Method for controlling the operation of a solenoid valve of an agricultural spreading machine

Abstract

The invention relates to a method for controlling the operation of a solenoid valve (10) used to control the flow rate of a spraying liquid in an agricultural spreading machine, wherein the solenoid valve (10) has a valve armature (16) movable between a first end position and a second end position by energizing the solenoid valve (10), comprising the steps of: energizing the solenoid valve (10) according to an energizing specification within the framework of a control process, wherein energizing the solenoid valve (10) causes movement of the valve armature (16), and detecting end position times (t E1a -t E1c , t E2a -t E2c), at which the valve armature (16) of the solenoid valve (10) assumes the first end position and / or the second end position after a movement, by means of an electronic data processing device (26) and adjustment of the current setting for the solenoid valve (10) taking into account the detected end position times (t E1a- t E1c , t E2a -t E2c ).

Description

[0001] The invention relates to a method for controlling the operation of a solenoid valve of an agricultural spreading machine according to the preamble of patent claim 1 and to a spreading system for spreading spray liquid according to the preamble of patent claim 14.

[0002] Agricultural sprayers typically have several solenoid valves that can be used to control the flow rate of the spray liquid. The flow rate control allows the desired amount of spray liquid to be applied to the agricultural field.

[0003] The application rate of the spray fluid can be roughly adjusted by specifying a specific spray pressure, or vice versa, since the application rate and spray pressure can be correlated. However, studies have shown that this is only approximately true, as the pressure of the spray fluid at the spray nozzle varies over time due to the opening and closing of the solenoid valve, which is not constant. Furthermore, the solenoid valve generates a pressure drop that is dependent on the volume flow.

[0004] To apply the intended amount of spray fluid, the pressure of the spray fluid and the duration of time the solenoid valve is actually open must be known. However, the duration of time the solenoid valve is actually open can only be approximately determined from the current flow to the solenoid valve, since the current flow is based on a theoretical valve behavior that deviates from the actual valve behavior.

[0005] The object underlying the invention is therefore to enable an improved solenoid valve control in which the period of time in which the solenoid valve is actually open is taken into account more precisely.

[0006] The object is achieved by a method of the type mentioned at the outset, wherein, within the scope of the method according to the invention, at least one state parameter of the spray liquid is detected by a sensor in a measuring range by means of a measuring device and the detection of the end position assumption times at which the valve armature of the solenoid valve assumes the first end position and / or the second end position after a movement is carried out by evaluating the state parameter of the spray liquid detected by a sensor.

[0007] The invention takes advantage of the discovery that, alternatively or in addition to evaluating the solenoid valve current supply, the state of the spray fluid can also be used to detect the times at which the valve armature reaches its final position. The opening and closing of the solenoid valve creates characteristic states in the spray fluid, which can be detected by the measuring device and evaluated to determine the times at which the valve armature reaches its final position.

[0008] The measuring device can, for example, be a sensor that determines the condition parameter of the spray liquid within a measuring range. The solenoid valve is preferably controlled by pulse width modulation, in particular pulse width frequency modulation. The solenoid valve is controlled, for example, at a frequency between 0 and 50 Hz. The solenoid valve is preferably opened by the magnetic force generated by the current flow through the solenoid valve coil. The solenoid valve is preferably closed by a return spring of the solenoid valve. Due to these different mechanisms, the opening and closing times vary and depend on condition parameters of the spray liquid, such as the pressure of the spray liquid.

[0009] In a preferred embodiment of the method according to the invention, the state parameter sensed by the measuring device is dependent on the pressure of the spray liquid in the measuring area or relates to the pressure of the spray liquid in the measuring area. The measuring device can therefore comprise a pressure sensor or be designed as a pressure sensor. Alternatively or additionally, the state parameter sensed by the measuring device can be dependent on the volume flow of the spray liquid in the measuring area or relate to the volume flow of the spray liquid in the measuring area. In this case, the measuring device can, for example, comprise a volume flow sensor or be designed as a volume flow sensor.

