EP1662133A1 - Injection valve - Google Patents

Abstract

Injection valve comprises a pressure-maintaining valve (4) arranged between a feed channel (140) leading to a control valve (3) of the injection valve and a spring chamber (105). A pressure is applied to the spring chamber in the feed channel and the pressure maintained by the pressure-maintaining valve acts with a pre-tensioned spring (110) on an injection needle (170) of the injection valve. Preferred Features: The diameter of the pump piston (210) of a pump (2) supplying the injection valve with fuel is reduced to 6.0-6.5 mm, preferably 6.25 mm. The pressure-maintaining valve is arranged in the spring chamber.

Description

The invention relates to an injection valve or injection nozzle for injecting a fluid, in particular for injecting fuel into a combustion chamber of an automobile engine, in particular a diesel engine.

For a good preparation of the fuel-air mixture, the fuel, depending on the combustion process, with a pressure between 350 and more than 2,000 bar injected into a combustion chamber of an engine and thereby with the greatest possible accuracy per injection (pre-injection and main injection, possibly. clocked) are dosed. In order to achieve a compromise between low fuel consumption and compliance with emission limits (exhaust gases and engine noise), it is necessary to precisely control the injection process. Important parameters are the start of injection (pre- and main injection), the duration of injection, the respective end of injection and the dynamic behavior of the injection needle at the beginning and at the end of the injection. Since very high fuel pressures are necessary, there are high demands on a dynamic behavior of the injection valves.

One such injection system is the unit injector (UIS) unit, in which a pump, a control valve and the injector form a unit. Per engine cylinder, such a unit injector unit is installed in the cylinder head of a diesel engine and driven either directly via a plunger or indirectly via a rocker arm of an overhead camshaft. In this system, the required injection pressure is generated in each case at the time of injection, wherein the injection rate course not only by the design of the cam contour, but also by the control of the control valve (magnet or piezobetätigt) can be influenced. The higher the fuel pressure, the more fuel that can be forced through the injector's small holes in the short amount of time available (a few thousandths of a second). The pump-nozzle system can build up the high pressure well because it is generated in a very small space directly where it is injected.

Injector injector systems are prone to increased noise emissions in idle mode, which are mechanically and hydraulically excited. The mechanical noise emissions arise as a result of a sudden loading and unloading of the power-conducting components of the pump-nozzle drive during control and Absteuern, whereas the hydraulically induced noise emissions result in relief of high-pressure chambers. To create z. B. at Absteuern in the lower and medium speed range gaseous voids that implode shortly after their emergence abruptly (cavitation) and predominantly high-frequency noise stimulate. These cavities are formed wherever the instantaneous local pressure falls below the boiling pressure of the fuel.

In the prior art, attempts have been made to counteract the mechanically induced noise emissions by means of a lowest possible, statically adjustable opening pressure of the injection needle.

Furthermore, attempts have been made in the prior art to counteract the hydraulically induced noise emissions by means of a dynamic throttle in an inlet bore of the injection valve and a throttled connecting bore arranged in the nozzle chamber between the control valve and the dynamic throttle. Hereby, the closing force on the injection needle can be increased by means of a piston guided in the spring chamber. However, such a closing force increase presupposes pressure in the inlet, which is present only during the shut-off and before the feed, so that an advantageous from the point of view of emissions increase the opening pressure of the injection needle in the main injection and thus the pressure level in the spring chamber low in the lower speed range fails.

From EP 0 675 282 B1, such a pump-nozzle arrangement is known, in which fuel from a fuel tank is provided to a fuel pump via a control valve. The fuel pump is connected via a line to a pressure chamber in which an injection needle of the injection valve is arranged. The injection needle has a pressure shoulder in the pressure chamber, on which the injection needle can be raised by means of a fuel pressure from its sealing seat. The injection needle is biased by a biasing spring, which is arranged in a spring chamber, against the sealing seat. The spring chamber is connected via a fuel line to an overflow valve seat and to a check valve. By coupling the spring chamber to the supply line, the injection needle is pressed by the fuel pressure in addition to the biasing spring against the sealing seat. Depending on a closed position of the overflow valve, the fuel compressed by the fuel pump is fed back into the pressure chamber or via the supply line to the fuel tank. An injection begins when the overflow valve is closed during the compression process of the pump and thereby the fuel pressure in the pressure chamber rises above a predetermined value, so that the injection needle is lifted due to the pressure in the pressure chamber against the bias of the biasing spring and against the fuel pressure in the spring chamber from the sealing seat.

It is an object of the invention to provide a low-noise pump-nozzle unit available, which can realize today's and future foreseeable emission targets and beyond that is inexpensive to produce.

The object of the invention is achieved on the one hand by an injection valve in which a pressure-maintaining valve is provided in or on a spring chamber of the injection valve, by means of which it is possible to couple the spring chamber to a pressure in the inlet. This applied to the spring chamber fluid pressure, together with a spring, preferably acts on a piston in the spring and forth movable piston, which is acted upon by the force of the spring and the force due to the fluid pressure in the spring chamber, the piston these two forces in Substantially axially transfers to the injection needle of the injection valve.

