JP2013169023A - Electrically-driven linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrically-driven linear actuator capable of preventing or suppressing a ball screw nut or mechanical end from being broken even when the ball screw nut runs away while being fitted to a driven component.SOLUTION: An electrically-driven linear actuator includes a ball screw rod 2 having a male screw 21 formed on an outer peripheral surface, a ball screw nut 3 having a female screw 31 capable of threadably engaging the male screw 21 on an inner peripheral surface, and rotation restriction means of restricting the ball screw nut 3 from rotating, and a part of the ball screw rod 2 as a part which is between a limit position of a control stroke range and a mechanical end 6 set more outside the control stroke range than the limit position, and corresponds to the size of the ball screw nut 3 in an axial direction A is set to be a male screw non-formation area 22.

Description

  The present invention can be used in a state of being incorporated in various mechanical devices such as an electric bed, an electric table, an electric chair, and a lifter, or can be applied for driving wings such as airplanes and missiles, or for driving rocket nozzles. The present invention relates to a simple electric linear actuator.

  Conventionally, an electric linear actuator including a ball screw rod and a ball screw nut capable of reciprocating in the axial direction of the ball screw rod while being engaged with the ball screw rod is known.

  In such an electric linear actuator, when the ball screw rod is rotated by an electric motor or the like and the rotational force is transmitted to the ball screw nut, the ball screw nut whose rotation is restricted by an appropriate means is the same as the ball screw rod. It is possible to reciprocate in the linear direction while maintaining the engaged state.

  In addition, for example, during development of an electric linear actuator, the ball screw nut may run away due to a malfunction or erroneous operation of the control device. In this case, if disc springs are installed at both ends of the sleeve, the runaway ball screw nut collides with the disc spring, and the ball energy at the position where the kinetic energy of the ball screw nut and the potential energy due to the disc spring contracting are balanced. The screw nut stops.

  However, there is a limit to the kinetic energy that can be absorbed by the disc spring. Therefore, as shown in FIG. 3, the present applicant forms a ball screw nut by rotating the ball screw rod 102 when the control of the electric linear actuator 1010 becomes impossible due to a failure of an external device or the like. When the ball screw nut 103 whose rotation is constrained by the non-rotating key 105 that interferes with the key groove moves in the direction a in FIG. Based on the structure in which the ball screw nut 103 is removed from the rotation stop key 105 by releasing the interference state of the rotation stop key, a technology for releasing the rotation restraint of the ball screw nut 103 is proposed. FIG. 3 shows a mode in which the rotation prevention key 105 is attached to the sleeve 104.

  With such a technique, the ball screw nut 103 is rotated (rotated) in synchronization with the rotation of the ball screw rod 102 by releasing the rotation restraint of the ball screw nut 103. Inertia and inertia such as the electric motor M connected to the ball screw rod 103 via the reduction gear G or the like are not converted into linear equivalent mass. Further, by reducing the linear equivalent mass, the kinetic energy when colliding with the mechanical end 106 can be reduced, and damage to the ball screw nut 103 and the mechanical end 106 can be prevented / suppressed.

Japanese Patent No. 3644223

  However, when the ball screw nut 103 of the electric linear actuator 101 shown in FIG. 3 is coupled to the driven component, the rotation restraint of the ball screw nut 103 by the detent key 105 is released when the ball screw nut 103 runs away. Even so, the coupling portion with the driven component serves to regulate the rotation of the ball screw nut 103, and the rotation of the ball screw nut 103 remains constrained.

  As a result, in the structure described in Patent Document 1, the above-described function cannot be exhibited unless the electric linear actuator is a single unit, and the above-described function cannot be exhibited when the electric linear actuator is attached to the driven component.

  The present invention has been made paying attention to such problems, and its main purpose is to prevent damage to the ball screw nut and the mechanical end even when the ball screw nut goes out of control while attached to the driven component. An object of the present invention is to provide an electric linear actuator that can be prevented and suppressed.

