Planetary set of a planetary screw drive

Abstract

A planetary gear set of a planetary roller screw drive formed by a plurality of planets (3) provided with feed grooves (9) and guide grooves (10) arranged around the planetary axis, wherein the feed grooves (9) are provided for engagement with a screw thread (5) of a threaded spindle (1) and the guide grooves (10) are provided for engagement with nut-side grooves (4) of a spindle nut (2), and wherein the planets (3) are provided with markings (11), and the planets (3) of the planetary gear set have a pin (8) arranged coaxially with the planetary axis at both axial ends, wherein at least one of the planets (3) is provided on only one of its two pins (8) with a groove pattern (12) forming the marking (11), characterized in that the groove pattern (12) consists of a plurality of axially adjacent coding grooves (13) arranged around the planetary axis,wherein both the number of coding grooves (13) and the axial spacing of successive coding grooves (13) form the groove pattern (12).,

Description

[0001] The present invention relates to a planetary gear set of a planetary roller screw drive.

[0002] From DE 195 16 199 C2 and DE 197 50 585 A1, a planetary roller screw drive was known which had a threaded spindle and a spindle nut arranged on the threaded spindle. A planetary set consisting of a plurality of planets is arranged between the threaded spindle and the spindle nut. The spindle nut is provided on its inner circumference with nut-side grooves arranged around the spindle axis. The threaded spindle is provided with a screw thread wound around the spindle axis. The planets have feed grooves and guide grooves arranged around the planet axis. The feed grooves are designed to engage with the screw thread of the threaded spindle. The guide grooves are designed to engage with the nut-side grooves of the spindle nut.

[0003] The planets, known as rollers, are arranged in a specific order, whereby the determination of this specific order is made possible by the provision of a corresponding marking on the end face of the rollers.

[0004] The object of the present invention was to provide a planetary gear set which provides improved marking of the planets in order to enable a perfect formation of the planetary gear set.

[0005] According to the invention, this object was achieved by the planetary gear set according to claim 1. The fact that the planets of the planetary gear set have a pin arranged coaxially to the planetary axis at both axial ends, with at least one of the planets being provided with a groove pattern on only one of its two pins, results in the following advantages: Firstly, the journal can have a dual function: firstly, it can support the groove pattern, and secondly, the planets can be guided in cages in a conventional manner. These cages are provided with bores corresponding to the number of planets in the planetary gear set, into which the planetary journals engage. In this way, the planets can be distributed around the circumference with equal spacing from one another. Secondly, the groove pattern can be formed into the outer surface of the journal by non-cutting forming. This is easily achieved using appropriate tools. If the groove pattern has coding grooves, these coding grooves can also enable improved lubrication of the journals in the guide cage during operation of the planetary roller screw drive if lubricant is stored in or supplied to these coding grooves of the groove pattern.

[0006] The groove pattern enables a good assignment of planets to a planetary set. If, for example, a planetary kit is provided that includes planets with five different diameters and three different offset types, a total of 15 different planets are provided in this kit. An offset type refers to planets in which the feed grooves are not mirror-symmetrical on the planets, but are axially offset from the center according to their position in the planetary set. This axial offset of the feed grooves is necessary if the planets are to be arranged axially flush in the planetary roller screw drive. This is because due to the pitch of the thread on the lead screw, the feed grooves on the planets must be aligned according to the pitch.

[0007] In the example mentioned, a groove pattern can be advantageous in which a total of up to four coding grooves are formed on only one pin of the planets.

[0008] This groove pattern is formed by at least one coding groove arranged around the planetary axis. These coding grooves can, for example, be formed onto the outer surface of the pins at no additional cost if the guide grooves and the feed grooves are formed onto the planets using appropriate rolling tools. These coding grooves can also be provided in the rolling tools.

[0009] In this manufacturing method described above, it is advantageous if the groove pattern consists of several axially adjacent coding grooves, whereby both the number of coding grooves and the axial spacing of successive coding grooves form the groove pattern.

