EP1525390A1

EP1525390A1 - Fuel injection device for an internal combustion engine

Info

Publication number: EP1525390A1
Application number: EP03709648A
Authority: EP
Inventors: Peter Boehland
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2002-07-20
Filing date: 2003-02-25
Publication date: 2005-04-27
Anticipated expiration: 2023-02-25
Also published as: DE50301949D1; DE10233099A1; US7017553B2; EP1525390B1; WO2004016938A1; US20050178362A1; JP2005533967A

Abstract

Disclosed is a fuel injection device comprising a high-pressure fuel pump (10) and a fuel injection valve (12) that is connected thereto and is provided for each cylinder of the internal combustion engine. Said high-pressure fuel pump (10) comprises two pump pistons (18, 118) that are driven by the internal combustion engine in a lifting movement and define a pump working chamber (22) to which fuel is fed from a fuel reservoir (24). A second pump piston is guided in an at least approximately coaxially displaceable manner within a first pump piston (18). Both pump pistons (18, 118) can optionally be coupled to each other such that said pistons (18, 118) move as a unit during a delivery stroke, or the second pump piston (118) can be fixed in a passive position such that only the first pump piston (18) performs a delivery stroke. The fuel injection valve (12) is provided with two injection valve members (28, 128), a second injection valve member (128) which is at least indirectly impinged upon by the pressure prevailing in a control pressure chamber (52) being guided in a displaceable manner within the first injection valve member (28). The control pressure chamber (52) is provided with a connection (53) to the pump working chamber (22), which is controlled by the second pump piston (118), the control pressure chamber (52) being separated from the pump working chamber (22) if the second pump piston (118) is placed in the passive position.

Description

Fuel injection device for an internal combustion engine

State of the art

The invention relates to a Kraf material injection device for an internal combustion engine according to the preamble of claim 1.

Such a fuel injection device is known from EP 0 987 431 A2. This Kraf substance injection device has a

High-pressure fuel pump and a fuel injection valve connected to this for each cylinder of the internal combustion engine. The high-pressure fuel pump has a pump piston which is driven by the internal combustion engine in a stroke movement and which delimits a pump working space. The fuel injection valve has a pressure chamber connected to the pump work chamber and an injection valve member through which at least one injection opening is controlled and which can be moved in the opening direction to release the at least one injection opening by the pressure prevailing in the pressure chamber against a closing force. A control valve is provided through which a connection of the pump work space to a relief space and a pressure source is controlled. When the control valve is open, the pump work space is filled with fuel from the pressure source during the suction stroke of the pump piston. The aim is that the high-pressure pump already at a low speed Internal combustion engine a high pressure is generated so that high performance and high torque of the internal combustion engine is achieved. However, the pressure generated by the high-pressure pump increases with the speed of the internal combustion engine, the maximum pressure generated having to be limited in order to ensure sufficient durability of the high-pressure pump. With a given drive of the high pressure pump and a given diameter of the pump piston, a compromise in the design must be found here, on the one hand to achieve a sufficiently high pressure at low speed and on the other hand not to exceed the maximum pressure specified for reasons of durability. The injection cross section, which is controlled by the injection valve member of the fuel injection valve, is always the same size. This does not enable optimal fuel injection under all operating conditions of the internal combustion engine.

Advantages of the invention

The fuel injection device according to the invention with the features according to claim 1 has the advantage that the pressure generated by the high pressure pump can be limited by the second pump piston is brought into its passive position and only the first pump piston delivers fuel. It can be provided that both pump pistons are coupled to one another and carry out a delivery stroke at low engine speed, while at high speed the second pump piston is arranged in its passive position and only the first

Pump piston performs a delivery stroke so that the pressure generated is reduced. The diameter of the first pump piston can be such that a high pressure is generated even at low speed. In addition, the fuel injection device according to the invention has the advantage that with the second injection valve member may be released to the at least one second Einspritzöffnμng additional injection cross section or closed, so ^'that the injection cross section on the

Operating conditions of the internal combustion engine can be optimally adjusted. The control of the injection cross section is carried out in a simple manner by the second pump piston, so that no further effort is required for this.

Advantageous refinements and developments of the fuel injection device according to the invention are specified in the dependent claims. The embodiment of claim 2 enables an increase of the opening pressure of the second injection valve member when in _its, passive position disposed second pump piston. The embodiment according to claim 3 enables a reduction in the opening pressure of the second injection valve member with the second pump piston arranged in its passive position. The embodiment according to claim 4 enables an advantageous arrangement of the second pump piston in its passive position. The training according to claim 5 enables easy manufacture of the first Pu piston. The embodiment according to claim 8 enables pressure equalization between the pump work space and the space in the first pump piston in the event of a leak. The configuration according to claim 9 ensures that when pump pistons are coupled to one another, no fuel can flow out of the pump work space through the through hole in the second pump piston. The design according to claim 10 ensures that the second pump piston abuts against the boundary of the pump working space in the region of the inner dead center of the pump piston. The design according to claim 12 ensures that with the second pump piston arranged in its passive position during the delivery stroke of the first pump piston, through the through hole in the second

