CN113914993B - Thermostat normally-open fault diagnosis method and thermostat normally-open fault diagnosis device - Google Patents
Thermostat normally-open fault diagnosis method and thermostat normally-open fault diagnosis device Download PDFInfo
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- CN113914993B CN113914993B CN202111024517.0A CN202111024517A CN113914993B CN 113914993 B CN113914993 B CN 113914993B CN 202111024517 A CN202111024517 A CN 202111024517A CN 113914993 B CN113914993 B CN 113914993B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P11/00—Component parts, details, or accessories not provided for in, or of interest apart from, groups F01P1/00 - F01P9/00
- F01P11/14—Indicating devices; Other safety devices
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P11/00—Component parts, details, or accessories not provided for in, or of interest apart from, groups F01P1/00 - F01P9/00
- F01P11/14—Indicating devices; Other safety devices
- F01P11/16—Indicating devices; Other safety devices concerning coolant temperature
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P7/00—Controlling of coolant flow
- F01P7/14—Controlling of coolant flow the coolant being liquid
- F01P7/16—Controlling of coolant flow the coolant being liquid by thermostatic control
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
- F01P—COOLING OF MACHINES OR ENGINES IN GENERAL; COOLING OF INTERNAL-COMBUSTION ENGINES
- F01P2031/00—Fail safe
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Abstract
The application relates to the technical field of automobile detection, in particular to a thermostat normally-open fault diagnosis method and device. The method comprises the following steps: acquiring a first temperature change signal and a second temperature change signal in real time, wherein the first temperature change signal is a temperature variable of coolant flowing out of an engine, and the second temperature change signal is a temperature variable of the coolant in a radiator; determining an engine start warm-up phase based on the first temperature change signal and the second temperature change signal; calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal; and in the engine starting and warming-up stage, judging whether the thermostat is normally open or not based on the state duration of the first temperature difference signal. The device is used for realizing the method.
Description
Technical Field
The application relates to the technical field of automobile detection, in particular to a thermostat normally-open fault diagnosis method and device.
Background
The thermostat is a valve that controls a flow path of the cooling fluid. The temperature-sensing device is an automatic temperature-sensing device and usually comprises a temperature-sensing component. The flow of air, gas or liquid is turned on and off by thermal expansion or contraction. The water quantity entering the radiator is automatically adjusted according to the temperature of the cooling water, and the circulation range of the water is changed, so that the heat dissipation capacity of the cooling system is adjusted, and the engine is ensured to work in a proper temperature range. The thermostat must maintain good state of technology or otherwise seriously affect the normal operation of the engine. For example, if the main valve of the thermostat is opened too late, the engine will be overheated, and if the main valve is opened too early, the preheating time of the engine will be prolonged, so that the temperature of the engine is too low. In general, the thermostat functions to keep the engine from overheating or overcooling.
For example, after the engine is operating normally, at a winter start, the temperature of the engine may be too low without the thermostat. When the cooling temperature is lower than the specified value, the thermostat valve closes a channel between the engine and the radiator under the action of the spring, and the cooling liquid returns to the engine through the water pump to perform small circulation in the engine. When the temperature of the cooling liquid reaches a specified value, the valve is opened. At this time, the cooling liquid flows back to the engine through the radiator and the thermostat valve and then through the water pump to perform large circulation. The thermostat is mostly not known in the cylinder head outlet line.
Because the thermostat often opens and closes during operation, produce the oscillation phenomenon to thereby appear the thermostat card easily and make the coolant liquid that flows from the engine exit end can not reach the warm-up temperature of this engine always in normally open state, perhaps need the long time can reach the warm-up temperature, be unfavorable for the fuel economy nature that the engine started. However, the reliability of detecting the normally open fault of the thermostat is low in the related technology, especially for the hot start of an engine, for example, the engine is started between 40 ℃ and 55 ℃, the related technology is easy to cause the problem that the fault that the thermostat is stuck at the normally open position cannot be diagnosed, and the report is missed.
Disclosure of Invention
The application provides a thermostat normally-open fault diagnosis method and device, which can solve the problem of low reliability of thermostat normally-open fault detection in the related technology.
