CN111379639B - Method for estimating air flow in brake pump inflow manifold during braking - Google Patents
Method for estimating air flow in brake pump inflow manifold during braking Download PDFInfo
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- CN111379639B CN111379639B CN201811627064.9A CN201811627064A CN111379639B CN 111379639 B CN111379639 B CN 111379639B CN 201811627064 A CN201811627064 A CN 201811627064A CN 111379639 B CN111379639 B CN 111379639B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
- F02D—CONTROLLING COMBUSTION ENGINES
- F02D41/00—Electrical control of supply of combustible mixture or its constituents
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- F02D41/18—Circuit arrangements for generating control signals by measuring intake air flow
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Abstract
The invention provides a method for estimating the air flow of a brake pump flowing into a manifold during braking, which is characterized in that the air flow influence factor of a connecting pipeline between the brake pump and the manifold is researched to obtain that the air inflow of the connecting pipeline is irrelevant to whether braking is stepped on or not, and the air inflow is only relevant to the pressure ratio of the downstream and the upstream of the connecting pipeline, so that the influence of a brake signal does not need to be considered in the design of the method for estimating the air flow of the brake pump flowing into the manifold, the method can better give consideration to the performance of extreme working conditions when the brake signal is not reset or set due to the hardware installation of a brake pedal or the continuous stepping on of the brake by a driver, and the like, and can effectively avoid the problems of idling fluctuation and even flameout and the like caused by the fact that mixed air is slightly diluted or the self-learning deviation of air leakage of a throttle valve is overlarge due to stepping on the brake under the extreme working conditions.
Description
Technical Field
The invention relates to the technical field of automobiles, in particular to a method for estimating the air flow in a brake pump flowing into a manifold during braking.
Background
On traditional energy source car, in order to make the driver more laborsaving when stepping on brake braking, often need install the brake pump on whole car, and the vacuum state in the brake pump is the key that whether the brake can be easily stepped on, in order to guarantee still have sufficient vacuum degree host computer factory in the brake pump when stepping on the brake except that linking together brake pump and vacuum pump, still can utilize the vacuum degree in the intake manifold often, can install the connecting pipe of check valve between brake pump and manifold for this reason, can make the vacuum degree in the make full use of manifold when stepping on the brake, but the air in the brake pump can be discharged into intake manifold when stepping on the brake, do benefit to and guarantee brake performance like this but can produce following problem:
1) For the project of calculating the air input of the gasoline engine by the mass flow meter, the part of air entering a manifold from a brake pump cannot be sensed by the mass flow meter when a brake is stepped on, so that the air input calculated by a sensor is smaller than the actual air input, the problem that the mixed gas of the engine is too thin occurs, and the engine is possibly flameout when the idling of the engine is unstable and extreme due to the fact that the mixed gas is too thin.
2) For the project of calculating the air input of the engine by the manifold pressure sensor, although the redundant air can be sensed by the sensor and the problem of lean mixed air is not easy to occur, the air leakage of the throttle valve is too large in self-learning, the throttle valve is actively closed when the brake is stepped on, and the opening of the throttle valve is too small in extreme conditions, so that the engine is stalled when the rotating speed falls into a pit and is severe due to the fact that the throttle valve is too small and the air quantity of the engine is insufficient in a short time because the manifold does not have the extra air from the brake pump, and the throttle valve is too small.
In order to avoid the above problems, it is generally necessary to add a calculation function of "brake make-up air" to the engine control system, i.e. calculate the air flow from the brake vacuum pump to the intake manifold when the brake is stepped on by a model, add the air flow to the calculation of the intake charge of the engine in a mass flow meter system to calculate the total intake air amount of the engine, and subtract the air flow when the throttle air leakage self-learning is performed in a pressure sensor system to avoid the problem of the throttle air leakage mis-learning.
In the prior art, the calculation of air supplement amount during brake treading needs to be triggered by a brake pedal signal, and the basic calculation logic is as follows:
and estimating the air inflow in a period of time after the brake signal is set. The formula is as follows:
M1＝Mnormal1klaf (ps/pu) f (tavdk) fho formula (1');
and estimating the air inflow within a period of time after the brake signal is reset. The formula is as follows:
M2＝Mnormal2klaf (ps/pu) f (tavdk) fho formula (2');
in the above formula Mnormal1And Mnormal2Are the nominal junction line air leakage, Klaf (ps/pu) represents the junction line flow condition correction coefficient based on input of the ratio of manifold pressure ps to ambient pressure (barometric pressure) pu, f (tavdk) represents the temperature correction coefficient with input of pre-throttle temperature, tavdk, and fho represents the ratio of current barometric pressure pu to standard barometric pressure 1013.
