EP1503073A1 - Unit injector - Google Patents

Abstract

The pump module (1) incorporates a piston (11) spring-loaded (14) upwards and pushed downwards in a cylinder (12) to pump the fuel. The electronic control module (2) has a socket (26) for an electrical connection. The electronic control module has an adjustment device (24) and a control valve (231) with a valve seat (234). Fuel is admitted into a nozzle feed line (21) via a throttle (27). Return fuel (22) may be admitted into a control chamber (232).

Description

The invention relates to a pump-nozzle device with a Pump, a valve and a nozzle unit. Such a pump-nozzle device is used in particular for fuel supply in a combustion chamber of a direct injection internal combustion engine, used in particular a diesel internal combustion engine. The pump, a control unit, in addition to the valve also a Actuator comprises, which preferably consists of a piezo stack is formed, and the nozzle unit form a structural unit. The drive of a piston of the pump is preferably carried out via a camshaft of an internal combustion engine by means of a rocker arm. The pump is connected via the valve to a low-pressure fuel supply device hydraulically coupled. It is hydraulically coupled on the output side with the nozzle unit. Start of injection and injection quantity are by the Valve and its actuator determined. Due to the compact Construction of the pump-nozzle device results in a very low High pressure volume and high hydraulic stiffness. There are so very high injection pressures of about 2000 bar allows. This high injection pressure in conjunction with the good controllability of the start of injection and the injection quantity enable a significant reduction in emissions at the same time low fuel consumption when used in Internal combustion engines.

From DE 198 35 494 C2, a pump-nozzle device is known with a pump and a valve with a valve member, the hydraulic coupling of a Absteuerraums with a Flow channel controls. The drainage channel is hydraulically coupled with the pump and a nozzle unit. An inlet channel is provided which is hydraulically coupled to the Absteuerraum. The valve member is a piezoelectric actuator assigned, via which the valve member between two end positions can be adjusted. In a first end position of the valve member, the drainage channel is hydraulically coupled with a Absteuerraum and this in turn with the inlet channel. In a second end position of the valve member is the Drain channel hydraulically decoupled from the discharge chamber. In the first end position of the valve member is during a Delivery strokes of the pump fluid from the inlet channel via the Absteuerraum and the drainage channel sucked by the pump. While a working stroke of a pump piston of the pump is in the first end position of the valve member fluid from the pump pushed back via the supply channel, the discharge chamber in the drainage channel. In the second end position of the valve member can during the delivery stroke of the pump piston because of the missing hydraulic coupling of the drainage channel with the discharge chamber and no fluid is pushed back to the drain channel and the pump piston generates high pressure. With crossing a predetermined pressure threshold opens a nozzle needle the Nozzle unit, a nozzle of the nozzle unit and there is a Injection of the fluid. The end of injection is determined by that the valve member by means of the actuator in its first end position is controlled and so fluid over the Return flow channel in the Absteuerraum and the inlet channel can, which has the consequence that the pressure in the pump and thus also decreases in the nozzle unit, which in turn to a closing of the nozzle unit leads. In this so-called. Absteuervorgang High noise emissions are generated. such Noise emissions are measured by the driver of a motor vehicle, in which the pump-nozzle device can be installed, perceived as unpleasant and need on the one hand with regard to on the highest possible comfort and on the other hand due to ever stricter legal provisions regarding Noise emissions from vehicles are largely avoided.

The object of the invention is a pump-nozzle device which ensures low noise emissions during operation.

The task is solved by the characteristics of the independent Claim. Advantageous developments of the invention are characterized in the subclaims.

The invention is based on the recognition that during the Operation of the Prior Art Pump-Nozzle Device substantially caused noise emissions are due to cavitations after making the hydraulic Coupling between the drainage channel with high pressure standing fluid and the Absteuerraum and the drainage channel. Of the resulting Absteuerimpuls leads to pressure waves of high amplitude in the fluid in the region of the discharge chamber and the feed channel, in the form of sound waves from the pump-nozzle device be transmitted to the outside.

