Hydraulic drive system, and compressor with a hydraulic drive system

Abstract

The present disclosure relates to a hydraulic drive system (1), in particular for compressing hydrogen, with a hydraulic cylinder (2), with a fluid feed means (3) and with a control means (4), wherein an interior space (5) of the cylinder (2) is divided by means of a piston (6) of the cylinder (2) into two chambers (51, 52), into which a fluid (7) can be fed by way of the fluid feed means (3) in opposite directions in order to move the piston (6) to and fro, wherein the control means (4) is connected to the fluid feed means (3) and is configured to open-loop and / or closed-loop control a to and fro movement of the piston (6) by corresponding actuating commands to the fluid feed means (3), wherein the control means (4) is configured to calculate a current position of the piston (6) by means of source data stemming from state descriptions of the hydraulic cylinder (2) and / or the fluid feed means (3). The present disclosure also relates to a compressor with a hydraulic drive system (1) of this type.

Description

[0001] Hydraulic drive system and compressor with a hydraulic drive system

[0002] Description

[0003] The present invention relates to a hydraulic drive system according to the preamble of claim 1. The present invention further relates to a compressor with a hydraulic drive system.

[0004] Background of the invention

[0005] Such hydraulic drive systems are, for example, part of compressors for hydrogen, i.e. so-called hydrogen compressors. Known hydraulic drive systems comprise a hydraulic cylinder, a fluid supply device, and a control device. The interior of the cylinder is divided into two chambers by means of a piston of the cylinder, into which chambers a fluid can be alternately supplied with the fluid supply device to move the piston back and forth. The control device is connected to the fluid supply device and configured to control and / or regulate the reciprocating movement of the piston by issuing appropriate control commands to the fluid supply device. The piston position of the preferably double-acting hydraulic cylinder is normally detected by means of position sensors. A measured value, namely a corresponding signal, of the current position of the piston is then continuously available for controlling and / or regulating the position of the piston.At least a plurality of measured values ​​can be determined in each of the two reversal regions of the cylinder in which the piston changes its direction of movement and is subsequently decelerated and accelerated accordingly. The plurality of measured values ​​can be generated by a plurality of sensors and / or by a plurality of markings on the piston which can be detected by at least one sensor. The plurality of or continuously available measured values ​​enable the position of the piston to be controlled and / or regulated, in particular the reversal of the piston at the desired position in the cylinder. However, the device-related expenditure for this is high and a correspondingly large installation space is still required. If a plurality of sensors are arranged penetrating a cylinder housing, problems with sealing the interior of the cylinder can still be expected.

[0006] Brief description of the invention

[0007] The present invention is based on the object of providing a hydraulic drive system and a compressor with a hydraulic drive system that reduce or eliminate the problems of the prior art. In particular, the control and / or regulation of the hydraulic drive system should be simplified and, furthermore, particularly, feasible with minimal equipment complexity.

[0008] This object is firstly achieved by a hydraulic drive system according to claim 1.

[0009] Further advantageous embodiments are the subject of the subclaims.

[0010] More precisely, the object is achieved by a control device which is designed to calculate a current position of the piston by means of source data based on state descriptions of the hydraulic cylinder and / or the fluid supply device.

[0011] This means that the source data used is that which is only indirectly related to the position of the piston. Depending on the system information, i.e. the source data, a simulated actual position is mapped, i.e. the current position of the piston is calculated. The control device is thus designed to advantageously detect and regulate the position of the piston without a direct position measuring system, so that the control and / or regulation is simplified overall and can be carried out with less equipment complexity. Advantageously, the control device is designed to regulate the position of the piston using the calculated current position of the piston. In this case, a control difference is formed from a target position and the calculated current position. The respective current position of the piston orWith such a control system, its movement can be realized with particular precision, particularly with regard to the optimal compression of a useful fluid such as hydrogen. An open or a closed system is formed by means of the hydraulic cylinder and the fluid supply device. The piston movement is generated by means of corresponding controls of valves and / or a pump. Such valves and / or such a pump then form part of the fluid supply device. The aforementioned source data then preferably contain measured operating variables of the valves and / or the pump. The current position of the piston can then be calculated using the source data and known physical dependencies, namely the state descriptions. These physical dependencies, namely the state descriptions, are preferably stored in the control device in the form of executable program code.

