JP2011196532A - Ball screw device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ball screw device capable of reducing the moment of inertia of a rotary part, by reducing a diameter in the ball screw device.SOLUTION: A ball screw nut 3 is of an end cap system composed of a nut body 11 and a pair of end caps 12 and 13 arranged on both ends thereof. A plurality of engaging claws 15 arranged at a predetermined interval in the peripheral direction are formed in the upper end part of the nut body 11. A plurality of fitting recessed places 16 are formed in an outer peripheral part of the upper end cap 12. The respective engaging claws 15 are respectively fitted in the respective fitting recessed places 16, and its tip part is projected from the upper end cap 12.

Description

  The present invention relates to a ball screw device, and more particularly to a ball screw device used in a form in which a screw shaft moves linearly.

  When the ball screw device is used in an actuator, an electromagnetic shock absorber, or the like, the ball screw nut may rotate and the screw shaft may move linearly.

  As such a ball screw device, Patent Document 1 discloses that a ball screw nut through which a screw shaft is passed is connected to a rotating cylinder disposed around the screw shaft so as not to rotate with each other, and via a bearing. The ball screw nut is rotatably supported by the housing, one end of the ball screw nut is spline-fitted to the one end of the rotating cylinder, and a motor stator for applying a damping force is provided in the housing. What forms the rotor of a motor is disclosed.

JP 2009-168093 A

  In the electromagnetic shock absorber of a vehicle, it is preferable to reduce the diameter of the rotating member including the ball screw nut in order to reduce the moment of inertia of the rotating portion of the ball screw nut. As the ball screw nut, an end cap type is common, and in Patent Document 1, it is necessary to arrange a member (rotating cylinder) that transmits torque to the motor at a position larger than the end cap outer diameter. It is difficult to reduce the moment of inertia any further.

  An object of the present invention is to provide a ball screw device in which the diameter of the ball screw device can be reduced and thereby the moment of inertia of a rotating part can be reduced.

  In the ball screw device according to the present invention, a ball screw nut through which a screw shaft is passed is connected to a rotating cylinder disposed around the screw shaft so as not to rotate with each other. It is an end cap type consisting of a main body and a pair of end caps provided at both ends, and a plurality of engaging claws arranged at predetermined intervals in the circumferential direction are formed at one end of the nut main body, A plurality of fitting recesses are formed on the outer peripheral portion of the end cap on one end side, and the respective engaging claws are fitted into the respective fitting recesses so that the tip ends protrude from the end cap. It is characterized by being.

  In the ball screw device, the ball screw nut is connected so as to be integrally rotatable with a rotating cylinder (for example, a rotor forming member of a motor), and an engaging claw is circumferentially connected to the ball screw nut for the connection. Are provided at predetermined intervals. The engaging claws are fitted into engaging recesses provided in the rotating cylinder, whereby the nut and the rotating cylinder are connected, and a connecting nut for connecting them becomes unnecessary.

  The ball screw nut is composed of a nut body and a pair of end caps respectively attached to both ends thereof by a plurality of bolts (end cap type). The engaging claw is provided at one end of the nut body.

  In the end cap type ball screw device, a ball passage formed on the screw shaft and a ball screw race provided on the nut body form a main passage where the ball rolls, and penetrates the peripheral wall of the nut body. A return path is formed, and the end cap is provided with a direction change path that connects the main path and the return path. The ball is disposed in the main passage, the direction changing passage, and the return passage, and the ball rolling on the main passage guides the relative rotation of the screw shaft and the ball screw nut, and the screw shaft and the ball screw nut rotate relative to each other. As a result, the screw shaft and the ball screw nut relatively move in the axial direction.

  When an engaging claw is provided in an end cap type ball screw nut, the engaging claw is provided in the nut body, and the engaging claw inner diameter≈the end cap outer diameter, and the engaging claw outer diameter≈ The outer diameter of the end cap + the thickness of the engaging claw × 2. In order to reduce the moment of inertia, it is preferable to reduce the outer diameter of the rotating member composed of the ball screw nut and the rotating cylinder connected to the nut, and for this purpose, it is effective to reduce the outer diameter of the engaging claw. Become. Therefore, in the ball screw device according to the present invention, a plurality of fitting recesses into which the respective engaging claws are respectively fitted are formed on the outer peripheral portion of the end cap. The outer diameter can be made smaller than the outer diameter, and the circumscribed diameter of the engaging claw can be reduced without reducing the thickness of the engaging claw.

