Bearing Arrangement

Technical Field of the invention

The invention relates to a bearing arrangement for the crankshaft of a reciprocating engine, especially for a combustion engine, which has at least one first bearing, main bearing, for supporting the crankshaft in a housing of the reciprocating engine and at least one second bearing, rod bearing, to support a conrod on the crankshaft.

Background of the invention

Bearing arrangements of this kind are normally used when a crankshaft of a combustion engine has to be supported in a housing and a number of conrods has to be supported on the crankshaft. Usually, for the support of the crankshaft in the housing as well as for the support of the conrods on the crankshaft plain bearings are used. It is very important, that all plain bearings in the system are supplied with sufficient lubricant. Therefore, pressurized oil is conducted into the arrangement. The oil is forwarded to all plain bearings under pressure.

Such a solution is known e.g. from US 5,163,341 and from US 5,799,547. Here, the crankshaft is equipped with a number of bores which are machined in such a way that all bearing points of the plain bearings are connected to the conduit system. When high pressure oil is supplied to the conduit system oil reaches all bearing points of the plain bearings. By this arrangement not only the plain bearings which support the crankshaft relatively to the housing and

which therefore are stationary in the housing are well supplied with oil, but also the bearings which support the conrods and which therefore move during the operation of the combustion engine are sufficiently supplied with lubricant.

For supplying the conduit with sufficient oil a respective oil pump is necessary. The oil pump consumes rather large amounts of energy. There is a desire to reduce the total energy consumption of for example a car. Therefore, there is a general aim to look for a solution, which would reduce the amount of pressurized oil needed. The oil pump would then not need to work as hard, or could even be replaced by a smaller oil pump, leading to reducing to the total energy consumption of for example a vehicle.

Summary of the invention

An object of the invention is to provide a solution which reduces the total energy consumption of for example a vehicle, by reducing the consumption of energy of an oil pump, which oil pump provides pressurized oil to one or more plain bearings. According to the invention it has been found out that it is possible to change the bearings which support a crankshaft in a housing from plain bearings to rolling element bearings. This seems currently not to be easily done for the bearings which support the conrods on the crankshaft. However, if rolling element bearings are employed to support the crankshaft in the housing the consumption of pressurized oil could be significantly reduced, thus reducing the amount of energy consumed by the oil pump. In spite of this, pressurized oil would further be necessary to supply the plain bearings that support the conrods on the crankshaft.

The supply of pressurized oil to the remaining plain bearings pose a problem. By introducing rolling element bearings to support the crankshaft in the housing, the currently known methods of providing pressurized oil to the remaining plain bearings does not work. The problem is that the gap between the outer and inner ring of a rolling element bearing makes it impossible to feed pressurized oil through the rolling element bearing to the plain bearings.

It is therefore a further o bj e c t of the invention to create an improved bearing arrangement for the crankshaft of a reciprocating engine, especially for a combustion engine, with at least one first bearing for supporting the crankshaft in the housing and at least one second bearing to support the conrods on the crankshaft which makes it possible to supply pressurized oil via the at least one first bearing to the at least one second bearing. So, it is aimed to substitute the pre-known plain bearings, which support the crankshaft in the housing, by rolling element bearings, and at the same time ensure that sufficient lubricant is supplied to the second bearings, i. e. to the plain bearings.

A s o l u ti on according to the invention is characterized in that rolling element bearings are employed for supporting the crankshaft of the reciprocating engine, which can be a combustion engine as well as a compressor, but that - as usual - plain bearings are used to support the conrods on the crankshaft. It is at the same time enabled that pressurized oil can be transferred through the rolling element bearings and that this oil is fed into a conduit which leads to the bearing points of the plain bearings for the conrods.

