JP2018017186A - Evaporated fuel treatment device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an evaporated fuel treatment device capable of performing purge control with high accuracy while limiting the heating of a canister as required only.SOLUTION: The evaporated fuel treatment device includes a purge passage, a canister, a purge valve, concentration detecting means for measuring or estimating the concentration of evaporated fuel, heating means for heating the canister, and a control part connected to the purge valve and the heating means. The control part opens the purge valve to perform purge control of the evaporated fuel accumulated on the canister, and controls the heating means during performing the purge control so that the concentration of the evaporated fuel measured or estimated by the concentration detecting means falls within a predetermined range.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an evaporated fuel processing apparatus capable of stably supplying evaporated fuel inside a canister to an engine intake pipe.

  Conventionally, an evaporative fuel processing apparatus for processing evaporative fuel generated in a fuel tank of an automobile is known. A typical fuel vapor processing apparatus includes a purge passage extending between a fuel tank and an engine intake pipe connected to the upstream side of the engine. In addition, a canister for receiving activated carbon or the like that receives and accumulates the evaporated fuel flowing from the fuel tank is provided on the purge passage. The evaporated fuel in the fuel tank is discharged from the fuel tank and accumulated in the canister through the purge passage. When the evaporated fuel accumulated in the canister is supplied to the engine intake pipe, the throttle valve in the engine intake pipe is throttled at a predetermined purge timing to generate a negative pressure in the purge passage. The evaporated fuel accumulated in the canister is sucked out toward the downstream side of the purge passage by the negative pressure generated in the purge passage, and is supplied to the engine through the engine intake pipe.

  In recent years, in order to improve fuel consumption, it is required to precisely control the combustion conditions in the engine cylinder, particularly the air-fuel ratio. Therefore, when supplying the evaporated fuel to the engine, the concentration of the evaporated fuel supplied to the engine cylinder can be accurately measured or estimated so that the target air-fuel ratio can be achieved when the evaporated fuel is supplied into the engine cylinder. It has been demanded. For example, Patent Document 1 is known as a technique that can measure the concentration of the evaporated fuel.

  On the other hand, Patent Document 2 discloses a canister heating device as a technique for promoting the desorption of evaporated fuel accumulated in a canister from the canister during purge control.

JP 2009-138561 A Japanese Patent Laying-Open No. 2015-63971

  Conventionally, it has been considered preferable to heat the canister at all times, and no detailed examination has been made on timing control for efficient heating.

  The present inventor has found a problem that if the canister is heated when the concentration of the evaporated fuel is sufficiently high, concentration unevenness occurs and purge control cannot be realized with high accuracy.

  Then, the present inventor limits the heating of the canister when necessary by performing feedback control that stabilizes the concentration by using the concentration of the evaporated fuel measured by the technique described in Patent Document 1 or the like. I found out that it would be possible.

  The present invention has been made in view of the above situation, and an object of the present invention is to provide an evaporative fuel processing apparatus capable of performing purge control with high accuracy by limiting canister heating when necessary. .

  The present invention provides a purge passage extending from a fuel tank toward an engine intake pipe, a canister provided on the purge passage and receiving and storing evaporated fuel from the fuel tank, and a downstream side of the canister on the purge passage A purge valve provided in the apparatus, a concentration detection means for measuring or estimating the concentration of the evaporated fuel, a heating means for heating the canister, and a control unit connected to the purge valve and the heating means, The control unit opens the purge valve to perform purge control of the evaporated fuel accumulated in the canister and measures or estimates the concentration detected by the concentration detection means while performing the purge control. An evaporative fuel processing apparatus characterized in that the heating means is controlled so that the concentration of evaporative fuel falls within a predetermined range. That.

  According to the present invention, while the purge control is being performed, the heating unit is controlled so that the concentration of the evaporated fuel measured or estimated by the concentration detection unit is within a predetermined range, so that the canister can be effectively heated. The purge control can be performed with high accuracy as a result.

