Propeller shaft arrangement

Abstract: The propeller shaft arrangement which connects a transmission (T) with a differential gear (D) of a vehicle includes a first propeller shaft segment (1) connected to the transmission at one end thereof and a second propeller shaft segment (2) connected to the differential gear at one end thereof. The first and second propeller shaft segments (1, 3) are made of aluminium. The other end of the second propeller shaft segment is connected with one end of a steel-made centre bearing (2) via a universal joint (6). Serrations (12, 13) are formed at the other end of the centre bearing and at the other end of the first propeller shaft segment (1) such that the serrations of the centre bearing (2) are engaged with those of the first propeller shaft segment and a locking nut (15) is screwed down over the engaging serrations to join the first propeller shaft segment with the centre bearing. Since the centre bearing (2) is made of steel whereas most of the propeller shaft (1, 3) is made of aluminium, the weight of the propeller shaft is reduced while ensuring a sufficient strength of the centre bearing. Further,the first propeller shaft segment is connected with the centre bearing by the serrations and the locking nut. Therefore, welding the aluminium shaft with the steel bearing, which is technically difficult to perform, is not necessary.

Description: This invention relates to a propeller shaft arrangement for connecting a transmission and a differential gear of an automobile, and more particularly to a propeller shaft arrangement, most of which is made of aluminium. A propeller shaft for an automobile is generally made of steel and connects a transmission with a differential gear. Generally, the propeller shaft includes a universal joint since the vibration system (or manner) on the transmission side and that on the differential gear side differ from each other. If a universal joint is provided, the propeller shaft is divided into two segments and these two segments are supported by a centre bearing mounted on the vehicle body. Recently, there has grown a demand to reduce the weight of the propeller shaft and experiments have been made using aluminium propeller shafts. However, since the aluminium is weaker than steel, the diameter of the propeller shaft should be increased to ensure it has sufficient strength. A larger centre bearing is required to support a propeller shaft having a larger diameter. Further, the circumferential speed of the propeller shaft is raised as its diameter becomes greater. The centre bearing (which is generally a ball bearing) may not be able to cope with such a raised circumferential speed. In addition, the oil seal which protects the centre bearing from dust and water may not function appropriately if a large centre bearing is employed. In this case, the centre bearing and the aluminium propeller shaft may contact each other directly with the result that abrasion is accelerated. An object of the present invention is to provide a propeller shaft arrangement, most of which is made from aluminium and which does not cause any problems concerning a centre bearing. According to the present invention, there is provided a propeller shaft arrangement as set out in claim 1. In one embodiment of the invention the propeller shaft includes a first propeller shaft segment connected to the transmission at one end thereof and a second propeller shaft segment connected to the differential gear at one end thereof, the first and second propeller shaft segments are made of aluminium or aluminium alloy, the other end of the second propeller shaft segment is connected with one end of a steel-made centre bearing via a universal joint, and serrations are formed at the other end of the centre bearing and at the other end of the first propeller shaft segment such that the serrations of the centre bearing are engaged with those of the first propeller shaft segment and a locking nut is screwed down over the engaging serrations to join the first propeller shaft segment with the centre bearing. According to the present invention, the centre bearing is made of steel whereas most of the propeller shaft arrangement is made of aluminium or aluminium alloy. Therefore, the weight of the propeller shaft arrangement is reduced while ensuring a sufficient strength of the centre bearing. Further, the first propeller shaft segment is connected with the centre bearing with the serrations and the locking nut. Therefore, welding the aluminium shaft onto the steel bearing, which is technically difficult to perform, is not necessary. Further optional features are defined in the dependent