JP2012229636A - Fuel tank system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel tank system that can reliably suppress fuel vaporization in a fuel pump.SOLUTION: When an tank inner pressure in the fuel tank 14 lowers, a pressurizing unit is driven to pressurize the fuel tank so that the tank inner pressure becomes the sum of a fuel vapor pressure and a pressure loss in a fuel inlet port of the fuel pump.

Description

  The present invention relates to a fuel tank system.

  The fuel in the fuel tank is sent to the engine etc. by the fuel pump, but when the fuel is vaporized in the fuel pump, the drive of the fuel pump is affected by bubbles (so-called “vapor lock phenomenon”). It is desirable to suppress this.

  For example, Patent Document 1 describes a technique in which when the fuel temperature exceeds a predetermined temperature, the on-off valve that communicates the canister and the atmosphere is closed to increase the tank internal pressure, thereby suppressing fuel vaporization.

  By the way, because of the structure of the fuel pump, the internal pressure of the fuel pump may be lower than the internal pressure of the fuel tank (pressure loss occurs) at the fuel inlet portion, for example, because the fuel passes through the filter. For this reason, for example, when the vapor pressure of the fuel is high and the internal pressure of the fuel tank is low, the fuel is easily vaporized in the fuel pump (inlet portion). Even in such a situation, it is desired to more reliably suppress fuel vaporization.

JP 2005-214135 A

  An object of the present invention is to obtain a fuel tank system that can more reliably suppress fuel vaporization in a fuel pump in consideration of the above facts.

  According to the first aspect of the present invention, a fuel tank for storing fuel, a fuel pump for delivering fuel in the fuel tank to the outside, a pressurizing means capable of pressurizing the fuel tank, and tank internal pressure Has a control device for driving the pressurizing means so as to be equal to or higher than the sum of the fuel vapor pressure and the pressure loss at the fuel inlet of the fuel pump.

  In this fuel tank system, the control device drives the pressurizing means to pressurize the fuel tank so that the tank internal pressure becomes equal to or higher than the sum of the fuel vapor pressure and the pressure loss at the fuel inlet of the fuel pump. For this reason, at the fuel inlet portion of the fuel pump, even if there is a pressure loss, the fuel pressure is maintained higher than the fuel vapor pressure. For this reason, the vaporization of the fuel in a fuel pump can be suppressed effectively.

  According to a second aspect of the present invention, in the first aspect of the invention, a failure diagnosis pressurizing pump capable of pressurizing the inside of the fuel tank for failure diagnosis is provided, and the pressurizing means is configured to add the fault diagnosis. It is a pressure pump.

  A fuel tank system failure can be detected by pressurizing the inside of the fuel tank (which may include other parts) by a failure diagnosis pressurizing pump.

  Since the fault diagnosis pressurizing pump also serves as the pressurizing means, there is no need to add a pressurizing means. Further, the pressurizing means is driven by the control device to pressurize the inside of the fuel tank during vehicle travel, but the failure diagnosis pressurization pump is not driven during vehicle travel. That is, it is possible to perform both the pressurizing operation and the failure diagnosis in the fuel tank by using one failure diagnosis pressurizing pump.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, a canister that adsorbs and desorbs evaporated fuel generated in the fuel tank with an adsorbent, and a negative pressure of the engine is the canister. A purge pipe for acting on the canister, and the control device suppresses the negative pressure acting on the canister while the pressurizing means is being driven.

  The evaporated fuel in the fuel tank can be adsorbed by the adsorbent of the canister, and the adsorbed evaporated fuel can be desorbed and sent to the engine by the negative pressure from the engine.

  The control device suppresses the negative pressure acting on the canister during driving of the pressurizing means (preferably the negative pressure does not act at all). As a result, the tank internal pressure (pressurization by the pressurizing means) can be prevented from escaping to the canister, and the tank internal pressure can be easily maintained.

  According to a fourth aspect of the present invention, in the first aspect of the present invention, the tank temperature sensor that detects the temperature of the fuel tank, and the tank internal pressure that detects the internal pressure of the fuel tank. An actual fuel from the tank internal pressure detected by the tank internal pressure sensor and the tank temperature detected by the tank temperature sensor on the basis of a preset fuel vapor pressure. The vapor pressure is estimated and the pressurizing means is driven based on the estimation result.

