DE20300359U1 - Propulsion system for especially road finisher has torque divided transmission, whereby at least two outputs of finisher are connected to common transmission branch which is main transmission - Google Patents

Abstract

The propulsion system for especially a road finisher has a torque divided transmission, whereby at least two outputs of the finisher are connected to a common transmission branch. The common transmission branch is a main transmission. At least one travelling drive (18) and at least one drive for the conveyor belt (38) are connected to a common drive shaft (24). The torque divided transmission may have at least one three-shaft summing gear through which are connected the main transmission and auxiliary transmissions.

Description

Drive system for working machines, in particular for Road pavers Description

The invention relates to a drive system for work machines, in particular for road pavers.

Road pavers are mobile work machines that are mainly used to lay asphalt mixes in road construction. When in use, the road paver pushes a truck or other delivery vehicle loaded with asphalt in front of it. The so-called bunker walls are folded down to allow the material to be transferred from the truck or delivery vehicle to the road paver. The truck or delivery vehicle tips the material into the road paver's bunker. From there, the material is conveyed through the machine on a conveyor belt, the so-called scraper belt, and falls out the rear wall of the road paver. At this point, the mix is distributed crosswise by augers. The subsequent screed (working device) pulled by the road paver floats on the material and smooths it out, thus creating the surface profile.

The screed usually has several compaction units, such as tamper bars, vibrators, or pressure bars for pre-compaction. The final compaction is then achieved by road rollers.

The installation height is adjusted by changing the setting

The angle at which the screed runs in relation to the direction of travel is adjusted. To do this, the height of the articulation points of the screed's drawbar arms is changed using so-called leveling cylinders.
5

Road pavers usually have the following individual drives, which are integrated into a drive system:
Rotary drives for the chassis, rotary drives for the scraper belts, rotary drives for the augers, linear drives for the bunker wall cylinder, linear drives for the leveling cylinder, linear drives for raising and lowering the screed, linear drives for telescoping the screed and rotary drives or a rotary drive system for the compaction devices of the screed, which usually work rotary or pulse hydraulically linear with mechanical crank or eccentric gears or unbalance exciters.

For road pavers, purely mechanical drive systems, purely hydrostatic drive systems and diesel-electric drive systems are known from EP 0 489 969 Al.

In a purely hydrostatic drive system, a combustion engine usually drives all hydraulic pumps via a pump distribution gearbox. These hydraulic pumps feed different hydraulic motors, which feed the individual drives.

It is well known that earth reduction gears are used for travel drives. Such gears are also often used for scraper belts and augers, as this may be more cost-effective than the additional costs for the hydraulic slow-running motors that would otherwise be required.

The machine power is mainly converted into the rotary drives of the undercarriage, the scraper belts and the augers.

It is also known that the scraper belts and augers are also operated with separate supply pumps. A road paver also has various (fixed) pumps, some of which function as feed pumps and some as supply pumps for the other units, such as compaction drives, lifting and other hydraulics.

It is also known to use a generator for electrical screed heating. Heating parts of the screed is necessary to prevent the material being laid from cooling down too quickly and "sticking".

Good control of the travel speed of a road paver is of essential importance from an application point of view. The actual speed of the travel drives is usually recorded on gears of the earth reduction gear with the help of proximity sensors and fed back to a control and regulating device which regulates the speed via hydraulic adjustment elements. In measurement terms, the actual speed value recording is a frequency count. The proximity sensors deliver pulses which are counted over a fixed time interval. The number of pulses is then proportional to the output speed. At ever lower speeds the number of pulses drops so that at some point control is no longer possible. For this reason the working speed is limited downwards. The lowest working speed known for road pavers is 1 m/min.

In very few individual cases, a working speed below this limit may be sensible. However, it is more important for the drive that the full effective machine power can be used across the entire working speed range.

is. Road pavers can be equipped with either a wheeled chassis or a crawler chassis. Road pavers with a wheeled chassis have individually driven rear wheels or a driven rear axle with a differential gear. They are equipped with one or two front axles or two or four individually suspended front wheels. The front wheels/axles are often additionally driven to improve traction. In addition to the very easy-to-control and controllable stepless transmission of hydrostatic transmissions, such transmissions also have their typical disadvantages.

