JP6752663B2 - Electric actuator - Google Patents

Description

The present invention relates to an electric actuator.

In recent years, electrification has been progressing for the purpose of labor saving and fuel efficiency of vehicles, etc. For example, a system that operates automatic transmissions, brakes, steering, etc. of automobiles by the power of a motor has been developed and put on the market. Has been done. As an actuator used for such an application, an electric actuator using a ball screw mechanism that converts a rotary motion generated by driving a motor into a linear motion is known.

Further, among the actuators using the ball screw mechanism, when considering that a motor having as small an output as possible obtains a predetermined output, a configuration in which the motor and the ball screw mechanism are arranged in series is preferable (for example, Patent Document 1). See). In such a configuration, in order to move the screw shaft of the ball screw mechanism in the axial direction, it is conceivable to directly connect the motor and the nut of the ball screw mechanism and support the nut rotatably with a bearing ( For example, see Patent Document 2).

Japanese Unexamined Patent Publication No. 2009-156415 Japanese Unexamined Patent Publication No. 2013-234735

When adopting a structure that rotatably supports the nut of the ball screw mechanism, as described in Patent Document 2, rolling bearings that rotatably support the nut are arranged at two locations separated in the center line direction. The configuration is preferable. However, the actuator described in Patent Document 2 has a structure in which the screw shafts protrude on both sides in the center line direction of the nut, so that the case accommodating the ball screw mechanism including the nut is divided into a plurality of cases. I'm taking it. Therefore, two rolling bearings that rotatably support the nut are attached to separate cases. In this case, the center of rotation of each bearing shifts due to an error when assembling the cases, and the center of rotation of the nut supported by these bearings shifts or tilts with respect to the center line of the screw shaft. There is a risk of becoming. When the actuator is driven with the nut portion displaced or tilted with respect to the screw shaft in this way, the power transmission efficiency of the ball screw mechanism is reduced by the above-mentioned deviation or inclination, and in some cases ( (If the tilt is severe), the nut may be locked to the screw shaft and smooth linear motion may not be possible.

In view of the above circumstances, the present specification solves the problem of providing an electric actuator capable of obtaining excellent power transmission efficiency by suppressing the misalignment and inclination of the rotating portion with respect to the linear moving portion as much as possible. It should be a technical issue.

The solution to the above problems is achieved by the electric actuator according to the present invention. That is, this actuator includes a motor, a motion conversion mechanism for converting rotational motion generated by driving the motor into linear motion, and a case in which the motion conversion mechanism is housed. The motion conversion mechanism includes a linear motion unit and a linear motion unit. In an electric actuator having a rotating portion arranged on the outer periphery of the moving portion, the rotating portion is supported by two bearings arranged apart from each other in the direction of the center line, and the two bearings are inside the case. It is characterized by the fact that it is attached to a cylindrical surface with a constant inner diameter provided on the circumference.

As described above, in the present invention, the rotating portion of the motion conversion mechanism is supported by two bearings, and the two bearings are provided on the inner circumference of the case accommodating the motion conversion mechanism with a constant inner diameter. I tried to attach it to the cylindrical surface. By providing the mounting surfaces of the two bearings in one case in this way, it is possible to avoid being affected by an assembly error or the like as compared with the case where the bearings are mounted across a plurality of cases. Furthermore, since the mounting surfaces of the two bearings are both equal-diameter cylindrical surfaces with constant inner diameter dimensions, compared to the case where two surfaces with different inner diameter dimensions are used as bearing mounting surfaces, for example, through a step. The shape accuracy (machining accuracy) of the mounting surface can be easily improved. Therefore, it is possible to match the rotation centers of each bearing with high accuracy and prevent the rotation center of the rotating portion supported by these bearings from shifting or tilting with respect to the center line of the linear motion portion as much as possible. Alternatively, the above-mentioned deviation and inclination can be suppressed as small as possible. This makes it possible to efficiently transmit the driving force transmitted from the motor to the rotating portion to the linear moving portion. Further, by improving the position accuracy of the linear motion portion, it is possible to control the actuator with high accuracy.

Further, in the electric actuator according to the present invention, the case may have a metal tubular member integrally, and an equal-diameter cylindrical surface may be provided on the inner circumference of the tubular member.

The case of this type of actuator cannot usually have a simple cylindrical shape for accommodating a motion conversion mechanism such as a ball screw mechanism, and has to have a complicated shape other than the cylindrical shape. The more complicated the shape of the case, the more difficult it is to process the inner peripheral surface, and it is difficult to finish the mounting surface into an equal-diameter cylindrical shape. On the other hand, if an equal-diameter cylindrical surface to be a mounting surface is provided on the tubular member and the tubular member is provided integrally with the case, the bearing mounting surface can be provided without being affected by the shape of the case. It can be finished in an equal diameter cylindrical shape. Further, by making this tubular member made of metal, deformation due to press-fitting or the like can be minimized, and the shape accuracy of the mounting surface (equal diameter cylindrical surface) after mounting the bearing can be maintained. At the same time, the material of the case body can be made of resin, which is more mass-producible. Therefore, it is suitable not only in terms of position accuracy but also in terms of processing cost.

Further, in the electric actuator according to the present invention, the case has a small diameter portion having an inner diameter smaller than that of the equal diameter cylindrical surface on one side of the equal diameter cylindrical surface in the axial direction, and moves linearly on the inner circumference of the small diameter portion. A sliding surface on which the portion can slide may be provided.

By providing the case with a small diameter portion and providing a sliding surface of the linear motion portion on the inner circumference of the small diameter portion in this way, the support portion (bearing) of the rotating portion and the linear motion portion can be provided in one component (case). A support portion (sliding surface) can be provided. As a result, the center of rotation of the rotating part and the center line of the linearly moving part can be aligned with higher accuracy than when each support part is provided in a separate case, so that the sliding resistance during linear motion can be matched. Can be further reduced to further improve the power transmission efficiency.

