EP1269008B1 - Injection valve with bypass throttle - Google Patents

Description

The invention relates to an injection valve according to the preamble of claim 1. In a common rail injection system The fuel is at a pressure of up to 2,000 bar injected into the combustion chamber of an internal combustion engine. The high fuel pressure requires precise control of the Injection time and injection quantity. It is still for Internal combustion engines powered by diesel fuel necessary an exact pre-injection with a low Fuel quantity to carry out the noise of the internal combustion engine and also to minimize pollutant emissions. For the reasons mentioned, it is necessary, the injection valve To tune very precisely, so that an optimal injection molding is reached.

From the article "A Common Rail Injection System For High Speed Direct Injection Diesel Engines ", SAE paper 980803, from N. Guerrassi et al., Is a fuel injector for a common rail injection system known which has a control chamber that is from a fuel line via an inlet throttle is supplied with fuel. The control chamber is connected to a drain line via an outlet throttle, which has an electromagnetic valve with a Fuel reservoir is connectable. Furthermore, a bypass throttle provided that a connection between the Fuel line and the drain line creates. The control chamber is bounded by a nozzle needle, which is axially movable is arranged in a nozzle body. The nozzle needle is passed through a nozzle chamber, with the fuel line communicates. Furthermore, the nozzle needle pressure surfaces on that with the fuel pressure in the nozzle chamber prevails, are charged and the nozzle needle in the direction apply force to the control chamber. In the control chamber a nozzle spring is provided which the nozzle needle in Direction to her sealing seat pretensions. The pressure in the Pressure chamber is dependent on the opening position of the electromagnetic Valve controlled. If the valve is open, so fuel flows out of the pressure chamber via the outlet throttle from and at the same time less fuel flows through the inlet throttle too, so that the pressure in the control chamber drops. When The result is the nozzle needle in the direction of the nozzle chamber moves, with the nozzle needle with its tip of a Sealing seat lifts off and a connection between the fuel line and injection holes releases.

Now, if the electromagnetic valve is closed, then flows both via the inlet throttle and via the bypass throttle and the outlet throttle fuel into the control chamber. On this way, the pressure in the control chamber is increased rapidly, so that the nozzle needle relatively quickly on its sealing seat in the nozzle body is pressed and thus the injection ends quickly.

The injection valve described has the disadvantage that the nozzle spring is in the control chamber and thus a relatively large control chamber is necessary, which is a large Represents harmful volume. Furthermore, by installing the Nozzle spring in the control chamber at risk Installation dirt particles enter the control chamber and themselves in the outlet throttle and the operability of the injection valve. Cavitation bubbles, the in the inlet throttle, can damage the nozzle spring.

The object of the invention is an injection valve to provide a simpler structure in which the Operation of the hydraulic control not impaired becomes.

The object of the invention is achieved by the features of the claim 1 solved.

Preferably, a part of the return line is a valve chamber trained, in which a bypass throttle opens. In this meadow a compact design of the injector is achieved.

Further advantageous embodiments of the invention are in the specified dependent claims. Preferably, a chamber, through which a coupling rod is guided, which is a control piston connects to the nozzle needle, directly to the fuel line connected the fuel under high pressure leads. In addition, no leakage line is connected to the chamber. In this way there will be a leak across the chamber largely avoided.

An advantageous construction of the injection valve is characterized achieved that the control chamber bounded by a control piston is, via a rod with the nozzle needle in operative connection stands. The rod is guided through a chamber, in a needle spring for biasing the nozzle needle is arranged. In this way, the control chamber is free of moving parts, causing contamination of the control chamber is excluded by introduced components. moreover the control chamber can be carried out particularly lead, whereby reduces the dead volume bein driving the nozzle needle is.

The cross section of the control piston is preferably equal to Cross-section of the guided portion of the nozzle needle formed. In this way, only one guide is to be made, thereby the injection valve is inexpensive.

Preferably, a closing member is inserted in the valve chamber, which is biased against a sealing seat by a spring is, which is also arranged in the valve chamber.

