Abstract:
A method/system for controlling upshifting in an automated mechanical transmission system ( 10 ) utilized on a vehicle having an ECU ( 28 ) operated friction upshift brake ( 26 ) capable of applying two or more levels of retardation to a transmission input shaft ( 16 ).

Description:
RELATED APPLICATIONS 
     This application is related to copending U.S. Ser. No. 09/573,873 filed May 17, 2000 and assigned to EATON CORPORATION, assignee of this application. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a control method/system for controlling upshifting in an at least partially automated mechanical transmission system. In particular, the present invention, in one preferred embodiment, relates to the control of upshifting in a vehicular automated mechanical transmission system wherein the system senses conditions indicative of a requirement for an upshift from a currently engaged gear ratio (GR) and evaluates, in sequence, the desirability of unaided upshifts and then upshift brake-assisted upshifts and commands upshifts deemed desirable. 
     More particularly, the present invention relates to a control method/system for controlling upshift brakes in potential upshift brake-aided upshifts as a function of one or more of the thermal characteristics of the upshift brake, the estimated current temperature of the brake, the period of time since the previous upshift brake-aided upshift and/or the expected heat energy generated by the previous upshift brake-aided upshift and/or the by the upshift under consideration at differing levels of brake caused retardation. 
     2. Description of the Prior Art 
     Fully or partially automated mechanical transmission systems for vehicular use are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,361,060; 4,648,290; 4,722,248; 4,850,236; 5,389,053; 5,487,004; 5,435,212 and 5,755,639, the disclosures of which are incorporated herein by reference. The use of engine brakes (also known as compression brakes, exhaust brakes or Jake brakes) and transmission controls utilizing same are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,409,432 and 5,425,689, the disclosures of which are incorporated herein by reference. 
     The use of friction devices to retard transmission input shaft rotation, such as inertia brakes (also known as upshift brakes or input shaft brakes) and actuators therefor, for providing quicker upshifts is known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,086,659 and 5,713,445, the disclosures of which are incorporated herein by reference. 
     Controls for automated mechanical transmission systems, especially wherein shifting is accomplished while maintaining the master clutch engaged, wherein single and/or skip shift feasibility is evaluated are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 4,576,065; 4,916,979; 5,335,566; 5,425,689; 5,272,939; 5,479,345; 5,533,946; 5,582,069; 5,620,392; 5,489,247; 5,490,063; 5,509,867, and 6,149,545, the disclosures of which are incorporated herein by reference. 
     Controls for automated mechanical transmission systems including control of friction upshift brakes are known in the prior art as may be seen by reference to U.S. Pat. No. 6,123,643, the disclosure of which is incorporated herein by reference. 
     In the system described in U.S. Pat. No. 6,149,545, a control for a vehicular automated mechanical transmission system will sense conditions indicative of upshifting from a currently engaged gear ratio, will evaluate, in sequence, the desirability of large skip upshifts, then single skip upshifts, unaided single upshifts and then upshift brake-aided single upshifts, and will command an upshift to the first target ratio deemed to be feasible under current vehicle operating conditions. 
     The upshift feasibility rules comprise a two-part test, (a) can the upshift be completed above a minimum engine speed? and (b) when completed, will the engine, in the target ratio, provide sufficient torque at the drive wheels to allow at least a minimum vehicle acceleration? Feasibility of skip and/or single upshifts also may require that an upshift is expected to be completed within a period of time less than a maximum acceptable time (T&lt;T MAX ?). 
     SUMMARY OF THE INVENTION 
     The control of the present invention relates to controlling a friction upshift brake which may be operated at two or more levels of retardation to provide variable additional deceleration, during a shift with the master clutch engaged, to a transmission input shift and the engine crank shaft and master clutch rotating therewith. This retardation is additive to the natural rate of deceleration of the engine called “engine speed decay” due to friction and the like. Actuation of the upshift brake will apply an added retarding force to the input shaft, clutch and, engine assembly to provide an additional deceleration of the input shaft. 
     To prevent undue wear and/or damage of friction-type upshift brakes, the predicted maximum deceleration available from the upshift brake without causing the brake to overheat (TEMP p &lt;TEMP MAX ) is estimated or simulated. This maximum deceleration is then compared to the deceleration necessary to complete a potential downshift. 
     If the additional deceleration needed to complete a shift above a minimal engine speed and/or within a maximum acceptable time exceeds the maximum additional deceleration the upshift brake can provide without damage, usually thermal damage, an upshift into the target gear is not commanded. 
