JP2018031350A - Supercharging device for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To inhibit air flowing back in a bypass passage from entering into a purge passage when an operation of a supercharger is stopped.SOLUTION: A supercharging device for an engine includes: an intake passage 21 for guiding air to a combustion chamber 7 of the engine 1; a supercharger 28 provided in the intake passage; a bypass passage 36 for connecting an upstream side and a downstream side of the supercharger 28 in the intake passage 21; a control valve 38 for opening/closing the bypass passage; control means 102 for operating the supercharger 28 and controlling the control valve 38 to a closed state in a first operating region and stopping an operation of the supercharger 28 and controlling the control valve 38 to an opened state in a second operating region; and a purge passage 50 connected to the upstream side of the supercharger 28 in the intake passage to introduce evaporation fuel generated in a fuel tank 90 to the intake passage 21. When transferred from the first operating region to the second operating region, the control means 102 controls the control valve 38 to the opened state to continue the operation of the supercharger 28 for a predetermined time.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an engine supercharging device configured to be switchable between a supercharging state in which intake via a supercharger is performed and a natural intake state in which intake is performed bypassing the supercharger.

  A supercharger may be provided in the intake system of an automobile engine. By operating the supercharger, fuel consumption performance is improved by lean burn operation while suppressing a decrease in output torque. Can be miniaturized.

  As a supercharger, in addition to a turbocharger that uses an exhaust turbine as a driving source, for example, an engine-driven mechanical supercharger as disclosed in Patent Document 1, and further, an electric motor driven by an electric motor. Superchargers are known. When a clutch is provided between the supercharger and the drive source, switching between the operation and stop of the supercharger can be controlled according to the operating state by the on / off control of the clutch.

  In an intake system of an engine equipped with this type of supercharger, an upstream portion and a downstream portion of the supercharger in the intake passage are connected via a bypass passage, and a bypass valve is provided in the bypass passage. is there. In this case, in the supercharging operation region, the supercharger is operated with the bypass valve closed, and in the non-supercharging operation region, the operation of the supercharger is stopped with the bypass valve fully opened, Natural air intake bypassing the turbocharger is performed.

  In the intake system configured as described above, a purge passage, a blow-by passage, an EGR passage, and the like may be connected to a portion of the intake passage upstream of the supercharger. For example, when a canister that adsorbs the evaporated fuel generated in the fuel tank is connected to the intake passage via the purge passage, the evaporated fuel collected in the canister is purged (introduced) into the intake passage via the purge passage. ) Can be. Further, when the engine crankcase and the intake passage communicate with each other via the blow-by passage, the blow-by gas sucked from the crankcase can return to the intake passage via the blow-by passage, and the exhaust passage and the intake passage When the passage is connected to the passage through the EGR passage, a part of the exhaust gas can return to the intake side through the EGR passage.

  In a gasoline engine or the like that employs premixed compression ignition (HCCI) technology that performs self-ignition combustion, the throttle valve is often fully opened, so that an operation state in which the intake passage becomes negative pressure is caused. In such a case, in order to make it possible to forcibly purge the evaporated fuel into the intake passage, a purge assister composed of an electric pump or the like may be provided in the purge passage.

Japanese Patent Laid-Open No. 7-09728

  By the way, when the natural intake via the bypass passage is performed in the non-operating state of the supercharger as described above, the air flow in the intake passage is blocked by the supercharger. In particular, in the intake passage provided with the Rishorum type supercharger, the air flow is almost completely cut off. Therefore, the air on the upstream side of the non-operating supercharger is sent to the downstream side of the supercharger exclusively through the bypass passage.

  In the engine intake system configured as described above, during operation of the supercharger with the bypass valve closed, the downstream side of the supercharger in the intake passage is at a higher pressure than the upstream side. By shifting from the supercharging operation region to the non-supercharging operation region in this state, when the operation of the supercharger is stopped and the bypass valve is fully opened, the intake passage has a relatively high pressure on the downstream side of the supercharger. The air that has become easy to flow back to the upstream side of the supercharger through the bypass passage.

  At this time, since the air flow in the intake passage is hindered by the supercharger, the air that has flowed back to the upstream side of the supercharger through the bypass passage may enter the purge passage and further back flow. is there. As a result, purging of the evaporated fuel into the intake passage may be hindered, or air that has flowed back through the purge passage may be released to the atmosphere together with the evaporated fuel via the canister.

  At this time, blow-by gas that is sucked out from the engine and exists in the intake system may be drawn into the purge passage by being drawn by the flow of air that flows back through the bypass passage and the purge passage. As a result, when blowby gas adheres to the purge valve that opens and closes the purge passage, the purge passage may be clogged easily.

