DE102006018806A1 - Power-split transmission for commercial motor vehicle, has a chain variator, where coupling of planetary gear with chain variator is divided in two classes, that is, with input or output planetary gear set - Google Patents

Abstract

The transmission has a combination of a stepped variable transmission with continuous variable transmission. The continuous variable transmission is implemented as cone pulley belt transmission. The coupling of a planetary gear with a chain variator is divided in two classes, that is, with input or output planetary gear set. In each of these two classes there are alternative arrangements of the multi-range transmission.

Description

The increase in fuel costs and the need to further reduce emissions require new technical solutions that allow optimization of the entire powertrain. Accordingly, the use of chain variators in the passenger car segment is also expanding. Further applications will be added to the series produced Audi multitronic ^® in the VL300 version and its further development VL380 with 420 Nm variator torque as well as the Ford / ZF CFT30. The optimization of the powertrain also makes sense on buses, vans or commercial vehicles, since they cause a significant proportion of emissions.

One Commercial vehicle manufacturers focused on the goal of spreading the Gear so big and to make that engine more or less stationary in one Lowest fuel consumption and lowest emissions can be. A motor optimization in exactly this area offers then additional Potential for improvement. The for Such a transmission required variator was based on the LuK series components positively evaluated and a development started.

If one compares the data of an Audi A6 with the data of different commercial vehicles with each other, then the task appears initially as not solvable. A whole series of goals not only demand a doubling, but even a jump in the order of magnitude, such as 1 clarified.

1 shows data and goals compared car and commercial vehicle application of a CVT.

As The variator data must show to meet these requirements be optimized more than just a single component. With all these Aspects of transmission structures via disk sets and pump system to chain the following chapters concern.

in the Course of development is becoming increasingly clear that the challenge to realize a commercial vehicle CVT is acceptable.

A the key technologies in this CVT application, this is also described in the LuK Colloquium 2002 Principle of power split and the use of multiple stepless Driving ranges. The concepts for passenger car transmission constructions presented with this technology cover benefits up to over 200 kW and corresponding moments, and thus transfer to the commercial vehicle segment.

With This technological background allows tailor-made transmission structures be developed as e.g. also on Hydrostaten based Driven the case. The chain variator offers in comparison to Hydrostat acoustic advantages, which is especially necessary for use in the bus is. Compared to purely electrical power conversion lies the advantage of the chain converter in terms of cost and efficiency and at the higher Power density.

In principle, to provide is usually a high-drive stage, because commercial vehicle engines their performance unfold at lower speeds. In some of the illustrated Transmission architectures can use this feature directly in for an input side Branching provided planetary gear set. Also to be provided is a manual transmission, which is quite common with the usual in commercial vehicles Jaw clutches can work when a speed sync is shown elsewhere.

The possibilities of coupling a planetary gearset and a chain variator via matching stages can be divided into only two classes, namely with input-side or output-side planetary gearset. In each of these two classes, there are then alternative arrangements of the multi-range manual transmission. Some possibilities 2 represents.

2 shows three transmission structure alternatives with transmission and performance characteristics.

at The class shown on the left is the planetary gear set on the input side arranged and the transmission in parallel to the variator power path. If the leading to the manual transmission Wave can be braked, is also an unbranched driving range represented. Under the sketch of the transmission architecture can be found an example, as with suitable transmission ratios several stepless Driving ranges are displayed. The diagram at the bottom shows the proportion of power used to load the variator.

ever after application can the advantages of one or the other architectural class predominate. The transmission shown on the left results in low driving ranges with very low variator load - favorable for an almost stationary used Implement. When changing from one driving range to the next, the variator sets back.

The middle column shows a gearbox whose gearbox assembly has two non-coaxial input waves. In contrast to the left Gearboxes shown range changes are possible without return adjustment. For that the must The variator transmits on average 50% of the engine power - more than the one on the left Transmission, but this is sufficient for light trucks or vans.

