HYDRAULIC ARRANGEMENT WITH TWO DRIVE MOTORS

Abstract

A hydraulic drive arrangement (1) for the pressure supply of a hydraulic steering system (20), particularly for construction or agricultural machines, including a hydraulic pump (2) and an electric drive. It is essential that the electric drive is designed in a redundant fashion and has two separately controlled electric drive engines (3a, 3b), which are mechanically coupled via the hydraulic pump (2) in a rigid fashion, and that the separate control circuits (6a, 6b, 7a, 7b) are provided by which a variable load distribution can be specified for the electric drive engines (3a, 3b).

Claims

1. A hydraulic drive arrangement (1) for pressure supply of a hydraulic steering system, comprising a hydraulic pump (2), a redundant electric drive that comprises two separately controlled electric drive engines (3a, 3b) that are mechanically coupled to each other via the hydraulic pump (2) in a rigid fashion, and separate control circuits (6a, 6b, 7a, 7b) by which a variable load distribution over the electric drive engines (3a, 3b) is specified.

2. The hydraulic drive arrangement (1) according to claim 1, wherein the electric drive engines (3a, 3b) each comprise motor controllers (6a, 6b) that are embodied to control the electric drive engines (3a, 3b).

3. The hydraulic drive arrangement (1) according to claim 2, wherein the control circuits (7a, 7b) are each integrated in the motor controllers (6a, 6b), and the motor controllers (6a, 6b) each are formed with a motor control and a control logic acting as the control circuit (7a, 7b).

4. The hydraulic drive arrangement (1) according to claim 1, wherein the control circuits (6a, 6b, 7a, 7b) are embodied to monitor each other for malfunctions.

5. The hydraulic drive arrangement (1) according to claim 4, wherein in case of a detected malfunction the control circuit (6a, 6b, 7a, 7b) not affected by the malfunction is configured to adjust an output of an associated one of the electric drive engines (3a, 3b).

6. The hydraulic drive arrangement (1) according to claim 1, wherein the control circuits (6a, 6b, 7a, 7b) are embodied such that one of the control circuits (6a, 6b, 7a, 7b) operates as a master control circuit, which specifies a load distribution for the electric drive engines (3a, 3b) and specifies to the other control circuit (6a, 6b, 7a, 7b) operating as a slave control circuit an operating output for the electric drive engine (3a, 3b) controlled thereby.

7. The hydraulic drive arrangement (1) according to claim 6, wherein the control circuits (6a, 6b, 7a, 7b) are embodied to coordinate a master and slave allocation in reference to each other.

8. The hydraulic drive arrangement (1) according to claim 1, further comprising an additional control circuit as a master control circuit that controls the electric drive engines (3a, 3b) via the respective motor controller (6a, 6b).

9. The hydraulic drive arrangement (1) according claim 1, further comprising a communication network (11) for the communication between the control circuits (6a, 6b, 7a, 7b) with each other.

10. The hydraulic drive arrangement (1) according to claim 1, wherein the hydraulic pump (2) is embodied as a gear pump

11. The hydraulic drive arrangement (1) according to claim 10, wherein the gear pump has a drive at both sides.

12. The hydraulic drive arrangement (1) according to claim 1, wherein the two drive engines (3a, 3b) are mechanically coupled via a common shaft.

13. The hydraulic drive arrangement (1) according to claim 12, wherein the two drive engines (3a, 3b) and the hydraulic pump (2) are arranged on a common shaft (11), and the hydraulic pump (2) is arranged between the two drive engines (3a, 3b).

14. The hydraulic drive arrangement (1) according to claim 1, wherein the two drive engines (3a, 3b) are mechanically coupled via the hydraulic pump (2).

15. The hydraulic drive arrangement (1) according to claim 14, wherein the two drive engines (3a, 3b) are mechanically coupled via the pump gears of the hydraulic pump (2), and a rotor (4a, 4b) of the two drive engines (3a, 3b) is arranged on a common shaft (11) with at least one pump gear of the hydraulic pump (2).