On the other hand, the object of the invention is realized by reducing a pump piston diameter of a pump associated with the injection valve, which supplies the injection valve with fuel. In the prior art, such a pump piston diameter is currently 7.65 mm. By means of a reduction to about 6.0 to 6.5 mm, in particular 6.25 mm is achieved due to the concomitant reduction of the pump piston area, a reduction in peak forces in the drive by about 30%, which the mechanical noise excitation at the same pressure level significantly reduced.

By means of this arrangement, the nozzle opening pressure at idle the engine with less than or equal to 160 bar in the new state of the injector noise optimal selectable. The criterion for the lower limit of the nozzle opening pressure is the safety against gas entry from the engine cylinder. This lower limit is the drop in nozzle orifice pressure over the life of the injector - typically 25 to 30 bar - from the hydraulic closing force due to the pressure in the spring chamber, from the mechanical closing force due to the force of the spring in the spring chamber to the piston and from the maximum Engine cylinder pressure determined during nozzle closing. By selecting a suitable biasing spring then the nozzle opening pressure is freely selectable.

Furthermore, the device according to the invention for a timed injection is very well suited because due to the Absteuerns a pilot injection, the resulting pressure wave opens the pressure-holding valve and increases the pressure in the spring chamber.

Thus, the opening pressure for the main injection and thus the pulse with which the fuel can be injected into the combustion chamber, which is advantageous in particular for lower pollutant emissions, also increases.

In a preferred embodiment, the pressure-holding valve is provided at the top in the spring chamber, wherein an inlet of the pressure-holding valve branches off from an inlet bore, through which the fuel is conveyed into a pump chamber of the pump. A valve member of the pressure relief valve seals this inlet bore biased. An abutment of the pressure holding valve is preferably located above in the spring chamber and preferably consists of a spring in the chamber via a press-fitted sleeve, which supports on its upper side a valve spring of the valve member of the pressure holding valve. At the bottom of the sleeve, a biasing spring provided in the spring chamber is supported by the injection needle.

This embodiment is particularly advantageous because already existing pump-nozzle concepts can be equipped with elaborate design measures with the pressure-holding valve.

In a variant of the invention, the pressure-holding valve is not provided at the top in the spring chamber, but outside the spring chamber, wherein the valve member of the pressure-holding valve seals a branch (portion of an inlet bore, which connects the inlet channel with the spring chamber) biased by the inlet bore. In this case, valve member, the sealing seat, inlet channel and branch can be arranged such that the valve member is guided to reduce fluttering. The abutment of the pressure holding valve is in a preferred embodiment, a simple bore in which a valve spring is arranged, which has a valve body at its free end. Preferably, this valve spring chamber is relieved by means of a vent hole. In a preferred embodiment of the invention, the vent hole leads from an upper portion of the valve spring space to an upper portion of the spring chamber, wherein the vent hole is formed as a throttle.

In a preferred embodiment of the invention, a sealing portion (valve body) of the valve member of the pressure holding valve is a ball, in particular a hemisphere, which is sealingly seated on a correspondingly shaped sealing seat, preferably a conical seat, in a closed state of the pressure retaining valve. This arrangement is very simple and therefore cost-effective to implement, with a hemisphere valve member as a particularly compact design can be achieved.

To reduce a transverse movement of the valve member or valve body (ball, hemisphere) this is preferably performed at its outer diameter with a close game. Preferably, this game is 3 to 5μm, in particular 4μm. Furthermore, in such an embodiment, a throttled connection between the sealing section / seat and the spring chamber for reducing a flutter tendency of the valve is particularly advantageous. This is particularly advantageous for small pressure differences and for influencing the pressure rise in the spring chamber.

In a preferred embodiment of the invention, a dynamic throttle is provided in the inlet channel (from the fuel reservoir) of the injection valve, wherein the inlet to the pressure retaining valve branches off downstream of the dynamic throttle downstream of the inlet channel. Downstream to mean that in an intake stroke of the pump of the injection valve, the fuel is conveyed from the fuel reservoir through the inlet channel into the pump chamber of the pump, wherein the inlet bore is arranged behind the dynamic throttle.

The surface of the dynamic throttle is designed so that up to medium engine speeds of the back pressure in the inlet channel (and the inlet bore to the pressure relief valve) and consequently held by the pressure holding valve pressure in the spring chamber increase only slightly. Thus, the increase of the Opening pressure of the injection needle before the first closing (pilot injection) of the control valve small, which has a favorable effect on the metering accuracy of small pilot injection quantities in an emission-determining region of the engine map. Ie. up to average rotational speeds of the engine, the pressure in the spring chamber for a pre-injection of an injection does not increase significantly, whereby a fast opening (low opening force) of the injection needle is ensured. On the other hand, there is an increased pressure level in the spring chamber after Absteuern the pilot injection due to the pressure wave in the inlet channel (see above), which allows for a following the pilot injection main injection increased opening pressure, which in turn has a positive effect on the pollutant emissions.

In a preferred embodiment of the invention, the dynamic throttle, a portion of the inlet channel and preferably also the inlet bore and its branch downstream of the throttle in a plate is provided, which closes and seals the spring chamber upwards. Preferably, in this case, the sealing seat of the pressure holding valve is formed in the plate. Such an arrangement allows a simple production of the inlet bore and the dynamic throttle, which is inexpensive to manufacture and also inexpensive in the maintenance of the injection valve. Further, in the plate also means for the high pressure side of the injection valve, such as. B. a pump room throttle and a portion of the pressure channel may be provided.

