DE102004028618A1 - Common rail injector for introducing fuel into an engine comprises an intermediate lift stop for a first valve body - Google Patents

Abstract

Common rail injector comprises an intermediate lift stop (54) for a first valve body (38). The valve body is stopped using the stop when it is moved from a closing position into a central position. Preferred Features: The intermediate lift stop is arranged on a stop element (55) which interacts with a second valve body (58). The second valve body has a closing unit which releases a flow path between the valve chamber (33) and a control chamber (24) when the first valve body is moved with the second valve body over the intermediate lift stop.

Description

The The invention relates to a common rail injector with an injector housing, the having a fuel inlet, which with a central high-pressure power source outside of the injector housing and communicating with a pressure space within the injector housing in dependence from the pressure in a first and in a second control room, with High-pressure fuel in a combustion chamber of an internal combustion engine is injected when a first nozzle needle and / or a second nozzle needle take off from their seat or takes off, the pressure in the control rooms is controlled by an actuator, in particular a piezoelectric actuator, which cooperates with a valve having a first valve body with a first closing member that has a flow path between a valve chamber and a return chamber interrupts or releases when the first valve body its closed position leaves.

to Control of the pressures in the control rooms can different valve types are used. Depending on valve design It is difficult to use the two nozzle needles to drive exactly.

task The invention is a common rail injector with an injector, the having a fuel inlet, which with a central high-pressure power source outside of the injector housing and with a pressure space inside the injector housing in Compound stands, from which, depending on the pressure in one first and in a second control room, with high pressure fuel is injected into a combustion chamber of an internal combustion engine, if a first nozzle needle and / or a second nozzle needle take off from their seat or takes off, the pressure in the control rooms is controlled by an actuator, in particular a piezoelectric actuator, which cooperates with a valve having a first valve body with a first closing member that has a flow path between a valve chamber and a return chamber interrupts or releases when the first valve body its closed position leaves, to create, which allows a better control of the nozzle needles.

presentation the invention

The Task is with a common rail injector with an injector housing, which having a fuel inlet, which with a central high-pressure power source outside of the injector housing and communicating with a pressure space within the injector housing in dependence from the pressure in a first and in a second control room, with High-pressure fuel in a combustion chamber of an internal combustion engine is injected when a first nozzle needle and / or a second nozzle needle take off from their seat or takes off, the pressure in the control rooms is controlled by an actuator, in particular a piezoelectric actuator, which cooperates with a valve having a first valve body with a first closing member that has a flow path between a valve chamber and a return chamber, also called unpressurized Room can be called, interrupts or releases when the first valve body its closed position leaves, by solved, that for the first valve body a Zwischenhubanschlag is provided, on which the first valve body in Stop comes when he moves from its closed position to a middle position is moved. In the context of the present invention it has been found that the positioning of a 3/3-way valve in the middle position by Production-related scattering of the piezo actuators and due to In operation occurring vibrations is difficult. By the Zwischenhubanschlag invention may be the first valve body be safely positioned in the middle position.

One preferred embodiment of the injector is characterized in that the Zwischenhubanschlag is formed on a stop element, with a second valve body cooperates, which has a second closing member, the one flow between the valve chamber and the second control chamber releases, if the first valve body together with the second valve body over the Zwischenhubanschlag is moved out. That provides the advantage that the second nozzle needle regardless of the first nozzle needle can be controlled by the actuator.

A further preferred exemplary embodiment of the injector is characterized in that the stop element is formed by a stop pin which is guided back and forth movably in the injector housing, one end of which represents the intermediate stroke stop for the first valve body and the second valve body bears against the other end thereof. The second valve body is preferably held in its closed position by a prestressed spring device, in which the flow path between the valve chamber and the second control chamber is interrupted. The biasing force of the spring device is selected so that the second valve body is held in its closed position when the first valve body is moved from its closed position to its central position. If the first valve body is moved beyond its center position, then this movement over the stopper bolt on the second valve body over wear, so that the flow path between the valve chamber and the second control chamber is released.

One Another preferred embodiment of the injector is characterized in that on the stop pin at least one flattening is formed, which is the flow path creates between the valve chamber and the second control chamber. Of the flow is released when the second shutter opens.

