SE525208C2 - Injectors - Google Patents

Abstract

The invention relates to a fuel injector 8, a method for injection of fuel, and a combustion engine with a fuel injector 8. The fuel injector 8 comprises a connection 22 for pressurised fuel 12, an accumulator space 26 for fuel 12, and a nozzle needle 28 which intermittently blocks apertures 30,32 to a combustion chamber 18, while the injector 8 further comprises a piston 46 which is connected to the high-pressure space 26 via a duct 58 and is movable within a space 47 and which, when moved directly or indirectly under the influence of a control unit 67 before the beginning of an injection period, can assume a position such that pressurised fuel is supplied to the space 47, whereby the fuel column 73 from the connection 22 for pressurised fuel 12 is set in motion before injection takes place. The dynamic energy, i.e. the mass moment of inertia, in the fuel flow can thereby be used for the injection into the combustion chamber, making it possible to achieve a high injection pressure throughout the injection period.

Description

v ~ .. .... . . ._ '_ _ __ __ _ _-_ -z _..__-... _.._...; . . _ _ ..: .. * n .. e z n ... o ... n q 4 v - e »H n.

The problem that the injection pressure is lower at the beginning of the injection period than just before the end of the injection period is solved according to the invention by designing a fuel injector according to the preamble of claim 1 with the features stated in the characterizing part of claim 1.

Because the fuel injector comprises the features of claim 1, the advantage is achieved that the dynamic energy, i.e. mass inertia, in the fuel fl fate can be used for the injection into the sörbrannningrurnmet whereby a high injection pressure can be achieved during the entire injection period. The fuel column is set in motion before the start of the injection process, which gives a higher injection pressure and injection flow at the beginning of the injection period compared to known systems.

The features of the dependent claims further achieve the advantages that: 15 - shorter needle opening time is achieved since the mass in the control mechanism consists only of the spreading targets, which in turn gives higher pressure and fl fate at the beginning and at the end of the injection period. shorter reaction times than the reaction times of prior art systems are achieved, since the control system according to the invention also operates with unstriped fates. 2 O - no leakage fuel fl Fatalities occur past the needle control in between the injection periods, which reduces the energy consumption of the high-pressure pump and the cooling demand for the fuel.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will be further elucidated below with reference to the accompanying drawings, in which: Figure 1 schematically shows a fuel injection system for an internal combustion engine in a vehicle, Figure 2 schematically shows a prior art fuel injector in idle mode. Figure 3 schematically shows a fuel injector according to the invention in idle mode, Figure 4 schematically shows the fuel injector according to Figure 3 in a position just before the start of the injection period, and Figure 5 schematically shows the fuel injector according to Figure 3 in a position just after start of injection period.

Description of Preferred Embodiments Similar, though non-identical, parts of the various figures are designated by like reference numerals.

Figure 1 schematically shows a fuel injection system 2 for an internal combustion engine, e.g. a diesel engine or a petrol engine, in a vehicle. The fuel injection system 2 comprises a fuel tank 4, at least one high-pressure pump 6 connected to the fuel tank 4 via a low-pressure line 14, at least one injector 8 connected to the high-pressure pump 6 via a high-pressure pipe 16, and preferably also at least one between the high-pressure pump 6 and the injector 10 such as, for example, a fuel strip which is also called a "rail", which accumulator has a fixed volume, ie. the volume of the accumulator 10 does not vary.

The fuel injection system 2 operates as follows: The fuel 12 is sucked by the high pressure pump 6 through the low pressure line 14 from the fuel tank 4 to the high pressure pump 6, where the fuel 12 is pressurized to the desired system pressure level, after which the fuel 12 is passed through the high pressure pipe 16 either directly or via the accumulator to the injector 8 and from there on to the combustion chamber 18 of the internal combustion engine via the combined fuel return and spreader needle control channel 20 back to the fuel tank 4.

Preferably, a single high pressure pump 6 is used to pressurize the fuel 12, after which the fuel 12 is led to a single accumulator 10, from where one or more of the high pressure pipes 16 leads the fuel 12 to one or more injectors 8 which open into one or more combustion chambers 18, where the number of high pressure pipes 16 out from the accumulator 10 depends on the number of diffusers 8. It is also possible that lO 15 20 šzs v, »|| ':': '20. - v | - q ». | «» - 525 208 i -a u, ø - - - u arrange a high pressure pump 6 per injector 8, with or without intermediate accumulator 10.

The accumulator 10 can be arranged in such a way that the high-pressure pipes 16 out of the accumulator 10 are always pressurized or in such a way that the accumulator 10 puts on, ie. benefits, a pressure in each of the high pressure pipes 16 at the time when the respective associated injector 8 is intended to inject pressurized fuel 12 into the respective combustion chamber 18.

