Intake passage structure for internal combustion engine

Abstract

To enhance measurement accuracy of an air flow sensor at low flow speed in an intake passage.SOLUTION: A control device for an internal combustion engine includes: a combustion chamber 3; an intake passage 4 leading to the combustion chamber 3; an air flow sensor 30 provided in the intake passage 4; a flow passage cross section variable mechanism 40 interposed in the intake passage 4 at least upstream of the air flow sensor 30; and flow passage cross section control means 22 for contracting a flow passage cross section at least on the upstream side of the air flow sensor 30 by actuating the flow passage cross section variable mechanism 40 when a flow speed of intake air flowing in the intake passage 4 is a predetermined value or lower.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an intake passage structure for an internal combustion engine. [Background technology]

[0002] An engine (internal combustion engine) mounted on a vehicle controls the intake amount, fuel injection amount, ignition timing, etc. based on a required torque, which is set based on the accelerator opening, engine speed, etc.

[0003] The intake air amount can be detected by a sensor such as an air flow sensor provided in the intake passage. Examples of air flow sensors include those described in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 6-10752 [Patent Document 2] Special Publication No. 2013-528750 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the detection accuracy of the airflow sensor is not always consistent, and there is a problem that it is easily affected by pulsations and backflow from the downstream combustion chamber, especially at low flow rates. If measurement accuracy is reduced due to the effects of pulsations and backflow from the combustion chamber, the accuracy of calculations of engine torque and throttle opening will also decrease, and the engine may not be able to perform to its full potential.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the measurement accuracy of an air flow sensor when the flow velocity in the intake passage is low. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs a control device for an internal combustion engine that includes a combustion chamber, an intake passage leading to the combustion chamber, an airflow sensor provided in the intake passage, a flow passage cross-section varying mechanism interposed in the intake passage at least upstream of the airflow sensor, and flow passage cross-section control means that activates the flow passage cross-section varying mechanism to reduce the flow passage cross-section at least upstream of the airflow sensor when the flow velocity of intake air flowing through the intake passage is equal to or lower than a predetermined value (Configuration 1).

[0008] In configuration 1, the flow path cross-section varying mechanism includes a first portion located upstream of the air flow sensor and inclined so that the flow path cross-section gradually decreases toward downstream, a second portion located downstream of the first portion and inclined so that the flow path cross-section gradually increases toward downstream, and an actuator capable of changing the inclination angle of the first portion with respect to the flow direction of the intake passage, and the flow path cross-section control means can employ a configuration in which the flow path cross-section is reduced by operating the actuator to increase the inclination angle of the first portion (configuration 2).

[0009] In addition, in configuration 2, the flow path cross-section varying mechanism can have a first portion upstream of the air flow sensor that is inclined so that the flow path cross-section gradually decreases toward the downstream side, and a second portion downstream of the first portion that is inclined so that the flow path cross-section gradually increases toward the downstream side, and a configuration can be adopted in which the inclination angle of the first portion with respect to the flow direction of the intake passage is set larger than the inclination angle of the second portion with respect to the flow direction of the intake passage (configuration 3).

[0010] In addition, in configuration 2, the flow path cross-section varying mechanism has a first portion upstream of the air flow sensor that slopes so that the flow path cross-section gradually decreases toward the downstream side, and a second portion downstream of the first portion that slopes so that the flow path cross-section gradually increases toward the downstream side, and has a first connecting portion that rotatably connects the upstream end of the first portion to the intake passage, and a second connecting portion that rotatably connects the first portion and the second portion, an actuator is connected to the second portion, and the flow path cross-section control means can employ a configuration that operates the actuator to slide the downstream end of the second portion along the flow direction of the intake passage, thereby reducing the flow path cross-section (configuration 4).

[0011] In configuration 4, a configuration can be adopted in which the air flow sensor is provided protruding into the intake passage, and the first part and the second part are provided opposite each other with the air flow sensor sandwiched between them along the inner surface of the intake passage (configuration 5).

[0012] In configuration 2, the flow path cross-section varying mechanism has a third part connecting the first part and the second part, an actuator is connected to the third part, and the flow path cross-section control means can employ a configuration in which the flow path cross-section is reduced by operating the actuator to tighten the third part toward the axis of the intake passage (configuration 6).

