Linear motion unit and electric actuator

Abstract

This invention provides an electric actuator that uses bearings for linear motion members to effectively slide loads using balls, and can inexpensively improve the rigidity of a table. [Solution] The electric actuator of the present invention comprises a slider 50 having a base portion having two linear bushing shafts 40 and a slider body having left and right linear bushings 60 attached to the two linear bushing shafts 40, wherein the slider body has a slit between the left and right linear bushings, and an adjustment member for adjusting the distance between the left and right linear bushings is press-fitted into the slit.

Description

Technical Field

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

Background Art

[0002] Conventionally, as a linear unit of a linear rolling guide having ball rows one by one from left to right, a structure in which rolling elements are brought into contact with each raceway groove on both sides of a casing and a track rail has been proposed. Furthermore, there is also a structure in which the rolling elements are brought into four-point contact with the raceway surface on one side and the rolling elements are brought into two-point contact with the raceway surface on the other side (Patent Document 1).

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

[0004] However, in the sliding structure described above, since the load input to the table is held by balls that contact the raceway surface at a 45-degree angle, there is a problem that when an up-and-down load or a left-and-right load is applied to the table, the load cannot be received efficiently. Also, at the time of assembly, it is necessary to assemble the slider, the casing, and the balls individually, so assembly is difficult, and since it is necessary to ensure the dimensional accuracy of each component, there is a problem that the cost becomes high.

[0005] Therefore, the present inventors have proposed a linear unit and an electric actuator including a slider having a base portion having a screw shaft for a feed screw or a ball screw formed in a cylindrical shape with an upper portion open and connected to an electric motor, and two linear bush shafts each having a connecting portion connected to a left wall surface or a right wall surface, left and right linear bushes attached to the two linear bush shafts, and a slider body having left and right linear bush mounting holes to which the linear bushes are respectively attached.

[0006] However, while it is possible to maintain high precision when manufacturing sliders and base parts by machining, it was difficult to ensure product precision when manufacturing them by extrusion molding, and there was a problem that looseness was likely to occur. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 5-141416 [Patent Document 2] Japanese Patent Publication No. 2024-157371 [Disclosure of the Invention] [Problems that the invention aims to solve]

[0008] The present invention has been made in light of these problems, and aims to provide a linear motion unit and an electric actuator that can efficiently receive the load applied to the table and slide the balls using a linear motion member bearing (hereinafter referred to as "linear bush"), thereby reducing rattle that occurs in the horizontal direction of the slider. [Means for solving the problem]

[0009] To achieve the above-mentioned objectives, the present invention employs the following means.

[0010] The linear motion unit according to the present invention is A base portion formed in a cylindrical shape with the top open, having a screw shaft for a lead screw or ball screw connected to an electric motor, and two linear bush shafts, each having a connecting portion connected to the left wall or the right wall, A slider having a screw hole that engages with the screw shaft, left and right linear bushings attached to the two linear bushing shafts, and a slider body having left and right linear bushing mounting holes to which the linear bushings are respectively attached, Equipped with, The slider body is characterized in that a slit is provided between the left and right linear bushings, and an adjustment member for adjusting the distance between the left and right linear bushings is press-fitted into the slit.

[0011] The linear motion unit according to the present invention uses commercially available linear bushings as linear guides, and by receiving ball contacts 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, thereby increasing the rigidity of the table. However, in the case of a linear motion unit having a slider of the type in which linear bushings are attached to two linear bushing shafts having a connecting part connected to the left or right wall of the base, it is easy to ensure accuracy in the vertical direction, but it is difficult to ensure accuracy in the pitch between the left and right linear bushing shafts of the base. As a result, gaps may occur between the balls of the left and right linear bushings and the linear bushing shafts, or they may interfere with each other, resulting in sliding resistance. Furthermore, if these parts are manufactured by extrusion molding, it becomes even more difficult to ensure accuracy. Therefore, in the present invention, a slit and an adjustment member that can be press-fitted into this slit to adjust the slit width are provided in the slider, so that the spacing between the linear bushings on the slider can be adjusted and rattle can be prevented.

[0012] Furthermore, in the linear motion unit according to the present invention, the slit may be provided in a manner that it communicates from the screw hole to the bottom surface. By adopting such a configuration, the gap of the slit can be easily widened, making it easier to adjust the width of the slit.

