Patent Description:
It is known to lubricate the teeth of the gears of transmissions by spraying oil through nozzles which are positioned relatively close to the gear concerned. In this way, the teeth are lubricated one after the other as the teeth pass the nozzle. Transmissions subjected to heavy loads, such as a planetary gearing in a vehicle gearbox, require a relatively large quantity of lubricant. In spite of this, lubrication is often effected intermittently by means of such nozzles. Further, it is difficult to lubricate the gear teeth effectively with the aid of a lubricant spray and at the same time provide sufficient cooling of the teeth. This can be a particular problem for a sun gear in a planetary transmission.

An alternative to such lubrication systems is described in <CIT>. In this case, a planetary gearing comprises a component in the form of a ring gear provided with internal splines substantially matching the profile of the teeth on the sun gear. The tips of the splines are terminated before the root section between adjacent teeth on the sun gear. This allows lubricant under pressure to flow in ducts from a central supply duct in the main shaft, radially outwards to the internal splines on the ring gear and towards the meshing teeth between the sun gear and the planetary gears of the planetary gearing.

A problem with this arrangement is that the manufacturing of such components will be relatively complicated and therefore expensive and time consuming. Also, the mounting of the component and the sealing of the ducts supplying lubricant will be relatively complex.

The object of the invention is to provide an improved arrangement for lubricating gears that solves the above problems relating to lubrication and cooling of gears under heavy loads, as well as providing an arrangement that is more cost effective to manufacture and easier to assemble.

The above problems have been solved by an arrangement as claimed in the appended claims. In the subsequent text, the term "vehicle" is intended to describe any type of land-based vehicle, airborne vehicles or marine vessel that can comprise a transmission provided with a lubricating arrangement according to the claims.

According to the claims, the arrangement is suitable for toothed gearings in general. The claimed arrangement is intended for use in connection with transmissions comprising toothed gearings requiring a continuous flow of lubricant to provide both lubrication and cooling to a set of meshing teeth between cooperating gears. This type of lubrication arrangement is particularly suited for a transmission under heavy loading. A typical example of such a transmission is a gearbox comprising a planetary gearing, as described in the published application <CIT>. The operation of a planetary gearbox is described in detail in this document. Examples of how the arrangement can be applied is described below with reference to such a planetary gearing. However, the application of the arrangement is not limited to planetary gearings. <CIT> discloses an arrangement according to the preamble of claim <NUM>.

According to a first aspect, the invention relates to an arrangement for lubricating a gear in a toothed gearing as defined in claim <NUM>.

A non-exclusive list of toothed gearings for which the arrangement is applicable includes vehicle transmissions, in particular heavy-duty transmissions and transmissions for marine vessels, in particular vessels comprising an in-board power unit with a transmission.

Arrangements for lubricating gears in a toothed gearing are commonly connected to a supply of lubricant under pressure. A source of pressure such as a suitable pump can supply lubricant to the arrangement directly or via a pressurized tank. Lubricant can be directed to desired locations by means of individual conduits in the form of pipes or by using conduits within rotating shafts or shafts within a transmission. Such means for supplying lubricant under pressure are well known in the art and will not be described in further detail.

According to one example the toothed gearing is a planetary gearing in a vehicle transmission and the component comprising a central annular portion is an engaging ring of the planetary gearing. The annular portion of the component is press-fitted onto the shoulder on the gear. The gear in this example is a sun gear in said planetary gearing. According a further example the shoulder has a diameter greater than the root circle of the gear. This can be achieved by machining the teeth of the sun gear at an end portion thereof until a portion of the root section between adjacent teeth remain. In this way, the axial discontinuities or recesses are formed by axial extensions of roots between each gear tooth and extend axially along the length of the peripheral surface of the shoulder. The discontinuities form recesses for guiding and distributing lubricant to the roots of the sun gear.

