DE102004051756A1 - Fuel injection valve for internal combustion engines - Google Patents

Abstract

A fuel injection valve having a valve body (1) in which a valve outer needle (5) and a longitudinally displaceably guided inside valve needle (7) are arranged, which control the opening of at least one injection port (20; 22). A Stuerraum (27) is bounded both by the outer end face (36) of the valve outer needle (5) and the inner end face (34) of the valve inner needle (7), thereby exerting a closing force on the valve needles (5; 7) , In the control chamber (27) opens an inner inlet throttle (40) and an outer inlet throttle (42), can be passed through the high-pressure fuel in the control chamber (27), while the Stuerraum (27) only via exactly one outlet throttle (27 44) with a valve chamber (51) of a control valve (50) and thus connectable to a leakage oil space. On the inner end face (34) of the inner valve needle (7), a sealing region (38) is formed, with which the inner valve needle (7) rests against an abutment in an open position, thereby causing the inner inlet throttle (40) to move against the rest of the control chamber (27 ) is sealed. Thus, by controlling the flow rate of only one outlet throttle (44), both one of the valve needle (5; 7) and both valve needles (5; 7) can be opened (FIG. 1).

Description

The invention is based on a fuel injection valve, as for example from the document DE 103 38 228 A1 is known. The known fuel injection valve for internal combustion engines has a valve body in which a valve outer needle and therein a longitudinally displaceably guided inner valve needle are arranged. Both the valve outer needle and the valve inner needle cooperate with a valve seat and thereby control the opening of at least one injection port. If the valve needles release the respective injection openings as a result of their longitudinal movement, fuel is injected from the pressure chamber through the injection openings into the combustion chamber of the corresponding internal combustion engine.

The Valve needles limit by their end faces facing away from the valve seat a control room, in which over an inner inlet throttle and an outer inlet throttle fuel can be initiated under high pressure. To have a good control the opening To reach the two valve pins, closes the valve inner needle at their opening stroke movement then when she arrives with her forehead at a stop, the inner inlet throttle and thereby reduces the inflow of fuel under high pressure in the control room, because now only the outer inlet throttle open is. this makes possible it, even one of the two valve pins aufzusteuern while the others in their closed position remains. The fuel injection then takes place only by a Part of the injection openings, which is cheaper in the partial load range Conditions in the combustion chamber results.

That from the DE 103 38 228 A1 known fuel injection valve operates in such a way that when the valve outer needle and the valve inner needle at the respective stop the control chamber is separated into an outer subspace and an inner subspace. Both the inner subspace and the outer subspace are connected via a respective outlet throttle with a control valve, so that can be set on the flow of pressure in the control room and thus the pressure in the respective subspaces. Here, it is disadvantageous that two flow restrictors must be formed, which are each very expensive to manufacture, since they are to be produced with very high precision. In addition, the controller shown there does not allow the opening of the valve inner needle in front of the valve outer needle, which is often desired.

Advantages of invention

The Fuel injection valve according to the invention with the characterizing features of claim 1, the across from the advantage that a precise control of the opening stroke both the valve inner needle as well as the valve outer needle precise and with little effort is possible. For this purpose the control room is over exactly one outlet throttle is connected to a valve chamber of a control valve, the valve space in turn by the control valve with a Oil leakage chamber connectable, in which a correspondingly lower pressure prevails. By suitable control of the control valve can be pressure conditions in the control room, which allow it, either only the valve inner needle or the valve inner needle together with the valve outer needle to open and so either through a part or through all the injection openings Inject fuel into the combustion chamber.

In a first advantageous embodiment of the control room is through the installation of the valve inner needle to a corresponding throttle disc, the the inner inlet throttle contains, in an inner subspace, the through the front of the valve inner needle and the throttle plate is limited, and an outer subspace separated. This leaves the pressure in the two subspaces can be adjusted selectively so that the opening dynamics the valve outer needle targeted can control. It is particularly advantageous if the two sub-areas hydraulically are separated from each other and if the outlet throttle only the outer subspace connects to the valve chamber. This increases the controllability at the opening of the valve outer needle.

