Linear motion unit and electric actuator

Abstract

To provide an electric actuator capable of effectively sliding a load by a ball using a bearing for a linear motion member, and capable of inexpensively improving the rigidity of a table.SOLUTION: An electric actuator of the present invention comprises: a base part having a shaft 40 for a linear bushing; and a slider 50 having left and right linear bushings 60 attached to the shaft for a linear bushing, and a slider body having left and right linear bushing attachment holes to which the linear bushings 50 are respectively attached. The slider 50 comprises a pressing member 70 that is arranged between the linear bushing attachment holes and the linear bushings 60, and presses the linear bushings 60 in a horizontal direction and in a direction of pressing it against the shaft 40 for a linear bushing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a linear motion unit and an electric actuator. [Background technology]

[0002] Conventionally, a linear motion unit of a linear motion rolling guideway having one row of balls on each side has been proposed in which rolling elements contact the raceway grooves on both sides of the casing and the track rail. There is also a structure in which the rolling elements contact the raceway surface on one side at four points and the raceway surface on the other side at two points (Patent Document 1).

[0003] In this structure, by setting the number of surfaces where the rolling elements come into contact with the raceway surface according to the direction of the load applied to the slider, it is possible to allow for machining errors in the raceway grooves and provide a margin of error in machining accuracy. Also, there is an effect that the slider can slide smoothly on the track rail even when the track rail slides with an unbalanced load applied to the casing.

[0004] However, in the above-mentioned sliding structure, the load input to the table is held by the balls that contact the raceway surface at a 45-degree angle, so if a load is applied to the table from above or below or to the left or right, the load cannot be efficiently received.In addition, the slider, casing, and balls must be assembled separately during assembly, making the assembly difficult, and the need to ensure dimensional accuracy for each part increases the cost. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 5-141416 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] The present invention has been made in light of these problems, and aims to provide a linear motion unit and electric actuator that uses bearings for linear motion components (hereinafter referred to as "linear bushings") to support the contact points between the base and slider at two points above, two points below, one point to the right, and one point to the left, thereby efficiently supporting the ball that slides against the load applied to the table, thereby improving the rigidity of the table and reducing the occurrence of rattling due to the gap between the slider and the ball. [Means for solving the problem]

[0007] In order to achieve the above object, the present invention employs the following means.

[0008] The linear motion unit according to the present invention comprises: A base portion formed in a cylindrical shape with an open top, having a screw shaft for a feed screw or ball screw connected to an electric motor, and two linear bushing shafts each having a connecting portion connected to a left wall surface or a right wall surface, a slider including left and right linear bushes attached to the linear bushing shaft, and a slider body having left and right linear bushing attachment holes to which the linear bushings are respectively attached; Equipped with the linear bushing includes a left linear bushing having an opening portion disposed so that the left side is open relative to the slider, and a right linear bushing having an opening portion disposed so that the right side is open, The left linear bushing has balls arranged up and down within ±10° of the center vertical direction and on the right side within ±10° of the center horizontal direction, The right-side linear bushing has balls arranged up and down within ±10° of the center vertical direction and on the left side within ±10° of the center horizontal direction, The slider is characterized in that it is provided with a pressing member that is arranged between the linear bush mounting hole and the linear bush and presses the linear bush horizontally in a direction pressing it against the linear bush shaft.

[0009] The linear motion unit of the present invention uses a ready-made linear bushing in the linear motion guide, and by receiving the ball contact points at two points above, two points below, one point to the right, and one point to the left, the load applied to the table can be efficiently received by the sliding balls, and the rigidity of the table can be increased. Also, the linear motion unit of the present invention prevents the occurrence of a gap between the linear bushing and the linear bushing shaft by pressing the linear bushing against the linear bushing shaft with a pressing member, and effectively prevents the slider from rattling in the horizontal direction due to the load.

[0010] In addition, in the linear motion unit according to the present invention, the pressing member may be formed by bending a metal plate into a U-shape, and may be characterized in that a fold is provided that bulges toward the linear bush so as to be able to press the linear bush at the portion that comes into contact with the linear bush.

[0011] By adopting such a configuration, when mounting the linear bushing in the mounting hole, the linear bushing can be mounted simply by sandwiching the U-shaped portion and fitting it into the linear bushing mounting hole.

[0012] Furthermore, in the linear motion unit according to the present invention, the linear bushing mounting hole may be provided with a pressing member recess so that the pressing member can be disposed therein.

[0013] By adopting such a configuration, it is possible to attach a pressing member having a thickness greater than the distance by which the linear bushing is moved when pressed.

[0014] Furthermore, in the linear motion unit according to the present invention, a cross section of the linear bushing mounting hole may be formed into an ellipse so that the linear bushing can move horizontally by 0.1 mm to 0.4 mm.

