Diagnostic device for evaporated fuel treatment system

Abstract

To provide a diagnostic device for an evaporated fuel treatment system that can eliminate or prevent a foreign body caught in a switching valve (and eliminate or prevent wrong diagnosis) without adding new (dedicated) hardware.SOLUTION: A diagnostic device 77 for an evaporated fuel treatment system comprises: a pump 772 for generating negative pressure; and a switching valve 771 for switching between a state in which communication is established between a pump passage 776 made to communicate with a suction port of the pump 772, and an evaporation passage 775 made to communicate with a canister 71, and a state in which communication is established between an orifice passage 777 connected to the pump passage 776, and in which a reference orifice 774 is interposed, and an atmosphere passage 778 of which one end is opened to the atmosphere. When a predetermined cleaning control execution condition is established, an ECU 50 drives the switching valve 771 and drives the pump 772 so as to establish communication between the evaporation passage 775 and the pump passage 776 in a throttled state or establish communication between the atmosphere passage 778 and the orifice passage 777 in a throttled state.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a diagnostic device for diagnosing the presence or absence of an abnormality in an evaporative fuel treatment system that sucks and burns evaporative fuel generated in a fuel tank in an intake system of an engine for treatment.

Background Art

[0002] Conventionally, in order to prevent the release of evaporative fuel generated in a fuel tank into the environment (atmosphere), the evaporative fuel is temporarily adsorbed by an adsorbent (e.g., activated carbon, etc.) in a canister, and the adsorbed evaporative fuel is sucked and burned in an intake system of an engine under predetermined operating conditions for treatment. An evaporative fuel treatment system (evaporative purge system) is widely used.

[0003] By the way, in North American OBD2 (On Board Diagnostics Second Generation), it is required to diagnose the presence or absence of an abnormality in such an evaporative fuel treatment system.

[0004] Therefore, for example, Patent Document 1 discloses an evaporative gas purge system leak diagnostic device (ELCM: Evaporative Leak Check Module) including an electric negative pressure pump, a reference pressure detection unit in which a reference hole (a hole having a predetermined hole diameter corresponding to a minute leak hole) is formed, a passage switching valve (switching valve) that switches a path for introducing a negative pressure into the reference pressure detection unit by the negative pressure pump and a path for introducing a negative pressure into the evaporative system by the negative pressure pump, and a pressure sensor.

[0005] In this diagnostic device, a negative pressure is introduced into the reference pressure detection unit by the negative pressure pump to detect the pressure in the reference pressure detection unit, that is, the reference pressure regulated by the reference hole. Then, the negative pressure introduction path of the pump is switched by the passage switching valve, a negative pressure is introduced into the evaporative system to detect the pressure in the evaporative system, and the presence or absence of a minute leak is determined by comparing the reference pressure with the pressure in the evaporative system.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-300997 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] By the way, for example, foreign matters such as fine particles of activated carbon discharged from the canister of an evaporation fuel treatment system or resin pieces mixed in the manufacturing process may get caught in a switching valve (passage switching valve) that constitutes a diagnostic device. When foreign matters such as activated carbon particles get caught in the switching valve, there is a risk that the diagnostic device of the evaporation fuel treatment system may make a misdiagnosis due to a sealing failure (for example, misdiagnose that a small leak has occurred). In addition, in order to prevent foreign matters from getting caught in the switching valve, a filter is provided in the canister, but from the viewpoint of suppressing (avoiding) an increase in pressure loss due to the filter, a relatively coarse filter is used, so it has been difficult to completely prevent (avoid) the intrusion of minute activated carbon particles and the like.