  That is, the present invention includes a ball screw rod having a male screw formed on the outer peripheral surface, a ball screw nut assembled to the ball screw rod and having a female screw that can be screwed to the male screw on the inner peripheral surface, The present invention relates to an electric linear actuator comprising a rotation restricting means for restricting rotation and configured to be able to advance and retract within a control stroke range in which a ball screw nut is set in the axial direction of the ball screw rod. Here, the “control stroke range” means a controllable stroke range. In such an electric linear actuator, when the ball screw rod rotates and the rotational force is transmitted to the ball screw nut, the ball screw nut itself does not rotate by the rotation restricting means, and the engagement state with the ball screw rod is not achieved. It can move forward and backward (reciprocate) within the control stroke range while maintaining it.

  The electric linear actuator of the present invention is a portion corresponding to the limit position of the control stroke range between the ball screw rod and the mechanical end set outside the control stroke range from the limit position and at least in the axial direction. A portion corresponding to the dimension of the ball screw nut along the line is set in a male screw non-forming region where no male screw is formed.

  With such an electric linear actuator, the stroke length can be increased by moving the ball screw nut back and forth within the control stroke range while maintaining the screwed state of the female screw and the male screw along the axial direction of the ball screw rod. On the other hand, if the ball screw nut runs out of control stroke range limit position and can move toward the mechanical end while it can be adjusted, the control stroke range limit position and mechanical position of the ball screw rod Since the part corresponding to the dimension of the ball screw nut along the axial direction is set in the male screw non-formation region, the ball screw nut does not collide with the mechanical end. The screwed state of the female screw and the male screw can be reliably released at the previous time point, Both the Lumpur screw rod and the ball screw nut can be idle.

  Therefore, the electric linear actuator of the present invention reduces the kinetic energy when the ball screw nut collides with the mechanical end beyond the limit position of the control stroke range even when connected to the driven component. It is possible to prevent / suppress damage to the ball screw nut and the mechanical end.

  Here, the control stroke range set in the axial direction of the ball screw rod is defined by the maximum stroke limit position where the stroke length is maximum and the minimum stroke limit position where the stroke length is minimum. The mechanical end is set at a position outside the control stroke range from the limit position, but the electric linear actuator of the present invention has at least one limit position and a position outside the control stroke range from the limit position. A male screw non-formation region may be set only at a portion between the mechanical end and corresponding to the dimension of the ball screw nut along at least the axial direction, or each limit position and each limit position. Between the mechanical end and the position outside the control stroke range. A portion corresponding to the dimensions of the ball screw nut along at least the axial direction, may be obtained by setting the male screw formed area, respectively. That is, the electric linear actuator of the present invention includes both a configuration in which a male screw non-formation region is set only at one place in the ball screw rod and a configuration in which a male screw non-formation region is set at two locations in the ball screw rod. Is.

  If the electric linear actuator of the present invention is used in a state where it is connected to a driven component, the ball screw nut is inserted into the ball screw nut before the ball screw nut collides with the mechanical end beyond the control stroke range. By reaching the male screw non-formation region of the rod, both the ball screw rod and the ball screw nut can be idled. As a result, the kinetic energy when the ball screw nut collides with the mechanical end is reduced, and damage to the ball screw nut and the mechanical end can be prevented and suppressed.

The cross-sectional schematic diagram of the electric linear actuator which concerns on one Embodiment of this invention. FIG. 1 is a view corresponding to FIG. 1 in a state where a ball screw nut has reached a male screw non-formation region in the electric linear actuator according to the embodiment. The cross-sectional schematic diagram of the conventional electric linear actuator.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIGS. 1 and 2, the electric linear actuator 1 according to this embodiment includes a ball screw rod 2 having a male screw 21 formed on the outer peripheral surface and a female screw 31 that can be screwed into the male screw 21. A ball screw nut 3 formed on the surface and a rotation restricting means 5 for restricting the rotation of the ball screw nut are provided. The linear actuator 1 of this embodiment includes a sleeve 4 that covers the ball screw rod 2 and the ball screw nut 3, and is attached to the sleeve 4 and is disposed in a key groove provided in the ball screw nut 3. The key 5 constitutes a rotation restricting means.

