Method and control unit for releasing a tooth-to-tooth position of a positive-locking shifting element of an automated shifting transmission

Abstract

The invention relates to a method for releasing a tooth-on-tooth position of a positive-locking shifting element of an automated shifting transmission, wherein the transmission ratio of the automated shifting transmission is changed by means of a shifting actuator (10, 11, 12) which can be operated by a pressure medium. If a tooth-on-tooth position occurs on the positive-locking shifting element when changing the transmission ratio of the automated shifting transmission, the control of the shifting actuator (10, 11, 12) which can be operated by a pressure medium is changed in order to release the tooth-on-tooth position.

Description

Technical Field

[0001] The invention relates to a method for releasing a tooth-to-tooth position of a positive-locking shifting element of an automated shifting transmission and also to a control unit designed to carry out the method and a corresponding computer program for executing the method on the control unit. Background Art

[0002] When shifting in an automated transmission with the involvement of a positive-locking shift element, a so-called tooth-on-tooth position may occur on the positive-locking shift element, which prevents the positive-locking shift element from closing. To perform the shift, this tooth-on-tooth position must be released.

[0003] A tooth-to-tooth position can be detected, for example, when the shifting path of a shifting device for engaging a transmission ratio step does not reach the final position but remains stationary in an intermediate position or when the gear to be engaged is not engaged within a predetermined time period.

[0004] A method for releasing a tooth-to-tooth position on a positive-locking shift element of a transmission is known from DE 10 2013 218 426 A1. Summary of the invention

[0005] The object of the present invention is to propose a novel method for releasing a tooth-to-tooth position occurring on a positively locking shifting element. In addition, a control unit designed to carry out the method and a computer program for executing the method on the control unit are to be specified.

[0006] From the perspective of method technology, this object is achieved by a method according to the invention for releasing a tooth-to-tooth position of a positively locking shifting element of an automated shifting transmission. The invention also relates to a control unit and a computer program for implementing the method according to the invention. Features described in conjunction with the method are also intended to apply in conjunction with the control unit according to the invention and the computer program according to the invention, and vice versa, so that reference can always be made to each other with regard to the disclosure of the individual aspects of the invention.

[0007] According to the invention, a method for releasing a tooth-on-tooth position of a positive-locking shifting element of an automated shifting transmission is provided. The transmission ratio of the automated shifting transmission can be changed by means of a shifting actuator that can be operated with a pressure medium. The method for releasing a tooth-on-tooth position provides that when a tooth-on-tooth position occurs on a positive-locking shifting element when changing the transmission ratio of the automated shifting transmission, the control of the shifting actuator that can be operated with a pressure medium is changed so that the pressure force present at the tooth-on-tooth position is reduced.

[0008] By reducing the contact pressure at the tooth-on-tooth position by means of a change in the activation of the pressure medium-actuated switching actuator, the torque that can be transmitted via the tooth-on-tooth position is also reduced, whereby the tooth-on-tooth position can be released more easily.

[0009] An automated switching transmission here particularly refers to a multi-speed transmission, in which a plurality of transmission ratio stages, i.e. a fixed transmission ratio between two shafts of the transmission, can be automatically switched by means of a switching element. Such a transmission is mainly used in motor vehicles in order to suitably match the speed and torque output characteristics of the drive unit to the driving resistance of the motor vehicle. An automated switching transmission can be configured, for example, as a group transmission of a motor vehicle configured as a commercial vehicle. By correspondingly controlling the switching element, the transmission can be brought into a neutral position in which the drive unit is separated from the output. A form-locking switching element can be, for example, a tooth-type switching element. A form-locking switching element or a tooth-type switching element can be configured asynchronously or synchronously. A form-locking switching element can be configured, in particular, as a switching clutch.

[0010] The pressure medium-actuated shift actuator for adjusting the positive-locking shift element can be designed as a pneumatically or hydraulically actuatable pressure medium cylinder. The shift mechanism of the transmission is actuated by means of the shift actuator in order to adjust the positive-locking shift element during the shifting process.

[0011] The position of the shifting element can be detected during the shifting process by means of a sensor. The sensor can be designed as a position sensor, which can be arranged on the shift actuator or on the shifting element of the transmission, for example on a shift rail or a shift fork.

