Engine delivery cold test machine top dead center detection method

Abstract

A method for detecting a top dead center of a machine in an engine delivery cold test belongs to the technical field of engine cold tests, and is characterized by comprising the following steps: installing a cylinder pressure sensor on a cylinder 1, installing a pressure sensor at the position of the cylinder 1 of a cylinder cover air inlet channel, and installing an external signal amplifier; the method comprises the following steps: calibrating a top dead center, controlling a test bench, performing waveform test, and outputting an oscillogram; a heat loss angle is measured, a one-cylinder top dead center sensor is installed on an engine body, the sensor and a crankshaft position sensor are connected into a combustion analyzer, and a physical top dead center is measured through turning; calculating the position of a top dead center; a pressure sensor is additionally arranged at an air inlet cover plate of the short-engine cold test bench, and the engine tested by the test bench is loaded to the cold test bench; carrying out data statistics, and carrying out statistics on factory machine samples; after the limit value setting is completed, arranging workshop implementation and management and control; the quality of the outgoing engine is improved, the service life of the engine is prolonged, the overall oil consumption level of the outgoing engine is controlled, and customer experience is further improved.

Description

Technical Field

[0001] The invention belongs to the technical field of engine cold test equipment, and in particular relates to a method for detecting the mechanical top dead center of an engine during a factory cold test. Background Art

[0002] Engine testing is an important way to improve the quality of engines leaving the factory, and it is also an important link in the final stage of engine development. During the engine research and development process, all electronic fuel injection calibrations are based on the top dead center position of the calibration machine. Inaccurate top dead center position can lead to problems such as detonation, performance degradation, increased fuel consumption, and reduced reliability. In the past, factory engines were unable to effectively identify the mechanical top dead center during both the hot test and cold test processes, resulting in the factory engine possibly having a large top dead center deviation problem, and the ignition angle and other data had certain differences from the calibration data, which would lead to reduced reliability and may eventually cause after-sales quality problems. Therefore, the control of the top dead center position of the factory engine is very important. Summary of the Invention

[0003] The purpose of the present invention is to provide a method for detecting the mechanical top dead center during a cold test of an engine. During the cold test, the intake pressure signal, the crankshaft position signal, and the camshaft position signal are used to output waveforms relative to the angle of the crankshaft. The position of the top dead center can be accurately determined by the position of the three signals corresponding to the crankshaft angle. The technical solution is as follows: A method for detecting the mechanical top dead center during a cold test of an engine before leaving the factory, characterized in that it comprises the following steps: S1: Mount the engine on the test bench, install a cylinder pressure sensor on cylinder 1, install a pressure sensor on the cylinder head intake duct at cylinder 1, install an external signal amplifier, and connect the cylinder 1 compression pressure signal, cylinder 1 intake pressure signal, camshaft position signal, and crankshaft position signal to an oscilloscope; S2: First, perform top dead center calibration, control the test bench, reverse the engine to 1500 rpm, perform waveform testing, output a waveform graph, and determine the relative relationship between the compression pressure signal of cylinder 1 and the intake pressure signal of cylinder 1; S3: Measure the heat loss angle (the angle difference between the physical top dead center and the cylinder pressure sensor top dead center). Install a top dead center sensor for cylinder 1 on the engine. Connect this sensor and the crankshaft position sensor to the combustion analyzer. Turn the engine to measure the physical top dead center. After the measurement, calculate the heat loss angle = the position of the cylinder pressure sensor top dead center relative to the crankshaft angle - the position of the physical top dead center relative to the crankshaft angle. S4: Calculate the top dead center position, which is the position of the intake pressure signal of cylinder 1 relative to the crankshaft angle - the position of the compression pressure signal of cylinder 1 relative to the crankshaft angle + the heat loss angle; S5: Add a pressure sensor to the intake cover of the short-engine cold test bench. Load the engine tested on the test bench onto the cold test bench. Connect the intake pressure signal, camshaft position signal, and crankshaft position signal to the output waveform of the cold test bench. Drive the engine to 1500 rpm, output the test results, and set the median value. S6: Perform data statistics, count factory machine samples, and set the upper and lower limits of the top dead center deviation based on the factory machine theoretical deviation and actual measurement results; S7: After the limit value is set, the workshop is arranged to implement and control it. The machine that exceeds the tolerance will be treated as a top dead center unqualified fault machine, and the machine will be shipped normally if there is no problem. The number of S6 samples is generally based on 500 units. According to the median position and calibration theoretical deviation, it is generally -3° and +3°.

