EP1466087A1

EP1466087A1 - Injector for high pressure fuel injection

Info

Publication number: EP1466087A1
Application number: EP02779159A
Authority: EP
Inventors: Michael Kurrle; Reiner Koch; Joerg-Peter Fischer
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-11-23
Filing date: 2002-10-15
Publication date: 2004-10-13
Anticipated expiration: 2022-10-15
Also published as: KR20040062871A; US20040050367A1; WO2003046369A1; US6994272B2; DE50209448D1; ES2281549T3; DE10157411A1; EP1466087B1; JP2005510658A

Abstract

The invention relates to an injector for high pressure injection of fuel in auto-igniting internal combustion engines. The injector comprises an actuator valve for opening and closing the injector, an injector needle (17) which seals at least one injection opening (18) when the injector is in a closed state, a metering valve (4) producing a hydraulic connection between the actuator valve and the discharge area (6) of the injector, a pressure maintenance device (33) which is used to maintain the pressure required for the metering valve (4), a first line (20) for control amounts (34) flowing via the actuator valve and a second line (43) for control amounts flowing via the metering valve (4). The pressure maintenance device (33) dynamically separates the control amounts (35) from the metering valve from the control amounts (34) from the actuator valve by means of a hydraulic vibration damper.

Description

High pressure fuel injector

Technical field

The common rail injection system is used for high-pressure injection of fuel into direct-injection ner internal combustion engines. In this accumulator injection system, pressure generation and injection are decoupled from one another in time and place. A separate high-pressure pump generates the injection pressure in a central high-pressure fuel reservoir. The start of injection and the injection quantity are determined by the actuation time and duration of electrically actuated injectors which are connected to the high-pressure fuel reservoir via fuel lines.

State of the art

DE 100 01 099 AI relates to a control valve for an injector of a fuel injection system. The control valve comprises an actuator and is actuated by an actuator. A hydraulic connection between a fuel return and a control chamber of the injector can be established by means of the control valve. When the control valve is opened, fuel flows from the control room into the fuel return. As a result, the pressure in the control chamber drops and the hydraulic force acting on the end face of the nozzle needle decreases. As soon as this hydraulic force is less than the hydraulic force acting in the opening direction, the nozzle needle opens so that the fuel can get into the combustion chamber through the injection holes of the injection nozzle. This indirect control of the nozzle needle via a hydraulic power booster system is necessary because the large forces required to open the nozzle needle quickly cannot be generated directly with the control valve.

DE 196 50 865 AI relates to a solenoid valve for controlling an electrically controlled fuel injection valve. The valve needle of the fuel injection valve is loaded by pressure prevailing in a control chamber in the closing direction. The solenoid valve discharges the control chamber to initiate injection when the solenoid of the solenoid valve is energized. The valve needle of the injection valve is then lifted off its seat under the action of the high pressure acting on it in the opening direction. In the prior art, in addition to the amount of fuel injected into the combustion chamber, a so-called “control amount” is required for the indirect actuation of the valve needle. When the solenoid valve is opened, a control quantity reaches the low-pressure area of the fuel tank via the solenoid valve and via a control quantity line. When the solenoid valve closes, the control valve changes to another switching position, which also results in a control quantity. To maintain a master pressure necessary for the control valve function, a pressure control valve with an upstream inlet throttle is used in another control quantity line, through which the control quantity flows from the control valve. Behind the pressure control valve, the control quantities flow from the solenoid valve and from the control valve in a common line as a total leakage quantity into the low pressure range. The pressure control valve is therefore used not only to maintain the mentioned master pressure but also to separate the pressure potentials of both control quantities (the control valve and the solenoid valve).

In this injector in the prior art, however, when the control valve is switched, pressure fluctuations can occur in the control quantity line from the control valve, which continue to the valve needle of the solenoid valve and, in the worst case, can lead to an undesired opening of the solenoid valve.

Presentation of the invention

The solution according to the invention has the advantage that pressure vibrations in the control quantity line are damped and undesired opening of the actuator valve is prevented by the effects of the pressure vibrations. Furthermore, the solution according to the invention enables a compact, space-saving design of the pressure control valve.

