WO2002048519A2

WO2002048519A2 - Turbo compound unit and housing thereto and combustion engine including a turbo compound unit

Info

Publication number: WO2002048519A2
Application number: PCT/SE2001/002694
Authority: WO
Inventors: Henrik Grenfeldt
Original assignee: Scania Cv Ab (Publ)
Priority date: 2000-12-12
Filing date: 2001-12-06
Publication date: 2002-06-20
Also published as: SE0004589D0; SE0004589L; SE518021C2; DE10197014T1; AU2002218635A1; WO2002048519A3

Abstract

A housing (14, 14') for a turbocompound unit (5) for a combustion engine (1) and with an output shaft (10) which is arranged to transmit power from the power turbine to a flywheel of the combustion engine. The housing is provided with aligning elements (17, 20, 23) for oriented fastening to the engine block (2) of the combustion engine. The invention also relates to a turbocompound unit and combustion engine equipped with such a unit.

Description

Turbo compound unit and housing thereto and cumbustion engine including a turbo compound unit

Technical field

The present invention relates to a housing for a turbocompound unit according to the preamble to patent claim 1. The invention also relates to a turbocompound unit including such a housing and to a combustion engine including such a turbocompound unit.

State of the art

Turbocompound units are used for utilising part of the energy content of the exhaust gases from a combustion engine. To this end, the unit is situated in the exhaust line so that the exhaust gases drive a power turbine of the unit. The latter, by means of its shaft, two sets of mechanical gears and a hydraulic coupling, provides the engine's power transmission with extra power as a result of the output shaft of the unit being designed to cooperate with the engine's flywheel.

In the case of a turbocharged engine with turbine-driven inlet air compressor, the power turbine of the turbocompound unit is situated downstream from the turbocharging unit.

A conventional turbocompound unit incorporates a first set of gears between the power turbine and the hydraulic coupling. A second set of gears is situated after the hydraulic coupling and includes a gearwheel on the unit's output shaft and an intermediate gear between this and a crankshaft gearwheel which is rigidly connected to the engine's flywheel. The conventional turbocompound unit is fastened by its housing to the outside of a flywheel casing which encloses the flywheel, the intermediate gear and the crankshaft gearwheel. The unit's output shaft passes through a recess in the casing.

Turbocompound technology involves a source for increasing the power and reducing the fuel consumption of combustion engines, particularly in the case of turbocharged diesel engines for heavy vehicles. However, the technology has been called into question not only on the basis of the additional cost of the unit but also because of problems of operational reliability. In particular, experience has revealed limited service life of the mechanical gear after the hydraulic coupling, involving gearwheel damage requiring inspection, repair and sometimes unit replacement.

Objects and most important characteristics of the invention

One object of this invention is to indicate a housing for a turbocompound unit, together with a turbocompound unit, which solves or reduces the problems of the state of the art and provides a reliable and long-lasting solution whereby the need for repairs can be reduced.

This object is achieved according to the invention with a housing for a turbocompound unit of the kind mentioned in the introduction having the features indicated in the characterising part of patent claim 1.

The housing thus being provided with means for oriented fastening to the engine block and not, as in conventional technology, to the flywheel casing prevents incorrect engagement between the gearwheel on the turbocompound unit's output shaft and cooperating gearwheels. This is because placing the unit on the engine block gives the unit's output shaft an alignment which corresponds in parallelism with the gearwheels with which the output shaft's gearwheel has to engage. This contrasts with a unit which, according to conventional technology, is attached to the flywheel casing and is therefore subject to bending movements and vibrations which occur during operation between the engine and the vehicle's gearbox. These movements have been found to affect gear engagement precision and hence gradually in serious cases to lead to gear damage. The invention results instead in more reliable gear engagement and substantially longer service life.

The incorporation in the housing of contact surfaces in at least two mutually angled planes, for cooperation with corresponding aligning surfaces on the engine block, creates the possibility of reliable and appropriate alignment of the housing on the engine block, while at the same time the machining tolerances can be kept reasonable, particularly as regards machining the engine block's aligning surfaces. This is a great advantage in that the machining can be carried out with such conventional equipment as is used for other machining of the engine block. Thus no special machining will be required.

