JP2007040490A - Ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ball screw device of a long service life converting the linear motion of a nut once into swing motion of a swing arm, and converting the swing motion again into rotary motion to drive a driven body. <P>SOLUTION: In the swing arm 21 swinging around a driven shaft 23 for taking out rotary motion, and a groove 13a of a nut 13 screwed with a ball screw shaft 12 driven by a motor 18, contact points between a false triangular tip part 21a which is a constant width pattern of the swing arm 21 and a groove 13a of a nut 13 are points P1, P2 including the centerline of a ball screw shaft 12 when the swing arm 21 is in a vertical position. When the nut 13 moves to the right, the tip part 21a inclines within the groove 13a of the nut 13, and the contact points move to P3, P4, but even if the swing arm 21 inclines by 30° from the vertical position, the moving quantity d is small, and large rotational moment having adverse effect on a ball circulating passage of the nut 13 does not occur. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a ball screw device, and more particularly to a ball screw device that can be used for a general industrial machine and a power operating mechanism of a transmission for a vehicle.

  As a driving method of a driven body by a ball screw device, a driving system that drives a driven body by rotating a screw shaft and moving a nut screwed to the screw shaft in the screw shaft direction is widely used. In this configuration, the linear motion of the nut is generally used as it is as the linear motion of the driven body. However, the linear motion of the nut is once converted into the swing motion of the swing arm, and the swing arm swings. A drive system is also used in which a dynamic motion is converted into a rotational motion again to drive a driven body (see Patent Document 1).

  FIGS. 5 to 7 are diagrams for explaining an electric drive device for transmission (hereinafter referred to as a drive device) 100 that operates a vehicle transmission using the above-described conventional ball screw device using a motor as power. FIG. 6 is a view for explaining the arrangement of the drive device 100, FIG. 6 is an example of a shift pattern of an operation lever of the vehicle transmission device, and FIG.

  First, an outline of the overall configuration will be described. As shown in FIG. 5, the drive device 100 is installed on the case 103 of the vehicle transmission, the operation lever of the vehicle transmission is connected to the drive pin denoted by reference numeral 108 in FIG. It is configured to move according to the shift pattern shown in FIG. 6 and to switch the gear of the vehicle transmission.

  The driving device 100 includes a main housing 104 and a sub housing 105 (see FIG. 5). In FIG. 7, a switching shaft 107 is coaxially disposed inside the shift sleeve 112 inside the main housing 104, and the switching shaft 107 is supported so as to be rotatable about the axial direction and the axis. The switching shaft 107 is provided with a drive pin 108 and protrudes outside the main housing 104.

  A male serration 111 is formed on the right side of the switching shaft 107 in FIG. 7, and is coupled to one end of the shift sleeve 112 via the female serration 113 of the shift sleeve 112. The rotation of the shift sleeve 112 is switched via the serration coupling described above. It is transmitted to the shaft 107.

  In addition, an arc-shaped rack 116 concentric with the switching shaft 107 is formed on the right side of the switching shaft 107 in FIG. 7, and is driven by a motor 109 (see FIG. 5) in an opening 119 formed in the shift sleeve 112. The switching shaft 107 moves to the left and right in the axial direction by the rotation of the pinion 117 that meshes with the rack 116.

  The shift sleeve 112 is provided with two swing arms 122 on the left and right in the vicinity of the opening 119 where the rack 116 and the pinion 117 mesh with each other. A nut 128 is swingably attached via a pin 129. The holding hole 130 of the swing arm 122 that holds the pin 129 is formed as an elongated hole for the reason described later.

  The nut 128 is screwed into a ball screw shaft 124 driven by a motor 110 (see FIG. 5). The rotation of the ball screw shaft 124 causes the nut 128 to move in the axial direction of the ball screw shaft 124 (in FIG. 7, the direction perpendicular to the paper surface). ) And the shift sleeve 112 arranged coaxially with the switching shaft 107 is swung around its axis via the swing arm 122.

