EP1260705B1 - Fuel injection system for internal combustion engine - Google Patents

Description

State of the art

The invention is based on one Fuel injection device for an internal combustion engine according to the preamble of claim 1.

Such a fuel injector is through the EP 0 823 549 A known. This fuel injector has one for each cylinder of the internal combustion engine Fuel pump and a fuel injector on that form a structural unit. The fuel pump has one by the internal combustion engine in one stroke driven pump piston on which a pump work space limited. It is a first electrically controlled one Control valve provided through which a connection of the Pump work space is controlled with a relief space. The fuel injection valve has an injection valve member on, controlled by the at least one injection opening and that through the one with the pump work room connected pressure chamber prevailing pressure against a Closing force is movable in the opening direction. It is a second electrically controlled control valve provided, through which the in a control pressure room of the Pressure prevailing fuel injector is controlled through which the injection valve member at least indirectly in Closing direction is applied. By the second Control valve connects the control pressure chamber with controlled the pump work space. This Fuel injector allows at one Injection cycle a pre-injection in succession a small amount of fuel, a main injection one large amount of fuel and post-injection one low fuel quantity. Both control valves are through a common actuator in the form of an electromagnet controlled. To make this possible, the two valves be arranged axially to each other, whereby the assembly from Fuel pump and fuel injector a great one Has overall height.

Advantages of the invention.

The fuel injection device according to the invention with the Features according to claim 1 has the advantage that the two control valves in any way, for example can be arranged side by side so that the Unit consisting of fuel pump and fuel injection valve only has a low overall height.

In the dependent claims are advantageous Refinements and developments of the invention Fuel injector specified. Training according to claim 5 enables fuel injection with graduated pressure increase.

drawing

An embodiment of the invention is in the drawing shown and in the description below explained. 1 shows a Fuel injection device for an internal combustion engine in a schematic representation, Figure 2 shows a pressure curve Injection openings of a fuel injector Fuel injection device and Figure 3 die Fuel injection device in a longitudinal section.

Description of the embodiment

In Figures 1 and 3 is one Fuel injection device for an internal combustion engine shown a motor vehicle. The Fuel injection device is a so-called pump-nozzle system trained and has the for each cylinder Internal combustion engine each have a fuel pump 10 and a Fuel injection valve 12, which is an assembly. form. The fuel pump 10 has one in a cylinder 16 tightly guided pump piston 18 by a Cam 20 of a camshaft of the internal combustion engine against the Force of a return spring 19 in one stroke is driven. The pump piston 18 delimits in the cylinder 16 a pump working space 22, in which the pump piston 18 Fuel is compressed under high pressure. the Pump workspace 22 becomes fuel from a Fuel tank 24 supplied, for example by means of a low pressure pump, not shown.

The fuel injector 12 is below the Fuel pump 10 to the combustion chamber of the internal combustion engine arranged and connected to the pump work space 22. The Fuel injection valve 12 has a valve body 26 on, which can be formed in several parts, in which a piston-shaped injection valve member 28 in a bore 30 is guided longitudinally. The valve body 26 instructs its the combustion chamber of the cylinder of the internal combustion engine facing end region at least one, preferably several Injection openings 32 on. The injection valve member 28 has at its end area facing the combustion chamber for example, approximately conical sealing surface 34, which with a valve seat 36 formed in the valve body 26 cooperates, from or after which the injection openings 32 lead away. In the valve body 26 is between the Injection valve member 28 and bore 30 to valve seat 36 an annular space 38 is present, through a radial Widening the bore 30 into the injection valve member 28 surrounding pressure chamber 40 passes. The Injection valve member 28 has in the area of pressure chamber 40 a pressure shoulder 42. At the end facing away from the combustion chamber of the injection valve member 28 engages a biased Closing spring 44 through which the injection valve member 28 is pressed towards the valve seat 36. The closing spring 44 is arranged in a spring chamber 46 of the valve body 26, the connects to the bore 30. To the spring chamber 46 closes at the end facing away from the bore 30 Valve body 26 to a further bore 48 in which a Piston 50 is guided tightly with the Injection valve member 28 is connected. The piston 50 limited with its end face facing away from the spring chamber 46 a control pressure chamber 52 in the valve body 26. The pressure chamber 40 is via a channel 54 running in the valve body 26 connected to the pump workspace 22. The control pressure room 52 has a constantly open connection with one Relief space on than that for example the Serves fuel tank 24, and in the at least a throttle point 56 is provided.

