JP2019158110A - Linear motion actuator - Google Patents

Abstract

A compact linear actuator having excellent movement accuracy is provided. A base portion provided with a groove-shaped guide portion extending over a predetermined distance, and a screw portion extending along a direction in which the guide portion extends, and sliding with the guide portion. A screw shaft 2 having a projecting portion 21 projecting in a direction intersecting the axis X of the screw portion 22 and rotating while being screwed to the screw portion 22, so that the screw shaft 2 cannot be rotated relative to the base portion 1. A linear actuator A comprising a drive unit 3 for reciprocating movement, wherein a contact portion P between the convex portion 21 and the guide portion 11 is linearly formed along the direction of reciprocation. [Selection diagram] FIG.

Description

  The present invention relates to a linear actuator that reciprocates a screw shaft with respect to a base portion.

  Conventionally, as such a linear actuator, for example, there is one described in Patent Document 1 below.

  This linear motion actuator includes a threaded portion having a male threaded portion on the outer peripheral surface, a nut having a female threaded portion to be screwed to the threaded portion on the inner peripheral surface, and a rollable portion between the threaded portion and the nut. A plurality of balls to be mounted and a torque transmission member for rotating the nut are provided.

  A pin member protruding in a direction orthogonal to the axis is provided on one end side of the screw portion, and this pin member slides along a linear groove provided in the housing. For this reason, the screw portion reciprocates without rotating with respect to the housing.

  On the other hand, a locking portion protruding in the direction of the axis is formed at the tip of the nut. When the nut rotates and the threaded portion moves linearly and the pin member approaches the tip of the nut, the locking portion comes into contact with the pin member and stops the rotation of the nut.

  With such a configuration, even when the collision force when the locking portion comes into contact with the pin member is large, the collision force is transmitted to the housing via both end portions and the groove portion of the pin member, and the screw portion and the nut. It is said that the influence of the collision force that is received will be suppressed.

Japanese Patent Laid-Open No. 2006-196927

  In such a linear motion actuator, it is necessary that the linear motion is accurate and that the linear motion is started and stopped smoothly. For this purpose, for example, rattling between the pin member of the screw portion and the groove portion needs to be eliminated as much as possible. If the rattling is present, the threaded portion is rotatable by a predetermined angle with respect to the groove, and the stopping accuracy of the threaded portion is impaired. Further, when the operation of the screw portion is started or stopped, the pin member collides with the groove portion, and vibration and noise are generated.

  In the linear motion actuator described in Patent Document 1, the cylindrical pin member extends along the radial direction of the threaded portion, and the contact portion between the pin member and the groove portion is a screw thread on the surface of the pin member. It is formed linearly along the radial direction of the part.

  For this reason, in order to prevent the contact force between the pin member and the groove from excessively increasing, it is necessary to set the length of the contact portion along the radial direction of the screw portion to a predetermined length. Therefore, the diameter of the linear motion actuator is increased, which is not suitable for making the size of the linear motion actuator compact.

  Further, when the screw portion reciprocates, the abutting portion of the pin member slides on an area of the surface of the groove portion, which is obtained by multiplying the length of the abutting portion and the moving distance of the screw portion. For this reason, a wide contact surface is formed on the groove portion side. In order for the pin member to move smoothly, it is particularly necessary that the contact surface formed in the groove is clean. However, in this configuration, when the contact surface is widened, foreign matter or the like is likely to adhere. Therefore, the pin member or the groove portion is likely to be worn, and the progress of rattling may be accelerated and the moving accuracy of the screw portion may be reduced.

  For these reasons, there is room for improvement in the above-mentioned conventional technology to obtain a compact linear actuator with excellent movement accuracy, and there is a need for such a compact linear actuator with excellent movement accuracy. It has been.