According a further example the shoulder has a diameter equal to or greater than the root circle of the gear. In this example, the teeth of the sun gear at an end portion of the shoulder can be machined away partly, until a portion of the root section between adjacent teeth remains, or entirely until no portion of the teeth remain. The annular portion of the component to be fitted onto the shoulder is then provided with axial discontinuities along its inner peripheral surface. In the case where the teeth of the sun gear are machined away entirely, the axial discontinuities in the annular portion will form recesses for guiding and distributing lubricant to the roots of the gear. In the case where the teeth of the sun gear are machined so that a portion of the root section between adjacent teeth remains, then the axial discontinuities in both the shoulder and the annular portion will form combined recesses for guiding and distributing lubricant.

According a further example the outer peripheral surface of the shoulder can comprise an undercut adjacent the teeth of the lubricated gear. The undercut is a circumferential undercut or groove that has been machined into the shoulder adjacent the teeth of the sun gear to be lubricated. The undercut provides stress relief and eliminates the risk of cracks forming at the transition between the shoulder and the teeth of the sun gear. The undercut also facilitates mounting of the annular portion of the ring gear flush against a radial surface formed by the end of the teeth of the sun gear.

According a further example the depth of an outer portion of the axial discontinuities forming recesses for guiding and distributing lubricant to the roots of the gear increases in the direction of the component. The increase in depth is achieved by machining the outer end of each axial discontinuity, providing it with an angled surface that slopes radially inwards in the direction of the free end of the shoulder. This arrangement increases the cross-sectional surface area of the outer portion of the axial discontinuity, which causes an increase of the area at the opening the axial discontinuity where lubricant under pressure is supplied. The increased area will in turn cause an increased flow rate of the lubricant into the axial discontinuity. An effect of the increased flow rate is that the velocity of the lubricant will increase when the lubricant reaches the portion of the axial discontinuity that has not been machined.

According a further example the width of an outer portion of the axial discontinuities forming recesses for guiding and distributing lubricant to the roots of the gear increases in the direction of the component. The increase in width is achieved by machining the outer end of each axial discontinuity, providing it with a pair of opposed angled side surfaces that diverge outwards in the direction of the free end of the shoulder. As described in the above example, this arrangement increases the cross-sectional surface area of the outer portion of the axial discontinuity, which causes an increase of the area at the opening the axial discontinuity where lubricant under pressure is supplied. The increased area will in turn cause an increased flow rate of the lubricant into the axial discontinuity. An effect of the increased flow rate is that the velocity of the lubricant will increase when the lubricant reaches the portion of the axial discontinuity that has not been machined.

According a further example both the width and the depth of an outer portion of the axial discontinuities increase in the direction of the component. Combining the above examples will contribute to a further increase in the flow rate of the lubricant into the axial discontinuity, and an increase in the velocity of the lubricant reaching the gear teeth.

According to a second aspect the invention relates to a vehicle comprising a transmission with a lubrication arrangement as described above.

One advantage of the arrangement described above is that it requires considerably less machining of the component parts, resulting in fewer and less complex manufacturing steps for the ring component and the sun gear. The ring component can according to one example simply be provided with an annular portion that can be press-fitted onto a shoulder of the sun gear. The ring gear can be made without the need for machining splines and reducing the number of seals required for lubricating ducts. The sun gear merely needs to be machined at one end to provide a shoulder having suitable dimensions for fitting the annular portion of the ring component.

A further advantage is that the arrangement of the axial discontinuities allows them to be modified for different embodiments of a gearbox. When a type of gearbox requires an increased amount of lubricant for, e.g. the planetary gearing, then the entrance portions of the axial discontinuities in the shoulder of the sun gear can be modified to provide an enlarged cross-sectional area.

In the following text, the invention will be described in detail with reference to the attached drawings. These schematic drawings are used for illustration only and do not in any way limit the scope of the invention. In the drawings:.