16. The hydraulic drive arrangement (1) according to claim 1, wherein the two drive engines (3a, 3b) are embodied as brushless electric engines, and a rotary encoder (12a, 12b) is provided at least at one of the two drive engines (3a, 3b).

17. The hydraulic drive arrangement (1) according to claim 1, wherein common motor cooling for the two drive engines (3a, 3b) is provided via a hydraulic fluid of the hydraulic pump (2).

18. The hydraulic drive arrangement (1) according to claim 1, wherein the hydraulic drive arrangement (1) is embodied for a front axle and/or a rear axle steering system.

19. A method for operating a hydraulic drive arrangement (1) for pressure supply to a hydraulic steering system (20) with a hydraulic pump (2) and an electric drive, wherein the electric drive comprises two separately controlled electric drive engines (3a, 3b) with separate control circuits (6a, 6b, 7a, 7b) and the method comprises driving the separately controlled drive engines via the control circuits (6a, 6b, 7a, 7b) and providing a variable load distribution to the electric drive engines (3a, 3b).

20. A steering system (20) comprising a hydraulic drive arrangement (1) according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Additional preferred features and exemplary embodiments of the hydraulic drive arrangement according to the invention as well as the device according to the invention and the steering system according to the invention are explained hereinafter based on an exemplary embodiment and the figures. Shown are:

[0054] FIG. 1 a schematic illustration of a first exemplary embodiment of a hydraulic drive arrangement according to the invention comprising a steering system;

[0055] FIGS. 2A and 2B schematic illustrations of a second exemplary embodiment of a hydraulic drive arrangement according to the invention with two variants in the image details;

[0056] FIG. 3 a schematic illustration of a third exemplary embodiment of a hydraulic drive arrangement according to the invention;

[0057] FIG. 4 a schematic illustration of an exemplary embodiment of a steering system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0058] In FIGS. 1 to 4, identical reference characters indicate identical elements or elements with the same effect.

[0059] FIG. 1 shows a schematic illustration of a first exemplary embodiment of a hydraulic drive arrangement according to the invention.

[0060] The hydraulic drive arrangement 1 comprises a hydraulic pump 2 and two drive engines 3a, 3b. The drive engines 3a, 3b are each embodied with a rotor 4a, 4b and a stator 5a, 5b and each comprise a motor controller 6a, 6b.

[0061] In the present case the two drive engines 3a, 3b are embodied as brushless electric engines.

[0062] In a redundant embodiment in the present case additionally a control circuit 7a, 7b is provided for each of the two drive engines.

[0063] The hydraulic pump 2 is embodied as a gear pump with a drive at both sides. Via the two connections 2a, 2b the hydraulic liquid is fed to the hydraulic cylinder 25, shown in FIG. 4. The hydraulic pump 2 is arranged between the two drive engines 3a, 3b.

[0064] The hydraulic drive arrangement with the two drive engines 3a, 3b is supplied with two power supplies 8a, 8b for the two drive engines 2, 3. Additionally, a device (battery surveillance) 9 is provided to monitor the charge status of the batteries of the voltage supplies (charge status monitoring), in the present case provided with the additional function to compensate the charge conditions (balancer function).

[0065] A communication network 10, which in the present case is embodied as a bus-system, connects the two control circuits 7a, 7b to the two motor controllers 6a, 6b of the drive engines 3a, 3b and the two power supplies 8a, 8b and the charge status monitoring 9.

[0066] Additionally, a steering wheel 21 is shown schematically comprising sensors 21a, 21b for detecting the steering angle of the steering wheel 21 and the torque applied to the steering wheel. Common sensors can be used as the sensors 21a, 21b for the steering systems. The sensors 21a, 21b are integrated in the communication network 10. Here, the sensors, particularly those known for steering systems, are embodied in a redundant fashion and/or at least the signals are redundant and provided by the sensors, already checked for plausibility.

