Description

TRANSMISSION DOWNSHIFT CONTROL SYSTEM

Technical Field

The present disclosure is directed to a transmission control system and, more particularly, to transmission downshift control system.

Background

Machines such as, for example, wheel loaders, dozers, backhoes, dump trucks, and other heavy equipment are used to perform many tasks. To effectively perform these tasks, the machines require an engine that provides significant torque through a transmission to one or more ground engaging devices or work implements. Often, these machines utilize an automatic transmission having a plurality of gears that are selectively engaged in predetermined combinations to produce desired gear output ratios.

Under certain circumstances, a downshift procedure may be necessary. In addition, skipping a gear output ratio during the downshift procedure may be more efficient than downshifting through each gear output ratio. Conventional automatic transmissions determine such circumstances by relying on a combination of operator inputs, sensed machine conditions, and environmental conditions. When determining whether to skip a gear output ratio during a downshift operation, the transmission control system compares the machine and environmental conditions to algorithms, maps, charts, and/or graphs. However, because the control system must receive and interpret data from the operator, machine, and environment, which requires a certain amount of time, determining whether to skip a gear output ratio during a downshift may contribute to an undesirable delay between the moment conditions require downshifting and the moment the downshift function actually occurs.

U.S. Patent No. 6,553,301 (the '301 patent) issued to Chhaya et al. on 22 April 2003 discloses a method that may reduce the delay between the moment conditions require a downshift and the moment the shift actually occurs. The system disclosed in the '301 patent continuously monitors and stores torque requests made by a driver. The system uses the stored torque request data to determine whether the driving style of the driver is aggressive or conservative. If the driver is aggressive, more frequent, faster, and higher torque variations may be required. If the driver is conservative, less frequent, slower, and lower torque variants may be required. As the vehicle is driven, the transmission control system anticipates the driver's gear shifting needs based on the driving style of the driver. In particular, the control system anticipates the optimal transmission gear output ratio for a particular situation that meets the needs of the driver's driving style before the situation actually occurs.

Although the system disclosed by the '301 patent may reduce the delay between the moment conditions require a downshift procedure and the moment the shift actually occurs, its use may be limited. In particular, the system focuses on the operator's driving style when anticipating the optimal transmission gear output ratio for the current situation. However, machine and environmental conditions independent of an operator's driving style may require skipping a gear output ratio during a downshift procedure. Under such circumstances, the system of the '301 patent may not be able to reduce the delay between the moment a downshift procedure is needed and the moment the shift actually occurs.

The disclosed system is directed to overcoming one or more of the problems set forth above.

Summary

In one aspect, the present disclosure is directed toward a power train for a machine including a transmission having a plurality of gears configured to produce multiple output ratios when selectively engaged. In addition, the power train includes at least one sensor configured to sense at least

one parameter indicative of a condition requiring a disablement of a gear output ratio during a downshifting event. The power train further includes a controller configured to regulate the transmission in either a first or a second mode in response to the at least one parameter. At least one of the gear output ratios is disabled during downshifting events occurring while the controller regulates the transmission in the first mode. Furthermore, all gear output ratios are available during downshifting events occurring while the controller regulates the transmission in the second mode.

Consistent with another aspect of the disclosure, a method is provided for operating a transmission. The method includes sensing at least one parameter indicative of a current condition requiring a disablement of a gear output ratio during downshifting events. In addition, the method includes comparing the at least one current condition to at least one previous condition occurring during previous downshifting events. The method further includes selectively engaging a plurality of gears in either a first or a second mode in response to the comparison.

Brief Description of the Drawings

Fig. 1 is a diagrammatic illustration of a machine at a worksite;

Fig. 2 is a pictorial illustration of an exemplary disclosed operator station for use with the machine of Fig. 1 ;

Fig. 3 is an exemplary disclosed power train for use with the machine of Fig. 1; and

Fig. 4 is a flow diagram illustrating an exemplary method for operating the transmission of the power train illustrated in Fig. 3.