Wherein M isnormal1And Mnormal2All are calibrated values, which need to be calibrated based on actual performance, and Klaf (ps/pu) and f (tavdk) are inherent physical properties and are not changed generally.
The flow chart of the steps of calculating the air inlet quantity of the brake pump in the prior system is shown in FIG. 1, and the detailed implementation steps are as follows:
s1': executing step S2 'if the rising edge of the brake signal is captured, otherwise executing step S4';
S2': calculating the air inflow of the brake pump by adopting the formula (1'), and starting timing;
s3': executing step S4 ' if the counted time reaches T1 ', otherwise executing step S2 ';
s4': executing the step S5 'if the falling edge of the brake signal is captured, otherwise executing the step S7';
s5': calculating the air inflow of the brake pump by adopting the formula (2'), and starting timing at the same time;
s6': executing step S7 ' if the counted time reaches T2 ', otherwise executing step S5 ';
s7': setting the air input of a brake pump to be 0;
s8': and finishing the calculation.
The adoption of the air inflow calculation scheme of the brake pump has the following problems:
1) in the formula for calculating the air supplement amount, the input of the flow characteristic curve is ps/pu (manifold pressure/ambient pressure), but the upstream pressure of the connecting pipeline is the pressure in the brake pump instead of the ambient pressure; the temperature correction coefficient input is tavdk (throttle inlet temperature), and the upstream air of the connecting pipeline is the temperature of the air in the brake pump; the difference between the calculated value and the actual value of the model can cause the calculation of the air supplement amount (namely the air input of the brake pump) to have deviation;
2) the air supplement amount calculation takes the change of a brake signal as input, but the situation that the signal is not reset when the brake is continuously stepped is often easy to occur in the practical application, at the moment, the calculated air input amount is far smaller than the air input amount actually entering an engine cylinder, and the problems that the air mixture is lean and further causes the idling shake of the engine and even flameout and the like can be caused.
Aiming at the defects of the brake pump air inflow calculation strategy in the prior art, the technical personnel in the field are always searching for a solution.
Disclosure of Invention
The invention aims to provide a method for estimating the air flow in a brake pump inflow manifold during braking so as to solve the problem of using a brake pump air inflow calculation strategy in the prior art.
In order to solve the above technical problem, the present invention provides a method for estimating an amount of airflow flowing into a manifold of a brake pump during braking, wherein the method for estimating an amount of airflow flowing into a manifold of a brake pump during braking includes:
s1: judging whether the rotating speed of the engine is zero, if so, controlling the flow of the brake pump flowing into the manifold to be 0; otherwise, go to S2;
s2: judging whether the vehicle has a brake pump pressure sensor, if so, executing S3; otherwise, go to S4;
s3: judging whether the pressure sensor has faults or not, and if yes, executing S4; otherwise, go to S5;
s4: calculating the air flow of the brake pump flowing into the manifold by adopting an alternative scheme;
s5: calculating the air flow flowing into a manifold from a brake pump in real time by adopting a formula (1);
wherein mlbr is the flow rate of the brake pump flowing into the manifold; m is the nominal air leakage when the connecting pipeline is fully opened, the connecting pipeline is a pipeline which is arranged between the brake pump and the manifold and is provided with a throttle valve, and the connecting pipeline is divided into an upstream pipeline and a downstream pipeline by taking the throttle valve as a boundary; dpbkvps is the pressure difference between the upstream pressure and the downstream pressure of the connecting pipeline, f (dpbkvps) is the correction coefficient of the nominal air leakage amount of different opening degrees of the connecting pipeline, and f (dpbkvps) belongs to [0,1 ]; KLAF (ps/pbkvr) is the flow regime correction factor, ps is the manifold pressure, and pbkvr is the brake pump pressure; tumg is the temperature upstream of the connecting line.
Optionally, in the method for estimating the amount of airflow flowing into the manifold by the brake pump during braking, the alternative is to calculate the amount of airflow flowing into the manifold by the brake pump as the amount of airflow flowing into the manifold by the brake pump.