In a preferred embodiment of the invention, the space below the needle piston, which can be moved up and down in the spring chamber and presses substantially axially onto the injection needle, is connected to the inlet channel upstream of the dynamic throttle by means of a bore or a channel. Furthermore, it is possible, this room not with the inlet channel, but with another drainage or leakage line, the z. B. leads to the fuel tank to connect. Here, the game of the needle piston on the inner wall of the Spring chamber selected such that the pressure in the spring chamber in each case a first injection (pre-injection) is substantially completely degraded and corresponds to the pressure in the inlet channel. This ensures that each injection (or each injection cycle: pilot / pilot injection, single or multiple main injections) always takes place under the same pressure conditions and that the behavior of the unit injector is predictable. Furthermore, this ensures that there is no or only a slight fluid pressure level in the spring chamber for a rapid opening of the injection needle during a pilot injection.

In order to prevent tilting of the needle piston whose circumferential side wall is formed crowned.

Further, preferred embodiments of the invention will become apparent from the other dependent claims.

Fig. 1

einen prinzipiellen Aufbau einer Pumpe-Düse-Einheit ohne Fluiddruckbeaufschlagung einer Einspritznadel in einem Federraum,

Fig. 2

eine erfindungsgemäße Pumpe-Düse-Einheit mit einem zentralen Druckhalteventil,

Fig. 3

einen Ausschnitt A der Fig. 2

Fig. 4

einen Ausschnitt B der Fig. 2,

Fig. 5

eine bevorzugte Ausführungsform eines Dichtabschnitts eines Druckhalteventils der erfindungsgemäßen Pumpe-Düse-Einheit,

Fig. 6

eine weitere erfindungsgemäße Pumpe-Düse-Einheit mit einem dezentralen Druckhalteventil,

Fig. 7a

eine erste Schnittansicht des Bereichs C aus der Fig. 6, und

Fig. 7b

eine zweite Schnittansicht des Bereichs C aus der Fig. 6,

Fig. 8a

eine erste Ausführungsform einer Entlüftung eines Druckhalteventilfederraums,

Fig. 8b

eine zweite Ausführungsform der Entlüftung,

Fig. 8c

eine dritte Ausführungsform der Entlüftung, und

Fig. 8d

eine vierte Ausführungsform der Entlüftung.

The invention will be explained in more detail below with reference to Ausführungsbespielen with reference to the accompanying drawings. In the drawing show:

Fig. 1

a basic structure of a pump-nozzle unit without Fluiddruckbeaufschlagung an injection needle in a spring chamber,

Fig. 2

a pump-nozzle unit according to the invention with a central pressure-maintaining valve,

Fig. 3

a section A of FIG. 2

Fig. 4

a section B of Fig. 2,

Fig. 5

a preferred embodiment of a sealing portion of a pressure holding valve of the pump-nozzle unit according to the invention,

Fig. 6

Another pump-nozzle unit according to the invention with a decentralized pressure maintenance valve,

Fig. 7a

a first sectional view of the region C of FIG. 6, and

Fig. 7b

a second sectional view of the area C of FIG. 6,

Fig. 8a

a first embodiment of a venting of a pressure retaining valve spring chamber,

Fig. 8b

a second embodiment of the vent,

Fig. 8c

a third embodiment of the vent, and

Fig. 8d

a fourth embodiment of the vent.

Hereinafter, a Absteuern a control valve 3 of an injection valve 1 to mean that the control valve piston is moved to its rest position (not energized state of the control valve 3), wherein the control valve 3 is open, i. allows fluid communication between a fuel supply and a pump 2 of the injection valve 1. A control of the control valve 3 is intended to mean that the control piston of the control valve 3 is closed (control valve 3 is in the energized state), whereby a high-pressure region of the injection valve 1 is separated from the fuel reservoir and compressing a fuel 192 by means of the pump. 2 is possible.

Fig. 1 shows a schematic embodiment of a pump-nozzle unit without additional Fluiddruckbeaufschlagung the injection needle in the spring chamber. The pump-nozzle unit for injecting fuel into a combustion chamber 190 of an internal combustion engine, in particular a diesel engine, has a fuel pump (hereinafter referred to as pump) 2, in which a pump piston 210 in a pump cylinder 230 back and forth. The pump piston 210 is driven directly or indirectly via an unillustrated, overhead camshaft of the internal combustion engine. The compression space of the pump cylinder 230 is the pump space 220, which is connected via a fuel line 240 to a valve seat of a piezoelectrically or electromagnetically operated control valve 3. The control valve 3 serves to either close the fuel line 240 or to connect it to a fuel low pressure region, represented by an inlet channel 140, from which fuel can be drawn. In the open rest position of the control valve 3, fuel is drawn from the fuel reservoir via a line in the cylinder head, the inlet channel 140 and via the cylinder piston of the control valve 3 into the pump chamber 220 with a movement of the pump piston 210 directed upward in relation to FIG. If the control valve 3 is still in its open position and the pump piston 210 is moving downwards, fuel previously drawn into the pump chamber 220 can be pushed back again into the fuel low pressure region. In a control of the control valve 3 (control valve 3 is energized) closes off this fluid communication between fuel pipe 240 and the inlet conduit 140. In a downward movement of pump piston 210, the fuel in the pump chamber 220 is compressed, whereby a high pressure p ₂₂₀ generated in the pump chamber 220 becomes.

