JP5598406B2 - Engine control device - Google Patents

Description

  The present invention relates to a control device that controls valve lift amounts of an intake valve and an exhaust valve of an engine.

  2. Description of the Related Art Conventionally, an engine having a variable valve mechanism for changing the operation of an intake valve and an exhaust valve has been developed for the purpose of reducing fuel consumption of a vehicle, improving output, and reducing exhaust emission. As the functions mounted on the variable valve mechanism, there are mainly two types of functions. The first function is a variable valve timing (VVT) function that makes the valve opening and closing timing variable. The second function is a variable valve lift that makes the valve opening amount (valve lift amount) variable. VVL, Variable Valve Lift) function.

  The variable valve timing function is realized by a mechanism that changes the relative rotational phase of the camshaft with respect to the crankshaft, for example. As a result, the opening / closing timing of the valve is changed, and the phase corresponding to the opening start timing and the opening end timing of the valve is controlled to advance or retard. The variable valve lift function is realized by a mechanism that changes the magnitude of the swing transmitted from the cam fixed to the camshaft to the rocker arm, for example. As a result, the distance that the valve reciprocates is changed, and the amount of air introduced into the cylinder, the pressure in the intake manifold, and the like are controlled.

  By the way, in an engine equipped with a variable valve mechanism, the inertia effect of intake and exhaust changes by overlapping the period when the intake valve is opened and the period when the exhaust valve is opened, so that the charging efficiency and the amount of fresh air blown are changed. Changes. Therefore, a technique for controlling the combustion state of the engine by changing the opening overlap period (valve overlap) of the intake and exhaust valves has been developed.

  For example, Patent Document 1 describes a technique for controlling an air-fuel ratio by controlling valve overlap during lean combustion of an engine. In this technology, it is said that the exhaust air flow ratio is increased or decreased by increasing or decreasing the amount of fresh air blown into the cylinder in the expansion stroke, and exhaust emission can be prevented from deteriorating while ensuring exhaust energy. .

JP 2009-293621 A

In a direct injection engine that injects fuel into a cylinder, as described in Patent Document 1, the fuel supply amount is controlled separately from the amount of fresh air introduced into the cylinder. That is, it is possible to perform control such that fuel is injected after the exhaust valve is closed so that blow-off of fresh air stops, and the valve overlap can be controlled relatively freely.
On the other hand, in the case of a port injection engine that injects fuel into the intake passage, the fuel is injected into the intake air immediately before being introduced into the cylinder, so the amount of intake air blown directly into the exhaust emission performance Therefore, it is difficult to perform the control as described in Patent Document 1. For example, the longer the valve overlap period is, the more HC (unburned fuel component) flows out to the exhaust port side, which must be purified by the exhaust catalyst on the exhaust passage. It will be disadvantageous.
As described above, in a port injection type engine, a change in valve overlap may not be preferable in terms of control, and there is a problem that it is difficult to improve exhaust emission performance and fuel consumption.

One of the purposes of the present case was invented in view of the above-described problems, and is to improve the exhaust performance and fuel consumption in a port injection engine.
The present invention is not limited to this purpose, and is a function and effect derived from each configuration shown in the embodiments for carrying out the invention described later, and other effects of the present invention are to obtain a function and effect that cannot be obtained by conventional techniques. Can be positioned.

  (1) An engine control device disclosed herein includes detection means for detecting an overlap width between opening periods of an intake valve and an exhaust valve of an engine, and fuel injection means for injecting fuel into the intake passage of the engine. . Further, a valve lift for at least one of the pair of the intake valve and the exhaust valve facing the flow direction of the intake air in the cylinder into which the fuel is injected according to the overlap width detected by the detection means. Valve lift amount control means for reducing the amount is provided.

(2 ) It is preferable that an intake pressure detection means for detecting an intake pressure of the engine is provided, and the valve lift amount control means decreases the valve lift amount according to the overlap width and the intake pressure.

