Electric actuator

Abstract

An electric actuator (10) comprises: an end plate (32) that covers an end portion of a ball screw (14); a housing (34) through which the ball screw (14) passes; and a top cover (18) that is attached to a first upper end surface (38) of the end plate (32) and a second upper end surface (40) of the housing (34) and covers the upper side of the ball screw (14). A total length (L) of the top cover (18) in a longitudinal direction is longer than a gap (G) between the end plate (32) and the housing (34) in the longitudinal direction, and is shorter than a dimension (A) obtained by adding a length (S2) of the second upper end surface (40) in the longitudinal direction and the gap (G).

Description

Electric Actuator

[0001] The present disclosure relates to an electric actuator.

[0002] Electric actuators are widely used in automated production lines in factories and the like to transport workpieces. For example, Japanese Patent Laid-Open Publication No. 8-33264 discloses an electric actuator that drives a table with a ball screw. In this electric actuator, a workpiece is attached to the table. Furthermore, to prevent foreign matter from getting caught in the ball screw, the ball screw is covered with a top cover.

[0003] When performing maintenance or troubleshooting on an electric actuator, the top cover may need to be removed from the housing for inspection. However, with conventional electric actuators, the top cover is covered by the workpiece. Therefore, removing the top cover requires removing the workpiece from the table, which is a cumbersome process.

[0004] An object of the present invention is to solve the above-mentioned problems.

[0005] One aspect of the present disclosure is an electric actuator having a ball screw extending in the longitudinal direction, a drive unit that rotates the ball screw, a table driven by the ball screw, an end plate that covers an end of the ball screw, a housing adjacent to the drive unit and through which the ball screw passes, and a top cover attached to a first upper end surface of the end plate and a second upper end surface of the housing and covering above the ball screw, wherein the total longitudinal length L of the top cover is longer than the longitudinal gap G between the end plate and the housing and shorter than a dimension A obtained by adding the longitudinal length S2 of the second upper end surface and the gap G.

[0006] The electric actuator of the above aspect allows the top cover to be removed without removing the workpiece from the table.

[0007] The above objects, features and advantages will be easily understood from the following description of the embodiments, which will be described with reference to the accompanying drawings.

[0008] FIG. 1 is a perspective view of an electric actuator according to an embodiment. FIG. 2 is a side view of the electric actuator of FIG. 1. FIG. 3 is a side view showing a modified example of the housing of FIG. 1. FIG. 4 is a diagram illustrating a method for removing the top cover of FIG. 1 by sliding it in a first direction. FIG. 5 is a diagram illustrating the removal direction when there is an obstacle in the first direction of the electric actuator of FIG. 1. FIG. 6 is an explanatory diagram illustrating an operation for removing the top cover of FIG. 5 from the end plate. FIG. 7 is an explanatory diagram illustrating an operation for pulling out the top cover of FIG. 6 at an angle. FIG. 8 is a perspective view of an electric actuator according to a modified example of the embodiment.

[0009] 1 and 2, an electric actuator 10 according to an embodiment is capable of high-speed and accurate operation and is therefore suitable for use in, for example, transporting wafers in a semiconductor manufacturing factory. The electric actuator 10 is used by attaching a workpiece W (see FIG. 4) to a table 16 having a pair of fixing portions 28. An example of the workpiece W is a chuck that holds a wafer.

[0010] The electric actuator 10 will be described in detail below. In the following description, the terms longitudinal direction, width direction, and up-down direction are used to describe the relative positions of the components of the electric actuator 10. These directions are perpendicular to one another. The longitudinal direction corresponds to the extension direction of the ball screw 14, and the direction away from the drive unit 12 is referred to as the first direction (tip direction), and the opposite direction is referred to as the second direction (proximal direction). In the up-down direction, the direction from the linear guide rail 30 toward the top cover 18 is referred to as the upper side or upward, and the opposite direction is referred to as the lower side or downward. Note that the terms up and down are used to describe the relative positions of the components of the electric actuator 10 and do not limit the orientation of the electric actuator 10.

