Motor Vehicle Having at Least Two Drive Motors and Having an Automatic Transmission Which Has a Fixed and a Power Split Gear Ratio

Abstract

A motor vehicle has at least two drive motors, at least one of which is an electric motor, a high-voltage accumulator, and an automatic transmission which has at least one fixed gear ratio and at least one power-split gear ratio for transmission ratio adjustment starting from the at least one fixed gear ratio. The motor vehicle includes an electronic control unit having a speed control module which can be activated during a change of transmission ratio. The speed control module is designed in such a way that a setpoint speed is calculated in advance, by which setpoint speed both the speed gradient and also the speed curvature can be limited, the target speed of the at least one drive motor being continuously compared with a maximum allowed speed gradient and with a maximum allowed speed curvature.

Claims

1-7. (canceled)

8. A motor vehicle, comprising: at least two drive motors, wherein at least one drive motor is an electric motor; a high-voltage accumulator; an automatic transmission which has at least one fixed gear ratio (G1) and at least one power-split gear ratio (E-CVT) for gear ratio adjustment starting from the at least one fixed gear ratio (G1); and an electronic control unit (SG) which contains a speed control module (DRM) which is activatable during a ratio change and is configured such that a setpoint speed (y) is calculated in advance, by which both a speed gradient (Δy) and a speed curvature (ΔΔy) can be limited, wherein a target speed (x_target) of the at least one drive motor is continuously compared with a maximum allowed speed gradient (dy_limits) and with a maximum allowed speed curvature (dy.sup.2_limits).

9. The motor vehicle according to claim 8, wherein limitation of the speed gradient (Δy) and the speed curvature (ΔΔy) is extended by a braking function (fA), wherein the speed control module continuously determines how much speed gradient (dy_br_limits) is still allowed in order to hit a target speed curve (x) exactly tangentially with the setpoint speed (y) while maintaining a currently allowed speed curvature (dy.sup.2_limits) and at a currently available rate of change (dx/dt) of the target speed (x_target).

10. The motor vehicle according to claim 9, wherein in the speed control module (DRM), a gradient limitation (C) of the braking function (fA) directly adjoins a first-order gradient limitation (B), and a second-order gradient limitation (A) adjoins the gradient limitation (C).

11. The motor vehicle according to claim 9, wherein in the speed control module (DRM), the gradient limitation (C) of the braking function (fA) directly adjoins the second-order gradient limitation (A), and the second-order gradient limitation (A) adjoins a first-order gradient limitation (B).

12. An automatic transmission for a motor vehicle comprising: an epicyclic gearbox (UG); at least one shift element (K1 and/or B2); at least one electric motor as a drive motor which is part of a variator; and actuators which are controllable by an electronic control unit, wherein the electronic control unit contains a speed control module (DRM) which is activatable during a speed change and is configured such that a setpoint speed (y) is calculated in advance, by which both a speed gradient (Δy) and a speed curvature (ΔΔy) can be limited, wherein a target speed (x_target) of the drive motor is continuously compared with a maximum allowed speed gradient (dy_limits) and with a maximum allowed speed curvature (dy.sup.2_limits).

13. An electronic control unit for a motor vehicle, the motor vehicle having: at least two drive motors, wherein at least one drive motor is an electric motor; a high-voltage accumulator; and an automatic transmission which has at least one fixed gear ratio (G1) and at least one power-split gear ratio (E-CVT) for gear ratio adjustment starting from the at least one fixed gear ratio (G1), as well as shift elements (K1, B2); the electronic control unit comprising: a speed control module (DRM) for controlling the at least two drive motors (VM, EMA, EMB) and the shift elements (K1, B2) such that a setpoint speed (y) is calculated in advance, by which both a speed gradient (Δy) and a speed curvature (ΔΔy) can be limited, wherein the target speed (x_target) of at least one drive motor (VM, EMA, EMB) is continuously compared with a maximum allowed speed gradient (dy_limits) and with a maximum allowed speed curvature (dy.sup.2_limits).

