Event-dependent clutch filling

Abstract

Method carried out by a control device (8) for transferring a hydraulic coupling (1) from the unactuated state to an actuated state, wherein the coupling (1) has a piston chamber (4) and a pressure regulator (6) by means of which a hydraulic fluid to be supplied to the piston chamber (4) can be regulated to a set pressure (A), comprising - detection of a reversal request (I); - setting and maintaining a rapid fill pressure level (III); - a reduction of the rapid filling pressure level to a filling equalization pressure level with a gradient profile (IV); - setting and maintaining a filling pressure level (V); characterized in that a classification of the reversing request is carried out on the basis of a vehicle speed present at the time of the reversing request, a vehicle inclination present at the time of the reversing request, a detection of a loading and / or unloading point and / or an obstacle detection (II), and that depending on this classification a filling pressure (p, p1, p2, p3) in the form of a pressure difference (Δp) and / or an interval length (Δt) for the duration of maintaining the rapid filling pressure level are varied.

Description

[0001] The present invention relates to a method and a control device for the event-dependent filling of a hydraulic clutch of a transmission for a vehicle. The invention further relates to a hydraulic clutch with such a control device.

[0002] A hydraulic clutch is a friction-based switching element in a drivetrain that can essentially assume three operating states: In the first (unactuated) state, the clutch input and output are completely separated, so no torque or rotational movement is transmitted. In the second (actuated) state, hydraulic pressure is applied, so that the transmission input and output are connected in such a way that torque or rotational movement is transmitted. In particular, the same rotational speed and direction are present at the transmission input and output. The third operating state describes a slipping operation of the clutch. In this state, the transmission input and output can have a speed difference or even different directions of rotation.The hydraulic coupling can be designed as a multi-plate coupling or as any other type of hydraulic coupling.

[0003] The vehicle in question is, for example, a work machine, such as a construction or agricultural machine. A reversing clutch is provided in the drivetrain, primarily in the transmission, to reverse the direction of travel. The method according to the invention can be applied to this clutch; however, all other hydraulic clutches in a (powershift, power-split, CVT) transmission can also be operated using this method.

[0004] From DE 10 2014 222 948 A1, it is known to implement the filling of the piston chamber via a pressure regulator. The pressure of the fluid flow supplied to the piston chamber can be adjusted to a setpoint specified by the pressure regulator. Furthermore, it is known to carry out the filling of the coupling in two phases. In a rapid filling phase, a rapid filling pressure is specified to the pressure regulator in order to regulate the hydraulic fluid supplied to the piston chamber to a relatively high pressure. This enables rapid filling of the coupling's piston chamber. In a subsequent filling equalization phase, a lower filling equalization pressure is specified to the pressure regulator to compensate for any filling differences that occurred during the rapid filling. At the end of the filling equalization phase, the coupling is at the engagement point.

[0005] DE 44 244 56 A1 relates to the control of an automatic transmission driven by an internal combustion engine, in which a shift from a first to a second gear ratio is achieved by opening a first clutch and closing a second clutch. An electronic control unit controls the pressure profile of the first and second clutches during the shifting process via electromagnetic valves. Based on input variables, the electronic control unit determines either a first or second shift mode. The first shift mode is an upshift during acceleration or a downshift during deceleration, and the second shift mode is a downshift during acceleration or an upshift during deceleration. In the first shift mode, the shift consists of a rapid filling phase, a fill compensation phase, a load transfer phase, a gradient setting phase, a sliding phase, a gradient reduction phase, and a closing phase.In the second circuit type, the circuit consists of a rapid filling phase, a filling compensation phase, a gradient setting phase, a sliding phase, a gradient reduction phase, a load transfer phase and a closing phase.

[0006] From DE 195 462 92 A1, a method for the automated coordination of the filling and positioning process of hydraulically actuated and hydraulically or electronically individually controllable switching elements is known, the filling and positioning process of which can be divided into a rapid filling phase and a filling compensation phase and has at least a rapid filling time, a rapid filling pressure, a filling compensation time and a filling compensation pressure as parameters, for the optimization of which two of the four parameters are specified and for the other two parameters an optimal value of the first parameter to be optimized is determined by means of a specified, time-dependent pressure profile, in which a pressure increase phase follows the rapid filling phase and the filling compensation phase, such that, starting from a respective predefinable initial value, this value is changed stepwise untiluntil a change in rotational speed occurs at the beginning of the pressure increase phase and the parameter to be optimized is determined, the process is carried out stepwise at the optimal value of the first parameter to be optimized and starting from the respective predefinable initial value of this parameter until a change in rotational speed occurs at least approximately simultaneously with the beginning of the pressure increase phase.

