JP3551060B2 - Thermostat abnormality detector - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a thermostat abnormality detection device that detects the presence or absence of an abnormality in a thermostat that adjusts the temperature of a cooling medium that cools a device to be cooled.
[0002]
[Prior art]
In a device to be cooled such as an internal combustion engine for a vehicle, a thermostat is used to circulate cooling water as a cooling medium through a cooling water circulation passage and a radiator that is a heat radiating portion of the cooling medium, and to adjust the temperature of the cooling water to an appropriate temperature. I have. For example, a thermostat provided in a cooling water circulation passage that circulates cooling water between a cooling water passage (water jacket) and a radiator is used when the temperature of the cooling water as a cooling medium becomes lower than a predetermined temperature, such as during a warm-up operation immediately after engine start. When the temperature is low, the thermostat is closed to prevent the cooling water from circulating to the radiator, to obtain heat from the internal combustion engine to quickly raise the cooling water temperature to an appropriate value. When the temperature of the cooling water exceeds the appropriate temperature range, the thermostat opens, circulates the cooling water to the radiator, and the heat of the cooling water is radiated by the radiator, and the temperature of the cooling water falls to the appropriate temperature range.
[0003]
By the way, the thermostat may be stuck in a fully open state or a half open state due to deterioration of the members. In such a case, since the heat of the cooling water is constantly radiated from the radiator, the engine is in a supercooled state, and not only the efficiency of the heater is reduced, but also the fuel injection amount is increased when the engine is at a low temperature. There is a problem in that the warm-up is always performed, and the fuel consumption and the emission are deteriorated.
[0004]
In order to solve this problem, a "thermostat failure detecting device for an engine cooling system" described in Japanese Patent Application Laid-Open No. 10-184433 detects a cooling water temperature of a cooling water circulation passage of an engine by a cooling water temperature detecting means, and assumes a normal state of the thermostat. A determination value in consideration of a change in the cooling water temperature expected under the above conditions is calculated from the operating state of the internal combustion engine and the like, and the presence or absence of a thermostat failure is detected based on the cooling water temperature and the determination value detected by the cooling water temperature detection means. ing. In addition, a configuration is adopted in which the determination value and the like are corrected based on the outside air temperature that affects the heat radiation amount of the cooling water temperature.
[0005]
[Problems to be solved by the invention]
However, in the above-described conventional technology, when the determination value or the like is corrected, the correction is performed by simply taking only the outside air temperature into consideration, and thus there is a problem that the correction accuracy is poor. That is, the factor that affects the heat radiation of the cooling water temperature is the difference between the cooling water temperature and the outside air temperature, and simply correcting with the outside air temperature lacks reliability.
[0006]
The present invention has been made in view of such circumstances, and in estimating the temperature change of the cooling medium, accurately reflects the difference between the cooling medium temperature and the outside air temperature to accurately detect the presence or absence of an abnormality in the thermostat. The purpose is to do.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is a cooling medium passage formed in the device to be cooled, a heat radiating portion that radiates heat of the cooling medium, a thermostat provided in the middle of the cooling medium passage, and an operation state of the device to be cooled. Cooling medium temperature estimating means for estimating the temperature of the cooling medium, and cooling medium temperature detecting means for detecting the temperature of the cooling medium, wherein the estimated cooling medium temperature and the detected cooling medium temperature estimated by the cooling medium temperature estimating means are provided . A thermostat abnormality detecting device for detecting the presence or absence of abnormality in the thermostat based on the cooling medium temperature detected by the means, comprising an outside air temperature detecting means for detecting an outside air temperature, and a cooling medium estimating means estimated by the cooling medium estimating means. It is characterized in that a correction value obtained from a difference between the cooling medium temperature and the outside air temperature is reflected on the temperature.
[0008]
According to the above configuration, when detecting the presence or absence of a thermostat abnormality based on the estimated coolant temperature and the coolant temperature estimated by the coolant temperature estimating means, the correction value obtained from the difference between the coolant temperature and the outside air temperature is cooled. It is reflected on the estimated medium temperature. That is, the estimated cooling medium temperature is calculated based on the difference between the cooling medium and the outside air temperature, and the effect of the heat radiation of the cooling medium can be accurately estimated. Therefore, the accuracy of estimating the estimated cooling medium temperature can be improved, and the presence or absence of abnormality in the thermostat can be accurately detected.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment in which a thermostat failure diagnosis device according to the present invention is applied to a cooling system of a water-cooled automobile internal combustion engine (engine) will be described below with reference to the drawings.
