Patent Application
20150198507
The present disclosure relates generally to steering pump assemblies, and more particularly, to systems and methods for determining operational readiness of emergency steering pump systems.
Steering pumps are commonly used in the relevant art to, for instance, facilitate a machine operator's ability to steer, maneuver or otherwise control vehicles, work machines, and the like. As a safety feature, some machines are integrated with emergency steering mechanisms which provide an alternative or a secondary power source designed to supply backup power to the steering pump in emergency situations. Such emergency steering systems enable the operator to maintain control of the machine or vehicle in the event of a failure in the primary power source, such as due to leakage, a pump malfunction, or the like.
Emergency steering mechanisms are also further implemented with an operational readiness test or feature that is automatically performed at machine startup to ensure proper functionality of the emergency system. In a typical operational readiness test, the emergency steering pump is briefly activated to determine if the resulting pressure supplied by the secondary energy source is sufficient to take over the steering system if necessary. Correspondingly, the typical emergency steering mechanism requires means to rapidly accumulate pressure within a relatively short period of time.
Conventional systems with electrically driven emergency steering mechanisms rely on steering pumps with a fixed pressure relief valve adapted to provide rapid pressure accumulation that is sufficient for not only the operational readiness tests at startup but also for actual emergency conditions. However, such systems accumulate pressure irrespective to the overall system or demands thereof and force the emergency pump to operate at maximum relief. Due to the high levels of pressure involved and the time required to reach threshold pressures, these assemblies are prone to premature failure such as overheating conditions in the electric motor and/or associated motor relays.
Also used in the art are unloader-type steering pumps which allow the emergency pump to build pressure based on system demand, and thereby reduce premature failures commonly associated with pumps using fixed pressure relief valves. Unloader-type steering pumps provide some advantages, but unlike an emergency pump using a fixed relief valve, an unloader-type emergency steering pump alone may not provide the output pressure needed for differentiation over the primary pump standby pressure required to satisfy the operational readiness test.
The present disclosure is directed at addressing one or more of the deficiencies set forth above. However, it should be appreciated that the solution of any particular problem is not a limitation on the scope of this disclosure or of the attached claims except to the extent express noted. Additionally, the inclusion of any problem or solution in this Background section is not an indication that the problem or solution represents known prior art except as otherwise expressly noted.
In one aspect of the present disclosure, a method of determining readiness of an emergency steering pump system is provided. The method may include the steps of detecting a startup condition; determining a standby pressure provided by a primary pump and a margin pressure to be provided by a secondary pump; engaging the secondary pump for a predefined duration based on the standby pressure and the margin pressure; and determining readiness based on a cumulative pressure of the standby pressure and the margin pressure as compared to a predefined threshold corresponding to load demand.
In another aspect of the present disclosure, an emergency steering pump system is provided for a primary pump providing a standby pressure. The emergency steering pump system may include a secondary pump for providing a margin pressure, a pressure control mechanism in communication with at least one of the primary pump and the secondary pump, and a controller in communication with each of the primary pump and the secondary pump. The resolver may be configured to accumulate the margin pressure based at least partially on load demand. The controller, upon startup, may be configured to engage the secondary pump for a predefined duration, monitor a cumulative pressure of the standby pressure and the margin pressure, and determine readiness of the secondary pump based on the cumulative pressure as compared to a predefined threshold corresponding to the load demand.
In yet another aspect of the present disclosure, an emergency steering pump system is provided for a primary pump providing at least standby pressure upon startup. The emergency steering pump system may include a secondary pump for providing a margin pressure, and a resolver in communication with each of the primary pump and the secondary pump. The resolver may be configured to accumulate the margin pressure provided by the secondary pump such that a sum of the standby pressure and the margin pressure substantially approximates load demand.
Reference will now be made in detail to specific embodiments or features, examples of which are illustrated in the accompanying drawings. Generally, corresponding reference numbers will be used throughout the drawings to refer to the same or corresponding parts.
Referring to
The power source 102 may be an engine such as, for example, a diesel engine, a gasoline engine, a gaseous fuel powered engine such as a natural gas engine, or any other engine apparent to one skilled in the art. The power source 102 may also embody another source of power such as a fuel cell, a power storage device, or any other source of power known in the art. The traction devices 104 may include wheels 108, for example, located on each side of the work machine 100. Alternatively, the traction devices 104 may include tracks, belts or other traction devices. In other embodiments, the fraction devices 104 may incorporate a differential gear assembly configured to divide power from the power source 102 between the wheels 108 located on either side of the work machine 100. For instance, the differential gear assembly may allow the wheels 108 on one side of the work machine 100 to turn faster than the wheels 108 located on an opposite side of the work machine 100.