In a further advantageous embodiment, the control valve includes a valve chamber in which a valve element is arranged, which can be moved by an actuator. Here, the valve element can assume at least two switching positions, wherein in a first switching position, the connection of the valve chamber is interrupted with the leakage oil space, while this connection is open in a second switching position of the valve element. Particularly advantageous in this case is the configuration in which an additional bypass throttle opens into the valve space, via which the valve space can be connected to a high-pressure region of the fuel injection valve. In this case, the valve element closes the bypass throttle in its second switching position while it is released in the first switching position, so that the valve space is connected not only via the outlet throttle to the control chamber but also to the high-pressure region of the fuel injection valve. This allows a quick pressure build-up in the Valve chamber after it has been relieved of pressure via the connection to the leakage oil chamber. Particularly advantageous here is the embodiment in which the valve element has a circular sealing surface whose diameter corresponds at least approximately to the diameter of the junction of the bypass throttle in the valve chamber. The resulting hydraulic conditions at the junction of the bypass throttle in the valve chamber make it possible to drive the valve element, for example by means of a piezoelectric actuator in any intermediate position between the first and the second switching position without hydraulic forces acting on the valve element, which could affect such controllability.

In A further advantageous embodiment is the valve outer needle guided in a valve seat facing away from area in a sleeve, the the control room to the outside limited. In the sleeve is the outer inlet throttle trained, over the control chamber with the high pressure region of the fuel injection valve connected is. Such a sleeve is easy and inexpensive to produce as a separate part.

In In another advantageous embodiment, the inner inlet throttle opens then when the valve inner needle with its front side in the open position abuts the stop, in one on the front side of the valve inner needle trained recess. The recess is in turn via the outer inlet throttle, which is formed in the valve inner needle, with the second subspace connected to the control room. This comes into play when the Valve inside needle in its open position is and the outer subspace on this outer inlet throttle filled with fuel becomes. The formation of the outer inlet throttle in the valve inner needle offers the advantage that the components of the Fuel injection valve is easier to manufacture, as an inlet throttle at the easily accessible Valve inner needle is formed, which can be produced more cost-effectively and with higher precision is, as corresponding recesses in the valve body.

drawing

In the drawing is an embodiment of the illustrated fuel injection valve according to the invention. It shows:

1 a longitudinal section through a fuel injection valve according to the invention,

2 shows the course of the pressure in the control chamber together with the course of the stroke of the valve element and the needle stroke,

3 the same representation as 2 in another mode of operation,

4 a further embodiment, wherein only the area of the control room is shown schematically,

5 a further embodiment in the same representation as 4 and

6 the course of the force acting on the valve element over the stroke of the valve element.

description of the embodiment

1 shows a schematic representation of a longitudinal section through a fuel injection valve according to the invention. The fuel injection valve has a valve body 1 , a throttle disc 2 , a valve disc 4 and a holding body 6 on. These components of the fuel injection valve are arranged in this order and are pressed against each other by a mechanical tensioning device, not shown in the drawing. In the valve body 1 is a pressure room 3 formed, over one, in the throttle plate 2 and the valve disc 4 and the holding body 6 extending inlet channel 12 can be filled with fuel under high pressure. The pressure room 3 is at the combustion chamber end of the fuel injection valve of a conical valve seat 14 limited, from the outer injection openings 20 and inner injection openings 22 out. The inner injection openings 22 have a smaller diameter in the embodiment shown here than the outer injection openings 20 However, these ratios can be reversed.

In the pressure room 3 is a valve outer needle 5 arranged longitudinally displaceable, which has a substantially sleeve shape and at its valve seat side end an outer sealing surface 24 having. The valve outer needle 5 acts with its outer sealing surface 24 with the valve seat 14 together and closes here by investing in the valve seat 14 the outer injection openings 20 so that the outer injection openings 20 both against the interior of the valve outer needle 5 , as well as sealed against their outdoor area. The valve outer needle 5 is in a middle section on the wall of the pressure chamber 3 led, whereby over recesses 19 it is ensured that the upstream and the downstream part of the pressure chamber 3 hydraulically connected to each other to provide a flow of fuel to the injection ports 20 . 22 to enable. At the valve seat end remote from the valve outer needle 5 from a sleeve 16 surround, located at one end to the throttle plate 2 supports and at the other end by a closing spring 17 is applied to the sleeve 16 against the Dros selscheibe 2 suppressed. The closing spring 17 relies on one of the valve outer needle 5 trained paragraph 18 from and has a compressive bias, so that in each position of the valve outer needle 5 a corresponding force on the sleeve 16 and according to the valve outer needle 5 is exercised. By the closing spring 17 so will the valve outer needle 5 against the valve seat 14 pressed, if not more forces act.