[0013] In the sixth aspect, the air flow sensor may be positioned in a region where the third portion is present in the flow direction of the intake passage (seventh aspect). [Effects of the Invention]

[0014] According to the present invention, the measurement accuracy of the air flow sensor can be improved when the flow velocity in the intake passage is low. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a configuration diagram showing a control device for an internal combustion engine according to an embodiment of the present invention; [Figure 2] 1 is an enlarged front view of a main portion of an intake passage structure according to a first embodiment of the present invention; [Figure 3] FIG. 3 is a plan view of FIG. 2. [Figure 4] FIG. 6 is an enlarged front view of a main portion of an intake passage structure according to a second embodiment of the present invention. [Figure 5] FIG. 5 is a plan view of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0016] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram showing the configuration of an engine (internal combustion engine) E and a control device for the engine E according to this embodiment.

[0017] The engine E in this embodiment is a four-stroke gasoline engine for an automobile. A piston 2 is housed in a cylinder 1 of the engine E. A combustion chamber 3 is formed by the inner surface of the cylinder 1, the upper surface of the piston 2, etc.

[0018] The engine E is equipped with an intake passage 4 that sends intake air into the combustion chamber 3 of each cylinder, which houses a piston 2, and an exhaust passage 5 that leads out from the combustion chamber 3. The intake passage 4 is composed of an intake port formed integrally with the cylinder head and an intake manifold connected to the intake port, and is a passage that extends upstream from the intake manifold to a surge tank 13 and an air cleaner 11. The exhaust passage 5 is composed of an exhaust port formed integrally with the cylinder head and an exhaust manifold connected to the exhaust port, and is a passage that extends downstream from the exhaust manifold to an opening to the outside. The intake valve hole and exhaust valve hole, which are the openings of the intake port and exhaust port to the combustion chamber 3, are opened and closed by intake valves 6 and exhaust valves 7, respectively.

[0019] The intake passage 4 is provided with a throttle valve 12 that adjusts the flow cross section of the intake passage 4 to control the flow rate of intake air. Also provided in the intake passage 4 is an air flow sensor (intake pressure sensor) 30 that detects the flow velocity (flow rate) of the air passing through. Also provided in the exhaust passage 5 is an exhaust purification device 15 that removes harmful components contained in the exhaust. Furthermore, the exhaust passage 5 is provided with an exhaust sensor 14 and the like that detect the components contained in the exhaust.

[0020] The engine E also includes a fuel injection device 10 that injects fuel. In the embodiment, the fuel injection device 10 is a direct injection valve that injects fuel into the combustion chamber 3, but it may also be a port injection valve that injects fuel into an intake port. The combustion chamber 3 also includes an ignition device (spark plug) 9 that generates an ignition spark to combust the air-fuel mixture.

[0021] 1 mainly shows components and means directly related to the present invention, and omits other components, etc. Also, although the drawing shows only one cylinder, the number of cylinders of engine E is not limited.

[0022] A vehicle equipped with this engine E is equipped with an electronic control unit 20. The electronic control unit 20 acquires information from various sensors in the intake passage 4 and the exhaust passage 5, as well as from a rotation sensor that detects the rotation speed of the crankshaft of the engine E, a water temperature sensor that detects the temperature of the coolant that cools the cylinder block etc., a vehicle speed sensor that detects the speed of the vehicle, and other sensors that acquire information necessary for controlling the engine E, and utilizes this information for controlling the engine E. In addition, information on the operation of the ignition, accelerator, brake, and other devices performed by the driver is input to the electronic control unit 20.

[0023] The control means 21 provided in the electronic control unit 20 controls the intake air amount, fuel injection amount, ignition timing, etc., so as to obtain the required torque determined according to the accelerator opening, engine speed, and other driving conditions. At this time, the control means 21 controls the opening of the throttle valve 12 and the fuel injection device 10 based on the intake air amount obtained from the air flow sensor 30. The control means 21 also controls the intake valve 6, exhaust valve 7, and other devices necessary for the operation of the engine E.

[0024] The air flow sensor 30 is inserted into a hole provided in the intake passage 4 from outside the intake passage 4, with its tip protruding into the intake passage 4.

[0025] In this invention, for the purpose of improving the measurement accuracy of the air flow sensor 30 particularly at low flow velocities, a flow path cross-section varying mechanism 40 is provided in the intake passage 4, which is located at least in the upstream region of the air flow sensor 30 and is capable of varying the flow path cross-section of the intake passage 4 in the region upstream of the air flow sensor 30. In this embodiment, the flow path cross-section varying mechanism 40 is located across the upstream region and downstream region of the air flow sensor 30.