(Feature configuration)
The characteristic configuration of the linear actuator according to the present invention is as follows:
A base portion provided with a groove-shaped guide portion extending over a predetermined distance;
A screw shaft having a thread portion along the extending direction of the guide portion, and a protruding portion that slides with the guide portion and projecting in a direction intersecting the axis of the screw portion;
A drive unit that rotates while being screwed to the screw unit, and reciprocally moves the screw shaft so as not to rotate relative to the base unit;
A contact portion between the convex portion and the guide portion is formed in a linear shape along the reciprocating direction.

(effect)
When the driving force is transmitted from the rotating drive part to the screw part as the linear actuator is driven, the convex part comes into contact with the guide part to prevent the screw part from rotating. While the rotation of the drive unit continues, the convex part is pressed against the guide part to prevent the screw part from rotating, and in this state, the convex part reciprocates along the axis of the screw part with respect to the guide part. To do.

  In this configuration, the contact portion between the convex portion and the guide portion is formed linearly along the movement direction of the convex portion, and therefore the distance from the axial center of the screw portion to the contact portion is a substantially constant value. Become. In this case, the contact force per unit area between the convex portion and the guide portion can be reduced by appropriately setting the length of the convex portion along the axis. In this way, with this configuration, a linear actuator having a compact configuration in which the outer diameter of the convex portion is kept at a predetermined length and excellent in durability can be obtained.

  In addition, when the convex portion comes into contact with the guide portion at a certain distance from the axis when the screw portion is about to rotate as in this configuration, it is easy to calculate the moment of the contact force acting on the convex portion. . As a result, the strength setting and material selection of the convex portion and the guide portion are facilitated.

  Furthermore, it is easy to set the shape of both members by specifying the contact portion between the convex portion and the guide portion, and it is possible to set the gap dimension between both members more precisely. It is possible to obtain a linear actuator with little play when moving.

(Feature configuration)
In the linear motion actuator according to the present invention, when viewed in a direction along the axis, the region including the contact portion and a gap dimension D1 between the convex portion and the guide portion is 0.1 mm or less, Conveniently, it is formed with a length of 20 × D1 or more along the surface of the convex portion or the guide portion.

(effect)
By configuring the surface of the convex portion and the surface of the guide portion as in this configuration, it is possible to suppress an increase in stress generated at the contact portion between the two. The convex portion or the guide portion is formed of a metal material or a resin material, but some deformation occurs when contacting each other. In that case, by defining the interval between the regions adjacent to the contact portion, there is an opportunity for the convex portion and the guide portion to contact each other even in the adjacent region, and the local surface pressure increases. Can be suppressed. As a result, wear of the convex portion and the guide portion is suppressed, and the convex portion and the guide portion can maintain a smooth sliding state.

(Feature configuration)
In the linear motion actuator according to the present invention, in a phantom line connecting the shaft core and the contact portion in a direction view along the shaft core, a portion closer to the shaft core than the contact portion. Of the tangent lines of the convex portion and the guide portion in the contact portion, the angle formed by the portion closer to the shaft core than the contact portion is advantageously formed within 40 degrees.

(effect)
As in this configuration, the angle at which the tangent line and the virtual line intersect with each other is set to a certain value or less, so that when the threaded portion receives the rotational force from the driving portion and the convex portion comes into contact with the guide portion, the convex portion Dispersion of the pressing force applied to the guide portion along the surface of the guide portion can be suppressed.

  If the angle at which the tangent line and the imaginary line intersect is large and the component of the force to be dispersed is large, when the convex part comes into contact with the guide part, slippage between both tends to occur. For this reason, either the convex portion or the guide portion is likely to be worn, and the gap between the two is widened, so that noise and vibration are generated each time the rotation direction of the screw portion is reversed. Further, as a result of the gap being widened, the speed at which the convex portion comes into contact with the guide portion is increased, and the impact force when the two members are brought into contact with each other is increased, so that the progress of wear is further accelerated.

