CN113586302A - Method for detecting valve tightness based on pressure drop characteristics - Google Patents
Method for detecting valve tightness based on pressure drop characteristics Download PDFInfo
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- CN113586302A CN113586302A CN202110867177.1A CN202110867177A CN113586302A CN 113586302 A CN113586302 A CN 113586302A CN 202110867177 A CN202110867177 A CN 202110867177A CN 113586302 A CN113586302 A CN 113586302A
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- 238000000034 method Methods 0.000 title claims abstract description 13
- 238000001514 detection method Methods 0.000 claims abstract description 33
- 239000000446 fuel Substances 0.000 claims abstract description 28
- 230000008859 change Effects 0.000 claims abstract description 11
- 238000012360 testing method Methods 0.000 claims description 4
- 238000005070 sampling Methods 0.000 claims description 3
- 238000013480 data collection Methods 0.000 claims 1
- 238000007789 sealing Methods 0.000 abstract description 11
- 238000003745 diagnosis Methods 0.000 abstract description 4
- 239000007788 liquid Substances 0.000 abstract description 4
- 239000003921 oil Substances 0.000 description 61
- 230000009467 reduction Effects 0.000 description 6
- 230000003213 activating effect Effects 0.000 description 2
- 238000002347 injection Methods 0.000 description 2
- 239000007924 injection Substances 0.000 description 2
- 230000007257 malfunction Effects 0.000 description 2
- 238000005299 abrasion Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000002283 diesel fuel Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 239000000295 fuel oil Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000008569 process Effects 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02M—SUPPLYING COMBUSTION ENGINES IN GENERAL WITH COMBUSTIBLE MIXTURES OR CONSTITUENTS THEREOF
- F02M65/00—Testing fuel-injection apparatus, e.g. testing injection timing ; Cleaning of fuel-injection apparatus
- F02M65/006—Measuring or detecting fuel leakage of fuel injection apparatus
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- Engineering & Computer Science (AREA)
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- Fuel-Injection Apparatus (AREA)
Abstract
一种基于压降特征检测阀密封性的方法属于柴油机高压共轨系统故障诊断领域。高压油泵的出油阀在实际使用过程中会随着使用周期的增加发生磨损，导致密封性发生改变，进而引起燃油泄漏、轨压无法正常建立的问题。高压油泵的进出油阀位于油泵壳体的内部，传统的故障检测方法很难实现对高压油泵的不解体在线密封性检测。本专利根据液体流动原理，将高压共轨的轨压压降特征与高压油泵出油阀的密封情况联系起来，通过测量由燃油泄漏引起的实际轨压变化，并与标准轨压变化值对比，可以实现对高压油泵出油阀的在线故障诊断。本发明相对于现有的共轨柴油机燃油系统故障诊断方法来说具有更高的故障识别率。
A method for detecting valve tightness based on pressure drop characteristics belongs to the field of fault diagnosis of diesel engine high pressure common rail systems. In actual use, the oil outlet valve of the high-pressure oil pump will wear with the increase of the service cycle, resulting in the change of the sealing performance, which will lead to the problems of fuel leakage and the failure of the rail pressure to be established normally. The oil inlet and outlet valves of the high pressure oil pump are located inside the oil pump housing, and it is difficult to realize the online sealing detection of the high pressure oil pump without disassembly by the traditional fault detection method. According to the principle of liquid flow, this patent links the rail pressure drop characteristics of the high-pressure common rail with the sealing condition of the oil outlet valve of the high-pressure oil pump. By measuring the actual rail pressure change caused by fuel leakage, and comparing it with the standard rail pressure change It can realize the online fault diagnosis of the oil outlet valve of the high pressure oil pump. Compared with the existing common rail diesel engine fuel system fault diagnosis method, the present invention has a higher fault identification rate.
Description
Technical Field
The invention belongs to the field of fault diagnosis of a high-pressure common rail system of a diesel engine, and particularly relates to a method for detecting the sealing performance of a valve on line based on pressure drop characteristics.
Background
The high-pressure oil pump is an energy conversion device for converting mechanical energy into fuel pressure energy as a power component of the high-pressure common rail system. The high-pressure oil pump fault is a common problem of a high-pressure common rail system of a diesel engine, and an oil outlet valve of a high-pressure oil pump is abraded along with the increase of a use period in the actual use process, so that the high-pressure common rail fuel system firstly encounters the problem of fuel leakage of the high-pressure oil pump caused by abrasion of the oil valve.
The problem of tightness of an oil outlet valve of a high-pressure oil pump can cause that the rail pressure of a common rail system cannot be normally established, so that the emission risk of an engine is greatly increased, which is not allowed by regulations.
The oil inlet and outlet valves of the high-pressure oil pump are positioned in the oil pump shell, fault detection is carried out in a mode of disassembling the high-pressure oil pump in the traditional method, and the fault recognition rate is low.
