RU2374527C1 - Device for transformation of rotary motion into progressive (versions) - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: device for transformation of motion consists of screw, casing with covers and thread rolls. Thread rolls with ends installed in casing with ability of rotation around its axis and allows cylindrical threaded surfaces engaged to screw. At ends of each thread roll there are implemented spherical projections centres of which are located on axis of roller. At each cover there are implemented spherical angular clearances centres of which are also located on axis of corresponding roller. Additionally radius of spherical angular clearances in covers for 2-3% more than radius of spherical projections implemented on corresponding to it ends of each threaded roll. Device is outfitted by two pins which are provided for angular attitude of covers relative to casing.

EFFECT: increasing of output capability and durability of device, decreasing of its overall dimensions.

3 cl, 5 dwg

Description

The invention relates to mechanical engineering and can be used as a mechanical screw drive for converting rotational motion into translational.

Known planetary roller screw transmission, see Reshetov D.N. "Machine Details", a textbook for students of engineering and mechanical specialties of universities, 4th edition, Moscow, Mechanical Engineering, 1989, p. 314, consisting of a screw, a nut and threaded rollers installed between them. The rollers with their end necks are installed in the separators. To exclude spontaneous unscrewing of the rollers, they are additionally connected at 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-thread is performed on the screw, and an internal multi-thread is performed on the nut.

The main disadvantage of this planetary roller screw transmission is the technological complexity of manufacturing on the inner surface of the nut, hardened to high hardness, high-precision multi-thread (usually five- or six-way). It is mainly for this reason that it is difficult to master the production of planetary roller-helical gears, which in most operating parameters are superior to other gears for converting rotational motion into translational motion. In the world, only a few companies have mastered the manufacture of planetary roller screw drives.

In this case, the threaded nut of the planetary roller screw drive under consideration performs the following functions:

- perceives axial force from the actuator and transfers it through the rollers to the screw:

- keeps the rollers from moving in the radial direction from the axis of the screw to the nut;

- participates in the conversion of rotational motion to translational.

Of the known technical solutions, the closest in technical essence to the claimed device is a device for converting rotational motion into translational, see RF patent No. 2310785 "Device for converting rotational motion into translational", F16H 25 / 00-25 / 24, F16H 1/34 , BI No. 32, 2007, which is selected as a prototype.

This device consists of a screw, a housing with covers fixed to it, threaded rollers, each of which is mounted in the housing with the possibility of rotation around its own axis, two or more rings installed in ball separators, the number of which is twice as many as the number of threaded rollers, and seals. During operation of the device, usually, the screw rotates, and the housing, along with the threaded rollers, performs a translational motion. The working axial force in the device is transmitted from the screw to the rollers due to the threaded mates of the turns of these parts, and then from the threaded rollers to one of the housing covers through the balls installed in the separator. To do this, spherical undercuts are made at the ends of each threaded roller, and ring grooves are made on the inner end surfaces of the covers. Each ball is simultaneously installed in the undercut of the threaded roller and in the annular radius groove of the cap. Moreover, the radius of the ball should be less than the radius of the undercut in the threaded rollers and the annular groove in the covers, and when this condition is fulfilled, the ratios of the three indicated radii can be arbitrary.

To balance the radial force exerted by the screw on the threaded roller, ring grooves are made directly into the cylindrical threaded surface into which the rings are mounted. To stabilize the movement of the threaded rollers, the constancy of the transfer function of the device and eliminate the misalignment of the threaded rollers, the latter are connected to the housing by two gears, and the balls installed at each cover are additionally installed in the separator.

This device has the following main disadvantages.

1. The device has a low load capacity due to the low contact strength at the place of interfacing of the ball with an annular radius groove in the cover. It is known that the contact strength of parts in such mates depends on the ratio of the main curvatures of the parts at the point of initial contact. One main curvature of the specified groove is equal to the radius of its profile, and the second is zero. Hence, the area of the contact spot at the place of interfacing of the ball with the specified groove is small, and the contact stresses are large.

2. All balls installed in the annular radial groove of the lid are also installed in the spherical undercuts of various threaded rollers and, in addition, in the separator. Therefore, a lot of connections are imposed on the ball. All specified parts are made with inaccuracies. Threaded rollers, even connected by gears to the housing, can lag or be ahead of each other during operation of the device. The threaded rollers are skewed in the plane formed by the axes of the screw and the roller at different angles under the action of the axial load acting on the roller. It should be noted that the total axial force transmitted by the device is unevenly distributed between the rollers. Hence, the axis of the holes in the separator for balls does not coincide with the axis of the ball, which is determined by the contact forces with the cover and the roller. The consequence of this is a decrease in efficiency due to additional sliding in the conjugation of the balls and the separator and a decrease in the load capacity and durability of the device.

The objective of the invention is to increase the load capacity and durability of the device for converting rotational motion into translational motion by increasing the contact strength at the interface of the threaded roller or ball with the housing cover, as well as by eliminating separators from the structure of the device. In addition, the inventive device is structurally simpler and has smaller dimensions.

