Power control system for traction motor and tool pump motor of electromechanical machine

Abstract

An electric power system for a machine includes an electric power source. The power system also includes a tool pump for powering the work tool and a tool pump electric motor. An electric traction motor is operably coupled to the traction device. The electronic controller stores a plurality of rim tension torque curves. The electronic controller is configured to determine whether the electric power source is in a power limited state, after it is determined that the electric power source is in the power limited state, action is adopted to reduce the rim tension torque of the traction device from a first rim tension torque curve in the multiple rim tension torque curves to a lower second rim tension torque curve in the multiple rim tension torque curves; wherein the selection of the second rim tension torque curve is based on the power usage of the tool pump electric motor.

Description

Technical Field

[0001] The present invention relates generally to an electric machine having separate traction motor and tool pump motor, and more particularly to a system for controlling the distribution of electrical power between the two motors. Background Art

[0002] Many machines used in construction and mining environments include power systems for actuating traction devices (e.g., tires) and work tools (e.g., buckets). More specifically, these power systems typically include a power source that provides torque through a transmission to one or more traction devices of the machine and a pump associated with a hydraulic system that drives the work tool to move. An internal combustion engine is a common power source used in the power systems of such machines. The power system of an internal combustion machine generally also includes a multi-stage or continuously variable transmission. In the case of a machine powered by an internal combustion engine with a multi-stage transmission, the physical connection between the engine, traction devices, and the transmission manages the power delivery to the traction devices and the tool pump, including coordination between the traction devices and the tool pump when limited power is available. This management of power delivery to the traction devices and the tool pump is controlled by the machine having a continuously variable transmission.

[0003] Internal combustion engines may emit undesirable exhaust emissions and other pollutants during operation. In addition, improving the fuel efficiency of machinery has become increasingly important, for example, due to the rising costs associated with fossil fuels. One solution to these problems is a power system that utilizes electric motors to provide torque to the traction device and tool pump of the machine. However, the use of electric motors in the power system of a machine may pose other challenges. For example, operating an electric machine may provide unfamiliar feedback to an operator who is accustomed to operating a machine powered by an internal combustion engine.

[0004] U.S. Patent No. 9,139,981 ("the '981 patent"), assigned to the assignee of the present application, describes a system for reducing rim pull on a machine having independent front and rear power systems and hydraulic systems. The system disclosed in the '981 patent is capable of reducing rim pull from the rear wheels first and then from the front wheels when it is determined that a machine tool is being used for operation. However, the '981 patent does not recognize the problems associated with power management and control in electric power systems. Summary of the invention

[0005] In one aspect, the present invention describes an electric power system for a machine having a traction device and a work tool. The electric power system includes an electric power source and a tool pump for providing power to the work tool. An electric traction motor is operably coupled to the electric power source for driving the traction device. A tool pump electric motor is operably coupled to the electric power source and the tool pump. An electronic controller stores a plurality of rim pull torque curves. The electronic controller is configured to determine whether the electric power source is in a power limited state. Upon determining that the electric power source is in a power limited state, the controller takes action to reduce the rim pull torque of the traction device from a first rim pull torque curve of the plurality of rim pull torque curves to a lower second rim pull torque curve of the plurality of rim pull torque curves, wherein the selection of the second rim pull torque curve is based on the power usage of the tool pump electric motor.

[0006] In another aspect, the present invention describes a machine comprising a frame, a traction device supported on the frame, and a work tool supported on the frame. An electric power system is supported on the frame for driving the traction device and providing power to the work tool. The electric power system includes an electric power source, a tool pump for providing power to the work tool, an electric traction motor operably connected to the electric power source for driving the traction device, and a tool pump electric motor operably connected to the electric power source and the tool pump. An electronic controller stores a plurality of rim pull torque curves. The electronic controller is configured to determine whether the electric power source is in a power-limited state. Upon determining that the electric power source is in a power-limited state, the controller takes action to reduce the rim pull torque of the traction device from a first rim pull torque curve among the plurality of rim pull torque curves to a lower second rim pull torque curve among the plurality of rim pull torque curves, wherein the selection of the second rim pull torque curve is based on the power usage of the tool pump electric motor.

