Two-stage reduction gear and hinge containing a two-stage reduction gear

Abstract

Proposed is a two-stage reduction gear comprising a housing and, arranged inside said housing, gears connected to one another so as to transmit rotational motion. Said gears are provided in the form of a planetary stage and a ballscrew stage. The planetary stage comprises an input component and an output component, and the ballscrew stage comprises an input component and an output component. The output component of the planetary stage and the input component of the ballscrew stage form a single part. Also proposed is a hinge containing the claimed two-stage reduction gear. The result is an increase in torque transmission over a wide range of transmission ratios, together with a decrease in the size and weight characteristics of the reduction gear and an increase in resistance to shock loads.

Description

F03D 15 / 00, F03D 80 / 70 A TWO-STAGE REDUCER AND A JOINT CONTAINING A TWO-STAGE REDUCER Field of technology

[0001] The present invention pertains to general mechanical engineering, specifically to a two-stage gearbox consisting of a planetary gear and a roller screw, as well as to a joint containing such a two-stage gearbox. The proposed inventions can be used in equipment requiring high-power transmission with high positioning accuracy, particularly in robotic manipulators, steering columns, yoke drives, machine tools, and medical equipment. State of the art

[0002] Various types of gearboxes are known - planetary, worm, bevel, roller screw, and others, each of which has its own advantages and disadvantages. Canadian patent CA3089805A1 (IC indexes F16H1 / 28, F16H55 / 08, F16H1 / 26, F16H1 / 46, published September 26, 2019) discloses a planetary gearbox comprising a single-tooth sun wheel, a crown wheel, planet gears, and a carrier on which the planet gears are rotatably mounted. The sun wheel, planet gears, and crown wheel have involute engagement.

[0003] Russian: From Russian patent RU2760068C1 (index MIC F16H1 / 28, published on November 22, 2021), the description of which is incorporated into this application in its entirety by reference, a roller-screw gearbox is known, comprising a housing that has an internal thread section, a satellite located in the housing, fixed against axial movement relative to the housing and having an external thread section that is engaged with said internal thread section of the housing, wherein the lead angles of said external thread section and said internal thread section are equal and their directions coincide. The gearbox also comprises a sun wheel located in the housing and configured to drive said satellite, and a planet carrier configured to rotate relative to the housing, and said satellite is connected to the planet carrier so as to rotate in a bearing support installed in the planet carrier. The aforementioned gearboxes have a limited range of gear ratios.

[0004] Multi-stage gearboxes have been proposed to expand the range of gear ratios. Chinese patent CN211314459 (IPC indexes F03D 15 / 00, F03D 80 / 70, published August 21, 2020) describes a gearbox comprising three planetary gear stages connected to each other. This known gearbox offers a wide range of gear ratios, but it also has a low specific torque—the ratio of the transmitted torque to the gearbox's dimensions. Furthermore, this known gearbox cannot withstand the axial loads that occur during gearbox operation. Other known solutions involve connecting different types of gearboxes using transition links, particularly couplings. However, these also cannot provide a high specific torque due to their lack of compact design.

[0005] The objective of the present invention is to create a two-stage gearbox with a compact design and high transmittable torque, and consequently, high specific torque. Another objective of the present invention is to create a two-stage gearbox that is resistant to impact loads. Another objective of the present invention is to create a compact and position-accurate joint with such a two-stage gearbox. Disclosure of the essence of the invention

[0006] To address these technical challenges, a two-stage gearbox is proposed, comprising a housing and gear trains housed within it, interconnected to transmit rotary motion. The gearbox is unique in that the transmissions comprise a planetary stage with an input and output link, and a roller screw stage with an input and output link. The planetary stage's output link and the roller screw stage's input link are designed as a single component. The proposed gearbox enables the transmission of high torques over a wide range of gear ratios and with high efficiency, as the inclusion of a roller screw stage increases the transmitted torque compared to similarly sized multi-stage gearboxes consisting solely of planetary stages.In addition, the proposed gearbox has a compact design, since it does not have intermediate links between stages of different types, which increase the dimensions of the gearbox.

