JP6254040B2 - Telescopic actuator - Google Patents

Description

  The present invention relates to a telescopic actuator provided with a feed screw mechanism that converts the rotational motion of an electric motor into reciprocating linear motion of an output rod.

  As a conventional technique, for example, Patent Document 1 discloses a ball screw mechanism that converts a rotational motion of a motor into a reciprocating linear motion of a push rod (output shaft) in order to adjust the length of a wheel guide member. .

  The ball screw mechanism includes a ball screw shaft that is coaxially formed integrally with the push rod, a screw nut that is externally fitted to the ball screw shaft, and a plurality of rollers that roll between the ball screw shaft and the screw nut. It consists of a ball.

Special table 2012-511465 gazette

  By the way, in the structure disclosed in Patent Document 1, a ball screw mechanism is used. However, in order to reduce the manufacturing cost, it is necessary to replace the ball screw shaft with, for example, a feed screw mechanism such as a trapezoidal screw. There is.

  When the feed screw mechanism is used, the properties of the grease interposed between the feed screw shaft and the feed nut may deteriorate due to, for example, heat generation at the sliding portion between the feed screw shaft and the feed nut. .

  The present invention has been made in view of the above points, and an object thereof is to provide a telescopic actuator capable of avoiding deterioration of the properties of grease.

  To achieve the above object, the present invention comprises a feed screw shaft having a threaded portion and a feed nut screwed into the threaded portion, and a feed screw mechanism that converts the rotational motion of an electric motor into a reciprocating linear motion, In a telescopic actuator comprising an output rod displaced by the feed screw mechanism, the screw portion has a male screw composed of a crest and a trough, and the feed screw shaft is in the axial direction of the feed screw shaft. Formed in the feed nut, which is formed between the groove portion which is formed in the middle portion along the groove and where the mountain portion is not formed, and between the mountain portion and the groove portion which are closest to the groove portion on both sides of the groove portion A taper portion that is formed in a substantially tapered shape in a non-contact manner with the female screw, and the depth (D1) of the bottom surface of the groove portion is the same as the depth (D2) of the valley portion, or the valley Formed deeper than the depth (D2) of the part ( 1 ≧ D2), wherein the groove, grease, characterized in that it is filled.

  According to the present invention, the taper portion is interposed between the groove portion filled with the grease and the heat source that is a sliding portion where the screws of the feed screw shaft and the feed nut portion are engaged with each other, whereby the groove portion is formed into the heat source. It can arrange | position in the position (position which moves away) away from. As a result, in the present invention, deterioration of the properties of grease can be suitably avoided.

  Moreover, according to this invention, the both ends which pinched | interposed the groove part are always obstruct | occluded by the thread surface of a feed nut. For this reason, in this invention, the discharge | emission amount of the grease in the axial movement range (maximum movement range) of the feed nut with respect to a feed screw shaft can be suppressed, and a favorable lubrication state can be maintained over a long period of time.

  Furthermore, according to the present invention, the grease filled in the groove portion by the dead weight of the grease itself, the centrifugal force due to the rotational motion of the feed screw shaft, and the vibration transmitted from the outside to the feed screw shaft is reduced on the feed nut side. It becomes easy to adhere to the thread surface. For this reason, excess grease is collected again in the groove portion, and an appropriate amount of grease can be supplied between the feed screw shaft and the feed nut with a simple structure.

  Furthermore, according to the present invention, the difference between the static friction coefficient and the dynamic friction coefficient can be reduced by maintaining the sliding portion between the feed screw shaft and the feed nut in a good lubrication state. As a result, in the present invention, it is possible to suppress the occurrence of stick-slip phenomenon and reduce the occurrence of abnormal noise.

  Furthermore, according to the present invention, since a low friction coefficient can be obtained stably, the amount of heat generated at the sliding portion between the feed screw shaft and the feed nut can be suppressed. For this reason, in this invention, while the temperature rise of the sliding part of a feed screw axis | shaft and a feed nut is suppressed, while being able to obtain the stable lubrication state, stabilization of screw efficiency can be achieved. Thereby, in this invention, since the power consumption in an electric motor can be reduced and an electric motor can be reduced in size, manufacturing cost can be reduced.

In the present invention, the telescopic actuator is an actuator mounted on an arm that constitutes a suspension device of a vehicle, and the groove portion is in a state in which the feed nut has moved to one side to the maximum, and the one side In any state of the maximum movement to the other side of the opposite side, the feed nut is in a position covered by the feed nut, and the movement amount (S) of the feed nut is the total axial length of the feed nut. It is characterized by being set smaller than (L) (S <L).

According to the present invention, the amount of movement of the feed nut (S), because they are smaller than the total axial length of the feed nut (L) (S <L) , the amount of movement of the feed nut is one side and the other Even in the maximum case, the groove is located in the feed nut and is covered with the feed nut. Thereby, it can avoid suitably that a groove part exposes outside.

