Internal-combustion engines – Engine speed regulator – Having plural throttle valve structure
Reexamination Certificate
2000-02-22
2002-02-26
Argenbright, Tony M. (Department: 3747)
Internal-combustion engines
Engine speed regulator
Having plural throttle valve structure
C073S116070
Reexamination Certificate
active
06349699
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method of operating of a vacuum accumulator provided in an internal combustion of a motor vehicle, which provides an auxiliary energy required for a servo function of the internal combustion engine in form of a vacuum, and which is loaded with a vacuum acting in a suction pipe of the internal combustion engine.
The present invention also relates to a corresponding control device for such an internal combustion engine.
In motor vehicles it is known that servo braking systems and servo steering systems draw their auxiliary energy from a vacuum accumulator which is connected to a suction pipe. This suction pipe serves for supplying the internal combustion engine with air or oxygen required for combustion. The suction pipe vacuum is stored in the vacuum accumulator, and it is connected through a check valve with the suction pipe.
In order to provide a sufficient servo support, for example servo braking force, a sufficiently long vacuum must be maintained in the suction pipe, in order to guarantee the corresponding vacuum in the vacuum accumulator. With a low suction pipe pressure, air flows from the accumulator into the suction pipe. The pressure in the vacuum accumulator drops thereby minimal to the suction pipe pressure. During the actuation of the brake, the vacuum is connected through a valve with an adjusting device which amplifies the braking force. Thereby air flows into the vacuum accumulator and increases the accumulator pressure.
In the internal combustion engines of the above mentioned general type, a throttle flap is further provided in the suction pipe, for adjusting the air supplied into the combustion chamber. In conventional internal combustion engines, in particular in an Otto motor, the throttle flap closes often in the cases in which the driver during braking removes the foot from a gas paddle, whereby a substantial present accumulator vacuum remains obtained. Therefore in such internal combustion engines it is guaranteed that also during a braking process the vacuum accumulator provides the vacuum required for the servo brake and also during a long braking process.
In the new internal combustion engines with gasoline direct injection (GDI) it is however no longer guaranteed. For example, during a heating process of a substantially available catalyst, the throttle flap opens so wide that no longer sufficient vacuum is provided in the suction pipe and in the vacuum accumulator the vacuum required for the servo system no longer can be available.
Furthermore, in the internal combustion engines with GDI the throttle flap is controlled depending on the position of the pedal value transmitter, thereby suction pipe vacuum for servo functions is available only in a limited extent. Examples for this are operational conditions during the suction pipe injection with a late ignition angle for heating of the catalyst in hot operation. In these operational conditions a desired efficiency great worsening must be compensated by opening of the throttle flap. This leads to an increase of the suction pipe pressure. The shift region during direct injection is a comparable operational condition, in which the throttle flap also in condition of low load is completely open and thereby no suction vacuum is available.
It therefore can be seen that during the operation of the vehicle at high level, for example during mountain driving, the difference with respect to the atmospheric pressure is no longer sufficient for the servo function.
It is especially critical that with the servo braking system in the event of sufficient vacuum, there is no braking force available, or the desired operational condition can not be reached from safety regions, which lead to worsening in exhaust gas or consumption.
It is known to provide helping measures in that the throttle flap opening is designed so that always a sufficient vacuum is formed. During the catalyst heating it leads for example to the situation that the design of the throttle flap opening can not be considered as optimal for exhaust gas. In GDI-operating vehicles further a vacuum switch is used. When the pressure in the braking force amplifier exceeds a threshold value, the shift operation is switched to homogenous operation.
As an alternative solution, an additional vacuum pump or servo pump is integrated in the vehicle, for compensating for substantially failing differential pressure. This leads however to increased costs.
SUMMARY OF THE INVENTION
It is therefore an object of present invention to provide a method of and a device for operating a vacuum accumulator for servo functions, which avoid the disadvantages of the prior art and in particular increase the operational safety during the operation of the vacuum accumulator, which can be used for machine applications, and thereby with the safer operation of the vacuum accumulator minimizes cost expenses.
In keeping with these objects and with others which will become apparent hereinafter, one feature of present invention resides, briefly stated in a method in which the pressure acting in the vacuum accumulator is determined by computations. In accordance with the basic model, mass flows are supplied to the vacuum accumulator when at least one corresponds to a servo function, and the mass flows are guided from the vacuum accumulator when the pressure acting in the suction pipe is smaller than the pressure acting in the vacuum accumulator. The pressure acting in the vacuum accumulator is supplied from the mass balance of the vacuum accumulator and computed from the mass flows withdrawn from the pressure accumulator.
The basic concept which underlies the present invention is that the pressure in the vacuum accumulator and thereby also the vacuum in a servo system, for example of the braking force amplifier, is determined by a computations from known signals. The difference pressure in the vacuum accumulator or the accumulator of the servo system is computed by a model. This model determines from the mass balance of the inflow and outflow of air in the accumulator volume, the corresponding pressure in the accumulator.
The compressibility of the gas in the accumulator can be taken into consideration by the state equation for ideal gas. The mass flow in the accumulator can preferably be computed from the difference of the accumulator pressure and the suction pressure with consideration of the flow resistance in the conduits to the accumulator. The mass flow flowing out from the accumulator can be determined from the traveling conditions, for example a curve travel with a corresponding action on the servo steering system or a vehicle deceleration with a corresponding action on the servo braking system.
In known internal combustion engines, the initial variables on which the inventive concept is based are known from the corresponding motor control, for example the motor control system “Motronic”. For example in anti blocking braking system (ABC) interfaces to motor control are available, which transmit the air consumption in the servo brake to the motor control. Also, the informations about a suction pipe pressure, atmospheric pressure and changes of the vehicle speed are conventionally available in the known motor controls. The additional required sensors such as a pressure sensor or pressure sensors in the pressure accumulator are also available in corresponding systems. Therefore during a realization of the inventive method advantageously no additional component features are needed for existing internal combustion engines.
In accordance with a preferable embodiment, the required differential pressure is compared with the available differential pressure. If there is no sufficient differential pressure available, the motor operational state changes. An operational state with increased suction pipe pressure is adjusted by a reduced throttle flap opening of the motor control.
In a further embodiment of the invention, an additional throttling is performed in the shift operation. During a catalyst heating by means of late ignition angle,
Kuesell Matthias
Melchior Gerard
Ries-Mueller Klaus
Wagner Wolfgang
Wild Ernst
Argenbright Tony M.
Robert & Bosch GmbH
Striker Michael J.
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