More specifically, the invention suggests that the at least one first bearing for supporting the crankshaft in the housing is a rolling element bearing, having

at least one outer ring and at least one inner ring, between which rolling elements are arranged, and the at least one second bearing which supports the conrods on the crankshaft is a plain bearing, wherein a fluidic connection is established by an oil channel in the crankshaft between the at least one first bearing and the at least one second bearing for supplying the second bearing with pressurized oil and wherein an oil guidance device is arranged between the at least one outer ring and the at least one inner ring of the at least one first bearing for supplying pressurized oil from one ring to the other and to the oil channel.

Preferably, the crankshaft is supported in the housing by a plurality of first bearings and a plurality of conrods is supported on the crankshaft by a plurality of second bearings. With respect to the inner ring of the rolling element bearings it is preferred that the inner ring of the first bearing is formed by a section of the crankshaft, especially by a cylindrical section of the crankshaft.

The oil guidance device can form an oil passage between the outer ring and the inner ring of the first bearing. In this case the oil passage can be sealed against the outer ring and/or the inner ring of the first bearing. For sealing specific elements can be employed. It is also possible to achieve a sealing effect by using a small gap between the respective parts so that only a minor amount of high pressure oil can escape from the oil passage. This would have even the beneficial effect that this leaking amount would lubricate the rolling element bearing, i.e. the first bearing. The oil passage can be in fluidic connection with an oil inlet hole in the outer ring. An oil inlet device can be inserted into the oil inlet hole in the outer ring which can be connected to a source for pressurized oil. The oil inlet device can also form a fixation device for the outer ring in the housing, i.e. by inserting the inlet device a mechanical

fixation of the outer ring in the housing can occur in both axially and radially/circumferentially. The oil inlet device can further have the form of a hollow cylinder that is inserted with one axial end into a cylindrical section of the oil inlet hole.

With respect to the design of the oil guidance device it is beneficial that it has two ring-shaped side walls which are arranged with an axial distance relatively to another, between which the oil passage is established. In this case at least one bridge can be arranged between the two ring-shaped side walls to keep them in defined axial distance relatively to another. The bridge can extend along a part of the circumference of the side walls; here a preferred embodiment has bridges which extend along 5° till 30° of the circumference of the side walls. Preferably, a plurality of bridges are used which extend between the two ring-shaped side walls. A high mechanical stability of the oil guidance device is reached when the side walls and the bridge have a H-shape in radial cross section.

A preferred embodiment of the invention has the oil guidance device connected to one of the bearing rings of the first bearing. In this case one of the bearing rings can have a ring-shaped groove in which the oil guidance device is inserted. Preferably, the oil guidance device has a radial outer or inner section which is reduced in width and which is inserted into the groove. The oil guidance device, especially its radial inner or outer section, can be arranged with an axial interference fit in the groove. Furthermore, the oil guidance device can be connected to one of the bearing rings of the first bearing by means of a snap fit connection. Another possibility of connection is that the oil guidance device is glued, soldered or welded with one of the bearing rings of the first bearing.

An alternative solution has the oil guidance device formed as one piece with one of the bearing rings of the first bearing, especially with its outer ring.

A further alternative has the oil guidance device formed as one piece with a cage for the rolling elements of the first bearing.

As already mentioned above, it can be beneficial that a small radial gap is arranged between the oil guidance device and a bearing ring of the first bearing to which the oil guidance device is not attached.

To facilitate or to allow easy assembly of the bearing assembly, the outer ring and/or the inner ring of the first bearing can be segmented. Specifically, the rings can consist of two parts. Correspondingly, the cage can have an intersection at at least one location of its circumference. If the material of the cage is sufficient elastic/flexible a single intersection around the circumference can be sufficient to mount the cage by spreading the cage during assembly. Of course, the cage can also consists of two parts. Finally, the oil guidance device can have an intersection at at least one location of its circumference. Also here, a single intersection can be sufficient for mounting if the material is elastic/flexible. Normally, the oil guidance device will also consist of two parts.