  In the electric linear actuator 1 of the present embodiment, an electric motor M is connected to a ball screw rod 2 via a reduction gear G or the like, and the rotational force from the electric motor M is straightened by a key 5 for preventing rotation. By converting to a thrust to be moved, the ball screw nut 3 is moved back and forth (reciprocated) within a predetermined control stroke range set in the axial direction A of the ball screw rod 2 to change the stroke length. FIG. 2 shows a state where the male screw 21 of the ball screw rod 2 and the female screw 31 of the ball screw nut 3 are screwed together within the control stroke range. Here, the control stroke range is a controllable stroke range and a range shorter than the total length (mechanical stroke range) of the ball screw rod 2. In the electric linear actuator 1 of the present embodiment, this control stroke range is used. The mechanical end 6 is provided outside the control stroke range from the limit position.

  In this embodiment, the mechanical end 6 is provided corresponding to only the limit position (maximum stroke limit position) of the control stroke that defines the maximum value of the changeable stroke length. A mechanical end may be provided corresponding to each of the limit position (minimum stroke limit position) and the maximum stroke limit position of the control stroke that defines the minimum stroke length of the electric linear actuator 1.

  And the electric linear actuator 1 which concerns on this embodiment is a part corresponding to between the maximum stroke limit position and the mechanical end 6 set outside the control stroke range from this maximum stroke limit position in the ball screw rod 2. The portion corresponding to the dimension of the ball screw nut 3 along the axial direction A (the width dimension of the ball screw nut 3) is set in the male screw non-forming region 22 where the male screw 21 is not formed. That is, in the ball screw rod 2, a region near one end is set as the male screw non-forming region 22.

  In the present embodiment, the tolerance of the ball screw rod 2 and the ball screw nut 3 is taken into consideration, and the position of the ball screw rod 2 that is displaced outside the control stroke range by the tolerance from the maximum stroke limit position of the control stroke range. To the end of the ball screw rod 2 and an area corresponding to the width dimension of the ball screw nut 3 (in the illustrated example, an area larger than the width dimension of the ball screw nut 3 by a predetermined dimension) The formation area 22 is set. In the electric linear actuator 1 of the present embodiment, the outer diameter of the male screw non-forming region 22 of the ball screw rod 2 is set to the same diameter as the thread groove valley diameter of the region where the male screw 21 is formed. .

  In this type of electric linear actuator 1, it is assumed that the ball screw nut 3 runs out of control due to a failure of the electric motor M or the like during a development test or use attached to the driven component H. .

  In the electric linear actuator 1 of this embodiment, when the ball screw nut 3 runs away and moves toward the mechanical end 6 beyond the maximum stroke limit position of the control stroke range, as shown in FIG. Arrives at the male screw non-formation region 22 of the ball screw rod 2 before the collision with the mechanical end 6. Since the male screw non-formation region 22 is formed continuously over a portion corresponding to the width of the ball screw nut 3 in the ball screw rod 2, the tip of the ball screw nut 3 in the runaway direction is formed. Before the portion collides with the mechanical end 6, the entire ball screw nut 3 reaches the male screw non-formation region 22, and the ball screw rod 2 and the ball screw via the male screw 21 and the female screw 31 are engaged. The engaged state of the nut 3 is released. As a result, when the entire ball screw nut 3 reaches the male screw non-forming region 22, the ball screw nut 3 does not rotate (rotate) in conjunction with the rotation of the ball screw rod 2. And the ball screw nut 3 is idled.

  When the ball screw rod 2 and the ball screw nut 3 are idled, the inertia of the ball screw rod 2 itself and the inertia of the electric motor M connected to the ball screw rod 2 through the reduction gear G or the like are generated. The inertial mass in the linear direction is only the mass of the ball screw nut 3 alone, and the kinetic energy when colliding with the mechanical end 6 is reduced, and the mechanical end 6 and the ball screw nut 3 are damaged. It can be prevented / suppressed.

