Motor Vehicle Comprising at Least Two Drive Motors and Comprising an Automatic Gearbox Having a Fixed Gear Ratio and a Power-Split Gear Ratio

Abstract

A motor vehicle includes at least two drive motors, an automatic gearbox, and an electronic control unit, which, during a gear ratio adjustment between an engagement and a loading of a shift element, causes the shift element to be loaded with a predefined torque gradient at a first point in time at which at least one tooth-to-tooth position exists, up to a second point in time, cause the predefined torque to be limited to a maximum permissible torque during a predefined waiting period from the second point in time up to a third point in time, and cause the shift element to be further loaded with the previously predefined torque gradient after the waiting period or when the engaged state is detected.

Claims

1-9. (canceled)

10. A motor vehicle comprising: at least two drive motors, wherein at least one drive motor is an electric machine; a high-voltage battery; an automatic gearbox comprising: at least one fixed gear ratio and at least one power-split gear ratio (E-CVT); and/or at least one serial gear ratio for gear ratio adjustment towards the at least one fixed gear ratio; and an electronic control unit configured to, during a ratio adjustment between an engagement of a shift element and a loading of the shift element, in order to control an internal combustion engine and the electric machine: cause the shift element to be loaded with a predefined torque gradient at a first point in time at which at least one tooth-on-tooth position exists up to a second point in time; cause the predefined torque to be limited to a maximum permissible torque during a predefined waiting period from the second point in time up to a third point in time; and cause the shift element to be further loaded with the previously defined torque gradient after the waiting period or when an engaged state is detected.

11. The motor vehicle according to claim 10, wherein the electronic control unit is configured to: control the torque in a pulsed manner during the predefined waiting period.

12. The motor vehicle according to claim 10, wherein the maximum permissible torque is determined from an estimated frictional torque to be overridden and an additional torque.

13. The motor vehicle according to claim 12, wherein the estimated frictional torque to be overridden is estimated based on an effective radius, an assumed friction value, and an available actuating force of a shift element actuator of the shift element.

14. The motor vehicle according to claim 12, wherein the additional torque is determined based on a predefined maximum permissible shift element differential speed and an effective mass moment of inertia.

15. The motor vehicle according to claim 10, wherein the predefined waiting period is determined based on an effective mass moment of inertia, a maximum rotational angle, and a maximum defined differential speed gradient.

16. The motor vehicle according to claim 10, wherein the automatic gearbox comprises: an epicyclic gearing; the shift element; and actuators configured to be actuated by the electronic control unit; wherein the at least one electric machine is part of a variator.

17. An electronic control unit for a motor vehicle or an automatic gearbox, the electronic control unit configured to: during a ratio adjustment between an engagement of a shift element and a loading of the shift element: cause the shift element to be loaded with a predefined torque gradient at a first point in time at which at least one tooth-on-tooth position exists up to a second point in time; cause the predefined torque to be limited to a maximum permissible torque during a predefined waiting period from the second point in time up to a third point in time; and causing the shift element to be further loaded with the previously defined torque gradient after the waiting period or when an engaged state is detected.

18. The electronic control unit according to claim 17, further configured to: control the torque in a pulsed manner during the predefined waiting period.

19. The electronic control unit according to claim 17, wherein the maximum permissible torque is determined from an estimated frictional torque to be overridden and an additional torque.

20. The electronic control unit according to claim 19, wherein the estimated frictional torque to be overridden is estimated based on an effective radius, an assumed friction value, and an available actuating force of a shift element actuator of the shift element.

21. The electronic control unit according to claim 19, wherein the additional torque is determined based on a predefined maximum permissible shift element differential speed and an effective mass moment of inertia.

22. The electronic control unit according to claim 17, wherein the predefined waiting period is determined based on an effective mass moment of inertia, a maximum rotational angle, and a maximum defined differential speed gradient.

23. A method for shifting an automatic gearbox in a motor vehicle, the method comprising: during a gear ratio adjustment between an engagement of a shift element and a loading of the shift element, in order to control an internal combustion engine and an electric machine: loading the shift element with a predefined torque gradient at a first point in time at which at least one tooth-on-tooth position exists, up to a second point in time; limiting the predefined torque to a maximum permissible torque during a predefined waiting period from the second point in time up to a third point in time; and further loading the shift element with the previously defined torque gradient after the waiting period or when an engaged state is detected.