[0007] According to a preferred embodiment, the gearbox housing comprises a housing part for accommodating a planetary stage and a housing part for accommodating a roller screw stage, connected to each other, wherein the housing part for accommodating the roller screw stage comprises a section of an internal cylindrical surface on which at least one section with a thread is located, the planetary stage comprises a sun wheel in interaction with each other, a crown wheel performing the function of an input link of the planetary stage and the gearbox, a central shaft passing through the said housing parts, a carrier mounted with the possibility of rotation together with the central shaft, satellites mounted in the carrier with the possibility of rotation and having two toothed rims, a connecting gear performing the function of an output link of the planetary stage, and the roller screw stage comprises a connecting gear in interaction with each other,a carrier that functions as the input link of the roller screw stage, which is mounted in the housing so as to be able to rotate relative to the shaft and in which at least one threaded roller is mounted so as to be able to rotate, comprising at least one section of an external thread interacting with the thread of the said section of the internal cylindrical surface, a gear wheel connected to the said at least one threaded roller interacting with the connecting gear wheel. The said design of the two-stage gearbox ensures the most efficient use of the internal space of the gearbox housing and, thus, ensures an increase in the specific torque, which is the transmitted torque related to the volume occupied by the gearbox.

[0008] In one particular embodiment, the input link of the planetary gear has an external gear ring for interaction with an external source of rotational motion.

[0009] According to another particular variant, the output link of the roller screw transmission has a mount for connection to an external actuator.

[0010] According to another specific embodiment, the inner cylindrical surface section of the roller screw stage contains two threaded sections, with the threads running in opposite directions, and at least one threaded roller also has two external threaded sections, with the threads running in opposite directions to match the threaded sections of the cylindrical surface of the roller screw stage. This improves the gearbox's resistance to impact loads.

[0011] A hinge is also proposed, comprising a two-stage gearbox according to the present invention, a first hinge portion fixedly secured to the gearbox housing, and a second hinge portion fixedly secured to a screw-type drive shaft. The proposed hinge, thanks to its use of the proposed gearbox, can be effectively used in equipment requiring high-power transmission with high positioning accuracy, particularly in robotic manipulators, steering columns, yoke drives, machine tools, and medical equipment. Brief description of the drawings

[0012] The present invention will now be described in detail with reference to the accompanying drawings, in which: FIG. 1 shows a sectional view of the proposed two-stage gearbox according to a preferred embodiment, FIG. 2 shows a side view of the proposed two-stage gearbox according to the preferred embodiment, with a partial section to illustrate the coupling assembly for connecting the gearbox to the drive mechanism, FIG. 3 shows a sectional view of the proposed two-stage gearbox according to a preferred embodiment with an external source of rotary motion, FIG. 4 shows an illustration of a hinge containing the proposed two-stage gearbox. Implementation of the invention

[0013] FIG. 1 shows a sectional view of the proposed two-stage gearbox according to a preferred embodiment, which comprises a housing 1 consisting of a connected housing part 17 for a roller screw transmission, having a section of an internal cylindrical surface on which two sections with threads are located, wherein the direction of said threads is opposite, and a housing part 23 for a planetary transmission, having a section of an internal cylindrical surface for accommodating bearings 8 of a crown wheel 2 on it, and a gear ring for fastening a sun wheel 5 of a planetary transmission. The gearbox also comprises a planetary gear transmission (planetary stage of the gearbox), located in part 23 of the housing, a roller screw transmission (roller screw stage of the gearbox), located in part 17 of the housing, and a central shaft 6, passing through parts 17 and 23 of the housing, which is made hollow.The shaft 6 is mounted in bearings 10, which are restrained from axial movement by retaining rings and a spacer 29 located between the bearings 10. The bearings 10 are ball bearings mounted with support on a roller screw stage, while the planetary stage is mounted in part 23 of the housing with support on the shaft 6, as will be described below. According to other embodiments, the shaft 6 can be made solid, and the bearings 10 can be made in the form of bearings of other types, for example, roller bearings. Parts 17 and 23 of the housing 1 of the gearbox are connected to form the internal space of the housing of the two-stage gearbox using a screw connection 11.