  However, according to this configuration, since the convex portion comes into contact with the guide portion at an angle close to perpendicularity, the two do not slide easily, and it is difficult to cause wear and a highly durable linear actuator can be obtained.

(Feature configuration)
The linear motion actuator according to the present invention can be configured such that the tangent line and the imaginary line overlap when viewed in the direction along the axis.

(effect)
If it is this structure, a convex part will contact | abut from the normal line direction in the contact position of a guide part with respect to a guide part, and both slip hardly arises. Therefore, the durability of the convex part and the guide part is extremely high.

  Further, when the shape of the base portion on which the guide portion is formed is cylindrical, the direction in which the convex portion exerts an external force on the guide portion is a direction along the circumferential direction of the base portion as viewed in the direction along the axis. Thus, since the direction of the external force is not directed in the radial direction of the base portion, that is, in the thickness direction, the possibility that the guide portion itself is deformed is reduced. That is, even when the thickness of the base portion is reduced, the base portion is not easily deformed by the contact of the convex portion, and the linear motion actuator can be configured to be lightweight and compact.

(Feature configuration)
In the linear motion actuator according to the present invention, when viewed in a direction along the axis, either one of the surface of the convex portion and the surface of the guide portion is adjacent to both sides of the contact portion. Can be configured in a straight line that overlaps the virtual line.

(effect)
The present configuration is intended to form a contact portion of one of the convex portion and the guide portion on a plane. By forming one side as a flat surface in this way, there is a manufacturing error on the other curved surface, and the tangent direction on both sides coincides with the virtual line even when the contact position on both sides is different from the predetermined position. Therefore, it is possible to form an abutting portion in which the abutting direction of both surfaces is stable and slipping or the like hardly occurs.

The partial cross section perspective view which shows the structure of the linear motion actuator of 1st Embodiment. Explanatory drawing which shows the convex part and guide part of 1st Embodiment Explanatory drawing which shows the detail of the convex part and guide part of 1st Embodiment Explanatory drawing which shows the convex part and guide part of 2nd Embodiment

[First Embodiment]
(Overview)
The linear actuator A according to the present invention reciprocates a part of the apparatus in a linear direction by a motor drive or the like, and transmits an external force to various operation units mounted on a vehicle, for example.

  As shown in FIG. 1, the linear motion actuator A includes a base portion 1 and a screw shaft 2 that moves back and forth relative to the base portion 1. The base portion 1 is provided with, for example, a linear and groove-like guide portion 11 extending over a predetermined distance, and a convex portion 21 provided on a part of the screw shaft 2 extends along the guide portion 11. The movement direction of the screw shaft 2 is determined.

  The screw shaft 2 includes a screw portion 22 having an axis X along the extending direction of the guide portion 11. A pair of convex portions 21 projecting in a direction intersecting the axis X is formed at the tip of the screw portion 22 so as to rotate integrally with the screw portion 22. However, this convex part 21 may protrude in only one direction along the radial direction. The protruding direction of the convex portion 21 is a direction perpendicular to the axis X in FIG. 1, but is not necessarily a vertical direction. As long as the outer diameter of the convex portion 21 is larger than that of the screw portion 22 and can contact the guide portion 11, the convex portion 21 may protrude in any direction.

  The screw portion 22 is a male screw formed to have a predetermined length along the direction of the axis X. The screw portion 22 is inserted into, for example, a cylindrical drive portion 3 and is screwed into a female screw formed on the inner surface of the drive portion 3. The drive unit 3 includes, for example, an annular gear unit (not shown) at one end, and is driven to rotate in both forward and reverse directions by a separately provided drive motor. A bearing portion 4 is provided across the other end portion of the driving portion 3 and the base portion 1, and a ball bearing 41 is disposed between the base portion 1. As a result, the driving unit 3 rotates smoothly with respect to the base unit 1.