A particular advantage is that, according to one aspect of the invention, at least one contact surface cooperates with an aligning spigot, thereby further reducing the engine block machining required. Machining is thus reduced to forming an aligned spigot hole. It is in particular preferable that two contact surfaces be arranged to accommodate the aligning spigot between them. This results in particularly reliable guidance of the housing before tightening by means of threaded connections or the like. It is most preferable that the contact surfaces be arranged according to claim 6, whereby alignment is easy to achieve by moving the housing in the output shaft direction so that the groove encloses the spigot.

Further advantages are achieved by the features indicated in the other dependent claims, and will be indicated in the following description of an embodiment.

Brief description of the drawings

An embodiment of the invention will now be described with reference to the drawings, in which:

Fig. 1 depicts schematically a turbocompound unit in conjunction with a turbocharged combustion engine.

Fig. 2 depicts part of a housing for a turbocompound unit according to the invention in a first sideview. Fig. 3 depicts the housing in Fig. 2 viewed from below, and

Fig. 4 depicts a section through the housing in Figs. 2 and 3 in cooperation with a transmission plate.

Description of an embodiment

In Fig. 1 ref. 1 denotes a turbocharged diesel engine for a heavy vehicle. The engine is equipped in a conventional manner with arrangements for cooling of charge air and radiator fluid. Ref. 2 denotes an engine block and ref. 3 an exhaust manifold which leads the exhaust gases from cylinders of the engine to a turbocharging unit 4. Situated downstream from the turbocharging unit 4, as viewed in the exhaust line flow direction, is a power turbine 6 of a turbocompound unit 5.

The power turbine 6 has running from it a turbine shaft 7 for transmitting power generated by the power turbine, via a first gear set 8, to a hydraulic coupling 9 which is inserted to allow speed differences between the input and output shafts of the coupling.

A second gear set 11 is then arranged to further reduce the speed of the turbine shaft and allow cooperation between the shaft and the flywheel 12. Ref. 13 denotes a casing for the flywheel, a casing which in the conventional solution supports the turbocompound unit 5, a practice which does not apply to the unit according to the invention. For comprehension of the approximate combined gear ratio of the gear sets, it may be stated that the speed of the power turbine may range up to several tens of thousands of revolutions per minute, e.g. 60,000 rpm, while the flywheel speed during normal cruising of the vehicle ranges up to about 1100 rpm.

Fig. 2 depicts a section 14 of a housing for a turbocompound unit according to the invention. In principle, the construction of this unit is the same as the unit in Fig. 1. The same reference notations are used for corresponding parts. A cover (not depicted in this diagram) is intended to be fitted to the surface 14'. The housing also includes a bearing abutment 15 to accommodate a roller bearing for the output shaft. Ref. 16 denotes an oil outlet from the unit.

The unit's housing is designed to cooperate positionally with the engine block for a combustion engine. To this end, the housing incorporates a number of contact portions and guides for cooperation with corresponding aligning surfaces on the engine block.

First contact portions 17 and 20 have respective contact surfaces 18 and 21 which cooperate with first aligning surfaces PI and P2 respectively on the engine block. These first contact portions 17, 20 also constitute fixing portions in that each of them is provided with a drilled hole in which a screw (hinted at by broken lines at 19 and 22 respectively) is inserted to cooperate with a threaded hole in the region of the first aligning surfaces PI and P2.

A second contact portion 23 incorporates an inner groove with laterally situated second contact surfaces 24 for guided cooperation with an aligning spigot 25 which is firmly fitted in a oriented manner in, and protrudes from, the engine block. It should thus be noted that the second contact portion 23 does not abut directly against any aligning surface on the engine block but is only indirectly aligned via the spigot 25.