Pump piston no fuel from the pump work space can drain off. Due to the design according to claim 13, a pressure equalization between the through bore in the second pump piston and the pump working space is achieved in the area of the inner dead center of the pump piston. Through the design according to claim 14, a secure contact of the second pump piston with the boundary is achieved. An arrangement of the second pump piston in its passive position is achieved in a simple manner by the design according to claim 15.

drawing

Several embodiments of the invention are shown in the drawing and explained in more detail in the following description. 1 shows a

Fuel injection device for an internal combustion engine in a schematic representation in a longitudinal section according to a first embodiment, FIG. 2, the fuel injection device in sections according to a second embodiment, FIG

III designated section in an enlarged view, Figure 4 shows a section of the fuel injection device designated IV in Figure 1 in an enlarged view with two pump pistons in a coupled state in an outer dead center, Figure 5 shows the section IV with the pump piston in an inner dead center, Figure 6 den Neck IV with an ^'in a passive position arranged pump piston and a cylinder disposed in an outer dead center pump piston 7 shows the detail IV with the pump piston in uncoupled condition in an inner

Dead center and Figure 8 is a curve of the ^' pressure at the injection openings of a fuel injection valve of the fuel injection device over time.

Description of the embodiment In Figures 1 to 7 is one

Fuel injection device for an internal combustion engine of a motor vehicle shown. The internal combustion engine is preferably a self-igniting internal combustion engine. The fuel injection device is preferably designed as a so-called pump-nozzle unit and has for each cylinder of the internal combustion engine a high-pressure fuel pump 10 and a fuel injection valve 12 connected to it, which form a common structural unit. Alternatively, the

Fuel injection device can also be designed as a so-called pump-line-nozzle system, in which the high-pressure fuel pump and the fuel injection valve of each cylinder are arranged separately from one another and are connected to one another via a line. The

High-pressure fuel pump 10 has a pump body 14 with a cylinder bore 16, in which two pump pistons 18, 118 are arranged, a first pump piston 18 with a large diameter being tightly guided in the cylinder bore 16 and at least indirectly by a cam 20

Camshaft of the internal combustion engine is driven against the force of a return spring 19 in one stroke. A second pump piston 118 is arranged at least approximately coaxially within the first pump piston 18. The pump pistons 18, 118 are explained in more detail below. The front sides of the two pump pistons 18, 118 delimit a pump working chamber 22 in the cylinder bore 16, in which fuel is compressed under high pressure during the delivery stroke of the pump pistons 18, 118. The pump workspace 22 is fuel from a

Fuel reservoir 24 of the motor vehicle is supplied by means of a pressure source, which is preferably a feed pump 23.

The fuel injection valve 12 has a valve body 26 which is connected to the pump body 14 and which can be formed in several parts, and in which a first injection valve member 28 is guided longitudinally in a bore 30. The valve body 26 has at least one first, preferably a plurality of first injection openings 32 at its end region facing the combustion chamber of the cylinder of the internal combustion engine. The first injection valve member 28 has, for example, an approximately conical sealing surface 34 on its end region facing the combustion chamber, which cooperates with a first valve seat 36 formed in the valve body 26 in its end region facing the combustion chamber, from or after which the first injection openings 32 lead away. In the valve body 26 there is an annular space 38 between the first injection valve member 28 and the bore 30 towards the first valve seat 36, which in its end region facing away from the first valve seat 36 merges into a pressure space 40 surrounding the first injection valve member 28 by a radial expansion of the bore 30 , The first injection valve member 28 has a pressure shoulder 42 at the level of the pressure chamber 40 by reducing the cross section. At the end of the first injection valve member 28 facing away from the combustion chamber, a prestressed first closing spring 44 engages, by means of which the first injection valve member 28 is pressed toward the first valve seat 36. The first closing spring 44 is in a first spring chamber 46 of the

Arranged valve body 26 which connects to the bore 30.

The first injection valve member 28 of the fuel injection valve 12 is hollow, as shown in FIG. 3, and a second injection valve member 128 is slidably guided therein in a bore formed coaxially in the first injection valve member 28. The second injection valve member 128 controls at least one second, preferably a plurality of second injection openings 132 in the valve body 26. The second injection ports 132 are in the direction of the longitudinal axis of the injection valve members 28, 128 to the first

Injection openings 32 arranged offset to the combustion chamber. The second injection valve member 128 has, for example, an approximately conical sealing surface 134 on its end region facing the combustion chamber, which cooperates with a second valve seat 136 formed in the valve body 26 in its end region facing the combustion chamber, from or after which the second injection openings 132 lead away. The second

Injection valve member 128 runs through the first spring chamber 46 and projects into a second spring chamber 146 adjoining the first spring chamber 46. A second closing spring 144 is clamped between the bottom of the second spring chamber 146 and the second injection valve member 128, by means of which the second injection valve member 128 is acted upon in a closing direction towards the second valve seat 136. Near the end of the second injection valve member 128 on the combustion chamber side, a pressure surface 142 is formed thereon, on which the first one is open

Injection valve member 28, the pressure prevailing in pressure chamber 40 acts in opening direction 29.

