JPH02176241A - Rolling differential screw feed mechanism - Google Patents

Abstract

PURPOSE:To obtain great thrust and largely change the feed rate of the subject mechanism by arranging a plurality of roller screws in such a manner as each capable of meshing with the male screw of a driving screw shaft, the roller screws including male screws with the same pitch as that of the male screw of the driving screw shaft and also different from each other in at least either one among their pitch diameters, the directions of their threads and the numbers of their threads. CONSTITUTION:Two roller screws 41, 42 with respective male screws 31, 32 which have the same pitch as that of the male screw 1 of a driving screw shaft 2 and which also are different from each other in at least either one among their pitch diameters, the directions of their threads and the number of their threads, are provided in such a manner as each being capable of rolling and rotating after rotation of the driving screw shaft 2 while in its state wherein it is capable of meshing with the male screw 1 of the driving screw shaft 2 and also meshes therewith, and either one of the roller screws is made to mesh with the screw 1. In this case, the feed rate can be switched to both the coarse and slow motion by varying the pitch diameters D1, D2 of the roller screws 41, 42 or the directions of the threads of the male screws 31, 32 of both roller screws 41, 42 or even by varying the numbers S1, S2 of the threads of the male screws.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rolling differential screw feed v1 lateral that converts the rotational motion of a drive screw shaft into a linear motion. In particular, the present invention relates to a feeding mechanism that allows variable feeding speed.

For example, it can be used as a feeding mechanism for tables and heads of A111 machines and PP1FL machines.

[Prior Art] Conventionally, as a mechanism for converting rotational motion of a drive shaft into linear motion, a friction roller is pressed against the circumferential surface of the drive shaft, and the axial portion of the drive shaft generated on the friction roller as the drive shaft rotates. Friction feeding mechanisms are known that perform feeding operations using force (thrust).

Among the friction feed mechanisms, mechanisms that can vary the feed speed include those configured so that the lead angle of a friction roller pressed against the circumferential surface of the drive shaft can be varied to different angles with respect to the axis of the drive shaft; It is known that a plurality of sets of friction rollers having different lead angles with respect to the axis of the drive shaft are provided so that these rollers can be selectively pressed against the outer circumferential surface of the drive shaft.

[Problems to be Solved by the Invention] However, in any of the above-mentioned structures, a large pressing force is required to obtain frictional force, and the thrust force obtained is also small, so that the fields in which they can be used are limited. was. Also, it is not possible to have a large variable range of feed speed.

Here, the object of the present invention is to replace such conventional screw feed v
It is an object of the present invention to provide a rolling differential screw feeding mechanism which can solve the problem of a single mechanism, obtain a large thrust, and can change the feeding speed significantly.

[Means for Solving the Problems] Therefore, in the present invention, a drive screw shaft having a male thread on the outer circumferential surface is rotatably provided in one of the two relatively movable members along the direction of relative movement, and On the other of the two movable members, a plurality of roller screws having male threads having the same pitch as the male threads of the drive screw shaft but different in at least one of effective diameter, thread direction, and number of threads are attached to the male threads of the drive screw shaft. The roller screws are provided so that they can be engaged and can roll and rotate following the rotation of the drive screw shaft in the engaged state, and are provided with a switching mechanism that engages any one of the roller screws with the male thread of the drive screw shaft. do.

[Operation] When one of the roller screws is meshed with the male thread of the drive screw shaft by the switching mechanism and the drive screw shaft is rotated, the two members move relative to each other via the roller screw meshed with the drive screw shaft. . At this time, when the drive screw shaft rotates, the roller screw meshed with the drive screw shaft also rotates due to the friction between the two members, so the relative movement between the two members is only the amount of movement due to the rotation of the drive screw shaft. Rather, 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. 2. As shown in FIG. 2, 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 circumferential surface, and a male thread 3 that meshes with the male thread 1 at the same pitch is provided on the movable member 6. A roller screw 4 is provided 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. .

At this time, when the drive screw shaft 2 rotates, the roller screw 4 also rotates due to Ia friction between it and 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. , 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 of the entire mechanism will decrease.

