EP2119903A2 - Fuel injector and combustion engine - Google Patents

Abstract

The injector (1) has an injecting valve element (12) axially adjusted by a control valve (31) operated by an actuator (37). An amount of fuel flows from a high pressure region (6) to a low pressure region (34) of the injector through the opened valve. The low pressure region is provided with an injector return connection (7). Cooling holes (45, 48) arranged hydraulically adjacent to the valve is provided in a housing part (11). The holes are located such that a partial volume of the fuel amount flows through the holes before reaching the connection to output heat energy at the housing part. An independent claim is also included for an internal combustion engine comprising a fuel injector.

Description

State of the art

The invention relates to a fuel injector, in particular a common rail injector, for injecting fuel into a combustion chamber of an internal combustion engine according to the preamble of claim 1 and an internal combustion engine according to claim 11.

Hub-controlled common rail injectors whose injection valve element is servo-operated are known. Piezo and solenoid valves are used as pressure actuators with which the servo circuit (control circuit) is controlled. The fuel control amount of the servo circuit and possibly leaks on guides lead to high temperatures, as these amounts of fuel are relaxed from high system pressure to low pressure. The resulting temperature increases in the fuel injector lead to material problems. In particular, the actuator is critical, both in solenoid valves and piezo valves. For solenoid valves, the plastics used for coil carriers and encapsulation are not suitable for extremely high temperatures, and the coil resistance increases with the temperature, so that changes the coil design.

Particularly in the case of top-head injector designs in which the control valve (servo valve) and the actuator are arranged in the injector head, the permissible temperature range of the actuators is frequently exceeded, in particular therefore, because the heat loss in the head area over the injector is low. As a result, the life of the actuators, in particular of solenoid actuators or piezo actuators, significantly reduced.

From the DE 41 22 384 A1 a fuel injector is known in which for cooling purposes in the low pressure region, fuel is supplied from the outside. The supplied fuel mixes with the fuel control amount of the servo cycle and leads to a reduction in the actuator temperature. A disadvantage of the known fuel injector is the need to realize an additional connection for the supply of cooling fuel and a corresponding cooling line system.

From the JP 2004-150276 A a fuel injector is known, which is provided with a separate heat sink. The heat sink is located on the outside of an injector body and is supplied from the outside with coolant. A disadvantage of the known injector is the complex structure of the cooling device and a cooling line network and the resulting increased injector width.

Disclosure of the invention Technical task

The invention has for its object to provide a simply constructed fuel injector, are avoided in the excessively high temperatures in the temperature-critical area. Furthermore, the object is to propose an internal combustion engine with at least one fuel injector, are avoided in the excessively high temperatures in the critical temperature range.

Technical solution

This object is achieved with regard to the fuel injector with the features of claim 1 and with respect to the internal combustion engine having the features of claim 11. Advantageous developments of the invention are specified in the subclaims. All combinations of at least two features disclosed in the description, the claims and / or the figures fall within the scope of the invention.

The invention is based on the idea to cool the control circuit using the fuel control amount, preferably, without relying on separate cooling liquids, such as separately supplied fuel. In order to make this possible, the invention proposes to guide at least one partial volume flow, the quantity of fuel emerging from the control valve into the low-pressure region of the fuel injector, through at least one cooling bore, which is introduced directly into a housing part of the fuel injector. As it flows through the cooling hole, the amount of fuel can deliver heat energy to the housing part, whereby the temperature of the flowing through the cooling hole amount of fuel is reduced. The cooled fuel quantity can, in particular after complete passage through the cooling bore, be used in a targeted manner to cool at least one specific area, preferably the actuator, of the fuel injector before the fuel quantity is removed again via the injector return port. If necessary, the cooling bore can extend through a plurality of housing parts which are preferably arranged adjacent to one another in the axial direction. In the guided through the cooling hole amount of fuel is preferably in the first Line by a fuel control amount, which flows with an open control valve (servo-valve) from a control chamber in the low pressure region of the fuel injector and thereby relaxed to low pressure. Depending on the design of the fuel injector, the amount of fuel guided through the cooling bore may additionally include fuel leakage quantities from guide gaps. In particular, when the cooling described is the only liquid cooling of the fuel injector, it is possible to dispense with a separate coolant feed connection. Although it may be necessary to increase the material thickness in order to ensure the necessary stability of the housing part provided with the at least one cooling bore. Even in this case, however, a significant increase in diameter of the fuel injector, as this from the proposed solution of JP 2004-150276 A results, avoided. Reducing the fuel temperature in the servo loop eliminates material issues, increasing the life of the fuel injector. The invention described above can be implemented particularly preferably in so-called top-head fuel injectors, in which the actuator is arranged in the injector head. Such a fuel injector preferably has an overhead, preferably centrically arranged, injector return port. However, the invention is not limited to top-head fuel injectors.

