Patent Description:
The main function of an engine is to provide torque output. Realization of this function involves a lot of hardware and as such the function can fail or degrade over time.

In order to allow for a cost effective repair, (i.e. replacing the failed or degraded component rather than the entire engine), failed part identification capability is needed. As the engine becomes more complex and legal requirements on emissions become more stringent, demands on accurately identifying failed parts also increase.

In the art, it is known to measure the time taken in a cylinder test of an internal combustion engine when accelerating between a low engine speed and a higher engine speed. To this end a speed measurement device can be coupled to the engine to generate a series of pulses corresponding to an engine cycle; and the time periods between successive pulses can be measured. By varying the cylinders under test and evaluating the respective performance of the internal combustion engine a practical performance test is provided that indicates a health condition of individual cylinders. Such a method is eg known from <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>.

For such tests, test kits have been developed that interface with an internal combustion engine, e.g. by adapting it to a central control unit, that has program logic to control the internal combustion unit. When connected, the test kit takes over engine control and tests can be carried out where the engine speed performance is measured in a condition of stand still, e.g. when the truck is in the repair shop and the engine provides no external torque.

To this end a test module is programmed to execute a sequence of individual cylinder tests, wherein the test module comprises computer code for measuring, in each cylinder test, a first engine performance value and further computer code for providing an amount of fuel to one cylinder under test to differ from an amount of fuel provided to the rest of the plurality of cylinders.

However, in some circumstances, it was found despite a negative assessment of the cylinder quality, and after extensive and time consuming repair activities, a cylinder engine did not prove to be faulty, despite a negative cylinder test. To this end it is an object to further improve the test kits for obtaining a test result wherein a cylinder under test is evaluated with more confidence, which may prevent loss of time and unnecessary replacement of cylinder parts.

In summary, the invention concerns a test kit comprising a testing program programmed to control an internal combustion engine for testing the internal combustion engine with the engine kept at a fixed load condition, provided with.

The further test module offers a distinction between an increase in parasitic loss that may lower the tested cylinder acceleration likewise and which cannot be distinguished from a less performing cylinder due to a component failure. By providing the test kit with the further test module, a testing routine may be provided that is able to filter out test results that suffer from parasitic losses that may occur during a testing sequence, e.g. by for instance due to activation of air compressor, airco, coolant pump, etc.. During the idling part in between accelerations the fuel-value required to idle the engine (which is then done on all cylinders) can be observed. If this deviates too much between accelerations; this will indicate a difference in parasitic losses; rendering the results unreliable.

This is advantageous since the test kit is not able to control all potential contributors to parasitic losses, and is therefore not able to fully prevent the above described issue. However, by detecting if a change in parasitic losses occurs the test can be aborted and the engineer may be informed that the test results are not reliable.

This test kit may significantly improve quality and accuracy assurance of a cylinder test used to identifying cylinder power contribution and as such improve accurate failed part identifying, thereby providing capability to the technician to replace the proper parts to bring the engine back into compliance. Accordingly a workshop engineer may now more reliably identify a cylinder at fault, since the test routine results are no longer compromised by faulty test conditions.

Aspects of the invention pertain to an improved test kit for interfacing with an internal combustion engine. The test kit comprising a testing program programmed to control the internal combustion engine for testing the internal combustion engine. The testing program is provided with a test module programmed to execute a sequence of individual cylinder tests, wherein the test module comprises first computer code for measuring, in each cylinder test, a first engine performance value and further comprises second computer code for providing an amount of fuel to one cylinder under test to differ from an amount of fuel provided to the rest of the plurality of cylinders. A further test module is programmed to measure, in an idle period between subsequent individual cylinder tests of said sequence of individual cylinder tests, a second engine performance value. The further test module comprises third computer code to discard at least some of the individual cylinder tests if the second engine performance measured by the further test module value passes a threshold. The further test module may be programmed to keep the internal combustion engine at a fixed engine speed in the idle period, by varying the amount of fuel provided in a closed loop control and wherein the second performance value is the amount of fuel provided in the idle condition. Alternatively, the further test module may programmed to provide the internal combustion engine with a fixed amount of fuel; wherein the second engine performance value is a measured engine speed. While both alternatives are possible, the first alternative has a practical benefit that typically, in an internal combustion engine control unit already a feedback control is provided to vary the amount of fuel in a closed loop control with the engine speed. In an embodiment the second computer code provides a standard amount of fuel provided to the rest of the plurality of cylinders, and provides the cylinder under test with less fuel than the standard amount. In such condition the third computer code discards a cylinder test, if the first engine performance measured with the cylinder under test differs from the engine performance measured for any other cylinder test after completion of the sequence of individual cylinder tests. While the amount of fuel may vary, for obtaining clear results, it is advantageous if the amount of fuel provided to the cylinder under test is zero. While in principle, a fixed counter torque may be applied to the engine, e.g. by an electrical generator, preferably, the engine is kept at a load condition that keeps the motor running free without any external load.

While the invention primarily pertains to the said test kit, another aspect of the invention pertains to a method of testing an internal combustion engine comprising a plurality of cylinders, wherein each of the plurality of cylinders are tested individually with the engine kept at a fixed load condition, the method comprising the steps of.

Embodiments may be described with reference to schematic and/or crosssection illustrations of possibly idealized embodiments and intermediate structures of the invention.

Turning to <FIG>, a practical example is shown. In a first step S <NUM>, the test state will be rendered active. Next, when a series of test entry conditions Q <NUM> are met (vehicle is in standstill, running idle, with no further appliances) the test becomes `armed' in step S2.

