DE102006049533A1 - Piezoelectrically actuated injector for injection system i.e. common rail fuel injection system, has actuator, and control valve with valve unit with ball and pressure pin, where ball is guided in guiding borehole of valve housing - Google Patents

Abstract

The injector has a nozzle needle, a control valve (3) and a piezoelectric actuator, where the valve has a valve unit (35) and controls a hydraulic connection between a control chamber and a fuel return. The valve unit has a ball (37) and a pressure pin (39), where the ball is guided in a guiding borehole (43) of a valve housing (33). A linear contact surface (45) is provided between the ball and the borehole and is interrupted by a flat portion in the ball surface, where the pin is arranged in the borehole.

Description

State of the art

injectors for fuel injection systems of internal combustion engines are well known. Especially In common-rail fuel injection systems are advantageously Injectors are used in which the control valve of piezo actuators is switched. These control valves have a valve pin, which needs to be ground very precisely. For reasons of space is It is not possible, however Valve pin in the valve body to lead what to increased Can cause wear.

Disclosure of the invention

Of the Invention is based on the object, a control valve for a To provide injector whose components easier and cheaper can be produced and in which reduces the wear of the valve member so that the life of the injector increases.

These Task is according to the invention in a Injector for an injection system of an internal combustion engine, with a nozzle needle, with a control valve and with an actuator, wherein the control valve a Valve member comprises, and wherein the control valve is a hydraulic Controls the connection between a control room and a fuel return, solved by that the valve member comprises a ball and a pressure pin, and that the ball is in a guide hole a valve housing guided is.

at the control valve according to the invention can the valve member, in particular in the region of the ball, in a guide bore be guided of the valve housing. As a result, the valve member always has a defined position, so that in particular when hitting the valve member on a sealing seat in the valve housing no relative movements between valve member and valve seat occur can, the wear of the Include valve member and / or the valve seat with it.

There Balls of hardened Steel in very big numbers and can be produced very inexpensively with extremely low tolerances is by using a purchased ball of hardened steel the manufacture of a valve member according to the invention is greatly simplified and its production costs significantly reduced. To buy from an Ball of hardened Steel an inventive valve member it is only necessary to make a pressure pin on the ball, for example by welding, to fix. This pressure pin can be made of a bar material cut Be and requires no special post-processing.

Such For example, balls are used by manufacturers of ball bearings manufactured with very small tolerances in largest quantities. Thereby are the costs in spite of the big ones precision and quality relatively low. Because ball bearing balls with different tolerance levels commercially are offered, it is still possible to use the guide bore relatively large tolerances and then with a valve member according to the invention whose ball has the appropriate diameter to mate. This will be the manufacturing costs further reduced, without compromising on the quality of the leadership of the Valve member in the guide bore smears to have to make.

Around the outflow of fuel with open Control valve and in some cases allow it in the first place, is provided that a linear contact surface between the ball and the guide hole interrupted by at least a first flattening in the spherical surface is. This allows the fuel between ball and guide bore flow through, although the ball in the guide hole guided becomes.

It has proven to be advantageous if, for example, three first Flattening evenly over the Scope of the ball be distributed. This will make the ball also with open control valve loaded symmetrically and there are only slight lateral forces on the Ball on.

Around to be able to operate the valve member in a simple manner is provided, the pressure pin in the guide hole to arrange, wherein the pressure pin advantageously protrudes from the guide bore and on an actuator, preferably a hydraulic coupler or a piezoactuator, but also an electromagnetic actuator, is applied.

It has further proven to be advantageous when the guide bore designed as a stepped bore is, and if a paragraph in the guide hole as a stop and / or as a sealing seat for the Valve member is used. This makes it possible in the control valve according to the invention provide three switch positions, which in particular in connection with one or more pilot injections and split main injections or additional Post injections can be beneficial.

It has proved to be advantageous if the guide bore is formed in a valve plate. Furthermore, it has proved to be advantageous if a sleeve is attached to the pressure bolt at one end remote from the ball, and when between the sleeve and the injector, in particular the valve plate, a compression spring is clamped. This makes it possible First, valve plate and valve member to mount before assembly in the injector as a captive assembly. On the other hand, the compression spring serves to bring the valve member in a defined switching position with a pressureless injector.

Especially, if the guide bore and the ball of the valve member according to the invention with each other paired to achieve optimal tolerances is it of great Advantage, if after this pairing of guide bore and valve member this insoluble be connected with each other and captive. It has proved to be advantageous when the sleeve is pressed with the pressure pin becomes.