  During the rotation of the drive unit 3, the convex portion 21 is pressed against the guide unit 11 and the rotation of the screw shaft 2 is prevented. As a result, the screw shaft 2 is thrust-moved with respect to the guide portion 11, and the other operation member is pushed and pulled by the output portion 23 provided at the end of the screw shaft 2.

(Shape of convex part and guide part)
FIG. 2 is a sectional view showing the convex portion 21 and the guide portion 11, and FIG. 3 is an enlarged view of the contact portion P between the convex portion 21 and the guide portion 11. The shape of the convex part 21 here is a spindle shape when viewed in the direction along the axis X. Further, when viewed in a direction perpendicular to the axis X, the shape is rectangular as shown in FIG.

  The guide part 11 is a pair of grooves that hold the convex part 21. Inside the guide portion 11, for example, a cylindrical moving chamber 12 in which the screw shaft 2 can reciprocate is provided. The pair of guide portions 11 are connected to a point-symmetrical position with respect to the moving chamber 12 when viewed in the direction along the axis X.

  As shown in FIGS. 2 and 3, the tip of the convex portion 21 is formed in a spindle shape, and the convex portion 21 makes point contact with the guide portion 11 when viewed in the direction along the axis X. The contact portion P that makes contact in this way is provided in the convex portion 21 over the entire width of the convex portion 21 along the direction of the axis X. On the other hand, the guide portion 11 is provided by a predetermined distance along the axial center X direction as indicated by a dotted line in FIG. As described above, the abutting portion P between the convex portion 21 and the guide portion 11 is formed in a linear shape along the reciprocating direction of the screw shaft 2.

  If it is this structure, the contact position of each convex part 21 and the guide part 11 will be set to the position equidistant from the axis X. In this case, by appropriately setting the length of the convex portion 21 along the axis X, the length of the contact portion P between the convex portion 21 and the guide portion 11 is adjusted, and the convex portion 21 and the guide portion 11 are thereby adjusted. The contact force per unit area can be reduced. As a result, it is possible to obtain a linear actuator A having a compact configuration in which the outer diameter of the convex portion 21 is kept at a predetermined length and having excellent durability.

  In addition, when the contact portion P is set at a certain distance from the axis X, the moment calculation of the contact force exerted on the guide portion 11 by the convex portion 21 becomes easy. As a result, the strength setting and material selection of the convex portion 21 and the guide portion 11 are optimal, and each component member can be made compact.

  Furthermore, by specifying the position of the contact portion P between the convex portion 21 and the guide portion 11 with respect to the axis X, it becomes easy to set the shape of both members, and the gap dimension between the two members is more strict. Can be set. Therefore, it is possible to obtain a linear actuator A with high accuracy and little play when the convex portion 21 is moved.

(Specific example of the contact portion between the convex portion and the guide portion)
The contact portion P1 (P) between the convex portion 21 and the guide portion 11 is changed when the rotation direction of the driving portion 3 is reversed. The contact portion P1 shown in FIGS. 2 and 3 is when the screw shaft 2 rotates counterclockwise on the paper surface. In this state, the contact portion P <b> 2 on the opposite side of the convex portion 21 is slightly separated from the guide portion 11. Therefore, every time the rotation direction of the screw shaft 2 is reversed, the convex portion 21 and the guide portion 11 collide at a predetermined speed. By repeating this, the convex part 21 or the contact part P of the guide part 11 is deformed or worn.

  If the curvature at the contact portion P of the convex portion 21 or the guide portion 11 is small and sharp when viewed in the direction along the axis X, the wear of the contact portion P is likely to proceed due to each collision. When the curvature of the contact part P of the convex part 21 or the guide part 11 is small, the pointed contact part P is intensively worn by each collision, and the height of the contact part P is reduced. The interval between the guide 21 and the guide portion 11 is expanded at an early stage. As a result, the play between the convex portion 21 and the guide portion 11 becomes excessive.

