Disclosure of Invention
The invention aims to provide a fault diagnosis and coping control method for rail pressure of a high-pressure common rail diesel engine, so as to avoid potential safety hazards caused by rail pressure faults.
Therefore, the invention provides the following technical scheme:
a method for diagnosing and dealing with rail pressure fault of a high-voltage common rail diesel engine comprises the steps of obtaining a voltage value of a rail pressure pre-output signal based on phase and time sampling and a rail pressure sensor power supply fault signal, judging whether the rail pressure pre-output signal voltage value based on phase sampling is in a normal range, and outputting a substitute value if the rail pressure sensor has a power supply fault or a rail pressure pre-output signal fault; if the rail pressure sensor has no power supply fault and the rail pressure pre-output signal based on phase sampling has a fault, outputting a rail pressure pre-output signal based on time sampling; if the rail pressure sensor has no power supply fault and the rail pressure signal based on the phase sampling has no fault, outputting the rail pressure signal based on the phase sampling; if the rail pressure sensor has poor contact faults, namely the rail pressure pre-output pressure signal based on time sampling jumps, jump fault information is output.
Further, the substitute value refers to a target rail pressure value set last time.
Further, the rail pressure pre-output signal fault means that: the voltage value of the rail pressure pre-output signal sampled based on the phase is greater than the upper rail pressure threshold uMax or less than the lower rail pressure threshold uMin, and the voltage value of the rail pressure pre-output signal sampled based on the time is greater than the upper rail pressure threshold uMax or less than the lower rail pressure threshold uMin.
Further, the rail pressure jump refers to: and if the difference between the current rail pressure and the last rail pressure sampling value is greater than the threshold value dpMax, the rail pressure is considered to jump.
Further, the specific process of the rail pressure jump is as follows: when the track voltage jumps, the counting accumulator is added with 1, and the timer is cleared and times again; if the count of the counter exceeds a set value num1, carrying out fault detection on the track pressure jump test state flag position 1; and if the value of the counter is less than or equal to num1 and the value of the timer exceeds t1 and no jump is detected, resetting the position of the rail pressure jump test state flag at 0, and counting again when the jump occurs next time.
Further, after the rail pressure jump test state flag position 1, the rail pressure jump final fault confirmation further includes: marking the position 1 of the rail pressure jump temporary fault mark, and performing temporary fault alarm; if the rail pressure jump temporary fault duration is longer than the set fault confirmation time num2, the rail pressure jump final fault flag position 1 is cancelled, and final fault alarm is carried out; and if the rail pressure jump temporary fault duration is less than or equal to the set fault confirmation time num2, jumping the rail pressure to the final fault mark position 0, and if the rail pressure jump temporary fault is recovered and the temporary fault recovery time is greater than the set fault elimination time num3, canceling the rail pressure jump fault state and recovering the normal state of the rail pressure signal.
Compared with the prior art, the invention has the beneficial effects that: the invention can judge the rail pressure signal temporarily and finally and process the fault. When the rail pressure sensor is in poor contact, namely when the rail pressure frequently jumps, whether the monitoring fault duration is longer than a set threshold value or not is judged to determine fault information, if so, the rail pressure sensor is judged to be in poor contact fault, and therefore the problem that the ECU misjudges that the software system has the fault because the rail pressure signal exceeds the limit at the moment is avoided. Therefore, whether contact is poor or not can be judged, and the normal control effect can be ensured, so that the rail pressure signal fault caused by system faults is prevented, and the driving safety is ensured.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, and it should be understood that the preferred embodiments described below are only for the purpose of illustrating and explaining the present invention, and are not to be construed as limiting the present invention.