[0011] The electric actuator 10 includes, as its main components, a drive unit 12, a ball screw 14, a table 16, and a top cover 18. The drive unit 12 has a motor 20 and a rotation transmission unit 22. The motor 20 rotates the ball screw 14. The rotation transmission unit 22 connects the rotating shaft of the motor 20 to the ball screw 14 and transmits the rotational motion of the motor 20 to the ball screw 14. The rotation transmission unit 22 has a box-shaped housing 22a. The housing 22a is formed, for example, from a transparent resin member and is configured so that the internal state can be visually confirmed from the outside. The rotation transmission unit 22 may have a built-in reduction gear, etc., as necessary. The housing 22a may protrude above the top cover 18.

[0012] The ball screw 14 extends in the longitudinal direction. The end of the ball screw 14 in the second direction is inserted into the rotation transmitting part 22 and is rotated by the rotation transmitting part 22. A screw groove is formed on the outer circumferential surface of the ball screw 14. A table 16 is threadedly engaged with the ball screw 14.

[0013] The table 16 engages with linear guide rails 30 that cover the bottom and sides of the ball screw 14. The linear guide rails 30 extend in the longitudinal direction. The table 16 slides in the longitudinal direction while being guided by the linear guide rails 30. The table 16 has a pair of fixing portions 28 on both sides in the width direction. The pair of fixing portions 28 are spaced apart in the width direction. The fixing portions 28 are provided with fixing holes 28a for fixing, for example, a workpiece W (see FIG. 4). The workpiece W is fixed so that it spans the pair of fixing portions 28.

[0014] An end plate 32 is joined to the end of the linear guide rail 30 in the first direction, and a housing 34 is joined to the end of the linear guide rail 30 in the second direction. The end plate 32 is a plate-shaped member along a plane perpendicular to the longitudinal direction, and covers the end of the ball screw 14 in the first direction (the direction away from the drive unit 12). The end plate 32 rotatably supports the end of the ball screw 14 via a bearing or the like (not shown).

[0015] The end plate 32 has a first upper end surface 38 at its upper end. The first upper end surface 38 is a smooth surface without any protruding parts extending upward, and supports the top cover 18 so that it can slide in the longitudinal direction. The first upper end surface 38 is formed over a range from the end of the end plate 32 in the first direction to the end of the end plate 32 in the second direction.

[0016] The first upper end surface 38 has a top surface 38a and a pair of side surfaces 38b. The top surface 38a is formed as a flat surface parallel to the longitudinal and width directions. The side surfaces 38b are located on both sides of the top surface 38a and extend at an angle relative to the top surface 38a. The top surface 38a and the side surfaces 38b face the cover plate 46 and the side wall 48 of the top cover 18, respectively. The end plate 32 has screw holes at predetermined positions on the top surface 38a for fastening fixing members 44 such as screws or bolts. The top cover 18 is fixed to the first upper end surface 38 by the fixing members 44.

[0017] The housing 34 is located between the linear guide rail 30 and the drive unit 12 and is adjacent to the drive unit 12. The ball screw 14 extends in the second direction through the housing 34. The housing 34 rotatably supports the ball screw 14 via a bearing or other bearing member.

[0018] The housing 34 further has a second top surface 40 and a protrusion 42. The second top surface 40 is formed at the upper end of the housing 34. The second top surface 40 has a top surface 40a and a pair of side surfaces 40b. The top surface 40a is formed as a flat surface parallel to the longitudinal and width directions and is sandwiched between the pair of side surfaces 40b. The side surfaces 40b are located on both sides of the top surface 40a and extend at an inclination in the vertical direction relative to the top surface 40a. The top surface 40a and the side surfaces 40b face the inner surface of the top cover 18. The housing 34 has screw holes at predetermined positions on the top surface 40a for fastening fixing members 44, such as screws or bolts, that secure the top cover 18. The second top surface 40 is formed as a smooth surface without any protrusions protruding upward, and supports the top cover 18 so that it can slide longitudinally. The second upper end surface 40 is formed over a range from the end of the housing 34 in the first direction to the protruding portion 42. The length S2 of the second upper end surface 40 in the longitudinal direction is longer than the length S1 of the first upper end surface 38 of the end plate 32 in the longitudinal direction.