<FIG> shows a schematically indicated vehicle <NUM> with a transmission comprising a lubrication arrangement according to the invention. The vehicle <NUM> is provided with an internal combustion engine (ICE) <NUM> connected to a transmission with a gearbox <NUM>, such as an automated manual transmission (AMT), for transmitting torque to a vehicle drive shaft (not shown). The lubrication arrangement is arranged to lubricate at least one gear in a toothed gearing inside the gearbox <NUM>. The ICE <NUM> is connected to a radiator arrangement <NUM> for cooling engine coolant and oil from the ICE <NUM>. The gearbox <NUM> is controlled by the driver or automatically via an electronic control unit (ECU) <NUM>. The ECU <NUM> is provided with control algorithms for controlling the transmission independently during, for instance, an engine start requested by the driver. The transmission gearbox is controlled to select a gear ratio between the engine <NUM> and a pair of driven wheels <NUM>.

<FIG> shows a schematic diagram of a gearbox <NUM> comprising a lubrication arrangement according to the invention. The gearbox shown in <FIG> is a stepped compound splitter and range transmission comprising a clutch <NUM>, a splitter section <NUM>, a main section <NUM> and a range section <NUM> with a planetary gear <NUM>. The operation of such a gearbox is well known in the art and will not be described in further detail here. The subsequent examples describe a lubrication arrangement arranged to lubricate at least one gear in the planetary gear <NUM>. The gearbox <NUM> is enclosed by an outer gearbox casing <NUM> which comprises transverse walls <NUM>, <NUM> providing support for the rotary shafts of the different gearbox sections.

<FIG> shows a schematic cross-section of a planetary gear <NUM> in the range section <NUM> of a gearbox <NUM> as shown in <FIG>. The planetary gear <NUM> comprises an input shaft or main shaft <NUM>, which is the output shaft from the main section <NUM> shown in <FIG>. An engaging ring <NUM> and a sun wheel <NUM> are rotatably fixed to the end of the main shaft <NUM> by means of axial splines or similar suitable fixing means. A central portion <NUM> of the engaging ring <NUM> is directly connected to the sun wheel <NUM>, for instance by means of press-fitting. The sun wheel <NUM> is a central gear that is in driving connection with planet gears <NUM> rotatable about individual planet gear axles <NUM> supported by a planet carrier <NUM> that can be fixed to or, as shown in <FIG>, part of a gearbox output shaft <NUM>. The main shaft <NUM> and the gearbox output shaft <NUM> are arranged to rotate about a common axis X. The planetary gear <NUM> further comprises an outer ring gear <NUM> in driving connection with the planet gears <NUM>. The outer ring gear <NUM> comprises teeth around its inner periphery and is displaceable in the axial direction of the planetary gear <NUM>, in order to provide a low range mode or a high range mode of operation (see <FIG>). The planetary gear <NUM> is enclosed by a casing <NUM> at one end of the gearbox casing <NUM> shown in <FIG>. The gearbox output shaft <NUM> is supported by a bearing <NUM> relative to the casing <NUM> surrounding the planetary gear <NUM>.

<FIG> shows a cross-section A-A through <FIG> at right angles to the axis X of the main shaft <NUM>. <FIG> shows the central sun wheel <NUM> in driving contact with four planet gears <NUM> which are rotatable about their respective planet gear axles <NUM>. The figure further shows the outer ring gear <NUM> in driving connection with each of the four planet gears <NUM>.