[0014] The planetary stage of the gearbox comprises a sun wheel 5 having a toothed rim, which is fixedly mounted on the shaft 6 in interaction with the toothed rim of part 23 of the housing 1, a carrier 7, which rotates together with the shaft 6, satellites 22 and a crown wheel 2, which is the input link of the gearbox. The planetary stage also comprises a coupling gear 14, which is the output link in the planetary transmission and is mounted in part 23 of the housing 1 on the shaft 6 on bearings 28, i.e. with the possibility of rotation relative to the shaft 6. The crown wheel 2 has an external gear ring, access to which is provided from the outside of the part 23 of the housing 1, and an internal gear ring facing the inside of the part 23 of the housing 1, and is installed in the bearing supports 8 of the crown wheel, which are interconnected bearings mounted on the specified section of the internal cylindrical surface of the part 23 of the housing.The bearing supports 8 are installed in the housing 1 without the possibility of axial movement, resting on one side against the shoulder formed in part 23 of the housing and against the shoulder on the crown wheel 2, and on the other side, held from movement by a retaining ring installed in the crown wheel 2 and in part 23 of the housing 1. Between the bearing supports 8 there is a spacer ring.

[0015] The planet carrier 7 of the planetary stage is also mounted on the shaft 6 without the possibility of axial movement and has openings in which the bearing supports 9 of the satellites are mounted, fixed from axial movement by the retaining ring 13. The planet carrier 7 is also fixed from axial movement on the shaft 6 by retaining rings. The planetary satellites 22 are mounted in the said openings in the planet carrier 7 on the bearing supports 9. The satellites 22 are made composite and comprise a first part of the satellite with the first toothed rim 3, which has a cylindrical surface on which the bearing supports 9 are mounted, and a splined section, and a second part of the satellite, which is made in the form of a gear wheel with a second toothed rim 4, mounted on the splined section of the first part of the satellite. The parts of the satellite 22 are thus connected to each other by a splined connection, and their mutual movement is prevented by installing a retaining ring 12.

[0016] The bearing supports 8 of the crown wheel 2 are preferably ball bearings. The bearing supports 9 of the planetary stage satellites 22 are preferably roller bearings, but radial thrust ball bearings may also be used. The bearing supports 10 of the shaft 6 are preferably ball bearings 10, but tapered roller bearings may also be used.

[0017] The number of satellites 22, according to the preferred embodiment, is three. The number of satellites may be greater or less than three, depending on the force transmitted by the gearbox. In this case, the holes in the carrier 7 are made in such a way as to ensure the placement of the satellites while maintaining the satellite proximity and coaxiality conditions. The first gear ring 3 of the planetary satellites 22 meshes with the gear ring of the sun wheel 5 and the internal gear ring of the crown wheel 2, and the second gear ring 4 of the planetary satellites meshes with the gear wheel 14.

