Patent Application
20060102137
This application claims priority under 35 USC ยง119 to European Patent Application Nos. 04105806.6, filed Nov. 16, 2004 and 04105838.9 filed Nov. 17, 2004.
1. Field of the Invention
The present invention relates to systems and methods for controlled shutdown and direct starting of an internal combustion engine.
2. Background Art
One concept for improving fuel consumption of a vehicle is to shut down the internal combustion engine if there is no requirement for power instead of allowing it to continue to idle. One application is stop and go traffic that may occur in traffic jams on freeways as well as at traffic lights, railroad crossings, etc.
One problem with the concepts that shut down the internal combustion engine when it is not required to improve fuel consumption is the necessity to restart the internal combustion engine. When the internal combustion engine is shut down in an uncontrolled way, the crankshaft and the camshaft stop in an unknown random position. Consequently, the position of the pistons in the individual cylinders is also unknown. Accurate crankshaft position information is, however, useful for restarting the engine in an uncomplicated manner that is as fast and efficient as possible and thus saves fuel. For example, in engines with direct injection, it is possible to start or restart the engine directly from the stationary state without a starter motor by injecting fuel directly into the combustion chambers and igniting the fuel/air mixture using a spark plug. To be carried out successfully, it is advantageous if the crankshaft is at or near a specific position at the commencement of the starting so that at least one piston is in a position where a fuel injection and subsequent ignition of the air/fuel mixture lead to movement of the piston within the cylinder. In a four-stroke internal combustion engine, the piston would have to be in the expansion or working stroke with at least one associated exhaust valve closed. As such, this method for direct starting or restarting requires an accurate indication of the crankshaft position or piston position to select appropriate cylinders for the fuel injection to start the engine.
In an internal combustion engine equipped with an electronically regulated ignition and/or an electronically regulated injection, crankshaft or camshaft sensors may be used to control the ignition and injection timing. However, these sensors require rotation of the crankshaft to provide a signal and provide ambiguous information for a number of cylinder firings immediately after starting or restarting the engine so that some time is required to synchronize the crank angle position and the engine control parameters. In addition, devices have to be provided for starting or restarting the internal combustion engine, such as a conventional starter motor, electric motor, or a similar device suitable for rotating the crankshaft.
Various concepts have been proposed in the prior art for controlling the stopping position of the crankshaft (or adjusting the position after the engine is stopped) and for restarting the engine. These concepts may generally be categorized as either active or passive. The active adjustment devices either require additional components, such as an additional electric motor, to apply an adjustment torque, or operate using an additional fuel injection or ignition in the same way as when selective combustion processes are initiated in order to set the predefined crank angle position. Concepts that employ active devices that require additional fuel or electrical energy are contrary to the basic goal of shutting down the engine to save fuel or energy to improve fuel economy.
Passive adjustment devices may use the rotational movement of the crankshaft during shut down after fuel and/or ignition have ended to control the stopping position of the crankshaft in a predefined advantageous position. For example, an intake/exhaust (gas exchange) valve control system may be used as a passive adjustment device to exert a stopping or braking force on the engine or crankshaft to control deceleration and stopping position. However, many of the disclosed concepts are not suitable for controlling the stopping position of the crankshaft with the necessary accuracy to facilitate direct restart.
A system and method for controlling stopping position of a crankshaft during shutdown of an internal combustion engine include influencing fluid pressure to influence drive torque of a corresponding fluid pump driven by the crankshaft so that the crankshaft stops in a position favorable for restarting.
In one embodiment of the present invention a power steering system includes a controllable variable flow device to change pressure within the power steering system to increase or decrease the corresponding drive torque of the power steering pump during shutdown. Another embodiment of the invention includes a fuel distribution system with a controllable variable flow device to change pressure within the fuel distribution system to increase or decrease the corresponding drive torque of the fuel pump. The controllable variable flow device may include a valve and/or a variable throughput pump.
The present invention provides a number of advantages. For example, the present invention controls one or more engine fluid pumps that are already included on conventional engines to carry out a controlled shutdown so that additional adjustment devices are unnecessary. The present invention uses passive adjustment rather than active adjustment to place the crankshaft in a favorable position for restarting. The fluid pump acts as a passive adjustment device that exerts a torque on the crankshaft until the crankshaft comes to a standstill in a desired position. Use of a passive adjustment device provides the advantage that its energy consumption is lower because it does not initiate a rotational movement of the crankshaft but instead controls deceleration of the existing rotational movement of the crankshaft and is therefore energy and fuel efficient.
The above advantages and other advantages and features of the present invention will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
Throughout the description of the preferred embodiments of the present invention, the same reference numerals have been used for components having the same or substantially similar function as a previously described component such that the description is not unnecessarily repeated.