[0008] The present invention has been made to solve the above problems, and an object of the present invention is to provide a diagnostic device for an evaporation fuel treatment system that can eliminate or prevent foreign matters from getting caught in a switching valve (and eliminate or prevent misdiagnosis) without adding new (dedicated) hardware. [Means for Solving the Problems]

[0009] The diagnostic device for an evaporation fuel processing system according to one aspect of the present invention includes a pump that generates negative pressure, a pump passage communicating with the suction port of the pump, and an evaporation passage communicating with a canister that constitutes the evaporation fuel processing system. A switching valve that switches between a state of communicating the pump passage and the evaporation passage and a state of communicating an orifice passage connected to the pump passage with a reference orifice interposed therebetween and an atmosphere passage having one end opened to the atmosphere, and a control unit that controls the driving of the switching valve and the pump and diagnoses the presence or absence of an abnormality in the evaporation fuel processing system based on the pressure in the evaporation passage and the pressure in the orifice passage when the pump is driven. When a predetermined cleaning control execution condition is satisfied, the control unit drives the switching valve so as to communicate the evaporation passage and the pump passage in a constricted state or to communicate the atmosphere passage and the orifice passage in a constricted state, and executes cleaning control for driving the pump.

[0010] According to the diagnostic device for an evaporation fuel processing system according to one aspect of the present invention, when a predetermined cleaning control execution condition is satisfied, the switching valve is driven so as to communicate the evaporation passage and the pump passage in a constricted state or to communicate the atmosphere passage and the orifice passage in a constricted state, and the pump is driven (cleaning control is executed). Therefore, the flow rate at the switching valve can be increased to blow off foreign matter caught in the switching valve. Further, the control by the control unit can eliminate or prevent the biting of foreign matter, and it is not necessary to add new (dedicated) hardware. That is, it is possible to eliminate or prevent the biting of foreign matter without adding new (dedicated) hardware.

Effects of the Invention

[0011] According to the present invention, it is possible to eliminate or prevent the biting of foreign matter in the switching valve (and to eliminate or prevent misdiagnosis) without adding new (dedicated) hardware.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0013] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts will be denoted by the same reference numerals. Also, in each figure, the same elements are denoted by the same reference numerals, and redundant explanations are omitted.

[0014] First, with reference to FIGS. 1 to 6 together, the configuration of the diagnostic device 77 for an evaporative fuel processing system according to the embodiment will be described. FIG. 1 is a diagram showing the configuration of the diagnostic device 77 for an evaporative fuel processing system and the configuration of the engine 10 to which the diagnostic device 77 for the evaporative fuel processing system is applied. FIG. 2 is a cross-sectional view showing the configuration (off state) of the switching valve 771 that constitutes the diagnostic device 77 for the evaporative fuel processing system. Further, FIG. 3 is a cross-sectional view showing the configuration (on state) of the switching valve 771. FIG. 4 is a diagram showing the opening degree (gap) of the switching valve 771 during the cleaning control of the diagnostic device 77 for the evaporative fuel processing system, where (a) shows the opening degree (gap) during the execution of the cleaning control, (b) shows the state at full off (fully open), and (c) shows the state at full on (fully closed). FIG. 5 is a diagram for explaining the relationship between the applied current to the switching valve 771 and the opening degree (gap) during the cleaning control. FIG. 6 is a diagram showing an example of the current pattern applied to the switching valve 771 during the execution of the cleaning control.

[0015] The engine 10 is, for example, a horizontally opposed four-cylinder gasoline engine. Further, the engine 10 is an in-cylinder injection type engine that directly injects fuel into the cylinder (inside the cylinder). In the engine 10, the air inhaled from the air cleaner 16 is throttled by an electronically controlled throttle valve (hereinafter, also simply referred to as "throttle valve") 13 provided in the intake pipe 15, passes through the intake manifold 11, and is inhaled into each cylinder formed in the engine 10. Here, the amount of air inhaled from the air cleaner 16 (the amount of air inhaled into the engine 10) is detected by an air flow meter 14 disposed between the air cleaner 16 and the throttle valve 13. Also, inside the collector portion (surge tank) that constitutes the intake manifold 11, a vacuum sensor 30 for detecting the pressure in the intake manifold 11 (intake manifold pressure) is disposed. Further, a throttle opening sensor 31 for detecting the opening degree of the throttle valve 13 is disposed on the throttle valve 13.