<FIG> show schematic cross-sections of a planetary gear <NUM> of the same type as described for <FIG>. The planetary gear <NUM> comprises a main shaft <NUM> extending from the main section <NUM> shown in <FIG>. An engaging ring <NUM> and a sun wheel <NUM> are rotatably fixed to the end of the main shaft <NUM>. A central portion <NUM> of the engaging ring <NUM> is directly connected to the sun wheel <NUM>, for instance by means of press-fitting. The sun wheel <NUM> is in driving connection with planet gears <NUM> rotatable about individual planet gear axles <NUM> supported by a planet carrier <NUM> that is part of a gearbox output shaft <NUM>. The main shaft <NUM> and the gearbox output shaft <NUM> are arranged to rotate about a common axis X. The planetary gear <NUM> further comprises an outer ring gear <NUM> in driving connection with the planet gears <NUM>. The outer ring gear <NUM> comprises teeth around its inner periphery and is displaceable in the axial direction of the planetary gear <NUM>. The planetary gear <NUM> is enclosed by a casing <NUM> at one end of the gearbox casing <NUM> shown in <FIG>. The gearbox output shaft <NUM> is supported by a bearing <NUM> relative to the casing <NUM> surrounding the planetary gear <NUM>.

<FIG> shows the planetary gear <NUM> in a low range mode of operation. In the low range mode, the ring gear <NUM> is displaced into a first position as indicated by the arrow A. In the first position, the ring gear <NUM> is connected to the casing <NUM> and is fixed against rotation. Input torque from the main section of the gearbox (see <FIG>) causes rotation of the main shaft <NUM> and its sun wheel <NUM>, which will in turn rotate the planet gears <NUM> relative to the non-rotating ring gear <NUM>. Subsequently, the planet gear axles <NUM> supporting the planet gears <NUM> will rotate about the sun wheel <NUM> and cause a rotation of the planet carrier <NUM> and the gearbox output shaft <NUM>. This mode of operation causes a speed reduction from the main shaft <NUM> to the gearbox output shaft <NUM>.

<FIG> shows the planetary gear <NUM> in a high range mode of operation. In the high range mode, the ring gear <NUM> is displaced into a second position indicated by the arrow B. In the second position, the internal teeth of the ring gear <NUM> are connected to a toothed outer periphery (not shown) of the engaging ring <NUM> and is allowed to rotate with the main shaft <NUM>. Input torque from the main section of the gearbox (see <FIG>) causes rotation of the main shaft <NUM>, which will in turn rotate the engaging ring <NUM> and the planet gears <NUM>. Since the planet gears <NUM> are prevented from rotation relative to the planet carrier <NUM> by the engaging ring <NUM> and the ring gear <NUM>, a direct driving connection is provided between the main shaft <NUM>, the planet carrier <NUM> and the gearbox output shaft <NUM>. This mode of operation causes the main shaft <NUM> and the gearbox output shaft <NUM> to rotate at the same speed.

<FIG> shows a schematic cross-section through a first example of an arrangement suitable for lubricating a toothed gearing such as a sun wheel <NUM> and a set of cooperating planetary wheels <NUM> in a planetary gear of the type described above. In <FIG>, the planetary wheels <NUM> are mounted on shafts <NUM> supported on a planet carrier (not shown; see <FIG>, "<NUM>"). The arrangement in <FIG> comprises a main shaft <NUM> on which the sun wheel <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the sun wheel <NUM>, respectively. The sun wheel <NUM> is fixed in a predetermined axial position on the main shaft <NUM> by means of a retaining nut <NUM> mounted at a threaded end section <NUM> of the main shaft <NUM>. An engaging ring <NUM> is arranged on the opposite side of the sun wheel <NUM>. A central portion <NUM> of the engaging ring <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the central portion <NUM>, respectively. The location and function of the engaging ring <NUM> has been described in connection with <FIG> above. The central portion <NUM> of the engaging ring <NUM> can be located in a predetermined axial position on the main shaft <NUM> by a stepped section (not shown) provided on the main shaft <NUM>. The central portion <NUM> is arranged around the main shaft <NUM> and comprises a radial surface <NUM> that is facing and spaced from an end surface <NUM> the sun gear <NUM>. The central portion <NUM> further comprises an annular portion <NUM> with an inner peripheral surface <NUM>. The annular portion <NUM> extends towards an outer peripheral surface <NUM> of a shoulder <NUM> on the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> has an inner diameter less than the pitch circle of the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> is fixed in position on the shoulder <NUM> of the sun gear <NUM> by press-fitting.