     If an upshift is feasible, the upshift brake will be utilized to provide a degree of deceleration to allow the shift to occur above the minimum engine speed, and, if possible, within a desirable period of time (such as, for example, within 1.2 seconds for a heavy-duty truck). 
     Accordingly, an improved upshift control for automated mechanical transmissions is provided which will automatically evaluate and command an acceptable level of upshift brake actuation for a proposed upshift brake-aided upshifts and which provides thermal protection for the friction-type upshift brake. 
     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 DRAWINGS 
     FIG. 1 is a schematic illustration, in block diagram format, of an automated mechanical transmission system utilizing the control of the present invention. 
     FIG. 2 is a schematic illustration, in graphical format, illustrating shift point profiles for the transmission system of FIG. 1 according to the present invention. 
     FIGS. 3A and 3B are schematic illustrations, in flow chart format, of the control of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     An at least partially automated mechanical transmission system intended for vehicular use is schematically illustrated in FIG.  1 . The automated transmission system  10  includes a fuel-controlled engine  12  (such as a well-known diesel engine or the like), a multiple-speed, change-gear transmission  14 , and a non-positive coupling  16  (such as a friction master clutch) drivingly interposed between the engine and the input shaft  18  of the transmission. The transmission  14  may be of the compound type comprising a main transmission section connected in series with a splitter- and/or range-type auxiliary section. Transmissions of this type, especially as used with heavy-duty vehicles, typically have 9, 10, 12, 13, 16 or 18 forward speeds. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 5,390,561 and 5,737,978, the disclosures of which are incorporated herein by reference. 
     A transmission output shaft  20  extends outwardly from the transmission  14  and is drivingly connected with the vehicle drive axles  22 , usually by means of a prop shaft  24 . The illustrated master friction clutch  16  includes a driving portion  16 A connected to the engine crankshaft/flywheel and a driven portion  16 B coupled to the transmission input shaft  18  and adapted to frictionally engage the driving portion  16 A. An upshift brake  26  (also known as an input shaft brake or inertia brake) may be used for selectively decelerating the rotational speed of the input shaft  18  for more rapid upshifting, as is well known. Upshift brake  26  may have two or more selectable levels of retardation or may be actuated to provide infinitely variable levels of retardation. Friction type input shaft or upshift brakes are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,655,407 and 5,713,445. 
     A microprocessor-based electronic control unit (or ECU)  28  is provided for receiving input signals  30  and for processing same in accordance with predetermined logic rules to issue command output signals  32  to various system actuators, such as upshift brake actuator  26 A, and the like. ECU  28  may include a clock or other timing device  28 A. Microprocessor-based controllers of this type are well known, and an example thereof may be seen by reference to U.S. Pat. No. 4,595,986. 
     System  10  includes a rotational speed sensor  34  for sensing rotational speed of the engine and providing an output signal (ES) indicative thereof, a rotational speed sensor  36  for sensing the rotational speed of the input shaft  16  and providing an output signal (IS) indicative thereof, and a rotational speed sensor  38  for sensing the rotational speed of the output shaft  20  and providing an output signal (OS) indicative thereof. A sensor  40  may be provided for sensing the displacement of the throttle pedal and providing an output signal (THL) indicative thereof. A shift control console  42  may be provided for allowing the operator to select an operating mode of the transmission system and for providing an output signal (GR T ) indicative thereof. 
     As is known, if the clutch  16  is engaged without slip, the rotational speed of the engine may be determined from the speed of the input shaft and/or the speed of the output shaft and the engaged transmission ratio (ES=IS=OS*GR). Also, with the clutch engaged, input shaft  18 , clutch  16  and the engine flywheel and crankshaft will rotate as a unit. 
     System  10  also may include sensors  44  and  46  for sensing manual operation of the vehicle foot brake (also called service brakes) and/or engine compression brakes (ECB), respectively, and for providing signals FB and EB, respectively, indicative thereof. 
     The master clutch  16  may be controlled by a clutch pedal  48  or by a clutch actuator  50  responding to output signals from the ECU  28 . Alternatively, an actuator responsive to control output signals may be provided, which may be overridden by operation of the manual clutch pedal. In the preferred embodiment, the clutch is manually controlled and used only to launch the vehicle (see U.S. Pat. Nos. 4,850,236; 5,272,939 and 5,425,689). The transmission  14  may include a transmission actuator  52 , which responds to output signals from the ECU  28  and/or which sends input signals to the ECU  28  indicative of the selected position thereof. Shift mechanisms of this type, often of the so-called X-Y shifter type, are known in the prior art, as may be seen by reference to U.S. Pat. Nos. 5,305,240 and 5,219,391. Actuator  52  may shift the main and/or auxiliary section of transmission  14 . The engaged and disengaged condition of clutch  16  may be sensed by a position sensor (not shown) or may be determined by comparing the speeds of the engine (ES) and the input shaft (IS). 
