Motor vehicle having at least two drive motors and having an automatic gearbox that has one fixed and one power-split transmission ratio

Abstract

A motor vehicle has at least two drive motors, at least one drive motor being an electric machine; a high-voltage accumulator; and an automatic gearbox, having at least one fixed transmission ratio and at least one power-split transmission ratio for transmission regulation starting from the at least one fixed transmission ratio. The motor vehicle further includes an electronic control unit, which is designed such that, when a gear change command is present, the shifting element to be opened of the fixed transmission ratio to be disengaged is unloaded in a torque-controlled manner by at least two of the drive motors. For the shifting element to be opened, the torque load is calculated and observed. The torque load is observed with the objective of bringing about a load change by way of a zero crossing in order to produce a no-load state at the shifting element. For producing the no-load state of the shifting element to be opened, a first drive motor and a second drive motor are controlled in a power split manner such that they, in terms of rotational speeds, maintain the transmission of the previously engaged fixed transmission ratio, and, in terms of torque, put the shifting element to be opened in an at least nearly no-load state, and a load change is brought about at the shifting element to be opened by a differential rotational speed, opposite the calculated torque load at the shifting element to be opened, being specified at the shifting element.

Claims

1. A motor vehicle, comprising: at least two drive motors, wherein at least one drive motor of the at least two drive motors is an electric motor; a high-voltage accumulator; an automatic transmission which has at least one fixed gear ratio and at least one power-split gear ratio for gear ratio adjustment starting from the at least one fixed gear ratio; and an electronic control unit operatively configured such that, when a gear change command is present: a shift element to be opened of the fixed gear ratio to be disengaged is relieved in a torque-controlled manner by at least two of the at least two drive motors, a torque load is calculated and observed for the shift element to be opened, the torque load is observed with an objective of bringing about a load change by way of a zero crossing in order to establish freedom from load at the shift element, for establishing the freedom from load for the shift element to be opened, a first drive motor of the at least two drive motors and a second drive motor of the at least two drive motors are controlled in a power-split so as to maintain the gear ratio of the previously engaged fixed gear ratio in terms of speeds and put the shift element to be opened in an at least nearly load-free state in terms of torques, and the load change is brought about at the shift element to be opened by a differential speed, opposite the calculated torque load at the shift element to be opened, being specified at the shift element, wherein when a defined threshold value of the observed torque load on the shift element to be opened is exceeded, a sign of a required differential speed on the shift element to be opened is changed for a speed controller.

2. The motor vehicle according to claim 1, wherein an I term of an already active speed regulation of the power split or a functional module comparable to a behavior of the I term is used to actively bring about the load change at the shift element to be opened, wherein the I term represents the required differential speed on the shift element to be opened.

3. The motor vehicle according to claim 1, wherein an actuator for opening the shift element is already controlled before a start of the load change.

4. The motor vehicle according to claim 1, wherein the automatic transmission comprises: an epicyclic gearbox; the shift element; the electric motor as the drive motor which is part of a variator; and actuators which are controllable by the electronic control unit.

5. The motor vehicle according to claim 1, wherein the electronic control unit comprises: a functional module for controlling the at least two drive motors and the shift element such that: the shift element to be opened of the fixed gear ratio to be disengaged is relieved in a torque-controlled manner by the at least two drive motors, the torque load is calculated and observed for the shift element to be opened, the torque load is observed with the objective of bringing about a load change by means of a zero crossing in order to establish freedom from load at the shift element, for establishing the freedom from load for the shift element to be opened, the first drive motor and the second drive motor are controlled in the power-split manner such that they maintain the gear ratio of the previously engaged fixed gear ratio in terms of speeds and put the shift element to be opened in an at least nearly load-free state in terms of torques, and the load change is brought about at the shift element to be opened by the differential speed, opposite the calculated torque load at the shift element to be opened, being specified at the shift element.

