GB2316141A

GB2316141A - Hydrodynamic torque converter with bridging clutch

Info

Publication number: GB2316141A
Application number: GB9719327A
Authority: GB
Inventors: Robert Fischer
Original assignee: LuK Getriebe Systeme GmbH
Current assignee: LuK Getriebe Systeme GmbH
Priority date: 1993-09-17
Filing date: 1994-09-07
Publication date: 1998-02-18
Anticipated expiration: 2014-09-07
Also published as: GB2316141B; GB9719327D0; GB2316140A; GB9719325D0; GB2316140B

Abstract

The disclosure is the same as in GB 2281952, but the claims are directed to a process for controlling a drive system, and to a drive system controlled by the process, in which control of a slip-controlled bridging clutch 12 depends on the torque to be transferred through a hydrodynamic converter, this being in two ranges: the first extending up to 10% to 60% of the maximum torque of the engine and the second range being higher than the first.

Description

1 2316141 Vehicle with hydrodynamic torque converter and process for

controllinq a toraue transfer system with toraue converter The invention relates to a drive system with internal combustion engine, more particularly for motor vehicles, which has a hydrodynamic torque converter, as well as a bridging clutch which acts in parallel with same and is slip-controlled so that the torque transferable by same can be set in dependence on the existing operating conditions to a certain value dependent on these operating conditions.

The invention further relates to a process for controlling a torque transfer system which is in active connection with the driven part of a drive assembly, for example the internal combustion engine of a vehicle, is in driving connection with the input part of an automatic gearbox and has a hydrodynamic torque converter and a friction clutch parallel therewith, a multi-value detector system and a central computer unit or processor wherein the force biasing of the friction clutch and thus the torque transferable by same can be accurately altered in conjunction with the central computer unit.

The invention is to be used advantageously in drive systems or torque transfer systems which have a hydrodynamic torque converter with a pump wheel, a turbine wheel, a guide wheel and a converter housing which surrounds the turbine wheel and is in driving connection with the pump wheel central with the axis of rotation wherein locally between a radial area of the converter housing and the turbine wheel is a ring piston which is provided radially outwards with at least one clutch friction face and radially inwards is positioned centred on a driven component of the torque converter, such as eg a hub or gear input shaft.

Such drive systems or torque transfer systems are known for SP1433.P38 Sepcember 1 1. 1997 example through DE-OS 31 30 871, US-PS 5 029 087 and US-PS 4 577 737.

From the aforementioned prior art there is also known a process for controlling torque transfer systems wherein the torque to be transferred by the friction clutch is adjusted by intentionally adjusting the pressure in an operating chamber or the differential pressure between the pressure chambers either side of a piston of a friction clutch which is mounted parallel to a converter and bridges same when necessary.

Thus in DE-OS 31 30 871 in connection with a torque transfer system of the kind mentioned above a regulating process is described where the slip values occurring between the drive and driven sides are measured, compared with predetermined slip values and adjusted if any difference is detected.

This is achieved by regulating the fluid pressure in a chamber so that a speed difference between the drive and driven sides is set at least in a low speed range. This concerns a control process based on the classic slip control.

From US-PS 5 029 087 a control process is likewise known for converters with parallel mounted friction clutch wherein the slip on the clutch is measured, compared with predetermined ideal slip values and changed in dependence on any deviations determined in the pressure in the disengagement chamber of the friction clutch. Similarly here this concerns a typical slip control wherein the slip is regulated at least in a lower speed range.

Such systems having a controlled influence on the torque transferable by the friction clutch of a torque transfer system of the kind previously discussed have not proved satisfactory or completely satisfactory in practice. Thus SP1433.P38 septemt>er 11, 1997 in the case of systems according to DE-OS 31 30 871 and USPS 4 577 737 the slip in the clutch is set in a low or bottom speed range following the idling speed of the internal combustion engine. In this lower speed range, viewed over the overall operating time, the system is however mainly operated so that as a result of the existing slip which with these known systems is necessary for insulating vibrations, there is an increased energy consumption or fuel consumption. Furthermore the slip adjustable in this speed range or the speed difference between the drive side and driven side as a result of the operating conditions or operating parameters existing in this speed range, such as in particular the adjustable contact pressure for closing the bridging clutch, cannot be is set to a low level which is desired per se. This is due amongst other things to the fact that as a result of the low pressure level required in the converter or on the piston of the bridging clutch for the ensuing low torque it is very difficult to accurately adjust this pressure level to achieve a definite slip. As a result of the low pressure level required even slight fluctuations in pressure cause considerable changes in the slip speed. Furthermore it is to be considered that even the valves required for regulating or controlling the torque converter have a certain hysteresis which is due for example to the friction of the piston on the housing so that even for these valves a certain pressure level is required in order to ensure satisfactory functioning.

The possibility of accurately controlling the torque to be transferred by the bridging clutch thus becomes more difficult the smaller the torque. Furthermore with these known systems there is the problem that as a result of the low load existing in the said lower speed range of the drive motor under numerous operating or driving conditions or as a result of the ensuing relatively low average torque and SP1433-P39 September 11. 199 7 the torque fluctuations with comparatively low amplitude superimposed on same there is often temporary sticking conditions between the friction faces of the clutch each followed again by a sliding period. Through these sticking- sliding transitions impulses are introduced into the output train or into the gearbox which can cause rattling noises in the gearbox and/or droning in the drive train or in the vehicle. The sticking-sliding transitions more particularly cause sudden changes in the gear input moment. Such sticking-sliding transitions can only be avoided by setting a correspondingly large slip value which is disadvantageous from the energy point of view.

A further drawback with the known systems is that in the bottom or lower speed range in which the system is mainly operated with partial load the torque to be transferred by the friction clutch can only be set to the desired low value at a very high expense, namely because this torque is not dependent on the clutch engagement force alone but is also dependent on the friction value of the friction lining which in turn is subject to considerable fluctuations in dependence on the temperature, slip speed, condition of the oil used and other factors. This means that with the known systems a minimum slip speed must be observed in order to guarantee a slip speed which is fast enough to insulate vibrations even in the event of fluctuations in the system conditions.