The application provides a thermostat normally-open fault diagnosis method, which comprises the following steps:
acquiring a first temperature change signal and a second temperature change signal in real time, wherein the first temperature change signal is a temperature variable of coolant flowing out of an engine, and the second temperature change signal is a temperature variable of the coolant in a radiator;
determining an engine start warm-up stage based on the first temperature change signal and the second temperature change signal;
calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal;
and in the engine starting and warming-up stage, judging whether the thermostat is normally open or not based on the state duration of the first temperature difference signal.
Optionally, the step of determining the engine start warm-up phase based on the first temperature change signal and the second temperature change signal comprises:
determining an initial time of an engine starting phase;
determining the time when the change rate of the first temperature change signal and the change rate of the second temperature change signal are stable as the end time of the engine starting stage;
determining a phase between the initial time and the end time as the engine start phase.
Optionally, the step of calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal comprises:
according to the formula:
ΔC(t)＝C1(t)-C2(t)，t∈[t0，t1]
calculating the first temperature difference signal, wherein Δ C (t) is a first temperature difference signal, C1(t) is a first temperature change signal, C2(t) is a second temperature change signal, t0 is an initial time of the engine start phase, and t1 is an end time of the engine start phase.
Optionally, the step of determining whether the thermostat is normally open and failed based on the state duration of the first temperature difference signal in the engine starting and warming-up phase includes:
determining a steady state accumulated time length of the first temperature difference signal in the engine starting and warming-up stage;
and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the steady state accumulated time length.
Optionally, the step of determining the steady state accumulated duration of the first temperature difference signal during the engine warm-up phase comprises:
determining the first temperature difference signal, and a temperature difference change stable interval in the engine starting and warming-up stage;
determining the time length of the temperature difference change stable interval;
and calculating the sum of the time lengths of all the temperature difference change stable intervals, wherein the sum of the time lengths is the stable state accumulated duration of the first temperature difference signal.
Optionally, the step of determining the first temperature difference signal, and the temperature difference change stable interval in the engine startup warm-up stage, includes:
obtaining a filtered signal of the first temperature difference signal by subjecting the first temperature difference signal to a high-pass filter;
and determining that the interval in which the signal value of the filtering signal is smaller than the filtering threshold value in the engine starting and warming-up stage is the temperature difference change stable interval of the first temperature difference signal.
Optionally, the step of determining whether the thermostat is normally open and failed based on the accumulated steady state duration in the engine startup and warm-up phase includes:
determining a total duration of the engine warm-up phase;
calculating the steady state accumulated time, wherein the steady state accumulated time accounts for the ratio of the total time of the engine starting and warming-up stages;
and when the proportion of the accumulated time length in the stable state is greater than or equal to the proportion threshold value, determining that the thermostat is in a normally open fault.
Optionally, the method further comprises:
determining an invalid time period in the engine warm-up starting phase based on the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal;
subtracting the invalid time length from the total time length to obtain an effective time length of the engine starting and warming-up stage;
and calculating the ratio of the stable state accumulated duration to the effective duration to obtain the stable state accumulated duration.
Optionally, the step of determining whether the thermostat is normally open and failed based on the state duration of the first temperature difference signal in the engine starting and warming-up phase includes:
determining the accumulative duration of the unstable state of the first temperature difference signal in the engine starting and warming-up stage;
and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the unstable state accumulated time.
Optionally, the step of determining the cumulative length of the unsteady-state of the first temperature difference signal in the engine startup warm-up phase includes:
determining the first temperature difference signal, wherein the temperature difference change in the engine starting and warming-up stage is an unstable interval;
determining the time length of the temperature difference change unstable interval;
and calculating the sum of the time lengths of all the temperature difference change unstable intervals, wherein the sum of the time lengths is the unstable state accumulated time length of the first temperature difference signal.
Optionally, the step of determining the first temperature difference signal, the unstable interval of temperature difference change in the engine start warming-up stage, includes:
obtaining a filtered signal of the first temperature difference signal by subjecting the first temperature difference signal to a high-pass filter;
and determining the interval in which the signal value of the filtering signal is greater than or equal to the filtering threshold value in the engine starting and warming-up stage as the unstable interval of the temperature difference change of the first temperature difference signal.