The invention is characterized in that in the inlet channel a throttle element is provided. The throttle element causes a rapid increase in pressure in the Absteuerraum and slows down the outflow of fluid into the inlet channel. Thereby becomes the time within which cavitations occur greatly reduced and so the generation of sound emissions strongly attenuated in a simple way. Through the throttle element in particular high-frequency noise components significantly reduced during the Absteuervorgangs. By the Reducing the cavitation time is also the so-called. Cavitation erosion on the valve member and on the walls of the Absteuerraums significantly reduced. Cavitation erosion is caused by the imploding of gas bubbles, the cavitation by Evaporation of the fluid can be formed. During the period, within which cavitations occur in the region of the valve member is the pressure gradient on the different valve surfaces the valve member is extremely unsteady and precise Setting the position of the valve member thus difficult to achieve. Thus, the reduction in cavitation time, which is caused by the throttle element, also a more precise control of the valve member.

In an advantageous embodiment of the invention that is Throttle arranged near the Absteuerraums. So be the noise emissions are particularly effectively reduced. Further This is also a sealing connection between the inlet channel and a fuel supply device associated therewith, which is usually spared by means of an O-ring and thus increases their life.

In a further advantageous embodiment of the invention are the Absteuerraum and the throttle element designed so that the pump via the inlet channel at a given Low pressure value in the inlet channel completely with fluid over the inlet channel within a predetermined period of time is fillable. This has the advantage that then the operation the pump-nozzle device, d. H. the earliest possible start of injection and the maximum possible injection quantity the throttle element are not affected.

In a further advantageous embodiment of the invention are the Absteuerraum and the throttle element designed so that an end of the injection of fluid through the nozzle unit is controllable by means of the valve member and that independently from the throttle element. This has the advantage that the Do not reduce the noise emissions to an influence the possible end of the injection leads. The throttle element thus does not affect the end of the injection.

In a further advantageous embodiment of the invention is the throttle element in the form of a stepped bore of the inlet channel educated. This has the advantage of being easy is to produce.

In a further advantageous embodiment of the invention At least two throttle elements are arranged in the inlet channel. This results in a further improved reduction the noise emissions.

In a further advantageous embodiment of the invention the at least two throttle elements are arranged so spaced apart, that they have predetermined frequencies of pressure oscillations of the fluid in the inlet duct or in predetermined others Transform frequency ranges. This results in a very effective reducing z. B. audible to humans Sound emissions.

Figur 1

ein erstes Ausführungsbeispiel einer Pumpe-Düse-Vorrichtung,

Figur 2

eine Ausschnittsvergrößerung der Pumpe-Düse-Vorrichtung gemäß Figur 1,

Figur 3

ein zweites Ausführungsbeispiel der Pumpe-Düse-Vorrichtung,

Figur 4

den Verlauf des Drucks innerhalb des Hochdruckbereichs der Pumpe-Düse-Vorrichtung aufgetragen über die Zeit t und

Figur 5

der eingespritzte Kraftstoffmassenstrom Qinj aufgetragen über die Zeit t.

Embodiments of the invention are explained below with reference to the schematic drawings. Show it:

FIG. 1

A first embodiment of a pump-nozzle device,

FIG. 2

an enlarged detail of the pump-nozzle device according to Figure 1,

FIG. 3

A second embodiment of the pump-nozzle device,

FIG. 4

the course of the pressure within the high pressure region of the pump-nozzle device over the time t and

FIG. 5

the injected fuel mass flow Qinj is plotted over time t.

Elements of the same construction and function are cross-figurative provided with the same reference numerals.

A pump-nozzle device (Figure 1) comprises a pump unit 1, a control unit 2 and a nozzle unit 5. The Pump-nozzle device is preferably used for feeding of fuel into the combustion chamber of a cylinder of an internal combustion engine. The internal combustion engine is preferably as Diesel internal combustion engine trained. The internal combustion engine has an intake tract, which by means of gas inlet valves with cylinders can be coupled and is sucked in through the air. The Internal combustion engine also has an exhaust tract over controlled the exhaust valve to eject from the cylinders Discharges gases. The cylinders are each assigned pistons, each via a connecting rod with a crankshaft are coupled. The crankshaft is with a camshaft coupled.

