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

Abstract

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 sub-transmission (II) of the dual-clutch transmission are shifted by means of shift partners or gear shift elements (S1, S2), with the common sub-transmission (II) locked, characterized in that the method has a test routine by means of which a disengagement of the parking lock is tested when a test torque (MP) is applied to the locked sub-transmission (II).

Description

The invention relates to a method for testing a parking lock function of a dual clutch transmission which can be installed in a vehicle according to the preamble of claim 1 and to a testing unit according to claim 8.In such a dual clutch transmission, a parking lock function can be realized with little transmission-related complexity, in which two gears (namely a preselection gear and a locking gear) of a common partial transmission of the dual clutch transmission can be shifted simultaneously by means of gear shift elements. Due to the different transmission ratios, the wheel planes of the shifted gears become blocked. By blocking the two gear planes located in the same subtransmission, a rotational movement of the transmission output shaft is blocked. Such a generic parking lock function is known from DE 199 50 696 A1.When the vehicle is parked on a roadway gradient and when the parking lock is engaged, a slope-driven force acts on the vehicle. As a result, a clamping torque is introduced from the vehicle wheels onto the transmission output side, which leads to a mutual bracing of the shift partners incorporated in the parking lock function.Due to unfavourable geometry and / or surface tolerances, an excessively large frictional resistance can build up between the shift partners during parking lock disengagement. In order to ensure a laying safety despite high frictional resistance, the respective gear shifting element must be actuated with a correspondingly large laying force.In the prior art, the following measures which are complicated in terms of production are taken in order that disengagement safety is ensured in the above parking situation: in the prior art, the component tolerances and / or surface tolerances of the transmission components are manufactured in a low tolerance band in a manner which is complicated in terms of production in order to avoid an excessively high frictional resistance between the shift partners during disengagement of the parking lock. Alternatively and / or additionally, the actuating drive of the gear shift elements incorporated in the parking lock can be dimensioned with a correspondingly large drive power in order to reliably move the gear shift element out of the parking lock position even in the case of excessively high frictional resistance.DE 10 2019 130 481 A1 discloses a method for operating a dual clutch transmission for a motor vehicle. DE 10 2009 030 084 A1 discloses a method for releasing a parking lock of a motor vehicle.The object of the invention is to provide a method for checking a parking lock function of a dual clutch transmission which can be installed in a vehicle, in which a disengagement safety of the parking lock function can be checked in a simple manner.The object is achieved by the features of claim 1 or 8. Preferred developments of the invention are disclosed in the dependent claims.The invention is based on a method for checking a parking lock function of a dual clutch transmission which can be installed in a vehicle. When the parking lock is engaged, two gears, namely a preselection gear and a locking gear, of a common partial transmission of the dual clutch transmission are shifted by means of gear shift elements. In this way, the common partial transmission and thus also a rotational movement of the transmission output shaft is blocked.The invention relates specifically to a parking situation in which the vehicle is parked on a roadway gradient and when the parking lock is engaged and / or the parking brake is released if appropriate. In this case, a slope output force acts on the vehicle. As a result, a clamping torque is introduced from the vehicle wheels onto the transmission output side, which leads to a mutual bracing of the shift partners incorporated in the parking lock function.Due to unfavourable geometry and / or surface tolerances, an excessively large frictional resistance can build up between the shift partners during parking lock disengagement, which frictional resistance has to be overcome by the actuating drive of the gear shift element to be shifted.According to the characterizing part of claim 1, the method has the following test routine, by means of which disengagement of the parking lock is checked in the case of a test torque applied to the locked subtransmission. The test routine can be implemented, for example, in the case of a tape end test in a vehicle-construction work or in a transmission-construction work.In a preferred process sequence, the parking lock is engaged in a first process step. For this purpose, a preselection gear of the subtransmission to be checked is first shifted. Subsequently, an associated locking gear is shifted in the same subtransmission. In a second process step, a simulation of a parking situation on a roadway gradient takes place. For this purpose, the test torque is applied to the blocked partial transmission, by means of which the shift partners which are incorporated in the parking lock function are braced against one another. The test torque simulates a clamping torque which acts on the transmission output side via the vehicle wheels in a parking situation with a roadway gradient.In a third process step, disengagement of the parking lock is started when the test torque is applied. During the disengagement process, one of the gear shift elements (i.e. the gear shift element of the ratchet) is acted upon by an associated actuating drive with a defined disengagement force in order to shift the gear shift element from its parking lock position. A fourth process step follows, in which an off-hook check is carried out. In the disengagement test, it is determined whether the parking lock is properly disengaged despite the test torque being applied. If the disengagement of the parking lock takes place within a defined period of