  For example, various loads such as a tensile load, a compressive load, and a torsional load are applied to the actuator mounted on the arm constituting the suspension device of the vehicle. In the present invention, within the range of the maximum amount of movement of the feed nut, the groove is always covered with the feed nut, and the feed nut is strong against the axial load and bending load of compression and tension. Bear the burden. Further, since the friction coefficient is stable with respect to the torsional load, the input of the friction torque is suppressed and the stress can be reduced as compared with the prior art. As a result, the present invention can be preferably applied to the actuator mounted on the arm of the suspension device.

  In the present invention, it is possible to obtain a telescopic actuator capable of avoiding deterioration of the properties of grease.

1 is a perspective view of a rear suspension device in which a toe control actuator according to an embodiment of the present invention is incorporated. It is an arrow view seen from the arrow A direction of FIG. It is a longitudinal cross-sectional view along the axial direction of the toe control actuator which concerns on embodiment of this invention. It is a partially expanded sectional view of the feed screw mechanism shown in FIG. It is a disassembled perspective view of the planetary gear mechanism which comprises a toe control actuator. FIG. 4 is an enlarged vertical sectional view taken along line VI-VI in FIG. 3. (A) is an enlarged front view of the elastic coupling as viewed from the carrier side, (b) is an enlarged cross-sectional view taken along line VIIB-VIIB in (a), and (c) is a VIIC-VIIC in (a). It is an expanded sectional view along a line. It is explanatory drawing which shows the relationship between the movement amount of a female screw member, and full length. It is explanatory drawing which shows the state by which the grease hold | maintained in the grease holding groove is prevented from flowing out to the outside. (A)-(d) is sectional drawing which shows the manufacturing process of an external thread member. (A)-(c) is sectional drawing which shows the assembly process of a feed screw mechanism. It is explanatory drawing which shows the positional relationship of the sliding site | part of a screw, and a grease holding groove. It is explanatory drawing which shows the spreading | diffusion state of the grease with which it filled in the grease holding groove.

  Next, embodiments of the present invention will be described in detail with reference to the drawings as appropriate. FIG. 1 is a perspective view of a rear suspension device incorporating a toe control actuator according to an embodiment of the present invention, and FIG. 2 is an arrow view seen from the direction of arrow A in FIG. Note that “front and rear” indicated by arrows in each figure indicates the front and rear direction of the vehicle, “up and down” indicates the vertical direction of the vehicle (vertical direction), and “left and right” indicates the left and right direction (vehicle width direction). ).

  The rear suspension device 10 shown in FIGS. 1 and 2 is of a double wishbone type and is disposed on the left rear wheel of a four-wheel steering vehicle (not shown). The rear suspension device 10 includes a knuckle 12 that rotatably supports a rear wheel W, an upper arm 14 and a lower arm 16 that are connected to a vehicle body frame so that the knuckle 12 can move up and down, and a knuckle to control a toe angle of the rear wheel W. 12 and a toe control actuator (extension actuator) 18 for connecting a vehicle body frame (not shown), and a damper 20 with a suspension spring for buffering the vertical movement of the rear wheel W.

  The base ends of the upper arm 14 and the lower arm 16 are connected to a vehicle body frame (not shown) by rubber bush joints 22a and 22b, respectively. The tips of the upper arm 14 and the lower arm 16 are connected to the upper and lower portions of the knuckle 12 via ball joints 24a and 24b, respectively.

  The base end of the toe control actuator 18 is connected to a vehicle body frame (not shown) via a rubber bush joint 26a. The tip of the toe control actuator 18 is connected to the rear part of the knuckle 12 via a rubber bush joint 26b.

  The upper end of the damper 20 with the suspension spring is fixed to the vehicle body (upper wall 28 of the suspension tower shown in FIG. 2). The lower end of the suspension spring-equipped damper 20 is connected to the upper portion of the knuckle 12 via a rubber bush joint 26c.

  When the toe control actuator 18 is driven in the extending direction, the rear portion of the knuckle 12 is pushed outward in the vehicle width direction, and the toe angle of the rear wheel W changes in the toe-in direction. On the other hand, when the toe control actuator 18 is driven in the contracting direction, the rear portion of the knuckle 12 is pulled inward in the vehicle width direction, and the toe angle of the rear wheel W changes in the toe-out direction. Therefore, in addition to normal front wheel steering by operating a steering wheel (not shown), the toe angle of the rear wheel W is controlled according to the vehicle speed and the steering angle of the steering wheel, thereby improving the straight running stability and turning performance of the vehicle. Can be made.

  Next, the structure of the toe control actuator 18 will be described in detail below with reference to FIGS.

