Vehicle with a dual-clutch transmission

Abstract

The invention relates to a vehicle with a dual-clutch transmission, the first sub-transmission (I) and the second sub-transmission (II) of which can be activated by actuating respective first and second disconnect clutches (K1, K2), wherein a time period (tv) for preparing a subsequent shift consists of a disconnect clutch opening process (t K ) and consists of a gear engagement process (tz). To reduce the preparation time (tv), the evaluation module (30) controls a shift control unit (31) so that the gear engagement process (tz) is completed before the disconnect clutch opening process (t) has finished. K ) starts, so that the disconnect coupling opening process (t K ) and the gear engagement process (t K ) superimpose in an overlap time interval (Δt).

Description

[0001] The invention relates to a vehicle with a dual-clutch transmission according to the preamble of claim 1 and to a method for engaging a target gear in such a dual-clutch transmission according to claim 8.

[0002] In a dual-clutch transmission of this type, its first and second sub-transmissions can be activated by actuating their respective first and second disconnect clutches. Each sub-transmission has at least one synchronizing clutch, which allows a gear to be engaged. During driving, a sequential shift is performed automatically by an electronic shift control unit to engage the target gear. To prepare for the subsequent shift, the shift control unit engages the target gear in a gear-engagement operation in the passive, i.e., the inactive, sub-transmission. Before the gear-engagement operation, an evaluation module checks whether the disconnect clutch of the passive sub-transmission is closed.Such a closed disconnect clutch in the passive sub-transmission occurs in a special situation, for example in a process for determining the kiss point, which defines the position of a disconnect clutch actuator from which the clutch clearance is exhausted and torque transmission takes place via the disconnect clutch.

[0003] When the passive sub-transmission's disconnect clutch is engaged, the evaluation module activates a clutch control unit to fully open the disconnect clutch during a disconnect clutch opening process, ensuring torque-free engagement of the target gear. The time required to prepare for the next gear shift therefore comprises the disconnect clutch opening process and the gear engagement process.

[0004] In the prior art, the gear engagement process only starts after the disconnect clutch opening process is complete. Therefore, in the prior art, the time until the subsequent shifting is initiated is correspondingly long.

[0005] A multi-stage automatic transmission is known from EP 1 445 516 B1. A method for minimizing interruption of traction during upshifting of an automated manual transmission is known from DE 10 2006 060 285 A1. Upon receiving an upshift signal, a control device initiates the opening of the friction clutch as quickly as possible, followed, or simultaneously, by disengaging the original gear and engaging the target gear. After engaging the target gear, the friction clutch is adjusted to transmit torque between the drive motor and the input shaft of the automated manual transmission within a slip range, and the torque generated by the drive motor is actively influenced.

[0006] From DE 10 2016 202 286 A1 a method for operating a dual-clutch transmission of a motor vehicle is known, wherein a first clutch is operated in the closed position and thereby drives a first transmission branch in which a current actual gear is engaged, and in a pre-selection phase for a gear change to a target gear in a second transmission branch the target gear is engaged and a clutch hydraulic system is filled at a second clutch and thereby the second clutch is closed.

[0007] The object of the invention is to provide a vehicle with a dual-clutch transmission in which the overall shift time is reduced compared to the prior art.

[0008] The problem is solved by the features of claim 1 or 8. Preferred embodiments of the invention are disclosed in the dependent claims.

[0009] The invention relates to a dual-clutch transmission, the first and second sub-transmissions of which can be activated by actuating their respective first and second disconnect clutches. Each sub-transmission has at least one synchronizing clutch with which a gear can be engaged. During driving, a sequential shift is performed automatically by an electronic shift control unit to engage the target gear. To prepare for the sequential shift, the shift control unit engages the target gear in a gear-engagement operation in the passive, i.e., inactive, sub-transmission. Before the gear-engagement operation, an evaluation module checks whether the disconnect clutch of the passive sub-transmission is closed.Such a closed disconnect clutch in the passive sub-transmission occurs in a special situation, for example in a process for determining the kiss point, which defines the position of a disconnect clutch actuator from which the clutch clearance is exhausted and torque transmission takes place via the disconnect clutch.

[0010] When the passive sub-transmission's disconnect clutch is engaged, the evaluation module activates a clutch control unit to fully open the disconnect clutch during a disconnect clutch opening process, ensuring torque-free engagement of the target gear. The time required to prepare for the next gear shift therefore comprises the disconnect clutch opening process and the gear engagement process.

