WO2008075541A1 - Movable element coupling structure in nut member - Google Patents

Abstract

A movable element coupling structure which can absorb fixing error of a nut member such as a spline nut (11) and a screw nut (3) with respect to the movable element and can fix the nut member easily and compactly to the movable element. The movable element coupling structure comprises a plurality of ball holding pockets (6) provided on the outer circumferential surface of the nut member along the circumferential direction, a large number of engaging balls (7) having spherical surfaces being received partially in the ball holding pocket (6), and a flange plate (5) formed in a ring shape while having a hollow portion to which the nut member is fitted idly, being secured to the movable element and engaging with the nut member through the engaging ball (7), wherein a ball containing groove (8) opposing the ball holding pocket (6) is formed in the inner circumferential surface of the flange plate (5) along the axial direction of the nut member, and the flange plate (5) is engaging with the nut member to be able to incline freely.

Description

 Specification

 Movable body connection structure in nut member

 Technical field

 [0001] The present invention relates to a nut member that moves along a shaft member such as a spline nut that moves while being fitted to a spline shaft, or a screw nut that moves while being screwed to a screw shaft. The present invention relates to a connection structure for coupling to a movable body.

 Background art

 Conventionally, a feed screw mechanism in which a screw shaft and a screw nut are combined is known as a drive mechanism that gives a predetermined feed amount to a movable body such as a table capable of linear reciprocation. In this feed screw mechanism, a screw shaft in which a helical screw groove is formed is disposed in parallel with the linear motion path of the movable body, and a screw nut screwed to the screw shaft is fixed to the movable body. The rotary motion applied to the screw shaft by the motor is converted into the linear motion of the screw nut, thereby driving the movable body in the linear motion path.

 [0003] However, in such a feed screw mechanism, even when the linear motion path of the movable body and the screw shaft are provided in parallel with high accuracy, the mounting accuracy of the screw nut to the movable body is poor. As a result, there is a problem that the axial center of the screw nut is tilted with respect to the center of rotation of the screw shaft. If such an inclination exists, the feed accuracy of the movable body deteriorates due to an increase in the rotational resistance of the screw shaft, and the life of the device is shortened due to uneven wear of the screw nut.

[0004] On the other hand, in a ball spline that linearly guides a movable body such as a table, a similar problem occurs when the spline nut is fixed to the movable body. The ball spline is composed of a spline shaft in which a spline groove is formed along the axial direction, and a spline nut that moves along the spline shaft. For example, when a movable body is guided by arranging two-axis ball splines in parallel, even if the spline shafts are arranged in parallel with high accuracy, at least one of the spline nuts attached to the movable body is poor. The spline nut is tilted with respect to the axis of the spline shaft. As a result, the resistance acting on the movement of the spline nut increases and the movement accuracy of the movable body deteriorates. In addition, there is a problem ^S that the equipment life is shortened due to uneven wear of the spline nut.

 [0005] As structures for absorbing the mounting error of these nut members to the movable body, those disclosed in JP-A-6-229454 and JP-A-8-270649 are known. In these attachment error absorbing structures, a movable plate is interposed between the nut member and the movable body, and for example, the movable plate and the nut member are connected to be movable in the vertical direction, while the movable plate and the movable member are movable. The nut member and the movable body are coupled to each other so as to be displaceable in the left-right direction, and the nut member and the movable body are coupled with a degree of freedom in all directions. Patent Document 1: JP-A-6-229454

 Patent Document 2: JP-A-8-270649

 Disclosure of the invention

 Problems to be solved by the invention

However, since such a conventional attachment error absorbing structure connects the nut member and the movable body via the movable plate, it takes time to assemble the nut member for the movable body. There is a problem that a large space is required for mounting, and the interior of the straight line of the movable body becomes large.

 Means for solving the problem

[0007] The present invention has been made in view of such problems, and an object of the present invention is to be able to absorb attachment errors of nut members such as spline nuts and screw nuts to the movable body. It is an object of the present invention to provide a movable body connecting structure capable of easily and compactly attaching a nut member to a movable body.