The pump unit comprises a piston 11, a pump body 12, a pumping chamber 13 and a pump return means 14, the is preferably designed as a spring. The piston 11 is in built-in state in an internal combustion engine with a camshaft coupled, preferably by means of a rocker arm, and is driven by this. The piston 11 is in one Recess of the pump body 12 out and determined dependent from its position the volume of a pumping space 13. The pump return means 14 is designed and arranged that limited by the piston 11 volume of the pump chamber 13 has a maximum value when on the piston no outer Forces, d. H. Forces beyond the coupling with the camshaft be transmitted.

The nozzle unit 5 comprises a nozzle body 51 in which a Nozzle return means 52, as a spring and possibly in addition is designed as a damping unit, and a needle 53 is arranged are. The needle 53 is in a recess of the nozzle body 51 arranged and is in the range of a needle guide 55 led. In a first state, the needle 53 is located at a Needle seat 54 and thus closes a nozzle 56, the Feeding the fuel into the combustion chamber of the cylinder Internal combustion engine is provided. The nozzle unit 5 is preferably, as illustrated, as an inwardly opening nozzle unit intended.

In a second state, the needle 53 is slightly spaced to the needle seat 54 toward the nozzle return means 52 and thus releases the nozzle 56. In this second state, fuel enters the combustion chamber metered to the cylinder of the internal combustion engine. The first or second state is taken depending on a balance of forces from the force generated by the nozzle return means 52 acting on the needle 53 and from the counteracting this Force caused by the hydraulic pressure in the area of the needle heel 57 is caused.

The control unit comprises an inlet channel 21 and an outlet channel 22. The inlet channel 21 and the outlet channel 22 are hydraulically coupled by means of a valve. The inlet channel 21 is from a low-pressure side port of the pump-nozzle device led to the valve. The drainage channel 22 is hydraulically coupled to the pumping chamber 13 and is out led to the needle heel 57 and is hydraulically dependent from the state occupied by the needle 53 the nozzle 56 coupled.

The valve comprises a valve member 231, preferably as so-called A-valve is formed, d. H. it opens to the outside against the flow direction of the fluid. The valve includes a Absteuerraum 232, which is hydraulically coupled with the inlet channel 21 and by means of the valve member 231 with a high pressure chamber 233 is hydraulically coupled. The high pressure room 233 is hydraulically coupled to the drainage channel 22nd

In the closed position of the valve member 231 is the Valve member 231 on a valve seat 234 of a valve body 237 on. Furthermore, a valve return means 235 is provided, which is arranged and adapted to be the valve member 231 in an open position, d. H. spaced to the Valve seat 234 presses when by an actuator 24th acting on the valve member forces are less than that Forces generated by the valve return means 235 on the valve member 231 act. The actuator 24 is preferably as Piezo stack formed. But he can also do another One skilled in the art and suitable for such an application Actuator, such as an electromagnetic actuator be.

The actuator 24 is preferably by means of a transformer, which preferably amplifies the stroke of the actuator 24, coupled to the valve member 231. On the actuator 24 is preferably also a plug 26 for receiving of electrical contacts for controlling the actuator 24 provided.

In the open position of the valve member 231 is in one movement of the piston 11, the upward d. H. towards the way directed from the nozzle 56, fuel via the inlet channel 21 sucked towards the pump room 13. As long as the valve member 231 during a subsequent downward movement of the piston 11, d. H. with a movement directed towards the nozzle 56, still in its open position, the one in the Pump chamber 13 located fuel back through the valve in the Absteuerraum 232 and possibly in the inlet channel 21st pushed back.

