Methods for Calibration and Inspection of Valve Profiles in Electro-hydraulic Variable Valve Train

Abstract

This invention provides a method for calibrating and verifying valve profiles of an electro-hydraulic variable valve timing mechanism, comprising: operating a valve lift target curve calibration platform to run a target profile calibration test to obtain raw test data for calibrating the target valve motion profile, and obtaining a target valve motion profile database through a target profile calibration data analysis process; running a valve motion profile index verification test; extracting verification test data and performing comparative analysis; and generating a report after analyzing the verification test data. This invention provides a method for quickly calibrating and analyzing the valve motion profile output of a camless electro-hydraulic variable valve timing mechanism under a certain control signal input.

Description

Technical Field

[0001] This invention belongs to the technical field of valve train control methods, specifically a method for calibrating and inspecting valve profiles using an electro-hydraulic variable valve train mechanism. Background Technology

[0002] Compared to traditional valve trains, camless electro-hydraulic variable valve trains produce valve motion profiles that are more flexible and free. Traditional valve trains are constrained by the cam, and once the cam is designed, the valve motion profile is determined. Therefore, such mechanisms do not require valve motion profile calibration. For camless electro-hydraulic variable valve trains, the valve motion profile is less constrained and is determined by the responsiveness of the valve components, hydraulic fluidity, and the oil supply pressure. Due to variations in hydraulic oil pressure and temperature, the cyclic consistency of the valve motion profile in camless electro-hydraulic variable valve trains is worse than that of traditional valve trains, especially in the presence of system defects such as leaks or hydraulic oil cavitation. Under the same control signal input, the system output exhibits significant inconsistencies. This inconsistency in valve motion profiles can severely affect engine performance. Therefore, in order to apply such mechanisms to actual engines, valve motion profile calibration and verification are necessary. Summary of the Invention

[0003] To address the aforementioned technical problems, this invention provides a method for calibrating the target valve motion profile in a camless variable valve timing mechanism. This method is applicable not only to electro-hydraulic camless variable valve timing mechanisms but also to electromagnetic and electrical camless variable valve timing mechanisms.

[0004] The specific technical solution is as follows:

[0005] The method for calibrating and inspecting valve profiles of electro-hydraulic variable valve timing mechanisms includes the following procedures:

[0006] Target profile open-loop calibration and verification process:

[0007] S1: Users operate the valve lift target curve calibration platform to run the target profile calibration test to obtain the original test data for calibrating the target valve motion profile, and obtain the target valve motion profile database through the target profile calibration data analysis process;

[0008] S2: The user runs the valve motion profile verification test through the human-machine interaction platform of the operating mechanism; the human-machine interaction platform will extract the ideal target valve motion profile from the valve motion curve database according to the target valve motion profile and compare it with the verification test valve motion profile to facilitate the user to make a preliminary judgment.

[0009] S3: Users extract verification test data from the mechanism operation index verification operation human-computer interaction platform through the operation mechanism operation index verification data analysis human-computer interaction platform and perform comparative analysis.

[0010] S4: Verification test data will be analyzed and reported.

[0011] In S1, the target valve motion profile calibration method includes the following steps:

[0012] S1.1: Identify and extract all valve opening and closing times in the test curve by using the monotonicity and statistics of the valve motion profile. At the same time, subtract the valve opening time displacement value from all values ​​in this cycle. If the valve closing time is not 0, force it to be set to 0.

[0013] S1.2: Given the maximum valve timing under a single operating condition, compare it with all valve timings in the test curve. If there is no test valve timing that exceeds this maximum value, proceed to S1.3.

[0014] S1.3: Subtract the maximum valve timing from all test valve timings, take the modulus of 2, and add zeros before the valve motion profile formed by the division in S1.2 according to this value. Then add zeros after the valve closing time until the duration of the test valve motion profile is the same as the given maximum valve timing.