FIG. 1 shows the fuel injection device according to a first exemplary embodiment, in which the second spring chamber 146, on its end facing away from the first spring chamber 46, is followed by a smaller bore 48 in diameter than the second spring chamber 146, in which a bore connected to the second injection valve member 128 Control piston 50 is tightly guided. A control pressure chamber 52, which has a connection 53 to the pump working chamber 22, is delimited in the bore 48 by the control piston 50. The connection 53 of the control pressure chamber 52 opens into the pump work chamber 22 at least approximately coaxially to the cylinder bore 16. The control piston 50 and, via this, the second injection valve member 128 is opened by the valve Control pressure chamber 52 applied pressure in a closing direction to the second valve seat 136. The second closing spring 144 is thus supported by the pressure prevailing in the control pressure chamber 52.

In one illustrated in Figure 2 the second • embodiment of the fuel injection means a service associated with ^this' control piston 250 is adjacent to the second injection valve element 128 protrudes the side remote with its the second injection valve element 128 end in a second spring chamber 146th A second closing spring 144 is clamped between the base of the second spring chamber 146 and the control piston 250, by means of which the second injection valve member 128 is acted upon in a closing direction towards the second valve seat 136 via the control piston 250. Between the first spring chamber 46 and the second spring chamber 146 there is a smaller bore 248 in diameter than the latter, in which the control piston 250 is tightly guided. The bore 248 and corresponding to the control piston 250 are stepped in diameter, these having sections with a larger diameter toward the second spring chamber 146 than toward the first spring chamber 46. On the control piston 250 has a ring shoulder ^'251 it is formed by the Durchmesserstufung, an annular space is delimited in the bore 252 through 248, which forms a control pressure chamber. The control pressure chamber 252 has a connection 253 to the pump work chamber 22, which opens into the pump work chamber 22 at least approximately coaxially to the cylinder bore 16. Due to the pressure prevailing in the control pressure chamber 252, a force directed against the force of the second closing spring 144 in the opening direction 29 is generated on the control piston 250 and thus on the second injection valve member 128.

A channel 60 leads from the pump work chamber 22 through the pump body 14 and the valve body 26 to the pressure chamber 40 Fuel injection valve 12. A connection 66 leads from the pump work chamber 22 or from the channel 60 to a relief chamber, which can serve, for example, at least indirectly as the fuel reservoir 24 or the pressure side of the feed pump 23, and to the feed pump 23. The connection 66 is controlled by an electrically operated control valve 68. The control valve 68 can be designed as a 2/2-way valve. The control valve 68 can have an electromagnetic actuator or a piezo actuator and is controlled by an electronic control device 72.

The structure of the high-pressure fuel pump 10 with the two pump pistons 18, 118 is explained in more detail below with reference to FIGS. 4 to 7. The first pump piston 18 has an at least approximately coaxial blind bore 80 which is open to the front side of the pump piston 18 delimiting the pump working chamber 22. The mouth of the blind bore 80 on the end face of the first pump piston 18 has, for example, an at least approximately conical bevel 81, so that the diameter of the blind bore 80 increases. Near the base 82 of the blind bore 80, the first pump piston 18 has a transverse bore 83, which connects the blind bore 80 to a longitudinal groove 84, which is made in the longitudinal direction and extends on the outer jacket of the pump piston 18. The longitudinal groove 84 extends from the transverse bore 83 both in the direction of the pump working space 22 and away from it. The first pump piston 18 also has another in a central region of its longitudinal extent

Cross bore 85, which connects the blind bore 80 with a further longitudinal groove 86 made on the outer jacket of the pump piston 18. The longitudinal groove 86 extends from the transverse bore 85 to the pump working space 22. A transverse bore 87 is provided in the cylinder bore 16 and is connected to a low-pressure region and with which the longitudinal groove 84 of the first pump piston 18 is connected over the entire stroke of the pump piston 18. In the low pressure range, for example, there is at least approximately atmospheric pressure. The cylinder bore 16 has in its end region, in which the pump work chamber 22 is arranged, a section 116 with a somewhat larger diameter than in its remaining region, in which the first pump piston 18 is tightly guided. The cylinder bore 16 and thus the pump working chamber 22 formed therein has a delimitation 17 which is arranged at least approximately perpendicular to the longitudinal axis of the first pump piston 18 and which is opposite the end face of the pump piston 18 which delimits the pump working chamber 22.

