JP2016044684A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device down-sized in the axial direction while regulating the position of a coil spring excellently.SOLUTION: A ball screw device 22 comprises: a ball nut 30 having a female screw groove 33; a screw shaft 28 having a male screw groove 34; a cylindrical piston 17 having an opposed wall 17c opposed to a first end face 301A of the ball nut 30; a ball train L; and a coil spring 70 accommodated in an orbital passage K formed by the female screw groove 33 and the male screw groove 34. A first end part 33A of the female screw groove 33 is jointed to the first end face 301A. An opposed wall 17b contains a stopper area 60 opposed to the first end part 33A of the female screw groove 33. A second end part 72 of the coil spring 70 is directly received by the stopper area 60.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a ball screw device.

In a ball screw device in which a ball row is interposed between a male screw groove on the outer periphery of the screw shaft and a female screw groove on the inner periphery of the ball nut, a ball at the end of the ball row, and a pocket-shaped recess provided at the end of the ball nut, It has been proposed to interpose a coil spring between them (for example, see Patent Document 1).
In this type of ball non-circulation type ball screw device, when the screw shaft is driven to rotate with a low axial force applied, the coil spring does not contract, so the balls in the ball row and the ball nut do not move relative to each other. . Accordingly, the ball screw strokes while causing a slip between the balls of the ball row and the screw shaft.

  On the other hand, when the screw shaft is rotationally driven with a high axial force applied, the ball screw strokes while rolling the ball relative to both the ball nut and the screw shaft. Thereby, highly efficient screw transmission is achieved.

Special table 2010-505072 gazette

In the configuration described in Patent Document 1, since the pocket nut for regulating the position of the coil spring is provided in the ball nut, the ball nut is enlarged in the axial direction by the axial length of the pocket recess, and as a result The ball screw device is enlarged in the axial direction.
SUMMARY OF THE INVENTION An object of the present invention is to provide a ball screw device in which the position of a coil spring is well regulated and the axial size is reduced.

  In order to achieve the above object, the invention according to claim 1 is characterized in that a screw is formed over the inner circumference (30a), the end surface (301A) in the axial direction (X), and the entire axial direction of the inner circumference. A screw nut (28) including a ball nut (30) including a female screw groove (33), an outer periphery (28a), and a male screw groove (34) formed with a screw on the outer periphery, and inserted into the ball nut. ), A ball row (L) including a plurality of balls (29) housed in a raceway (K) formed by the female screw groove and the male screw groove, and the outer periphery of the ball nut A cylinder including an inner periphery (17b) and an opposing wall (17c) facing the end face of the ball nut, the opposing wall including a stopper region (60; 60A) facing the end of the female screw groove; Shaped housing (17) and end of said ball row (La) has a first end (71) that engages with the ball (29a) and a second end (72) received directly by the stopper region, and is received in the track. A ball screw device (22; 22A) including a coil spring (70) is provided.

According to a second aspect of the present invention, a recess (171) is formed in the stopper region, and the recess has a seating surface (172) that directly receives the second end of the coil spring. The ball screw device according to claim 1.
The invention according to claim 3 is the ball screw according to claim 2, wherein the recess extends in a tangential direction (T) of the female screw groove and in a lead angle direction (Q) of the female screw groove. Device.

  In the above description, numbers in parentheses represent reference numerals of corresponding components in the embodiments described later, but the scope of the claims is not limited by these reference numerals.

  According to the structure of Claim 1, the 2nd end part of the coil spring accommodated in the internal thread groove is directly received by the stopper area | region of the opposing wall facing the edge part of an internal thread groove. Therefore, unlike the conventional case, the ball nut is not provided with a recess for regulating the second end of the coil spring. Therefore, the ball nut can be miniaturized in the axial direction. As a result, it is possible to provide a ball screw device in which the second end portion of the coil spring is well regulated and the size in the axial direction is reduced.

According to the structure of Claim 2, the 2nd end part of a coil spring is directly received by the seat surface of the recessed part formed in the stopper area | region. Since the second end portion of the coil spring is received while being accommodated in the recess, the second end portion of the coil spring can be regulated more stably.
According to the configuration of the third aspect, the second end of the coil spring is regulated in the recess so as to extend in the same direction as the coil spring housed in the female screw groove. Thereby, a coil spring can be supported more stably.