The object of the present invention was to avoid the 30 aforesaid disadvantages and to ensure a better vibration insulation between the drive machine and the drive tain connected to the output side thereof. Furthermore the bridging clutch for a torque converter according to the invention is to have a cost-effective design with a space- saving compact construction. A further aim of the invention is to design the bridging clutch so that this ensures SP1433 ' P38 Sepcember 11, 199'7 throughout the entire operating range of the drive system and torque transfer system a satisfactory vibration insulation without the need for increased energy or fuel.

According to the invention, there is provided a process for controlling a drive system with a slip-controlled bridging clutch in dependence on the torque to be transferred for a hydrodynamic torque converter wherein a control based on energy and efficiency related points of view is active at least in all forward gear phases.

The drive system according to the invention can advantageously be used in conjunction with a process for controlling a bridging clutch which is slip-controlled in dependence on the instantaneous torque to allow a control based on energy and efficiency points of view at least in all forward gear phases of the gearbox. The drive system according to the invention can however also be used in connection with gearbox controls or regulations which leave the bridging clutch fully open in the first and/or second forward gear phase.

More particularly the design of the drive system or bridging clutch according to the invention can be used in connection with a process for controlling a torque transfer system as described in German Patent Application P 43 28 182.6. The disclosure in this application should also be a constituent part of the present application. Reference is particularly made to this application regarding the control possibilities of the converter bridging clutch according to the invention.

In this process, the torque control or torque regulation of the bridging clutch of a hydrodynamic torque converter can be carried out so that the bridging clutch has at least two operating ranges in which the adjustment of the size of the torque transferable by the bridging clutch in relation to SP1433.P3B Septemtmr 11. 199.7 the ensuing torque of the drive machine is carried out from other points of view or according to a different mode. Thus for example with a torque control according to the aforementioned German Patent Application P 43 28 182.6 at least one of the correction factors K. (torque distribution factor), Kk.., (correction factor for compensating multiplying faults), Mkc)x"ot (correction moment for compensating faults which are added to the engine torque) and Mk., (correction moment for compensating faults which are added to the clutch torque) evaluates differently in the two operating ranges. This means that the size of at least one of these factors and thus also the ef f ect of this value on the torque transferable by the bridging clutch is defined differently in the two ranges. It can be particularly advantageous if is in a first range the torque transferable by the bridging clutch is in the order of between 10 and 60%, preferably between 15 and 50% of the maximum torque of the drive machine, such as in particular the internal combustion engine, and in the adjoining second range the torque transferable by the bridging clutch lies above the upper torque boundary value of the first range, ie thus becomes greater than 50% or 600-5 of the maximum torque of the internal combustion engine. It can be particularly expedient if the maximum torque transferable in the first operating range by the bridging clutch agrees at least substantially with the stop moment of the torsion damper of the bridging clutch. Through such a design it is ensured that torque vibrations with smaller amplitudes are filtered or absorbed through the torsion damper whilst vibrations with torque peaks which lie above the stop moment of the torsion damper can be damped at least substantially by slipping through the bridging clutch.

The torque regulation or control of the bridging clutch in 35 the first range can advantageously be carried out so that the torque transferable by the bridging clutch at least SP 1: 33. P3B Septeffiber 1. 199.7 substantially over the entire first range is greater than the ensuing torque of the internal combustion engine which is provided by this as a result of the amount of fuel supplied to same. The torque transferable by the bridging clutch can thereby be adjusted over the first speed range so that this torque at least over a significant area of the first speed range changes roughly in synchronisation with the torque variation in the internal combustion engine in the first range. This thus means that with a decrease in the torque delivered by the internal combustion engine there is also a decrease in the torque transferable by the bridging clutch wherein this does however remain greater than the torque of the internal combustion engine. With an increase in the torque delivered by the internal combustion engine the torque transferable by the bridging clutch becomes correspondingly greater. It can thereby be expedient if the torque transferable by the bridging clutch amounts to 1 to at least 1.2 times the relevant ensuing engine torque of the internal combustion engine.

According to a further modified embodiment of the invention the torque transferable in the first range by the bridging clutch can be set at least approximately to a constant value wherein this value can be in the order of between 25 and 60% of the maximum torque of the internal combustion engine, preferably in the order of 30 to 50% of the maximum torque.

Advantageously this value can correspond at least approximately to the stop moment or bridging moment of the torsion damper of the bridging clutch, preferably however somewhat larger eg 1.05 to 1.2 times this bridging torque.

According to another suitable embodiment the adjustment to the torque transferable by the bridging clutch in the first speed range can also be carried out so that in a lower partial area of this first range which advantageously adjoins the idling speed of the combustion engine the torque >131-13.

11. 1997 transferable by the bridging clutch is kept at least approximately to a constant level and in the adjoining second partial area of the first range the torque transferable by the bridging clutch follows the torque development of the combustion engine. The latter means that if the torque of the combustion engine is greater in the second partial area then the transferable torque of the bridging clutch also becomes greater and vice versa. In this second partial area the torque transferable by the bridging clutch is at least the same size and preferably somewhat greater than the relevant ensuing torque of the combustion engine.

In order to ensure an accurate control or regulation of the torque transferable by the bridging clutch it can be particularly advantageous if the torque transferable by the bridging clutch in the first speed range does not drop below 1-. of the maximum torque of the combustion engine, and is preferably kept greater than 1% of this maximum torque. A minimum pressure is thereby guaranteed for the bridging clutch which can still be set satisfactorily with the known valves. As a result of the minimum pressure level it is thus possible to keep this pressure within comparatively narrow limits.

In many cases it can be advisable if the first range extends from idling speed to a maximum of 3000 rpm, preferably up to a maximum of a value lying between 2000 and 2500 rpm.

However in many other cases it can also be expedient if the upper value is above 3000 rpm or below 2000 rpm.

more expediently within the scope of a further development of the invention the torque transferable by the bridging clutch, viewed over the entire operating range of the drive system, can be produced so that in a first lower range of this overall operating range the vibration uncoupling is SP1433.P35 Septeffiber 11. 1997 carried out at least substantially through the damper and in a second adjoining range the vibration uncoupling is guaranteed substantially through adjusting the slip in the bridging clutch. In this second range the existing damper can additionally come into effect timewise ie the energy accumulators of the damper can be relaxed and compressed again but in this second range this damper has a secondary roll regarding the uncoupling of the vibrations.

