Linear actuator

Abstract

The present invention provides a linear actuator capable of holding the linear motion member of a screw mechanism in a predetermined axial position without requiring power to be supplied to the electric motor when reverse input torque is applied to the screw mechanism. [Solution] The linear actuator 1 comprises an electric motor 2, a planetary reduction mechanism 3, a reverse input blocking clutch 4, and a motion conversion mechanism, the motion conversion mechanism being a screw mechanism 5 in which a nut 52 moves linearly in the axial direction as a screw shaft 51 rotates. The reverse input blocking clutch 4 comprises an output shaft 41 that rotates integrally with the screw shaft 51, an outer ring 42 that houses the planetary gears 36 and planetary carrier 38 of the planetary reduction mechanism 3, and an engaging element 43 that moves between two positions, a locked position and an unlocked position. As the planetary carrier 38 rotates in response to the rotational output of the electric motor 2, a column portion 38a provided on the planetary carrier 38 positions the engaging element 43 in the unlocked position, and a support pin 37 (37A) that rotatably supports the planetary gear 36 relative to the planetary carrier 38 engages with the output shaft 41 in the circumferential direction.

Description

Technical Field

[0001] The present invention relates to a linear actuator.

Background Art

[0002] In recent years, the electrification of automobiles has been progressing for the purposes of labor saving, fuel consumption reduction, function improvement, etc. For example, systems that utilize the power of an electric motor for operations such as an automatic transmission, brakes, and steering of an automobile have been developed and marketed. In such systems, a linear (electric) actuator equipped with an electric motor and a motion conversion mechanism that converts its rotational output into linear motion is widely used.

[0003] For example, in Patent Document 1 below, a linear actuator incorporated in an electric cylinder for generating hydraulic pressure that is converted into braking force in an automobile braking system is described. In this actuator, an electric motor, a screw mechanism as a motion conversion mechanism, and a planetary reduction gear mechanism as a reduction mechanism for reducing the rotational output of the electric motor and transmitting it to the screw mechanism are coaxially arranged, and a part of a piston that generates hydraulic pressure by linearly moving in the axial direction within the cylinder is constituted by a linear member (nut) of the screw mechanism.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the linear actuator described in Patent Document 1, the reaction force generated when hydraulic pressure is produced is input to the electric motor as a reverse input torque via a screw mechanism. Therefore, in order to restrict the unintended rotation of the motor's rotating shaft (axial movement of the nut constituting the piston) caused by this reverse input torque, it is necessary to take measures such as energizing the electric motor when hydraulic pressure is produced and continuously applying a torque to the motor's rotating shaft that can counteract the reverse input torque. However, taking such measures would lead to increased power consumption and raise concerns that the electric motor may be more prone to problems such as abnormal heat generation.

[0006] In view of the aforementioned problems, the present invention aims to provide a linear actuator that can hold a linear member of a screw mechanism in a predetermined axial position without requiring the electric motor to be energized when a reverse input torque is applied to the screw mechanism. [Means for solving the problem]

[0007] As a result of various studies to achieve the above objective, the inventors decided to install a mechanical reverse input blocking clutch that does not require power for operation between the electric motor and the screw mechanism. However, simply adding a mechanical reverse input blocking clutch may lead to an increase in the size, complexity, and cost of the actuator. Therefore, the inventors conceived the idea of ​​utilizing essential components of a planetary reduction gear mechanism as components of the reverse input blocking clutch, and thus came up with the present invention.

