EP1543238B1 - Method for determining a position of a part in a stepped bore of a housing, and injector for injecting fuel - Google Patents

Abstract

The invention relates to a method and an injector for determining a position of a second part (10) inside a stepped boring (6). This part should assume an exact distance (H) from a first part (2). In order to determine the distance (H) between both parts (2, 10), a collar (3) is firstly introduced into a second boring (6b) of the stepped boring (6) until it rests upon a step (16) of the stepped boring (6). Afterwards, a punch (4), together with a touch probe (5), which is located inside a longitudinal boring (d), is placed upon a lower annular surface (17) of the collar (3) or on an underside (17a) of the first part (2), and the collar (3) is compressed until the predetermined distance (H) is obtained. The distance (H) is measured to a reference measure (x) between a projecting end piece (E) of the touch probe (5) and a reference mark (B) outside of the punch (4). The stamping process is stopped once the reference measure (x) has been obtained.

Description

The invention proceeds from a method for determining a position of a second component in a stepped bore of a housing, in particular an injector housing, which has two bores with two different diameters, wherein the second component is arranged in the second bore with a predetermined distance to a first component is to be, which is already fixed in the smaller first bore and wherein in the larger second bore an embossing ring is inserted to a stage of the stepped bore, the squeezing a punch compresses until the predetermined distance is achieved to the first component and then wherein the second Component is inserted to the compressed stamping ring.

In particular, injectors for fuel injection into an internal combustion engine having a piezoelectric actuator as a drive unit must be manufactured with the greatest precision, since on the one hand, the change in length of the actuator generated by a voltage pulse is only in the micron range and thus extremely minimal. On the other hand, the quantities of fuel to be injected must be precisely metered in order to optimize the combustion processes in the engine and to comply with the required emission limits. In order to meet these requirements, in particular the mechanical parts of the injector must be made with the utmost precision. Even length measures with tight manufacturing tolerances can add up to impermissible errors in the sum.

So far, for example, this problem was solved in that the individual components were measured exactly and then precisely manufactured shims were inserted into the hole, with which the calculated incorrect dimensions in the exact Positioning of individual components in the injector could be compensated. This method requires storage of many different shims. This procedure is therefore very complex and increases the manufacturing costs for the injector to a considerable extent.

From the DE 199 56 256 A1 Furthermore, a method has become known in which a stamped disc is introduced into a stepped bore of an injector. The embossing disc is placed on the stage, which adjusts at the transition of two holes of the stepped bore. The embossing disk is then pressed together with an embossing tool until the desired distance to a first component already fixed in the stepped bore is reached. In order to control the embossing process, an electrical sensor is installed isolated at the top of the embossing die, which delivers a shutdown signal to a drive unit of the embossing die, as soon as the fixed first component is touched. Unfavorable here appears that the measuring point of the electrical sensor at the top of the stamping die during the pressing process is not visible, since it is located within the stepped bore and can not be observed there. This can lead to faulty control if, for example, a dirt particle has settled on the sensor head and as a result the sensor shuts off the drive unit too early. Since there is virtually no control, this can easily lead to an unrecognized manufacturing error.

The object of the invention is to position in a housing, in particular in an injector for the fuel injection, the position of the components which are to be installed in the housing, with a predetermined distance in a stepped bore of the housing exactly. In addition, the object is to provide an improved injector. The object is achieved with the features of the independent claims 1 and 7.

The inventive method for setting a position of a second component in a stepped bore with the characterizing features of claim 1 has the advantage that the measuring point is outside the bore and the distance from the fixed part in the bore can be read on a probe, the one Reference dimension between the protruding end of the probe and a reference mark of the stamping die forms. As a result, the measurement process can be controlled at any time in a simple manner, so that the manufacturing reliability improves. It is considered to be particularly advantageous that the embossing process can be continuously monitored and thus already the approximation to the reference dimension can be easily observed and checked.

The measures listed in the dependent claims advantageous refinements and improvements of the method given in claim 1 are given.

It is considered to be particularly advantageous that the reference dimension can be greater by a predetermined value than the predetermined distance. This achieves in an advantageous manner that after installation, the two components have a certain distance from each other, which can be used as Leerhub for the actuator.

A particularly simple detection of the reference dimension is given with a known mechanical or optical measuring devices such as feeler gauge, dial gauge, eyepiece, camera, interference method, etc. The measuring devices work reliably and are easy to operate even by untrained personnel.

In the course of an automatic series production appears particularly favorable to capture the reference dimension with an electrical measuring device, for example with a simple electrical contact. It is particularly advantageous that the measurement process can be automated so that less qualified personnel is needed and the manufacturing costs can be reduced.

