GEAR SYSTEM

Abstract

A gear system includes a planetary gear and a frame structure including connection sections for attaching the frame structure to an external mechanical structure such as a nacelle of a wind power plant. The planetary gear includes a planet carrier, a sun wheel, a gear ring, and planet wheels meshing with the sun wheel and with the gear ring. The planet carrier includes a mechanical interface structure for connecting to an external rotating element such as a wind rotor. The frame structure includes a front cover shield that is a single piece of material, attached to the gear ring, and shaped to constitute a bearing cover for covering and supporting a bearing that supports the planet carrier. Thus, there is no need for a separate bearing cover.

Claims

1. A gear system comprising a frame structure comprising connection sections for attaching the frame structure to a mechanical structure external to the gear system, and a first planetary gear comprising: a sun shaft comprising a sun wheel and being rotatable with respect to the frame structure, a gear ring stationary with respect to the frame structure, a planet carrier comprising a mechanical interface structure for connecting to a rotating element external to the gear system, first and second bearings supporting the planet carrier rotatably with respect to the frame structure, and planet wheels supported rotatably with respect to the planet carrier and meshing with the sun wheel and with the gear ring, wherein the first bearing is axially between the gear ring and the mechanical interface structure of the planet carrier, and the frame structure comprises a front cover shield being a single piece of material, attached to the gear ring, and shaped to constitute a bearing cover for covering and supporting the first bearing, the bearing cover covering the first bearing to be non-seeable when the mechanical interface structure of the planet carrier is viewed axially along an axial direction of the planet carrier, and the front cover shield comprises the connection sections of the frame structure.

2. The gear system according to claim 1, wherein a diameter of a portion of the planet carrier being in contact with the first bearing is greater than a diameter of an aperture of the front cover shield through which the mechanical interface structure of the planet carrier is arranged to protrude.

3. The gear system according to claim 1, wherein the mechanical interface structure of the planet carrier and an end-section of the planet carrier constitute a single piece of material, the end-section of the planet carrier supporting first ends of planet wheel shafts of the planetary gear and another end-section of the planet carrier supporting second ends of the planet wheel shafts.

4. The gear system according to claim 2, wherein the mechanical interface structure of the planet carrier and an end-section of the planet carrier constitute a single piece of material, the end-section of the planet carrier supporting first ends of planet wheel shafts of the planetary gear and another end-section of the planet carrier supporting second ends of the planet wheel shafts.

5. The gear system according to claim 1, wherein the gear ring (108) of the first planetary gear constitutes a part of the frame structure so that an outer surface of the gear ring of the first planetary gear constitutes a part of an outer surface of the gear system.

6. The gear system according to claim 1, wherein the gear system comprises a seal between an outer surface of the mechanical interface structure of the planet carrier and a wall of an aperture of the front cover shield through which the mechanical interface structure of the planet carrier is arranged to protrude.

7. The gear system according to claim 1, wherein the gear system comprises a second planetary gear whose planet carrier is connected in a torque transferring way to the sun shaft of the first planetary gear.

8. The gear system according to claim 7, wherein the frame structure comprises an intermediate portion connected to the gear ring of the first planetary gear and to a gear ring of the second planetary gear.

9. The gear system according to claim 8, wherein the gear ring of the second planetary gear constitutes a part of the frame structure so that an outer surface of the gear ring of the second planetary gear constitutes a part of an outer surface of the gear system.

10. The gear system according to claim 7, wherein the gear system comprises a cylindrical gear comprising first and second gear wheels meshing with each other, the first gear wheel being connected in a torque transferring way to a sun shaft of the second planetary gear.

11. The gear system according to claim 1, wherein the first bearing is one of the following: a cylindrical roller bearing, a ball bearing, a plain bearing, a tapered roller bearing.