[0011] According to the characterizing part of claim 1, the following measure is taken to reduce the preparation time: The evaluation module controls the shift control unit to start the gear engagement process even before the disconnect clutch opening process has finished. According to the invention, the disconnect clutch opening process and the gear engagement process therefore overlap within a time interval, resulting in a reduced overall shift time compared to the prior art.

[0012] The invention is based on the understanding that the disengaging clutch opening process can be divided into a torque-bearing opening phase until a kiss point is reached, and a torque-free opening phase after reaching the kiss point, in which a torque-free clutch clearance builds up in the disengaging clutch. According to the invention, the evaluation module controls the shift control unit in such a way that the gear engagement process starts early, at least during the torque-free opening phase of the disengaging clutch opening process.

[0013] The invention is based, alternatively and / or additionally, on the finding that the gear engagement process can also be divided into a torque-free engagement phase and a torque-generating engagement phase, in which a synchronizing friction torque builds up in the gearshift assembly. Against this background, the evaluation module can control the shift control unit in such a way that the gear engagement process starts even before the kiss point in the disconnect clutch of the passive sub-transmission is reached. The kiss point of the disconnect clutch of the second sub-transmission is therefore reached at a time when the torque-free engagement phase of the gear engagement process is already underway. After reaching the kiss point, the torque-generating engagement phase of the gear engagement process begins.

[0014] The evaluation module is connected to a clutch sensor that detects the contact pressure acting on the disconnect clutch of the passive sub-transmission, or a corresponding parameter. Based on, among other things, the detected contact pressure and the corresponding torque transmission, the evaluation module can determine the disconnect clutch's "kiss point." The kiss point defines the position of a disconnect clutch actuator from which, with increasing contact pressure, torque is transmitted via the disconnect clutch, and from which, with decreasing contact pressure, a torque-free clutch clearance is established.

[0015] Once the target gear has been selected, i.e., after the preparation period has elapsed, the subsequent shift can be carried out. In this shift, the evaluation module activates the clutch control unit to close the disconnect clutch of the still passive sub-transmission. Simultaneously, the clutch control unit opens the disconnect clutch of the active sub-transmission, thus completing the subsequent shift.

[0016] In a specific embodiment, a vehicle drive unit, in particular an internal combustion engine, is connected to a power output shaft via the two load-shiftable disconnect clutches of the dual-clutch transmission, alternatingly to either a first or a second drive shaft. The first or the second sub-transmission can be activated by means of the two drive shafts. Fixed and loose gears are arranged on the two drive shafts and on an output shaft, which is particularly parallel to the axis. These gears are grouped into gear sets to form gear stages, in which the loose gears can be coupled to the respective transmission shaft by means of the gearshift elements.

[0017] The gearshift elements installed in the dual-clutch transmission can preferably be implemented as axially adjustable synchronous clutches, either on one or both sides. Such a synchronous clutch has a sliding sleeve that is axially adjustable over a shift path by means of a shift fork. The shift fork can be adjusted over this path, for example, by a hydraulically operated actuator. An internal toothing of the sliding sleeve is axially adjustable on a corresponding external toothing of a sliding sleeve carrier that is fixed to a rotation on a transmission shaft. The sliding sleeve can be moved by means of the shift fork into a shift position in which the internal toothing of the sliding sleeve is in mesh with both the external toothing of the sliding sleeve carrier and the external toothing of a loose-gear clutch body.

[0018] An exemplary embodiment is described below with reference to the attached figures.

[0019] They show: Fig. 1 the transmission structure of a vehicle's powertrain with a dual-clutch transmission installed therein; Fig. 2 a diagram illustrating the temporal sequence of preparation for a subsequent circuit according to a comparative example not covered by the invention; and Fig. 3 a diagram according to the Fig. 2, in which the temporal sequence of a preparation of the subsequent circuit according to the invention is illustrated.

[0020] In the Fig. Figure 1 shows a transmission structure of a motor vehicle drivetrain, which essentially consists of an internal combustion engine 1 and a dual-clutch transmission. The dual-clutch transmission has a first drive shaft 7 and a second drive shaft 9. These are arranged coaxially and can be connected to a power output shaft 10 of the internal combustion engine 1 via two, for example, hydraulically actuated, load-shiftable disconnect clutches K1, K2, alternatingly and in a torque-conducting manner. The first drive shaft 7 is in the Fig. The first drive shaft 1 is a solid shaft, which is guided coaxially inside the second drive shaft 9, which is a hollow shaft. An output shaft 13 is provided parallel to the two drive shafts 7 and 9. This output shaft drives, via a gear stage 15 with spur gears, an input shaft 19 of an axle differential 21. From the axle differential 21, flanged shafts 23 lead on both sides to vehicle wheels (not shown).