[0013] Furthermore, the linear motion unit according to the present invention may be characterized in that the slit is provided with a press-fit hole for press-fitting an adjustment member. By adopting such a configuration, it is possible to prevent the adjustment member from moving up and down within the slit, and to reliably fix the adjustment member within the slit.

[0014] Furthermore, in the linear motion unit according to the present invention, the press-fit hole may be characterized in that it has a circular cross-section and is tapered so that the inner diameter decreases towards the back, and the adjustment member is manufactured in the shape of a frustoconical pyramid formed along the taper of the press-fit hole. By adopting such a configuration, the width of the slit can be adjusted according to the press-fit amount, and finer adjustment of the slit width becomes possible.

[0015] Furthermore, in the linear motion unit according to the present invention, the slider may be characterized in that the distance between the left and right linear bushings is manufactured to be narrower than a predetermined position. By adopting such a configuration, it is possible to prevent the distance between the left and right linear bushings from being too wide due to manufacturing errors in the initial state before adjustment, and the adjustment member can be used to reliably adjust the distance to the appropriate level.

[0016] The present invention provides an electric actuator characterized by comprising the aforementioned linear motion unit and an electric motor as a drive source. The present invention provides an electric actuator having the aforementioned effects. [Effects of the Invention]

[0017] According to the linear motion unit and the electric actuator of the present invention, it is possible to provide an electric actuator that can effectively slide a load by using a linear bush and can improve the rigidity of a table at a low cost. Further, by making the interval between the left and right linear bushes adjustable, it is possible to adjust the optimum interval of the linear bushes with respect to the shaft for the linear bushes, prevent rattling, and enable smooth sliding.

Brief Description of the Drawings

[0018] [Figure 1] FIG. 1 is a perspective view showing an electric actuator 100 according to an embodiment. [Figure 2] FIG. 2 is a perspective view showing the internal structure of the electric actuator 100 according to an embodiment. [Figure 3] FIG. 3 is a sectional view taken along the line A - A of the electric actuator 100 according to an embodiment. [Figure 4] FIG. 4 is a sectional view of a base frame 26 according to an embodiment. [Figure 5] FIG. 5 is a perspective view of a slider 50 according to an embodiment. [Figure 6] FIG. 6 is a perspective view of a slider body 59 according to an embodiment. [Figure 7] FIG. 7 is a perspective view showing another embodiment of a press - fitting hole 57 and an adjustment member 70. [Figure 8] FIG. 8 is a sectional view taken along the line B - B of FIG. 3.

Embodiments for Carrying Out the Invention

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

[0020] Figure 1 shows a perspective view of the electric actuator 100 according to this embodiment. Figure 2 shows a perspective view showing the internal structure of the electric actuator 100. Figure 3 shows an AA cross-sectional view of the electric actuator 100 (cross-sectional lines are omitted for clarity). The electric actuator 100 mainly comprises an electric motor 10 and a linear motion unit consisting of a screw shaft 30, a linear bushing shaft 40, and a slider 50 arranged within the base portion 20, as shown in Figure 2. The linear motion unit is a mechanical element that converts the rotational motion of the electric actuator 100 into linear motion, and the difference lies in whether or not its operation can be directly controlled by the electric motor 10. Therefore, the explanation of the electric actuator 100 will suffice for the explanation of the linear motion unit.

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

[0022] The base portion 20 consists of a long member having a hollow portion 25 inside, and has a base frame 26 (see Figure 4) having a linear bush shaft 40, and a screw shaft 30 connected to an electric motor 10 located inside the base frame 26, with a slider 50 positioned inside.

[0023] The screw shaft 30 is a threaded shaft used to move 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 along the entire length of the base portion 20 of the electric actuator 100 in the longitudinal direction (front-to-back direction). By rotating this screw shaft 30, the slider 50 can be moved in the front-to-back direction.

[0024] The linear bush shafts 40 are shafts positioned within the linear bush 60, and two of them are provided along the longitudinal direction of the base portion 20. As shown in Figure 3, these linear bush shafts 40 are formed in a substantially cylindrical shape, and each side is connected along 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 bush shafts 40 are rod-shaped and hollow without the connecting portion 45.

