JP2016044685A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device having a cheap price while regulating the position of a coil spring satisfactorily.SOLUTION: A ball screw device comprises: a ball nut having a female screw groove; 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; a coil spring 70 accommodated in a raceway track K formed by a ball train, a female screw groove and a male screw groove 34; and a stopper ball 90 accommodated in the raceway track on the side opposed to the ball train with respect to the coil spring 70. The opposed wall 17c is disposed at a position capable of abutting against the stopper ball 90.EFFECT: A second end part 72 of the coil spring 70 is received by the stopper ball 90 which is clamped and positioned by the opposed wall 17c, a female screw groove and/or a male screw groove 34.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a ball screw device.

In a ball screw device in which a ball train is interposed between a male screw groove on the outer periphery of a screw shaft and a female screw groove on the inner periphery of a ball nut, a coil is interposed between a ball at the end of the ball train and a stopper pin fixed to the ball nut. It has been proposed to interpose a spring (see, for example, 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 in a state where a high axial force is applied, the coil spring contracts, so that the ball screw strokes while rolling with respect 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 stopper pin fixed to the fixing hole of the ball nut is used to restrict the position of the coil spring, the number of parts is large. In addition, a process for press-fitting the stopper pin into the fixing hole of the ball nut is required, which increases the assembly cost.
Accordingly, an object of the present invention is to provide an inexpensive ball screw device while favorably regulating the position of a coil spring.

  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 main balls (29) accommodated in a raceway (K) formed by the female screw groove and the male screw groove, and the outer periphery of the ball nut A cylindrical housing (17) including an inner periphery (17b) and an opposing wall (17c) facing the end face of the ball nut, and a main ball (29a) at an end (La) of the ball row The first end (71) and the second end (72) And a coil spring (70) accommodated in the track, and a stopper ball (90) accommodated on the opposite side of the ball row with respect to the coil spring in the track, the facing wall comprising: Provided is a ball screw device (22) provided at a position capable of contacting the stopper ball.

  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 configuration of the first aspect, the coil spring and the stopper ball are accommodated in this order when viewed from the ball row, and the opposing wall is provided at a position where the opposing wall can contact the stopper ball. ing. When the wall surface of the opposing wall is not along the lead angle of the female screw groove and the male screw groove, the stopper ball is sandwiched between the opposing wall of the housing and the female screw groove and / or the male screw groove, whereby the ball row side Movement of the stopper ball in the direction toward the opposite side is restricted. The second end of the coil spring is received by the positioned stopper ball. Therefore, the conventionally used stopper pin can be eliminated, and the manufacturing cost can be reduced through the reduction of the number of parts and the number of assembly steps. Thus, an inexpensive ball screw device is provided while favorably regulating the position of the coil spring.

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 the schematic which shows the relationship between the 2nd edge part of a coil spring, and a stopper ball | bowl. It is a figure explaining the state in which the stopper ball is clamped by the opposing wall and the internal thread groove and / or the external thread groove. It is sectional drawing explaining the state in which the stopper ball is clamped by the opposing wall and the internal thread groove and / or the external thread groove. It is sectional drawing seen from the cut surface line VII-VII of FIG.

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 includes a first end portion 151 and a second end portion 152 that face each other in the axial direction AX. 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 end portion 152 of the head. 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 is fixed to the first backup plate 4.

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 an O-ring housed in a housing groove provided on the inner circumference of the cylinder 13 (the inner circumference 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.

Hydraulic pressure that urges the piston 17 toward the disk 2 may be supplied into the cylinder 13 from a hydraulic path (not shown). In that case, the cylinder 13 and the piston 17 constitute a hydraulic actuator.
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 main 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 main ball 29 in a row 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.
The plurality of main balls 29 held in the female screw groove 33 of the ball nut 30 constitute a ball row L arranged along the track path K formed between the female screw groove 33 and the male screw groove 34. The ball row L includes a first end La and a second end Lb. The female thread groove 33 is formed over the entire area of the inner periphery 30b of the ball nut 30 in the ball nut axial direction X. That is, the first end portion 33A of the female thread groove 33 is formed up to the first end face 301A. ing.

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 ball screw device 22 includes a coil spring 70 disposed on the track K. The coil spring 70 includes a first end 71 that engages with the main ball 29 a of the first end La of the ball row L, and a second end 72. The ball screw device 22 includes a stopper ball 90 accommodated on the opposite side of the ball row L with respect to the coil spring 70 in the track path K. That is, the coil spring 70 and the stopper ball 90 are accommodated in the track path K in this order as viewed from the ball row L.

