JP2016156456A - Top-type ball screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a top-type ball screw which can be formed by press-processing a top member from a steel plate at a low cost and high accuracy, and can be fixed to a nut with high workability.SOLUTION: A top-type ball screw is formed by press-processing a top member 5 from a steel plate, and has a split structure which is split at a center part along a connecting groove 7 which is formed in an S-shape, and the split structures are integrated by making separated faces abut on each other. The top-type ball screw comprises a top main body 9 having the connecting groove 7 at an internal periphery, and an attachment part 10 which is protruded from the center part of the top main body 9 in a longitudinal direction. The attachment part 10 comprises a base part 11 which extends to the outside of a radial direction from the separated face, and a wing 12 which horizontally extends from the base part 11. A lock part 13 in which a tip of the wing 12 is inclined to the radial direction is formed, and locked to an internal peripheral face of a top window 6 in a deformed state.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a ball screw used for an electric power steering of an automobile, an actuator for a transmission and a brake, and more particularly to a piece type ball screw using a piece member which is a ball circulation part.

  The ball screw is composed of a screw shaft having a helical thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft, and a spiral screw groove formed on the inner peripheral surface, and both opposing screw grooves. It is equipped with a large number of balls accommodated in the formed rolling path and a circulation mechanism having the rolling path as a circuit path, and is used as a motion conversion mechanism that linearly moves the screw shaft by rotating the nut, for example. ing.

  Generally, there are various types of ball screws having different ball circulation mechanisms, and one of them is called a piece type. This piece-type ball screw has a threaded groove connection path, and a circulation piece member with a rolling path as a circulation path is attached to the nut. The structure is relatively simple and compact. There are advantages you can do.

  In recent years, a system for freely controlling a transmission, a brake, and the like with an electric actuator using an electric motor and a ball screw instead of manually has been developed against the background of fuel efficiency reduction, safety improvement, and comfort pursuit of an automobile. Generally, a piece member of a piece type ball screw is formed by cutting, sintering, forging, etc., but the shape is complicated, and the ball is smoothly circulated to satisfy wear, strength and durability. In order to secure the surface hardness and dimensional accuracy necessary for the manufacturing, there is a problem that the cost increases. FIG. 6A shows a typical example of a piece type ball screw that solves such a problem. This piece-type ball screw 51 includes a screw shaft 52 having a helical thread groove 52a formed on the outer peripheral surface, and a nut externally fitted to the screw shaft 52 and having a helical screw groove 53a formed on the inner peripheral surface. 53, a large number of balls 54 accommodated in a rolling path formed by the opposing screw grooves 52a and 53a, and a piece member 55 serving as a circulation member for these balls 54.

  An elongated piece window (piece insertion port) 56 that penetrates the inner and outer peripheral surfaces and cuts out a part of the thread groove 53a is formed in the body portion of the cylindrical nut 53. A piece member 55 serving as a circulation member for the ball 54 is fitted into the piece window 56. A connecting groove (ball return groove) 55a that connects adjacent one rounds of the screw groove 53a is formed inside the piece member 55. The piece window 56 is formed with a positioning surface 57 and a locked surface 58 which is an inner stepped portion. The angle formed by the positioning surface 57 and the locked surface 58 is processed with an acute angle so that the piece member 55 does not easily come off.

  As shown in (b), the piece member 55 is formed by press work and includes a piece main body 59 and a locking portion 60. The piece body 59 includes end portions 59a formed in a semicircular shape in alignment with the piece window 56 of the nut 53 at both ends in the longitudinal direction. And the shape of the connection groove | channel 55a continuous in the longitudinal direction of the piece main body 59 has comprised the substantially S shape.

  The outer shape of the piece main body 59 is formed to be slightly smaller than the inner shape of the piece window 56 so that a slight gap is generated between the piece body 59 and the piece window 56. In other words, the piece body 59 is formed with a slight gap between the inner shape of the piece window 56 so that the piece body 59 can swing during the ball screw operation.

