JPH02173453A - Rolling differential screw feed mechanism - Google Patents

Abstract

PURPOSE:To enable a lead to be set smaller than a pitch of a drive screw by forming mutually meshing external threads of a roller screw and a drive screw shaft in a reverse thread further the roller screw larger in its effective size than 1/2 the effective size of the drive screw. CONSTITUTION:Even when an effective size D of an external thread 27 in a roller screw 28 is formed larger than 1/2 the effective size (d) of an external thread 12 in a drive screw shaft 13 further smaller than the effective size (d), that is, in a relation where d/2<D<d, a feed can be performed by a lead smaller than a pitch (p) of the external thread 12. For instance, when assumed a relation setting pitches (p), P of the external threads 12, 27 to p=P=1.5mm, effective size (d) of the external thread 12 to d=15mm and the effective size D of the external thread 27 to D=14mm, a lead x otains a relation where x=15(1-15/14+1)=-0.10714 0.1mm from an expression x=p(s+d/D.S). Now when the effective size D of the external thread 27 is equalized to the effective size (d) of the external thread 12, the lead can be obtained to 0.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention is directed to a rolling differential screw feed I! that converts rotational motion of a drive screw shaft into linear motion. Regarding the structure.

For example, it can be used as a feeding mechanism for tables and heads of measuring machines, machine tools, etc.

[Prior Art] In general, feed mechanisms that convert rotational motion into linear motion can be classified into the following three types: A: sliding screw, B: rolling screw, and C: non-contact screw6. A: A sliding screw has a structure that combines a normal screw shaft and a nut, and is used in micrometer spindle feeding mechanisms, etc.

B:Korokari screws are also available in ■hole screw type,
■Can be divided into planetary roller screw type. B-
(2): The pole nozzle type has a structure in which a plurality of balls are arranged between the screw shaft and the nut, and these balls circulate within the neck 1 as the screw shaft rotates. B-■: The planetary roller screw type has a structure in which multiple planetary rollers are placed between the screw shaft and the nut to mesh with them, and the planetary rollers revolve around the screw shaft as the screw shaft rotates. .

C: A non-contact screw has a structure in which air is interposed between the screw shaft and the neck 1, as typified by a static pressure screw.

[Invention or problem to be solved] Types A to C described above have the following drawbacks.

A: Sliding screw types are widely used because of their simple structure, but they have problems in terms of efficiency and durability because the contact surfaces between the screw shaft and the nuts 1 - slip. Further, the amount of movement of the nut per rotation of the screw shaft, ie, the lead, is the thread pitch of the screw shaft.

B-■ The two-hole screw type is mainly used in machine tools because of its high efficiency, or it has problems such as vibration and noise due to ball circulation, and difficulty in separating the screw shaft and nut. There is a problem with that. Further, the lead is the thread pitch of the screw shaft.

B-■: The planetary roller screw type is often used as a high-speed precision feed mechanism in precision machine tools due to its large load capacity, or its structure is complex because it requires at least three planetary rollers. There is a problem. Moreover, since these planetary rollers are structured to revolve around the screw shaft, there is a problem that the feeding mechanism itself becomes large. Also, although the lead can be changed by changing the number of threads on the screw shaft and nut, drastic changes cannot be expected.

C: Since the non-contact screw type requires air to be interposed between the screw shaft and the nut, air supply is essential.

SUMMARY OF THE INVENTION An object of the present invention is to provide a rolling differential screw feeding mechanism that solves the problems of conventional screw feeding mechanisms. In other words, it is highly efficient and durable, and
It is an object of the present invention to provide a rolling differential screw feed am that can easily and miniaturize the J7f4 feeder and, in particular, can set the lead to a minute lead smaller than the pitch of the male screw of the drive screw shaft.

In the invention, the effective diameter of the male thread of the roller screw is D,
When the effective diameter of the male thread of the drive screw shaft is d, it is characterized in that it is formed so that D>d.