However, as soon as the downward movement of the piston 11, the valve member 231 is controlled in its closed position, is in the pump chamber 13 and thus also in the flow channel 22nd and compresses the fuel located in the high pressure space 233, causing the pressure with increasing downward movement of the piston 11 in the pump chamber 13, in the high-pressure chamber 233 and in the Drain channel 22 increases. According to the rising pressure in the Drain passage 22 also increases due to the hydraulic pressure caused force on the needle heel 57 in the direction an opening movement of the needle 53 to release the nozzle 56th acts. When the pressure in the drain channel 22 exceeds a value, in which caused by the hydraulic pressure Force on the needle heel 57 is greater than this counteracting force of the nozzle return means 52, moves The needle 53 moves away from the needle seat 54 and so gives the nozzle 56 for the fuel supply to the cylinder of the internal combustion engine free. The needle 53 then moves back in the needle seat 54 and thus closes the nozzle 56 when the Hydraulic pressure in the drain channel 22 falls below the value, in which the caused by the hydraulic pressure at the needle heel 57 Force is smaller than that through the nozzle return means 52 induced force. The time at which this value is exceeded and thus the fuel metering can be stopped by controlling the valve member 231 from its closed position to an open position to be influenced.

By controlling the valve member from its closed position in its open position, the hydraulic coupling between the high-pressure chamber 233 and the Absteuerraum 232 and the Inlet channel 21 made. Due to the prevailing when opening high pressure difference between the fluid in the High-pressure chamber 233 and the fluid in the Absteuerraum 232 and the inlet channel 21 then flows from the fuel of the high-pressure chamber 233 at very high speed, as a rule at the speed of sound, in the Absteuerraum 232 and on in the inlet channel 21. This then the pressure in the High-pressure chamber 233, in the pump chamber 13 and the drain passage 22nd rapidly reduced so much that of the nozzle return means 52 forces acting on the needle 53 cause the needle 53 moves into the needle seat 54 and thus then the nozzle 56 closes.

In the inlet channel 21 (Figure 2), a throttle element 27 is arranged. The throttle element 27 causes a fast Pressure increase in the Absteuerraum 232 and slows down the outflow of the fuel in the inlet channel 21. This is the length of time within which cavitations occur is strong reduces and thus the generation of sound emissions to simple Way strongly muted. Be through the throttle element especially high-frequency noise during the Absteuervorgangs significantly reduced. By reducing the Cavitation time, d. H. the time while the fuel is from High-pressure chamber 233 toward the Absteuerraum 232 with sound velocity flows and at which vapor bubbles form, the then in a region of lower flow velocity implode again and thereby generate sound and also damage on the valve body, greatly reduced. So The generation of sound emissions is easy heavily steamed.

By the throttle element 27 are in particular higher-frequency Noise components during the Absteuervorgangs significantly reduced. By reducing the cavitation time will too the cavitation erosion on the valve member 231 and on the walls the Absteuerraums significantly reduced. This is preferred Throttling element 27 is arranged very close to the diversion chamber 232, as shown in Figure 2. The closer the throttle element 27 is arranged at the Absteuerraum, the more effective the noise emissions are reduced. Furthermore, it will be like that a sealing connection between the inlet channel and a this associated fuel supply device, which usually done by means of an O-ring, spared and so their Lifespan increased.

The throttle element is particularly easy through a stepped bore produced. For this purpose, preferably a first Pilot hole and the holes can then be rounded hydroerosiv become. In the hydroerosive rounding effect in Particles containing fluid round off the given Areas. However, the throttle element 27 can also be used as an insert be used in the inlet channel 21.

In a further embodiment of the pump-nozzle device (Figure 3) are at least two throttle elements 16, 61, 62, 63rd arranged in the inlet channel 21. By a suitable dimensioning the throttle elements 60 to 63 and a suitable one Spacing the throttle elements 60 to 63 can predetermined Frequencies of the pressure oscillations of the fuel in the inlet channel Be intentionally subdued or into predetermined others, preferably inaudible to humans, frequency ranges be transformed. The throttle elements act 60 to 63 in conjunction with the inlet channel 21 as Resonators and reflect each pressure waves with a given wavelength, so that the corresponding wave dissipated.