This is particularly the poor efficiency, which is between 50% and 80% depending on the operating state. Even when only in operational mode, the machines consume considerable amounts of energy for the drag power of the hydraulic drives. In addition, high noise emissions and possible oil leaks from a hydrostatic drive are disadvantageous. The high noise emissions are also exacerbated by the cooling air flow required for engine and oil cooling.

In addition to a high environmental impact, the required coolers also require a lot of installation space in road pavers with purely hydrostatic drives. Furthermore, the necessary sound insulation is often only poorly implemented because there is no installation space available for it. Furthermore, the combustion engine must be relatively large because it must also provide the high hydraulic losses in the form of mechanical energy. This means that the engine must be designed larger than it should be in terms of the application's performance requirements, which in turn results in unnecessary energy losses, noise emissions, larger engine coolers and the associated installation space consumption. Another disadvantage of the hydraulic system is the high operating costs due to the high fuel consumption.

A particular disadvantage of purely mechanical drive systems for road pavers is that stepless control is very difficult to implement. Linear drives are also very difficult to implement. Other disadvantages include complex overload protection, a relatively unfavorable power-to-weight ratio, a high space requirement, unfavorable energy transfer to the working device and a low power density.

Diesel-electric drive systems for road pavers only have good efficiency in a very limited working range. Other disadvantages include a high power-to-weight ratio, linear drives that are practically impossible to implement, high electrical and electronic manufacturing costs, a high susceptibility to failure and the associated cost disadvantage.

It is therefore the object of the present invention to provide a drive system for work machines, in particular road pavers, which enables greater efficiency of the paver and eliminates the aforementioned disadvantages of the known drive systems. This should make it possible to achieve lower fuel consumption with the same performance. Furthermore, the drive system according to the invention should be accompanied by lower noise emissions.

This object is achieved according to the invention by the features in the characterizing part of claim 1 in conjunction with the features in the preamble. Expedient embodiments of the invention are contained in the subclaims.

A particular advantage of the drive system according to the invention is that the main part of the power for a working machine, in particular a road paver,

via a transmission branch with high efficiency, e.g. a mechanical transmission branch and only a small part of the power is transmitted via a continuously variable transmission branch, e.g. a hydrostatic transmission branch, thereby increasing the overall efficiency of the drive system.

For this purpose, a drive system according to the invention for a work machine, in particular a road finisher, has a power-split transmission, wherein at least two outputs of the finisher are connected to a common transmission branch. Preferably, the common transmission branch is the main transmission of the power-split transmission.

According to the invention, at least one travel drive and at least one drive for a conveyor belt are connected to a common drive shaft.

Furthermore, the power-split transmission has at least one summing transmission, wherein the main transmission and the at least one auxiliary transmission are connected via a summing transmission.

The main transmission can be a mechanical transmission or an electric transmission.

The at least one auxiliary transmission may be a hydrostatic transmission or an electric transmission or a hydrodynamic transmission or a pneumatic transmission or a mechanical transmission.

In a preferred embodiment, the drive system may comprise a drive shaft and/or a drive chain. The drive shaft may be a cardan shaft.
Furthermore, in a preferred embodiment, the drive system can comprise drives for at least one chassis and/or at least one conveyor belt and/or at least one distribution screw and/or at least one bunker wall cylinder and/or at least one leveling cylinder and/or at least one lifting cylinder and/or at least

a screed telescopic cylinder and/or at least one compaction device.

The conveyor belt can be a scraper belt.

The drive system can have an internal combustion engine as the primary drive. This internal combustion engine is preferably a diesel engine.

Furthermore, in a preferred embodiment, a central distribution gear is provided, which can be a modified pump distribution gear with a mechanical output and at least one output for a hydrostatic pump.

In the method according to the invention for driving finishers, several outputs use a common transmission branch of a power-split transmission as the main transmission. Preferably, a common drive shaft supplies at least one drive for a conveyor belt and at least one travel drive. This means that the majority of the power can be transmitted, for example, via a mechanical transmission branch with high efficiency, with as little as possible being transmitted via a continuously variable transmission branch with lower efficiency.

