Hydraulic control system for a sprayer boom on an agricultural field sprayer

Abstract

The invention relates to a hydraulic control system for adjusting the profile of a sprayer boom on an agricultural field sprayer, wherein the control system comprises a first and a second hydraulic cylinder for bending the boom arms in and out, and wherein the control system comprises a first proportional valve associated only with the first hydraulic cylinder and a second proportional valve associated only with the second hydraulic cylinder, such that the first proportional valve is connected via a first working pressure line only to the second cylinder chamber of the first hydraulic cylinder and the second proportional valve is connected via a second working pressure line only to the second cylinder chamber of the second hydraulic cylinder, which hydraulic control system is designed in such a way that the two proportional valves are each in the form of a 4 / 3 proportional directional control valve having four ports and three switching positions, wherein one working port is connected to the corresponding working pressure line and the other working port is connected to a control pressure line, and wherein a first hydraulic stop-check valve is provided in the first working pressure line and a second hydraulic stop-check valve is provided in the second working pressure line.

Description

[0001] Hydraulic control system for a spray boom on an agricultural field sprayer

[0002] The invention relates to a hydraulic control system for adjusting the profile of a spray boom on an agricultural field sprayer, as well as to a spray boom with a corresponding hydraulic control system. The spray boom has a central section and a first and a second boom arm, each of which is articulated laterally to the central section via a pivot axis. The control system comprises a first and a second hydraulic cylinder for angling and deflecting the boom arms about the pivot axis, both of which are double-acting and each have a cylinder housing and a piston with a piston rod movable therein, wherein a first and a second cylinder chamber are formed in the cylinder housing, separated by the piston.Furthermore, the control system comprises a first proportional valve which is assigned only to the first hydraulic cylinder, and a second proportional valve which is assigned only to the second hydraulic cylinder, such that the first proportional valve is connected via a first working pressure line only to the second cylinder chamber of the first hydraulic cylinder, and the second proportional valve is connected via a second working pressure line only to the second cylinder chamber of the second hydraulic cylinder, and no further working pressure lines connect the proportional valves to one of the two hydraulic cylinders.

[0003] Field sprayers with spray booms are used for the even application of liquid substances, particularly plant protection products, to an agricultural target area. In a field, this could be the soil or the plant itself, for example. To ensure the distribution of the applied substances as evenly as possible across the entire width of the spray boom, the distance of the spray boom to the target area must be adjustable. Especially with very wide spray booms, it is important to adapt the inclination and profile of the spray boom to a slope or to different plant heights. To adjust the profile, the boom arms can each be pivoted around a pivot axis, thus angled or bent.

[0004] Such spray booms and a control system for adjusting the inclination and profile are described in detail, for example, in DE 202011111069 U. A vertically adjustable main frame is provided on the field sprayer to adjust the general distance of the spray boom from the target area. The spray boom consists of a central section and two lateral boom arms. The inclination of the central section of the spray boom, and thus the entire spray boom, can be adjusted relative to the main frame using hydraulic cylinders. In addition, the arms, each of which is mounted on the central section via a pivot point, can be angled or deflected using an adjusting cylinder. This means they are pivoted up or down to change the horizontal profile of the spray boom. The adjusting cylinders are controlled by separate levers. The control system is not further described.

[0005] EP 3753407 A1 describes a hydraulic control system for such a spray boom in more detail. The variants shown there have the disadvantage that they require many electronic outputs to control the various valves. For example, the three control valves and three check valves shown require six electronic outputs. This requires a lot of cabling and is prone to failure under harsh operating conditions.

[0006] Another variant is hydraulic control systems for spray booms, for example from EP 3629725 A1. This describes how, without a center section and with only two boom arms, both the inclination and the profile of the spray boom can be adjusted using a control system with two hydraulic cylinders. The disadvantage of this design is that the combination of inclination and profile adjustment requires a complicated wiring of the control valves. This results in a high level of effort for the hydraulic piping. Furthermore, the suspension of the two boom arms is inadequately implemented, as a very large hydraulic accumulator would be necessary to reliably decouple the inclination of the boom arms from vibrations or fluctuations of the vehicle.