[0015] A small gap is provided in advance, and the linear bushing 60 is pressed against the linear bushing shaft 40 to prevent the occurrence of the gap and thus the occurrence of rattling.

[0016] The present invention also provides an electric actuator comprising the linear motion unit described above and an electric motor as a drive source, thereby making it possible to provide an electric actuator having the above-mentioned effects. Effect of the Invention

[0017] The linear motion unit and electric actuator of the present invention can provide an electric actuator that uses linear bushings to effectively slide a load using balls and can inexpensively improve the rigidity of the table. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view showing an electric actuator 100 according to an embodiment. [Diagram 2] FIG. 2 is a perspective view showing the internal structure of the electric actuator 100 according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view taken along line AA of the electric actuator 100 according to the embodiment. [Figure 4] FIG. 4 is a cross-sectional view of the base frame 26 according to the embodiment. [Diagram 5] FIG. 5 is a perspective view of a slider 50 according to the embodiment. [Figure 6] FIG. 6 is a perspective view of a slider body 59 according to the embodiment. [Figure 7] FIG. 7 is an explanatory diagram for explaining the variation of the pressing member 70 according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the embodiment and drawings described below are intended to exemplify a part of the embodiment of the present invention, and are not intended to be used for the purpose of limiting the present invention to these configurations. Also, the same or similar reference symbols are used for corresponding components in each drawing. Note that in the present invention, "up and down," "front and back," and "left and right" refer to the directions shown in FIG. 1.

[0020] FIG. 1 shows a perspective view of an electric actuator 100 according to this embodiment. FIG. 2 shows a perspective view showing the internal structure of the electric actuator 100. FIG. 3 shows a cross-sectional view of the electric actuator 100 taken along line AA (the cross-sectional line is omitted to ensure visibility). As shown in FIG. 2, the electric actuator 100 mainly includes an electric motor 10 and a linear motion unit consisting of a screw shaft 30 arranged in a base portion 20, a linear bush shaft 40, and a slider 50. Note that the linear motion unit is a mechanical element of the electric actuator 100 that converts the rotational motion into linear motion, and the difference lies in whether or not the operation can be directly controlled by the electric motor 10. Therefore, the linear motion unit will be described below with reference to the electric actuator 100.

[0021] The electric motor 10 is a motor that rotates the screw shaft 30 of a feed screw or a ball screw. The type of motor is not particularly limited, but it is preferable to use a stepping motor or a servo motor that can precisely control the angle and number of rotations.

[0022] The base portion 20 has a base frame 26 (see Figure 4) made of a long member having a hollow portion 25 inside, in which a shaft 40 for a linear bush is formed, and a screw shaft 30 connected to an electric motor 10 arranged inside this base frame 26, and a slider 50 is arranged inside.

[0023] The screw shaft 30 is a threaded shaft used for moving the slider 50 via a nut portion 52 provided on the slider 50. The screw shaft 30 is connected to the electric motor 10, and is provided over the entire length in the longitudinal direction (front-rear direction) of the base portion 20 of the electric actuator 100. By rotating this screw shaft 30, the slider 50 can be moved in the front-rear direction.

[0024] The linear bushing shaft 40 is a shaft disposed within the linear bushing 60, and two are provided along the longitudinal direction of the base portion 20. The linear bushing shaft 40 is formed in a substantially cylindrical shape, and each side surface is connected over its entire length to the right inner wall 21 or the left inner wall 22 of the base frame 26 by a connecting portion 45. This ensures high rigidity, unlike when the linear bushing shaft 40 does not have a connecting portion 45 and is disposed hollow in a rod shape.

[0025] As shown in FIG. 3, the slider 50 is disposed so as to form a gap with respect to the inner wall of the hollow portion 25 of the base frame 26, and is disposed so as to be slidable back and forth within the hollow portion 25. As shown in FIG. 5, the slider 50 includes a nut portion 52 (thread grooves are omitted) that screws onto the screw shaft 30, left and right linear bushes 60 formed to insert the linear bush shaft 40 described above, a pressing member 70 that presses the linear bush 60, and a table mounting portion 80 formed on the upper surface of the base frame 26 and connected to the slider 50. As shown in FIG. 7, the linear bush 60 is mounted in the linear bush mounting hole 54, which is provided in the slider body 59 and into which the linear bush 60 can be inserted. The relationship between the linear bush mounting hole 54 and the linear bush 60 will be described later. As shown in FIG. 3, the slider 50 is disposed in the hollow portion 25, the screw shaft 30 is inserted into the nut portion 52, and the linear bushing shaft 40 is inserted into the linear bushing 60.

