Methods for regulating the gear ratio of an automatic power-branched transmission, and automatic power-branched transmission

• US 20050227809A1
• Filed: 01/27/2003
• Published: 10/13/2005
• Est. Priority Date: 02/07/2002
• Status: Active Grant

• Current Assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG
• Original Assignee: LuK Lamellen und Kupplungsbau Beteiligungs KG
• Inventors: Homm, Manfred, Stehr, Reinhard, Vornehm, Martin, Bitzer, Franz, Reuschel, Michael, Lauinger, Christian, Muller, Eric, Walter, Bernhard, Teubert, Andre
• Granted Patent: US 7,493,203 B2
• Time in Patent Office: Days
• US Class Current: 477/37
• CPC Class Codes: F16H 2037/025 CVT's in which the ratio coverage is used more than once to produce the overall transmission ratio coverage, e.g. by shift to end of range, then change ratio in sub-transmission and shift CVT through range once again
• CPC Class Codes: F16H 2037/088 Power split variators with summing differentials, with the input of the CVT connected or connectable to the input shaft
• CPC Class Codes: F16H 2061/6614 Control of ratio during dual or multiple pass shifting for enlarged ration coverage
• CPC Class Codes: F16H 2061/6616 the shifting of the transmission being manually controlled
• CPC Class Codes: F16H 37/084 at least one power path being a continuously variable transmission, i.e. CVT
• CPC Class Codes: F16H 37/0846 CVT using endless flexible members
• CPC Class Codes: F16H 61/66254 controlling of shifting being influenced by a signal derived from the engine and the main coupling
• CPC Class Codes: F16H 61/66272 characterised by means for controlling the torque transmitting capability of the gearing

Abstract

A method for regulating or controlling the transmission ratio of an automatic power-branched transmission. Power is transmitted through a shaft driven by an engine, a variable speed drive, a gear transmission, a driven shaft, and at least two control clutches. The variable speed drive and the gear transmission are connected to each other in such a way that the regulating range of the variable speed drive is traversed in one direction within a first range of transmission ratios, and is traversed in the opposite direction within a second range of transmission ratios during traversing of the entire range of transmission ratios. The shifting strategies result in reduced wear of the endless belt device and allow for comfortable changing between the transmission ratio ranges.

Claims

1. A method for regulating the transmission ratio of a power-branched automatic transmission that includes an input shaft drivable by an engine, a variator with a continuously variable transmission ratio, a gear transmission, an output shaft and at least two control clutches through which the variator and the gear transmission can be operatively connected, said method comprising the steps of:

traversing the overall transmission ratio range of the power-branched transmission in a first direction within a first transmission ratio range;

traversing the overall transmission ratio range of the power-branched transmission within a second transmission ratio range in a second direction opposite from the first direction, wherein at least one regulator parameter of an adjustment regulator utilized to set the transmission ratio of the variator changes its sign during a transition between the transmission ratio ranges.

2. A method according to claim 1, wherein an output signal of the adjustment regulator changes its sign during the transition between the transmission ratio ranges.

3. A method according to claim 1, wherein the output signal of the adjustment regulator is changed in accordance with a momentary value of di_ges/di_var, whereby i_ges is the transmission ratio of the power-branched transmission and i_var is the transmission ratio of the variator.

4. A method according to claim 3, wherein the adjustment regulator is a PID regulating unit and the P component of the regulating unit is multiplied by the momentary value of di_ges/di_var.

5. A method according to claim 3, wherein an input signal of the adjustment regulator in accordance with a deviation between a target rotational speed and an actual rotational speed is changed in accordance with the momentary value of di_ges/di_var.

6. A method according to claim 1, including the step of reducing input signals to the adjustment regulator during the transition between the transmission ratio ranges.

7. A method according to claim 6, including the step of changing an anticipatory control of a difference of contact pressures of disk pairs of the variator during a transition between the transmission ratio ranges in accordance with changing torque.

8. A method according to claim 1, including the step of changing an integral component of the adjustment regulator during the transition between the transmission ratio ranges.

9. A method according to claim 1, including the following steps:

calculating an actual transmission ratio i_var of the variator and an actual overall transmission ratio of the power-branched transmission on the basis of measured rotational speeds and a shift condition of the control clutches,

calculating an actual rotational speed n_actual of the input shaft of the variator on the basis of overall transmission ratio and a measured motor vehicle wheel rotational speed,

calculating a change in the actual rotational speed n_actual and a change in a target rotational speed n_target of the input shaft,

calculating a shift rotational speed n_um at which a shift of the control clutches must take place exactly at a current wheel rotational speed and

determining a gear change on the basis of the calculated values.

10. A method according to claim 9, wherein shifting takes place before reaching the shift rotational speed n_um and further shifting is possible only after expiration of an idle period.

11. A method according to claim 1, including the step of controlling the clutches based upon predetermined conditions so that the transmission transfers no torque and the transmission ratio of the variator is rapidly distorted in that condition.