[0025] As shown in Figure 3, the slider 50 is positioned such that a gap is formed between it and the inner wall of the hollow portion 25 of the base frame 26, and is slidably positioned back and forth within the hollow portion 25. As shown in Figure 5, the slider 50 includes a nut portion 52 (the threading groove is omitted) that screws onto the screw shaft 30, left and right linear bushes 60 formed to accommodate the aforementioned linear bush shaft 40, 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 Figure 6, the linear bushes 60 are attached to linear bush mounting holes 54 provided in the slider body 59, into which the linear bushes 60 can be press-fitted. Between the left and right linear bushes 60, there is a slit 55 that can be slightly widened by press-fitting an adjustment member 70. As shown in Figure 6, it is preferable that the slit 55 is provided in communication from the nut portion 52 to the bottom surface, but it is not necessary that it is provided in communication with the nut portion 52. The shape of the adjustment member 70 is preferably a frustoconical shape with a taper, as shown in Figure 6, but it is not limited to this. As long as it is formed in a tapered shape with a narrow tip, such as a flat plate shape with a taper, as shown in Figure 7, and can widen the slit 55 by press-fitting, it is not particularly limited. The slit 55 should be provided with a press-fit hole 57 that can contact the side surface of the adjustment member 70, as shown in Figure 6. That is, the press-fit hole 57 should be formed to have the same taper angle as the taper of the adjustment member 70, so that the force does not concentrate at one point by contacting the adjustment member 70 with a surface. As shown in Figure 8, such a press-fit hole 57 is formed so that the adjustment member 70 can be press-fitted from the front and back. The initial spacing of the linear bushings 60 should be made slightly narrower than the appropriate spacing (spacing that allows smooth movement without rattle during sliding), assuming that the adjustment member 70 will widen the spacing between the left and right linear bushings 60. By manufacturing in this way, if the parts are manufactured at predetermined intervals from the start, manufacturing errors may cause the intervals to widen, potentially leading to overlaps that make sliding difficult or adjustment impossible. This method helps to avoid such problems.The slider 50 thus manufactured is placed in the hollow section 25 as shown in Figure 3, with the screw shaft 30 inserted through the nut section 52 and the linear bush shaft 40 inserted through the linear bush 60.

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

[0027] The linear bush 60 is a bearing for a linear motion member, and in this embodiment, an open-type linear bush 60 having at least three rows of balls is used. The linear bush 60 has a cylindrical cross-section with an opening 64 for passing the connecting portion 45 of the linear bush shaft 40. As shown in Figure 5, the linear bush 60 includes a left-side linear bush 60a positioned so that the opening 64 opens to the left with respect to the slider 50, and a right-side linear bush 60b positioned so that the opening 64 opens to the right. Furthermore, the linear bush shaft 40 is inserted into each linear bush 60, and a connecting portion 45 connecting the linear bush shaft 40 and the base portion 20 is provided so as to be positioned in the opening 64.

[0028] As shown in Figure 3, the linear bush 60 has at least three rows of balls 61. Preferably, at least one or both of the three rows of balls 61 in the left linear bush 60a or the right linear bush 60b are arranged as follows. 1. The three rows of balls in the left linear bush 60a are arranged as follows: - A position above the cross-sectional center of the linear bush 60 where the angle A1 between the vertical direction V1 of the cross-sectional center and the center of the ball 61 is within the range of 15° to 25° (upper ball row 61a). - A position below the cross-sectional center of the linear bush 60 where the angle A2 between the vertical direction V1 of the cross-sectional center and the center of the ball 61 is within the range of 15° to 25° (lower ball row 61b). • A position to the right of the cross-sectional center of the linear bush, where the angle A3 between the horizontal H1 of the cross-sectional center of the linear bush 60 and the center of the ball 61 is within the range of 0° to 25° upwards (the central ball row 61c). 2. The three rows of balls in the right-side linear bushing 60b are arranged symmetrically with respect to the perpendicular line V3 to the center of the slider cross-section, compared to the case of the left-side linear bushing. Specifically, they are arranged as follows: • A position above the cross-sectional center of the linear bush 60 where the angle A4 between the vertical direction V2 of the cross-sectional center and the center of the ball 61 is within the range of 15° to 25° (upper row of balls). • A position below the cross-sectional center of the linear bush 60 where the angle A5 between the vertical direction V2 of the cross-sectional center and the center of the ball 61 is within the range of 15° to 25° (lower ball row). • A position to the left of the cross-sectional center of the linear bush, where the angle A6 between the horizontal H1 of the cross-sectional center of the linear bush 60 and the center of the ball 61 is within the range of 0° to 25° upwards (the central row of balls).