[0019] The protrusion 42 is located near the end of the housing 34 in the second direction and protrudes above the second upper end surface 40. The protrusion 42 is adjacent to the drive unit 12 and abuts against the rotation transmission unit 22 of the drive unit 12. The second upper end surface 40 extends in the second direction to a portion reaching the protrusion 42. The longitudinal length S2 of the second upper end surface 40 is the longitudinal length from the end of the housing 34 in the first direction to the boundary between the second upper end surface 40 and the protrusion 42. Note that, as shown in FIG. 3 , a housing 34A according to another embodiment may not have the protrusion 42. In this case, in the housing 34A, the second upper end surface 40 extends to the end of the housing 34 in the second direction. The longitudinal length S2 of the second upper end surface 40 in FIG. 3 is the longitudinal distance from the end of the housing 34 in the first direction to the boundary between the second upper end surface 40 and the drive unit 12.

[0020] 1 and 2, the top cover 18 is a plate-shaped member extending in the longitudinal direction and covering the upper side of the ball screw 14. The top cover 18 has a cover plate portion 46 and a pair of side wall portions 48. The cover plate portion 46 is formed as a flat surface parallel to the width direction and the longitudinal direction. The side wall portions 48 are provided on both sides of the cover plate portion 46 in the width direction and extend downward from the cover plate portion 46. The lower surface of the cover plate portion 46 faces the top surfaces 38a, 40a, and the insides of the side wall portions 48 face the side surface portions 38b, 40b.

[0021] 2 , the end of the top cover 18 in the first direction is placed on the first upper end surface 38 of the end plate 32 and is fixed to the end plate 32 by a fixing member 44 so as to cover the first upper end surface 38. The end of the top cover 18 in the second direction is placed on the second upper end surface 40 of the housing 34 and is fixed to the housing 34 by the fixing member 44 so as to cover the second upper end surface 40. By removing the fixing member 44, the top cover 18 is released from the end plate 32 and the housing 34.

[0022] The length from the end of the top cover 18 in the first direction to the end of the top cover 18 in the second direction is referred to in this specification as the total longitudinal length L of the top cover 18. The total longitudinal length L of the top cover 18 is longer than the longitudinal gap G between the end plate 32 and the housing 34. The total longitudinal length L of the top cover 18 is also shorter than the dimension A obtained by adding the longitudinal length S2 of the second upper end surface 40 of the housing 34 and the gap G. When the top cover 18 is fixed with the fixing member 44, the end of the top cover 18 in the second direction is spaced apart from the protrusion 42 in the longitudinal direction.

[0023] The electric actuator 10 of this embodiment is configured as described above. The operation of the electric actuator 10 will now be described.

[0024] As shown in Figure 4, the electric actuator 10 is used with a workpiece W attached to the fixed portion 28 of the table 16. To remove the top cover 18, the fixing member 44 is removed to release the fixed state of the top cover 18. Then, as shown in the figure, an operation is performed to slide the top cover 18 in a first longitudinal direction. This causes the top cover 18 to slide longitudinally under the workpiece W, and the top cover 18 can be removed without removing the workpiece W from the table 16.

[0025] As shown in Figure 5, depending on the placement position of the electric actuator 10, an obstacle 50 may be present adjacent to the electric actuator 10 in the first direction. In such a case, it is not possible to slide the top cover 18 in the first direction as shown in Figure 4. Furthermore, because the top cover 18 interferes with the drive unit 12 located in the second direction, the top cover 18 cannot be removed by simply sliding it in the second direction.