[0018] The roller screw stage of the gearbox also comprises a connecting gear wheel 14, which is the input link in the roller screw stage, and a plurality of satellites of the roller screw stage, which are threaded rollers 16. The gear wheel 14 is thus formed as a single part and is mounted with the possibility of rotation relative to the shaft 6 on a bearing 28, which in the illustrated embodiment is a needle bearing. Furthermore, the gear wheel 14 is fixed against axial movement by means of a bearing support 21 of the carrier and retaining rings, which fix the bearing support 21 from movement on the gear wheel 14. The threaded rollers 16 have two sections of external thread, wherein the direction of these threads is opposite, and are arranged in part 17 of the housing 1 evenly around the circumference. The thread sections can be separated by a groove.According to another embodiment, the roller screw stage may have a single threaded roller 16, with the number of rollers being selected depending on the availability of free space sufficient to accommodate the rollers with the required clearance between them, and on the magnitude of the torque applied to the output link of the gearbox. The external thread sections of the threaded rollers 16 are engaged with the said thread of the section of the internal cylindrical surface of part 17 of the housing. The pitch angle of the said section of the external thread of the threaded rollers 16 and the said thread of the section of the internal cylindrical surface of part 17 of the housing are equal, and their directions coincide. The multidirectional threading of the threaded rollers 16 prevents axial movement of the said rollers 16, while allowing them to roll along the internal thread of part 17 of housing 1 of the gearbox.The presence of the two sections of threads with opposite directions on the threaded rollers 16 and part 17 of the housing 1 also makes it possible to balance the axial forces that arise when applying torque to the output link of the gearbox and acting between the satellite and the housing.

[0019] The roller screw stage also comprises flanges 15 and 27, which are rigidly connected to one another and form the carrier of the roller screw stage. The threaded rollers 16 have cylindrical sections on both sides of the threaded sections, on which bearings 19 are mounted, supporting the radial load acting on the threaded rollers 16 and allowing said rollers 16 to rotate about their axes. The bearings 19, in turn, are mounted in holes uniformly distributed around the circumference of the flanges 15 and 27. In the embodiment shown, the bearings 19 are designed as needle bearings to reduce the overall dimensions of the gearbox; however, in other embodiments, said bearings may be designed as, for example, ball bearings. Flanges 15 and 27 are installed in part 17 of housing 1 with the possibility of rotation around their axis in bearings 18, which are installed in part 17 of housing 1, and in bearings 10, which are installed on shaft 6.Thus, the threaded rollers are secured in the roller screw carrier without the ability to move radially. According to one embodiment, the output element of the proposed gearbox is the roller screw carrier. According to another embodiment, the output element of the gearbox is the gearbox housing 1.

[0020] Implementation options are possible in which the inner cylindrical surface of part 17 of housing 1 has one internal thread section, and each threaded roller 16 has one external thread section or more than two external thread sections. It should be noted that the number of thread sections on part 17 of housing 1 and threaded roller 16 depends on the required torque on the output shaft. The more thread sections, given the increased total length of the threads engaged, the greater the torque that can be applied to the output link and the greater the gearbox's resistance to impact loads and torque overloads on the output link.

[0021] The roller screw stage also comprises gear wheels 20 fixedly mounted on the threaded rollers 16, for example by means of a splined connection, which is realized by placing a key in keyways made in the connecting part of the threaded rollers 16, which has a cylindrical shape and on which there is no thread or toothed crown, and the corresponding keyways made on the inner cylindrical surface of the mounting hole of the gear wheels 20. Preventing the movement of the gear wheel 20 relative to the threaded roller 16 can also be ensured by installing a retaining ring in a groove made in the connecting part of the threaded rollers 16, or by using an adhesive or welding when connecting the gear wheel 20 and the threaded roller 16. The gear wheels 20 are in mesh with the gear wheel 14, so that the transmission of rotation from the input link of the roller screw stage to the threaded rollers 16 is ensured.

[0022] To perform its function as the input link of the roller screw stage and the output link of the planetary stage, the gear wheel 14 has two toothed rims, one of which meshes with the second toothed rim 4 of the planetary gear satellites, and the second meshes with the gear wheel 20 of the roller screw. According to another embodiment, the gear wheel 14 may have a single toothed rim of sufficient length to mesh with the rim 4 and the gear wheel 20. A bearing support 21 of the carrier is installed between the gear wheel 14 and the carrier of the roller screw, allowing the carrier to rotate relative to the gear wheel 14.

