EP1383999A2

EP1383999A2 - Fuel injection device for an internal combustion engine

Info

Publication number: EP1383999A2
Application number: EP02740251A
Authority: EP
Inventors: Gérard Duplat; Raphael Pourret; Peter Voigt
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2001-04-21
Filing date: 2002-04-12
Publication date: 2004-01-28
Anticipated expiration: 2022-04-12
Also published as: EP1383999B1; HUP0301200A2; JP2004519588A; DE10119603A1; PL359100A1; US20040025840A1; US6889661B2; WO2002086305A2; WO2002086305A3; DE50207204D1

Abstract

The invention relates to an internal combustion engine comprising a high-pressure fuel pump (10) and a fuel injection valve (12) for a cylinder in the combustion engine. Said high-pressure fuel pump (10) comprises a working chamber (22) and the fuel injection valve (12) comprises an injection valve member (28) which controls at least one injection opening (32) and which can be displaced in the direction of the opening (29) counter to the force of a closing spring (44), whereby the closing spring (44) is supported by a injection valve member (28) and a displaceable accumulator piston (50), which is impinged upon by pressure produced in the working chamber (22) of the pump on the side facing away from the closing spring (44). Said accumulator piston (50) can be displaced counter to the force of the closing spring (44) into the accumulator chamber (54) and the alternative stroke of the piston (50) into the accumulator chamber (54) is limited by a stop (53). The accumulator piston (50) comprises a shaft section (64) having a small diameter arranged in an output position in a connecting bore (56) and a shaft section (63) having a larger diameter arranged outside the connecting bore (56) in the direction of the working chamber (22) of the pump. The shaft section (63) of the accumulator piston having a larger diameter plunges into the connecting bore (56) during the alternating stroke of the accumulator piston (50) when said piston moves into the accumulator chamber (54).

Description

Fuel injection device for an internal combustion engine

State of the art

The invention is based on one

Fuel injection device for an internal combustion engine according to the preamble of claim 1.

Such a fuel injection device is known from DE 39 00 763 AI. This fuel injection device has a high-pressure fuel pump and a fuel injection valve for a cylinder of the internal combustion engine. The high-pressure fuel pump has a pump piston which is driven by the internal combustion engine and delimits a pump work space, a connection of the pump work space to a relief space being controlled by an electrically controlled valve. The fuel injection valve has an injection valve member, through which at least one injection opening is controlled and which can be moved in an opening direction against the force of a closing spring by the pressure prevailing in a pressure chamber connected to the pump work chamber. The closing spring is supported on the one hand at least indirectly on the injection valve member and on the other hand at least indirectly on a storage piston. On its side facing away from the closing spring, the storage piston is acted upon by the pressure in the pump work space and can be moved in a stroke movement against the force of the closing spring. The accumulator piston can be moved into the accumulator chamber from an initial position at low pressure in the pressure chamber, the deflection stroke movement of the accumulator piston in the accumulator chamber being limited by a stop. The storage piston has a shaft part which is guided in a connecting bore between the storage space and the pump working space and a larger cross section outside the connecting bore in the storage space than on the shaft part. By one between the Connection bore and the shaft part existing throttle gap is damped the evasive stroke movement of the pump piston, since in this case fuel displaced from the pump working space into the storage space must pass through the throttle gap, which leads to damping the movement of the storage piston. The damping of the movement of the storage piston can be constant over the stroke of the storage piston or in such a way that the damping is strong at the beginning of the evasive stroke movement and then decreases. It was found that the damping achieved here is not sufficient, so that the accumulator piston hits the stop at high speed and thereby causes disturbing noises.

Advantages of the invention

The fuel injection device according to the invention with the features according to claim 1 has the advantage that by forming the storage piston with the shaft part, the shaft section arranged in the connecting position in the closed position of the storage piston with a smaller cross-section and the shaft section immersed in the connecting bore during the evasive stroke movement has a larger cross-section, at the beginning of the evasive stroke movement there is less damping and with increasing evasive stroke movement there is greater damping of the movement of the accumulator piston, so that it hits the stop only at a low speed and does not cause any disturbing or less noise.