For the 1st variant of the device, the task is achieved in that it is equipped with two pins that are designed for the angular orientation of the covers relative to the housing, spherical protrusions are made on the ends of each threaded roller, the centers of which are located on the axis of the threaded roller, and spherical undercuts are made on each cover , the centers of which are also located on the axis of the corresponding threaded roller, and the radius of the spherical undercuts in the covers is 2-3% larger than the radius of the spherical protrusions made at the ends of the dogo threaded roller. It is possible to implement this device, for which it is equipped with two rings that are installed in annular grooves made on the cylindrical threaded surface of each roller, and these grooves are made as close as possible to the opposite ends of the threaded rollers, on the cylindrical threaded surface of each roller or in one of its of ring grooves, a turnkey hexagon is made, and the width of the ring grooves on the threaded rollers is greater than the ring width by at least 1.5 ... 2 screw thread steps.

For the 2nd embodiment of the device, spherical undercuts are made at the ends of the threaded rollers, the centers of which are located on the axis of the threaded roller, and there are balls installed in the indicated undercuts of the threaded rollers. The task is achieved in that the device is equipped with two pins that are designed for the angular orientation of the covers relative to the housing, spherical undercuts are made on each cover, the centers of which are located on the axis of the corresponding threaded roller, and the radius of the spherical undercuts made on the ends of the threaded rollers is equal to the radius of the spherical the undercuts made in the covers, the radius of the balls is 2-3% less than the radius of the spherical undercuts made in the covers, and each ball is additionally installed in fericheskom undercut appropriate cover.

The invention is illustrated by the accompanying drawings, where:

- figure 1 shows a General view of the device;

- figure 2 shows a section a - a in figure 1 for the main version of the 1st embodiment of the device;

- figure 3 shows a section a - a in figure 1 for additional performance of the 1st variant of the device;

- figure 4 shows the place B in figure 2 for the 1st variant of the device with a higher load capacity;

- figure 5 shows the place B in figure 2 for the 2nd variant of the device for which the transfer of load from the threaded rollers to the cover is made through balls.

A device for converting rotational motion into translational (option 1), see figure 1, consists of a screw 1 and a node performing translational movement with the basic elements "B" (trunnions for bearings), which are designed to connect the specified node with the actuator. The specified node, see figure 2, consists of a housing 2 and two covers 3, which are connected to the housing with screws 4 with spring washers 5 and two pins 6. At least between the cover 3 and the housing 2 is installed a set of shims or compensator 7. There are other possible versions of this node, which provide the assembly and operation of the device.

To the outer end surface of each cover 3, see FIG. 2, a L-shaped sleeve 8 is attached, which holds the oil deflector 9 with axial and radial clearance.

Inside the case, see figure 2, threaded rollers 10 are installed, the number of which is usually chosen from the conditions of the neighborhood to be the greatest to increase the load capacity of the device (the minimum number of threaded rollers is three). The thread turns of the rollers 10 engage with the threads of the screw 1. At the ends of each threaded roller 10, see figure 2, perform spherical protrusions "G" with a radius R _p , the center of which is located on the axis of the threaded roller. On the inner end surface of each cover, spherical undercuts “D” are made with radius R _K , the center of which is also located on the axis of the threaded roller, and the number of undercuts on one cover is equal to the number of rollers. In order for the axes of all the rollers to be parallel to the axis of the screw, the angular orientation of the covers relative to the housing is necessary, which is carried out using two pins 6.

A feature of the assembly of this device, see figure 2, is the selection of the thickness of the set of shims or compensator 7. The specified thickness should be such that the contact of the spherical protrusions "G" of each roller with the spherical undercuts "D" in the opposite covers was without axial clearance in points "E" and "G" located on the nominal axis of the roller.

During operation of the device, the screw rotates, leading all the rollers to rotate around its own axis, and the housing along with the rollers performs translational motion. In this case, from the screw side, axial and radial forces act on each roller, which must be balanced at points “E” and “G”, see Fig. 2, of the initial contact of the spherical protrusions “G” of the roller and the spherical undercuts “D” in opposite covers . So that under the influence of radial forces the points "E" and "G" practically did not shift from the nominal position of the roller axis, it is necessary that R _K be 2-3% more than R _P , see figure 2, but no more. Otherwise, the device may jam.

The 1st version of the device may have an additional design. For him, see figure 3, on the cylindrical threaded surface of the rollers 10 perform two grooves "And". The device is equipped with two rings 11, which are made of spring steel and have significant radial stiffness. Each ring 11 is installed in the corresponding groove "And". The sizes of the rings 11 must be such that they create a slight preload in the threaded coupling of the rollers 10 with the screw 1, at which the device does not jam.

