Hydrostatic drive with gearbox

Abstract

Hydrostatic drive (1) for vehicles, wherein the hydrostatic drive (1) comprises a first hydraulic circuit for providing the drive energy for at least one axial piston motor (2) in a swashplate configuration, wherein the axial piston motor (2) provides a torque and a speed at an output shaft (30) depending on a helix angle or swivel angle (22) of the axial piston motor (2), and wherein a transmission (3) is included which has at least two switchable transmission stages, of which a first transmission stage or a second transmission stage can be coupled to the output shaft (30), wherein a swivel angle sensor (23) for detecting the helix angle or swivel angle (22) and a second hydraulic circuit for adjusting the helix angle or swivel angle (22) are included.swivel angle (22) is designed, wherein the second hydraulic circuit has a working pressure which is independent of the working pressure of the first hydraulic circuit and the tilt angle or swivel angle (22) can be adjusted via the second hydraulic circuit and the swivel angle sensor (23) to a value to provide a speed for synchronous switching from the first to the second gear stage and back, wherein the axial piston motor (2) is a large-angle motor type.

Description

[0001] The invention relates to a hydrostatic drive according to the preamble of claim 1 and a method for operating a hydrostatic drive according to the preamble of claim 8.

[0002] Hydrostatic drives are known from the prior art, for example, using an axial piston motor in the applicant's product "Compact Drive". Depending on the required driving task and power curve, such drives or motors can be equipped with gearbox units that provide a specific speed range at an output shaft, depending on the adjustment options of the hydraulic motor. Such configurations are known from the prior art, for example, in the applicant's product "Modul Drive". Furthermore, corresponding modular configurations are described in DE 10 2008 024 831 A1. The technology and function of an axial piston motor or swashplate variable displacement motor are also known to those skilled in the art.

[0003] From DE 10 2011 006 683 A1, a drive unit for a vehicle drive is known, comprising a transmission driven by an internal combustion engine and continuously variable by means of at least one adjusting device, and a mechanical transmission directly or indirectly connected thereto, in which at least two gear stages can be selected via a switching device, and an electronic control unit connected to both the adjusting device and the switching device, wherein the gear stages of the transmission can each be selected via non-synchronized, positive-locking clutches, and wherein the electronic control unit is connected to a braking device that can be actuated during a shifting operation of the transmission and to at least one of the adjusting devices, wherein the continuously variable transmission can be adjusted by means of the at least one adjusting device to such an extent thatthat torque relief can be achieved at a gearbox input shaft of the manual transmission.

[0004] From DE 199 01 443 B4, a drive train for a vehicle is known which comprises an internal combustion engine, a clutchless transmission with at least two gear ratios switchable by means of an electronic control unit and actuating devices, and a hydrostatic transmission whose hydraulic pump and hydraulic motor are connected in a closed circuit, wherein the speed of the hydraulic motor can be controlled as a function of a control signal to the actuating device of the hydraulic pump and / or to the actuating device of the hydraulic motor, which the control unit calculates by means of a setpoint specification via an accelerator pedal or as a function of the drive speed of the internal combustion engine, wherein the gear ratios can be switched by means of the actuating devices, wherein the control unit controls the actuating device of the hydraulic pump as well as the actuating devices for the transmission for its electronic synchronization by means of a characteristic curve.which represents the speed ratio of the hydraulic motor to the hydraulic pump as a function of a control signal to the adjustment device of the hydraulic pump for a load-free state of the transmission.

[0005] A disadvantage of the known hydrostatic drives is that the speed and / or force range available at an output shaft is limited by the possible variation of the axial piston motor or gearbox.

[0006] The object of the invention is therefore to improve hydrostatic drives according to the prior art, in particular to expand their operating conditions at the output shaft. Furthermore, the improvements should relate to the driving comfort and the economy of such drives.

