hydraulic system

Abstract

The present invention relates to a hydraulic system 1 with a hydraulic consumer V and a first line arrangement 12. The first line arrangement 12 connects the hydraulic consumer V to a pressure line P via a first electrically actuated valve 20 and to a tank line T via a second electrically actuated valve 22. A first hydraulic sensor 16 is arranged in the first line arrangement 12 downstream of the first electrically actuated valve 20 as viewed from the pressure line D and upstream of the second electrically actuated valve 22 as viewed from the hydraulic consumer V. The invention is characterized in that the hydraulic system 1 further comprises a functional diagnostic unit 2 for executing a first test sequence and a second test sequence. In the first test sequence, a first hydraulic test signal is applied by controlling the first electrically actuated valve 20 for a first time interval t1.The functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor M1 and to compare the measurement signal from the first hydraulic sensor M1 with the first hydraulic test signal. In the second test sequence, a second hydraulic test signal is applied by controlling the second electrically actuated valve 22 for a second time interval t2. The functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor M1 and to compare the measurement signal from the first hydraulic sensor M1 with the second hydraulic test signal.

Description

[0001] The present invention relates to a hydraulic system with 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 regularly applied to the hydraulic consumer via a pressure line and a first electrically actuated valve. The hydraulic consumer is then relieved of pressure to a tank line via the first electrically actuated valve or a second electrically actuated valve. 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 while maintaining the lowest possible complexity. Monitoring the individual components of the hydraulic system is particularly important to ensure reliable operation of the hydraulic system and prevent any damage in the event of defects.

[0004] For this purpose, hydraulic systems typically have displacement or position sensors mounted on the electrically actuated valves, which monitor the positions of the individual valves. This detects any valve malfunction, such as jamming in a closed or open switching 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 the vicinity of the hydraulic system, as precise control is no longer guaranteed.

[0005] However, such sensors are associated with high costs and also increase the complexity of the hydraulic system, since the measurement signals from a large number of sensors must 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 line arrangement. The first line 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 line arrangement downstream of the first electrically actuated valve, as viewed from the pressure line, and upstream of the second electrically actuated valve, as viewed 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 configured to receive a measurement signal from the first hydraulic sensor and compare the measurement signal from the first hydraulic sensor with the first hydraulic test signal. In the second test sequence, a second hydraulic test signal is applied by controlling the second electrically actuated valve for a second time interval. The functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor and compare the measurement signal from the first hydraulic sensor with the second hydraulic test signal.

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

[0010] By arranging the first hydraulic sensor in the first line arrangement, the state within the first line arrangement can be reliably determined. The first hydraulic sensor is therefore arranged in the first line arrangement such that it is located between the hydraulic consumer on one side and the first electrically actuated valve and the second electrically actuated valve on the other side. In the hydraulic system described below as an example, the first hydraulic sensor is described using the example of a pressure sensor. The first electrically actuated valve and the second electrically actuated valve can each be designed as a directly controlled 2 / 2-way valve. In particular, the first electrically actuated valve and the second electrically actuated valve can be designed as a seat valve.It is also conceivable for the first electrically actuated valve and the second electrically actuated valve to be provided as valve cartridges. The electrically actuated valves are preferably preloaded 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 preload.

[0011] In this example, the first test sequence includes a first hydraulic test signal. The first hydraulic test signal is generated by opening the first electrically actuated valve for a defined first time interval and then closing the first electrically actuated valve after the first defined time interval has elapsed. Opening the first electrically actuated valve, which is connected to the pressure line, regularly causes the pressure in the first line arrangement to rise. The rising pressure and thus the pressure change is detected by the first hydraulic sensor and recorded by the functional diagnostic unit. The functional diagnostic unit compares the pressure change recorded via the measurement signal of the first hydraulic sensor with a pressure change expected for the first 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 has elapsed, or if the pressure change is lower than the expected pressure change, 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 has elapsed, the first electrically actuated valve will not close again after activation. The functional diagnostic unit issues an error message if the pressure change deviates from the expected pressure change.