[0067] The two drive engines are mechanically coupled rigidly to each other via the hydraulic pump 2. For this purpose the two drive engines 3a, 3b are arranged in the present case on a common shaft 11 with the hydraulic pump 1. They are connected via shaft couplings 23a and 23b to a common shaft 11 and thus to the hydraulic pump 2, as shown in FIGS. 2A and 2B.

[0068] Alternatively the drive of the pump can directly occur via one of the shafts of the drive engines.

[0069] The electric drive of the hydraulic drive arrangement is designed redundantly via the two drive engines 3a, 3b. The two drive engines 3a, 3b can each be controlled via the corresponding control circuit 7a, 7b. For this purpose the two control circuits 7a, 7b issue control commands to the motor controllers 6a, 6b of the drive engines 3a, 3b. The power electronic for the control of the drive engines 2, 3 is located in the motor controllers 6a, 6b. The control circuits 7a, 7b assume redundantly the processing of the control signals (speed, maximum current) depending on the steering requirements detected by the sensors 21a and 21b.

[0070] A variable load distribution to the electric drive engines occurs via the two control circuits 7a, 7b in order to achieve the specified output of the hydraulic drive arrangement. The two drive engines 3a, 3b can each be controlled via the respectively allocated control circuit 7a, 7b. Alternatively the two drive engines can be controlled by the respectively other control circuit. It is also possible that both drive engines are controlled by one of the control circuits 7a, 7b.

[0071] Here, the control circuits specify the speed and the maximally permitted power input by each drive engine. In order to determine these parameters the control circuits detect the operating status of the drive engines and the status of the energy supply, and then calculate the optimal energy distribution with respect to the power demands according to life span and condition of the components (drive engines, power supply). This is then transferred in the form of a specified speed and maximum power to the motor controllers respectively allocated.

[0072] In the present case the control circuit 7a operates as the master control circuit. The control circuit 7b is embodied such that it operates as a slave control circuit and monitors and/or checks the specifications of the master control circuit 7a for plausibility. In order to reach the drive output specified by the two control circuits 7a, 7b the engine controllers 6a, 6b control the drive engines 3a, 3b.

[0073] In case of a failure or a malfunction of one of the two drive engines 3a, 3b the drive engine not affected by the failure or malfunction assumes the provision of the required hydraulic output up to its maximum capacity. The control occurs via the control circuits 7a, 7b, which in case of a failure of one of the two drive engines 3a, 3b increase the power demand (in the form of specified speed and maximum current) to the remaining drive engine.

[0074] In case of a failure or a malfunction of one of the two control circuits 7a, 7b the control circuit not affected by the failure or the malfunction assumes the control of the two drive engines 3a, 3b. This reliability is therefore activated both in case of a malfunction of one of the two controls as well as a malfunction of one of the two drive engines.

[0075] In case of a steering motion (commonly a rotation of the steering wheel 21) the sensors 21a, 21b detect the steering angle and the torque of the steering wheel 21. This information is forwarded by the communication network 10 to the control circuit 7a as the master control circuit. The control circuit 7a then issues appropriate control commands to the engine controllers 6a and 6b. The control circuit 7b performs a plausibility check of the control commands of the control circuit 7a.

[0076] In order to reach the drive output specified by the master control circuit 7a the engine controllers 6a, 6b adjust the drive engines 3a, 3b to the specified speed in consideration of the respectively specified maximum current.

[0077] In case of a malfunction or a failure of one of the two control circuits 7a, 7b or the drive engine 3a, 3b the tasks of one control circuit 7a, 7b or one of the drive engines 3a, 3b are assumed by the control circuit 7a, 7b not affected or the drive engine 3a, 3b not affected by the malfunction. For example, the control circuit 7a, 7b not affected by the malfunction can operate the remaining drive engine 3a, 3b with a higher output in order to compensate the malfunction.