It is advantageous if the or the Drosselelemte 27, 60th to 63 and the diversion room are designed so that the Pumping chamber 13 via the inlet channel 21 even at a predetermined Low pressure value, preferably 3 to 10 bar in the inlet channel 21 can be filled within a predetermined period of time is. The predetermined period of time depends on the Speed of the crankshaft selected. This ensures that that the operation of the pump-nozzle device, d. H. the earliest possible start of injection and the maximum possible Injection amount through the throttle element 27, 60 to 63 not to be influenced.

It is also advantageous if the Absteuerraum 232 and the or the throttle elements 27, 60 to 63 are formed that an end of the injection of fluid through the nozzle unit is controllable by means of the valve member 231 and that independently from the throttle element or elements 27, 60 to 63. This has the advantage of reducing the noise emissions not to influence the possible end of the Injection leads. In Figure 4 are different pressure gradients plotted over time t for different embodiments the pump-nozzle device shown. The threshold pthr of pressure is the value at which the pressure Amount of force on needle heel 57 amount of the Force caused by the nozzle return means 52 becomes. When the pressure rises, the Nozzle 56 released. When the pressure drops, the nozzle becomes 56 closed by the needle 53rd

The solid line in Figure 4 shows an exemplary Pressure curve in a pump-nozzle device according to FIG 2 in the drain channel 22. At a time t1 is the Threshold pthr of pressure exceeded and thus begins the fuel metering into the cylinder, as in FIG. 5 Plotted on the basis of the metered amount of fuel Qinj the time t is shown. At a time t4 is then the threshold value pthr of the pressure falls below again and thus ending the fuel metering.

The throttle element 27 is formed and arranged and also the Absteuerraum 27 is formed so that in Comparison to a pump-nozzle device without the throttle element 27 the pressure drop at pressures above the threshold pthr is identical (see dashed line of Pressure).

Dotted the pressure curve is shown for the case at the throttle element 27 is dimensioned so that in the given low pressure value no complete filling of the Pump room 13 is guaranteed. In this case, the Pressure build-up in the pump chamber 13 only delayed and the Threshold pthr is only reached at time t2. The Throttle element 27 is dimensioned in this case so that after a Absteuern of the valve by the throttle effect of Throttle element 27, the pressure already above the threshold pthr drops more slowly than in the unthrottled case. This also has the consequence that the end of the fuel metering only delayed occurs at time t5.

The dotted line sets the course of the dotted Line in the event that the throttle element 27 so dimensioned is that its throttling effect only below the Threshold pthr to a change in pressure drop in Comparison with the unthrottled case leads.

Claims (7)

A pump-nozzle apparatus comprising a pump and a valve having a valve member (231) which controls the hydraulic coupling of a discharge chamber (232) to a drain passage (22) hydraulically coupled to the pump and a nozzle unit (5) an inlet channel (21) is provided, which is hydraulically coupled to the Absteuerraum (232), characterized in that the inlet channel (21) comprises a throttle element (27, 60 to 63). Pump-nozzle device according to claim 1, characterized in that the throttle element (27, 60 to 63) is arranged near the Absteuerraums (232). Pump-nozzle device according to one of the preceding claims, characterized in that the Absteuerraum (232) and the throttle element (27, 60 to 63) are formed so that the pump via the inlet channel (21) even at a predetermined low pressure value in the Inlet channel (21) is completely filled with fluid through the inlet channel (21) within a predetermined period of time. A pump-nozzle device according to any one of the preceding claims, characterized in that the spill space (232) and the throttle element (27, 60 to 63) are formed so that an end of the injection of fluid through the nozzle unit (5) by means of the valve member (231) is controllable independently of the throttle element (27, 60 to 63). Pump-nozzle device according to one of the preceding claims, characterized in that the throttle element (27, 60 to 63) in the form of a stepped bore of the inlet channel (21) is formed. Pump-nozzle device according to one of the preceding claims, characterized in that at least two throttle elements (60 to 63) in the inlet channel (21) are arranged. A pump-nozzle device according to claim 6, characterized in that the throttle elements (60 to 63) are arranged at a distance such that they dampen predetermined frequencies of the pressure oscillations of the fluid in the inlet channel (21) or transform them into predetermined other frequency ranges.

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