Furthermore, the pump-nozzle unit comprises an injection nozzle 1, which has an injection needle 170 which can be moved back and forth between a closed position and an open position. On the injection needle 170, a biasing spring 110 acts via a needle piston 115 and a shaft 117 with a closing force determined by the spring constant of the biasing spring 110. The biasing spring 110 is clamped between the needle piston 115 and the upper end of the spring chamber 105 (blind hole). A section of the injection needle 170 having a pressure shoulder 172 is surrounded by a pressure chamber 176, which communicates with the pump chamber 220 via a pressure channel 145. Depending on the throttle effect of the pressure channel 145 and possibly other throttle devices, not shown, a third pressure p _{176 is} built up by the pressure p ₂₂₀ prevailing in the pump chamber ₂₂₀ in the pressure chamber 176. The fuel standing in the pressure chamber 176 under the pressure p ₁₇₆ exerts an upward opening force on the pressure shoulder 172 with respect to the illustration of FIG. 1 on the injection needle 170. The injection needle 170 assumes its open position as soon as the opening force caused by the pressure p ₁₇₆ is greater than the sum of the opening of the injection needle 170 opposite Friction forces and the force exerted by the biasing spring 110 downward force on the injection needle 170 is.

The space above the needle piston 115 is acted upon by a fluid pressure which, via the needle piston 115, further biases the injection needle 170 with respect to its sealing seat above an engine compartment 190. Since a complete and permanent sealing of the spring chamber 105 with respect to the injection needle 170 or the needle piston 115 and the shaft 117 is not possible, the needle piston 115 is guided in the spring chamber 105 with a sealing gap, the space (with respect to FIG Spring chamber 105 is connected via a bore to the inlet channel 140.

Start of injection and injection quantity of the injection valve 1 are determined by the fast switching control valve 3 (solenoid valve or, preferably, piezoelectrically actuated valve), these variables are freely selectable in the map. The control valve 3 allows in the open state, a free passage from the fuel inlet of the low pressure region via the pump 2 to the high pressure region and back to the low pressure region in the cylinder head of the engine, whereby filling the pump chamber 220 during a suction stroke of the pump piston 210 and a squeezing of fuel during a delivery stroke the pump piston 210 is made possible. By energizing the solenoid valve during a delivery stroke of the pump piston 210, this bypass is closed, which leads to a pressure build-up in the high pressure region of the injector 1 and after exceeding a nozzle opening pressure P _{176 leads} to the injection of fuel 192 into the combustion chamber of the engine. Due to the compact design of the unit injector unit results in a very low high pressure volume and a large hydraulic streaking.

The control valve 3 receives its control signals from an electronic control, the known input information such. B. accelerator pedal position, engine speed, camshaft position, Intake manifold temperature, intake manifold pressure and coolant temperature processed and outputs corresponding control signals to the control valve 3.

The injection period is initiated by energizing and closing the control valve 3 during the delivery stroke of the pump piston 210. After pressure build-up in the high-pressure range and reaching the nozzle opening pressure P ₁₇₆ , the pre-injection begins. The end of the pilot injection results in addition to a Fluiddruckbeaufschlagung the spring chamber 105 by means of the provision according to the invention of a pressure holding valve 4 (see below) on the spring chamber 105 z. B. additionally by the opening of a valve (bypass piston), which abruptly lowers the pressure in the high-pressure chamber 176 and the injection needle 170 closes. Hub and shaft diameter of the bypass piston determine the time interval between the end of the pilot injection and the beginning of the main injection, ie the break in spraying.

Fig. 2 shows a pump-nozzle unit according to the invention with the injection valve 1 according to the invention, wherein mainly the low-pressure region in Fig. 2 can be seen. As can additionally be seen in FIG. 2, there is a fuel inlet 142, as well as the inlet channel 140 in a section of the injection valve 1, in which the spring chamber 105 is also formed. At the top of this section is followed by a plate 150, which closes the section above fluid-tight. U. a. the inlet channel 140 is guided through this plate 150 and an inlet bore 152 of a pressure holding valve 4 is formed in the plate 150, wherein the pressure-maintaining valve 4 is explained in more detail below.

In the spring chamber 105, the biasing spring 110 acts via a needle piston 115 and the shaft 117 substantially axially from above on the injection needle 170, which is movable in a lower portion of the injection valve 1 via a small stroke up and down. As already explained with reference to FIG. 1, the pressure shoulder 172 of the injection needle 170 is in the Pressure chamber 176 is arranged, which is in fluid communication with the pressure channel 145 and the fuel line 240.

