Vehicle with a dual-clutch transmission

Abstract

The invention relates to a vehicle with a dual-clutch transmission in which, in preparation for a target gear shift in a separating clutch opening process (t K ) the still closed separating clutch (K1) of the first partial transmission (I) is fully opened, so that a torque-free disengagement of the current gear (G3) is ensured, and in a gear disengagement process (t G ) a current gear (G3) in the first partial transmission (I) is disengaged without torque. According to the invention, the gear disengagement process (t G ) before the end of the separating clutch opening process (t K ), which starts the separating clutch opening process (t K ) and the gear disengagement process (t G ) 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 operating such a dual-clutch transmission according to claim 8.

[0002] In a dual-clutch transmission, the first and second sub-transmissions can be activated during driving by actuating respective first and second separating clutches. Each of the sub-transmissions has at least one synchronizing clutch with which a gear can be engaged.

[0003] With an electronic shift control unit of the dual-clutch transmission, an indirect gear shift without interruption in traction can be carried out, in which, during driving, a shift is made from a current gear of the first sub-transmission to an intermediate gear of the second sub-transmission and then further to the target gear of the first sub-transmission.

[0004] To prepare for such a target gear shift, an evaluation module controls a clutch control unit to fully open the still-closed clutch of the first sub-transmission in a clutch disengagement process, ensuring torque-free disengagement of the current gear. The evaluation module also controls the shift control unit to disengage the current gear in the first sub-transmission without torque during a gear disengagement process.

[0005] In the prior art, the gear disengagement process is only performed after the clutch disengagement process is complete, i.e., only when the clutch is fully disengaged. Therefore, in the prior art, the time required to prepare the target gear shift—that is, the time until the target gear is finally engaged—is correspondingly long.

[0006] DE 10 2014 103 672 A1 discloses a generic control method for a drive train. DE 100 48 239 A1 discloses a method for shifting a gear-change transmission. DE 10 2005 049 178 A1 discloses a control method for an automated manual transmission that enables a gear change, i.e., a downshift, with minimal interruption in traction by arranging the phase of reducing the drive torque of the drive motor, the phase of disengaging the power transmission in the automated manual transmission, and the phase of adjusting the speed of the transmission input shaft to a suitable target speed in such a way that they at least partially overlap in time.

[0007] DE 10 2006 058 973 A1 discloses a method for controlling the operation of a parallel transmission with two sub-transmissions, each of whose input shafts can be connected to a drive shaft by means of a clutch and whose output shafts act on a common output shaft. During a target shift from a current gear engaged in one sub-transmission, whose clutch is engaged, to a target gear engaged in the other sub-transmission, whose clutch is disengaged, the engaged clutch is progressively disengaged, and simultaneously the disengaged clutch is progressively engaged. As the clutch associated with the sub-transmission containing the target gear progressively engages, an attempt is made to disengage the current gear.

[0008] The object of the invention is to provide a vehicle with a dual-clutch transmission in which the total shift time for a gear change in the same sub-transmission is reduced compared to the prior art.

[0009] The object is achieved by the features of claim 1 or 8. Preferred developments of the invention are disclosed in the subclaims.

[0010] The invention relates to a vehicle with a dual-clutch transmission in which, during driving, the first sub-transmission and the second sub-transmission can be activated by actuating respective associated first and second separating clutches. Each of the sub-transmissions has at least one synchronizer clutch with which a gear can be engaged. An electronic shift control unit of the dual-clutch transmission enables indirect gearshifting without interruption of traction. During driving, the current gear of the first sub-transmission is shifted first to an intermediate gear of the second sub-transmission, and then further to the target gear of the first sub-transmission.To prepare for such a target gear shift, an evaluation module controls a clutch control unit to fully open the still-closed clutch of the first sub-transmission in a clutch disengagement process, ensuring torque-free disengagement of the current gear. The evaluation module also controls the shift control unit to disengage the current gear in the first sub-transmission without torque during a gear disengagement process.