[0010] In a further preferred embodiment of the method according to the invention, the electronic data processing device monitors the temporal progression of the state parameter when evaluating the sensor-detected state parameter of the spray liquid. In particular, the electronic data processing device records the times at which the end position is reached based on characteristic progression sections in the temporal progression of the state parameter. For example, when evaluating the sensor-detected state parameter of the spray liquid, the electronic data processing device monitors the temporal progression of the pressure of the spray liquid in the measuring range and records the times at which the end position is reached based on characteristic progression sections in the temporal pressure progression. The measuring device preferably samples the pressure of the spray liquid in the measuring range at high frequency.Preferably, the pressure of the spray liquid is sampled at such a high frequency that the actual volume flow rate can be determined from the pressure integral. Preferably, the electronic data processing device determines the actual volume flow rate from the pressure integral.

[0011] Furthermore, a method according to the invention is advantageous in which the measuring range in which the condition parameter of the spray liquid is detected by sensor is located downstream of the solenoid valve in the flow direction of the spray liquid or upstream of the solenoid valve in the flow direction of the spray liquid, in particular directly upstream of the solenoid valve. The measuring range is preferably located between the solenoid valve and a spray nozzle via which the spray liquid is released towards the agricultural area. The condition parameter can also be detected in several measuring ranges. One measuring range can, for example, also be located in the solenoid valve. One measuring range can, for example, also be located in the spray nozzle and / or directly upstream of the spray nozzle. The application rate can also be precisely calculated using the pressure in the spray nozzle or the pressure directly upstream of the spray nozzle.

[0012] In an advantageous development of the method according to the invention, the detection of the end position assumption times comprises the detection of first end position assumption times and / or the detection of the second end position assumption times. At the first end position assumption times, the valve armature of the solenoid valve assumes the first end position after a movement and the solenoid valve is open. At the second end position assumption times, the valve armature of the solenoid valve assumes the second end position after a movement and the solenoid valve is closed. The evaluation of the state parameter thus allows the determination of a time at which the solenoid valve assumes the fully open state and the determination of a time at which the solenoid valve assumes the fully closed state.

[0013] In another preferred embodiment of the method according to the invention, the solenoid valve whose end-position times are detected is a reference solenoid valve. The current supply specification is uniformly adjusted for a plurality of solenoid valves, taking into account the detected end-position times of the reference solenoid valve. Assuming that the solenoid valves have very small manufacturing tolerances or flow rate variations, the end-position times can be detected at one solenoid valve, and the resulting current supply adjustment can then be performed at all solenoid valves.

[0014] The method according to the invention is further advantageously further developed in that the electronic data processing device determines a current supply specification for the solenoid valve that is matched to the detected end position assumption times in order to adapt the current supply specification and determines an actual value of the opening proportion in the switching cycle of the solenoid valve on the basis of the detected end position assumption times in order to determine the current supply specification that is matched to the detected end position assumption times.The actual value of the opening proportion in the switching cycle of the solenoid valve refers to the ratio between the length of time the solenoid valve is actually open within the switching cycle and the actual cycle duration of the solenoid valve's switching cycle, whereby the actual cycle duration of the switching cycle is made up of the length of time the solenoid valve is actually open within the switching cycle and the length of time the solenoid valve is actually closed within the switching cycle. The actual value of the opening proportion in the switching cycle of the solenoid valve can also be referred to as the actual duty cycle. The actual value of the opening proportion in the switching cycle of the solenoid valve specifies the actual flow rate of the spray liquid through the solenoid valve, particularly in the case of central pressure control, so that the actual application rate of the spray liquid depends on the actual value of the opening proportion in the switching cycle of the solenoid valve.