With reference to FIGS. 2 and 3, the pressure holding valve 4 is provided at the top of the spring chamber 105, which is supported on an abutment 405. The abutment 405 of the pressure holding valve 4 is fixed in an upper region of the spring chamber 105, wherein a press fit is well suited for the attachment. Down to the abutment 405 abuts in this embodiment, the biasing spring 110, wherein the abutment 405 is also an abutment of the biasing spring 110. In a preferred embodiment of the invention, this abutment 405 is a U-shaped sleeve, wherein the horizontal portion of the sleeve 405 is disposed further down in the spring chamber 105. Other abutments 405 of the pressure holding valve 4 are also possible, such as. B. a pressed-in disc or recesses in the spring chamber inner wall, on which the biasing spring 110 and / or pressure-maintaining valve 4 are supported. The abutment 405 allows due to holes or slots fluid communication between the space above the abutment 405 and the space below, the actual spring chamber 105, too. Preferred for the pressure equalization between these two spaces is a central bore in the horizontal portion of the sleeve 405th

In a preferred embodiment of the pressure holding valve 4, a valve spring 415 is supported on the abutment 405 and biases a valve member 410 against a sealing seat 430. The valve member 410 consists in a simple embodiment only of an at least partially spherical body 420, z. As a ball or a hemisphere, sitting directly on the valve spring 415, which is supported on the abutment 405 and biases the body 420 against the sealing seat 430. In a preferred embodiment, the partially spherical body 420, in particular the hemisphere, sits on a disc 440, which in turn is connected to the valve spring 415. The outer dimensions of the disc 440 are slightly smaller than the inner dimensions of the spring chamber 105, so that this disc 440 is guided in the spring chamber 105 with some play, which is the Sealing body 420 of the pressure holding valve 4 gives a sufficient vertical guidance in the spring chamber 105. Further, the disc 440 may be seated at the top of the vertical portions of the sleeve 405 (FIG. 3), giving the pressure holding valve 4 a defined maximum lift and preventing the valve member 410 from fluttering or uncontrolled movements. Thus, when the disc 440 resting on the vertical sections of the sleeve 405 still a pressure exchange between the area above the pressure holding valve 4 and below in sufficient time is possible, the disc 440 holes or grooves on its underside / peripheral side have.

The sealing seat 430 of the pressure retaining valve 4 is preferably formed in the plate 150, wherein the sealing seat 430 cooperates with the sealing portion 422 of the valve member 410 such that in a closed position of the pressure retaining valve 4 over this area no fluid can be transported. In a preferred embodiment, the sealing seat 430 is a conical seat, from which a blind hole continues upward into the plate 150, wherein the inlet bore 152 branches off from the blind hole bore to the inlet channel 140. It is also possible that the inlet bore 152 leads away directly from the sealing seat 430.

In the plate 150, a bore is further provided, which is part of the inlet channel 140 of the injection valve 1, so that the inlet channel 140 from the lower portion of the injector 1 coming, can continue to the valve seat of the control valve 3 through the plate 150 therethrough. In a preferred embodiment of the invention, the portion of the inlet channel 140, which is located in the plate 150, formed with a dynamic throttle 154, which narrows the inlet channel 140. Downstream, ie in the case of an intake stroke of the pump 2 in the flow direction behind the dynamic throttle 154, the inlet bore 152 preferably branches off within the plate 150 to the pressure retaining valve 4, whereby a fluid connection between inlet channel 140 and sealing seat 430 of the pressure retaining valve 4 is created. In a further embodiment of the invention can the inlet bore 152 z. B. branch off directly from Staudrossel 154.

By means of the inventive provision of the pressure holding valve 4 in the spring chamber 105, it is possible to impose a pressure downstream of the dynamic throttle 154 of the inlet channel 140 to the spring chamber 105. The pressure-maintaining valve 4 is designed such that it only allows the pressure in the inlet channel 140 to be impressed on the spring chamber 105, whereby a pressure P ₁₄₀ in the inlet channel 140 (downstream of the vertical throttle 154) must be above the pressure p ₁₀₅ in the spring chamber 105. If the spring chamber pressure P _{105 is} greater than the pressure P ₁₄₀ in the inlet channel 140 (downstream of the dynamic throttle 154), the pressure-maintaining valve 4 remains closed and the pressure p ₁₀₅ in the spring chamber 105 is maintained. Due to the structural design of the pressure-maintaining valve 4, there is only a pressure transfer from the inlet channel 140 to the spring chamber 105, and only when the pressure in the inlet channel 140 is above that of the spring chamber 105. This now prevailing in the spring chamber 105 pressure p ₁₀₅ acts (together with the biasing spring 110) via the needle piston 115 and the shaft 117 to the injection needle 170 in the direction of the sealing seat, which is shown in Fig. 4.

In a preferred embodiment of the invention, the pump chamber 220 adjoins the plate 150 upwardly (FIG. 3), allowing for a compact unit injector.

Fig. 4 shows a lower portion of the spring chamber 105, in which the needle piston 115 is guided. Down to the needle piston 115, the shaft 117 connects, which can be configured integrally either with the needle piston 115 or with the injection needle 170. Furthermore, the needle piston 117 may also be guided as a separate part in a bore above the injection needle 170. On the needle piston 115 act two forces, a static, due to the biasing spring 110, and a hydraulic, due to the fluid pressure P ₁₀₅ in the spring chamber 105. These two forces are by means of the needle piston 115 and the shaft 117 to the injection needle 170th forwarded, which bias this with a force in the direction of their sealing seat.

The shaft 117 is preferably formed in an upper region over almost its entire length as a triflate, so that a fluid connection between the spring chamber 105 and an annular space 120 which is provided in an upper region of the injection needle 170. The shaft 117 preferably acts as a damping element for the injection needle 170, wherein for damping a movement of the injection needle 170, a control edge 118 of the shaft 117 cooperates with a control edge 119 in the injection valve 1, said portion (with control edge 119) in the injection valve body z. B. may be formed as so-called. Damping plate. The two control edges 118, 119 cooperate in such a way that with a corresponding position of the injection needle 170, the annular space 120 is separated from the spring chamber 105.