[0015] S1.4: The displacement value with the highest frequency of occurrence of the valve movement profile in a single cycle is obtained through statistical analysis and is taken as the maximum stable lift of this cycle; when the valve displacement value is less than or equal to the displacement value at a certain moment from the moment the valve starts moving, it is considered that the valve has reached the maximum stable lift stage; within this extreme range, if a displacement value higher than this value appears, it is reset to the maximum stable lift; if a displacement value lower than this value appears, the difference between it and the displacement value at the previous moment is calculated. If it is higher than a certain threshold, it is set as the displacement value at the previous moment.

[0016] S1.5: Calculate the average and median values ​​of the displacement values ​​at the same time for all processed test curves, and combine the average and median values ​​of the displacement values ​​at all times to form the average value type target valve motion profile and the median value type target valve motion profile.

[0017] The beneficial effects of this invention are as follows:

[0018] (1) Camless electro-hydraulic variable valve timing mechanisms suffer from inherent hydraulic pressure and temperature fluctuations, as well as leakage due to sealing issues and cavitation problems caused by hydraulic oil supplied from the oil supply system. These problems severely affect the cyclic consistency of valve timing, maximum stable valve lift, and fill factor. During the matching process between the engine and the camless electro-hydraulic variable valve timing mechanism, open-loop calibration tests and subsequent experimental data analysis are necessary to determine the impact of this cyclic consistency on engine performance. This invention provides a method for quickly calibrating and analyzing the valve motion profile output of a camless electro-hydraulic variable valve timing mechanism under a specific control signal input.

[0019] (2) Whether a camless electro-hydraulic variable valve timing mechanism can be applied to a real engine depends on the consistency of its operating cycle. Therefore, the cycle consistency of this mechanism needs to be tested during the design and development stage or the factory inspection stage. This test can provide a reference for evaluating the performance of the camless electro-hydraulic variable valve timing mechanism, and can also provide a basis for developing response control algorithms for the camless electro-hydraulic variable valve timing mechanism. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the camless electro-hydraulic variable valve timing mechanism of the present invention;

[0021] Figure 2 This is a schematic diagram of the electronic control unit of the camless electro-hydraulic variable valve timing mechanism of the present invention.

[0022] Figure 3 This is a flowchart of the open-loop calibration and verification process for the target profile of this invention;

[0023] Figure 4 This is the calibration process for the target valve motion profile of the present invention;

[0024] Figure 5 This invention relates to a method for acquiring and processing target profile data.

[0025] Figure 6 This is the calibration process for the target valve motion profile data of the present invention;

[0026] Figure 7 This is the verification process for the operational indicators of the invention. Detailed Implementation

[0027] The specific technical solutions of the present invention will be described with reference to the embodiments.

[0028] The schematic diagram of the camless electro-hydraulic variable valve mechanism is as follows: Figure 1As shown, the structure includes, in sequence, a high-pressure side 1 of the blocking chamber, a plunger 2, a low-pressure side 3 of the plunger chamber, a spring disc 4, a valve spring 5, and a valve 6; the high-pressure side 1 of the blocking chamber is connected in sequence to an accumulator 7, a valve drive valve 8, a hydraulic pressure control proportional solenoid valve 9, an oil pump 10, and an oil tank 11; the low-pressure side 3 of the plunger chamber is connected to the oil tank 11 through the valve drive valve 8.

[0029] When the mechanism is operating, the high-frequency solenoid valve opens, and the high-pressure hydraulic oil output from the oil pump, controlled by the proportional solenoid valve, flows to the high-pressure side of the plunger chamber. Driven by the high-pressure oil, the plunger pushes the valve to overcome the valve spring preload and open. At this time, the low-pressure side of the plunger chamber is connected to the oil tank, and the valve is open. The high-pressure oil pressure is maintained stable by the accumulator. When the high-frequency solenoid valve closes, the high-pressure side of the plunger chamber is connected to the low-pressure oil circuit, and the valve sits down under the action of the spring. Valve timing is controlled by the pulse width control of the high-frequency solenoid valve. The maximum stable valve lift is controlled by the high-pressure oil circuit pressure. Since the high-pressure oil circuit pressure is controlled by the proportional solenoid valve, the maximum stable valve lift can be controlled by the proportional solenoid valve.