Optionally, the step of determining whether the thermostat is normally open and failed based on the cumulative length of time of the unstable state in the engine starting and warming-up phase includes:
calculating effective unstable state accumulated time length in the unstable state accumulated time length;
and in the engine starting and warming-up stage, when the effective unstable state accumulated time length is less than the unstable state accumulated time length threshold, determining that the thermostat is in a normally open fault.
Optionally, the method further comprises: the step of calculating the effective unstable state accumulated time length in the unstable state accumulated time length includes:
determining an invalid time period in the engine start-up and warm-up stage based on the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal;
and subtracting the invalid time length from the unstable state accumulated time length to obtain the effective unstable state accumulated time length.
Optionally, the invalid time period is a length of a time period in which the first temperature difference signal is unstable due to a temperature difference between an initial temperature of the first temperature change signal and an initial temperature of the second temperature change signal.
The application also provides a thermostat normally-open fault diagnosis device, which comprises a processor and a memory, wherein at least one program or instruction is stored in the memory, and the processor is used for acquiring and executing the program or instruction to realize the thermostat normally-open fault diagnosis method.
The technical scheme at least comprises the following advantages: determining an engine starting and warming-up stage according to the first temperature change signal and the second temperature change signal; calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal; and in the engine starting and warming-up stage, judging whether the thermostat is in the normally open fault or not based on the state duration of the first temperature difference signal, and being beneficial to improving the diagnosis reliability of whether the thermostat is in the normally open fault or not.
Drawings
In order to more clearly illustrate the detailed description of the present application or the technical solutions in the prior art, the drawings needed to be used in the detailed description of the present application or the prior art description will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative efforts.
FIG. 1a shows a schematic diagram of an engine coolant-mounted circulation piping of a thermostat system;
FIG. 1b shows a schematic flow diagram of coolant in the circulation piping during a large circulation phase;
FIG. 2 is a graph showing a coolant temperature change at the engine warm-up start phase;
FIG. 3 is a flow chart illustrating a thermostat normally open fault diagnostic method provided in accordance with a first embodiment of the present application;
FIG. 4 illustrates a graph of a first temperature change signal and a second temperature change signal when the thermostat is in a normally open fault;
FIG. 5 is a flow chart illustrating a thermostat normally open fault diagnostic method according to another embodiment of the present application:
fig. 6 shows a structural block diagram of a thermostat normally open fault diagnosis device provided by the present application.
Detailed Description
The technical solutions in the present application will be described clearly and completely with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, and do not indicate or imply that the device or element being referred to must have a particular orientation, be constructed and operated in a particular orientation, and thus, should not be construed as limiting the present application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; the connection can be mechanical connection or electrical connection; the two elements may be directly connected or indirectly connected through an intermediate medium, or may be communicated with each other inside the two elements, or may be wirelessly connected or wired connected. The specific meaning of the above terms in the present application can be understood in a specific case by those of ordinary skill in the art.
In addition, the technical features mentioned in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.
FIG. 1a illustrates a schematic diagram of the engine coolant-mounted circulation piping of a thermostat system, which, as can be seen in FIG. 1, includes a thermostat 110, a first water temperature sensor 120, and a second water temperature sensor 130. The circulation piping of the engine coolant includes a large circulation line 101 and a small circulation line 102 connected in parallel between an inlet port 141 and an outlet port 142 of the engine 140, the large circulation line 101 and the small circulation line 102 communicating with the engine 140 through a common line.
I.e., the inlet of the large circulation line 101 is connected to the inlet of the small circulation line 102 and is connected to the outlet port 142 of the engine 140 through the first common line 113, and the thermostat 110 is installed at a position where the inlets of the large circulation line 101 and the small circulation line 102 are connected to control the flow of the coolant flowing out of the engine 140 to the large circulation line 101 or the small circulation line 102. The outlet of the large circulation line 101 is connected to the outlet of the small circulation line 102 and is connected to the inlet end 141 of the engine 140 through the second common line 123.
A first water temperature sensor 120 is mounted in the first common line 113, i.e. the outlet end 142 of the engine 140, for detecting output temperature information of the coolant flowing out from the outlet end of the engine.