claims. An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, of which: Figure 1 illustrates a propeller shaft arrangement according to an embodiment of this invention; Figure 2 is an enlarged view of a centre bearing and peripheral components of the propeller shaft arrangement shown in Figure 1; and Figure 3 is an exploded view of major parts of the propeller shaft arrangement shown in Figure 1. Referring first to Figure 1, the propeller shaft arrangement includes a first propeller shaft segment 1 which is connected with a transmission T, a centre bearing 2 supported by a vehicle frame (not shown) and a second propeller shaft segment 3 connected with a differential gear D. The first and second propeller shaft segments are made of aluminium or aluminium alloy and the centre bearing 2 is made of steel. Each propeller shaft segment includes a pipe portion and a universal joint. Specifically, the first propeller shaft segment 1 has a first universal joint 4 for connection with the transmission T and the second propeller shaft segment 2 has a second universal joint 5 for connection with the differential gear D. The pipe portion of each propeller shaft segment is made from a combination of 6061 aluminium alloy and ceramic particles (e.g., alumina particles). The alumina particles occupy 20% in volume. The pipe portion has a general diameter of 101.6 mm and a thickness of 3 mm. Aging treatment is applied to the pipe portion to improve its strength. The universal joint is made from 6000 aluminium alloy or its family. For example, employed is an HS60 alloy whose Mg, Si and Cu contents are appropriately adjusted. The first pipe portion 20 of the first propeller shaft segment 1 is provided with the universal joint 4 at one end thereof for connection with the transmission T. The universal joint 4 is made from aluminium alloy (HS60 alloy) and welded onto the pipe portion 20. A connecting element 10 made from aluminium alloy (HS60 alloy) is welded onto the other end of the pipe portion 20 to close the other end of the pipe portion 20 and to connect the pipe portion 20 with a steel shaft 7 of the centre bearing 2. The second propeller shaft segment 3 has an intermediate universal joint 6 at one end thereof for mechanical connection with the shaft 7 of the centre bearing 2 and a universal joint 5 at the other end thereof for connection with the differential gear D. The second propeller shaft segment 3 includes a second pipe portion 23 made from 6061 aluminium alloy and a slide shaft 22. The slide shaft 22 is provided to adjust the shaft length. The slide shaft 22 is welded onto a root 24 of the intermediate universal joint 6. This shaft 22 includes a spline tube 25 having spline grooves on the inside and a spline shaft 26. The spline shaft 26 engages the spline tube 25 so that it can move in the axial direction of the spline tube 25. The spline tube 25 is made from 6061 aluminium alloy and the spline shaft 26 is made from HS60 alloy. The spline shaft 26 is welded to the hollow pipe portion 23. The spline shaft 26 is provided on its periphery (outer face) with a plastic resin coating 27 such as nylon. Burning or seizure between the spline shaft 26 and the spline tube 25 is prevented by the plastic resin coating 27. The coating layer 27 is made by the following process: the spline shaft 26 undergoes solution heat treatment and aging treatment (T6 treatment). Immediately after the aging treatment, a resin powder is painted on the spline shaft 26 in accordance with a fluid dipping method to harden it. This process provides a resin coating without reheating since the coating layer 27 is formed taking advantage of calorific capacity generated upon the aging treatment. Accordingly, the strength at the time of aging treatment is maintained. Referring to Figure 2, the centre bearing 2 has the steel-made shaft 7 which transfers driving power, a ball bearing 8 which rotatably supports the shaft 7 and a housing 9 which houses the ball bearing 8. The housing 9 is mounted on the vehicle frame. The shaft 7 has a flange-like connection 11 on its transmission side. The connection 11 has the same diameter as the connection 10 of the first propeller shaft segment 1. Behind the connection 11 (right hand in Figure 2), a seal portion 29 is formed on the shaft 7. The seal portion 29 contacts a shaft seal 28 of the housing 9. Subsequent to the seal portion 29, a step portion 30 is formed to bear a thrust load of the ball bearing 8. The remainder of the shaft 7 is a shaft portion 31, part of which engages the ball bearing 8. Behind the ball bearing 8, a cylindrical element 32 fits over the shaft portion 31 to receive a joint portion 6b