  In order to regulate such a reverse flow of blow-by gas, it is conceivable to provide a check valve in the downstream portion of the purge valve in the purge passage, but such a measure causes an increase in the passage resistance of the purge passage. This is not desirable for promoting the purge of the evaporated fuel into the intake passage or reducing the discharge pressure of the purge assister.

  Then, this invention makes it a subject to suppress that the air which flowed back in the bypass passage enters into a purge passage when the operation of a supercharger is stopped.

  In order to solve the above-mentioned problems, the engine supercharging device according to the present invention is configured as follows.

First, the invention according to claim 1 of the present application is
An intake passage for guiding air to the combustion chamber of the engine;
A supercharger provided in the intake passage;
A bypass passage connecting the upstream side and the downstream side of the supercharger in the intake passage;
A control valve for opening and closing the bypass passage;
The supercharger is operated in the first operation region and the control valve is controlled to be closed, and the operation of the supercharger is stopped and the control valve is opened in a second operation region different from the first operation region. Control means for controlling the state;
A purge passage connected to an upstream side of the supercharger in the intake passage to guide the evaporated fuel generated in a fuel tank to the intake passage;
When the control means is shifted from the first operation region to the second operation region, the control means controls the control valve to be in an open state and continues the operation of the supercharger for a predetermined time.

  In addition, the “closed state” of the control valve in this specification includes not only the fully closed state in which the control valve is completely closed, but also the control valve in comparison with the fully closed state for supercharging pressure control or the like. A slightly opened state is also included.

The invention according to claim 2 is the invention according to claim 1,
The control means controls the control valve to be in an open state when purging the evaporated fuel from the purge passage to the intake passage at the time of transition from the first operation region to the second operation region. Then, the operation of the supercharger is continued for the predetermined time, and the operation of the supercharger is stopped when the purge is not performed.

The invention according to claim 3 is the invention according to claim 1 or 2,
The predetermined time is a time set to be longer as the boost pressure is higher in accordance with the boost pressure at the time of transition from the first operation region to the second operation region.

The invention according to claim 4 is the invention according to any one of claims 1 to 3,
The supercharger is a mechanical supercharger connected to the engine via a predetermined connection / disconnection means,
The control means controls the connection / disconnection means to switch between an operating state and an operation stop state of the supercharger.

  First, according to the supercharging device for an engine according to the first aspect of the present invention, when the first operating region where supercharging is performed is shifted to the second operating region where supercharging is not required, the bypass passage is In the opened state, the operation of the supercharger is continued for a predetermined time. Therefore, even when the relatively high pressure air on the downstream side of the turbocharger flows back to the upstream side of the relatively low pressure turbocharger through the bypass passage during the transition from the first operation region to the second operation region, Then, the air can be guided again downstream of the intake passage by the supercharger. Further, during this time, since the control valve of the bypass passage is in an open state, the differential pressure between the upstream side and the downstream side of the supercharger communicated via the bypass passage is reduced. Further backflow in the bypass passage can be suppressed.

  Therefore, it is possible to suppress the air that flows backward through the bypass passage from entering the purge passage at the time of transition from the first operation region to the second operation region. As a result, the backflow of air in the purge passage is suppressed, so that inhibition of the purge of the evaporated fuel from the purge passage to the intake passage can be suppressed, and the air that has flowed back in the purge passage passes with the evaporated fuel via the canister. Release to the atmosphere can be suppressed.

  In addition, since blow-by gas existing in the intake system can be suppressed from being drawn into the purge passage by the air, it is possible to suppress blow-by gas from adhering to a valve or the like provided in the purge passage. Clogging can be suppressed.

  According to the second aspect of the present invention, when the evaporated fuel is purged from the purge passage to the intake passage during the transition from the first operation region to the second operation region, as described above. The operation of the turbocharger is continued for a predetermined time with the bypass passage opened, so that the purge is inhibited from being inhibited by the air flowing back through the bypass passage. By quickly stopping the operation of the charger, it is possible to reduce power loss for driving the supercharger.

  According to the third aspect of the invention, the higher the supercharging pressure at the time of transition to the second operation region, the longer the time required to eliminate the backflow phenomenon in the bypass passage, Since the operation of the supercharger is continued for a longer time as the supercharging pressure at the time of shifting to the two operation region is higher, it is possible to reliably suppress the air that has flowed back through the bypass passage from entering the purge passage.

