KR20030017632A - Fuel injection device - Google Patents

Abstract

A fuel injector for an engine is proposed that includes a fuel injector and a pressure intensifier that can be supplied with fuel from a high pressure fuel source. In this arrangement, the shutoff pistons 13 and 113 of the injector protrude into the shutoff pressure chambers 12 and 112 so that fuel pressure can be applied to the shutoff pistons to obtain a force acting on the shutoff pistons in the shutoff direction, The return chambers 27 and 127 and the pressure chambers 12 and 112 of the augmentation device are formed through the common shutoff pressure return chambers 12, 27, 41; 112, 127 and 141, and all parts of the shutoff pressure return chamber. The sections 12, 27; 112, 127 are permanently connected to each other (41; 141) for the exchange of fuel so that a relatively low nozzle pressure can be achieved despite the low pressure build up through the pressure intensifier.

Description

FUEL INJECTION DEVICE}

German patent 43 11 627 is already known with a fuel injector in which an integral pressure boosting piston can raise the fuel injection pressure above the value provided by the common rail system through the filling or discharging of the return chamber.

U.S. Patent No. 6 113 000 discloses an injection system comprising a high pressure reservoir and an intermediate pressure reservoir, which may optionally be fueled.

German Patent No. 199 10 970 discloses a fuel injector having a pressure intensifier and a separate control valve respectively arranged in the injector and the pressure intensifier.

German patent 43 11 627 discloses an injection device which requires an additional four-way sliding valve in addition to the control valve.

The present invention relates to a fuel injection device according to the general type of the independent claims.

Embodiments of the present invention are shown in the drawings and described in detail in the following description.

1 shows a fuel injection device.

2 shows two graphs.

3 shows a second fuel injection device.

4 shows a piezoelectric valve.

5 shows another fuel injection device.

6 is a graph showing the pressure relationship for various opening and closing speeds.

Fig. 7 shows the open / close state when using a 3/3 way valve.

8 shows another fuel injection device.

9 shows another graph.

10 illustrates another alternative embodiment.

The fuel injection device according to the invention comprising the features disclosed in the independent claims is a pressure controlled device, for example in the form of a pressure intensifier having a low pressure buildup ratio of approximately 1: 1.5 to 1: 3. Compared with the fuel injection device, a relatively low injection opening pressure is realized. Low pressure build-up ratios work advantageously, because this reduces the installation space of the injector or the space of the pressure intensifier, the small volume speeds up the decompression process or the pressure building process, and the relief loss. ), The volume flow in the system and the feed rate of the fuel pump are kept to a minimum, and the range of 1,400 bar or less already available in current production systems, even at high injection pressures where the required pressure level in the pump and rail exceeds 2,000 bar. Because it can be maintained. The volumetric flow in the low pressure system is also kept small. The device according to the invention makes it possible to take advantage of this advantage even when a small amount of fuel must be supplied accurately. This is done by adjusting the pressure in the shutoff pressure chamber at the moment of injection of the fuel. This achieves a low pressure buildup ratio, in which case the open pressure does not have an excessive value such that it is impossible to accurately supply a small amount of fuel. In addition, a high breaking pressure is ensured, which results in rapid needle breaking even under high injection pressures. In this connection there is an advantage that at least the fuel pressure of the high pressure fuel source can be provided continuously (regardless of the pressure vibrations occurring in the system) in the high pressure chamber. Preferably, this ensures that a high injection pressure is already provided at the injection port at the time of initial opening of the injector, and that the fuel can be supplied accurately to the combustion chamber within a short period of time. The structure of the pressure intensifier can also be designed to be simple and robust, since in addition to the low pressure system only one other fuel system with higher fuel pressure is mounted.

The measures specified in the dependent claims allow other desirable forms and improvements of the fuel injection device described in the independent claims.

When the pressure chamber function of the injector is fulfilled by the high pressure chamber of the pressure intensifier, a smaller amount of dead volume is formed after the pressure intensifier, which must be compressed at high pressure. In addition, since a shortened flow path is formed between the blocking pressure chamber and the pressure chamber, in some cases, the amplitude of vibrations that may occur between the blocking pressure chamber and the pressure chamber is reduced. Therefore, a reliable driving method capable of quick opening and closing as a whole is provided.

In another preferred embodiment in which the conduit connection with the chamber and / or the shutoff pressure chamber of the pressure build-up device is arranged in the opposite direction, fuel circulation can be continued in these chambers during operation. Continuous fuel circulation is ensured in these chambers, especially at low injection volumes. This suppresses local overheating of the fuel in these chambers due to continuous compression and relaxation, thus preventing component damage. In addition, the accumulation of contaminants in such chambers is prevented.