[0012] In order to reduce the extrusion force existing at the tooth-to-tooth position, it is provided in a preferred embodiment of the present invention that the pressure in the pressure chamber of the switching actuator that is loaded with a pressure medium for changing the transmission ratio stage is reduced. The pressure in the pressure chamber of the switching actuator that is loaded with a pressure medium can be reduced to ambient pressure, for example. Ambient pressure should be understood as the air pressure of the atmosphere. If the pressure in the pressure chamber of the switching actuator reaches ambient pressure, the switching actuator no longer applies force to the form-locked switching element. As a result, the torque that can be transmitted via the tooth-to-tooth position becomes zero and the force-locked connection at the tooth-to-tooth position is released. The switching claws of the form-locked switching element can then be twisted relative to each other. Then, the pressure in the pressure chamber of the switching actuator is increased again to engage the transmission ratio stage of the automated switching transmission. If the tooth-to-tooth position appears again when the transmission ratio stage is engaged, the pressure in the pressure chamber of the switching actuator can be repeatedly reduced.

[0013] The release of the tooth-to-tooth position can be supported by applying an external torque to the positively locked switching element. The external torque is to be understood as a torque acting on the positively locked switching element independently of the control of the switching actuator. For this purpose, an actuator that is in operative connection with the half of the switching element on the drive side and an actuator that is in operative connection with the half of the switching element on the output side can be considered. As an actuator for releasing the tooth-to-tooth position, for example, an internal combustion engine, an electric motor, a service brake of a motor vehicle that can be connected to the transmission input shaft via a separating clutch, for example, a transmission brake arranged on the intermediate shaft of an automated switching transmission, or a reducer that can be configured as a main reducer or auxiliary reducer and acts on the transmission shaft can be selected and controlled.

[0014] In a further embodiment of the invention, it can be provided that in order to reduce the pressing force present at the tooth-on-tooth position, the pressure in the counterpressure chamber of the switching actuator is increased. Here, the release of the tooth-on-tooth position can also be supported by applying an external torque to the positively locking switching element. If the tooth-on-tooth position has already been released when the pressing force is reduced, the pressure in the counterpressure chamber of the switching actuator is reduced again. If the tooth-on-tooth position cannot be released in the first attempt, another attempt can be carried out to release the tooth-on-tooth position, wherein the level of the pressure applied to the counterpressure chamber of the switching actuator is changed.

[0015] If a pressure chamber of a switching actuator that can be operated with a pressure medium is pressurized in order to change a transmission ratio stage, the switching actuator is actuated in the desired actuation direction. A pressure chamber of a switching actuator is understood to be a counterpressure chamber, which, when pressurized, exerts a force on the switching actuator that acts counter to the desired actuation direction.

[0016] The pressure level is determined in this case so that switching in a switching direction opposite to the desired switching direction is avoided. The pressure level can be determined based on a model, for example by a linear state observer. By determining the level of the pressure acting on the counterpressure chamber, the switching valve can be controlled in a targeted manner for pressure regulation, thereby avoiding reaction forces occurring on the form-locking switching element. The so-called dead time of the switching valve can also be taken into account when controlling the switching valve.

[0017] In order to reduce the compression forces present at the tooth-to-tooth position, it is provided in a preferred embodiment of the invention that not only the pressure in the pressure chamber of the switching actuator, which is loaded with pressure medium for switching the transmission ratio stage, but also the pressure in the corresponding counterpressure chamber of the switching actuator is increased. The pressure chamber and the counterpressure chamber can be loaded with pressure simultaneously.

[0018] Here, the counterpressure chamber can be loaded with a higher pressure, which leads to a reduction in the compression force present at the tooth-to-tooth position. When determining the level of the pressure loaded on the pressure chamber or the counterpressure chamber, the effective surface of the pressure chamber is also taken into account.

[0019] The invention also relates to a controller configured to carry out the method according to the invention. The controller comprises means for carrying out the method according to the invention. These means are hardware means and software means. The hardware means of the controller are data interfaces for exchanging data with components involved in carrying out the method according to the invention. For this purpose, the controller is also connected to the necessary sensors and, where necessary, also to other controllers in order to receive decision-relevant data or to transmit control instructions. The controller can be configured, for example, as a transmission controller. Furthermore, the hardware means of the controller are a processor for data processing and, if necessary, a memory for data storage. The software means are program modules for carrying out the method according to the invention.