Optionally, in the method for estimating an amount of airflow flowing into a manifold of a brake-time brake pump, the alternative includes the following steps:
s11: judging whether the capture signal is the falling edge of the brake signal, if so, executing S12; otherwise, go to S14;
s12: calculating the flow of air flowing into a manifold of the brake pump by adopting a formula (2), and starting timing;
wherein, mlbr2The amount of air flow into the manifold from the brake pump for a period of time to release the brakes; m is a group of2The nominal air leakage of the connecting pipeline when the brake is released; ps is manifold pressure, pu is atmospheric pressure, 1013 is a standard atmospheric pressure value;
s13: judging whether the timing time reaches the first time (T1), if yes, executing S14; otherwise, go to S12;
s14: judging whether the capture signal is the rising edge of the brake signal, if so, executing S15; otherwise, go to S17;
s15: calculating the air flow in an inflow manifold of the brake pump by adopting a formula (3), and starting timing;
Wherein, mlbr1The flow rate of the brake pump flowing into the manifold within a period of time for stepping on the brake; m1The nominal air leakage of the connecting pipeline is realized when the brake is stepped; ps is manifold pressure, pu is atmospheric pressure, 1013 is a standard atmospheric pressure value;
s16: judging whether the timing time reaches a second time (T2), if so, executing S17; otherwise, go to S15;
s17: the brake pump inflow manifold internal air flow rate is set to 0.
Optionally, in the method for estimating the amount of air flow in the brake pump inflow manifold during braking, the nominal air leakage (M) when the connecting pipeline is fully opened and the correction coefficient (f (dpbkvps)) of the nominal air leakage at different opening degrees of the connecting pipeline are calibrated based on the working condition performance, and the calibration process is as follows:
starting the engine, enabling the engine to be in an idling working condition, and continuously stepping on a brake pedal;
for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the values of the nominal air leakage (M) when the connecting pipeline is fully opened and the correction coefficient (f (dpbkvps)) of the nominal air leakage with different opening degrees of the connecting pipeline until the values of the nominal air leakage and the correction coefficient are substituted into the formula (1) to calculate the air flow of the brake pump flowing into the manifold and the air flow increment of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped on; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
And (5) finishing calibration.
Optionally, in the method for estimating the amount of air flow in the brake pump inflow manifold during braking, the nominal air leakage (M) of the connecting pipeline during braking is set1) And calibrating based on the working condition performance, wherein the calibration process is as follows:
starting an engine and enabling the engine to be in an idling working condition, and artificially manufacturing a brake pump pressure sensor fault;
continuously keeping the state of stepping on the brake pedal;
for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow flowing into the manifold by the brake pump according to the data sensed by the manifold pressure sensor before and after the brake is stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the nominal air leakage (M) of the connecting pipeline during braking1)Until the value is substituted into the air flow quantity of the brake pump flowing into the manifold calculated by the formula (3) and before and after the brake is stepped onCalculating the increase amount of the air flow in the brake pump flowing manifold according to the data sensed by the manifold pressure sensor; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
And (5) finishing calibration.
Optionally, in the method for estimating the amount of air flowing into the manifold of the brake pump during braking, the nominal air leakage (M) of the connecting pipeline during releasing the brake2) And calibrating based on the working condition performance, wherein the calibration process is as follows:
stepping down the brake pedal, keeping for a period of time until the air inflow of the engine is restored to the level before stepping down the brake, and then releasing the brake pedal;
for the condition that a manifold pressure sensor is installed on the manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensor before and after the brake is released; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the nominal air leakage (M) of the connecting lines when the brake is released2) Until the air flow quantity of the brake pump flowing into the manifold calculated by substituting the numerical value into the formula (2) is consistent with the increment of the air flow quantity of the brake pump flowing into the manifold calculated according to the data sensed by the manifold pressure sensors before and after the brake is released; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after the brake is released needs to be ensured to be basically consistent;
And finishing calibration.
Optionally, in the method for estimating the amount of air flow of the brake pump into the manifold during braking, a throttle model is used to calculate the amount of air flow passing through the connecting pipeline, and the amount of air flow passing through the connecting pipeline is equal to the mass flow passing through the throttle, and the calculation formula is as follows:
Massflow＝Mnormal*KLAF(Pdown/Pup)*f(Pup/P0)*f(Tup) … … formula (4)
Wherein Massflow is the mass flow through the throttle valve; mnormalThe air inlet quantity of the throttle valve in the nominal state corresponding to different opening degrees is obtained; KLAF (P)down/Pup) For correction of coefficient of flow, PdownFor the pressure value, P, downstream of the connecting lineupIs the pressure value upstream of the connecting pipeline; f (P)up/p0) As a pressure correction factor, P0Is a standard atmospheric pressure value; f (T)up) As temperature correction coefficient, TupIs the gas temperature value upstream of the connecting pipeline.
Optionally, in the method for estimating the amount of air flowing into the manifold of the brake pump during braking, the pressure correction coefficient is calculated according to the following formula:
f(Pup/P0)＝Pupequation (5) of/1013.
Optionally, in the method for estimating the amount of air flowing into the manifold of the brake pump during braking, the calculation formula of the temperature correction coefficient is as follows:
optionally, in the method for estimating the amount of air flowing into the manifold by the brake pump during braking, the upstream pressure of the connecting line corresponds to the pressure of the brake pump, and the downstream pressure of the connecting line corresponds to the pressure of the manifold; the temperature upstream of the connecting line corresponds to the air temperature in the brake pump.
