JP7103734B2 - Ball screw device - Google Patents

Description

The present invention relates to a ball screw device capable of adjusting a preload amount.

The ball screw device is a mechanical element capable of mutually converting rotary motion and linear motion, and is intended to convert rotary motion generated by a servomotor into linear motion in various machine tools, conveyors, industrial robots, etc. It is often used in. The ball screw device includes a large number of balls, a screw shaft having a spiral rolling groove on which these balls roll, formed on the outer peripheral surface thereof, and a nut member screwed around the screw shaft via the balls. And have.

In order to increase the rigidity between the screw shaft and the nut member and prevent the occurrence of backlash when the screw shaft is reversed, the ball screw device uses the screw shaft and the nut member according to the intended use. Appropriate preload is applied to the balls arranged between and.

A so-called double nut method is known as a structure for applying a preload to the ball. In this double nut method, a spacer is sandwiched between a pair of nut members screwed into the screw shaft, and a preload of a ball existing between each nut member and the screw shaft is applied according to the thickness of the spacer. Can be given.

On the other hand, even in a ball screw device in which an appropriate preload is applied to the ball at the beginning of use, the preload of the ball is caused by wear due to use over time and thermal expansion of the nut member. There is a possibility of causing so-called preload release, which reduces the amount. When this preload release occurs, the ball screw device cannot exert sufficient rigidity against the applied load, the positioning accuracy is lowered due to the occurrence of backlash, and the screw shaft and the nut member are subjected to deterioration. There is a concern that uneven wear may occur due to the ball slipping.

As a countermeasure when such preload release occurs, it is conceivable to replace the spacer with a thicker one or replace the ball screw device itself with a new one. For that purpose, the ball screw device itself is machined. It needs to be removed from mechanical devices such as machines and industrial robots, and requires laborious and time-consuming large-scale work.

As a double nut type ball screw device capable of adjusting the preload amount of the ball without pulling out the nut member from the screw shaft, those disclosed in Patent Document 1 and Patent Document 2 are known.

In the ball screw device disclosed in Patent Document 1, a spacer provided between a pair of nut members is composed of two preload pieces, and these preload pieces are slopes inclined with respect to the axial direction of the nut member. Are in contact with each other. These two preload pieces form a so-called taper give, and when one preload piece is slid with respect to the other preload piece by increasing or decreasing the fastening amount of the adjusting screw, the thickness of the spacer is a pair of nut members. The amount of preload of the ball is changed accordingly.

Further, in the ball screw device disclosed in Patent Document 2, by adjusting the fastening amount of the four adjusting screws provided at the connecting portion of the pair of nut members, the other is around the axis of one nut member. The nut member is slightly rotated to shift the phase, thereby changing the preload amount of the ball with the same effect as when the thickness of the spacer is increased or decreased.

JP-A-2007-285350 JP 2016-223493

However, in the ball screw device disclosed in Patent Document 1 or Patent Document 2, there is no fixed relationship between the tightening amount of the adjusting screw and the preload amount of the ball, and the preload amount of the ball depends on the fastening amount of the adjusting screw. Was difficult to manage.

The present invention has been made in view of such a problem, and an object of the present invention is that the amount of preload of the ball can be appropriately controlled and the nut member is pulled from the screw shaft when the preload is released. It is an object of the present invention to provide a ball screw device capable of preloading a ball again without removing the ball.

That is, the ball screw device of the present invention includes a screw shaft in which a rolling groove of a ball is spirally formed by a predetermined lead, and a nut member screwed into the screw shaft via a large number of balls. .. The nut member exhibits a first nut element and a second nut element arranged in series with each other with respect to the screw shaft, and a rotational movement of the first nut element and the second nut element around the screw shaft. It includes a detent member to be synchronized and a spacer arranged between the first nut element and the second nut element to press these nut elements in opposite axial directions. Further, the spacer is formed by combining a fixing plate and an adjusting plate formed in a ring shape through which the screw shaft is inserted, and by rotating the adjusting plate with respect to the fixing plate in the circumferential direction of the screw shaft. The amount of preload of the ball changes.