  In order to prevent such inconvenience, for example, as the shapes of the convex portion 21 and the guide portion 11, it is preferable to define the extent of the gap between adjacent regions around the contact portion P. Specifically, as shown in FIG. 3, when the specified value of the gap dimension D1 between the convex part 21 and the guide part 11 is 0.1 mm, for example, the gap dimension D1 including the contact part P is 0.1 mm or less. The dimension of the region is configured so as to have a length of 20 × D1 or more along the surface of the convex portion 21 or the surface of the guide portion 11.

  By configuring the convex portion 21 and the guide portion 11 in this way, it is possible to suppress an increase in stress generated at the contact portion P between the two. The convex portion 21 or the guide portion 11 is formed of a material such as metal or resin, but some deformation occurs when contacting. In that case, by appropriately setting the gap dimension D1 of the region including the contact portion P, an opportunity to contact the portion adjacent to the contact portion P also occurs, and the increase in local surface pressure is suppressed. Can do. That is, the convex portion 21 or the guide portion 11 comes into contact with a wide area while wearing is small. As a result, the concentration of the contact force is alleviated, further wear is suppressed, and the convex portion 21 and the guide portion 11 can maintain a smooth sliding state.

  Note that the coefficient to be multiplied by D1 can be appropriately set according to the material used as the guide part 11 and the convex part 21 or according to the shape of the convex part 21 and the like.

(Installation posture of contact part)
In the present embodiment, as viewed in the direction along the axis X as shown in FIG. 2, the imaginary line L1 connecting the axis X and the contact part P is closer to the axis X than the contact part P. Of the tangent line L2 of the convex portion 21 and the guide portion 11 in the contact portion P and the angle θ formed by the portion closer to the axis X than the contact portion P is formed within 40 degrees, for example. Convenient.

  Thus, by setting the angle θ at which the tangent line L2 and the virtual line L1 intersect to be equal to or less than a certain value, the external force acting on the guide part 11 from the convex part 21 when the convex part 21 abuts on the guide part 11 is reduced. The direction can be brought close to the normal line on the surface of the guide portion 11. Therefore, it is possible to suppress the external force from being distributed along the surface of the guide portion 11.

  As shown in FIG. 2, the force F acting on the contact portion P along the direction perpendicular to the virtual line L1 is equal to the force F1 in the direction perpendicular to the tangent line L2 at the contact portion P of the guide portion 11 and the tangent line. Dispersed in the force F2 along the direction of L2. Therefore, the component of the force F2 increases as the angle θ between the tangent line L2 and the virtual line L1 increases.

  When the force F <b> 2 is increased, when the convex portion 21 comes into contact with the guide portion 11, it becomes easy to slip on both. Therefore, at least one of the convex portion 21 and the guide portion 11 is easily worn, and the gap between the convex portion 21 and the guide portion 11 is widened. As a result, every time the rotation direction of the screw portion 22 is reversed, abnormal noise or vibration is generated.

  Further, as a result of the gap being widened, the collision speed of the convex portion 21 against the guide portion 11 is increased, the contact force between the two members is increased, and the progress of wear is further accelerated. However, with this configuration in which the convex portion 21 abuts at an angle close to the normal line of the guide portion 11, the linear actuator A having high durability can be obtained because both are difficult to slip and wear is not likely to occur.

  About the installation posture of such a contact part P, it is particularly preferable that the tangent line L2 between the convex part 21 and the guide part 11 and the imaginary line L1 overlap when viewed in the direction along the axis X.

  With this configuration, when the convex portion 21 comes into contact with the guide portion 11, the force F from the convex portion 21 acts perpendicularly to the guide portion 11. As a result, the slippage of the two parts does not occur, the wear of the convex portion 21 and the guide portion 11 is suppressed, and the durability is extremely high.