[0007] The object of the invention is to develop a simpler hydraulic control system for a spray boom, as well as a corresponding spray boom, which can be implemented cost-effectively and operated reliably.

[0008] The object is achieved by a hydraulic control system according to claim 1. Further advantageous features are mentioned in the dependent claims.

[0009] The embodiment according to the invention is characterized in that the two proportional valves are each designed as a so-called 4 / 3 proportional directional control valve with four connections and three switching positions, each having two working connections (A, B), one pressure connection (P), one tank return connection (T) and only one solenoid coil, wherein one working connection (A) is connected to the corresponding working pressure line and the other working connection (B) is connected to a control pressure line, and wherein a first hydraulically releasable check valve is present in the first working pressure line and a second hydraulically releasable check valve is present in the second working pressure line, wherein the two check valves are each connected to at least one of the control pressure lines.

[0010] A key advantage of the inventive design is that, thanks to the inventive wiring, only two electronic outputs are required for adjusting the profile—one for each of the 4 / 3 proportional directional control valves to control the solenoid coil. The check valves require no additional electronic signals, as they are hydraulically controlled, i.e., unlocked, by the 4 / 3 proportional directional control valves via the control lines. This type of control can be implemented more cost-effectively and with less effort than conventional controls. Furthermore, it is very robust and reliable. The hydraulically pilot-operated check valves are designed to unlock when control pressure is applied, allowing the return flow from the corresponding cylinder chamber of the hydraulic cylinder. If no control pressure is applied, they block the return flow.This means that as long as no control pressure is applied, the check valves block the respective hydraulic cylinder and the boom arm is held in its current position. If the check valves are released via the control pressure, the corresponding boom arm is lowered. And if the hydraulic cylinder is supplied with working pressure via the proportional valve, the boom arm is raised.

[0011] With the design according to the invention, the linkage arms and their hydraulic cylinders can be controlled individually and independently of each other via the associated proportional valve. If the respective hydraulic cylinder is pressurized via the working pressure line in the second cylinder chamber by switching the associated proportional valve to the corresponding switching position, the linkage arm is angled. This means that the linkage arm pivots upward around the pivot axis, retracting the hydraulic cylinder.

[0012] The pressure port of the proportional valves is connected to a pressure supply or pressure source. This could be, for example, a pressure source for constant pressure supply or a load-sensing pump. The tank return port is connected to a hydraulic tank so that draining hydraulic fluid can flow into the hydraulic tank.

[0013] In a particularly advantageous embodiment, the two hydraulic cylinders are arranged so that the first cylinder chamber is the so-called piston chamber and the second cylinder chamber, which is connected to the working pressure line, is the so-called annular chamber. The annular chamber is the cylinder chamber through which the piston rod passes, and the piston chamber is the cylinder chamber on the other side of the piston. The annular chamber therefore has a smaller piston pressure area than the piston chamber, which has the entire surface of the piston as its piston pressure area. The advantage of this arrangement is that the cylinder housing with its connections for the working pressure lines is connected to the central section and not to the moving rod arms. This means that the connections remain relatively stationary when the piston is extended and the connected working pressure lines do not have to be as flexible.

[0014] A further improvement of the control system can be achieved if the first check valve is connected to the first proportional valve via the control pressure line, allowing it to be unlocked via this control pressure line, and if the second check valve is connected to the second proportional valve via the control pressure line, allowing it to be unlocked via this control pressure line. This means that the two check valves can also be controlled individually and independently of the proportional valve assigned to them.