The main gearbox and auxiliary gearboxes are interconnected via summing gearboxes.

When the paver is in operation, the input speeds of the summing gearboxes are designed so that the input shaft on the main gearbox side forms the total power shaft. The hydrostatic auxiliary gearboxes can be supplied by fixed displacement pumps.

In the transport gear of the paver, the input speeds of the summing gears are designed so that the main gear

side input shaft and the auxiliary gearbox side input shaft form partial power shafts. The conveyor belts and screws can be stopped mechanically.
5

The invention is explained in more detail below in an embodiment using drawings. They show:

Fig.l: a schematic representation of a drive system according to the invention,

Fig. 2: a schematic representation of the transmission of a drive system according to the invention.

Fig. 1 shows a schematic of a drive system according to the invention for a road finisher. A common mechanical drive is provided for the main drives, the travel drives 18, the conveyor belts 38 and the augers 34.

This drive is connected via a cardan shaft 14 and a central transfer case 3 0 to a diesel engine 10, which serves as the primary drive. The central transfer case 3 0 can be, for example, a modified pump transfer case, which has a mechanical drive in addition to outputs for hydrostatic pumps 12. The mechanical transmission can be implemented by means of a drive shaft 24 and/or drive chain 36 or in another way.
The common drive shaft 24 is connected to the drive wheels of the travel drive 18, the worms 34 and the conveyor belts 38 via summing gears 20 (three-shaft gears), with a hydraulic motor 16 located on the second input shaft of the summing gears 20. The summing gears 20 are summing gears

of several hydrostatic-mechanical power-split transmissions with a common mechanical supply.
The worms 34 and other outputs can be connected in a similar way. However, since the worm drives are not aligned with the drive shaft 24, a second transmission, designed as a drive chain 36, must be provided to the worms in the sense of a further distribution gear. The number of outputs can be increased or decreased as required.

According to the invention, the advantages of hydrostatics are combined with the good efficiency of a mechanical transmission. For this purpose, a drive system for road pavers comprises a power-split transmission, with at least two outputs of the paver being connected to a common transmission branch, which is preferably the main transmission.

The basic idea is that the majority of the power is transmitted via a transmission branch with the highest possible efficiency, e.g. via a mechanical transmission branch, and only as little of the power as possible is transmitted via a continuously variable transmission branch, e.g. hydrostatic transmission branch. The two partial transmissions are combined in a summing transmission 2 0 before the final drive.
A general distinction can be made between main transmission and auxiliary transmission. The continuously variable transmission does not necessarily have to be hydrostatic, of course. Nor does the main transmission branch have to be mechanical. The invention makes use of the fact that, apart from wheeled pavers with differential transmissions, the main drives of road pavers are almost flush on one axle. The main drives are the two rear travel drives and the drive(s) of the conveyor belts, the so-called scraper belts.

Furthermore, the invention takes into account the fact that the drive speed of all main drives, i.e. the conveyor belts and the travel drives, are similarly low and, in absolute terms, have a very limited adjustment range.

Fig. 2 shows a schematic representation of the transmissions of a drive system according to the invention for a road finisher. The main transmission 28 can be located in front of or behind the inner distribution transmission 3 0. The distribution transmission 3 0 can have additional converters. The converters, the distribution transmission 3 0 and the main transmission 28 are housed in a common transmission housing and form the central distribution transmission 26. To design the common drive branch, it is obvious to set the speed of the common drive shaft 24 to the speed required in main operation or at the main operating point of the largest power consumer, so that no power is transmitted via the continuously variable auxiliary transmissions 32 at this operating point. This means that the respective continuously variable auxiliary transmission 32 is set to the speed 0 (zero) for this operating point. All summing transmissions 2 0 can have a basic gear ratio such that the typical or most frequently selected working speed is achieved when the continuously variable partial transmission is at a standstill. The highest possible efficiency achieved with the drive system according to the invention is particularly advantageous. Furthermore, a lower cooling capacity is required with a hydrostatic drive in the continuously variable branch. Since the hydrostatic power component has been reduced, there is also less noise emission. Furthermore, less powerful and therefore less expensive hydraulic components can be used for a system according to the invention compared to the prior art.