In the valve outer needle 5 is a valve inner needle 7 arranged longitudinally displaceable, which is formed substantially piston-shaped and in the valve seat facing away from the valve outer needle 5 is guided. The valve inner needle 7 tapers, starting from the guided section to form an inner pressure shoulder 30 and goes at its valve seat-side end in an inner sealing surface 26 over, with the valve inner needle 7 so with the valve seat 14 cooperates, that when plant the valve inner needle 7 on the valve seat 14 the inner injection openings 22 be closed. The between the valve inner needle 7 and the valve outer needle 5 trained space 9 is about one in the valve outer needle 5 trained connecting throttle 11 with the pressure room 3 connected so that when the valve inner needle 7 from the valve seat 14 has lifted fuel from the pressure chamber 3 over the connecting throttle 11 in the gap 9 flows and from there over the inner injection openings 22 is injected into the combustion chamber.

The valve inner needle 7 has an inner end face at its end remote from the valve seat 34 on, as well as the valve outer needle 5 an outer face 36 having. The faces 34 . 36 the valve needles 5 . 7 limit together with the sleeve 16 and the throttle disc 2 a control room 27 , depending on the pressure in the control room 27 a hydraulic force in the direction of the valve seat 14 on the valve inner needle 7 and the valve outer needle 5 is exercised. The control room 27 is via an internal inlet throttle 40 and an outer inlet throttle 42 connected to the high pressure area of the fuel injection valve, wherein the high pressure area the pressure chamber 3 and the inlet channel 12 includes, in which there is always a high, predetermined fuel pressure prevails. The control room 27 is beyond an outlet throttle 44 with a valve chamber 51 a control valve 50 connected. The valve room 51 is in turn about a leak oil connection 54 connectable with a leakage oil space, not shown in the drawing and on the other hand via a bypass throttle 46 with the pressure room 3 where the bypass throttle 46 an inlet opening 146 in the valve room 51 forms. In the valve room 51 is a valve element 52 arranged, which is connected to a likewise not shown in the drawing, electrically operated actuator. This actuator may be a piezo actuator, for example, which allows the valve element 52 in the valve room 51 so move it between a first switching position where the leak oil connection 54 is closed, and a second switching position in which the bypass throttle 46 closed and the leak oil connection 54 is opened, can be moved back and forth. If a piezoelectric actuator is used, then also every position between the first and the second switching position of the valve element can be 52 approach. The valve element 52 here has a front page 53 on, the inlet opening 146 the bypass throttle 46 opposite. Is the front side 53 on the throttle plate 2 on, so will the inlet opening 146 closed while otherwise through the valve element 52 is released.

