GB2317645A

GB2317645A - I.c. engine toothed-belt cooling arrangement

Info

Publication number: GB2317645A
Application number: GB9719180A
Authority: GB
Inventors: Dirk Warnecke
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1996-09-11
Filing date: 1997-09-10
Publication date: 1998-04-01
Anticipated expiration: 2017-09-10
Also published as: DE19636829C2; FR2753232A1; GB2317645B; JPH10121962A; FR2753232B1; DE19636829A1; GB9719180D0; KR19980024322A

Abstract

The camshaft 3 is driven from the crankshaft 1 by a toothed-belt 6 which is enclosed by a housing 12. The hub of the crankshaft belt pulley 8 has air-conveying blades 11 which cause cooling air to flow upwardly through the housing 12 to a thermostatically-controlled outlet valve 13 which is closed until a preset temperature is reached. The crankshaft belt pulley 8 may be covered by a suction hood (20, figs. 2-4) containing an air filter 26. In a modification (fig.5), filtered air is supplied to the housing 12 from a secondary pump (30), obviating the need for the blades 11 and filter 26.

Description

2317645

DESCRIPTION

A COOLING DEVICE FOR A RECIPROCATING-PISTON INTERNAL COMBUSTION ENGINE The present invention relates to a cooling device.for a reciprocating- piston internal combustion engine.

DE-41 06 684 C2 discloses a generic cooling device having an air feed device designed as a secondary air pump. in this case, the. air stream is supplied via air ducts to a plurality of constructional units of an internal combustion engine of a vehicle, such as, for example, an alternator, a central electronic unit or an exhaust manifold. These constructional units may be subjected to the air stream in parallel with one another from a pipe branch or else in series or in a combination of both. The secondary air pump is assigned a control unit which, for the purpose of controlling the throughflow, actuates valve devices arranged in the air ducts upstream and/or downstream of the constructional units. Such an arrangement involves a high outlay in terms of components and is cost-intensive, since all the valve devices have to cooperate separately with the control unit, these valve devices require actuators, for example in the form of pneumatic cells, and these, in turn, would have to be subjected to a control pressure. Electrical actuation of the valve devices would entail a comparable outlay, and in this case, in particular, the weight and costs of the electromagnetic actuators would be a disadvantage.

Belt control drives of internal combustion engines, in particular toothedbelt drives, are, as a rule, exposed to increased thermal load as result of the incidence of heat on the engine side and due to the flexing work occurring during the transmission of power, thus leading to marked reductions in the life of the belts. This problem is aggravated by casings which are intended to protect the belt against the influence of extraneous media, such as dust and water.

DE 40 21 002 Al, for example, proposes. as a solution to the abovementioned problem, to provide the V-belt pulley with radial blower blades between the hub and outer circumference. A radially directed air stream is thereby generated, which cools the V-belt pulley and therefore also the V-belt which is in contact with it. Furthermore, DE 41 36 748 Al discloses a solution for an encased toothed-belt drive of a liquid-cooled internal combustion engine, in which a fan wheel is arranged on a pump shaft. The fan wheel is assigned an air-guide housing with a separate air duct which leads from the air-guide housing to a belt casing, passes through the wall of the latter and guides an air stream directly onto the toothed belt. In this case, the fan wheel likewise works as a radial blower.

An aim of the present invention is based to provide a cooling device for a reciprocating -piston internal combustion engine having an air feed device guiding an air volume stream to at least one component for cooling purposes. the said cooling device influencing in the simplest possible way, by means of a valve device working in a parameter -dependent manner, the air volume which is conveyed over the component to be cooled.

According to the present invention there is provided a cooling device for a reciprocating-piston internal combustion engine, comprising an air feed device which conveys an air volume stream to at least one component of the internal combustion engine for cooling purposes, and a valve device, arranged downstream of the component and working in a parameterdependent manner, for influencing the air volume conveyed over the component, the valve device being designed as a regulating member working automatically in a temperature-dependent manner and being arranged in a geodetically upper region of a housing guiding the air volume stream.

According to the present invention, there is provision for designing the valve device as a regulating member working automatically in a temperature-dependent manner and for arranging the said valve device in a geodetically upper region of a housing guiding the air volume stream. Advantageously, therefore, a separate control unit is not required for influencing the air volume conveyed over the component. Corresponding connecting and control lines are thereby dispensed with. Arranging the valve device in a geodetically upper region ensures a complete flow through the housing, assisted by the natural convection flow which occurs due to the fact that the cooling air supplied is heated by the component to be cooled.