Now, the pitch of the male screws 1 and 3 is P, P, the effective diameter of the male screw 1 (twice the distance from the axis of the drive screw shaft 2 to the point where it contacts the roller screw 4) is d, and the effective diameter of the male screw 3 (the roller 21 of the distance from the axis of the screw 4 to the point where it contacts the drive screw shaft 2
8) Let the respective screw multipliers of the drive screw shaft 2 and roller screw 4 be SS. Note that s, s, and s are + for the thread direction or right-hand thread, and - for left-hand thread.

Under this condition, the amount of movement when the drive 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 ΔX for the entire frame structure is Δx=p (s+d/D −S)...
...(1).

Therefore, from equation (1), if a plurality of roller screws having male threads with different effective diameters, thread directions, and number of threads are selectively engaged with the male thread of the drive screw shaft, feeding with different leads can be achieved. It turns out that it can be done.

In the present invention, a plurality of roller screws each having a male thread having the same pitch as the male thread of the drive screw shaft and different in at least one of effective diameter, thread direction, and number of threads can be engaged with the male thread of the drive screw shaft and are meshed with each other. Since these roller screws are designed to roll and rotate following the rotation of the drive screw shaft, if these roller screws are selectively engaged with the male screw of the drive screw shaft using a switching mechanism, feeding with different leads can be performed. .

For example, as shown in FIG.
Two roller screws 4. having male threads 33□ with the same pinch and different effective diameter, thread direction, and number of threads. ．． Let us consider a case in which the screws 42 are provided so as to be able to mesh with the male threads 1 of the drive screw shaft 2 and to be able to roll and rotate following the rotation of the drive screw shaft 2 in the meshed state.

Here, the pitch p of the male thread 1 of the drive screw shaft 2 is ρ-1,
5 [+11+], effective diameter d = 15 [kan], right-handed 1
In other words, under the condition that s=1, the effective diameter of the male thread 3 of the first roller screw 4 is Dl=5 [mII],
The effective diameter D2 of the male thread 32 of the second roller screw 4□ is set to D2.
=30 [11111], the first roller screw 4.
When the screw is engaged with the male screw 1, the glued ΔX and the second
The lead Δx2 when the roller screw 42 is engaged with the male screw 1 is calculated from equation (1) as follows: Δx + = 1, 5 (i + 15 / 5
1 ) = 6 [city] ΔX2 = 1.5 (L + 15/30X1) = 2.
25 [Become Ichiko. However, male thread 3. ．． 32 is a single right-handed thread, that is, S=1. Therefore, by changing the effective diameter D2 of the male thread 3 of the first roller screw 4 and the male thread 32 of the second roller screw 4, the feed speed can be switched between coarse movement and fine movement.

In addition, under the conditions that the pitch P, effective diameter d, thread direction, and thread number S of the male screw 1 are the same as above, the first roller screw 4
1 and 2nd roller screw 4□ male screw 3. ．． 32 as the effective diameter, D2 are equal to each other (D, =Dt =l
7 [1] and reverse thread, that is, the male thread 31 has one right-hand thread (S = 11), and the male thread 32 has one left-hand thread (S = -1), then each roller screw 30, 32 meshes with the male thread 1. The leads Δxl and Δx2 when
235 [citrus] ΔX2 = 1.5 (1115/L7X 1)': 0
．． 1764 [n+n]. Therefore, even if the thread direction of the male thread 3I of the first roller screw 4 and the male thread 3□ of the second roller screw 4□ is changed, the feed speed can be switched between coarse movement and fine movement.

In addition, under the same conditions as the pitch p, effective diameter d, thread direction, and thread number S of the male screw 1, the first roller screw 4
The male threads 31.3□ of the first and second roller screws 4□ have an effective diameter, and D2 and the thread direction are equal to each other <D
, = D2 = 17 [Season]) and the number of threads is different, that is, 3 male threads are 2 right-hand threads (S = 2>, and 3 male threads are 1 right-hand thread (S = 1), then each roller screw 3
Glue ΔX+Δ when 1 and 32 are engaged with male thread 1
From equation (1), x2 is ΔX+ ==1.5 (1+15/17X2)', 4.
1470 [related] ΔX 2 = 1, 5 (1+ 1 5 /
17 X 1 > ring 2.8235 [nn]. Therefore, even if the number of threads of the male thread 3□ of the first roller screw 41 and the male thread 3□ of the second roller screw 42 is changed, the feed speed can be switched between driving and fine movement.

