EP0328602B1 - Device for introducing fuel into the combustion chamber of an internal combustion engine - Google Patents

Abstract

In the process described, a compressed gas is withdrawn from the cylinder during a working cycle, temporarily stored, and introduced into the cylinder, together with the fuel, during the next working cycle. The process comprises the following steps: a) timed withdrawal of a small quantity, in particular 2 to 6 cm3, of hot compressed gas through a valve which opens into the combustion chamber of the cylinder, b) storage of the hot gas withdrawn in a chamber of the valve, c) injection of fuel into the hot gas, d) blowing of the stored fuel-gas mixture through the valve which opens into the cylinder. The process is carried out by a device which has an insufflation valve (2) with a chamber (18) facing toward the valve and a chamber (20) facing away from the valve, and a valve (16) which opens into the combustion chamber of the internal combustion engine and controls the gas exchange between the combustion chamber (3) and the chamber (18) facing toward the valve. Said chamber (18) serves as a storage reservoir (4) for the gases withdrawn from the combustion chamber (3). The valve (16) is actuated by a drive element (14) which delimits the chamber (20) facing away from the valve. The chamber (18) facing towards the valve is connected to the chamber (20) facing away from the valve via a non-return valve (32). A pressure-generating unit (5) delivers fuel to the chamber (20) facing away from the valve.

Description

The invention relates to a device for introducing fuel into the combustion chamber of an internal combustion engine with a delivery device for the fuel, a blow-in valve for removing compressed gas from the cylinder and for blowing the gas and the delivered fuel into the cylinder, with a valve-side space for storage of the gas, the valve of which controls the gas exchange between the combustion chamber and the valve-side space

As is known, in order to achieve the highest possible thermal efficiency and the lowest possible pollutant emissions in internal combustion engines, preferably in those with spark ignition, the aim is to achieve the combustion of the fuel as quickly and completely as possible in the area of the upper piston dead center. When fuel is injected into the combustion chamber or a fuel-air mixture is drawn in when the mixture is formed externally, these goals are never fully achieved because the combustion is impaired due to a lack of time for the mixture formation. The ignition timing must therefore also be set accordingly far before top dead center.

There are advantages if one proceeds to an external mixture formation at higher temperatures and this is already carried out during the working cycle preceding the ignition of the respective air-fuel mixture and then the mixture is blown into the combustion chamber during the following working cycle.

In this context, DE-AS 1 751 524 has disclosed a device with which the introduction of the fuel is achieved via a rotary valve provided jointly for all cylinders of an internal combustion engine. This rotary valve, consisting of a disc-shaped rotor, a thin disc-shaped distributor plate and a mushroom-shaped control slide, is together with a centrifugal pump that with the rotor on a common shaft, housed in a housing. The shaft and thus the pump and the rotor rotate in four-stroke engines with camshaft speed. Arranged in the rotor itself is a metering chamber which extends in the radial direction and has a plurality of control openings on its control surface facing the distributor plate. The rotor additionally has an accumulator opening running in the axial direction, through which the storage of compressed air taken from the cylinder spaces via an injection line can be controlled. This measure removes pressurized air from the respective cylinder space during the compression stroke, which is used as a compressed air source for blowing the fuel into the respective cylinder space.

A disadvantage of this device is in particular its complicated structure, as well as the fact that a central metering and control unit is used for all cylinders of a multi-cylinder engine. This results in long injection or extraction lines, which tend to become soiled in the extraction phase and in which fuel can cut off from the fuel-air mixture on the walls in the injection phase, which results in errors in the fuel metering that are difficult to control. In addition, the injection line, which is open to the cylinder, on the one hand causes exhaust gas to blow back into the injection line in the expansion phase of the engine, and on the other hand, a subsequent outflow of fuel-containing gas into the cylinder during the gas exchange phase, which inevitably leads to increased hydrocarbon emissions.

The timing of the injection or removal is given by the shaft of the control and metering device rotating at the camshaft or crankshaft speed. It is therefore not possible to adapt the start of injection, for example, to the requirements of the engine in order to reduce consumption and harmful emissions.

The fuel metering system according to DE-AS 1 751 524 works with a metering chamber which acts alternately or in succession with fuel pressure (which is lower than the air pressure in the injection or sampling line) and air pressure becomes. In order to be able to introduce the fuel into the metering chamber against the higher air pressure, the metering chamber must first be vented via a line into the intake manifold. This ventilation process represents a thermodynamic loss, since air drawn in by the engine is compressed, extracted, and returned to the intake manifold.

Furthermore, it is known from DE-C 565 925 to use an injection valve both for removing compressed gas and for injecting the gas and the fuel delivered into the cylinder. For this purpose, a valve-side space for storing the gas and at least parts of the fuel delivered is provided. During the blowing-in phase, the part of the fuel emerging from a metering device is directly included. the gas flow from the reservoir into the cylinder. The fuel pressure must open the injection valve partly against the excess pressure prevailing in the gas accumulator and keep it open, which disadvantageously always causes a large part of the fuel to enter the cylinder in liquid form.

As a further disadvantage of the design according to DE-C 565 925, it should be mentioned that the opening process of the injection valve is carried out by the fuel pressure, but the closing process is carried out by a separate mechanical device, which results in a not inconsiderable additional effort. Furthermore, such a blow-in valve soon has deposits, since the fuel cooling of the blow-in valve preferably results in surface temperatures in the range from 100 to 250 ° C., at which experience shows that coking is strongest.

Finally, from US-A 4 413 781, DE-C 233 660 and DE-C 833 736 further devices for introducing fuel into the combustion chamber of an internal combustion engine are known, which in addition to an injection valve, however, have separate removal devices with a certain excess pressure in the Have cylinder-opening check valves. The gases are extracted depending on the gas pressure in the cylinder.