  As the concentration detection means, the technique described in the above-mentioned conventional Patent Document 1 may be employed, but it is preferable to employ an evaporative fuel concentration estimation device for which the present inventor has applied for a patent separately.

  The evaporative fuel concentration estimating device includes a pressurizing pump provided between the canister on the purge passage and the purge valve, forcibly supplying gas in the purge passage to the purge valve, and on the purge passage. And a pressure sensor for detecting the pressure of the gas forcedly supplied by the pressurizing pump in a detection region between the pressurizing pump and the purge valve. The controller is also connected to the purge valve, the pressurizing pump, and the pressure sensor as part of a concentration detecting means (evaporated fuel concentration estimating device), and in a predetermined engine operating state, With the purge valve closed, the pressurizing pump is driven from a stopped state under a predetermined driving condition, and the concentration of the evaporated fuel is estimated based on the detection value of the pressure sensor.

  According to such an evaporative fuel concentration estimation device, the evaporation in the canister is driven by driving the pressurizing pump between the canister and the purge valve on the purge passage without being affected by the frequency of operation of the throttle valve. A negative pressure for sucking fuel from the canister can be generated. Based on the property that the detected value of the pressure sensor increases as the concentration of the evaporated fuel increases, the concentration of the evaporated fuel can be estimated with high accuracy based on the detected value of the pressure sensor.

  For example, the predetermined engine operating state is an engine stopped state. That is, according to such an evaporated fuel concentration estimation device, the concentration of evaporated fuel can be estimated with high accuracy even when the engine is stopped.

  Preferably, the control unit controls opening of the purge valve to perform purge control of the evaporated fuel accumulated in the canister based on the measured or estimated concentration of evaporated fuel. ing.

  In this case, the purge control of the evaporated fuel accumulated in the canister can be more effectively performed based on the concentration of the evaporated fuel estimated with high accuracy.

  In addition, when employ | adopting the said fuel vapor concentration estimation apparatus, you may abbreviate | omit the process of converting the detected value of a pressure sensor into the fuel vapor concentration. In this case, the present invention provides a purge passage extending from a fuel tank toward the engine intake pipe, a canister provided on the purge passage and receiving and storing evaporated fuel from the fuel tank, and the canister on the purge passage. A purge valve provided on the downstream side of the gas, and a pressure pump provided between the canister and the purge valve on the purge passage and forcibly supplying the gas in the purge passage to the purge valve side, A pressure sensor for detecting a pressure of gas forcedly supplied by the pressure pump in a detection region between the pressure pump and the purge valve on the purge passage; the purge valve; and the pressure pump And a control unit connected to the pressure sensor, wherein the control unit stops the pressurizing pump in a predetermined engine operating state with the purge valve closed. To obtain the detected value of the pressure sensor, then open the purge valve and execute the purge control to perform the purge control of the evaporated fuel accumulated in the canister. The evaporative fuel processing apparatus is characterized in that the heating means is controlled so that the detected value falls within a predetermined range.

  In this case, preferably, the control unit controls opening of the purge valve to perform purge control of the evaporated fuel accumulated in the canister based on the detected value.

  According to the present invention, while the purge control is being performed, the heating unit is controlled so that the concentration of the evaporated fuel measured or estimated by the concentration detection unit is within a predetermined range, so that the canister can be effectively heated. The purge control can be performed with high accuracy as a result.

1 is a system configuration diagram of a fuel vapor processing apparatus according to an embodiment of the present invention. It is a flowchart which shows an example of operation | movement of the evaporative fuel processing apparatus of FIG. 2 is a graph showing the interrelationship between the rotational speed of a pressurizing pump, the detected value of a pressure sensor, and the concentration of evaporated fuel estimated from them in the evaporated fuel processing apparatus of FIG. It is a time chart corresponding to the operation | movement of FIG.