In this way, by simply making at least one of the effective diameter, thread direction, and number of threads of the male thread of the roller screw different from each other, the feed speed can be changed significantly, and,
Since the thrust is obtained by the engagement of the drive thread shaft and the roller screw, it is possible to obtain a larger thrust than the conventional friction feed a mechanism.

[Example] Hereinafter, the present invention will be explained in detail based on the example shown in FIGS. 3 to 9.

In this example, the third
As shown in the figure, the table 21 is the third one for the bed 11.
It is provided so as to be movable back and forth in the left and right directions in the figure.

One side of these two relatively moving members, here the bed 1
lfl! ! A drive screw shaft 13 having a male thread 12 on its outer peripheral surface is rotatably provided in I along the reciprocating direction of the table 21. The male thread 12 has, for example, a pitch p = 1.5 [mm], an effective diameter d'' 15 [mm], and one right-hand thread, that is, s = 1. is rotatably supported by a bracket 14 (the left end in FIG. 3 is omitted), and
It is rotationally driven by a motor 15 connected to one end.

On the other hand, a mounting base 22 is fixed to the table 21 side. The -f stand 22 has a pair of left and right connecting arms 23A.
, 23B to the roller holding frame 24 or the drive screw shaft 1.
They are connected so as to be swingable about an axis parallel to the axis line of No. 3. As shown in FIG.
A line connecting the upper end rotation fulcrum of B and the axis of the drive screw shaft 13 (
However, when the roller holding frame 24 is in a horizontal state), the two rollers 25. ．． 25□ is rotatably supported parallel to the axis of the drive screw shaft 13.

Each roller screw 25. ．． The outer peripheral surface of 25□ has a pitch p,
, p2 has the same pitch as the male thread 12 of the drive screw shaft 13 (
p=P,=P2=1. ．． 5) and in which at least one of the effective diameters DI, D2, thread direction, and number of threads S, , S2 differ from each other. ．． 26□ are formed respectively.

Here, the roller screw 25. The effective diameter is 17[n+n] slightly larger than the effective diameter d of the male thread 12, and the thread direction and number of threads S are the same as the male thread 12 (S + = 1). or is formed. The roller screw 25□ has an effective diameter D2 or a male screw 26. equal to the effective diameter D1 of (D,
=D, =17 [Family]), one thread (S) on the left in the thread direction
A male thread 26□ of 2--1> is formed. In other words,
The roller screw 25252 has external threads 26. ．． 26□ is formed.

Therefore, by swinging the roller holding frame 24 using the upper ends of the connecting arms 23A, 23B as fulcrums, both roller screws 25.
．． 25□ can be selectively engaged with the male thread 12 of the drive screw shaft 13, and the engaged roller screw 251.25□ can be rolled and rotated following the rotation of the drive screw shaft 13''. Yes, male thread 12.
The thread shape of 2626□ is as shown in Fig. 5 (A>).
They are each formed into an arcuate shape that makes point contact on each other's effective circles. In this case, as shown in FIG. 5(B), the male thread 12 and the male thread 26. ．． 262, for example, the thread shape of the male thread 261.26□ is triangular,
The thread shape of the other one, that is, the male thread 12, may be an arcuate shape that makes point contact with the oblique side of the triangle.

Further, between the mounting base 22 and the roller holding frame 24, one of the roller screws 25. ．． A switching mechanism 31 is provided which engages the male thread 12 of the drive screw shaft 13 with the drive screw shaft 13. switching f
The im31 includes a plurality of shape memory alloys 32 provided between the mounting base 22 and the roller holding frame 24 on the front side, and a plurality of shape memory alloys 32 provided between the mounting base 22 and the roller holding frame 24 on the rear side. The shape memory alloy 33 is made up of a plurality of shape memory alloys 33. These shape memory alloys 32 and 33 are free to bend like normal copper wires before being energized, but when energized they have the property of shrinking by several percent of their total length and becoming shorter.