Other advantages are indicated by the features specified in the other dependent claims and the description below.

In Fig. 1 a fuel injector is shown, in which a fuel injector 1 comprising a pressure intensifier 7 is connected with a high pressure fuel source 2 via a fuel line 4 equipped with a throttle 3. . The high pressure fuel source comprises a plurality of members, such as fuel tanks, pumps and conventional common rail systems, not shown in detail here, the pumps transporting fuel from the tank to the high pressure rails up to 1600 bar on the high pressure rails. Provide pressure. Here, for each cylinder of the engine, an injector fueled from the high pressure rail is provided separately. The injector 1 illustrated by way of example in FIG. 1 comprises a fuel injection valve 6 with a shutoff piston 13, which via its inlet 9 has a combustion chamber 5 of the engine cylinder 5. Flows into). The pressure shoulder 16 of the blocking piston 13 is surrounded by a pressure chamber 17 which is connected to the high pressure chamber 28 of the pressure intensifier 7 via the high pressure tube 40. The shutoff piston 13 protrudes into the shutoff pressure chamber 12 at its opposite end from the combustion chamber, ie the guiding section 14, which is connected to the return chamber 27 of the pressure intensifier via a conduit 41. It may be connected to the high pressure fuel source 2 via fuel pipes 42 and 45 connected to the return chamber 27 and the 3/2 way valve 8. The valve 8 connects the conduit 42 with the conduit 45 in its first position, while the low pressure tube 44, which is guided to a low pressure system not shown in detail here, has its own connection to the valve 8. It is sealed at the end. In the second position of the valve, the conduit 42, which is guided to the return chamber 27 or the shutoff pressure chamber 12, is connected to the low pressure pipe 44, while the opposite end of the high pressure fuel source 2 of the conduit 45 is connected. The end connected to the valve is closed. The shutoff piston is disposed in the shutoff pressure chamber and is supported in a bufferable form via an adjustment spring 11 fixed between the housing 10 of the injection valve 6 and the shutoff piston 13, which adjustment spring The needle section 15 is pressed against the injection hole 9. The pressure intensifier 7 comprises a pressure intensifying piston 21 supported by a spring, which separates the high pressure chamber 28, which is connected to the high pressure tube 40, from the chamber 26, and this chamber. Is connected to the high pressure fuel source 2 via a conduit 4. The spring 25 used to support the piston is arranged in the return chamber 27 of the pressure intensifier. The piston 21 is designed in the form of a two part and comprises a first partial piston 22 and a second partial piston 23 of smaller diameter. The housing 20 of the pressure intensifier is divided into two sections via a partial piston 22 arranged in a movable form within the housing, which are separated from each other in a watertight manner until a leakage loss occurs. The first section is the chamber 26 connected to the high pressure fuel source, and the second section includes a stepped tapper. The second section includes a second partial piston 23, which tightly seals the reduction portion from the remaining chamber of the second section forming the return chamber 27. The section limited by the partial piston 23 in the reduction part forms a high pressure chamber 28 of the pressure intensifier, which is connected to the pressure chamber 17 of the injection valve, which comprises a check valve 29 and a fuel pipe ( 43 is connected to a conduit 4 which is guided to the high pressure fuel source 2. Both side pistons are separate components but may also be designed in combination with each other. The second partial piston 23 has a spring holder 24 which is larger than its diameter at the end in the direction of its first partial piston, so that the adjustment spring 25 fixed against the housing 20 has a second portion. Compress the piston with the first partial piston.

