JP2018168909A - Lubricant application method of linear motion actuator - Google Patents

Abstract

To enable application work of a grease in a linear motion actuator to be performed in a short time.SOLUTION: A linear motion actuator (ball screw device 17) includes: a screw shaft 18; a nut 19; and a bottomed cylindrical housing 21 on which the nut 19 is mounted. Before mounting an assembly 43 in which the nut 19 and the screw shaft 18 are integrated onto the housing 21, a grease 44 is provided in the housing 21. After mounting the assembly 43 on the housing 21, by relatively rotating the housing 21 with the nut 19 and the screw shaft 18, an end part 33 of the screw shaft 18 and a bottom part 32 of the housing 21 are brought closer together. Thus, the grease 44 is pushed to flow by the end part 33, and the grease 44 is made to intrude between the nut 19 and the screw shaft 18.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for applying a lubricant to a linear actuator.

  The linear actuator can convert rotational motion into linear motion, and is widely used in various fields. The linear actuator has a screw shaft and a nut provided on the outer peripheral side of the screw shaft. For example, the nut is moved linearly along the screw shaft by rotating the screw shaft by a motor. Can be made. Among such linear motion actuators, a ball screw device is known as a device that efficiently converts rotational motion into linear motion (see, for example, Patent Document 1).

  FIG. 8 is a cross-sectional view of an automobile brake device. The linear actuator provided in the brake device includes a ball screw device 90, and includes a screw shaft 91, a nut 92 provided on the outer peripheral side of the screw shaft 91, a spiral groove of the screw shaft 91, and a nut 92. A plurality of balls 93 provided between the spiral groove and a housing 94 to which a nut 92 is attached are provided. The housing 94 has a bottomed cylindrical shape, and a nut 92 is attached to the opening side (the right side in FIG. 8), and the housing 94 and the nut 92 are integrated. Inside the cylinder part (cylinder) 98 of the brake device, the housing 94 is provided so as to be movable in the axial direction and not rotatable in the circumferential direction. When the screw shaft 91 is rotated by a motor (not shown), a nut is provided. 92 and the housing 94 advance (or retract). In the case of the brake device, a pad 96 is attached to the housing 94 via a backup plate 95, and when the housing 94 moves forward, the pad 96 comes into contact with the disk 100 that rotates together with the wheels of the automobile, and the braking force. Can be generated.

JP 2016-35322 A

  In the linear motion actuator as described above, a lubricant is required between the screw shaft 91 and the nut 92, and grease is applied as the lubricant. Conventionally, as shown in FIG. 9, the grease is applied by inserting a nozzle 99 into a gap 97 between the screw shaft 91 and the nut 92 from the opening side of the housing 94 after the assembly of the linear actuator (ball screw device 90). This is done by inserting and injecting grease from the nozzle 99. However, since the gap 97 is narrow, the nozzle 99 used is thin, and it takes a long time to inject a predetermined amount of grease into the gap 97 through the nozzle 99 and apply it between the screw shaft 91 and the nut 92. Cost. Further, since a plurality of balls 93 and the like are provided between the screw shaft 91 and the nut 92, the nozzle 99 cannot be inserted deeply, and workability is poor. Such a problem occurs not only in the ball screw device 90 but also in other types of linear actuators (for example, by a combination of a nut having a trapezoidal screw and a screw shaft).

  Therefore, an object of the present invention is to provide a method that enables a grease application operation in a linear actuator to be performed in a short time.

  The present invention has a screw shaft, a nut provided on the outer peripheral side of the screw shaft, and a bottomed cylindrical shape that can accommodate one axial end of the screw shaft on one bottom side in the axial direction. And a housing to which the nut is attached on the other opening side in the axial direction, and a lubricant application method for a linear motion actuator, wherein an assembly in which the nut and the screw shaft are integrated is attached to the housing Before, grease is provided on the bottom side in the housing, and the assembly is attached to the housing, and then the housing, the nut, and the screw shaft are rotated relative to each other so that the end of the screw shaft and the By approaching the bottom portion of the housing, the grease is pushed and caused to flow by the end portion, and the grease enters between the nut and the screw shaft.

  According to this application method, in assembling the linear actuator, before attaching the assembly integrated with the nut and the screw shaft to the housing, the grease is provided in the housing, and after attaching the assembly to the housing, If the housing and nut and the screw shaft are rotated relative to each other, the grease is pushed by the screw shaft to flow and enters between the nut and the screw shaft, so that the grease can be applied in a short time. Become.

