Abstract:
The invention relates to a method and device for a coupling ( 2 ) in a motor vehicle transmission, the coupling being controlled and regulated during two operational states by way of a first regulating circuit ( 3 ). The regulated quantity corresponds to the actual value of a differential engine speed of the coupling ( 2 ). The first state corresponds to a starting action and the second state to operation with a variable transmission ratio.

Description:
FIELD OF THE INVENTION 
     The invention relates to a method and a device for controlling and regulating a coupling in a motor vehicle transmission in which an electronic control unit determines the behavior of the coupling by means of a regulating circuit. 
     BACKGROUND OF THE INVENTION 
     In the sense of the invention, the coupling is to be understood as a starting clutch. Under this designation fall clutches mounted between an internal combustion engine and an automatic transmission, lock up clutches and also clutches integrated in an automatic transmission which can be used both to start and as selector clutches. 
     A method for controlling a starting clutch has been disclosed, e.g. in DE 44 09 122 A1. Here the starting control comprises two phases. During a first phase, the input rotational speed of the clutch is brought to a theoretical rotational speed wherein the theoretical rotational speed is established from the driver&#39;s performance standard or the gradient and a driving activity. During the second phase, the difference between the input and the output rotational speeds of the clutch is reduced, according to a theoretical value curve to zero. DE 39 37 976 A1 disclosed a method for regulating the clutch which serves to neutralize vibration. The slip of the clutch is modified according to a revolution uniformity determined from the transmission output. From EP 0 214 989 B2, in turn, the use of a clutch integrated in the automatic transmission as a starting element is known. 
     Departing from the above described prior art, the problem on which the invention is based is to develop it, with regard to the multiple utilization of a single coupling, in combination with an automatic transmission. 
     SUMMARY OF THE INVENTION 
     According to the invention, the problem is solved by the present invention. It is advantageous that to control and regulate the coupling exclusively during two operational states, a single regulating circuit is used. The regulated quantity corresponds to the actual value of the differential rotational speed of the coupling. The two operational states correspond to a starting operation, as a first state, and to driving with a variable ratio, as a second state. 
     During a continuously variable adjustment, a specific regulating circuit, hereinafter designated as a second regulating circuit, determines the behavior of the continuously variable transmission. For this case, i.e. the second state, it is proposed that the first and second regulating circuits be interconnected, via an uncoupling network, wherein the uncoupling network has first and second signal paths. By the uncoupling network, the advantage that the two controllers do not influence each other in their action is thus obtained. 
     For both operational states, the theoretical value of the differential rotational speed of the coupling is determined from the addition of a theoretical value offset and a ratio-dependent differential rotational speed of the coupling. According to a first characteristic field, the ratio-dependent differential rotational speed is determined for a starting ratio of the continuously variable transmission. The ratio-dependent differential rotational speed for the non-starting ratios is determined via a second characteristic field. Both the first and the second characteristic fields each show a coordination of performance standard of the driver and an output rotational speed of the coupling. The second characteristic fields are configured in a manner such that at a vehicle speed lower than a limiting value, an increased theoretical value of the rotational speed difference results. An active protection against stalling for non-starting ratios is achieved. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING(S) 
     The invention is explained below with reference to the embodiments shown. In the drawings: 
     FIG. 1 is a summary of first and second regulating circuits; 
     FIG. 2 is a function block theoretical value standard; 
     FIG. 3 is a function block controller; 
     FIG. 4 is a first characteristic field for starting ratios; and 
     FIG. 5 is a second characteristic field for non-starting ratios. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a summary of the two regulating circuits. The first regulating circuit, for controlling and regulating the coupling  2 , is designated with the reference numeral  3 . The second regulating circuit, for controlling and regulating a continuously variable transmission  1 , is designated with reference numeral  4 . In FIG. 1, a variator is shown by the reference numeral  33 . By coupling  2  in the sense of the invention, a starting coupling is to be understood. This coupling can be front-mounted on the continuously variable transmission  1  or a lock-up coupling, or a coupling integrated in the transmission. Input variables  17  are fed to both the first and the second regulating circuits  3 ,  4 . The input variables are the signal of a driver&#39;s performance standard, e.g. throttle valve