[Means for Solving the Problem] In the invention described in claim 1, a drive screw shaft having a male thread on the outer peripheral surface is provided on one of the two relatively movable members so as to be rotatable along the relative movement direction. At the same time, on the other of the two relatively movable members, a roller screw having a male thread having the same pitch as the male thread of the drive screw shaft is meshed with the male thread of the drive screw shaft and follows the rotation of the drive screw shaft. The male thread of the roller screw and the male thread of the drive screw shaft are oppositely threaded to each other, and the effective diameter of the male thread of the roller screw is larger than 1/2 of the effective diameter of the male thread of the drive screw shaft. In the invention as set forth in claim 2, which is characterized in that, when the drive screw shaft is rotated, two members are formed via the roller screw meshed with the drive screw shaft. moves relatively. At this time,
When the drive screw shaft rotates, the roller screw meshed with the drive screw shaft also rotates due to friction between the two members, so the amount of relative movement between the two members is not only the amount of movement due to the rotation of the drive screw shaft. It is determined by the relative relationship with the amount of rotation of the roller screw.

Therefore, this point will be specifically explained using FIG. 1. As shown in FIG. 1, a movable member 6 is provided so as to be movable in the axial direction of a drive screw shaft 2 having a male thread 1 on its outer peripheral surface, and a male thread 3 that meshes with the male thread 1 at the same pitch is provided on the movable member 6. The roller screw 4 is provided so as to be able to roll and rotate following the rotation of the drive screw shaft 2, and when the drive screw shaft 2 is rotated by, for example, a motor 5, the movable member 6 is moved in the axial direction of the drive screw shaft 2. Ru.

At this time, when the drive screw shaft 2 rotates, the roller screw 4 also rotates due to friction with the drive screw shaft 2, so the amount of movement of the movable member 6 is not only the amount of movement due to the rotation of the drive screw shaft 2; It is determined by the relative relationship with the amount of rotation of the roller screw 4.

Here, if the amount of movement due to the rotation of the drive screw shaft 2 and the amount of movement due to the rotation of the roller screw 4 are in the same direction, the lead of the entire mechanism (the amount of movement of the movable member 6 per one rotation of the drive screw shaft 2 ) will increase, and if it is in the opposite direction, the lead will decrease.

Now, the pitch of male screws 1 and 3 is p, P, the effective diameter of male screw 1 (twice the distance from the axis of drive screw shaft 2 to the point where it contacts roller screw 4) is d, and the effective diameter of male screw 3 is (roller screw 4). (twice the distance from the axis of the screw 4 to the point where it contacts the drive screw shaft 2) is D, and the number of threads of each of the drive screw shaft 2 and the roller screw 4 is SS. However, s and S are - when the screw direction is right-handed, and - when the screw direction is left-handed.

Under this condition, the amount of movement when the drive screw shaft 2 rotates once is ps. At that time, since the roller screw 4 rotates d/D, the amount of movement due to the rotation of the roller screw 4 is d/D.
-pS. Therefore, the lead 8X for the entire mechanism is Δx=p(s-1-d/D-S)=-(1).

Therefore, from equation (1), for example, when male threads 1 and 3 are both one thread, male threads 1.3 are opposite threads, and the effective diameter of male thread 3 is 1/2 of the effective diameter d of male thread 1. It can be seen that if the lead ΔX is made larger, the lead ΔX can be set to a minute lead smaller than the pitch of the male thread of the drive screw shaft 2.

For example, the pitch P of the male thread 1 of the drive screw shaft 2 and the male thread 3 of the roller screw 4 is p=P=1°5 [mm], and the effective diameter d of the male thread 1 of the drive screw shaft 2 is d=15 [mm]. ], s=1.5--1, the number of threads is 1, the thread direction is reversed, and the effective diameter of the roller screw 4 is changed, the lead ΔX has the tendency shown in Fig. 2. Become.

