Operation of a multi-gear vehicle transmission

Abstract

The invention relates to the operation of a multiple-gear vehicle transmission. The vehicle transmission has a plurality of shift elements (A, B, C, D, E) for engaging gears in the vehicle transmission, wherein, in the neutral gear, a decoupling is provided between the input (AN) and the output (AB) of the vehicle transmission, and wherein, in the running gears, a coupling between the input (AN) and the output (AB) of the vehicle transmission is provided for propelling the vehicle by closing at least one shift element (B). In the method, at least one actuation state of a vehicle brake (11) and a transmission state with increased belt slip losses are identified in the event of the engagement of the neutral gear, wherein, in the event of the engagement of the neutral gear, if the actuation state of the vehicle brake (11) is identified as released and the transmission state with increased belt slip losses is present, the shift element (B) for the running gears is vented.

Description

TECHNICAL FIELD

[0001] The present application relates to a method for operating a multi-gear vehicle transmission, a controller and a computer-readable storage medium. BACKGROUND

[0002] Multi-gear transmissions are known in vehicle technology and are widespread in vehicle technology. The gears, also referred to as steps or transmission ratio steps, represent different transmission ratios of the transmission between the transmission input and the transmission output. The gears are selectively engageable. Thereby, the torque provided by the drive motor of the vehicle can be transmitted in a situationally appropriate manner. For example, a high transmission ratio can be provided in a start gear for accelerating the vehicle. In other running gears, smaller transmission ratios can be provided in order to advantageously maintain the vehicle speed with regard to consumption. The engagement of the individual gears takes place by means of shift elements of the transmission.

[0003] A preferred example of a multi-gear transmission can be found in DE 10 2005 002 337 A1.

[0004] In a neutral gear, also referred to as coasting operation, of a vehicle transmission, the transmission input and at least the transmission output for running are decoupled from one another. In order to engage the neutral gear, enough shift elements of the transmission are disengaged. In the neutral gear, the vehicle can be pushed or towed. In the neutral gear, the internal belt losses of the transmission can likewise be minimized. The engagement of the neutral gear can therefore be advantageous, for example, during a short-term stop of the vehicle, during which the drive motor of the vehicle continues to run. The engagement of the neutral gear can be requested by a user or an automatic device of the vehicle.

[0005] In practice, when the neutral gear is engaged, it is sought to shift as quickly and comfortably as possible into one of the running gears of the transmission, in particular into the start gear for starting. In order to prepare the shift, the so-called air gap of at least one of the shift elements for the start gear can be purposefully reduced.

[0006] In the case of a shift element of the transmission which is actuated by a pressure medium, the preparation takes place in such a way that, in the neutral gear, the actuating piston of the shift element is pre-charged with pressure medium. Here, a specific amount of pressure medium has been delivered to the actuating piston. The amount is dimensioned in such a way that the shift element has not yet closed. The closure process can then be initiated by further delivery of pressure medium and / or an increase in the pressure in the actuating piston. In particular, in the context of the pre-charging, the shift element is brought to (almost) the so-called contact point of the shift element.

[0007] The amount of pressure medium required for the prefilling depends on many factors. They are, inter alia, the component tolerances and the current wear state of the respective shift element as well as the current friction characteristics in the transmission. Sufficiently accurate sensors for precisely ascertaining the required prefilling and the already existing prefilling are usually not provided in a vehicle transmission. Too high a prefilling can lead to an unintended (partial) closure of the shift element. This can lead to an unintended slip of the vehicle in the neutral position. Too little prefilling can lead to a late and / or uncomfortable closure of the shift element when shifting from the neutral position to the drive position. SUMMARY

[0008] The task of the present application is to safely operate a multi-gear vehicle transmission.

[0009] This task is solved by the features of the independent claims respectively. Preferred embodiments thereof can be taken from the dependent claims.

[0010] The present application is therefore based on a multi-gear vehicle transmission having a plurality of shift elements for engaging a gear of the vehicle transmission. The transmission has at least one neutral position and a drive position. In the neutral position, a decoupling between an input and an output of the transmission is provided. The neutral position thus corresponds to an idling operation of the transmission. In contrast, in the drive position, a coupling of the input and the output is provided for propelling the vehicle. The coupling is achieved by closing at least one of the shift elements of the transmission. The gear shift from the neutral position to the drive position is thus achieved by closing at least this shift element. In particular, the shift element can be hydraulically or pneumatically actuated by a pressure medium.

