Patent Description:
A planetary gear comprises a planet wheel carrier, a sun shaft, a gear ring, and planet wheels supported by the planet wheel carrier so that the planet wheels are meshing with the sun shaft and with the gear ring. Bearings of the planet wheels can be splash lubricated so that the bearings are surrounded by droplets of oil when the planetary gear is operating. It is also possible that the bearings are lubricated with pressure-feed lubrication so that the planet wheel carrier comprises oil channels for conducting oil to the bearings. The pressure-feed lubrication is advantageous because an oil circulation path that comprises the above-mentioned oil channels can be provided with an oil filter so as to keep the oil clean. Furthermore, the oil circulation path can be provided with temperature control means for controlling the temperature of the oil to be in a desired temperature range. Furthermore, the above-mentioned oil channels can be designed so that the oil is directed to most critical places in the bearings and other parts of the planetary gear. An inherent challenge related to pressure-feed lubrication of the kind mentioned above is the need to supply oil from a stationary part of a planetary gear to a rotating planet wheel carrier. On one hand, oil leakage which takes place in an oil supply connection between the stationary part and the rotating planet wheel carrier should be so small that sufficient oil pressure can be maintained in oil channels of the planet wheel carrier. On the other hand, an oil supply connection where the leakage is sufficiently small has its own challenges. In cases where the oil supply connection is contactless, clearances of the oil supply connection between the stationary part and the rotating planet wheel carrier have to be small and thus there is a risk of unintentional mechanical contacts which may damage the surfaces touching each other. In cases where the oil supply connection comprises a seal element having mechanical contacts with both the stationary part and the rotating planet wheel carrier, the seal element may increase the need for maintenance work and thereby the operating costs of the planetary gear.

Publication <CIT> describes a planetary gearbox where an internal gear ring is arranged in a box body, a planetary carrier is rotatably supported in the box body with a cylindrical-surface bearing bush, and planetary wheels are rotatably supported in the planetary carrier with spherical bearing bushes and planetary wheel shafts. The cylindrical-surface bearing bush acts as an oil supply connection from the box body to the planetary carrier.

Publication <CIT> describes a wind power step-up gear box which comprises a box body, a planet carrier, a sun wheel, planet wheels, and an annular gear. At least one inner oil spray nozzle which sprays oil to the sun wheel and at least one outer oil spray nozzle which sprays oil to the annular gear are arranged on the planet carrier. A first lubricating oil circuit which supplies oil to the inner oil spray nozzle and to the outer oil spray nozzle is arranged in the planet carrier. A first annular oil groove which is communicated with the first lubricating oil circuit is formed in the end surface of one end of the planet carrier. The axis of the first annular oil groove and the axis of the planet carrier coincide. An oil spray ring is fixedly arranged on the box body, and one end of the oil spray ring is inserted into the first annular oil groove. The oil spray ring and the annular oil groove define a closed annular oil tank. An oil supply circuit is arranged on the box body, and an internal oil circuit which communicates the annular oil circuit and the oil supply circuit is arranged in the oil spray ring.

The following presents a simplified summary in order to provide a basic understanding of some aspects of various invention embodiments.

In accordance with the present invention, there is provided a new planet wheel carrier for a planetary gear. A planet wheel carrier according to the invention comprises the features of claim <NUM>.

The above-mentioned slide bearing is not only a bearing but also an oil supply connection from the frame to the planet wheel carrier whereas the one or more conical roller bearings receive both radial and axial forces thus allowing the slide bearing to be simple and cost effective. The arrangement comprising the slide bearing and the above-mentioned oil channels is suitable for implementing pressure-feed lubrication for the bearings of the planet wheels. The pressure-feed lubrication is advantageous especially when the bearings of the planet wheels are slide bearings.

In accordance with the present invention, there is provided also a new planetary gear that comprises:.

A number of exemplifying and non-limiting embodiments of the invention are described in accompanied dependent claims.

Various exemplifying and non-limiting embodiments of the invention both as to constructions and to methods of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific exemplifying embodiments when read in connection with the accompanying drawings.

The features recited in the accompanied dependent claims are mutually freely combinable unless otherwise explicitly stated.

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:.

