JP2011149536A - Feed screw device equipped with lock prevention mechanism - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a structure having excellent durability without requiring a high control and without generating an impact noise so as to prevent a lock state. <P>SOLUTION: A feed screw device includes a nut 16c, a screw 17c and a compression coil spring 49. A female screw part 50 is formed only in a portion near to the end tip of the inner peripheral surface of the nut 16c out of them. A male screw part 51 having an axial dimension shorter than the axial dimension of the deep part 52 of the nut 16c is formed only in a portion near to the end tip of the outer peripheral surface of the screw 17c. With the male screw part 51 going off the female screw part 50 and entering the deep part 52, elastic force is applied to the screw 17c in a direction for getting out of the nut 16c by the compression coil spring 49. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an improvement in a feed screw device constituting, for example, an electric parking brake device. Specifically, it is intended to realize a structure that can reliably prevent locking in a state of being displaced to the end portion with a structure having low cost and excellent durability.

  In order to brake a vehicle, a drum type brake device is widely used. It is also widely practiced to incorporate a parking brake device for maintaining the vehicle in a stopped state with respect to a so-called service brake device that decelerates or stops the running vehicle by depressing the pedal by the driver. .

As such a structure, Patent Document 1 describes a structure in which a mechanical parking brake device that is mechanically operated by a link mechanism is incorporated into a so-called leading trailing drum service brake device. Yes.
When the drum type parking brake device having the structure described in Patent Document 1 is operated, the driver operates the parking lever, the foot pedal, etc., so that the tip of the expansion lever is centered on the backing plate via the parking brake cable. Turn to the side. Then, the distance between the pair of brake shoes is increased via the distal end portion of the extension lever and the strut, and the braking force is generated by pressing the outer peripheral surface of the lining of both brake shoes against the inner peripheral surface of the drum. Note that the drum-type brake device described in Patent Document 1 shares the basic structure of the drum brake such as the pair of brake shoes and the drum between the service brake device and the parking brake device. .

  In contrast to such a mechanical parking brake device, an electric parking brake device that generates braking force by converting electric energy into axial force in response to the recent trend of advanced control of vehicles. However, various structures have been proposed. Such an electric parking brake device eliminates the need for a parking brake cable installation space, etc., and can be operated by an electric switch operation by the driver in addition to reducing costs and facilitating installation. The driver's labor can be reduced with respect to a mechanical parking brake device that pulls and operates the parking brake cable by a manual parking lever, a foot pedal, or the like.

  FIGS. 6-8 has shown the 1st example of the structure which this inventor considered previously as a structure of the drum brake apparatus with an electric parking brake. This drum brake device 1 with an electric parking brake electrically realized a drive device for rotating an expansion lever among the components of the mechanical drum parking brake device described in Patent Document 1 described above. Is. Since the structure of the hydraulic service brake device and the basic structure of the parking brake device are substantially the same as the structure that has been widely known from the past, such as described in Patent Document 1, the description will be simplified. Below, it demonstrates centering on the structure and effect | action of a drive device which are the characterizing parts of this example.

The electric parking brake-equipped drum brake device 1 drives a back plate 2, an anchor 77, a wheel cylinder 78, a pair of brake shoes 3 a and 3 b, a drum 4, an expansion / contraction device 5, and the expansion / contraction device 5. And a driving device 6 for the purpose.
Of these, the back plate 2 is supported and fixed to components of a suspension device such as a knuckle and an axle housing. The anchor 77 is supported and fixed to a radially outward portion of the back plate 2 in one circumferential direction. Further, the wheel cylinder 78 is fixed at a position near the outer diameter of the back plate 2 at a position opposite to the anchor 77 in the radial direction of the back plate 2. The wheel cylinder 78 has a pair of pistons oil-tightly fitted to both ends of the cylinder cylinder 79. By introducing hydraulic pressure to the inside of the center of the cylinder cylinder 79, the wheel cylinder 78 can be removed from both ends of the cylinder cylinder 79. The projecting amount of the two pistons is increased (the interval between the two pistons is increased).

  The brake shoes 3a and 3b support the displacement of the back plate 2 in the radial direction at two positions opposite to the radial direction of the back plate 2. The brake shoes 3a and 3b are substantially arc-shaped webs 7a and 7b, respectively, and back plates 8a and 8b in which the center portions in the width direction are fixed to the outer peripheral edges of the webs 7a and 7b by welding or the like, It consists of linings 9a and 9b attached and fixed to the outer peripheral surfaces of the back plates 8a and 8b. Then, the circumferential end of each web 7a, 7b is abutted against the anchor 77, the other end in the circumferential direction is formed on the bottom surface of the engaging groove formed at the tip portions of the pistons, and the expansion / contraction device 5 It is in contact. Further, the drum 4 is formed in a petri dish with cast iron or the like, is provided in a state of covering both the brake shoes 3a and 3b, and rotates together with the wheels.

The expansion / contraction device 5 includes a strut 10 and an expansion lever 11. Of these, the strut 10 is provided between the pair of brake shoes 3a, 3b, and the tip portion is connected to the web 7a of one brake shoe 3a of the brake shoes 3a, 3b. 7a is engaged so that it can be pressed radially outward. The strut 10 is extended by the feed screw mechanism 12 so that the outer peripheral surfaces of both the linings 9a and 9b in the non-braking state can be obtained regardless of the wear of the linings 9a and 9b of the brake shoes 3a and 3b. The gap (gap) with the inner peripheral surface of the drum 4 can be maintained at an appropriate value.
The expansion lever 11 has an intermediate portion pivotally supported by the base end portion of the strut 10 and an engagement portion 13 formed on the surface of the distal end portion facing the web 7b of the other brake shoe 3b. The other brake shoe 3b is engaged with the inner peripheral edge of the web 7b.

