EP1311755B1 - Fuel injection device - Google Patents

Description

State of the art

The invention relates to a fuel injection device according to the preamble of patent claim 1.

For a better understanding of the description and the claims, some terms are explained below: The fuel injection device according to the invention may be formed both stroke-controlled and pressure-controlled. In the context of the invention, a stroke-controlled fuel injection device is understood to mean that the opening and closing of the injection opening takes place by means of a displaceable valve member due to the hydraulic interaction of the fuel pressures in a nozzle space and in a control space. A pressure reduction within the control chamber causes a stroke of the valve member. Alternatively, the deflection of the valve member by an actuator (actuator, actuator) take place. In a pressure-controlled fuel injection device according to the invention, the valve member is moved by the pressure prevailing in the nozzle chamber of an injector fuel pressure against the action of a closing force (spring), so that the injection port for injection of the fuel from the nozzle chamber is released into the cylinder. The pressure with which fuel exits the nozzle chamber into a cylinder of an internal combustion engine is referred to as injection pressure , while a system pressure is understood to mean the pressure below which fuel is available or stored in the fuel injector. Fuel metering means to provide a defined amount of fuel for injection. Leakage is understood to mean an amount of fuel that arises during operation of the fuel injection device (eg a pilot leakage ), is not used for injection and is conveyed back to the fuel tank. The pressure level of this leakage may have a steady state pressure, with the fuel subsequently being expanded to the pressure level of the fuel tank.

A stroke-controlled injection has become known for example from DE 196 19 523 A1. The achievable injection pressure is limited here by the pressure storage space (rail) and the high pressure pump to about 1600 to 1800 bar.

To increase the injection pressure, a pressure booster unit is possible, as is known, for example, from US Pat. No. 5,143,291 or US Pat. No. 5,522,545. The disadvantage of these pressure-translated systems lies in a lack of flexibility of the injection and a poor quantity tolerance in the metering of small amounts of fuel.

A pressure booster unit arranged in the injector is known from EP 0 691 471 A1. A bypass line for a pressure injection and a pressure chamber of the pressure booster unit are in series, so that the bypass line only continuously is as long as a displaceable piston unit of the pressure booster unit is not moved and is fully retracted.

From EP 0 691 471 A a fuel injection device is known in which a pressure booster unit is arranged between a pressure storage space and a nozzle space, which has a displaceable piston unit in order to increase the pressure of the fuel to be supplied to the nozzle space. The piston unit for controlling the pressure booster unit has a transition from a larger to a smaller piston cross-section and a difference space formed thereby, which is connected via a filling path with a filling valve to the pressure storage space.

The state of the art WO 01/52916 A2 according to Article 54 (3) EPC for the states DE, FR, GB and IT discloses a fuel injection device in which a pressure booster unit is arranged between a pressure storage space and a nozzle space, which has a displaceable piston unit to increase the pressure of the fuel to be supplied to the nozzle chamber. The piston unit for controlling the pressure booster unit has a transition from a larger to a smaller piston cross-section and a difference space formed thereby, which is connected via a filling path with a filling valve to the pressure storage space. The piston unit is pressed by means of a spring in a low-pressure chamber via a stop for the spring in the region of the larger piston cross section in its initial position.

Subject and advantages of the invention

To increase the injection pressure and the flexibility of the injection in a common rail injection system, a pressure booster unit is advantageous. In order to keep the manufacturing costs and thus the manufacturing costs low, a control of the pressure booster unit is used with a simple 2/2-way valve.

To reduce the amount of control during the control of the pressure booster unit and to carry out a quick return of the piston unit of the pressure booster unit, a fuel injection device according to claim 1 is proposed.

Through the filling valve, an additional filling path is released for resetting the piston unit. The control of the filling valve without actuator by a pressure difference at the pressure booster unit to keep the design effort low.

In order to achieve a defined pressure difference on the valve body of the filling valve, a throttling can be formed between the valve body and the guide bore. An additional supply line with a preferably small-held throttle serves to initiate the provision of the piston unit. If the filling valve has a spring and corresponding pressure surfaces pressurizable by fuel for switching the filling valve, the valve body of the filling valve can be easily transferred to the closed position of the filling valve.

drawing

Fig. 1

eine erste Beschaltung der Druckübersetzungseinheit;

Fig. 2

eine zweite Beschaltung der Druckübersetzungseinheit.

