EP1543238A1

EP1543238A1 - Method for determining a position of a part in a stepped bore of a housing, and injector for injecting fuel

Info

Publication number: EP1543238A1
Application number: EP04706679A
Authority: EP
Inventors: Jürgen Dick; Willibald SCHÜRZ; Martin Simmet
Original assignee: Siemens AG
Current assignee: Continental Automotive GmbH
Priority date: 2003-02-04
Filing date: 2004-01-30
Publication date: 2005-06-22
Anticipated expiration: 2024-01-30
Also published as: EP1543238B1; DE10304458A1; EP1965072A1; WO2004070196A1; DE502004009123D1; DE502004011222D1; EP1965072B1; US7543382B2; US20060005388A1

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

description

Method for determining a position of a component in a stepped bore in a housing and injector for fuel injection

The invention is based on 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, the second component being arranged in the second bore at a predetermined distance from a first component should be, which is already fixed in the smaller first hole and in the larger second hole an embossing ring is inserted up to a step of the stepped hole, which a stamp presses together until the specified distance to the first component is reached and then the second Component is inserted up to the compressed embossing ring, or by an injector for fuel injection according to the type of the independent claims 1 and 7.

In particular, injectors for fuel injection into an internal combustion engine, which have a piezoelectric actuator as the 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 μm range and is therefore extremely minimal. On the other hand, the amount of fuel to be injected must be dosed precisely in order to optimize the combustion processes in the engine and to comply with the required emission limits. In order to be able to meet these requirements, the mechanical individual parts of the injector in particular must be manufactured with the greatest precision. Even length dimensions with narrow manufacturing tolerances can add up to inadmissible errors. So far, this problem has been solved, for example, by measuring the individual components precisely and then inserting precisely manufactured shims into the bore, with which the calculated errors in the exact positioning of individual components in the injector could be compensated. This method requires the storage of many different shims. This procedure is therefore very complex and increases the manufacturing costs for the injector considerably.

From DE 199 56 256 AI a method has also become known in which an embossing disk is inserted into a stepped bore of an injector. The embossing disc is placed on the step that occurs at the transition from two ^' holes of the step hole. The embossing disk is then pressed together with an embossing tool until the desired distance from a first component already fixed in the stepped bore is reached. In order to be able to control the stamping process, an insulated electrical sensor is installed at the tip of the stamp, which delivers a switch-off signal to a drive unit of the stamp as soon as the fixed first component is touched. It seems unfavorable here that the measuring point of the electrical sensor at the tip of the embossing stamp is not visible during the pressing process, since it is located inside the stepped bore and cannot be observed there. This can lead to incorrect controls if, for example, a dirt particle has settled on the sensor head and as a result the sensor switches off the drive unit too early. Since there is practically no control option, this can easily lead to an undetected manufacturing defect.

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

The method according to the invention for determining a position of a second component in a stepped bore and the injector with the characterizing features of the independent claims 1 and 7 have the advantage that the measuring point lies outside the bore and the distance from the component fixed in the bore a probe can be read, which forms a reference dimension between the protruding end piece of the probe and a reference mark of the stamp. As a result, the measuring process can be checked at any time in a simple manner, so that manufacturing safety is improved. It is considered particularly advantageous that the embossing process can be continuously monitored and thus the approaching of the reference dimension can be easily observed and checked.

The measures listed in the dependent claims provide advantageous developments and improvements to the method and the injector specified in the independent claims 1 and 7. It is considered to be particularly advantageous that the reference dimension can be greater than the predetermined distance by a predetermined value. It is thereby advantageously achieved that after installation the two components are at a certain distance from one another, which can be used as an idle stroke for the actuator.

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

In the course of automatic series production, it appears particularly cheap to use the reference dimension with an electrical measuring direction, for example with a simple electrical contact. It is particularly advantageous that the measuring process can be automated, so that fewer qualified personnel are required 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 has only a very small change in length due to its physical properties, maintaining the exact distance from a second component, for example a servo valve, a nozzle body, a deflection device or the like, is particularly important in order to make the available change in length of the actuator as possible to be able to use it completely.