When assembling this device, see figure 3, because of the specified interference, it is necessary to screw the rollers 10 with the rings 11 onto the screw in sequence. To do this, on each cylindrical threaded surface of each roller or in one of its grooves “I”, a turnkey hexagon “K” is performed, and the width L _{P of the} groove “I” is greater than the width L _{K of the} ring 11 by 1.5 ... 2 screw thread steps ( threaded roller) to ensure assembly of the device. Then the axial position of all the rollers is aligned according to one of the covers 3, the housing 2 is installed, connecting it with a pin and screws to this cover, and the second cover is fixed on the housing, adjusting the axial play of the housing with the covers relative to the set of rollers.

During operation of the device, an additional overturning moment from axial forces from the side of the screw and one of the covers acts on each roller. So that the ring 11, see figure 3, could more effectively perceive this overturning moment, the grooves "And" on the rollers should be made as close as possible to the opposite ends of the threaded rollers. That is, the distance between the grooves "And" (rings 11) should be the maximum possible. In this case, the force on the rings from the overturning moment will be the smallest and the roller in the plane formed by its axis and the axis of the screw will have the smallest skew angle, which will provide a more uniform load distribution between the turns of the threaded rollers along their axes, and therefore will increase the load capacity and durability of the claimed device.

Perhaps the second additional performance of the 1st variant of the device with a higher load capacity due to an increase in the main curvatures of the mating surfaces, leading to an increase in the contact area of these surfaces under load. For this, see figure 4, increase the radius of the spherical undercuts in the covers R _K and the radius of the spherical protrusions at the ends of the threaded rollers R _P , leaving their ratio unchanged.

To increase the efficiency of the device, in which the load capacity is slightly reduced, the 2nd variant of the claimed device is possible. For this, see figure 5, in the opposite ends of the threaded rollers perform spherical undercuts "L" and install balls 12 in them, which are also installed in spherical undercuts "D" made in the covers 3. The radii of the spherical undercuts "L" and " D "are equal, and the radius of the ball R _W 2-3% less than the radius of these undercuts. The largest ball radius R _{W, MAX} , which can be used for this variant of the device, should be less than half the diameter of the grooves of the thread of the roller. The value of R _W significantly affects the load capacity of the device.

In the prototype device, the load from the threaded roller to the cover is transmitted by balls. As noted above, the largest radius of the ball R _{W, MAX} has a size limit. In the prototype device, the balls are installed in the separator, which is why the value of R _{W, MAX} will be even less. This value is further reduced, since the ends of the rollers need to have key holes. Therefore, the largest radius of the ball K _{W, MAX} for the prototype device will be less than in the inventive device with balls. The value of R _{W, MAX} significantly affects the load capacity, since with increasing R _{W, MAX} contact stresses become less.

However, a more significant reduction in contact stresses and an increase in load capacity depends on the shape and size of the contacting surfaces in the covers of the device. In the prototype device, this surface is circular with a radius profile, one main curvature of which is equal to zero. Hence, the area of the contact spot between the ball and the annular groove is small. In the claimed device, this surface is spherical, both main curvatures of which are the same and reach the maximum possible value. Hence, the area of the contact spot of spherical undercut in the housing cover and the spherical protrusion of the threaded roller or ball (option 2) is much larger than in the prototype device.

In addition, the inventive device has a simpler design than the prototype device.

The inventive device, without gears and separators separating the balls, can have smaller dimensions.

Claims (3)

1. A device for converting rotational motion into translational, containing a screw, a housing with lids fixed to it, threaded rollers mounted in the housing with the possibility of rotation around its axis and having cylindrical threaded surfaces included in the threaded engagement with the screw, and ends, characterized in that the device is equipped with two pins that are designed for the angular orientation of the covers relative to the housing, spherical protrusions are made at the ends of each roller, the centers of which are located on the axis of the threads a roller, and on each cover spherical undercuts are made, the centers of which are also located on the axis of the corresponding threaded roller, and the radius of the spherical undercuts in the covers is 2-3% larger than the radius of the spherical protrusions made at the ends of each threaded roller. 2. The device according to claim 1, characterized in that it is provided with two rings that are installed in annular grooves made on the cylindrical threaded surface of each roller, and these grooves are made as close as possible to the opposite ends of the threaded rollers, on the cylindrical threaded surface of each roller or in one of its annular grooves, a turnkey hexagon is made, and the width of the annular grooves on the threaded rollers is greater than the width of the rings by at least 1.5 ... 2 screw thread steps. 3. A device for converting rotational motion into translational, containing a screw, a housing with lids fixed to it, threaded rollers mounted in the housing with the possibility of rotation around its axis and having cylindrical threaded surfaces engaged in threaded engagement with the screw, and ends in which spherical undercuts are made, the centers of which are located on the axis of the threaded roller, and balls installed in the indicated undercuts of the threaded rollers, characterized in that the device is equipped with two pins, which e are intended for the angular orientation of the covers relative to the housing, spherical undercuts are made on each cover, the centers of which are located on the axis of the corresponding threaded roller, and the radius of the spherical undercuts made on the ends of the threaded rollers is equal to the radius of the spherical undercuts made in the covers, the radius of the balls is 2-3 % less radius of the spherical undercuts made in the caps, and each ball is additionally installed in the spherical undercuts of the corresponding cap.

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