of the intermediate universal joint 6. Spline grooves 33 are formed on an outer face of the shaft portion 31 and an inner face of the cylindrical element 32 respectively so that the shaft portion 31 rotates with the joint portion 6b. Further, a bolt 18a projects from the rear face of the shaft portion 31. Thus, after the cylindrical element 32 is engaged over the shaft portion 31, a nut 18b is screwed down to fix the joint portion 6b onto the shaft 7. A front end 32a of the cylindrical element 32 co-operates with the step portion 30 of the shaft 7 to bear the thrust load of an inner race of the ball bearing 8. A presser or pressure plate 34 is provided on the cylindrical element 32 to close the rear end of the housing 9 and support an outer race of the ball bearing 8, and a sealing member 35 is provided between the presser plate 34 and the cylindrical element 32. Referring now to Figure 3, an anti-rotation formation in the form of an X-like arrangement of ridges and grooves or serrations 12 is formed on the exposed face (contact face) 10a of the connection 10 of the first propeller shaft segment 1. A corresponding formation of ridges and grooves or serrations 13 is formed on the exposed face (contact face) 11a of the connection 11 of the shaft 7 of the centre bearing 2. Further, a thread 14 is formed on the connection 10 of the first propeller shaft segment 1 and a locking nut 16 (e.g. box nut) fits over the connection 11 of the shaft 7. In this embodiment, the contact face 10a is made from aluminium alloy and the contact face 11a is made from steel. If water penetrates between these contact faces 10a and 11a, electrolytic corrosion may occur due to the different metals employed. Regarding this, the connection is coated with an anode coating 40 (e.g. galvanization) at its contact face 11a in order to maintain its electrical potential to the same value as the other contact face 10a. The opposite face of the connection 11 is also provided with an anode coating 40 for a similar reason. In order to join the first propeller shaft segment 1 with the centre bearing 2, the serrations 12 and 13 of the contact faces 10a and 11a are engaged with each other and the locking nut 15 is screwed over the thread 14 of the first propeller shaft segment 1. The locking nut 15 is made from aluminium alloy and/or coated with an anode coating. The screwing may be done with a jig 17. In such a case, openings 16 for the jig 17 are bored in the locking nut 15. Alternatively, a hexagonal locking nut 15a may be employed instead of a circular locking nut 15 and screwed down with a wrench. Referring back to Figure 2, the intermediate universal joint 6 which joints the centre bearing 2 with the second propeller shaft segment 3 has a first joint 6a on the second propeller shaft segment 3 side and the second joint 6b on the centre bearing 2 side. The first joint 6a is made of aluminium or its alloy whereas the second joint 6b is made of steel. It should be noted that the second joint 6b may be made of aluminium. Connecting pins for the universal joints 4, 5 and 6 are made of steel. Since the first and second propeller shaft segments 1 and 3 are made of aluminium or its alloy, their weight is reduced. Generally, their weight is reduced by 30-50%. On the other hand, the centre bearing 2 is made of steel so that it is not necessary to enlarge the diameter of the shaft 7. Further, since the connection of the aluminium-made first propeller shaft segment 1 with the steel-made centre bearing 2 is made by the serrations 12 and 13 and the locking nut 15, welding of aluminium and steel, which is technically difficult to perform, is unnecessary. Since the first and second propeller shaft segments are light in weight but have relatively large diameters respectively (aluminium shaft segments inevitably have a larger diameter), imbalances due to weight offsetting are small as compared with a steel propeller shaft. Therefore, vibrations are reduced. The contact face 11a and its opposite face of the steel connection 11 are coated with the anode coating layer 40 and the locking nut 15 is made from aluminium alloy. Thus, even if water penetrates between the connections 10 and 11, the contact faces 10a and 11a and the locking nut 15 are maintained at the same electric potential so that electrolytic corrosion is prevented. During operation, the second propeller shaft segment 3 fluctuates, with the universal joint 6 being a fulcrum, so that the second propeller shaft segment 3 changes its length. However, the length variations are adjusted or absorbed by the spline tube 25 and the spline shaft 26. The plastic coating 27 realizes smooth length adjustment.

