JP3761665B2 - Evaporative fuel emission prevention device for internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporative fuel emission preventing device for an internal combustion engine, and more particularly to an evaporative fuel emission preventing device for an internal combustion engine that prevents the evaporative fuel from being released from the fuel tank to the outside air when a filler cap of the fuel tank is opened during refueling.
[0002]
[Prior art]
In order to prevent the evaporated fuel in the fuel tank mounted on the vehicle from being released into the outside air, the fuel tank is connected to the intake pipe of the internal combustion engine via the canister, and the evaporated fuel in the fuel tank is connected to the internal combustion engine. A technique is known in which processing is performed by a canister when the engine is stopped, and combustion is performed by the internal combustion engine when the internal combustion engine is operated.
[0003]
In addition, the internal pressure of the fuel tank is excessively negative during operation of the internal combustion engine, and the internal pressure of the fuel tank is maintained at a negative pressure not only during operation of the internal combustion engine but also after the internal combustion engine is stopped. An evaporative fuel emission preventing device for an internal combustion engine has been already proposed that prevents the evaporative fuel in the fuel tank from being released to the outside air even when the valve is opened.
[0004]
In this apparatus, a temperature sensor for detecting the temperature of the fuel in the fuel tank and a tank pressure sensor for detecting the internal pressure of the fuel tank are provided, and the fuel tank is predicted according to the temperature of the fuel in the fuel tank. A target pressure value that is excessively negative in consideration of an increase in internal pressure is determined. Then, using the negative pressure in the intake pipe during operation of the internal combustion engine, the opening degree of the control valve is adjusted while feeding back the detected value of the tank pressure sensor so that the internal pressure of the fuel tank becomes the target pressure value. Control. Thereby, normally, the internal pressure of the fuel tank can be maintained at the target pressure value.
[0005]
[Problems to be solved by the invention]
However, in the conventional evaporative fuel emission prevention device for an internal combustion engine, the negative pressure in the fuel tank is only used by using the negative pressure in the intake pipe during the operation of the internal combustion engine. When there is no pressure state, or when it is not possible to secure a sufficient time for the negative pressure of the fuel tank depending on the operating conditions, there is a problem that it is difficult to properly reduce the negative pressure of the fuel tank.
[0006]
For example, in a state where a heavy load is applied to the internal combustion engine and the pressure in the intake pipe rises and the degree of the negative pressure is small, such as when climbing for a long time, it is difficult to make the fuel tank negative. In particular, when the pressure in the intake pipe is larger than the target pressure value, it is impossible to make the fuel tank have a proper negative pressure.
[0007]
Also, when the filler cap of the fuel tank is opened for refueling and the fuel tank is opened to the atmosphere, the negative pressure of the fuel tank is started by the subsequent operation of the internal combustion engine. When the operating time of the vehicle or the vehicle traveling time is short, the fuel tank due to the negative pressure in the intake pipe may be parked and stopped without being sufficiently negative pressure.
[0008]
As described above, depending on the operating conditions, there is a problem that the fuel tank may not be properly negatively pressured.
[0009]
The present invention has been made in order to solve the above-described problems of the prior art, and an object of the present invention is to provide an appropriate fuel tank even when it is difficult to make the fuel tank negative pressure by negative pressure in the intake pipe. An object of the present invention is to provide an evaporated fuel discharge prevention device for an internal combustion engine that can be maintained in a negative pressure state.
[0010]
[Means for solving problems]
In order to achieve the above-mentioned object, an evaporated fuel discharge preventing device for an internal combustion engine according to claim 1 is provided with an evaporated fuel passage connecting a fuel tank and an intake system of the internal combustion engine, a negative pressure chamber, and the negative pressure chamber. A negative pressure chamber passage connecting the evaporative fuel passage, a first control valve for opening and closing the negative pressure chamber passage, and a second control valve provided in the middle of the evaporative fuel passage for opening and closing the evaporative fuel passage And a control means for controlling the opening of the second control valve so that the internal pressure of the fuel tank becomes a negative pressure when the internal combustion engine is operated and stopped. .
[0011]
With this configuration, the negative pressure chamber passage is opened and closed by the first control valve. When the negative pressure chamber passage is closed, the fuel tank is communicated only with the intake system of the internal combustion engine, and the fuel tank is brought into a negative pressure only by the negative pressure of the intake system of the internal combustion engine. On the other hand, when the negative pressure chamber passage is opened, the negative pressure chamber is communicated with the fuel tank, the negative pressure in the negative pressure chamber acts on the fuel tank, and the negative pressure in the negative pressure chamber causes the fuel tank to become negative. It becomes possible. As a result, even when it is difficult to make the negative pressure of the fuel tank based on the negative pressure in the intake pipe due to the operation of the internal combustion engine, the negative pressure of the negative pressure chamber can maintain the fuel tank in an appropriate negative pressure state. it can.
