Patent Grant
11364914
Not applicable.
Not applicable.
This disclosure relates to hydrostatic transmission pressure monitoring systems and to work vehicles containing such pressure monitoring systems.
A hydrostatic infinitely variable transmission (IVT) contains a variable displacement pump-motor arrangement, which can be controlled to vary the input-output (I/O) speed ratio of the IVT. By common design, such a pump-motor arrangement contains a pair of reciprocating axial piston devices, which are fluidly interconnected by a hydraulic circuit. When the IVT is driven in a particular direction, one of the reciprocating axial piston devices operates as a pump, while the other axial piston device functions as a motor. By varying the swash angles of the axial piston devices, the torque and speed output of the IVT can be controlled over a continuous range encompassing a zero value with a relatively high degree of precision. These characteristics render hydrostatic IVTs well-suited for integration into work vehicles, which often contain engines placed under highly variable torque loads at lower ground speeds. In certain instances, a hydrostatic IVT may further incorporate a multi-modal (e.g., planetary) gear train, which enables on-the-fly selection between multiple gear ratios. In this case, the hydrostatic IVT may be more specifically referred to as a “hydromechanical IVT” and may utilize the hydrostatic pump-motor arrangement to provide the desired continuous output speed variability, while leveraging the multi-modal gearing to enhance IVT efficiency by minimizing power transfer losses. Certain hydromechanical IVTs further incorporate a power-splitting design to, for example, apportion torque output between a first IVT output shaft driving work vehicle propulsion and a second IVT output shaft utilized to supply mechanical power to other driven components onboard the work vehicle or contained in an interchangeable implement attached to the work vehicle.
Embodiments of a hydrostatic transmission pressure monitoring system include a hydrostatic transmission and a pressure sensor data source. The hydrostatic transmission includes, in turn, a transmission casing, a pivoting yoke assembly rotatably mounted in the transmission casing, a hydrostatic pump-motor arrangement containing a hydraulic pump-motor circuit at least partially formed in the pivoting yoke assembly, and a pressure scaling device fluidly coupled to the hydraulic pump-motor circuit. The pressure scaling device is configured to generate a pressure-scaled output signal substantially proportional to a peak circuit pressure within the hydraulic pump-motor circuit. The pressure sensor data source is fluidly coupled to the pressure scaling device and is further configured to generate pressure sensor data indicative of the pressure-scaled output signal.
In further embodiments, the hydrostatic transmission pressure monitoring system includes a hydrostatic pump-motor arrangement having a hydraulic pump-motor circuit, a pressure scaling valve (PSV), a pressure sensor, and a controller in signal communication with the pressure sensor. The PSV has a PSV sense port at which a peak circuit pressure of the hydraulic pump-motor circuit is received when hydrostatic pump-motor arrangement is driven in at least a first direction, as well as a signal outlet at which a pressure-scaled output signal generated. The pressure-scaled output signal is substantially proportional to the peak circuit pressure. The pressure sensor is in fluid communication with the signal outlet and is configured to generate pressure sensor data indicative of the pressure-scaled output signal, while the controller is configured to monitor the peak circuit pressure within the hydraulic pump-motor circuit utilizing the pressure sensor data.
Embodiments of a work vehicle equipped with a hydrostatic infinitely variable transmission (IVT) are further provided. In an embodiment, the work vehicle includes a controller in addition to the hydrostatic IVT. The hydrostatic IVT includes, in turn, a hydrostatic pump-motor arrangement having a hydraulic pump-motor circuit, a PSV, and a pressure sensor. The PSV has a PSV sense port at which a peak circuit pressure from the hydraulic pump-motor circuit is received, a baseline pressure inlet at which a baseline input pressure is received, and a signal outlet at which a pressure-scaled output signal generated. The pressure sensor is in fluid communication with the signal outlet and is configured to generate pressure sensor data indicative of the pressure-scaled output signal. The controller is configured to estimate the peak pressure within the hydraulic pump-motor circuit utilizing on the pressure sensor data received by the controller during operation of the hydrostatic IVT.
The details of one or more embodiments are set-forth in the accompanying drawings and the description below. Other features and advantages will become apparent from the description, the drawings, and the claims.
At least one example of the present disclosure will hereinafter be described in conjunction with the following figures:
Like reference symbols in the various drawings indicate like elements. For simplicity and clarity of illustration, descriptions and details of well-known features and techniques may be omitted to avoid unnecessarily obscuring the example and non-limiting embodiments of the invention described in the subsequent Detailed Description. It should further be understood that features or elements appearing in the accompanying figures are not necessarily drawn to scale unless otherwise stated.
Embodiments of the present disclosure are shown in the accompanying figures of the drawings described briefly above. Various modifications to the example embodiments may be contemplated by one of skill in the art without departing from the scope of the present invention, as set-forth the appended claims.