The invention will be explained in more detail below with reference to FIG. The figure shows the schematic structure of an injection valve for a common rail injection system. The injection valve has a housing 29, which via a supply line 30 is in communication with a fuel tank 10. The fuel storage 10 is for example of a controllable High-pressure pump supplied with fuel. The supply line 30 is guided to a fuel line 11 in the housing 29. The fuel line 11 is directly connected to a nozzle chamber 20 in connection, which opens into an injection space 31, emanating from the injection holes 22. The nozzle chamber 20 and the injection space 31 are inserted in a nozzle body 39, located at the bottom tip of the injector located. In the injection chamber 31 is a second sealing seat 21st arranged, with the closed state, a nozzle needle 32 rests with a needle tip 19. The needle point 19 is in communication with a guide portion 18 which is in Shape of a cylinder is formed.

The guide portion 18 is in a guide bore 33 of the Injection valve guided longitudinally movable. The guide hole 33 is in the form of a cylindrical recess in the housing 29 introduced. The guide bore 33 opens on a Side in the nozzle chamber 20 and on the other side in one Through hole 34, which is also cylindrical is and preferably a smaller cross section than the Guide bore 33 has. Preferably, grooves 40 are provided, which connect the nozzle chamber 20 with the chamber 25. The through hole 34 in turn opens into a chamber 25, which is also cylindrical and a larger Cross-section than the guide bore 33 has. In the Through hole is a coupling piece 35 is arranged on the guide portion 18 rests. In the chamber 25 is a Coupling rod 17 is arranged, which with a plate 23 on the Coupling piece 35 rests. The plate 23 is circular and has a larger cross-section than the cylindrical one Coupling rod 17 on. The plate 23 has the function a support collar for the needle spring 24.

As an alternative to the grooves 40, the guide 18 of the nozzle needle also completely omitted, leaving a circular cavity between Nozzle needle 32 and housing 29, the nozzle chamber 20 with the Chamber 25 connects. Furthermore, the chamber 25 also has a Connecting line 26 is connected directly to the high-pressure line 11 become.

The chamber 25 opens on the side of the through hole 34 is opposite, in a second guide bore 36th Die second guide bore 36 also has a cylindrical shape on. In the second guide bore 36 is a cylindrical Control piston 16 arranged to be movable in the longitudinal direction, which is connected to the coupling rod 17. Between the top End of the control piston 16 and the housing 29 is in the second guide bore 36 a control chamber 15 is formed.

In the chamber 25, a needle spring 24 is arranged, which is the Coupling rod 17 includes and between the plate 23 and a Step 37 is arranged, wherein the step 37 in the transition region between the chamber 25 and the second guide bore 36 is arranged. The second guide bore 36 has a smaller diameter than the chamber 25. The functioning the needle spring 24 is that the needle spring 24, the nozzle needle 32 with the needle tip 19 on the second Tight fit 21 pretensioned. The chamber 25 is preferably over a connecting line 26 to the fuel line 11th connected.

The control chamber 15 is connected via an inlet throttle 13 with the Fuel line 11 and an outlet throttle 14 with a Valve chamber 9 in conjunction. The cross section of the inlet throttle 13 is smaller than the cross section of the outlet throttle 14th In the valve chamber 9 is a closing member 6 and a valve spring 8, wherein the closing member 6 of the valve spring 8 is biased in the direction of a sealing seat 7. The closing member 6 and the sealing seat 7 provide a servo valve 5 dar. The valve chamber 9 is above a drain hole 38 with a return 40 in conjunction. Furthermore, one is Bypass throttle 12 is provided in the form of a bore, which is the Fuel line 11 connects to the valve chamber 9. The Lines between the control chamber 15 and the servo valve. 6 represent the return line 27. In the drain hole 38 is a valve piston 4 is guided, which is connected to an actuator 3 is. The valve piston 4 is located with a pressure surface on a associated pressure surface of the closing member 6. The actor 3 is via electrical connections 2 with a control unit. 1 in connection.