A preferred and advantageous application of the method is seen in an injector for fuel injection, since here the distance between the components to be installed in the stepped bore of the injector housing must be maintained with particularly high precision.

Since a piezoelectric actuator due to its physical properties has only a very small change in length, maintaining the exact distance to a second component, such as a servo valve, a Düsennkörper, a deflection or the like is particularly important to use the available change in length of the actuator as completely as possible to be able to.

In the injector for the fuel injection is considered particularly advantageous that the ring width of the stamping ring is greater than the step width of the stepped bore. This results in a better bearing surface for the second component, which can be positioned thereby safer and more accurate in the stepped bore.

For a clearance-free positioning of the second component, a smooth and, in particular, polished bearing surfaces of the stamping ring also appear to be advantageous. Such precise surface would be very difficult to produce at the stage directly and with considerable additional effort, since the stage sits relatively deep in the hole and thus difficult to reach with a tool.

Several embodiments of the invention are illustrated in the drawings and will be explained in more detail in the following description.

FIG. 1a shows two embodiments of the invention with an injector,
FIG. 1b shows an enlarged section of the injector and
FIG. 2 shows a longitudinal section through an injector.

In FIG. 1a a housing 1 is shown in a schematic representation, which has a stepped bore 6 in the axial direction. The housing 1 may very generally be an assembly into which two components 2, 10 are to be installed with a predetermined distance from each other exactly and with small tolerances.

In the preferred application of the invention, an injector housing is used as the housing 1, in which the two components 2 and 10 are to be installed. The first component 2 is, for example, an actuator, in particular a piezoelectric actuator. A second component 10 should be installed with a predetermined distance H to the first component 2. But the first component 2 may also be a bottom plate of the actuator or the like.

The second component 10 is designed as an actuator, in particular it may be a Hubumkehrer, a nozzle body or an actuator of a servo valve or the like, which is to be actuated by the piezoelectric actuator 2.

Before the second component 10 can be installed, the first component 2 is first inserted and fixed in a first hole 6 a of the stepped bore 6 as accurately as possible at a designated location. An underside 17 a of the first component 2 forms a first reference surface for the predetermined distance H. The first bore 6 a is in the upper part of FIG. 1 recognizable and has a first diameter d1, which is smaller than a second diameter d2 of a second bore 6b. The second bore 6b is arranged in the lower part of the stepped bore 6. At the transition between the two holes 6a, 6b forms an annular step 16 due to the different diameters d1, d2.

In a next step, a stamping ring 3 is inserted into the second bore 6b with the larger diameter d2 until it rests on the annular step 16 of the stepped bore 6. The stamping ring 3 is formed such that it does not impair the function of the second component 10 to be subsequently installed.

The underside 17a of the first component 2 fixed in the first bore 6a thus forms a reference base for a distance H at a lower annular surface 17 of the embossing ring 3, with which the second component 10 is to be retained in the second bore 6b after embossing of the embossing ring 3 ,

The height of the stamping ring 3 is selected so that by compressing the stamping ring 3, the distance H, which is predetermined as a nominal size and measured between the bottom 17 a of the first component 2 and the lower annular surface 17 of the stamping ring 3, are produced with a predetermined value can.

After the embossing ring 3 has been placed on the step 16, an embossing punch 4 is inserted into the second bore 6b to the lower annular surface 17 of the embossing ring 3. The embossing punch 4 has a central longitudinal bore 18 with a diameter d into which a probe 5 can be inserted until its head end touches the underside 17 a of the first component 2. The length of the probe 5 is dependent on the applied measuring method and is for example so dimensioned that an end piece E of the probe 5 protrudes a small distance from the longitudinal bore 18 of the die 4.

In order to be able to produce the desired distance H by embossing the embossing ring 3, a first reference mark B, for example as a planar measuring surface, is arranged on the embossing stamp 4. Furthermore, on the tail E of the probe 5, a second reference mark C is applied, which may also be formed as a reference surface. Thus, between the first reference mark B on the embossing punch 4 and the second reference mark C on the probe 5, a reference dimension x are measured or read. The reference dimension x is chosen so that in the presence of the reference dimension x between the first and the second reference mark B, C, the lower annular surface 17 of the stamping ring 3 has the distance H to the bottom 17 a of the first component 2.

In an alternative embodiment of the invention, a marking or scaling 19 is applied to the end part E, at which the depth of the embossing or the distance between the bottom 17a of the first component 2 and the lower annular surface 17 of the embossing ring 3 can be monitored.