14. A method for shifting an automatic transmission in a motor vehicle, having: at least two drive motors, wherein at least one drive motor is an electric motor; a high-voltage accumulator; an automatic transmission which has at least one fixed gear ratio (G1) and at least one power-split gear ratio (E-CVT) for gear ratio adjustment starting from the at least one fixed gear ratio (G1); and an electronic control unit (SG) which contains a speed control module (DRM) which is activatable during a ratio change, the method comprising: after a gear shift command is present, calculating, via the electronic control unit, in advance a setpoint speed (y), by which both a speed gradient (Δy) and a speed curvature (ΔΔy) can be limited, wherein a target speed (x_target) of the at least one drive motor (VM, EMA, EMB) is continuously compared with a maximum allowed speed gradient (dy_limits) and with a maximum allowed speed curvature (dy.sup.2_limits).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 shows state 1 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0030] FIG. 2 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in state 1 of the entire shift sequence.

[0031] FIG. 3 shows state 2 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0032] FIG. 4 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in state 2 of the entire shift sequence.

[0033] FIG. 5 shows state 3 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0034] FIG. 6 schematically shows the main components of a motor vehicle or transmission according to the invention and their states in state 3 of the entire shift sequence.

[0035] FIG. 7 shows state 4 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0036] FIG. 8 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in state 4 of the entire shift sequence.

[0037] FIG. 9 shows state 5 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0038] FIG. 10 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in state 5 of the entire shift sequence.

[0039] FIG. 11 shows states 6 and 7 of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0040] FIG. 12 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in states 6 and 7 of the entire shift sequence.

[0041] FIG. 13 shows the essential intermediate step according to the invention between states 3 and 5, i.e., a special procedural design of a state 4 (see also FIGS. 7 and 8), of the entire shift sequence during a gear change with the automatic transmission according to the invention from a first fixed gear to a second fixed gear.

[0042] FIG. 14 schematically shows relevant speed curves for control by means of the speed control module (DRM) essential to the invention, shown in FIG. 13.

[0043] FIG. 15 schematically shows an exemplary embodiment of the speed control module (DRM) essential to the invention according to FIG. 13.

DETAILED DESCRIPTION OF THE DRAWINGS

[0044] 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.

[0045] FIG. 2 shows the most important components of the invention, which also apply for FIGS. 4, 6, 8, 10 and 12:

[0046] FIG. 2 schematically shows a hybrid vehicle comprising an automatic transmission, an internal combustion engine VM, a first electric motor EMA, a second electric motor EMB, a high-voltage accumulator HVS and an electronic control unit SG.

[0047] The automatic transmission comprises an epicyclic gearbox UG in the form of a power-splitting planetary gearbox, a variator comprising the two electric motors 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.

[0048] The number of two gear ratios here is only for better illustration; in practice, a greater number of gear ratios can also be used.

[0049] Furthermore, the automatic transmission comprises two transmission shafts, namely an input shaft in the form of a drive shaft by means of which the automatic transmission 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 transmission is coupled to the wheels R of the motor vehicle in a torque-transmitting manner.

[0050] The automatic transmission can also have three or more fixed gear ratios, in which case it would also have a correspondingly larger number of shift elements provided for engaging further gear ratios. Individual shift elements can also be provided for a plurality of gear ratios and/or a combination of a plurality of shift elements for one gear ratio.

[0051] The planetary gearbox UG comprises the carrier 1, the ring gear 2 and the sun 3. The epicyclic gearbox UG is coupled to both the input shaft and the output shaft in a torque-transmitting manner. Furthermore, the epicyclic gearbox 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-adjusting effect on the internal combustion engine VM. In an alternative embodiment, the shift elements K1, B2 can be provided for any torque-transmitting functions.

[0052] The shift elements K1, B2 are each formed as claw 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.

[0053] The variator functionality for gear ratio adjustment is provided by operating the first electric motor EMA as a generator and the second electric motor EMB as a motor. This allows kinetic energy and electrical energy to be converted into one another and thus the speeds of the two electric motors EMA, EMB to be decoupled from one another.