The second water temperature sensor 130 is installed in the radiator 150 near an outlet of the radiator 150 to detect the temperature of the coolant after the heat is radiated from the radiator 150. The radiator 150 is installed in the large circulation pipeline 101, the cooling liquid entering the large circulation pipeline 101 flows out to enter the engine cooling liquid circulation pipeline system after passing through the radiator 150 to perform the heat radiation process so as to cool the engine,
wherein the small circulation pipe 102 is used for realizing the self-circulation of the engine. In the early stage of the start-up phase of the vehicle, after the thermostat 110 is closed, a small circulation phase is performed in which the coolant circulates among the engine 140, the common line 103, and the small circulation line 102 to bring the engine temperature to the warm-up temperature as quickly as possible. With continued reference to FIG. 1a, the flow path of the coolant during the small circulation phase is shown by the arrows in FIG. 1 a.
Wherein the large circulation line 101 is used to circulate the coolant between the engine 140 and the radiator 150, which radiator 150 is installed in the large circulation line 101. After the thermostat 110 is turned on, a large circulation stage is performed, and the coolant circularly flows among the engine 140, the common pipeline 103, the large circulation pipeline 101 and the radiator 150, so that the coolant is radiated by flowing through the radiator 150, and the engine 140 is prevented from overheating and failing. Referring to FIG. 1b, a schematic flow diagram of the coolant in the circulation piping is shown during a large circulation phase, wherein the flow path of the coolant is shown by the arrows in FIG. 1 b.
Referring to fig. 2, a coolant temperature change map at the engine startup warm-up stage is shown. As can be seen from FIG. 2, the curve T1 is the temperature variation curve collected by the first water temperature sensor 120 in FIG. 1a or FIG. 1b, and the curve T2 is the temperature variation curve collected by the second water temperature sensor 130 in FIG. 1a or FIG. 1 b. The time period between time t0 and time t1 is the engine start warmup period, and time t0 is the initial time of the engine start warmup period. At time t0, the temperatures acquired by the first water temperature sensor 120 and the second water temperature sensor 130 are both temperatures C0.
At the beginning of this engine warm-up phase, the thermostat is closed, and a small cycle phase P11 is performed, the coolant flow path of this small cycle phase P11 being shown in FIG. 1 a. In the small circulation period P11, since the large circulation line is closed and the coolant flowing through the engine does not enter the radiator, the temperature of the coolant flowing out from the outlet end of the engine increases greatly, i.e., the curve T1 increases greatly in the small circulation period P11, while the temperature of the coolant in the radiator increases slowly, i.e., the curve T2 increases slightly in the small circulation period P11. And when the temperature of the cooling liquid flowing out from the outlet end of the engine rises to exceed the warm-up temperature C of the engine, the thermostat starts to control to close the small circulation pipeline and open the large circulation pipeline, and the engine enters the later stage of the engine start warm-up stage. As shown in fig. 2, at time t11, the temperature of the coolant flowing out of the outlet end of the engine is at temperature C1, and this temperature C1 is higher than the warm-up temperature C, so that the engine starts to enter the late stage of the engine startup warm-up phase at time t 11.
At the beginning of this engine warm-up phase, the thermostat opens and a large cycle phase P12 is performed, the coolant flow path of this large cycle phase P12 being shown in FIG. 1 b. In the large circulation stage P12, since the large circulation pipeline is opened and the small circulation pipeline is closed, the coolant flowing through the engine enters the radiator to perform the heat dissipation process and then flows through the engine again, so the temperature of the coolant flowing through the radiator is increased greatly, i.e. the curve T2 is increased greatly in the large circulation stage P12, while the temperature of the coolant flowing out of the outlet end of the engine is increased slowly, i.e. the curve T1 is increased less in the large circulation stage P12, until the speed increase of the curves T1 and T2 is stable, and the engine starts to warm up.
However, the thermostat is often opened and closed during operation, which tends to cause the thermostat to stuck open, i.e., the thermostat is stuck open, so that the coolant undergoes the large cycle phase shown in fig. 1b throughout the engine warm-up phase. Therefore, the coolant flowing out from the outlet end of the engine can not reach the warm-up temperature of the engine, or the coolant can only reach the warm-up temperature for a long time, which is not favorable for the fuel economy of the engine starting.