The object of the present invention is to propose a device for introducing fuel into the combustion chamber of an internal combustion engine, which has the disadvantages mentioned can be avoided and in particular an improvement in the efficiency of the internal combustion engine and a reduction in its pollutant emission can be achieved with simpler and more effective control.

• a) zeitlich steuerbare Entnahme einer kleinen Menge, insbesondere 2 bis 6 cm³ verdichteten heißen Gases über das in Richtung Brennraum des Zylinders öffnende Ventil,
• b) Speicherung des entnommenen heißen Gases, im ventilseiti gen Raum,
• c) Einspritzen von Krattstoff in das heiße Gas,
• d) Einblasen des gespeicherten Kraftstoff-Gasgemisches durch das in den Zylinder öffnende Ventil.

This object is achieved in that the injection valve has a valve-facing space in addition to the valve-side space, that the valve opens in the direction of the combustion chamber of the internal combustion engine and can be actuated via a drive member delimiting the valve-facing space, and that the valve-side space via at least one in the direction of valve-side opening check valve is connected to the valve-facing space, in which a pressure generating unit delivers fuel. The facility works as follows:

• a) time-controllable removal of a small amount, in particular 2 to 6 cm³ of compressed hot gas via the valve opening in the direction of the combustion chamber of the cylinder,
• b) storage of the extracted hot gas in the valve-side space,
• c) injecting scrap material into the hot gas,
• d) blowing the stored fuel-gas mixture through the valve opening into the cylinder.

This gives a very simple embodiment variant, in which on the one hand the injection valve also functions as a gas sampling valve and the valve-side space serves as a gas reservoir. The fuel is injected directly into the gas reservoir of the injection valve. Hydraulic actuation of the injection valve offers the advantage of greater actuation forces, variable opening speed and larger valve lifts compared to direct actuation by means of an electromagnet, rocker arm or cam.

Through the valve opening directly into the cylinder, the gas to be withdrawn goes directly to the preferably heat-insulated gas store, without having to pass long cold lines, where the increased temperature can keep the formation of coal out.

The device according to the invention is primarily designed for late injection in the last quarter to the last sixth of the engine cycle preceding the start of ignition.

With the device according to the invention, it is also possible for the fuel-gas mixture formed in the previous cycle to be blown in first by a fuel pump and then the fuel to be injected into the stored hot gas at a higher fuel pressure.

In a development of the device according to the invention it is proposed that a piston pump connected to the valve-facing space is provided via a pressure line, the pump space of which is connected to the fuel tank via a solenoid valve, wherein a second solenoid valve can be provided which is located in an additional, the fuel tank is arranged with the fuel line connecting the pressure line. While the injection duration and the injection quantity are coupled to one another in terms of time and duration by means of a single two-way valve, a second solenoid valve which is controlled independently of the first one succeeds in decoupling these two functions, which is an advantage when tuning the internal combustion engine with regard to low Represents consumption and emissions. In this case, a check valve can be arranged in the additional fuel line, via which excess amounts of fuel flow back into the fuel tank.

Decoupling of the injection duration and the injection quantity can also be achieved with only one solenoid valve and the associated power electronics if, according to the invention, the solenoid valve can be controlled by pulse-length-modulated clocking of the voltage applied to the solenoid of the solenoid valve with at least two different current intensities, whereby at least two different pressure levels can be achieved . At the low current and thus force level, an opening pressure is reached which is greater than the closing pressure of the injection valve, which opens it up to its stop. Subsequently, the pressure rises to such an extent that the force of the solenoid valve is no longer sufficient to close the return line into the tank and subsequently that of the Piston pump fed excess fuel flows back into the tank. Subsequently, the higher current is applied to the solenoid valve, causing it to close against the fuel pressure in the line. The pressure now rises further to a value at which the check valve in the connecting line to the gas accumulator opens and injection begins. The injection is ended when the force on the solenoid valve is reduced to a low pressure level or zero by appropriate control of the current, in which case the injection is ended at the same time.

Another embodiment of the invention provides that a piston or constant delivery pump is provided in connection with a hydraulic metering device, that the metering device has a metering piston guided in a housing which immerses in a drive-side space arranged in the housing and in a metering space, the stroke defined by two stops determining the amount of fuel to be injected, that the metering space via a pressure line to the valve-facing space of the injection valve and the drive-side space via a solenoid valve with the outlet the piston or constant feed pump is connected, and for the filling of the metering space a line is provided which emanates from the pump into the pressure line and is provided with a check valve. The amount of fuel injected per engine cycle is determined here by the stroke of the metering piston moving between two stops. This enables an exact metering of the fuel quantity.

In one embodiment of this variant, it is provided that when using a constant feed pump, for example a roller cell or gear pump, the part of the metering plunger which plunges into the drive-side space of the metering device has a larger pressure application area A₁ than that part with the area A₂ which delimits the metering space, so that hydraulic amplification of the injection pressure in the ratio A₁ / A₂ can be achieved. The achievable with the metering hydraulic gain can be achieved with a piston of smaller diameter with the area A₂ on the high pressure side and, for example, a piston of larger diameter with the area A₁ on the low pressure side.

It is further provided according to the invention that the drive-side space is delimited by a diaphragm which drives the metering piston and is acted upon by system pressure. The delivery stroke of the metering piston is accomplished by opening the solenoid valve in the inflow line.

According to the invention, the drive-side space can of course also be divided into a ring chamber into which the feed line from the solenoid valve opens and into a spring chamber for receiving the injection spring by a membrane driving the metering piston.

A control of the injection quantity depending on Machine parameters can be achieved according to the invention simply by one of the stops limiting the stroke of the metering piston being variable and being realized by an eccentric cooperating with a servomotor.