The fuel injector has two electrical controlled control valves 60,70 on the unit of fuel pump 10 and fuel injection valve 12 are arranged. A first control valve 60 is used Connection of the pump workspace 22 with a Relief chamber controlled, the relief chamber for example, the fuel tank 24 is or a other area where there is little pressure. The first control valve 60 can be used as a 2/2-way valve or preferably be designed as a 2/3-way valve. The first control valve 60 has a valve member 61 which against the force of a return spring 62 during training movable as a 2/2-way valve between two switching positions and when training as a 2/3 way valve between three Switch positions is movable.

The second control valve 70 connects the Control pressure chamber 52 of the fuel injection valve 12 with the pump work space 22 controlled. The second control valve 70 is designed as a 2/2-way valve and has a Valve member 71 on, against the force of a return spring 72 is movable between two switching positions.

The two control valves 60, 70 are activated by a common actuator 64 through which the pressure in one Actuator pressure chamber 66 is controlled. The actuator 64 can For example, a piezo actuator that is dependent on one its length applied to this electrical voltage changes. If there is no voltage at the actuator 64, it points this is a short length and the pressure in the Actuator pressure space 66 is small. With increasing to the actuator 64 applied electrical voltage increases Length and the pressure in the actuator pressure chamber 66 is increased. The Valve member 61 of the first control valve 60 is on the one hand acted upon by the pressure in the actuator pressure chamber 66 and on the other hand from the force of the preloaded return spring 62 low pressure in the actuator pressure chamber 66 is the first Control valve 60 due to the on the valve member 61st acting force of the return spring 62 in a first Switch position in which the pump working space 22 with the Fuel reservoir 24 is connected. For switching of the first control valve 60 into a second or third Switch position is such a high on the actuator 64 electrical voltage applied that the pressure in the Actuator pressure chamber 66 is sufficiently high that the through this force generated on the valve member 61 is greater than the force of the return spring 62 and the valve member 61 in another switch position is moved. When training the first control valve 60 as a 2/3 way valve is through this in a second switching position, the pump working space 22 via a throttle point 63 with the relief chamber 24 connected. In its second switch position, the first Control valve 60 brought by appropriate Actuation of the actuator 64, the pressure in the actuator pressure chamber 66 is increased such that the valve member 61 by the this acting pressure force against the force of the Return spring 62 to achieve the second Switch position performs the required stroke. In the third Switch position of the first control valve 60 is by this the pump work space 22 is separated from the relief space 24. In its third switching position becomes the first control valve 60 brought by by appropriate control of the actuator 64 the pressure in the actuator pressure chamber 66 is increased further, so that the valve member 61 by the compressive force acting thereon against the force of the return spring 62 to achieve the third switching position executes the required further stroke.

The second control valve 70 also has a valve member 71 on the one hand from the pressure in the actuator pressure chamber 66 and on the other hand by the force of the prestressed return spring 72 is applied. At low pressure in actuator pressure chamber 66 the control valve 70 is due to the the valve member 71 acting force of the return spring 72nd in a first switching position in which the control pressure chamber 52 is separated from the pump work space 22. For switching of the second control valve 70 into its second switching position, in which the control pressure chamber 52 with the pump work chamber 22 is connected, the actuator 64 is so high electrical voltage applied that the pressure in the Actuator pressure chamber 66 is sufficiently high that the through this force generated on the valve member 71 is greater than the force of the return spring 72 and the valve member 71 a Performs lifting movement in its second switching position.

The by the return spring 72 on the valve member 71 of the second control valve 70 force is greater than that by the return spring 62 on the valve member 61 of the first control valve 60 applied force, so that for the Switching the second control valve 70 into its second Switch position a higher pressure in the actuator pressure chamber 66 and thus actuation of the actuator 64 with a higher one electrical voltage is required than for that Switching the first control valve 60 into its second and third switch position. It is therefore possible to do the first Control valve 60 by increasing the pressure in the actuator pressure chamber 66 to switch to its second or third switching position, while the second control valve 70 in its first Switch position remains. With a further pressure increase the second control valve 70 is also in the actuator pressure chamber 66 switched its second switching position.