The first bearing can suitably be designed as a one-row rolling element bearing. Also, it can be a double-row rolling element bearing. In the latter case the oil guidance device can be arranged between both rows of the double-row rolling element bearing.

As rolling element bearing a plurality of types of bearings can be employed. Specifically, the bearing can be a cylindrical roller bearing, a toroidal bearing,

a taper roller bearing or a ball bearing, especially an angular contact ball bearing.

The oil guidance device can be made of steel or of a non-ferrous metal, e.g. brass. It can also be made of plastic material or rubber material. In this case it can be beneficial that the material of the oil guidance device is reinforced, e.g. by glass or carbon fibers.

Due to the proposed design of a bearing arrangement, a high pressure oil passage is achieved between the inner and the outer ring of the first bearing, i. e. of the rolling element bearing. Therefore, the supply with pressurized oil from the oil source to the plain bearings is facilitated. Consequently, the oil pump has a reduced demand of energy.

The suggested concept creates an oil guidance which transports at least most of the pressurized oil from the outer ring to the inner ring and into the corresponding hole of the oil conduit or oil channel in the crankshaft so that oil can be fed to the plain bearings of the conrods.

Further preferred embodiments of the invention are defined in the claims.

Brief description of the drawings

The drawings show embodiments of the bearing arrangement according to the invention.

Fig. 1 shows the crankshaft with the conrods and the pistons of a combustion engine, partially in sectional view,

Fig. 2 shows a perspective view of a first bearing of the bearing arrangement in sectional view,

Fig. 3 shows a perspective view of a first bearing of the bearing arrangement in the assembled state,

Fig. 4 shows a perspective view of the first bearing of the bearing arrangement in exploded view,

Fig. 5 shows a part of a cage with oil guidance device in perspective view,

Fig. 6 shows an alternative embodiment of a first bearing in a view, and

Fig. 7 shows a further alternative embodiment of a first bearing in a view.

Detailed description of the invention

Fig. 1 shows the crankshaft 110 of a combustion engine 100, designed as a four cylinder engine. The crankshaft 110 is supported by first bearings 130 relatively to a housing 180. All first bearings 130 are rolling element bearings. They have outer bearing rings 136 and inner bearing rings 138 between which rolling elements 132 are located. It should be mentioned that a cylindrical part of the crankshaft 110 functions as the inner ring 138, i. e. no separate part forms the inner ring. Not all first bearings 130 are depicted; in total 5 first bearings 130 are employed at the 5 bearings points of the crankshaft 110.

The combustion engine 100 has four conrods 120 which are supported on the crankshaft 110 be means of second bearings 124 which are plain bearings. At the upper end of the conrods 120 pistons 122 are arranged. To supply the second bearings 124, i. e. the plain bearings, with a sufficient amount of

lubricant, i. e. with pressurized oil, oil channels 112 are machined into the crankshaft 110. The oil is fed from a pressurized oil source (not shown) via an oil inlet device 140. This oil inlet device 140 suitably also has the function to mechanically fix the outer ring 126 of the bearing 130 axially and in circumferential direction relatively to the housing 180.

The specific design of the first bearing 230 for one embodiment of the invention is shown in fig. 2. The bearing 230 has the outer ring 236 and the crankshaft 210 functioning as inner ring 238. Between the rings 236 and 238 rolling elements 232 are arranged which are guided in known manner by a cage 234.

For transferring pressurized oil from an oil source via the oil inlet device 240 and the outer ring hole 242 to the oil channel 212 in the crankshaft 210 without a significant drop of the pressure of the oil an oil guidance device 250 is used.

The oil guidance device 250 has basically two rings forming side walls 262 of an oil passage 260 through which the pressurized oil is fed. Both side walls 262 are kept in a definite axial distance by means of a couple of bridges 266 which are distributed around the circumference of the side walls 262. As can be seen in the upper part of fig. 2, the side walls 262 and the bridge 266 have together in this embodiment a H-shape. Other shapes are also envisaged, such as U-shape and completely closed.