[0030] Camless electro-hydraulic variable valve timing (VVT) mechanisms can achieve fully flexible variable valve timing and lift, adapting well to various engine operating conditions. However, due to the lack of mechanical constraint from a cam, and the inherent time delay, nonlinearity, and disturbance issues of hydraulic actuation, it is impossible to establish an accurate relationship between the control signal and valve timing and lift. When the engine's demand for the optimal valve motion profile changes, the valve train controller struggles to calculate the required control signal to ensure that the valve motion profile output by the camless VVT is the optimal target profile. Furthermore, due to the inherent nonlinearity and disturbance characteristics of the camless VVT mechanism, the valve motion profile will differ between cycles under the same control signal. If the valve train has oil leaks, cavitation, or other systemic defects, the difference in valve motion profile between cycles will be even greater. Based on the above facts, in order to better meet the engine's requirements for the valve train, this invention proposes a method for calibrating the valve motion profile under different target valve timing and valve lift conditions under open-loop control, as well as a method for testing and verifying the performance of different camless electro-hydraulic variable valve trains.

[0031] As described above regarding the working principle of the camless electro-hydraulic variable valve timing mechanism, an open-loop control module is required to control the output oil pressure of the high-frequency solenoid valve and the proportional solenoid valve to control the valve timing and valve lift characteristics of the valve motion profile. Furthermore, to facilitate the calibration of the target valve motion profile and the testing and verification of different camless electro-hydraulic variable valve timing mechanisms, a corresponding data acquisition module is needed to monitor the operating status of the valve timing mechanism. The specific control framework is as follows: Figure 2As shown, the open-loop control module of the control system includes a DC-DC converter circuit, a high-frequency solenoid valve control chip drive circuit, a hydraulic pressure control proportional solenoid valve drive circuit, a crankshaft angle signal analog input circuit, a CAN communication interface circuit, and a core MCU. The control system data acquisition module includes a sensor signal receiving circuit, a signal conversion circuit, and a CAN communication interface circuit. The open-loop drive module of the control system is responsible for driving the camless electro-hydraulic variable valve timing mechanism. The high-frequency solenoid valve control chip drive circuit and the hydraulic pressure control proportional solenoid valve drive circuit directly drive the valve timing mechanism, while the crankshaft angle signal analog circuit provides a simulated crankshaft angle signal under bench test conditions, thus providing a control signal reference for the core MCU. During the target valve motion profile calibration stage, the core MCU receives the control signal commands from the host computer, specifically the high-frequency solenoid valve signal opening pulse width and the hydraulic pressure output from the hydraulic pressure control proportional solenoid valve drive circuit. During the valve timing mechanism operation effect verification stage, it receives the target valve motion profile characteristic commands from the host computer and, based on the commands, queries its own control signal MAP to output response control signals to drive the valve timing mechanism. The control system's data acquisition module is responsible for acquiring the 4-20mA analog current signal from the displacement sensor. The signal conversion circuit can convert the 4-20mA analog current into a 1-5V analog voltage signal. The signal sampling circuit can convert the analog voltage signal into a digital signal, encapsulate it in a communication protocol data frame, and send it to the host computer, thereby enabling the host computer to monitor the operation of the gas distribution mechanism and acquire experimental data.

[0032] The basic idea for calibrating the target valve motion profile is: first, the experimental data is extracted into multiple single-cycle data, then the average and median values ​​of the displacement values ​​at the same time in different cycles are calculated, and then combined into the average value type target valve motion profile and the median value type target valve motion profile.