Further, since the opening of the second control valve is controlled so that the internal pressure of the fuel tank becomes a negative pressure when the internal combustion engine is operated and stopped, the fuel tank is not only during the operation of the internal combustion engine but also after the stop. Holds negative pressure. Thereby, even if the filler cap is opened for refueling, it is possible to prevent the evaporated fuel in the fuel tank from being released to the outside air, and to prevent the evaporated fuel from being released without using a canister.
[0012]
Specifically, it is desirable to use, for example, an electromagnetic valve capable of controlling the flow rate as the second control valve, and to use an on-off valve or a three-way valve as the first control valve.
[0013]
An evaporative fuel emission preventing device for an internal combustion engine according to claim 2 is the evaporative fuel emission preventing device for the internal combustion engine according to claim 1, wherein a chamber negative pressure passage connecting the negative pressure chamber and the evaporative fuel passage, And a one-way valve provided in the chamber negative pressure passage and allowing a flow from the negative pressure chamber to the evaporated fuel passage.
[0014]
With this configuration, the flow from the negative pressure chamber to the evaporated fuel passage is permitted by the one-way valve. Thereby, when the internal pressure of the negative pressure chamber is larger than the internal pressure of the evaporated fuel passage, air or the like flows from the negative pressure chamber to the evaporated fuel passage, so that the negative pressure chamber is brought into a negative pressure state using the negative pressure of the intake system. be able to.
[0017]
The evaporated fuel release prevention device for an internal combustion engine according to claim 3 is the evaporated fuel release prevention device for the internal combustion engine according to claim 1 or 2 , wherein the first control valve is configured such that the pressure of the intake system of the internal combustion engine is the fuel. The negative pressure chamber passage is opened when the target pressure value of the tank and the internal pressure value of the fuel tank are larger than each other.
[0018]
With this configuration, when the pressure in the intake system of the internal combustion engine is larger than both the target pressure value of the fuel tank and the internal pressure value of the fuel tank, the negative pressure chamber passage is opened by the first control valve. Is done. As a result, the fuel tank and the negative pressure chamber communicate with each other and the negative pressure in the negative pressure chamber causes the fuel tank to become negative. Depending on the negative pressure in the intake system, the negative pressure of the fuel tank is reduced to the target pressure value. Even when it is not possible, the fuel tank can be maintained in a proper negative pressure state by the negative pressure of the negative pressure chamber.
[0019]
The evaporative fuel emission prevention device for an internal combustion engine according to claim 4 is the evaporative fuel emission prevention device for an internal combustion engine according to any one of claims 1 to 3 , wherein the first control valve is an internal pressure of the fuel tank. When the internal combustion engine is started when the value is substantially equal to atmospheric pressure, the negative pressure chamber passage is opened.
[0020]
With this configuration, when the internal combustion engine is started when the internal pressure value of the fuel tank is substantially equal to the atmospheric pressure, the first control valve and the negative pressure chamber passage are opened. As a result, the fuel tank and the negative pressure chamber communicate with each other, and the fuel tank is made negative by the negative pressure in the negative pressure chamber. Therefore, the operation time of the internal combustion engine after the fuel tank is opened to the atmosphere by refueling or the like is short. Even in such a case, the fuel tank can be negatively pressured relatively quickly by the negative pressure of the negative pressure chamber.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0022]
(First embodiment)
FIG. 1 is an overall configuration diagram showing the configuration of an evaporated fuel release prevention device for an internal combustion engine according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an internal combustion engine (hereinafter simply referred to as “engine”) having, for example, four cylinders, and a throttle valve 3 is arranged in the middle of an intake pipe 2 of the engine 1. A throttle valve opening (θTH) sensor 4 is connected to the throttle valve 3, and an electric signal corresponding to the opening of the throttle valve 3 is output to an electronic control unit (hereinafter referred to as “ECU”) 5. Supply.
[0023]
The fuel injection valve 6 is provided for each cylinder in the middle of the intake pipe 2 and slightly upstream of an intake valve (not shown) between the engine 1 and the throttle valve 3. Each fuel injection valve 6 is connected to a fuel tank 9 having a sealed structure through a fuel supply pipe 7, and a fuel pump 8 is provided in the middle of the fuel supply pipe 7. The fuel tank 9 has an oil supply port 10 for refueling, and a filler cap 11 is attached to the fuel supply port 10.