[0011] According to the characterizing part of claim 1, the following measure is taken to reduce the total shift time during a gear change in the same sub-transmission: The gear disengagement process no longer starts only after the separating clutch is fully opened, i.e., after the separating clutch opening process has been completed. Instead, the evaluation module controls the shift control unit so that the gear disengagement process starts before the separating clutch opening process has been completed. According to the invention, the separating clutch opening process and the gear disengagement process therefore overlap in an overlapping time interval, which overall leads to a reduced total shift time compared to the prior art.

[0012] The invention is based on the finding that the clutch disengagement process can be divided into an initial torque-carrying opening phase until a kiss point is reached, and a subsequent torque-free opening phase after the kiss point is reached, during which a torque-free clutch release clearance builds up in the clutch. According to the invention, the evaluation module controls the shift control unit such that the gear disengagement process begins at least during the torque-carrying opening phase of the clutch disengagement process.

[0013] The invention is alternatively and / or additionally based on the finding that the gear disengagement process can also be divided into an initial torque-leading disengagement start phase in which the gearshift element uses up a mechanical gearshift play without an adjustment movement of the gearshift element from its switching position to its neutral position, and into a subsequent switching phase in which the gearshift element adjusts from its switching position towards the neutral position.

[0014] Against this backdrop, the evaluation module can apply the following shifting strategy: The evaluation module can thus control the shift control unit so that the torque-carrying disengagement start phase begins before the kisspoint of the separating clutch of the first sub-transmission. In this case, the kisspoint of the separating clutch of the first sub-transmission is reached, while the torque-carrying disengagement start phase of the gearshift element is already underway. After reaching the kisspoint (i.e., after torque-free operation in the separating clutch is achieved), the shifting phase of the gear disengagement process begins, in which the gearshift element releases torque-free from its shift position toward the neutral position.

[0015] In a technical implementation, the evaluation module can be connected to a sensor that detects the contact pressure acting on the respective separating clutch or a parameter correlated with it. The evaluation module can determine the kiss point of the separating clutch based on the detected contact pressure and a corresponding transmittable clutch torque.

[0016] To achieve a target gear shift without interrupting traction, this can be implemented as an indirect shift, in which the current gear of the first sub-transmission is first shifted to an intermediate gear of the second sub-transmission. The intermediate gear of the second sub-transmission is then shifted to the target gear of the first sub-transmission.

[0017] After the current gear has been selected, i.e., after the preparation period has ended, the target gear shift is performed. During this process, the evaluation module controls the shift control unit so that the target gear is engaged in the first sub-transmission. The clutch control unit is then activated to close the separating clutch of the first sub-transmission, thus completing the target gear shift.

[0018] In a specific embodiment, a vehicle drive unit, in particular an internal combustion engine, with a power output shaft is alternately connected to either a first drive shaft or a second drive shaft via the two powershift clutches of the dual-clutch transmission. The first sub-transmission 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 in particular axially parallel thereto. These fixed and loose gears are combined to form gear sets, forming gear stages. In these gear sets, the loose gears can be coupled to the respective transmission shaft by means of the gearshift elements.

[0019] The gearshift elements installed in the dual-clutch transmission can preferably be implemented as synchronous clutches that are axially adjustable on one or both sides. Such a synchronous clutch has a sliding sleeve that is axially adjustable over a shift travel by means of a shift fork. The shift fork can be adjusted over the travel travel by, for example, a hydraulically operated actuator. An internal gearing of the sliding sleeve is mounted in an axially adjustable manner on a corresponding external gearing of a sliding sleeve carrier that is non-rotatably mounted on a transmission shaft. The sliding sleeve can be moved with the aid of the shift fork into a shift position in which the internal gearing of the sliding sleeve meshes with both the external gearing of the sliding sleeve carrier and the external gearing of a loose gear clutch body.

[0020] An embodiment is described below with reference to the attached figures.