  According to the fourth aspect of the present invention, the switching between the operation state and the operation stop state of the mechanical supercharger connected to the engine via the predetermined connecting / disconnecting means is performed by the drive source of the supercharger. The above-described effects can be obtained in a configuration that is easily performed by controlling the connecting / disconnecting means while the is operated.

It is a whole lineblock diagram showing the supercharging device of the engine concerning the embodiment of the present invention. It is a control system figure of the supercharging device of the engine shown in FIG. It is a graph which shows the relationship between the rotation speed of a purge assister, inflow gas density, and discharge pressure. 3 is a flowchart showing an example of a control operation of the engine supercharging device shown in FIG. 1. It is a time chart which shows an example of a time-dependent change of the various operation | movement of the supercharging apparatus of the engine shown in FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[overall structure]
First, the overall configuration of the engine supercharging device according to the present embodiment will be described with reference to the overall configuration diagram of FIG. 1 and the control system diagram of FIG.

  The engine 1 is, for example, an in-line four-cylinder gasoline engine. However, in FIG. 1, the engine 1 has only one cylinder, and the remaining three cylinders are not shown. In addition, the structure of the engine 1 demonstrated by this embodiment is only an example, and the kind and specific structure of an engine are not specifically limited in this invention.

  In the present embodiment, the engine 1 includes, for example, a direct injection type fuel supply device 16 (see FIG. 2) and, for example, a spark ignition type ignition device 18 (see FIG. 2).

  The fuel supply device 16 includes a fuel injection valve (not shown) disposed so as to face the combustion chamber 7 of the engine 1, and the fuel supplied from the fuel tank 90 is supplied to the fuel injection valve at the fuel injection timing. To the combustion chamber 7 directly.

  The fuel tank 90 is connected to the canister 92 via the evaporated fuel passage 94. The internal space of the canister 92 is communicated with the atmosphere via the outside air introduction passage 96. The evaporated fuel generated in the fuel tank 90 is temporarily taken into the canister 92 via the evaporated fuel passage 94 and then introduced into the canister 92 from the atmosphere via the outside air introduction passage 96 together with the intake air described later. It is purged (introduced) into the system 20 and finally burned in the combustion chamber 7. In addition, the outside air introduction passage 96 is provided with a filter 98 that restricts the passage of the evaporated fuel, and thereby the leakage of the evaporated fuel from the canister 92 to the atmosphere is suppressed.

  A specific configuration for purging the evaporated fuel from the canister 92 to the intake system 20 will be described later.

  The ignition device 18 has a spark plug 19 disposed so that the tip electrode faces the combustion chamber 7, and is configured to generate a discharge spark from the tip electrode of the spark plug 19 at the ignition timing. However, the ignition in the combustion chamber 7 may be appropriately switched between ignition by ignition of the spark plug 19 and self-ignition by the premixed compression ignition (HCCI) technique according to the operating state.

  The engine 1 includes a cylinder block 3 and a cylinder head 4 fixed to the upper portion of the cylinder block 3.

  The cylinder block 3 has a cylinder 5 extending in the vertical direction for each cylinder. A piston 6 connected to a crankshaft (not shown) is fitted in each cylinder 5 so as to be able to reciprocate, and a combustion chamber 7 is formed above the piston 6. A crankcase 8 that accommodates the crankshaft is formed below the piston 6.

  Further, the cylinder block 3 flows through an engine speed sensor 83 (see FIG. 2) for detecting the speed of the engine 1 and a water jacket (not shown), for example, by detecting the rotation angle of the crankshaft. An engine water temperature sensor 84 (see FIG. 2) for detecting the temperature of the engine cooling water is provided.

  In the cylinder head 4, for example, two intake ports 11 and two exhaust ports 12 that can communicate with the combustion chamber 7 are formed for each combustion chamber 7. An intake valve 13 is provided at the port opening of the intake port 11, and an exhaust valve 14 is provided at the port opening of the exhaust port 12. The intake valve 13 and the exhaust valve 14 are opened and closed independently at a predetermined timing by, for example, an electromagnetic VVT (electromagnetic variable valve timing mechanism).

  An intake passage 21 of the intake system 20 is connected to each intake port 11, and an exhaust passage 60 of the exhaust system is connected to each exhaust port 12. The intake passage 21 and the exhaust passage 60 may be connected via an EGR passage (not shown). In this case, a part of the exhaust gas in the exhaust passage 60 is returned to the intake passage 21 via the EGR passage. It becomes possible.

  The intake system 20 of the engine 1 includes an intake passage 21, a bypass passage 36, a ventilation passage 40, and a purge passage 50.