The drive device 6 is for driving the expansion / contraction device 5 and comprises a drive source (not shown) such as an electric motor, a speed reducer 14, and a feed screw device 15. Of these, the feed screw device 15 includes a nut 16 and a screw 17 which are screwed together.
Among these, the nut 16 has an internal thread 18 formed on the inner peripheral surface, and the base end side end surface is closed by the flange portion 23. The outer peripheral surface is screwed and fixed to the inner diameter side of the final gear 19 so that the outer peripheral surface can rotate integrally with the final gear 19 of the speed reducer 14. Further, the front end surface of a set screw 22 screwed into a screw hole 21 formed in the cylindrical portion 20 of the final gear 19 is abutted against the outer peripheral surface of the nut 16, and the screw between the nut 16 and the final gear 14 is engaged. The joint is designed to prevent loosening. The nut 16 is attached to a sleeve 30 in which a small-diameter convex portion 24 provided on one end surface (the left end surface in FIGS. 7 to 8) of the flange portion 23 is fitted and fixed in a support hole 29 of the holder 28 of the electric motor. By being locked, the holder 28 is rotatably supported.
The screw 17 is provided at a shaft portion 26 having a male screw 25 formed on the outer peripheral surface and a base end portion (right end portion in FIGS. 7 to 8) of the shaft portion 26, and the outer peripheral surface of the shaft portion 26. And a flange portion 27 protruding outward in the radial direction. The screw 17 can be displaced in the axial direction, and a locking portion 31 formed on one end surface (the right end surface in FIGS. 7 to 8) of the flange portion 27 is used as a base end of the expansion lever 11. Rotation is prevented by engaging with a portion (upper end in FIGS. 7 to 8).

  Of the drum brake device 1 with an electric parking brake configured as described above, when the service brake device for decelerating or stopping the running vehicle is operated, the wheel cylinder 78 is activated by depressing the brake pedal of the driver. The hydraulic pressure is introduced into the cylinder cylinder 79 to increase the protruding amount of the pistons from the cylinder cylinder 79. Then, the distance between the other circumferential edges of the webs 7a and 7b abutting against the tip portions of both pistons is increased, and the brake shoes 3a and 3b are radially outwardly centered on the anchor 77. Oscillating displacement. As a result, the outer peripheral surfaces of the linings 9a and 9b of these brake shoes 3a and 3b are pressed against the inner peripheral surface of the drum 4 to perform braking. When the hydraulic pressure in the wheel cylinder 78 is removed when the brake is released, both the brake shoes 3a and 3b push the pistons into the cylinder cylinder 79 by the elastic force of the return spring 80 and move radially inward. Displace.

  Further, when operating the electric parking brake device for maintaining the vehicle in the stopped state in the drum brake device 1 with the electric parking brake configured as described above, by operating the switch or the like by the driver, The electric motor as a drive source is operated, and the nut 16 is rotated via the speed reducer 14. Then, by screwing the nut 16 and the screw 17, the screw 17 is displaced in one axial direction (right direction in FIGS. 7 to 8), and the flange portion 27 of the screw 17 moves the expansion lever 11. The extension lever 11 is rotated in the clockwise direction in FIGS. Along with this rotation, the distal end portion of the expansion lever 11 presses the web 7b of the other brake shoe 3b and displaces the brake shoe 3b radially outward. Further, the contact portion between the web 7b of the other brake shoe 3b and the engaging portion 13 formed at the tip of the extension lever 11 serves as a fulcrum, and the intermediate portion of the extension lever 11 is shown by the arrow a in FIG. Displace in the direction. Then, by pressing the web 7a of the one brake shoe 3a through the strut 10, the one brake shoe 3a is displaced radially outward. In this way, braking is performed by pressing the outer peripheral surfaces of the linings 9a and 9b of the brake shoes 3a and 3b against the inner peripheral surface of the drum 4.

  On the other hand, when releasing the braking of the electric parking brake device, the nut 16 is rotated by the electric motor in the opposite direction to that in the brake operation described above, and the screw 17 is moved in the other axial direction (FIGS. 7 to 8). To the left). As a result, the extension lever 11 rotates counterclockwise in FIGS. 7 to 8, and the pressing force to the brake shoes 3a and 3b is released.

  By the way, when releasing the braking by the electric parking brake device, if the operation time of the electric motor is insufficient and the rotation amount of the nut 16 is insufficient, the displacement amount of the screw 17 in the other axial direction is insufficient. Due to insufficient return, so-called brake dragging occurs in which the outer peripheral surfaces of the linings 9a and 9b and the inner peripheral surface of the drum 4 remain slid. In order to solve such a shortage of return, if the operating time of the electric motor is made sufficiently long and the amount of displacement of the screw 17 in the other axial direction is increased, the drum type electric parking brake device 1 is operated. The amount of displacement of the screw 17 in one axial direction, which is required when the screw 17 is made, increases, and the time required until the braking force is generated becomes longer. Further, the amount of displacement of the screw 17 in the other axial direction becomes excessive, and the tip end surface 32 of the screw 17 comes into contact with the inner surface 33 of the nut 16 to prevent further displacement in the other axial direction. When the electric motor is further rotated from this state, the side surface of the female screw thread constituting the female screw 18 of the nut 16 and the side surface of the male screw thread constituting the male screw 25 of the screw 17 are strongly brought into contact with each other by the wedge action. A matching so-called biting state (locked state) occurs. When such a locked state occurs, it is necessary to flow a large current (unlock current) to the electric motor in order to release the locked state, and power consumption increases. If the locked state cannot be released by the starting torque of the electric motor, the screw 17 cannot be moved to the right in FIGS.

  As a method of preventing the occurrence of insufficient return or excessive return of the screw 17 as described above, it is conceivable to provide a system for controlling the operation time of the electric motor. However, such a system is difficult to control and it is difficult to ensure sufficient reliability. In addition, if the energization of the electric motor is controlled while detecting the axial position of the screw 17 using a rotation sensor or a pressing force sensor, the reliability of lock prevention can be ensured. However, in this case, since expensive parts such as both sensors are required, the cost increases.

Next, FIG. 9 shows a second example of the electric parking brake device previously considered by the present inventor as the structure of the disc type electric parking brake device. In addition, although this example is a structure only of a disk type electric parking brake device, it can also be a structure combined with a hydraulic service brake device.
This disc type electric parking brake device 34 is characterized in that the structure of the pressing device 37 for pressing the pads 35a, 35b against the brake rotor 36 is made electric. The other basic structure is substantially the same as a conventionally known disc brake device. The structure and operation of the characteristic part of this example will be described below.
The pressing device 37 includes an electric motor 38 and a feed screw device 15a. Of these, the feed screw device 15a includes a nut 16a and a screw 17a that are screwed together. The nut 16a has a female screw 18a formed on the inner peripheral surface thereof, and the axial displacement of the nut 16a is restricted by the bearing 40 in a state where the nut 16a can rotate integrally with the rotor 39 of the electric motor 38. Further, the screw 17a has a male screw 25a formed on the outer peripheral surface, and a flange portion 27a is provided at the base end portion (left end portion in FIG. 9). The screw 17a is restricted in rotation in an axially displaceable state and by engagement with the inner pad 35a. In this example, the speed reducer between the electric motor 38 and the feed screw device 15a is omitted, but a speed reducer can be provided if necessary.