The injector works as follows: In the fuel tank 10 is fuel at high pressure, so that in a closed servo valve 5, wherein the closing member 6 abuts the sealing seat 7, in the valve chamber 9, in the Control chamber 15, in the nozzle chamber 20, in the injection space 31st and in the chamber 25 high-pressure fuel is present is. Since the area with which the control piston 16 to the control chamber 15, larger than the area covered by the Nozzle needle 32 with pressure in the direction of the control chamber 15th is applied and additionally the biasing force of the needle spring 24, the nozzle needle 32 presses on the sealing seat 21, sits the nozzle needle 22 on the sealing seat 21 and separates the Injection space 31 from the injection holes 22. Thus takes place no injection.

If an injection should now take place, the control unit controls 1, the piezoelectric actuator 3 in such a way that the actuator 3 deflects and the valve piston 4 the Closing member 6 lifts off from the sealing seat 7. As a result, flows over the outlet throttle 14 from the control chamber 15 more fuel from, as on the inlet throttle 13 flows. The fuel flows via the outlet throttle 14 in the valve chamber. 9 and on via the drain hole 38 in the return line 27 to a fuel reservoir. As a result, the pressure drops in the control chamber 15. The pressure in the nozzle chamber 20 remains continue at the level of the fuel line 11. As a result outweighs the force that the nozzle needle 32 from the second Sealing seat 21 lifts, so that the nozzle needle 32, the second Seal seat 21 releases and a connection between the injection space 31 and the injection holes 22 opens. Thus, will Fuel from the injection chamber 31 via the injection holes 22 delivered.

In this position also flows via the bypass throttle 12 Fuel in the valve chamber 9 and the drain hole 38 for return 27.

If now the injection should be stopped, then that controls Control unit 1, the piezoelectric actuator 3 in the way, that the actuator 3 is shortened. Thus, the closing member 6 again pressed by the valve spring 8 on the sealing seat 7, so that the connection to the return line 27 is interrupted. about the bypass throttle 12 continues to flow fuel out of the Fuel line 11 in the valve chamber 9 and of the valve chamber 9 via the outlet throttle 14 in the control chamber 15th At the same time fuel flows via the inlet throttle 13 of the Fuel line 11 into the control chamber 15. Thus, is quickly a high fuel pressure in the fuel chamber again 15 is reached, so that the nozzle needle 32 from the pressure, which prevails in the control chamber 15, again to the second Sealing seat 21 is pressed. Consequently, the connection between the injection space 31 and the injection holes 22 interrupted.

By connecting the chamber 25 to the pressure of the fuel line 11 via the connecting line 26 or the grooves 40, a hydraulic connection of the chamber 25 is achieved. As a result, a particularly low-friction movement of the nozzle needle 32 possible. In addition, leakage occurs via the chamber 25 towards the control chamber 15 only when the servo valve 5 is open and a slight pressure in the control chamber 15 prevails. Furthermore, the connection of the chamber 25 to the Fuel line 11 has the advantage that the guide fit between the guide portion 18 and the guide bore 33rd do not have to be as precise as there is no sealing between the nozzle chamber 20 and the chamber 25 is necessary. This allows a cost saving in the production of the injection valve.

The guide fit between the control piston 16 and the second pilot hole must continue to be made very precise be to seal between the control chamber 15 and the Chamber 25 to ensure.

• Keine Dauerleckage außerhalb des Schaltvorgangs/Einspritzvorgangs des Einspritzventils, da die Kammer unter Hochdruck steht;
• Beibehaltung einer separaten Kammer für die Nadelfeder, wodurch ein kleines Steuerraumvolumen, d. h. geringer Schadraum erreicht wird.
  Vermeidung von Schmutzproblemen am Servoventil bzw. von Kavitationsschäden an der Feder;
• Einbeziehung der Kammer 25 in das Hochdruckvolumen der Düsenkammer, wodurch eine Vergrößerung des Hochdruckvolumens vor der Düse erreicht wird;
  Verringerung des Druckeinbruchs infolge der Kompressibilität von Dieselöl in der Hochdruckleitung nach dem Öffnen;
  Verbesserung der Zerstäubung des Dieselöls in den Einspritzlöchern nach dem Öffnen, da mehr Druck zur Verfügung steht;
• Nur eine genau zu fertigende Führung der Düsennadel;
• Verwendung einer Bypassdrossel zur Unterstützung des Schließvorgangs der Düsennadel;
• Einbeziehung der Hochdruckkammer, die das Servoventil und die Ventilfeder enthält, in die Ausführung der Bypassdrossel.