As discussed above, certain work vehicles are equipped with hydrostatic infinitely variable transmissions (IVTs) having power-splitting designs and incorporating multi-modal (e.g., planetary) gear train subsystems. Such power-splitting hydromechanical IVTs are well-suited for deployment onboard work vehicles to provide continuously variable transmission ratios, high power transfer efficiencies, and other benefits. When integrated into a tractor, for example, a hydromechanical IVT may provide a first torque transfer path extending through the IVT and the hydrostatic pump-motor arrangement; and a second torque transfer path extending through the IVT, while bypassing the hydrostatic pump-motor arrangement. The first torque transfer path may mechanically link the tractor engine to the driven wheels of the tractor and other variable loads, thereby enabling the hydrostatic pump-motor arrangement to provide a continuously-adjustable output speed over a rotational speed range optimized for tractor propulsion. Comparatively, the second torque transfer path may mechanically link the tractor engine to a power takeoff (PTO) shaft of the tractor; that is, a rotating shaft that, when coupled to a mating shaft provided on an interchangeable implement towed by the tractor, transmits a fraction of the rotational power generated by the tractor engine to movable components onboard the implement.
While providing the above-described benefits, power-splitting hydromechanical IVTs (and power-splitting hydrostatic transmissions, generally) encounter certain technical challenges. One such challenge arises when attempting to accurately monitor the torque division or apportionment between the different torque transfer paths through the IVT. Generally, the torque division between the hydraulic torque transfer path (that is, the torque transfer path extending through the hydrostatic pump-motor arrangement) and the non-hydraulic (e.g., PTO) torque transfer path can be determined as follows. First, the hydraulic torque transfer through the hydrostatic pump-motor arrangement may be estimated. The estimated hydraulic torque transfer may then be compared with the current power output of the engine to deduce the current torque transfer through the non-hydraulic (e.g., PTO) torque transfer path. The magnitude of the hydraulic torque transmission through the hydrostatic pump-motor arrangement can also be calculated in a relatively straightforward manner; e.g., as function of pump displacement, the current peak (or “high side”) pressure within the hydraulic pump-motor circuit, and other secondary factors, such as hydrostatic efficiency. Per-rotation pump displacement may, in turn, be estimated by comparing the relative rotational speeds of the pump-motor (axial piston) devices included in the pump-motor arrangement, while compensating for leakage or other hydrostatic inefficiencies. In other instances, hydrostatic pump displacement can be approximated in another manner; e.g., by considering known geometries and measuring the respective swash angles of the axial piston hydraulic devices.
Additional technical challenges may be encountered when attempting to measure the peak or “high side” circuit pressure within the hydraulic pump-motor circuit. Such technical challenges tend to arise when the hydraulic pump-motor circuit is formed within a movable subassembly or “pivoting yoke assembly” contained with a larger, static housing of the transmission referred to herein as the “transmission casing.” Additionally, the peak or high side pressures within the hydraulic pump-motor circuit can reach highly elevated levels during transmission operation. For example, in at least some implementations, the peak or high side circuit pressure may reach levels surpassing 700 bar and, perhaps, levels approaching or exceeding 1000 bar. Such conditions render it highly challenging to directly measure the peak circuit pressure within the hydraulic pump-motor circuit in a manner that is accurate, cost effective, and structurally robust for the reasons discussed below.
It may be possible to integrate a specialized pressure sensor having elevated pressure sensing capabilities into the pivoting yoke assembly to locally measure the peak (high side) circuit pressure; however, such specialized pressure sensors tend to be relatively costly and to have inadequate durability for work vehicle (off-road) applications. Further, routing electrical power to and signals from such an integrated pressure sensor typically requires undesirably complex wire routing schemes in which internal wires are submerged in heated oil, while external wires are supported by one or more wiring harnesses affixed to the pivoting yoke assembly. Such issues can be mitigated, to a limited extent, by locating the pressure sensor offboard the pivoting yoke assembly and routing the peak circuit pressure to the remotely-located pressure sensor. Routing such highly elevated peak circuit pressures through a hose (or similar flexible conduit capable of accommodating the swiveling action of the pivoting yoke assembly) to enable a remote sensing architecture poses additional problems, however, such as issues associated with hose leakage and stiffening under such high pressure loads. Further, such a remote sensing approach still typically necessitates the usage of a specialized pressure sensor having high pressure sensing capabilities associated with the limitations mentioned above. In an alternative approach, the peak circuit pressure (or, more accurately, the hydraulic fluid carrying the peak circuit pressure) can be routed through a bearing support of the pivoting yoke assembly and ultimately ported to a sensor external to the pivoting yoke assembly. However, such a routing scheme typically necessitates the usage of a high pressure rotary seal, which tends to be costly and leakage prone. Also, once again, such a solution fails to circumvent the need for specialized pressure sensor having sufficiently elevated pressure sensing capabilities to sample the peak (high side) circuit pressure.
