Planetary transmission for a vehicle

Abstract: The invention relates to a planetary transmission for a vehicle, comprising a planet carrier (2), on which at least one planet wheel (4) is mounted, a hub (16) arranged for a vehicle wheel (25) and connected to the planet carrier (2), and a static housing (28) which is connected to the vehicle and in which the hub (16) is mounted. An outer gear ring (30') is arranged so as to interact with the at least one planet wheel (4) and is connected to the static housing (28) by means of a second splined connection (42, 74).

Description: The present invention relates to a planetary transmission for a vehicle, comprising a planet carrier, on which at least one planet wheel is mounted, a hub arranged for a vehicle wheel and connected to the planet carrier, a static housing which is connected to the vehicle and in which the hub is mounted, and an outer gear ring arranged so as to interact with the at least one planet wheel, wherein the outer gear ring is connected to the static housing by means of a splined connection. The closest prior art document US 4,649,772 relates to a wheel drive assembly for a vehicle with such a planetary transmission. The gear ring has an integral hub defining an external bearing seat and an internal coupling spline that intermeshes with an external coupling spline of the static housing. It is previously known from e.g. GB 2 220 178 to arrange a planetary transmission in conjunction with the wheel of a vehicle. The drive shaft of the vehicle is then provided with an inner sun wheel for the planetary transmission, and a static housing surrounding the planetary transmission is provided with an outer gear ring. The sun wheel and the gear ring interact with planet wheels which are arranged on a planet carrier. The planet carrier is connected to a hub which is mounted in the static housing, and a vehicle wheel can be mounted on the hub by means of wheel bolts. By arranging a planetary transmission in conjunction with the wheel of a vehicle, an increase in torque from the drive shaft to the wheel is obtained. In order to brake the vehicle, friction discs are arranged on the periphery of the planet carrier, which interact with disc plates which are arranged in the static housing. The construction of the known planetary transmission is such that it is not suitable for large and heavy vehicles, such as industrial machinery, which would require, for example, a stronger hub bearing arrangement and thus a longer hub in the axial direction. This would, however, place greater demands on the connection between the planet carrier and the hub, at the same time as it is desirable to keep the planetary transmission as a whole as compact as possible. An object of the present invention is to produce a planetary transmission of the type indicated in the introduction, which eliminates the problems indicated above and aims to obtain as compact a construction as possible. A further object of the invention is to produce a planetary transmission which comprises relatively few components and is easy and inexpensive to manufacture. According to the invention, this is achieved by virtue of the fact that splines arranged on an outer periphery of the outer gear ring and splines arranged in the housing form said splined connection. Such a planetary transmission is compact and comprises fewer components than the known planetary transmission in spite of the fact that the planetary transmission is dimensioned so as to absorb considerably greater forces than the known construction. The invention will be described in greater detail below with reference to the appended drawing which shows an exemplary embodiment and in which: Fig. 1 shows a sectional side view of a planetary transmission according to an exemplary embodiment of the present invention. In Fig. 1, reference number 1 designates a planetary transmission for a vehicle, which planetary transmission 1 comprises a planet carrier 2, on which a number of planet wheels 4 are arranged. From the engine or gearbox (not shown) of the vehicle, a drive shaft 6 extends, the outer end 8 of which comprises an inner sun wheel 10 for the planetary transmission 1, which inner sun wheel 10 is intended to interact with the planet wheels 4 on the planet carrier 2. The number of planet wheels 4 according to the exemplary embodiment in Fig. 1 is three, but it is also possible for the number of planet wheels 4 to be two, four or more. The term vehicle is intended to mean both vehicles which are intended to be driven on the road and vehicles which are intended to be driven off-road, for example in the forest. Such vehicles may be dumpers, wheeled loaders, excavators or other industrial machinery. The planet carrier 2 comprises a through-hole 12 which is provided with splines 14. The centre line 15 of the hole 12 coincides with the axis of rotation of the planet carrier 2. A hub 16, which at a first end 18 comprises a journal 20 with splines 21, is arranged in the hole 12 of the planet carrier 2 and is thus radially connected to the planet carrier 2. A plate 19 is connected to the hub 16 by means of screws 23 and ensures that the hub 16 is axially connected to the planet carrier 2. The hub 16 comprises at a second end 22 a fastening arrangement for a wheel for the vehicle. The hub 16 is mounted by means of roller bearings 26 in a static housing 28 which is connected to the vehicle. The hub 16 therefore rotates in relation to the housing 28. Arranged in the housing 28 is an outer gear ring 30' for the planetary transmission 1, which ring is intended to interact with the planet wheels 4 on the planet carrier 2. The planetary transmission comprises the outer gear ring 30' which is arranged so as to engage with the splines 42 which are formed in the housing 28. The height of the splines 42 has, in a portion that interacts with the gear ring 30', been reduced so as to form a stop or a bearing surface for the gear ring 30'. The outer gear ring 30' is, on an outer periphery, provided with splines 74 which engage with the splines 42 in the housing 28 to form a splined connection. The friction brake 34 comprises a set of friction discs 36 which are arranged on the periphery of the planet carrier 2. According to the first exemplary embodiment shown, the number of friction discs 36 is four, but an arbitrary number of friction discs 36 is possible. The friction discs 36 are axially displaceable on splines which are arranged on the periphery of the planet carrier 2. The friction discs 36 are locked on the planet carrier 2 in the circumferential direction. A set of disc plates 40 is arranged on splines 42 in the housing 28. The disc plates 40 are axially displaceable but locked in the circumferential direction relative to the housing 28. The number of disc plates 40 is preferably the same as the number of friction discs 36. Alternatively, the disc plates 40 may be arranged on the periphery of the planet carrier 2 and the friction discs 36 may be arranged in the housing 28. The disc plates may be made of, for example, metal, plastic or carbon fibre. It is also possible to use other materials. The gear ring 30' forms a first pressure plate 32' for the friction discs 36 and the disc plates 40 which form the friction brake 34. The friction brake 34 preferably operates in a fluid which is made to circulate through a cooling device (not shown) by means of a pipe 72. A second pressure plate is arranged so as to compress the friction discs 36 and the disc plates 40 against the first pressure plate 32' when the rotation of the planet carrier 2 and thus the movement of the vehicle are to be braked. The second pressure plate can be displaced axially by a number of hydraulic pistons 46' which are distributed along the second pressure plate. The hydraulic pistons 46' displace the second pressure plate axially by means of hydraulic fluid under pressure acting on the hydraulic pistons 46'. The hydraulic fluid is contained in an annular duct arranged in the housing 28. The hydraulic fluid is supplied to the annular duct through a mouthpiece 50 and a bore 51 in the housing 28. The first and second pressure plates and also the friction discs 36 and the disc plates 40 are preferably annular but they may also be arranged in segments in a circular shape around the centre line 15 of the planet carrier 2. As an alternative, a sensor may also be arranged in the housing 28, which senses the speed of rotation of the planet carrier 2 and thus also the speed of the vehicle. The sensor is suitably arranged in a hole in the housing 28 at the first pressure plate 32' and is directed towards the splines on the periphery of the planet carrier 2, on which splines the first friction discs 36 are arranged. The sensor then senses how fast the bars of the splines pass the sensor, which is proportional to the speed of rotation of the planet carrier 2. In order to increase the accuracy of the sensing of the sensor, the planet carrier 2 may alternatively be provided with teeth or splines with a finer pitch next to the splines on which the first friction discs 36 are arranged. In Fig. 1, a self-adjustment member 52' is shown, which adjusts the initial position of the hydraulic piston 46' as the friction discs 36 wear.