When the case has a tubular member, the electric actuator according to the present invention has an end face support portion in which the tubular member projects inward in the radial direction from one side in the axial direction to support the axial end surface of the bearing. It may be a thing.

Since the rotating portion is supported by two bearings, the movement of the rotating portion in the axial direction (direction along the rotation center line) is restricted by providing an end face support portion that supports at least one bearing in the axial direction. be able to. Further, at this time, by providing the end face support portion of the bearing together with the cylindrical surface having the same diameter in one component (cylindrical member), not only the positioning in the radial direction of the bearing but also the positioning in the axial direction can be performed with high accuracy. Therefore, it is possible to improve the positional accuracy of the rotating portion supported by the bearing in the radial direction and the axial direction.

When the case has a small diameter portion, the small diameter portion of the electric actuator according to the present invention is composed of a sliding bearing made of sintered metal, and the case uses both the sliding bearing and the tubular member as insert parts. It may be a resin molded product.

When the small diameter portion is a sintered metal slide bearing as described above, for example, the slide bearing is impregnated with a lubricant such as lubricating oil or grease to further enhance the sliding lubricity with the linear motion portion. be able to. Therefore, it is possible to further reduce the sliding resistance. Further, by molding the case with resin by using both the slide bearing and the tubular member as insert parts, it is possible to make only the portion where shape accuracy (rigidity) is particularly required to be made of metal and the remaining portion to be made of resin. Therefore, the weight of the entire case that can exhibit the above-mentioned excellent performance can be reduced. Of course, it is also preferable that the center line between the sliding surface and the cylindrical surface having the same diameter can be easily and accurately aligned by accurately positioning each insert component on the insert mold.

Further, in the electric actuator according to the present invention, one or more flat surfaces whose sliding surfaces form a part in the circumferential direction, and a partial cylindrical surface which is connected to the flat surface and forms the rest in the circumferential direction. Of the outer peripheral surface of the linear motion portion, at least the region that slides with the sliding surface has a shape corresponding to the flat surface and the partially cylindrical surface constituting the sliding surface. May be good.

In this way, the shape of the sliding surface is made non-circular in cross section, and the shape of the region that slides with the sliding surface in the outer peripheral surface of the linear motion portion is made a shape corresponding to the sliding surface. The rotation around the center line of the linear motion portion can be regulated by the sliding surface. Therefore, it is possible to support the linearly moving portion freely in a linear motion while preventing the linearly moving portion from rotating only by the sliding surface.

As described above, according to the electric actuator according to the present invention, it is possible to obtain excellent power transmission efficiency by suppressing the misalignment and inclination of the rotating portion with respect to the linearly moving portion as much as possible.

It is a vertical sectional view of the electric actuator which concerns on 1st Embodiment of this invention. It is an external perspective view of the electric actuator shown in FIG. It is a partially disassembled perspective view of the electric actuator shown in FIG. It is a cross-sectional view of the electric actuator seen from the direction of arrow A in the cross section along the line AA of FIG. It is a partially disassembled perspective view of the electric actuator shown in FIG. It is a cross-sectional view of the electric actuator which looked at the cross section along the line BB of FIG. 1 from the direction of arrow B. It is an exploded perspective view of the ball screw shaft with a permanent magnet attached. It is a vertical sectional view of the electric actuator which concerns on 2nd Embodiment of this invention. It is a partially disassembled perspective view of the electric actuator shown in FIG. It is a vertical sectional view of the electric actuator which concerns on 3rd Embodiment of this invention. It is a partially disassembled perspective view of the electric actuator shown in FIG. FIG. 11 is a partially exploded perspective view of the electric actuator whose perspective direction is changed.

Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 7. In each drawing, substantially the same elements are designated by the same reference numerals as much as possible, and the detailed description thereof will be omitted after the description once. The same applies to the description of the second and subsequent embodiments of the present invention, which will be described later.

FIG. 1 shows a vertical sectional view of an electric actuator according to the first embodiment of the present invention. 2 is an external perspective view of the electric actuator shown in FIG. 1, and FIG. 3 is a partially exploded perspective view of the electric actuator shown in FIG. 1.

As shown in FIG. 1, the electric actuator 1 according to the present embodiment includes a drive unit 2 that generates a driving force, a motion conversion mechanism unit 3 that converts a rotational motion from the drive unit 2 into a linear motion, and a drive unit 2. The driving force transmission unit 4 that transmits the driving force from the motion conversion mechanism unit 3, the motion conversion mechanism support unit 5 that supports the motion conversion mechanism unit 3, and the operation unit 6 that outputs the motion of the motion conversion mechanism unit 3 Be prepared. In the present embodiment, the drive unit 2 has a motor for generating a driving force (driving motor 7), and the driving force transmitting unit 4 transmits the driving force received from the driving unit 2 to the motion conversion mechanism unit 3. It has a deceleration mechanism unit 8 as a force transmission mechanism.

Further, each element of the electric actuator 1 described above has a plurality of cases constituting the appearance of the electric actuator 1 (see FIG. 2). Specifically, the drive unit 2 has a motor cover 9 as a motor case for accommodating the drive motor 7, and the drive force transmission unit 4 is a speed reduction mechanism unit 8 (to be exact, a part of the speed reduction mechanism unit 8). Has a deceleration mechanism case 10 for accommodating. Further, the motion conversion mechanism unit 3 has a ball screw case 12 that houses the ball screw mechanism 11 as the motion conversion mechanism. The ball screw case 12 also serves as a case for accommodating the bearings 13 and 14 constituting the motion conversion mechanism support portion 5. In the present embodiment, the driving unit 2, the driving force transmitting unit 4, and the motion conversion mechanism unit 3 are configured to be connected and separated from each other for each case. Hereinafter, details of each element constituting the electric actuator 1 will be described.