1 is a schematic cross-sectional view of a brake device to which a ball screw device according to a first embodiment of the present invention is applied, and shows a non-braking time. It is an expanded sectional view of the principal part of the brake device which expanded a part of FIG. It is a schematic sectional drawing of the principal part of a ball screw apparatus. It is an enlarged view of the principal part of the ball screw apparatus which expanded a part of FIG. It is a schematic sectional drawing of the ball screw apparatus which concerns on the 2nd Embodiment of this invention. FIG. 6 is a cross-sectional view perpendicular to the axis of a ball screw device according to a second embodiment of the present invention, and is a cross-sectional view taken along the section line VI-VI in FIG. 5.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a schematic cross-sectional view of the brake device 1 to which the ball screw device 22 according to the first embodiment of the present invention is applied in a non-braking state. The brake device 1 is a device that applies a braking force by friction to a disk 2 that rotates integrally with a wheel of an automobile or the like.
The brake device 1 is, for example, a floating type caliper 3 supported so as to be movable by a knuckle (not shown) and a disk 2 and a first backup supported by the caliper 3 so as to be able to approach and separate from each other. The first pad 6 and the second pad fixed to the plate 4 and the second backup plate 5 and the first backup plate 4 and the second backup plate 5, respectively, and capable of pressing the corresponding side surfaces of the disk 2 respectively. 7.

The caliper 3 includes a first body 8 and a second body 9 that are fixed to each other, and a cover 10 that is fixed to the second body 9. The first body 8 includes a main body portion 11 to which one end of the second body 9 is fixed, and an arm portion 12 connected to the main body portion 11 in an orthogonal shape. The second backup plate 5 is fixed to the arm portion 12.
The second body 9 includes a cylinder 13 (corresponding to a brake cylinder) fixed to the main body portion 11 of the first body 8 and an extending plate 14 extending from the cylinder 13.

The cylinder 13 has a first end portion 151 and a second end portion 152 that face each other in the axial direction AX, and the cylindrical portion 15 with the first end portion 151 opened, and the second end of the cylindrical portion 15. And an end face plate 16 connected to the portion 152. The cylinder 13 accommodates a piston 17 (corresponding to a brake piston) that can move in the axial direction AX.
One end 171 of the piston 17 protrudes toward the disk 2 through an open portion of one end of the cylinder 13 (corresponding to the first end portion 151 of the cylindrical portion 15), and presses the first backup plate 4 in the axial direction AX.

Between both the outer periphery 17a of the piston 17 and the inner periphery of the cylinder 13 (corresponding to the inner periphery 15b of the cylindrical portion 15), a sealing member 18 is interposed for sealing between the two. The sealing member 18 may be a piston seal housed in a housing groove provided on the inner periphery of the cylinder 13 (the inner periphery 15b of the cylindrical portion 15).
Both the outer periphery 17a of the piston 17 and the inner periphery of the cylinder 13 (the inner periphery 15b of the cylindrical portion 15) are connected via a key 19 disposed across a key groove provided in both. . The movement of the piston 17 in the axial direction AX is guided through the key connection using the key 19 and the rotation of the piston 17 relative to the cylinder 13 is restricted.

The caliper 3 functions to generate a braking force by pressing the pads 6 and 7 against the disk 2. The caliper 3 converts the electric motor 20, the speed reducing device 21 that decelerates the rotation of the electric motor 20, and the rotational motion transmitted from the electric motor 20 through the speed reducing device 21 into a linear motion of the piston 17 in the axial direction AX. And a ball screw device 22 for performing the above operation.
The electric motor 20 includes a motor housing 23 fixed to the extending plate 14 of the second body 9 and an output shaft 24.

  The reduction gear 21 includes a drive gear 25 that is attached to one end of an output shaft 24 of the electric motor 20 so as to be integrally rotatable, an idle gear 26 that meshes with the drive gear 25, and a driven gear 27 that meshes with the idle gear 26. . The idle gear 26 is rotatably supported by the second body 9. The cover 10 is fixed to the second body 9 so as to cover the reduction gear 21.

  The ball screw device 22 includes a screw shaft 28 as an input member, and a ball nut 30 as a rotatable output member screwed onto the screw shaft 28 via a plurality of balls 29. The screw shaft 28 is inserted through the ball nut 30. The screw shaft 28 is supported by the second body 9 so as not to move in the axial direction (axial direction AX) and to be rotatable. The ball nut 30 is supported by the second body 9 so as to be movable in the axial direction (axial direction AX) and non-rotatable.

