Patent Application
20130345914
The present disclosure relates generally to limiting ground speed of machines equipped with an electronically controlled drive train, and more particularly, to a vehicle speed limit algorithm executed in an electronic transmission controller to issue engine control messages to limit machine speed based on a sensed machine state.
Vehicle speed limiting for most on-highway truck applications is typically done through a vehicle speed limiting strategy resident in the electronic engine controller. Off highway machines, such as trucks operated in shipping facilities, port facilities or large factory/warehouse operations, may not be on-highway legal, and are therefore not required to meet on-highway emissions regulations. In addition, these trucks often use less expensive so called “industrial engines” that do not have built in vehicle speed limiting strategies. Nevertheless, there still may exist vehicle speed limit regulations for off-highway machines in many jurisdictions. It may also be desirable to limit vehicle speed in response to an operating state of the vehicle. For instance, an off-highway machine speed may have a speed limit of 25 miles per hour, or a limit of 5 miles per hour while a certain vehicle system is operating. In addition, some on-highway machines have an engine, transmission, and chassis from different manufacturers. This makes it difficult for the engine software to execute vehicle speed limiting strategies. In these types of machines, vehicle speed limiting has typically been accomplished by gear binding the transmission, or not allowing shifts above a certain gear, and relying upon the top engine limit speed governor on the engine to effectively limit wheel speed in the highest gear. This strategy for limiting speed is often received with frustration by many operators and also includes several other drawbacks. For instance, vehicle speed limiting through gear binding necessarily reduces efficiency and increases fuel consumption, may increase engine wear and even increase noise due to the increased engine RPM.
The present disclosure is directed to one or more of the problems set forth above.
In one aspect, a method of limiting ground speed of a machine includes propelling the machine at a speed by transmitting engine power to a ground engaging member of the machine via a drive train that includes a transmission. At least one machine state is sensed by an electronic transmission controller. A vehicle speed limit is selected in the electronic transmission controller in response to the at least one machine state. A vehicle speed limit algorithm is executed in an electronic transmission controller to determine an engine control message. The engine control message is communicated to an electronic engine controller via a communication link. The machine speed is limited by executing an engine control algorithm in an electronic engine controller in response to the engine control message.
In another aspect, a transmission includes an electronic transmission controller attached to a housing. The electronic transmission controller includes a means for establishing a communication link with an electronic engine controller. The electronic transmission controller is configured to sense at least one machine state, select a vehicle speed in response to the at least one machine state, and execute a vehicle speed limit algorithm to generate an engine control message.
In still another aspect, a machine includes a plurality of ground engaging members attached to a chassis. A drive train that includes an engine coupled to the ground engaging members is attached to the chassis. The drive train includes a transmission with the electronic transmission controller. The electronic transmission controller is configured to sense at least one machine state, select a vehicle speed in response to the at least one machine state, and execute a vehicle speed limit algorithm to generate an engine control message. The machine also includes a means for communicating between the electronic transmission controller and the electronic engine controller. Finally, the machine includes means for reducing a power output of the engine responsive to a communication of the engine control message to the electronic engine controller.
a and 6b are illustrations of vehicles suitable for use with the vehicle speed limiting strategy according to the present disclosure.
Referring now to
The present disclosure contemplates several vehicle speed limiting strategies that may be implemented using public engine control message protocols or proprietary engine control messages. For instance, the present disclosure contemplates a vehicle speed limiting strategy as shown in
In any of the strategies, it will likely be necessary to enter into the software what vehicle speed limits are desired. This feature is shown in
In addition, there is at least one machine state sensor that is in electrical communication with the electronic transmission controller 28. The machine state sensor 5 could be a switch, a temperature sensor, a speed sensor, or other component that is known in the art. The machine state sensor 5 may communicate with the electronic transmission controller 28 via a voltage signal, a current signal, or a message over a communication link. Any number of machine state sensors 5 is possible, limited only by input/output and the software and memory of the electronic transmission controller 28. These machine state sensors 5 will be referred to as MSS1, MSS2, etc. up to MSSn.
For example, consider a dump truck having a dump body 30. An input from an operator is used to raise or tilt the dump body 30 using known methods. A machine state sensor 5, such as a switch, could be configured to indicate when the dump body 30 is not in the lowered position. Other sensors, such as linear position sensors or a rotary sensor could be used to indicate other positions of the dump body 30 between raised and lowered.
