Abstract: A process for determining a setpoint rotational speed of a work machine engine, having a continuously variable transmission, based on operation of power hydraulics. The setpoint rotational speed for highly productive operation is determined, without knowledge current operation of the power hydraulics, by a basic engine speed setting. With knowledge of the current operating state, the setpoint rotational speed is determined by the basic speed settings and low or high engine speed settings. The low speed setting alone determines setpoint rotational speeds that are lower than the basic speed setting or a combination of the low and basic speed settings. The high speed setting alone determines setpoint rotational speeds that are higher than the basic speed setting or a combination of the basic and high speed settings. The speed settings can comprise a setpoint rotational speed range of above a reciprocal transmission range of the variable transmission.

Abstract: A process for determining a setpoint rotational speed of a work machine engine, having a continuously variable transmission, based on operation of power hydraulics. The setpoint rotational speed for highly productive operation is determined, without knowledge current operation of the power hydraulics, by a basic engine speed setting. With knowledge of the current operating state, the setpoint rotational speed is determined by the basic speed settings and low or high engine speed settings. The low speed setting alone determines setpoint rotational speeds that are lower than the basic speed setting or a combination of the low and basic speed settings. The high speed setting alone determines setpoint rotational speeds that are higher than the basic speed setting or a combination of the basic and high speed settings. The speed settings can comprise a setpoint rotational speed range of above a reciprocal transmission range of the variable transmission.

Abstract: A method for performing a cold start in a vehicle having a power-spat transmission with a hydrostatic element comprising hydrostatic units. Several cold-start steps are performed sequentially for a cold start, the length of at least one of the cold-start steps is adapted depending on a temperature representing the start temperature of the power-split transmission. A state of the power-split transmission deviating from the temperature of the power-split transmission is monitored, during the execution of at least one of the cold-start steps, and, depending on this state, a transition from the respective cold-start steps to the subsequent cold-start step is performed, thus adapting the length of time of the respective cold-start steps.

Abstract: A method for operating a hydrostatic transmission of a drive train of a motor vehicle. An automatic creep function of the motor vehicle is made possible by the hydrostatic transmission. in order to be able to realize the creep function in a reliable manner, a current value of a first parameter that is independent of a pedal position of an accelerator and a current value of a second parameter that is dependent on the pedal position are compared to each another. The creep function is then activated as long as the current value of the first parameter is greater than the current value of the second parameter. In the context of the creep function, the current value of the first parameter is used to determine a current value of a target delivery quantity of a hydrostatic machine of the transmission operated as a pump.

Abstract: A method for the operation of a vehicle drive-train of a working machine having a drive motor, a transmission whose transmission ratio can be varied continuously, and a drive output. A rotational speed (nmot) of the drive motor can be varied by the driver, by the driver's actuation of a first control element (50), within a rotational speed range (53) delimited by an upper characteristic line (nmoto) and a lower characteristic line (nmotu). The characteristic lines (nmoto, nmotu) are functions of a reciprocal transmission ratio (irez) of the transmission. Furthermore, the rotational speed (nmot1) of the drive motor that can be set by the driver by way of the first control element (50), can be influenced by the driver's actuation of a second control element (51) and as a function of an operating condition of the working machine.

Abstract: A method of controlling a continuously variable transmission for a vehicle. The continuously variable transmission has a hydrostat with a position-regulating valve and is designed to co-operate in driving connection with a drive input shaft and a drive output shaft such that when the position-regulating valve is energized, the hydrostat is adjusted to accelerate the vehicle. The method includes monitoring the energization of the position-regulating valve cyclically by a safety function. The safety function is provided in order to recognize undesired energization of the position-regulating valve that leads to unwanted acceleration of the vehicle, and then to separate the transmission at least from the drive output shaft so as to prevent unwanted acceleration of the vehicle. The safety function is triggered at least when a limit value for the energization of the position-regulating valve is exceeded.

Abstract: A method for operating a vehicle drive-train having a continuously power-branched transmission with secondary coupling. In the open operating condition of reversing clutches of a reversing gear unit, torque applied in the area of a drive output can be supported by a range group in the area of a variator. In the event of a command to interrupt the power flow between a drive engine and the drive output, it is checked whether the vehicle is on an inclined surface and if the result of that inquiry is positive, the power flow between the drive engine and the transmission is interrupted at the latest when the rotational speed of the drive output is reduced to zero by opening the reversing clutches, while the active connection between the drive output and the variator is maintained by way of the range group.

Abstract: A method of controlling a continuously variable transmission for a vehicle. The continuously variable transmission has a hydrostat with a position-regulating valve and is designed to co-operate in driving connection with a drive input shaft and a drive output shaft such that when the position-regulating valve is energized, the hydrostat is adjusted to accelerate the vehicle. The method includes monitoring the energization of the position-regulating valve cyclically by a safety function. The safety function is provided in order to recognize undesired energization of the position-regulating valve that leads to unwanted acceleration of the vehicle, and then to separate the transmission at least from the drive output shaft so as to prevent unwanted acceleration of the vehicle. The safety function is triggered at least when a limit value for the energization of the position-regulating valve is exceeded.

Abstract: A method is described for determining a reference value of an actuating current that corresponds to a defined operating point of an electro-hydraulically actuated frictional shifting element of a continuously variable power-branched transmission, at which the shifting element transmission capacity is zero, and starting from which an increase of actuating force immediately increases the transmission capacity. The actuating current reference value of the shifting element, when closed with a further shifting element decoupled from the transmission output and when a transmission input rotational speed is higher than a defined threshold, is reduced until a rotational speed difference between the rotational speeds of the shifting element halves exceeds a predefined limit value such that, at the time when the limit value is exceeded, the reference value of the actuating current is the reference value of the actuating current that corresponds to the defined operating point of the shifting element.