In a further development of the invention is advantageously provided that not only a partial volume flow of effluent from the control valve fuel quantity, but the entire amount flowing out of the control valve fuel quantity can flow through the at least one cooling hole. Below this is Also understood an embodiment in which the entire amount of fuel is distributed to a plurality of cooling holes.

Of particular advantage is an embodiment in which the housing part provided with the at least one cooling bore is a housing part which is thermally coupled to the engine block when the fuel injector is mounted in an engine block. Preferably, the housing part lies with its outer circumference on the inner circumference of a fuel injector, at least partially, receiving bore in the engine block. Alternatively, it is conceivable to arrange a heat transfer element radially between the housing part and the engine block. Due to the thermal coupling between the housing part and the engine block, the amount of heat emitted by the amount of fuel flowing through the cooling bore to the housing part can be delivered to the cooler engine block.

The at least one housing part provided with a cooling bore is particularly preferably an injector body, which radially encloses the injection valve element directly on the outside.

In order to realize a targeted cooling of the, preferably electromagnetic or piezoelectric, actuator of the control valve, an embodiment of the fuel injector is preferred in which at least a partial volume flow emerging from the cooling hole, heat reduced fuel quantity, preferably the entire emerging from the at least one cooling hole, heat-reduced fuel amount is guided to the actuator. In the case of providing an electromagnetic actuator, an embodiment is preferred in which the cooled amount of fuel as possible near the at least one electromagnet (coil) flows past. For this purpose, the cooled fuel quantity preferably flows past the pole faces of the electromagnet facing an armature plate and then flows, preferably centrally, through the electromagnet arrangement through to the injector return port. In the case of providing a piezoelectric actuator, an embodiment is preferred in which the cooled fuel is led past the piezo-stack laterally before the cooled fuel quantity reaches the injector return port.

In order to obtain the longest possible cooling path for the amount of fuel flowing out of the control valve, an embodiment is preferred in which at least two cooling bores are provided, which are arranged offset to one another in the circumferential direction of the housing part and / or in the radial direction. It is important to connect the cooling holes hydraulically with each other, so that a cooling hole in the housing part and the other cooling hole out of the housing part out, preferably in the direction of the actuator leads.

Manufacturing technology, an embodiment is preferred in which the at least two cooling bores axially and preferably parallel to each other. The cooling bores preferably extend in the axial direction over at least a majority of the longitudinal extension of the housing part.

A particularly elegant way for the hydraulic connection of the at least two cooling bores is to hydraulically connect the cooling bores via a pocket, the end of the housing part, ie between the at least one cooling bore having housing part and an axially adjacent housing part, is provided. The bag can be realized for example by milling into the housing part and / or the adjacent housing part. As a result of such an arrangement of the at least two cooling bores, the quantity of fuel leaving the control valve preferably initially flows downwards in the axial direction in the direction of a nozzle hole arrangement and is then deflected in the pocket and flows upwards again in the direction of the injector head through the adjacent cooling bore.

In order to realize optimized cooling of an electromagnetic actuator, an embodiment is preferred in which an armature plate of the electromagnetic actuator is arranged in its own armature plate space, which is preferably not directly (axially) hydraulically connected to a control valve directly downstream valve space. Preferably, the fuel flowing out of the control valve, in order to reach the anchor plate space, first has to flow through the at least one cooling bore in the housing part. An embodiment is preferred in which the fuel entering the anchor plate space is guided centrally through the electromagnet arrangement to the injector return port.

