The present invention relates to a belt transmission in an internal combustion engine for driving at least one accessory device according to what is indicated in greater detail in the introduction to attached Patent Claim 1.

State of the art

In internal combustion engines, use is made of a number of different accessory devices for the engine, which devices are driven by the engine. In internal combustion engines for use in vehicles, these accessory devices can consist, for example, of a generator, an AC compressor, a cooling water pump and a steering servo pump. Driving of such accessory devices is usually brought about with the aid of a belt transmission at one end, usually a front end, of the engine, a belt pulley, which is connected firmly to the crankshaft of the engine, driving via one or more drive belts a belt pulley on each accessory device. At the same end of the engine, there can also be arranged drive transmissions for camshafts, a lubricating oil pump, any balancer shafts, any supercharging compressor and suchlike of the engine. These transmissions, in the event that these accessory devices need to be synchronised with the crankshaft of the engine, are usually designed as gear- belt transmissions, chain transmissions or gearwheel transmissions.

As a result of a number of different accessory aggregates thus being driven by the crankshaft of the engine at one end of the engine, the problem of finding room for all these units arises. This problem is especially obvious in engines for use in passenger cars and where the engine is arranged in the transverse direction of the vehicle. In this connection, the width of the vehicle limits the possibilities of allowing the dimensions of the engine to extend too far.

A further problem is that in the event that all accessory devices are driven by a single drive belt and this breaks, all drive to the remaining accessory devices also stops. Making use of a single drive belt also means that said drive belt is subjected to high stresses since it must in total transmit relatively

great forces. Increased forces in the drive belt mean that correspondingly high forces come to act on the bearings and attachments of the accessory aggregates.

As a solution to the abovementioned problem, it is already known to arrange transmissions for driving accessory devices also at the other end, usually a rear end, of the engine.

According to a solution which is described in greater detail in Patent Specification US 4,558,668, use is made of a gear ring fixed to the flywheel of the engine for driving a drive belt, which drive belt drives a belt pulley connected to a power take-off shaft. The same gear ring is used on starting for interaction with a starter motor pinion. In order that in this connection the starter motor pinion should not act on the drive belt, the starter motor is arranged along a part of the gear ring which is not covered by the drive belt. A disadvantage of this design isthatthe gear ring is arranged to be engaged around by the drive belt. In the event of any drive belt exchange, the possibility must be created of mounting the drive belt. In a vehicle engine, in which clutch and gearbox are directly connected to the flywheel, this means that, for example, the entire clutch must be demounted if a non-divisible drive belt is used. An alternative is to use a drive belt which can be opened, but this then means instead that a more complicated drive belt must be used.

The abovementioned disadvantages have meant that, at least in internal combustion engines for use in passenger cars and at least to any extent worth mentioning, no solution has come into practical use, which uses the flywheel of the engine for driving accessory, aggregates.

Aim of the invention

The aim of the present invention is to make possible a solution for driving accessory devices on the flywheel of the engine, but which does not display the disadvantages which characterise known solutions. In this way, exchange and mounting of a new drive belt shall be able to be carried out without large parts of the transmission needing to be demounted or the drive belt needing to be of openable design.

Brief description of the invention

For said purpose, the invention is characterised by the features which are indicated in the characterising part of attached Patent Claim 1.

According to the inventive idea, as a result of arranging the belt transmission with deflection members, it is made possible that the drive belt can be arranged in a loop around the driving flywheel or belt pulley, without the drive belt needing to cross the axis of rotation of the latter on mounting. In that previous problems on exchanging a drive belt are consequently solved, accessory devices can also be arranged at the rear end of the engine without difficulty. On the contrary, it is made possible that the number of accessory devices at the front end of the engine can be reduced with the consequence that the total axial extent of the engine and the accessory devices can be reduced.

Advantageous embodiments of the invention are indicated in the attached subclaims. Further features and advantages which characterise the invention emerge from the attached descriptive example of an advantageous embodiment.

Brief description of the figures

The descriptive example is given with reference to the attached drawings, in which

Figure 1 shows diagrammatically an internal combustion engine connected to the drive transmission of a vehicle, and Figure 2 shows diagrammatically an accessory device transmission on the flywheel of the engine.

Descriptive example

Figure 1 shows diagrammatically a multi-cylinder internal combustion engine 10, for example an Otto engine or a iesel engine, for a passenger car or other vehicle. The engine 10 comprises a crankshaft 11, at one end of which, in this case a front end, there is fixed a belt pulley 12 forming part of

a belt transmission 13 for driving an accessory device 14 for the engine 10 and/or the vehicle. In the figure, only one accessory aggregate 14 driven by one drive belt 15 is shown, but a number of such accessory devices can advantageously be arranged in conventional manner. All accessory devices can be driven by the same belt 15 or, alternatively, the belt pulley 12 of the crankshaft 11 can be designed with a number of different grooves, in which different separate drive belts fit for separate driving of the accessory devices.

The accessory device can, for example, consist of a coolant pump for the engine 10, a steering servo pump for the vehicle, a coolant compressor for the air conditioning system of the vehicle, a generator for producing electrical energy in the vehicle or a supercharging compressor for the engine 10.

