JP4247750B2 - Ball screw mechanism - Google Patents

Description

  The present invention relates to a ball screw mechanism that is assembled to a general industrial machine or used in an automobile.

  In recent years, labor saving of vehicles and the like has progressed, and for example, a system has been developed in which a transmission, a parking brake, and the like of an automobile are performed not by hand but by an electric motor. An electric actuator used for such an application may use a ball screw mechanism in order to convert the rotational motion transmitted from the electric motor into the axial motion with high efficiency.

However, normally, the ball screw mechanism is composed of a screw shaft, a nut, and a ball that rolls in a rolling path formed between the two. In the so-called top-type ball screw mechanism, the ball screw mechanism starts from one end of the rolling path. In order to return the ball to the other end, a member called a top is attached to the nut (see Patent Document 1).
U.S. Pat. No. 4,887,480

  Here, in the prior art described in Patent Document 1, after a reverse taper process is performed on a nut top mounting window and the top is attached to the mounting window, a spring clip having an expansion force is attached to the reverse taper side. To prevent the frame from coming off. However, the spring clip disclosed in Patent Document 1 has a problem that when the frame is mounted, the spring clip cannot be basically regulated without looseness. In addition, there is a possibility that the spring clip bends inward due to a pushing force acting on the frame (a force to pull the frame out of the nut), vibration, or the like, and in some cases, the spring clip may come off.

  The present invention has been made in view of the problems of the prior art, and an object of the present invention is to provide a ball screw mechanism capable of easily and reliably fixing a top to a nut.

The ball screw mechanism bearing of the present invention,
A screw shaft having a male screw groove formed on the outer peripheral surface;
A nut disposed so as to surround the screw shaft and having an internal thread formed on an inner peripheral surface thereof;
A plurality of balls arranged to freely roll along a rolling path formed between opposing screw grooves;
In a ball screw mechanism having a piece inserted into the mounting hole of the nut ,
The mounting hole is provided in a flat portion formed on the outer periphery of the nut,
A pair of linear notch grooves are formed on both side walls in the axial direction across the flat portion of the nut,
A fixing member including a pair of rod-like portions or plate-like portions inserted from a direction perpendicular to the radial direction of the nut along the flat surface portion into a space formed between the notch groove of the nut and the frame. Is provided,
At least a part of the fixing member mounted between the notch groove of the nut and the piece protrudes into the attachment hole, thereby preventing the piece inserted into the attachment hole from coming out,
The frame is characterized in that the displacement of the fixing member is limited within a predetermined range by a space formed between the top and the nut .

  According to the ball screw mechanism of the present invention, the fixing member is inserted into a space formed between the nut mounting portion and the top from a direction different from the insertion direction of the top, or a rod-like portion or plate Since the rod-shaped portion or the plate-shaped portion is inserted in the direction, the fixing member can be easily attached. In addition, since the frame has a shape that limits the displacement of the fixing member within a predetermined range by facing the mounting portion, unlike the conventional technique, even when a thrust force or vibration of the frame occurs, The displacement of the fixing member can be limited to prevent its falling off. In addition, since at least a part of the fixing member attached to the attachment portion protrudes into the attachment hole, the piece in the attachment hole is prevented from coming off, so that the piece is effectively removed. Can be prevented.

  It is preferable that the rod-like portion or the plate-like portion is bent at least partially because it can be fixed using its elastic force without improving the component accuracy.

  When the rod-shaped portion is formed by rounding a plate material, the rod-shaped portion can be prevented from falling off by using a diameter expanding action due to elastic deformation of the plate material.

  It is preferable that the top has a portion that can contact the fixing member in both the insertion direction and the withdrawal direction.

  It is preferable that the top is provided with a stopper that prevents the fixing member attached at the attachment position from coming off, because the fixing member can be prevented from being accidentally pulled out.

  The retainer is a protrusion provided on the surface of the top in the direction in which the fixing member mounted at the attachment position is withdrawn, and between the insertion end side of the attachment portion and the surface of the nut, When a relief (for example, a deleted portion) is formed, it is suppressed that the fixing member hits the nut when the fixing member gets over the protrusion at the time of mounting.

