DE102021209896A1 - PROCEDURE FOR STARTING IN A HYDROSTATIC DRIVE WITH BRAKE - Google Patents

Abstract

The present invention relates to a method for controlling a hydrostatic drive, the hydrostatic drive having at least two hydraulic machines (4, 8), of which a first hydraulic machine (4) has a drive machine (2) and a second hydraulic machine (8) has an output (14) can be coupled, the first hydraulic machine (4) being fluidically connected to the second hydraulic machine, the drive (14) comprising a brake (15) for blocking the output (14), the method comprising the following steps: a . Closing the brake (15) so that a rotational movement of the second hydraulic machine (8) is blocked; b. Pressure control of the first hydraulic machine (4) until the first hydraulic machine (4) reaches a target value; c. After the first hydraulic machine (4) has reached the desired value, detecting the swivel angle (41) of the first hydraulic machine (4); d. Regulation of the first hydraulic machine (4) so that the detected swivel angle is maintained or regulation of the first hydraulic machine (4) so that the volume flow dependent on the detected swivel angle is provided by the first hydraulic machine (4).

Description

TECHNICAL PART

The present invention relates to the field of a method for controlling a hydrostatic drive, which comprises a first hydraulic machine coupled to a drive and a second hydraulic machine coupled to an output, the drive having a brake for blocking the output.

STATE OF THE ART

In mobile working machines, drives for holding a position without torque of the driving machine are equipped with a braking device, which makes it possible to prevent the working machine from moving when it is stationary. Typical drives are e.g. cable winch drives. These drives can have both an open and a closed circuit with a hydraulic pump and a hydraulic motor, with the hydraulic pump typically being volumetrically controlled.

Under standard conditions, the hydraulic pump receives a drive from a motor and the hydraulic motor is designed to transmit the hydraulic energy received from the first hydraulic pump to an external consumer (e.g. a motor shaft) in the form of mechanical energy. The motor can be any internal combustion engine or electric motor or any other element capable of providing rotation to the hydraulic pump.

In order to release the braking device without moving the abrasion for restarting, it is necessary for the drive machine to apply the exact load torque in advance.

For this purpose, an algorithm is normally used, which controls a pre-determined low volume flow for restarting before opening the brake, which has the effect that after opening there should be a moment equilibrium and the winch thus stops. The pump volume flow against the load direction is necessary in order to compensate for the leakage volume flows in the hydraulics. The information about the necessary torque is obtained from a cable force measuring device in the cable deflection device (permanent, even when the brake is closed).

The problem with the solution described above is that during opening, the drive torque does not adapt to the load conditions and the driver's expectations, and sometimes there are undesirable behaviors on the part of the machine, so that balance is not created.

In particular, the determination of the volume flow required to open the holding brake without jerking is very complex. With hydromechanical position controllers on the pump, it is difficult to regulate the desired volume flow with the required accuracy. In particular, the current displacement volume of the pump can only be determined indirectly using the control values (electrical current through the control magnets).

DE 102014109918 A1 basically describes the rope force control of a closed circuit winch using a hydrostatic/pull-through pump and a control device. However, no reference is made here to the opening of the holding brake and the associated load transfer by the drive

The object of the present invention is precisely to solve the problems described above and therefore to implement a method for controlling the hydrostatic transmission which can automatically prevent undesirable behavior.

SHORT VERSION

In this application an example of prime mover is described in which a hydrostatic motor in closed circuit is driven by a hydrostatic pump. However, it is clear to a person skilled in the art that this invention can also be used in an open circuit.

1. a. Schließung der Bremse, sodass eine Drehbewegung der zweiten Hydromaschine blockiert wird;
2. b. Druckregelung der ersten Hydromaschine bis die erste Hydromaschine einen Sollwert erreicht;
3. c. Nachdem die erste Hydromaschine den Sollwert erreicht hat, Erfassung des Schwenkwinkels der ersten Hydromaschine;
4. d. Regelung der ersten Hydromaschine, sodass der erfasste Schwenkwinkel gehalten wird oder Regelung der ersten Hydromaschine sodass der von dem erfassten Schwenkwinkel abhängigen Volumenstrom durch die erste Hydromaschine bereitgestellt wird.