[0008] In other words, the present invention was devised to achieve the above objective, In a linear actuator in which an electric motor, a planetary reduction mechanism for reducing the rotational output of the electric motor, and a motion conversion mechanism for converting rotational motion into linear motion are arranged coaxially, and as a rotating member, which is composed of either a screw shaft or a nut fitted around its outer circumference, rotates, a linear member, which is composed of the other of the screw shaft and nut, moves linearly in the axial direction, The system includes a reverse input blocking clutch that prevents the reverse input torque, which is input to the rotating member via the linear motion member, from being transmitted to the electric motor. The above reverse input blocking clutch is An output shaft is connected to the above-mentioned rotating member so as to be rotatable as an integral part of the rotating member, A cylindrical stationary member housing the planetary components and planetary carriers of the planetary deceleration mechanism on its inner circumference, The output shaft has a wedge-shaped space formed between a cam surface provided on the outer circumference of the output shaft and the cylindrical inner surface of the stationary member, and an engaging element that is movable between two positions: a locked position in which it engages with both the cam surface and the cylindrical inner surface in the circumferential direction, and an unlocked position in which it does not engage with both the cam surface and the cylindrical inner surface in the circumferential direction. As the planetary carrier rotates in response to the rotational output of the electric motor, the support pins that rotatably support the planetary members relative to the planetary carrier engage with the output shaft in the circumferential direction, with the column portion provided on the planetary carrier positioned in the unlocked position.

[0009] As described above, the linear actuator according to the present invention has a (mechanical) reverse input blocking clutch that prevents the reverse input torque input to the screw mechanism as a motion conversion mechanism from being transmitted to the electric motor. Therefore, the linear member of the screw mechanism can be held in a predetermined axial position without requiring the electric motor to be energized when reverse input torque is input to the screw mechanism. Furthermore, when the electric motor rotates, the rotational output of the electric motor is transmitted to the rotating member of the screw mechanism using the planetary carrier (or the column portion provided on it), which is an essential component of the planetary reduction mechanism, and the support pins that rotatably support the planetary member relative to the planetary carrier (that is, the support pins of the planetary carrier and planetary member are utilized as components of the reverse input blocking clutch). This reduces the number of parts dedicated to the reverse input blocking clutch and avoids increasing the size and cost of the linear actuator.

[0010] In the above configuration, the planetary reduction mechanism can be one that includes a first-stage reduction unit that reduces the rotational output of the electric motor, and a second-stage reduction unit that reduces the rotational output of the first-stage reduction unit. In this case, the support pin that engages with the output shaft of the reverse input blocking clutch in the circumferential direction can be a component of the second-stage reduction unit.

[0011] The screw mechanism, which serves as a motion conversion mechanism for the linear actuator of the present invention, may be a so-called ball screw mechanism further comprising a plurality of balls that are rotatably interposed between a male screw groove formed on the outer circumferential surface of a screw shaft and a female screw groove formed on the inner circumferential surface of a nut, or it may be a so-called sliding screw mechanism in which the inner circumferential surface of a nut is screwed onto the outer circumferential surface of a screw shaft. [Effects of the Invention]

[0012] Based on the above, the present invention makes it possible to provide a linear actuator that can hold the linear member of a screw mechanism in a predetermined axial position without requiring the electric motor to be energized when reverse input torque is applied to the screw mechanism. [Brief explanation of the drawing]

[0013] [Figure 1] This is a longitudinal cross-sectional view of a linear actuator according to an embodiment of the present invention. [Figure 2] This is a magnified section of Figure 1. [Figure 3] Figure 1 is a cross-sectional view of the reverse input blocking clutch provided in the linear actuator shown, and Figure 2 is a cross-sectional view taken along the line AA. [Figure 4] This is an exploded perspective view of the reverse input cutoff clutch. [Figure 5] This is a perspective view of the output shaft of the reverse input blocking clutch, taken from a different direction than in Figure 4. [Figure 6] This is a cross-sectional view of the reverse input blocking clutch immediately after the electric motor is driven. [Figure 7] This is a cross-sectional view of the reverse input cutoff clutch when the electric motor is continuously driven. [Figure 8] This is a partially enlarged cross-sectional view of a linear actuator according to another embodiment. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the present invention will be described based on the drawings. In the following description, the "axial direction", "radial direction", and "circumferential direction" used refer to the direction along the central axis of the screw shaft 51 constituting the screw mechanism 5 shown in FIG. 1 etc., the radial direction of a circle centered on the central axis, and the circumferential direction of a circle centered on the central axis, respectively.

