Hydraulic system, hydraulic unit for maritime application and method for operating a hydraulic system

Abstract

The present invention relates to a hydraulic system 10 comprising a pump 12, a motor, a first line assembly 16, a second line assembly 18, and a control unit 20. The first line assembly 16 is connected to the pump 12 and a first consumer port 22. The second line assembly 18 is connected to the pump 12 and a second consumer port 24. A first check valve 26 is arranged in the first line assembly 16. A second check valve 32 is arranged in the second line assembly 18. The control unit 20 is configured to switch the motor 14 between a first pressurization mode, a second pressurization mode, and a stop mode.The motor 14 drives the pump 12 in the first pressurization mode in a first direction of rotation to pressurize the first line arrangement 16, and in the second pressurization mode in a second direction of rotation to pressurize the second line arrangement 18. The control unit 20 is further configured to operate the motor 14 in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and to operate it in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. The invention further relates to a hydraulic unit with a hydraulic system 10 and a method for operating the hydraulic system 10.

Description

[0001] The present invention relates to a hydraulic system, a method for operating such a hydraulic system, and a hydraulic unit comprising such a hydraulic system. The hydraulic unit is intended for maritime use and is specifically designed as a unit for trimming, tilting, and / or steering a boat propulsion system.

[0002] Such hydraulic systems are known from the prior art, for example from DE 10 2021 204 032 A1, EP 2 722 271 B1, or EP 2 493 756 B1. Hydraulic systems known from the prior art typically include a pump and a tank. If the hydraulic system is used with a hydraulic unit to steer a boat engine, a steering cylinder unit is typically provided as the hydraulic consumer. The steering cylinder unit has a first piston chamber, a cylinder-piston unit, and a second piston chamber separated from the first by the cylinder-piston unit. At least one piston rod is attached to the cylinder-piston unit, which deflects the boat drive as desired by pressurizing the respective piston chamber.

[0003] To pressurize the respective piston chambers, the pump is connected to the first piston chamber via a first pipe assembly and a first consumer connection, and to the second piston chamber via a second pipe assembly and a second consumer connection. When the second piston chamber is pressurized, the first piston chamber is also connected to the tank via the first pipe assembly by means of a first check valve that can be actuated when the second pipe assembly is pressurized. Similarly, when the first piston chamber is pressurized, the second piston chamber is connected to the tank via the second pipe assembly by means of a second check valve that can be actuated when the first pipe assembly is pressurized.

[0004] The pump is thus designed as a reversible pump, or two-quadrant pump, to selectively pressurize either the first or the second line arrangement. For this purpose, the pump is driven by a motor, which can be controlled via a controller to switch between a stop mode, a first pressurization mode for pressurizing the first line arrangement, and a second pressurization mode for pressurizing the second line arrangement. Such motors can be designed as brushed DC motors or as brushless DC motors, also known as BLDC motors. Due to the lower power density of brushed DC motors, brushless DC motors are generally preferred.

[0005] With known solutions using brushless DC motors, it is necessary to regularly know the rotor angle to ensure smooth starting. Sensors, such as Hall effect sensors, can be used to determine the motor angle before starting, thus ensuring the appropriate current is supplied to the stator coils for frictionless start-up. The disadvantages of this approach are the space requirements and the cost of the sensors.

[0006] Therefore, there are also sensorless solutions where the motor angle is derived from the motor inductance. For this purpose, short current pulses are applied, causing slight motor movement and thus generating a measurable current through inductance. This allows for an estimation of the motor angle and consequently a smooth start-up when the stator coils are energized accordingly.

[0007] Due to their design, brushless DC motors only deliver their full torque above a certain speed. If they then have to start against a high hydraulic pressure applied to the pump, the motor can reach its performance limit, resulting in a sluggish start or even a complete failure. These problems are exacerbated at low temperatures due to the increasing viscosity of the hydraulic fluid. Starting problems are therefore particularly common with sensorless systems, as the motor angle can only be determined through small movements.