  In general, the fuel vapor pressure varies depending on the type of fuel. Therefore, the fuel vapor pressure is set in advance, and the actual fuel vapor pressure is estimated from the tank internal pressure detected by the tank internal pressure sensor and the tank temperature detected by the tank temperature sensor. Thereby, the fuel vapor pressure can be known with higher accuracy. And it becomes possible to suppress vaporization of the fuel in a fuel pump, without pressurizing the inside of a fuel tank too much.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the control device can detect an operating current of the fuel pump, and based on a change in the current. To drive the pressurizing means.

  When the fuel is going to vaporize, the driving load of the fuel pump also changes, and this appears as the current value of the fuel pump. Since the control device drives the pressurizing means based on the change in the current value, it can know the sign of fuel vaporization and can suppress the fuel vaporization according to the actual situation.

  Since the present invention is configured as described above, a fuel tank system capable of more reliably suppressing fuel vaporization in the fuel pump can be obtained.

It is a schematic structure figure showing the fuel tank system of a 1st embodiment of the present invention. It is a graph which shows the relationship between the fuel vapor pressure curve in the fuel tank system of 1st Embodiment of this invention, the pressure loss in a fuel pump, and the pressurization amount of a fuel tank. It is a graph which shows the various patterns of the vapor pressure curve of the fuel in the fuel tank system of 1st Embodiment of this invention.

  FIG. 1 shows a fuel tank system 12 according to a first embodiment of the present invention. The fuel tank system 12 includes a fuel tank 14 that can store fuel therein. A fuel pump 16 is provided in the fuel tank 14, and when the fuel pump 16 is driven by the control device 18, fuel is sent to the engine through the fuel delivery pipe 20. In the fuel tank system 12 of the present embodiment, the control device 18 can detect a temporal change (current waveform) of the operating current of the fuel pump 16.

  A suction filter 24 is attached to the lower part of the fuel pump 16 (pump inlet 22). The fuel in the fuel tank 14 flows into the fuel pump 16 from the pump inlet 22 through the suction filter 24, so that foreign matters in the fuel are removed.

  Further, the fuel tank system 12 has a canister 26. The fuel tank 14 and the canister 26 are communicated with each other through a vapor pipe 28. In the canister 26, an adsorbent (activated carbon or the like) capable of adsorbing evaporated fuel is accommodated. The canister 26 is connected to an air release pipe 30. When the gas containing the evaporated fuel in the fuel tank 14 is sent to the canister 26, the evaporated fuel is adsorbed by the adsorbent in the canister 26. Then, the gas from which the evaporated fuel is removed is discharged from the atmosphere open pipe 30 into the atmosphere.

  Further, a purge pipe 32 that communicates with the engine is connected to the canister 26. The purge pipe 32 is provided with a purge opening / closing valve 34 controlled by the control device 18. When the engine is driven, the purge open / close valve 34 is opened to apply the negative pressure of the engine to the canister 26, so that the evaporated fuel adsorbed by the adsorbent in the canister 26 is desorbed (purged) and Can send.

  A tank internal pressure sensor 36 capable of detecting the tank internal pressure and a tank temperature sensor 38 capable of detecting the tank internal temperature are attached to the fuel tank 14. Data of the tank internal pressure and the tank internal temperature detected by these sensors are sent to the control device 18.

  The atmospheric discharge pipe 30 of the canister 26 is provided with a failure diagnosis pressurizing pump 40. The failure diagnosis pressurizing pump 40 is controlled by the control device 18 and can pressurize the fuel tank 14 through the canister 26 under specific conditions such as when the vehicle is stopped. Then, by detecting the tank internal pressure at the time of pressurization by the tank internal pressure sensor 36, a failure diagnosis of the fuel tank 14 can be performed.

  Next, the operation and action of the fuel tank system 12 of this embodiment will be described.

  When the fuel pump 16 is driven by the control device 18, the fuel in the fuel tank 14 is sent to the engine or the like through the fuel delivery pipe 20. Here, pressure loss occurs at the pump inlet portion 22 of the fuel pump 16 due to the passage of fuel through the suction filter 24 and the like. That is, the pressure at the pump inlet 22 of the fuel pump 16 is lower than the tank internal pressure in the fuel tank 14 by this pressure loss. Therefore, when the fuel vapor pressure is higher than the fuel pressure at the pump inlet portion 22 due to the above pressure loss in a state where the fuel vapor pressure is high and the tank internal pressure is low, the fuel is vaporized at the pump inlet portion 22 ( Cavitation occurs). Thereby, there is a possibility that the fuel cannot be sucked by the fuel pump 16.