[0016] In the cylinder head, an intake port 22 and an exhaust port 23 are formed for each cylinder (only one bank is shown in FIG. 1). An intake valve 24 and an exhaust valve 25 for opening and closing the intake port 22 and the exhaust port 23 are provided in each of the intake port 22 and the exhaust port 23. Between the intake camshaft 28 that drives the intake valve 24 and the intake cam pulley, the intake cam pulley and the intake camshaft 28 are relatively rotated to continuously change the rotational phase (displacement angle) of the intake camshaft 28 with respect to the crankshaft 10a, and a variable valve timing mechanism 26 for advancing and retarding the valve timing (opening and closing timing) of the intake valve 24 is disposed. The opening and closing timing of the intake valve 24 is variably set according to the engine operating state by this variable valve timing mechanism 26.

[0017] Similarly, between the exhaust camshaft 29 and the exhaust cam pulley, the exhaust cam pulley and the exhaust camshaft 29 are relatively rotated to continuously change the rotational phase (displacement angle) of the exhaust camshaft 29 with respect to the crankshaft 10a, and a variable valve timing mechanism 27 for advancing and retarding the valve timing (opening and closing timing) of the exhaust valve 25 is disposed. The opening and closing timing of the exhaust valve 25 is variably set according to the engine operating state by this variable valve timing mechanism 27.

[0018] An injector 12 for injecting fuel into the cylinder is attached to each cylinder of the engine 10. The injector 12 directly injects the fuel pressurized by the high-pressure fuel pump 60 into the combustion chamber of each cylinder.

[0019] The injector 12 is connected to a delivery pipe (common rail) 61. The delivery pipe 61 distributes the fuel pumped from the high-pressure fuel pump 60 through the fuel pipe 62 to each injector 12. The high-pressure fuel pump 60 boosts the fuel sucked up from the fuel tank 80 by the feed pump (low-pressure fuel pump) 64 to a high pressure (for example, 8 to 13 MPa) according to the operating state and supplies it to the delivery pipe 61. In this embodiment, a type of high-pressure fuel pump 60 driven by the camshaft 28 of the engine 10 is used.

[0020] In each cylinder head of each cylinder, an ignition plug 17 for igniting the air-fuel mixture and an in-igniter coil 21 for applying a high voltage to the ignition plug 17 are attached. In each cylinder of the engine 10, the air-fuel mixture of the inhaled air and the fuel injected by the injector 12 is ignited by the ignition plug 17 and burns. The exhaust gas after combustion is discharged through the exhaust pipe 18.

[0021] An air-fuel ratio sensor 19A that outputs a signal according to the oxygen concentration in the exhaust gas is attached to the exhaust pipe 18. As the air-fuel ratio sensor 19A, a linear air-fuel ratio sensor (LAF sensor) that can linearly detect the exhaust air-fuel ratio is used. Note that an O2 sensor that detects the exhaust air-fuel ratio on an on-off basis may be used as the air-fuel ratio sensor 19A.

[0022] Further, an exhaust gas purification catalyst (CAT) 20 is disposed downstream of the air-fuel ratio sensor 19A. The exhaust gas purification catalyst 20 is a three-way catalyst that simultaneously oxidizes hydrocarbons (HC) and carbon monoxide (CO) in the exhaust gas and reduces nitrogen oxides (NOx), and purifies harmful gas components in the exhaust gas into harmless carbon dioxide (CO2), water vapor (H2O), and nitrogen (N2). A rear (after CAT) O2 sensor 19B that detects the exhaust air-fuel ratio on an on-off basis is provided downstream of the exhaust gas purification catalyst 20.

[0023] Here, the engine 10 is provided with an evaporative fuel treatment system 70. The evaporative fuel treatment system 70 mainly includes a fuel tank 80, a canister 71, a first purge pipe 72a, a second purge pipe 72b, and a variable flow rate solenoid valve 73.

[0024] The fuel tank 80 stores the fuel supplied to the engine 10 (injector 12). The upper space of the fuel tank 80 communicates with a canister 71 that can adsorb the evaporative fuel generated in the fuel tank 80 via the first purge pipe 72a. The canister 71 has an adsorbent such as activated carbon inside and temporarily adsorbs the evaporative fuel in the fuel tank 80.

[0025] The upper space of the canister 71 is communicated with the intake manifold 11 via a second purge pipe 72b (the first purge pipe 72a and the second purge pipe 72b are collectively referred to as the purge pipe 72). A variable flow rate solenoid valve (hereinafter also referred to as a "purge solenoid valve") 73 whose opening degree is adjusted by the ECU 50 is interposed in the second purge pipe 72b.