Detailed Description

Fig. 1 illustrates an exemplary machine 10 having multiple systems and components that cooperate to accomplish a task. The tasks performed by machine 10 may be associated with a particular industry such as

-A-

mining, construction, farming, transportation, power generation, or any other industry known in the art. For example, machine 10 may embody a mobile machine such as the wheel loader depicted in Fig. 1, a bus, a highway haul truck, or any other type of mobile machine known in the art. Machine 10 may include an operator station 12, a work implement 14, and one or more traction devices 16. Referring to Fig. 1, machine 10 is illustrated approaching a pile of material 20. Pile 20 may include any of a variety of materials that are to be loaded into work implement 14 and dumped at another location. For example, pile 20 may include gravel, sand, dirt, and the like. It is contemplated that machine 10 may encounter any number of variations in piles of material to be loaded during its course of operation.

As illustrated in Fig. 2, operator station 12 may include devices that receive input from a machine operator indicative of a desired machine travel maneuver. Specifically, operator station 12 may include one or more operator interface devices 22 located proximate an operator seat 24. Operator interface devices 22 may initiate and/or regulate movement of machine 10 by producing signals that are indicative of a desired machine maneuver. In one embodiment, operator interface devices 22 may include a left foot pedal 26, a right foot pedal 28, and a gear skip switch 30. As an operator manipulates left foot pedal 26 and/or right foot pedal 28 (i.e., displaces left and/or right foot pedals 26 and 28 away from a neutral position), the operator may expect and affect a corresponding machine travel movement. In addition, as the operator moves gear skip switch 30 to an engaged position, the operator may affect a corresponding transmission operating mode such as, for example, a gear-skipping mode where a selected gear output ratio may be disabled during downshifting events. It is contemplated that operator interface devices other than foot pedals such as, for example, joysticks, levers, switches, knobs, wheels, and other devices known in the art, may additionally or alternatively be provided within operator station 12 for travel control of machine 10, if desired. It is further contemplated that operator

interface devices 22 may include more than one gear skip switch 30, wherein each gear skip switch 30 may correspond to disabling a particular gear output ratio. Alternatively, it is contemplated that gear skip switch 30 may be omitted. Work implement 14 (referring to Fig. 1) may include any device used to perform a particular task. For example, work implement 14 may include a bucket, a fork arrangement, a blade, a shovel, a ripper, a dump bed, a broom, a snow blower, a propelling device, a cutting device, a grasping device, or any other task-performing device known in the art. Work implement 14 may be connected to machine 10 via a direct pivot, via a linkage system, via one or more hydraulic cylinders, or in any other appropriate manner. Work implement 14 may be configured to pivot, rotate, slide, swing, lift, or move relative to machine 10 in any manner known in the art.

Traction devices 16 may embody wheels located on each side of machine 10 (only one side shown). Alternatively, traction devices 16 may include tracks, belts or other known traction devices. It is contemplated that any combination of the wheels on machine 10 may be driven and/or steered.

As illustrated in Fig. 3, power train 18 may be an integral package configured to generate and transmit power to traction devices 16. In particular, power train 18 may include a power source 32 operable to generate a power output, a torque converter 34, a transmission unit 36 connected to receive the power output and transmit the power output in a useful manner to traction devices 16 (referring to Fig. 1), one or more sensors 38, and a controller 40 configured to regulate the operation of transmission unit 36 in response to one or more inputs. Power source 32 may include an internal combustion engine having multiple subsystems that cooperate to produce a mechanical or electrical power output. For the purposes of this disclosure, power source 32 is depicted and described as a four-stroke diesel engine. One skilled in the art will recognize, however, that power source 32 may be any other type of internal combustion engine such as, for example, a gasoline or a gaseous fuel-powered engine. The

subsystems included within power source 32 may include, for example, a fuel system, an air induction system, an exhaust system, a lubrication system, a cooling system, or any other appropriate system.

Torque converter 34 may be a hydro-mechanical device configured to couple power source 32 to transmission unit 36. In particular, torque converter 34 may conduct pressurized fluid between the output of power source 32 and the input of transmission unit 36 to thereby drive transmission unit 36, while still allowing power source 32 to rotate somewhat independently of transmission unit 36. In this arrangement, torque converter 34 may selectively absorb and multiply the torque transferred between power source 32 and transmission unit 36 by either allowing or preventing slippage between the output rotation of power source 32 and the input rotation of transmission unit 36.

