EP1456528A1

EP1456528A1 - Fuel-injection device for an internal combustion engine

Info

Publication number: EP1456528A1
Application number: EP02792588A
Authority: EP
Inventors: Katja Matz; Uwe Schmidt; Hubert Greif
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-12-07
Filing date: 2002-11-02
Publication date: 2004-09-15
Anticipated expiration: 2022-11-02
Also published as: JP2005511965A; US6976638B2; EP1456528B1; DE10160263A1; HUP0401031A2; DE50204298D1; WO2003050408A1; US20040123840A1

Abstract

The invention relates to a fuel-injection device comprising a high-pressure fuel pump (10) for each cylinder of the internal combustion engine and a fuel-injection valve (12) that is connected to each cylinder. A pump plunger (18) of the high-pressure fuel pump (10) delimits a pump working chamber (22), which is connected to a pressure chamber (40) of the fuel injection valve (12), said valve having an injection valve member (28), which controls injection orifices (32) and which can be displaced in an opening direction (29) in opposition to a closing force by the prevailing pressure in the pressure chamber (40). A first control valve (68) controls a connection (66) from the pump working chamber (22) to a relief chamber (24) and a second control valve (70) controls a connection (64) from a control pressure chamber (52) that is linked to the pump working chamber (22) and is delimited by a control plunger (50) to a relief chamber (24). The control plunger (50) controls a flow cross-section of the connection (64) from the control pressure chamber (52) to the relief chamber (24) in accordance with the travel of the control plunger (50), in such a way that a greater flow cross-section is released when the injection valve member (28) is in a closed position than when said injection valve member (28) is in an open position.

Description

Fuel injection device for an internal combustion engine

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 injection device is known from EP 0 987 431 A2. This

Fuel 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 delimits a pump working space. The fuel injection valve has a pressure chamber connected to the pump working chamber and an injection valve member, through which at least one injection opening is controlled and which through the

Pressure chamber prevailing pressure is movable against a closing force in the opening direction to release the at least one injection opening. A first electrically operated control valve is provided, by means of which a connection of the pump work space to a relief space is controlled. A second electrically actuated control valve is also provided, by means of which a connection of a control pressure chamber to a relief chamber is controlled. The control pressure chamber is connected to the pump work chamber via a throttling point. The

Control pressure chamber is limited by a control piston which is supported on the injection valve member and which is in a closing direction by the pressure prevailing in the control pressure chamber of the injection valve member and. For a fuel injection, the first control valve is closed and the second control valve is opened, so that no high pressure can build up in the control pressure chamber and the fuel injection valve can open. When the second control valve is open, however, fuel flows out of the pump work chamber via the control pressure chamber, so that the amount of fuel available for injection is reduced by the amount of fuel delivered by the pump piston and also that for injection

Available pressure is reduced. It follows from this that the efficiency of the fuel injection device is 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 only a small flow cross-section is released from the control pressure chamber to the relief chamber when the second control valve is open for fuel injection and thus open, and thus only a small amount of fuel flows out, so that the fuel is available for injection standing pressure and the efficiency of the fuel injector is increased. At the beginning or at the end of the fuel injection, a quick opening or closing of the fuel injection valve is also achieved, which is made possible by a rapid pressure reduction or pressure build-up in the control pressure chamber which occurs as a result of the variable flow cross section when the second control valve is opened or closed.

Advantageous refinements and developments of the fuel injection device according to the invention are specified in the dependent claims. Training according to claim 2 enables control of the flow cross section in a simple manner. The design according to claim 3 enables simple formation of the bypass connection. The design according to claim 4 also enables simple formation of the bypass connection, which is also insensitive to possible contamination, since the groove is open when the fuel injector is closed and thus no dirt particles can settle in it.

drawing

An embodiment of the invention is 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 longitudinal section in a simplified representation, FIG. 2 shows a detail designated II in FIG. 1 in an enlarged representation, FIG. 3 shows a further enlarged detail III from FIG

4 shows section III with the fuel injection valve open, FIG. 5 shows section III of a fuel injection device according to a modified embodiment with the fuel injection valve closed, and FIG. 6 shows section III with the fuel injection valve open.