12. A method according to claim 1, including the step of utilizing the control clutches for shifting between the transmission ratio ranges, wherein in the event of a transmission ratio of the variator that is outside a transmission ratio value at which the transmission ratio of the power-branched transmission is independent from the activated transmission ratio range, the control clutches are shifted in such a way that in the case of tractive shifts acceleration power is released and in the case of retarding shifts delay power is released.

13. A method according to claim 1, including the step of controlling transmission control strategy so that at least at high torques transmitted from the variator in the adjacent regions of the transmission ratio ranges operation in a transmission ratio range with lower wear of an endless torque-transmitting means has priority over the rotational speed of the input shaft.

14. A method according to claim 1, wherein after a shift from one transmission ratio range into the other, renewed shifting takes place only after traversing a predetermined hysteresis region.

15. A method according to claim 1, wherein after shifting from one transmission ratio range into the other renewed shifting takes place only after expiration of a predetermined time period.

16. A method according to claim 1, wherein after shifting from one transmission ratio range into the other renewed shifting can only take place following a predetermined activation of a motor vehicle operating part.

17. A method according to claim 1, wherein a contact overpressure of disk pairs of the variator takes place during shifting between the transmission ratio ranges.

18. A method according to claim 1, wherein the torque transmission direction of the variator within the first transmission ratio range of the power-branched transmission is opposite to that within the second transmission ratio range, wherein an engaging clutch is engaged in a shift between transmission ratio ranges in such a way that the transmittable clutch torque for a short time lies slightly above the torque applied to the transmission.

19. A method according to claim 1, wherein the direction of torque transmission of the variator within the first transmission ratio range of the power-branched transmission is opposite to that within the second transmission ratio range, wherein a target rotational speed of the engine in the transmission ratio range of the transmission that corresponds to low motor vehicle speeds is limited to an upper limit that is dependent upon the motor vehicle speed.

20. A method according to claim 1, wherein while shifting between transmission ratio ranges, the engine power is changed before, during, and after the shift in accordance with different power consumption levels by control units for operating the transmission.

21. A method according to claim 1, wherein during a shift between the transmission ratio ranges the engine power is changed in accordance with different accelerations of rotatable components developing during the gear change.

22. A method according to claim 1, wherein during a shift between the transmission ratio ranges, the control clutches are actuated in accordance with the accelerations of rotatable components arising during shifting.

23. Method for regulating the transmission ratio of a power-branched automatic transmission that contains a input shaft drivable by a engine, a variator with continuously variable transmission ratio, a gear transmission, a output shaft and at least two control clutches by means of which the variator and the gear transmission can be connected with one another such that, when traversing the overall transmission ratio range of the branched transmission, within a first transmission ratio range the adjustment range of the CVT transmission is traversed in one direction and within a second transmission ratio range in the opposite direction, in which method, A method according to claim 1, wherein during a shift between transmission ratio ranges an assisting control impulse is superimposed on a transmission ratio adjustment regulating value.

24. A method according to claim 23, wherein the control impulse increases with increasing adjustment gradients.

25. A method according to claim 23, wherein the control impulse is a function of a value of an I component of the adjustment regulator before the shift.

26. A method according to claim 23, wherein the control impulse is superimposed on an I component of the adjustment regulator.

27. A method according to claim 1, wherein in the region of the shift between the transmission ratio ranges the target ratio of the variator is calculated directly from a target specification of the transmission ratio of the power-branched transmission and is supplied to the variator'"'"'s adjustment regulator as a target specification.

28. A method according to claim 1, wherein gear changes with manual preselection of transmission ratios in different transmission ratio ranges take place in that the control clutches are already activated before reaching the shift point lying between the transmission ratio ranges.

29. A method according to claim 1, wherein in the event of gear changes with manual preselection of the transmission ratio, a respectively engaged control clutch is disengaged, the variator rapidly adjusts to a desired new transmission ratio, and subsequently the control clutch is engaged again.

30. A method according to claim 1, wherein in branched operation of the transmission its gradient of the input rotational speed is changed in such a way that the acceleration power for internal transmission forces of inertia changes little or the output power changes evenly.

31. A method for controlling mutual contact pressures of conical disks of conical disk pairs of a variator, wherein each conical disk pair is allocated a contact pressure unit acted upon by the contact pressure dependent upon the torque transmitted by the variator and an adjustment unit acted upon by the adjustment pressure as a function of the desired ratio change, which method comprises the following steps:

determining required pressure forces on the disk pair,

determining the greater of the pressure forces F_max,

calculating contact pressure p_m and an adjustment pressure p_v so that both pressures are approximately equally large for attaining the pressure force F_max,

controlling the contact pressure unit and the adjustment unit of the disk pair acted upon with the greater pressure force with the determined pressure p_m,

determining the adjustment pressure p_v of the adjustment unit of the other conical disk pair so that when acted upon by its contact pressure unit with the pressure p_m and when acted upon by its adjustment unit with the adjustment pressure p_v, the required pressure force is achieved, and

controlling the contact pressure unit and the adjustment unit of the other disk pair with the forces p_m and p_v.