[0008] Another problem with the aforementioned hydraulic units may be that the controlled check valve may not close properly when switching to stop mode due to the hydraulic conditions.

[0009] It is therefore the object of the present invention to provide a cost-effective hydraulic system with improved start-up and reliable stopping behavior. This object is achieved with a hydraulic system according to claim 1, a hydraulic unit for maritime applications according to claim 6, and a method for operating such a hydraulic system according to claim 7. Advantageous embodiments are described in the dependent claims.

[0010] A hydraulic system is shown, comprising a reversible pump, a motor for driving the pump, a first piping arrangement, a second piping arrangement, and a control unit. The first piping arrangement is connected to the pump and a first consumer port. The second piping arrangement is connected to the pump and a second consumer port. A first actuated check valve is located in the first piping arrangement, and a second actuated check valve is located in the second piping arrangement. The control unit is configured to switch the motor between a first pressurization mode, a second pressurization mode, and a stop mode.The motor drives the pump in the first pressurization mode, rotating in a first direction to pressurize the first line assembly, and in the second pressurization mode, rotating in a second direction to pressurize the second line assembly. The motor is preferably a DC motor. The motor can be designed as a brushed DC motor or as a brushless DC motor.

[0011] The hydraulic system according to the invention differs from hydraulic systems known from the prior art in that the control system is designed to operate the motor in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and to operate it in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. Thus, the flow direction is reversed for a certain period of time during each mode change. On the one hand, this leads to a reduction in hydraulic pressure and therefore improved start-up behavior, and on the other hand, it improves the hydraulic conditions when the motor stops, ensuring that the correspondingly controlled check valve closes reliably.Since the motor does not have to start against high hydraulic pressure, the motor angle can be estimated as described above, thus demonstrating an overall sensor-free, and therefore cost-effective and simple, hydraulic system. Of course, sensors can also be used to determine the motor angle, as even with such a solution it is advantageous to depressurize the line to be pressurized beforehand or to improve the hydraulic conditions when the motor stops.

[0012] The first check valve is designed to open when the second line assembly is pressurized, and the second check valve is designed to open when the first line assembly is pressurized. This allows hydraulic fluid to flow back directly to the pump or tank of the hydraulic system via the line assembly that is not pressurized.

[0013] It is advantageous if the defined time interval is at least 5 milliseconds and at most 100 milliseconds. This prevents any movement of the hydraulic component connected to the consumer ports. It is conceivable that the defined time interval is variable and, for example, adjusted depending on external factors. External factors could include, for example, the ambient temperature, the temperature of the hydraulic fluid, or the pressure in the relevant pipework.

[0014] Preferably, the control system is configured to drive the motor in the second pressurization mode for the defined period when switching from stop mode to the first pressurization mode. In other words, the motor is preferably switched from stop mode to the second pressurization mode for the defined period and then back to the first pressurization mode. Preferably, the control system is further configured to drive the motor in the first pressurization mode for the defined period when switching from stop mode to the second pressurization mode. In other words, the motor is preferably switched from stop mode to the first pressurization mode for the defined period and then back to the second pressurization mode.This relieves pressure in the pipe assembly into which the fluid is to be pumped, as it is "emptied" before the actual pumping process. Therefore, the motor does not have to start against high hydraulic pressure, and a higher speed, and consequently full torque, can be achieved before the actual working pressure is required.

[0015] It is advantageous if the control system is configured to drive the motor in the second pressurization mode for the defined period when switching from the first pressurization mode to the stop mode. In other words, preferably, the system switches from the first pressurization mode to the second pressurization mode for the defined period and then to the stop mode. It is further advantageous if the control system is configured to drive the motor in the first pressurization mode for the defined period when switching from the second pressurization mode to the stop mode. In other words, preferably, the system switches from the second pressurization mode to the first pressurization mode for the defined period and then to the stop mode.This prevents, for example, trapped hydraulic pressure from preventing the safe closing of the respective controlled check valve.