[0020] The computer program according to the present invention is configured to: when the computer program is executed on the controller, the controller is prompted to implement the method according to the present invention or a preferred improvement. In this respect, a computer-readable medium also belongs to the subject matter of the present invention, on which the aforementioned computer program is stored in a callable manner. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Next, the present invention will be described in detail with reference to the accompanying drawings, from which other preferred embodiments and features of the present invention can be learned.

[0022] Figure 1 A schematic diagram showing an automated group transmission;

[0023] Figure 2 A schematic diagram showing a switching mechanism of an automated group transmission;

[0024] Figure 3 A schematic diagram showing a pneumatic switching cylinder;

[0025] Figure 4 A schematic diagram showing a pneumatic switch valve;

[0026] Figure 5 shows the structure of the state observer;

[0027] Figure 6 A block diagram showing a possible method for resolving a tooth-to-tooth position;

[0028] Figure 7 The first characteristic curve for releasing the tooth-to-tooth position is shown;

[0029] Figure 8The second characteristic curve for releasing the tooth-to-tooth position is shown;

[0030] Fig. 9 A third characteristic curve profile is shown for a released tooth-on-tooth position. DETAILED DESCRIPTION

[0031] Figure 1 The block diagram of a pneumatic shifting system of an automated shifting transmission of a vehicle in the form of a group transmission is shown very schematically.

[0032] Figure 1 A plurality of pressure medium cylinders 10, 11, 12 are shown, namely a pressure medium cylinder 11 for a so-called main gear group of a group transmission, a pressure medium cylinder 10 for a so-called front gear group of a group transmission, and a pressure medium cylinder 12 for a so-called rear gear group of a group transmission. The front gear group is also called splitter transmission and the rear gear group is also called range group.

[0033] Each pressure medium cylinder 10, 11, 12 has a piston 13, 14 or 15 arranged in a cylinder housing, which can be longitudinally displaced in the cylinder housing of the respective pressure medium cylinder 10, 11, 12 in order to implement a shift in the corresponding gear group of the group transmission. The respective pressure medium cylinder 10, 11, 12 can be supplied with compressed air from a pressure regulating chamber 16 of the transmission, wherein compressed air lines 17, 18 or 19, 20 or 21, 22 lead for this purpose from the pressure regulating chamber 16 in the direction of the respective pressure medium cylinder 10, 11, 12. The pressure regulating chamber 16 is also referred to as a transmission regulating chamber.

[0034] In the embodiment shown, two compressed air lines 17, 18 or 19, 20 or 21, 22 are respectively led to each pressure medium cylinder 10, 11, 12 in order to supply compressed air to the pressure chamber of the respective pressure medium cylinder 10, 11, 12. In this case, a valve 23 is arranged in each of the compressed air lines 17 to 22.

[0035] Compressed air can be supplied to the pressure regulating chamber 16 from a storage container 24, also referred to as a pressure cooker. Compressed air lines 25, 26 lead from the storage container 24 in the direction of the pressure regulating chamber 16 in order to convey compressed air from the storage container 24 to the pressure regulating chamber 16 depending on the position of a valve 27 arranged in the compressed air lines 25, 26. The switching valve 27 connected between the storage container 24 and the pressure regulating chamber 16 is also referred to as a main shutoff valve.

[0036] A pressure sensor 28 is arranged in the pressure regulating chamber 16, by means of which the pressure in the pressure regulating chamber 16 can be measured. The pressure in the pressure regulating chamber 16 is also referred to as switching pressure. The pressure prevailing in the pressure cooker 24 is also referred to as system pressure.

[0037] The actual switching pressure in the pressure regulating chamber 16 measured by means of the pressure sensor 28 can be compared with a desired target switching pressure in order to control the valve 27 as a function of the deviation between the actual switching pressure and the target switching pressure to set the switching pressure in the pressure regulating chamber 16. In addition to the measurement-based detection of the switching pressure in the pressure regulating chamber 16, the switching pressure in the pressure regulating chamber 16 can also be calculated during the ongoing switching operation.