The drive unit 2 mainly has a drive motor 7 such as a DC motor and a motor cover 9 that houses the drive motor 7. The motor cover 9 includes a bottomed cylindrical cover body 15 that covers the periphery of the drive motor 7, and a flange portion 16 that protrudes outward in the radial direction from one end opening side (left side in FIG. 1) of the cover body 15. Has.

The drive motor 7 is in a state of being inserted into the cover body 15 from one end opening side. At this time, the inner peripheral surface 15a of the cover body 15 is tapered in diameter from the opening side to the back side, and when the drive motor 7 is inserted into the cover body 15, the drive motor 7 The back side in the insertion direction is configured to come into contact with the inner peripheral surface 15a of the cover body 15 in a state of avoiding surface contact. On the other hand, a motor fitting portion 17 described later is fitted to the protrusion 7a on the output side (left side in FIG. 1) of the drive motor 7 with a predetermined fitting (for example, inlay). The drive motor 7 is supported by the cover main body 15 and the motor fitting portion 17 in a state of being housed in the cover main body 15. In the present embodiment, the O-ring 18 is interposed between the drive motor 7 and the inner bottom surface 15b of the cover body 15, and the output shaft of the drive motor 7 is suppressed while suppressing rattling in the axial direction of the motor. It prevents the outflow of grease and the like from 7b.

Further, as shown in FIG. 4, the drive motor 7 is provided with a pair of terminals 19 and 19 for connecting the drive motor 7 to the power source. One end 19a of each terminal 19 is connected by inserting it into the terminal insertion groove 7c of the drive motor 7, and the other end 19b is electrically connected to an external power source by crimping an electric wire (not shown) by crimping. ing. The pair of terminals 19 and 19 are held by a terminal holder 20 that can be fitted to the outer circumference of the drive motor 7 (see FIGS. 3 and 4), thereby retaining the drive motor 7 from the drive motor 7. There is. Further, a grommet 21 is fitted in the hole 15c provided at the bottom of the cover main body 15 (see FIGS. 1 and 3), and is shown through a pair of holes 21a and 21a provided in the grommet 21. It is possible to pull out the electric wire that does not.

As shown in FIG. 1, the driving force transmitting unit 4 is mainly composed of a deceleration mechanism unit 8 as a driving force transmission mechanism and a deceleration mechanism case 10 accommodating the deceleration mechanism unit 8. The speed reduction mechanism unit 8 is composed of, for example, a planetary gear speed reduction mechanism 22 composed of a plurality of gears or the like. The detailed configuration of the planetary gear reduction mechanism 22 will be described later.

As shown in FIG. 3, the speed reduction mechanism case 10 is fitted with the case body 23, which is generally tubular, and the ball screw case 12 projecting from the case body 23 to one end side in the axial direction (left side in FIG. 1). The screw case fitting portion 24 protrudes inward in the radial direction from the other end side (right side in FIG. 1) of the case body 23 in the axial direction, and has a predetermined fit (for example, inlay) with the protrusion 7a of the drive motor 7. It integrally has a motor fitting portion 17 that fits. In the case of adopting the above configuration, by attaching the speed reduction mechanism case 10 to the ball screw case 12 as shown in FIG. 1, the screw case fitting portion 24 of the speed reduction mechanism case 10 is housed in the ball screw case 12. Further, by attaching the motor cover 9 to the speed reduction mechanism case 10, a part of the case body 23 of the speed reduction mechanism case 10 and the motor fitting portion 17 are housed in the motor cover 9. As described above, when the screw case fitting portion 24 and the motor fitting portion 17 are integrally provided in the reduction mechanism case 10, the drive motor 7, the reduction mechanism portion 8, and the motion conversion mechanism (ball screw mechanism) described later are provided. Since 11) and 11) are arranged in series, it is preferable that the center line of the screw case fitting portion 24 and the center line of the fitting hole 17a of the motor fitting portion 17 coincide with each other. By fixing the protrusion 7a of the drive motor 7 to the motor fitting portion 17, the center line of the fitting hole 17a of the motor fitting portion 17 and the rotation center line X of the drive motor 7 (see FIG. 1). It becomes possible to match with high accuracy, and by extension, the rotation center line X of the drive motor 7 and the rotation center of the ball screw nut 30 are aligned by a common mounting surface (equal diameter cylindrical surface 37) described later. Is possible.

Further, in the present embodiment, the speed reduction mechanism case 10 integrally has a flange portion 25 extending outward in the radial direction from the case main body 23, and the flange portion 25, the flange portion 16 of the motor cover 9, and the flange portion 16 described later will be described later. The flange portion 26 of the ball screw case 12 is overlapped with each other and is connected to each other by, for example, a bolt 27 (see FIG. 3). At this time, O-rings 28 and 29 (see FIGS. 1 and 3) may be interposed between the flange portions 16, 25 and 26.

As shown in FIG. 1, the motion conversion mechanism unit 3 has a ball screw mechanism 11 as a motion conversion mechanism and a ball screw case 12 accommodating the ball screw mechanism 11 in the present embodiment. Of these, the ball screw mechanism 11 includes a ball screw nut 30 as a rotating portion, a ball screw shaft 31 as a movable portion (that is, a linear moving portion) that moves linearly, a large number of balls 32, and a frame 33 as a circulating member. It is composed of. Spiral grooves 30a and 31a are formed on the inner peripheral surface of the ball screw nut 30 and the outer peripheral surface of the ball screw shaft 31, respectively. A ball 32 is filled between the spiral grooves 30a and 31a, and a frame 33 is incorporated, whereby two rows of balls 32 circulate.