The main shaft <NUM> comprises a central duct <NUM> for supplying lubricant under pressure, which central duct <NUM> is connected to a source of lubricant for the toothed gearing. The main shaft <NUM> further comprises a number of radial ducts <NUM> each having an opening in the outer periphery of the main shaft <NUM> in an area located in proximity to the sun gear <NUM>. Specifically, the radial ducts <NUM> open up in a gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM>, respectively. The gap <NUM> is arranged for guiding and distributing lubricant from the radial ducts <NUM> and radially outwards to the meshing teeth <NUM>, <NUM> of the sun gear <NUM> and the planetary gears <NUM>. The facing surfaces <NUM>, <NUM> are shown as radial surfaces in <FIG> for reasons of clarity. Alternative surfaces, such as concave, convex or conical facing surfaces can be used within the scope of the invention. Similarly, the radial ducts <NUM> extending through the main shaft <NUM> can be arranged at any suitable angle within the scope of the invention.

Alternatively, lubricant under pressure can be supplied from a suitable source and be supplied to the gap <NUM> through the splines on the main shaft <NUM> and the central portion <NUM>, respectively. The flow of lubricant is indicated by a dashed arrow B'.

In order to guide lubricant from the gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM> and towards the meshing teeth, axial discontinuities <NUM> are provided between the shoulder <NUM> on the sun gear <NUM> and the annular portion <NUM> of the central portion <NUM>. In the example shown in <FIG>, the axial discontinuities <NUM> are arranged along the peripheral surface of the shoulder <NUM>, which axial discontinuities <NUM> form axial recesses guiding and distributing lubricant to the roots of the teeth <NUM> of the sun gear <NUM>. The axial discontinuities <NUM> are formed by machining a section of the sun gear <NUM> to remove an axial section of an outer portion of the gear teeth <NUM> when making the shoulder <NUM>. The sun gear <NUM> can be machined to a predetermined diameter, leaving a portion of the roots between teeth to provide axial discontinuities <NUM> with a cross-sectional area sufficient for supplying a desired flow rate of lubricant to the gear teeth. <FIG> shows a partial cross-section B-B through the gap <NUM> shown in <FIG>, wherein the reference numbering from <FIG> is retained. <FIG> indicates how the axial discontinuities <NUM> will comprise recesses in the form of axial extensions of the roots between each pair of gear teeth.

<FIG> shows a cross-section through a second example of an arrangement suitable for lubricating a toothed gearing such as a sun wheel <NUM> and a set of cooperating planetary wheels <NUM> in a planetary gear of the type described above. In <FIG>, the planetary wheels <NUM> are mounted on shafts <NUM> supported on a planet carrier (not shown; see <FIG>, "<NUM>"). The arrangement in <FIG> comprises a main shaft <NUM> on which the sun wheel <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the sun wheel <NUM>, respectively. The sun wheel <NUM> is fixed in a predetermined axial position on the main shaft <NUM> by means of a retaining nut <NUM> mounted at a threaded end section <NUM> of the main shaft <NUM>. An engaging ring <NUM> is arranged on the opposite side of the sun wheel <NUM>. A central portion <NUM> of the engaging ring <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the central portion <NUM>, respectively. The central portion <NUM> of the engaging ring <NUM> can be located in a predetermined axial position on the main shaft <NUM> by a stepped section (not shown) provided on the main shaft <NUM>. The central portion <NUM> is arranged around the main shaft <NUM> and comprises a radial surface <NUM> that is facing and spaced from an end surface <NUM> the sun gear <NUM>. The central portion <NUM> further comprises an annular portion <NUM> with an inner peripheral surface <NUM>. The annular portion <NUM> extends towards an outer peripheral surface <NUM> of a shoulder <NUM> on the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> has an inner diameter less than the pitch circle of the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> is fixed in position on the shoulder <NUM> of the sun gear <NUM> by press-fitting.

