hydraulic system

Abstract

Hydraulic system (10, 100) with a hydraulic consumer (V), a first line arrangement (12), a first hydraulic sensor (16), a first electrically actuated valve (20), a second electrically actuated valve (22), a pressure line (P) and a tank line (T), wherein the first line arrangement (12) connects the hydraulic consumer (V) to the pressure line (P) via the first electrically actuated valve (20) and wherein the first line arrangement (12) connects the hydraulic consumer (V) to the tank line (T) via the second electrically actuated valve (22), wherein the first hydraulic sensor (16) in the first line arrangement (12) is located downstream of the first electrically actuated valve (20) from the pressure line (D) and upstream of the second electrically actuated valve (22) from the hydraulic consumer (V), characterized by the fact that the hydraulic system (10, 100) further comprises a functional diagnostic unit (2) for performing a first test sequence and a second test sequence, wherein in the first test sequence a first hydraulic test signal is applied by actuating the first electrically actuated valve (20) for a first time interval (t1), and the functional diagnostic unit (2) is configured to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) of the first hydraulic sensor (16) with the first hydraulic test signal, and wherein in the second test sequence a second hydraulic test signal is applied by actuating the second electrically actuated valve (22) for a second time interval (t2) and the functional diagnostic unit (2) is configured to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) of the first hydraulic sensor (16) with the second hydraulic test signal.

Description

[0001] The present invention relates to a hydraulic system comprising a hydraulic consumer, a first line arrangement, at least one hydraulic sensor, and a plurality of electrically actuated valves.

[0002] Such hydraulic systems are known from the prior art. A desired pressure is typically applied to the hydraulic consumer via a pressure line and a first electrically actuated valve. The hydraulic consumer is then relieved of this pressure via the first electrically actuated valve, or possibly a second electrically actuated valve, to a tank line. Depending on the application, the hydraulic consumer can be, for example, a hydraulic cylinder or a hydraulic motor.

[0003] In general, there is a great need for flexible hydraulic systems that can be used for a wide range of applications with minimal complexity. Monitoring the individual components of the hydraulic system is particularly important to ensure reliable operation and to prevent damage in the event of defects.

[0004] Hydraulic systems typically have displacement or position sensors mounted on the electrically actuated valves to monitor the positions of the individual valves. This allows for the detection of valve malfunctions, such as jamming in a closed or open state, or incomplete opening or closing, which would impair the function of the entire hydraulic system. Furthermore, such a malfunction can also lead to damage to the hydraulic system itself, as well as to objects or people in its vicinity, since precise control is no longer guaranteed.

[0005] However, such sensors are associated with high costs and also increase the complexity of the hydraulic system, as the measurement signals from a large number of sensors have to be transmitted and processed.

[0006] It is an object of the present invention to provide a hydraulic system which is cost-effective and can reliably monitor the function of the valves.

[0007] The problem is solved with a hydraulic system according to claim 1. Advantageous further developments are described in the dependent claims.

[0008] According to the invention, a hydraulic system is provided with a hydraulic consumer and a first piping arrangement. The first piping arrangement connects the hydraulic consumer to a pressure line via a first electrically actuated valve and to a tank line via a second electrically actuated valve. A first hydraulic sensor is arranged in the first piping arrangement downstream of the first electrically actuated valve from the pressure line and upstream of the second electrically actuated valve from the hydraulic consumer. The hydraulic system further comprises a functional diagnostic unit for executing a first test sequence and a second test sequence. In the first test sequence, a first hydraulic test signal is applied by actuating the first electrically actuated valve for a first time interval.The functional diagnostic unit is designed to receive a measurement signal from the first hydraulic sensor and compare this signal with the first hydraulic test signal. In the second test sequence, a second hydraulic test signal is applied by actuating the second electrically operated valve for a second time interval. The functional diagnostic unit is designed to receive a measurement signal from the first hydraulic sensor and compare this signal with the second hydraulic test signal.

[0009] In other words, the functional diagnostic unit is designed in such a way that it performs a test sequence for each of the electrically actuated valves, which proceeds as follows: - Applying a hydraulic test signal by opening a corresponding electrically actuated valve for a correspondingly defined time interval, - Measuring the change in state at the first hydraulic sensor, - Transmitting the change in state to the functional diagnostic unit, - Comparison of the change of state with a change of state corresponding to the hydraulic test signal by the functional diagnostic unit, and - Determine whether the corresponding electrically actuated valve is defective.

[0010] By positioning the first hydraulic sensor within the first line assembly, the condition within the first line assembly can be reliably determined. The first hydraulic sensor is therefore positioned in the first line assembly between the hydraulic consumer on one side and the first and second electrically actuated valves on the other. In the hydraulic system described below as an example, the first hydraulic sensor is described using the example of a pressure sensor. The first and second electrically actuated valves can each be designed as direct-acting 2 / 2-way valves. In particular, the first and second electrically actuated valves can be designed as poppet valves.It is also conceivable that the first and second electrically actuated valves are provided as valve cartridges. The electrically actuated valves are preferably pre-tensioned to a closed state, so that when actuated, they are moved from the closed state to an open state and, after actuation, are returned to a closed state by the pre-tension.

