GB2321281A

GB2321281A - Fuel injection controller for an internal combustion engine

Info

Publication number: GB2321281A
Application number: GB9800772A
Authority: GB
Inventors: Ulrich Augustin
Original assignee: Daimler Benz AG
Current assignee: Daimler Benz AG
Priority date: 1997-01-17
Filing date: 1998-01-14
Publication date: 1998-07-22
Anticipated expiration: 2018-01-14
Also published as: GB9800772D0; FR2758593A1; ITRM980012A0; DE19701558A1; IT1298842B1; GB2321281B; FR2758593B1; ITRM980012A1

Abstract

A fuel injection controller for an internal combustion engine having a high-pressure pump is provided with a solenoid valve which is arranged between the high-pressure pump and injection nozzles. The solenoid valve has a magnetically actuated valve body 2 whose closing element 2a which is arranged in a low-pressure space 9 interacts with a valve seat 3 on the housing 1 of the solenoid valve. Fuel is sucked into the high-pressure pump in the injection intervals via a low-pressure system 10, 14,14a,13 connected to the low-pressure space 9, while the closing element 2a interrupts the connection to the low-pressure system 9 in the injection cycle by magnet actuation. A throttle point 12 is arranged in the low-pressure system 9 in such a way that, at the start of the injection interval, a pressure is built up in the low-pressure space 9 and causes the closing element 2a to be displaced in the direction of the closing position.

Description

1 Fuel Injection Controller for an Internal Combustion Engine 2321281 The

invention relates to a fuel injection controller for an internal combustion engine with a high-pressure pump and injection nozzles.

A solenoid valve which is arranged between a high-pressure pump and injection nozzles and which has a magnetically actuated valve body serves to control the fuel injection. The closing element of the valve body is arranged in a low-pressure space and interacts with a valve seat arranged on the housing of the solenoid valve, in such a way that fuel is sucked into the high-pressure pump in the injection intervals via a low-pressure system connected to the low-pressure space. On the other hand, in the injection cycle the closing element is pressed onto the valve seat by means of an appropriate magnet actuation, so that the connection to the low-pressure system is interrupted. There is complete pressure equalization of the solenoid valve, or the valve body, by means of internal and external pressures. This method of control is relatively simple in design, since, among other things, it requires neither a relief valve nor flowback throttles. However, the disadvantage with this method of control is that, at the end of an injection when the closing element of the solenoid valve opens and thus when a connection is made via the low-pressure space and a low-pressure line connected thereto, uncontrolled emptying of the high-pressure area into the lowpressure system may occur, resulting in the disadvantageous consequences of cavitation and fluctuation in quantities.

DE 44 06 901 A1 discloses a solenoid-valve-controlled injector for an internal combustion engine having a three-way servo valve with a throttle which has the function of avoiding undesired, sudden opening of the nozzle needle and of slowing down the movement of said nozzle needle in the emptying phase. This throttle does not have any influence on the movement behaviour of the valve itself.

DE 42 38 727 A1 discloses a solenoid valve for controlling a passage of a connection between a high-pressure space and a low-pressure space, a valve element which is axially guided in a hole of a valve body and which can be displaced electromagnetically being provided. In order to avoid cavitation damage in the area of the sealing faces, a throttle point is connected downstream of the sealing edge in the 2 area of the passage cross-section. This throttle point is intended to bring about further opening of the valve element, and thus support the opening of the valve element. The pressure in the downstream low-pressure port does not have any effect on the forces which act on the valve body and on the valve element, respectively. As a result of the supporting of the opening of the valve element, the disadvantages mentioned at the beginning in terms of uncontrolled emptying out of the high-pressure area into the lowpressure area occur.

The present invention therefore seeks to achieve controlled emptying of the high-pressure area at the end of the injection using simple means.

According to the present invention there is provided a fuel injection controller for an internal combustion engine having a high-pressure pump, and a solenoid valve arranged between the high-pressure pump and fuel injection nozzles and which has a magnetically actuated valve body, which is pressure-equalized in the injection cycle and has a closing element arranged in a low-pressure space and which interacts with a valve seat on the housing of the solenoid valve, fuel being sucked into the highpressure pump in the injection intervals via a low-pressure system, which is connected to the low-pressure space, while the closing element interrupts the connection to the lowpressure system in the injection cycle by magnet actuation, a throttle point being arranged in the low- pressure system in such a way that, at the start of the injection interval, a pressure is built up in the low-pressure space and causes the closing element to be displaced in the direction of the closing position.

The throttle point makes it possible for the valve scat to perform throttling in the opening phase of the valve body. This throttling is brought about by the build-up in pressure upstream of the throttle point in the low-pressure space, the opening pressure being opposed with a corresponding counterpressure. When a corresponding counterpressure is reached, this pressing force prevails and partially presses the closing element of the valve body back onto the valve seat. In this way, the valve. hody automatically assumes a position which produces a specific preselected pressure in the low-pressure space. Uncontrolled emptying out of the high-pressure system during the first opening phase is thus avoided in a simple way. By increasing or decreasing the throttle cross- section, relief can be provided to a greater or lesser degree. The pressure in the low-pressure chamber itself is also defined by means of the force of an opening 3 spring, which is generally present, for the valve body.

A further advantage of the present invention lies in the fact that the throttle point can also be easily integrated into existing systems without large physical changes.

The solenoid valve forms a control loop together with the throttle point.

Two embodiments of the invention are described below in principle with reference to the drawing, in which:

Fig. 1 shows a solenoid valve for injection nozzles of an internal combustion engine with associated fuel inflow and outflow lines, Fig. 2 shows a solenoid valve for injection nozzles of an internal combustion engine with associated fuel inflow and outflow lines in a different embodiment with a throttle point in a through-hole of the valve body.