[0021] The first and second drive shafts 7 and 9 each activate a first sub-transmission I and a second sub-transmission II of the dual-clutch transmission. The first sub-transmission I is located axially farther from the clutch, while the second sub-transmission II is located close to the clutch. Fixed and loose gears are arranged in the gear planes on both drive shafts 7 and 9, as well as on the output shaft 13. These are grouped into gear sets to form six forward gear stages G1 to G6 and one reverse gear stage R. In the figure, the loose gears of all gear stages are positioned on the output side of the output shaft 13. The loose gears can be shifted using gear selectors S1 to S4, which are also located on the output shaft 13.

[0022] Each of the gear-shifting elements S1 to S4 is implemented as a synchronous clutch with a sliding sleeve 24, which is axially adjustable on both sides by means of an indicated shift fork 25 over an adjustment path Δs. The sliding sleeve 24 sits with its internal teeth (not shown) on a corresponding external toothing of a sliding sleeve carrier 27, which is rotationally fixed on the output shaft 13. Each of the sliding sleeves 24 is in the Fig. 1 is positioned in a neutral position. Starting from the neutral position, the sliding sleeves 24 can be moved into a shift position to engage one of the gears G1 to G6 or R. In the shift position, the internal teeth of the sliding sleeves are engaged on one side with the sliding sleeve carrier 27 and on the other side with the external teeth of a clutch body 29 of a loose gear.

[0023] Each of the 25 shift forks is in the Fig. 1 in operative connection with, for example, a hydraulically operated actuator 26, which can be controlled by a switching control unit 31. Upon appropriate control, the switching fork 25 is axially adjusted over a travel Δs in order to bring the associated switching sleeve 24 into or out of clutch engagement with a loose gear.

[0024] In the Fig. The switching control unit 31 and a clutch control unit 35 can be controlled by an evaluation module 30. The evaluation module 30 is in signal communication with a sensor that detects the contact pressure acting in the disconnect clutches K1 and K2, or a corresponding parameter. Based on the detected contact pressure and a corresponding transmissible clutch torque, the evaluation module 30 determines the kiss point KP of the disconnect clutches K1 and K2.

[0025] Evaluation module 30 contains a shifting strategy to perform a sequential shift without interruption of traction into a target gear, in which the shift is made from a current gear of one sub-transmission (or alternatively from a neutral position) into the target gear of the other sub-transmission.

[0026] A key aspect of the invention is to reduce the overall switching time during automatically performed sequential switching. This is achieved by engaging the target gear earlier compared to the prior art.

[0027] For a simpler understanding of the invention, it will first be explained using the following: Fig. 2. A comparative example not covered by the invention is explained. In the diagram of the Fig. 2 considers the temporal course of the preparation of a subsequent shift (i.e. a shift into the target gear) carried out during driving operation, where, for example, the current gear is the third gear G3 in sub-transmission I and the target gear is the fourth gear G4 in sub-transmission II.

[0028] Accordingly, the evaluation module 30 first controls the clutch control unit 35 to move the gearshift element S1 (marked with a dashed line in the diagram) from its neutral position to its shift position during a gear engagement process tz, thereby engaging the target gear G4 in the still passive second sub-transmission II. Subsequently, the evaluation module 30 controls the clutch control unit 35 and the shift control unit 31 to select the current sub-transmission I and the current gear G3.

[0029] Before the gear engagement process tz begins, the evaluation module 30 checks whether the disconnect clutch K2 of the still passive sub-transmission II is closed. This is shown in the diagram of the Fig. 2 at time t=0. If such a closed disconnect clutch K2 of the passive sub-transmission II is present, the evaluation module 30 controls the clutch control unit 35 to initiate a disconnect clutch opening process t K to fully open the disconnect clutch K2 (marked with a solid line in the diagram) so that engagement of the target gear G4 is guaranteed without torque. The diagram of the Fig. The indicated time period tv for preparing the subsequent circuit therefore results from the disconnect coupling opening process t. K and from the gear engagement process tz. In the diagram of the Fig. 2. The gear engagement process tz only starts when the disconnect clutch K2 is fully open, that is, when the disconnect clutch opening process t is complete. Kis completely finished. Therefore, in the Fig. 2. The preparation for the subsequent shift (that is, shifting into fourth gear G4) requires a correspondingly large preparation time tv.