In an advantageous embodiment of the present invention there may be provision for providing the automatically working regulating member, as a thermostatically controlled, that is to say temperature-dependent regulating mechanism, with a closing member which closes an outflow crosssection when the temperature falls below a preset value and opens the same when the preset temperature is exceeded. This ensures a throughflow dependent on requirements, and the incidence of extraneous media is restricted to the time of the throughflow and, at most, is caused by this, since the ingress of extraneous media from outside is prevented by the overpressure prevailing during the throughflow.

Preferably, there may be provision for a belt pulley, arranged on a crankshaft stub and working as a torsional vibration damper, to act as a blower wheel by being provided with blades. Advantageously, in this case, a separate blower becomes unnecessary owing to the modification of an already existing component.

Such belt pulleys, as a rule, drive secondary assemblies and are axially arranged externally on the crankshaft stub. As a rule, the control belt runs, adjacent thereto, over a separate toothed-belt wheel. in this case, there is the advantageous effect that the axial air stream conveyed by the belt pulley acts directly on the adjacently running toothed belt in the region of its toothed-belt wheel. This ensures intensive cooling of that force transmission region of the belt drive which is subjected to the greatest load.

For a further improvement of the cooling effect, there is provision, particularly preferably, for the belt pulley to be covered by a suction h00d which has a fresh-air inlet and, if appropriate, may contain a filter element for filtering the cooling air supplied, thereby at all events avoiding the incidence of extraneous media. Alternatively, the fresh--air inlet may be connected by means of a hose guide to a point on the intake system which is located downstream of an air filter, with the result that a special filter may be dispensed with.

in order to avoid increasing the overall length of the internal combustion engine, there may be provision, in a further advantageous embodiment, for the suction hood to have an annular air-leading element which extends axially within an inner circumference of the belt pulley and which leads the air, supplied via the air inlet, onto the axial blades in a directed manner. The filter may be arranged so as to be integrated in this air-leading element.

whilst the above-described embodiment may pref erably be employed in autoignition internal combustion engines, it is also possible, in the case of spark-ignition internal combustion engines, to supply the cooling air by means of a secondary air pump. Advantageously, in this case, the already existing secondary air pump is utilized in other operating ranges in which it is usually not required. The air already filtered in the air filter and branched off downstream of the latter from the secondary air pump may be fed in via the above-described air hood in the region of the crankshaft stub, but, if there are particular requirements, also at another point on the belt. In this case. the delivery volume of the existing secondary air pump does not have to be changed. since the secondary-air injection function takes place only af ter a cold start and, in this case, there is still only a very small amount of heat introduced into the toothed belt.

Alternatively, in the case of a turbo-charged internal combustion engine, the compressor of the turbo-charger may be used as an air f eed device, in which case the slight oiling of the compressed intake air must be taken into account where the cooling of a toothed belt is concerned. However, this oiling may be advantageous, for example if a chain which has to be cooled is used.

irrespective of the type of air feed device, the valve device discharging and regulating the air volume stream may be designed, for example, as an element of expandable material or as a bimetalcontrolled element.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which:- Figure 1 shows a cross-section through a region, relevant here, of an internal combustion engine in a first embodiment, Figure 2 shows an enlarged detail of a modified embodiment according to Figure 1, Figure 3 shows a variant of the embodiment according to Figure 2, Figure 4 shows a view in the direction of the arrow X according to Figure 2, and Figure 5 shows diagrammatically a second embodiment of the invention.

A reciprocating-piston internal combustion engine provided with a crankshaft 1 has a toothed-belt drive, designated as a whole by 2, for driving a camshaft 3.

A belt wheel 5 for transmitting the drive power into a toothed belt 6 is arranged on a stub 4 of the crankshaft 1.

A belt pulley 8, containing a torsional vibration damper 7, for the drive of secondary assemblies of the internal combustion engine is arranged in front of the stub 4 on the belt wheel 5 in the axial extension of the latter.

A hub 9 of this belt pulley 8 hasaxially extending perforations 101 the circumferential limitations of which are designed as air-conveying blades 11.

For protection against extraneous media, the toothed belt 6 runs in its own housing 12 designed as a casing. A valve device 13 designed as a regulating member working automatically in a temperature-dependent manner is arranged on a geodetically upper region of this housing 12. The said valve device has a bimetalcontrolled closing member 14 which controls an outflow cross-section 15 of the housing 12.

When the cold internal combustion engine is running, the outflow crosssection 15 is closed, and the blades 11 supply only a minimal air volume stream which escapes via slight leaks or defined outflow slits not shown here. During the heating of the internal combustion engine while it is running, the introduction of heat into the housing 12 and therefore the transmission of heat to the toothed-belt drive 2 increase. When a preset temperature is reached at the valve device 13, the closing member 14 opens the outflow cross-section 15 increasingly, so that the belt pulley 8 can become fully effective in its special design as an axial scavenging- air blower. The air volume stream sucked in is first guided axially through the belt pulley 8 along the arrows marked in Figure 1 and subsequently acts on the belt wheel 5 and toothed belt 6 in the region of the stub 4. The air volume stream, which is already heating up at the same time, is guided in the housing 12 in the direction of the camshaft 3, with the assistance of convection flow, and is discharged into the surroundings via the open outflow cross-section 15.