The torsion damper of the bridging clutch designed substantially for the first speed range preferably has as already mentioned a stop or bridging moment which is in the order of between 10 and 60%, preferably between 15 and 50% of the maximum torque of the combustion engine. The torsion damper can however also be designed according to a further variation of the invention so that following the turning angle which corresponds to the aforesaid torque value the damper still has a comparatively small turning angle in which the spring rate amounts to a multiple or is very steep so that the torsion damper has a typical stop spring suspension which prevents the components causing the rotary restriction in the torsion damper from crashing against each other too severely. The stop noises which may arise can thereby be substantially reduced. The ratio between the turning angle allowed by the stop suspension and the remaining turning angle on the input side can advantageously be in the order of 1 to 2 to 1 to 5, preferably in the order of 1 to 2.5. The rotational stiffness caused by the stop spring suspension is advantageously 4 to 10 times greater than the rotational stiffness of the torsion damper connected in front of this suspension. Advantageously the end stop moment of the torsion damper caused by the stop suspension can amount to 2 to 5 times the aforesaid moment existing at the end of the f irst range. Advantageously however the maximum torque which can be transferred by this stop suspension is less than the maximum engine torque. The SP1433.P38 Septeffiber 11, 1997 turning angle covered by the stop suspension between the input part and output part of the torsion damper can be in the order of 0. 5 to 30 wherein it can be advantageous if this angle is in the order of 1 to 20. The stop suspension can also be designed so that it only acts in the pull direction.

By designing the torsion vibration damper for a bridging clutch according to the invention it is possible to avoid the already mentioned humming problems which occur when the torque is comparatively slight. This is probably due to the fact that the said sticking phases of the clutch are bridged by the rotationally elastic torsion damper.

According to a further suitable development of the invention when conditions arise having a high vibration amplitude in the drive train, such as for example with resonance, load change impact or the like the torque transferable by the bridging clutch at least in the first range can be reduced whereby the slip in the bridging clutch is increased. With a load change impact the torque transferable by the bridging clutch can if necessary be broken down practically completely in the pushing phase. A reduction in the torque transfer capacity of the bridging clutch with the aforementioned operating conditions can also advantageously take place in the second speed range.

According to a preferred embodiment the drive system or transmission system can be designed so that at least the main part of the characteristic field of the combustion engine used in the main driving range drops below the first range. This main driving range can advantageously include at least the ranges of the engine characteristic field which apply for the FTP75-cycle and/or for the ECE-cycle town, open road and motorway traffic (town, 90 km/h, 120 km/h).

SP1433. PIB Septemi>er 11, 1997 Through such a design it is guaranteed that in the main driving range the vibration insulation is mainly carried out by the damper and thus the converter is practically always bridged whereby an energy-saving or fuel- saving method of operation is ensured. This is not the case with the previously known drive systems with a slipping bridging clutch since with these a slip is just adjusted in the first speed range, as shown in the previously cited prior art.

Since according to the invention the torsion damper of the bridging clutch is advantageously designed for the main driving range a significantly better damping of the ensuing rotary vibrations can be achieved than would be possible where the damper is designed for a greater driving range.

This produces a particularly compact structure for the converter.

According to one design possibility of the invention the torque transferable by the bridging clutch in the second speed range can amount to 0.6 to about 1 times the relevant ensuing moment of the internal combustion engine, preferably 0.8 to 0.9 times. It is expedient if the torque transferable by the bridging clutch in the second speed range always remains below the ensuing engine torque.

Through such design it can be guaranteed that in the second operating range there is always a slight slip in the bridging clutch which serves to dampen the torque irregularities there which cause torsion vibrations.

With non-critical vehicles, ie in vehicles which have in the second speed range or operating range no greater irregularities in the torque output, the bridging clutch can also be practically closed which means that the torque transferable by the bridging clutch corresponds at least to the torque delivered by the internal combustion engine at the corresponding time, and preferably lies slightly above same.

SP1433.P3B Septe.ber 1 1 199.7 In the preceding description there is always mention of two operating ranges wherein here are meant the ranges which follow the idling speed. The invention is however not restricted to embodiments where the entire speed-dependent operating range of the drive system above the idling speed is only divided into two ranges, but also relates to embodiments where the entire operating range is divided into more than two ranges. Thus in many drive systems it may be expedient if the two ranges already described are followed by a third range wherein a complete converter bridging is provided in this third range. This third range thus comprises a speed range lying above that of the second range and the lower value of this third speed range must thereby be fixed so that above this level no harmful excitations can arise through the internal combustion engine so that no vibration damping through slip is required.

According to a further development of the invention it is possible to provide in the case of a transmission system with an internal combustion engine as drive assembly a device which at least during acceleration processes determines whether by opening the bridging clutch and keeping the same gear it is possible to increase the traction force through torque conversion wherein in this case the bridging clutch is opened and the engaged gear retained, otherwise the gearbox is changed down one gear stage wherein the clutch can then likewise be opened at least partially so that an increase in the slip in the bridging clutch takes place. The said device can be formed by an electronic computer unit or a processor which picks up the necessary values or parameters through corresponding sensors. Many of these parameters can however also be stored in the electronic unit in the form of f iles or characteristic fields. Thus for example the characteristic field of the internal combustion engine and/or the

SP1433.P3B Septemi"r 1 1, 1997 characteristic field of the converter and/or the characteristic field of the converter bridging clutch can be stored in the electronic unit. The operating state of the internal combustion engine can furthermore be determined in dependence on its speed, throttle flap angle or amount of fuel supply, suction pipe vacuum and if necessary on the injection time. Regarding the possible functioning of such an electronic unit for controlling a torque transfer system according to the invention reference is again made to German Patent Application P 43 28 182.6.

As already mentioned, with the drive system according to the invention a complete bridging of the converter can take place from a certain engine speed or a certain speed of the vehicle since above this engine speed a drive system which is practically rigid as a result of complete bridging is substantially unaffected by the torsion vibrations which occur there. Thus above this certain engine speed the bridging torque of the clutch can be set to a level which corresponds approximately to or lies above the engine torque.