[0021] They show: Fig. 1 the transmission structure of a drive train of a vehicle with a dual-clutch transmission installed therein; Fig. 2 is a diagram illustrating a timing sequence for a gear design according to a comparative example not covered by the invention; and Fig. 3 a diagram corresponding to the Fig. 2, in which the time sequence for a gear design according to the invention is illustrated.

[0022] In the Fig. 1 shows a transmission structure of a drive train of a motor vehicle, 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 in a torque-carrying manner to a power output shaft 10 of the internal combustion engine 1 via two, for example, hydraulically actuated power-shiftable separating clutches K1, K2. The first drive shaft 7 is in the Fig. 1 is realized as a solid shaft, which is guided coaxially within the second drive shaft 9, which is realized as a hollow shaft. An output shaft 13 is provided axially parallel to the two drive shafts 7, 9. This output shaft drives via a gear stage 15 with spur gears to an input shaft 19 of an axle differential 21. Flange shafts 23 lead from the axle differential 21 on both sides to vehicle wheels (not shown).

[0023] A first sub-transmission I and a second sub-transmission II of the dual-clutch transmission can be activated by means of the first and second input shafts 7, 9. In the figure, the first sub-transmission I is axially spaced from the dual clutch K1, K2 with the second sub-transmission II arranged therebetween. Fixed and loose gears are arranged in gear planes on the two input shafts 7, 9 and on the output shaft 13. These are combined to form gear sets, forming six forward gears G1 to G6 and one reverse gear R. In the figure, the loose gears for all gears are positioned on the output side of the output shaft 13. The loose gears can be shifted using gearshift elements S1 to S4, which are also positioned on the output shaft 13.

[0024] Each of the gear shift 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 toothing (not shown) on a corresponding external toothing of a sliding sleeve carrier 27 arranged in a rotationally fixed manner 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 sliding sleeve internal toothing meshes with the sliding sleeve carrier 27 on the one hand and with the external toothing of a clutch body 29 of a loose gear on the other.

[0025] Each of the shift forks 25 is in the Fig. 1 in operative connection with, for example, a hydraulically operating actuator 26, which can be controlled by a shift control unit 31. When appropriately controlled, the shift fork 25 is axially adjusted over a travel Δs in order to bring the associated shift sleeve 24 into or out of clutch engagement with a loose gear.

[0026] In the Fig. 1, the shift control unit 31 and a clutch control unit 35 are controlled by an evaluation module 30. The evaluation module 30 is connected via a signal to a sensor 37, which detects a contact pressure acting in the separating clutches K1, K2 or a parameter correlating therewith. The evaluation module 30 determines the kiss point KP of the separating clutch K1, K2 based on the detected contact pressure and a corresponding transmittable clutch torque.

[0027] A shifting strategy is stored in the evaluation module 30 in order to carry out an indirect gear change without interruption of traction, in which a shift is made from a current gear of one sub-transmission via an intermediate gear of the other sub-transmission to a target gear of one sub-transmission.

[0028] A core aspect of the invention is to reduce the overall shift time when changing gears from the current gear to the target gear. This is achieved by engaging the current gear earlier than in the prior art. This also allows the target gear shift, i.e., engaging the target gear, to occur at an earlier point in time. The target gear can only be engaged once the current gear is engaged, thus avoiding gearset jamming in the sub-transmission.

[0029] For a simpler understanding of the invention, the Fig. 2 illustrates a comparative example not covered by the invention. In the comparative example of Fig. 2, an indirect gearshift is considered as an example, in which the current gear is the third gear G3 in the first partial transmission I, while the target gear is the first gear G1 in the first partial transmission I and an intermediate gear is the second gear G2 in the second partial transmission II. Accordingly, in order to prepare the target gearshift, the evaluation module 30 controls the clutch control unit 35 in order to initiate a clutch opening process t K to fully open the still closed clutch K1 (see solid line in the diagram) of the first sub-transmission I. This ensures torque-free disengagement of the current gear G3. After completion of the clutch opening process t K the evaluation module 30 controls the switching control unit 31 in order to Gthe gearshift element S3 (see dashed line in the diagram) from its switching position to its neutral position, so that the current gear G3 in the first partial transmission I is designed torque-free. The Fig. The time duration tv indicated in Figure 2 for preparing the target gear shift therefore results from the clutch opening process t K and from the gear disengagement process t G . In the diagram of the Fig. 2 starts the gear disengagement process t G only when the separating clutch K1 is fully opened, i.e. when the separating clutch opening process t K is completely finished. Therefore, in the Fig. 2 the preparation for the target gear shift requires a correspondingly long preparation time tv.

