JP2013167320A - Lead screw supporting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lead screw supporting device that maintains a strand for pulling a pair of intermediate supports so that they are located in the middle between a nut and a bearing even if the strand is loose in a change over time.SOLUTION: A pair of intermediate supports 20A, 20B are attached to a slider 12 of a linear guide device 10 that is provided parallel to a screw stem 1 between bearings 5, 5 of both ends of the screw stem 1 so that the intermediate supports 20A, 20B and the screw stem 1 are slidably engaged. A pulley device 22 includes: moving pulleys 23A, 23B that are arranged in the intermediate supports 20A, 20B, respectively; and a strand 24A, one end of which is secured to one bearing 4B via an elastic element 9A and is wound on the moving pulley 23A provided in one of the intermediate supports 20A, and the other end of which is coupled to a nut 2; and a strand 24B, one end of which is secured to the other bearing 4A via an elastic element 9B and is wound on the moving pulley 23B provided in the other intermediate support 20B, and the other end of which is coupled to the nut 2.

Description

  In the present invention, when the feed screw support distance (span) is long, in order to avoid resonance of the feed screw due to the low speed range where the critical speed of the feed screw is low, the intermediate portion of the feed screw shaft is auxiliary The present invention relates to a feed screw support device for supporting.

It is dangerous if the vibration caused by the rotation of the screw shaft of the feed screw resonates with the natural frequency of the screw shaft. This critical speed is inversely proportional to the square of the support span of the screw shaft. When the table stroke is long, such as an NC control surface grinder, the screw shaft becomes long, and the support span of the screw shaft becomes long, so the critical speed becomes low. As the feed rate increases, the rotation speed of the feed screw increases and it may be necessary to use it in the critical speed range. In such a case, an intermediate support is provided to shorten the support span, and the natural frequency of the screw shaft. Means for increasing the height are known.
As such a feed screw support device, it uses a linear guide device that has the advantage of being able to move lightly by rolling friction to support the screw shaft intermediate support, and also provides a feed screw with means for always interlocking the nut and the intermediate support. A support device is disclosed (for example, refer to Patent Document 1).

  As shown in FIG. 2, the feed screw support device disclosed in Patent Document 1 includes a screw shaft 101 and a nut 102 screwed into the screw shaft 101. Both ends of the screw shaft 101 are rotatably supported by bearings 105 respectively attached to two bearing housings 104 and 104 fixed to the machine base 103 with a gap L, and one shaft end is a bearing housing. The rotary drive device M fixed to 104 is connected via a coupling 106. The nut 102 is attached to the machine table 108 via a nut housing 107. The machine table 108 is supported by a pair of linear guide devices (not shown) that are mounted on the machine base 103 in parallel with the screw shaft 101 at both the left and right side portions in the moving direction.

  This linear guide device includes a guide rail that extends in the axial direction and is fixed to the machine base 103, and a slider that is movably suspended on the guide rail and is fixed to the machine table 8. A ball rolling groove is arranged opposite to the inner surface of the slider, and a large number of balls are slidably loaded between these two ball rolling grooves, and the slider is moved through the rolling of the balls. It is structured to move lightly in the axial direction on the guide rail.

  In addition to the linear guide device that supports the machine table 108, another linear guide device 110 is arranged in parallel with the screw shaft 101. The guide rails 111 are fixed on a surface 103 a that is lowered by one step between the bearing housings 104 of the screw shaft 101 facing each other with a distance L between fulcrums, and two guide rails 111 are provided on the guide rail 111. The slider 112 is attached.

  A pair of intermediate supports 120A and 120B that receive the radial load of the screw shaft 101 are fixed to the upper surfaces of the two sliders 112, respectively. Each of the intermediate supports 120A and 120B is a slide bearing, and is inserted through the screw shaft 101 with a slight clearance. On the other hand, the slider 102 can move in the axial direction on the guide rail 111 very lightly through the rolling of the ball. Therefore, the intermediate supports 120A and 120B can move smoothly together with the slider 112. These intermediate supports 120A and 120B are disposed on both sides of the nut 102, and are connected to each other by a connecting rod 121 at an interval of about L / 2.

  Further, a pulley device 122 is provided between the intermediate supports 120A and 120B and the nut 102. That is, the movable pulleys 123A and 123B are attached to the intermediate supports 120A and 120B, respectively, and the rope 124 as a belt-like member is stretched between them in a loop shape. The cable 124 is locked to the machine base 103 at the center thereof, and is locked to the nut 102 on the opposite side. This cord 124 can be said to be substantially the same as one comprising two cords (124, 124) having one end locked to the machine base 103 and the other end locked to the nut 102. Accordingly, the intermediate supports 120A and 120B can slide in the axial direction in conjunction with the nut 102.