[0010] This axial distance between two consecutive grooves can be a single pitch or a multiple of this pitch, which is provided for all coding grooves. This means that, for example, a double pitch represents the omission of a coding groove. In this way, a binary coding system can be created for the groove pattern: either a coding groove is formed in the intended location or it is not formed. With a total of four coding grooves, 15 different planets can be identified in this way through appropriate combinations.

[0011] An expedient development of a planetary gear set according to the invention provides planets which have a central section with a larger diameter and side sections with smaller diameters located axially on both sides of the central section, the central section being provided with the feed grooves and the side sections being provided with the guide grooves.

[0012] The aforementioned pins can be integrally formed onto these end sections.

[0013] The invention is explained in more detail below using an exemplary embodiment illustrated in three figures. They show: Fig. 1 a planetary roller screw drive according to the invention in perspective view with broken spindle nut, Fig. 2 a planet of the planetary roller screw drive according to the invention Fig. 1, and Fig. 3 an enlarged section of the planet Fig. 2.

[0014] The Fig. The planetary roller screw drive according to the invention, shown in Figure 1, is provided with a threaded spindle 1, a spindle nut 2 arranged on the threaded spindle 1, and a planetary gear set formed from a plurality of planets 3. The planets 3 are arranged equidistantly around the circumference. The planets 3 are arranged between the threaded spindle 1 and the spindle nut 2, with the spindle nut 2 being provided on its inner circumference with nut-side grooves 4 arranged around the spindle axis. The threaded spindle 1 is provided with a screw thread 5 wound around the spindle axis.

[0015] The planets 3 are guided at their axial ends in cages 14 so that the planets 3 have the same angular distance from each other in the circumferential direction.

[0016] Fig. 2 shows an enlarged view of a single planet 3. All planets 3 have a larger-diameter central section 6 and smaller-diameter side sections 7, to which pins 8 are connected towards the free ends of the planet 3. In the exemplary embodiment, the planet 3, together with the pins 8, is a one-piece component. The central section 6 is provided with a plurality of feed grooves 9. The side sections 7 are provided with a plurality of guide grooves 10. The guide grooves 10 and the feed grooves 9 are annularly closed and arranged parallel to a transverse plane that is arranged transversely to the planet axis. The guide grooves 10 mesh with the nut-side grooves 4, and the feed grooves 9 mesh with the screw thread 5 of the threaded spindle 1.

[0017] The plurality of planets 3 form a planetary gear set, with the planets 3 being arranged axially flush in the spindle nut 2. Due to the axially flush arrangement of the planets 3, their center sections 6 must be axially offset from one another in successive planets 3, depending on the pitch of the screw thread 5. This means that the planets 3 of the planetary gear set must be installed in a specific order and orientation in the planetary roller screw drive.

[0018] For their identification, some of the planets 3 of the planetary gear set are provided with markings 11, which are formed by a groove pattern 12 in accordance with the invention.

[0019] The groove pattern 12 is formed by at least one coding groove 13 arranged around the planetary axis, which is formed on the pin 8.

[0020] Fig. 3 shows an enlarged section of planet 3 from Fig.2, whereby a total of three coding grooves 13 clearly belong to this groove pattern 12.

[0021] In the case of a planet 3 which is adjacent in the circumferential direction, a different groove pattern 12 is formed; for example, it is conceivable that instead of three coding grooves 13, only one coding groove 13 is formed.

[0022] In the exemplary embodiment, the feed grooves 9 as well as the guide grooves 10 and the coding grooves 13 are produced on the planets 3 in a forming process.

[0023] The axial offset of the feed grooves 9 depends on the number of planets 3 and the pitch of the threaded spindle 1. The axial offset between adjacent planets 3 corresponds to the ratio of the pitch to the number of planets 3.

