UTILITY VEHICLE, IN PARTICULAR MOTOR TRUCK, HAVING AT LEAST ONE DOUBLE-AXLE UNIT

Abstract

A utility vehicle, in particular a motor truck or motor bus, is provided having at least one double-axle unit. The double-axle unit has a driven first axle and a driven second axle, wherein the first axle can be driven by way of a mechanical drivetrain and the second driven axle can be driven by at least one hydraulic motor of a hydrostatic drive.

Claims

1. A utility vehicle comprising: at least one double-axle unit having a first driven axle and a second driven axle, wherein the first driven axle is driven by way of a mechanical drivetrain and the second driven axle is driven by at least one hydraulic motor of a hydrostatic drive.

2. The utility vehicle according to claim 1, wherein the hydrostatic drive further comprises a hydraulic pump driven by a drive engine and the at least one hydraulic motor which is connected to the hydraulic pump by way of hydraulic working lines.

3. The utility vehicle according to claim 1, wherein the first axle is the front axle of the double-axle unit in relation to a forward direction of travel of the vehicle, and the second axle is the rear axle of the double-axle unit in relation to the direction of travel.

4. The utility vehicle according to claim 1, wherein the hydraulic motor is flange-mounted onto the outside of the axle housing of the second drive axle, and a drive shaft of the hydraulic motor is operatively connected to an axle differential, arranged in the axle housing, of the second driven axle.

5. The utility vehicle according to claim 4, wherein the axle differential is a bevel-gear differential gearbox, including a crown gear, a pair of axle bevel gears and a pair of differential bevel gears, and wherein a drive gear seated on the drive shaft of the hydraulic motor is in engagement with the crown gear.

6. The utility vehicle according to claim 1, wherein the hydraulic motor is arranged in the axle housing of the second driven axle, and a part, which is rotatable coaxially with respect to the second axle, of the hydraulic motor is operatively connected to a cage of an axle differential of the second driven axle.

7. The utility vehicle according to claim 6, wherein in the cage, there is mounted an axle bolt which bears differential gears, wherein said differential gears mesh with axle shaft gears arranged on wheel drive shafts, and said gears are in the form of bevel gears; and

8. The utility vehicle according to claim 6, wherein the hydraulic motor is a radial piston motor having an outer, static cam ring and having an inner, rotating cylinder housing which is connected rotationally conjointly to the cage.

9. The utility vehicle according to claim 1, further comprising two hydraulic motors, wherein the second driven axle has two wheel drive shafts which are arranged coaxially and which, are connected rotationally conjointly at a wheel side to a wheel and, at the other end, are operatively connected to one of the two hydraulic motors.

10. The utility vehicle according to claim 9, wherein the two hydraulic motors are arranged in a central region of the axle housing of the second axle.

11. The utility vehicle according to claim 9, wherein the two hydraulic motors are arranged on different wheel-side end regions of the axle housing of the second axle.

12. The utility vehicle according to claim 11, wherein the two hydraulic motors are designed as wheel hub motors.

13. The utility vehicle according to claim 11, wherein the two hydraulic motors are arranged offset with respect to the respective wheel hub in an axial direction and are operatively connected to the wheels by way of an external planetary gear set.

14. The utility vehicle according to claim 1, wherein instead of a hydrostatic drive for the second axle, an electric drive is provided, such that the second driven axle is driven by at least one electric motor.

15. The utility vehicle according to claim 1, wherein the first or second axle of the double-axle unit is case designed for equal payloads.

16. The utility vehicle according to claim 1, wherein the first or second axle of the double-axle unit have similar tire configurations.

17. The utility vehicle according to claim 1, wherein the first or second axle of the double-axle unit have a spacing of less than 2 metres in the direction of travel of the utility vehicle.

18. The utility vehicle according to claim 1, wherein the first or second axle of the double-axle unit is designed as hypoid or external planetary axles.

19. The utility vehicle according to claim 1 comprising an admissible maximum speed of over 60 km/h.

20. The utility vehicle according to claim 1 comprising a wheel brake device which acts on at least two wheels of the utility vehicle.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] FIG. 1 shows a schematic plan view of a conventional double-axle unit;

[0028] FIG. 2 is a schematic illustration of a drive system for a motor vehicle according to the prior art with hydraulically driven wheel motors; and

[0029] FIGS. 3 to 6 are schematic illustrations of a hydraulically driven axle of a double-axle unit according to various embodiments of the present disclosure.

