DE102006036779A1 - Fuel injector with direct needle control and servo valve support - Google Patents

Abstract

The invention relates to an injector for injecting fuel in a combustion chamber of an internal combustion engine with an injection valve member (3) which closes or releases at least one injection opening (13) and which is actuated by a control piston (27), wherein between the injection valve member (3) and the control piston (27) is formed a control chamber (23) which is bounded on one side by an upper end face (21) of the injection valve member (3) and on the opposite side by a lower end face (25) of the control piston (27). The control piston (27) acts as a valve piston of a control valve (33) via which the control chamber (27) can be connected to a low-pressure region of a fuel return (63).

Description

State of the art

The The invention is based on an injector for injecting fuel in a combustion chamber of an internal combustion engine according to the preamble of claim 1.

Out DE-A 10 2004 015 744 For example, there is known a fuel injector for injecting fuel into a combustion chamber of an internal combustion engine having an injector housing having a fuel inlet communicating with a central fuel high pressure source outside the injector housing and with a pressure space within the injector housing depending on the position a control valve is injected with high pressure fuel. The control valve is actuated by means of a piezoelectric actuator. In order to achieve a sufficiently large stroke for the control valve, a coupling space is formed between the control valve and the piezoelectric actuator. This acts as a hydraulic translator on the valve piston of the control valve.

disadvantage the known from the prior art fuel injectors, the operated with a piezoelectric actuator is that the piezo actuator must be very long enough to get one huge To achieve way of the valve piston of the control valve. This leads to a huge overall length of the fuel injector.

Disclosure of the invention

Advantages of the invention

One formed according to the invention Injector for injecting fuel in a combustion chamber of a Internal combustion engine comprises an injection valve member, which at least one injection opening closes or which is activated with a control piston, wherein between the injection valve member and the control piston, a control chamber is formed, which on one side of an end face of the Einspritzven tilsgliedes and on the opposite side of a face of the control piston is limited. The control piston acts as a valve piston a control valve, over which the control room with a low pressure area of a fuel return is connectable. By connecting the actuator to the control piston and the direct action of the control piston on the control room let yourself activate the injection valve member directly. Another opening phase of the injection valve member begins when the control piston as a valve piston a servo valve acts and the control room with the low pressure area the fuel return connects. The essence of the invention lies in a combination of direct Control and servo valve control of the injection valve member. In addition, there is no translation room needed between actuator and control piston, making the actuator more compact can be built and so requires less space.

In an embodiment the control space of the injector is hydraulic with a valve space of the control valve connected. By the hydraulic connection of the control room with the valve chamber prevails when the control valve is closed in the control room and in the valve chamber the same pressure. With open control valve can fuel from the control room over flow the valve chamber into the fuel return, allowing the pressure in the control chamber to rise Return pressure drops. This will cause the opening speed of the injection valve member increases. In addition, by lowering the pressure in the control room of the hub of the injection valve member increases.

In a preferred embodiment is in the hydraulic connection of the control room with the valve chamber of the control valve, a throttle element added. Through the throttle element pressure fluctuations are damped, allowing a repulse of the injection valve is prevented.

The hydraulic connection of the control room with the valve chamber can For example, be designed as a channel in the injector. In a preferred embodiment is the hydraulic connection of the control room with the valve room but designed as a bore in the control piston. Advantage of drilling in the Control piston is that no additional Channel in the housing must be made and thus the housing are made smaller can.

In a first embodiment is the actuator used to operate the injector, a piezoelectric actuator. As the actuator heats up during operation and by the temperature increase it is preferred to ensure the function of the injector, that the actuator in a housing is taken, which is made of a material whose coefficient of thermal expansion corresponds to the actor. Suitable material is for example Invar.

Around compensate for any residual error in the stroke to be able to is in a preferred embodiment between the actuator and the housing taken a compensation element. As material for the compensation element is suitable for example aluminum

By the housing of a material having a coefficient of thermal expansion which corresponds to that of the actuator and optionally the compensation element is avoided that during operation of the injector and an associated Heating the actuator does not close the control valve tightly.

In a second embodiment is the actuator that controls the injector, a magnetic actuator with an armature and a magnetic coil. To a direct control In this case, the control piston with the armature of the Magnet actuator connected. By connecting the control piston with the armature of the magnetic actuator, it is possible to the fuel injector compact with solenoid valve. To open quickly and Shut down of the injector, the control piston is in a preferred embodiment force-balanced. For this purpose, a shoulder is formed on the control piston, which projects into the valve chamber and whose cross-sectional area of the Cross sectional area a face of the control piston, which limits the control space, wherein the shoulder and the face opposite each other. An optionally occurring change in length due to thermal expansion is in the case of a magnetic actuator operated injector by adjustment compensated for the residual air gap between the solenoid and armature.

advantage the inventively designed injector is that there is a direct control of the injection valve member can be realized at the same time compact design of the injector.

