JPH07103306A - Ball screw having damage detecting device - Google Patents

Abstract

PURPOSE:To instantly detect abnormality, and prevent the occurrence of an accident even when screw-fitting is disconnected like when a ball falls off in a reciprocating mechanism to move vertically by using a ball screw. CONSTITUTION:A load in the screw shaft direction is applied to a screw shaft or a nut metal fitting of a ball screw body 2 where the screw shaft 4 and the nut metal fitting 5 are screw-fitted to each other through balls 3 and one of the screw shaft or the nut metal fitting is held nonrotatably, and a support plate 6 having a locking pin 7 projecting in the screw shaft direction is installed on the nut metal fitting, and this support plate is engaged with the nut metal fitting so as to be movable only in the screw shaft direction, and slippin-off prevention is also applied, and a detector 9 is provided to detect a change in a distance 1 between the support plate and the nut metal fitting.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reciprocating mechanism that uses a ball screw and moves upward and downward, even if the screw in the ball screw is disengaged so that the ball may drop due to an unexpected accident. The present invention relates to a ball screw with a damage detection device that can immediately detect such abnormalities and prevent the screw shaft or the nut fitting from coming off.

[0002]

2. Description of the Related Art A ball screw is known in which a screw shaft and a nut fitting are screwed together via a ball to easily advance and retreat.
In such a ball screw, a large number of balls circulate in a gap between the screw shaft and the nut fitting when the screw advances and retreats, and the ball makes a screw motion while rolling between the screw surfaces of the male screw and the female screw. Therefore, the mechanical loss is remarkably smaller than that of the normal screw mechanism, and the reciprocating motion can be performed by highly efficient screwing back and forth.

[0003]

However, the balls are interposed in the ball screw as described above, and in the event that the ball falls off, the screw is instantly disengaged and the ball screw is disassembled. Invite. In particular, when a ball screw is adopted for vertical movement in which the screw shaft a is oriented vertically as shown in FIG. 4, a dangerous accident of dropping the screw shaft occurs.

In the range where the ball screw is used for purely advancing and retracting, there is almost no accident that the ball falls off, but due to an unexpected situation,
For example: (1) A large impact load accidentally acts in the screw axis direction,
The thread of the screw shaft or nut fitting is missing. (2) The external force acting laterally on the screw shaft exceeds the expectation and excessively acts, so that the ball or the screw surface is rapidly worn and the ball comes off. It may occur unexpectedly due to such reasons.

Therefore, when a ball screw is used for raising and lowering, a safety device that can surely prevent the screw shaft from falling is often required, and the appearance of such a device has been strongly demanded.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a ball screw with a damage detecting device which can immediately detect the disengagement of the screw fitting between the nut fitting of the ball screw and the screw shaft and can prevent the lifting motion member from falling.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to the screw shaft or nut of a ball screw body in which a screw shaft and a nut fitting are screwed together via a ball and one of the screw shaft and the nut fitting is held non-rotatably. In addition to applying a load in the screw axis direction to the metal fitting, a supporting plate having a locking pin protruding in the screw shaft direction is attached to the nut metal fitting, and this supporting plate is attached to the nut metal fitting screwed to the screw shaft in the screw axial direction. A ball screw with a damage detecting device, which is provided with a detector that engages only with movement of the support plate and prevents it from coming off and that detects a change in the distance between the support plate and the nut fitting.

The ball screw may have a structure in which the screw shaft is non-rotatably supported as shown in FIGS. 1 and 4 and a load is applied to the screw shaft, and as shown in FIG. It may be a case of being supported by rotation and applying a load to the nut fitting.

[0009]

With the above-described structure, even if the ball of the ball screw is accidentally dropped and the screw shaft and the screw fitting are disengaged from each other, the detector has the support plate and the nut fitting. By detecting the change in the distance between the two, the abnormal state of the screwed state can be grasped at an early stage and the occurrence of an accident can be prevented.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 4, a ball screw 1 with a damage detection device
Has a ball screw main body 2 of a well-known structure in which a screw shaft 4 and a nut fitting 5 are screwed together via a ball 3. In the ball screw main body 2, one of the screw shaft 4 and the nut fitting 5 is non-rotating. A load is applied in the screw shaft direction to the screw shaft 4 or the nut fitting 5 that is held by the non-rotating member.

