Method for adapting a control of a proportional valve to its functional operation as part of a fluid system

Description

[0001] The invention relates to a method for adapting the control of a proportional valve to its functional operation as part of a fluid system.

[0002] DE 10 2019 000 212 A1 discloses a method for operating a circuit arrangement for load-optimized lowering of loads using a fluid-driven working device. A proportional pressure relief valve is arranged in the return line of the circuit arrangement, which is designed as a fluid system. This valve serves to regulate the lowering speed of a respective load. A control device of the circuit arrangement, in which a characteristic curve map for the proportional pressure relief valve is stored, calculates a setpoint value for controlling the proportional pressure relief valve depending on a setpoint value specified by an operator, the current speed of the working device, and a pressure resulting from the load on the working device.

[0003] Further methods for adapting the control of a proportional valve can be found in DE 10 2004 005 401 A1, DE 10 2019 000 212 A1, DE 699 10 948 T2, DE 699 37 991 T2 and US 2018 / 0142709 A1.

[0004] The invention is based on the object of providing a method by which the integration of a proportional valve into a fluid system can be carried out precisely, simply and cost-effectively.

[0005] This object is achieved by a method according to the invention having the features of patent claim 1 in its entirety.

[0006] In According to the invention, it was first recognized that a manufacturer of a fluid system that connects a proportional valve to a fluid system in a fluid-conducting manner must adapt the control of the proportional valve to the fluid system in the sense of a teach-in process before the fluid system is put into operation for the first time. This is achieved by actively parameterizing the control device of the fluid system by an operator and, if necessary, by conducting a test operation, which is costly and time-consuming.

[0007] In accordance with the invention, it has further been recognized that the operating characteristics of identical proportional valves of the same type from one manufacturer differ at least slightly from one another due to manufacturing tolerances, in particular hydraulic and / or electrical ones. For example, when two proportional valves are controlled with the same current value and the same pressure at the input port of each proportional valve, the flow rate through one proportional valve may differ from the flow rate through the other proportional valve. Likewise, a change in the pressure at the input port of each proportional valve, with the same control current value, may result in a change in the flow rate of one proportional valve that differs from that of the other proportional valve.As a result, in order to obtain the same flow rate, all proportional valves of the same type from one manufacturer cannot be controlled using a single characteristic curve or, conversely, when all proportional valves of the same type from one manufacturer are controlled with the same current value, at least slightly different flow rates of two proportional valves are to be expected.

[0008] These conditions are taken into account in their entirety by the features of patent claim 1, according to which the inventive method for adapting the control of a proportional valve to its functional operation as part of a fluid system comprises the following method steps: determining measured values of the proportional valve during its operation outside the fluid system; creating a characteristic curve field based on the measured values; integrating the proportional valve into the fluid system; and adapting the control of the proportional valve to the fluid system based on the characteristic curve field by means of a control device.

[0009] In the present case, integrating the proportional valve into the fluid system is synonymous with the fluid-carrying and / or electrical connection of the proportional valve to the fluid system for its functional operation in the fluid system, whereas operating the proportional valve outside of this fluid system is synonymous with a proportional valve that is hydraulically and electrically unconnected to the fluid system, i.e., separated in this respect.

[0010] The aforementioned process steps eliminate the need for costly and time-consuming active adaptation of the proportional valve control to the fluid system into which the proportional valve is integrated, in the sense of a teaching process by the fluid system manufacturer. All proportional valves are therefore regularly subjected to an end-of-line test by their manufacturer, in which each proportional valve is tested for functionality at least in sections across its entire possible operating range, which may exceed the operating range required for use of the proportional valve in a particular fluid system. As part of the end-of-line test, measured values are collected across the entire possible operating range of the proportional valve and stored as a characteristic curve map for each proportional valve.A specific characteristic curve map associated with each proportional valve can be retrieved by the fluid system manufacturer for use in the control device of its fluid system to adapt the control of the proportional valve to the fluid system. For adaptation, the control device automatically selects at least one characteristic curve within the required operating range of the proportional valve, which is part of the total possible operating range of the proportional valve. Such adaptation is not only carried out when the fluid system is commissioned, but can also be performed if the pressure range at the inlet connection of the proportional valve changes during operation of the fluid system. This can be viewed as independent, valve-specific parameterization of the control device, without active intervention by an operator, thus saving time and costs.

