TECHNICAL FIELD OF THE INVENTION

The present invention relates to an engaging ring for engagement of a gear in a planetary gear set via an engaging sleeve, in accordance with the preamble of the accompanying claim 1. In particular, the invention will find its application in connection with automotive vehicles, and is intended to be a device for reducing noise originating especially from the planetary gear set .

STATE OF THE ART

A gear box in a vehicle transmission usually has an input rotating shaft and an output rotating shaft. The principal object is to transmit rotation with the possibility of selecting between various rotational gear ratios between input and output shaft.

The document US 4667538 discloses an example of a two- geared synchronized gear arrangement in a range gear box of the planetary gearing type, where the synchronization for each gear is constituted by an engaging ring, a synchronizing ring which co-operates with the engaging ring by means of friction surfaces and is axially displaceable, which synchronizing ring is arranged to rotate with an axially displaceable engaging sleeve, and a spring suspension element in the form of a garter spring. In this example of synchronization device a first engaging ring is fixedly connected with a range gear housing and a second engaging ring is fixedly connected with an output shaft of the range gear box. In another known range gear the second engaging ring can be arranged to connect the engaging sleeve to the input shaft of the range gear instead. This means that the synchronization device can be divided and arranged on each side of the ring gear of the planetary gearing. In the example explained through US 4667538 the entire synchronization device is provided on one side of the ring gear of the planetary gearing, which ring gear is fixed to the engaging sleeve. The purpose of said garter spring is to transmit bearing force from the ring gear to one of the synchronizing rings during synchronization and gear changing by means of co-operation with recesses in the engaging sleeve. During change of gear, for example from low-range position (large gear ratio) to high- range position (high gear with a low gear ratio usually 1:1), the rate of rotation of the ring gear shall be adjusted to the rate of rotation of the output shaft before it can be locked to or be engaged to the output shaft. This is achieved by means of the fact that a bearing force is applied to the engaging sleeve in an axial direction towards the synchronizing ring for high-range, that is, the synchronizing ring which shall adjust the rotation of the ring gear to the rate of rotation of the output shaft.

When synchronization of the rotation speed has been achieved, the ring gear/engaging sleeve is locked to the output shaft by means of the fact that the engaging sleeve now can be axially displaced and engage with the engaging ring for high-range, which engaging ring is rotationally connected with the output shaft. By means of bars for conveyance, which are provided on both synchronizing rings, these will always rotate with the engaging sleeve even when the ring gear is axially displaced in relation to the respective synchronizing ring. During synchronization and gear changing, the respective garter spring transmits bearing force from the ring gear to the respective synchronizing ring by means of co-operation with recesses in the ring gear.

When low range is engaged said engaging sleeve is connected to the range gear housing via said first engaging ring. When the planetary gear set is rotating the meshing of teeth of the gear wheels in the range gear can give rise to vibrations. These vibrations are transmitted to the range gear housing, when the low range gear is engaged. In worst case the whole range gear box can act as a resonance box, thus, amplifying the vibrations and transmitting them to the ambient air and creating noise to the environment. The connection between the engaging sleeve and the housing via said engaging ring is in the in US 4667538 disclosed example more or less 100% stiff since the engaging ring is designed with engaging ring teeth, which connect towards the housing and towards the engaging sleeve simultaneously. A known solution to dampen the noise is to encapsulate the range gear box and/or arrange sound shields on the outside of the range gear box in order to dampen the noise. The aim of the present invention is to decrease the noise in an alternative way.

SUMMARY OF THE INVENTION

Thus, the primary object of the present invention is to solve the above problem and to provide an improved device for noise reduction. This is achieved by a device as discussed in the introduction, the characteristics of which are defined by claim 1. Claims 2 to 8 describe different embodiments and developments of the device according to the invention.

The device according to the invention is based on an engaging ring for engagement of a gear in a planetary gear set via an engaging sleeve. Said engaging ring when said gear is engaged is arranged to connect the engaging sleeve to a housing. The invention is characterized in that a torsional damper is integrated in said engaging ring in order to dampen transmission of vibrations to the housing from the planetary gear set, when said gear is engaged. According to one embodiment of the invention said engaging ring comprises a first connection device arranged to connect the engaging ring to the housing and a second connecting device arranged to connect said engaging sleeve to the engaging ring. Said first and second connection devices are separated from each other. In a further embodiment of the invention a distance of said engaging ring between said first and said second connection devices and in a radial and/or an axial direction, in relation to a geometrical centre axis of said engaging ring, is such that as to allow a predetermined twisting of said engaging ring between said first and said second connection device in order to dampen said vibrations.

Additional advantageous embodiments of the invention will be apparent from the appended dependent claims (claims 2-8) .

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further described in the following with reference to the annexed drawings, which in order to exemplify show additional preferred embodiments of the invention and technical background.

Figures 1 to 6 disclose a section through a central geometrical axis of six different embodiments of an engaging ring according to the invention. Only the upper part of such an engaging ring section is disclosed for each embodiment.