[0054] Shifting the automatic transmission 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.

[0055] According to FIGS. 1 and 2, the first fixed gear ratio G1 is engaged, i.e., the first shift element K1 is closed and the second shift element B2 is open. Furthermore, the variator is decoupled; i.e., the electric motors 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 motor EMA can be operated as a generator to charge the high-voltage accumulator HVS.

[0056] To shift to the second fixed gear ratio G2, the shift element K1 of the current (old) fixed gear G1 is now relieved, as shown in FIG. 3.

[0057] 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 gearbox UG via the shaft in a torque-transmitting manner. In other words, the second electric motor EMB is motor-operated with the output or with the ring gear 2 or with the wheels R and is fed by the high-voltage accumulator HVS. The internal combustion engine VM can be switched off.

[0058] By means of the variator, the first shift element K1 is now relieved via the output shaft by a torque superposition (K1 shown dashed).

[0059] At this point, the core of the invention begins and will be explained again with reference to FIGS. 13 and 14.

[0060] 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.

[0061] 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 the first shift element K1 is opened, the ratio of the second gear ratio (fixed gear) G2 is set by a continuous gear ratio adjustment of the variator or the electric motor EMA. The brake B2 is still open here.

[0062] This means that a 3-shaft operation is established, whereby the differential speed at the second shift element B2 is reduced.

[0063] FIG. 9 shows the state 5 in which the shift element B2 is closed for the new fixed gear G2.

[0064] FIG. 10 shows here 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 motor EMB). The brake B2 is not yet loaded (dashed B2).

[0065] In FIG. 11, state 6 and directly associated with it state 7 or again 1 is reached, in which the new shift element B2 can be loaded (fully closed B2 in FIG. 12).

[0066] FIG. 12 concludes the switching sequence of a gear change (G1=>G2).

[0067] Summary of the entire shifting sequence with the intermediate state according to the invention starting from the current fixed gear (here G1): [0068] Relieving of the old shift element K1 by the drive machines (state 2), [0069] Opening of the old shift element K1 (state 3) (change to an E-CVT mode), [0070] Speed adaptation for gear ratio adjustment (nG1=>nG2) in the transmission via the E-CVT mode (state 4) by activating the speed control module DRM according to the invention, [0071] Engagement of the new shift element (B2) (state 5), [0072] Loading of the new shift element (B2) (state 6), [0073] “Dropping” of the E-motors EMA and EMB (state 7=state 1)=>new fixed gear G2.

[0074] FIG. 13 shows “state 4” according to the invention with the speed control module DRM.

[0075] FIG. 14 shows three relevant curves of the speed n for an exemplary upshift (negative target speed jump x_target at time t1) with acceleration (increasing target speed x_target before and after t1). The following curves are shown: [0076] solid line: target speed x_target [0077] dashed line: setpoint speed y [0078] dot-and-dash line: actual speed y_act

[0079] For the control of the speed n, the time range T between the times t1 to t4 is considered. At time t1 the speed change phase of the upshift starts and at time t4 it is complete. At a time t2 the speed gradient is considered. At a time t3 the speed curvature is considered. Between the individual points in time there is a first partial consideration period A between t1 and t2, a second partial consideration period B between t2 and t3, and a third partial consideration period C between t3 and t4.

[0080] The functionality of the speed control module DRM according to the invention shown in FIG. 15 is used to determine the setpoint speed y on the basis of the target speed x target and to calculate other required variables or parameters.