Through the design of the torsion damper according to the invention in conjunction with the regulator or control strategy for the torque transferable by the bridging clutch it is possible to at least reduce the torque impulses which are provided in the partial load range of the internal combustion engine on the friction faces of the bridging clutch, which are due to transitions between the sticking and sliding states and which can cause droning noises on the vehicle. Furthermore in this first range no jolting vibrations can build up as a result of the set low bridging torque of the clutch. The softness of the torsion damper must be matched to each drive system or to each vehicle. If the torsion damper has a resonance range which has to be passed through during the operation of the vehicle then as Sp 1433.P38 September 11. 1997 soon as this range appears a slip must be allowed in the clutch. This prevents droning or rattling.

In order to limit the load change in the first range there is not only the small turning angle of the torsion damper but also the adjustment of the bridging clutch to a torque which lies at a relatively low level compared with the maximum torque of the internal combustion engine. As already mentioned the adjustment can be carried out so that at least in the first operating range the torque transfer capacity of the bridging clutch lies only just above the ensuing engine torque. A vibration excitation of the drive train through load change processes can thus be substantially avoided through the design of the drive system according to the invention. In the second speed range which corresponds to a higher load of the internal combustion engine, the bridging is with a smaller torque than the ensuing engine torque, which leads to slip. This slip likewise acts to avoid noise in a certain torque range, particularly in conjunction with the torsion damper since in this range there is still a matter of sticking/sliding transitions between the friction faces of the bridging clutch.

In the entire operating range or in the entire characteristic field range of the drive machine, such as in particular an internal combustion engine there is then advantageously only bridging where it appears expedient for energy reasons. There are namely ranges in which it is more advisable to drive without bridging instead of partial or full bridging. Also should the driver wish to accelerate the bridging clutch is opened to produce torque conversion.

The drive system according to the invention and/or the 35 process steps according to the invention for setting the torque which can be transferred by the bridging clutch can SP'433.P38 September 11. 199 ' - is - be used advantageously in conjunction with a soft torque converter. The characteristic features of such a soft torque converter are described in the German Patent Application P 43 28 182.6 already cited whose contents are 5 to be considered in conjunction with the present invention.

The use of a soft converter of this kind allows a better acceleration behaviour in the case of motor vehicles since such a converter has a greater torque conversion and thus a greater conversion range can be used. Furthermore the better degree of efficiency of the soft converter in wide ranges compared to conventionally designed converters can be utilised whereby the loss of power and thus consumption and oil temperature can be reduced. The range of the poorer is degree of efficiency of the soft torque converter is bridged or skipped, namely in that the converter bridging clutch in relation to the ensuing engine torque is closed to a torque value allowing a certain slip. Through such regulation or control of the converter or its bridging clutch it is possible to ensure that in all driving states it is possible to drive with a better degree of efficiency and with a lower loss of power. Since through the design of the drive system according to the invention bridging is possible in all driving stages of the gearbox the fuel consumption of the vehicle equipped with such drive system can be substantially reduced to the level of a vehicle with converter-free or conventional switch gear.

The bridging clutch of the drive system can also contain a torsion damper whose stop moment is less than the maximum torque of the internal combustion engine. In this way, the torsion damper is not as with the previously known prior art set to the full load of the drive assembly orinternal combustion engine. As soon as the stop moment is reached the bridging clutch or its torsion damper behaves in the rotary drive direction as a rigid drive member. Since the SP1433.P3B SeptemDer 11, 199,7 torsion damper according to the invention f or a bridging clutch of a hydrodynamic torque converter is only set for a partial load area this torsion damper can be made particularly simple so that a cost-effective production is also guaranteed. Furthermore the energy accumulators of the torsion damper such as in particular the coil springs can be made weaker so that these also take up less space whereby the structural space required f or the bridging clutch or torsion damper can likewise be reduced. Furthermore there is also a saving in weight. In order to protect the energy accumulators of the torsion damper against overloading it is preferable if special stops are provided between the input part and output part of the torsion vibration damper of the bridging clutch.

is In most cases it has proved expedient if the stop moment or bridging moment of the torsion damper lies in the order of between 10 and 60% of the maximum torque of the internal combustion engine, preferably in the order of 25 to 50%. In many cases however the bridging moment or stop moment of the torsion damper can also have larger or smaller values.

According to a further development of the invention a torsion damper designed in this way for a bridging clutch has no special friction device. This means therefore that between the input part and output part of the torsion damper there are only energy accumulators which counteract a relative rotation between these parts.

Through the design of the torque transfer capacity of the torsion damper according to the invention it is possible to achieve very good damping of the vibrations which occur in the partial load area, thus in the area with drive moments in the order of between 10 and 60% or between 25 and 50% of the maximum torque.

It can be particularly expedient if the damper allows a SP1433.P39 September 11. 1997 turning angle which is relatively small compared to the previously known turning angles of dampers for converter bridging clutches. This turning angle can be in the order of 2 to 80, preferably in the order of 3 to 60. The overall turning angle of the damper, thus the overall turning angle for both turning directions thus amounts to 40 to 16'>, preferably 60 to 120. As a result of the comparatively small turning angle of a torsion damper for bridging clutches designed according to the invention it can be guaranteed that with a change of load, thus when changing from push operation to pull operation and vice versa, the deflections in the damper are kept small so that the rocking of the drive train can be restricted or avoided altogether. Advantageously the torque shocks or torque proportions of is these shocks which lie above the stop moment of the torsion damper can be damped or filtered by slip or slipping through of the bridging clutch so that these are kept at least substantially away from the output train or gearbox.

For most cases it can be expedient if the damper has a rotational stiffness which is in the order of between 7 and 30 Nm/", preferably between 8 and 15 Nm/0. In many cases however this torsional stiffness can also be lower or higher. In most cases the bridging clutch or torsion damper can be designed so that it has a stop moment in the order of between 30 and 90 Nffi, preferably in the order of between 40 and 70 Nffi. For low capacity motorized vehicles the stop moment can however be even smaller. Similarly it may be necessary in the case of high capacity motorized vehicles with comparatively high weight to make the stop moment greater.