  3 is a longitudinal sectional view along the axial direction of the toe control actuator according to the embodiment of the present invention, FIG. 4 is a partially enlarged sectional view of the feed screw mechanism shown in FIG. 3, and FIG. 6 is an exploded perspective view of the planetary gear mechanism, FIG. 6 is an enlarged vertical sectional view taken along line VI-VI in FIG. 3, and FIG. 7A is an enlarged front view of the elastic coupling as seen from the carrier side. 7 (b) is an enlarged cross-sectional view taken along line VIIB-VIIB in FIG. 7 (a), and FIG. 7 (c) is an enlarged cross-sectional view taken along line VIIC-VIIC in FIG. 7 (a).

  As shown in FIGS. 3 and 4, the toe control actuator 18 includes a first housing 30a integrally provided with a rubber bush joint 26a connected to the body frame side, and a rubber bush joint connected to the knuckle 12 side. 26b is provided with a second housing 30b that supports the output rod 32 provided integrally therewith so as to extend and contract. Opposing portions of the first housing 30a and the second housing 30b are integrally coupled by fastening the coupling flanges 36a and 36b with a plurality of bolts 38 in an inlay-fitted state via the seal member 34. Yes.

  A chamber 40a inside the first housing 30a accommodates a brushed motor (electric motor) 42 as a driving source and a planetary gear mechanism 44 (see FIG. 5) functioning as a speed reducer. An elastic coupling 46 and a feed screw mechanism 48 using trapezoidal screws are housed in the chamber 40b inside the second housing 30b. These motor 42, planetary gear mechanism 44, elastic coupling 46, and feed screw mechanism 48 are arranged in series on the axis L of the toe control actuator 18.

  The motor 42 includes an annular stator 50 that is fixed to the first housing 30 a side, and a rotor 52 that is rotatably supported in the stator 50. The outer shell of the motor 42 includes a yoke 56 formed in a cup shape having a flange 54, and a bearing holder 58 that is abutted against and fixed to the flange 54 of the yoke 56. The rotor 52 has a rod-shaped rotating shaft (motor shaft) 60. One end of the rotating shaft 60 is rotatably supported by a ball bearing 62 a provided at the bottom of the yoke 56. The other end of the rotating shaft 60 is rotatably supported by a ball bearing 62 b provided in the bearing holder 58.

  On the inner surface of the bearing holder 58, a brush 66 is supported that is slidably contacted with a commutator 64 that is engaged with the outer peripheral surface of the rotating shaft 60 and rotates integrally with the rotating shaft 60. A conductive wire 68 extending from the brush 66 and electrically connected to the brush 66 is drawn out of the first housing 30a via a grommet 70 provided in the first housing 30a.

  As shown in FIGS. 3 and 5, the planetary gear mechanism 44 includes a ring gear 74 fitted and fixed in the substantially cylindrical opening 72 of the first housing 30 a, and the tip of the rotating shaft 60 of the motor 42. A sun gear 76 formed directly on the ring, a carrier 78 having a smaller diameter than the ring gear 74 and formed in a substantially disk shape, three pinion pins 80 that are press-fitted into the support holes 102 of the carrier 78 and are cantilevered, Each pinion pin 80 includes three pinions 84 that are rotatably supported and mesh with the ring gear 74 and the sun gear 76 at the same time. The planetary gear mechanism 44 has a function of decelerating and transmitting the rotational movement of the sun gear 76 as an input member to the carrier 78 as an output member.

  A carrier 78 that is an output member of the planetary gear mechanism 44 is connected to an input flange 86 that is an input member of the feed screw mechanism 48 via an elastic coupling 46.

  The carrier 78 has a substantially disk shape, and has a circular first end surface 79 that faces the elastic coupling 46, and a circular second end surface 81 that faces the pinion 84 on the opposite side of the first end surface 79. . On the first end surface 79 of the carrier 78, four claw portions 85 are arranged at equal angular intervals along the circumferential direction, and project along the axis L direction.

  As shown in FIG. 5, the elastic coupling 46 is formed of, for example, a rubber body such as silicone rubber or a resin body. In the elastic coupling 46, a single annular portion 46a and a plurality of arm portions 46b are integrally formed. The annular portion 46a has a ring shape, and a circular through hole 92 is formed at the center thereof. A plurality (eight examples in FIG. 5) of arm portions 46b are arranged on the outer peripheral surface of the annular portion 46a so as to be spaced apart from each other by a predetermined angle, and project radially outward from the outer peripheral surface of the annular portion 46a. Is arranged. Between the arm portions 46b and 46b adjacent to each other, a trough portion 46c formed of a substantially V-shaped groove portion when viewed from the front is provided.

  A coil spring 94 is inserted through the through hole 92 of the elastic coupling 46. One end of the coil spring 94 is in contact with the carrier 78, and the other end of the coil spring 94 is in contact with the input flange 86 (see FIG. 3). The carrier 78 and the input flange 86 are urged away from each other by the spring force of the coil spring 94.