[0010]
FIG. 1 is a schematic diagram showing a cooling system for a vehicular internal combustion engine to which a thermostat abnormality detection device according to the present invention is applied. As is well known, the four-cylinder engine 1 includes a piston 3 that reciprocates in a cylinder 2, a connecting rod 5 that converts the reciprocating motion of the piston 3 into a rotational motion of a crankshaft 4, and the like. A water jacket 7 is provided around the cylinder 2 and inside the cylinder head 6, and cooling water is injected into the water jacket 7. Here, the water jacket 7 corresponds to a cooling medium passage, and the cooling water corresponds to a cooling medium.
[0011]
The radiator 8 and the water jacket 7 are communicated by a cooling water circulation passage 9, and a thermostat 10 is provided at an outlet of the water jacket 7 in the cooling water circulation passage 9. The thermostat 10 is a valve that opens and closes mechanically according to the temperature of the cooling water. In this embodiment, when the temperature of the cooling water is 82 ° C. or lower, the thermostat 10 is closed and the cooling water circulation passage 9 and the water jacket 7 are closed. The communication is cut off to prevent the cooling water in the water jacket 7 from being radiated by the radiator 8. The thermostat 10 opens when the cooling water temperature exceeds 82 ° C., connects the water jacket 7 to the radiator 8 via the cooling water circulation passage 9, and radiates the heat of the cooling water by the radiator 8 to cool the cooling water. The temperature is lowered, and the engine 1 is cooled to an appropriate temperature. Here, the cooling water circulation passage 9 corresponds to a cooling medium circulation passage, and the radiator 8 corresponds to a radiator. The water temperature sensor 41 provided on the inner wall of the water jacket 7 detects the temperature THW of the cooling water, and sends a detection signal to the electronic control unit ECU 51.
[0012]
Next, an electronic control unit ECU 51 for controlling and diagnosing each part of the engine including the thermostat 10 based on the operating state of the engine 1 will be described.
[0013]
FIG. 2 is a block diagram schematically showing an engine control device. The ECU 51 includes a central processing unit CPU 52, a read-only memory ROM 53, a random access memory RAM 54, a backup RAM 55, a timer counter 56, and the like. The ECU 51 constitutes a logical operation circuit formed by connecting these components to the external input circuit 57 and the external output circuit 58 via a bus 59. Here, the ROM 53 stores in advance programs related to various kinds of operation control and failure diagnosis. The RAM 54 temporarily stores the calculation results of the CPU 52 and the like. The backup RAM 55 is a non-volatile memory that stores data even after the engine stops. The timer counter 56 can perform a plurality of timing operations simultaneously. The external input circuit 57 includes a buffer, a waveform circuit, a hard filter (a circuit including an electric resistor and a capacitor), an A / D converter, and the like. The external output circuit 58 includes a drive circuit and the like. As described above, the water temperature sensor 41 detects the cooling water temperature THW in the water jacket 7. The throttle sensor 42 detects a throttle valve opening TA in accordance with the amount of depression of an accelerator pedal (not shown). The rotation speed sensor 43 detects the rotation speed of the crankshaft 4, that is, the engine rotation speed NE. The oxygen sensor 44 detects the concentration of oxygen in the exhaust gas. The intake pressure sensor 45 detects the intake pressure. The vehicle speed sensor 46 detects a vehicle speed SPD. The intake air temperature sensor 47 detects the temperature (intake air temperature) THA of the intake air introduced into the air cleaner. The CPU 52 executes various programs stored in the ROM 53 based on the detection signals of the sensors 41 to 47, and executes various operation controls and failure diagnosis, for example, control of the fuel injection amount and fuel injection timing by the injector 48. .
[0014]
Next, among the various controls executed by the ECU 51, the contents of the control relating to the abnormality detection of the thermostat 10 will be described.