In the injector for fuel injection, it is considered particularly advantageous that the ring width of the stamping ring is larger than the step width of the step bore. This results in a better contact surface for the second component, which can thus be positioned more securely and precisely in the stepped bore.

For a play-free positioning of the second component, a smooth and in particular polished contact surface of the embossing ring also appears to be advantageous. Such a precise surface would be very difficult to produce directly on the step and would require considerable additional effort, since the step sits relatively deep in the bore and is therefore difficult to reach with a tool. Several embodiments of the invention are shown in the drawing and are explained in more detail in the following description.

Figure la shows two embodiments of the invention with an injector,

Figure lb shows an enlarged section of the injector housing and

Figure 2 shows a longitudinal section through an injector.

In Figure la, a housing 1 is shown in a schematic representation, which has a stepped bore 6 in the axial direction. In general, the housing 1 can be an assembly into which two components 2, 10 are to be installed with a predetermined distance from one another exactly and with small tolerances. In the preferred application according to the invention, an injector housing is used as the housing 1, into 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 is to be installed at a predetermined distance H from the first component 2. However, the first component 2 can also be a base plate of the actuator or the like.

The second component 10 is formed as an actuator, in particular it can be a ^¬ sondere Hubumkehrer, a nozzle body or an operating member of a servo valve or the like to be operated by the piezoelectric actuator. 2

Before the second component 10 can be installed, the first component 2 is first inserted and fixed as precisely as possible in a first bore 6a of the stepped bore 6 at a location provided for this purpose. An underside 17a of the first component 2 forms a first reference surface for the predetermined distance H. The first bore 6a is in the upper part of FIG Figure 1 recognizable and has a first diameter dl, 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 bores 6a, 6b, an annular step 16 is formed due to the different diameters d1, d2.

In a next step, an embossing ring 3 is inserted into the second hole 6b with the larger diameter d2 until it rests on the annular step 16 of the step hole 6. The embossing ring 3 is shaped in such a way that it does not impair the function of the second component 10 to be installed subsequently.

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

The height of the stamping ring 3 is selected such that the distance H, which is specified as the desired dimension and is measured between the underside 17a of the first component 2 and the lower ring surface 17 of the stamping ring 3, is compressed by pressing the stamping ring 3 together with a predetermined value can be manufactured.

After the embossing ring 3 has been placed on the step 16, an embossing stamp 4 is inserted into the second bore 6b up to the lower ring surface 17 of the embossing ring 3. The stamping die 4 has a central longitudinal bore 18 with a diameter d, into which a measuring probe 5 can be inserted until its head end touches the underside 17a of the first component 2. The length of the measuring probe 5 is dependent on the measuring method used and is dimensioned, for example, such that an end piece E of the measuring probe 5 protrudes a little 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 is arranged on the embossing stamp 4, for example as a flat measuring surface. Furthermore, a second reference mark C is applied to the end piece E of the probe 5, which can also be designed as a reference surface. A reference dimension x can thus be measured or read between the first reference mark B on the embossing die 4 and the second reference mark C on the probe 5. The reference dimension x is selected such that when the reference dimension x is present between the first and the second reference mark B, C, the lower ring surface 17 of the embossing ring 3 is at a distance H from the underside 17a 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 underside 17a of the first component 2 and the lower ring surface 17 of the embossing ring 3 can be monitored.

With a known stamping device (not shown in FIG. 1 a), the stamping ring 3 is now deformed until the predetermined value x for the reference dimension and thus the distance H between the lower ring surface of the stamping ring 3 and the underside 17a of the first component 2 is reached , The stamping ring 3 is made for this purpose, for example, from a corresponding cold heading and cold extrusion steel according to DIN 1654.

Alternatively, provision is also made to end the deformation of the embossing ring 3 somewhat earlier. In this case, the embossing path is somewhat shorter. 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 contact-free with a certain distance from one another should be installed. This results in an idle stroke with the value dx for the actuator 2.