  When the disk-type electric parking brake device 34 is operated, the electric motor 38 is operated to rotate the nut 16a. As the nut 16a rotates, the screw 17a is displaced in one axial direction (leftward in FIG. 9), and the flange portion 27a of the screw 17a moves the inner pad 35a out of the pair of pads. Press against the inner side of the brake rotor 36. Then, as a reaction of this pressing force, the caliper claw 42 of the caliper 41 presses the outer side pad 35 b against the outer side surface of the brake rotor 36.

  On the other hand, when releasing the braking force of the disk-type electric parking brake device 34, the electric motor 38 is operated in the opposite direction to the operation described above, and the nut 16a is rotated. With this rotation, the screw 17a is displaced in the other axial direction (the right direction in FIG. 9). At this time, if the amount of displacement of the screw 17a in the other axial direction increases, the time until the brake operation increases due to excessive return as in the case of the first example. Further, the electric motor 38 is further moved from the state in which the tip end surface 32a of the screw 17a and the bottom surface of the concave portion 44 provided at the center of the inner surface (left surface in FIG. 9) of the cap member 43 of the caliper 41 are in contact. If it rotates, the screwing part of the internal thread 18a of the said nut 16a and the external thread 25a of the screw 17a will be in a locked state.

FIG. 10 shows a conventional structure for restricting the return amount of the screw in order to prevent a locked state when releasing the braking force of the electric parking brake devices 1 and 34 as described above. In this structure, a pair of locking portions 45, 45 are formed on the tip surface of the nut 16b (upper right side end surface in FIG. 10) by cutting the tip surface in a spiral shape by half a circumference in the circumferential direction. In addition, a pair of locking projections 46 and 46 are formed at positions symmetrical with respect to the radial direction in a portion where the male screw 25b is not formed at the axial intermediate portion of the outer peripheral surface of the screw 17b.
In the case of such a conventional structure, when the screw 17b is displaced in one axial direction (lower left in FIG. 10) with respect to the nut 16b as the nut 16b rotates, the screw 17b is displaced by a predetermined amount. As shown in FIG. 10 (B), the locking portions 45, 45 and the locking projections 46, 46 engage with each other, and the nut 16b and the screw 17b do not rotate relative to each other. For this reason, the nut 16b and the screw 17b are no longer displaced relative to each other in the axial direction, and the amount of return of the screw 17b in the axial direction is excessive, thereby preventing the locked state from occurring. .

  The structure shown in FIG. 10 is effective in terms of locking prevention, but an impact sound is generated by a collision when the locking portions 45, 45 and the locking projections 46, 46 are engaged. Further, the durability of the nut 16b and the screw 17b may be reduced due to the impact at the time of the collision. On the other hand, if the rigidity of the members 16b and 17b is increased in order to improve the durability, the weight of the members 16b and 17b increases.

  In view of the circumstances as described above, the present invention is a feed screw device having a lock prevention mechanism that can be configured at low cost without requiring high-level control, has no impact sound, and has excellent durability. Invented to realize the above.

  The feed screw device provided with the lock prevention mechanism of the present invention is provided between the first member and the second member and moves both the first and second members far and away. A male screw member and a female screw member which are installed so as to be screwed together are provided.

In particular, in the case of the feed screw device provided with the lock preventing mechanism of the present invention, the female screw member forms a female screw portion on a part of the inner peripheral surface in the axial direction.
The male screw member has a male screw part in a part of the outer peripheral surface in the axial direction.
Further, one of the male screw member and the female screw member is supported on the first member in a state where the screw member is rotatable and is prevented from being displaced in the axial direction with respect to the first member. One screw member can be driven to rotate in both directions.
The other screw member is engaged with the second member in a state in which the other screw member can be displaced in the axial direction and prevented from rotating.
Further, in a state in which these both screw members are relatively displaced to one end of the stroke of the feed screw device, the screwing of the female screw portion and the male screw portion is released.
Further, in order to prevent the female screw portion and the male screw portion from locking, the other screw member can be displaced in the one end direction of the stroke in a state where this screwing is disengaged (actually, Since the male screw part and the female screw part are disengaged from each other, there is no further displacement in the one end direction.
Further, an elastic member is provided that provides an elastic force in a direction in which the male screw portion and the female screw portion are engaged with each other in a state where the screw engagement is disengaged.

As a specific structure for implementing the feed screw device having the lock prevention mechanism of the present invention as described above, for example, a structure like the invention described in claims 2 to 4 can be adopted.
In the case of the structure according to the second aspect of the present invention, the female screw portion is formed only at the portion near the tip of the inner peripheral surface of the female screw member. Further, the inner diameter of the inner portion of the female screw member is made larger than the inner diameter of the female screw portion. In addition, this inner part is a space formed by the inner peripheral surface of the female screw member itself, or a member different from the inner peripheral surface of the female screw member (for example, the cap member 43 having the structure shown in FIG. 9). This is the space formed by the inner peripheral surface.
In addition, a male screw portion having an outer diameter smaller than the inner diameter of the inner portion of the female screw member and an axial dimension smaller than the axial dimension of the inner portion is formed only at a portion near the tip of the outer peripheral surface of the male screw member. Further, the outer diameter of the base is made smaller than the outer diameter of the male screw part and the inner diameter of the female screw part.
Further, the female screw portion and the male screw portion are disengaged in a state where the male screw member and the female screw member are relatively displaced to the stroke contraction side end portion.

In the case of the structure according to the third aspect of the present invention, the one screw member is a male screw member in which a male screw portion is formed only in a portion near the base end of the outer peripheral surface.
Further, the other screw member is a female screw member in which a female screw portion is formed only at a portion near the tip of the inner peripheral surface.
Further, in the state where the male screw member and the female screw member are relatively displaced to the extension side end portion of the stroke and the male screw portion and the female screw portion are disengaged, the male screw portion is the female screw member. The base end surface of the female screw member does not abut against the portion facing the base end surface. The portion facing the base end surface corresponds to, for example, the inner peripheral surface of the holder of the electric motor.