Thus, with increasing stroke of the injection needle 170, the control edge 118 of the shaft 117 in the region of the control edge 119 and thereby closes the annular space 120 with respect to the spring chamber 105, so that the fuel enclosed in the annular space 120 must be compressed, which dampens the lifting movement of the injection needle 170. Preferably, the profile of the control edges 118 and / or 119 as a continuously differentiable function is designed such that there is a dependent on the speed of the motor damping effect. At high speed and correspondingly fast stroke movement of the injection needle 170 results due to fluid mechanical processes increased damping effect. At low engine speed, however, results in a reduced damping effect.

In the space under the needle piston 115 there is a pressure which is either lower (after pre-injection and during the main injection phase) or equal to (immediately before the pre-injection) the pressure P ₁₀₅ in the spring chamber 105. For a proper function of the injection valve 1, it is advantageous for ensuring the stability from stroke to stroke of the injection needle 170. that the pressure in the space below the needle piston 115 is reduced in each case during a first injection (usually pre-injection) such that it corresponds to a pressure p ₁₄₀ in the inlet channel 140 upstream of the dynamic throttle 154, or another low pressure. For this purpose, the space below the needle piston 115 is connected by means of a fluid connection 180 to the inlet channel 140. However, this fluid connection 180 may also be led to other drainage or leakage channels, whereby the pressure below the needle piston 115 is different than in the inlet channel 140 upstream of the dynamic throttle 154.

In order to allow a pressure reduction in the spring chamber 105, the game (sealing gap 445) between the needle piston 115 and the inner wall of the spring chamber bore 105 is designed such that the pressure p ₁₀₅ is degraded in the spring chamber 105 via the fluid connection 180 in each case before a first injection. Ie. During a break in spraying, the pressure p ₁₀₅ in the spring chamber 105 must be reduced via the sealing gap 445 such that rapid opening of the injection needle 170 is still possible. The thus set pressure in the spring chamber 105 corresponds either to the pressure in the inlet channel 140 upstream Staudrossel 154 or the pressure of another drainage line.

For the dimensioning of the sealing gap 445, a compromise has to be found over the speed range of the motor. Ideally, the pressure below the needle piston 115 is reduced prior to a first injection over the entire speed range. If one wants to realize this also for high speeds, then a pressure drop in the low to medium speed range before a main injection is too high, which can run counter to a safe keeping closed the injection needle 170 in this speed range at a selected biasing spring 110. It would then have a stronger biasing spring 110 can be selected, which would lead to an increased opening pressure of the injection needle 170.

In order to compensate for tilting of the needle piston 115 and to avoid tilting of the needle piston 115 is the needle piston 115 preferably rounded on its circumference.

Fig. 5 shows a preferred embodiment of a sealing portion of the pressure holding valve 4 in a closed and an open position, wherein the sealing body 420 is guided with a small clearance. This small clearance is preferably realized by means of a guide bore 450, which has a diameter of approximately 1 to 6 μm, preferably 3 to 5 μm, particularly preferably 4 ± 0.5 μm, larger diameter than the outer diameter of the sealing body 420. Preferably, the guide bore 450 is formed in the plate 150, preventing transverse movement of the valve member 410.

In order to avoid fluttering of the valve member 410, a fluid connection between the spring chamber 105 and the sealing seat 430 of the pressure holding valve 4 is carried out by means of at least one throttle 435.

A favorable area ratio of seat and guide bore for the sealing body 420 is about 1: 1.1 to 1: 3, preferably 1: 1.2 to 1: 2.5, particularly preferably 1: 1.5 to 1: 2, 0th

Figures 6, 7a and 7b and Figures 8a to 8d show a second variant of the invention, wherein like reference numerals are used for like components with the above embodiments.

According to the invention, the pressure holding valve 4 is not arranged in the spring chamber 105, but outside of the spring chamber 105, wherein the pressure-holding valve 4 is preferably adjacent to an upper region of the spring chamber 105. This in turn allows for easy production and provision of dimensionally machined portions of the pressure holding valve 4 in the plate 150. Another position of the pressure holding valve 4 in the injection valve 1 is of course possible, with corresponding line holes to the valve body 420 back and from Valve body 420 away to the spring chamber 105 must be provided.

In this embodiment, the valve body 420 of the pressure holding valve 4 centrally seals an inlet bore 153, which branches off from the inlet channel 140 and leads into an upper region of the spring chamber 105, which can be seen in FIGS. 7a and 7b. Preferably, an upstream portion of the inlet bore 153 (see Fig. 7a) extends vertically through the plate 150, wherein in a lower portion of the plate 150, the sealing seat 430 of the pressure holding valve 4 adjoins the upstream portion of the inlet bore 153. Below the sealing seat 430, an annular space adjoins, from which an oblique section (see Fig. 7b) of the inlet bore 153 opens into an upper region of the spring chamber 105. This section may, for. B. be designed as a throttle.

In a preferred embodiment, the pressure-maintaining valve has a valve member 410, which comprises a valve spring 415 and at the free end thereof a valve body 420 which is preferably designed as a hemisphere, the valve spring 415 being seated in a bore 460 provided in a part of the injection valve which also the spring chamber 105 is configured. The valve body 420 is biased in its sealing position on preferably designed as a conical seat sealing seat 430. In its open position, the valve body 420 is seated with its lower edge preferably on the component of the injection valve, in which also the spring chamber 105 is executed. Further, the valve body 420 is guided vertically at its outer diameter to reduce a flutter tendency in the plate 150 in a short dimensionally accurate guide bore 450. Relief of the space below the valve member 420 can be done via the sealing gap between the guide bore 450 and valve body 420.