information DKI or the gradient thereof, the torque of an internal combination engine (not shown), which drives the continuously variable transmission  1  and an input/output rotational speed of the coupling  2 . The first regulating circuit  3  consists of the blocks: theoretical value standard  5 , controller  6 , factor  7 , mass ratio  8 , absolute value  9  and constant  10 . The theoretical value standard  5  delivers the theoretical value of the differential rotational speed dnK_SW coupling  2  and the controlled torque MK(ST) of the coupling  2 , as output variables, the same as the dynamic engine torque MDYN_MOT. The inner structure of the theoretical value standard  4  is explained with reference to FIG.  2 . The input variables  17 , the theoretical value dnK_SW of the differential rotational speed of the coupling  2 , the same as the actual value dnK_IST of the differential rotational speed of the coupling  2 . The inner structure of controller  6  is explained in with reference to FIG.  3 . The regulated torque MK(RE) of coupling  2  is the output variable of controller  6 . From the regulated torque MK(RE) of the coupling  2  and the dynamic engine torque MDYN_MOT results the regulated summation torque MK(RE)′, summation point A. This is summed up at point B with the controlled torque MK(ST) of the coupling  2  generated from the theoretical value standard  5  and the uncoupling torque M_CVT of the continuously variable transmission. From this sum, by means of function block  9 , an absolute value is formed and the result weighed with a constant at function block  10 . The output variable is a summed up pressure pSUM. A pressure offset pAK_OFF is superimposed to this summed up pressure pSUM at summation point C. The pressure level pAK, resulting herefrom, is the pressure level acting upon the coupling  2 . The second regulating circuit  4  consists of: theoretical value standard  11 , controller  12 , factor  13 , mass ratio  14 , the same as the product of engine inertia sequence of the continuously variable adjustment. From the input variables  17 , the function block theoretical value standard  11  determines the theoretical value n_SW of the continuously variable adjustment, the controlled portion of the regulated quantity of the CVT Y_ST. The theoretical value n_SW is compared at summation point D with the actual value n_IST of the continuously variable adjustment. The actual value n_IST is determined from output variables of the continuously variable transmission  1 . The resulting deviation is the input variable of the controller  12 . The controller output value Y_RE is added at summation point E to the dynamic torque portion Y_MDYN from the theoretical value standard  11 . From here results the regulated portion Y_RE′. The latter is added, at summation point F, to the controlled portion Y_ST and to the uncoupling portion Y_ENT. A regulated quantity is formed, for the continuously variable transmission from the result. The result is the regulated quantity Y_GES for the variator  33 . 
     The first and second regulating circuits  3 ,  4  are interconnected via an uncoupling network. The uncoupling network contains a first signal path in which the function block  7  and the function block  8  is situated. The input variable of the first signal path is the regulated summation torque MK(RE)′. This is multiplied by a factor at function block  7 . The factor is adjusted on the basis of tests. The result is weighted in function block  8  with the mass ratio of engine-mass to the sum of engine-mass and transmission-mass. The output variable is the uncoupling portion Y_ENT of coupling  2 . The second signal path of the uncoupling network has function blocks  13  and  14 , the input variable of which is the regulated portion Y_RE′ of the continuously variable gear shift. The output variable of the second signal path is the uncoupling torque of the continuously variable ratio M_ENT. 
     In FIG. 2 the inner structure of the theoretical value standard  5  is shown. To this is fed the input variables  17 . In function block  18 , theoretical value management, a rough theoretical value of the differential rotational speed of the coupling  2  is determined from the input variables rotational speed of the internal combustion engine throttle valve information DKI and torque of the internal combustion engine. The value is then filtered by filter  19  usually designed as PT 1  element with a gradient limitation. An output variable of filter  19  is the theoretical value dnk_SW of the differential rotational speed of the coupling  2 . This theoretical value is available at the output of the theoretical value standard  5 . One other output variable of filter  19  is linked in function block  20  with the engine inertia torque Theta-MOT and a factor, reference numeral  23 A. The output variable is then the dynamic torque of the internal combustion engine MDYN_MOT. From the input variable output rotational speed of the coupling nAB, the angular speed gradient dOmega/dt is determined by means of the function block  21 . The result is multiplied in function block  22  by the engine inertia torque Theta-MOT and the actual ratio of the continuously variable transmission  1 . The output variable is the dynamic torque MDYN_K on the coupling  2  during a continuously variable adjustment. The following equations apply here: 
     in the gradient adjustment phase: 
       MDYN   —   K=Theta - MOT .i1. dOmega/dt;   
     or in the sliding phase: 
     