According to the method for estimating the air flow of the brake pump flowing into the manifold during braking, the influence of the brake signal does not need to be considered in the process of designing the method for estimating the air flow of the brake pump flowing into the manifold, so that the method can better give consideration to the performance of extreme working conditions when the brake signal is not reset or set due to the hardware installation of the brake pedal or the continuous braking stepping of a driver and the like, and can effectively avoid the problems of idle fluctuation and even flameout and the like caused by the fact that mixed air is lean or the self-learning deviation of the air leakage of a throttle valve is overlarge due to the fact that the brake pedal is stepped.
On the other hand, the method for estimating the air flow in the brake pump inflow manifold also considers the replacement scheme when the brake pump pressure sensor is in fault or has no brake pump pressure sensor, although the measure cannot give consideration to the accuracy of the calculation result under various extreme working conditions like the main scheme, the method can furthest and effectively ensure the accuracy of air flow calculation when the brake pump pressure sensor is in fault or has no brake pump pressure sensor, and further improves the redundancy of the system.
Additional features and advantages of the invention will be set forth in the detailed description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims thereof as well as the appended drawings.
Drawings
FIG. 1 is a flowchart of a prior art procedure for calculating brake pump intake air;
FIG. 2 is a flow chart of a method for estimating the amount of airflow in the brake pump inlet manifold during braking according to one embodiment of the present invention;
FIG. 3 is a flow chart of the steps of an alternative embodiment of the present invention;
FIG. 4 is a graph showing the performance of an engine mixture in a certain project under an extreme condition of continuous brake application and no reset of brake signals according to an embodiment of the present invention.
Detailed Description
The method for estimating the amount of air flowing into the manifold of the brake-time brake pump according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
The following embodiments of the present invention are provided by way of specific examples, and other advantages and effects of the present invention will be readily apparent to those skilled in the art from the disclosure herein. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Certain terms are used throughout the description and claims to refer to particular system components. As one skilled in the art will appreciate, different companies may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the description and claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to …".
As used in this application and in the claims, the terms "a," "an," "the," and/or "the" are not intended to be inclusive in the singular, but rather are intended to include the plural, unless the context clearly dictates otherwise. In general, the terms "comprises" and "comprising" are intended to cover only the explicitly identified steps or elements as not constituting an exclusive list and that the method or apparatus may comprise further steps or elements.
Furthermore, each embodiment described below has one or more technical features, and this does not mean that all the technical features in any embodiment must be implemented simultaneously by the inventor or that only some or all the technical features in different embodiments can be implemented separately. In other words, based on the disclosure of the present invention and according to design specifications or implementation requirements, a person skilled in the art can selectively implement some or all of the technical features of any embodiment or selectively implement some or all of the technical features of a plurality of embodiments, thereby increasing the flexibility of the implementation of the present invention.
The present invention will be described in more detail with reference to the accompanying drawings, in order to make the objects and features of the present invention more comprehensible, embodiments thereof will be described in detail below, but the present invention may be implemented in various forms and should not be construed as being limited to the embodiments described.
Please refer to fig. 2, which is a flowchart illustrating a method for estimating an amount of airflow flowing into a manifold of a brake pump during braking according to an embodiment of the present invention. As shown in fig. 2, the method for estimating the amount of air flowing into the manifold by the brake-time brake pump includes:
first, step S1 is executed: judging whether the rotating speed of the engine is zero, if so, controlling the flow of the brake pump flowing into the manifold to be 0; otherwise, go to S2;
next, step S2 is executed: judging whether the vehicle has a brake pump pressure sensor, if so, executing S3; otherwise, go to S4;
next, step S3 is executed: judging whether the pressure sensor has faults or not, and if yes, executing S4; otherwise, go to S5;
next, step S4 is executed: calculating the air flow of the brake pump flowing into the manifold by adopting an alternative scheme;
in step S4, the alternative is to calculate the amount of air flowing into the manifold from the brake pump as the amount of air flowing into the manifold from the brake pump.