Transmission unit 36 may include numerous components that interact to transmit power from power source 32 to traction device 16. In particular, transmission unit 36 may be a multi-speed bidirectional mechanical transmission having a neutral gear output ratio, a plurality of forward gear output ratios, a reverse gear output ratio, and one or more clutches 42. The clutches 42 may be selectively actuated to engage predetermined combinations of gears 44 to produce a desired output gear output ratio. It is contemplated that transmission unit 20 may be an automatic-type transmission, with shifting based on a power source speed, a maximum selected gear output ratio, and a shift map. The output of transmission unit 36 may be connected to and configured to rotatably drive traction device 16 via an output shaft 46, thereby propelling machine 10.

Transmission unit 36 may be at least partially controlled with left and right foot pedals 26 and 28. That is, as left and right foot pedals 26 and 28 are manipulated by an operator, the foot pedals may provide electric signals signifying a desired driven element output such as, for example, a desired torque output and/or a desired speed limit. For example, left and right foot pedals 26 and 28 may have a minimum position and be movable through a range of

positions to a maximum position. Sensors 48 and 50 may be provided in association with each of left and right foot pedals 26 and 28, respectively, to sense the displacement positions thereof and produce corresponding signals responsive to the displaced positions. Sensors 48 and 50 may be any sensor capable of sensing the displacement of foot pedals 26 and 28 such as, for example, a switch or potentiometer. The displacement signals from each of sensors 48 and 50 may be directed through controller 40 to transmission unit 36 to control clutches 42 and gears 44.

Sensors 38 may be situated throughout machine 10 and may be configured to sense various parameters indicative of machine conditions and environmental factors that may be useful for determining when to skip a gear output ratio when performing a downshifting event. Such conditions and factors may include a global position of machine 10, inclination of the ground over which machine 10 may be traveling, a position of work implement 14, a condition of work implement 14 (i.e., whether work implement 14 is carrying a load or not), an identity of an operator, or any other condition that may be useful when determining whether to operate in the gear-skipping mode. In addition, sensors may be any type of sensing device such as, for example, magnetic pickup type sensors, proximity sensors, GPS receivers, or any other type of sensing device capable of sensing the above-mentioned conditions and factors. Signals generated by sensors 38 may be sent continuously, on a periodic basis, or only when prompted to do so by controller 40.

Controller 40 may be configured to operate in either a default mode or a gear-skipping mode and may embody a single microprocessor or multiple microprocessors for controlling the operation of transmission unit 36 in response to various received signals. Numerous commercially available microprocessors can be configured to perform the functions of controller 40. It should be appreciated that controller 40 could readily embody a general machine microprocessor capable of controlling numerous machine functions. Controller

40 may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with controller 40 such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry. When operating in the default mode, controller 40 may cause transmission unit 36 to perform a downshifting event without disabling any gear output ratios. For example, controller 40 may receive a downshift request when transmission unit 36 is operating in a third gear output ratio. If controller 40 is operating in the default mode, controller 38 may cause transmission unit 36 to downshift from the third gear output ratio to a second gear output ratio before downshifting to a first gear output ratio. It should be understood that controller 40 may operate in the default mode unless the operator, machine conditions, and/or environmental factors cause controller 38 to operate in the gear-skipping mode. Controller 40 may operate in the gear-skipping mode in response to signals received from gear skip switch 30 and/or sensors 38, 48, and 50. The operator may cause controller 40 to operate in the gear-skipping mode by actuating gear skip switch 30. In addition, controller 40 may operate in the gear- skipping mode if current machine conditions and/or environmental factors are substantially similar to machine conditions and/or environmental factors that existed during previous downshifting events when controller 40 was operating in gear-skipping mode. Furthermore, such signals received from gear skipping switch 30 and sensors 38, 48, and 50, may be stored in the memory of controller 40 if the signals are received during a downshifting event and controller 40 is operating in the gear-skipping mode.