One Another preferred embodiment of the injector is characterized in that the second valve body of a valve ball is formed, which represents the second closing member and by a spring between the second nozzle needle and the valve ball is clamped against a valve seat is pressed. This solution is production technology easily and inexpensively feasible.

One Another preferred embodiment of the injector is characterized in that the stop element from one in the injector housing guided back and forth Stop pin is formed, which starts from the second valve body. By the one-piece Formation of valve body and stop bolts, the number of required components is reduced and simplifies assembly.

One Another preferred embodiment the injector is characterized in that at the second valve body a biting edge is formed, which is the second closing member and by a spring which is clamped between the second nozzle needle and the second valve body, against the injector housing depressed becomes. This will be a safe interruption of the flow path ensured between the valve chamber and the second control room.

One Another preferred embodiment the injector is characterized in that the first control chamber via a Outflow throttle is in communication with the valve chamber. About the Outflow throttle can change the opening speed the first nozzle needle be set.

One Another preferred embodiment the injector is characterized in that the second control chamber via a further outlet throttle is in communication with the valve chamber. About the others Outflow throttle can change the opening speed the second nozzle needle be set.

One Another preferred embodiment the injector is characterized in that the first control chamber via a Inlet throttle is in communication with the fuel inlet. About the inlet throttle can the closing speed the first nozzle needle be set.

One Another preferred embodiment the injector is characterized in that the second control chamber via a another inlet throttle is in communication with the first control chamber. About the another inlet throttle, the closing speed of the second nozzle needle be set.

One Another preferred embodiment the injector is characterized in that the second control chamber via a further inlet throttle is in communication with the fuel inlet. By the direct supply of the additional inlet throttle with the rail pressure can the closing speed the second nozzle needle be better controlled.

The previously mentioned closing members can each from one to the valve body trained sealing edge are formed, which provided with a on the injector sealing surface interacts. The closing organs can but also formed by a formed on the valve body sealing surface be with a provided on the injector housing sealing edge interacts.

Further Advantages, features and details of the invention will become apparent the following description, with reference to the drawing various embodiments are described in detail.

drawing

It demonstrate:

1 the lower part of an injector according to the invention in longitudinal section;

2 the upper part of an injector according to the invention according to a first embodiment in longitudinal section;

3 an enlarged section 2 ;

4 the upper part of an injector according to the invention according to another embodiment in longitudinal section;

5 a plot of the voltage over time;

6 a plot of the valve lift over time;

7 a plot of pressure in the Control spaces over time and

8th a plot of needle stroke over time.

description the embodiments

The in the 1 and 2 or 1 and 3 illustrated embodiments of the injector according to the invention have a total of 1 designated injector on. The injector housing 1 includes a nozzle body 2 , which projects with its lower free end into the combustion chamber of the internal combustion engine to be supplied. With its upper, combustion chamber remote end face is the nozzle body 2 by means of a (not shown) clamping nut axially against a valve body 3 and an injector body 4 braced.

In the nozzle body 2 is an axial guide hole 6 spared. In the guide hole 6 is a first nozzle needle 8th guided axially displaceable. At the top 9 the nozzle needle 8th a sealing edge is formed, which cooperates with a sealing surface, which on the nozzle body 2 is trained. If the tip 9 the nozzle needle 8th with its sealing edge in abutment with the sealing surface, which can also be referred to as a sealing seat, are two (not shown) spray-hole rows in the nozzle body 2 closed or ste hen hen not connected to the high-pressure fuel storage. If the nozzle needle tip 9 lifts off from their seat, the first of the two injection holes rows is released and injected with high pressure fuel injected through the first spray hole row into the combustion chamber of the internal combustion engine.

At the first nozzle needle 8th is a pressure shoulder 10 trained in a pressure room 11 disposed in the injector housing 2 is provided. The pressure room 11 is via a pressure channel 12 with high pressure fuel from a central high pressure fuel source (not shown), also referred to as a high pressure fuel reservoir, outside the injector housing 1 supplied, as by an arrow 13 is indicated.