[0012] In a preferred embodiment of the hydraulic drive system, at least one sensor, in particular a position sensor, is arranged and / or can be arranged on the hydraulic cylinder for detecting a specific current position of the piston. The sensor is preferably arranged in a control block. By means of the position sensor, a signal, in particular a signal pulse, can be transmitted to the control device when the piston has a specific position relative to the sensor, in particular when it passes the sensor. The exact position of the sensor and / or the associated position of the piston when the signal, in particular the signal pulse, is generated by the sensor is determined during assembly and stored in the control device. The signal, in particular the signal pulse, thus contains the information that the piston is currently in the specific and known position at the time the signal is generated.It is also conceivable that a signal is continuously transmitted to the control device and then a specific change in the signal is detected by the control device when the piston is arranged in the specific relative position to the sensor or passes this specific relative position.

[0013] Advantageously, the control device is configured to initialize, calibrate, and / or correct the calculated current position of the piston using the signal generated by the sensor of the determined current position of the piston. The simulated actual position mapped based on the system information is calibrated with an initially determined actual position determined by a direct position measuring system, in particular by the sensor. With sufficiently accurate state descriptions, a one-time calibration, namely the so-called initialization at the beginning of cylinder operation, is sufficient. The sensor can then be used once and subsequently removed from the cylinder.Advantageously, however, the calculated, current piston position is also compared and / or corrected during operation, thus reducing the effort required to create the condition descriptions. For example, leaks in the drive system and / or aging processes such as wear and tear on the drive system can be neglected when creating the condition descriptions.

[0014] According to an advantageous embodiment of the hydraulic drive system, the position sensor is designed as a Hall sensor. Such a Hall sensor interacts in particular with an edge of the piston, which is formed, for example, between a front side of the piston and an outer circumference of the piston or which is formed on the outer circumference of the piston. When this edge then passes the Hall sensor, a signal pulse is generated and forwarded to the control device. By means of the signal pulse and the known information about the position of the piston during the generation of this signal pulse, the initialization, adjustment and / or correction of the calculated, current position of the piston is then possible. As an alternative to the Hall sensor, the use of a magnetostrictive sensor is also conceivable, by means of which such a signal pulse can also be generated.

[0015] According to a further embodiment of the hydraulic drive system, the sensor is designed as a pressure sensor. A specific pressure value is then assigned to the determined current position of the piston. The pressure sensor can advantageously be arranged near the end face of the cylinder or near the inner circumference of the cylinder. When the specified pressure value is reached, the corresponding position of the piston is then used to initialize, adjust, and / or correct the calculated current position of the piston.

[0016] Further preferably, the piston is movable back and forth between two end positions. The end positions are the two positions of the piston in which the direction of movement of the piston reverses. In the end positions, the piston thus has a speed of zero during cylinder operation. Adjacent to the end positions, so-called reversal regions of the cylinder are formed, in which the piston is decelerated accordingly during operation, namely when moving toward the end position, and accelerated accordingly, namely when moving away from the end position.

[0017] Preferably, a sensor is assigned to each of the two end positions. The sensors can detect the piston in a specific current position at a specific distance from the corresponding end position. Essentially, at this specific distance, a deceleration process begins when the piston moves toward the corresponding end position.

[0018] To reverse the piston, namely to reverse its direction of movement, in the respective end position, a sensor is arranged on each side to detect a current position “before” the respective end position. The exact position of both sensors and / or the corresponding positions of the piston when the respective signals, in particular signal pulses, are generated by the respective sensor are determined during assembly and stored in the control device. This enables repeated referencing, namely the initialization, calibration and / or correction, of the drive system and precise end position positioning. Precise end position positioning means that the fluid supply device is operated in such a way that the piston changes its direction of movement at exactly the desired position, in particular with regard to optimal compression, e.g. of hydrogen.