  The locking portion 60 is formed to be obliquely shifted so as to follow the S groove shape of the connecting groove 55a. In addition, each of the pair of locking portions 60 protrudes from both sides to a substantially central portion in the longitudinal direction of the flange portion 60a formed around the opening side of the piece main body 59 having a U-shaped cross section. Then, it is folded once from the base side bent portion 60b to the outer surface side of the locking portion 60, and then bent outward from the position of the tip side bent portion 60c to the piece body 59 to form a locking end portion 60d. Yes. The planar shape of the locking end portion 60 d is a rectangular shape that is aligned with the locked surface 58 of the frame window 56 in order to fit the frame window 56 of the nut 53.

  When the piece member 55 is fixed, the locking end portion 60d of the locking portion 60 has an angle formed at the tip portion thereof, and the wedge shape is formed by the acute angle shape formed by the tip portion fitted into the locked surface 58 of the nut 53. The piece member 55 can be more firmly fixed to the nut 53 (see, for example, Patent Document 1).

JP 2004-251296 A

  In such a conventional piece type ball screw 51, the piece member 55 is formed by pressing from a thin metal plate, and has a feature of being fixed to the nut 53 by the action of a wedge. However, since the shape of the piece member 55 is complicated and the press work requires many molding steps, the cost increases and the dimensional and shape accuracy necessary for smoothly circulating the ball 54 is ensured. There was a problem that it was difficult.

  The present invention has been made in view of such circumstances, paying attention to separating the piece members on the left and right sides of the S-shaped connecting groove, and forming the piece members from the steel plate with high accuracy at low cost by pressing. An object of the present invention is to provide a piece-type ball screw that can be fixed to a nut with high workability.

  In order to achieve such an object, the invention according to claim 1 of the present invention includes a screw shaft having a spiral thread groove formed on the outer peripheral surface thereof, and is externally fitted to the screw shaft and spirally formed on the inner peripheral surface. A nut formed with a thread groove, a plurality of balls accommodated in a rolling path formed by the opposing thread groove, and a piece window bored in a body portion of the nut. A piece-type ball screw having an S-shaped connecting groove formed around a path, and the piece member is composed of two members joined at a central portion along the connecting groove. ing.

  As described above, the screw shaft is formed with a spiral screw groove on the outer peripheral surface, the nut is fitted on the screw shaft and the spiral screw groove is formed on the inner peripheral surface, and the opposing screw groove is formed. A plurality of balls housed in the rolling path, a piece member mounted on a piece window drilled in the trunk of the nut, and formed with an S-shaped connecting groove having the rolling path as a circulation path; Since the piece member is composed of two members joined at the center along the connecting groove, the piece member can be reduced by pressing the steel piece from a steel plate or by injection molding a synthetic resin. It can be formed with high accuracy at low cost.

  Preferably, as in the invention described in claim 2, the piece member includes a piece main body in which the connection groove is formed on an inner periphery, and an attachment portion formed to protrude from a central portion in the longitudinal direction of the piece main body. The mounting portion includes a base portion extending radially outward from the separation surface, and a wing extending horizontally from the base portion, and a locking portion is formed in which a distal end of the wing is inclined in the radial direction, If it is locked in an elastically deformed state on the inner peripheral surface of the piece window, the base portions can be brought into contact with each other and can be fixed to the nut with high workability.

  According to a third aspect of the present invention, the piece window is configured by a through hole formed in a circular cross section and a recess formed in a large diameter in an opening portion on the outer diameter side of the through hole. If the recesses are formed in a pair on the opposing inner periphery of the through hole and are formed in an arc shape so as to match the shape of the locking portion of the piece member, the thread groove of the connecting groove nut of the piece member Thus, the piece member can be positioned and fixed easily and accurately without play.

  Further, as in the invention described in claim 4, if the locking portion of the piece member is formed to be inclined inward in the radial direction from the tip of the wing, the depth of the recess of the piece window is minimized. It can be set as shallow as possible, and the outer diameter of the nut can be reduced to achieve compactness.