( 3 ) Further, when the intake pressure is higher than the exhaust pressure (for example, when the turbocharger is provided with a supercharger that supercharges air in the cylinder), It is preferable to reduce the valve lift.
For example, when a supercharger that supercharges air in the cylinder is provided and supercharging is performed, the intake pressure becomes larger than the exhaust pressure. Even in the case where the supercharger is not provided, the intake pressure may be larger than the exhaust pressure in an operation region where the intake throttle is small (when the throttle opening is almost fully open). As means for grasping the exhaust pressure, an exhaust pressure detection means (exhaust pressure sensor) for detecting the exhaust pressure of the engine may be provided, or the exhaust pressure may be estimated from the operating state of the engine. Good.

( 4 ) It is preferable that a rotation speed detection means for detecting the engine speed of the engine is provided, and the valve lift amount control means decreases the valve lift amount according to the overlap width and the engine speed. .
(5) In addition, when each of the intake valve and the exhaust valve is provided and the valve lift amount control means has the overlap width equal to or greater than a predetermined width, at least one of the pair of intake valves and exhaust valves. It is preferable to pause one operation. That is, it is preferable that the valve lift amount control means sets the valve lift amount to 0 when the overlap width is equal to or greater than a predetermined width.
(6) Moreover, it is preferable that the said fuel injection means injects the said fuel toward between the stem of the said intake valve, and the outer peripheral surface of the said cylinder.

(7) The engine is a multi-valve engine having a pair of intake valves and a pair of exhaust valves that operate in synchronization with each other, wherein the valve lift amount control means includes the pair of intake valves and the pair of exhaust valves. Among the exhaust valves, the other intake valve opposed to the other exhaust valve that stops one exhaust valve facing one intake valve that introduces intake air into the cylinder and exhausts air to the exhaust passage Is preferably paused.
In other words, it is preferable that the valve lift amount control means is arranged in a staggered arrangement in the top view of the cylinder in the arrangement of the intake valve and the exhaust valve that are opened (or closed).

  According to the disclosed engine control device, in a port injection type engine, the opening amount of at least one of a pair of opposed valves is controlled in accordance with valve overlap. The blow-through to the can be suppressed. Thereby, fuel consumption and exhaust performance can be improved.

It is a block diagram which illustrates the control device of the engine concerning one embodiment. It is the perspective view of the cylinder upper part which saw through the intake valve and exhaust valve of the engine of FIG. FIG. 3 is a schematic top view of the cylinder of FIG. 2. It is a graph for demonstrating the driving | running state which concerns on the control implemented with the control apparatus of FIG. It is a flowchart for demonstrating the control content implemented with the control apparatus of FIG. It is a cylinder top view for demonstrating the intake valve and exhaust valve which become the control object by the control apparatus of the engine which concerns on a modification.

  The control device will be described with reference to the drawings. Note that the embodiment described below is merely an example, and there is no intention to exclude various modifications and technical applications that are not explicitly described in the following embodiment.

[1. Device configuration]
[1-1. Engine structure]
The engine control apparatus of this embodiment is applied to the multi-valve engine 10 shown in FIG. Here, one of a plurality of cylinders 19 (cylinders) provided in the multi-cylinder engine 10 is shown. The piston 16 that reciprocates in the cylinder 19 is connected to the crankshaft 17 via a connecting rod.

  The shape of the combustion chamber of the cylinder 19 is a pent roof type as shown in FIG. 2, and the upper portion of the combustion chamber is formed in a triangular roof shape in the longitudinal section of the cylinder 19. A pair of intake ports 11 is provided on one slope of the triangular roof, and a pair of exhaust ports 12 is provided on the other slope. Moreover, as shown in FIG. 1, the spark plug 13 is provided in the center part of the cylinder 19 top surface in the state which made the front-end | tip protrude to the combustion chamber side.