[0026] The nut portion 52 is screwed into the screw shaft 30 and constitutes a feed screw or ball screw mechanism together with the screw shaft 30. When the screw shaft 30 is rotated by the electric motor 10, the nut portion 52 converts the rotation into a linear motion in the longitudinal direction of the base portion 20, and moves the slider 50 over the entire length of the base portion 20.

[0027] The linear bushing 60 is a bearing for a linear motion member, and in this embodiment, an open type linear bushing 60 having at least three ball rows is used. The linear bushing 60 has a cylindrical cross section having an open portion 64 for passing the connecting portion 45 of the linear bushing shaft 40. The linear bushing 60 includes a left linear bushing 60a disposed such that the open portion 64 is open to the left side with respect to the slider 50, and a right linear bushing 60b disposed such that the open portion 64 is open to the right side. In each linear bushing 60, the linear bushing shaft 40 is inserted, and the connecting portion 45 connecting the linear bushing shaft 40 and the base portion 20 is disposed in the open portion 64.

[0028] As shown in FIG. 3, at least three rows of balls 61 are arranged in the linear bushing 60. In the left linear bushing 60a, two rows of balls 61 are arranged vertically within a range of ±10 degrees at an angle A1 of the center of the cross section of the linear bushing 60 with respect to the vertical direction V1. In addition, in the left linear bushing 60a, one row of balls 61 is arranged on the right side within a range of ±10 degrees at an angle A2 of the center of the cross section of the linear bushing 60 with respect to the horizontal direction H1. Similarly, in the right linear bushing 60b, two rows of balls 61 are arranged vertically within a range of ±10 degrees at an angle A3 of the center of the cross section of the linear bushing 60 with respect to the vertical direction V2. In addition, in the right linear bushing 60b, one row of balls 61 is arranged on the left side within a range of ±10 degrees at an angle A4 of the center of the cross section of the linear bushing 60 with respect to the horizontal direction H1. In this way, at least three rows of balls 61 are provided in one linear bushing 60, two rows vertically and one row horizontally. By arranging the linear bushings 60 in this manner, the load in the vertical direction can be received by the upper and lower rows of four balls 61 at an angle of within ±10 degrees of the two linear bushings 60, and in the horizontal direction, the left and right linear bushings 60 can receive the load by rows of balls 61 on the right and left sides, respectively, at angles of within ±10 degrees to the central horizontal direction. Therefore, it has high rigidity against loads.

[0029] 3, the upper and lower balls 61 arranged in the left linear bush 60a and the upper and lower balls 61 arranged in the right linear bush 60b are preferably arranged symmetrically with respect to the vertical center line C of the slider 50. By arranging them symmetrically in this way, a load applied to the table from above is easily applied evenly to both sides, preventing an unbalanced load from being applied to one side. This prevents wear on only one side, and extends the life of the electric actuator 100.

[0030] Furthermore, the upper and lower balls 61 arranged in the left linear bushing 60a and the upper and lower balls 61 arranged in the right linear bushing 60b are preferably arranged in the vertical direction V2 at the center of the cross section, and the right ball 61 arranged in the left linear bushing 60a and the left ball 61 arranged in the right linear bushing 60b are preferably arranged in the horizontal direction H1 at the center of the cross section. By adopting such a configuration, the load applied to the table can be efficiently received by the sliding balls 61 more effectively, and the rigidity of the table can be increased.

[0031] The pressing members 70 (71 to 73) are disposed between the linear bushing 60 and the linear bushing mounting hole 54, and press the linear bushing 60 in the horizontal direction in a direction pressing the linear bushing 60 against the linear bushing shaft 40. As shown in FIG. 7A, the pressing members 70 may be formed by bending a metal plate into a U-shape, and may be formed with a fold 71a that bulges toward the linear bushing 60 so that the pressing member 70 can be pressed at a portion that contacts the linear bushing 60. The pressing members 70 are not particularly limited, and may be any member that is disposed between the linear bushing 60 and the linear bushing mounting hole 54 and has a function of pressing the linear bushing 60 in the horizontal direction in a direction pressing the linear bushing 60 against the linear bushing shaft 40. For example, as shown in FIG. 7B, a metal plate 72 with slight folds 72a may be provided on both sides, instead of bending the metal plate into a U-shape, or a rubber plate 73 may be used as shown in FIG. 7C. The linear bushing mounting hole 54 is provided with a pressing member recess 74 so that such a pressing member 70 can be disposed therein. This allows for example, even if the distance to be moved by pressing the linear bushing 60 is about 0.1 mm to 0.3 mm, a member thicker than this (for example, a metal plate having a thickness of 1.2 mm) to be placed. Note that the pressing force of the pressing member 70 needs to be set to a level that does not cause rattling due to loads applied in the horizontal left and right directions when used as a linear motion unit.