Please refer to fig. 3, which is a flowchart illustrating an alternative embodiment of the present invention. As shown in fig. 3, the replacement scheme specifically includes the following steps (S11 to S17):
first, step S11 is executed: judging whether the capture signal is the falling edge of the brake signal, if so, executing S12; otherwise, go to S14;
Then, step S12 is executed: calculating the flow of air flowing into a manifold of the brake pump by adopting a formula (2), and starting timing;
wherein, mlbr2The flow of the brake pump into the manifold for a period of time to release the brakes; m is a group of2Nominal air leakage of the connecting pipeline when the brake is released; ps is manifold pressure, pu is atmospheric pressure, 1013 is a standard atmospheric pressure value;
specifically, the nominal air leakage M of the connecting pipeline when the brake is released2And calibrating based on the working condition performance, wherein the calibrating process comprises the following steps:
s120: stepping down a brake pedal, keeping the brake pedal for a period of time, and releasing the brake pedal after the air inflow of the engine is restored to the level before stepping on the brake;
s121: for the condition that a manifold pressure sensor is installed on the manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensor before and after the brake is released; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
s122: constantly adjusting nominal air leakage M of connecting pipeline when brake is released2Until the air flow quantity of the brake pump flowing into the manifold calculated by substituting the numerical value into the formula (2) is consistent with the increment of the air flow quantity of the brake pump flowing into the manifold calculated according to the data sensed by the manifold pressure sensors before and after the brake is released; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after the brake is released needs to be ensured to be basically consistent;
S123: and finishing calibration.
Then, step S13 is executed: judging whether the timing time reaches a first time T1, if so, executing S14; otherwise, go to S12;
then, step S14 is executed: judging whether the capture signal is the rising edge of the brake signal, if so, executing S15; otherwise, go to S17;
then, step S15 is executed: calculating the air flow in an inflow manifold of the brake pump by adopting a formula (3), and starting timing;
wherein, mlbr1The flow rate of the brake pump flowing into the manifold within a period of time for stepping on the brake; m1The nominal air leakage of the connecting pipeline is realized when the brake is stepped; ps is manifold pressure, pu is atmospheric pressure, 1013 is standard atmospheric pressure value.
Specifically, the nominal air leakage M of the connecting pipeline during braking1And calibrating based on the working condition performance, wherein the calibration process is as follows (S150-S154):
s150: starting the engine and enabling the engine to be in an idling working condition, and artificially manufacturing a brake pump pressure sensor fault;
s151: continuously keeping the state of stepping on the brake pedal;
s152: for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
S153: continuously adjusting nominal air leakage M of connecting pipeline during brake treading1Until the air flow quantity of the brake pump flowing into the manifold calculated by substituting the numerical value into the formula (3) is consistent with the increment of the air flow quantity of the brake pump flowing into the manifold calculated according to the data sensed by the manifold pressure sensors before and after the brake is stepped on; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
s154: and finishing calibration.
Then, step S16 is executed: judging whether the timing time reaches a second time T2, if so, executing S17; otherwise, go to S15;
then, step S17 is executed: the brake pump inflow manifold internal air flow rate is set to 0.
The first time T1 and the second time T2 may be selected as desired.
Next, step S5 is executed: calculating the air flow flowing into a manifold from a brake pump in real time by adopting a formula (1);
wherein mlbr is the flow rate of the brake pump flowing into the manifold; m is the nominal air leakage when the connecting pipeline is fully opened, the connecting pipeline is a pipeline which is arranged between the brake pump and the manifold and is provided with a throttle valve, and the connecting pipeline is divided into an upstream pipeline and a downstream pipeline by taking the throttle valve as a boundary; dpbkvps is the pressure difference between the upstream pressure and the downstream pressure of the connecting pipeline, f (dpbkvps) is the correction coefficient of the nominal air leakage amount of different opening degrees of the connecting pipeline, and f (dpbkvps) belongs to [0,1 ]; KLAF (ps/pbkvr) is the flow regime correction factor, ps is the manifold pressure, and pbkvr is the brake pump pressure; tumg is the temperature upstream of the connecting line.
In step S5, the correction coefficients f (dpbkvps) of the nominal air leakage amount M when the connecting pipeline is fully opened and the nominal air leakage amount of the connecting pipeline at different opening degrees are calibrated based on the working condition performance, and the calibration process is as follows (S50-S53):
s50: starting the engine, enabling the engine to be in an idling working condition, and continuously stepping on a brake pedal;
s51: for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
s52: continuously adjusting the numerical values of the nominal air leakage M when the connecting pipeline is fully opened and the correction coefficient f (dpbkvps) of the nominal air leakage of different opening degrees of the connecting pipeline until the air flow of the brake pump flowing into the manifold, which is calculated by substituting the numerical values into the formula (1), is consistent with the increment of the air flow of the brake pump flowing into the manifold, which is calculated according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped on; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
S53: and finishing calibration.