  A plurality of projecting portions 96 are provided on the distal end side of the arm portion 46 b of the elastic coupling 46. The plurality of projecting portions 96 are arranged at substantially equal angular intervals in the circumferential direction. Of the eight protrusions 96, four protrusions 96 a are arranged to protrude from the side surface of the arm part 46 b facing the carrier 78, and every other adjacent arm part 46 b, and face the input flange 86. On the side surface of the arm portion 46b, four protruding portions 96b are arranged for every other adjacent arm portion 46b.

  In other words, on the distal end side of the arm portion 46b of the elastic coupling 46, among the eight projecting portions 96, a projecting portion 96a projecting toward the carrier 78 side and a projecting portion 96b projecting toward the input flange 86 side. And are arranged alternately. The projecting portion 96 a projecting toward the carrier 78 side is provided so as to be able to contact the first end surface 79 of the carrier 78, and the projecting portion 96 b projecting toward the input flange 86 side is opposed to the input flange 86. It is provided so as to be able to contact the surface 98.

  As shown in FIG. 3, the input flange 86 has a substantially disk shape, and is supported rotatably by sandwiching the front and back surfaces of the outer peripheral portion between a pair of thrust bearings 88a and 88b. The pair of thrust bearings 88a and 88b is held by the second housing 30b by an annular lock nut 90 fastened to the inner peripheral surface of the second housing 30b. Of the pair of thrust bearings 88a and 88b, one thrust bearing 88a supports the thrust load between the second housing 30b and the input flange 86, and the other thrust bearing 88b includes the lock nut 90 and the input flange 86. Support thrust load between.

  As shown in FIG. 5, four claw portions 100 are arranged at equal angles along the circumferential direction on the facing surface 98 of the input flange 86 facing the carrier 78 in the axis L direction, and A predetermined length protrudes toward the elastic coupling 46 side (carrier 78 side). The four claw portions 85 provided on the first end surface 79 of the carrier 78 and the four claw portions 100 provided on the opposing surface 98 of the input flange 86 are shifted in phase by about 45 degrees in the circumferential direction. (Refer to FIG. 6).

  Further, as shown in FIG. 7A, a plurality of projecting portions projecting alternately toward the carrier 78 side and the input flange 86 side at the radially outer end portion of the arm portion 46b of the elastic coupling 46. 96 is provided. In this case, as shown in FIGS. 7B and 7C, the arm portions 46b are elastically deformed (flexed) with the plurality of projecting portions 96 as fulcrums. At this time, the reaction force generated in the projecting portion 96 serving as a fulcrum urges the carrier 78 in the direction of the axis L with the input flange 86 as a reference, thereby preventing the carrier 78 from falling down. As shown in FIG. 6, the plurality of projecting portions 96 a and 96 b are disposed along the circumferential direction between the claw portion 85 of the carrier 78 and the claw portion 100 of the input flange 86.

  Between the pinion pin 80 and the pinion 84, for example, a bearing member (not shown) such as a sliding bearing or a needle bearing is interposed. The thickness of the pinion 84 that is rotatably supported by the bearing member is set to be larger than the length of the pinion pin 80 in the axial direction. For this reason, the pinion 84 is pinched by pinching the end surface of the pinion 84 (a surface substantially orthogonal to the tooth portion formed on the outer periphery) between the second end surface 81 of the carrier 78 and the inner diameter flange portion 74a of the ring gear 74. Can be controlled.

  Every four claw portions 85 of the carrier 78 are engaged with the eight valley portions 46c of the elastic coupling 46, and the four troughs 85 of the input flange 86 are out of phase with the claw portions 85 of the carrier 78. Every other nail | claw part 100 engages. That is, as shown in FIG. 6, the claw portions 85 of the carrier 78 and the claw portions 100 of the input flange 86 are alternately engaged with the eight valley portions 46c of the elastic coupling 46 along the circumferential direction.

  Accordingly, the rotational torque of the carrier 78 is transmitted from the claw portion 85 of the carrier 78 to the input flange 86 through the arm portion 46 b of the elastic coupling 46 and the claw portion 100 of the input flange 86. At that time, the elastic coupling 46 formed of an elastic body is elastically deformed by its elastic force, thereby absorbing the axial deviation between the carrier 78 and the input flange 86 (core deviation) and a sudden change in rotational torque. Can be absorbed to achieve smooth power transmission.

  As shown in FIG. 5, the carrier holding member 106 is obtained by pressing a metal plate, and is fastened to the ring gear 74 via a bolt (not shown). The carrier holding member 106 includes a main body portion 106a made of an annular flat plate and a flange portion 106b obtained by bending the inner periphery of the main body portion 106a into an L-shaped cross section.