[0032] The cross-sectional circle of the linear bushing attachment hole 54 is made into a slightly horizontally elongated ellipse, and is made so that a gap is formed to allow the linear bushing 60 to move horizontally by about 0.1 mm to 0.4 mm when inserted. Therefore, there is a margin between the linear bushing 60 and the linear bushing attachment hole 54 when fitting, and it is possible to prevent the linear bushing shaft 40 from interfering with each other and becoming unable to be fitted. By disposing a pressing member 70 between the linear bushing 60 and the linear bushing attachment hole 54, the created gap eliminates rattling of the linear bushing 60, and it is possible to prevent the occurrence of lateral rattle due to lateral loads applied to the table.

[0033] The reason for providing such a pressing member 70 is as follows. When the base frame 26 is produced by extrusion molding, as shown in FIG. 4, the vertical pitch E of the left linear bushing shaft 40 and the vertical pitch F of the right linear bushing shaft 40 are short, making it easy to achieve precision in the product. However, the pitch G between the linear bushing shafts 40 is long, and in the case of extrusion molding, the metal is wrapped around, so there is a problem that it is difficult to achieve precision if even a slight distortion occurs. If the pitch G between the linear bushing shafts 40 is too wide, rattling occurs, and if it is too narrow, the linear bushing 60 may not fit or large friction may occur. Therefore, by providing a pressing member that absorbs processing variations, the linear bushing 60 is pressed against the linear bushing shaft 40 to prevent gaps and interference, and thus prevent rattling.

[0034] The electric actuator 100 manufactured as described above can be manufactured easily and quickly by using the ready-made linear bush 60 for the linear guide. In addition, by using the open-type linear bush 60 to connect the linear bush shaft 40 to the wall surface of the base portion 20, it is possible to effectively resist the load applied to the linear bush shaft 40. Furthermore, by receiving the contact points of the ball 61 at two points above, two points below, one point to the right, and one point to the left, the load applied to the table can be efficiently received by the sliding ball 61, and the rigidity of the table can be increased.

[0035] Furthermore, even with a manufacturing method such as extrusion molding, which makes it more difficult to achieve dimensional accuracy compared to cutting, it is possible to prevent gaps from occurring between the linear bush shaft 40 and the linear bush 60, thereby preventing horizontal wobble.

[0036] The electric actuator 100 as described above can be used not only in factories but also as a seat rail for vehicles. [Industrial Applicability]

[0037] As shown in the above-described embodiment, the present invention is industrially applicable as a seat rail device for a vehicle. [Explanation of symbols]

[0038] 10...electric motor, 20...base portion, 21...right inner wall, 22...left inner wall, 25...hollow portion, 26...base frame, 30...screw shaft, 40...shaft for linear bushing, 45...connecting portion, 50...slider, 52...nut portion, 54...hole for mounting linear bushing, 59...slider body, 60...linear bushing, 60a...left linear bushing, 60b...right linear bushing, 61...ball, 64...opening portion, 70...pressure member, 71a...fold, 72...metal plate, 72a...fold, 73...rubber plate, 74...recess for pressure member, 80...table mounting portion, 100...electric actuator

Claims

1. A base portion formed in a cylindrical shape with an open top, and having a screw shaft for a feed screw or ball screw connected to an electric motor, and two linear bushing shafts each having a connecting portion connected to a left wall surface or a right wall surface, a slider including left and right linear bushes attached to the linear bushing shaft, and a slider body having left and right linear bushing attachment holes to which the linear bushings are respectively attached; Equipped with the linear bushing includes a left linear bushing having an opening portion disposed so that the left side is open relative to the slider, and a right linear bushing having an opening portion disposed so that the right side is open, The left linear bushing has balls arranged up and down within ±10° of the center vertical direction and on the right side within ±10° of the center horizontal direction, The right-side linear bushing has balls arranged up and down within ±10° of the center vertical direction and on the left side within ±10° of the center horizontal direction, A linear motion unit characterized in that the slider is arranged between the linear bush mounting hole and the linear bush and is provided with a pressing member that presses the linear bush horizontally in a direction pressing it against the linear bush shaft.

2. The linear motion unit according to claim 1, characterized in that the pressing member is formed by bending a metal plate into a U-shape, and has a fold that bulges toward the linear bush so that it can be pressed at the portion that comes into contact with the linear bush.

3. 2. The linear motion unit according to claim 1, wherein the linear bushing mounting hole is provided with a pressing member recess so that the pressing member can be disposed therein.

4. 2. The linear motion unit according to claim 1, wherein a cross section of the linear bushing mounting hole is formed into an ellipse so that the linear bushing can move horizontally by 0.1 mm to 0.4 mm.

5. A linear motion unit according to any one of claims 1 to 4, An electric actuator comprising: an electric motor as a drive source.

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