Furthermore, in the case of the structure of the invention described in claim 4, the one screw member is a female screw member in which a female screw portion is formed only at a portion near the tip of the inner peripheral surface.
Further, the other screw member is a male screw member in which a male screw portion is formed only at a portion near the tip of the outer peripheral surface.
Further, in the state where the male screw member and the female screw member are relatively displaced to the extension side end portion of the stroke and the male screw portion and the female screw portion are disengaged, the male screw portion is the female screw member. The base end surface of the male screw member is not in contact with the portion facing the base end surface.

In the case of the feed screw device having the lock prevention mechanism of the present invention as described above, the female screw member forms a female screw portion only in a part of the axial direction of the inner peripheral surface, and the male screw member is included in the outer peripheral surface. By forming the male screw part only in a part of the axial direction, the amount of relative displacement in the axial direction between these two members is restricted to the distance at which these two members are screwed together. For this reason, it is possible to prevent the return amount from becoming excessive.
In addition, in a state where the male screw portion and the female screw member are disengaged, the other screw member can be displaced in the one end direction of the stroke of the feed screw device (actually, the male screw portion and the (Since the threaded engagement with the female thread portion is disengaged, there is no further displacement in the one end direction.). For this reason, it is possible to prevent the locked state from occurring.
Further, in a state where the male screw part and the female screw member are disengaged, the male screw member and the female screw member are given elasticity in a direction in which the male screw part and the female screw part are engaged by the elastic member. Yes. For this reason, in order to relatively displace these two members, when these two members are relatively rotated, they are screwed together with almost no idling (stopping idling less than one rotation at most). Can do.

Sectional drawing of the lead screw apparatus which shows the 1st example of embodiment of this invention. The fragmentary sectional view which shows the state (B) which act | operated the drum type electric parking brake incorporating the feed screw device of this 1st example similarly to the state (A) which released the brake. The figure similar to FIG. 2 which shows the 2nd example of embodiment of this invention. The figure similar to FIG. 2 which shows the 3rd example. The figure similar to FIG. 2 which shows the 4th example. The front view which shows the 1st example of the structure of a prior invention in the state integrated in the drum type electric parking brake. Similarly, XX sectional drawing of FIG. The Y section enlarged view of FIG. Sectional drawing which shows the 2nd example of the structure of a prior invention in the state integrated in the disk type electric parking brake. The perspective view which shows the conventional structure for preventing an excessive return in the state (B) after engaging similarly to the state (A) before the engaging part of a nut and the engaging convex part of a screw engage. .

[First example of embodiment]
1 and 2 show a first example of an embodiment of the present invention corresponding to claims 1 and 2. The feature of this example is the structure of the feed screw device that constitutes the drive device for rotating the expansion lever of the drum type electric parking brake device. Regarding the drum type electric parking brake main body part other than this feed screw device, the structure of the prior invention shown in FIGS. Can be configured. Therefore, illustrations and descriptions relating to parts equivalent to the structure of the above-described invention will be omitted or simplified, and the following description will focus on the features of this example.

The feed screw device 15b of this example includes a nut 16c that is a female screw member, a screw 17c that is a male screw member, and a compression coil spring 49 that is an elastic member.
Of these, the nut 16 c includes a cylindrical member 47 and a cap member 48. The cylindrical member 47 has a female thread portion 50 formed only at a portion near the tip of the inner peripheral surface (the right side portion in FIGS. 1 and 2). Further, a base end side inner peripheral surface of the female screw portion 50 is not formed, and the inner diameter D ₅₂ of the inner portion 52, larger than the inner diameter D ₅₀ of the female screw portion 50 (D _52> D ₅₀₎ .
Further, the cap member 48 is provided with a flange portion 53 at a central portion in the axial direction. A large-diameter convex portion 54 having an outer diameter substantially the same as the inner diameter D ₅₂ of the inner portion 52 is provided on one end side of the flange portion 53 (on the right side in FIGS. Further, a small-diameter convex portion 55 having a smaller diameter than the large-diameter convex portion 54 is provided on the other end side (the left side in FIGS. 1 and 2) of the flange portion 53. Such a cap member 48 is assembled in a state where the large-diameter convex portion 54 is fitted and fixed to the proximal end side opening of the cylindrical member 47.
Further, the nut 16c is fitted into the sleeve 28 by fitting the small-diameter convex portion 55 of the cap member 48 into a sleeve 30 fitted in a support hole 29 provided on the inner peripheral surface of the holder 28 of the electric motor. Is supported so as to be freely rotatable. The nut 16c is supported and fixed on the inner diameter side of the final gear 19 by press-fitting and fixing the outer peripheral surface of the cylindrical member 47 to the inner peripheral surface of the final gear 19 of the speed reducer 14. It rotates integrally with the gear 19. Further, the end surface of the set screw 22 screwed into the screw hole 21 formed in the cylindrical portion 20 of the final gear 19 is abutted against the outer peripheral surface of the cylindrical portion 47, so that the nut 16 c and the final gear 19 are connected. It is intended to prevent the screwed part from loosening.

The screw 17c includes a shaft portion 26a and a flange portion 27b.
Of these, the shaft portion 26a forms a male screw portion 51 only at a portion near the tip of the outer peripheral surface (left side in FIGS. 1 and 2). Outer diameter D ₅₁ of the external thread portion 51 is smaller than the inner diameter D ₅₂ of the inner part 52 of the nut _{16c (D 52> D 51)} . Also, the axial dimension L ₅₁ of the male thread 51 is the axial dimension of the inner part 52 (from the axial proximal end edge of the female thread 50 to the distal end surface of the large-diameter convex part 54 of the cap 48. dimension) smaller than the _{L 52 (L 52> L 51} ). Further, the outer diameter D ₅₆ of the base portion 56 of the shaft portion 26a, is smaller than the inner diameter D ₅₀ of the outer diameter D ₅₁ and the internal thread portion 50 of the external thread portion _{51 (D 51> D 56,} D 50> D ₅₆ ).
The flange portion 27b is provided on the proximal end side (right side in FIGS. 1 and 2) of the shaft portion 26a in a state of projecting radially outward from the outer peripheral surface of the shaft portion 26a. Further, a locking portion 31 for locking the expansion lever 11 is formed on one end surface (the right side surface in FIGS. 1 and 2) of the flange portion 27b. Further, a support portion 57 for supporting the base end portion of the compression coil spring 49 is formed near the other end of the outer peripheral surface of the flange portion 27b.
Such a screw 17c is installed so as to be displaceable in the axial direction, and is prevented from rotating by engaging the base end portion of the expansion lever 11 with the locking portion 31 of the flange portion 27b. Yes.