At the Gearboxes on the right are simply the roles between and exchanged output. This has mainly influence in the present example on the torque and speed ranges of the components - not but on the performance.

to Representation of a "Geared-Neutral" gear is basically the To set planetary gearset on the output side. When the planet is driving side arranged, the opposite can be shown: very long translations until the translation "Geared-Zero", in which the engine stationary.

in the Driving is the advantage of all illustrated architectures in the for Commercial vehicle comparatively small number of gears and thus range changes. Illustratively, for example, four driving ranges after starting only switched once and in the city virtually without change of area drove. At the exit is another change of area necessary and on the highway then a last.

For a variator development beyond 500 Nm, the main dimension is the center distance.

To increase the torque capacity, it is necessary to increase the main dimensions. The chosen axle distance of 220 mm compared to the 160-190 mm that can be realized in a car relaxes a whole series of aspects. In part, the effect is even significantly stronger than the 25% increase in axial distance, as the following list shows. The changes are indicated by arrows whose number reflects the relation to the axial distance increase: reason consequences Chain run radii ↑ Chain pull forces ↓, contact forces ↓ Number of chain links ↑ Forces per rocker (WD) or joint (WG) ↓↓ Chain kink angle ↓ Better load distribution on both latches of the chain Force per swing joint ↓↓ Bending of WG ↓, straining at the edge of the chain ↓↓ Shaft diameter ↑ Bending stiffness ↑↑, efficiency ↑ Curvature of the surface ↓ Pressing ↓, wear ↓, wear per WG ↓↓

By strengthen the combination There are still several relief effects, so the maximum starting at 600 Nm of the 420 Nm already realized in series with the VL380 at cleaner Interpretation of all such aspects are not too high.

to confirmation above considerations as well as the results published by research institutes and simulations were measured at LuK on a new high-performance dynamometer efficiencies. Since a complete map space consists of several translations, Speeds and moments (in some cases even contact pressures) are traversed This also put considerable demands on the test field - the installed Power E machine has e.g. a nominal power of 720 kW.

The result is that chain variators achieve efficiencies of over 97%. 3 shows as an example the 600 Nm efficiency map at constant drive speed of 2500 min ^-1 .

3 shows a chain variator efficiency map.

Shown here are the raw measured values (except for smoothing for noise suppression) of the test gear including the losses of the disc set bearing (spherical roller bearing). The rigidity of the test gear is due to a design with interchangeable disc plates even below the target stiffness. The We In other words, the degree of efficiency could be even higher in reality.

Of the Center distance of 220 mm thus shows the expected positive effect.

The pulley technology implemented on the Audi VL380 is the basis for use at even higher torques. Of central importance is the infinitely variable variable hydromechanical torque sensor (vMF) implemented in the interior of the pressure chambers in a space - saving manner 4 shown in the series implemented construction with sheet metal forming parts.

4 shows a drive pulley set with infinite torque sensor vMF for Audi VL380 with 420 Nm variator torque.

• • Präzise, dem tatsächlichen Moment proportionale Anpressung bei allen Übersetzungen
• • Dynamische Sicherheit, um Schäden auch bei Sprüngen des Momentes vorzubeugen

The vMF has the features required for safe, continuous operation in commercial vehicles:

• • Precise, proportional to the actual moment of contact for all translations
• • Dynamic safety to prevent damage even in the event of a jump in the moment

The Function of the vMF is that along the blue in the picture shown Components introduced moment over To convert ball ramps into an axial force. This yellow shown Balls are arranged inside the mechanism. The moment arrives then over the counter ramp of the brown colored Component on the shaft and from there to the solid disk or over the Sliding toothing to the green inked, axially moveable windscreen components.

The However, axial force generated by the balls does not act directly on the cone pulley, but closes with the blue component one hydraulic drainage hole. This mechanism regulates with high Dynamics a proportional to the moment hydraulic pressure. The pressure then generates over size Pressing on the actual contact pressure for the green Wegscheiben components. The same pressure is also the output pulley set fed to the contact pressure.

The dependence on the translation is achieved in that the ball-ramp mechanism has different ramp slopes at different radii. The appropriate ramp for the respective translation angle is achieved by the radial positioning of the balls by means of the guide surfaces, the translation depending axially move with the spacer (in 4 also shown in green).