[0029] As described above, by arranging the three rows of balls 61, for example, when the left linear bush 60a is arranged as described above, the linear bush shaft 40 is pressed toward the center perpendicular V3 of the slider cross-section (right side in Figure 3) by the upper row of balls 61a and the lower row of balls 61b, and pressed toward the opposite wall surface (left wall surface in Figure 3) by the central row of balls 61c. This makes it easier to prevent horizontal rattle between the left linear bush 60a and the linear bush shaft 40.

[0030] In the linear motion unit manufactured as described above, when the slider 50 is attached to the base 20, the distance between the left and right linear bushings 60 is initially slightly narrow, resulting in a small gap on the inside between the left and right linear bushing shafts 40. By pressing the adjustment member 70 into the press-fit hole 57 of the slit 55 of the slider 50 in this state, the distance between the linear bushings 60 is widened to the optimal distance. This makes it possible to position the left and right linear bushings 60 in the optimal position and prevents rattling.

[0031] The electric actuator 100 manufactured as described above can be easily and quickly produced by using a commercially available linear bush 60 as a direct-acting guide. Furthermore, by using an open-type linear bush 60 and connecting the linear bush shaft 40 to the wall surface of the base portion 20, the load applied to the linear bush shaft 40 can be effectively resisted. In addition, by receiving 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, thereby increasing the rigidity of the table.

[0032] Furthermore, even with manufacturing methods that make it more difficult to achieve dimensional accuracy compared to machining, such as extrusion molding, pitch misalignment between the linear bush shafts 40 can be effectively prevented.

[0033] The electric actuator 100 described above can be used not only in factories but also as a seat rail for vehicles. [Industrial applicability]

[0034] As shown in the embodiments described above, it is industrially applicable as a seat rail device for vehicles. [Explanation of Symbols]

[0035] 10...Electric motor, 20...Base section, 21...Side wall, 22...Left inner wall, 25...Hollow section, 26...Base frame, 30...Screw shaft, 40...Linear bush shaft, 45...Connecting section, 50...Slider, 52...Nut section, 54...Linear bush mounting hole, 55...Slit, 57...Press-fit hole, 59...Slider body, 60...Linear bush, 60a...Left linear bush, 60b...Right linear bush, 61...Ball, 61a...Ball row, 61b...Ball row, 61c...Ball row, 64...Open section, 70...Adjustment member, 80...Table mounting section, 100...Electric actuator

Claims

1. A base portion formed in a cylindrical shape with the top open, having a screw shaft for a lead screw or ball screw connected to an electric motor, and two linear bushing shafts, each having a connecting portion connected to the left wall or the right wall, A slider having a screw hole that engages with the screw shaft, left and right linear bushings attached to the two linear bushing shafts, and a slider body having left and right linear bushing mounting holes to which the linear bushings are respectively attached, Equipped with, The linear motion unit is characterized in that the slider body has a slit provided between the left and right linear bushings, and an adjustment member for adjusting the distance between the left and right linear bushings is press-fitted into the slit.

2. The linear motion unit according to claim 1, characterized in that the slit is provided in communication from the screw hole to the bottom surface.

3. The linear motion unit according to claim 1, characterized in that the slit is provided with a press-fit hole for press-fitting an adjustment member.

4. The linear motion unit according to claim 3, characterized in that the press-fit hole has a circular cross-section and is tapered so that the inner diameter decreases towards the back, and the adjustment member is manufactured in the shape of a frustoconical shape formed along the taper of the press-fit hole.

5. The linear motion unit according to claim 1, characterized in that the slider is manufactured in advance so that the distance between the left and right linear bushings is narrower than a predetermined position.

6. A linear motion unit according to any one of claims 1 to 5, An electric actuator characterized by comprising an electric motor as a driving source.

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