RU2610747C1 - Rotary-to-linear motion converter - Google Patents

Abstract

FIELD: machine engineering.

SUBSTANCE: invention relates to machine engineering, and more particularly to the rotary-to-linear motion converters. A rotary-to-linear motion converter consists of the screw (1) and the assembly casing. The casing consists of part (2) and (3) connected with the fastening screws (4) and the pins (5). Two sleeves (6) are fixed in the casing, each of them has an inner tooth ring, and the rollers (7) are mounted. In addition, a split collet (8), two separators (9) and a thin-walled nut (10) with the annular "A" belt arranged at its end and intended for the axial nut fixing in the casing, are fixed in the casing.

EFFECT: invention contributes to the simplification of the structure.

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Description

The invention relates to mechanical engineering and can be used as a backlash-free helical gear for converting rotational motion into translational motion, for example, in the grips of robots or in table drives of high-precision metal cutting machines.

Known planetary roller screw transmission, see Reshetov D.N. Machine parts. Textbook for students of engineering and mechanical specialties of universities, 4th ed. M .: Engineering, 1989, p. 314, which is an analogue. The transmission consists of a screw, a solid nut and rollers installed between them, which are mounted in separators with their end necks. To exclude spontaneous unscrewing of the rollers, they are additionally connected along the ends with a nut by gears. The turns of the rollers are in threaded engagement with the turns of the screw and nut. At the same time, an external multi-start thread is made on the screw, an internal multi-start thread is on the nut, and an external thread is usually made on rollers, as a rule, with one run.

This planetary roller screw transmission is characterized by low axial rigidity and low kinematic accuracy due to the presence of lateral gaps between the mating threads of the screw and rollers, rollers and nuts. It is impossible to assemble this gear without the indicated gaps.

Of the known technical solutions, the closest in technical essence and the achieved technical result to the claimed invention is a device for converting rotational motion into translational, see RF patent for invention No. 2392517, BI No. 17 dated 06/20/2010, which is selected as the closest analogue.

This device consists of a screw passed through the housing, consisting of two parts connected by fixing screws and pins, and fixed in the housing of a single thin-walled nut having an outer surface in the middle of the annular girdle. To reduce its rigidity, the annular band is cut along the axis with grooves. In the case with the possibility of planetary motion, rollers are installed in the separators (number n provided that n≥3), interacting with the turns of their thread made on the outer surface with the threads of the screw and thin-walled nut. To exclude spontaneous unscrewing of the rollers, they are additionally connected along the ends with a nut by gears. Each body part has an inner conical surface that interacts with the outer conical surface of the split collet. The inner cylindrical surface of each collet interacts with the outer cylindrical surface of the thin-walled nut, and the ends of the split collets abut on different sides in the annular zone of the thin-walled nut. In this case, each split collet is cut in a checkerboard pattern from opposite ends with grooves that end with holes.

To select the lateral gaps between the mating threads of the screw and rollers, rollers and nuts during the assembly of the device, a thin-walled nut is radially compressed by two split collets. For this, the body parts come together along the axis by tightening the fixing screws. In this case, the axial force created by the fixing screws is converted due to the mating conical surfaces of the body parts and split collets into a radial load, which compresses a thin-walled nut in the radial direction.

Compared with the above analogue, this device, which is a clearance-free mechanism, has higher axial stiffness and kinematic accuracy.

However, this device has the following disadvantages:

- a complex structure (two split collets, two body parts with a high-precision internal conical surface) and a complex manufacturing technology;

- body parts and split collets are made within the tolerance fields for their most important dimensions. Hence, due to the indeterminate axial position of the thin-walled nut in the housing, the accuracy of its axial position along the axis of the screw decreases, and therefore the transmission accuracy.

The technical result of the present invention is to improve the accuracy of the claimed device and simplify its design and manufacturing technology.

