BACKGROUND OF THE INVENTION RELATED APPLICATIONS
This application is related to granted US Patent 6,520,889 (against copending U.S. Serial No. 09/704,288) titled : ADAPTIVE ENGINE CONTROL FOR SHIFTING TO NEUTRAL and assigned to Eaton Corporation, assignee of this application).
FIELD OF THE INVENTION
The present invention relates to a vehicular automated mechanical transmission system and in particular to a method for controlling dynamic shifting in a vehicular mechanical transmission system for selecting, as a function of sensed system operating parameters, either (i) a shift sequence involving master clutch disengagement or (ii) a shift sequence not involving master clutch disengagement, in an automatic mechanical transmission system including an automated master friction clutch.
DESCRIPTION OF THE PRIOR ART
Automate mechanical transmission systems (i.e. systems having transmissions wherein gear ratios are engaged and disengaged by jaw clutches) having automated master clutch operators are known in the prior art as may be seen by reference to U.S. Patent Nos : 4,081,065; 4,361,060; 4,648,290; 4,936,428; 5,960,916, 5,947,847; and 5,634,867, the disclosures of which are incorporated herein by reference. Automated mechanical transmission systems not having an automatic master clutch actuator and requiring manual master clutch operation, usually only to launch the vehicle, are also known in the prior art as may be seen by reference to U.S. Patent Nos: 6,145,399; 5,582,558; 6,146,310; 5,272,939; 5,335,566; and 5,425,689, the disclosures of which are incorporated herein by reference.
The prior art automated transmissions systems not having an automated master clutch actuator, by necessity, utilized a shift sequence for dynamic automatic shifting not requiring disengagement of the vehicle master........
clutch. Typically, engine fueling was controlled to relieve torque lock, allowing a shift from a previously engaged ratio into neutral and then the engine was caused to rotate at a substantially synchronous speed for engaging a target ratio, all with the master clutch remaining engaged. Systems of this type may be seen by reference to U.S. Patent No's: 4,850,263; 5,820,104; 4,593,580; 5,582,558; 6,126,570; and 6,145,399, the disclosures of which are incorporated herein by reference.
The prior art automated mechanical transmission systems having an
automated master clutch actuator tended to utilize a shift strategy or sequence for all dynamic shifts which included disengaging and then re-engaging the master friction clutch at least once during each shift, regardless if that shift could have been acceptably and/or preferably performed without disengaging and re-engaging the master clutch.
SUMMARY OF INVENTION
In accordance with the present invention, the drawbacks of the
prior art, automated mechanical transmission systems are minimized by providing a control for an automated mechanical transmission system having an automated master clutch operator which, on a shift-by-shift basis, and as a function of sensed vehicle operating conditions, will determine if (i) a shift strategy retaining the master clutch engaged or (ii) a shift strategy involving disengaging and re-engaging the master clutch, is most appropriate for a dynamic shift from an existing gear ratio into a target gear ratio. Accordingly, it is an object of the present invention to provide a
new and improved automated mechanical transmission system having automatic master clutch operator which will evaluate and implement the most effective of (i) a shift sequence retaining the master clutch engaged and (ii) a shift sequence involving disengaging and then re-engaging the master clutch, for dynamic shifts from an engaged ratio into a target gear ratio.
This and other objects and advantages of the present invention will
become apparent from a reading of the following description of the preferred embodiment taken in connection with the attached drawings.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 is a schematic illustration of a vehicular drivetrain using an
automated mechanical transmission system including an automatic master clutch
operator. Fig. 2 is a schematic illustration, in flow chart format, of the control
of the present invention. Fig. 3 is a schematic illustration of a preferred engine control
sequence for relieving torque lock in a shift sequence retaining the master clutch
engaged.