[0015] FIG. 1 is a longitudinal sectional view of a linear actuator 1 according to an embodiment of the present invention, FIG. 2 is a partial enlarged view of FIG. 1, FIG. 3 is a sectional view taken along the line A-A of FIG. 2, and FIG. 4 is an exploded perspective view of a reverse input blocking clutch. This linear actuator 1 is used, for example, as an electric cylinder for generating hydraulic pressure that is converted into braking force in an automobile braking system or for generating hydraulic pressure that is converted into vibration damping force in an automobile suspension device, and includes an electric motor 2, a planetary reduction mechanism 3, a reverse input blocking clutch 4, a screw mechanism 5 as a motion conversion mechanism, and a casing 6 that houses these. The electric motor 2, the planetary reduction mechanism 3, the reverse input blocking clutch 4, and the screw mechanism 5 are coaxially arranged in series in the axial direction within the casing 6.

[0016] The electric motor 2 includes a motor body 21 including a stator core and a stator coil, and a motor output shaft 22. The stator coil is electrically connected to a power source (not shown). The electric motor 2 is provided with a detection unit for detecting the rotation angle of the motor output shaft 22. The detection unit includes a magnet 23 attached to the motor output shaft 22 and a rotation sensor 24 arranged to face the magnet 23 with an axial gap therebetween. Therefore, for the electric motor 2, a motor in which the rotation of the rotor (motor output shaft 22) is controlled based on the detection value of the rotation sensor 24, for example, a three-phase brushless motor, is used.

[0017] The casing 6 includes a first case 61, a second case 62, and a third case 63 that are axially coupled. Here, a bottomed cylindrical first case 61 that houses the electric motor 1 is attached to one axial side of the cylindrical second case 62 that houses the planetary reduction mechanism 3 and the reverse input blocking clutch 4 (the side where the electric motor 2 is disposed, which is the right side of the paper surface in FIG. 1. The same applies hereinafter), and a bottomed cylindrical third case 63 that houses the screw mechanism 5 is attached to the other axial side of the second case 62 (the side where the screw mechanism 5 is disposed, which is the left side of the paper surface in FIG. 1. The same applies hereinafter), thereby forming the casing 6.

[0018] The screw mechanism 5 converts the rotational output of the motor rotating shaft 22 input via the planetary reduction mechanism 3 and the reverse input blocking clutch 4 into linear motion, and includes a screw shaft 51 having a male screw groove 51a formed on its outer peripheral surface, a cylindrical nut 52 fitted on the outer periphery of the screw shaft 51 and having a female screw groove 52a formed on its inner peripheral surface, a plurality of balls 53 that are rotatably arranged in a spiral rolling path formed between the male screw groove 51a and the female screw groove 52a facing each other, and a ball 54 as a circulation member for circulating the balls 53 within the nut 52. That is, the screw mechanism 5 of the present embodiment is a so-called ball screw (ball screw mechanism).

[0019] In this screw mechanism 5, the screw shaft 51 constitutes a rotating member that receives the rotational output of the motor output shaft 22 input via the planetary reduction mechanism 3 and the reverse input blocking clutch 4 and rotates, and the nut 52 constitutes a linear motion member that linearly moves in the axial direction as the screw shaft 51 rotates. A bottomed cylindrical piston 55 that closes the other end opening of the nut 52 is attached to the other end of the nut 52 that constitutes the linear motion member. This screw mechanism 5 is provided with a rotation prevention structure for restricting the rotation of the nut 52 that constitutes the linear motion member around the central axis of the screw shaft 51. The rotation prevention structure in the illustrated example is formed by fitting a rotation prevention member 56 attached to the nut 52 so as to protrude radially outward of the nut 52 into an axial groove 63a formed on the inner peripheral surface of the third case 63.

[0020] The planetary reduction mechanism 3 reduces the rotational output of the electric motor 2 and outputs it. The planetary reduction mechanism 3 in this embodiment comprises a first-stage reduction unit that reduces the rotational output of the electric motor 2, and a second-stage reduction unit that further reduces the rotational output of the electric motor 2 that has been reduced by the first-stage reduction unit. The two reduction units are arranged coaxially in the axial direction and are of a two-stage reduction type.