[0019] Preferably, the current position of the piston can be calculated using a rotational speed of a pump of the fluid supply device coupled to the hydraulic cylinder, a valve position of a valve arrangement of the fluid supply device coupled to the hydraulic cylinder, a temperature of the fluid for actuating the hydraulic cylinder, and / or a viscosity of the fluid for actuating the hydraulic cylinder. In particular, the physical variables necessary to calculate the volume flow of the fluid to and from the interior of the cylinder with sufficient accuracy are used for this purpose. Furthermore, since the dimensions of the hydraulic cylinder, including its piston, are known, the current position of the piston can then be easily calculated using the volume flow.

[0020] It may be advantageous if the control device is configured to calculate a piston speed. In particular, the control device is designed to control the piston speed and thus only indirectly its position, advantageously in a central region of the piston between the two reversal regions. In the two reversal regions, the position is preferably controlled directly, namely, a so-called position control.

[0021] The object underlying the invention is also achieved by a compressor according to claim 10.

[0022] More precisely, the task is then solved by a compressor with a hydraulic drive system as described above, wherein the compressor is designed to compress a working fluid, in particular hydrogen. Other substances, preferably in gaseous form, such as helium, could also be used as the working fluid. The working fluid can be compressed by means of piston rods protruding from a cylinder housing and firmly connected to the piston. These piston rods move with the piston as the piston moves. By means of the hydraulic cylinder, a high force density can be achieved via its piston rods during operation, thus enabling particularly high and effective compression of the working fluid.

[0023] In summary, the described hydraulic drive system and compressor are suitable for a wide range of applications, such as the compression of hydrogen for filling stations, (pressure) storage and / or pipelines.

[0024] Short description of the characters

[0025] Preferred embodiments are described in more detail below with reference to the accompanying figures. Figure 1 shows a schematic hydraulic circuit diagram of the hydraulic drive system.

[0026] Description of preferred embodiments

[0027] The hydraulic drive system 1 according to Fig. 1 , in particular for compressing hydrogen, has, among other things, a hydraulic cylinder 2, a fluid supply device 3 and a control device 4. An interior 5 of the cylinder 2 is divided by means of a preferably double-acting piston 6 of the cylinder 2 into two chambers 51, 52, into which a fluid 7 for moving the piston 6 back and forth can be alternately fed by the fluid supply device 3. The control device 4 is connected to the fluid supply device 3 and is designed to control and / or regulate a reciprocating movement of the piston 6 by means of corresponding actuating commands to the fluid supply device 3. A connection between the control device 4 and the fluid supply device 3 for transmitting the actuating commands and / or data is symbolized here by means of a dash-dotted line. This can be a cable arranged between the control device 4 and the fluid supply device 3.However, wireless transmission of the control commands and / or data is also conceivable.

[0028] The control device 4 is designed to calculate a current position of the piston 6 using source data based on state descriptions of the hydraulic cylinder 2 and / or the fluid supply device 3. For this purpose, the control device 4 has, for example, a computer and / or microcontroller, by means of which appropriate software can be executed, by means of which the said calculation can be carried out. In particular, the source data are transmitted to the control device 4 via the said connection between the control device 4 and the fluid supply device 3. The source data are then available in the said software for calculating the current position of the piston 6. The control device 4 is further designed to regulate the position of the piston 6 using the currently calculated position of the piston 6. During the regulation, a control difference between a target position and the currently calculated position is calculated.From the control difference, a control variable, namely the control command, for the fluid supply device 3 is determined by means of a controller, which is preferably implemented using software executed with the control device 4. At least one sensor 8, in particular a position sensor 8, is arranged and / or can be arranged on the hydraulic cylinder 2 to detect a specific current position of the piston 6. The sensor 8 is arranged and / or can be arranged, for example, centrally on the cylinder 2. A connection between the sensor 8 and the control device 4 for transmitting data, in particular the signals generated by the sensor, is symbolized here by a dash-dotted line.

