TORQUE CONTROL OF HYDRAULIC WORK MACHINES

TECHNICAL FIELD

[0001]The present disclosure relates to torque control of hydraulic work machines, such as earth moving machines. More particularly, the present disclosure relates to torque control by controlling the hydraulic flow rate change to applicable mechanisms that realize motion of work machine components.

BACKGROUND

[0002]Traditional swing systems are developed to meet higher slope capability requirements that require a higher torque system. Having additional torque available during operation on level ground can introduce unnecessary loads on swing motors, swing gears, swing pumps.

[0003]Japanese patent document JPH05263926A discloses a hydraulically driven circuit. When a sum of a travel load pressure and a working machine load pressure exceeds a sum of a spring and a pilot control pressure, an opening/closing valve is opened to decrease the amount of tilt in a variable capacity hydraulic pump and to limit the travel load pressure. The pilot control pressure is decreased by an electromagnetic proportional valve. A voltage applied to a solenoid portion of the electromagnetic proportional pressure reducing valve is adjusted by a control circuit. When the vehicle is on an ascending slope, the greater the angle of inclination, the greater the applied voltage is. When the vehicle is on a descending slope, the greater the angle of inclination, the voltage is decreased.

[0004]Engineering and product development resources continue to be deployed to reduce the system output torque during regular operation and to provide the additional torque for special operations at slopes that fall outside of the normal operating pitch and roll angle ranges.

SUMMARY

[0005]In one aspect of the present inventive concept, a torque control apparatus of a work machine is constructed to control motion of a work tool relative to a swing body of the work machine through a hydraulic system thereof. The control apparatus includes a pose sensor constructed to generate orientation data indicating an orientation of the work machine relative to the swing body thereof. A hydraulic flow control component is constructed to generate torque magnitude data corresponding to the orientation data. A machine control component is constructed to generate hydraulic flow rate data corresponding to the torque magnitude data. A variable flow rate pump is constructed to impel a flow rate in the hydraulic system corresponding to the hydraulic flow rate change data.

[0006]In an additional aspect of the present inventive concept, the hydraulic flow rate change control component is further constructed to select between torque magnitudes corresponding to respective orientations of the work machine.

[0007]In an additional aspect of the present inventive concept, the hydraulic flow rate change rate change control component reduces the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0008]In an additional aspect of the present inventive concept, the threshold condition is an angle from zenith of the undercarriage along roll or pitch axes.

[0009]In an additional aspect of the present inventive concept, wherein the variable flow rate pump is a variable displacement pump.

[0010]In an additional aspect of the present inventive concept, wherein the hydraulic flow rate change control component controls the pump upstroke/destroke of the variable displacement pump.

[0011]In an additional aspect of the present inventive concept, wherein the flow rate is controlled by a proportional integral control process.

[0012]In another aspect of the present inventive concept, an excavator is constructed to perform earth moving job tasks with a work tool positioned by a hydraulic system installed on the excavator. The excavator includes a pose sensor constructed to generate orientation data indicating an orientation of the excavator relative to a swing body thereof. A hydraulic flow rate change control component is constructed to generate torque magnitude data corresponding to the orientation data. A machine control component is constructed to generate pump upstroke/destroke rate data corresponding to the torque magnitude data. A variable flow rate pump constructed to impel a flow rate in the hydraulic system corresponding to the pump upstroke/destroke rate data.

[0013]In an additional aspect of the present inventive concept, wherein the hydraulic flow control component is further constructed to select between torque magnitudes corresponding to respective orientations of the work machine.

[0014]In an additional aspect of the present inventive concept, wherein the hydraulic flow control component reduces the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0015]In an additional aspect of the present inventive concept, wherein the threshold condition is an angle from zenith of the swing body along roll or pitch axes.

[0016]In an additional aspect of the present inventive concept, wherein the variable flow rate pump is a variable displacement pump.

[0017]In an additional aspect of the present inventive concept, wherein the machine control component controls the pump upstroke/destroke of the variable displacement pump.

[0018]In an additional aspect of the present inventive concept, wherein the flow rate is controlled by a proportional integral control process.

[0019]In yet another aspect of the present inventive concept, a torque control method of a work machine constructed to control motion of a work tool relative to a swing body of the work machine through a hydraulic system thereof. The method includes generating orientation data indicating an orientation of the work machine relative to the swing body thereof, generating torque magnitude data corresponding to the orientation data, generating pump upstroke/destroke data corresponding to the torque magnitude data, and impelling, by a variable displacement pump, a flow rate in the hydraulic system corresponding to the pump upstroke/destroke data.