[0030] In departure from the Fig. 2 is in the diagram of the Fig. 3 shows the timing of a gear design according to the invention. The gear design according to the invention is based on the following finding: The clutch opening process t K divided into an initial moment-leading opening phase t K1 , which continues until a kisspoint KP is reached, and into a subsequent moment-free opening phase t K2 , which starts with the kiss point KP. In the moment-free opening phase t K2 a torque-free clutch release clearance builds up in the separating clutch K1.

[0031] The kiss point KP defines a position of a separating clutch actuator from which torque is transmitted via the separating clutch when the contact pressure increases, and from which torque-free clutch release occurs when the contact pressure decreases.

[0032] In the same way, the gear disengagement process t Gdivided into an initial moment-leading design start phase t G1 , and into a subsequent switching phase t G2 . In the lay-out start phase t G1 the gearshift element S3 requires a mechanical gearshift play, without any actuating movement of the gearshift element S3. In the subsequent switching phase t G2 On the other hand, the gear shift element S3 is adjusted by a travel distance Δs ( Fig. 1) from its switching position towards its neutral position.

[0033] According to the diagram of the Fig. 3, this knowledge is used as follows when changing gears: The evaluation module 30 controls the shift control unit 31 so that the torque-leading disengagement start phase t G1 not first after completion of the separating coupling opening process t Kbegins, but is started before the kisspoint KP of the separating clutch K1 of the first sub-gearbox I. As soon as the separating clutch K1 of the first sub-gearbox I reaches the kisspoint KP, the torque-leading disengagement start phase t G1 of the gearshift element S3. After reaching the kisspoint KP (and before the clutch release process t K ) starts the switching phase t G2 of the gear disengagement process t G to move the gear shift element S3 from its switching position towards the neutral position without any torque. Fig. 2) gear disengagement process t brought forward in time G The separating clutch opening process t K and the gear disengagement process t G in an overlap time interval Δt. The preparation time tv for preparing the target gear shift is thus shorter than in the state of the art ( Fig. 2) significantly reduced.

[0034] After the third gear G3 has been disengaged, i.e., after the preparation period tv has been completed, the target gear shift is performed. During the target gear shift, the evaluation module 30 controls the shift control unit 31 so that the target gear G1 in the first sub-transmission I is engaged torque-free by adjusting the gear shift element S4. Subsequently, the clutch control unit 35 is controlled to re-engage the separating clutch K1 of the first sub-transmission I. LIST OF REFERENCE SYMBOLS: 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 shaft 21 axle differential 23 flange shafts 24 Shift sleeve 25 shift fork 26 Actuator 27 Shift sleeve carrier 29 Loose gear clutch body 30 evaluation module 31 Switch control unit 35 Clutch control unit 37 Sensor technology G1 to G6 forward gears R Reverse gear K1, K2 separating couplings S1 to S4 gearshift elements KP Kisspoint Δs travel t K Separating coupling opening process t K1 torque-leading opening phase t K2 torque-free opening phase t G Gear disengagement process t G1 torque-leading design start phase t G2 Switching phase Δt overlap time interval tv preparation time

