EP1260702B1 - A fuel injection system for an internal combustion engine - Google Patents

Description

The invention relates to a fuel injection device for Internal combustion engine according to the preamble of claim 1.

Such a fuel injection device is described by DE-A1-4118236 known. This fuel injection device has for each cylinder of the internal combustion engine on a fuel pump, the one by the internal combustion engine in a reciprocating motion driven pump piston having a pump working space limited, the fuel from a fuel tank is supplied and connected to a fuel injection valve is. The fuel injection valve has an injection valve member , is controlled by the at least one injection port and that by the one in a connected to the pump working space Pressure chamber prevailing pressure against a closing force in one Opening direction is movable. It is a first electric controlled control valve provided by a connection of the Pump work space is controlled with a discharge space. Between the pump working space and the first control valve is a arranged to the first control valve opening pressure-retaining valve, by the one opposite to the pressure prevailing in the discharge space increased pressure is maintained. It's also a second one electrically controlled control valve provided by the likewise a connection of the pump work space with a discharge space is controlled. When the first control valve is open and the second Control valve is closed, it is a fuel injection with the pressure level determined by the pressure holding valve. If both the first control valve and the second control valve is closed, so is a fuel injection with the by the stroke of the pump piston certain pressure curve. The Opening and closing movement of the injection valve member of Fuel injector is controlled by the in the pump workspace controlled pressure prevailing, wherein the injection valve member opens when the force generated by the pressure on this is greater than the bias of a closing spring. The one in the pump workroom prevailing pressure is through the first and second control valves controlled. The opening and closing movement of Injection valve member and the pressure buildup in the pump working space are thus coupled with each other and can not independently to be controlled.

By EP-A2-957261 is also a Fuel injection known.

These Fuel injection device has a fuel pump for each cylinder of the internal combustion engine, the one by the internal combustion engine in a lifting movement having driven pump piston, the one Pump work space limited to the fuel from one Fuel tank is supplied. Of the Pump work space is with a fuel injector connected, having an injection valve member, through the at least one injection port is controlled and that by the one connected to the pump working space Pressure chamber prevailing pressure against a closing force in Opening direction is movable. It is a first electric controlled control valve provided by the one Connection of the pump work space with the Fuel tank controlled as a relief space becomes. It is also a second electrically controlled one Control valve provided by the in one Control pressure chamber is controlled controlling pressure, by the injection valve member at least indirectly in Closing direction is acted upon. A disadvantage of this known fuel injection device is that through the Use of unpressurized fuel tank or the pressure side of a feed pump as a discharge space of the Pressure in the pump work space and in the associated with this Areas of the fuel injection device in the Connection with the discharge space drops sharply and thus the danger of cavitation exists. In addition, the Efficiency of the fuel injector thereby not optimal.

Advantages of the invention

The fuel injection device according to the invention with the Features according to claim 1 has the advantage that by the second control valve one from the pressure in the pump working space independent control of the opening and closing movement of the Injection valve member is enabled and that by the Check valve a decoupling of the pump working space of the allowed by the pressure holding valve maintained pressure level is, whereby leakage in the fuel pump can be avoided can. In addition, by the check valve from the Pressure holding valve maintained pressure level in the pressure chamber also at Suction stroke of the pump piston can be ensured.

drawing

An embodiment of the invention is in the drawing shown and in the following description in more detail explained. FIG. 1 shows a Fuel injection device for an internal combustion engine in a schematic representation according to a first Embodiment, Figure 2 shows a curve of a pressure Injection openings of a fuel injection valve of Fuel injection device, Figure 3 in part a modified version of Fuel injection device and Figure 4 in part another modified version of Krafstoffeinspritzeinrichtung.