[0033] For electro-hydraulic camless variable valve timing mechanisms, the open-loop calibration and inspection process for the target valve motion profile is to calibrate first and then inspect. By calibrating the target motion profile on a prototype, a standard curve library output by the standard prototype under different target valve timings and lifts is obtained, along with a MAP diagram of the control signals required by the electronic control unit of the valve timing mechanism to output the standard valve motion profile.

[0034] like Figure 3As shown, during the target valve motion profile calibration stage, the user inputs a control signal at the valve motion target curve calibration platform. The platform then sends this control signal instruction to the lower-level computer via the communication bus. The electronic control unit of the electro-hydraulic variable valve timing mechanism outputs a control signal according to this instruction. The platform can obtain the valve timing and valve lift for each valve motion cycle through the displacement sensor signal acquired by the camless electro-hydraulic variable valve timing mechanism and through valve motion profile feature extraction, and calculate the variance of the difference between the test valve motion profile feature and the target valve motion profile feature in real time. By inputting different control signals, the user obtains the control signal with the minimum variance of the difference between the test valve motion profile feature and the target valve motion profile feature, along with the corresponding valve motion profile test data. Post-processing this valve motion profile test data yields the average and median target valve motion profiles and the target valve motion profile variation range, thus constructing a valve motion target curve database. The specific method for obtaining the target valve motion profile will be described later. Once the calibration experiment is completed, a MAP diagram of the control signal output of the gas distribution mechanism can be obtained.

[0035] During the mechanism operation performance verification phase, the user inputs two valve motion profile features—target valve timing and target valve lift—into the mechanism operation index verification test human-machine interface. The platform then extracts the target valve motion profile from the valve motion target curve database based on the target valve timing and target valve lift, displaying it on the platform interface. Users can then make a preliminary judgment on the system's operational performance by observing the test valve motion profile and the target valve motion profile in real time.

[0036] After the test is completed, the human-machine interface platform for verifying the mechanism's operational indicators will store the test data in the valve motion verification test database. Then, the mechanism's operational indicator verification data analysis platform will extract the test profile and compare it with the target valve motion profile. The main analysis contents include: 1. Whether the test valve motion profile is within the range of variation of the target valve motion profile. 2. Counting the number and distribution of data points in the test valve motion profile that are not within the range of the target valve motion profile. 3. Counting the number and distribution of valve motion profiles that are within the range of the target valve motion profile. Afterwards, the user can generate a mechanism operational indicator verification report based on the relevant analysis results and relevant standards.

[0037] The specific procedure for calibrating the target valve motion profile is as follows: Figure 4As shown, a human-machine interface platform for target valve motion profile calibration was first developed. This platform includes modules for providing users with target valve timing and lift inputs, a high-frequency solenoid valve pulse width signal input module for calibrating different target valve timing and lift, and a proportional solenoid valve control signal input module. It also provides a communication module for communication between the calibration platform and the electronic control unit of the valve train. After the user inputs the target valve timing, target valve lift, high-frequency solenoid valve pulse width signal, and proportional solenoid valve control signal, the valve train starts operating and displays the test valve timing and lift, as well as the target valve timing and lift, in real time. Simultaneously, after a single calibration test, the calibration platform displays the variance of the errors in the test valve motion profile timing and lift compared to the target valve motion profile timing and lift. The user can decide whether to complete the single calibration based on the displayed variance value. After calibration is completed, the target valve motion profile calibration platform will automatically extract the target valve motion profile.

[0038] The calibration process for the target valve motion profile is extremely crucial for the experimental data processing. Figure 5 The diagram shows the entire process of experimental data from the sensor to the final processing, including analog signal conversion starting from the experimental stage, single-cycle interception during experimental processing, and finally post-processing of the experimental data to obtain the final target valve motion profile.

