Procedure for testing a parking lock function in a dual-clutch transmission

Abstract

A method for testing the parking lock function of a dual-clutch transmission installed in a vehicle, in which, when engaged, two gears (G2, G4) of a common sub-transmission (II) of the dual-clutch transmission are engaged by means of gearshift elements (S1, S2), with the common sub-transmission (II) locked, wherein, to engage the parking lock, one gear (G4) is engaged as a pre-select gear and another gear (G2) is engaged as a locking gear, and wherein the method includes a test routine by means of which an engagement test of the parking lock is performed, characterized in that the test routine verifies the proper engagement of the locking gear (G2) in its parking lock position, with the pre-select gear (G4) already engaged, with the transmission output side blocked or braked, and with a test torque (M) applied to the common sub-transmission (II) under test. P ).

Description

[0001] The invention relates to a method for testing a parking lock function of a dual-clutch transmission that can be installed in a vehicle according to the preamble of claim 1 and a test unit according to claim 9.

[0002] In such a dual-clutch transmission, a parking lock function can be implemented with minimal transmission engineering effort, allowing two gears (namely a pre-select gear and a locking gear) of a common sub-transmission of the dual-clutch transmission to be engaged simultaneously using gearshift elements. Due to the different gear ratios, the gear planes of the engaged gears lock together. This locking of the two gear planes located in the same sub-transmission prevents rotation of the transmission output shaft. Such a generic parking lock function is known from DE 199 50 696 A1.

[0003] The parking lock function is activated by an electronic control unit during a vehicle stop, based on current driving parameters. To activate the parking lock, the two disconnect clutches of the dual-clutch transmission are first disengaged. A pre-selected gear is then engaged. As soon as the control unit detects that the vehicle has come to a standstill, the locking gear is engaged in its parking lock position.

[0004] The invention specifically relates to a parking situation in which both disconnect clutches are disengaged, the preselector gear is already engaged, and the vehicle's drive unit (for example, an internal combustion engine) is still running. In this case, a slight basic drag torque is transmitted from the vehicle's drive unit to the transmission's output side via the disengaged disconnect clutches. When this basic drag torque is applied to the gear plane of the engaged preselector gear, and due to the stationary transmission output side, any backlash in the preselector gear's sub-transmission is eliminated. Therefore, the preselector gear's sub-transmission is backlash-free.

[0005] The backlash-free state leads to the following problem when the locking gear is subsequently shifted into its parking lock position: The play required between the locking gear switching partners for a smooth shifting process is already exhausted. Therefore, a backlash-inducing compensating movement between the locking gear switching partners is not possible. During the shifting process, an excessively high frictional resistance may therefore build up between the locking gear switching partners, which the locking gear shifting element must overcome.

[0006] In the prior art, the following measures are taken to ensure reliable engagement of the parking lock in the parking situation described above: The component and / or surface tolerances of the locking gear switching partners are manufactured within a tight tolerance range using complex manufacturing techniques to prevent excessively high frictional resistance between the locking gear switching partners when engaging the parking lock. Alternatively and / or additionally, the actuator of the gear switching element can be dimensioned with a sufficiently high drive power to reliably move the gear switching element into its parking lock position even in the event of excessively high frictional resistance.

[0007] DE 10 2015 217 975 A1 discloses a method for engaging a parking lock in a dual-clutch transmission of a motor vehicle. DE 10 2017 121 170 A1 discloses a method for engaging and disengaging a parking lock in a vehicle transmission. WO 2004 / 036079 A2 discloses a method for controlling an actuator in a vehicle drivetrain. DE 10 2014 226 024 A1 discloses a method for engaging a parking lock. DE 43 16 784 A1 discloses a drive unit for a motor vehicle. US 5 807 205 A discloses a parking lock device.

[0008] The object of the invention is to provide a method for testing a parking lock function in a dual-clutch transmission, by means of which the functionality of the parking lock can be determined in a simple manner.

[0009] The problem is solved by the features of claim 1 or 9. Preferred embodiments of the invention are disclosed in the dependent claims.

[0010] The invention relates to a dual-clutch transmission with a parking lock function. When the parking lock is engaged, two gears of a common sub-transmission of the dual-clutch transmission are engaged by means of gearshift elements. In this way, the common sub-transmission, and thus the rotational movement of the transmission output shaft, is locked. To engage the parking lock (or to activate the parking lock function), one gear in the common sub-transmission is first engaged as a pre-select gear, and then another gear is engaged as a locking gear.

[0011] The parking lock function is activated by an electronic control unit during a stop, based on current driving parameters. To activate the parking lock, the two disconnect clutches of the dual-clutch transmission are first disengaged. A pre-selected gear is then engaged. As soon as the control unit detects that the vehicle has come to a standstill, the locking gear is engaged in its parking lock position.

