Systems and methods for maintaining desired accumulator pressure based on cylinder positions

Abstract

A method is provided for maintaining a desired pressure in an accumulator supplying hydraulic fluid to one end of a cylinder. The method comprises the steps of determining a position of the cylinder, calculating an expected pressure in the accumulator based on the position of the cylinder, measuring an actual pressure in the accumulator, determining whether the actual pressure is within a tolerance of the expected pressure, and if it is determined that the actual pressure is not within the tolerance of the expected pressure, adjusting a volume of hydraulic fluid in the accumulator.

Description

SYSTEMS AND METHODS FOR MAINTAINING DESIRED ACCUMULATOR PRESSURE BASED ON CYLINDER POSITIONSCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Application 63 / 441,959, filed on January 30, 2023, the disclosure of which is hereby incorporated by reference in its entirety.TECHNICAL FIELD

[0002] The present invention relates to systems and methods for maintaining a desired accumulator pressure. More particularly, the invention relates to systems and methods for maintaining a desired accumulator pressure in a hydraulic float and flex system in an agricultural header.BACKGROUND OF THE INVENTION

[0003] Draper headers for use in a field to harvest agricultural crops are known in the art. Typical draper headers include a header frame with side wing sections that pivot upwardly and downwardly relative to a middle frame section to contour to the field as the draper header is moved across the field for harvesting crops. Some draper headers include a hydraulic float and flex (HFF) system, which support a majority of the weight of the draper header, thereby leaving a relatively small proportion of the weight to rest on the ground. These HFF systems allow the draper header to float upwardly and downwardly as it follows the ground, and thus allow the draper header to quickly adapt to changing ground conditions. One example of an HFF system can be found in U.S. Patent No. 10,617,059, which is incorporated herein by reference.

[0004] The accumulators on the HFF system that provide lift support pressure need to provide a relatively controlled pressure throughout a wide temperature range. This pressure must be maintained even if there is a slight leakage of oil from the system. It is difficult to precisely control this pressure as oil flows in and out of the accumulator as the float and flex cylinders strokethrough their range. Pushing oil into the accumulator will increase the pressure while relieving oil out will reduce the pressure. Without knowing how much oil is in the accumulator, it is difficult to precisely know what pressure should be maintained.SUMMARY OF THE INVENTION

[0005] According to one aspect of the invention, a method is provided for maintaining a desired pressure in an accumulator supplying hydraulic fluid to one end of a cylinder. The method comprises the steps of determining a position of the cylinder, calculating an expected pressure in the accumulator based on the position of the cylinder, measuring an actual pressure in the accumulator, determining whether the actual pressure is within a tolerance of the expected pressure, and if it is determined that the actual pressure is not within the tolerance of the expected pressure, adjusting a volume of hydraulic fluid in the accumulator.

[0006] According to another aspect of the invention, a hydraulic system is provided comprising a cylinder, an accumulator, and a controller. The accumulator is configured to supply hydraulic fluid to one end of the cylinder. The controller is configured to determine a position of the cylinder, calculate an expected pressure in the accumulator based on the position of the cylinder, measure an actual pressure in the accumulator, and determine whether the actual pressure is within a tolerance of the expected pressure. If the controller determines that the actual pressure is not within the tolerance of the expected pressure, the controller is configured to adjust a volume of hydraulic fluid in the accumulator.

[0007] According to another aspect of the invention, a hydraulic system is provided comprising a cylinder, an accumulator, a pressure sensor, a control valve and a controller. The accumulator is configured to supply hydraulic fluid to one end of the cylinder. The pressure sensor is configured to measure an actual pressure in the accumulator. The control valve is configured to adjust the amount of hydraulic fluid in the accumulator. Thecontroller is configured to determine a position of the cylinder, calculate an expected pressure in the accumulator based on the position of the cylinder, measure the actual pressure in the accumulator using the pressure sensor, and determine whether the actual pressure is within a tolerance of the expected pressure. If the controller determines that the actual pressure is not within the tolerance of the expected pressure, the controller is configured to adjust a volume of hydraulic fluid in the accumulator using the control valve.BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein :

[0009] Figure 1 is a perspective view of a draper header according to one embodiment of the present invention;

[0010] Figure 2 is a fragmentary top view of the header frame of the draper header of Figure 1 mounted to a feeder house;