[0011] In this example, the first test sequence includes an initial hydraulic test signal. This signal is generated by opening the first electrically actuated valve for a defined time interval and then closing it after this interval has elapsed. Opening the first electrically actuated valve, which is connected to the pressure line, regularly causes the pressure in the first line assembly to rise. This pressure increase, and thus the pressure change, is detected by the first hydraulic sensor and recorded by the diagnostic unit. The diagnostic unit compares the pressure change detected by the first hydraulic sensor with the expected pressure change for the initial hydraulic test signal. If the actual pressure change deviates from the expected pressure change, the first electrically actuated valve is defective.If the pressure remains unchanged after the first time interval, or if the pressure change is lower than expected, the first electrically actuated valve will not open, or will not open completely, when activated. If the pressure continues to rise after the first time interval, the first electrically actuated valve will not close again after activation. The diagnostic unit will issue an error message if the pressure change deviates from the expected pressure change.

[0012] Analogous to the first test sequence, the functional diagnostic unit then executes the second test sequence. In this example, the second test sequence includes a second hydraulic test signal. This second hydraulic test signal is generated by opening the second electrically actuated valve for a defined second time interval and then closing it after this interval has elapsed. Regularly, opening the second electrically actuated valve, which is connected to the tank line, causes a drop in pressure in the first line assembly. The first hydraulic sensor detects this pressure drop, and thus the pressure change, which is then measured by the functional diagnostic unit. The functional diagnostic unit compares the pressure change detected by the first hydraulic sensor with the pressure change expected for the second hydraulic test signal.If the actual pressure change deviates from the expected pressure change, the second electrically actuated valve is defective. If the pressure remains unchanged after the second time interval, or if the pressure change is lower than the expected pressure change, the second electrically actuated valve will not open, or will not open completely, when actuated. If the pressure continues to drop after the second time interval, the second electrically actuated valve will not close again after actuating. The diagnostic unit issues a fault message if the pressure change deviates from the expected pressure change. The expected pressure changes depend primarily on the load of the hydraulic consumer.

[0013] Thus, a hydraulic system is provided with a functional diagnostic unit that can detect defects in individual electrically actuated valves by applying a hydraulic test signal to a hydraulic sensor that is usually already present in the system. In other words, no individual position or displacement sensors are required for the electrically actuated valves. The hydraulic system according to the invention is therefore cost-effective to manufacture and, thanks to the functional diagnostic unit, can ensure reliable operation of the electrically actuated valves. The functional diagnostic unit can be part of a control unit or designed as a standalone unit.

[0014] Preferably, the hydraulic consumer is a hydraulic cylinder. The hydraulic cylinder comprises a piston, a first working chamber, and a second working chamber separated from the first by the piston. The first working chamber is connected to the first pipe assembly. Thus, the hydraulic system can be operated with a common hydraulic consumer such as a hydraulic cylinder. Alternatively, it is also conceivable to use, for example, a hydraulic motor as the hydraulic consumer of the hydraulic system.

[0015] It is advantageous if the hydraulic system also has a second line arrangement. This second line arrangement connects the second working chamber to the pressure line via a third electrically actuated valve and to the tank line via a fourth electrically actuated valve. The functional diagnostic unit is further equipped to execute a third and a fourth test sequence. In the third test sequence, a third hydraulic test signal is applied by actuating the third electrically actuated valve for a third time interval. In the fourth test sequence, a fourth hydraulic test signal is applied by actuating the fourth electrically actuated valve for a fourth time interval.

[0016] Preferably, the functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor and to compare this signal with the third hydraulic test signal. Preferably, the functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor and to compare this signal with the fourth hydraulic test signal.

[0017] By incorporating the second line arrangement with the third and fourth electrically actuated valves, the hydraulic cylinder can be precisely controlled. Furthermore, the third and fourth test sequences ensure that the third and fourth electrically actuated valves do not malfunction in a way that could damage the hydraulic system during operation. The third test sequence follows the second and is structured analogously to the first.

[0018] In the hydraulic system described below as an example, the third and fourth electrically actuated valves are designed as direct-acting 2 / 2-way poppet valves. The third test sequence in this example includes a third hydraulic test signal. This signal is generated by opening the third electrically actuated valve for a defined time interval and then closing it. Regularly, opening the third electrically actuated valve, which is connected to the pressure line, increases the pressure in the second line assembly and thus in the second working chamber of the hydraulic cylinder. This pressure increase in the second working chamber is transmitted via the piston to the first working chamber and thus to the first line assembly, in which the first hydraulic sensor is located.The pressure increase, and thus the pressure change, is detected by the first hydraulic sensor and recorded by the diagnostic unit. The diagnostic unit compares the pressure change detected via the first hydraulic sensor's measurement signal with the pressure change expected for the third hydraulic test signal. If the actual pressure change deviates from the expected pressure change, a defect in the third electrically actuated valve is present. If the pressure remains unchanged after the third time interval, or if the pressure change is lower than the expected pressure change, the third electrically actuated valve will not open, or will not open completely, when actuated. If the pressure continues to rise after the third time interval, the third electrically actuated valve will not close again after actuating. The diagnostic unit issues a fault message if the pressure change deviates from the expected pressure change.

