JP6292541B2 - Evaporative fuel processing equipment - Google Patents

Description

  The present invention relates to an evaporated fuel processing apparatus, and more particularly to an evaporated fuel processing apparatus capable of supplying evaporated fuel to an engine with high accuracy.

  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. A canister made of activated carbon or the like that receives and accumulates 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 due to the negative pressure generated in the purge passage, and supplied to the engine through the engine intake pipe (for example, Patent Document 1).

JP 2009-138561 A

  In recent years, the development of a system that reduces the pump loss of the engine by constantly opening the throttle valve disposed on the upstream side of the engine has been advanced. In such a system, there is almost no opportunity to throttle the throttle valve, and it is difficult to purge the evaporated fuel accumulated in the canister. Therefore, in such a system, instead of the throttle valve, a pressurizing pump for generating a negative pressure in the purge passage is arranged, and by operating the pressurizing pump, the evaporated fuel accumulated in the canister is sucked, The engine is supplied to the engine supply pipe.

  However, when a pressurizing pump is used, there is a problem that the controllability of the supply amount when supplying evaporated fuel to the engine supply pipe is deteriorated. That is, when a pressurizing pump is disposed in the purge passage, the minimum required for sucking fuel from the viewpoint of preventing an increase in the size of the pressurizing pump and an increase in energy required for driving the pressurizing pump. Limited output is used. When a pressure pump with a relatively low output is used, the differential pressure in the purge passage before and after the pressure pump is not so high, so that the pressure fluctuation of the pressure pump, the intake pipe pulsation, etc. Even small pressure fluctuations are greatly affected by the pressure pump output. Thereby, the difference between the target supply amount of the evaporated fuel and the amount of the evaporated fuel actually supplied to the engine supply pipe may increase.

  Therefore, the present invention has been made to solve the above-described problems, and it is possible to control the supply amount of the evaporated fuel to the engine supply pipe with high accuracy regardless of the fluctuation of the pressurizing pressure of the pressurizing pump. It is an object of the present invention to provide an evaporative fuel treatment device that can be used.

  In order to solve the above-described problems, the present invention provides a purge passage that extends from a fuel tank to an engine supply pipe, and is provided on the purge passage downstream of the fuel tank and accepts evaporated fuel from the fuel tank. A canister that accumulates, an air release valve for introducing fresh air into the canister, and a pressure pump that is provided on the purge passage downstream of the canister and generates a negative pressure in the canister An evaporative fuel treatment apparatus comprising a first purge valve provided between the pressurization pump and the supply pipe on the purge passage, wherein the pressurization pump, the first purge valve, A second passage having a valve diameter that is smaller than the diameter of the first purge valve, and a branch passage that branches from the purge passage. And when the concentration of the evaporated fuel flowing from the canister is higher than a predetermined value, the second purge valve is controlled to open, and the first purge valve is closed to evaporate. Fuel is supplied to the engine supply pipe from the branch passage.

  According to the present invention thus configured, a purge passage in which a first purge valve is formed and a branch passage in which a second purge valve is formed between a pressurizing pump and an engine supply pipe. Two passages can be formed. When the concentration of the evaporated fuel flowing from the canister is higher than a predetermined value, the second purge valve having a small valve diameter is controlled to open, and the first purge valve is closed to evaporate. The fuel can be supplied to the engine supply pipe while suppressing the flow rate of the fuel. If the amount of evaporated fuel is relatively large and if it is attempted to control the amount of evaporated fuel through a valve having a relatively large valve diameter, the amount of evaporated fuel supplied will fluctuate significantly due to fluctuations in the pressure pump and intake pipe pulsation. End up. On the other hand, when the amount of evaporated fuel is relatively large as in the present invention, even if the pressurizing pressure of the pressure pump fluctuates by using the second purge valve having a relatively small valve diameter. As a result, fluctuations in the amount of fuel vapor supplied can be suppressed.

  Further, in this case, when the concentration of the evaporated fuel flowing from the canister is lower than a predetermined value, both the first purge valve and the second purge valve are controlled to open the evaporated fuel. It is preferable to supply the engine supply pipe from the purge passage and the branch passage.