For at least these reasons, a second, more specific technical problem arises in attempting to measure the highly elevated peak or “high side” circuit pressures within the hydraulic pump-motor circuit of a hydromechanical IVT (or other hydrostatic transmission). Embodiments of the hydrostatic transmission pressure monitoring system address this technical problem. Specifically, embodiments of the hydrostatic transmission pressure monitoring system incorporate a unique mechanical pressure scaling device, which includes or assumes the form of one or more pressure scaling valves (PSVs). Such PSVs mechanically sample the peak circuit pressures within a hydraulic pump-motor circuit and convert such elevated pressures to corresponding low pressure fluidic signals. These fluidic signals are referred to herein as “pressure-scaled output signals” and are generated by a given PSV to be substantially proportional to (or otherwise indicative of) the peak circuit pressures occurring within a hydraulic pump-motor circuit at any given point in time. Concurrently, when the pump-motor arrangement is driven in a particular direction and placed under load, the pressure-scaled output signal has a pressure significantly less than the peak circuit pressure; e.g., in embodiments, the pressure-scaled output signal may be scaled downwardly by a factor of ten or more relative to the peak (high side) circuit pressure. Due to its reduced magnitude, the pressure-scaled output signal can be measured utilizing readily available, non-specialized pressure sensors having reduced pressure sensing capabilities. Such “non-specialized” pressure sensors (hereafter, “high durability pressure sensors”) may be less costly, more accurate, and/or may possess greater structural durability relative to specialized pressure sensors having high pressure sensing capacities.
Depending upon implementation, one or more high durability pressure sensors may be included in a pressure sensor data source, which is fluidly coupled to the pressure scaling device and operably coupled to a processing subsystem or “controller” further contained in the pressure monitoring system. During IVT operation, the controller utilizes pressure sensor data from the pressure sensor data source to monitor the peak or high side circuit pressure within the hydraulic pump-motor circuit. Further, in implementations, the controller may further utilize the peak circuit pressure to determine other pressure-related parameters, such as an estimated magnitude of the torque currently transmitted through the hydrostatic pump-motor arrangement; or, more broadly, through the hydraulic torque transfer path of the IVT when possessing a torque- or power-splitting design. Moreover, in embodiments in which the hydrostatic transmission pressure monitoring system is deployed onboard a tractor (or similar work vehicle) having a PTO shaft, the controller may repeatedly calculate a current torque transmitted through the hydrostatic pump-motor arrangement based, in part, on the peak circuit pressure; and may selectively vary a power output of the work vehicle engine in response to variations in the current torque transmitted through the hydrostatic pump-motor arrangement relative to an estimated torque transmitted through the PTO shaft. Additionally or alternatively, the controller may provide numerical read-out or graphical display of the current torque level transmitted through the hydrostatic pump-motor arrangement, the current torque level transmitted through the PTO shaft, or other such parameters on a display device located within the cabin or operator station of the work vehicle.
In embodiments in which the hydrostatic transmission pressure monitoring system includes a pivoting yoke assembly, the pressure sensor data source (e.g., including one or more high durability pressure sensors) can be integrated into the pivoting yoke assembly itself or mounted to an exterior surface thereof. In other instances, the pressure sensor data source may be located offboard the pivoting yoke assembly, with the high durability pressure sensor(s) potentially affixed to the transmission casing such that the pivoting yoke assembly rotates relative to the pressure sensor(s) when the swash angles of the axial piston devices are adjusted during transmission operation. Such remote positioning of the pressure sensor data source is facilitated due to the reduced pressure of the pressure-scaled output signal relative to the peak (high side) circuit pressure. In particular, the hydraulic fluid carrying the pressure-scaled output signal can be routed through flexible tubing or other conduits with a decreased risk of leakage and with reduced conduit stiffening due to the reduced hydraulic pressures under transport. Alternatively, the pressure-scaled output signal can be routed to the pressure sensor data source through a bearing interface supporting the pivoting yoke assembly, while utilizing a reduced cost, low pressure rotary seal due to the decreased pressure of the pressure-scaled output signal. As a still further benefit, locating the high durability pressure sensor(s) offboard the pivoting yoke assembly may also ease sensor access and replacement during maintenance procedures. The end result, then, is a hydromechanical IVT or other hydrostatic transmission permitting monitoring of the peak circuit pressure of a hydraulic pump-motor circuit in an accurate, reliable, high durability manner suitable for usage within the harsh environments in which work vehicles often operate.