[0026] When the purge solenoid valve 73 is opened and the negative pressure in the intake manifold 11 acts on the canister 71, outside air (air) is introduced into the canister 71 via a diagnostic device 77 of the evaporative fuel treatment system (details will be described later), and the evaporative fuel adsorbed on the activated carbon etc. in the canister 71 is desorbed. The desorbed evaporative fuel is inhaled into the intake manifold 11 of the engine 10 through the second purge passage 72b together with the air introduced via the diagnostic device 77 of the evaporative fuel treatment system. Then, the evaporative fuel inhaled into the intake manifold 11 is burned and processed in the cylinder of the engine 10.

[0027] A diagnostic device (ELCM (Evaporative Leak Check Module)) 77 of the evaporative fuel treatment system is connected to the canister 71. The diagnostic device 77 of the evaporative fuel treatment system mainly includes a switching valve 771, a pump 772, an orifice 774, and a pressure sensor 773, and diagnoses the presence or absence of an abnormality (such as leakage of evaporative fuel) in the evaporative fuel treatment system 70.

[0028] The switching valve 771, the pump 772, and the orifice 774 are connected to each other by an evaporative passage 775, an atmospheric passage 778, a pump passage 776, and an orifice passage 777. More specifically, one end of the evaporative passage 775 is connected to the canister 71, and the other end is connected to the switching valve 771. That is, the evaporative passage 775 communicates the canister 71 and the switching valve 771.

[0029] The atmosphere passage 778 is open to the atmosphere at one end via a filter 779, and the other end is connected to the discharge port of the pump 772 and the switching valve 771 respectively. That is, the atmosphere passage 778 communicates the open end open to the atmosphere with the discharge port of the pump 772 and the switching valve 771 respectively. The pump passage 776 has one end connected to the suction port of the pump 772 and the other end connected to the switching valve 771. That is, the pump passage 776 communicates the suction port of the pump 772 with the switching valve 771.

[0030] The orifice passage 777 has one end connected to the evaporation passage 775 and the other end connected to the pump passage 776. That is, the orifice passage 777 communicates the evaporation passage 775 with the pump passage 776. Further, a reference orifice (reference hole) 774 (hereinafter, sometimes simply referred to as "orifice 774") is provided in the orifice passage 777. Note that the reference orifice 774 is set according to the size of the opening allowing leakage (for example, φ0.5 mm).

[0031] The pump 772 is a negative pressure pump (vacuum pump) that generates negative pressure. For the pump 772, for example, an electric vane pump driven by an electric motor or the like is used. The pump 772 (electric motor) is driven (controlled) by an ECU 50 described later.

[0032] The switching valve 771 switches between a state where the evaporation passage 775 and the pump passage 776 communicate with each other (evaporation path) and a state where the atmosphere passage 778 and the orifice passage 777 communicate with each other (orifice path).

[0033] As shown in FIG. 2, when the switching valve 771 is fully off (when power supply is stopped), the atmosphere passage 778 and the orifice passage 777 communicate with each other, and the evaporation passage 775 and the pump passage 776 are blocked.

[0034] On the other hand, as shown in FIG. 3, when the switching valve 771 is fully on (when power is supplied), the evaporation passage 775 and the pump passage 776 communicate with each other, and the atmosphere passage 778 and the orifice passage 777 are blocked.

[0035] However, during the cleaning control described later, when the switching valve 771 connects the atmosphere passage 778 and the orifice passage 777 (when off), it does not completely block the evaporator passage 775 and the pump passage 776, but rather communicates with a slight gap (throttle). Or, when the switching valve 771 connects the atmosphere passage 778 and the orifice passage 777 (when on), it does not completely block the atmosphere passage 778 and the orifice passage 777, but rather communicates with a slight gap (throttle). The switching valve 771 is driven (controlled) by the ECU 50. Details will be described later.