  As shown in FIG. 3, the first slide bearing 108a is fixed to the inner peripheral surface of the intermediate portion in the axis L direction of the second housing 30b. A second slide bearing 108b is fixed to the inner peripheral surface of the end member 110 that is screwed to the end portion of the second housing 30b in the axis L direction. The output rod 32 is slidably supported along the axis L direction by the first slide bearing 108a and the second slide bearing 108b.

  The feed screw mechanism 48 has a function of converting the rotational motion of the input flange 86 into the reciprocating linear motion of the output rod 32. As shown in FIG. 3, the feed screw mechanism 48 is screwed into a male screw member (feed screw shaft) 112 formed integrally with the input flange 86 and having a male screw formed on the outer peripheral surface thereof, and a male screw of the male screw member 112. A female screw member (feed nut) 114 that has a female screw in a part of the inner peripheral surface and is fitted to the inner peripheral surface of the hollow output rod 32 and fixed to the output rod 32 is provided.

  As shown in FIG. 4, the female screw member 114 is formed of a substantially cylindrical body, and is fixed to the inner peripheral surface of the output rod 32 via a lock nut 115. A female screw portion 117 a is provided on the inner peripheral surface of the female screw member 114. The female screw portion 117 a has a mountain portion 121 and a valley portion 123.

  A male screw part 112 a is provided on the outer peripheral surface of the male screw member 112. The male threaded portion 112a has a peak portion 129 that has a substantially trapezoidal cross section and projects outward in the radial direction, and a trough portion 131 that has a substantially trapezoidal cross sectional shape and is recessed in the radial inward direction.

  The male screw member 112 is formed with a grease holding groove 200 that holds the grease G filled between the male screw member 112 and the female screw member 114. The grease holding groove 200 is composed of a bottom surface 202 that is a low groove and a tapered portion 204 that is formed to face both sides of the bottom surface 202. The grease holding groove 200 is formed continuously from the outer circumference of the male screw member 112 at least from one half to one circumference, or is formed at one or more locations along the circumferential direction of the outer circumference of the male screw member 112. It is preferred that

  Further, the grease holding groove 200 is located at the center (intermediate portion) of the sliding length (sliding range) X of the female screw member 114 (see FIG. 8 to be described later), and is a circumferential surface that extends over the entire circumference of the male screw member 112. It is formed with. The grease holding groove 200 functions as a “groove portion in which no peak portion is formed”.

  The taper portion 204 is positioned between the top of the incomplete thread portion 129a and the bottom surface 202 of the grease holding groove 200, and is formed so that the groove width gradually decreases toward the bottom surface 202 of the grease holding groove 200. . The incomplete thread portion 129 a is a peak portion that is closest to the grease holding groove 200 on both sides in the axial direction across the grease holding groove 200. The taper portion 204 is preferably formed at least once around the outer peripheral surface of the male screw member 112.

  A clearance 206 is formed between the tapered portion 204 and the top of the crest 121 of the female screw portion 117 a formed on the female screw member 114. Due to this clearance 206, the top of the crest 121 of the female screw portion 117a and the tapered portion 204 are formed in a non-contact state. In addition, in the peak portion 129 of the male screw member 112, only the peak portions on both sides sandwiching the grease holding groove 200 are formed as incomplete screw portions 129a, and the other peak portions 129 are formed as complete screw portions. ing. The height of the top of the incomplete thread 129a is formed lower than the height of the top of the complete thread.

  As shown in FIG. 4, the depth (D1) from the top of the peak portion 129 of the male screw portion 112a to the bottom surface 202 of the grease holding groove 200 is deeper than the depth (D2) of the valley portion 131 of the male screw portion 112a. It is formed (D1> D2). In the present embodiment, the depth (D1) to the bottom surface 202 of the grease holding groove 200 is formed deeper than the depth (D2) of the valley 131 of the male screw portion 112a, but is not limited to this. Instead, the depth (D1) to the bottom surface 202 of the grease holding groove 200 may be the same as the depth (D2) of the valley (D1 = D2). Further, the depth (D1) to the bottom surface 202 of the grease holding groove 200 is preferably deeper as long as possible in terms of strength and durability design, since a larger amount can hold the grease G.

  FIG. 8 is an explanatory view showing the relationship between the moving amount of the female screw member and the total length. In FIG. 8, the female screw member and the male screw member are depicted in a simplified manner for convenience.

  In FIG. 8, the female screw member 114 indicated by a solid line shows a state of maximum movement to one side (maximum movement amount to one side), and the female screw member 114 indicated by a two-dot chain line is opposite to the one side. It shows the state of maximum movement to the other side (maximum movement amount to the other side). The moving amount S of the female screw member 114 is set to be smaller than the total length L along the axial direction of the female screw member 114 (S <L).

  By setting the relationship as described above, it is ensured that the grease holding groove 200 is exposed to the outside (external) from the female screw member 114 even when the female screw member 114 has moved to the maximum side and the other side. It can be avoided (L ≧ S + grease holding groove width).