  Further, a first spiral groove is formed on the outer periphery of the screw shaft, a second spiral groove is formed on the inner periphery of the nut, and the linear motion actuator further includes the first spiral groove and the second spiral groove. A ball screw device including a plurality of balls provided between the nut, the ball, and the screw shaft before attaching the assembly to the housing. Grease is provided on the bottom side, and the assembly is attached to the housing, and then the housing, the nut, and the screw shaft are rotated relative to each other so that the end portion of the screw shaft and the bottom portion of the housing approach each other. Accordingly, it is preferable that the grease is pushed and caused to flow by the end portion, and the grease is allowed to enter between the first spiral groove and the second spiral groove. According to this application method, grease is filled in the raceway between the first spiral groove and the second spiral groove, and a plurality of balls exist, and this application method is a method of applying grease to the ball screw device. It is suitable as.

  The housing is attached with an inner peripheral surface to which an outer peripheral surface of the nut is fitted, an annular surface that is in contact with one end surface in the axial direction of the nut, and a retaining ring that is in contact with the other end surface in the axial direction of the nut. It is preferable that the nut is not allowed to fall off from the other axial side of the housing and is pressed against the annular surface by attaching the retaining ring to the groove. . In this case, the grease can enter between the nut and the screw shaft in preference to the fluid flowing and entering between the nut and the housing.

  According to the present invention, the grease application operation can be performed in a short time, and the production efficiency of the linear actuator is improved.

It is sectional drawing which shows an example of a brake device. It is a disassembled perspective view of a ball screw device. It is sectional drawing of a ball screw apparatus. It is sectional drawing which expands and shows a ditch | groove and a retaining ring. It is sectional drawing which shows the 1st process of the coating method. It is sectional drawing which shows the 2nd process of the coating method. It is sectional drawing which shows the 3rd process of the coating method. It is sectional drawing of the linear motion actuator which the brake device of a motor vehicle has. It is sectional drawing explaining the conventional coating method.

  A linear motion actuator to which grease, which is a lubricant, is applied by the application method of the present invention is used, for example, in a brake device of a vehicle (automobile). FIG. 1 is a cross-sectional view showing an example of the brake device 5. The brake device 5 applies a braking force by friction to the disk 6 that rotates integrally with the wheel of the automobile. In order to generate this braking force, the brake device 5 includes a linear actuator, and the linear actuator shown in FIG. In FIG. 1, the brake device 5 is in a non-braking state.

  The brake device 5 includes a floating type caliper 7 supported by a knuckle or the like (not shown) and a pair of pads 8 that sandwich the disk 6. The caliper 7 includes a first body 9, a second body 10 integrated with the first body 9, and a cover 11 attached to the first body 9. The pad 8 on one side (right side in FIG. 1) is supported by a first backup plate 12 attached to a later-described housing 21 of the ball screw device 17, and the pad 8 on the other side (left side in FIG. 1) It is supported by a second backup plate 13 attached to the second body 10.

  The first body 9 has a cylindrical shape (bottomed cylindrical shape) including a cylindrical main body portion 14 and a bottom plate portion 15 and opens toward the disk 6 side. A ball screw device 17 is provided inside the tube main body portion 14, and the ball screw device 17 includes a screw shaft 18, a nut 19, a plurality of balls 20, and a housing 21. A center line C of the screw shaft 18 becomes a center line of the ball screw device 17, and a direction parallel to the center line C is referred to as an axial direction.

  A through hole 16 is formed in the bottom plate portion 15 of the first body 9. A rolling bearing 22 is attached to the through-hole 16, and the screw shaft 18 can be rotated in the circumferential direction around the center line C and immovable in the axial direction by the first body 9 via the rolling bearing 22. It is supported. A key 24 is provided between the housing 21 and the cylinder main body 14, and the housing 21 can reciprocate in the axial direction with respect to the cylinder main body 14, but cannot rotate in the circumferential direction around the center line C. It has become.

  As will be described later, the nut 19 and the housing 21 are integrated, and when the screw shaft 18 rotates in one direction (forward rotation), the nut 19 and the housing 21 are axially one side along the screw shaft 18 ( Move to the left side in FIG. On the other hand, when the screw shaft 18 rotates in the other direction (reverse rotation), the nut 19 and the housing 21 move along the screw shaft 18 to the other side in the axial direction (right side in FIG. 1). In the brake device 5 shown in FIG. 1, the moving housing 21 functions as a piston, and the first body 9 (cylinder main body portion 14) functions as a cylinder that accommodates and guides the housing 21.