[0019] Analogous to the second test sequence, the fourth test sequence is executed following the third. The fourth test sequence includes a fourth hydraulic test signal. This signal is generated by opening the fourth electrically actuated valve for a defined time interval and then closing it. Regularly, opening this valve, which is connected to the tank line, causes a pressure drop in the second line assembly and consequently in the second working chamber of the hydraulic cylinder. This pressure drop is transmitted via the piston to the first working chamber and to the first line assembly, where the first hydraulic sensor is located. The pressure drop, and thus the pressure change, is detected by the first hydraulic sensor and recorded by the diagnostic unit.The diagnostic unit compares the pressure change detected by the first hydraulic sensor's measurement signal with the pressure change expected by the fourth hydraulic test signal. If the actual pressure change deviates from the expected pressure change, the fourth electrically actuated valve is defective. If the pressure remains unchanged after the fourth time interval, or if the pressure change is lower than the expected pressure change, the fourth electrically actuated valve will not open, or will not open completely, when actuated. If the pressure continues to drop after the fourth time interval, the fourth electrically actuated valve will not close again after actuating. The diagnostic unit issues a fault message if the pressure change deviates from the expected pressure change.

[0020] Alternatively or additionally, a second hydraulic sensor is arranged in the second pipe configuration downstream of the third electrically actuated valve (viewed from the pressure line) and upstream of the fourth electrically actuated valve (viewed from the hydraulic consumer). This additional second hydraulic sensor in the second pipe configuration allows the condition of the hydraulic system to be reliably determined in both pipe configurations.

[0021] Preferably, the functional diagnostic unit is further configured to receive a measurement signal from the second hydraulic sensor and to compare the measurement signal of the second hydraulic sensor with the first hydraulic test signal during the execution of the first test sequence, and / or with the second hydraulic test signal during the execution of the second test sequence, and / or with the third hydraulic test signal during the execution of the third test sequence, and / or with the fourth hydraulic test signal during the execution of the fourth test sequence, analogous to the comparison described above with regard to the first hydraulic sensor. In other words, the functional diagnostic unit can use either the measurement signals of the first hydraulic sensor, the measurement signals of the second hydraulic sensor, or the measurement signals of the first hydraulic sensor and the measurement signals of the second hydraulic sensor for comparison with the hydraulic test signals.By comparing the measurement signals of the second hydraulic sensor with the hydraulic test signals, the functional diagnostic unit can more reliably detect a defect in an electrically actuated valve. For example, the measurement signal of the second hydraulic sensor could be compared with the third hydraulic test signal during the third test sequence and with the fourth hydraulic test signal during the fourth test sequence, while the measurement signals of the first hydraulic sensor would be compared with the first hydraulic test signal during the first test sequence and with the second hydraulic test signal during the second test sequence. In other words, the measurement signals of the hydraulic sensor that is connected to the corresponding electrically actuated valves in a pipe arrangement can be used for comparison.

[0022] It is also conceivable that the first hydraulic sensor is a pressure sensor or a flow sensor. The second hydraulic sensor can therefore be either a pressure sensor or a flow sensor. The measurement signal from the first hydraulic sensor can thus indicate a change in pressure or a change in flow rate. The measurement signal from the second hydraulic sensor can also indicate a change in pressure or a change in flow rate. By using pressure sensors or flow sensors, the test procedures can be reliably carried out with cost-effective sensors that are common in hydraulic systems.

[0023] In this context, it should be noted that the respective measurement signal of the first hydraulic sensor or the second hydraulic sensor can be processed by the functional diagnostic unit in such a way that a change in the measurement parameter, and not an absolute value, is available. In other words, if the first hydraulic sensor is a pressure sensor, then a measured value within the meaning of the present invention can be understood as either an absolute pressure value or a pressure change, which is compared by the functional diagnostic unit with the corresponding expected value.

[0024] It is advantageous if the functional diagnostic unit is designed to execute the first, second, third, and / or fourth test sequences once, preferably after the hydraulic system is switched on. This allows defects in individual electrically actuated valves to be detected immediately after the hydraulic system is switched on, before any defects in the hydraulic system's operation cause damage. This ensures the proper functioning of the hydraulic system in a simple and direct manner.

[0025] Furthermore, it is conceivable that the functional diagnostic unit is designed to periodically superimpose a hydraulic control signal during the operation of the hydraulic system by executing the first, second, third, and / or fourth test sequences. By periodically superimposing the hydraulic control signal with the hydraulic test signals of the corresponding test sequences, defects in the electrically actuated valves can be continuously detected during operation of the hydraulic system. In the event of a defect occurring during operation, the hydraulic system can be immediately shut down to prevent potential damage. The hydraulic test signals must be selected in such a way that they do not influence the hydraulic control signal to such an extent that precise control of the hydraulic system is prevented.

[0026] Advantageously, the first time interval, the second time interval, the third time interval, and / or the fourth time interval are individually configurable. Individual configuration of the time intervals ensures reliable test sequences for each electrically actuated valve. The time intervals can be configured, for example, based on the loads applied to the hydraulic system. The configuration of the time intervals can be performed manually or, alternatively, automatically, for example, by the functional diagnostic unit. Adaptive adjustment of the individual time intervals is also conceivable.In adaptive adjustment, the functional diagnostic unit can, for example, if the measurement signals of a hydraulic sensor deviate from a hydraulic test signal within a predefined limit value, extend a corresponding time interval until a reliable statement about a defect can be made.

