JP5772232B2 - Ball screw and ball screw nut rigidity control method - Google Patents

Description

  The present invention relates to a ball screw, and more particularly to a technique for controlling the thermal expansion of a nut generated when the ball screw is driven.

As a prior art for cooling a nut of a ball screw, for example, techniques disclosed in Patent Documents 1 and 2 are disclosed.
In the technique described in Patent Document 1, a through hole is provided along the axial direction of the nut, and the nut is cooled by passing a cooling medium through the through hole.
Further, Patent Document 2 explains that the nut contracts in the direction of increasing the preload depending on the preload method by cooling the nut. The problem that the dynamic friction torque increases when the preload is increased due to heat shrinkage of the nut is solved by adopting a two-point contact preload in the pulling direction as the nut preloading method.

JP 2002-310258 A JP 2010-133556 A

However, since the technique described in Patent Document 1 is intended only to cool the nut, the rigidity of the nut cannot be controlled in accordance with the driving conditions.
The same applies to the technology described in Patent Document 2. By adopting a two-point contact preload in the pulling direction as the nut preloading method, the preloading load hardly changes due to the thermal contraction of the nut. Although the rise can be suppressed, it is insufficient to positively control the rigidity of the nut.

  Therefore, the present invention has been made paying attention to such problems, and it is possible to positively control the rigidity of a nut in accordance with changes in driving conditions, and a method for controlling the nut rigidity of a ball screw. The purpose is to provide.

In order to solve the above-mentioned problems, a first invention of the present invention has a screw shaft having a helical thread groove on the outer peripheral surface and a screw groove facing the screw groove of the screw shaft on the inner peripheral surface. A ball screw having a nut externally fitted through a plurality of rolling elements loaded between the opposing screw grooves, wherein the preload type is a compression direction preload ball screw, an oversize ball preload A ball screw, or a fine clearance ball screw provided with play in the axial direction of the nut or the screw shaft when no load is applied, the temperature adjusting means capable of cooling and heating the nut, and the temperature adjusting means a control unit for controlling the preload and nuts rigidity thereby cool or heat the nut, and a temperature measuring means for measuring the temperature of said nut, set to the ball screw is incorporated And a drive information setting means for setting a driving information according to the driving conditions in the control unit acquires the temperature measurement information from the temperature measuring means, and a drive information from the drive information setting means, The temperature adjusting means is controlled based on the acquired temperature measurement information and driving information to control the temperature of the nut to a predetermined temperature corresponding to the driving condition .

According to the ball screw of the first invention, the temperature adjusting means capable of cooling and heating the nut, the controller for controlling the preload and the rigidity of the nut by cooling or heating the nut by the temperature adjusting means, and the nut Temperature measuring means for measuring the temperature of the motor, and drive information setting means for setting drive information according to the driving conditions in the equipment in which the ball screw is incorporated , and the control unit includes temperature measurement information from the temperature measuring means and The drive information from the drive information setting means is acquired, and the temperature adjusting means is controlled based on the acquired temperature measurement information and drive information to control the temperature of the nut to a predetermined temperature according to the drive conditions . The rigidity of the nut can be positively controlled in accordance with changes in driving conditions.
That is, the preload and nut rigidity have a relationship as shown in the following formula (1), and the rigidity of the nut is proportional to the 1/3 power of the preload. Further, FIG. 1 is a graph showing changes in temperature and driving torque when the nut of the compression preload ball screw is cooled. As can be seen from FIG. 1, the nut is thermally contracted by cooling the nut. As a result, the preload is increased, and as a result, the driving torque is increased. From the above, it can be seen that the preload can be actively changed by controlling the temperature of the nut of the ball screw, and as a result, the rigidity of the nut can be controlled.

  Here, in the ball screw according to the first invention, when the nut is cooled by the temperature adjusting means, the nut contracts in the axial direction and the radial direction. At this time, if the preload type is a compression preloaded ball screw, the radial direction -The preload is increased by contraction in the axial direction, and the total preload is greatly increased. On the other hand, during heating, the overall preload is greatly reduced. Therefore, if the ball screw according to the present invention is a compression preload ball screw, it is characterized in that the rate of change in preload load and nut rigidity with respect to temperature change is large.

