JP2019032044A - Driving screw shaft support device - Google Patents

Abstract

To avoid thermal displacement of a screw shaft, and enhance rigidity in both of a radial direction and a moment direction, to considerably improve a risk rotational speed (eigen frequency) of the screw shaft.SOLUTION: A driving screw shaft support device 10 comprises: a screw shaft 12; a nut 13 screwed into the screw shaft 12; a rotation drive part for rotationally driving the screw shaft 12, installed on one end side of the screw shaft 12; a first pivot part 21 rotatably supporting an installation side end part of the rotation drive part in the screw shaft 12; and a second pivot part 31 rotatably supporting the other installation side end part of the rotation drive part in the screw shaft 12. The second pivot part 31 comprises a combined angular contact ball bearing 32 composed of a DB structure where two single-row angular contact ball bearings 32a, 32b are arranged in a back-to-back combination.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drive screw shaft support device.

  A screw shaft support device for driving may be used for a machine tool feeding device or the like. This type of driving screw shaft support device includes a mechanism that rotates a screw shaft by a rotational drive source such as a motor and moves a nut that is screwed to the screw shaft along the screw shaft. The drive screw shaft support device can move the external member connected to the nut relative to the base by the movement of the nut. Further, both ends of the screw shaft are supported by a pair of shaft support portions via bearings, and the pair of shaft support portions are fixed to the base while holding the bearings. As a method for supporting the screw shaft in the conventional screw shaft support device for driving according to the prior art, the support structure at both ends is set to “fixed-fixed” in order to increase the dangerous rotational speed (natural frequency) of the screw shaft. The method was general (see, for example, Patent Document 1 below).

JP-A-4-19452

  In recent industry, due to the demand for expansion of the application range of the feed mechanism, it is required to improve the functions of the screw shaft support device for driving, such as rotating the screw shaft at high speed or increasing the length of the screw shaft. It was. However, if the screw shaft is rotated at a higher speed or longer, an excessive load is generated on the bearing or the like constituting the support structure fixedly disposed at both ends of the screw shaft due to the thermal displacement of the screw shaft. There was a problem that problems such as early breakage occurred. As a countermeasure against such a problem, there is a structure in which the displacement is absorbed by a spring, a piezoelectric element, or the like in the prior art. However, in the countermeasure according to the conventional technique, the axial direction of the screw shaft generated by the spring or the piezoelectric element is present. Since the radial direction and the moment direction are restrained only by the frictional force, the restraining force is weak and the rigidity value does not increase greatly, and the critical rotational speed cannot be greatly improved.

  Further, when the screw shaft is rotated at a high speed or lengthened, vibration occurs in the screw shaft, and there is a problem that the rotational speed (acceleration) of the screw shaft cannot be increased due to the influence. In particular, the oscillation phenomenon of the screw shaft is remarkable at the shaft end portion on the side opposite to the motor installation in the screw shaft, and there has been a demand for realizing a mechanism that can suitably prevent vibration of the screw shaft. Furthermore, there have been no proposals for effective countermeasures in the prior art represented by Patent Document 1 listed above for various problems existing in these prior arts.

  The present invention has been made in view of the various problems existing in the above-described prior art. The purpose of the present invention is to increase the rigidity in the radial direction and the moment direction while releasing the thermal displacement of the screw shaft. An object of the present invention is to provide a drive screw shaft support device that can greatly improve the dangerous rotational speed (natural frequency) of the drive.

  A screw shaft support device for driving according to the present invention includes a screw shaft, a nut screwed to the screw shaft, a rotation drive unit installed on one end side of the screw shaft to rotationally drive the screw shaft, A first shaft support portion rotatably supporting an installation side end portion of the rotation drive portion in the screw shaft; and a second shaft support portion rotatably supporting a counter installation side end portion of the rotation drive portion in the screw shaft. , Wherein the second shaft support portion includes a combination angular ball bearing having a DB structure in which two single-row angular ball bearings are arranged in a rear combination. It is.

  According to the present invention, it is possible to greatly improve the critical rotational speed (natural frequency) of the screw shaft by increasing the rigidity in the radial direction and the moment direction while missing the thermal displacement of the screw shaft. It is possible to provide a driving screw shaft support device.

