Starting method in a hydrostatic drive with brakes

Abstract

The invention relates to a method for controlling a hydrostatic drive, wherein the hydrostatic drive has at least two hydraulic machines (4, 8), wherein a first hydraulic machine (4) can be coupled to a drive machine (2) and a second hydraulic machine (8) can be coupled to an output device (14), wherein the first hydraulic machine (4) is fluidically connected to the second hydraulic machine, wherein the drive (14) comprises a brake (15) for locking the output device (14), wherein the method comprises the following steps: a. closing the brake (15) such that the rotational movement of the second hydraulic machine (8) is locked; b. pressure regulation of the first hydraulic machine (4) until the first hydraulic machine (4) reaches a target value; c. detection of the swing angle (41) of the first hydraulic machine (4) after the first hydraulic machine (4) has reached the target value; d. regulation of the first hydraulic machine (4) such that the detected swing angle is maintained or regulation of the first hydraulic machine (4) such that a volume flow associated with the detected swing angle is provided by the first hydraulic machine (4).

Description

Technical Field

[0001] The present invention relates to the field of methods for controlling a hydrostatic drive device, the hydrostatic drive device comprising a first hydraulic press coupled to a drive device and a second hydraulic press coupled to an output device, wherein the drive device has a brake for locking the output device. Background Technology

[0002] In mobile work machines, the drive unit is equipped with a braking device to maintain position in the absence of drive torque, preventing the work machine from moving while stationary. A typical drive unit is, for example, a cable winch drive. These drive units can have both open circuits with hydraulic pumps and motors, and closed circuits with hydraulic pumps and motors, where the hydraulic pump is typically regulated in terms of displacement.

[0003] Under standard conditions, the hydraulic pump is driven by a motor, and the hydraulic motor is configured to transfer hydraulic energy, in the form of mechanical energy received from the first hydraulic pump, to an external load (e.g., a motor shaft). This motor can be any internal combustion engine or electric motor, or any other element capable of providing rotation to the hydraulic pump.

[0004] In order to release the braking device for restarting without moving the output device, it is necessary to pre-apply accurate load torque to the drive motor.

[0005] For this purpose, an algorithm is typically used that manipulates a previously determined lower volumetric flow rate before the brake is released, ensuring torque balance upon release and thus stopping the winch for restart. A pump volumetric flow rate against the load direction is necessary to compensate for leakage volumetric flow rates present in the hydraulic system. Information regarding the necessary torque is obtained from a cable force measuring device in the cable steering mechanism (persistently obtained even when the brake is closed).

[0006] The problem with the solution described above is that, during the opening phase, the drive torque does not match the load conditions and the driver's expectations, and sometimes the machine exhibits undesirable behavior that makes it impossible to achieve balance.

[0007] In particular, determining the volumetric flow rate necessary for the smooth opening of the holding brake is extremely complex. Adjusting the desired volumetric flow rate with the required precision using the hydrodynamic position adjuster on the pump is also complex. Specifically, the pump's current displacement can only be determined indirectly through control values ​​(via the current to the control magnet).

[0008] DE 102014109918 A1 describes in principle the regulation of cable force in a closed-loop winch using a hydrostatic pump / pull pump and a control device. However, it does not address the maintenance of the brake being open and the resulting load bearing through the drive mechanism. Summary of the Invention

[0009] The object of the present invention is to solve the problems described above, and thus to provide a method for controlling a hydrostatic drive device that can automatically prevent undesirable behavior.

[0010] This application describes an example of a drive in which a hydrostatic motor is driven by a hydrostatic pump in a closed loop. However, it will be apparent to those skilled in the art that the invention can also be used in open loops.

[0011] This invention relates to a method for controlling a hydrostatic drive device, wherein the hydrostatic drive device has at least two hydraulic presses, wherein a first hydraulic press is coupled to a drive unit and a second hydraulic press is coupled to an output device, wherein the first hydraulic press and the second hydraulic press are fluidly connected, wherein the drive unit includes a brake for locking the output device, and wherein the method includes the following steps:

[0012] a. Close the brake to lock the rotational motion of the second hydraulic press;

[0013] b. Adjust the pressure of the first hydraulic press until it reaches the target value;

[0014] c. After the first hydraulic press reaches the target value, the swing angle of the first hydraulic press is detected;

[0015] d. Adjust the first hydraulic press so that the detected swing angle is maintained, or adjust the first hydraulic press so that a volumetric flow rate related to the detected swing angle is provided through the first hydraulic press.