Fig. 1 is a schematic diagram of a method for diagnosing and responding to rail pressure faults of a high-pressure common rail diesel engine, as shown in fig. 1, the method comprises the following specific steps:
step S1: phase-based and time-based sampling of rail pressure values and rail pressure sensor power supply fault signals are obtained from an ECU
Acquiring whether the power supply of a rail pressure sensor is failed and voltage values of rail pressure pre-output signals from a CAN bus of an ECU (electronic control Unit), wherein the voltage values of the rail pressure pre-output signals comprise voltage values based on time sampling and phase sampling; when the power supply fault mark position of the rail pressure sensor is 1, the rail pressure does not have power supply fault, and when the power supply fault mark position is 0, the rail pressure sensor has power supply fault.
Step S2: judging whether the rail voltage pre-output signal voltage value based on phase sampling is in a normal range
Fig. 2 is a control flow chart of the rail pressure signal fault diagnosis of the high-pressure common rail diesel engine based on phase sampling, which comprises the following specific steps:
step S2.1: acquiring a rail pressure pre-output signal based on phase sampling;
step S2.2: judging whether the rail pressure pre-output signal is greater than uMax or less than uMin, if so, marking the position 1 of a rail pressure fault based on phase sampling; if not, normally controlling and outputting a rail pressure signal, specifically: and if the rail pressure pre-output signal voltage value based on the phase sampling is in a normal range and the rail pressure sensor has no power supply fault, converting the rail pressure pre-output signal voltage value based on the phase sampling into a pressure signal through a fuel pressure sensor MAP, and outputting the pressure signal as a currently output rail pressure signal.
Step S3: if the rail pressure sensor has power supply faults or rail pressure pre-output signal faults based on phase sampling and time sampling, outputting a target rail pressure value set last time as a substitute value, and if the rail pressure is in open-loop control of a limping mode last time, checking an MAP (MAP) MAP according to volume flow to obtain a substitute value and outputting a rail pressure signal; if the fault occurs during the running process and a corresponding processing mode is not adopted, the rail pressure may be lower than the actual rail pressure, but due to the existence of negative feedback, the system can increase oil injection to cause sudden acceleration of the vehicle, and the safety is affected.
The target rail pressure value set last time is used as a substitute value, namely the target rail pressure value pset set last time by rail pressure, if the last rail pressure is in open-loop control of the limp mode, the substitute value is obtained by checking a MAP (MAP) by open-loop control volume flow in the limp mode, wherein the volume flow is equal to the sum of the set flow of the last fuel metering unit and the total fuel demand of the last fuel injection system. The rail pressure pre-output signal fault means that the rail pressure pre-output signal voltage value based on phase sampling is greater than a rail pressure upper limit threshold value uMax or less than a rail pressure lower limit threshold value uMin; the rail pressure pre-output signal voltage value based on time sampling is larger than a rail pressure upper limit threshold value uMax or smaller than a rail pressure lower limit threshold value uMin.
Fig. 3 is a control flow chart of the rail pressure signal fault diagnosis of the high-pressure common rail diesel engine based on time sampling, which comprises the following specific steps:
step S3.1: acquiring a rail pressure pre-output signal based on time sampling;
step S3.2: judging whether the rail pressure pre-output signal is greater than uMax or less than uMin, if not, executing the step S3.3; if the value is greater than uMax or less than uMin, executing a step S3.4;
step S3.3: normally controlling, and outputting a rail pressure signal;
step S3.4: setting the temporary fault flag bit with the rail pressure exceeding the upper limit or exceeding the lower limit to be 1, judging whether the final fault is the final fault, if so, setting the final fault flag bit with the rail pressure exceeding the upper limit or exceeding the lower limit to be 1, and canceling the temporary fault flag bit; if not, setting the final fault flag bit of the rail pressure exceeding the upper limit or the lower limit to be 0;
the method specifically comprises the following steps: if the rail pressure sensor has no power supply fault, judging that the rail pressure exceeds the upper limit final fault if the rail pressure exceeds the upper limit temporary fault duration is longer than the set fault confirmation time t2Def, and marking the rail pressure exceeds the upper limit final fault to be at a position 1; when the rail pressure exceeds the upper limit temporary fault recovery time and is greater than the set fault recovery time t2OK, clearing the upper limit final fault and marking the rail pressure exceeding the upper limit final fault at a position 0; if the duration time of the rail pressure over-lower limit temporary fault is longer than the set fault confirmation time t3Def, judging the rail pressure over-lower limit final fault, and marking the rail pressure over-lower limit final fault at a position 1; when the rail pressure exceeding lower limit temporary fault recovery time is greater than the set fault recovery time t3OK, clearing the exceeding lower limit final fault, and marking the rail pressure exceeding lower limit final fault at a position 0; if the rail pressure sensor has power supply faults, the rail pressure overrun temporary fault mark position 1 and the final fault mark position 0 are determined;
step S3.5: any fault mark position 1 exceeding the upper limit or the lower limit and the rail pressure fault mark position 1
And if the rail pressure exceeds the upper limit or the lower limit, namely the final fault mark position or the temporary fault mark position 1, the rail pressure exceeds the final fault mark position 1 or the temporary fault mark position 1.