[0081] The following apply here: [0082] x_target=target speed [0083] Δt=sample time/step width [0084] dy_limits=maximum allowed speed gradient (positive and negative) [0085] dy.sup.2_limits=maximum allowed speed curvature (positive and negative) [0086] dy_br_limits=maximum allowed braking speed gradient (positive and negative) [0087] dx/dt=derivation of a signal with respect to time (gradient formation) [0088] l/z=signal feedback (value of the previous time step) [0089] y=setpoint speed n [0090] ΔΔy=gradient of the setpoint speed (change of y within one time step Δt) [0091] ΔΔy=curvature of the setpoint speed (change of Δy within one time step Δt) [0092] y_act=actual speed n

[0093] The target speed x_target changes abruptly at the time t1 due to the changed gear ratio of the fixed gear G2 to be newly engaged compared with that of the old fixed gear G1. In the event of such a shift, the speed controller usually has to realize a speed change of at least 300 rpm up to 2500 rpm or more. In order to reduce the variance of the operating point of the speed controller, according to the invention a continuous signal, the setpoint speed y, over the time range T is generated by a first-order gradient limitation in the partial consideration period B, by a second-order gradient limitation in the partial consideration period A, and by a braking function fA with gradient limitation in the partial consideration period C.

[0094] The speed gradient of the setpoint speed y of the internal combustion engine VM, for example, which can be converted into the required total change in the internal combustion engine torque on the basis of acting mass moments of inertia and vice versa, is thus limited in advance to the operating range of the internal combustion engine (dy_limits).

[0095] The maximum permissible curvature dy.sup.2_limits of the setpoint speed y of the internal combustion engine VM can be converted into the required torque gradient of the internal combustion engine VM similarly to the calculation of the speed gradient of the setpoint speed y, and vice versa. Therefore, the curvature ΔΔY of the speed n over time that can be represented by the internal combustion engine VM can also be calculated in advance and included in the curve of the setpoint speed y.

[0096] The actual speed y_act of the internal combustion engine VM represents an exemplary curve which can be adjusted on the basis of a suitable controller in conjunction with feedforward control via the setpoint speed y and its time derivative.

[0097] The braking function fA determines the setpoint speed change dy_br_limits allowed for the current time step using the information on the maximum allowed speed curvature dy.sup.2_limits, the current step size, the setpoint speed of the previous calculation step, and the current gradient of the target speed.

[0098] In other words, the first-order gradient limitation in the partial consideration period B is such that the maximum torque gradients that can be set by the drive motors VM and EMA and/or EMB are not exceeded; i.e., for example: y′=dy/dt=MIN ((M_VM, M_EMA)/J) (MIN=minimum selection; J=moment of inertia). The second-order gradient limitation in the partial consideration period A is such that the maximum torque gradients which can be set by the drive motors VM and EMA and/or EMB are not exceeded; i.e., for example: y″=MIN ((dM_VM/dt, dM_EMA/dt)/J). The time range T is determined by the braking function fA.

[0099] The following relationship applies for the braking function fA:

[00001]${\mathrm{dy}}_{{\mathrm{br}}_{\mathrm{limit}}}=\frac{{\mathrm{dx}}_{\mathrm{target}}}{\mathrm{dt}}-{\mathrm{dy}}_{\mathrm{limit}}^2*\sqrt{.Math.\frac{2*\left(x_{\mathrm{target}}-y\right)}{{\mathrm{dy}}_{\mathrm{limit}}^2}.Math.}$

[0100] In the root term, the currently expected braking time (t−t4) is determined on the basis of the difference between target and setpoint speed, as well as the representable speed curvature.

[0101] Based on the braking time and the maximum allowed speed curvature dy.sup.2_limits, the currently allowed speed gradient of the setpoint speed is in turn calculated.

[0102] The overall function shown arranges the braking function fA directly after the first-order gradient limitation; the second-order gradient limitation is in third place. This arrangement has the advantage that the setpoint speed y observes the required limits for speed gradients and speed curvature under all circumstances.

[0103] In one variant of the overall function, the braking function can be arranged in the third position for limiting the gradient of the setpoint speed. However, this variant bears the risk that the limit values of the setpoint speed in gradient and curvature cannot be observed under all circumstances.

[0104] Depending on the magnitude of the speed jump of x_target, it can lead to the fact that the partial consideration period B must be skipped, i.e., the maximum speed gradient is not reached, and it is necessary to jump directly from the partial consideration period A into the partial consideration period C.