Method for real-time hydraulic cylinder drift monitoring

Abstract

A method of monitoring drift in a hydraulic cylinder, the method comprising: providing a work machine having an implement actuated by the hydraulic cylinder, a sensor attached to the hydraulic cylinder and configured to measure a displacement of the hydraulic cylinder, and a controller; identifying the start of circulation of the hydraulic cylinder; marking the end of the circulation of the hydraulic cylinder; calculating the drift rate of the hydraulic cylinder; determining whether the drift rate is greater than a drift threshold; and under the condition that the drift rate is larger than the drift threshold value, a maintainer is informed that the hydraulic cylinder needs to be maintained.

Description

Technical Field

[0001] The present disclosure relates generally to work machines and, more particularly, to hydraulic cylinders for implements of work machines. Background Art

[0002] Mobile work machines can be used in heavy industries such as mining and construction to transport materials and personnel. These work machines are generally large in size and require an operator (e.g., driver) to manually operate the machine so that the machine performs its designated / intended operation.

[0003] Certain work machines, such as loaders, use implements to perform various tasks on the job site. These implements may need to carry and transport heavy loads and, therefore, may utilize hydraulic systems to assist in operating the implement's mechanisms. These hydraulic systems need to be rugged to withstand these heavy loads, and failure of hydraulic components can often have dangerous consequences.

[0004] In the field of hydraulic systems, the phenomenon of hydraulic cylinder drift poses a significant challenge. Cylinder drift is the unintended, gradual movement of a piston within a hydraulic cylinder, typically in a downward direction. Cylinder drift can be caused by a variety of factors, such as internal fluid leaks (such as oil leaking from a seal within the cylinder), faults in the hydraulic system (such as a malfunctioning pressure relief valve), external leaks, or other factors. Cylinder drift can occur at a drift rate, which is defined as a certain amount of drift over time, and can be small (e.g., only on the order of 10 mm / min to 100 mm / min) and can be difficult for an operator to detect.

[0005] Hydraulic cylinder drift can cause inefficiencies and potentially dangerous situations in a variety of industrial and mechanical applications. Addressing hydraulic cylinder drift is key to maintaining system accuracy, stability, and overall operational safety.

[0006] In view of the above shortcomings, there is still a need for a method for real-time monitoring of hydraulic cylinder drift. In addition, there is still a need for a method for monitoring hydraulic cylinder drift that can notify operators and maintenance personnel that the hydraulic cylinder needs maintenance. Summary of the Invention

[0007] According to one aspect of the present disclosure, a work machine may be provided. The work machine may include a frame; a ground engaging member supporting the frame; an engine supported by the frame; and a controller configured to control the operation of the work machine. The work machine may include an implement supported by the frame. The work machine may include a hydraulic cylinder connected to the implement and the frame, the hydraulic cylinder configured to be actuated by an operator input connected to the controller. The work machine may include a sensor attached to the hydraulic cylinder and connected to the controller. The sensor of the work machine may be configured to measure actuation of the hydraulic cylinder over time. The controller may be configured to receive actuation data from the sensor, evaluate a drift rate of the hydraulic cylinder, and provide a maintenance notification if the drift rate is greater than a drift threshold.

[0008] According to another aspect of the present disclosure, a hydraulic cylinder may be provided. The hydraulic cylinder may include a cylinder body having a first body end and a second body end, the cylinder body having a cylinder connector at the second body end, the cylinder body being hollow. The hydraulic cylinder may include a rod having a first rod end and a second rod end, the rod having a rod connector at the first rod end. The hydraulic cylinder may include a piston connected to the second rod end, the piston interfacing with an inner wall of the cylinder body. The hydraulic cylinder may include a sensor disposed on the hydraulic cylinder, the sensor being configured to measure actuation of the hydraulic cylinder. The hydraulic cylinder may include a controller connected to the sensor. The controller may be configured to receive a measurement of the actuation from the sensor, evaluate a drift rate of the hydraulic cylinder, and provide a maintenance notification if the drift rate is greater than a drift threshold.

[0009] According to yet another aspect of the present disclosure, a method for monitoring drift in a hydraulic cylinder may be provided. The method may include providing a work machine having an implement actuated by the hydraulic cylinder; providing a sensor attached to the hydraulic cylinder and configured to measure the displacement of the hydraulic cylinder; and providing a controller. The method may include identifying a start of a cycle for the hydraulic cylinder; and identifying an end of a cycle for the hydraulic cylinder. The method may include calculating a drift rate for the hydraulic cylinder; and determining whether the drift rate is greater than a drift threshold. The method may include notifying maintenance personnel that the hydraulic cylinder requires maintenance if the drift rate is greater than the drift threshold.

[0010] These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 is a perspective view of a work machine constructed in accordance with an embodiment of the present disclosure.