  Further, the compression coil spring 49 is in a state in which the proximal end portion is supported by the support portion 57 of the flange portion 27b, and the distal end portion from the intermediate portion to the other direction than the flange portion 27b (left direction in FIGS. 1 and 2). Protruding.

  The drum-type electric parking brake device incorporating the feed screw device 15b of this example as described above acts as follows to generate a braking force. An electric motor is operated by a driver's operation of a switch or the like, and the nut 16c is rotated in the operating direction via the speed reducer. Then, the screw 17c is displaced in one axial direction (right direction in FIG. 2) from the state of FIG. 2A to the state of FIG. 2B, and the expansion is performed by the flange portion 27b of the screw 17c. The lever 11 is pressed to rotate the extension lever 11 in the clockwise direction in FIG. Along with this rotation, the outer peripheral surfaces of the linings 9a and 9b of the pair of brake shoes 3a and 3b are placed on the drum 4 (see FIGS. 7)) to press against the inner peripheral surface.

On the other hand, when releasing the braking of the drum type electric parking brake device of the present example, the electric motor is rotated in the opposite direction to the case where the brake is operated by the operation of the switch or the like by the driver, and the speed reducer 14 Then, the nut 16c is rotated in the releasing direction. With this rotation, the screw 17c is displaced in the other axial direction (leftward in FIG. 2) from the state of FIG. 2 (B) to the state of FIG. 2 (A). Then, the extension lever 11 rotates counterclockwise in FIG. 2, and the pressing of the brake shoes 3a and 3b against the drum 4 (see FIGS. 6 to 7) by the linings 9a and 9b is released. In the state of FIG. 2A in which the braking is released in this way (the state in which the screw 17c and the nut 16c are relatively displaced to the contraction side end of the stroke of the feed screw device 15b), the male screw 51 Is removed from the female screw portion 50 and enters the inner portion 52 of the nut 16c. For this reason, the screw 17c is no longer displaced in the other axial direction regardless of the rotation of the nut 16c. The axial dimension L ₅₁ of the male screw part 51 is restricted to be smaller than the axial dimension L ₅₂ of the back part 52. Therefore, a gap 58 remains between one end surface of the large-diameter convex portion 54 of the cap 48 and the tip end surface 32b of the screw 17c. Further, a gap remains between the front end surface of the nut 16c and the other end surface of the flange portion 27b of the screw 17c. Thus, it is possible to displace the screw 17c substantially in the other axial direction (actually, since the male screw portion 51 and the female screw portion 50 are disengaged from each other, the other in the axial direction is further increased. Will not be displaced.) Accordingly, the side surface of the thread of the female screw portion 50 and the side surface of the thread of the male screw portion 51 are not strongly pressed, and the locked state as described above is not caused. Since no lock state occurs, an increase in power consumption due to the lock current can be prevented. Furthermore, it is possible to prevent the occurrence of a failure in which braking becomes impossible due to the lock without being unable to release the locked state.

2A, the compression coil spring 49 supported by the flange portion 27b of the screw 17c is compressed between the housing 28 of the electric motor and the flange portion 27b. Therefore, the screw 17c is given elasticity in the direction of coming out from the nut 16c (the right direction in FIG. 2 and the direction in which the male screw portion 51 and the female screw portion 50 are engaged). Therefore, when the nut 16c is rotated in the direction in which the brake is operated, the female screw portion 50 and the male screw portion 51 are immediately screwed together with almost no idle rotation. For this reason, the braking state can be realized quickly and reliably.
Further, since the return amount of the screw 17c is regulated by the lengths of the nuts 16c and the screw portions 50 and 51 of the screw 17c, there is no need to provide an expensive system for controlling the operation time of the electric motor. .
Further, unlike the conventional structure shown in FIG. 10, it is not necessary to provide the locking portions 45, 45 of the nut 16b and the locking projections 46, 46 of the screw 17b. For this reason, no collision noise is generated, the durability of the nut and screw is not reduced by the collision, and the weight of the parts is not increased.

[Second Example of Embodiment]
FIG. 3 shows a second example of an embodiment of the present invention corresponding to claims 1 and 2. The feed screw device 15c of this example includes a nut 16d that is a female screw member, a screw 17d that is a male screw member, and a compression coil spring 49 that is an elastic member.

Of these, the screw 17d has a male threaded portion 51a formed near the tip of the outer peripheral surface. Further, a large-diameter shaft portion 59 is coupled and fixed to the proximal end side of the screw 17d so that the screw 17d and the large-diameter shaft portion 59 rotate as an integral member. Further, a convex portion 60 is provided on the other end side (left side in FIG. 3) of the large diameter shaft portion 59.
Further, the screw 17d is rotatable with respect to the holder 28 by fitting the convex portion 60 into a sleeve 30 fitted in a support hole 29 provided on the inner peripheral surface of the holder 28 of the electric motor. It is supported. The screw 17d is supported and fixed at the central portion of the final gear 19 by press-fitting the large-diameter shaft portion 59 into the central hole of the final gear 19 of the speed reducer 14. Rotate with. Further, the end face of the set screw 22 screwed into the screw hole 21 formed in the cylindrical portion 20 of the final gear 19 is abutted against the outer peripheral surface of the large-diameter shaft portion 59, and the screw 17 d and the final gear 19. To prevent rotation and retention.