That is, the present invention is a structure for connecting a nut member that moves along a linear shaft member to a movable body, and a plurality of nut members are provided along the circumferential direction of the outer peripheral surface of the nut member. A ball holding pocket formed in a ring shape having a plurality of engaging balls in which a part of a spherical surface is accommodated in the ball holding pocket and a hollow portion in which the nut member is loosely fitted. And a flange plate that engages with the nut member via the engaging ball, and is formed on the inner peripheral surface of the flange plate with the ball holding pocket. A ball receiving groove is formed along the axial direction of the nut member, and the flange plate is tiltably engaged with the nut member.

 [0009] According to such technical means, the engaging ball accommodated in the ball holding pocket on the nut member side slides in the ball accommodating groove of the flange plate, so that the force and the flange plate are applied to the nut member. Therefore, if the movable body is directly fixed to the flange plate, even if there is an error in the mounting accuracy of the flange plate with respect to the movable body, the force and error will be reduced to the flange. Absorbing force S between the plate and the nut member can be achieved, and the axis of the nut member can be aligned with the axis of the shaft member such as the screw shaft or spline shaft.

 [0010] This makes it possible to improve the movement of the nut member relative to the shaft member, improve the movement accuracy of the movable body, and prevent shortening of life due to uneven wear of the nut member. It becomes possible.

 [0011] Further, since the flange plate is in sliding contact with the engagement ball, the flange plate can be tilted with respect to the nut member, so that the steel ball is used as the force engagement ball. If a rigid body such as this is used, the axial linear motion and circumferential rotational motion of the nut member are reliably transmitted between the nut member and the flange plate. That is, the movement of the nut member can be reliably transmitted to the movable body fixed to the flange plate.

 FIG. 1 is a cross-sectional view showing an example in which the present invention is applied to a screw nut of a ball screw device.

 [FIG. 2] A view of the screw nut shown in FIG.

 FIG. 3 shows another example in which the present invention is applied to a spline nut of a ball spline device.

 FIG. 4 is a plan view showing a mechanism for reciprocally driving a slider of a curve guide device by a ball screw device using the present invention.

 BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the movable body connecting structure for a nut member according to the present invention will be described in detail with reference to the accompanying drawings. To do.

 FIG. 1 shows an example in which the movable body connecting structure of the present invention is applied to a screw nut 3 of a ball screw device 1. This ball screw device 1 includes a screw shaft 2 in which a spiral ball rolling groove 20 is formed on the outer peripheral surface with a predetermined lead, and a screw nut 3 that is screwed onto the screw shaft 2 via a large number of balls 4. The force S can be directly fixed to a movable body such as a table via a flange plate 5 engaged with the screw nut 3.

 The screw nut 3 has a hollow portion through which the screw shaft 2 passes, and is formed in a cylindrical shape. The inner peripheral surface surrounding the hollow portion faces the ball rolling groove 20 of the screw shaft 2. A spiral load rolling groove 30 is formed! The load rolling groove 30 and the ball rolling groove 20 of the screw shaft 2 form a load passage for the ball 4, and the ball 4 applies the load while applying a load between the screw nut 3 and the screw shaft 2. Roll through the passage. Although not shown in FIG. 1, the screw nut 3 is provided with a no-load passage that connects both ends of the load passage so that the ball 4 that has loaded a load in the load passage When it reaches the no-load passage, it is released from the load, rolls in the no-load passage with no load, and then returns to the load passage again.

That is, an infinite circulation path of the ball 4 is configured by the load passage and the no-load passage. When the screw shaft 2 rotates with respect to the screw nut 3, the ball 4 circulates in the endless circulation path, The screw nut 3 can be continuously moved along the screw shaft 2.

 In addition, a pair of seal members 31 that seal the gap between the screw nut 3 and the screw shaft 2 are provided at both ends of the screw nut 3 in the axial direction. Is prevented from entering, and the lubricant is prevented from flowing out of the screw nut 3.

The flange plate 5 is formed in a ring shape that is loosely fitted to the outside of the screw nut 3, and is engaged with one end of the screw nut 3 in the axial direction. Fig. 2 is a view taken along the arrow A in Fig. 1, and the left half is a cross-sectional view taken along the line II-II. A fixing hole 50 is formed in the flange plate 5 to allow the fixing bolt to pass through and be locked. The port 5 can be directly fixed to the movable body.

