Method for selecting position of engine knock sensor

Abstract

The invention provides a method for selecting the position of an engine knock sensor, and belongs to the technical field of engine detection. According to the method, the point selection program is simplified, the point selection process is streamlined, the operation execution effectiveness is high, and the position point selection accuracy is high. The method comprises the following steps: loading an engine on a test bed, connecting a test tool, confirming test boundary conditions, setting detection variables, obtaining knock data based on LMS vibration noise test equipment, drawing a knock energy curve, processing and analyzing the collected test data by using Testlab software to draw a knock cloud picture, analyzing to obtain a knock sensor mounting point, and detecting the knock sensor mounting point according to the knock cloud picture. And finally, detecting the qualification degree of the set point of the knock sensor by using Kibox equipment. According to the method, the maximum position of the vibration acceleration is measured through LMS vibration noise, a test tool is replaced with a knock sensor on the point, the vibration signal strength in a knock cloud picture is checked through Kibox equipment to judge whether the point is appropriate or not, the test structure is accurate and reliable, the process is clear, and the operation execution effectiveness is high.

Description

Technical Field

[0001] The invention belongs to the technical field of engine detection, and in particular relates to a method for selecting a position of an engine knock sensor. Background Art

[0002] Knocking is an abnormal combustion phenomenon in an engine, caused by an advanced engine ignition angle, excessively high temperature, or too low a fuel octane number. It can lead to abnormal engine vibration, weakened engine output power, increased temperature, and increased fuel consumption.

[0003] After the engine bench calibration is completed, during the vehicle test and user use, detonation may be induced due to the inability to guarantee the boundaries. If detonation cannot be effectively identified, it will cause a series of serious problems such as engine damage.

[0004] Therefore, engine knock identification is particularly important, but so far there is still a lack of methods for selecting the location of engine knock sensors. Summary of the Invention

[0005] In order to solve the problems existing in the above-mentioned background technology, the present invention provides a method for selecting the position of an engine knock sensor, which simplifies the point selection procedure, streamlines the point selection process, has high operation efficiency, and high position selection accuracy.

[0006] The technical solution adopted by the present invention to solve the technical problem is: a method for selecting the position of an engine knock sensor, comprising the following steps; Step 1: Mount the confirmed engine on the performance test bench, confirm the test boundary conditions, connect and install the test fixture, and then perform the knock test; Step 2: Using the LMS vibration and noise test equipment, add detection variables to the oscilloscope, increase the actual ignition advance angle to create knock, collect vibration data under knock conditions, and simultaneously compare the knock condition of the copper tube with the KP-PK knock energy curve of the combustion analyzer to verify whether it is a knock state; Step 3: Use Test-lab software to process and analyze the collected test data. Retrieve data on vibration acceleration, sampling frequency, speed, and torque, and draw a schematic diagram of vibration collection at different measurement points. Based on the results shown in the schematic, calibrate the knock sensor placement point and replace the test fixture with the knock sensor. Step 4: Connect the knock sensor to the Kibox device, retest the above operating conditions and draw a knock cloud map, debug INCA, and perform knock sensor set point qualification verification.

[0007] The test tooling in step 1 includes a vibration sensor, a combustion analyzer and a copper tube. The test boundary conditions are that the outlet water temperature and the oil temperature are ≥80°C, the relative humidity is 40-60°C, and the exhaust temperature is <850°C.

[0008] The detection variables in step 2 include engine speed, bench test conditions, signal acquisition frequency and vibration acceleration, wherein the bench test conditions are set to 4000 rpm, the corresponding torque is set to 100% load, and vibration data of the knock state at a frequency of 12 kHz to 16 kHz is collected.

[0009] In the step 4, the knock signals are qualified if they all exceed the knock identification threshold, and the knock identification threshold is that the knock signal intensity exceeds 2 times the background noise.

