AU2019101416A4

AU2019101416A4 - Method and apparatus for timely replacement of hydraulic piston pumps and motors

Info

Publication number: AU2019101416A4
Application number: AU2019101416A
Authority: AU
Inventors: Graham Jeremy Manuel
Original assignee: Individual
Current assignee: Individual
Priority date: 2019-11-18
Filing date: 2019-11-18
Publication date: 2020-01-02
Anticipated expiration: 2027-11-18

Abstract

A method for monitoring a hydraulic pump or motor comprising the steps of: providing two or more sensors for attachment to the pump or motor for producing electrical signals indicative of operating parameters of said pump or motor; operating an electronic controller to monitor said sensors for recording the parameter values corresponding to the electrical signals at sampling intervals in a digital memory; and operating said controller to indicate pump condition based upon the recorded parameter values; wherein at least one of the sensors comprises an output pressure sensor for measuring an output pressure of the pump or motor and at least one of the sensors comprises a case drain flow meter for measuring case drain flow. (1)) a), < 0 C/)U 7' CU) C) a)

Description

METHOD AND APPARATUS FOR TIMELY REPLACEMENT OF HYDRAULIC PISTON PUMPS AND MOTORS

TECHNICAL FIELD

The present invention concerns monitoring the condition of piston pumps and motors to allow for replacement of the hydraulic apparatus prior to its performance deteriorating or failure occurring.

BACKGROUND

Any references to methods, apparatus or documents of the prior art are not to be taken as constituting any evidence or admission that they formed, or form part of the common general knowledge.

Hydraulic pumps and motors are prone to wear. It is highly advantageous that they be replaced before such wear causes them to fail or become impractically inefficient.

Figure 1 is a cross sectional view through an example of a piston pump being a swash plate hydraulic piston pump 1. Pump 1 comprises a casing 3 which houses a piston barrel 5 with a concentric polar array of axial bores 7 formed therethrough, typically seven or nine in number.

A shaft 9 extends concentrically from the barrel 5 with an end 11 of the shaft extending through the casing for application of torque, for example from a diesel engine or power take-off of a vehicle. Respective pistons 13 locate in the barrel bores 7. A swashplate 15 is provided with a central hole 17 through which the shaft 9 passes. The swashplate 15 does not rotate with rotation of the shaft. Heads of the pistons 13 are seated in shoes 19 that abut the swashplate 15. The barrel 5 is spring-loaded against the swashplate 15 to keep the piston shoes 19 in contact with the swashplate 15. The swashplate 15 can be tilted about a diameter thereof, relative to the shaft 9, by an auxiliary piston 21 that extends from a chamber 23 that is supplied with pilot hydraulic fluid via line 25 from swashplate angle adjust control assembly 27. As the shaft 9 rotates it in turn rotates the barrel 5 and thus the pistons 13 rotate around the shaft, with the piston shoes 19 in contact with and sliding along the swash plate 15. It will be realized that when the tilt angle Θ of the swash plate 15 is tilted to 90 degrees so that it becomes orthogonal to the shaft 9 the relative motion of the shoes 19 against the swash plate 15 imparts no axial force to the pistons as the barrel 5 rotates. Thus whilst the swashplate 15 is in the orthogonal “zero stroke tilt angle Θ = 90 degrees no displacement of the pistons 13 occurs. Upon increasing the swash plate angle or “stroke”, the pistons 13 reciprocate in and out of the bores 7 of the barrel 5 as they follow the angle of the swash plate. The pistons 13 move out of the cylinder barrel 5 during one half of the cycle of rotation, the inlet side 23, thereby generating an increasing volume in their associated bore to draw in fluid, while during the other half of the rotating cycle, the outlet side 25, the pistons move into the cylinder barrel thereby decreasing the available volume in their bore and pushing out fluid within the bore.

The reciprocating motion of the pistons within the barrel bores results in the drawing in and pumping out of the fluid. The pump’s capacity, i.e. the volume of fluid pumped each revolution of the barrel can be controlled by altering the swash plate angle Θ by variation of pilot pressure.

The casing 3 is formed with a hydraulic fluid inlet port 27 for receiving unpressurised hydraulic fluid and directing it to bores 7 of the barrel 5 currently adjacent the inlet side 23 with a hydraulic fluid outlet port 29 for conveying pressurized fluid from bores of the barrel currently adjacent the outlet side 25 of the swash plate.