The solenoid valve illustrated in Figures 1 and 2 is basically of a known design and is also operated in a known manner, for which reason details are given below only on the parts which are essential for the invention.

A valve housing 1 accommodates a valve body 2 of the solenoid valve, a valve seat 3, with which a closing element 2a of the valve body interacts, a high-pressure connecting line 4 to an injection nozzle (not illustrated) and a high-pressure inflow line 5, which is connected to a pump piston of a high-pressure pump (not illustrated). The valve body 2 is attracted, with an armature plate 6 attached to it, by a magnet 7 counter to the force of a spring 8 when current is supplied. The system is filled with fuel via a low-pressure chamber 9 which is connected to a low-pressure supply system via a low-pressure line 10. An armature plate space 11, in which the armature plate 6 on the side remote from the low- pressure space 9 moves, is also connected to the lowpressure system via a port 13.

This valve design of the solenoid valve has complete pressure equalization by means of internal and external pressures. In the feeding intervals, the high-pressure system is supplied with fuel from the low- pressure line 10 by the high-pressure pump, since the valve body 2 is in the open position during this time; i.e. the closing element 2a is lifted off from the valve seat 3. In this position, fuel is sucked in by the highpressure pump. In order to pass on fuel under high pressure via the high-pressure connecting line 4 to an injection nozzle, the closing element 2a of the valve body 2 is pressed onto the valve seat 3 by supplying current to the magnet 7 and as a result 4 attracting the armature plate 6, causing the connection to the low- pressure system to be interrupted. At the end of an injection process, the supply of current to the magnet 7 is interrupted, the closing element 2a of the valve body 2 lifts off from the valve seat 3 and fuel flows back into the low-pressure space 9, and thus into the low-pressure system, via the low-pressure line 10.

A throttle point 12, which forms a control system with the valve seat 3 and the spring 8, is arranged in the low-pressure line 10, the external pressure equalization being cancelled. At the end of an injection, pressure in fact builds up in the pressure space 9 owing to the throttle point 12 when fuel is diverted into the low-pressure system, said pressure thus acting on the valve body 2 counter to the opening force of the spring 8. At a preset pressing force, for example of approximately 20 bar, the pressing force in the pressure space 9 prevails and partially closes the valve. In this way, the closing element 2a of the valve body 2 automatically assumes a position which produces a preselected pressure in the pressure space 9. As a result, uncontrolled emptying of the system in the first opening phase is avoided. The throttle point 12 will expediently be configured in such a way that adequate charging can nevertheless take place via it in the fuel intake phase. As a matter of principle, the throttle point 12 is not configured in such a way that throttling of quantities takes place, but rather merely in such a way that in the pressure space 9 a pressure is built up which displaces the closing element 2a of the valve body 2 in the closing direction.

Fig. 2 illustrates a solenoid valve which is basically of the same design as the solenoid valve illustrated in Fig. 1 and also basically functions in the same way. For this reason, in this exemplary embodiment the same reference symbols have also been retained for the same parts.

The significant difference with respect to the exemplary embodiment according to Fig. 1 is that in this case the valve body 2 is provided with an axial connecting hole 14 which starts from the pressure space 9 and which leads via a transverse line 14a to the armature plate space 11. In this exemplary embodiment, the connecting hole 14 replaces the transverse hole 14a and the line 13 replaces the low-pressure line 10. The throttle point 12 is in this case arranged in the connecting hole 14 and acts in the same way as the throttle point 12 in the low-pressure line 10. In this embodiment, the separate low-pressure line 10 is thus dispensed with.

Claims

1. A fuel injection controller for an internal combustion engine having a highpressure pump, and a solenoid valve arranged between the highpressure pump and fuel injection nozzles and which has a magnetically actuated valve body, which is pressureequalized in the injection cycle and has a closing element arranged in a low-pressure space and which interacts with a valve seat on the housing of the solenoid valve, fuel being sucked into the high-pressure pump in the injection intervals via a low-pressure system, which is connected to the low-pressure space, while the closing element interrupts the connection to the low-pressure system in the injection cycle by magnet actuation, a throttle point being arranged in the low-pressure system in such a way that, at the start of the injection interval, a pressure is built up in the low-pressure space and causes the closing element to be displaced in the direction of the closing position.

2. A controller according to Claim 1, wherein the throttle point is arranged in a low-pressure line which starts from the low-pressure space.

3. A controller according to Claim 1, wherein the valve body is provided with an axial connecting hole which produces a connection between the lowpressure space on one side of the valve body and a low-pressure area on the other side of the valve body, and the throttle point is arranged in the connecting hole.

4. A controller according to Claim 3, wherein the connecting hole leads, via a transverse hole, into an armature plate space of the solenoid valve.

5. A fuel injection controller for an internal combustion engine substantially as described herein with reference to, and as illustrated in, the accompanying drawings.

-(47 - Amendments to the claims have been filed as follows Clai 1. A fuel injection controller for an internal combustion engine having a highpressure pump, and a solenoid valve with a housing, which valve is arranged between the high-pressure pump and fuel injection nozzles and which has a magnetically actuated valve body, which is pressure-equalized in an injection cycle and has a closing element having a closing position, which element is arranged in a low-pressure space and which interacts with a valve seat on the housing of the solenoid valve, fuel being sucked into the highpressure pump in injection intervals via a low-pressure system, which is connected to the low-pressure space, while the closing element interrupts the connection to the lowpressure system in the injection cycle by magnet actuation, a throttle point being arranged in the low-pressure system in such a way that, at the start of the injection interval, a pressure is built up in the low-pressure space and causes the closing element to be displaced in the direction of the closing position.

2. A controller according to Claim 1, wherein the throttle point is arranged in a lowpressure line which starts frorn the low-pressure space.