The first nozzle needle 8th is equipped with a central through hole, in which a second nozzle needle 14 is guided back and forth movable. At the top 15 the second nozzle needle 14 is a sealing edge 16 formed, which cooperates with a sealing surface or a sealing seat, or on the nozzle body 2 is trained. If the tip 15 the second nozzle needle 14 with its sealing edge 16 is located in contact with the sealing seat, the second of the spray hole rows in the nozzle body 2 closed or not with the pressure chamber 11 in connection. If the tip 15 the second nozzle needle 14 takes off from its seat, and if at the same time the first nozzle needle 8th with her tip 9 is lifted from its seat, then high pressure beauf beat fuel injected through both spray holes in the combustion chamber of the engine. The injection thus takes place either only through the first spray hole row or through both spray hole rows. The injected high pressure fuel passes through an annulus 17 from the pressure room 11 to the top 9 the first nozzle needle 8th , The high-pressure fuel is thus located in the immediate vicinity of the tip 9 the first nozzle needle 8th , If the tip 9 the nozzle needle 8th lifts off from its seat, then the high-pressure fuel also reaches the top 15 the second nozzle needle 14 ,

Opening and closing the first nozzle needle 8th is about the pressure in a first control room 18 controlled, the at the combustion chamber remote end of the first nozzle needle 8th in the guide hole 6 of the nozzle body 2 is trained. The first control room 18 becomes radially inward through the second nozzle needle 14 and through a control chamber sleeve 20 limited, which at the combustion chamber remote end of the second nozzle needle 14 is performed in a sealing manner. At the control room sleeve 20 is how in 2 you can see a biting edge 21 formed on the combustion chamber facing the end face of the valve body 3 is applied. In the axial direction between the control chamber sleeve 20 and the first nozzle needle 8th is a compression spring 22 clamped, through which the control chamber sleeve 20 with its biting edge 21 in contact with the valve body 3 is held. Radial inside the control chamber sleeve 20 is a second control room 24 formed, in the axial direction through the combustion chamber remote end of the second nozzle needle 14 and by the combustion chamber facing the end face of the valve body 3 is limited.

In 2 you can see that the pressure channel 12 through the valve body 3 passes through and with a fuel inlet 26 communicating, as by an arrow 27 is indicated, with the central fuel high pressure source outside the injector 1 communicates.

The fuel feed 26 is via a first inlet throttle 29 in the valve body 3 is arranged with the first control room 18 in connection. The first control room 18 is via a second inlet throttle 30 in the control room sleeve 20 is arranged with the second control room 24 in connection. The first control room 18 stands over an outlet throttle 32 in the valve body 3 is arranged with a valve chamber 33 in communication in the injector body 4 is trained. The valve room 33 In turn, there is a through hole 35 in the injector body 4 is omitted, with a Fuel return area 36 in conjunction, which is also in the injector body 4 is omitted. The fuel return chamber 36 is connected via a (not shown) return line to the fuel tank in connection.

In the injector body 4 is a first valve body 38 taken in the axial direction movable back and forth, as by a double arrow 39 is indicated. The first valve body 38 has at its combustion chamber remote end of a. plunger 41 on, which is hydraulically coupled via a hydraulic coupling space with a piezoelectric actuator (not shown). About the energization of the piezoelectric actuator, the first valve body 38 in the direction of the double arrow 39 be moved back and forth. Following the valve piston 41 has the first valve body 38 a frustoconical rejuvenation 42 on, whose tapered end in a connecting bolt 43 passes in the area of the through hole 35 is arranged. At the end of the connecting bolt 43 is a closing organ 44 formed, which has substantially the shape of a hemisphere. The closing organ 44 has a hemispherical sealing surface on the outside 45 on, which is in contact with a valve seat 46 located inside the injector body 4 is trained. Following the closing organ 44 has the first valve body 38 a spring plate 48 on which a valve pin 50 emanates. Between the spring plate 48 and the valve body 3 is a compression spring 52 clamped. By the biasing force of the compression spring 52 becomes the closing organ 44 in attachment to the service area 46 held.

The combustion chamber facing the end of the valve pin 50 is at a distance to a Zwischenhubanschlag 54 arranged, that of the combustion chamber remote end of the stop pin 55 is formed. The stop bolt 55 is in a central through-hole 56 guided back and forth in the valve body 3 is omitted. The combustion chamber near end of the stop pin 55 lies on a valve ball 58 on, by a compression spring 59 between the valve ball 58 and the combustion chamber distal end of the second nozzle needle 14 is clamped against a sealing surface 61 (see enlarged view of 3 ) is pressed, which at the combustion chamber near the end of the through hole 56 on the valve body 3 is trained.