  Further, in the ball screw according to the first invention, if the preload type is an oversized ball preload ball screw, the preload increases in the radial direction and the axial direction due to the shrinkage of the nut during cooling. On the other hand, when heated, the preload decreases in the radial direction due to expansion of the nut, but the preload increases due to expansion in the axial direction, so that the preload does not change comprehensively. In other words, the oversized ball preloaded ball screw is characterized in that the preload increases during cooling but does not change during heating.

  Further, in the ball screw according to the first invention, if the preload type is a fine clearance ball screw, the preload ball screw is formed by contracting in the radial direction and the axial direction at the time of cooling. Therefore, when rigidity is required (for example, during machining), the nut can be cooled to increase the preload as a preload ball screw, thereby increasing the nut rigidity. On the other hand, during high-speed movement such as conveyance, the nut is heated to form a fine clearance ball screw, thereby reducing the dynamic friction torque during driving and improving the service life by reducing the preload.

  Here, in the ball screw according to the first invention, the temperature adjusting means has a tube that spirally surrounds the outer periphery of the nut, and cools or heats the nut by circulating a liquid in the tube. It is preferable that it has become like this. The temperature adjusting means has a pipe disposed on the inner periphery of the nut and between the opposing screw grooves, and cools or heats the nut by circulating a liquid in the pipe. It is preferable that it has become like this. Such a configuration is suitable for uniformly temperature-controlling the entire circumference of the nut, and thus more stable preload management and rigidity management can be performed.

In addition, the second invention of the present invention has a screw shaft having a helical thread groove on the outer peripheral surface, a screw groove facing the screw groove of the screw shaft on the inner peripheral surface, and the opposing screw groove. A nut that is externally fitted so as to be relatively movable via a plurality of rolling elements loaded between them, and the preload type is a compression direction preload ball screw, an oversized ball preload ball screw, or the above-mentioned when no load is applied A method for controlling the rigidity of the nut used in a fine clearance ball screw provided with play in the axial direction of the nut or the screw shaft, wherein the temperature measurement information of the nut and driving in equipment in which the ball screw is incorporated It acquires the driving information corresponding to the condition, on the basis of the acquired temperature measurement information and drive information, cooling the nut by cooling and heatable temperature regulating means the nut or Thermally controlling the preload and nuts rigidity, characterized by controlling the temperature of said nut to a predetermined temperature in accordance with the driving condition.

According to the nut stiffness control method of the ball screw according to the second aspect of the invention, the temperature measurement information of the nut and the drive information corresponding to the drive condition in the equipment in which the ball screw is incorporated are acquired, and the acquired temperature measurement Based on the information and drive information , the preload and the rigidity of the nut are controlled by cooling or heating the nut by means of temperature adjustment means capable of cooling and heating the nut, and the nut temperature is adjusted to a predetermined temperature according to the driving conditions. Since the control is performed, the rigidity of the nut can be positively controlled in accordance with the change of the driving condition, as in the first aspect.

  As described above, according to the present invention, it is possible to positively control the rigidity of the nut in accordance with changes in driving conditions.