In the case of providing a piezoelectric actuator, an embodiment is preferred in which a piezoelectric actuator receiving actuator space is not directly hydraulically connected to a control valve directly downstream valve chamber and the fuel exiting the control valve to enter the actuator, first the at least must flow through a cooling hole. Within the actuator space flows the cooled fuel preferably immediately past the piezoelectric actuator, wherein the piezoelectric actuator is preferably protected, for example by a suitable coating or a protective sheath, from an immediate fuel impact.

The invention also relates to an internal combustion engine having a fuel injector fixed to an engine block, the fuel injector being constructed as described above. Particularly, an embodiment of the internal combustion engine in which the at least one, provided with at least one cooling bore housing part is thermally coupled to the engine block, preferably by directly abutment against the engine block or on a voltage applied to the engine block heat transfer element, in a region radially outside the at least one cooling hole. In this way, a particularly good heat transfer between the housing part and the cooler engine block is possibly realized via a heat transfer element, whereby the dissipated by the amount of fuel to the housing part heat energy can be delivered quickly to the engine block. Particularly preferred is an embodiment in which the cooling hole having housing part at least over a large part (more than 50%) of the longitudinal extension of the cooling bore is thermally coupled to the engine block, preferably by concerns.

Short description of the drawing

Fig. 1:

eine schematische Darstellung eines Kraftstoff- Injektors mit in einem Injektorkörper (Gehäuse- teil) eingebrachten Kühlbohrungen, durch die eine aus einem Steuerventil austretende Kraftstoffmen- ge geleitet wird, bevor diese den Injektor- rücklauf erreicht.

Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. This shows in the only one

Fig. 1:

a schematic representation of a fuel injector with in an injector body (housing part) introduced cooling holes through which a leaking from a control valve fuel quantity is ge passed before it reaches the injector return.

Embodiment of the invention

In Fig. 1 is a designed as a common rail injector fuel injector 1 (top-head injector) for injecting fuel in a combustion chamber of an internal combustion engine, not shown, of a motor vehicle. A high pressure pump 2 delivers fuel from a reservoir 3 in a high-pressure fuel storage 4 (Rail). In this fuel, especially diesel or gasoline, under high pressure, of about 2000 bar in this embodiment, stored. To the high-pressure fuel accumulator 4, the fuel injector 1 is connected via other, not shown, injectors via a supply line 5. The supply line 5 opens into a pressure chamber 6 (high pressure region) of the fuel injector 1 and flows from there in an injection process directly into the combustion chamber of an internal combustion engine. The fuel injector 1 is connected via an injector return connection 7, which is located centrally in a cover 8 of an (upper) injector body 9, to a return line 10 which leads to the reservoir 3. Via the return line 10, a later to be explained fuel control amount can flow from the fuel injector 1 to the reservoir 3 and are fed back from there from the high pressure circuit.

Within the housing part 11 designed as an injector body 9, which is provided with a stepped bore, an injection valve element 12 which is integral in this exemplary embodiment and, if necessary, can also be designed in several parts, is arranged so as to be adjustable in the axial direction. In this case, the injection valve element 12 is guided within a nozzle body 13 (further housing part) on its outer circumference. The nozzle body 13 is clamped by means of a union nut, not shown, directly with the formed as an injector body 9 housing part 11.

The injection valve element 12, which does not have a low-pressure stage, has at its tip 14 a closing spring 15 with which the injection valve element 12 can be brought into a tight contact with an injection valve element seat 16 formed inside the nozzle body 13. When the injection valve element 12 bears against its injection valve element seat 16, ie is in a closed position, the fuel outlet from a nozzle hole arrangement 17 is blocked. If, on the other hand, it is lifted off its injection valve element seat 16, fuel can flow directly from the pressure chamber 6 formed in the housing part 11 through axial passages 19 formed in a guide section 18 on the outer circumference of the injection valve element 12 into a lower plane radially between the injection valve element 12 and the nozzle body 13 trained, annular space 20 to the injection valve element seat 16 pass over to the nozzle hole assembly 17 and there are substantially injected under the high pressure (rail pressure) standing in the combustion chamber of the internal combustion engine.

From an upper end face 21 of the injection valve element 12 and a lower in the plane of the sleeve-shaped portion 22 of a valve body 23, a control chamber 24 is limited, via a radially extending in the sleeve-shaped portion 22 of the valve body 23 inlet throttle 25 with high-pressure fuel from the pressure chamber 6 is supplied. The sleeve-shaped portion 22 with control chamber 24 enclosed therein is enclosed radially on the outside by high-pressure fuel, so that an annular guide gap 26 is comparatively fuel-tight radially between the sleeve-shaped portion 22 and the injection valve element 12.