[0024]
The fuel injection valve 6 is electrically connected to the ECU 5, and the fuel injection valve opening timing is controlled by a signal from the ECU 5.
[0025]
An intake pipe absolute pressure (PBA) sensor 13 for detecting an intake pipe absolute pressure PBA and an intake air temperature (TA) sensor 14 for detecting an intake air temperature TA as an outside air temperature are provided downstream of the throttle valve 3 in the intake pipe 2. It is installed. The fuel tank 9 includes a tank internal pressure (Pt) sensor 15 that detects a tank internal pressure (absolute pressure) Pt of the fuel tank 9 and a fuel temperature (Tg) sensor 16 that detects a temperature Tg of the fuel in the fuel tank 9. And are provided respectively. The detection signals of these sensors 13 to 16 are supplied to the ECU 5. Furthermore, an atmospheric pressure (PA) sensor 45 that detects an atmospheric pressure (absolute pressure) PA and a vehicle speed (V) sensor 50 that detects a vehicle speed V are provided. These detection signals are also supplied to the ECU 5.
[0026]
Next, the evaporative fuel release inhibiting system 31 composed of the fuel tank 9, the evaporative fuel passage 20, the negative pressure chamber 40, the three-way valve 41 (first control valve) and the like will be described.
[0027]
The fuel tank 9 is connected to the downstream side of the throttle valve 3 of the intake pipe 2 through the evaporated fuel passage 20, and a tank pressure control valve 30 (second tank) that opens and closes the evaporated fuel passage 20 in the middle of the evaporated fuel passage 20. Control valve). The control valve 30 is an electromagnetic valve configured to control the flow rate of the evaporated fuel generated in the fuel tank 9 by changing the on / off duty ratio of the control signal. The operation of the control valve 30 is performed by the ECU 5. Controlled by The control valve 30 may be an electromagnetic valve whose opening degree can be changed linearly.
[0028]
A three-way valve 41 is provided in the middle of the evaporated fuel passage 20 between the control valve 30 and the intake pipe 2. Further, a negative pressure chamber 40 is connected to the three-way valve 41 via a negative pressure chamber passage 42.
[0029]
The three-way valve 41 is electrically connected to the ECU 5, and makes either the negative pressure chamber 40 or the intake pipe 2 communicate with the fuel tank 9 by a signal from the ECU 5. That is, the three-way valve 41 closes / opens either the negative pressure chamber passage 42 or the evaporated fuel passage 20 with respect to the fuel tank 9.
[0030]
The negative pressure chamber 40 is further connected to the evaporated fuel passage 20 via a chamber negative pressure passage 43. The chamber negative pressure passage 43 is connected to the evaporated fuel passage 20 between the three-way valve 41 and the intake pipe 2, and a one-way valve 44 is provided in the middle of the chamber negative pressure passage 43. The one-way valve 44 is a valve that allows only the flow of fluid from the negative pressure chamber 40 to the evaporated fuel passage 20, and the limit pressure for opening the valve depends on, for example, the temperature Tg of fuel in the fuel tank 9 described later. The predetermined pressure limit is set based on the lower limit value (curve D in FIG. 3) of the target pressure value (absolute pressure) Po (mmHg) of the fuel tank 9. Thus, the internal pressure of the negative pressure chamber 40 is always maintained at the predetermined limit pressure using the negative pressure in the intake pipe 2.
[0031]
A cut-off valve 21 is provided at the connection between the evaporated fuel passage 20 and the fuel tank 9. The cut-off valve 21 is a float valve that closes when the fuel tank 9 is full or when the inclination of the fuel tank 9 increases.
[0032]
The ECU 5 shapes input signal waveforms from various sensors, corrects the voltage level to a predetermined level, and converts an analog signal value into a digital signal value, a central processing circuit (hereinafter referred to as “CPU”). A storage means for storing a calculation program executed by the CPU, a calculation result, and the like, an output circuit for supplying a drive signal to the fuel injection valve 6 and the control valve 30, and the like.
[0033]
The CPU of the ECU 5 controls the amount of fuel supplied to the engine 1 according to the output signals of various sensors such as the θTH sensor 3 and the PBA sensor 13. Since the fuel amount control is not the subject of the present invention, the description thereof is omitted.
