JP6200640B2 - Driving screw system with ball screw support unit - Google Patents

Description

  The present invention relates to a rotary driving screw system for linearly aligning cooperating members, such as translation nuts.

  The drive screw system is typically used to align a cooperating member, commonly referred to herein as a drive nut, in response to rotation of the drive screw.

  The speed of linear movement of the drive nut parallel to the rotation axis of the driving screw is directly proportional to the rotation speed of the driving screw. Therefore, in order to obtain a linear displacement as quickly as possible, it is desirable to rotate the driving screw as quickly as possible.

  However, the variable rotational speed of the driving screw generates vibrations, particularly when the rotational speed matches one of the natural frequencies of the driving screw system. Excessive vibration such as this results in noise and wears or damages the system. Specifically, the natural frequency of the drive screw system varies depending on the position of the nut, the diameter of the drive screw, and the length of the unsupported portion of the screw. The speed at which the driving screw can be rotated within a range where the driving screw does not reach the first natural frequency becomes lower as the diameter / length ratio of the driving screw is smaller. Therefore, the longer the driving screw, the lower the rotational speed needs to be maintained. Therefore, the speed at which the nut moves along the driving screw also decreases. In addition, axial compression loads applied to the drive screw system can cause buckling.

  In order to increase the effective length and rotational speed of the drive screw and increase the amount of axial compression load without causing buckling, US Pat. No. 5,531,557 discloses a drive screw system. It is suggested to provide a plurality of bearing assemblies arranged coaxially with each other to support the driving screw. That is, the bearing assembly automatically moves back and forth with the drive nut between the proximal and distal ends of the drive screw and automatically maintains a predetermined unsupported maximum length of the drive screw. It is supposed to be. Each bearing assembly includes two bearing supports that are connected to each other at regular intervals.

  With such additional bearing assembly, the lowest natural frequency of the system is increased. For this reason, a higher rotational speed is possible. However, this further bearing assembly vibrates and creates its own noise, especially when the driving screw changes direction. Furthermore, since the bearing assembly is free to move linearly along the drive screw, the residual vibration of the drive screw may cause intense and uncontrollable movement in one direction or another.

  In order to avoid such intense movement of the further bearing assembly, US Pat. No. 5,720,202 proposes to provide a rope and pulley system to couple the further bearing assembly with a drive nut. Has been. Here, the position of the bearing is always related to the position of the drive nut, so that the bearing is moved at half the speed of the drive nut. However, rope and pulley systems have been found to be unreliable over time. Also, these documents do not solve the problem that noise occurs when the driving screw changes direction.

The present invention aims to improve the reliability of the driving screw system. According to the first aspect of the present invention,
A stationary track,
A driving screw attached to the stationary track so as to rotate around a screw shaft;
In order to linearly displace parallel to the screw shaft according to the rotation of the driving screw, a nut that is screwed into the driving screw; and
And is capable of moving on the stationary track in parallel with the screw shaft, and includes at least one sliding bearing for supporting and guiding the driving screw in a radial direction,
The sliding bearing includes at least one first friction pad that is movable at least in a first direction that is a lateral direction of the screw shaft with respect to the sliding bearing, the friction pad, and the first friction pad with respect to the stationary track. A drive screw system is provided, characterized in that it has spring means for displacement in one direction.

  The repulsion between the plain bearing and the stationary track is compensated by this friction pad. For this reason, even if the tolerance of the stationary track is large, the sliding bearing can move smoothly and safely on the stationary track. The friction pad slides over a stationary track. Thanks to the provision of spring means, pressure is maintained in a controlled manner between the friction pad and the stationary track. This controlled pressure will control the friction between the friction pad and the stationary track. This contributes to stabilizing the position of the sliding bearing along the screw shaft.

  According to a preferred embodiment, the plain bearing comprises a first guide surface perpendicular to the screw shaft. The first guide surface guides the first friction pad and prevents the first friction pad from moving in a direction parallel to the screw shaft with respect to the sliding bearing. The first friction pad slides on the first guide surface and moves parallel to the first guide surface.