  According to the present invention configured as described above, when the concentration of the evaporated fuel flowing from the canister is lower than a predetermined value, both the first purge valve and the second purge valve are controlled to open. A relatively large flow path can be secured by controlling the opening of the two purge valves. As a result, a large amount of evaporated fuel can be supplied to the engine supply pipe.

  As described above, according to the present invention, it is possible to control the amount of evaporated fuel supplied to the engine supply pipe with high accuracy regardless of fluctuations in the pressure applied by the pressurizing pump.

1 is a system configuration diagram of a fuel vapor processing apparatus according to an embodiment. FIG. It is a flowchart for demonstrating operation | movement of the evaporative fuel processing apparatus by embodiment of this invention. It is a flowchart which shows operation | movement of the evaporation fuel processing apparatus by embodiment of this invention, and is a flowchart which shows the process which estimates the density | concentration of evaporation fuel. It is a map which shows the relationship between the pressure difference ((DELTA) P) and density | concentration ((rho)) which the evaporative fuel processing apparatus by embodiment of this invention uses. It is a graph which shows the relationship between the amount of intake air (Qa) which the vaporized fuel processing apparatus by embodiment of this invention uses, the estimated density | concentration ((rho)) of vaporized fuel, and the purge valve by which valve opening control is carried out. It is a graph which shows the opening-and-closing duty of the 1st purge valve and the 2nd purge valve which the evaporative fuel processing apparatus by embodiment of this invention uses.

  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.

  First, as shown in FIG. 1, the evaporated fuel processing apparatus 1 includes a purge passage 7 that extends between the engine intake pipe 3 and the fuel tank 5. The engine supply pipe 3 is configured to supply the air introduced from the air cleaner 9 to the engine 11. A throttle valve 13 for adjusting the amount of air supplied to the engine 11 is provided in the engine supply pipe 3. In the present embodiment, for example, the engine 11 performs self-ignition operation in a low load region, and the throttle valve 13 is basically always open. An intake pressure sensor 15 for detecting the pressure in the engine intake pipe 3 is provided in the engine intake pipe 3.

  Further, a canister 17 that receives and accumulates the evaporated fuel in the fuel tank 5 is provided downstream of the fuel tank 5 in the purge passage 7.

  The canister 17 contains an adsorbent such as activated carbon, for example. The evaporated fuel flowing from the fuel tank 5 is once adsorbed by the adsorbent. Via a canister 17 and an air release valve 19, it is connected to an air release port 21 opened to the atmosphere.

  On the downstream side of the canister 17 in the purge passage 7, for example, a centrifugal pump, a pressurizing pump 23 for changing the pressure in the purge passage 7, and a first purge valve 25 for opening and closing the purge passage 7 are provided. Is provided. A pressure accumulation chamber 27 and a purge pressure sensor 29 for detecting the pressure in the pressure accumulation chamber 27 are provided between the pressure pump 23 and the first purge valve 25 in the purge passage 7. A branch pipe 31 extending from the pressure accumulation chamber 27 to the engine supply pipe 3 is further connected to the pressure accumulation chamber 27.

  The branch pipe 31 branches from the purge passage 7 and extends to the engine supply pipe 3 from the pressure accumulation chamber 27. In the branch pipe 31, a second purge valve 33 that opens and closes the branch pipe 31 is provided. The second purge valve 33 is controlled independently of the first purge valve 25 and has a valve diameter smaller than that of the first purge valve 25. As an example, the first purge valve 25 has a valve diameter capable of flowing a gas of about 40 L / min, and the second purge valve 33 has a valve diameter capable of flowing a gas of about 20 L / min. .

  The evaporative fuel processing apparatus 1 further controls the throttle valve 13, the atmosphere release valve 19, the pressurizing pump 23, the first purge valve 25, and the second purge valve 33, the intake pressure sensor 15, and the purge An ECU 35 that receives a detection value from the pressure sensor 29 is provided.

  Next, the operation of the evaporated fuel processing apparatus 1 will be described. FIG. 2 is a flowchart for explaining the operation of the fuel vapor processing apparatus.