[0021] The first-stage reduction gear comprises a sun gear 31 that rotates integrally with the motor output shaft 22, a ring gear 32 fixed to the casing 6 and having internal teeth 32a formed on its inner surface, a plurality (in this case, three) of first planetary gears 33 arranged between the sun gear 31 and the ring gear 32 so as to be able to rotate and revolve, a first planetary carrier 35 that extracts the revolving motion of the first planetary gears 33, and a total of three first support pins 34 that support each first planetary gear 33 so as to be able to rotate (rotate) relative to the first planetary carrier 35. The first planetary carrier 35 integrally has a disc portion 35a to which the ends of the first support pins 34 are fitted and fixed, and a cylindrical sun gear portion 35b with external teeth formed on its outer surface so as to function as the sun gear of the second-stage reduction gear.

[0022] The second stage reduction unit comprises a sun gear section 35b provided on the first planetary carrier 35, a plurality (in this case, three) of second planetary gears 36 arranged between the sun gear section 35b and the ring gear 32 so as to be able to rotate and revolve, a second planetary carrier 38 for extracting the orbital motion of the second planetary gears 36, and a total of three second support pins 37 that support each second planetary gear 36 so as to be able to rotate (rotate) relative to the second planetary carrier 38. As shown in Figures 3 and 4, the radially outer end of the second planetary carrier 38 has a circumferentially extending arc shape, with a plurality (three) of columnar sections 38a that protrude in the other axial direction and are spaced apart in the circumferential direction.

[0023] Of the three second support pins 37, one is longer than the other two. The relatively longer second support pin 37 (37A) is held by the second planetary carrier 38 such that its other axial end protrudes axially outward from the second planetary carrier 38 (see Figures 2 and 4). The relatively shorter second support pin 37 (37B) is held by the second planetary carrier 38 such that its other axial end does not protrude axially outward from the second planetary carrier 38 (see Figure 2).

[0024] The reverse input blocking clutch 4 is provided between the planetary reduction mechanism 3 and the screw mechanism 5, and prevents the reverse input torque input to the screw mechanism 5 from being transmitted to the electric motor 2. The reverse input blocking clutch 4 is rotatably connected to the screw shaft 51, which is a rotating member of the screw mechanism 5, and comprises an output shaft 41 that is rotatably supported relative to the casing 6 by a rolling bearing 7, and an annular outer ring 42 that houses the second planetary gear 36, which is a "planetary member" and the second planetary carrier 38, which is a "planetary carrier" that constitute the planetary reduction mechanism 3 (the second stage reduction section). The outer ring 42 is fixed to the casing 6 (the second case 62) in a state of being prevented from rotating by a plurality of anti-rotation pins 10 and mounting bolts 11, together with the motor bracket 64 that holds the electric motor 2 and the ring gear 32 of the planetary reduction mechanism 3. Therefore, the outer ring 42 constitutes a "static member" as defined in this invention.

[0025] As shown in Figures 3 and 4, the output shaft 41 integrally comprises a bottomed cylindrical connecting portion 41a to which a screw shaft 51 is connected in a manner that allows torque transmission, and a flange portion 41b extending radially outward from one axial end of the connecting portion 41a.

[0026] A spline (female spline) 41c is formed on the inner circumferential surface of the connecting portion 41a of the output shaft 41, and this female spline 41c is spline-fitted with a male spline formed on the outer circumference of one end of the screw shaft 51. In this embodiment, a bolt member 46 is screwed through the output shaft 41 into a bolt hole provided on one end face of the screw shaft 51. With this configuration, the output shaft 41 of the reverse input blocking clutch 4 and the screw shaft 51 of the screw mechanism 5 can rotate together.

[0027] Multiple cam surfaces 41d are formed on the outer circumferential surface of the flange portion 41b at intervals in the circumferential direction. Each cam surface 41d forms a wedge-shaped space 45 between itself and the inner circumferential surface 42a of the outer ring 42, which is formed in the shape of a cylindrical surface with a constant diameter. Each wedge-shaped space 45 incorporates a pair of engaging elements 43 (43A, 43B) arranged at intervals in the circumferential direction, and an elastic member 44 interposed between the pair of engaging elements 43A, 43B in a state of circumferential compression deformation. In this embodiment, the engaging elements 43 and the elastic member 44 are a cylindrical roller and a coil spring (compression coil spring), respectively.