[0012] Figure 2is a perspective view of a work machine constructed in accordance with an embodiment of the present disclosure, the work machine having an implement arm with a hydraulic cylinder.

[0013] Figure 3 is a cross-sectional view of a hydraulic cylinder constructed according to an embodiment of the present disclosure.

[0014] Figure 4 is a flow chart depicting a sample sequence of steps for monitoring drift in a hydraulic cylinder that may be implemented in a locomotive according to the present disclosure. DETAILED DESCRIPTION

[0015] Referring now to the drawings, and in particular to Figure 1 , depicts a work machine and generally refers to the work machine using the reference numeral 10. Work machine 10 is illustratively implemented in the form of a loader. Although work machine 10 is depicted as a loader, it should be noted that the type of machine used is merely exemplary and illustrative in nature. It should be understood that the teachings of the present disclosure can be similarly applied to other types of work machines, including but not limited to on-highway and off-highway trucks, excavators, crawler tractors, mining vehicles, and other types of machines having hydraulic cylinders known to those skilled in the art.

[0016] A work machine, and in particular a loader, can be used to lift, transport, and deposit materials from one location to another. Work machine 10 is supported by a frame 11. Work machine 10 may include a drive train 12 powered by an engine 13 and configured to drive ground engaging members 14 that contact the ground and support frame 11 for operating work machine 10.

[0017] The work machine 10 may also include an implement 15 for performing work tasks. Figure 1 In the view of FIG, since work machine 10 is a loader, implement 15 is illustratively depicted as an unloading bucket, but for other machines, the implement may be other types of work implements known to those skilled in the art. Implement 15 may be connected to the work machine's frame 11 by implement arms 16 and may be actuated by hydraulic cylinders 17. Work machine 10 may also include a cab 18, which allows an operator to control the operation of work machine 10. Cab 18 may include controls 19, which the operator uses to direct work machine 10.

[0018] Figure 2A work machine 10 is depicted as a loader loading material onto a dump truck 20. The operator of the work machine 10 controls the operation of the implement arm 16 and the implement 15 via a controller 19 to scoop, lift, and deposit the material into the dump truck 20. In the amount of work that the work machine 10 may be capable of, assistance is required to lift the load, and to perform this operation, a hydraulic cylinder 17 is provided on the work machine.

[0019] exist Figure 2 In work machine 10, several of hydraulic cylinders 17 are connected to various components of work machine 10 so that an operator can control operations of several types of movements, such as movement of implement 15 relative to implement arm 16, movement of implement arm 16 relative to frame 11, etc. Although work machine 10 is depicted as having multiple of hydraulic cylinders 17, other known machines may include one or more of hydraulic cylinders 17 where hydraulic actuation assistance is desired.

[0020] Figure 3 The hydraulic cylinder 17 is depicted in cross-section. The hydraulic cylinder 17 may be comprised of a cylinder body 30 having an outer surface 31 and an inner surface 32. The cylinder body 30 may have a first body end 33 and a second body end 34. Figure 3 In the hydraulic cylinder 17, the first body end 33 is depicted as having a cylinder connector 35, which can be an eye end connector or any other connector known in the art. The second body end 34 is at Figure 3 30 is shown as having a cover 36 for sealing the second body end 34, however, other embodiments of the second body end 34 may include a housing that is integral with the cylinder body 30. To connect the cover 36 to the cylinder body 30, fasteners 37 may be provided. Figure 3 In the depiction of FIG, the fasteners 37 are described as bolts, but any other known fasteners may be utilized.

[0021] A rod 40 is disposed within the cylinder body 30. The rod 40 may further include a first rod end 41 and a second rod end 42. The rod 40 may further include a rod connector 43 disposed on the first rod end 41. Like the cylinder connector 35, the rod connector 43 may be an eye-end connector, or may be any other known connector. A rod hole 44 may be formed in the cover 36 of the cylinder body 30, allowing the rod 40 to move relative to the cylinder body 30.

[0022] The rod 40 includes a piston 45 disposed on the second rod end 42. The piston 45 may be attached to the second rod end 42 by a fastener 46. Figure 337, but like the fasteners 37, other known fasteners or connection techniques may be utilized to connect the piston 45 to the second rod end 42. The piston 45 extends outward within the hydraulic cylinder 17 such that the outer surface of the piston 45 interacts with the inner surface 32 of the cylinder body 30.

[0023] Due to this extension of the piston 45, two volumes are formed within the hydraulic cylinder 17. A first volume 50 is formed between the first body end 33 and the piston 45, and a second volume 51 is formed between the second body end 34 and the piston 45. The second volume 51 surrounds the rod 40 within the cylinder body 30. A first hole 52 can be provided at the first body end 33 of the cylinder body 30 and can be connected to the first volume 50 via a first fluid passage 53. Similarly, a second hole 54 can be provided at the second body end 34 and can be connected to the second volume 51 via a second fluid passage 55. Figure 3 As depicted, a second aperture 54 and a second fluid passage 55 may be provided within the cover 36 .