A further development according to the invention provides that an electrically actuable flow control unit is arranged in the feed line to the drive-side space of the metering device, by means of which the stroke speed of the valve in the injection valve can be controlled. With the help of a flow control unit, the flow rate can be steplessly controlled. The injection of the required amount of fuel takes place at low needle stroke speeds, i. i.e., at part load later than at high needle stroke speeds (full load). This has the advantage that at high loads, part of the fuel enters the combustion chamber directly in the same cycle and thus increases the internal cooling, whereas at partial load the entire fuel is pre-evaporated in the accumulator and thus ensures the lowest possible emissions. The charge stratification, which in turn has an influence on the emission behavior of the engine, can also be controlled by controlling the entry pulse of the gas jet into the combustion chamber.

A differently designed control possibility is given in that the piston of the injection valve has a shoulder for realizing a variable valve lift, which forms an annular space with the wall of the housing, the shoulder being pressurizable in the closing direction of the valve, and the annular space being interposed a check valve is connected on the one hand to the valve-facing space and on the other hand via the check valve to the valve-side space. In this variant, the valve lift of the injection valve is variable in proportion to the amount of fuel injected (simultaneous control). Compared to the versions without variable valve lift, this gives advantages in terms of operating the engine at low loads or at full load.

Furthermore, it can be provided that the piston of the injection valve has a shoulder for realizing a variable valve stroke, which forms an annular space with the wall of the housing, the shoulder being pressurizable in the opening direction of the valve, and that the annular space with the interposition of a check valve on the one hand communicates with the pressure line and, on the other hand, with the valve-side space via the check valve. In this embodiment, the injection into the gas reservoir takes place at the end of the charging phase of the gas reservoir during the closing process of the valve in the injection valve. At this time, gas flows from the combustion chamber into the accumulator, so that the injected fuel remains in the accumulator until the subsequent cycle.

To protect the valve spring in the injection valve, it can be provided in one embodiment of the invention that a compression or tension spring of the injection valve is arranged in a spring chamber separated from the valve-side space by an intermediate wall, the intermediate wall having an opening for the valve stem.

However, it is entirely within the scope of the invention that only the gas pressure acting on the valve cross section in the combustion chamber of the internal combustion engine is used to close the valve. This eliminates the need for a spring or spring chamber.

As a further simplification of the device according to the invention, it is proposed that a metering device with a metering chamber is arranged in the housing of the injection valve, the metering piston of which is arranged coaxially with the piston of the injection valve and is in engagement therewith that the valve-facing space of the injection valve simultaneously serves as the drive-side space of the metering device that the metering chamber is connected on the one hand to the valve-facing space via a reducing valve and on the other hand to the valve-side space via the check valve, and that the valve-facing space is connected to the fuel supply line from the pressure generating unit. In this embodiment variant, the injection valve and metering device form a unit, the pistons of which are in engagement with one another.

According to the invention, the pressure generating unit can consist of a constant feed pump, a downstream electronically controlled flow control unit, and a pressure limiting valve arranged on the pump outlet side, a three-way solenoid valve being provided which connects the valve-facing space in one position to the flow control unit and in another position to a return line in the fuel tank . In this embodiment variant, the valve only reaches its stop at approximately full load, while at partial load, depending on the valve lifting speed, it only covers part of its way. The valve lift is proportional to the amount of fuel injected and the injection takes place during the closing movement of the valve.

To limit the maximum lifting speed or the maximum closing speed of the valve, it is proposed that a fixed throttle is arranged in the line between the flow control unit and the three-way solenoid valve, and in the return line to the fuel tank.

In one embodiment of the above-mentioned embodiment variant, instead of the flow control unit connected in series, an electronically controlled pressure control unit arranged parallel to the constant feed pump can be arranged.

In a further advantageous development of the invention it is provided that the valve-facing space of the injection valve is limited on the valve side by a membrane arranged normal to the valve axis, which drives the metering piston on the one hand and the injection valve on the other hand, the lower membrane space also having its own pressure line coming from the constant feed pump Pressure can be applied. This measure advantageously replaces the closing spring in the injection valve, with a multi-cylinder engine automatically equalizing the closing force of all valves, regardless of tolerances of the spring forces. This is also very important for achieving the same injection quantities for all cylinders.

To protect a seal against the valve stem seals the gas pressure in the gas accumulator, it is provided according to the invention that the connecting line leading into the valve-side space of the injection valve opens into an annular gap arranged concentrically to the valve stem, from which the fuel exits in the direction of the valve into the gas accumulator.

Finally, as a particularly simple embodiment of a blow-in valve, the space facing away from the valve can be connected to the space on the valve side via a continuous annular gap concentrically arranged with the valve stem, with an expansion of the annular gap including a seal surrounding the valve stem with a prestressing element, e.g. a hose spring is arranged as a check valve. This seal seals the valve stem from bottom to top, that is from the valve-side space to the valve-facing space against a high pressure and from top to bottom against a much lower pressure.

• Fig. 1 eine Einrichtung gemäß der Erfindung, die
• Fig. 2, 4, 4a, 5, 6, 8 10, 12 und 14 Ausführungsvarianten nach Fig. 1,
• Fig. 3 ein Diagramm über den Spannungs- (U) bzw. Kraftverlauf (F) aufgetragen gegen den Kurbelwinkel α der Ansteuerung eines Magnetventils nach Fig. 1, die
• Fig.4b, 7, 9, 11 und 13 Diagramme, welche den Nadelhub S bzw. die Einspritzmenge β in Abhängigkeit des Kurbelwinkels α darstellen,
• Fig. 15 ein erfindungsgemäßes Einblaseventil im Detail,
• Fig. 16 eine Ausführungsvariante des Einblaseventils nach Fig. 15 sowie Fig. 17 ein Detail aus Fig. 16.