[0028] Of the outer circumferential surface of the flange portion 41b, the portion other than the cam surface 41d is formed as a circular arc surface 41e concentric with the inner circumferential surface 42a of the outer ring 42, and the column portion 38a provided on the second planetary carrier 38 is positioned in the arc-shaped space formed between this circular arc surface 41e and the inner circumferential surface 42a of the outer ring 42.

[0029] As shown in Figure 5, a groove 41f is formed on one end face of the flange portion 41b of the output shaft 41, and the other end projection of the second support pin 37A, which constitutes the planetary reduction mechanism 3 (the second stage reduction section), is fitted into this groove 41f. As shown in Figure 3, when the electric motor 2 is stopped, a circumferential gap is interposed between the groove 41f and the second support pin 37A (the other end projection), preventing them from contacting each other in the circumferential direction.

[0030] The radial width of the wedge-shaped space 45 is largest at the circumferential center of the wedge-shaped space 45, and gradually decreases as it shifts from the circumferential center to one side and the other side. The radial width of the wedge-shaped space 45 at the circumferential center is a predetermined amount larger than the diameter of the engaging element 43, and the radial width at both ends of the wedge-shaped space 45 is a predetermined amount smaller than the diameter of the engaging element 43. Therefore, as shown in Figure 3, when the electric motor 2 is stopped and there is no torque input to the planetary reduction mechanism 3, both of the pair of engaging elements 43 (43A, 43B) arranged in the wedge-shaped space 45 are in a locked position where they engage in the circumferential direction with both the output shaft 41 (cam surface 41d) and the outer ring 42 (cylindrical inner surface 42a) due to the elastic restoring force of the elastic member 44.

[0031] Thus, when the engaging elements 43 (43A, 43B) are in the locked position, the rotation of the output shaft 41 relative to the outer ring 42, which acts as a stationary member, is restricted, and consequently, the rotation of the screw shaft 51, which is rotatably connected to the output shaft 41, is also restricted. Therefore, even if a reverse input torque is applied to the screw shaft 51 via the nut 52 in this state, that reverse input torque is not transmitted to the planetary reduction mechanism 3 and the electric motor 2.

[0032] On the other hand, when the electric motor 2 is driven, for example as shown in Figure 6, a torque is input to the planetary reduction mechanism 3 that rotates the second planetary carrier 38 counterclockwise. At this point, the column portion 38a of the second planetary carrier 38 comes into contact with the engaging element 43 (in this case, engaging element 43B) adjacent to it on its forward side in the direction of rotation, and pressurizes the engaging element 43B in the circumferential direction. When the engaging element 43B is pressed in the circumferential direction, as shown in Figure 7, the elastic member 6 interposed between the pair of engaging elements 43A and 43B is elastically compressed and deformed, causing the engaging element 43B to move from the locked position to an unlocked position where it does not engage in the circumferential direction with both the output shaft 41 (cam surface 41d) and the outer ring 42 (inner circumferential surface 42a). Of the pair of engaging elements 43A and 43B arranged in the wedge-shaped space 45, engaging element 43A rotates freely without engaging with the output shaft 41 and the outer ring 42 in the circumferential direction, even when a counterclockwise torque is input to the second planetary carrier 38.

[0033] Furthermore, as the second planetary carrier 38 rotates counterclockwise, as shown in Figures 6-7, the second support pin 37A (the protruding part at the other end) held by the second planetary carrier 38 contacts the inner wall surface of the groove 41f of the output shaft 41, slightly after the column portion 38a contacts the engaging element 43B. This allows the second planetary carrier 38 and the output shaft 41 to rotate together counterclockwise. Consequently, as the second planetary carrier 38 rotates further counterclockwise, the engaging element 43 and the elastic member 6 between the output shaft 41 and the outer ring 42 move circumferentially in a counterclockwise direction, and the second planetary carrier 38, the output shaft 41, and the screw shaft 51 of the screw mechanism 5, which is connected to the output shaft 41 so as to be rotatable together, rotate counterclockwise. As the screw shaft 51 rotates in this way, the nut 52 fitted to the outer circumference of the screw shaft 51 in an anti-rotation state moves linearly in the axial direction.