  A pair of rod-like portions or plate-like portions of the fixing member is provided, and when the end portions of the pair of rod-like portions or plate-like portions engage with the nut attaching portions substantially simultaneously, the fixing member can be smoothly mounted. Can be realized.

  The mounting hole of the nut has a long hole shape extending in a direction intersecting with the axial direction and the direction orthogonal to the axial line on the cylindrical outer surface of the nut, and the mounting portion is the mounting hole in the mounting hole. A pair of notch grooves formed on both side walls in the axial direction of the nut, and a second relief (for example, a deleted portion) is formed on the surface of the nut on the insertion end side of the notch groove; Alternatively, it is preferable because the end of the plate-like part can be engaged with the attaching part of the nut almost simultaneously.

  It is preferable that the lengths of the pair of rod-shaped portions or plate-shaped portions are different from each other because the end portions of the pair of rod-shaped portions or plate-shaped portions can be engaged with the nut mounting portions substantially simultaneously.

  It is preferable that at least one of the pair of rod-shaped portions or plate-shaped portions be bent at the tip after assembly because, for example, a stopper can be formed.

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a partial cross-sectional top view of the ball screw mechanism according to the present embodiment, FIG. 2 is a diagram of the configuration of FIG. 1 viewed in the direction of arrow II, and FIG. 3 is the configuration of FIG. FIG. 4 is a view taken along line IV-IV and viewed in the direction of the arrow. FIG. 4 is a view taken along line IV-IV and viewed in the direction of the arrow. FIG. FIG. 6 is an enlarged view of a portion indicated by an arrow VI in the configuration of FIG. 5. 7 is a top view of the frame, FIG. 8 is a diagram of the frame of FIG. 7 viewed in the direction of arrow VIII, and FIG. 9 is a diagram of the frame of FIG. 7 viewed in the direction of arrow IX. FIG. 10 is a perspective view of the fixing member.

  In FIG. 1, a male screw groove 1a is formed on the outer peripheral surface of a screw shaft 1 connected to a driven member and supported so as not to rotate but to move only in the axial direction. A cylindrical nut 2 supported so as to be rotatable only with respect to a housing (not shown) is disposed so as to surround the screw shaft 1 and has a female screw groove 2a formed on an inner peripheral surface thereof. A plurality of balls 3 are arranged so as to be able to roll in a spiral rolling path formed between the opposing screw grooves.

  As shown in FIGS. 3 and 4, an elongated flat surface portion 2 c perpendicular to the radial direction is formed on the outer periphery of the nut 2, and a coma hole (attachment hole) 2 b is formed so as to be positioned in the flat surface portion 2 c. Here, the top 4 is attached in a manner to be described later. As shown in FIGS. 7 to 9, the top 4 includes an oval head 4 a corresponding to the top hole 2 b and a similar oval thick portion 4 b having a smaller diameter than the top 4 a, and the thick portion 4 b A circulation path 4c is formed on the lower surface of the. A convex portion 4d and groove portions 4e extending in the longitudinal direction are formed on both sides of the upper surface of the head portion 4a. The top hole 2b forms a groove (attachment portion) 2d at a position facing the groove 4e when the top 4 is attached. It should be noted that the head 4a overhanging the top 4 abuts against the flat surface portion 2c of the nut 2 so that the top 4 is prevented from dropping into the back side.

  As shown in FIG. 10, the fixing member 5 disposed outside the top 4 is formed by bending a metal wire (preferably spring steel) having a circular cross section into a U shape. More specifically, as shown in FIG. 10, the fixing member 5 includes a pair of leg portions 5a and 5a extending in parallel, and a locking portion 5b for connecting ends of the leg portions 5a and 5a. Consists of.

  The operation of the present embodiment will be described. When the nut 2 is rotationally driven by an electric motor (not shown), the rolling path rolls and from one end of the rolling path to the other end via the circulation path 4c of the top 4. The rotating ball 3 efficiently converts the rotational motion into the axial motion of the screw shaft 1, and a driven member (not shown) connected thereto can be moved in the axial direction.