The casing 3 is also formed with a casing drain 31 through which excess fluid within the casing 3, surrounding the barrel, pistons and swashplate is able to exit. It will be appreciated that hydraulic pumps and motors contain multiple small passageways and sliding surfaces separated by tight tolerances. For example, each piston shoe 19 contains grooves to provide hydrostatic balance to offset the load from fluid pressure.

Hydraulic pumps and motors are designed with tolerances that are sufficient to allow some non-pumped fluid, referred to as “leakage”, to pass between adjacent parts to provide lubrication between and through the various parts. Accordingly, excess leakage fluid passes out through the casing drain 31. Over time the leakage may increase due to wear of the parts so that ultimately the pump or motor becomes inefficient or fails. Since hydraulic pumps and motors are often used in critical areas, it is common practice to replace a pump or motor well before it is at risk of failure. Replacing a pump or motor too early is expensive. On the other hand, if the pump or motor is not replaced and then fails then its failure may lead to prolonged downtime and thus may be even more expensive. Furthermore, prior to failure the pump or motor may run inefficiently and thus be unduly expensive to power for a considerable period of time.

Fixed displacement pumps and motors work in a similar way except that the tilting swashplate is fixed so that every revolution produces a fixed displacement of oil. Apart from swashplate pumps and motors other types of pumps and motors, e.g. radial piston pumps, bend axis pumps, screw pumps and rotary vane pumps are also known and are similarly susceptible to wear and failure over time.

It is an object of the invention to provide a method and apparatus that addresses or at least ameliorates the above described problem.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a method for monitoring a hydraulic pump or motor comprising the steps of:

providing two or more sensors for attachment to the pump or motor for producing electrical signals indicative of operating parameters of said pump or motor;

operating an electronic controller to monitor said sensors for recording the parameter values corresponding to the electrical signals at sampling intervals in a digital memory; and operating said controller to indicate pump condition based upon the recorded parameter values; wherein at least one of the sensors comprises an output pressure sensor for measuring an output pressure of the pump or motor and at least one of the sensors comprises a case drain flow meter for measuring case drain flow.

Operating the controller to indicate pump condition based upon the recorded parameter values may comprise generating a graph showing a trendline indicating a pump condition value.

Operating the controller to indicate pump condition based upon the recorded parameter values may comprise raising an alarm upon the values complying with a predetermined condition.

Where the tilt angle of a swashplate of the pump or motor is adjustable then at least one of the sensors preferably comprises a pilot pressure sensor for measuring a pilot pressure of the pump or motor for adjusting tilt angle of the swash plate of the pump or motor.

Preferably the method includes operating the controller to produce a sum of weighted values of the parameters for each sampling interval (SOWR).

Preferably the method comprises averaging the weighted values of the parameters over an averaging time period. For example, the averaging time period may comprise a day or another time period such as a twelve hour (or longer or shorter) operating shift of the pump or motor.

The method may include operating the controller to discard (SOWR) values that are smaller than a significance threshold prior to averaging them.

Preferably the step of operating said controller to raise the alarm comprises raising the alarm upon determining that an average of the (SOWR) exceeds a predetermined threshold value.

The parameters may include case drain flow rate (CDR) wherein the method includes providing a case drain sensor for attachment to the pump or motor for the controller to monitor an electrical signal therefrom indicating the CDR.

The parameters may include case operating temperature (OT) wherein the method includes providing an operating temperature sensor for attachment to the pump or motor for the controller to monitor an electrical signal therefrom indicating the OT.

The parameters may include output pressure (OP) wherein the method includes providing an output pressure sensor to the pump or motor for the controller to monitor an electrical signal therefrom indicating the OP.

The weights may be identical. For example, in one embodiment the weights may all be 1/60,000. Alternatively, the weights may be varied to emphasise and de-emphasise the importance of various of the monitored pump or motor operational parameters in deciding if a fault condition is approaching.

Preferably the method includes operating the processor to send a message across a data network to an electronic device of an operator to thereby indicate to the operator that the alarm has been raised for the operator to take action to replace the pump or motor.

According to a further aspect of the present invention there is provided a hydraulic pump or motor monitoring assembly including:

an electronic controller;

two or more sensors coupled to said controller for producing electrical signals indicative of operating parameters of said pump;

the electronic controller being configured to monitor said sensors for recording pump or motor operating parameter values corresponding to the electrical signals from the sensors at sampling intervals in a digital memory; and raise an alarm based upon the recorded parameter values complying with a predetermined condition; wherein at least one of the sensors comprises an output pressure sensor and wherein at least one of the sensors comprises a case drain flow sensor.