[0034]
The CPU of the ECU 5 controls the operation of the three-way valve 41 and the control valve 30 based on output signals from the fuel temperature sensor 16, the tank internal pressure sensor 15, the PA sensor 45, the PBA sensor 13, and the like.
[0035]
FIG. 2 shows a program for performing a control process for preventing evaporative fuel release in the evaporative fuel release preventing apparatus according to the first embodiment of the present invention.
[0036]
First, it is determined whether or not the fuel tank 9 has been opened to the atmosphere by opening the filler cap 11 for refueling (step S201). Whether or not the fuel tank 9 has been opened to the atmosphere is determined based on, for example, the detection value of the tank internal pressure sensor 15 (tank internal pressure Pt) and the detection value of the PA sensor 45 (atmospheric pressure PA), and the tank internal pressure Pt becomes the atmospheric pressure PA. When it becomes substantially equal, it is determined that the fuel tank 9 is opened to the atmosphere.
[0037]
If the result of determination in step S201 is that the fuel tank 9 is not open to the atmosphere, it is determined whether or not the engine 1 is in operation by detecting cranking of the engine 1 or the like (step S205). As a result, if the engine 1 is operating, the intake pipe absolute pressure PBA is detected (step S206), the fuel temperature sensor 16 detects the temperature Tg of the fuel in the fuel tank 9 (step S207), and then The tank internal pressure sensor 15 detects the tank internal pressure Pt of the fuel tank 9 (step S208), and calculates the target pressure value Po in the fuel tank 9 based on the setting method of the target pressure value Po in the fuel tank 9 described later. (Step S209). At this time, the target pressure value Po is excessively reduced in anticipation of a predicted tank pressure increase in the fuel tank 9 so that the negative pressure in the fuel tank 9 can be maintained even after the engine 1 is stopped. Value is set.
[0038]
As a factor of the increase in the internal pressure of the fuel tank 9 that can be predicted, the component that evaporates at a temperature lower than the fuel temperature among the components contained in the fuel evaporates due to the amount of heat stored in the fuel tank 9 at that temperature. In addition, due to a rise in the temperature of the fuel in the fuel tank 9 due to a rise in the outside air temperature, a part of the fuel evaporates as described above.
[0039]
After the process of step S209, it is determined whether or not the intake pipe absolute pressure PBA is larger than both the target pressure value Po and the tank internal pressure Pt, that is, whether PBA> Po and PBA> Pt are satisfied ( Step S210). If either PBA ≦ Po or PBA ≦ Pt is established as a result of the determination, the three-way valve 41 closes the negative pressure chamber passage 42 and opens the evaporated fuel passage 20 (step S211). A difference ΔP between the tank internal pressure Pt of the tank 9 and the target pressure value Po is calculated (step S212), and the opening degree of the control valve 30 is controlled so that the difference ΔP becomes 0 (step S213). Exit. Thereby, the tank internal pressure Pt of the fuel tank 9 can be held at the target pressure value Po.
[0040]
If the engine 1 is stopped as a result of the determination in step S205, the CPU of the ECU 5 closes the control valve 30 in order to maintain the negative pressure in the fuel tank 9 controlled to the target pressure value Po. (Step S203), the process is terminated.
[0041]
On the other hand, if the result of determination in step S201 is that the fuel tank 9 has been released to the atmosphere, it is determined whether or not the engine 1 has been started (step S202). Whether or not the engine 1 has been started is determined by detecting cranking or the like. Note that it may be determined whether or not the vehicle has traveled instead of starting the engine 1. Whether or not the vehicle has traveled is determined by the detection value of the vehicle speed sensor 50.
[0042]
If the engine 1 is started as a result of the determination in step S202, the negative pressure chamber passage 42 is opened by the three-way valve 41 and the evaporated fuel passage 20 is closed (step S204). Thereby, since the negative pressure chamber 40 communicates with the fuel tank 9, even if the operation time of the engine 1 after the fuel tank 9 is opened to the atmosphere is short, a predetermined pressure in the negative pressure chamber 40 is reached. The negative pressure of the fuel tank 9 can be achieved in a relatively short time by the limit pressure. Next, the process proceeds to step S212.
[0043]
On the other hand, if the engine 1 is not started in step S202, the process proceeds to step S203.
[0044]
If it is determined in step S210 that PBA> Po and PBA> Pt holds, the process proceeds to step S204. As a result, the negative pressure chamber 40 communicates with the fuel tank 9, so that the target pressure value Po is lower than the intake pipe absolute pressure PBA. Depending on the negative pressure in the intake pipe 2, the tank internal pressure Pt is set to the target pressure. Even when the pressure cannot be reduced to the value Po, the negative pressure of the fuel tank 9 can be reduced by the negative pressure chamber 40.