When operating in the gear-skipping mode, controller 40 may cause a selected gear output ratio to be disabled during downshifting events. For example, controller 40 may receive a downshift request when transmission unit 36 is operating in a third gear output ratio. If controller 40 is operating in the

gear-skipping mode and a second gear output ratio is selected to be disabled, controller 40 may cause transmission unit 36 to downshift directly from the third gear output ratio to a first gear output ratio. The selected gear output ratio may be preprogrammed into the memory of controller 40, thereby permitting controller 40 to disable only a particular gear output ratio whenever operating in the gear- skipping mode. For example, if controller 40 is preprogrammed to disable the second gear output ratio, the second gear output ratio may be the only gear output ratio disabled whenever controller 40 operates in the gear-skipping mode. Alternatively, the gear output ratio to be disabled may be dynamically selected, thereby permitting any gear to be disabled during a particular downshift event. For example, the operator may select the third gear output ratio for disablement during a first downshift event and select the second gear output ratio for disablement during a second downshift event by actuating the gear skip switch 30 corresponding to the third and second gear output ratios, respectively. In addition, controller 40 may select the third gear output ratio for disablement when current machine conditions and environmental factors are similar to machine conditions and environmental factors present during a previous third gear output ratio disablement and select the second gear output ratio for disablement when current machine conditions and environmental factors are similar to machine conditions and environmental factors present during a previous second gear output ratio disablement.

It is contemplated that in some embodiments, the gear output ratio to be disabled may be both preprogrammed and dynamically selected. In one exemplary embodiment, operator interface devices 22 may include only one gear skip switch 30. In such an embodiment, the gear output ratio to be disabled may be preprogrammed when the operator initiates the gear-skipping mode. However, controller 40 may be configured to dynamically select the gear output ratio to be disabled as disclosed above if the machine conditions and/or environmental factors cause controller 40 to operate in the gear-skipping mode and the operator

has not actuated gear skip switch 30. In another exemplary embodiment, operator interface devices 22 may include more than one gear skip switch 30. In such an embodiment, the gear output ratio to be disabled may be dynamically selected by the operator. However, the selected gear output ratio may be preprogrammed into the memory of controller 40 so that when the operator has not actuated any gear skip switches 30 and machine conditions and/or environmental factors cause controller 40 to operate in the gear-skipping mode, controller 40 may disable only the one preprogrammed gear output ratio during any downshift event.

Fig. 4, which is discussed in the following section, illustrates the operation of machine 10 utilizing embodiments of the disclosed system. Fig. 4 illustrates an exemplary method used to anticipate the need to skip a gear during a downshifting event.

Industrial Applicability

The disclosed system may reduce or eliminate the undesirable delay that may occur between the moment conditions require downshifting and the moment the downshifting event actually occurs. In particular, the disclosed system may analyze previous conditions that were present during past downshifting events and determine whether to disable a gear output ratio before conditions requiring a downshifting event occur. Because the gear output ratio disablement determination may be made prior to the moment conditions require a downshifting event, the determination may be prevented from contributing to the undesired delay, thereby reducing or eliminating such delay. The method for determining whether to disable a gear output ratio will now be explained.

Fig. 4 illustrates a flow diagram depicting an exemplary method for determining when a gear may need to be skipped during a downshifting event. The method may begin by determining whether gear skip switch 30 has been actuated (step 200). Controller 40 may determine that gear skip switch 30 has been actuated by receiving a signal from gear switch 30 indicating that it is actuated. In embodiments having more than one gear skip switch 30, controller

40 may determine which gear skip switch 30 has been actuated by receiving a signal from the particular gear skip switch 30 that has been actuated. If controller 40 determines that gear skip switch 30 has been actuated (step 200: Yes), controller 40 may either begin to or continue to operate in a gear-skipping mode (step 202). In the gear skipping mode, controller 40 may regulate transmission unit 36 so that upon any downshift, a selected gear output ratio may be disabled. The selected gear output ratio may be preprogrammed if operator interface devices 22 include only one gear skip switch 30. In such an embodiment, controller 40 may disable only the preprogrammed gear output ratio during any downshift event. Alternatively, the operator may dynamically select the gear output ratio to be disabled if operator interface devices 22 include more than one gear skip switch 30. The dynamic selection may be made by actuating any one of the gear skip switches 30. It should be understood that the selected gear output ratio may be disabled during downshifting events only as long as the associated gear skip switch 30 is actuated and controller 40 is operating in the gear-skipping mode. After beginning to or continuing to operate in the gear-skipping mode, step 200 may be repeated (i.e., controller 40 may determine whether gear skip switch 30 has been actuated).