[0030] In departure from the Fig. 2 is in the diagram of the Fig. 3 The temporal sequence for the preparation of the subsequent circuit according to the invention is indicated, which is based on the following finding: Thus, the disconnect coupling opening process t K subdivide into an initial moment-guiding opening phase t K1 , which continues until a kiss point KP is reached, and into a subsequent moment-free opening phase t K2 , which starts with the Kisspoint KP. In the moment-free opening phase t K2A torque-free clutch clearance builds up in the K2 disconnect coupling. The Kisspoint KP defines a position of a disconnect coupling actuator from which, with increasing contact pressure, torque transmission occurs via the K2 disconnect coupling, and from which, with decreasing contact pressure, the torque-free clutch clearance is established.

[0031] The gear insertion process tz can be divided into the following four phases: a moment-free first insertion phase t Z1 , in which the gearshift element S1 uses up a mechanical play without any positioning movement of the gearshift element S1 taking place; a torque-free second engagement phase t Z2 , in which the gearshift element S1 moves from the neutral position until it encounters the still-locking synchronizer ring (i.e., the synchronization point is reached); a torque-carrying third engagement phase t Z3, in which the gearshift element S1 remains until the input shaft is synchronized to the synchronizing speed by the acting frictional torque of the synchronizer pack; and a torque-carrying fourth engagement phase t Z4 , in which the synchronizing ring rotates until the locking effect is released and the gear actuator can move the sliding sleeve further into the toothing, up to its switching position, thereby engaging the target gear G4.

[0032] According to the diagram of Fig. 3 This finding is used as follows: The evaluation module 30 controls the switching control unit 31 in such a way as to prepare the subsequent circuit (i.e., switching to the target path G4) so ​​that the torque-free insertion phase t Z1 starts even before the Kisspoint KP of the disconnect clutch K2 of the second sub-transmission. As soon as the disconnect clutch K2 is in the disconnect clutch opening process t KOnce the kiss point KP is reached, at least the moment-free insertion phase t is already underway. Z1 or the moment-free second insertion phase t Z2 of the gear shift element S1. After reaching the kiss point KP (and before the disengagement clutch process has finished t) K ) starts the torque-generating third insertion phase t Z3 with subsequent moment-bearing fourth insertion phase t Z4 of the gear engagement process tz, in which the gear shift element S1 is moved into its shift position. Due to the (compared to the Fig. 2) The gear engagement process tz, which is brought forward in time, overlaps with the disengaging clutch opening process t. K and the gear engagement process tz within an overlap time interval Δt. The preparation time tv for preparing the target gear sequence is therefore, compared to the state of the art ( Fig. 2) significantly reduced.

[0033] After the target gear G4 has been engaged, i.e. after the preparation time tv has been completed, the subsequent switching is carried out, in which the evaluation module 30 controls the clutch control unit 35 to close the disconnect clutch K2 of the still passive sub-transmission II, with an overlapping opening of the disconnect clutch K1 of the still active sub-transmission I, thereby completing the subsequent switching. REFERENCE MARK LIST: 1 internal combustion engine 7 first drive shaft 9 second drive shaft 10 Power output shaft 13 Output shaft 15 Spur gear stage 19 Input wave 21 axle differential 23 flange shafts 24 Switch sleeve 25 shift fork 26 actuator 27 Switch sleeve carriers 29 Loose gear coupling body 30 Evaluation module 31 Switching control unit 35 Clutch control unit 37 Sensors G1 to G6 forward gears R Reverse gear K1, K2 disconnect couplings S1 to S4 gearshift elements KP Kisspoint Δs travel distance t K Disconnect coupling opening process t K1 moment-leading opening phase t K2 moment-free opening phase t Z Gear engagement process t Z1 , t Z2 Moment-free insertion phases t Z3 , t Z4 torque-leading insertion phases Δt overlap time interval t V Preparation time