· · &idigr; .· &igr;♦♦

UUUUU

It is also advantageous to increase the lower speed of the mechanical drive branch. This is particularly desirable because higher speeds require lower torques and therefore lower strength requirements for the mechanical components. This is possible insofar as the speed of the common drive train is set using a constructively sensible but relatively high value, so that with an input speed of 0 (zero) of the respective continuously variable transmission branch, a speed above the highest working speed would be set at the drive of the summing gear 20. The desired working speed must then be set via the respective continuously variable branch so that it counteracts the common supply, i.e. always supplies reactive power. The main transmission-side input shaft of the summing gear 20 is then always the total power shaft when the machine is running. The continuously variable branch reduces the main transmission-side speed during operation.

This solution, which is not optimal in terms of energy, offers considerable design advantages. The speed in the main gearbox 28 can be selected to be higher. Therefore, the elements of the main gearbox branch can be dimensioned smaller for the same machine power. Furthermore, the drive in the auxiliary gearboxes 32 does not necessarily have to be continuously adjustable through speed 0 (zero). Therefore, variable displacement pumps or other adjustment devices in the auxiliary gearboxes 32 can be dispensed with, since adjustment, e.g.

can only be implemented on the output side, e.g. via adjustable hydraulic motors. The hydrostatic auxiliary gears 32 can therefore be supplied via constant pumps. This means that the number of hydraulic pumps can be reduced, since several pumps can be replaced by one pump with current sharing. The central distribution gear can also be

can be dimensioned more compactly due to a smaller number of output shafts. A typical drive for a road finisher according to the state of the art in the medium to upper power class has two variable displacement pumps for the travel drive 18 and one variable displacement pump each for conveyor belts 38 and augers 34. The travel drives usually comprise variable displacement motors. According to the embodiment according to the invention, the * six adjustment elements could be reduced to four adjustment elements, combined with a saving of up to three output shafts of the central distribution gear for pumps. In addition, however, there would be the output for the main gear 28, so that there would be a saving of two hydraulic adjustment elements and two outputs of the central distribution gear compared to the state of the art.

If a higher speed of the travel drives is required in the transport gear as opposed to the work gear, this required higher working speed for the travel drives can be generated by reversing the direction of rotation of the motors (via a switching valve) in the auxiliary gear 32. The drive shaft 24 then becomes the overall power shaft and the main and auxiliary gears 28, 32 become partial power shafts. The conveyor belts 38 and screws 34 can be set to a speed of 0 (zero) either hydrostatically or mechanically (by braking). In the case of mechanical adjustment, the motors become pumps whose flow rate can be switched to that of the hydrostatic supply (by means of switching valves), so that a further increase in the speed of the travel drives is possible.

In addition to a mechanical-hydrostatic structure of a power-split drive system according to the invention, other transmission types can also be considered for the main and auxiliary transmissions.

It is particularly useful to construct a mechanical-electric, power-split transmission with a mechanical main transmission and electric auxiliary transmissions, whereby the travel drives and the drives for the conveyor belts 3 8 use a common transmission branch as the main transmission and are supplied via a common drive shaft 24. In comparison to the design variant according to Figure 1, the hydrostatic pumps 12 are to be replaced by generators; hydraulic motors 16 become electric motors. The advantage over a diesel-electric non-power-split transmission according to the state of the art is that the electrical components can be designed for relatively low power outputs. This increases the overall efficiency of the drive system. In partial load and engine braking mode, excess electrical energy can be used, for example, to heat the screed or for other electrical consumers. This means that the generator, which is actually only responsible for heating the screed, can be saved.

Furthermore, the construction of a power-split transmission according to the invention for a road finisher can also be carried out electrically. It is therefore advisable to design the main transmission electrically because the electric motor can be designed for an almost fixed speed. This is advantageous because electric motors, especially three-phase motors, only have their optimum efficiency in a very narrow speed range. In this design variant, too, electrical power reserves can be made available for heating the screed or for other electrical consumers in the partial load range of the generator or in the braking mode of the motor in the main transmission or in the braking mode of motors in auxiliary transmissions.

