Powertrain torque control

Abstract: A control system/method for controlling engine (12) output torque in a vehicular powertrain system (10) including an electronically controlled engine and a torque load limited drivetrain system (11) is provided. The control will sense values of a control parameter (GR, OS) indicative of potential overloading of the drivetrain at maximum engine output torque and will cause engine output torque to be limited to a value less than the maximum value thereof.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a control system/method for limiting the torque applied to vehicular drivelines. In particular, the present invention relates to controls for vehicular powertrains preferably including an electronically controlled engine and a drivetrain having a limited torque transfer capacity wherein the value of a control parameter indicative of operating conditions at which potentially undesirably high torque loads in the drivetrain may occur (for example, vehicle speed) are monitored and engine output (flywheel) torque is limited during the occurrence of potentially undesirably high driveline torque loading operating conditions. Description of the Prior Art Vehicular powertrains for vehicles including fuel-controlled engines, such as diesel engines, and drivetrains including a multiple-speed, change-gear transmission and a drive axle, are well known in the prior art. Examples of such vehicular powertrains and components thereof may be seen by reference to U.S. Patents No. 3,105,395; 3,448,635; 4,361,060; 4,977,972; 4,595,986; 5,033,795 and 5,305,213. Electronically controlled engines which include an engine microprocessor control and which communicate with other vehicle controllers, such as the transmission controller, over electronic data links are also known in the prior art. Typically, the engine controller and data link operate in accordance with an industry standard protocol, such as SAE J-1922, SAE J-1939, ISO 11898 or the like. Power control systems for controlling the output torque of the engine of a drivetrain including a torque converter are well known from the state of the art, as is to be seen from US Patent No. 5,065,319. The known system comprises means for determining the speed ratio of the converter and for calculating a capacity factor of the converter based upon the speed ratio. A detection means detects an overload state by comparing the calculated transmission input torque with an allowable input torque and sends a torque decrease signal to the engine when an overtorque is detected. This system will not prevent overload of powertrain components driven by the transmission with the transmission in a low ratio. Other prior art powertrain systems were not totally satisfactory, as, if sized to handle the maximum torque loading at low-speed operation, they were oversized for the majority of operating conditions and, if sized to handle the normally expected torque loads, were subject to damage at low-speed operation where the engine may generate a maximum or "burst" torque output. SUMMARY OF THE INVENTION In accordance with the present invention, the drawbacks of the prior art are minimized by the provision of a powertrain control which monitors the value of one or more control parameters and compares that value or values to a reference or references selected to be indicative of the existence of potentially undesirably high drivetrain torque loading. If potentially undesirably high drivetrain torque loading operating conditions are determined to exist, the torque output of the engine is limited to a value less than the maximum torque output thereof. Preferably, the engine is an electronically controlled engine communicating with an electronic data link using an industry standard protocol, such as SAE J-1922, SAE J-1939, ISO 11898 or the like, having one or more torque-limiting control modes. Accordingly, it is an object of the present invention to provide a new and improved vehicular powertrain control method/system which will limit engine output torque during operating conditions, such as low vehicle speed conditions, wherein full or burst engine output could result in undesirably high drivetrain torque loading. This and other objects and advantages of the present invention will become apparent from a reading of the detailed description of the preferred embodiment taken in connection with the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic illustration of a vehicular powertrain system utilizing the present invention. Figure 2 is a schematic illustration, in flow chart format, of the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENT A typical vehicular powertrain 10 for a land vehicle, such as a heavy-duty truck, is schematically illustrated in Fig. 1. Powertrain 10 includes a drivetrain 11 driven by a prime mover 12, such as a well-known diesel engine. The drivetrain 11 includes a multiple-speed, change-gear transmission 14 connected to the engine 12 by a normally engaged master clutch 16 and having an output shaft 18 connected to a final drive 19, such as a transfer case and/or a drive axle. The crankshaft 20 of engine 12 drives the input elements 22 of clutch 16, which are frictionally engageable to and disengageable from output elements 24, which are fixed to the transmission input shaft 26. A manual or automatic control 27 controls the engagement and disengagement of clutch 26. Transmission 14 is preferably a 7-to-18-forward-speed transmission controlled by a manual shift lever 28 acting on a shift bar housing or shift shaft mechanism 29. A throttle pedal monitor assembly 30 monitors the position or displacement of the throttle pedal 32 and provides an output signal 34 indicative thereof. The engine 12 includes a controller, preferably a microprocessor-based controller 36, which communicates over an electronic data link DL and is effective to fuel the engine in accordance with commands over the data link. Typically, commands will request fueling to match operator throttle settings or to achieve a required engine speed and/or to provide a maximum output ( i.e ., flywheel) torque. A microprocessor-based system controller 48 receives input signals, such as signal 34 from the throttle pedal sensor, signal GR from the engaged gear ratio sensor 54 and/or signal OS from the output shaft rotational speed sensor 56, and processes same according to predetermined logic rules to issue command output signals 52, including signals on the data link DL to the engine controller 36. Assuming the drivetrain 11 is configured and sized to handle a torque load less than the maximum possible torque load at low transmission ratios and maximum (burst) engine output torques, some protection for the driveline should be provided. To provide a drivetrain which is economically sized while providing protection thereof under possible unusual, extraordinarily high torque loading operating conditions, a control parameter (such as vehicle speed (sensed as output shaft speed OS)) is sensed and compared to a reference value indicative of the value of the control parameter at potentially damaging high driveline torque operating conditions. By way of example, if the engaged ratio is not greater than low gear and if vehicle speed is not greater than 4 mph (6km/k), then engine output torque should be limited to less than maximum burst output torque to protect the vehicle drivetrain. The limits on engine output torque may vary with the value of the control parameter. For example, assuming an engine burst output torque of 150% of rated output torque, at engagement of a deep reduction ratio (such as greater than 12:1), maximum engine output torque might be limited to 100% of rated output torque, while engagement of about a 10:1 reduction ratio will require that maximum engine output torque be limited to 120% of rated output torque, and engagement of a ratio having a reduction of less than 10:1 will not require any limitation on engine output torque. Fig. 2 is a flow chart representation of the control method/system of the present invention.