[0016] In this context, it should be noted that, for example, when switching directly from the first pressurization mode to the second, the pump's delivery direction, and therefore the motor's direction of rotation, must be reversed. Therefore, preferably in such a case, the system first switches to stop mode and then to the second pressurization mode. Preferably, the sequence is as follows: the motor is initially in the first pressurization mode, and then the motor is switched to the second pressurization mode for a defined period. Following this, the motor is briefly in stop mode and then switched back to the first pressurization mode for a defined period before switching to the second pressurization mode.

[0017] According to the invention, the method for operating a hydraulic system provides that the motor is driven in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. This results in the aforementioned advantages.

[0018] Furthermore, a hydraulic unit comprising a hydraulic system and a hydraulic consumer is shown according to the invention. The hydraulic consumer is connected to the first consumer port and the second consumer port. The hydraulic unit is designed particularly for maritime applications. The hydraulic unit is preferably configured as a hydraulic unit for trimming, tilting, and / or steering a boat propulsion system. The boat propulsion system can, for example, be an outboard motor or a Z-drive.

[0019] The invention will now be explained in more detail with reference to an embodiment shown in the figures. These figures schematically show: Fig. 1 a boat with a hydraulic unit according to the invention; Fig. 2 a hydraulic circuit diagram of a hydraulic unit according to the invention with a hydraulic system according to the invention; Fig. 3 An exemplary flowchart for the operation of the hydraulic system according to the invention.

[0020] In Fig. Figure 1 shows a boat 100 with a hull 102 and a boat propulsion system 104. In this embodiment, the boat propulsion system 104 is designed as an outboard motor. The outboard motor 104 can be pivoted to the left or right about an axis of rotation relative to the hull 102 from its depicted central position in order to steer the boat 100. For this purpose, a hydraulic unit 110 according to the invention is provided, which in this embodiment is designed as a hydraulic unit 110 for steering the outboard motor 104. However, this is not to be understood as a limitation, since the hydraulic unit can, for example, also be designed as a trim unit, a tilt unit, or a combined trim-tilt unit.

[0021] The hydraulic unit 110 according to the invention comprises a steering cylinder unit 112, see also Fig. 2. The steering cylinder unit 112 is designed as a constant-velocity cylinder and has a cylinder housing 114 with a first piston chamber 116 and a second piston chamber 118. The first piston chamber 116 is separated from the second piston chamber 118 by a cylinder piston unit designed as a single cylinder piston 120. As shown from Fig. As can be seen in Figure 2, the cylinder piston 120 has two piston rods 122, 124 extending in opposite directions from the cylinder housing 114 of the steering cylinder unit 112. For pressurizing the first piston chamber 116 and the second piston chamber 118, and thus for moving the cylinder piston 120 (and therefore for moving the boat drive 101 relative to the hull of the boat 100 by means of the piston rods), the hydraulic unit 110 further comprises a hydraulic system 10 according to the invention.

[0022] The hydraulic system 10 according to the invention comprises a reversible pump 12, a motor 14 for driving the pump 12, a first line arrangement 16, and a second line arrangement 18. The motor 14 is designed as a brushless DC motor and is controlled via a control unit 20 of the hydraulic system 10. This is described in Fig. 2 is indicated by the dotted line between motor 14 and control 20.

[0023] The first line assembly 16 is connected to the pump 12 and a first consumer connection 22. The second line assembly 18 is also connected to the pump 12 and to a second consumer connection 24. As shown, the first piston chamber 116 of the steering cylinder unit 112 is connected to the first line assembly 16 via the first consumer connection 22. Furthermore, the second piston chamber 118 of the steering cylinder unit 112 is connected to the second line assembly 18 via the second consumer connection 24.

[0024] In the first line assembly 16, a controllable first check valve 26 and a first throttling device 28 are arranged. The first check valve 26 is connected to the second line assembly 18 via a first control line 30 such that pressurizing the second line assembly 18 controls the first check valve 26. Similarly, in the second line assembly 18, a controllable second check valve 32, which is connected to the first line assembly 16 via a second control line 36, and a second throttling device 34 are arranged. Thus, the second check valve 32 is hydraulically controlled when the first line assembly 16 is pressurized.