DESCRIPTION OF THE INVENTION

Figure 1 discloses an engaging ring 1 with a first connection device 2 arranged to connect the engaging ring to a housing (not disclosed) . The housing can for example be a transmission housing of a planetary gear set such as a range gearbox housing, as disclosed in mentioned US 4667538. A cone shaped friction surface 4 is arranged to interact with a corresponding surface on a not disclosed synchronizing ring. A second connecting device 3 is arranged to connect an engaging sleeve (not disclosed) to the engaging ring 1 in a known way (see for example US 4667538) . Thus, according to the invention said first and second connection devices are separated from each other in order to allow a relative movement in a circumferential direction. A vibration originating in the planetary gear set and transmitted to the second connection device via the engaging sleeve will be damped on its way to the first connection device and the transmission housing by a torsional damper 5 integrated in the engaging ring 1. The part 5 of the engaging ring that acts as a torsional damper can be extended from the first connection device 2 all the way to the second connection device 3. Thus, a distance of said torsional damper part 5 between said first and said second connection devices and extending in a radial and an axial direction, in relation to the geometrical centre axis of said engaging ring, is such that as to allow a certain predetermined twisting of said engaging ring between said first and said second connection device in order to dampen said vibrations. Further, selected thickness of the material of the torsional damper part 5 will influence the damping characteristics. Of coarse selected material will also affect the damping characteristics. In the embodiment of figure 1 the torsional damper part 5 of the engaging ring is formed so that a section of the torsional damper basically has the shape of a relatively wide U.

Figure 2 gives another example of the shape of an engaging ring 21 according to the invention. A cone shaped friction surface 4, a first 2 and a second 3 connection device in the embodiment of figure 2 can be identical as in the embodiment of figure 1. In this embodiment a torsional damper part 25 of the engaging ring has a minimal extension in an axial direction. Thus, the torsional damper part 25 basically has the shape of a narrow U. The embodiments according to the invention in figures 4, 5 and 6 all disclose different variants of an engaging ring 41, 51 and 61 respectively of the engaging ring disclosed in figure 1. A cone shaped friction surface, a first and a second connection device in the embodiments of figures 4, 5 and 6 can be identical as in the embodiment of figure 1. The only important difference is that the engaging rings 41, 51 and 61 each comprise of two rings, a first ring comprising the first connection device 2 and a second ring comprising a second connection device 3.

In the embodiment of figure 4 an embodiment of an engaging ring 41 according to the invention is shown where a first ring 42 comprises the first connection device 2 and most of the torsional damper part 45. A second ring 43 comprises the second connection device 3 and the cone shaped friction surface 4. The first and second ring are fixed to each other by a third connection device 46 arranged on said first ring and a fourth connection device 47 arranged on said second ring.

In the embodiment of figure 5 an embodiment of an engaging ring 51 according to the invention is shown where a corresponding first ring 52 comprises basically only the first connection device 2. A corresponding second ring 53 here comprises the second connection device 3, the cone shaped friction surface 4 and most of a torsional damper part 55. The first and second ring are also here fixed to each other by a corresponding third connection device 56 arranged on said first ring and a corresponding fourth connection device 57 arranged on said second ring.

In the embodiments of figures 4 and 5 said third and fourth connection devices are disclosed as meshing teeth (or splines) . In the shown examples these teeth extend mostly in an axial direction in relation to a geometrical central axis of the shown engaging rings.

Also in the embodiment of figure 6 an embodiment of an engaging ring 61 according to the invention is shown where a corresponding first ring 62 comprises basically only the first connection device 2. A corresponding second ring 63 here also comprises the second connection device 3, the cone shaped friction surface 4 and most of the torsional damper part 65. The first and second ring are also here fixed to each other by a corresponding third connection device 66 arranged on said first ring ^' and a corresponding fourth connection device 67 arranged on said second ring. In the embodiments of figure 6 said third and fourth connection devices are also disclosed as meshing teeth (or splines) . In this example these teeth extend mostly in a radial direction in relation to a geometrical central axis of the shown engaging ring.

The embodiment disclosed by figure 3 shows an engaging ring 31 according to the invention that has some similarities with the divided engaging ring embodiments described through figures 4 to 6. A cone shaped friction surface 4, a first 2 and a second 3 connection device in the embodiment of figure 3 can be identical as in the embodiments of the other figures. Also in the embodiment of figure 3 an embodiment of an engaging ring 31 according to the invention is shown where a corresponding first ring 32 comprises basically only the first connection device 2. A corresponding second ring 33 here also comprises the second connection device 3, the cone shaped friction surface 4 and most of a torsional damper part 35. The first and second ring are also here fixed to each other by a corresponding third connection device 36 arranged on said first ring and a corresponding fourth connection device 37 arranged on said second ring. In the embodiments of figure 3 said third and fourth connection devices are also disclosed as meshing teeth. In this example the teeth of the third connection device 36 extend mostly in an axial direction and the teeth of the fourth connection device 37 extend mostly in a radial direction. The torsional damper part 35 basically has the shape of a mirror-inverted wide and some what squashed S.

In an alternative embodiment of the embodiment in figure 3 the torsional damper part 35 can be mirror- inverted and forming a part of the first ring 32. Thus, said second ring will in this embodiment basically only comprise of the second connection device, the cone shaped friction surface and the fourth connection device.

The design, dimensions and material especially of the torsional damper parts 5, 25, 35, 45, 55 and 65 are chosen so as to allow a predetermined twisting of said engaging ring between said first and said second connection device in order to dampen said vibrations. Practical experiments has shown that a stiffness in said torsional damper part allowing a twisting of around 0,00018 radians/kNm gives an adequate vibration damping result. Said torsional damper parts according to the invention can be designed so that a twisting is allowed within the range of 0,00015 radians/kNm to 0,00025 radians/kNm, which results in an adequate vibration damping.

The embodiments in figures 3 to 6 contribute to a simpler manufacturing of the engaging ring by the engaging ring being divided in a first and a second ring that are fixed to each other.

In the shown embodiment said first and second connection devices can for example be engaging teeth according to prior art. In corresponding way the third and fourth connection devices can be teeth meshing with each other or a splined coupling.

An example of material used for said damper part or parts can be carburizing steel. Other steels such as quenched and tempered steel can be used as well. Different composites are also possible.

The invention should not be deemed to be limited to the embodiments described above, but rather a number of further variants and modifications are conceivable within the scope of the following patent claims.