The main shaft <NUM> comprises a central duct <NUM> for supplying lubricant under pressure, which central duct <NUM> is connected to a source of lubricant for the toothed gearing. The main shaft <NUM> further comprises a number of radial ducts <NUM> each having a radial opening in the outer periphery of the main shaft <NUM> in an area located in proximity to the sun gear <NUM>. Specifically, the radial ducts <NUM> open up in a gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM>, respectively. The gap <NUM> is arranged for guiding and distributing lubricant from the radial ducts <NUM> and radially outwards to the meshing teeth <NUM>, <NUM> of the sun gear <NUM> and the planetary gears <NUM>. The facing surfaces <NUM>, <NUM> are shown as radial surfaces in <FIG> for reasons of clarity. Alternative surfaces, such as concave, convex or conical facing surfaces can be used within the scope of the invention. Similarly, the radial ducts <NUM> extending through the main shaft <NUM> can be arranged at any suitable angle within the scope of the invention.

In order to guide lubricant from the gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM> and towards the meshing teeth, axial discontinuities <NUM> are provided between the shoulder <NUM> on the sun gear <NUM> and the annular portion <NUM> of the central portion <NUM>. In the example shown in <FIG>, the axial discontinuities <NUM> are arranged along the inner peripheral surface of the annular portion <NUM>, which axial discontinuities <NUM> form axial recesses guiding and distributing lubricant to the roots of the teeth <NUM> of the sun gear <NUM>. The axial discontinuities <NUM> can be formed by machining a number of axial slots or recesses into the inner peripheral surface of the annular portion <NUM>. The number of axial slots is preferably equal to the number of roots on the sun gear in order to achieve an even distribution of lubricant to all teeth. By selecting suitable dimensions for the radial thickness of the annular portion <NUM> and the width and/or depth of the axial discontinuities <NUM>, the cross-sectional area of the axial discontinuities <NUM> can be varied depending on the requirement for lubrication. Also, a section of the sun gear <NUM> is machined to remove an axial section of an outer portion of the gear teeth <NUM> when making the shoulder <NUM>. The sun gear <NUM> can be machined to a predetermined diameter, either removing the teeth completely or leaving a portion of the roots between teeth. The diameter of the shoulder is preferably selected to equal to the root diameter of the sun gear to ensure a flow of lubricant to the gear teeth from the axial discontinuities <NUM> directly into the roots between adjacent teeth. <FIG> shows a partial cross-section C-C through the gap <NUM> shown in <FIG>, wherein the reference numbering from <FIG> is retained. <FIG> indicates how the axial discontinuities <NUM> will comprise recesses in the form of axial recesses into the inner peripheral surface <NUM> of the annular portion <NUM>. The axial recesses must be indexed with the roots between each pair of gear teeth <NUM> when assembling the central portion <NUM> and the sun gear <NUM>.

<FIG> shows a cross-section through a lubricating arrangement suitable for lubricating a toothed gearing such as a sun wheel <NUM> and a set of cooperating planetary wheels <NUM> in a planetary gear of the type described above. In <FIG>, the planetary wheels <NUM> are mounted on shafts <NUM> supported on a planet carrier (not shown; see <FIG>, "<NUM>"). The arrangement in <FIG> comprises a main shaft <NUM> on which the sun wheel <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the sun wheel <NUM>, respectively. The sun wheel <NUM> is fixed in a predetermined axial position on the main shaft <NUM> by means of a retaining nut <NUM> mounted at a threaded end section <NUM> of the main shaft <NUM>. An engaging ring <NUM> is arranged on the opposite side of the sun wheel <NUM>. A central portion <NUM> of the engaging ring <NUM> is fixed against rotation by means of cooperating splines <NUM> on the main shaft <NUM> and the central portion <NUM>, respectively. The location and function of the engaging ring <NUM> has been described in connection with <FIG> above. The central portion <NUM> of the engaging ring <NUM> can be located in a predetermined axial position on the main shaft <NUM> by a stepped section (not shown) provided on the main shaft <NUM>. The central portion <NUM> is arranged around the main shaft <NUM> and comprises a radial surface <NUM> that is facing and spaced from an end surface <NUM> the sun gear <NUM>. The central portion <NUM> further comprises an annular portion <NUM> with an inner peripheral surface <NUM>. The annular portion <NUM> extends towards an outer peripheral surface <NUM> of a shoulder <NUM> on the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> has an inner diameter less than the pitch circle of the sun gear <NUM>. The annular portion <NUM> of the central portion <NUM> is fixed in position on the shoulder <NUM> of the sun gear <NUM> by press-fitting.