As those of ordinary skill in the art will understand, various features of the present invention as illustrated and described with reference to any one of the embodiments or Figures may be combined with features illustrated in one or more other embodiments or Figures to produce embodiments of the present invention that are not explicitly illustrated or described. The combinations of features illustrated provide representative embodiments for typical applications. However, various combinations and modifications of the features consistent with the teachings of the present invention may be desired for particular applications or implementations.
The internal combustion engine 1 has four (n=4) cylinders 2a, 2b, 2c, 2d and a fuel pump 4 driven by crankshaft 3. Fuel pump 4 is supplied with fuel via inlet 5 from a fuel tank container 7. The fuel is fed by fuel pump 4 from the inlet 5 to the outlet opening 6 into a composite fuel line 8 which adjoins the outlet.
Four (n=4) fuel lines 9a, 9b, 9c, 9d branch off composite fuel line 8 with each leading to one of the four cylinders 2a, 2b, 2c, 2d to supply the cylinders with fuel.
To influence the drive torque of fuel pump 4, a fuel return line 11 with a shut-off element 12 is provided and coupled to composite fuel line 8 downstream of fuel lines 9a, 9b, 9c, 9d. Fuel return line 11 and shut-off element 12 serve to influence the pressure in the fuel lines 8, 9a, 9b, 9c, 9d and thus serve as means 10 for controlling the necessary drive torque of the fuel pump 4. A valve is used as a shut-off element 12.
After internal combustion engine 1 has been shut down, i.e. after the spark ignition and fuel injectors associated with cylinders 2a, 2b, 2c, and 2d have been stopped, fuel pump 4 continues to feed fuel into the fuel lines 8, 9a, 9b, 9c, 9d as crankshaft 3 coasts to a stop, even though fuel is no longer required to keep the internal combustion engine 1 operating. As such, the pressure in fuel lines 8, 9a, 9b, 9c, 9d continues to be maintained or increases. As a result, fuel pump 4 feeds against a rising fuel pressure, which leads to an increase in the necessary drive torque of fuel pump 4.
A fuel return line 11 is provided to influence the fuel pressure in fuel lines 8, 9a, 9b, 9c, 9d and the resulting necessary drive torque of fuel pump 4 be returning fuel from fuel lines 8, 9a, 9b, 9c, 9d to fuel tank container 7 to form an enclosed fuel circuit. The quantity of fuel removed or recirculated is controlled by valve 12 arranged in fuel return line 11, which influences pressure in fuel lines 8, 9a, 9b, 9c, 9d. Because the drive torque necessary to drive fuel pump 4 depends on this pressure, the drive torque of fuel pump 4 is also influenced by opening and closing valve 12. Closing valve 12 leads to an increased fuel pressure and a corresponding larger drive torque becomes necessary. Conversely, opening of valve 12 leads to a lower pressure in fuel lines 8, 9a, 9b, 9c, 9d so that the necessary drive torque to operate fuel pump 4 decreases. By decreasing or increasing the flow cross section of the shut-off element 12 and thus the flow resistance which is changed in this way it is possible to increase or decrease the pressure in the corresponding fuel lines.
A first pressure sensor 13 senses the instantaneous pressure in fuel lines 8, 9a, 9b, 9c, 9d and communicates with an engine control system (not illustrated) that actuates valve 12 arranged in fuel return line 11. According to the inventive method, valve 12 is controlled in such a way that the energy emitted by internal combustion engine 1 until it comes to a standstill after the ignition and/or the fuel supply has been switched off is consumed by means of the drive torque of fuel pump 4 in a controlled fashion such that the internal combustion engine 1, i.e. crankshaft 3, is stopped in a position favorable for restarting.
In order to be able to set a specific preferred position of the crankshaft precisely, a plurality of information items is in fact necessary and/or helpful. In this context, it is helpful to have recourse to all the data which has already been measured for the customary engine control and/or data which has been derived, in particular to the engine speed, the crankshaft angle, the temperature of the engine and/or a temperature which is correlated thereto such as the coolant temperature and/or the intake pressure in the intake manifold. The aforesaid variables have according to the invention the largest influence on the coasting movement of the internal combustion engine and/or of the crankshaft.
To determine and control stopping position of the crankshaft it may be necessary and/or helpful to determine how much kinetic energy is present in the drive train and/or in the crankshaft after the internal combustion engine has been shut down. A model of the coasting movement of an internal combustion engine is described, for example, in the European patent application No. 03101379.0. This model takes into account the current kinetic energy of the drive train, the friction losses and/or the compression and expansion processes in the cylinders of the internal combustion engine. Such a model can be acquired on the basis of theoretical considerations and implemented in the form of mathematical equations. However, the model is preferably acquired entirely or at least partially empirically, i.e. by observing the engine behavior and conditioning of the measured data acquired in the process (for example as a lookup table).