Advantageous refinements and developments of the fuel injection device according to the invention are specified in the dependent claims. The embodiment according to claim 2 enables a stronger damping, which is only effective after a partial escape stroke of the storage piston. The embodiment according to claim 3 enables a further reduction in the speed at which the storage piston hits the stop, since the effective cross-sectional area on the storage piston, to which the pressure in the pump work chamber acts, is reduced when the shaft section with the larger cross section is immersed.

drawing

An embodiment of the invention is shown in the drawing and explained in more detail in the following description. 1 shows a

Fuel injection device for an internal combustion engine in a simplified schematic representation, FIG. 2 shows a detail designated by II in FIG. 1 in an enlarged representation with a storage piston in a starting position, FIG. 3 shows the storage piston in a cross section along line III-III in FIG. 2 and FIG. 4 shows detail II with the accumulator piston in an alternative position.

Description of the embodiment

In Figures 1 to 3 is one

Fuel injection device for an internal combustion engine

10 of a motor vehicle shown. The internal combustion engine has one or more cylinders, each for

A fuel injector with a cylinder

High pressure fuel pump 10 and one

Fuel injection valve 12 is provided. The

High pressure fuel pump 10 and that

Fuel injection valve 12 are a so-called

Pump-nozzle unit summarized. The

High-pressure fuel pump 10 has a pump body 14, in which a pump piston 18 is tightly guided in a cylinder 16, which is supported by a cam 20 of a camshaft Internal combustion engine is driven against the force of a return spring 19 in one stroke. The pump piston 18 delimits a pump working chamber 22 in the cylinder 16, in which fuel is compressed under high pressure during the delivery stroke of the pump piston 18. During the suction stroke of the pump piston 18, fuel is supplied to the pump working chamber 22 from a fuel reservoir 24, for example by means of a feed pump. The pump working chamber 22 has a connection to a relief chamber, which can serve as the fuel reservoir 24, for example, and which is controlled by an electrically controlled valve 23. The electrically controlled valve 23 is connected to a control device 25.

The fuel injection valve 12 has a valve body 26 which can be formed in several parts and which is connected to the pump body 14. In the valve body 26, an injection valve member 28 is guided to be longitudinally displaceable in a bore 30. The bore 30 runs at least approximately parallel to the cylinder 16 of the pump body 14, but can also run at an incline to the latter. The valve body 26 has at least one, preferably a plurality of injection openings 32 at its end region facing the combustion chamber of the cylinder of the internal combustion engine. The injection valve member 28 has at its end region facing the combustion chamber an, for example, approximately conical sealing surface 34 which interacts with a valve seat 36, for example also approximately conical in the valve body 26 in its end region facing the combustion chamber, from or after which the injection openings 32 lead away.

In the valve body 26 there is an annular space 38 between the injection valve member 28 and the bore 30 towards the valve seat 36, which in its end region facing away from the valve seat 36 by a radial expansion of the bore 30 in passes a pressure chamber 40 surrounding the injection valve member 28. The injection valve member 28 has a pressure shoulder 42 facing the valve seat 36 at the level of the pressure chamber 40 due to a reduction in cross section. At the end of the injection valve member 28 facing away from the combustion chamber, a prestressed closing spring 44 engages, by means of which the injection valve member 28 is pressed toward the valve seat 36. The closing spring 44 is arranged in a spring chamber 46 which adjoins the bore 30. The pressure chamber 40 is connected to the pump working chamber 22 via a channel 48 running through the valve body 26 and the pump body 14.