[0038] according to Figure 2 A part of a shift mechanism 30 of an automated group transmission is shown. The shift mechanism 30 depicted is used to adjust the shift clutch of the main gear group of the group transmission. The main gear group is constructed in three stages with three transmission ratios G1, G2, G3 for forward travel and a transmission ratio R for reverse travel.

[0039] The main gear group of the group transmission is implemented in the form of a countershaft structure and has a main shaft W and two countershafts (not shown here), one of which can be provided with a controllable transmission brake. The idler gears of the transmission ratio stages G1, G2, G3 and R are each rotatably supported on the main shaft W and can be shifted via an associated shifting clutch. The associated fixed gear is arranged on the countershaft (not shown here) in a rotationally fixed manner.

[0040] The shifting clutches of the transmission ratio steps G3 and G2 and the shifting clutches of the transmission ratio steps G1 and R are each combined in a common shifting set S3 / 2 or S1 / R. The main transmission is designed to be shiftable in an unsynchronized manner.

[0041] Here, the control of the switching clutch is controlled or set via a controller in order to adjust the desired target transmission ratio level G3, G2, G1, R. The controller can preferably be configured as a transmission controller. The switching clutch can be operated by means of a pressure medium cylinder 11. The pressure medium cylinder is currently configured as a pneumatic drag cylinder. For this purpose, the switching mechanism 30 includes at least two switching forks SG1 and SG2, and the switching forks can be operated via a switching rail to engage the target transmission ratio level of the main gear group due to the operation of the pressure medium cylinder 11 in the axial direction. The switching forks SG1 and SG2 are respectively embedded in the switching sleeve of the switching mechanism 30. The switching sleeve is arranged on the main shaft W in an axially movable manner. The switching sleeve has an external tooth portion here. When implementing the switching process, the respective switching sleeves are operatively connected to or separated from the clutch body of the gear. The target transmission ratio level can be selected via the selection actuator WA of the switching mechanism. When the target transmission ratio level is engaged, a tooth-to-tooth position that prevents the engagement of the target transmission ratio level may occur. In the tooth-to-tooth position, the shift claws of the shift sleeve and the shift claws of the clutch body of the gear wheel touch each other and rotate at the same speed. Due to the shift claws of the positive-locking shift element touching each other, it is impossible to engage the target transmission ratio.

[0042] exist Figure 3 , a schematic diagram of a pressure medium cylinder 11 configured as a pneumatic drag cylinder is shown in FIG. The pressure medium cylinder 11 has a piston rod 34, via which the pressure medium cylinder 11 is connected to the switching rail of the switching mechanism 30. The piston rod 34 is guided in a cylinder housing 35 in an axially movable manner. The drag piston 33 is movably arranged on the piston rod 34. In addition, drag rings 31 and 32 are arranged between the drag piston 33 and the cylinder housing 35. The drag rings 31 and 32 are guided on the drag piston 33 in a sliding manner. Sealing elements are arranged not only between the drag rings 31 and 32 and the drag piston 33 but also between the drag rings 31 and 32 and the cylinder housing 35. Through this arrangement, the pneumatic pressure medium cylinder 11 has a plurality of pressure chambers 36, 37, and 38.

[0043] Depending on the direction of movement (+ / -), the following effective volumes are obtained in the individual pressure chambers 36, 37, 38 of the pressure medium cylinder 11:

[0044]

[0045] Among them, V ± V ± is the effective volume during switching, is the effective volume of the pressure medium cylinder in the middle position (neutral position), V s + is the effective volume related to positioning, A ±is the active piston area of ​​the respective pressure chamber 36, 37, 38, s is the current shift position, and s0 is the shift position in the neutral position. Piston area A + The volume in each pressure chamber 36, 37, 38 is a structural parameter and is therefore known. The piston position s is measured during the shifting process by means of a displacement sensor and is therefore also known. The displacement sensor can be designed as a displacement sensor or position sensor that can be arranged on the shifting mechanism 30 of the group transmission or on the pressure medium cylinder 11.