[0007] DE 196 203 28 A1 discloses a system for closing a friction connection in a motor vehicle with an automatic transmission, which includes a hydrodynamic converter, at least one planetary gear set, at least two switchable friction connections, which are preferably designed as friction clutches or transmission brakes, wherein the actuating cylinder of the friction connection to be closed for the predetermined direction of travel is pre-filled with hydraulic fluid after the direction of travel has been selected, until the friction surfaces are in contact without play, and the friction connection to be released for the predetermined direction of travel is separated.The friction connection to be closed is closed in such a controlled manner that the vehicle starts smoothly at engine idle as well as under any throttle demand without disproportionate engine revving, by increasing the hydraulic pressure as a function of time, whereby the control has a model-based control algorithm into which the rotational speeds of the engine, respectively converter pump wheel and converter turbine wheel, respectively friction connection primary side, as well as the moment of inertia of the engine and that of the converter turbine and the torque of the engine, converter pump wheel, converter turbine wheel, auxiliary unit consumer and friction connection as well as the converter characteristic curves parameters or input variables are taken.

[0008] DE 10 2007 013 495 A1 relates to a method for controlling an automated friction clutch of a dual-clutch transmission, which is arranged in the drivetrain of a motor vehicle between the drive shaft of a drive motor and the input shaft of a sub-transmission of the dual-clutch transmission and can be engaged and disengaged by means of a controllable clutch actuator, wherein the following method steps are carried out to determine a current value of the contact point of the friction clutch with the drive motor running and gears engaged in the respective sub-transmission: complete disengagement of the clutch, detection of the engine speed of the drive motor, detection of the speed of the input shaft of the sub-transmission, successive engagement of the clutch until a change in the speed of the input shaft of the sub-transmission in the direction of the engine speed of the drive motor of the clutch is detected.Determination of the current value of an actuating parameter proportional to the engagement degree of the clutch, calculation of the current contact point of the clutch by subtracting an offset value from the determined value of the actuating parameter, and complete opening of the clutch.

[0009] EP 2 019 234 A2 describes a method for operating an automatic transmission of a vehicle with several friction-fit switching elements whose transmission capabilities can be varied depending on actuation pressures adjustable via a hydraulic system. The actuation pressure of at least one switching element, which is in the open state, is subjected to a pressure fill value lower than the fill pressure of a filling equalization phase for at least a certain period of time and is then reduced again to a pressure level equivalent to the open state of the switching element when the piston element of the switching element in question is in its first end position.When a pressure is applied to a contact surface of the piston element, a total force component acts on the piston element, resulting from the pressure, a spring force, a spring mechanism acting on the piston element, and a frictional force acting on the piston element, such that movement of the piston element from its first end position towards its second end position is essentially prevented. After the specified time period, the volume of a piston chamber of the switching element, equivalent to the open state of the switching element, is at least approximately completely filled with hydraulic fluid.

[0010] DE 10 2009 028 150 A1 relates to a method for operating a drive train comprising a drive unit, a transmission with several switching elements and at least one clutch connected between the drive unit and an output, wherein the switching element or elements and the clutch or elements are actuated hydraulically or electro-hydraulically for closing or engaging them, such that the respective switching element and / or clutch to be closed is filled from an empty state.A control unit automatically detects the current operating situation of the drive train, whereby the control unit determines filling parameters for the respective switching element and / or coupling to be closed, depending on the detected operating situation of the drive train, on the basis of which the respective switching element and / or coupling to be closed is filled.

[0011] DE 10 2015 112 060 A1 concerns the operation of a powertrain disconnect clutch for a hybrid vehicle circuit. In one example, the pressure of a working fluid supplied to the powertrain disconnect clutch is adjusted in response to a rate of change of the accelerator pedal position. Furthermore, the pressure of the working fluid can be reduced in response to selected operating conditions.

[0012] From WO 2006 / 097209 A1, a control device for an automatic transmission of a vehicle is known, comprising a hydraulic control system controllable via an electrical transmission control unit. This system includes several pressure control valves electrically controlled by the transmission control unit and several switching valves and pressure regulating valves, each controllable by a hydraulic pilot pressure adjustable by the pressure control valves. Each switching element is assigned a separate pressure control valve. Furthermore, an engagement prevention valve is provided, which, in the direction of a first switching position, can be actuated against a spring mechanism with a control pressure of the first switching element to represent the reverse gear ratio, and which, in the direction of a second switching position, can be actuated with a pressure signal equivalent to the control pressure of the first switching element to represent the reverse gear ratio.A pressure supply line of the second switching element for representing the translation for reverse travel is blocked in the first switching position of the switching prevention valve and released in the second switching position of the switching prevention valve.