First, the operation mode and the operation mode in the case where only through the inner injection openings 22 Fuel should be injected. The valve element 52 is located at the beginning in the first switching position, in which the leak oil connection 54 is closed. As a result, on the one hand the valve chamber 51 over the bypass throttle 46 with the fuel pressure in the pressure chamber 3 flooded and on the other hand prevails in the control room 27 also the high pressure from the inlet channel 12 or the pressure chamber 3 because he has the inner inlet throttle 40 and the outer inlet throttle 42 connected with it. By the pressure in the control room 27 results in a hydraulic force on the outer face 36 the valve outer needle 5 and also on the inner face 34 the valve inner needle 7 so that both valve needles 5 . 7 against the valve seat 14 be pressed and so the outer injection openings 20 or the inner injection openings 22 close. Through the connection choke 11 and the recesses 19 prevails both in the pressure room 3 , as well as in the gap 9 a consistently high fuel pressure. If an injection takes place, the valve element is activated via the actuator 52 moved from the first switching position to the second switching position, so that the leak oil connection 54 is opened while at the same time the bypass throttle 46 is closed. This reduces the pressure in the valve chamber 51 off and thus because of the outlet throttle 44 also in the control room 27 , This process is in 2 shown where the pressure p _s in the control room 27 worn off against the time t. Likewise, in the middle curve, the stroke h _{v of} the valve element 51 worn off against time t. The timing at which the valve element 51 is moved and the injection cycle begins, is designated t ₀ . As already mentioned, the pressure p, starting from the time t ₀ to the time point t ₁ from where it reaches the pressure p _oe1 . This corresponds to the opening pressure of the valve inner needle 7 , ie the pressure to which the opening hydraulic forces on the inner pressure shoulder 30 and on parts of the inner sealing surface 26 sufficient, the closing pressure, by the hydraulic forces in the control room 27 on the inner face 34 is exercised to overcome. The valve inner needle 7 emotional from the valve seat 14 away and gives the inner injection openings 22 free with fuel from the gap 9 be supplied. By the movement of the valve inner needle 7 in the control room 27 in there the pressure rises again, what in 2 between the times t ₁ and t _{2 is} shown. At the bottom is also the stroke h _{i of} the valve inner needle 7 shown, which reaches its maximum at the time t ₂ , that is, the valve inner needle 7 has reached its stop, so on the throttle plate 2 , The inner face 34 the valve inner needle 7 is structured and has a sealing area 38 on, which is designed as a ring edge. When installing the inner valve needle 7 at the throttle plate 2 becomes the control room 27 so in an inner subspace 127 and an outer subspace 227 separated, with the inner subspace 127 through the inside of the sealing area 38 lying part of the inner end face 34 and the throttle disk 2 is limited while the outer subspace 227 the rest of the control room 27 includes. The internal inlet throttle 40 So it is through the system of the inner valve needle 7 at the throttle plate 2 from the outer subspace 227 hydraulically isolated. In the inner subspace 127 is via the inner inlet throttle 40 Immediately the pressure in the inlet channel 12 set. Because of a chamfer 28 on the valve inner needle 7 but only a partial area of the inner end face 34 is acted upon by the full fuel pressure, the lowered pressure in the outer subspace 227 out, the valve inner needle 7 to keep in their open position.

At time t ₂ , the control valve 50 again actuated by the valve element 52 moves into an intermediate position, ie between the first and the second switching position. This will cause the bypass throttle 46 slightly open while the leak oil connection 54 something is closed. There in the valve room 51 still lower pressure prevails than in the inlet channel 12 , the pressure in the outer subspace decreases 227 again and reaches after a certain time a pressure p ₂ , which is so low that the inner valve needle 7 remains in its open position while the valve outer needle 5 by the hydraulic pressure in the outer part space 227 is still held in its closed position. If the injection is to be ended, then the control valve 50 pressed again and the valve element 52 moves back to its first switch position. About the bypass throttle 46 A high fuel pressure builds up very quickly in the valve chamber 51 on and over the outer inlet throttle 52 and the now serving the inlet outlet throttle 44 also in the outer subspace 227 , This in turn increases the hydraulic force on the chamfer 28 so that the valve inner needle 7 is pressed back into its closed position.

Target through all injection openings 20 . 22 Fuel is injected, then the valve element 52 also driven at the beginning of the injection from the first to the second switching position. The course of pressure p _s , stroke h _{v of} the valve element 51 , Stroke h _{i of} the valve inner needle 7 and stroke h _{a of} the valve outer needle 5 is in 3 shown. The course up to the time t ₂ corresponds to the course already in the injection through the inner injection openings 22 was presented. At time t ₂ , the control valve 50 but now not operated, but remains in its second switching position. As a result, the pressure p _s decreases in the. outer subspace 227 further below the opening _pressure p _{oe2 of} the valve _{outer needle} 5 off, so that now on the valve outer needle 5 by the hydraulic forces also the outer pressure shoulder 32 and on parts of the outer pressure surface 24 from the valve seat 14 moved away and the outer injection openings 20 releases. The timing at which the valve outer needle 5 sets in motion is in the 3 denoted by t ₂ '. After a certain time the valve outer needle reaches 5 their maximum stroke, that is, they are in abutment with the throttle plate 2 comes. The outer face 36 the valve outer needle 5 here is slightly bevelled, so that the outer face 36 still the fuel pressure of the outer subspace 227 remains charged. To complete the injection, the valve element 52 moved back to the first shift position and the fuel pressure builds up in the control room 27 open again and push the valve inner needle 7 and the valve outer needle 5 back to their respective closed position.