Description of the embodiment

In Figures 1 to 6 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 injector is preferably as So-called pump-nozzle unit is formed 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 a pump piston 18 is tightly guided, which is at least indirectly driven by a cam 20 of a camshaft of the internal combustion engine against the force of a return spring 19 in a lifting movement. The pump piston 18 delimits 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 piston 18. The pump working chamber 22 is supplied with fuel from a fuel tank 24 of the motor vehicle.

The fuel injection valve 12 has a valve body 26 which is connected to the pump body 14 and which can be constructed in several parts and in which an injection valve member 28 is guided so as to be longitudinally displaceable in a bore 30. The valve body 26 has at least one, preferably a plurality of injection openings 32 at its end region facing the combustion chamber of the cylinder of the internal combustion engine. The injection valve member 28 has at its end region facing the combustion chamber an, for example, approximately conical sealing surface 34 which interacts with a valve seat 36 formed in the valve body 26 in its end region facing the combustion chamber, from or after which the injection openings 32 lead away. in the

Valve body 26 is between the injection valve member 28 and of the bore 30 towards the valve seat 36 there is an annular space 38 which, in its end region facing away from the valve seat 36, merges into a pressure space 40 surrounding the injection valve member 28 by a radial expansion of the bore 30. The 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 injection valve member 28 facing away from the combustion chamber, a prestressed closing spring 44 engages, by means of which the injection valve member 28 is pressed toward the valve seat 36. The closing spring 44 is arranged in a spring chamber 46 of the valve body 26, which adjoins the bore 30.

At the end of the bore 30 facing away from the bore 30 in the valve body 26 there is another bore 48, in which a control piston 50 is tightly connected, which is connected to the injection valve member 28. The bore 48 forms a control pressure chamber 52 which is delimited by the control piston 50 as a movable wall. The control piston 50 is supported on the injection valve member 28 via a piston rod 51 which is smaller in diameter than this and can be connected to the injection valve member 28. The control piston 50 can be formed in one piece with the injection valve member 28, but is preferably connected to the injection valve member 28 as a separate part for reasons of assembly.

According to FIG. 1, 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 of the fuel injection valve 12

Pump working chamber 22 or from channel 60 leads a channel 62 to control pressure chamber 52. A channel 64 also opens into control pressure chamber 52, which forms a connection to a relief chamber than which at least indirectly fuel tank 24 or another area can serve, in which a smaller one There is pressure. from Pump working chamber 22 or from channel 60 leads a connection 66 to a relief chamber 24, which is controlled by a first electrically operated control valve 68. The control valve 68 can, as shown in FIG. 1, be designed as a 2/2 way valve. The connection 64 of the

Control pressure chamber 52 with the relief chamber 24 is controlled by a second electrically operated control valve 70, which can be designed as a 2/2-way valve. A throttle point 63 is provided in the connection 62 of the control pressure chamber 52 to the pump work chamber 22. The control valves 68, 70 can have an electromagnetic actuator or a piezo actuator and are controlled by an electronic control device 72.

Between the pump body 14 of the high-pressure fuel pump 10 and the valve body 26 of the fuel injection valve 12, an intermediate disk 54 is arranged, which forms a boundary of the control pressure chamber 52 on its side facing away from the injection valve member 28. The surface 53 of the intermediate disk 54 delimiting the control pressure space 52 is arranged at least approximately perpendicular to the longitudinal axis 49 of the control piston 50. The channel 62 from the channel 60 to the control pressure chamber 52 is formed in the intermediate disk 54 and the throttle point 63 is designed as a throttle bore in the intermediate disk 54. The throttle bore 63 opens into an edge region of the control pressure chamber 52 offset to the longitudinal axis 49 of the control piston 50. A bore 55 is arranged in the intermediate disk 54, which forms part of the connection 64 of the control pressure chamber 52 to the relief chamber 24.