Figure 2 schematically shows a previously known fuel injector in idle mode. The injector 8 comprises a high-pressure connection 22 through which pressurized fuel 12 is led in from a high-pressure pipe 16 to the injector 8. The fuel 12 is then passed on the one hand via a channel 24 to an accumulator space 26 for pressure and volume and from there on via one or more of a spreader needle 28 occasionally blocked openings 30,32 to an combustion chamber 18 of the internal combustion engine, and on the other hand via a channel 34, a control space 36, and a combined fuel return and spreader needle control channel 20 back to the fuel tank 4.

The accumulator compartment 26 has a fixed volume.

This prior art injector 8 is controlled by opening a control valve 38 in the combined fuel return and injector needle control channel 20, whereby fuel 12 can bleed out. Thereby, the pressure at the end of the spray nozzle 28 which is located near the combined fuel return and nozzle needle guide channel 20 is lowered, the spray nozzle 28 being displaced axially in the direction away from the openings 30,32 so that pressurized fuel 12 can flow out through the openings 30,32 into the combustion chamber 18. When the control valve 38 is closed, the pressure again increases at the end of the spray nozzle 28 which is located near the combined fuel return and spray target control channel 20, the spray nozzle 28 being displaced axially by means of a return spring 40 towards the openings 30, 32 and shutting off the flow of fuel 12. by blocking these openings 30,32. In prior art injectors 8 of this kind, the injection pressure is lower at the beginning of the injection period than just before the end of the injection period. The flow in the combined fuel return and diffuser needle guide channel 20 is, depending on, for example, throttles 42,44, usually 15 to 20% of the flow through the openings 30,32.

Figure 3 schematically shows a fuel injector 8 according to the invention, i.e. an injector 8 where the fuel fl fate to and in the injector is in motion before the start of the injection period. The injector 8 comprises a high-pressure connection 22 through which pressurized fuel 12 is led in from a § 15 @ 25. o - - «-u 525 208 l: jjëlffš-: ffff 'high-pressure pipe 16 to the injector 8. The fuel 12 is then passed via a channel 24 to a high-pressure space 26 for fuel, for example an accumulator space for pressure and volume and / or a high-pressure duct, and from there on via one or more of a spreading target 28 occasionally blocked openings 30,32 to a combustion chamber 18 of the internal combustion engine.

In addition to a spreader needle 28, there is also a piston 46 arranged in a space 47 in the injector 8.

The space 47 is connected to the high pressure connection 22 via a channel 58, the accumulator space 26, and the channel 24. Thus, since the accumulator space 26 and one end 56 of the piston 46 (the one furthest from the spring 54) are connected to the channel 58, more pressurized fuel is allowed to flow. into the injector 8 via the high-pressure connection 22 when the piston 46 is displaced in the downward direction according to the direction, since a part of the space 47 here is filled with pressurized fuel. Both the piston 46 and the spreading targets 28 are held in their first end positions 50,52 by a common spring 54. In the space 60 between the spreading targets 28 and the piston 46 (ie in the space 60 where the spring 54 is housed) a channel 62 goes to a, preferably independent , three-way control valve 64, preferably a solenoid valve, which is operated by an electronic control unit 67, preferably via a solenoid 66. The electronic control unit 67 operates both the high-pressure pump and the piston 46.

The injection process will be described below with reference to Figures 4 and 5.

Figure 4 schematically shows the fuel injector 8 according to figure 3 in a position just before the start of the injection period. The control unit 67 provides an electrical pulse to the three-way control valve 64 which as a result assumes a position where the space 60 between the spray targets 28 and the piston 46 is connected to the fuel return duct 20 with the result that fuel located in the space 60 begins to drain to the fuel tank 4 from the space 60. area on the top of the piston 46 which is exposed to pressurized fuel is larger than the area in the accumulator space 26 which presses the spreading targets in the upward direction, a pressure drop occurs over the piston 46 which sets it in motion, i.e. it is displaced, towards its lower end position as shown in the figure. As the fuel volume 71 in the high pressure inlet portion 70 of the injector 8 thereby increases, the fuel column 72,73 in the high pressure portion 70 is set in motion from the high pressure tube 16 and the pressurized fuel connection 22 via the accumulator space 26 to the first end of the piston 46. Thus, the entire fuel volume is set in motion from the high-pressure pump 6. When the piston 46 reaches its lower 10 15 20 §25 -la-o - | c - »-. . - - u. 525 208 u u. - q v. - - u ». -. . s. end position, the pressure in the space 60 between the spreader needle 28 and the piston 46 drops rapidly at the same time as a pressure pulse is generated by forcing the fuel column 72 to decelerate when the movement of the piston 46 stops. The piston 46 here assumes a position so that pressurized fuel is supplied to the space 47, whereby the fuel column 73 from the connection 22 for pressurized fuel 12 is set in motion before injection takes place.