It is a graph which shows an example of the relationship between the torque in a ball screw, and a temperature change. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a first embodiment of a ball screw according to the present invention (peripheral spiral type temperature adjusting means + compression direction preload ball screw). It is sectional drawing along the axial direction of 1st embodiment (compression direction preload ball screw) of the ball screw which concerns on this invention. In the drawing, the outer peripheral spiral type temperature adjusting means is shown by a simplified image of the axial through hole (32) (hereinafter the same in other drawings except FIG. 7). It is a figure explaining the effect (at the time of cooling) of 1st embodiment of the ball screw concerning the present invention. It is a figure explaining the effect (at the time of a heating) of 1st embodiment of the ball screw which concerns on this invention. It is a figure explaining 2nd embodiment (inner spiral type temperature control means) of the ball screw concerning the present invention. It is a figure explaining the cooling structure of 3rd embodiment of the ball screw which concerns on this invention, The figure (a) is the front view seen from the axial direction, (b) is the side surface which shows a nut along the axis line FIG. It is sectional drawing along the axial direction of 4th embodiment (oversized ball preload ball screw) of the ball screw which concerns on this invention. It is sectional drawing along the axial direction of 5th embodiment (fine clearance ball screw) of the ball screw which concerns on this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 2, the ball screw 1 of the first embodiment includes a screw shaft 10 having a helical screw groove 10 a on the outer peripheral surface and a screw groove 20 a facing the screw groove 10 a of the screw shaft 10. And a nut 20 on the peripheral surface. The nut 20 is formed in a cylindrical shape having an inner diameter larger than the outer diameter of the screw shaft 10. The screw shaft 10 is externally fitted to the screw shaft 10 so as to be relatively movable by being screwed through a plurality of rolling elements 15 loaded so as to be freely rollable between the opposing screw grooves 10a and 20a. Here, in this example, as shown in FIG. 3, between the screw groove 10a of the screw shaft 10 and the screw groove 20a of the nut 20, the preload direction is the compression direction, and a preload load Fa0 is thereby added. Thus, a plurality of rolling elements 15 are incorporated in the state of offset lead preload (compression direction preload ball screw).

  Returning to FIG. 2, a tube 32 that spirally surrounds the outer peripheral surface 20 b of the nut 20 is wound around the nut 20. The pipe 32 is used as a passage for the cooling medium, and both ends of the pipe 32 are connected to a circulation device 34 for circulating the cooling medium in the pipe 32. The circulation device 34 includes a heat exchanger 36, and the temperature adjustment means 30 is configured by the circulation device 34 and the pipe 32. Thereby, the cooling medium in the pipe 32 cooled or heated by the heat exchanger 36 in the circulation device 34 can be cooled or heated by circulating the tube 32 by the circulation device 34. In this example, the pipe 32 used as a passage for the cooling medium has a configuration of an outer peripheral spiral type temperature adjusting means that spirally surrounds the outer peripheral surface 20b of the nut 20, and therefore, cooling is performed with a symbol H in FIG. As shown in the range (the range indicated by the broken line and hatching), it is suitable for cooling or heating the nut 20 uniformly as a whole.

  Furthermore, in this example, a thermometer 40 is attached to the surface of the nut 20 as a temperature measuring means, and temperature measurement information acquired by the thermometer 40 is input to the control unit 50. The control unit 50 is configured to include a microcomputer, and in addition to temperature measurement information, information related to driving conditions from a computer that controls equipment in which the ball screw 1 is incorporated (for example, processing requiring low speed and high accuracy). Driving information at the time, driving information at high speed movement that requires high speed movement but is not so high, etc.). The control unit 50 controls the heat exchanger 36 and the circulation device 34 based on the acquired temperature measurement information and driving condition change information, and sets the temperature of the nut 20 to a predetermined temperature corresponding to the driving condition. It comes to control.

  Hereinafter, with reference to FIG. 4 and FIG. 5, the mechanism and effect of control by the control unit 50 to a predetermined temperature according to the driving conditions will be described. 4 and 5 show a control operation of the heat exchanger 36 and the circulation device 34 by the control unit 50 in the ball screw 1 (compression direction preload ball screw) of the first embodiment in which the compression direction is the preload direction. It is the figure which showed the relationship with nut contraction at the time of being cooled thru | or heated by.

  As shown in FIG. 4, when the nut 20 is cooled in the compression direction preload ball screw in which the two-point contact preload in the compression direction is applied to the nut 20, the thermal contraction f1 in the radial direction causes the preload load Fa0. In addition, the heat shrinkage f2 in the axial direction also acts in the direction of increasing the preload Fa0 (see FIG. 5B). For this reason, the overall preload is greatly increased (see (c) in the figure).

