Calibrating a hydraulic clutch

Abstract

A method for calibrating a hydraulic clutch (22) of a vehicle comprises: switching the clutch (22) from an open to a closed state, wherein the clutch (22) is subjected to a first pressure (32a) in a first switching interval (30a), and in a second switching interval (30b) after the first switching interval (30a) is subjected to a second pressure (32b) which is less than the first pressure (32a); determining a relative rotational speed (34) of two shafts (14, 18) coupled via the clutch (22), wherein the relative rotational speed (34) is determined for a predefined time (t2) after the end of the first switching interval (30a) within the second switching interval (30b); determining a rotational speed difference (36) of the relative rotational speed (34) to a reference rotational speed (38); and adjusting the length (t1) of the first shift interval (30a) for further shifting operations of the clutch (22) depending on the speed difference (36).

Description

[0001] The invention relates to a method, a computer program, and a computer-readable medium for calibrating a hydraulic clutch of a vehicle. The invention further relates to a control system for a vehicle system and the vehicle system itself.

[0002] Automatic transmissions for vehicles typically include one or more hydraulic clutches that open and close during gear changes. To ensure the fastest and most precise engagement of such a clutch, it is common practice to apply relatively high pressure at the beginning of the engagement process. This pressure is maintained until the clutch is in a position where only a small movement is required for complete closure. The time interval during this so-called quick-filling process is defined and preset in the control unit. Over time, however, wear and tear can cause the clutch to respond differently to the quick-filling process than it did at the beginning of its service life.

[0003] The object of the invention is to maintain accurate and precise shifting behavior of a clutch throughout its entire service life. A further object of the invention is to adapt the rapid filling process of a clutch to the wear of the clutch.

[0004] These problems are solved by the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims and from the following description.

[0005] One aspect of the invention relates to a method for calibrating a hydraulic clutch of a vehicle, such as a car, truck, or bus. The hydraulic clutch may be a component of the vehicle's automatic transmission. The method can be performed automatically by a vehicle control system, which may be a control system for the clutch and / or the transmission. In particular, the method can be performed during normal operation of the transmission by controlling the transmission to shift gears, thereby converting the rotational speed of the vehicle's engine into the rotational speed of the vehicle's wheels while the vehicle is in motion.

[0006] According to one embodiment, the method comprises: switching the clutch from an open to a closed state, wherein the clutch is subjected to a first pressure in a first switching interval, and in a second switching interval after the first switching interval is subjected to a second pressure which is less than the first pressure.

[0007] The two switching intervals are consecutive time intervals whose durations are stored in the clutch control unit. This procedure calibrates the length of the first switching interval. The first switching interval occurs at the beginning of the closing process. The second switching interval can be the start of a sequence of switching intervals, in which the pressure is progressively increased to achieve optimal clutch closure.

[0008] The two shift intervals initiate the clutch engagement process with a so-called rapid filling procedure. This engagement involves moving the clutch components from an open state (i.e., no friction between the components) to a closed state (i.e., maximum friction between the components). The relatively high pressure during the first shift interval fills the clutch's hydraulic cylinder relatively quickly, allowing the clutch to rapidly move into a position where frictional engagement can begin.

[0009] The pressure can be supplied by the vehicle's and / or transmission's hydraulic system, which includes a hydraulic pump. The pressure level can be adjusted using a corresponding valve, which can be controlled as needed to regulate the pressure.

[0010] According to one embodiment, the method comprises: determining a relative rotational speed of two shafts coupled via the clutch, wherein the relative rotational speed is determined for a predefined time after the end of the first switching interval within the second switching interval; determining a speed difference of the relative rotational speed to a reference rotational speed; and adjusting the length of the first switching interval for further clutch switching operations depending on the speed difference.