Additional description of an example hydrostatic transmission pressure monitoring system onboard a work vehicle will now be discussed in connection with
Referring to
As indicated by dashed lines connecting the various shafts 26, 28, 30 in the schematic of
In the illustrated example, the hydromechanical IVT 24 contains a multi-modal planetary subsystem 44 and a hydrostatic subsystem 46. Addressing first the multi-modal planetary subsystem 44, the subsystem 44 includes (among other non-illustrated components) a planetary gear train 48 and one or more clutch modules 50. The clutch module(s) 50 can be selectively activated or engaged by the below-described controller 52 (e.g., via transmission of commands to associated actuators, such as valve-actuated pistons) to vary the gear ratio through the planetary gear train 48. For example, in embodiments, activation or engagement of a particular clutch module 50 may alter which gear member (e.g., a sun gear, a ring gear, or a planet-carrier unit) serves as the mechanical input and/or mechanical output of the planetary gear train 48, thereby enabling the selection of two or more discrete gear ratio options for I/O speed and torque speed conversion. This enables the controller 52 to choose an optimal gear ratio best suited for various operational conditions encountered when operating the tractor 20 including, for example, tractor operation at low ground speeds and high torque demands (as commonly encountered when the tractor 20 is utilized to perform certain work tasks), as well as tractor operation at higher ground speeds and lower torque loads (as commonly encountered when the tractor 20 is engaged in transport over public or private roadways). By virtue of this structural arrangement, the hydromechanical IVT 24 is imparted with an enhanced 1/O variability between the input shaft 26 and the output shaft 30 exceeding that otherwise achievable solely through the inclusion of the hydrostatic subsystem 46. Further, the overall efficiency of the hydromechanical IVT 24 is boosted due to the reduced power losses provided by the multi-modal planetary subsystem 44 relative to comparable, but purely hydrostatic IVT. These benefits notwithstanding, the hydromechanical IVT 24 may lack such a multi-modal planetary (or other gearing) subsystem 44, or otherwise vary relative to the illustrated example, in further implementations of the hydrostatic transmission pressure monitoring system 22.
The IVT hydrostatic subsystem 46 contains a hydrostatic pump-motor arrangement 54 and a pressure scaling device 56, which is fluidly coupled to a hydraulic circuit contained in the pump-motor arrangement 54. The hydrostatic pump-motor arrangement 54 can include, in turn, any combination of fluidly interconnected hydraulic machines or devices suitable for converting a rotating input power (torque and speed) to a variable rotating output power (torque and speed). In one common design, the hydrostatic pump-motor arrangement 54 contains a first axial piston device, a second axial piston device, and a hydraulic pump-motor circuit fluidly interconnecting the axial piston devices. The hydrostatic pump-motor arrangement 54 may be reversible in embodiments and, therefore, may be capable of being driven in either rotational direction; the term “rotational direction,” as appearing in this context, define with respect to the rotational direction of the output shaft of the hydrostatic pump-motor arrangement 54. Each of the axial piston devices may operate as either a pump or motor in certain implementations, depending upon the particular direction in which the hydrostatic pump-motor arrangement 54 is driven at a given juncture in time. The pump-motor arrangement 54 need not be reversible in all implementations, however; thus, in alternative embodiments of the hydrostatic transmission pressure monitoring system 22, and depending upon the particular design of the transmission at issue, the pump-motor arrangement 54 may be driven exclusively in a single direction. Additional description of a hydrostatic pump-motor arrangement suitable for usage as the pump-motor arrangement 54 is provided below in connection with the flow schematic of
With continued reference to
The pressure-scaled output signal 60 is supplied to a pressure sensor data source 62, which is fluidly coupled to the PSV 58 (or PSVs 58) contained in the pressure scaling device 56. The pressure sensor data source 62 includes or assumes the form of at least one pressure sensor 64, which generates pressure sensor data (an electronic signal) for input to the electronic controller 52 further included in the hydrostatic transmission pressure monitoring system 22. Accordingly, in embodiments, the pressure sensor 64 (or the pressure sensors 64) included in the pressure sensor data source 62 may be a transducer for converting the fluidic signal (the pressure-scaled output signal 60) to an electrical (digital or analog) signal suitable for application to the controller 52 via a wired or wireless connection represented by the arrow 66. The data generated by the pressure sensor data source 62 is generally referred to herein as “pressure sensor data” and may also contain additional data in embodiments, such data indicative of a low side pressure further contained in the hydraulic pump-motor circuit in implementations in which the pressure scaling device 56 contains multiple PSVs 58, as further discussed below in connection with
The term “controller,” as appearing throughout this document, is utilized in a non-limiting sense to generally refer to the processing architecture of the hydrostatic transmission pressure monitoring system 22. The controller 52 can encompass or may be associated with any practical number of processors, control computers, computer-readable memories, power supplies, storage devices, interface cards, and other standardized components. Further, the controller 52 of the hydrostatic transmission pressure monitoring system 22 may include or cooperate with any number of firmware and software programs or computer-readable instructions designed to carry-out the various process tasks, calculations, and control/display functions described herein. In one embodiment, the controller 52 includes or assumes the form of an engine control unit (ECU) associated with the tractor engine 34. During operation of the hydrostatic transmission pressure monitoring system 22, the controller 52 receives the pressure sensor data from the pressure sensor(s) 46, which the controller 52 utilizes this data to monitor the peak circuit pressure within the hydraulic pump-motor circuit of the pump-motor arrangement 54 and potentially perform other calculation or monitoring functions, as further discussed below. Additionally or alternatively, the controller 52 may output the current peak or high side circuit pressure (or other pressure-related parameters) to a display device located in the cabin of the tractor 20 for visual presentation to an operator of the tractor as, for example, a numerical readout, a virtual gauge, or other such graphic expressed on the screen of the display device.
