METHOD AND DEVICE FOR CONTROLLING A HYDRAULICALLY ACTUATED DRIVE UNIT OF A VALVE

Description

[0001] In hydraulically operated valve actuators, e.g. on ships traveling from arctic to subtropical regions, a change in ambient temperature of often over 100°C changes the viscosity of the hydraulic fluid, so that the change in viscosity also results in a change in the time within which a valve is moved by the hydraulically operated drive unit, e.g. from the open to the closed position.

[0002] At low temperatures and therefore high viscosity, the valve often cannot be moved or adjusted quickly enough, while at higher temperatures and low viscosity, a valve is often moved too quickly, so that pressure surges, so-called water hammer, can occur in a pipeline in which the valve is installed.

[0003] However, essentially consistent response times are important in practice, especially for ship fittings that have to operate under very different ambient temperatures.

[0004] From EP 0 111 637 A1, a device for detecting and controlling the speed of a piston in hydraulic working cylinders is known, whereby a piston speed that is as constant as possible is to be achieved even under varying load conditions. For this purpose, the actual speed of the piston is detected and a target speed is adjusted by means of a control system via a throttling device with different throttle cross-sections. In this way, it is possible to react to a changing load or stress, which is to be actuated by the device, while maintaining a constant pressure.

[0005] EP 2 123 594 A1 describes a hydraulically actuated drive unit for a forklift truck, in which two different types of continuous position sensors are used to adjust the actual speed of the pistons to a predefined target speed for the forklift's adjustment movement. This is intended to utilize, but not exceed, the maximum speed required for safety reasons, thus enabling the lifting of loads of varying weights at the highest possible speed. A sophisticated control system is employed for this purpose, which also calculates the relative adjustment speeds in relation to the stationary parts of the forklift truck.

[0006] The object of the invention is to design the control of hydraulically actuated drive units, in particular of valves, in such a way that essentially the same actuation times are always maintained when adjusting the valve, regardless of changing ambient temperatures.

[0007] This problem is solved by a method for controlling a hydraulically actuated drive unit with a predetermined stroke according to claim 1 and by a device with the features of claims 6 or 7. Advantageous embodiments and further developments of the invention are the subject of the dependent claims.

[0008] This problem is solved according to the invention, in particular, by determining the actuating speed at least on part of the actuator's travel path and comparing it with a predetermined target actuating speed stored in an electronic memory. If a difference occurs between the target and actual values, the control of the actuator is corrected so that the actuator completes the travel path within the predetermined travel time. According to the invention, the actuating speed can be determined directly via appropriate sensors or indirectly. The latter can be achieved, for example, by measuring both distance and time. If the actuator moves too quickly on the measured part of the travel path, the actuating speed for the remaining travel path can be adjusted, e.g.,The speed can be reduced by temporarily stopping the drive unit, while if the drive unit's positioning movement is too slow, the positioning speed over the remaining positioning distance is increased, for example, by further reducing the pressure of the hydraulic fluid on a spring-loaded piston of the respective drive unit, in order to achieve the specified positioning time over the entire specified positioning distance.

[0009] In this way, valves can be adjusted independently of the ambient temperature and therefore independently of the viscosity, with consistently consistent response times. This enables more precise control of such valves, even under extreme environmental conditions.

[0010] According to the invention, the actuation time is recorded on a section of the actuation path of the drive unit and the time required for the drive unit to travel the entire actuation path is calculated from the speed value obtained, so that the total actuation time can be calculated on the basis of a single measured value.

[0011] Preferably, the actuating speed is measured at the beginning of the actuating stroke, starting from the end position. However, it is also possible to measure the speed within the actuating stroke over a partial distance that begins from an intermediate position of the piston in the drive unit.

[0012] The advantage of the intermediate time measurement according to the invention, compared to temperature measurement for determining the drive speed of the drive unit, is that the intermediate time measurement directly captures the response time at the current operating point. Temperature measurement would only allow for indirect determination of the influence of the hydraulic fluid viscosity on the response times, requiring measurement series at different temperatures and the storage of these values ​​in the program code of a control unit. Furthermore, temperature measurement would not capture other influences on the response time, such as varying hydraulic losses.

