WO2012004173A2

WO2012004173A2 - Continuous hydrostatic-mechanical power splitting transmission, method for operating such a power splitting transmission, and wheel loader comprising such a power splitting transmission

Info

Publication number: WO2012004173A2
Application number: PCT/EP2011/060944
Authority: WO
Inventors: Markus Liebherr; Peter Dziuba; Josef HÄGLSPERGER; Erich Eckhardt; Patrick Wohlhauser; Franz-Josef Schwede
Original assignee: Mali Holding Ag
Priority date: 2010-07-09
Filing date: 2011-06-29
Publication date: 2012-01-12
Also published as: WO2012004173A3; EP2591250A2; RU2013105451A

Abstract

The invention relates to a continuous hydrostatic-mechanical power splitting transmission (40) for a utility vehicle, in particular a wheel loader, in which power splitting transmission (40) the power output by an internal combustion engine (20) to a drive shaft (21) is divided by means of a planetary drive (22) to a mechanical branch (26, 29) and a hydrostatic branch (H1, H2) and is added up on the output side with the aid of summation means (41), wherein the hydrostatic branch (H1, H2) comprises at least one first hydrostatic unit (H1) which has an adjustable capacity and operates as a pump (P), and at least one second hydrostatic unit (H2) which has an adjustable capacity and operates as a motor (M), said hydrostatic units being hydraulically connected to each other, wherein a forward travel range (V) and a reverse travel range (R) are provided. In such a power splitting transmission, a compact design and, at the same time, a high starting torque and a wide speed range during forward and reverse travel are achieved in that both the forward travel range (V) and the reverse travel range (R) can be continuously crossed merely by adjusting the capacities of the hydrostatic units (H1, H2), in that two second hydrostatic units (H2) are provided, which operate as motors (M), and in that a reversing gearbox (32, 33, 34) is provided in order to change between the forward travel range (V) and the reverse travel range (R).

Description

Stepless hydrostatic-mechanical power split transmission, method for operating such a power split transmission, and wheel loader with such a power split transmission

The present invention relates to the field of vehicle drives. It relates to a continuously variable hydrostatic-mechanical power split transmission according to the preamble of claim 1, which is preferably intended for use in wheel loaders.

For earthmoving work but also for the absorption and transport of goods or other objects wheel loaders are used on a large scale and in the most diverse performance classes because they are fast and agile and are characterized by a high degree of flexibility. An exemplary wheel loader of a higher performance class, as it is known from US D540352, is shown in Fig. 1 in the side view. The wheel loader 1 0 of FIG. 1 comprises a front part 1 1 and a H interteil 1 2, which are pivotable for steering the vehicle against each other about a vertical pivot axis. In the front part 1 1, a front axle 1 3 is arranged with corresponding wheels, in H interteil 1 2 A H interachse 1 4th

At the front part 1 1, a hydraulically movable arm 1 8 is arranged at the front end of a hydraulically movable blade 1 6 is attached. A part of the hydraulic system can be seen and designated by the reference numeral 1 7. Between the two axes 1 3 and 14, a cabin 1 9 is provided for the driver. The wheel loader 10 is driven by an internal combustion engine 20, which is arranged behind the rear axle 1 4 for reasons of weight compensation. From the driven rear axle 14 a propeller shaft 1 5 runs to the front axle 1 3, which is also driven. To steer the vehicle, the front part 1 1 is hydraulically pivoted relative to the H interteil 1 2.

Such a wheel loader 1 0 has just in Erdbewegungsarbeiten partially greater distances in both forward drive and in reverse drive. Furthermore, if For example, the scoop 1 6 is pushed to receive soil in the ground, a high initial torque needed to overcome the resistance during insertion of the blade 1 6. Overall, therefore, there is a desire to have a high torque at the wheels available at the beginning of the driving range and to be able to cover a large speed range as possible without traction interruption both in forward drive and in reverse.