[0012] The invention specifically relates to a parking situation in which both disconnect clutches are disengaged, the pre-selector gear is engaged, and the vehicle's drive unit (for example, an internal combustion engine) is still running. In this case, a slight basic drag torque is transmitted from the vehicle's drive unit to the transmission's output side via the disengaged disconnect clutches. When this basic drag torque is applied to the gear plane of the engaged pre-selector gear, and due to the stationary transmission output side, any backlash in the pre-selector gear's sub-transmission is eliminated. Therefore, the pre-selector gear's sub-transmission is backlash-free.

[0013] The backlash-free state leads to the following problem when the locking gear is subsequently shifted into its parking lock position: The play required between the locking gear switching partners for a smooth shifting process is already exhausted. Therefore, a backlash-inducing compensating movement between the locking gear switching partners is not possible. During the shifting process, an excessively high frictional resistance may therefore build up between the locking gear switching partners, which the locking gear shifting element must overcome.

[0014] According to the characterizing part of claim 1, the method comprises a test routine that can be implemented, for example, during end-of-line testing in a vehicle or transmission manufacturing plant: The test routine can be performed with the vehicle parked or with the transmission output side blocked or braked. The test routine verifies the proper shifting of the locking gear with the preselector gear already engaged and with a test torque applied to the common sub-transmission.

[0015] The test routine can be structured as follows: In the first step, the disconnect clutches of the dual-clutch transmission are disengaged, and the preselected gear is engaged in the sub-transmission under test (i.e., the common sub-transmission). In the second step, the transmission output side, specifically a transmission output shaft, can be torsionally blocked or braked. Subsequently, in the third step, the test torque is applied to the sub-transmission under test. With the test torque applied, a shift of the locking gear is initiated in the fourth step. In the final fifth step, an engagement test is performed. This engagement test determines whether the locking gear has been correctly engaged in its park position despite the applied test torque, i.e., whether the park lock has been properly engaged.Provided that the parking lock is engaged within a defined period of time, the insertion test is passed.

[0016] If the parking lock is not properly engaged, the engagement force required to engage the parking lock is greater than the maximum engagement force that the locking gear actuator can provide. In this case, the vehicle or (in the transmission manufacturing plant) the dual-clutch transmission undergoes rework. This ensures that the maximum engagement force that the locking gear actuator can provide is sufficiently high in the customer-relevant parking situation defined above.

[0017] The invention is not limited to end-of-line testing in the vehicle manufacturing plant or the transmission manufacturing plant. Alternatively, the testing routine according to the invention can also be carried out in the workshop, for example after repair work has been carried out on the dual-clutch transmission.

[0018] The test torque simulates, in particular, the maximum possible basic drag torque with the dual clutch disengaged. By applying the test torque to the gear plane of the engaged pre-selector gear and due to the stationary transmission output side, any backlash in the pre-selector gear's sub-transmission is eliminated. Therefore, a backlash-free state exists in the pre-selector gear's sub-transmission.

[0019] During the test routine, the transmission output side is blocked or braked. Such a blockage or braking of the transmission output side can be achieved by applying the vehicle brakes or by means of an external test system.

[0020] In a technical implementation, the test torque in the third process step can be generated by a vehicle drive unit, i.e., an internal combustion engine and / or an electric motor. The test torque can then be applied to the drive side of the transmission under test using the vehicle drive unit.

[0021] To apply the test torque, a test module is used, for example, to close or slip the disconnect clutch located between the sub-transmission under test and the vehicle drive unit. This creates a load path in which the test torque generated by the vehicle drive unit is transmitted via the disconnect clutch to the selected gear level of the sub-transmission under test.

[0022] 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 into the parking lock position by means of the shift fork, 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.

[0023] Each sliding sleeve or actuator can be equipped with a position and / or displacement sensor that detects the current gear selector position and / or the current travel of the respective gear selector element and / or its actuator. In this case, during the insertion test (i.e., in the fifth process step), the presence of a correctly engaged parking lock can be determined using the position and / or displacement sensor. Depending on the position or displacement measurement, it can be concluded that a correctly engaged parking lock is present.

[0024] An exemplary embodiment is described below with reference to the attached figure.

[0025] The figure 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 transmitting torque. 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).

[0026] The first and second drive shafts 7, 9 each activate a first sub-transmission I and a second sub-transmission II of the dual-clutch transmission 3. In the figure, the first sub-transmission I is axially spaced from the dual clutch K1, K2, with the second sub-transmission II positioned between them. Fixed and loose gears are arranged in gear planes on the two drive shafts 7, 9 and 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 by means of gear shift elements S1 to S4, which are also positioned on the output shaft 13.