[0013] The invention relates to a method according to claim 1.

[0014] The invention also relates to a hydraulically actuated drive unit according to claims 6 or 7.

[0015] The invention will be explained in more detail below, for example, with reference to the drawing. The drawing shows... Fig. 1 a schematic view of the control of a drive unit with spring-loaded pistons for a valve not shown, Fig. 2 in a diagram the determination and correction of the actuation time in the case of a drive unit operating too fast, Fig. 3 a diagram accordingly Fig. 2 In the case of a drive unit that operates too slowly, Fig. 4 shows a schematic representation of a control device with a control unit, Fig. 5 shows a corresponding view. Fig. 1 a drive unit with a piston acted upon by hydraulic fluid on both sides, and Fig. 6 + 7 diagrams accordingly Fig. 2 and 3 the control of the drive unit in Fig. 5 , and Fig. 8 shows another embodiment.

[0016] Fig. 1 Figure 1 shows a piston 1 in a cylinder 2, wherein on one side of the piston 1 is acted upon by a spring 3, and on the opposite side of the piston 1, the pressure of a hydraulic fluid is applied at port 2.1, which holds the piston 1 in a position against the force of the spring 3. By changing the pressure of the hydraulic fluid, the piston 1 is moved against the force of the spring 3 or by the spring 3.

[0017] In this embodiment, the piston 1 in the cylinder 2, acted upon by the spring 3, forms a drive unit that adjusts a fitting not shown, for example pivoting a flap in a pipeline.

[0018] In the illustrated embodiment, the stroke to be traveled by piston 1 runs as follows: Fig. 1 from S1 to S2, where S2 corresponds to 100% of the travel distance starting from S1.

[0019] From S1 to S3, a section of the adjustment path is specified; S1 corresponds, for example, to the open position of the valve and S2 to the closed position.

[0020] Cylinder 2 is supplied with hydraulic fluid from a reservoir 5 via a supply line 4a and 4b by a pump 6 driven by a motor M. A check valve in line section 4a is designated by reference numeral 7.

[0021] References 8 and 9 represent control valves in a parallel connection in a return line 10 leading to reservoir 5. References 8.1 and 9.1 each have a throttle valve upstream of their respective control valves, which can be optionally provided.

[0022] In the illustrated switching position, the pressure built up by the pump 6 in the supply line 4b is maintained because the two control valves 8 and 9 are closed and the check valve 7 prevents backflow. By switching one or both of the two control valves, the flow cross-section from the supply line 4b to the reservoir 5 via the return line 10 can be opened, so that the pressure in the supply line 4b is reduced and the piston 1 can be moved by the spring 3 in the direction indicated by the arrow.

[0023] Control valves 8 and 9 are shown as electrically actuated two-way valves. It is also possible to use a different valve design to control the actuator unit consisting of elements 1 to 3, as described below.

[0024] In the illustrated embodiment, the piston 1 is moved in the direction of the arrow by the spring 3 as soon as the pressure of the hydraulic fluid is reduced by opening one of the control valves 8 or 9.

[0025] Fig. 2 The diagram shows the stroke S of piston 1 over the stroke time t, where a dashed line represents the theoretically ideal target stroke velocity v with which piston 1 travels the specified target stroke from S1 to S2 in the specified target stroke time t = 100%.

[0026] The target positioning time is specified, in particular taking into account the type of valve driven by the drive unit and the fluid to be controlled by the valve, e.g. a flap in a pipeline, which is pivoted by the piston 1 of the drive unit over a specified angle of rotation by turning a gear by means of a rack displaced by the piston.

[0027] For example, in Fig. 2 After a predetermined time unit ta or after a certain portion sa of the stroke from S1 to S3 has been traveled, preferably starting from the end position at S1 at the beginning of the stroke, the velocity of piston 1 is measured. The measured piston velocity v' is then compared with the target velocity v stored in a memory unit, and it is determined that the drive is operating too fast or that piston 1 is moving too quickly, for example, because high ambient temperatures have reduced the viscosity of the hydraulic fluid. To correct the excessively fast operation of the drive unit, the control valve 8 and / or 9 at S3 is closed, for example, stopping the drive at S3 for a predetermined time, as indicated by a horizontal profile of the piston velocity v'.