From document WO 2009 / 047036A1 a power split transmission with a hydrostatic power branch and a mechanical power branch is known which should be suitable for wheel loaders via a first drive range clutch a first drive range and a second drive range clutch a second drive range and a clutch for reversing a reverse range to Provides. The hydrostatic power branch is formed by two hydrostats operating as pump and motor, which are only synchronously adjustable with each other via a common component. The subdivision of the forward driving range by mechanical transmission means in a first and second driving range is mechanically complex. The positively coupled adjustment of the two hydrostats leads to severe limitations of the working area.

The same applies to the power split transmission from WO 2009 / 047037A1, WO 2009 / 047038A1 and WO 2009 / 047042A1.

The publication DE 2335629 discloses a drive device, in particular for agricultural and construction-use vehicles, which operates with a hydrostatic-mechanical power split and has a hydrostatic primary machine and two hydrostatic secondary machines in the hydrostatic power branch, which are fixedly coupled to one another via a common shaft , This known drive device completely dispenses with mechanical switching means. The transition between reverse and forward is thereby by changing the direction of rotation of the secondary machinery causes. The disadvantage here is that the speed range for reversing only about half as large as in the forward drive.

It is therefore an object of the present invention to provide a power split transmission, in particular for wheel loader, which is simple and compact, provides a high initial torque is available and covers a largely equal speed range when driving forward and reversing. It is a further object of the invention to provide a method for operating such a power split transmission, as well as a wheel loader with such a transmission.

The objects are achieved by the features of claims 1, 7 and 9.

In the case of the power split transmission according to the invention, the power delivered by an internal combustion engine to a drive shaft is distributed via a planetary drive to a mechanical branch and a hydrostatic branch and summed on the output side with the aid of summation means, the hydrostatic branch having at least one first pump operating volume in the displacement volume or conveying volume adjustable hydrostats and at least one second, acting as a motor, adjustable in displacement volume Hydrostat, which are hydraulically connected to each other, wherein a forward drive range and a reverse range are provided. It is characterized in that both the forward drive range and the reverse drive range are steplessly passable exclusively by adjusting the displacement volumes of the hydrostatic drives, that two second hydrostatic drives are provided which operate as motors and that a reversing drive is provided for changing between the forward drive range and the reverse drive range is.

An embodiment of the power split transmission according to the invention is characterized in that the reversing gear at the output of the power split transmission bes is arranged, and that the reversing comprises a reversing clutch with which the summed power can be given either via a first drive unit for forward drive or a second drive unit for the reverse drive to an output shaft. H hereby a particularly compact construction of the transmission is made possible.

However, it is also conceivable that the reversing gear is arranged at the input of the power branching transmission, and that the reversing gear comprises a reversing clutch with which the input power either via a first drive unit for forward drive or a second Cetriebeein unit for reversing on the Power branching gear can be given.

Another embodiment of the power split transmission according to the invention is characterized in that the two second hydrostats have the same design, that the two second hydrostats each have a maximum displacement that corresponds to the maximum displacement of the first hydrostat, and that the two second hydrostats are synchronously adjustable. As a result, a high torque at the beginning of the driving range is available.

Another embodiment of the power split transmission according to the invention is characterized in that the two second hydrostats are connected to each other in a rotationally fixed manner via a common shaft and that the common shaft acts as a summation shaft for the summation of the powers of the two power branches. This measure also reduced space requirements.

Another embodiment of the power split transmission according to the invention is characterized in that the hydrostats are designed as swivellable oblique-axis hydrostats in wide-angle technology and in particular in each case pivoting having from 0 ° to at least 45 °. In this way, a high efficiency can be achieved over a wide speed range.

Another embodiment of the inventive power split transmission is characterized in that the drive shaft is guided as a central shaft through the transmission and drives at the output of the transmission arranged pump units.

The inventive method for operating a power split transmission according to the invention is characterized in that to achieve a continuous forward range before starting first the displacement or delivery volume of the first Hydrostaten to zero and the displacement of the second Hydrostaten is set to maximum, that in a first phase the sip volume of the second hydrostats is kept at maximum and the sip volume of the first hydrostate in the forward direction is increased until it reaches its maximum in the forward direction, and in a second phase the sip volume of the first hydrostate is maintained at its maximum and the sump volume of the second hydrostats is maintained Maximum is reduced to zero.

