wt% is a waste of material.
Therefore, a nickel content in the range of 6.5 to 8.5 wt% is suitable as a material for the piece member 7 having a caulking structure, and is balanced with mechanical strength such as tensile load and surface hardness. Material.

  FIG. 6 shows another embodiment of the present invention. In this ball screw 1A, the nut 3 does not have the trunnion shaft portion 14 (FIG. 2) in the first embodiment, and is provided with a groove 16 for engaging other components. In the groove 16, the cross-sectional shape of the groove bottom along the groove longitudinal direction is an arc shape. Two piece members 7 of the nut 3 are provided at both ends. Other configurations and effects in this embodiment are the same as those in the first embodiment shown in FIGS.

Next, a test example regarding the material of the piece member 7 will be described. The test was performed on the piece member 7 in the ball screw 1 according to the first embodiment. The following three types of materials are typical for MIM.
(1) .SUS316L
(2) .SUS630
(3) .FEN8
According to the JIS standard, the specifications regarding the components and strength of these materials are as shown in Table 1.

これら３種類の材料を用い、駒部材７の加締部１１を専用の工具で上側より変形させ、加締試験を行った。その結果を表２に示す。各材料の供試体はそれぞれ５個とし、各５個を総合した判定結果を表２に示した。

Using these three kinds of materials, the caulking portion 11 of the piece member 7 was deformed from above with a dedicated tool, and a caulking test was performed. The results are shown in Table 2. The number of specimens for each material was set to five, and Table 2 shows the judgment results obtained by combining the five specimens.

表２の結果からは、材料は(1).ＳＵＳ３１６Ｌか、(3).ＦＥＮ８が望ましい。
ただし、(1).ＳＵＳ３１６Ｌは、強度面（引張強さ）で機械部品としてはやや小さい値である。このため、駒部材としては、(3).ＦＥＮ８の方が望ましい。(3).ＦＥＮ８は、ＳＳ４００と同程度の強度を持つ。
(2).ＳＵＳ６３０は、オーステナイト系ステンレス鋼であり、析出硬化型と呼ばれる。そのため、焼結時の温度で硬度上昇が起こり、耐摩耗特性は向上するが、じん性を失うため、冷間塑性加工として、加締を行うことは不利になっている。

From the results in Table 2, the material is preferably (1) .SUS316L or (3) .FEN8.
However, (1) .SUS316L is a slightly small value as a mechanical part in terms of strength (tensile strength). For this reason, (3). FEN8 is preferable as the piece member. (3). FEN8 has the same strength as SS400.
(2) SUS630 is an austenitic stainless steel and is called a precipitation hardening type. For this reason, the hardness rises at the sintering temperature and the wear resistance is improved. However, since the toughness is lost, it is disadvantageous to perform caulking as cold plastic working.

  From this test result, when the piece member 7 fixed by the caulking portion 11 is made of MIM, it is considered that a steel material having a nickel content of 6.5 to 8.5 wt% like FEN8 is optimal.

  7 to 9 show an example of a shift mechanism in an automatic manual transmission (AMT) using the ball screw 1 according to these embodiments. The shift mechanism 30 shifts, in other words, shift gears (not shown) by moving a plurality of arbitrary shift rails 32 installed in parallel in the housing 31 in the longitudinal direction (Y direction). ) Is switched. Each shift rail 32 has a notch 32a, and the shift finger 33 of FIG. 8 can be engaged therewith. By the engagement / disengagement of the shift finger 33, the shift rail 32 to be advanced / retreated is selected.

The first motor 34 and the first ball screw 36 are used to move the shift finger 33 forward and backward for the selection. Further, the second motor 35 and the second ball screw 37 of FIG. 9 are used for the operation of swinging the shift finger 33 and moving the shift rail 32 forward and backward. As the first ball screw 36 of FIG. 8, the ball screw 1A of the embodiment shown in FIG. 6 is used. As the second ball screw 37 of FIG. 9, the ball screw 1 of the embodiment shown in FIGS. 1 to 5 is used.
The automatic manual transmission includes the two ball screws 36 and 37 as described above, and the ball screws 1A and 1 for automobiles of the above-described embodiments are used as the ball screws 36 and 37, respectively.