[0078] By the redundant design with the two drive engines 3a, 3b the failure rate of the hydraulic drive arrangement is reduced. In spite thereof, the hydraulic drive arrangement only requires a relatively small structural space and this way can easily be positioned near the steering gear.

[0079] In order to avoid unnecessary repetitions hereinafter only the differences between the figures will be discussed.

[0080] FIGS. 2A and 2B show schematic illustrations of two variants for the arrangement of the two drive engines 3a, 3b in reference to each other and/or the hydraulic pump 2.

[0081] FIG. 2A shows a first variant of the arrangement of the drive engines 3a, 3b. The hydraulic pump 2 is arranged between the two drive engines 3a, 3b. Here, the two drive engines 3a, 3b and the hydraulic pump 2 are arranged on a common shaft 11 and mechanically coupled in a rigid fashion. For this purpose the two drive engines 3a, 3b are connected via shaft couplings 23a and 23b to a common shaft 11 and this way to the hydraulic pump 2.

[0082] FIG. 2B shows a second variant of the arrangements of the drive engines 3a, 3b. The hydraulic pump 2 is also arranged here between the drive engines 3a, 3b. In the present case, however, the drive engine 3a is coupled to a first pump sprocket of the hydraulic pump. The dive engine 3b is however coupled to a second sprocket of the hydraulic pump. The two drive engines 3a, 3b are therefore not arranged on a common shaft. The coupling occurs via the sprockets of the hydraulic pump 2.

[0083] Depending on the structural space available in which the hydraulic drive arrangement shall be placed one of the two above-described variants can be selected.

[0084] FIG. 3 shows a schematic illustration of a detail of a hydraulic drive arrangement according to the invention.

[0085] The two drive engines 3a, 3b are arranged with the hydraulic pump 2 on a common shaft. The hydraulic pump 2 is arranged between the two drive engines 3a, 3b. One rotary angle encoder 12a, 12b each is arranged at the drive engines 3a, 3b.

[0086] The respective status of the rotor can be determined via the rotary angle encoder 12a, 12b. This allows to control optimal cooperation of the two drive engines. In order to achieve maximum hydraulic output the two drive engines operate in a synchronized fashion. The control architecture of both drive engines 3a, 3b is here designed such that via parameterizing an adjustment of the controllers to the different operating conditions is possible and they can be adjusted such that even errors developing by the coupling of the drive engines 3a, 3b can be compensated.

[0087] FIG. 4 shows a schematic illustration of a first exemplary embodiment of a steering system 21 according to the invention. The steering system 21 is in the present case controlled by displacement, as known from prior art. The steering system 21 comprises a steering wheel 20, a steering column 22, sensors 21a, 21b for detecting the steering angle of the steering wheel 21, a hydraulic drive arrangement 1, a mechanical steering gear 33, and a steering cylinder 25 for providing steering power in an effective connection to the hydraulic drive arrangement 1.

[0088] The steering gear 33 and the steering cylinder 25 are arranged cooperating at the tie rod 28 in connection with the drop arms 27 and the front axle 26.

[0089] The hydraulic drive arrangement 1 is embodied in the present case as a hydraulic drive arrangement 1 according to the invention with two drive engines 3a, 3b and one hydraulic pump 2. Via the two connections 2a, 2b the hydraulic liquid is fed to the hydraulic cylinder 25. The hydraulic drive arrangement 1 is embodied as described in FIGS. 1 and 3.

[0090] During a steering motion the rotary motion of the steering wheel 21 is detected by the sensors 21a, 21b and transferred via the steering column 22 to the mechanical steering gear 33. The information of the sensors 21a, 21b is transferred via the communication network 10 to the control circuit 7a, 7b of the hydraulic drive arrangement 1.

[0091] The hydraulic drive arrangement 1 operates as described for FIG. 1. Here, support of the steering force occurs by the hydraulic drive arrangement via the steering cylinder 25, acting via the drop arms 27 and the front axle 26 upon the wheels 24a, 24b.