BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis showing a shift pattern for a vehicle that is towing a trailer and is not towing a trailer for up-shifts;
FIG. 2 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis showing additional shift lines for a vehicle towing a trailer based on the weight of the trailer for up-shifts, according to the invention;
FIG. 3 is a plan view of a vehicle towing a trailer, and including a control system for setting the shift pattern of the vehicle based on the weight of the trailer, according to an embodiment of the present invention;
FIG. 4 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis showing the shift pattern for a vehicle that is towing a trailer and is not towing a trailer for down-shifts; and
FIG. 5 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis showing a torque converter control apply/release schedule for a vehicle that is towing a trailer and is not towing a trailer.
DETAILED DESCRIPTION OF THE EMBODIMENTS
The following discussion of the embodiments of the invention directed to a system and method for selectively changing the shift pattern of a vehicle based on the weight of a trailer it is towing is merely exemplary in nature, and is in no way intended to limit the invention or its applications or uses.
FIG. 2 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis that shows the same shift lines that are in FIG. 1. According to the invention, a system is provided that selectively changes the shift pattern of the vehicle based on the weight of the trailer it is towing. To illustrate the invention, hypothetical up-shift lines for the shift between gear 3 and gear 4 are shown that could be used depending on the weight of the trailer. For example, the shift line 20 would be for a trailer at the upper towing weight limit of the vehicle, and shift lines 22, 24 and 26 could be used for the weight of a trailer as it increases to the maximum weight. If desirable, other shift lines can be provided between gears 1 and 2 and between gears 2 and 3 based on the weight of the trailer. Once the weight of the trailer is known, a controller can linearly interpolate the shift table to change the shifts for that weight, or can calculate a non-linear relationship based on vehicle calibration. The invention contemplates any suitable technique for determining the weight of the trailer, and making the appropriate control change in response thereto.
FIG. 3 is a plan view of a vehicle 30 towing a trailer 32. The vehicle 30 includes a hitch post 34 and the trailer 32 includes a tongue 36 to provide the connection between the vehicle 30 and the trailer 32 in the normal matter. A controller 40 on the vehicle 30 sets the shift pattern of the transmission 42 of the vehicle 30 based on the weight of the trailer 32. The weight of the trailer 32 can be provided by any suitable technique. For example, a switch 44 can be provided on the steering column of the vehicle 30 or the dashboard of the vehicle 30 which is selectively engaged by the vehicle operator. The switch 44 can be a multi-function switch where each time the vehicle operator engages the switch 44 it increases or decreases the weight for the trailer 32, such as in 1,000 pound increments, and sets the shift pattern accordingly. A display 46 can be provided that indicates what weight has been selected. In another embodiment, the switch 44 can set the weight of the trailer 32 for low, medium or high. Further, the switch 44 can be designed to provide a continuous selection of the weight of the trailer 32 from zero to a maximum towing capability of a vehicle. As long as the vehicle operator has a reasonable estimation of the weight of the trailer 32, he can selectively engage the switch 44 for that weight.
In another embodiment, a load cell 50 can be provided on the hitch post 34 that is able to measure the weight of the trailer 32 when it is connected thereto. The load cell 50 will provide a weight signal to the controller 40 of the measured weight, and the controller 40 can automatically set the shift pattern of the transmission 42 without any intervention from the vehicle operator. Load cells that can be used for this purpose are well known to those skilled in the art.
Additionally, the vehicle 30 can include a grade sensor 52 that provides an indication of whether the vehicle 30 is going uphill or downhill, and the controller 40 can use this information to also selectively change the shift pattern of the transmission 42. It is known in the art to calculate whether the vehicle 30 is going uphill or downhill without a grade sensor just by the performance of the engine using a suitable algorithm.
The discussion above refers to an up-shift pattern when the vehicle 30 is accelerating for different trailer weights. Other shift patterns could be provided for down-shifts and a torque converter control (TCC) apply/release schedule. For example, FIG. 4 is a graph with vehicle speed on the horizontal axis and percentage of the throttle position on the vertical axis showing down-shift lines for a full-size. Particularly, shift line 60 is for a down-shift from gear 2 to gear 1, shift line 62 is for a down-shift from gear 3 to gear 2 and shift line 64 is for a down-shift from gear 4 to gear 3 when the vehicle 30 is not towing the trailer 32. Shift line 66 is for a down-shift from gear 2 to gear 1, shift line 68 is for a down-shift from gear 3 to gear 2 and shift line 70 is for a down-shift from gear 4 to gear 3 when the vehicle 30 is towing the trailer 32. In the same manner as discussed above, the position of the down-shifts can be selectively changed based on the weight of the trailer 32.
FIG. 5 is a graph with vehicle speed on the horizontal axis and percentage of throttle position on the vertical axis showing a TCC apply/release schedule for a full-size truck. Graph line 72 shows the TCC apply/release line for gear 4 for the vehicle 30 when it is not towing the trailer 32 and graph line 74 shows the TCC apply/release line for gear 3 for the vehicle 30 when it is not towing the trailer 32. Graph line 76 is the TCC apply/release line for gear 4 when the vehicle 30 is towing the trailer 32 and graph line 78 is the TCC apply/release line for gear 3 for the vehicle 30 when it is towing the trailer 32. In the same manners discussed above, the position of the TCC apply/release schedule can be selectively changed based on the weight of the trailer 32.
The foregoing discussion discloses and describes merely exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the spirit and scope of the invention as defined in the following claims.
Patent Application
20070271017