[0015] In another preferred embodiment of the method according to the invention, the electronic data processing device adapts a control value of the opening portion in the switching cycle of the solenoid valve based on the determined actual value of the opening portion in the switching cycle of the solenoid valve in order to achieve a target value of the opening portion in the switching cycle of the solenoid valve in order to determine the current supply specification coordinated with the detected end position assumption times.The control value of the opening portion in the switching cycle of the solenoid valve refers to the ratio between the time period in which the solenoid valve should theoretically be open within a switching cycle according to the current control and the control cycle duration of the solenoid valve's switching cycle. The control cycle duration of the switching cycle is composed of the time period in which the solenoid valve should theoretically be open within the switching cycle according to the current control and the time period in which the solenoid valve should theoretically be closed within the switching cycle according to the current control. The control value of the opening portion in the switching cycle of the solenoid valve can also be referred to as the control duty cycle.The target value of the opening portion in the switching cycle of the solenoid valve refers to the ratio between the time period during which the solenoid valve should be open within a switching cycle and the target cycle duration of the solenoid valve's switching cycle. The target cycle duration of the switching cycle is composed of the time period during which the solenoid valve should be open within the switching cycle and the time period during which the solenoid valve should be closed within the switching cycle. The target value of the opening portion in the switching cycle of the solenoid valve can also be referred to as the target duty cycle.At the start of the control process, the control value of the opening portion in the switching cycle of the solenoid valve preferably corresponds to the setpoint value of the opening portion in the switching cycle of the solenoid valve. By recording the end position assumption times, it is then determined that the control value of the opening portion in the switching cycle of the solenoid valve does not result in the actual value of the opening portion in the switching cycle of the solenoid valve corresponding to the setpoint value of the opening portion in the switching cycle of the solenoid valve, and an adjustment of the control value of the opening portion in the switching cycle of the solenoid valve is necessary. The setpoint value of the opening portion in the switching cycle of the solenoid valve is preferably assigned to an application rate of spray liquid, so that when a specific application rate of spray liquid is set by the machine operator, a setpoint value of the opening portion in the switching cycle of the solenoid valve is defined and can be retrieved or calculated.

[0016] In an advantageous development of the method according to the invention, the current supply specification determined by the electronic data processing device and matched to the detected end position assumption times comprises a modified pull-in current of the solenoid valve, which leads to a modified pull-in duration of the solenoid valve. The pull-in current leads to the movement of the valve armature from one end position in which the solenoid valve is closed to another end position in which the solenoid valve is open. The pull-in duration refers to the time from the application of the supply voltage until the valve armature reaches the end position in which the solenoid valve is open. The modified pull-in current leads, for example, to a shortened pull-in duration or to a longer pull-in duration. The modified pull-in current can refer to a weaker pull-in current or a stronger pull-in current.

[0017] In an advantageous development of the method according to the invention, the current supply specification determined by the electronic data processing device and adjusted to the detected end-position times comprises a modified holding current supply to the solenoid valve, which leads to a modified holding time of the valve armature. The holding current supply leads to the valve armature being held in the end position in which the solenoid valve is open. The holding time refers to the period of time during which the valve armature is held by a holding current in the end position in which the solenoid valve is open. The modified holding current supply leads, for example, to a shortened holding time or to an extended holding time.

[0018] In another preferred embodiment of the method according to the invention, the current supply specification determined by the electronic data processing device and matched to the detected end position assumption times comprises a modified drop-out current supply to the solenoid valve, which leads to a modified drop-out duration of the valve armature. The drop-out current supply leads to the preferably spring-assisted movement of the valve armature from the end position in which the solenoid valve is open to the end position in which the solenoid valve is closed. The drop-out duration refers to the time period from the application of a negative supply voltage until the valve armature reaches the end position in which the solenoid valve is closed. The modified drop-out current supply leads, for example, to a shortened drop-out duration or to a longer drop-out duration. The modified drop-out current supply can refer to a weakened drop-out current supply or an increased drop-out duration.For example, for a specific current supply specification, it can also be provided that the current supply to the solenoid valve is at least temporarily interrupted during the dropout period or that it is supplied with the supply voltage. The supply voltage can be 12 V or 24 V, for example.