The position of the outer inlet throttle 42 can also be varied. In 4 is another embodiment shown schematically, wherein only the area of the control room 27 is shown. The external inlet throttle 42 is here in the sleeve 16 trained and connects so directly to the pressure chamber 3 with the control room 27 , The outer face 36 is, unlike the embodiment according to 1 , beveled so that on the inner edge of the outer face 36 an edge is created in the open position of the valve outer needle 5 at the throttle plate 2 is applied. Care must be taken in the throttle plate 2 to provide a corresponding recess, so that the outlet throttle 44 both with the outer subspace 227 , as well as in the inner subspace 127 stays connected.

In 5 is shown a further embodiment, in which the second inlet throttle 42 in the valve inner needle 7 is trained. This is on the inner end face 34 a recess 47 formed, which has the shape of a blind hole. From the recess 47 goes the outer inlet throttle 42 radially outward and thus connects when the valve inner needle 7 on the stop, so on the throttle plate 2 , the inner subspace 127 with the äuße ren subspace 227 , The filling of the outer subspace 227 thus takes place through the series reactors, namely the inner inlet throttle 40 and the outer inlet throttle 42 , Otherwise, the function of both the in 4 presented, as well as in 5 illustrated embodiment as described above.

In 6 is the force F on the valve element 52 by the hydraulic forces in the valve chamber 51 represented with respect to the stroke h _{v of} the valve element 52 , where a stroke of h _v = 0 corresponds to the first switching position. I is the course of the force F over the stroke h _v , as it results when the circular front side 53 of the valve element 52 significantly larger than the diameter of the mouth 146 the bypass throttle 46 , In order to achieve the necessary maximum force F _max , which is necessary to the valve element 52 to move out of the first switching position, a voltage U ₁ must be applied to the piezo actuator, here the valve element 52 to move. As can be seen on the course of the curve I increases the movement of the valve element 52 necessary force F due to the hydraulic conditions in the valve chamber 51 with the stroke h _v stronger than the force of the piezo actuator. As a result, the valve element moves 52 , without the piezo actuator could intervene, continue to the end position h _e , which practically corresponds to the second switching position. An intermediate stroke of the valve element 52 can thus be adjusted only in the area that in the 6 is denoted by A.

Indicates the front side 53 however, approximately the same diameter as the mouth 146 the bypass throttle 46 , so there is a curve between force F and stroke h _{v of} the valve element 52 , as it corresponds to the curve II. After reaching the maximum force F _max , the voltage at the piezoelectric actuator must be further up-regulated, ie from the voltage U ₁ to a voltage U ₂ and beyond, to the valve element 52 to move between the first and the second switching position. As a result, an arbitrary intermediate stroke between the first and the second switching position can be set if, for example, for the position of the valve element 52 for partial injection, a stroke in the range Δh must be approached. This is a stable control of the pressure in the outer subspace 227 possible. In principle, any position of the valve element can be 52 approach in the area that is in 6 is denoted by B.