This invention relates to a method for controlling a hydrostatic drive, the hydrostatic drive having at least two hydraulic machines, of which a first hydraulic machine can be coupled to a drive machine and a second hydraulic machine to an output, the first hydraulic machine being fluidically connected to the second hydraulic machine. wherein the drive comprises a brake for blocking the output, the method comprising the following steps:

1. a. Closing the brake so that a rotational movement of the second hydraulic machine is blocked;
2. b. Pressure control of the first hydraulic machine until the first hydraulic machine reaches a setpoint;
3. c. After the first hydraulic machine has reached the target value, the swivel angle of the first hydraulic machine is recorded;
4. i.e. Control of the first hydraulic machine so that the detected swivel angle is maintained or control of the first hydraulic machine so that the volume flow dependent on the detected swivel angle is provided by the first hydraulic machine.

The essence of this invention lies in the fact that the necessary volume flow is determined when the brake is closed by adjusting the pump to the expected holding pressure and measuring the swivel angle (and preferably the speed) of the pump. The advantage is that the system automatically adapts to changing operating conditions and aging.

character list

• 1 zeigt schematisch einen Schaltplan einen als Fahrantrieb ausgebildeten hydrostatischen Antrieb gemäß einem Ausführungsbeispiel der vorliegenden Erfindung.

The present invention is described with reference to the accompanying figures, in which the same reference numbers refer to the same parts and/or to similar parts and/or to corresponding parts of the system. About the figures:

• 1 FIG. 12 schematically shows a circuit diagram of a hydrostatic drive designed as a travel drive according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION

In the following, the present invention will be described with reference to specific embodiments as shown in the attached figures. Nevertheless, the present invention is not limited to the particular embodiments described in the following detailed description and shown in the figures, but the described embodiments are merely illustrative of some aspects of the present invention, the scope of which is defined by the claims.

Other modifications and variations of the present invention will be apparent to those skilled in the art. The present description thus includes all modifications and/or variations of the present invention, the scope of protection of which is defined by the claims.

According to 1 has a hydrostatic travel drive a hydraulic pump 4, which is fluidically connected in a closed hydraulic circuit via the working lines 5 and 6 with a hydraulic motor 8 to the pressure medium supply. In this case, the hydraulic pump 4 is coupled to a drive machine 2 via a drive shaft for the transmission of a torque. In this example, the coupling is geared so that the speed of the drive machine 2 and the hydraulic pump 4 are different. However, the translation is not required.

The hydraulic pump 4 is designed as an axial piston pump with a swash plate design and can be operated in both directions of rotation and both in pump and motor mode. It normally has an adjustable displacement volume and preferably an adjustment device 10 designed as a double-acting hydraulic cylinder.

The adjustment device 10 is controlled by a control unit 100 . In this exemplary embodiment, the hydraulic pump 4 can be both pressure-controlled and quantity-controlled by means of the control unit 100 . In this example, the hydraulic motor is not adjustable. It is clear to the person skilled in the art that the present invention can also function with an adjustable hydraulic motor.

The hydraulic motor is connected to an output 14 . The output 14 has a brake 15 for blocking the output 14, when the brake 15 is closed, a rotary movement of the hydraulic motor 8 is blocked. The brake 15 is provided with an actuator 17 configured to actuate the brake 15 (to open and to close).

The hydrostatic drive of the present invention is a hydrostatic drive of a mobile work machine, the output preferably being a cable winch drive which can lift, lower or pull loads 16 using a cable winch. However, this invention can also be used with other working machines that require low volume flows, preferably with working machines whose hydraulic pump is volume-controlled, such as with a road sweeper or with milling machines.