It is a longitudinal cross-sectional side view for demonstrating the specific structure of the screw shaft support apparatus for drive which concerns on 1st embodiment. It is the longitudinal cross-sectional side view which showed the screw shaft support apparatus for drive concerning a prior art. It is a figure which shows the measurement result of the natural frequency of 1st embodiment and a prior art. It is a figure which shows the dangerous rotational speed assumption value computed from the measurement result of the natural frequency shown in FIG. It is a longitudinal cross-sectional side view for demonstrating the specific structure of the screw shaft support apparatus for drive which concerns on 2nd embodiment. It is a longitudinal cross-sectional side view for demonstrating the specific structure of the screw shaft support apparatus for drive which concerns on 3rd embodiment.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments for carrying out the invention will be described with reference to the drawings. The following embodiments do not limit the invention according to each claim, and all combinations of features described in each embodiment are essential to the solution means of the invention. Not exclusively.

[First embodiment]
First, a specific configuration of the drive screw shaft support device 10 according to the first embodiment will be described with reference to FIG. Here, FIG. 1 is a longitudinal sectional side view for explaining a specific configuration of the drive screw shaft support device according to the first embodiment.

  The drive screw shaft support device 10 according to the first embodiment includes a base member 11 serving as a device installation reference. The base member is a long casing formed extending in the longitudinal direction (left and right direction in FIG. 1). For the base member 11, a screw shaft 12 formed extending in the longitudinal direction; A nut 13 that is screwed onto the screw shaft 12 is installed. In the first embodiment, a rotation driving unit (not shown) including a motor is installed on one end side (left side of the paper in FIG. 1) of the screw shaft 12.

  Further, a first shaft support portion 21 is installed to rotatably support an installation side end portion (the end portion on the left side in FIG. 1) of a rotation drive unit (not shown) in the screw shaft 12, while the screw shaft 12, a second shaft support portion 31 is installed to rotatably support the opposite end portion (the end portion on the right side of the paper in FIG. 1) of the rotation drive unit (not shown). The first shaft support portion 21 and the second shaft support portion 31 support both shaft end portions of the screw shaft 12 by a member such as a bearing, which will be described later, installed with respect to the base member 11, thereby changing the axial direction of the screw shaft 12. A stable rotational movement of the screw shaft 12 around the rotation center is made possible. Therefore, the screw shaft 12 rotates when a rotation drive unit (not shown) receives electric power from the external power source and transmits the rotation driving force to the screw shaft 12. When the screw shaft 12 rotates, the nut 13 screwed to the screw shaft 12 moves in the axial direction of the screw shaft 12 and exerts a driving force on the external member. In the first embodiment shown in FIG. 1, it is assumed that the screw shaft 12 and the nut 13 are rolling element screw devices assembled through a plurality of rolling elements. You may be comprised as a sliding screw apparatus screwed together without interposing.

  And in the screw shaft support device 10 for drive which concerns on 1st embodiment, the counter-installation side edge part (edge part of the paper surface right side in FIG. 1) of the rotation drive part not shown in the screw shaft 12 is supported rotatably. The second shaft support 31 has a significant feature in the configuration. That is, the 2nd axial support part 31 concerning 1st embodiment is provided with the combination angular contact ball bearing 32 which consists of DB structure which has arranged two single row angular contact ball bearings 32a and 32b by the back combination. The combination angular contact ball bearing 32 having a DB structure arranged in the rear combination has an advantage that the load capacity of the moment load is increased because the distance between the operating points of the two bearings is large. In particular, vibration is large when the screw shaft 12 is rotated at a high speed at the opposite end portion (the right end portion in FIG. 1) of the rotational drive portion of the screw shaft 12 where the second shaft support portion 31 is disposed. Therefore, the screw shaft 12 can be supported with a strong restraining force by installing the combination angular ball bearing 32 having a DB structure having a large moment load capacity.