[0019] In another preferred embodiment of the method according to the invention, the current supply specification determined by the electronic data processing device and adjusted to the detected end-position times includes a modified pull-in duration of the valve armature, during which the pull-in current is applied to the solenoid valve. Increasing the pull-in duration ultimately also increases the release time of the valve armature, since the solenoid valve or valve armature is magnetized more strongly due to the increased pull-in duration.

[0020] In an advantageous development of the method according to the invention, the current supply specification determined by the electronic data processing device and adjusted to the detected end-position times results in a changed cycle duration of the switching cycle of the solenoid valve. Alternatively, the current supply specification determined by the electronic data processing device and adjusted to the detected end-position times does not result in a changed cycle duration of the switching cycle of the solenoid valve.

[0021] The object underlying the invention is further achieved by a dispensing system of the type mentioned above, wherein the control device of the dispensing system according to the invention is configured to control the operation of the solenoid valves according to one of the embodiments described above. With regard to the advantages and modifications of the dispensing system according to the invention, reference is therefore made to the advantages and modifications of the method according to the invention.

[0022] Preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying drawings. Fig. 1 a closed solenoid valve of a dispensing system according to the invention in a schematic representation; Fig. 2 that in the Fig. 1 depicted solenoid valve in an open state in a schematic representation; Fig. 3 shows the voltage and pressure curve during an inventively controlled operation of a solenoid valve in a diagrammatic representation; and Fig. 4 shows the method steps carried out within the scope of a method according to the invention when adapting the current supply specification in a schematic flow diagram.

[0023] The Fig. 1 and Fig. 2 shows a solenoid valve 10 of a spreading system, which can, for example, be part of a field sprayer. The solenoid valve 10 is used to control the flow rate so that a desired amount of spray liquid, for example, crop protection agent, can be applied to an agricultural field.

[0024] Alternatively or additionally, the solenoid valve 10 can be used for pressure control or spray pressure regulation, so that an intended spray pressure of the spray liquid can be set within the agricultural field sprayer and / or along the supply line(s).

[0025] The solenoid valve 10 has a valve inlet 12 and a valve outlet 14. The spray liquid to be dispensed enters the solenoid valve 10 via the valve inlet 12. The spray liquid to be dispensed can be discharged from the solenoid valve 10 via the valve outlet 14. The discharged spray liquid is fed to a spray nozzle via line section 28.

[0026] The fluid connection between the valve inlet 12 and the valve outlet 14 can be blocked and released via a valve armature 16. The solenoid valve 10 shown is a normally closed valve, whereby the valve armature 16 can be raised by energizing the solenoid valve 10, thus fluidly connecting the valve inlet 12 to the valve outlet 14.

[0027] The solenoid valve 10 is connected to a control device 24 via a power supply line 22. The control device 24 comprises an electronic data processing device 26 and serves to regulate the operation of the solenoid valve 10. The coil 18 of the solenoid valve 10 is energized via the power supply line 22. Energizing the coil 18 creates a magnetic field that causes the valve armature 16 to move upwards. The valve armature 16 is coupled to a return spring 20, which applies a closing force to the valve armature 16. The return spring 20 moves the valve armature 16 back into the closed position if the coil 18 is not energized or is insufficiently energized.

[0028] The electronic data processing device 26 of the control device 24 is designed to determine the end position times t E1a -t E1c , t E2a -t E2cto which the valve armature 16 of the solenoid valve assumes a first end position and a second end position after a movement.

[0029] The Fig. 1 shows the solenoid valve 10 in the closed state. In the closed state, the valve armature 16 is in an end position. Fig. Figure 2 shows the solenoid valve 10 in the open state. In the open state, the valve armature 16 is in the other end position.

[0030] The control device 24 is designed to provide a current supply specification for the solenoid valve 10 taking into account the detected end position times t E1a -t E1c , t E2a -t E2c to adapt.