  When the engine is started and a series of processes starts, in step S1, the evaporated fuel processing apparatus 1 determines whether or not the evaporated fuel purge condition is satisfied. This process is executed by the ECU 35 monitoring the operating state of the engine 11 and determining whether or not the engine 11 has reached a predetermined operating state.

  Next, in step S <b> 2, the evaporated fuel processing apparatus 1 estimates the concentration of the evaporated fuel in the purge passage 7 when the evaporated fuel is purged from the canister 17. Various methods are known as a method for estimating the concentration of the evaporated fuel. As an example, the following estimation method can be applied.

  FIG. 3 is a flowchart showing a process for estimating the concentration of the evaporated fuel in step S2. The flowchart shown in FIG. 3 is executed along with the start of engine driving, and is repeatedly executed until the engine stops.

  When a series of processes starts, the evaporated fuel processing apparatus 1 drives the pressurizing pump 23 in step S201. Further, when the atmosphere release valve 19 is in the closed state, the atmosphere release valve 19 is opened. This process is performed by applying a driving voltage to the pressurizing pump 23 under the control of the ECU 35, driving the pressurizing pump 23 at a predetermined rotational speed, and controlling the atmosphere release valve 19. When the pressurizing pump 23 is driven at a predetermined number of revolutions, an airflow that flows into the purge passage 7 through the atmosphere opening 21 and the canister 17 is generated. Due to this air flow, the evaporated fuel accumulated in the canister 17 flows toward the downstream side of the purge passage 7.

  Next, in step S <b> 202, the evaporated fuel processing apparatus 1 closes the first purge valve 25 and the second purge valve 33. Thereby, the space between the output side of the pressurizing pump 23 and the first purge valve 25 and the second purge valve 33, that is, the pressure accumulating chamber 27 is substantially closed.

  Next, in step S <b> 203, the evaporated fuel processing apparatus 1 detects the pressure in the pressure accumulation chamber 27. That is, when the first purge valve 25 and the second purge valve 33 are closed in step S202, the pressure accumulation chamber 27 that is a substantially closed space is pressurized by the pressure pump 23, and the pressure in the pressure accumulation chamber 27 is reduced. To rise. When the pressure in the pressure accumulation chamber 27 reaches a certain pressure, the gas from the pressurizing pump 23 cannot flow into the pressure accumulation chamber 27. Thereby, the pressure in the pressure accumulating chamber 27 is stabilized, and the amount of gas flowing in from the pressurizing pump 23 becomes zero. The ECU 35 detects the pressure in the pressure accumulating chamber 27 when the gas inflow amount Q becomes zero.

  Next, in step S204, the evaporated fuel processing apparatus 1 estimates the concentration of the evaporated fuel. As a method for estimating the concentration of the evaporated fuel, the pressure in the pressure accumulating chamber 27 when a gas containing no evaporated fuel is caused to flow into the pressure accumulating chamber 27 by the pressurizing pump 23 in the evaporation processing apparatus 1. In addition, data indicating the relationship between the pressure difference (ΔP) in the pressure accumulating chamber 27 when the gas containing the evaporated fuel flows into the pressure accumulating chamber 27 and the concentration (ρ) of the evaporated fuel is stored in advance. There is a method for estimating the concentration of the evaporated fuel based on the data. The pressure (P1) in the pressure accumulating chamber 27 when the gas not containing the evaporated fuel is caused to flow into the pressure accumulating chamber 27 by the pressurizing pump 23 is a value measured in advance and stored in the evaporated fuel processing device 1. is there. In order to measure the pressure related to the gas that does not include the evaporated fuel, the same pump as the pressurizing pump 23 is used, and in the space having the same volume as the pressure accumulating chamber 27, under the same conditions as the driving conditions of the pressurizing pump 23 Drive to let gas flow in.

