WO2013045502A1

WO2013045502A1 - Accumulator injection system and method for the pressure control of an accumulator injection system

Info

Publication number: WO2013045502A1
Application number: PCT/EP2012/068980
Authority: WO
Inventors: Thomas Kraft
Original assignee: Continental Automotive Gmbh
Priority date: 2011-09-28
Filing date: 2012-09-26
Publication date: 2013-04-04
Also published as: DE102011083628A1

Abstract

The invention relates to an accumulator injection system of a motor vehicle and to a method for the pressure control of such an accumulator injection system. The system has a single volumetric-flow-based pressure regulator both for a volumetric flow valve and for a high-pressure discharge valve (10). The high-pressure discharge valve (10) is designed as a switchable high-pressure volumetric flow valve, the valve body of which can be moved back and forth between a closed position and an open position by controlling the single pressure regulator. In the method for pressure control, the high-pressure discharge valve (10) is controlled in such a way that the high-pressure discharge valve accurately discharges the fuel discharge amount demanded by the pressure regulator.

Description

description

Storage injection system and method for pressure control of a storage injection system

The present invention relates to a storage injection system of a motor vehicle with a high-pressure pump, a high ^¬ pressure accumulator, injectors and a control unit in which a volume flow-based pressure regulator via a volume flow valve, the fuel delivery amount of the high-pressure pump is discharged high-pressure ^¬ discharge valve fuel from the high-pressure accumulator.

Such a storage injection system (common rail system) is known. The high-pressure pump delivers fuel into the high ^¬ pressure accumulator from which the injectors take fuel and meter the combustion chamber. Depending on the load condition of the engine, a different pressure level is required in the accumulator, which is regulated by the high-pressure pump.

In modern injection systems, the pressure in the high-pressure accumulator is regulated by the delivery quantity of the high-pressure pump. For this purpose, a flow valve is used. If the high-pressure pump delivers the quantity which corresponds to the injector consumption, the pressure in the high-pressure ^accumulator remains constant. To build up pressure, the high pressure pump must deliver more fuel into the high pressure accumulator than is taken from the injectors. When pressure is reduced, more fuel must be withdrawn from the high-pressure accumulator than the high-pressure pump supplies. Since the injectors do not inject during the engine's overrun phase and they only have very little to no leakage in modern injection systems, the pressure must be reduced with an additional high-pressure relief valve. This high-pressure discharge valve is m customary Speichererein ^¬ injection systems designed as a force-based high pressure valve (PCV = Pressure Control Valve), which is ver ^{¬ used} for pressure reduction. About the associated solenoid of the valve, a force is set, which leads to a certain high pressure. The resulting dynamic pressure on the closing body of the PCV, caused by the outflowing volume flow, is in equilibrium with the magnetic force. Thus, the applied force is equivalent to the pressure.

The problem with this embodiment of a storage injection system, the switching between the flow valve, which supplies the high-pressure pump with fuel, and the force-based high-pressure relief valve (PCV). Since the two valves work according to physically different principles (on the one hand the volumetric flow is determined via the opening cross-section, and on the other hand the high pressure is set in the memory via the force of the valve), two regulators are needed, between which it is necessary to switch back and forth. Each switching process, however, causes pressure fluctuations in the high-pressure accumulator. In addition, an additional volume flow via the PCV is needed for the pressure control to work, which is energetically poor. The additional volume flow added to the system consumption is set on the volume flow valve (VCV = Volume Control Valve) and accordingly compressed by the high-pressure pump, only to release it from the high-pressure accumulator via the PCV.

The present invention has for its object to provide a storage injection system of the type described above, which is characterized by a particularly simple structure. This object is solved by the invention with a spoke pure ^¬ injection system of the type indicated, that the system comprises a single volume-flow-based pressure regulator for both the volume flow control valve and for the high-pressure relief valve and that the high-pressure relief valve is designed as a switchable high-pressure flow valve whose valve ^¬ body by driving the single Pressure regulator between a closed and open position back and forth. In the inventively designed storage injection system, a single volume flow-based pressure regulator is used. To regulate the high pressure, it is no longer necessary, as in the previous storage injection systems, between two physically different control principles back and forth. The uniform control concept results in improved pressure control performance.