[0013] The present invention is based on the objective of proposing an improved method for filling a hydraulic coupling.

[0014] The problem is solved by a method, a control device, and a clutch according to the following claims. According to the method of the invention, a hydraulic clutch is switched from an unactuated state to an actuated state. In other words, the clutch is closed, whereby a slipping actuation state can also be achieved between the unactuated state and the actuated state.

[0015] The clutch has a piston chamber and a pressure regulator. The pressure regulator allows the hydraulic fluid supplied to the piston chamber to be regulated to a target pressure specified by the regulator. The hydraulic fluid can be oil or an oil mixture with appropriate additives. However, it can also be a fluid other than oil.

[0016] The procedure further includes the detection of a reversing request. This can be, in particular, a manual reversing instruction by a vehicle operator. In autonomously operated vehicles or when using driver assistance systems, the reversing request can also be triggered by a corresponding control unit, such as a vehicle control computer. In this context, reversing refers to a change in the vehicle's direction of travel. This is achieved, for example, by an overlapping circuit of two direction-of-travel couplings, where one direction-of-travel coupling is assigned to a gear ratio for forward travel and the other to a gear ratio for reverse travel. Consequently, a reversing request represents a signal that requests or initiates a reversing process.

[0017] Furthermore, the procedure includes setting and maintaining a rapid filling pressure level. This means that, in order to perform a reversing operation, a (partially) emptied clutch must first be filled with hydraulic fluid. A rapid filling pressure is then set, which is maintained for a defined period of time. This describes the maintenance of the rapid filling pressure level.

[0018] Furthermore, the procedure includes lowering the rapid filling pressure level to a leveling pressure. The rapid filling pressure decreases gradually until a leveling pressure is reached. Maintaining this leveling pressure for a defined period is called maintaining the leveling pressure. The leveling pressure is chosen so that the hydraulic coupling is just engaged, but no torque is yet transmitted.

[0019] The procedure classifies the reversing requirement based on specific events. As a result, parameters of the rapid filling pressure level vary depending on these events. Classifying the reversing requirement involves checking for characteristic events that can influence the transition of the hydraulic clutch from an unactuated to an actuated state. Fluid temperature, the degree of prior emptying of the clutch (completely empty or partially / fully filled), or even the output speed of a drive train can affect the time required to maintain the rapid filling pressure. Consequently, the actual clutch filling can fluctuate significantly; in particular, the actual pressure can sometimes deviate considerably from the (ideal) target pressure. This can lead to an under- or overfilled clutch, which negatively impacts reversing performance.Besides reduced comfort, poor reversing quality also leads to increased wear and tear or increased stress on the clutch.

[0020] Parameters for the rapid fill pressure level include the fill pressure itself or the duration for maintaining that fill pressure. In other words, a change in fill pressure can occur in the form of a pressure differential. Simultaneously or alternatively, the interval length for maintaining the rapid fill pressure level can be varied.

[0021] In a further development of the process, the filling pressure and interval length are varied such that a reduction in filling pressure results in a longer interval length. Conversely, an increase in filling pressure leads to a reduction in the interval length. This relationship follows logically from the relationship between filling pressure and filling time.

[0022] According to a first aspect of the invention, an event is characterized by the vehicle speed present at the time the reversing request is made. Thus, a slower reversing process may be desirable (or technically advantageous) when driving at a (comparatively) high vehicle speed, while a faster reversing process is required at a low vehicle speed. Besides increasing comfort, this also results in a less stressful impact on the drivetrain. As an example of a desired fast reversing process, reference is made to the digging of a wheel loader into a pile of material. In this case, the vehicle is already decelerated by the digging process itself, meaning less friction work has to be performed by the clutch, and at the same time, the vehicle is almost at a standstill at the time the reversing request is made.Furthermore, it is essential to execute and complete the reversing process as quickly as possible. This can also improve the overall performance of the vehicle, as it enables more efficient operation.

[0023] According to a second aspect of the invention, an event is characterized by a vehicle inclination present at the time the reversing request is made, particularly in the longitudinal direction of the vehicle. This means that whether the reversing occurs in the direction of a downhill slope or an uphill slope has an influence. For example, when reversing while traveling downhill towards an uphill slope (in the direction of the slope), the clutch must be engaged differently than in the opposite direction.

