EP0997635A2 - Method for testing a throttle point, especially a throttle point of an injector - Google Patents

Abstract

A method for testing a throttle point, in particular the throttle point of an injector, is proposed. This is acted upon by a pump with a first constant pressure level (p1) on the primary side, whereby the volume flow Q of the hydraulic pressure medium supplied by the pump is recorded. A first and further operating points are determined. The other operating points are determined by changing a second, predeterminable secondary pressure level (p2). The first operating point determines a characteristic field (KF), which has a range of permissible and non-permissible operating points. A positive or negative test result is detected on the basis of the position of the further operating points in the characteristic field (KF).

Description

The invention relates to a method for testing a throttle point, in particular the Throttle point of an injector on a test bench. The injector is used by one Pump applied with a first constant pressure level on the primary side. In addition becomes the volume flow of the hydraulic pressure medium provided by the pump detected.

With common rail systems, the consistency from injection to injection is decisive determined on the constancy of the atomization of the fuel. The degree of atomization again clearly depends on the injector. As is well known, the quality of the injectors can spread within a series, they are evaluated on a test bench. On Such a test bench is known for example from DE 31 28 072 C2. Here is a Injection nozzle with nozzle holder on flow rate, opening pressure, click behavior, Tightness of the nozzle holder combination, seat tightness and needle clearance of the nozzle checked. In In practice, however, it has been shown that the static determination of the quality is an injector on such a test bench the behavior of the same injector is rather imperfect dynamic operation, d. H. after installation in an internal combustion engine, reflected. in the In extreme cases, this can lead to an injector being assessed positively on the test bench after installation in the internal combustion engine to very different injection results can lead.

Starting from the prior art described above, the invention lies in that The task is to develop this further.

A first solution according to the invention is that a first and another Operating points are determined, the first operating point being a significant one Characteristic field determined. The other operating points become the characteristic field assigned which is a range of permissible and non-permissible operating points having. Then, based on the position of the other operating points in the characteristic field a positive or negative test result can be detected.

In an embodiment of this, it is proposed that both the first and the further Operating points are largely determined by a first and second parameter. The first parameter is calculated from the first pressure level on the primary side and a second, predeterminable secondary pressure level of the injector. The second The parameter is largely determined by the measured volume flow and the first and second Pressure level determined. According to claim 3, the other operating points largely determined by the increase in the second pressure level.

The method according to the invention is a dynamic measuring method. Starting from the first operating point, the other operating points are iterated over the Increasing the secondary pressure level determined. Since the injector under dynamic aspects is checked, is therefore a clear statement about the dynamic behavior of the same injector in active operation, d. H. after installation in the Internal combustion engine, possible. By determining the first and second parameters can be a clear statement about the flow geometry within the tested Meet the injector. Under flow geometry in the sense of the invention is the degree of Rounding a throttle point, its quality to understand. With the invention In general, the process can be used to produce a throttle body assign different grades. The following are relevant for an injector Throttling points available: control throttle such as inlet and outlet throttles as well Injector itself.

According to claim 4, the test method is carried out until the first parameter is equal to a limit. The limit is chosen so that the flow of the injector remains in the stable range. As stated in claim 6, a negative Test result is detected when an operating point falls within the impermissible range of the Characteristic field is assigned. Alternatively, according to claim 7, a is not permissible operating point counted in a total memory. Only when the content of the Total memory exceeds a limit value, a negative test result is detected, d. H. the injector is faulty. The advantage of this configuration is that the tolerance of the electrode is also taken into account.

A second solution to the problem of the invention is that a first and second operating point can be determined, a deviation from the first and second Operating point is determined and then a negative test result is detected if the deviation exceeds a limit. This will be the first and second Operating point as described above depending on the first and second parameters certainly. This two-point test method offers the advantage that a larger number of Injectors can be evaluated within a certain time.

Figur 1:

ein Diagramm

Figur 2:

Programmablaufplan der ersten Lösung

Figur 3 A, B, C:

Unterprogramm zu Figur 2

Figur 4:

Programmablaufplan der zweiten Lösung

A preferred embodiment of the invention is shown in the figures. Show it:

Figure 1:

a diagram

Figure 2:

Program flowchart of the first solution

Figure 3 A, B, C:

Subroutine for Figure 2

Figure 4:

Program flow chart of the second solution

p1

primärseitiges am Injektor anstehendes Druckniveau (Injektor-Eingang)

p2

sekundärseitiges Druckniveau (Injektor-Ausgang)

A diagram is shown in FIG. The first parameter K1 is plotted on the abscissa. The second parameter K2 is plotted on the ordinate. The first parameter K1 is calculated from the pressure ratio of the first p1 and second p2 pressure levels according to the following relationship: K1 (1) = p1 - p2 (1) / p2 (1) With:

p1

primary pressure level at the injector (injector inlet)

p2

secondary pressure level (injector outlet)

The second parameter K2 is calculated from the measured volume flow Q and the first p1 and second pressure level p2. This second parameter K2 describes completely generally the area actually flowed through in a throttle point, which the injector represents. This second parameter K2 can be analyzed analytically using the Bernoulli equation be calculated. As is known, the area flowed through is proportional to that Volume flow and inversely proportional to the pressure difference between the first p1 and second p2 pressure level.