The closing spring 44 is supported on the one hand at least indirectly, for example via a spring plate, on the injection valve member 28 and on the other hand at least indirectly, for example likewise via a spring plate 51, on a storage piston 50. The storage piston 50 is arranged with its end region facing the closing spring 44 in the spring space 46 and projects through a bore 52 in a partition 53 between a storage space 54 and the spring space 46 into the storage space 54. The bore 52 has a smaller diameter than the spring space 46 and the storage space 54. The storage piston 50 has an area 55 in the storage space 54 with a larger diameter than the bore 52, so that a stroke movement of the storage piston 50 into the spring space 46 thereby delimits is that the area 55 of the accumulator piston 50 comes to rest against the partition 53 as a stop.

From the storage space 54, a connecting bore 56 leads from the end facing away from the spring space 46 to the pump working space 22 through a partition 57. The connecting bore 56 has a smaller diameter than the region 55 of the storage piston 50. The storage piston 50 faces the connecting bore 56 Area 55 then a sealing surface 58 which is, for example, approximately conical. The sealing surface 58 cooperates with the mouth of the connecting bore 56 in the storage space 54 on the partition 57 as a seat, which can also be approximately conical. The storage piston 50 has a shaft 60 which projects into the connecting bore 56 and whose diameter is smaller than that of the region 55. Following the sealing surface 58, the shaft 60 initially has a substantially smaller diameter than the connecting bore 56 and then towards its free end a shaft part 62 with a diameter that is only slightly smaller than the diameter of the connecting bore 56.

The shaft part 62 is divided into a shaft section 63 with a larger cross section arranged towards the free end and a shaft section 64 with a smaller cross section arranged towards the shaft 60. The shaft section 63, which is larger in cross section, has, for example, an at least approximately circular cross section and is designed in the shape of a circular cylinder. The shank section 64 with a smaller cross section can also have an at least approximately circular cross section but with a smaller diameter than the shank section 63 and is designed in the form of a circular cylinder. The smaller cross section of the shaft section 64 is preferably formed by at least one flat 65 from the shaft section 63. Only one, two, three or more flats 65 can be provided distributed over the circumference of the shaft section 64. The full diameter of the shaft section 63 is preferably present between the flats 65, so that the shaft section 64 is also guided in the connecting bore 56. In the manufacture of the shaft sections 63, 64, it can be assumed that a circular cylindrical shaft has a constant diameter of the shaft section 63 and on which the flats 65 are formed to form the shaft section 64 with a smaller cross section. The flats 65 end at the transition to the shaft section 63 on the jacket of the shaft section 63 in control edges 66.

When the storage piston 50 is in a starting position in which it rests with its sealing surface 58 on the partition 57 at the mouth of the connecting bore 56. The storage space 54 is separated from the pump work space 22. In the initial position of the accumulator piston 50, its shaft section 64 is arranged in the connecting bore 56 and its shaft section 63 is arranged outside the connecting bore 56 towards the pump working chamber 22. The pressure prevailing in the pump work chamber 22 acts on the end face of the shaft section 63 and, via a gap 68 present between the circumference of the shaft section 64 and the connecting bore 56, on the sealing surface 58 of the storage piston 50 corresponding to the diameter of the connecting bore 58. The storage piston 50 is driven by the force the closing spring 44 is held in its initial position against the pressure prevailing in the pump working chamber 22 when the force exerted on the accumulator piston 50 by the pressure in the pump working chamber 22 is less than the force of the closing spring 44. The accumulator piston 50 is shown in its initial position in FIG.