» ♦

«
•t

The invention is not limited to the embodiment shown here. Rather, it is possible to realize further embodiments by combining and modifying the means and features mentioned without departing from the scope of the invention.

List of reference symbols

10 Diesel engine

12 hydrostatic pump

14 Cardan shaft

16 Hydraulic motor

18 Drive

2 0 summing gear

22 Plank (working tool)

24 common drive shaft

2 6 central transfer case

2 8 Main gearbox

3 0 Transfer case

32 hydrostatic auxiliary transmission

34 Auger (working tool)

36 Drive chain

3 8 Conveyor belt (scraper belt) 20

• *

t··

Claims (22)

1. Drive system for work machines, in particular for road pavers, characterized in that the drive system has a power-split transmission, wherein at least two outputs of the paver are connected to a common transmission branch. 2. Drive system according to claim 1, characterized in that the common transmission branch is a main transmission ( 28 ). 3. Drive system according to claim 1 or 2, characterized in that at least one travel drive ( 18 ) and at least one drive for a conveyor belt ( 38 ) are connected to a common drive shaft ( 24 ). 4. Drive system according to claims 1 to 3, characterized in that the power-split transmission has at least one three-shaft transmission, wherein the main transmission ( 28 ) and the at least one secondary transmission ( 32 ) are connected via a three-shaft transmission. 5. Drive system according to claim 4, characterized in that the three-shaft transmission is a summing transmission ( 20 ). 6. Drive system according to claims 1 to 5, characterized in that the main transmission ( 28 ) is a mechanical transmission or an electric transmission. 7. Drive system according to claims 1 to 6, characterized in that the at least one auxiliary transmission ( 32 ) is a hydrostatic transmission or an electric transmission or a hydrodynamic transmission or a pneumatic transmission or a mechanical transmission. 8. Drive system according to claims 1 to 7, characterized in that the drive system has at least one drive shaft and/or one drive chain ( 36 ). 9. Drive system according to claim 8, characterized in that the drive shaft is a cardan shaft ( 14 ). 10. Drive system according to claims 1 to 9, characterized in that the drive system has drives for at least one chassis and/or at least one conveyor belt ( 38 ) and/or at least one auger ( 34 ) and/or at least one bunker wall cylinder and/or at least one leveling cylinder and/or at least one screed lifting cylinder and/or at least one screed telescoping cylinder and/or compaction devices. 11. Drive system according to claim 3 or 10, characterized in that the conveyor belt ( 38 ) is a scraper belt. 12. Drive system according to claims 1 to 11, characterized in that the drive system has an internal combustion engine as primary drive. 13. Drive system according to claim 12, characterized in that the internal combustion engine is a diesel engine ( 10 ). 14. Drive system according to claims 1 to 13, characterized in that the drive system has a central transfer case ( 26 ). 15. Drive system according to claim 14, characterized in that the central transfer case ( 26 ) is a modified pump transfer case which has a mechanical output and at least one output for a hydrostatic pump ( 12 ). 16. Drive system according to claims 1 to 15, characterized in that several outputs use a common transmission branch of a power-split transmission as the main transmission ( 28 ). 17. Drive system according to claim 16, characterized in that a common drive shaft ( 24 ) is connected to at least one drive for a conveyor belt ( 38 ) and at least one travel drive. 18. Drive system according to claim 16 or 17, characterized in that the main transmission ( 28 ) and the secondary transmission ( 32 ) are interconnected via summing transmissions ( 20 ). 19. Drive system according to claim 18, characterized in that the input speeds of the summing gears ( 20 ) are designed such that the main gear side input shaft forms the total power shaft in the working cycle of the paver. 20. Drive system according to claim 18, characterized in that the hydrostatic auxiliary transmissions ( 32 ) are connected to constant pumps. 21. Drive system according to claim 18, characterized in that the input speeds of the summing gears ( 20 ) are designed such that the main gear input shaft and the auxiliary gear input shaft form partial power shafts in the transport gear of the paver. 22. Drive system according to claim 21, characterized in that conveyor belts ( 38 ) and screws ( 34 ) are designed to be mechanically stopped.