[0045]
With this process, the tank internal pressure Pt of the fuel tank 9 can be maintained at the target pressure value Po by controlling the opening degree of the control valve 30 during the operation of the engine 1. At that time, the negative pressure in the intake pipe 2 due to the operation of the engine 1 is normally used. However, when the operation time of the engine 1 after the fuel tank 9 is opened to the atmosphere is short, for example, long climbing traveling When the absolute pressure PBA in the intake pipe increases due to high load operation, the negative pressure in the negative pressure chamber 40 is used instead of the intake pipe 2.
[0046]
Here, a method for setting the target pressure value Po in the fuel tank 9 in step S209 in FIG. 2 will be described with reference to FIG. FIG. 3 is a graph showing a fuel temperature-tank internal pressure curve for explaining setting criteria for the target pressure value Po in the fuel tank 9.
[0047]
The set range value of the target pressure value Po in the fuel tank 9 in FIG. 3 is stored as a map in the storage means of the ECU 5.
[0048]
In the graph of FIG. 3, the horizontal axis indicates the temperature Tg (° C.) of the fuel in the fuel tank 9, and the vertical axis indicates the tank internal pressure Pt (mmHg) of the fuel tank 9. Here, the tank internal pressure Pt on the vertical axis is indicated by the absolute pressure as described above, and the pressure is lower in the lower part of the graph.
[0049]
Hereinafter, the curves A, B, A + B, C, A + C, D, and E in FIG. 3 will be described.
[0050]
Curve A shows that the inside of the fuel tank 9 is excessively negative while the vehicle is running so that the internal pressure of the fuel tank 9 is maintained at a negative pressure even when the engine 1 stops and the negative pressure of the fuel tank 9 stops. The upper limit value of the target pressure value Po of the tank internal pressure Pt for increasing the pressure, and the fuel in the components contained in the fuel depending on the amount of heat held at the temperature Tg of the fuel in the fuel tank 9 immediately after the engine 1 stops The upper limit value of the target pressure value Po of the tank internal pressure Pt in consideration of the increase in the tank internal pressure Pt of the fuel tank 9 due to the evaporation of the component that evaporates at a temperature lower than the temperature is shown. The opening degree of the control valve 30 is controlled so that the tank internal pressure Pt of the fuel tank 9 becomes the curve A or less regardless of the fuel temperature Tg. In the curve A, the tank internal pressure Pt decreases as the fuel temperature Tg increases.
[0051]
Curve B shows that the inside of the fuel tank 9 is excessively negative while the vehicle is running so that the internal pressure of the fuel tank 9 is maintained at a negative pressure even when the engine 1 stops and the negative pressure of the fuel tank 9 stops. This is the upper limit value of the target pressure value Po of the tank internal pressure Pt for pressure increase, and the outside temperature rises to a predetermined assumed maximum outside temperature 40.6 ° C. while the vehicle is parked or parked, and the fuel temperature Tg is also 40. An upper limit value of the target pressure value Po of the tank internal pressure Pt in consideration of the increase in the tank internal pressure Pt of the fuel tank 9 when the temperature rises to 6 ° C. is shown. The predetermined assumed maximum outside temperature 40.6 ° C. is the maximum value of the outside temperature assumed at the time of vehicle design. In curve B, the tank internal pressure Pt increases as the fuel temperature Tg increases.
[0052]
A curve A + B is a curve that satisfies the conditions of the curve A and the curve B at the same time. In the curve A + B, when the fuel temperature Tg is around 25 ° C., the tank internal pressure Pt takes the minimum value. When 40.6 ° C. is selected as the assumed maximum outside air temperature, the opening degree of the control valve 30 is controlled so that the tank internal pressure Pt of the fuel tank 9 becomes the curve A + B or less regardless of the fuel temperature Tg.
[0053]
A curve C represents an upper limit value of the target pressure value Po of the tank internal pressure Pt when a predetermined assumed maximum outside air temperature is set to 45 ° C., which is severer than 40.6 ° C. under the same conditions as the curve B.
[0054]
Curve A + C is a curve that satisfies the conditions of curve A and curve C simultaneously. When 45 ° C. is selected as the assumed maximum outside air temperature, the opening of the control valve 30 is controlled so that the tank internal pressure Pt of the fuel tank 9 is equal to or lower than the curve A + C regardless of the fuel temperature Tg.