[0026] The flow path cross-section varying mechanism 40 is controlled to reduce the flow path cross-section at least on the upstream side of the air flow sensor 30 when the flow velocity (flow rate) of the intake air flowing through the intake passage 4 is equal to or lower than a predetermined value. This control is performed by a flow path cross-section control means 22 provided in the electronic control unit 20. Furthermore, information on the flow velocity (flow rate) obtained from the air flow sensor 30 is processed by a flow rate analysis means 23 provided in the electronic control unit 20. The predetermined value is set to a value at which, if the flow velocity of the intake air becomes smaller than this value, problems may arise in measurement accuracy due to the influence of pulsation from downstream, etc. This value is determined appropriately depending on the type of sensor and the specifications of the engine E.

[0027] In this invention, the flow path cross section is reduced only when the flow velocity in the intake passage 4 is equal to or lower than a predetermined value. Therefore, at low flow velocities where measurement accuracy is poor, the flow velocity is increased to ensure the measurement accuracy of the air flow sensor 30, and at high flow velocities, the flow path cross section is kept normal, which has the advantage of not impeding the flow in the intake passage 4.

[0028] A first embodiment of an intake passage structure equipped with a flow passage cross-section varying mechanism 40 is shown in Figures 2 and 3. Figure 2 is a view of the inside of the intake passage 4 around the flow passage cross-section varying mechanism 40, viewed from a direction perpendicular to the insertion direction of the air flow sensor 30, and Figure 3 is a view of the inside of the intake passage 4, viewed from the insertion direction of the air flow sensor 30.

[0029] The flow path cross-section varying mechanism 40 of the first embodiment varies the flow path cross-section of the intake passage 4 by operating a flow path member 41. The flow path member 41 includes a first portion 41b, which is inclined so that the flow path cross-section gradually decreases toward the downstream side, upstream of the air flow sensor 30, and a second portion 41c, which is inclined so that the flow path cross-section gradually increases toward the downstream side, downstream of the first portion 41b.

[0030] In this embodiment, the first portion 41b and the second portion 41c are each formed of a plate-like member and are connected to each other. A set of flow path members 41 consisting of the first portion 41b and the second portion 41c is provided along the inner surface of the intake passage 4, and the set of flow path members 41 is provided on both sides of the air flow sensor 30, facing each other across the axis O of the intake passage 4 (see FIG. 3). That is, in this embodiment, the set of flow path members 41 is provided on a wall surface of the inner surface of the intake passage 4 that faces in a direction perpendicular to the insertion direction of the air flow sensor 30. This makes it possible to suppress variations in the amount of intake air passing through the air flow sensor 30 in the insertion direction of the air flow sensor 30 when the flow path cross-section varying mechanism 40 is activated.

[0031] The upstream end of the first portion 41b is rotatably connected to the intake passage 4 by a first connecting portion 41d. The first portion 41b and the second portion 41c are rotatably connected by a second connecting portion 41e. The first connecting portion 41d and the second connecting portion 41e are each formed by a hinge mechanism.

[0032] An actuator 42 is connected to the second portion 41c. An operating member (rod) 43 of the actuator 42 is connected to a third connecting portion (bracket) 41f provided at the downstream end of the second portion 41c. The downstream end of the second portion 41c is slid along the flow direction of the intake passage 4 by the operation of the actuator 42, thereby changing the flow path cross section of the intake passage 4. That is, when the downstream end of the second portion 41c is moved upstream along the flow direction of the intake passage 4, the flow path cross section is reduced (see the state indicated by the solid line in FIG. 3), and when it is moved downstream, the flow path cross section returns to its normal state before reduction (see the state indicated by the dashed line in FIG. 3). The reduction in the flow path cross section increases the flow velocity from arrow A to arrow B shown in FIGS. 2 and 3.

[0033] Since the flow path cross-section varying mechanism 40 can vary the flow path cross-sectional area of ​​the intake passage 4 in the region upstream of the airflow sensor 30, the second connection part 41e is provided so as to be located upstream of the airflow sensor 30 at least when the flow path cross-section varying mechanism 40 is activated (the flow path cross-sectional area is reduced). Furthermore, the first connection part 41d is provided upstream of the airflow sensor 30, and the actuator 42 is provided downstream of the airflow sensor 30. In other words, when the flow path cross-section varying mechanism 40 is activated, the first part 41b extends from upstream of the airflow sensor 30 to near the airflow sensor 30 on the upstream side of the airflow sensor 30, and the second part 41c extends from the downstream end of the first part 41b to downstream of the airflow sensor 30.