[0046] From the pneumatic gas equation, assuming an anisotropic pressure build-up, the rate of change of pressure in the individual pressure chambers 36 , 37 , 38 of the pressure medium cylinder 11 can be calculated as follows:

[0047] p ± *V ± =m ± *R*T, (4)

[0048]

[0049] Among them, m ± is the mass of air in the respective pressure chamber, R is the unit gas constant, T is the absolute air temperature, n is the anisotropy index, is the rate of change of pressure, p ± is the pressure in the respective pressure chamber, and is the mass flow in the respective pressure chamber. The air mass flow into the respective pressure chamber of the pressure medium cylinder 11 is It is controlled by a pneumatic valve 23. The valve 23 can be designed as a switching valve or as a proportional valve, for example. Figure 3 In the embodiment of the invention, the pressure medium cylinder 11 is in one of its end positions, that is to say a transmission ratio step is engaged in the automatic transmission. For this purpose, the pressure chamber 36 is loaded with pressure medium and the piston rod 34 of the pressure medium cylinder 11 is already displaced in the direction of movement (-). In the pressure chamber 36 there is an effective volume relevant to the position.

[0050] exist Figure 4 A schematic diagram of a pneumatic switching valve 23 is shown in FIG. The switching valve 23 can be electromagnetically operated. Figure 4 In the left drawing of FIG. 1 , the switching valve 23 is driven to fill the pressure chamber of the pressure medium cylinder 11 with pressure medium to switch the transmission. From which the switching pressure p 前 The pressure regulating chamber 16 flows into the pressure medium cylinder 11, where a corresponding pressure p ±In the corresponding pressure chamber. Figure 4 In the middle drawing of FIG. 1 , the switching valve 23 is actuated to vent the pressure chamber of the pressure medium cylinder 11. In this case, the air mass flow The pressure medium flows out from the pressure chamber of the pressure cylinder 11 to the atmosphere. The throttling function of the switching valve 23 is Figure 4 The throttle is a narrowing of the line cross section and therefore acts as a local flow resistance. The blockage occurs before the narrowing of the cross section, so there is a pressure difference p 前 / p ± .

[0051] Air mass flow through the switching valve can be modeled as follows:

[0052]

[0053] in, Where C is the conductance of the valve, ρ0 is the air density, T0 is the absolute temperature of the air in the standard state, ψ(p 前 ,p ± ) is the outflow function, bb is the critical pressure ratio of the valve, p 前 is the air pressure before the throttle and p ± It is the air pressure after the throttle.

[0054] The valve parameters C and b can be determined using equations (6) and (7). To determine the valve parameters, it is necessary to be able to measure the pressure p in the respective pressure chamber. ± and p1. These valve parameters are necessary for model-based detection and resolution of the tooth-to-tooth position. The movement of the piston of the pressure medium cylinder 11 can preferably be modeled according to the following formula:

[0055]

[0056] Where m is the mass of the piston, is the acceleration of the piston, p0 is the atmospheric air pressure, F 外部 is the sum of all forces acting on the piston from the outside (such as friction), and F is the force exerted by the piston.

[0057] In a model-based method for identifying tooth-to-tooth positions, information about the model behavior can be used in an advantageous manner. In this case, the movement of the piston of the pressure medium cylinder 11 described by the mathematical equation derived above is simulated in real time. At the same time, the simulated variables are compared with the actually measured variables. If there is a deviation between the simulated value and the measured value, the model behavior is automatically corrected in order to converge the error. A simulation model that is corrected in real time with measured values ​​is also called an observer. The general structure of such an observer is described in Figure 5 , wherein the observer is designed as a linear state observer. The transmission as a reference system is provided with the reference numeral 39 , while the observer is provided with the reference numeral 40 .

[0058] In the observer design, the quality function can preferably be minimized over an infinite time horizon according to the following formula:

[0059]

[0060] where Q is a symmetric positive definite weighting matrix and r is a positive scalar. The optimization problem formulated in equation (10) requires the solution of the following algebraic Riccati equation, from which the optimal observer gain can be calculated as follows:

[0061] P*A T +A*PP*c T *r -1 *c*P+Q=0, (11)

[0062] l=-r -1 *P*c T (12)

[0063] The advantage of a linear state observer is that, in addition to the system output, it can also estimate other state variables. Since only the position of the piston of the pressure medium cylinder 11 is measured in the method according to the invention for detecting the tooth-to-tooth position, other states such as the piston speed or the piston force can be estimated by the observer.