  Hereinafter, an evaporated fuel processing apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a system configuration diagram of the fuel vapor processing apparatus according to the present embodiment.

  An evaporative fuel processing apparatus 1 shown in FIG. 1 is mounted on a general automobile and includes a purge passage 7 extending between an engine intake pipe 3 and a fuel tank 5. A canister 9 that receives and accumulates the evaporated fuel in the fuel tank 5 is provided on the downstream side of the fuel tank 5 in the purge passage 7.

  The canister 9 contains an adsorbent such as activated carbon. As a result, the evaporated fuel flowing from the fuel tank 5 is once adsorbed by the adsorbent in the canister 9. Further, the canister 9 is connected to the atmosphere opening port 13 opened to the atmosphere via the atmosphere opening valve 11. Further, the canister 9 is provided with a heater 9h.

  On the downstream side of the canister 9 in the purge passage 7, a pressurizing pump 15 configured by, for example, a centrifugal pump or a Wesco pump is provided. A purge valve 17 for opening and closing the purge passage 7 is provided further downstream of the pressurizing pump 15. A region between the pressure pump 15 and the purge valve 17 in the purge passage 7 is a pressure detection region 19 by the pressure sensor 21. Specifically, the pressure detection region 19 is a space in a pipe connecting the downstream side of the pressurizing pump 15 and the purge valve 17 and has a capacity of about 100 cc to 300 cc. A pressure sensor 21 for detecting pressure is provided in the pressure detection area 19.

  The evaporative fuel processing apparatus 1 includes an ECU 23 (control unit) for controlling various devices of the vehicle including the heater 9h, the atmosphere release valve 11, the pressurizing pump 15, the purge valve 17, and the pressure sensor 21. A storage unit 25 is further connected to the ECU 23. Correspondence between the drive rotation speed of the pressurizing pump 15 and the detected value of the pressure sensor 21 and the concentration of evaporated fuel estimated from them is connected to the ECU 23. A graph or table showing the relationship is stored.

  In addition, the ECU 23 is connected to an outside air temperature sensor 41 that measures the outside air temperature of the automobile, an atmospheric pressure sensor 43 that measures the atmospheric pressure around the automobile, and a fuel temperature sensor 45 provided in the fuel tank 5. Has been.

  Next, the operation of the evaporated fuel processing apparatus 1 as described above will be described in detail. FIG. 2 is a flowchart showing an example of the operation of the evaporated fuel processing apparatus.

  In the example shown in FIG. 2, first, it is determined whether or not the concentration diagnosis time has come under the control of the ECU 23 (step S01). The diagnosis time is, for example, a time when a predetermined time has elapsed since the previous concentration diagnosis.

  When the concentration diagnosis time has arrived, it is determined whether or not the traveling vehicle equipped with the evaporated fuel processing apparatus 1 of the present embodiment is traveling in EV (step S02). If yes, the engine is stopped. If no, the engine is in operation.

  In the case of YES, the air release valve 11 is controlled to the valve open state according to the control of the ECU 23 (step S03). This step is executed when the ECU 23 determines the state of the air release valve 11 and the air release valve 11 is in the closed state (if the air release valve 11 is already in the open state, the state is It is confirmed).

  Then, the pressurizing pump 15 is driven for a predetermined time (for example, 5 seconds) at a driving speed of 40000 rpm (step S04).

  When the pressurizing pump 15 is driven under the driving conditions as described above, an airflow that flows into the purge passage 7 through the atmosphere opening 13 and the canister 9 is generated. By the air flow, the evaporated fuel accumulated in the canister 9 is sucked and flows toward the downstream side of the purge passage 7.

  Next, the purge valve 17 is closed under the control of the ECU 23 (step S05). This step is executed when the ECU 23 determines the state of the purge valve 17 and the purge valve 17 is open (if the purge valve 17 is already closed, the state is confirmed). ). By this step S05, the pressure detection region between the output side of the pressurizing pump 15 and the purge valve 17 becomes a substantially closed space having a constant volume.