[0011] Furthermore, the control signal of the proportional valve emitted by the control device can be adjusted to the proportional valve with a particularly high resolution, whereby a controlled and precise regulation of the movement sequence of at least one piston rod of the working device can be achieved.

[0012] In a particularly preferred embodiment, it is provided that the measured values of a flow through the proportional valve are determined outside the fluid system as a function of a varied control current of an actuating device of the proportional valve in at least one predetermined pressure range at the inlet connection of the proportional valve. Derived from this, it is preferably provided that the characteristic curve field has, for each pressure range at the inlet connection of the proportional valve, a characteristic curve of the flow through the proportional valve as a function of the control current of the actuating device of the proportional valve. This embodiment is based on the fact that the flow, i.e. the volume flow, through the proportional valve is essentially dependent on the fluid pressure at the inlet connection of the proportional valve and the opening cross-section of the proportional valve, which in turn depends on its control current.

[0013] In a further preferred embodiment, the proportional valve is controlled by the control device as a function of a setpoint specified by an operator of the fluid system, based on a respective characteristic curve of the characteristic field suitable for the operation of the proportional valve in the fluid system. Preferably, a working device is connected, in particular directly, to the proportional valve integrated into the fluid system, and the control is adapted such that the characteristic curve of the characteristic field most suitable for the operation of the proportional valve in the fluid system is selected based on the measured load pressure at the input connection of the proportional valve.Particularly preferably, the assignment between the respective proportional valve and its characteristic curve map is established by means of a unique identifier, which is preferably permanently attached to the proportional valve. These features further support the cost- and time-saving adaptation of the control of the proportional valve to the fluid system, requiring only minimal operator intervention.

[0014] In a further preferred embodiment, measured values of the travel distance and / or travel speed of a piston rod of the working device are determined, and these measured values are incorporated into the control of the proportional valve. This improves the functional reliability of the fluid system, in particular the desired change in movement of at least one piston rod of the working device, and increases the accuracy of the control of the proportional valve. This makes it possible to create a closed control loop.

[0015] In a further preferred embodiment, it is provided that a travel movement of a piston rod of at least one working cylinder of the working device is monitored within setting limits (expected values) after the proportional valve has been integrated into the fluid system, in particular following adjustment of the control. The teaching and / or test operation of the proportional valve, which may take place after this monitoring in the prior art, can be omitted according to the invention.

[0016] In a further preferred embodiment, it is provided that the fluid used is a hydraulic fluid, such as hydraulic oil, and accordingly all components of the hydraulic fluid system, in particular the proportional valve, are hydraulic components.

[0017] Furthermore, a fluid system is provided for fluidically controlling a working device, which can be supplied with a fluid of predeterminable pressure via an inlet from a motor-pump unit for lifting a load. It has a return line for discharging fluid from the working device when lowering this load, into which a proportional valve, in particular for regulating the lowering speed, is connected. Control of the proportional valve is adapted to its functional operation as part of the fluid system by means of the aforementioned method according to the invention.

[0018] In a particularly preferred embodiment, the return line is otherwise free of any flow cross-section restriction devices, in particular variably adjustable ones. Compared to the prior art, this eliminates at least one valve in the return line, allowing the fluid system, particularly in a block design, to be designed more compactly and the load to be lowered with optimized back pressure. Furthermore, the proportional valve can be better utilized within its technical limits.

[0019] An industrial truck is also provided with a fork, a working device which has at least one working cylinder by means of which the fork can be moved, and a hydraulic fluid system mentioned above for controlling the respective working cylinder.