[0034] Subsequently, when the electric motor 2 stops, the engaging element 43B, receiving circumferential pressure due to the release of the elastic restoring force accumulated in the elastic member 6, moves clockwise within the wedge-shaped space 45 and engages circumferentially with both the output shaft 41 (cam surface 41d) and the inner ring 42 (inner circumferential surface 42a). As a result, the reverse input blocking clutch 4 returns to the locked state shown in Figure 3, which is capable of blocking the reverse input torque.

[0035] To summarize the characteristic configuration of the linear actuator 1 of this embodiment described above, First, it is equipped with a reverse input blocking clutch 4 that prevents the reverse input torque input to the screw mechanism 5, which acts as a motion conversion mechanism, from being transmitted to the electric motor 2. This reverse input blocking clutch 4 is The output shaft 41 is connected to the screw shaft 51 as a rotating member so as to be rotatable together with it, The outer ring 42, which serves as a stationary member, houses the second planetary gear 36 and the second planetary carrier 38 of the planetary reduction mechanism 3 (the second stage reduction section that constitutes it), Within a wedge-shaped space 45 formed between the cam surface 41d of the output shaft 41 and the cylindrical inner circumferential surface 42a of the outer ring 42 facing it, there is an engaging element 43 that is movable between two positions: a locked position in which it engages with both of the opposing surfaces 41d and 42a in the circumferential direction, and an unlocked position in which it does not engage with both of the surfaces 41d and 42a in the circumferential direction. As the second planetary carrier 38 rotates in response to the rotation of the electric motor 2, the column portion 38a provided on the second planetary carrier 38 positions the engaging element 43 in the unlocked position, and the second support pin 37 (37A), which rotatably supports the second planetary gear 36 relative to the second planetary carrier 38, engages with the output shaft 41 in the circumferential direction (see Figure 7).

[0036] Thus, the linear actuator 1 of this embodiment has a mechanical reverse input blocking clutch 4 that prevents the reverse input torque input to the screw mechanism 5, which acts as a motion conversion mechanism, from being transmitted to the electric motor 2. Therefore, the nut 52, which is a linear member of the screw mechanism 5, can be held in a predetermined axial position without requiring the electric motor 2 to be energized when reverse input torque is input to the screw mechanism 5.

[0037] Furthermore, when the electric motor 2 rotates, the rotation of the electric motor 2 is transmitted to the screw shaft 51 of the screw mechanism 5 using the support pin (second support pin 37A) that rotatably supports the planetary carrier (second planetary carrier 38), which is an essential component of the planetary reduction mechanism 3, and the second planetary gear 36, which is a planetary component, relative to the second planetary carrier 38 (that is, the support pin 37A of the second planetary carrier 38 and the second planetary gear 36 are utilized as components of the reverse input blocking clutch 4). As a result, the number of parts dedicated to the reverse input blocking clutch 4 can be reduced. Therefore, a linear actuator 1 can be realized that is compact, inexpensive, consumes little power, and is less prone to problems such as abnormal heat generation in the electric motor 2.

[0038] Although a linear actuator 1 according to one embodiment of the present invention has been described above, the linear actuator 1 can be modified as appropriate without departing from the spirit of the present invention.

[0039] For example, in the linear actuator 1 described above, the screw mechanism 5 as a motion conversion mechanism is configured as a ball screw mechanism. However, the screw mechanism 5 can also be replaced with a so-called sliding screw mechanism in which the numerous balls 53 interposed between the radially opposing male screw grooves 51a and female screw grooves 52a are omitted, and the male screw grooves 51a and female screw grooves 52a are directly screwed together.