The function of Fuel injector explained. The common one Actuator 64 of the control valves 60, 70 is controlled by an electrical Control device 74 controlled. During the suction stroke of the Pump piston 18 is the first control valve 60 in its first switching position, so that the connection of the Line part 56 with the fuel tank 24 is open and in the pump work room 22 and in Pressure chamber 40 of fuel injector 12 no Can build high pressure. The second control valve 70 is located also in its first switching position, so that the Control pressure chamber 52 is separated from the pump work chamber 22. When the injection is to start, the actuator becomes 64 controlled by the control device 74 such that the Pressure in the actuator pressure chamber 66 becomes so high that the first Control valve 60 in its second or third switching position is switched. The pump workspace 22 is then only still via the throttle point 63 with the relief chamber 24 connected or separated from this, so that in Pump work chamber 22 and an increased pressure in the pressure chamber 40 builds. If the prevailing in the pressure chamber 40 Pressure across the pressure shoulder 42 on the injector member 28 acting force is greater than that by the closing spring 44 force generated on the injection valve member 28, moves the injection valve member 28 in the opening direction 29 and releases the at least one injection opening 32 through which Fuel into the combustion chamber of the cylinder Internal combustion engine is injected. The Fuel injection takes place as one Pre-injection with relatively low pressure and with low Quantity. In Figure 2 is the course of the to Injection openings 32 of the fuel injection valve 12 prevailing pressure P during an injection cycle over the Time t shown. The pilot injection is I in FIG. 2 designated. The second remains during the pre-injection Control valve 70 in its first switching position, so that the Control pressure chamber 52 is separated from the pump work chamber 22 and there is no high pressure in the control pressure chamber 52.

To end the pre-injection, the first Control valve 60 by reducing the corresponding to the Actuator 64 applied voltage and thus reduced pressure in Actuator pressure chamber 66 again in its first switching position switched so that the pump working chamber 22 is not throttled is connected to the relief chamber 24 and in this the Pressure drops so that the fuel injector 12th due to the force of the closing spring 44 closes. To a subsequent main injection is by the Control device 74 to actuator 64 first of all high voltage is applied that the pressure in the actuator pressure chamber 66 rises so much that the first control valve 60 in its second switch position and the pump workspace 22 with the relief chamber 24 via the throttle point 63 connected is. In the pump work chamber 22 and in the pressure chamber 40 thus builds high pressure according to the profile of the Cam 20 on, however, by the throttled connection with the relief chamber 24 is somewhat reduced. If the by the pressure prevailing in the pressure chamber 40 via the Pressure shoulder 42 acting on the injection valve member 28 Force is greater than that by the closing spring 44 on the Injection valve member 28 generated force, so it moves Injection valve member 28 in the opening direction 29 and gives the at least one injection port 32 free through which Fuel into the combustion chamber of the cylinder Internal combustion engine is injected. The main injection, which is denoted by II in Figure 2, thus begins with a relatively low pressure and with low Injection quantity. With a time delay the Control device 74 to the actuator 64 an increased voltage applied so that the pressure in the actuator pressure chamber 66 is so strong increases that the first control valve 60 into its third Switched switching position and the pump working space 22 from Relief chamber 24 is separated. In the pump work room 22 and In the pressure chamber 40, a further increase is built High pressure according to the profile of the cam 20 so that the further main injection with high pressure and large Injection quantity takes place. The pressure at which that Fuel injection valve 12 for the main injection opens, can by the time of switching the first Control valve 60 in its second and / or third Switch position can be influenced. The later the control valve 60 is switched, the higher the pressure at which the Main injection begins.

To end the main injection, the Control device 74 a further increased voltage on the Actuator 64 applied so that the pressure in the actuator pressure chamber 66 becomes high that the second control valve 70 in its second Switched position. The first control valve 60 remains in its third switching position, so that the Pump working space 22 is separated from the relief space 24. Due to the high pressure now prevailing in the control pressure chamber 52, which acts on the piston 48 and the closing spring 44th assists, the fuel injection valve 12 closes. Subsequent injection follows, which is shown in FIG is designated III by the control device 74 a lower voltage is again applied to the actuator 64 is so that the pressure in the actuator pressure chamber 66 is so strong drops the second control valve 70 in its first Switched switching position and the control pressure chamber 52 from Pump work space 22 is separated. The first control valve 60 remains in its third with post-injection Switch position, so that the pump working space 22 from Relief chamber 24 is separated and the post-injection with a pressure profile corresponding to the profile of the cam 20 he follows. To end the post-injection, the Control device 74 only a small voltage to the Actuator 64 applied so that the pressure in the actuator pressure chamber 66 is small that the first control valve 60 in its first Switched switching position in which the pump workspace 22nd is connected to the relief chamber 24. The second Control valve 70 is then in its first Switch position in which the control pressure chamber 52 from Pump work space 22 is separated.