The invention will be explained with reference to Figures 1 to 9 in which:

SP1433.P32 September 11. 1997 Figure 1 is a semi-sectional view of a diagrammatic illustration of a torque transfersystem with a converter and a lock-up clutch as well as with a diagram of the associated pressure medium control; Figure 2 shows diagrammatically the division of the engine torque into a torque to be transferred by the torque converter and a torque to be transferred by the bridging clutch in dependence on the slip appearing at the converter and the friction clutch bridging same; is Figure 3 shows a torque transfer system with friction clutch bridging a hydrodynamic converter; Figures 4 and 5 show details of the torsion vibration damper according to Figure 3; Figure 6 shows a possible torsion characteristic line for the damper of a lock-up clutch; Figure 7 is a view of the output characteristic field of a "softly" designed converter; Figure 8 is a view of a torsion vibration damper; Figure 9 shows the torsion vibration damper according to Figure 8 as well as the adjoining components of a torque converter in section.

The torque transfer system 10 shown in Figure 1 comprises a torque converter 11 and a bridging clutch ^12 which is connected in parallel with the torque converter and can be operated by a pressurised medium flow. The torque transfer SP1433.P38 September 11, 1997 system is in active connection with the shaf t 13 of an internal combustion engine (not shown) and in turn is in driving connection on the output side through an output part 14 with an automatic gearbox (likewise not shown) mounted on 5 the output side in the output train.

As shown diagrammatically by the semi-sectional view of the torque transfer system 10 in connection with the pressure control diagram, the torque converter 11 is a conventional torque converter. This torque converter consists of a converter cover 16 connected to the output of an internal combustion engine, a pump wheel 17 forming together with the converter cover the converter housing, a turbine wheel 18 connected in turn through an output hub 14 with the automatic gearbox (not shown), and a guide wheel 19 mounted between the pump and turbine wheel. The friction clutch 12 bridging the converter is mounted between the turbine wheel 18 and the converter cover 16 and has a clutch disc 20 which is in rotary connection with the output hub 14 or with the turbine wheel 18 of the converter and whose friction face 21 interacts with a counter face 22 of the converter cover 16.

The friction clutch also has a rear chamber 24 facing the turbine wheel 18 and a front chamber 25 facing the radial wall of the converter cover 16. The clutch disc 20 has a piston 20a which is connected by a torsion damper 20b to the output hub 14 and separates the two chambers 24, 25 axially from each other.

The converter 11 is in known way supplied with pressurised flow medium from a pressurised medium source (not shown) through a pipe 30 opening on the side of the pump wheel into the converter housing wherein the pressure is controlled by a control valve 31 which is controlled in turn by a control element 32. This control element 32 can be formed by a proportional valve or a pulse-width modulated valve which is adjusted by a computer unit or processor 32a, namely in SP1433.P3B September 11, 1997 dependence on the ensuing input values or parameters as well as the characteristic fields recorded in the processor. The pressurised flow medium is discharged through a pipe (not shown) to a cooler 33. In addition to the biasing of the turbine wheel 18 the pressure of the pressurised flow medium also acts on the downstream side of the pump wheel 17 in the rear chamber 24 of the friction clutch 12. The pressurised medium biases the piston 20a and presses this against the counter face 22 of the converter cover 16. Since according to the invention the clutch is driven with slip at least in many operating ranges, the pressurised flow medium biasing the front chamber 25 can be controlled by means of a valve 31 connected to this chamber by a pipe 34 so that an adjustable differential pressure acting between the rear and front chambers 24 and 25 respectively determines the torque transferable by the friction clutch.

In view of the parallel arrangement of the converter 11 and the friction clutch 12 bridging same the engine torque equals the sum of the torques (M) transferred by the converter and/or the pump wheel and the clutch thus MEngino " MClutch + MPump Whal The gearbox torque leaving aside the losses in the transmission system, is likewise the sum of the torques transferred by the converter and/or the turbine wheel, thus M,,,. = Mlu,., + wl or MC1.t.h + (MPump Whe1 X conversion).

Dividing the engine torque into a torque to be transferred by the converter and a torque to be transferred by the bridging friction clutch is shown in Figure 2 in dependence on slip. It can be seen that as the slip increases so the part of the engine torque transferred by the converter rises and thus the torque transferred by the clutch drops.

S P14T3.M September 11. 1997 In the preferred method of control in the operating states in which slip is desired this slip is not regulated directly, but the part of the engine torque to be transferred by the friction clutch 12 is determined in dependence on the operating state of the engine and the differential pressure required for transferring the predetermined torque is set on the friction clutch through a computer unit, such as a microprocessor 32a. The slip is then produced by itself.

The torque transfer system 110 shown by way of example in Figure 3 is a hydrodynamic torque converter 111 with a bridging clutch 112 and a damper unit 135 operating between the torque converter and bridging clutch.

The torque converter 111 comprises a pump wheel 117 which is in rotationally secured driving connection with an internal combustion engine (not shown), a turbine wheel 118 in active connection with a hub 114 on the output side, a guide wheel 119 mounted in the flow circuit between the pump wheel and turbine wheel, and also comprises a converter cover 116 connected rotationally secured to the pump wheel and enclosing the turbine wheel.

The converter cover 116 is connected rotationally secured to the pump wheel 117 and provides the driving connection thereof with the internal combustion engine through entrainment areas 116a which protrude on the side remote from the pump wheel 118 and serve for fixing a drive disc (not shown) of the internal combustion engine.

Between the turbine wheel 118 and the radial area of the converter cover 116 is a ring piston 136 which is central with the rotary axis of the converter and is f ormed by a shaped sheet metal part. This ring piston is set radially SP1433.P3B September Ll. 1997 inwards on an output hub 114 rotationally secured with the turbine wheel 118. This ring piston forms radially outwards a conical area which is fitted with suitable lining 121.

The ring piston 136 interacts with a suitably conically 5 designed counter friction face 122 of the converter cover 116.

The lock-up clutch 112 has a rear pressure chamber 124 between the ring piston 136 and the turbine wheel 118 and a front pressure chamber 125 between the ring piston 136 and the converter cover 116. The piston 136 is operated in its coupling position interacting with the counter friction face 122 by biasing the front pressure chamber 125 with flow medium. The size of the torque to be transferred by the friction clutch 112 is produced in dependence on the differential pressure set between the pressure chambers 124, 125.