As generically indicated by an arrow 68 in
Turning now to
The hydromechanical IVT 24 further contains a multi-modal planetary subsystem 44 including a planetary gear train 48, as previously described above in conjunction with
The backside of the pivoting yoke assembly 72 is depicted more clearly in the cutaway view of
Advancing to
The hydrostatic transmission pressure monitoring system 22 further includes a pressure scaling device 56 and a pressure sensor data source 62. In the illustrated example, the pressure sensor data source 62 contains or assumes the form of a single pressure sensor 64. The pressure sensor 64 may be transducer for converting the fluidic signal received via flow line 122 (the pressure-scaled output signal generated by the PSV 58, as described below) to an electrical signal suitable for application to the controller 52 via the wired or wireless data connection 66 (
In the illustrated example, the PSV 58 assumes the form of a spool-type valve including a housing or sleeve 112 in which a translating valve element or piston (hereafter, “spool 114”) is slidably disposed. In addition to the spool 114 and the surrounding sleeve 112, the PSV 58 further includes the follow ports, most or all of which are formed in the sleeve 112: (i) a first port (herein, the “PSV sense port”) fluidly coupled to the pump-motor circuit 108, 110 by a flow line 116, (ii) a second port (herein, the “PSV baseline pressure inlet”) fluidly coupled to a baseline pressure source 118 by a flow line 120, (iii) a third port (herein, the “PSV signal outlet”) fluidly coupled to the pressure sensor 64 by a flow line 122, (iv) a fourth port (herein, the “PSV drainage outlet”) fluidly coupled to a sump 124 by a flow line 126, (v) a fifth port (herein, the “PSV pressure balance port”) fluidly coupled to flow line 122 via a pressure balance flow line 128.
As further symbolically indicated in
Describing now the baseline (e.g., charge) pressure source 118 in greater detail, the baseline pressure source 118 can be realized utilizing any hydraulic device or combination of hydraulic devices suitable for supplying hydraulic fluid at a baseline pressure less than the peak circuit pressure within the hydraulic pump-motor circuit 108, 110. It may also be desirable for the pressure source 118 to supply hydraulic fluid at a baseline (e.g., charge) pressure at or above a maximum desired reading of the pressure sensor 64; a pressure sensor reading corresponding to torque saturation in the illustrated example. As indicated in
In the example flow schematic 102 of
The maximum permissible charge pressure, as selected via tuning of the pressure relief valve 136, will vary between different implementations. This stated, the maximum charge pressure may be less than 100 bar, preferably less than 50 bar, and more preferably less than or equal to 20 bar in at least some implementations. Due to the below-described functioning of the PSV 58, the pressure-scaled output signal generated by the pressure scaling device 56 and ultimately supplied to the pressure sensor 64 is maintained at or below the baseline (e.g., charge) pressure input supplied by the baseline pressure source 118. Consequently, when the charge is selected to be relatively low as compared to the peak or high side circuit pressures occurring within the hydraulic pump-motor circuit 108, 110 (which may approach or exceed 700 to 1000 bar in embodiments), the maximum or peak magnitude of the pressure-scaled output signal generated by the PSV 58 will likewise be limited to a small fraction of the peak (high side) circuit pressure occurring within the hydraulic pump-motor circuit 108, 110, as further discussed below.
