JP2006523793A - Fuel injection device with reduced pressure vibration in return rail - Google Patents

Abstract

A fuel injection device (1) for an internal combustion engine, the fuel injection device comprising at least one injector for injecting fuel into the combustion chamber of the engine, said injector being a high-pressure connection (10 ), Fuel under high pressure is supplied to the injector through the high-pressure connection (10), and a control valve (64) for controlling the injection of the injector An injector low pressure connection (12) is provided for deriving a control flow rate generated during injection control, and is provided with a leak line (11). The leak line (11) maintains pressure. A valve (15) is connected to the fuel return line (17), and the pressure holding valve (15) opens toward the fuel return line when a predetermined pressure is exceeded. For models with pressure A throttling device (20) is provided beside the valve (15), and the throttling device (20) is arranged so that the reflection of the pressure wave coming from the injector as a negative pressure wave is weakened when the pressure holding valve is open. Is formed. Negative pressure waves traveling from the pressure holding valve toward the injector leakage connection are reduced or suppressed. This can reduce the risk of breakage due to cavitation.

Description

  The invention starts from a fuel injection device of the type described in the superordinate concept of claim 1. The pressure holding valve can be adjusted to a relative pressure of 0.5 bar (ie relative to the ambient pressure of the fuel injector) and is exclusively connected to the leak-collection line (= return rail) This helps to prevent idling of at least one injector with a line and / or a leak-collection line. In such fuel injectors, the injector can include an electrically operated solenoid valve that controls the injector injection process by a change in pressure in the control chamber. In another fuel injector, the pressure holding valve can be adjusted to a relative pressure of, for example, 30 bar. In such a fuel injection device, a hydraulic coupler is generally provided in an injector, and the coupler is operated by a piezo actuator. Based on its functionality, the hydraulic coupler is surrounded by the aforementioned fuel under a pressure of about 30 bar, so that the hydraulic coupler can always function. In both described fuel injectors, the fuel return rail leads directly to the fuel tank of the internal combustion engine. In the latter group of the fuel injectors, the line connected to the end of the pressure holding valve opposite to the injector is connected to the first pump for raising the fuel from the fuel tank to a pressure of about 5 bar, for example. It is connected to a connecting line between the pump inlet and the pump. The present invention can be used for the fuel injection apparatus described above.

  With accumulators it is known to connect the valve to a high-pressure line towards the injector (EP 0780869, Fig. 13B), the valve being spherical and movable preloaded (preloaded) by a spring. A valve member is provided. The valve member opens when the fuel flows toward the injector and closes almost completely when the fuel does not flow. Complete closure is prevented by the fact that a circular outflow in cross-section is radially expanded by a longitudinally extending groove downstream of the valve seat. The groove is not intended to be covered by a movable valve part. Thus, in the closed state of the valve, the valve forms a throttle, which is suitable for attenuating pressure waves traveling from the injector to the high-pressure line, as recognized from a professional point of view, and thus Further adjustment of pressure fluctuations in the channel can be avoided.

Advantages of the Invention According to the advantages of the fuel injection device according to claim 1 of the present invention, known disadvantages are reduced or eliminated. The disadvantage is due to the following process. When the injector starts the injection process, the control flow rate flows into the leak line with the above-described control valve operating, and the pressure holding valve opens during the continuous operation and is substantially the same as the control flow rate. Flow out through the pressure holding valve. The inflow of the described control flow rate causes a flow collision into the leak line and creates a pressure wave toward the pressure holding valve. The pressure wave is then reflected as a negative pressure wave in the open state of the pressure holding valve (the reflection of the pressure wave at the pressure node relative to the open line end or pressure belly is performed as a negative pressure wave). Such negative pressure waves cause cavitation, which causes damage to the injector in the long run, thereby shortening the useful life of the injector. Cavitation occurs when below the vapor pressure of the fuel. It is believed that the greater the risk of cavitation, the lower the normal pressure in the leak collecting line, and thus the standard pressure in the individual leak line of the injector. Cavitation occurs when a negative pressure wave collides with the control valve when the control valve is shut off and the pressure downstream of the control valve is below the fuel vapor pressure due to a sudden interruption of flow from the control valve. The risk of this can be particularly high. According to the present invention, the negative pressure wave propagating from the pressure holding valve to the injector leakage connection is reduced or eliminated.