For example, as shown in FIG. 2, when the fuel in the fuel tank 14 has the vapor pressure characteristic indicated by the curve A, for example, the pressure loss ΔP at the pump inlet portion 22 with respect to the tank internal pressure P _0. Therefore, the actual pressure is P ₁ = P ₀ −ΔP. Therefore, in the example of the graph of FIG. 2, fuel vaporization does not occur when the temperature is in the range of T ₀ or less, but there is a possibility that fuel vaporization occurs when the temperature exceeds the temperature T ₀ . Even if the temperature is maintained at T ₀ , even when the tank internal pressure becomes lower than P 0, the fuel pressure is further reduced at the pump inlet portion 22 by the pressure loss ΔP, so that fuel vaporization occurs. There is a fear.

Here, in the fuel tank system 12 of this embodiment, the tank internal pressure sensor 36 detects the tank internal pressure. When the pressure obtained by subtracting the pressure loss ΔP from the tank internal pressure falls below the fuel vapor pressure, the control device 18 drives the failure diagnosis pressurizing pump 40. Specifically, the inside of the fuel tank 14 is pressurized so that the tank internal pressure is equal to or higher than the sum of the fuel vapor pressure and the pressure loss at the pump inlet 22 (the pressure increase is ΔP ′ in FIG. 2). ). Thus, the absolute pressure P ₂ of fuel increases at the pump inlet 22, is vaporized fuel (cavitation) is suppressed at the pump inlet 22, influence on the operation of the fuel pump 16 is suppressed.

  At this time, as the pressure increase ΔP ′, as described above, if the fuel vapor pressure is equal to or greater than the sum of the pressure loss at the pump inlet 22, it is sufficient to suppress fuel vaporization, It is not necessary to pressurize the fuel tank 14 excessively.

  The control device 18 closes the purge on-off valve 34 when the pressure pump 40 for failure diagnosis is driven to pressurize the fuel tank 14 in this way. As a result, there is no waste in the pressurizing action in the fuel tank 14 by driving the failure diagnosis pressurizing pump 40, and the tank internal pressure is easily maintained.

  In the present embodiment, the fuel vapor pressure of the fuel in the fuel tank 14 can be specified with high accuracy by the following method.

  First, after completion of refueling to the fuel tank 14 and before starting the engine (this is referred to as “refueling determination”), the purge on-off valve 34 is temporarily closed and pressurization for failure diagnosis is performed. The drive of the pump 40 is stopped (the atmosphere release pipe 30 is closed). Thereby, the fuel tank 14 is sealed. With the fuel tank 14 sealed in this manner, the tank temperature sensor 38 detects the tank internal temperature, and the tank internal pressure sensor 36 detects the tank internal pressure.

  In FIG. 3, an example of a vapor pressure curve pattern stored in advance in the control device 18 is shown as a curve C. As described above, in a state where the fuel tank 14 is sealed (at the time of fuel supply determination), the tank internal pressure is atmospheric pressure (101.3 kPa). At this time, if the tank internal temperature is T3, the curve C is used. Thus, it can be estimated that the partial pressure of the fuel vapor is P3.

  Next, it is assumed that the temperature in the tank changes to T4 while the fuel tank 14 is sealed, such as when the vehicle is running. Based on the curve C, the partial pressure of the fuel vapor at this time is changed to P4, and it is considered that the internal pressure of the fuel tank 14 is increased by (P4-P3). However, as shown in FIG. 3, if the increase Δp of the tank internal pressure actually detected by the tank internal pressure sensor 36 is different from (P4−P3), the actual fuel vapor pressure is corrected accordingly. it can. For example, as shown in FIG. 3, when the increase Δp of the tank internal pressure is smaller than (P4−P3), the curve C is shifted downward by these differences, that is, (p4−P3) −Δp. If this is the case (the vapor pressure curve after the shift is indicated by a curve C ′), the estimation of the fuel vapor pressure based on the corrected curve C ′ becomes closer to reality. When the increase Δp of the tank internal pressure is larger than (P4−P3), the curve C is shifted upward by Δp− (P4−P3) to obtain a corrected curve C ′. That's fine.

  Further, in the fuel tank system 12 of the present embodiment, the control device 18 can detect a temporal change in the operating current of the fuel pump 16. When fuel vaporization occurs at the pump inlet 22 of the fuel pump 16, it is assumed that the operating current changes with time, which is different from the normal time. Thus, the occurrence of fuel vaporization can be suppressed in advance. For example, when a current difference between the peak-to-peak (from a specific maximum value to a minimum value) of the current waveform is detected and this value exceeds a predetermined value, it can be determined that it is a sign of fuel vaporization. Furthermore, when the fuel pump 16 is actually driven, if the fuel pump 16 is driven and controlled so that the current value of the operating current of the fuel pump 16 is maintained at a certain value or more at a specific time interval, the fuel vaporization is not generated. It becomes possible to suppress more reliably.