Step S4: and if the rail pressure sensor has no power supply fault and the rail pressure pre-output signal based on the phase sampling has a fault, outputting the rail pressure pre-output signal based on the time sampling as an output rail pressure signal.
Step S5: and if the rail pressure sensor has no power supply fault and the rail pressure pre-output signal based on the phase sampling is normal, taking the rail pressure pre-output signal based on the phase sampling as an output rail pressure signal.
Step S6: if the rail pressure sensor has poor contact faults, namely the rail pressure pre-output signal based on time sampling has jump, jump fault information is output; and the rail pressure jump means that the rail pressure jumps when the difference between the current rail pressure and the last rail pressure sampling value is larger than a threshold value dpMax.
FIG. 4 is a control flow chart of the rail pressure jump fault diagnosis of the high-pressure common rail diesel engine of the invention:
when the engine is in an operating condition, the rail pressure sensor has no power supply fault, and the rail pressure jumps, the counting accumulator is added with 1, and the timer is cleared and times again; if the count of the counter exceeds a set value num1, carrying out fault detection on the track pressure jump test state flag position 1; and if the value of the counter is less than or equal to num1, judging whether the timing time of the timer is greater than the set time t1, if the value of the timer exceeds t1 and no jump is detected, resetting the rail pressure jump test state flag position 0, resetting the counter, counting again when jump occurs next time, and setting the rail pressure jump temporary fault position 0, and if the value of the timer does not exceed t1, continuing timing by the timer.
After the rail pressure jump test state flag position 1, the rail pressure jump final fault confirmation step further includes:
marking the position 1 of the rail pressure jump temporary fault mark, and performing temporary fault alarm; if the rail pressure jump temporary fault duration is longer than the set fault confirmation time num2, judging a rail pressure jump final fault, marking the rail pressure jump final fault at position 1, canceling the temporary fault marking bit, and performing final fault alarm; if the rail pressure jump temporary fault duration is less than or equal to the set fault confirmation time num2, jumping the rail pressure to the final fault mark position 0, and if the rail pressure jump temporary fault is recovered, namely: and when the rail pressure jump temporary fault flag bit is 0 and the temporary fault recovery time is greater than the set fault elimination time num3, canceling the rail pressure jump fault state and recovering the normal state of the rail pressure signal.
The above-described final failure and temporary failure do not exist simultaneously, i.e., when the final failure is confirmed, the temporary failure flag is set to 0. And when the temporary fault flag bit or the final fault flag bit is 1 caused by any reason, performing temporary fault alarm or final fault alarm. And if the temporary fault flag bit is changed from 1 to 0, canceling the alarm and recording historical fault information. The fault alarm comprises a temporary fault alarm lamp, a final fault alarm lamp and a fault recovery lamp.
The present invention has been described in detail, but the above description is only for the understanding of the present invention and is not limited thereto, and can be modified by those skilled in the art according to the principle of the present invention. Therefore, modifications made in accordance with the principles of the present invention should fall within the scope of the present invention.