[0031] To record the final position times t E1a -t E1c , t E2a -t E2cThe electronic data processing device 26 is connected to a measuring device 30. The measuring device 30 is configured to sensor-detect a state parameter p of the spray liquid in a measuring range 32. The state parameter p of the spray liquid, which is sensor-detected by the measuring device 30, is the pressure of the spray liquid within the measuring range 32. The detection of the end position times t E1a -t E1c , t E2a -t E2c is carried out by evaluating the sensor-detected state parameter p of the spray liquid.

[0032] In the Fig. 3, the voltage U applied to the solenoid valve 10 is plotted over time t. Furthermore, the pressure p of the spray liquid in the measuring area 32 is plotted over time t.

[0033] The voltage curve U v shows three recurring characteristic time periods, namely the duration t An, the holding period t H and the decay time t Ab . During the tightening period t An A supply voltage is applied to the solenoid valve 10, so that the valve armature 16 is moved from the end position in which the valve armature 16 is in the closed state of the solenoid valve 10, to the end position in which the valve armature 16 is in the open state of the solenoid valve 10. The end position times t E1a -t E1c are therefore within the operating time t An .

[0034] In order to keep the solenoid valve 10 in the open state, during the holding time t H the current is impressed into the coil 18 of the solenoid valve 10 via a pulse-width modulated voltage signal.

[0035] To close the solenoid valve 10, at the beginning of the drop period t Aba negative supply voltage is applied, which promotes the spring-assisted movement of the valve armature 16. The decay time t Ab ends with a final position taking time t E2a -t E2c, in which the valve armature 16 has reached the end position in which the solenoid valve 10 is closed.

[0036] This results in a time period t o , in which the solenoid valve 10 is open, and a time period t g , in which the solenoid valve 10 is closed. This results in an actual cycle time t Z of the switching cycle of the solenoid valve 10, whereby the actual cycle time t Z of the switching cycle from the time period t o , in which the solenoid valve 10 is actually opened within the switching cycle, and the time period t g , in which the solenoid valve 10 is actually closed within the switching cycle.

[0037] To determine the final position times t E1a -t E1c , t E2a -t E2c the electronic data processing device 26 monitors the sensor-detected pressure p of the spray liquid in the measuring area 32 and, based on characteristic sections of the pressure curve over time, records the end position times t E1a -t E1c , t E2a -t E2c . The measuring device 30 samples the pressure of the spray liquid in the measuring area 32 at high frequency, so that characteristic sections in the pressure curve p V can be recognized. The characteristic sections in the pressure curve p V , from which the final position times t E1 ,-t E1c , t E2a -t E2c can be derived are characteristic curve gradients.

[0038] The electronic data processing device 26 calculates from the time period to , the time period t g and the cycle duration t Z an actual value for the opening portion in the switching cycle of the solenoid valve 10. The actual value of the opening portion in the switching cycle of the solenoid valve 10 concerns the relationship between the time period t o , in which the solenoid valve 10 is actually opened within the switching cycle, and the actual cycle time t Z of the switching cycle of the solenoid valve 10. The actual value of the opening portion in the switching cycle of the solenoid valve 10 can also be referred to as the actual duty cycle.