As a high-pressure relief valve is a simple switchable high-pressure volume flow valve use, the valve body can take only two positions, namely a

Closed position and an open position. The valve body is reciprocated between these two positions to completely lock and fully open the associated drain line. With the high-pressure drain valve provided according to the invention, exactly what is required by the volumetric flow regulator can be achieved

Amount be drained from the high-pressure accumulator. To discharge the required quantity, the high-pressure relief valve opens, and the pressure difference (high-pressure - ambient pressure) above the drainage hole determines the outflowing volume flow. The drain hole here is the throttle point, and there is no

Back pressure on the valve body, which corresponds to the accumulator pressure. Required by the regulator from ^¬ let amount is then adjusted on the driving time of the high pressure relief valve (opening ^¬ state of the valve). When the opening state or open position of the valve is mentioned, not necessarily the desired end position of the valve body is meant. Rather, the valve body can also assume an end position corresponding to a balistic area (before the setpoint end position).

Thus, there is a simple and inexpensive valve as a high pressure relief valve use, which realizes a druckregier requested from the high-precision amount of discharge from the high-pressure accumulator ^¬ using the information of a high-pressure sensor. During pressure reduction, only the necessary amount of fuel ^{¬ is} discharged from the high-pressure accumulator, which is required to achieve the desired pressure value.

Preferably, the high pressure relief valve is a digital high pressure relief valve. This can be opened and closed by the drain hole of the high-pressure accumulator open and close, so that by controlling the valve required by the regulator discharge amount can be precisely dissipated.

In a further development of the invention, a drainage hole is arranged in the housing of the high pressure accumulator, which is opened or closed by the valve body of the high pressure relief valve. In this embodiment, therefore, the high-pressure relief valve is arranged directly on the high pressure accumulator, so that there is a simple and space-saving design.

In another embodiment, the open and closed drain hole from the valve body is arranged as a throttle in the valve itself, for example in a plate arranged in the valve body. The present invention further relates to a method for pressure control of a storage injection system of a motor ^¬ vehicle, which has a high-pressure pump, a high-pressure accumulator, injectors and a control unit, in which a volumetric flow-based pressure regulator via a volume flow valve, the fuel delivery amount of the high pressure pump and thus regulates the pressure in the high pressure accumulator and in which fuel is discharged from the high-pressure accumulator via a high-pressure discharge valve. Such a method is known and is carried out with the known storage injection system described above. As mentioned, a volumetric flow valve (VCV) and a force-based high-pressure valve (PCV) are used, which operate according to physically different principles, so that two different regulators are required for the two valves, between which must be switched back and forth.

To overcome the disadvantages of such a method, the present invention proposes that the volume-flow-based pressure regulator controls the high-pressure relief valve in addition to the volume flow valve that is set at a required pressure reduction in the high-pressure accumulator over the drive time to open the high-pressure relief valve exactly the required by the pressure regulator fuel drainage.

Preferably, the volume flow-based pressure regulator controls a digital high-pressure relief valve.

The actuation time of the high-pressure relief valve is dependent on the high pressure in the high-pressure accumulator and is preferably stored in a map, which is accessed by the pressure regulator. Appropriately, the control of the Hochdruckab ^¬ lassventils takes place according to the controller cycle time in small time ^¬ intervals. The process according to the invention proceeds in the following manner. In the pressure reduction phase, the volume flow-based pressure regulator outputs a negative volume flow. The flow control valve (VCV) then supplies less by that amount into the high-pressure accumulator than the system consumes (injectors). If now in the

Shear phase of the engine, the injectors nothing more from the high-pressure accumulator take, closes the VCV. The volume-flow-based pressure regulator (volumetric flow controller) still requires a negative volume flow in order to achieve the desired pressure reduction. In this case, will now via the high-pressure relief valve, which is preferably formed as a digital high ^¬ pressure relief valve (DPDV = Digital Pressure Decay Valve) from ^¬ discharged exactly the amount required by the controller from the high-pressure accumulator. To discharge the required quantity, the DPDV opens, and the pressure difference (high pressure - ambient pressure) above the drainage hole determines the outgoing flow rate. The discharge quantity required by the regulator is then set via the actuation time of the DPDV.