[0039] During the test, the ECU first converts the analog signal collected by the sensor into a voltage analog signal, and then the AD conversion module integrated inside the MCU converts the voltage analog signal into a digital signal. The MCU main program then converts this digital signal into a data frame format supported by the communication protocol and uploads it to the host computer. After the test is completed, the host computer program automatically decrypts the data frame according to the communication protocol data format and converts it into the same data value corresponding to the actual system operating status collected. Due to the unavoidable influence of electromagnetic interference, calibration errors, and mechanism vibrations during the test, high-frequency interference components and fluctuations in the valve displacement reference will inevitably appear in the data collected by the sensor. Therefore, it is impractical to judge the valve movement cycle based on the valve displacement value. This invention utilizes the unique monotonicity of the valve movement profile during the rise and fall process and the stability of the valve movement profile when it reaches its maximum stable lift, which are characteristic of the camless electro-hydraulic variable valve timing mechanism, to identify valve timing and valve lift. After identification, the valve opening time and valve closing time are calibrated as displacement value 0. The camless electro-hydraulic variable valve timing mechanism is affected by oil pressure fluctuations and oil temperature disturbances between cycles, resulting in differences in valve timing between cycles. Therefore, if we want to obtain the average target valve motion profile and the median target valve motion profile at the same time in different cycles, we must format the data extracted from the test data, that is, process the original test data into test cycle data of the same length.

[0040] The specific method is as follows: First, a maximum valve timing within a single operating condition is given. If a curve exceeding this timing appears during the test, the test is considered a failure due to a defect in the mechanism. If no test valve movement profile exceeds this timing range, zero points are added to the newly captured test valve movement profile by centering the test valve timing with the given maximum valve timing. This means zero points are added before valve opening and after valve closing. Furthermore, the experimental data needs to be filtered. The experimental data shows that because the valve rise and seat processes occupy a relatively short portion of the valve movement cycle time, high-frequency noise mostly appears during the stabilization period after the valve reaches its maximum stable lift. The main data processing program determines whether the valve has reached its maximum stable lift based on monotonicity, then statistically analyzes the displacement value that appears most frequently after the valve reaches its maximum stable lift and marks this displacement value as the maximum stable lift. If the displacement value collected by the sensor in the experimental data is higher than this value, it is corrected back to this value. When the valve movement displacement value falls below this range, it is corrected back to this value, thus obtaining the target valve movement profile under a given operating condition. The specific process is as follows: Figure 6 As shown. Under this operating condition, the input control signal will be recorded and ultimately formed into a control signal MAP diagram for searching the target valve timing and target valve lift.

[0041] The method for calibrating the target valve motion profile is as follows:

[0042] Step 1: Identify and extract all valve opening and closing times in the test curve by using the monotonicity and statistics of the valve motion profile. At the same time, subtract the valve opening time displacement value from all values ​​in this cycle. If the valve closing time is not 0, force it to be set to 0.

[0043] Step 2: Given the maximum valve timing under a single operating condition, compare it with all valve timings in the test curve. If there is no test valve timing exceeding this maximum value, proceed to Step 3. If there is a test valve timing exceeding this maximum value, the test is considered a failure. At this point, it is necessary to check whether the mechanism or measuring equipment is normal.

[0044] Step 3: Subtract the maximum valve timing from all test valve timings, take the modulus of 2, and add zeros before the valve motion profile formed in Step 2 begins. Then add zeros after the valve closing time until the duration of the test valve motion profile is the same as the given maximum valve timing.

[0045] Step 4: Statistical analysis is used to determine the displacement value with the highest frequency of occurrence of the valve movement profile within a single cycle, which is then used as the maximum stable lift for that cycle. When the valve displacement value at a certain moment, starting from the moment the valve begins to move, is less than or equal to the displacement value at the previous moment, the valve is considered to have reached the maximum stable lift stage. Within this extreme range, if a displacement value higher than this value appears, it is reset to the maximum stable lift. If a displacement value lower than this value appears, the difference between it and the displacement value at the previous moment is calculated; if it exceeds a certain threshold, it is set as the displacement value at the previous moment.