FIG. 3 is a flow chart illustrating a thermostat normally open fault diagnostic method provided in accordance with a first embodiment of the present application for diagnosing a fault with the thermostat 110 of FIGS. 1a and 1b stuck in the normally open position. As can be seen from fig. 3, the thermostat normally open fault diagnosis method includes the following steps S31 to S35, which are sequentially performed, wherein:
step S31: the method comprises the steps of acquiring a first temperature change signal and a second temperature change signal in real time, wherein the first temperature change signal is a coolant temperature variable flowing out of an engine along with the time after the engine is started, and the second temperature change signal is a coolant temperature variable in a radiator along with the time after the engine is started.
Step S32: and determining an engine starting warm-up stage based on the first temperature change signal and the second temperature change signal.
In the process of determining the engine start-up warming-up stage, the initial time t0 of the engine start-up warming-up stage may be determined, and then the time when the change rate of the first temperature change signal and the change rate of the second temperature change signal are stable may be determined as the end time t1 of the engine start-up warming-up stage based on the change rates of the first temperature change signal and the second temperature change signal. The period between the initial time t0 and the end time t1 is the engine start warm-up period.
Step S33: and calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal in the engine starting and warming-up stage.
Calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal based on the acquired first temperature change signal and second temperature change signal. Illustratively, C1(t) is a first temperature change signal, C2(t) is a second temperature change signal, and a first temperature difference signal Δ C (t) between the first temperature change signal C1(t) and the second temperature change signal C2(t) is C1(t) -C2(t), te [ t0, t1], where t represents a time variable, t0 represents an initial time of an engine start warm-up phase, and t1 represents an end time of the engine start warm-up phase.
Step S34: and in the engine starting and warming-up stage, judging whether the thermostat is normally open or not based on the state duration of the first temperature difference signal.
Wherein the states of the first temperature difference signal include a steady state and an unsteady state.
Referring to fig. 2, the first temperature difference signal gradually increases and then gradually decreases during the engine warm-up phase when the thermostat can be opened and closed normally, and then starts to stabilize. In a small cycle stage P11 at the initial stage of the engine starting and warming-up stage, the speed of the first temperature change signal T1 is increased faster than that of the second temperature change signal T2, and the first temperature difference signal is gradually increased; in a large cycle period P12 later than the engine start warm-up period, the first temperature change signal P11 increases in speed slower than the second temperature change signal P12, and the first temperature difference signal gradually decreases. Wherein the first temperature difference signal varies more throughout the small cycle phase P11 and before the large cycle phase P12 in fig. 2, the first temperature difference signal of this phase being in an unstable state.
Reference may be made to fig. 4, which illustrates a graph of a first temperature change signal and a second temperature change signal when the thermostat is in a normally open fault. As can be seen from fig. 4, the first temperature difference signal ac (t) is substantially constant or varies little during the engine warm-up phase when the thermostat is in the normally open fault. That is, the first temperature variation signal C1(t) and the second temperature variation signal C2(t) are substantially identical in speed increase. Namely, the first temperature difference signal Δ c (t) in fig. 4 is in a steady state.
Because the thermostat is when normally opening the trouble, it is long that its first difference in temperature signal is in the duration of steady state, and the duration that first difference in temperature signal is in unsteady state is short, therefore can the engine starts the warm-up stage, based on the state duration of first difference in temperature signal judges whether the trouble is normally opened to the thermostat.
The following processes of judging whether the thermostat is normally open and has a fault are explained from the two aspects of whether the duration of the first temperature difference signal in the stable state is longer and whether the duration of the first temperature difference signal in the non-stable state is shorter.
The step of judging whether the thermostat is normally open or not from the angle of whether the duration of the first temperature difference signal in the stable state is longer or not comprises the following steps S341 to S342 which are sequentially performed, wherein:
step S341: and determining the steady state accumulated time length of the first temperature difference signal in the engine starting and warming-up stage.
In determining the steady-state accumulated time duration of the first temperature difference signal, for example, the first temperature difference signal Δ C (t) may be processed by a high-pass filter to obtain a filtered signal Δ C' (t) of the first temperature difference signal Δ C (t). The filtered signal ac' (t) is used to represent the stability of the first temperature difference signal. When the signal value of the filtered signal Δ C' (t) is smaller than the filtering threshold value in a certain period of time, it is determined that the first temperature difference signal Δ C (t) in the certain period of time is in a steady state. Wherein the filtering threshold value can be preset according to requirements.