The hydraulic pump 4 can preferably be controlled by means of an electronic swivel angle regulation, with the swivel angle regulation taking place on the basis of the swivel angle sensor 41 on the first hydraulic machine 4 in order to improve the positioning accuracy.

The hydraulic pump 4 can preferably be controlled by means of an electronic pressure regulator 100, the pressure regulation taking place on the basis of pressure sensor signals 101, 103 in the working lines of the first hydraulic machine in order to improve the setting accuracy

In the following paragraphs, a hydrostatic drive control method according to an embodiment of the present invention is described. This method makes it possible to balance the load 16 when the brake 15 is released.

In a first step, the brake 15 is closed by means of the actuator 17, so that a rotary movement of the hydraulic motor is blocked. Before the brake 15 was closed, the pump was volume-controlled, so that a certain volume flow was delivered to the hydraulic motor 8 .

After receiving this information, the controller 100 will start to regulate the pressure of the hydraulic pump 4 until a certain pressure is reached by the pump. The reason for this is that in this situation rotation of the hydraulic motor 8 is blocked and, due to the leakage, if the hydraulic pump were at a standstill, the pressure in the working lines 5 and 6 would drop. For this reason it is necessary to operate the hydraulic pump 4 so that these losses are compensated. Because of this, the controller 100 will receive information about the target pressure that is required after opening the brake 15 in order to obtain a balance for the load.

This information is obtained either by a pressure sensor 101 arranged downstream of the hydraulic pump 4 or by the force sensor 102 which detects a load. When the information is received from the force sensor 102, this information is converted into a target pressure in the controller 100. FIG.

For this reason, the hydraulic pump 4 is pressure-controlled until when the specified pressure is reached. After the hydraulic pump 4 has reached the target value, the swivel angle of the hydraulic pump 4 is detected by the swivel angle sensor 41 .

The hydraulic pump is then regulated in such a way that the detected swivel angle is maintained or so that the volume flow dependent on the detected swivel angle is provided by the hydraulic pump 4 . In particular, if the speed of the hydraulic pump 4 remains constant, only the swivel angle can be controlled directly. However, if the speed changes, the new speed must be taken into account, since the volumetric flow depends on the speed. For this reason, with the hydraulic pump 4 or with the external drive (as in 1 shown), a speed sensor 21 is arranged, which is configured to supply information about the speed of the hydraulic pump 4 to the controller 100 .

After this step, the hydrostatic drive is ready to re-open the brake 15. For this reason, if the driver wishes to re-open the brake 15, the controller 100 will enable this action. This solution will not result in any unwanted movement when the brake 15 is opened, since the system-related leakage volume flow has been compensated for by this method. This leakage volume flow depends on numerous system states and the aging of the components, and the solution described eliminates the effect.

In a further embodiment of the present invention, when the speed of the hydraulic pump 4 changes, the volume flow of the hydraulic pump 4 is adjusted accordingly, with the change in the leakage volume flow being taken into account in the adjustment. The reason for this is that at higher speeds, there are higher leakage volume flows.

In a further embodiment of the present invention, the method described above is used to determine a characteristic curve that can be used in the future to display information about the target swivel angle or about the target volume flow as a function of a target pressure. Thanks to this characteristic, it will no longer be necessary in the future to carry out the method described above every time, since the information about the target swivel angle or about the target volume flow can be determined from the characteristic. The only information that is required is the target pressure, which can be determined by means of a pressure sensor or by means of a force sensor (as explained in the course of the description).

In order to determine this characteristic curve, the method described above is repeated for different target pressures and the value for the target swivel angle or for the target volume flow is stored for each pressure. A function is then determined from these stored values. For this reason, the target pressures are distributed as evenly as possible over the working pressure range of the actuator.

This function is then saved and can also be used for various purposes. In a further exemplary embodiment, this function is used to control the hydraulic pump 4 when the brake 15 is open, so that the position of the load 16 can be held.