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

All mechanical, optical or electrical measuring arrangements known per se can be used as the measuring device 7 with which the reference dimension x or x-dx is recorded. In a preferred embodiment, for example, an optical measuring device 7 of the LM series from Heidenhain GmbH is used, which can be used in particular in automation technology. This measuring device 7 has a laser interferometric probe, with which measuring accuracies are achieved which are in the nanometer range. A He-Ne laser is used for the measurement, the light of which is fed to a miniature interferometer located at the measuring point. The miniature interferometer detects the measuring movement of a measuring quill, which corresponds to the distance between the two reference marks B and C on the embossing die 4 and on the measuring probe 5, and converts this movement into an optical interference signal. The optical measurement signal is then transmitted via an optical fiber to an optical evaluation and supply unit and is output as a measurement result either on a digital display or on the monitor of a computer. Furthermore, the measurement signal is used to control or switch off the embossing device with the embossing die 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 attached between the end piece E of the probe 5 and the embossing die 4, said electrical contact being easily visible and adjustable from the outside. The electrical contact is adjusted so that it delivers a switch-off signal to the embossing device when the intended reference dimension x or x-dx is reached. Such an electrical measuring arrangement is shown schematically in the lower part of FIG. A contact tab 31 is arranged on the embossing die 4, the contact of which is directed onto the longitudinal bore 18. The height of the contact lug can be adjusted by means of an adjusting screw 31 and, if necessary, an idle stroke dx can be set. In this case, the end piece E of the probe 5 is somewhat shorter and is insulated from the die 4. When the embossing disc 3 is embossed, the embossing stamp 4 moves relative to

Measuring 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 measuring probe 5 and the embossing stamp 4. This signal is then used to end the embossing process.

Figure 1b shows an enlarged view of the embossing process. The stamping ring 3 can be seen, which adapts to the contour of the step 16 in the wall of the housing 1 by the stamping process. The use of the stamp 4, which has a flat and smooth stamping surface, which is also precisely ground at a 90 ° angle to the longitudinal axis, means that the stamped surface, i.e. the lower ring surface 17 of the embossing ring 3 is rectangular and smooth. As a result, the inserted second component 10 lies precisely 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.

According to FIG. 1b, the embossing ring 3 preferably has a ring width d3 which is greater than the width of the step 16 which has a step width d4. Level 16 itself is not so favorable as a bearing surface for the second component 10, since on the one hand its step width d4 is relatively narrow and on the other hand its surface has a certain roughness and unevenness due to the processing tools. It would also be disadvantageous that the surface is difficult to machine flat because of the long stepped bore 6.

After the specified reference dimension x-dx has been reached, the stamp 4 is removed with the probe 5 from the second bore 6b and the second component 10 is pushed into the lower ring surface 17 of the compressed stamping ring 3 until it is in place.

Figure 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 of all, an injector housing 1 with a stepped bore 6 can be seen. The step 16 results from the two bores 6a, 6b of the stepped bore 6 with their different diameters. On the step 16, the embossing ring 3 is inserted and stamped to the desired thickness with the setting dimension 12. As the first component 2, a piezoelectric actuator was inserted into the smaller, first bore 6a and fastened 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 a predetermined installation dimension 15 for the first component 2, the actuator, with respect to the lower ring surface 17 of the embossing ring 3. Together with the setting dimension 12 of the stamping ring, the two dimensions 15 + 12 give the predetermined distance H as a dimension between the underside 17a of the actuator 2 and the lower ring surface 17 of the stamping ring 3.

According to an embodiment of the invention, the second component 10 is designed as a stroke transformer, which acts as a stroke reverser. The stroke reverser rests on the lower ring surface 17 of the embossing ring 3 with no play and moves its lower part upwards, according to the arrows shown the actuator 2 extends downwards. When the actuator 2 is not activated, the stroke reverser 10 presses a servo valve 20 via a plunger 13, so that the latter is closed. The servo valve 20 regulates the fuel outflow from a control chamber 21, which is supplied with fuel via an inlet throttle. The control chamber 21 is delimited by a movably mounted nozzle needle 14. The fuel pressure biases the nozzle needle 14 onto a sealing seat 24. In this position, the injection holes 25 of the injection valve are closed, which after the

Sealing seat of the servo valve 20 are arranged. The nozzle needle 14 is arranged in the control chamber 21, which is supplied via a feed line 22.