The control chamber 24 is connected via a arranged in the valve body 23 drain passage 27 with kavitierender flow restrictor 28 with a valve body 23 in the end face valve chamber 29 which is bounded in the axial direction by a valve ball 30 of a control valve 31 (servo-valve). On the valve ball 30 is an axially adjustable valve piston 32, the end operatively connected to an anchor plate 33, preferably formed integrally therewith. From the valve chamber 29 can flow an amount of fuel (here control amount) with the control valve 31 open in the low pressure region 34, and indeed directly into a valve chamber 35 which is hydraulically arranged downstream of the control valve 31. In Fig. 1 the control valve 31 is shown in a closed state, wherein the valve ball 30 rests against its valve body 23 formed on the control valve seat 36. For adjusting the valve piston 32 and thus the valve ball 30 in the drawing plane upwards, ie away from the control valve seat 36, an electromagnetic actuator 37 with an electromagnet 38 (coil) is provided, which is connected to the anchor plate 33, which is arranged in an anchor plate space 39, cooperates. When the electromagnet 38 is energized, the valve piston 32, which is operatively connected to the armature plate 33, or the axially adjacent valve ball 30 lifts off from its control valve seat 36 formed on the valve body 23. The flow cross-sections of the inlet throttle 25 and the outlet throttle 27 are matched to one another such that when open control valve 31, a net outflow of fuel (fuel control amount) from the control chamber 24 via the valve chamber 29 in the low pressure region 34 of the fuel injector 1 and from there on a to be explained later way to injector return port 7 and from this through the return line 8 into the reservoir 3. As a result, the pressure in the control chamber 24 decreases rapidly, whereby the injection valve element 12 lifts off from its injection valve element seat 16, so that fuel can flow out of the pressure chamber 6 through the nozzle hole arrangement 17.

The amount of fuel flowing through the outlet throttle 28 into the low-pressure region 34 is strongly heated due to the strong pressure release.

To end the injection process, the energization of the electromagnet 38 is interrupted, whereby the valve piston 32 and subsequently the frontally arranged valve ball 30 by means of a control spring 40 which is supported on the anchor plate 33, is moved in the drawing plane down to the control valve seat 36. The fuel flowing in through the inlet throttle 25 into the control chamber 26 provides for a rapid pressure increase in the control chamber 24 and thus for a closing force acting on the injection valve element 12. Optionally, the closing movement by a, not shown, acting on the injection valve element 12, closing spring 15 are supported.

In order to prevent the control valve 31 from flowing into the low-pressure region 34 or the valve space 25, fuel quantity strongly heated by the expansion in the outlet throttle 28, directly into the anchor plate space 39 and thus to the electromagnetic actuator 37, the anchor plate space 39 is hydraulic separated from the valve space 35 via a plate portion 41. The plate portion 41 has a central bore 42 in which the valve piston 32 is guided axially displaceable. The plate portion 41 is part of a sleeve-shaped, in cross-section H-shaped, component 43 which is axially supported on the upper side of the valve body 23. The component 43 in turn supports the electromagnetic actuator 37, which is clamped in the axial direction with the aid of the screwed to the housing part 11 cover 8.

So that the amount of fuel flowing out of the control valve 31 can flow out via the injector return port 7, the amount of fuel is initially guided downwards through a bore 44 in the valve body 23 in the axial direction. The bore 44 is aligned in the axial direction with a cooling bore 45 in the housing part 11. More specifically, the axially extending cooling bore 45 is introduced directly into the cylindrical wall 46 of the housing part 11 designed as an injector body 9. The cooling hole 45 extends in the axial direction down and meets there on a pocket 47, which is frontally inserted into the wall 46 of the housing part 11. About the pocket 47, the amount of fuel flows in the radial direction outward to a radial to the Cooling hole 45 offset arranged further cooling bore 48, which runs parallel to the cooling hole 45 and the fuel again leads in the axial direction upwards. The pocket 47 is bounded in the axial direction by the nozzle body 13, which rests against the front of the housing part 11. The wall 46 of the housing part 11 is located in an area below the radially projecting Injektorkopfes directly to an engine block of an internal combustion engine, not shown, whereby the flowing of the through the cooling holes 45, 48 amount of fuel to the housing part 11, more precisely, the wall 46, heat emitted directly can be dissipated to the engine block.