  Each intake port 11 is provided with an intake valve 14, and the exhaust port 12 is provided with an exhaust valve 15. The intake port 11 and the combustion chamber are communicated or closed by opening and closing the intake valve 14, and the exhaust port 12 and the combustion chamber are communicated or blocked by opening and closing the exhaust valve 15. The pair of intake valves 14 operate synchronously (simultaneously), and the pair of exhaust valves 15 also operate synchronously (simultaneously).

  The upper ends of the intake valve 14 and the exhaust valve 15 are connected to one ends of rocker arms 35 and 37, respectively. The rocker arms 35 and 37 are swing members pivotally supported on the rocker shaft, and the intake valve 14 and the exhaust valve 15 are reciprocated in the vertical direction by swinging of the respective rocker arms 35 and 37. The other ends of the rocker arms 35 and 37 are provided with cams 36 and 38 that are pivotally supported by the camshaft. Thereby, the rocking | fluctuation pattern of the rocker arms 35 and 37 becomes a thing according to the shape (cam profile) of the cams 36 and 38. FIG.

[1-2. Valve system]
The engine 10 is provided with a variable valve mechanism 6 that controls the operation of the rocker arms 35 and 37 or the cams 36 and 38. The variable valve mechanism 6 is a mechanism that changes the maximum valve lift amount and the valve timing individually or in conjunction with each of the intake valve 14 and the exhaust valve 15. The variable valve mechanism 6 includes a variable valve lift mechanism 6a and a variable valve timing mechanism 6b as mechanisms for changing the swing amount and swing timing of the rocker arms 35 and 37.

  The variable valve lift mechanism 6 a is a mechanism that continuously changes the maximum valve lift amount of the intake valve 14 and the exhaust valve 15. The variable valve lift mechanism 6a has a function of changing the magnitude of the swing transmitted from the cams 36, 38 to the rocker arms 35, 37. A specific structure for changing the magnitude of rocking of the rocker arms 35 and 37 is arbitrary.

  Taking the intake valve 14 side as an example, a rocking member is separately interposed between a cam 36 fixed to the camshaft and a rocker arm 35, and the rotational movement of the camshaft is controlled by the rocker arm 35 via this rocking member. It can be considered that the structure is converted into a swing motion. In this case, by moving the position of the swing member to change the contact position with the cam 36, the swing amount of the swing member changes and the swing amount of the rocker arm 35 also changes. Thereby, the valve lift amount of the intake valve 14 can be continuously changed. The same applies to the exhaust valve 15 side, and the valve lift amount of the exhaust valve 15 can be adjusted by providing a swinging member between the cam 38 and the rocker arm 37.

  The variable valve timing mechanism 6 b is a mechanism that changes the opening / closing timing (valve timing) of the intake valve 14 and the exhaust valve 15. The variable valve timing mechanism 6b has a function of changing the rotational phase of the cams 36 and 38 or the camshaft that causes the rocker arms 35 and 37 to swing. By changing the rotational phase of the cams 36 and 38 or the camshaft, it is possible to continuously shift the rocking timing of the rocker arms 35 and 37 with respect to the rotational phase of the crankshaft 17.

[1-3. Intake and exhaust system]
An injector 18 (fuel injection means) that injects fuel is provided in the intake port 11. As shown in FIG. 3, the injector 18 is arranged on the upstream side of the intake air from the position where the two intake ports 11 merge. When one symbol of the pair of intake valves 14 is set to 14A and the other is set to 14B, the injection direction of the fuel injected from the injector 18 is set to the outer peripheral side of the cylinder 19 relative to the valve stem 50 of the one intake valve 14A. Set to the direction toward. The amount of fuel injected from the injector 18 is electronically controlled by the engine control device 5 described later. The opening of the intake port 11 closed by one intake valve 14A is called a first intake port opening 11A, and the opening of the other intake port 11 is called a second intake port opening 11B.

