WO2001088365A1

WO2001088365A1 - Injection assembly for an accumulator fuel-injection system of an internal combustion engine

Info

Publication number: WO2001088365A1
Application number: PCT/DE2001/001123
Authority: WO
Inventors: Andreas Kellner
Original assignee: Robert Bosch Gmbh
Priority date: 2000-05-18
Filing date: 2001-03-23
Publication date: 2001-11-22
Also published as: DE50107694D1; EP1287253A1; KR20020019538A; EP1287253B1; DE10024703A1; JP2003533635A; ATE306613T1

Abstract

The invention relates to an injection assembly for an accumulator fuel-injection system comprising an injection nozzle (18) which projects into a combustion chamber (16) and which can be supplied with fuel from a high-pressure fuel distributor (12) via a high-pressure fuel supply route and a nozzle needle (32) which opens and closes the injection nozzle depending on the pressure in a valve control chamber (58). The fuel is supplied to the valve control chamber by a supply channel (60) branching off from the fuel supply route and opening into said control chamber. The fuel flows out of the valve control chamber via an outflow route (64) originating from said chamber. In addition, an auxiliary channel (72), which opens into the outflow route, branches off from the fuel supply. The outflow route can be shut off downstream of the mouth of the auxiliary channel to prevent the outflow of fuel, using a shut off device (68). To avoid leakages which cannot be used for control purposes, the shut-off device is configured to shut off the auxiliary channel to the outflow of fuel, in such a way that when the outflow route is shut off, the auxiliary channel is open and vice versa.

Description

Injection arrangement for a fuel

Storage injection system α of an internal combustion engine

State of the art

The invention is based on an injection arrangement for a fuel storage injection system of an internal combustion engine according to the type defined in more detail in claim 1.

As is generally known in practice, fuel accumulator injection systems, for example common rail injection systems, have a high-pressure fuel distributor or rail for an internal combustion engine with a plurality of combustion chambers, from which a plurality of high-pressure fuel supply paths, each to one of the combustion chambers of the internal combustion engine protruding injection nozzle. The fuel injection into the respective combustion chamber is controlled by means of a nozzle needle, which opens and closes the respective injection nozzle depending on the pressure in a valve control chamber. To build up pressure in the valve control chamber, for example, an always open inlet channel can be provided, through which the fuel under the rail pressure from the respective can flow into the valve control chamber. A separate drain eg allows fuel to be drained from the valve control chamber, thus relieving pressure in the valve control chamber. The drain path can be blocked at a shut-off point by means of a shut-off device, so that the pressure level in the valve control chamber and thus the position of the nozzle needle can be influenced by optionally blocking and releasing the drain path.

With an inward opening valve, the drain path is opened to open the valve, fuel flowing out of the valve control chamber. The associated drop in pressure in the valve control chamber leads to the lifting of the nozzle needle from the injection nozzle, and fuel emerges from the injection nozzle. If the drainage path is blocked again, the pressure in the valve control chamber increases again due to the fuel flowing in via the inlet channel. As a result of this pressure increase, the nozzle needle is pressed against the injection nozzle again and closes it. The drain path and the inlet channel are usually designed so that when the drain path is open, the flow rate of the fuel flowing through the drain path is greater than the flow rate of the fuel flowing through the inlet channel, so that the fuel volume in the valve control chamber is effectively smaller.

In order to be able to precisely meter the amount of fuel injected, it is essential that the injector can be opened and closed quickly. The closing process in particular has proven to be critical in practice. Because of the comparatively small Passage cross section of the inlet channel often flows in too little fuel to achieve the desired fast closing times. This is particularly true if the pressure in the control chamber does not drop very far below the pressure in the fuel supply path after the valve has closed, during the injection process. The then only comparatively small pressure difference between the fuel supply path and the valve control chamber leads to a correspondingly low inflowing fuel flow.

In order to be able to replace the fuel losses in the valve control chamber that were previously suffered by opening the discharge path when the injection nozzle is closed, a solution is known from practice in which a bypass duct branches off from the fuel supply path and opens directly into the discharge path upstream of the shut-off point of the drainage path, if one considers the fuel's drainage direction along the drainage path. If the downstream part of the outlet path is blocked, this bypass channel forms an auxiliary channel connected in parallel to the inlet channel, through which an additional quantity of fuel can flow from the fuel supply path via the upstream part of the outlet path into the valve control chamber. It has been shown that higher closing speeds of the nozzle needle can be achieved in this way.