[0027] It is also conceivable that the first hydraulic sensor is integrated into one of the first or second electrically actuated valves, and / or that the second hydraulic sensor is integrated into one of the third or fourth electrically actuated valves. By integrating the first and / or the second hydraulic sensor, very precise measurement signals from the first hydraulic sensor can be acquired directly at one of the first and second electrically actuated valves, and / or measurement signals from the second hydraulic sensor can be acquired directly at one of the third or fourth electrically actuated valves with minimal interference.

[0028] The hydraulic system described above, with four electrically actuated valves, can thus be designed as a square-control hydraulic system without the use of a spool valve. Instead, the square control according to the invention is implemented via the four individually electrically actuated valves, which are preferably designed as poppet valves and, more preferably, as 2 / 2-way valves. To achieve reliable square control, the hydraulic system can include a control unit that actuates the individual electrically actuated valves accordingly.

[0029] The control unit can, for example, incorporate an artificial neural network. One advantage of using a neural network is the ability to extract useful output correlations from a multitude of input parameters, which can then be used for signal processing within the control loop. Furthermore, a neural network can adaptively learn new rules and adjust to new situations, thereby compensating for gradual effects such as valve wear or gradually changing properties of the hydraulic fluid. This allows for the compensation of aging effects caused, for example, by friction changes over time or hydraulic sensor drift. It also makes it possible to consider and compensate for environmental influences, such as temperature fluctuations.

[0030] A further advantage is the ability to train the neural network using existing datasets for a specific target situation, such as a particular operating point, which can improve the alignment of setpoints and actual values. It is therefore also beneficial if the individual electrically actuated valves form a valve network and are interconnected, for example, via a bus system.

[0031] It is particularly advantageous if the individual electrically operated valves are identical in design. This allows for easy and quick replacement and also the stocking of spare valves that are relatively universally applicable in the hydraulic system.

[0032] The invention further comprises a diagnostic method for checking the functionality of the electrically actuated valves provided in the hydraulic system with a functional diagnostic unit, as described above.

[0033] The invention will now be explained in more detail with reference to the embodiments shown in the figures. The figures schematically show: Fig. 1 a hydraulic system according to a first embodiment with a pipe arrangement; Fig. 2 a hydraulic system according to a second embodiment comprising a hydraulic cylinder, two pipe arrangements and two hydraulic sensors; Fig. 3 exemplary test sequences of the electrically actuated valves of the second embodiment and the measurement signals of the hydraulic sensors; and

[0034] In Fig. Figure 1 shows a circuit diagram of a hydraulic system 10 according to the invention. The hydraulic system 10 comprises a hydraulic consumer V, which is connected to a first line assembly 12. Within the first line assembly 12, a first hydraulic sensor 16, a first electrically actuated valve 20, and a second electrically actuated valve 22 are arranged. The first line assembly 12 hydraulically connects the hydraulic consumer V to a pressure line P and to a tank line T.

[0035] The first electrically actuated valve 20 and the second electrically actuated valve 22 are designed as direct-acting 2 / 2-way poppet valves and are spring-loaded in a closed position. The first electrically actuated valve 20 and the second electrically actuated valve 22 can be electromagnetically switched to an open position by energizing them or applying a corresponding signal. The first electrically actuated valve 20 is arranged in the first line assembly 12 such that opening the first electrically actuated valve 20 allows hydraulic fluid to flow from the pressure line P into the first line assembly 12. The second electrically actuated valve 22 is arranged in the first line assembly 12 such that opening the second electrically actuated valve 22 allows hydraulic fluid to flow from the first line assembly 12 into the tank line T.

[0036] The first hydraulic sensor 16 is arranged in the first line assembly 12 downstream of the first electrically actuated valve 20, viewed from the pressure line P, and upstream of the second electrically actuated valve 22, viewed from the hydraulic consumer V. In the present embodiment, the first hydraulic sensor 16 is a pressure sensor that measures the pressure within the first line assembly 12. Alternatively, the first hydraulic sensor 16 can also be a flow sensor that measures the flow rate within the first line assembly 12. The first hydraulic sensor 16 can also be integrated directly into one of the housings of the first electrically actuated valve 20 or the second electrically actuated valve 22.

[0037] The first electrically actuated valve 20 and the second electrically actuated valve 22 are controlled by a control unit 1. As shown, the first hydraulic sensor 16 is also connected to the control unit 1. A measurement signal M1 from the first hydraulic sensor 16 is transmitted to the control unit 1. In this case, the control unit 1 includes a functional diagnostic unit 2. However, the functional diagnostic unit 2 can also be a separate unit from the control unit 1.

[0038] The functional diagnostic unit 2 is designed to perform a first test sequence and a second test sequence. The first and second test sequences can be executed once by the functional diagnostic unit 2 after the hydraulic system 10 is switched on, or they can be repeated continuously and periodically during the operation of the hydraulic system 10. During continuous repetition in operation, a hydraulic control signal is successively superimposed by the first and second test sequences in such a way that, due to the inertia of the hydraulic consumer V, only minor changes occur at the hydraulic consumer V compared to the desired hydraulic control signal.