[0011] The clutch couples two shafts, such as the engine's output shaft and one of the wheels' drive shafts. The relative speed can be the difference in speed between the two shafts or the speed of the rotating shaft while the other is stationary. The relative speed is determined at a specific point in time. This point in time is at the end of a predefined period after the first shift interval. By this time, a desired incomplete frictional engagement should already have occurred, causing the speeds of the two shafts to align somewhat. The relative speed is compared to a speed reference, which could be, for example, zero or the speed of one of the two shafts before the first shift interval. If this difference deviates too much from zero, it indicates that the duration of the first shift interval needs to be adjusted or calibrated.If the difference is too small, then the first switching interval must be lengthened; if it is too large, then the first switching interval must be shortened.

[0012] The position of the clutch after the first shift can change over the clutch's service life, even with the same pressure and duration. For example, clutch components can wear, resulting in increased or decreased friction between these parts. Additionally, the pressure supplied by the hydraulic system and the pressure set by the valve can change over time, again potentially due to wear.

[0013] Determining the relative rotational speed at the predefined time after the first shift interval can be performed during normal clutch operation, for example, when predefined clutch conditions prevail. This can occur when the vehicle starts moving, when the vehicle is stationary and first gear is engaged via the manual transmission.

[0014] Furthermore, it is possible that several relative rotational speeds are determined during multiple clutch engagements and then averaged. The new length of the first shift interval can then be determined from this average. Alternatively, several new lengths of the first shift interval are first determined from the relative rotational speeds of multiple shifts, and then an average new length of the first shift interval is calculated.

[0015] Finally, the newly determined length of the first switching interval is stored in the control unit, and the length of the first switching interval is set accordingly for subsequent switching operations.

[0016] According to one embodiment, the length of the first switching interval is not adjusted if the magnitude of the speed difference is less than a threshold value. As long as the deviation from the desired relative speed is not too large, the length of the first switching interval does not need to be adjusted. In this way, short-term fluctuations in the measurements can be compensated for.

[0017] According to one embodiment, the length of the first switching interval is increased if the speed difference is less than a minimum value, and / or the length of the first switching interval is decreased if the speed difference is greater than a maximum value. In principle, the length of the switching interval can be increased if the speed difference is less than 0 and decreased if the speed difference is greater than 0. This can be determined non-linearly, for example, using a table of parameters and / or a function stored in the controller.

[0018] According to one embodiment, the length change of the first switching interval is determined as a function of the speed difference from a characteristic curve stored in a controller that executes the method. This characteristic curve can be compiled from empirical data.

[0019] According to one embodiment, the change in the length of the shift interval as a function of the speed difference depends on further state parameters of the clutch. A function and / or a characteristic curve used to determine the length of the shift intervals from the speed difference may depend on these additional state parameters. These state parameters could include, for example, the clutch temperature, the shift state of the transmission in which the clutch is installed, and / or the vehicle speed.

[0020] According to one embodiment, the reference speed is the relative speed of the two shafts at the beginning or end of the first switching interval. The speed difference can be determined relative to the beginning of the first switching interval or to the start of the rapid filling process. Thus, the difference corresponds to the reduction in speed at the predetermined time after the first switching interval.

[0021] According to one embodiment, the method further comprises: increasing the pressure applied to the clutch to a maximum pressure higher than the initial pressure in a third switching interval following the second switching interval. After the second switching interval, the clutch can be fully engaged in a third switching interval. Starting with the second switching interval, the pressure is progressively increased until the clutch is fully engaged.

[0022] According to one embodiment, the first pressure during the first shifting interval is at least 60%, for example at least 80%, of the maximum pressure applied to the clutch. The second pressure can be at most 40%, for example at most 20%, of the maximum pressure applied to the clutch. The percentages are relative to the difference between the minimum and maximum pressures of the hydraulic system; that is, 0% corresponds to the minimum pressure and 100% to the maximum pressure. The first pressure should be as high as possible to achieve the shortest possible quick-filling process. The second pressure should be chosen to allow the clutch's hydraulic system to relax.