[0007] In yet another aspect, the present invention describes a method for controlling an electric power system of a machine. The electric power system includes an electric power source, a tool pump for providing power to a work tool, an electric traction motor for driving a traction device, and a tool pump electric motor. The method includes determining whether the electric power source is in a power-limited state. After determining that the electric power source is in a power-limited state, the method includes reducing the rim pull torque of the traction device from a first rim pull torque curve among a plurality of rim pull torque curves to a lower second rim pull torque curve among a plurality of rim pull torque curves. The selection of the second rim pull torque curve is based on the power usage of the tool pump motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 is a side view of an exemplary machine having a power control system according to the present invention.

[0009] Figure 2 is used for Figure 1 Schematic diagram of the mechanical electric power system.

[0010] Figure 3 yes Figure 1 A diagram of transmission output speed versus rimpull torque of a traction motor and a transmission of an electric power system includes a plurality of exemplary reduced rimpull torque curves according to the present invention.

[0011] Figure 4 is shown for controlling Figure 2 Flowchart of an exemplary process for an electric power system. DETAILED DESCRIPTION

[0012] Referring now to the drawings, wherein like reference numerals represent like elements throughout the drawings whenever possible, Figure 1 The mobile machine 100 is shown in a specific embodiment of a wheel loader, in this case, for loading, transporting and conveying materials around a work site. However, while the present invention focuses on the mobile machine 100 in the wheel loader embodiment, aspects of the present invention may be applicable to other types of mobile machines that perform some type of operation associated with industries such as mining, construction, agriculture, transportation, etc.

[0013] In the illustrated embodiment, the machine 100 includes a frame 102. To facilitate maneuverability, such as making sharp turns, the frame 102 may be an articulated frame, wherein the front and rear ends are pivotally connected at an articulated joint 104. To enable the machine 100 to move around a work surface in a mobile manner, the frame 102 may be supported on a plurality of traction devices 106, such as rotatable wheels that may include rubber tires. The wheels may be designated as power drive wheels for propelling the machine 100, steerable wheels for adjusting the direction of a wheel loader, or a combination thereof. Other suitable embodiments of the machine may include different traction devices 106, such as a continuous crawler including a closed belt member, the belt member being disposed around rollers and / or sprockets, whereby translation of the belt member transports the machine to the work surface.

[0014] In order to perform work-related tasks during operation, the machine 100 may include a work tool 108, in the illustrated embodiment a bucket, which in this case is operably associated with a lift mechanism 110 that can vertically raise and lower the work tool 108 relative to the work surface. The lift mechanism 110 can be a mechanical linkage assembled from a plurality of rigid links connected by pivot joints that can be articulated and moved relative to each other to controllably displace or reposition the work tool 108. In particular, the work tool 108 can be pivotally disposed at a distal end of the lift mechanism 110, which in turn can be pivotally connected (via a pivot joint 116) to a front end of the frame 102. A tilt mechanism 112 can also be provided to pivot the work tool 108 relative to the lift mechanism 110. In other embodiments of mobile machines, it should be understood that the work tool 108 can be other than a bucket, such as a fork member, a knife member, an auger member, etc.

[0015] The work tool 108 may have an associated hydraulic system 115 (see Figure 2 ), the hydraulic system 115 provides pressurized hydraulic fluid to operate the work tool 108. In this case, the hydraulic system 115 can provide pressurized hydraulic fluid to the lift mechanism 110 and the tilt mechanism 112 associated with the work tool 108. To this end, the mechanical hydraulic system may include a tool pump 117 having an outlet port (see Figure 2 ), the fluid is provided to the hydraulic system 115 through the outlet port. In some embodiments, the tool pump 117 can also provide power to other mechanical systems such as braking systems, steering systems, and transmission lubrication systems.