  With the above configuration, when the motor 109 (see FIG. 5) is driven, the switching shaft 107 moves in the axial direction via the pinion 117 and the rack 116, and the drive pin 108 moves in the select direction (the horizontal direction passing through the neutral position N in FIG. 6). ), The shift lever of the vehicle transmission device is moved to the gear switching step selection position, and the gear switching step is selected by the shift lever of the vehicle transmission device connected to the drive pin 108.

  Next, when the motor 110 (see FIG. 5) is driven, the swing arm 122 swings around its axis via the ball screw shaft 124, the nut 128, and the swing arm 122, and is connected to the drive pin 108. The shift lever of the vehicle transmission is set to the meshing position with the gear of the previously selected gear switching stage.

In the configuration described above, the nut 128 moves in the axial direction of the ball screw shaft 124 and causes the shift sleeve 112 to swing around its axis (same as the axis of the switching shaft 107) via the swing arm 122. Since the distance between the nut axis and the shift sleeve axis varies, the holding hole 130 provided in the swing arm 122 that holds the nut mounting pin 129 can cope with the above-described variation in distance. As shown in FIG. 7, the elongated holes are formed in the vertical direction.
JP 2002-317871 A.

  It is not always desirable in terms of the structure to handle a large load when the variation of the gap between the nut axis and the shift sleeve axis as described above is solved by the elongated hole provided in the shift sleeve. Thus, a configuration as described below is proposed, but there is a disadvantage in that the operating point where the nut acts on the oscillating arm is deviated and the life of the ball screw device is shortened. Hereinafter, the configuration and problems to be solved will be described.

  FIG. 8 and FIG. 9 are diagrams for explaining a drive mechanism composed of a swing arm and a ball screw of the proposed electric drive device for transmission, and FIG. 8 shows a part of the drive mechanism in cross section. FIG. 9A is a front view showing a state in which the nut is moved to the right side in the drive mechanism of FIG. 8, and FIG. 9B is a view when the nut is moved to the right side and the swing arm is inclined. It is a figure explaining the state of the front-end | tip part.

  In FIG. 8, the ball screw shaft 203 of the drive mechanism is rotatably supported by a ball bearing 202 held by the housing 200, and one end of the ball screw shaft 203 is connected to the motor 205 via the reduction gear device 204. . When the ball screw shaft 203 is rotated by the rotation of the motor 205, the nut 210 screwed with the ball screw shaft 203 moves in the axial direction. The ball screw mechanism itself composed of the ball screw shaft 203 and the nut 210 is not different from a conventionally known ball screw mechanism.

  The nut 210 has guides 210c on the outer edges of the left and right sides (the side indicated by the solid line (front side) and the side indicated by the solid line (back side)) in FIG. Grooves (slots) 210a and 210b having a width L provided with 210d are formed.

  As described above, the swing arms 220 and 221 are formed on the substantially disc-shaped tip portions 220a and 221a that fit into the grooves 210a and 210b of the nut 210 as described above, and the substantially disc-shaped tip portion 220a. And 221a have the same diameter as the width L of the grooves (slots) 210a and 210b. Therefore, the substantially disc-shaped tip 220a of the swing arm 220 fits along the guide 210c without looseness in the groove 210a. The substantially disc-shaped tip 221a of the swing arm 221 fits in the groove 210b along the guide 210d without looseness.

  The other ends of the swing arms 220 and 221 are fixedly coupled to a shift sleeve 230 that is a driven shaft, and even if the swing arms 220 and 221 swing, the shift sleeve 230 that is a driven shaft The axis does not move, and the swing arms 220 and 221 are configured to rotate around the axis of the shift sleeve 230.

  The operation of the drive mechanism described above will be described. Since the relationship between the swing arm 220 and the groove 210a of the nut 210 and the relationship between the swing arm 221 and the groove 210b of the nut 210 are the same, in the following description, the relationship between the swing arm 220 and the groove 210a of the nut 210 will be described. Only explained.