  In the first embodiment, the collar 33 is inserted between the two single-row angular ball bearings 32a and 32b, and the distance between the operating points of the two bearings is further increased. Between the two single-row angular ball bearings 32 a and 32 b, a combination angular ball bearing 32 having a DB structure arranged in a back surface combination is disposed on one end side of the screw shaft 12, and the combination angular ball bearing 32 is further configured. By inserting the collar 33, the load capacity of the moment load can be further increased, and the screw shaft 12 can be supported with a strong restraining force.

  Further, in the second shaft support portion 31 according to the first embodiment, a linear motion guide mechanism 34 that allows displacement in the axial direction of the screw shaft 12 is installed outside the combination angular ball bearing 32. The linear motion guide mechanism 34 is arranged in the axial direction of the screw shaft 12 via a spline shaft 34a installed on the outer ring side of the combined angular ball bearing 32 and balls 34c which are a plurality of rolling elements with respect to the spline shaft 34a. And a spline nut 34b assembled so as to be reciprocally movable.

  The spline shaft 34a is a member having a substantially hollow cylindrical shape so that it can be stably fixed to the outer ring side of the combined angular ball bearing 32, and a rolling groove (not shown) for rolling the ball 34c is provided at an upper position. Is formed. A rolling groove (not shown) is formed so as to be parallel to the axial direction of the screw shaft 12. On the other hand, a spline nut 34b is disposed outside the spline shaft 34a so as to surround the entire outer peripheral surface of the spline shaft 34a. The spline nut 34b is also a member having a substantially hollow cylindrical shape, and is a rolling groove (not shown) for rolling the ball 34c at a position facing a rolling groove (not shown) formed on the spline shaft 34a. ) Is formed. Then, a plurality of balls 34c are incorporated in a rolling manner in a rolling path formed by rolling grooves (not shown) of the spline shaft 34a and rolling grooves (not shown) of the spline nut 34b. Yes.

  Further, a housing member 35 is installed on the outer side of the spline nut 34b, and the housing member 35 is a member that fixedly connects the spline nut 34b and the base member 11. That is, the housing member 35 and the spline nut 34b are fixedly installed on the base member 11 serving as an installation reference. On the other hand, the spline shaft 34a and the combined angular ball bearing 32, the collar 33, and the screw shaft 12 are fixed to these fixed members. Such a member can be moved in the axial direction of the screw shaft 12. Therefore, for example, even if thermal displacement occurs in the screw shaft 12, this thermal displacement can be released by the action of the linear motion guide mechanism 34. At the same time, the rigidity in the radial direction and the moment direction can be increased by the action of the combined angular contact ball bearing 32 and the collar 33 in addition to the linear motion guide mechanism 34, so that the rigidity value of the apparatus can be suitably improved. Become. Therefore, according to the drive screw shaft support device 10 according to the first embodiment, the critical rotational speed (natural frequency) of the screw shaft 12 can be greatly improved.

  Note that the linear motion guide mechanism 34 according to the first embodiment employs a configuration in which preload is applied to the plurality of balls 34c. Specifically, the clearance of the rolling path formed by the rolling groove (not shown) of the spline shaft 34a and the rolling groove (not shown) of the spline nut 34b is designed with a tolerance of zero dimension so that the rolling path can pass through. The diameter of the ball 34c is configured to be slightly larger than the path diameter. With this configuration, the rigidity value of the linear motion guide mechanism 34 can be further improved, and the critical rotational speed (natural frequency) of the screw shaft 12 can be greatly improved.

  In the linear motion guide mechanism 34 according to the first embodiment, the plurality of balls 34c are configured as finite strokes. It is preferable to configure the plurality of balls 34c as a finite stroke because clogging of the balls 34c due to repeated minute movements due to vertical vibration of the screw shaft 12 can be prevented.