According to a further aspect of the present invention there is provided a pump or motor monitoring assembly including:

an electronic controller;

two or more sensors coupled to said controller for producing electrical signals indicative of operating parameters of said pump or motor;

the electronic controller being configured to monitor said sensors for recording pump or motor operating parameter values corresponding to the electrical signals from the sensors at sampling intervals in a digital memory; and to indicate pump condition based upon the recorded parameter values; wherein at least one of the sensors comprises an output pressure sensor and wherein at least one of the sensors comprises a case drain flow sensor.

Preferably the electronic controller is configured to indicate pump condition as a graph showing a trendline indicating a pump condition value.

The electronic controller may be configured to indicate pump condition by raising an alarm based upon the values complying with a predetermined condition.

Where the pump or motor comprises a variable displacement pump or motor with an angle adjustable swash plate and at least one of the sensors preferably comprises a pilot pressure sensor for measuring a pilot pressure of the pump or motor for adjusting tilt angle of a swash plate of the pump or motor.

The assembly may include a temperature sensor wherein the controller is further configured to indicate pump condition based upon recorded parameter values including temperature values from the temperature sensor indicating operating temperature of the pump.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred features, embodiments and variations of the invention may be discerned from the following Detailed Description which provides sufficient information for those skilled in the art to perform the invention. The Detailed Description is not to be regarded as limiting the scope of the preceding Summary of the Invention in any way. The Detailed Description will make reference to a number of drawings as follows:

Figure 1 is a somewhat simplified cross-sectional view of an exemplary hydraulic pump or motor in the form of a swash plate axial piston pump.

Figure 2 is a diagram of a pump monitoring assembly according to a preferred embodiment of the present invention, shown installed to the pump of Figure 1.

Figure 3 is a block diagram of a controller of the pump monitoring assembly of Figure 2.

Figure 4 is a flowchart of a method implemented by the microprocessor of the controller according to instructions comprising a software product stored in a digital memory of the controller.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring now to Figure 2, there is shown a pump or motor monitoring assembly 35 according to a preferred embodiment of the present invention shown installed on pump 1. The pump 1 is shown in use in Figure 2 with output 29 coupled to a hydraulic circuit 32 to be worked. For example, the hydraulic circuit 32 may include one or more actuators such as hydraulic motors and/or hydraulic cylinders. The fluid from the hydraulic circuit 32 and also from case drain 31 is returned to a fluid reservoir 34 which is then drawn back into input port 27 of the pump 1.

The monitoring assembly 25 includes an electronic controller 36 and a number of sensors that are coupled to the controller 35 and which produce electrical signals indicative of operating parameters of pump 1.

In the presently described preferred embodiment the sensors include:

a pilot pressure (PP) sensor 37 for measuring pilot pressure of the pump 1;

a case drain flow rate (CDR) sensor 39 to monitor the rate of flow through port 31 of the pump 1;

a case operating temperature (OT) sensor 41 for monitoring operating temperature of the pump 1; and an output pressure (OP) sensor 43 which monitors the pressure at the output port 29 of hydraulic fluid leaving the pump.

Figure 3 is a block diagram of the electronic controller 36 shown in use coupled to lines 46 from sensors 37, 39, 41 and 43 and in data communication with an electronic device 63 of an operator 65 via a data communications network 61.

The controller 36 includes a microprocessor 45 that is in data communications via bus 47 with a number of other assemblies, namely:

Read-only memory 49, which includes startup and operating system instructions for the microprocessor 49;

Read-write memory 51, which includes instructions for microprocessor 45 comprising a sensor monitoring and processing program 53;

communications port 55 for the microprocessor 45 to establish communications with an external data network 61;

input/output ports 57 which are analog and/or digital ports for receiving signals from the various external sensors; and clock 59 which is typically a resistor-capacitor (RC) circuit, that may be supplemented by an external crystal based oscillator, which produces clock signals to synchronize the operation of each of the assemblies of the controller 36.

The controller 36 may be implemented as a cloud based virtual machine in other embodiments.

Figure 4 is a flowchart of a method for operation of the microprocessor 45. The method is coded as instructions that comprise the software product 53 that is stored in the digital memory comprising read-write memory 51.