The pressure of the high pressure fuel source 2 is guided through the conduit 4 to the injector. In the second position of the valve 8 the injection valve is not driven and no injection is made. In this case the rail pressure in chamber 26 is passed through conduits 42 and valves 8 in return chamber 27, through conduits 41 and valves in shutoff pressure chamber 12, and in the high pressure chamber ( 28 and through conduit 43 in pressure chamber 17 to valve 8. This applies rail pressure to all pressure chambers of the pressure intensifier and adjusts the pressure of the pressure intensifier piston. That is, the pressure intensifier is deactivated and no pressure build-up occurs. The pressure boosting piston is in this state returned to its initial position via the adjustment spring. At this time, the high pressure chamber 28 is filled with fuel through the check valve 29. Hydraulic shutoff force is applied to the shutoff piston via the rail pressure in the shutoff pressure chamber 12. In addition, the adjustment spring 11 provides a spring force for blocking. Thus, the injection valve is not inadvertently opened and rail pressure is continuously provided in the pressure chamber 17. The supply of fuel to the combustion chamber 5 takes place via activation of the 3/2 way valve 8. That is, by switching the valve to its second position. This allows the return chamber 27 to be disconnected from the high pressure fuel source and connected to the reflux tube 44, and the pressure in the return chamber is reduced. This activates the pressure intensifier and the two-part piston presses the fuel in the high pressure chamber 28, thereby increasing the pressure acting in the open direction in the pressure chamber 17 connected to the high pressure chamber. At the same time, when the valve is switched to its second position, the fuel pressure in the shutoff pressure chamber 12 is lowered, so that the pressure applied to the shutoff piston in the shutoff direction is reduced. In other words, the value of the fuel pressure required for opening the injection valve in the pressure chamber 17 is lowered at the moment when the injection valve should be opened, and the shutoff piston as in the situation where the pressure in the shutoff pressure chamber 12 is kept constant. The needle section 15 of the needle section 15 previously opens the injection hole 9 in a state where the pressure in the pressure chamber 17 is low. In the state where the return chamber 27 is depressurized, the pressure intensifier remains activated and presses fuel in the high pressure chamber 28. The compressed fuel is delivered to the injection port and injected into the combustion chamber. To end the injection process the valve 8 is switched back to its first position. The valve separates the return chamber 27 and the pressure chamber 17 from the reflux tube 44 and connects them back to the supply pressure of the high pressure fuel source or to the high pressure rail of the common rail system. This reduces the pressure in the high pressure chamber to the rail pressure, and now the rail pressure is again applied in the pressure chamber 17, so that the blocking piston is controlled by hydraulic pressure and shut off by the force of the spring 11, thereby terminating the injection process. do. After the pressure adjustment of the system is made, the pressure boosting piston is returned to its initial position via an adjustment spring, where the high pressure chamber 28 is filled through the conduit 43 and the check valve 29 of the high pressure fuel supply.

In an alternative embodiment, the shutoff pressure chamber may be connected directly via the fuel pipe, not indirectly with the valve 8 via the return chamber 27 of the pressure intensifier. In other words, instead of a conduit 41 connected to the return chamber, a conduit is provided which is guided directly to the valve 8 in the blocking pressure chamber.

2 shows the change in fuel pressure p with the stroke h and time t of the shutoff piston during the injection cycle. The pressure of the high pressure fuel source is represented by PRail, and the pressure in the pressure chamber 12 at the time when the injection valve is opened is represented by Poe. The maximum stroke distance of the valve is expressed in hmax and the maximum fuel pressure achievable in the high pressure chamber 28 is expressed in Pmax. Curve 310 represents the temporal change of fuel pressure in the high pressure chamber or pressure chamber and curve 320 represents the pressure change in the shutoff pressure chamber.

When the valve is switched from the first position to the second position at time t _o , the pressure 310 in the high pressure chamber and the pressure chamber is increased from the pressure of the high pressure fuel source to the maximum pressure Pmax that can be reached. Is determined by the ratio of the cross sectional area of the two partial pistons and the pressure of the high pressure fuel source. At the same time the pressure 320 in the shutoff pressure chamber drops to a low pressure value (fuel pressure formed in a low pressure system not shown in detail here). The injection valve opens as soon as the pressure in the pressure chamber 17 acting in the opening direction exceeds the sum of the pressure in the blocking pressure chamber 12 acting in the blocking direction and the force of the regulating spring 11. That is, the stroke value h is converted from zero to the maximum value hmax. This situation occurs when the fuel pressure has a value Poe in the pressure chamber (see pressure change 310). At a later point in time t ₁ , the valve 8 switches back to its first position, whereby the fuel pressures in the pressure chamber and the shutoff pressure chamber are mutually opposite until they reach the value of the high pressure fuel source again. Very close. The valve is shut off again. That is, the stroke value h is converted back to zero.

3 shows a fuel injection device, wherein the same components as those in FIG. 1 are denoted by the same reference numerals. Unlike FIG. 1, the check valve is connected to conduit 41 via conduit 70 rather than to a high pressure fuel source via conduit 43.

Unlike FIG. 1, when the valve 8 is switched from the first position to the second position, the high pressure chamber is not charged directly from the high pressure fuel source but from the return chamber 27 and / or the shutoff pressure chamber 12.

In other alternative embodiments the conduit 70 may be directly connected to the return chamber 27 or to the shut off pressure chamber 12 without being connected to the conduit 41.