In this exemplary embodiment, the inlet channel 140 is guided past the pressure-maintaining valve 4 (see Fig. 7a). Here, in the Fig. 7a in the plate 150 obliquely extending portion of the inlet channel 140 may be designed as a throttle 154.

For the pressure holding valve 4 of the second variant advantageous relative dimensions of guide bore 450 and valve body 420 and a favorable area ratio of seat and guide bore of the valve body 420 correspond to the information given in FIG.

8a to 8d show a venting of a pressure retaining valve spring chamber 460, referred to below as the valve spring chamber 460, wherein FIGS. 8a and 8b show a preferred embodiment of the pressure retaining valve 8d according to the invention.

Between the valve spring chamber 460 and preferably the spring chamber 105 there is a fluid connection 462, which is designed as a vent hole 462 and the valve spring chamber 460 vented. The vent hole 462 branches off in an upper region of the spring chamber 105, preferably above the sleeve 405, and extends obliquely down to the valve spring chamber 460 and opens into it. The oblique course allows a simple and cost-effective production of the vent hole 462 in the injection valve body, wherein the vent hole 462 preferably has defined hydraulic properties and is preferably designed as a throttle 464.

Of course, the venting bore 462 may also be provided at a different location in the injection valve 1 between the valve spring chamber 460 and the spring chamber 105. Furthermore, it is possible for purposes of venting the valve spring chamber 462 not fluidly connected to the spring chamber 105 but with a different space at least partially a lower pressure level than the valve spring chamber 460th

The inlet bore 153 may be configured as a simple bore, or as a throttle 435, wherein the pressure in the inlet bore 153 is slightly delayed the spring chamber 105 is impressed. Preferably, the effective diameter of the vent hole 462 at the same pressures less than or equal to the effective diameter of the inlet bore 153 and the throttle 435, so that the spring chamber 105, a sufficiently high pressure can be impressed and the pressure-maintaining valve 4 does not close too quickly or even open.

A special embodiment of the vent hole 462 in the region of the valve spring chamber 460 is shown in FIG. 8c. Such a widening in the region of the opening of the venting bore 462 enables a more homogeneous pressure reduction and reduces the fluttering tendency of the pressure-retaining valve 4.

In these embodiments (FIGS. 8a to 8d), a preferred radius of the valve body 420 designed as a hemisphere is approximately 1-6 mm, with radii of 2.5 mm or 4 mm being particularly preferred. The stroke of the valve member is about 100-250μm, with 150μm are particularly preferably realized.

LIST OF REFERENCE NUMBERS

1

Injector

105

spring chamber

110

biasing spring

115

needle piston

117

Shank (preferably designed as a damping element)

118

control edge

119

control edge

120

annulus

140

inlet channel

142

inlet

145

pressure channel

150

plate

152

inlet bore

153

Inlet bore (2nd variant)

154

storage choke

170

Injection needle

172

pressure shoulder

174

needle chamber

176

pressure chamber

180

fluid communication

190

engine compartment

192

fuel

2

Pump, fuel pump

210

pump pistons

220

pump room

230

pump cylinder

240

Fuel line

245

piston spring

3

control valve

4

Pressure holding valve

405

Abutment, sleeve

410

valve member

415

valve spring

420

spherical body, valve body, sphere, hemisphere

422

Sealing section (of valve member 410)

430

sealing seat

435

throttle

440

disc

445

Sealing gap (play of the needle piston 115 in the spring chamber 105)

450

guide bore

460

(Pressure retaining) valve spring chamber, bore

462

Fluid connection, vent hole

464

Throttle, vent throttle

p ₁₀₅

Spring chamber pressure 105

p ₁₄₀

Supply channel pressure 140 downstream of the dynamic throttle 154

p ₁₇₆

Pressure chamber pressure 176

p ₂₂₀

Pump room pressure 220

Claims (24)