Initially at box 67 the microprocessor 45 initializes variables that will be used and sets them all to zero. At box 69, if the value of time variable “t” is less than 1 day then control progresses to box 71. At box 71 the microprocessor 45 reads the values of each of the sensors at the current time. At box 73 the microprocessor calculates a Sum of Weighted Readings (SOWR) and sets that value to variable SOWR for the current time. At box 75 the microprocessor 45 appends the SOWR value for the current time to a data log which is stored in a digital memory such as memory 51 of the controller 36.

At box 77, after the time has incremented by a sampling period, e.g. 0.25 seconds, set by “interval”, control diverts back to box 69. At box 69, once the time over which the sampling exceeds one day (or another suitable time period, such as a 12 hour shift for example) then control diverts to box 79. At box 79 the microprocessor reads the data log for the preceding day and discards SOWR value that are less than a significance threshold. For example, depending on how the sensor data is scaled the significance threshold may be “1” so that all values that are less than “1” are discarded. At box 81 the microprocessor 45 sets a variable DayAvg to equal the average value of the non-discarded SOWR values for the preceding day. At box 83 the DayAvg value is logged and graphed on a webpage as shown in Figure 5. The DayAvg value is preferably scaled to be a number in the range of 0-100 which indicates pump condition as a Pump Serviceability (PS) number as shown in Figure 5 to display a trendline 101 of PS values so that a maintenance planner or any other personnel can quickly see the overall serviceability of each pump or motor on a particular machine. With reference to Figure 5, it can be seen that in response to the PS number for a pump, shown in dashed line 102, crossing the PS 100 change out line 103 the pump has been replaced. At box 85 the microprocessor checks to see if the DayAvg value for the preceding day is greater than a predetermined constant “SetPoint”. The SetPoint value has previously been determined, for the model of pump or motor being used, as being indicative of pump or motor failure or significant pump or motor impairment arising.

If at box 85 microprocessor 45 determines that the DayAvg value is not greater than SetPoint then control diverts to box 91 where the day variable is incremented and the time variable is reinitialized. The microprocessor then repeats the procedures of boxes 69 to 77 and then, once “t” has just exceeded a value of one day of time, box 69 to 83 to log a further day of sensor readings.

If at box 85 the DayAvg value is found to be greater than SetPoint then that indicates pump or motor impairment or failure to be imminent so that control diverts to box 87. At box 87 the microprocessor 45 operates comms port 55 to send an alarm via data network 61, for example the Internet, to electronic device 63 of operator 65 to thereby alert the operator that the pump or motor needs to be replaced. Once the pump or motor has been replaced the operator 65 can send a message back to the controller. The controller will then recognize at box 89 that the pump or motor has been replaced and thus proceed to box 67 where the entire logging and monitoring procedure is recommenced for the replacement pump or motor.

The Inventor believes that by monitoring at least the combination of output pressure with case drain flow it is possible to gain an indication of the degree of wear of the pump or motor since case drain flow is proportional to output pressure and output flow (which is a constant in fixed displacement pumps and inversely proportional to pilot pressure in variable displacement pumps and motors). Monitoring the additional sensors is advantageous because they help to provide more information regarding the internal condition of the pump. The various sensor output values that are collected can then be weighted by altering the w1, w2,... weights that the microprocessor executes at box 73 in order to fine tune failure prediction over time.

As can be seen from the graph of Figure 5, the pump whose PS line is indicated in dashed line was changed during a 500 hr service on the 24^th of July. It was identified in June that it would need to be done and the maintenance planner began the planning stages. Four extra OEM fitters are brought in to complete the specific task in 7.1/2 hrs. By doing an independent valuation of the used pump it is possible to verify if the OEM specs for the pump are correct or if the pump could have continued in service longer. Changes to the pump replacement line can be made if necessary.

In an embodiment of the invention, by monitoring pump pressure and temperature 24/7, pumps that are being overworked become evident. The pumps may be overworked due to several reasons including; machine design, digging conditions, rock fragmentation from blasting and individual machine operators. Machine design where the pump is not fit for purpose is an OEM issue that cannot be changed at site level. Digging conditions, blasting and machine operation can all be changed at the mine if the data was known. For instance double benching may cause excessive force on the dipper cylinder which will increase pump wear. Not having good blast fragmentation requires more breakout force. If the dipper arm stops, before the boom is lifted during the dig cycle, over pressurizing of the dipper circuit will result. Similarly if the operator begins swinging before the bucket is clear will load up the swing motors. These are all things that cause excessive wear and heat build-up in the pump.