The invention is explained in more detail below with reference to drawings. Some of them show in a schematic representation:

• Fig. 1 shows a device according to the invention, the
• 2, 4, 4a, 5, 6, 8 10, 12 and 14 variants of FIG. 1,
• Fig. 3 shows a diagram of the voltage (U) or force (F) plotted against the crank angle α of the control of a solenoid valve according to Fig. 1, the
• 4b, 7, 9, 11 and 13 diagrams which represent the needle stroke S or the injection quantity β as a function of the crank angle α,
• 15 an injection valve according to the invention in detail,
• 16 shows an embodiment variant of the injection valve according to FIG. 15 and FIG. 17 shows a detail from FIG. 16.

The embodiment variant of a system with piston pump and constant needle stroke shown in FIG. 1 shows a blow-in valve 2 connected to the combustion chamber 3 of an internal combustion engine (not shown), the space 18 of which faces the valve 16 simultaneously as a gas reservoir 4 serves. A removal valve is advantageously omitted here and the fuel is injected directly into the gas accumulator 4 of the injection valve 2. The gas is removed from the combustion chamber 3 by the injection valve 2 itself, in that it is kept open for a correspondingly long time after the injection process has ended. The injection valve 2 consists of a housing 13 in which the piston 14 loaded by the spring 15 in the closing direction is axially slidably mounted. The spring can also be omitted if the gas pressure prevailing in the gas accumulator automatically closes the valve if the effective surfaces of the piston and the valve are designed accordingly. The valve 16 opening into the combustion chamber 3 is connected to the piston 14 by the shaft 17. The valve-facing space 20 above the piston 14 is connected to the gas accumulator 4 via a connecting line 37, which has a check valve 32. However, it is also possible that the connecting line 37 opens into the pressure line 35 and is thus connected to the space 20.

The pressure generating unit, a piston pump 5, connected to the space 20 of the injection valve 2 via the pressure line 35 has a plunger 23 which is slidably arranged in the pump cylinder 22 and is loaded by a spring 24 against the cam 25 driving it. The cam 25 or its camshaft 26 is driven by the internal combustion engine in a known manner. The fuel sucked in from the fuel tank 28 via the line 29 reaches the pump cylinder 22 via a solenoid valve 60. It is also possible to provide a regulating device for adjusting the fuel quantity, for example in the pump cylinder 22 having an evasive piston (not shown here) with an adjustable stroke stop can be.

FIG. 2 shows a variant of FIG. 1, in which the injection duration and the injection quantity are coupled to one another in terms of the point in time and the duration by the joint control of the injection duration (= opening duration of the injection valve) and the injection quantity by means of a single two-way solenoid valve 60. The device according to FIG. 2 succeeds by means of a second solenoid valve controlled independently of the first 61, which is arranged in an additional line 62 connecting the fuel tank 28 to the pressure line 35, a decoupling, which is an advantage when tuning the internal combustion engine with regard to low consumption and favorable emission values.

The opening pressure of the injection valve 2 with p₁, that of a check valve 63 in line 62 with p₂ and that of the check valve 32 with p₃. At the beginning of the blowing process, the solenoid valve 60 closes and the valve 61 remains open. When the pressure p 1 on the injection valve 2 is reached, it opens until the piston 14 abuts its stop. Then the pressure continues to rise to p₂, whereby the check valve 63 opens and the excess amount of fuel flows back into the tank. The beginning of the injection process in the gas reservoir 4 is initiated by closing the solenoid valve 61, causing the pressure in the injection line to rise to p 3 and the check valve 32 to open. The injection alone is ended either by opening valve 61 or together with the injection by opening valve 60. The quantity is metered by the closing time of the solenoid valve 61 and by the cam stroke of the injection pump 5 that took place during this time.

The diagram in FIG. 3 shows a variable voltage profile U or the resulting force profile F on a solenoid valve, with which the advantages of the embodiments according to FIGS. 1 and 2 can be combined. Due to the special type of control of the solenoid valve 60 in FIG. 1, the injection duration and the injection duration and thus the quantity metering can also be decoupled with only one solenoid valve and associated power electronics. With reference to FIG. 1, the solenoid valve 60 is driven with two different current intensities. This can be done in various ways, for example by pulse-length-modulated clocking out of the voltage applied to the electromagnet. As a result, two different force levels F 1 and F 2 are achieved at the solenoid valve 60. At the lower current and thus force level F₁, an opening pressure that is greater than the pressure p₁ is reached, whereby the injection valve 2 opens until it stops. In further consequence, the pressure rises so far (to p₂) that the force of the solenoid valve is no longer sufficient to close the return line into the tank 28 and, as a result, the quantity of fuel delivered by the piston pump 5 flows back into the tank. Subsequently, the higher current is applied to the solenoid valve 60, whereby it closes again against the fuel pressure in the line. The pressure now increases further to the value p₃ at which the check valve 32 opens and the injection begins. The injection is ended when the force on the solenoid valve 60 is reduced to F 1 or 0 by appropriate control of the current, in which case the injection is ended at the same time.

Fig. 4 shows a modification of the system of Fig. 1, a system with low pressure drive and constant needle stroke. Instead of the high pressure plunger pump 5 is a constant feed pump 5 ', for example in a known manner, a roller cell or gear pump in connection with a hydraulic booster and Dosing device 64 used. The metering device 64 has a metering piston 66, which is guided in a housing 65 and divides the housing into a drive-side chamber 67 and a metering chamber 68. The hydraulic reinforcement results from a piston of smaller diameter with the area A₂ on the high pressure side and an elastic membrane or a piston of larger diameter with the area A₁ on the low pressure side. The metering piston 66 and the membrane 69 are connected to one another. This association moves between a fixed and a variable stop 70, the variable stop, as shown, can be on the low-pressure side or else on the high-pressure side. The path between the stops is related to the amount of fuel to be injected. The hydraulic amplification translates the pressure generated by the constant feed pump 5 ', typically 2 to 8 bar, in the ratio A₁ / A₂ / A₄ to the pressure required for the present fuel injection system of approx. 10 to 40 bar, A₄ being the cross section of the hydraulic piston 14 represents for actuation of the injection valve 2. The amount of fuel injected per cycle is changed once by the variable stroke reciprocating metering piston 66 accomplished per cycle. The variable stroke stop is implemented, for example, by an eccentric 70 or a cam, which is rotated by an actuator with position feedback or by a stepper motor with electronic control.

