JP2007224804A - Leak check device and leak check method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a leak check device and leak check method performing accurate leak check even in a case that temperature of an inside of a fuel tank is low. <P>SOLUTION: A temperature sensor 30 and a pressure sensor 40 are attached to a fuel tank 10, detect temperature and pressure of the inside of the fuel tank 10 respectively and output detection signal to ECU 60. A ceramic heater 50 is installed under fuel in the fuel tank 10. The ceramic heater 50 heats fuel in the fuel tank 10 and raises temperature of the inside of the fuel tank 10 when electricity carry to the same is turned on. The ECU 60 measures temperature of the inside of the fuel tank 10 from the detection signal of the temperature sensor 30. The ECU 60 electrifies the ceramic heater 50 and performs leak check after raising temperature of the inside of the fuel tank 10 to a normal range when temperature of the inside of the fuel tank 10 is lower than a predetermined low limit temperature. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a leak check apparatus and a leak check method for checking an evaporative system leak based on a pressure change of an evaporative system that purges evaporated fuel generated in a fuel tank into an intake passage of an internal combustion engine.

2. Description of the Related Art Conventionally, in a leak check device for checking an evaporative leak that purges evaporated fuel generated in a fuel tank into an intake passage, for example, by detecting a pressure change over time of a sealed evaporative system after the internal combustion engine is stopped. It is known to perform an evaporative leak check (see, for example, Patent Document 1).
By the way, if the temperature in the fuel tank has not risen to a predetermined temperature, the amount of evaporated fuel generated in the fuel tank is small, so that the pressure in the evaporation system does not rise sufficiently. When the evaporation system pressure is low in this way, the pressure near the boundary between normal and abnormal leaks can be determined with high accuracy, for example, due to errors in the detection signal of the pressure sensor or changes in the surrounding environment during the leak check. Is difficult. In such a state, if the pressure of the evaporation system is detected and a leak check is performed, there is a possibility that the leak is erroneously determined.

  In Patent Document 1, the leak check is canceled if the temperature in the fuel tank does not rise above a predetermined temperature. However, if the leak check is canceled, the frequency of the leak check is reduced, so that there is a problem that the leak cannot be detected at an early stage even if a leak occurs in the evaporation system.

US Pat. No. 6,321,727

  The present invention has been made to solve the above problem, and an object of the present invention is to provide a leak check device and a leak check method that perform a leak check with high accuracy even when the temperature in the fuel tank is low.

  According to the first to seventh aspects of the present invention, when the temperature in the fuel tank is lower than the predetermined lower limit temperature, the evaporation system in which the temperature in the fuel tank is raised to the lower limit temperature or more and then the opening / closing portion is closed. A leak check is performed based on the pressure change. By raising the temperature in the fuel tank above a predetermined lower limit temperature, the amount of evaporated fuel generated in the fuel tank increases and the pressure in the evaporation system rises. As a result, it becomes easy to determine the pressure near the boundary between normal and abnormal leaks, so that erroneous determination of leaks can be reduced, and evaporation leaks can be checked with high accuracy.

Even when the temperature inside the fuel tank is low, the leak check is performed by forcibly raising the temperature inside the fuel tank above the specified lower limit temperature without canceling the leak check. Rises. Therefore, an evaporative leak abnormality can be detected early.
According to the invention described in claim 2, since the temperature in the fuel tank is raised by the heater installed in the fuel tank, the temperature in the fuel tank rises quickly. Therefore, the leak check time can be shortened.

Here, if the temperature in the fuel tank is too high, the temperature variation in the fuel tank increases due to changes in the surrounding environment, and as a result, the pressure fluctuation in the evaporation system also increases. In such a state, it is difficult to perform a leak check of the evaporation system with high accuracy based on the pressure change of the evaporation system.
Therefore, according to the invention described in claim 3, when the temperature in the fuel tank is higher than the predetermined upper limit temperature, the pressure of the evaporation system in which the temperature in the fuel tank is lowered below the upper limit temperature and then the opening / closing portion is closed. Check for leaks based on changes. By lowering the temperature in the fuel tank below a predetermined upper limit temperature, temperature fluctuations in the fuel tank when performing a leak check are prevented from becoming too large. As a result, the pressure fluctuation of the evaporation system is prevented from becoming too large, so that the leakage of the evaporation system can be checked with high accuracy.