Therefore, when the shape memory alloy 32 on the front side is energized, the roller holding frame 211 swings as shown in FIG.
It meshes with 2. Also, if the current is applied to the shape memory alloy 33 on the rear side, the roller holding frame 24 will swing as shown in FIG. 7, so the roller screw 25. External thread 26. or drive screw shaft 1
Further, between the mounting base 22 and the roller holding frame 24, between the mounting base 22 and the roller holding frame 24, on both sides thereof, there are provided screws 6 that are engaged with the male threads 12 of the drive screw shaft 13 by the switching mechanism 31. Roller screw 25. ．． A pressing mechanism 41 is provided that presses the shaft 25□ against the drive shaft 13 with a constant force. Pressing machine 4'1l
t41 is constituted by a pair of springs 42A, 42B that maintains the inclined state of the roller holding frame 24 when the pair of connecting arms 23A, 23B swings using the upper end as a fulcrum, that is, when the roller holding frame 24 is inclined. has been done.

Further, inside the roller holding frame 24, as shown in FIGS. 8 and 9, one of the negative roller screws 25+ and 252 is engaged with the male screw 12 of the drive screw shaft 13 by the switching R mechanism 31. Time roller screw 25. ．． 252
A same 1tJI machine coffin 51 is provided which rotates the drive screw shaft 13 synchronously with the male thread 12 of the drive screw shaft 13 so as to be able to engage with it. In the synchronization mechanism 51 of this embodiment, both roller screws 251,
Since the male threads 261 and 262 of 252 are opposite threads,
four gears 52, 53 for rotating the free roller screw not engaged with the male thread 12 of the drive screw shaft 13 in the opposite direction with respect to the roller screw meshed with the male thread 12 of the drive screw shaft 13;
54.55. In other words, a gear 52.53 fixed to the shafts of both roller screws 25I, 252, and an intermediate gear 54 disposed between both gears 52.53.
．． It consists of 55. In addition, if the thread directions of the roller screws are the same, it becomes a synchronization mechanism that rotates in the same direction.

Next, the action of Honji jFiρ will be explained.

(Coarse feed) To coarsely feed the table 21 with respect to the bed 11,
Electricity is applied to the shape memory alloy 33. Then, roller holding frame 2
4 swings as shown in FIG. 7, the roller screw 25. External thread 26. The drive screw shaft 13 is engaged with the male thread 12 of the drive screw shaft 13. At this point, the power to the shape memory alloy 33 is turned off. In this state, the drive screw shaft 13 is
When rotated, the roller screw 25. follows the rotation of the drive screw shaft 13. is moved while rolling and rotating.

At this time, the roller screw 25. The male thread 261 has an effective diameter D
+ = 17 [ms+], since it is a single right-handed thread (S=1), the roller thread is 25. The lead ΔX when meshing with the male screw 12 is calculated from equation (1) as follows: Δx, = 1.
5 (1+15/17X1)'=2, 8235
[m+o], that is, the table 21 can be coarsely moved relative to the bed 11 with a lead of 2.8235 [own].

(Following feed) To finely feed the table 21 with respect to the bend 11,
Electricity is applied to the shape memory alloy 32. Then, roller holding frame 2
4 or as shown in FIG. 6, the roller screw 252 is in a state of meshing with the male thread 26□ or the male thread 12 of the drive screw shaft 13. In this state, when the drive screw shaft 13 is rotated by the motor 15, the roller screw 25□ is moved while rolling and rotating, following the rotation of the drive screw shaft 13.

At this time, the male thread 26□ of the roller screw 25□ has an effective diameter of D.
2 = 17 [kan], 1 left-hand thread (S = -1>, so
The lead Δx2 when the roller screw 25□ is engaged with the male screw 12 is calculated from equation (1) as follows: ΔX 2 = 1, 5
(1115 / 17 X~1) Cape 0. 1764
[City] In other words, table 21 is 0 for bet 11.
．． Fine movement can be performed with a lead of 1764 [mwI].

Therefore, according to this embodiment, the male thread 1 of the drive screw shaft 13 is
Two roller screws 25.2 having male threads 261.26□ with the same pitch as 26. ．． 25
2 is provided so that it can engage with the male thread 12 of the drive screw shaft 13 and can roll and rotate following the rotation of the drive screw shaft 13 in the engaged state, and any one roller screw 2525 Since a switching mechanism 31 is provided that engages with the cut t! ! ! !
11[31 allows the roller screw 261 with the same screw direction as the male screw 12 to be engaged with the drive screw shaft 13 for coarse feed, and the roller screw 252 with the screw direction opposite to the male screw 12 to be engaged with the drive screw shaft 13.
By meshing with the drive screw shaft 13, it is possible to switch to fine movement feed.