Two embodiments of the inventive circuit of a pressure booster unit of a fuel injection device are shown in the schematic drawing and are explained in the following description. It shows:

Fig. 1

a first connection of the pressure booster unit;

Fig. 2

a second circuit of the pressure booster unit.

Description of the embodiments

Fig. 1 shows a part of a common rail system. This comprises a pressure booster unit 1, the drive of which is apparent from FIG. 1, and an injector (nozzle needle displaceable to carry out the injection process). To control the pressure booster unit 1, the pressure in the formed by a transition from a larger to a smaller piston cross-section differential space 2 is used. For refilling and deactivating the pressure booster unit 1, the differential space 2 is acted upon by a supply pressure (rail pressure) by connecting the pressure booster unit 1 via a supply line 3 to a common pressure storage space (rail) of the common rail system, not shown in FIG. Then prevail at all pressure surfaces of a piston unit 4, the same pressure conditions (rail pressure). The piston unit 4 is druckausgegfichen. By an additional spring 5, the piston unit 4 is pressed into its starting position. To activate the pressure booster unit 1, the differential space 2 is depressurized by means of a valve 6 and the pressure booster unit 1 generates a pressure boost according to the area ratio. By this type of control can be achieved that for resetting the pressure booster unit 1 and for refilling a pressure chamber 7, a large primary chamber 8 need not be depressurized. With a small hydraulic ratio, the relaxation losses can be greatly reduced. Furthermore, this type of control of the pressure booster unit 1 can be achieved by means of a simple 2/2-way valve.

To control the pressure booster unit 1 serve a check valve 9, a filling valve 10 and a throttle 11. The throttle 11 and the filling valve 10 connect the differential chamber 2 with standing under supply pressure fuel from the pressure storage chamber. The 2/2-way valve 6 connects the differential chamber 2 to a leakage line 12. To activate the pressure booster unit 11 opens valve 6. The differential chamber 2 is relieved of pressure via the valve 6. The pressure in the differential space 2 drops sharply. While the valve 2 is open, flows via the throttle 11, a loss amount in the leakage line 12. The throttle 11 should be designed as small as possible become. The amount of control during injection is reduced. The throttle 11 may be integrated in the valve body or the valve seat in the filling path 13. Likewise, the throttle 11 may be integrated into the piston unit 4 or formed by the gap leakage of the piston guides. Possibly. can be dispensed with appropriate design and the throttled inlet 13 '.

The pressure in the differential space 2 is used to control the filling valve 10. If the pressure drops in the differential chamber 2 during activation of the pressure booster unit 1, the filling valve 10 closes the filling path 13. Thus, no loss can flow through the filling path 13 in the leakage.

To deactivate the pressure booster unit 1, the valve 6 is closed and in the differential space 2 is built on the throttle 11, the rail pressure. Then the filling valve 10 opens and releases the filling path 13. The required when deferring the piston unit 4 filling the differential space 2 can be done quickly and without strong throttling. As a result, a smaller spring force is required to return. This brings great structural advantages, since in modern engines in the existing space no large spring forces can be realized.

The filling valve 10 is designed so that it closes at a certain pressure difference Δp1 between the valve inlet and the differential chamber 2. For this purpose, the valve body 14 has a pressure surface for the valve inlet and a pressure surface for the differential space 2. Furthermore, the valve body 14 is acted upon by an opening spring force. If the pressure in the differential chamber 2 falls below the set pressure difference Δp1 in relation to the pressure in the valve inlet, then the filling valve 10 rises. If the pressure booster unit 1 deactivates, the pressure in the differential chamber 2 rises again and reaches the pressure in the valve inlet minus the pressure difference Δp1, the filling valve opens 10 and the filling path 13 is released again.

This results in a fast filling of the differential space 2. The pressure difference necessary for switching the filling valve 10 is determined by the spring force and the pressure surfaces. To achieve a defined pressure difference at the formed by a ball valve body 14, a restriction between the valve body 14 and the valve housing must be present. This can be done, for example, by limiting the valve lift or by throttling between the valve body 14 and its guide bore.