[0046] Step 5: Calculate the average and median values ​​of the displacement values ​​at the same time for all processed test curves, and combine the average and median values ​​of the displacement values ​​at all times to form the average value type target valve motion profile and the median value type target valve motion profile.

[0047] A database of target valve motion profiles was obtained after calibration using a large amount of experimental data. When it is necessary to verify the cyclic consistency performance of a new camless electro-hydraulic variable valve timing mechanism, it can be verified using certain testing methods. The specific process is as follows: Figure 7As shown. During the test, the user can input the target valve timing and target valve lift into the mechanism operation index verification platform, sending the target valve motion profile command to the ECU while simultaneously retrieving the target valve motion profile from the target valve motion profile library. During the test, the ECU will query the control signal MAP diagram according to the target valve motion profile command and output control signals to control the operation of the camless electro-hydraulic variable valve timing mechanism actuator. At the same time, the ECU will collect valve motion displacement through sensors and upload it to the mechanism operation index verification platform. The user can observe whether there are any serious deficiencies in the test curve through the real-time display interface on the mechanism operation index verification platform. After the test, the mechanism operation index verification platform will call the data processing program to extract different cycles of the test valve motion profile according to the same data processing method described above, and quantitatively compare the displacement values ​​of the valve motion profile at the same time in different cycles with the corresponding displacement values ​​of the target valve motion profile. If the valve displacement value is within a certain range constrained by the target valve motion profile, the mechanism is considered to be in good operating condition without faults; otherwise, it is considered that the mechanism has defects. A report is generated after comparative analysis.

Claims

1. A method for calibrating and inspecting valve profiles using an electro-hydraulic variable valve timing mechanism, characterized in that, Includes the following processes: S1: Users operate the valve lift target curve calibration platform to run the target profile calibration test to obtain the original test data for calibrating the target valve motion profile, and obtain the target valve motion profile database through the target profile calibration data analysis process; S2: The user runs the valve motion profile index verification test through the operating mechanism operation index verification human-machine interaction platform; the operating mechanism index verification human-machine interaction platform extracts the ideal target valve motion profile from the target valve motion profile database according to the target valve motion profile and compares it with the test valve motion profile to facilitate the user to make a preliminary judgment. S3: Users extract verification test data from the mechanism operation index verification operation human-computer interaction platform through the operation mechanism operation index verification data analysis human-computer interaction platform and perform comparative analysis. S4: Verify that the experimental data has been analyzed and reported; In S1, the target valve motion profile calibration method includes the following steps: S1.1: Identify and extract all valve opening and closing times in the test curve by using the monotonicity and statistics of the valve motion profile. At the same time, subtract the valve opening time displacement value from all values ​​in this cycle. If the valve closing time is not 0, force it to be set to 0. S1.2: Given the maximum valve timing under a single operating condition, compare it with all valve timings in the test curve. If there is no test valve timing that exceeds this maximum value, proceed to S1.

3. S1.3: Subtract the maximum valve timing from all test valve timings, take the modulus of 2, and add zeros before the valve motion profile formed by the division in S1.2 according to this value. Then add zeros after the valve closing time until the duration of the test valve motion profile is the same as the given maximum valve timing. S1.4: The displacement value with the highest frequency of occurrence of the valve movement profile in a single cycle is obtained through statistical analysis and is taken as the maximum stable lift of this cycle; when the valve displacement value is less than or equal to the displacement value at a certain moment from the moment the valve starts moving, it is considered that the valve has reached the maximum stable lift stage; within this extreme range, if a displacement value higher than this value appears, it is reset to the maximum stable lift; if a displacement value lower than this value appears, the difference between it and the displacement value at the previous moment is calculated. If it is higher than a certain threshold, it is set as the displacement value at the previous moment. S1.5: Calculate the average and median values ​​of the displacement values ​​at the same time for all processed test curves, and combine the average and median values ​​of the displacement values ​​at all times to form the average value type target valve motion profile and the median value type target valve motion profile.

Images