12. A wind power plant comprising: a wind rotor, a generator for producing electric power, and a gear system for transferring mechanical power from the wind rotor to the generator, wherein gear system comprises a frame structure comprising connection sections attaching the frame structure to support structures of a nacelle of the wind power plant, and a first planetary gear comprising: a sun shaft comprising a sun wheel and being rotatable with respect to the frame structure, a gear ring stationary with respect to the frame structure, a planet carrier comprising a mechanical interface structure connected to the wind rotor in a torque transferring way, first and second bearings supporting the planet carrier rotatably with respect to the frame structure, and planet wheels supported rotatably with respect to the planet carrier and meshing with the sun wheel and with the gear ring, wherein the first bearing is axially between the gear ring and the mechanical interface structure of the planet carrier, and the frame structure comprises a front cover shield being a single piece of material, attached to the gear ring, and shaped to constitute a bearing cover for covering and supporting the first bearing, the bearing cover covering the first bearing to be non-seeable when the mechanical interface structure of the planet carrier is viewed axially along an axial direction of the planet carrier, and the front cover shield comprises the connection sections of the frame structure.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0023] Exemplifying and non-limiting embodiments of the invention and their advantages are explained in greater detail below in the sense of examples and with reference to the accompanying drawings, in which:

[0024] FIGS. 1a, 1b, and 1c illustrate a gear system according to an exemplifying and non-limiting embodiment, and

[0025] FIG. 2 illustrates a wind power plant according to an exemplifying and non-limiting embodiment.

DESCRIPTION OF EXEMPLIFYING AND NON-LIMITING EMBODIMENTS

[0026] The specific examples provided in the description below should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description are not exhaustive unless otherwise explicitly stated.

[0027] FIGS. 1a and 1b show a gear system 101 according to an exemplifying and non-limiting embodiment. FIG. 1c shows a section taken along polylines A-A shown in FIGS. 1a and 1b. A part of the geometric section surface is parallel with the yz-plane of a coordinate system 199 and another part of the geometric section surface is parallel with the xz-plane of the coordinate system 199. The gear system 101 comprises a frame structure 102 that comprises connection sections 103 and 104 for attaching the frame structure 102 to a mechanical structure external to the gear system 101. The connection sections 103 and 104 prevent the frame structure 102 from rotating with respect to the external mechanical structure when the connection sections are attached to the external mechanical structure. The external mechanical structure can be for example a support structure in a nacelle of a wind power plant. In the exemplifying case illustrated in FIGS. 1a-1c, the gear system 101 comprises a first planetary gear 105, a second planetary gear 119, and a cylindrical gear 123. It is however also possible that a gear system according to an exemplifying and non-limiting embodiment comprises a planetary gear only, or only a cylindrical gear in addition to a planetary gear, or some other gear arrangement in addition to a planetary gear.

[0028] The planetary gear 105 comprises a sun shaft 106 comprising a sun wheel 107. The sun shaft 106 is rotatable with respect to the frame structure 102. The planetary gear 105 comprises a gear ring 108 that is stationary with respect to the frame structure 102. The planetary gear 105 comprises a planet carrier 109 that comprises a mechanical interface structure 110 for connecting to a rotating element external to the gear system. The external rotating element can be for example a wind turbine. The planet carrier 109 is rotatably supported with respect to the frame structure 102 with the aid of first and second bearings 111 and 112, where the first bearing 111 is axially, i.e. in the axial direction, between the gear ring 108 and the mechanical interface structure 110 of the planet carrier 109 and the second bearing 112 is axially between the first and second planetary gears 105 and 119. In FIGS. 1a-1c, the axial direction is parallel with the z-axis of the coordinate system 199. In this exemplifying case, the first and second bearings 111 and 112 are cylindrical roller bearings. The first bearing 111 can be some other bearing than a cylindrical roller bearing. For example, the first bearing 111 can be a ball bearing or a plain bearing. It is also possible that the first bearing 111 is a tapered roller bearing and the axial clearance of the tapered roller bearing is adjusted with means for adjusting the axial position of the planet carrier 109, where the means are located between the planetary gears 105 and 119. Correspondingly, the second bearing 112 can be some other bearing than a cylindrical roller bearing, e.g. a ball bearing, a plain bearing, or a tapered roller bearing. The first bearing 111 and the second bearing 112 can represent different bearing types. Thus, the invention is not limited to any specific bearing types.