  In FIG. 8, the first shaft member 38 is installed in the housing 31 so as to be able to advance and retreat, and a sleeve 39 is fitted to the outer periphery thereof so that it can only advance and retreat. The sleeve 39 can rotate integrally with the first shaft 38. The shift finger 34 is provided on the sleeve 39. The screw shaft 2 of the first ball screw 36 is disposed in parallel with the first shaft member 38 and is rotatably supported by the housing 31. One end of the screw shaft 2 is coupled to the output shaft of the first motor 34. It is connected via 40 so that rotation can be transmitted. The nut 3 of the ball screw 36 has a groove 16 (FIG. 6), and an engagement piece 41 provided on the sleeve 39 engages with the groove 16 in the nut advancing / retreating direction. For this engagement, when the screw shaft 2 of the ball screw 36 is rotated by the motor 34, the nut 3 is advanced and retracted, and the sleeve 39 and the shift finger 33 can be advanced and retracted together with the nut 3. By this advance and retreat, the shift finger 33 can be engaged with the notch 32a of any shift rail 32.

  In FIG. 9, the screw shaft 2 of the second ball screw 37 is rotatably installed on the housing 31 and is connected to the output shaft of the motor 35 via a coupling 42 so as to be able to transmit the rotation. The trunnion shaft portion 16 provided on the nut 3 of the ball screw 37 is engaged with an engagement notch 44 a provided on the lever 44. The lever 44 is integrally fixed to a rotation shaft 46 that is rotatably supported on the housing 31 by a support portion 45, and can swing forward and backward around the axis of the rotation shaft 46. When the screw shaft 2 of the second ball screw 37 is rotated by the second motor 35, the nut 3 advances and retracts, and the rotation shaft 46 is rotated together with the lever 44 by the advance and retreat of the nut 3. The rotation shaft 46 is provided in parallel with the first shaft 38 in FIG. 8, and the rotation can be transmitted to the first shaft 38 via a drive transmission means (not shown) such as a lever. . For this reason, the screw shaft 2 of the second ball screw 37 is rotated by the second motor 35, and the nut 3 is advanced and retracted thereby, via the lever 44, the rotating shaft 46, and the first shaft 38. Thus, the sleeve 39 is rotated. By the rotation of the sleeve 39, the shift rail 32 engaged with the shift finger 34 is advanced and retracted, and a switching operation of a transmission gear (not shown) can be performed.

(A) is a partially omitted sectional view of the ball screw according to the first embodiment of the present invention, (B) is a partial development view showing a piece member fitting portion of the nut, and (C) is a piece member of the nut. The longitudinal cross-sectional view of a fitting part, (D) is a schematic perspective view of the same piece member. It is a front view of the ball screw. It is an expanded sectional view of the opening formation part for fitting of the nut, and a front view of the opening for fitting. (A)-(C) are the bottom view which is the figure which looked at the piece member from the inner diameter side of the nut, respectively, the top view which is the figure seen from the outer diameter side of the nut, and the side view. It is sectional drawing of the same piece member, and sectional drawing of the state after crimping of the crimping part. It is a front view of the ball screw concerning other embodiments of this invention. It is a top view of the switching mechanism of the manual manual transmission using the ball screw. It is an AA line expanded sectional view of FIG. FIG. 8 is an enlarged sectional view taken along line B-B in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,1A ... Ball screw 2 ... Screw shaft 3 ... Nut 4, 5 ... Screw groove 6 ... Ball 7 ... Piece member 8 ... Opening 8a for fitting ... Spreading part 9 ... Connecting groove 10 ... Wing part 11 ... Clamping part

Claims (6)

  A screw shaft and a nut formed with opposing thread grooves for rolling the balls, a plurality of balls interposed between the opposing screw grooves, and a fitting opening formed in the nut, and the nut In the ball screw provided with the piece member having the connecting groove for ball circulation for connecting the screw grooves, the material of the piece member is mainly composed of iron and contains 3.0 to 10.0 wt% of nickel. A ball screw characterized by being a thing.   The ball screw according to claim 1, wherein the nickel content in the piece member is 6.5 to 8.5 wt%.   3. The ball screw according to claim 1, wherein the piece member is manufactured by a metal injection molding method.   4. The wing portion according to claim 1, wherein the piece member has a wing portion that engages with a screw groove of the nut and prevents the piece member from dropping to the nut outer diameter side. Ball screw.   The ball screw according to any one of claims 1 to 4, wherein the piece member has a caulking portion fixed to an outer diameter portion of a nut.   6. The ball screw according to claim 1, wherein the ball screw is used for an automobile actuator.

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