The specific process of obtaining formula (1) is as follows (mainly referring to formula (4) to formula (8)):
because the connecting pipeline is a pipeline which is arranged between the brake pump and the manifold and is provided with the throttle valve, the air flow passing through the connecting pipeline is equal to the mass flow passing through the throttle valve, the air flow passing through the connecting pipeline is calculated by adopting a throttle valve model, and the calculation is carried out by adopting a formula (4):
Massflow＝Mnormal*KLAF(Pdown/Pup)*f(Pup/P0)*f(Tup) … … formula (4)
In the formula (4), Massflow is the mass flow passing through the throttle valve; mnormalThe air inlet quantity of the throttle valve in the nominal state corresponding to different opening degrees is obtained; KLAF (P)down/Pup) For correction of coefficient of flow, PdownFor the pressure value, P, downstream of the connecting lineupIs the pressure value upstream of the connecting pipeline; f (P)up/p0) As a pressure correction factor, P0Is a standard atmospheric pressure value, P0Value 1013 pa; f (T)up) As temperature correction coefficient, TupIs the gas temperature value upstream of the connecting pipeline.
Wherein the pressure correction coefficient is calculated by formula (5):
f(Pup/P0)＝Pupequation (5) of/1013.
The temperature correction coefficient is calculated by adopting a formula (6):
in combination with the construction of the brake pump, the manifold and the connecting pipeline with the throttle valve arranged thereon, it can be known that the upstream pressure of the connecting pipeline corresponds to the brake pump pressure pbkvr, and generally, the brake pump pressure pbkvr can be directly measured; the downstream pressure of the connecting pipeline corresponds to manifold pressure ps, and the manifold pressure ps can be directly measured through a pressure sensor; the temperature upstream of the connecting line corresponds to the air temperature in the brake pump.
In summary, in the case where the brake pump pressure pbkvr can be directly measured, the amount of airflow mlbr of the brake pump flowing into the manifold can be calculated by equation (7).
Equation (7), except for Mnormal(the intake air amount of the throttle valve in the nominal state corresponding to different opening degrees, namely the nominal air leakage amount in any case), other values belong to known and fixed parameters. For MnormalThe value of the pressure difference between the pressure difference and the air leakage quantity of the pipeline is determined by calibrating, the opening of the throttle valve is related to the pressure difference between the front and the back of the pipeline, and therefore the air leakage quantity of the pipeline is corrected through the pressure difference correction curve. Wherein, the nominal air leakage M under any conditionnormalCan be expressed by equation (8):
Mnormal(dpbkvps) equation (8);
in the formula (8), M represents the nominal air leakage when the connecting pipeline is fully opened, dpbkvps represents the pressure difference between the front and the rear of the connecting pipeline, f (dpbkvps) is a correction coefficient of the nominal air leakage of the connecting pipeline with different opening degrees, the maximum value of the correction coefficient is 1, the minimum value of the correction coefficient is 0, the dpbkvps value when the coefficient is 1 can be input by a client, and the correction coefficient between 0 and 1 can be calibrated according to the actual effect.
The formula (1) can be obtained by combining the formulas (4), (5), (6), (7) and (8).
It can be seen from formula (1) that the air intake of the connecting pipeline is independent of whether the brake is applied or not, and is only dependent on the downstream and upstream pressure ratio of the connecting pipeline, for this reason, when a brake pump pressure sensor is installed in the EMS (i.e. an engine management system) and the signal is normal, the air intake of the connecting pipeline can be directly calculated by formula (1).
Nevertheless, when the system has no brake pump pressure sensor or the pressure sensor signal is faulty, the system cannot calculate the air flow of the connecting pipeline according to the formula (1), and therefore the system needs to have an alternative (i.e. execute step S4), and although the alternative is still the one that needs to guarantee the performance of the system to the maximum, the alternative is considered from the viewpoint of system safety in the worst case, the brake pump is in the state of being directly connected to the atmosphere, i.e. completely leaking air, at this time, the upstream pressure of the connecting pipeline can be regarded as the atmospheric pressure pu, and the pressure correction is changed to the plateau correction system fho, i.e. pu/1013. Meanwhile, the pu is always greater than the manifold pressure ps under various working conditions such as an idling working condition, so that the change of a brake signal needs to be considered for compensation at the moment in order to avoid the problem of transient compensation of air leakage of a brake pump; furthermore, the amount of air flow from the brake pump into the manifold is different for the brake application and brake release, and therefore the brake application and brake release behavior must be considered separately. Specifically, the flow of air from the brake pump into the manifold under the alternative is expressed by equations (2) and (3).
To verify the effectiveness of the scheme of the present invention, please refer to fig. 4 for understanding.