  According to a preferred embodiment, the sliding bearing comprises a second friction pad that is movable relative to the sliding bearing in a second direction that is opposite to the first direction, and the spring means comprises the second friction pad. The pad is displaced in the second direction with respect to the stationary track. For this reason, the sliding bearing is maintained without being repelled in the first direction and the second direction with respect to the stationary track.

The spring means includes a compression spring for displacing the first friction pad and the second friction pad in the first direction and the second direction, which are lateral directions, between the first friction pad and the second friction pad, respectively. May be included. This provides a very simple structure and the number of parts is minimized. According to a preferred embodiment, the compression spring is mounted between two parallel surfaces of the first friction pad and the second friction pad, whereby the first friction pad and the second friction pad are respectively The first guide surface and the second guide surface are oriented to be displaced. In one embodiment, the two parallel surfaces of the first friction pad and the second friction pad are perpendicular to the screw axis and the geometric plane including the first direction and the second direction, and It intersects one and second directions and the geometric plane that is oblique to the screw axis.

  According to a preferred embodiment, the stationary track is provided with a passage having two opposite sides parallel to the screw axis. The plain bearing is accommodated between the side surfaces, and the friction pad is supported on the side surfaces. The friction pad preferably slides against these sides.

  According to a further preferred embodiment, the first friction pad is movable with respect to the sliding bearing in a first direction and in a first vertical direction perpendicular to the screw axis, and the spring means comprises a first friction pad. The first vertical direction is displaced. The spring means may include a compression spring that acts between the sliding bearing and the first friction pad to displace the first friction pad in the first vertical direction.

  Similarly, the second friction pad may be movable relative to the sliding bearing in a second direction and a second vertical direction that is perpendicular to the screw axis, and the spring means moves the second friction pad to the second vertical direction. Displace in the direction. The spring means may include a compression spring that acts between the sliding bearing and the second friction pad to displace the second friction pad in the second vertical direction. The first vertical direction and the second vertical direction may be the same or opposite.

  The passage may comprise a further surface that supports the friction pad and is perpendicular to two opposite sides parallel to the screw axis. More particularly, the opposing parallel surfaces and further surfaces may form a U-shaped passage.

  The driving screw system may further include a second sliding bearing, and may further include a connecting rod for maintaining a constant distance between the first sliding bearing and the second sliding bearing. The first sliding bearing and the second sliding bearing are preferably similar members.

  According to another aspect of the invention, a plain bearing is provided for the drive screw system described above.

  Other advantages and features of the invention will become more apparent from the following description of specific embodiments of the invention, presented by way of non-limiting example and shown in the accompanying drawings.

  Throughout this specification and the drawings, the same reference numbers are used to indicate the same or similar elements of the various embodiments.

It is a figure which shows the driving screw system which concerns on one Embodiment of this invention. FIG. 2 is a cross-sectional view of the driving screw system of FIG. 1. FIG. 3 is a three-dimensional exploded view of the plain bearing of the driving screw system of FIG. 1. It is a three-dimensional exploded view of a plain bearing according to another embodiment of the present invention. It is a side view of the sliding bearing of FIG. FIG. 5 is a cross-sectional view of a drive screw system including the plain bearing of FIG. 4.

  Referring to FIG. 1, a drive screw system 10 includes a frame 12 made of an extruded aluminum profile. The frame 12 includes a central track 14 for receiving a drive screw 16 and two lateral tracks 18 disposed on each side of the central track 14. The driving screw 16 is provided to rotate about the screw shaft 20 in parallel to the central track 14 and the two lateral tracks 18 with respect to the stationary frame 12. Power is supplied to one end of the driving screw 16 by a motor (not shown), and the other end 22 is accommodated in a stationary bearing 24.

  A carriage 26 is attached on the frame 12. The carriage 26 is supported on a roller transporter 28 housed in two lateral tracks 18 of the frame 12. One roller transporter 28 is connected to the ball nut 30 via the side arm 31. The ball nut 30 is housed in the central track 14 and is engaged with the driving screw 16 in a screwed manner. The ball nut 30 is parallel to the screw shaft in accordance with the rotation of the driving screw 16 in the front-rear direction without rotating. To move.