The ball screw nut 30 receives a driving force generated by the driving motor 7 and rotates in either the forward or reverse direction. On the other hand, the rotation of the ball screw shaft 31 is restricted by a sliding surface 34 (the left end portion of the ball screw case 12 in FIG. 1) as a detent mechanism described later. Therefore, when the ball screw nut 30 rotates, the ball 32 circulates along the spiral grooves 30a, 31a and the frame 33, and the ball screw shaft 31 moves linearly (or reciprocating straight line) in one direction along the axial direction thereof. Exercise). FIG. 1 shows a state in which the ball screw shaft 31 is arranged at the initial position retracted to the rightmost side of the figure. The ball screw shaft 31 is arranged so as to be parallel to the output shaft 7b of the drive motor 7, and more specifically, the center lines of the shafts 31 and 7b coincide with each other, and the drive motor is provided via the drive force transmission unit 4. The rotational motion transmitted from No. 7 is converted into a linear motion in the axial direction parallel to the output shaft 7b by the ball screw shaft 31. In this case, the tip end portion (left end portion in FIG. 1) of the ball screw shaft 31 in the forward direction functions as an operation unit (actuator head) 6 for operating the operation target.

The ball screw case 12 is generally tubular (see FIG. 2), and is located on one end side (left side in FIG. 1) of the case body 35 and the case body 35 in the axial direction, and has an outer diameter dimension from the case body 35. It has a small diameter portion 36 having a small diameter, and a flange portion 26 located on, for example, the other end side (right side in FIG. 1) of the case body 35 in the axial direction. Further, between the ball screw case 12 and the ball screw nut 30 having the above configuration, two bearings 13 and 14 are arranged so as to be separated from each other in the center line direction (left-right direction in FIG. 1) of the case body 35. The ball screw nut 30 is rotatably supported by these two bearings 13 and 14. In the present embodiment, the two bearings 13 and 14 are both rolling bearings, and the outer rings 13a and 14a are both predetermined on an equal-diameter cylindrical surface 37 provided on the inner circumference of the case body 35 and having a constant inner diameter. They are fitted together (see Figure 1).

Further, the screw case fitting portion 24 protruding toward one end side in the axial direction (left side in FIG. 1) of the reduction mechanism case 10 is attached to the equal diameter cylindrical surface 37 with a predetermined fit (for example, spigot). .. As a result, the screw case fitting portion 24 and the two bearings 13 and 14 are both fixed to the ball screw case 12 in a centered state with reference to the uniform diameter cylindrical surface 37. The screw case fitting portion 24 is automatically attached by, for example, attaching the reduction mechanism case 10 to the ball screw case 12 by fastening bolts between the flange portions 25 and 26 (see FIG. 3).

In the present embodiment, the ball screw case 12 integrally has a metal tubular member 38. In this case, the equal-diameter cylindrical surface 37 is composed of the inner peripheral surface of the tubular member 38. Therefore, the inner peripheral surface of the tubular member 38 is in a state where the cylindricity and the like are finished with high accuracy. Further, the tubular member 38 integrally has an end face support portion 39 protruding inward in the radial direction from one end side in the axial direction (left side in FIG. 1) of the equal-diameter cylindrical surface 37. The inner side surface 39a of the end face support portion 39 is exposed in the inner space of the ball screw case 12, and the inner side surface 39a is one end side in the axial direction of the tubular member 38 of the two bearings 13 and 14 (FIG. 1). It is in contact with the bearing 13 located on the left side). Therefore, the bearing 13 is positioned in the axial direction with reference to the inner side surface 39a, and the bearing 13 is supported in the axial direction by the end face support portion 39.

A ball screw shaft 31 as a linear motion portion is inserted through the small diameter portion 36 (see FIG. 1). Further, a sliding surface 34 on which the ball screw shaft 31 can slide is provided on the inner circumference of the small diameter portion 36. In the present embodiment, the sliding bearing 40 made of sintered metal is provided on the inner peripheral portion of the tip of the small diameter portion 36, and the sliding surface 34 is formed on the inner peripheral circumference of the sliding bearing 40. The slide bearing 40 may be impregnated with a lubricant such as grease or lubricating oil to continuously supply the lubricant to the sliding surface 34.

Further, in the present embodiment, the sliding surface 34 is provided with a detent mechanism for the ball screw shaft 31. Specifically, as shown in FIGS. 1 and 5, the sliding surface 34 has one flat surface 34a forming a part in the circumferential direction and a partial cylinder connected to the flat surface 34a and forming the rest in the circumferential direction. It is composed of a surface 34b. Further, as shown in FIGS. 1 and 5, at least the sliding region 31b that slides with the sliding surface 34 of the outer peripheral surface of the ball screw shaft 31 is flat corresponding to the flat surface 34a constituting the sliding surface 34. It is composed of a surface portion 31b1 and a partial cylindrical surface portion 31b2 corresponding to the partial cylindrical surface 34b. In this case, the dimensions of the flat surface portions 31b1 of the ball screw shaft 31 are such that the flat surface portions 31b1 are in contact with (engage) with the flat surface 34a at least at the maximum outer diameter portion (boundary portion with the partial cylindrical surface portion 31b2). It is set. As a result, the flat surface 34a plays a role of restricting the rotation of the ball screw shaft 31 around the center line. The member indicated by reference numeral 41 in FIGS. 1 and 5 is a retaining ring, and by attaching the ball screw shaft 31 at a predetermined position in the axial direction, a member having a sliding surface 34 (here, a slide bearing 40) and an end surface thereof. By contacting each other, the ball screw shaft 31 plays a role of restricting the movement in the axial direction.

As described above, when the ball screw case 12 has the tubular member 38 and the slide bearing 40, the ball screw case 12 is, for example, a resin molded product in which both the tubular member 38 and the slide bearing 40 are insert parts. It is possible. At this time, for the purpose of accurately positioning the tubular member 38 in the axial direction, for example, as shown in FIGS. 1 and 5, even if the positioning hole 12a of the tubular member 38 is provided in the resin portion of the ball screw case 12. Good.