The pressure translation and metering device 64 and the blowing process are controlled by a three-way solenoid valve 71, which is controlled by appropriate control electronics. The solenoid valve 71 opens a line 72 to a surrounding the metering piston 66 by the membrane 69 delimited annular chamber 73, the system pressure generated by the pump 5 'via the pressure maintaining valve 74 the metering piston 66 against the spring force of the injection spring 78 against the variable stop 70 (suction stroke ) emotional. At the same time, the pressure line 35 and the metering chamber 68 are filled with fuel via a check valve 76 arranged in the line 75. When the solenoid valve 71 is subsequently closed, the annular chamber 73 delimited by the membrane 69 is released into the tank 28 via a return line 77, the injection spring 78 arranged in the housing 65 moving the metering piston 66 in the conveying direction (conveying stroke). At the beginning of this movement, when the opening pressure on the injection valve 2 is exceeded, this is opened up to its stop — via the quantity of fuel delivered. As a result, the pressure continues to rise, and if the opening pressure of the check valve 32 is exceeded, the remaining fuel quantity still to be delivered is injected into the gas storage space 4 of the injection valve 2. The quantity of fuel required to open the injection valve is constant for each cycle with a constant valve stroke, so that only the injection quantity is varied via the variable stroke stop of the metering piston 66 (sequence control).

In a further embodiment, shown in FIG. 4a, the line 72 opens into the space 67 on the side of the membrane 69 facing the variable stroke stop 70. The delivery stroke is now accomplished by opening the valve 71, whereas the relief takes place via the line 77 triggers the suction stroke. The spring 78 can be omitted in this case. The backward movement of the metering piston 66 is ensured by the application of space 68 with system pressure.

The injection valve 2 closes here due to the fuel pressure on the annular surface 99 facing the valve 16. The check valve 32 remains closed until the injection valve 2 rests on its valve seat. The pressure in line 37 now rises further above the opening pressure p₃, so that the check valve 32 opens and fuel is fed into the gas accumulator 4. This process is complete when the metering piston 66 has reached its end stop on the high-pressure side. This position is the rest or home position of the system.

The blowing-in process begins with the relief of the low-pressure space 67 via the three-way solenoid valve 71. In the return line 77 into the tank 28, e.g. Electronically controlled flow control unit 100 is provided, which controls the valve opening speed of the injection valve 2. The opening of the injection valve is accomplished by the spring chamber 85 'facing the compression spring 15' seated compression spring 15, which at the same time also provides for a resetting of the metering piston 66, the injection quantity being fed via the check valve 76 by the pump 5 'into the high pressure line. The metering device 64 does not require a spring in this embodiment.

The needle stroke S and injection quantity curve β is shown in FIG. 4b. The advantage of this system compared to that in Fig. 4 is that the injection takes place only after the end of the blowing process and that due to the given constellation of pressure and area ratios, a somewhat lower pressure level can be maintained on the high pressure side, which reduces the performance of the fuel pump can be.

Instead of the low-pressure supply unit shown with a constant feed pump, a high-pressure unit with a piston pump can also be used, which eliminates the pressure booster. Furthermore, one can also be discontinuous promotional high pressure stamp pump with electronic control intervention can be used. The valve stroke speed is regulated in all cases by the flow control unit 100 located in the return line 77.

In all of the cases mentioned, “high pressure” is understood to mean pressures above 10 bar.

A further advantage results from a simplification of the device according to FIG. 4. Thus, the membrane 69 or a possible piston with the surface A 1 and the spring 78 driving the metering piston can be omitted if the required hydraulic transmission ratio is achieved by a corresponding cross section A₄ of the piston 14 is ensured in the injection valve 2, as shown in Fig. 5. The metering piston 66 with the area A₂ has only a metering function in this case. The valve 16 of the injection valve 2 begins to lift in this embodiment when the three-way solenoid valve 71 releases the line from the constant feed pump 5 'to the metering piston. The valve 16 subsequently moves up to its stroke stop in the valve body. The subsequent injection phase, like the hold-open period of the injection valve 2, is ended by switching over the three-way valve 71, the space 67 in the return line 77 to the tank 28 being relieved. The pressure line 35 is then filled via the check valve and in this case also the pressure reducing valve 76 and the metering piston 66 is pushed back into its starting position. The pressure drop across the valve 76 or its opening pressure must be so great in this embodiment that the injection valve 2 is certainly not opened by the filling pressure.

FIG. 6 shows a variant of the device according to FIG. 5. With the aid of a flow control unit 79 controlled by a control unit (not shown), the needle stroke speed can be controlled, as shown in FIG. 7 for the flow rates α, β and μ. The required amount of fuel is injected later at low needle stroke speeds (partial load) than at high needle stroke speeds (full load). This results in the advantage that at high loads part of the fuel enters the combustion chamber directly in the same cycle and thus increases the internal cooling, whereas at partial load the entire fuel is pre-evaporated in the accumulator and thus ensures the lowest possible emissions. Furthermore, the variable needle stroke speed serves to control the entry pulse of the gas jet into the combustion chamber and thus to control the charge stratification, which in turn has an influence on the emission behavior of the engine.