  The position of the grease holding groove 200 formed on the outer peripheral surface of the male screw member 112 is such that the groove center of the grease holding groove 200 is the maximum movement amount on one side of the female screw member 114 and the other side, as shown in FIG. It is preferable that the center position (X / 2) of the sliding range X, which is the maximum movement amount.

FIG. 9 is an explanatory view showing a state in which the grease held in the grease holding groove is prevented from flowing out to the outside.
As shown in FIG. 9, the grease holding groove 200 is closed by a set of mountain portions 121 of the female screw member 114 sandwiching the grease holding groove 200. That is, the grease G held in the grease holding groove 200 passes through the clearance 206 to the valley 131 side between the incomplete screw portion 129a and the complete screw portion 129b adjacent to the incomplete screw portion 129a. Try to flow along the direction of the arrow. However, since the thread 121 of the female screw member 114 and the wall surface falling from the top of the incomplete screw portion 129a to the complete screw portion 129b side are in contact with each other (see the cross in FIG. 9), the complete screw portion 129b side is reached. The outflow of grease G is suppressed. For this reason, the grease G is prevented from flowing out from the grease holding groove 200.

  In this regard, in the conventional feed screw structure, even if grease is applied at the time of assembly, the grease is pushed to the left and right outside of the sliding section X (see FIG. 8), and the state of application at the beginning of assembly continues for a long time. There is no. For this reason, the contact surface of the sliding surface of the screw is close to fixed lubrication in the boundary lubrication region. Therefore, in the conventional feed screw structure, the friction coefficient increases in the low speed region, and the difference from the friction coefficient when it starts to move (high speed region) increases. As a result, the stick-slip phenomenon that did not occur at the beginning of assembly is likely to occur as the number of uses increases. Along with this, with the conventional feed screw structure, intermittent abnormal noise is generated, the merchantability is deteriorated, and the load due to stick-slip phenomenon is repeatedly input to the power transmission part, so durability Deteriorate. For this reason, in the conventional feed screw structure, the strength must be designed in consideration of the above points, and there is a problem that the system becomes large.

  On the other hand, in the present embodiment, excess grease G generally remains in the space formed by the grease holding groove 200 and the incomplete screw portion 129a. It is possible to suppress interruption.

  Returning to FIG. 3, an annular stopper 116 is attached to the outer periphery of the output rod 32. When the output rod 32 is displaced to the maximum position in the extending direction, the stopper 116 comes into contact with the end member 110 fixed to the second housing 30b, whereby the displacement is restricted and the stopper function is exhibited. By providing this stopper 116, it is possible to reliably prevent the output rod 32 from falling off the second housing 30b.

  A seal mechanism is provided between the second housing 30b and the output rod 32 in order to prevent water (moisture) or dust from entering the gap between the second housing 30b and the output rod 32. This sealing mechanism is composed of a rubber boot 120 having a bellows part that can be expanded and contracted, and bands 122 a and 122 b of different diameters that fasten fitting parts at both ends of the boot 120. One end of the boot 120 is fitted into an annular step 118 formed on the outer peripheral surface of the end of the second housing 30b, and the other end of the boot 120 is fitted into an annular groove 119 formed in the output rod 32. It is provided to do.

  When the output rod 32 extends and displaces, the volumes of the chambers 40a and 40b in the first housing 30a and the second housing 30b increase. On the contrary, when the output rod 32 contracts and displaces, the first housing 30a and the second housing 30b. The volume of the chambers 40a and 40b in 30b decreases. For this reason, the pressures in the chambers 40a and 40b may fluctuate and hinder smooth operation of the toe control actuator 18. However, in this embodiment, since the internal space of the hollow output rod 32 and the internal space of the boot 120 communicate with each other via the vent hole 124 formed in the output rod 32, the pressure fluctuation is caused by the deformation of the boot 120. The toe control actuator 18 can be operated smoothly.

  The second housing 30b is provided with a stroke sensor 126 that detects the stroke position (displacement amount) of the output rod 32 and feeds back a detection signal to a control device (not shown) when the toe control actuator 18 is expanded and contracted. . The stroke sensor 126 is a sensor main body 134 in which a permanent magnet 130 fixed to the outer peripheral surface of the output rod 32 via a bolt 128 and a detection unit 132 such as a coil for magnetically detecting the position of the permanent magnet 130 are housed. With. The second housing 30b is formed with a long groove (opening) 136 extending in the direction of the axis L in order to avoid interference with the permanent magnet 130 as the output rod 32 is displaced.

  The rear suspension apparatus 10 to which the toe control actuator 18 according to the present embodiment is assembled is basically configured as described above. Next, its operation, action and effect will be described.