The three-way valve 8 included in the embodiment according to FIGS. 1 and 3 can be designed as a magnetically driven valve as well as a piezoelectrically driven valve according to FIG. 4. In the case of the piezoelectric driven embodiment according to FIG. 4, the valve housing 50 is connected with three connecting tubes 42, 44, 45 as shown in FIGS. 1 and 3. In the valve housing there is a valve body 51 which is supported in a movable form, the hemispherical side of which is first valve seat via an adjustment spring 52 fixed between the valve body and the valve housing in the shown stationary state. Pressed against 53. The second valve seat 54 in connection with the conduit 45 is on the opposite side of the valve body formed with a flat surface. In the stationary state shown there is an intermediate chamber between the valve body and the second valve seat. The first valve seat 53 is connected to a conduit 55 to which the low pressure pipe 44 is connected at the opposite end of the valve body. The first power transmission piston 56 resides on the side of the hemispherical valve body that seals the conduit and projects from the conduit through a closed opening disposed on the side wall opposite the valve body of the conduit so that the movement of the power transmission piston outside the valve housing. Force can be applied onto the valve body. The extended end of the piston 56 is filled with clutch fluid and protrudes into the clutch chamber 58 schematically shown. On the opposite side of the clutch chamber the second power transmission piston 57 protrudes. The second power transmission piston is fixed to the electrically driveable piezoelectric actuator 59, which can change its length when a voltage is applied. The base member 60 fixed on the opposite side of the piezoelectric actuator maintains the same distance as the clutch chamber even when the electrical state of the piezoelectric actuator changes.

The illustrated state of the valve body corresponds to the first position of the 3/2 way valve. In this state, the valve body breaks the connection between the conduit and the chamber where the valve body is supported in a movable form, so that the conduit 42 can only exchange fuel through the conduit 45. The piezoelectric actuator 59 must be electrically driven when the valve is switched to its second position to supply fuel to the combustion chamber. In order to compensate for the change in length with the temperature of the piezoelectric actuator, and in the preferred embodiment, only the schematic representation of the force and distance between the clutch chamber 58 and the change in length with temperature, the piezoelectric actuator is provided with a power transmission piston (57). And the power transmission piston 56 through the clutch chamber 58. When the piezoelectric actuator is driven, the piezoelectric actuator is inflated and transmitted through the clutch chamber to transmit a force onto the valve body, which forces the valve body up from the first valve seat and presses onto the second valve seat. ) Is connected to the conduit 45 instead of the conduit 44.

As shown in FIGS. 1 and 3, the piezoelectric valve may be connected to conduit 4 via conduit 45. Alternatively, the valve may be connected directly to the chamber 26 instead of the conduit 4.

5 shows another embodiment in which a pressure enhancer integrated into the injector housing 100 is included. The same parts shown in Figs. 1 and 3 are denoted by the same reference numerals and will not be described again. In the injector housing, three parts which are relatively movable to each other, namely the pressure intensifying piston 121, the blocking piston 113 and the hollow valve piston 206, are supported by springs. The pressure intensifying piston 121 includes a first partial piston 122 and a second partial piston 123. The first partial piston 122 is guided watertightly in the axial direction by the injector housing until the leak loss state is reached. A stepped reduction part is formed on one side of the first partial piston, and an adjustment spring 125 of the pressure enhancer is disposed between the injector housing and the first partial piston. The adjustment spring 125 is fixed between the spring holder 124 disposed in the reduction portion and the restriction member 200 fixed to the injector housing, and the opposite side of the adjustment spring of the restriction member functions as a limit stop for the pressure enhancing piston. The reduction part of the first partial piston is prevented from colliding with the injector housing. The chamber 126 between the injector housing and the first partial piston in which the regulating spring 125 is arranged corresponds to the chamber 26 of FIG. 1, likewise connected to the high pressure fuel source 2 via the conduit 4. . The first partial piston 122 is converted to the second partial piston 123 of smaller diameter on the opposite side of the chamber 126, part of which is likewise guided by the injector housing, for this reason This is because the housing has a stepped reduction in the section of the second partial piston. The chamber between the second partial piston and the injector housing forms a return chamber 127 of the pressure intensifier, the pressure intensifier forming a blocking pressure chamber 112 through a bore 141 in the second partial piston. It is connected to the hollow inner chamber of the partial piston. The blocking piston 113 protrudes into the blocking pressure chamber. The opposite end of the blocking piston protrudes into the needle section 115 and blocks the injection port 9. Between the blocking piston section and the needle section protruding into the blocking pressure chamber there is a guide section 114 of the blocking piston which ensures that the blocking piston is guided axially along the injector housing. The guide section is larger in diameter than the needle section. The guide section has, for example, a flow path 205 in the form of a through bore, so that fuel is exchanged with each other in the chamber between the small diameter shut off piston section and the needle section and the injector housing connected to the guide section at the back of the needle section. Can be. Between the blocking piston section and the guide section 114 protruding into the blocking pressure chamber, an annular member 203 protruding into the cylinder symmetric groove 202 of the injector housing is attached around the blocking piston without being in contact with the housing. The annular member 203 functions to support the adjustment spring 111, which presses the blocking piston against the injection port. For this purpose the adjustment spring 111 is supported at the radial projection of the hollow valve cylinder 106 which is guided by the blocking piston and not in contact with the injector housing. The hollow valve piston has a pointed end running in the direction of the annular sealing edge, which end is pressed by the adjustment spring 111 to the front of the second partial piston, so that the hollow valve piston exists between the blocking piston and the injector housing. The high pressure chamber 128 formed by the rear surface may be sealed against the blocking pressure chamber 112, ie the hollow valve piston may function as the check valve 129 with the front of the second partial piston. The annular member 203 is formed with bores 204 that support the exchange of fuel between the high pressure chamber sections on both sides of the annular member. Between the end of the needle section toward the injection port and the annular member, the blocking piston has two sections having a diameter smaller than the diameter of the section projecting into the blocking pressure chamber. One of the sections is the main portion (waist portion) between the guide section and the annular member, and the other section is the section between the guide section and the end of the blocking piston facing the injection port.