  The rotating member including the ball screw nut and the rotating cylindrical body connected to the ball screw nut is preferably rotatably supported by the housing via the bearing, and the bearing for this is a single row ball bearing or a double row ball. In this case, it is preferable that a raceway of the ball bearing is formed on the outer peripheral surface of the nut body of the ball screw nut, and the inner ring of the ball bearing is integrated with the nut body. If it does in this way, the inner ring of a ball bearing will become unnecessary and the nut for inner ring fixation for fixing this will become unnecessary.

  In the ball screw device of the present invention, the end cap on the one end side has a plurality of recesses for fitting at predetermined intervals in the circumferential direction, so that a convex portion exists between adjacent recesses, The direction change path provided in the end cap on the part side is provided so that its end is located on one of these convex parts, and a screw for cap coupling with the nut body on some of the remaining convex parts It is preferable that a through hole is formed. For example, when two ball screw raceways are provided, six fitting recesses and six convex portions are formed at equal intervals in the circumferential direction, and two convex portions separated by 180 ° are used. And the edge part of a direction change path is arrange | positioned here, and a nut main body and an end cap are fixed using four remaining convex parts.

  The ball screw device according to the present invention may be used as an actuator (a configuration in which a ball screw nut is rotated by a motor, whereby the screw shaft moves linearly), and a shock absorber (the screw shaft is driven by an external force). In some cases, the ball screw nut is rotated linearly, whereby the electromagnetic force generated by the motor becomes a damping force.

  The screw shaft and ball screw nut are made of carbon steel such as S45C and S55C or SAE4150 steel, and the ball is made of bearing steel (SUJ2), for example. The ball screw nut may be made of bearing steel (SUJ2).

  According to the ball screw device of the present invention, the ball screw nut is an end cap type consisting of a nut main body and a pair of end caps provided at both ends thereof, and at one end of the nut main body at a predetermined interval in the circumferential direction. A plurality of engaging claws are formed at the outer peripheral portion of the end cap on one end side, and each of the engaging claws is formed in each fitting recess. Since the front end of the engaging claw is protruded from the end cap, the inscribed diameter of the engaging claw can be made smaller than the outer diameter of the end cap. Can be reduced. Therefore, it is possible to reduce the diameter of the ball screw device, thereby reducing the moment of inertia of the rotating portion.

FIG. 1 is a longitudinal sectional view showing an embodiment of a ball screw device according to the present invention. 2A and 2B are views showing a ball screw nut which is a main part of the ball screw device according to the present invention. FIG. 2A is an enlarged longitudinal sectional view and FIG. 2B is a plan view thereof. FIG. 3 is a view of the end cap of the ball screw device according to the present invention as viewed from the inside in the axial direction. FIG. 4 is a view showing a ball screw nut as a comparative example of the ball screw device according to the present invention and corresponds to FIG. 2, FIG. 4 (a) is an enlarged vertical sectional view, and FIG. 4 (b) is FIG.

  Embodiments of the present invention will be described below with reference to the drawings. In the following description, the top and bottom refer to the top and bottom of FIG.

  As shown in FIG. 1 to FIG. 3, the ball screw device (1) according to the present invention is a vertical screw provided with two ball screw raceways (2a) and six ball spline raceways (2b) extending in the vertical direction. A steel screw shaft (2) that extends, a rotatable steel ball screw nut (3) screwed onto the ball screw raceway (2a) of the screw shaft (2) via a ball (4), and a screw shaft ( 2) a steel ball spline outer cylinder (5) fitted on the spline raceway (2b) via the ball (6) on the lower end side of 2) to guide the vertical (axial) linear motion of the screw shaft (2); And a steel rolling bearing (7) that rotatably supports the ball screw nut (3).

  In this ball screw device (1), for example, the ball spline outer cylinder (5) and the outer ring (17) of the rolling bearing (7) are supported in a non-rotatable manner by a housing (not shown), and the ball screw nut (3) is The screw shaft (2) is used in a form that is rotated by a motor (not shown) and the screw shaft (2) is linearly moved accordingly. In this case, the ball screw nut (3) through which the screw shaft (2) is passed is rotated integrally with a cylindrical motor rotor (rotating cylinder) (8) disposed around the screw shaft (2). Connected. The ball screw nut (3) is provided with a plurality (six in the figure) of engaging claws (15) arranged at predetermined intervals in the circumferential direction for connection with the motor rotor (8). The engaging claws (15) are fitted into engaging recesses provided in the motor rotor (8), whereby torque from the motor is transmitted to the ball screw nut (3).