With one in the FIG. 1a Not shown, known embossing device is now the stamping ring 3 is deformed until the predetermined value x for the reference dimension and thus the distance H between the lower annular surface of the stamping ring 3 and the bottom 17 a of the first component 2 is achieved. The stamping ring 3 is made for this purpose, for example, from a corresponding cold heading and Kaltfließpressstahl according to DIN 1654 for this purpose.

Alternatively, it is also provided to finish the deformation of the stamping ring 3 a little earlier. The embossing path is slightly shorter in this case. This sets a distance H + dx, which corresponds to a reference dimension with the value x-dx. This is advantageous if, for example, the two components 2.10 are to be installed without contact with a certain distance from each other. For the actuator 2, this results in an idle stroke with the value dx.

Since the desired reference dimension can be continuously observed during the pressing process, the pressing process can be stopped prematurely when the desired distance H + dx is reached with the mounting dimension x-dx. The method described sets the distance to a precise value, so that the individual component tolerances are compensated effectively and cost-effectively.

As a measuring device 7, with the reference x or x-dx is detected, all per se known mechanical, optical or electrical measuring arrangements come into question. In a preferred embodiment, for example, an optical measuring device 7 of the LM series by Heidenhain GmbH is used, which can be used in particular in automation technology. This measuring device 7 has a laser interferometric probe, with the measurement accuracies are achieved, which are in the nanometer range. For the measurement, a He-Ne laser is used whose light is fed to a miniature interferometer, which is located at the measuring point. The miniature interferometer detects the measuring movement of a measuring spindle, which correspond to the distance between the two reference marks B and C on the embossing punch 4 or on the probe 5, and converts this movement into an optical interference signal. The optical measurement signal is then transmitted via an optical waveguide to an optical evaluation and supply unit and output as a measurement result either on a digital display or on the monitor of a computer. Furthermore, the measuring signal is used to control or switch off the embossing device with the embossing punch 4 when the intended distance H or H + dx or the reference dimension x or x-dx has been reached.

Alternatively, an electrical contact can be made between the end piece E of the probe 5 and the die 4, which is easily visible and adjustable from the outside. The electrical contact is adjusted so that it delivers a shutdown signal to the embossing device when reaching the intended reference dimension x or x-dx. In the lower part of FIG. 1a a detail of such an electrical measuring arrangement is shown schematically. On the die 4, a contact lug 31 is arranged, the contact is directed to the longitudinal bore 18. By means of an adjusting screw 31, the contact lug can be adjusted in height and optionally set a Leerhub dx. The tail E of the probe 5 is slightly shorter in this case and executed isolated against the die 4. When embossing the embossing disc 3, the die 4 moves relative to the probe 5 upwards. When the contact lug 31 touches the probe 5, the reference dimension x-dx is reached. The contact lug 31 closes a circuit I via the probe 5 and the punch 4. This signal is then used to complete the embossing process.

FIG. 1b shows in an enlarged view the embossing process. It can be seen the stamping ring 3, which adapts by the stamping process to the contour of the step 16 in the wall of the housing 1. By using the die 4, which has a flat and smooth embossing surface, which is also precisely ground at 90 ° to the longitudinal axis, it follows that the embossed surface, ie the lower annular surface 17 of the embossing ring 3 is executed rectangular and smooth. As a result, the inserted second component 10 lies exactly and without play on the embossing ring 3, so that a predetermined distance H or H + dx or the predetermined reference dimension x or x-dx can be exactly maintained.

The stamping ring 3 has accordingly FIG. 1b Preferably, a ring width d3, which is greater than the width of the step 16, which has a step width d4. The step 16 itself is not as support surface for the second component 10 favorable, since their step width d4 on the one hand is relatively narrow and on the other hand their surface has a certain roughness and unevenness by the processing tools. Another disadvantage would be that the surface is difficult to plan because of the long stepped bore 6.

After reaching the predetermined reference dimension x-dx, the embossing punch 4 is removed with the probe 5 from the second bore 6b and the second component 10 is inserted until it is placed on the lower annular surface 17 of the compressed embossing ring 3.