The nut 16 d includes a cylindrical portion 61 and a flange portion 62.
Among these, the cylindrical part 61 forms the female thread part 50a only at the end portion (left side in FIG. 3) of the inner peripheral surface.
Further, the flange portion 62 is provided on the proximal end side (right side in FIG. 3) of the cylindrical portion 61 so as to protrude radially outward from the outer peripheral surface of the cylindrical portion 61. A locking portion 63 for locking the base end portion of the expansion lever 11 is formed on one end surface (the right side surface in FIG. 3) of the flange portion 62. In addition, a support portion 64 for supporting the base end portion of the compression coil spring 49 is formed near the other end of the outer peripheral surface of the flange portion 62.
Such a nut 16d is installed so as to be displaceable in the axial direction, and is prevented from rotating by engaging the base end portion of the expansion lever 11 with the locking portion 63 of the flange portion 62. Yes.

In addition, the compression coil spring 49 has its proximal end supported by the support portion 64 of the flange portion 62 of the nut 16d, and the tip portion from the intermediate portion to the other direction than the flange portion 62 (the left direction in FIG. 3). ).
The structure of this example is a structure in which the male screw member and the female screw member are reversed with respect to the structure of the first example of the embodiment described above. Since the configuration and operation of the other parts are the same as those in the first example of the above-described embodiment, redundant description is omitted.

[Third example of embodiment]
FIG. 4 shows a third example of an embodiment of the present invention corresponding to claims 1 and 3. The feed screw device 15d of this example includes a nut 16e that is a female screw member, a screw 17e that is a male screw member, and a compression coil spring 49 that is an elastic member.

Of these, the screw 17e has a male threaded portion 51b in a portion near the base end of the outer peripheral surface. In addition, a large-diameter shaft portion 59a is fixed to the base end side of the screw 17e integrally with the screw 17e and concentrically with the screw 17e. Further, a convex portion 60 is provided concentrically with the large diameter shaft portion 59a on the other end side (left side in FIG. 4) of the large diameter shaft portion 59a.
Further, the screw 17e is rotatable with respect to the holder 28 by fitting the convex portion 60 into a support hole 29 provided on the inner peripheral surface of the holder 28 of the electric motor via a sleeve 30. It is supported. The screw 17e is supported and fixed at the central portion of the final gear 19 by press-fitting the large-diameter shaft portion 59a into the central hole of the final gear 19 of the speed reducer 14. And rotate together. Further, the end face of the set screw 22 screwed into the screw hole 21 formed in the cylindrical portion 20 of the final gear 19 is abutted against the outer peripheral surface of the large-diameter shaft portion 59a, so that the screw 17e and the final gear 19 are contacted. To prevent rotation and retention.

Further, the nut 16e is spaced in the width direction between both ends in the width direction (front and back direction in FIG. 4) of the female screw portion 50b provided at the tip end and both width direction ends of the pressing portion 65 provided at the base end portion. A long rectangular frame is formed by being connected by a pair of connecting portions 76 arranged with a gap. Further, a support shaft portion 66 protruding from the side surface is provided on the side surface on one end side (right side in FIG. 4) of the pressing portion 65.
Such a nut 16e supports a portion near the tip (left side in FIG. 4) inside a support hole 67 formed in the holder 28 of the electric motor through a sleeve 68 so as to be slidable. Further, the support shaft portion 66 is slidably supported through a sleeve 70 in a support hole 69 formed in the holder 28. The nut 16e does not rotate due to the engagement with the base end portion of the expansion lever 11.

  Further, the compression coil spring 49 is engaged with an engaging member 72 engaged with an engaging groove 71 formed on the outer peripheral surface of the distal end of the screw 17e, and the distal end of the compression coil spring 49 is engaged with the screw 17e. The screw 17e is mounted on the outer diameter side portion of the distal end of the screw 17e in a state of being directed in the proximal direction (left direction in FIG. 4).

  The drum-type electric parking brake device incorporating the feed screw device 15d of this example as described above acts as follows to generate a braking force. An electric motor is operated by a driver's operation of a switch or the like, and the screw 17e is rotated in the operating direction via the speed reducer 14. Then, the nut 16e is displaced in the other axial direction (left direction in FIG. 4) from the state of FIG. 4 (A) to the state of FIG. 4 (B), and the inner surface of the pressing portion 65 of the nut 16e. The expansion lever 11 is pressed by (the left side surface in FIG. 4), and the expansion lever 11 is rotated counterclockwise in FIG. Along with this rotation, the outer peripheral surfaces of the linings 9a and 9b of the pair of brake shoes 3a and 3b are placed on the drum 4 (see FIGS. 7)) to press against the inner peripheral surface. In the case of this example, the rotation direction of the expansion lever 11 when the brake is operated is opposite to the drum-type electric parking brake device of the previous invention, the first example of the embodiment, and the second example. is there. For this reason, the basic structure of the drum brake is reversed with respect to the structure shown in FIGS.

  On the other hand, when releasing the braking of the drum type electric parking brake device of the present example, the electric motor is rotated in the opposite direction to the case where the brake is operated by the operation of the switch or the like by the driver, and the speed reducer 14 Then, the screw 17e is rotated in the release direction. Along with this rotation, the nut 16e is displaced in one axial direction (rightward in FIG. 4) from the state of FIG. 4 (B) to the state of FIG. 4 (A). Then, the extension lever 11 rotates clockwise in FIG. 4, and the pressing of the brake shoes 3a and 3b against the drum 4 (see FIGS. 6 to 7) by the linings 9a and 9b is released. In the state of FIG. 4A in which the braking is released in this manner (the state where the screw 17e and the nut 16e are relatively displaced to the extension side end portion of the stroke of the feed screw device 15d), the male screw portion 51b. And the female screw portion 50b are unscrewed. For this reason, the nut 16e is no longer displaced in the axial direction regardless of the rotation of the screw 17e. In this state, the outer side surface (the right side surface in FIG. 4) of the pressing portion 65 of the nut 16e does not contact the holder 28 of the electric motor or the sleeve 70 facing the side surface. A gap remains between. Thus, it is possible to displace the nut 16e substantially in one axial direction (actually, since the male screw portion 51b and the female screw portion 50b are disengaged from each other, the axial one side is further increased. Will not be displaced.) Therefore, the side surface of the thread of the female screw portion 50b and the side surface of the screw thread of the male screw portion 51b are not strongly pressed, and the locked state as described above is not obtained. Since no lock state occurs, an increase in power consumption due to the lock current can be prevented. Furthermore, it is possible to prevent the occurrence of a failure in which braking becomes impossible due to the lock without being unable to release the locked state.