[0026] 5, the top cover 18 is removed by the following operations. First, as shown in the figure, the table 16 is moved in a first direction to displace the table 16 to a position as close as possible to the end plate 32. Next, all of the fixing members 44 that fix the top cover 18 are removed.

[0027] Next, the top cover 18 is slid in the second direction. The sliding of the top cover 18 in the second direction is restricted by the protrusion 42. However, the overall length L of the top cover 18 is shorter than the dimension A obtained by adding the longitudinal length S2 of the second upper end surface 40 of the housing 34 and the gap G (see FIG. 2 ). Therefore, as shown in FIG. 6 , before the sliding of the top cover 18 in the second direction is restricted by the protrusion 42, the end of the top cover 18 in the first direction comes off the end plate 32 and falls toward the ball screw 14. As a result, the top cover 18 is tilted so that the end in the first direction is lower and the end in the second direction is higher.

[0028] As a result, the gap between the top cover 18 and the workpiece W in the vertical direction widens, and an extension line 52 of the top cover 18 (an extension line of the lower end of the side wall portion 48) extends diagonally upward. By using the gap between the top cover 18 and the workpiece W to further lift the end of the top cover 18 in the second direction upward, the extension line 52 of the top cover 18 passes above the drive unit 12 as shown in the figure. Thereafter, as shown in Figure 7, an operation is performed to pull out the top cover 18 along the extension line 52 while maintaining the inclination of Figure 6, and the top cover 18 is removed without removing the workpiece W from the table 16.

[0029] (Modification of the embodiment) In the illustrated example of the above embodiment, the drive unit 12 is arranged with the motor 20 and the rotation transmission unit 22 aligned in the longitudinal direction, but the drive unit 12 of this embodiment is not limited to this arrangement.

[0030] As in the electric actuator 10A according to the modified example shown in FIG. 8 , the drive unit 12 may have a motor 20 disposed adjacent to a side portion of the ball screw 14 in the width direction. In this case, the rotational motion of the motor 20 is transmitted to the ball screw 14 by a rotation transmission unit 22A extending in the width direction. The rotation transmission unit 22A has a housing 22b extending in the width direction, and the housing 22b is disposed so as to cover the end of the motor 20 and the base end of the ball screw 14 from the second direction. The rotation transmission unit 22A transmits the rotational motion of the motor 20 to the ball screw 14 via an internal belt and pulley. The housing 22b is formed of a transparent resin and configured so that its interior can be seen from the outside. The other configurations of the electric actuator 10A are similar to those of the electric actuator 10 shown in FIG. 1 , and therefore detailed description thereof will be omitted.

[0031] The following additional notes are further disclosed regarding the above embodiment.

[0032] (Supplementary Note 1) The electric actuator (10) of the present disclosure includes a ball screw (14) extending in the longitudinal direction, a drive unit (12) that rotates the ball screw, a table (16) that is driven by the ball screw, an end plate (32) that covers an end of the ball screw, a housing (34) that is adjacent to the drive unit and through which the ball screw passes, and a top cover (18) that is attached to a first upper end surface (38) of the end plate and a second upper end surface (40) of the housing and covers above the ball screw, and the total longitudinal length (L) of the top cover is longer than the longitudinal gap (G) between the end plate and the housing and is shorter than a dimension (A) obtained by adding the longitudinal length (S2) of the second upper end surface and the gap (G).

[0033] The above-described electric actuator allows the top cover to be slid and removed from either the first direction or the second direction in the longitudinal direction without removing the workpiece from the table.

[0034] (Supplementary Note 2) The electric actuator according to Supplementary Note 1 may further include a fixing member (44) that fixes the top cover to the end plate and the housing, and the top cover fixed by the fixing member may be spaced apart from the drive unit in the longitudinal direction. By sliding the top cover toward the drive unit, the electric actuator can detach the end of the top cover in the first direction from the end plate and drop it.