  Further, when the shape of the base portion 1 on which the guide portion 11 is formed is cylindrical, the direction in which the convex portion 21 exerts an external force on the guide portion 11 is the circumferential direction of the base portion 1 in the direction along the axis X. The direction along. Thus, since the direction of the external force is not directed in the radial direction of the base body portion 1, that is, the thickness direction, the possibility that the guide portion 11 itself is deformed is reduced. That is, even when the thickness of the base portion 1 is reduced, the base portion 1 is not easily deformed by the abutment of the convex portion 21, and the linear motion actuator A can be configured to be lightweight and compact.

(Specific examples of the shape of the convex part and the guide part)
In the example of FIG. 3, when viewed in the direction along the axis X, the shape of the region including the convex portion 21 and the contact portion P in the guide portion 11 is a curved shape. However, either one can be formed linearly.

  FIG. 4 shows an example in which the straight portion 11a is formed on the guide portion 11 side, that is, a flat surface is formed in a region including the contact portion P. In this case, it is easier to set the position of the contact portion P than when both are curved. If both are curved, when the axis of the screw shaft 2 and the guide portion 11 is shifted due to manufacturing errors or mounting errors of the parts, the position of the abutting portion P of both members changes. The direction can change significantly. As a result, the transmission mode of the contact force between the convex portion 21 and the guide portion 11 is not appropriate, and there is a possibility that the degree of occurrence of friction or the like changes significantly.

  However, by configuring one surface as a flat surface, even when the position of the contact portion P between the convex portion 21 and the guide portion 11 is slightly changed, the direction of the force F acting on the guide portion 11 from the convex portion 21 is almost the same. It does not change. Therefore, it is possible to obtain the linear actuator A that easily exhibits the desired performance.

  Further, in the example of FIG. 4, a linear portion 11 a is formed in which a plane formed on the guide portion 11 overlaps the virtual line L <b> 1 when viewed in the direction along the axis X. As a result, as described above, slippage between the convex portion 21 and the guide portion 11 does not occur, wear of the convex portion 21 and the guide portion 11 is suppressed, durability is increased, and the base portion 1 is configured to be thin. A compact linear actuator A can be obtained.

  The characteristic configuration according to the present invention can be widely applied to a linear motion actuator having a portion that comes into contact with a guide portion formed on a base portion and having a screw shaft that reciprocally moves along the guide portion so as not to rotate.

DESCRIPTION OF SYMBOLS 1 Base part 11 Guide part 2 Screw shaft 21 Convex part 22 Screw part 3 Drive part A Direct acting actuator L1 Virtual line L2 Tangent line P Contact part X Axis axis θ Angle

Claims (5)

A base portion provided with a groove-shaped guide portion extending over a predetermined distance;
A screw shaft having a thread portion along the extending direction of the guide portion, and a protruding portion that slides with the guide portion and projecting in a direction intersecting the axis of the screw portion;
A drive unit that rotates while being screwed to the screw unit, and reciprocally moves the screw shaft so as not to rotate relative to the base unit;
A linear motion actuator in which a contact portion between the convex portion and the guide portion is linearly formed along the reciprocating direction. In a direction view along the axis,
A region including the contact portion and having a gap dimension D1 between the convex portion and the guide portion of 0.1 mm or less is formed with a length of 20 × D1 or more along the surface of the convex portion or the guide portion. The linear motion actuator according to claim 1. In a direction view along the axis,
Of the imaginary line connecting the shaft core and the contact portion, a portion on the side of the shaft core from the contact portion;
The angle between the tangent line of the convex portion and the guide portion in the contact portion and the portion closer to the shaft core than the contact portion is formed within 40 degrees. Linear actuator. In a direction view along the axis,
The linear motion actuator according to claim 3, wherein the tangent line and the virtual line overlap each other. In a direction view along the axis,
The linear motion according to claim 4, wherein either one of the surface of the convex portion and the surface of the guide portion is configured in a straight line in which regions adjacent to both sides of the contact portion overlap the virtual line. Actuator.

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