[0029] The planetary gear 105 comprises planet wheels supported rotatably with respect to the planet carrier 109 and meshing with the sun wheel 107 and with the gear ring 108. In FIG. 1c, one of the planet wheels is denoted with a reference 113. The frame structure 102 comprises a front cover shield 114 that is a single piece of material such as e.g. steel or cast iron. The front cover shield 114 is attached to the gear ring 108, and the front cover shield 114 is shaped to constitute a bearing cover for covering and supporting the first bearing 111. The bearing cover covers the first bearing 111 so that the first bearing 111 is not seeable when the mechanical interface structure 110 of the planet carrier is viewed axially along the positive z-direction of the coordinate system 199. As shown in FIG. 1c, the diameter D1 of a portion of the planet carrier 109 being in contact with the first bearing 111 is greater than the diameter D2 of an aperture of the front cover shield 114 through which the mechanical interface structure 110 of the planet carrier is arranged to protrude. As the front cover shield 114 is shaped to act as the bearing cover, there is no need for a separate bearing cover and therefore the number of components of the gear system as well as the number of assembly phases is reduced.

[0030] In the exemplifying gear system 101 illustrated in FIGS. 1a-1c, the mechanical interface structure 110 of the planet carrier 109 and an end-section 115 of the planet carrier constitute a single piece of material. The end-section 115 supports first ends of planet wheel shafts of the planetary gear, and the planet carrier comprises another end-section that supports second ends pf the planet wheel shafts. The arrangement where the mechanical interface structure 110 and the end-section 115 constitute a single piece of material provides a compact and mechanically strong construction.

[0031] In the exemplifying gear system 101 illustrated in FIGS. 1a-1c, the gear ring 108 of the planetary gear 105 constitutes a part of the frame structure 102 so that an outer surface of the gear ring 108 constitutes a part of an outer surface of the gear system 101. It is also possible that a frame structure of a gear system according to an exemplifying and non-limiting embodiment constitutes a housing so that a gear ring is inside the housing.

[0032] FIG. 1c shows a magnification of a part 118 of the section view of the gear system 101. The exemplifying gear system 101 comprises a seal 116 between the outer surface of the mechanical interface structure 110 and a wall of the aperture of the front cover shield 114 through which the mechanical interface structure 110 is arranged to protrude. The seal 116 can be for example a felt seal that is axially supported with a support plate 117. It is also possible that the seal 116 is a flinger ring seal.

[0033] The second planetary gear 119 comprises a planet carrier 120 that is connected in a torque transferring way to the sun shaft 106 of the first planetary gear 105. Furthermore, the second planetary gear 119 comprises a gear ring 122, a sun shaft 125 comprising a sun wheel, and planet wheels rotatably supported with respect to the planet carrier 120 and meshing with the gear ring 122 and with the sun wheel of the second planetary gear 119.

[0034] In the exemplifying gear system 101 illustrated in FIGS. 1a-1c, the frame structure 102 comprises an intermediate portion 121 connected to the gear ring 108 of the first planetary gear 105 and to the gear ring 122 of the second planetary gear 119. The gear ring 122 of the second planetary gear 119 constitutes a part of the frame structure 102 so that an outer surface of the gear ring 120 of the second planetary gear constitutes a part of the outer surface of the gear system 101.

[0035] The cylindrical gear 123 comprises a first gear wheel 124 that is connected in a torque transferring way to the sun shaft 125 of the second planetary gear 119. The cylindrical gear 123 comprises a second gear wheel 126 that can be connected to a device external to the gear system 101. The external device can be for example a generator.

[0036] The front cover shield 114 comprises the connection sections 103 and 104 for attaching the frame structure 102 to a mechanical structure external to the gear system 101. In this exemplifying case, the connection sections 103 and 104 are radially protruding projections. It is also possible that both the front cover shield 114 and the intermediate portion 121 comprise connection sections for attaching the frame structure 102 to a mechanical structure external to the gear system.

[0037] FIG. 2 illustrates a wind power plant according to an exemplifying and non-limiting embodiment. The wind power plant comprises a wind rotor 250, a generator 252 for producing electric power, and a gear system 201 for transferring mechanical power from the wind rotor 250 to the generator 252. The gear system 201 can be for example such as the gear system 101 illustrated in FIG. 1a-1c. The wind rotor 250 is connected in a torque transferring way to the planet carrier of the first planetary gear of the gear system 201, and the frame structure of the gear system 201 is attached to support structures of a nacelle 251 of the wind power plant.

[0038] The specific examples provided in the description given above should not be construed as limiting the scope and/or the applicability of the accompanied claims. Lists and groups of examples provided in the description given above are not exhaustive unless otherwise explicitly stated.