Therefore, in the invention described in claim 1, the male thread of the roller screw and the male thread of the drive screw shaft are opposite to each other, and
Since the effective diameter of the male thread of the roller screw is larger than 1/2 of the effective diameter of the male thread of the drive screw shaft, the lead can be set to a minute lead smaller than the pitch of the male thread of the drive screw shaft. Furthermore, since roller screws roll and rotate following the rotation of the drive screw shaft, they are superior in efficiency and durability compared to sliding screws.Furthermore, only one roller screw is required and the structure does not revolve. Structurally, it is simple and can be miniaturized.

Further, in the invention described in claim 2, since the effective diameter of the male thread of the roller screw is larger than the effective diameter of the male thread of the drive screw shaft, the lead is larger than O and smaller than the pitch of the male thread of the drive screw shaft. In this state, the rotational direction component of the force other than the frictional force exerted by the threads of the roller screw is in the direction of rotating the roller screw, so the roller screw rolls regardless of the frictional force. Therefore, the lead can be stabilized.

[Example] Hereinafter, the present invention will be explained in detail based on examples.

Figures 3 to 6 show examples of the first real bear in which u1 falls. In this embodiment, the present invention is applied to a table feeding device, and as shown in FIG. 3, a table 21 is provided so as to be movable back and forth in the left and right directions in FIG. 3 relative to the bed 11.

One side of these two relatively moving members, here the bed 1
On the 1 side, there is a drive screw shaft 13 having a male thread 12 on the outer peripheral surface.
It is rotatably provided along the reciprocating direction of the table 21. The male thread 12 has a pitch of p, an effective diameter of d, and one right-handed thread, that is, s=1. Drive screw shaft 1
3 is entirely made of magnetic material, and
Both ends are rotatably supported by brackets 14 (the left end in FIG. 3 is omitted) provided on the bed 11, and
It is rotationally driven by a motor 15 connected to one end.

On the other hand, on the table 21 side, as shown in FIGS. 4 and 5, a support member 24 made of a non-magnetic material is attached via a leaf spring 23. The leaf spring 23 is fixed to the table 21 via the mounting base 22 at its base end, and is elastically deformable at its distal end, that is, the support member 24 side in a direction perpendicular to the axis of the drive screw shaft 13. It has become.

Side plates 2 made of magnetic material are provided on both sides of the support member 24 side.
5A and 25B are fixed. Both side plates 25A, 25B
In between, a roller screw 28 made of a non-magnetic material and having a male thread 27 having the same pitch as the male thread 12 of the drive screw shaft 13 is connected to the male thread 12 of the drive screw shaft 13 via a support shaft 26 made of a non-magnetic material. It is provided so that it can roll and rotate following the rotation of the drive screw shaft 13 while being engaged with the drive screw shaft 13. In addition, the drive screw shaft 13 is passed from the side plate 25A to the side plate 2.
A permanent magnet 29 forming a magnetic circuit returning to 5B is attached.

A radial bearing 31 is interposed between the roller screw 28 and the support shaft 26. Furthermore, thrust bearings 32 are interposed between both end surfaces of the roller screw 28 and each side plate 25A, 25B.

Here, the male thread 27 formed on the roller screw 28 and the male thread 12 formed on the drive screw shaft 13 have pitches P, P
are the same (P=p), but are formed as single thread threads with opposite thread directions (S=-1, 5=1). That is, the male thread 12 is formed with one right-hand thread, and the male thread 27 is formed with one left-hand thread. Moreover, the effective diameter of the male thread 27 is slightly larger than the effective diameter d of the male thread 12.

In addition, the thread shape of the male thread 12.27 is shown in Fig. 6 (A).
As shown in the figure, they are each formed in an arcuate shape that makes point contact on each other's effective circles. In this case, as shown in FIG. 6(B), one of the male threads 12 and 27, for example, the male thread 27, has a triangular thread shape, and the other, that is, the male thread 12, has a triangular thread shape. It may also be an arcuate surface that makes point contact with the oblique side.

Next, the operation of this embodiment will be explained.

Drive screw shaft 13 and side plate 25A are connected by two permanent magnets.
Since a magnetic circuit is formed between the drive screw shaft 13 and the roller screw 25B, the magnetic force of the magnetic circuit causes the drive screw shaft 13 and the roller screw 2 to
8 are pressed against each other. In other words, this pressing force provides a preload for pressing the roller screw 28 against the drive screw shaft 13.