In Figure 3 is the fuel injector excerpts according to an executed construction shown. The assembly of fuel pump 10 and Fuel injection valve 12 has valve body 26, with which a pump body 11 is connected, in which the Cylinder 16 is formed, in which the pump piston 18 is led. In the pump body 11 and / or in the valve body 26 leads a channel 80 from the pump working space 22, which closes branches the two control valves 60,70. The two Control valves 60, 70 are arranged side by side, the Direction of movement of their piston-shaped valve members 61.71 at least approximately parallel to one another and parallel to the direction of movement of the pump piston 18. The Control valves 60, 70 are between the fuel pump 10 and arranged the fuel injection valve 12. In the valve body 26 is between the control valves 60, 70 and Pump work space 22, the actuator pressure chamber 66 is formed in with the valve members 61, 71 of the control valves 60, 70 protrude their ends. The valve members 61, 71 are thus on their end faces from the one prevailing in the actuator pressure chamber 66 Pressure applied. The actuator pressure chamber 66 is over a Channel 82 with an actuator 64 at least indirectly limited workspace 84 connected. Through the actuator 64 depending on its length extension, that of the on these applied voltage is dependent from the work space 84 Fuel displaces and with it the pressure in the actuator pressure chamber 66 changed. The actuator 64 is next to the fuel pump 10 arranged and its longitudinal extent runs for example inclined to the direction of movement of the Pump piston 18.

The valve members 61, 71 of the control valves 60, 70 are each slidably guided in a cylinder bore 86.87, wherein on the front side facing away from the actuator pressure chamber 66 each the return spring 62.72 attacks. The valve member 61 of the first control valve 60 has one in one Actuator pressure chamber 66 leading section 86a of the Cylinder bore 86 tightly guided section 61a and a section facing the return spring 62 86b of the cylinder bore 86 arranged section 61b. The Diameter of section 86a of cylinder bore 86 and of the portion 61a of the valve member 61 is larger than that Diameter of section 86b of cylinder bore 86 and of section 61b of valve member 61. Between the Sections 61a and 61b is the diameter of the valve member 61 reduced in a section 61c, at the transition of the Section 61a to section 61c, for example conical sealing surface 88 is formed, which in one by expanding the cross-section of the cylinder bore 86 formed space 90 is arranged. At the transition from room 90 to section 86b of cylinder bore 86 is a valve seat 89 formed, which is, for example, conical. In the Room 90 opens the channel 80 to the pump work room 22 and from The space 54 leads the channel 54 into the pressure space 40. from Section 86b of the cylinder bore 86 leads to Fuel reservoir 24 leading as a relief space Channel 91 onwards. The area of section 86b of FIG Cylinder bore 86 in which the return spring 62 is arranged is also with the fuel tank 24 as Relief room connected. Through the valve member 61 of the the first control valve 60 becomes a connection of the space 90 and thus the pump workspace 22 with the Fuel reservoir 24 controlled as a relief space. If the pressure in the actuator pressure chamber 66 is low, it will Valve member 61 through the return spring 62 in the Actuator pressure chamber 66 pushed into its first Switch position in which the sealing surface 88 at a distance from Valve seat 89 is arranged so that the space 90 over a between the portion 61c of the valve member 61 and the Section 86b of the cylinder bore 86 formed annular gap with the channel 91 leading away from this and with the Fuel reservoir 24 is connected. If the pressure is increased in the actuator pressure chamber 66, that moves Valve member 61 against the force of the return spring 62 in its second switching position, in which the valve member 61 with its sealing surface 88 does not yet abut the valve seat 89 and the space 90 via the restriction 63 with the section 86b of the cylinder bore 86 and from this via the channel 91 is connected to the fuel tank 24. The Throttle point 63 can be between the sealing surface 88 and the valve seat 89 may be formed. If the pressure in the Actuator pressure chamber 66 is further increased, so the valve member 61 in its third switching position, in which it moves its sealing surface 88 abuts the valve seat 89 and thus the Space 90 is separated from the fuel tank 24.