       
           MDYN   —   K=Theta   —   MOT .i2. dOmega/dt;   
       
     
     MDYN_K: dynamic torque coupling; 
     Theta_MOT: the inertia torque of the internal combustion engine; 
     i1: first ratio step; 
     i2: second ratio step; 
     dOmega/dt: gradient angular speed coupling. 
     At summation point E, the dynamic torque of coupling  2  is then linked with torque MMOT generated by the internal combustion engine. The result is added, at summation point F, to the previously calculated dynamic torque of the internal combustion engine MDYN_MOT. The result is weighted in function block  23  with an adjustable factor, and the output variable of which is the controlled torque MK(ST) of coupling  2 . 
     FIG. 3 shows the inner structure of controller  6 . To this is fed the input variables  17 , the same as the theoretical value dnK_SW and the actual value dnK_IST of the differential rotational speed of coupling  2 . The absolute value is formed in function block  24  from the actual value dnK_IST. The absolute value is then the input variable for divisor  27  and summation point G. The theoretical value dnK_SW of the differential rotational speed of the coupling  2  is passed as a second input variable to divisor  27 . The quotient is passed to function block  28 , characteristic line dynamic lowering. Over the characteristic line is artificially increased at very low slipping values such as less than  19  revolutions, the input value of integrator  31 . An additional ramp-like pressure reduction is obtained. The zero point results from a ratio of actual to theoretical value of the rotational speed difference of coupling  2 . The input variable throttle valve information DKI is the input signal for a dT 1 -element  29 . The output signal of this filter is then the input signal for the “quickly open” characteristic line  30 . The input value of integrator  31  is artificially increased over this characteristic line during quick gas re-utilization according to the driver&#39;s desired performance or the gradient thereof. An additional ramp-like pressure reduction results. The pressure reduction can be changed over the characteristic line. 
     At summation point G, the theoretical value dnK_SW is summed up with the absolute value of the actual value of the differential rotational speed coupling  2  formed in function block  24 . On one hand, the result is then passed parallel, via a function block P-portion  25  and, on the other, via an I-portion  26 . The output variable of the P-portion  25  acts upon summation point H. The output variable of function block  26  acts upon the limited integrator  31 . The output value of the limited integrator  31  is linked, at summation point H, with the proportional part from function block  25  and passed to the active factor function block  32 . Via the active factor, the direction in which the actual regulating torque must act. This is needed to determine the uncoupling portion Y_ENT is determined. 
     In FIG. 4 a first characteristic field KF 1 (i) of the continuously variable transmission  1  is shown. The characteristic field is used for a starting operation. A gear-dependent differential rotational speed dn_SW(i) is determined by means of the characteristic field KF 1 (i). Input variable of the first characteristic field is the output rotational speed nAB of the coupling  2 , the same as the throttle valve information DKI. A range defined by the two limiting lines F 1  and F 2  is shown within the characteristic field. The limiting line F 2  corresponds to the throttle valve value of 0%. The limiting line F 1  corresponds to the throttle valve value of 100%. An assemblage of characteristic lines of several throttle valve values is shown within the range. The sequence of the method is the following: the operating point A results from the actual output rotational speed value nAB of coupling  2 , the value n 1 , and the actual throttle valve value, such as 50%. From this, in turn, results the gear-dependent differential rotational speed value dnK_SW(i), here the value nA. In FIG. 4 a rotational speed overshoot, point B, at an output rotational speed of 3000 revolutions is additionally plotted. Via the rotational speed overshoot n(B) a neutralization of vibrations between internal combustion engine and output of continuously variable transmission  1  is obtained. The position of point B or value n(B) depends on the internal combustion engine used and is defined in the adaptation phase of the continuously variable transmission. 
     In FIG. 5 a second gear-dependent characteristic field KF 2 (i) is shown. Via this second characteristic field KF 2 (i) the differential rotational speed dn_SW(i), for non-starting ratios of the continuously variable transmission, is determined. The input and output variables correspond to those of the first characteristic field. The characteristic field also contains a range defined by the two limiting characteristic lines F 1  and F 2 . The limiting line F 2  corresponds to 0% and the limiting line F 1  corresponds to 100% throttle valve information DKI. Point C is plotted on limiting line F 1 . This rotational speed overshoot value n(c) causes the coupling to be kept in slipping state so as to obtain an active neutralization of vibration. A shaded range is shown within the characteristic field. The range serves for protection against stalling, i.e. at low output rotational speed nAB of coupling  2 , it is loaded with a defined theoretical value of the differential rotational speed. The stalling protection is also calculated according to the following equation: 
     
       
         
               
               
             
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                 dnK_SW(i) &gt; NMOT)_MIN-nAB; 
               
             
          
           
               
                   
                 NMOT_MIN: 
                 is the minimal rotational speed of the internal 
               
               
                   
                   
                 combustion engine; 
               
               
                   
                 nAB: 
                 is an output rotational speed of coupling 2. 
               