[0028] After a holding time determined by the computing unit, one of the control valves 8, 9 is opened again, so that the piston 1 is moved over a further partial distance by the force of the spring 3, whereupon a pulse-wise control of the drive unit is repeated according to the steps specified by the computing unit, as shown by the stepped line of the piston velocity v' in Fig. 2 The following is shown. The holding time can vary from stage to stage. Similarly, the actuation time can change depending on the result of the calculation in the processing unit over the length of a section of the actuation path, especially if a further check of the piston speed is carried out on another intermediate section.

[0029] Fig. 3 This shows the control of the drive unit in the case of a drive that is operating too slowly. A measured value of the actuation time ta at which piston 1 reaches position S3 of its stroke indicates, in this example, that the drive is operating too slowly when compared with the theoretically ideal speed v. By increasing the pressure drop in the hydraulic fluid in the supply line 4b through a corresponding increase in the flow cross-section by opening both control valves 8 and 9, the pressure in cylinder 2 can be reduced more quickly when the hydraulic fluid has a high viscosity. This allows piston 1 to travel a greater stroke per unit of time, as shown by the steeper line of the piston speed v' after ta in the diagram. Fig. 3 shows.

[0030] In the Fig. 2 and 3In the illustrated embodiment, the drive unit is controlled by sequentially opening and closing one or both control valves 8, 9 in such a way that a predetermined setpoint time is maintained for a predetermined stroke, whereby the piston speed v' is measured on a partial stroke and compared with the setpoint v, whereupon, in the case of a difference between actual value and setpoint, the control of the drive unit is changed so that the predetermined setpoint time is maintained.

[0031] Instead of two control valves 8 and 9, which serve to increase the flow cross-section for the hydraulic fluid during pressure reduction in cylinder 2, a single control valve can also be provided, by means of which the flow cross-section in the return line 10 can be adjusted to be larger or smaller.

[0032] It is also possible that the control valves 8 and 9 have different flow cross-sections, so that the pressure reduction at piston 1 can be controlled differently when one or the other control valve is opened.

[0033] The positioning time is measured using three position-dependent switches. One switch is located at each of the end positions S1 and S2. The third switch, at S3, serves as the basis for calculating the positioning time from S1 to S3. Once the piston velocity v' between S1 and S3 has been determined by the processing unit, this measured piston velocity (or positioning velocity) can be used to calculate the positioning time over the remaining travel distance.

[0034] In the illustrated embodiment, the actuation time t = 100% of the drive unit is preset for low temperatures, i.e., high viscosity. This presetting can also be performed at higher temperatures. To ensure a constant actuation time at higher temperatures, the actuator is adjusted when closing the valve in the direction of the arrow. Fig. 2 The third position switch at S3 detects the actuation time or actuation speed, whereupon the control valves 8, 9 are opened and closed in a pulsed manner via the corresponding calculation in the computing unit.

[0035] To open the valve by moving the piston 1 against the force of the spring 3, the pressure build-up in the cylinder 2 can be controlled differently by the pump 6.

[0036] In the embodiment according to the Fig. 1 bis 3 The drive unit will only move during the piston stroke in the direction of the arrow. Fig. 1 Controlled in cycles.

[0037] If the piston stroke is also to be carried out in the opposite direction, i.e. against the force of spring 3, within a specified target time, a small distance is drawn from the end position S2. Fig. 1 Position switch S4, indicated by dashed lines, is provided, which is used to determine the actuating speed v' of piston 1 in the opposite direction.

[0038] If the positioning speed of piston 1 deviates from the target positioning speed v, increased speed of the drive motor M via pump 6 allows pressure to build up more quickly in cylinder 2, thus moving piston 1 more rapidly towards the end position S1 against the force of spring 3. Conversely, a slower movement of piston 1 in the opposite direction can be achieved by reducing the speed of motor M or by switching motor M off and on intermittently.

