JPS59196152A - Overrun preventing mechanism for ball screw - Google Patents

Abstract

PURPOSE:To reduce the degree of impact force in time of overrun happening as well as to make an automatic stop at the side of a nut attainable, by installing a straight shank, which has the same diameter with that of a root in a thread groove and larger in length than that of the nut, at both ends of a ball screw shaft in an extended manner. CONSTITUTION:In case of a mechanism that with rotation of a ball screw shaft 5 by a motor, a ball screw nut 8 screwed in this screw shaft 5 is shifted in both directions, while a slide base or the like holding the said nut 8 is moved in the same direction, a straight shank 13 as a noneffective thread, having the same diameter with that of a root of a thread groove 5a and longer than axial length l2 of the ball screw nut 8, is formed at both ends of an effective thread part l1 of the ball screw shaft 5 so as to extend this thread part. In addition, at both end parts of the screw shaft 5, a pressure plate 15 energized by a coil spring 14 is installed with some play.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a ball screw overrun prevention mechanism comprising a combination of a ball screw shaft and a ball screw nut.

Ball screws have a much smaller coefficient of friction and are more efficient than general screws with full-thread contact, so they are widely used as feeders for various modifications, and an example thereof is shown in FIG. This is illustrated with a slide base device using a ball screw, where 1 is a fixed base, 2 is a fixed base 1
A guide rail provided above, 3 a slide base that runs on the guide rail 2, 5 a bearing 5a,
5b, the pole screw 4 is horizontally suspended on the fixed base 1, and is rotated and driven by the motor 7.
Ball-type shaft (hereinafter simply referred to as the shaft)
It is. 1, 8 is a ball screw nut (hereinafter simply referred to as the nut) screwed onto the shaft 5, and this nut 8
is fixed to the lower surface tc of the slide base 3, and by rotating the shaft 5 one turn, the slide base 3 travels on the guide rail 2 along with the nut 8 due to its thrust. Then Sarako Slide Base 3 (Natsuto 8) overran and that Natsuto 8! liI Uke 6a or 6b? In order to prevent this from colliding, fixed base 1 and slide base 31 are each provided with Lυ constant side stopper 9.
and movable (141 stopper 1.0 (these stoppers 9. [.

(sometimes equipped with a cushion Isokita),
The amount of movement of the slide base 3 is limited in advance by the contact between these stoppers 9 and 10.

Note that 11 is a position detector, and 12 is a coupling that connects the motor and the shaft 5.

However, in the #J pit above, as mentioned above, The amount of movement of the slide base is directly limited by the contact between the stoppers 9 and 10. If the stoppers 9 and 10 of the same size collide, the base 3b will slide.
If the remote motor 7 attempts to further rotate the shaft 5, the ball screw 4 and The problem is that the more impossible the motor 7ζ is added and the ball screw speed j + JJ is brought about, the more shock the valley part receives as well as the motor.

In view of the above points, the present invention aims to provide a structure in which the impact blade is small even in the event of an overrun, and no undue force is applied to the ball hitch, motor, etc. For this purpose, the present invention is characterized in that a straight shaft portion having the same diameter as the thread groove and a length equal to or longer than the nut length is provided at both ends of the shaft. It is said that As a result, even if the nut side overruns, the jll will automatically stop as soon as the spring groove is interrupted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the same parts as those in the prior art described above are given the same reference numerals.

In other words, FIGS. 1 and 3 show an embodiment of the present invention, and as shown in the figures, a spiral thread groove 5a is formed at both ends of an effective threaded portion B of a ball screw shaft 5. , h are extended, and a straight detail that is an ineffective threaded part has the same diameter as the valley A of the threaded groove 5a and has a length of 12 or more in all directions of the 80 axis of the ball threaded nut. 13, and press plates 15 biased by coil springs 14 are loosely fitted to both rough portions of the ball screw shaft 5.

However, according to the above configuration, as shown in FIG. 4, even if the slide base 3 exceeds the specified amount of movement, the motor 7 continues to rotate for some reason, and the ball screw nut 8 6b, the ball nut 8 moves at the terminal end 1 of the thread groove 5a, which is the effective thread part, and comes off the thread groove 5a, causing the shaft part 13 (fi
When moving to ll, the screw rM:5a is interrupted at that stage, so the ball screw shaft 5 rotates, and the ball screw nut 8 stops at that position. ) Ball screw nut 8 and bearing 6a-! or 6b is avoided.

At this time, the ball screw nut 8 is attached to the coil spring 14.
contacts the suppression plate 15 while being compressed.

In addition, even if the ball screw nut 8 is inserted into the shaft part 13,
In case the bearing 6at or 6b is about to collide due to inertial force, the fixed base 1 and the slide base 3 are provided with a fixed side stopper 9A and a DJ' dynamic stopper 1. It is recommended to set up an OA.

In this case, the valley stoppers 9A and 10A have the ability to receive only the inertial force of the nut 8 (because they are sufficiently capable, it is natural that they would be smaller than the conventional ones).

On the other hand, if screw g5a is removed and the ball screw nut 8, which has overrun the knock-out according to the 4131 rule, returns to the screw @5 a1 rule and moves in the opposite direction, Since the nut 8 itself is biased by the coil spring 14, the ball screw shaft 5 only needs to be reversed. As a result, the ball screw nut 8-, which has once overrun, can be easily restored to its original state.

Incidentally, if a retainer 16 is provided on the ball screw nut 8 side as shown in FIG. 5, it is effective to prevent the balls 17 from falling off while being loaded into the ball screw nut 8. In other words, by providing the retainer 16, the ball screw shaft 5 and the nut 8 can be easily separated while completely preventing the balls 17 from falling off. Even if the ball 8 falls off, the ball 17 does not fall out, and it can be easily restored.

As is clear from the above description, according to the present invention, by providing a straight shaft portion having the same diameter as the root diameter of the threaded groove at both ends of the ball screw shaft, even if the ball screw nut overruns, Not only is no unreasonable force applied to the ball screw, motor, etc., but the impact force is also much smaller, which has the effect of extending the life of the ball screw and motor.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram showing an example of a slide base device using a ball screw, Figure 2 is an explanatory diagram of a slide base using the ball screw of the present invention, and Figure 3 is an enlarged view of the ball screw in Figure 2. 44 is an explanatory diagram of the operation of FIG. 3, and FIG. 5 is a detailed diagram of the ball adjustment tool. 4.Ball screw, 5.12 ball shaft, 5a...
Thread groove, 8 - Hole screw nut, 13 Shaft.

Claims (1)

[Claims] (1) Predetermined thread grooves are formed 1. A ball screw O consisting of a combination of a ball screw shaft and a ball nut screwed onto the ball screw shaft,
At the inner end of the ball screw shaft, there is a straight M that matches the groove diameter of the screw groove and liJ stop, and is larger than the ball A2 and the capacity of the nut.
A ball screw overrun prevention mechanism that is completely characterized by the formation of a film.