Figure 5 schematically shows the fuel injector 8 according to figure 3 in a position just after the start of the injection period. When the movement of the piston 46 stops and the pressure in the space 60 between the spreader needle 28 and the piston 46 falls, the spreading targets 28 begin to move towards their upper end position as can be seen in the figure, opening the connection 30, 32 to the combustion chamber, wherein injection of fuel 12 into the combustion chamber 18 begins with a pressure corresponding to the pressure in the high-pressure pipe 16 plus the pressure pulse from the retarded fuel column 72. The dynamic energy, i.e. mass inertia, of the fuel flow in the entire amount of fuel in both the injector 8 and the high pressure pipe 16 can be used for the injection in the combustion chamber 18 whereby a high average injection pressure can be maintained throughout the injection period.

When the electrical pulse from the control unit 67 ceases, the three-way control valve 64 returns to the position (see the position of the valve 64 shown in Fig. 3) where the space 60 between the spreader needle 28 and the piston 46 is dry-connected to the high-pressure part of the injector 8. The space 60 is pressurized to at least the same pressure as in the accumulator space 26 for fuel 12, the spreading needle 28 returning to its lower end position of the spring collar, after which the piston 46 returns to its upper end position, i.e. that the piston 46 remains in its lower end position until the spreading targets 28 reach their lower end position. The spreading targets 28 hereby close the connection 30,32 to the combustion chamber 18 and the injection of fuel 12 into the combustion chamber 18 is terminated. The injection process has thus been completed, and the injector 8 has returned to the rest position shown in Figure 3.

Claims (9)

10 15 20: 25 f 30 I - - v v u n v r - .u 525 208 u u. n ~. . , «N« »«. -s Patent claims 1. A fuel injector comprising a connection (22) for pressurized fuel (12), a high pressure space (26) for fuel (12), and a spreader needle (28) occasionally blocking openings (30,3 2) to a combustion chamber (18) , characterized in that the injector (8) further comprises a piston (46) displaceable to the high-pressure space (26) connected via a channel (58) in a space (47), which then directly or indirectly under the influence of a control unit (67) displaced before the start of the injection period can take a position so that pressurized fuel is supplied to the space (47), whereby the fuel column (73) from the connection (22) for pressurized fuel (12) is set in motion before injection takes place. Fuel injector according to claim 1, characterized in that the high-pressure space (26) for fuel (12) and the end (56) of the piston (46) located furthest from the spreading targets (28) are connected to the channel (58). Fuel injector according to one of the preceding claims, characterized in that a channel (62) runs from a space (60) between the spreader needle (28) and the piston (46) to a three-way control valve (64) which in turn is connected to a fuel return channel (20). Fuel injector according to one of the preceding claims, characterized in that the piston (46) and the spreader needle (28) are held by a common spring (54) in their first end positions (50 and 52, respectively). Fuel injector according to Claim 4, characterized in that the edema (54) is housed in the space (60) between the spreading targets (28) and the piston (46). A method of injecting fuel into an internal combustion chamber (18) of an internal combustion engine using a fuel injector comprising a connection (22) for pressurized fuel (12), a high pressure space (26) for fuel (12), and an occasional spreading target (28) blocking openings (30, 32) to the combustion chamber (18), characterized by the steps of: - draining pressurized fuel from a space (60) between the spreading targets (28) and another. Q o u | u v - c; Q a. . . . ., l v. ... u s 1. .. .we . . . .,. , 'I 0 o .. s and Q »- u u f a s. v u v. v - | . . =. The high-pressure space (26) via a channel (58) connected to a displaceable piston (46) is started, whereby the piston (46) is set in motion by a pressure drop which occurs over the piston (46), the fuel volume in the injector (8) is increased, and the fuel column (73 ) from the connection (22) before pressurized fuel (12) is set in motion, - the movement of the piston (46) is stopped, the spreading targets (28) opening the connection (30, 32) to the combustion chamber (18) because the pressure in the space (60) between the spreading needle (28) and the piston (46) falls, starting injection of fuel (12) into the dry combustion chamber (18), and the space (60) between the spreading targets (28) and the piston (46) is pressurized to at least the same pressure as in the high pressure space. (26) for fuel (12), the spreading targets (28) closing the connection (30, 32) to the combustion chamber (18) and injecting fuel (12) into the dry combustion chamber (18). 1 5 A method of injecting fuel according to claim 6, characterized in that pressurized fuel from the space (60) between the spreading targets (28) and the dry-sliding piston (46) is drained via a three-way control valve (64). 2 0 A method of injecting fuel according to claim 7, characterized in that the style valve (64) is controlled by an electronic control unit (67). Internal combustion engine, characterized in that it comprises a fuel injector according to any one of claims 1 to 5.