One Another advantage of using a piezoelectric actuator as an actuator is that by the pressure relief of the control room already a short Aktorweg and a short actuator is sufficient to operate the injector. This leads as well to a reduction of the needed Size of the injector.

Brief description of the drawings

embodiments The invention is illustrated in the drawings and in the following Description closer explained.

It demonstrate

1 an inventively designed fuel injector with piezoelectric actuator,

2 an inventively designed fuel injector with solenoid valve.

Embodiments of the invention

1 shows an inventively designed fuel injector with piezoelectric actuator.

A fuel injector 1 includes an injection valve member 3 which is in a leadership 5 in a lower housing part 7 is guided. At the injection valve member 3 is a sealing edge 9 trained, which in a seat 11 is adjustable to at least one injection port 13 to close. In addition to the embodiment shown here with an injection opening 13 it is also possible that the fuel injector 1 several injection openings 13 having.

The injection valve member 3 is from a nozzle room 15 enclosed in an inlet channel 17 empties. The inlet channel 17 is about a fuel feed 19 connected to a high pressure accumulator of a common rail system.

With its the injection port 13 opposite end limits the injection valve member 3 with an upper end face 21 a control room 23 , On the upper face 21 becomes the control room 23 through a lower end face 25 a control piston 27 limited. Via a throttle element 29 is the control room 23 with the inlet channel 17 connected.

At the control piston 27 is a sealing edge 31 a control valve 33 trained in a seat 35 is adjustable. Through the control valve 33 is a connection from a valve room 37 in a return channel 39 lockable or releasable. With a second throttle element 41 is the valve room 37 with the inlet channel 17 connected.

The control room 23 is via a hydraulic connection 43 with the valve room 37 connected. In the embodiment shown here is the hydraulic connection 43 as a bore in the control piston 27 executed. For this purpose, a transverse bore in the control piston 45 trained in the valve room 37 empties. Furthermore, in the control piston 27 a hole 47 formed in the axial direction, on the one hand in the transverse bore 45 and then in the control room 23 empties. To pressure fluctuations and a concomitant kickback of the injection valve member 3 To avoid is in the hydraulic connection 43 a throttle element 49 educated.

In the in 1 illustrated embodiment is the control piston 27 with an actor 51 connected, which is designed as a piezoelectric actuator. On the control piston 27 opposite side is the actuator 51 with a plate 53 connected. The actor 51 is of a spring element 55 open-minded, which with the control piston 27 on the one hand and the plate 53 on the other hand. The spring element 55 is preferably designed as a tube spring tension spring. To compensate for stroke errors resulting from a change in length of the actuator 51 due to temperature fluctuations, is the actuator 51 in a housing 57 received, which is preferably made of a material having a thermal expansion coefficient, the coefficient of thermal expansion of the actuator 51 equivalent. To any occurring Residual error is between the plate 53 that with the actor 51 connected, and the housing 57 a compensation element 59 added. The compensation element 59 is made of aluminum, for example.

The housing 57 forms an actuator room 61 in which the actor 51 is included. In the actuator room 61 opens the return channel 39 , As a result, the actuator 51 lapped by fuel under recoil pressure. From the actuator room 51 the fuel flows through a fuel return 63 in the low pressure area.

In the embodiment illustrated here, the fuel injector 1 operated inversely. This means that the at least one injection port 13 with energized actuator 51 and thus length-extended actor 51 is closed and to release the at least one injection port 13 and for starting the injection process, the energization of the actuator 51 is lifted, so that the actor 51 contracts.

To start the injection process, the energization of the actuator 51 completed. As a result, the actor pulls 51 together. The one with the actor 51 connected control pistons 27 will be in the direction of the actuator 51 emotional. By the movement of the control piston 27 the lower face moves 25 of the control piston 27 from the control room 23 , The volume in the control room 23 is enlarged. Due to the increasing volume of the control room 23 the pressure in the control room drops 23 , so that a lower pressure force on the upper face 21 the injection valve member acts. At the same time acts on a pressure edge 65 at the injection valve member 3 System pressure due to the fuel under system pressure in the nozzle chamber 15 , The injection valve member 3 rises with the sealing edge 9 from his seat 11 and releases the at least one injection port. The drop in pressure in the control room 23 is achieved by the throttle element 29 the fuel supply from the supply line 27 is delayed.