[0027] 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 one or both sides by means of an indicated shift fork 25 over a travel distance Δs. The sliding sleeve 24, with its internal teeth (not shown), sits 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 positioned in a neutral position in the figure. Starting from the neutral position, the sliding sleeves 24 can be moved into a shift position to engage a gear. In the shift position, the internal toothing of the sliding sleeve is in mesh with the sliding sleeve carrier 27 on one side and with the external toothing of a clutch body 29 of a loose gear on the other.

[0028] Each of the shift forks 25 is shown in the figure in operative connection with, for example, a hydraulically operated actuator 26, which can be controlled by a switching control unit 31. With appropriate control, the shift fork 25 is axially adjusted over a travel distance Δs in order to bring the associated shift sleeve 24 into or out of clutch engagement with a loose gear.

[0029] During a vehicle stop, the following parking lock function is implemented with the aid of an electronic control unit: The two disconnect clutches K1 and K2 are disengaged. Additionally, the first gear selector S1 is moved to a clockwise position, thus engaging forward gear G4 as a preselected gear. As soon as the control unit detects that the vehicle has come to a standstill, the second gear selector S2 is moved to a clockwise position, thus engaging forward gear G2 as a locked gear. In this way, two gears, G2 and G4, are engaged simultaneously in sub-transmission II by means of gear selectors S1 and S2. Due to the different gear ratios, the gear sets of the engaged gears G2 and G4 lock together. This locking of the two gear sets in the second sub-transmission II prevents the second sub-transmission II from rotating and thus prevents the output shaft 13 from rotating.

[0030] When designing the dual-clutch transmission, reliable engagement of the parking lock function must be guaranteed for all customer-relevant parking situations. In one specific parking situation, a basic drag torque M can occur after selecting gear G4. G The power is transmitted from the internal combustion engine 1 via the disengaged clutches K1, K2 into the sub-transmissions I, II. With the action of the basic drag torque M GWhen the backlash in sub-gearbox II of the engaged pre-selector gear G4 is exhausted, sub-gearbox II is in a backlash-free state. This leads to the following problem when subsequently shifting the locking gear G2 into its parking lock position: The backlash required for a smooth shifting operation between the locking gear components—that is, the sliding sleeve 24, the sliding sleeve carrier 27, and the loose gear clutch body 29—is already exhausted. Therefore, a backlash-inducing compensating movement between the locking gear components is not possible. During the shifting operation, an excessively high frictional resistance may build up between the locking gear components, which the gear shift element S2 of locking gear G2 must overcome. In addition to the frictional force, the shafts must be twisted by the engagement force in the backlash-free state. Thus, the axial component from the counter-torque due to the drivetrain torsion also acts.

[0031] To ensure secure insertion, a functional test of the parking lock function is performed using test module 30. This functional test can be carried out as part of an end-of-line inspection at the vehicle assembly plant or the transmission assembly plant. Alternatively, the functional test can also be performed in a workshop after a transmission repair.

[0032] In the figure, the test module 30 is connected to the shift control unit 31, an engine control unit 33 of the internal combustion engine 1, a clutch control unit 35 of the dual clutch K1, K2, and a brake control unit 39, by means of which a service brake 41 of the vehicle wheels, indicated in the figure, can be actuated. The test module 30 executes a test routine in which, in a first process step, the test module 30 controls the clutch control unit 35 to disengage the two disconnect clutches K1, K2. In addition, the test module 30 controls the shift control unit 31 to engage preselected gear G4 in the subtransmission II under test.

[0033] In a second process step, the transmission output, i.e., the transmission output shaft 13, is locked torsionally. This can be achieved, for example, by applying the vehicle brakes. Alternatively, the test module 30 can activate the brake control unit 39 to initiate automated braking.

[0034] The test module 30 then starts a third process step, in which the basic drag torque M is applied to the sub-gearbox II to be tested. G simulating test torque M P is applied. To apply the test torque M P Can the test module 30 control the engine control unit 33 so that the internal combustion engine I can deliver the test torque M P The test module also controls the clutch control unit 35 to close or slip the disconnect clutch K2. In this way, a load path is formed in which the test torque M is generated. P The current is introduced from the internal combustion engine 1 via the disconnect clutch K2 into the drive side of the sub-transmission II under test. The test torque M is applied. P Due to the pressure applied to the sub-gearbox II under test and the blocked gearbox output side, a backlash-free state is created in the sub-gearbox II under test.

