JP3887583B2 - Fuel injection device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a fuel injection device for an internal combustion engine.
[0002]
[Prior art]
In order to facilitate understanding of the specification and claims, the following concepts are described: The fuel injection device according to the present invention may be formed in a stroke control type or a pressure control type. It may be. Within the framework of the present invention, a stroke-controlled fuel injection device is a nozzle needle whose opening and closing of the injection opening is movable based on hydraulic cooperation between the fuel pressure in the nozzle chamber and the fuel pressure in the control chamber. It means to be done. The pressure drop inside the control chamber causes the nozzle needle to lift. Alternatively, the displacement of the nozzle needle may be performed by an actuating member (actuator). In the pressure-controlled fuel injection device according to the present invention, the nozzle needle is moved against the action of the closing force (spring) by the fuel pressure formed in the nozzle chamber of the injector. Open for fuel injection from the chamber into the cylinder. The pressure applied to the fuel flowing out from the nozzle chamber into the cylinder is called the injection pressure , whereas the system pressure is the pressure applied to the fuel provided or stored in the fuel injection device. Means. Fuel metering means that fuel is supplied to the nozzle chamber by a metering valve. In combined fuel metering, one common valve is used to meter different injection pressures. In the pump / nozzle unit (PDE), the injection pump and the injector form one unit. For each cylinder, a unit of this type is assembled to the cylinder head and driven by the engine camshaft either directly via a tappet or indirectly via a rocker arm. The pump / line / nozzle system (PLD) works in the same way. Here, the high-pressure line leads to the nozzle chamber or the nozzle holder.
[0003]
PDE or PLD is used to reduce emissions by high maximum injection pressure and linear boost. Furthermore, it has been found that it is advantageous if the injection pressure is independent of the engine speed and load and can be variably adjusted in the characteristic map. Multistage injection is also advantageous. Therefore, a common rail system (CRS) is used.
[0004]
[Problems to be solved by the invention]
The object of the present invention is to improve the fuel injection system of the type mentioned at the outset by combining the advantages of CRS flexible multistage injection and pressure regulation with the advantages of high PDE injection pressure and linear pressure increase. is there.
[0005]
[Means for Solving the Problems]
In order to solve this problem, according to the configuration of the present invention, in a fuel injection device for an internal combustion engine, at least one of a pump / nozzle unit or a pump / pipe / nozzle system for compressing fuel is disposed corresponding to each injector. One of the local pump element, and is a central pressure accumulator is provided which is connected to the injector, accumulating divider and separate pump element is connected to the pressure line leading to the injector, the pressure tube The connecting line of the pressure accumulator to the passage has a check valve and a throttle connected in parallel to the check valve.
[0006]
【The invention's effect】
According to the invention, it is ensured that injection can be performed at any time by means of a pressure accumulator connected to a stroke-controlled injector. This is important, for example, for the regeneration of the filter and catalyst system. Furthermore, the fuel injection device according to the present invention can realize pilot injection and post injection. In this case, both injections may be independent of the cam stroke. For boosting, PDE / PLD elements are used to use the advantages of high pressure and linear boosting. In the fuel injection device according to the present invention, the injection pressure can be adjusted, and this injection pressure can be adapted to the requirements of the engine in the characteristic map. For the reduction of the device structure, the filling of the pressure accumulator can be achieved by the PDE / PLD element.
[0007]
When the pressure accumulator is filled via the pump element and the throttle, a loss is generated. In order to avoid this amount of loss, a filling valve is proposed which shuts off the connection to the injector during boosting by the pump element (ie even during injection). After the pump element has been pumped, the connection to the injector is formed again. Filling the accumulator is accomplished primarily from the amount of relief generated as a loss in the system of the injector volume.
[0008]
It is particularly advantageous if the filling valve is combined with a check valve already provided in the system, whereby the equipment costs are not increased unnecessarily. Basically, the filling valve may be formed as a separate valve, combined with another valve of the system, or operated by an actuator if necessary.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
In the following, embodiments of the present invention will be described in detail with reference to the drawings.
[0010]
Each cylinder is provided with a pump / nozzle unit (PDE) or a pump / pipe / nozzle system (PLD). Each pump / nozzle unit is formed of a pump element 1 and an injector 2. One pump / nozzle unit per engine cylinder is assembled to the cylinder head. The pump element 1 is driven by the engine camshaft directly via a tappet or indirectly via a rocker arm. The electronic adjustment device can appropriately affect the amount of fuel to be injected (injection progress). In the first embodiment of the stroke control type fuel injection device 3 shown in FIG. 1, the low-pressure pump 4 pumps the fuel 5 from the stock tank 6 to the pump element 1 through the pressure feed line 7. The control valve 8 serves to fill the pump chamber 9 of the pump element 1. High pressure is generated during the cam stroke with the control valve 8 closed. As a result, pressure increase is started, and fuel under pressure is guided to the injector 2 through the check valve 10.