[0036] Returning to FIG. 1, a pressure sensor 773 is attached downstream of the orifice 774 in the orifice passage 777 (between the orifice 774 and the pump passage 776 (pump suction port)). The pressure sensor 773 detects the pressure in the evaporator passage 775 (in the evaporator path) when the switching valve 771 is turned on and the pump 772 is driven during diagnosis. Also, the pressure sensor 773 detects the pressure in the orifice passage 777 (in the orifice system path) when the switching valve 771 is turned off and the pump 772 is driven during diagnosis. The pressure sensor 773 is connected to the ECU 50, and an electrical signal (e.g., voltage) corresponding to the pressure is read by the ECU 50.

[0037] In addition to the above-described air flow meter 14, LAF sensor 19A, O2 sensor 19B, vacuum sensor 30, throttle opening sensor 31, and pressure sensor 773, a cam angle sensor 32 for determining the cylinders of the engine 10 is attached near the camshaft of the engine 10. Further, a crank angle sensor 33 for detecting the rotational position of the crankshaft 10a is attached near the crankshaft 10a of the engine 10. Here, a timing rotor 33a having protrusions of 34 teeth with two teeth missing at 10° intervals, for example, is attached to the end of the crankshaft 10a, and the crank angle sensor 33 detects the rotational position of the crankshaft 10a by detecting the presence or absence of the protrusions of the timing rotor 33a. As the cam angle sensor 32 and the crank angle sensor 33, for example, electromagnetic pickup type sensors or the like are used.

[0038] These sensors are connected to the ECU 50. Further, various sensors such as a water temperature sensor 34 for detecting the temperature of the cooling water of the engine 10, an oil temperature sensor 35 for detecting the temperature of the lubricating oil, an accelerator opening sensor 36 for detecting the depression amount of the accelerator pedal, that is, the opening (operation amount) of the accelerator pedal, and an outside air temperature sensor 37 for detecting the outside air temperature are also connected to the ECU 50.

[0039] The ECU 50 includes a microprocessor that performs calculations, an EEPROM that stores programs and the like for causing the microprocessor to execute each process, a RAM that stores various data such as calculation results, a backup RAM whose stored content is retained by a battery, and an input / output I / F and the like. Further, the ECU 50 includes an injector driver that drives the injector 12, an output circuit that outputs an ignition signal, and a motor driver that drives the electronically controlled throttle valve 13 (electric motor 13a). Furthermore, the ECU 50 also includes a driver that drives the solenoid valve 606 that constitutes the high-pressure fuel pump 60, a driver that drives the purge solenoid valve 73, a driver that drives the pump 772 (electric motor), a driver that drives the switching valve 771, and the like.

[0040] In the ECU 50, the cylinder is discriminated from the output of the cam angle sensor 32, and the engine speed is obtained from the output of the crank angle sensor 33. Also, in the ECU 50, based on the detection signals input from the various sensors described above, various information such as the intake air amount, intake pipe negative pressure, accelerator pedal opening degree, air-fuel ratio of the air-fuel mixture, intake air temperature, atmospheric pressure, and the water temperature and oil temperature of the engine 10 are acquired. Then, the ECU 50 comprehensively controls the engine 10 by controlling various devices such as the fuel injection amount, ignition timing, throttle valve 13, purge solenoid valve 73, and switching valve 771 and pump 772 (electric motor) based on the various information thus acquired.

[0041] The ECU 50 turns off the switching valve 771 to communicate the atmosphere passage 778 and the orifice passage 777, drives the pump 772 to detect the pressure (reference pressure) in the orifice passage 777, and then turns on the switching valve 771 to communicate the evaporation passage 775 and the pump passage 776, drives the pump 772 to detect the pressure in the evaporation passage (evaporation passage internal pressure), and then diagnoses the presence or absence of an abnormality (such as a leak) in the evaporative fuel treatment system 70 based on the reference pressure and the evaporation passage internal pressure.

[0042] In particular, the ECU 50 has a function of eliminating or preventing the biting-in of foreign matter in the switching valve 771 (and eliminating or preventing misdiagnosis) without adding new (dedicated) hardware. In the ECU 50, the function is realized by the program stored in the EEPROM or the like being executed by the microprocessor. That is, the ECU 50 functions as the control unit described in the claims.