According to the invention, these advantages are achieved by an injector for high-pressure injection of fuel in self-igniting internal combustion engines. The injector in this case comprises an actuator valve for opening and closing the injector, a nozzle needle which closes at least one injection opening in the closed state of the injector, a metering valve which establishes a hydraulic connection between the actuator valve and a control chamber of the injector, a pressure maintaining device for compliance serves a stand pressure necessary for the metering valve, a first control quantity line for control quantities that flow via the actuator valve and a second control quantity line for control quantities that flow via the metering valve. The pressure maintaining device dynamically separates the control quantities of the metering valve from the control quantities of the actuator valve and also serves as a hydraulic vibration damper. The pressure maintaining device is therefore designed in such a way that it dampens pressure vibrations of the fuel. In particular, these are pressure fluctuations that arise in the associated control quantity line when the metering valve is switched.

In a preferred embodiment of the present invention, the actuator valve is a solenoid valve. In another variant of the invention, the actuator of the actuator valve is a piezo actuator. The advantage of a piezo actuator is that large actuating forces and a quick response of the actuator are guaranteed.

drawing

The invention is explained in more detail below with the aid of the drawing.

It shows:

FIG. 1 shows a schematic illustration of an injector according to the invention with a solenoid valve, metering valve and pressure-maintaining device and a high-pressure fuel accumulator connected thereto,

Figure 2 shows a section of a pressure maintaining device according to the present invention and

Figure 3 shows a pressure maintaining device according to the present invention.

Design variants.

Figure 1 shows the schematic representation of an injector according to the invention with a solenoid valve, a metering valve and a Druckl oldeinrichtung. A fuel high-pressure accumulator (common rail) connected to this is also shown.

The system shown is a pressure-controlled common rail injection system. In a high-pressure fuel reservoir 1 (common rail), fuel is stored under high pressure (up to 1400 bar). A high-pressure pump 2 pumps the fuel into the high-pressure fuel reservoir 1. The high-pressure fuel reservoir 1 is connected to a metering valve 4 via a high-pressure line 3. The metering valve 4 provides a hydraulic connection between a solenoid valve 5 and the relief space 6 of an injection nozzle 7 ago. Metering valve 4 is a 3/2-way valve. An adjusting piston 8 is arranged displaceably in the interior of the hollow metering valve 4. The actuating piston 8 has a seat edge 9. In one switching position a, the actuating piston in the metering valve body 11 is displaced such that the seat edge 9 bears against a valve seat 10 formed in the metering valve body 11. In this switching position a of the metering valve 4, the high-pressure line 3 is hydraulically separated from the injection nozzle 7. Two lines 12, 13 run from the metering valve 4 to the injection nozzle 7. The first line 12 connects a partial space 14 of the metering valve 4 to the relief chamber 6 of the injection nozzle 7. The second line 13 runs from an annular space 15 in the metering valve body 11 a fuel reservoir 16 which surrounds the nozzle needle 17 of the injection nozzle 7. As a result, no high pressure can build up in the fuel storage space 16, so that the nozzle needle 17 remains closed.

In the second switching position b of the metering valve 4, the actuating piston 8 in the metering valve body 11 is displaced in the opening direction 50. In this switching position b, a section 52 of the actuating piston 8 with a larger diameter seals off a section 53 of the metering valve body 11, so that the section 14 of the metering valve 4 is hydraulically separated from the annular chamber 15. In this switching position b, there is a connection between the high-pressure line 3, the subspace 23 of the metering valve 4, the annular space 15, the line 13 to the injection nozzle 7 and the fuel supply space 16.

In the closed state of the injector, the nozzle needle 17 closes injection openings 18 which open into the combustion chamber 19 of the internal combustion engine. A compression spring 20 generates a closing force on the nozzle needle 17.

The solenoid valve 5 and the metering valve 4 are connected to one another via a control line 21. An inlet throttle element 22 runs through the actuating piston 8 of the metering valve 4 and opens into two partial spaces 23, 24 inside the metering valve body 11, one partial chamber 23 being connected to the high pressure line 3 and the other partial chamber 24 to the control line 21 containing an outlet throttle element 63.