Specifically, the screw shaft 28 is rotatable and cannot move in the axial direction (axial direction AX) by the rolling bearing 32 held on the inner periphery of the support hole 31 provided in the end face plate 16 of the cylinder 13. It is supported. A driven gear 27 is connected to one end 281 of the screw shaft 28 so as to be integrally rotatable.
2 is an enlarged cross-sectional view of a main part of the brake device 1 in which a part of FIG. 1 is enlarged. FIG. 3 is a schematic cross-sectional view of the ball screw device 22. The ball nut 30 includes an outer periphery 30a and an inner periphery 30b in which a female screw groove 33 is formed. The screw shaft 28 includes an outer periphery 28a in which a male screw groove 34 is formed. A row of balls 29 is interposed between the female screw groove 33 and the male screw groove 34.

The outer periphery 30 a of the ball nut 30 includes a rotation restricting portion 36 that engages with the rotation restricting portion 35 of the inner periphery 17 b of the piston 17, and a cylindrical surface portion 38 that is fitted to the cylindrical surface portion 37 of the inner periphery 17 b of the piston 17. The relative rotation between the piston 17 and the ball nut 30 is restricted by the engagement between the rotation restricting portions 35 and 36.
The ball nut 30 includes a first end 301 on the disk 2 side and a second end 302 opposite to the first end 301 with respect to the ball nut axial direction X (axial direction AX).

  A first end surface 301 </ b> A of the first end 301 of the ball nut 30 is in contact with the opposing wall 17 c of the piston 17. The opposing wall 17c is provided in the positioning step portion 39 on the inner periphery 17b of the piston 17. A retaining ring 40 fitted in an annular groove provided on the inner periphery 17 b of the piston 17 is engaged with the end surface of the second end portion 302 of the ball nut 30. As a result, the piston 17 and the ball nut 30 are coupled so as to be able to move integrally in the axial direction AX (ball nut axial direction X).

When the rotation of the output shaft 24 of the electric motor 20 is transmitted via the speed reducer 21 and the screw shaft 28 rotates, the ball nut 30 moves in the ball nut axial direction X (axial direction AX). At this time, the piston 17 moves together with the ball nut 30 in the axial direction AX by the guidance of the key 19.
FIG. 4 is an enlarged view of a main part of the ball screw device 22 in which a part of FIG. 3 is enlarged.

  3 and 4, the plurality of balls 29 held in the female screw groove 33 of the ball nut 30 are aligned along the track path K formed between the female screw groove 33 and the male screw groove 34. Is configured. The ball row L includes a first end La and a second end Lb. The female thread groove 33 is threaded over the entire area of the inner periphery 30b of the ball nut 30 in the ball nut axial direction X, and the first end 33A of the female thread groove 33 is connected to the first end surface 301A. Yes. That is, the first end portion 33A of the female thread groove 33 is exposed to the first end surface 301A.

As described above, the piston 17 serving as a housing for housing the ball nut 30 includes the outer periphery 17a, the inner periphery 17b fitted to the outer periphery 30a of the ball nut 30, and the first end 301 of the ball nut 30. And an opposing wall 17c facing the end surface 301A. The facing wall 17 c includes a stopper region 60 that faces the first end 33 </ b> A of the female screw groove 33.
The ball screw device 22 includes a coil spring 70 disposed on the track K. The coil spring 70 has a first end 71 that engages with the ball 29a of the first end La of the ball row L and a second end directly received by the stopper region 60 of the opposing wall 17c of the piston 17. 72.

  As described above, according to the first embodiment, the second end 72 of the coil spring 70 accommodated in the female screw groove 33 is disposed on the piston 17 facing the first end 33 </ b> A of the female screw groove 33. It is received directly by the stopper area 60. Therefore, unlike the conventional case, the ball nut 30 is not provided with a recess for restricting the second end 72 of the coil spring 70. Therefore, the ball nut 30 can be reduced in size in the ball nut axial direction X (axial direction AX). Accordingly, it is possible to provide the ball screw device 22 in which the second end portion 72 of the coil spring 70 is well regulated and the size of the ball nut axial direction X (axial direction AX) is reduced.