Figs. 4A and 4B are schematic illustrations, in flow chart formats of
an alternate embodiment of the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
An automated vehicular drivetrain system 10 using the shift sequence selection control technique of the present invention is schematically illustrated in Fig. 1. In system 10, a change-gear transmission 12 comprising an automatically shifted main transmission section 14 connected in series with an splitter-type auxiliary transmission section 16 is drivingly connected to an internal combustion engine 18, such as a well-known gasoline or diesel engine, by a automatically operated master friction clutch 20. Preferably,, auxiliary transmission section 16 is of the three-layer, four-speed combined splitter/ range type, as illustrated in U.S. Pat. No's. 4,754,665 and 5.390.561. the disclosures of which are incorporated herein by reference.
Engine 18 includes a crankshaft 22, which is attached to a driving
member 24 of master clutch 20, which is normally frictionally engaged with a driven member 26, which is attached to the input shaft 28 of the transmission. A transmission output shaft 30 extends from the auxiliary transmission section 16 for driving connection to the vehicular drive wheels, as through a drive axle 31 or the like. For purposes of illustration, transmission 12 is illustrated as a (2 + 1) x (2) x (2) type transmission providing nine or ten selectable forward ratios. Transmissions of this general type are well known in
the prior art and are sold by the assignee of this application, EATON CORPORATION, under the trademark "Super-10" and may be seen in greater detail by reference to U.S. Pat. No's. 6,015,366; 5,974,906; and 5,974,354, the disclosures of which are incorporated herein by reference. An inertia or input shaft brake 29 may be provided to selectively retard the rotational speed of input shaft 28. The engine may also include an engine brake device such as engine compression brake ECB. Transmission system 10 further includes rotational speed
sensors 32 for sensing engine rotational speed (ES), 34 for sensing input shaft rotational speed (IS), and 36 for sensing output shaft rotational speed (OS), and providing signals indicative thereof. A sensor 37 provides a signal THL indicative of throttle pedal position. The signal is usually a percentage (0% to 100%) of fuel throttle position. Engine 18 may be electronically controlled, including an electronic controller 38 communicating over an electronic data link (DL) operating under an industry standard protocol such as SAE J-1922, SAE J-1939, ISO 11898 or the like. An automated actuator 39 may be utilized to selectively engage and disengage normally engaged master clutch 20, as is well known in the prior art. A sensor 20A maybe provided to sense the condition of clutch 20 and to provide a signal C indicative thereof. Clutch controller 39 may be of any known type, such as a piston operated device, a ball ramp operated device or the like, see for example U.S. Patent No's.: 4,08."1,065.; 4,361,060; 4,865,173; 5,964,330; and 6,022,295.] A shift actuator 40 is provided to control shifting of the transmission sections. Shift actuator 40 is preferably an X-Y shift actuator, which by way of example may be of the types illustrated in U.S. Pat. No's.: 5,481,170; 5,281,902; 4,899,609; and 4,821,590. Actuator 40 will preferably include a position sensor 40A operable to sense the X-Y position of a shift member and to provide signals indicative thereof. X-Y position sensors are known in the prior art and examples thereof may be seen by reference to U.S. Pat. No's.: 5,743,143; 5,894,758; 5,950,491; and 5,911,787, the disclosures of which are incorporated herein by reference
A shift selector 42 provides a signal GRs of the mode of operator
selected by the operator. System 10 includes a control unit, preferably a microprocessor-based control unit 46 of the type illustrated in U.S. Patent. No's.: 4,595,986; 4,361,065; and 5,335,566, the disclosures of which are incorporated herein by reference, for receiving input signals 54 and processing same according to predetermined logic rules to issue command output signals 56 to system actuators, such as engine controller 38, clutch actuator 39, auxiliary section shift actuator 40, and the like. Control unit 46 may include a timing circuit or clock 48.