To illustrate the translation dependence of the vMF, the detail enlargement of the blue component with the different steep ramps, 5 ,

5 shows a VMF ramp contour with translation-dependent angle and resulting contact pressure curve.

in the The result is the torque related pressure in the underdrive biggest and falls continuously towards the overdrive. The three-dimensional shape of the components is optimal at the among diverse Conditions determined contact pressure adjusted.

The dynamic safety achieved by the direct hydromechanical principle is determined by the measurement in 6 exemplified.

6 shows a dynamic safety of the vMF-Anpress-system in a jump of the drive torque.

at The measurement shown excites a targeted jump in the drive torque a decaying driveline vibration on the test bench. In the real vehicle this corresponds, for example, to a sudden cogging with Nachruckeln. As you can see, between the measured moment and the through the moment sensor adjusted and measured pressure virtually no delay available. Even quantitatively, the regulated pressure is congruent at all times with the target pressure calculated from the measured torque has been.

The double-piston principle already implemented in the multitronic ^® makes it possible to hydraulically operate all the desired rapid changes in the ratio even with a small installed pump capacity. The resulting consumption advantage is also aimed at commercial vehicles. Due to the required extremely fast adjustments in the present multi-range transmission structure, the double piston principle is even un accessible for efficient hydraulics. It forms the basis of the subsequent hydraulic and pump development.

A independent Control of the adjustment pieces is realized.

In spite of Upscaling of the entire system and the piston surfaces lead the much higher compared to cars Thrust torque due to engine braking devices to an increase in required peak pressures up to 100 bar. This requires higher pressure reinforcements the corresponding valves for the adjusting pressure chambers. By an independent control of both valves is this high valve gain also below the volume flows up to 19 l / min stable and the hydraulics gain in drive precision.

The tasks of the pressure and adjustment system and the solution implemented by this hydraulic system are clear in 7 shown. For stationary operation, the variator requires two forces on the pulley sets, which are in a certain ratio dependent on the ratio, the so-called support (or else K _p / K _s .) The support value is 1 for the LuK CVT chain in traction mode , 05 (UD) up to a maximum of 1.6 (OD) In overrun mode, it is the inverse inverse ratio, ie, from about 0.95 (OD) to 0.6 (UD), depending on the required support value The task of the red plungers shown is to generate the basic contact forces on both pulley sets, with high pressure oil being exchanged between the pistons during the variator adjustment to generate the rest forces necessary for balancing and the additional adjustment forces.

7 shows a double piston principle and an independent adjustment pressure control to balance the required forces in the variator.

These Hydraulics not only offers a high degree of stability and precision in the control of the pressures, but allowed by independence the pressure control also still further functions, e.g. a increase the Anpress-security on a bad road or suitable Design of the torque sensor a minor one Reduction of contact pressure e.g. for compensation of residual fluid pressure forces. in the As a result, efficiency optimization during operation is achieved.

at Adjustment of the translation becomes the balance of power left regulated. This can optionally be reduced by an adjustment pressure be and / or the other adjustment pressure can be increased. This degree of freedom is just in the fast adjustments of a multi-range transmission advantageous.

Here So the advantages of several systems are combined: the fully variable torque sensor brings the robustness and dynamic safety, and the independent Druckansteuerbar speed the Verstellkammern brings the liberties of the software controlled free contact pressure. A combination with a slip control of Contact pressure is also possible with this system, without the advantages of torque sensor to lose.

In transmissions in the power class above 400 kW, the lubricating oil and cooling power requirements of the clutch, variator, gears and bearings make the use of a low-pressure pump useful. After identifying the design-relevant operating point (full-load hill-start with maximum contact pressure and clutch cooling), a low-pressure pump in gerotor design with a displacement of 29 cm ³ results for the elaborated power split concept.

The smaller-volume high-pressure pump required, for example, for pressing the variator is designed as a symmetrically divided double-flow fully compensated vane pump with a delivery volume of 10 cm ^{3 in} total. A similar pump developed by LuK is also in series production in the Autotronic ^® from DaimlerChrysler.