FIG. 8 shows an embodiment of the injection system in a modification of that in FIG. 5, in which the needle stroke of the injection valve 2 is variable in proportion to the amount of fuel injected (simultaneous control). In comparison to the versions without a variable needle stroke, this results in advantages with regard to the operation of the motor at low loads or at full load, the statements under FIGS. 6 and 7 correspondingly applying.

8, the piston 14 of the injection valve 2 has a shoulder 80, which forms an annular space 81 with the wall of the housing 13. The shoulder can be pressurized in the closing direction of the valve 16 on an annular surface A₆, the annular space being connected on the one hand to the space 20 facing away from the valve with the interposition of a check valve 82 and on the other hand via the check valve 32 to the space 18 on the valve side.

The annular space 81 with the effective area A₆ is subjected to system pressure via the check valve 82. At the start of injection, i.e. when the metering piston begins to deliver, the piston 14 of the injection valve 2 subsequently moves downward and the valve 16 opens. At the same time, fuel is displaced from the annular space 81 and injected into the gas storage space 4 via the check valve 32. The valve 16 of the injection valve 2 opens only to the extent that it corresponds to the injection quantity conveyed by the metering piston 66, as a result of which an increase in the valve lift with increasing engine load is realized.

8 is the the entire injection quantity at the beginning of the injection phase during the opening process is injected into the gas space 4 of the injection valve 2, as shown in the diagrams in FIG. 9. At this time, gas flows from the gas accumulator 4 into the combustion chamber 3 of the engine, so that a large part of the injected fuel is transported directly into the combustion chamber with the gas flow (V ... full load, T ... part load).

In the embodiment shown in FIG. 10, the piston 14 of which has a shoulder 83 which can be acted upon in the opening direction of the valve 16, the injection into the gas reservoir takes place at the end of the charging phase of the gas reservoir 4 during the closing process of the valve 16. At this time, gas flows from Combustion chamber 3 in the gas accumulator 4, so that the injected fuel remains in the accumulator until the subsequent cycle, as shown in the diagram in FIG. 11.

The corresponding areas exposed to the respective pressure in the low pressure system are designed so that the hydraulic transmission ratio and thus the pressure increase in the injection line is so large that all pressure forces, pressure drops via check valves and frictional forces in the injection valve are overcome via the area A₄ of the piston .

The metering pistons with variable stroke required for each cylinder unit and the associated three-way solenoid valves can, as shown in FIGS. 4, 5, 6, 8 and 10, be combined in a control block independent of the injection valve 2 and connected to the respective injection valve via lines. This provides an advantage in the adjustment and synchronization of the metering pistons. However, it is equally possible to equip each injection valve 2 with a metering device, the drive for adjusting the stops of the metering pistons coming to rest on the cylinder head of the engine. The former version offers advantages for engines with more than one row of cylinders, the latter for engines with only one row of cylinders.

The injection valves with variable valve lift can your Type can also be used in connection with high pressure ram pumps, as shown in FIGS. 1 and 2.

In all versions, the spring 15 of the injection valve 2 can be arranged in a spring chamber 85 separated from the valve-side space 18 by an intermediate wall 84 for heat insulation. The spring chamber can have a relief line 91 (leakage oil line) in the low pressure range.

FIG. 12 shows a further embodiment of a mixture injection system with a variable needle stroke speed. In this case, a metering device 64 'with a metering chamber 68' is arranged in the housing 13 of the injection valve 2, the metering piston 66 'of which is arranged coaxially with the piston 14 of the injection valve 2 and is in engagement therewith. The valve-facing space 20 of the injection valve 2 also serves as the drive-side space of the dosing device 64 ', the dosing space 68' on the one hand via a reducing valve 86 with the valve-facing space 20 and on the other hand via the check valve 32 with the valve-side space 18 in connection. In this version, the valve needle only reaches its stop at full load, while in partial load, depending on the valve stroke speed, it only covers part of its way. The valve lift is proportional to the amount of fuel injected, and the injection takes place during the closing movement of the valve needle.

The pressure generating unit consists of a constant feed pump 5 '(about 6 bar), a pressure relief valve 74 with the opening pressure p₂ and an electronically controlled flow control unit 79 in the main flow. The latter can be, for example, a throttle of variable cross section or the like. The injection valve 2 consists of a valve 16 which is driven via its shaft 17 by a membrane 87 (as shown) or by a piston with the area A 1. A closing spring 15 holds the valve 16 in the closed position. As soon as the three-way solenoid valve 71 opens and acts on the valve-facing space 20 with the system pressure p₂, the valve 16 begins to open. This happens with one Speed which is determined by the fuel flow into the space 20 regulated by the flow control unit 79 and by the force of the closing spring 15. Accordingly, the valve 16 opens faster with large flow and vice versa. The flow can also be controlled by a pressure control unit 88 in the bypass flow (corresponding to FIG. 14).

The fixed throttle 89 between the flow control unit 79 and the solenoid valve 71 limits the maximum lifting speed. When opening the injection valve 2, the metering chamber 68 'is filled with fuel via the reducing valve 86. The filling pressure is less than the opening pressure of the check valve 32 in the connecting line 37. The opening movement is ended by opening the three-way valve 71, the upper membrane space or space 20 facing away from the valve being relieved into the tank 28 via a return line 77. A throttle 90 in the return line 77 limits the closing speed of the valve 16.

During the closing process, the metering piston 66 'displaces a fuel quantity corresponding to the respective stroke, which is injected into the gas accumulator 4 via the check valve 32. The injection is brought about by the force of the closing spring 15 and the gas pressure acting on the valve stem cross section. The described mode of operation can be modified by a corresponding redesign of the metering piston 66 'so that the injection takes place instead of during the closing while the valve is being opened. The first version is used primarily in engines that have to meet strict emission regulations, since the storage of the fuel in the gas storage device 4 reduces the hydrocarbon emissions in the exhaust gas. The latter version results in better internal cooling in high-performance motors, since the heat of vaporization of the fuel entering the cylinder is extracted directly from the cylinder charge.