  FIG. 8 described above shows a state where the swing arm 220 of the drive mechanism is in the neutral position, that is, the center axis of the swing arm 220 is perpendicular to the axis of the ball screw shaft 203. In this state, the contact point P between the tip 220a of the swing arm 220 and the guide 210c of the groove 210a of the nut 210 is at P1 and P2 on the plane including the axis of the ball screw shaft 203. No special reaction force acts on.

  When the nut 210 moves to the right side by the rotation of the ball screw shaft 203 from the state shown in FIG. 8, the state shown in FIG. The tip 220a of the swing arm 220 is tilted by rotating inside the groove 210a (here, rotating 30 ° counterclockwise), but the other end 220e of the swing arm 220 is shifted so that the axis does not move. Since the swing arm 220 is fixed to the sleeve 230, the tilt of the swing arm 220 results in the movement of the tip 220 a of the swing arm 220 toward the shift sleeve 230 (upward in FIG. 9A). The contact point between the tip 220a and the guide 210c of the groove 210a of the nut 210 moves from P1, P2 to P3, P4, and a shift occurs in the point of action P where the nut 210 acts on the swing arm 220. The magnitude of the deviation of the action point P is defined as a movement amount d0.

  Due to the deviation of the action point P, as shown in FIG. 9B, the nut 210 has a rotational moment M (M = F ×) obtained by multiplying the axial force F acting on the contact point by the movement amount d0. d0) acts. As a result, a uniform axial force does not act on the ball loaded in the ball screw, and a large surface pressure is partially applied to the ball screw shaft or the ball rolling surface of the nut. The generation of a large surface pressure causes inconvenience that the rolling fatigue of the ball screw is promoted and the life of the ball screw device is shortened.

  In order to reduce the rotational moment M (M = F × d0) acting on the nut 210 as much as possible, the ball at the contact point P between the tip 220a of the swing arm 220 and the guide 210c of the groove 210a of the nut 210 is used. The amount of movement d0 from the screw shaft may be reduced.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a ball screw device that solves the above-mentioned disadvantages and prevents the occurrence of deviation of the operating point of the swing arm and can maintain the long life of the ball screw device. is there.

  The present invention solves the above-mentioned problems, and the invention of claim 1 circulates and moves through a screw shaft, a nut screwed to the screw shaft, and a ball circulation path formed between the screw shaft and the nut. A ball screw mechanism composed of a plurality of balls, and a tip end formed in a constant width pattern having one end fixed to the driven shaft and the other end having a predetermined constant width regardless of the rotation angle, The tip of the constant width pattern includes a swing arm that swingably fits into a groove formed on the outer edge of the nut, and converts the rotational motion of the screw shaft into a linear motion of the nut. The ball screw device converts a linear motion of the nut into a swing motion of the driven shaft via the swing arm.

  The constant width pattern formed at the tip of the arm is preferably a substantially triangular pattern formed from three arcs of a predetermined radius centered on the apex of the regular triangle.

  In this case, one of the vertices of the substantially triangular pattern may be on a line that intersects the central axis of the arm at a right angle.

  The groove formed in the outer edge of the nut is a groove extending in a direction perpendicular to the axis of the screw shaft, and the swing arm is fitted in the groove and orthogonal to the axis of the screw shaft. Can be moved to.

  The driven shaft is a shaft that swings about an axis extending in a direction orthogonal to the axis of the screw shaft.

  According to the present invention, since the tip of the swing arm that swings around the axis of the driven shaft is formed in a constant width pattern, the nut with which the tip of the swing arm is screwed onto the ball screw shaft Even if the swing arm is tilted by the linear movement of the nut by fitting in the groove formed on the outer edge of the nut, the tip of the swing arm (constant width pattern, pseudo-triangle pattern) and the nut outer edge The contact point with the groove slightly moves up and down from the plane including the central axis of the ball screw shaft, and a large rotational moment is generated that adversely affects the ball circulation path of the nut screwed into the ball screw shaft. There is nothing. With this configuration, it is possible to provide a ball screw device with a simple configuration and a long lifetime.