  On the other hand, as shown in FIG. 5, in this compression direction preload ball screw, when the nut 20 is heated, the thermal expansion f1 in the radial direction acts in a direction to reduce the preload Fa0 (see FIG. 5A). At the same time, the thermal expansion f2 in the axial direction also acts in a direction to decrease the preload Fa0 (see FIG. 5B). For this reason, the overall preload is greatly reduced (see (c) in the figure).

Therefore, in the ball screw 1 of this first embodiment (a ball screw in which a two-point contact preload in the compression direction is applied to the nut 20), the total preload is greatly increased or decreased by cooling or heating the nut 20. be able to. Therefore, the rigidity of the nut 20 of the ball screw 1 can be positively controlled efficiently in accordance with changes in driving conditions.
Note that the ball screw and the nut rigidity control method according to the present invention are not limited to the above-described embodiments, and various modifications can be made without departing from the spirit of the present invention. .

  For example, in the first embodiment described above, the pipe 32 used as the cooling medium passage has been described as an outer peripheral spiral type temperature adjusting means that spirally surrounds the outer peripheral surface 20b of the nut 20. However, the tube 32 may be configured as an inner peripheral spiral type temperature adjusting means provided on the inner peripheral surface 20c of the nut 20 as in the second embodiment of the ball screw according to the present invention shown in FIG. Good. In FIG. 6, the circulation device 34, the thermometer 40, and the control unit 50 are not shown.

  In the second embodiment shown in the figure, a multi-strip configuration is used in which the circulation path of the rolling elements 15 in the nut 20 is a plurality of strips, of which a strip that does not circulate the rolling members 15 is provided and the pipe 32 is disposed on this strip. It is configured to do. Such a configuration is suitable for cooling or heating the nut 20 uniformly as a whole, as shown in FIG. In addition to this effect, since there is a cooling flow path inside the nut 20 as compared with the temperature control means of the outer peripheral spiral type as in the first embodiment, deformation due to thermal expansion of the nut 20 due to cooling or heating is prevented. High responsiveness.

Here, the inner and outer peripheral spiral type temperature adjusting means as in the first to second embodiments is suitable for uniformly cooling or heating the nut 20 as a whole, but the present invention is not limited to this. For example, as in the third embodiment shown in FIG. 7, the through holes 32 in the axial direction (in this example, four places are provided at equal intervals in the circumferential direction as shown in FIG. 7A) are cooled. You may employ | adopt as the pipe | tube 32 used as a channel | path of a medium. However, in this case, as shown in FIG. 7A by the symbol H, the cooling range is indicated by the symbol H. However, it is not sufficient to uniformly cool or heat the nut 20 as a whole, but it is preferable to simplify the configuration. .
In the above embodiment, the example in which the preload type of the ball screw 1 is a compression direction preload ball screw has been described. However, the preload type of the ball screw 1 is not limited to this, and an oversized ball preload ball screw, It can be a clearance ball screw.

For example, the fourth embodiment shown in FIG. 8 is an example in which the preload type of the ball screw 1 is an oversized ball preload ball screw. In addition, since it can be set as the same structure except the 1st thru | or 3rd embodiment demonstrated above, and a preload system, description is abbreviate | omitted about structures other than a preload system.
This ball screw 1 incorporates a plurality of rolling elements 15 that are slidably loaded between the opposing screw grooves 10a and 20a and whose diameter is slightly larger than the opposing distance between the screw grooves 10a and 20a. This is an oversized ball preloaded ball screw preloaded with

  If the preload type is an oversized ball preload ball screw, the preload increases in both radial and axial directions due to the shrinkage of the nut during cooling. On the other hand, when heated, the preload decreases in the radial direction due to expansion of the nut, but the preload increases due to expansion in the axial direction, so that the preload does not change comprehensively. In other words, the oversized ball preloaded ball screw is characterized in that the preload increases during cooling but does not change during heating. Because of such characteristics, the preload is applied by cooling or heating the heating nut 20 by the control operation of the heat exchanger 36 and the circulation device 34 by the control unit 50 using an oversized ball preloading ball screw. Since the preload does not decrease from the normal time, the minimum rigidity can be secured, and the rigidity can be increased by cooling when performing heavy cutting or the like.

