DE102008001735A1 - Fuel injector and internal combustion engine - Google Patents

Abstract

The invention relates to a fuel injector (1), in particular a 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 is actuated with an actuator (37), wherein with open control valve (31) an amount of fuel from a high-pressure region in a Injektorrücklaufanschluss (7) provided low pressure region (34) of the fuel injector (1) flows , According to the invention, there is provided in the housing part (11) at least one cooling bore (45, 48) arranged hydraulically downstream of the control valve (31), which is arranged such that at least a partial volume flow of the fuel quantity flows through it before reaching the injector return port (7) can give off heat energy to the housing part (11).

Description

State of the art

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

Known are stroke-controlled common rail injectors whose injector element is servo-operated is. Piezo and solenoid valves are in use as pressure actuators, with which the servo circuit (control circuit) is controlled. The fuel control quantity of the servo circuit and possibly leaks on guides lead to high temperatures, because these fuel quantities from high system pressure to low pressure to be relaxed. The resulting temperature increases in the fuel injector lead to material problems. Critical is in particular the actuator, both in solenoid valves as also with piezo valves. For solenoid valves are used Plastics for coil carriers and encapsulation not suitable for extremely high temperatures, and the coil resistance decreases with the temperature so that the coil design changes.

Especially in top-head injector designs where the control valve (servo-valve) and the actuator are arranged in the injector head, the permissible Temperature range of the actuators frequently exceeded, especially because the heat dissipation in the head area over the injector housing is low. This will increase the life the actuators, in particular magnetic actuators or piezoactuators, 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

Of the Invention is based on the object, a simple design To propose fuel injector in which too high temperatures in the temperature-critical area, be avoided. It also exists the task is an internal combustion engine with at least one To propose fuel injector in which too high temperatures be avoided in the temperature-critical area.

Technical solution

These Task is with regard to the fuel injector with the features of claim 1 and with regard to the internal combustion engine with the features of claim 11 solved. Advantageous developments of Invention are specified in the subclaims. In the Within the scope of the invention, all combinations are omitted at least two of in the description, the claims and / or features disclosed in the figures.

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. The amount of fuel passed through the cooling bore is preferably primarily a fuel control quantity which, when the control valve is open (servo valve), flows from a control chamber into the low-pressure region of the fuel injector and is thereby expanded 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 When the fuel injector is operating, a separate coolant feed connection can be dispensed with. 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 Development of the invention is provided with advantage that not only a partial flow of the effluent from the control valve Amount of fuel, but the entire effluent from the control valve Flow amount of fuel through the at least one cooling hole can. This is also understood to mean an embodiment in which distributes the entire amount of fuel to several cooling holes becomes.

From particular advantage is an embodiment in which the with the at least one cooling bore provided housing part a housing part which is mounted in an engine block Fuel injector is thermally coupled to the engine block. Preferably, the housing part lies with its outer periphery on the inner circumference of a fuel injector, at least in part, receiving bore in the engine block. Alternatively, it is conceivable radial between the housing part and the engine block, a heat transfer element to arrange. Due to the thermal coupling between the housing part and the engine block may be that of the through the cooling hole flowing amount of fuel to the housing part amount of heat delivered to the cooler engine block be delivered.

Especially Preferably, the at least one is with a cooling hole provided housing part to an injector body, the radially outside of the injection valve element directly encloses.

Around a targeted cooling of, 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 from the cooling hole exiting, heat-reduced fuel amount, preferably the entire emerging from the at least one cooling hole, reduced amount of heat led to the actuator is. In the case of providing an electromagnetic actuator an embodiment is preferred in which the cooled Fuel quantity AS POSSIBLE close to the at least one Electromagnet (coil) flows past. Preferably flows the cooled amount of fuel to this an anchor plate facing pole faces of the electromagnet and then flows, preferably centric, through the electromagnet assembly to the injector return port. In the case of providing a piezoelectric actuator, an embodiment is preferred when the cooled fuel side of the piezo stack passed over before the cooled fuel quantity reached the injector return port.

Around a long cooling section for the amount of fuel flowing out of the control valve obtained, an embodiment is preferred in which at least two cooling holes are provided in the circumferential direction the housing part and / or in the radial direction to each other are arranged offset. It is important, the cooling holes hydraulically connect to each other, leaving a cooling hole into the housing part and the other cooling hole out of the housing part, preferably in the direction of Actuator, leads.

manufacturing technology an embodiment is preferred in which the at least two cooling holes axially and preferably parallel to each other run. Preferably, the cooling holes extend in the axial direction at least a large part the longitudinal extent of the housing part.