The torsion damper 135 is designed so that its bridging torque or stop moment is smaller than the maximum torque of the internal combustion engine driving the torque converter 110. This means that the energy accumulators 137 of the torsion damper 135 are designed so that they cannot resiliently take up the entire torque of the internal combustion engine. The relative rotation between the input part 138 of the torsion damper 135 connected rotationally secured with the piston 136, and the flange-like output part 139 can take place through the blocking of the windings of the springs 137 or preferably through stops provided between the input part 138 and the output part 139. The output part 139 of the damper 135 is connected rotationally secured with the turbine hub 114 in known way by an axial push-in connection formed by toothed gearing.

As can be seen from Figure 4 the input part 138 interacting with the energy accumulators 137 can be formed by segment- SP1433.P38 Septe.ber 1 1, 1997 shaped components 140 wherein each two such components 140 are provided diametrically opposite one another back to back. These pairs of segment-shaped components 140 are connected rotationally secured to the piston 136 by rivet connections 141. The flange-like output part 139 is shown in plan view in Figure 5. The flange 139 has a ring-shaped base element 139a as well as two diametrically opposite radial extension arms 142 with recesses 143 for the energy accumulators 137. The extension arms 142 are housed axially between the pairs of components 140. viewed circumferentially, the pairs of segment-shaped components which are lying back to back f orm sockets 145 for the extension arms 142 between their fixing areas 144. In Figure 5 the stop contours 146 formed by the segment-shaped components 140 for the extension arms 142 are shown by broken lines. The piston 136 has circumferentially distributed axial indentations which form projections 147 set in the direction of the turbine wheel 118 and supporting the fixing areas 144 of the segment-shaped components 140 facing the piston 136. The components 140 likewise have recesses 148 for the springs 137. These recesses 148 are in the illustrated embodiment aligned axially with the recesses 143 of the output part 139. In the embodiment according to Figures 3 to 5 the energy accumulators 137 are set play-free in the recesses 143 and 148. In many cases it can however also be expedient if at least one of the springs 137 has play relative to a recess 143 and/or 148. Also at least one of the springs 137 can be installed with a certain pretension in a window 143 and/or window 148.

Since the torsion damper 20b or 135 according to the invention is only designed for a partial load area it can have a particularly simple construction which also allows a cost-effective manufacture.

The torsion damper 135 can be designed according to an SP1433.P313 September 11, 1997 embodiment according to the invention so that about 40 to 50% of the maximum torque of the internal combustion engine can be transferred through the springs 137. The relative turning angle covered by the energy accumulators 137 between the input part 138 and the output part 139 can be in the order of 50, as shown in Figure 6. In Figure 6 the relative turning angle between the input part 138 and output part 139 of the damper 135 is shown during the pulling operation of the motor vehicle. In the pushing operation this relative turning angle can be of the same size or can have a dif f erent value. The torsional rigidity of the torsion damper 135 can also have different values in the pushing direction and pulling direction. This is achieved by providing the windows 143 and 148 and springs 137 with is suitable dimensions. Also the torsion damper 135 can have a multi-stepped characteristic line wherein the characteristic lines ranges which correspond to the pushing operation and pulling operation can likewise have different paths.

It can be seen from Figure 6 that the torsion damper 135 is bridged at 50 angle or reaches a stop and the torque transferable by the elasticity or compression of the springs 137 is restricted to about 45 Nm. A torsion damper 135 designed in this way can advantageously be used in connection with hydrodynamic torque converters which have a slip-controlled bridging clutch. The stop moment of 45 Nm is suitable for engines which have a nominal maximum torque in the order of 80 to 200 Nm.

The bridging moment of the damper 135 is preferably dimensioned so that it preferably covers the entire main driving range of a motor vehicle. By main driving range is meant the range which is most frequently used when considered over the entire operating time of a motor SP1433. PIB September 11, 1997 vehicle. This main driving range preferably comprises at least the areas of the engine characteristic field which apply for the FTP75-cycle and/or for the ECE-cycle (town, 90 km/h, 120 km/h). The main driving range is thus that range in which the vehicle is operated the most. Owing to the traffic infrastructures which exist in the various countries this driving range can vary somewhat from country to country.

In the output characteristic field of a torque converter 110 shown in Figure 7 having a soft converter design the main driving range is shown as a closely shaded surface. In this conversion area the bridging clutch 112 is open. The main driving range is enclosed by an area in which driving is advantageously with minimum slip in the bridging clutch 112. The main driving range extends from a lower speed A up to an upper speed B. The lower speed A thereby corresponds at least substantially to the idling speed which can lie in the order of 700 to 800 revolutions. The upper speed limit B can lie in a speed range between 2000 and 3000 revolutions and can have for example the value 2200 rpm. The range with slip can have an upper speed limit C which can correspond to the maximum speed of the internal combustion engine, but can also advantageously lie below same and can have for example 25 a value between 3000 and 4000 rpm.

Through the design of the torsion damper 135 according to the invention it is possible to bridge the torque converter 110 completely in the main driving range, thus the bridging clutch 112 can be operated without slip. In this main driving range the vibration insulation between the internal combustion engine and the gearbox connected to the output side thereof is carried out practically entirely by the torsion vibration damper 135. Only peak torques are taken up by the slip in the bridging clutch 112. To this end the bridging clutch 112 is controlled and regulated in the main SPI433.P3B September 1 1. 1997 driving range so that in relation to the maximum torque of the internal combustion engine this transfers a comparatively low torque which is however greater than the torque of the internal combustion engine ensuing just at 5 that time.

In the area with slip the bridging clutch 112 is controlled and regulated so that a certain slip exists between the friction faces 121, 122 of the bridging clutch 112. As a result of this slip there is also relative rotation between the pump wheel 117 and the turbine wheel 118.

In the area with slip according to Figure 7 the adverse torque irregularities which still occur in this area are is mainly dampened through the slip.

In the main driving range as well as in the range with slip the transferable torque of the bridging clutch 112 can be reduced for a better insulation of the vibrations where conditions arise in the drive train with high vibration amplitude such as for example in the case of resonance, load change impact or the like.