The cylinder bore 87 in which the valve member 71 of the second control valve 70 is arranged, has one in the Actuator pressure chamber 66 opening section 87a and a opposite section 87b, in which the Return spring 72 is arranged. Between the sections 87a and 87b of the cylinder bore 87 is through a radial Extension formed a room 92, from which a channel 93 to Control pressure chamber 52 leads away. The valve member 71 has one arranged in the section 87a of the cylinder bore 87 Section 71a and one in section 87b of the cylinder bore 87 tightly guided section 71b. Between The valve member 71 has sections 71a and 71b Section 71c with a reduced diameter. At the transition from section 71b to section 71c of valve member 71 on this, for example, a conical sealing surface 94 educated. In section 87a of the cylinder bore 87 is on Transition to room 92, for example a conical one Valve seat 95 formed. The pump work room 22nd leading channel 80 opens into section 87a of the Cylinder bore 87. The area of section 87b of the Cylinder bore 87 in which the return spring 72 is arranged is with the fuel tank 24 as Relief room connected. If that's through the return spring 72 force exerted on the valve member 71 is greater than that by the pressure prevailing in the actuator pressure chamber 66 Valve member 71 exerted force, so that is Valve member 71 in its first switching position, in the this rests with its sealing surface 94 on the valve seat 95. The space 92 and thus the control pressure space 52 is therefore from Pump work space 22 separately. If the pressure in the Actuator pressure chamber 66 is so high that through this on the Valve member 71 force is greater than the force of Return spring 72, the valve member 71 moves in ' his second switch position, in which this with his Sealing surface 94 is lifted off the valve seat 95 and the space 92 via a between the section 71c of the valve member 71 and the section 87a of the cylinder bore 87 Annular gap with channel 80 and thus the pump work area 22 is connected.

Claims (7)

1. Fuel injection device for an internal combustion engine, having a fuel pump (10) for each cylinder of the internal combustion engine, which has a pump piston (18) which is driven in a reciprocating movement by the internal combustion engine and delimits a pump working chamber (22) which is connected to a fuel injection valve (12) which forms a structural unit with the fuel pump (10) and has an injection valve element (28), by which at least one injection opening (32) is controlled and which can be moved in the opening direction (29) counter to a closing force by the pressure prevailing in a pressure chamber (40) connected to the pump working chamber (22), a first electrically driven control valve (60) being provided, by which, at least indirectly, a connection between the pump working chamber (22) and a relief chamber (24) is controlled, and a second electrically driven control valve (70) being provided, by which a connection between a control pressure chamber (52) of the fuel injection valve (12) and the pump working chamber (22) is controlled, the injection valve element (28) being loaded, at least indirectly, in the closing direction by the pressure prevailing in the control pressure chamber (52), and both control valves (60, 70) being driven by a common actuator (64), characterized in that the pressure in an actuator pressure chamber (66) is driven by the actuator (64), and in that the two control valves (60, 70) each have a valve element (61, 71) loaded by the pressure prevailing in the actuator pressure chamber (66).
2. Fuel injection device according to Claim 1, characterized in that, when the actuator pressure chamber (66) is unpressurized, the second control valve (70) is in a switching position in which the control pressure chamber (52) is isolated from the pump working chamber (22).
3. Fuel injection device according to Claim 1 or 2, characterized in that the control pressure chamber (52) has a connection which is always open to a relief chamber (24), in which connection at least one throttling point (63) is provided.
4. Fuel injection device according to one of Claims 1 to 3, characterized in that the two control valves (60, 70) are arranged beside each other.
5. Fuel injection device according to one of Claims 1 to 4, characterized in that the first control valve (60) is formed as a 2/3-way directional valve, by means of which, in a first switching position with low pressure in the actuator pressure chamber (66), a non-throttled connection between the pump working chamber (22) and the relief chamber (24) is opened, by means of which, in a second switching position with increased pressure in the actuator pressure chamber (66), a connection having the throttling point (63) between the pump working chamber (22) and the relief chamber (24) is opened, and by means of which, in a third switching position with further increased pressure in the actuator pressure chamber (66), the pump working chamber (22) is isolated from the relief chamber (24).
6. Fuel injection device according to one of the preceding claims, characterized in that the actuator (64) is a piezoelectric actuator.
7. Fuel injection device according to one of the preceding claims, characterized in that the valve elements (61, 71) of the two control valves (60, 70) can in each case be moved counter to the force of a return spring (62, 72), and in that the force of the return spring (72) acting on the valve element (71) of the second control valve (70) is greater than the force of the return spring (62) acting on the valve element (61) of the first control valve (60).

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