Adding additional pressure and temperature transducer to each pump and feeding that data back to the cloud will enable both production and maintenance to better understand machine operation. This data can be used to change behaviours that are causing excessive pump wear and contamination, shortening life expectancy.

In use an operator either installs the various sensors to the pump or motor and then couples them to the controller or alternatively, in some circumstances pumps are provided with at least an output pressure sensor that can be used.

In compliance with the statute, the invention has been described in language more or less specific to structural or methodical features. The term “comprises and its variations, such as “comprising” and “comprised of’ is used throughout in an inclusive sense and not to the exclusion of any additional features. It is to be understood that the invention is not limited to specific features shown or described since the means herein described comprises preferred forms of putting the invention into effect. The invention is, therefore, claimed in any of its forms or modifications within the proper scope of the appended claims appropriately interpreted by those skilled in the art.

Throughout the specification and claims (if present), unless the context requires otherwise, the term substantially or about will be understood to not be limited to the value for the range qualified by the terms.

Any embodiment of the invention is meant to be illustrative only and is not meant to be limiting to the invention. Therefore, it should be appreciated that various other changes and modifications can be made to any embodiment described without departing from the spirit and scope of the invention.

Claims

1. A method for monitoring a hydraulic pump or motor comprising the steps of:

2. A method according to claim 1, wherein operating the controller to indicate pump condition based upon the recorded parameter values may comprise generating a graph showing a trendline indicating a pump condition value.

3. A method according to claim 1 or claim 2, wherein operating the controller to indicate pump condition based upon the recorded parameter values may comprise raising an alarm upon the values complying with a predetermined condition.

4. A method according to any one of the preceding claims, wherein, where the tilt angle of a swashplate of the pump or motor is adjustable then at least one of the sensors comprises a pilot pressure sensor for measuring a pilot pressure of the pump or motor for adjusting tilt angle of the swash plate of the pump or motor.

2019101416 18 Nov 2019

5. A method according to any one of the preceding claims including operating the controller to produce a sum of weighted values of the parameters for each sampling interval (SOWR).

6. A method according to anyone of the preceding claims, including averaging the weighted values of the parameters over an averaging time period.

7. A method according to claim 3, wherein the step of operating said controller to raise the alarm comprises raising the alarm upon determining that an average of the (SOWR) exceeds a predetermined threshold value.

8. A method according to any one of the preceding claims, wherein the parameters include a case drain flow rate (CDR) wherein the method includes providing a case drain sensor for attachment to the pump or motor for the controller to monitor an electrical signal therefrom indicating the CDR.

9. A method according to any one of the preceding claims, wherein the parameters include a case operating temperature (OT) wherein the method includes providing an operating temperature sensor for attachment to the pump or motor for the controller to monitor an electrical signal therefrom indicating the OT.

10. A method according to any one of the preceding claims, wherein the parameters include output pressure (OP) wherein the method includes providing an output pressure sensor to the pump or motor for the controller to monitor an electrical signal therefrom indicating the OP.

11. A hydraulic pump or motor monitoring assembly including:

an electronic controller;

the electronic controller being configured to monitor said sensors for recording pump or motor operating parameter values corresponding to the

2019101416 18 Nov 2019 electrical signals from the sensors at sampling intervals in a digital memory; and to indicate pump condition based upon the recorded parameter values; wherein at least one of the sensors comprises an output pressure sensor and wherein at least one of the sensors comprises a case drain flow sensor.

12. An assembly according to claim 11, wherein the electronic controller is configured to indicate pump condition as a graph showing a trendline indicating a pump condition value.

13. An assembly according to claim 11 or claim 12, wherein the electronic controller may be configured to indicate pump condition by raising an alarm based upon the values complying with a predetermined condition.

14. An assembly according to any one of claims 11 to 13, wherein the pump or motor comprises a variable displacement pump or motor with an angle adjustable swash plate and at least one of the sensors preferably comprises a pilot pressure sensor for measuring a pilot pressure of the pump or motor for adjusting tilt angle of a swash plate of the pump or motor.

15. An assembly according to any one of claims 11 to 14, including a temperature sensor wherein the controller is further configured to indicate pump condition based upon recorded parameter values including temperature values from the temperature sensor indicating operating temperature of the pump.