An embodiment of the method according to the invention is characterized in that to achieve a continuous reverse range of the direction of rotation at the input or output of the power split transmission is reversed by a reversing, and that is reversed in the direction of rotation of the stepless forward range.

The wheel loader according to the invention is equipped with a front axle and a H interachse, as well as arranged between two axles cabin and an arranged behind the rear axle combustion engine. It is characterized in that in front of the internal combustion engine in the region of the H interachse a power-split transmission connected to the internal combustion engine is provided according to the invention. An embodiment of the wheel loader according to the invention is characterized in that the H interachse of the wheel loader is driven via the power split transmission.

An embodiment of the wheel loader according to the invention is characterized in that the front axle of the wheel loader is also driven via a cardan shaft.

The invention will be explained in more detail below in connection with the drawing with reference to embodiments. Show it

Fig. 1 in side view of an exemplary wheel loader, as from the prior

Technik and is suitable for the installation of the power split transmission according to the invention;

2 shows the transmission diagram of a power split transmission according to an embodiment of the present invention;

Fig. 3 based on three sub-figures 3a), 3b) and 3c) the adjustment of the hydrostats of the power split transmission of Figure 2 for sweeping the forward drive range, wherein for the sake of simplicity, only one of the two second hydrostat is shown. and

Fig. 4 in a comparable to Fig. 3 representation the adjustment of the hydrostatic at

Reverse drive without use of reversing gear.

In Fig. 2, the transmission diagram of a power split transmission according to an embodiment of the present invention is shown. The power split transmission 40 is connected via a drive shaft 21 with an internal combustion engine 20, which is symbolized by an indicated crankshaft. The drive shaft 21 is rotatably connected to the planet carrier 23 of a planetary drive 22, which has a sun gear 25, 26, a Planetary gear 24 and a ring gear 27 includes. About the ring gear 24 and a gear 28 is a first Hydrostat H l, which operates as a pump P, with the planetary gear 22 in operative connection.

The part 26 of the sun gear 25, 26 meshes with a gear 29 which is non-rotatably mounted on a summation shaft 41. The summation wave 41 is at the same time the common connecting shaft of two second hydrostatic units H2, which operate as motors M and are supplied with hydraulic pressure fluid from the first hydrostatic unit H1 via lines which are not shown. On the summation shaft 41, a second gear 31 is further arranged rotatably, which meshes with a gear 30 which is connected via a hollow shaft with a reversing coupling 32. The first and second hydrostats H 1, H 2 are preferably of the oblique-axis type and implemented in a wide-angle technique and can be carried out as described and shown in the publication WO 2006 / 042434A1.

The Reversierkupplung 32 switches the power taken from the summation of wave 41 selectively via a first Cetriebeeinheit 33 or a second Cetriebeeinheit 34 on a propeller shaft 35, which connects the provided with a bevel gear 36 H interaxis HA with the front axle VA. The first Cetriebeeinheit 33 is designed for the forward drive V, the second Cetriebeeinheit 34 by reversing the direction of rotation for the reverse drive R. The power split transmission 40 is preferably disposed immediate area of the rear axle HA and can be combined with the bevel gear 36 to a structural unit.

If the reversing is performed alternatively at the input of the power split transmission 40 (not shown in the figures), the input of the reversing clutch 32 is connected to the drive shaft 21 and switches the power either over the first Ce gear unit 33 or the second gear unit 34 on the planet carrier 23 of the power branching gear 40th

The sun gear 25, 26 of the planetary drive 22 is connected via a hollow axle. Through this hollow axle, as well as through the other hollow shaft which connects the gear 30 with the reversing coupling 32 extends in extension of the drive shaft 21, a central shaft 37 through the transmission and drives two pump units 38 and 39, which the hydraulics of the wheel loader with hydraulic Supply pressure fluid.