  The arrangement of the throttle next to the pressure holding valve is understood as follows. A not-so-large interval is desired, so that the throttle action is not adversely affected by the negative pressure wave with respect to negative pressure, and the leakage flow rate of several, preferably all injectors connected to a single pressure holding valve is reduced. Desired to flow through the described aperture. In an embodiment of the invention, the throttle is arranged before and after the pressure holding valve as viewed from the injector or is structurally integrated with the valve element of the pressure holding valve.

  In the described embodiment according to the invention, a slider is provided, which is advantageously formed as a complete cylinder and resists the spring force in a notch, in particular a hole, that fits the slider. If it is guided in a slidable manner and fuel outflow from the leak collecting line through the pressure holding valve is desired, it must be slid against the spring force. In one embodiment, at least one groove is formed in the cylinder wall, the groove being closed at the rear end by the hole wall and open at the front end when the pressure holding valve is stationary. In the state where the cylinder is slid sufficiently, the rear end protrudes from the hole region, so that the groove simultaneously forms a throttle and extends continuously as a whole. In a further embodiment, instead of a complete cylinder without a groove in the wall, a groove is formed in the wall of the hole, which is preferably in the stationary state of the valve, at the front end. Is closed by the cylinder surface of the cylinder, whereas the rear end is always open, and when the cylinder is fully slid, the front end of the groove is opened and the throttle is similarly Make it. In another combined embodiment, at least one of the aforementioned grooves is formed in both the cylinder wall and the hole wall. Of course, instead of a single groove, a plurality of grooves may be provided.

  In all the described embodiments, advantageously, the restriction acts on a particular fuel injection device, in principle, by exchanging a single member or when selecting an appropriate member during valve assembly, and each It can be adapted to the relationships generally known for internal combustion engines. In other words, the diaphragm wave resistance of the diaphragm, or the diaphragm wave resistance combined when there are multiple diaphragms (as described, parallel connection of the diaphragms or series connection of the diaphragms can be implemented) is precisely adapted. Is desirable.

  Further advantages and advantageous embodiments of the invention can be taken from the description of the examples, the drawings and the claims.

DESCRIPTION OF THE EMBODIMENTS Next, embodiments of the injection device of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a fuel injection device 1 provided, for example, for diesel fuel. The fuel injection device 1 includes several (for example, six) injectors 3 known in the art. During operation, fuel is injected through the injection opening 5 (see FIG. 6) into the correspondingly arranged combustion chambers of the diesel engine. The accumulator 7 is filled with fuel under high pressure (for example 1600 bar) via a line 8. The fuel is supplied to the high-pressure connection 10 of each injector 3 through each high-pressure line 9. The leakage flow rate and control flow rate of the injector, which are generated when the control valve that controls the injection process of the injector, is supplied from the low pressure connection 12 to the leakage collecting pipeline 13 (leakage rail) via each leakage pipeline 11. For example, the injector 3 is an injector that is controlled by an electrically operated solenoid valve that, when activated, lowers the pressure in the control chamber in a known manner, thereby starting the injection process. When the control valve is opened, fuel flows out of the control chamber and flows into the leak line 11. All the leak pipes of the illustrated injector are connected to the leak collecting pipe 13. One end of the leakage collecting line 13 is closed, and the other end (right side in FIG. 1) is connected to a reflux line 17 for fuel via a pressure holding valve 15. The pipe line 17 leads to the fuel tank. From the fuel tank, the fuel is sucked out in a known manner and finally brought to a high pressure by one or more pumps, and the fuel is supplied to the pressure vessel 7 under high pressure. The pressure holding valve 15 opens, for example, when the pressure in the leakage collecting pipe 13 is a positive pressure of about 0.5 bar with respect to the pressure in the reflux pipe 17. This 0.5 bar pressure is to prevent the leak line from becoming empty. Such arrangements as described are known. According to a new aspect of the arrangement shown in FIG. 1 with respect to the prior art, a throttling which is located beside the pressure holding valve 15 and serves to substantially prevent undesirable pressure wave reflections in the leak collecting line 13. A device 20 is provided.

  FIG. 2 shows a combination of a throttling device and a pressure holding valve as the constituent unit 25. The diaphragm device is formed by a single diaphragm 27, and the diaphragm 27 is formed as a hole by being drilled in a block 28 that can be appropriately selected at the time of assembly. The block 28 is disposed on the upstream side of the pressure holding valve as viewed in the flow direction of FIG. 1, that is, from the left side to the right side. In the arrangement structure of FIG. 1, the constituent unit 25 is assembled in a compact manner by screw connection.

  The combination 30 of the pressure maintaining valve and the throttle device shown in FIG. 3 is different from the combination of FIG. 2 in that the throttle device is disposed on the downstream side of the actual pressure maintaining valve.