Several characteristics are shown in FIG. The curve ACB (1) and K2 (1) represents the permitted range. The test procedure is as follows:

At the beginning, a first operating point B (1) is determined. This first operating point is determined from the first parameter K1 and the second parameter K2. In Figure 1 corresponding to the two points K1 (1) and K2 (1). The first operating point B (1) largely determines the characteristic field here. In other words: the first operating point B (1) serves as a reference point for all further operating points B (i). This is shown in FIG. 1 as a changeable baseline, corresponding to the route K2 (1) and B (1), arrows I and II.
Typical values for determining the first operating point B (1) are e.g. B. p1 = 100 bar and p2 = 1 bar. Then another operating point is determined by the second pressure level p2 by a predeterminable value dp, z. B. 1 bar is increased. This further operating point, designated B (i) in FIG. 1, is then assigned to the characteristic field. The abscissa value K1 (i) and the ordinate value K2 (i) belong to this operating point B (i). In Figure 1, this further operating point B (i) lies in the permissible range of the characteristic field. The next operating point is set by increasing the second pressure level p2 again. An iterative loop is thus run through, with a further operating point B (i) (i = 1, 2, 3 ...) being determined with each run.

If all determined operating points B (i) lie within the permissible range, the test procedure is ended when the first parameter K1 is equal to a limit value GW. This limit value GW is shown on the abscissa in FIG. The limit value GW is selected so that an error-free statement about the flow conditions can still be made. In other words, values of K1 between the origin and this limit value GW are not determined because this would describe an unstable flow state. A typical value for this limit value GW is e.g. B. the mathematical value 1, ie p1 = 100 bar and p2 = 50 bar. If it is determined that an operating point B (i) lies in the inadmissible range of the characteristic field, the injector measured is determined to be faulty, ie a negative test result is detected.
As an alternative to this, the method can also be carried out in such a way that a negative test result is only detected when a certain number of operating points lie outside the permissible range. As an extreme value, e.g. B. this can be carried out so that the complete characteristic curve is detected for a faulty injector. In Figure 1, for. B. such a characteristic curve not in the permissible range is shown with the points DEB (1).

In addition, the inventive method can be carried out so that the number of Injectors with a negative test result can be counted. In this way it can be determined whether the manufacturing process of the injectors is defective overall. It can be thus carry out a so-called "100% test".

FIG. 2 shows a program flow chart for the first solution according to the invention. In step S1, a counter variable i = 1 is set. In step S2, the first pressure level p1 is then set, e.g. B. 100 bar. In step S3, a second pressure level p2 (1) is set. The starting value of this second pressure level is z. B. 1 bar, ie atmospheric pressure. In step S4, the volume flow Q (1) which is established is then measured. In step S5, the first parameter K1 (1) is determined from the first p1 and second p2 (1) pressure level. This can be done according to the following name: K1 (1) = p1 - p2 (1) / p2 (1)

In step S6, the second parameter K2 (1) is determined. This results from the measured volume flow Q (1) and the first p1 and second p2 pressure level. Based this first K1 (1) and second parameter K2 (1) then becomes the first operating point B (1) determined. When querying in step S8, it is checked whether the operating point B (i) in the permissible range. The first time the loop is run, this request is always positive, since the first operating point B (1) serves as the base point. It is then checked in step S9 whether the first parameter K1 (1) is equal to the limit value GW according to FIG. 1. Since this is the first Pass is not yet the case, the query result is negative. The program branches then to step S10, in which the count variable i is incremented. At step S11 the second pressure level p2 (1) by a predeterminable value dp, z. B. 1 bar increased. Herewith is the loop closed.

The next time the program is run, a further step is carried out in steps S3 to S7 Operating point B (i) determined. If the query in step S8 is the further one Operating point B (i) is not within the permissible range, the program branches to the point B. This branch is described in connection with Figures 3 A to 3 C. Becomes determined in step S9 that the first parameter K1 (i) is equal to the limit value GW, so the injector is evaluated as error-free in step S12. It will be a positive test result detected. The program sequence is now finished.

Three alternative subroutines are shown in FIGS. 3A to 3C. These subroutines are activated when an operating point B (i) lies in the inadmissible range during the program run according to FIG. 2 in step S8. In FIG. 3A, the injector is then immediately recognized as faulty in step S13 and a negative test result is detected. The program sequence is then ended.
In FIG. 3B, a sum memory SUM is increased by 1 in step S14. The number of operating points in the inadmissible range of the characteristic field is counted in this total memory. In step S15 it is then checked whether the content of the sum memory SUM is less than a limit value GW. If the result of the query is positive, ie the number of inadmissible operating points B (i) has not yet exceeded the limit value GW, the program branches to point C in the program flow chart of FIG. 2. If the result of the query is negative in step S15, the injector becomes defective in step S16 determined and a negative test result detected. The program sequence is then ended.