In addition, the fifth embodiment shown in FIG. 9 is an example in which the preload type of the ball screw 1 is a fine clearance ball screw. In addition, since it is the same structure except the 1st thru | or 3rd embodiment demonstrated above, and a preload system, description is abbreviate | omitted about structures other than a preload system.
In this ball screw 1, a plurality of rolling elements 15 loaded so as to be freely rollable between the opposing screw grooves 10 a and 20 a have a diameter slightly smaller than the opposing distance between the screw grooves 10 a and 20 a. This is a fine clearance ball screw that creates clearance in the nut and provides play in the axial direction of the nut or screw shaft. Although the fine clearance ball screw has backlash as much as the gap is provided, the temperature rise during driving is lower than the preloaded ball screw, and the dynamic friction torque during driving is also low, so high-speed driving that does not require positioning accuracy Suitable for

  If the preload type is a fine clearance ball screw, it will become a preloaded ball screw by contracting in the radial direction and axial direction during cooling. Therefore, when rigidity is required (for example, during machining), the nut can be cooled to increase the preload as a preload ball screw, thereby increasing the nut rigidity. On the other hand, during high-speed movement such as conveyance, the nut is heated to form a fine clearance ball screw, thereby reducing the dynamic friction torque during driving and improving the service life by reducing the preload.

DESCRIPTION OF SYMBOLS 1 Ball screw 10 Screw shaft 15 Rolling element 20 Nut 30 Temperature control means 32 Pipe (cooling medium passage)
34 Circulator 36 Heat exchanger 40 Thermometer (Temperature measuring means)
50 Control unit

Claims (4)

A screw shaft having a spiral thread groove on the outer peripheral surface, a thread groove facing the screw groove of the screw shaft on the inner peripheral surface, and a plurality of rolling elements loaded between the opposing screw grooves. A ball screw provided with a nut that is fitted so as to be relatively movable via
The preload type is a compression direction preload ball screw, an oversized ball preload ball screw, or a fine clearance ball screw provided with play in the axial direction of the nut or the screw shaft when no load is applied,
A temperature adjusting means capable of cooling and heating the nut; a control unit for controlling a preload and a nut rigidity by cooling or heating the nut by the temperature adjusting means; and a temperature measuring means for measuring the temperature of the nut. Driving information setting means for setting driving information according to the driving conditions in the equipment in which the ball screw is incorporated ,
The control unit acquires temperature measurement information from the temperature measurement unit and drive information from the drive information setting unit, and controls the temperature adjustment unit based on the acquired temperature measurement information and drive information. A ball screw , wherein the temperature of the nut is controlled to a predetermined temperature according to the driving condition .   2. The temperature adjusting means includes a pipe that spirally surrounds the outer periphery of the nut, and the nut is cooled or heated by circulating a liquid in the pipe. Ball screw as described in.   The temperature adjusting means has a pipe disposed on the inner periphery of the nut and between the opposing screw grooves, and cools or heats the nut by circulating a liquid in the pipe. The ball screw according to claim 1, wherein: A screw shaft having a spiral thread groove on the outer peripheral surface, a thread groove facing the screw groove of the screw shaft on the inner peripheral surface, and a plurality of rolling elements loaded between the opposing screw grooves. A preload type that provides play in the axial direction of the nut or the screw shaft when no load is applied. A method for controlling the rigidity of the nut used in the fine clearance ball screw comprising:
The temperature measurement information of the nut and the driving information according to the driving conditions in the facility in which the ball screw is incorporated are acquired, and the temperature at which the nut can be cooled and heated based on the acquired temperature measurement information and driving information The preload and the nut rigidity are controlled by cooling or heating the nut by an adjusting means, and the nut temperature is controlled to a predetermined temperature according to the driving conditions . Control method.

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