Moreover, these feeds are controlled by the drive screw shaft 13 and each opening-round screw 25. ．． 252, a larger thrust force can be obtained compared to conventional friction feeding mechanisms.

In particular, in coarse feed, the effective diameter D of the roller screw 25 is
1 was made slightly larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, that is, since the effective diameter d of the male thread 12 was 15 [stop], D + = 17 [IWII],
Approximately 1.
9x read (Δx+J.

8235 [M]) allows coarse movement of the table 21. By the way, roller screw 25. By making the effective diameter D1 smaller than the effective diameter d of the male thread 12, a lead that is more than twice the pitch p of the male thread 12 can be obtained.

On the other hand, for fine movement feed, the thread direction of the roller screw 25□ is opposite to the male thread 12 of the drive screw shaft 13, and the effective diameter D2 is made slightly larger than the effective diameter d of the male thread 12. In other words, the effective diameter d of the male thread 12 = 15 [oo
a], D 2 = 17[,,], so the minute lead (ΔX2'=0.1764 [nm]) is much smaller than the pitch p of the male screw 12 (=1°5 [nun]).
]) The table 21 can be moved slightly.

In other words, the feed speed can be changed significantly.

Further, since the effective diameter D2 of the male thread 26□ of the roller screw 25□ is formed larger than the effective diameter d of the male thread 12 of the drive screw shaft 13, the lead is larger than O and smaller than the pitch P of the male thread 12. In this state, due to the rotation of the drive screw shaft 13, the roller screw 25□ generates a force 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 D2 of the roller screw 25□ is smaller than the effective diameter d of the drive screw shaft 13, the rotational force will be in the opposite direction to the rotational direction of the roller screw 25□, or if the effective diameter D2 is larger than the effective diameter d. , the force in the rotational direction is the roller screw 2
Since it is in the same direction as the rotation direction of 5□, there is no tendency for it to slip and the reed is more stable.

In addition, the roller screw 25. ．． The thread shapes of the male thread 2626□ of 25□ and the male thread 12 of the drive screw shaft 13 are arcuate, or one is triangular and the other is arcuate.
．． ．． 252 can always be brought into point contact on the effective circle. Drive screw shaft 13 and roller screw 25. ．． If the point where 25
5. ．． 25□ can be always brought into point contact on the effective circle diameter, which can stabilize the lead ΔX.

In addition, since the roller screw 251.25□ rotates following the rotation of the drive screw shaft 13, in other words, the contact surfaces do not make sliding contact like a sliding screw, but roll contact, so efficiency is high and wear is reduced. It also has an excellent effect on durability.

In addition, the switching machine tR31 is connected to four shape memory alloys 32°33
With this configuration, the switching mechanism is simple, as the coarse movement feed can be switched by energizing the shape memory alloy 33, and the fine movement feed can be switched by energizing the shape memory alloy 32.

Also, one of the roller screws 25. which is engaged with the male screw 12 of the drive screw shaft 13. ．． Since a pressing mechanism 41 is provided to press 25□ against the drive screw shaft 13 with a constant force, the roller screws 25+ and 25□ can follow the rotation of the drive screw shaft 13 without backlash or twisting. It can be rolled and rotated. Moreover, since the pressing mechanism 41 is constituted by the springs 42A and 42B, it is structurally simple.

Also, when any one of the roller screws 251.25□ is engaged with the male screw 12 of the drive screw shaft 13, the curved roller screw 25. ．． Since the synchronous R mechanism 51 is provided to synchronously rotate the roller screws 25, . There is no condition in which the thread of the free roller screw engages with the thread of the drive screw shaft when switching the roller screw 25. ．． 25□ drive screw shaft 1
3 can be properly engaged. Therefore, switching can be smoothly performed at any position.

In the above embodiment, the roller screw 25. ．． 25□ effective diameter, D2, thread direction, number of threads of 8182, the thread directions were set as opposite threads, but the effective diameter D1. D2 or the number of threads S, , S2 may be made different from each other, and furthermore, the effective diameter D1D2, the thread direction, the number of threads S+, 2 of S2
The above configuration may be different from each other.

Further, the number of roller screws is not limited to two as described in the above embodiment, but may be three or more. If there are three or more roller screws, the feed speed can be changed in three or more stages.