[0011] Figure 3 is a cross-sectional side view of the draper header of Figure 1;

[0012] Figure 4 is an enlarged fragmentary rear perspective view of the draper header of Figure 1;

[0013] Figure 5 is a schematic illustration of a hydraulic float and flex system for the draper header of Figure 1; and

[0014] Figure 6 is a flow diagram illustrating an exemplary method for maintaining a desired accumulator pressure according to one embodiment of the present invention.DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

[0015] Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a header for harvesting agricultural crops is shown generally at 10. As is known in the art, the header 10 is mounted on an agricultural machine, such as a combine or a swather, and travels with the agricultural machine through a field containing the crops to be harvested. It should be appreciated that the header 10 may be a combine header, windrow header, corn header, pick-up header or other crop header as are known in the agricultural industry without varying from the scope of the invention. Referring to Figures 1-2, the header 10 is a draper header and includes a header frame 12 with a front portion 14 and a rear portion 16 extending longitudinally between opposite ends 18. The header frame 12 is divided into a middle frame section 20 pivotally coupled between a pair of side wing sections 22. Each side wing section 22 can pivot upwardly and downwardly relative to the middle frame section 20 to contour to the field as the draper header 10 moves across the field harvesting crops.

[0016] The header frame 12 includes a discontinuous rear support beam 24 extending laterally across the rear portion 16 of the header frame 12 between the ends 18. Referring to Figure 2, each side wing section 22 of the header frame 12 is pivotally and operatively coupled to the middle frame section 20 between a pair of laterally spaced-apart and generally L-shaped support legs 26 extending between the front and rear portions 14, 16 of the header frame 12. The draper header 10 may additionally include a plurality of similar L-shaped auxiliary support legs 28 extending between the front and rear portions 14, 16 of the header frame 12 in a similar manner for further stability and support of the header frame 12 and for coupling with additional components of the draper header 10, such as a transport system or a gauge wheel system. It is to be appreciated that the draper header 10 may include any suitable number of support legs 26 and auxiliary support legs 28 without varying the scope of the invention.

[0017] A cutter bar assembly 30 operatively extends across the front portion 14 of the header frame 12 between the opposite ends 18 for cutting the crops to be harvested. Crop pick-up reels 32 are positioned generally above the front portion 14 of the header frame 12 for engaging the crops to be harvested. Referring to Figure 3, the crop pick-up reels 32 include a reel beam 34 on which the crop pick-up reels 32 rotate. The reel beam 34 is carried on reel support arms 36 which extend from the reel beam 34 rearwardly and upwardly to a support bracket 38 attached to the rear support beam 24. The reel support arms 36 can be raised and lowered by a reel cylinder 40 connected between the reel support arm 36 and the rear support beam 24 to vertically position the crop pick-up reels 32 relative to the cutter bar assembly 30. The reels 32 may also be adjusted fore and aft relative to the cutter bar assembly 30. A skid plate 42 is connected to the header 10 behind the cutter bar assembly 30. The skid plate 42 supports the header 10 when cutting crop close to the ground.

[0018] The header 10 further includes a draper belt assembly 44 supported by the header frame 12. The draper belt assembly 44 extends behind the cutter bar assembly 30 and above the support legs 26. Referring to Figure 1, the draper belt assembly 44 includes a pair of side draper belts 46 on the side wing sections 22, which transport harvested agricultural crops to a feed draper belt 48 on the middle frame section 20, which then directs the harvested crops to a discharge location at a feeder house 50 of a combine harvester.

[0019] Referring to Figures 2-3, the header 10 is carried on an adapter 52 attached to the feeder house 50. The adapter 52 includes an adapter frame 54 and a pair of adapter arms 56 pivotably connected to opposite sides of the adapter frame 54 with pivot pins 58. The adapter frame 54 is configured to attach to the feeder house 50, and the adapter arms 56 extend forwardly under the respective support legs 26 on the header frame 12. Each adapter arm 56 can be raised and lowered by a respective float cylinder 60. A barrel side 62 of the float cylinder 60 is connected to a stub arm 64 mounted on the adapter arm 56, and a rod side 66 of the float cylinder 60 is connectedto the adapter frame 54. The float cylinder 60 provides tension on the stub arm 64 pulling it upwardly around the pivot pin 58, which acts to pull the respective adapter arm 56 up and provide a lifting force under the header 10 along the respective support leg 26. A position sensor 68 is configured to determine the position of the float cylinder 60 in its stroke range.