[0016] In an embodiment, the machine 100 may include a machine operator cabin 114 to accommodate an operator and / or operator input devices or controls for machine operation. For example, the input devices in the operator cabin 114 may include a travel input to control the movement of the machine 100 and a lift input to manipulate the work tool 108. Examples of the travel input and the lift input may include a hand wheel, a joystick, a pedal, a control lever, a knob, a keyboard, etc. The travel input may be configured to increase or decrease the travel speed of the machine 100 relative to the travel direction to accelerate, decelerate and / or stop the machine travel.

[0017] Reference Figure 2To provide power to one or more of the traction device 106 and the tool pump 117, the machine 100 includes an electric power system 120. The illustrated electric power system 120 includes an electric power source 122, which may include, for example, a battery pack supported on the frame 102. The battery pack may include one or more rechargeable batteries that store electrical energy that may be used to drive the operation of the electric power system 120 of the machine 100. In other embodiments, the electric power source 122 may utilize electricity supplied, for example, from an internal combustion engine operating in series with an associated generator or fuel cell.

[0018] The electric power system 120 also includes an electric traction motor 124 also supported on the frame 102 for providing power to the traction device and a tool pump electric motor 125 also supported on the frame for providing power to the tool pump 117. In particular, the electric power system 120 can be configured such that the electric power source 122 provides electrical energy to power the electric traction motor 124 and the tool pump electric motor 125. Although mentioned in the singular, more than one electric motor can be used for the traction motor and the tool pump motor, for example, two or more electric motors mechanically combined by a gear or gear train. The electric traction motor 124 and the tool pump electric motor 125 can be any known AC or DC motor, such as permanent magnet, induction, switched reluctance, or a hybrid configuration of the above, and can also be sealed, brushless and / or liquid cooled. Furthermore, in some embodiments, electric traction motor 124 may be configured and controlled such that machine 100 may be decelerated while using electric traction motor 124 as a generator, thereby converting kinetic energy associated with the wheel loader into electrical energy that may be stored in electric power source 122 or other electric power storage device.

[0019] In the illustrated embodiment, the electric traction motor 124 has an associated inverter 126 that is configured to convert and control electricity supplied by the electric power source 122 to the electric traction motor 124. For example, the inverter 126 may be configured to control the frequency of the electric power provided to the traction motor 124, thereby controlling the speed and output torque of the motor.

[0020] To further adjust the speed and / or torque generated by the electric traction motor 124, the electric power system 120 may include a multi-speed transmission 130. More specifically, the multi-speed transmission 130 may include a gear train or gearbox supported on the frame 102 that facilitates adjusting the power generated by the electric traction motor 124 and transmitting it to the traction device 106 of the machine 100. The multi-speed transmission 130 may be adapted to be operably coupled to the electric traction motor 124. Such coupling may be achieved, for example, by selectively using one or more clutches, such as a forward travel clutch and a reverse travel clutch. As with the electric power source 122, the electric traction motor 124, and the tool pump electric motor 125, the multi-speed transmission 130 may be supported on the frame 102.

[0021] The multi-speed transmission 130 may be configured to set a plurality of different gear ranges that may enable the machine 100 to achieve motion in both a forward direction and a reverse direction. For example, the multi-speed transmission 130 may be configured to adjust the output speed and torque from the electric traction motor 124 to a plurality of ranges or settings, such as two, three, four or more forward output speed and torque ranges and one reverse speed and torque range. The multi-speed transmission 130 may also include a transmission output shaft 132, through which the power output (e.g., rotational power output) received from the electric traction motor 124 may be delivered to other components of the electric power system 120.