[0023] As can be seen in FIG. 2, the housing 1 of the proposed gearbox may comprise a hollow portion 30, which has a cylindrical surface and in which a unit 37 for connection with a drive mechanism is located. The said unit 37 comprises a shaft 31 for connection with a drive mechanism (motor). The shaft 31 has a cylindrical surface with a keyway. Instead of a keyway, a spline can be made to form a splined connection with the bushing of the drive mechanism. The unit 31 also comprises bearing supports 33 and 34, which are located on the cylindrical surface of the hollow portion 30 without the possibility of axial movement and in which the shaft 31 is mounted, while a gear wheel 32 is fixedly fixed on the shaft 31, which is engaged with the external teeth of the crown wheel 2 and is also a part of the unit 31 for connection with the drive mechanism. The axis of the shaft 31 is offset from the axis of the housing 1 of the gearbox.The gearbox may also contain a cover 35, covering the hollow part 30 of the housing 1 and attached to the housing 1 with screws, wherein the cover fixes the shaft 31 and bearings 33 and 34 from axial movement by providing corresponding thrust flanges on the cover.

[0024] Alternatively, as shown in FIG. 3, the crown wheel 2 can engage with the gear wheel 41 of the external drive mechanism 40, which does not require changing the design of the housing 1.

[0025] When the output element of the gearbox is a roller screw carrier, the proposed gearbox operates as follows. When the crown wheel 2 of the planetary stage rotates by the externally toothed ring gear, it drives the planetary stage satellites 22. The satellites 22 of the planetary stage, rolling with their first toothed crown 3 on the sun wheel 5, set the planet carrier 7 in motion. The satellites 22 of the planetary stage, with their second toothed crown 4, transmit to the toothed wheel 14 the joint rotation of the planet carrier 7 and the first toothed crown 3 of the satellites of the planetary stage, thereby setting in rotation the moving parts of the roller-screw stage of the gearbox, namely, first of all, the toothed wheels 20, which are engaged with the toothed sun wheel 14, are set in rotation, thus the toothed wheels 20 perform a planetary motion, rotating around their axis and the axis of the gearbox.Along with the gear wheels 20, the threaded rollers 16 roll along the threaded section of the housing portion 17, thereby also performing planetary motion. During this rolling motion, the threaded rollers 16 generate a circumferential force (a force directed tangentially to the circumference on which the threads of the rollers 16 and the housing portion 17 meet), which is transmitted via the bearings 19 to the roller screw carrier, causing it to rotate. This generates a torque between the carrier and the gearbox housing 1, and a change in torque and rotational speed occurs between the sun wheel 14 and the roller screw carrier.

[0026] When the gearbox output link is gearbox housing 1, the planet carrier remains stationary, and after the planetary stage sets gear wheel 14 in rotation, gear wheels 20, which are engaged with it, rotate about their axes. Threaded rollers 16, connected to gear wheels 20, then rotate about their axes and generate a circumferential force, which causes housing 1 to rotate about its axis. This generates a torque between the planet carrier and housing 1, and the magnitude of the torque and the speed of rotation between sun wheel 14 and housing 1 change.

[0027] The proposed two-stage gearbox can be used in a hinge. FIG. 4 shows an embodiment of such a hinge. The hinge in this embodiment comprises a first hinge portion 50, fixed in place on the gearbox housing 1 using screws 52, which pass through openings made in the housing portion 17, and a second hinge portion 51, fixed in place on the carrier (flange 15) of the roller screw stage of the gearbox using screws 53. Depending on which gearbox link is the output, either the first or the second hinge portion can be driven into rotation using the gearbox.The hinge, thanks to the use of the proposed two-stage gearbox, can be used in tools and equipment that require high power transmission with high positioning accuracy, in particular in robotic manipulators, steering columns, stock drives, metalworking machines, and medical equipment.