[0039] In an embodiment that does not fall under the claimed subject matter, instead of determining the piston or actuating speed v' on a partial section of the actuating path ( Fig. 2 and 3 The positioning speed v' is also continuously measured and compared with the specified target positioning speed v. In this process, the control valve (or possibly several control valves) intended for controlling the drive unit is continuously actuated to keep the piston speed v' closer to the theoretical target positioning speed v.

[0040] For example, a continuously adjustable throttle can be provided in a control valve 8 or 9 to continuously change the flow cross-section.

[0041] An alternative method for determining the actuation time, which does not fall under the claimed subject matter, can be achieved by continuously measuring the position at the drive unit, e.g. by means of a potentiometer, through which the actuation distance is recorded over the entire actuation range from S1 to S2.

[0042] It is also possible, in electro-hydraulic systems, to control the electric motor M used to drive the hydraulic pump 6 in a timed manner, as shown above when the piston 1 retracts to its end position at S1 in the drive unit. Fig. 1 was described.

[0043] Fig. 4 Figure 11 schematically shows, as an example, a computing unit 11 with a memory 12 in which the target positioning speed v specified for the respective valve is stored. A comparison unit 13 compares the measured positioning speed v' with the target positioning speed v. If there is a difference, the computing unit 11 determines how the drive should be corrected: if the operation is too fast, by stopping the piston movement; or if the operation is too slow, by increasing the pressure drop.

[0044] The computing unit 11 sends a control signal to a control unit 14, which controls the control valves 8, 9 accordingly.

[0045] In the exemplary embodiment in Fig. 1 A spring-loaded piston 1 in a cylinder 2 is represented as a drive unit.

[0046] The clocked control according to the invention is possible in the same way for a piston of a drive unit that is acted upon by hydraulic fluid on both sides.

[0047] Fig. 5 shows in a view accordingly Fig. 1 A piston 1 of the drive unit, pressurized with hydraulic fluid from both sides. Connections 2.1 and 2.2 are designated as connections of hydraulic lines 4.1 and 4.2, which are controlled by a common control valve 15. In the illustrated switching position of the control valve 15, which can be designed as an electromagnetically actuated 4-way valve, the two hydraulic lines 4.1 and 4.2 are closed, thus holding the piston 1 in its position.

[0048] In the schematically represented switching position Yb1 of the control valve 15, the hydraulic line 4.2 is connected to the line section 4.3, so that the pressure on the lower side of the piston 1 is reduced and hydraulic fluid is directed into the reservoir 5, while the line section 4.4 with the pump 6 is connected to the hydraulic line 4.1, so that pressurized hydraulic fluid is present at the port 2.1.

[0049] In the switching position Yb2 of the control valve 15, the line section 4.3 is connected to the hydraulic line 4.1 and the line section 4.4 to the line 4.2, with the direction of the arrow indicating the flow direction of the hydraulic fluid.

[0050] In the pipe section 4.4 between control valve 15 and reservoir 5, the pump 6 is arranged with the check valve 7. A pressure accumulator is designated by 16. During normal operation, when pressure builds up in cylinder 2, pressure is directed from the pressure accumulator 16 to one of the ports 2.1 and 2.2, so that the pump 6 does not have to operate every time the piston 1 is pressurized.

[0051] After a certain pressure drop in the pressure accumulator 16, the pressure of the hydraulic fluid is rebuilt by the pump 6 in the pressure accumulator 16.

[0052] Furthermore, a throttle 17 is arranged in this line section 4.4, which is bypassed by a bypass line 4.41 in which a valve 18 is arranged, which in this embodiment corresponds to one of the valves 8 and 9 in Fig. 1 corresponds.

[0053] In the illustrated switching position of the valve 18, the bypass line 4.41 is closed, so that in the event of switching the control valve 15 to one of the positions Yb1 or Yb2, pressure of the hydraulic fluid passes through the throttle 17 to the cylinder 2.

[0054] In the switching position Ya of the valve 18, the throttle 17 is bypassed, so that the hydraulic pressure of the pressure accumulator 16 passes directly to the cylinder 2 via the full cross-section of the line.