[0012] Analogous to the first test sequence, the functional diagnostic unit executes the second test sequence following the first test sequence. In this example, the second test sequence includes a second hydraulic test signal. The second hydraulic test signal is generated by opening the second electrically actuated valve for a defined second time interval and then closing the second electrically actuated valve after the second defined time interval has elapsed. The pressure in the first line arrangement regularly drops when the second electrically actuated valve, which is connected to the tank line, opens. The falling pressure and thus the pressure change is recorded by the first hydraulic sensor in the functional diagnostic unit. The functional diagnostic unit compares the pressure change recorded via the measurement signal of the first hydraulic sensor with a pressure change expected for the second hydraulic test signal.If the actual pressure change deviates from the expected pressure change, the second electrically operated valve is defective. If the pressure remains unchanged after the second time interval has elapsed, or if the pressure change is lower than the expected pressure change, the second electrically operated valve will not open or will not open completely when activated. If the pressure continues to drop after the second time interval has elapsed, the second electrically operated valve will not close again after activation. The functional diagnostic unit issues an error message if the pressure change deviates from the expected pressure change. The expected pressure changes depend in particular on the load of the hydraulic consumer.

[0013] Thus, a hydraulic system is provided with a functional diagnostic unit that can detect defects in the 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 can thus be manufactured cost-effectively 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 be designed as a standalone unit.

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

[0015] It is advantageous if the hydraulic system further comprises a second line arrangement. The 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 configured to execute a third test sequence 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 compare the measurement signal from the first hydraulic sensor with the third hydraulic test signal. Preferably, the functional diagnostic unit is configured to receive a measurement signal from the first hydraulic sensor and compare the measurement signal from the first hydraulic sensor with the fourth hydraulic test signal.

[0017] By providing the second line arrangement with the third electrically actuated valve and the fourth electrically actuated valve, the hydraulic cylinder can be precisely controlled. The third test sequence and the fourth test sequence also ensure that the third electrically actuated valve and the fourth electrically actuated valve do not malfunction, which could lead to damage to the hydraulic system during operation. The third test sequence follows the second test sequence and is structured analogously to the first test sequence.

[0018] In the hydraulic system described below as an example, the third electrically actuated valve and the fourth electrically actuated valve are designed as directly actuated 2 / 2-way seat valves. In this example, the third test sequence comprises a third hydraulic test signal. The third hydraulic test signal is generated by opening the third electrically actuated valve for a defined third time interval and then closing the third electrically actuated valve. Opening the third electrically actuated valve, which is connected to the pressure line, regularly increases the pressure in the second line arrangement and thus in the second working chamber of the hydraulic cylinder. The pressure increase in the second working chamber is transmitted via the piston to the first working chamber and thus to the first line arrangement in which the first hydraulic sensor is arranged.The pressure increase and thus the pressure change is recorded by the first hydraulic sensor in the functional diagnostic unit. The functional diagnostic unit compares the pressure change recorded via the measurement signal of the first hydraulic sensor with a pressure change expected from the third hydraulic test signal. If the actual pressure change deviates from the expected pressure change, the third electrically operated valve is defective. If the pressure remains unchanged after the third time interval has elapsed, or if the pressure change is lower than the expected pressure change, the third electrically operated valve will not open or will not open completely when activated. If the pressure continues to rise after the third time interval has elapsed, the third electrically operated valve will not close again after activation. The functional diagnostic unit issues an error message if the pressure change deviates from the expected pressure change.

[0019] Analogous to the second test sequence, the fourth test sequence is carried out following the third test sequence. The fourth test sequence includes a fourth hydraulic test signal. The fourth hydraulic test signal is generated by opening the fourth electrically operated valve for a defined fourth time interval and then closing the fourth electrically operated valve. Opening the fourth electrically operated valve, which is connected to the tank line, regularly causes the pressure in the second line arrangement and thus also in the second working chamber of the hydraulic cylinder to drop. The pressure drop in the second working chamber is transferred via the piston to the first working chamber and to the first line arrangement in which the first hydraulic sensor is arranged. The pressure drop and thus the pressure change is recorded by the first hydraulic sensor in the functional diagnostic unit.The functional diagnostic unit compares the pressure change recorded via the measurement signal of the first hydraulic sensor with a pressure change expected from the fourth hydraulic test signal. If the actual pressure change deviates from the expected pressure change, the fourth electrically operated valve is defective. If the pressure remains unchanged after the fourth time interval has elapsed, or if the pressure change is lower than the expected pressure change, the fourth electrically operated valve will not open or will not open completely when activated. If the pressure continues to drop after the fourth time interval has elapsed, the fourth electrically operated valve will not close again after activation. The functional diagnostic unit issues an error message if the pressure change deviates from the expected pressure change.