Any product can be used for the bearings 13 and 14, and for example, a rolling bearing such as a deep groove ball bearing can be preferably used. In the present embodiment, as shown in FIGS. 1 and 5, the ball screw nut 30 has a large diameter portion 30b at an intermediate position in the axial direction thereof, and two on both outer circumferences of the large diameter portion 30b. Two bearings (rolling bearings) 13 and 14 are attached. In this illustrated example, as the bearing 13 on the side closer to the operation unit 6 (the side far from the drive motor 7), a bearing 13 having both the outer ring 13a and the inner ring 13b is used, and the side far from the operation unit 6 (for drive). As the bearing 14 (on the side closer to the motor 7), a bearing 14 having only an outer ring 14a and no inner ring is used, but of course, the bearing 14 is not limited to this, and a bearing 14 having both an outer ring and an inner ring is used. You may.

Further, in the present embodiment, as shown in FIGS. 1 and 5, the bearing 13 on the side close to the operation portion 6 is axially supported by the end face support portion 39 of the tubular member 38 via the plate-shaped elastic member 42. It is supported. As the plate-shaped elastic member 42, for example, a wave washer can be used. When the inside of the ball screw case 12 is configured as described above, the screw case fitting portion 24 of the speed reduction mechanism case 10 is fitted to the equal-diameter cylindrical surface 37 of the ball screw case 12 as shown in FIG. In the state where the reduction mechanism case 10 is attached to the ball screw case 12, the screw case fitting portion 24 is in a state where the bearing 14 on the side closer to the drive motor 7 is pressed in the axial direction. The member indicated by reference numeral 43 in FIGS. 1 and 5 is a spacer washer, which plays a role of preventing interference between the plate-shaped elastic member 42 and the inner ring 13b of the bearing 13.

A boot 44 for preventing foreign matter from entering the ball screw case 12 is attached between the small diameter portion 36 and the ball screw shaft 31 (see FIG. 1). The boot 44 is made of resin or rubber, and is composed of a large-diameter end portion 44a and a small-diameter end portion 44b, and a bellows portion 44c that connects the large-diameter end portion 44a and the small-diameter end portion 44b and expands and contracts in the axial direction. There is. The large-diameter end 44a is fastened and fixed to the mounting portion on the outer peripheral surface of the small-diameter portion 36 by the first boot band 45, and the small-diameter end 44b is fastened and fixed to the mounting portion on the outer peripheral surface of the ball screw shaft 31 by the second boot band 46. It is tightened and fixed. Further, a boot cover 47 covering the boot 44 is arranged around the boot 44 (see FIGS. 1 and 5). The boot cover 47 is attached to, for example, a ball screw case 12 adjacent in the axial direction. Although not shown, the ball screw case 12 may be provided with a ventilation hole for the purpose of alleviating a sudden pressure fluctuation in the internal space of the boot 44 when the boot 44 expands and contracts.

Here, the planetary gear reduction mechanism 22 will be described with reference to FIGS. 1, 3, and 6. FIG. 3 is an exploded perspective view of the planetary gear reduction mechanism 22, and FIG. 6 is a cross-sectional view of a cross section taken along line BB of FIG. 1 as viewed from the direction of arrow B.

The planetary gear reduction mechanism 22 includes a ring gear 48, a sun gear 49, a plurality of planetary gears 50, a planetary gear carrier 51, and a planetary gear holder 52. The ring gear 48 may be manufactured separately from the ball screw case 12, and then fixed to the ball screw case 12, for example. However, when the tubular member 38 or the slide bearing 40 is used as an insert component as described above, the ring gear 48 may be fixed to the ball screw case 12. For example, the metal ring gear 48 may be integrally molded with the ball screw case 12 as an insert component like the tubular member 38 and the like. Of course, if there is no problem in terms of rigidity, the ring gear 48 may be formed of resin as a part of the resin portion of the ball screw case 12.

As shown in FIG. 6, the sun gear 49 is arranged in the center of the ring gear 48, and the output shaft 7b of the drive motor 7 is connected to the sun gear 49 by press-fitting or the like (see FIG. 1). Further, between the ring gear 48 and the sun gear 49, each planetary gear 50 is arranged so as to mesh with the ring gear 48 and the sun gear 49 (see FIG. 6). Each planetary gear 50 is rotatably supported by a planetary gear carrier 51 and a planetary gear holder 52. The planetary gear carrier 51 has a cylindrical portion 51a on the outermost diameter side thereof (see FIG. 3), and the cylindrical portion 51a is connected to the outer peripheral surface of the ball screw nut 30 by press-fitting or the like (FIG. 1). reference). As a result, the driving force from the driving motor 7 can be transmitted to the ball screw nut 30 as a rotational force via the planetary gear carrier 51.

In the planetary gear reduction mechanism 22 configured as described above, when the drive motor 7 is rotationally driven, the sun gear 49 connected to the output shaft 7b of the drive motor 7 rotates, and each planetary gear 50 rotates accordingly. While revolving along the ring gear 48. Then, the planetary gear carrier 51 rotates due to the revolution motion of the planetary gear 50. As a result, the rotational movement of the drive motor 7 is decelerated and transmitted to the ball screw nut 30, and is transmitted to the ball screw nut 30 in a state where the rotational torque as the driving force is increased. By transmitting the driving force via the planetary gear reduction mechanism 22 in this way, the driving force transmitted to the ball screw shaft 31 and the output of the ball screw shaft 31 can be obtained to be large, so that the driving force can be obtained. It is possible to reduce the size of the motor 7 (change to a motor having a smaller output).

The electric actuator 1 is equipped with a position detection device for detecting the position of the operation unit 6 provided on the ball screw shaft 31 in the linear movement direction (stroke direction). As shown in FIGS. 1 and 7, the position detection device is provided at a predetermined position of the permanent magnet 53 (see FIG. 1) as a sensor target provided at a predetermined position of the ball screw shaft 31 and a boot cover 47. It has a magnetic sensor 54 as a position detection sensor.