The radially outer cooling bore 48 opens into a lower, lateral Flächenanschliff 49 of the valve body 23 and flows through this in the radial direction outwardly into a low pressure region 34 belonging annular chamber 50, which encloses the component 43 and thus the valve chamber 35 and the armature plate space 39 radially outward , The annular chamber 50 extends in the axial direction up to the lid. 8

By means of a radial bore 51 in the component 43, cooled fuel can flow in the radial direction into the armature plate space 39 and flows there past the electromagnet 38, as a result of which it is cooled. Thereafter, the cooled amount of fuel flows centrally through a solenoid support 52, past the control spring 40 to the arranged in the cover 8 Injektorrücklaufanschluss 7. By the cooling effect of the cooling holes 45, 48 flowed through amount of fuel overheating of the electromagnetic actuator 37 is prevented. Instead of an electromagnetic actuator, a piezoelectric actuator can also be used and cooled by means of the cooled fuel quantity.

Claims (12)

Fuel injector, in particular common-rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, with at least one housing part (11) and with an axially adjustable injection valve element (12), which by means of a control valve (31) is switchable, which in turn with an actuator (37) can be actuated, wherein with the control valve open (31), an amount of fuel from a high-pressure region flows into a low pressure region (34) of the fuel injector (1) provided with an injector return port (7),
characterized,
in that at least one cooling bore (45, 48) disposed hydraulically downstream of the control valve (31) is arranged in such a way that at least a partial volume flow of the amount of fuel flows through it before reaching the injector return port (7), thereby applying heat energy to the Housing part (11) can deliver. Fuel injector according to claim 1,
characterized,
in that the quantity of fuel flowing out of the control valve (31) is conducted such that the entire amount of fuel can flow through the at least one cooling bore (45, 48). Fuel injector according to one of claims 1 or 2, characterized
in that the housing part (11) is thermally coupled to the engine block when the fuel injector (1) is mounted in an engine block, preferably abutting directly on the engine block and / or on a heat transfer element resting against the engine block. Fuel injector according to one of the preceding claims,
characterized,
that the housing part (11) is an injector (9) is arranged radially within which the injection valve element (12). Fuel injector according to one of the preceding claims,
characterized,
in that at least a partial volume flow of the heat-reduced fuel quantity emerging from the cooling bore (45, 48), preferably the entire amount of heat-reduced fuel leaving the cooling bore (45, 48), is led to the actuator (37). Fuel injector according to claim 5,
in that the at least two cooling bores (45, 48) arranged hydraulically connected to one another in the circumferential direction of the housing part (11) and / or in the radial direction are provided. Fuel injector according to claim 6,
characterized,
in that the cooling bores (45, 48) extend in the axial direction. Fuel injector according to one of claims 6 or 7, characterized
that the cooling bores (45, 48) are hydraulically connected to each other through a pocket (47), preferably between the housing part (11) and an axially on this housing part (11) is formed adjacent other housing part. Fuel injector according to one of the preceding claims,
characterized,
in that the actuator (37) is an electromagnetic actuator whose armature plate (33) operatively connected to a control valve element is arranged in an armature plate space (39) which is hydraulically connected to a valve space (35) immediately downstream of the control valve (31), preferably except for any leading gaps exclusively, via which at least one cooling bore (45, 48) is connected. Fuel injector according to one of claims 1 to 8, characterized
in that the actuator (37) is a piezoelectric actuator which is arranged in an actuator space which is hydraulically connected to a valve chamber (35) immediately downstream of the control valve (31), preferably excluding any guide gaps, via the at least one cooling bore (45, 48 ) connected is. Internal combustion engine with a fuel injector (1) fixed to an engine block according to one of the preceding claims. Internal combustion engine according to claim 11
characterized,
in that the housing part (11) is thermally coupled to the engine block, preferably by abutment directly on the engine block and / or on a heat transfer element resting against the engine block in a region radially outside the at least one cooling bore (45, 48).

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