The second pump piston 118 is displaceably guided in the blind bore 80 of the first pump piston 18 and protrudes with its end delimiting the pump working chamber 22 from the blind bore 80. At its end protruding from the blind bore 80, the second pump piston 118 has a section 150 with an enlarged diameter, on which an annular shoulder 151 facing the first pump piston 18 is formed. The second pump piston 118 has a through-channel 180 running in the longitudinal direction thereof, which can be designed as a through-hole extending from the end face delimiting the pump working space 22 to the end face of the second pump piston 118 'opposite the bottom 82 of the blind bore 80 in the first pump piston 18. extends. A throttle point 181 is provided in the through bore 180 of the second pump piston 118. The end face of the second pump piston 118 opposite the boundary 17 of the pump working chamber 22 is, for example, beveled in such a way that it is in the radial direction inwards to the mouth of the

Through hole 180 is recessed. As a result, the end face of the second pump piston 118 is radial to the latter outer edge has an annular edge which forms a sealing surface 152.

At its end arranged in the blind bore 80, the second pump piston 118 has a reduced diameter

Section 154. At the transition of the second pump piston 118 from its full diameter to its section 154, an annular shoulder 155 facing the bottom 82 of the blind bore 80 is formed. A space 153 is delimited in the blind bore 80 by the second pump piston 118 and is connected to the low-pressure region by the transverse bore 83 in the first pump piston 18. The end face of the second pump piston 118 opposite the base 82 of the blind bore 80 is, for example, beveled in such a way that it is recessed in the radial direction inwards towards the mouth of the through bore 180. As a result, there is an annular edge on the end face of the second pump piston 118 at its radially outer edge, which forms a sealing surface 156. A spring 158 is clamped between the base 82 of the blind bore 80 and the annular shoulder 155 of the second pump piston 118 and is designed, for example, as a helical compression spring surrounding the section 154 of the second pump piston 118. In a central region of the second pump piston 118, viewed in its longitudinal extent, a transverse bore 160 is provided which connects the through bore 180 with an annular groove 161 made in the outer jacket of the second pump piston 118. The second pump piston 118 is guided in the blind bore 80 of the first pump piston 18, at least in its region between the transverse bore 160 and the section 150 projecting from the blind bore 80, with little play. The second pump piston 118 is preferably guided tightly in the blind bore 80 with little play, at least in part of the area between the transverse bore 160 and the annular shoulder 155. 1 and 2, the connection 53 or 253 of the control pressure chamber 52 or 252 opens approximately coaxially with the pump pistons 18, 118.

It is provided that in the high-pressure fuel pump 10 both pump pistons 18, 118 can optionally be coupled to one another and perform a delivery stroke as one unit. During the delivery stroke, the pump pistons 18, 118 move from an outer dead center, in which they protrude the furthest from the cylinder bore 16, as shown in FIG. 4, to an inner dead center, in which, as shown in FIG. 5, they are most immersed in the cylinder bore 16 , If both pump pistons 18, 118 are coupled to one another, then the second pump piston 118 plunges into the blind bore 80 of the first pump piston 18 until it rests with its sealing surface 156 on the base 82 of the blind bore 80, as is shown in FIGS. 4 and 5 , In this position of the second pump piston 118, its annular groove 161 overlaps with the transverse bore 85 of the first pump piston 18 and the spring 158 is compressed to its shortest length. The pressure prevailing in the pump working chamber 22 acts on the end face of the second pump piston 118 and generates a compressive force acting thereon, through which the second

Pump piston 118 is pressed with its sealing surface 156 against the base 82 of the blind bore 80 against the force of the spring 158 and against the low pressure prevailing in the space 153. Through the sealing surface 156, the through hole 180 of the second pump piston 118 is from the space 153 and thus from

Low pressure area separated, so that no fuel can flow out of the pump work chamber 22 through the through hole 180. Should there still be a leak between the sealing surface 156 and the base 82, a small amount of fuel can be caused by the

Through hole 80 in the second pump piston 118 in the room 153 and flow into the Niederdruckbereiσh, but the flow is limited by the throttle point 181. During the delivery stroke of the pump pistons 18, 118, the entire end face of the pump pistons, that is to say the annular end face of the first pump piston 18 and the end face of the second pump piston 118 lying therein, are effective for generating pressure in the pump work chamber 22, so that a high pressure is generated in the pump work chamber 22. High-pressure generation in the pump work chamber 22 by the pump pistons 18, 118 takes place as long as the control valve 68 is closed and the pump work chamber 22 is separated from the relief chamber 24 and the feed pump 23.