  The ball screw nut (3) is of an end cap type, and is a pair of upper and lower end caps respectively attached to the nut body (11) and a plurality of cap coupling bolts (14 in the figure) at both ends (14 in the figure). (12) Consists of (13).

  The rolling bearing (7) includes an outer ring (17) formed with an outer ring raceway groove (17a), an inner ring raceway groove (18) formed on the outer peripheral surface of the nut body (11), and a corresponding raceway groove (17a). It consists of a plurality of balls (19) interposed between (18). That is, the inner ring of the rolling bearing (7) is integrated with the nut body (11), so that the inner ring is unnecessary and the nut for fixing the inner ring is also unnecessary.

  The nut body (11) is provided with two ball screw raceways (female thread grooves) (11a) corresponding to the two ball screw raceways (male thread grooves) (2a) of the screw shaft (2). These ball screw raceways (2a) and (11a) are opposed to the main passage (ball passage) (21) in which the ball (4) rolls.

  The engaging claw (15) for connection with the motor rotor (8) is provided integrally with the upper end surface of the nut main body (11) so as to protrude above the upper end cap (12). A plurality of fitting recesses (16) into which the respective engaging claws (15) are fitted are formed on the outer peripheral portion of the upper end cap (12).

  As shown in FIG. 2 (b), the plurality of engaging claws (15) are formed to have an inscribed circle (IC) and a circumscribed circle (OC) common to all the engaging claws (15). The outer peripheral surface and the inner peripheral surface of each engaging claw (15) have a circular arc shape that forms a part of the circle (IC) (OC). The bottom surface of each fitting recess (16) is formed in a circular arc shape in contact with the inner peripheral surface of each engaging claw (15). Thereby, the diameter of the circumscribed circle (OC) of the engaging claw (15) is smaller than the outer diameter of the nut body (11).

  As shown in FIG. 3, the upper end cap (12) is provided with two groove-shaped direction change paths (22) for guiding the ball (4) rolled in the main path (21) radially outward. The nut main body (11) is provided with a return passage (23) communicating with the radially outer end of each direction changing passage (22) at a position indicated by a broken line in the drawing. . Although not shown, the lower end cap (13) has the same shape as the conventional end cap, and the lower end cap (13) is also provided with a direction change path (22) having the same shape as the upper end cap (12). It has been. Although the return passage (23) is not shown in FIGS. 1 and 2, the nut main body (11) is axially moved at the same position in the radial direction parallel to the screw hole into which the cap coupling bolt (14) is screwed. The hole has a circular cross section that penetrates the entire length.

  The ball (4) is disposed in the main passage (21), the direction changing passage (22) and the return passage (23), and the ball (4) rolling in the main passage (21) is connected to the screw shaft (2). It guides the relative rotation of the ball screw nut (3). When the screw shaft (2) and the ball screw nut (3) rotate relative to each other, the screw shaft (2) and the ball screw nut (3) relatively move in the axial direction. At this time, the ball (4) rolling on the main passage (21) is changed in direction by the direction change path (22) of one end cap (12) (13) and returned to the return path (23 of the nut body (11)). ), The ball (4) moved in the return passage (23) to the other end cap (13) (12) side and moved through the return passage (23) is moved to the other end cap (13) ( The direction is changed by the direction change path (22) of 12) and introduced into the main passage (21).

  A plurality of (specifically six) fitting recesses (16) are formed at predetermined intervals (specifically at intervals of 60 °) in the circumferential direction, so that they are adjacent to the upper end cap (12). There are six convex portions (24) and (25) between the concave portions (16). As shown in FIG. 3, the two direction change paths (22) provided in the upper end cap (12) are such that the radially outer ends thereof are 180 ° of these convex portions (24) and (25). The cap is connected to the nut body (11) on the two remaining convex parts, that is, the convex part for changing direction (24), and the remaining four convex parts, ie, the bolt arranging convex part (25). An insertion hole (26) for the bolt (14) is formed.

  FIG. 4 shows an end cap type ball screw nut (30) for comparison.