  When such an electric linear actuator 1 is used in a state where the ball screw nut 3 is coupled to the driven component H, the coupling portion between the ball screw nut 3 and the driven component H serves as a detent key. Even if the rotation of the ball screw nut 3 remains constrained, the ball screw nut 3 that has reached the male screw non-formation region 22 beyond the maximum stroke limit position of the control stroke range can be reliably idled. Thus, the kinetic energy when colliding with the mechanical end 6 is reduced, and damage to the mechanical end 6 and the ball screw nut 3 can be prevented and suppressed.

  Thus, in the electric linear actuator 1 according to the present embodiment, when the ball screw nut 3 faces the situation where it can collide with the mechanical end 6 beyond the maximum stroke limit position of the control stroke range, Since the region from the maximum stroke limit position to the mechanical end 6 and corresponding to the width dimension of the ball screw nut 3 is set as the male screw non-forming region 22, the ball screw rod 2 and the ball screw nut 3 are Each can be idle, and even when the driven component H is attached, the kinetic energy when colliding with the mechanical end 6 can be reduced, and damage to the ball screw nut 3 and the mechanical end 6 can be prevented and suppressed. be able to.

  The electric linear actuator 1 according to the present embodiment having such functions and effects can be suitably used, for example, for driving a rocket nozzle or for driving a wing such as an aircraft and a missile. . Moreover, the electric linear actuator 1 according to the present embodiment can be suitably used even in a state where the electric linear actuator 1 is incorporated in various mechanical devices such as an electric bed, an electric table, an electric chair, and a lifter.

  In addition, this invention is not limited to embodiment mentioned above. For example, in the above-described embodiment, the ball screw rod is located between the maximum stroke limit position of the control stroke range and the mechanical end provided outside the control stroke range from the maximum stroke limit position and the width dimension of the ball screw. Although the aspect which set only the area | region corresponded to as an external thread non-formation area was illustrated, the following aspects may be sufficient. That is, in the ball screw rod, a region between the maximum stroke limit position of the control stroke range and the mechanical end provided outside the control stroke range than the maximum stroke limit position and corresponding to the width dimension of the ball screw, The area between the minimum stroke limit position of the control stroke range and the mechanical end provided outside the control stroke range from the minimum stroke limit position and corresponding to the ball screw width dimension is set as the male screw non-formation area. Or the area of the ball screw rod between the minimum stroke limit position of the control stroke range and the mechanical end provided outside the control stroke range from the minimum stroke limit position and corresponding to the width dimension of the ball screw Only set in male thread non-formation area It is also possible to employ the like. If it is the former aspect, a male screw non-formation area will be formed in two places (for example, both ends or near both ends) of a ball screw rod.

  In addition, a buffer member for absorbing collision energy (for example, a disc spring or the like) can be disposed in the vicinity of the mechanical end.

  Further, the detent key can be disposed so as to be disengaged from the ball screw nut in a region outside the control stroke range. Furthermore, in the above-described embodiment, the aspect in which the rotation restricting means for restricting the rotation of the ball screw nut is configured by the detent key attached to the sleeve is illustrated, but the rotation restricting means is configured by using other members and structures. You can also. For example, if it is an electric linear actuator that does not have a sleeve and a part of the ball screw nut or ball screw rod is exposed to the outside, the coupling part between the ball screw nut and the driven part functions as a rotation restricting means. It is possible to make it.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Electric linear actuator 2 ... Ball screw rod 21 ... Male screw 22 ... Male screw non-formation area | region 3 ... Ball screw nut 5 ... Rotation restriction member (Key for rotation prevention)
6 ... Mechanical end

Claims (1)

A ball screw rod having a male screw formed on the outer peripheral surface, a ball screw nut assembled to the ball screw rod and having a female screw that can be screwed to the male screw on the inner peripheral surface, and rotation of the ball screw nut An electric linear actuator configured to be capable of moving forward and backward within a control stroke range in which the ball screw nut is set in the axial direction of the ball screw rod.
Of the ball screw rod, the ball corresponding to a portion between a limit position of the control stroke range and a mechanical end set outside the control stroke range from the limit position and at least along the axial direction An electric linear actuator characterized in that a portion corresponding to a dimension of a screw nut is set in a male screw non-formation region where the male screw is not formed.

Images