[0011] It is now provided that, in the event of the engagement of the neutral position, at least one actuation state of the vehicle brake and a transmission state with increased belt slip losses in the vehicle transmission are identified. In particular, the actuation states "vehicle brake released" (vehicle can slip) and "vehicle brake actuated" (vehicle is braked) are distinguished.

[0012] It is furthermore now provided that, in the event of the engagement of the neutral position, the mentioned shift element provided for the drive position is vented if it is identified that:

[0013] a. the vehicle brake is released, and

[0014] b. a transmission state with increased belt slip losses is present,

[0015]

[0016] ​By venting the switching element, the switching element is brought into a state of safe disconnection. The preparation of the switching element for shifting into the drive range, if it has already been prepared, is reversed. In particular, the air gap of the switching element, which was reduced by the preparation, is re-established. If the switching element has been pre-tensioned in the range of the preparation, this pre-tensioning is purposefully reduced. If the switching element can be operated by means of pressure medium and has been pre-charged in the range of the preparation, the pre-charge is discharged from the switching element. The switching element is thus not actually filled with air during the venting.

[0017] In particular, the switching element, which can be operated by means of pressure medium, is switched to be pressureless, i.e. to ambient pressure, for this purpose. In particular, a pressure connection is established between the operating piston of the switching element and a pressure medium reservoir here. This is achieved in particular by means of one or more valves of the vehicle transmission. The pressure medium reservoir has ambient pressure, i.e. the air pressure prevailing in the surroundings of the vehicle transmission. Due to the established pressure connection, the operating piston then also essentially has ambient pressure.

[0018] In the event of the engagement of the neutral, the switching element can be (again) prepared for shifting without danger later on, i.e. can be pre-charged or pre-tensioned. This is in particular carried out as soon as the vehicle brake is operated again and / or as soon as there is no longer a transmission state with increased belt slip loss. As a result, it is still possible to start up quickly and comfortably in the drive range later on.

[0019] Thus, a distinction is currently made between, on the one hand, a pre-charged or pre-tensioned state of the switching element and, on the other hand, a closed state. In the pre-charged or pre-tensioned state, a (main) force or torque transmission through the switching element is not provided. In the closed state, on the other hand, a force or torque transmission through the switching element is provided.

[0020] The invention is based on the knowledge that, in the event of the engagement of the neutral, there is no danger of vehicle starting as long as the vehicle brake is operated in any case. Only after the vehicle brake is released can the pre-charging or pre-tensioning of the switching element lead to an undesired start-up. It is furthermore recognized that an unintended start-up in the event of the engagement of the neutral and the release of the service brake can in fact only occur in a transmission state with increased belt slip loss. In this transmission state, increased belt slip loss occurs in the transmission compared to the normal warm-up operating state.

[0021] There is a transmission state with increased belt wear losses especially when the vehicle transmission has not yet reached sufficient temperature. With a cold transmission, the lubricant contained therein, usually transmission oil, has a relatively high viscosity. The component friction and churning losses in the transmission are correspondingly high. Switching elements that are correctly pre-filled or pre-tensioned under normal operating conditions can still inadvertently transmit torque in these situations. This transmission state is therefore synonymous with a "cold" vehicle transmission, among other things. This transmission state can exist, for example, when the transmission lubricant is below a certain temperature, in particular 40°C. This can be determined, for example, by means of a temperature sensor of the vehicle transmission.

[0022] As has been set out above, the vehicle transmission is a multi-gear vehicle transmission having a plurality of switching elements for engaging into the gears of the vehicle transmission. The switching elements can be referred to as transmission switching elements and are configured as clutches and / or brakes. At least the switching elements for the drive gears can be configured for actuation by pressure medium. Preferably, all switching elements for the drive gears of the transmission are thus actuated. In particular, the lubricant of the vehicle transmission is used as pressure medium. Preferably, one or more switching elements are frictionally acting switching elements, in particular multi-plate clutches or brakes, respectively. The vehicle transmission is in particular an automatic transmission in the manner of a planetary structure.

[0023] The control effected via the actuation of the switching elements is carried out by a transmission controller which is likewise proposed. The transmission controller thus causes a situation-compliant actuation of the switching elements.