[0015]
3 and 4 show a “thermostat abnormality detection routine” according to the thermostat abnormality detection of the present embodiment. A program relating to this routine is stored in the ROM 53 of the ECU 51 in advance, and is repeated every second until the normal or abnormal state of the thermostat is determined after the ignition switch is turned “ON”.
[0016]
In this thermostat abnormality detection routine, it is determined in step 101 whether an abnormality detection execution condition is satisfied. The abnormality detection execution conditions are as follows: when the routine is first executed (that is, at the time of starting), “the cooling water temperature THW is −10 ° C. to 35 ° C.”, “the intake air temperature THA is −10 ° C. to 35 ° C.”, This is when all the conditions of “the difference between the cooling water temperature THW and the intake air temperature THA at the time of starting are −15 ° C. or more and 7 ° C. or less” are satisfied. If the abnormality detection execution condition is satisfied in step 101,
Proceeding to step 102, if the abnormality detection execution condition is not satisfied in step 101, there is a possibility of causing an erroneous determination, so that abnormality detection is not performed, and this routine ends. In the present routine, the estimation accuracy of the cooling water temperature is improved by performing the limitation at the time of starting (the limitation of cold) as described above.
In step 102, it is determined whether or not the start recognition flag F is 1. The start-time recognition flag F is initialized to 0 when the ignition switch is turned "ON". Therefore, when this routine is executed for the first time, a negative determination is made and the routine proceeds to step 103.
[0017]
In step 103, the cooling water temperature THW at that time is set as the starting cooling water temperature THWst, and the intake air temperature THA is set as the starting intake air temperature THAst. In step 104, the starting cooling water temperature THWst is compared with the starting intake air temperature THAst. If THWst ≦ THAst, the routine proceeds to step 105, where THWst is adopted as the initial value of the water temperature counter value ecthwsm and the water temperature counter raw value ecthw. If it is determined at step 104 that THWst> THAst, the routine proceeds to step 106, where THAst is adopted as the initial value of the water temperature counter value eththsm and the water temperature counter raw value ecthw. When steps 105 and 106 are executed, the start-time recognition flag F is set to 1 in step 107.
That is, by executing steps 102 to 106, the starting water temperature detected by the water temperature sensor 41 and the intake air temperature (outside temperature) detected by the intake air temperature sensor 47 are set as the initial values of the water temperature counter value ecthwsm and the water temperature counter raw value ecthw. Temperature). This is because when the intake air temperature THA is lower than the cooling water temperature THW, the cooling water temperature THW is unlikely to increase, so that the initial value of the water temperature counter value ethwsmsm should be set as low as possible, and the time to reach the determination temperature A described later should be delayed. This is because erroneous determination can be prevented.
[0018]
Subsequently, at step 108, the water temperature counter value eththwsm and the raw water temperature counter value eththw are adopted as the previous values ethwsmi-1 and ecthwi-1, respectively, and the process proceeds to step 109.
[0019]
In step 109, the difference α between the previous value of the water temperature counter value eththsm-1 and the minimum intake temperature ethamin is calculated. Here, the minimum intake air temperature value ethamin is a substitute value for the outside air temperature. That is, since the intake air temperature sensor is installed in the engine room, the value of the intake air temperature sensor indicates a value higher than the outside air temperature and does not indicate a value lower than the outside air temperature. Therefore, the minimum intake air temperature value ethamin measured by the intake air temperature sensor from the start of the start, which is considered to be closest to the outside air temperature, is adopted as the outside air temperature. The calculation method of the intake air temperature minimum value ethamin monitors the intake air temperature THA read every predetermined routine, and when the intake air temperature THA is lower than the stored intake air temperature minimum value ethamin, the intake air temperature THA is reduced to the intake air temperature minimum. The value may be updated and calculated as the value ethamin.