  And the pressure (P2) after pressurization is measured also about the gas containing evaporative fuel of a different density | concentration with the same measuring method. Then, for each density value, a difference (ΔP) between the value (P2) and the value (P1) is calculated, and a map showing the relationship between the difference (ΔP) and the density (ρ) as shown in FIG. Created and stored in the evaporated fuel processing apparatus 1. Since the concentration of particles in the gas and the pressure of the gas show a proportional relationship, the relationship between the difference (ΔP) and the concentration (ρ) shows a proportional relationship as shown by the line L1. When estimating the concentration of the evaporated fuel, the ECU 35 causes the value (P2) detected by the purge pressure sensor 29 and a pre-measured gas not including the evaporated fuel to flow into the pressure accumulating chamber 27. The difference (ΔP) from the pressure (P1) in the pressure accumulating chamber 27 is calculated. Next, the ECU 35 refers to the map shown in FIG. 4 based on the difference (ΔP) and estimates the concentration (ρ) of the evaporated fuel.

  After performing the evaporative fuel concentration estimation process, the evaporative fuel processing apparatus 1 executes the processes after step S3 in FIG.

  In step S3, the evaporated fuel processing apparatus 1 determines whether or not the estimated concentration of evaporated fuel is equal to or higher than a predetermined reference concentration. This process is performed by the ECU 35 comparing the concentration of the evaporated fuel estimated in step S2 with a predetermined reference concentration. Then, when the estimated concentration of the evaporated fuel is equal to or higher than a predetermined reference concentration, the processes after step S4 are executed.

  In step S <b> 4, the evaporated fuel processing apparatus 1 calculates the intake air amount to the engine 11. This process is performed by the ECU 35 referring to the operating state of the engine 11 and the gas flow rate in the engine intake pipe 3.

  Next, in step S5, the evaporated fuel processing apparatus 1 determines whether or not the calculated intake air amount is equal to or greater than a predetermined reference air amount. This process is performed by the ECU 35 comparing the calculated intake air amount with a predetermined reference air amount. Then, when the calculated intake air amount is equal to or greater than a predetermined reference air amount, the processes after step S6 are performed.

  In step S <b> 6, the evaporated fuel processing apparatus 1 detects the differential pressure between the upstream side and the downstream side of the first purge valve 25 and the second purge valve 33. In this process, the ECU 35 refers to the detected value of the purge pressure sensor 29 on the upstream side of the first purge valve 25 and the second purge valve 33 and the detected value of the intake pressure sensor 15 in the engine supply pipe 3. It is done by doing.

  Next, in step S <b> 7, the evaporated fuel processing apparatus 1 controls the opening of the first purge valve 25. More specifically, the ECU 35 sets the drive duty of the first purge valve 25 based on the differential pressure between the upstream side and the downstream side of the first purge valve 25 and the second purge valve 33 detected in step S6. The calculation is performed by opening and closing the first purge valve 25 at predetermined intervals based on the calculated duty. Thereby, the evaporated fuel in the purge passage 7 flows into the engine supply pipe 3 and is supplied to the engine 11.

  On the other hand, if it is determined in step S5 that the calculated intake air amount is not equal to or greater than the predetermined reference air amount, the evaporated fuel processing device 1 performs the opening control of the second purge valve 33 in step S8. The differential pressure between the upstream side and the downstream side of the first purge valve 25 and the second purge valve 33 is detected, and the second purge valve 33 is controlled to open in step S9. The process in step S8 is the same process as the process in step S6, and the process in step S9 is the same process as the process in step S7, and thus detailed description thereof is omitted.

  If it is determined in step S3 that the estimated concentration of the evaporated fuel is not equal to or higher than the predetermined reference concentration, the evaporated fuel processing device 1 calculates the intake air amount in step S10 and the calculated in step S11. It is determined whether or not the calculated intake air amount is equal to or greater than a predetermined reference air amount. Note that the process in step S10 is the same as the process in step S4, and the process in step S11 is the same as the process in step S5, and thus detailed description thereof is omitted.

  Next, when it is determined in step 11 that the calculated intake air amount is equal to or greater than a predetermined reference air amount, the evaporated fuel processing device 1 turns on both the first purge valve 25 and the second purge valve 33. In order to perform valve opening control, a differential pressure between the upstream side and the downstream side of the first purge valve 25 and the second purge valve 33 is detected in step S12, and the first purge valve 25 and the second purge valve are detected in step S13. The valve 33 is controlled to open.