  The assembly of the top 4 of the ball screw mechanism according to the present embodiment will be described. 3 and 4, the frame 4 is inserted into the mounting hole 2b of the nut 2, and the head 4a is abutted against the flat portion 2c. At this time, as shown in FIG. 6, a space having a circular cross section is formed between the groove 2d of the nut 2 and the groove 4e of the top 4, so that each leg 5a which is a rod-like portion into the space. The fixing member 5 is inserted along the plane portion 2c from a direction orthogonal to the radial direction of the nut 2 (a direction different from the insertion direction of the top 4). In this case, since a pair of leg part 5a can be inserted at once, the assembling property is high. The fixing member 5 is positioned at a predetermined position by bringing the locking portion 5b into contact with the convex portion 4d of the top 4. In such a state, the leg portion 5a of the fixing member 5 attached to the groove portion 2d protrudes into the attachment hole 2b, thereby preventing the top 4 from being removed from the attachment hole 2b. Furthermore, since the top 4 restricts the displacement of the fixing member 5 by facing the groove 2d and prevents the top 4 from falling off the groove 2d, even if a large radial force or vibration occurs in the top 4 during operation, Both the fixing member 5 and the top 4 are prevented from coming out.

  FIG. 11 is a cross-sectional view similar to FIG. 5 according to a modification of the present embodiment. In the embodiment shown in FIG. 5, there is a slight gap between the head 4a of the top 4 and the mounting hole 2b of the nut 2, but in the modification shown in FIG. 11, the head 4a 'of the top 4'. Between the nut 2 and the mounting hole 2b of the nut 2 so that there is almost no gap. That is, the top 4 ′ has the groove 4e ′ having a semicircular cross-sectional shape so as to contact the fixing member 5 in both the insertion direction and the withdrawal direction, so that the top 4 ′ enters the back side. This eliminates the need to form a stepped portion on the nut to increase the ease of manufacture. Since the other points are the same as those in the above-described embodiment, the description thereof is omitted.

  FIG. 12 is a cross-sectional view similar to FIG. 6 according to yet another modification. 13 and 14 are perspective views of a fixing member applicable to such a modification. In the embodiment shown in FIG. 12, the shape in the cross section of the groove 2d of the nut 2 coincides with the shape in the cross section of the leg 5a of the fixing member 5, but in the modification shown in FIG. The shape in the cross section of the groove 2d ′ is larger than the shape in the cross section of the leg portion 5a ′ of the fixing member 5 ′. In this modification, as shown in FIG. 13, when the leg portion 5a ′ is bent in a hem shape and inserted into the space between the groove portion 2d ′ of the nut 2 ′ and the groove portion 4e of the frame 4, Since the elastic deformation occurs, there is no backlash of the fixing member 5 ′ in the space, and the retaining force in the inserting direction of the fixing member 5 ′ can be realized by the friction force generated between them. The leg portion is not limited to a letter shape, and may be bent in two stages or in an arc shape like a leg portion 5a ″ of the fixing member 5 ″ shown in FIG. Since the other points are the same as those in the above-described embodiment, the description thereof is omitted.

  In addition, the shape of a groove part is not restricted to the above form. As shown in FIG. 15, the groove 2d ″ of the nut 2 ″ as the attachment portion may be a V-shaped groove, and the top 4 ″ may be a flat surface 4e ″ that faces the side surface of the groove 2d ″. , 14 are preferably used.

  FIG. 16 is a cross-sectional view similar to FIG. 6 according to another modification. FIG. 17 is a perspective view of a fixing member applicable to such a modification. In the embodiment shown in FIG. 6, the fixing member 5 has a shape in which a wire is bent in a U shape. However, in the modification shown in FIG. 16, the fixing member 5 ′ ″ has a bar shape with a C-shaped cross section. Such a fixing member 5 ′ ″ can be formed by rounding a thin plate having a spring property, and is inserted into a space between the groove 2d of the nut 2 and the groove 4e of the top 4 while being reduced in diameter. After the mounting, the elastic deformation returns and the groove portions 2d and 4e are pressed to prevent the fixing member 5 ′ ″ from falling off. Two fixing members 5 ′ ″ are required in accordance with the groove portions on both sides. become.

