Patent Publication Number: US-7900739-B2

Title: Control system for a vehicle system with a continously variable transmission

Description:
TECHNICAL FIELD 
     This invention applies to the field of vehicle control systems and, more specifically, to a control system for a vehicle with a continuously variable transmission. 
     BACKGROUND 
     Continuously variable transmissions (CVT) are becoming more commonly available in vehicles, including agricultural tractors. These transmissions, in combination with electronically controlled engines, provide the capability to smoothly change the transmission ratio and engine speed (revolutions per minute or RPM) to maintain or reach a desired power output and speed. In order to take full advantage of the CVT, conventional systems for the controlling engine speed include a variety of operator controls, which are fairly complex and confusing to many operators. A major contributor to this complexity is the control of the engine speed. An operator may wish to set the range of engine speed based on factors such as PTO operation, hydraulic requirements, the noise signature of the engine, and fuel economy. 
     Conventional systems for controlling engine speed of an agricultural tractor with a CVT typically include a hand throttle and a spring-loaded foot throttle to set the desired engine speed, and include additional switches or knobs to set operating modes. In some operating modes, the systems vary the engine speed within certain limits to minimize fuel consumption or to optimize other parameters. The amount of engine speed variation allowed and the proper usage of the modes are often not well understood by the operators. This can result in less-than-ideal operation of the agricultural tractor and may negate the advantages of the CVT. 
     Thus, there is a need in the vehicle control system field to create an improved control system for a vehicle with a continuously variable transmission. This invention provides such an improved control system. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIGS. 1 ,  2 , and  3  are schematic drawings of the control system of the first preferred embodiment of the invention with a first variation of the first and second control. 
         FIG. 4  is a schematic drawing of the control system of the first preferred embodiment of the invention with a second variation of the first and second control. 
         FIG. 5  is a schematic drawing of the control system of the first preferred embodiment of the invention with a third variation of the first and second control. 
         FIG. 6  is a schematic drawing of the control system of the first preferred embodiment of the invention with a fourth variation of the first and second control. 
         FIG. 7  is a schematic drawing of the vehicle system of the second preferred embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments of the invention is not intended to limit the invention to these preferred embodiments, but rather to enable any person skilled in the art to make and use this invention. 
     As shown in  FIGS. 1-6 , the control system  10  of the first preferred embodiment includes a user interface  12  with a first control  14  that designates a maximum bound of a sub-range of engine speeds and a second control  16  that designates a minimum bound of a sub-range of engine speeds. The control system  10  of the first preferred embodiment also includes a processor  18  connected to the engine and to the user interface  12  that functions to, based on the required power output of the vehicle system, select a discrete engine speed from the sub-range of engine speeds. The control system  10  of the first preferred embodiment was designed for controlling engine speed of a vehicle system having an engine and a required power output, but may be used in any suitable environment. 
     The user interface  12  functions to provide an interface for an operator to designate a maximum bound and a minimum bound of a sub-range of engine speeds for the engine. There are an endless number of sub-ranges of engine speeds that an operator may wish to designate. The sub-range of engine speeds allows the operator to base the speed of the engine on more than one parameter or function of the engine, such as power output, fuel efficiency, and noise signature. In a first example, as shown in  FIG. 1 , the operator may set the minimum bound of the sub-range at the engine speed that provides peak fuel efficiency, while setting the maximum bound of the sub-range at the engine speed that provides maximum power output. With this setting, the processor  18  will select an appropriate engine speed within this sub-range. In a second example, as shown in  FIG. 2 , the operator may set both the minimum and the maximum bounds of the sub-range at the engine speed that provides maximum power output. With this setting, the processor  18  will continuously select the engine speed that provides the maximum power output, regardless of the required power output. In a third example, as shown in  FIG. 3 , the operator may set both the minimum and the maximum bounds of the sub-range at the engine speed that idles the engine. With this setting, the processor  18  will continuously select the engine speed that idles, regardless of the required power output. By allowing the selection of a sub-range of engine speeds, the processor  18  can function to better match the intention of the operator and the required power output of the vehicle system. 
