JP2006189071A - Ball screw actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw actuator of wide-useful structure with a small number of parts items and capable of preventing rotation of a screw shaft thereof at low costs. <P>SOLUTION: The screw shaft 4a screwed to a rotating nut 4b through a ball 4c is provided with an eccentric hole 7 displaced from the shaft center, and a rotation stopper pin 8 fixed to a rear cover 1b of a housing 1 is inserted into the eccentric hole 7 with a little clearance. With this widely useful structure, rotation of the screw shaft 4a of the ball screw actuator can be stopped at low costs with a small number of parts items. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a ball screw actuator that rotates a nut of a ball screw mechanism to linearly move a screw shaft.

  A ball screw actuator that rotates a nut of a ball screw mechanism and linearly moves a screw shaft is an electric brake device that rotates a nut by an electric motor and presses a brake member against a member to be braked by a linear motion of the screw shaft It is used for. This type of ball screw actuator requires a screw shaft detent mechanism to prevent the screw shaft from rotating together with the nut.

  Since it is difficult to directly prevent the screw shaft that moves linearly on the inner diameter side of such a nut, conventionally, the screw shaft is indirectly prevented by rotating the connecting member connected to the screw shaft. is doing. For example, for a ball screw actuator used in an electric brake device, a pair of detent shafts are provided on a push member that is integrally connected and fixed to a screw shaft and presses a friction pad, and these detent shafts are connected to a ball screw. A screw shaft detent mechanism that is slidably inserted into a bearing hole provided in the rotary cylinder at a position outside the nut is proposed (for example, see Patent Document 1).

JP 2002-323075 A

  In the ball screw actuator's screw shaft detent mechanism described in Patent Document 1, a pair of detent shafts are provided in a separate pushing member connected and fixed to the screw shaft, and these detent shafts are connected to the ball screw actuator. Since it is slidably inserted into a bearing hole provided in a rotary cylinder portion as a housing at a position outside the nut, the non-rotating shaft provided on the pushing member and the housing depending on the form of the separate pushing member It is necessary to change the design of the bearing hole provided in the case, and there is a problem that lacks versatility.

  Further, since two pairs of detent shafts and two bearing holes into which these are slidably inserted are required, the number of parts and machining parts are increased, and machining of the two bearing holes is performed. Has a problem that the manufacturing cost becomes high. Furthermore, since the non-rotating shaft and the bearing hole slide relative to each other, it is necessary to take a separate wear prevention measure in order to prevent wear due to the sliding.

  Therefore, an object of the present invention is to prevent the screw shaft of the ball screw actuator from rotating at a low cost with a small number of parts, with a versatile configuration.

  In order to solve the above-described problems, the present invention provides a ball screw actuator that rotates a nut of a ball screw mechanism in which a plurality of balls are interposed between screw threads of a screw shaft and a nut, thereby causing the screw shaft to linearly move. The screw shaft is provided with an eccentric hole eccentric from the shaft center, and a detent pin fixed to the fixed portion is inserted into the eccentric hole with a slight gap between the eccentric hole and the screw shaft is inserted. A non-rotating configuration was adopted.

  In other words, an eccentric hole that is eccentric from the shaft center is provided in the screw shaft, and a non-rotating pin that is fixed to the fixed portion of the housing or the like is inserted into the eccentric hole with a slight clearance between the eccentric hole and the general purpose. The screw shaft of the ball screw actuator can be prevented from rotating at a low cost with a small number of parts. The eccentric hole only needs to have a fixing pin inserted from either one, and may be a through hole or a dead end.

  The screw shaft is carburized and hardened, and the surface of the screw groove and the surface of the eccentric hole are simultaneously hardened and hardened. Wear can be prevented. That is, since the surface of the screw groove of the screw shaft of the ball screw actuator is originally hardened and hardened to prevent wear due to contact with the rolling ball, carburizing and quenching for this surface hardening is used. The surface of the eccentric hole of the screw shaft is also hardened and hardened, so that a separate wear prevention measure can be eliminated.