Japanese Patent No. 2867386

However, in the feed screw support device disclosed in Patent Document 1, each intermediate support is fixed to a nut and a fixed (support) bearing by loosening a cable for pulling a pair of intermediate supports with each other over time. May not come in between. As a result, if it is driven in such a state, there is a possibility that the critical speed is reduced or the nut may come into contact with the intermediate support, and there is room for improvement.
Therefore, the present invention has been made paying attention to the above-mentioned problems, and its purpose is to provide each intermediate support with a nut even if the rope for pulling the pair of intermediate supports to each other is loosened with time. It is another object of the present invention to provide a feed screw support device that is maintained so as to be positioned between a fixed (support) bearing and a fixed (support) bearing.

In a feed screw support device according to claim 1 of the present invention for solving the above-described problem, a nut is screwed onto a screw shaft that is rotatably supported at both ends via a bearing, In the feed screw support device in which a pair of intermediate supports that receive the radial load of the screw shaft and that are linked in the screw shaft direction are located on both sides of the nut and connected to each other,
A linear guide device is provided at least between the bearings at both ends of the screw shaft in parallel with the screw shaft, and the pair of intermediate supports are attached to the slider of the linear guide device, and the intermediate support and the screw shaft are slid. The movable pulleys engaged with each other and both intermediate supports, and one end fixed to one bearing via an elastic body and wound around the movable pulley provided on one intermediate support Two ends are connected to the nut, and one end is fixed to the other bearing through an elastic body and wound around the moving pulley provided on the other intermediate support, and the other end is connected to the nut. It consists of a belt-like member, and is characterized in that a pulley device is also provided that also serves to transmit the movement force of the nut to the intermediate support and to regulate the amount of movement of the intermediate support relative to the amount of movement of the nut.
The feed screw support device according to claim 2 of the present invention is the feed screw support device according to claim 1, wherein the intermediate support includes a rolling bearing that supports the screw shaft via a rolling element. It is a feature.

  According to the present invention, even if a cable for pulling a pair of intermediate supports is loosened with time, each intermediate support is maintained so as to be positioned between the nut and the fixed (supporting) bearing. A support device can be provided.

It is a figure which shows the structure in one Embodiment of the feed screw support apparatus which concerns on this invention, (a) is a top view, (b) is a right view. It is a figure which shows the structure of the conventional feed screw support apparatus, (a) is a top view, (b) is a right view.

Hereinafter, an embodiment of a feed screw support device according to the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration in an embodiment of a feed screw support device according to the present invention, in which (a) is a plan view and (b) is a right side view.
As shown in FIGS. 1A and 1B, the feed screw support device includes a screw shaft 1, a ball screw nut (tube-type single flange double nut) 2 screwed to the screw shaft 1, a linear It has a guide device 10, an intermediate support 20, and a pulley device 22. Both ends of the screw shaft 1 are rotatably supported by bearings 5 respectively attached to two bearing housings 4 and 4 fixed to the machine base 3 with a gap L, and one shaft end is a bearing housing. 4 is coupled to a rotary drive device M fixed to 4 via a coupling 6. The nut 2 is attached to the machine table 8 via a nut housing 7. The machine table 8 is supported by a pair of linear guide devices (not shown) that are mounted on the machine base 3 in parallel with the screw shaft 1 at both the left and right sides with respect to the moving direction. The linear guide device includes a guide rail that extends in the axial direction and is fixed to the machine base 3, and a slider that is movably suspended on the guide rail and that is fixed to the machine table 8. A ball rolling groove is arranged opposite to the inner surface of the slider, and a large number of balls are slidably loaded between these two ball rolling grooves, and the slider is moved through the rolling of the balls. It is of a known structure that moves lightly on the guide rail in the axial direction.

<Linear guide device>
Apart from the linear guide device that supports the mechanical table 8, another linear guide device 10 is arranged in parallel with the screw shaft 1. The guide rail 11 is fixed on a surface 3 a that is lowered by one step between the bearing housings 4 A and 4 B of the screw shaft 1 facing each other with a distance L between the fulcrums. Two sliders 12 are attached.