  In order from the upstream side to the intake passage 21, an inlet 22 that is open to the atmosphere, an air cleaner 24 that filters air sucked from the inlet 22, a throttle valve 26 that throttles the intake passage 21, and compresses and supercharges the intake air A supercharger 28 that generates pressure, an intercooler 32 that cools air compressed by the supercharger 28, and a surge tank 34 that temporarily stores intake air before being supplied to the intake port 11 are provided.

  An air flow sensor 85 that detects the intake air flow rate is provided in a portion of the intake passage 21 between the air cleaner 24 and the throttle valve 26. The airflow sensor 85 is, for example, a hot wire type, and the airflow sensor 85 has a built-in intake air temperature sensor 86 (see FIG. 2).

  An upstream passage portion 21a located upstream of the supercharger 28 in the intake passage 21, more specifically, a portion between the throttle valve 26 and the supercharger 28 in the upstream passage portion 21a A negative pressure sensor 87 for detecting the negative pressure in the passage portion is provided.

  A supercharging pressure for detecting a supercharging pressure is applied to a downstream passage portion 21b located downstream of the supercharger 28 in the intake passage 21, more specifically, to a surge tank 34 located in the downstream passage portion 21b. A sensor 88 is provided.

  The most downstream portion of the intake passage 21 is branched into a plurality of extended passage portions 21c that together with the surge tank 34 constitute an intake manifold. The extension passage portion 21c is provided for each intake port 11, and each intake port 11 is connected to the surge tank 34 via the extension passage portion 21c.

  The supercharger 28 is a mechanical supercharger that is drivingly connected to the crankshaft of the engine 1 via a belt, for example. Although the compression method of the supercharger 28 is, for example, a Rishorum type, it is not particularly limited to this. The supercharger 28 is connected to the crankshaft via the electromagnetic clutch 30 and operates when the power of the engine 1 is transmitted when the electromagnetic clutch 30 is engaged or slip-controlled, and the electromagnetic clutch 30 is released. Thus, the operation is stopped when the connection with the crankshaft is released.

  The bypass passage 36 is connected to the intake passage 21 so as to bypass the supercharger 28. That is, one end of the bypass passage 36 is connected to the upstream passage portion 21 a of the intake passage 21, and the other end of the bypass passage 36 is connected to the downstream passage portion 21 b of the intake passage 21.

  In the upstream passage portion 21 a of the intake passage 21, the connection portion with the bypass passage 36 is disposed between the throttle valve 26 and the supercharger 28, and is disposed upstream of the negative pressure sensor 87. . In the downstream passage portion 21 b of the intake passage 21, the connection portion with the bypass passage 36 is disposed between the intercooler 32 and the surge tank 34.

  The bypass passage 36 is provided with, for example, a butterfly-type bypass control valve 38 that opens and closes the bypass passage 36. The bypass control valve 38 is closed when the supercharger 28 is operated, thereby blocking the bypass passage 36 and promoting air compression by the supercharger 28. The bypass control valve 38 is opened when the operation of the supercharger 28 is stopped, thereby realizing natural intake air that bypasses the supercharger 28.

  The ventilation passage 40 is a passage used for ventilation of the crankcase 8 of the engine 1, and includes a blow-by passage 41 as a first ventilation passage and an air introduction passage 42 as a second ventilation passage.

  One end of the blow-by passage 41 is connected to the crankcase 8 via, for example, the cylinder head 4, and the other end of the blow-by passage 41 is connected to the upstream-side passage portion 21 a of the intake passage 21. In the upstream passage portion 21 a, the connection portion with the blow-by passage 41 is disposed between the throttle valve 26 and the supercharger 28 and upstream of the negative pressure sensor 87.

  A PCV (Positive Crankcase Ventiration) valve 44 is provided in the blow-by passage 41. The PCV valve 44 is a check valve that allows the passage of air only in the direction from the crankcase 8 side toward the intake passage 21 side. The PCV valve 44 is configured to open when the pressure in the upstream passage portion 21 a of the intake passage 21 is lower than the pressure in the crankcase 8. In the state where the PCV valve 44 is opened, the blow-by gas leaked from the combustion chamber 7 to the crankcase 8 is sucked into the upstream-side passage portion 21 a via the blow-by passage 41.

  The PCV valve 44 is configured so that the opening degree thereof changes in accordance with the negative pressure of the upstream passage portion 21a of the intake passage 21. Thereby, the blow-by gas sucked from the crankcase 8 to the upstream passage portion 21a. Is adjusted to an appropriate amount in accordance with the negative pressure in the upstream passage portion 21a.