FIG. 3C shows a third alternative, which has the identical steps S14, S15 and S16 according to FIG. 3B contains. In addition, a result memory is stored in step S17 N incremented. This result memory N counts the faulty injectors. After that In step S18, it is checked whether the number of faulty injectors exceeds a limit GW is. If this is not the case, the program flow branches to point A of the Program flow chart of Figure 2. If the result of the query is positive, i. H. the number of faulty injectors is greater than the limit value GW, this becomes in step S19 Manufacturing process determined as defective. The program sequence is then ended.

FIG. 4 shows a program flow chart of the second solution according to the invention. Steps S1 to S7 correspond to the same steps from FIG. 2, so that there is no further description at this point. In step S8, it is checked whether the run variable i is 2. This is not the case during the first program run, so that the program continues at step S9 and the run variable i is increased by 1. In step S10, the second pressure level p2 (i) is increased by a predeterminable value dp. The loop is hereby closed, ie the program continues with step S3.
The second operating point B2 is determined during the second program run. Since the check at step S8 shows that the running variable i is equal to 2, the process continues with step S11. In step S11, the deviation from the first B1 to the second B2 operating point is determined. This can be done by forming a difference or by forming a quotient. In step S12, it is checked whether the deviation dB is greater than a limit value GW. The limit value dB in FIG. 1 can correspond, for example, to the difference between the two ordinate values K2 (1) and point A. A value of 1, 2 has proven itself in practice. If this is not the case, the injector is assessed as error-free in step S13 and a positive test result is detected. If the test in step S12 shows that the deviation dB is greater than the limit value GW, the injector is determined as faulty in step S14 and a negative test result is detected. The program flow chart is then ended.

Reference list

S1 to S19

steps

KF

Characteristic field

Claims (13)

Method for testing a throttle point, in particular the throttle point of an injector, to which a first, constant pressure level (p1) is applied by a pump and which detects the volume flow (Q) of the hydraulic pressure medium provided by the pump,
characterized by
that a first (B (i), i = 1) and further (B (i), i = 2, 3, 4 ...) operating points are determined, the first operating point (B (i), i = 1) is decisive a characteristic field (KF) determines (KF = f (B (i)), the other operating points (B (i), i = 2, 3, 4, ...) are assigned to the characteristic field (KF), the characteristic field ( KF) has a range of permissible and non-permissible operating points and a positive or negative test result is detected based on the position of the further operating points (B (i), i = 2, 3, 4 ...) in the characteristic field (KF). Method according to Claim 1, characterized in that both the first (B (i), i = 1) and the further operating points (B (i), i = 2, 3, 4 ...) are significantly different from a first (K1 (i)) and the second parameter (K2 (i)) is determined, the first parameter (K1 (i)) is determined from the first pressure level (p1) and a second, predeterminable secondary pressure level (p2 (i)) of the injector and the second parameter (K2 (i)) is largely determined by the measured volume flow (Q (i)) and the first (p1) and second pressure level (p2 (i)). Method according to claim 2, characterized in that the further operating points (B (i), i = 2, 3, 4 ...) are determined essentially by the increase (dp) of the second pressure level (p2 (i)) (p2 ( i) = (p (i) + dp)). Method according to claims 1 to 3, characterized in that it is checked whether the first parameter (K1 (i)) is equal to a limit value (GW) (K1 (i) = GW). Method according to Claim 4, characterized in that, if the query result is positive (K1 (i) = GW), a positive test result is detected. Method according to claims 1 to 3, characterized in that a further operating point (B (i), i = 2, 3, 4 ...) assigned to the inadmissible region of the characteristic field (KF) is detected as a negative test result. Method according to claims 1 to 3, characterized in that a further operating point (B (i), i = 2, 3, 4 ...) assigned to the inadmissible area of the characteristic field (KF) is counted in a total memory (SUM) and it is checked whether the sum memory (SUM) is less than a limit value (GW) (SUM <GW). Method according to Claim 7, characterized in that if the result of the query is negative (SUM> GW), a negative test result is detected or if the result of the query is positive (SUM <GW) the next operating point is determined. Method according to Claim 7, characterized in that, if the query result is negative (SUM <GW), a negative test result is detected and the content of a result memory (N) is also incremented and the content of the result memory (N) is compared with a limit value (GW). Method according to Claim 9, characterized in that if the query result is positive (N> GW), an incorrect manufacturing method is detected. Method according to the preamble of claim 1, characterized in that a first (B1) and second (B2) operating point are determined, a deviation (dB) from the first (B1) and second operating point (B2) is determined and a negative test result is detected , if the deviation (dB) exceeds a limit value (GW) (dB> GW). A method according to claim 11, characterized in that both the first (B1) and the second operating points (B2) are largely determined by a first (K1 (i), i = 1, 2) and a second parameter (K2 (i)) , the first parameter (K1 (i)) is determined from the first pressure level (p1) and a second, predeterminable secondary pressure level (p2 (i)) of the injector, and the second parameter (K2 (i)) is largely determined by the measured volume flow (Q (i)) and the first (p1) and second pressure level (p2 (i)) is determined. Method according to claim 12, characterized in that the second operating point (B2) is largely determined by the increase (dp) of the second pressure level (p2 (i)) (p2 (i) = (p2 (i) + dp)).

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