The specified technical result is achieved by the fact that in the device for converting rotational motion into translational motion, comprising a screw, a prefabricated housing consisting of two interconnected fasteners and pins of parts, the first of which has an internal conical surface, a thin-walled nut secured in the prefabricated housing with an outer ring girdle, two bushings with internal gear rims, a collet and two ring seps mounted in a prefabricated housing with the possibility of rotation about its axis a rotor with holes and n (n≥3) rollers, each of which has gear rims at the ends of the threaded part that engage with the internal gear rims of the bushings, and trunnions at the ends, and the threads of each roller along its entire length along one generatrix mesh with the threads of the screw, and along the opposite generatrix with the threads of the nut, the journal of the rollers enter the separator holes with a gap, and the collet is staggered from the opposite ends of the grooves, which end with holes, has an outer conical surface b, interacting with the inner conical surface of the first part of the precast housing, and the inner cylindrical surface, interacting with the outer cylindrical surface of the thin-walled nut, while the outer annular belt of the thin-walled nut is cut along its axis with grooves, and all the rollers in the two separators can rotate relative to the axis of the screw , new is that the thin-walled nut is placed in the first part of the prefabricated housing, the outer ring girdle is placed on the end of the thin-walled nut and fixed n in the axial direction of one of the bushings with an internal gear rim and the first part of the precast housing, and on the second part of the precast housing an end stop is made for axial fixing of the collet.

The invention is illustrated by graphic materials on which:

- in FIG. 1 - device, end view;

- in FIG. 2 is a section AA in FIG. one;

- in FIG. 3 - split collet device.

A device for converting rotational motion into translational motion consists of a screw 1, on the outer surface of which a multi-thread is made, and a prefabricated housing consisting of two connected parts. The first part 2 of the prefabricated housing has an inner conical surface "B" and an inner annular groove "C", and the second part 3 has an end stop surface "G" (end stop). Parts 2 and 3 of the precast housing are connected by fixing screws 4 after their relative alignment with pins 5.

In the prefabricated housing there are: two bushings 6, each of which has an internal gear rim; rollers 7; split collet 8; two separators 9; thin-walled nut 10 with an external annular protrusion (girdle) "D" made on its end. To reduce its rigidity, the annular girdle is cut along the axis with grooves (not shown).

In the assembled position of the device, the bushings 6 are fixed in the end bores of the parts 2 and 3 of the assembled housing. In the sleeves 6 rotary annular separators 9 are placed, fixed from axial movement in the sleeves by the locking rings 11 installed in the sleeves 6.

The separators 9 have holes in which the end trunnions (positions are not indicated) with a gap with the possibility of rotation placed covering the shaft 1 of the rollers 7.

To increase the load capacity, rigidity and accuracy of the device, the number of rollers n (n≥3) is usually selected from the condition of the neighborhood as high as possible.

A thread is made on the outer surface of each roller 7, and spur gears are cut at the end sections, directly along the thread, which engage with the gear crowns of the bushings 6 to synchronize the rotation of the rollers. The rollers, as a rule, have a single-thread, which is engaged with multi-thread threads of the screw 1 and thin-walled nut 10.

Thin-walled nut 10 is located outside with respect to the rollers and on the outer surface is covered by a split collet 8.

The cutting collet 8 is placed in the cavity of the housing part 2, its conical part is in contact with the inner conical surface “B” of the housing part 2, and the end of the split collet is in contact with the end contact surface “G” of the housing part 3.

To increase the flexibility of the split collet 8, it is necessary to assign its dimensions as follows, see FIG. 3:

- choosing the total number of slots, determine the size a from the axis of the hole to the groove in the circumferential direction;

- hole axis advisable to locate at a distance a from the end of the collet. Then the pairing of the collet around the hole will be equally strong in the axial and circumferential sections.

As shown by the practice of designing split collets of this design and calculations, with this size designation, the distance l, see Fig. 3 will be approximately 90% of the length of the collets L. Also, to increase the flexibility of the split collets, it is necessary that the mates around the holes at the opposite ends of the collets have equal or close compliance. To do this, the outer conical surface at the right in the plane of the drawing (base) end of the collet in the place of the specified pairing is interrupted and goes into a cylindrical surface. The thickness of the split collet at the right end in the area where the holes are located is constant and equal to its thickness h at the opposite end.