<FIG> shows a section view of a planetary gear according to an exemplifying and non-limiting embodiment of the invention. The section is taken along a section plane which is parallel with the yz-plane of a coordinate system <NUM> and which coincides with the geometric center line of the of the planetary gear. In <FIG>, the geometric center line is depicted with a dash-and-dot line. The planetary gear comprises a sun shaft <NUM>, a gear ring <NUM>, planet wheels, and a planet wheel carrier <NUM> according to an exemplifying and non-limiting embodiment of the invention for supporting the planet wheels so that the planet wheels are meshing with the sun shaft <NUM> and with the gear ring <NUM>. <FIG> shows a section view of one of the planet wheels. The planet wheel shown in <FIG> is denoted with a reference <NUM>. The number of the planet wheels can be for example <NUM>, <NUM>, <NUM>, or <NUM>. Increasing the number of the planet wheels decreases torque transferred by each planet wheel and thereby smaller gear teeth are sufficient to transfer the torque. Another way to see the effect of increasing the number of the planet wheels is that increasing the number of the planet wheels increases the amount of those of the gear ring teeth and correspondingly the amount of those of the planet wheel teeth as well as the amount of those of the sun shaft teeth which, at each moment of time, are involved in torque transfer. In many cases, the outer diameter of the gear ring <NUM> can be smaller when there are e.g. five planet wheels than when there are e.g. four or three planet wheels.

The planet wheel carrier <NUM> comprises a carrier body <NUM> for supporting the shafts of the planet wheels. <FIG> shows a section view of the shaft of the planet wheel <NUM>. The shaft shown in <FIG> is denoted with a reference <NUM>. The carrier body <NUM> comprises a connection section <NUM> that can be connected to an external mechanical system that can be, for example but not necessarily, a rotor of a wind turbine. The carrier body <NUM> comprises a first end-section <NUM> for supporting first ends of the shafts of the planet wheels and a second end-section <NUM> for supporting second ends of the shafts of the planet wheels. In this exemplifying case, the carrier body <NUM> comprises a support structure <NUM> that connects the first and second end-sections <NUM> and <NUM> to each other in order to increase the mechanical stiffness of the carrier body <NUM>. The support structure <NUM> is located between the first and second end-sections <NUM> and <NUM> in the axial direction and between the planet wheels in the circumferential direction of the planet wheel carrier <NUM>. The axial direction is parallel with the z-axis of the coordinate system <NUM>.

The carrier body <NUM> and the shafts of the planet wheels comprise oil channels for conducting oil to the bearings of the planet wheels. In <FIG>, an oil channel of the carrier body <NUM> is denoted with a reference <NUM>, an oil channel of the shaft <NUM> of the planet wheel <NUM> is denoted with a reference <NUM>, and the bearings of the planet wheel <NUM> are denoted with references <NUM> and <NUM>. In the exemplifying planetary gear illustrated in <FIG>, the bearings of the planet wheels are cylindrical roller bearings. The planet wheel carrier <NUM> comprises a slide bearing <NUM> for rotatably supporting a first end <NUM> of the carrier body <NUM> with respect to a frame <NUM> of the planetary gear. <FIG> shows a magnified view of a figure portion <NUM> so as to illustrate the slide bearing <NUM>. The slide bearing <NUM> comprises an oil channel <NUM> for conducting oil from an oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. A part of the oil supplied via the oil channel <NUM> of the frame <NUM> lubricates the slide bearing <NUM> and the rest of the oil is delivered to the planet wheel carrier <NUM> and thereby to the bearings of the planet wheels. Therefore, the slide bearing <NUM> is used as an oil supply connection which enables pressurized oil supply to the bearings of the planet wheels. The planet wheel carrier <NUM> comprises conical roller bearings for rotatably supporting a second end <NUM> of the carrier body <NUM> with respect to the frame <NUM>. The conical roller bearings are capable of receiving axial forces directed to the carrier body <NUM>. Therefore, the slide bearing <NUM> that supports the first end <NUM> of the carrier body <NUM> can be simple and cost effective. In this exemplifying case, the conical roller bearings comprise axially successive first and second conical roller bearings <NUM> and <NUM> whose coning angles open towards each other. Thus, the combination of the conical roller bearings <NUM> and <NUM> is capable of receiving axial forces which have the positive z-direction of the coordinate system <NUM> as well as axial forces which have the negative z-direction of the coordinate system <NUM>.