[0055]
Curve D represents the lower limit of the target pressure value Po of the fuel tank 9 that is the lower limit of suction of the fuel pump 8 that transfers fuel from the fuel tank 9 to the engine 1. If the tank pressure Pt in the fuel tank 9 is equal to or lower than the curve D, the fuel pump 8 cannot suck the fuel from the fuel tank 9, so that the tank pressure Pt in the fuel tank 9 needs to be higher than the curve D. . In the curve D, the tank internal pressure Pt increases as the fuel temperature Tg increases. Further, the lower limit value of the target pressure value Po of the tank internal pressure Pt according to the curve D is smaller than the upper limit value of the target pressure value Po of the tank internal pressure Pt according to the curve A + C.
[0056]
Finally, the curve E is a so-called limit line where the fuel retains its characteristics as a fuel (so-called limit line where gasoline runs out). When the tank internal pressure Pt of the fuel tank 9 is lowered to the curve E or less, the fuel in the fuel tank 9 loses easily volatile components in the fuel and cannot maintain its characteristics as a fuel. In the curve E, the tank internal pressure Pt increases as the fuel temperature Tg increases. The tank internal pressure Pt according to the curve E is smaller than the lower limit value of the target pressure value Po of the tank internal pressure Pt according to the curve D.
[0057]
In the first embodiment, 45 ° C., which is a more severe condition, is selected as the predetermined assumed maximum outside air temperature in the graph of FIG. That is, the curve C is considered instead of the curve B. Therefore, in order to keep the tank internal pressure Pt of the fuel tank 9 at a negative pressure even when the engine 1 is stopped and the negative pressure of the fuel tank 9 is stopped, the opening degree of the control valve 30 is the curve A, It is necessary to control so as to satisfy all the conditions of C, A + C, D, and E. Specifically, the control region of the control valve 30 is indicated by the hatched portion in FIG. 3, and the control valve 30 is configured so that the value of the tank internal pressure Pt in the fuel tank 9 falls within this region according to the fuel temperature Tg. To be controlled.
[0058]
According to the first embodiment, normally, during operation of the engine 1, the negative pressure in the intake pipe 2 acts on the fuel tank 9, and the fuel tank 9 is held at a predetermined target pressure value Po. The On the other hand, the engine 1 is started after the fuel tank 9 is opened to the atmosphere, and the fuel tank 9 using the negative pressure in the intake pipe 2 due to the operation of the engine 1 is used as in the case of stopping the engine 1 in a short time. Even when the time for the negative pressure is not sufficient, the fuel tank 9 can be maintained in an appropriate negative pressure state by the negative pressure of the negative pressure chamber 40. Similarly, when the absolute pressure PBA in the intake pipe rises due to a high load and the negative pressure in the fuel tank 9 using the negative pressure in the intake pipe 2 is difficult, such as during long-time climbing, fuel The tank 9 can be maintained in a proper negative pressure state.
[0059]
As a result, even if the outside air temperature rises to 45 ° C., the evaporated fuel in the fuel tank 9 can be prevented from being released to the outside air even if the filler cap 11 is opened for refueling. Further, since the inside of the fuel tank is set to a negative pressure, a canister is not required, and it is possible to prevent the evaporative fuel from being released with a simpler configuration and lower cost.
[0060]
In addition, since the one-way valve 44 that allows only the flow of fluid from the negative pressure chamber 40 to the three-way valve 41 is provided in the middle of the chamber negative pressure passage 43, the internal pressure of the negative pressure chamber 40 is set to the intake pipe 2 A negative pressure state can always be obtained by utilizing the negative pressure inside. Therefore, it is possible to facilitate the quick execution of the negative pressure processing of the fuel tank 9 by the negative pressure chamber 40 described above.
[0061]
In the first embodiment, the three-way valve 41 may be provided in the middle of the evaporated fuel passage 20 between the control valve 30 and the cut-off valve 21. In this case, the three-way valve 41 is provided with a function similar to that of the control valve 30 (function capable of controlling the flow rate by changing the duty ratio). In step S213 in FIG. 2, the three-way valve 41 opens the negative pressure chamber passage 42. When it is, it is preferable that the control valve 30 closes the evaporated fuel passage 20 and that the three-way valve 41 controls the negative pressure of the fuel tank 9 based on the difference ΔP instead of the control valve 30.