  Embodiments of the present invention will be described below. FIGS. 1 and 2 are views for explaining a ball screw device including a swing arm and a ball screw mechanism according to an embodiment of the present invention. The drive mechanism described above with reference to FIGS. It is an improvement.

  FIG. 1A is a front view showing a state in which the swing arm 21 of the ball screw device 10 is in a position perpendicular to the ball screw shaft 12 of the ball screw mechanism 11, and FIG. It is sectional drawing which looked at the nut 13 of the ball screw mechanism 11 cut | disconnected along the DD line | wire from the top.

  2A is a front view showing a state when the nut 13 of the ball screw mechanism 11 is moved in the right direction, and FIG. 2B is a state where the nut 13 is moved to the right side and the swing arm 21 is inclined. It is a figure explaining the state of the tip part at the time.

  1 and 2, the ball screw shaft 12 of the ball screw mechanism 11 is rotatably supported by ball bearings 14 and 15 held by a housing 19, and one end of the ball screw shaft 12 passes through a reduction gear mechanism 17. The motor 18 is connected. When the ball screw shaft 12 rotates through the reduction gear mechanism 17 by the rotation of the motor 18, the nut 13 screwed to the ball screw shaft 12 moves in the axial direction. The ball screw mechanism 11 itself is the same as a conventionally known ball screw mechanism.

  The nut 13 extends in a direction perpendicular to the axis of the ball screw shaft 12 on the outer edge on the left side (the side indicated by the solid line in FIG. 1, the front side) as viewed from the axis of the ball screw shaft 12 to be screwed. A groove (slot) 13a provided with guides 13c and 13d is formed. In the groove 13a, a distal end portion 21a of a swing arm 21 to be described later is not loosened, and the shaft of the ball screw shaft 12 is pivoted. It is slidably fitted in the vertical direction. In addition, the shape of the front-end | tip part 21a is a shape called a constant width pattern, and is a pseudo-triangular pattern here.

  Similarly, the nut 13 is on the right side (on the opposite side to the side indicated by the solid line in FIG. Grooves (slots) 13b provided with extending guides 13e and 13f are formed. A tip end portion 22a of a swing arm 22 (to be described later) is not loosened in the groove 13b, and the axis of rotation and the axis of the ball screw shaft 12 is formed. Are slidably fitted in the vertical direction. In addition, the shape of the front-end | tip part 22a is also a constant width pattern (pseudo-triangular pattern) similarly to the front-end | tip part 21a.

  The swing arm 21 and the swing arm 22 are fixedly coupled to the driven shaft 23 (corresponding to the shift sleeve 230 having the configuration described in FIG. 8), and the axis of the driven shaft 23 does not move. Reference numerals 21 and 22 are configured to rotate around the axis of the driven shaft 23.

  The fitting state between the groove 13a and the quasi-triangular tip portion 21a of the swing arm 21 and the fitting between the groove 13b and the tip portion 22a of the constant width pattern (pseudo-triangular pattern) of the swing arm 22 are as follows. Since the state is a structure that is symmetrical with respect to the axis of the ball screw shaft 12, hereinafter, a constant width pattern (pseudo-triangular shape) of the groove 13a and the swing arm 21 indicated by a solid line in FIGS. The configuration in which the tip portion 21a of the pattern) is fitted will be described.

  FIG. 1A shows a state in which the nut 13 is near the left end of the ball screw shaft 12 and the swing arm 21 is in a position perpendicularly intersecting the ball screw shaft 12. At this time, the contact point P between the guides 13c and 13d of the groove (slot) 13a and the quasi-triangular tip portion 21a of the swing arm 21 fitted thereto is a plane including the axis of the ball screw shaft 12. The upper contact points P1 and P2.