If the pressure in the pump working space 22 rises so much that the force generated on the storage piston 50 is greater than the force of the closing spring 44, the storage piston 50 moves in an evasive movement out of the pump working space 22 into the storage space 54 Storage piston 50, fuel is displaced from the pump working space 22 into the storage space 54, which is formed by the gap 68 between the shaft section 64 of the Storage piston 50 and the connecting hole 56 must pass through. As a result, the evasive movement of the storage piston 50 is damped. If the storage piston 50 has lifted with its sealing surface 58 from the mouth of the connecting bore 56 on the partition 57, the larger diameter region 55 of the storage piston 50 is reduced by the pressure prevailing in the pump working chamber 22 due to the pressure losses during the throttling through the gap 68 acts so that a greater force acts on the accumulator piston 50 against the closing spring 44. The shaft section 64 of the storage piston 50 with a larger cross section is arranged outside the connecting bore 56 at the beginning of the evasive movement of the storage piston 50. After a partial escape stroke h1 of the storage piston 50, the shaft section 63 dips into the connecting bore 56, between which and the connecting bore 56 only a very small gap 68 remains, so that only a small pressure acts on the area 55 of the storage piston 50 and the pressure only acts on the end face of the shaft section 63 in the pump work chamber 22. As a result, the evasive stroke movement of the accumulator piston 50 is strongly damped, so that the region 55 of the accumulator piston 50 hits the partition wall 53 only at a low speed, which forms a stop for limiting the evasive stroke movement of the accumulator piston 50. In Figure 3, the accumulator piston 50 is shown with its maximum evasive stroke.

A throttle point 49 can be provided in the connection of the pressure chamber 40 to the pump work chamber 22 via the channel 49. The throttling point 49 can also be omitted, so that the pressure chamber 40 has an unthrottled connection to the pump working chamber 22. The connection of the connecting bore 56, in which the shaft part 62 of the accumulator piston 50 is arranged, to the pump work chamber 22 is likewise carried out via the Throttle point 49. It can also be provided that the pressure chamber 40 has an unthrottled connection to the pump work chamber 22 and the connection bore 56 is connected to the pump work chamber 22 via the throttle point 49.

The function of the fuel injection device is explained below. The pump working chamber 22 is filled with fuel during the suction stroke of the pump piston 18. During the delivery stroke of the pump piston 18, the control valve 23 is initially open, so that no high pressure can build up in the pump work chamber 22. When the fuel injection is to begin, the control valve 23 is closed by the control device 25, so that the pump working space 22 is separated from the fuel reservoir 24 and builds up in this high pressure. If the pressure in the pump work chamber 22 and in the pressure chamber 40 is so high that the force acting on the injection valve member 28 via the pressure shoulder 42 in the opening direction 29 is greater than the force of the closing spring 44, the injection valve member 28 moves in the opening direction 29 and gives the at least one injection opening 32 free, through which fuel is injected into the combustion chamber of the cylinder. The accumulator piston 50 is in its initial position. The pressure in the pump work chamber 22 subsequently increases further in accordance with the profile of the cam 20.

If the force exerted on the accumulator piston 50 by the pressure prevailing in the pump work chamber 22 becomes greater than the force exerted on the accumulator piston 50 by the closing spring 44, the accumulator piston 50 executes its evasive stroke movement and moves into the accumulator chamber 54. This results in a pressure drop caused in the pump work chamber 22 and also the bias of the closing spring 44th increases, which is supported on the storage piston 50. The pressure drop in the pump work chamber 22 and in the pressure chamber 40 results in a lower force in the opening direction 29 on the injection valve member 28 and, due to the increase in the pretension of the closing spring 44, there is an increased force in the closing direction on the injection valve member 28, so that it moves again in the closing direction is, with its sealing surface 34 comes to rest on the valve seat 36 and closes the injection openings 32, so that the fuel injection is interrupted. The fuel injection valve 12 is only open for a short period of time and only a small amount of fuel is injected into the combustion chamber as a pre-injection. The amount of fuel injected is essentially determined by the opening pressure of the accumulator piston 50, that is the pressure in the pump working chamber 22 at which the accumulator piston 50 begins its evasive stroke movement. The opening stroke of the injection valve member 28 during the pre-injection can be hydraulically limited by a damping device. Such a damping unit is known from DE 39 00 762 AI and the corresponding US Pat. No. 5,125,580 and DE 39 00 763 AI and the corresponding US Pat. No. 5,125,581, the content of which hereby belongs to the content of the present patent application.