  The driving screw system 10 further includes a pair of plain bearings 32. Each sliding bearing 32 is provided with a cylindrical through-hole 33, and these holes are preferably provided in a line with a bearing cylinder having the same diameter as the cover of the driving screw. The cylindrical through-hole 33 is for receiving the driving screw 16 in a sliding contact and supporting the driving screw 16 in the radial direction.

  Each plain bearing 32 is guided in the central track 14 in the front-rear direction. In order to compensate for repulsion with the frame and the like, each sliding bearing 32 is provided with two friction pads 34 facing each other. These friction pads 34 are movable relative to the sliding bearing 32 towards the upper wall 14.1 of the central track 14 and in the longitudinal direction towards the adjacent side wall 14.3 of the central track 14. . More specifically, each friction pad 34 has a generally triangular columnar shape, with a somewhat triangular horizontal upper base surface 34.1 facing the upper wall 14.1 of the central track. The triangular lower base surface 34.2 is parallel to the upper base surface 34.1 and faces the horizontal surface 32.2 of the sliding bearing 32, the vertical side surface 34.3 being adjacent to the central track Opposite the side wall 14.3. A vertical inner surface 34.4 having an angle between 30 ° and 60 ° with respect to the screw axis, preferably 45 °, and a vertical guide surface 34.5 perpendicular to the screw axis guide the friction pad 34. It faces the guiding wall 32.5. The guide wall 32.5 perpendicular to the screw shaft 20 may be provided with a transverse groove 32.51 and the guide surface 34.5 may have a corresponding protruding strip 34.51. This protruding strip 34.51 is inserted into the lateral groove 32.51 with a slight gap, guiding the friction pad 34 in the lateral direction and the "vertical" direction of the friction pad 34, i.e. the lateral direction and The free movement in the direction perpendicular to the screw shaft 20 is restricted.

  The compression spring 36 is attached between the inner walls 34.4 of these two friction pads 34. The spring 36 applies a spring force to each friction pad 34 in a direction substantially perpendicular to the inner wall 34.4. Therefore, the spring force has a component perpendicular to the guide wall 32.5 and a component parallel to the guide wall 32.5. Thus, each friction pad 34 is supported by a corresponding guide wall 32.5 and is elastically displaced laterally toward the adjacent side wall 14.3 of the central track.

  A compression spring 38 is mounted between the lower base surface 34.2 of each friction pad 34 and the “horizontal” surface 32.2 of the sliding bearing 32 so that the friction pad 34 is connected to the upper wall of the central track 14. It is elastically displaced toward 14.1.

  The plain bearing 32 including the friction pad 34 and the springs 36 and 38 constitutes one subunit, and can be easily assembled in advance. When this sliding bearing 32 is inserted into the central track 14 in the operating position, the friction pad 34 is supported on the corresponding side wall 14.3 and the upper wall 14.1 of the central track 14 and the lower surface of the sliding bearing 32. 32.6 is supported by the lower wall 14.6 of the track 14.

  The driving screw 16 preferably includes at least two such plain bearings 32. The plain bearing 32 is connected to each other by a pair of fixed rods 40.

  In order to explain the operation of the driving screw system, the nut 30 constituting the subunit, the transporter 28, and the carriage 26 are at an intermediate point from both ends of the driving screw, and two sliding bearings 32 are provided from the nut 30. It is assumed that the sliding bearings 32 are arranged at equal intervals, and that each sliding bearing 32 is arranged between the nut 30 and one of the two ends of the driving screw 16. When power is applied to the motor, the drive screw 16 rotates about the screw shaft 20 and causes the nut 30, the transporter 28, and the carriage 26 to move to the first of the two ends of the drive screw 16. Move in one direction. Initially, these two sliding bearings 32 remain stationary and the driving screw 16 rotates into the through-hole 33 of the sliding bearing 32 that radially supports the driving screw 16 by sliding contact. To do. When the nut moves toward the first end of the driving screw 16, it reaches a first sliding bearing of the two sliding bearings 32 at a certain stage, and moves the first sliding bearing 32 along the driving screw 16. Thus, it is pushed toward the first end of the driving screw 16. The second sliding bearing 32 connected to the first sliding bearing via the rod 40 is forcibly pulled. When the direction of rotation of the driving screw is reversed, the nut 30 moves in a different direction toward the second sliding bearing 32 and the second end of the driving screw 30. These two sliding bearings 32 remain stationary until the nut 30 reaches the second sliding bearing 32. When the nut 30 reaches the second sliding bearing 32, the second sliding bearing 32 is pushed toward the second end of the driving screw 30 in front of the nut 30, and the first sliding bearing 32 is forced. Will be pulled.