[0020]In an additional aspect of the present inventive concept, further including selecting between torque magnitudes corresponding to respective orientations of the work machine.

[0021]In an additional aspect of the present inventive concept, further including reducing the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0022]In an additional aspect of the present inventive concept, wherein the threshold condition is an angle from zenith of the swing body along roll or pitch axes.

[0023]In an additional aspect of the present inventive concept, further including controlling the upstroke/destroke data in accordance with a proportional integral control process.

[0024]In an additional aspect of the present inventive concept, further including controlling the pump upstroke/destroke of the variable displacement pump.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025]FIG. 1 is an illustration of an exemplary excavator by which the present inventive concept can be embodied.

[0026]FIG. 2 is a schematic block diagram of an exemplary torque control apparatus by which the present inventive concept can be embodied.

[0027]FIG. 3 is a graph of an exemplary controlled flow rate in an embodiment of the present inventive concept.

[0028]FIG. 4 is a flow diagram of an exemplary torque control process by which the present inventive concept can be embodied.

DESCRIPTION OF EXAMPLE EMBODIMENTS

[0029]The present inventive concept is best described through certain embodiments thereof, which are described in detail herein with reference to the accompanying drawings, wherein like reference numerals refer to like features throughout. It is to be understood that the term invention, when used herein, is intended to connote the inventive concept underlying the embodiments described below and not merely the embodiments themselves. It is to be understood further that the general inventive concept is not limited to the illustrative embodiments described below and the following descriptions should be read in such light.

[0030]Additionally, the word exemplary is used herein to mean, “serving as an example, instance or illustration.” Any embodiment of construction, process, design, technique, etc., designated herein as exemplary is not necessarily to be construed as preferred or advantageous over other such embodiments.

[0031]The figures described herein include schematic block diagrams illustrating various interoperating functional modules. Such diagrams are not intended to serve as electrical schematics and interconnections illustrated are intended to depict signal flow, various interoperations between functional components and/or processes and are not necessarily direct electrical connections between such components. Moreover, the functionality illustrated and described via separate components need not be distributed as shown, and the discrete blocks in the diagrams are not necessarily intended to depict discrete electrical components.

[0032]The techniques described herein are directed to torque control of heavy machinery. Upon review of this disclosure and appreciation of the concepts disclosed herein, the ordinarily skilled artisan will recognize other torque control contexts in which the present inventive concept can be applied. The scope of the present invention is intended to encompass all such alternative implementations.

[0033]FIG. 1 is an illustration of an exemplary excavator 10 by which the present inventive concept can be embodied. While an excavator is used as an example herein, it is to be understood that work machines other than excavators can embody the present inventive concept. Excavator 10 may include a swing body 30 pivotally coupled to an undercarriage 20 through a slew mechanism 25. Accordingly, swing body 30 may be rotated relative to the undercarriage 20 by command of an operator in operator cabin 32. Excavator 10 may also include a boom 12, a stick 14 and a work implement, such as bucket 16, by which job tasks are performed.

[0034]Excavator 10 may be outfitted with onboard signal/data processing resources that include processing and memory circuitry through which excavator control apparatus 150 may be realized. Excavator control apparatus 150 may include a pose sensor 154 constructed or otherwise configured to generate signals indicating an orientation in space of excavator 10. As used herein, the term “pose” is intended to connote roll/pitch/yaw (see coordinates 19) of excavator 10, as measured at swing body 30, relative to level ground (see coordinates 18).

[0035]Excavator control apparatus 150 may include a machine control component 156 that controls, among other things, hydraulic flow rate change in a swing hydraulic circuit of hydraulic system 40. As used herein, the term “hydraulic flow change rate” is intended to refer to changes in the volume of hydraulic fluid that passes through a reference plane per unit time. Swing torque may be determined from the hydraulic flow rate change. Machine control component 156 may implement a proportional-integral (PI) control technique that uses hydraulic flow change rate, such as may be provided by hydraulic flow rate control component 154, as a set point.

[0036]Excavator control apparatus 150 may include a variable flow rate pump 160 that impels hydraulic fluid through a hydraulic system 40 to achieve a desired torque. A pump control component 158 of machine control component 156 may follow the PI controlled signal/data provided thereto.