[0022] To facilitate controlled operation of the electric power system 120, the electric power system 120 may be operatively associated with a control system embodied in an electronic controller 140, sometimes referred to as an electronic control module (ECM) or an electronic control unit (ECU). The electronic controller 140 may be a programmable computing device and may include one or more microprocessors for executing software instructions and processing computer-readable data. Examples of suitable microprocessors include programmable logic devices such as field programmable gate arrays ("FPGAs"), dedicated or custom logic devices such as application-specific integrated circuits ("ASICs"), gate arrays, complex programmable logic devices, or any other suitable type of circuit or microchip. To store application software and data for controlled operation of the electric power system, the electronic controller 140 may include non-transitory computer-readable and / or writable memory, such as read-only memory ("ROM"), random access memory ("RAM"), EPROM memory, flash memory, or another more permanent storage medium such as magnetic or optical memory. To interact and network with other operating systems on the machine 100, the electronic controller 140 may include an input / output interface for electronically sending and receiving non-transitory data and information. The input / output interface may be physically implemented as a data port, serial port, parallel port, USB port, jack, etc., to communicate via wires, cables, optical fibers, or other communication bus systems through any suitable communication protocol (such as CAN bus, WiFi, Bluetooth, or cellular communication standards). The electronic controller 140 may be associated with other software, including any suitable instruction sets, programs, applications, routines, libraries, databases, etc., for performing its functions. Although in Figure 2 Electronic controller 140 is shown as a single discrete unit, but in other embodiments, electronic controller 140 and its functionality may be distributed among a number of different and separate components, including various components and functions located on machine 100 and / or at an off-machine operator station.

[0023] In this case, the electronic controller 140 can communicate with the inverter 126, the electric traction motor 124, the multi-speed transmission 130, and the tool pump electric motor 125. The data lines of the electronic communication network between the electronic controller 140 and these systems of the electric power system 120 are Figure 2 It is represented by dotted lines, which can be embodied as a CAN bus or a similar protocol, and can use wires or optical fibers as physical transmission media.

[0024] When the electric power source 122 is in a power limited state, i.e., when the electric power source 122 has limited available power, the electronic controller 140 may be configured to coordinate how much power is consumed between the electric traction motor 124 and the tool pump electric motor 125 during certain operating conditions. Under such operating conditions, the combined power usage of the electric traction motor 124 and the tool pump electric motor 125 exceeds a predetermined threshold power level. To this end, the controller 140 may be configured to monitor the current electric traction motor power usage and the current tool pump electric motor power usage. For example, the electric traction motor power usage may be monitored via a sensor 142 that is arranged to monitor the speed of the output shaft 132 of the multi-speed transmission 130 and communicates with the electronic controller 140, while the tool pump electric motor power usage may be monitored by the electronic controller 140 via a feedback signal from the tool pump electric motor 125.

[0025] According to some embodiments, the predetermined threshold power level may be based on a percentage of the maximum power output of the electric power source 122 at a particular time and operating condition. More specifically, the predetermined threshold power level may be at or near the maximum power output of the electric power source 122 at a given time. Alternatively, the predetermined threshold power level may be based on the remaining or available electric power of the electric power source 122. In other words, when the power usage of the electric traction motor 124 and the tool pump electric motor 125 will cause the remaining electric power of the electric power source 122 to be less than a predetermined amount of available power, the power demand may be considered to exceed the predetermined threshold. In such a case, the available power output from the electric power source 122 is in a restricted or limited state, and the electronic controller 140 is called upon to determine how the power from the electric power source 122 should be allocated between the electric traction motor 124 and the tool pump electric motor 125. In particular, when the available power is limited, the controller may need to send less power to the electric traction motor 124 than the power required by the operator to ensure that the power delivered to the tool pump electric motor 125 is at or near the level required by the operator. In such a situation, the electronic controller 140 will prioritize power delivery to the tool pump electric motor 125 over power delivery to the electric traction motor 124 .

[0026] To assist the electronic controller 140 in determining how to distribute electrical power between the electric traction motor 124 and the tool pump electric motor 125 , the electronic controller 140 may be configured with a plurality of rim pull curves. Figure 3Exemplary plots of output speed versus rim-pull torque of the multi-speed transmission 130 are provided, including a plurality of rim-pull torque curves 143, 144, 145, 146, 147, and 148. Each rim-pull curve provides a potential transmission output speed versus rim-pull response achievable at a traction device via the electric traction motor 124 operating through the multi-speed transmission 130, depending on the amount of electric power available from the electric power source 122 and the power required by the tool pump electric motor 125.