In the exemplifying case illustrated in <FIG>, the slide bearing <NUM> comprises two axially successive bearing elements so that there is an axial gap between the bearing elements. As shown by the magnified view of the figure portion <NUM>, the axial gap constitutes the oil channel <NUM> for conducting oil from the oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. One of the axially successive bearing elements comprises bearing bushes <NUM> and <NUM> and the other one of the bearing elements comprises bearing bushes <NUM> and <NUM>. The bearing bushes <NUM>-<NUM> can be according to known slide bearing technology. For example, the bearing bushes <NUM> and <NUM> can be made of material that is softer than the material of the bearing bushes <NUM> and <NUM>. It is, however, also possible that the bearing bushes <NUM> and <NUM> are made of material that is softer than the material of the bearing bushes <NUM> and <NUM>. The softer material can be for example white metal and the harder material can be for example steel. It is also possible that the bearing bushes <NUM> and <NUM>, or the bearing bushes <NUM> and <NUM>, are multilayer bearing bushes each of which comprises a backing made of e.g. steel, one or more intermediate layers made of one or more suitable materials that are softer than the material of the backing, and a surface coating for providing appropriate sliding properties and wear resistance. It is also possible that a surface of the carrier body <NUM> is adapted to act as a siding surface and each of the axially successive bearing elements comprises only one bearing bush. It is, however, advantageous that all sliding surfaces of the slide bearing <NUM> are implemented with replaceable components such as the bearing bushes <NUM>-<NUM>.

<FIG> shows a section view of a planetary gear not being a part of the invention. The section is taken along a section plane which is parallel with the yz-plane of a coordinate system <NUM> and which coincides with the geometric center line of the of the planetary gear. In <FIG>, the geometric center line is depicted with a dash-and-dot line. The planetary gear comprises a sun shaft <NUM>, a gear ring <NUM>, planet wheels, and a planet wheel carrier <NUM> for supporting the planet wheels so that the planet wheels are meshing with the sun shaft <NUM> and with the gear ring <NUM>. <FIG> shows a section view of one of the planet wheels. The planet wheel shown in <FIG> is denoted with a reference <NUM>.

The planet wheel carrier <NUM> comprises a carrier body <NUM> for supporting the shafts of the planet wheels. <FIG> shows a section view of the shaft of the planet wheel <NUM>. The shaft shown in <FIG> is denoted with a reference <NUM>. The carrier body <NUM> comprises a connection section <NUM> that can be connected to an external mechanical system that can be, for example but not necessarily, a rotor of a wind turbine. The carrier body <NUM> and the shafts of the planet wheels comprise oil channels for conducting oil to the bearings of the planet wheels. In <FIG>, an oil channel of the carrier body <NUM> is denoted with a reference <NUM>, an oil channel of the shaft <NUM> of the planet wheel <NUM> is denoted with a reference <NUM>, and the bearings of the planet wheel <NUM> are denoted with a reference <NUM>. In the exemplifying planetary gear illustrated in <FIG>, the bearings of the planet wheels are slide bearings which comprise radial slide bearing sections and axial slide bearing sections. The slide bearings of the planet wheels can be according to known slide bearing technology. The slide bearings of the planet wheels make it possible to reduce the diameters of the sun shaft <NUM>, the planet wheels, and the gear ring <NUM> compared to a planetary gear whose planet wheels are supported with rolling bearings because slide bearings need less room in the radial direction than rolling bearings with the same bearing capacity would do.