In this embodiment, the screw shaft 4 is held non-rotatably. Further, in this example, as shown in FIG.
In order to raise and lower the welding tool 12 which is held so as to be movable up and down, a ball screw body 2 is provided on its support portion. Therefore, the welding tool 12 is fixed to the axial lower end of the screw shaft 4,
A load is applied to the screw shaft 4 in its axial direction, and when the ball screw main body 2 is unscrewed, the welding tool 12 falls and a serious accident occurs.

The screw shaft 4 has a work W at the lower end as shown in FIG.
Is a straight rod body having a circular cross section to which the welding tool 12 which is
A screw 4a is screwed on the peripheral surface over substantially the entire length. The screw 4a has a thread root having a radius substantially equal to the diameter of the ball 3, and the ball 3 rolls on this thread root. Welding tool 12
Has a long pin body 13 inserted through the gate-shaped frame 11 on the upper side and lower side to prevent the rotation of the screw shaft 4.

The nut fitting 4 forms a gate-shaped frame 11 and a bearing 15 is attached to a base portion 14 fixed to the floor body immovably.
The rotating member 16 is rotatably supported and horizontally rotatable, and the nut member 17 is screwed into the central hole of the rotating member 16 and integrally fixed to the rotating member 16 by keying or the like.

The nut member 17 has a female screw 1 formed on its inner peripheral surface 12 at the same pitch as the screw 4a of the screw shaft 4.
7a is screwed, and a large number of balls 3 ... Are loaded in series in a gap formed by the female screw 17b and the screw 4a of the screw shaft 4. As a result, the screw shaft 4 and the nut fitting 5
Are screwed together via balls 3. Note that the nut member 1
7 has a return path 19 which connects both ends of the female screw 17a and through which the balls 3 return, and in this embodiment, the ball screw body 2
Is formed as a circulating ball screw.

The rotating member 16 has a tooth portion 21 that meshes with a pinion 20 that is fixed to the output shaft of the reduction gear M having a rotating shaft core parallel to the screw shaft 4. Therefore, the nut fitting 5 rotates as the reduction motor M is driven, and this rotation allows the screw shaft 4 to move up and down via the ball 3.

However, in the ball screw body 2, the screw shaft 4 and the nut fitting 5 are screwed together via the ball 3, and when the ball 3 does not exist, both members are in a loose fitting state.

On the other hand, when a lateral force is applied to the screw shaft 4 or the like, the thread 4A or the female screw 7a lacks a mountain portion, or the ball 3 falls off in the return path. Since the ball 3 does not exist in the ball screw body 2, the screw shaft 4 is not held by the nut fitting 5, and the screw shaft 4 may fall.

However, in this example, the support plate 6 is attached to the nut fitting 5. The support plate 6 is the rotating member 1
6, a plurality of locking pins 7 protruding in the direction of the screw shaft 4, and an operating plate 24 having a detection surface 23 that is locked by the locking pins 7 and is orthogonal to the screw shaft 4. Have.

The operating plate 24 is provided with a hole 24a into which the locking pin 7 is loosely fitted, and is arranged in the gap between the operating plate 24 and the nut fitting 5 and the operating plate 24 is fitted into the nut fitting. Spring 25 urged in a direction away from 5 ...
And a nut 26 that is screwed to the locking pin 7 and locks the operating plate 24 from the opposite direction to the spring 25, so that the operating plate 24 and the nut fitting 5 maintain a constant distance l. It is possible to rotate together with the nut fitting 5 while facing each other.

Further, the operating plate 24 has a through hole 27 through which the screw shaft 4 is inserted in the center thereof, and the through hole 27 is spirally wound around the screw 4a of the screw shaft 4 at an equal pitch. A projecting piece 29 projecting toward the root surface of the screw 4a is integrally formed. This protruding piece 29 is different from the valley surface of the screw 4a.
Since the screw shafts 4 are provided opposite to each other with a small gap g therebetween, they do not interfere with each other even when the screw shafts 4 are screwed back and forth.

Further, a detector 9 for detecting the change of the support plate 6 in the screw axis direction with the detection surface 23 is attached to the base portion 14 via a supporting leg 30 rising from the base portion 14. In the present embodiment, the detector 9 is formed as a gap detector which has a minute gap G between its detection end and the detection surface 23 of the support plate 6 and which detects a variation in this gap G. There is.

When the reduction motor M is driven, however, the nut fitting 5 gear-connected to the reduction motor M rotates as shown in FIG. Further, the rotation causes the screw shaft 4 to move up or down, so that the work W can be moved in the vertical direction.