The solenoid valve 5 contains a solenoid valve needle 25 which can be opened via a magnet armature 26 and an electromagnet 27. A compression spring 28 generates a closing force on the solenoid valve needle 25. The spring chamber 47 of the solenoid valve 5 is connected via a compensating throttle 48 to a container 49 which can be closed to the control line 21 by the solenoid valve needle 25. Via the compensating throttle 48, the pressure in the container 49 can be applied to the solenoid valve needle 25 in the opening direction 50 acts, and the pressure in the spring chamber 47 of the solenoid valve 5, which generates forces on the solenoid valve needle 25 both in the opening direction 50 and in the closing direction 51, are equalized. At the same pressure in the container 49 and in the spring chamber 47, the forces on the solenoid valve needle 25 in the opening and closing directions 50, 51 are in equilibrium, since the effective areas are of the same size. Accordingly, the solenoid valve 5 is kept closed only by the force of the compression spring 28. A first control quantity line 29 runs from the solenoid valve 5 into a control quantity container 30 and from there an overall leakage line 32 into a low pressure area 31, for example the fuel tank of the internal combustion engine.

The control quantity container 30 is part of a pressure holding device 33. The pressure holding device 33 serves on the one hand to maintain a standing pressure necessary for the metering valve 4 and on the other hand to dynamically separate the control quantities 34 of the solenoid valve 5 and the control quantities 35 of the metering valve 4. The separation is dynamic, since the control quantities 35 of the metering valve 4 execute vibrations and are therefore highly dynamic and the control quantities 34 of the solenoid valve 5 are quasi-stationary, since the container 49 has an anti-vibration effect. Both tax amounts 34, 35 do not influence one another dynamically. In the present invention, the pressure maintaining device 33 also has the function of a hydraulic vibration damper. In addition to the control quantity container 30, it contains a pressure holding valve 36, a volume accumulator 37, an inlet throttle 38, an outlet throttle 39 and an inlet container 40. In this preferred embodiment of the present invention, the pressure holding valve 36 is a spring-loaded valve, in particular a spring-loaded ball valve. which comprises a compression spring 41 and a ball 42. The control quantities 35 of the metering valve 4 pass through the first line 12, the relief chamber 6 of the injection nozzle 7, the spring chamber 64 and a second control quantity line 43 to the pressure maintaining device 33. When the pressure holding valve 36 is open, the control quantities 35 of the metering valve 4 flow through the second control quantity line 43 the inlet container 40. From there they reach the control quantity container 30 via the inlet throttle 38, the volume accumulator 37, the pressure holding valve 36 and the outlet throttle 39.

In the preferred embodiment of the present invention shown in FIG. 1, the pressure holding device 33 contains an inlet throttle 38 which is arranged between the second control quantity line 43 and the pressure holding valve 36. The pressure-maintaining device 33 also preferably contains an outlet throttle 39, which is arranged at the outlet 46 of the pressure-maintaining valve 36. Finally, in the preferred embodiment of the present invention shown, the pressure maintaining device 33 comprises a volume storage device. rather 37, which is arranged between the inlet throttle 38 and the inlet 45 of the pressure control valve 36.

The control quantities 35 of the metering valve 4 and the control quantities 34 of the solenoid valve 5 mix in the control quantity container 30 and are passed as a total leakage quantity 44 via the total leakage line 32 into the low-pressure region 31.

An injection process takes place in the following way:

First, the solenoid valve 5 is closed. As a result, the control line 21 to the container 49 is closed. The metering valve 4 is in switching position a, i.e. the actuating piston 8 is displaced in the closing direction 51 in the metering valve body 11, so that the seat edge 9 rests on the valve seat 10. The first partial space 23 of the metering valve 4 is accordingly sealed against the annular space 15. The fuel under high pressure is in this switching position a of the metering valve 4 in the first subspace 23 and is from there via the inlet throttle element 22 in the second subspace 24 and in the control line 21. It generates a force in the closing direction 51 in the second subspace 24, which acts on the actuating piston 8 and thereby presses the seat edge 9 of the actuating piston 8 onto the valve seat 10. In the annular space 15, in the partial space 14, in the first and second lines 12, 13, in the fuel storage space 16 and in the relief space 6 of the injection nozzle 7, there is a uniform pressure that is reduced compared to the high pressure. The nozzle needle 17 closes the injection openings 18 toward the combustion chamber 19 primarily due to the spring force of the compression spring 20. In this switching position a, the pressure-maintaining valve 36 is closed and neither control quantities 34 of the solenoid valve 5 nor control quantities 35 of the metering valve 4 flow. A stand pressure arises from the subspace 14 of the metering valve to the inlet tank 40.