  Further, when it is determined in step S11 that the calculated intake air amount is not equal to or greater than the predetermined reference air amount, the evaporated fuel processing apparatus 1 performs the first control in step S14 to control the opening of the first purge valve 25. The differential pressure between the upstream side and the downstream side of the first purge valve 25 and the second purge valve 33 is detected, and the opening of the first purge valve 25 is controlled in step S15. Note that the processing in step S12 and step S14 is the same processing as the processing in step S6, and the processing in step S13 and step S15 is the same processing as the processing in step S7, and thus detailed description thereof is omitted.

  According to the example process described above, it is possible to select a purge valve for valve opening control based on the fuel vapor concentration estimated in step S2 and the intake air amount calculated in steps S4 and S10.

  FIG. 5 is a graph showing the relationship between the intake air amount (Qa), the estimated concentration (ρ) of evaporated fuel, and the purge valve that is controlled to open. The graph shown in FIG. 5 shows the concentration (ρ) of the evaporated fuel estimated along the X axis, and the intake air amount (Qa) calculated along the Y axis. Then, the evaporated fuel processing apparatus 1 selects a purge valve for valve opening control based on the two values of the calculated intake air amount (Qa) and the estimated concentration (ρ) of the evaporated fuel.

  When the calculated intake air amount (Qa) is not less than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is not not less than the reference concentration (ρr), that is, the relationship between the two is shown in FIG. 2 (when the processing is performed in the order of step S3, step S10, step S11, step S12, and step S13 in the flowchart shown in FIG. 2), the evaporated fuel processing device 1 The purge valves of both the purge valve 25 and the second purge valve 33 are controlled to open. Thus, the amount of evaporated fuel supplied from the purge passage 7 into the engine supply pipe 3 can be set to the maximum amount that can be supplied by the evaporated fuel processing apparatus 1. When the calculated intake air amount (Qa) is not less than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is not not less than the reference concentration (ρr), the required fuel amount from the engine 11 And the amount of evaporated fuel in the purge passage 7 is small (in other words, the amount of evaporated fuel accumulated in the canister 17 is small). When the amount of evaporated fuel in the purge passage 7 is small, even if the amount of gas flowing from the purge passage 7 into the engine supply pipe 3 is increased, fluctuations in the amount of evaporated fuel supplied or errors with respect to the target supply amount Less. Therefore, in this case, in order to purge more evaporated fuel, both the first purge valve 25 and the second purge valve 33 are controlled to open, and the gas flow from the purge passage 7 to the engine supply pipe 3 is controlled. Increase inflow.

  FIG. 6 is a graph showing the opening / closing duty of the first purge valve and the second purge valve. As shown in FIG. 6, the ECU 35 preferably performs control so as to alternately open and close the first purge valve 25 and the second purge valve 33.

  On the other hand, when the calculated intake air amount (Qa) is not equal to or greater than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is equal to or greater than the reference concentration (ρr), that is, the relationship between the two. Is applied to the area A4 shown in FIG. 5 (in the flowchart shown in FIG. 2, the process is performed in the order of step S3, step S4, step S5, step S8, and step S9), the evaporated fuel processing apparatus 1 Only the second purge valve 33 is controlled to open. As a result, the amount of evaporated fuel supplied from the purge passage 7 into the engine supply pipe 3 can be made the minimum amount that can be supplied by the evaporated fuel processing device 1. When the calculated intake air amount (Qa) is not equal to or greater than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is equal to or greater than the reference concentration (ρr), a fuel request from the engine 11 is obtained. This indicates that the amount is small and the amount of evaporated fuel in the purge passage 7 is large (in other words, the amount of evaporated fuel accumulated in the canister 17 is large). When the amount of evaporated fuel in the purge passage 7 is large, if the amount of gas flowing from the purge passage 7 into the engine supply pipe 3 is increased, the variation in the amount of evaporated fuel supply or an error with respect to the target supply amount increases. Become. Further, if a large amount of evaporated fuel is supplied into the engine supply pipe 3 in a state where the amount of fuel requested from the engine 11 is small, there is a possibility that the evaporated fuel cannot be completely processed by the engine 11. Accordingly, in this case, in order to reduce the amount of evaporated fuel supplied to the engine 11, only the second purge valve 33 having a small valve diameter is controlled to open, and the gas from the purge passage 7 to the engine supply pipe 3 is controlled. Increase the amount of inflow.