     Fueling of the engine is preferably controlled by an electronic engine controller  54 , which accepts command signals from and/or provides input signals to the ECU  28 . Preferably, the engine controller  54  will communicate with an industry standard data link DL which conforms to well-known industry protocols such as SAE J1922, SAE 1939 and/or ISO 11898. The ECU  28  may be incorporated within the engine controller  54 . 
     For automated shifting, the ECU  28  must determine when upshifts and downshifts are required and if a single or skip shift is desirable (see U.S. Pat. Nos. 4,361,060; 4,576,065; 4,916,979; 4,947,331 and 6,149,545). 
     FIG. 2 is a graphical representation of shift point profiles utilized to determine when shift commands should be issued by the ECU  28  to system actuators including the shift actuator  52 . Line  60  is the default upshift profile, while line  62  is the default downshift profile. Shift profile  60  is a graphical representation of the engine speeds at which upshifts from a currently engaged ratio (GR) are indicated (ES U/S ) for various degrees of throttle displacement (ie., demand). As is known, if the vehicle is operating to the right of upshift profile  60 , an upshift of transmission  14  should be commanded, while if the vehicle is operating to the left of downshift profile  62 , a downshift should be commanded. If the vehicle is operating in between profiles  60  and  62 , no shifting of the transmission is then required. 
     According to the control of a preferred embodiment of the present invention, if an upshift from a currently engaged ratio (GR) is required (i.e., if at current throttle displacement engine speed (ES) is greater than the upshift engine speed (ES U/S ) on shift point profile  60 ), a sequence is initiated for identifying the desirable upshift target ratio (GR TARGET ), if any. In a preferred embodiment, the control, in sequence, will evaluate unaided and/or aided skip upshifts and then unaided single upshifts and then upshift brake-aided single upshifts for desirability and command an upshift to the first potential target ratio deemed desirable. 
     In a preferred embodiment, a maximum time for completion of an upshift is established based upon considerations for shift quality, vehicle performance, etc. For heavy-duty trucks, by way of example, this time value may have a value of about 0.8 to 2.0 seconds. 
     A two-part feasibility test is established: 
     (1) Will the engine speed be at a synchronous value above a preselected minimum engine speed ES MIN , given current/assumed engine and vehicle deceleration rates? The ES MIN , by way of example, is selected at about 1100 to 1300 rpm, which for a typical heavy-duty diesel engine is at or near a peak torque rpm. 
     The engine deceleration rate may be evaluated with or without the use of engine braking. This logic may be appreciated by reference by U.S. Pat. Nos. 5,335,566 and 5,425,689, the disclosures of which are incorporated herein by reference. The friction upshift brake  26  may be used separately or in addition to an engine brake. Use of engine brakes (also called exhaust and Jake brakes) to enhance upshifting is known, as may be seen by reference to U.S. Pat. No. 5,409,432; and 
     (2) At completion of a proposed upshift, will torque at the drive wheels provide sufficient torque for at least minimal vehicle acceleration? (See U.S. Pat. Nos. 5,272,939 and 5,479,345, the disclosures of which are incorporated herein by reference. 
     Feasibility also may require that a potential upshift be expected to be completed in a time (T) less than the maximum acceptable time (T&lt;T MAX ). If one or more of these parts of the feasibility test are not satisfied, the proposed upshift to an evaluated target ratio (GR+1, 2, 3, . . . ) is not feasible and will not be commanded. 
     To provide a maximized upshift braking effect, while thermally protecting the friction-type upshift brake, the maximum additional input shift deceleration available using the friction upshift brake  26  is calculated using a simulation technique wherein the expected brake temperature (TEMP P ) at completion of a potential shift is set equal to a maximum allowable temperature to determine a maximum additional input shaft deceleration value. For example, as disclosed in copending application Ser. No. 09/573,873, TEMP p , the predicted temperature may be a calculated or simulated from a relationship such as: 
     
       
         
           TEMP 
           MAX 
           =TEMP 
           p 
           =TEMP 
           i 
           +TEMP 
           b 
           −TEMP 
           c 
         
       
     
     where: 
     TEMP p =predicted brake temperature at completion of an upshift brake-aided upshift; 
     TEMP i =initial (present) brake temperature; 
     TEMP b =temperature rise due to brake-aided upshift; and 
     TEMP c =temperature decline during brake-aided upshift. 