The pressure in the pump work chamber 22 subsequently increases further in accordance with the profile of the cam 20, so that the pressure force acting on the injection valve member 28 increases again in the opening direction 29 and increases the closing force due to the increased preload of the closing spring 44, so that the

Fuel injection valve 12 opens again. A larger amount of fuel is injected over a longer period of time than during the pre-injection. The time period and the amount of fuel injected during this main injection are determined by the time at which the control valve 23 is opened again by the control device 25. After opening the control valve 23, the pump work chamber 22 is again with the

Fuel reservoir 24 connected so that it is relieved and the fuel injection valve 12 closes. The storage piston 50 is moved back into its starting position by the force of the closing spring 44. The time offset between the pilot injection and the main injection is mainly determined by the evasive stroke of the accumulator piston 50.

Claims

Expectations

1. Fuel injector for one

Internal combustion engine with a high-pressure fuel pump (10) and a fuel injection valve (12) for a cylinder of the internal combustion engine, the high-pressure fuel pump (10) having a pump piston (18) driven by the internal combustion engine and defining a pump working space (22), with an electrically controlled valve (23 ), through which a connection of the pump work chamber (22) to a relief chamber (24) is controlled, the fuel injection valve (12) having an injection valve member (28), through which at least one injection opening (32) is controlled and which through which in one with the pressure chamber (40) connected to the pump work chamber (22) can be moved in an opening direction (29) against the force of a closing spring (44), the closing spring (44) on the one hand at least indirectly on the injection valve member (28) and on the other hand at least indirectly on one slidable storage piston (50) is supported on its the closing Spring (44) facing away from the pressure prevailing in the pump work chamber (22), the accumulator piston (50) can be moved from a starting position against the force of the closing spring (44) into a accumulator chamber (54) and the evasive stroke movement of the accumulator piston ( 50) in the storage space (54) is limited by a stop (53), the storage piston (50) being guided in a connecting bore (56) between the storage space (54) and the pump working space (22) and a shaft part (62) Storage area (54) arranged area (55) with having a larger cross-section than the shaft part (62) and wherein a gap (68) between the shaft part (62) and the connecting bore (56) dampens the lifting movement of the storage piston (50), characterized in that the shaft part (62 ) of the accumulator piston (50) has in its starting position in the connecting bore (56) arranged shaft section (64) with a smaller cross-section and an outside of the connecting hole (56) to the pump work chamber (22) arranged shaft section (63) with a larger cross-section and that at the evasive stroke movement of the accumulator piston (50) into the accumulator chamber (54), the shaft section (63) of which has a larger cross section and dips into the connecting bore (56).

2. Fuel injection device according to claim 1, characterized in that the shaft portion (63) with a larger cross section only after a partial escape stroke (hl) of the accumulator piston (50) is immersed in the connecting bore (56).

3. Fuel injection device according to claim 1 or 2, characterized in that during the evasive stroke movement of the storage piston (50) as long as the shaft portion (63) with a larger cross-section outside the connecting bore (56) is arranged in the storage space (54) arranged area (55) of the Storage piston (50) is pressurized and that when the shaft section (64) immersing in the connecting bore (56) has a larger cross-section, only its cross-sectional area is acted upon by the pressure in the pump work chamber (22).

4. Fuel injection device according to one of claims 1 to 3, characterized in that the transition from the shaft section (63) with a larger cross section of the storage piston (50) to the shaft section (64) with a smaller one Cross section (64) takes place in a control edge (66) which runs out on the jacket of the shaft part (62).

5. Fuel injection device according to one of the preceding claims, characterized in that the shaft section (64) with a smaller cross section of the storage piston (50) starting from the shaft section (63) with a larger cross section is formed by at least one flattened portion (65) on the circumference of the shaft part (62) is.

6. Fuel injection device according to claim 5, characterized in that the shaft portion (63) with a larger cross section of the storage piston (50) is at least approximately circular cylindrical.