As shown in FIG. 2, the control piston 50 has, on its end face facing the intermediate disk 54, a hollow cylindrical projection 56 which has a smaller diameter than the control piston 50 in its area which is sealingly guided in the bore 48. At the the An annular sealing surface 57 is formed between the intermediate face 54 of the end face of the extension 56. A recess 58 is thus formed in the extension 56 and an annular depression 59 is formed on the control piston 50 around the extension outside the extension 56. The depression 58 is arranged at least approximately coaxially to the bore 55 in the intermediate disk 54 and has at least approximately the same diameter as the bore 55. The sealing surface 57 can be at least approximately flat and perpendicular to the longitudinal axis 49 of the control piston 50. However, the sealing surface 57 is preferably bevelled in such a way that it slopes radially inwards towards the recess 58, as is shown in FIGS. 3 to 6. The throttle bore 63 in the intermediate disk 54 opens into the control pressure chamber 52 outside the shoulder 56 of the control piston 50 in the region of the depression 59. The bore 55 in the intermediate disk 54 forms a discharge to the second control valve 70 and via the shoulder 56 of the control piston 50 to the relief room 24.

In an embodiment of the fuel injection device shown in FIGS. 2 to 4, a throttle bore 80 is arranged in the hollow cylindrical extension 56 of the control piston 50, which connects the depression 59 outside the extension 56 to the depression 58 within the extension 56. The throttle bore 80 extends, for example, approximately radially to the longitudinal axis 49 of the control piston 50 through the shoulder 56. When the fuel injection valve 12 is closed, the injection valve member 28 is in a closed position in which the sealing surface 34 rests on the valve seat 36 and the injection openings 32 closes. Accordingly, the control piston 50 is then in a stroke position, in which it with its sealing surface 57 at a distance from the limit of the

Control pressure chamber 52 forming surface 53 of the washer 54 is arranged, as shown in Figure 3. Between the sealing surface 57 of the control piston 50 and the surface 53 of the washer 54, a large flow cross-section 84 is released for the connection 64 of the control pressure chamber 52 to the second control valve 70

The inflow of fuel into the control pressure chamber 52 from the channel 60 via the channel 62 and the throttle bore 63 is limited by the throttle bore 63. However, the outflow of fuel from the control pressure chamber 52 to the second control valve 70 takes place via the between the sealing surface 57 of the

Control piston 50 and the washer 54 with the main connection 84 released large flow cross-section unthrottled, the throttle bore 80 in the control piston 50 is ineffective.

When the fuel injection valve 12 is open, the injection valve member 28 is in an open position, in which it is arranged with its sealing surface 34 at a distance from the valve seat 36 and opens the injection openings 32. Correspondingly, the control piston 50 is then in a stroke position, in which it rests with its sealing surface 57 on the surface 53 of the intermediate disk 54, as shown in FIG. 4. The surface 53 of the intermediate disk 54 thus forms a valve seat with which the sealing surface 57 of the control piston 50 interacts. As a result of the beveling of the sealing surface 57, this lies essentially only with its outer edge against the surface 53 of the intermediate disk 54, as a result of which line contact with high surface pressure and thus reliable sealing is achieved. Between the sealing surface 57 of the control piston 50 and the intermediate disk 54 as a valve seat, the main connection 84 is controlled from the control chamber 52 to the bore 55 in the intermediate disk 54 as a connection between the control pressure chamber 52 and the second control valve 70 and the relief chamber 24. This main connection 84 is opened when the fuel injection valve 12 is closed and closed when the fuel injection valve 12 is open. If the control piston 50 rests with its sealing surface 57 on the surface 53 of the intermediate disk 54 and closes the main connection 84, a bypass connection from the control pressure chamber 52 to the bore 55 is opened via the throttle bore 80 in the control piston 50, the flow cross section of which is determined by the throttle bore 80, which is substantially smaller than the flow cross section of the main connection 84 when it is open.