[0055] At times t,1 and t,0, valve 18 is in the position shown. Fig. 5 closed (Ya = 0) while the control valve 15 is in position Yb2 = 1 at time t,1 and in the position Yb2 = 1 at t,0. Fig. 5 is in the displayed blocking position (Yb2 = 0).

[0056] Fig. 6 shows accordingly Fig. 2 the course of the velocity v' of piston 1, where ta indicates the time until reaching the switching point S3 at the end of the part sa of the actuating path between S1 and S3.

[0057] Fig. 7 shows accordingly Fig. 3 The switching operations at control valves 15 and 18 when the actuator is too slow. At time t,2, valve 18 is in the open position (Ya = 1), while control valve 15 is in the switching position Yb1 = 1.

[0058] In other words, if the engine is driven too fast, the following occurs: Fig. 6 over the time span t,0 of the in Fig. 5 The switching state shown at valves 15 and 18 is maintained while, over time t,1, the two hydraulic lines 4.1 and 4.2 are in switching position Yb2, so that pressure is directed into hydraulic line 4.2 via the throttle 17.

[0059] Similarly, if the drive is too slow, Fig. 7 The throttle 17 is bypassed during time t,2 to increase the pressure on the underside of the piston 1, while over time t,1 the valve 18 is closed and the pressure build-up occurs via the flow cross-section of the throttle 17.

[0060] In the exemplary embodiment of the Fig. 1 With a spring-loaded piston 1, the drive unit is actuated in a pulsed manner by valve control in the return line 10, whereas in the exemplary embodiment in Fig. 5 With piston 1 acting on both sides, a change in the flow cross-section is provided in the supply line 4.4. The piston stroke is only in the direction of the arrow. Fig. 1 and 5 controlled in stages.

[0061] If the piston stroke is opposite to the direction indicated by the arrow in Fig. 1 and 5Since the specified travel distance is also to be traversed within a specified travel time, a further switch S4 is provided on a section starting from the end position S2 in order to determine the piston speed on the return journey.

[0062] As shown by the Fig. 1 As described, the actuation time of piston 1 can be changed by changing the pressure in the supply line.

[0063] Instead of the valve control shown, on the one hand in the return line in Fig. 1 and on the other hand in the preliminary line in Fig. 5 In an electro-hydraulic drive, the motor M of the pump 6 can be controlled in a pulsed manner to maintain a predetermined positioning time of the piston 1.

[0064] In the arrangement in Fig. 5 The pressure accumulator 16, the valve 18, and the throttle 17 can be omitted, as shown here. Fig. 8 shows, whereby the pump 6 is operated in a clocked manner. Fig. 8 By switching the motor M on and off, both strokes of the piston 1 can be controlled in a pulsed manner, depending on the position of the control valve 15.

[0065] Instead of the number of control stages shown in the Fig. 2 , 3 and Fig. 6 , 7 Fewer or more stages can also be provided. Theoretically, only one stage of stopping the piston movement or piston acceleration could be provided to adjust the positioning time of piston 1 over the entire stroke to a predetermined positioning time.

[0066] The figures show the individual stages of the clocked control of the drive unit at equal time intervals t. However, it is also possible to set the stages to different lengths along the travel range in order to traverse the entire travel range within the specified travel time.

[0067] The described correction of the actuating speed of the drive unit is preferably carried out with each adjustment of the valve, so that the actuating speed of the drive unit is always adapted to the current conditions.

[0068] The correction of the actuation time of a hydraulically actuated drive unit can also be used in areas other than the actuation of valves, particularly on ships. For example, the drive unit controlled according to the invention in a clocked manner can also actuate a lever mechanism that must execute a predetermined stroke within a predetermined time.