A particularly elegant way to at least hydraulic connection two cooling holes is the cooling holes over hydraulically connecting a bag to each other, the end of the housing part, ie between the at least one Cooling bore having housing part and a axially adjacent housing part, is provided. The pocket For example, by milling into the housing part and / or the adjacent housing part can be realized. Due to such an arrangement of at least two cooling holes flows out of the control valve escaping amount of fuel preferably initially in the axial direction downwards in the direction a nozzle hole arrangement and is then deflected in the pocket and flows back through the adjacent cooling hole above in the direction of the injector head.

In order to realize an optimized cooling of an electromagnetic actuator, an embodiment is preferred in which an anchor plate of the electromagnetic actuator is arranged in its own anchor plate space, which is preferably not directly (axially) hydraulically connected to a control valve immediately downstream valve chamber. 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 is an embodiment preferred in which a piezoelectric actuator receiving Actuator not directly hydraulically with a control valve immediately downstream valve space is connected and the off fuel exiting the control valve to enter the actuator space to arrive, first the at least one cooling hole must flow through. Within the actuator space flows the cooled fuel prefers immediately. at the piezoelectric Actuator over, with the piezoelectric actuator preferred, for example by a suitable coating or protective cover, protected against direct fuel impact is.

The Invention also leads to an internal combustion engine with a fixed to an engine block fuel injector, wherein the Fuel injector is carried out as described above. Particularly, an embodiment of the internal combustion engine, at least one, with at least one cooling hole provided housing part thermally coupled to the engine block is, preferably by direct contact with the engine block or on a heat transfer element resting against the engine block, 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 optionally via a heat transfer element realized, thereby reducing the amount of fuel to the housing part dissipated heat energy quickly delivered to the engine block can be. Particularly preferred is an embodiment in which the cooling hole having housing part at least a large part (more than 50%) of the Longitudinal extension of the cooling hole thermally with the engine block, preferably by concerns coupled.

Short description of the drawing

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

1 : A schematic representation of a fuel injector with incorporated in an injector body (housing part) cooling holes through which an emerging from a control valve fuel quantity is passed before it reaches the injector return.

Embodiment of invention

In 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 Promotes 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 storage 4 is the fuel injector 1 besides other, not shown, injectors via a supply line 5 connected. The supply line 5 flows into a pressure room 6 (High pressure area) of the fuel injector 1 and flows from there during an injection process directly into the combustion chamber of an internal combustion engine. The fuel injector 1 is via an injector return port 7 that is centrically in a lid 8th an (upper) injector body 9 located on a return line 10 connected to the reservoir 3 leads. About the return line 10 may be a later to be explained fuel control amount from the fuel injector 1 to the reservoir 3 drain and be fed from there from the high pressure circuit again.

Inside the injector body 9 trained housing part 11 , which is provided with a stepped bore, is a one-piece injection valve element in this embodiment 12 , which can also be made in several parts if necessary, arranged adjustable in the axial direction. In this case, the injection valve element 12 within a nozzle body 13 (further housing part) guided on its outer circumference. The nozzle body 13 is by means of a union nut, not shown, directly with the injector body 9 trained housing part 11 braced.

The low-pressure stage having injection valve element 12 points at its peak 14 a closing spring 15 on, with which the injection valve element 12 in a tight contact with one inside the nozzle body 13 trained injection valve element seat 16 can be brought. When the injection valve element 12 at its injection valve element seat 16 is applied, that is, is in a closed position, the fuel outlet from a nozzle hole arrangement 17 blocked. On the other hand, is it from its injection valve element seat 16 lifted, can force material directly from the housing part 11 trained pressure room 6 through in a guide section 18 on the outer circumference of the injection valve element 12 formed by polished axial channels 19 in a plane lower in the drawing plane, radially between the injection valve element 12 and the nozzle body 13 trained, annulus 20 at the injection valve element seat 16 over to the nozzle hole arrangement 17 flow and there are essentially injected under the high pressure (rail pressure) standing in the combustion chamber of the internal combustion engine.