[0062]
(Second embodiment)
FIG. 4 is an overall configuration diagram showing the configuration of the evaporated fuel emission preventing device for the internal combustion engine according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in the configuration of the evaporated fuel release inhibiting system 31. That is, in the second embodiment, a negative pressure chamber passage control valve 47 (first control valve) is provided in place of the three-way valve 41, and the means for negative pressure in the negative pressure chamber 40 is a one-way valve. The difference from the first embodiment is that a negative pressure pump 49 is used instead of 44. In FIG. 4, the same components as those of the evaporated fuel release preventing device according to the first embodiment are denoted by the same reference numerals.
[0063]
In the second embodiment, the evaporated fuel release inhibiting system 31 includes a fuel tank 9, an evaporated fuel passage 20, a negative pressure chamber 40, a negative pressure chamber passage control valve 47, a negative pressure pump 49, and the like.
[0064]
A negative pressure chamber 40 is connected between the control valve 30 and the intake pipe 2 in the middle of the evaporated fuel passage 20 via a negative pressure chamber passage 46. In the middle of the negative pressure chamber passage 46, a negative pressure chamber passage control valve 47 is provided. The negative pressure chamber passage control valve 47 is electrically connected to the ECU 5 and opens and closes the negative pressure chamber passage 46 in response to a signal from the ECU 5.
[0065]
A negative pressure pump 49 is connected to the negative pressure chamber 40 via a chamber negative pressure passage 48. The negative pressure pump 49 is driven by an electric motor (not shown), and always maintains the negative pressure chamber 40 in a constant negative pressure state (for example, the lower limit value of the target pressure value Po described above, curve D in FIG. 3). In addition, as long as the negative pressure chamber 40 can be negative pressure, a means using other power such as a spring instead of the negative pressure pump 49 may be used.
[0066]
Other points in the evaporated fuel release inhibiting system 31 and the configuration other than the evaporated fuel release inhibiting system 31 in the present apparatus are the same as those in the first embodiment.
[0067]
In the configuration as described above, in the second embodiment, the same processing as in FIG. 2 is performed. However, in step S204 of FIG. 2 (communication to the negative pressure chamber 40), the negative pressure chamber passage control valve 47 opens the negative pressure chamber passage 46, and step S211 of FIG. 2 (communication to the intake pipe 2). Then, processing is performed so that the negative pressure chamber passage control valve 47 closes the negative pressure chamber passage 46.
[0068]
According to the second embodiment, the same effects as in the first embodiment can be obtained.
[0069]
In the second embodiment, the connection position of the negative pressure chamber passage 46 may be provided in the middle of the evaporated fuel passage 20 between the control valve 30 and the cutoff valve 21. In this case, the negative pressure chamber passage control valve 47 is a control valve having the same configuration as the control valve 30 (the flow rate can be controlled by changing the duty ratio). In step S213 of FIG. When the pressure chamber passage control valve 47 is opened, the control valve 30 closes the evaporated fuel passage 20, and the negative pressure chamber passage control valve 47 replaces the control valve 30 with the fuel tank based on the difference ΔP. It is preferable to perform the negative pressure control 9.
[0070]
In the first and second embodiments, the tank internal pressure Pt of the fuel tank 9 is controlled using a value 45 ° C. that is set in advance as the assumed maximum outside air temperature. The tank internal pressure Pt of the fuel tank 9 may be controlled using a value set by providing means. Thus, for example, the assumed maximum outside air temperature can be set according to the ambient temperature environment of the vehicle, such as 45 ° C. in summer and 25 ° C. in winter, so that the pressure value in the fuel tank 9 is set to the ambient temperature of the vehicle. On the other hand, it can be set to an appropriate value, and an excessively negative value can be prevented.
[0071]
In the first and second embodiments, the negative pressure chamber passage 42 is opened when PBA> Po and PBA> Pt is satisfied in step S210 of FIG. 2, but PBA> Po is If established, the negative pressure chamber passage 42 may be opened regardless of the tank internal pressure Pt.
[0072]
【The invention's effect】
As described above in detail, according to the evaporated fuel discharge prevention device for an internal combustion engine according to claim 1, when the negative pressure chamber passage is opened by the first control valve, the negative pressure chamber negative Even when the pressure acts on the fuel tank and it is difficult to reduce the pressure of the fuel tank based on the negative pressure in the intake pipe due to the operation of the internal combustion engine, the negative pressure in the negative pressure chamber causes the fuel tank to have an appropriate negative pressure. Can be maintained in a state. In addition, since the inside of the fuel tank is maintained at a negative pressure not only during the operation of the internal combustion engine but also after stopping, it is possible to prevent the evaporated fuel in the fuel tank from being released to the outside air even if the filler cap is opened for refueling. In addition, the evaporative fuel can be prevented from being released without using a canister.