[0020] Alternatively or additionally, a second hydraulic sensor is arranged in the second line arrangement downstream of the third electrically actuated valve as viewed from the pressure line and upstream of the fourth electrically actuated valve as viewed from the hydraulic consumer. The additional second hydraulic sensor in the second line arrangement allows the state of the hydraulic system in both line arrangements to be reliably determined.

[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 from the second hydraulic sensor with the first hydraulic test signal when executing the first test sequence and / or to compare it with the second hydraulic test signal when executing the second test sequence and / or to compare it with the third hydraulic test signal when executing the third test sequence and / or to compare it with the fourth hydraulic test signal when executing the fourth test sequence, analogously to the comparison described above with respect to the first hydraulic sensor. In other words, the functional diagnostic unit can use either the measurement signals from the first hydraulic sensor, the measurement signals from the second hydraulic sensor, or the measurement signals from the first hydraulic sensor and the measurement signals from the second hydraulic sensor for comparison with the hydraulic test signals.By comparing the measurement signals from 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, it is conceivable to compare the measurement signals from the second hydraulic sensor with the third hydraulic test signal when executing the third test sequence and with the fourth hydraulic test signal when executing the fourth test sequence, while comparing the measurement signals from the first hydraulic sensor with the first hydraulic test signal when executing the first test sequence and with the second hydraulic test signal when executing the second test sequence. In other words, the measurement signals from the hydraulic sensor that is arranged in a line arrangement with the corresponding electrically actuated valves can be used for the comparison.

[0022] It is also conceivable that the first hydraulic sensor is a pressure sensor or a volume flow sensor. The second hydraulic sensor can therefore be a pressure sensor or a volume flow sensor. The measurement signal from the first hydraulic sensor can thus indicate a change in pressure or a change in volume flow. The measurement signal from the second hydraulic sensor can indicate a change in pressure or a change in volume flow. By using pressure sensors or volume flow sensors, the test sequences can be reliably performed using cost-effective sensors that are commonly used in hydraulic systems.

[0023] In this context, it should be noted that the respective measurement signal from the first hydraulic sensor or the second hydraulic sensor can be calculated by the functional diagnostic unit in such a way that a change in the measurement parameter, rather than an absolute value, is available. In other words, if the first hydraulic sensor is a pressure sensor, a measured value within the meaning of the present invention can be understood as both an absolute pressure value and 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 configured to execute 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 the hydraulic system is switched on. This allows defects in the 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 provides a simple way to directly ensure the proper functioning of the hydraulic system.

[0025] It is further conceivable for the functional diagnostic unit to be designed to periodically superimpose a hydraulic control signal during ongoing operation of the hydraulic system by executing the first test sequence and / or the second test sequence and / or the third test sequence and / or the fourth test sequence. By periodically superimposing the hydraulic control signal with the hydraulic test signals of the corresponding test sequences, defects in the corresponding electrically actuated valves can be continuously detected during operation of the hydraulic system, and the hydraulic system can be immediately shut down if a defect occurs during operation in order to prevent any damage to the hydraulic system. The hydraulic test signals must be selected such 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 is individually configurable and / or the second time interval is individually configurable and / or the third time interval is individually configurable and / or the fourth time interval is individually configurable. Individual configuration of the individual time intervals ensures reliable test sequences for the individual electrically actuated valves. The time intervals can be configured, for example, depending on the loads applied to the hydraulic system. The time intervals can be configured manually or, alternatively, automatically, for example, by the functional diagnostic unit. Adaptive adjustment of the individual time intervals is also conceivable.In the case of adaptive adjustment, for example, if the measurement signals of a hydraulic sensor deviate from a hydraulic test signal within a predefined limit value, the functional diagnostic unit can extend a corresponding time interval until a reliable statement about a defect can be made.

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

[0028] The above-described hydraulic system with four electrically actuated valves can thus be designed as a hydraulic system with square control without the use of a slide valve. Rather, the square control according to the invention is implemented via the four individually electrically actuated valves, which are designed in particular as seat valves and preferably as 2 / 2-way valves. To implement a reliable square control, the hydraulic system can have a control unit that controls the individual electrically actuated valves accordingly.