  In FIG. 2A, the ball screw shaft 12 is rotated by the motor 18, the nut 13 moves near the right end of the ball screw shaft 12, and the swing arm 21 intersects the ball screw shaft 12 perpendicularly. It shows a state where it is at a position rotated counterclockwise by 30 ° from the position shown in FIG. At this time, the contact point P between the guides 13c and 13d of the groove (slot) 13a and the tip portion 21a of the constant width pattern (pseudo-triangular pattern) of the swinging arm 21 fitted to the guide 13c is a ball screw shaft. Move to contact points P3 and P4 on a plane parallel to a plane including 12 axes. That is, as the swing arm 21 rotates, the contact point P shifts from the contact points P1 and P2 to the contact points P3 and P4. The amount of displacement of the contact point P is defined as a movement amount d.

  Due to the displacement of the contact point P, as shown in FIG. 2B, the nut 13 has a rotational moment M (M = F ×) obtained by multiplying the axial force F acting on the contact point P by the moving amount d. Although d) acts, the movement amount d of the contact point P is smaller than the movement amount d0 shown in FIG. The increase in rotational moment M is slight. This is obtained by the shape of the tip 21 a of the swing arm 21. Hereinafter, the shape of the tip portion 21a will be described.

  3A and 3B are views for explaining the shape of the tip 21a of the swing arm 21, FIG. 3A is a diagram showing the shape of the tip 21a of the swing arm 21, and FIG. 3B is the geometry of the tip 21a. It is a figure explaining a geometric shape.

  This will be described with reference to FIG. The geometric shape of the tip 21a is such that a circle Sa having a radius R equal to the width L of the groove (slot) 13a described above is drawn around the vertex A of the equilateral triangle, and the radius R is also the same around the point B on the circle Sa. A circle Sb is drawn, and a circle Sc having the same radius R is drawn around the intersection C of the circles Sa and Sb.

  A pseudo triangle composed of an arc AB connecting the vertices A and B of the regular triangle, an arc BC connecting the vertices B and C, and an arc CA connecting the vertices C and A is called a constant width figure or a constant width pattern. And the width between the arbitrary point on the arc BC, the width between the apex B and the arbitrary point on the arc AC, and the width between the apex C and the arbitrary point on the arc AB are constant (= R = L). .

  Therefore, when the shape of the tip end portion 21 a of the swing arm 21 is the above-described constant width pattern, the nut 13 is moved by the rotation of the ball screw shaft 12 so that the swing arm 21 is perpendicular to the axis of the ball screw shaft 12. The tip 21a of the oscillating arm 21 is spaced from the groove 13a of the nut 13 even if it is rotated at an arbitrary angle from the intersecting position and moved in the direction perpendicular to the axis of the ball screw shaft 12. The movement of the nut 13 in the ball screw shaft direction can be accurately transmitted to the rotation of the swing arm 21.

  FIG. 3A shows an example in which the tip 21a of the swing arm 21 described in FIG. 3B is formed in a pseudo triangle. That is, the vertex A is set to ½ L (L is the width of the groove (slot) 13 a) on the line perpendicularly intersecting the central axis of the swing arm 21. Further, vertices B and C are determined based on the description of the geometric shape, and an arc connecting vertices A and B, an arc connecting vertices B and C, and an arc connecting vertices C and A are drawn. By disposing the arm of the swing arm 21 between the two, the swing arm 21 having the configuration shown in FIGS. 1 and 2 is completed.

  In this configuration, as described with reference to FIG. 2, when the nut 13 is moved by the rotation of the ball screw shaft 12, the contact point P between the groove (slot) 13 a and the pseudo triangle of the swing arm 21 is the ball screw shaft 12. Is moved from the contact points P1 and P2 to the contact points P3 and P4 by a movement amount d in a direction perpendicular to the axis of

  FIG. 4 is a diagram showing the relationship between the rotation angle of the swing arm of the present invention and the amount of movement of the contact point P between the nut groove (slot) of the ball screw device. Also shown is the relationship between the amount of movement of the contact point between the tip formed in the circular shape and the nut groove (slot) of the ball screw device.

  In FIG. 4, the horizontal axis represents the rotation angle (°) of the swing arm, the vertical axis represents the amount of movement (mm) from the reference position of the contact point P (the plane including the axis of the ball screw shaft 12), and the line ( A) shows the movement of the contact point P of the tip (pseudo-triangular constant width pattern) of the swing arm according to the present invention, and line (B) shows the tip of the swing arm (circular pattern) in the case of the conventional configuration. The movement of the contact point P is shown.