The method comprises the steps of setting the opening and closing of equipment in a fuel system and detecting the opening and closing of the equipment to meet test conditions, forming a closed high-pressure system from an oil outlet valve to a fuel injector, collecting a real-time rail pressure value, comparing an actual rail pressure reduction value with a standard rail pressure reduction value, and further realizing non-disassembly online directional detection on the sealing performance of the oil outlet valve of the high-pressure oil pump.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art, and provides a method and a standard rail pressure drop curve for realizing non-disassembly online directional detection of the leak tightness of an oil valve.
The technical scheme of the invention is as follows: a method for detecting the tightness of a valve based on pressure drop characteristics comprises the following steps,
s1, activating the setting program, and setting the detected target rail pressure p by the programcThe range of the target rail pressure is 800-1600 bar, and the rail pressure value pcThe detection condition can be met when the pressure is more than or equal to 800 bar; setting the detection time T to be 15 s; the detection step length Delta T is 1s, and the initial value T0＝0；
S2, detecting an accelerator pedal signal and a brake signal, and if the accelerator pedal signal is zero and the brake signal lasts for more than 2S, stopping oil injection of the oil injector and enabling the oil injector to be in a closed state, so that the detection condition is met; if the above condition is not satisfied, the detection is terminated;
s3, detecting whether the fuel metering valve is in a closed state, and ensuring that a closed high-pressure system is formed from the oil outlet valve of the high-pressure oil pump to the oil injector; if the fuel metering valve is in a closed state, carrying out the next detection; if the fuel metering valve is not closed, the detection is terminated;
s4, detecting a pressure value p in the common rail pipe, and if the pressure in the high-pressure common rail reaches a target rail pressure value, namely p is more than or equal to 800bar, carrying out the next detection; if the target rail pressure value is not reached, the detection is terminated;
s5, after the pressure in the high-pressure common rail pipe reaches a target rail pressure value, acquiring a real-time rail pressure value in the high-pressure common rail pipe by using a rail pressure sensor with a sampling frequency not less than 1000Hz, wherein the acquisition time length delta T is 1S;
s6, after the real-time rail pressure data acquisition is finished, judging the size of T, and if T is larger than or equal to 15, carrying out the next detection; if T < 15, T ═ T +1, and steps S2 to S5 are repeated;
s7, acquiring real-time rail pressure data in 15 sets of common rail pipes through steps S1 to S6, analyzing the acquired rail pressure data, drawing a rail pressure change curve in 15S, and calculating an actual rail pressure drop value (the actual rail pressure drop value is the target rail pressure value — the actual rail pressure value);
s8, comparing the actual rail pressure drop curve with a standard rail pressure drop curve, and if the actual rail pressure exceeds a tolerance range of the standard rail pressure change rate (the tolerance range is the standard drop value ± the standard drop value × 10%), the sealing performance of the oil outlet valve of the high-pressure oil pump is poor, where the standard rail pressure drop curve is a reference value obtained by the standard high-pressure oil pump (a brand new high-pressure oil pump) under the target rail pressure value and the detection condition, as shown in fig. 2;
as a further improvement, the ECU activates a malfunction warning strategy when a leak tightness problem occurs in the high-pressure oil pump outlet valve in step S8.
The principle on which the invention is based is as follows:
according to the liquid flow principle, as shown in fig. 1, if the accelerator pedal signal is zero and the brake signal lasts for more than 2s, the fuel injector stops injecting fuel, when the rail pressure in the high-pressure common rail system reaches the target rail pressure value, the fuel metering valve is closed, a closed high-pressure system is formed between the fuel outlet valve and the fuel injector, and the pressure in the system is the same as the rail pressure. The oil inlet end of the oil outlet valve is connected with a low-pressure oil pipe with smaller pressure intensity, the front side and the rear side of the oil outlet valve have larger pressure intensity difference, if the sealing performance of the oil outlet valve fails, fuel oil can leak from the high-pressure side to the low-pressure side, according to the following formula,
in the formula:
QL-liquid leakage rate, kg/s;
Cdthe liquid leakage coefficient is usually 0.6-0.64;
a-area of leakage surface, m2；
p-pressure in common rail pipe, Pa;
p0-the low pressure side pressure of the oil outlet valve, Pa;
rho-density of diesel oil, kg/m3。
If the leak tightness of the outlet valve is changed, as shown in fig. 2, the leakage amount of the fuel from the high-pressure end to the low-pressure end is increased, and the magnitude of the rail pressure change value Δ p is different from the standard pressure drop value in a certain period of time. Therefore, by measuring the pressure change of the rail pressure in a certain time and comparing the pressure change with the standard pressure drop value, if the actual pressure drop value exceeds the tolerance range of the standard pressure drop value, the sealing performance of the oil outlet valve can be directionally indicated to be in failure.
Drawings
FIG. 1 is a schematic diagram of a high pressure common rail fuel system.