In the enlarged view of the 3 you also see that on the stop bolt 55 longitudinal flats 64 . 65 . 66 . 67 are formed, the passage of fuel from the second control room 24 in the valve room 33 allow if the valve ball 58 from the sealing surface 61 takes off.

In the in the 2 and 3 shown switching position is the first valve body 38 with his closing organ 44 in contact with the valve seat 46 , In the two control rooms 18 and 24 as well as in the valve room 33 there is rail pressure. Rail pressure refers to the pressure in the central high-pressure fuel source, also referred to as rail or common rail, outside the injector housing 1 prevails. When the (not shown) piezoelectric actuator is energized, then the valve body 38 to the valve body 3 moved to the combustion chamber near the end of the valve pin 50 at the intermediate stroke stop 54 comes to the plant. This lifts the closing organ 44 from the valve seat 46 off, allowing the pressure in the valve chamber 33 to the fuel return chamber 36 is reduced down. About the outlet throttle 32 is also the pressure in the first control room 18 mined, leaving the first nozzle needle 8th with her tip 9 lifts off the associated seat.

When energizing the piezoelectric actuator, the voltage of the actuator is brought to an average value, whereby the valve body 38 with the valve pin 50 only up to the Zwischenhubanschlag 54 on the stop bolt 55 is moved. The first inlet throttle 29 and the outlet throttle 32 are flowed through, reducing the pressure in the first control room 18 drops. From a certain pressure, by the diameter ratios of the nozzle needles 8th and 14 is definable, opens the first nozzle needle 8th and the injection starts.

Because the second control room 24 via the second inlet throttle 30 directly with the first control room 18 is connected, the pressure falls in the second control room 24 also off. When the voltage at the actuator is reduced again, close the valve seat 46 and the first nozzle needle 8th , whereby the injection is terminated.

However, if the voltage on the actuator continues to increase above the mean value, then the first valve body will become 38 moved to the combustion chamber until the combustion chamber near the end of the valve pin 50 on the valve body 3 is applied. The valve pin presses 50 the stop bolt 55 and the valve ball 58 in the second control room 24 into it, reducing the sealing surface 61 , which is also referred to as the second valve seat is opened. As part of the second control room 24 fuel at the flats 65 to 67 over in the valve room 33 can drain, the pressure falls in the control room 24 continue down to the top 15 the second nozzle needle 14 takes off from its associated seat.

When the voltage at the actuator is reduced again, the inner nozzle needle closes first 14 , When the actuator is completely retracted, so too does the valve seat 46 closes, then closes the outer nozzle needle 8th , If the Voltage at the actuator is quickly reduced from the maximum voltage to zero, then close both nozzle needles 8th and 14 simultaneously.

In 5 the course of the actuator voltage U over the time t is shown. First, the voltage increases continuously until it has reached a medium value. This mean value is kept constant for a while. Then the voltage is further increased until the maximum value of the voltage is reached. Then the voltage drops continuously to zero.

In 6 the associated course of the valve lift V over the time t is shown. The valve body 38 moves when increasing the voltage of the actuator to an average of its in 2 shown starting position to the combustion chamber, until the Zwischenhubanschlag 68 is reached. As long as the actuator voltage is constant, the valve lift remains the same. When the voltage is further increased, then the first valve body moves 38 together with the valve ball 58 further.

In 7 the associated course of the pressure p over the time t is plotted. The pressure curve in the first control room 18 is represented by a solid line. The pressure curve in the second control room 24 is shown by a dashed line. First of all, there are two control rooms 18 and 24 Rail pressure. Then the pressure drops in the first control room 18 a bit stronger than in the second control room 24 until an intermediate value is reached. When the actuator voltage is increased above its average, then the pressure in the second control chamber drops 24 continue down while the pressure in the first control room 18 remains constant.

In 8th the associated needle lift N is plotted over time t. The needle stroke of the first nozzle needle 8th is shown by a solid line. The needle stroke of the second nozzle needle 14 is shown with a dashed line. In 8th you can see that the first nozzle needle 8th in front of the second nozzle needle 14 opens and after the second nozzle needle 14 closes.

In 4 is a similar embodiment as in the 2 and 3 shown. To denote the same parts, the same reference numerals are used. To avoid repetition, the preceding description of the 2 and 3 directed. In the following, only the differences between the two embodiments will be discussed.