[0029] The control unit can, for example, comprise 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 in the control loop. Furthermore, a neural network can adaptively learn new rules and adapt to new situations, which can compensate for gradually occurring effects such as valve wear or gradually changing material properties of the hydraulic fluid. This makes it possible to compensate for aging effects caused, for example, by changes in friction over time or hydraulic sensor drift. It is also possible to consider and compensate for environmental influences, for example, those caused by temperature fluctuations.

[0030] Another particularly advantageous feature is the ability to train or teach the neural network to a specific target situation, such as a specific operating point, using existing data sets. This can be beneficial for improved setpoint-actual value alignment. It is therefore also advantageous if the individual electrically actuated valves form a valve network and are connected to each other, 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 availability of replacement valves that can be used relatively universally 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 is explained in more detail below with reference to exemplary embodiments shown in the figures. Here, schematically: Fig. 1 shows a hydraulic system according to a first embodiment with a line arrangement; Fig. 2 a hydraulic system according to a second embodiment with a hydraulic cylinder, two line arrangements and two hydraulic sensors; Fig. 3 exemplary test sequences of the electrically actuated valves of the second embodiment and the measuring 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 arrangement 12. Arranged within the first line arrangement 12 are a first hydraulic sensor 16, a first electrically actuated valve 20, and a second electrically actuated valve 22. The first line arrangement 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 directly controlled 2 / 2-way seat valves and are preloaded into a closed position by a spring. The first electrically actuated valve 20 and the second electrically actuated valve 22 can be electromagnetically switched to an open position by energizing or applying a corresponding signal. The first electrically actuated valve 20 is arranged in the first line arrangement 12 in such a way that opening the first electrically actuated valve 20 causes hydraulic fluid to flow from the pressure line P into the first line arrangement 12. The second electrically actuated valve 22 is arranged in the first line arrangement 12 in such a way that opening the second electrically actuated valve 22 causes hydraulic fluid to flow from the first line arrangement 12 into the tank line T.

[0036] The first hydraulic sensor 16 is arranged in the first line arrangement 12 downstream of the first electrically actuated valve 20, as seen from the pressure line P, and upstream of the second electrically actuated valve 22, as seen from the hydraulic consumer V. In the present exemplary embodiment, the first hydraulic sensor 16 is a pressure sensor that measures the pressure within the first line arrangement 12. Alternatively, however, the first hydraulic sensor 16 can also be a volume flow sensor that measures a volume flow within the first line arrangement 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. The control unit 1 here comprises 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 configured to execute a first test sequence and a second test sequence. The first test sequence and the second test sequence 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 ongoing operation of the hydraulic system 10. During continuous repetition during ongoing operation, a hydraulic control signal is successively superimposed by the first test sequence and the second test sequence such 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. The first test signal is generated by opening the first electrically actuated valve 20 for the duration of a first time interval t1. By opening the first electrically actuated valve 20, hydraulic fluid flows from the pressure line P into the first line arrangement 12, whereby the pressure in the first line arrangement 12 increases. The first hydraulic sensor 16 measures the pressure increase in the first line arrangement 12 and transmits the measurement signal M1 of the first hydraulic sensor 16 to the functional diagnostic unit 2. From the pressure increase in the first line arrangement 12, the functional diagnostic unit 2 determines the recorded pressure change 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 recorded 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 is not defective.

[0041] If the recorded pressure change of the first hydraulic test signal is greater than the pressure change expected 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 because it does not move completely back to the closed position. The functional diagnostic unit 2 issues an error message to the user.

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

[0043] If the first electrically actuated valve 20 is not defective, the functional diagnostic unit 2 subsequently 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. The second test signal is generated by opening the second electrically actuated valve 22 for a second time interval t2. By opening the second electrically actuated valve 22, hydraulic fluid flows from the first line arrangement 12 into the tank line T, causing the pressure in the first line arrangement 12 to drop. The first hydraulic sensor 16 measures the pressure drop in the first line arrangement 12 and transmits the measurement signal M1 of the first hydraulic sensor 16 to the functional diagnostic unit 2.The functional diagnostic unit 2 determines the recorded pressure change from the pressure drop in the first line arrangement 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 recorded 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 arrangement 12.

[0044] If the recorded pressure change of the second hydraulic test signal agrees with the expected pressure change for the second hydraulic test signal, the second electrically actuated valve 22 is not defective.

[0045] If the recorded pressure change of the second hydraulic test signal is greater than the pressure change expected 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 because it does not move completely back to the closed position. The functional diagnostic unit 2 issues an error message to the user.