  Of the pair of exhaust valves 15, the one facing the one intake valve 14 </ b> A is denoted by reference numeral 15 </ b> A, and the other is denoted by reference numeral 15 </ b> B. Here, “opposite” means that the intake air introduced from the respective intake valves 14A and 14B faces each other in the flow direction in the cylinder 19 in a top view of the cylinder 19. In the present embodiment, as shown in FIG. 3, one exhaust valve 15 </ b> A is arranged so as to face one intake valve 14 </ b> A across a one-dot chain line X corresponding to the ridge on the top surface of the cylinder 19. The other exhaust valve 15B is disposed at a position facing the other intake valve 14B across the broken line X. The opening of the exhaust port 12 closed by the one exhaust valve 15A is referred to as a first exhaust port opening 12A, and the opening of the other exhaust port 12 is referred to as a second exhaust port opening 12B.

  As shown in FIG. 1, an intake manifold 20 (hereinafter referred to as an intake manifold) is provided upstream of the injector 18 in the intake air flow. The intake manifold 20 is provided with a surge tank 21 for temporarily storing air flowing toward the intake port 11 side. The intake manifold 20 on the downstream side of the surge tank 21 is formed to branch toward the plurality of cylinders 19, and the surge tank 21 is located at the branch point. The surge tank 21 functions to mitigate intake pulsation and intake interference generated in each cylinder 19.

  A throttle body 23 is connected to the upstream end of the intake manifold 20. An electronically controlled throttle valve 24 is built in the throttle body 23, and the amount of air flowing to the intake manifold 20 is adjusted according to the opening (throttle opening) of the throttle valve 24. The throttle opening is electronically controlled by the engine control device 5.

  An intake passage 25 is connected further upstream of the throttle body 23. An air filter 28 is interposed further upstream of the intake passage 25. Thus, fresh air filtered by the air filter 28 is supplied to the cylinder 19 of the engine 10 via the intake passage 25 and the intake manifold 20.

  On the other hand, an exhaust manifold 30, an exhaust catalyst 32, and an exhaust passage 39 are provided downstream of the exhaust port 12 in the exhaust flow. The exhaust manifold 30 is formed so as to merge from the plurality of cylinders 19 and is connected to an exhaust passage 39 on the downstream side thereof. The exhaust catalyst 32 is a catalyst device interposed on the exhaust passage 39, and has a function of purifying HC (hydrocarbon) components, carbon monoxide, nitrogen oxides, etc. contained in the exhaust, for example, It is an oxidation catalyst or a three-way catalyst. HC in the exhaust discharged from the combustion chamber of the engine 10 is oxidized and removed by the action of the exhaust catalyst 32.

  The intake / exhaust system of the engine 10 is provided with a turbocharger 31 (supercharger) that supercharges intake air into the cylinder 19 using exhaust pressure. The turbocharger 31 is a supercharger interposed across both the intake passage 25 and the exhaust passage 39. The turbocharger 31 rotates the turbine 27 with the exhaust pressure in the exhaust passage 39 and drives the compressor 26 using the rotational force, thereby compressing the intake air on the intake passage 25 side and supercharging the engine 10. I do. An intercooler 29 is provided on the intake passage 25 on the downstream side of the intake air flow with respect to the compressor 26 to cool the compressed air.

[1-4. Detection system]
The crankshaft 17, the crank angle sensor 33 (rotational speed detecting means) is provided for detecting the rotation angle theta _CR. The amount of change per unit time of the rotation angle θ _CR is proportional to the actual rotation speed Ne of the engine 10. Therefore, it can be said that the crank angle sensor 33 has a function of detecting the actual rotational speed Ne of the engine 10. Information on the actual rotational speed Ne detected (or calculated) here is transmitted to the engine control device 5. The engine control device 5 may calculate the actual rotational speed Ne based on the rotational angle θ _CR detected by the crank angle sensor 33. Hereinafter, the actual rotational speed Ne of the engine 10 is also simply referred to as the engine rotational speed Ne.