[0010] Beneficial effects of the present invention: The present invention adopts LMS vibration noise to measure the maximum position of vibration acceleration, replaces the test tooling with a knock sensor at this point, uses the Kibox device to check the vibration signal intensity in the knock cloud map to determine whether this point is appropriate, and provides a comprehensive multi-angle knock point selection method for the knock sensor measurement point position, making the results more accurate and convincing, and provides a test condition for knock collection, making the work more concise and clear, and streamlining the knock position selection process, which can more accurately judge whether the knock point selection is qualified, and the operation execution is highly effective, making the engine knock signal position selection more reliable and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In the attached figure: Figure 1 is a flow chart of knock sensor position selection of the present invention; Figure 2 is a vibration signal diagram measured by the present invention; Figure 3 It is the detonation cloud map measured by the present invention. DETAILED DESCRIPTION

[0012] The present invention will now be described in further detail with reference to the accompanying drawings, which are simplified schematic diagrams that illustrate the basic structure of the present invention in a schematic manner.

[0013] A method for selecting a position of an engine knock sensor comprises the following steps: Step 1: Load the engine that has been confirmed to have no problems on the performance test bench and confirm the test boundary conditions. The test boundary conditions guarantee the bench parameters and ensure that the engine allows for knock testing. During the test, the outlet water temperature is ≥80°C, the relative humidity is between 40 and 60°C, and the exhaust temperature is <850°C. Install the test tooling, which includes a vibration sensor, a combustion analyzer, and a copper tube, and then perform the knock test.

[0014] Step 2. Use the LMS vibration and noise test equipment to add detection variables to the oscilloscope. The detection variables include engine speed, bench test conditions, signal acquisition frequency, and vibration acceleration. Set the bench test conditions to 4000 rpm, adjust the corresponding torque to 100% load, adjust the ignition advance angle MAP table to increase the actual ignition advance angle to create detonation, perform a detonation test according to the test conditions, and collect vibration data under the detonation state at a frequency of 12KHZ-16Khz. Simultaneously compare the detonation condition of the copper tube with the KP-PK detonation energy curve of the combustion analyzer to verify whether it is a detonation state.

[0015] Step 3: Use Test-lab software to process and analyze the collected test data, and retrieve vibration acceleration, sampling frequency, speed and torque, as shown in the attached manual. Figure 2 The figure shows the vibration diagram under the knock state with the bench test condition set to 4000 rpm and the corresponding torque being 100% load. 1 to 4 represent different vibration measurement points, the horizontal axis is frequency, and the vertical axis is time. The denser the points in the figure and the more points are connected by horizontal lines, the better the knock recognition. The vibration measurement points are sorted. According to the knock recognition performance shown in the figure, 1>3>2>4, the test tool at position 1 is replaced with a knock sensor.

[0016] Step 4: Use the Kibox device to connect the wiring harness behind the knock sensor plug, retest the above working conditions and draw the knock cloud diagram (that is, obtain the diagram as shown in the attached manual). Figure 3 (See the knock cloud diagram shown in the figure), debug INCA, and perform a knock sensor set point qualification test. During knock, if the knock signals exceed the knock identification threshold, the system is qualified. When the ignition advance angle is increased to create a strong knock, the number of points in the knock cloud diagram exceeding the knock identification threshold increases, which is basically consistent with the performance of the copper tube and combustion analyzer. When the knock cloud diagram, copper tube, and combustion analyzer results are consistent, the system is qualified. Among them, if the vibration signals in the knock cloud diagram exceed the knock identification threshold, the system is qualified. If the minimum knock identification threshold is not met, the data is unqualified and needs to be readjusted. The knock identification threshold is the knock signal intensity exceeding 2 times the background noise. When the knock signal intensity exceeds 2 times the background noise, it is identified as knock. Generally, the minimum multiple of 2 is set to be the minimum knock threshold.

[0017] During the specific operation, the engine is first loaded onto the performance test bench, the test boundary conditions are confirmed, and it is ensured that the engine allows for knock testing. The water outlet temperature is set to 88°C, the oil temperature is 90°C, the relative humidity is 52°C, and the exhaust temperature is 792°C during the test. A vibration sensor, a combustion analyzer, and a copper tube are installed between the engine and the performance test bench respectively.