[0064] In the tooth-to-tooth position, the shift claws of the positively locking shift element are pressed against each other and are thus connected to each other in a non-positive manner. The maximum torque that can be transmitted via the non-positive connection can be approximately determined according to the following formula:

[0065]

[0066] Where F is the extrusion force, μ R is the friction coefficient, is the average friction radius and M 最大 is the maximum transmittable torque.

[0067] The tooth-to-tooth position can be released by falling below the maximum transmittable torque, wherein the static friction between the shifting claws of the form-locking shifting element is suppressed. As a result, the relative rotation between the shifting claws of the form-locking shifting element can cause the shifting claws to slip, which can ultimately lead to the engagement of the shifting claws.

[0068] Figure 6 The block diagram with a possible method for releasing the tooth-on-tooth position is shown. If a tooth-on-tooth position is detected in block S1 when changing the transmission ratio of the automated shifting transmission, the shifting process can be triggered again in block S2. For this purpose, the pressure in the pressure chamber 36 of the pressure medium cylinder 11, which is loaded with pressure, is reduced, so that the torque that can be transmitted via the tooth-on-tooth position becomes zero and the static friction between the shifting claws of the form-locking shifting element can be suppressed in block S3. Subsequently, the pressure in the pressure chamber 36 of the pressure medium cylinder 11 is increased again to engage the transmission ratio of the automated shifting transmission.

[0069] Starting from block S1 , in order to release the tooth-on-tooth position, it can be provided in block S4 that the maximum transmittable torque M in the tooth-on-tooth position is suppressed. 最大 . For this purpose, it is possible to transfer from frame S4 ​​to frame S8, wherein an external torque is applied to the positively locking shifting element, by which the tooth-to-tooth position is released. Starting from frame S4, the release of the tooth-to-tooth position can be achieved in frame S5 by reducing the pressing force existing at the tooth-to-tooth position. For this purpose, the pressure in the pressure chamber 36 of the pressure medium cylinder 11 loaded with pressure can be reduced in frame S6 or the pressure in the counter-pressure chamber 38 can be increased in frame S7. In addition to the pressure adjustment performed in frame S6 or S7, the release of the tooth-to-tooth position can also be achieved by applying an external torque to the positively locking shifting element.

[0070] exist Figure 7 1 shows the first characteristic curve for the release of the tooth-to-tooth position. At time t0, it is detected that a transmission ratio should be engaged in the automatic transmission. For this purpose, the switching valve 23 is actuated to fill the pressure chamber 36 of the pressure medium cylinder 11 with compressed air for the transmission shift. Starting from the neutral position s0s0 of the pressure medium cylinder 11, after the dead time t t At time t1, the pressure chamber 36 of the pressure medium cylinder 11 is then charged with compressed air to engage the target transmission ratio. At time t2, a tooth-to-tooth position is established on the positively locking shift element. After a detection time t of, for example, 40 ms has elapsed, D The tooth-to-tooth position is then detected. After an optional waiting time t WAfter that, at time t3, the switching valve 23 is deactivated (waiting during this period to see whether the tooth-to-tooth position is automatically released). t At time t4, the pressure chamber 36 of the pressure medium cylinder 11 is then vented. W It can be, for example, 50 ms. A During this time, the pressure in the pressure chamber 36 is reduced in order to release the tooth-on-tooth position, until the pressure drops to the level of the ambient pressure at time t5. After the tooth-on-tooth position is released, the pressure chamber 36 of the pressure medium cylinder 11 is again charged with compressed air in order to end the shifting process. When the transmission ratio stage is engaged, the pressure medium cylinder 11 is in its end position s - The switching pressure pprep in the pressure regulating chamber 16 is constant during the switching process and is approximately 8 bar in this case.