  Furthermore, in the linear motion guide mechanism 34 according to the first embodiment, the number of balls 34c included in the linear motion guide mechanism 34 is four or more, or the multiple balls included in the linear motion guide mechanism 34 It is preferable to configure so as to satisfy one of two conditions that the ball center pitch of “outer-outer” of 34c is not less than three times the ball diameter. Note that “the“ outer-outer ”ball center pitch of the plurality of balls 34c included in the linear motion guide mechanism 34 is not less than three times the ball diameter” means that the plurality of balls 34c in FIG. FIG. 1 shows the condition that the distance between the center of a ball 34c and the leftmost ball 34c is at least three times the ball diameter. For example, in FIG. The distance between the ball centers of a certain ball 34c and the leftmost ball 34c is four times the ball diameter, indicating that the above condition is satisfied. The above-mentioned two conditions are obtained as empirical knowledge based on researches and experiments by the inventors, and the effect that the rigidity in the moment direction of the screw shaft 12 can be improved is obtained.

  In addition, about the 1st axial support part 21 which concerns on 1st embodiment, unlike the 2nd axial support part 31, the combination angular contact ball which consists of DF structure which has arrange | positioned two single row angular ball bearings 22a and 22b by front combination. A bearing 22 is arranged. As described above, the first shaft support portion 21 for rotatably supporting the installation side end portion (the end portion on the left side in FIG. 1) of the rotation drive unit (not shown) in the screw shaft 12 is a combination angular structure having a DF structure. The reason why the ball bearing 22 is configured is that high rigidity is not required as compared with the second shaft support portion 31. This configuration has also been obtained as empirical knowledge based on research and experiments by the inventors.

  The specific configuration of the drive screw shaft support device 10 according to the first embodiment has been described above. Next, a performance comparison result between the first embodiment confirmed by the present inventors and the prior art will be described. Here, FIG. 2 is a vertical cross-sectional side view showing the driving screw shaft support device 100 according to the prior art. Moreover, FIG. 3 is a figure which shows the measurement result of the natural frequency of 1st embodiment and a prior art. Further, FIG. 4 is a diagram showing the estimated dangerous rotation speed value calculated from the measurement result of the natural frequency shown in FIG.

  Inventors prepared the drive screw shaft support apparatus 100 which concerns on a prior art, in order to perform the performance evaluation of the drive screw shaft support apparatus 10 which concerns on 1st embodiment (refer FIG. 2). The drive screw shaft support device 100 according to the prior art is different in the configuration of the second shaft support portion 31 provided in the drive screw shaft support device 10 according to the first embodiment, and is not shown in the screw shaft 12. A bearing disposed at the opposite end (the end on the right side in FIG. 2) of the rotation drive unit is configured as a deep groove ball bearing 132. Further, there is no configuration corresponding to the linear motion guide mechanism 34 installed in the first embodiment.

In order to evaluate the performance of these two drive screw shaft support devices 10 and 100, first, the natural frequencies of the devices were measured. The result is shown in FIG. Here, in the graph shown in FIG. 3, the horizontal axis indicates the frequency [Hz], and the vertical axis indicates the value [m / s ² / N] obtained by dividing the force by the acceleration. In FIG. 3, the transfer function with the origin at the installation side end (the end on the left side in FIG. 1 and FIG. 2) of the rotation drive unit (not shown) in the screw shaft 12 was measured. As is apparent from FIG. 3, it can be seen that the peak position of the natural frequency is shifted to the high frequency side in the first embodiment compared to the prior art, and the natural frequency is improved.

  Further, in the graph shown in FIG. 4, the estimated dangerous speed calculated from the measurement result of the natural frequency shown in FIG. 3 is shown, and the screw shaft 12 is shown as the slider position [mm] on the horizontal axis. The position of the nut 13 with respect to is shown, and the converted speed V [mm / s] calculated based on the natural frequency is shown on the vertical axis. As for the slider position [mm] on the horizontal axis, the position of the nut 13 is moved from the “motor (rotation drive unit) side to the non-motor (rotation drive unit) side” from the left side to the center position in FIG. 4 is the “folding point” of the nut 13, and from the paper center position to the right side of FIG. 4 is “from the counter-motor (rotation drive unit) side”. The slider position [mm] when the position of the nut 13 is moved to the “motor (rotation drive unit) side” is shown.

  Furthermore, the calculation method of the conversion speed V [mm / s] shown on the vertical axis will be described. The natural frequency p [Hz] can be expressed by the following formula 1.