Abstract: A device for varying the swept volumes of first and second hydraulic machines, whose swept volumes depends upon pivoting positions of adjustable axes thereof which can be connected to one another by first and second lines. The axes can be coupled to a piston-cylinder device which is adjustable by a control valve unit for pivoting the axes. Pressures in the area of the hydraulic machines can be limited by the control valve unit. The control valve unit can be coupled to a respective first or second line with the highest pressure. A device for determining an existing actual pressure is located upstream of the control valve unit, at least in the area of one of the first and the second lines that connects with the first and the second hydraulic machines. The control valve unit can be actuated based on the actual pressure value determined by the device.

Abstract: A method for the operation of a vehicle drive-train of a working machine having a drive motor, a transmission whose transmission ratio can be varied continuously, and a drive output. A rotational speed (nmot) of the drive motor can be varied by the driver, by the driver's actuation of a first control element (50), within a rotational speed range (53) delimited by an upper characteristic line (nmoto) and a lower characteristic line (nmotu). The characteristic lines (nmoto, nmotu) are functions of a reciprocal transmission ratio (irez) of the transmission. Furthermore, the rotational speed (nmot1) of the drive motor that can be set by the driver by way of the first control element (50), can be influenced by the driver's actuation of a second control element (51) and as a function of an operating condition of the working machine.

Abstract: A method for determining a draining behavior of a hydraulically actuated transmission shifting element. By applying actuating pressure, the shifting element is changed from a completely drained, open operating condition to a completely filled closed operating condition, and the reference filling time, until the closed condition has been reached, is determined. Upon recognition of the closed condition, then by adjusting the actuating pressure for a predefined draining time, the shifting element is changed to its open condition and, thereafter, again completely filled and closed. Upon recognition of the closed condition, the shifting element is actuated direction toward the open condition by reducing the actuating pressure. Then, before completely opening, the shifting element is again returned to its closed operating condition and the filling time, until the partially drained shifting element has reached the completely filled and closed operating condition, is determined.

Abstract: A method for operating a vehicle drive-train having a continuously power-branched transmission with secondary coupling. In the open operating condition of reversing clutches of a reversing gear unit, torque applied in the area of a drive output can be supported by a range group in the area of a variator. In the event of a command to interrupt the power flow between a drive engine and the drive output, it is checked whether the vehicle is on an inclined surface and if the result of that inquiry is positive, the power flow between the drive engine and the transmission is interrupted at the latest when the rotational speed of the drive output is reduced to zero by opening the reversing clutches, while the active connection between the drive output and the variator is maintained by way of the range group.

Abstract: A method for determining a draining behavior of a hydraulically actuated transmission shifting element. By applying actuating pressure, the shifting element is changed from a completely drained, open operating condition to a completely filled closed operating condition, and the reference filling time, until the closed condition has been reached, is determined. Upon recognition of the closed condition, then by adjusting the actuating pressure for a predefined draining time, the shifting element is changed to its open condition and, thereafter, again completely filled and closed. Upon recognition of the closed condition, the shifting element is actuated direction toward the open condition by reducing the actuating pressure. Then, before completely opening, the shifting element is again returned to its closed operating condition and the filling time, until the partially drained shifting element has reached the completely filled and closed operating condition, is determined.

Abstract: A method is described for determining a reference value of an actuating current that corresponds to a defined operating point of an electro-hydraulically actuated frictional shifting element of a continuously variable power-branched transmission, at which the shifting element transmission capacity is zero, and starting from which an increase of actuating force immediately increases the transmission capacity. The actuating current reference value of the shifting element, when closed with a further shifting element decoupled from the transmission output and when a transmission input rotational speed is higher than a defined threshold, is reduced until a rotational speed difference between the rotational speeds of the shifting element halves exceeds a predefined limit value such that, at the time when the limit value is exceeded, the reference value of the actuating current is the reference value of the actuating current that corresponds to the defined operating point of the shifting element.

Abstract: A device for varying the swept volumes of first and second hydraulic machines, whose swept volumes depends upon pivoting positions of adjustable axes thereof which can be connected to one another by first and second lines. The axes can be coupled to a piston-cylinder device which is adjustable by a control valve unit for pivoting the axes. Pressures in the area of the hydraulic machines can be limited by the control valve unit. The control valve unit can be coupled to a respective first or second line with the highest pressure. A device for determining an existing actual pressure is located upstream of the control valve unit, at least in the area of one of the first and the second lines that connects with the first and the second hydraulic machines. The control valve unit can be actuated based on the actual pressure value determined by the device.

Abstract: A method of operating a vehicle drive-train during a starting process. The drive-train has a drive mechanism which can couple a continuously-variable power-branched transmission in which a plurality of transmission ratios can be engaged. The transmission ratios can be varied continuously by adjusting a variator, the transmission driving a drive output. A force flow between the drive mechanism and the drive output can be produced by a frictional shifting element by appropriately adjusting the transmission capacity of the shifting element. When a start command is issued, a starting transmission ratio is engaged in the area of the transmission device. During the engagement of the starting transmission ratio the transmission capacity of the frictional shifting element is adjusted to values greater than zero.

Abstract: A method of operating a vehicle drive-train during a starting process. The drive-train has a drive mechanism which can couple a continuously-variable power-branched transmission in which a plurality of transmission ratios can be engaged. The transmission ratios can be varied continuously by adjusting a variator, the transmission driving a drive output. A force flow between the drive mechanism and the drive output can be produced by a frictional shifting element by appropriately adjusting the transmission capacity of the shifting element. When a start command is issued, a starting transmission ratio is engaged in the area of the transmission device. During the engagement of the starting transmission ratio the transmission capacity of the frictional shifting element is adjusted to values greater than zero.