In this known solution, however, a certain amount of fuel from the fuel supply path flows unused through the bypass channel and the downstream when the drain path is open Part of the drain path. In order to keep this leakage quantity, which is not available for control purposes, low, a throttle is built into the bypass duct in the known solution. Although this causes a reduction in the amount of leakage, it also reduces the flow rate of the additional fuel entering the valve control chamber when the drain path is blocked. Since the desired fast closing times of the nozzle needle have not yet been achieved in this way, a throttle is additionally installed in the fuel supply path in the known solution, specifically after the branch point of the inlet channel, if one considers the direction of flow of the fuel in the fuel supply path. In the downstream parts of the fuel supply path, a counterforce is derived from the prevailing fuel pressure on the nozzle needle, which counteracts the force exerted on the nozzle needle by the pressure in the valve control chamber. The throttle in the fuel supply path now brings about a pressure drop in these downstream parts of the fuel supply path and thus a reduction in the counterforce. A lower pressure in the valve control chamber is then sufficient to move the nozzle needle into its closed position.

In this known solution, the two throttles in the bypass channel and in the fuel supply path entail considerable additional expenditure in terms of production technology, since they are very small structures in which compliance with the permissible tolerances is very difficult in terms of production technology. In addition, the throttle in the fuel supply path leads to a reduced injection pressure with which the power substance is injected into the combustion chamber. The loss of injection pressure can easily amount to up to 200 bar.

Advantages of the invention

The injection arrangement according to the invention for a fuel accumulator injection system of an internal combustion engine with the features of claim 1 has the advantage that, by quickly closing the nozzle needle, a highly precise metering of the fuel injection quantity with little leakage and a valve that is easy to manufacture is possible. For this purpose, the injection arrangement has an injection nozzle which projects into a combustion chamber of the internal combustion engine and can be supplied with fuel from a high-pressure fuel distributor of the accumulator injection system via a high-pressure fuel supply path, and an injection needle which opens and closes the injection nozzle depending on the pressure in a valve control chamber. For the introduction of fuel into the valve control chamber, an inlet channel branching off from the fuel supply path opens into the valve control chamber, and an outlet path starting from the valve control chamber enables the fuel to flow out of the valve control chamber. An auxiliary channel opening into the drain path also branches off from the fuel supply path. In this case, a shut-off device is provided, by means of which the drainage path — based on a fuel drainage device — downstream of the junction parts of the auxiliary channel in the drainage path can be blocked against fuel drainage. According to the invention, the shut-off device is also used to block the auxiliary channel against fuel flow. is formed, in such a way that when the drain path is blocked, the auxiliary channel is unlocked and vice versa.

In the solution according to the invention, the auxiliary channel can be blocked. If the drain path is open during an injection process, fuel can thus be prevented from flowing unused through the auxiliary channel from the fuel supply path. When designing the auxiliary channel, there is no need to compromise between the smallest possible leakage quantity and the greatest possible additional fuel flow into the valve control chamber. Instead, the auxiliary channel can be optimized essentially only so that the valve control chamber is refilled as quickly as possible after the drain path has been blocked, and the nozzle needle is moved back into its closed position as quickly as possible.

It has been shown in particular that the auxiliary channel can be substantially unthrottled over its entire length. This simplifies the manufacture of the injection arrangement.

It has also been shown that by suitable, in particular throttle-free design of the auxiliary channel with a blocked drain path, such a total fuel flow can be obtained via the inlet and the auxiliary channel into the valve control chamber that a forced pressure reduction in the parts of the fuel near the nozzle is obtained - supply routes can be dispensed with. This allows the fuel supply path to be designed in an essentially unrestricted manner over its length leading from the branch point of the inlet channel to the injection nozzle. This also leads to a reduction in production costs.

In the context of the present invention, it is fundamentally not excluded that the shut-off device has two separately operable shut-off bodies for the auxiliary channel and the drainage path. This can be expedient, for example, if the auxiliary channel and the drain path are not to be opened or locked in a time-synchronous manner, but rather with a time delay. However, a solution can be implemented with less effort in which the shut-off device has shut-off surfaces formed on a common shut-off body for locking the drain path and for locking the auxiliary channel.