Description of the embodiment

In Figures 1,3 and 4 is a Fuel injection device for an internal combustion engine a motor vehicle shown. The internal combustion engine is preferably a self-igniting internal combustion engine. The Fuel injection device is preferably as trained so-called pump-line-nozzle system and has one for each cylinder of the internal combustion engine Fuel pump 10, a fuel injection valve 12 and a the fuel injection valve 12 with the Fuel pump 10 connecting line 14. The Fuel pump 10 has one in a cylinder 16 tight guided pump piston 18, which by a cam 20 a camshaft of the internal combustion engine against the force a return spring 19 driven in a lifting movement becomes. The pump piston 18 limited in the cylinder 16 a Pump work chamber 22, in which the delivery stroke of Pump piston 18 fuel is compressed under high pressure. The pump working chamber 22 is by means of the delivery pressure of a Feed pump 21 fuel from a Fuel tank 9 of the motor vehicle supplied. It can be provided that by the feed pump 21st Fuel from the fuel tank 9 in a Memory area 24 is promoted, in which a pressure according to the delivery pressure of the feed pump 21, for example, may be about 4 to 6 bar. From the Storage area 24 reaches fuel during the intake stroke of Pump piston 18 in the pump chamber 22. Between the Storage area 24 and the pump chamber 22 is a for Pump working chamber 22 opening check valve 23 arranged. In the line 14 is a from the Pump workspace 22 opening another check valve 25th arranged. The delivery line 13 from the feed pump 21 opens between the pump working chamber 22 and the other Check valve 25. The pump working space 22 can alternatively also via a through the pump piston 18th controlled connection to the storage area 24 for filling 18 be connected to the suction stroke of the pump piston. Of the Pump piston 18 acts with a control edge with a in the pump working chamber 22 opening opening of the compound to the storage area 24 through the pump piston 18 is closed or released. The check valve 23 can be omitted.

The fuel injection valve 12 is separate from the Fuel pump 10 is arranged and via the line 14 with connected to the pump working space 22. The Fuel injection valve 12 has a valve body 26 on, which may be formed in several parts, in the one Injection valve member 28 in a bore 30th is guided longitudinally displaceable. The valve body 26 indicates its the combustion chamber of the cylinder of the internal combustion engine facing end region at least one, preferably a plurality Injection openings 32. The injection valve member 28 has at its the combustion chamber end facing a For example, about conical sealing surface 34, which with one in the valve body 26 in the combustion chamber facing End region formed valve seat 36 cooperates, from or after which the injection openings 32 dissipate. in the Valve body 26 is between the injection valve member 28 and the bore 30 to the valve seat 36 toward an annular space 38th present, in its the valve seat 36 facing away End region by a radial extension of the bore 30 in a pressure chamber 40 surrounding the injection valve member 28 passes. The injection valve member 28 has the height of the Pressure chamber 40 by a cross-sectional reduction a Pressure shoulder 42 on. At the end of the combustion chamber facing away from the Injector member 28 engages a biased Closing spring 44, through which the injection valve member 28th is pressed toward the valve seat 36. The closing spring 44 is arranged in a spring chamber 46 of the valve body 26, the adjoins the bore 30. To the spring chamber 46 closes at the bore 30 facing away from the end in Valve body 26 a further bore 48, in which a Piston 50 is tightly guided, with the Injection valve member 28 is connected. The piston 50 limited with its the injection valve member 28 facing away Front side a control pressure chamber 52 in the valve body 26. Im Valve body 26, a channel 54 is formed, in which the Line 14 to the fuel pump 10 opens and in the Pressure chamber 40 opens.

From the channel 54 of the fuel injection valve 12 branches one Connection 56 to the control pressure chamber 52 from. The Fuel injector has a near the Fuel pump 10 arranged first control valve 60, for example, be integrated into the fuel pump 10 can. Through the first control valve 60 is a connection 59 of the pump working chamber 22 of the fuel pump 10 with controlled a discharge space, as the at least indirectly the memory area 24 can serve. The compound 59 branches downstream of the check valve 25 from the line 14 from. In connection 59 is upstream of the first Control valve 60, a pressure holding valve 62 is arranged. The Pressure holding valve 62, for example, by a Closing spring 63 loaded valve member 64 which against the Force of the closing spring 63 to the first control valve 60 out in Opening direction is movable. By the pressure holding valve 62nd becomes one compared to the pressure in the discharge chamber 24 increased Pressure in the line 14 and thus also in the pressure chamber 40th maintained.