According to the present invention, the preload amount of the ball arranged between the screw shaft and the nut member is changed only by rotating the adjusting plate constituting the spacer in the circumferential direction of the screw shaft with respect to the fixing plate. Therefore, it is possible to appropriately manage the amount of preload of the ball, and it is possible to preload the ball again without pulling out the nut member from the screw shaft when the preload is released.

It is a perspective view which shows the 1st Embodiment of the ball screw apparatus to which this invention is applied. It is sectional drawing which shows the screwed state of a screw shaft, a 1st nut element and a 2nd nut element. It is an exploded perspective view of the nut member which concerns on 1st Embodiment. It is a figure which shows the contact state of the fixing plate and the adjusting plate. It is a figure which shows the change of the thickness of the spacer when the adjusting plate is rotated with respect to the fixing plate. It is a perspective view which shows the 2nd Embodiment of the ball screw apparatus to which this invention was applied.

Hereinafter, the ball screw device of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 shows a first embodiment of a ball screw device to which the present invention is applied.

The ball screw device 1 has a screw shaft 2 in which a ball rolling groove 20 is spirally formed on the outer peripheral surface, and a cylindrical nut member 3 screwed around the screw shaft 2 via a large number of balls. It is composed of and. The ball is interposed between the screw shaft 2 and the nut member 3. For example, by rotating the screw shaft 2 with respect to the nut member 3, the nut member 3 is moved in the axial direction of the screw shaft 2. The screw shaft 2 moves in the axial direction of the nut member 3 by moving to or rotating the nut member 3 with respect to the screw shaft 2.

The nut member 3 includes a first nut element 31 and a second nut element 32 arranged in series along the axial direction of the screw shaft 2. Further, a spacer 33 for adjusting the distance between the first nut element 31 and the second nut element 32 is arranged between the first nut element 31 and the second nut element 32.

The first nut element 31 has a through hole through which the screw shaft 2 is inserted and is formed in a cylindrical shape. A load rolling groove (not shown) facing the spiral rolling groove 20 formed on the screw shaft 2 is formed on the inner peripheral surface of the through hole. The balls 4 are arranged between the rolling groove of the screw shaft 2 and the load rolling groove of the first nut element, and while applying a load, the balls 4 are placed between the first nut element 31 and the screw shaft 2. Roll. Further, a collar portion 30 is formed at one end of the first nut element 31 in the axial direction. The crosspiece 30 is provided with a fixing bolt mounting hole 30a, and the nut member 3 is fixed to another mechanical device by a fixing bolt penetrating the crossguard 30.

The second nut element 32 has substantially the same configuration as the first nut element 31. However, the flange portion 30 does not exist in the second nut element 32, and this point is significantly different from the first nut element 31.

A detent member 34 is provided between the first nut element 31 and the second nut element 32 so as to straddle them. The detent member 34 is formed in a rod shape having a rectangular cross section, and one end in the longitudinal direction fits into the groove 31a formed in the first nut element 31, while the other end fits into the second nut element 32. It is fitted in the formed groove 32a. Due to the presence of the detent member 34, the rotational movements of the first nut element 31 and the second nut element 32 around the screw shaft 2 are synchronized.

FIG. 2 is a diagram showing a screwed state of the screw shaft 2, the first nut element 31, and the second nut element 32. A load rolling groove 21 facing the rolling groove 20 of the screw shaft 2 is formed on the inner peripheral surfaces of the first nut element 31 and the second nut element 32. The first nut element 31 and the second nut element 32 are screwed onto the screw shaft 2 via a large number of balls 22 that roll through the rolling groove 20 and the load rolling groove 21. In the figure, the axial pitch of the rolling groove 20 and the load rolling groove 21 is P, and the rotational movement of the first nut element 31 and the second nut element 32 around the screw shaft 2 is the said. Synchronized by the detent member 34, the positional relationship between the first nut element 31 and the second nut element 32 in the axial direction of the screw shaft 2 is constrained by the ball 22. That is, the first nut element 31 and the second nut element 32 are integrated without being separated with respect to the axial direction of the screw shaft 2, and if the spacer 33 does not exist, the first nut element 31 and the second nut element 32 are integrated. The distance L between the two nut elements 32 is naturally determined.