[0024] According to a third aspect of the invention, an event is characterized by the detection of a loading and / or unloading point. If a loading / unloading point is detected by suitable sensors, the parameters can, for example, be varied predictively. Suitable sensors include, by way of example, radar, lidar, optical / imaging, or GPS sensors. However, a loading / unloading process can also be inferred from the actuation / change in the actuation state of the hydraulic system by appropriate load-measuring sensors in the hydraulic system.

[0025] In addition to a loading / unloading point, an event can also be characterized by obstacle detection. The aforementioned sensors can sometimes be used for this purpose. If an obstacle is detected directly in front of the vehicle and a collision is likely, a rapid reversing maneuver could prevent a collision, while a slow reversing maneuver would cause one. Accordingly, a rapid reversing maneuver could be initiated even if a different reversing process would be required due to other events. Sometimes, a prioritization of different events can be implemented. This prioritization can be stored in a memory element or entered by an operator as individual preferences.

[0026] However, other events are also conceivable. For example, an upcoming maintenance interval or a wear limit or remaining service life of a component can characterize an event. It is also conceivable that the operator makes a pre-selection regarding maximum performance output or optimal vehicle lifespan.

[0027] With regard to the events described above, it should be noted that these, individually or in any combination, can influence the variation of the parameters.

[0028] The events described above can be assigned different values ​​for filling pressure and interval length, which can then be stored in a characteristic field. In its simplest form, this is a table in which the corresponding values ​​are assigned to the events. This table can be stored in the memory element. Data exchange with a cloud-based server is also possible via appropriate interfaces (for example, a wireless connection). It is also conceivable that the values ​​for filling pressure and interval length could be calculated in real time, taking the events into account. In particular, artificial intelligence in the form of neural networks or similar technologies could be used to optimize the assignment of these values.

[0029] According to a further aspect of the present invention, a control device for controlling the setpoint pressure of a pressure regulator of a hydraulic coupling is proposed. The setpoint pressure can be regulated by the pressure regulator, whereby the hydraulic fluid is supplied to the piston chamber. The control device is configured to execute the method according to the invention. In particular, the control device can include the storage element. A configuration of the control device for executing a method is understood to mean the specific programming of the device for executing the method.

[0030] Furthermore, the invention relates to a hydraulic coupling with a pressure regulator and a control device. The pressure regulator and the control device are configured to move the hydraulic coupling from the open state to the engagement point according to the method of one of the previously described embodiments. For an understanding of the individual features and their advantages, reference is made to the above explanations.

[0031] The invention is described in more detail using the figures. They show: Fig. 1: a diagram showing the course of the filling pressure over time; Fig. 2: a comparison of two diagrams showing the course of the filling pressure over time in two embodiments; Fig. 3: a schematic representation of a hydraulic coupling; Fig. 4: a flowchart of the process steps of the process according to the invention.

[0032] The diagram in Fig. Figure 1 shows the pressure p over time t with a target pressure A and an actual pressure B. Time t is plotted on the abscissa, while the pressure p is plotted on the ordinate. The target pressure A is shown as a solid line, and the actual pressure B is shown as a dashed line.

[0033] At time t0, a reversal request is made. The fill pressure p of the target pressure A is 0 at this point. At time t1, the fill pressure p abruptly increases to p3. This value is maintained until time t2. The interval length Δt is the difference between t2 and t1. Between time t2 and time t3, the fill pressure p drops to a value p1. Within the interval bounded by t2 and t3, the target pressure A exhibits a strictly monotonic, continuous gradient. The value p1 is maintained until time t4. At time t4, the filling process is complete.

[0034] The interval length Δt defines the range in which the rapid filling pressure level is set and maintained at the filling pressure p3. Conversely, the time points t3 and t4 define the range in which the compensating filling pressure level is set and maintained. The value p3 of the filling pressure is greater than the value of the filling pressure p1.

[0035] In contrast to the target pressure A, the actual pressure B follows the amplitudes of the filling pressure p with a time lag and also in a different way. The increase in the filling pressure p occurs significantly later, shortly before reaching time t2. Furthermore, the curve does not show a sudden increase, but rather an almost exponential rise. A maximum of the actual pressure B is only reached after time t2, and at the same time, the maximum value is also significantly higher than the value p3.

[0036] Immediately after reaching its maximum, the actual pressure p of the fill level B drops sharply until time t3, at which point it passes through the fill level p1 and then briefly dips further. Between times t3 and t4, the actual pressure B asymptotically approaches the fill level p1. In addition to a time delay in the start of the actual filling process, a temporal compression occurs, and pressure peaks are reached compared to the target pressure A.