The housing 14 further incorporates a first fastening portion 26 and a second fastening portion 27 which are likewise not intended to abut directly against any aligning surface on the engine block. These fastening lugs are fastened instead at a distance therefrom by means, for example, of a positional error compensating fastening device not further described here but known per se such as, for example, that referred to in the applicant's Swedish patent no. 501 741. These fastening devices serve to fix and stabilise the housing 14 relative to the engine block after alignment of the contact portions relative to corresponding aligning surfaces or spigots. As may be seen in the diagram, the fastening lugs protrude considerably sideways as viewed from the bearing abutment 15 of the output shaft. This arrangement results in stable fixing to the engine block.

Fig. 3 shows the housing 14 with the bearing abutment 15 as viewed from behind and partly concealed by the boss of the oil outlet 16. It further shows not only fixing portions 26 and 27 but also a flange 29 for connecting a casing for a power turbine to the housing section 14. The diagram shows on the right of the housing section 14 the first and second contact portions 17, 20 and 23, and in the case of this latter the delineations of the second contact surfaces 24 are hinted at by broken lines. In this version the groove formed in the second contact portion 23 is open forwards but is ended by a transverse wall 24'.

Fig. 4 is a sectional view of the housing section 14 including inter alia the hydraulic coupling 9 and the output shaft 10. The bearing abutment 15 is intended to serve as a guide element for the housing section 14 by means of the peripheral circular cylindrical surface 28. This guide surface 28 is arranged to cooperate with a guide hole 31 formed in a transmission plate 30 which is itself orientedly fastened by means of guide pins (not depicted) to the engine block in the latter' s rear region, i.e. in the direction towards the engine's transmission. Also visible in this diagram is a gearwheel 32 which is mounted on the unit's output shaft 10 and forms part of the second gear set, corresponding to that denoted by ref. 11 in Fig. 1.

In the design depicted, the output shaft and, in particular, this gearwheel 32 are well guided by a rolling bearing 33 inserted in the bearing abutment, with the bearing adjacent to the gearwheel. This illustrates the bearing abutment's dual function not only as a bearing seat but also as a guide element for the turbocompound unit. This dual function provides reliable and easy guidance of the housing and, in particular, of the shaft 10 and its gearwheel 32, resulting in reliable engagement with the intermediate gear (not depicted) with which the gearwheel has to cooperate. With advantage, this intermediate gear is supported by a pivot pin fastened to the transmission plate.

Ref. 34 denotes a seal inserted between the housing and the transmission plate. Ref. 14" denotes the previously mentioned cover which in this diagram is fitted to the surface 14' of the housing section 14.

Fitting the turbocompound unit to the combustion engine entails placing the unit's housing 14, 14' against the engine block with the contact surfaces 18 and 21 abutting against corresponding aligning surfaces PI and P2 on the engine block (see Fig. 3). Thereafter, the housing 14, 14' is moved in the direction of the arrow A corresponding to leftward movement in Figs. 1 and 4 and movement upwards from the plane of the paper in Fig. 2. The spigot 25 is thus guided in between the second contact surfaces 24 in the groove in the second contact portion 23, and the guide surface 28 of the bearing abutment 15 is guided into the guide hole 31 in the transmission plate 30. When a position of sufficient insertion has been reached, the screws are tightened inside the first contact portions 17 and 20, followed by tightening of the fastening elements which pass through the fastening portions 26 and 27. The result is very good alignment of the turbocompound unit relative to the gearwheels of the second gear set. Such is the case irrespective of whether the engine is subject to powerful vibrations or whether deflections due to deformations occur in the region of the flywheel casing. It may be mentioned in this context that the suspension points for the engine and the associated transmission in today's vehicles are situated further apart than in previous installations. This fact has made the region of the flywheel casing increasingly unsuitable for fastening the turbocompound unit, owing to the increased deformations arising from this suspension principle.

• A great advantage of the solution described is that placing at least the first contact portions and preferably also the second contact portion at a distance from the region for guidance cooperation on the output shaft, and still more preferably at the greatest distance possible in practice therefrom, i.e. on the section of the housing which is opposite to the region of the output shaft, results in very good alignment precision with moderate tolerance requirements. A slight deviation vertically of, for example, the surfaces PI and P2 causes only a minimal change of direction of the gearwheel 32 of the output shaft 10. This is a great advantage of the invention in making it possible for the surfaces PI and P2 to be machined by means of machine-tools which are conventionally used in engine manufacture. The machining tolerances for the surfaces thus present only moderate requirements. There is therefore no need of special machines.