time, the disengagement check is passed.If a parking lock that is not designed correctly is present, the disengagement force required for parking lock disengagement is greater than the disengagement force that can be provided at the maximum by the actuating drive. In this case, the vehicle or (in the transmission-manufacturing plant) the dual clutch transmission is subjected to a post-processing. The post-processing can ensure that the maximum deployment force that can be provided by the actuating drive is sufficiently great in all customer-relevant situations. It should be noted that the maximum deflection force during the test is proportional to the test torque at the output / drive. Thus, the test does not always have to be tested with the maximum laying force.However, the invention is not limited to a band end test in the vehicle construction plant or in the transmission construction plant. Alternatively, the test routine according to the invention can also be carried out at the workshop side, for example after repair measures have been carried out at the dual clutch transmission.In one technical implementation, the simulation of the parking situation on the roadway gradient carried out in the above third process step can be carried out with the aid of a vehicle-external drive machine of a test system which is provided within the scope of a final strip test. With the aid of the drive machine external to the vehicle, the test torque can be applied in particular on the output side to the blocked subtransmission.In an alternative embodiment variant, the simulation of a parking situation on a roadway gradient can be carried out by actuating a vehicle drive unit (i.e. an internal combustion engine and / or an electric machine). With the aid of the vehicle drive unit, a test torque can be generated which can be applied on the drive side or output side to the blocked subtransmission.In the simulation of a parking situation on a roadway gradient, in a preferred embodiment variant, the partial transmission that is not locked in park can be incorporated. In this case, a gear can be shifted in the non-locked subtransmission. In addition, a separating clutch arranged between the non-locked subtransmission and the vehicle drive unit can be closed and / or controlled in a slipping manner. In this way, a load path is formed in which the test torque is conducted via the separating clutch to the vehicle drive side and further via the shifted gear of the non-locked partial transmission to the transmission output side. On the transmission output side, the test torque is present at the blocked subtransmission.The gear shift elements installed in the dual clutch transmission can preferably be realized as synchronizer clutches that can be axially adjusted on one or both sides. Such a synchronous clutch has a sliding sleeve which can be axially adjusted by means of a shift fork over a shift path. The shift fork can be adjusted over the actuating path by means of, for example, a hydraulically operating actuating drive. A sliding sleeve internal toothing is mounted axially adjustably on a corresponding external toothing of a sliding sleeve carrier arranged on a transmission shaft in a rotationally fixed manner. The sliding sleeve can be moved with the aid of the shift fork into a shift position (for example parking lock position) in which the sliding sleeve internal toothing is in toothed engagement both with the external toothing of the sliding sleeve carrier and with the external toothing of a loose gearwheel clutch body.When parking on a roadway gradient and when a parking lock is engaged, the shift partners involved in the parking lock function are braced with respect to one another by a clamping torque (which correlates with the slope output force). Due to unfavourable geometry and / or surface tolerances, an excessively large frictional resistance can therefore build up between the shift partners during parking lock disengagement. As such, the sliding sleeve must be adjusted by the actuator from the park position with a sufficiently large disengagement force.The sliding sleeve or the actuating drive can each be assigned a position and / or travel sensor which detects a current gear actuator position and / or a current actuating travel of the respective gear shift element and / or its actuating drive. In this case, during the disengagement check (i.e. in the fourth process step), the presence of a correctly configured parking lock can be determined using the position and / or travel sensor. Depending on the position or path detection, it is possible to draw conclusions as to the presence of a correctly designed parking lock.An exemplary embodiment is described below with reference to the attached figure.The figure shows a transmission structure of a drive train of a motor vehicle, which is essentially composed 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-transmitting manner alternately to a power output shaft 10 of the internal combustion engine 1 via two, for example hydraulically actuatable power-shiftable separating clutches K 1, K 2. The first drive shaft 7 is realized in FIG. 1 as a solid shaft, which is guided coaxially within the second drive shaft 9, realized as a hollow shaft. An output shaft 13 is provided axially parallel to the two drive shafts 7, 9. This drives via a gear stage 15 with spur gears onto an input shaft 19 of an axle differential 21. From the differential axle 21, flange shafts 23 lead on both sides to vehicle wheels, not shown.By means of the first and second drive shafts 7, 9, a first partial transmission I and a second partial transmission II of the dual clutch transmission can be activated. The first subtransmission I is axially spaced apart from the dual clutch K 1, K 2 in the figure with the second subtransmission II interposed. Fixed and idler gears are arranged on the two drive shafts 7, 9 and on the output shaft 13 in wheel planes. These are combined to form gear sets, forming six forward gear stages G 1 to G 6 and one reverse gear stage R. In the figure, the idler gears of all gear stages are positioned on the output side on the output shaft 13. The idler gears are shiftable by means of gear shifting elements S1 to S4, which are also positioned on the output shaft 13.Each of the gear shift elements S 1 