[0043] Therefore, when the predetermined cleaning control execution conditions are satisfied, the ECU 50 drives the switching valve 771 so that the air passage 778 and the orifice passage 777 communicate with each other in a narrowed state, or the evaporation passage 775 and the pump passage 776 communicate with each other in a narrowed state, and also drives the pump 772 (executes cleaning control). That is, the flow rate is increased by narrowing the flow path of the switching valve 771, and foreign matter adhering to the switching valve 771 is blown off.

[0044] That is, during cleaning control, when the ECU 50 communicates the air passage 778 and the orifice passage 777 (when the switching valve 771 is off), it does not completely block the evaporation passage 775 and the pump passage 776, but communicates with a slight gap (throttle) and drives the pump 772. Or, when the ECU 50 communicates the evaporation passage 775 and the pump passage 776 (when the switching valve 771 is on), it does not completely block the air passage 778 and the orifice passage 777, but communicates with a slight gap (throttle) and drives the pump 772. That is, the flow rate is increased by narrowing the flow path of the switching valve 771, and foreign matter adhering to the switching valve 771 is blown off.

[0045] For example, when the ECU 50 determines that an abnormality has occurred in the evaporative fuel treatment system 70, and determines that the predetermined cleaning control execution conditions are satisfied, the ECU 50 executes the above-described cleaning control.

[0046] Here, the opening degree (gap) of the switching valve 771 during cleaning control is shown in FIG. 4(a). For reference, the state at full off (fully open) is shown in (b), and the state at full on (fully closed) is also shown in (c).

[0047] As shown in FIG. 4(b), when it is fully off (fully open), the passage cross-sectional area increases and the flow velocity decreases. Therefore, the fluid force acting on the foreign matter becomes small, making it difficult to blow off the foreign matter. Also, as shown in FIG. 4(c), when it is fully on (fully closed), the valve (valve element) 771a is pressed against the foreign matter. Therefore, the load for retaining the foreign matter becomes high, and the foreign matter cannot be blown off.

[0048] On the other hand, as shown in FIG. 4(a), when communicating with a minute gap (throttle), the passage cross-sectional area becomes small and the flow velocity becomes fast. Also, since the valve (valve element) 771a is not pressed against the foreign matter, the load for retaining the foreign matter is low. Therefore, the foreign matter can be blown off by the fluid force.

[0049] That is, the ECU 50 drives the pump 772 (generates negative pressure) with the communication between the evaporation passage 775 and the pump passage 776, or the communication between the atmosphere passage 778 and the orifice passage 777 (switching valve 771) restricted, to increase the flow velocity at the switching valve 771 and blow off (expel) the foreign matter caught in the switching valve 771.

[0050] Note that when the atmosphere passage 778 and the orifice passage 777 are communicated in a restricted state, or when the evaporation passage 775 and the pump passage 776 are communicated in a restricted state during the execution of the cleaning control, the valve gap (opening degree) of the switching valve 771 is set based on the size of the foreign matter caught in the switching valve 771. More specifically, for example, when the diameter of the foreign matter is 0.5 to 0.7 mm, it is preferable to set the valve gap (opening degree) to about 0.8 mm.

[0051] Furthermore, for example, even if the characteristics change due to variations in the individual dimensions of the switching valve 771, temperature changes, etc., in order to surely blow off the foreign matter, the ECU 50 periodically changes the current (or voltage) applied to the switching valve 771 during the execution of the cleaning control. That is, the gap (throttle) of the switching valve 771 is periodically changed.

[0052] Here, the relationship between the opening degree (gap) of the switching valve 771 and the applied current in the cleaning control is shown in FIG. 5. The horizontal axis in FIG. 5 is the current (A), and the vertical axis is the valve gap (mm). Also, FIG. 6 shows an example of the current pattern applied to the switching valve 771 during the execution of the cleaning control. The horizontal axis in FIG. 6 is the time (msec), and the vertical axis is the current (A).

[0053] As shown in FIG. 6, for example, when the current applied to the switching valve 771 is changed in a sawtooth shape (changing between I A and I B ), as shown in FIG. 5, the valve gap changes between G A and G B . By setting so that the optimum value of the gap is included between the valve gaps G A and G B , even if the characteristics change, foreign matter can be more reliably blown off.