The switching mechanism 31 is limited to one that utilizes the shape memory alloys 32 and 33 described in the above embodiments.
Alternatively, a cylinder may be used to swing the roller holding frame 24.

Further, double roller screw 25. ．． 252 constitute a switching mechanism having a neutral state in which they do not mesh with the drive screw shaft 13, it is possible to float the table, that is, to manually move the table to an arbitrary position.

Further, the suppressing mechanism 41 is not limited to the springs 42A and 42B described in the above embodiments, but is also applicable to the drive screw shaft 1, for example.
3 and roller screws 25, . 252, and the magnetic force of this magnetic circuit causes the roller screw 25. 252 and the drive screw shaft 13 are attracted to each other, and the roller screws 251 and 252 are attached to the drive screw shaft 13.
Alternatively, elastic deformation of a leaf spring or the like may be used.

Further, the synchronization mechanism 51 is not limited to the one using the gears 52 to 55 described in the above embodiments, but is, for example, a roller screw 25. ．． 25□ may be directly engaged,
Alternatively, the mechanism shown in FIG. 10 or 11 may be used. The mechanism shown in FIG.
are arranged in the roller holding frame 24 while being shifted in the axial direction, and gears 56 and 57 that mesh with each other are integrally formed at adjacent ends of each of the roller screws 251 and 252. This has the advantage of simplifying the configuration. Also,
The mechanism shown in FIG. 11 includes each roller screw 25. ．． Timing gears 58 and 59 are attached to the 25□ shaft, and a timing belt 60 is passed across both timing gears 58 and 59 to rotate them.

Further, in the above embodiment, the drive screw shaft 13 is long and the roller screw 25. It may be a shorter version of 25□, or vice versa. That is, as shown in FIG. 12, the drive screw shaft 13 is formed short, and a roller screw 25. is selectively engaged with the drive screw shaft 13. ．． 25□ may be formed to be sufficiently longer than the drive screw shaft 13. In this way, both roller screws 25. ．． Since the gears for synchronizing the gears 52 and 53 are also provided at a position where they do not interfere with the drive screw shaft 13, the gears 52 and 53 of the four light
．． No need to use 54.55, two gears 52.53
There are advantages that can be achieved with

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

[Effects of the Invention] According to the present invention, a plurality of roller screws each having a male thread having the same pitch as the male thread of the drive screw shaft and different in at least one of effective diameter, thread direction, and number of threads are attached to the male thread of the drive screw shaft. Since these roller screws are designed to be able to engage and to roll and rotate following the rotation of the drive screw shaft in the engaged state, if these roller screws are selectively engaged with the male thread of the drive screw shaft using a switching mechanism, different leads can be used. can be sent.

At this time, since the thrust is obtained by the engagement of the drive screw shaft and roller b, conventional I-rubbing feed a! Compared to fI, a larger thrust can be obtained and the feed rate can be changed significantly.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining the present invention in detail, and FIG. 2 is a diagram for explaining its technical basis. Figures 3 to 9 show one embodiment of the present invention.
The figure is a front view, FIG. 4 is a side view, FIG. 5 is a diagram showing the thread shape of the drive screw shaft and roller screw, FIGS. 6 and 7 are side views showing the switching state of the roller screw, and FIG. Figure 8 shows synchronous R
A plan view showing the ellipse, and FIG. 9 is a side view thereof. FIGS. 10 and 11 are diagrams showing different modifications of the synchronization mechanism, and FIG. 12 is a diagram showing a modification of the drive screw shaft and the roller screw. 11.21...Bed and table (two relatively movable members), 2...Male thread, 3...Drive screw shaft, 5. 25□・・・Roller screw, 6,. 26□...Male thread, 1...Switching mechanism, PIP2...Pitch D, D2...Effective diameter, S,, S2...Number of threads.

Claims (1)

[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 plurality of roller screws having male threads having the same pitch as the male threads of the shaft and different in at least one of effective diameter, thread direction, and number of threads can be engaged with the male threads of the drive screw shaft, and in the meshed state, the drive screw shaft is rotated. A rolling differential screw feeding mechanism, characterized in that the rolling differential screw feeding mechanism is provided so as to be able to roll and rotate in accordance with the driving screw, and is provided with a switching mechanism that engages one of the roller screws with the male thread of the drive screw shaft.