If the 2/2-way valves 6 and 16 are closed, the injector is under the pressure of the pressure storage chamber 7. The pressure booster unit 1 is in the starting position. Now, by opening the valve 16, an injection with rail pressure can take place, because a nozzle needle 17 can lift off from a sealing surface 18 as a result of the hydraulic pressure conditions at the nozzle needle 17. If an injection with a higher pressure is desired, the 2/2-way valve 6 is activated (opened) and thus reaches a pressure boost.

An alternative control of the pressure booster unit 1 results from FIG. 2. The inlet to the differential space 2 is regulated by the throttle 11 and the filling valve 19. The inlet side (in front of the sealing seat) of the filling valve 19 is pressure balanced. In the region of the sealing seat is a pressure surface 20 which is acted upon by a pressure present in the differential space 2. If the pressure in the differential chamber 2 below the closing pressure, the pressure force 20 is smaller than the force of a spring 23 and the filling valve 19 closes the filling path 13. If the pressure in the differential chamber 2 on the closing pressure increases, the pressure force on the pressure surface 20 is greater than the force of Spring 23 and the filling valve 19 opens the filling path 13.

To achieve a defined pressure difference on the valve body of the filling valve 19, a restriction must be formed in the sealing seat or an additional throttle 23 must be connected upstream of the filling valve 19. The piston unit 4 may be formed in one piece as well as in several parts. The filling valve 19 may also be integrated in the piston unit 4. The piston unit 4 may be formed in one piece as well as in several parts. The filling valve 10, 19 may also be integrated in the piston unit 4. When the pressure booster unit is deactivated, the rail pressure is guided via the check valve 9 downstream to the injector. Therefore, the inlet of the filling valve 10, 19 may also be connected downstream of the check valve 9. This results in a connection of the filling valve inlet with standing under supply pressure fuel from the accumulator chamber via the check valve. 9

LIST OF REFERENCE NUMBERS

1

Pressure booster unit

2

differential chamber

3

supply line

4

piston unit

5

feather

6

Valve

7

pressure chamber

8th

primary chamber

9

check valve

10

filling valve

11

throttle

12

leakage line

13

fill path

13 '

Intake

14

valve body

15

sealing seat

16

Valve

17

nozzle needle

18

sealing surface

19

filling valve

20

print area

21

leakage line

22

feather

23

throttle

Claims (7)

1. Fuel injection device with a pressure intensification unit (1) which is arranged between a pressure storage space and a nozzle space and which has a displaceable piston unit (4) in order to intensify the pressure of the fuel to be supplied to the nozzle space, the piston unit (4), for the control of the pressure intensification unit (1), having a transition from a larger to a smaller piston cross section and a differential space (2) which is formed by this means and is connected via a filling path (13) with a filling valve (10; 19) to the pressure storage space, a spring (5) which presses the piston unit (4) into its starting position being provided in the differential space (2), characterized in that the filling valve (10; 19) can be controlled by the pressure ratios in the differential space (2).
2. Fuel injection device according to Claim 1, characterized in that the differential space (2) is additionally connected via a feed line (13') with a throttle (11) to the pressure storage space.
3. Fuel injection device according to one or more of the preceding claims, characterized in that the filling valve (19) has a throttling in the sealing seat.
4. Fuel injection device according to one or more of the preceding claims, characterized in that the filling valve (10; 19) has a spring and corresponding pressure surfaces, which can be pressurized by fuel, for switching the filling valve (10; 19).
5. Fuel injection device according to one or more of the preceding claims, characterized in that the filling valve (10; 19) is designed in such a manner that the filling valve (10; 19) is opened if the pressure in the differential space (2) is higher than the pressure in the valve inlet minus the pressure difference Δp1 which has been set.
6. Fuel injection device according to one or more of the preceding claims, characterized in that the filling valve (10; 19) is designed in such a manner that the filling valve (10; 19) is closed if the pressure in the differential space (2) is lower than the pressure in the valve inlet minus the pressure difference Δp1 which has been set.
7. Fuel injection device according to one or more of the preceding claims, characterized in that a 2/2-way directional control valve (6) is provided between the differential space (2) and the leakage line (12) to control the pressure intensification unit (1).

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