From an upper front side 21 the injection valve element 12 and a lower, sleeve-shaped section in the plane of the drawing 22 a valve body 23 becomes a control chamber 24 bounded over a radially in the sleeve-shaped portion 22 of the valve body 23 running inlet throttle 25 with high-pressure fuel from the pressure chamber 6 is supplied. The sleeve-shaped section 22 with enclosed control chamber 24 is radially outwardly surrounded by fuel under high pressure, so that an annular guide gap 26 radially between the sleeve-shaped portion 22 and the injection valve element 12 is comparatively fuel-tight.

The control chamber 24 is about one in the valve body 23 arranged drainage channel 27 with cavitating outlet throttle 28 with one in the valve body 23 frontally formed valve chamber 29 in the axial direction of a valve ball 30 a control valve 31 (Servo valve) is limited. At the valve ball 30 is an axially adjustable valve piston 32 at the end with an anchor plate 33 operatively connected, preferably integrally formed with this, is. From the valve chamber 29 can a fuel quantity (here control quantity) with open control valve 31 in the low pressure area 34 , directly into a valve chamber 35 flow, which hydraulically the control valve 31 is immediately downstream. In 1 is the control valve 31 shown in a closed state, wherein the valve ball 30 at her on the valve body 23 trained control valve seat 36 is applied. For adjusting the valve piston 32 and thus the valve ball 30 in the plane of the drawing up, so from the control valve seat 36 away, is an electromagnetic actuator 37 with an electromagnet 38 (Coil) provided with the anchor plate 33 standing in an anchor plate room 39 is arranged, cooperates. When the electromagnet is energized 38 he lifts with the anchor plate 33 Actively connected valve pistons 32 or the axially adjacent valve ball 30 from her on the valve body 23 trained control valve seat 36 from. The flow cross sections of the inlet throttle 25 and the outlet throttle 27 are matched to one another in such a way that when the control valve is open 31 a net outflow of fuel (fuel tax amount) from the control chamber 24 over the valve chamber 29 in the low pressure area 34 of the fuel injector 1 and from there on a later to be explained way to injector return port 7 and from this through the return line 8th in the reservoir 3 flows. This reduces the pressure in the control chamber 24 rapidly, causing the injection valve element 12 from its injection valve element seat 16 lifts off, leaving fuel from the pressure chamber 6 through the nozzle hole arrangement 17 can flow out.

The through the outlet throttle 28 in the low pressure area 34 outgoing fuel quantity is strongly heated due to the strong pressure release.

To stop the injection process is the energization of the electromagnet 38 interrupted, causing the valve piston 32 and subsequently the valve ball arranged on the face side 30 by means of a control spring 40 that are on the anchor plate 33 supported, in the drawing plane down on the control valve seat 36 is adjusted. The through the inlet throttle 25 in the control chamber 26 inflowing fuel ensures a rapid pressure increase in the control chamber 24 and thus for one on the injection valve element 12 acting closing force. Optionally, the closing movement of a, not shown, on the injection valve element 12 acting, closing spring 15 get supported.

To prevent the control valve 31 one in the low pressure area 34 or the valve space 25 outflowing, by relaxing in the outlet throttle 28 strongly heated, amount of fuel directly into the anchor plate space 39 and thus to the electromagnetic actuator 37 is the anchor plate space 39 hydraulically from the valve chamber 35 over a plate section 41 separated. The plate section 41 has a central hole 42 on, in which the valve piston 32 is guided axially displaceable. The plate section 41 is part of a sleeve-shaped, in cross-section H-shaped, component 43 , which is located axially at the top of the valve body 23 supported. The component 43 in turn carries the electromagnetic actuator 37 , which with the help of the housing part 11 screwed lids 8th is braced in the axial direction.

So that from the control valve 31 Outflowing fuel through the injector return port 7 can flow, the amount of fuel is first through a hole 44 in the valve body 23 guided in the axial direction down. The hole 44 Aligns in the axial direction with a cooling hole 45 in the housing part 11 , More specifically, the axially extending cooling hole 45 directly into the cylindrical wall 46 of the injector body 9 trained housing part 11 brought in. The cooling hole 45 runs in the axial direction below and meets there on a bag 47 , the front side in the wall 46 of the housing part 11 is introduced. About the bag 47 The amount of fuel flows in the radial direction outward to a radial to the cooling hole 45 staggered arranged further cooling hole 48 parallel to the cooling hole 45 runs and the fuel leads back up in the axial direction. The pocket 47 is limited in the axial direction of the nozzle body 13 , the front side of the housing part 11 is applied. The wall 46 of the housing part 11 is located in an area below the radially protruding Injektorkopfes directly to an engine block, not shown, of an internal combustion engine, whereby by the through the cooling holes 45 . 48 flowing amount of fuel to the housing part 11 , more precisely, the wall 46 , discharged heat can be dissipated directly to the engine block.