6. A method for shifting an automatic transmission in a motor vehicle, the motor vehicle having: at least two drive motors, wherein at least one drive motor of the at least two drive motors is an electric motor; a high-voltage accumulator; an automatic transmission which has at least one fixed gear ratio and at least one power-split gear ratio for gear ratio adjustment starting from the at least one fixed gear ratio; and an electronic control unit; the method comprising: relieving the shift element to be opened of the fixed gear ratio to be disengaged in a torque-controlled manner by the at least two drive motors; calculating the torque load and observing for the shift element to be opened, wherein the torque load is observed with the objective of bringing about a load change by way of a zero crossing in order to establish freedom from load at the shift element; controlling, for establishing the freedom from load for the shift element to be opened, a first drive motor of the at least two drive motors and a second drive motor of the at least two drive motors in a power-split manner such that they maintain the gear ratio of the previously engaged fixed gear ratio in terms of speeds and put the shift element to be opened in an at least nearly load-free state in terms of torques, and bringing about a load change at the shift element to be opened by a differential speed opposite the calculated torque load at the shift element to be opened being specified at the shift element, wherein when a defined threshold value of the observed torque load on the shift element to be opened is exceeded, a sign of the required differential speed on the shift element to be opened is changed for a speed controller.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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.

(2) 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.

(3) 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.

(4) 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.

(5) 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.

(6) FIG. 6 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in state 3 of the entire shift sequence.

(7) 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.

(8) 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.

(9) 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.

(10) 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.

(11) 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.

(12) 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.

(13) FIG. 13 shows the essential intermediate step according to the invention between states 2 and 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.

(14) FIG. 14 schematically shows the essential components of a motor vehicle or transmission according to the invention and their states in the intermediate step of the entire shifting sequence.

DETAILED DESCRIPTION OF THE DRAWINGS

(15) 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.

(16) FIG. 2 shows the most important components of the invention, which also apply for FIGS. 4, 6, 8, 10, 12 and 14:

(17) 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.

(18) 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.

(19) The number of two fixed gear ratios here is only for better illustration; in practice, a different number of gear ratios can also be used.

(20) 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.

(21) 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.

(22) 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.

(23) The shift elements K1, B2 are each formed as claw clutches. This means that they are interlocking shift elements and require only a small retention force 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.

(24) 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 mechanical 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.

(25) 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.

(26) 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 do not take on a torque-transmitting function. All speeds nG1 are the same. The electric motors EMA, EMB can be operated as generators and as motors to charge the high-voltage accumulator HVS or boost drive power from the HVS.

(27) 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.

(28) 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.

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

(30) At this point, the core of the invention begins and will be explained again with reference to FIGS. 13 and 14.

(31) 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.

(32) 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.

(33) This means that a 3-shaft operation is established, whereby the differential speed at the second shift element B2 is reduced.

(34) FIG. 9 shows the state 5 in which the shift element B2 is closed for the new fixed gear G2.

(35) 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).

(36) 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). FIG. 12 concludes the switching sequence of a gear change.

(37) In FIG. 13, the intermediate state according to the invention between state 2 and 3 is shown by a functional module DZA or by a method carried out by the control unit, the effect of which on the component behavior is shown in FIG. 14: The shift element K1 to be opened is relieved in a torque-controlled manner by the two electric motors EMA and EMB (see also state 2). The torque load is calculated and observed for the shift element K1 to be opened of the engaged fixed gear G1. The torque load is observed with the objective of bringing about a load change by means of a zero crossing in order to establish freedom from load at the shift element K1. For establishing the freedom from load for the shift element K1 to be opened, the first electric motor EMA and the internal combustion engine VM are controlled in a power-split manner such that they maintain the gear ratio of the previously engaged fixed gear G1 in terms of the speeds nG1 and put the shift element K1 to be opened in an at least nearly load-free state in terms of the torques. A load change is brought about at the shift element K1 to be opened by a differential speed dn/dn opposite the calculated torque load at the shift element K1 to be opened being specified at the shift element K1. At the same time, the actuator of the shift element K1 is activated for opening, in order to generate a preload which, in the case of the so to speak random zero crossing, leads to easy opening of the shift element K1 on account of the above-mentioned speed regulation, speed adaptation and differential speed specification.

(38) Summary of the entire shifting sequence with the intermediate state according to the invention starting from the current fixed gear: Relieving of the old shift element K1 by the E-motors (state 2). Activation of the functional module for speed adaptation DZA (generation of a load change at the shift element K1 to be opened and simultaneous control of the actuator for opening the shift element K1). Opening of the old shift element K1 (state 3) (change to an E CVT mode). Speed adaptation for gear ratio adjustment (nG1=>nG2) in the transmission via the E CVT mode (state 4). Engagement of the new shift element (B2) (state 5). Loading of the new shift element (B2) (state 6). Dropping of the E-motors EMA and EMB (state 7=state 1)=>new fixed gear G2.