In the embodiment according to FIG. 5, the nozzle chamber 17 and the high pressure chamber 28 of the embodiment according to FIG. 1 are combined to form the high pressure chamber 128. The function is similar to that of the structure according to FIG. 1. The check valve for filling the high pressure chamber 128 is formed through the check valve 129 described above. Similarly, fuel is supplied to the combustion chamber 5 through the activation of the 3 / 2-way control valve 8. By doing so, the return chamber 127 and the shutoff pressure chamber 112 are depressurized and the pressure intensifier is activated. The fuel in the high pressure chamber 128 is compressed and delivered to the injector through the flow path 205. The pressure required to move the blocking piston upwards due to the pressure reduction in the shutoff pressure chamber drops below the required value under the hypothetical condition that the pressure in the shutoff pressure chamber remains constant. The shutoff piston thus opens the inlet due to the decreasing opening pressure in the blocking pressure chamber at the same time as the increasing opening pressure in the high pressure chamber, and fuel is injected into the combustion chamber. The hollow valve piston 206 then presses the high pressure chamber 128 against the blocking piston via a guide, in which case the hollow valve piston is movable in the axial direction and pressure build up during the compression of the fuel in the high pressure chamber. Move to the nozzle with the piston. Also as already explained the hollow valve piston presses the high pressure chamber against the second partial piston via its sealing edge. Thus, the compressed fuel is prevented from entering the blocking pressure chamber. To terminate the injection process, the return chamber 127 is separated from the conduit 44 by a control valve 8 and connected to a high pressure fuel source, which establishes the rail pressure in the return chamber and the shutoff pressure chamber and The internal pressure drops to the rail pressure. The shutoff piston is now hydraulically adjusted and shut off by the force of the adjustment spring 111 to end the injection process. As a result of the pressure adjustment, the pressure boosting piston 121 is now also returned to its initial position by the adjustment spring 125, where the pressure chamber 128 is connected to the shutoff pressure chamber 112 or through the check valve 129. Filled in return chamber 127.

Additional structural measures can be taken to dampen vibrations that may occur in some cases between the high-pressure fuel source and the injector to stabilize the opening and closing process. In addition to designing the throttle 3 into a suitable structure, a one-way throttle check valve may alternatively or in combination be installed at any position in the feed duct 4, 42, 45. The bore 204 may be omitted. have. The pressure enhancing piston, blocking piston and hollow valve piston may also have other forms. In the case of a shutoff piston, it is important that the fuel supply to the injection port is ensured and that in the high pressure chamber section the fuel must be supplied to the acting surface which effectively exerts an axial force on the shutoff piston arranged in the direction of the pressure enhancing piston.

In all embodiments the shutoff pressure chambers 12, 112 and the return chambers 27, 127 are realized via one co-blocking pressure return chamber 12, 27, 41 or 112, 127, 141, All partial sections (12, 27) or (112, 127) of the shutoff pressure return chamber are for example fueled via at least one fuel conduit 41 or at least one bore 141 integral to the pressure intensifying piston. Are constantly connected to each other for exchange. In addition, the pressure chamber 17 and the high pressure chamber 28 may be formed through one common injection chamber 17, 28, 40, and all partial sections of the injection chamber are connected to each other for fuel exchange. The pressure chamber 17 and the high pressure chamber 28 may be connected to each other through one fuel pipe 40 (compare FIGS. 1 and 3), or the pressure chamber may be formed through the high pressure chamber 128 (FIG. 5). compare).