And determining a section in which the signal value of the filtering signal is smaller than the filtering threshold value in the engine starting and warming-up stage as a temperature difference change stable section of the first temperature difference signal based on the relation between the filtering signal delta C' (t) and the filtering threshold value.
And then determining the time length of the temperature difference change stable interval, if a plurality of temperature difference change stable intervals exist, respectively calculating the time length of each temperature difference change stable interval, wherein the sum of the time lengths of the temperature difference change stable intervals is the stable state accumulated time length of the first temperature difference signal delta C (t).
Step S342: and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the stable state accumulated time.
For example, the degree of the steady state accumulated time period can be judged according to the proportion of the first temperature difference signal in the steady state in the total time period of the engine starting warm-up stage.
I.e. the total duration of the engine warm-up phase may be determined first.
Then calculating the steady state accumulated time length, wherein the steady state accumulated time length in the total time length of the engine starting and warming-up stage accounts for the ratio; and when the proportion of the accumulated time length in the stable state is greater than or equal to the proportion threshold value, determining that the thermostat is in a normally open fault.
When the accumulated time length of the stable state exceeds the duty ratio threshold, the first temperature difference signal Δ C (t) is in the stable state for a longer time, that is, the increasing speed of the first temperature change signal C1(t) and the second temperature change signal C2(t) is basically consistent for a longer time, so that the normally open fault of the thermostat can be determined.
However, in some operating conditions, the temperature difference between the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal is large, so that if the thermostat continues to start the engine in a subsequent stage when a normally open fault occurs, the change rate of the first temperature change signal and the change rate of the second temperature change signal may be inconsistent for a period of time, and the change of the first temperature difference signal in the period of time is large. For example, when the engine is started up, the initial temperature of the first temperature change signal is higher than that of the second temperature change signal, so that if the thermostat has a normally open fault and continues to start the engine, the increase speed of the second temperature change signal is higher than that of the first temperature change signal within a period of time, and the first temperature difference signal changes in a reducing mode within the period of time. This reduced variation time period can adversely affect the determination of a thermostat normally open fault.
For this reason, the invalid time duration is also removed from the total time duration in step S342 to avoid a determination error. The invalid time period is the length of a time period in which the first temperature difference signal is unstable due to the temperature difference between the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal.
That is, the above-mentioned invalid period in the engine start warmup phase is determined based on the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal.
And then subtracting the invalid time length from the total time length to obtain the valid time length of the engine starting and warming-up stage.
And then calculating the ratio of the stable state accumulated time length to the effective time length to obtain the stable state accumulated time length.
Wherein, from the perspective of the duration of the first temperature difference signal in the unstable state, the step of determining whether the thermostat is normally open includes the following steps S351 to S352 performed in sequence, wherein:
step S351: and determining the accumulative length of the unstable state of the first temperature difference signal in the engine starting and warming-up stage.
In determining the non-steady state accumulated time period of the first temperature difference signal, for example, step S3511 may be performed first: the first temperature difference signal Δ C (t) is processed by a high-pass filter, so that a filtered signal Δ C' (t) of the first temperature difference signal Δ C (t) is obtained. The filtered signal ac' (t) is used to represent the stability of the first temperature difference signal. When the signal value of the filtered signal Δ C' (t) is greater than or equal to the filtering threshold value in a certain period of time, it is determined that the first temperature difference signal Δ C (t) in the certain period of time is in an unstable state. Wherein the filtering threshold value can be preset according to requirements.
And then, the step S3512 is carried out: and determining the interval in which the signal value of the filtered signal is greater than or equal to the filtering threshold value in the engine starting and warming-up stage as the unstable interval of the temperature difference change of the first temperature difference signal based on the relation between the filtered signal deltaC' (t) and the filtering threshold value.
Then, step S3513 is performed: and determining the time length of the temperature difference change unstable interval, if a plurality of temperature difference change unstable intervals exist, respectively calculating the time length of each temperature difference change unstable interval, wherein the sum of the time lengths of each temperature difference change unstable interval is the unstable state accumulated time length of the first temperature difference signal delta C (t).
Step S352: and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the unstable state accumulated time.