The maximum valve lift required for the respective operating state is determined by the valve lift speed and the opening duration, which is controlled by the electronics via the solenoid valve 71. 13 shows the course of the valve lift s and the injection quantity β over the crank angle α. The injection takes place during the closing stroke of the needle and ends when the valve plate is placed on the valve seat, regardless of the amount injected. The start of injection and thus the injection quantity is determined by the inclination δ of the opening line a and µ of the closing line b and the opening time of the valve from the start of injection EB to the end of injection EE. The injection rate is determined by the inclination μ of the closing line b, which is given by the closing spring force, the gas force on the valve stem cross section and the cross section of the throttle 90.

In a further embodiment, as already mentioned in FIG. 14, the flow regulator is replaced by a pressure regulator 88 in the secondary flow. In cooperation with the throttle 90 and the counterpressure in the lower diaphragm space 92, this determines the inclination δ of the opening line a in FIG. 13. The pressurization of the lower diaphragm space replaces the closing spring 15 in FIG. 12. Thus, in the case of a multi-cylinder engine, the closing force is automatically equalized and thus the inclination µ of the closing line b of all valves regardless of the tolerances of the spring forces. This is of great importance for the equalization of the injection quantity of the individual cylinders. The valve 94 regulates the pressure in the lower diaphragm space 92 during the opening stroke of the valve 16 via the line 93 and thus the inclination δ of the opening line a for all valves simultaneously. In all other details, the mode of operation corresponds to that of the device according to FIG. 12.

The general advantage of low-pressure technology is that the entire system becomes cheaper due to the elimination of expensive components such as the stamp pump and the high-pressure solenoid valves. The metering device via a piston ensures a very precise metering of the amount of fuel to be injected, regardless of any tolerances in the flow properties or switching times of the solenoid valves, so that the production costs of the solenoid valves can also be reduced.

15 shows the simplified illustration of a blow-in valve 2 as described above. It consists of the valve 16, which is displaceably mounted with its shaft 17 in a two-part housing 13. The valve 16 is held in its closed position by its closing spring 15. The valve-facing space 20 is pressurized with fuel pressure, whereby the valve 16 opens. The gas reservoir 4 or the space 18 facing away from the valve is sealed off from the upper pressure space 20 by an elastomeric seal 95 (for example an O-ring). To protect this seal from the high gas temperatures, the fuel to be injected into the gas accumulator 4 is injected directly under the seal 95 into an annular gap 94 of the valve guide arranged concentrically with the valve stem 17. The fuel passes through this annular gap 94 into the gas accumulator 4, where it evaporates. Due to the narrowness of the gap, gas access to the seal 95 against the direction of flow of the fuel is prevented, so that practically no contamination or overheating of the seal can occur.

Another version of the valve stem seal relates to versions of the injection system according to FIGS. 1 to 6 with "sequential control". As mentioned, the valve 16 is opened up to its stop by acting on the valve-facing space 20 and thus the effective cross section of the valve needle. As a result, the pressure continues to rise above the opening pressure of the check valve 32 and fuel is injected into the gas accumulator. The check valve 32 can now be replaced by a seal 96 shown in FIG. 16, which seals against a high pressure from bottom to top and against a substantially lower pressure from top to bottom. If the fuel pressure required to open the valve is exceeded after the valve has stopped at full opening, the radial sealing force F _{r set} on the sealing lip 97, for example by a hose spring 98, is exceeded and fuel overflows. The sealing force increases to F _r + ΔF _r , so that an equilibrium is established at the radial gap width W. The gap width W is in the range from a thousandth to a few hundredths of a millimeter, so that the seal 96 can withstand a large number of load cycles without wear. After the injection has taken place when the pressure in the space 20 facing away from the valve closes, the sealing lip 97 closes again, so that no backflow of gases can take place.

Claims (23)

1. Device for introducing fuel into the combustion chamber of an internal combustion engine with a delivery device for the fuel, a blast valve (2) for withdrawing compressed gas from the cylinder and for blowing in the gas and the delivered fuel into the cylinder, with a chamber (18) associated with the valve for storing the gas, its valve (16) controlling the interchange of gas between the combustion chamber (3) and the chamber (18) associated with the valve, characterised in that the blast valve (2) has in addition to the chamber (18) associated with the valve a chamber (20) on the other side of the valve, that the valve (16) opens in the direction of the combustion chamber (3) of the engine and is actuated through a drive member (147; 87) bounding the chamber (20) away from the valve, and that the chamber (18) associated with the valve is connected through at least one non-return valve (32; 96) opening in the direction towards the chamber (18) associated with the valve to the chamber (20) away from the valve, into which a pressure generating unit (5; 5′) delivers fuel.

2. Device according to claim 1, characterised in that a piston pump (5) is provided, connected to the chamber (20) away from the valve through a pressure pipe (35), the chamber of the pump being in communication with the fuel tank (28) through a magnetic valve (60).
3. Device according to claim 2, characterised in that a second magnetic valve (61) is provided, arranged in an additional fuel pipe (62) connecting the fuel tank (28) to the pressure pipe(35). 47. Device according to claim 3, characterised in that there is arranged in the additional fuel pipe (62) a non-return valve (63 ) through which excess quantities of fuel flow back to the fuel tank (28).

5. Device according to claim 2, characterised in that the magnetic valve (60) is controlled for example by pulse-length modulated signals of the voltage applied to the winding of the magnetic valve (60) with at least two different current levels, whereby at least two different levels of pressure are obtainable.