With the power split transmission 40 of FIG. 2, a continuous forward range and a continuously variable reverse range can be realized. The associated adjustments of the hydrostats H 1 and H 2 are shown in FIG. 3 (forward travel range). For the sake of simplicity, only one of the two second hydrostats H2 is shown and the reversing gearbox is completely omitted. The forward drive range begins with the standstill shown in FIG. 3a), in which the first hydrostat H l is not pivoted and thus has a vanishing displacement volume or delivery volume, while the second hydrostat H2 is fully (approximately 45 °) pivoted and the maximum absorption volume Has. For starting, the first hydrostat is swung out to the responsible for the forward movement upper side, whereby the vehicle is picking up speed. The maximum deflection of the second hydrostatic units H2 ensures a high torque (high tensile force) at a low rotational speed. If the first hydrostat H l is fully deflected (FIG. 3 b), it is held there and the second hydrostatic units H 2 are swung back inwards to the zero position (vanishing displacement volume) (FIG. 3 c). The decreasing absorption volume in the second hydrostat H2 ensures ever higher rotational speed with decreasing torque.

In the normal reverse drive the same adjustment cycle as shown in FIG. 3 is run through, with the difference that the reversing gear 32, 33, 34 switched to reverse drive is (the reversing clutch 32 connects to the responsible for the reverse drive R Cetriebeeinheit 34 ago). In this way, the entire speed range of the forward drive is also available for the reverse drive.

However, it is also conceivable to effect a limited reversing without actuation of the reversing clutch 32 by passing through an adjustment cycle according to FIG. 4. In the reverse drive according to FIG. 4, the same standstill configuration (FIG. 4a) is assumed as in the forward drive (FIG. 3a). However, the first hydrostat H l is pivoted in the opposite direction until it has reached its maximum deflection (FIG. 4 b). The fully deflected second hydrostatic units H2 are then pivoted back into the zero position (FIG. 4c). This results in a reversal of the direction of rotation of the second hydrostat H2, which makes the use of the reversing gear superfluous.

With a power split transmission 40 of the type described, for example, a power of 90 kW can be transmitted. The wheel loader 1 0 reaches a speed of 50 km / h at a speed of the internal combustion engine 20 of 2200 U / min. In this case, the pumping first hydrostat H 1 has, for example, a maximum displacement volume or delivery volume of 1 60 cm ³ , and the hydrostatic units H 2 working as motors each have a maximum absorption volume of likewise approximately 1 60 cm ³ . Of course, if the hydrostat is designed accordingly (eg with several 1 00 cm ³ displacement), also significantly higher power can be transmitted. It is therefore quite conceivable that such a transmission is also used in ship propulsion or track vehicles.

Since the absorption volume of the first hydrostat H l and the displacement of the second hydrostatic units H2 are adjustable independently of one another, it is possible and advantageous that the adjustment of the displacement volumes takes place in accordance with the high pressure prevailing in the hydraulic circuit of the hydrostats. It is particularly advantageous if, in a starting region, the second hydrostatic units H2 are operated in the region of their maximum absorption volume, and if the intake volume of the first hydrostatic unit H1 is controlled to control the traction force.

In particular, this can be done by adjusting the displacement of the first hydrostatic valve H l via a spring-centered actuating system subjected to a speed-proportional control pressure, and to control the first hydrostatic valve H 1 in such a way that the high-pressure-proportional actuating forces are combined with the spring-centered actuating system and the speed-proportional control pressure, the desired tensile force or torque characteristic result.

LIST OF REFERENCE NUMBERS

1 0 Wheel loader

1 1 front part

1 2 rear part

1 3 front axle

14 interchanges

1 5 propshaft

1 6 scoop

1 7 Hydraulics

1 8 arm

1 9 cabin

20 internal combustion engine

21 drive shaft

22 planetary drive

23 planet carrier

24 planetary gear 25.26 sun wheel

27 ring gear

28-31 gear

32 Reversing clutch

33.34 Cetriebeeinheit

35 cardan shaft

36 bevel gearbox

37 central shaft

38.39 pump unit

40 power split transmissions (stepless, hydrostatic-mechanical)

41 summation wave

H 1 .H 2 hydrostat (e.g., sloped axis type)