Together with the low-pressure pump, it forms a structural unit as a tandem pump. 8th , on a shaft that is driven by the engine translated into speed. The supply of low-pressure oil ensures a cavitation-free supply of the high pressure pump and allows a compact design of the intake system as well as an efficient filter concept.

8th shows a hydraulic tandem pump from low-pressure gerotor assembly (blue) and double-lobe high-pressure vane pump (red).

The Pump efficiency is due to an intelligent control of pump floods increased.

Compared to a single-flow high-pressure section, the hydraulic power requirement is significantly reduced by intelligent control of the second pump flood. For this purpose, an electric switching valve is included in the hydraulic control, whose function in 9 is explained.

9 shows a control of the high and low pressure flow rates for various consumers.

In the position shown on the left of the flood control slide is the second tide of the vane pump switched to circulation. The drive torque of the pump is characterized in the proportionally dominant driving situations drastically lowered. Through the return feed go this oil not lost to the low pressure consumers for lubrication and cooling.

In the right repeated image section is the flood control valve electrically so controlled (turned off) that the second flood on a check valve is united with the first pump surge. That's enough pressure oil for the fastest Variator adjustments available, e.g. when starting or when changing the driving range.

The pump losses of this transmission - as well as the multitronic ^® and the Autotronic ^® - are low thanks to the optimized design. An alternative concept with only one pump for all customers would have threefold power requirement without cost advantage, because the cost of a high-pressure pump scale unfavorable than that of a low-pressure pump.

A Consistent application of the positive effects on the car application surface technologies for wear protection - e.g. hard anodizing or chemical nickel coating of the piston - ensures trouble-free Hydraulic function even with the long service life expectancy Commercial vehicles.

The increasing experience and process optimization with the strength-optimized Light-tab Geometry have the moment capacity the 37 mm wide LK3708 chain increased so much that after first attempts with 220 mm center distance for 600 Nm variator torque no chain widening necessary. All results presented in this article are with this 37 mm wide chain retracted. The at the LuK-Colloquium 2002 relationship between center distance, increase in strength and torque capacity will be at big wheelbases even exceeded.

10 shows a torque capacity of the chain variator with different chain types.

The chain spectrum in 10 is rounded in the lower torque range by narrower chains and chains with reduced pitch. In order for the 600 Nm shown here not to be the end, is also on a chain with increased pitch, ie LK10 tab worked with stronger latches. Thanks to stronger rocker pressure pieces, the forces introduced from the edge of the chain are more evenly distributed over the adjacent flaps.

The strength-side suitability for the intended application was demonstrated on the basis of damage calculations with the commercial vehicle collective. The power strokes of a tab are in the comparison between passenger car and truck collective (including the reduction achieved by Leistungsverzeigung) in 11 shown. The greater mileage of the power strokes due to the mileage is at a similar force level in the commercial vehicle as in the passenger car. Despite the doubled maximum torque, only a small increase in the maximum power strokes of both groups occurs comparably seldom.

11 shows a collective of the Laschen power strokes for cars and commercial vehicles.

In Considering the enormous mileage expectations of over one Million km must pay special attention to the topic of wear be dedicated. However, the high efficiency values already allow low wear values expect: wear needs namely usually energy loss. For CVT counts as a friction gear not only the material wear - quantifiable in weight per rubbing energy -, but even the quality wear of the friction surfaces - quantifiable e.g. as a coefficient of friction change or roughness change.

Based on the developed materials and test experience, both aspects are in intensive and successful testing on several high performance endurance testers. Some intermediate results on the long-term stability of the metallic tribosystem shows 12 , Here, over the term of several thousand hours, the change in the support value is shown. The support value is a good indi capacitor for changes in friction coefficients.

12 shows above a change in the support at endurance runs of different variators and cycles and below a width wear of the cradles at these endurance runs.

In the upper half of 12 are shown in black the results of a reference car application with center distance 171 mm. The noticeable slight change in the support value (indicates that the coefficient of friction μ has changed only minimally) The lifespan target of 3000 h of a car can be checked by gathering within about 150 h The car system is very stable and offers noticeably high reserves.