  Further, as in the invention according to claim 5, if the locking portion of the piece member is formed to be inclined radially outward from the tip of the wing, it is easy to mount the piece member, When the ball member is subjected to a load such that the piece member is pulled out to the outer diameter side of the nut, the locking portion is locked to the inner peripheral surface of the recess, so that the removal effect is increased and the reliability is improved.

  Moreover, if the piece member is formed by pressing from a steel plate as in the invention described in claim 6, the shape becomes complicated as in the case of a conventional steel plate piece member. It eliminates the need for many molding processes such as finishing processes and finishing processes for removing surplus materials, greatly reducing the number of processes, and can be molded with two identical molds, providing excellent mass productivity. In addition to cost reduction, as in the past, parts such as connecting grooves that have to be drawn can be bent, so the necessary dimensional and shape accuracy for smooth circulation of the ball can be achieved. Can be secured.

  Further, as in the invention described in claim 7, if the piece member is formed by injection molding from a thermoplastic synthetic resin filled with a fibrous reinforcing material, the cost and weight of the ball screw can be further reduced. Can be achieved.

  The piece ball screw according to the present invention includes a screw shaft having a helical thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft, and a spiral screw groove formed on the inner peripheral surface, A plurality of balls accommodated in a rolling path formed by the thread grooves facing each other, and a piece window formed in the trunk portion of the nut, and an S-shape having the rolling path as a circulation path In the piece-type ball screw provided with a piece member formed with a connecting groove, the piece member is composed of two members joined at a central portion along the connecting groove, so the piece member is pressed from a steel plate. It can be formed with high accuracy at low cost by processing or injection molding synthetic resin.

(A) is a top view which shows one Embodiment of the piece type ball screw which concerns on this invention, (b) is a longitudinal cross-sectional view along the II line | wire of (a). It is a cross-sectional perspective view which shows the nut with which the piece member which concerns on this invention was mounted | worn. It is a top view of the piece member concerning the present invention. (A) is a perspective view which shows the single-piece | unit state of the piece member based on this invention, (b) is a perspective view which shows the state which match | combined the piece member of (a). (A) is a principal part top view which shows the state in which the piece member based on this invention was mounted | worn, (b) is principal part sectional drawing along the III-III line of Fig.1 (a), (c) is It is principal part sectional drawing which shows the modification of the piece member of (b). (A) is a longitudinal cross-sectional view which shows the conventional piece type | formula ball screw, (b) is a perspective view which shows the piece member of (a).

  A screw shaft having a helical thread groove formed on the outer peripheral surface, a nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface, and a roller formed by the opposing screw groove. A plurality of balls housed in a movement path, a piece member attached to a piece window drilled in a body portion of the nut, and formed with an S-shaped connection groove having the rolling path as a circulation path; A piece-type ball screw comprising: a piece in which the piece member is formed by pressing from a steel plate and joined at a central portion along the connecting groove, and the connecting groove is formed on the inner periphery. A main body, and a mounting portion formed so as to protrude from a longitudinal center portion of the piece main body, the mounting portion including a base portion extending radially outward from the separation surface, and a wing extending horizontally from the base portion. In addition, the locking part where the tip of this wing is inclined in the radial direction Is formed, it is engaged in a state of being elastically deformed to the inner peripheral surface of the bridge window.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
1A is a plan view showing an embodiment of a piece ball screw according to the present invention, FIG. 1B is a longitudinal sectional view taken along line II of FIG. 1A, and FIG. FIG. 3 is a cross-sectional perspective view showing a nut mounted with a piece member according to the present invention, FIG. 3 is a plan view of the piece member according to the present invention, and FIG. 4A is a perspective view showing a single state of the piece member according to the present invention. FIG. 5B is a perspective view showing a state in which the piece members of FIG. 5A are combined, FIG. 5A is a plan view of a main part showing a state in which the piece member according to the present invention is mounted, and FIG. These are principal part sectional drawings along the III-III line of Fig.1 (a), (c) is principal part sectional drawing which shows the modification of the piece member of (b).