Claims (11)

Fuel injection valve for internal combustion engines with a valve body ( 1 ), in which a valve outer needle ( 5 ) and a longitudinally displaceably guided inside valve needle ( 7 ) are arranged, wherein both the valve outer needle ( 5 ) as well as the valve inner needle ( 7 ) with a valve seat ( 14 ) and by longitudinal movement the opening of at least one injection opening ( 20 ; 22 ), and with a control room ( 27 ), which both the valve seat facing away from the outer face ( 36 ) of the valve outer needle ( 5 ) and the valve seat facing away from the inner end face ( 34 ) of the inner valve needle ( 7 ) acted upon hydraulically, and with an inner inlet throttle ( 40 ) and an outer inlet throttle ( 42 ), via the high pressure fuel into the control room ( 27 ), wherein at the inner end face ( 34 ) of the inner valve needle ( 7 ) a sealing area ( 38 ) is formed, with which the inner valve needle ( 7 ) abuts against an abutment in an open position such that thereby the inner inlet throttle ( 40 ) against the remaining control room ( 27 ), characterized in that the control room ( 27 ) via exactly one outlet throttle ( 44 ) with a valve space ( 51 ) of a control valve ( 50 ) is connectable, wherein the valve space ( 51 ) is connectable to a leakage oil space. Fuel injection valve according to Claim 1, in which the stop on one of the control chambers ( 27 ) limiting throttle plate ( 2 ) is formed, in which the inner inlet throttle ( 40 ), wherein the inner valve needle ( 7 ) by contact with the throttle plate ( 2 ) the control room ( 27 ) into an inner subspace ( 127 ) passing through the inner face ( 34 ) of the inner valve needle ( 7 ) and the throttle plate ( 2 ) and in an outer subspace ( 227 ), the remaining control room ( 27 ) is shared. Fuel injection valve according to Claim 2, in which the inner subspace ( 127 ) and the outer subspace ( 227 ) in the open position of the valve inner needle ( 7 ) are hydraulically separated. Fuel injection valve according to Claim 2 or 3, in which the outlet throttle ( 44 ) only the outer subspace ( 227 ) with the valve space ( 51 ) connects. Fuel injection valve according to Claim 1, in which the control valve is in the valve chamber ( 51 ) arranged valve element ( 52 ), which interrupts the connection with the leakage oil space in a first switching position, and opens the connection to the leakage oil space in a second switching position. Fuel injection valve according to claim 1, in which a bypass throttle (in the valve space ( 46 ), via which the valve space ( 51 ) with a high pressure area ( 3 ; 12 ) of the fuel injection valve is connectable, and with one in the valve chamber ( 51 ) movably arranged valve element ( 52 ), which interrupts the connection with the leakage oil space in a first switching position, while the bypass throttle ( 46 ) is opened, and in a second switching position opens the connection with the leakage oil chamber, while the bypass throttle ( 46 ) is closed, where at the control room ( 27 ) to the valve space ( 51 ) leading outlet throttle ( 44 ) stays open all the time. Fuel injection valve according to Claim 6, in which the valve element ( 52 ) a circular sealing surface ( 53 ) having an inlet opening ( 146 ) of the bypass throttle ( 46 ) in the valve space ( 51 ) and in the second switching position, the bypass throttle ( 46 ), wherein the diameter of the circular sealing surface ( 53 ) and the diameter of the inlet opening ( 146 ) are at least approximately equal. Fuel injection valve according to Claim 1, in which the valve outer needle ( 5 ) an outer end face ( 36 ), which is chamfered and thereby has the shape of a truncated cone, so that on the outer end face ( 46 ) a sealing area ( 38 ) is formed. Fuel injection valve according to Claim 2, in which the fuel pressure in the outer subspace ( 127 ) a part of the inner end face ( 34 ) of the inner valve needle ( 7 ). Fuel injection valve according to Claim 1, in which the valve outer needle ( 5 ) in a control room ( 27 ) outwardly limiting sleeve ( 16 ), wherein the outer inlet throttle ( 42 ) in the sleeve ( 16 ) is trained. Fuel injection valve according to Claim 1, in which the inner valve needle ( 7 ) on its inner end face ( 34 ) a recess ( 47 ), into which the inner inlet throttle ( 40 ) in the open position of the valve inner needle ( 7 ), when the inner valve needle ( 7 ) with its sealing area ( 38 ) rests in the open position on the stop, wherein the outer inlet throttle ( 42 ) in the valve inner needle ( 5 ) is formed and the recess ( 47 ) with the second subspace ( 227 ) connects.