The engine 10 is connected at its other, rear side to a drive transmission for driving the vehicle. In this connection, the crankshaft 11 is connected at its rear end to a flywheel 16, to which there is fixed a friction clutch 17 which interacts with the flywheel 16. From the clutch 17, torque given off from the engine 10 is transmitted further to the driving wheels of the vehicle via a gearbox 18. Both the clutch 17 and the gearbox 18 which form part of the drive transmission consist of the usual type for vehicles and are therefore reproduced in simplified form in Figure 1. On its outer periphery, the flywheel 16 is designed on the one hand with a cylindrical part 19 with a smooth surface along its periphery and on the other hand with a gear ring 20 intended on starting to interact with a pinion 21 on a starter motor 22.

Figure 1 shows the pinion 21 in engagement with the gear ring 20, as is the case during starting. After starting, the pinion 21 is brought out of this engagement in a manner which is conventional perse.

Attached Figure 2 shows in greater detail but still only diagrammatically, in a view according to the cross-section 2-2 according to Figure 1, the belt transmission 23 on the flywheel 16. In this connection, only the smooth part 19 of the flywheel 16 is shown. The accessory device 26 is shown in the form of a belt pulley for the driving of the flywheel. Additionally, there are included two freely rotatable belt pulleys 27, 28 forming part of deflection members which are used to deflect the drive belt 24 forming part of the transmission 23. All belt pulleys 26, 27, 28 rotate around axes of rotation

which are parallel to one another and which are also parallel to the axis of rotation 31 of the flywheel 16. Expediently, the drive belt 24 consists of a continuous, non-openable flat belt with a smooth inner surface 29 and a smooth outer surface 30. The drive belt 24 bears with its inner surface 29 against the three belt pulleys 26, 27, 28, while its outer surface 30 bears against the smooth part of the flywheel 16, which in this connection consists of a belt pulley integrated with the flywheel 16. Both the deflection members 27, 28 have the task of ensuring contact of the belt 24 against the flywheel 16. The belt 24 should bear against the flywheel 16 along a sector angle a of between 120 and 180 degrees. The greater the contact angle a, the more reliable the driving and an angle a of around 180 is thus most advantageous. The angle a indicated of 120 degrees thus corresponds to a suitable lower limit.

Both the deflection members 27, 28 are fixed directly to the engine 10 or indirectly via a bracket or suchlike. The accessory device 26 also is fixed in similar manner. On the accessory device 26 or on one of the deflection members 27, 28, there should be arranged a tensioning arrangement which makes it possible to adjust the tension of the drive belt 24. The tensioning arrangement is expediently designed as a tensioning arrangement which is conventional for belt transmissions.

The belt transmission 23 according to the invention at the rear end of the engine 10 means that a space not previously used can be used for driving accessory devices. This means that the previous problem of finding room for a number of accessory devices at the front end of the engine 10 can be avoided or at least reduced.

By virtue of the fact that the drive belt 24 is arranged in a deflected manner so that the axis of rotation 31 of the flywheel 16 lies outside the area 32 which is enclosed by the drive belt 24, exchange of the drive belt 24 in a simple manner is made possible. This is dependent on the fact that the drive belt 24 does not need to cross the axis of rotation 31 of the flywheel 16 on mounting. Normally, the crankshaft 11 of the engine 10, the clutch 17 and the gearbox 18 form units which are interconnected in a manner which does not allow a drive belt to be simply guided over the same.

Which of the accessory devices given as examples in the introduction are to be arranged on the front side or rear side respectively of the engine 10 can in principle be chosen freely according to requirement. Advantageously, however, an accessory device which needs to be driven with a relatively high speed of rotation can be placed at the rear side of the engine 10. The flywheel 16 usually has a diameter which is considerably greater than the belt pulley 12 which is fixed at the front end of the crankshaft 1 1 , which means that a great ratio can be obtained between the flywheel 16 and the accessory device 26.

Within the scope of the attached patent claims, the invention can be modified and designed other than exemplified in the description. For example, instead of a flat drive belt 24, a V-belt with a smooth outside and a conical inside can be used. In this connection, the belt pulleys 26, 27, 28 can be designed with usual V-shaped grooves, while the smooth outside of the belt bears against the smooth surface 19 of the flywheel 16. When it is necessary to further connect one or two accessory devices at the rear side of the engine, one or both of the deflection arrangements 27, 28 can advantageously be replaced by this accessory device or these accessory devices.

In the example, a conventional flywheel 16 is described, which is adapted to be integrated into a belt transmission. This is advantageous since it means that the same flywheel 16 can be used irrespective of whether or not a belt transmission 23 is arranged at the rear end of the engine 10. However, the flywheel 16 can also be adapted and designed in other ways for the belt transmission, for example, by designing it with grooves or suchlike. It is also possible to use a separate belt pulley which is firmly mounted directly onto and forms a unit with the flywheel.

In certain vehicle transmissions, for example those in which automatic hydraulic gearboxes are included, conventional flywheels are not used. In such transmissions, the invention can still be used if the drive transmission is provided with a member corresponding to the flywheel. Such a member can in this connection be adapted completely to the belt transmission.

In the description, the front side and the rear side of the engine are indicated in relation to the engine and the clutch and gearbox following. In vehicles with a transverse-mounted drive aggregate, this means that the engine directions front and rear will be oriented in the transverse direction of the vehicle. The invention described is especially advantageous when applied in such transverse-mounted drive aggregates, since it means that the extent of the engine can be made short.