  Such linear movement of the plain bearing 34 ensures that the driving screw 16 can be used over its entire length.

  The tension of the compression springs 36, 38 is selected so that the sliding bearing 32 does not move in the radial direction of the track.

  While the above example describes a preferred embodiment of the present invention, it should be noted that various other configurations of the drive screw system 10 can be envisaged within the scope of the appended claims.

  The terms “horizontal” and “vertical” directions are used on the premise that the longitudinal direction of the driving screw is horizontal. However, it will be apparent that the drive screw system may be oriented in any direction, eg, a vertical longitudinal direction.

  Multiple pairs of plain bearings may be provided.

  The springs 36 and 38 may be of any kind, for example, a leaf spring. Instead of one spring, two springs may be used to propel the two friction pads separately toward the two side walls of the track. Conversely, a single spring may be used to propel the rebound compression pad laterally and upward.

  Here, another embodiment of the slide bearing for the driving screw assembly will be described with reference to FIGS. The sliding bearing is provided with a cylindrical through hole for receiving and guiding the driving nut 16. As shown in FIG. 6, the plain bearings are housed in a central track 14 of the frame 12 of the drive screw system 10, similar to the drive screw system of FIG.

  The sliding bearing 32 is also provided with one friction pad 34. The friction pad 34 is movable relative to the sliding bearing 32 toward the upper wall 14.1 of the central track 14 in a direction perpendicular to the through hole. The friction pad 34 has a generally parallelepiped shape, with the horizontal upper base surface 34.1 facing the upper wall 14.1 of the central track and the lower base surface 34.2. Parallel to the upper base surface 34.1 and facing the horizontal surface 32.2 of the sliding bearing 32, the two vertical side surfaces 34.3 facing the adjacent side wall 14.3 of the central track. The two vertical guide surfaces 34.5 are perpendicular to the screw shaft and face the guide wall 32.5 of the friction pad 32. The guide wall 32.5 perpendicular to the screw shaft 20 may be provided with a transverse groove 32.51 and the guide surface 34.5 may have a corresponding protruding strip 34.51. This protruding strip 34.51 is inserted into the transverse groove 32.51 with a slight gap, guiding the friction pad 34 laterally, and the "vertical" direction of the friction pad 34, i.e. the lateral direction and The free movement in the direction perpendicular to the screw shaft 20 is restricted. The upper base surface 34.1 is provided with a groove 34.11. The groove 34.11 is aligned with a similar groove 32.11 provided in the sliding bearing and is provided parallel to the longitudinal direction of the driving screw. These grooves 34.11, 32.11 cooperate with guide ribs 14.11 projecting from the upper wall 14.1 of the central track 14 and extending in the longitudinal direction of the driving screw. It should be noted that slight play is ensured between the side surface of the guide rib 14.11 and the side surface of the groove 34.11, and the leading end of the guide rib 14.11 and the grooves 32.11, 34. 11 is that a larger gap is left between the bottom of 11.

  A pair of compression springs 38 are provided between the lower base surface 34.2 of each friction pad 34 and the “horizontal” surface 32.1 of the sliding bearing 32, so that the friction pad 34 can be It is elastically displaced toward the upper wall 14.1.

  The slide bearing 32 including the friction pad 34 and the spring 38 constitutes one subunit and can be easily assembled in advance. When the sliding bearing 32 is inserted into the central track 14 in the operating position, the friction pad 34 is supported on the upper wall 14.1 of the central track 14 and the lower surface 32.6 of the sliding bearing 32 is Supported by the lower wall 14.6. The lateral position of the sliding bearing 32 and the lateral position of the friction pad are defined by the guide ribs 14.11 and the grooves 32.11, 34.11.