[0073]
According to the evaporated fuel release preventing device for an internal combustion engine according to claim 2, the one-way valve allows the flow from the negative pressure chamber to the evaporated fuel passage, and the internal pressure of the negative pressure chamber is set to the internal pressure of the evaporated fuel passage. When the air pressure is larger, air or the like flows from the negative pressure chamber to the evaporated fuel passage, so that the negative pressure chamber can be brought into a negative pressure state using the negative pressure of the intake system.
[0075]
According to the evaporated fuel release prevention device for an internal combustion engine according to claim 3, when the pressure of the intake system of the internal combustion engine is larger than both the target pressure value of the fuel tank and the internal pressure value of the fuel tank, the first Since the negative pressure chamber passage is opened by one control valve, the fuel tank and the negative pressure chamber communicate with each other, and the negative pressure in the negative pressure chamber causes the fuel tank to become negative. Therefore, even if the negative pressure in the intake system cannot reduce the fuel tank to the target pressure value, the negative pressure in the negative pressure chamber can maintain the fuel tank in an appropriate negative pressure state. .
[0076]
According to the evaporative fuel emission preventing device for an internal combustion engine according to claim 4 , when the internal combustion engine is started when the internal pressure value of the fuel tank is substantially equal to the atmospheric pressure, the first control valve Since the negative pressure chamber passage is opened, the fuel tank communicates with the negative pressure chamber, and the negative pressure in the negative pressure chamber causes the fuel tank to become negative. Therefore, even when the operation time of the internal combustion engine after the fuel tank is opened to the atmosphere by refueling or the like is short, the fuel tank can be negatively pressured relatively quickly by the negative pressure of the negative pressure chamber.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a configuration of an evaporative fuel emission preventing device for an internal combustion engine according to a first embodiment of the present invention. FIG. 2 is an evaporative fuel emission preventing device in the evaporative fuel emission preventing device according to the embodiment. It is a flowchart of the program which performs control processing.
FIG. 3 is a fuel temperature-tank internal pressure graph for explaining a target pressure value Po in the fuel tank 9 in the embodiment.
FIG. 4 is an overall configuration diagram showing a configuration of an evaporated fuel emission preventing device for an internal combustion engine according to a second embodiment of the present invention.
1 Internal combustion engine
2 Intake pipe 5 Electronic control unit 9 Fuel tank 15 Tank internal pressure sensor 20 Evaporated fuel passage 30 Tank pressure control valve (second control valve)
31 Evaporative fuel emission suppression system 40 Negative pressure chamber 41 Three-way valve (first control valve)
42 Negative pressure chamber passage 43 Chamber negative pressure passage 44 One-way valve 45 PA (atmospheric pressure) sensor 46 Negative pressure chamber passage 47 Negative pressure chamber passage control valve (first control valve)
48 Channel negative pressure passage

Claims (4)

An evaporative fuel passage connecting the fuel tank and the intake system of the internal combustion engine, a negative pressure chamber, a negative pressure chamber passage connecting the negative pressure chamber and the evaporative fuel passage, and opening and closing the negative pressure chamber passage A first control valve that is provided in the middle of the evaporative fuel passage, and opens and closes the evaporative fuel passage. The internal pressure of the fuel tank is negative when the internal combustion engine is operated and stopped. And a control means for controlling the opening degree of the second control valve so as to become an evaporative fuel release prevention device for an internal combustion engine.   A chamber negative pressure passage connecting the negative pressure chamber and the evaporated fuel passage, and a one-way valve provided in the chamber negative pressure passage and allowing a flow from the negative pressure chamber to the evaporated fuel passage The evaporative fuel emission preventing device for an internal combustion engine according to claim 1, comprising: The first control valve opens the negative pressure chamber passage when the pressure of the intake system of the internal combustion engine is larger than both the target pressure value of the fuel tank and the internal pressure value of the fuel tank. The evaporative fuel emission preventing device for an internal combustion engine according to claim 1 or 2, characterized in that Said first control valve, when the internal pressure value of the fuel tank starting of the internal combustion engine when approximately equal to the atmospheric pressure is performed, according to claim 1, characterized by opening said vacuum chamber for passage The evaporative fuel discharge | release prevention apparatus of the internal combustion engine of any one of -3 .

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