The location at which the peak or high side pressure occurs within the hydraulic pump-motor circuit 108, 110 varies with time depending upon the direction in which the hydrostatic pump-motor arrangement 54 is driven. Consider an example scenario in which the hydraulic device 104 operates as a pump, the hydraulic device 106 operates as a motor under load, and the hydrostatic pump-motor arrangement 54 is driven in a first rotational direction in which flow within the hydraulic pump-motor circuit 108, 110 occurs in a clockwise direction in the context of the illustrated flow schematic 102. In this instance, the peak or high side pressure occurs within the right side of the hydraulic pump-motor circuit 108, 110 (within the flow loop section 110) as the hydraulic fluid discharged from the hydraulic device 104 (here, operating as a pump) performs work to turn the shaft of the hydraulic device 106 (operating as a motor) and thereby satisfy the torque demands placed on the hydrostatic pump-motor arrangement 54. Pressure build-up or accumulation consequently occurs within the flow loop section 110 resulting in a peak (high side) circuit pressure at this location of the hydraulic pump-motor circuit 108, 110. Concurrently, a low hydraulic pressure develops within the flow loop section 108 (the “low side” of the hydraulic pump-motor circuit 108, 110), with the charge pressure delivered to the flow loop section 108 via non-illustrated conduits and valving to reduce the likelihood of cavitation within the hydraulic device(s) 104, 106. Conversely, in an example scenario in which the hydraulic pump-motor circuit 108, 110 is driven in the opposing direction (e.g., counterclockwise in the schematic of
Different approaches can be employed to address this locational variability in the peak or high side circuit pressure. In the example of
The switching valve 138 is positioned to route the pressure within the flow loop section 108 to the sense port of the PSV 58 when the hydrostatic pump-motor arrangement 54 is driven in a direction at which the peak (high side) circuit pressure occurs within the left side or flow loop section 108 of the hydraulic pump-motor circuit 108, 110. Conversely, the switching valve 138 is positioned to port the pressure within the flow loop section 110 to the PSV 58 when the hydrostatic pump-motor arrangement 54 is driven in an opposing direction at which the peak (high side) pressure occurs within the opposing flow loop section 110. The switching valve 138 can transition between these positions in any suitable manner. In various embodiments, the switching valve 138 is pressure-actuated and transitions between the bistable positions in response to variations in the pressure differential across the inlets of the switching valve 138. In such embodiments, the switching valve 138 is conveniently implemented as a self-actuating or pressure-actuated ball valve; however, the switching valve 138 can assume any form suitable for providing such a self-actuated, pressure-routing function. In other instances, the switching valve 138 may be actuated in another manner, such as utilizing a solenoid operably coupled to the controller 52. In still other implementations, such a switching valve can be integrated into a common structure with a non-illustrated directional flow valve utilized to selectively route the charge pressure generated by the baseline (e.g., charge) pressure source 118 to the low side of the hydraulic pump-motor circuit 108, 110.
The operation of the PSV 58 will now be discussed in greater detail with reference to
The spool 114 of the PSV 58 is movable between two positional or translational extremes, as previously described. In a seated position, the spool 114 positioned such that the pin face 170 of the spool 114 (and the surrounding shoulder of the spool 114) seats on the ledge adjacent the PSV sense port 146. This position corresponds to the position denoted on the right side of the PSV spool symbol in
When the hydrostatic pump-motor arrangement 54 is driven under load, a highly elevated, peak circuit pressure occurs within the hydraulic pump-motor circuit 108, 110. This peak circuit pressure is routed to the PSV sense port 146 of the PSV 58 via operation of the switching valve 138 (
In the illustrated position shown in
In the above-described manner, the PSV 58 serves as a mechanical scaling mechanism, which generates a pressure-scaled output signal substantially proportional to the magnitude of the peak circuit pressure applied to the PSV sense port 146. For example, in various embodiments, the PSV 58 may be tuned (e.g., via sizing of the effective areas of the spool 114, the location and dimensions of the PSV ports, and the characteristics of the spring 166, if present) such that approximately 0% of the baseline input pressure appears at the PSV signal outlet 150 when the peak circuit pressure is below a minimum value (or at a zero value), approximately 50% of the baseline input pressure appears at the PSV signal outlet 150 when the peak circuit pressure is abut 50% of the expected operational pressure range, and approximately 100% (or some predetermined maximum fraction) of the baseline input pressure appears at the PSV signal outlet 150 when the peak circuit pressure reaches approximately 100% of the expected operational pressure range. The pressure sensing capabilities of the pressure sensor 64 may likewise be selected to accommodate the maximum expected pressures appearing at the PSV signal outlet 150, which will be equal to or less than the baseline (e.g., charge) input pressure across all positions of the PSV spool 114.