In this state, when the drive screw shaft 13 is rotated by the drive of the motor 15, the male thread 1 of the drive screw shaft 13 is rotated.
2 and the male thread 27 of the roller screw 28 are in mesh with each other, so the roller screw 2 follows the rotation of the drive screw shaft 13.
8 is moved in the axial direction of the drive screw shaft 13 while rolling and rotating.

In other words, the table 21 is moved. At this time, the male screws 12 and 27 are twisted in opposite directions and are slightly larger than the effective diameter of the male screw 27 or the effective diameter d of the male screw 12, so the table 21 is connected to the table 2 with a minute lead that is much smaller than the pitch p of the male screw 12. is moved.

For example, the pitch p of male thread 12.27, P is pP=1
, 5 [rnm], the effective diameter d of the male thread 12 is d15
[Same] The effective diameter of the male screw 27 is D-16 [mm']
Then, the lead ΔX is Δx=1.5 from equation (1).
(115/16X1) 0.09375', 0.1 [mm].

Therefore, according to this embodiment, the drive screw shaft 1 is attached to the bed 11.
3, a roller screw 28 is provided on the table 21 so as to be able to roll and rotate following the rotation of the drive screw shaft 13, and the male thread 12 of the drive screw shaft 13 and the male thread 27 of the roller screw 28 are oppositely threaded to each other. In addition, since the effective diameter of the male thread 27 of the roller screw 28 is made larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, the table 21 is rotated by rotation of the drive screw shaft 13 with a lead smaller than the pitch p of the male thread 12. can be moved.

In particular, since the effective diameter D of the male thread 27 of the roller screw 28 is formed to be slightly larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, the table 21 can be moved with a minute lead that is much smaller than the pitch p of the male thread 12. Can be done. For example, the pitch p of the male thread 1227 is p = P = 1
, 5 [mm], the effective diameter d of the male thread 12 is d=15
[mm], the effective diameter of the male thread 27 is D = 16 [mm], and the lead ΔX is the pitch P of the male thread 12 = 1.5 [mm].
The table 21 can be moved with a minute lead of about 1/15 of rnm, that is, 0.1 [mm].

Moreover, since the effective diameter of the male thread 27 of the roller screw 28 is made larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, the lead is larger than O and the pitch p of the male thread 12 is larger than the effective diameter d of the male thread 12 of the drive screw shaft 13.
become smaller. In this state, as shown in FIG. 10, due to the rotation of the drive screw shaft 13, the roller screw 28 is subjected to a force C in the moving direction, a force trying to separate from the drive screw shaft 13, and a force in the rotation direction. If the effective diameter of the 60-round screw 28 that generates is smaller than the effective diameter d of the drive screw shaft 13, the force in the rotational direction becomes F, which is opposite to the rotational direction of the roller screw 28, but the effective diameter or the effective diameter If it is larger than d, the force in the rotational direction is E, that is, in the same direction as the rotational direction of the roller screw 28, so there is no tendency for it to slip, and the lead becomes more stable.

In addition, the male thread 27 of the roller screw 28 and the drive screw shaft 1
Since the thread shapes of the male screws 12 in No. 3 are both arcuate, or one is triangular and the other is arcuate, the drive screw shaft 13 and roller screw 28 are always brought into point contact on an effective circle. I can do it. When the point where the drive screw shaft 13 and the roller screw 28 touch, that is, the effective diameter changes,
(1) Since the road ΔX fluctuates, the drive screw shaft 1
3 and the roller screw 28 can always be brought into point contact on an effective circle, which can stabilize the lead ΔX.

In addition, since the roller screw 28 rotates following the rotation of the drive screw shaft 13, that is, the contact surfaces are not in sliding contact as in conventional sliding screws, but in rolling contact, resulting in high efficiency and less wear and tear. It also has an excellent effect on durability.