In a further step S3, the test becomes active on an activation trigger P1, e.g. when an operator depresses and holds the accelerator pedal down. In this initial step S3 an idle condition is set up, wherein the engine settles to a consistent idle engine speed before the start of the test measurements in S4. In this phase, a sequence of individual cylinder tests is executed, wherein, for each individual cylinder test, an engine performance value is measured in a condition that an amount of fuel provided to one cylinder under test differs relative to an amount of fuel provided to the rest of the plurality of cylinders. A typical engine performance value is a completion time for completing a specified increase of engine speed from a first (idle) engine speed to a second speed, higher than idle condition. Another engine performance value may be the completion time to complete a predetermined number of revolutions. To this end, the testing program programmed to control the internal combustion engine is provided with a test module programmed to execute the sequence of individual cylinder tests wherein in each cylinder test the engine performance value is measured by means of computer code specifically programmed to that purpose and further comprises additional computer code for providing an amount of fuel to one cylinder under test to differ from an amount of fuel provided to the rest of the plurality of cylinders. in the test five cylinders can be fed with the same amount of fuel and the cylinder under test is fed with a lesser amount of fuel, which can, in particular, be zero fuel. To this end a 'negative quantity offset' can be added to the standard quantity provided to the cylinders.

During acceleration of for example cylinder #<NUM> of six cylinders, five good cylinders will contribute with power and cylinder #<NUM> will contribute with less power - because it is driven with a different amount of fuel, which may be zero. Since during acceleration tests of cylinders #<NUM>-#<NUM>, in case cylinder #<NUM> is faulty, only four good cylinders will contribute with power it means that the completions times of cylinder tests #<NUM>-#<NUM> will be less than the completion time of cylinder time #<NUM>, where five good cylinders contribute. This means that the completion time for the first cylinder will be shorter than the completion time for the other cylinders and this will take a shorter time to complete a fixed number of injections set by the test, which is a measure of averaged engine speed.

Thus, the completion time for acceleration number one being significantly shorter than that of remaining accelerations indicates to a workshop technician that cylinder <NUM> may be faulty. While a cylinder may be faulty by generating less power, there may occur conditions that the cylinder generates more than desired power, e.g. by a defective fuel inlet. When the faulty cylinder is omitted a 'standard' completion time will be achieved that is lower than the normal time. This is likewise implemented in the test program.

This test cycle is repeated for all cylinders, which are typically six cylinders, and after completion, the test state moves to a finished condition S5, where the engine is kept in idle state until the engine is halted by switching it off. During the test, if any of the test conditions occur, a stop command is generated by an test module Q2, which directly moves the computer stage from step S4 to S5, without completion of the test; while an indication is generated that the test is aborted. The test module Q2 to this end is programmed to measure, in an idle period between subsequent individual cylinder tests of said sequence of individual cylinder tests, a second engine performance value; and said further test module comprising third computer code to discard at least some of the individual cylinder tests if the second engine performance measured by the further test module value passes a threshold as further will be illustrated in subsequent figures.

In <FIG> an example of a disturbance during cylinder acceleration function test is shown. Reliability of engine test routines can be enhanced by choosing specific engine settings, like an engine speed that is higher than normal idle condition or a start condition for the test, e.g. a start engine speed that triggers the testing program to start the measurement of the engine performance value; or a closed EGR valve. The sensitivity of the component under test for disturbances is typically handled by getting rid of potential disturbances. A disturbance can be e.g. a cooling fan which is activated during a test, resulting in fluctuating engine torque and speed. When the engine load changes during the idle phase, a fuel injection quantity will be adjusted accordingly: load increase due to parasitic loss may result in an increase of fuel injection for the same engine idle speed. This detected fuel injection value, which can be regarded as a performance value, can be low pass filtered. By way of example line A shows the air pressure level of the vehicle system. In the displayed measurement no signal was available indicating the air compressor status. Therefore the air pressure level is used to see if the air compressor was active. At the moment that the air pressure level increases, the air compressor is activated, meaning that the engine has an increased amount of parasitic losses to drive the air compressor to generate the pressure, which leads to an increased fuel consumption.

The acceleration events are visible in the engine speed traces B. It can be seen at C that when the compressor becomes active an increased fuel quantity is required to maintain the same idle speed. Since the cylinder acceleration test algorithm uses a pre-determined fuel quantity for the acceleration, when more fueling is needed to maintain idle speed, it means less fuel excess is available for the acceleration, which results in a slower acceleration and as such more time is needed to achieve the pre-determined amount of engine revolutions, thereby falsely indicating an issue with the cylinder.

As a result the fuel quantity differs during test execution, which will impact the test results.

In <FIG> a similar test trace is shown as in <FIG>, with six engine performance tests shown by speed traces B and fuel dosage C. It is shown that a threshold E is provided and a signal D measures a difference of a fuel dosage compared to a reference value. In such condition, the performance value may be a difference value of an amount of fuel provided in the idle condition, relative to a reference value, and all cylinder tests are accepted because line D does not pass threshold line E.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description and drawings appended thereto. For the purpose of clarity and a concise description features are described herein as part of the same or separate embodiments.

Claim 1:
A test kit for interfacing with an internal combustion engine, said test kit comprising a testing program programmed to control the internal combustion engine for testing the internal combustion engine, said testing program provided with a test module programmed to execute a sequence of individual cylinder tests, wherein the test module comprises first computer code for measuring, in each cylinder test, a first engine performance value and further comprises second computer code for providing an amount of fuel to one cylinder under test to differ from an amount of fuel provided to the rest of the plurality of cylinders;
characterized by a further test module programmed to measure, in an idle period between subsequent individual cylinder tests of said sequence of individual cylinder tests, a second engine performance value; and said further test module comprising third computer code to discard at least some of the individual cylinder tests if the second engine performance measured by the further test module value passes a threshold.