In the exemplary embodiment shown, the stroke reverser 10 bears directly on the underside 17a of the actuator 2. Alternatively, an idle stroke can also be provided between the actuator 2 and the stroke reverser 10. If the actuator 2 is activated by applying a voltage, the actuator 2 expands and presses on the stroke reverser 10. The stroke reverser moves the plunger 13 upward, so that the closing element of the servo valve 20 lifts off the sealing seat due to the fuel pressure acting on it. The servo valve 20 thus opens, so that fuel flows out of the control chamber 21. Although fuel flows into the control chamber 21 at the same time via an inlet throttle, the inflow is less than the outflow. The pressure in the control chamber 21 thus drops. 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. This opens the injection holes 25 and fuel is injected into the combustion chamber of the engine. If the actuator is released, the servo valve 20 is closed, the pressure in the control chamber 21 is increased and the nozzle needle 14 is pressed onto the sealing seat 24. This ends the injection.

Claims

claims

1. Method for determining a position of a second component (10) in a stepped bore (6) of a housing (1), in particular an injector housing, which has two bores (6a, 6b) with two different diameters (dl, d2), wherein the second component (10) is to be arranged in the second bore (6b) at a predetermined distance (H) from an underside (17a) of a first component (2) that is already in the first bore (6a) with a smaller diameter (dl) is fixed and in the larger second bore (6b) an embossing ring (3) is inserted up to a step (17) of the stepped bore (6), with a lower ring surface (17) of the embossing ring (3) from an embossing stamp (4) is pressed together until the predetermined distance (H) between the lower ring surface (17) of the embossing ring (3) and the first component (2) is reached, characterized in that a longitudinal bore (18 ) is arranged, in which a probe (5) to ^' To touch the first component (2) is introduced that a first reference mark (B) is arranged on the embossing die (4) and a second reference mark (C) is arranged on an end piece (E) of the probe (5), between the two Reference marks (B, C) a reference dimension (x) is formed for the predetermined distance (H), and that the embossing process is ended when a value of the reference dimension (x) is reached, which corresponds to a desired distance (H).

2. The method according to claim 1, characterized in that the reference dimension (x) is monitored with a mechanical or optical measuring device (7) during the pressing in of the embossing ring (3).

3. The method according to claim 1, characterized in that the reference dimension (x) is detected with an electrical measuring device (7).

4. The method according to any one of the preceding claims, characterized in that the two components (2,10) are inserted into a stepped bore (dl, d2) of a housing (1) of a fuel injector.

5. 'Method according to one of the preceding claims, characterized in that the first component (2) is designed as a piezoelectric actuator.

6. The method according to any one of the preceding claims, characterized in that the first component (2) is designed as a base plate of the actuator.

7. injector for fuel injection into an internal combustion engine of a motor vehicle, with a first component (2), which is fixed in a smaller first bore (6a) of a stepped bore (6) of the injector housing (1), and with a stamping ring (3), which rests on a step (16) of the stepped bore (6), which is formed by a larger second bore (6b) and that the height of the embossing ring (3) with an embossing stamp (4) exactly on a given to the first component (2) Distance (H) is characterized, characterized in that the embossing ring (3) has a ring width (d3) which is wider than the step width (d4) of the step (16) in the step bore (6), whereby the force between the second Component (10) and the stepped bore (1) over an enlarged contact area of the ring width (d3) of the embossing ring (3) is formed.

8. Injector according to claim 7 or 10, characterized in that the embossing ring (3) on the bearing surface for the second component (10) is smooth, preferably polished and / or flat, preferably perpendicular to the axis of the stepped bore (6) ,

9. Injector according to one of claims 7, 8 or 10, characterized characterized in that the second component (10) is designed as a stroke reverser.

10. Injector according to claim 7, 8 or 9, characterized in that the second component is designed as a nozzle body or actuating element of a servo valve.