24. The method according to claim 23, further comprising: controlling the torque in a pulsed manner during the predefined waiting period.

25. The method according to claim 23, wherein the maximum permissible torque is determined from an estimated frictional torque to be overridden and an additional torque.

26. The method according to claim 25, wherein the estimated frictional torque to be overridden is estimated based on an effective radius, an assumed friction value, and an available actuating force of a shift element actuator of the shift element.

27. The method according to claim 25, wherein the additional torque is determined based on a predefined maximum permissible shift element differential speed and an effective mass moment of inertia.

28. The method according to claim 23, wherein the predefined waiting period is determined based on an effective mass moment of inertia, a maximum rotational angle, and a maximum defined differential speed gradient.

29. The method according to claim 23, further comprising: controlling the at least one electric machine as part of a variator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] FIG. 1 shows state 1 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0032] FIG. 2 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states in state 1 of the entire shift sequence,

[0033] FIG. 3 shows state 2 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0034] FIG. 4 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states in state 2 of the entire shift sequence,

[0035] FIG. 5 shows state 3 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0036] FIG. 6 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states in state 3 of the entire shift sequence,

[0037] FIG. 7 shows state 4 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0038] FIG. 8 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states in state 4 of the entire shift sequence,

[0039] FIG. 9 shows state 5 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0040] FIG. 10 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states in state 5 of the entire shift sequence,

[0041] FIG. 11 shows states 6 and 7 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear,

[0042] FIG. 12 schematically shows the essential components of a motor vehicle or gearbox according to the invention and their states at state 6 and 7 of the entire shift sequence,

[0043] FIG. 13 shows the essential intermediate step according to the invention between states 5 and 6 of the entire shift sequence during a gear change with the automatic gearbox according to the invention from a first fixed gear to a second fixed gear, and

[0044] FIG. 14 shows schematically the torque curve resulting from the invention at the shift element concerned.

DETAILED DESCRIPTION

[0045] FIG. 1 shows the initial state, state 1, with the first gear engaged (fixed gear G1) before a gear change command. This is followed by a gear change command in an electronic control unit SG by a corresponding input signal.

[0046] FIG. 2 shows the most important components of the present disclosure, which also apply for FIGS. 4, 6, 8, 10 and 12:

[0047] FIG. 2 schematically shows a hybrid vehicle that has a DHT automatic gearbox, an internal combustion engine VM, a first electric machine EMA, a second electric machine EMB, a high-voltage battery HVS, and an electronic control unit SG.

[0048] The automatic gearbox comprises an epicyclic gearing UG in the form of a power-splitting planetary gearing, a variator comprising the two electric machines EMA and EMB, and a first shift element K1 provided for engaging a first fixed gear ratio G1 (hereinafter also referred to as fixed gear G1) and a second shift element B2 provided for engaging a second fixed gear ratio G2.

[0049] The number of two translation levels here is only for better illustration; in practice, a higher number of translation levels can also be used.

[0050] Furthermore, the automatic gearbox comprises two gearbox shafts, namely an input shaft in the form of a drive shaft by means of which the automatic gearbox is coupled to the internal combustion engine VM in a torque-transmitting manner, and an output shaft in the form of a driven shaft by means of which the automatic gearbox is coupled to the wheels R of the motor vehicle in a torque-transmitting manner.

[0051] The automatic gearbox can also have three or more fixed gear ratios, in which case it would also have a correspondingly greater number of shift elements provided for engaging further gear ratios. Individual shift elements can also be provided for several gear ratios and/or a combination of several shift elements for one gear ratio.

[0052] The planetary gearing UG comprises the carrier 1, the ring gear 2, and the sun 3. The planetary gearing UG is coupled to both the input shaft and the output shaft in a torque-transmitting manner. Furthermore, the epicyclic gearing UG comprises a shaft via which it can be coupled to the input shaft in a torque-transmitting manner by means of the first shift element K1, which here forms a clutch, and can be coupled to the second shift element B2, which here forms a brake, in a torque-transmitting manner. The shaft has a speed-setting effect here on the internal combustion engine VM. In an alternative embodiment, the shift elements K1, B2 can be provided for any torque-transmitting functions.