[0007] According to the invention, this problem is solved by a hydrostatic drive for vehicles, according to the features of claim 1. The hydrostatic drive comprises a first hydraulic circuit for providing the drive energy for at least one axial piston motor in a swashplate configuration, wherein the axial piston motor provides a torque and a speed at an output shaft, depending on a swashplate angle or swivel angle of the axial piston motor. It further comprises a transmission having at least two switchable transmission stages, of which at least one first transmission stage or a second transmission stage can be coupled to the output shaft. It is provided that a swivel angle sensor for detecting the swashplate angle or swivel angle and a second hydraulic circuit for adjusting the swashplate angle or swivel angle are included.is designed with a swivel angle, wherein the second hydraulic circuit has a working pressure which is independent of the working pressure of the first hydraulic circuit and the tilt angle or swivel angle can be adjusted via the second hydraulic circuit and the swivel angle sensor to a value to provide a speed for synchronized switching from the first to the second gear stage and back, wherein the axial piston motor is a large-angle motor type.

[0008] The provision of a second hydraulic circuit, and the resulting decoupling of working and control pressure, enables a very precise and reproducible adjustment of the swivel angle, which is also detectable by the swivel angle sensor. The synchronization of the motor speed with the required switching speed achieved in this way provides a virtually seamless switching transition without the often associated jerky load changes and noise.

[0009] In a preferred embodiment, the swivel angle sensor and a hydraulic actuator for adjusting the swivel angle form a control loop. By incorporating the swivel angle detected by the sensor as a disturbance variable in this control loop with the actuator, a very precise and reproducible adjustment of the swivel angle, and thus of the motor speed, is possible. This, in turn, allows for precise synchronization with the speeds required during each switching operation. The switching operation can therefore be performed with virtually no wear.

[0010] Preferably, direct angle adjustment is achieved by means of a microcontroller with a precise angle sensor mounted directly on the angle adjustment mechanism. A proportional pressure reducing valve, decoupling the working and control pressures, enables direct (and therefore rapid) angle adjustment, thus allowing direct and continuous monitoring of the switching position or speed. The large-angle motor can be configured with a swivel angle between 0° and 45°. Large-angle motors offer a wide range of speed variations and are therefore particularly suitable for controlling gear stages for different driving tasks (1st stage, possibly a reduction gear for high power requirements; 2nd stage, possibly a gear reduction for high-speed movement).

[0011] In a further advantageous embodiment of the invention, the coupling means connects the output shaft positively to the first or second gear stage, in particular via a star-shaped shift claw, and is preferably lockable in the respective position by means of a shift cylinder. In a further preferred embodiment, the locking of the shift claw and thus of the shift stages is effected by an adapted geometry, in particular by a detent element, for example an undercut in the shift claw, preferably in a star-shaped shift claw.

[0012] The use of a positive-locking coupling is made possible by the precise synchronization of the rotational speed during the shifting process. This allows for a very short shift time with virtually no wear. The use of a star-shaped shift claw enables direct positive engagement in a rotationally symmetrical arrangement around the output shaft. The star-shaped shift claw is axially displaceable on the output shaft and can be moved from the positive engagement in the first gear stage to the second gear stage by means of a shift rod and a shift cylinder. For a more detailed explanation, please refer to the embodiment described later.

[0013] In a preferred embodiment, a gap is provided between an output gear of the first gear stage and an output gear of the second gear stage. This gap accommodates the coupling element without interference with both the first and second gear stages, enabling uncoupled neutral operation. Preferably, the coupling element can be locked in this position. Providing neutral operation is necessary, for example, for towing the hydrostatic drive.

[0014] The inventive method for operating a hydrostatic drive is characterized in that, when switching from the first gear stage to the second gear stage, the transmission is first disengaged from the first gear stage without torque, then the rotational speed is adjusted to the desired speed adapted to a given driving speed in the second gear stage, and the transmission is then engaged in the second gear stage without torque.