[0039] The electronic data processing device 26 determines, in order to adapt the current supply specification for the solenoid valve 10, a time t E1 at E1 c, t E2a -t E2ccoordinated current supply specification for the solenoid valve 10, wherein the actual value of the opening portion in the switching cycle of the solenoid valve 10 is calculated to determine this current supply specification for the solenoid valve 10. If the actual value of the opening portion in the switching cycle of the solenoid valve 10 deviates from a target value of the opening portion in the switching cycle of the solenoid valve 10, the electronic data processing device adjusts a control value of the opening portion in the switching cycle of the solenoid valve 10.The control value of the opening portion in the switching cycle of the solenoid valve 10 relates to the ratio between the time period in which the solenoid valve 10 should theoretically be open within a switching cycle according to the current control and a control cycle duration of the switching cycle of the solenoid valve 10. The control cycle duration of the switching cycle is composed of the time period in which the solenoid valve 10 should theoretically be open within the switching cycle according to the current control and the time period in which the solenoid valve 10 should theoretically be closed within the switching cycle according to the current control. The control value of the opening portion in the switching cycle of the solenoid valve 10 can also be referred to as the control duty cycle.The target value of the opening portion in the switching cycle of the solenoid valve 10 relates to the ratio between the time period during which the solenoid valve 10 should be open within the switching cycle and a target cycle duration of the switching cycle of the solenoid valve 10. The target cycle duration of the switching cycle is composed of the time period during which the solenoid valve 10 should be open within the switching cycle and the time period during which the solenoid valve 10 should be closed within the switching cycle. The target value of the opening portion in the switching cycle of the solenoid valve 10 can also be referred to as the target duty cycle.

[0040] The Fig. 4 shows an example of a process flow when adjusting the current supply specification.

[0041] In method step 100, a target duty cycle of the solenoid valve 10 is first defined. The target duty cycle describes the target value of the opening portion in the switching cycle of the solenoid valve 10 and thus relates to the relationship between the period of time during which the solenoid valve 10 should actually be open within a switching cycle and the target cycle duration of the solenoid valve's switching cycle. Since the application rate of the spray liquid is directly dependent on the duty cycle of the solenoid valve 10, the target duty cycle is specified, for example, by the intended application rate of spray liquid. The target duty cycle can be, for example, 60% or 0.6. The solenoid valve 10 should therefore be open for 60% of the switching cycles.

[0042] At the beginning of a control process, a control duty cycle is set, which initially corresponds to the target duty cycle. The control duty cycle is a control value of the opening portion in the switching cycle of solenoid valve 10 and thus relates to the ratio between the time period in which the solenoid valve should theoretically be open within a switching cycle according to the current control, and a control cycle duration of the switching cycle of the solenoid valve. Therefore, in method step 102, a control duty cycle is set that corresponds to the target duty cycle. In the present example, this would be 60% or 0.6.

[0043] In process step 104, the end position times t E1a -t E1c , t E2a -t E2cof the solenoid valve 10 is recorded and evaluated to determine the actual duty cycle. The actual duty cycle describes the actual opening portion of the switching cycle of the solenoid valve 10 and thus relates to the relationship between the time period in which the solenoid valve 10 is actually open within a switching cycle and the actual cycle duration of the switching cycle of the solenoid valve. To determine the end position times t E1a -t E1c , t E2a -t E2c the electronic data processing device 26 monitors the sensor-detected pressure p of the spray liquid in the measuring area 32 and, based on characteristic sections of the pressure curve over time, records the end position times t E1 at E1 c, t E2 ,-t E2 ,. The measuring device 30 samples the pressure of the spray liquid in the measuring area 32 at high frequency, so that characteristic sections in the pressure curve p Vcan be recognized. The characteristic sections in the pressure curve p V , from which the final position times t E1a -t E1c , t E2a -t E2c can be characteristic curve gradients, both increasing and decreasing. In other embodiments, the characteristic curve sections can also be defined by local maximum or minimum values ​​in the pressure curve p V The characteristic curve sections can also refer to specific curves in the pressure curve p V The final position acquisition time t E1a -t E1c , t E2a -t E2c The actual duty cycle determined can, for example, be 64% or 0.64.

[0044] In the subsequent method step 106, the recorded actual duty cycle is then compared with the target duty cycle. If the actual duty cycle matches the target duty cycle or is at least within a tolerance range, the intended amount of spray liquid is already being applied and an adjustment of the current supply for the solenoid valve 10 is not necessary. In this case, the current actual duty cycle would be determined again in method step 104. If the actual duty cycle deviates from the target duty cycle or is outside a tolerance range, the intended amount of spray liquid is not applied and an adjustment of the current supply for the solenoid valve 10 is necessary. In the present example, the actual duty cycle deviates by 64% or 0.64 from the target duty cycle of 60% or 0.6.