  18 is a top view of a frame according to still another modified example, and FIG. 19 is a side view thereof, and the fixing member 5 shown in FIG. 10 (shown here by a dotted line) is attached to the mounting position. Shown in state. The top 4A of the present modification has a protrusion 4f as a retainer on its upper surface. The protrusion 4f is formed so as to be separated from the convex portion 4d by the wire diameter of the fixing member 5, and the locking portion 5b of the fixing member 5 is mounted between them. In the mounted fixing member 5, the locking portion 5b is restrained by the protrusion 4f, so that the fixing member 5 is prevented from coming out. It is preferable that a tapered surface 4g that increases toward the convex portion 4d is formed on the upper surface of the protrusion 4f because the fixing member 5 can be easily attached. Regarding the other configuration, the frame 4A is the same as the frame 4 shown in FIGS.

  20 is a top view similar to FIG. 1 when the frame 4A shown in FIGS. 18 and 19 is attached to the nut 2 and the fixing member 5 is mounted. FIG. 21 is a view of the nut 2 taken along line XXI-XXI in FIG. 20 and viewed in the direction of the arrow. As shown in FIG. 20, the mounting hole 2 b has a long hole shape extending in a direction intersecting the axial direction and the direction orthogonal to the axial line on the cylindrical outer surface of the nut 2. In order to provide, the flat part 2c formed so as to cut off the outer periphery is not halfway through the end part of the nut 2 in this example, and is halfway. If the flat part 2c penetrates, the sharp part may be generated. It is possible to prevent the nut 2 from being cracked or chipped due to the edge. Furthermore, since the pair of grooves 2d as the attachment portions are a pair of notch grooves formed on both side walls in the axial direction of the nut 2 in the attachment hole 2b, only the groove 2d on the left side in the drawing is geometrically elongated.

  Here, when the fixing member 5 is inserted into the groove 2d, the first leg 5a starts to be engaged from the insertion end (point A) of the first groove 2d, and when it is inserted to some extent, the other leg 5a. Starts engaging from the insertion end (point B) of the other groove 2d. Therefore, the fixing member 5 must be inserted in a state where only one leg portion 5a is engaged, and only one leg portion 5a receives frictional force from the groove 2d during that period, and the rigidity of the fixing member 5 is low. In such a case, the deformation may occur or a competition with the groove 2d may occur.

  Further, as shown in FIG. 21, when the groove 2d is formed, the upper wall formed in the nut 2 (the portion sandwiched between the outer surface of the nut 2 and the groove 2d: point C) becomes a sharp edge. However, when the fixing member 5 is inserted, the locking portion 5b is deformed when it climbs over the protrusion 4f of the top 4. However, this may cause stress by abutting against the sharp edge of the nut 2 to cause chipping or the like. is there. In the following modifications, such a problem can be effectively suppressed.

  FIG. 22 is a top view similar to FIG. 1, showing the top 4 </ b> A attached to a nut 2 </ b> A which is a modification, and the fixing member 5 being attached. FIG. 23 is a view of the nut 2A taken along the line XXIII-XXIII of FIG. 22 and viewed in the direction of the arrow. The nut 2A according to the present modified example is obtained by deleting one of the insertion ends (left side in FIG. 22) of the groove 2d formed on both side walls in the axial direction of the mounting hole 2b into a groove shape (or a slope). The escape 2e is formed. As a result, the length of the left groove 2d 'is shorter than the example shown in FIG.

  Further, as shown in FIG. 23, the first wall 2f is formed by deleting the upper wall (the portion indicated by the point C in FIG. 21) of the nut 2 near the insertion end of the groove 2d '.