[0020]
When the deviation α is calculated in step 109, the process proceeds to step 110, where it is determined whether the vehicle is traveling. Here, the reason for determining whether or not the vehicle is running is as follows. The cooling capacity of the radiator is improved as the amount of air passing through the radiator is increased, and heat radiation of the cooling water is promoted. That is, as the vehicle speed increases, the amount of air passing through the radiator increases, and the influence on the heat radiation of the cooling water increases. Further, as the vehicle speed increases, the vehicle speed wind introduced into the engine room increases, and the degree of cooling of the engine body by the vehicle speed wind increases, so that the heat received from the engine by the cooling water decreases. Therefore, the behavior of the cooling water temperature THW cannot be considered in the same manner during running and during idling. In step 110, it is determined whether the vehicle is traveling or idle. If the vehicle is traveling, the process proceeds to step 112. If the vehicle is idle, the process proceeds to step 111. For example, when the vehicle speed SPD obtained by the vehicle speed sensor 46 is 3 km / h or more, it is determined that the vehicle is traveling, and when the vehicle speed is less than 3 km / h, it is determined that the vehicle is idling.
[0021]
In step 112, it is determined whether or not the fuel is being cut. If the fuel is being cut, the process proceeds to step 113. If the fuel is not being cut but the fuel is being injected, the process proceeds to step 114. During the fuel cut, the calorific value of the engine is almost 0, and only the heat radiation term should be taken into account as a factor affecting the cooling water temperature. In addition, the influence of the cooling water temperature due to the heat generated by the engine must be taken into account. Therefore, even if the difference between the cooling water temperature and the outside air temperature is the same, the behavior of the cooling water temperature is completely different during fuel cut and during fuel injection.
[0022]
In step 111, the counter addition value Δ is obtained from the map 1 shown in FIG. 6 based on the deviation α. Similarly, in step 113 and step 114, the counter addition value Δ is obtained from map2 and map3 shown in FIGS. 7 and 8, respectively . Map1,2,3 in here are those that you created experimentally, it is different by vehicle.
[0023]
During fuel injection, the amount of heat generated from the engine varies depending on the amount of air-fuel mixture introduced into the combustion chamber. Therefore, the rate of rise in cooling water temperature, which is a heat radiation term, is affected by the difference between the outside air temperature and the cooling water temperature. Therefore, during traveling during fuel injection, the counter addition value Δ is determined by a two-dimensional map taking into account the difference α (ecthwsm-ethamine) between the cooling water temperature and the outside air temperature and the intake air amount, such as map3 shown in FIG. I do. For example, even if the value of the difference α between the cooling water temperature and the outside air temperature is the same, the counter addition value Δ increases as the intake air amount increases. That is, the water temperature counter value ethwsmsm increases.
[0024]
Further, the map may be changed depending on the vehicle speed (for example, 0 to 20 km / h, 20 to 40 km / h, and 40 to 60 km / h) during fuel cut and during fuel injection, respectively. By taking into account the vehicle speed, the effect of the vehicle speed wind on the engine cooling degree can be taken into account. Therefore, the effect on the behavior of the cooling water temperature THW can be obtained with higher accuracy, and the water temperature counter change amount α can be calculated with higher accuracy. For example, as the vehicle speed increases, the cooling capacity of the radiator improves, and the airflow on the engine body increases, so that the degree of cooling of the engine increases. That is, as the vehicle speed increases, the rate of increase of the cooling water temperature THW decreases.
[0025]
After obtaining the counter addition value Δ in steps 111, 113, and 114, the process proceeds to step 115, and the water temperature counter calculation is performed by adding the currently obtained counter addition value Δ to the water temperature counter raw value ecthwi−1 determined in the previous routine. formula,
ecthw = ecthwi-1 + (counter added value Δ)
Then, the current water temperature counter raw value ecthw is calculated, and the process proceeds to step 116.
[0026]
In step 116, a heat conduction delay process (smoothing process) is performed on the current water temperature counter value ethwi calculated in step 115 by the following equation.
ecthwsm =
ecthwsmi-1 + (ecthwi-ecthwsmi-1) / (average rate)
The heat conduction delay processing as described above is performed to determine the water temperature counter value eththwsm.