[0035] (Supplementary Note 3) In the electric actuator according to Supplementary Note 2, the first upper end surface of the end plate and the second upper end surface of the housing may support the top cover so that the top cover is slidable in the longitudinal direction. This electric actuator enables smooth removal of the top cover.

[0036] (Supplementary Note 4) In the electric actuator described in Supplementary Note 3, the length (S2) of the second upper end surface in the longitudinal direction may be longer than the length (S1) of the first upper end surface in the longitudinal direction. This electric actuator can increase the range over which the top cover can slide in the second direction, making it possible to more reliably remove the top cover.

[0037] (Supplementary Note 5) In the electric actuator according to Supplementary Note 3 or 4, when the fixing member is removed and the top cover is slid toward the drive unit, the top cover may come off the end plate and fall toward the ball screw, causing it to tilt. By sliding the top cover while tilting it, this electric actuator makes it possible to remove the top cover even when there is an obstacle nearby.

[0038] (Supplementary Note 6) In the electric actuator according to Supplementary Note 5, the drive unit may protrude above the second upper end surface of the housing, and an extension line (52) of the inclined top cover may pass above the drive unit. This electric actuator allows the top cover to be removed without being obstructed by the drive unit by sliding the top cover while tilting it.

[0039] (Supplementary Note 7) In the electric actuator described in Supplementary Note 6, the top cover may include a cover plate portion (46) parallel to the linear guide rail (30) and a pair of side wall portions (48) protruding downward from both widthwise sides of the cover plate portion, and the first upper end surface of the end plate and the second upper end surface of the housing may each have a top surface (38a, 40a) facing the cover plate portion and a pair of side surface portions (38b, 40b) facing from the inside to the pair of side wall portions. This electric actuator allows the top cover to be removed while preventing displacement of the top cover in the widthwise direction, making it even easier to attach and detach the top cover.

[0040] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

Claims

1. An electric actuator (10) comprising: a ball screw (14) extending in the longitudinal direction; a drive unit (12) that rotates the ball screw; a table (16) driven by the ball screw; an end plate (32) that covers an end of the ball screw; a housing (34) adjacent to the drive unit and through which the ball screw passes; and a top cover (18) attached to a first upper end surface (38) of the end plate and a second upper end surface (40) of the housing and covering above the ball screw, wherein the total longitudinal length (L) of the top cover is longer than the longitudinal gap (G) between the end plate and the housing and shorter than a dimension (A) obtained by adding the longitudinal length (S2) of the second upper end surface and the gap.

2. An electric actuator according to claim 1, further comprising a fixing member (44) for fixing the top cover to the end plate and the housing, and the top cover fixed by the fixing member is spaced apart from the drive unit in the longitudinal direction.

3. An electric actuator according to claim 2, wherein the first upper end surface of the end plate and the second upper end surface of the housing support the top cover so that the top cover can slide in the longitudinal direction.

4. An electric actuator according to claim 3, wherein the length (S2) of the second upper end surface in the longitudinal direction is longer than the length (S1) of the first upper end surface in the longitudinal direction.

5. An electric actuator according to claim 3 or 4, wherein when the fixing member is removed and the top cover is slid toward the drive unit, the top cover comes off the end plate, drops toward the ball screw, and tilts.

6. An electric actuator as set forth in claim 5, wherein the drive unit protrudes above the second upper end surface of the housing, and an extension line (52) of the inclined top cover passes above the drive unit.

7. An electric actuator as set forth in claim 6, wherein the top cover comprises a cover plate portion (46) parallel to the linear guide rail (30) and a pair of side wall portions (48) protruding downward from both widthwise sides of the cover plate portion, and the first upper end surface of the end plate and the second upper end surface of the housing each have a top surface (38a, 40a) facing the cover plate portion and a pair of side surfaces (38b, 40b) facing the pair of side wall portions from the inside.

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