  According to the present modification, since the second relief 2e is formed in the nut 2, when the fixing member 5 is inserted into the pair of grooves 2d, the pair of leg portions 5a is substantially omitted from the insertion ends of the pair of grooves 2d. Engagement is started at the same time, and frictional force is simultaneously applied to the pair of legs 5a, so that deformation of the fixing member 5 and competition with the groove 2d can be suppressed.

  Furthermore, according to this modification, since the first relief 2f is formed in the nut 2, when the fixing member 5 is inserted, when the locking portion 5b gets over the protrusion 4f of the top 4, the nut 2 is pressed. However, the occurrence of chipping or the like is suppressed.

  FIG. 24 is a perspective view of a fixing member 5A according to a modification. In this modification, one leg 5a 'of the fixing member 5A is longer than the other leg 5a. Therefore, when the fixing member 5A is inserted into the nut 2 where the second relief is not formed as shown in FIG. 20, both the leg portions 5a ′ and 5a are engaged substantially simultaneously from the insertion ends of the pair of grooves 2d. Since the frictional force is simultaneously applied to the pair of leg portions 5a ′ and 5a, the deformation of the fixing member 5A and the competition with the groove 2d can be suppressed.

  FIG. 25 is a top view similar to FIG. 1 showing the top 4B attached to the nut 2A and the fixing member 5A attached. In this example, instead of removing the protrusion from the frame, the fixing member 5A itself is deformed to prevent it from coming off after assembly. Therefore, in the top 4B, as shown in FIGS. 26 and 27, the convex portion 4d is cut to form a side surface 4k so as to have a line-symmetric shape. More specifically, the pair of leg portions 5a 'and 5a of the fixing member 5A are respectively inserted into the pair of grooves 2d and assembled at predetermined positions, and then the tip of the longer leg portion 5a' is protruded. The heel part 5c is formed by bending along the side surface 4k of the part 4a.

  Then, the locking portion 5b and the flange portion 5c of the fixing member 5A sandwich the convex portion 4d of the top 4 from both sides, whereby the fixing member 5A can be prevented from coming off. Of course, both of the pair of legs 5a 'and 5a may be bent. According to this example, it is not necessary to provide a convex portion on the top, and stress applied to each portion when the fixing member gets over the convex portion is eliminated, and insertion is easy.

  The present invention has been described above with reference to the embodiments. However, the present invention should not be construed as being limited to the above-described embodiments, and can be modified or improved as appropriate. For example, it is good also as a structure which inserts a plate-shaped part in the space between the groove part of a nut, and the groove part of a top. The coma is preferably formed by pressing, sintering or forging when a metal is used as a raw material, and is preferably formed by injection molding when a resin is used as a raw material. Is not limited to these.

It is a partial cross section top view of the ball screw mechanism which is this Embodiment. It is the figure which looked at the structure of FIG. 1 in the arrow II direction. It is the figure which cut | disconnected the structure of FIG. 1 by the III-III line | wire, and looked at the arrow direction. It is the figure which cut | disconnected the structure of FIG. 1 by the IV-IV line and looked at the arrow direction. It is the figure which cut | disconnected the structure of FIG. 1 by the VV line and looked at the arrow direction. FIG. 6 is an enlarged view showing a part indicated by an arrow V in the configuration of FIG. 5. It is a top view of a top. It is the figure which looked at the top of Drawing 7 in the direction of arrow VIII. It is the figure which looked at the top of Drawing 7 in the direction of arrow IX. It is a perspective view of a fixing member. It is sectional drawing similar to FIG. 5 concerning the modification of this Embodiment. It is sectional drawing similar to FIG. 6 concerning another modification. It is a perspective view of the fixing member concerning a modification. It is a perspective view of the fixing member concerning a modification. It is sectional drawing similar to FIG. 6 concerning another modification. It is sectional drawing similar to FIG. 6 concerning another modification. It is a perspective view of the fixing member concerning a modification. It is a top view of the top 4A concerning another modification. It is a side view of the top 4A concerning another modification. FIG. 20 is a top view similar to FIG. 1 when the top 4A shown in FIGS. 18 and 19 is attached to the nut 2 and the fixing member 5 is mounted. It is the figure which cut | disconnected the nut 2 by the XXI-XXI line | wire of FIG. 20, and looked at the arrow direction. FIG. 4 is a top view similar to FIG. 1, showing a state in which the top 4 </ b> A is attached to a nut 2 </ b> A which is a modified example, and a fixing member 5 is attached. It is the figure which cut | disconnected the nut 2A by the XXIII-XXIII line | wire of FIG. 22, and looked at the arrow direction. It is a perspective view of fixing member 5A concerning a modification. FIG. 2 is a top view similar to FIG. 1, showing a state where the top 4 is attached to the nut 2 </ b> A and the fixing member 5 </ b> A is attached. It is a top view of the top 4B concerning another modification. It is a side view of the top 4B concerning another modification.