[0023] According to one embodiment, the procedure is performed when the vehicle is stationary. The procedure can also be performed when the vehicle is starting to move. In this case, the relative speed can be the speed of the engine shaft at the measurement time after the end of the first switching interval, and the reference speed can be the speed of the engine shaft at the beginning of the first switching interval.

[0024] Another aspect of the invention relates to a computer program which, when executed on at least one processor, performs the method according to one of the preceding claims. Such a computer program can be executed by a clutch and / or transmission control unit.

[0025] Another aspect of the invention relates to a computer-readable medium on which such a computer program is stored. The computer program can be stored in non-volatile memory of the controller. A computer-readable medium can be a hard disk, a USB storage device, RAM, ROM, EPROM, or FLASH memory. A computer-readable medium can also be a data communication network, such as the internet, which allows the download of program code.

[0026] Another aspect of the invention relates to a control unit for a vehicle system designed to carry out the method as described above and below. For this purpose, the control unit can include a processor and memory. The processor can execute a computer program stored in the memory, which controls the clutch and thus carries out the method.

[0027] Another aspect of the invention relates to a vehicle system comprising a clutch and a control unit for controlling the clutch, as described above and below. The vehicle system can be part of the vehicle's drive system. The clutch can be a clutch in the vehicle's transmission.

[0028] It should be understood that features of the process, as described above and below, may also be features of the vehicle system and vice versa.

[0029] In the following, exemplary embodiments of the invention are described in detail with reference to the accompanying figures. Fig. Figure 1 schematically shows a vehicle system according to an embodiment of the invention. Fig. Figure 2 shows a diagram with a pressure curve and a speed curve, which describes a method according to an embodiment of the invention.

[0030] The reference symbols used in the figures and their meanings are summarized in the list of reference symbols. Generally, identical or similar parts are designated with the same reference symbols.

[0031] The Fig. Figure 1 shows a vehicle system 10 or vehicle 10, which drives a shaft 14 via a drive or motor 12. The shaft 14 is connected to the wheels 20 of the vehicle 10 via a transmission 16 and another shaft 18. The transmission 16 is, for example, an automatic transmission and / or the vehicle 10 is an automatic vehicle. The transmission 16 includes a hydraulically operated clutch 22. The transmission 16 and / or the clutch 22 are controlled by a controller 24, which can, for example, actuate corresponding actuators, such as hydraulic valves, to shift gears and / or engage the clutch.

[0032] The Fig. Figure 2 shows a diagram with a pressure curve 26 and a speed curve 28.

[0033] The diagram also illustrates a procedure for calibrating the hydraulic coupling 22. This procedure can be performed automatically by the controller 24. The controller 24 can include a processor and memory, with the procedure being carried out by a computer program stored in the memory and executed by the processor.

[0034] The pressure curve shows how the clutch 22, and in particular a hydraulic cylinder of the clutch 22, is pressurized during the closing of the clutch 22. The switching process, in which the clutch 22 switches from an open to a closed state, can be divided into three switching intervals 30a, 30b, 30c.

[0035] The first switching interval 30a is located at the beginning of the closing process of the clutch 22. In the first switching interval 30a, the clutch 22 is subjected to an initial pressure 32a. Due to the relatively high pressure 32a in the first switching interval 30a, the hydraulic cylinder of the clutch 22 is filled relatively quickly, so that the clutch 22 is quickly moved into a position where frictional engagement can begin.

[0036] The second switching interval 30b follows the first switching interval 30a. In the second switching interval 30b, the clutch 22 is subjected to a second pressure 32b, which is lower than the first pressure 32a. Between the two switching intervals 30a and 30b, the pressure can be briefly reduced below the second pressure 32b to compensate for hysteresis of components of the clutch 22.