Further, the supporting plate 6 is locked by a nut 26 fixed to the locking pin 7 in a direction away from the nut fitting 5, and is biased toward the nut 26 side by a spring 25. Therefore, the support plate 6 is a nut fitting 6
The same distance 1 is maintained with respect to and the nut fitting 5 rotates together.

During the operation, the nut 26 of the locking pin 7 is adjusted so that the space between the trough surface of the screw shaft 4 and the screw 4a and the surface of the projecting piece 29 of the support plate 6 is adjusted. , A small gap g is formed. Therefore, the screw shaft 4 can move upward and downward without contacting the support plate 6.

Here, when the ball 3 of the ball screw main body 2 falls off, as shown in FIG. 3, the screw shaft 4 and the nut fitting 5 are disengaged from each other, and the screw shaft 4 falls. With the drop, the screw 4a of the screw shaft 4 abuts on the projecting piece 29 of the support plate 6 and drops the support plate 6 together with the screw shaft 4 against the biasing force of the spring 25. As a result, the gap G between the detection surface 23 of the support plate 6 and the detector 9 widens, that is, the distance 1 between the support plate 6 and the nut fitting 5 changes, and the detector 9 detects this and the reduction motor. Stop M. The support plate 6
The support plate 6 by overlapping with the nut fitting 5.
Also, the separation and fall of the screw shaft 4 are prevented.

FIG. 5 shows another embodiment in which the nut fitting 5A of the ball screw body 2A is held non-rotatably.

In this example, the screw shaft 4A is directly connected to the output shaft of the reduction motor M mounted on the base 32 with the output shaft facing upward.
And the nut fitting 5A is screwed onto the screw shaft 4A via the ball 3A.
Is non-rotatably locked by a pin body 13A rising from the base 32.

Therefore, the screw shaft 4A rotates with the drive of the reduction motor M, and the rotation causes the nut fitting 5A to move upward.
You can move down. Also, for the nut fitting 5A,
Support frame 33 that is framed above it and on which the work W is placed
Is provided.

The nut fitting 5A has substantially the same structure as the support plate 6 shown in FIG. 1 and is provided with a support plate 6A having a locking pin 7A. The nut fitting 4A has a support leg 3A.
A detector 9A for detecting a change in the distance 1 between the support plate 6A and the nut fitting 5A via 0A is provided.

However, when the ball screw main body 2A is unscrewed and the nut fitting 5A falls, the support plate 6A is engaged with the screw shaft 4A, so that the support plate 6A is prevented from falling and therefore the support plate 6A The distance 1 with the nut fitting 5A changes. A detector 9A fixed to the nut fitting 5A detects this change in the distance l, and the detection output of the detector 9A activates the braking means B provided between the nut fitting 5A and the pin body 13A in this example to operate the nut fitting. Prevent the 5A crash.

In the present invention, the screw shaft is upward,
The present invention can be applied not only to the downward moving up and down but also to the horizontal moving in which the screw shaft is diagonally or horizontally oriented, and the present invention can be modified into various aspects.

[0032]

As described above, the ball screw with a damage detecting device of the present invention is a detection device that detects a change in the distance between the support plate having the above-mentioned configuration and the support plate and the nut fitting of the ball screw body in the ball screw body. Since the ball screw main body is equipped with a container, the ball screw body can prevent the screw shaft or the nut fitting from falling even if the screw is disengaged such as when the ball falls off, and the operation safety can be improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view showing the normal state.

FIG. 3 is a partial cross-sectional view showing a state of the abnormal state.

FIG. 4 is a front view showing an example of its use.

FIG. 5 is a front view showing another embodiment.

[Explanation of symbols]

 2, 2A Ball screw body 3, 3A Ball 4, 4A Screw shaft 5, 5A Nut fitting 6, 6A Support plate 7, 7A Locking pin 9, 9A Detector l Distance

Claims (1)

[Claims] 1. A load in the screw axis direction is applied to the screw shaft or the nut fitting of the ball screw body in which the screw shaft and the nut fitting are screwed together via a ball and one of the screw shaft and the nut fitting is held non-rotatably. In addition to this, a support plate having locking pins protruding in the screw axis direction is attached to the nut fitting, and this support plate engages with the nut fitting that is screwed onto the screw shaft so that it can move only in the screw axis direction. A ball screw with a damage detecting device, which is provided with a detector for preventing a change in the distance between the support plate and the nut fitting and preventing the slip-out.