32. A method according to claim 31, wherein the calculated contact pressure p_m is increased and the adjustment pressure of the disk pair acted upon with the higher pressure force F_max is correspondingly reduced until either the increased contact pressure attains a specified minimum pressure or the adjustment pressure of the other pair of conical disks calculated on the basis of the increased contact pressure reaches the specified minimum pressure.

33. A power-branched automatic transmission for a motor vehicle comprising:

an input shaft drivable by a engine, a variator with continuously variable transmission ratio, a gear transmission, an output shaft and at least two control clutches by means of which the variator and the gear transmission can be connected with one another such that, when traversing the overall transmission ratio range of the power-branched transmission, within a first transmission ratio range the adjustment range of the variator is traversed in one direction and within a second transmission ratio range in the opposite direction, sensors for detecting operating parameters of the power train of the motor vehicle, and control apparatus for control of the operation of actuators of the transmission, which control apparatus regulates the transmission ratio of the transmission depending at least upon the activation of an accelerator and the motor vehicle speed.

34. A transmission according to claim 33, wherein rotational speed sensors are provided for detecting the rotational speed of the input shaft and the output shaft of the variator.

35. A transmission according to claim 33, wherein the input shaft of the variator is coupled through a first control clutch with a first gear that is in rotary engagement with a second gear through an idler gear, and an output shaft of the variator is non-rotatably connected with the sun gear of a planetary transmission and is coupled with the second gear through a second control clutch, which second gear is nonrotatably connected with the planet carrier of the planetary transmission.

36. A transmission according to claim 33, wherein the variator control apparatus applies equally great maximum contact pressure forces on both disk sets.

37. A transmission according to claim 33, including a starting clutch for coupling the engine with a variator input shaft, an output shaft that is coupled with an input sun gear of a planetary transmission, which input sun gear meshes with a first ring gear through planet gears of a first planet carrier, said ring gear forming a second planet carrier whose planet gears mesh with a second sun gear and a second ring gear, wherein the first ring gear is non-rotatably connected with an output shaft, wherein the second sun gear is fixed in position through a first control clutch, and the input shaft is coupled with the first planet carrier through a second control clutch, which planet carrier is non-rotatably connected with the second ring gear.

38. A transmission according to claim 33, wherein an additional clutch is provided, with which the first planet carrier is fixed in position, which additional clutch is utilized together with the first control clutch as a starting clutch.

39. A transmission according to claim 33, wherein the variator is connected on the input side with a second planetary transmission through a second control clutch, whose operation can be changed using a first control clutch, wherein the variator is connected on the output side with a first planetary transmission and the input of the second planetary transmission is connected with the second control clutch, and outputs of both planetary transmissions are jointly connected with an output shaft of the transmission, wherein the transmission ratios of the planetary transmissions are selected such that an inertia factor is minimum for the conical disk pair most distant from the engine.

40. A transmission according to claim 39, wherein the transmission ratio i₂ of the second planetary transmission is greater than the transmission ratio i₁ of the first planetary transmission.

41. A transmission according to claim 40, wherein i₁ is approximately −

1.5 and i₂ is approximately −

2.5.

42. A transmission according to claim 39, wherein gearing is provided for adapting the transmission ratio range of the variator.

43. A transmission according to claim 33, including a cascade valve containing a valve element slidable in a cylindrical housing staged in cross section and which has an end face that borders a chamber acted upon with pilot pressure, a first annular chamber constructed between two collars of the valve element and the housing whose annular surface facing the pilot pressure has a larger diameter than its annular surface facing away from the pilot pressure, and a second annular chamber constructed between two collars of the valve element and the housing, wherein in a pressure control position of the valve element the first annular chamber is connected to a first inlet connected with a hydraulic pump and a first outlet connected with a user, and the second annular chamber is connected with a second inlet connected with the hydraulic pump, and a second outlet extending from the housing between the two inlets is separated from the second annular chamber by a control edge formed by a collar of the valve element constructed between the two annular chambers, and in the pressure control position of the valve element a return extending from the housing is separated by a control edge formed by a pilot pressure side collar of the valve element, and the first inlet is separated from the first annular chamber by a control edge formed by the collar of the valve element constructed between the two hollow spaces, and the second annular chamber is connected with the second inlet and the second outlet.

44. A transmission according to claim 43, including a hydraulic control circuit for controlling the variator that includes two conical disk pairs, wherein a displaceable disk of each conical disk pair is allocated one contact pressure unit and one adjusting unit, containing a hydraulic pump that is connected with the inlets of a first cascade valve, whose first outlet is connected with the contact pressure units of the variator, and whose second outlet is connected with the inlets of a second cascade valve, whose first outlet is connected with one of the adjustment units of the variator and whose second outlet is connected with the inlets of a third cascade valve, whose first outlet is connected with the other adjustment unit of the variator and whose outlet is connected with at least one further unit of the variator supplied with hydraulic fluid.