[0039] In the first test sequence, the functional diagnostic unit 2 applies a first test signal to the hydraulic system 10. This first test signal is generated by opening the first electrically actuated valve 20 for a first time interval t1. Opening the first electrically actuated valve 20 allows hydraulic fluid to flow from the pressure line P into the first line assembly 12, causing the pressure in the first line assembly 12 to rise. The first hydraulic sensor 16 measures the pressure increase in the first line assembly 12 and transmits the measurement signal M1 from the first hydraulic sensor 16 to the functional diagnostic unit 2. The functional diagnostic unit 2 determines the recorded pressure change in the first line assembly 12 from the pressure increase for a period that begins with the application of the first test signal and lasts longer than the first time interval t1.The functional diagnostic unit compares the detected pressure change with the pressure change expected for the first hydraulic test signal. The pressure change expected for the first hydraulic test signal depends on the pressure in the pressure line and the load of the hydraulic consumer.

[0040] If the recorded pressure change of the first hydraulic test signal matches the expected pressure change for the first hydraulic test signal, the first electrically actuated valve 20 has no defect.

[0041] If the measured pressure change of the first hydraulic test signal is greater than the expected pressure change for the first hydraulic test signal, the first electrically actuated valve 20 remains in an open position after the first hydraulic test signal is applied. The first electrically actuated valve 20 is therefore defective, as it does not fully return to the closed position. The functional diagnostic unit 2 displays an error message to the user.

[0042] If the detected pressure change of the first hydraulic test signal is less than the expected pressure change for the first hydraulic test signal, or if no pressure change is detected, the first electrically actuated valve 20 was not fully opened, or not opened at all, by the application of the first hydraulic test signal. The first electrically actuated valve 20 is therefore defective, as it does not move fully, or at all, into the open position. The functional diagnostic unit 2 displays an error message to the user.

[0043] If the first electrically actuated valve 20 is not defective, the functional diagnostic unit 2 then executes the second test sequence. In the second test sequence, the functional diagnostic unit 2 applies a second test signal to the hydraulic system 10. This second test signal is generated by opening the second electrically actuated valve 22 for a second time interval t2. Opening the second electrically actuated valve 22 causes hydraulic fluid to flow from the first line assembly 12 into the tank line T, thereby reducing the pressure in the first line assembly 12. The first hydraulic sensor 16 measures the pressure drop in the first line assembly 12 and transmits the measurement signal M1 from the first hydraulic sensor 16 to the functional diagnostic unit 2.The functional diagnostic unit 2 determines the measured pressure change from the pressure drop in the first line order 12 for a period that begins with the application of the second test signal and lasts longer than the second time interval t2. The functional diagnostic unit 2 compares the measured pressure change with a pressure change expected for the second hydraulic test signal. The pressure change expected for the second hydraulic test signal depends on the pressure within the first line order 12.

[0044] If the recorded pressure change of the second hydraulic test signal matches the expected pressure change for the second hydraulic test signal, the second electrically actuated valve 22 has no defect.

[0045] If the detected pressure change of the second hydraulic test signal is greater than the expected pressure change for the second hydraulic test signal, the second electrically actuated valve 22 remains in an open position after the second hydraulic test signal is applied. The second electrically actuated valve 22 is therefore defective, as it does not fully return to the closed position. The functional diagnostic unit 2 displays an error message to the user.

[0046] If the detected pressure change of the second hydraulic test signal is less than the expected pressure change for the second hydraulic test signal, or if no pressure change is detected, the second electrically actuated valve 22 was not fully opened, or not opened at all, by the application of the second hydraulic test signal. The second electrically actuated valve 22 is therefore defective, as it does not move fully, or at all, into the open position. The functional diagnostic unit 2 displays an error message to the user.

[0047] In Fig. Figure 2 shows a circuit diagram of a further embodiment of a hydraulic system 100 according to the invention. The hydraulic system 100 comprises a first line arrangement 12 and a second line arrangement 14, as well as a hydraulic cylinder 28 as a hydraulic consumer. The hydraulic cylinder 28 includes a hydraulic cylinder housing 36 in which a first working chamber 32 and a second working chamber 34 are arranged. A piston 30 is movably arranged between the working chambers 32 and 34, and a piston rod is provided on the piston rod, which extends through the first working chamber 32.

[0048] The first line arrangement 12 hydraulically connects the first working chamber 32 to a pressure line P and a tank line T. Within the first line arrangement 12, a first hydraulic sensor 16, a first electrically actuated valve 20 and a second electrically actuated valve 20 are arranged, the arrangement of the first line arrangement 12 corresponding to the first embodiment and therefore not explained in more detail below.

[0049] The second line assembly 14 hydraulically connects the second working chamber 34 to a pressure line P and a tank line T. Within the second line assembly 14 are arranged a second hydraulic sensor 18, a third electrically actuated valve 24, and a fourth electrically actuated valve 26. The third electrically actuated valve 24 and the fourth electrically actuated valve 26 are also designed as direct-acting 2 / 2-way poppet valves and are spring-loaded to a closed position. The third electrically actuated valve 24 and the fourth electrically actuated valve 26 can be electromagnetically switched to an open position. The third electrically actuated valve 24 is arranged in the second line assembly 14 such that opening the third electrically actuated valve 24 allows hydraulic fluid to flow from the pressure line P into the second line assembly 14.The fourth electrically actuated valve 26 is arranged in the second line arrangement 14 such that when the fourth electrically actuated valve 26 is opened, hydraulic fluid flows from the second line arrangement 14 into the tank line T.

