DE10227821A1 - Determining the load torque and output current of a vehicle generator by measuring the excitation current - Google Patents

Abstract

The invention relates to a device and a method for determining the output current (Igen) of a vehicle generator, the output voltage of which is regulated by a generator regulator. In order to improve the accuracy in determining the output current (Igen), it is proposed to measure the generator speed (n) and the excitation current (Ierr) and to output the measured values to a processing unit which determines the generator current (Igen) of the generator on the basis of the measured Values determined.

Description

The invention relates to a method and a device for determining the output current of a vehicle generator according to the generic term of claim 1 or 6.

Load moment and output current of a vehicle generator are important parameters for the installation an energy balance in an electrical system or for carrying out a effective engine management in a motor vehicle.

The generator output current is usually calculated from the generator speed n, the excitation current Ierr and the air gap d between the rotor and the stator with the aid of a characteristic diagram determined for the respective generator. The excitation current Ierr is estimated from the pulse duty factor Tein / (Tein + Taus) of a switching transistor with which the excitation field is switched, the excitation field temperature T, which is determined indirectly via the temperature of the engine compartment, the excitation field resistance R and parasitic loss resistances in the excitation path Rpar , The following therefore applies to the determination of the generator current Igen:
Igen = f (n, T, R, Rpar, Ubat, d)

Thereby the generator speed n and the generator output voltage Ubat are measured. On the other hand in particular form the excitation field temperature T, the excitation field resistance R due to its temperature dependence and the parasitic loss resistances Rpar difficult to determine sizes that can strongly influence the result. Deviations in the actual Temperature T of the excitation field when determining the excitation field resistance R and the actually Voltage applied to the excitation field has a direct effect on the Calculation of the generator output current Igen.

The following relationship applies to the calculation of the generator load torque Mgen:
Mgen = f (Igen, Ubat, n) ,

As can be seen, it also works the relatively imprecise determinable generator output current Igen on.

The accuracy in the calculation of the generator output current Igen or the generator load torque Mgen is for Loading balance calculations or for engine management, especially when the engine is idling, is too low. The Determination of the sizes mentioned is also relatively computationally expensive.

It is therefore the object of the present invention the accuracy in the calculation of the generator output current or to increase the load torque and at the same time reduce the computing effort.

This object is achieved according to the invention by the features specified in claim 1 and 6. Further Embodiments of the invention are the subject of dependent claims.

The main idea of the invention consists of the excitation current preferably directly in the generator controller to measure and the measured value via a suitable interface to a control unit Output (processing unit) and from it the generator output current or to calculate the load moment. By directly measuring the excitation current can the inaccuracies in the estimation of the Excitation current avoided and the calculation of generator output current and load torque can be significantly improved.

This results in the following relationship for calculating the generator output current Igen and the load torque Mgen in the control unit:
Igen = f (n, Ierr, d)
Mgen = f (Igen, Ubat, n)

Generator output current and / or load torque are preferably made from corresponding characteristic curves or tables determined, which can be stored in the control unit, for example.

Is in the system e.g. a generator current / speed characteristic field or a load torque / speed characteristic field is stored, so can taking into account the generator output current or the generator load torque the remaining sizes (n, Ubat, d) can be output directly. Output current or load torque can be selected can also be calculated.

By directly measuring the excitation current (using a suitable ammeter), essentially only precisely determinable variables remain for determining the generator output current and the load torque. The only unknown significant quantity is the air gap d of the generator. A is usually used for the air gap d Average from manufacturing. Depending on the actual air gap d, this can be relatively imprecise.

To further improve the Achieving accuracy can be achieved with a generator test (test bench measurement) Really measured generator output current, which is at a given Excitation current and specified speed has been used to compare the characteristics stored in the system and to the actual Adjust the air gap of the generator. For example, a correction factor can be determined with which the generator output current stored in the system or the load torque is corrected for the influence of the air gap to eliminate d. Optionally, based on the test bench measurement even on the actual Air gap d calculated back who then for the determination of generator output current or load torque is used can be.

The invention is illustrated below the attached Exemplary drawings closer explained.

Show it:

1 an example of a generator current / speed characteristic field;

2 a flowchart to illustrate the method by which the generator current is determined;

3 is a schematic representation of a device for determining the output current of a vehicle generator.

1 shows a generator current / speed characteristic field stored in the system, in which the influence of excitation current Ierr and air gap d on the generator output current Igen is shown. As can be seen, the generator output current Igen increases with increasing excitation current Ierr (Ierr1> Ierr3).

At the lowest current characteristic (Ierr3) is about it beyond the influence of Air gap d shown, it can be seen that the generator output current Igen slightly decreases with increasing air gap.

In order to calculate generator output current and generator load torque the inaccuracy due to different greater Eliminating air gaps d becomes the result of a test bench measurement real measured generator output current is used. From the test bench measurement results under defined conditions (excitation current Ierr and Speed n) a generator current, based on which the characteristic curves have it corrected accordingly.

In addition to the current separation lines are preferred also torque characteristics stored in the system (not shown) which the current load torque can be read out.

2 shows a flow chart to illustrate a method with which the generator output current Igen is easily determined.

In the procedure for determining the Output current Igen are first in a first step 1 Generator speed n and in a second step 2 the excitation current Ierr measured. In a third step, the generator current then becomes Igen determined on the basis of the measured values. This is done using Characteristic curves or tables in a processing facility (Control unit) are.

When evaluating the characteristic curves becomes the actual Size of the air gap d of the generator is taken into account, the previously in test bench measurements was determined.

By directly measuring the excitation current The generator output current Igen can be determined very precisely.

3 shows a device for determining the output current Igen of a vehicle generator 9 , whose output voltage from a generator regulator 7 is regulated. The device further comprises a device 8th for measuring the generator speed n and a device 6 for measuring the excitation current Ierr. The measured values are sent to a processing device 10 supplied, which determines the generator output current Igen based on the measured values. The generator output current Igen can be read out directly from tables or characteristic curves stored in the system.

1-3

steps

6

measuring device

7

regulator

8th

Rev counter

9

generator

10

processing unit

igen

generator power

ierr

excitation current

d

air gap

n

rotational speed

Claims (7)

Method for determining the output current (Igen) of a Vehicle generator, its output voltage from a generator regulator is regulated, characterized by the following steps: - Measure up the generator speed (s), - measuring the excitation current (Ierr) - Output the measured values to a processing device, and - Determine of the generator output current (Igen) based on the measured Values. A method according to claim 1, characterized in that the excitation current (Ierr) is measured in the generator controller. A method according to claim 1 or 2, characterized in that the output current (Igen) and / or the load torque determined from characteristic curves or tables that are stored in the system. Method according to one of the preceding claims, characterized characterized in that at a value comparison to determine the generator output current (Igen) is carried out with a real measured generator output current (Igen), to the actual Air gap (d) to be taken into account. Method according to one of the preceding claims 1 to 3, characterized in that the size of the actual Air gap (d) from test bench measurements determined and when determining the output current (Igen) or of the load torque is taken into account becomes. Device for determining the output current (Igen) of a Vehicle generator, its output voltage from a generator regulator is regulated, characterized by - a device for measuring the generator speed (s), and - a device for measuring the excitation current (Ierr), - where the measured values be forwarded to a processing facility that the Generator output current (Igen) based on the measured values determined. Apparatus according to claim 6, characterized in that the Device for measuring the excitation current (Ierr) in the generator controller is arranged.