  According to the fifth and seventh aspects of the invention, since the leak check is performed in a state where the fuel in the fuel tank after the internal combustion engine is stopped is warmed, for example, the fuel in the fuel tank is warmed immediately after the start of the internal combustion engine. The temperature in the fuel tank can be raised to the lower limit temperature or higher in a shorter time than when the state is not set. Therefore, the leak check time can be shortened.

  The functions of the plurality of means provided in the present invention are realized by hardware resources whose functions are specified by the configuration itself, hardware resources whose functions are specified by a program, or a combination thereof. Further, the functions of the plurality of means are not limited to those realized by hardware resources that are physically independent of each other.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(Evaporation system)
In FIG. 1, the fuel tank 10 and the canister 12 are connected by a passage 100, and the canister 12 and the intake passage 16 on the downstream side of the throttle valve 18 are connected by a purge passage 102. A purge valve 14 is installed in the purge passage 102. The evaporated fuel generated in the fuel tank 10 passes through the passage 100 and is adsorbed by an adsorbent such as activated carbon in the canister 12. The purge valve 14 is an electromagnetic valve, and the amount of evaporated fuel purged from the canister 12 to the intake passage 16 is adjusted by controlling the opening of the purge valve 14 by duty ratio control or the like. The purge valve 14 is closed with the power off. The on-off valve 20 that opens and closes the atmosphere opening side of the canister 12 is an electromagnetic valve. The on-off valve 20 is opened with the power off, and the canister 12 is opened to the atmosphere. The purge valve 14 and the opening / closing valve 20 are an evaporation system opening / closing portion constituted by the fuel tank 10, the canister 12, the purge valve 14, the opening / closing valve 20, the passage 100, and the purge passage 102.

(Leak check device)
A leak check device according to an embodiment of the present invention includes a temperature sensor 30, a pressure sensor 40, a ceramic heater 50, and an engine control device (hereinafter referred to as ECU) 60. The leak check device performs the evaporative leak check described above. The temperature sensor 30 and the pressure sensor 40 are attached to the fuel tank 10, detect the temperature and pressure in the fuel tank 10, respectively, and output detection signals to the ECU 60 as check means. The pressure sensor 40 is not limited to the fuel tank 10 and may be installed anywhere in the evaporation system as long as it can detect the above-described evaporation system pressure. A ceramic heater 50 as a heater as a temperature raising means is installed in the fuel of the fuel tank 10. When energized, the ceramic heater 50 heats the fuel in the fuel tank 10 and raises the temperature in the fuel tank 10.

  The ECU 60 has a CPU, a ROM, an I / O interface, and the like. The ECU 60 controls the opening and closing of the purge valve 14 and the on-off valve 20 by the CPU executing a control program recorded in the ROM, inputs detection signals from the temperature sensor 30 and the pressure sensor 40, and energizes the ceramic heater 50. Control.

(Leak check)
Next, the operation of the leak check device will be described. FIG. 2 shows a change in pressure of the evaporation system in accordance with the amount of leak after the internal combustion engine is stopped, and FIG. 3 shows a flowchart of a leak check. The pressure of the evaporation system is measured by the ECU 60 from the detection signal of the pressure sensor 40.
(1) First, the ECU 60 determines in step 300 in FIG. 3 whether the internal combustion engine has stopped. When the internal combustion engine stops, the energization to the purge valve 14 and the on-off valve 20 is turned off. That is, the purge valve 14 is closed and the on-off valve 20 is opened.

(2) When the internal combustion engine stops, the ECU 60 measures the temperature in the fuel tank 10 from the detection signal of the temperature sensor 30 (step 302). In step 304, the temperature in the fuel tank 10 is equal to or higher than a predetermined lower limit temperature. It is determined whether it is in a normal range below a predetermined upper limit temperature.
(3) If the temperature in the fuel tank 10 is within the normal range, the ECU 60 turns off the energization to the ceramic heater 50 if the energization to the ceramic heater 50 is turned on in Step 306, and the on-off valve in Step 308. The energization to 20 is turned on and the on-off valve 20 is closed. Since the purge valve 14 has already been closed, by closing the opening / closing valve 20 in step 308, the opening / closing position of the evaporation system is closed and the evaporation system is sealed.