As can be seen f rom Figure 6, the torsion damper of the bridging clutch 112 can also be designed so that following a turning angle with relatively low turning angle rigidity the damper has a comparatively small turning angle in which the torsional rigidity amounts to a multiple of that of the first turning angle. In Figure 6 this second turning angle extends over 20. The torsional rigidity in this second turning angle can be 7 to 15 times the torsional rigidity in the first turning angle. In the embodiment shown in Figure 6 the torsional rigidity in the first turning Angle lies in the order of 8 Nm/0 and in the second turning angle in the order of 70 Nm/c.

SP143M3B Septer 11, 1997 In the main driving range according to Figure 7 the torque transferable by the bridging clutch 112 is set to about 1.

1 to 1. 2 times the engine torque actually arising. The regulation or control of the torque transferable by the bridging clutch 112 can be carried out in the main driving range so that the torque transferable by the bridging clutch 112 does not understep a minimum value. This value should amount to at least 1% of the maximum torque of the internal combustion engine. The minimum torque transferable by the bridging clutch 122 in the main driving range can amount for example to 5 Nm. This lower limit can however also be moved down or up depending on the type of use. Thus the minimum torque transferable in the main driving range by the bridging clutch 112 can be set to a value which is very close, preferably slightly less than, the maximum engine torque occurring in the main driving range.

In the range marked "range with slip,' in Figure 7 the torque transferable by the bridging clutch 112 is set to 0.8 to 0.95 times the torque of the internal combustion engine arising at that time. The torque transfer capacity of the bridging clutch 112 is thus dependent on the relevant ensuing torque of the internal combustion engine which has to be transferred. In other wards this means that as the torque of the internal combustion engine rises so the torque transferable by the bridging clutch increases and with a drop in the torque delivered by the internal combustion engine the torque transfer capacity of the bridging clutch 112 likewise decreases.

The modified embodiment of a bridging clutch 212 shown in Figures 8 and 9 for a hydrodynamic torque converter has a twin-phase torsion damper 235 which has a first set of energy accumulators 237 and a second set of energy accumulators 250. The bridging clutch 212 is designed as a SP143M38 September 1 1. 1997 multi-plate clutch with an inner plate support 251 and an outer plate support 252. The outer plate support 252 is rotationally secured with the housing 216 of the torque converter. The plate support 252 has a supporting plate 253 on its end area facing the turbine wheel 218. The housing 216 forms in conjunction with a piston 236 a pressure chamber 254 which can be biased with a fluid medium in order to set the torque which is to be transferred by the bridging clutch 212. The output part of the bridging clutch 212 formed by the plate support 251 has radially inwards a profiled area 255 formed by toothed gearing and engaging with play with a counter profiled area 256 of an output part in the form of a turbine hub 214. The profiled areas 256 are formed by a ring-shaped component of sheet metal which is fixed or rigidly connected to the hub 214. The torsion vibration damper 235 has an input part 238 which is in driving connection with the output part 251 of the bridging clutch 212. The input part 238 of the damper 235 is formed by a ring-shaped component which has radially inwards extension arms or tongues 257 which engage in slit-like recesses 258 of the output part 251 of the bridging clutch 212. Through this engagement a practically play-free connection in the circumferential direction is guaranteed between the two components 251 and 238. As can be seen in particular from Figure 8 the ring-shaped component 238 has cut-out recesses 259, 260 for the energy accumulators 237, 250. The energy accumulators 250 are housed with play in both rotary directions in the recesses 260. The ring-shaped component 238 is housed axially between two discs 260, 261.

The two disc-like components 260, 261 are fitted on each other and fixed together radially outside the ring-shaped component 238. The disc-like component 261 facing the turbine wheel 218 extends radially inwards up t o the hub 214 and is connected rotationally secured with same. As can be seen from Figure 9 the outer turbine shell 218a, the disclike component 261 and the ring-like component 256 are SP1433.P3B September 1 1, 1997 rigidly connected with the output hub 214 jointly by connecting points which are formed by rivet connections 262. The torsion vibration damper 235 can have a torsion characteristic line corresponding to the lines 263, 264 according to Figure 6. The first characteristic line area 263 is thereby covered by the energy accumulators 237. On exceeding the first turning angle range 263 the springs 250 additionally come to act with a higher spring rate parallel to the springs 237. This produces the steep characteristic line range 264. At the end of the characteristic line range 264 the inner toothed gearing 255 of the clutch output part 251 comes to adjoin the external toothed gearing 256 of the output hub 214 whereby a positive practically rigid connection is ensured between the component 251 and the output hub 214 - in the corresponding direction of rotation.

The damper 235 is thus bridged by the stop of the toothed gearings 255, 256. There is thus a force flow which is parallel to the force flow running over the springs 237, 250 and which leads directly from the output part 251 of the bridging clutch 212 into the output part 214. Overstraining the springs 237, 250 or components 238, 260, 261 can thereby be avoided.

Through the design of the converter bridging clutch according to the invention and its control it is possible to achieve optimum operation of a motor vehicle from the energy point of view. Since driving is carried out with slip-free bridging clutch in the most frequently used operating states a significant saving of fuel can be achieved compared to the converter bridging clutches which are not bridged in these operating states or which work with slip. The main speed range lies between about 600 and 2200 to 3000 revolutions per minute and the mean value is about 1800 revolutions per minute. In the main driving range, the bridging clutch is thus substantially closed so that the prevailing engine torque is transferred by the bridging clutch without SP1433.P3B September 1 1, 1997 significant slip. The vibration damping is carried out in this main driving range by the rotary vibration dampers 20b, 135, 235 provided in the force or torque flow of the converter bridging clutch 12, 112, 212. The torsion damper 20b, 135, 235 is thereby provided with a comparatively small turning angle and the stop moment of the torsion damper corresponds approximately to the upper boundary moment of the main driving range. This upper boundary moment can amount to 15 to 50 OW of the maximum engine torque depending on the motoring and vehicle weight. With a damper constructed in this way vibrations can be produced in the driving range with lower drive torques which produce adverse droning. Adverse load change reactions in the drive train are suppressed or avoided by the comparatively small turning angle of the torsion damper. The load change shocks are restricted by the friction faces of the bridging clutch slipping relative to each other on exceeding the stop moment or bridging moment of the damper. The torque being transferred is thereby restricted. The torque peaks are dampened by the slip in the bridging clutch. Above the main driving range or in the driving range in which the ensuing torques are greater than the boundary moment transferable by the damper the bridging clutch is controlled so that a slip is present. Adverse load change reactions are avoided by the slip thus set. In speed ranges or torque ranges above the main driving range in which there are no adverse vibration excitations, the clutch can likewise be closed to a torque value which is greater than the ensuing engine torque. For certain speed ranges in which there are adverse excitations the bridging clutch can again be opened to slip. The latter can be particularly expedient in the case of a resonance speed.