Since the leakage depends on various conditions that can change over time, the function can be updated regularly. For this reason, the method can be repeated at time intervals for one or more setpoint pressures, and the function can be corrected with the determined information about the setpoint swivel angle.

While the present invention has been described with reference to the embodiments described above, it is for those skilled in the art It will be appreciated that it is possible to implement various modifications, variations and improvements of the present invention in light of the above teachings and within the scope of the appended claims, without departing from the scope of the invention.

For this reason, although an example of prime mover is described in this application in which a hydrostatic motor is driven in a closed circuit by a hydrostatic pump, this invention can also be used in an open circuit.

Accordingly, the invention should not be limited by the specific illustrative embodiments, but only by the scope of the appended claims.

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DE 102014109918 A1 [0008]

Claims (13)

Method for controlling a hydrostatic drive, the hydrostatic drive having at least two hydraulic machines (4, 8), of which 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 (14). , wherein the first hydraulic machine (4) is fluidly connected to the second hydraulic machine, wherein the drive (14) comprises a brake (15) for blocking the output (14), the method comprising the following steps: a. Closing the brake (15) so that a rotational movement of the second hydraulic machine (8) is blocked; b. Pressure regulation of the first hydraulic machine (4) until the first hydraulic machine (4) reaches a desired value; c. After the first hydraulic machine (4) has reached the desired value, the swivel angle (41) of the first hydraulic machine (4) is detected; i.e. Regulation of the first hydraulic machine (4) so that the detected swivel angle is maintained or regulation of the first hydraulic machine (4) so that the volume flow dependent on the detected swivel angle is provided by the first hydraulic machine (4). procedure after claim 1 , the setpoint for the pressure control of the pump depending on load information of the output (14). procedure after claim 1 or 2 , wherein the desired value for the pressure control of the pump is a detected pressure before the brake (15) is closed, the pressure preferably being detected downstream of the first hydraulic machine (4). Procedure according to one of Claims 1 until 3 , where after step d. the brake (15) is opened again. Procedure according to one of Claims 1 until 4 , wherein the first hydraulic machine (4) is in a closed circuit with the second hydraulic machine (8). Procedure according to one of Claims 1 until 5 , where steps a. to c. are repeated for different target values for the pressure control of the pump, with the consideration of the recorded values of the swivel angle a function is determined which is a function for the target swivel angle of the first hydraulic machine (4) or for the target volume flow dependent on the swivel angle first hydraulic machine (4) as a function of a value for the pressure control of the first hydraulic machine (4). procedure after claim 6 , wherein the function is stored and wherein the function is time-spaced by performing steps a. to c. is adjusted for at least one setpoint for the pressure control of the pump. procedure after claim 6 or 7 , the function being used in the method in order to control the first hydraulic machine (4) when the brake (15) is released. Procedure according to one of Claims 1 until 8th , wherein the hydrostatic drive is a hydrostatic drive of a mobile machine. procedure after claim 9 , wherein the output (14) is a cable winch drive. Procedure according to one of Claims 1 until 10 , wherein in step d., when the speed of the first hydraulic machine (4) changes, the volume flow of the first hydraulic machine (4) is adjusted accordingly, the change in the leakage volume flow being taken into account in the adjustment. Procedure according to one of Claims 1 until 11 , wherein in step d. the first hydraulic machine (4) is controlled by means of an electronic swivel angle controller (100), the swivel angle being controlled on the basis of the swivel angle sensor (41) on the first hydraulic machine (4) in order to improve the positioning accuracy. Procedure according to one of Claims 1 until 12 , wherein in step b. the first hydraulic machine (4) is controlled by means of an electronic pressure regulator (100), the pressure regulation taking place on the basis of pressure sensor signals (101, 103) in the working lines of the first hydraulic machine in order to improve the positioning accuracy.

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