[0037]Embodiments of the present inventive concept reduce the swing system output torque during regular operation and provide additional torque for special operations at slopes that fall outside of the normal operating pitch and roll angle ranges. For example, if the working angles that fall outside ±5° from level, more torque is needed. Such may be achieved using a variable displacement pump 160 under control of a pump controller 158. A pump upstroke/destroke control component 154 may be constructed or otherwise configured to select between high and reduced torque operational modes. Switching between such operational modes may depend on the pose of excavator 10 meeting a threshold condition on pitch and/or roll angle thereof as measured by pose sensor 152.

[0038]FIG. 2 is a schematic block diagram of an exemplary torque control apparatus 200 by which the present inventive concept can be embodied. A pitch/roll monitor 210 may be deployed to determine an orientation of excavator 10 relative to level ground. When the orientation of excavator 10 meets a threshold condition, e.g., a maximum grade on which excavator 10 can operate without reducing torque, a torque controller 220 may select between high and reduced torque modes. This may be performed without human intervention according to the pose of excavator 10 by embodiments of the present inventive concept. Torque controller 220 may generate a signal indicating the pump upstroke/destroke rate that produces the appropriate torque magnitude, which may be provided to PI controller 225. PI controller 225 may track the flow rate change that produces torque in a swing motion of swing body 30. Additionally, PI control component may correct throughput of variable displacement pump 235, through variable displacement pump control component 230 to maintain a desired swing torque during swing motion/stall conditions. Variable displacement pump 235 may include an internal control valve in the pump to control the pump upstroke and destroke. Pump upstroke/destroke rate determines swing torque regarding linkage inertia. The upstroke/destroke signal produced by PI controller 225 may be provided to variable displacement pump controller 230, which compels a variable displacement pump 235 to generate the appropriate torque.

[0039]FIG. 3 is a graph of an exemplary torque in an embodiment of the present inventive concept. In region 310, excavator 10 may be on a slope that meets a threshold condition, e.g., slope being greater than θ_R. At some time, excavator 10 may become more inclined and greater torque is desired. In region 320, excavator 10 may be operated in a reduced torque mode that depends on a pitch/roll angle. The torque for a given slope angle may be contained in a lookup table in lookup table memory 240. It is to be understood that, while FIG. 3 depicts a linear relationship between torque and slope angle in region 320, other torque/slope relationships, including nonlinear relationships, may be implemented by embodiments of the present inventive concept. When the slope angle is greater than angle θ_F, excavator 10 may transition to maximum torque mode in region 330, in which no further torque may be achieved.

[0040]FIG. 4 is a flow diagram of an exemplary torque control process 400 by which the present inventive concept can be embodied. In operation 405, excavator 10 may perform job tasks and in operation 415, it may be determined whether a current machine pose 410 is greater than a threshold for high torque operation. If so, process 400 may transition to operation 420 by which the hydraulic fluid flow rate change generating the torque is reduced for reduced torque operation. If the threshold condition of operation 415 is not met, process 400 may transition back to operation 405 and may continue from that point. In operation 425, it is determined whether the current job task is complete and, if so, process 400 may terminate. Otherwise, process 400 may transition back to operation 405 and may continue from that point.

[0041]Certain embodiments of the present general inventive concept provide for the functional components to manufactured, transported, marketed and/or sold as processor instructions encoded on computer-readable media. The present general inventive concept, when so embodied, can be practiced regardless of the processing platform on which the processor instructions are executed and regardless of the manner by which the processor instructions are encoded on the computer-readable medium.

[0042]It is to be understood that the computer-readable medium described above may be any non-transitory medium on which the instructions may be encoded and then subsequently retrieved, decoded and executed by a processor, including electrical, magnetic and optical storage devices. Examples of non-transitory computer-readable recording media include, but not limited to, read-only memory (ROM), random-access memory (RAM), and other electrical storage; CD-ROM, DVD, and other optical storage; and magnetic tape, floppy disks, hard disks and other magnetic storage. The processor instructions may be derived from algorithmic constructions in various programming languages that realize the present general inventive concept as exemplified by the embodiments described above.

[0043]Embodiments of the disclosed subject matter can also be as set forth according to the following parentheticals.

[0044](1). A torque control apparatus of a work machine constructed to control motion of a work tool relative to a swing body of the work machine through a hydraulic system thereof, the control apparatus comprising a pose sensor constructed to generate orientation data indicating an orientation of the work machine relative to the undercarriage thereof, a hydraulic flow control component constructed to generate torque magnitude data corresponding to the orientation data, a machine control component constructed to generate hydraulic flow rate change data corresponding to the torque magnitude data, and a variable flow rate pump constructed to impel a flow rate in the hydraulic system corresponding to the hydraulic flow rate change rate data.