It is structurally particularly simple if the shut-off body is designed as a seat element which can be moved back and forth between two opposite valve seats, one of the valve seats forming a shut-off point for the drainage path and the other valve seat forming a shut-off point for the auxiliary channel. However, it is also conceivable that the shut-off body is designed as a slide element of a slide valve.

A piezoelectric actuator arrangement can preferably be used to actuate the shut-off device, but alternatively an electromagnetic actuator arrangement can also be provided.

Further advantages and advantageous configurations of the subject matter of the invention can be gathered from the description, the drawing and the patent claims. drawing

An embodiment of the injection arrangement according to the invention for a fuel storage injection system is shown in the drawing and is explained in more detail in the following description. Show it

1 shows a schematic, partial representation of a storage injection system according to the invention with an injector assembly for internal combustion engines shown in longitudinal section, and

FIG. 2 shows a simplified, partial illustration of a shut-off valve of the injector assembly according to FIG. 1.

Description of the embodiment

The storage injection system shown in FIG. 1, which represents a so-called common rail injection system, has a symbolically indicated pressure source 10, which preferably feeds diesel fuel into a manifold or rail 12 at a high pressure of, for example, more than 1500 bar. From the manifold 12 go several fuel supply lines 14, each one for supplying fuel

Combustion chamber 16 of a multi-cylinder internal combustion engine, not shown, such as a motor vehicle internal combustion engine, projecting injection nozzle 18. The injection nozzle 18 is part of an injector assembly, generally designated 20, which can be used as a preassembled structural unit in a cylinder block of the internal combustion engine. The injector assembly 20 has a housing assembly 22 with a nozzle housing 24 and a valve housing 26. In the nozzle housing 24, a guide bore 30 is formed which extends along a housing axis 28 and in which an elongated nozzle needle 32 is guided so as to be axially movable. At a needle tip 34, the nozzle needle 32 has a closing surface 36 with which it can be brought into tight contact with a needle seat 38 formed on the nozzle housing 24.

When the nozzle needle 32 abuts the needle seat 38, i.e. is in the needle closed position, the fuel outlet from a nozzle hole arrangement 40 is blocked at the end of the nozzle housing 24 which projects into the combustion chamber 16. On the other hand, is it lifted off the needle seat 38, i.e. In the needle opening position, fuel can flow from an annular space 42 formed between the nozzle needle 32 and the peripheral jacket of the guide bore 30 past the needle seat 38 to the nozzle hole arrangement 40 and be injected there into the combustion chamber 16.

The nozzle needle 32 is biased towards its closed position by a biasing spring 44. The biasing spring 44 is accommodated in a spring chamber 46 formed in the nozzle housing 24. On the one hand, it is supported on the housing assembly 22 by a sleeve 48 which seals the end of the nozzle needle 32 remote from the combustion chamber, but which is axially movable and bites into the valve housing 26 with a biting edge. On the other hand, it is supported on the nozzle needle 32 by means of a spring plate 50 plugged onto the nozzle needle 32. A bore 52 formed in the housing assembly 22 opens into the spring chamber 46, into which fuel which is essentially under high pressure or rail pressure is introduced via the relevant fuel supply line 14. From the spring chamber 46, the fuel passes into the annular space 42 via a channel formed in the nozzle housing 24 or — as here — past a system of flats or incisions 54 machined into the peripheral jacket of the nozzle needle 32.

A valve control chamber 58 is delimited between an end face 56 of the nozzle needle 32, the sleeve 48 and the valve housing 26 which is remote from the combustion chamber and into which an inlet duct 60 designed as a throttle opens. Fuel can flow from the spring chamber 46 into the valve control chamber 58 through the inlet throttle 60. Fuel can flow out of the valve control chamber 58 to a relief chamber (not shown in more detail) via an outlet duct 64 containing an outlet throttle 62. By means of an only symbolically indicated actuator

A shut-off valve 68, preferably a piezoelectric actuator 66, which can be actuated, allows the fuel outflow to the relief chamber to be shut off. If desired, an electromagnetic actuator can of course also be used instead of a piezoelectric actuator.