FIG. 3 is an exploded perspective view of the nut member 3. As shown in the figure, the spacer 33 arranged between the first nut element 31 and the second nut element 32 includes a fixing plate 33a and an adjusting plate 33b. The fixing plate 33a and the adjusting plate 33b have a through hole through which the screw shaft 2 is inserted and are formed in a ring shape, and the axial end surface of the first nut element 31 and the second nut are overlapped with each other. It is sandwiched between the element 32 and the axial end face.

A plurality of pressure receiving surfaces 40 are formed along the circumferential direction on the axial end surface of the fixing plate 33a facing the adjusting plate 33b. The pressure receiving surface 40 is inclined with respect to a plane orthogonal to the axial direction of the nut member 3, and has a saw blade-like unevenness along the circumferential direction of the fixing plate 33a. On the other hand, a plurality of pressing surfaces 41 in contact with the pressure receiving surface 40 of the fixing plate 33a are formed on the axial end surface of the adjusting plate 33b facing the fixing plate 33a. Like the pressure receiving surface 40, these pressing surfaces 41 are also inclined with respect to a plane orthogonal to the axial direction of the nut member 3, and the inclination direction is the same as that of the pressure receiving surface 40. That is, the plurality of pressing surfaces 41 also have saw blade-like irregularities along the circumferential direction of the adjusting plate 33b.

A key groove 42 is provided on the outer peripheral surface of the fixing plate 33a, and the detent member 34 bridged between the first nut element 31 and the second nut element 32 is fitted in the key groove 42. It fits. Therefore, the fixing plate 33a is integrated with the first fixing element 31 and the second fixing element 32 in the circumferential direction of the screw shaft 2.

On the other hand, a relief groove 43 is provided on the outer peripheral surface of the adjusting plate 33b at a position overlapping the key groove 42 of the fixing plate 33a. The groove width of the relief groove 43 is set to be larger than that of the key groove 42, and the detent member 34 bridged between the first fixing element 31 and the second fixing element 32 is the relief groove 43. I'm playing around with. Therefore, the fixing plate 33a is locked in the circumferential direction by the detent member 34, but the adjusting plate 33b has a range of the groove width of the relief groove 43 regardless of the presence of the detent member 34. It can rotate in the circumferential direction. A locking surface on which a tool such as a hexagon wrench is hooked can be formed on the outer peripheral surface of the adjusting plate 33b, and the adjusting plate 33b can be rotated in the circumferential direction of the screw shaft 2 by using the tool. ..

FIG. 4 is a diagram showing a contact state between the pressure receiving surface 40 of the fixing plate 33a and the pressing surface 41 of the adjusting plate 33b. The left-right direction of the paper surface in the figure coincides with the axial direction of the nut member 3, and the vertical direction of the paper surface coincides with the circumferential direction of the nut member 3. Since the pressure receiving surface 40 and the pressing surface 41 are inclined with respect to a plane orthogonal to the axial direction of the nut member 3, the adjustment is made with respect to the fixing plate 33a as shown by an arrow A in the drawing. When the plate 33b is rotated in the circumferential direction, the thickness of the spacer 33 composed of the fixing plate 33a and the adjusting plate 33b increases. FIG. 4 shows a case where the thickness of the spacer 33 is the minimum. Further, FIG. 5 shows a case where the adjusting plate 33a is rotated in the circumferential direction to increase the thickness of the spacer 33.