     The first control  14  of the first preferred embodiment functions to designate the maximum bound of a sub-range of engine speeds, while the second control  16  of the first preferred embodiment functions to designate a minimum bound of a sub-range of engine speeds. The first control  14  and the second control  16  are preferably made of plastic or metal, but may be alternatively made from any suitable, durable material. The first control  14  and the second control  16  may be rectangular, circular, or any other suitable geometry to properly interface with the operator. The controls may include a grip portion including geometry such as indents for fingers and a second material such as rubber to facilitate gripping or moving by hand or with fingers. The first control  14  and the second control  16  are preferably one of several variations. 
     In a first variation, as shown in  FIGS. 1 ,  2 , and  3 , the first control  14  and the second control  16  are sliding controls that can be slid along a linear path in a track, groove, or in any other suitable device or manner. An operator may slide the first sliding control  12  to a point such that the first sliding control designates the maximum bound. Similarly, the operator may slide the second sliding control  14  to a point such that the second sliding control  14  designates the minimum bound. The first control  14  and the second control  16  may be located in the same track or groove, in separate tracks or grooves located near one another, in separate tracks or grooves located in different regions of the user interface, or in any other suitable configuration in any suitable region of the user interface. The first control  14  and the second control  16  preferably include an interlocking mechanism such that the maximum bound cannot be set below the minimum bound and the minimum bound cannot be set above the maximum bound. Preferably, the first control  14  has a portion that extends towards and mates with a portion of the second control  16  such that the first control  14  and the second control  16  can only slide on one side of each other. Alternatively, the interlocking mechanism may be located below the first control  14  and the second control  16  in the track or groove or in any other suitable location. 
     In a second variation, as shown in  FIG. 4 , the first control  14  and the second control  16  are levers that can be pivoted about an axis. In this variation, an operator may push, pull, pivot, or move the first control  14  to a point such that the first control designates the maximum bound. Similarly, the operator may push, pull, pivot, or move the second control  16  to a point such that the second control  16  designates the minimum bound. The first control  14  and the second control  16  may be located on the same pivot point, located near one another in the same region of the user interface, located in different regions of the user interface, or in any other suitable configuration in any suitable region of the user interface. The first control  14  and the second control  16  preferably include an interlocking mechanism such that the maximum bound cannot be set below the minimum bound and the minimum bound cannot be set above the maximum bound. The interlocking mechanism may be incorporated into the geometry of the first control  14  and the second control  16 , or alternatively, the locking mechanism may be located below the first control  14  and the second control  16  at the pivot point in any other suitable location. 
     In a third and fourth variation, as shown in  FIGS. 5 and 6 , the first control  14  and the second control  16  are dials that can be rotated about an axis (that, unlike the lever of the second variation, preferably intersects the operator). An operator may turn or rotate the first control  14  to a point such that the first control  14  designates the maximum bound. Similarly, the operator may turn or rotate the second control  16  to a point such that the second control  16  designates the minimum bound. In this variation, the first control  14  and the second control  16  may include an arrow, a dot, a line, or any other suitable indicator on the dial, adjacent to the dial, or in both locations such that the operator may rotate the first control  14  and the second control  16  to a specific point to designate the maximum and minimum bound respectively. The first control  14  and the second control  16  may be located near one another in the same region of the user interface, located in different regions of the user interface, or in any other suitable configuration in any suitable region of the user interface (shown in  FIG. 5 ). In the fourth variation (shown in  FIG. 6 ), the first control  14  and the second control  16  are dials and the first control  14  and the second control  16  are concentrically located and rotate about the same axis. The first control  14  and the second control  16  are preferably standard dials and may be circular, polygonal (hexagonal, octagonal, etc.), rectangular or any other suitable geometry such that the operator may turn or rotate them. The first control  14  and the second control  16  preferably include an interlocking mechanism such that the first control  14  cannot rotate beyond a certain point and designate the maximum bound below the minimum bound and the second control  16  cannot rotate beyond the first control  14  and designate the minimum bound above the maximum bound. The interlocking mechanism may be incorporated into the geometry of the first control  14  and the second control  16 . Preferably, the first control  14  has a portion that extends towards and mates with a portion of the second control  16  such that the first control cannot rotate beyond the second control and vice versa. As in the fourth variation, where the dials are located concentrically, the dials may fit into one another such that the first control  14  cannot rotate beyond the second control  16  and vice versa. Alternatively, the locking mechanism may be located below the first control  14  and the second control  16  or in any other suitable location. 