  One end of the air introduction passage 42 of the ventilation passage 40 is connected to the upstream passage portion 21 a of the intake passage 21, and the other end of the air introduction passage 42 is connected to the crankcase 8 via the cylinder head 4. . In the upstream passage portion 21 a of the intake passage 21, a connection portion with the air introduction passage 42 is disposed between the air cleaner 24 and the throttle valve 26. The air introduction passage 42 is provided with a one-way valve 46 that allows passage of air only in the direction from the intake passage 21 side toward the crankcase 8 side.

  When blow-by gas is sucked into the intake passage 21 from the crankcase 8 via the blow-by passage 41, the air introduced into the intake passage 21 from the atmosphere and filtered by the air cleaner 24 is supplied to the crankcase 8 from the air introduction passage 42. This causes the crankcase 8 to be ventilated.

  One end of the purge passage 50 is connected to the upstream passage portion 21 a of the intake passage 21, and the other end of the purge passage 50 is connected to the canister 92. In the upstream passage portion 21 a of the intake passage 21, the connection portion with the purge passage 50 is disposed between the throttle valve 26 and the supercharger 28 and upstream of the negative pressure sensor 87.

  The purge passage 50 is provided with a purge valve 52 that opens and closes the purge passage 50. The purge valve 52 is composed of, for example, an electromagnetic valve, and the opening and closing and the opening degree of the purge valve 52 can be electrically controlled.

  If a negative pressure is generated on the upstream passage portion 21a side of the intake passage 21 in a state in which the purge valve 52 is opened, the evaporated fuel collected in the canister 92 is introduced from the atmosphere into the canister 92 through the outside air introduction passage 96. The air is purged to the upstream passage portion 21a of the intake passage 21 through the purge passage 50 and further to the combustion chamber 7 through the intake passage 21 or through both the bypass passage 36 and the intake passage 21. The fuel is supplied and burned in the combustion chamber 7 together with the fuel supplied by the fuel supply device 16.

  The purge valve 52 is not limited to one that can be controlled to open and close, but is a check that is configured to mechanically open only when negative pressure is generated on the upstream passage portion 21a side. It may be a valve.

  The purge passage 50 is provided with a purge assister 54 as a pressurizing means for increasing the pressure in the purge passage 50 on the upstream side (canister 92 side) of the purge valve 52. The purge assister 54 is constituted by, for example, an electric centrifugal pump. In the purge passage 50, chambers 56 and 58 are provided on the upstream side and the downstream side of the purge assister 54, respectively. A discharge pressure sensor 89 that detects the discharge pressure of the purge assister 54 is provided in the downstream chamber 58.

  When the pressure in the purge passage 50 is increased by operating the purge assister 54, evaporation from the purge passage 50 to the intake passage 21 is performed even in a state where no negative pressure is generated on the upstream passage portion 21a side of the intake passage 21. The fuel can be purged.

[Control system]
As shown in FIG. 2, various controls related to the operation of the engine 1 are performed by an ECU (Electronic Control Unit) 100 as a control device. The ECU 100 includes, for example, a microprocessor as a main part.

  The ECU 100 includes an accelerator sensor 81 for detecting an operation amount and an operation speed of an accelerator pedal (not shown), an air-fuel ratio sensor 82 provided in the exhaust passage 60 (see FIG. 1), and the engine speed sensor 83 described above. The engine water temperature sensor 84, the air flow sensor 85, the intake air temperature sensor 86, the negative pressure sensor 87, the supercharging pressure sensor 88, and the discharge pressure sensor 89 are electrically connected, and output signals from these sensors 81 to 89 are input. It has become so.

  Further, the ECU 100 is electrically connected to various devices related to the operation of the engine 1 such as the throttle valve 26, the fuel supply device 16, the ignition device 18, the electromagnetic clutch 30, the bypass control valve 38, the purge valve 52, and the purge assister 54 described above. , And is configured to control various operations of the engine 1 by transmitting control signals based on signals received from the various sensors 81 to 89 described above to various devices.

  The ECU 100 includes an engine control unit 101 that controls basic operations of the engine 1, a supercharging control unit 102 that controls operations related to the supercharger 28, and a purge control that controls operations related to the purge of evaporated fuel. Part 103.

  The engine control unit 101 includes a throttle valve 26, a fuel supply device, based on input signals from an accelerator sensor 81, an air-fuel ratio sensor 82, an engine speed sensor 83, an engine water temperature sensor 84, an air flow sensor 85, an intake air temperature sensor 86, and the like. 16 and various operations of the ignition device 18 are controlled. For example, the air / fuel ratio control by the engine control unit 101 is based on the output value of the air / fuel ratio sensor 82, the output value of the air flow sensor 85, and the like when the water temperature detected by the engine water temperature sensor 84 is a predetermined temperature. This is performed by adjusting the fuel injection amount by 16.