  A motor (electric motor) 51 and a speed reducer 23 are provided outside the cylinder body 14. A command signal is input to the motor 51 from the control unit 52. Based on this command signal, the motor 51 rotates forward, reversely, and stops. The reduction gear 23 includes a first gear 25 fixed to the output shaft of the motor 51, a second gear 26 fixed to the other axial end of the screw shaft 18, and the gears 25, 26. And an intermediate gear 27 provided between the two. The speed reduction device 23 may have other configurations.

  With the above configuration, when the motor 51 rotates, the nut 19 and the housing 21 move in the axial direction. That is, the rotational motion of the screw shaft 18 transmitted from the motor 51 via the speed reduction device 23 is converted into a linear motion in the axial direction of the housing 21 by the ball screw device 17. As a result, the pair of pads 8 sandwich the disk 6 to generate a braking force.

  FIG. 2 is an exploded perspective view of the ball screw device 17. FIG. 3 is a cross-sectional view of the ball screw device 17. As shown in FIGS. 2 and 3, the ball screw device 17 includes a screw shaft 18 as an input member and a nut 19 as an output member provided on the outer peripheral side of the screw shaft 18. A first spiral groove 29 is formed on the outer periphery of the screw shaft 18, and a second spiral groove 30 is formed on the inner periphery of the nut 19. The screw shaft 18 is longer in the axial direction than the nut 19, and a first spiral groove 29 is formed in a range wider than the nut 19 (second spiral groove 30) in the axial direction. The plurality of balls 20 are provided between the first spiral groove 29 and the second spiral groove 30. In the present embodiment, as will be described later, a coil spring 53 is also provided between the first spiral groove 29 and the second spiral groove 30.

  The housing 21 has a bottomed cylindrical shape including a cylindrical portion 31 and a bottom portion 32, and can accommodate an end portion 33 on one axial direction side of the screw shaft 18 on the bottom portion 32 side which is one axial direction side. A nut 19 is attached on the opening side which is the other side in the axial direction. In order to attach (fix) the nut 19 to the housing 21, the ball screw device 17 includes a C-shaped retaining ring 28 that contacts the other end surface 38 in the axial direction of the nut 19.

  In FIG. 3, the cylindrical portion 31 of the housing 21 includes an inner peripheral surface 35 to which the outer peripheral surface 34 of the nut 19 is fitted, an annular surface 37 that contacts the end surface 36 on one axial side of the nut 19, and a retaining ring 28. And a recessed groove 39 for mounting. By inserting the nut 19 into the inner peripheral surface 35 of the housing 21 and attaching the retaining ring 28 to the concave groove 39, the nut 19 is sandwiched between the annular surface 37 of the housing 21 and the retaining ring 28 in the axial direction. The nut 19 cannot be removed from the other axial side of the housing 21. The space formed on the inner peripheral side of the housing 21 includes a small-diameter hole 49 located on one side in the axial direction from the annular surface 37 (the inner peripheral edge thereof) and the annular surface 37, and the other side in the axial direction from the annular surface 37. The large-diameter hole portion 48 is located on the (opening side), and the nut 19 is attached to the large-diameter hole portion 48.

  FIG. 4 is an enlarged cross-sectional view showing the recessed groove 39 and the retaining ring 28. In order to fit the retaining ring 28 into the concave groove 39, the retaining ring 28 is elastically deformed in the direction of diameter reduction. In addition, the retaining ring 28 is elastically deformed slightly in the diameter-reducing direction (from the natural state) while being fitted in the concave groove 39, and an elastic force in the diameter-enlarging direction is generated as its restoring force. The concave groove 39 has an inclined groove side surface 41 on the other side in the axial direction. The groove side surface 41 is a tapered surface having a diameter that decreases toward the other side in the axial direction. The retaining ring 28 has an inclined surface 50 having a shape corresponding to the groove side surface 41 on the other side in the axial direction. In the state where the retaining ring 28 is fitted in the concave groove 39, the retaining ring 28 has the elastic force in the diameter increasing direction as described above, so that the inclined surface 50 of the retaining ring 28 contacts the groove side surface 41. Thus, the retaining ring 28 urges the nut 19 toward one side in the axial direction. That is, a force that pushes the nut 19 in one axial direction is generated. Therefore, the nut 19 is strongly pressed against the annular surface 37 (see FIG. 3) of the housing 21. As described above, in the present embodiment, the retaining ring 28 is attached to the concave groove 39 so that the nut 19 cannot be removed from the other axial side of the housing 21 and the nut 19 is pressed against the annular surface 37 of the housing 21. An axial force can be applied.