to S 4 is realized as a synchronous clutch with a sliding sleeve 24, which can be adjusted axially on one or both sides over a control travel Δs by means of an indicated shift fork 25. The sliding sleeve 24 is seated with its internal toothing, not shown, on a corresponding external toothing of a sliding sleeve carrier 27 which is arranged on the output shaft 13 in a rotationally fixed manner. Starting from the neutral shift position, the sliding sleeves 24 can be moved into a shift position in order to shift a gear. In the switching position, the sliding sleeve internal toothing is in toothed engagement on the one hand with the sliding sleeve carrier 27 and on the other hand with the external toothing of a clutch body 29 of a loose gearwheel.Each of the shift forks 25 is operatively connected in the figure to an actuating drive 26, which operates hydraulically, for example, and which can be controlled by a shift control unit 31. Upon appropriate actuation, the shift fork 25 is axially adjusted over a displacement path Δs in order to bring the associated shift sleeve 24 into or out of clutch engagement with a loose gearwheel.The following parking lock function is implemented by means of an electronic control unit: During a vehicle stopping process, the separating clutches K 1, K 2 are released. In addition, the first gear shift element S 1 is shifted to a shift position to the right, whereby the forward gear G 4 is shifted as a preselection gear. As soon as the control device recognizes a vehicle standstill, the second shifting element S 2 is shifted into a shifting position to the right, whereby the forward gear G 2 is shifted as a reverse gear. In this way, two gears are simultaneously shifted in the partial transmission II by means of the gear shifting elements S 1, S 2. Due to the different transmission ratios, the gear sets of the shifted gears G 2 and G 4 become blocked. By blocking the two gear sets in the second subtransmission II, the second subtransmission II or a rotational movement of the output shaft 13 is blocked.When the vehicle is parked on a roadway gradient and when the parking lock is engaged, a slope-driven force acts on the vehicle. As a result, a clamping torque Ms is introduced to the output shaft 13 via the vehicle wheels. The clamping torque Ms leads to a mutual clamping of the shift partners incorporated in the parking lock function. In particular, an increased torque-proportional frictional / sliding friction force results between the contact flanks of the tooth arrangements of the sliding sleeve 24, the sliding sleeve carrier 27 and the respective idler gear clutch body 29, which force is proportional to the applied normal force or to the bracing torque. The coefficients of friction remain almost constant. In the event of an unfavorable geometry / surface tolerance between friction pairings of the above shift partners, an excessive friction resistance may occur during a parking lock disengagement, which is to be overcome by the actuating drive 26.In order to ensure safety against disengagement, a function test of the parking lock function is carried out with the aid of a test module 30. The function test can be carried out, for example, in the context of a belt end test in the vehicle-construction plant or in the transmission-construction plant. Alternatively, the function test can also be carried out in a workshop after a transmission repair.In the figure, the test module 30 is in signal connection with the shift control device 31, a motor control device 33 of the internal combustion engine 1 and a clutch control device 35 of the dual clutch K 1, K 2. The test module 30 executes a test routine, in which the shift control device 31 is activated in a first process step in order to engage the parking lock.In a second process step, a simulation of a parking situation on a roadway gradient takes place. In the simulation, a test torque M P is applied to the locked partial transmission II, by means of which test torque the transmission components incorporated in the parking lock function are braced against one another.By way of example, for simulating a parking situation on a roadway gradient, the non-locked subtransmission I can be incorporated. In this case, the test module 30 can actuate the shift control device 31 in order to shift one of the forward gears G 5, G 3 or G 1 in the non-locked subtransmission I. In addition, the test module 30 controls the motor control unit 33 so that the internal combustion engine 1 generates the test torque M P. Furthermore, the test module 30 controls the clutch control unit 35 in order to close or control the separating clutch K 1 in a slipping manner. In this way, a load path is formed in which the test torque M P is conducted from the internal combustion engine 1 via the separating clutch K 1 and via a shifted gear G 5, G 3 or G 1 in the first subtransmission I to the output shaft 13, at which the test torque M P is applied to the blocked subtransmission II.In a third process step, the test module 30 controls the shift control device 31 in order to start disengagement of the parking lock when the test torque M P is applied. For this purpose, an disengagement force is applied to one of the gear shift elements S 1, S 2 by the respectively assigned actuating drive 26 in order to shift the gear shift element S 1, S 2 from its parking lock position in the direction of the neutral position.In a fourth process step, an disengagement check is carried out, in which it is determined whether or not the parking lock has been properly disengaged despite the test torque M P being applied. The disengagement check is carried out using position and / or travel sensors 37, which record a position or a displacement path Δs of the respective shift fork 25. In the figure, the position and / or displacement sensors 37 are in signal connection with the test module 30.LIST OF REFERENCE CHARACTERS: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 Differential axis 23 Flange shafts 24 Shift sleeve 25 Shift fork 26 Actuating drive 27 Shift sleeve carrier 29 Loose gearwheel clutch body 30 Test module 31 Shift control unit 33 Motor control unit 35 Clutch control unit 37 Sensors K 1, K 2 Separating clutches S 1 to S 4 Gearshift elements Δs Actuating travel M P Test torque M S Clamping torque