[0035] In a fourth process step, the test module 30 controls the switching control unit 31 to switch the blocking gate G2 when the test torque M is applied. P to start. For this purpose, the actuator 26 assigned to the gearshift element S2 is subjected to an insertion force in order to move the gearshift element S2 to its parking lock position to the right.

[0036] In a fifth process step, an insertion test is carried out to determine whether the parking lock engages despite the applied test torque M. P The insertion test is performed using position and / or displacement sensors 37, which detect the position or travel Δs of the locking gear switching fork 25. In the figure, the position and / or displacement sensors 37 are connected to the test module 30 via a signal. 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 Test module 31 Switching control unit 33 Engine control unit 35 Clutch control unit 37 sensors 39 Brake control unit 41 Service brake K1, K2 disconnect couplings S1 to S4 gearshift elements Δs travel distance M P Test moment M G Basic drag torque

Claims

[1] Method for testing a parking lock function of a dual-clutch transmission that can be installed in a vehicle, in which, in the engaged state, two gears (G2, G4) of a common partial transmission (II) of the dual-clutch transmission are engaged by means of gearshift elements (S1, S2), specifically while locking the common partial transmission (II), wherein to engage the parking lock, one gear (G4) is engaged as a preselect gear and another gear (G2) is engaged as a locking gear, and wherein the method comprises a test routine by means of which an engagement test of the parking lock is carried out, characterized by that the test routine checks for proper switching of the locking gear (G2) into its parking lock position, namely when the pre-select gear (G4) is already engaged, when the gearbox output side is blocked or braked, and when a test torque (M P ). [2] Method according to claim 1, characterized bythat in the test routine - in a first process step, the separating clutches (K1, K2) of the dual-clutch transmission are released and the preselect gear (G4) is engaged in the partial transmission (II) to be tested, - in a first process step, the gearbox output side, namely a gearbox output shaft (13), is torsionally rigidly blocked or braked, - in a third process step, the test torque (M P ) is created, - in a fourth process step, the locking gear (G2) is switched when the test torque (M P ) is started, and - in a fifth process step, the insertion test is carried out, which determines whether the locking gear (G2) is able to operate despite the applied test torque (M P ) is switched correctly. [3] Method according to claim 1 or 2, characterized by that with the application of the test torque (M P) to the partial transmission (II) to be tested and with the transmission output side blocked, there is a play-free condition in the partial transmission (II) to be tested, so that during the subsequent switching of the locking gear (G2) no play-related compensating movement between the locking gear switching partners is possible. [4] Method according to claim 1, 2 or 3, characterized by that when the locking gear (G2) is switched, an associated gearshift element (S2) with its actuator (26) is subjected to an engagement force in order to adjust the gearshift element (S2) into its parking lock position. [5] Method according to one of the preceding claims, characterized by that when carrying out the test routine, the blocking or braking of the gearbox output side is ensured by actuating the vehicle brake or by means of a test system external to the vehicle. [6] Method according to one of the preceding claims, characterized by that the test torque (M P) a maximum possible basic drag torque (M G ) with the double clutch (K1, K2) open, and / or that the test torque (M P ) is generated by controlling a vehicle drive unit, by means of which the test torque (M P ) is applied to the drive side of the partial gearbox (II) to be tested. [7] Method according to one of the preceding claims, characterized bythat a gearshift element (S2) of the locking gear (G2) can be adjusted by means of the actuator (26) over an adjustment path (Δs) between a parking lock position in which the parking lock is activated and a further switching position, and that a position and / or travel sensor (37) is assigned to the gearshift element (S1, S2) and / or the actuator (26), which detects a position and / or an adjustment path (Δs) of the gearshift element (S1, S2) and / or its actuator (26), and that in the engagement test carried out in the fifth process step, the presence of a correctly engaged parking lock is determined using the position and / or travel sensor (37). [8] Method according to one of the preceding claims, characterized bythat the vehicle drive unit (1) with a power output shaft (10) via two power-shiftable separating clutches (K1, K2) of the dual-clutch transmission alternately drives either a first drive shaft (7) or a second drive shaft (9), that a first partial transmission (I) or a 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 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 gear shift elements (S1 to S4), and that for engaging the parking lock, a first and a second gear shift element (S1, S2) of a common partial transmission (II) can be switched to a parking lock position are,in which the idler gears of two gear sets of the common partial transmission (II) are coupled to the associated transmission shaft (7, 9) so that the two gear sets mutually block each other to lock the common partial transmission (II). [9] Test unit for carrying out a method according to one of the preceding claims, wherein the test unit has a test module (30) by means of which an engagement test of the parking lock is carried out, in which a proper switching of the locking gear (G2) into its locking switching position can be checked, namely with the preselect gear (G4) already engaged, with the transmission output side blocked or braked and with a test torque (M P ).

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