[0018] Secondly, through the principle of the knock sensor and the previous measurement of vibration signals, it is known that the knock signal is positively correlated with the vibration signal in the vertical direction of the knock boss platform. Vibration sensors are installed on multiple platforms of the cylinder body, and measurements are performed using LMS vibration and noise testing equipment. A detection variable is added to the oscilloscope, where the detection variable is vibration acceleration. The bench test conditions are set to include four groups of speeds at 2000, 3000, 4000 and 5000 rpm, and the corresponding torques are adjusted to two groups of loads at 80% and 100% respectively, for a total of eight groups of conditions. The eight groups of conditions are executed in sequence through adjustment on the performance test bench. Knock tests are performed according to the test conditions, and test data is collected under the knock state of each group of conditions. The knock condition generates ≥10 knocks within one minute. If KP-PK>0.5×speed / 1000, it is deemed to be knock.

[0019] Then, the Test-lab software is used to process and analyze the collected test data, retrieve the vibration acceleration, that is, the sampling frequency data, and observe the engine knock conditions under monitoring at different measuring points. First, debug the original state under the knock edge condition. After that, debug INCA to increase the ignition advance angle. After knock occurs, start measuring and viewing the vibration signals at different frequencies. The greater the vibration acceleration, the more obvious the signal, which means that the selected point location is more reasonable. The various measuring points are comprehensively sorted, and the test fixture at the optimal point location is replaced with a knock sensor. If no vibration signal is identified or the vibration signals are consistent, the corresponding test data is unqualified and needs to be readjusted.

[0020] Finally, the Kibox device is used to measure whether the knock signal generated by increasing the ignition advance angle exceeds the knock threshold, thereby determining whether it is qualified.

[0021] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A method for selecting an engine knock sensor position, characterized in that: The following steps are included: Step 1: Mount the confirmed engine on the performance test bench, confirm the test boundary conditions, connect and install the test fixture, and then perform the knock test; Step 2: Using the LMS vibration and noise test equipment, add detection variables to the oscilloscope, increase the actual ignition advance angle to create knock, collect vibration data under knock conditions, and simultaneously compare the knock condition of the copper tube with the KP-PK knock energy curve of the combustion analyzer to verify whether it is a knock state; Step 3: Use Test-lab software to process and analyze the collected test data. Retrieve data on vibration acceleration, sampling frequency, speed, and torque, and draw a schematic diagram of vibration collection at different measurement points. Based on the results shown in the schematic, calibrate the knock sensor placement point and replace the test fixture with the knock sensor. Step 4: Connect the knock sensor to the Kibox device, retest the above operating conditions and draw a knock cloud map, debug INCA, and perform knock sensor set point qualification verification.

2. The method for selecting an engine knock sensor position according to claim 1, wherein: The test tooling described in step 1 includes a vibration sensor, a combustion analyzer, and a copper tube.

3. The method for selecting an engine knock sensor position according to claim 2, wherein: The test boundary conditions described in step 1 are that the outlet water temperature and the oil temperature are ≥80°C, the relative humidity is between 40°C and 60°C, and the exhaust temperature is less than 850°C.

4. The method for selecting an engine knock sensor position according to claim 3, wherein: The detection variables in step 2 include engine speed, bench test conditions, signal acquisition frequency, and vibration acceleration, wherein the bench test conditions are set to 4000 rpm, and the corresponding torque is set to 100% load.

5. The method for selecting an engine knock sensor position according to claim 4, wherein: The second step is to collect vibration data of the knock state at a frequency of 12KHZ-16Khz.

6. The method for selecting an engine knock sensor position according to claim 5, characterized in that: In step 4, if the knock signals exceed the knock identification threshold during the knock, the system is qualified. The knock identification threshold is that the knock signal intensity exceeds 2 times the background noise.

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