[0016] The core of this invention lies in determining the necessary volumetric flow rate when the brake is closed by adjusting the pump to the desired holding pressure and measuring the pump's oscillation angle (and preferably the rotational speed). The advantage is that the system automatically adapts to changing operating conditions and aging. Attached Figure Description

[0017] The invention will be described with reference to the accompanying drawings, wherein the same reference numerals denote the same and / or similar and / or corresponding parts of the system. Wherein:

[0018] Figure 1 The schematic diagram illustrates a circuit diagram of a hydrostatic drive device configured as a driving device according to an embodiment of the present invention. Detailed Implementation

[0019] The invention will now be described with reference to specific embodiments shown in the accompanying drawings. However, the invention is not limited to the specific embodiments described in the following detailed description and shown in the drawings, but rather the described embodiments only illustrate some aspects of the invention, the scope of which is defined by the claims.

[0020] Other modifications and variations of the present invention will be apparent to those skilled in the art. Therefore, this specification includes all modifications and / or variations of the present invention, the scope of which is defined by the claims.

[0021] according to Figure 1 The hydrostatic drive unit includes a hydraulic pump 4, which is fluidly connected to a hydraulic motor 8 in a closed hydraulic circuit via working lines 5 and 6 to supply it with a pressurized medium. Here, the hydraulic pump 4 is coupled to the drive motor 2 via a drive shaft to transmit torque. In this example, the coupling is speed-changing, so that the rotational speed of the drive motor 2 and the hydraulic pump 4 are different. However, speed changing is not necessary.

[0022] The hydraulic pump 4 is designed as an axial piston pump with a swashplate structure and is capable of operating in both directions of rotation, and can be operated as a pump or a motor. This hydraulic pump typically has an adjustable displacement and preferably has an adjustment device 10 designed as a double-acting hydraulic cylinder.

[0023] The regulating device 10 is controlled by the control unit 100. In this embodiment, the hydraulic pump 4 can be pressure regulated and flow controlled by the control unit 100. In this example, the hydraulic motor is not adjustable. It will be clear to those skilled in the art that the present invention can also be operated with an adjustable hydraulic motor.

[0024] A hydraulic motor is connected to an output device 14. The output device 14 has a brake 15 for locking the output device 14, wherein when the brake 15 is closed, the rotational movement of the hydraulic motor 8 is locked. The brake 15 is provided with an actuator 17 configured to operate (for opening and closing) the brake 15.

[0025] The hydrostatic drive device of the present invention is a hydrostatic drive device for mobile work machines, wherein the output device is preferably a cable winch drive device capable of raising, lowering, or pulling the load 16 by means of a cable winch. However, the present invention can also be applied to other work machines requiring low volumetric flow rates, preferably to work machines whose hydraulic pumps are flow-regulated, for example, in sweepers or milling machines.

[0026] Preferably, the hydraulic pump 4 can be controlled by means of an electronic swing angle adjuster, wherein the swing angle adjuster is based on the swing angle sensor 41 on the first hydraulic press 4 in order to improve the adjustment accuracy.

[0027] Preferably, the hydraulic pump 4 can be controlled by means of an electronic pressure regulator 100, wherein the pressure regulator is executed based on the pressure sensor signals 101, 103 in the working circuit of the first hydraulic press, so as to improve the adjustment accuracy.

[0028] The following paragraphs describe a method for controlling a hydrostatic drive device according to an embodiment of the present invention. This method enables the load 16 to be balanced when the brake 15 is open.

[0029] In the first step, the brake 15 is closed by means of the actuator 17, thereby locking the rotational motion of the hydraulic motor. Before the brake 15 is closed, the pump performs flow regulation so that a certain volumetric flow rate is supplied to the hydraulic motor 8.

[0030] Upon receiving this information, the controller 100 will begin pressure regulation of the hydraulic pump 4 until a certain pressure is reached by the pump. This is because, in this situation, the rotation of the hydraulic motor 8 is locked, and if the hydraulic pump is stopped, the pressure in the working lines 5 and 6 will decrease due to leakage. For this reason, it is necessary to manipulate the hydraulic pump 4 to compensate for these losses. Therefore, the controller 100 will obtain information about the target pressure required after the brake 15 is opened to achieve load balancing.