[0020] In the following, the method according to the invention for adapting the control of a proportional valve to its functional operation as part of a fluid system is explained in more detail with reference to the fluid system and the drawing. In a schematic representation and not to scale, the Fig. 1 in the form of a hydraulic circuit diagram, the fluid system comprising the proportional valve; and Fig. 2 in a Cartesian coordinate system, a control device of the fluid system comprising Fig. 1 stored characteristic curve field for controlling the proportional valve, in which a pressure at the input connection of the proportional valve and a flow through the proportional valve are plotted against a control current of the proportional valve.

[0021] A manufacturer of a proportional valve 10 regularly performs a final production test on all proportional valves 10 it manufactures. In this test, the manufacturer checks the functionality of each proportional valve 10 across its entire operating range. During the final production test of each proportional valve 10, the manufacturer collects measured values according to the invention.

[0022] Using the measured values, a characteristic curve map 12 is created for each proportional valve 10, from which the operating behavior of the proportional valve 10 can be derived across its entire possible operating range. The characteristic curve maps 12 of all proportional valves 10 are stored centrally by the manufacturer of the proportional valve 10, for example, on a server.

[0023] If a respective proportional valve 10 is integrated into the fluid system 14 by a manufacturer of a fluid system 14 after its delivery, the manufacturer of the fluid system 14 can retrieve the characteristic curve field 12 belonging to this proportional valve 10 from the server of the proportional valve manufacturer and implement it in a control device 18 of the fluid system 14. This is where the manufacturer of the fluid system 14 differs from the manufacturer of the proportional valve 10. The assignment between the proportional valve 10 and its characteristic curve field 12 takes place by means of a unique identifier that is attached to the valve 10, such as a Quick Response Code (QR Code) or a character string, and by means of which the manufacturer of the fluid system 14 gains access to the characteristic curve field 12 of the proportional valve 10 used in the system.The proportional valve 10 can now be controlled according to the operating range required in this fluid system 14 using at least one characteristic curve 16 of the characteristic curve field 12, without an operator having to parameterize the control device 18 of the fluid system 14 in this regard and / or without a test operation of the proportional valve 10 having to take place.

[0024] The respective fluid system 14 in which the proportional valve 10 is used can be designed as shown in the Fig. 1 The fluid system 14 shown is preferably used in industrial trucks for controlling working cylinders 20 in the form of lifting cylinders 22 for lifting devices, such as lifting forks, for lifting and lowering loads. The gravity-induced lowering of lifted loads is achieved via a lowering valve 10, in this case in the form of the proportional valve 10.

[0025] The fluid system 14 has a motor-pump unit 24, the pump 26 of which is fluidly connected with its suction side to a fluid storage tank T via a first fluid line 28 and with its high-pressure side to a pressure supply port P of the fluid system 14 via a second fluid line 30. A first branching point 34 is provided in the second fluid line 30, to which a return line 38 leading to the tank T is connected, into which the electromagnetically controllable proportional valve 10 is connected.

[0026] An inlet 40 of the fluid system 14 is formed by the fluid path starting from the tank T via the first fluid line 28, the pump 26 and the second fluid line 30 up to the pressure supply connection P. A return 42 of the fluid system 14 is formed by the fluid path starting from the pressure supply connection P via a part of the second fluid line 30 and the return line 38, into which the proportional valve 10 is connected, up to the tank T. The return 42 thus differs at least partially from the inlet 40. With the exception of the proportional valve 10, the entire fluid path of the return 42 is free of devices for restricting the flow cross-section, which devices can be variably adjustable and / or externally controllable.

[0027] A solenoid actuator 44 of the proportional valve 10 can be controlled by the electronic control device 18 of the fluid system 14. The control device 18 receives measured values from a pressure sensor 46, which measures the fluid pressure in the second fluid line 30, and setpoints from an input device 48, such as a joystick, for inputting lifting and lowering commands by an operator.