  The supercharging control unit 102 mainly controls on / off of the electromagnetic clutch 30 and opening / closing or opening of the bypass control valve 38 based on input signals from the engine speed sensor 83, the airflow sensor 85, and the like.

  In the control by the supercharging control unit 102, when the operating state obtained from the output value of the engine speed sensor 83, the output value of the airflow sensor 85, etc. belongs to a predetermined supercharging region, the bypass control valve 38 is in the closed state. At the same time, the supercharger 28 is operated by turning on (fastening) the electromagnetic clutch 30. Thereby, the air can be efficiently compressed by the supercharger 28 in a state where the bypass passage 36 is blocked.

  At this time, the bypass control valve 38 does not necessarily need to be fully closed, and the bypass control valve 38 may be slightly opened in order to suppress an excessive increase in the supercharging pressure. In this case, the supercharging control unit 102 may control the opening degree of the bypass control valve 38 based on the output value of the supercharging pressure sensor 88 so as to obtain a desired supercharging pressure.

  The supercharging area is a first operation area that is set in advance as an area that requires supercharging. Specifically, for example, an operation region in a high load / high rotation state in which the engine load and the engine speed are equal to or higher than predetermined values is set as the supercharging region. Further, the second operation region other than the supercharging region is set as a non-supercharging region that does not require supercharging.

  When the operating state obtained by the output value of the air flow sensor 85 and the output value of the engine speed sensor 83 belongs to the non-supercharging region, the bypass control valve 38 is opened (for example, fully open state) in the control by the supercharging control unit 102. ) And the electromagnetic clutch 30 is turned off (released), whereby the operation of the supercharger 28 is stopped. As a result, natural intake air that bypasses the supercharger 28 is realized.

  The purge control unit 103 mainly controls the opening / closing of the purge valve 52 and the on / off of the purge assister 54 and the rotational speed.

  In the control by the purge control unit 103, for example, the purge valve 52 is opened in a state where the air-fuel ratio control can be properly performed by the engine control unit 101, that is, in a state where the water temperature detected by the engine speed sensor 83 is equal to or higher than a predetermined value. Thus, the evaporated fuel is purged from the purge passage 50 to the intake passage 21.

  In addition, the purge control unit 103 operates the purge assister 54 as necessary while the purge valve 52 is open. Specifically, for example, when the negative pressure is not generated in the upstream passage portion 21a of the intake passage 21 based on the output value of the negative pressure sensor 87, the purge assister 54 is operated.

  When purging the evaporated fuel, the purge control unit 103 appropriately controls the opening degree of the purge valve 52 and / or the rotational speed of the purge assister 54 so that the purge amount according to the operation state is obtained. More specifically, the opening degree of the purge valve 52 and / or the rotational speed of the purge assister 54 is calculated based on the purgeable amount calculated based on the engine rotational speed, the engine load, and the like, the temperature of the fuel tank, and the like. Control is appropriately performed based on the evaporative fuel generation amount, the ease of purging calculated based on the output value of the negative pressure sensor 87, and the like.

  The concentration of the evaporated fuel in the air flowing through the purge passage 50 can be calculated based on the output value of the discharge pressure sensor 89. For the calculation of the concentration, a map stored in advance in the memory of the ECU 100 is used.

  For example, as shown in FIG. 3, the map is information that defines the relationship among the rotational speed of the purge assister 54, the inflowing gas density, and the discharge pressure. The relationship between the rotational speed, the inflowing gas density and the discharge pressure of the purge assister 54 shown in the map of FIG. 3 is that the inflowing gas density becomes larger as the discharge pressure is higher if the rotation speed is constant, and the discharge pressure is constant. The relationship is such that the lower the rotational speed, the larger the inflow gas density.

  Therefore, the purge control unit 103 is based on the map shown in FIG. 3, the command value of the rotation speed of the purge assister 54 by the purge control unit 103, and the discharge pressure of the purge assister 54 detected by the discharge pressure sensor 89. The density of the air flowing into the purge assister 54 from the canister 92 side is calculated, and thereby the concentration of the evaporated fuel corresponding to the density is obtained. The concentration value of the evaporated fuel calculated in this way is used for air-fuel ratio control by the engine control unit 101.

[Control example of supercharging control unit]
Hereinafter, an example of the control operation by the supercharging control unit 102 will be described with reference to the flowchart of FIG. 4 and the time chart of FIG.

  The control operation shown in FIG. 4 is repeatedly executed by the supercharging control unit 102 when the engine 1 is driven.