In shown in blue are the results of the same construction with center distance 171 mm, however, the scaled loads of the commercial vehicle application is suspended. This scaling means that the moments are like that were reduced, that the resulting pin-specific forces a 220 mm system. This experimentally-related intermediate step already proves the service life potential of a wheelbase enlargement. The truck life target of over 15,000 h could be achieved by gathering within 1000 h. The test was even extended to cover up to 2500 h running time. The different symbol shapes show different test procedures at. The procedure symbolized by squares becomes the translation changed in several stages, so that on the rocker pressure piece there is a high concentration of stress, but on the disk Not. The test procedure symbolized by diamonds takes place with fixed translation, so that the contact stresses on both the rocker, as also focus on the disc (the two friction partners can but also adapt well to each other). The results of the fixed translation confirmed variator Again, that mixing cycles are the hardest and thus represent the most efficient experimental methodology.

The results of a genuine 220 mm variator, which are still incomplete at the time of printing, are exposed in green, which is exposed to the unscaled loads of commercial vehicle applications up to 600 Nm. The initially rapid change in support as well as the initially high width wear (lower half of 12 ) result from the fact that in the test program the maximum load points were tested first. The then stable behavior is also the result of a later described sequencing sequence optimization of the chain.

The here in Kettenvariator converted tribosystem of chain, disc set surface and suitable oil shows overall a stable behavior of the coefficients of friction and confirms the Accessibility of ambitious life-time goals.

The second durability aspect is the chain-side wear of the faces, which leads to a decrease in the chain width. In the long-term experiments described above, this end-face wear was determined with regular findings. These results show the lower half of 12 with consistent color and symbol choice.

Of the Total low wear on the face is one Feature of optimized heat treatment.

The design of the rocker pressure end faces ensures that the stresses relevant to wear, such as the Hertzian pressure, do not exceed the permissible level. 13 shows an analysis of the contact locations and properties on these faces, calculated using the three-dimensional chain calculation program "CHAIN", which also takes into account all elastic deformations from the waves to the cradles.

13 shows a CHAIN screenshot with visualization of the contact properties on the drive disk set in the Underdrive.

The color surfaces are the contact ellipses whose pressure is visualized by the color becomes. This calculation is taken into account with the LuK calculation program CHAIN all elastic and dynamic effects of disc sets and Chain, as well as the joint kinematics of the rocker. In order to load details are traceable and can be used in the chain construction considered become.

With regard to further increase in runtime, the optimization of the division sequence can also contribute 14 , If the acoustic priority is taken into account, division sequences consisting of long and short tabs are available in which the direct sequence of two long tabs is specifically excluded. The reason for this is that the highest end loadings experimentally and computationally in exactly these places occur. Such optimized chains not only show lower wear rates, but can also endure more total wear because the width reduction of the chain is more uniform.

14 shows a correlation of the local width wear with the sequence of long and short tabs. The optimized chain avoids the direct sequence of two long tabs.

To the successful series production of the Audi VL380 with 420 Nm variator torque, realized with the LuK CVT components disc sets with a new full variable Torque sensor, optimized chain LK3308 and hydraulic control with vane pump, is looking for ways, this technology also for commercial vehicle applications to be used with power split and variator torques up to 600 Nm. The challenges regarding structure development, variator design, Pump and hydraulic development as well as chain construction he demanded careful considerations and the courage to act, by the positive test results is rewarded.

Out the interplay of the variety of detailed work now arises for the Power-split application in commercial vehicles as well as for torque-enhanced car applications a promising situation.

First Prototypes of a special transmission structure will be developed together with a customer established in the commercial vehicle segment.

Claims (4)

Power split transmission, in particular for commercial vehicles, characterized by the combination of at least one step subtransmission with at least one stepless partial transmission. Transmission according to claim 1, characterized that the continuously variable transmission (CVT) as a conical-pulley transmission accomplished is. Transmission according to one of claims 1 or 2, characterized through a high-driver stage. Transmission according to one of the preceding claims, characterized through the use of a planetary gear.