The first control valve 60 is electrically controllable and has an actuator 61, which is an electromagnet or a Piezoelectric actuator can be, which is electrically controlled and through which a valve member of the control valve 60 is movable. The first control valve 60 may be pressure compensated or not be formed pressure balanced. The first control valve 60 is formed as a 2/2-way valve and by this In a first switching position, the connection 59 to Relief space 24 opened and in a second Switching position is the connection 59 to the discharge space 24th separated. The control valve 60 is powered by an electric Control device 66 in dependence on operating parameters the internal combustion engine controlled.

To control the pressure in the control pressure chamber 52 is a second control valve 68 is provided, through which a Connection 70 of the control pressure chamber 52 with a Relief space, for example, the relief space 24, is controlled. The second control valve 68 is electrical controllable and has an actuator 69, the one Electromagnet or a piezoelectric actuator can be, the electric is controlled and by a valve member of the Control valve 68 is movable. The second control valve 68 is preferably formed pressure balanced. The second Control valve 68 is designed as a 2/2-way valve, by the connection 70 in a first switching position the control pressure chamber 52 is opened with the discharge chamber 24 is and by that in a second switching position the Connection 70 of the control pressure chamber 52 with the Relief space 24 is disconnected. In compound 59 of the Control pressure space 52 with the line 14 is a Throttle 58 and provided in the connection 70 of the Control pressure space 52 with the fuel tank 24 is between the control pressure chamber 52 and the second control valve 68 another throttle point 71 is provided. The second Control valve 68 is also controlled by the controller 66 controlled. The control of the control valves 60,68 through the controller 66 is dependent on Operating parameters of the internal combustion engine, such as For example, speed, load and temperature.

Below is the function of Fuel injection device explained. During the suction stroke of the Pump piston 18 is from the storage area 24 fuel through the open check valve 23 via the line thirteenth fed into the pump working chamber 22. During the delivery stroke of the Pump piston 18 closes the check valve 23 and the Check valve 25 opens, wherein the first control valve 60th is open, so that the connection 59 with the Relief space 24 is open. The fuel injection begins with a pre-injection, the first Control valve 60 is opened by the control device 66, so that the connection 59 to the relief space 24 is opened is. In the pump working chamber 22 and in the line 14 and in the Pressure chamber 40 of the fuel injection valve 12 may be thus only build up a pressure, as he through the Pressure holding valve 62 is adjusted. If that by the Pressure retention valve 62 set pressure is exceeded, so opens the pressure-holding valve 62 and fuel flows through the opened first control valve 60 and the connection 59 in the relief space 24. Subsequently remains in the Line 14 and the pressure chamber 40 prevailing pressure at least almost constant. The opening pressure of the pressure holding valve 62 is due to the bias of its closing spring 63rd certainly. The pre-injection takes place with a through the Pressure retention valve 62 limited pressure. The second Control valve 68 is controlled by the control device 66 open, so that in the control pressure chamber 52 despite its Make connection 56 with the line 14 no high pressure can, but this reduced to the discharge space 24 down becomes. By the throttle points 58 and 71 it is achieved that from the channel 54 only a small amount of fuel in the Relief space 24 can drain. When in the pressure room 40th prevailing pressure has reached such a level that this on the pressure shoulder 42 on the Injection valve member 28 acting in the opening direction 29 Exerts force that is greater than the force of the closing spring 44, so lifts the injection valve member 28 with his Sealing surface 34 from the valve seat 36 and fuel is through the injection openings 32 into the combustion chamber of Cylinder of the internal combustion engine injected. Of the Opening pressure of the fuel injection valve 12 is at opened second control valve 68 from the force of Closing spring 44 and by the control pressure in the space 52nd prevailing residual pressure on the piston 50 generated force dependent.

In Figure 2, the course of the pressure p to the Injection openings 32 of the fuel injection valve 12 via time t during an injection cycle. The Pre-injection corresponds to one in Figure 2 with I designated injection phase.

To end the pilot injection, the second Control valve 68 closed by the control device 66, so that the control pressure chamber 52 from the discharge space 24th is separated and in the control pressure chamber 52 via the Compound 56 with the line 14 builds high pressure. This is on the piston 50 on the Injector member 28, a force of the closing spring 44th generates supportive force so that the Injection valve member 28 against its opening direction 29th moved and with its sealing surface 34 on the valve seat 36 to Plant comes and the pre-injection is finished.