At the same time it rises by the movement of the control piston 27 also the sealing edge 31 from her seat 35 and thus gives the connection from the valve chamber 37 in the fuel return 63 over the return channel 39 and the actuator room 61 free. Through the hydraulic connection 43 of the control room 23 with the valve room 27 the pressure in the control room drops 23 continue down. Also about the throttle element 29 in the control room 23 and via the throttle element 41 in the valve room 27 inflowing fuel under system pressure flows directly into the fuel return 63 , A pressure build-up in the control room 23 is thus with open control valve 33 not possible. Due to the strong pressure drop in the control room 23 due to the increase in volume and the simultaneous fuel flow, the movement of the injection valve member 3 in the control room 23 accelerated into it. Also, the stroke is thereby increased.

To end the injection process again, the actuator 51 energized. As a result, the actuator expands 51 out. By expanding the actuator 51 becomes the control piston 27 in the direction of the injection valve member 3 emotional. The sealing edge 31 will be in the seat 35 and thus becomes the control valve 33 locked. About the throttle element 41 Under system pressure, fuel flows into the valve chamber 37 and about the hydraulic connection 43 in the control room 23 , At the same time, fuel under system pressure flows via the throttle element 29 directly into the control room 23 , Through the two inlets into the control room 23 becomes the control room 23 quickly filled and a quick pressure build-up in the control room 23 is achieved. The rapid pressure build-up in the control room 23 causes the injection valve member 3 with the sealing edge 9 fast in the seat 11 is provided. A quick closing of the injection opening 13 is thus possible.

2 shows a fuel injector designed according to the invention with a magnetic actuator.

At the in 2 illustrated embodiment, the fuel injector 1 instead of an actuator designed as a piezoelectric actuator 51 with a magnetic actuator 71 actuated. The magnetic actuator 71 includes a coil 73 that in a core 75 is included. Furthermore, the magnetic actuator comprises 71 an anchor 77 that with the control piston 27 connected is.

Unlike the inversely controlled fuel injector 1 as he is in 1 is shown, the injection port 13 at the in 2 shown fuel injector released when the coil 73 is energized.

By energizing the coil 73 a magnetic field forms, through which the armature 77 is attracted. The anchor 77 moves in the direction of the coil 73 , As a result, also moves the control piston 27 , which is firmly connected to the armature, in the direction of the coil 73 , By the movement of the control piston 27 becomes the lower end face 25 from the control room 23 moves, causing the volume in the control room 23 increased. The pressure in the control room 23 falls off. This acts on the upper end face 21 of the injection valve member 3 a lower force and the injection valve member 3 rises with the sealing edge 9 from the seat 11 , The injection opening 13 will be released.

At the same time it rises by the movement of the control piston 27 the sealing edge 31 from the seat 35 , The connection from the valve room 37 on the Return channel 39 in the fuel return 63 will be released. The pressure in the valve chamber 37 drops to return pressure. Through the hydraulic connection 43 with which the control room 23 with the valve room 37 is connected, also falls the pressure in the control room 23 at return pressure. This leads to a further opening movement of the injection valve member 3 , A quick opening of the injection valve member 3 is made possible.

To the movement of the injection valve member 3 to dampen, is at the injection valve member 3 an edition 79 formed, against which a spring element 81 supported. With the other side, the spring element is supported 81 against a wall 83 of the control room 23 from. The spring element 81 is preferably designed as a compression spring coil spring.

Also at the in 1 illustrated embodiment, it is possible in the control room 23 the edition 79 with the spring element 81 to accommodate the movement of the injection valve member 3 to dampen.

To end the injection process again, the energization of the coil is canceled. As a result, the magnetic field is canceled and the anchor 77 can be different from the coil 73 move away. This movement of the anchor 77 is by a spring element 85 , which is located with one side against the Injektorgehäuse 87 and on the other hand against the anchor 77 supports, supports. The spring element 85 is preferably designed as a compression spring coil spring. By the movement of the anchor 77 in the direction of the injection valve member 3 also becomes the control piston 27 in the direction of the injection valve member 3 emotional. This movement makes the sealing edge 31 on the control piston 27 back in the seat 35 posed. The connection from the valve room 37 in the return channel 39 and from there into the fuel return 63 is closed. About the throttle element 41 fuel flows into the valve chamber 37 , At the same time, the fuel also flows via the hydraulic connection 43 in the control room 23 , This builds up in the control room 23 Press again until system pressure is reached. Due to the increasing pressure in the control room 23 an increased pressure force acts on the upper face 21 at the injection valve member 3 , The injection valve member 3 will be in the direction of the injection opening 13 moved it up with its sealing edge 9 in the seat 11 stands and so the injection opening 13 closes.