Of these, the magnetic sensor 54 is integrally formed with the sensor substrate 55 as shown in FIGS. 1 and 5, and the sensor substrate 55 is fixed to the sensor case 57 by an appropriate connecting member 56. Then, the magnetic sensor 54 is booted by attaching the sensor assembly 58, which is formed by attaching the sensor substrate 55 to the sensor case 57, to the sensor attachment portion 47a provided at a predetermined position in the circumferential direction of the boot cover 47 by fitting or the like. The cover 47 is installed at a predetermined position in the circumferential direction, and is in a state of facing the permanent magnet 53 via the boot 44 and the boot cover 47 (see FIG. 1). In this case, the magnetic sensor 54 is covered with the boot cover 47 and the sensor case 57 (see FIG. 1).

Any type of magnetic sensor 54 can be used, and among them, a type of magnetic sensor such as a Hall IC or a linear Hall IC that can detect the direction and magnitude of a magnetic field by utilizing the Hall effect can be preferably used.

Further, the sensor case 57 and the boot cover 47 that cover the periphery of the magnetic sensor 54 are both preferably made of a non-magnetic material, for example, made of resin.

On the other hand, the permanent magnet 53 serving as a sensor target is arranged on the ball screw shaft 31 serving as a movable portion. Specifically, as shown in FIG. 1, a permanent magnet 53 is arranged between the operation portion 6 and the spiral groove 31a of the ball screw shaft 31.

FIG. 7 shows an exploded perspective view of the ball screw shaft 31 in a state where the sensor target unit 59 including the permanent magnet 53 is attached. As shown in FIG. 7, a notch 31c is formed at a predetermined position in the axial direction of the ball screw shaft 31, and a sensor target unit 59 is attached to the notch 31c.

On the other hand, as shown in FIG. 7, the sensor target unit 59 includes a permanent magnet 53, a first magnet holder 60 for holding the permanent magnet 53, and a second magnet holder 61. The first magnet holder 60 is provided with a pair or a plurality of pairs (two pairs in the illustrated example) of fitting claws 60a that can be fitted in the notch portion 31c of the ball screw shaft 31. Further, an accommodating portion 60b capable of accommodating the permanent magnet 53 is provided on the side opposite to the protruding side of the fitting claw 60a.

The fitting claw 60a has a shape substantially following the outer peripheral surface of the ball screw shaft 31 to be attached (see FIG. 5). For example, by pushing the first magnet holder 60 from the flat surface portion 31b1 side, the first magnet holder 60 is pushed in. Each pair of fitting claws 60a is deformed (elastically deformed) in a direction away from each other, and then restored toward a shape in close contact with the surface of the notch portion 31c.

The shape of the accommodating portion 60b is set according to the permanent magnet 53 to be accommodated. In this illustrated example, as shown in FIG. 7, the accommodating portion 60b having a cylindrical shape is formed in the first magnet holder 60 according to the permanent magnet 53 having a cylindrical shape. The accommodating portion 60b is open only on one end side in the axial direction, and a permanent magnet 53 is inserted from the side of the opening 60b1 and a second magnet holder 61 is cut out so as to close the opening 60b1. The permanent magnet 53 can be sandwiched by the first and second magnet holders 60 and 61 at predetermined axial positions by fitting the magnet 53 into the magnet. Therefore, by attaching the sensor target unit 59 having the above configuration to the notch portion 31c, the permanent magnet 53 is fixed at a predetermined axial position on the ball screw shaft 31 (see FIG. 1).

The materials of the magnet holders 60 and 61 having the above configuration are basically arbitrary. For example, when considering the influence of the permanent magnet 53 on the magnetic field formed around it, the magnet holders 60 and 61 are preferably formed of a non-magnetic material, and when the elastic deformability of the fitting claw 60a is also considered. , It is better to use resin.

Further, the permanent magnet 53 has a magnetizing direction in a direction orthogonal to both end surfaces 53a and 53b (see FIG. 1). That is, it is in a state of being magnetized so that one end face 53a is the north pole and the other end face 53b is the south pole. As a result, the magnetizing direction of the permanent magnet 53 when attached to the ball screw shaft 31 is made to coincide with the linear motion direction of the ball screw shaft 31 (see FIG. 1).

In the position detecting device configured as described above, when the ball screw shaft 31 moves forward and backward, the position of the permanent magnet 53 with respect to the magnetic sensor 54 changes, and the magnetic field at the location where the magnetic sensor 54 is arranged also changes accordingly. Therefore, by detecting the change in the magnetic field (for example, the direction and strength of the magnetic flux density) with the magnetic sensor 54, the stroke direction position of the permanent magnet 53 and the stroke of the operation unit 6 provided on one end side of the ball screw shaft 31 The direction position can be obtained.

The configuration and operation of the electric actuator 1 of the present embodiment are as described above. Hereinafter, the effects of the present invention will be described with respect to the electric actuator 1 of the present embodiment.