[0015] The hydrostatic drive is designed to include a first hydraulic circuit for providing drive energy to at least one axial piston motor in a swashplate design, wherein the axial piston motor provides a torque and a speed on an output shaft depending on a swashplate angle or swivel angle of the axial piston motor, and wherein a transmission is included which has at least two switchable transmission stages, of which at least one first transmission stage or a second transmission stage can be coupled to the output shaft.Furthermore, a swivel angle sensor is provided for detecting the swivel angle and a second hydraulic circuit for setting the swivel angle, wherein the swivel angle is set via the second hydraulic circuit and the swivel angle sensor to values ​​for providing a rotational speed corresponding to the process requirement for the speed in the switching process of the drive, wherein the second hydraulic circuit sets a change of the swivel angle by 10° in a maximum of one second, wherein the set swivel angle is detected via the swivel angle sensor.

[0016] By controlling the rotational speed through the precise adjustment of the swivel angle, the switching process is performed without torque, and therefore without a jerk during switching.

[0017] Preferably, the second hydraulic circuit has a working pressure that is set independently of the working pressure of the first hydraulic circuit and is preferably kept constant.

[0018] In this way, pressure fluctuations in the main circuit, which is responsible for the motor's power output, cannot affect the precision of the swivel angle and thus the precision of the set speeds. Such pressure fluctuations occur due to varying power demands and different swivel angle settings resulting from the varying displacement volume of the hydraulic motor. These influences are not noticeable in the separate second circuit.

[0019] It is also preferred that the swivel angle detected by the swivel angle sensor is included as a disturbance variable in the control loop of the actuator for the swivel angle in the second hydraulic circuit. By integrating the detected swivel angle into a control loop, a short-term, precise, and monitored adjustment of the speed at the hydraulic motor is possible in order to provide the desired synchronization during the shifting process between motor speed and the transmission stages.

[0020] In particular, this makes it possible for the second hydraulic circuit to adjust the swivel angle by 10° in a maximum of 0.5 seconds.

[0021] Due to the short switching time required for a smooth transition between gear stages, the clutch operation can be performed without torque, thus enabling a positive-locking clutch with virtually wear-free actuation. The short pivoting time is facilitated by the use of a separate hydraulic circuit. The application of a control loop – as described above – provides the necessary precision for setting the target angle.

[0022] To further improve performance, it is advantageous to compensate for or regulate changes in the viscosity of a hydraulic fluid, particularly hydraulic oil, in at least one hydraulic circuit by means of measuring its temperature. This allows for the compensation of deviations in the desired precision of the speed control, which typically occur during the operation of an unmonitored system or motor. Such deviations can then be incorporated into the disturbance variable of the control loop.

[0023] A torque-free switching process, as defined in the invention, is a switching process without any noticeable jerk or abrupt movement, in which the drive system switches from one switching stage to the other without any significant perceptible load change and the load is only applied after the switching process has been completed.

[0024] For further explanation, the invention is presented using the exemplary embodiment described below. However, the invention is not limited to this exemplary embodiment; rather, it encompasses all those embodiments that make use of the features of the independent claims.

[0025] They show Fig. 1: a partially cutaway view of a slant-axis adjustment motor with attached two-stage gearbox; Fig. 2: a cutaway view of a two-stage gearbox with the first gear stage engaged; Fig. 3: a cutaway view of a two-stage gearbox with the second gear stage engaged; Fig. 4: A cutaway view of a two-stage gearbox with the gearbox stage disengaged.

[0026] In detail, it shows Fig. 1 A possible assembly of a hydrostatic drive 1, which comprises a swashplate variable speed motor 2 and a 2-stage gearbox unit 3. Here, the swashplate variable speed motor is also referred to as an axial piston motor and the 2-stage gearbox unit 3 is also referred to as a gearbox.

[0027] The swashplate adjustment motor 2 drives a motor input shaft 4 for the 2-stage gearbox 3, which is connected to an input spur gear ZE1 of the first gearbox stage and an input spur gear ZE2 of the second gearbox stage.