[0050] The second hydraulic sensor 18 is located in the second line assembly 14 downstream of the third electrically actuated valve 24, as viewed from the pressure line P, and upstream of the fourth electrically actuated valve 26, as viewed from the hydraulic cylinder 28. In this case, the second hydraulic sensor 18 is a pressure sensor that measures the pressure within the second line assembly 12. Alternatively, the second hydraulic sensor 18 can also be a flow sensor, as described above for the first hydraulic sensor 16. The second hydraulic sensor 18 can also be integrated directly into one of the housings of the third electrically actuated valve 24 or the fourth electrically actuated valve 26.

[0051] The first electrically actuated valve 20, the second electrically actuated valve 22, the third electrically actuated valve 24, and the fourth electrically actuated valve 26 are controlled by a control unit 1. During operation of the hydraulic system 100, the first electrically actuated valve 20 and the fourth electrically actuated valve 26, as well as the second electrically actuated valve 22 and the third electrically actuated valve 24, are actuated simultaneously. In other words, when hydraulic fluid flows into one of the two line arrangements 12, 14, hydraulic fluid is discharged from the other of the two line arrangements 12, 14 to precisely enable the piston 30 to move within the hydraulic cylinder 28.The first and fourth electrically actuated valves 20, 26 and the second and third electrically actuated valves 22, 24 function like a 4 / 3-way valve due to the common control and can be controlled in such a way that the piston rod of the hydraulic cylinder 28 extends, retracts or holds its position.

[0052] The measurement signal M1 from the first hydraulic sensor 16 and a measurement signal M2 from the second hydraulic sensor 18 are transmitted to the control unit 1. The control unit 1 comprises a functional diagnostic unit 2.

[0053] The functional diagnostic unit 2 is designed to perform a first test sequence, a second test sequence, a third test sequence, and a fourth test sequence. The first and second test sequences correspond to the first and second test sequences of the first embodiment and are therefore not described again below.

[0054] If the second electrically actuated valve 22 is not defective, the functional diagnostic unit 2 then executes the third test sequence. The third test sequence is performed for the third electrically actuated valve 24 using a third hydraulic test signal, analogous to the first test sequence.

[0055] In the third test sequence, the functional diagnostic unit 2 applies a third test signal to the hydraulic system 100. This third test signal is generated by opening the third electrically actuated valve 24 for a third time interval t3. Opening the third electrically actuated valve 24 causes hydraulic fluid to flow from the pressure line P into the second line assembly 14, thereby increasing the pressure in the second line assembly 14. In the illustrated embodiment, the second hydraulic sensor 18 measures the pressure increase in the second line assembly 14 and transmits the measurement signal M2 from the second hydraulic sensor 18 to the functional diagnostic unit 2.

[0056] Alternatively, the pressure increase in the second line assembly 14 could also be measured indirectly via the first hydraulic sensor 16. If the pressure in the second line assembly 14 increases, the pressure in the second working chamber 34 of the hydraulic cylinder 28 also increases. The piston 30 transmits the pressure to the first working chamber 32 and thus to the first line assembly 12. The increasing pressure of the first line assembly 12 can then be measured by the first hydraulic sensor 16. Similarly, the pressure increase of the first line assembly 12 for the first and second test sequences could also be measured via the second hydraulic sensor 18, or the pressure increases of all test sequences could be measured in parallel by the first hydraulic sensor 16 and the second hydraulic sensor 18.

[0057] The functional diagnostic unit 2 determines the measured pressure change from the pressure increase in the second line order 14 for a period that begins with the application of the third test signal and lasts longer than the third time interval t3. The functional diagnostic unit 2 compares the measured pressure change with a pressure change expected for the third hydraulic test signal. The pressure change expected for the third hydraulic test signal depends on the pressure of the pressure line and the load applied to the piston rod of the hydraulic cylinder 28.

[0058] If the recorded pressure change of the third hydraulic test signal matches the expected pressure change for the third hydraulic test signal, the third electrically actuated valve 24 has no defect.

[0059] If the measured pressure change of the third hydraulic test signal is greater than the expected pressure change for the third hydraulic test signal, the third electrically actuated valve 24 remains in an open position after the third hydraulic test signal is applied. The third electrically actuated valve 24 is therefore defective, as it does not fully return to the closed position. The functional diagnostic unit 2 displays an error message to the user.

[0060] If the detected pressure change of the third hydraulic test signal is less than the expected pressure change for the third hydraulic test signal, or if no pressure change is detected, the third electrically actuated valve 24 was not fully opened, or not opened at all, by the application of the third hydraulic test signal. The third electrically actuated valve 24 is therefore defective, as it does not move fully, or at all, into the open position. The functional diagnostic unit 2 displays an error message to the user.