[0030] Identical or functionally equivalent elements are denoted by the same reference designations throughout the figures.

DETAILED DESCRIPTION

[0031] The aspects, shown in the figures, of the embodiments which, in FIGS. 1 and 2, relate to the prior art and, in FIGS. 3 to 6, relate to the present disclosure partially correspond, wherein similar or identical parts are denoted by the same reference designations and, for the explanation thereof, reference will also be made to the description of one or more other embodiments in order to avoid repetitions.

[0032] FIG. 3 shows a cross-sectional, highly schematic diagrammatic illustration of one of the two driven axles 30 of a double-axle unit of a utility vehicle. In the present case, the axle 30 constitutes the rear axle of the double-axle unit as viewed in a forward direction of travel. The front axle (not shown) is designed in a manner known per se and is driven by way of a mechanical drivetrain of the utility vehicle, as shown for example in FIG. 1.

[0033] The equalization of axle load between the two driven axles may be realized either by way of a pivotable central bearing, that is to say the axles are connected to one another by way of a rocker or are pivotable relative to one another by way of a central bearing. These embodiments are known as so-called leaf-spring-mounted double-axle units. Alternatively, the double-axle unit may be designed as an air-spring-mounted double-axle unit.

[0034] In a manner known per se, the second axle 30 has two wheel drive shafts 15, 16, and an axle differential 13 which is arranged in between and which is in the form of a conventional bevel-gear differential gearbox, of which FIG. 3 shows only the drive gear, in the form of a crown gear 14, and the cage 15. In the cage 15 there is mounted an axle bolt which bears differential gears, wherein the differential gears mesh with axle shaft gears arranged on the wheel drive shafts (in each case not illustrated). The differential or axle shaft gears are in each case in the form of bevel gears. The vehicle wheels that are driven by the wheel drive shafts are likewise not illustrated. Furthermore, in order to place the emphasis on the hydrostatic drive according to the present disclosure, further components and parts that are arranged in the axle housing, such as for example brackets, oil sump, baffle plates etc., which may be designed in the conventional manner, are not illustrated in FIG. 3 or in the following figures.

[0035] By contrast to the embodiment of the double-axle unit that is shown in FIG. 1 and known from the prior art, no drive-through from the first axle to the second axle 30 for the purposes of driving the crown gear 14 and thus the second axle 30 is provided.

[0036] Instead, the second driven axle 30 is driven by a hydraulic motor 20 of a hydrostatic drive. The hydraulic motor 20 is flange-mounted on the outside of the axle housing 12 of the second axle 30 at a flange region 19. A drive shaft 17 that is driven by the hydraulic motor has, on its distal end, a drive bevel gear 18 which meshes with the crown gear 14 of the axle differential 13, arranged in the axle housing 12, of the second axle 30. The hydraulic motor 20 is integrated into a closed hydrostatic circuit such as is known per se, for example analogously to the example shown in FIG. 2, wherein a hydraulic pump is mechanically driven by way of the drivetrain 4 of the vehicle and is hydraulically connected to the hydraulic motor 20 by way of fluid lines.

[0037] The prior art has disclosed various ways in which the hydraulic pump, for example a fixed displacement hydraulic pump, can be driven by way of the mechanical drivetrain. For example, the hydraulic pump may be driven by wheels and connected to the wheels of a mechanically driven axle via a fixed mechanical transmission ratio. A clutch, for example a multiplate powershift clutch, is provided between said axle and the fixed displacement hydraulic pump. In a further variant, it is for example possible for the internal combustion engine of the vehicle (or a crankshaft of the internal combustion engine) to be connected with driving action by way of a clutch to an input shaft of a power-splitting epicyclic gearbox. The epicyclic gearbox, for example in the form of a planetary gearbox, branches the power input via the input shaft into a hydrostatic power branch and a mechanical power branch. In particular, a first output shaft of the epicyclic gearbox directly drives a differential gearbox of the first axle of the double-axle unit and thereby forms the mechanical power branch. A second output shaft of the epicyclic gearbox drives, via a gearwheel stage, a hydraulic pump, and thus forms the hydrostatic power branch. The hydraulic pump in turn drives the one or more hydraulic motors 20 via hydraulic lines. The hydraulic motor 20 can be activated and deactivated by way of a control valve. Furthermore, a feed pump may be arranged so as to compensate internal and external leakage quantities that arise. In general, external leakage quantities are to be understood to mean quantities which are not evident to the naked eye. Hydraulic motor 20 and the hydraulic pump are in each case in the form of hydrostatic radial piston machines.