[0053] The shift elements K1, B2 are each configured as dog clutches. This means that they are interlocking shift elements and require only a small amount of pressure to be held in the closed position. In an alternative embodiment, the shift elements K1, B2 can be any other suitable shift elements, for example frictionally engaging shift elements.

[0054] The variator functionality for gear ratio adjustment is provided by operating the first electric machine EMA as a generator and the second electric machine EMB as a motor. This allows kinetic energy and electrical energy to be converted into one another and thus allows the speeds of the two electric machines EMA, EMB to be decoupled from one another.

[0055] Shifting the automatic gearbox from a first gear ratio (fixed gear) G1 to a second fixed gear ratio (fixed gear) G2 is performed in accordance with the shift sequence illustrated with reference to FIGS. 3, 5, 7, 9 11 and 13.

[0056] According to FIGS. 1 and 2, the first fixed gear ratio G1 is engaged, that is to say, the first shift element K1 is closed and the second shift element B2 is open. Furthermore, the variator is decoupled; i.e., the electric machines are not coupled to either the input shaft or the output shaft in a torque-transmitting manner. All speeds nG1 are the same. The first electric machine EMA can be operated as a generator to charge the high-voltage battery HVS.

[0057] To switch to the second fixed gear ratio G2, the shift element K1 of the current (old) fixed ratio G1 is now relieved, as shown in FIG. 3.

[0058] As can be seen in FIG. 4, the variator is coupled to the output shaft in a torque-transmitting manner and is also coupled to the epicyclic gearing UG via the shaft in a torque-transmitting manner. In other words, the second electric machine EMB is operated as a motor with the output or with the ring gear 2 or with the wheels R and is fed by the high-voltage battery HVS. The internal combustion engine VM can be switched off.

[0059] By means of the variator, the first shift element K1 is now relieved via the output shaft by a torque superposition (K1 shown dashed).

[0060] At this point, the essence of the present disclosure begins, which will be explained again with reference to FIGS. 13 and 14.

[0061] According to state 3, which is shown activated in FIG. 5, the shift element K1 is then disengaged, as shown in FIG. 6 with K1 open.

[0062] This is followed by state 4 according to FIG. 7, namely the preferably electrical and continuous gear ratio adjustment in a power-split gear ratio (E-CVT). This is illustrated in FIG. 8 by means of the speed shift at the sun 3. Accordingly, after opening the first shift element K1, the gear ratio of the second gear ratio (fixed gear) G2 is set by a continuous gear ratio adjustment of the variator or the electric machine EMA. The brake B2 is still open here.

[0063] This means that a 3-shaft operation is established, whereby the differential speed at the second shift element B2 is reduced.

[0064] FIG. 9 shows the state 5 in which the shift element B2 is closed for the new fixed gear G2.

[0065] It can be seen here in FIG. 10 that the second shift element B2 is closed as soon as the differential speed has been reduced to zero or has fallen below a certain limit value. This causes the second shift element B2 to take over the load from the variator, and the variator can be decoupled (see FIG. 10, dashed electric machine EMB). The brake B2 is not yet loaded (dashed B2).

[0066] In FIG. 11, state 6 and, directly associated therewith, state 7 or 1 again is reached, in which the new shift element B2 can be loaded (completely closed B2 in FIG. 12). With FIG. 12 the shift sequence of a gear change is finished.

[0067] In FIG. 13, the intermediate state between state 5 and 6 according to the present disclosure is shown by a functional module ZW (tooth twisting prevention) in the control unit SG or by a process executed by the control unit SG, the effect of which on the course of the torque M at the shift element SE (here B2) is shown in FIG. 14 over time t:

[0068] The following is an exemplary embodiment with the resulting torque curve M according to FIG. 14:

[0069] An actuating force of 200 N for example acts on an interlocking shift element SE (for example B2) in tooth-on-tooth position, which has an effective radius of 100 mm, for example. The assumed coefficient of friction is 0.15, for example. This results in an estimated frictional torque M1 of 3 Nm to be overridden. Due to the effective mass moment of inertia (J), the ratio of the differential speed gradient to the effective torque (M−M1) is 10 rad/Nms.sup.2. In the worst case, the shift element SE must turn 28° in order to engage, but must not engage with more than 10 rad/s differential speed.