<Intermediate support>
A pair of intermediate supports 20A and 20B that receive the radial load of the screw shaft 1 are fixed to the upper surfaces of the two sliders 12, respectively. Each of the intermediate supports 20 </ b> A and 20 </ b> B has a rolling bearing that supports the screw shaft 1 via a rolling element, and can move smoothly in the axial direction with respect to the screw shaft 1. In this way, by using a rolling bearing such as a ball screw or linear bush as a linear motion guide structure for the intermediate support for the screw shaft, not only can the intermediate support for the screw shaft be moved smoothly, but also feed screw support It is possible to cope with speeding up of the apparatus. On the other hand, the slider 2 can also move in the axial direction on the guide rail 11 very lightly through the rolling of the ball. Therefore, the intermediate supports 20A and 20B can move smoothly together with the slider 12. These intermediate supports 20A and 20B are disposed on both sides of the nut 2 and are connected to each other by a connecting rod 21 with an interval of about L / 2.

<Pulley unit>
A pulley device 22 is provided between the intermediate supports 20A and 20B and the nut 2. The pulley device 22 includes moving pulleys 23A and 23B attached to the intermediate supports 20A and 20B, and two ropes 24A and 24B that are belt-like members wound around the moving pulleys 23A and 23B, respectively.
Here, as a countermeasure against the critical speed of the feed screw support device, the intermediate supports 20A and 20B are fixed at both ends of the screw shaft 1, and the positions of the bearing housings (fixed (support) bearings) 4A and 4B and the nuts 2 are supported. Must be in the middle of In particular, in order to position the intermediate supports 20A and 20B so as to be surely maintained at a half distance between the nut 2 and the support bearings 4A and 4B, the cables 24 are maintained so that a certain tension is maintained. There is room for improvement in 24 deflections.

  Therefore, the cable 24A has one end fixed to one bearing 4B via the elastic body 9A and wound around a moving pulley 23A provided on one intermediate support 20A, and the other end is provided below the nut 2. It is connected to the bracket 2A. On the other hand, the cable 24B has one end fixed to the other bearing 4A via the elastic body 9B, wound around a moving pulley 23B provided on the other intermediate support 20B, and the other end provided at the lower part of the nut 2. It is connected to the bracket 2A. As shown in FIGS. 1 (a) and 1 (b), the cable 24A, one end of which is fixed to one bearing 4B, passes through a through hole 20B ′ provided in the other intermediate support 20B, and a moving pulley 23A. It is preferable in terms of design space to be wound around. Similarly, it is preferable in terms of design space that the cable 24B, one end of which is fixed to the other bearing 4A, is wound around the movable pulley 23B through the through hole 20A 'provided in the one intermediate support 20A.

Here, in the case where the elastic bodies 9A and 9B are springs, there are many cases in which both end portions are hooked. Further, when the ropes 24A and 24B are wire ropes, their tips are often formed in an annular shape, or metal fittings are often attached to their tips. Therefore, the connection between the cable 24A and the elastic body 9A, and the cable 24B and the elastic body 9B is, for example, a ring-shaped tip of the cables 24A and 24B or a hook attached to the tip of the elastic bodies 9A and 9B. It is done by hooking the tip. When the elastic bodies 9A and 9B have a hook-shaped tip, it is quite rare, but when the ropes 24A and 24B are extremely loose, the elastic bodies 9A are removed from the fittings of the ropes 24A and 24B. 9B may come off. Therefore, it is safer to connect the cable 24A and the elastic body 9A and between the cable 24B and the elastic body 9B by using a connecting bracket.
As a result, even if the ropes 24A and 24B pulled by the movable pulleys 23A and 23B loosen due to deterioration over time, the ropes 24A and 24B are given a stable tension, and the intermediate supports 20A and 20B are interlocked with the nut 2 in the axial direction. Can be moved smoothly.

Next, the drive mode of the feed screw support device configured as described above will be described with reference to FIGS. 1 (a) and 1 (b).
When the screw shaft 1 is rotated in a predetermined direction by being driven by the rotation driving device M, the nut 2 is moved to the left in FIGS. 1A and 1B, for example, and the machine table 8 is moved to both sides thereof. Is smoothly moved while being guided by the linear guide device. At this time, the distance between supporting points L of the screw shaft 1 is long, the value of the critical speed u is inversely proportional to the value of L ² is small, the screw shaft 1 is likely to resonate relatively low speed. However, since the intermediate supports 20A and 20B are provided, the distance between the fulcrums (support span) is L / 2 even at the maximum value. As a result, the critical speed is significantly increased to four times u, and it is difficult to resonate.