  (4) When the evaporation system is sealed, the ECU 60 checks the pressure change of the evaporation system from the detection signal of the pressure sensor 40 in step 310. FIG. 2 shows an example of an evaporative pressure change measured from the detection signal of the pressure sensor 40. A curve 200 indicates a characteristic in which there is no leakage in the evaporation system including the purge valve 14 and the on-off valve 20 in a state where the purge valve 14 and the on-off valve 20 are closed.

  Curves 202, 204, and 206 indicate that the amount of evaporation leakage increases in this order. The ECU 60 sets the boundary pressure between normal (OK) and abnormal (NG) leakage according to the temperature in the fuel tank 10 measured from the detection signal of the temperature sensor 30. Then, the time change of the evaporation system pressure measured from the detection signal of the pressure sensor 40 is compared with the map of the pressure change corresponding to the passage of time stored in the ROM of the ECU 60 or the like, and the evaporation system leak check is performed. Instead of the correspondence map of time and pressure, the pressure may be approximated by a function of time and compared with the pressure change of the evaporation system. In FIG. 2, the ECU 60 determines that the characteristics of the curves 200 and 202 are normal, and determines that the curves 204 and 206 are abnormal. Moreover, the leak diameter of the evaporation system can be measured by comparing with the correspondence map or the approximate function.

  Here, when the temperature in the fuel tank 10 is low, the amount of evaporated fuel generated in the fuel tank 10 is small, and the pressure in the evaporation system is not sufficiently increased. In this state, the characteristic pressures of the curves 200, 202, 204, and 206 shown in FIG. 2 and the boundary pressure between normal and abnormal leaks are reduced as a whole. It becomes difficult to determine abnormality. On the other hand, if the leak check is canceled in order to prevent such an erroneous determination due to the temperature in the fuel tank 10 not rising sufficiently, the frequency of the leak check decreases.

  (5) Therefore, if the temperature in the fuel tank 10 is not in the normal range in step 304 in FIG. 3, the ECU 60 determines in step 312 that the temperature in the fuel tank 10 is lower than the predetermined lower limit temperature. Then, the energization of the ceramic heater 50 is turned on to raise the temperature in the fuel tank 10. Since the inside of the fuel tank 10 is heated by 50 with the ceramic heater installed in the fuel tank 10, the temperature in the fuel tank 10 rises rapidly. Therefore, the time required to raise the temperature in the fuel tank 10 can be shortened.

When the energization to the ceramic heater 50 is turned on in step 314, the ECU 60 shifts the process to step 304 and turns on the energization to the ceramic heater 50 until the temperature in the fuel tank 10 rises and reaches the normal range.
As described above, when the temperature in the fuel tank 10 is lower than the predetermined lower limit temperature, the temperature in the fuel tank 10 is forcibly increased by increasing the temperature in the fuel tank 10 with the temperature increasing means such as the ceramic heater 50. To increase the evaporation system pressure. Therefore, the evaporative leak check can be performed with high accuracy without canceling the leak check and without making a false determination based on the detection signal of the pressure sensor 40.

  (6) The ECU 60 determines that the temperature in the fuel tank 10 is not in the normal range in step 304, and the temperature in the fuel tank 10 is not lower than the predetermined lower limit temperature in step 314, that is, the temperature in the fuel tank 10 is predetermined. When the temperature is higher than the upper limit temperature, the process returns to the determination process of step 304. In this case, since the on-off valve 20 serving as the temperature lowering means is open, the fuel temperature in the fuel tank 10 decreases as the fuel in the fuel tank 10 higher than the upper limit temperature evaporates as vaporized fuel. Then, when the temperature in the fuel tank 10 decreases and reaches the normal range, the process proceeds to step 306 and the subsequent steps, and a leak check is performed.

(Other embodiments)
In the above embodiment, when the temperature in the fuel tank 10 is higher than the upper limit temperature, the fuel tank 10 waits until the temperature in the fuel tank 10 decreases due to the heat of vaporization of the evaporated fuel and reaches the normal range. If the temperature in the fuel tank 10 falls and does not reach the normal range even after the standby time has passed, the processing in FIG. 3 may be stopped. Further, the processing when the temperature in the fuel tank 10 is higher than the upper limit temperature may be omitted.