     TEMP i , the simulated initial or present temperature of the brake, is the greater of (i) a minimum value (about 200° F.) or (ii) the last predicted value decreased at a selected cooling rate since the last brake actuation (such as −7° F. per second). 
     TEMP b , the expected temperature rise due to brake actuation, is a function of one or more of (i) a target engine deceleration, (ii) the natural engine decay rate, (iii) engine inertia (I), often available on the data link, (iv) present engine speed (RPM), (v) step of proposed shift; (vi)t he rate of engine deceleration; and (vii) a constant. 
     TEMP c , the cooling during the assisted shift, is a function of (i) a transmission sump temperature (TEMP s ), (ii) an expected shift time and (iii) a second constant. 
     As may be seen, the expected temperature of the brake at completion of a proposed shift (TEMP p ) may be simulated using various system parameters and may be compared or set equal to a maximum reference value (TEMP MAX ) (such as about 350° F.) to determine if upshift brake assist for a particular upshift is allowable and/or the maximum level of added retardation that the brake can provide without risk of undue wear or damage. 
     The parameters used to simulate the predicted temperature (TEMP p ) may include one or more of (i) a simulated initial brake temperature, (ii) time since last brake actuation, (iii) an estimated brake cooling rate when not active, (iv) temperature at completion of last assisted upshift, (vi) a desired engine deceleration rate, (vii) an engine decay rate, (viii) present engine speed, (ix) synchronous engine speed, (x) engine inertia, (xi) ratio step, (xii) calculated shift time, (xiii) cooling rate during brake actuation and/or (xiv) various assumed constants. Of course, less than or more than the above parameters may be used to estimate or simulate an expected brake temperature (TEMP p ). A prior art temperature simulation technique may be seen by reference to U.S. Pat. No. 4,576,263, the disclosure of which is incorporated herein by reference. 
     The “additional deceleration” provided by the upshift brake is deceleration in addition to the natural decay rate of the engine. The input brake  26  may have several levels of engine rotational speed retardation or may provide infinitely valuable levels of retardation. 
     As used herein, deceleration is taken as a positive quantity, i.e. a greater retarding force will result in a more positive or greater deceleration. For example, −5 RPM/sec 2  is a smaller deceleration then −10 RPM/sec 2 . 
     In addition to calculating the maximum allowable additional engine speed deceleration available from the upshift brake (MAX Decel), the control logic will also calculate or determine; 
     a) the additional engine speed deceleration necessary to complete the shift in a desirable time (Desired Decel). The desirable time may be, for example, between 1.0 and 1.2 seconds; and 
     b) the additional engine deceleration necessary to complete the proposed upshift at above a selected speed engine (Required Decel). 
     The control logic will then issue command output signals to the transmission shifter  52 , the engine controller  54  and/or the input brake actuator  26 A according to the following logic. 
     If an upshift is required, i.e. if , for a given throttle position, ES is to the right of upshift profile  60 , shifts to a potential target gear ration GR T  are evaluated as follows: 
     a) if the desired deceleration is less then zero (Desired Decel&lt;0), then the shift to GR T  is initiated without the use of the inertia or upshift brake  26 . 
     b) if the maximum deceleration is less than the required deceleration (Max Decel&lt;Required Decel), then the proposed upshift to GRT is not initiated. 
     c) if the desired deceleration is greater than zero (Desired Decel &gt; 0 ) and required deceleration is less than maximum deceleration (Required Decel&lt;Max Decel) and desired deceleration is greater than required deceleration (Desired Decel&gt;Required Decel), then initiate the shift to GR T  using the upshift brake  26  at the retardation level for desired deceleration; and 
     (d) if the desired deceleration is greater than zero (Desired Decel &gt;0), and the required deceleration is less than maximum deceleration (Required Decel&lt;Max Decel) and desired deceleration is less than required deceleration (Desired Decel&lt;Required Decel) then initiate the upshift to GR T  using the upshift brake  26  at the retardation level providing required deceleration. 
     This logic differs from logic utilized for evaluating potential upshifts aided by engine brakes, as using the engine brake (usually an engine compression brake) for upshifts is not a first option due to potentially objectionably noisy and/or slower and/or rough shifting, other than for wear, no such drawback is associated with use of the friction upshift brake  26 . 
     FIGS. 3A and 3B illustrate the present invention in a flow chart format. 
     Although the present invention has been described with a certain degree of particularity, it is understood that the description of the preferred embodiment is by way of example only and that numerous changes to form and detail are possible without departing from the spirit and scope of the invention as hereinafter claimed.