  As is clear from FIG. 4, it can be seen that the movement amount is much smaller in the case of the constant-width pattern having a pseudo triangle at the tip.

  In the embodiment of the invention described above, the ball screw device of the invention has been described as being applied to a power operating mechanism of a transmission for a vehicle. However, the ball screw device of the invention is a power of a transmission for a vehicle. Needless to say, the present invention is not limited to the operation mechanism and can be widely applied to a drive mechanism of a general mechanical device.

  This is a ball screw device having a long life, in which the linear motion of the nut is once converted into the swing motion of the swing arm and then converted into the rotational motion again to drive the driven body. The tip of the oscillating arm that swings around the driven shaft that extracts the rotational motion is formed in a constant width pattern (pseudo-triangular shape) and fits into a groove formed on the outside of the nut that is screwed onto the ball screw shaft. Even if the swinging arm is inclined by the linear motion of the nut, the tip of the swinging arm slightly moves in the groove, and a large rotational moment that adversely affects the ball circulation path of the nut is not given.

The front view which showed a part of drive device comprised from the rocking | fluctuation arm and ball screw mechanism of embodiment of this invention in the cross section. The front view which shows a state when the nut of the drive device shown in FIG. 1 moves rightward. The figure explaining the shape of the front-end | tip part of a rocking | fluctuating arm. The relationship between the rotation angle of the swing arm and the amount of movement of the contact point between the swing arm and the nut groove of the ball screw device according to the embodiment of the present invention, and the conventional rotation angle of the swing arm and the ball screw device The figure which shows the relationship with the moving amount | distance of a contact point with the groove | channel of a nut. The figure explaining arrangement | positioning of the electric drive device for transmissions using the conventional ball screw apparatus. The figure explaining an example of the shift pattern of the operation lever of the transmission for vehicles shown in FIG. Sectional drawing in alignment with the AA line of the transmission for vehicles shown in FIG. The figure explaining the rocking | fluctuating arm and ball screw mechanism part of the conventional drive device. The figure explaining operation | movement of the conventional drive device shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Ball screw apparatus 11 Ball screw mechanism 12 Ball screw shaft 13 Nut 13a, 13b Groove 13c, 13d Guide 13e, 13f Guide 14, 15 Ball bearing 17 Reduction gear mechanism 18 Motor 19 Housing 21, 22 Swing arm 21a, 22a Tip part (Pseudo-triangular tip that is a constant-width pattern)
23 Driven shaft

Claims (5)

A ball screw mechanism including a screw shaft, a nut screwed to the screw shaft, and a plurality of balls that circulate and move in a ball circulation path formed between the screw shaft and the nut;
One end is fixed to the driven shaft, and the other end has a tip portion formed in a constant width pattern having a predetermined constant width regardless of the rotation angle, and the tip portion of the constant width pattern is formed on the outer edge of the nut. A swing arm that is swingably fitted into the groove formed,
A ball screw device that converts a rotational motion of the screw shaft into a linear motion of a nut, and further converts a linear motion of the nut into a rocking motion of the driven shaft via the rocking arm. The constant width pattern formed at the tip of the arm is a substantially triangular pattern formed from arcs of three predetermined radii centered on the apex of an equilateral triangle. Ball screw device. 3. The ball screw device according to claim 2, wherein one of the apexes of the substantially triangular pattern is on a line perpendicular to the central axis of the arm. The groove formed on the outer edge of the nut is a groove extending in a direction orthogonal to the axis of the screw shaft, and the swing arm is fitted in the groove and moves in a direction orthogonal to the axis of the screw shaft. The ball screw device according to claim 1, wherein the ball screw device is possible. 3. The ball screw device according to claim 1, wherein the driven shaft is a shaft that swings about an axis extending in a direction orthogonal to the axis of the screw shaft.

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