  In FIG. 3, when the motor 42 is driven based on a drive signal output from a control device (not shown) to change the toe angle of the rear wheel W, the rotational motion of the sun gear 76 formed on the rotary shaft 60 of the motor 42 is It is decelerated by the planetary gear mechanism 44 (the ring gear 74 and the pinion 84 meshing simultaneously with the sun gear 76) and output to the carrier 78. The rotational movement of the carrier 78 is transmitted to the input flange 86 through the elastic coupling 46 and rotates the male screw member 112 integrally connected to the input flange 86. When the male screw member 112 rotates, the female screw member 114 engaged with the male screw member 112 is displaced in the direction of the axis L, and the output rod 32 connected to the female screw member 114 moves forward and backward from the second housing 30b, thereby toe control actuator. 18 expands and contracts to change the toe angle of the rear wheel W.

Next, a manufacturing method of the feed screw mechanism 48 used in the present embodiment will be described.
10 (a) to 10 (d) are cross-sectional views illustrating the manufacturing process of the male screw member.
As shown in FIG. 10 (a), the molding material 300 of the male screw member 112, which is a molded product, is formed of a substantially cylindrical body, and a cutout portion having a tapered cross section that becomes the grease holding groove 200 after molding is formed at the center thereof. 302 is formed. The notch 302 is substantially equal to the outer diameter (depth) of the valley 131 of the male thread 112a, and the minimum area is set equal to that of the male thread 112a. The cutout portion 302 is connected to the material outer diameter portion 306 by tapered surfaces 304 on both sides thereof.

  FIG. 10B shows a state in which the molding material 300 is set in the cavities of the rolling dies 308a and 308b. From this set state, for example, when the upper rolling die 308a and the lower rolling die 308b are pressed into the molding material 300 with respect to each other (pressed), the result is as shown in FIG. The material outer diameter portion 306 of the molding material 300 is pressed by the molding convex portions of the rolling dies 308a and 308b, and the meat wraps around the concave portions between the adjacent molding convex portions to form the mountain portion 129 of the male screw member 112. To go. However, since the bottom 302a and the tapered surface 304 of the notch 302 are not pressed by the forming convex part at all or gradually decrease from the material outer diameter part 306 to the notch 302, the rolling die The amount filled into the notch 302 of 308a, 308b decreases according to the amount.

  Finally, a male screw member 112 which is a molded product shown in FIG. 10D is formed. In the molded product, the taper portion 204 gradually decreases in width and height from the top portion to the bottom surface 202 of the grease holding groove 200, thereby forming a smooth shape, and an incomplete screw portion 129a is formed.

  In the present embodiment, when the tapered surface 304 is formed on both sides of the notch 302 in the state of the molding material 300 and the thread surface is molded by rolling to the molding material 300, the grease retaining groove 200 of the molded product is formed. The shape is such that the incomplete threaded portion 129a at both ends gradually transitions to the complete threaded portion 129b. In the present embodiment, the male screw member 112 can be easily manufactured with a simple structure and manufacturing method by using rolling forming.

Next, the assembly order of the feed screw mechanism 48 will be described.
FIGS. 11A to 11C are cross-sectional views showing the assembly process of the feed screw mechanism.
As shown in FIG. 11A, first, a predetermined amount of grease G is applied to the entire outer peripheral surface along the axial direction of the male screw member 112, and the grease G is filled in the center grease holding groove 200. Thereafter, the male screw member 112 is screwed into the female screw member 114 and incorporated.

  Subsequently, as illustrated in FIG. 11B, in the complete screw portion 129 b, the grease G is pushed out by the female screw member 114, but the male screw member 112 extends from the incomplete screw portion 129 a on one side to the grease holding groove 200. Since the height and width of the crest of the ridge are reduced, there is no extrusion of the grease G, and the grease G stays at that site. As shown in FIG. 11C, when the female screw member 114 moves again to the complete screw portion 129 b on the other side of the male screw member 112, the grease holding groove 200 and the tapered portions on both sides of the grease holding groove 200 are sandwiched. In 204, grease G remains. The remaining grease G exhibits a subsequent lubricating action.

FIG. 12 is an explanatory diagram showing a positional relationship between the sliding portion of the screw and the grease holding groove.
As shown in FIG. 12, in this embodiment, a taper is provided between the grease holding groove 200 filled with the grease G and the heat source that is a sliding portion where the screws of the male screw member 112 and the female screw member 114 mesh with each other. By interposing the portion 204, the grease holding groove 200 can be disposed at a position (a position away from the heat generation source) in the axial direction of the male screw member 112. As a result, in this embodiment, deterioration of the properties of the grease G can be suitably avoided.

  As shown in FIG. 9, in this embodiment, both end sides sandwiching the grease holding groove 200 are always closed by the thread surfaces of the crests 121 of the female screw member 114. For this reason, in this embodiment, the discharge amount of the grease G in the axial movement range (maximum movement range) of the female screw member 114 relative to the male screw member 112 can be suppressed, and a good lubrication state can be maintained for a long period of time.