If the pump pistons 18, 118 according to FIG. 5 are in the area of the inner dead center, the longitudinal groove 86 of the first pump piston 18 is immersed in the section 116 of the cylinder bore 16, so that the through bore 180 in the second pump piston 118 via the longitudinal groove 86 and the transverse bore 85 in the first pump piston 18 and the annular groove 161 and the transverse bore 160 in the second pump piston 118 is connected to the pump working chamber 22. During the subsequent suction stroke of the pump pistons 18, 118, they move away from their inner dead center to their outer dead center. The control valve 68 is opened so that fuel with the pressure generated by the feed pump 23 in the

Pump working space 22 flows. Depending on the speed of the internal combustion engine and thus the speed / at which the pump pistons 18, 118 move from the inner dead center during the suction stroke, a pressure drop to a lower pressure than the feed pump pressure results in the pump working chamber 22 compared to the pressure generated by the feed pump 23. The first pump piston 18 moves during its suction stroke due to the force of the return spring 19 in accordance with the shape of the cam 20 at a predetermined speed. The second pump piston 118 moves during the suction stroke due to the. its end face pressure acting in the pump work chamber 22 also away from the inner dead center if the force generated by the pressure prevailing in the pump work chamber 22 on the second pump piston 118 is greater than the counteracting force, which is the sum of the force of the spring 158 and that of the spring 153 prevailing low pressure on the second pump piston 118 generated force. The second pump piston 118 moves away from the inner dead center during the suction stroke and, with its sealing surface 156, comes into contact with the bottom 82 of the blind bore 80 in the first pump piston 18 at the latest when the outer dead center is reached. During the subsequent delivery stroke, the pump pistons 18, 118 then move again as a unit inwards towards inner dead center.

In the coupling of the two pump pistons 18, 118 explained above and their common delivery stroke, the mouth of the connection 53 or 253 of the control pressure chamber 52 or 252 is open, so that at least approximately the same high pressure prevails in the control pressure chamber 52 or 252 as in FIG

Pump work chamber 22. In the first exemplary embodiment of the fuel injection device according to FIG. 1, the high pressure prevailing in the control pressure chamber 52 generates a large closing force on the second injection valve member 128, so that the latter only opens at high pressure in the pressure chamber 40 or remains in its closed position and the second injection openings 132 are closed. It then only opens the first injection valve member 28 and opens the first injection openings 32. In the second exemplary embodiment of the fuel injection device according to FIG. 2, the high pressure prevailing in the control pressure chamber 152 reduces the closing force acting on the second injection valve member 128, so that the second injection valve member 128 opens in addition to the first injection valve member 28 and the second injection openings even at relatively low pressure in the pressure chamber 40 132 releases. It is also provided that the second pump piston 118 can optionally be arranged in a passive position in which it does not perform a delivery stroke and only the first pump piston 18 performs a delivery stroke. This is shown in Figures 6 and 7. In its passive position, the second pump piston 118 with its sealing surface 152 is in contact with the boundary 17 of the pump working chamber 22. The through hole 180 in the second pump piston 118 is then separated from the pump working chamber 22 by the sealing surface 152. Should be between the sealing surface 152 and the restricting a leak be present so ^■ a low fuel can close from the pump working chamber 22 through the through hole 180 into the space 153 and flow to the low pressure region, wherein the flow rate is limited by the throttle point 181st During the suction stroke, only the first pump piston 18 moves away from the inner dead center into the outer dead center according to FIG. 6, while the second pump piston 118 remains in its passive position. Due to the prevailing in the pump work room 22

Pressure is generated via the annular shoulder 151 of the second pump piston 118, a pressure force directed toward the boundary 17 thereon. In addition, the second pump piston 118 is pressed against the limit 17 by the spring 158 and the force generated by the low pressure prevailing in the space 153. During the suction stroke of the first pump piston 18, the spring 158 relaxes. During the delivery stroke of the first pump piston 18, only its annular end face is effective for generating pressure, so that a correspondingly lower maximum pressure is generated in the pump working chamber 22 than in the case of coupled pump pistons 18, 118. In the ^' inner dead center position, the pump pistons 18, 118 are shown in FIG. 7.

If the second pump piston 118 is arranged in its passive position, the control pressure chamber is also through it 52 and 252 of the fuel injection device separated from the pump work chamber 22. In the control pressure chamber 52 or 252 there is then no longer a high pressure, but only the pressure of the feed pump 23 to which the control pressure chamber 52 or 252 is connected through the through-bore 180 in the second pump piston 118. At the first

Embodiment of the fuel injection device according to Figure 1 is generated by the low pressure in the pressure chamber 52 only a small force in the closing direction on the second injection valve member 128, so that it can open at relatively low pressure in the pressure chamber 40 in addition to the first injection valve member 28 and the second injection openings 132 f there. In the second exemplary embodiment of the fuel injection device according to FIG. 2, the low pressure in the control pressure chamber 252 generates only a small force in the opening direction 29 on the second injection valve member 128, so that the second injection valve member 128 only opens at high pressure in the pressure chamber 40 or not at all and the second Injection ports 132 remain closed.