For example, whether the thermostat is normally open to fail may be determined according to the length of the accumulated time duration of the unsteady state.
However, for the same reason as above, there is a time period in which the first temperature difference signal is unstable in the engine startup warm-up phase due to the temperature difference between the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal, and the time period is an invalid time period.
In order to improve the closeness of the diagnosis result to the length of the non-steady state accumulated time period, it is necessary to flush the invalid time period from the non-steady state accumulated time period determined in step S351 in determining whether the thermostat is normally open to fail.
Step S352 may thus include: firstly, calculating effective unstable state accumulated time length in the unstable state accumulated time length; and in the engine starting and warming-up stage, when the effective unstable state accumulated time length is smaller than the unstable state accumulated time length threshold, determining that the thermostat is in a normally open fault state.
Fig. 5 is a flowchart illustrating a method for diagnosing a normally open fault of an thermostat according to the present application, where the embodiment illustrated in fig. 5 is based on the above embodiments, and on the basis of determining whether the thermostat is in a normally open fault process according to a state duration of a first temperature difference signal, a step of calculating a maximum value of the first temperature difference signal may be further performed, and whether the thermostat is in a normally open fault is determined based on the state duration of the first temperature difference signal and the maximum value of the first temperature difference signal.
That is, the state duration of the first temperature difference signal satisfies the above steps S341 to S342, or satisfies the above steps S351 to S352, and on the basis of determining whether the maximum value of the first temperature difference signal is smaller than the temperature difference threshold, if so, it is determined that the thermostat has a normally open fault.
Fig. 6 shows a block diagram of a thermostat normally open fault diagnosis device provided in the present application, and as can be seen from fig. 6, the thermostat normally open fault diagnosis device includes a processor 610 and a memory 620, where the memory 620 has at least one program or instruction stored therein, and the processor 610 is configured to obtain and execute the program or instruction to implement the thermostat normally open fault diagnosis method shown in any one of fig. 1 to fig. 5 in the present application. Wherein the processor 610 and the memory 620 interact with each other.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of this invention are intended to be covered by the scope of the invention as expressed herein.
Claims (14)
1. A thermostat normally open fault diagnosis method is characterized by comprising the following steps:
acquiring a first temperature change signal and a second temperature change signal in real time, wherein the first temperature change signal is a temperature variable of coolant flowing out of an engine, and the second temperature change signal is a temperature variable of the coolant in a radiator;
determining an engine start warm-up phase based on the first temperature change signal and the second temperature change signal;
calculating a first temperature difference signal between the first temperature change signal and the second temperature change signal;
in the engine starting and warming-up stage, whether the thermostat is normally open or not is judged based on the state duration of the first temperature difference signal;
the step of determining the engine start warm-up stage based on the first temperature change signal and the second temperature change signal comprises the following steps:
determining an initial moment of an engine starting phase;
determining the time when the change rate of the first temperature change signal and the change rate of the second temperature change signal are stable as the end time of the engine starting stage;
determining a phase between the initial time and the end time as the engine start phase.
2. The thermostat normally open fault diagnostic method of claim 1, wherein said step of calculating a first temperature difference signal between said first temperature change signal and a second temperature change signal comprises:
according to the formula:
ΔC(t)＝C1(t)-C2(t)，t∈[t0，t1]
calculating the first temperature difference signal, wherein Δ C (t) is a first temperature difference signal, C1(t) is a first temperature change signal, C2(t) is a second temperature change signal, t0 is an initial time of the engine start phase, and t1 is an end time of the engine start phase.
3. The thermostat normally open fault diagnostic method of claim 1, wherein said step of determining whether the thermostat normally open fault is present during the engine warm-up phase based on the state duration of the first temperature difference signal comprises:
determining a steady state accumulated time length of the first temperature difference signal in the engine starting and warming-up stage;
and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the stable state accumulated time.
4. The thermostat normally open fault diagnostic method of claim 3, wherein the step of determining a steady state cumulative duration of the first temperature difference signal during the engine warm-up phase comprises:
determining the first temperature difference signal, and a temperature difference change stable interval in the engine starting and warming-up stage;
determining the time length of the temperature difference change stable interval;
and calculating the sum of the time lengths of all the temperature difference change stable intervals, wherein the sum of the time lengths is the stable state accumulated time length of the first temperature difference signal.