FIG. 4 is a diagram showing the performance of the engine mixture in a certain project under the extreme condition that the brake is continuously applied and the brake signal is not reset. Specifically, in fig. 4, reference numeral 1 represents engine speed (nmot _ w), reference numeral 3 represents an actual excess air factor measured by an oxygen sensor (Lamsoni _ w), reference numeral 3 represents an amount of air flow (mlbr _ ua) entering a manifold of a brake pump when a brake is applied, reference numeral 2 represents a brake signal (b _ brakes), reference numeral 5 represents a closed loop state (b _ lr), and reference numeral in fig. 4 represents an open loop control state. The result mapping shown in fig. 4 is enough to verify that the scheme of the invention can accurately obtain the air flow in the brake pump inflow manifold during braking through self-learning, and effectively avoid the problems of idle fluctuation and even flameout.
In summary, in the method for estimating the air flow of the brake pump flowing into the manifold during braking provided by the invention, through the research on the influence factors of the air flow of the connecting pipeline between the brake pump and the manifold, the air inflow of the connecting pipeline is not related to whether braking is applied, and the air inflow is only related to the pressure ratio between the downstream and the upstream of the connecting pipeline, so that the influence of a brake signal does not need to be considered in the process of designing the method for estimating the air flow of the brake pump flowing into the manifold, the method can better give consideration to the performance of extreme working conditions when the brake signal is not reset or set due to the hardware installation of a brake pedal or the continuous application of the brake by a driver, and the like, and can effectively avoid the problems of idle speed fluctuation and even flameout and the like caused by the fact that mixed air is lean or the self-learning deviation of the air leakage of a throttle valve is too large due to the application of the brake under the extreme working conditions.
On the other hand, the method for estimating the air flow in the brake pump inflow manifold also considers the replacement scheme when the brake pump pressure sensor is in fault or has no brake pump pressure sensor, although the measure cannot give consideration to the accuracy of the calculation result under various extreme working conditions like the main scheme, the method can furthest and effectively ensure the accuracy of air flow calculation when the brake pump pressure sensor is in fault or has no brake pump pressure sensor, and further improves the redundancy of the system.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A method of estimating the amount of air flowing into a manifold of a brake-time brake pump, comprising:
s1: judging whether the rotating speed of the engine is zero, if so, controlling the flow of the brake pump flowing into the manifold to be 0; otherwise, go to S2;
S2: judging whether the vehicle has a brake pump pressure sensor, if so, executing S3; otherwise, go to S4;
s3: judging whether the pressure sensor has faults or not, and if yes, executing S4; otherwise, go to S5;
s4: calculating the air flow of the brake pump flowing into the manifold by adopting an alternative scheme;
s5: calculating the air flow flowing into a manifold from a brake pump in real time by adopting a formula (1);
wherein mlbr is the flow rate of the brake pump flowing into the manifold; m is the nominal air leakage when the connecting pipeline is fully opened, the connecting pipeline is a pipeline which is arranged between the brake pump and the manifold and is provided with a throttle valve, and the connecting pipeline is divided into an upstream pipeline and a downstream pipeline by taking the throttle valve as a boundary; dpbkvps is the pressure difference between the upstream pressure and the downstream pressure of the connecting pipeline, f (dpbkvps) is the correction coefficient of the nominal air leakage amount of different opening degrees of the connecting pipeline, and f (dpbkvps) belongs to [0,1 ]; KLAF (ps/pbkvr) is the flow regime correction factor, ps is the manifold pressure, and pbkvr is the brake pump pressure; tumg is the temperature upstream of the connecting line.
2. The method of estimating the amount of air flowing from a brake-time brake pump into a manifold as recited in claim 1, wherein the alternative is to calculate the amount of air flowing from the brake pump into the manifold based on a change in the braking signal.
3. The method of estimating the amount of air flow in a brake-time brake pump inflow manifold of claim 2, wherein said alternative comprises the steps of:
s11: judging whether the capture signal is the falling edge of the brake signal, if so, executing S12; otherwise, go to S14;
s12: calculating the air flow in an inflow manifold of the brake pump by adopting a formula (2), and starting timing;
wherein, mlbr2The amount of air flow into the manifold from the brake pump for a period of time to release the brakes; m2The nominal air leakage of the connecting pipeline when the brake is released; ps is manifold pressure, pu is atmospheric pressure, 1013 is a standard atmospheric pressure value;
s13: judging whether the timing time reaches the first time (T1), if yes, executing S14; otherwise, go to S12;
s14: judging whether the capture signal is the rising edge of the brake signal, if so, executing S15; otherwise, go to S17;
s15: calculating the air flow in an inflow manifold of the brake pump by adopting a formula (3), and starting timing;
wherein, mlbr1The flow rate of the brake pump flowing into the manifold within a period of time for stepping on the brake; m1The nominal air leakage of the connecting pipeline is realized when the brake is stepped; ps is manifold pressure, pu is atmospheric pressure, 1013 is a standard atmospheric pressure value;
S16: judging whether the timing time reaches the second time (T2), if yes, executing S17; otherwise, go to S15;
s17: the brake pump inflow manifold air flow rate was set to 0.