Fig. 2 is a graph of the rail pressure drop of the standard rail pressure.
FIG. 3 is a flow chart of the present invention.
Wherein, 1-ECU, 2-oil tank, 3-filter, 4-oil inlet valve, 5-high pressure oil pump, 6-oil outlet valve, 7-high pressure oil pipe, 8-rail pressure sensor, 9-high pressure oil rail, 10-oil injector.
The specific implementation mode is as follows:
the invention will be further described with reference to specific embodiments shown in the drawings.
Referring to fig. 3, a method for detecting valve leakage based on pressure drop characteristics includes the steps of,
s1, activating the setting program, and setting the detected target rail pressure p by the programcThe range of the target rail pressure is 800-1600 bar, and the rail pressure value pcThe detection condition can be met when the pressure is more than or equal to 800 bar; setting the detection time T to be 15 s; the detection step length Delta T is 1s, and the initial value T0＝0；
S2, detecting an accelerator pedal signal and a brake signal, and if the accelerator pedal signal is zero and the brake signal lasts for more than 2S, stopping oil injection of the oil injector and enabling the oil injector to be in a closed state to meet the detection state; if the condition is not met, the detection is terminated;
s3, detecting whether the fuel metering valve is in a closed state, and ensuring that a closed high-pressure detection system is formed; if the fuel metering valve is in a closed state, starting to acquire rail pressure in real time; if the fuel metering valve is not closed, the detection is terminated;
s4, detecting a pressure value p in the common rail pipe, and if the pressure in the high-pressure common rail reaches a target rail pressure value, namely p is more than or equal to 800bar, carrying out the next detection; if the target rail pressure value is not reached, the detection is terminated;
s5, after the pressure in the high-pressure common rail pipe reaches a target rail pressure value, acquiring a real-time rail pressure value in the high-pressure common rail pipe by using a rail pressure sensor with a sampling frequency not less than 1000Hz, wherein the acquisition time is 1S;
s6, after the real-time rail pressure data acquisition is finished, judging the size of T, and if T is larger than or equal to 15, carrying out the next detection; if T < 15, T ═ T +1, and steps S2 to S5 are repeated;
s7, analyzing the collected 15 groups of real-time rail pressure data, making a 15S internal rail pressure change curve, calculating an actual rail pressure reduction value (the actual rail pressure reduction value is the target rail pressure value-the actual rail pressure value), and comparing the actual rail pressure reduction value with a standard rail pressure reduction curve;
s8, comparing the actual rail pressure drop with a standard rail pressure drop, and if the actual rail pressure drop exceeds a tolerance range of a standard drop, which is a reference value of a standard high-pressure oil pump (a brand new high-pressure oil pump) obtained under the target rail pressure and the set conditions, the sealing performance of the oil outlet valve of the high-pressure oil pump is poor, wherein the tolerance range is the standard drop ± standard drop × 10%.
In step S8, the ECU activates a malfunction alerting strategy when a leak tightness problem occurs in the delivery valve of the high pressure oil pump.
The invention has the beneficial effects that: by comparing the actual drop value of the pressure in the high-pressure common rail pipe with the standard drop value, the leak tightness of the oil outlet valve of the high-pressure oil pump can be judged in an online directional manner, an alarm strategy can be activated when the leak tightness of the oil outlet valve is poor, the ultrahigh fuel pressure is guaranteed to be established, and the fuel consumption and the emission risk are reduced; after the rail pressure in the high-pressure oil pipe reaches a target rail pressure value, the fuel metering valve is in a closed state, and the high-pressure fuel in the oil outlet valve of the self-oil sprayer to the high-pressure oil pump is in a closed system, so that the real-time rail pressure value in the high-pressure oil pipe can be accurately detected, and the effectiveness of judging the sealing property of the oil outlet valve is improved; the method is suitable for testing the operation stage of the high-pressure oil pump, belongs to evaluation in use, ensures the sealing performance of the oil outlet valve, and monitors the service life cycle of the whole high-pressure oil pump.
The foregoing description is only of the preferred embodiments of the present invention, and it should be noted that those skilled in the art can make various changes and modifications without departing from the mechanism of the present invention, which will not affect the effect of the implementation of the present invention and the utility of the patent.
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| CN202110867177.1A CN113586302A (en) | 2021-07-29 | 2021-07-29 | Method for detecting valve tightness based on pressure drop characteristics |
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2021
- 2021-07-29 CN CN202110867177.1A patent/CN113586302A/en active Pending
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| CN102182601A (en) * | 2011-02-01 | 2011-09-14 | 潍柴动力股份有限公司 | Method and device for diagnosing and calibrating faults in high-pressure common rail system |
| CN202091080U (en) * | 2011-02-01 | 2011-12-28 | 潍柴动力股份有限公司 | Device for diagnosing faults in the high-pressure co-rail system of engine |
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Application publication date: 20211102 |