In addition, since only one roller screw 28 is required and it is an addendum that does not revolve around the drive screw shaft 13, it is structurally simple and can be miniaturized. In other words, in the case of a planetary roller screw, multiple planetary rollers are required, and these planetary rollers revolve around the drive screw shaft, making it structurally complex and large. However, in the case of this embodiment, since it is different from these, the structure can be simplified and miniaturized.

Further, since the roller screw 28 and the drive screw shaft 12 can be easily separated, assembly and disassembly are also easy. In this respect, in the case of a ball screw, it is difficult to separate the shaft and nut.

In addition, the drive screw shaft 12 and the side plate 25 are connected to each other by the permanent magnet 29.
A and 25B are configured to form a magnetic circuit, and the magnetic force of this magnetic circuit is used to obtain a preload for pressing the roller screw 28 against the drive screw shaft 13. using the roller screw 28 to drive the screw shaft 1.
There is an advantage that there is no need to deal with the reaction force that occurs when pressing 3.

In the first embodiment, a magnetic circuit is formed between the drive screw shaft 13 and the side plates 25A and 25B by the permanent magnet 29, and the roller screw 28 is attached to the drive screw shaft 13 using the magnetic force of this magnetic circuit. In addition to obtaining a preload for pressing, elastic deformation pressure, stress of a spring or a piezoelectric element, etc. may be used.

Further, in the above embodiment, the radial bearing 31 and the thrust bearing 32 are used for the roller screw 28, or an angular ball bearing, a pivot ball bearing, or the like may be used.

. A second embodiment of the direct-lambration system is shown in FIGS. 7 to 9. In the explanation of these figures, the same constituent elements as those of the first embodiment are given the same reference numerals, and the explanation thereof will be omitted.

In this embodiment, three roller screws 28A having a male screw 27 having the same pitch as the male screw 12 of the drive screw shaft 13 are provided on the table 21 side (not shown) via a holder 41;
28B and 28C are provided so that they can roll and rotate following the rotation of the drive screw shaft 13 in a state where they are meshed with the male thread 12 of the drive screw shaft 13.

Each roller screw 28A, 28B, 28C is connected to the boulder 4.
The drive screw shafts 13 are respectively rotatably supported at positions spaced apart by 120 degrees around the drive screw shaft 13. Furthermore, the male threads 27 formed on the outer peripheral surface of each of the roller screws 28A, 28B, and 28C are opposite threads to the male threads 12 of the drive screw shaft 13, and have an effective diameter slightly larger than the effective diameter d of the male threads 12. has been done.

The holder 41 is formed into a cylindrical shape having a through hole 42 in the center through which the drive screw shaft 13 is inserted.

Further, in the peripheral wall thereof, a slit 4 is formed that reaches from the outer circumferential surface to the front side of the through hole 42, leaving a thin wall portion between the through hole 42 and the peripheral wall.
3 is formed, and a slot 44 extending from the through hole 42 to the outer peripheral surface is formed at a position away from the slit 43. A bolt 45 is screwed together with a slotted groove 44 in between. Therefore, when tightening the pole I-45, the diameter of the holder 41 is reduced by the thin wall portion of the slit 43. In other words, each roller screw 28A, 28B
, 28B are meshed with the male thread 12 of the drive screw shaft 13 while being given the necessary preload (pressure).

Therefore, according to this repair example, in addition to the effects described in the first embodiment, since the three roller screws 28A, 28B and 280 are provided at equal intervals across the drive screw shaft 13,
Even relatively heavy tables can be moved reliably.

In addition, in each of the above embodiments, the male thread 12 of the drive screw shaft 13
is a right-hand thread, roller screws 28, 28A28B, 28C
Although the male thread 27 is a left-handed thread, the opposite may be used. In short, the male screw 12 of the drive screw shaft 13 and the roller screws 28, 28
It is sufficient if the male threads 27 of A, 28B, and 28C are opposite to each other.