Claims (10)

A stationary track (14);
A driving screw (16) attached to the stationary track (14) to rotate about a screw shaft (20);
A nut (30) engaged with the driving screw (16) in a screwing manner so as to be linearly displaced parallel to the screw shaft (20) in response to the rotation of the driving screw (16);
At least one first sliding bearing (32) which is movable on the stationary track (14) parallel to the screw shaft (20), and which supports and guides the driving screw (16) in a radial direction; , And
The first sliding bearing (32)
At least one first friction pad (34) movable at least in a first lateral direction, which is a direction across the screw shaft (20), with respect to the first sliding bearing (32);
A second friction pad (34) that is movable relative to the first sliding bearing (32) in a second lateral direction that is opposite to the first lateral direction ;
The first friction pad (34) is displaced in the first lateral direction with respect to the stationary track (14), and the second friction pad (34) is displaced with respect to the stationary track (14) in the second lateral direction. Spring means (36, 38) for displacing in a direction,
The first sliding bearing (32) guides the first friction pad (34), and the first friction pad (34) moves the screw shaft (20) relative to the first sliding bearing (32). A first guide wall (32.5) perpendicular to the screw shaft (20) is provided.
The first sliding bearing (32) guides the second friction pad (34), and the second friction pad (34) moves the screw shaft (20) relative to the first sliding bearing (32). A second guide wall (32.5) parallel to the first guide wall (32.5),
The spring means (36, 38) are compression springs for displacing the first friction pad (34) and the second friction pad (34) in the first lateral direction and the second lateral direction, respectively. Including between the first friction pad (34) and the second friction pad (34).
In the compression spring, the first friction pad (34) and the second friction pad (34) are respectively against the first guide wall (32.5) and the second guide wall (32.5). Drive screw system (10), characterized in that it is provided between two parallel surfaces of the first friction pad (34) and the second friction pad (34) oriented to be displaced. . The stationary track (14) includes a passage having two opposing side walls (14.3) parallel to the screw shaft (20), and the first sliding bearing (32) 2. Driving according to claim 1, characterized in that it is accommodated between the side walls (14.3) and the first and second friction pads (34) are supported by the two side walls (14.3). Screw system (10). The first friction pad (34) is movable relative to the first sliding bearing (32) in a first vertical direction perpendicular to the first lateral direction and the screw shaft (20), and the spring 3. A driving screw system (10) according to claim 1 or 2 , characterized in that the means (36, 38) displace the first friction pad (34) in the first vertical direction. The spring means (36, 38) is disposed between the first sliding bearing (32) and the first friction pad (34) to displace the first friction pad (34) in the first vertical direction. 4. The drive screw system (10) according to claim 3 , characterized in that it comprises a compression spring acting in The second friction pad (34) is movable relative to the first sliding bearing (32) in a second vertical direction perpendicular to the second lateral direction and the screw shaft (20), and the spring 5. A driving screw system (10) according to claim 3 or 4 , characterized in that the means (36, 38) displace the second friction pad (34) in the second vertical direction. The spring means (36, 38) is disposed between the first sliding bearing (32) and the second friction pad (34) to displace the second friction pad (34) in the second vertical direction. Drive screw system (10) according to claim 5 , characterized in that it comprises a compression spring acting in 7. The driving screw system (10) according to claim 5 or 6 , characterized in that the first vertical direction and the second vertical direction are the same. The passage comprises a further wall (14.1) parallel to the screw shaft (20) and perpendicular to the opposing side walls (14.3), the first and second friction pads 8. Drive screw system (10) according to claim 7, when citing claim 2 , characterized in that (34) is supported on said further wall (14.1 ). It further comprises a second sliding bearing (32) and a connecting rod (40) for maintaining a constant distance between the first sliding bearing (32) and the second sliding bearing (32). to, drive screw system according to any one of claims 1-8 (10). The first slide bearing (32) and the second sliding bearing (32) is characterized by a similar member, drive screw system according to claim 9 (10).

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