[0031] This information is obtained either through a pressure sensor 101 located downstream of the hydraulic pump 4, or through a force sensor 102 that detects the load. When information is received from the force sensor 102, this information is converted into a target pressure in the controller 100.

[0032] For this reason, the hydraulic pump 4 is pressure regulated until the preset pressure is reached. After the hydraulic pump 4 reaches the target value, the swing angle of the hydraulic pump 4 is detected by means of the swing angle sensor 41.

[0033] The hydraulic pump is then adjusted such that the detected oscillation angle is maintained, or that the hydraulic pump 4 provides a volumetric flow rate related to the detected oscillation angle. Specifically, if the rotational speed of the hydraulic pump 4 remains constant, the oscillation angle can be controlled directly. However, if the rotational speed changes, the new speed must be considered, as the volumetric flow rate is related to the rotational speed. For this reason, in the hydraulic pump 4 or in an external drive device (such as…) Figure 1 A speed sensor 21 is arranged in the (shown) and is configured to provide information about the speed of the hydraulic pump 4 to the controller 100.

[0034] Following this step, the hydrostatic actuation unit is ready to reopen brake 15. For this reason, if the driver wishes to reopen brake 15, the controller 100 will activate this action. With this solution, undesirable movement does not occur when brake 15 is open because the leakage volumetric flow rate caused by the system is compensated for by this method. This leakage volumetric flow rate is related to various system conditions and component aging, and its effects are eliminated by the described solution.

[0035] In another embodiment of the invention, when the rotational speed of the hydraulic pump 4 changes, the volumetric flow rate of the hydraulic pump 4 is adapted accordingly, wherein changes in leakage volumetric flow rate are taken into account in the adaptation. This is because the leakage volumetric flow rate is higher at higher rotational speeds.

[0036] In another embodiment of the invention, the method described above is used to determine a characteristic curve that can be used in the future to show information about a target swing angle or target volumetric flow rate related to a target pressure. Because of this characteristic curve, it is no longer necessary to perform the method described above every time, as information about the target swing angle or target volumetric flow rate can be determined from the characteristic curve. The only information required is the target pressure, which can be determined by means of a pressure sensor or force sensor (as explained in the description).

[0037] To determine the characteristic curve, the previously described method was repeated for different target pressures, and the value of the target swing angle or the target volumetric flow rate was saved for each pressure. The function was then derived from these stored values. For this reason, the target pressure was distributed as evenly as possible within the operating pressure range of the drive unit.

[0038] The function is then saved and can also be used for various purposes. In another embodiment, the function is used to control the hydraulic pump 4 when the brake 15 is open, thereby maintaining the position of the load 16.

[0039] Because leakage is related to various conditions that may change over time, the function can be updated periodically. For this reason, the method can be repeated at regular intervals for one or more target pressures, and the function can be corrected using the identified information about the target swing angle.

[0040] What can be set is, such as Figure 1 As shown, the traction device (cable winch) is guided on the steering roller, wherein the force sensor 102 may include a force-measuring pin, on which the steering roller is rotatably supported. Various types of corresponding force-measuring pins are commercially available, thus enabling accurate force measurement in a simple and cost-effective manner.

[0041] It should be pointed out tactfully that even Figure 1 The hydraulic motor 8 is described as a motor with a constant displacement, but the present invention can also use a hydraulic motor 8 whose displacement is adjustable. In this case, it is preferable to increase the swing angle of the hydraulic pump 4 at low speeds of the cable winch. If the swing angle of the hydraulic pump has reached its maximum position and the speed is to be further increased, the swing angle (displacement) of the hydraulic motor is decreased.

[0042] In addition, operating elements are provided ( Figure 1 (Not shown in the diagram), this operating element is also connected to the controller 100. The operating element is, for example, configured as an operating lever capable of swinging in two opposite directions starting from a central position. In the spring-preloaded central position, the winch does not move. From the operator's perspective, when the operating lever swings forward, the load 16 decreases, with the rate of decrease approximately proportional to the lever deflection; when the operating lever swings backward, the load 16 increases, with the rate of increase approximately proportional to the lever deflection. The position of the operating element is preferably transmitted to the controller 100 in the form of an electrical or digital signal.