As described above, in the electric actuator 1 of the present embodiment, the ball screw nut 30 as the rotating portion of the motion conversion mechanism is supported by the two bearings 13 and 14, and the two bearings 13 and 14 are supported by the ball screw mechanism. The ball screw case 12 accommodating 11 is attached to a cylindrical surface 37 having a constant inner diameter and provided on the inner circumference. By providing the mounting surfaces of the bearings 13 and 14 on one ball screw case 12 in this way, the bearings 13 and 14 are not affected by the assembly error and the like as compared with the case where the bearings 13 and 14 are mounted across the plurality of cases. It's done. Further, since the mounting surfaces of the two bearings 13 and 14 are both equal-diameter cylindrical surfaces 37 having a constant inner diameter dimension, for example, two surfaces having different inner diameter dimensions via a step are used as mounting surfaces of the bearings 13 and 14, respectively. The shape accuracy (machining accuracy) of the mounting surface can be easily improved as compared with the case of. Therefore, the rotation centers of the bearings 13 and 14 are matched with high accuracy, and the rotation center of the ball screw nut 30 supported by the bearings 13 and 14 is relative to the center line of the ball screw shaft 31 as the linear motion portion. It is possible to prevent the situation of shifting or tilting as much as possible, or to suppress the shifting or tilting as small as possible. As a result, the driving force transmitted from the driving motor 7 to the ball screw nut 30 can be efficiently transmitted to the ball screw shaft 31. Further, by increasing the position accuracy of the ball screw shaft 31, the electric actuator 1 can be controlled with high accuracy.

In particular, in the present embodiment, the ball screw case 12 is provided with a metal tubular member 38 integrally provided, and an equal-diameter cylindrical surface 37 is provided on the inner circumference of the tubular member 38. In this way, even if the shape of the ball screw case 12 is complicated, only the mounting surfaces of the bearings 13 and 14 can be finished into an equal-diameter cylindrical shape without being affected by the shape. Further, by making the tubular member 38 made of metal, the shape accuracy of the mounting surface (equal diameter cylindrical surface 37) can be maintained even when the bearings 13 and 14 are mounted, and the ball screw case 12 can be used. The material can be made of resin with better mass productivity. Therefore, it is suitable not only in terms of position accuracy but also in terms of processing cost.

Hereinafter, the second embodiment of the present invention will be described with reference to FIGS. 8 and 9.

FIG. 8 shows a vertical sectional view of the electric actuator 101 according to the second embodiment of the present invention. Further, FIG. 9 shows a partially exploded perspective view of the electric actuator 101 shown in FIG. As shown in these figures, the electric actuator 101 according to the present embodiment has a configuration in which the reduction mechanism portion 8 is omitted. Compared with the electric actuator 1 shown in FIG. 1, instead of omitting the reduction mechanism portion 8 (planetary gear reduction mechanism 22), a coupling 62 is provided as a connecting portion, and the drive motor 7 is provided by the coupling 62. And the ball screw nut 30 are directly connected. In this case, the coupling 62 has a flat surface 62a on the outer circumference, and is fitted and fixed to, for example, the inner peripheral surface 30c (see FIG. 8) on the other end side in the axial direction of the ball screw nut 30. Allows connection with the ball screw nut 30 and torque transmission.

On the other hand, the configurations other than the above are the same as those of the electric actuator 1 according to the first embodiment. That is, in the present embodiment, the speed reduction mechanism case 10 according to the first embodiment is used as it is as the driving force transmission mechanism case for accommodating the coupling 62. Therefore, as shown in FIG. 9, the ring gear 48 constituting the planetary gear reduction mechanism 22 remains, but the member housed in the reduction mechanism case 10 is one of the coupling 62 and the output shaft 7b of the drive motor 7. Since it is only a part of the portion and the ball screw nut 30, there is no possibility of interfering with the ring gear 48. Therefore, the speed reduction mechanism case 10 according to the first embodiment can be used as it is as the driving force transmission mechanism case. As described above, in the electric actuator 1 shown in FIG. 1 and the electric actuator 101 shown in FIG. 8, only a part of parts (reduction mechanism portion 8 and coupling 62) is replaced, and many other parts are common parts. Can be configured with. As a result, the types of parts to be prepared can be reduced, and the above-mentioned series of electric actuators can be realized at low cost.

Since the rotation support structure of the ball screw nut 30 is the same as that of the first embodiment in this embodiment as well, the rotation centers of the bearings 13 and 14 are aligned with each other with high accuracy and supported by the bearings 13 and 14. It is possible to prevent the rotation center of the ball screw nut 30 from being displaced or tilted with respect to the center line of the ball screw shaft 31 as the linear motion portion as much as possible, or to suppress the deviation or tilt as small as possible. .. Therefore, the driving force transmitted from the driving motor 7 to the ball screw nut 30 can be efficiently transmitted to the ball screw shaft 31.

Hereinafter, the third embodiment of the present invention will be described with reference to FIGS. 10 to 12.

FIG. 10 shows a vertical sectional view of the electric actuator 201 according to the third embodiment of the present invention. 11 is a partially exploded perspective view of the electric actuator 201 shown in FIG. 10, and FIG. 12 is an exploded perspective view of a main part of the electric actuator 201 whose perspective direction is different from that of FIG. As shown in these figures, the electric actuator 201 according to the present embodiment has a different type of drive motor as compared with the electric actuator 1 shown in FIG. 1, specifically, the first and second embodiments. In addition to changing to a drive motor 63 having a larger output than the drive motor 7 according to the above, the power supply structure of the drive motor 63 is changed.

Specifically, as shown in FIG. 10, the driving force transmission mechanism case 64 has the same case body 23, the screw case fitting portion 24, and the motor fitting portion 17, as in the reduction mechanism case 10 shown in FIG. And the flange portion 25 are integrally provided. On the other hand, a pair of bus bars 65 for connecting the drive motor 63 to the power source are attached (built-in) to the drive force transmission mechanism case 64. As shown in FIG. 12, one end 65a of each bus bar 65 is connected to a terminal 63a protruding in the axial direction from the drive motor 63 by, for example, being brought into close contact with the terminal 63a, and the other end 65b is a case. It is exposed to the outside from the main body 23 (flange portion 25) (see FIGS. 10 to 12). This enables an electrical connection between the drive motor 63 and the power source via the bus bar 65. In this case, since the grommet 21 (see FIG. 3) is unnecessary, there is no hole (closed) in the bottom of the motor cover 66.