  In the pressure detection region 19 that has become a substantially closed space, the pressure rises when the pressure pump 15 is driven. When the pressure in the pressure detection area 19 reaches a certain pressure, the gas to be supplied from the pressure pump 15 cannot flow into the detection area 19. In such an equilibrium state, the pressure in the pressure detection region 19 is stable, and the amount of gas inflow from the pressurizing pump 15 becomes zero. The pressure sensor 21 detects the pressure in the pressure detection region 19 (when the gas inflow amount becomes zero) in such an equilibrium state (step S06).

  Next, the ECU 23 estimates the concentration of the evaporated fuel based on the graph or table stored in the storage unit 25. Specifically, the ECU 23 estimates the concentration of the evaporated fuel based on the rotational speed of the pressurizing pump 15 in this embodiment of 40000 rpm and the detected value of the pressure sensor 21 (step S07).

  For example, FIG. 3 shows the rotational speed of the pressurizing pump 15, the detected value of the pressure sensor 21, and the concentration (%) of the evaporated fuel estimated from them in the evaporated fuel processing apparatus 1 of the present embodiment. It is a graph which shows a mutual relationship. (The graph in FIG. 3 may be corrected (calibrated) by the outside air temperature around the automobile measured by the outside air temperature sensor 41 and the atmospheric pressure around the automobile measured by the atmospheric pressure sensor 43. Furthermore, the outside (The measured value of the fuel temperature sensor 45 may be used instead of the measured value of the temperature sensor 41.)

  Next, the ECU 23 compares the estimated concentration of evaporated fuel with a predetermined threshold (step S08). When the estimated concentration of the evaporated fuel is smaller than a predetermined threshold (for example, 80%), the purge control is not performed and the process of the present embodiment is terminated. If the estimated concentration of the evaporated fuel is equal to or greater than a predetermined threshold value, the engine is started and purge control is started in order to reliably prevent evaporation of the evaporation into the atmosphere (step S10).

  In the example of FIG. 2, the purge control is also started when NO in step S02.

  When starting the purge control, the ECU 23 determines whether or not an execution condition for the purge control of the evaporated fuel is satisfied (step S11). Specifically, (i) whether the air-fuel ratio is stable, (ii) whether the fuel learning process has been completed, (iii) whether there is a purge control prohibition request from another control system, etc. The condition is determined.

  If the execution condition of the purge control of the evaporated fuel is not satisfied, step S11 is repeated to wait for the execution condition to be satisfied.

  If the execution condition of the purge control of the evaporated fuel is satisfied, the pressure pump 15 is driven at 30000 rpm (step S12), and the target opening of the purge valve 17 is determined in consideration of the estimated concentration of the evaporated fuel. In step S13, purge control is performed.

  Regarding step S13, even if NO in step S02, steps S06 and S07 are performed once to estimate the concentration of the evaporated fuel, and then step S13 is performed. Alternatively, in the case of NO in step S02, the concentration of the evaporated fuel is estimated with the aid of a conventionally known concentration estimation technique (for example, the technique of Patent Document 1) that is performed by throttle the throttle valve during engine operation. Above, step S13 is implemented.

  Specifically, the purge control is performed by, for example, the ECU 23 opening and closing the purge valve 17 based on a predetermined duty pulse. The opening / closing duty of the purge valve 17 is determined based on the estimated concentration of evaporated fuel. That is, when the estimated concentration of the evaporated fuel is high, the amount of evaporated fuel accumulated in the canister 9 is large, so that it is necessary to suppress the amount of evaporated fuel supplied to the engine supply pipe 3. Accordingly, in this case, the purge valve 17 is driven according to a duty pulse having a relatively short pulse width. Thereby, even when the accumulation amount of the evaporated fuel is large, an appropriate amount of the evaporated fuel can be supplied to the engine supply pipe 3.