[0070] This results accordingly in the time span T2−T1 in FIG. 14 (t=2.Math.Δφ/Δω)) with 0.1 s (waiting period) and an angular acceleration of 100 rad/s.sup.2. The ratio of the differential speed gradient to the effective torque (M−M1) results in a maximum permissible additional torque dM of 10 Nm. This means that 3 Nm+10 Nm=13 Nm (M1+dM=M2) must not be exceeded at the shift element SE. Thus, a reduced torque plateau M2 of M1+dM, here 13 Nm, is defined over a waiting period of T2−T1, here 0.1 s. Before the waiting period T2−T1 is reached and after it has elapsed, the originally required torque gradient dM/dt is converted at the shift element SE: predefined torque gradient dM/dt from T0 to T1 and from T2 to T3. T0 is the time here from which it can be assumed that the actuator of the shift element SE has moved the shift element SE at least into the tooth-on-tooth position, ideally of course into the engagement range. Only from T0 onwards may the interlocking shift element SE (here B2) to be newly engaged be loaded with torque M in accordance with the proposed functional sequence in order to avoid damage or discomfort. The torque gradient dM/dt from T2 to T3 is defined until the torque M3 is reached in the fully loaded fixed gear—here G2.

[0071] If the torque is not to be kept constant in the time range from T1 to T2, but is to be increased slightly, it still applies that the 13 Nm must not be exceeded, but the duration for reliable engagement will increase, since the required rotation angle must still be achieved (see dashed lines in FIG. 14).

[0072] FIG. 14 thus shows an example of an engagement process of a shift element SE in conjunction with the control of internal combustion engine VM and/or electric motor generator EMA in a DHT for reliable engagement of the shift element SE, also from a possible tooth-on-tooth position.

[0073] The following is a summary of the entire shift sequence with the intermediate state according to the present disclosure starting from the current fixed gear: [0074] relief of the old shift element K1 by the electric machines (state 2); [0075] activation of the functional module for speed adjustment DZA (generation of a load change at the shift element K1 to be opened and simultaneous control of the actuator to open the shift element K1); [0076] opening of the old shift element K1 (state 3) (change to an E-CVT mode); [0077] speed adjustment for ratio adjustment (nG1=>nG2) in the gearbox via the E-CVT mode (state 4); [0078] engagement of the new shift element (B2) (state 5); [0079] activation of the functional module ZW according to the present disclosure in the control unit SG for carrying out a method for the reliable engagement of interlocking shift elements SE (here B2); [0080] loading the new shift element (B2) (state 6); and [0081] “dropping” of the electric machines EMA and EMB (state 7=state 1)=>new fixed gear G2.

[0082] The following is a summary of a method carried out by means of the functional module ZW according to the present disclosure: [0083] an application of torque (M) to the shift element (SE; B2) to be engaged begins at a time (T0) at which at least a tooth-on-tooth position can be assumed (by chance, the gear could also already be engaged), with a predefined torque gradient (dM/dt); [0084] in particular depending on the effective radius, on an assumed friction value and on the available actuating force of the actuator of a shift element (SE), a frictional torque (M1) to be overridden is estimated; [0085] in particular depending on the effective mass moment of inertia, on a maximum rotational angle and on a maximum defined differential speed gradient, a defined waiting period (T2−T1) is determined; [0086] during the waiting period (T2−T1), a maximum permissible torque (M1) is defined which is determined from the estimated frictional torque (M1) to be overridden and an additional torque (dM); [0087] the additional torque (dM) is determined in particular from the ratio of the establishing differential speed gradient to the effective torque (M−M1) or on the basis of the effective mass moment of inertia (J) in relation to the shift element to be engaged; and [0088] after the waiting period (T2−T1) (or if the gear has already been engaged without tooth-on-tooth position), the defined torque gradient (dM/dt) is again defined for torque control until the fully loaded torque (M2) is reached (at time T3) in the new fixed gear (here G2).