[0061] If the third electrically actuated valve 24 is not defective, the functional diagnostic unit 2 then executes the fourth test sequence. The fourth test sequence is structured analogously to the second test sequence. In the fourth test sequence, the functional diagnostic unit 2 applies a fourth test signal to the hydraulic system 100. This fourth test signal is generated by opening the fourth electrically actuated valve 26 for a fourth time interval t4. By opening the fourth electrically actuated valve 26, hydraulic fluid flows from the second line assembly 14 into the tank line T, causing the pressure in the second line assembly 14 to drop. The second hydraulic sensor 18 measures the pressure drop in the second line assembly 14 and transmits the measurement signal M2 from the second hydraulic sensor 18 to the functional diagnostic unit.The functional diagnostic unit 2 determines the measured pressure change from the pressure drop in the second line order 14 for a period that begins with the application of the fourth test signal and lasts longer than the fourth time interval t4. The functional diagnostic unit 2 compares the measured pressure change with a pressure change expected for the fourth hydraulic test signal. The pressure change expected for the fourth hydraulic test signal depends on the pressure within the second line order 14.

[0062] If the recorded pressure change of the fourth hydraulic test signal matches the expected pressure change for the fourth hydraulic test signal, the fourth electrically actuated valve 22 has no defect.

[0063] If the measured pressure change of the fourth hydraulic test signal is greater than the expected pressure change for the fourth hydraulic test signal, the fourth electrically actuated valve 26 remains in an open position after the fourth hydraulic test signal is applied. The fourth electrically actuated valve 26 is therefore defective, as it does not fully return to the closed position. The functional diagnostic unit 2 displays an error message to the user.

[0064] If the detected pressure change of the fourth hydraulic test signal is less than the expected pressure change for the fourth hydraulic test signal, or if no pressure change is detected, the fourth electrically actuated valve 26 was not fully opened, or not opened at all, by applying the fourth hydraulic test signal. The fourth electrically actuated valve 26 is therefore defective, as it does not move fully, or at all, into the open position. The functional diagnostic unit 2 displays an error message to the user.

[0065] Fig. Figure 3 shows two corresponding diagrams illustrating the time sequence of the test procedures. The diagram above shows the current I applied to the electrically actuated valves 20, 22, 24, 26 over time t. The diagram below shows the corresponding pressure profile based on the measurement signals M1, M2 of the first and second hydraulic sensors 16, 18 over time t.

[0066] Initially, the first electrically actuated valve 20 is activated by the functional diagnostic unit 2 for a first time interval t1 as part of the first test sequence. During this time, the first electrically actuated valve 20 opens. As can be seen from the measurement signal M1, the pressure measured by the first hydraulic sensor 16 in the first line arrangement 14 increases and reaches a constant pressure after the first electrically actuated valve 20 is activated during the first pause interval tw1. The measured pressure change corresponds to the pressure change expected for the first test signal. Therefore, the first electrically actuated valve 20 is not defective.

[0067] After the first pause interval tw1 has elapsed, the functional diagnostic unit 2 executes the second test sequence. For a second time interval t2, the second electrically actuated valve 22 is activated so that it is fully open. As a result, the pressure measured by the first hydraulic sensor 16 within the first line assembly 14 decreases and, after the second electrically actuated valve 22 is activated during the second pause interval tw2, reaches a constant pressure, as can be seen from the measurement signal M1. The measured pressure change also corresponds to the pressure change expected for the second test signal. Therefore, the second electrically actuated valve 22 is not defective.

[0068] After the second pause interval tw2 has elapsed, the functional diagnostic unit 2 executes the third test sequence. For a third time interval t3, the third electrically actuated valve 24 is controlled so that it opens to its maximum extent. The pressure measured by the second hydraulic sensor 18 within the second line arrangement 14 increases and, after the third electrically actuated valve 24 is activated in the third pause interval tw3, reaches a constant pressure, as can be seen from the measurement signal M2. Here, too, the measured pressure change corresponds to the pressure change expected for the third test signal. The third electrically actuated valve 24 therefore does not exhibit a defect.

[0069] Finally, after the third pause interval tw3 has elapsed, the functional diagnostic unit 2 executes the fourth test sequence. For a fourth time interval, the fourth electrically actuated valve 26 is activated. During this test, the fourth electrically actuated valve 24 opens to its maximum. As can be seen from the measurement signal M2, the pressure measured by the second hydraulic sensor 18 within the second line arrangement 14 decreases and reaches a constant pressure. The measured pressure change corresponds to the pressure change expected for the fourth test signal. Therefore, the fourth electrically actuated valve 26 is not defective.

[0070] The diagram below shows, as an example, a measurement signal M1 as a dashed line and a measurement signal M2 as a dotted line, as they can occur in the event of a defect in the second electrically actuated valve 22 and a defect in the third electrically actuated valve 24, respectively.

[0071] The dashed line of the measurement signal M1 indicates that the pressure measured by the first hydraulic sensor 16 does not drop after the second electrically actuated valve 22 is activated, but remains constant. The measured pressure change is therefore smaller than the pressure change expected for the second test signal. Consequently, the second electrically actuated valve 22 does not open as desired, but remains completely closed. In such a case, the functional diagnostic unit 2 issues an error message to the user.