Claims

1. Method for controlling a hydraulically actuated drive unit (1-3) with a predetermined displacement especially for a valve or control device, wherein at least on a part of the displacement of the drive unit the displacement speed (v') is detected and compared with a predetermined target displacement speed (v) by means of a combination of distance measurement and time measurement of the displacement at at least two measuring points, by means of at least three path-dependent switches (S1 to S3) with respective switching points and a control unit (14), wherein a first switch and a second switch are each provided in end positions (S1 and S2) and a third switch in an intermediate position (S3) serves for the detection of the displacement time as a basis for calculation, whereupon in the case of a difference between actual value (v') and target value (v) of the speed, the controlling of the drive unit (1-3) is changed such that the displacement speed (v') of the drive unit is adapted to the target value (v), so that the drive unit (1-3) travels the displacement in a predetermined displacement time, wherein the displacement speed (v') of the drive unit (1-3) is measured on a partial section (S1 to S3) and used as a basis for calculating the time for displacing over the remaining displacement path for satisfying the predetermined displacement time.

2. Method according to claim 1, wherein the displacement speed (v') at the beginning of the displacement starting from the end position (S1) is measured on the partial section (S1 to S3).

3. Method according to one of the preceding claims, wherein for a drive unit having a spring-loaded piston (1), the hydraulic pressure acting on the piston is controlled by changing the passage cross-section in a return line (10).

4. Method according to one of claims 1 or 2, wherein for a drive unit having a piston (1) acted on by hydraulic fluid on both piston sides, the hydraulic fluid is controlled by changing the passage cross-section in the pressure-conducting hydraulic line (4.4).

5. Method according to one of claims 1 or 2, wherein for an electrohydraulic drive the controlling of the drive unit is controlled by changing the motor rotational speed or by switching the motor (M) on and off.

6. Hydraulically actuated drive unit, especially a fitting, comprising a hydraulic cylinder (2), a feed line (4), a return line (10), a control unit (14) and a processing unit (11), a piston (1) spring-loaded by a spring (3) in the hydraulic cylinder (2) with a predetermined displacement path, a hydraulic pump (6) for pressurising the spring-loaded piston (1) through the feed line (4), and at least a control valve (8, 9) in the return line (10) for opening and closing a cross-section of the return line, wherein the cross-section of the return line (10) is controllable through the control unit (14), which is connected to the processing unit (11), in which a predetermined target displacement speed (v) is stored and which is configured to compare the actual value of the piston speed (v') with the target speed (v), and which is formed to output a control signal to the control unit (14) such that a predetermined displacement time for the displacement is maintained, wherein a first switch and a second switch each in end positions (S1 and S2) are provided and a third switch in an intermediate position (S3) serves for the detection of the displacement time as a basis for calculation.

7. Hydraulically actuated drive unit, especially a fitting, comprising a hydraulic cylinder (2) with a piston (1), a feed line and a return line (4.1, 4.2, 4.3, 4.4), a drive motor (M) and a hydraulic pump (6) driven by the drive motor (M) for acting on the piston (1), having a predetermined displacement, of the drive unit in the hydraulic cylinder (2) with hydraulic fluid, wherein the piston is acted on, on both sides, by hydraulic fluid in the hydraulic cylinder, a control valve (15) for switching the hydraulic lines leading to the hydraulic cylinder between feed- and return line, wherein the drive motor (M) is controllable through the control unit (14), which is connected to the processing unit (11), in which a predetermined target displacement speed (v) is stored and which is configured to compare the actual value of the piston speed (v') with the target displacement speed (v), and which is formed to output a control signal to the control unit (14) for synchronised operation manner of the motor (M) or for a change in the rotational speed of the motor (M), so that a predetermined displacement time for the displacement is maintained, and wherein a first switch and a second switch each in end positions (S1 and S2) are provided and a third switch in an intermediate position (S3) serves for the detection of the displacement time as a basis for calculation.

8. Drive unit according to claim 7, further comprising: a bypass line (4.41), a valve (18) and a throttle (17) arranged in the feed line (4.4) between pressure source (6, 16) and control valve (15), which throttle is bypassed by the bypass line (4.41) in which the valve (18) is arranged for opening and closing the bypass line (4.41), wherein the passage cross-section of the feed line (4.4) and the valves (15, 18) are controllable through the control unit (14), which is connected to the processing unit (11).

9. Drive unit according to one of claims 6 to 8, wherein for detecting the displacement speed of the drive unit, a further switch (S4) is provided on the partial section of the displacement path.