For a subsequent main injection, the second Control valve 68 opened by the controller 66, so that the control pressure chamber 52 is relieved again and the Fuel injection valve 12 opens. The first control valve 60 may be open at the beginning of the main injection, so the connection 59 to the relief space 24 is open and in the conduit 14 and the pressure chamber 40 of the Fuel injection valve 12 through the pressure-holding valve 62 established pressure. The main injection begins then with a pressure level as well as the pre-injection is done. The main injection starts when closed first control valve 60 with a higher pressure level than at initially opened first control valve 60. Subsequently becomes the first control valve 60 by the controller 66 closed, so that the connection 59 with the Relief space 24 is disconnected and the main injection continues with a pressure as he according to the Profile of the cam 20 in the pump working chamber 22 is generated. It can also be provided that initially the first Control valve 60 is closed, but the second Control valve 68 is still closed, so that no Injection takes place. The second control valve 68 then becomes delayed until it opens, causing the beginning of the Main injection is delayed and also the Main injection starts at a higher pressure. The Main injection corresponds in Figure 2 one with II designated injection phase, wherein the pressure curve with shown by the solid line in the event that the first control valve 60 is opened at the beginning, and the Pressure curve with dashed line in case is shown that the first control valve 60 is already closed Beginning is closed.

To finish the main injection, the second Control valve 68 closed by the control device 66, so that the control pressure chamber 52 from the discharge space 24th is separated and in the control pressure chamber 52 by the Connection with the line 14 and thus the Pump work space 22 builds high pressure, through which the Fuel injection valve 12 is closed. The first Control valve 60 remains closed, so that the Connection 59 to the accumulator 62 is disconnected. For one Nacheinspritzung the second control valve 68 through the Control device 66 opened again, so that the Control pressure chamber 52 is relieved again and the Fuel injection valve 12 opens. The post-injection takes place with a pressure curve corresponding to the profile of Cam 20. To end the post-injection is the second control valve 68 by the control device 66 closed and / or the first control valve 60 through the Control device 66 opened. The post-injection corresponds to a designated in Figure 2 with III Injection phase.

After completion of the post-injection remains the second Control valve 68 closed. Another, in Figure 2 with Dashed lines shown post-injection can by the pressure set by the pressure-holding valve 62 take place in the pressure chamber 40, the channel 54 and the line 14. In this case, the pressure chamber 40, the channel 54 and the act Line 14 as memory elements that make up the Fuel quantity taken for further post-injection becomes. For the further post-injection is the first Control valve 60 is opened and the second control valve 68 is also open for a short time. The pump piston 18 can at the time of further post-injection in the intake stroke located, the pump working space 22 through the closed check valve 25 from the line 14th disconnected.

FIG. 3 shows another embodiment of the invention Fuel injection device shown in which the basic structure essentially the same as in the the above-explained embodiment is, however, the arrangement and training the second control valve 168 modified is. The second control valve 168 is electrically controllable and has an actuator 169, which is an electromagnet or may be a piezoelectric actuator, which is electrically controlled and by a valve member of the control valve 168 movable is. The second control valve 168 is in the connection 56 the control pressure chamber 52 is arranged with the channel 54. The second control valve 168 is as a 3/2-way valve formed by the in a first switching position the Connection 56 of the control pressure chamber 52 with the channel 54 and so that the pump working chamber 22 is open and the Control pressure chamber 52 is separated from the discharge chamber 24. In a second switching position of the second control valve 168 is the control pressure chamber 52 with the discharge space 24th connected and the connection 56 to the channel 54 and thus to Pump workspace 22 is disconnected. To enable the Opening of the fuel injection valve 12 becomes the second Control valve 168 by the controller 66 in his second switching position brought in the control pressure chamber 52 is relieved in the discharge chamber 24, and to Closing the fuel injection valve 12 becomes the second Control valve 168 brought into its first switching position, in the control pressure chamber 52 is connected to the channel 54.