[0037] In a third switching interval 30c, which follows the second switching interval 30b, the pressure applied to the clutch 22 is further increased to a maximum pressure 32c. Thus, after the second switching interval 30b, the clutch is fully closed in the third switching interval 30c. In the third switching interval 30c, the pressure can increase continuously, for example, in one or more sections with a linear gradient.

[0038] The first pressure 32a during the first shift interval 30a can be at least 60%, for example at least 80%, of the maximum pressure 32c. The second pressure 32b can be at most 40%, for example at most 20%, of the maximum pressure 32c applied to the clutch. The percentages are relative to the difference between a minimum pressure 32d and the maximum pressure 32c provided by a hydraulic system of the vehicle 10 and / or the transmission 16. The pressure level can be adjusted by a corresponding valve, which is controlled accordingly by the controller 24.

[0039] The time lengths of the successive time intervals 30a, 30b, 30c as well as the pressures 32a, 32b and the time course of the pressure or the pressure curve 26 during the switching interval 30c are stored in the control unit 24 of the clutch 22.

[0040] The following steps of the procedure calibrate the length t1 of the first switching interval. These steps can be performed during normal operation of the clutch 22 and, in particular, during the switching process described above.

[0041] The Fig. Figure 2 further shows a speed curve 28, which represents the relative speed of the two shafts 14, 18 over time. At the beginning of the shifting process, i.e., at the beginning of the first shifting interval 30a, the relative speed between the two shafts 14, 18 is at its maximum. After the end of the first shifting interval 30a, within the second shifting interval 30b, the clutch 22 begins to close and the relative speed begins to decrease. At the end of the shifting process, i.e., at the end of the third shifting interval 30c, the clutch is fully closed and the relative speed is 0.

[0042] During the switching process, the relative rotational speed 34 of the shafts 14 and 18 coupled via the clutch 22 is determined at a specific time t2. This predefined time t2 occurs a predefined period after the end of the first switching interval 30a. This can be done, for example, using one or more sensors on the shafts 14 and 18. The relative rotational speed 34 can also be determined by calculating it from other parameters available in the controller 24.

[0043] A speed difference 36 is determined from the relative speed 34 by subtracting the relative speed 34 from the reference speed 38. The reference speed 38 can be the relative speed of the two shafts 14, 18 at the beginning of the first switching interval 30a. The speed difference 36 then corresponds to the reduction in speed at the predetermined time t2 after the first switching interval 30a.

[0044] Determining the relative speed 34 for the predefined time t2 after the first shift interval 30a can be performed during normal operation of the clutch 22, for example, when predefined conditions for the clutch 22 prevail. This can occur when the vehicle starts moving, when the vehicle is stationary and first gear is engaged via the transmission. In this case, the relative speed 34 can be the speed of the motor shaft 14, and the reference speed 38 can be the speed of the motor shaft 14 at the beginning of the first shift interval 30a.

[0045] The desired length t1 of the first switching interval 30a is calculated from the speed difference 36. The desired length t1 and / or a change in the length of the first switching interval 30a can be determined as a function of the speed difference 36 from a characteristic curve stored in the controller 24. This characteristic curve can be compiled from empirical data. Furthermore, it is possible to calculate the desired length t1 and / or the change in the length of the first switching interval 30a using a function implemented in the controller 24.

[0046] The desired length t1 and / or the change in length of the first shift interval 30a can be determined depending on the speed difference 36 and other state parameters of the clutch 22. The function and / or the characteristic curve may depend on further state parameters, such as clutch temperature, the shift state of the transmission 16, and / or the vehicle speed.

[0047] The function and / or characteristic curve can be implemented based on the following conditions. The length t1 of the first switching interval 30a is not adjusted if the magnitude of the speed difference 36 is less than a threshold value.

[0048] As long as the deviation from the desired relative speed 34 is not too large, the length t1 of the first switching interval 30a does not need to be adjusted. Furthermore, the length t1 of the first switching interval 30a is increased if the speed difference 36 is less than a minimum value, and decreased if the speed difference 36 is greater than a maximum value. These dependencies can also be implemented non-linearly.

