Power plants – Pressure fluid source and motor – Utilizing lubricant – starter motor – cooling fluid – or fluid...
Reexamination Certificate
2002-08-09
2004-05-18
Look, Edward K. (Department: 3745)
Power plants
Pressure fluid source and motor
Utilizing lubricant, starter motor, cooling fluid, or fluid...
C060S411000, C060S418000
Reexamination Certificate
active
06735942
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to a method and a device for operating a vacuum reservoir provided in an internal combustion engine, in particular of a motor vehicle. The vacuum reservoir supplies the auxiliary power, in the form of a vacuum pressure, needed for at least one servo power-assist (one servo booster) unit, and is acted upon by a vacuum pressure prevailing in an intake manifold of the internal combustion engine and in an, in particular, electrical suction pump.
BACKGROUND INFORMATION
German Patent No. 31 25 923, and German Published Application No. 44 44 013 discuss power brake and power steering systems in motor vehicles that draw their auxiliary power from a vacuum reservoir which is coupled to an intake manifold. This intake manifold may be used to supply the internal combustion engine with the air (i.e., the oxygen) that is needed for the combustion. In this context, the intake manifold's vacuum pressure may be stored temporarily in the vacuum reservoir, which may be coupled via a non-return valve to the intake manifold.
Accordingly, to provide adequate servo power assistance, for example servo braking power, a vacuum pressure must have been present for a long enough time in the intake manifold to ensure the proper vacuum pressure in the vacuum reservoir. In response to low manifold pressure, air flows out of the reservoir into the intake manifold. The thus minimally attainable pressure in the vacuum reservoir corresponds to the prevailing manifold pressure. In response to actuation of the brake, the vacuum reservoir is connected via a valve to an actuator which boosts the braking power. In the process, air flows into the vacuum reservoir, thereby increasing the reservoir pressure.
In internal combustion engines of the afore-mentioned type, a throttle valve, which may be used to adjust the air supplied to the combustion chamber, may also be provided in the intake manifold. In conventional internal combustion engines, in particular in the Otto spark-ignition (gas) engine, the throttle valve closes, even when the driver, during braking, removes his/her foot from the accelerator, so that a possibly existing vacuum pressure in the reservoir may be retained. Therefore, in these internal combustion engines, it may be ensured that the vacuum reservoir is able to supply the vacuum pressure required for the servo power-assisted brake even during a relatively long braking action.
However, this is not always ensured in newer internal combustion engines having gasoline direct injection (GDI) or electronic throttle control (e-gas). For example, during the process of heating an existing catalytic converter, the throttle valve may be open to the point where there is no longer an adequate vacuum pressure in the intake manifold. As a result, the vacuum pressure required for the servo system(s) may no longer be able to be made available in the vacuum reservoir.
In addition, in internal combustion engines having GDI or electronic throttle control (e-gas), the throttle valve may be controlled independently of the pedal sensor position, so that the manifold vacuum pressure is restricted in terms of its availability for servo functions.
Examples of this include operating states where manifold injection is accompanied by retarded ignition timing for catalytic converter heating during warm-up. In these operating states, it may be necessary to compensate for a wanted loss of efficiency by opening the throttle valve. This may lead to an increase in the manifold pressure. Stratified operation accompanied by direct injection may be a comparable operating state, where, even at a low load, the throttle valve is fully open, so that, as a result, no manifold vacuum pressure may be available.
In this context, it may also happen during vehicle operation at high altitudes, for example during uphill driving, that the difference relative to the ambient pressure no longer suffices for the servo functions.
The servo power-assisted brake system may be especially critical with respect to safety. If adequate vacuum pressure is not provided, then no brake assistance may be available, or the desired operating state may not be able to run due to safety considerations, thereby leading to deterioration of the exhaust gas or fuel consumption.
A remedy has been discussed in which the throttle opening is designed in such a way that sufficient vacuum pressure is always available. As a result, the throttle opening may not always be able to be optimally designed, in terms of the exhaust gas, for example during the catalyst heating. In addition, in GDI (gasoline direct injection) operated vehicles, a vacuum-operated switch may be used. If the pressure in the brake booster rises above a threshold value, then the switch may be made from stratified operation to homogeneous operation.
In an internal combustion engine, the vehicle may have a built-in suction pump, which compensates for the lacking pressure differential as soon as the pressure in the intake manifold no longer suffices for evacuating the vacuum reservoir. To keep costs low, the suction pump should be a relatively simple component, which is only put into operation in truly necessary cases. Due to cost considerations, the outlay required to detect a necessary switching on or a possible cut off of the suction pump should likewise be kept as low as possible.
It is, therefore, an object of the present invention to provide a method as well as a corresponding device, which, without substantial outlay and with the greatest dependability, will enhance the operational reliability of the vacuum reservoir and minimize mechanical and, thus, also cost expenditures, and at the same time achieving a reliable operation of the vacuum reservoir.
SUMMARY OF THE INVENTION
In an example method according to the present invention, quantity flows are fed to the vacuum reservoir, in a computational model, when at least one servo unit is actuated. Quantity flows are removed from the vacuum reservoir when the pressure prevailing in the intake manifold is lower than the pressure prevailing in the vacuum reservoir. Quantity flows are removed from the vacuum reservoir when the electrical suction pump is switched on. The pressure prevailing is determined in the vacuum reservoir from the balance of the flow quantities fed to and removed from the vacuum reservoir.
According to the present invention, the pressure in the vacuum reservoir, and, therefore, also the vacuum pressure in a servo system, for example in the brake booster are determined by calculation. In this context, the pressure differential in the vacuum reservoir, i.e., in the reservoir of the servo system, is calculated by a model. From the balance of air-inflow and air-outflow quantities to and from the reservoir volume, this model determines the specific pressure in the reservoir.
The compressibility of the gas in the reservoir may be considered in a state equation for ideal gases. The flow quantity into the reservoir may be calculated from the difference between the reservoir pressure and the intake manifold pressure and between the reservoir pressure and the minimal suction pump pressure, allowing for the resistances to flow in the lines to the reservoir. Flow quantities flowing out of the reservoir may be determined from the driving states, e.g., cornering, with the power steering system being loaded to this effect, or a vehicle deceleration, with the power brake system being loaded to this effect.
In internal combustion engines, certain output variables may already be known from such a motor control. In anti-lock braking systems (ABS), for example, motor control interfaces are already present which transmit information on the air consumption in the servo brake to the engine management system. Information on intake manifold pressure, ambient pressure, change in vehicle speed, and the operating state of the suction pump is also usually available in conventional engine management systems. The additionally required sensors, such as pressure switches or pressure boost sensors in the pressure re
Eberle Kristina
Reuschenbach Lutz
Wild Ernst
Kenyon & Kenyon
Leslie Michael
Look Edward K.
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