FIG. 4 is a schematic view showing the relationship between the second end 72 of the coil spring 70 and the stopper ball 90.
The ball screw device 22 includes a stopper ball 90 interposed between the second end portion 72 of the coil spring 70 and the opposing wall 17c of the piston 17. The diameter D of the stopper ball 90 is made larger than the inner diameter E of the end turn portion 721 as the second end portion 72 of the coil spring 72 (D> E).

5 and 6 are diagrams illustrating a state in which the stopper ball 90 is sandwiched between the opposing wall 17c and the female screw groove 33 and / or the male screw groove 34. FIG. In FIG. 5, the ball nut 30 is not shown for easy viewing of the main part.
As shown in FIG. 6, the edge cut part 17d is provided in the inner peripheral end of the opposing wall 17c. The edge cut portion 17d is provided so as to be able to contact the stopper ball 90 in the track K.

  Consider a case where the ball stopper 90 approaches the opposing wall 17c and eventually comes into contact with the opposing wall 17c as the screw shaft 28 is driven to rotate. In this case, the opposing wall 17c has a flat surface perpendicular to the axis, and the male screw groove 34 and the female screw groove 33 extend along the lead angle Q (see FIG. 5), so that they are accommodated in the track path K. The stopper ball 90 is sandwiched between the edge cut portion 17d of the opposing wall 17c of the piston 17 and the female screw groove 33 and / or the male screw groove 34, whereby the female screw groove 33 directed to the opposite side to the ball row L side. Movement of the stopper ball 90 in the lead angle direction Q1 (see FIG. 5) is restricted. That is, the stopper ball 90 is positioned.

FIG. 7 is a cross-sectional view taken along section line VII-VII in FIG.
As shown in FIGS. 3 and 7, the ball screw device 22 regulates the displacement of the main ball 29b by projecting into the track K and engaging with the main ball 29b of the second end Lb of the ball row. A convex portion 80 is provided as a stopper.
As shown in FIG. 7, the convex portion 80 is a portion of the stopper pin 800 that is press-fitted into the fixing hole 81 that penetrates the ball nut 30, and is configured by a portion that protrudes into the female screw groove 33. The fixing hole 81 extends in the tangential direction T of the female screw groove 33.

As described above, according to this embodiment, the coil spring 70 and the stopper ball 90 are accommodated in the track path K in this order as viewed from the ball row L, and the stopper ball 90 is accommodated in the opposing wall 17c. It is provided so that it can contact.
Since the wall surface of the opposing wall 17c has a flat surface perpendicular to the axis and does not follow the lead angle Q of the female screw groove 33 and the male screw groove 34, the stopper ball 90 has the opposing wall 17c of the piston 17 and the female screw groove 33. And / or the male screw groove 34, thereby restricting the movement of the stopper ball 90 in the lead angle direction Q <b> 1 (see FIG. 5) of the female screw groove 33 toward the opposite side to the ball row L side. Is positioned. As a result, the second end 72 of the coil spring 70 is received by the positioned stopper ball 90. Therefore, the conventionally used stopper pin can be eliminated, and the manufacturing cost can be reduced through the reduction of the number of parts and the number of assembly schools. Thereby, an inexpensive ball screw device 22 can be provided while the position of the coil spring 70 is well regulated.

Further, since the stopper ball 90 is interposed between the opposing wall 17c and the second end portion 72 of the coil spring 70, the second rotation of the coil spring 70 is performed when the screw shaft 28 is driven to rotate (during power transmission). It is possible to stabilize the posture of the end portion 72 and to suppress the distortion of the shape of the coil spring 70. As a result, the posture of the coil spring 70 can be stabilized.
As mentioned above, although one Embodiment of this invention was described, this invention can also be implemented with another form.

For example, although not shown, two or more stopper balls 90 may be accommodated in the track path K on the side opposite to the ball row L with respect to the coil spring 70.
Moreover, in each said embodiment, you may interpose a coil spring (not shown) in the intermediate part of the ball row | line | column L in one or several places.
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, 28 ... Screw shaft, 28a ... Outer periphery, 29 ... Main ball, 29a ... Main ball, 30 ... Ball nut, 30a ... Inside Numeral 33, female thread groove, 34 male thread groove, 70 coil spring, 71 first end, 72 second end, 90 stopper ball, 301A first end face, K raceway, L ... Ball train, La ... First end, X ... Ball nut axial direction

Claims (1)

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 row of balls including a plurality of main balls housed in a track formed by the female screw groove and the male screw groove;
A cylindrical housing including an inner periphery fitted to the outer periphery of the ball nut, and an opposing wall facing the end surface of the ball nut;
A coil spring that has a first end that engages with a main ball at an end of the ball row, and a second end;
In the track, including a stopper ball accommodated on the opposite side of the ball row with respect to the coil spring,
A ball screw device, wherein the opposing wall is provided at a position capable of contacting the stopper ball.

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