Another example would be a truck mounted with a power take off (PTO) 35. The PTO 35 could be powered by the engine using a known method. For example, the PTO 35 could be driven by the transmission 15. The PTO 35 could be engaged by a switch or other command. The electronic transmission controller 28 could then detect the message on the control network corresponding to an active signal for MSS1.
The electronic transmission controller 28 uses the inputs from the machine state sensors 5 to determine which vehicle speed limit will be active. For instance, an active input from MSS1 will result in activation of VSL1. An active input from MSS2 will result in activation of VSL2, etc. No active inputs from any machine state sensors 5 will result in activation of VSL0, the default vehicle speed limit 61.
Next, there may also be data entered into the electronic transmission controller 28 relating the ratio of transmission shaft output speed to vehicle speed. This is shown as Item 62 in
Referring now to
Referring now to
The TSC1 torque limit strategy 70 shown in
Referring now to
The present disclosure finds potential application in any machine with an electronically controlled drive train in need of vehicle speed limiting. For instance, some fleet owners desire their machines to be limited in speed, and/or vehicle speed limits may be required by regulation in certain jurisdictions. Other reasons for limiting speed may be due to machine function. The present disclosure is especially applicable to machines that do not include vehicle speed limiting algorithms resident on their electronic engine controller. For instance, the present disclosure is applicable to machines that utilize so called industrial engines, such as for use in off-highway applications. The present disclosure is also applicable to machines that use transmissions and engines from different manufacturers. In other cases it may be desirable to limit vehicle speed in response to a certain vehicle function.
In some cases it may be desirable for a vehicle to have more than one programmed vehicle speed limit 61. For example, a dump truck having a tilting dump body may have an owner-preferred maximum speed limit of 65 mph. An example of such a dump truck is depicted in
A truck mounted with a power take off (PTO) 35 is another example of a case where it may be desirable for a vehicle to have more than one programmed vehicle speed 61. Such a truck may have an owner-preferred maximum speed limit of 65 mph. This speed limit could be defined as VSL0 and could serve as the default speed limit for the truck. In addition, the truck could have a second vehicle speed limit VSL1 of, say, 15 mph that is linked to a sensed machine state MSS1. The PTO 35 could be engaged by a switch or other command. The electronic transmission controller 28 could then detect the message on the control network corresponding to an active signal for MSS1. The electronic transmission controller 28 would therefore activate VSL1. Other examples of an appropriate MSS1 could come from a switch in the PTO activation circuit, a pressure sensor relative to a driven pump, or a speed sensor. The electronic transmission controller 28 would compare VSL0 (65 mph) and VSL1 (15 mph) and choose the lower (15 mph) to use in the vehicle speed limit control algorithm 140 or 240. Limiting the vehicle speed in such a way would have uses on trucks that use a PTO 35 to power accessories. Such applications include water trucks, herbicide/insecticide sprayers, highway stripers, and cement trucks. An example of such a PTO-equipped truck is depicted in
A refuse truck is another example of a case where it may be desirable for a vehicle to have more than one programmed vehicle speed limit 61. Such a refuse truck could include controls on both the driver side and passenger side. In some jurisdictions a vehicle driven from passenger side controls is to be limited to a lower speed, say 20 mph. The refuse truck could also include a dumpster hoist. It may be desirable to limit the refuse truck speed to 5 mph when the hoist is not in the lowered position. Such a refuse truck could have as many as three programmed vehicle speed limits. The first, VSL0, could be programmed with the default value of 65 mph. The second, VSL1, could be programmed with 20 mph. VSL1 would be activated when an active signal from MSS1 is detected by the electronic transmission controller 28. MSS1 could correspond to something related to the passenger side controls of the refuse truck, such as a seat occupant switch, a gear selector switch, or a J1939 message from one of the inputs. A third vehicle speed limit, VSL2, could be programmed with 5 mph. VSL2 would be activated when an active signal from MSS2 is detected by the electronic transmission controller 28. MSS2 could correspond to a switch or position sensor in communication with the refuse truck dumpster hoist system. In the refuse truck example, the default vehicle speed limit VSL0 (65 mph) is selected by electronic transmission controller 28 when there are no active signals from machine state sensors 5.