Of Furthermore, it is recommended that the ball and the pressure pin with each other to weld. This is manufacturing technology very easy to master and results in a durable and durable connection. It is also possible to use the Pressure pin to a hardened So to weld ball so that the balls in the area of the contact line also still the welding process still sufficiently hard and wear-resistant. This also decreases the number of processing steps required and, consequently, also the manufacturing cost of the control valve according to the invention.

In an advantageous further embodiment of the invention is Control valve designed as a flat seat valve and has the ball at a pressure pin opposite End a second flattening, with the second flattening with a flat seat of the control valve stays together ??

Thereby Is it possible, in conventional and commercial Injectors, the flat seat valves, by replacing the Valve plate and inserting a control valve according to the invention, in a Valve plate is housed, this new and inventive control valve without further changes to be installed on already mass-produced injectors.

Further Advantages and advantageous embodiments of the invention are the subsequent drawing, the description and the claims can be removed. All features disclosed in the drawings, the description and the claims can be essential to the invention both individually and in any combination.

Brief description of the drawings

It demonstrate:

1 a piezoelectric actuator in a simplified representation in partial longitudinal section; and

2 a hydraulic coupler and an embodiment of a control valve according to the invention in an enlarged view.

Embodiments of the invention

In 1 is an embodiment of a piezo-operated injector according to the invention 1 shown. As the present invention is essentially a control valve 3 concerns, the injector 1 not explained in detail, but essentially only the design of the control valve 3 and its connection to a piezoelectric actuator 5 described. The function of an injector 1 are known to a person skilled in the art of injection technology and therefore require no further explanation.

The injector 1 has a high pressure connection 7 , Via the high pressure connection 7 becomes the injector 1 supplied with high pressure fuel (not shown). If an injection is to take place in the combustion chamber (not shown) of an internal combustion engine, a nozzle needle lifts 9 from her seat, not shown, and are also free injection holes, not shown. The nozzle needle is controlled 9 from the control valve 3 , which is a piezoelectric actuator 5 is pressed. Between the piezoelectric actuator 5 and the control valve 3 is a hydraulic coupler 11 arranged, which in 2 together with the control valve according to the invention 3 is shown enlarged.

The hydraulic coupler 11 consists essentially of a valve piston 13 and a translator piston 15 in a coupler housing 17 be guided. Between the valve piston 13 and the translator piston 15 is a coupler gap 19 present, which is filled with fuel (not shown). This coupler gap 19 is among other things necessary because of the temperature expansion coefficients of the piezoelectric actuator 5 and the metallic components of the injector 1 strongly different.

With his valve piston 13 actuates the hydraulic coupler 11 the control valve 3 while the translator piston 15 with a lead 21 to the piezoelectric actuator 5 is applied. The translator piston 15 is by a bourdon tube 23 subjected to a compressive bias. The bourdon is supported 23 with her first end against a heel 25 of the coupler housing 17 from. With its second end, the bourdon tube is supported 23 against a dial 27 from. About the dial 27 and a projection (not numbered) becomes the spring force of the Bourdon tube 23 on the piezoelectric actuator 5 transfer.

So that the bourdon tube 23 concentric to the hydraulic coupler 11 and concentric too to the piezoelectric actuator 5 is arranged, the diameter D _{1 of} the paragraph 25 so on the inner diameter of the Bourdon tube 23 matched that the bourdon tube 23 Slightly widened when on the heel 25 is postponed. As the bourdon tube according to the invention 23 has a groove extending over the entire length (not shown), can be the Bourdon tube 23 relatively easily widen so far that they are on the heel 25 fits.

When the Bourdon tube 23 is subjected to a compressive bias, it is sufficient if it can be supported at their ends in the axial direction, as in 1 is shown.

In 1 is good to see that below the control valve 3 a so-called throttle plate 29 is available. Below the throttle plate 29 is a tax room 31 present, which at one end of the nozzle needle 9 is limited in a conventional manner.

Out 2 it can be seen that the control valve 3 in a valve plate 33 is arranged. The division of the injector into different plates, namely in particular the valve plate 33 and the throttle plate 29 , in order to simplify the manufacture and to improve the mountability.

A valve member of the control valve according to the invention 3 is in 2 with the reference number 35 Mistake. The valve member 35 includes a ball 37 , which preferably consists of hardened steel, and a pressure pin 39 , The pressure pin 39 is at the ball 37 welded. The associated weld has in 2 the reference number 41 ,

The ball 37 of the valve member 35 is in a first section of the stepped pilot hole 43 recorded, said first portion has a diameter which provides a play-free guidance of the ball 37 allowed. Between the guide hole 43 and the ball 37 there is a linear contact area. This contact line is in 2 with the reference number 45 Mistake.