Injection valve for injecting a fluid, in particular for injecting fuel into a combustion chamber of a motor vehicle engine, with a
Pressure retaining valve (4) for fluid pressure of a spring chamber (105), wherein
the pressure-maintaining valve (4) is arranged between an inlet channel (140) of the fluid to a control valve (3) of the injection valve (1) and the spring chamber (105), and via the pressure-maintaining valve (4) a fluid connection in one direction from the inlet channel (140) produced to the spring chamber (105) and thereby the spring chamber (105) a pressure (p ₁₀₅ ) in the inlet channel (140) is impressed, and
the pressure (p ₁₀₅ ) maintained by the pressure-maintaining valve (4) acts on an injection needle (170) of the injection valve (1) together with a biasing spring (110) disposed in the spring chamber (105). Injection valve according to Claim 1, characterized in that the diameter of a pump piston (210) of a pump (2) supplying the injection valve (1) with fluid is reduced to 6.0 to 6.5 mm, in particular to 6.25 mm. Injection valve according to claim 1 or 2, characterized in that the pressure-retaining valve (4) in the spring chamber (105) is arranged and an abutment (405) of the pressure-holding valve (4) in the spring chamber (105) is fixed, wherein a valve member (410) of the pressure-holding valve (4) a biased from the inlet channel (140) inlet bore (152) of the pressure holding valve (4) seals biased. Injection valve according to claim 1 or 2, characterized in that the pressure retaining valve (4) outside the spring chamber (105) is arranged, wherein an abutment of the pressure holding valve (4) is preferably provided in a component of the injection valve, in which also the spring chamber (105). educated is, and a valve member (410) of the pressure holding valve (4) a biased bore (153) seals biased, which connects the inlet channel (140) with the spring chamber (105). Injection valve according to claim 3, characterized in that the abutment (405) is in the spring chamber (105) fixed sleeve (405), wherein on one side of the sleeve (405) has a valve spring (415) of the pressure holding valve (4) and on the the opposite side of the biasing spring (110) is supported, wherein the sleeve (405) allows fluid communication between both sides. Injection valve according to one of claims 1 to 5, characterized in that the valve member (410) of the pressure-holding valve (4) as a sealing portion (422) has an at least partially spherical body (420), in particular a hemisphere, at an at least partially positive Sealing seat (430), in particular a conical seat, in a closed state of the pressure holding valve (4) sealingly ansitzt. Injection valve according to claim 6, characterized in that the body (420) is guided to reduce transverse movements at its outer diameter with close play, wherein the game is preferably 3 to 5μm, in particular 4μm. Injection valve according to claim 6 or 7, characterized in that a fluid connection between the sealing seat (430) of the pressure holding valve (4) and the spring chamber (105) of the injection valve (1) via at least one throttle (435) is made. Injection valve according to one of claims 6 to 8, characterized in that an area ratio of seat to guide bore 1: 1.2 to 1: 2.5, in particular 1: 1.85. Injection valve according to one of claims 1 to 9, characterized in that the pressure-retaining valve (4) is provided in an upper region in or on the spring chamber (105). Injection valve according to one of claims 1 to 10, characterized in that for venting a pressure retaining valve spring chamber (460) there is a fluid connection (462) between the pressure retaining valve spring chamber (460) and the spring chamber (105) or the fluid connection (462) between the pressure retaining valve spring chamber (460) and a space with at least temporarily lower pressure than in the pressure retaining valve spring chamber (460). Injection valve according to claim 11, characterized in that the effective diameter of the fluid connection (462) is smaller than the effective diameter of the inlet bore (153), wherein in the fluid connection (462) is preferably a throttle (464) is provided. Injection valve according to one of Claims 1 to 12, characterized in that the pressure (p ₁₀₅ ) maintained in the spring chamber (105) by means of the pressure retention valve (4) and the pretensioning spring (110) arranged in the spring chamber (105) are directed to a spring chamber (105). reciprocable needle piston (115) act, which in turn acts substantially axially on the injection needle (170) of the injection valve (1). Injection valve according to one of claims 1 to 13, characterized in that a flow restrictor (154) is provided in the inlet channel (140) and the inlet bore (152, 153) of the pressure retaining valve (4) downstream of the flow restrictor (154) from the inlet channel (140). branches. Injection valve according to claim 14, characterized in that the dynamic throttle (154), the inlet bore (152, 153) and optionally further bores and throttles, such as a pump chamber throttle between the pressure channel (145) and a pump chamber (220) the pump (2), in a plate (150) are provided, which seals the spring chamber (105) above. Injection valve according to claim 15, characterized in that the plate (150) is a boundary side of a pump chamber (220) of the pump (2), in particular the bottom of the pump chamber (220). Injection valve according to one of claims 1 to 16, characterized in that in a region of the spring chamber (105), which faces away from the biasing spring (110), there is a fluid connection (180) to the inlet channel (140). Injection valve according to claim 17, characterized in that the fluid connection (180) branches off with the inlet channel (140) between the injection needle (170) and the needle piston (115), preferably at the bottom of the spring chamber (105). Injection valve according to one of claims 13 to 18, characterized in that the play of the needle piston (115) on the inner wall of the spring chamber (105) is dimensioned such that the fluid pressure in the spring chamber (105) degraded in each case a first injection of an injection cycle substantially is and corresponds to a low pressure in the inlet channel (140). Injection valve according to one of claims 13 to 19, characterized in that the needle piston (115) via a circumferential sealing gap (160) from the inner wall of the spring chamber (105) is spaced and / or that the fluid connection (180) is designed as a throttle. Injection valve according to one of claims 13 to 20, characterized in that a side wall of the needle piston (115), which faces the inner wall of the spring chamber (105), is designed as a higher-order surface, in particular as a part spherical surface. Injection valve according to one of Claims 1 to 21, characterized in that the injection needle (170) has a shaft (117), preferably integrally formed with the injection needle (170), on the spring-chamber-side end, on which a control edge (118) is formed with a second in the injection valve (1) provided control edge (119), cooperates such that the control edges (118, 119) control a fluid flow along the shaft (117) in response to the stroke of the injection needle (170). Injection valve according to claim 22, characterized in that an annular space (120) formed around the shaft (117) is provided at the injection needle-side end of the shaft (117), which, depending on the position of the control edges (118, 119), is connected to the spring chamber (105). can come into fluid communication. Injection valve according to claim 22 or 23, characterized in that the needle piston (115) acts on the injection needle (170) via the shaft (117).

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