  In the control operation of FIG. 4, first, in step S1, it is determined whether or not the operating state belongs to the non-supercharging region.

  If the result of determination in step S1 is that it belongs to the supercharging region, the electromagnetic clutch 30 is turned on (engaged) (step S2), and the bypass control valve 38 is closed (step S3). As a result, the supercharger 28 is operated in a state where the bypass passage 36 is blocked, thereby generating a supercharging pressure.

  On the other hand, if the result of determination in step S1 is that the vehicle belongs to the non-supercharging region, it is determined in step S4 whether or not the operating state has just shifted from the supercharging region to the non-supercharging region. More specifically, in step S4, it is determined whether or not the elapsed time from the transition from the supercharging region to the non-supercharging region is equal to or less than a predetermined period set in advance.

  If the result of determination in step S4 is not immediately after the transition from the supercharging region to the non-supercharging region, the electromagnetic clutch 30 is turned off (released) (step S5), and the bypass control valve 38 is opened (step S13). . Thus, natural intake is performed via the opened bypass passage 36 in a state where the operation of the supercharger 28 is stopped.

  On the other hand, if the result of determination in step S4 is immediately after the transition from the supercharging region to the non-supercharging region (see symbol A in FIG. 5A), the purge control unit 103 purges the evaporated fuel in step S6. It is determined whether or not it is being executed, that is, whether or not the purge valve 52 is controlled to be in an open state.

  If the result of determination in step S6 is that purging has not been performed (see symbol B in FIG. 5B), the electromagnetic clutch 30 is turned off (released) (step S5) (sign in FIG. 5D). C), the operation of the supercharger 28 is stopped, and the bypass control valve 38 is opened (step S13) (see symbol D in FIG. 5 (e)). Inhalation is performed.

  At this time, there is a possibility that the air in the downstream passage portion 21b, which has a higher pressure than the upstream passage portion 21a, may flow back through the bypass passage 36. However, since the purge of the evaporated fuel is not executed, the bypass passage 36 Thus, the purge is not hindered when the backflow occurs. At this time, since the purge valve 52 is closed (see symbol B in FIG. 5B), the backflow of air does not occur in the purge passage 50 at least upstream of the purge valve 52. Therefore, it is possible to prevent the air that has flowed back through the purge passage 50 from being released into the atmosphere together with the evaporated fuel via the canister 92 and the outside air introduction passage 96.

  On the other hand, if the purge is executed as a result of the determination in step S6, it is determined in step S7 whether or not a predetermined timer time T has been set.

  If the time T is not set as a result of the determination in step S7, the supercharging pressure at the time of transition to the non-supercharging region detected by the supercharging pressure sensor 88 is read in step S8, and in step S9, The timer time T is set according to the supercharging pressure read in step S8. More specifically, the time T is set to a longer time as the supercharging pressure is higher. Here, the relationship between the supercharging pressure and the time T is, for example, a proportional relationship.

  Therefore, for example, as indicated by reference symbol E in FIG. 5C, when the set time T of the timer when the supercharging pressure at the time of transition to the non-supercharging region is the pressure P1 is the time t1, FIG. As indicated by symbol F in c), the timer time T when the supercharging pressure at the time of transition to the non-supercharging region is a pressure P2 higher than the pressure P1 is set to a time t2 longer than the time t1. The

  When the timer time T is set in step S9, or when it is determined in step S7 that the time T has been set, the time T is counted down (step S10).

  In the following step S11, it is determined whether or not the remaining time T of the timer is greater than zero, that is, whether or not the elapsed time from the transition to the non-supercharged region is less than the time T.

  Based on the determination in step S11, the state in which the electromagnetic clutch 30 is continuously turned on (engaged) from before the transition to the non-supercharging region until the time T elapses after the transition to the non-supercharging region. While continuing (step S12) (see symbol G in FIG. 5D), the bypass control valve 38 is switched from the closed state to the open state (step S13) (see symbol D in FIG. 5E).

  Thereby, the operation of the supercharger 28 is continued for a predetermined time T in a state where the bypass passage 36 is opened, so that the relatively high pressure air in the downstream passage portion 21b is opened when the bypass control valve 38 is opened. Even if the air flows backward through the bypass passage 36 to the upstream passage portion 21a having a relatively low pressure, the backflowed air can be guided again to the downstream passage portion 21b by the supercharger 28 in which the operation is continued.

  Further, while the operation of the supercharger 28 is continued (see reference numeral G in FIG. 5 (d)), the upstream-side passage portion 21a and the downstream-side passage portion 21b that communicate with each other via the opened bypass passage 36. The pressure difference between the first and second pressures decreases, so that further backflow in the bypass passage 36 can be suppressed.