The actuation time of the DPDV for the discharge amount is dependent on the high pressure and the fuel temperature and is preferably stored in a map. Appropriately, the control of the DPDV takes place in small time intervals in accordance with the controller cycle time (in this case, for example, it makes sense segment ^¬ synchronously with the engine) to produce the most uniform possible pressure reduction.

As soon as a positive volume flow is requested again from the pressure regulator (pressure reduction has taken place), the DPDV is no longer actuated (closed) and the VCV takes over the pressure regulation again. In contrast to the conventional high-pressure valves (PCV), only the necessary amount of fuel is drained from the high-pressure accumulator during pressure reduction, which is necessary to achieve the

Pressure setpoint is required. As described above, the PCV requires a volume flow through the valve for pressure control. This volume flow is much higher than would be necessary for a pressure reduction, which is energetically very bad, since the additional amount had to be compressed beforehand. Wei ^¬ terhin operates the PCV in the prior art for a different physical principle as the VCV what a way

Switching between two regulators requires and makes a clean pressure control difficult to control.

The inventive method thus energy can be saved once, since only the necessary amount from the high ^¬ accumulator to achieve the reduction in pressure is released while the engine overrun phase. There is no additional amount drained as when using a PCV. To regulate the high pressure, it is no longer necessary with the inventive method, as in the previous storage injection systems between two physically different control principles back and forth. Furthermore, a cost saving by using a simple valve (digital valve), achieved by a simplified controller calibration and by a simplified control concept in the function ^¬ development.

Thus, with the high-pressure ^discharge valve used ^{according to} the invention, it is not possible to set a variable fuel ^discharge quantity, but the valve can only close completely or open completely, ie the valve body can not assume an intermediate position. The discharge of the prescribed by the pressure regulator drainage is therefore only by setting a certain opening time, during which the valve is in the fully open state. Therefore, the driving time of the high pressure relief valve determines the volume flow to be drained Vo ^¬. As mentioned, as the valve is preferably cyclically driven, ie cyclically opened and closed, to dissipate the corresponding discharge amount.

The invention will be explained in more detail below with reference to exemplary embodiments in conjunction with the drawing. Show it :

Figure 1 is a schematic representation of a high-pressure pump according to the prior art;

Figure 2 is a schematic representation of a digital

High pressure relief valve in closed and open condition; and

Figure 3 is a schematic section through another

Embodiment of a high-pressure discharge valve.

Figure 1 shows a schematic representation of a high-pressure pump of a storage injection system of a motor vehicle according to the prior art. The high pressure pump has a pump piston ^¬ , with the fuel from a low pressure side 3 to a high pressure side 4, which is a high-pressure accumulator is promoted. In the corresponding fuel line, an inlet valve 7 and an outlet valve 8 are provided. On the low pressure side 3 of the pump is a volume ^¬ flow valve 2, by means of which the fuel delivery amount of the high pressure pump by variable opening of the

Passage cross section of the fuel line is adjusted. On the high pressure side 4 of the pump is a high pressure valve 6, by means of the excess fuel over a return line 5 is discharged. The high-pressure valve 6 is a force-based high-pressure valve, via the electromagnet, a force is set, which leads to a certain high pressure in the high-pressure accumulator. The resulting back pressure on the valve body or closing body of the high-pressure valve, caused by the outflow Volu ^¬ menstrom, is in equilibrium with the magnetic force, so that the force used is equivalent to the pressure. The volume flow valve 2 and the high pressure valve 6 each have their own controller (not shown) assigned, between which must be switched back and forth during operation of the system. Each of these switching operations causes pressure fluctuations in the

High-pressure accumulator, which are undesirable.