Claims

[1] Vehicle with a dual-clutch transmission, the first sub-transmission (I) and the second sub-transmission (II) of which can be activated by actuating their respective first and second disconnect clutches (K1, K2), wherein each sub-transmission (I, II) has at least one gear shift element (S1 to S4) with which a gear can be engaged, wherein a shift control unit (31) can be used to perform a sequential shift in which a target gear (G4) is engaged during driving, wherein the shift control unit (31) engages the target gear (G4) in a gear engagement operation (tz) in the passive, i.e., in the inactive, sub-transmission (II) to prepare for the sequential shift, wherein the shift control unit (31) has an evaluation module (30) which checks, before the gear engagement operation (tz), whether the disconnect clutch (K2) of the passive sub-transmission (II) is closed,wherein the evaluation module (30) controls a clutch control unit (35) when a disconnect clutch (K2) of the passive sub-transmission (II) is closed, in order to initiate a disconnect clutch opening process (t, K ) to fully open the disconnect clutch (K2) so that torque-free engagement of the target gear (G4) is ensured, and a time duration (t) V ) to prepare the subsequent circuit from the disconnect coupling opening process (t K ) and from the gear-engaging process (t Z ) is composed of, characterized by , that to reduce the preparation time (t V ) the evaluation module (30) controls the shift control unit (31) in such a way that the gear engagement process (t Z ) before the disconnect coupling opening process has finished (t K ) starts, so that the disconnect coupling opening process (t K ) and the gear engagement process (t Z ) superimpose in an overlap time interval (Δt). [2] Vehicle according to claim 1, characterized by , that the disconnect coupling opening process (t K ) is divided into an initial moment-bearing opening phase (t K1 ) until reaching a kiss point (KP) and into a subsequent moment-free opening phase (t K2 ) after reaching the kiss point (KP), in which a torque-free clutch clearance builds up in the disconnect clutch (K2), and that the evaluation module (30) controls the switching control unit (31) in such a way that at least already in the torque-free opening phase (t K2 ) of the disconnect coupling opening process (t K ) the gear engagement process (t Z ) starts. [3] Vehicle according to claim 1 or 2, characterized by , that the gear insertion process (tz) is divided into at least one moment-free insertion phase (t Z1 , t Z2 ) and into at least one moment-guiding insertion phase (t Z3 , t Z4), in which a synchronizing friction torque builds up in the gear shift package, and that the evaluation module (30) controls the shift control unit (31) in such a way that the torque-free engagement phase (t Z1 , t Z2 ) starts before reaching the kiss point (KP) of the disconnect clutch (K2) of the second sub-transmission (II), so that the kiss point (KP) of the disconnect clutch (K2) of the second sub-transmission (II) is reached at a time when the torque-free engagement phase (t Z1 , t Z2 ) of the gear engagement process (t Z ) is already running, and after reaching the kiss point (KP), the moment-leading insertion phase (t) begins. Z3 , t Z4 ) of the gear engagement process (t Z ) starts. [4] Vehicle according to any of the preceding claims, characterized by, that the evaluation module (30) is in signal connection with a sensor (37) which detects a contact pressure acting in the disconnect clutch (K2) of the passive sub-transmission (II) or a parameter corresponding thereto, and that the evaluation module (30) determines the kiss point (KP) of the disconnect clutch (K2) on the basis of the detected contact pressure and a corresponding transmissible clutch torque, or that in a dry clutch system the evaluation module (30) has a displacement measuring system for determining the kiss point (KP). [5] Vehicle according to any of the preceding claims, characterized by, that after the target gear has been engaged, i.e. after completion of the preparation time (tv), the subsequent switching can be carried out, in which the evaluation module (30) controls the clutch control unit (35) to close the disconnect clutch (K2) of the still passive sub-transmission (II), namely with overlapping opening of the disconnect clutch (K1) of the still active sub-transmission (I), thereby completing the subsequent switching. [6] Vehicle according to any one of the preceding claims, characterized by , that the disconnecting clutch (K2) of the passive sub-transmission (II) is closed in a special situation, for example during a process to determine the kiss point (KP), which defines the position of an actuator of the disconnecting clutch (K2), from which, with increasing contact pressure, a torque transmission via the disconnecting clutch (K2) takes place, and from which, with decreasing contact pressure, a torque-free clutch clearance is established. [7] Vehicle according to any of the preceding claims, characterized by , that a vehicle drive unit (1) with a power output shaft (10) alternately drives either a first drive shaft (7) or a second drive shaft (9) via the two load-shiftable disconnect clutches (K1, K2) of the dual-clutch transmission, that the first sub-transmission (I) or the second sub-transmission (II) can be activated by means of the two drive shafts (7, 9), and that fixed and loose gears are arranged on the two drive shafts (7, 9) as well as on an axially parallel output shaft (13), which are grouped into gear sets to form forward gear stages (G1 to G6), in which the loose gears can be coupled to the respective transmission shaft (7, 9, 13) by means of the gear shift elements (S1 to S4). [8] Method for engaging a target gear (G4) in a dual-clutch transmission of a vehicle according to any of the preceding claims.

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