  As shown in FIG. 2, the outer peripheral shape of the end portion 40 on one side in the axial direction of the nut 19 is a polygon, and one end in the axial direction of the inner peripheral surface 35 of the housing 21 is the end portion of the nut 19. It is a polygon corresponding to 40 shapes. As described above, the nut 19 and the housing 21 are integrated, and the nut 19 and the housing 21 are relatively unrotatable.

  The ball screw device 17 of the present embodiment (see FIG. 3) is a non-circulation system in which the ball 20 does not circulate, and a plurality of balls are provided in the track path 42 between the first spiral groove 29 and the second spiral groove 30. In addition to 20, a coil spring 53 (see FIG. 2) is provided.

  The lubrication system of the ball screw device 17 having the above configuration is grease lubrication, and grease is applied to the raceway 42 in which the plurality of balls 20 are provided. This grease is applied when the ball screw device 17 is assembled. Hereinafter, this coating method will be described.

  As shown in FIG. 5, a nut 19 is provided on the outer peripheral side of the screw shaft 18, and a plurality of balls 20 (and a coil spring 53 shown in FIG. 2 in this embodiment) are provided between the screw shaft 18 and the nut 19. Intervene (first step). Thereby, an assembly 43 in which the nut 19, the ball 20 and the screw shaft 18 are integrated is obtained. Before the assembly 43 is attached to the housing 21, grease 44 (a lump of grease 44) is provided on the bottom 32 side in the housing 21. Although the posture of the housing 21 may be other than the posture shown in FIG. 5, in this embodiment, the bottom portion 32 on the one axial side of the housing 21 is placed on a horizontal plane, and the opening on the other axial side of the housing 21 is the upper side. The posture is suitable for

  When the assembly 43 is completed, the assembly 43 is attached to the housing 21 (second process: see FIG. 6). That is, the nut 19 included in the assembly 43 is fitted to the inner peripheral surface 35 of the housing 21, the retaining ring 28 is attached to the concave groove 39, and the nut 19 is integrated with the housing 21. In this state, the grease 44 provided in the housing 21 exists in a space 54 formed between the bottom portion 32 of the housing 21 and the end portion 33 of the screw shaft 18.

  As shown in FIG. 6, after attaching the nut 19 of the assembly 43 to the housing 21, the housing 21, the nut 19 and the screw shaft 18 are rotated relative to each other (third step: see FIG. 7). In the present embodiment, the screw shaft 18 is rotated around the center line C with respect to the housing 21 in a fixed state. As shown in FIG. 7, this rotation advances the screw shaft 18 toward one side in the axial direction (downward in FIG. 7) and brings the end 33 of the screw shaft 18 and the bottom 32 of the housing 21 closer to each other. The grease 44 is pushed and caused to flow by the portion 33, and the grease 44 enters between the first spiral groove 29 and the second spiral groove 30 (track path 42). The screw shaft 18 is advanced to the stroke end where the end 33 of the screw shaft 18 contacts the bottom 32 of the housing 21 (via a portion of the crushed grease 44). The grease 44 passes through the annular space 47 formed between the outer peripheral surface 45 of the end 33 of the screw shaft 18 and the inner peripheral surface 46 on one axial side of the housing 21, and passes through the first spiral groove 29 and the second It enters between the spiral groove 30. For this reason, the annular space 47 is also filled with a part of the grease 44. Even if the grease 44 is present in the annular space 47, the housing 21 has a bottomed cylindrical shape, so that the grease 44 does not flow out to the outside.

  In the first step (see FIG. 5), the volume (amount) of the grease 44 provided in advance in the housing 21 is such that the small diameter hole 49 of the housing 21 and the screw shaft 18 are advanced to the stroke end shown in FIG. The volume of the space formed between the nut 19 and the screw shaft 18 is (slightly) larger. For this reason, the grease 44 can reach the other side of the nut 19 in the axial direction (that is, the opening side of the housing 21), and the grease 44 is spread over the entire area of the raceway 42.

  In the present embodiment, as described above (see FIG. 4), the retaining ring 28 is attached to the concave groove 39, so that the nut 19 is pressed against the annular surface 37 (see FIG. 6) of the housing 21. For this reason, the nut 19 is in close contact with the annular surface 37. For this reason, during the period shown in FIGS. 6 to 7 (third step), the grease 44 crushed by the end portion 33 of the screw shaft 18 flows and flows between the nut 19 and the housing 21 (annular surface 37). Prior to entering, it is possible to enter between the nut 19 and the screw shaft 18.