  A piece ball screw 1 shown in FIGS. 1 (a) and 1 (b) has a screw shaft 2 having a spiral thread groove 2a formed on the outer peripheral surface thereof, and is externally fitted to the screw shaft 2 and spiraled on the inner peripheral surface thereof. Nut 3 in which a thread groove 3a is formed, a large number of balls 4 accommodated in a rolling path formed by opposing screw grooves 2a and 3a, and a piece member 5 serving as a circulating member for these balls 4 And.

  The cross-sectional shape of each thread groove 2a, 3a may be a circular arc shape or a Gothic arc shape, but here, it has a Gothic arc shape that allows a large contact angle with the ball 4 and a small axial clearance. Is formed. Thereby, the rigidity with respect to an axial load becomes high and generation | occurrence | production of a vibration can be suppressed.

  The cylindrical nut 3 is provided with a piece window 6 having a substantially circular cross section that penetrates the inner and outer peripheral surfaces and cuts out a part of the screw groove 3a. The piece member 5 is fitted into the piece window 6. It is worn. A connecting groove 7 is formed on the inner side of the piece member 5 so as to connect adjacent one rounds of the screw groove 3a, and the ball 4 rolls between the connecting groove 7 and the substantially one round part of the screw groove 3a. Constitutes the road. A large number of balls 4 interposed between the inner and outer screw grooves 2a and 3a in the rolling path roll along the screw grooves 2a and 3a, are guided by the connecting grooves 7 of the piece member 5, and are screw shafts. 2 over the thread 2 and return to the adjacent screw groove 3a, and roll along the screw grooves 2a and 3a again.

  As shown in FIG. 2, the connecting groove 7 of the piece member 5 is formed to be curved in an S shape, and the end portions 7 a and 7 a of the connecting groove 7 are groove edges 3 b of the adjacent screw grooves 3 a and 3 a of the nut 3. 3b is smoothly connected so as to match 3b. The depth of the connecting groove 7 is set to a depth at which the ball 4 can exceed the thread of the screw groove 2 a in the screw shaft 2 in the connecting groove 7.

  Here, as shown in FIG. 3, the piece member 5 is composed of two members including a first piece member 5a and a second piece member 5b, and is formed from a cold-rolled steel plate (JIS standard SPCC system or the like). It is formed by press working. The first piece member 5a includes a first piece main body 9a in which a connecting groove 7a is formed on the inner periphery, and a first attachment portion formed so as to protrude from the central portion in the longitudinal direction of the first piece main body 9a. 10a. Similarly, the second piece member 5b includes a second piece main body 9b in which a connecting groove 7b is formed on the inner periphery, and a second piece formed so as to protrude from the longitudinal central portion of the second piece main body 9b. Mounting portion 10b.

  Here, the cold rolled steel plate is exemplified as the material of the piece member 5, but not limited to this, a stainless steel plate having corrosion resistance, for example, a ferritic stainless steel plate (JIS standard SUS430 series or the like) or austenitic stainless steel. It may be a steel plate (JIS standard SUS304, etc.).

  Here, the connection groove 7 of the piece member 5 is configured by the connection grooves 7a and 7b of the first piece member 5a and the second piece member 5b abutting each other. In other words, the piece member 5 is separated and formed at the center (groove bottom) of the S-shaped connecting groove 7, and the connecting pieces 7a and 7b of the first piece member 5a and the second piece member 5b are formed. An integral piece member 5 is formed by abutting the separation surfaces 8a and 8b. Even if there is a step in the joining portion 8 formed by the abutment of the separation surfaces 8a and 8b, it becomes the groove bottom of the connecting groove 7, so that it does not come into contact with the ball 4 and the ball 4 circulates on the connecting groove 7. In addition, no vibration or abnormal noise is generated.

  As shown in FIG. 4A, the first mounting portion 10a includes a first base portion 11a extending radially outward from the separation surface 8a, and a first wing 12a extending horizontally from the first base portion 11a. And a first locking portion 13a is formed in which the tip of the first wing 12a is inclined radially inward. Similarly, the second mounting portion 10b includes a second base portion 11b extending radially outward from the separation surface 8b, and a second wing 12b extending horizontally from the second base portion 11b. A second locking portion 13b is formed in which the tip of the wing 12b is inclined radially inward.