  On the contrary, when the estimated concentration of evaporated fuel is low, the amount of evaporated fuel stored in the canister 9 is small, so that it is not necessary to suppress the amount of evaporated fuel supplied to the engine supply pipe 3. Therefore, in this case, the purge valve 17 is driven according to a duty pulse having a relatively long pulse width. Thereby, even when the accumulation amount of the evaporated fuel is small, a sufficient amount of the evaporated fuel can be supplied to the engine supply pipe 3.

  In the present embodiment, during the purge control, the pressure in the pressure detection region 19 is detected at the timing when the purge valve 17 is closed based on a predetermined duty pulse (step S21).

  Next, the ECU 23 newly estimates the concentration of the evaporated fuel based on the graph or table stored in the storage unit 25. Specifically, the ECU 23 estimates the concentration of the evaporated fuel based on the rotational speed of the pressurizing pump 15 in the present embodiment of 30000 rpm and the detected value of the pressure sensor 21 (step S22).

  Then, the ECU 23 controls the heater 9h of the canister 9 in accordance with the expected change in the concentration of the evaporated fuel (step S23).

  Specifically, as shown in the time chart of FIG. 4, when the evaporated fuel is supplied from the canister 9 to the engine intake pipe 3 by executing the purge control, the evaporative fuel is desorbed from the canister 9, At this time, the canister temperature decreases due to the influence of latent heat of vaporization ((1) in FIG. 4).

  As the temperature of the canister 9 decreases, the desorption of the evaporated fuel from the canister 9 is suppressed, and the concentration of the evaporated fuel starts to decrease (correspondingly, the acquired pressure detection value starts to decrease). ((2) in FIG. 4).

  Based on the decreasing tendency of the evaporated fuel concentration (decreasing tendency of the pressure detection value), the ECU 23 starts heating the heater 9h so that the concentration of the evaporated fuel (pressure detection value) falls within a predetermined target range. (Or increase the heating amount of the heater) ((3) in FIG. 4). As a result, the detachment of the evaporated fuel from the canister 9 continues to be promoted, and the concentration of the evaporated fuel (pressure detection value) changes so as to be within a predetermined target range.

  As described above, conventionally, the concentration of the evaporated fuel has decreased as shown by the broken line in FIG. 4. According to the present embodiment, the concentration of the evaporated fuel (pressure detection value) falls within a predetermined target range. Can be stabilized.

  Thereafter, when the purge control is continued, the process returns to step S13, and the target opening of the purge valve 17 is determined again in consideration of the concentration of the evaporated fuel estimated in step S22, and the purge control is performed. Then, steps S21 to S23 are repeated.

  Regarding step S23, the concentration of the evaporated fuel may start to increase depending on the actual situation of the purge control. In such a case, the ECU 23 determines that the concentration of the evaporated fuel (pressure detection value) is high. There may be a case where the heating amount of the heater 9h is reduced so as to be within a predetermined target range.

  When the purge control is finished, the pressurizing pump 15 is stopped (step S14), the purge valve 17 is closed (step S15), and if YES in step S02 (when EV running). The engine stops and returns to EV running (steps S16 and S17). Thereby, the process of this embodiment is complete | finished.

  As described above, according to the present embodiment, while the purge control is being performed, the heater 9h is controlled so that the estimated concentration of the evaporated fuel is within a predetermined range, so that the canister can be effectively heated. The purge control can be performed with high accuracy as a result.

  Further, according to this embodiment, even when the engine is stopped, by driving the pressurizing pump 15 between the canister 9 on the purge passage 7 and the purge valve 17, the evaporated fuel in the canister 9 is removed from the canister 9. 9 can generate a negative pressure for suction. Based on the property that the detected value of the pressure sensor 21 increases as the concentration of the evaporated fuel increases, the concentration of the evaporated fuel can be estimated with high accuracy based on the detected value of the pressure sensor 21. Thus, the purge control can be started by starting the engine at a suitable timing in order to reliably prevent the evaporation of the evaporation into the atmosphere.