If controller 40 determines that gear skip switch 30 has not been actuated (step 200: No), controller 40 may receive current machine condition and environmental data from sensors 38, 48, and 50 (step 204). Such data may include, for example, operator identification, global position of machine 10, position of work implement 14, status of work implement 14 (i.e., whether work implement 14 is carrying a load or not), or any other machine condition and/or environmental factor useful for determining when to disable a gear output ratio during a downshifting event.

After receiving current data from sensors 38, 48, and 50, controller 40 may compare the received data to data stored in the memory of controller 40 (step 206). Such data stored in the memory of controller 40 may describe

machine conditions and/or environmental factors that were present during past downshifting operations where a gear output ratio was disabled. After comparing the current data to the stored data, controller 40 may determine whether current machine conditions and/or environmental factors require a gear output ratio to be disabled during downshifting events (step 208).

When comparing the current and stored data, controller 40 may use any machine condition or environmental factor to determine whether a gear output ratio should be disabled. In one example where machine 10 is used to remove material from pile 20, the global position of machine 10 may be used to determine whether a gear output ratio should be disabled. While machine 10 travels toward pile 20, gears 44 may be set to a third gear output ratio. However, as soon as work implement 14 hits pile 20, gears 44 may need to be set to a first gear output ratio. The data stored in the memory of controller 40 may indicate that when machine 10 is at a particular global position relative to pile 20, a second gear output ratio may be disabled during downshifting events where transmission 36 downshifts from the third gear output ratio to the first gear output ratio. If the current data indicates that machine 10 is in a substantially similar location as the one described above, controller 40 may determine that the second gear output ratio may need to be disabled during downshifting events until the position of machine 10 changes.

In another example, the data stored in the memory of controller 40 may indicate that whenever a particular operator operates machine 10, the third gear output ratio may be disabled during all downshifting events. Therefore, if the current data indicates that the above-mentioned operator is operating machine 10, controller 40 may determine that the third gear output ratio may need to be disabled during downshift events.

If controller 40 determines that current machine conditions and/or environmental factors require a gear output ratio to be deactivated during downshifting events (step 208: Yes), controller 40 may either begin to or continue

to operate in the gear-skipping mode (step 210). After beginning to or continuing to operate in the gear-skipping mode, step 200 may be repeated (i.e., controller 40 may determine whether gear skip switch 30 has been actuated). If controller 40 determines that current machine conditions and/or environmental factors do not require a gear output ratio to be disabled during downshifting events (step 208: No), controller 40 may either begin to or continue to operate in the default mode (step 212). In the default mode, no gear output ratios are ever disabled during downshifting events. After beginning to or continuing to operate in the default mode, step 200 may be repeated (i.e., controller 40 may determine whether gear skip switch 30 has been actuated).

The disclosed system may be able to anticipate when future downshifting events may require a particular gear output ratio to be disabled. In particular, the controller may determine that a gear output ratio may need to be disabled during a downshifting event in response to an operator input, machine data and/or environmental data prior to the downshifting event. Because the gear output ratio disablement determination may be made prior to the downshifting event, the determination may be prevented from contributing to the undesired delay between the moment conditions require a downshifting event the moment a downshifting event actually occurs, thereby reducing or eliminating the delay. In addition, basing the determination on operator input, machine data, and/or environmental data may increase the variety of circumstances in which the disclosed system may be able to reduce the delay between he moment conditions require a downshift event and the moment the downshift event actually occurs. It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary

only, with a true scope being indicated by the following claims and their equivalents.