[0043] It can be set that, while the deflection of the operating element is below a preset limit value, a maximum first displacement is set on at least one first hydraulic press 4, wherein a reduced first displacement relative to the maximum first displacement is also set. Thus, when the operating element deflects significantly, the cable winch can move particularly quickly. The aforementioned limit value can be selected differently depending on the deflection direction of the operating element, i.e., according to the desired direction of movement of the load 16.

[0044] The present invention has been described with reference to the embodiments described above, and it will be clear to those skilled in the art that various modifications, variations and improvements to the present invention can be made in accordance with the teachings described above and within the scope of the appended claims without departing from the protection scope of the present invention.

[0045] For this reason, even though an example of a drive mechanism is described in this application, in which a hydrostatic motor in a closed loop is driven by a hydrostatic pump, the present invention can also be used in open loops.

[0046] Therefore, the present invention should not be limited to the embodiments specifically described, but is only limited by the scope of protection of the appended claims.

Claims

1. A method for controlling a hydrostatic drive device, wherein the hydrostatic drive device has at least two hydraulic presses, a first hydraulic press (4) of the at least two hydraulic presses being coupled to a drive unit (2), and a second hydraulic press (8) being coupled to an output device (14), wherein the first hydraulic press (4) is fluidly connected to the second hydraulic press, wherein the drive device includes a brake (15) for locking the output device (14), wherein the method comprises the following steps: a. Close the brake (15) to lock the rotational movement of the second hydraulic press (8); b. Adjust the pressure of the first hydraulic press (4) until the first hydraulic press (4) reaches the target value; c. After the first hydraulic press (4) reaches the target value, the swing angle of the first hydraulic press (4) is detected; d. Adjust the first hydraulic press (4) so ​​that the detected swing angle is maintained, or adjust the first hydraulic press (4) so ​​that a volumetric flow rate related to the detected swing angle is provided through the first hydraulic press (4).

2. The method according to claim 1, wherein the target value for pressure regulation of the first hydraulic press (4) is related to the load information of the output device (14).

3. The method according to claim 1 or 2, wherein the target value for pressure regulation of the first hydraulic press (4) is the pressure detected before the brake (15) is closed.

4. The method according to claim 1 or 2, wherein the brake (15) is opened again after step d.

5. The method of claim 1 or 2, wherein, The first hydraulic press (4) and the second hydraulic press (8) are in a closed loop.

6. The method according to claim 1 or 2, wherein, Steps a. to c. are repeated for different target values ​​for pressure regulation of the first hydraulic press (4), wherein a function is obtained taking into account the value of the detected swing angle, which is a function of the target swing angle of the first hydraulic press (4) in relation to the pressure regulation value of the first hydraulic press (4) or a function of the target volume flow rate of the first hydraulic press (4) in relation to the swing angle.

7. The method of claim 6, wherein the function is stored, and wherein, At regular intervals, the function is adapted to at least one target value for pressure regulation of the first hydraulic press (4) by means of performing steps a to c.

8. The method according to claim 6, wherein, In the method, the function is used to control the first hydraulic press (4) when the brake (15) is opened.

9. The method according to claim 1 or 2, wherein the hydrostatic drive device is a hydrostatic drive device for a mobile work machine.

10. The method according to claim 9, wherein, The output device (14) is a cable winch drive device.

11. The method according to claim 1 or 2, wherein, In step d, when the rotational speed of the first hydraulic press (4) changes, the volumetric flow rate of the first hydraulic press (4) is adapted accordingly, wherein the change in leakage volumetric flow rate is taken into account in the adaptation.

12. The method according to claim 1 or 2, wherein in step d, the first hydraulic press (4) is controlled by means of an electronic swing angle adjuster, wherein the swing angle adjuster is based on a swing angle sensor (41) on the first hydraulic press (4) to improve adjustment accuracy.

13. The method according to claim 1 or 2, wherein in step b, the first hydraulic press (4) is controlled by means of an electronic pressure regulator (100), wherein the pressure regulator is based on pressure sensor signals (101, 103) in the working circuit of the first hydraulic press in order to improve the adjustment accuracy.

14. The method according to claim 1 or 2, wherein the target value for pressure regulation of the first hydraulic press (4) is the pressure detected before the brake (15) is closed, wherein the pressure is detected downstream of the first hydraulic press (4).

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