[0046] If the recorded pressure change of the second hydraulic test signal is smaller than the pressure change expected for the second hydraulic test signal, or if no pressure change is present, the second electrically actuated valve 22 was not fully opened or not opened at all by applying the second hydraulic test signal. The second electrically actuated valve 22 is therefore defective because it does not move fully or not at all into the open position. The functional diagnostic unit 2 issues 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 has a first line arrangement 12 and a second line arrangement 14, as well as a hydraulic cylinder 28 as the hydraulic consumer. The hydraulic cylinder 28 comprises 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, 34, on which a piston rod is provided, 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 corresponding to the first line arrangement 12 of the first embodiment and is therefore not explained in more detail below.

[0049] The second line arrangement 14 hydraulically connects the second working chamber 34 to a pressure line P and a tank line T. A second hydraulic sensor 18, a third electrically actuated valve 24, and a fourth electrically actuated valve 26 are arranged within the second line arrangement 14. The third electrically actuated valve 24 and the fourth electrically actuated valve 26 are also designed as directly controlled 2 / 2-way seat valves and are preloaded into a closed position by a spring. 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 arrangement 14 in such a way that opening the third electrically actuated valve 24 causes hydraulic fluid to flow from the pressure line P into the second line arrangement 14.The fourth electrically actuated valve 26 is arranged in the second line arrangement 14 such that by opening the fourth electrically actuated valve 26, hydraulic fluid flows from the second line arrangement 14 into the tank line T.

[0050] The 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. In this case, the second hydraulic sensor 18 is a pressure sensor that measures the pressure within the second line arrangement 12. Alternatively, however, the second hydraulic sensor 18 can also be a volume flow sensor, as already 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 controlled jointly. In other words, when hydraulic fluid flows into one of the two line arrangements 12, 14, hydraulic fluid is drained from the other of the two line arrangements 12, 14 to enable precise displacement of the piston 30 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 the position.

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

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

[0054] If the second electrically actuated valve 22 is not defective, the functional diagnostic unit 2 subsequently executes the third test sequence. The third test sequence is executed for the third electrically actuated valve 24 with 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. The third test signal is generated by opening the third electrically actuated valve 24 for a third time interval t3. By opening the third electrically actuated valve 24, hydraulic fluid flows from the pressure line P into the second line arrangement 14, causing the pressure in the second line arrangement 14 to rise. In the embodiment shown, the second hydraulic sensor 18 measures the pressure increase in the second line arrangement 14 and transmits the measurement signal M2 of the second hydraulic sensor 18 to the functional diagnostic unit 2.

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

[0057] From the pressure increase in the second line arrangement 14, the functional diagnostic unit 2 determines the recorded pressure change 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 recorded 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 in 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 agrees with the expected pressure change for the third hydraulic test signal, the third electrically actuated valve 24 is not defective.

[0059] If the recorded pressure change of the third hydraulic test signal is greater than the pressure change expected 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 because it does not move completely back to the closed position. The functional diagnostic unit 2 issues an error message to the user.

[0060] If the recorded pressure change of the third hydraulic test signal is smaller than the pressure change expected for the third hydraulic test signal, or if no pressure change is present, the third electrically actuated valve 24 was not fully opened or not opened at all by applying the third hydraulic test signal. The third electrically actuated valve 24 is therefore defective because it does not move fully or not at all into the open position. The functional diagnostic unit 2 issues 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. The fourth test signal is generated by opening the fourth electrically actuated valve 26 for the duration of a fourth time interval t4. By opening the fourth electrically actuated valve 26, hydraulic fluid flows from the second line arrangement 14 into the tank line T, whereby the pressure in the second line arrangement 14 drops. The second hydraulic sensor 18 measures the pressure drop in the second line arrangement 14 and transmits the measurement signal M2 of the second hydraulic sensor 18 to the functional diagnostic unit.The functional diagnostic unit 2 determines the recorded pressure change from the pressure drop in the second line arrangement 14 for a period beginning with the application of the fourth test signal and lasting longer than the fourth time interval t4. The functional diagnostic unit 2 compares the recorded 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 arrangement 14.

[0062] If the recorded pressure change of the fourth hydraulic test signal agrees with the expected pressure change for the fourth hydraulic test signal, the fourth electrically actuated valve 22 is not defective.