Explanation of symbols

1 Screw shaft 2, 2 ', 2A Nut 3 Ball 4, 4', 4 ", 4A, 4B Top 5, 5 ', 5", 5'", 5A Fixing member

Claims (10)

A screw shaft having a male screw groove formed on the outer peripheral surface;
A nut disposed so as to surround the screw shaft and having an internal thread formed on an inner peripheral surface thereof;
A plurality of balls arranged to freely roll along a rolling path formed between opposing screw grooves;
In a ball screw mechanism having a piece inserted into the mounting hole of the nut,
The mounting hole is provided in a flat portion formed on the outer periphery of the nut,
A pair of linear notch grooves are formed on both side walls in the axial direction across the flat portion of the nut,
A fixing member including a pair of rod-like portions or plate-like portions inserted from a direction perpendicular to the radial direction of the nut along the flat surface portion into a space formed between the notch groove of the nut and the frame. Is provided,
At least a part of the fixing member mounted between the notch groove of the nut and the piece protrudes into the attachment hole, thereby preventing the piece inserted into the attachment hole from coming out,
The ball screw mechanism is characterized in that a displacement of the fixing member is limited within a predetermined range by a space formed between the top and the nut.   The rod-like portion or the plate-like portion is bent in a direction in which an elastic force is generated between the nut and the top when at least a part of the rod-like portion or the plate-like portion is mounted in the notch groove of the nut. The described ball screw mechanism.   The said rod-shaped part is formed by rounding a board | plate material in the direction which produces an elastic force between the said nut and the said top, when it mounts | wears with the notch groove | channel of the said nut. Ball screw mechanism.   The ball screw mechanism according to any one of claims 1 to 3, wherein the top has a portion that can contact the fixing member in both the insertion direction and the withdrawal direction.   The top is provided with a stopper that prevents the fixing member attached at the attachment position from coming off, and the stopper is a protrusion provided on the surface of the top, and the protrusion inserts the fixing member. 5. The ball screw mechanism according to claim 1, wherein a surface in a direction to be tapered is a taper surface, and the fixing member is fixed between the convex portion of the top and the protrusion. The ball screw mechanism according to any one of claims 1 to 5 , wherein end portions of the pair of rod-like portions or plate-like portions are inserted into the pair of notch grooves of the nut substantially simultaneously. The mounting hole of the nut has a long hole shape extending in a direction intersecting the axial direction and the direction orthogonal to the axial direction on the cylindrical outer surface of the nut, and the nut on the insertion end side of one notch groove The ball screw mechanism according to claim 6 , wherein a relief reaching the notch groove is formed from the surface of the lens so that the fixing member can be inserted into the pair of notch grooves substantially simultaneously.   The ball screw mechanism according to claim 7, wherein the relief is formed to a range where at least the fixing member gets over a protrusion provided on a surface of the top.   8. The ball screw mechanism according to claim 7, wherein the fixing members of the pair of rod-shaped portions or plate-shaped portions have different lengths and are inserted into the pair of notch grooves of the nut substantially simultaneously. . The ball screw mechanism according to any one of claims 6 to 9, wherein at least one of the pair of rod-like portions or plate-like portions is bent at a tip end thereof in a shape that prevents removal after assembly.

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