[0037] Fig. Figure 2 shows a comparison of two diagrams. On the left side, the previously shown in Fig. Diagram 1 is shown. On the right side, a pressure curve for a target pressure A and an actual pressure B over time is also shown. In this case, however, the parameters of the rapid fill pressure were varied. Instead of setting the value p3 for the rapid fill pressure at time t1, the fill pressure p only increases to a value p2, where p2 lies between p1 and p3, resulting in a pressure difference Δp. At the same time, the interval length Δt was adjusted, in this case increased. The curve of the target pressure A from time t2 corresponds to the representation according to [reference missing]. Fig. 1.

[0038] The course of the actual pressure B, however, deviates more strongly from that in Fig. The representation described in section 1. The variation in the interval length Δt results in the increase in the actual pressure being closer to time t1 than to time t2 (in the representation according to Fig. (1, this is the reverse). Furthermore, the target pressure A is already reached by the actual pressure B when approximately half of the interval length Δt is reached. In other words, the target pressure A is reached by the actual pressure B within the interval length Δt. The deviation between target pressure A and actual pressure B between times t2 and t3 is also significantly smaller; essentially, the actual pressure B follows the target pressure A. As a result, by adjusting the rapid filling pressure level and the interval length Δt, the target and actual pressures A and B are considerably closer, thus optimizing the filling of the coupling.

[0039] Fig. 3 shows Fig. Figure 1 schematically shows a hydraulic coupling 1. The coupling 1 has multi-plate clutches 2 that can be engaged by axial relative displacement. When the multi-plate clutches 2 are engaged, a torque can be transmitted between them. The relative displacement of the multi-plate clutches 2 is initiated by a piston 3, which is mechanically connected to one of the multi-plate clutches 2. The piston 3 adjoins a piston chamber 4. By changing the pressure of a fluid, for example oil, located in the piston chamber 4, the piston 3 can be moved and the coupling 1 engaged.

[0040] Fig.Figure 4 shows a highly simplified flowchart illustrating the process steps of the method according to the invention. In a first process step I, a reversing request is initially detected. In a second process step II, the reversing request is classified based on events. Depending on the classification, parameters of the rapid filling pressure level, for example, the value of the filling pressure p and / or the interval length Δt, are varied.

[0041] In a third process step III, the determined value for the rapid filling pressure level is set and maintained before the filling pressure p is reduced to a filling equalization pressure level in a fourth process step IV. Finally, in a fifth process step V, the filling equalization pressure level is set and maintained.

Claims

[1] Method carried out by a control device (8) for transferring a hydraulic coupling (1) from the unactuated state to an actuated state, wherein the coupling (1) has a piston chamber (4) and a pressure regulator (6) by means of which a hydraulic fluid to be supplied to the piston chamber (4) can be regulated to a set pressure (A), comprising - detection of a reversal request (I); - setting and maintaining a rapid fill pressure level (III); - a reduction of the rapid filling pressure level to a filling equalization pressure level with a gradient profile (IV); - setting and maintaining a level of pressure equalization (V); characterized by, that a classification of the reversing request is based on a vehicle speed present at the time of the reversing request, a vehicle inclination present at the time of the reversing request, a detection of a loading and / or unloading point and / or an obstacle detection (II), and that depending on this classification a filling pressure (p, p1, p2, p3) in the form of a pressure difference (Δp) and / or an interval length (Δt) for the duration of holding the rapid filling pressure level are varied. [2] Method according to claim 1, characterized by , that the filling pressure (p, p1, p2, p3) and the interval length (Δt) vary such that a reduction in the filling pressure (p, p1, p2, p3) results in a larger interval length (Δt) and vice versa. [3] Method according to any one of the preceding claims, characterized by, that the vehicle speed present at the time of the reversing request, the vehicle inclination present at the time of the reversing request, the detection of a loading and / or unloading point and / or the obstacle detection are assigned values ​​for filling pressure (p, p1, p2, p3) and interval length (Δt) in a characteristic field. [4] Control device (8) for controlling a setpoint pressure (p) of a pressure regulator (6) of a hydraulic coupling (1), with which a hydraulic fluid to be supplied to a piston chamber (4) of the coupling (1) can be regulated to a setpoint pressure (A) specified to the pressure regulator (6), wherein the control device (8) is configured to carry out the method according to one of the preceding claims. [5] Hydraulic coupling (1) with a pressure regulator (6) and a control device (8) according to claim 4 for transferring the hydraulic coupling (1) from the open state to the contact point according to the method according to one of claims 1 to 3.

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