[0015] An advantageous development of the control system is achieved if the first cylinder chamber of the first hydraulic cylinder is connected to the first cylinder chamber of the second hydraulic cylinder via a connecting line, and if this connecting line is connected to a hydraulic tank via a drain line, wherein this drain line contains an additional hydraulically releasable check valve. This additional check valve can lock the two hydraulic cylinders by locking the hydraulic fluid in the first cylinder chambers of the two hydraulic cylinders. In this way, the two boom arms can be held rigidly in their current position, even if all working pressure lines are depressurized. For example, if the external forces acting on the hydraulic cylinders are reversed due to dynamic processes when spraying the spray agent.Furthermore, the boom arms can be held rigidly in the angled position when the field sprayer is not working but is being transported or driven on the road. There is also a transport position in which the boom arms are coiled and also folded to the side.

[0016] It is particularly advantageous if this additional check valve is connected to both proportional valves via a control pressure line, with this control pressure line containing a shuttle valve arranged between the first proportional valve and the second proportional valve so that the control pressure line to the additional check valve can be pressurised by the first or second proportional valve depending on the switching state and pressure level. This allows the additional check valve to be controlled and unlocked individually and independently of each of the two proportional valves. This means that each rod arm can be controlled and raised individually and independently of the one assigned proportional valve. The shuttle valve is designed so that it releases the control line with the higher pressure.

[0017] To achieve suspension and damping of the pivoting movement of the rod arms, a hydraulic accumulator can be provided branching off from the working pressure line, each of which is connected to the working pressure line via a flow resistance. The suspension can be adjusted by the size and the gas-side filling pressure in the hydraulic accumulator, and the damping is achieved by the flow resistance. This can suppress unwanted vibrations of the rod arms. The flow resistance can be designed as a throttle, for example. The hydraulic accumulator is designed to contain an enclosed gas volume.

[0018] Furthermore, the object is achieved by a spray boom according to the invention according to claim 7 with a control system according to the invention, as described above. In addition to the control system, the spray boom according to the invention comprises the following components:

[0019] - a main frame which can be adjusted vertically and is otherwise rigidly attached to a frame of the machine,

[0020] - a central section which is attached to the main frame via a pivot axis,

[0021] - a first and a second boom arm, each of which is attached to the side of the middle section via a pivot axis, wherein the boom arms can be angled and bent via a first and a second double-acting hydraulic cylinder on the spray boom, respectively, - a further double-acting hydraulic cylinder on the spray boom, via which the inclination of the middle section relative to the main frame can be adjusted.

[0022] The characteristic features and the associated advantages arise analogously from the advantages already described for the control system. Further advantageous features for the spray boom are described in the corresponding dependent claims.

[0023] Additionally, it is advantageous if the first and second double-acting hydraulic cylinders are arranged so that the respective cylinder housing is articulated to the center section, and the respective piston with its piston rod is articulated to the respective linkage arm. This ensures that the connections for the working pressure lines on the cylinder housing remain relatively stationary when the piston is extended.

[0024] In a further advantageous embodiment of the spray boom, an additional hydraulic control system is provided that controls the additional hydraulic cylinder. This additional control system comprises a working pressure line to the additional hydraulic cylinder and, branching off from it, a hydraulic accumulator that is connected to this working pressure line via a throttle. This provides the center frame with suspension and damping, so that vibrations and fluctuations from the vehicle are not transmitted to the spray boom. Additional suspension and damping for the pivoting movement of the boom arms are thus no longer necessary, simplifying the control system for the boom arms.

[0025] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the illustrated combination, but also individually combined with one another. The figures show in detail: Fig. 1: An exemplary embodiment of a spray boom according to the invention.

[0026] Fig.2 Embodiment of a hydraulic control system according to the invention

[0027] The figures are described in more detail below. Like reference numerals indicate like or similar parts or components.

[0028] Figure 1 schematically shows an embodiment of the spray boom 20 according to the invention with a hydraulic control system according to the invention. The main frame 24 is connected to the field sprayer in a vertically height-adjustable manner. This can be a self-propelled field sprayer, a trailer for a tractor, or an attachment on a tractor. The vertical height adjustment allows the distance h to the target surface 40 to be adjusted. The target surface 40 can be, for example, the soil or the plant itself in a field.