[0025] The pump 12 is connected to a tank 40 of the hydraulic system 10 via a pressure-controlled selector valve 38 and via the first line arrangement 16 and the second line arrangement 18. Depending on the delivery direction of the pump 12, either the first line arrangement 16 or the second line arrangement 18 can be pressurized, as will be explained in more detail below.

[0026] The first throttling device 28 and the second throttling device 34 each have a bypass line with a check valve opening in the flow direction towards the cylinder unit 112 and a throttle. Regarding the function of the throttling devices 28, 34 as flow regulators and their specific design, reference is made by way of example to DE 10 2021 204 032 B4, the content of which is to be incorporated into the present disclosure.

[0027] The control unit 20 is configured to start and operate the motor 14 in a first direction of rotation in a first pressurization mode and in a second direction of rotation in a second pressurization mode. Furthermore, the control unit is configured to switch the motor 14 into a stop mode in which the motor is not operated.

[0028] In the first pressurization mode, the motor 14 rotates such that the first line assembly 16 is pressurized via the pump 12. The first check valve 26 is opened by the pressure in the first line assembly 16, and the first piston chamber 116 is supplied with pressure without restriction due to the first throttle device 28. The cylinder piston 120 moves relative to the cylinder housing 114 (in Fig. (2 to the right), so that the first piston rod 122 retracts and the second piston rod 124 extends. Simultaneously, the second check valve 32 is opened by the pressure now present in the second control line 36. The cylinder piston 120 displaces hydraulic fluid from the second piston chamber 118 into the second line assembly 18. Due to the second throttle device 34, the displaced hydraulic fluid flows out at a controlled rate to prevent the cylinder piston 120 from overextending. Since the second check valve 32 is open, the returning hydraulic fluid can be drawn directly back in via the pump 12. The pressure in the first line assembly 16 switches the selector valve 38 so that the second line assembly 18 is connected to the tank 40. Any potential difference in hydraulic fluid volume can thus be drawn directly from the tank 40 via the second line assembly 18.

[0029] In the second pressurization mode, the motor 14 rotates in the opposite direction, thus pressurizing the second line assembly 18 via the pump 12. The second check valve 32 is opened by the pressure in the second line assembly 18, and the second piston chamber 118 is supplied with pressure without restriction due to the second throttle device 34. The cylinder piston 120 moves relative to the cylinder housing 114 (in Fig. (2 to the left), so that the first piston rod 122 extends and the second piston rod 124 retracts. Simultaneously, the first check valve 26 is opened by the pressure now present in the first control line 30. The cylinder piston 120 displaces hydraulic fluid from the first piston chamber 116 into the first line assembly 16. Due to the first throttle device 28, the displaced hydraulic fluid flows out at a controlled rate to prevent the cylinder piston 120 from overextending. Since the first check valve 26 is open, the returning hydraulic fluid can be drawn directly back in via the pump 12. The pressure in the second line assembly 18 switches the selector valve 38 so that the first line assembly 16 is connected to the tank 40. Any potential difference in hydraulic fluid volume can thus be drawn directly from the tank 40 via the first line assembly 16.

[0030] Furthermore, the hydraulic system 10 has a first safety line 42 and a second safety line 44. The first safety line 42 connects the first consumer port 22 or the first line assembly 16 and the first piston chamber 116 to the tank 40, and the second safety line 44 connects the second consumer port 24 or the second line assembly 18 and the second piston chamber 118 to the tank 40. A pressure relief valve is arranged in each safety line 42, 44, which opens at a certain safety pressure and relieves the pressure at the respective consumer port 22, 24 to the tank 40. This prevents damage to the hydraulic unit 110 during operation.

[0031] The controller 20 is configured to operate the motor 12 in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and to operate it in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. The defined period is in a range between 5 milliseconds and 100 milliseconds, for example, 25 milliseconds.

