Data processing: measuring – calibrating – or testing – Measurement system – Weight
Reexamination Certificate
2001-04-09
2003-02-04
Shah, Kamini (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system
Weight
C702S175000, C701S029000, C073S862090, C073S117020
Reexamination Certificate
active
06516287
ABSTRACT:
The invention relates to a method for mass simulation of motor vehicles on stationary test stands according to the preamble of the patent claim
1
as well as an apparatus for carrying out this method according to the preamble of the patent claim
5
.
For stationary vehicle testing, roller test stands are predominantly used as stationary test stands. In this context, the drive wheels of a motor vehicle are coupled with the rollers of the test stand with respect to the rotational moment or torque. Since the vehicles do not move on these test stands, the inertial forces resulting from the acceleration of the vehicle mass must be simulated by the test stand, if the mass inertial moment of the test stand does not correspond with that of the vehicle mass. Hereby it is typical to simulate the difference of the inertial forces through a loading moment, which is generated, for example, by means of a direct current machine. The magnitude of the loading moment is regulated by a dynamic regulating circuit or closed control loop dependent on the respective acceleration.
For example, in order to exactly determine the exhaust gas properties of a vehicle determined on such test stands, the automobile industry and the environmental agencies place high demands on the measuring accuracy of such roller test stands. Therefore, all of the masses of the vehicle must be taken into consideration, which are not accelerated while driving on the test stand in comparison to driving on the street. These are, on the one hand, the translatory masses of the vehicle, such as the weight as well as the rotatable parts of the non-driven axles on the test stand.
In practice, these rotatable still-standing or non-moving masses were previously not exactly determined, but instead were approximately estimated based on empirical values. This was carried out because, although the weight of a vehicle is simple to determine, however it is not simple to determine the inertial moments of the rotating parts such as the wheels including the drive train, the clutch, the transmission and the like. Such a mass determination of these parts has previously been made more difficult, because frictional losses always additionally arise for these rotatable vehicle parts. For this reason, the sought-after inertia values have been approximately determined from the weight of the vehicle. Thus, from the vehicle weight, an increase or add-on of 3% to be added to the vehicle mass has been assumed for the rotatable vehicle parts. For a test stand run, that meant an increase or add-on of 1.5% onto the vehicle mass per non-rotating vehicle axle.
Such an estimation of the rotatable vehicle masses, which are not accelerated during the testing process on the test stand, can lead to an error of the mass simulation in unfavorable cases, whereby this error by itself already exceeds the required total measuring accuracy. Especially, this leads to considerable errors in the mass simulation if the distribution of the rotating inertias on the driven and non-driven axles is non-uniform.
Therefore, the invention is based on the object of improving the accuracy of the mass simulation on vehicle test stands.
This object has been achieved by the invention defined in the patent claims
1
and
5
. Further developments and advantageous example embodiments of the invention are defined in the dependent claims.
The invention has the advantage that essentially all rotatable vehicle masses can be exactly determined by a measurement, and thereby consequent errors in the calculation of the driving resistances as well as of the mass simulation are avoidable.
The invention is described in further detail in connection with an example embodiment, which is illustrated in the drawing. The drawing shows a schematic illustration of a roller test stand with a regulating circuit or closed control loop
9
, which contains an evaluation device
10
with a memory circuit
13
and a test input device
11
, a junction point
8
and a regulator
12
, and which regulates the direct current machine
1
corresponding to the vehicle mass that is to be simulated.
In the drawing, a direct current machine
1
is illustrated, which is rotatably connected with two testing stand rollers
6
via a connecting shaft
2
. A vehicle
5
is schematically illustrated on the two test stand rollers
6
, whereby the vehicle
5
is connected with one axle and the two vehicle wheels
4
in a force transmitting manner with the test stand rollers
6
. Furthermore, the test stand rollers
6
are connected via the same shaft
2
with a rotational speed detection device, which is embodied as a tacho-generator
7
. A rotational moment or torque pick-up
3
, which is electrically connected with the regulating circuit
9
, is arranged on the connecting shaft
2
between the direct current machine
1
and the test stand rollers
6
positioned opposite thereto. Thereby, the regulating circuit
9
consists of an evaluating device
10
, onto which a memory circuit
13
and a test input device
11
are connected, a regulator
12
and a junction point
8
. The tacho-generator
7
is connected with the evaluating device
10
on the input side. Furthermore, the junction point
8
is arranged between the regulator
12
, the force pick-up
3
, and the output of the evaluating device
10
and establishes an electrical connection therebetween. The regulator
12
provides a regulating signal via its output to the direct current machine
1
. The direct current machine
1
can be operated both as a generator as well as a motor.
The test input device
11
connected with the evaluating device
10
contains two inputs for inputting a vehicle velocity v and the associated time t, and an output which supplies to the evaluating device
10
the delay −a determined from the inputs. The evaluating device
10
contains another input for inputting the translatory vehicle mass m
F
, which is inputtable as a previously known value. Moreover, the evaluating device
10
is still further connected with a memory circuit
13
, which stores the test results determined on the test stand, such as the test stand mass m
p
, the mass of the rotatable vehicle drive masses m
Rad h
on the rear axle and the mass of the remaining rotatable vehicle mass m
Rad v
on the non-driven front axle.
The above described apparatus operates according to the following method steps: In the testing of a vehicle
5
on a roller test stand, the drive axle of the vehicle
5
as the test sample drives, via its vehicle wheels
4
, the test stand rollers
6
. On the other hand, the test stand rollers
6
can also be driven via the direct current machine
1
. This is carried out preferably when the non-driven wheels
4
of a vehicle axle are located on the test stand rollers
6
. Thereby, the tacho-generator
7
and the direct current machine
1
are simultaneously moved along via the connecting shaft
2
. Thereby the tacho-generator
7
generates a signal, which is proportional to the velocity v or the angular velocity &ohgr;. In the above described known differentiating evaluating method, the accelerating vehicle force which acts on the test stand rollers
6
can be derived from the angular velocity signal &ohgr;. On the other hand, during the motor operation of the direct current machine
1
, the force effect expended for the acceleration of the rotatable vehicle masses can also be determined by the differentiation of the velocity signal v or &ohgr;. Therefrom, by means of the evaluating device
10
, the corresponding mass values such as the test stand mass m
P
, the mass m
Rrad h
rotating with the drive axle, the mass m
Rad v
that is rotatable with the non-driven front axle, are calculable.
For the simulation of all of the vehicle masses that are effective on the street, first all of these individual masses must be determined or calculated, in order to then determine their effect by means of a roll-out test on the street. Then, from these measurement results, a driving resistance characteristic curve or corresponding values can be fixed or determined, which serve
Fasse W. F.
Fasse W. G.
Schenck Pegasus GmbH
Shah Kamini
LandOfFree
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