[0029] The control device 4 is configured to perform an initialization, a comparison, and / or a correction of the calculated, current position of the piston 6 using the signal generated by the sensor 8 of the determined current position of the piston 6. The current position of the piston 6 is calculated during operation of the piston 6, for example, as a function of a known, initially measured position of the piston 6 and the distance traveled by the piston 6 from the time of measurement. A particularly first measurement of the current position of the piston 6 is also referred to as initialization. After initialization, upon renewed detection of a signal generated by the sensor 8, a comparison is possible in which a difference between the calculated, current position of the piston 6 and the current position of the piston 6 detected by the sensor 8 is determined. E.g.Based on this difference, the calculation of the current position of the piston 6 can be optimized, namely, in particular, the state descriptions of the hydraulic cylinder 2 and / or the fluid supply device 3 can be improved. Furthermore, the calculated, current position of the piston 6 is corrected using the current position determined, among other things, by means of the sensor 8; in particular, the calculated, current position of the piston 6 for a specific point in time is replaced by the current position of the piston 6 determined, among other things, by means of the sensor 8, which can also be referred to as reinitialization.

[0030] The position sensor 8 is designed, for example, as a Hall sensor. Such a Hall sensor has a semiconductor element through which current flows, which is constantly magnetically biased by a magnetic field from a permanent magnet permanently installed behind it. When the piston, which consists of a ferromagnetic material and / or at least partially comprises such a ferromagnetic material, penetrates this magnetic field, its field strength is influenced, whereby a change in the voltage in the semiconductor element is detected. This voltage then represents the signal from the sensor 8. The aforementioned signal pulse corresponds in particular to a specific change in the signal, in particular this voltage. The sensor 8, in particular the position sensor 8, in particular the Hall sensor, is arranged, for example, on a side of a housing 11 of the cylinder 2 forming the interior 5, said side facing away from the interior 5 of the cylinder 2.It would also be conceivable for the sensor 8 to penetrate such a housing 11 and / or to be arranged within the interior space 5, so that at least one measuring area of ​​the sensor 8 is arranged in the interior space 5 and in particular has contact with the fluid 7.

[0031] The sensor 8 could also be designed as a pressure sensor, in which case a specific pressure value is assigned to the specific current position of the piston 6. This assignment can be made by means of the sensor 8 itself and / or by means of the control device 4.

[0032] The piston 6 can be moved back and forth between two end positions 91, 92. The piston 6 is shown in each of the two end positions 91, 92 with dashed lines. When the piston 6 moves towards the corresponding end position 91, 92, the piston 6 decelerates until it has a speed of zero in the end position 91, 92. From this end position 91, 92, the piston 6 accelerates towards the other end position 92, 91. Preferably, the piston 6 is moved at an essentially constant speed between the acceleration process after reaching one of the end positions 91, 92 until the deceleration process to reach the other end position 92, 91.

[0033] One sensor 8 each, shown in Fig. 1 with dashed lines including the associated connections for transmitting data, is optionally assigned to each of the two end positions 91, 92. When using these two sensors 8 assigned to the two end positions 91, 92, it is preferable to dispense with the sensor 8 arranged in the middle of the cylinder 2. The piston 6 can then be detected by means of the two sensors 8, shown here with dashed lines, in a specific current position at a specific distance from the associated end position 91, 92, wherein the braking process essentially begins at this specific distance when the piston 6 moves towards the associated end position 91, 92.The current position of the piston 6 can be calculated by means of a rotational speed of a pump 10 of the fluid supply device 3 coupled to the hydraulic cylinder 2, by means of a valve position of a valve arrangement of the fluid supply device 3 coupled to the hydraulic cylinder 2, by means of a temperature of the fluid 7 for actuating the hydraulic cylinder 2 and / or by means of a viscosity of the fluid 7 for actuating the hydraulic cylinder 2. According to Fig. 1, the fluid supply device 3 is formed by the pump 10 and lines arranged between the connections of the pump 10 and the chambers 51, 52. Instead of the pump 10, a different type of pressure source, such as a corresponding pressure accumulator, could also be used. It is also conceivable that valves of a valve arrangement are arranged between such a pressure source, in particular the pump 10 and / or the pressure accumulator, and the cylinder 2, in particular its chambers 51, 52.As pump 10, for example, an axial piston pump, a radial piston pump and / or a vane pump, each preferably with adjustable displacement volume, could be provided.