[0054] And when the abnormality of the evaporative fuel processing system 70 is not eliminated even after the ECU 50 executes the cleaning control, it is preferable to turn on a warning lamp (warning lamp) that notifies the occurrence of the abnormality.

[0055] Next, with reference to FIG. 7, the operation of the diagnostic device 77 of the evaporative fuel processing system will be described. FIG. 7 is a flowchart showing the processing procedure of the cleaning control by the diagnostic device 77 of the evaporative fuel processing system. This processing is repeatedly executed by the ECU 50 at a predetermined timing.

[0056] First, in step S100, for example, based on the operating state of the engine 10 and the like, it is determined whether or not the diagnostic execution condition of the evaporative fuel processing system 70 is satisfied. Here, if the diagnostic execution condition is not satisfied, the process exits temporarily from this process. On the other hand, when the diagnostic execution condition is satisfied, the process proceeds to step S102.

[0057] In step S102, based on the pressure in the evaporation passage 775 (the pressure inside the evaporation path) when the pump 772 is driven and the pressure in the reference orifice passage 777 (the reference pressure), the presence or absence of an abnormality (such as a leak, etc.) in the evaporation fuel treatment system 70 is diagnosed.

[0058] Next, in step S104, a determination is made as to whether or not it is diagnosed that there is no abnormality in the evaporation fuel treatment system 70. Here, if it is diagnosed that there is no abnormality, the process exits temporarily. On the other hand, when it is diagnosed that there is an abnormality, the process proceeds to step S106.

[0059] In step S106, cleaning control of the switching valve 771 is executed. That is, the pump 772 is driven with the switching valve 771 in a slightly open valve state. Then, foreign substances such as fine particles of activated carbon caught in the switching valve 771 are blown off. Since the cleaning control is as described above, detailed description is omitted here.

[0060] Next, in step S108, again, based on the pressure in the evaporation passage 775 (the pressure inside the evaporation path) when the pump 772 is driven and the pressure in the orifice passage 777 (the reference pressure), the presence or absence of an abnormality (such as a leak, etc.) in the evaporation fuel treatment system 70 is diagnosed.

[0061] Then, in step S110, a determination is made as to whether or not it is diagnosed that there is no abnormality in the evaporation fuel treatment system 70. Here, if it is diagnosed that there is no abnormality, the process exits temporarily. On the other hand, when it is diagnosed that there is an abnormality, the process proceeds to step S112.

[0062] In step S112, a warning lamp (warning light) indicating that there is an abnormality in the evaporation fuel treatment system 70 is lit. Then, the process exits.

[0063] As described in detail above, according to the present embodiment, when predetermined cleaning control execution conditions are satisfied, the switching valve 771 is driven so as to communicate in a state where the evaporation passage 775 and the pump passage 776 are narrowed, or to communicate in a state where the atmosphere passage 778 and the orifice passage 777 are narrowed, and the pump 772 is driven (cleaning control is executed). Therefore, the flow velocity at the switching valve 771 can be increased to blow off (eject) foreign matter caught in the switching valve 771. In addition, the biting-in of foreign matter can be eliminated or prevented by the control by the ECU 50, and the addition of new (dedicated) hardware is unnecessary. As a result, it is possible to eliminate or prevent the biting-in of foreign matter in the switching valve 771 (and to eliminate or prevent misdiagnosis) without adding new (dedicated) hardware.

[0064] According to the present embodiment, when the switching valve 771 is in the full-on state, the evaporation passage 775 and the pump passage 776 are communicated (the atmosphere passage 778 and the orifice passage 777 are blocked), and when the switching valve 771 is in the full-off state, the atmosphere passage 778 and the orifice passage 777 are communicated (the evaporation passage 775 and the pump passage 776 are blocked). Therefore, the communication state can be appropriately switched by turning the switching valve 771 on and off.

[0065] According to the present embodiment, when the cleaning control is executed, the current (or voltage) applied to the switching valve 771 is periodically varied. Therefore, the throttle (gap) of the switching valve 771 can be periodically changed, and for example, even if there are variations in the individual dimensions of the switching valve 771 or the characteristics change due to temperature changes, foreign matter can be more reliably blown off.