The second pump piston 118 is arranged in its passive position during the suction stroke depending on operating parameters of the internal combustion engine, in particular depending on its speed. If the second pump piston

118 is to be arranged in its passive position, the control valve 68 is closed by the control device 72 at a certain time and for a certain period of time during the suction stroke, so that the connection of the pump working space 22 to the feed pump 23 is interrupted and into the pump working space 22 no fuel can flow in. The first pump piston 18, caused by the return spring 19, moves away from the inner dead center toward the outer dead center in accordance with the shape of the cam 20. As a result, the volume of the

Pump workspace 22 enlarged and there is no fuel in flowing in, the pressure in the pump work chamber 22 drops below the delivery pressure of the feed pump 23. Thus, only a small pressure acts on the end face of the second pump piston 118 in the pump work chamber 22, which produces a lower force on the second pump piston 118 directed towards the first pump piston 18 as the counteracting force as the sum of the force of the spring 158 and the force generated by the low pressure acting in the space 153. The second pump piston 118 thereby moves inwards until it is with its

Sealing surface 152 comes to rest on the boundary 17 of the pump work chamber 22.

Subsequently, the control valve 68 is opened again by the control device 72, so that the pressure in the pump work chamber 22 rises again. When the second pump piston 118 is arranged in its passive position, the pressure in the pump working chamber 22 does not act on the end face thereof in the direction of the first pump piston 18, but rather on the annular shoulder 151 of the second pump piston 118 and thus towards the boundary 17 and generates a contact pressure on the second one Pump piston 118 towards the limit 17. The first pump piston 18 executes a suction stroke to the outer dead center and then a delivery stroke to the inner dead center. When the first pump piston 18 reaches the area of the inner dead center, the through-bore 180 of the second pump piston 118 is via the transverse bore 160, the annular groove 161 and the transverse bore 85 and the longitudinal groove 86 in the first pump piston 18, which in the section 116 of the cylinder bore 16th immersed, connected to the pump workspace 22. The pressure in the pump work chamber 22 then acts on the end face of the second pump piston 118 facing the boundary 17, so that the second pump piston 118 with its sealing surface 152 lifts off the boundary 17. In the subsequent suction stroke, you can then close the Control valve 68 of the second pump piston 118 can be arranged in its passive position or, if the control valve 68 remains open, the second pump piston 118 follow the suction stroke of the first pump piston 18 so that the two pump pistons 18, 118 remain coupled.

With increasing speed of the internal combustion engine, the speed of the pump pistons 18, 118, with which they move during the suction stroke and the delivery stroke, also increases. If an approximately constant delivery pressure is generated by the feed pump 23, then in the pump working chamber 22 during the suction stroke of the pump pistons 18, 118, as a result of the speed of the pump pistons 18, 118 increasing with the speed, an increase in pressure drop with the speed relative to the delivery pressure nominally generated by the delivery pump 23, since the pump working space 22 cannot be filled with fuel quickly enough. The first pump piston 18 executes its suction stroke due to the return spring 19 in accordance with the profile of the cam 20. If the pressure in the pump working chamber 22 drops sharply, the second pump piston 118 can no longer follow the suction stroke of the first pump piston 18, since only a small force acts on the first pump piston 18, which is less than the counteracting force as the sum of the force the spring 158 and the force generated by the low pressure prevailing in the space 153. The second pump piston 118 therefore moves towards the boundary 17 and comes into contact with its sealing surface 152 and is in its passive position. Thus, even when a certain limit speed is reached or exceeded, at which the pressure in the pump work chamber 22 drops sufficiently during the suction stroke, an arrangement of the second pump piston 118 in its passive position can be achieved. However, it is preferably provided that the control valve 68 is closed during the suction stroke in the region of the limit speed, as explained above, in order to ensure that the second pump piston 118 is arranged in its passive position. At a significantly higher speed than the limit speed, the closing of the control valve 68 can be omitted, since it is then ensured that the second control piston 118 is arranged in its passive position due to the pressure drop in the pump work chamber 22.

It can be provided that both pump pistons 18, 118 are coupled to one another and carry out a delivery stroke up to a predetermined limit speed. In this case, a high pressure can be generated in the pump work chamber 22 even at low speeds. When the predetermined limit speed is reached or exceeded, the second pump piston 118 is brought into its passive position as described above, so that only the first is left

Pump piston 18 executes a delivery stroke and the pressure in the pump work chamber 22 is reduced. As a result, the maximum pressure in the pump work chamber 22 and thus the mechanical load on the components of the fuel injection device can be limited. The

Limit speed, ah, that the second pump piston 118 is arranged in its passive position can be predefined or can be variable depending on further operating parameters of the internal combustion engine. Provision can also be made for the second pump piston 118 to be arranged in its passive position as a function of operating parameters of the internal combustion engine, in particular as a function of the load. It can be provided, for example, that the two pump pistons 18, 118 are coupled at high load and carry out a delivery stroke together, while at low load the second pump piston 118 is arranged in its passive position and only the first pump piston 18 carries out a delivery stroke. At low load, fuel is thus injected at a lower pressure than at high load. The shape of the cam 20 in the area in which the suction stroke of the first pump piston 18 takes place determines the speed of the first pump piston 18 during the suction stroke. By varying the shape of the cam 20 in this area, the speed of the first pump piston 18 during the suction stroke and thus the pressure drop in the pump work chamber 22 can thus be changed and thus also the

Limit speed from which the second pump piston 118 is arranged in its passive division. The pressure generated by the feed pump 23 also determines the limit speed from which the second pump piston 118 is arranged in its passive position. The higher the pressure generated by the feed pump 23, the higher the limit speed. In order to enable a variation in the limit speed, it can be provided that the pressure generated by the feed pump 23 is variable.