[0024] To actuate the hydraulic cylinder 17, a hydraulic system may be provided to deliver hydraulic fluid to both the first volume 50 and the second volume 51. The hydraulic system may include a pump 60 and a hydraulic line 61 to deliver the hydraulic fluid to the first bore 52 and the second bore 54. The hydraulic fluid needs to be contained within the first volume 50 and the second volume 51, particularly during actuation of the rod 40 within the cylinder body 30. Therefore, a piston seal 56 is provided on the outer surface of the piston 45 to maintain the bifurcation between the first volume 50 and the second volume 51, and a rod seal 57 is provided around the rod 40 at the second body end 34 to prevent fluid from leaking from the second volume 51 through the rod bore 44.

[0025] A sensor 70 may be provided on the hydraulic cylinder 17 to measure various actuation parameters of the hydraulic cylinder 17. The sensor 70 may be a position sensor, and the actuation of the hydraulic cylinder 17 may be measured based on the displacement of the rod 40 relative to the cylinder body 30. The sensor 70 may also be an angle sensor, and the actuation of the hydraulic cylinder 17 may be measured based on a change in the rotational position of the hydraulic cylinder 17. Additionally, the hydraulic system may include a first volume pressure sensor 71 and a second volume pressure sensor 72 to monitor the fluid pressures of the first volume 50 and the second volume 51, respectively.

[0026] Industrial Applicability

[0027] In operation, the teachings of the present disclosure may be applicable to work machines used in many industries, including but not limited to those used in the earthmoving, mining, agricultural, and construction industries. Although depicted and described in conjunction with a loader, such teachings may also be applicable to other machines, such as on- and off-highway trucks, excavators, crawler tractors, mining vehicles, and other types of machines having hydraulic cylinders known to those skilled in the art.

[0028] Figure 4 A visual representation of a method 100 for monitoring drift in a hydraulic cylinder 17 is illustrated. In a first step 101, controller 19 performs a preliminary reading of sensor 70 and first and second volume pressure sensors 71 and 72. In a second step 102, corresponding to the start of actuation of hydraulic cylinder 17, certain conditions are identified as true. These conditions may include a starting pressure in both first and second volumes 50 and 51, indicating that implement 15 is unloaded, a starting displacement of hydraulic cylinder 17, and an indication that the operator has provided zero input. In parallel, if these conditions are true, controller 19 may determine in a third step 103 whether a cycle has begun. If not, controller 19 may record the starting displacement and start time of the start of the cycle for hydraulic cylinder 17 in a fourth step 104.

[0029] Once the actuation of the hydraulic cylinder 17 is complete, in a fifth step 105, the controller 19 may mark certain condition registers as false, such as the end pressures in the first and second volumes 50, 51, the end displacement of the hydraulic cylinder 17, and an indication that the operator has again provided a zero input. The controller 19 may then indicate whether the cycle has been completed. If so, in a sixth step 106, the controller 19 may again record the end displacement and end time of the end of the cycle for the hydraulic cylinder 17.

[0030] The controller 19 can then calculate the drift rate of the hydraulic cylinder 17 during the cycle. In a seventh step 107, the controller 19 can calculate the change in displacement (also known as differential displacement) for the cycle and the change in time (also known as differential time) for the cycle. The controller 19 can be programmed to accept data only for cycles with a differential time greater than a minimum time. In an eighth step 108, the controller 19 references the minimum time to determine whether the differential time for a particular cycle is greater than the minimum time. If not, the cycle data is not used, and in a ninth step 109, the controller 19 resets the cycle.

[0031] If the difference time is greater than the minimum time, then in a tenth step 110, the controller 19 calculates a drift rate based on the difference displacement within the difference time. Optionally, the controller may use the calculated drift rate and, in an eleventh step 111, apply a digital filter to the calculated drift rate to remove outliers and excess noise. While the digital filter in step 111 is depicted as a moving average filter, any other known digital filter may be used. In a twelfth step 112, the controller 19 determines whether the drift rate is greater than a drift threshold. If not, in a thirteenth step 113, the controller 19 records the cycle data and the method 100 is restarted. If so, in a fourteenth step 114, the controller 19 provides a notification via the operator display in the cab 18 of the work machine 10, or via telematics to a remote location where maintenance personnel may be located. Method 100 may be repeated numerous times during operation of the work machine 10, for example, for each actuation of the hydraulic cylinder 17.