A plurality of ball holding pockets 6 are formed at predetermined intervals in the circumferential direction at the end of the screw nut 3 with which the flange plate 5 engages. The engagement ball 7 is held. The ball holding pocket 6 is formed in a concave spherical shape that follows the spherical surface of the engaging ball 7 so that the accommodated engaging bonus 7 is not displaced. 4 is configured to carry. Of course, when it is difficult to machine the Bonole holding pocket 6 into such a concave spherical shape, the two concave curved surfaces are combined to form the ball holding pocket 6, and the engaging ball 7 is attached to each concave curved surface. The engagement balls 7 accommodated in the ball holding pocket 6 can be stabilized by force.

 On the other hand, a ball housing groove 8 is formed at a position facing the ball holding pocket 6 on the inner peripheral surface of the flange plate 5 formed in a ring shape. The ball receiving groove 8 extends in the thickness direction of the flange plate 5, and as can be seen from FIG. 2, the cross-sectional shape of the ball receiving groove 8 is a concave curved surface that follows the spherical surface of the engaging ball 7. . Thereby, the displacement of the engagement ball 7 with respect to the circumferential direction of the flange plate 5 can be prevented. Further, the cross-sectional shape of the ball receiving groove 8 may be a so-called Gothic arch shape. In such a case, the engaging ball 7 contacts the ball receiving groove 8 at two points. Displacement of the engagement ball 7 with respect to the circumferential direction of the plate 5 can be prevented. On the other hand, the profile of the ball receiving groove 8 along the axial direction of the screw nut 3 has a concave curved surface. A part of the ball 7 accommodated in the ball holding pocket 6 of the screw nut 3 is accommodated in the ball accommodating groove 8 and is in sliding contact with the ball accommodating groove 8.

When assembling the flange plate 5 to the screw nut 3, the flange plate 5 is loosely fitted to the screw nut 3, the ball holding pocket 6 and the ball receiving groove 8 are opposed to each other, and then the ball is held. The engaging ball 7 is pushed into the pocket 6 and finally the locking nut 9 is screwed into the end of the screw nut 3 to form the engaging ball 7 with the ball holding pocket 6 and the ball receiving groove 8. Enclose in space. As a result, the engagement ball 7 cannot be detached from the borehole holding pocket 6, and the flange plate 5 is screwed through the engagement ball 7. It will be in the state engaged with Yunut 3.

 [0022] The flange plate 5 engaged with the screw nut 3 in this way is engaged with the ball receiving groove 8 by the engagement ball 7 so that the screw nut 3 as shown in FIG. It is possible to tilt freely with respect to the axial direction. Further, since the engaging ball 7 is held by the ball holding pocket 6 of the screw nut 3 and the ball receiving groove 8 of the flange plate 5, the flange plate 5 rotates in the circumferential direction with respect to the screw nut 3. Therefore, rotational torque can be transmitted between the flange plate 5 and the screw nut 3. The range in which the flange plate 5 tilts can be set according to the length of the ball receiving groove 8, in other words, according to the thickness of the flange plate 5.

 [0023] Therefore, when the flange plate 5 is fixed to the movable body using a fixing bolt, for example, with respect to the movable body of the flange plate 5 where the processing accuracy of the mounting surface of the flange plate 5 on the movable body is poor. Even if the mounting accuracy is poor, the flange plate 5 is tilted with respect to the screw nut 3 so that the screw nut 3 is aligned with the axis of the screw shaft 2 so that the screw nut 3 is aligned. Can be coupled to the movable body.

 [0024] This means that the ball screw device can be used without problems even when the processing accuracy of the mounting surface of the screw nut on the movable body is low. When using a ball screw device for an application, it is important in that it can reduce the work of moving the movable body and reduce the manufacturing cost of the feed screw mechanism.

FIG. 3 shows another example of the movable body connecting structure of the present invention, and the present invention is applied to the spline nut 11 of the ball spline device 10. In FIG. 3, the spline shaft 12 is indicated by a one-dot chain line.

In the example shown in FIGS. 1 and 2, the force that directly forms the ball holding pocket 6 with respect to the screw nut 3 In the example shown in FIG. 3, the inner ring 13 is fitted to the outer peripheral surface of the spline nut 11, A ball holding pocket 6 was formed on the inner ring 13. Lock nuts 14 are screwed onto both ends of the outer peripheral surface of the spline nut 11, and the inner ring 13 is fixed to the outer peripheral surface of the spline nut 11 so as to be sandwiched between the positioning collar 15 and the lock nut 14. The inner ring 13 rotates against the spline nut 11. In order to prevent twisting, a key 16 is inserted between the inner ring 13 and the spline nut 11.