[0020] A header tilt cylinder 70 extends from the center of the adapter 52 forwardly to the support bracket 38 of the real beam 34. The header tilt cylinder 70 controls the pitch angle of the header 10 relative to the adapter 52, thereby adjusting the cut angle of the cutter bar assembly 30 relative to ground.

[0021] Referring to Figure 4, the rear support beam 24 includes a gap 72 between the middle frame section 20 and each side wing section 22. A pivot coupling 74 extends between the middle frame section 20 and each side wing section 22 so that each side wing section 22 is supported at its inner end on the middle frame section 20 while the outer ends can pivot upwardly and downwardly. The outboard weight of each side wing section 22 is supported on a flex cylinder 76. A barrel side 78 of the flex cylinder 76 is connected to the middle frame section 20, and a rod side 80 of the flex cylinder 76 is connected to the side wing section 22. A position sensor 82 is configured to determine the position of the flex cylinder 74 in its stroke range.

[0022] Both the hydraulic float cylinder 60 and hydraulic flex cylinder 76 allow the draper header 10 to adapt to changing ground conditions. The float cylinders 60 support the majority of the weight of the header 10, and the flex cylinders 76 support the majority of the weight of the side wing sections 22, thereby leaving a relatively small proportion of the weights to rest on the skid plates 42 along the ground. Each end 18 of the header 10 can float upwardly and downwardly as it follows the ground by independent flexing of the float cylinders 60. And each side wing section 22 can flex upwardly and downwardly as it follows the ground by independent flexing of the flex cylinders 76.

[0023] Referring to Figure 5, each side of the header 10 has a hydraulic float and flex (HFF) system 84 that controls the flow of hydraulic fluid to the hydraulic float cylinder 60 and hydraulic flex cylinder 76. The HFF system 84 includes a pressure sensor 86 that monitors the pressure of hydraulic fluid on the barrel side 62 of the float cylinder 60, and a valve assembly 88 that controls the flow of hydraulic fluid into and out of the barrel side 62 of the float cylinder 60. The HFF system 84 also includes a pressure sensor 90 that monitors the pressure of hydraulic fluid on the barrel side 78 of the flex cylinder 76, and a valve assembly 92 that controls the flow of hydraulic fluid into and out of the barrel side 78 of the flex cylinder 76.

[0024] The HFF system 84 includes two accumulators 94, 96. The lift accumulator 94 supplies hydraulic fluid to the rod sides 66, 80 of the float and flex cylinders 60, 76, while the control accumulator 96 supplies hydraulic fluid to the valve assemblies 88, 92 .

[0025] The lift accumulator 94 has a pressure sensor 98 to monitor the pressure of hydraulic fluid in the lift accumulator 94, and a control valve 100 to control the flow of hydraulic fluid into and out of the lift accumulator 94. The control accumulator 96 has a pressure sensor 102 to monitor the pressure of hydraulic fluid in the control accumulator 96, and a control valve 104 to control the flow of hydraulic fluid into and out of the control accumulator 96.

[0026] A hydraulic pump 106 supplies hydraulic fluid to the HFF system 84, and a controller 108 controls the flow of hydraulic fluid into and out of the barrel sides 62, 78 of the cylinders 60, 78. The HFF system 84 also includes a shutoff valve 109 to deactivate the floating action of the float and flex cylinders 60, 76.

[0027] The lift accumulator 94 applies sufficient pressure to the rod side 66 of the float cylinder 60 to exceed the pressure necessary to float the header 10. The controller 108 adjusts the pressure supplied by the valve assembly 88 to the barrel side 62 of the float cylinder 60 to overcome the liftpressure and add ground pressure on the header 10. To increase the lifting force, the controller 108 reduces the pressure supplied by the valve assembly 88, and to reduce the lifting force, the controller 108 increases the pressure supplied by the valve assembly 88.

[0028] The lift accumulator 94 also applies sufficient pressure to the rod side 80 of the flex cylinder 76 to exceed the pressure necessary to flex the side wing section 20. The controller 108 adjusts the pressure supplied by the valve assembly 92 to the barrel side 78 of the flex cylinder 76 to overcome the lift pressure and add ground pressure on the side wing section 20. To increase the lifting force, the controller 108 reduces the pressure supplied by the valve assembly 92, and to reduce the lifting force, the controller 108 increases the pressure supplied by the valve assembly 92.