The further function of the

Fuel injector explained. In Figure 8 the

Course of the pressure p at the injection openings 32 of the

Kraftstoffei ^{'nspritzventils} 12 over the time t during an injection cycle. During the suction stroke of the pump piston

18 this fuel is supplied from the fuel tank 24. During the delivery stroke of the pump pistons 18, 118, the fuel injection begins with a pre-injection, the control valve 68 being closed by the control device 72, so that the pump working chamber 22 is separated from the relief chamber 24. If the pressure in the pump work chamber 22 and thus in the pressure chamber 40 of the fuel injection valve 12 is so great that the pressure force exerted on the first injection valve member 28 via the pressure shoulder 42 is greater than the force of the closing spring 44, the injection valve member 28 moves in the opening direction 29 and releases the at least one injection opening 32. To end the pilot injection, the first control valve 68 is opened by the control device, so that the pump working chamber 22 is relieved. The pre-injection corresponds to one in the figure 6 injection phase labeled I. It can be provided that only the first injection valve member 28 opens and the first injection openings 32 open during the pre-injection, while the second injection valve member 128 remains in its closed position and the second injection openings 132 remain closed.

For a subsequent main injection, which corresponds to an injection phase designated II in FIG

Control valve 68 opened by the control device 72 so that the pressure in the pump work chamber 22 rises again. As explained above, depending on the operating parameters of the internal combustion engine, only the first pump piston 18 or both pump pistons 18, 118 perform a delivery stroke, as a result of which the pressure in the pump working chamber 22 is determined. In the fuel injection valve 12, either only the first injection valve member 28 opens and opens the first injection openings 32 or, with a time delay, the second injection valve member 128 also opens and the second injection openings 132 open.

To terminate the main injection, the control valve 68 is brought by the control means 72 in its open switching position such that the pump work chamber 22 is connected to the relief space 24 and only wirkt- a small compressive force on the injection valve element 28 in opening direction 29 and ^'the injection valve members 28,128 of Close fuel injector 12 due to the force of the respective closing spring 44, 144.

When the control valve 68 is activated by the control device 72. Fuel injection requires information to be available in control device 72 as to whether both pump pistons are present

18, 118 execute a conveying stroke or only the first Pump piston 18 executes a delivery stroke since the pressure in the fuel injection varies accordingly. During the transition from the common delivery stroke of both pump pistons 18, 118 in the coupled state to the sole delivery stroke of the first pump piston 18, the

Pump work space 22 generated pressure from one delivery stroke to the next delivery stroke, so that the. Control time and in particular the control duration of the control valve 68 must be corrected accordingly by the control device 72 in order to ensure continuity of the injected fuel quantity and proper operation of the internal combustion engine.

Claims

Expectations

1. Fuel injector for one

Internal combustion engine with a high-pressure fuel pump (10) and a fuel injection valve (12) connected thereto for each cylinder of the internal combustion engine, the high-pressure fuel pump (10) driving at least one stroke movement of the internal combustion engine

Pump piston (18), which delimits a pump work chamber (22) to which fuel is supplied from a fuel reservoir (24), the fuel injection valve (12) having a pressure chamber (40) connected to the pump work chamber (22) and at least a first one

Injection valve member (28) through which at least one first injection opening (32) is controlled and which, when acted upon by the pressure prevailing in the pressure chamber (40), can be moved against a closing force in an opening direction (29) to release the at least one injection opening (32), with a control valve (68) through which at least indirectly a connection (66) of the pump work chamber (22) with a relief chamber (24) and a pressure source (23) for filling the pump work chamber (22) is controlled during the suction stroke of the at least one pump piston (18) characterized in that the high-pressure fuel pump (10) has two pump pistons (18, 118), a first pump piston (18) being provided, in which a second pump piston (118) is at least approximately coaxially displaceable, both pump pistons (18, 118) the

Pump work space (22) limit that the first pump piston (18) is driven in one stroke movement, that either both pump pistons (18, 118) can be coupled to one another and move as a unit during the delivery stroke, or the second pump piston (118) can be fixed in a passive position, so that only the first pump piston (18) has a delivery stroke explains that the fuel injection valve (12) has a second injection valve member ^* (128), which is displaceably guided within the hollow first injection valve member (28) and through which at least one second injection opening (132) is controlled and which is controlled by the one in the pressure chamber (40) Pressurized against a closing force can be moved in an opening direction (29), that the second injection valve member (128) is acted upon at least indirectly by the pressure prevailing in a fuel-filled control pressure chamber (52; 252) and that the control pressure chamber (52; 252) has one through second pump piston (118) controlled connection (53; 253) to the pump work space (22) , the control pressure chamber (52; 252) is separated from the pump work chamber (22) when the second pump piston (118) is arranged in its passive position.