[0032] The control sequence of motor 14 is in Fig. 3 shown schematically.

[0033] In step S1, the controller 20 checks whether the motor 14 is in stop mode and should be switched to the first pressurization mode, for example, due to a steering command to move the outboard motor 104. If this is the case, the controller 20, according to process P1, switches the motor 14 to the second pressurization mode for the defined period and only then to the first pressurization mode. This initially relieves the pressure in the first line assembly 16, as the pressure in the first line assembly 16 is reduced by the pump 12. The subsequent switch to the first pressurization mode pressurizes the first line assembly 16 via the pump 12. Thus, the motor 14 does not start against a relatively high pressure, but against the already relieved pressure in the first line assembly 16.This allows a higher rotational speed, and therefore the full torque, to be achieved before the actual working pressure is needed.

[0034] If, in step S1, it is determined that motor 14 should not be switched from stop mode to the first pressurization mode, the controller checks in step S2 whether motor 14 should be switched from stop mode to the second pressurization mode. If so, the controller 20, according to process P2, switches motor 14 to the first pressurization mode for the defined period and only then to the second pressurization mode. This relieves the pressure in the second line assembly 18, as pump 12 reduces the pressure in the second line assembly. In the subsequent second pressurization mode, the second line assembly 18 is pressurized, with motor 14 starting not against a relatively high pressure, but against the relieved pressure in the second line assembly 18.This allows a higher motor speed (14), and therefore full torque, to be achieved before the actual working pressure is required.

[0035] If, in step S2, it is determined that motor 14 should not be switched from stop mode to the second pressurization mode, the controller 20 checks in step S3 whether motor 14 should be switched from the first pressurization mode to stop mode. If so, the controller 20, according to process P3, switches motor 14 directly to the second pressurization mode for the defined period. The resulting short pressure pulse in the second line assembly 18 ensures that the second check valve 32 closes securely and does not remain unintentionally open or partially open due to residual pressure. The controller then switches motor 14 to stop mode.

[0036] If, in step S3, it is determined that motor 14 should not be switched from the first pressurization mode to the stop mode, the controller 20 checks in step S4 whether motor 14 should be switched from the second pressurization mode to the stop mode. If so, the controller 20, according to process P4, switches motor 14 directly to the first pressurization mode for the defined period. The resulting short pressure pulse in the first line assembly 16 ensures that the first check valve 26 closes reliably and does not remain unintentionally open or partially open due to residual pressure.

[0037] It should be noted that the sequence of steps S1 to S4 is purely exemplary and can be changed. Furthermore, steps S1 to S4 can also be performed in parallel.

[0038] The defined time interval must be adjusted to the hydraulic system 10 or the hydraulic unit 100 so that it is long enough to achieve the desired effect, but not so long that a twitch or slight movement is detectable in the steering cylinder unit 112. Furthermore, the defined time interval need not always be identical. It is conceivable that a first defined time interval is used when the motor 14 is switched from the first or second pressurization mode to stop mode, and a second defined time interval is used when the motor 14 is switched from stop mode to the first or second pressurization mode.

[0039] Finally, it should be noted that the terms "first" and "second" used in this revelation do not define a desired order, but merely serve to conceptually distinguish the individual elements. Thus, for example, it is also part of this revelation that there is a "second" element without a "first" element. REFERENCE MARK LIST 10 Hydraulic system 12 Pump 14 engine 16 first line arrangement 18 second line arrangement 20 Control 22 first consumer connection 24 second consumer connection 26 first check valve 28 first throttle device 30 first control line 32 second check valve 34 second throttle device 36 second control line 38 Selector valve 40 Tank 42 first safety line 44 second safety line 100 boat 102 hull 104 Boat propulsion 110 Hydraulic unit 112 Steering cylinder unit 114 cylinder housings 116 first piston chamber 118 second piston chamber 120 cylinder pistons 122 first piston rod 124 second piston rod S1-S4 steps P1-P4 processes