  As shown in FIG. 4B, the first piece main body 9a and the second piece main body 9b constitute a piece body 9 of the piece member 5, and the first attachment portion 10a and the second attachment portion. The mounting portion 10 is configured by abutting 10b. The first base portion 11a, the first wing 12a, and the first locking portion 13a constitute the first mounting portion 10a, and the second base portion 11b, the second wing 12b, and the second engagement portion. The second attachment portion 10b is configured by the stop portion 13b.

  The ball 4 is assembled by attaching the piece member 5 to the piece window 6 of the nut 3, then applying the nut 3 from the shaft end of the screw shaft 2, and inserting the ball 4 between the screw grooves 2 a and 3 a sequentially. 3 is rotated to move the nut 3 to the screw shaft 2. In addition, after the piece member 5 is mounted on the piece window 6 of the nut 3, the ball 4 may be similarly inserted using a temporary shaft.

  Here, the mounting of the piece member 5 to the nut 3 is performed by elastically deforming the mounting portion 10 of the piece member 5 from the outer diameter side of the nut 3. Specifically, as shown in FIGS. 5A and 5B, the piece window 6 penetrates the inner and outer peripheral surfaces of the body portion of the cylindrical nut 3 and is formed in a substantially circular shape. And a recess 6b formed in an opening on the outer diameter side of the through hole 6a and having a larger diameter than the through hole 6a. A pair of the recesses 6b are formed on the inner periphery of the through-hole 6a facing each other, and are formed in an arc shape so that the outer shape matches the shape of the locking portion 13 of the mounting portion 10 in the piece member 5.

  The dimension in the longitudinal direction of the mounting portion 10 in the piece member 5 is set to be slightly larger than the dimension between the recesses 6 b and 6 b of the piece window 6. Thus, when the piece member 5 is inserted into the piece window 6, the locking portions 13 (13a, 13b) of the mounting portion 10 of the piece member 5 abut against the recess 6b, and the first base portion 11a and the second base portion 11b is brought into close contact with each other, the mounting portion 10 (10a, 10b) is elastically deformed, and the piece member 5 is fitted to the piece window 6. As described above, when the piece member 5 composed of the first piece member 1a and the second piece member 5b is inserted into the piece window 6 of the nut 3, the mounting portion 10 is elastically deformed and fitted. Since the recess 6b of the piece window 6 is formed at a desired position so that the connecting groove 7 of the piece member 5 is connected to the screw groove 3a of the nut 3 (not shown). Can be positioned and fixed easily and accurately.

  In the present embodiment, the locking portion 13 of the mounting portion 10 in the piece member 5 is formed so as to be inclined radially inward from the tip of the horizontally extending wing 12, so that the recess 6 b of the piece window 6 is formed. The depth can be set to a minimum and the outer diameter of the nut 3 can be reduced to achieve compactness. On the other hand, as shown in FIG. 5C, the locking portion 13a ′ (13b ′) of the attachment portion 10a ′ (10b ′) is formed to be inclined radially outward from the tip of the wing 12a (12b). Thus, the mounting of the piece member 5 is facilitated, and when the load indicated by the arrow is drawn by the circulation of the ball 4 so that the piece member 5 ′ is pulled out to the outer diameter side of the nut 3, the engaging portion 13 ′ is recessed. It is locked to the inner peripheral surface of the place 6b, and the removal effect becomes high, and the reliability is improved.

  The piece member 5 according to the present invention has a half-divided structure that is separated at the center along the S-shaped connection groove 7, and the connection grooves 7a and 7b of the first piece member 5a and the second piece member 5b are separated. Since the single piece member 5 is formed by abutting the surfaces 8a and 8b, the shape is complicated as in the case of a conventional steel plate piece member for rough finishing process, intermediate finishing process, and removal of surplus materials. Many molding processes such as finishing processes are not required, the number of processes can be greatly reduced, and molding can be performed with the same two molds, which is excellent in mass productivity and cost reduction. As described above, since a portion such as a connecting groove that must be drawn can be bent, the necessary dimensional and shape accuracy for smoothly circulating the ball can be ensured.