In the state shown in FIG. 4A, the compression coil spring 49 supported on the tip of the screw 17e is formed between the end surface of the female screw portion 50b and the locking member 72 locked to the tip of the screw 17e. Compressed between. Therefore, the nut 16e is given elasticity in a direction in which the male screw portion 51b and the female screw portion 50b of the nut 16e are screwed together.
Therefore, when the screw 17e is rotated in the direction in which the brake is operated, the female screw portion 50b and the male screw portion 51b are immediately screwed together with almost no idle rotation. For this reason, the braking state can be realized quickly and reliably.
Further, since the return amount of the nut 16e is regulated by the lengths of the nut 16e and the screw portions 50b and 51b of the screw 17e, it is necessary to provide an expensive system for controlling the operation time of the electric motor. There is no.
Further, unlike the conventional structure shown in FIG. 10, it is not necessary to provide the locking portions 45, 45 of the nut 16b and the locking projections 46, 46 of the screw 17b. For this reason, no collision noise is generated, the durability of the nut and screw is not reduced by the collision, and the weight of the parts is not increased.

[Fourth Example of Embodiment]
FIG. 5 shows a fourth example of an embodiment of the present invention corresponding to claims 1 and 4. The feed screw device 15e of this example includes a nut 16f that is a female screw member, a screw 17f that is a male screw member, and a compression coil spring 49 that is an elastic member.

Of these, the nut 16f has the same structure as the nut 16c (FIGS. 1 and 2) of the first example of the embodiment described above. For this reason, detailed explanation is omitted.
The screw 17f is composed of a male screw portion 51c provided at the distal end portion and a long rectangular frame portion 74 provided at the proximal end portion. The long rectangular frame portion 74 includes a rectangular member 75 and an inner side surface (the left side surface in FIG. 5) of the disc-shaped pressing portion 65a, which are arranged at intervals in the axial direction (left and right direction in FIG. 5). They are connected by a pair of connecting portions 76a arranged at an interval in the width direction (front and back direction in FIG. 5). The pressing portion 65a has an outer diameter larger than the dimension in the height direction (vertical direction in FIG. 5) of the connecting portion 76a. Further, a support portion 73 for supporting the base end portion of the compression coil spring 49 is formed over the entire circumference at a portion closer to one end (right end portion in FIG. 5) of the outer peripheral surface of the pressing portion 65a.
Further, a support shaft portion 66a protruding from the side surface is provided on the side surface on one end side (right side in FIG. 5) of the pressing portion 65a.
In such a screw 17f, the male screw portion 51c is screwed into a female screw portion 50c provided at the tip of the nut 16f. The support shaft 66a is slidably supported through a sleeve 70 in a support hole 69 formed in the holder 28 of the electric motor. Note that the screw 17 f does not rotate due to the engagement with the expansion lever 11.

  The compression coil spring 49 has a proximal end portion supported by a support portion 73 formed on the outer peripheral surface of the distal end portion of the pressing portion 65a, and the distal end portion from the intermediate portion to one side of the pressing portion 65a (see FIG. 5 in the right direction).

  The drum type electric parking brake device incorporating the feed screw device 15e of this example as described above acts as follows to generate a braking force. An electric motor is operated by a driver's operation of a switch or the like, and the nut 16f is rotated in the operating direction via the speed reducer 14. Then, the screw 17f is displaced in the other axial direction (leftward in FIG. 5) from the state of FIG. 5 (A) to the state of FIG. 5 (B), and the inner surface of the pressing portion 65a of the screw 17f. Thus, the expansion lever 11 is pressed to rotate the expansion lever 11 counterclockwise in FIG. Along with this rotation, the outer peripheral surfaces of the linings 9a and 9b of the pair of brake shoes 3a and 3b are placed on the drum 4 (see FIGS. 7)) to press against the inner peripheral surface. In the case of this example as well, as in the third example of the above-described embodiment, the basic structure of the drum brake is opposite to the conventional structure shown in FIGS.

  On the other hand, when releasing the braking of the drum type electric parking brake device of the present example, the electric motor is rotated in the opposite direction to the case where the brake is operated by the operation of the switch or the like by the driver, and the speed reducer 14 Then, the nut 16f is rotated in the releasing direction. With this rotation, the screw 17f is displaced in one axial direction (right direction in FIG. 5) from the state of FIG. 5 (B) to the state of FIG. 5 (A). Then, the extension lever 11 rotates clockwise in FIG. 5, and the pressing of the brake shoes 3a and 3b against the drum 4 (see FIG. 3) by the linings 9a and 9b is released. In the state shown in FIG. 5A in which the braking is released in this manner (the state in which the nut 16f and the screw 17f are relatively displaced to the end portion on the extension side of the stroke of the feed screw device 15e), the female screw portion 50c. And the male threaded portion 51c are disengaged. For this reason, the screw 17f is no longer displaced in the axial direction regardless of the rotation of the nut 16f. In this state, a gap remains on the outer side surface (right side surface in FIG. 5) of the pressing portion 65a of the screw 17f without coming into contact with the holder 28 of the electric motor facing the side surface or the sleeve 70. Thus, it is possible to displace the nut 16f substantially in one axial direction (actually, since the male screw portion 51c and the female screw portion 50c are disengaged, the axial one side is further increased. Will not be displaced.) Accordingly, the side surface of the thread of the female screw portion 50c and the side surface of the thread of the male screw portion 51c are not strongly pressed, and the locked state as described above is not obtained. Since no lock state occurs, an increase in power consumption due to the lock current can be prevented. Furthermore, it is possible to prevent the occurrence of a failure in which braking becomes impossible due to the lock without being unable to release the locked state.

In the state shown in FIG. 5A, the compression coil spring 49 supported at the tip of the pressing portion 65a is compressed between the inner surface of the holder 28 and the outer surface of the pressing portion 65a. Has been.
Accordingly, the screw 17f is given elasticity in a direction in which the male screw portion 51c of the screw 17f and the female screw portion 50c of the nut 16f are screwed together. Therefore, when the nut 16f is rotated in the direction in which the brake is operated, the female screw portion 50c and the male screw portion 51c are immediately screwed together with almost no idle rotation. For this reason, the braking state can be realized quickly and reliably. In the state shown in FIG. 5A, from the front end side of the nut 16f toward the right in FIG. 5 so that the center of the nut 16f and the center of the screw 17f remain in alignment. In addition, a holding cylinder portion can be provided. The inner diameter of the holding cylinder part is slightly larger than the outer diameter (crest diameter) of the male screw part 51c.
The structure of this example is a structure in which the position of the compression coil spring is changed by reversing the arrangement of the male screw member and the female screw member with respect to the structure of the third example of the embodiment shown in FIG. . Since the configuration and operation of the other parts are the same as those in the third example, overlapping description is omitted.