  The ball screw nut (30) includes a nut body (31) and a pair of upper and lower end caps (32) and (33) attached to both ends by a plurality of cap coupling bolts (34). A plurality of engaging claws (35) are provided on 31). The engaging claw (35) is provided so as to be integral with the upper end surface of the nut body (31) and protrude upward from the upper end cap (32). The plurality of engaging claws (35) are formed to have an inscribed circle (ID) and a circumscribed circle (OD) common to all the engaging claws (35). The outer peripheral surface and the inner peripheral surface have a circular arc shape that forms a part of the circle (ID) (OD). In order to avoid interference between the engaging claws (35) and the upper end cap (32), the inner peripheral surface of each engaging pawl (35) is slightly spaced from the outer peripheral surface of the upper end cap (32). It is formed in an opposing cross-section arc shape, and the diameter of the inscribed circle (ID) of the engaging claw (35) is substantially equal (slightly larger) than the outer diameter of the end cap (32), and the engaging claw (35 The circumscribed circle (OD) of) is equal to the outer diameter of the nut body (31).

  As can be seen from a comparison between FIG. 2 and FIG. 4, in the ball screw device (1) according to the present invention, a plurality of fittings in which the respective engaging claws (15) are fitted into the outer peripheral portion of the upper end cap (12). By forming the joint recess (16), the inscribed diameter (IC) of the engaging claw (15) can be made smaller than the outer diameter of the upper end cap (12), and the engaging claw (15 ), The circumscribed diameter (OC) of the engaging claw (15) can be reduced. Thereby, the circumscribed diameter (OC) of the engaging claw (15) is smaller than the circumscribed diameter (OD) of the engaging claw (35) shown in FIG. That is, according to the ball screw device (1) of the present invention, it is possible to reduce the diameter of the rotating member including the ball screw nut (3) and the motor rotor (8) connected to the ball screw nut, thereby reducing the moment of inertia of the rotating part. Reduction is possible.

  In the upper end cap (32) shown in FIG. 4, it is easy to arrange the four cap coupling bolts (34) at equal intervals of 90 °, but the upper end cap shown in FIG. 2 and FIG. In the cap (12), the four cap coupling bolts (14) are not completely spaced apart, but at intervals of 120 ° -60 ° -120 ° -60 °.

  The ball screw device (1) of the present invention is used, for example, for an electromagnetic shock absorber of an automobile. In such an electromagnetic shock absorber, the screw shaft (2) is guided to the ball spline outer cylinder (5) by an external force transmitted from a tire. As a result, the ball screw nut (3) and the motor rotor (8) rotate along with this, and the rotational motion is taken into the motor, and the electromagnetic force generated by the motor is used as the damping force. The

  The ball screw device (1) is not limited to an electromagnetic shock absorber, and can also be used as an electric actuator. In this case, the rotational driving force of the motor is converted into the axial thrust of the screw shaft (2) through the ball screw nut (3), and the axial reaction force of the thrust is supported by the rolling bearing (7) and screw shaft ( 2) is moved linearly, the axial load acting on the screw shaft (2) is applied by the ball screw nut (3), and the torque is supported by the ball spline outer cylinder (5).

(1) Ball screw device
(2) Screw shaft
(3) Ball screw nut
(8) Motor rotor (rotating cylinder)
(11) Nut body
(12) Upper end cap
(13) Lower end cap
(14) Cap coupling bolt (cap coupling screw)
(15) Claw for engagement
(16) Recess for fitting
(22) Direction change path
(24) Convex part for direction change path placement
(25) Convex part for bolt placement
(26) Insertion hole

Claims (2)

In a ball screw device in which a ball screw nut through which a screw shaft is passed is coupled so as not to rotate with respect to a rotating cylinder disposed around the screw shaft.
The ball screw nut is an end cap type consisting of a nut main body and a pair of end caps provided at both ends thereof, and a plurality of engaging claws arranged at predetermined intervals in the circumferential direction at one end of the nut main body. Are formed, and a plurality of fitting recesses are formed on the outer peripheral portion of the end cap on one end side, and each of the engaging claws is fitted into each of the fitting recesses, A ball screw device which is projected from the end cap.   In the end cap on one end side, a plurality of recesses for fitting are formed at predetermined intervals in the circumferential direction, so that a convex portion exists between adjacent recesses and is provided on the end cap on one end side. The direction change path is provided so that the end thereof is located at any one of these convex portions, and insertion holes for cap coupling screws with the nut body are formed in some of the remaining convex portions. The ball screw device according to claim 1.

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