The planet wheel carrier <NUM> comprises a slide bearing <NUM> for rotatably supporting a first end <NUM> of the carrier body <NUM> with respect to a frame <NUM> of the planetary gear. <FIG> shows a magnified view of a figure portion <NUM> so as to illustrate the slide bearing <NUM>. The slide bearing <NUM> comprises oil channels <NUM> for conducting oil from an oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. A part of the oil supplied via the oil channel <NUM> of the frame <NUM> lubricates the slide bearing <NUM> and the rest of the oil is delivered to the planet wheel carrier <NUM> and thereby to the slide bearings of the planet wheels. Therefore, the slide bearing <NUM> is used as an oil supply connection which enables pressurized oil supply to the slide bearings of the planet wheels. The planet wheel carrier <NUM> comprises conical roller bearings for rotatably supporting a second end <NUM> of the carrier body <NUM> with respect to the frame <NUM>. The conical roller bearings are capable of receiving axial forces directed to the carrier body <NUM>. Therefore, the slide bearing <NUM> that supports the first end <NUM> of the carrier body <NUM> can be simple and cost effective.

In this exemplifying case, the conical roller bearings comprise axially successive first and second conical roller bearings <NUM> and <NUM> whose coning angles open towards each other. Thus, the combination of the conical roller bearings <NUM> and <NUM> is capable to receive axial forces which have the positive z-direction of the coordinate system <NUM> as well as axial forces which have the negative z-direction of the coordinate system <NUM>.

In the exemplifying case illustrated in <FIG>, the sliding surfaces of the slide bearing <NUM> comprise circumferential grooves and the slide bearing <NUM> comprises radial apertures for conducting oil from the channel <NUM> of the frame <NUM> to the circumferential grooves and for conducting oil from the circumferential grooves to the oil channel <NUM> of the carrier body <NUM>. It is also possible that only one of the sliding surfaces of the slide bearing <NUM> comprises a circumferential groove. As shown by the magnified view of the figure portion <NUM>, the circumferential grooves and the radial apertures of the slide bearing <NUM> constitute the oil channels <NUM> for conducting oil from the oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. The slide bearing <NUM> comprises bearing bushes <NUM> and <NUM>. The bearing bushes <NUM> and <NUM> can be according to known slide bearing technology. For example, the bearing bush <NUM> can be made of material that is softer than the material of the bearing bush <NUM>. It is, however, also possible that the bearing bush <NUM> is made of material that is softer than the material of the bearing bush <NUM>. The softer material can be for example white metal and the harder material can be for example steel. It is also possible that the bearing bush <NUM>, or the bearing bush <NUM>, is a multilayer bearing bush which comprises a backing made of e.g. steel, one or more intermediate layers made of one or more suitable materials that are softer than the material of the backing, and a surface coating for providing appropriate sliding properties and wear resistance. It is also possible that a surface of the carrier body <NUM> is adapted to act as a siding surface and the slide bearing <NUM> comprises only one bearing bush <NUM>. It is, however, advantageous that both sliding surfaces of the slide bearing <NUM> are implemented with replaceable components such as the bearing bushes <NUM> and <NUM>.

<FIG> shows a section view of a planetary gear according to an exemplifying and non-limiting embodiment of the invention. The section is taken along a section plane which is parallel with the yz-plane of a coordinate system <NUM> and which coincides with the geometric center line of the of the planetary gear. In <FIG>, the geometric center line is depicted with a dash-and-dot line. The planetary gear comprises a sun shaft <NUM>, a gear ring <NUM>, planet wheels, and a planet wheel carrier <NUM> according to an exemplifying embodiment of the invention for supporting the planet wheels so that the planet wheels are meshing with the sun shaft <NUM> and with the gear ring <NUM>. <FIG> shows a section view of one of the planet wheels. The planet wheel shown in <FIG> is denoted with a reference <NUM>.

The planet wheel carrier <NUM> comprises a carrier body <NUM> for supporting the shafts of the planet wheels. <FIG> shows a section view of the shaft of the planet wheel <NUM>. The shaft shown in <FIG> is denoted with a reference <NUM>. The carrier body <NUM> and the shafts of the planet wheels comprise oil channels for conducting oil to the bearings of the planet wheels. In <FIG>, an oil channel of the carrier body <NUM> is denoted with a reference <NUM> and an oil channel of the shaft <NUM> of the planet wheel <NUM> is denoted with a reference <NUM>. The planet wheel carrier <NUM> comprises a slide bearing <NUM> for rotatably supporting a first end <NUM> of the carrier body <NUM> with respect to a frame <NUM> of the planetary gear. <FIG> shows a magnified view of a figure portion <NUM> so as to illustrate the slide bearing <NUM>. The slide bearing <NUM> comprises oil channels <NUM> for conducting oil from an oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. A part of the oil supplied via the oil channel <NUM> of the frame <NUM> lubricates the slide bearing <NUM> and the rest of the oil is delivered to the planet wheel carrier <NUM> and thereby to the bearings of the planet wheels. Therefore, the slide bearing <NUM> is used as an oil supply connection which enables pressurized oil supply to the bearings of the planet wheels. The planet wheel carrier <NUM> comprises conical roller bearings for rotatably supporting a second end <NUM> of the carrier body <NUM> with respect to the frame <NUM>.