[0028] The proportional valve 10 is designed as a 2 / 2-way proportional directional control valve 10. The valve piston 50 of the proportional valve 10 can be moved from a first end position shown in the figure to a second end position by means of the actuating device 44 against the force of a compression spring 52. In the first end position shown in the figure, the valve piston 50 of the valve 10 separates its inlet port 54 and outlet port 56 from each other, which the valve piston 50 connects to each other in a fluid-conducting manner via a fluid path in the second end position. The inlet port 54 of the proportional valve 10 is connected to the first branching point 34, and the outlet port 56 is connected to the tank T, preferably directly in each case. Particularly preferably, the branching point 34 corresponds to the pressure supply port P.

[0029] A check valve 58 is connected to the second fluid line 30 between the first branching point 34 and the pump 26, which opens against the force of a compression spring in the direction of the pressure supply connection P. The check valve 58 prevents a backflow of fluid from the pressure supply connection P via the pump 26 to the tank T. A second branching point 36 is provided in the second fluid line 30 between the check valve 58 and the pump 26. An inlet connection 60 of a pressure relief valve 62 is fluid-conductingly connected to the second branching point 36, the outlet connection 64 of which is fluid-conductingly connected to the return line 38 between the proportional valve 10 and the tank T. The pressure relief valve 62 protects the second fluid line 30 against inadmissible overpressure to the tank T. A suction filter 66 is connected to the first fluid line 28.

[0030] The working cylinder 20 of a fluidically driven working device 68 is connected to the fluid system 14. For this purpose, a piston-side working chamber 70 of the working cylinder 20 is fluidically connected to the pressure supply port P, in particular permanently, preferably free of interposed flow cross-section constriction devices, particularly preferably directly connected. The piston-side working chamber 70 of the working cylinder 20 is supplied with fluid of a predeterminable pressure via the inlet 40 of the fluid system 14 to lift a load and is relieved of pressure to lower the load by discharging fluid from the piston-side working chamber 70 via the return 42 of the fluid system 14 to the tank T. The proportional valve 10, which can be designed as a slide or seat valve, functions as a lowering valve 10.The check valve 58 prevents a lifted load from being lowered via the pump 26, and the pressure relief valve 62 provides protection against lifting excessively heavy loads.

[0031] In addition to the measured values of the pressure sensor 46, which correspond to the load pressure p of a respective load, the control device 18 can be supplied with measured values from a displacement sensor 72, which detects the travel distance and / or the travel speed of a piston rod unit 74 of the working cylinder 20. These measured values are incorporated into the control of the proportional valve 10.

[0032] The fluid system 14 as well as the working device 68, the two sensors 46, 72, the control device 18 and the input device 48 are part of a fluid conveying vehicle not shown in the figures, such as a forklift truck, which has a fork for load handling, which can be moved up and down by means of the working cylinder 20 in the form of a lifting cylinder 22.

[0033] With regard to the use of the proportional valve 10 in the fluid system 14 described above, the manufacturer of the proportional valve 10 collects, as part of the final production test, measured values of the flow rate Q through the proportional valve 10 as a function of a varied control signal in the form of the control current I of the actuating device 44 of the proportional valve 10 in several pressure ranges at the inlet connection 54 of the proportional valve 10. In this case, application limits of the proportional valve 10, such as a control current value I for a minimum flow rate Q through the proportional valve 10, a control value I for a maximum flow rate Q and the resolution of the opening cross-section adjustment of the proportional valve 10, can be determined.

[0034] Accordingly, the Fig. 2 The characteristic curve field 12 shown shows for each pressure range a characteristic curve 16 of the flow rate Q [liters / minute] and another characteristic curve 17 of the fluid pressure p [bar], each as a function of the control current I [milliampere]. The pressure ranges, as shown in Fig. 2 shown, can be provided, for example, at approximately 10 bar (reference numeral 78), 20 bar (reference numeral 80), 50 bar (reference numeral 82), 100 bar (reference numeral 84), 150 bar (reference numeral 86) and 200 bar (reference numeral 88).