[0045](2). The torque control apparatus of (1), wherein the hydraulic flow control component is further constructed to select between torque magnitudes corresponding to respective orientations of the work machine.

[0046](3). The torque control apparatus of (2), wherein the hydraulic flow control component reduces the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0047](4). The torque control apparatus of (3), wherein the threshold condition is an angle from zenith of the undercarriage along roll or pitch axes.

[0048](5). The torque control apparatus of (1), wherein the variable flow rate pump is a variable displacement pump.

[0049](6). The torque control apparatus of (5), wherein the hydraulic flow control component controls the pump upstroke/destroke of the variable displacement pump.

[0050](7). The torque control apparatus of (1), wherein the flow rate is controlled by a proportional integral control process.

[0051](8). An excavator constructed to perform earth moving job tasks with a work tool positioned by a hydraulic system installed on the excavator, the excavator comprising a pose sensor constructed to generate orientation data indicating an orientation of the excavator relative to a swing body thereof, a hydraulic flow control component may be constructed to generate torque magnitude data corresponding to the orientation data, A machine control component may be constructed to generate pump upstroke/destroke rate data corresponding to the torque magnitude data; and a variable flow rate pump constructed to impel a hydraulic flow rate change in the hydraulic system corresponding to the pump upstroke/destroke rate data.

[0052](9). The excavator of (8), wherein the hydraulic flow control component is further constructed to select between torque magnitudes corresponding to respective orientations of the work machine.

[0053](10). The excavator of (9), wherein the hydraulic flow control component reduces the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0054](11). The excavator of (10), wherein the threshold condition is an angle from zenith of the swing body along roll or pitch axes.

[0055](12). The excavator of (8), wherein the variable flow rate pump is a variable displacement pump.

[0056](13). The excavator of (12), wherein the machine control component controls the pump upstroke/destroke of the variable displacement pump.

[0057](14). The excavator of (8), wherein the flow rate is controlled by a proportional integral control process.

[0058](15). A torque control method of a work machine constructed to control motion of a work tool relative to a swing body of the work machine through a hydraulic system thereof, the method comprising generating orientation data indicating an orientation of the work machine relative to the swing body thereof, generating torque magnitude data corresponding to the orientation data, generating pump upstroke/destroke data corresponding to the torque magnitude data, and impelling, by a variable displacement pump, a hydraulic flow rate change in the hydraulic system corresponding to the pump upstroke/destroke data.

[0059](16). The torque control method of (15), further comprising selecting between torque magnitudes corresponding to respective orientations of the work machine.

[0060](17). The torque control method of (16), further comprising reducing the torque magnitude responsive to the orientation of the work machine meeting a threshold condition.

[0061](18). The torque control method of (17), wherein the threshold condition is an angle from zenith of the swing body along roll or pitch axes.

[0062](19). The torque control method of (15), further comprising controlling the upstroke/destroke data in accordance with a proportional integral control process.

[0063](20). The torque control method of (15), further comprising controlling the pump upstroke/destroke of the variable displacement pump.

INDUSTRIAL APPLICABILITY

[0064]Large hydraulic earth moving machines require additional torque during operation on sloped ground. When on a slope, an excavator, for example, must contend with the inertia of the swing body, particularly when the excavator bucket is loaded. On level ground, the axis of rotation of the swing body is perpendicular to that level ground, thus the swing mechanism is subject only to forces in a plane that is parallel to the level ground. On sloped ground, however, the axis of rotation is nonparallel to the level ground, the swing mechanism is subject to additional forces in a plane that is perpendicular to the level ground.

[0065]Operating on level ground at high torque can introduce unnecessary loads on swing motors, swing gears, swing pumps, additional heat, and in general, a reduction in machine fuel efficiency. Reducing torque on level surfaces can thus extend the lifetime of certain components over constant torque applications. The present inventive concept identifies the slope angle on which the excavator is positioned and adjusts the torque accordingly. A variable displacement pump, for example, may be used to increase or decrease the output torque by adjustments to the stroke/destroke distances within the pump. By way of the present inventive concept, the lifetime of the swing mechanism can be extended.

[0066]The descriptions above are intended to illustrate possible implementations of the present inventive concept and are not restrictive. Many variations, modifications and alternatives will become apparent to the skilled artisan upon review of this disclosure. For example, components equivalent to those shown and described may be substituted therefore, elements and methods individually described may be combined, and elements described as discrete may be distributed across many components. The scope of the invention should therefore be determined not with reference to the description above, but with reference to the appended claims, along with their full range of equivalents.