  In the above description, the fuel tank system 12 including the tank internal pressure sensor 36 that detects the tank internal pressure of the fuel tank 14 is described. However, the tank internal pressure value can be obtained without using the tank internal pressure sensor 36. Thus, the tank internal pressure sensor 36 can be dispensed with. For example, if the altitude can be specified from the position information of the vehicle using a satellite positioning system or the like, the tank internal pressure sensor 36 becomes unnecessary by estimating that the tank internal pressure is equivalent to the atmospheric pressure at the altitude. When the tank internal pressure is detected using the tank internal pressure sensor 36 as in the above embodiment, the pressurization control of the fuel tank 14 by the failure diagnosis pressurizing pump 40 can be performed with higher accuracy. In addition, by applying pressure while detecting (monitoring) the tank internal pressure by the tank internal pressure sensor 36, it is possible to prevent the fuel tank 14 from being excessively pressurized, and the pressure resistance of the fuel tank 14 need not be excessively increased.

  Even if the tank temperature sensor 38 is not provided, for example, when the tank temperature is high, the fuel tank 14 is pressurized by driving the pressurizing means (pressure pump 40 for failure diagnosis). The fuel vaporization at the pump inlet 22 of the fuel pump 16 can be suppressed. In this case, the tank internal pressure may be sufficiently increased so that the fuel is not vaporized even when the temperature becomes highest within the range of the assumed fuel temperature.

  In the above description, the configuration using the fault diagnosis pressurizing pump 40 is taken as an example of the pressurizing means of the present invention, but the pressurizing means is not limited to the fault diagnosis pressurizing pump 40. For example, a new pump for pressurizing the fuel tank 14 may be provided, but the use of the failure diagnosis pressurizing pump 40 eliminates the need for a new pump. In a configuration in which a new pump is provided, the canister 26, the purge pipe 32, and the purge opening / closing valve 34 are not necessary for executing the essential operation of the present application.

  Moreover, the failure diagnosis pressure pump 40 performs failure diagnosis, which is the original purpose, when the vehicle is stopped, and the failure diagnosis pressure pump 40 is driven while the vehicle is running for failure diagnosis. Absent. In contrast, in the present embodiment, it is during vehicle travel that the failure diagnosis pressurizing pump 40 is driven to pressurize the fuel tank 14. As a result, the failure diagnosis and the pressurization of the fuel tank 14 can be performed by one failure diagnosis pressurizing pump 40 without affecting each other.

DESCRIPTION OF SYMBOLS 12 Fuel tank system 14 Fuel tank 16 Fuel pump 18 Control apparatus 20 Fuel delivery piping 22 Pump inlet part 24 Suction filter 26 Canister 28 Vapor piping 30 Air release pipe 32 Purge piping 34 Purge on-off valve 36 Tank internal pressure sensor 38 Tank temperature sensor 40 Pressure pump for fault diagnosis (pressurizing means)

Claims (5)

A fuel tank containing fuel;
A fuel pump for delivering fuel in the fuel tank to the outside;
Pressurizing means capable of pressurizing the fuel tank;
A control device for driving the pressurizing means to pressurize the fuel tank so that the tank internal pressure is equal to or higher than the sum of the fuel vapor pressure and the pressure loss at the fuel inlet of the fuel pump;
Having fuel tank system. It has a pressure pump for failure diagnosis that can pressurize the fuel tank for failure diagnosis,
The fuel tank system according to claim 1, wherein the pressurizing unit is the fault diagnosis pressurizing pump. A canister that adsorbs and desorbs evaporated fuel generated in the fuel tank with an adsorbent;
A purge pipe for applying a negative pressure of the engine to the canister;
Have
3. The fuel tank system according to claim 1, wherein the control device suppresses the negative pressure acting on the canister during driving of the pressurizing unit. A tank temperature sensor for detecting the temperature of the fuel tank;
A tank internal pressure sensor for detecting an internal pressure of the fuel tank;
Have
The control device estimates the actual fuel vapor pressure from the tank internal pressure detected by the tank internal pressure sensor and the tank temperature detected by the tank temperature sensor based on a preset fuel vapor pressure, and this estimation The fuel tank system according to any one of claims 1 to 3, wherein the pressurizing unit is driven based on a result.   The fuel tank system according to any one of claims 1 to 4, wherein the control device is capable of detecting an operating current of the fuel pump and drives the pressurizing means based on a change in the current.

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