4. The method for estimating the amount of air flow in a brake-time brake pump-inflow manifold according to claim 3, wherein the nominal air leakage (M) when the connecting line is fully open and the correction factor (f) (dpbkvps) for the nominal air leakage at different opening degrees of the connecting line are calibrated based on the behavior of the operating conditions, and the calibration is performed as follows:
starting the engine, enabling the engine to be in an idling working condition, and continuously stepping on a brake pedal;
for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the values of the nominal air leakage (M) when the connecting pipeline is fully opened and the correction coefficient (f (dpbkvps)) of the nominal air leakage with different opening degrees of the connecting pipeline until the values of the nominal air leakage and the correction coefficient are substituted into the formula (1) to calculate the air flow of the brake pump flowing into the manifold and the air flow increment of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is continuously stepped on; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
And (5) finishing calibration.
5. Method for estimating the amount of air flowing in the brake-on brake pump manifold according to claim 3, characterized in that said nominal leakage (M) of the connecting line when the brake is applied is determined by the method1) And calibrating based on the working condition performance, wherein the calibration process is as follows:
starting an engine and enabling the engine to be in an idling working condition, and artificially manufacturing a brake pump pressure sensor fault;
continuously keeping the state of stepping on the brake pedal;
for the condition that a manifold pressure sensor is installed on a manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensors before and after the brake is stepped; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the nominal air leakage (M) of the connecting pipeline during braking1) Until the air flow quantity of the brake pump flowing into the manifold calculated by substituting the numerical value into the formula (3) is consistent with the increment of the air flow quantity of the brake pump flowing into the manifold calculated according to the data sensed by the manifold pressure sensors before and after the brake is stepped on; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after braking is basically consistent;
And (5) finishing calibration.
6. Method for estimating the air flow in a brake-time brake pump inflow manifold according to claim 3, characterized in that the nominal air leakage (M) of the connecting lines when the brake is released is determined2) Base ofAnd calibrating the working condition performance, wherein the calibration process comprises the following steps:
stepping down a brake pedal, keeping the brake pedal for a period of time, and releasing the brake pedal after the air inflow of the engine is restored to the level before stepping on the brake;
for the condition that a manifold pressure sensor is installed on the manifold, calculating the increment of the air flow of the brake pump flowing into the manifold according to the data sensed by the manifold pressure sensor before and after the brake is released; for the condition that a manifold pressure sensor is not installed on the manifold, calibrating by adopting a closed-loop control method for closing the mixed gas;
continuously adjusting the nominal air leakage (M) of the connecting lines when the brake is released2) Until the air flow quantity of the brake pump flowing into the manifold calculated by substituting the numerical value into the formula (2) is consistent with the increment of the air flow quantity of the brake pump flowing into the manifold calculated according to the data sensed by the manifold pressure sensors before and after the brake is released; for the condition that a manifold pressure sensor is not installed on a manifold, the performance of mixed gas before and after the brake is released needs to be ensured to be basically consistent;
And (5) finishing calibration.
7. The method of estimating the amount of air flow in a brake-time brake pump into a manifold of claim 1, wherein a throttle model is used to calculate the amount of air flow through a connecting line, the amount of air flow through the connecting line being equal to the mass flow through the throttle, as follows:
Massflow＝Mnormal*KLAF(Pdown/Pup)*f(Pup/P0)*f(Tup) … … formula (4)
Wherein Massflow is the mass flow through the throttle valve; m is a group ofnormalThe air inlet quantity of the throttle valve in the nominal state corresponding to different opening degrees is obtained; KLAF (P)down/Pup) For correction of coefficient of flow, PdownFor the pressure value, P, downstream of the connecting lineupIs the pressure value upstream of the connecting pipeline; f (P)up/p0) As a pressure correction factor, P0Is a standard atmospheric pressure value; f (T)up) As temperature correction coefficient, TupFor connecting pipelinesAnd (4) a free air temperature value.
8. The method of estimating the amount of air flowing into the manifold of a brake-time brake pump according to claim 7, wherein the pressure correction coefficient is calculated as follows:
f(Pup/P0)＝Pupequation (5) of/1013.
9. The method of estimating the amount of air flowing into the manifold of a brake-time brake pump according to claim 8, wherein the temperature correction coefficient is calculated as follows:
10. the method of estimating the amount of brake-time brake pump-in manifold air flow according to claim 9, wherein the connecting line upstream pressure corresponds to a brake pump pressure and the connecting line downstream pressure corresponds to a manifold pressure; the temperature upstream of the connecting line corresponds to the air temperature in the brake pump.
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