  Explaining this principle, the bearings are attached to the nuts of the intermediate supports 20A and 20B, and when the nut 2 advances by one lead, the lead moves forward by the movable pulleys 23A and 23B. Since the nut 2 and the nuts of the intermediate supports 20A and 20B are set to the same lead, they should travel the same distance, but the other half lead is absorbed by the bearings of the nuts of the intermediate supports 20A and 20B. Therefore, the distance traveled by the intermediate supports 20A and 20B is always half that of the nut 2.

On the other hand, the intermediate supports 20A and 20B are connected to the opposing intermediate support by the connecting rod 21, and thus are pushed by the opposing intermediate support and proceed.
In this embodiment, the nut 2 and the intermediate supports 20A and 20B are further linked via the pulley device 22.
When the nut 2 reaches the left end of the screw shaft 1 and comes into contact with the left intermediate support 20A, a limit switch (not shown) is actuated to stop the rotation driving device M, and the rotation of the screw shaft 1 is stopped. Needless to say, the intermediate supports 20A and 20B are also stopped to ensure safety.

Next, when the rotation driving device M is rotated in the opposite direction, the nut 2 starts moving rightward in FIG.
When the nut 2 moves from the left end to the right, the support span between the bearing 5 and the intermediate support 20B is continuously reduced.
Since the mechanical table 8 and the intermediate supports 20A and 20B are fed not only by the ball nut 2 but also by the operation of the slider 12 in the linear guide device 10, it is extremely smooth and has good followability even at high speed, and the screw shaft. With respect to 1, the up-down and left-right swings are also suppressed, and high accuracy is achieved. In the linear guide device 10, the guide rail 11 and the slider 12 have high rigidity and high strength via a large number of balls that roll in ball rolling grooves provided to face the side surfaces of the guide rail 11 and the slider 12. This is because the linear mobility of the slider 12 is very light and stable.

  When the nut 2 moves the distance L and the intermediate supports 20A and 20B reach the right end portion of the screw shaft 1 in conjunction with this, a limit switch (not shown) similar to that at the left end portion is actuated to operate the rotary drive device M. Is stopped, and the rotation of the screw shaft 1 is stopped, and at the same time, the machine table 8 and the intermediate supports 20A and 20B are also stopped. Thereby, except when the position of the nut 2 is at both ends of the screw shaft 1, the support span of the screw shaft 1 by the intermediate supports 20A and 20B is always shorter than the conventional one, and therefore the shaft critical speed is increased to the safe side. .

  As described above, according to the present embodiment, each of the intermediate supports is provided with an elastic body that urges each of the intermediate supports in a direction opposite to the direction in which the intermediate supports face each other. A certain tension can be given to prevent the danger speed from being lowered. That is, a feed screw support device is provided that maintains each intermediate support so that it is positioned between the nut and the fixed (support) bearing even if the rope for pulling the pair of intermediate supports is loosened with time. To do.

In addition, since the intermediate support has a rolling bearing that supports the screw shaft via a rolling element, the intermediate support with respect to the screw shaft can be moved smoothly, and the feed screw support device can be increased in speed. can do.
As mentioned above, although embodiment of this invention has been described, this invention is not limited to this, A various change and improvement can be performed.

DESCRIPTION OF SYMBOLS 1 Screw shaft 2 Nut 5 Slider 9 Elastic body 10 Linear guide apparatus 12 Slider 20A, 20B Intermediate support 22 Pulley apparatus

Claims (2)

A nut is screwed onto a screw shaft that is rotatably supported at both ends via a bearing, and in the axial direction of the nut, a pair of intermediate supports that receive a radial load of the screw shaft and interlock with the screw shaft direction, In the feed screw support device arranged on both sides of the nut and connected,
A linear guide device is provided between the bearings at both ends of the screw shaft in parallel with the screw shaft, the pair of intermediate supports are attached to the slider of the linear guide device, and the intermediate support and the screw shaft are engaged with each other. And one end fixed to one bearing via an elastic body and the other end wrapped around the moving pulley provided on one intermediate support. Are connected to the nut, and one band is fixed to the other bearing through an elastic body and wound around the movable pulley provided on the other intermediate support, and the other end is connected to the nut. A feed screw characterized by comprising a pulley device which is also made of a member and serves as both a transmission of the movement force of the nut to the intermediate support and a restriction of the movement amount of the intermediate support with respect to the movement amount of the nut Lifting apparatus.   The feed screw support device according to claim 1, wherein the intermediate support includes a rolling bearing that supports the screw shaft via a rolling element.

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