[0035] After the fluid-carrying connection of the proportional valve 10 to the fluid system 14, the manufacturer of the fluid system 14 retrieves the characteristic curve field 12 associated with the proportional valve 10 from the manufacturer of the proportional valve 10 using the unique identification and transfers it to the control device 18 of the fluid system 14. The control device 18 then independently selects the most suitable characteristic curve profile 16 of the characteristic curve field 12 in this load pressure range based on the measured load pressure p of a respective load, whereby the control of the proportional valve 10 is adapted to the fluid system 14 in a valve-specific and automatic manner. This enables a particularly well-coordinated resolution of the control current I to the proportional valve 10.

[0036] If an operator of the fluid system 14 issues a command to lower the load via the input device 48, which corresponds to a specific travel path and / or a specific travel speed of the piston rod unit 74 of the working cylinder 20 and thus to a specific opening cross-section of the proportional valve 10 or flow rate Q through the proportional valve 10, the valve-specific control current I required to execute this command is determined via the selected characteristic curve 16 and transmitted by the control device 18 to the actuating device 44 of the proportional valve 10, in particular for adjusting the lowering speed of the load. This enables particularly precise and controlled regulation of the movement sequence of the piston rod unit 74 of the working device 68. The control current I can be a pulse-width-modulated current signal (PWM signal). The load is raised, as in the prior art, by operating the pump 26.

Claims

1. Method for adjusting an actuation of a proportional valve (10) for its functional operation as part of a fluid system (14), having the following steps: - acquiring measurements from the proportional valve (10) during its operation outside the fluid system (14); - preparing a characteristic diagram (12) based on the measurements; - integrating the proportional valve (10) into the fluid system (14), and - adapting the actuation of the proportional valve (10) to the fluid system (14) on the basis of the characteristic diagram (12) by means of a control device (18).

2. Method according to claim 1, characterised in that acquiring measurements and preparing the characteristic diagram (12) are performed by a manufacturer of the proportional valve (10) and adapting the actuation is performed by a manufacturer of the fluid system (14).

3. Method according to either claim 1 or claim 2, characterised in that the characteristic diagrams (12) of all manufactured proportional valves (10) are stored by their manufacturer and in that the characteristic diagram (12) of a respective proportional valve (10) integrated in the fluid system is retrieved by the fluid system manufacturer from the manufacturer of said proportional valve (10) and transferred to a control device (18) for the fluid system (14).

4. Method according to any of the preceding claims, characterised in that, outside the fluid system (14), the measurements of a flow (Q) through the proportional valve (10) are acquired as a function of an actuation signal (I) of an actuating device (44) of the proportional valve (10) in at least one predefined pressure range at the inlet port (54) of the proportional valve (10).

5. Method according to any of the preceding claims, characterised in that the characteristic diagram (12) for each pressure range at the inlet port (54) of the proportional valve (10) comprises at least one characteristic curve (16) for the flow (Q) through the proportional valve (10) as a function of the actuation signal (I) of the actuating device (44) of the proportional valve (10).

6. Method according to any of the preceding claims, characterised in that the proportional valve (10) is actuated by the control device (18) as a function of a setpoint specified by a person operating the fluid system (14) using a respective characteristic curve (16) from the characteristic diagram (12), said curve being suited to operation of the proportional valve (10) in the fluid system (14).

7. Method according to any of the preceding claims, characterised in that an operating device (68) is connected to the proportional valve (10) integrated in the fluid system (14) and in that adjusting the actuation accordingly takes place in that the characteristic curve (16) from the characteristic diagram (12) suited to operation of the proportional valve (10) in the fluid system (14) is selected based on the measured load pressure (p) at the inlet port (54) of the proportional valve (10).

8. Method according to claim 7, characterised in that measurements of the displacement path and / or the displacement speed of at least one piston rod (74) of the operating device (68) are acquired and in that these measurements are also used when actuating the proportional valve (10).

9. Method according to any of the preceding claims, characterised in that the association between the respective proportional valve (10) and its characteristic diagram (12) is established by means of a unique identifier, which is preferably connected permanently to the proportional valve (10).

10. Method according to any of claims 7 to 9, characterised in that a displacement movement of the operating device (68) is controlled within adjustment limits.