[0071] Figure 8 The second characteristic curve for the disengaged tooth-to-tooth position is shown. At time t0, it is detected that a transmission ratio step is to be engaged in the automatically shifted transmission. For this purpose, the switching valve 23 is actuated to fill the pressure chamber 36 of the pressure medium cylinder 11 with pressure medium for the transmission shift. Starting from the neutral position s0 of the pressure medium cylinder 11, after the dead time t of the switching valve 23, the pressure chamber 36 of the pressure medium cylinder 11 is filled with pressure medium for the transmission shift. t At time t1, the pressure chamber 36 of the pressure medium cylinder 11 is then charged with compressed air to engage the target transmission ratio. At time t2, a tooth-to-tooth position is established on the positively locking shifting element. After a detection time t of, for example, 35 ms has elapsed, D The tooth-to-tooth position is then detected. After an optional waiting time t W After that, the switching valve 23 is activated at time t3 (waiting during this period to see whether the tooth-to-tooth position is automatically released). t At time t4, the counterpressure chamber 38 of the pressure medium cylinder 11 is then filled with compressed air. W It can be, for example, 50 ms. A During this time, the pressure in the counterpressure chamber 38 is increased in order to release the tooth-on-tooth position, thereby reducing the pressure force at the tooth-on-tooth position. At time t5, the tooth-on-tooth position at the form-locking shifting element is released and the pressure in the counterpressure chamber 38 is reduced again. When the transmission ratio stage is engaged, the pressure medium cylinder 11 is in its end position s - The switching pressure p in the pressure regulating chamber 16 前 During the switching process, it is constant and in this case is approximately 8 bar.

[0072] exist Fig. 9Another characteristic curve trend for releasing the tooth-to-tooth position is shown in FIG. Figure 7 and Figure 8 The characteristic curves shown in FIG. 1 differ in particular in that the switching pressure p in the pressure control chamber 16 is not set constantly during the switching process. 前 Rather, in this switching process, only the compressed air present in the pressure control chamber 16 is made available for engaging the new transmission ratio stage.

[0073] At time t0, it is detected that a transmission ratio should be engaged in the automatically shifted transmission. For this purpose, the switching valve 23 is actuated to fill the pressure chamber 36 of the pressure medium cylinder 11 with pressure medium for the transmission shift. Starting from the neutral position s0 of the pressure medium cylinder 11, after the dead time t t At time t1, the pressure chamber 36 of the pressure medium cylinder 11 is then charged with compressed air to engage the target transmission ratio. Since only the compressed air present in the pressure regulating chamber 16 is available for engaging the new transmission ratio, the switching pressure p in the pressure regulating chamber 16 is 前 The switching pressure p in the pressure regulating chamber 16 is reduced, and the pressure chamber 36 of the pressure medium cylinder 11 is filled with compressed air. 前 For example, a pressure level of approximately 6 bar is present. At time t2, a tooth-to-tooth position is established on the positively locking shifting element. After a detection time t of, for example, 35 ms has elapsed, D The tooth-to-tooth position is then detected. After an optional waiting time t W After that, at time t3, the switching valve 23 is activated, and the switching valve is used to release the tooth-to-tooth position after the dead time t t At time t4, compressed air is then applied to the counterpressure chamber 38 of the pressure medium cylinder 11. At time t3, the switching valve 27 is also activated to set the switching pressure p in the pressure regulating chamber 16. 前 In this case, compressed air flows from the pressure cooker 24 into the pressure regulating chamber 16 until the switching pressure p in the pressure regulating chamber 16 reaches 1. 前 If a tooth-to-tooth position is detected, then the pressure is adjusted to 8 bar again. A During this time, both the pressure chamber 36 and the counter-pressure chamber 38 are filled with compressed air in order to release the tooth-on-tooth position. Due to the differently designed active surfaces of the pistons of the pressure medium cylinders, the resultant force of the pistons and thus the pressing force at the tooth-on-tooth position is reduced. At time t5, the tooth-on-tooth position at the form-locking shifting element is released and the pressure in the counter-pressure chamber 38 drops again. When the transmission ratio stage is engaged, the pressure medium cylinder 11 is in its end position s - Optional waiting time tW It may be 50 ms, for example.

[0074] The proposed method for disabling a tooth-to-tooth position in an automated shifting transmission is very efficient and requires little memory and little computational effort, since no complex characteristic curve complexes are required.