[0032] Optionally, the controller 19 can use the captured data to predict when the drift rate is likely to exceed a threshold in the future. For example, the drift rate may increase over several cycles. In step 115, the controller 19 can estimate the rate of change of the drift rate, provide a prediction of when the drift rate will exceed the drift threshold in step 116, and provide a notification in step 117, similar to the maintenance notification of step 114.

[0033] Method 100 for monitoring drift in hydraulic cylinders describes the operation of the primary embodiment work machine 10 and, during operation, how work machine 10 can assess the operability of any of the hydraulic cylinders 17 operated by work machine 10. Method 100 allows work machine 10 to identify when drift, if any, in hydraulic cylinder 17 becomes excessive before an operator can identify it. As specified in method 100, real-time monitoring eliminates the need for additional maintenance testing of hydraulic cylinder 17. However, once excessive drift is identified, maintenance personnel still need to diagnose the cause of the drift, whether it be seal wear, valve failure, external leakage, or other causes.

[0034] The method 100 can be adapted for use with any work machine 10 requiring only a software update for retrofitting. The method 100 can also be adapted for use in other industries and any machine that utilizes hydraulic cylinders to actuate machine mechanisms.

[0035] It should be understood that this disclosure is intended to be illustrative and that various changes may be made by adding, modifying, or eliminating details without departing from the fair scope of the teachings contained herein. Therefore, the present invention is not limited to the specific details of this disclosure, except as the following claims must be so limited. Sensor 70 may also be other known sensors that can be used to measure changes in hydraulic cylinder 17 other than those that may be attributed to actuation of hydraulic cylinder 17.

Claims

1. A hydraulic cylinder, comprising: a cylinder body having a first body end and a second body end, the cylinder body having a cylinder connector at the second body end, the cylinder body being hollow; a rod having a first rod end and a second rod end, the rod having a rod connector at the first rod end; a piston connected to the second rod end, the piston interfacing with an inner wall of the cylinder body; a sensor disposed on the hydraulic cylinder, the sensor being configured to measure actuation of the hydraulic cylinder; and A controller is coupled to the sensor, the controller being configured to receive measurements of the actuation from the sensor, evaluate a drift rate of the hydraulic cylinder, and provide a maintenance notification if the drift rate is greater than a drift threshold.

2. The hydraulic cylinder according to claim 1, further comprising: a first volume within the cylinder body, the first volume being located between the piston and an end of the second body; and a second volume within the cylinder body, the second volume surrounding the rod between the piston and the first body end.

3. The hydraulic cylinder according to claim 2, further comprising: a first bore located at the first body end of the cylinder body, the first bore having a first fluid passage connecting the first bore to the first volume; and a second bore at the second body end of the cylinder body, the second bore having a second fluid passage connecting the second bore to the second volume.

4. The hydraulic cylinder according to claim 3, further comprising: a first pressure sensor configured to measure a first pressure of the first volume; and a second pressure sensor configured to measure a second pressure of the second volume, the controller configured to calculate the actuation of the hydraulic cylinder based on changes in the first and second pressures.

5. The hydraulic cylinder of claim 1, wherein the sensor is a position sensor and the actuation of the hydraulic cylinder is measured as a function of displacement of the rod relative to the cylinder body. 6 . The hydraulic cylinder of claim 1 , wherein the sensor is an angle sensor, and the actuation of the hydraulic cylinder is measured as a change in a rotational position of the hydraulic cylinder.

7. A method of monitoring drift in a hydraulic cylinder, the method comprising: providing a work machine having an implement actuated by the hydraulic cylinder, a sensor attached to the hydraulic cylinder and configured to measure displacement of the hydraulic cylinder, and a controller; marking the start of a cycle of the hydraulic cylinder; marking the end of a cycle of the hydraulic cylinder; calculating a drift rate of the hydraulic cylinder; determining whether the drift rate is greater than a drift threshold; as well as When the drift rate is greater than the drift threshold, maintenance personnel are notified that the hydraulic cylinder needs to be repaired.

8. The method of claim 7, wherein the step of identifying the start of the cycle further comprises recording a start displacement and a start time of the hydraulic cylinder; and the step of identifying the end of the cycle further comprises recording an end displacement and an end time of the hydraulic cylinder.

9. The method according to claim 8, wherein calculating the drift rate further comprises: Calculating a differential displacement between the start displacement and the end displacement, and calculating a differential time between the start time and the end time; as well as Determining whether the difference time is greater than a minimum time; and calculating the drift rate according to the difference displacement divided by the difference time.

10. The method according to claim 7, further comprising the following steps after calculating the drift rate: calculating a rate of change of the drift rate; forecasting a target date by which the drift rate will exceed the drift threshold; as well as Maintenance personnel are notified that the hydraulic cylinder needs to be serviced by the target date.

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