  As described above, according to the lubricant application method of the present embodiment, as shown in FIG. 5, before the assembly 43 in which the nut 19 and the screw shaft 18 are integrated is attached to the housing 21, the bottom portion 32 in the housing 21. Grease 44 is provided on the side. Then, after the assembly 43 is attached to the housing 21 (see FIG. 6), the screw shaft 18 is rotated to advance the end portion 33 of the screw shaft 18 toward the bottom portion 32 of the housing 21. The grease 44 is pushed and caused to flow by the end portion 33 by approaching the bottom portion 32, and the grease 44 enters between the nut 19 and the screw shaft 18.

  According to this coating method, in assembling the ball screw device 17, the grease 44 provided in advance in the housing 21 is pushed by the screw shaft 18 and flows to enter between the nut 19 and the screw shaft 18. . Therefore, the grease 44 can be applied in a short time, and the production efficiency of the ball screw device 17 is improved. In particular, in the ball screw device 17, since a relatively large gap is generated in the raceway 42 between the nut 19 and the screw shaft 18, the flowing grease 44 is easy to enter, and the grease 44 is in the entire raceway 42. Widely spread. That is, the application method is suitable as a method of applying the grease 44 to the ball screw device 17.

  In addition, although the ball screw apparatus 17 was demonstrated as a linear motion actuator, other than this may be sufficient. That is, the linear motion actuator may be any one that converts one rotary motion of the housing 21 and the screw shaft 18 into the other linear motion of the housing 21 and the screw shaft 18. However, it may be a linear motion actuator in which a trapezoidal screw is formed on the outer periphery of the screw shaft, and a trapezoidal screw that meshes with the trapezoidal screw is formed on the inner periphery of the nut. In the case of a linear actuator using a trapezoidal screw, a relatively large axial clearance in the threaded portion is preferable in terms of ease of grease flow.

  The embodiments disclosed above are illustrative in all respects and not restrictive. That is, the coating method of the present invention is not limited to the illustrated form, and may be other forms within the scope of the present invention. For example, the ball screw device 17 of the above embodiment is a non-circulation system in which the ball 20 does not circulate, but may be a circulation system. Moreover, although the case where the ball screw apparatus 17 was used for a brake device was demonstrated, it is applicable also to another apparatus.

17: Ball screw device (linear motion actuator) 18: Screw shaft 19: Nut 20: Ball 21: Housing 28: Retaining ring 29: First spiral groove 30: Second spiral groove 32: Bottom 33: End 34: Outer peripheral surface 35: inner peripheral surface 36: end surface 37: annular surface 38: end surface 39: recessed groove 43: assembly 44: grease

Claims (3)

A screw shaft, a nut provided on the outer peripheral side of the screw shaft, and a bottomed cylindrical shape that can accommodate one axial end of the screw shaft on the bottom side of one axial direction and the other axial direction A housing to which the nut is attached on the opening side of the actuator, and a lubricant application method for a linear motion actuator comprising:
Before attaching an assembly in which the nut and the screw shaft are integrated to the housing, grease is provided on the bottom side in the housing,
After the assembly is attached to the housing, the end portion of the screw shaft and the bottom portion of the housing are brought close to each other by rotating the housing, the nut, and the screw shaft relative to each other. A method for applying a lubricant to a direct acting actuator, wherein grease is pushed to flow and the grease enters between the nut and the screw shaft. A first spiral groove is formed on the outer periphery of the screw shaft, a second spiral groove is formed on the inner periphery of the nut, and the linear actuator is further provided between the first spiral groove and the second spiral groove. A ball screw device comprising a plurality of balls provided in
Before attaching the assembly integrated with the nut, the ball and the screw shaft to the housing, grease is provided on the bottom side in the housing,
After the assembly is attached to the housing, the end portion of the screw shaft and the bottom portion of the housing are brought close to each other by rotating the housing, the nut, and the screw shaft relative to each other. The method of applying a lubricant for a linear actuator according to claim 1, wherein the grease is pushed and fluidized to allow the grease to enter between the first spiral groove and the second spiral groove. The housing has a concave groove for attaching an inner peripheral surface to which the outer peripheral surface of the nut is fitted, an annular surface that contacts one end surface in the axial direction of the nut, and a retaining ring that contacts the other end surface in the axial direction of the nut. And having
The linear motion according to claim 1 or 2, wherein the retaining ring is attached to the concave groove so that the nut cannot be removed from the other axial side of the housing and the nut is pressed against the annular surface. Actuator lubricant application method.

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