As illustrated in
The extension and retraction of the steering cylinder 114 may be accomplished by creating an imbalance of force on a piston assembly (not shown) disposed within a tube of the steering cylinder 114. In one embodiment, each of the steering cylinders 114 may include a first chamber and a second chamber separated by the piston assembly. The piston assembly may include a piston axially aligned with and disposed within the tube. The piston may include two opposing hydraulic surfaces, one associated with each of the first and second chambers. The first and second chambers may be selectively supplied with a pressurized fluid and drained of the pressurized fluid to create an imbalance of force on the two surfaces that causes the piston assembly to axially move within the tube. For example, a fluid pressure within the first hydraulic chamber acting on a first hydraulic surface being greater than a fluid pressure within the second hydraulic chamber acting on a second opposing hydraulic surface may cause the piston assembly to displace to increase the effective length of steering cylinder 114. Similarly, when fluid pressure acting on the second hydraulic surface is greater than fluid pressure acting on the first hydraulic surface, the piston assembly may retract within the tube to decrease the effective length of steering cylinder 114.
Still referring to
In one embodiment, the primary pump 120 may be a fixed displacement pump, a variable displacement pump, a variable flow pump, or any other source of pressurized fluid known in the art. The primary pump 120 may be configured to provide a flow of pressurized fluid in the steering system 106. The primary pump 120 may be operatively coupled to an output of the power source 102, for example, via a countershaft, a belt, an electrical circuit, or any other suitable manner. It should be noted that the primary pump 120 may also supply the pressurized fluid to other circuits in the work machine 100. The secondary pump 122 may include a ground-driven pump, an accumulator, or an electrically-driven unloader-type pump. For example, the secondary source pump 122 may be driven by an electric motor 126 coupled thereto. The electric motor 126 may be an AC drive motor or a DC drive motor, depending on the application.
Turning to
Upon startup of the work machine 100, the primary pump 120 of
More specifically, in the embodiment of
Furthermore, the emergency steering pump systems 200 of
A person of ordinary skill in the art will appreciate that the configurations shown in the accompanied figures depict example configurations. Other arrangements or configurations of the primary pump 120 and the secondary pump 122 may be employed. It should be understood that the secondary pump 122 may be provided as a backup power source in the event that the primary pump 120 may experience a failure, such as deactivated, defected, damaged, or otherwise inoperable. As currently configured, the operational health or readiness of the secondary pump 122 and/or the overarching emergency steering pump system 200 may be determined, for example, automatically upon startup of the work machine 100, at periodic intervals, or manually upon user request, and the like. Moreover, the operational readiness tests may be initiated once the controller 216 first confirms that the power source or engine 102 is operating and the relevant steering valves 124 of the steering system 106 are closed.
In the configurations of
If the cumulative pressure substantially reaches the predefined threshold, or approximates the predefined threshold within acceptable limits, upon or prior to expiration of the predefined test duration, the controller 216 may designate the emergency steering pump system 200 as operational and ready to at least temporarily support the load demand in the event of a failure in the primary pump 120. If, however, the cumulative pressure is less than or does not sufficiently approximate the predefined threshold upon expiration of the predefined test duration, the controller 216 may designate the emergency steering pump system 200 as inoperative or not ready. Furthermore, if the emergency steering pump system 200 is determined to be operational, the controller 216 may proceed to normal machine operations. Additionally or optionally, the controller 216 may signal or provide indications of the successful test, for instance, to an operator of the work machine 100 via any one or more interfaces that are disposed in relation to the work machine 100. Alternatively, if the emergency steering pump system 200 is determined to be inoperative or deficient in any manner, the controller 216 may signal or provide indications informing or warning the operator of the failed test prior to proceeding with normal machine operations.
Work machines can be provided with a secondary source of pressurized fluid or secondary pump either as standard equipment or as optional attachments to meet local regulations and/or customer preferences. The secondary pump may serve as a backup steering power source in the event that the primary source of pressurized fluid or primary pump experiences failure. In the instance of using a secondary pump, such as an unloader-type pump driven by an electric motor, additional regulations may require an ability to test the functionality of the emergency steering pump system, or the combined primary pump and secondary pump, and communicate an indication of an appropriate status to the operator, based on whether certain predetermined test thresholds are achieved. The present disclosure serves to provide such features in a manner which minimizes design complexity and the overall costs of implementation and maintenance. Moreover, the present disclosure provides means to quickly and adequately accumulate and maintain pressure within an emergency steering pump system during an operational readiness test while reducing wear to the associated backup or secondary pump.