[0024] The vehicle transmission is preferably configured as a transmission according to DE 10 2005 002 337 Al. The disclosure of this document is expressly incorporated for more detailed particulars of these transmissions. In particular, the vehicle transmission is preferably configured according to Figure 4 therein. The switching elements contained therein are denoted with A, B, C, D, E. The vehicle transmission can be configured for use in a motor vehicle, for example in a passenger car, a van or a bus. However, the vehicle transmission can also be configured for use in a rail vehicle or an agricultural vehicle or another vehicle.

[0025] The drive gears are understood to be one or more gears of the vehicle transmission which are set for propelling the vehicle, i.e. the forward gears and, if present, the reverse gear. Here, the transmission input and the transmission output of the vehicle transmission are coupled to one another by at least one of the switching elements of the transmission. In contrast, in the neutral gear of the vehicle transmission it is provided that the transmission input and the transmission output are separated from one another. In the neutral gear, no propulsion of the vehicle by the vehicle transmission is provided.

[0026] The described switching element vented in the above-mentioned conditions a) and b) is preferably used as a switching element for engaging a launch gear for starting the vehicle. In other words, the driving gear according to the claim is the launch gear. Such a launch gear is in particular a gear having a high transmission ratio compared to the other gears of the vehicle transmission. In particular, the other gears of the vehicle transmission have a lower transmission ratio. Such a launch gear is in particular the first gear. The launch gear can change depending on the current situation. For example, upon recognition of a low load of the vehicle, the second or third gear can also be selected as the launch gear. It is also possible that, depending on the situation, the reverse gear is selected as the launch gear. In the neutral gear, the switching element associated with the selected launch gear can then be pre-filled or pre-tensioned in order to prepare a gear shift to the launch gear. When the mentioned conditions a) and b) are present, the switching element is vented.

[0027] Preferably, the operation of the vehicle transmission is monitored continuously or at regular intervals. It is inter alia learned here whether the neutral gear is engaged, whether the vehicle brake is released, and whether a state with increased belt slip loss is present, and whether a rolling state of the vehicle is present. For this purpose, inter alia, sensor information of sensors of the vehicle and the vehicle transmission is evaluated, which is indicative of these conditions.

[0028] It is inter alia learned whether the neutral gear is actually engaged. This can be done arbitrarily. This can be done, for example, by means of a control signal for a valve for the vehicle transmission for actuating the switching element. Alternatively or additionally, this can be done by means of a pressure signal of one or more pressure sensors of the vehicle transmission for a pressure medium. Alternatively or additionally, this can be done by means of a rotational speed signal of one or more rotational speed sensors of the vehicle transmission. Further learning methods not explicitly mentioned here can also be used. The learning is inter alia also carried out for other purposes, in particular in order to correctly actuate the transmission by the transmission controller, and / or in order to display the currently engaged gear on a screen in the vehicle interior.

[0029] It is also possible to determine arbitrarily whether a transmission condition with increased belt-pile losses exists. As described above, this is done particularly by means of transmission temperature, especially the temperature of the transmission lubricant (oil temperature). For this purpose, it is preferable to install a temperature sensor on the vehicle transmission. Alternatively or additionally, this can be done by means of a temperature model of the vehicle transmission. Alternatively or additionally, this can be done by means of the time elapsed since the engine of the vehicle, which is coupled to or may be coupled to the vehicle transmission, was started. Other methods of determination, not explicitly mentioned here, can also be used. Preferably, the known transmission temperature or the elapsed time is compared with a threshold. If the transmission temperature or the elapsed time is below the threshold, then it is assumed that a transmission condition with increased belt-pile losses exists. Conversely, if the transmission temperature or the elapsed time is above the threshold, then it is assumed that a transmission condition with increased belt-pile losses does not exist. The transmission is then warmed up, thereby sufficiently reducing belt-pile losses in the transmission. The temperature threshold is preferably between 30°C and 50°C. Particularly suitable temperature thresholds are between 35°C and 45°C, especially 40°C.

[0030] It is also possible to determine arbitrarily whether a vehicle brake is released. When a vehicle brake is released, no deceleration or braking force resulting from the brake is required. Conversely, when a vehicle brake is applied, a certain amount of deceleration or braking force resulting from the brake is required. Vehicle brakes, especially service brakes, are particularly important for braking systems in vehicles equipped with disc or drum brakes. In particular, this is achieved using a brake signal. This brake signal can represent the deceleration or braking force desired by the vehicle operator or the system. The brake signal can be output by a position sensor mounted on the vehicle's brake pedal or brake lever. The brake pedal and brake lever are used to preset the deceleration or braking force resulting from the vehicle operator, respectively. Alternatively or additionally, this can be achieved using the braking pressure present in the braking system. For example, if the brake signal or braking pressure is below a certain threshold or is absent, then the vehicle brake is released. Other methods of determination not explicitly mentioned here can also be used.