[0045] In method step 108, the control duty cycle, i.e., the control value of the opening portion in the switching cycle of solenoid valve 10, is then adjusted to achieve a change in the actual duty cycle. The adjustment is determined by the data processing device 26 based on the difference between the actual duty cycle and the target duty cycle, as well as an internally stored calculation routine. In the present example, the control duty cycle is set to 56% or 0.56.

[0046] In the method steps 110a, 110b and 110c, of which one, two or all can be carried out, the electronic data processing device 26 then generates a time interval t E1a -t E1c , t E2a -t E2c coordinated current supply specification is determined.

[0047] In method step 110a, the electronic data processing device 26 generates a time interval t E1 at E1 c, t E2a -t E2c coordinated current specification is determined, which has a changed pull-in current of the solenoid valve 10, which leads to an adapted pull-in time t which changes the actual duty cycle An of the valve armature 16.

[0048] In method step 110b, the electronic data processing device 26 generates a time interval t E1a -t E1c , t E2a -t E2c coordinated current specification is determined, which has a changed holding current of the solenoid valve 10, which leads to an adjusted holding time t which changes the actual duty cycle H of the valve armature 16.

[0049] In method step 110c, the electronic data processing device 26 generates a time interval t E1a -t E1c , t E2a -t E2c coordinated current supply specification is determined, which has a changed drop-out current supply of the solenoid valve 10, which leads to an adapted drop-out time t which changes the actual duty cycle Ab of the valve armature 16.

[0050] Subsequently, in method step 104, the current actual duty cycle is determined again and in method step 106 it is checked whether the adjustment of the control duty cycle has resulted in the actual duty cycle now corresponding to the target duty cycle. List of reference symbols 10 Solenoid valve 12 valve inlet 14 Valve outlet 16 valve anchors 18 coil 20 return spring 22 Power supply line 24 Control device 26 Data processing facility 28 line sections 30 measuring device 32 measuring range 100-110c Process steps p pressure p V Pressure curve t Ab Waste duration t An Tightening time t E1a -t E1c Final position times t E2a -t E2c Final position times t o Duration t H Holding period t o Duration t Z Cycle duration U voltage U V Voltage curve