[0038] FIGS. 4 to 6 illustrate further possible embodiments of the present disclosure. Here, components with identical reference designations correspond to the components of FIG. 3, and will not be described separately. Below, only the differences and special features of the embodiments will be emphasized.

[0039] A special feature of the embodiment shown in FIG. 4 lies in the fact that the hydraulic motor 20 is not flange-mounted on the outside of the axle housing 12 but is arranged in the interior of the axle housing 12 of the second axle 40. Here, the hydraulic motor 20 replaces the crown gear 14 and, instead, directly drives the cage 15 of the axle differential 13. The hydraulic motor 20 is a radial piston motor having an outer, static cam ring and an inner, rotating cylinder housing which is connected rotationally conjointly to the cage 15 and which can thus set the latter in rotational motion. In turn, an axle bolt which bears differential gears is mounted in the cage 15, wherein said differential gears mesh with axle shaft gears which are arranged on wheel drive shafts and which are each in the form of bevel gears. The drive shaft 17 and the drive bevel gear 18 are therefore likewise not required in the embodiment of FIG. 4.

[0040] A special feature of the embodiment shown in FIG. 5 lies in the fact that two hydraulic motors 20 are mounted in the centre of the axle housing 12 of the second axle 50. The two wheel drive shafts 15a, 16a are in the form of splined shafts and are connected rotationally conjointly at a wheel side to a wheel and, at the other end, are operatively connected to one of the two hydraulic motors 20. The axle differential is omitted. Each of the wheel drive shafts 15a, 16a is thus driven by one of the two hydraulic motors 20. The operative connection between hydraulic motor 20 and the wheel drive shaft may optionally also be realized via an external planetary gear set in order to realize an increase in torque.

[0041] A special feature of the embodiment shown in FIG. 6 lies in the fact that the two hydraulic motors 20 are arranged in each case on different wheel-side end regions 12a, 12b of the axle housing 12 of the second axle 60. The wheel drive shafts 15b, 16b are again in the form of splined shafts, but are now of correspondingly shorter form. In this embodiment, too, an axle differential is no longer required, because the hydraulic motors 20 can drive the two wheel drive shafts 15b, 16b in each case independently of one another.

[0042] The hydraulic motors 20 may transmit their drive power to the wheels optionally with or without an external planetary gear set. The two hydraulic motors may be arranged inwardly offset with respect to the respective wheel hub in an axial direction. The two hydraulic motors may however also be designed as wheel hub motors, that is to say may be positioned directly on the wheel hub, analogously to the example described in FIG. 2 and in document EP 1 886 861 A2.

[0043] Even though the present disclosure has been described with reference to particular exemplary embodiments, it is evident to a person skilled in the art that various changes may be made, and equivalents used as substitutes, without departing from the scope of the present disclosure. Furthermore, numerous modifications may be made without departing from the associated scope. Consequently, the present disclosure is not intended to be restricted to the exemplary embodiments disclosed, but rather is intended to encompass all exemplary embodiments which fall within the scope of the appended patent claims. In particular, the present disclosure also claims protection for the subject matter and the features of the subclaims independently of the claims referred back to.

LIST OF REFERENCE DESIGNATIONS

[0044] 1 Wheel [0045] 2 Drive shaft [0046] 3 Front axle [0047] 4 Drivetrain [0048] 5 Main pump [0049] 6 Feed pump [0050] 7 Control valve [0051] 8 Pressurized-oil distributor [0052] 9 Front axle of the double-axle unit [0053] 10 Rear axle of the double-axle unit [0054] 11 Drive-through [0055] 12 Axle housing [0056] 13 Axle differential, e.g. bevel-gear differential gearbox [0057] 14 Drive gear of the axle differential, e.g. crown gear [0058] 15 Cage [0059] 15, 15a, 15b, 16, 16a, 16b Wheel drive shaft [0060] 17 Drive shaft [0061] 18 Drive bevel gear [0062] 19 Flange region [0063] 20 Hydraulic motor [0064] 30, 40, 50, 60 Second, hydrostatically driven axle of the double-axle unit [0065] RM Hydraulic wheel-hub motors