[0029] The spray boom 20 comprises the central section 23 and the two boom arms 21, 22. In the illustrated embodiment, the central section 23 is mounted on the main frame 24 so as to be rotatable about the axis of rotation 30. The inclination of the central section 23 and thus of the spray boom 20 relative to the main frame 24 and thus to the vehicle can be adjusted via the additional hydraulic cylinder 9. The additional control system (not shown) for the additional hydraulic cylinder 9 preferably contains a hydraulic accumulator which is connected to the working pressure line to the additional hydraulic cylinder 9 via a throttle. The throttle effects damping and the hydraulic accumulator effects suspension. As a result, the central section 23 and thus the spray boom are decoupled from vibrations and fluctuations in the vehicle.

[0030] The two boom arms 21, 22 are each pivotally attached to the center section 23 via the pivot axis 31, 32. They are also connected to the center section 23 via the double-acting hydraulic cylinders 1, 2 and can be angled or bent independently of one another by extending and retracting the pistons. In addition to the inclination, the profile of the spray boom 20 can also be adjusted in order to adapt the spray boom 20 as evenly as possible to the contour of the target surface 40. The goal is for the distance h to the target surface for the entire spray boom 20 to be as even as possible across the width and to lie at least within a specified distance range.

[0031] The two hydraulic cylinders 1, 2 are installed in such a way that the cylinder housing is connected to the middle part 23 and the piston and the piston rod to the respective linkage arm 21, 22.

[0032] If the entire spray boom 20 is sprung and damped relative to the main frame 24, the control system for the boom arms 21, 22 does not require any suspension and damping.

[0033] Fig. 2 schematically illustrates the hydraulic control system 10 according to the invention for the linkage arms 21, 22. The double-acting hydraulic cylinders 1, 2 each have a cylinder housing with two ports and a displaceable piston 18 located therein. In the embodiment shown, the cylinder housing is connected to the central part 23. The piston rod is attached to one side of the piston 18, which, in the embodiment shown, is connected to the respective linkage arm 21, 22.

[0034] The hydraulic cylinder 1, 2 has the first and second cylinder chambers 11, 12 in the cylinder housing, which are separated by the piston 18 and each of which is assigned to one of the connections on the cylinder housing. The second cylinder chamber 12 is arranged on the side of the piston 18 that is connected to the linkage arm 21, 22, and the first cylinder chamber 11 is arranged on the side that is connected to the central part 23. This means that if the second cylinder chamber 12 is pressurized, the linkage arm 21, 22 is angled, i.e., raised.

[0035] In the illustrated embodiment, the second cylinder chamber 12 is the so-called annular chamber, which is penetrated by the piston rod. The first cylinder chamber 11 is the piston chamber. The piston chamber has a larger piston pressure area than the annular chamber surrounding the piston rod. Alternatively, the hydraulic cylinders 1, 2 could also be installed the other way around, in which case the first cylinder chamber would be the annular chamber and the second cylinder chamber the piston chamber.

[0036] The control system 10 also includes the first and second proportional valves 3, 4, both designed as 4 / 3 proportional directional control valves—each with two working ports A, B, the pressure port P connected to a pressure source, and the tank return port T connected to a hydraulic tank. These proportional valves 3, 4 each have only one solenoid coil. This allows them to be controlled with a single electronic input and switched back and forth between the three switching positions. This eliminates the need for complex wiring.

[0037] The second cylinder chamber 12 of the respective hydraulic cylinders 1, 2 is connected to the working port A of the associated proportional valve 3, 4 via the working pressure line 13, 14. If the proportional valve 3, 4 is switched so that the working port A is connected to the pressure source, the second cylinder chamber 12 is pressurized and the linkage arm 21, 22 is angled.

[0038] The check valves 5, 6 prevent the rod arm 21, 22 from unintentionally lowering again. Each of the proportional valves 3, 4 is connected to its associated hydraulically releasable check valve 5, 6 via the respective control pressure line 15a, 15b, which is connected to working port B. If the control pressure line 15a, 15b is pressurized, the corresponding check valve 5, 6 is released, allowing hydraulic fluid to flow from the second cylinder chamber 12. The corresponding rod arm 21, 22 is angled.