[0034] The control device 4 is configured to calculate a speed of the piston 6. Then, at least in sections, the speed of the piston 6 can also be controlled by the control device 4.

[0035] The hydraulic drive system 1 is part of a compressor (not shown here) that is designed to compress a working fluid, in particular hydrogen. During operation of the compressor, the working fluid is compressed by piston rods 12 that protrude from a housing 11 of the cylinder 2 and are firmly connected to the piston 6. The compressed working fluid can be stored, in particular, in a corresponding pressure accumulator and / or a system of two or more pressure accumulators.

[0036] 1 Hydraulic drive system

[0037] 2 hydraulic cylinders

[0038] 3 Fluid supply device

[0039] 4 Control device

[0040] 5 Interior of cylinder 2

[0041] 51 first chamber of the interior 5

[0042] 52 second chamber of the interior 5

[0043] 6 pistons of cylinder 2

[0044] 7 Fluid

[0045] 8 Sensor, especially position sensor

[0046] 91 first end position

[0047] 92 second end position

[0048] 10 Pump

[0049] 11 housings

[0050] 12 piston rods

Claims

Claims 1. A hydraulic drive system (1), in particular for compressing hydrogen, comprising a hydraulic cylinder (2), a fluid supply device (3), and a control device (4), wherein an interior space (5) of the cylinder (2) is divided into two chambers (51, 52) by means of a piston (6) of the cylinder (2), into which chambers a fluid (7) for reciprocating the piston (6) can be alternately supplied by the fluid supply device (3), wherein the control device (4) is connected to the fluid supply device (3) and is configured to control and / or regulate reciprocating movement of the piston (6) by means of corresponding actuating commands to the fluid supply device (3), characterized in that the control device (4) is configured to calculate a current position of the piston (6) by means of source data based on state descriptions of the hydraulic cylinder (2) and / or the fluid supply device (3).

2. Hydraulic drive system (1) according to claim 1, characterized in that at least one sensor (8), in particular a position sensor (8), is arranged and / or can be arranged on the hydraulic cylinder (2) for detecting a specific current position of the piston (6).

3. Hydraulic drive system (1) according to claim 2, characterized in that the control device (4) is set up to carry out an initialization, an adjustment and / or a correction of the calculated, current position of the piston (6) by means of the signal of the determined current position of the piston (6) generated by the sensor (8).

4. Hydraulic drive system (1) according to one of the preceding claims 2 or 3, characterized in that the position sensor (8) is designed as a Hall sensor.

5. Hydraulic drive system (1) according to one of the preceding claims 2 to 4, characterized in that the sensor (8) is designed as a pressure sensor, wherein a specific pressure value is assigned to the specific current position of the piston (6).

6. Hydraulic drive system (1) according to one of the preceding claims, characterized in that the piston (6) can be moved back and forth between two end positions (91, 92).

7. Hydraulic drive system (1) according to claim 6, characterized in that a sensor (8) is assigned to each of the two end positions (91, 92), the piston (6) being detectable by means of the sensors (8) in a specific current position at a specific distance from the associated end position (91, 92), a braking process being started substantially at this specific distance when the piston (6) is moved towards the associated end position (91, 92).

8. Hydraulic drive system (1) according to one of the preceding claims, characterized in that the current position of the piston (6) can be calculated by means of a rotational speed of a pump (10) of the fluid supply device (3) coupled to the hydraulic cylinder (2), by means of a valve position of a valve arrangement of the fluid supply device (3) coupled to the hydraulic cylinder (2), by means of a temperature of the fluid (7) for acting on the hydraulic cylinder (2) and / or by means of a viscosity of the fluid (7) for acting on the hydraulic cylinder (2).

9. Hydraulic drive system (1) according to one of the preceding claims, characterized in that the control device (4) is arranged to calculate a speed of the piston (6).

10. Compressor with a hydraulic drive system (1) according to one of the preceding claims, wherein the compressor is prepared to compress a useful fluid, in particular hydrogen.

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