5. The thermostat normally open fault diagnostic method as claimed in claim 4, wherein said step of determining a temperature difference change stability interval of said first temperature difference signal in an engine warm-up starting phase comprises:
obtaining a filtered signal of the first temperature difference signal by subjecting the first temperature difference signal to a high-pass filter;
and determining that the interval in which the signal value of the filtering signal is smaller than the filtering threshold value in the engine starting and warming-up stage is the temperature difference change stable interval of the first temperature difference signal.
6. The thermostat normally open fault diagnostic method of claim 3, wherein said step of determining whether the thermostat normally open fault is present during the engine warm-up phase based on the steady state accumulated time period comprises:
determining a total duration of the engine warm-up phase;
calculating the steady state accumulated time, wherein the steady state accumulated time accounts for the ratio of the total time of the engine starting and warming-up stages;
and when the proportion of the accumulated time length in the stable state is greater than or equal to the proportion threshold value, determining that the thermostat is in a normally open fault.
7. The thermostat normally open fault diagnostic method of claim 6, further comprising:
determining an invalid time period in the engine start-up and warm-up stage based on the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal;
subtracting the invalid time length from the total time length to obtain an effective time length of the engine starting and warming-up stage;
and calculating the ratio of the stable state accumulated duration to the effective duration to obtain the stable state accumulated duration.
8. The thermostat normally open fault diagnostic method of claim 1, wherein said step of determining whether the thermostat normally open fault is present during the engine warm-up phase based on the state duration of the first temperature difference signal comprises:
determining the accumulative duration of the unstable state of the first temperature difference signal in the engine starting and warming-up stage;
and in the engine starting and warming-up stage, judging whether the thermostat is normally open and has a fault or not based on the unstable state accumulated time.
9. The thermostat normally open fault diagnostic method as claimed in claim 8, wherein said step of determining an integrated period of non-steady state of said first temperature difference signal during said engine warm-up starting phase comprises:
determining the first temperature difference signal, wherein the temperature difference change in the engine starting and warming-up stage is an unstable interval;
determining the time length of the temperature difference change unstable interval;
and calculating the sum of the time lengths of all the temperature difference change unstable intervals, wherein the sum of the time lengths is the unstable state accumulated time length of the first temperature difference signal.
10. The thermostat normally open fault diagnostic method as claimed in claim 9, wherein said step of determining said first temperature difference signal, a temperature difference change non-steady-state interval in an engine warm-up phase, comprises:
obtaining a filtered signal of the first temperature difference signal by subjecting the first temperature difference signal to a high-pass filter;
and determining the interval in which the signal value of the filtering signal is greater than or equal to the filtering threshold value in the engine starting and warming-up stage as the unstable interval of the temperature difference change of the first temperature difference signal.
11. The thermostat normally open fault diagnostic method of claim 8, wherein said step of determining whether the thermostat normally open fault is present during the engine warm-up phase based on the cumulative length of time of the non-steady state includes:
calculating effective unstable state accumulated time length in the unstable state accumulated time length;
and in the engine starting and warming stage, when the effective unstable state accumulated time length is smaller than the unstable state accumulated time length threshold, determining that the thermostat is in a normally open fault.
12. The thermostat normally open fault diagnostic method of claim 11, further comprising: the step of calculating the effective unstable state accumulated time length in the unstable state accumulated time length includes:
determining an invalid time period in the engine start-up and warm-up stage based on the initial temperature of the first temperature change signal and the initial temperature of the second temperature change signal;
and subtracting the invalid time length from the unstable state accumulated time length to obtain the effective unstable state accumulated time length.
13. The thermostat normally open fault diagnostic method according to claim 7 or 12, wherein the invalid period of time is a length of a period of time during which the first temperature difference signal is unstable due to a temperature difference between an initial temperature of the first temperature change signal and an initial temperature of the second temperature change signal.
14. A thermostat normally open fault diagnosis device, characterized in that the thermostat normally open fault diagnosis device comprises a processor and a memory, wherein the memory stores at least one program or instruction, and the processor is used for acquiring and executing the program or instruction to realize the thermostat normally open fault diagnosis method according to any one of claims 1 to 12.
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