By actuating the solenoid valve 5 (excitation of the electromagnet 27), the magnet armature 26 moves in the opening direction 50 until it bears against the electromagnet 27. The solenoid valve needle 25 opens and the fuel flows from the second subspace 24 of the metering valve 4 and the control line 21 via the container 49 and the first control quantity line 29. As a result, the force in the opening direction 50 on the actuating piston 8 becomes greater than the force in the closing direction 51 due to the pressure difference between the second subspace 24 and the first subspace 23, so that the actuating piston 8 moves into the switching position b. The portion 52 of the actuating piston 8, with its larger diameter, reaches the portion 53 of the metering valve body 11 and thus interrupts the hydraulic connection between the annular space 15 and the portion 14. In this switching position b, however, the first portion 23 is open towards the annular space 15, so that fuel under high pressure from the high-pressure line 3 passes through the first partial space 23, the annular space 15 and the second line 13 into the fuel storage space 16. The high pressure in the fuel storage chamber 16 generates a force in the opening direction 50 on the nozzle needle 17 which is greater than the force of the compression spring 20 and the lower pressure in the relief chamber 6 in the closing direction 51. As a result, the nozzle needle 17 opens and fuel becomes overpressurized the injection openings 18 are injected into the combustion chamber 19. In this switch position b, a control quantity 34 flows continuously via the inlet throttle element 22, the outlet throttle element 63, the control line 21, the container 49 and the first control quantity line 29 into the control quantity container 30 and from there via the total leakage line 32 into the low pressure region 31 Pressure holding valve 36 is closed and no control quantities 35 of metering valve 4 flow via second control quantity line 43.

To terminate the injection event, the solenoid valve 5 closes by turning off the _r electromagnet 27 and by the force of the compression spring 28. The pressure in the second compartment 24 of the metering valve 4 rises again, thereby to move the adjusting piston 8 in the switching position a. As a result of this switching movement, a control quantity 35 flows into subspace 14 of the metering valve 4. This control quantity 35, which is moved in abrupt fashion, causes hydraulic vibrations in the line 12, in the relief chamber 6, in the second control quantity line 43 and in the inlet tank 40 Control amount 35, via the volume memory 37 damping the hydraulic vibrations. The pressure holding valve 36 opens as soon as the stand pressure set by the design of the pressure holding valve 36 is exceeded and consequently the control quantity 35 flows via the outlet throttle 39 into the control quantity container 30 and from there into the low pressure region 31. The pressure in the control quantity container 30 through the The control quantity 35 also acts on the solenoid valve needle 25 in the opening direction 50 via the first control quantity line 29. In the present invention, the inlet and outlet throttles 38, 39 and the volume accumulator 37 are dimensioned with regard to their diameter or volume such that the pressure in the control quantity container 30 a maximum pressure, for example 5 bar, is not exceeded. In particular, this ensures that the pressure in the spring chamber 47 of the solenoid valve remains limited to this maximum pressure, for reasons of the coil tightness of the electromagnet 27. Furthermore, the diameter of the inlet throttle (38) and the outlet throttle (39) is suitably chosen to ensure that pressure vibrations have no effect on the actuator valve, in particular on the movement of the actuator valve needle, in the second control quantity line (43). The compensation throttle 48 prevents hydraulic vibrations or shocks in the first control quantity line 29 from being transmitted to the armature 26. The preferred embodiment of the present invention shown in FIG. 1 offers, in addition to the advantage that it prevents an undesired opening of the solenoid valve 5, also advantageously the possibility of keeping the pressure holding valve 36 very small by the arrangement of the throttles 38, 39 and the volume accumulator 37 , The high-pressure injection system shown schematically in FIG. 1 can be a so-called PCS (Pressure Controlled Common Rail System), in which the metering valve 4 is integrated in the injector. However, it can also be a DCRS (pressure-controlled common rail system) in which the metering valve 4 is a module isolated from the injector.

Figure 2 shows a section of a pressure maintaining device according to the present invention.

A pressure holding valve body 54 is shown, in which the ball 42 and the compression spring 41 of a spring-loaded ball valve are arranged along its longitudinal axis 55. In the closed state of the valve, the ball 42 is pressed against a valve ball seat 57 contained in the transition part 56. A ball holder 58 is used to connect the ball 42 to the compression spring 41. The volume storage 37 is only shown in part. A sealing ring 62 seals the pressure switch device when installed. The control quantities 35 of the metering valve 4 (not shown) reach the outlet throttle 39 via the volume accumulator 37 when the ball valve is open and the outlet throttle 39. The outlet throttle 39 is located in a prestressing device 60 which limits the spring chamber 59 and at the same time keeps the compression spring 41 preloaded. After the control quantity 35 of the metering valve 4 has passed the discharge throttle 39, it is brought together with the control quantity 34 of the (not shown) solenoid valve 5 at point 61 and all control quantities are passed as a total leakage quantity 44 into a low-pressure area.