               
                   
                   
               
             
          
         
       
     
     The first characteristic field KF 1 ( 1 ) with i=1 or 2 is used for a starting ratio. The second characteristic field KF 2 (i), i=3 to n, is used for non-starting ratios. A specific characteristic field thus exists for each ratio. The transition from the first KF 1 (i) to the second KF 2 (i) characteristic field occurs during continuously variable adjustment of the continuously variable transmission  1 . This means that the curve of the characteristic lines, according to the first characteristic field KF 1 (i) of FIG. 4, is approximated, via intermediate characteristic fields, to a curve according to FIG.  5 . These characteristic fields are not shown. 
     The sequence of this inventive method is as follows. In the first stage, that is, in the starting ratio, the ratio-dependent differential rotational speed dn_SW(i) is determined by means of the first characteristic field KF 1 (i). The value corresponds to the theoretical value of the differential rotational speed dnK_SW of coupling  2 , since the theoretical value offset dnK_SW is zero. With increasing output rotational speed nAB of coupling  2 , this theoretical speed is reduced, according to FIG. 4, for increasing the comfort a higher theoretical value is adjusted in order to achieve a neutralization of vibrations. If a continuously variable adjustment is now initiated, a change is effected from the first characteristic field KF 1 (i) to the second characteristic field KF 2 (i), according to FIG.  5 . During the continuously variable adjustment, an uncoupling portion M_CVT is added, via the uncoupling network, by the second signal path to the controlled torque MK(ST) and regulated summation torque MK(RE)′. An uncoupling portion Y_ENT of coupling  2  is added to the variator  33  to be adjusted via the first signal path. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 Reference numerals 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                  1 
                 continuously variable transmission 
               
               
                  2 
                 coupling 
               
               
                  3 
                 first regulating circuit 
               
               
                  4 
                 second regulating circuit 
               
               
                  5 
                 theoretical value standard 
               
               
                  6 
                 controller 
               
               
                  7 
                 factor 
               
               
                  8 
                 calculation block mass ratio 
               
               
                  9 
                 absolute value 
               
               
                 10 
                 constant 
               
               
                 11 
                 theoretical value standard 
               
               
                 12 
                 controller 
               
               
                 13 
                 factor 
               
               
                 14 
                 calculation block: mass ratio 
               
               
                 15 
                 — 
               
               
                 16 
                 — 
               
               
                 17 
                 input variables 
               
               
                 18 
                 theoretical value management 
               
               
                 19 
                 filter 
               
               
                 20 
                 inertia torque 
               
               
                 21 
                 calculation block dOmega/dt 
               
               
                 22 
                 calculation block 
               
               
                 23, 23A 
                 factor 
               
               
                 24 
                 absolute value 
               
               
                 25 
                 P-portion 
               
               
                 26 
                 I-portion 
               
               
                 27 
                 divisor 
               
               
                 28 
                 characteristic line dynamic lowering 
               
               
                 29 
                 dT1 element 
               
               
                 30 
                 characteristic line “quickly open” 
               
               
                 31 
                 limited integrator 
               
               
                 32 
                 active factor 
               
               
                 33 
                 variator 
               
               
                 dn_SW(i) 
                 ratio-dependent differential rotational speed 
               
               
                 dnK_SW 
                 theoretical value differential rotational speed coupling 
               
               
                 dnK_IST 
                 actual value differential rotational speed coupling 
               
               
                 MK(ST) 
                 controlled torque coupling 
               
               
                 MK(RE) 
                 regulated torque coupling 
               
               
                 Y_ENT 
                 uncoupling portion of the regulated quantity of the 
               
               
                   
                 variator 
               
               
                 pAK_OFF 
                 pressure offset starting coupling 
               
               
                 pSUM 
                 summed up pressure 
               
               
                 pAK 
                 pressure level coupling 
               
               
                 MDYN_K 
                 dynamic torque coupling 
               
               
                 pLS_OFF 
                 pressure offset gear shift under load 
               
               
                 nAB 
                 output rotational speed coupling 
               
               
                 n_SW 
                 theoretical value rotational speed 
               
               
                 n_IST 
                 actual value rotational speed 
               
               
                 Y_ST 
                 controlled portion of the regulated quantity of the variator 
               
               
                 Y_RE 
                 regulated portion of the regulated quantity of the variator 
               
               
                 Y_RE′ 
                 sum of the portions Y_RE and Y_MDYN 
               
               
                 Y_ENT 
                 uncoupling portion of the regulated quantity of the 
               
               
                   
                 variator 
               
               
                 Y_MDYN 
                 theoretical gradient portion of the regulated quantity 
               
               
                   
                 of the variator 
               
               
                 Y_GES 
                 regulated quantity for variator 
               
               
                 MMOT 
                 engine torque 
               
               
                 MDYN_MOT 
                 dynamic engine torque 
               
               
                 M_CVT 
                 uncoupling torque of the variator regulation 
               
               
                 DKI 
                 throttle valve information = load position 
               
               
                 dnLS_SW 
                 theoretical value offset 
               
               
                 Theta-MOT 
                 engine inertia torque 
               
               
                 i_CVT 
                 actual variator ratio