  The arrangement shown in FIGS. 2 and 3 is realized in the embodiment of the invention in the exact same manner of operation by means of a suitable connection, for example by screwing two separate parts, in essence. This is realized simply by combining a component having a throttle hole and a conventional pressure holding valve.

  In the arrangement structure shown in FIG. 4, the throttle and the pressure holding valve form a unit that cannot be separated from each other. The valve arrangement structure 40 opens when a counter pressure acts on the left side of FIG. 4 against the pressure acting on the right side of FIG. The valve arrangement structure is substantially formed as a slide valve. The slider (complete cylindrical body) 41 is guided by a guide surface in the longitudinal direction of the substantially cylindrical valve arrangement structure 40. Therefore, the slider 41 can slide against the force of the compression coil spring 44 in the hole 42 of the central member 43. In the stationary position shown in FIG. 4, the slider 41 is in contact with the stopper device 45, and the stopper device 45 is formed as a perforated plate and does not hinder the fuel flow as a whole. A vertical groove 47 is formed in the wall portion of the hole of the central member 43, and the vertical groove 47 is open toward the right side, but ends before the end of the slider 41 toward the left side. In the illustrated position of the slider 41, the fuel does not flow into the groove 47 forming the throttle simultaneously from the left side. When the pressure acting on the left side in FIG. 4 has such a magnitude that the slider 41 slides to the right side by a sufficient distance, the groove 47 is finally opened at the front end, and the fuel flows into the groove 47. At this point, the valve arrangement is open because it can flow through. Functionally, the throttle can also be provided downstream of the valve opening.

  Unlike the embodiment shown in FIG. 4, the throttle-valve combination 50 shown in FIG. 5 has a groove 51 forming a throttle arranged on the cylindrical outer peripheral surface of the slider 52. On the other hand, the hole of the central member 54 is formed flat. Here, the groove 51 is always open on the left side, and the right end is opened for the flow of the groove when the slider 54 slides to the right side with a sufficient distance. Functionally, the throttle can also be provided upstream of the valve opening.

  In the embodiment not shown, the groove 47 shown in FIG. 4 and the groove 51 shown in FIG. 5 are provided. In this case, both grooves should not overlap when the valve arrangement is closed. Such an embodiment of the valve arrangement may provide additional motion and no cylinder sliding is required to open the valve, but instead rotation is achieved, or in another embodiment A slight slide is realized for a large degree of rotation. This means that the slide movement itself does not cause the flow of the throttle to be released, but rather a pivot connected to the slide, in which case the throttle moves the groove to the overlapping position. The movement by the linear slide is the simplest.

  The function of the arrangement structure will be described with reference to FIGS. Assuming that a pressure is formed in the leakage collecting pipe 13, the pressure holding valve 15 is opened at a pressure slightly higher than this pressure. When the injection is performed by one of the injectors, as described above, this opens a control valve that realizes the flow of a certain amount of fuel (control amount) from the control chamber of the injector. On the other hand, in a general injector, since the control chamber is always connected to the connection portion of the injector connected to the high-pressure line through the restriction, the outflow occurs. On the other hand, when the valve is opened, the fuel is additionally pushed out of the control chamber by the force acting on the valve piston that opens and closes the injection opening at the lower end, so that the outflow occurs. Such opening of the control valve causes a rapid pressure increase in the leak collecting pipe. Such a pressure rise opens the pressure holding valve, the connection on the right side of the pressure holding valve in FIGS. 1 and 2 forms an open pipe end, the pipe end coming from the injector The positive pressure wave is reflected as a negative pressure wave. This reflection is reduced by the diaphragm device and suppressed with a precisely adapted diaphragm dimension setting. In order to suppress reflections in this way to the maximum, the following dimensions are advantageous for the diaphragm:

  In the present invention, the antireflection effect of the throttle occurs when the pressure holding valve is open (fuel guide). In the shut-off state of the pressure holding valve, fuel does not flow through the throttle.

In this embodiment, the leak collecting conduit has a wave resistance (Wellenwiderstand) of about 0.8 bar · ms / mm ³ . The flow coefficient of the throttle has a value of 660 cm ³ / min with a differential pressure of 100 bar.

The above values are based on a 3 mm ² round pipe cross section under the use of diesel fuel. Thus, the single stop provided as a round hole provided in FIG. 2 has a diameter of about 0.4 mm. The length of the diaphragm, for example 1 mm, has been selected in consideration of the actual situation, and the length itself is not very important with respect to the function as a diaphragm.