HA H interaxis

M engine

P pump

R reverse drive

Front axle VA

V forward drive

Claims

claims

1 . Stepless hydrostatic-mechanical power split transmission (40) for a commercial vehicle, in particular a wheel loader (1 0), wherein power split transmission (40) from an internal combustion engine (20) to a drive shaft (21) output power via a planetary gear (22) to a mechanical Branch (26, 29) and a hydrostatic branch (H l, H2) is divided and summed with the aid of summation means (41) on the output side, wherein the hydrostatic branch (H l, H2) at least a first, as a pump (P) working , in the displacement volume or delivery volume adjustable Hydrostaten (H l) and at least a second, operating as a motor (M), adjustable in displacement hydrostatic (H2), which are hydraulically connected to each other, wherein a forward driving range (V) and a reverse range (R ) are provided, characterized in that both the forward driving range (V) and the reverse range (R) exclusively dur Adjusting the displacement volumes of the hydrostats (H l, H 2) are steplessly passable, that two second hydrostats (H 2) are provided, which operate as motors (M), and that for switching between the forward driving range (V) and the reversing range (R) a reversing gear (32, 33, 34) is provided.

2. power split transmission according to claim 1, characterized in that the reversing gear (32, 33, 34) at the output of the power split transmission (40) is arranged, and that the reversing gear comprises a reversing clutch (32) with which the summed power either via a first Cetriebeeinheit (33) for the forward travel (V) or via a second gear unit (34) for the reverse drive (R) on an output shaft (35) can be given.

3. power split transmission according to claim 1, characterized in that the reversing gear (32, 33, 34) is arranged at the input of the power split transmission (40), and that the reversing gear comprises a reversing clutch (32) with which the input power either via a first Cetriebeeinheit ( 33) for the forward travel (V) or via a second gear unit (34) for the reverse drive (R) can be given to the power split transmission (40).

4. power split transmission according to one of claims 1 -3, characterized in that the two second hydrostatic units (H2) are identical, that the two second hydrostatic units (H2) each have a maximum displacement that the maximum displacement of the first Hydrostaten (H l ), and that the two second hydrostats (H2) are synchronously adjustable.

5. power split transmission according to claim 4, characterized in that the two second hydrostat (H2) via a common shaft are rotatably connected to each other, and that the common shaft acts as a summation wave (41) for the summation of the power of the two power branches.

6. power split transmission according to one of claims 1 -5, characterized in that the hydrostat (H l, H2) are designed as a swiveling bent-axis hydrostat in wide-angle technology and in particular each have pivoting ranges ranging from 0 ° to at least 45 °.

7. power split transmission according to one of claims 1 -6, characterized in that the drive shaft (21) as a central shaft (37) is guided through the transmission and arranged at the output of the transmission pump units (38, 39) drives.

8. A method for operating a power split transmission according to one of claims 1 -7, characterized in that to achieve a continuous forward range before starting first, the displacement of the first Hydrostaten (H l) to zero and the displacement of the second Hydrostaten (H2) to maximum is made, that in a first phase, the displacement of the second Hydrostaten (H2) held at the maximum and the displacement of the first Hydrostaten (H l) is increased in the forward direction until it reaches its maximum in the forward direction, and that in a second phase Suction volume of the first Hydrostaten (H l) is kept at the maximum and the sip volume of the second Hydrostaten (H2) is reduced from the maximum to zero.

9. The method according to claim 8, characterized in that for the realization of a continuous reverse range of rotation at the input or output of the power split transmission by the reversing gear (32, 33, 34) is reversed, and that is reversed in the direction of rotation of the stepless forward range.

10. wheel loader (10) having a front axle (1 3) and a rear axle (14), a arranged between the two axles cabin (1 9) and behind the rear axle (14) arranged internal combustion engine, characterized in that in front of the internal combustion engine (20 ) in the region of the rear axle (14) with the internal combustion engine (20) connected to power split transmission (40) is provided according to one of claims 1-6.

1 1. Wheel loader according to claim 1 0, characterized in that via the power split transmission (40), the rear axle (14) of the wheel loader (1 0) is driven.

2. Wheel loader according to claim 1 1, characterized in that via a propeller shaft (35) and the front axle (1 3) of the wheel loader (1 0) is driven.