In contrast to the embodiment of
Internal combustion engine 1 shown in
If the throughput rate of fuel pump 4 is increased, pump 4 feeds large quantities of fuel into the fuel lines 8, 9a, 9b, 9c, 9d, with the pressure in the fuel lines 8, 9a, 9b, 9c, 9d rising owing to the lack of consumption of fuel. Fuel pump 4 must then pump against an increased pressure at outlet 6, which requires an increased drive torque. Conversely, the necessary drive torque can be decreased by reducing the throughput rate.
Alternatively, fuel pump 4 may have a variable outlet 6 with which the flow resistance of outlet 6 can be varied as means for influencing its drive torque. By decreasing or increasing the cross-section of outlet 6, the flow resistance is changed such that the pressure in fuel pump 4 is decreased or increased, respectively, to vary the drive torque of fuel pump 4. Adjustment in the direction of closing and thus a decrease in the outlet cross section of outlet 6 leads to an increased pressure in fuel pump 4 and an increased drive torque. Conversely, adjustment in the direction of opening and thus an increase in the outlet cross section of outlet 6 leads to a lower pressure in fuel pump 4 and a decreased drive torque.
As a result, the embodiment illustrated in
As such, in order to influence the drive torque of the fuel pump, means are provided with which the power tapped from the crankshaft by the fuel pump can be varied. In other words, the fuel pump, which is considered an energy consumer, is operated in such a way that the consumption of energy as the crankshaft coasts after fuel and ignition are switched off has a profile that results in the crankshaft stopping in a desired position with the necessary accuracy favorable for restarting the engine, whether using direct starting or a conventional starter motor.
Hydraulic pump 24 supplies pressurized oil to a working cylinder 27, such as a toothed rack hydraulic steering system, via supply line 25. Supply line 25 adjoins outlet 26 of hydraulic pump 24. Oil return line 28 returns oil into a tank container 29 which in turn feeds the hydraulic pump 24 via inlet 30. A rotary slide valve 31 is arranged between hydraulic pump 24 and working cylinder 27.
To shut down internal combustion engine 22 in a controlled fashion according to the present invention, i.e. to bring crankshaft 23 to a standstill in a position favorable for restarting, the drive torque of hydraulic pump 24 is controlled so that the energy of internal combustion engine 22 is consumed by the drive torque of hydraulic pump 4 in a controlled fashion. As previously described, kinetic energy of the engine may be determined using a analytic or empirical model and used in controlling the stopping position of crankshaft 23.
In the embodiment illustrated in
By decreasing or increasing the flow cross section of shut-off element 32 the flow resistance is changed and as a result the pressure in supply line 25 between shut-off element 32 and outlet 26 of hydraulic pump 24 changes. The drive torque necessary to drive hydraulic pump 24 is dependent on this pressure so that the drive torque can be influenced by controlling the cross section of shut-off element 32.
Closing shut-off element 32 leads to an increased oil pressure in supply line 25, as a result of which a larger drive torque becomes necessary. Conversely, opening shut-off element 32 leads to a lower pressure in supply line 25 so that a smaller drive torque is necessary. An electronically controlled valve 33 that preferably can be controlled in an infinitely variable fashion may be used as a shut-off element 32, as a result of which the accuracy in controlling the stopping position of the crankshaft 23 can be increased.
Of course, power steering system 21 may include both a shut-off element 32 in supply line 25 and a variable throughput hydraulic pump 24 to influence the drive torque of hydraulic pump 24. Use of both elements increases the flexibility and accuracy during the controlled shutting down of the internal combustion engine 22.
By using the hydraulic pump of the power steering system, a component of the internal combustion engine which is already present is used to bring about controlled shutting down. As such, it is not necessary to provide additional adjustment devices. In particular, it is not necessary to provide an active adjustment device such as an electric motor to rotate the crankshaft into the desired position after the internal combustion engine has been switched off. In this context, the hydraulic pump can be referred to as a passive adjustment device which exerts a torque on the crankshaft until the crankshaft comes to a standstill, preferably in the desired preferred position. In comparison with an active adjustment device, a passive adjustment device provides the advantage that its energy consumption is lower since it does not initiate a rotational movement of the crankshaft but rather merely suitably decelerates an existing rotational movement of the crankshaft.
Controlling stopping position of the crankshaft according to the present invention Such a method makes it possible to provide direct start, i.e. to start directly from the stationary state by injecting fuel into the combustion chambers of the stationary internal combustion engine and igniting by means of a spark plug. Of course, the present invention is also advantageous for engines having conventional starter motors in that the crankshaft and camshaft positions are known from commencement of the starting process so that a synchronization period is not required.
While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 04105806.6 | Nov 2004 | EP | regional |
| 04105838.5 | Nov 2004 | EP | regional |