[0040] Furthermore, while the screw mechanism 5 of the linear actuator 1 described above uses the screw shaft 51 as the rotating member (rotating side) and the nut 52 as the linear member (linear side), the present invention can also be applied to a linear actuator 1 employing a screw mechanism 5 in which the nut 52 is the rotating member and the screw shaft 51 is the linear member.

[0041] Furthermore, although the linear actuator 1 described above employs a two-stage reduction type planetary reduction mechanism 3, the present invention can also be applied to a linear actuator 1 employing a single-stage reduction type or a multi-stage reduction type planetary reduction mechanism 3 with three or more stages.

[0042] Furthermore, in the linear actuator 1 described above, in order to connect the output shaft 41 of the reverse input blocking clutch 4 and the screw shaft 51 of the screw mechanism 5 so that they can rotate as a single unit, a bolt member 46 screwed into the screw shaft 51 via the output shaft 41 is used to restrict the axial separation of the output shaft 41 and the screw shaft 51. However, as shown in Figure 8, a retaining ring 12 may be used to restrict the axial separation of the output shaft 41 of the reverse input blocking clutch 4 and the rotating member of the screw mechanism 5 by placing a retaining ring 12 in the annular space defined between an annular groove 41g formed on the inner circumferential surface of the connecting portion 41a of the output shaft 41 and an annular groove 51c formed on the small diameter outer circumferential surface 51b of the screw shaft 51.

[0043] The present invention is not limited in any way to the embodiments described above, and can be implemented in various other forms without departing from the spirit of the invention. [Explanation of symbols]

[0044] 1 Linear Actuator 2 Electric motor 3. Planetary deceleration mechanism 4. Reverse input blocking clutch 5. Screw mechanism (motion conversion mechanism) 22 Motor output shaft 37. Second support pin (support pin) 38. Planetary Carrier No. 2 (Planetary Carrier) 41 Output shaft 41d Cam surface 43 Engagement element 51 Screw shaft (rotating component) 52 Nut (linear motion component) 53 Ball

Claims

1. In a linear actuator in which an electric motor, a planetary reduction mechanism for reducing the rotational output of the electric motor, and a motion conversion mechanism for converting rotational motion into linear motion are arranged coaxially, and as a rotating member, which is composed of either a screw shaft or a nut fitted around its outer circumference, rotates, a linear member, which is composed of the other of the screw shaft and the nut, moves linearly in the axial direction, The system includes a reverse input blocking clutch that prevents the reverse input torque, which is input to the rotating member via the linear motion member, from being transmitted to the electric motor. The aforementioned reverse input blocking clutch is An output shaft is connected to the aforementioned rotating member so as to be rotatable together with it, A cylindrical stationary member housing the planetary members and planetary carriers of the planetary deceleration mechanism on its inner circumference, The output shaft has a wedge-shaped space formed between a cam surface provided on the outer circumference of the output shaft and the cylindrical inner surface of the stationary member, and an engaging element that is movable between two positions: a locked position in which it engages with both the cam surface and the cylindrical inner surface in the circumferential direction, and an unlocked position in which it does not engage with both the cam surface and the cylindrical inner surface in the circumferential direction. A linear actuator characterized in that, as the planetary carrier rotates in response to the rotational output of the electric motor, a support pin that rotatably supports the planetary member relative to the planetary carrier engages with the output shaft in the circumferential direction, with the column portion provided on the planetary carrier positioning the engaging element in the unlocked position.

2. The planetary reduction mechanism includes a first-stage reduction unit that reduces the rotation of the electric motor, and a second-stage reduction unit that reduces the rotational output of the first-stage reduction unit. The linear actuator according to claim 1, wherein the support pin that engages circumferentially with the output shaft of the reverse input blocking clutch is a component of the second-stage reduction unit.

3. The linear actuator according to claim 1 or 2, wherein the screw mechanism is further configured as a ball screw mechanism comprising a plurality of balls that are rotatably interposed between a male screw groove formed on the outer circumferential surface of the screw shaft and a female screw groove formed on the inner circumferential surface of the nut.

4. The linear actuator according to claim 1 or 2, wherein the screw mechanism is configured as a sliding screw mechanism in which the inner surface of the nut is screwed onto the outer surface of the screw shaft.

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