[0004] The beneficial effects of the present invention are: realizing the setting of the mechanical top dead center reference and the measurement of the actual value, controlling the consistency of the top dead center of the factory-made machine, improving the quality of the factory-made engine, increasing the service life of the engine, controlling the overall fuel consumption level of the factory-made machine, and further improving the customer experience. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] Figure 1 It is a schematic diagram of the overall block diagram of the present invention. DETAILED DESCRIPTION

[0006] Reference Figure 1 The method for detecting the mechanical top dead center of an engine during a factory cold test is characterized by comprising the following steps: S1: Mount the engine on the test bench, install a cylinder pressure sensor on cylinder 1, install a pressure sensor on the cylinder head intake duct at cylinder 1, install an external signal amplifier, and connect the cylinder 1 compression pressure signal, cylinder 1 intake pressure signal, camshaft position signal, and crankshaft position signal to an oscilloscope; S2: First, perform top dead center calibration, control the test bench, reverse the engine to 1500 rpm, perform waveform testing, output a waveform graph, and determine the relative relationship between the compression pressure signal of cylinder 1 and the intake pressure signal of cylinder 1; S3: Measure the heat loss angle (the angle difference between the physical top dead center and the cylinder pressure sensor top dead center). Install a top dead center sensor for cylinder 1 on the engine. Connect this sensor and the crankshaft position sensor to the combustion analyzer. Turn the engine to measure the physical top dead center. After the measurement, calculate the heat loss angle = the position of the cylinder pressure sensor top dead center relative to the crankshaft angle - the position of the physical top dead center relative to the crankshaft angle. S4: Calculate the top dead center position, which is the position of the intake pressure signal of cylinder 1 relative to the crankshaft angle - the position of the compression pressure signal of cylinder 1 relative to the crankshaft angle + the heat loss angle; S5: Add a pressure sensor to the intake cover of the short-engine cold test bench. Load the engine tested on the test bench onto the cold test bench. Connect the intake pressure signal, camshaft position signal, and crankshaft position signal to the output waveform of the cold test bench. Drive the engine to 1500 rpm, output the test results, and set the median value. S6: Perform data statistics, count factory machine samples, and set the upper and lower limits of the top dead center deviation based on the factory machine theoretical deviation and actual measurement results; S7: After the limit value is set, the workshop is arranged to implement and control it. The machine that exceeds the tolerance will be treated as a top dead center unqualified fault machine, and the machine will be shipped normally if there is no problem. The number of S6 samples is generally based on 500 units. According to the median position and calibration theoretical deviation, it is generally -3° and +3°.

[0007] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A method for detecting the mechanical top dead center during a cold test of an engine before leaving the factory, characterized by: The following steps are involved: S1: Mount the engine on the test bench, install a cylinder pressure sensor on cylinder 1, install a pressure sensor on the cylinder head intake duct at cylinder 1, install an external signal amplifier, and connect the cylinder 1 compression pressure signal, cylinder 1 intake pressure signal, camshaft position signal, and crankshaft position signal to an oscilloscope; S2: First, perform top dead center calibration, control the test bench, reverse the engine to 1500 rpm, perform waveform testing, output a waveform graph, and determine the relative relationship between the compression pressure signal of cylinder 1 and the intake pressure signal of cylinder 1; S3: Measure the heat loss angle (the angle difference between the physical top dead center and the cylinder pressure sensor top dead center). Install a top dead center sensor for cylinder 1 on the engine. Connect this sensor and the crankshaft position sensor to the combustion analyzer. Turn the engine to measure the physical top dead center. After the measurement, calculate the heat loss angle = the position of the cylinder pressure sensor top dead center relative to the crankshaft angle - the position of the physical top dead center relative to the crankshaft angle. S4: Calculate the top dead center position, which is the position of the intake pressure signal of cylinder 1 relative to the crankshaft angle - the position of the compression pressure signal of cylinder 1 relative to the crankshaft angle + the heat loss angle; S5: Add a pressure sensor to the intake cover of the short-engine cold test bench. Load the engine tested on the test bench onto the cold test bench. Connect the intake pressure signal, camshaft position signal, and crankshaft position signal to the output waveform of the cold test bench. Drive the engine to 1500 rpm, output the test results, and set the median value. S6: Perform data statistics, count factory machine samples, and set the upper and lower limits of the top dead center deviation based on the factory machine theoretical deviation and actual measurement results; S7: After the limit value is set, the workshop is arranged to implement and control it. The machine that exceeds the tolerance will be treated as a top dead center unqualified fault machine, and will be shipped normally if there is no problem.

2. The method for detecting the mechanical top dead center during a cold test of an engine before leaving the factory according to claim 1, characterized in that: S6: Perform data statistics on samples of factory machines, generally taking 500 units as the base number. According to the median position and the calibrated theoretical deviation, the theoretical deviation of the factory machine and the actual measurement results, the top dead center deviation is generally set within the range of -5°CA and +5°CA.

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