  Further, according to the present embodiment, the evaporated fuel accumulated in the canister 9 is purged based on the estimated evaporated fuel concentration, so that the amount of evaporated fuel flowing into the engine intake pipe 3 is taken into consideration. In addition, the air-fuel ratio in the cylinder can be controlled with high accuracy.

  In the flow of FIG. 2, the concentration of the evaporated fuel is estimated based on the detection value of the pressure sensor 21, but the steps (step S06, step S22) are omitted, and the pressure sensor 21 in steps S07, S08. The detected value itself may be an evaluation target.

DESCRIPTION OF SYMBOLS 1 Evaporated fuel processing apparatus 3 Engine intake pipe 5 Fuel tank 7 Purge passage 9 Canister 9h Heater 11 Atmospheric release valve 13 Atmospheric release port 15 Pressurizing pump 17 Purge valve 19 Pressure detection area 21 Pressure sensor 23 ECU
25 Storage Unit 41 Outside Air Temperature Sensor 43 Atmospheric Pressure Sensor 45 Fuel Temperature Sensor

Claims (5)

A purge passage extending from the fuel tank toward the engine intake pipe;
A canister provided on the purge passage for receiving and accumulating evaporated fuel from the fuel tank;
A purge valve provided downstream of the canister on the purge passage;
Concentration detecting means for measuring or estimating the concentration of the evaporated fuel;
Heating means for heating the canister;
A control unit connected to the purge valve and the heating means;
With
The control unit opens the purge valve to perform purge control of the evaporated fuel accumulated in the canister and measures or estimates the concentration detected by the concentration detection means while performing the purge control. The evaporative fuel processing apparatus is characterized in that the heating means is controlled so that the concentration of the evaporative fuel falls within a predetermined range. A pressurizing pump provided between the canister on the purge passage and the purge valve, forcibly supplying the gas in the purge passage to the purge valve;
A pressure sensor for detecting the pressure of the gas forcedly supplied by the pressurization pump in a detection region between the pressurization pump and the purge valve on the purge passage;
Further comprising
The concentration detecting means drives the pressure pump from a stopped state under a predetermined driving condition with the purge valve closed in a predetermined engine operating state, and the concentration of the evaporated fuel based on a detection value of the pressure sensor. The evaporative fuel processing apparatus according to claim 1, wherein the evaporative fuel processing apparatus is estimated. The control section controls opening of the purge valve to perform purge control of the evaporated fuel accumulated in the canister based on the measured or estimated concentration of evaporated fuel. Or the evaporative fuel processing apparatus of 2. A purge passage extending from the fuel tank toward the engine intake pipe;
A canister provided on the purge passage for receiving and accumulating evaporated fuel from the fuel tank;
A purge valve provided downstream of the canister on the purge passage;
A pressurizing pump provided between the canister on the purge passage and the purge valve, forcibly supplying the gas in the purge passage to the purge valve;
A pressure sensor for detecting the pressure of the gas forcedly supplied by the pressurization pump in a detection region between the pressurization pump and the purge valve on the purge passage;
A control unit connected to the purge valve, the pressurizing pump and the pressure sensor;
With
The control unit, in a predetermined engine operating state, drives the pressurizing pump from a stopped state under a predetermined driving condition with the purge valve closed, acquires a detection value of the pressure sensor, and then the canister The purge valve is opened in order to perform the purge control of the evaporated fuel accumulated in the tank, and the heating means is controlled so that the detected value falls within a predetermined range during the purge control. The evaporative fuel processing apparatus characterized by the above-mentioned. 5. The evaporated fuel processing apparatus according to claim 4, wherein the control unit controls opening of the purge valve to perform purge control of the evaporated fuel accumulated in the canister based on the detected value. 6. .

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