[0049] If a new desired length t1 and / or a change in the length of the first switching interval 30a is determined, this length t1 of the first switching interval 30a is stored in the control unit 24 for subsequent switching operations of the clutch 22. The length t1 of the first switching interval 30a is then set accordingly for subsequent switching operations of the clutch 22.

[0050] It should also be noted that "comprehensive" does not exclude any other elements or steps, and "a" or "an" does not exclude a plurality. Furthermore, it should be noted that features or steps described with reference to one of the above embodiments may also be used in combination with other features or steps from other embodiments described above. Reference numerals in the claims are not to be considered as limitations. Reference sign 10 Vehicle systems 12 Drive 14 wave 16 gearboxes 18 wave 20 wheels 22 Clutch 24 Control 26 Pressure curve 28 Speed ​​curve 30a first switching interval 30b second switching interval 30c third switching interval 32a first printing 32b second print 32°C maximum pressure 32d minimum print t1 Length of the first switching interval t2 specific time after first switching interval 34 relative speed 36 Speed ​​difference 38 Reference speed

Claims

[1] Method for calibrating a hydraulic clutch (22) of a vehicle, the method comprising: Switching the clutch (22) from an open to a closed state, wherein the clutch (22) is subjected to a first pressure (32a) in a first switching interval (30a), and in a second switching interval (30b) after the first switching interval (30a) is subjected to a second pressure (32b) which is less than the first pressure (32a); Determining a relative rotational speed (34) of two shafts (14, 18) coupled via the coupling (22), wherein the relative rotational speed (34) is determined for a predefined time (t2) after the end of the first switching interval (30a) within the second switching interval (30b); Determining a speed difference (36) of the relative speed (34) to a reference speed (38); Adjusting the length (t1) of the first shift interval (30a) for further shift operations of the clutch (22) depending on the speed difference (36). [2] Method according to claim 1, wherein the length (t1) of the first switching interval (30a) is not adjusted if an amount of the speed difference (36) is less than a threshold value. [3] Method according to claim 1 or 2, wherein the length (t1) of the first switching interval (30a) is increased if the speed difference (36) is less than a minimum value; and / or where the length (t1) of the first switching interval (30a) is reduced if the speed difference (36) is greater than a maximum value. [4] Method according to one of the preceding claims, wherein a change in length of the first switching interval (30a) as a function of the speed difference (36) is determined from a characteristic curve which is stored in a controller (24) which carries out the method. [5] Method according to one of the preceding claims, wherein a change in length of the first switching interval (30a) as a function of the speed difference (36) depends on further state parameters of the clutch (22), such as a clutch temperature, a switching state of a transmission in which the clutch is installed; a speed of the vehicle. [6] Method according to any of the preceding claims, wherein the reference speed (38) is the relative speed of the two shafts (14, 18) at the beginning or end of the first switching interval (30a). [7] Method according to any one of the preceding claims, further comprising: Increasing the pressure applied to the clutch (22) to a maximum pressure (32c) that is higher than the first pressure (32a) in a third shift interval (30c) after the second shift interval (30b). [8] Method according to any one of the preceding claims, wherein the first pressure (32a) is at least 60% of a maximum pressure (32c) applied to the coupling (22); and / or wherein the second pressure (32b) is at most 40% of a maximum pressure (32c) applied to the coupling (22). [9] Method according to any of the preceding claims, wherein the method is carried out when the vehicle is stationary. [10] Computer program which, when executed on at least one processor, performs the method according to any of the preceding claims. [11] Computer-readable medium on which a computer program according to claim 9 is stored. [12] Control system for a vehicle system (10) designed to perform the method according to any one of claims 1 to 9. [13] Vehicle system (10), comprising: a clutch (22), a control (24) according to claim 12 for controlling the clutch.

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