FIG. 2 shows a schematic representation of a longitudinal section through an injector for fuel injection for an internal combustion engine of a motor vehicle. First, an injector 1 with a stepped bore 6 can be seen. Through the two holes 6a, 6b of the stepped bore 6 with their different diameters, the step 16 results on the step 16 of the stamping ring 3 is inserted and stamped to the desired thickness with the Einstellmaß 12. As the first component 2, a piezoelectric actuator has been inserted into the smaller, first bore 6a and attached to the upper part of the housing 1 at a connection point A with the housing 1. The underside 17a of the piezoelectric actuator 2 has, in relation to the lower annular surface 17 of the stamping ring 3, a predetermined installation dimension 15 for the first component 2, the actuator. Together with the Einstellmaß 12 of the stamping ring results from the two dimensions 15 and 12 of the predetermined distance H as a measure between the bottom 17 a of the actuator 2 and the lower annular surface 17 of the stamping ring. 3

According to one embodiment of the invention, the second component 10 is designed as a lifting transformer, which acts as a Hubumkehrer. The Hubumkehrer is free of play on the lower annular surface 17 of the stamping ring 3 and moves according to the arrows shown its lower part upwards when the actuator 2 expands downwards. In the non-activated state of the actuator 2, the Hubumkehrer 10 presses on a Plunger 13 on a servo valve 20 so that it is closed. The servo valve 20 controls the fuel drain from a control chamber 21, which is supplied via an inlet throttle with fuel. The control chamber 21 is bounded by a movably mounted nozzle needle 14. The fuel pressure biases the nozzle needle 14 to a sealing seat 24. In this position, the injection holes 25 of the injection valve are closed, which are arranged as seen in the flow direction after the sealing seat of the servo valve 20. The nozzle needle 14 is arranged in the control chamber 21, which is supplied via a supply line 22.

In the illustrated embodiment, the Hubumkehrer 10 is located directly on the bottom 17 a of the actuator 2. Alternatively, an idle stroke between the actuator 2 and the Hubumkehrer 10 may be provided. If the actuator 2 is activated by applying a voltage, then the actuator 2 expands and presses on the Hubumkehrer 10. The Hubumkehrer moves the plunger 13 upwards, so that lifts off because of the acting fuel pressure, the closing member of the servo valve 20 from the sealing seat. This opens the servo valve 20, so that fuel flows from the control chamber 21. Although it flows through an inlet throttle simultaneously fuel into the control chamber 21, but the inflow is less than the drain. Thus, the pressure in the control chamber 21 decreases. The nozzle needle 14 is thus relieved. Fuel pressure, which acts on pressure surfaces of the nozzle needle 14, lifts the nozzle needle 14 from the sealing seat 24. Thus, the injection holes 25 are opened and fuel is injected into the combustion chamber of the engine. If the actuator is de-energized, then the servo valve 20 is closed, the pressure in the control chamber 21 increases and the nozzle needle 14 is pressed onto the sealing seat 24. This ends the injection.

Claims (7)

1. Method for determining the position of a second component (10) in a stepped bore (6) of a housing (1), in particular an injector housing, having two bores (6a, 6b) with two different diameters (d1, d2), the second component (10) to be arranged in the second bore (6b) at a predefined distance (H) from a lower side (17a) of a first component (2), which is already fixed in the first bore (6a) with a smaller diameter (d1) and a ferrule (3) being inserted into the larger second bore (6b) up to a step (17) of the stepped bore (6), a lower annular surface (17) of the ferrule (3) being compressed by a die (4) until the predefined distance (H) is achieved between the lower annular surface (17) of the ferrule (3) and the first component (2), characterized in that a longitudinal bore (18) is arranged in the die (4), into which a probe (5) is inserted until it comes into contact with the first component (2), a first reference mark (B) is marked on the die (4) and a second reference mark (C) is marked on an end piece (E) of the probe (5), a reference measurement (x) being created for the predefined distance (H) between the two reference marks (B, C) and the stamping process being terminated when a value is achieved for the reference measurement (x) which corresponds to a required distance (H).
2. Method according to claim 1, characterised in that

   - the ferrule (3) has an annular width (d3) which is greater than the width of the step (16) in the stepped bore (6) and

   - the ferrule (3) essentially adjusts to the contour of the step (16) by means of the embossing process.
3. Method according to claim 1 or 2, characterised in that during compression of the ferrule (3) the reference measurement (x) is monitored using a mechanical or optical measuring device (7).
4. Method according to claim 1 or 2, characterised in that the reference measurement (x) is recorded using an electrical measuring device (7).
5. Method according to one of the preceding claims, characterised in that the two components (2, 10) are inserted into a stepped bore (d1, d2) of a housing (1) of a fuel injector.
6. Method according to one of the preceding claims, characterised in that the first component (2) is configured as a piezo-electric actuator.
7. Method according to one of the preceding claims, characterised in that the first component (2) is configured as the base plate of the actuator.

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