[0029] The control accumulator 96 ensures sufficient flow of hydraulic fluid to the valve assemblies 88 and 92 to meet the requirements for rapid flow of fluid into the barrel sides 62, 78 of the cylinders 60, 76 if required. Thus, if the hydraulic pump 106 has insufficient flow rate at startup or during operation, the flow may be provided by the control accumulator 96.

[0030] During calibration of the HFF system 84, the accumulator oil set point pressure (Pl) is determined. Pl is the desired pressure in the lift accumulator 94 when the system is near the midpoint of float and flex (i.e., when the header 10 is at mid-float and the side wing section 22 is at midflex). The gas pressure and the volume of hydraulic fluid in the lift accumulator 94 are also determined. The amount of hydraulic fluid in the lift accumulator 94 is adjusted to ensure that the pressure is at Pl when the system is near the midpoint of float and flex.

[0031] After calibration, the controller 108 performs the method 110 shown in Figure 6 to ensure that the lift accumulator 94 maintains proper pressure during operation. The controller 108 is provided with the accumulator oil set point pressure (Pl) (step 112). The controller 108 determines the positions 68, 82 of the float and flex cylinders 60, 76 (step114). Based on the positions 68, 82 of the cylinders 60, 76 and Pl, the controller 108 calculates the expected pressure (P2) in the lift accumulator 94 (step 116). The controller 108 also measures the actual pressure in the lift accumulator 94 (step 118), and determines whether the actual pressure is within a tolerance range of the P2. Thus, controller 108 determines whether the actual pressure is less than the P2 minus the tolerance (step 120). If the actual pressure is less than P2 minus the tolerance, the controller 108 adjusts the control valve 100 to add enough hydraulic fluid to the lift accumulator 94 so that the pressure is within the tolerance of the P2 (step 122). If the controller 108 determines that the actual pressure is not less than the P2 minus the tolerance, the controller 108 determines whether the actual pressure exceeds P2 plus the tolerance (step 124). If the actual pressure exceeds P2 plus the tolerance, the controller 108 adjusts the control valve 100 to remove enough hydraulic fluid from the lift accumulator 94 so that the pressure is within the tolerance from P2 (step 126). The controller 108 then returns to step 114 and continues to monitor the pressure in the lift accumulator 94.

[0032] The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used, is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced other than as specifically described.

Claims

CLAIMS1. A method for maintaining a desired pressure in an accumulator supplying hydraulic fluid to one end of a cylinder, the method comprising the steps of: determining a position of the cylinder; calculating an expected pressure in the accumulator based on the position of the cylinder; measuring an actual pressure in the accumulator; determining whether the actual pressure is within a tolerance of the expected pressure; and if it is determined that the actual pressure is not within the tolerance of the expected pressure, adjusting a volume of hydraulic fluid in the accumulator.

2. The method of claim 1, wherein the step of determining whether the actual pressure is within the tolerance of the expected pressure comprises the steps of: determining whether the actual pressure is less than the expected pressure minus the tolerance; and if it is determined that the actual pressure is less than the expected pressure minus the tolerance, increasing the volume of hydraulic fluid in the accumulator.

3. The method of claim 1, wherein the step of determining whether the actual pressure is within the tolerance of the expected pressure comprises the steps of: determining whether the actual pressure is greater than the expected pressure plus the tolerance; andif it is determined that the actual pressure is greater than the expected pressure plus the tolerance, decreasing the volume of hydraulic fluid in the accumulator.

4. The method of claim 1, wherein the step of calculating the expected pressure comprises the steps of: calculating a change in the volume of hydraulic fluid in the accumulator based on the position of the cylinder; and calculating the expected pressure in the accumulator based on the change in the volume of hydraulic fluid in the accumulator.

5. The method of claim 1, further comprising the steps of: supplying a second hydraulic fluid to a second end of the cylinder; and adjusting a pressure applied by the second hydraulic fluid to the second end of the cylinder based on the position of the cylinder.