The structure of the illustrated embodiment is a structure in which the feed screw device of the present invention is applied to a drum-type electric parking brake device. The feed screw device of the present invention is, for example, a disc-type electric motor shown in FIG. It can also be applied to parking brakes. Further, the present invention is not limited to the electric parking brake, and can be applied to various mechanical devices to obtain the same operation and effect as the above-described embodiment.
Further, the elastic member provided between the nut and the screw is not limited to the compression coil spring, but may be another spring structure or an elastomer such as rubber. Further, the position where the elastic member is provided is not limited to the above-described structure, and various structures that can provide elasticity in a direction in which the male screw member and the female screw member constituting the feed screw device are separated from each other are adopted. Can do.

DESCRIPTION OF SYMBOLS 1 Drum brake device with electric parking brake 2 Back plate 3a, 3b Brake shoe 4 Drum 5 Expansion / contraction device 6 Drive device 7a, 7b Web 8a, 8b Back plate 9a, 9b Lining 10 Strut 11 Expansion lever 12 Feed screw mechanism 13 Engagement Part 14 Reducer 15, 15a, 15b, 15c, 15d, 15e Feed screw device 16, 16a, 16b, 16c, 16d, 16e, 16f Nut 17, 17a, 17b, 17c, 17d, 17e, 17f Screw 18, 18a Female screw DESCRIPTION OF SYMBOLS 19 Final gear 20 Cylindrical part 21 Screw hole 22 Set screw 23 Flange part 24 Small-diameter convex part 25, 25a, 25b Male thread 26, 26a Shaft part 27, 27a, 27b Flange part 28 Holder 29 Support hole 30 Sleeve 31 Locking part 32, 32a, 32b End surface 33 Back surface 34 Disc type electric parking brake device 35a, 35b Pad 36 Brake rotor 37 Press device 38 Electric motor 39 Rotor 40 Bearing 41 Caliper 42 Caliper claw 43 Cap member 44 Recess 45 Locking portion 46 Locking convex portion 47 Cylindrical member 48 Cap 49 Compression coil spring 50, 50a, 50b, 50c Female thread part 51, 51a, 51b, 51c Male thread part 52 Deep part 53 Flange part 54 Large diameter convex part 55 Small diameter convex part 56 Base part 57 Support part 58 Clearance 59, 59a Large Radial shaft portion 60 Convex portion 61 Cylindrical portion 62 Flange portion 63 Locking portion 64 Support portion 65, 65a Pressing portion 66, 66a Support shaft portion 67 Support hole 68 Sleeve 69 Support hole 70 Sleeve 71 Locking groove 72 Locking member 73 Support Part 74 long rectangular frame part 75 rectangular member 76, 6a connecting portion 77 anchor 78 wheel cylinder 79 cylinder barrel

JP 2009-168228 A

Claims (4)

A male screw member and a female screw member, which are provided between the first member and the second member and are installed concentrically and capable of relative rotation so as to move the first and second members far and near, and are screwed together. A feed screw device comprising:
The female screw member forms a female screw part in a part of the axial direction of the inner peripheral surface,
The male screw member forms a male screw part in a part of the axial direction of the outer peripheral surface,
Of these male screw members and the female screw members,
One screw member is supported on the first member in a state where the first member can rotate and the axial displacement of the first member is prevented, and the one screw member can be driven to rotate in both directions by a driving source.
Similarly, the other screw member is engaged with the second member in a state where axial displacement of the other screw member is possible and rotation is prevented,
In a state in which these both screw members are relatively displaced up to one end of the stroke of the feed screw device, the screwing of the female screw part and the male screw part is released,
In order to prevent the female screw portion and the male screw portion from locking, the other screw member is capable of displacement in the one end direction of the stroke in a state where the screw engagement is released,
A feed screw device provided with an anti-locking mechanism, characterized in that an elastic member is provided that provides elasticity in a direction in which the male screw portion and the female screw portion are screwed in a state where the screw is disengaged. The female screw member is formed by forming a female screw portion only at a portion near the tip of the inner peripheral surface, and the inner diameter of the inner portion is larger than the inner diameter of the female screw portion,
The male screw member forms a male screw part having an outer diameter smaller than the inner diameter of the inner part of the female screw member and an axial dimension smaller than the axial dimension of the inner part only at the end portion of the outer peripheral surface, The outer diameter of the base portion is smaller than the outer diameter of the male screw portion and the inner diameter of the female screw portion, and the female screw member and the female screw member are relatively displaced to the stroke contraction side end portion, and the female screw The feed screw device provided with the lock prevention mechanism according to claim 1, wherein the screw engagement between the part and the male screw part is released. The one screw member is a male screw member in which a male screw part is formed only in a portion near the base end of the outer peripheral surface,
The other screw member is a female screw member in which a female screw part is formed only at a portion near the tip of the inner peripheral surface,
In a state where the male screw member and the female screw member are relatively displaced to the end portion on the extension side of the stroke and the male screw portion and the female screw portion are disengaged, the male screw portion is an inner portion of the female screw member. The feed screw device provided with the lock prevention mechanism according to claim 1, wherein there is no interference with a peripheral surface, and a base end surface of the female screw member does not abut against a portion facing the base end surface. The one screw member is a female screw member in which a female screw portion is formed only at a portion near the tip of the inner peripheral surface,
The other screw member is a male screw member in which a male screw part is formed only at a portion near the tip of the outer peripheral surface,
In a state where the male screw member and the female screw member are relatively displaced to the end portion on the extension side of the stroke and the male screw portion and the female screw portion are disengaged, the male screw portion is an inner portion of the female screw member. The feed screw device provided with the lock prevention mechanism according to claim 1, wherein the male screw member does not interfere with a peripheral surface, and a base end surface of the male screw member does not contact a portion facing the base end surface.

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