Referring now to
According to the method 300 of
Once a startup condition or an otherwise sufficient triggering event is detected, the controller 216 in step 300-2 may first ensure that all machine parameters satisfy prerequisite conditions prior to proceeding with the health check or operational readiness test. In accordance with the method 300 of
If all prerequisite conditions are satisfied in step 300-2, for example, if the engine 102 is confirmed to be operating and the steering valves 124 are confirmed to be closed, the controller 216 may proceed to determine or monitor the standby pressure provided by the primary pump 120 in step 300-3. The controller 216 may observe the standby pressure via any one or more pressure sensors 214 that are dedicated to or otherwise associated with the primary pump 120. In step 300-4, the controller 216 may be configured to engage the secondary pump 122 for a predefined test duration. For example, in an unloader-type secondary pump 122 that is driven by an electric motor 126, the controller 216 may engage the electric motor 126 for a duration that has been preprogrammed within the controller 216. Once the secondary pump 122 is operating, the controller 216 may monitor the margin pressure provided by the secondary pump 122 in step 300-5, in essence, by monitoring the cumulative pressure provided by the emergency steering pump system 200. In particular, the controller 216 may be configured to obtain the cumulative pressure via one or more pressure sensors 214 that are configured, for example in conjunction with the resolver 210-1 of
Based on such pressure measurements and/or calculations, the controller 216 may be configured to, either by way of the margin pressure or by way of the cumulative pressure, determine if a predefined pressure threshold has been reached in step 300-6. More specifically, the pressure threshold may be a preprogrammed value which corresponds to the anticipated or detected load demand for a given steering input. If the detected margin pressure provided by the secondary pump 122 is sufficient to provide a cumulative pressure which substantially meets the given load demand or the corresponding pressure threshold, the controller 216 may be configured to disengage the secondary pump 122 and designate a successful health check in step 300-7 irrespective of the time remaining in the test duration. If, however, the cumulative pressure for a given iteration is sufficiently less than the predefined pressure threshold by more than an allowed deviation, the controller 216 may proceed to step 300-8 to determine whether the test duration has expired.
If the predefined test duration has not yet expired and time remains in the health check routine, the controller 216 may be configured to return to steps 300-5 and 300-6 and continue monitoring the cumulative pressure in relation to the pressure threshold. Moreover, the controller 216 may repeat such cycle either until the cumulative pressure substantially reaches the predefined threshold, or until the test duration expires, whichever event occurs first. If the cumulative pressure substantially reaches the predefined threshold before the test duration expires, the controller 216 may disengage the secondary pump 122 and designate a successful health check, as described in accordance with step 300-7 above. If the test duration expires before the cumulative pressure reaches the pressure threshold, the controller 216 may disengage the secondary pump 122 and designate the health check as unsuccessful in step 300-9. In further modifications, the controller 216 may additionally signal, alert or otherwise provide indications corresponding to passed and/or failed health check results to an operator of the associated work machine 100.
Correspondingly, according to the method 400 of
If all prerequisite conditions are satisfied in step 400-2, for example, if the engine 102 is confirmed to be operating and the steering valves 124 are confirmed to be closed, the controller 216 may proceed to determine or monitor the standby pressure provided by the primary pump 120 in step 400-3. The controller 216 may observe the standby pressure via any one or more pressure sensors 214 that are dedicated to or otherwise associated with the primary pump 120. In step 400-4, the controller 216 may be configured to activate the 2-position, 3-way solenoid 210-3, or the like, so as to communicate the primary standby pressure to the emergency load sense, and engage the secondary pump 122 for a predefined test duration similar to step 300-4 of method 300 in
Based on such pressure measurements and/or calculations, the controller 216 may be configured to, by way of the margin pressure or by way of the cumulative pressure, determine if a predefined pressure threshold has been reached in step 400-6. More specifically, the pressure threshold may be a preprogrammed value which corresponds to the anticipated or detected load demand for a given steering input. If the detected margin pressure provided by the secondary pump 122 is sufficient to provide a cumulative pressure which substantially meets the given load demand or the corresponding pressure threshold, the controller 216 may be configured to disengage the secondary pump 122, and designate a successful health check in step 400-7 irrespective of the time remaining in the test duration. For example, the controller 216 may deactivate or open an on/off solenoid in the secondary pump load sense line to disengage the secondary pump. If, however, the cumulative pressure for a given iteration is sufficiently less than the predefined pressure threshold by more than an allowed deviation, the controller 216 may proceed to step 400-8 to determine whether the test duration has expired.
If the predefined test duration has not yet expired and time remains in the health check routine, the controller 216 may be configured to return to steps 400-5 and 400-6 and continue monitoring the cumulative pressure in relation to the pressure threshold. Moreover, the controller 216 may repeat such cycle either until the cumulative pressure substantially reaches the predefined threshold, or until the test duration expires, whichever event occurs first. If the cumulative pressure substantially reaches the predefined threshold before the test duration expires, the controller 216 may disengage the secondary pump 122, for example by deactivating or opening an on/off solenoid in the secondary pump load sense line, and designate a successful health check, as described in accordance with step 400-7 above. If the test duration expires before the cumulative pressure reaches the pressure threshold, the controller 216 may disengage the secondary pump 122, such as by deactivating or opening an on/off solenoid in the secondary pump load sense line, and designate the health check as unsuccessful in step 400-9.
From the foregoing, it will be appreciated that while only certain embodiments have been set forth for the purposes of illustration, alternatives and modifications will be apparent from the above description to those skilled in the art. These and other alternatives are considered equivalents and within the spirit and scope of this disclosure and the appended claims.