Claims

Method for testing a parking lock function of a dual clutch transmission which can be installed in a vehicle, in which, in the engaged state, two gears (G2, G4) of a common subtransmission (II) of the dual clutch transmission are shifted by means of shift partners or gear shift elements (S1, S2), to be precise with locking of the common subtransmission (II), characterized in that the method has a test routine by means of which disengagement of the parking lock is tested when a test torque (M P) is applied to the locked subtransmission (II).Method according to Claim 1, characterized in that in the test routine - in a first process step the parking lock is engaged, - in a second process step a simulation of a parking situation on a roadway gradient takes place, in which a test torque (M P) is applied to the locked subtransmission (II), by means of which the shift partners which are incorporated in the parking lock function are braced against one another, - in a third process step disengagement of the parking lock is started with the test torque (M P) applied, in which disengagement force is applied to one of the shift partners or the gear shift elements (S1, S2) by a respectively assigned actuating drive (26), in order to adjust the gear shift element (S1, S2) from a parking lock position, and, in a fourth process step, an off-hook check is carried out, in which it is determined whether the parking lock is designed correctly despite the test torque (M P) being applied.Method according to Claim 2, characterized in that, in the third process step, the simulation of the parking situation on a roadway gradient takes place via a vehicle-external drive machine of a test installation, by means of which the test torque (M P) is applied on the output side to the blocked subtransmission (II).Method according to Claim 2, characterized in that, in the third process step, the simulation of a parking situation on a roadway gradient takes place via actuation of a vehicle drive unit (1), namely an internal combustion engine and / or an electric machine, by means of which the test torque (M P) is applied on the drive side or output side to the blocked subtransmission (II), and in that, in the event of introduction on the drive side, the test torque (M P) is generated by the vehicle drive unit (1) and is introduced into the dual clutch (K1, K2) via a force output shaft (10), and / or in that, in the event of introduction on the output side, the test torque (M P) is generated by an electric machine incorporated in the drive train and is introduced into the output shaft (13).Method according to Claim 4, characterized in that, for simulating a parking situation on a road surface gradient, the non-blocked subtransmission (I) is incorporated, and in that, in order to apply the test torque (M P) in the non-blocked subtransmission (I), a gear is shifted and a separating clutch (K1, K2) arranged between the non-blocked subtransmission (I) and the vehicle drive unit (1) is closed or controlled in a slipping manner, with the result that a load path is formed in which the test torque (M P) is conducted from the vehicle drive unit (1) via the separating clutch (K1) and the shifted gear (G3) of the non-blocked subtransmission (I) to the transmission output side, where the test torque (M P) is applied to the blocked subtransmission (II).Method according to one of the preceding claims, characterized in that the gear-shifting element (S1, S2) is adjustable by means of the actuating drive (26) over a control path (Δs) between a parking lock position, in which the parking lock is activated, and a further shift position, and in that a position and / or travel sensor (37) is assigned to the gear-shifting element (S1, S2) and / or the actuating drive (26), said position and / or travel sensor detecting a position and / or a control path (Δs) of the gear-shifting element (S1, S2) and / or of its actuating drive (26), and in that, in the disengagement test carried out in the fourth process step, the presence of a correctly disengaged parking lock is determined using the position and / or travel sensor (37).Method according to one of the preceding claims, characterized in that the internal combustion engine with a power output shaft (10) alternately drives either a first drive shaft (7) or a second drive shaft (9) via two powershiftable separating clutches (K1, K2) of the dual clutch transmission, in that a first subtransmission (I) or a second subtransmission (II) can be activated in each case by means of the two drive shafts (7, 9), and in that fixed and loose gearwheels are arranged on the two drive shafts (7, 9) and on an output shaft (13) which is axially parallel thereto, said fixed and loose gearwheels being combined to form gearwheel sets forming forward gear stages (G1 to G6), in which the loose gearwheels can be coupled to the respective transmission shaft (7, 9, 13) by means of gearshift elements (S1 to S4), and in that a first and a second gearshift element (S1, 13) are arranged for engaging the parking lock, S2) of a common subtransmission (II) can be shifted into a parking lock position in which the idler gears of two gear sets of the common subtransmission (II) are coupled to the associated transmission shaft (7, 9), so that the two gear sets interlock with one another in order to lock the common subtransmission (II).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 disengagement of the parking lock can be checked when the test torque (M P) applied to the locked subtransmission (II).

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