[0034] The inclination angle α of the first portion 41b relative to the flow direction (direction of the axis O) of the intake passage 4 is always set larger than the inclination angle β of the second portion 41c relative to the flow direction (direction of the axis O) of the intake passage 4. The actuator 42 reduces the flow path cross section by increasing the inclination angle α of the first portion 41b. This ensures an appropriate flow velocity at the position of the airflow sensor 30 and suppresses the generation of turbulence, such as vortices, in the flow downstream (see arrow C in Figures 2 and 3). Considering the loss coefficient of the flow path, it is desirable to set the maximum inclination angle α of the first portion 41b to 60 degrees and the maximum inclination angle β of the second portion 41c to 10 degrees. This is because if the inclination angle β of the second portion 41c exceeds 10 degrees, the pipe resistance increases dramatically.

[0035] Here, the actuator 42 may be connected to the first portion 41b. In this case, too, it is desirable that the actuator 42 be configured to reduce the flow passage cross section by increasing the inclination angle α of the first portion 41b with respect to the flow direction of the intake passage 4 (the direction of the axis O).

[0036] A second embodiment of the intake passage structure is shown in FIGS.

[0037] In the second embodiment, the flow path member 41 includes a first portion 41b, which is inclined so that the flow path cross section gradually decreases toward the downstream side, upstream of the air flow sensor 30, and a second portion 41c, which is inclined so that the flow path cross section gradually increases toward the downstream side, downstream of the first portion 41b. The flow path member 41 also includes a third portion 41a that connects the first portion 41b and the second portion 41c.

[0038] In the embodiment, the first portion 41b, the second portion 41c, and the third portion 41a are made of a cylindrical resin material or a cylindrical rubber material that is flexible and has a certain degree of rigidity. The flow path member 41, which includes the first portion 41b, the second portion 41c, and the third portion 41a, is provided along the entire inner surface of the intake passage 4.

[0039] The upstream end of the first portion 41b and the downstream end of the second portion 41c are fixed to the intake passage 4. The first portion 41b, the third portion 41a, and the second portion 41c are integrally molded as a continuous cylindrical member.

[0040] An actuator (motor) 42 is connected to the third portion 41a. An operating member (winding member) 43 of the actuator 42 is connected to a band 45 wound around the outer periphery of the third portion 41a. The band 45 is wound around the entire area of ​​the third portion 41a in the flow direction. The airflow sensor 30 passes through a hole 44 provided in the third portion 41a of the flow path member 41 and the band 45, and airtightness is always maintained between the inner periphery of the hole 44 and the outer periphery of the airflow sensor 30.

[0041] By operating the actuator 42, the third portion 41a is tightened toward the axis O of the intake passage 4, which causes the flow path member 41 to elastically deform and change the flow path cross section of the intake passage 4. That is, when the actuator 42 winds (pulls) the operating member 43, the third portion 41a is tightened and contracts in diameter, thereby reducing the flow path cross section, and when the actuator 42 unwinds the wound operating member 43 in the opposite direction (releases the tension), the elastic deformation of the flow path member 41 is released and the flow path cross section returns to its normal state before contraction. The dimension w in the figure is the dimension reduced in diameter by tightening the band 45. When the reduction in the flow path cross section is released, the dimension w = 0.

[0042] In the second embodiment, the flow path member 41 is provided around the entire circumferential direction of the intake passage 4, centered on the axis O of the intake passage 4. This ensures a stable flow velocity of at least a predetermined value around the axis O of the intake passage 4. The airflow sensor 30 is located in an area where the third portion 41a is interposed with respect to the flow direction of the intake passage 4. The third portion 41a is provided substantially parallel to the flow direction of the intake passage 4, i.e., along the wall surface of the intake passage 4. This ensures a stable flow velocity from the upstream end to the downstream end of the airflow sensor 30 (without significant changes along the way). The third portion 41a does not necessarily need to be parallel to the flow direction of the intake passage 4; it only needs to be inclined at an angle smaller than the inclination angles of the first portion 41b and the second portion 41c.

[0043] In each embodiment, the flow velocity increases as the cross-sectional area of ​​the flow passage is reduced, and the airflow sensor 30 acquires information after the flow velocity has increased. Here, the flow velocity after the cross-sectional area of ​​the flow passage is reduced is referred to as the post-cross-sectional area reduction flow velocity, and the flow velocity without the cross-sectional area being reduced is referred to as the pre-cross-sectional area reduction flow velocity. The flow rate analysis means 23 converts the post-cross-sectional area reduction flow velocity to the pre-cross-sectional area reduction flow velocity, calculates the intake volume based on the converted pre-cross-sectional area reduction flow velocity, and uses the calculated intake volume for controlling the engine E. This conversion can be achieved, for example, by correcting the post-cross-sectional area reduction flow velocity to the pre-cross-sectional area reduction flow velocity based on the reduction ratio of the cross-sectional area of ​​the intake passage 4, or by providing a map showing the relationship between the reduction ratio of the cross-sectional area of ​​the flow passage and the post-cross-sectional area reduction flow velocity and the pre-cross-sectional area reduction flow velocity.