In the case of the accumulator injection system designed according to the invention, the high-pressure valve or high-pressure discharge valve used is the digital high-pressure relief valve shown in FIG. 2, which is shown in the upper illustration in the closed and in the lower depiction of FIG. 2 in the open state. This digital high-pressure relief valve (DPDV) 10 is arranged directly on the high ^¬ pressure accumulator 11 of the storage injection system and opens and closes a drain hole 12 of the high-pressure accumulator 11. The valve is from an open position into a

Closed position and reversible switchable, i. the valve body or closing body can occupy only two positions, namely the closed position shown in Figure 2 above and the open position shown in Figure 2 below. In the above shown

Closed position, the drain hole 12 is locked so that no fuel can be discharged from the high-pressure accumulator. In the open position shown in Figure 2 below, the closing body releases the drain hole 12, so that fuel can be discharged downwards via the line 13, as indicated at 14. The drained amount of fuel is thereby through the Activation time of the high-pressure relief valve, over which the

Closing body is opened, set. This activation time for the amount of discharge is dependent on the high pressure and the force ^¬ fuel temperature and is stored in a characteristic diagram. Preferably, the control of the high-pressure discharge valve takes place in accordance with the controller cycle time in small time intervals in order to produce the most uniform possible pressure reduction. As soon as a positive volume flow is requested again from the pressure regulator, the high-pressure relief valve is no longer activated and closed. The volume flow control valve 2 then takes over again the pressure control alone.

FIG. 3 shows a further embodiment of a high-pressure discharge valve in a schematic longitudinal section. Guide die in this off the open and by a valve body 20 closed throttled discharge hole 21 is arranged in the valve itself, in a 23 in the valve housing 22 are ^¬ translated platelets Incidentally, the valve is substantially conventional and has a pole core 25 , a magnet 26, an armature 27 and a spring 28. If the

Valve body 20, the drain hole 21 opens, fuel flows from the high-pressure accumulator via the valve housing 22 provided in the drain hole 21 and outlet hole 24 from.

Claims

Memory injection system of a motor vehicle with a high-pressure pump, a high-pressure accumulator, Inj ectors and a control unit in which a volume flow-based pressure regulator via a volume flow valve, the ^¬ fuel delivery amount of the high pressure pump and thus regulates the pressure in the high-pressure ^accumulator and drained in the memory via a high-pressure relief valve fuel from the high-pressure ^¬ memory is characterized in that the system has a single volume flow based

Pressure regulator for both the flow control valve (2) and for the high pressure relief valve (10) and that the high pressure relief valve (10) is designed as a switchable high ^¬ pressure flow valve whose Ven ^¬ tilkörper by driving the single pressure regulator between a closed and open position and is movable.

Storage injection system according to claim 1, characterized in that the high-pressure discharge valve (10) is a digital high-pressure discharge valve.

Storage injection system according to claim 1 or 2, characterized in that in the housing of the high-pressure accumulator (11), a drain hole (12) is arranged, which is opened or closed by the valve body of the high-pressure discharge valve (10).

Storage injection system according to claim 1 or 2, characterized in that the from the valve body (20) of the high pressure relief valve open and closed Ab ^¬ lassbohrung (21) is arranged as a throttle in the valve itself. A method for pressure control of a storage injection system of a motor vehicle having a high-pressure pump, a high-pressure accumulator, injectors and a control unit, in which a volume flow-based pressure regulator via a volume flow valve, the Kraft ^¬ stofpliefermenge the high-pressure pump and thus the pressure in the high-pressure accumulator controls and in a high-pressure relief valve Fuel from the high-pressure ^¬ memory is drained, characterized in that the volume flow-based pressure regulator in addition to the flow control valve, the high-pressure relief valve controls such that at a required pressure reduction in the high-pressure accumulator over the drive time to open the high-pressure relief valve exactly ge the ge ^¬ demanded pressure release ^valve set.

A method according to claim 5, characterized in that the activation time of the high-pressure relief valve from the high ^¬ pressure in the high-pressure accumulator is dependent and stored in a map to which the pressure regulator accesses ^¬ .

A method according to claim 5 or 6, characterized in that the volume flow-based pressure regulator controls a digital high-pressure relief valve (DPDV).

Method according to one of claims 5 to 7, characterized in that the control of the Hochdruckab ^¬ lassventils takes place in small time intervals according to the controller cycle time.