To speed up the closing process, it is possible as in 1 represented, the control room 23 with a throttle element with the inlet channel 17 connect to. Then, fuel under system pressure does not just flow out of the valve chamber 37 over the hydraulic connection 43 in the control room 23 but also directly from the inlet channel 17 ,

Instead of the hydraulic connection 43 in the control piston 27 is formed, it is also possible to use the hydraulic connection 43 , as in 2 shown in dashed lines, in the injector 87 train. Furthermore, it is also possible both the hydraulic connection 43 in the control piston 27 as well as the in 2 dashed lines shown hydraulic connection 43 in the injector housing 87 train. Through the two hydraulic connections 43 the flow area is increased so that the fuel from the control room 23 can drain faster and the control room 23 can also be filled faster.

For a quick movement of the control piston 27 Magnetic actuator operated fuel injector 1 To achieve, it is preferred that the control piston 27 balanced force. For this purpose, the control piston 27 from an upper section 89 , a middle section 91 and a lower section 93 manufactured. The upper section 89 is made in a diameter d ₁ , the middle portion in a diameter d ₂ and the lower portion in a diameter d ₃ . At the transition from the upper section 89 to the middle section 91 is at the middle section 91 one shoulder 95 educated. The transition from the middle section 91 to the lower section 93 via a conical section, through which the sealing edge 31 is formed. To force balance on the control piston 27 To achieve this, the cross-sectional area of the shoulder needs to be 95 be as large as the cross-sectional area of the lower end face 25 because on the shoulder 95 and the lower end face 25 oppositely directed pressure forces act. Due to the hydraulic connection 43 of the valve chamber 37 in the shoulder 95 towers and the control room 23 passing through the lower end face 25 is limited, the pressure in the valve chamber 37 and in the control room 23 prevails, the same size. The cross-sectional areas of the shoulder 95 and the lower end face 25 are then the same size if: d ₂ ² - d ₁ ² = d ₃ ² .

Due to the force balanced control piston 27 must be through the magnetic actuator 43 no additional pressure on the control piston 27 works, be overcome. This is a fast movement of the control piston 27 possible.

Claims (12)

Injector for injecting fuel into a combustion chamber of an internal combustion engine with an injection valve member ( 3 ), which is controlled by an actuator ( 51 . 71 ) actuated at least one injection opening ( 13 ) closes or releases, wherein the actuator ( 51 . 71 ) with a control piston ( 27 ) together acts, and wherein between the injection valve member ( 3 ) and the control piston ( 27 ) a control room ( 23 ) formed on one side of an upper end face ( 21 ) of the injection valve member ( 3 ) and on the opposite side from a lower end face ( 25 ) of the control piston ( 27 ) is limited, characterized in that the control piston ( 27 ) as a valve piston of a control valve ( 33 ) is formed, via which the control room ( 27 ) with a low-pressure region of a fuel return ( 63 ) is connectable. Injector according to claim 1, characterized in that the control room ( 23 ) with a valve space ( 37 ) of the control valve ( 33 ) by a hydraulic connection ( 43 ) connected is. Injector according to claim 2, characterized in that the valve space ( 37 ) of the control valve ( 33 ) with open control valve ( 33 ) with the fuel return ( 63 ) of the low-pressure region is connected. Injector according to claim 2 or 3, characterized in that in the hydraulic connection ( 43 ) of the control room ( 23 ) with the valve space ( 37 ) of the control valve ( 33 ) a throttle element ( 49 ) is recorded. Injector according to one of claims 2 to 4, characterized in that the hydraulic connection ( 43 ) of the control room ( 23 ) with the valve space ( 27 ) as a bore ( 45 . 47 ) in the control piston ( 27 ) is executed. Injector according to one of claims 1 to 5, characterized in that the actuator ( 51 . 71 ) firmly with the control piston ( 27 ) connected is. Injector according to one of claims 1 to 6, characterized in that the actuator ( 51 ) is a piezoelectric actuator. Injector according to claim 6, characterized in that the actuator ( 51 ) in a housing ( 57 ), which is made of a material whose coefficient of thermal expansion corresponds to that of the actuator ( 51 ) corresponds. Injector according to claim 6 or 7, characterized in that between the actuator ( 51 ) and the housing ( 57 ) a compensation element ( 59 ) is recorded. Injector according to one of claims 1 to 6, characterized in that the actuator is a magnetic actuator ( 71 ) with an anchor ( 77 ) and a coil ( 73 ). Injector according to claim 10, characterized in that the control piston ( 27 ) with the anchor ( 77 ) of the magnetic actuator ( 71 ) connected is. Injector according to claim 10 or 11, characterized in that on the control piston ( 27 ) one shoulder ( 95 ) formed in the valve space ( 37 ) and their cross-sectional area of the cross-sectional area of the lower end face ( 25 ) of the control piston ( 27 ) corresponding to the control room ( 23 ), whereby the shoulder ( 95 ) and the lower end face ( 25 ) of the control piston ( 23 ) are opposed to each other, so that the control piston ( 23 ) is force-balanced.