  Further, since the second end 72 of the coil spring 70 is received by the opposing wall 17c facing the first end 33A of the female thread groove 33, the second end 72 of the coil spring 70 is more stably supported. Can be regulated. In particular, the opposing wall 17c in contact with the first end surface 301A is closer to the first end 33A of the female thread groove 33. Therefore, the second end portion 72 of the coil spring 70 can be regulated more stably.

FIG. 5 is a schematic cross-sectional view of a ball screw device 30A according to the second embodiment of the present invention. FIG. 6 is a cross-sectional view taken along section line VI-VI in FIG.
In the constituent elements of the second embodiment, the same constituent elements as those of the first embodiment are denoted by the same reference numerals as those in FIGS.
The ball screw device 30A according to the second embodiment of the present invention is different from the ball screw device 30 according to the first embodiment in that a concave portion 171 is formed in the stopper region 60A. As shown in FIGS. 5 and 6, the concave portion 171 extends in the tangential direction T of the female thread groove 33 and in the lead angle direction (lead angle direction Q) of the female thread groove 33. The recess 171 has a seat surface 172 that directly receives the second end 72 of the coil spring 70. The seating surface 172 has a surface that is perpendicular to both the tangential direction T of the female thread groove 33 and the lead angle direction (lead angle direction Q) of the female thread groove 33.

  According to 2nd Embodiment, there can exist an effect equivalent to the case of 1st Embodiment. Further, the second end 72 of the coil spring 70 is directly received by the seating surface 172 of the recess 171 formed in the stopper region 60A. Since the second end portion 72 of the coil spring 70 is received while being accommodated in the recess 171, the second end portion 72 of the coil spring 70 can thereby be more stably regulated.

Further, since the second end 72 of the coil spring 70 is regulated by the recess 171 so as to extend in the same direction as the coil spring 70 accommodated in the female thread groove 33, this favorably supports the coil spring 70. it can.
As mentioned above, although two embodiment of this invention was described, this invention can also be implemented with another form.

  For example, in each embodiment, the female screw groove 33 is not formed up to the first end surface 301A of the ball nut 30, and the first end portion 33A of the female screw groove 33 is more than the first end surface 301A of the ball nut 30. Alternatively, it may be located slightly closer to the second end 302 side. In this case, the inner periphery 30b between the first end portion 33A of the female thread groove 33 and the first end surface 301A is the inner periphery 30b so that the first end portion 33A is exposed to the first end surface 301A. You may provide in the large diameter part made into one step larger diameter than the other part.

In each embodiment, a coil spring (not shown) may be interposed in one or a plurality of locations in the intermediate portion of the ball row L.
In addition, the present invention can be variously modified within the scope of the claims.

DESCRIPTION OF SYMBOLS 17 ... Piston (housing), 17b ... Inner periphery, 17c ... Opposite wall, 22 ... Ball screw apparatus, 22A ... Ball screw apparatus, 28 ... Screw shaft, 28a ... Outer periphery, 29 ... Ball, 29a ... Ball, 30 ... Ball nut 30a ... inner circumference, 33 ... female screw groove, 34 ... male screw groove, 60 ... stopper region, 60A ... stopper region, 70 ... coil spring, 71 ... first end portion, 72 ... second end portion, 171 ... concave portion 172 ... Seating surface, 301A ... First end face, K ... Track, L ... Ball row, La ... First end, Q ... Lead angle direction, T ... Tangent direction, X ... Ball nut axial direction

Claims (3)

A ball nut including an inner periphery, an axial end surface, and an internal thread groove in which a screw is formed over the entire axial direction of the inner periphery;
A screw shaft including an outer periphery and a male screw groove having a screw formed on the outer periphery, and inserted through the ball nut;
A ball row including a plurality of balls housed in a track formed by the female screw groove and the male screw groove;
A cylinder including an inner periphery fitted to the outer periphery of the ball nut and an opposing wall facing the end face of the ball nut, the opposing wall including a stopper region facing the end of the female screw groove; Shaped housing,
A first end that engages with a ball at an end of the row of balls, and a second end that is directly received by the stopper region, and includes a coil spring housed in the track. Ball screw device. A concave portion is formed in the stopper region,
The ball screw device according to claim 1, wherein the recess has a seating surface that directly receives the second end of the coil spring.   The ball screw device according to claim 2, wherein the recess extends in a tangential direction of the female screw groove and in a lead angle direction of the female screw groove.

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