The pressure scaling function of the PSV 58 is achieved, at least in part, due to the low magnitude of the baseline input pressure as compared to the peak circuit pressure; and, further, due to differential in the effective surface areas of the opposing faces 168, 170 of the PSV spool 114. In this latter regard, the effective area of the spool face 168 exposed within the pressure balance chamber 162 may be at least twice, if not at least 10 times the effective area of the sense pin face 170 exposed at the PSV sense port 146 in various implementations of the PSV 58. Moreover, and as noted above, the baseline input pressure supplied to the baseline pressure inlet 148 may be significantly less (e.g., at least ten times less) than the peak circuit pressure in embodiments. In this regard, the baseline input pressure may be less than 50 bar, and perhaps may be around 20 bar, while the peak circuit pressure may approach or exceed 700 bar when the hydrostatic pump-motor arrangement 54 is driven in a particular direction under load. Further, and depending upon the manner in which the hydrostatic transmission pressure monitoring system 22 is implemented, the baseline input pressure may vary within limits; e.g., in one embodiment, variations of 25% or less in the baseline pressure may occur during operation of the baseline (e.g., charge) pressure source 118 (
Turning now to
There has thus been provided an example embodiment of a hydrostatic transmission pressure monitoring system including a pressure scaling device, which generates a reduced pressure, scaled fluidic signal (the pressure-scaled output signal) indicative of the peak or high side circuit pressure within a hydraulic pump-motor circuit of a hydromechanical IVT (or other hydrostatic transmission). In the above-described example embodiment, the pressure scaling device contained a single PSV, which was fluidly coupled to both sides or loop sections of the hydraulic pump-motor circuit via a switching valve. In embodiments in which the hydrostatic transmission contains a hydrostatic pump-motor arrangement driven exclusively in a single direction such that the peak circuit pressure occurs consistently within a particular side or loop section of the corresponding hydraulic pump-motor circuit, such a switching valve may be omitted and the sense port of the PSV may be directly fluidly coupled to the loop section in which the peak circuit pressure consistently occurs. Similarly, a switching valve may be omitted from the hydrostatic transmission pressure monitoring system in implementations in which the pressure scaling device contains two PSVs, each fluidly connected to a different side or loop section of the hydraulic pump-motor circuit. An example of such a hydraulic architecture will now be described in conjunction with
Addressing lastly
During operation of the hydrostatic transmission pressure monitoring system 186, and depending upon the particular direction in which the hydrostatic pump-motor arrangement 54 is driven, the peak or high side circuit pressure occurring within the hydraulic pump-motor circuit 108, 110 is supplied to the sense port of one of the PSVs 58-1, 58-2, which then generates a pressure-scaled output signal substantially proportional to or otherwise indicative of the sensed pressure. The corresponding pressure sensor 64-1, 64-2 then converts this fluidic signal to an electronic (digital or analog) signal included in the pressure sensor data 144, which is then forward to a controller (e.g., analogous to the controller 52 shown in
By virtue of the inclusion of two PSVs 58-1, 58-2 within the pressure scaling device 188, the hydrostatic transmission pressure monitoring system 186 achieves several benefits. First, the need for a switching valve, such as the switching valve 138 (
The following examples of the debris accumulation control system are further provided and numbered for ease of reference.
1. A hydrostatic transmission pressure monitoring system includes a hydrostatic transmission and a pressure sensor data source. The hydrostatic transmission includes, in turn, a transmission casing, a pivoting yoke assembly rotatably mounted in the transmission casing, a hydrostatic pump-motor arrangement containing a hydraulic pump-motor circuit at least partially formed in the pivoting yoke assembly, and a pressure scaling device fluidly coupled to the hydraulic pump-motor circuit. The pressure scaling device is configured to generate a pressure-scaled output signal substantially proportional to a peak circuit pressure within the hydraulic pump-motor circuit. The pressure sensor data source is fluidly coupled to the pressure scaling device and is configured to generate pressure sensor data indicative of the pressure-scaled output signal.
2. The hydrostatic transmission pressure monitoring system of example 1, further including a controller coupled to the pressure sensor data source and configured to utilize the pressure sensor data to monitor the peak circuit pressure within the hydraulic pump-motor circuit.
3. The hydrostatic transmission pressure monitoring system of example 2, wherein the hydrostatic transmission pressure monitoring system is utilized onboard a work vehicle having a work vehicle engine and a power takeoff (PTO) shaft. Further, the controller is configured to: (i) calculate a current torque transmitted through the hydrostatic pump-motor arrangement based, in part, on the peak circuit pressure; and (ii) selectively vary a power output of the work vehicle engine in response to variations in the current torque transmitted through the hydrostatic pump-motor arrangement relative to an estimated torque transmitted through the PTO shaft.
4. The hydrostatic transmission pressure monitoring system of example 1, wherein the hydrostatic transmission pressure monitoring system is utilized onboard a work vehicle. Additionally, the hydrostatic transmission further includes an input shaft, a first output shaft rotatably coupled to the input shaft along a first torque transmission path bypassing the hydrostatic pump-motor arrangement, and a second output shaft coupled to the input shaft along a second torque transmission path extending through the hydrostatic pump-motor arrangement.
5. The hydrostatic transmission pressure monitoring system of example 1, wherein the pressure scaling device includes a first pressure scaling valve (PSV) fluidly coupled to the pressure sensor data source and configured to generate the pressure-scaled output signal when the hydrostatic pump-motor arrangement is driven in at least a first rotational direction.
6. The hydrostatic transmission pressure monitoring system of example 5, wherein the pressure sensor data source includes a first pressure sensor fluidly coupled to the first PSV and located offboard the pivoting yoke assembly.
7. The hydrostatic transmission pressure monitoring system of example 5, wherein the first PSV includes a baseline pressure inlet at which a baseline input pressure is received, as well as a signal outlet at which the pressure-scaled output signal is generated from the baseline input pressure.