In the assembled position of the device, the inner conical surface "B" of the body part 2 interacts with the outer conical surface of the split collet 8, and its inner cylindrical surface interacts with the outer cylindrical surface "E" of the thin-walled nut 10. In this case, the thin-walled nut 10 is fixed in axial position due to placing its annular protrusion "D" in the annular groove "B" of the body part 2 and due to the adjacent end face of the sleeve 6 (left in the drawing plane of Fig. 2).

The fastening of the bushings 6 in parts 2 and 3 is carried out by the locking screws 12.

In the process of assembling the device when tightening the fixing screws 4, the idle torque of the device is monitored, which judges the compensation of gaps and loading of the mating threads of the screw, rollers and nuts with a preliminary load. To carry out this operation, typical recommendations are used to regulate the optimal idle torque value depending on the size of the clearance-free roller screw transmission.

After completion of the assembly process, the body parts 2 and 3, the split collet 8 and the thin-walled nut 10 become a single whole, that is, the split collet and the thin-walled nut are fastened in the precast housing by friction forces. Moreover, the threads of each roller along its entire length along one generatrix are engaged with the threads of the screw, and along the opposite generatrix with the threads of the nut.

The device operates as follows.

We consider the operation of the device using the example of moving in the horizontal plane of the table of a boring machine (not shown).

For the operation of the device, the shaft 1, connected to the electric motor, is mounted rotatably in the supports fixed on the fixed bed of the machine. Basic elements, for example, trunnions (not shown), are carried out or fixed on the device body, by means of which the device body is connected to the machine table. The machine table, and therefore the device body with the parts placed on it, can only move in a horizontal plane along the guides along the axis of the screw.

When the motor is turned on, the rotary screw 1 drives the rollers 7 into rotation due to threaded engagement and friction forces. All the rollers 7 perform a planetary motion, running around the gear rims of the bushings 6, mounted in the housing. Each roller rotates around its own axis and all the rollers, together with the separators, rotate around the axis of screw 1. The dimensions of the screw, rollers, thin-walled nut and gear rims on the rollers and bushings are selected so that rolling friction is realized at the points of interaction of the mating turns of the screw and rollers with high efficiency. The specified rotation of the rollers allows you to convert the rotation of the screw into the translational motion of the thin-walled nut, which is kept from rotation, and, together with it, of the case fixed on the machine table.

The electric motor develops the torque necessary to move along the guides of the machine table, on which the workpiece can be installed during its processing. In this case, the torque is converted into the interaction forces of the mating turns of the screw and the rollers. The workload is the sum of the axial projections of these forces. Similarly, the axial load is transferred from the turns of the rollers to the turns of the nut and is the force that moves the machine table.

Compared with the closest analogue device, the claimed device has a higher kinematic accuracy, since the thin-walled nut in the device case has a strictly defined axial position in the case.

In addition, the inventive device has, in comparison with the closest analogue device, a simpler design, since the body parts are structurally simpler, there is no need to use a second collet.

Claims (1)

A device for converting rotational motion into translational motion, comprising a screw, a prefabricated housing consisting of two interconnected fasteners and pins of parts, the first of which has an internal conical surface, a thin-walled nut with an outer ring girdle fixed in an assembly, two bushings with inner two ring separators with holes and n (n≥3) rollers, each of which it has gear rims at the ends of the threaded part that engage with the internal gear rims of the bushings, and trunnions at the ends, moreover, the threads of each roller along its entire length engage along one generatrix with the threads of the screw, and along the opposite generatrix with the threads of the nut and trunks the rollers enter with a gap in the holes of the separators, and the collet is staggered from the opposite ends of the grooves, which end with holes, has an outer conical surface that interacts with the inner conical surface the first part of the prefabricated housing, and the inner cylindrical surface interacting with the outer cylindrical surface of the thin-walled nut, while the outer ring girdle of the thin-walled nut is cut along its axis with grooves, and all the rollers in the two separators have the ability to rotate relative to the axis of the screw, characterized in that the thin-walled the nut is placed in the first part of the prefabricated housing, the outer ring girdle is placed on the end of the thin-walled nut and axially fixed to one of the bushings with the inner gear the first crown and the first part of the precast casing, and on the second part of the precast casing an end stop is made for axial fixing of the collet.

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