[0066] According to the present embodiment, when it is determined that an abnormality has occurred in the evaporation fuel processing system 70 and it is determined that predetermined cleaning control execution conditions are satisfied, the cleaning control is executed. Therefore, it is possible to eliminate an abnormality caused by the biting-in of foreign matter in the switching valve 771 at a more appropriate timing.

[0067] According to this embodiment, when the air passage 778 and the orifice passage 777 communicate with each other in a constricted state during the execution of cleaning control, or when the evaporation passage 775 and the pump passage 776 communicate with each other in a constricted state, the valve gap (opening degree) of the switching valve 771 is set based on the size of foreign matter that bites into the switching valve 771. Therefore, the flow velocity can be increased further to accurately blow off the foreign matter on the switching valve 771.

[0068] As described above, the embodiments of the present invention have been described. However, the present invention is not limited to the above embodiments, and various modifications are possible. For example, the cleaning control execution conditions are not limited to the above embodiments and can be arbitrarily set according to requirements and the like. For example, the cleaning control may be executed periodically.

[0069] In the above embodiment, a linear solenoid that changes the opening degree according to the applied current value is used for the switching valve 771. However, instead of the linear solenoid, for example, a duty solenoid that changes the opening degree according to the duty ratio of the voltage may be used.

[0070] In the above embodiment, the present invention is applied to a gasoline engine vehicle. However, the present invention can also be applied to engines such as HEV (hybrid vehicle) and PHEV (plug-in hybrid vehicle).

[0071] In the above embodiment, when it is diagnosed as abnormal after the cleaning control is executed, the warning light is lit. However, the cleaning control and the abnormality diagnosis may be repeatedly executed a plurality of times.

[0072] In the above embodiment, the present invention is applied to a vacuum type ELCM. However, the present invention can also be applied to a pressure type ELCM.

Explanation of Reference Numerals

[0073] 10 Engine 50 ECU 70 Evaporative fuel treatment system 71 Canister 72 Purge pipe 72a First purge pipe 72b Second purge pipe 73 Variable flow rate solenoid valve (purge solenoid valve) 77 Diagnostic device for evaporative fuel processing system (ELCM) 771 Switching valve 771a Valve (valve body) 772 Pump 773 Pressure sensor 774 Orifice 775 Evaporative passage 776 Pump passage 777 Orifice passage 778 Atmosphere passage 779 Filter 80 Fuel tank

Claims

1. A pump that generates negative pressure, a switching valve that switches between a state in which a pump passage communicating with the suction port of the pump and an evaporation passage communicating with a canister constituting an evaporation fuel treatment system are in communication, and a state in which an orifice passage connected to the pump passage with a reference orifice interposed therebetween and an atmosphere passage with one end open to the atmosphere are in communication, a control unit that controls the driving of the switching valve and the pump, and diagnoses the presence or absence of an abnormality in the evaporation fuel treatment system based on the pressure in the evaporation passage and the pressure in the orifice passage when the pump is driven, and when a predetermined cleaning control execution condition is satisfied, the control unit drives the switching valve so that the evaporation passage and the pump passage communicate in a constricted state, or the atmosphere passage and the orifice passage communicate in a constricted state, and executes cleaning control for driving the pump. A diagnostic device for an evaporation fuel treatment system, characterized in that.

2. The diagnostic device for an evaporation fuel treatment system according to claim 1, wherein the switching valve communicates the evaporation passage and the pump passage when fully open, and communicates the atmosphere passage and the orifice passage when fully closed.

3. The diagnostic device for an evaporation fuel treatment system according to claim 2, wherein the control unit periodically changes the current or voltage applied to the switching valve during the execution of the cleaning control.

4. The diagnostic device for an evaporation fuel treatment system according to claim 3, wherein when the control unit determines that an abnormality has occurred in the evaporation fuel treatment system, it determines that the predetermined cleaning control execution condition is satisfied and executes the cleaning control.

5. The diagnostic device for an evaporation fuel treatment system according to claim 4, wherein the valve gap of the switching valve when the atmosphere passage and the orifice passage communicate in a constricted state, or when the evaporation passage and the pump passage communicate in a constricted state during the execution of the cleaning control, is set based on the size of foreign matter that bites into the switching valve.

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