6. Device according to claim 1, characterised in that a piston pump or constant delivery pump (5; 5′) is provided in conjunction with a hydraulic metering device (64), that the metering device (64) has a metering piston (66) which is guided in a housing (65) and which enters a chamber (67) arranged in the housing (65) at the drive end and enters a metering chamber (68), its stroke, defined by two stops, determining the quantity of fuel to be injected, that the metering chamber (68) is connected through a pressure pipe (35) to that chamber (20) of the blast valve (2) which faces away from the valve and the chamber (67) at the drive end is connected through a magnetic valve (71) to the output of the piston pump or constant-delivery pump (5; 5′), and that to fill the metering chamber (68) there is provided a pipe (75) leading from the pump (5; 5′), opening into the pressure pipe (35) and equipped with a non-return valve (76).

7. Device according to claim 6, characterised in that using a constant delivery pump (5′), for example a roller cell or gear pump, the part of the metering piston (66) which enters the chamber (67) at the drive end of the metering device (64) has a larger surface area A₁ exposed to pressure than that part having the surface A₂ which forms a wall of the metering chamber (68), so that a hydraulic boosting of the injection pressure in the ratio A₁/A₂ is achieved.

8. Device according to claim 7, characterised in that the chamber (67) at the drive end is defined by a diaphragm (69) actuating the metering piston (66) and exposed to system pressure.

9. Device according to claim 7, characterised in that the chamber (67) at the drive end is divided by a diaphragm (69) actuating the metering piston (66) into an annular chamber (73) into which opens the pipe (72) from the magnetic valve (71) and a spring chamber for receiving the injection spring (78).

10. Device according to one of claims 6 to 9, characterised in that a stop which limits the stroke of the metering piston (66) is adjustable and is formed by an eccentric (70) co-operating with an adjusting motor.

11. Device according to claim 6, characterised in that there is arranged in the pipe to the chamber (67) at the drive end of the metering device (64) an electrically actuated flow-regulating unit ( 79), by which the velocity of the stroke of the valve (16) in the blast valve (2) is controlled.

12. Device according to claim 6, characterised in that the piston (14) of the blast valve (2), for achieving a variable valve stroke, has a shoulder (80) which co-operates with the wall of the housing (13) to form an annular chamber (81), the shoulder (80) being exposed to pressure in the direction of closing of the valve (16), and that the annular chamber (81) communicates, with the interposition of a non-return valve (82), on the one hand with the chamber (20) away from the valve and on the other hand through the non-return valve (32) with the chamber (18) towards the valve

13. Device according to claim 6, characterised in that the piston (14) of the blast valve (2) , for achieving a variable valve stroke, has a shoulder (83) which co-operates with the wall of the housing to form an annular chamber (81), the shoulder (83) being exposed to pressure in the direction of opening of the valve (16), and that the annular chamber (81) communicates, with the interposition of a non-return valve (82), on the one hand with the pressure pipe (35) and on the other hand through the non-return valve (32) with the chamber (18) towards the valve.

14. Device according to one of claims 1 to 13 characterised in that a compression or tension spring (15) of the blast valve (2) is arranged in a spring chamber (85, 85′) separated from the chamber (18) which is towards the valve by a partition wall (84) which has an opening for the valve stem (17).

15. Device according to one of claims 1 to 13, characterised in that the gas pressure in the combustion chamber (3) of the internal combustion engine acting on the valve cross-section serves exclusively for closing the valve (16).

16. Device according to claim 1, characterised in that there is arranged in the housing (13) of the blast valve (2) a metering device (64′) having a metering chamber (68′) of which the metering piston (66′) is arranged co-axially with respect to the piston (14) of the blast valve (2) and is in engagement with the latter, that the chamber (20) of the blast valve (2) which faces away from the valve serves simultaneously as the chamber at the drive end of the metering device (64′) , that the metering chamber (68′) communicates on the one hand through a reducing valve (86) with the chamber (20) away from the valve and on the other hand through the non-return valve (32) with the chamber (18) towards the valve, and that the chamber (20) away from the valve is connected to the fuel feed pipe (35) from the pressure-generating unit.

17. Device according to claim 16, characterised in that the pressure generating unit comprises a constant delivery pump (5′), an electronically controlled flow-regulating unit (79) connected to it and a pressure-limiting valve (74) arranged on the outlet side of the pump, a three-way magnetic valve (71) being provided, connecting the chamber (20) away from the valve in one position to the flow-regulating unit (79) and in another position to a return flow pipe (77) leading into the fuel tank (28).

18. Device according to claim 17, characterised in that a respective fixed restriction (89,90) is arranged in the pipe (35) between the flow-regulating unit (79) and the three-way magnetic valve (71) as well as in the return flow pipe (77) to the fuel tank (28).

19. Device according to claim 17, characterised in that in place of the series-connected flow-regulating unit (79) there is an electronically controlled pressure-regulating unit (88) arranged in parallel with the constant delivery pump (5′).

20. Device according to one of claims 16 to 19, characterised in that the chamber (20) of the blast valve (2) away from the valve is defined at the valve end by a diaphragm (87) which is arranged perpendicular to the axis of the valve and which actuates on the one hand the metering piston (66′) and on the other hand the blast valve (2).

21. Device according to claim 20, characterised in that the lower diaphragm chamber (92) is exposed to pressure through a separate pressure pipe (93) leading from the constant delivery pump.

22. Device according to one of claims 1 to 21, characterised in that the connecting pipe (37) leading into the chamber (18) of the insufflation valve (2) which is towards the valve opens into an annular gap (94) which is arranged concentrically with respect to the valve stem (17) and from which the fuel emerges into the gas reservoir (4) in the direction of the valve (16).

23. Device according to one of claims 1 to 22, characterised in that the chamber (20) away from the valve is connected to the chamber (18) towards the valve through a continuous annular gap (94) arranged concentrically with respect to the valve stem (17), a seal embracing the valve stem (17) and provided with a pre-loading element, e.g. a garter spring (98), being arranged in a widened portion of the annular gap (94) as a non-return valve.

Images