Figure 1A illustrates a typical jaw clutch assembly 70 for selectively engaging and disengaging a gear 72 to a shaft 74, such as a transmission main shaft, for engaging and disengaging a transmission ratio. Briefly, jaw clutch member 76 is splined to shaft 74 for axial movement relative thereto and rotation therewith. Jaw clutch member 76 carries external clutch teeth 78 for engaging internal clutch teeth 80 formed in the inner diameter bore of gear 72. The jaw clutch member 76 is axially positioned by a shift fork (not shown) or the like. The shift fork is typically axially positioned by a shift rail, a shift shaft, a ball ramp or ball screw, a piston, or a functionally similar device. As is known, to disengage a jaw clutch in a vehicular mechanical
transmission, especially in a heavy-duty vehicle, it is necessary to relieve torque lock at the engaged jaw clutch. If opening the master clutch 20 is not desirable, torque lock can be relieved by fueling the engine to cause assumed zero driveline torque and/or by forcing torque reversals which will positively cause crossings of zero driveline torque.
Fully or partially automated mechanical transmission systems that, upon determining that a dynamic shift from a currently engaged ratio into neutral and then into a target ratio is desirable, will, while maintaining the vehicle master friction clutch engaged, initiate automatic fuel control to cause reduced torque across the jaw clutches to be disengaged, are known in the prior art as may be seen by reference to U.S. Patent No's.: 4,850,236; 5,820,104; 5,582,558; 5,735,771; 5,775,639; 6,015,366; and 6,126,570, the disclosures \ of which are incorporated herein by reference. These systems include systems
that attempt to fuel the engine to achieve a sustained zero driveline torque, and systems that force torque reversals, see U.S. Patent No.: 4,850,236. These systems, upon sensing a neutral condition, will, while maintaining the master clutch engaged, cause the engine to rotate at a speed determined to cause synchronous conditions for engaging the target ratio.
Control of engine torque to achieve a desired output or flywheel is
"known as and may be seen by reference to U.S. Patent No.: 5,620,392, the disclosure of which is incorporated herein by reference. Engine torque as used herein refers to a value indicative of an engine torque, usually gross engine torque, from which an output or flywheel torque may be calculated or estimated. The relationship of gross engine torque to flywheel torque is discussed in U.S. Patent No's.: 5,509,867 and 5,490,063, the disclosures of which are incorporated herein by reference. One or more engine torque value may be commanded on, or read from, and industry standard data line, DL, such as SAE J-1922, SAE J-1939 or ISO11898 compliant datalink.
According to one embodiment of the present invention, upon
sensing that a shift from an engaged ratio to neutral, without disengaging the master clutch 20, is required, the engine is first commanded to ramp to a value of engine torque determined or calculated, based upon sensed system operating parameters, to correspond to zero driveline torque.
Referring to Fig. 3, if the shift initiates at a drive condition 110, the
engine torque will be commanded to ramp down 112 to the calculated value 114 assumed to correspond to the zero driveline torque condition. Similarly, if the shift to neutral initiates at a coast condition 116, the engine torque will be commanded to ramp up 118 to the calculated value 114. Preferably, the slope of the ramps 112 and 11 6 (i.e., the rate of change of engine torque) will be functions of the ratio being disengaged and/or current throttle position THL. Upon achieving the assumed zero driveline torque condition 120 (at time T,) the engine will be commanded to remain at this condition 122 for a period of T time (T2-T1) The period of time (T2-T1) is typically about 1 50-300 milliseconds. At expiration of that period of time 124, the sensed velocity of a shift member,
such as for example, a shift fork or shift finger, is compared to a reference value REF. If the shift member velocity equals or exceeds the reference value ((d/dt(SLY.Y))>REF), this indicates that the shift member is moving at a rate "towards jaw clutch disengagement indicative of non-torque lock conditions and a torque bump routine is not necessary or desirable. In such conditions, the engine will be commanded to continue generating an output torque assumed to correspond to zero driveline torque (solid line 126) until transmission neutral is sensed.
If the sensed shift member velocity does not equal or exceed the
reference value ((d/dt(SLY.Y)