The radially outer cooling hole 48 opens into a lower, lateral Flächenanschliff 49 of the valve body 23 and flows through this in the radial outward direction into a low-pressure region 34 belonging annular chamber 50 that the component 43 and thus the valve space 35 as well as the anchor plate space 39 encloses radially on the outside. The annular chamber 50 extends in the axial direction up to the lid 8th ,

Through a radial bore 51 in the component 43 can cooled fuel in the radial direction in the anchor plate space 39 inflow and flows past the electromagnet 38 , whereby this is cooled. Thereafter, the cooled amount of fuel flows centrically through a solenoid carrier 52 through, on the control spring 40 over to the lid 8th arranged injector return port 7 , Due to the cooling effect of the cooling holes 45 . 48 flowed through amount of fuel is overheating of the electromagnetic actuator 37 prevented. Instead of an electromagnetic actuator and a piezoelectric actuator is set and cooled by means of the cooled amount of fuel.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 4122384 A1 [0004]
• - JP 2004-150276 A [0005, 0008]

Claims (12)

Fuel injector, in particular common-rail injector, for injecting fuel into a combustion chamber of an internal combustion engine, having 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 ) is operable, with open control valve ( 31 ) an amount of fuel from a high pressure area into one with an injector return port ( 7 ) provided low pressure area ( 34 ) of the fuel injector ( 1 ) flows, characterized in that in the housing part ( 11 ) at least one of the control valve ( 31 ) hydraulically downstream cooling bore ( 45 . 48 ) is provided, which is arranged such that at least a partial volume flow of the amount of fuel before reaching the Injektorrücklaufanschlusses ( 7 ) and thereby heat energy to the housing part ( 11 ). Fuel injector according to claim 1, characterized in that the from the control valve ( 31 ) amount of fuel is conducted such that the total amount of fuel through the at least one cooling bore ( 45 . 48 ) can flow. Fuel injector according to one of claims 1 or 2, characterized in that the housing part ( 11 ) in an engine block mounted fuel injector ( 1 ) is thermally coupled to the engine block, preferably rests directly on the engine block and / or on a voltage applied to the engine block heat transfer element. Fuel injector according to one of the preceding claims, characterized in that the housing part ( 11 ) an injector body ( 9 ) is, radially within which the injection valve element ( 12 ) is arranged. Fuel injector according to one of the preceding claims, characterized in that at least a partial volume flow from the cooling bore ( 45 . 48 ) exiting, heat-reduced fuel amount, preferably the entire of the cooling hole ( 45 . 48 ) exiting, heat reduced fuel quantity to the actuator ( 37 ) is guided. Fuel injector according to claim 5, that the at least two in the circumferential direction of the housing part ( 11 ) and / or radially offset hydraulically interconnected cooling bores (US Pat. 45 . 48 ) are provided. Fuel injector according to claim 6, characterized in that the cooling holes ( 45 . 48 ) extend in the axial direction. Fuel injector according to one of claims 6 or 7, characterized in that the cooling holes ( 45 . 48 ) over a bag ( 47 ) are hydraulically connected to each other, preferably between the housing part ( 11 ) and an axial to this housing part ( 11 ) adjacent further housing part is formed. Fuel injector according to one of the preceding claims, characterized in that the actuator ( 37 ) is an electromagnetic actuator, whose operatively connected to a control valve element anchor plate ( 33 ) in an anchor plate space ( 39 ) arranged hydraulically with a control valve ( 31 ) immediately downstream valve space ( 35 ), preferably apart from any guide gaps exclusively, via the at least one cooling bore ( 45 . 48 ) connected is. 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 control valve ( 31 ) immediately downstream valve space ( 35 ), preferably apart from any guide gaps exclusively, via the at least one cooling bore ( 45 . 48 ) connected is. Internal combustion engine with a fuel injector fixed to an engine block ( 1 ) according to any 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 voltage applied to the engine block heat transfer element in a region radially outside the at least one cooling bore ( 45 . 48 ).