Further, in each of the above embodiments, the roller screws 2828A, 28
The effective diameter of the male thread 27 in B and 28C is larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, that is, D>d.
Even if the diameter is larger than 1/2 and smaller than the effective diameter d, that is, d/2 and D<d, it is only possible to feed with a lead smaller than the pitch p of the male screw 12.

For example, the pitch p of male thread 12.27, P is pP=1
, 5 [Inm], the effective diameter d of the male thread 12 is d15
[+nn+], the effective diameter of the male screw 27 is D-14 [mm
], the lead ΔX is calculated from equation (1) as Δx=15
(1-15/14X1) =-0,10714 0,1[n+nl]. By the way, the effective diameter of the male thread 27 is the male thread 12.
If the effective diameter d is made the same as the effective diameter d, the lead can be set to 0.

Further, in each of the above embodiments, the male thread 12 and the male thread 27
The number of threads of the threads is not limited to this.

Note that the present invention is not limited to the table feeding device described in the above embodiment, but may also be applied to a column or spade of a machine tool, for example, and can be applied to general feeding mechanisms of two members that move relative to each other.

[Effect of the invention] In the invention described in claim 1, the male thread of the roller screw and the male thread of the drive screw shaft are opposite to each other, and the effective diameter of the male thread of the roller screw is equal to the effective diameter of the male thread of the drive screw shaft. 1
Since the pitch is larger than /2, the lead can be set to a minute lead smaller than the pitch of the male thread of the drive screw shaft.

Furthermore, since roller screws roll and rotate following the rotation of the drive screw shaft, they are superior in efficiency and durability compared to sliding screws.Furthermore, only one roller screw is required and the structure does not revolve. Structurally, it can be easily miniaturized.

Further, in the invention described in claim 2, the lead is larger than 0 and smaller than the pitch of the male thread of the drive screw shaft.

In this state, the rotational direction component of the force other than the frictional force applied to the threads of the roller screw is in the direction that rotates the roller screw, so the roller screw rolls regardless of the frictional force. Therefore,
The lead can be stabilized.

[Brief explanation of the drawing]

Figure 1 is a diagram for explaining the technical basis of the present invention, Figure 2 is a diagram for explaining the technical basis of the present invention.
The figure shows the lead when the thread direction of the male thread of the roller screw is reversed with respect to the male thread of the drive screw shaft and the effective diameter is changed. 3 to 6 show a first embodiment of the present invention, in which FIG. 3 is a front view showing the overall configuration, FIG. 4 is a side view, FIG. 5 is a perspective view, and FIG. A) and (B) are diagrams showing the thread shapes of the male thread of the drive screw shaft and the male thread of the roller screw. 7 to 9 show a second embodiment of the present invention, in which FIG. 7 is a perspective view showing the main parts, FIG. 8 is a front view thereof, and FIG. 9 is an IX-IX in FIG. FIG. FIG. 10 is a diagram for explaining the force generated on the roller screw due to the rotation of the drive screw shaft. 11.21...Bed and table (two members movable relative to each other), 12...Male thread of drive screw shaft, 13...Driving screw shaft, 27...Male thread of roller screw, 28.28A to 28C -o-Round thread, P...pitch, D...effective diameter, S...number of threads.

Claims (2)

[Claims] (1) One of the two relatively movable members is provided with a drive screw shaft having a male thread on the outer peripheral surface so as to be rotatable along the direction of relative movement, and the other of the two relatively movable members is provided with the drive screw shaft. A roller screw having a male thread with the same pitch as the male thread of the shaft is provided so as to be able to roll and rotate following the rotation of the drive screw shaft while meshing with the male thread of the drive screw shaft, and the male thread of the roller screw and the drive screw shaft A rolling differential screw feeding mechanism characterized in that the male threads of the roller screw are oppositely threaded to each other, and the effective diameter of the male thread of the roller screw is larger than 1/2 of the effective diameter of the male thread of the drive screw shaft. (2) When the effective diameter of the male thread of the roller screw is D, and the effective diameter of the male thread of the drive screw shaft is d, the roller screw is formed so that D>d. Rolling differential screw feed mechanism.