On the other hand, the configuration other than the above is the same as that of the electric actuator 101 according to the second embodiment. That is, in the present embodiment, the motion conversion mechanism unit 3 (ball screw mechanism 11 and ball screw case 12), the motion conversion mechanism support unit 5, the operation unit 6, the drive motor 63, and the ball according to the second embodiment. The connecting portion (coupling 62) for connecting with the screw nut 30 is used as it is. As described above, in the electric actuator 101 shown in FIG. 8 and the electric actuator 201 shown in FIG. 10, only some parts (reduction mechanism case 10 and driving force transmission mechanism case 64) are mainly replaced, and many other parts are replaced. The parts can be composed of common parts. As a result, the types of parts to be prepared can be reduced, and the above-mentioned series of electric actuators can be realized at low cost. As a specific example of multi-product development accompanying the series of electric actuators 1, 101 and 201, an electric mechanism using a conventional solenoid such as an EGR valve for an automobile including a motorcycle and a transmission control valve will be exemplified. be able to.

In the above embodiment (third embodiment), a case having a driving force transmission mechanism case 64 having a bus bar 65 but not a deceleration mechanism unit 8 has been illustrated, but of course, a driving force transmission mechanism case. It is also possible to configure an electric actuator having both 64 and the speed reduction mechanism unit 8.

The motion conversion mechanism unit 3 is not limited to the ball screw mechanism 11, and may be a sliding screw device. However, the ball screw mechanism 11 is more preferable from the viewpoint of reducing the rotational torque and reducing the size of the drive motor 7. Further, in the above-described embodiment, the configuration in which deep groove ball bearings are used is exemplified as the bearings 13 and 14 that support the motion conversion mechanism unit 3, but the present invention is not limited to this, and for example, angular contact ball bearings may be used. Furthermore, depending on the conditions, the bearings 13 and 14 are not limited to rolling bearings, but other types of bearings such as slide bearings can also be used.

1,101,201 Electric actuator 2 Drive unit 3 Motion conversion mechanism unit 4 Drive force transmission unit 5 Motion conversion mechanism support unit 6 Operation unit 7 Drive motor 7a Protrusion 7b Output shaft 7c Terminal insertion groove 8 Deceleration mechanism 9 Motor cover 10 Deceleration mechanism case 11 Ball screw mechanism 12 Ball screw case 12a Positioning holes 13, 14 Bearings 13a, 14a Outer ring 13b Inner ring 15 Cover body 15a Inner peripheral surface 15b Inner bottom surface 15c Hole 16, 25, 26 Flange part 17 Motor fitting part 17a Fitting holes 18, 28, 29 O-ring 19 Terminal 19a One end 19b The other end 20 Terminal holder 21 Glomet 21a Hole 22 Planetary gear reduction mechanism 23 Case body 24 Screw case Fitting 27 Bolt 30 Ball screw nut 30a Spiral groove 30b Large diameter part 30c Inner peripheral surface 31 Ball screw shaft 31a Spiral groove 31b Sliding area 31b1 Flat surface part 31b2 Partial cylindrical surface part 31c Notch 32 Ball 33 Top 34 Sliding surface 34a Flat surface 34b Partial cylindrical surface 35 Case body 36 Small diameter 37 Equal diameter Cylindrical surface 38 Cylindrical member 39 End face support 39a Inner surface 40 Sliding bearing 41 Stop ring 42 Plate-shaped elastic member 43 Space washer 44 Boot 44a Large diameter end 44b Small diameter end 44c Bellows 45 First Boot band 46 Second boot band 47 Boot cover 47a Sensor mounting part 48 Ring gear 49 Sun gear 50 Planet gear 51 Planet gear carrier 51a Cylindrical part 52 Planet gear holder 53 Permanent magnet 53a, 53b End face 54 Magnetic sensor 55 Sensor board 56 Connecting member 57 Sensor case 58 Sensor assembly 59 Sensor target unit 60 First magnet holder 60a Fitting claw 60b Accommodating part 60b1 Opening 61 Second magnet holder 62 Coupling 62a Flat surface 63 Driving motor 63a Terminal 64 Driving force transmission mechanism case 65 Bus bar 65a One end 65b The other end 66 Motor cover

Claims (5)

It includes a motor, a motion conversion mechanism that converts a rotational motion generated by driving the motor into a linear motion, and a case in which the motion conversion mechanism is housed. The motion conversion mechanism includes a linear motion unit and the linear motion. In an electric actuator having a rotating portion arranged on the outer periphery of the portion,
The case is an insert molded product having a metal tubular member as an insert part.
The rotating portion is supported by two bearings arranged apart from each other in the direction of the center line, and is supported by two bearings.
The two bearings are attached to an equal-diameter cylindrical surface having a constant inner diameter dimension provided on the inner circumference of the case , and the equal-diameter cylindrical surface is formed by the inner peripheral surface of the tubular member . An electric actuator characterized by this. The electric actuator according to claim 1 , wherein the tubular member has an end face support portion that projects inward in the radial direction from one side in the axial direction to support the axial end face of the bearing. The case has a small diameter portion having an inner diameter smaller than that of the equal diameter cylindrical surface on one side in the axial direction of the equal diameter cylindrical surface, and the linear motion portion can slide on the inner circumference of the small diameter portion. The electric actuator according to claim 1 , wherein the sliding surface is provided. The electric actuator according to claim 3 , wherein the small diameter portion is made of a slide bearing made of sintered metal, and the case is a resin molded product in which both the slide bearing and the tubular member are insert parts. The sliding surface is composed of one or two or more flat surfaces forming a part in the circumferential direction, and a partial cylindrical surface connected to the flat surface and forming the rest in the circumferential direction.
Claim 3 or 4 in which at least a region of the outer peripheral surface of the linear motion portion that slides with the sliding surface has a shape corresponding to the flat surface and the partial cylindrical surface constituting the sliding surface. The electric actuator described in.

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