2. Fuel injection device according to claim 1, characterized in that the second injection valve member (128) is acted upon by the pressure prevailing in the control pressure chamber (52) at least indirectly in a closing direction.

3. Fuel injection device according to claim 1, characterized in that the second injection valve member (128) is acted upon by the pressure prevailing in the control pressure chamber (252) at least indirectly in the opening direction (29).

4. Fuel injection device according to one of claims 1 to 3, characterized in that g-e indicates that the second pump piston

(118) in his _. Passive position with one end at one Boundary (17) of the pump work chamber (22) lies in the area of an • inner dead center of the stroke movement of the pump pistons (18, 118), in which the pump pistons (18, 118) are located at the end of a delivery stroke and at the beginning of a suction stroke.

5. Fuel injection device according to one of claims 1 to 4, characterized in that the first pump piston (18) has an open to the pump working space (22) delimiting front side blind bore (80) in which the second pump piston (11-8) is displaceable is led.

6. Fuel injection device according to claim 5, characterized in that a space (153) is limited by the second pump piston (118) in the blind bore (80), which is connected to a low pressure region.

7. Fuel injection device according to claim 5 or 6, characterized in that in the coupled state of the two pump pistons (18, 118) the second pump piston (118) rests with one end on the base (82) of the blind bore (80) of the first pump piston (18).

8. Kra tstoffeinspritzeinrichtung according to claim 6 or 7, characterized in that the second pump piston (118) has a through channel (180) through which the

Pump work space (22) can be connected to the space (153) and in which at least one throttle point (181) is provided.

9. Fuel injection device according to claim 7 and 8, characterized in that on the bottom (82) of

Blind end (80) facing the end of the second pump piston (118) is arranged a sealing surface (156) through which the mouth of the through-channel (180) to the space (153) is closed when the second pump piston (118) with the sealing surface (156 ) at the bottom (82) of the blind hole (80) is applied so that the space (153) is separated from the through channel (180).

10. Fuel injection device according to one of claims 5 to 9, characterized in that a spring (158) is clamped between the first pump piston (18) and the second pump piston (118), through which the second pump piston (118) from the blind bore (80) is pushed out.

11. Fuel injection device according to claim 10, characterized in that the spring (158) between the base (82) of the blind bore (80) and one on the second pump piston (118) is clamped by a cross-sectional reduction on this annular shoulder (155).

12. Fuel injection device according to claim 4 and 8, characterized in that at the boundary (17) of the pump work chamber (22) facing the end of the second pump piston (118) a sealing surface (152) is arranged through which the mouth of the through-channel (180) Pump work space (22) is closed when the second pump piston (118) with the sealing surface (152) abuts the boundary (17) of the pump work space (22), so that the pump work space (22) is separated from the through-channel (180).

13. Fuel injection device according to one of claims 8 to 12, characterized in that the through-channel (180) of the second pump piston (118) has a connection (85, 86, 160, 161) controlled by the first pump piston (18) with the pump work chamber (22), that when the first pump piston (18) is located in the region of the inner dead center, the through-channel (180) is connected to the pump working chamber (22) and that when the first pump piston (18) is located outside the region of the inner dead center Through channel (180) is separated from the pump work space (22).

14. Fuel injection device according to one of claims 4 to 13, characterized in that the second

Pump piston (118) near its end that comes into contact with the boundary (17) of the pump work space (22) has an annular surface (151) facing away from the boundary (17), which is acted upon by the pressure prevailing in the pump work space (22) and thus opens up the second pump piston

(118) to the limit (17) directed force is generated.

15. Fuel injection device according to one of the preceding claims, ^' characterized in that for the arrangement of the second pump piston (118) in its

Passive position, the control valve (68) is closed during the suction stroke '^{' of} the pump pistons (18, 118) and thereby the connection of the pump work space (22) to the pressure source (23) is interrupted, so that there is a pressure drop in the pump work space (22), as a result of which the second

Pump piston (118) is decoupled from the first pump piston (18), and that the control valve (68) is subsequently opened again during the suction stroke, so that the second pump piston (118) is arranged in its passive position due to the pressure prevailing in the pump work chamber (22) becomes.

16 Kraf sto fine spraying device according to one of the preceding claims, characterized in that in the pump work chamber (22) during the suction stroke of the pump piston (18,118) with increasing speed of the internal combustion engine results in an increasing pressure drop and that the pressure when reaching or exceeding a predetermined - limit speed decreases in the pump working space (22) so strongly ^', in consequence, the second pump piston (118) is abgekoppekt from the first pump piston (18) and is arranged in its passive position.