If the refuse truck is operated from passenger side controls, an active signal is created from machine state sensor 5, MSS1. The active signal from MSS1 is detected by electronic transmission controller 28 which selects vehicle speed limit VSL1 (20 mph).
If the refuse truck is operated with the dumpster hoist out of the lowered position, an active signal is created from machine state sensor 5, MSS2. The active signal from MSS2 is detected by electronic transmission controller 28 which selects vehicle speed limit VSL2 (5 mph).
If the electronic transmission controller 28 detects more than one active machine state sensor, it selects the vehicle speed limit with the lowest speed value. In the refuse truck example, if the truck was operated from the passenger side and the dumpster hoist was not in the lowered position, the electronic transmission controller 28 would select VSL2 (5 mph).
Other examples of where machine function-based vehicle speed limiting could be used are cement trucks, water spraying trucks, highway stripers, mobile cranes, agricultural tractors, and construction machines.
Examples of machine state sensors could be limit switches, linear and rotary position sensors, rotary speed sensors, temperature sensors, pressure sensors, or other devices that produce an electrical output from a physical input.
In all applicable cases, an electronically controlled transmission includes an electronic transmission controller that executes a vehicle speed limit algorithm to determine an engine control message. The engine control message is communicated to the electronic engine controller. The present disclosure might also have potential application in limiting vehicle speeds in other applications, such as low speeds associated with paint sprayers and/or highway herbicide sprayers where the engine resident VCL or vehicle speed limiting strategy or cruise control strategies in the on-highway engines are not sufficiently designed to operate at low speeds. The present disclosure is also applicable to transmission manufacturers whose electronically controlled transmissions may be mated to divergent engines when installed in a machine that is subject to vehicle speed limiting regulations and/or other requirements. For instance, the present disclosure is applicable to transmissions that might be paired with either on-highway or off-highway machines.
The vehicle speed limit strategy using engine speed control strategy 60 of
Other considerations might also apply. For instance, the engine speed limit strategy 60 of
In some configurations, the vehicle speed limit algorithm may detect when the vehicle ground speed is approaching within the predetermined vehicle speed limit. When that vehicle speed is within a tolerance of the vehicle's speed limit, the vehicle speed limit algorithm 40 generates an engine control message that is communicated to the electronic engine controller 29 to limit power output from the engine via an engine speed limit control message, an engine torque limit control message or an engine power limit control message. When the electronic engine controller 29 executes its engine control algorithm, the resulting limitation in power output carries through the vehicle dynamics to result in the vehicle speed limit not being exceeded. Implementation of a vehicle speed limit algorithm 40 according to the present disclosure might utilize the standard gear binding vehicle speed limit strategy in the default and only enable the alternative vehicle speed limit strategies previously discussed if certain conditions are met, such as an appropriate communication link being maintained between electronic transmission controller 28 and the electronic engine controller 29. The present disclosure also contemplates implementations of the vehicle speed limit algorithm that may allow the operator to selectively enable the vehicle speed limit algorithm 40 through some type of Boolean input, such as a hard-wired switch, a J1939 message or some mode button. In addition, the present disclosure contemplates implementations of vehicle speed limiting that may also eventually allow the operator to actively change the prescribed vehicle speed limit via some appropriate interface. The present disclosure also contemplates an error detection mode where, if the vehicle speed exceeds a vehicle speed limit by some margin, then the algorithm may assume that the engine is no longer accepting engine control messages from the electronic transmission controller 28. In such a case, the transmission may revert to gear binding as a method of limiting vehicle speed.
A vehicle speed limit strategy resident in the electronic transmission controller has several advantages over conventional gear binding strategies known in the art. For instance, operator perception should be more favorable with an engine controlled according to the present disclosure. In addition, fuel savings could be substantial due to the fact that an operator can do the same work at a lower engine RPM and hence consume far less fuel than what might be consumed using a gear binding vehicle speed limiting strategy. For instance, the fuel savings can be on the order of 15-20% or more. In addition, apart from the fuel savings and efficiency increase, one could expect far less noise by the need to rev the engine at a lower RPM to achieve the same vehicle speeds than RPM's associated with gear binding strategies.
It should be understood that the above description is intended for illustrative purposes only, and is not intended to limit the scope of the present invention in any way. Thus, those skilled in the art will appreciate that other aspects of the invention can be obtained from a study of the drawings, the disclosure and the appended claims.