  Further, for the constant αl corresponding to the eigenvalue that is a variable included in the above formula 1, the boundary condition can be appropriately set by the mounting method of the screw shaft 12, but the inventors obtain the result shown in FIG. Therefore, in the calculation performed this time, the value shown in Table 1 below was adopted as the constant αl.

After calculating the natural frequency p [Hz] according to the above-described Equation 1 in which the constant αl shown in Table 1 is substituted, the calculated natural frequency p [Hz] is substituted into the following Equation 2; A critical rotational speed N [min ⁻¹ ] can be obtained.

Further, the critical speed V [mm / s] can be obtained by substituting the critical rotational speed N [min ⁻¹ ] calculated by the mathematical formula 2 into the following mathematical formula 3. In other words, the critical speed V calculated by Equation 3 is shown as the converted speed V [mm / s] that is the vertical axis of FIG.

  As is apparent from FIG. 4 created using the conversion speed V [mm / s] obtained by the calculation method described above, the first embodiment is converted at all slider positions compared to the prior art. The speed V [mm / s] shows a high value. As described above, from the verification results shown in FIGS. 3 and 4, it is possible to greatly improve the dangerous rotational speed (natural frequency) of the screw shaft 12 in the first embodiment as compared with the prior art. Became clear.

  The specific configuration of the drive screw shaft support device 10 according to the first embodiment and the effects thereof have been described above. Note that the scope of the present invention is not limited to the configuration of the drive screw shaft support device 10 according to the first embodiment illustrated in FIG. Variations can be employed. Then, next, the specific structure of the screw shaft support apparatus 50 for drive which concerns on 2nd embodiment is demonstrated using FIG. In FIG. 5, members that are the same as or similar to the members described in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted.

[Second Embodiment]
FIG. 5 is a longitudinal sectional side view for explaining a specific configuration of the drive screw shaft support device according to the second embodiment. The drive screw shaft support device 50 according to the second embodiment has a configuration in which a spring unit 51 is further added to the second shaft support portion 31 of the drive screw shaft support device 10 according to the first embodiment. It has become. The spring unit 51 of the second embodiment includes a spring housing 52 fixedly installed on the inner side wall surface of the housing member 35, and a coil spring 53 as an elastic body disposed in the spring housing 52. The pressing member 54 is arranged in the direction in which the elastic force of the coil spring 53 is exerted. Since the pressing member 54 is disposed between the coil spring 53 and the spline shaft 34 a fixed to the outer ring side of the combination angular ball bearing 32, the elastic force of the coil spring 53 is combined angularly via the pressing member 54. The outer ring side of the ball bearing 32 is pressed in the axial direction of the screw shaft 12.

  By arranging the spring unit 51 that exerts an elastic force as described above, the restraining force on the screw shaft 12 can be further improved. Therefore, according to the drive screw shaft support device 50 according to the second embodiment, the critical rotational speed (natural frequency) of the screw shaft 12 can be further greatly improved.

  The drive screw shaft support device 50 according to the second embodiment has been described above with reference to FIG. However, the present invention can adopt another form. Therefore, next, a specific configuration of the drive screw shaft support device 60 according to the third embodiment will be described with reference to FIG. In FIG. 6, members that are the same as or similar to the members described in the first and second embodiments described above are denoted by the same reference numerals and description thereof is omitted.

[Third embodiment]
FIG. 6 is a longitudinal sectional side view for explaining a specific configuration of the driving screw shaft support device according to the third embodiment. The drive screw shaft support device 60 according to the third embodiment is a modification to the first shaft support portion 21 of the drive screw shaft support device 10 according to the first embodiment. A configuration in which a collar 63 is inserted between the two single-row angular ball bearings 22a and 22b constituting the first shaft support portion 21 according to the embodiment is adopted. Thus, by adding the collar 63 to the member constituting the first shaft support portion 21 according to the third embodiment and arranging the two single-row angular ball bearings 22a and 22b so as to sandwich the collar 63, The advantage is that the distance between the operating points of the two bearings is increased, and the load capacity of the moment load is increased. The two single-row angular ball bearings 22a and 22b shown in FIG. 6 adopt an arrangement in which a collar 63 is inserted into the combination angular ball bearing 22 having a DF structure arranged in front combination. The arrangement of these two single-row angular ball bearings 22a and 22b can be configured as a combination angular ball bearing having a DB structure arranged in a rear combination.