[0024] Depending on the size of the planetary screw drive and the number of planets 3 used, so-called asymmetrical planets 3 can be installed twice in a planetary screw drive by installing them in opposite orientations. While a symmetrical planet 3 can be installed in its predetermined installation position in both orientations in the planetary screw drive, this is only possible in one of the two orientations for an asymmetrical planet 3 at the specified installation position.

[0025] The number of different planets 3 can be reduced using the asymmetrical planets 3, namely by a factor of 0.5 for an even number of planets 3 and by a factor of A = 1 + 1 / 2 x (n-1) for an odd number of planets 3, where n is the number of planets 3 in the planetary set.

[0026] In the exemplary embodiment, for example, an assembly instruction can be provided that describes the sequence of the planets 3 of the planetary gear set by specifying the groove pattern 12 for the respective planet 3. With the three coding grooves 13 shown here, a total of eight different groove patterns 12 can be created by omitting one or two coding grooves 13.

[0027] The planetary gear set according to the invention can have a planet 3 whose groove pattern 12 includes the omission of all coding grooves 13. In any case, at least one of the planets 3 of the planetary gear set is provided with a coding groove 13.

[0028] The axial distance of the coding grooves 13 is predetermined, whereby, for example, if the middle coding groove 13 is omitted, the distance between the two outer coding grooves 13 corresponds to a multiple of a simple pitch. Position number list 1 threaded spindle 2 spindle nuts 3 Planet 4 nut-side groove 5 screw threads 6 Middle section 7 page section 8 cones 9 Feeding glasses 10 guide groove 11 Marking 12 groove patterns 13 Coding groove 14 cage

Claims

[1] A planetary gear set of a planetary roller screw drive, which is formed by a plurality of planets (3) which are provided with feed grooves (9) and guide grooves (10) arranged around the planetary axis, wherein the feed grooves (9) are provided for engagement with a screw thread (5) of a threaded spindle (1) and the guide grooves (10) are provided for engagement with nut-side grooves (4) of a spindle nut (2), and wherein the planets (3) are provided with markings (11), and the planets (3) of the planetary gear set have a pin (8) arranged coaxially with the planetary axis at both axial ends, wherein at least one of the planets (3) is provided with a groove pattern (12) forming the marking (11) on only one of its two pins (8), characterized bythat the groove pattern (12) consists of a plurality of axially adjacent coding grooves (13) arranged around the planetary axis, wherein both the number of coding grooves (13) and the axial spacing of successive coding grooves (13) form the groove pattern (12). [2] Planetary gear set according to claim 1, wherein an axial distance between two consecutive coding grooves (13) is a simple pitch or a multiple of this pitch, which is the same for all coding grooves. [3] Planetary gear set according to at least one of claims 1 and 2, the planets (3) of which have a central section (6) of larger diameter and side sections (7) of smaller diameter located axially on both sides of the central section (6), the central section 6 being provided with the feed grooves (9) and the side sections (7) being provided with the guide grooves (10). [4] Planetary gear set according to at least one of claims 1 to 3, the planets (3) of which are provided at one of their free ends with the pin (8) having the groove pattern (12). [5] Planetary gear set according to at least one of claims 1 to 4, the coding grooves (13) of which are formed onto the planet (3) by a forming process. [6] Planetary roller screw drive, with a threaded spindle (1) and with a spindle nut (2) arranged on the threaded spindle (1) and with a planetary set formed from a planet (3) according to at least one of claims 1 to 5, the planets (3) of which are arranged distributed over the circumference between the threaded spindle (1) and the spindle nut (2), wherein the spindle nut (2) is provided on its inner circumference with nut-side grooves (4) arranged around the spindle axis and wherein the threaded spindle (1) is provided with a screw thread (5) wound around the spindle axis and wherein the planets (3) are in engagement with their feed grooves (9) in the screw thread (5) of the threaded spindle (1) and with their guide grooves (10) in engagement with the nut-side grooves (4) of the spindle nut (2).

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