Claims

[1] Hydraulic system (10) comprising a reversible pump (12), a motor (14) for driving the pump (12), a first line arrangement (16), a second line arrangement (18) and a control system (20), wherein the first line arrangement (16) is connected to the pump (12) and a first consumer connection (22), wherein the second line arrangement (18) is connected to the pump (12) and a second consumer connection (24), wherein a first controllable check valve (26) is arranged in the first line arrangement (16), wherein a second controllable check valve (32) is arranged in the second line arrangement (18), wherein the control (20) is configured to switch the motor (14) between a first pressurization mode, a second pressurization mode and a stop mode, wherein the motor (14) drives the pump (12) in the first pressurization mode in a first direction of rotation to pressurize the first line arrangement (16) and in the second pressurization mode in a second direction of rotation to pressurize the second line arrangement (18), characterized by , that the control unit (20) is designed to operate the motor (14) in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and to operate it in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. [2] Hydraulic system (10) according to claim 1, characterized by that the defined time span is at least 5 milliseconds and at most 100 milliseconds. [3] Hydraulic system (10) according to claim 1 or 2, characterized by, that the control (20) is designed to drive the motor (14) first in the second pressurization mode for the defined period of time when switching from stop mode to the first pressurization mode and first in the first pressurization mode for the defined period of time when switching from stop mode to the second pressurization mode. [4] Hydraulic system (10) according to any one of the preceding claims, characterized by , that the control (20) is designed to drive the motor (14) first in the second pressurization mode for the defined period of time when switching from the first pressurization mode to the stop mode, and first in the first pressurization mode for the defined period of time when switching from the second pressurization mode to the stop mode. [5] Hydraulic system (10) according to any one of the preceding claims, characterized by, that the motor (14) is a DC motor, preferably a brushless DC motor or a DC brushed motor. [6] Hydraulic unit (110) for maritime application, wherein the hydraulic unit (110) comprises a hydraulic system (10) according to one of the preceding claims and a hydraulic consumer (112), wherein the hydraulic consumer (112) is connected to the first consumer port (22) and the second consumer port (24), and wherein the hydraulic unit (110) is preferably a hydraulic unit for trimming, tilting and / or steering a boat propulsion (104). [7] Method for operating a hydraulic system (10), wherein the hydraulic system (10) comprises a reversible pump (12), a motor (14) for driving the pump (12), a first line arrangement (16) and a second line arrangement (18), wherein the first line arrangement (16) is connected to the pump (12) and a first consumer connection (22), wherein the second line arrangement (18) is connected to the pump (12) and a second consumer connection (24), wherein a first controllable check valve (26) is arranged in the first line arrangement (16), wherein a second controllable check valve (32) is arranged in the second line arrangement, wherein the motor (14) is switchable between a first pressurization mode, a second pressurization mode and a stop mode, wherein the motor (14) drives the pump (12) in the first pressurization mode in a first direction of rotation to pressurize the first line arrangement (16) and in the second pressurization mode in a second direction of rotation to pressurize the second line arrangement (18), characterized by, that the motor (14) is driven in the second pressurization mode for a defined period of time when switching between the first pressurization mode and the stop mode, and is driven in the first pressurization mode for a defined period of time when switching between the second pressurization mode and the stop mode. [8] Method for operating a hydraulic system (10) according to claim 7, characterized by that the defined time span is at least 5 milliseconds and at most 100 milliseconds. [9] Method for operating a hydraulic system (10) according to claim 7 or 8, characterized by, that when switching from stop mode to first pressurization mode the motor (14) is first driven in the second pressurization mode for the defined period of time and when switching from stop mode to second pressurization mode it is first driven in the first pressurization mode for the defined period of time. [10] Method for operating a hydraulic system (10) according to any one of the preceding claims 7 to 9, characterized by , that when switching from the first pressurization mode to the stop mode, the motor (14) is initially driven in the second pressurization mode for the defined period of time, and when switching from the second pressurization mode to the stop mode, it is initially driven in the first pressurization mode for the defined period of time.

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