  The surface hardness of the eccentric hole is preferably HRC50 or more.

  The ball screw actuator of the present invention is provided with an eccentric hole eccentric from the shaft center on the screw shaft, and a slight clearance is provided between the eccentric pin and the detent pin fixed to the fixing portion of the housing or the like. Since it is inserted, it is possible to prevent the screw shaft of the ball screw actuator from rotating with a versatile configuration and with a small number of parts.

  By carburizing and quenching the screw shaft, the surface of the screw groove and the surface of the eccentric hole are quenched and hardened at the same time, so that wear of the eccentric hole due to sliding with the fixed pin can be avoided without taking additional measures to prevent wear. Can be prevented.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this ball screw actuator includes an electric motor 2, a planetary gear reduction mechanism 3, and a ball screw mechanism 4 incorporated in a housing 1, and the rotation of the rotor 2 b of the electric motor 2 is caused by a planetary gear reduction mechanism. 3 is transmitted to the nut 4b of the ball screw mechanism 4 and the rotation of the nut 4b is converted into a linear motion of the screw shaft 4a. The housing 1 includes a cylindrical main body 1a, a front lid 1b having an opening from which a tip of the screw shaft 4a protrudes, and a rear lid 1c to which a detent pin described later is attached.

  The stator 2a of the electric motor 2 is fixed to the inner diameter surface of the main body 1a of the housing 1, and the sun gear 3a of the planetary gear reduction mechanism 3 is provided on the outer diameter surface of the forward extension of the rotor 2b. A planetary gear 3c is meshed between internal gears 3b fixed to the inner diameter surface. The planetary gear 3c is rotatably supported on the shaft 5 using the nut 4b of the ball screw mechanism 4 as a carrier.

  A nut 4b of a ball screw mechanism 4 that rotates as a carrier of the planetary gear 3c is supported by a ball bearing 6 on the inner surface of the main body 1a, and a screw shaft 4a is screwed to the nut 4b via a ball 4c.

  As shown in FIG. 2, the screw shaft 4 a of the ball screw mechanism 4 is provided with an eccentric hole 7 eccentric from the axis O on the rear end side, and a detent pin fixed to the rear lid 1 c in the eccentric hole 7. 8 is inserted with a slight gap. Accordingly, the screw shaft 4a is prevented from rotating by the rotation prevention pin 8, and linearly moves while sliding with the rotation prevention pin 8 by the rotation of the nut 4b. The screw shaft 4a is carburized and hardened, and the eccentric hole 7 is also hardened and hardened together with the screw groove on which the ball 4c rolls, and the surface hardness thereof is HRC50 or more.

  In the embodiment described above, the eccentric hole of the screw shaft is a dead end, but it may be penetrated back and forth. In addition, the rotation of the electric motor is transmitted to the nut of the ball screw mechanism through the planetary gear speed reduction mechanism, but is transmitted to the nut directly through another speed reduction mechanism or without the speed reduction mechanism. It may be.

Vertical sectional view showing an embodiment of a ball screw actuator Sectional view along the line II-II in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 1a Main body 1b Front lid 1c Rear lid 2 Electric motor 3 Planetary gear reduction mechanism 3a Sun gear 3b Internal gear 3c Planetary gear 4 Ball screw mechanism 4a Screw shaft 4b Nut 4c Ball 5 Shaft 6 Ball bearing 7 Eccentric hole 8 Non-rotating pin

Claims (3)

  A ball screw actuator in which a nut of a ball screw mechanism in which a plurality of balls are interposed between a screw shaft and a screw groove of the nut is rotated to linearly move the screw shaft. A ball screw actuator characterized by comprising a hole, and inserting a detent pin fixed to the fixed part in the eccentric hole with a slight gap between the eccentric hole and detenting the screw shaft.   The ball screw actuator according to claim 1, wherein the screw shaft is carburized and hardened, and the surface of the screw groove and the surface of the eccentric hole of the screw shaft are quenched and hardened simultaneously.   The ball screw actuator according to claim 2, wherein the surface hardness of the eccentric hole is HRC50 or more.

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