[0027]
In step 117, if the water temperature counter value eththwsm calculated in step 116 is lower than the determination water temperature A, the process proceeds to step 118 for performing a normal determination of the thermostat. If the water temperature counter value eththwsm is equal to or higher than the determination water temperature A, the process is terminated. The process proceeds to step 120 for performing abnormality determination. Here, the determination water temperature A is a predetermined determination temperature for performing abnormality detection of the thermostat 10, and is a criterion for opening the thermostat 10 in consideration of a valve opening temperature error of the thermostat and a detection error of the water temperature sensor. The temperature is set 7 to 10 ° C lower than the temperature (82 ° C as a standard). That is, the determination water temperature A is a criterion for performing a thermostat abnormality determination, and the lower limit value that the thermostat valve opening temperature can take in consideration of the component tolerance in order to prevent erroneous determination due to the component tolerance is set as the determination water temperature A. Further, the value of the determination water temperature A also coincides with the value of the cooling water temperature at which failure diagnosis other than the thermostat 11 (for example, failure diagnosis of the oxygen sensor 44) is permitted.
[0028]
In step 118, if the output value of the water temperature sensor 41, that is, the actual cooling water temperature THW is lower than the determination water temperature A used in step 117, the fault diagnosis is temporarily terminated. If the actual cooling water temperature THW is equal to or higher than the determination water temperature A, the process proceeds to step 119, where it is determined that the thermostat 10 is operating normally, and the routine is terminated. That is, as shown in FIG. 5, before the water temperature counter value ethwsms estimated from the parameters contributing to the calorific value of the engine 1 and the parameters contributing to heat radiation rises to the determination water temperature A, the actual cooling water temperature THW becomes equal to the determination water temperature A. This is because the thermostat 11 is considered to be operating properly without failure and the cooling water temperature THW is appropriately rising. When the normality determination is made in step 119 and this routine processing is ended, the ECU 51 prohibits the execution of the interrupt of the routine processing again.
[0029]
If it is determined in step 117 that the water temperature counter value eththwsm is equal to or greater than A, the process proceeds to step 120, where it is determined that "there is an abnormality in the thermostat 10." That is, even though the water temperature counter value eththwsm estimated from the parameters contributing to the calorific value of the engine 1 and the parameters contributing to heat radiation is equal to or higher than the determination water temperature A, the normal determination of the thermostat is performed in step 119 to detect the abnormality of the thermostat. If the routine is not finished, the thermostat 10 is fixed in the valve open state, the cooling water circulation passage and the radiator are kept in communication, the cooling water continues to radiate heat from the radiator, and the cooling water temperature THW does not rise properly. It is considered that. That is, as shown in FIG. 5, if the thermostat is normal, before the water temperature counter value eththwsm reaches the determination water temperature A, the cooling water temperature THW always reaches the determination water temperature A, and a normality determination is made in step 119. The detection routine ends. However, if the cooling water temperature THW is lower than the determination water temperature A after the water temperature counter value eththwsm reaches the determination water temperature A, that is, if this routine is not completed, it is determined that the thermostat is abnormal. Then, when it is determined in step 120 that the thermostat has an abnormality, the thermostat abnormality detection routine is terminated, and execution of another interrupt to this routine is prohibited. Then, a warning is given to the driver by turning on a warning light.
[0030]
According to the above-described embodiment of the present invention, the water temperature counter value eththwsm is calculated based on the deviation α between the water temperature counter value eththsmi−1 and the intake air temperature minimum value ethamin. That is, based on the difference between the cooling water temperature and the outside air temperature, the water temperature counter value ecthwsm, in other words, the cooling water temperature value when the thermostat 10 is normal is calculated. Therefore, the cooling water temperature value (water temperature counter value eththsm) that accurately reflects the influence of the cooling water radiation can be calculated in consideration of the cooling water temperature and the temperature gradient between the outside air temperature, and thus a more accurate and reliable thermostat can be calculated. Anomaly detection can be performed.
[0031]
In the above-described embodiment, the water temperature counter value ecthwsm was calculated from the deviation α between the water temperature counter value ethwsmi-1 and the intake air temperature minimum value ethamine. However, the water temperature counter value ethwsmi-1 is set as the actual cooling water temperature THW, The water temperature counter value ecthwsm may be obtained from the deviation of the intake air temperature minimum value ethamin. Further, the outside air temperature may be directly used instead of the intake air temperature minimum value ethamin.
[0032]
Hereinafter, preferred embodiments of the present invention will be described below.
[0033]
Aspect 1
2. The thermostat abnormality detecting device according to claim 1, wherein the minimum value of the intake air temperature is used as the outside air temperature. With this configuration, the outside air temperature can be detected without providing an outside air temperature sensor.