Otherwise, the functioning of the Fuel injection device according to this modified Same execution as in the according to FIG. 1

In Figure 4 is a further embodiment of Fuel injection device shown in which the basic structure essentially the same as in the Embodiment of Figure 1 is, however, the arrangement and Training the second control valve 268 is modified. The second control valve 268 is electrically controllable and has an actuator 269, which is an electromagnet or a Piezoelectric actuator can be, which is electrically controlled and by a valve member of the control valve 268 movable is. On the second control valve 268 on the one hand the Line 14 connected and on the other hand is to this the Channel 54 to the pressure chamber 40 and the connection 56 to Control pressure chamber 52 connected. The second control valve 268 is formed as a 3/2-way valve, through which in a first switching position, the connection 56 of the Control pressure chamber 52 is open with the channel 54 and the Channel 54 from the line 14 and thus from the pump working space 22 is disconnected. In a second switching position of the second Control valve 268 is through this the control pressure chamber 52nd separated from the channel 54 and the channel 54 is with the line 14 and thus connected to the pump working space 22. Of the Control pressure chamber 52 has a connection 270 with the Relief 24 on, in the one to the relief space 24th opening check valve 272 is arranged and also a throttle point may be provided. To enable the opening of the fuel injection valve 12 is the second control valve 268 by the controller 66 in brought his second switch position in which the Control pressure chamber 52 is separated from the channel 54 and the channel 54 is connected to the line 14 so that the of the Fuel pump 10 generated pressure in the pressure chamber 40 of the Fuel injection valve 12 passes, the Control pressure chamber 52 is relieved in the discharge chamber 24. To close the fuel injection valve 12 is the second control valve 268 in its first switching position brought in the control pressure chamber 52 with the channel 54th However, the channel 54 is connected from the line 14th is disconnected. The in the pressure room 40 of the Fuel injection valve 12 prevailing pressure acts also in the control pressure chamber 52, causing the Fuel injection valve 12 is closed. Otherwise is the operation of the fuel injection device according to this modified version same as in accordance with FIG. 1

Claims (4)

1. Fuel injection device for internal combustion engines, having a fuel pump (10) for every cylinder of the internal combustion engine, which fuel pump (10) has a pump piston (18) which is driven in a reciprocal movement by the internal combustion engine and delimits a pump working chamber (22) to which fuel is fed from a fuel reservoir container (9) and which is connected to a fuel injection valve (12) which has an injection valve element (28) by which at least one injection opening (32) is controlled and which can be moved in an opening direction (29) counter to a closing force by the pressure which prevails in a pressure space (40) which is connected to the pump working chamber (22), having a first electrically controlled control valve (60) by which one connection (59) of the pump working chamber (22) to a relief space (24) is controlled, a pressure-holding valve (62) which opens towards the first control valve (60) being arranged between the pump working chamber (22) and the first control valve (60), by means of which pressure-holding valve (62) a pressure is maintained which is higher than the pressure which prevails in the relief space (24), characterized in that a second electrically controlled control valve (68; 168; 268) is provided by which the pressure which prevails in a control pressure space (52) of the fuel injection valve (12) is controlled, by means of which pressure the injection valve element (28) is acted on at least indirectly in the closing direction, in that a non-return valve (25) which opens towards the pressure-holding valve (62) is arranged between the pump working chamber (22) and the pressure-holding valve (62), by means of which non-return valve (25) the pump working chamber (22) can be decoupled from the pressure space (40) and from the pressure-holding valve (62), and in that the pump working chamber (22) has a connection (13) to the fuel reservoir container (9) or an accumulator region (24), which connection (13) opens between the said pump working chamber (22) and the non-return valve (25).
2. Fuel injection device according to Claim 1, characterized in that the second control valve (168) is configured as a 3/2-way valve by which the control pressure space (52) is connected to the pump working chamber (22) and separated from a relief space (24) in a first switching position, and by which the control pressure space (52) is connected to the relief space (24) and separated from the pump working chamber (22) in a second switching position.
3. Fuel injection device according to Claim 1, characterized in that the second control valve (268) is configured as a 3/2-way valve by which the control pressure space (52) is separated from a pressure space (40) of the fuel injection valve (12) and the pressure space (40) is connected to the pump working chamber (22) in a first switching position, and by which the control pressure space (52) is connected to the pressure space (40) and the pressure space (40) is separated from the pump working chamber (22) in a second switching position.
4. Fuel injection device according to Claim 3, characterized in that the control pressure space (52) has a connection (270) to a relief space (24), in which connection (270) a non-return valve (272) which opens towards the relief space (24) is preferably arranged.

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