Further, when the temperature in the fuel tank 10 is higher than the upper limit temperature, in addition to the heat of vaporization of the evaporated fuel, the temperature in the fuel tank 10 may be lowered by a cooler as a temperature lowering means installed in the fuel tank 10. Good.
In the above embodiment, the leak check is performed after the internal combustion engine is stopped. However, even when the leak check is performed during the operation including when the internal combustion engine is started, the fuel is increased by the temperature increasing means or the temperature decreasing means. The leak check may be performed after the temperature in the tank is set within the normal range. Thus, by performing a leak check during the operation of the internal combustion engine, the number of leak checks is increased, so that a leak can be detected early.
As described above, the present invention is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.

The typical block diagram which shows the leak check apparatus by this embodiment. The characteristic view which shows the pressure change of an evaporation system. The flowchart of a leak check.

Explanation of symbols

10: fuel tank (evaporation system), 12: canister (evaporation system), 14: purge valve (evaporation system), 16: intake passage, 20: on-off valve (evaporation system, temperature lowering means), 30: temperature sensor, 40 : Pressure sensor, 50: ceramic heater (temperature raising means), 60: ECU (check means), 100: passage (evaporation system), 102: purge passage (evaporation system)

Claims (7)

In the leak check device for checking the leakage of the evaporation system that purges the evaporated fuel generated in the fuel tank into the intake passage of the internal combustion engine based on the pressure change of the evaporation system with the opening / closing portion closed,
A pressure sensor for detecting the pressure of the evaporation system;
A temperature sensor for detecting the temperature in the fuel tank;
Temperature raising means for raising the temperature in the fuel tank;
A detection signal of the temperature sensor is determined, and if the temperature in the fuel tank is equal to or higher than a predetermined lower limit temperature, the opening / closing portion is closed and a leak check is performed based on the detection signal of the pressure sensor, When the temperature of the fuel tank is lower than the lower limit temperature, the temperature increase means raises the temperature in the fuel tank to the lower limit temperature or higher, and then closes the open / close position and performs a leak check based on the detection signal of the pressure sensor. Checking means for performing
A leak check device comprising:   The leak check apparatus according to claim 1, wherein the temperature raising means includes a heater that is installed in the fuel tank and raises the temperature in the fuel tank. A temperature lowering means for lowering the temperature in the fuel tank;
The check means determines a detection signal of the temperature sensor, and if the temperature in the fuel tank is equal to or higher than the lower limit temperature and equal to or lower than a predetermined upper limit temperature, the opening / closing portion is closed and the pressure sensor is detected. A leak check is performed based on the signal, and when the temperature in the fuel tank is higher than the upper limit temperature, the temperature lowering means lowers the temperature in the fuel tank below the upper limit temperature, and then the opening / closing portion is opened. The leak check device according to claim 1, wherein the leak check device is closed and performs a leak check based on a detection signal of the pressure sensor.   The check means determines a detection signal of the temperature sensor, and when the temperature in the fuel tank is higher than the upper limit temperature, keeps the evaporation system open, and the temperature in the fuel tank is higher than the upper limit temperature. The leak check device according to claim 3, wherein after waiting until the temperature falls, the evaporation system is sealed and a leak check is performed based on a detection signal of the pressure sensor.   The leak check device according to any one of claims 1 to 4, wherein the check unit performs a leak check by determining a detection signal of the temperature sensor after the internal combustion engine is stopped. In the leak check method for checking the leakage of the evaporation system that purges the evaporated fuel generated in the fuel tank into the intake passage of the internal combustion engine based on the pressure change of the evaporation system with the open / close position closed,
When the temperature in the fuel tank is equal to or higher than a predetermined lower limit temperature, a leak check is performed based on a pressure change in the evaporation system with the opening / closing portion closed, and the temperature in the fuel tank is lower than the lower limit temperature A leak check method for performing a leak check based on a change in pressure of the evaporation system with the opening / closing portion closed after raising the temperature in the fuel tank to the lower limit temperature or higher. The leak check method according to claim 6, wherein a leak check is performed by determining a temperature in the fuel tank after the internal combustion engine is stopped.

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