Machine element or mechanism – Gearing – With fluid drive
Reexamination Certificate
2000-01-28
2001-08-14
Marmor, Charles A (Department: 3681)
Machine element or mechanism
Gearing
With fluid drive
C074S733100
Reexamination Certificate
active
06272950
ABSTRACT:
BACKGROUND OF THE INVENTION
It is generally necessary in the operation of vehicle drives because of relatively narrow usable speed range of internal combustion engines, transmission and gear devices which allow load-dependent or speed-dependent operation of the drive train are used with such engines. Since, on account of their performance characteristics, internal combustion engines can in principle only provide a low torque at low rotational speeds, it is also necessary to provide a separating device or clutch which makes possible the starting of a vehicle or running of an engine. Furthermore, in particular in the case of vehicles, synchronizing devices which allow shifting between different transmission stages during operation or during the journey are conventionally used in the gearbox. Corresponding gearboxes are of a complex structural design.
Mechanical, manually operated gearboxes without a clutch or synchronizing device are also used in vehicles with internal combustion engines, or in combination with hydrostatic gearboxes, where the hydraulic pump and hydraulic motor of which are connected in a closed circuit. The hydrostatic gearbox serves in this case merely as a clutch or torque converter. When synchronizing devices are absent, it is often necessary to stop the vehicle for changing the transmission ratio, or at least reducing the speed to a minimum in order to avoid considerable mechanical wearing of the manually operated gearbox.
It is therefore the object of the present invention to provide a drive train in which the hydrostatic gearbox acts together with an electronic control unit to make rapid and dependable separation or synchronized gear changing possible in a simple way without further coupling or synchronizing devices in the gearbox. At the same time, the object of the method of controlling the drive train is to control the change between different transmission ratios of the gearbox during the journey by means of digital electronics.
SUMMARY OF THE INVENTION
A drive train for a vehicle has an internal combustion engine, a clutchless gearbox, which can be shifted by means of an electronic control unit and by means of actuating devices and has at least two transmission stages, and a hydrostatic gearbox. The shiftable clutchless gearbox may be designed in particular without additional synchronizing devices. The hydrostatic gearbox comprises a hydraulic pump and a hydraulic motor, which are connected in a closed circuit. The arrangement is such that the rotational speed of the hydraulic motor is controllable in dependence on a control signal to the adjusting device of the hydraulic pump and/or to the adjusting device of the hydraulic motor. The control unit calculates the control signal by means of setpoint input via an accelerator pedal or as a function of the rotational drive speed of the internal combustion engine, with shifting of the transmission stages being possible by means of the actuating devices. The control unit is designed such that it controls the adjusting device of the hydraulic pump as well as the actuating devices for the shiftable clutchless gearbox for the electronic synchronization of the latter by means of a characteristic curve. This characteristic curve represents the speed ratio of the hydraulic motor to the hydraulic pump in dependence on an actuating signal to the adjusting device of the hydraulic pump for a loadfree state of the gearbox.
The configuration allows a synchronization of the shiftable clutchless gearbox in a simple and reproducible way without the use of conventional synchronizing devices. The hydrostatic gearbox compensates for a sudden change in the transmission stage occurring during shifting. Consequently, a change between different transmission ratios of the gearbox during the journey by means of the corresponding digital electronics is also possible.
The control unit is designed such that the characteristic curve, which can be determined in the form of a learning curve as a setup before putting the drive train into operation, can be stored there. For determining the learning curve, the actuating signals to the adjusting devices of the hydraulic pump and/or hydraulic motor are continuously increased until the maximum speed ratio of the hydraulic motor to the hydraulic pump is reached. This determinability and storability of the characteristic curve in the control unit allows simple and reproducible controlling of the drive train.
It is preferred that a proportional valve to be provided, to adjust the pivoting angle of the hydraulic pump to adjust its volumetric delivery. The required actuating signal is supplied by the control unit on the basis of a setpoint input via an accelerator pedal or in dependence on the drive speed of the internal combustion engine, which can be picked up by means of a first speed sensor.
For ensuring the function of the drive train, it is preferred for a switch which delivers to the control unit a signal as to whether the gearbox is in a neutral position or whether a transmission stage (gear) is engaged to be provided on the shiftable gearbox.
It is preferred that for the actuating devices to be shifted, valves or electromagnets be activated by the control unit. They can be disengaged again by means of spring force as soon as a corresponding switching signal of the control unit is reset and the gearbox is brought by the control system into a loadfree state by the actuating signal as determined by the characteristic curve.
For the electronic synchronization of operation, a second speed sensor, for measuring the input speed of the gearbox, and a third speed sensor, for measuring the output speed of the gearbox, are provided in the region of the input shaft and output shaft, respectively, of the gearbox.
The method of controlling a drive train comprised of an internal combustion engine, a clutchless gearbox without a mechanical synchronizing device and a hydrostatic drive or a hydrostatic gearbox with a hydraulic pump, a hydraulic motor and a control unit, involves the control unit calculating a maximum achievable synchronous speed of the hydraulic motor. The appropriately electronically controlled hydrostatic gearbox is then used to compensate for the sudden change in the transmission stage. The calculation by the control unit takes place by means of a characteristic curve. The curve represents the speed ratio of the hydraulic motor to the hydraulic pump which are in dependence on an actuating signal to the adjusting device of the hydraulic pump and/or to the adjusting device of the hydraulic motor for a loadfree state of the gearbox.
This method of using a characteristic curve makes possible the optimum, dependable and rapid activation of the system with regard to the maximum possible speeds in the respective transmission ratios of the gearbox of the drive train by calculating the maximum possible synchronous speed of the hydraulic motor in dependence on the speed of the hydraulic pump.
It is preferred for the control unit to activate actuating devices for the transmission stages of the gearbox in a way corresponding to a desired operating point on the characteristic curve. Consequently, the control electronics can derive the actuating signal respectively required to operate the gearbox in a loadfree state for disengaging in a particularly simple and rapid manner on the basis of the current operating point on the characteristic curve.
It is particularly preferred in the method of controlling the drive train according to the invention to record the characteristic curve in the form of a learning curve as a set-up at least for each new hydrostatic drive or for each new hydrostatic gearbox. This makes possible an individual adaptation to the respective components used and consequently dependable functioning of the drive train.
In a preferred embodiment of the method, the respectively current transmission ratio of the gearbox during the journey is shifted into the neutral position, by de-activating a corresponding output of the control unit, and by bringing the gearbox into the loadfree state fo
Braun Tom
Taylor Lloyd
Marmor Charles A
Pang Roger
Sauer-Danfoss Inc.
Zarley McKee Thomte, Voorhees & Sease PLC
LandOfFree
Drive train for a vehicle and method of controlling a drive... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Drive train for a vehicle and method of controlling a drive..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Drive train for a vehicle and method of controlling a drive... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2441890