[0063] If the recorded pressure change of the fourth hydraulic test signal is greater than the pressure change expected 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 because it does not move completely back to the closed position. The functional diagnostic unit 2 issues an error message to the user.

[0064] If the recorded pressure change of the fourth hydraulic test signal is smaller than the pressure change expected for the fourth hydraulic test signal, or if no pressure change is present, 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 because it does not move fully or not at all into the open position. The functional diagnostic unit 2 issues an error message to the user.

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

[0066] First, 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. 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, after the first electrically actuated valve 20 is activated, reaches a constant pressure in the first pause interval tw1. The measured pressure change corresponds to the pressure change expected for the first test signal. The first electrically actuated valve 20 therefore has no defect.

[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 controlled so that it is fully open. As a result, the pressure measured by the first hydraulic sensor 16 within the first line arrangement 14 drops and, after the second electrically actuated valve 22 is controlled in 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. The second electrically actuated valve 22 therefore does not exhibit a defect.

[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 such that it opens to its maximum. 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 controlled 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 has no defect.

[0069] Finally, after the third pause interval tw3 has elapsed, the functional diagnostic unit 2 executes the fourth test sequence. The fourth electrically actuated valve 26 is activated for a fourth time interval. 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. The fourth electrically actuated valve 26 therefore does not exhibit a defect.

[0070] By way of example, the lower diagram shows a measurement signal M1 as a dashed line and a measurement signal M2 as a dash-dot line, as they can occur in the event of a defect in the second electrically actuated valve 22 or a defect in the third electrically actuated valve 24.

[0071] The dashed line of the measurement signal M1 shows that the pressure measured by the first hydraulic sensor 16 does not drop after the second electrically actuated valve 22 is activated, but remains at a constant pressure. The measured pressure change is therefore smaller than the pressure change expected for the second test signal. The second electrically actuated valve 22 therefore does not open as desired but remains completely closed. In such a case, the functional diagnostic unit 2 outputs 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 the third electrically actuated valve 24 is activated, but rather continues to rise. The measured pressure change is thus greater than the pressure change expected for the third test signal. In such a case, the functional diagnostic unit 2 also issues an error message to the user. LIST OF REFERENCE SYMBOLS 1 control unit 2 functional diagnostic unit 10, 100 Hydraulic system 12 First line arrangement 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 pressure t time I current t1 First time interval t2 Second time interval t3 Third time interval t4 Fourth time interval tw1 First pause interval tw2 Second pause interval tw3 Third pause 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) is arranged in the first line arrangement (12) downstream of the first electrically actuated valve (20) as seen from the pressure line (D) and upstream of the second electrically actuated valve (22) as seen from the hydraulic consumer (V), characterized by , that the hydraulic system (10, 100) further comprises a functional diagnostic unit (2) for executing a first test sequence and a second test sequence, wherein in the first test sequence a first hydraulic test signal is applied by controlling the first electrically actuated valve (20) for a first time interval (t1), and the functional diagnosis unit (2) is designed to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) from 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 controlling the second electrically actuated valve (22) for a second time interval (t2), and the functional diagnosis unit (2) is designed to receive a measurement signal (M1) from the first hydraulic sensor (16) and to compare the measurement signal (M1) from the first hydraulic sensor (16) with the second hydraulic test signal. [2] Hydraulic system (100) according to claim 1, characterized by in 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 line 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 to the tank line (T) via a fourth electrically actuated valve (26), and wherein the functional diagnosis 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 in that the functional diagnosis unit (2) is designed to receive a measurement signal (M1) of 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 diagnosis unit (2) is further designed to receive a measurement signal of 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 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 bythat the functional diagnosis unit (2) is further designed to receive a measurement signal (M2) of 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 executing the first test sequence and / or to compare it with the second hydraulic test signal when executing the second test sequence and / or to compare it with the third hydraulic test signal when executing the third test sequence and / or to compare it with the fourth hydraulic test signal when executing 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 volume flow sensor and / or the second hydraulic sensor (18) is a pressure sensor or a volume flow sensor. [8] Hydraulic system (10, 100) according to one of the preceding claims, characterized bythat the functional diagnosis unit (2) is further designed to carry out 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 one of claims 1 to 7, characterized by that the functional diagnosis unit (2) is further designed to periodically superimpose a hydraulic control signal during 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 bythat 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.

Images