FIG. 13 is an explanatory view showing a diffusion state of the grease filled in the grease holding groove.
As shown in FIG. 13, in this embodiment, the grease holding groove 200 is filled by the own weight of the grease G itself, the centrifugal force due to the rotational motion of the male screw member 112, and the vibration transmitted to the male screw member 112 from the outside. The applied grease G is likely to adhere to the thread surface (valley 123) on the female thread member 114 side. For this reason, excess grease G is collected again in the grease holding groove 200, and an appropriate amount of grease G can be supplied between the male screw member 112 and the female screw member 114 with a simple structure. In the present embodiment, the lubricant filled in the grease retaining groove 200 is limited to a semi-solid lubricant such as grease, and it is not preferable to use a liquid lubricant.

  Furthermore, in the present embodiment, the sliding portion between the male screw member 112 and the female screw member 114 is kept in a good lubricating state by the grease G, so that the difference between the static friction coefficient and the dynamic friction coefficient can be reduced. As a result, in this embodiment, by suppressing the occurrence of the stick-slip phenomenon, it is possible to reduce the occurrence of abnormal noise due to the stick-slip phenomenon.

  Furthermore, in this embodiment, since a low coefficient of friction can be obtained stably, the amount of heat generated at the sliding portion between the male screw member 112 and the female screw member 114 can be suppressed. For this reason, in this embodiment, the temperature rise of the sliding part of the external thread member 112 and the internal thread member 114 can be suppressed, a stable lubrication state can be obtained, and stabilization of the screw efficiency can be achieved. Thereby, in this embodiment, since the power consumption in the motor 42 can be reduced and the motor 42 can be reduced in size, manufacturing cost can be reduced.

  Furthermore, in this embodiment, since the moving amount (S) of the female screw member 114 is set to be smaller than the total axial length (L) of the female screw member 114 (S <L), the moving amount of the female screw member 114 is set. Is the maximum, the grease retaining groove 200 is located in the female screw member 114 and is covered with the female screw member 114. Thereby, it can avoid suitably that the grease holding groove 200 is exposed to the outside.

  Furthermore, various loads such as a tensile load, a compressive load, and a torsional load are applied to the toe control actuator 18 incorporated in the rear suspension apparatus 10. In the present embodiment, the grease retaining groove 200 is always covered with the female screw member 114 within the range of the maximum movement amount (X) of the female screw member 114, and the axial load and bending load of compression / tensile are applied. The female screw member 114 bears the strength of the male screw member 112. In other words, the male screw member 112 is reinforced by the female screw member 114 against the axial load and the bending load of compression and tension.

  Further, since the friction coefficient is stable with respect to the torsional load, the input of the friction torque is suppressed and the stress can be reduced as compared with the prior art. As a result, the present embodiment can be preferably applied to the toe control actuator 18 incorporated in the rear suspension device 10.

  Although the present embodiment has been described based on the toe control actuator 18 incorporated in the rear suspension device 10 of the vehicle, the present invention is not limited to this, and other telescopic actuators that reciprocate the output member can also be used. Can be applied.

18 Toe control actuator
32 Output rod 42 Motor (electric motor)
48 Feed screw mechanism 112 Male thread member (Feed screw shaft)
112a Male thread (thread)
114 Female thread member (feed nut)
117a Female thread part (Female thread)
129 Mountain part 131 Valley part 200 Grease holding groove (groove part)
202 Bottom surface 204 Tapered portion G Grease S Travel distance L Overall length D1 Depth of bottom surface of grease holding groove D2 Depth of valley portion

Claims (2)

Extending and contracting comprising a feed screw shaft having a screw part and a feed nut screwed into the screw part, the feed screw mechanism converting the rotational motion of the motor into a reciprocating linear motion, and an output rod displaced by the feed screw mechanism In the actuator
The screw part has a male screw composed of a peak part and a valley part,
The feed screw shaft is
A groove portion formed in an intermediate portion along the axial direction of the feed screw shaft, wherein the peak portion is not formed;
A taper portion which is located between the crest portion and the groove portion closest to the groove portion on both sides of the groove portion, and is formed in a substantially tapered shape without contact with a female screw formed on the feed nut;
Have
The depth (D1) of the bottom surface of the groove is the same as the depth (D2) of the valley or is deeper than the depth (D2) of the valley (D1 ≧ D2),
A telescopic actuator, wherein the groove is filled with grease. The telescopic actuator according to claim 1,
The telescopic actuator is an actuator mounted on an arm constituting a suspension device of a vehicle,
The groove portion is covered by the feed nut in either the state where the feed nut is moved to the maximum side or the state where the feed nut is moved to the maximum side opposite to the one side. In position
The extension actuator is characterized in that the moving amount (S) of the feed nut is set smaller than the total length (L) in the axial direction of the feed nut (S <L).

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