When the minimum thickness of the spacer 33 is slightly larger than the distance L between the first nut element 31 on which the spacer 33 is arranged and the second nut element 32, that is, when the thickness of the spacer 33 is L + α, the spacer 33 is concerned. When the spacer 33 is forcibly sandwiched between the first nut element 31 and the second nut element 32, the spacer 33 puts the first nut element 31 and the second nut element 32 on the screw shaft 2 with each other. It will be pressed in the opposite direction. The pressing force at this time corresponds to the extra thickness α of the spacer 33. As a result, the ball 22 existing between the first nut element 31 and the screw shaft 2 and the ball 22 existing between the second nut element 32 and the screw shaft 2 correspond to the thickness α. It is compressed by the pressing force, and a preload is applied to the ball 22.

On the other hand, with the spacer 33 having a thickness L + α sandwiched between the first nut element 31 and the second nut element 32, the adjusting plate 33b is oriented with respect to the fixing plate 33a in the direction of arrow A in FIG. When rotated to, the thickness of the spacer 33 increases to L + β (β> α). As a result, the force with which the spacer 33 presses the first nut element 31 and the second nut element 32 in opposite directions is increased, and a larger preload is applied to the ball 22. That is, the preload applied to the ball 22 can be arbitrarily increased by rotating the adjusting plate 33b of the spacer 33 in the circumferential direction.

On the contrary, in a state where the spacer 33 having a thickness of L + β is sandwiched between the first nut element 31 and the second nut element 32, the adjusting plate 33b is shown with respect to the fixing plate 33a. When the spacer 33 is rotated in the direction opposite to the arrow A direction in 4, the thickness of the spacer 33 decreases to L + α. Therefore, the force with which the spacer 33 presses the first nut element 31 and the second nut element 32 in opposite directions is reduced, and the preload applied to the ball 22 is reduced.

The magnitude of the preload applied to the ball 22, that is, the preload amount corresponds to the force with which the spacer 33 presses the first nut element 31 and the second nut element 32, and the pressure receiving surface 40 of the fixing plate 33a. It is proportional to the pressure generated between the pressing surface 41 of the adjusting plate 33b and the pressing surface 41 of the adjusting plate 33b. Therefore, the preload amount of the ball 22 is proportional to the magnitude of the torque for rotating the adjusting plate 33b in the circumferential direction.

Therefore, by controlling the magnitude of the torque for rotating the adjusting plate 33b, that is, the input torque, the preload amount of the ball 22 in the ball screw device 1 can be appropriately managed. For example, the preload amount of the ball 22 at the time of shipment of the ball screw device 1 can be easily managed, and the preload amount of the ball 22 can be easily managed even after the ball screw device 1 is assembled to another mechanical device such as a machine tool. It is possible to adjust. Further, even when so-called preload release occurs due to wear due to use over time or thermal expansion of the nut member 3, the ball 22 is rotated by rotating the adjusting plate 33b with a constant input torque. The preload amount can be easily restored to a predetermined value. Further, when the preload applied to the ball 22 is excessive, it is possible to reduce this and optimize the preload amount.

When a preload is applied to the ball 22, the pressure receiving surface 40 of the fixing plate 33a and the pressing surface 41 of the adjusting plate 33b are in pressure contact with each other, and a certain amount of frictional force is generated between the two. It's working. Therefore, if the inclination angle between the pressure receiving surface 40 of the fixing plate 33a and the pressing surface 41 of the adjusting plate 33b is small, the thickness of the spacer 33 tends to be reduced by the pressing force of the fixing plate 33a. It does not rotate naturally.

FIG. 6 shows a second embodiment of the ball screw device to which the present invention is applied, and is an exploded perspective view similar to FIG.

The ball screw device 5 of the second embodiment is the same as the ball screw device 3 of the first embodiment in a basic configuration, but the first is that the adjusting plate of the spacer 33 is rotated by using a worm gear. Different from the embodiment.