  Furthermore, since the piece member 5 is separated at the center of the S-shaped connecting groove 7, for example, PA (polyamide) 66 filled with 10 to 40 wt% of a fibrous reinforcing material such as GF (glass fiber) or the like It is also possible to form the thermoplastic synthetic resin by injection molding. As a result, the cost and weight of the ball screw can be further reduced.

  The embodiment of the present invention has been described above, but the present invention is not limited to such an embodiment, and is merely an example, and various modifications can be made without departing from the scope of the present invention. Of course, the scope of the present invention is indicated by the description of the scope of claims, and further, the equivalent meanings described in the scope of claims and all modifications within the scope of the scope of the present invention are included. Including.

  The piece type ball screw according to the present invention can be applied to a piece type ball screw used for an electric actuator of an automobile or the like.

DESCRIPTION OF SYMBOLS 1 Piece type ball screw 2 Screw shaft 2a, 3a Screw groove 3 Nut 3b Groove edge part 4 Ball 5, 5 'Piece member 5a First piece member 5b Second piece member 6 Piece window 6a Through-hole 6b Recess 7 Connection Grooves 7a, 7b Connecting groove ends 8 Joints 8a, 8b Separation surface 9 Frame body 9a First frame body 9b Second frame body 10 Mounting section 10a, 10a ′ First mounting section 10b, 10b ′ Second Mounting portion 11 base portion 11a first base portion 11b second base portion 12a first wing 12b second wing 13a, 13a ′ first locking portion 13b, 13b ′ second locking portion 51 piece type ball screw 52 Screw shafts 52a, 53a Thread groove 53 Nut 54 Ball 55 Piece member 55a Connection groove 56 Piece window 57 Positioning surface 58 Locked surface 59 Piece body 59a Piece body end 60 Locking portion 60a Fence portion 60b Base side bent portion 60c Folding end The lower part 60d locking end part

Claims (7)

A screw shaft having a helical thread groove formed on the outer peripheral surface;
A nut externally fitted to the screw shaft and having a spiral thread groove formed on the inner peripheral surface;
A plurality of balls accommodated in a rolling path formed by the opposing thread grooves;
A piece-type ball screw provided with a piece member attached to a piece window drilled in the trunk portion of the nut and having an S-shaped connection groove having the rolling path as a circulation path,
The piece-type ball screw characterized in that the piece member is composed of two members joined at a central portion along the connecting groove.   The piece member includes a piece main body in which the connection groove is formed on the inner periphery, and an attachment portion formed to protrude from a central portion in the longitudinal direction of the piece main body, and the attachment portion is arranged in a radial direction from the separation surface. A base portion extending outward and a wing extending horizontally from the base portion are formed, and a locking portion in which the tip of the wing is inclined in the radial direction is formed, and is locked in an elastically deformed state on the inner peripheral surface of the piece window. The piece type ball screw according to claim 1.   The piece window is composed of a through hole formed in a circular cross section and a recess formed in a large diameter in an opening portion on the outer diameter side of the through hole, and the recess is an inner circumference facing the through hole. The piece type ball screw according to claim 1, wherein the piece type ball screw is formed in a circular arc shape so as to match a shape of a locking portion of the piece member.   The piece-type ball screw according to claim 2 or 3, wherein the locking portion of the piece member is formed to be inclined inward in the radial direction from the tip of the wing.   4. The piece type ball screw according to claim 2, wherein a locking portion of the piece member is formed to be inclined radially outward from a tip of the wing. 5.   The piece type ball screw according to any one of claims 1 to 5, wherein the piece member is formed of a steel plate by press working.   The piece type ball screw according to any one of claims 1 to 5, wherein the piece member is formed by injection molding from a thermoplastic synthetic resin filled with a fibrous reinforcing material.

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