[0031] Preferably, when the vehicle is in neutral and the vehicle brakes are engaged, the shifting element for engaging the driving gear is preferably at least pre-tightened or pre-filled with a pressurized medium. As explained above, this prepares the shifting element in neutral for shifting to the driving gear. Therefore, the shift from neutral to driving gear can be performed quickly and comfortably. However, as also explained above, if conditions a) and b) are met, the shifting element is vented for safety.

[0032] The vehicle transmission is preferably configured such that at least two switching elements of the transmission are closed when in a driving gear. In other words, at least two switching elements must be closed in order to engage a driving gear. Here, when neutral is engaged, if it is detected that:

[0033] a. The vehicle brakes were released, and

[0034] b. There exists a vehicle transmission with increased belt-driven losses.

[0035] Then the first switching element of the switching element is ventilated.

[0036] Therefore, this corresponds to conditions a) and b) above. The first switching element is specifically brought to a safe disconnected state. Thus, in the first safety level, the vehicle is prevented from starting even when it is in neutral.

[0037] Conversely, when in neutral, if the following is detected:

[0038] a. The vehicle brakes were released, and

[0039] b. There exists a transmission condition with increased belt-driven losses, and

[0040] c. The vehicle is in a rolling state. In this rolling state, the vehicle moves forward.

[0041] Then the second switching element in the switching element is ventilated.

[0042] Therefore, the second switching element is ventilated only if, in addition to conditions a) and b) mentioned above, an additional condition c) exists. If the vehicle is still in motion (rolling) even though the first switching element has been ventilated, then condition c) exists. Thus, the second switching element is also ventilated for safety. Therefore, the second switching element is also specifically brought to a safe disengaged state. This prevents the vehicle from starting even when it is in neutral, thus preventing it from starting in the second safety level.

[0043] The presence of rolling can be determined arbitrarily. This is especially true using the output speed of the vehicle's transmission, i.e., the speed at the transmission output. For this purpose, a speed sensor can be installed at the transmission output. This speed sensor is usually already configured for other purposes. Alternatively or additionally, this can be determined using the vehicle's wheel speeds. For this purpose, for example, a speed sensor from the vehicle's anti-lock braking system (ABS) can be used. Alternatively or additionally, this can be determined using the vehicle's acceleration. For this purpose, for example, a vehicle acceleration speed sensor can be used. For example, if the speed or acceleration exceeds a certain threshold, then the vehicle is rolling. Other methods of determination, not explicitly mentioned here, can also be used.

[0044] Preferably, in the case of engaging the neutral gear and in the case of the vehicle brake being actuated,

[0045] - a first of the two shift elements for engaging the drive gear is preloaded, or pre-charged with pressure medium, and

[0046] - a second of the two shift elements for engaging the drive gear is closed.

[0047] Thus, both shift elements are ready for a shift into the drive gear. Thereby, a change from the neutral gear to the drive gear can be effected particularly quickly and comfortably. In the presence of the above-mentioned conditions a) and b), only the first shift element is vented in order to be safely disconnected. In the additional presence of the above-mentioned condition c), the second shift element is also vented in order to safely disconnect this second shift element. As already set out, the drive gear is in particular a launch gear. Thus, in such a transmission, at least these two or exactly these two shift elements must be closed in order to engage the launch gear.

[0048] The vehicle transmission is preferably configured such that, in the drive gear, at least three or exactly three shift elements of the vehicle transmission are closed. In other words, at least these three or exactly these three shift elements must be closed in order to engage the drive gear. In the case of engaging the neutral gear and in the case of the vehicle brake being actuated, now

[0049] - a first of these shift elements is preloaded or pre-charged with pressure medium, and

[0050] - a second of these shift elements is closed, and

[0051] - a third of these shift elements is vented.

[0052] In this way, all three shift elements are ready for a shift into the drive gear. In a vehicle transmission configured in this way, this procedure has proven particularly appropriate in order to quickly and comfortably change from the neutral gear to the drive gear. In the presence of the above-mentioned conditions a) and b), here too only the first shift element is vented in order to safely disconnect it. In the additional presence of the above-mentioned condition c), the second shift element is also vented in order to safely disconnect it. Since the third shift element is already vented and thus safely disconnected, no further measures are required here. As already set out, the drive gear is in particular a launch gear. Thus, in such a transmission, at least these three or exactly these three shift elements must be closed in order to engage the launch gear.