[0027] In this case, the outermost rim-pull curve 143 represents the rim-pull curve used during normal operation, i.e., when there is sufficient power from the electric power source 122 to normally operate the electric traction motor 124 (i.e., when the electric power source 122 is not in a power-limited state). However, when the electric power source 122 is in a limited condition, such as when the combined power usage of the electric traction motor 124 and the tool pump electric motor 125 exceeds a predetermined power level, the electronic controller 140 can be configured to reduce the power of the electric traction motor 124 by switching the electric traction motor 124 and the multi-speed transmission 130 to a rim-pull torque curve 144, 145, 146, 147, or 148 that is lower or reduced than the current rim-pull torque curve (e.g., 143) in order to provide the required power to the tool pump electric motor 125. The reduced rim pull curve 144, 145, 146, 147 or 148 allows the electric traction motor 124 to consume less electric power from the electric power source 122, leaving more power available for the tool pump electric motor 125. In addition, as the operator requires more power for the tool pump electric motor 125, the controller will continuously reduce the rim pull torque at the traction device to a lower rim pull curve 145, 146, 147 or 148 to further reduce the power consumption of the electric traction motor 124, thereby making more power available for the tool pump electric motor 125. Figure 3 The decreasing direction with increasing tool pump electric motor power is indicated by arrow 149. Figure 3 In the illustrated embodiment, a total of six rim-pull force curves 143, 144, 145, 146, 147, and 148 are stored in the electronic controller 140. However, in other embodiments, the electronic controller 140 may be provided with more or fewer rim-pull force torque curves.

[0028] Industrial Applicability

[0029] The present invention is applicable to any type of electric power system that provides power to both an electric traction motor and a tool pump electric motor. Thus, the present invention is applicable to a variety of machines that have the ability to move around a work site while performing some type of operation using a work tool. In addition, the multiple rim pull curves 143, 144, 145, 146, 147 and 148 stored and utilized by the electronic controller can be configured to provide the operator of the machine 100 with the feel of a power system that is powered by an internal combustion engine (such as a diesel engine). In particular, the use of a series of continuously decreasing rim pull curves 143, curves 144, 145, 146, 147 and 148 and the shape of each curve can be designed to allow the electric power system 120 to mimic the performance and operator feel of a machine powered by a diesel engine under the same or substantially similar operating conditions, i.e., when a diesel engine-driven machine is operated under power-limited or power-restricted conditions. Providing a familiar operating feel to the operator can improve the operating performance and acceptance of the machine powered by electricity.

[0030] Reference Figure 4 , and generally in accordance with the preceding figures, an exemplary process 150 is shown that may be executed by the electronic controller 140 for controlling the distribution of electric power to the electric traction motor 124 and the tool pump electric motor 125 in the machine 100 having the electric power system 120. As described above, the disclosed process has particular applicability to situations when the electric power source 122 is in a power-limited state. Figure 4 The process depicted in the flowchart of for accomplishing these tasks may include a series of steps or instructions implemented as non-transitory computer-executable software code in the form of an application or program executed by the electronic controller 140.

[0031] In step 152 of process 150, the electronic controller 140 receives signals indicating an electric traction motor power demand and a tool pump electric motor demand. For example, these demands may be initiated by an operator of the machine 100, such as via an input device disposed in the operator's cabin 114. In step 154, the electronic controller 140 determines current electric traction motor power usage. This may be determined, at least in part, using a signal from a transmission output speed sensor 142 that is in communication with the electronic controller 140. In step 156, the electronic controller 140 determines current tool pump power usage. The electronic controller 140 may determine tool pump power usage, at least in part, using a feedback signal from the tool pump electric motor 125.