FIG. 6 shows the temporal change of the fuel pressure in the high pressure chambers 28 and 128 for various opening and closing speeds of the 3/2 way piezoelectric valve according to FIG. Curve 310 represents the pressure change when the piezoelectric valve is operating quickly, and curve 311 represents the pressure change when the piezoelectric valve is operating slowly. The first position of the valve with the valve body pressed against the first valve seat 53 is hereafter referred to as the stop position, and the second position with the valve body pressed against the second valve seat 54 is then referred to. It is referred to as the final position. When the valve is operating quickly, the piezoelectric actuator is electrically driven so that the valve body moves quickly from the stop position to the final position, and when the valve is operating slowly, the voltage supplied to the piezoelectric actuator increases slowly, so that the valve body is slow The speed is moved from the stop position to the final position. Curves 320 and 310 represent pressure changes over time t in the return chamber of the pressure intensifier. PRail represents the pressure in the high pressure fuel source or the pressure in the high pressure rail of the common rail system, Pmax represents the maximum fuel pressure achievable in the high pressure chamber, hmax represents the maximum stroke of the valve body.

In the rest position of the valve body the pressure intensifier is deactivated and the piston of the pressure intensifier is restored to its initial position and no injection is made. Rail pressure PRail is applied not only to the high pressure chamber but also to the return chamber (see the section from the initial time point to the time point t ₁ in the curves 310, 311, 320, 321). At the final position hmax of the valve body the pressure intensifier is fully activated, the pressure in the return chamber has a small value corresponding to almost zero and the pressure in the high pressure chamber has its own maximum value Pmax. The blocking piston is lifted up and sprayed. In the elapsed section between the stop position and the final position, the pressure intensifier is partially activated, the pressure in the return chamber decreases with increasing stroke of the piezoelectric valve and the pressure intensifying piston generates a medium injection pressure, which is the valve As it is strengthened with increasing stroke, the injection process takes place at increased pressure. The graph shown in FIG. 6 is a schematic diagram, based on the fact that the nozzle opening pressure is approximately equal to the rail pressure. If the valve operates slowly after the time point t ₁ (curve 331), the pressure in the return chamber continues to decrease until time point t ₂ (curve 321), while the pressure in the high pressure chamber is It is gradually increased to Pmax (curve 311). When the nozzle opening pressure is reached immediately after the time point t ₁ , the shutoff piston is lifted up from the injection port and fully opens the injection port, so that the increased amount of fuel at the increased pressure is injected. At the time point t ₂ , the maximum opening stroke hmax and the maximum injection pressure Pmax of the valve body are reached. The blocking process at time t ₃ proceeds quickly to ensure rapid decompression at the end of the injection ("rapid spill" is used as the technical English terminology for this). At time t ₃ , that is, at the time when the length expansion of the piezoelectric actuator is reversed, the pressure in the return chamber as well as the pressure in the high pressure chamber are returned to the rail pressure and the blocking piston shuts off the injection port again. On the contrary, when the valve is operated rapidly at the time point t ₁ (curve 330), the elapsed section moves rapidly, and the pressure in the high pressure chamber increases to the maximum pressure Pmax just before the time point t ₂ (curve While at the same time the pressure in the return chamber rapidly decreases (see curve 320). Correspondingly, an almost perpendicular form of pressure progression appears (curve 310). In order to ensure rapid depressurization at the end of the injection, it is preferred that the shutoff process proceed accordingly as described above.

FIG. 7 shows the pressure change for the case where the piezoelectric valve according to FIG. 4 is a 3/2 way valve, for example. In this case the valve body has an intermediate position as well as a stop position and a final position, where the valve body can hold this position for at least a predetermined period of time, where the conduit 42 is not only the conduit 45 but also the conduit 44. ) Is also connected. During this period, the pressure is equilibrated to the intermediate pressure level PZ1 in the return chamber, which is determined by the amount exiting the low pressure system and coming from the high pressure fuel source. Curve 410 represents the pressure change in the high pressure chamber, and curve 420 represents the pressure change in the return chamber. The h (t) graph shown at the bottom shows the temporal change for the stroke of the blocking piston, and the third graph shows the piezoelectric stroke H, that is, the temporal change for the operation of the valve body. Where Hmax represents the maximum value of the piezoelectric stroke, and the final position of the valve body, with the return chamber connected only to the low pressure system, can be set to this maximum value. The open pressure Poe in the high pressure chamber is the pressure necessary to raise the blocking piston upward. t ₁ to t ₅ represent a plurality of sequential time points within one injection cycle, where one injection cycle is boot injection, ie the first injection process at low pressure levels and the second at high pressure levels. Spraying process.