At the in 4 illustrated embodiment is on the first valve body 38 no hemispherical closing member formed, but a closing member 74 that has a substantially cone-shaped butt-like sealing surface 75 having. The sealing surface 75 of the closing organ 74 is in contact with a sealing edge 76 in the injector body 4 is trained.

In addition, comes in the in 4 illustrated embodiment instead of the valve ball a valve body 78 for use, which essentially has the shape of a circular disk, at its combustion chamber remote end side radially outside a biting edge 79 is formed, which on the valve body 3 is applied. In addition, the stopper bolt 55 integral with the valve body 78 educated. In addition, the second control room 24 via a second inlet throttle 70 supplied directly from the fuel inlet with fuel. Finally, from the through hole 56 a second outlet throttle 71 made a connection between the second control room 24 and the valve room 34 creates when the valve body 78 takes off from his seat.

Claims (12)

Common rail injector with an injector housing ( 1 ), which has a fuel feed ( 26 ) having a central high-pressure power source outside the injector housing ( 1 ) and with a pressure chamber ( 11 ) within the injector housing ( 1 ), from which, depending on the pressure in a first ( 18 ) and in a second ( 24 ) Control space, high-pressure fuel is injected into a combustion chamber of an internal combustion engine when a first nozzle needle ( 8th ) and / or a second nozzle needle ( 14 ) takes off from its seat, the pressure in the control rooms ( 18 . 24 ) is controlled by an actuator, in particular a piezoelectric actuator, which cooperates with a valve having a first valve body ( 38 ) with a first closing member ( 44 ) having a flow path between a valve space ( 33 ) and a return space ( 36 ) interrupts or releases when the first valve body ( 38 ) Leaves its closed position, characterized ge denotes that for the first valve body ( 38 ) a Zwischenhubanschlag ( 54 ) is provided, on which the first valve body ( 38 ) comes into abutment when it is moved from its closed position to a middle position. Injector according to claim 1, characterized in that the Zwischenhubanschlag ( 54 ) on a stop element ( 55 ) formed with a second valve body ( 58 ), which has a second closing member, which defines a flow path between the valve space (FIG. 33 ) and the second control room ( 24 ) releases when the first valve body ( 38 ) together with the second valve body ( 58 ) via the intermediate stroke stop ( 54 ) is moved out. Injector according to claim 2, characterized in that the stop element of a in the Injektorgehäuse ( 1 ) reciprocally guided stop bolts ( 55 ) is formed, one end of the Zwischenhubanschlag for the first valve body ( 38 ) and at the other end of the second valve body ( 58 ) is present. Injector according to claim 3, characterized in that on the stop pin ( 55 ) at least one flat ( 64 - 67 ) is formed, which the flow path between the valve space ( 33 ) and the second control room ( 24 ) creates. Injector according to claim 3 or 4, characterized in that the second valve body of a valve ball ( 58 ) is formed, which represents the second closing member and by a spring ( 59 ) between the second nozzle needle ( 14 ) and the valve ball ( 58 ) is clamped against a valve seat ( 61 ) is pressed. Injector according to claim 1 or 2, characterized in that the stop element of a in the injector ( 1 ) reciprocally guided stop bolts ( 55 ) formed by the second valve body ( 78 ). Injector according to claim 6, characterized in that on the second valve body ( 78 ) a biting edge ( 79 ) is formed, which is the second closing member and by a spring ( 59 ) between the second nozzle needle ( 14 ) and the second valve body ( 78 ) is clamped against the injector housing ( 1 ) is pressed. Injector according to one of the preceding claims, characterized in that the first control chamber ( 18 ) via an outlet throttle ( 32 ) with the valve space ( 33 ). Injector according to claim 8, characterized in that the second control room ( 24 ) via another outlet throttle ( 71 ) with the valve space ( 33 ). Injector according to one of the preceding claims, characterized in that the first control chamber ( 18 ) via an inlet throttle ( 29 ) with the fuel feed ( 26 ). Injector according to one of the preceding claims, characterized in that the second control chamber ( 24 ) via a further inlet throttle ( 30 ) with the first control room ( 18 ). Injector according to claim 10, characterized in that the second control room ( 24 ) via a further inlet throttle ( 70 ) is in communication with the fuel inlet.