Interrelated power delivery controls – including engine control – Plural engines – Electric engine
Reexamination Certificate
2001-04-02
2003-01-14
Wright, Dirk (Department: 3681)
Interrelated power delivery controls, including engine control
Plural engines
Electric engine
Reexamination Certificate
active
06506139
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a transmission, especially for motor vehicles, with at least two shafts, i.e. an input shaft, an output shaft, and in some cases a countershaft. The transmission has at least two or more pairs of gears, each pair consisting of a free gear and a fixed gear. The free gears have shift clutches by which they can be selectively coupled or uncoupled in rotation-locking engagement with a first shaft. The fixed gears are permanently tied to share the rotation of their shaft(s).
Transmissions of this kind are generally known in the field of automotive technology. They suffer from the draw back that they cannot transmit power during gear shifts. Consequently, there is an interruption in the tractive force when shifting gears to change the transmission ratio.
Furthermore, in vehicles with a transverse layout of the combustion engine, the axial space available for the power train is limited, which imposes severe design constraints on integrating an axially mounted electro-mechanical energy converter for generating electrical energy from kinetic energy and/or as a supplementary drive source. However, the use of electro-mechanical energy converters performing multiple functions is a desirable feature in modern power train concepts.
OBJECT OF THE INVENTION
It is therefore the object of the present invention to improve the design of a transmission of the aforementioned kind and to optimize the spatial layout, so that an electro-mechanical energy converter can be integrated in the transmission to perform the functions of, e.g., a starter for the combustion engine, an electric generator, or a supplementary drive source. In the latter function, the electro-mechanical energy converter serves to eliminate or at least reduce the temporary loss in traction during gear shifts.
SUMMARY OF THE INVENTION
According to the invention, the foregoing objective is met by a transmission, specifically a shiftable gear transmission with at least two shafts, i.e., an input shaft, an output shaft, and in some cases a countershaft. The input shaft is driven by a combustion engine by means of a crankshaft. The transmission has two or more gear pairs and an electro-mechanical energy converter. The electro-mechanical energy converter has a rotor and a stator. At least one clutch in the transmission serves to couple the electro-mechanical energy converter to at least one of the shafts.
The rotor can be coaxially arranged on the input shaft, output shaft, or another shaft of the transmission, with a clutch between the rotor and the shaft. A second shaft may also be equipped to be coupled to the electro-mechanical energy converter through a clutch. The electro-mechanical energy converter can also have its own rotor shaft, running parallel to one of the transmission shafts, where the rotor shaft can be driven or can drive one of the transmission shafts, e.g., by way of one of the fixed gears or through a separate gear provided specifically for this purpose. Belt drives or chain drives, including those with an automatically variable ratio such as a continuously variable cone-pulley transmission, are especially advantageous. As a further possibility, the electro-mechanical energy converter could be coupled to a flywheel, particularly a flywheel of the combustion engine.
A transmission according to the invention can, in principle, include a shiftable gear transmission with at least two shafts, e.g., an input shaft, an output shaft, and in some cases countershaft. The transmission has at least two or more pairs of gears, each pair consisting of a first gear (also called free gear) and a second gear (also called fixed gear). The free gears have shift clutches or sliding sleeves by which they can be selectively coupled or uncoupled in rotation-locking engagement with a first shaft. The fixed gears are permanently locked to a second shaft. To change the transmission ratio, at least one of the shift clutches or sliding sleeves is designed to be moved automatically by an actuator, e.g., an electric motor, electro-magnet, or by a hydraulic or pneumatic device. A shift clutch can be a friction-locking or form-locking clutch. Shift clutches as well as sliding sleeves (which serve to couple and uncouple the connections of free gears to their shafts) can be equipped with appropriate synchronization means.
In a transmission according to the invention, it can further be of advantage if the electro-mechanical energy converter can be switched selectively between the at least two shafts, e.g., between the input shaft and the output shaft of the transmission. In another embodiment of the invention, only one shaft, i.e., either the output shaft or the input shaft of the transmission, is configured to be connectable to the electro-mechanical energy converter by means of a clutch that can be moved into and out of engagement by an automated actuator of the kind described above.
To contribute further to the solution of the problem targeted by the invention, the electro-mechanical energy converter can be operated in such a way that during a gear shift for changing the transmission ratio from one level to another, the electro-mechanical energy converter is used to reduce the temporary loss in vehicle traction by delivering a driving torque to the output shaft. For example, in a gear shift with the steps of disengaging the start-up clutch, shifting out of the current gear, shifting into the new gear, and re-engaging the start-up clutch, the electric motor generator can be activated at the point where the start-up clutch begins to slip, i.e., where it no longer transmits the full amount of the engine torque to the input shaft of the transmission. The decrease and loss of torque passing through the start-up clutch can be at least partially compensated by an increasing contribution of torque from the electro-mechanical energy converter. Since the time interval for a gear shift is very short, it can be advantageous if the electro-mechanical energy converter is designed for a nominal continuous-duty power capacity that is less than the peak amount of torque which has to be compensated during a gear shift. Thus, the electro-mechanical energy converter will be under a thermal overload during a short time interval, e.g., at up to 300% of nominal power capacity, but this has the advantage that the dimensions of the motor/generator can be kept at a minimum. The deployment of the torque generated by the electro-mechanical energy converter is advantageously controlled in a manner where the torque on the output shaft varies smoothly, e.g., in a linear or other continuous transition, from the torque level required with the previously engaged gear to the torque level required for the new gear level. Especially with motor/generators of very small dimensions, it can also be advantageous if the traction-supporting torque of the motor/generator available during the interruption in vehicle traction is kept smaller than the lesser of the torques required for the previous or new gear ratio, e.g., between 100% and 30%, but preferably between 100% and 50% of the torque needed for the gear that requires the lower amount of torque.
It is further advantageous, if the transmission input shaft can be connected to the crankshaft of the combustion engine, e.g., through a start-up clutch that is controlled either automatically by means of an actuator or manually. The start-up clutch can be a dry-friction clutch, laminar disc clutch, or a hydrodynamic clutch such as a hydrodynamic torque converter or a fluid coupling (also called Fottinger coupling) which in some cases may have a converter-bypass clutch. Also advantageous is a design where the start-up clutch is arranged on a dual-mass flywheel. The start-up clutch can be advantageously accommodated in the clutch bell housing between the combustion engine and the transmission, or it can be arranged inside the transmission. Furthermore, the clutch that connects the electro-mechanical energy converter to the input shaft can be configured as a dual clutch together with the start-up
Brandt Martin
Hirt Gunter
LuK Lamellen und Kupplungsbau Beteiligungs KG
Wright Dirk
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