[0039] In the embodiment shown here, an additional hydraulically unlockable check valve 7 is provided, which is arranged in the drain line 17. The drain line 17 connects the connecting line 16 between the first cylinder chambers 11 of the two hydraulic cylinders to the hydraulic tank. If one of the rod arms 21, 22 is angled, the piston 18 of the corresponding hydraulic cylinder 1, 2 moves and hydraulic fluid is sucked from the hydraulic tank into the first cylinder chamber 11 via the check valve 7. If one of the rod arms 21, 22 is to be angled, the check valve 7 is unlocked via the control line 15c so that hydraulic fluid can flow out of the corresponding first cylinder chamber 11.

[0040] The control line 15c is connected to both the first and second proportional valves 3, 4 by being connected to the respective working port B. The shuttle valve 8 is provided in the control line 15c between the two proportional valves 3, 4, which releases the control line 15c from the side of the shuttle valve 8 where the higher pressure is applied. Thus, the first hydraulic cylinder 1 can be raised or lowered independently by the first proportional valve 3, and the second hydraulic cylinder 2 can be controlled independently by the second proportional valve 4.

[0041] When the check valve 7 is closed, the hydraulic fluid is trapped in the first cylinder chambers 11 of the hydraulic cylinders 1, 2. This allows the linkage arms 21, 22 to be held in their position even when the working pressure lines to the hydraulic cylinders are depressurized.

[0042] List of reference symbols

[0043] 1 first hydraulic cylinder

[0044] 2 second hydraulic cylinder

[0045] 3 first proportional valve

[0046] 4 second proportional valve

[0047] 5 first check valve

[0048] 6 second check valve

[0049] 7 additional check valve

[0050] 8 shuttle valve

[0051] 9 additional hydraulic cylinders

[0052] 10 Control system

[0053] 11 first cylinder chamber

[0054] 12 second cylinder chamber

[0055] 13 first working pressure line

[0056] 14 second working pressure line

[0057] 15,15 a,b,c control pressure lines

[0058] 16 connecting line

[0059] 17 Drain line

[0060] 18 pistons

[0061] 20 spray booms

[0062] 21 first linkage arm

[0063] 22 second linkage arm

[0064] 23 Middle section

[0065] 24 main frames

[0066] 30 axis of rotation

[0067] 31 first swivel axis

[0068] 32 second swivel axis

[0069] 40 Target area h Distance to target area

Claims

Patent claims 1. Hydraulic control system (10) for adjusting the profile of a spray boom (20) on an agricultural field sprayer, wherein the spray boom has a central part and a first and a second boom arm (21, 22), which are each laterally articulated to the central part (23) via a pivot axis (31, 32), wherein the control system (10) comprises a first and a second hydraulic cylinder (1, 2) for angling and bending the boom arms (1, 2) about the respective pivot axis (31, 32), which are both double-acting and each have a cylinder housing and a piston (18) with a piston rod movable therein, wherein a first and a second cylinder chamber (11, 12) are formed in the cylinder housing separately by the piston (18), and wherein the control system (10) has a first proportional valve (3), which is assigned only to the first hydraulic cylinder (1), and a second Proportional valve (4),which is only assigned to the second hydraulic cylinder (2), such that the first proportional valve (3) is connected via a first working pressure line (13) only to the second cylinder chamber (12) of the first hydraulic cylinder (1), and the second proportional valve (4) is connected via a second working pressure line (14) only to the second cylinder chamber (12) of the second hydraulic cylinder (2), and no further working pressure lines connect the proportional valves (3, 4) to one of the two hydraulic cylinders (1, 2), characterized in that the two proportional valves (3, 4) are each designed as a so-called 4 / 3 proportional directional control valve with four ports and three switching positions, each having two working ports (A, B), one pressure port (P), one tank return port (T) and only one solenoid coil, each one working port (A) being connected to the corresponding working pressure line (13,14) and the other working connection (B) is connected to a control pressure line (15a, 15b), and wherein in the first working pressure line (13) there is a first hydraulically releasable check valve (5) and in the second working pressure line (14) there is a second hydraulically releasable check valve (6), wherein the two, Check valves (5,6) are each connected to at least one of the control pressure lines (15a, 15b).