In order to guide lubricant from the gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM> and towards the meshing teeth, axial discontinuities <NUM> are provided between the shoulder <NUM> on the sun gear <NUM> and the annular portion <NUM> of the central portion <NUM>. In the example shown in <FIG>, the axial discontinuities <NUM> are arranged along the peripheral surface of the shoulder <NUM>, which axial discontinuities <NUM> form axial recesses guiding and distributing lubricant to the roots of the teeth <NUM> of the sun gear <NUM>. The axial discontinuities <NUM> are formed by machining a section of the sun gear <NUM> to remove an axial section of an outer portion of the gear teeth <NUM> when making the shoulder <NUM>. The sun gear <NUM> can be machined to a predetermined diameter, leaving a portion of the roots between teeth to provide axial discontinuities <NUM> with a cross-sectional area sufficient for supplying a desired flow rate of lubricant to the gear teeth.

<FIG> shows an enlarged view of the circled area D shown in <FIG>, wherein the reference numbering from <FIG> is retained. <FIG> shows the outer peripheral surface <NUM> of the shoulder <NUM> on the sun gear <NUM> in contact with the inner peripheral surface <NUM> of the annular portion <NUM> extending from the central portion <NUM>. <FIG> shows a circumferential undercut <NUM> that has been machined into the shoulder <NUM> adjacent the teeth of the sun gear <NUM> to be lubricated. The undercut <NUM> provides stress relief and eliminates the risk of cracks forming at the transition between the shoulder and the teeth of the sun gear. The undercut <NUM> also facilitates mounting of the annular portion <NUM> flush against a radial surface formed by the end of the teeth <NUM> of the sun gear <NUM>.

<FIG> and <FIG> illustrate axial discontinuities in a shoulder of the type described in connection with the example in <FIG> and <FIG>. However, the undercut shown in <FIG> can also be used in a shoulder according to the example shown in <FIG> and <FIG>.

<FIG> shows an enlarged view of the circled area E shown in <FIG>, wherein the reference numbering from <FIG> is retained. <FIG> shows the outer peripheral surface <NUM> of the shoulder <NUM> on the sun gear <NUM> in contact with the inner peripheral surface <NUM> of the annular portion <NUM> extending from the central portion <NUM>. <FIG> shows one of the axial discontinuities <NUM> forming a recess for guiding and distributing lubricant to one of the roots <NUM> between two adjacent teeth <NUM> of the sun gear <NUM>. The axial discontinuities <NUM> in this example form an extension of the root <NUM> between adjacent teeth into the outer peripheral surface <NUM> of the shoulder <NUM>.

<FIG> shows that the depth of an outer portion <NUM> of the axial discontinuity <NUM> adjacent the free end of the shoulder <NUM> increases in the direction of the central portion <NUM>. The increase in depth is achieved by machining the outer end of each axial discontinuity, providing it with an angled surface <NUM> that slopes radially inwards in the direction of the gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM>. This arrangement increases the cross-sectional surface area of the outer portion <NUM> of the axial discontinuity <NUM>, which causes an increase of the area at the opening the axial discontinuity <NUM>. The increased area will in turn cause an increased flow rate of the lubricant into the axial discontinuity <NUM>.