[0028] The swashplate variable speed motor 2 comprises a plate 10 on its input shaft 4, with receiving devices for pistons 11 (only one piston is designated), which are pivotably mounted in the plate 10. The pistons 11 project into cylinder bores of a cylinder drum 12. The cylinder drum 12 can be pivoted about the pivot axis 13 by means of adjustment devices, in accordance with the known technology of a swashplate variable speed motor 2, in order to provide different speeds and torques. The cylinder drum 12 is arranged in a pivot housing 15 within a motor housing 16.

[0029] To provide a pivoting movement, an adjusting piston 21 for the pivoting angle 22 about the pivoting axis 13 is provided in a control cover 20. The pivoting angle 22 is detected by the pivoting angle sensor 23 and fed into a control loop for controlling the adjusting piston 21 as an actuator for the pivoting angle 22.

[0030] The two-stage gear unit 3 comprises an output shaft 30, which can be connected via coupling means to either an output spur gear ZA1 of the first gear stage or an output spur gear ZA2 of the second gear stage. The gear unit 3 is flanged to the swashplate adjustment motor 2 in its housing 31 via screws 32 and can be designed to be modularly interchangeable depending on requirements.

[0031] Further explanations regarding the components of the gearbox are provided in the Fig. 2 to 4 described.

[0032] The Fig. 2, Fig. 3 and Fig. Figure 4 shows the three available switching states of the transmission unit 3. Identical components are marked with the same reference symbols.

[0033] Fig. Figure 2 shows the engaged state of the first gear stage. The input shaft 4 of the swashplate adjustment motor 2 is connected to the input spur gears ZE1 and ZE2. These input spur gears ZE1 and ZE2, in accordance with the function of a spur gear transmission, engage with the output spur gears ZA1 and ZA2 and provide the gear ratio corresponding to the respective gear stage.

[0034] To provide the transmission of the first gear stage at the output shaft 30, the clutch mechanism 40, consisting of a shift fork 41 and shift jaws 42 arranged thereon, is brought into positive engagement with corresponding jaws 43 on the output spur gear ZA1 to enable torque transmission. Due to the desired positive engagement, the shifting process, i.e., the movement of the jaws 42 and 43 into the respective gaps 44 and 45, must be carried out almost without torque, which is achieved by adjusting the required engine speed and corresponding synchronization.

[0035] The movement of the clutch mechanism is effected by a shift rod 50, which is moved within a shift cylinder 51. A locking mechanism, for example by mechanical clamping, is enabled via a projection 52 guided through the shift cylinder.

[0036] Fig. Figure 3 shows the state of the transmission unit 3 with the second gear stage engaged. The shift fork 42 is engaged with the forks 60 of the output spur gear ZA2 and thus transmits the corresponding gear ratio of the second gear stage to the output shaft 30.

[0037] Fig. Figure 4 shows the neutral position, in which the shift fork 42 is positioned between the jaws 43 and 60 of the spur gears ZA1 and ZA2. The gap 61 is dimensioned such that the shift fork 42 can be positioned without transmitting any torque from either of the two output spur gears ZA1 and ZA2 to the output shaft. This allows for neutral operation, for example, for towing or other applications. Reference symbol list 1 hydrostatic drive 2 swashplate adjustment motors 3 2-stage gearbox unit 4 Engine input shaft 10 plates 11 pistons 12 cylinder drum 13 Swivel axis 15 swivel housings 16 Motor housings 20 tax caps 21 Adjusting pistons 22 swivel angles 23 Swivel angle sensor 30 Output shaft 31 cases 32 screws 40 Coupling agents 41 Shift fork 42 Shift claw 43 Claw 44, 45 space 50 shift rod 51 switching cylinders 52 continuation 60 claws ZE1 single-drive spur gear ZE2 single-drive spur gear ZA1 Output spur gear ZA2 output spur gear