The outer ring 236 has a ring groove 244 in which the radial outer end region of the oil guidance device 250 is inserted, wherein this radial outer region is formed as a lip or rib 264 for connection to the outer ring 236. An interference fit in axial direction between the groove 244 and the lip or rib 264 connects

the oil guidance device 250 firmly with the outer ring 238. The radial inner end of the oil guidance device 250 abuts with a small radial gap 270 to the inner ring 238. Thereby a sealing effect is achieved. Of course, this seal is not absolutely tight, but sufficiently tight to prevent a relevant pressure drop of the oil. On the other hand, a minor leakage due to the gap 270 supplies the rolling element bearing with some oil, which can be beneficial.

Fig. 3 shows the first bearing 330 in the mounted state. It can be seen that the outer ring 336 is split, i. e. is consists of two parts 337. The same applies for the oil guidance 350 and for the cage 334 which both consist of two parts.

This is also depicted in fig. 4. Here an exploded view of the first bearing is shown.

In fig. 5 an alternative embodiment is shown. Here the cage and the oil guidance device are made as one piece, specified with reference numeral 554. One of the side walls 562 of the oil passage is formed by one of the side rings of the cage, the other side wall 562 is kept in relative position by the bridges 566.

Fig. 6 shows an alternative embodiment with a first bearing 631 designed as a double-row rolling element bearing, i. e. two rows of rolling elements 632 are arranged between the outer ring 636 and the inner ring 638. The oil inlet device 640 is arranged axially between both rows of rolling elements 632. Here, also the oil guidance device 650 is positioned. It can also be combined with one or the other cage.

The embodiment according to fig. 7 shows a further alternative solution. Here, the outer ring 736 and the oil guidance device 750 are made as one

piece, specified with reference numeral 756. Both side walls 762, between the oil passage 760 is extending, are formed from the material of the outer ring 736.

Is should be mentioned that the oil guidance device can be connected to one of the bearing rings or to the cage. It is also possible that it is just inserted between the inner ring and the outer ring of the bearing, not being fixed to one of the rings and not to the cage.

Reference Numerals:

100 Reciprocating engine (four cylinder engine / compressor)

110 Crankshaft

112 Oil channel in crankshaft

120 Conrod

122 Piston

124 Second bearing (plain bearing)

130 First bearing (rolling element bearing) - single row

132 Rolling element

136 Outer ring

138 Inner ring

140 Oil inlet device (fixation device)

180 Housing

210 Crankshaft

212 Oil channel in crankshaft

230 First bearing (rolling element bearing)

232 Rolling element

234 Cage

236 Outer ring

238 Inner ring

240 Oil inlet device

242 Outer ring hole for oil inlet

244 Groove (ring groove)

250 Oil guidance device

260 Oil passage of oil guidance device

262 Side wall of oil passage

264 Radial outer or inner section

(lip/rib for connection to outer ring)

266 Bridge

270 Gap

330 First bearing (rolling element bearing)

332 Rolling elements

334 Cage

336 Outer ring

337 Split outer ring

340 Oil inlet device

350 Oil guidance device

360 Oil passage of oil guidance device

362 Side wall of oil passage

366 Bridge

432 Rolling elements

435 Split cage

437 Split outer ring

440 Oil inlet device

442 Outer ring hole for oil inlet

452 Split oil guidance device

554 Oil guidance device combined with cage

562 Side wall of oil passage

566 Bridge

610 Crankshaft

612 Oil channel

631 First bearing (rolling element bearing) - double row

632 Rolling element

634 Cage

636 Outer ring 638 Inner ring

640 Oil inlet device

650 Oil guidance device

736 Outer ring 740 Oil inlet device

750 Oil guidance device

756 Oil guidance device being part of outer ring

760 Oil passage of oil guidance device

762 Side wall