<FIG> shows a partial cross-section F-F through the diverging portion of the lubricant duct in <FIG> shows that the width of an outer portion <NUM> of the axial discontinuity <NUM> adjacent the free end of the shoulder <NUM> increases in the direction of the central portion <NUM>. The increase in width is achieved by machining the outer end of each axial discontinuity, providing it with a pair of opposed angled surfaces <NUM> that diverge outwards in the direction of the gap <NUM> between the facing radial surfaces <NUM>, <NUM> of the central portion <NUM> and the sun gear <NUM>. This arrangement further increases the cross-sectional surface area of the outer portion <NUM> of the axial discontinuity <NUM>, which causes an additional increase of the area at the opening the axial discontinuity <NUM>. The increased area will in turn cause an increased flow rate of the lubricant into the axial discontinuity <NUM>.

The example illustrated in <FIG> shows an axial discontinuity <NUM> with an outer portion <NUM> that increases both in depth and in width. Depending on the required flow rate of lubricant into the axial discontinuity <NUM> it is of course also possible to enlarge the cross-sectional area of the outer portion <NUM> by increasing either one of the width or the depth separately.

<FIG> illustrate axial discontinuities in a shoulder of the type described in connection with the example in <FIG> and <FIG>. However, the enlargement of the outer portion of the axial discontinuities <NUM> as shown in <FIG> can also be used in a shoulder according to the example shown in <FIG> and <FIG>, specifically for examples where the shoulder has been machined to leave a portion of the roots in the outer surface thereof.

Claim 1:
Arrangement for lubricating a gear (<NUM>; <NUM>; <NUM>; <NUM>) in a toothed gearing comprising,
- a shaft (<NUM>; <NUM>; <NUM>; <NUM>) on which the gear (<NUM>; <NUM>; <NUM>; <NUM>) is arranged,
- an engaging ring (<NUM>; <NUM>; <NUM>; <NUM>) which is arranged around said shaft (<NUM>; <NUM>; <NUM>; <NUM>) and comprises a surface (<NUM>; <NUM>; <NUM>; <NUM>) that is facing and spaced from an end surface (<NUM>; <NUM>; <NUM>; <NUM>) of the gear (<NUM>; <NUM>; <NUM>; <NUM>) creating a gap (<NUM>; <NUM>; <NUM>; <NUM>) for guiding and distributing lubricant to the gear,
- at least one first duct (<NUM>, <NUM>; <NUM>; <NUM>, <NUM>; <NUM>; <NUM>, <NUM>; <NUM>; <NUM>, <NUM>; <NUM>) for supplying lubricant under pressure, whereby said duct has at least one opening into the gap (<NUM>; <NUM>; <NUM>; <NUM>) adjacent said gear (<NUM>; <NUM>; <NUM>; <NUM>) to be lubricated,
wherein
the engaging ring comprises an annular portion (<NUM>; <NUM>; <NUM>; <NUM>) with an inner peripheral surface mounted onto an outer peripheral surface of a shoulder (<NUM>; <NUM>; <NUM>; <NUM>) on the gear;
where the annular portion has an inner diameter less than the pitch circle of the gear; and where axial discontinuities (<NUM>; <NUM>; <NUM>; <NUM>) are provided between the shoulder (<NUM>; <NUM>; <NUM>; <NUM>) and the annular portion of the engaging ring, which discontinuities form recesses for guiding and distributing lubricant to the roots of the gear (<NUM>; <NUM>; <NUM>; <NUM>), characterised in that,
the annular portion of the engaging ring (<NUM>; <NUM>; <NUM>; <NUM>) is press-fitted onto the shoulder (<NUM>; <NUM>; <NUM>; <NUM>) on the gear (<NUM>; <NUM>; <NUM>; <NUM>).