[0053] Preferably, in the vehicle transmission, at least or exactly three shift elements are closed in all drive gears. Such a transmission proves to be comfortable and economical. DE 10 2005 002 337 Al shows a preferred variant of such a transmission.

[0054] In a particularly preferred procedure for operating a multi-gear vehicle transmission, the following steps are provided in the following sequence:

[0055] 1. The neutral gear of the vehicle transmission is engaged, for example automatically or upon request by the user of the vehicle. For this purpose, one or more shift elements of the vehicle transmission are opened.

[0056] 2. If the vehicle brake is operated while the neutral gear is engaged, at least one shift element operated by pressure medium is at least pre-filled for engaging the start gear. This shift element is to be closed when shifting into the start gear. If two shift elements operated by pressure medium are to be closed for engaging the start gear, a first of the shift elements can be pre-filled and a second of the shift elements can already be closed. If three shift elements operated by pressure medium are to be closed for engaging the start gear, a first of the shift elements can be pre-filled and a second of the shift elements can already be closed and a third of the shift elements can be vented.

[0057] 3. If the vehicle brake is released while the neutral gear is engaged and a transmission state with increased belt slip losses is present, the pre-filled (first) shift element is vented.

[0058] 4. If additionally a rolling state of the vehicle is present, the closed (second) shift element is additionally vented.

[0059] The proposed method is controlled by a likewise proposed transmission controller. This means that the method is executed by the transmission controller. The proposed transmission controller is therefore specifically set up in such a way that it carries out the method with the steps explained respectively. To this end, the transmission controller has, inter alia, an input and an output as well as a computing device. To this end, the transmission controller also has, inter alia, a storage medium (data memory) in which commands are stored that are specifically required for the execution. The input of the transmission controller is set up in such a way that it delivers the required information to the transmission controller, for example the current transmission temperature, the current output rotational speed and / or the current brake signal. The output of the transmission controller is set up for outputting the required actuation signals for actuating the switching elements, for example signals for opening and closing valves of the switching elements, by the transmission controller. The computing device carries out the commands stored in the storage medium, wherein here the computing device processes the incoming information and outputs the corresponding actuation signals for the switching elements. The computing device is, inter alia, a microprocessor.

[0060] A computer-readable storage medium is also proposed. The storage medium comprises instructions which, when executed by a computer, cause the computer to carry out the proposed method. By executing the stored instructions with the transmission controller, the transmission controller is able to carry out the proposed method. BRIEF DESCRIPTION OF DRAWINGS

[0061] Figure 1 The application is explained in detail from Figure 1 Further preferred embodiments of the application can be derived. DETAILED DESCRIPTION

[0062] Figure 1 The arrangement of the shafts AN, AB, 1, 2, 3, 4, 5, 6, 7, 8 and the switching elements A, B, C, D, E of the preferred multi-gear vehicle transmission in the form of a planetary gear set RS1, RS2, RS3, RS4 in a star structure is shown in a schematic view. For a better overview, only the upper half of the vehicle transmission is shown. The lower half is constructed, inter alia, mirror-symmetrically to the upper half. Figure 1 The structure and mode of operation of the vehicle transmission of DE 10 2005 002 337 A1 correspond to the structure and mode of operation of Fig. 4 of this document. Therefore, the relevant explanations in this document are expressly incorporated for more detailed details.

[0063] The drive shaft AN is generally coupled to the drive motor of the vehicle or can be coupled thereto by means of a separate clutch, for example, inter alia, by means of a hydrodynamic torque converter. The output shaft AB is generally coupled to the drive wheels of the vehicle or can be coupled thereto.

[0064] In Figure 1In the middle, a transmission controller 10 is additionally shown, which serves to actuate the shift elements A, B, C, D, E of the transmission. Thus, the controller 10 causes the shift elements A, B, C, D, E to be selectively opened and closed. Thereby, in the respective case the gear which is appropriate or which is requested by the vehicle operator is engaged. For this, the controller 10 is supplied with the respective information via the controller input. The controller 10 processes this information and outputs the respective signals for actuating the shift elements A, B, C, D, E via the controller output.