Claims

[1] Hydrostatic drive (1) for vehicles, wherein the hydrostatic drive (1) comprises a first hydraulic circuit for providing the drive energy for at least one axial piston motor (2) in a swashplate design, wherein the axial piston motor (2) provides a torque and a speed at an output shaft (30) depending on a helix angle or swivel angle (22) of the axial piston motor (2), and wherein a transmission (3) is included which has at least two switchable transmission stages, of which a first transmission stage or a second transmission stage can be coupled to the output shaft (30), wherein a swivel angle sensor (23) for detecting the helix angle or swivel angle (22) and a second hydraulic circuit for adjusting the helix angle or swivel angle (22) are included.swivel angle (22) is designed, wherein the second hydraulic circuit has a working pressure which is independent of the working pressure of the first hydraulic circuit and the tilt angle or swivel angle (22) can be adjusted via the second hydraulic circuit and the swivel angle sensor (23) to a value to provide a speed for synchronous switching from the first to the second gear stage and back, wherein the axial piston motor (2) is a large-angle motor type. [2] Hydrostatic drive according to claim 1, characterized by , that the swivel angle sensor (23) forms a control loop with a hydraulic actuator for adjusting the swivel angle (22). [3] Hydrostatic drive according to any of the preceding claims, characterized by , that the axial piston motor (2) has a possible swivel angle (22) between 0° and 45°. [4] Hydrostatic drive according to any of the preceding claims, characterized by , that a coupling means (40) connects the output shaft (30) positively to the first or the second gear stage. [5] Hydrostatic drive according to claim 4, characterized by , that the connection is made via a star-shaped switching claw (42) and the coupling means (40) can be locked in the respective position via a switching cylinder (51). [6] Hydrostatic drive according to any of the preceding claims, characterized by , that a space is provided between an output gear (ZA1) of the first gear stage and an output gear (ZA2) of the second gear stage, wherein the space accommodates the coupling means (40) without interference to the first and second gear stages in order to enable uncoupled idling. [7] Hydrostatic drive according to claim 6, characterized by that the coupling means (40) is preferably lockable in this position. [8] Method for operating a hydrostatic drive for vehicles according to one of the preceding claims, wherein the hydrostatic drive (1) comprises a first hydraulic circuit for providing the drive energy for at least one axial piston motor (2) in a swashplate design, wherein the axial piston motor provides a torque and a speed at an output shaft (30) depending on a helix angle or swivel angle (22) of the axial piston motor (2), wherein a transmission (3) is included which has at least two switchable transmission stages, of which at least one first transmission stage or a second transmission stage can be coupled to the output shaft (30), wherein a swivel angle sensor (23) is provided for detecting the swivel angle and a second hydraulic circuit is provided for adjusting the swivel angle.wherein, via the second hydraulic circuit and the swivel angle sensor (23), the swivel angle (22) is adjusted to values ​​for providing a rotational speed such that, when switching from the first gear stage to the second gear stage, the transmission is first disengaged from the first gear stage without torque, then the rotational speed is set to the desired speed adapted to a given travel speed in the second gear stage, and finally, the transmission is engaged in the second gear stage without torque, wherein the second hydraulic circuit sets a change in the swivel angle (22) of 10° in a maximum of one second, and the set swivel angle (22) is detected via the swivel angle sensor (23). [9] Method according to claim 8, characterized by that the second hydraulic circuit has a working pressure which is set independently of the working pressure of the first hydraulic circuit. [10] Method according to claim 9, characterized bythat the working pressure is kept constant. [11] Method according to at least one of claims 8 to 10, characterized by , that the swivel angle (22) detected by the swivel angle sensor (23) enters the control loop of the actuator for the swivel angle (22) in the second hydraulic circuit as a disturbance variable. [12] Method according to claim 8, 9, 10 or 11, characterized by , that the second hydraulic circuit sets a change in the swivel angle (22) of 10° in a maximum of 0.5 seconds. [13] Method according to any one of claims 8 to 12, characterized by that compensation or regulation of the change in viscosity of the hydraulic fluid is carried out via means for measuring the temperature of a hydraulic fluid in at least one hydraulic circuit.

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