[0011]
Injection is effected via a fuel metering by a nozzle needle 11 which is axially movable in a guide hole, with a conical valve seal surface 12 at one end. The valve seal surface 12 of the nozzle needle 11 cooperates with a valve seat surface provided in the injector housing. An injection opening is provided in the valve seat surface of the injector housing. A nozzle chamber 13 and a control chamber 14 are formed. Inside the nozzle chamber 13, the pressure receiving surface directed in the opening direction of the nozzle needle 11 is exposed to the pressure formed in the nozzle chamber 13. This pressure is supplied to the nozzle chamber 13 via the pressure line 15. Furthermore, a plunger 17 acts on the nozzle needle 11 coaxially with the compression spring 16. The plunger 17 partitions the control chamber 14 with an end surface 18 on the side opposite to the valve seal surface 12. The control chamber 14 has an inflow passage provided with a throttle 19 extending from the fuel pressure connection portion, and an outflow passage controlled by a valve unit 21 extending toward the pressure relief pipe or the throttle 20. The plunger 17 is pressure-loaded in the closing direction via the pressure in the control chamber 14. When the valve unit 21 is operated, the pressure in the control chamber 14 can be reduced. As a result, the pressure in the nozzle chamber 13 acting on the nozzle needle 11 in the opening direction is pushed by the pressure acting on the nozzle needle 11 in the closing direction. Over pressure. The valve seal surface 12 is lifted from the valve seat surface, and fuel is injected. In this case, the process of releasing the pressure in the control chamber 14 and thus the stroke control of the nozzle needle 11 can be influenced through the dimension setting of the first throttle 19 and the second throttle 20. The end of injection is introduced by a new operation (closing) of the valve unit 21. Since this operation shuts off the control chamber 14 from the leak line 22 again, a pressure capable of moving the nozzle needle 11 in the closing direction is formed in the control chamber 14 again.
[0012]
Furthermore, the injector 2 is connected via a check valve 23 and a throttle 24 to a central pressure accumulator 25 provided for all of the injectors. This accumulator 25 is filled via a throttle 24 during injection. The fuel escape amount generated when the fuel escapes from the injection pressure to the rail pressure in the injector region is supplied to the pressure accumulator 25 through the throttle 24.
[0013]
The accumulator 25 can supply fuel to the injector 2 independently of the pump element 1. Injection, flexible multistage injection, and injection progress formation are always possible. By changing the control time of the valve unit 21 and the control valve 8, the course of the injection pressure can be influenced in different ways. For example, boot-type injection is made possible by first injecting fuel with rail pressure at the boot stage. Thereafter, the pressure increase in the pump chamber 9 is controlled during the injection, and the pressure increase and the second injection stage with a high pressure are performed. The square injection course is formed by first increasing the pressure, and after this pressure increase, the injector 2 is controlled in relation to the injection.
[0014]
Furthermore, the injection pressure can be adapted to the engine requirements. This can be done in different ways. At the time of injection, the injector remains closed for some time after the start of pressure increase. This dams up high pressure. Thereafter, injection is performed under this pressure. In this case, however, boot-type injection is no longer possible. Rail pressure can be increased. This creates a higher base pressure. This moves the entire injection to a higher pressure level. In this case, the possibility of forming one injection course, for example, boot-type injection, is maintained.
[0015]
If the filling amount for filling the pressure accumulator 25 via the throttle 24 is not sufficient, a local pressure accumulator provided in the injector 2 or increased to increase the relief control amount (Absteermenge). Injector / duct volume may be used. A separate high-pressure pump 26 (see FIG. 2) may be provided in the fuel injection device 27.
[0016]
As shown in FIGS. 3 to 6, for example, instead of the throttle 24 (see FIG. 1) used in the fuel injection device 3, a combined filling valve / check valve can be formed in the fuel injection valve. .
[0017]
In the first structure of this configuration, FIG. 3 shows a fuel injection device 28 that includes a pump element 29, a control valve 30, and an injector 31, as compared with the fuel injection device 3. The injector 31 is connected to a pressure accumulator 33 via a combined filling / check valve 32. Fill valve / check valve 32 adjusts the connection from injector 31 to accumulator 33. When the pump element 29 is not working, the filling valve / check valve 32 is in the first switching position. The flow connection from the pump element 29 to the injector 31 is interrupted, and the accumulator 33 supplies fuel of a prescribed pressure to the injector 31.
[0018]
When the pump element 29 is pumped, the filling valve / check valve 32 is in the second switching position. The flow connection from the accumulator 33 to the injector 31 is interrupted, and the flow connection from the pump element 29 to the injector 31 is released.