[0065] In particular, the information Br, T and n AB are supplied to the controller 10. The information Br is a brake signal of the service brake of the vehicle, which represents the actuation state of the brake. Figure 1 Only the brake pedal 11 of the service brake is shown. Br is known, for example, by a position sensor of the brake pedal 11. The information T is a temperature signal, which represents the temperature of the transmission. T is known, for example, by a temperature sensor in the transmission. The information n AB is a rotational speed signal, which represents the rotational speed on the output shaft AB.

[0066] The shift elements A, B, C, D, E are usually actuated by pressure medium. For this, each shift element A, B, C, D, E is assigned an actuating piston, which can be individually loaded with the pressure of the pressure medium. For this, the valves assigned to the actuating pistons are actuated by the controller 10. In Figure 1 the shown transmission, the lubricant of the transmission (transmission oil) is usually used as pressure medium.

[0067] The transmission can be shifted into neutral, wherein the drive shaft AN is separated from the output shaft AB. For this, a sufficient number of shift elements A, B, C, D, E, in particular the shift elements B, C, D, E, are opened. The running gears of the transmission serve for the movement of the vehicle. Thus, eight forward gears and one reverse gear can be used as running gears. In Figure 1 the shown transmission, in the running gears three of the five shift elements A, B, C, D, E are always closed, while the remaining two shift elements A, B, C, D, E are opened.

[0068] With the launch gears, the vehicle is accelerated from standstill or from very low speeds. Thus, the launch gears have a relatively high transmission ratio. Depending on the load state and the desired direction of travel, a first gear (shift elements A, B, C are closed and D, E are opened) or a second gear (shift elements A, B, E are closed and C, D are opened) or a reverse gear (shift elements A, B, D are closed and C, E are opened) is particularly suitable as launch gear of the transmission.

[0069] In the following, the Figure 1The following describes a preferred procedure for operating the transmission with the neutral engaged. This procedure can also be used for other vehicle transmissions. It is carried out by a correspondingly specially designed transmission controller 10. The engagement of the neutral is requested, for example, by a vehicle operator or an automatic device, as already described above. For the neutral, at least the switching elements B, C, D, E are opened. In the present example, the first gear is used as the launch gear. To this end, the switching elements A, B, C must be closed, while the switching elements D, E must be open.

[0070] It is ascertained whether the service brake of the vehicle has been released. This is carried out, inter alia, by having the transmission controller 10 acquire and evaluate a brake signal Br of the vehicle brake system.

[0071] It is also ascertained whether the transmission is in a state with increased belt slip losses. This is carried out, inter alia, by having the controller 10 compare the current temperature T of the transmission with a threshold value. The threshold value is, for example, 40°C. If the ascertained temperature T is below this threshold value, the transmission is still relatively cold and the transmission lubricant is correspondingly highly viscous. As a result, a transmission state with increased belt slip losses is considered to be present, taking into account the relatively high belt slip losses in the transmission. If the ascertained temperature T is above this threshold value, the transmission is sufficiently hot and the lubricant is correspondingly less viscous. As a result, a transmission state with increased belt slip losses is considered to be absent, taking into account the low belt slip losses in the transmission. As already described above, the presence or absence of this transmission state can also be ascertained in other ways.

[0072] It is also ascertained whether a rolling state of the vehicle is present. In other words, it is checked whether the vehicle is starting with the neutral engaged. To this end, it is inter alia ascertained whether a rotational speed n AB > 0 is present on the output shaft AB.

[0073] If the service brake is not released, i.e. is thus actuated, the vehicle is prevented from starting by the service brake. As a result, with the neutral engaged, the transmission can be prepared for a shift into the launch gear. This enables a subsequent quick and comfortable shift into the drive gears. To this end, the switching element A is closed and the switching element B is pre-filled. The switching element C is vented or remains vented. The switching elements B, C are thus open. The switching elements D, E are likewise open.

[0074] If the service brake is released while the vehicle is in the neutral gear, the vehicle can in principle move, since it is no longer protected against starting. In this case, the preparation for shifting into the starting gear described above can still be performed or maintained, if the state with the increased belt wear loss is not present. Despite the release of the service brake and the engagement of the neutral gear, there is no increased risk of starting the vehicle. However, if the state with the increased belt wear loss is present in this case, the switching element B is vented for safety. The possible pre-charge of the switching element B, which can already be present, is then discharged, and the switching element B is brought into the state of safe disconnection. In this way, an unintentional starting in the neutral gear is prevented in the first safety level.