  As described above, it is possible to further improve the restraining force on the screw shaft 12 by inserting and installing the collar 63 in the first shaft support portion 21 as well. Therefore, according to the screw shaft support device 60 for driving which concerns on 3rd embodiment, the dangerous rotational speed (natural frequency) of the screw shaft 12 can be improved further greatly.

  As mentioned above, although preferred embodiment of this invention was described, the technical scope of this invention is not limited to the range as described in the said embodiment. Various modifications or improvements can be added to the embodiment.

  For example, any rolling element can be used for the ball 34c of the linear motion guide mechanism 34 constituting the drive screw shaft support devices 10, 50, 60 according to the first to third embodiments described above. That is, all kinds of rolling elements such as rollers and rollers can be adopted for the plurality of rolling elements constituting the linear motion guide mechanism according to the present invention.

  It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

  DESCRIPTION OF SYMBOLS 10 Drive screw shaft support apparatus which concerns on 1st embodiment, 11 Base member, 12 Screw shaft, 13 Nut, 21 1st axial support part, 22 Combination angular contact ball bearing, 22a, 22b Single row angular contact ball bearing, 31 2nd Shaft support, 32 Combined angular contact ball bearing, 32a, 32b Single row angular contact ball bearing, 33 Collar, 34 Linear motion guide mechanism, 34a Spline shaft, 34b Spline nut, 34c Ball, 35 Housing member, 50 According to the second embodiment Screw shaft support device for driving, 51 Spring unit, 52 Spring housing, 53 Coil spring, 54 Press member, 60 Screw shaft supporting device for driving according to the third embodiment, 63 Collar, 100 Screw shaft support for driving according to the prior art Device, 132 deep groove ball bearing.

Claims (8)

A screw shaft;
A nut screwed onto the screw shaft;
A rotational drive unit installed on one end side of the screw shaft to rotationally drive the screw shaft;
A first shaft support portion rotatably supporting an installation side end portion of the rotation drive portion in the screw shaft;
A second shaft support portion that rotatably supports an end portion on the opposite side of the rotation drive portion of the screw shaft;
A screw shaft support device for driving comprising:
The screw shaft support device for driving, wherein the second shaft support portion includes a combination angular ball bearing having a DB structure in which two single-row angular ball bearings are arranged in a back combination. The drive screw shaft support device according to claim 1,
The second shaft support portion includes a linear guide mechanism that allows displacement in the axial direction of the screw shaft on the outer side of the combined angular ball bearing,
The linear motion guide mechanism is
A spline shaft installed on the outer ring side of the combined angular contact ball bearing;
A spline nut assembled to the spline shaft so as to reciprocate via a plurality of rolling elements;
A screw shaft support device for driving. In the drive screw shaft support device according to claim 2,
The drive shaft support device according to claim 1, wherein the linear motion guide mechanism is configured to apply a preload to the plurality of rolling elements. The drive screw shaft support device according to claim 2 or 3,
The screw shaft support device for driving, wherein the plurality of rolling elements included in the linear motion guide mechanism are configured as a finite stroke. In the screw shaft support device for driving according to any one of claims 2 to 4,
The drive screw shaft support device, wherein the number of rolling elements of the plurality of rolling elements included in the linear motion guide mechanism is four or more. In the screw shaft support device for driving according to any one of claims 2 to 4,
The plurality of rolling elements provided in the linear motion guide mechanism have an outer-outer rolling element center pitch of three or more times the diameter of the rolling element. In the drive screw shaft support device according to any one of claims 1 to 6,
A screw shaft support device for driving, wherein a collar is inserted between two single-row angular ball bearings constituting the combined angular ball bearing. In the drive screw shaft support device according to any one of claims 1 to 7,
A drive screw shaft support device comprising an elastic body that presses the outer ring side of the combined angular ball bearing in the axial direction of the screw shaft.

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