     Although the first control  14  and the second control  16  are preferably one of these four variations, the first control  14  and the second control  16  may be any suitable device such that the first control  14  designates the maximum bound and the second control  16  designates the minimum bound of a sub-range of engine speeds. 
     As shown in  FIGS. 1 ,  2 , and  3 , the control system  10  may further include indicia  20 . The indicia  20  of the first preferred embodiment function to identify the engine speeds that the first control  14  and the second control  16  may designate as the maximum bound and the minimum bound respectively. The indicia  20  are preferably one of several variations. In a first variation, the indicia  20  are one or more numerical values (in RPM units or any other suitable units), symbols (such as a tortoise and hare or any other suitable symbols), or colors that correspond to engine speeds. In a second variation, the indicia  20  are one or more words or symbols that correspond to a parameter or function of the engine, such as power output, fuel efficiency, and noise signature. The indicia  20  are preferably engravings, labels attached with durable adhesive, or markings molded into the user interface, the first control  14 , and/or the second control  16 . Alternatively, the indicia  20  may be any other suitable markings on the control system  10 , first control  14 , and/or second control  16  in any other suitable manner. Although the indicia  20  are preferably one of these two variations and any combination of these two variations, the indicia  20  may be any suitable markings to identify the engine speeds that the first control  14  and the second control  16  may designate as the maximum bound and the minimum bound respectively. 
     The processor  18  of the first preferred embodiment is connected to the user interface and to the engine and functions to select a discrete engine speed from the sub-range of engine speeds selected by the operator. The processor  18  preferably selects the discrete speed based on the required power output of the vehicle system. The processor  18  may further select the discrete speed based on the noise signature of the engine and/or fuel efficiency of the engine. The processor  18  is preferably a conventional processor but may alternatively be any suitable device to perform the desired functions. 
     As shown in  FIG. 7 , the vehicle system  100  of the second preferred embodiment includes an engine  102 , a continuously variable transmission  104  connected to the engine that functions to deliver the power output from the engine to the vehicle system and to deliver a range of output speeds to the vehicle system, and the control system  10  of the first preferred embodiment. 
     The engine  102  of the second preferred embodiment functions to power the vehicle system. The engine  102  is preferably an internal combustion engine, but may alternatively be any suitable engine or power source. The engine  102  preferably operates within a range of engine speeds and provides a power output in the form of rotational motion at a given angular velocity. Within the range of engine speeds, the engine  102  preferably has a peak engine efficiency speed and a peak engine power speed. 
     The continuously variable transmission (CVT)  104  of the second preferred embodiment functions to allow the engine to operate within the range of engine speeds while delivering the power output from the engine and a wide range of output speeds to the vehicle system. The CVT  104  functions to change the speed ratio between the engine and the vehicle system. The CVT  104  preferably allows continuous variability between the highest and lowest ratios of engine speed to output speed, but may alternatively function in multiple discrete steps or shifts (preferably more than 12) between ratios. The CVT  104  is preferably the CVT that is described in U.S. Pat. No. 6,913,555 issued on 05 Jul. 2005 and entitled “CVT Transmission for Motor Vehicles, in Particular for Agricultural Tractors”, which is incorporated in its entirety by this reference, but may be any suitable transmission that changes the speed ratio between the engine and the vehicle system. 
     Although omitted for conciseness, the preferred embodiment include every combination and permutation of the various control systems  10 , user interfaces  12 , first controls  14 , second controls  16 , processors  18 , indicia  20 , vehicle systems  100 , engines  102 , and continuously variable transmissions  104 . 
     As a person skilled in the art will recognize from the previous detailed description and from the figures and claims, modifications and changes can be made to the preferred embodiments of the invention without departing from the scope of this invention defined in the following claims.