  Therefore, it is possible to suppress the air flowing back through the bypass passage 36 from entering the purge passage 50 when the fuel vapor purge is performed and the supercharging region is shifted to the non-supercharging region.

  The time required to eliminate the reverse flow phenomenon in the bypass passage 36 tends to become longer as the supercharging pressure at the time of transition to the non-supercharging region increases, but by setting the time T in step S9 described above, Since the operation of the supercharger 28 is continued for a longer time as the supercharging pressure at the time of transition to the non-supercharging region is higher (see symbol H in FIG. 5D), the air that has flowed back through the bypass passage 36 The entry into the purge passage 50 can be reliably suppressed.

  Accordingly, since the backflow of air in the purge passage 50 is suppressed, it is possible to prevent the purge of the evaporated fuel from the purge passage 50 to the intake passage 21 from being inhibited, and the air that has flowed back through the purge passage 50 canister 92. In addition, it is possible to prevent the vaporized fuel from being released into the atmosphere via the outside air introduction passage 96.

  Further, in the intake system 20, blow-by gas existing especially in the bypass passage 36 and its peripheral portion can be prevented from entering the purge passage 50 due to the air flowing back through the bypass passage 36. Can be suppressed, and thereby, clogging of the purge passage 50 can be suppressed.

  Thereafter, based on the determination in step S11, when the time T has elapsed since the transition to the non-supercharging region, the electromagnetic clutch 30 is turned off (released) (step S5), and the operation of the supercharger 28 is stopped. Thereby, the power loss of the engine 1 can be reduced. At this time, there is a high possibility that the above-described reverse flow phenomenon in the bypass passage 36 has been eliminated. Therefore, even if the operation of the supercharger 28 is stopped, the reverse flow in the purge passage 50 and problems associated therewith occur. Can be suppressed.

  While the present invention has been described with reference to the above-described embodiments, the present invention is not limited to the above-described embodiments.

  For example, in the above-described embodiment, the supercharger 28 is a supercharger that is driven by the power of the engine 1. However, in the present invention, the type of the supercharger is not limited to this. For example, it may be an electric type driven by the power of an electric motor.

  As described above, according to the present invention, when the operation of the supercharger is stopped, it is possible to suppress the air that has flowed back through the bypass passage from entering the purge passage. It may be suitably used in the manufacturing industry field.

DESCRIPTION OF SYMBOLS 1 Engine 3 Cylinder block 4 Cylinder head 8 Crankcase 20 Intake system 21 Intake passage 21a Upstream passage part 21b Downstream passage part 21c Extension passage part 26 Throttle valve 28 Supercharger 30 Electromagnetic clutch 36 Bypass passage 38 Bypass control valve 40 Ventilation Passage 41 Blow-by passage 42 Air introduction passage 44 PCV valve 50 Purge passage 52 Purge valve 54 Purge assister 60 Exhaust passage 88 Supercharging pressure sensor 90 Fuel tank 92 Canister 100 ECU
101 Engine control unit 102 Supercharging control unit (control means)
103 Purge control unit

Claims (4)

An intake passage for guiding air to the combustion chamber of the engine;
A supercharger provided in the intake passage;
A bypass passage connecting the upstream side and the downstream side of the supercharger in the intake passage;
A control valve for opening and closing the bypass passage;
The supercharger is operated in the first operation region and the control valve is controlled to be closed, and the operation of the supercharger is stopped and the control valve is opened in a second operation region different from the first operation region. Control means for controlling the state;
A purge passage connected to an upstream side of the supercharger in the intake passage to guide the evaporated fuel generated in a fuel tank to the intake passage;
The control means controls the control valve to be in an open state and continues the operation of the supercharger for a predetermined time when the control unit shifts from the first operation region to the second operation region. Supercharger.   The control means controls the control valve to be in an open state when purging the evaporated fuel from the purge passage to the intake passage at the time of transition from the first operation region to the second operation region. 2. The operation of the supercharger is continued for the predetermined time, and when the purge is not performed, the operation of the supercharger is stopped. Engine supercharger.   The predetermined time is a time set so as to increase as the boost pressure increases in accordance with a boost pressure at the time of transition from the first operation region to the second operation region. The supercharger for an engine according to claim 1 or 2. The supercharger is a mechanical supercharger connected to the engine via a predetermined connection / disconnection means,
4. The switch according to claim 1, wherein the control unit performs switching between an operation state and an operation stop state of the supercharger by controlling the connection / disconnection unit. 5. The engine supercharger described.

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