[0019]
The fill / check valve 32 has a ball seat 34 for the check valve. The ball seat 34 is opened when the pump is pumped. Further, a spool seal portion for connection to the pressure accumulator 33 is provided. The spool seal portion is closed when the ball seat 34 is opened.
[0020]
FIG. 4 shows another configuration of the combined fill / check valve 35 of the fuel injector 36. Here, the check valve is formed as a conical seat 37. When the valve piston is opened, the flat seat 38 is closed, so that the connection to the pressure accumulator is interrupted.
[0021]
According to FIG. 5, the filling valve / check valve 39 of the fuel injection device 40 is formed with a common valve ball 41 with respect to the filling valve / check valve 39. When the valve ball 41 is opened, the valve seat 42 is opened and the valve seat 43 is closed.
[0022]
In order to influence the pressure increase after the pump element pumping is completed, a throttle 44 of the fuel injection device 45 is provided (see FIG. 6). Slow depressurization occurs after the pump element pumping is completed. During this decompression, post-injection with high pressure can be realized. This post injection is located outside the cam pumping range. Thereby, a pressure peak between the main injection and the post injection can be avoided. This pressure peak occurs when the nozzle needle is hydraulically controlled during pump element pumping and moved from the open position to the closed position. The check valve 46 serves to supply fuel from the accumulator to the injector without being throttled. The check valve 46, which can be placed anywhere between the pump element and the injector, can also be placed directly between the accumulator and the filling / check valve 39. By changing the control time of the valve unit 47 and the control valve 48, the injection process can be influenced.
[Brief description of the drawings]
FIG. 1 is a view showing a first fuel injection device.
FIG. 2 shows a second fuel injection device with an additional high pressure pump.
FIG. 3 shows a third fuel injector with a combined fill valve / check valve.
FIG. 4 shows a fourth fuel injector with another combined fill / check valve.
FIG. 5 shows a fifth fuel injector with another combined fill / check valve.
FIG. 6 shows a sixth fuel injector with another combined fill / check valve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Pump element, 2 Injector, 3 Fuel injection apparatus, 4 Low pressure pump, 5 Fuel, 6 Stock tank, 7 Pressure feed line, 8 Control valve, 9 Pump chamber, 10 Check valve, 11 Nozzle needle, 12 Valve seal surface, 13 nozzle chamber, 14 control chamber, 15 pressure line, 16 compression spring, 17 plunger, 18 end face, 19 throttling, 20 throttling, 21 valve unit, 22 leakage pipe, 23 check valve, 24 throttling, 25 accumulator, 26 High Pressure Pump, 27 Fuel Injection Device, 28 Fuel Injection Device, 29 Pump Element, 30 Control Valve, 31 Injector, 32 Filling Valve / Check Valve, 33 Pressure Accumulator, 34 Ball Seat, 35 Filling Valve / Check Valve, 36 Fuel injector, 37 conical seat, 38 flat seat, 39 filling valve / check valve, 40 fuel injector, 41 valve ball, 42 valve seat, 43 valve seat 44 diaphragm, 45 a fuel injector, 46 a check valve, 47 valve unit, 48 control valve

Claims (7)

In a fuel injection device (3; 27) of an internal combustion engine, at least one local pump arranged corresponding to each injector (2) of a pump / nozzle unit or pump / line / nozzle system for compressing fuel An element (1) and a central pressure accumulator (25) connected to the injector (2) are provided, and the pump element (1) is connected to the injector (2) separately from the accumulator (25). is connected to the pressure line (15) leading, connecting line of the pressure accumulator (25) to said pressure line (15), a check valve (23), with respect to the check valve (23) And a throttle (24) connected in parallel.   The pump element (1) is connected to the control chamber (14) and the nozzle chamber (13) of the injector (2) via the pressure line (15), and the pressure line (15) is connected to the pressure accumulator (15). 25) The fuel injection device according to claim 1, connected to 25). Accumulator (25) is adapted to be filled with fuel compressed by the pump element (1), a fuel injection device according to claim 1 or 2 wherein.   The fuel injection device according to any one of claims 1 to 3, wherein a filling valve (32; 35; 39) for connecting the injector to the pressure accumulator and the pump element is provided.   5. The fuel injection device according to claim 4, wherein the filling valve (32; 35; 39) interrupts the connection between the injector and the accumulator during pumping of the pump element (1).   6. The fuel injection device according to claim 4 or 5, wherein the filling valve is formed by a combined filling valve / check valve (32; 35; 39).   A combined filling / check valve (32; 35; 39) connects the injector to the accumulator (25) in the first switching position, and the pump element (1) in the second switching position. The fuel injection device according to claim 6, wherein the fuel injection device is connected to the fuel injection device.

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