  Further, when the calculated intake air amount (Qa) is not equal to or greater than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is not equal to or greater than the reference concentration (ρr), that is, the relationship between the two is a region. When A2 is true, the amount of evaporated fuel to be processed is small and the supply amount of the evaporated fuel is less likely to vary due to the variation of the pressurizing pump 23. Therefore, only the first purge valve 25 is controlled to open, Evaporated fuel is supplied to the engine supply pipe 3.

  Further, when the calculated intake air amount (Qa) is equal to or greater than the reference air amount (Qr) and the estimated concentration (ρ) of the evaporated fuel is equal to or greater than the reference concentration (ρr), that is, the relationship between the two. In the case of the region A3, although the amount of evaporated fuel to be processed is large, the amount of fuel required by the engine 11 is large. Therefore, only the first purge valve 33 is controlled to open.

  As described above, according to the present embodiment, the purge passage in which the first purge valve 25 is formed and the second purge valve 33 are formed between the pressurizing pump 23 and the engine supply pipe 3. Two passages can be formed with the branch passage. When the concentration of the evaporated fuel flowing from the canister 17 is higher than the reference concentration (ρr), the second purge valve 33 having a small valve diameter is controlled to open, and the first purge valve 25 is closed. By controlling the valve, the flow rate of the evaporated fuel can be supplied to the engine supply pipe 3 while being suppressed. Thereby, even if the pressure of the pressurizing pump 23 fluctuates by using the second purge valve 33 having a smaller valve diameter compared to the valve diameter of the first purge valve 25, the evaporated fuel It is possible to suppress fluctuations in the supply amount.

DESCRIPTION OF SYMBOLS 1 Evaporative fuel processing apparatus 3 Engine supply pipe 5 Fuel tank 7 Purge channel | path 17 Canister 19 Atmospheric release valve 23 Pressurization pump 25 1st purge valve 31 Branch pipe 33 2nd purge valve

Claims (4)

A purge passage extending from the fuel tank to the engine supply pipe;
A canister provided on the downstream side of the fuel tank on the purge passage for receiving and accumulating evaporated fuel from the fuel tank,
An air release valve for introducing fresh air into the canister,
A pressure pump provided on a downstream side of the canister and generating a negative pressure in the canister on the purge passage;
An evaporative fuel processing apparatus comprising a first purge valve provided between the pressurizing pump and the supply pipe on the purge passage;
A branch passage branching from the purge passage between the pressurizing pump and the first purge valve;
A second purge valve provided on the branch passage and having a valve diameter smaller than that of the first purge valve;
When the concentration of the evaporated fuel flowing from the canister is higher than a predetermined value, the second purge valve is controlled to open, and the first purge valve is closed to supply the evaporated fuel to the branch passage. An evaporative fuel processing device, wherein the evaporative fuel processing device supplies the fuel to an engine supply pipe.   When the concentration of the evaporated fuel flowing from the canister is lower than a predetermined value, both the first purge valve and the second purge valve are controlled to open, and the evaporated fuel is supplied to the purge passage and the branch. The evaporated fuel processing apparatus according to claim 1, wherein the evaporated fuel processing apparatus supplies the engine supply pipe from the passage.   When the amount of intake air to the engine is larger than a predetermined value, the first purge valve is controlled to open, and the second purge valve is closed to allow the evaporated fuel to flow from the air distribution passage. The evaporative fuel processing apparatus of Claim 1 supplied to an engine supply pipe | tube.   When the amount of intake air to the engine is lower than a predetermined value, the first purge valve is controlled to open, and the second purge valve is closed to evaporate fuel from the air distribution passage. The evaporative fuel processing apparatus of Claim 2 supplied to an engine supply pipe.

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