The invention may be varied within the scopes of the patent claims. Thus the contact portions may be shaped differently and need not, for example, be directly adjacent to threaded fastening devices. The second contact surfaces may be replaced by a single surface situated at an angle to the surfaces PI, P2. The aligning spigot 25 may be replaced by some other element, e.g. even by an aligned and machined projecting part of the engine block. It is preferable that the aligning spigot be circular cylindrical, but other shapes may arise, such as cylindrical with non-circular cross-section.

The guiding elements in the region of the output shaft may also be of some other kind, although the embodiment depicted is preferable for the reasons stated above. Thus it is possible, with a certain reduction in precision, for the unit housing 14 to cooperate in this region with, for example, a fastening lug on the engine block via a guide element designed otherwise than as an outer surface for a protruding bearing abutment. The contact portions may also be designed differently, e.g. be arranged further apart laterally and/or constitute a larger area. They may also be separate from fastening devices such as screws.

Claims

Patent claims:

1. A housing (14,14') for a turbocompound unit (5) for a combustion engine (1) and incorporating an output shaft (10) which is arranged to transmit power from the power turbine to a flywheel of the combustion engine, characterised in being provided with aligning elements (17,20,23) for oriented fastening to the engine block (2) of the combustion engine, which aligning elements include contact surfaces (18,21,24) arranged on the housing in at least two mutually angled planes for cooperation with corresponding aligning surfaces (P1,P2,25) on the engine block.

2. A housing according to claim 1, characterised in that the contact surfaces include at least one contact surface (18,21) which is situated on at least one first contact portion (17,20) and faces towards the engine, and at least one second contact surface (24) which is situated on at least one second contact portion (23) and runs substantially perpendicular thereto and hence substantially parallel with the direction towards the combustion engine, and which in use is parallel with the output shaft of the turbocompound unit.

3. A housing according to claim 2, characterised in that each second contact surface (24) is designed to cooperate with an aligning spigot (25) inserted in the engine block.

4. A housing according to claim 3, characterised in that the aligning spigot (25) is circular cylindrical.

5. A housing according to claim 3 or 4, characterised by including two second contact surfaces (24) which are mutually parallel and face in opposite directions and are designed to fit together in order to cooperate with the aligning spigot (25).

6. A housing according to claim 5, characterised in that said second contact surfaces (24) are arranged inside a groove which is open towards the output shaft and closed in the opposite direction.

7. A housing according to any one of the foregoing claims, characterised by being provided, in the region of the output shaft (10), with a protruding guide element (15) for cooperation with a transmission plate (30) fastened to the engine block (2).

5 8. A housing according to claim 7, characterised in that said guide element consists of a protruding bearing abutment (15) for a bearing (33) for the output shaft (10).

9. A housing according to any one of the foregoing claims in conjunction with claim 2, characterised in that each first contact surface (18,21) is arranged in a region of the

10 housing which is at a distance from the region of the output shaft.

10. A housing according to claim 9, characterised in that each first contact surface (18,21) is situated on a region of the housing which is substantially opposite to the output shaft.

15

11. A housing according to any one of the foregoing claims in conjunction with claim 2, characterised in that each first contact portion is arranged protrudingly from the housing.

12. A housing according to claim 11, characterised in that said first protruding portion 20 also includes a hole or recess for a fastening element.

13. A housing according to claim 11 or 12, characterised by including at least one fastening portion which is intended for fastening to the engine block but not intended for alignment and abutment against the engine block.

25

14. A housing according to claim 13, characterised in that each fastening portion is intended to cooperate with a positional error compensating device which is anchored to the engine block.

30 15. A turbocompound unit, characterised by including a housing according to any one of claims 1-14.

16. A combustion engine, characterised in that its engine block is equipped with aligning surfaces for aligned fastening of a turbocompound unit according to claim 15, and by including such a unit.