Aspect 2
2. The thermostat abnormality detecting device according to claim 1, wherein a difference between the cooling medium temperature and the outside air temperature is a difference between the estimated cooling medium temperature and the outside air temperature estimated by the cooling medium temperature estimating means. In this configuration, since the difference between the estimated cooling medium temperature and the outside air temperature is used as a factor affecting the heat radiation of the cooling medium, the cooling medium temperature is lower than when the difference between the actual cooling medium temperature and the outside air temperature is used. The estimation accuracy is increased.
[0034]
Aspect 3
2. The abnormality detection device for a thermostat according to claim 1, wherein the actual cooling medium temperature exceeds the predetermined judgment value before the estimated cooling medium temperature estimated by the cooling medium temperature estimating means exceeds a predetermined judgment value. In this case, the thermostat is determined to be normal at that time, and the actual cooling medium temperature remains at the predetermined determination value until the estimated cooling medium temperature estimated by the cooling medium temperature estimation means exceeds the predetermined determination value. If the temperature does not exceed, the thermostat abnormality detection device determines that the thermostat is abnormal. According to this configuration, when the cooling medium temperature exceeds the determination value before the estimated cooling medium temperature exceeds the predetermined determination value, it is determined that the temperature is normal and the abnormality detection is terminated, so that the detection time can be reduced.
[0035]
It is needless to say that any one of the above-described embodiments 1 to 3 may be combined with each other or all of them.
[0036]
【The invention's effect】
When detecting the presence or absence of a thermostat failure based on the estimated coolant temperature and the coolant temperature estimated by the coolant estimation means, a correction value obtained from the difference between the coolant temperature and the outside air temperature is used as the estimated coolant temperature. To reflect. Therefore, it is possible to accurately estimate the influence of heat radiation of the cooling medium, improve the accuracy of estimating the estimated cooling medium temperature, and accurately detect the presence or absence of abnormality in the thermostat.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing an example of a cooling system for a vehicle internal combustion engine to which a thermostat abnormality detection device according to an embodiment of the present invention is applied.
FIG. 2 is a block diagram schematically showing a control device for a vehicle internal combustion engine according to an embodiment of the present invention.
FIG.
FIG. 4 is a flowchart showing a procedure for detecting a thermostat abnormality in the embodiment of the present invention.
FIG. 5 is a time chart showing an example of a change in cooling water temperature and a change in water temperature counter value after engine start according to the embodiment of the present invention. FIG. 6: Correction during idling in the second embodiment of the present invention. Map 1
FIG. 7 is a correction map 2 of F / C = ON during traveling according to the second embodiment of the present invention.
FIG. 8 is a correction map 3 of F / C = OFF during traveling in the second embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Engine, 2 ... Cylinder, 3 ... Piston, 4 ... Crankshaft, 5 ... Connecting rod, 6 ... Cylinder head, 7 ... Water jacket, 8 ... Radiator, 9 ... Cooling water circulation passage, 10 ... Thermostat, 41 ... Water temperature sensor, 42 ... Throttle sensor, 43 ... Rotation sensor, 44 ... Intake pressure sensor, 45 ... Oxygen sensor, 46 ... Vehicle speed sensor, 47 ... Intake temperature sensor, 51 ... ECU, 52 ... CPU, 53 ... ROM, 54 ... RAM, 55 ... Backup RAM, 56: timer counter, 57: external input circuit, 58: external output circuit, 59: bus

Claims (1)

A cooling medium passage formed in the device to be cooled, a radiator for radiating heat of the cooling medium, a thermostat provided in the middle of the cooling medium passage, and cooling for estimating a temperature of the cooling medium based on an operation state of the device to be cooled. a medium temperature estimating means, and a cooling medium temperature detecting means for detecting the temperature of the cooling medium, the cooling medium temperature detected coolant estimated temperature and estimated by the estimating means by said coolant temperature detecting means cooling medium temperature A thermostat abnormality detecting device for detecting the presence or absence of an abnormality in the thermostat based on an external air temperature detecting means for detecting an external air temperature, and a cooling medium estimated temperature estimated by the cooling medium estimating means; abnormality detection apparatus for a thermostat, characterized in that to reflect the correction value obtained from the difference between the air temperature.

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