The spacer 33 is composed of a fixing plate 33a and an adjusting plate 33c. A worm wheel 44 is provided on the outer peripheral surface of the adjusting plate 33c along the circumferential direction, and the adjusting plate 33c is configured to rotate in the circumferential direction by rotating the worm 45 that meshes with the worm wheel 44. Has been done. A semi-cylindrical housing 6 is fixed to the first nut element of the nut member 3, and the worm 45 is rotatably provided with respect to the support hole 60 of the housing 6. A hexagonal hole 46 is provided on the axial end surface of the worm 45, and the worm 45 can be rotated by an arbitrary amount by using the hexagonal hole 46. Since the configurations other than those to be described above are the same as those of the ball screw device 1 of the first embodiment, the same reference numerals as those in FIG. 2 are given in FIG. 6, and detailed description thereof will be omitted here.

As described above, in the ball screw device 5 of the second embodiment, the adjusting plate 33c of the spacer 33 is rotated in the circumferential direction of the screw shaft 2 by rotating the worm 45, and the first embodiment described above. Similar to the form, the preload applied to the ball 22 can be arbitrarily increased. At this time, by managing the magnitude of the torque for rotating the worm 45, that is, the input torque, it is possible to appropriately manage the preload amount of the ball 22 as in the ball screw device 1 of the first embodiment. It becomes.

Further, when the advance angle of the teeth of the worm becomes small, so-called self-locking occurs in which it is theoretically impossible to rotate the worm from the worm wheel. Therefore, in a state where the worm wheel 44 of the adjusting plate 33b is engaged with the worm 45, the adjusting plate 33b does not rotate in the circumferential direction unless the worm 45 is positively rotated. Therefore, the combination of the worm 45 and the worm wheel 44 also serves as a lock mechanism for securely fixing the adjusting plate 33b at a predetermined position, and the worm 45 is rotated to adjust the preload amount of the ball 22. After that, the adjusted preload amount can be reliably maintained as long as no acquired factors such as wear due to use over time and thermal expansion of the nut member 5 occur.

1 ... ball screw device, 2 ... screw shaft, 3, 5 ... nut member, 20 ... rolling groove, 21 ... load rolling groove, 22 ... ball, 31 ... first nut element, 32 ... second nut element, 33 ... Spacer, 33a ... Fixing plate, 33b ... Adjusting plate, 40 ... Pressure receiving surface, 41 ... Pressing surface

Claims (4)

A screw shaft in which a rolling groove of a ball is spirally formed by a predetermined lead and a nut member screwed into the screw shaft via a large number of balls are provided.
The nut member
The first nut element and the second nut element arranged in series with each other with respect to the screw shaft,
A detent member that synchronizes the rotational movement of the first nut element and the second nut element around the screw shaft.
A spacer disposed between the first nut element and the second nut element to press these nut elements in opposite axial directions.
The spacer is a combination of a ring-shaped fixing plate and an adjusting plate through which the screw shaft is inserted.
The fixing plate is provided with a key groove on the outer peripheral surface into which the detent member is fitted.
The adjusting plate is provided with a relief groove in which the detent member is loosely fitted at a position overlapping the key groove on the outer peripheral surface, and can rotate in the circumferential direction within the groove width of the relief groove.
A ball screw device characterized in that the preload amount of the ball is changed by rotating the adjusting plate with respect to the fixing plate in the circumferential direction of the screw shaft. The ball screw device according to claim 1, wherein the preload amount of the ball is controlled by the magnitude of the input torque for rotating the adjusting plate with respect to the fixed plate. The fixing plate of the spacer is provided with a plurality of pressure receiving surfaces inclined with respect to a plane orthogonal to the axial direction of the screw shaft, and these pressure receiving surfaces are arranged in the circumferential direction of the fixing plate formed in a ring shape. on the other hand,
The adjusting plate is provided with a plurality of pressing surfaces facing the plurality of pressure receiving surfaces and in contact with the pressure receiving surfaces, and these pressing surfaces are arranged in the circumferential direction of the adjusting plate formed in a ring shape. The ball screw device according to claim 1 or 2. The ball screw device according to claim 3, wherein a worm wheel is provided on the adjusting plate, and the adjusting plate is rotated in the circumferential direction of the screw shaft by rotating a worm that meshes with the worm wheel.

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