Claims: Planetary transmission for a vehicle, comprising a planet carrier (2), on which at least one planet wheel (4) is mounted, a hub (16) arranged for a vehicle wheel and connected to the planet carrier (2), a static housing (28) which is connected to the vehicle and in which the hub (16) is mounted, and an outer gear ring (30') arranged so as to interact with the at least one planet wheel (4), wherein the outer gear ring (30') is connected to the static housing (28) by means of a splined connection (42,74) characterized in that splines (74) arranged on an outer periphery of the outer gear ring (30') and splines (42) arranged in the housing (28) form said splined connection (42,74). Planetary transmission according to claim 1, characterized in that a friction brake (34) is arranged at an outer periphery of the planet carrier (2) and intended to brake the rotation of the planet carrier (2) in relation to the static housing (28). Planetary transmission according to claim 2, characterized in that the friction brake (34) comprises a set of first friction discs (36) arranged on the periphery of the planet carrier (2) and a set of second friction discs (40) arranged on an inner side of the static housing (28), said second friction discs (40) being arranged to engage with the splines (42) in the housing (28). Planetary transmission according to any one of claims 1-3, characterized in that the outer gear ring (30') forms a first pressure plate (32') which is arranged so as to compress, on braking, the first and second friction discs (36,40). Planetary transmission according to any one of claims 1-4, characterized in that the hub (16) and the planet carrier (2) are interconnected by means of a further splined connection (14, 21).

Inventors: KINGSTON TIM, KINGSTON, TIM
Applicants: VOLVO CONSTR EQUIP COMPONENTS, VOLVO CONSTRUCTION EQUIPMENT COMPONENTS AB
Application year: 1998
Main classification: B60K17
IPC codes: F16H57, F16D55, B60T1, F16D65, B60K17, F16H1