In a modified embodiment of the fuel injection device shown in FIGS. 5 and 6, instead of the throttle bore 80 in the control piston 50, a groove 82 is formed in the sealing surface 57 which extends, for example, approximately radially to the longitudinal axis 49 of the control piston 50 and which is open to the intermediate disk 54. The cross section of the groove 82 can be of any design and the groove 82 connects the depression 59 outside the shoulder 56 to the depression 58 inside the shoulder 56 of the control piston 50. When the fuel injection valve 12 is closed and the

Control piston 50 is arranged with its sealing surface 57 at a distance from the surface 53 of the intermediate plate 54, as shown in Figure 5, the main connection 84 to the bore 55 with a large flow cross section is released by the control piston 50 and the throttle groove 82 is ineffective. When the fuel injection valve 12 is open and the control piston 50 with its sealing surface 57 is in contact with the surface 53 of the intermediate disk 54, as shown in FIG. 6, the main connection 84 is closed by the control piston 50 and it is only that

Bypass connection via throttle groove 82 with a small flow cross-section released. If the control piston 50 is arranged with its sealing surface 57 at a distance from the surface 53 of the intermediate disk 54, the groove 82 is open, so that any dirt particles which may be present cannot get stuck in the groove and the predetermined ones Reduce flow area and become one

Functional impairment of the fuel injector can lead.

The cross section of the throttle bore 63 in the intermediate disk 54 and the throttle bore 80 or the throttle groove 82 in the control piston 50 are matched to one another in a suitable manner for optimal functioning of the fuel injection device.

The function of

Fuel injector explained. During the suction stroke of the pump piston 18, fuel is supplied to it from the fuel reservoir 24. During the delivery stroke of the pump piston 18, the fuel injection begins with a pre-injection, the first control valve 68 being closed by the control device 72, so that the pump working chamber 22 is separated from the relief chamber 24. The control device 72 also opens the second control valve 70 so that the control pressure chamber 52 is connected to the relief chamber 24. In this case, no high pressure can build up in the control pressure chamber 52, since this is relieved towards the relief chamber 24. If the pressure in the pump work chamber 22 and thus in the pressure chamber 40 of the fuel injector 12 is so great that the pressure on the pressure shoulder 42 on it

Injection valve member 28 pressure force is greater than the sum of the force of the closing spring 44 and the pressure force acting on the control piston 50 by the residual pressure acting in the control pressure chamber 52, so that moves

Injection valve member 28 in the opening direction 29 and releases the at least one injection opening 32. The control piston 50 assumes its stroke position shown in FIGS. 4 and 6, so that only the bypass connection via the throttle bore 80 or the throttle groove 82 is small

Flow cross section is released. From that through the Pump piston 18 pumped fuel can thus only flow a small portion through the throttle bore 63 and the throttle bore 80 or the throttle groove 82 and the opened second control valve 70 into the relief chamber 24. It can also be provided that the

Fuel injection valve 12 for pre-injection opens only with a partial stroke of the injection valve member 28, so that the control piston 50 with its sealing surface 57 does not come into contact with the intermediate disk 54 and does not completely close the main connection, although the

Flow cross-section of the main connection is reduced.

To end the pilot injection, the second control valve 70 is closed by the control device, so that the control pressure chamber 52 is separated from the relief chamber 24. The first control valve 68 remains in its closed position. High pressure builds up in the control pressure chamber 52 as in the pump work chamber 22, so that a large pressure force acts in the closing direction on the control piston 50 and the injection valve member 28 is moved into its closed position.

The second control valve 70 is opened by the control device 72 for a subsequent main injection. The fuel injection valve 12 then opens due to the reduced pressure force on the control piston 50 and the injection valve member 28 moves over its maximum opening stroke into its open position. During the opening movement of the injection valve member 28, the large flow cross-section via the main connection 84 is first released through the control piston 50 until the injection valve member 28 is opened with its maximum opening stroke and the control piston 50 with its sealing surface 57 abuts the surface 53 of the intermediate disk 54 and the main connection 84 closes and only that

Bypass connection via the throttle bore 80 or Throttle groove 82 is released. This enables the fuel injection valve 12 to be opened quickly. When the fuel injection valve 12 is fully open, only a small amount of fuel can flow out to the relief chamber 24 via the throttle bore 63 and the throttle bore 80 or the throttle groove 82, so that only a small part of the fuel delivered by the pump piston 18 is not suitable for the injection Available.