[0028] The preferred embodiments of the proposed two-stage gearbox and joint are presented above, but those skilled in the art will recognize that other embodiments are possible without significantly departing from the essence of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed in the description for illustrative purposes, but encompasses all possible modifications and alternatives within the scope of the present invention, as defined by the following claims. List of reference designations: 1 - gearbox housing, 2 - planetary stage crown wheel, 3 - the first gear ring of the planetary stage satellites, 4 - the second gear ring of the planetary stage satellites, 5 - solar wheel of the planetary stage, 6 - central shaft of the gearbox, 7 - planetary stage carrier, 8 - bearing supports of the planetary stage crown wheel, 9 - bearing supports of planetary stage satellites, 10 - bearing supports of the central shaft of the gearbox, 11 - screws, 12, 13 - planetary stage retaining rings, 14 - connecting gear (output link of the planetary stage and input link of the roller screw stage), 15 - flange of the roller screw stage carrier, 16 - threaded rollers of the roller-screw stage (satellites of the roller-screw stage), 17 - part of the gearbox housing in which the roller-screw stage is located, 18 - bearing of the roller-screw stage carrier 19 - bearing of the threaded roller of the roller screw stage - gear wheels of the roller screw stage, - bearing support of the roller screw stage carrier, - planetary stage satellites, - part of the gearbox housing for placing the planetary gear, - flange of the roller screw stage carrier, - gear wheel bearing, - spacer, - hollow part of the body, - shaft for connection with the drive mechanism, - gear wheel, , 34 - bearing supports of the shaft for connection with the drive mechanism - cover, - a unit for connecting to a drive mechanism, - external drive mechanism, - gear wheel of the external drive mechanism, - the first part of the hinge - the second part of the hinge, , 53 - screws

Claims

CLAUSES OF THE INVENTION 1. A two-stage gearbox comprising: a housing and gear transmissions located in it, connected to each other with the possibility of transmitting rotary motion, characterized in that the said transmissions are a planetary stage having an input and output link, and a roller screw stage having an input and output link, wherein the output link of the planetary stage and the input link of the roller screw stage are made in the form of a single part.

2. A gear reducer according to item 1, characterized in that the gearbox housing comprises a housing part for accommodating a planetary stage and a housing part for accommodating a roller-screw stage, connected to each other, wherein the housing part for accommodating the roller-screw stage comprises a section of an internal cylindrical surface on which at least one section with a thread is located, the planetary stage comprises a sun wheel, a crown wheel, which performs the function of the input link of the planetary stage and a gearbox, which are in interaction with each other, a central shaft passing through the specified parts of the housing, a carrier mounted with the possibility of rotation together with the central shaft, satellites mounted in the carrier with the possibility of rotation and having two toothed rims, a connecting toothed wheel, which performs the function of the output link of the planetary stage, and the roller screw stage comprises a connecting gear wheel, which interacts with each other and performs the function of the input link of the roller screw stage, a carrier, which is mounted in the housing with the possibility of rotation relative to the shaft and in which at least one threaded roller is mounted with the possibility of rotation, comprising at least one section of an external thread, interacting with the thread of the said section of the internal cylindrical surface, a gear wheel, connected to the said at least one threaded roller, interacting with the connecting gear wheel.

3. A gear reducer according to any of paragraphs. 1-2, characterized in that the input link of the planetary transmission has an external toothed rim for interaction with an external source of rotary motion.

4. A gear reducer according to any one of paragraphs 1-3, characterized in that the output link of the roller screw transmission has a fastening for connection to an external actuator.

5. A gearbox according to claim 2, characterized in that the section of the inner cylindrical surface of the roller screw stage contains two sections with threads, wherein the direction of said threads is opposite, and at least one threaded roller also has two sections of external threads, wherein the direction of these threads is opposite to correspond to the sections of the threads of the cylindrical surface of the roller screw stage.

6. A hinge comprising a gearbox according to any one of paragraphs 1-5, a first part of the hinge fixed without the possibility of movement on the housing of the gearbox, and a second part of the hinge fixed on the carrier of the roller screw transmission without the possibility of movement relative to it.

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