Claims: A propeller shaft arrangement for connecting a transmission (T) with a differential gear (D) of a vehicle, comprising: a first propeller shaft segment (1) for connection to the transmission (T); a second propeller shaft segment (3) for connection to the differential gear (D); an element (7) for connecting the first propeller shaft segment (1) with the second propeller shaft segment (3); and means (2, 8, 9) for supporting the connecting element (7), characterized in that the first propeller shaft segment (1) is made substantially of aluminium or aluminium alloy; the second propeller shaft segment (3) is made substantially of aluminium or aluminium alloy; the connecting element is a shaft (7) made substantially of steel; and the supporting means includes a ball bearing means (2, 8, 9) for mounting on a vehicle frame to rotatably support the steel shaft (7). The propeller shaft arrangement of claim 1, characterized in that most of the first and second propeller shaft segments (1, 3) are comprised of hollow pipes (20, 23) made from aluminium alloy, respectively. The propeller shaft arrangement of claim 2, characterized in that the material of each hollow pipe (20; 23) further includes a proportion of ceramic particles. The propeller shaft arrangement of any one of claims 1 to 3, characterized in that the first and second propeller shaft segments (1, 3) have universal joints (4, 5) for connection with the transmission (T) and the differential gear (D), respectively. The propeller shaft arrangement of any one of claims 1 to 4, further including mechanical connection means (10, 11, 15) for connecting the first propeller shaft segment (1) with the steel shaft (7). The propeller shaft arrangement of claim 5, characterized in that the mechanical connection means (10, 11, 15) includes a first connecting element (10) having antirotation formations (12) at one end of the first propeller shaft segment (1), a second connecting element (11) having anti-rotation formations (13) at one end of the steel shaft (7) and locking nut means (14, 15, 15a) for abutting and connecting the first with second connecting elements (10, 11) at their anti-rotation formations (12, 13). The propeller shaft arrangement of claim 6, characterized in that the locking nut means (14, 15, 15a) includes a box nut (15, 15a) provided on one of the connecting elements and a thread (14) formed on a periphery of the other connecting element thereby engaging the box nut (15, 15a) with the thread (14) and joining the connecting elements. The propeller shaft arrangement of claim 6 or claim 7, characterized in that the connecting element (11a) of the steel shaft (7) is coated with an anode coating (40). The propeller shaft arrangement of any one of claims 1 to 8, characterized in that the ball bearing means (2, 8, 9) includes a housing (9) for mounting on the vehicle frame and a ball bearing (8) received in the housing (9) for rotatably supporting the steel shaft (7). The propeller shaft arrangement of any one of claims 1 to 9, further including an intermediate universal joint (6) for connecting the steel shaft (7) with the second propeller shaft segment (3). The propeller shaft arrangement of any one of claims 1 to 10, characterized in that the second propeller shaft segment (3) includes a slide shaft portion (22) for adjusting the length of the second propeller shaft segment (3), and a pipe element (23). The propeller shaft arrangement of claim 11, characterized in that the slide shaft portion (22) includes a spline tube (25) connected to the steel shaft (7) and a spline shaft (26) fitted inside the spline tube (25) and slidable in an axial direction of the spline tube, and the spline shaft (26) is integrally connected with the pipe element (23). The propeller shaft arrangement of claim 12, characterized in that the spline shaft (25) is coated with a resin coating on its periphery.

Inventors: EBE YOICHI, HINO HARUMICHI, KAWAI HIDENOBU, KAWATA YUTAKA, EBE, YOICHI, HINO, HARUMICHI, KAWAI, HIDENOBU, KAWATA, YUTAKA, EBE, YOICHI, C/O NIPPON LIGHT METAL CO., LTD., HINO, HARUMICHI, C/O NIKKEI TECHNO-RESEARCH, KAWAI, HIDENOBU, C/O NIKKEI TECHNO-RESEARCH, KAWATA, YUTAKA, C/O JIDOSHA BUHIN KOGYO CO., LTD.
Applicants: JIDOSHA BUHIN KOGYO KK, JIDOSHA BUHIN KOGYO CO.LTD.
Application year: 1993
Main classification: B60K17
IPC codes: F16D1, B60K17, F16C3