An objective of the application is to avoid permanent leakage. For this purpose, the chamber 25, which contains the needle spring, connected along the leadership of the nozzle needle with the high pressure in the nozzle chamber. The only hydraulically effective piston surface which controls the movement of the nozzle needle is thus the cross section of the guide of the control piston. With the needle open and the servo valve closed, the compressive forces acting on the needle and spool band are almost balanced. The closing process is essentially initiated by the needle spring. In order not to get too large pressure drop in the control room by the downward closing movement of the needle and control piston, the Baypassdrossel is arranged. The bypass throttle is irrelevant to the opening of the nozzle needle when it is made small enough so as not to affect the pressure reduction via the servo valve 5. When closing, it serves as an additional inlet throttle with which the control chamber can be filled via the outlet throttle. The combination of a single hydraulically active guide of the needle to avoid permanent leakage on the one hand, and the bypass throttle to improve the function on the other hand, the following advantages:

• No permanent leakage outside of the switching process / injection process of the injector, as the chamber is under high pressure;
• Maintaining a separate chamber for the needle spring, whereby a small control chamber volume, ie small dead space is achieved.
  Avoidance of dirt problems on the servo valve or cavitation damage to the spring;
• Inclusion of the chamber 25 in the high pressure volume of the nozzle chamber, whereby an increase in the high pressure volume is achieved in front of the nozzle;
  Reducing the pressure drop due to the compressibility of diesel oil in the high pressure line after opening;
  Improvement of the atomization of the diesel oil in the injection holes after opening, as more pressure is available;
• Only a precise to be made leadership of the nozzle needle;
• Use of a bypass throttle to assist the closing of the nozzle needle;
• Including the high-pressure chamber, which contains the servo valve and the valve spring, in the execution of the bypass throttle.

Due to the operation of the piezoelectric actuator, it is advantageous an inward (against the high pressure working) servo valve to use. The resulting chamber can be used as a drain line used to connect the high pressure line via the bypass throttle to connect with the outlet of the outlet throttle.

Claims (7)

1. Injection value with a fuel line (11), which is routed to a control chamber (15) via an inflow throttle (13),

   with an outflow throttle (14) which links the return line (27) to the control chamber,

   with a control valve (5) which is connected in the return line (27) upstream of a return flow (40),

   with a bypass throttle (12) which links the fuel line (11) to the return line (27),

   with a nozzle needle (32) arranged moveably in a nozzle chamber (20), the nozzle chamber being linked to the fuel line (11),

   the nozzle needle (32) being linked to a control piston (16), whereby

   the control piston (16) forms the boundary of the control chamber (15), and whereby a part of the return line (27) is configured as a valve chamber (9) and the bypass throttle (12) flows into the valve chamber (9).
2. Injection valve according to Claim 1,
   characterised in that
   the control piston (16) is linked to the nozzle needle (32) via a rod (17) and that said rod (17) is routed through a chamber (25).
3. Injection valve according to Claim 2,
   characterised in that
   the chamber (25) is linked to the fuel line (11).
4. Injection valve according to one of Claims 1 to 3,
   characterised in that
   the cross-section of the control piston (16) is equal to the cross-section of the routed area (18) of the nozzle needle (32).
5. Injection valve according to one of Claims 1 to 4,
   characterised in that
   a closing element (6) is arranged in the valve chamber (9), said closing element being preloaded against a sealing seat (7) by a spring (8).
6. Injection valve according to one of Claims 2 to 5,
   characterised in that
   grooves (40) are provided to link the nozzle chamber (20) to the chamber (25).
7. Injection valve according to one of Claims 2 to 5,
   characterised in that
   a spring (24) is arranged in the chamber (25), said spring preloading the nozzle needle (32) in the direction of a sealing seat (21).

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