Claims

[1] Vehicle with a dual-clutch transmission, the first partial transmission (I) and the second partial transmission (II) of which can be activated by actuating the respectively assigned first and second separating clutches (K1, K2), wherein each partial transmission (I, II) has at least one gearshift element (S1 to S4) with which a gear can be engaged, wherein a gearshift control unit (31) can be used to carry out a gearshift in which, during driving operation, a current gear (G3) of the first partial transmission (I) is to be shifted into a target gear (G1) of the first partial transmission (I), wherein, in preparation for the target gearshift, an evaluation module (30) controls a clutch control unit (35) in order to, in a separating clutch opening process (t K) to completely open the still closed separating clutch (K1) of the first partial transmission (I), so that a torque-free disengagement of the current gear (G3) is ensured, wherein the evaluation module (30) controls the shift control unit (31) in order to disengage the current gear (G3) in a gear disengagement process (t G ) to design the current gear (G3) in the first partial transmission (I) without torque, and wherein a time period (tv) for preparing the target gear shift results from the separating clutch opening process (t K ) and from the gear disengagement process (t G ), characterized by , that in order to reduce the preparation time (tv) the evaluation module (30) controls the switching control unit (31) in such a way that the gear disengagement process (t G ) before the end of the separating clutch opening process (t K ) starts, which initiates the separating clutch opening process (t K ) and the gear disengagement process (t G) are temporally superimposed in an overlap time interval (Δt), and that the separating clutch opening process (t K ) is divided into an initial moment-leading opening phase (t K1 ) until a kiss point (KP) is reached and into a subsequent moment-free opening phase (t K2 ) after reaching the kiss point (KP), in which a torque-free clutch release play builds up in the separating clutch (K2), and that the evaluation module (30) controls the shift control unit (31) in such a way that the gear disengagement process (t G ) at least already in the moment-leading opening phase (t K1 ) of the separating clutch opening process (t K ) starts. [2] Vehicle according to claim 1, characterized by that the gear disengagement process (t G ) is divided into an initial moment-leading design start phase (t G1), in which the gearshift element (S3) uses up a mechanical gearshift play, without any actuating movement of the gearshift element (G3), and into a subsequent switching phase (t G2 ), in which the gear shift element (G3) moves from its switching position towards a neutral position. [3] Vehicle according to one of the preceding claims, characterized by that the evaluation module (30) controls the switching control unit (31) in such a way that the torque-leading design start phase (t G1 ) starts before reaching the kiss point (KP) of the separating clutch (K1) of the first partial transmission (I), whereby the separating clutch (K1) of the first partial transmission (I) reaches the kiss point (KP) during the torque-leading disengagement start phase (t G1 ) is reached, and after reaching the kiss point (KP) the switching phase (t G2 ) of the gear disengagement process (t G ) starts. [4] Vehicle according to one of the preceding claims, characterized bythat the evaluation module (30) is in signal connection with a sensor (37) which detects a contact pressure acting in the respective separating clutch (K1, K2) or a parameter correlating therewith, and that the evaluation module (30) determines the kiss point (KP) of the separating clutch (K1, K2) on the basis of the detected contact pressure and a corresponding transmittable clutch torque. [5] Vehicle according to one of the preceding claims, characterized by that after the current gear (G3) has been designed, that is to say after the preparation period (tv) has ended, the target gear shift can be carried out, in which the evaluation module (30) controls the shift control unit (31) in such a way that the target gear (G1) is engaged in the first partial transmission (I), and then controls the clutch control unit (35) in such a way that the separating clutch (K1) of the first partial transmission (I) is closed, whereby the target gear shift is completed. [6] Vehicle according to one of the preceding claims, characterized by that the target gear shift is an indirect shift without interruption in traction, in which the current gear (G3) of the first partial transmission (I) is first shifted to an intermediate gear (G2) of the second partial transmission (II), and then the gear shift is continued to the target gear (G1) of the first partial transmission (I). [7] Vehicle according to one of the preceding claims, characterized bythat 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 powershiftable separating clutches (K1, K2) of the dual-clutch transmission, that the first partial transmission (I) or the second partial 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) and on an output shaft (13) axially parallel thereto, which are combined to form gears (G1 to G6, R) into gear sets, in which the loose gears can be coupled to the respective transmission shaft (7, 9, 13) by means of the gearshift elements (S1 to S4). [8] Method for operating a dual-clutch transmission of a vehicle according to one of the preceding claims.

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