  As shown in FIG. 6, the injector 3 includes a process-controlled plunger valve 60, and the movement of the plunger valve 60 is controlled by the pressure in the control chamber 62. When this pressure is reduced by opening the control valve 64 (for example, electromagnetic type), the plunger valve 60 is opened and fuel is injected into the combustion chamber of the cylinder of the internal combustion engine via the injection opening 5.

  In the described embodiment, fuel under pressure suitable for injection is supplied from the accumulator to the injector. The present invention can also be used in another fuel injection device in which the control flow rate in the leak line causes a pressure collision during injection control. For example, a device in which a pump-nozzle-unit (Unit Pump Injector) unique to each cylinder is arranged correspondingly is known. The pump of this unit can be supplied with a fuel pressure that is not sufficient for injection, but can be increased to the required injection pressure by the pump. Since the start and / or end of the desired injection does not always coincide with the course of the pumping process, the injector or pump is provided with a control valve leading to the leak passage, and the control valve The pump is able to deliver fuel to the injection opening. When the control valve is opened, the fuel conveyed from the pump is led to the leak line. Again, a pressure collision occurs in the leak line when the control valve is open, which is also the case if the control valve is already open at the start of the pumping process.

It is the schematic which shows the fuel-injection apparatus by this invention provided with the several injector and the pressure holding valve provided with the throttle. FIG. 2 is an enlarged longitudinal sectional view showing a combination of a pressure holding valve and a throttle provided in the arrangement structure shown in FIG. 1. It is a figure which shows the combination of the pressure holding valve and throttle | throttle provided in another Example of this invention different from the Example of FIG. In another fuel injection device of the present invention, an arrangement structure provided in place of the valve arrangement structure in FIGS. 2 and 3 in which a throttle is provided in a wall portion of a hole for slidably housing a complete cylindrical body. FIG. FIG. 5 is a view showing a pressure holding valve different from the embodiment of FIG. 4 in which a throttle is formed as a groove in a wall portion of a complete cylinder formed in another embodiment of the present invention. It is a figure which shows the main components of the injector shown in FIG. 1 of the fuel-injection apparatus provided with the electromagnetically operated control valve.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Fuel injection device, 3 Injector, 5 Injection opening, 7 Accumulator, 8 Pipe line, 9 High pressure line, 10 High pressure connection part, 11 Leakage line, 12 Low pressure connection part, 13 Leakage collecting line, 15 Pressure holding valve, 17 reflux line, 20 throttle device, 25 component unit, 27 throttle, 28 block, 30 combination, 40 valve arrangement structure, 41 slider, 42 hole, 43 central member, 44 compression coil spring, 45 stopper device, 47 long hole, 50 combinations, 51 grooves, 52 sliders, 54 center members

Claims (5)

A fuel injection device (1) for an internal combustion engine comprising:
The fuel injector is
At least one injector for injecting fuel into the combustion chamber of the engine, the injector comprising a high pressure connection (10), via the high pressure connection (10), Of fuel is to be supplied,
A control valve (64) for controlling the injection of the injector is provided, and a low pressure connection part (12) of the injector is provided for deriving a control flow rate generated during the control of the injection,
A leak line (11) is provided, and the leak line (11) is connected to the fuel return line (17) via a pressure holding valve (15), and the pressure holding valve (15) Is of a type that opens toward the fuel return line (17) when a predetermined pressure is exceeded,
A throttling device (20, 27, 47, 51) is provided beside the pressure holding valve (15), and the reflection of the pressure wave coming from the injector as a negative pressure wave is weakened when the pressure holding valve is opened. Thus, the throttle device (20, 27, 47, 51) is formed.   2. The fuel injection device according to claim 1, wherein the throttle device is arranged upstream of the pressure holding valve as viewed in a flow direction from the injector toward the fuel return pipe.   2. The fuel injection device according to claim 1, wherein the throttle device is disposed on the downstream side of the pressure holding valve as viewed in the flow direction from the injector toward the fuel return pipe.   The pressure holding valve is formed as a slide valve having sliders (41, 52) that can slide against a preload by positive pressure to be derived, and the sliders (41, 52) are formed in the guide. Guided, at least one groove (47, 51) is provided in at least one of the slider and slider guide components, and a passage for fuel is provided at the defined open slider position. In contrast, in the closed position of the slider, the end of the groove is closed by the non-grooved portion (slider guide, slider) of the slider valve. The fuel injection valve according to claim 1.   The fuel injection device according to any one of claims 1 to 4, wherein a passage forming a part of the throttle device is provided in a separate member inserted when the valve or the throttle device is assembled.

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