8. The hydrostatic transmission pressure monitoring system of example 7, further including a charge pressure source and a conduit. The charge pressure source is configured to supply the hydrostatic pump-motor arrangement with a charge pressure, while the conduit fluidly couples the charge pressure source to the baseline pressure inlet such that the charge pressure serves as the baseline input pressure.
9. The hydrostatic transmission pressure monitoring system of example 7, wherein the first PSV further includes a PSV sense port fluidly coupled to the hydraulic pump-motor circuit and at which the peak circuit pressure is received when the hydrostatic pump-motor arrangement is driven in at least the first rotational direction.
10. The hydrostatic transmission pressure monitoring system of example 9, wherein the first PSV further includes a spool and a sleeve in which the baseline pressure inlet, the signal outlet, and the PSV sense port are formed. The spool has a translational position within the sleeve controlling flow impedance from the baseline pressure inlet to the signal outlet, the translational position of the spool varying in conjunction with fluctuations in the peak circuit pressure received at the PSV sense port.
11. The hydrostatic transmission pressure monitoring system of example 5, wherein the hydraulic pump-motor circuit includes a first loop section containing the peak circuit pressure when the hydraulic pump-motor circuit is driven in the first rotational direction, and a second loop section containing the peak circuit pressure when the hydraulic pump-motor circuit is driven in a second rotational direction opposite the first rotational direction.
12. The hydrostatic transmission pressure monitoring system of example 11, wherein the hydrostatic transmission pressure monitoring system further includes a switching valve having a first inlet coupled to the first loop section, a second inlet coupled to the second loop section, and an outlet coupled to the first PSV.
13. The hydrostatic transmission pressure monitoring system of example 12, wherein the switching valve contains a valve element movable between: (i) a first position in which the switching valve routes a high pressure within the first loop section to the first PSV, while fluidly isolating the first PSV from the second loop section; and (ii) a second position in which the switching valve routes a high pressure within the second loop section to the first PSV, while fluidly isolating the first PSV from the first loop section.
14. The hydrostatic transmission pressure monitoring system of example 5, wherein the pressure sensor data source further includes a second PSV fluidly coupled to the pressure sensor data source. The second PSV is configured to generate the pressure-scaled output signal when the hydrostatic pump-motor arrangement is driven in a second rotational direction opposite the first rotational direction.
15. The hydrostatic transmission pressure monitoring system of example 1, wherein pressure-scaled output signal is at least ten times less than the peak circuit pressure when the hydrostatic pump-motor is driven in the first rotational direction.
There has thus been provided embodiments of a hydrostatic transmission pressure monitoring system, such a hydrostatic IVT pressure monitoring system, well-suited for deployment onboard work vehicles. The hydrostatic transmission pressure monitoring system incorporates unique structural features, including a pressure scaling device containing one or more PSVs, which facilitate peak or “high side” pressure monitoring during transmission operation. The pressure scaling device generates a pressure-scaled output signal, which is substantially proportional to (or otherwise indicative of) the peak pressure. At the same time, the pressure-scaled output signal is significantly less than the peak circuit pressure; e.g., in embodiments, the pressure-scaled output signal may be reduced relative to the peak circuit pressure by a factor of ten or more. Due to its reduced magnitude relative to the peak or high side circuit pressure, the pressure-scaled output signal can be measured utilizing pressure sensors having lower costs, higher accuracies, and/or greater durability levels as compared to specialized pressure sensors having high pressure sensing capabilities. Further, such pressure sensor(s) can be located offboard the pivoting yoke assembly, when included in the hydrostatic transmission, to ease sensor access and provide other benefits. A controller operably coupled to the sensor(s) can then utilize the data provided thereby to monitor the peak circuit pressure during transmission operation and, perhaps, utilize this data input to monitor other pressure-related parameters pertaining to the hydrostatic transmission, such as the torque transmitted through the hydrostatic pump-motor arrangement at any given juncture in time.
As used herein, the singular forms “a”, “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. Explicitly referenced embodiments herein were chosen and described in order to best explain the principles of the disclosure and their practical application, and to enable others of ordinary skill in the art to understand the disclosure and recognize many alternatives, modifications, and variations on the described example(s). Accordingly, various embodiments and implementations other than those explicitly described are within the scope of the following claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 9046160 | Hoff | Jun 2015 | B2 |
| 20090143952 | Chisholm | Jun 2009 | A1 |
| 20150120148 | Henson | Apr 2015 | A1 |
| Number | Date | Country |
|---|---|---|
| 102006000784 | Aug 2006 | DE |
| 102013221241 | May 2014 | DE |
| Entry |
|---|
| German Search Report issued in Germany Patent Application No. 102021115735.8, dated Jan. 3, 2022, 5 pages. |
| Number | Date | Country | |
|---|---|---|---|
| 20220024455 A1 | Jan 2022 | US |