Due to the prestressing spring 44 and the action of the pressure prevailing in the valve control chamber 58 on the needle end face 56, a closing force directed axially towards the combustion chamber 16 is exerted on the nozzle needle 32. This closing force counteracts an opening force axially, which as a result of the action of the Annulus 42 prevailing pressure is exerted on a step surface 70 formed on the nozzle needle 32 on the nozzle needle 32. If the shut-off valve 68 is in its blocking position and the fuel outflow through the outlet channel 64 is thus blocked, the closing force is greater than the opening force in the stationary state, which is why the nozzle needle 32 then assumes its closed position. If the shut-off valve 68 is then opened, fuel flows out of the valve control chamber 58.

The flow cross-sections of the always open inlet throttle 60 and the outlet throttle 62 are matched to one another in such a way that the inflow through the inlet throttle 60 is less than the outflow through the outlet channel 64 and accordingly a net outflow of fuel results. The following pressure drop in the valve control chamber 58 causes the closing force to drop below the opening force and to lift the nozzle needle 32 inward from the needle seat 38.

If the injection is to be ended, the shut-off valve 68 is brought back into its blocking position. This blocks the fuel outflow through the outlet channel 64. Fuel continues to flow from the spring chamber 46 into the valve control chamber 58 through the inlet throttle 60, and the pressure in the valve control chamber 58 increases again. As soon as the pressure in the valve control chamber 58 reaches a level at which the closing force is greater than the opening force, the nozzle needle 32 goes into it

Closed position, which stops fuel leakage from the nozzle hole assembly 40. In order to achieve rapid needle closing speeds, a rapid increase in pressure in the valve control chamber 58 after the shut-off valve 68 has been blocked and during the closing movement of the nozzle needle 32 must be provided for sufficient flow. The flow through the inlet throttle 60 is comparatively low. An increase in the flow cross section of the inlet throttle 60 is only considered within very narrow limits, because otherwise there is the risk that when the shut-off valve 68 is opened, the net outflow of fuel is no longer sufficient to open the nozzle needle 32.

An auxiliary channel 72 is therefore provided, by means of which an additional fuel flow into the valve control chamber 58 is achieved when the shut-off valve 68 is blocked. The auxiliary channel 72 branches off from the bore 52 and, like the inlet throttle 60, is fed with fuel which is essentially under the rail pressure. The additional fuel flow through the auxiliary channel 72, after the shut-off valve 68 has been blocked, causes the pressure in the valve control chamber 58 to rise to the level required to move the nozzle needle 32 from its opening position into its closing position more quickly than when it is filled by the inlet throttle 60 alone to convince lung. Ultimately, the amount of fuel injected into the combustion chamber 16 can be metered more finely.

Reference is now also made to the schematic sketch in FIG. 2. The shut-off valve 68 not only controls the fuel flow through the drain channel 64, but also the fuel flow through the auxiliary channel 72. It is designed as a 3/2-way valve, three of which Connections of an upstream part 64 ′ of the discharge channel 64, a downstream part 64 ″ of the discharge channel 64 and the auxiliary channel 72 are occupied, based on the fuel discharge direction.

In a first switch position, which represents a blocking position, the shut-off valve 68 blocks the downstream part 64 ″ of the outlet channel 64, but releases a flow connection between the auxiliary channel 72 and the upstream part 64 ′ of the outlet channel 64. In this first switching position, a fuel outflow from the valve control chamber 58 to the relief chamber is impossible, but a fuel inflow into the valve control chamber 58 via the auxiliary duct 72 and the upstream part 64 'of the outlet duct 64 is possible.

In its second switch position, which represents an open position, the shut-off valve 68 allows fuel to flow out of the valve control chamber 58 through the upstream part 64 'of the outlet channel 64 into its downstream part 64' ', but blocks the auxiliary channel 72. A fuel flow through the auxiliary channel 72 thus occurs the second switching position, which is why in this second switching position no leakage has to be accepted beyond the amount of fuel flowing out of the valve control chamber 58.

In the exemplary embodiment shown here, the shut-off valve 68 is designed as a seat valve with a seat element 76 arranged in a valve chamber 74, in the present case a spherical valve closing member. The seat element 76 is adjustable by means of the actuator 66 between two seats 78, 80 opposite one another in the adjusting direction of the actuator 66, one seat 78 of which corresponds to the first switching position and the other seat 80 of which corresponds to the second switching position.