Claims

[1] Method for controlling the operation of a solenoid valve (10) of an agricultural spreading machine used to control the flow rate of a spray liquid, wherein the solenoid valve (10) has a valve armature (16) which can be moved between a first end position and a second end position by energising the solenoid valve (10), comprising the steps of: - energizing the solenoid valve (10) according to an energization specification as part of a control process, wherein energizing the solenoid valve (10) causes a movement of the valve armature (16); - Recording of final position times (t E1a -t E1c , t E2a -t E2c ), to which the valve armature (16) of the solenoid valve (10) assumes the first end position and / or the second end position after a movement, by means of an electronic data processing device (26); and - Adjusting the current supply for the solenoid valve (10) taking into account the recorded end position times (t E1a- t E1c , t E2a - t E2C ); characterized by that in a measuring area (32) at least one state parameter (p) of the spray liquid is detected by means of a measuring device (30) and the detection of the end position times (t E1a -t E1c , t E2a -t E2c ) by evaluating the sensor-detected condition parameter (p) of the spray liquid. [2] Method according to claim 1, characterized by that the state parameter (p) detected by the measuring device (30) depends on the pressure of the spray liquid in the measuring area (32) or relates to the pressure of the spray liquid in the measuring area (32). [3] Method according to claim 1 or 2, characterized bythat the electronic data processing device (26) monitors the temporal progression of the state parameter (p) when evaluating the sensor-detected state parameter (p) of the spray liquid and, on the basis of characteristic progression sections in the temporal progression of the state parameter (p), determines the final position times (t E1a -t E1c , t E2a -t E2c ) recorded. [4] Method according to one of the preceding claims, characterized by that the measuring range (32) in which the state parameter (p) of the spray liquid is detected by sensors, - in the flow direction of the spray liquid behind the solenoid valve (10), or - in the flow direction of the spray liquid, is located upstream of the solenoid valve (10), in particular directly upstream of the solenoid valve (10). [5] Method according to one of the preceding claims, characterized by , that - recording the final position times (t E1a-t E1c , t E2a -t E2c ) the recording of first final position times (t E1a -t E1c ), to which the valve armature (16) of the solenoid valve (10) assumes the first end position after a movement and the solenoid valve (10) is open, and / or - recording the final position times (t E1a- t E1c , t E2a -t E2c ) the determination of second final position times (t E2a -t E2c ), to which the valve armature (16) of the solenoid valve (10) assumes the second end position after a movement and the solenoid valve (10) is closed. [6] Method according to one of the preceding claims, characterized by that the solenoid valve (10), whose end position times (t E1a -t E1c , t E2a -t E2c) are recorded, is a reference solenoid valve and the current supply specification for a plurality of solenoid valves taking into account the recorded end position times (t E1a- t E1c , t E2a -t E2c ) of the reference solenoid valve is uniformly adjusted. [7] Method according to one of the preceding claims, characterized by that the electronic data processing device (26) for adapting the current supply specification generates a time constant based on the detected end position times (t E1a -t E1c , t E2a -t E2c ) coordinated current supply for the solenoid valve (10) is determined and used to determine the recorded end position times (t E1a -t E1c , t E2a -t E2c ) coordinated current supply specification based on the recorded end position times (t E1a -t E1c , t E2a -t E2c ) determines an actual value of the opening portion in the switching cycle of the solenoid valve (10). [8] Method according to claim 7, characterized by that the electronic data processing device (26) for determining the recorded final position times (t E1a- t E1c , t E2a -t E2c ) adjusted current supply specification, a control value of the opening portion in the switching cycle of the solenoid valve (10) is adjusted on the basis of the determined actual value of the opening portion in the switching cycle of the solenoid valve (10) in order to achieve a target value of the opening portion in the switching cycle of the solenoid valve (10). [9] Method according to claim 7 or 8, characterized by that the time of taking the final position (t E1a -t E1c , t E2a -t E2c ) coordinated current supply specification comprises a changed pull-in current of the solenoid valve (10), which leads to a changed pull-in time (t An ) of the valve armature (16). [10] Method according to one of claims 7 to 9, characterized by that the time of taking the final position (t E1a -t E1c , t E2a -t E2c ) comprises a changed holding current of the solenoid valve (10), which leads to a changed holding time (t H ) of the valve armature (16). [11] Method according to one of claims 7 to 10, characterized by that the time of taking the final position (t E1a -t E1c , t E2a -t E2c ) coordinated current supply specification comprises a changed drop current supply of the solenoid valve (10), which leads to a changed drop duration (t Ab ) of the valve armature (16). [12] Method according to one of claims 7 to 11, characterized bythat the time of taking the final position (t E1a- t E1c , t E2a -t E2c ) adjusted current specification a changed operating time (t An ) of the valve armature (16), during which the pull-in current of the solenoid valve (10) takes place. [13] Method according to one of claims 7 to 12, characterized by that the time of taking the final position (t E1a -t E1c , t E2a -t E2c ) coordinated current supply specification leads to a changed cycle duration of the switching cycle of the solenoid valve (10). [14] Application system for applying spray liquid to an agricultural area, with - several solenoid valves (10) used to control the flow rate, - a control device (24) by means of which the operation of the solenoid valves (10) can be controlled, and - a measuring device (30) which is designed to detect at least one state parameter (p) of the spray liquid by sensor in a measuring area (32); characterized by that the control device (24) is designed to control the operation of the solenoid valves (10) according to one of claims 1 to 13.

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