At the time point t ₁ , the valve body is moved to an intermediate position through proper drive of the piezoelectric actuator and maintains this intermediate position until the time point t ₃ is reached (see the graph H (t)). The pressure in the return chamber decreases to the intermediate pressure level PZ1, while the pressure in the high pressure chamber gradually increases. If this pressure exceeds the open pressure at time t ₂ , the injector is opened (see the h (t) graph) and the boot injection process proceeds to a pressure level between the rail pressure and the maximum pressure that can be reached by the pressure intensifier. do. When the piezoelectric valve is moved to its final position at stroke time Hmax at the time point t ₃ , the pressure in the return chamber is reduced to almost zero, while the injection port remains open and high pressure. The pressure in the chamber increases to the maximum value Pmax. This main injection process continues up to time point t ₄ , at which point the valve returns to its stop position (H = 0), so that the pressure is adjusted to the rail pressure level within the high pressure chamber and the return chamber, At time t ₅ , the blocking piston blocks the injection port (h = 0).

Alternatively, the intermediate position can also be used for an injection process with a low injection pressure, switching from the intermediate position back to the stop position. This occurs when a small injection amount is injected, for example as transported during primary injection or idling.

8 shows a variant of the embodiment according to FIG. 3, which has the same structure as the embodiment described above, but additionally a throttle is mounted in the conduit 70, such that the high pressure chamber 28 and the blocking pressure chamber 12 or The connection between the return chambers 27 is throttled. The cross section of the connecting path of the 3/2 way valve disposed between the conduit 45 and the conduit 42 is indicated by reference numeral 510 and hereinafter referred to as the valve cross section.

By additionally setting the flow cross section of the filling path 70 and the valve cross section 510 connecting the return chamber 27 to the pressure supply, and by selecting the flow cross section of the throttle 520 appropriately, the additional hydraulic pressure for blocking the needle Can be generated. The filling path 70 is designed to be very small via the throttle 520 for this purpose, but is designed to be large enough to ensure re-adjustment of the pressure intensifying piston until the filling of the high pressure chamber 28 and the next injection point. Depending on the design, an increase in pressure may occur in the return chamber. The valve cross section 510 is also designed large enough to allow rapid pressure build up to rail pressure in the return chamber 27, in which case an increase in pressure may occur in the return chamber, depending on the design of the conduit. Due to the rapid build up of pressure in the return chamber, rapid depressurization to the rail pressure level occurs in the high pressure chamber 28, and then pulsations below the rail pressure occur. Too fast pressure regulation between the chamber 28 and the chambers 12, 27 through the throttle 520 is prevented. At this stage, since the rail pressure continues to exist in the shutoff pressure chamber 12, a hydraulic force acting as a shutoff is applied to the nozzle needle.

In another alternative embodiment, the flow cross section of the fill path 70 is formed through the check valve 29 having a corresponding flow cross section instead of using a throttle.

9 shows a pressure change that can be realized through the embodiment according to FIG. 8. The temporal change of fuel pressure in the high pressure chamber 28 is indicated by reference numeral 1310, and the temporal change of fuel pressure in the return chamber 27 of the pressure intensifier is indicated by reference numeral 1320.

The end of the spraying process proceeds as follows. After deactivation of the valve 8, pressure build-up is achieved in the return chamber 27 and in the shut-off pressure chamber 12 to the rail pressure, thereby allowing rapid decompression to the rail pressure level simultaneously in the high pressure chamber 28. The latter decompression process proceeds so quickly that pulsations of pressure in the injector pressure chamber and in the high pressure chamber occur at levels below the rail pressure. It is at this stage that the needle shuts off, so additional hydraulic force is applied to the nozzle needle, which results in a quick needle shutoff and a more accurate amount of fuel can be supplied to the combustion chamber of the engine. In the other process, the rail pressure is also generated in the high pressure chamber and the pressure chamber. The pulsation above the rail pressure, shown in curve 1320, is generated hydraulically and can be minimized or suppressed by designing the conduit in a suitable configuration. Important for rapid depressurization in the high pressure chamber by the next pulsation below the rail pressure is rapid depressurization in the return chamber.

10 is a modified embodiment of the embodiment shown in FIG. In this embodiment, instead of the conduit 45, a fuel conduit 1450 is provided that is not directly connected to the conduit 4 but to the chamber of the pressure intensifier to which the conduit 4 is connected. Conduit 1450 is connected to the chamber at an end of the pressure intensifier chamber disposed on the opposite side of conduit 4. In addition to the conduit 41 according to FIG. 3, the conduit 41 shown in FIG. 3 is replaced by a fuel pipe 1410 connected to the return chamber behind the connection of the conduit 42 and the return chamber 27. . A conduit 1410 is also connected to the blocking pressure chamber 12 so that the conduit 1700 replacing the conduit 70 according to FIG. 3 can be connected and fixed to the blocking pressure chamber in the opposite direction. The other end of conduit 1700 is connected with high pressure chamber 28 via check valve 29 in accordance with the method described with reference to FIG. 3. The conduit 40 according to FIG. 3 is also replaced by a conduit 1400 which is connected to the high pressure chamber 28 via a conduit 1700 or check valve 29 in the opposite direction. Also, in the blocking pressure chamber, unlike the embodiment according to FIG. 3, the limiting member 2000 for limiting the opening stroke of the injector is fixed.