Claims: A method for controlling a vehicular powertrain system (10) comprising a fuel-controlled engine (12) drivingly connected to a vehicular drivetrain system (11) including a multiple-ratio, change-gear transmission (14) and a drive axle (19), said engine (12) having a maximum output torque and an engine controller (36) responsive to command signals to control fueling of the engine (12) and, in at least one mode of operation, effective to limit engine (12) output torque and said drivetrain (11) having a predetermined maximum torque loading capacity, said drivetrain (11) configured such that an expected torque loading on said drivetrain (11) under a predetermined set of drivetrain (11) high torque loading operating conditions and maximum engine output torque will exceed said predetermined maximum torque loading capacity, said method comprising sensing the value of a control parameter (OS) indicative of vehicle ground speed; comparing the sensed value of said control parameter (OS) to a reference value (REF) corresponding to a value of said control parameter (OS) during drivetrain high torque loading operating conditions; and if the sensed value of the control parameter (OS) is indicative of the existence of drivetrain high torque loading operating conditions, causing said engine controller (36) to limit engine output torque to a value less than maximum engine output torque. The method of claim 1 wherein if said drivetrain high torque loading operating conditions are determined to exist, engine output torque is limited to 70% or less of maximum engine output torque. The method of claim 1 wherein said engine controller is microprocessor-based and communicates over an electronic data link. The method of claim 1 wherein said transmission (14) is manually shifted. A system for controlling a vehicular powertrain system (10) comprising a fuel-controlled engine (12) drivingly connected to a vehicular drivetrain system (11) including a multiple-ratio, change-gear transmission (14) and a drive axle (19), said engine having a maximum output torque and an engine controller (36) responsive to command signals to control fueling of the engine (12) and, in at least one mode of operation, effective to limit engine output torque and said drivetrain (11) having a predetermined maximum torque loading capacity, said drivetrain (11) configured such that an expected torque loading on said drivetrain (11) under a predetermined set of drivetrain high torque loading operating conditions and maximum engine output torque will exceed said predetermined maximum torque loading capacity, said system comprising means for sensing the value of a control parameter (OS) indicative of the vehicle ground speed; comparing the sensed value of said control parameter to a reference value (REF) corresponding to a value of said control parameter (OS) during drivetrain high torque loading operating conditions; and means effective, if the sensed value of the control parameter (OS) is indicative of the existence of drivetrain high torque loading operating conditions, causing said engine controller (36) to limit engine output torque to a value less than maximum engine output torque. The system of claim 5 wherein if said drivetrain high torque loading operating conditions are determined to exist, engine output torque is limited to 70% or less of maximum engine output torque. The system of claim 5 wherein said engine controller (36) is microprocessor-based and communicates over an electronic data link. The system of claim 5 wherein said transmission is manually shifted.

Inventors: BRAUN EUGENE RALPH, GEE THOMAS ARTHUR, HOLMES RUSSELL CLYDE, SMEDLEY DANIEL GEORGE, BRAUN, EUGENE RALPH, GEE, THOMAS ARTHUR, HOLMES, RUSSELL CLYDE, SMEDLEY, DANIEL GEORGE
Applicants: EATON CORP, EATON CORPORATION
Application year: 1996
Main classification: B60K41
IPC codes: G06F19, B60W10, F16H59, F02D29, B60W30