6. A hydraulic system comprising: a cylinder; an accumulator configured to supply hydraulic fluid to one end of the cylinder; and a controller configured to: determine a position of the cylinder; calculate an expected pressure in the accumulator based on the position of the cylinder; measure an actual pressure in the accumulator; determine whether the actual pressure is within a tolerance of the expected pressure; andif the controller determines that the actual pressure is not within the tolerance of the expected pressure, the controller is configured to adjust a volume of hydraulic fluid in the accumulator.

7. The hydraulic system of claim 6, wherein when the controller determines whether the actual pressure is within the tolerance of the expected pressure, the controller is configured to: determine whether the actual pressure is less than the expected pressure minus the tolerance; and if the controller determines that the actual pressure is less than the expected pressure minus the tolerance, the controller is configured to increase the volume of hydraulic fluid in the accumulator.

8. The hydraulic system of claim 6, wherein when the controller determines whether the actual pressure is within the tolerance of the expected pressure, the controller is configured to: determine whether the actual pressure is greater than the expected pressure plus the tolerance; and if the controller determines that the actual pressure is greater than the expected pressure plus the tolerance, the controller is configured to decrease the volume of hydraulic fluid in the accumulator.

9. The hydraulic system of claim 6, wherein when the controller calculates the expected pressure, the controller is configured to: calculate a change in the volume of hydraulic fluid in the accumulator based on the position of the cylinder; and calculate the expected pressure in the accumulator based on the change in the volume of hydraulic fluid in the accumulator.

10. The hydraulic system of claim 6, wherein the controller is further configured to:supply a second hydraulic fluid to a second end of the cylinder; and adjust a pressure applied by the second hydraulic fluid to the second end of the cylinder based on the position of the cylinder.

11. The hydraulic system of claim 6, further comprising: a second cylinder, wherein the accumulator is configured to supply hydraulic fluid to a first end of the second cylinder; wherein the controller is further configured to: determine a position of the second cylinder; and calculate the expected pressure in the accumulator based on the position of the cylinder and the position of the second cylinder.

12. A hydraulic system comprising: a cylinder; an accumulator configured to supply hydraulic fluid to one end of the cylinder; a pressure sensor configured to measure an actual pressure in the accumulator; a control valve configured to adjust the amount of hydraulic fluid in the accumulator; and a controller configured to: determine a position of the cylinder; calculate an expected pressure in the accumulator based on the position of the cylinder; measure the actual pressure in the accumulator using the pressure sensor;determine whether the actual pressure is within a tolerance of the expected pressure; and if the controller determines that the actual pressure is not within the tolerance of the expected pressure, the controller is configured to adjust a volume of hydraulic fluid in the accumulator using the control valve.

13. The hydraulic system of claim 12, wherein when the controller determines whether the actual pressure is within the tolerance of the expected pressure, the controller is configured to: determine whether the actual pressure is less than the expected pressure minus the tolerance; and if the controller determines that the actual pressure is less than the expected pressure minus the tolerance, the controller is configured to increase the volume of hydraulic fluid in the accumulator.

14. The hydraulic system of claim 12, wherein when the controller determines whether the actual pressure is within the tolerance of the expected pressure, the controller is configured to: determine whether the actual pressure is greater than the expected pressure plus the tolerance; and if the controller determines that the actual pressure is greater than the expected pressure plus the tolerance, the controller is configured to decrease the volume of hydraulic fluid in the accumulator.

15. The hydraulic system of claim 12, wherein when the controller calculates the expected pressure, the controller is configured to: calculate a change in the volume of hydraulic fluid in the accumulator based on the position of the cylinder; and calculate the expected pressure in the accumulator based on the change in the volume of hydraulic fluid in the accumulator.

16. The hydraulic system of claim 12, further comprising: a valve assembly configured to supply a second hydraulic fluid to a second end of the cylinder; a second pressure sensor configured to measure a pressure applied to the second end of the cylinder; wherein the controller is further configured to: supply the second hydraulic fluid to the second end of the cylinder using the valve assembly; use the second pressure sensor to measure the pressure applied by the second hydraulic fluid to the second end of the cylinder; and adjust the pressure applied by the second hydraulic fluid to the second end of the cylinder based on the position of the cylinder.

17. The hydraulic system of claim 12, further comprising: a second cylinder, wherein the accumulator is configured to supply hydraulic fluid to a first end of the second cylinder; wherein the controller is further configured to: determine a position of the second cylinder; and calculate the expected pressure in the accumulator based on the position of the cylinder and the position of the second cylinder.

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