[0075] When, despite the venting of the switching element B, a rolling state is found, the switching element A is also vented. In this way, the switching element A is also brought into the state of safe disconnection. In this way, a further unintentional starting in the neutral gear is prevented in the second safety level.

[0076] Once it is determined later that the service brake is again operated while the vehicle is in the neutral gear, the preparation for shifting into the starting gear described above can be (re)performed.

[0077] List of reference signs

[0078] 1 shaft

[0079] 2 shaft

[0080] 3 shaft

[0081] 4 shaft

[0082] 5 shaft

[0083] 6 shaft

[0084] 7 shaft

[0085] 8 shaft

[0086] 10 transmission controller

[0087] 11 brake pedal

[0088] 100 step

[0089] 200 step

[0090] 300 step

[0091] 400 step

[0092] 500 step

[0093] 600 step

[0094] 700 step

[0095] A switching element

[0096] B Switching element

[0097] C Switching element

[0098] D Switching Element

[0099] E Switching element

[0100] AN drive shaft

[0101] AB output shaft

[0102] GG Case

[0103] RS1 Planetary Gear Set

[0104] RS2 Planetary Gear Set

[0105] RS3 Planetary Gear Set

[0106] SO3 Sun Gear

Claims

1. A method for operating a multi-gear vehicle transmission, said vehicle transmission having a plurality of switching elements (A, B, C, D, E) for engaging gears in the vehicle transmission, wherein, In neutral, the vehicle transmission is separated from its input (AN) to its output (AB), and in driving gear, the vehicle transmission is coupled to propel the vehicle by closing at least one switching element (B). In this method, when neutral is engaged, at least one operating state of the vehicle brake (11) and a transmission state with increased belt-running losses are identified. If, when neutral is engaged, the vehicle brake (11) is identified as released and a transmission state with increased belt-running losses exists, then the switching element (B) for driving gear is vented. In driving gear, at least two of the vehicle transmission switching elements (A, B) are closed. When neutral is engaged: - If it is detected that the vehicle brake (11) is released and there is a transmission state with increased belt pull loss, then the first switching element (B) of the switching elements (A, B) is vented, and - If it is detected that the vehicle brake (11) is released and there is a transmission state with increased belt loss and the vehicle is in a rolling state, then the second switching element (A) of the switching elements (A, B) is vented.

2. The method according to claim 1, wherein, To determine the state of a transmission with increased belt losses, consider - Transmission temperature (T), and / or - The duration of operation of the vehicle transmission from the start of the engine, which is coupled to or may be coupled to the drive motor of the vehicle transmission, and / or - Temperature model of vehicle transmission.

3. The method according to claim 1 or 2, wherein, When the vehicle is in neutral and the vehicle brake (11) is engaged, the gear shifting element (B) is pre-tightened or at least pre-filled with a pressure medium.

4. The method according to claim 1, wherein, To determine the scrolling status: - Output speed of the vehicle's transmission (n) AB ), and / or - Vehicle wheel speed, and / or - Vehicle acceleration.

5. The method according to claim 1, wherein, With the vehicle in neutral and the vehicle brake (11) engaged, - The first switching element (B) in the gear shifting elements (A, B) is pre-tightened or pre-filled with a pressurized medium, and - The second switching element (A) in the gear shifting elements (A, B) for driving gears is closed.

6. The method according to claim 1 or 2, wherein, In driving gear, at least three or exactly three switching elements (A, B, C) of the vehicle transmission are closed, wherein, when in neutral and when the vehicle brake (11) is actuated, The first switching element (B) of the switching elements (A, B, C) is pre-tightened or pre-filled with a pressure medium, and The second switching element (A) of the switching elements (A, B, C) is closed, and - The third switching element (C) of the switching elements (A, B, C) is ventilated.

7. The method according to claim 1 or 2, wherein, In a vehicle transmission, at least three or exactly three switching elements (A, B, C, D, E) are closed in all driving gears.

8. The method according to claim 2, wherein Transmission temperature refers to the temperature of the lubricant in a vehicle's transmission.

9. A transmission controller (10) for operating switching elements (A, B, C, D, E) of a vehicle transmission, characterized in that, The transmission controller (10) is configured to implement the method according to any one of claims 1 to 8.

10. A computer-readable storage medium comprising instructions that, when executed by a computer, cause the computer to perform the method according to any one of claims 1 to 8.

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