 The configurations of the flange plate 5 and the engagement ball 7 are the same as those shown in FIGS. 1 and 2, and a detailed description thereof will be omitted here. Further, the inner ring 13 is configured so that the locking ring 9 is screwed. After the engaging ball 7 is received in the ball holding pocket 6, the locking ring 9 is screwed to the inner ring 13. Thus, the disengagement of the engagement ball 7 is prevented.

 [0028] With regard to the spline nut 11 of the ball spline device 10 configured as described above, when the flange plate 5 is fixed to the movable body using a fixing bolt, for example, the mounting of the flange plate 5 on the movable body Even if the mounting accuracy of the flange plate 5 on the movable body is poor, the flange plate 5 is inclined with respect to the spline nut 11, so that the axis of the spline nut 11 is aligned with the spline shaft 12. The spline nut 11 can be coupled to the movable body in a state where it is aligned with the shaft center.

 [0029] The movable body connecting structure of the present invention is widely applicable to any nut member that moves along the shaft member, such as the spline nut 11 of the ball spline device 10 and the screw nut 3 of the ball screw device 1 as described above. Is possible. Further, as long as the nut member moves along the shaft member, the nut member may be in sliding contact with the shaft member without using a ball.

 [0030] In addition, the movable body connecting structure of the present invention has a slider 41 and a ball guided by the curve guide device 40 as shown in FIG. 4 as well as for the purpose of absorbing the mounting error of the nut member with respect to the movable body. This is also effective when connecting the screw nut 3 of the screw device 1.

 [0031] The curve guide device 40 includes a track rail 42 formed in an arc shape with a predetermined curvature, and a slider 41 that moves along the track rail 42. A movable body such as a table is a slider. It is mounted on 41 and guided in a curved line. While the slider 41 moves in a curved line, the screw nut 3 of the ball screw device 1 moves in a straight line. It was difficult to give a back-and-forth movement using the.

[0032] However, the flange plate 5 is designed as a curved line using the nut member connecting structure according to the present invention. If it is fixed to the slider 41 of the inner device 40, the flange plate 5 can be freely tilted with respect to the screw nut 3, so that as the screw nut progresses, the flange plate 5 gradually moves as shown by a two-dot chain line in FIG. To absorb the change in the attitude of the slider 41 with respect to the screw nut 3. In FIG. 4, reference numeral 43 denotes a track rail of the linear guide device, and reference numeral 44 denotes a slider which moves along the track rail 43. The change in the distance between the screw shaft 2 and the track rail 42 of the curve guide device 40 is changed. In order to absorb, it is interposed between the flange plate 5 and the slider 41 of the curve guide device 40.

 That is, if the movable body connecting structure of the present invention is used, the slider 41 of the curve guiding device 40 can be reciprocated along the curved track rail 42 using the ball screw device 1.

Claims

The scope of the claims  [1] A structure for connecting a nut member (3, 11) moving along a linear shaft member (2, 12) to a movable body,  A plurality of ball holding buckets (6) provided along the circumferential direction of the outer peripheral surface of the nut member (3, 11), and a number of engagements in which a part of the spherical surface is accommodated in the ball holding pocket (6). The ball (7) and the nut member (3, 11) have a hollow portion in which the nut member (3, 11) is loosely fitted and formed in a ring shape. The nut is fixed to the movable body and via the engagement ball (7). A flange plate (5) engaged with the members (3, 11),  A ball receiving groove (8) facing the ball holding pocket (6) is formed on the inner peripheral surface of the flange plate (5) along the axial direction of the nut members (3, 11). The movable body connection structure is characterized in that the nut (5) is tiltably engaged with the nut members (3, 11)!  [2] An inner ring (13) facing the flange plate (5) is fixed to the outer peripheral surface of the nut member (3, 11), and the ball holding pocket (6) is fixed to the outer peripheral surface of the inner ring (13). 2. The movable body connecting structure according to claim 1, wherein: