Procedure for adjusting the oil level on an automatic transmission of a motor vehicle

Abstract

Method for adjusting the oil level of an automatic transmission (2) of a motor vehicle, wherein a system pressure setpoint for operation of the automatic transmission (2) during the journey of the motor vehicle is stored in a transmission control unit (7) of the automatic transmission (2), wherein a system pressure setpoint based on the transmission design is read from the transmission control unit (7), and that the oil level adjustment is carried out depending on the system pressure setpoint based on the transmission design, characterized in that the system pressure setpoint based on the transmission design is read via a workshop tester (13), and that the execution of the oil level adjustment by the transmission control unit (7) is triggered via the workshop tester (13) depending on the system pressure setpoint based on the transmission design.

Description

[0001] The invention relates to a method for adjusting the oil level in an automatic transmission of a motor vehicle.

[0002] Automatic transmissions in motor vehicles have a transmission housing and shafts positioned within the transmission housing, as well as typically shifting elements positioned within the transmission housing, which can be designed as frictional or positive-locking shifting elements. An automatic transmission is supplied with transmission oil to, on the one hand, lubricate and cool the automatic transmission's components and, on the other hand, to control the transmission's shifting elements in particular with a defined hydraulic pressure. A transmission is designed for a defined oil level, which should develop in the sump of the transmission housing when the motor vehicle is operated with the transmission in the park position and a drive unit at idle speed in a horizontal orientation.To adjust the oil level defined by the transmission design, a system pressure target specification is specified for a hydraulic pump of the automatic transmission in order to operate the hydraulic pump in a pressure-controlled manner such that it provides an actual system pressure value which corresponds to the system pressure target specification, so that the desired oil level is then set in the transmission.

[0003] The same automatic transmission can be used in different vehicle configurations from different manufacturers. For example, the same automatic transmission can be installed in a sports car, a sedan, or an SUV. Since requirements, particularly regarding the automatic transmission's shifting design, vary depending on the specific vehicle configuration in which an automatic transmission is installed, it is common practice for a system pressure target specification from the transmission design to be replaced by a system pressure target specification from the driving mode. In practice, the system pressure target specification from the transmission design is then overwritten in the transmission control unit by the system pressure target specification from the driving mode.

[0004] If the system pressure target specification on the driving side deviates from the system pressure target specification on the transmission side, the hydraulic pump of the automatic transmission is operated with a different system pressure target specification than that provided for in the transmission design.

[0005] In the field, specifically when a service call occurs or during a workshop visit, it may be necessary to check or adjust the oil level of the automatic transmission. To do this, a horizontally aligned vehicle, preferably positioned on a lift, undergoes an oil level adjustment procedure. For this purpose, an oil plug is removed from an oil overflow hole formed on the hardware side of the transmission housing, opening the oil overflow hole.When the park position P is selected on the transmission selector lever and the oil plug is removed from the oil overflow hole, the transmission control unit automatically runs an oil adjustment procedure. For this purpose, the transmission control unit operates the automatic transmission's hydraulic pump depending on the system pressure target specification such that the hydraulic pump provides an actual system pressure value that corresponds to the system pressure target specification. When the system pressure target specification specified by the transmission design is used during the oil level adjustment procedure, an oil level is established in the transmission housing sump that leads to a defined oil leakage through the oil overflow hole.However, if the system pressure target specified by the transmission design has been replaced by a system pressure target specified by the driving operation on the application side, the transmission control unit will then operate the hydraulic pump during the oil level adjustment procedure based on the system pressure target specified by the driving operation. Depending on whether the system pressure target specified by the driving operation is greater or lesser than the system pressure target specified by the transmission design, a larger or smaller leakage will develop at the oil overflow hole than the leakage that would develop using the system pressure target specified by the transmission design and that is expected by the workshop. This leads to complaints in the field.

[0006] In this context, the documents DE 10 2013 200 389 A1 and DE 10 2014 207 805 A1 also disclose methods for adjusting the oil level in an automatic transmission.

[0007] Based on this, the invention is based on the object of creating a novel method for adjusting the oil level in an automatic transmission of a motor vehicle.

[0008] This object is achieved by a method according to claim 1. According to the invention, a system pressure target specification from the transmission design is read out from the transmission control device, wherein the oil level adjustment is carried out by the transmission control device as a function of the system pressure target specification from the transmission design.

[0009] The present invention proposes an oil level adjustment procedure that always depends on the system pressure target specified by the transmission design, even if a different system pressure target specified by the application is specified by the driving operation. The driving operation-side system pressure target is stored in a first memory area, and the transmission design-side system pressure target is stored in a second, separate, protected memory area of ​​the transmission control device. This second, separate, protected memory area of ​​the transmission control device cannot be re-data-read by the application, so the transmission design-side system pressure target is always stored there.

[0010] Furthermore, the system pressure target specified by the transmission design is read out via a workshop tester, and the transmission control unit initiates the oil level adjustment based on the system pressure target specified by the transmission design via the workshop tester. Reading the system pressure target specified by the transmission design from the second memory area of ​​the transmission control unit by the workshop tester and triggering the oil level adjustment by the transmission control unit based on the system pressure target specified by the transmission design via the workshop tester allows for automated oil level adjustment in the field during a customer service call or a workshop visit based on the system pressure target specified by the transmission design.

[0011] According to an advantageous further development, at least one target boundary condition is read from the transmission control device, which is decisive for the system pressure target specification on the transmission design side. The or each target boundary condition is compared with a corresponding actual boundary condition. If at least one actual boundary condition deviates from the respective target boundary condition by more than a limit value, the system pressure target specification on the transmission design side is adjusted and the oil level is adjusted depending on the adjusted system pressure target specification on the transmission design side. This is preferably done via the workshop tester. This further development has the advantage that the system pressure target specification on the transmission design side, which is only valid for defined target boundary conditions, can be automatically adjusted depending on a comparison of the target boundary conditions with the actual boundary conditions.In this case, an oil level adjustment can be performed even if at least one actual boundary condition deviates from a target boundary condition, for example, if the oil level adjustment is performed at an actual temperature that deviates from a target temperature for which the system pressure target specification specified by the transmission design is valid. This increases the flexibility in performing the oil level adjustment and can also reduce the time required for the oil level adjustment.

[0012] Preferably, a target temperature of the transmission and / or a target idle speed of a drive unit and / or a target inclination of the motor vehicle and / or a target installation position of the automatic transmission and / or a target cooler design of the automatic transmission is read out as a target boundary condition. This is preferably done via the workshop tester. Based on at least one of these target boundary conditions, the system pressure target specification specified by the transmission design can be automatically adjusted, namely when the corresponding target boundary condition deviates from the actual boundary condition.

[0013] Preferred developments emerge from the dependent claims and the following description. Exemplary embodiments of the invention are explained in more detail, without being limited thereto, with reference to the drawings. Herein: Fig. 1 a diagram of an automatic transmission to illustrate the method according to the invention for adjusting the oil level in an automatic transmission of a motor vehicle, Fig. 2 a control-side block diagram to illustrate the method according to the invention for adjusting the oil level in an automatic transmission of a motor vehicle.

[0014] The present invention relates to a method for adjusting the oil level in an automatic transmission of a motor vehicle.

[0015] Fig. 1 shows a highly schematic representation of a transmission housing 1 of an automatic transmission 2 of a motor vehicle, specifically in a defined installation position in a motor vehicle. Components of the automatic transmission 2, such as transmission shafts and preferably shifting elements of the automatic transmission 2, are accommodated in an interior space 3 of the housing 1 of the automatic transmission 2. The automatic transmission 2 can be supplied with oil via an inlet 4, and oil can also be drained from the automatic transmission 2 via an outlet 5. The oil supplied to the automatic transmission 2 serves, in particular, to cool and lubricate the components of the automatic transmission 2 positioned in the housing 1, and preferably also to control shifting elements of the automatic transmission 2. The oil can be supplied to the automatic transmission 2, specifically to the housing 1 thereof, via the inlet 4 by means of a hydraulic pump 6, wherein the hydraulic pump 6 is operated as a function of a set system pressure.

[0016] In terms of design, a system pressure target specification from the transmission design is stored in a transmission control device 7, wherein this system pressure target specification from the transmission design is dimensioned such that when an automatic oil level adjustment is carried out by the transmission control device 7, a defined oil level 9 is set in the transmission housing 1, namely in a sump 8 of the transmission housing 1, which is dimensioned such that a defined leakage is formed at the oil overflow hole 10 at a structurally provided, housing-side oil overflow hole 10 with the oil screw removed from the overflow hole 10.

[0017] The state I of the Fig. 1 accordingly shows the transmission 2 in a state which, with reference to the oil level 9, develops when, when carrying out an oil level adjustment, the hydraulic pump 6 is operated on the basis of the system pressure target specification of the transmission design.

[0018] When applying an automatic transmission 2, a driving operation-side system pressure target specification that differs from the transmission design-side system pressure target specification can be stored in the transmission control device 7 on the application side in order to provide different or deviating shift programs or shift speeds, for example, depending on the configuration of the motor vehicle in which the automatic transmission 2 is installed.

[0019] Fig. 1 shows, with state II, a state of the automatic transmission 2 which develops when, during an oil level adjustment, the hydraulic pump 6 is controlled or operated on the basis of a system pressure target specification on the driving side which deviates from the system pressure target specification on the transmission design side, wherein in state II the Fig. 1 the system pressure target specification on the driving side deviates from the system pressure target specification on the gearbox design side in such a way that when the oil level adjustment is carried out in the sump 8 of the gearbox housing 1, an oil level 9' is set which is lower than the desired or expected oil level 9, so that in state II the Fig. 1 no leakage occurs at the oil overflow hole 10 of the gearbox housing 1. This then leads to complaints in the field.

[0020] According to the present invention, when performing an oil level adjustment on the automatic transmission 2, the transmission design-side system pressure target specification is read from the transmission control device 7, which may differ from the driving-side system pressure target specification. For this purpose, the transmission control device 7 provides two memory areas: a first memory area 11, in which, among other things, the driving-side system pressure target specification is stored, and a second, separate memory area 12, in which, among other things, the transmission design-side system pressure target specification is stored.

[0021] This second, separate memory area 12 of the transmission control unit 7 cannot be re-data-ready by the application, so the system pressure target specified by the transmission design is always stored there. The second, separate memory area 12 is therefore a protected memory area.

[0022] To carry out the oil level adjustment, as already explained, the system pressure target specification from the transmission design is read out from the second memory area 12 and the oil level adjustment is then carried out by the transmission control device 7 as a function of this system pressure target specification from the transmission design, and not as a function of a system pressure target specification from the driving operation side that deviates therefrom.

[0023] If an oil level adjustment is carried out in the field during a customer service call or workshop visit, the condition III of the Fig. 1, which corresponds to state I of the Fig. 1, so that the desired oil level 9 is formed in the transmission housing 1, namely in the sump 8 thereof. Despite a possible system pressure target specification on the driving side that differs from the system pressure target specification on the transmission design side, according to the invention the system pressure target specification on the transmission design side is used for the oil level adjustment, so that the oil level adjustment then leads to the desired oil level 9 in the transmission housing 1.

[0024] The reading of the transmission design-side system pressure target specification from the memory area 12 of the transmission control device 7 is carried out in the case of customer service during a workshop visit with the aid of a Fig. 2, which can be connected to the motor vehicle for data exchange with the transmission control unit 7. The workshop tester 13 accordingly reads the system pressure target specification from the transmission design and triggers the execution of the oil level adjustment by the transmission control unit 7 depending on the system pressure target specification from the transmission design.

[0025] From the second memory area 12 of the transmission control device 7, not only the system pressure target specification based on the transmission design is read out, but preferably also at least one target boundary condition that is decisive for the system pressure target specification based on the transmission design. Such a target boundary condition can be a target temperature of the transmission oil of the automatic transmission 2 and / or a target idle speed of a drive unit of the motor vehicle and / or a target inclination of the motor vehicle and / or a target installation position of the automatic transmission 2 in the motor vehicle and / or a target cooler design for the automatic transmission 2.

[0026] The or each target boundary condition is compared with a corresponding actual boundary condition. If at least one actual boundary condition deviates from the respective target boundary condition by more than a limit value, the system pressure target specification from the gearbox design is adjusted, and the oil level adjustment is then carried out depending on the adjusted system pressure target specification from the gearbox design in order to compensate for disturbances to the oil level adjustment that arise due to deviations of the or each target boundary condition from the actual boundary condition.

[0027] The reading of the respective target boundary condition from the transmission control device 7, the comparison of the respective target boundary condition with the respective actual boundary condition and the adaptation of the transmission design-side system pressure target specification depending on the deviation between the respective target boundary condition and the respective actual boundary condition is preferably carried out via the workshop tester 13, which increases or reduces the transmission design-side system pressure target specification depending on the deviation between the respective actual boundary condition and the respective target boundary condition.

[0028] With the present invention, it is therefore possible to carry out an individual oil level adjustment on an automatic transmission 2 of a motor vehicle during a customer service case or a workshop visit in the field, specifically depending on the system pressure target specification on the transmission design side and thus independently of any deviating system pressure target specification on the driving operation side.

[0029] Furthermore, it is possible to adjust the system pressure target specification on the gearbox design side depending on actual boundary conditions that deviate from the target boundary conditions that are decisive for the system pressure target specification on the gearbox design side in order to compensate for deviations between the respective target boundary condition and the respective actual boundary condition when adjusting the oil level.

[0030] As already explained, the method is carried out by an interaction between the transmission control device 7 of the transmission 2 and the workshop tester 13.

[0031] When the oil level adjustment is to be carried out in the field during customer service or during a workshop visit, the motor vehicle is preferably parked on a lifting platform in the workshop and the workshop tester 13 is connected to the motor vehicle, namely to a corresponding data interface thereof, so that the workshop tester 13 can exchange data with the transmission control device 7.

[0032] The arrow 14 of the Fig. Figure 2 illustrates that the first memory area 11 of the transmission control unit 7, in which operating parameters for driving conditions and thus driving-related operating parameters are stored, can be read by the workshop tester 13. This includes, in particular, data on the actual boundary conditions of vehicle operation, such as data on an actual temperature, data on an actual inclination, and data on an actual idle speed of a drive unit.

[0033] Then, when the vehicle is parked in the workshop, for example, on a lifting platform, for the oil level adjustment to be carried out, an oil plug is removed from the oil overflow hole 10 of the transmission housing 1 of the automatic transmission 2, the drive unit is running or is started, and the park position P is selected on the transmission selector lever of the automatic transmission 2. Only when the transmission selector lever assumes the park position P is the oil level adjustment permitted by the transmission control device 7.

[0034] In addition, the workshop tester 13 reads a system pressure target specification from the transmission design from the second memory area 12. This is indicated by the arrow 15 of the Fig. 2 visualized.

[0035] Furthermore, the workshop tester 13 reads target boundary conditions from the second memory area 12, which are decisive for the system pressure target specification on the transmission design side. This is visualized by the arrow 16 of the Fig. 2.

[0036] The workshop tester 13 compares the target boundary conditions read from the memory area 12 with corresponding actual boundary conditions read from the memory area 11 and then, if at least one of the actual boundary conditions deviates from the respective target boundary condition by more than a defined limit value, automatically adjusts the system pressure target specification on the transmission design side in order to compensate for the respective deviation between the respective target boundary condition and the respective actual boundary condition for carrying out the oil level adjustment.

[0037] The workshop tester 13 provides the system pressure target specification, which may have been adjusted by the gearbox design, to the gearbox control device 7, whereby this is Fig. 2 is visualized by the arrow 17.

[0038] The transmission control device 7 then automatically carries out an oil adjustment procedure using the system pressure target specification adjusted by the transmission design, if necessary, so that when the oil level adjustment is carried out, the Fig.1, state III of the automatic transmission 2 develops, and accordingly, an expected leak develops at the oil overflow hole 10. While the oil level adjustment is being carried out, leaving the parking position is prevented. The transmission control device 7 ensures that all parameters for the oil level adjustment are implemented, such as the control of the hydraulic pump 6 depending on the system pressure target specified by the transmission design, the control of the transmission's shifting elements with defined pressures, or the control of the drive unit with a defined speed.

[0039] The oil adjustment procedure can be terminated via the workshop tester 13. After the oil level adjustment is completed, the automatic transmission 2 is released again for standard operation using the system pressure target specification from the driving mode side; in particular, leaving the park position is permitted again.

[0040] It is also possible to specify a new system pressure target for the oil level adjustment using the workshop tester. This allows the oil level to be adjusted individually for each vehicle.

[0041] The oil level adjustment to be performed by the transmission control unit is known in practice. The invention relates to the automatic selection and, if necessary, adjustment of the system pressure target specification from the transmission design for use as the system pressure target specification for the oil level adjustment to be performed by the transmission control unit, preferably via the workshop tester in conjunction with a protected memory area of ​​the transmission control unit in which at least the system pressure target specification from the transmission design is stored. Reference symbol 1 gearbox housing 2 automatic transmissions 3 Interior 4 Inlet 5 Procedure 6 Hydraulic pump 7 Transmission control device 8 Swamp 9 Oil level 10 Oil overflow hole 11 Storage area 12 Storage area 13 workshop testers 14 Data exchange 15 Data exchange 16 Data exchange 17 Data exchange

Claims

[1] Method for adjusting the oil level in an automatic transmission (2) of a motor vehicle, wherein a driving-side system pressure target specification for operating the automatic transmission (2) while the motor vehicle is traveling is stored in a transmission control device (7) of the automatic transmission (2), wherein a transmission-design-side system pressure target specification is read out from the transmission control device (7), and that the oil level adjustment is carried out as a function of the transmission-design-side system pressure target specification, characterized by that the system pressure target specification on the gearbox design side is read out via a workshop tester (13), and that the execution of the oil level adjustment by the gearbox control device (7) is triggered via the workshop tester (13) as a function of the system pressure target specification on the gearbox design side. [2] Method according to claim 1, characterized bythat the driving-side system pressure target specification is stored in a first memory area (11) and the transmission-design-side system pressure target specification is stored in a second, separate memory area (12) of the transmission control device (7). [3] Method according to one of claims 1 to 2, characterized by , that at least one target boundary condition is further read out from the transmission control device (7), which is decisive for the system pressure target specification on the transmission design side, the or each target boundary condition is compared with a corresponding actual boundary condition, if at least one actual boundary condition deviates from the respective target boundary condition by more than a limit value, the system pressure target specification on the gearbox design side is adjusted and the oil level adjustment is carried out depending on the adjusted system pressure target specification on the gearbox design side. [4] Method according to claim 3, characterized by that the or each desired boundary condition is stored in the second, separate memory area (12) of the transmission control device (7). [5] Method according to claim 3 or 4, characterized by that the or each target boundary condition is read out via the workshop tester (13), and that the system pressure target specification on the gearbox design side is adjusted via the workshop tester (13). [6] Method according to one of claims 3 to 5, characterized by that a target temperature of the automatic transmission (2) and / or a target idle speed of a drive unit and / or a target inclination of the motor vehicle is read out as the target boundary condition. [7] Method according to one of claims 3 to 6, characterized by that a target installation position of the automatic transmission (2) and / or a target cooler design of the automatic transmission (2) is read out as a target boundary condition. [8] Method according to one of claims 3 to 7, characterized by that depending on the deviation between the respective actual boundary condition and the respective target boundary condition, the system pressure target specification on the gearbox design side is increased or reduced. [9] Method according to one of claims 1 to 8, characterized by that the transmission control device (7) controls a hydraulic pump (6) of the automatic transmission (2) in order to carry out the oil level adjustment when the transmission selector lever is in the park position in such a way that the actual system pressure value provided by the hydraulic pump (6) corresponds to the system pressure target specification.

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