2. Control system (10) according to claim 1, characterized in that the hydraulic cylinders (1, 2) are arranged such that the first cylinder chamber (11) is the so-called piston chamber and that the second cylinder chamber (12), which is connected to the working pressure line (13, 14), is the so-called annular chamber, which is penetrated by the piston rod.

3. Control system (10) according to one of claims 1 or 2, characterized in that the first check valve (5) is connected to the first proportional valve (3) via the control pressure line (15a) and can be unlocked via this control pressure line (15a), and that the second check valve (6) is connected to the second proportional valve (4) via the control pressure line (15b) and can be unlocked via this control pressure line (15b).

4. Control system (10) according to one of the preceding claims, characterized in that the first cylinder chamber (11) of the first hydraulic cylinder (1) is connected to the first cylinder chamber (11) of the second hydraulic cylinder (2) via a connecting line (16) and that this connecting line (16) is connected via a drain line (17) is connected to a hydraulic tank, wherein a further hydraulically unlockable check valve (7) is present in the drain line (17).

5. Control system (10) according to claim 4, characterized in that the further check valve (7) is connected to both proportional valves (3, 4) via a control pressure line (15c), wherein in this control pressure line (15c) there is a shuttle valve (8) which is arranged between the first proportional valve (3) and the second proportional valve (4), so that the control pressure line (15c) to the further check valve (7) can be pressurized by the first or the second proportional valve (3,4) depending on the switching state and the pressure level.

6. Control system (10) according to one of the preceding claims, characterized in that a hydraulic accumulator is provided branching off from the working pressure line (13, 14), which are each connected to the working pressure line (13, 14) via a flow resistance, in particular via a throttle.

7. Spray boom (20) for an agricultural field sprayer for the controlled application of liquid to a target area (40), comprising - a main frame (24) which can be vertically adjusted and otherwise rigidly attached to a vehicle frame of the machine, - a central part (23) which is tiltably attached to the main frame via a pivot axis (30), - a first and a second boom arm (21, 22), each of which is laterally attached to the central part (23) via a pivot axis (31, 32), wherein the boom arms (21, 22) can be angled and bent via a first and a second double-acting hydraulic cylinder (1, 2) present on the spray boom, respectively, - another double-acting hydraulic cylinder (9) on the spray boom, by means of which the inclination of the central part (23) relative to the main frame (24) can be adjusted, - and a control system (10) according to one of claims 1 to 6, characterized in that the two proportional valves (3, 4) are each designed as a so-called 4 / 3 proportional directional control valve with four connections and three switching positions, each having two working connections (A, B), one pressure connection (P), one tank return connection (T) and only one solenoid coil, each of which has one working connection (A) connected to the corresponding working pressure line (13, 14) and the other working connection (B) connected to a control pressure line (15), and wherein a first hydraulically releasable check valve (5) is provided in the first working pressure line (13) and a second hydraulically releasable check valve (6) is provided in the second working pressure line (14), wherein the two check valves (5, 6) are each connected to at least one of the control pressure lines (15a, 15b).

8. Spray boom (20) according to claim 7, characterized in that the first and the second double-acting hydraulic cylinder (1, 2) are arranged so that the respective cylinder housing is articulated to the middle part (23) and the respective piston (18) with its piston rod is articulated to the respective boom arm (21, 22).

9. Spray boom (20) according to one of claims 7 and 8, characterized in that a further hydraulic control system is provided which controls the further hydraulic cylinder (9) and that this further control system comprises a hydraulic accumulator branching off from a working pressure line to the further hydraulic cylinder, which is connected to this working pressure line via a throttle.

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