The method of operation is almost the same as the embodiment according to FIG. 3, except that the cleaning of all the chambers by the fuel is forced by placing the connection of the fuel pipe in the opposite direction in the chamber of the pressure intensifier or in the shutoff pressure chamber of the injector This exists.

Claims (15)

A fuel injector capable of supplying fuel from a high pressure fuel source, and is equipped with a pressure intensifier comprising a movable pressure intensifier piston between the fuel injector and the high pressure fuel source, the pressure intensifier piston being connectable to the high pressure fuel source. The fuel pressure in the high pressure chamber can be changed by filling the return chamber of the pressure intensifier with fuel or by emptying the fuel in the return chamber, the fuel injector And a shutoff piston 13; 113 protrudes into the shutoff pressure chamber 12; 112 so that fuel pressure is applied to the shutoff piston to obtain a force acting on the shutoff piston in the shutoff direction; (12; 112) and return chambers (27; 127) are formed by common shutoff pressure return chambers (12, 27, 41; 112, 127, 141). And all of the partial sections 12, 27; 112, 127 of the shutoff pressure return chamber are permanently connected to each other for fuel exchange (41; 141), and provide a fuel to the injection port and block the force acting in the open direction. In the fuel injection device for an engine provided with a pressure chamber (17; 128) for applying to The high pressure chamber 28 is connected to the high pressure fuel source so that at least the fuel pressure of the high pressure fuel source can be continuously applied in the high pressure chamber irrespective of the pressure vibration (43; 70, 41, 42; 1700, 1410, 42). And a pressure chamber and a high pressure chamber are formed through the common injection chamber, and all partial sections of the injection chamber are permanently connected to each other for fuel exchange. 2. The fuel injection device according to claim 1, wherein the pressure chamber (17) and the high pressure chamber (28) are connected to each other via a fuel pipe (40). The fuel injector according to claim 1, wherein the pressure chamber is formed through the high pressure chamber (128). Fuel injection device according to any of the preceding claims, characterized in that the shutoff pressure chamber (12) and the return chamber (27) are connected to each other via conduits. The method of claim 1, wherein the shutoff pressure chamber 112 and the return chamber 127 are confined to one another via the partial piston 123 of the pressure intensifying piston 121, and within the partial piston. And at least one bore (141) connecting the shutoff pressure chamber and the return chamber. Fuel injection device according to any of the preceding claims, characterized in that the high pressure chamber (28) is connected (43) with the chamber (26) via a check valve (29). Fuel injection device according to any of the preceding claims, characterized in that the high pressure chamber (28; 128) is connected (70) with the shut-off pressure chamber (12; 112). Fuel injection device according to claim 7, characterized in that the connection (70) comprises a check valve (29; 129). 9. The connection between the high pressure chamber (28) and the shut off pressure chamber (12) according to claim 7 or 8, wherein the throttling (520; A fuel injection device characterized in that. Fuel injection device according to any of the preceding claims, characterized in that the return chamber (27; 127) is selectively connectable with the low pressure pipe (44) or the high pressure fuel supply (2) via a valve (8). 11. A valve according to claim 10, wherein the valve is a piezoelectric valve comprising a first position and a second position, the piezoelectric valve connecting the return chamber with the high pressure fuel source in the first position and the low pressure tube 44 in the second position. A fuel injector, characterized in that. 12. The fuel injection device according to claim 11, wherein the piezoelectric valve is formed so that the switching speed between the first position and the second position can be changed. 13. The fuel injection device according to any one of claims 10 to 12, wherein the valve can be switched to at least one intermediate position such that an intermediate pressure level is formed in the return chamber. 14. The fuel injection device according to claim 13, wherein the valve connects the return chamber with the low pressure pipe as well as the high pressure fuel supply in the intermediate position. The conduit according to any one of the preceding claims, which is connected to the chamber or to the chambers in at least one of the chambers 26, 27, 28 of the pressure intensifier and / or the shutoff pressure chamber 11 of the fuel injector. 4, 1450; 42, 1410; 1410, 1700; 1700, 29, 1400 are arranged such that cleaning of the chamber or the chambers by the fuel is forced when fuel flows into the conduits, in particular in the opposite direction Fuel injection device, characterized in that.