[0044] In the above embodiments, the flow velocity in the intake passage 4 is assumed to have two stages, low flow velocity and high flow velocity, with a predetermined value as the boundary, and the cross section of the intake passage 4 is reduced (by, for example, 25%) only at low flow velocity. However, for example, this may be configured to have three, four or more stages depending on the flow velocity, and the reduction rate of the cross section of the intake passage 4 may be set to a different value for each stage. Furthermore, the reduction rate of the cross section of the intake passage 4 may be changed continuously depending on the flow velocity.

[0045] Furthermore, in the above embodiment, the flow path member 41 of the flow path cross-section varying mechanism 40 is interposed across the upstream region and downstream region with respect to the airflow sensor 30, but an embodiment in which the flow path member 41 is interposed only in the upstream region with respect to the airflow sensor 30 is also conceivable. In this case, the flow path member 41 may be constituted by only the first portion 41b, or may be constituted by only the first portion 41b and the third portion 41a.

[0046] In the above embodiments, a vehicle equipped with only an engine E as a driving source for traveling is assumed, and the configuration of the invention has been described using an example of a control device for the engine E. However, this may also be a control device for the engine E of a hybrid vehicle equipped with an engine E and a motor as driving sources for traveling. Furthermore, the hybrid vehicle may in particular be a plug-in hybrid car in which the battery 50 can be directly charged (external charging) using an attachment plug from a household outlet or the like, or in which power can be directly supplied to household electrical appliances or the like from the battery 50 using an attachment plug (external power supply). [Explanation of symbols]

[0047] 3 Combustion chamber 4 Intake passage 12 Throttle valve 13 Fuel injection device 20 Electronic Control Unit 21 Control Means 22 Flow path cross section control means 23 Flow rate analysis means 30 Air flow sensor 40 Flow path cross section variable mechanism 41 Flow path member 41b First part 41c Second part 41a Third part 41d First connection part 41e Second connection part 41f Third connection part 42 Actuator E. Internal combustion engine (engine)

Claims

1. A control device for an internal combustion engine comprising: a combustion chamber; an intake passage leading to the combustion chamber; an airflow sensor provided in the intake passage; a flow passage cross-section varying mechanism interposed in the intake passage at least upstream of the airflow sensor; and flow passage cross-section control means for activating the flow passage cross-section varying mechanism to reduce the flow passage cross-section at least upstream of the airflow sensor when the flow velocity of intake air flowing through the intake passage is equal to or lower than a predetermined value.

2. the flow passage cross-section varying mechanism includes a first portion located upstream of the air flow sensor and inclined so that the flow passage cross-section gradually decreases toward the downstream side, a second portion located downstream of the first portion and inclined so that the flow passage cross-section gradually increases toward the downstream side, and an actuator capable of changing the inclination angle of the first portion with respect to the flow direction of the intake passage, 2. The control device for an internal combustion engine according to claim 1, wherein the flow passage cross section control means operates the actuator to increase the inclination angle of the portion, thereby reducing the flow passage cross section.

3. 3. The control device for an internal combustion engine according to claim 2, wherein an inclination angle of the first portion with respect to the flow direction of the intake passage is set to be larger than an inclination angle of the second portion with respect to the flow direction of the intake passage.

4. the flow passage cross-section varying mechanism includes a first connection portion that rotatably connects an upstream end of the first portion to the intake passage, and a second connection portion that rotatably connects the first portion and the second portion, 3. The control device for an internal combustion engine according to claim 2, wherein an actuator is connected to the second portion, and the flow passage cross-section control means operates the actuator to slide the downstream end of the second portion along the flow direction of the intake passage, thereby reducing the flow passage cross-section.

5. 5. The control device for an internal combustion engine according to claim 4, wherein the air flow sensor is provided so as to protrude into the intake passage, and the first portion and the second portion are provided along the inner surface of the intake passage opposite each other with the air flow sensor therebetween.

6. 3. The control device for an internal combustion engine according to claim 2, wherein the flow passage cross-section varying mechanism has a third portion connecting the first portion and the second portion, an actuator is connected to the third portion, and the flow passage cross-section control means operates the actuator to tighten the third portion toward the axis of the intake passage, thereby reducing the flow passage cross-section.

7. 7. The control device for an internal combustion engine according to claim 6, wherein the air flow sensor is located in a region of the intake passage where the third portion is present in the flow direction.

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