[0072] The dashed line of the measurement signal M2 shows that the pressure measured by the second hydraulic sensor 18 is not constant after actuating the third electrically actuated valve 24, but continues to rise. The measured pressure change is therefore greater than the pressure change expected for the third test signal. In such a case, the functional diagnostic unit 2 also outputs an error message to the user. REFERENCE MARK LIST 1 control unit 2 Functional diagnostic unit 10, 100 hydraulic system 12 First Management Order 14 Second line arrangement 16 First hydraulic sensor 18 Second hydraulic sensor 20 First electrically operated valve 22 Second electrically operated valve 24 Third electrically operated valve 26 Fourth electrically operated valve 28 hydraulic cylinders 30 pistons 32 First workroom 34 Second workroom 36 hydraulic cylinder housings P Pressure line T tank line V Hydraulic consumers p print t time I Current intensity t1 First time interval t2 Second time interval t3 Third time interval t4 Fourth time interval tw1 First break interval tw2 Second break interval tw3 Third break interval M1 Measurement signal of the first hydraulic sensor 16 M2 Measurement signal of the second hydraulic sensor 18

Claims

[1] Hydraulic system (10, 100) with a hydraulic consumer (V), a first line arrangement (12), a first hydraulic sensor (16), a first electrically actuated valve (20), a second electrically actuated valve (22), a pressure line (P) and a tank line (T), wherein the first line arrangement (12) connects the hydraulic consumer (V) to the pressure line (P) via the first electrically actuated valve (20) and wherein the first line arrangement (12) connects the hydraulic consumer (V) to the tank line (T) via the second electrically actuated valve (22), wherein the first hydraulic sensor (16) in the first line arrangement (12) is located downstream of the first electrically actuated valve (20) from the pressure line (D) and upstream of the second electrically actuated valve (22) from the hydraulic consumer (V), characterized by , that the hydraulic system (10, 100) further comprises a functional diagnostic unit (2) for performing a first test sequence and a second test sequence, wherein in the first test sequence a first hydraulic test signal is applied by actuating the first electrically actuated valve (20) for a first time interval (t1), and the functional diagnostic unit (2) is configured to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) of the first hydraulic sensor (16) with the first hydraulic test signal, and wherein in the second test sequence a second hydraulic test signal is applied by actuating the second electrically actuated valve (22) for a second time interval (t2) and the functional diagnostic unit (2) is configured to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) of the first hydraulic sensor (16) with the second hydraulic test signal. [2] Hydraulic system (100) according to claim 1, characterized by , that the hydraulic consumer (V) is a hydraulic cylinder (28), wherein the hydraulic cylinder (28) has a piston (30), a first working chamber (32) and a second working chamber (34) separated from the first working chamber (32) by the piston (30), and wherein the first working chamber (32) is connected to the first piping arrangement (12). [3] Hydraulic system (100) according to claim 2, characterized by , that the hydraulic system (100) further comprises a second line arrangement (14), a third electrically actuated valve (24), and a fourth electrically actuated valve (24), wherein the second line arrangement (14) connects the second working chamber (34) to the pressure line (P) via a third electrically actuated valve (24) and connects it to the tank line (T) via a fourth electrically actuated valve (26), and wherein the functional diagnostic unit (2) is further configured to execute a third test sequence and a fourth test sequence, wherein in the third test sequence a third hydraulic test signal is applied by actuating the third electrically actuated valve (24) for a first time interval (t3), and wherein in the fourth test sequence a fourth hydraulic test signal is applied by controlling the fourth electrically actuated valve (26) for a fourth time interval (t4). [4] Hydraulic system (100) according to claim 3, characterized by , that the functional diagnostic unit (2) is configured to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) of the first hydraulic sensor (16) with the third hydraulic test signal, and wherein the functional diagnostic unit (2) is further configured to receive a measurement signal from the first hydraulic sensor (M1) and to compare the measurement signal of the first hydraulic sensor (M1) with the fourth hydraulic test signal. [5] Hydraulic system (100) according to any one of the preceding claims 2 to 4, characterized by , that a second hydraulic sensor (18) is arranged in the second line arrangement (14) downstream of the third electrically actuated valve (24) as seen from the pressure line (P) and upstream of the fourth electrically actuated valve (26) as seen from the hydraulic cylinder (28). [6] Hydraulic system (100) according to claim 5, characterized by, that the functional diagnostic unit (2) is further configured to receive a measurement signal (M2) from the second hydraulic sensor (18) and to compare the measurement signal (M2) of the second hydraulic sensor (18) with the first hydraulic test signal when performing the first test sequence and / or with the second hydraulic test signal when performing the second test sequence and / or with the third hydraulic test signal when performing the third test sequence and / or with the fourth hydraulic test signal when performing the fourth test sequence. [7] Hydraulic system (10, 100) according to one of the preceding claims, characterized by , that the first hydraulic sensor (16) is a pressure sensor or a flow sensor and / or the second hydraulic sensor (18) is a pressure sensor or a flow sensor. [8] Hydraulic system (10, 100) according to one of the preceding claims, characterized by, that the functional diagnostic unit (2) is further designed to perform the first test sequence and / or the second test sequence and / or the third test sequence and / or the fourth test sequence once, preferably after switching on the hydraulic system (10, 100). [9] Hydraulic system (10, 100) according to any one of claims 1 to 7, characterized by , that the functional diagnostic unit (2) is further designed to periodically superimpose a hydraulic control signal during the ongoing operation of the hydraulic system (10, 100) by executing the first test sequence and / or the second test sequence and / or the third test sequence and / or the fourth test sequence. [10] Hydraulic system (10, 100) according to one of the preceding claims, characterized by, that the first time interval (t1) is individually configurable and / or the second time interval (t2) is individually configurable and / or the third time interval (t3) is individually configurable and / or the fourth time interval (t4) is individually configurable.

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