At the seat 78, the downstream part 64 ″ of the outlet channel 64 opens into the valve chamber 74, at the seat 80 the auxiliary channel 72. The upstream part 64 ′ of the outlet channel 64 opens laterally between the two seats

78, 80 into the valve chamber 74. In this way, the requirement can be met that the shut-off point for the drain channel 64, which is formed here by the seat 78, is downstream of the point at which the auxiliary channel 72 is in an imaginary, along the two parts

64 ', 64' 'of the drain channel 64 opens out via the valve chamber 74.

In Figure 2, the seat element or valve closing member 76 is shown in contact with the seat 78 with a solid line. The second switching position, in which the seat element 76 bears against the seat 80, is indicated by dashed lines. It is understood that the proportions in Figure 2 are not realistic. The adjustment path of the seat element 76 between the two seats 78, 80 can easily be in the range of only a few tens or hundreds of micrometers. The seat element 76 is expediently prestressed against the seat 78 by means of a valve spring 82 which can be seen in FIG. 1 and is accommodated in the valve chamber 74.

The auxiliary channel 72 is designed over its entire length without an essential throttling point. Since it is downstream If the outlet throttle 62 opens into the mentioned imaginary outlet path, there is anyway a throttle point, namely the outlet throttle 62, in the flow path that the fuel flow going through the auxiliary channel 72 into the valve control chamber 58 travels when the shut-off valve 68 is blocked.

Even in the parts of an imaginary fuel supply path running through the fuel supply line 14 to the nozzle hole arrangement 40, there is no substantial throttling of the flowing fuel, which is why the fuel is ejected from the nozzle hole arrangement 40 at approximately the rail pressure.

Claims

Expectations

1. Injection arrangement for a fuel accumulator injection system of an internal combustion engine, with a protruding into a combustion chamber (16) of the internal combustion engine, from a high pressure fuel distributor (12) of the accumulator injection system via a high pressure fuel supply path (14, 52, 46, 54) , 42) with an injection nozzle (18) which can be supplied with fuel and a nozzle needle (32) which opens and closes the injection nozzle (18) depending on the pressure in a valve control chamber (58), one of the fuel supply path (58) being used to introduce fuel into the valve control chamber (58). 14, 52, 46, 54, 42) branching inlet anal (60) opens into the valve control chamber (58) and an outlet path (64 ', 64 ", 74) emanating from the valve control chamber (58) leads the fuel to the outlet from the valve control chamber ( 58), an auxiliary channel (72) opening into the drain path (64 ', 64'', 74) branching off from the fuel supply path (14, 52, 46, 54, 42) and a shut-off valve device (68) is provided, by means of which the drainage path (64 ', 64'', 74) relates to a fuel drainage direction downstream of the junction parts of the auxiliary channel (72) in the discharge path (64 ', 64 ", 74) can be blocked against fuel discharge, characterized in that the shut-off device (68) is also designed to block the auxiliary duct (72) against fuel flow in such a way that when the discharge path is blocked

(64 ', 64' ', 74) the auxiliary channel (72) is unlocked and vice versa.

2. Injection arrangement according to claim 1, characterized in that the auxiliary channel (72) on its entire

Length is essentially unthrottled.

3. Injection arrangement according to claim 1 or 2, characterized in that the fuel supply path (14, 52, 46, 54, 42) on its from the branch point of the

Inlet channel (60) leading to the injection nozzle (18) is essentially unthrottled.

4. Injection arrangement according to one of claims 1 to 3, characterized in that the shut-off device (68) for locking the drainage path (64 ', 64 ", 74) and for locking the auxiliary channel (72) on a common shut-off body (76) formed shut-off surfaces having.

5. Injection arrangement according to claim 4, characterized in that the shut-off body (76) is designed as a reciprocating seat element between two opposite valve seats (78, 80), one (78) of the valve seats (78, 80) being a shut-off point for the Drain path (64 ', 64 ", 74) forms and the other

Valve seat (80) forms a shut-off point for the auxiliary channel (72).

6. Injection arrangement according to one of claims 1 to 5, characterized in that the shut-off device (68) can be actuated by means of a piezoelectric actuator arrangement (66).

7. Injection arrangement according to one of claims 1 to 5, characterized in that the shut-off device (68) can be actuated by means of an electromagnetic actuator arrangement.