Also in the main driving range or in the range of 35 comparatively small engine torques it can be expedient when passing through resonances to open the bridging clutch or SP1433.P38 seprember 1 1, 1 9, 97 - 31 considerably reduce the torque transferable by same.

Through the design according to the invention and control or regulation of the bridging clutch the so-called droning noises are avoided which cannot be removed through a partially closed, thus slipping bridging clutch, namely as a result of the sticking /sliding conditions which occur between the friction faces of this bridging clutch.

The invention is not restricted to the embodiments described and illustrated but also includes variations which can be formed in particularby a combination of individual features, elements and methods of functioning described in connection with the various embodiments. Furthermore the inventions disclosed in the present application are to be considered within the scope of and in conjunction with the prior art listed as well as the said earlier German Patent Application P 43 28 182.6. The prior art indicated in the present application and the earlier German Patent

Application are thus to form a supplement to the present application.

This application is divided out from application 9418040.3 which describes and claims a drive system with an internal combustion engine and slip-controlled bridging clutch for a hydrodynamic torque converter wherein the bridging clutch contains a torsion damper whose stop moment is less than the maximum torque of the internal combustion engine.

Also divided out from application 9418040.3 is application 9719'1'2-s', 4 (Agents ref (P1433.P3C) which describes and claims a drive system with internal combustion engine characterised in that at least during acceleration processes a device determines whether by opening the bridging clutch in the same gear an increase in the traction force can be achieved by torque conversion and opens in this case, SP1433.P3B September 11, 1 997 otherwise the gear is shifted back at least one gear stage.

SP1433.P38 September 11, 1997

Claims

PATENT CLAIMS

1 Process for controlling a drive system with a slip- s controlled bridging clutch in dependence on the torque to be transferred for a hydrodynamic torque converter wherein a control based on energy and efficiency related points of view is active at least in all forward gear phases.

2. Process for controlling a drive system with internal combustion engine as claimed in Claim 1, wherein the torque control of the bridging clutch is divided into at least two ranges of which the first extends in the range up to 10 to 60%, preferably 15 to 50% of the maximum torque of the is internal combustion engine and the second lies above same.

3. Process for controlling a drive system with internal combustion engine as claimed in Claim 2, wherein in the first range the torque transferable at any time by the bridging clutch is greater than the torque of the internal combustion engine at that time.

4. Process for controlling a drive system with internal combustion engine as claimed in Claim 3, wherein the torque transferable at any time by the bridging clutch amounts to 1.0 to at least 1.2 times the torque of the internal combustion engine at that time.

5. Drive system controlled by a process as claimed in any preceding claim, with internal combustion engine and slipcontrolled bridging clutch for a hydrodynamic torque converter wherein the bridging clutch contains a torsion damper, and wherein in the first range the vibration uncoupling is carried out at least substantiall y through the damper and in the second range substantially through the slip of the bridging clutch.

SP1433.P39 Septmber 11, 1997

6. Drive system as claimed in Claim 5, wherein in the first range in conditions with high vibration amplitude in the drive train, such as for example with resonance, load change impact or the like, the transferable torque of the bridging clutch can be reduced.

7. Drive system as claimed in Claim 5 or Claim 6, wherein the stop moment of the torsion damper corresponds at least approximately to the torque of the internal combustion engine arising at the end of the first range.

8. Drive system as claimed in any one of Claims 5 to 7, wherein at least over a partial area of the first range the minimum torque transferable by the bridging clutch is kept greater than 1% of the maximum engine torque.

9. Drive system as claimed in any one of Claims 5 to 8, wherein at least over a partial area of the first range the torque transferable by the bridging clutch is kept at least approximately at a constant level.

10. Drive system as claimed in any one of Claims 5 to 9, wherein at least the main part of the characteristic field of the engine utilised in the main driving range (for example the areas of the engine characteristic field which are relevant for the FTP75-cycle and/or the ECE-cycle [town, 90 km/h, 120 km/h] drops below the first range.

11. Drive system as claimed in any one of Claims 5 to 10, wherein the first range extends from idling speed to a maximum of 3000 rpm, preferably up to a maximum of between 2200 and 2500 rpm.

12. Drive system as claimed in any one of Claims 5 to 11, wherein in the second range the torque transferable by the SP1433.P39 September 11. 1997 bridging clutch at any time amounts to 0.6 to <1.0 times, preferably to 0. 8 to 0.9 times, the torque of the internal combustion engine at that time.

13. Drive system as claimed in any one of Claims 5 to 12, wherein at least during acceleration processes a device determines whether by opening the bridging clutch in the same gear an increase in the pulling force can be achieved by torque conversion and opens in this case, otherwise the gear is shifted back at least one gear stage.

14. Drive system as claimed in any one of Claims 5 to 13, wherein wherein the bridging clutch contains a torsion damper whose stop moment is less than the maximum torque of is the internal combustion engine.

15. Drive system as claimed in Claim 14, wherein the stop moment is between 10 to 60% of the maximum torque of the internal combustion engine, preferably between 25 and 50%.

16. Drive system as claimed in Claim 14 or Claim 15, wherein the damper has no inherent friction device.

17. Drive system as claimed in any one of Claims 14 to 16, wherein the damper allows a relatively small turning angle in the order of 2' to 80, pref erably of +3' to 6'.

18. Drive system as claimed in any one of Claims 14 to 17, wherein the damper has a rigidity of 17 to 30 Nm/'.

SP1433.P38 Sepz"k>er 11, 1997