Measuring and testing – Test stand – For engine
Utility Patent
1998-08-10
2001-01-02
Fuller, Benjamin R. (Department: 2855)
Measuring and testing
Test stand
For engine
C060S276000, C060S274000, C060S684000
Utility Patent
active
06167754
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention resides in a method of checking the lambda sensor connections in multi-cylinder internal combustion engines with at least two separate exhaust gas pipes of which each includes a catalytic converter and at least one lambda sensor arranged in each exhaust gas pipe with a lambda sensor control arrangement connected thereto.
The cylinders of multicylinder internal combustion engines are often arranged in several rows, so-called cylinder banks, comprising each two, four or six cylinders. Generally, however, an engine is limited to two banks which are arranged in the form of a V.
The more cylinders an engine includes, the smaller is the time gap between the ignition of the cylinders and the smoother is the engine torque curve. In order to prevent the exhaust gas discharge of the various cylinders from disturbing one another, several exhaust gas ducts are provided and connected to cylinders whose ignition timings are sufficiently spaced with respect to one another. In multi-row piston type internal combustion engines a separate exhaust gas duct is generally provided for each cylinder bank.
If the exhaust gas values of the internal combustion engine are to be monitored by a lambda sensor control arrangement, that is, the fuel/air mixture ratio is controlled depending on engine operating conditions and exhaust gas sensor values, it has to be taken into consideration that each cylinder bank is subject to individual disturbance factors such as air leakage and different flow rates of the fuel supply equipment. A separate lambda sensor circuit is therefore provided for each cylinder bank. A lambda sensor circuit generally includes a Lambda sensor arranged in the exhaust pipe and a control unit connected thereto.
There is however the possibility that the lambda sensors are transposed when they are installed that is they are connected to the incorrect lambda sensor circuit. For example, with an engine which has two cylinder banks and two lambda sensor control circuits one sensor of the first exhaust pipe may be connected to the second lambda sensor control circuit and, vice versa, the lambda sensor of the second exhaust pipe may be connected to the first lambda sensor control circuit. In such a case, the second lambda sensor for example will properly recognize an enriching of the fuel/air ratio of the first cylinder bank, but the sensor value is supplied to the second lambda sensor control circuit, that is, the lambda sensor control circuit for the second cylinder bank. The second control circuit will then adjust the mixture for the second cylinder bank toward a leaner mixture, which is sensed by the first Lambda sensor which supplies this value to the first Lambda sensor control circuit of the first cylinder bank. This leads to an increasingly lean adjustment for the second cylinder bank and to an increasingly rich adjustment for the first cylinder bank up to the adjustment limits for the lambda control circuits. As a result, the internal combustion engine will operate roughly and the driving comfort will suffer.
Basically, it would be possible to use components or connections for the sensor cable of the different lambda sensors which cannot be interchanged. However, this would require the manufacture and storage of a larger number of parts so that, preferably, the lambda sensors and connections are identical.
DE 44 23 344 A1 discloses a method of testing for a transposition of the Lambda sensors. In this method, the fuel injection valves of one of the two cylinder banks are kept closed for a period permitting the lambda sensors to react or, respectively, switch over. At the end of the shut-off period of the injection valves, the Lambda sensor signal is compared with a predetermined threshold value. If the lambda sensor signal is not in agreement with the threshold value the lambda sensors are connected in a transposed manner. However, this test procedure can be utilized only for an engine wherein the fuel injection valves of at least one cylinder bank can be shut off.
The publication MTZ, Motortechnische Zeitschrift 52, page 221 discloses a piston type internal combustion engine with twelve cylinders having two cylinder banks in a V-arrangement. Each cylinder bank is independent as far as intake and exhaust systems are concerned. Each cylinder bank has a catalytic converter with a lambda sensor arranged upstream of the catalytic converter. An electronic fuel injection control unit controls a secondary air pump for injecting air into the exhaust passages during engine warm up. In combination with the hot exhaust gases, this provides for a supplemental oxidation in the exhaust system which, on one hand, reduces the amount of emissions and, on the other hand, increases the exhaust gas temperature by the exothermic reaction. The air injection can be interrupted concurrently for both cylinder banks by a shut-off valve.
DE 42 25 361 A1 discloses a method for testing proper operation of the secondary air admission to the exhaust system of an internal combustion engine. The internal combustion engine includes only one cylinder bank with one exhaust system and one lambda sensor. After start up of the internal combustion engine, the secondary air pump and a control unit are activated and the signal of the lambda sensor is employed for examining the operation of the secondary air supply.
It is the object of the present invention to provide a method with which transposed connections of lambda sensors can be detected rapidly and in a simple manner and an internal combustion engine which permits the execution of this method.
SUMMARY OF THE INVENTION
In a method of checking for a transposition of the lambda sensors of a multicylinder internal combustion engine having at least two separate exhaust pipes connected to different cylinders, a catalytic converter arranged in each exhaust pipe, a lambda sensor arranged in each exhaust pipe upstream of the respective catalytic converter, a lambda sensor control circuit for each lambda sensor, and an air inlet connection associated with at least one exhaust pipe upstream of the respective lambda sensor, air is supplied to one of the exhaust pipes, and the signal provided by the respective lambda sensor is compared with a stored threshold signal value to determine whether the lambda sensor installed is operative and is connected to the proper lambda sensor control circuit.
During the examination period which is at least as long as the reaction time or, respectively, the switch-over time of the lambda sensor, air is supplied from an air source at least to one exhaust pipe upstream of the lambda sensor by way of at least one air supply connection preferably between the discharge side of the internal combustion engine and the lambda sensor. Independent of the actual air/fuel mixture supplied to the engine and of the fuel injection values the exhaust gas composition can in this way be rapidly changed over a wide range without any risk that a catalytic converter in the exhaust system is damaged or destroyed. The travel distance between the air supply connection and the lambda sensor is short so that the air-enriched exhaust gas reaches the lambda sensor immediately without affecting any engine equipment. The change in the exhaust gas composition can be rapidly recognized by the lambda sensor and the sensor signal can be processed as a clear and safe signal for indicating a transposition of the lambda sensors.
The invention and its advantages will become more readily apparent from the following description of preferred embodiments thereof on the basis of the accompanying drawing.
REFERENCES:
patent: 5113651 (1992-05-01), Kotzan et al.
patent: 5357938 (1994-10-01), Bedford et al.
patent: 5417109 (1995-05-01), Scourtes
patent: 5528932 (1996-06-01), Bauer et al.
patent: 5542292 (1996-08-01), Schneider et al.
patent: 42 25 361 (1994-02-01), None
patent: 44 23 344 (1996-01-01), None
patent: 44 41 432 (1996-05-01), None
patent: 0 691 465 (1996-01-01), None
J. Abthoff et al,“Der Neuer Zwölfzylinder-Motor F{umlaut over (u)}r Die Neue
Bach Klaus J.
Daimler-Chrysler AG
Davis Octavia
Fuller Benjamin R.
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