[0032] In step 158, the electronic controller 140 determines whether the electric power source 122 is in a power limited state. This may be accomplished using the determination of the current traction motor power usage from step 154 ​​and the determination of the current tool pump power usage from step 156. If the electronic controller 140 determines that the electric power source 122 is in a power limited state, then in step 160, the electronic controller 140 directs the electric power system 120 to provide the required electric traction motor power and tool pump electric motor power. If the electric power source 22 is in a power limited state, then in step 162, the electronic controller 140 reduces the rim pull torque at the traction device 106 using one of the plurality of reduced rim pull curves 144, 145, 146, 147, or 148 that is lower than the current rim pull curve, thereby reducing power to the electric traction motor 124. As described above, the selection of the reduced rim pull force curve 144, 145, 146, 147 or 148 will depend on the tool pump motor demand, with successively lower rim pull force torque curves being selected as the tool pump electric motor power demand increases. In step 164, this power reduction to the electric traction motor 124 allows the controller to send the required power to the tool pump electric motor 125.

[0033] It should be understood that the foregoing description provides examples of the disclosed systems and techniques. However, it is contemplated that other implementations of the present invention may differ from the foregoing examples in detail. All references to the present invention or its examples are intended to reference the specific examples discussed at the time and are not intended to imply any limitations on the scope of the present invention more generally. All distinctions and divergent language about certain features are intended to illustrate a lack of preference for these features, but are not completely excluded from the scope of the present invention, unless otherwise stated.

[0034] Unless otherwise indicated herein, recitation of ranges of values ​​herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or clearly contradicted by context.

[0035] In the context of describing the invention (especially in the context of the appended claims), the use of the terms "a" and "an" and "the" and "at least one" or the term "one or more" and similar referents should be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term "at least one" after a list of one or more items (e.g., "at least one of A and B" or "one or more of A and B") should be construed to mean one item selected from the listed items (A or B) or any combination of two or more of the listed items (A and B; A, A and B; A, B and B), unless otherwise indicated herein or clearly contradicted by context.

[0036] Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Additionally, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or clearly contradicted by context.

Claims

1. An electric power system for a machine having a traction device and a work tool, the electric power system comprising: Electric power source; a tool pump for providing power to the work tool; an electric traction motor operably coupled to the electric power source to drive the traction device; a tool pump electric motor operably coupled to the electric power source and the tool pump; as well as An electronic controller storing a plurality of rim pull torque curves, the electronic controller being configured to: determining whether the electric power source is in a power limited state; and Taking action to reduce the rim-pull torque of the traction device from a first rim-pull torque curve of the plurality of rim-pull torque curves to a lower second rim-pull torque curve of the plurality of rim-pull torque curves upon determining that the electric power source is in a power limited state, wherein selection of the second rim-pull torque curve is based on power usage of the tool pump electric motor.

2. The electric power system of claim 1, wherein the electric power source is a battery pack.

3. The electric power system of claim 1 further comprising a multi-speed transmission operably coupled to the electric traction motor and having an output shaft operably coupled to the traction device. 4 . The electric power system of claim 3 , further comprising a sensor arranged to sense a speed of the output shaft of the multi-speed transmission.

5. The electric power system according to claim 4, wherein: The electronic controller is in communication with the electric traction motor, the tool pump electric motor, the multi-speed transmission, and the sensors.

6. The electric power system according to claim 5, wherein: The electronic controller determines whether the electric power source is in the power limited state based on the signal from the sensor and a feedback signal from the tool pump electric motor.

7. The electric power system of claim 1, wherein: The electronic controller determines that the electric power source is in the power limited state when the power consumed by the electric traction motor and the tool pump electric motor exceeds a predetermined level.

8. The electric power system of claim 1, wherein: The electronic controller selects the second rimpull torque curve based on being able to provide all required power to the tool pump electric motor.

9. A machine comprising the electric power system of claim 1, the machine comprising: frame; The traction device supported on the frame; a working tool supported on the frame; as well as The electric power system is supported on the frame for driving the traction device and providing power to the work tool.

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