As is evident from Figures 2 to 4, the belt pulley 8 is covered by a suction hood 20 held on the housing 12. This hood is designed, in the region of the belt pulley 8, as an annular air-leading element 21 extending axially within an inner circumference of this belt pulley 8 and having outflow orifices 22. According to Figure 2, the suction hood 20 has a connection piece 23 for supplying the sucked-in fresh air, this connection piece 23 being part of a cover 24 which delimits an annular distributor duct 25 on one side. On the outflow side, this distributor duct 25 is delimited by the air-leading element 21 and its outflow orifices 22. A filter 26 for protecting the toothed belt 6 against extraneous media is arranged within the airleading element 21. According to the variant shown in Figure 3, the inflow of fresh air takes place, instead of via the connection piece 23, via a low-throttle annular gap 27 which supplies the fresh air uniformly over the circumference and which is formed between the cover 24 and suction hood 20.

A second embodiment of the invention, which can advantageously be used particularly in Otto engines, is shown in Figure 4. The system shown there is basically known to the extent of the supply of secondary air by means of a secondary air pump 30 via a conduit 31 into an outlet duct 32 of the internal combustion engine and is not the subject of this application, and its function will therefore also not be explained in any more detail.

The conduit 31 has a branch 33 which can guide a specific air volume stream to the housing 12. This branch 33 may be connected to the connection piece 23 explained in regard to the first embodiment and supply the fresh-air stream to the toothed-belt drive 2 at this point. In this case, the blades 11 and the filter 26 can then be dispensed with, since the secondary air pump 30 already supplies filtered air.

However, as shown in Figure 4, the cooling air may also be injected at another point. The feed point 34 shown there may at the same time be a temperature -measuring point for generating an electrical signal. This is delivered via an electrical line 35 to the control unit 36 of the secondary-air system, the said control unit switching the secondary air pump 30 on and off as a function of the signal.

Claims

1. A cooling device for a reciprocatingpiston internal combustion engine, comprising an air feed device which conveys an air volume stream to at least one component of the internal combustion engine for cooling purposes, and a valve device, arranged downstream of the component and working in a parameterdependent manner, for influencing the air volume conveyed over the component, the valve device being designed as a regulating member working automatically in a temperature-dependent manner and being arranged in a geodetically upper region of a housing guiding the air volume stream.

2. A device as claimed in claim 1, in which the regulating member is designed as a thermostat with a closing member which closes an outflow cross-section when the temperature falls below a preset value and which opens the same when the preset temperature is exceeded.

3. A device as claimed in claim 1 or claim 2, in which the air feed device is a belt pulley which is arranged on a crankshaft stub of the internal combustion engine, is provided with blades and acts as an axial blower wheel.

4. A device as claimed in claim 3, in which the air volume stream acts at least on one belt running in the housing between the crankshaft and at least one - crankshaft of the internal combustion engine.

5. A device as claimed in claim 4, in which a belt wheel for driving the belt is arranged on the stub downstream of the belt pulley in relation to the conveyed air volume stream.

6. A device as claimed in any one of claims 3, 4, or 5, in which a filter is assigned to the belt pulley upstream of the blades in relation to the conveyed air volume stream.

7. A device as claimed in claim 6, in which the belt pulley is covered by a suction hood which receives the filter.

8. A device as claimed in claim 1 or claim 2, in which the air feed device is a secondary air pump assigned to the internal combustion engine.

9. A device as claimed in claim 8. in which the air volume stream acts on at least one belt running in the housing between the crankshaft and at least one camshaft of the internal combustion engine.

10. A device as claimed in claim 9, in which a further belt pulley is arranged on a stub of the crankshaft axially in front of a belt wheel guiding the belt, and the said belt pulley is covered by a suction hood.

11. A device as claimed in claim 7 or claim 10, in which the suction hood has an annular airleading element extending axially within an.inner circumference of the belt pulley.

12. A device as claimed in claim 7 or claim 10, in which a cover delimiting a distributor duct for the fresh air supplied is assigned to the suction hood upstream of the belt pulley in relation to the conveyed air volume stream.

13. A device as claimed in claim 12, in which the sucked-in fresh air is supplied to the distributor duct via a separate connection piece.

14. A device as claimed in claim 12, in which an annular gap providing a flow connection into the distributor duct is arranged between the suction hood and cover.

15. A cooling device for a reciprocatingpiston internal combustion engine constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.