In the exemplifying case illustrated in <FIG>, the slide bearing <NUM> comprises a bearing bush <NUM> that is rotatable with respect to the frame <NUM> and/or with respect to the carrier body <NUM>. The bearing bush <NUM> comprises radial apertures which constitute the oil channels <NUM> for conducting oil from the oil channel <NUM> of the frame <NUM> to the oil channel <NUM> of the carrier body <NUM>. In this exemplifying case, a surface of the carrier body <NUM> is adapted to act as a sliding surface of the slide bearing <NUM> and/or a surface of the frame <NUM> is adapted to act as a sliding surface of the slide bearing <NUM>. Correspondingly, an inner surface of the bearing bush <NUM> constitutes a sliding surface of the slide bearing and/or an outer surface of the bearing bush <NUM> constitutes a sliding surface of the slide bearing.

It is worth noting that the planetary gears illustrated in <FIG>, <FIG>, and <FIG> are non-limiting examples only. For example the slide bearing supporting the planet wheel carrier may comprise two or more axially successive inner bearing bushes and a single outer bearing bush which has radial oil channels. It is also possible that the slide bearing comprises two or more axially successive outer bearing bushes and a single inner bearing bush which has radial oil channels. It is also possible that the slide bearing comprises two or more axially successive bearing bushes attached to the frame of the planetary gear and a surface of the carrier body of the planet wheel carrier is arranged to act as another sliding surface of the slide bearing. It is also possible that the slide bearing comprises a bearing bush having radial oil channels and a circumferential groove and being attached to the frame of the planetary gear, and a surface of the carrier body of the planet wheel carrier is arranged to act as another sliding surface of the slide bearing. It is also possible that the slide bearing comprises a bearing bush comprising radial oil channels and attached to the frame of the planetary gear, and a surface of the carrier body of the planet wheel carrier is arranged to act as another sliding surface of the slide bearing and the surface of the carrier body comprises a circumferential groove for receiving oil. It is also possible that one or more bearing bushes of the kind mentioned above is/are attached to the carrier body of the planet wheel carrier and a surface of the frame is arranged to act as another sliding surface of the slide bearing. As evident in light of the above-presented examples, the principle of using the above-mentioned slide bearing not only as a bearing but also as an oil supply connection from the frame to the planet wheel carrier is applicable with a number of different slide bearing structures.

Claim 1:
A planet wheel carrier (<NUM>, <NUM>) for a planetary gear, the planet wheel carrier comprising:
- a carrier body (<NUM>, <NUM>) for supporting shafts of planet wheels of the planetary gear, the carrier body and the shafts of the planet wheels comprising oil channels (<NUM>, <NUM>) for conducting oil to bearings of the planet wheels, and
- a slide bearing (<NUM>, <NUM>) for rotatably supporting a first end (<NUM>, <NUM>) of the carrier body with respect to a frame of the planetary gear,
wherein the slide bearing comprises at least one oil channel (<NUM>, <NUM>) for conducting oil from at least one oil channel of the frame of the planetary gear to the oil channels of the carrier body, characterized in that the planet wheel carrier comprises one or more conical roller bearings (<NUM>, <NUM><NUM>, <NUM>) for rotatably supporting a second end (<NUM><NUM>) of the carrier body with respect to the frame of the planetary gear and for receiving an axial force directed to the carrier body, and the slide bearing (<NUM>, <NUM>) comprises two axially successive bearing elements and an axial gap between the bearing elements constitutes the oil channel (<NUM>, <NUM>) of the slide bearing.