Figure 3 shows a pressure switch device according to the present invention.

As already described with reference to FIG. 2, it comprises the volume accumulator 37, the transition part 56, the ball 42, the ball holder 58, the compression spring 41 in the spring chamber 59, the sealing ring 62 and the outlet throttle 39. Furthermore, the metering valve 4 is on the pressure maintaining valve body 54 attached (but only shown in part). The control quantities 35 of the metering valve 4 reach the volume accumulator 37 via the inlet throttle 38. Behind the outlet throttle 39, these control quantities 35 are combined with the control quantities 34 of the (not shown) solenoid valve 5 to form a total leakage quantity 44. LIST OF REFERENCE NUMBERS

High-pressure fuel accumulator high-pressure pump high-pressure line metering valve solenoid valve relief chamber of the injector injection nozzle adjusting piston of the metering valve seat edge valve seat metering valve body first line between metering valve and injector second line between metering valve and injector sub-chamber of the metering valve annular space solenoid valve metering valve of the sub-chamber of the solenoid valve metering line of the valve chamber pressure control element Electromagnet compression spring first control quantity line control quantity container low pressure area total leakage line pressure holding device control quantities of the solenoid valve control quantities of the metering valve pressure holding valve 1(

volume storage

inlet throttle

outlet throttle

feed tank

compression spring

Sphere second control quantity line

Total amount of leakage

Inlet of the pressure control valve

Expiration of the pressure control valve

Spring chamber of the solenoid valve

Compensating choke

container

opening direction

closing direction

Part of the control piston

Part of the metering valve body

Pressure holding valve body

longitudinal axis

Transitional part

Valve ball seat

ball retainer

spring chamber

Vorspamieinrichtung

Packing rpunlct

seal

Outlet throttle element

spring chamber

Claims

Claims.

1. Injector for high-pressure injection of fuel in self-igniting internal combustion engines with a) an actuator valve for opening and closing the injector, b) a nozzle needle (17) which closes at least one injection opening (18) when the injector is closed, c) a metering valve (4), which establishes a hydraulic connection between the actuator valve and a relief chamber (6) of the injector, d) a pressure switch device (33) which ensures compliance with one for the metering valve

(4) necessary stand pressure and e) a first control quantity line (29) for control quantities (34) flowing through the actuator valve and a second control quantity line (43) for control quantities (35) flowing through the metering valve (4), characterized that the pressure switch device (33) dynamically separates the control quantities (35) of the metering valve (4) from the control quantities (34) of the actuator valve and serves as a hydraulic vibration damper.

2. Injector according to claim 1, characterized in that the actuator valve is a solenoid valve (5) with a solenoid valve needle (25) or a piezo actuator valve.

3. Injector according to claim 1, characterized in that the hydraulic vibration damper dampens pressure vibrations in the second control quantity line (43) due to the switching of the metering valve (4).

4. Injector according to claim 1, characterized in that the control quantities (35) of the metering valve (4) and the control quantities (34) of the actuator valve behind the pressure maintaining device (33) together via a total leakage line (44) into a low pressure area (31). be directed.

5. Injector according to claim 1, characterized in that the printing device (33) contains a pressure maintaining valve (36).

6. Injector according to claim 5, characterized in that the pressure holding valve (36) is a spring-loaded valve.

7. Injector according spoke 5, characterized in that the Drucklialteeinrichtung (33) contains an inlet throttle (38) which is arranged between the second control amount line (43) and the pressure maintaining valve (36).

8. Injector according to claim 5, characterized in that the pressure maintaining device (33) contains an outlet throttle (39) which is arranged on the outlet (46) of the pressure switch valve (36).

9. Injector according to claim 5, characterized in that the pressure holding device (33) contains a volume accumulator (37) which is arranged between the inlet throttle (38) and the inlet (45) of the pressure holding valve (36).

10. Injector according to claims 7 and 8, characterized in that the inlet throttle (38) and the outlet throttle (39) have diameters which ensure that pressure fluctuations in the second control quantity line (43) have no effect on the actuator valve.