[0075] Reference numerals list

[0076] 10 Pressure medium cylinder / switching actuator

[0077] 11 Pressure medium cylinder / switching actuator

[0078] 12 Pressure medium cylinder / switching actuator

[0079] 13 Piston

[0080] 14 Piston

[0081] 15 Piston

[0082] 16 Pressure regulating chamber

[0083] 17 Pressure medium line

[0084] 18 Pressure medium line

[0085] 19 Pressure medium line

[0086] 20 Pressure medium line

[0087] 21 Pressure medium line

[0088] 22 Pressure medium line

[0089] 23 valves

[0090] 24 storage containers

[0091] 25 Pressure medium line

[0092] 26 Pressure medium line

[0093] 27 valves

[0094] 28 Pressure Sensor

[0095] 30 Switching mechanism

[0096] 31 drag ring

[0097] 32 drag ring

[0098] 33 Drag piston

[0099] 34 piston rod

[0100] 35 cylinder housing

[0101] 36 Pressure chamber

[0102] 37 Pressure Chamber

[0103] 38 Pressure Chamber

[0104] 39 Transmission as a reference system

[0105] 40 Observer

[0106] SG1 First shift fork

[0107] SG2 Second shift fork

[0108] WA Select Actuator

[0109] G1 (First gear ratio stage of the main transmission)

[0110] G2 (Second gear ratio stage of the main transmission)

[0111] G3 (Third gear ratio stage of the main transmission)

[0112] R (Reverse gear ratio of the main transmission)

[0113] S1 / R (main transmission) shift kit

[0114] S3 / 2 shift kit (for main transmission)

[0115] W (main transmission) main shaft

Claims

1. A method for releasing a tooth-to-tooth position of a positively locking shifting element of an automated transmission, wherein: The automated shift transmission is constructed as a group transmission of a motor vehicle, wherein the transmission ratio of the automated shift transmission is changed by means of one or more shift actuators operable with a pressure medium, wherein one of the shift actuators is constructed as a pressure medium cylinder (11) for a main gear group of the group transmission, wherein when a tooth-to-tooth position occurs on the positively-locked shift element when changing the transmission ratio of the automated shift transmission, the control of the shift actuator operable with a pressure medium is changed, wherein the pressure in the counter-pressure chamber (38) of the pressure medium cylinder (11) of the main gear group is increased so that the extrusion pressure existing at the tooth-to-tooth position is reduced.

2. The method according to claim 1, characterized in that The pressure in a pressure chamber (36) of a pressure medium cylinder (11) of a main gear group, which is loaded with pressure medium for changing a transmission ratio step, is reduced.

3. The method according to claim 2, characterized in that The pressure in a pressure chamber (36) of a pressure medium cylinder (11) of the main gear group, which is acted upon by pressure medium, is reduced to ambient pressure.

4. The method according to claim 1, characterized in that The pressure in a pressure chamber (36) of a pressure medium cylinder (11) of a main gear group, which is loaded with pressure medium for changing a transmission ratio stage, and the pressure in a counter-pressure chamber (38) of the pressure medium cylinder (11) of the main gear group are increased, wherein the counter-pressure chamber (38) is loaded with a higher pressure.

5. The method according to claim 1 or 4, characterized in that: The level of the pressure in the counterpressure chamber (38) is determined by a state observer in such a way that a switching direction opposite to the desired switching direction is avoided.

6. The method according to any one of claims 1 to 4, characterized in that When actuating the pressure medium cylinder (11) of the pressure medium-actuated main gear group, the dead time of the switching valves (23, 27) is taken into account.

7. The method according to any one of claims 1 to 4, characterized in that The release of the tooth-on-tooth position is supported by applying an external torque to the positively locking shift element. 8 . A controller configured to carry out the method according to claim 1 . 9 . A computer program product, wherein the computer program product is configured to cause a controller to carry out the method according to claim 1 , when the computer program product is executed on the controller. 10 . An automated shifting transmission having a control unit according to claim 8 and operable according to a method according to claim 1 .

11. The automatic shifting transmission according to claim 10, characterized in that: The automated shift transmission is designed as a group transmission for a motor vehicle.

12. A motor vehicle having an automated shifting transmission according to claim 10 or 11.

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