Because the ball 37 in the guide hole 43 is performed without play, measures must be taken to allow fuel between the ball 37 and the pilot hole 43 can flow past when the control valve 3 is open. To ensure this, are on the perimeter of the ball 37 several first flats distributed over the circumference 47 intended. These first flattenings 47 can be made, for example by grinding. In the lower part of the 2 a section along the line AA is shown. From this representation it follows that the first flattenings 47 release a circular segment-shaped cross section through the fuel between the guide bore 43 and the ball 37 can flow past.

A paragraph 49 the guide hole 43 is frusto-conical and serves as a stop and / or sealing seat for the valve member 35 ,

Above the heel 49 closes a second section of the guide bore 43 on, one opposite the first section of the guide bore 43 having reduced diameter. Between this second section of the guide bore 43 and the pressure bolt extending therein 39 There is so much game available that with the control valve open 3 Fuel from an outlet throttle 51 at the ball 37 and on the pressure pin 49 passing through the guide hole 43 of the control valve 3 can flow. The outlet throttle 51 is usually with the control room 13 (please refer 1 ) hydraulically connected.

Above the guide hole 43 is on the pressure pin 39 a sleeve 53 pressed. Between the sleeve 53 and the valve plate 33 is a compression spring 55 provided, which ensures that the ball 37 of the valve member 35 with currentless piezoelectric actuator in contact with the paragraph 49 the valve plate 33 located.

In the in 2 shown switching position of the control valve 3 is the piezoelectric actuator 5 energized and pressed over the hydraulic Kopper 11 the valve member against one on the throttle plate 29 trained flat seat (without reference number). At the throttle plate 29 facing the end of the valve member 35 is a second flattening 57 at the ball 37 present, which together with the flat seat the outlet throttle 51 closes. In a middle switch position in which the second flattening 57 not on the flat seat of the throttle plate 29 rests and not on the ball 37 and not at the paragraph 49 the guide hole 43 rests, is the control valve 3 opened, leaving fuel from the control room 29 through the outlet throttle 51 and through the guide hole 53 can flow into a return, not shown, can flow.

Claims (10)

Injector for an injection system of an internal combustion engine, with a nozzle needle ( 9 ), with a control valve ( 3 ) and with an actuator ( 5 ), the control valve ( 3 ) a valve member ( 35 ), and wherein the control valve ( 3 ) a hydraulic connection between a control room ( 31 ) and a fuel return, characterized in that the valve member ( 35 ) a ball ( 37 ) and a pressure pin ( 39 ) and that the ball ( 37 ) in a guide bore ( 43 ) of a valve housing ( 33 ) is guided. Injector according to claim 1, characterized in that between the ball ( 37 ) and the guide bore ( 43 ) a linear contact surface ( 45 ), and that the linear contact surface ( 45 ) by at least one first flattening ( 47 ) is interrupted in the spherical surface. Injector according to one of the preceding claims, characterized in that the pressure pin ( 39 ) in the guide bore ( 43 ) is arranged. Injector according to one of the preceding claims, characterized in that the guide bore ( 43 ) is designed as a stepped bore, and that a paragraph ( 49 ) in the guide bore ( 43 ) as a stop and / or as a sealing seat for the valve member ( 35 ) serves. Injector according to one of the preceding claims, characterized in that the guide bore ( 43 ) in a valve plate ( 33 ) is trained. Injector according to one of the preceding claims, characterized in that on one of the ball ( 37 ) facing away from the end of the pressure bolt ( 39 ) a sleeve ( 53 ) on the pressure pin ( 39 ), and that between the sleeve ( 53 ) and the injector housing, in particular the valve plate ( 33 ), a compression spring ( 55 ) is clamped. Injector according to claim 6, characterized in that the sleeve ( 53 ) with the pressure pin ( 39 ) is compressed. Injector according to one of the preceding claims, characterized in that the ball ( 37 ) and the pressure pin ( 39 ) are welded together. Injector according to one of the preceding claims, characterized in that the control valve ( 3 ) is designed as a flat seat valve, and that the ball ( 37 ) on a pressure pin ( 39 ) opposite end a second flattening ( 57 ), and that the second flattening ( 57 ) interacts with a flat seat. Injector according to one of the preceding claims, characterized in that the control valve ( 3 ) of a piezoelectric actuator ( 5 ) or actuated by an electromagnetic actuator.