To finish the main injection, the second one

Control valve 70 is brought into its closed switching position by control device 72, so that control pressure chamber 52 is separated from relief chamber 24 and builds up in this high pressure and fuel injector 12 is closed via the force acting on control piston 50. During the closing movement of the injection valve member 28, the main connection 84 with a large flow cross section is released by the control piston 50, so that the pressure in the control pressure chamber 52 rises quickly and a high pressure force acts on the control piston 50, so that the fuel injection valve 12 closes quickly. For a post-injection of fuel, the second control valve 70 is opened again by the control device 72, so that the fuel injection valve 12 opens as a result of the reduced pressure in the control pressure chamber 52. To end the post-injection, the second control valve 70 is closed and / or the first control valve 68 is opened.

Claims

Expectations

1. Fuel injection device for an 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) having a pump piston (18) driven by the internal combustion engine in a stroke movement, which has a pump work space (22) limited and the fuel from one

Fuel storage tank (24) is supplied, the fuel injection valve (12) having a pressure chamber (40) connected to the pump working chamber (22) and an injection valve member (28) through which at least one injection opening (32) is controlled, which is formed on one of the latter Pressure area (42) is acted upon by the pressure prevailing in the pressure chamber (40) in an opening direction (29) and which can be moved against a closing force in the opening direction (29) to release the at least one injection opening (32), with a first control valve (68) , through which a connection (66) of the pump work chamber (22) is controlled with a relief chamber (24) and with a second control valve (70), through which a connection (64) of a control pressure chamber (52) of the fuel injection valve with a relief chamber (24) is controlled, the control pressure chamber (52) at least indirectly having a connection (62) to the pump work chamber (22) in which a throttle valve le (63) is provided, the control pressure chamber (52) being delimited by a control piston (50) which is limited to the

Injection valve member (28) acts in a closing direction, characterized in that the control piston (50) controls a flow cross-section of the connection (64) of the control pressure chamber (52) to the relief chamber (24) depending on the stroke of the control piston (50) such that when the injection valve member (28) is arranged in a closed position larger flow cross-section is released than when the injection valve member (28) is arranged in an open position.

2. Fuel injection device according to claim 1, characterized in that the control piston (50) releases a main connection (84) with a large flow cross-section when the injection valve member (28) is arranged in its closed position and that the control piston (50) with the injection valve member (28) arranged in its open position. the main connection closes and only a bypass connection (80; 82) with a small flow cross-section is released.

3. Fuel injection device according to claim 2, characterized in that the bypass connection by a

Throttle bore (80) is formed in the control piston (50).

4. Fuel injection device according to claim 2, characterized in that the bypass connection is formed by a throttle groove (82) which in one

The end face (57) of the control piston (50) facing away from the injection valve member (28) is arranged, the control piston (50) with this end face (57) when the injection valve member (28) is arranged in its open position at a boundary (54) of the control pressure chamber (52) Facility is coming.

5. Fuel injection device according to one of claims 2 to 4, characterized in that the control piston (50) on its end facing away from the injection valve member (28) has a sealing surface (57) with which it engages with one a valve seat (53) designed to control the main connection (84) cooperates with a boundary (54) of the control pressure chamber (52).

6. Fuel injection device according to claim 5, characterized in that the valve seat is formed by an at least approximately perpendicular to the longitudinal axis (49) of the control piston (50) arranged surface (53) of the boundary (54) of the control pressure chamber (52).

7. Fuel injection device according to claim 5 or 6, characterized in that the control piston (50) to the boundary (54) has a hollow cylindrical projection (56) which has a smaller cross section than the rest of the control piston (50) that on the end face of

Approach (56) the sealing surface (57) is arranged so that the bypass connection (80, -82) penetrates the approach (56) of the control piston (50) and that through the limitation (54) as part of the connection (64) of the control pressure chamber ( 52) with the relief chamber (24) within the approach (56) of the

Control piston (50) discharging drain (55) is arranged.

8. Fuel injection device according to one of claims 2 to 7, characterized in that the high-pressure fuel pump (10) and that

Fuel injection valve (12) form a common structural unit and that the boundary (54) of the control pressure chamber (52) is formed by an intermediate disk arranged between a pump body (14) of the high-pressure fuel pump (10) and a valve body (26) of the fuel injection valve (12).