An intake manifold pressure sensor 22 (intake pressure detection means) for detecting the intake pressure P ₁ is provided on the downstream side of the throttle valve 24. The intake manifold pressure sensor 22 is a sensor that detects the pressure in the surge tank 21 (pressure corresponding to the pressure in the intake port 11). The intake manifold pressure sensor 22 may be disposed in the intake port 11 of each cylinder 19. On the other hand, an exhaust pressure sensor 46 (exhaust pressure detecting means) for detecting the exhaust pressure P ₂ is provided at an arbitrary position downstream of the exhaust port 12 (for example, in the exhaust manifold 30 or the exhaust port 12). Here, the pressure of the exhaust gas before passing through the turbine 27 of the turbocharger 31 is detected. Information on the intake pressure P ₁ and the exhaust pressure P ₂ detected by these sensors is transmitted to the engine control device 5.

An accelerator pedal sensor 34 that detects an operation amount θ _AC corresponding to the amount of depression of the accelerator pedal is provided at an arbitrary position of the vehicle. The accelerator pedal depression operation amount θ _AC is a parameter corresponding to the driver's acceleration request, that is, corresponds to an output request to the engine 10. Information on the detected operation amount θ _AC is transmitted to the engine control device 5.

[1-5. Control system]
This vehicle is provided with an engine control device 5 (Engine Electronic Control Unit) as an electronic control device. The engine control device 5 is configured as, for example, an LSI device or an embedded electronic device in which a microprocessor, ROM, RAM, and the like are integrated, and other electronic control devices and variable motions are connected via communication lines such as CAN and FlexRay provided in the vehicle. It is connected to the valve mechanism 6 and various sensors.

  The engine control device 5 is an electronic control device that controls a wide range of systems related to the engine 10 such as an ignition system, a fuel system, an intake / exhaust system, and a valve system. Specific control objects of the engine control device 5 include the amount of fuel injected from the injector 18 and the injection timing, the ignition timing at the ignition plug 13, the valve lift amounts and valve timings of the intake valve 14 and the exhaust valve 15, and the throttle valve. 24 degrees of opening etc. are mentioned. In the present embodiment, the stop control for stopping the operation of the intake valve 14 and the exhaust valve 15 according to the open overlap period (valve overlap) of the intake valve 14 and the exhaust valve 15, and the throttle valve according to the valve overlap. Two controls, namely, throttle opening correction control for changing the throttle opening of 24, will be described in detail.

[2. Control configuration]
The engine control device 5 is provided with a valve timing control unit 1, a valve lift amount control unit 2, and a throttle opening degree control unit 3 as software or hardware that realizes a function for performing the above two types of control. .

[2-1. Valve timing control unit]
The valve timing control unit 1 (detection means) outputs a signal to the variable valve timing mechanism 6b in accordance with the engine speed Ne and the engine load, and the valve timings (open and close) of the intake valve 14 and the exhaust valve 15 respectively. The valve overlap (the overlap width of the open period) is controlled to increase or decrease by changing the timing. Here, for example, the engine load is determined based on the intake pressure P ₁ and the exhaust pressure P ₂ . Specific control details of valve overlap are arbitrary.
For example, the valve timing is controlled so that the valve overlap increases as the engine speed Ne increases. On the other hand, if the valve overlap is excessively increased, the charging efficiency is lowered. Therefore, when the engine speed is high to some extent, the valve overlap is reduced.

In the present embodiment, as shown in FIG. 4, target values OL _{1 to} OL ₈ for valve overlap are set based on a map using the engine speed Ne and the intake / exhaust pressure difference P ₂ -P ₁ as arguments. The valve timing of each of the intake valve 14 and the exhaust valve 15 is controlled so that the valve overlap becomes the target value. The magnitude relationship between the target values is OL ₁ <OL ₂ <... <OL ₇ <OL ₈ . The valve timing control unit 1 functions as means for detecting the overlap width of the open periods of the intake valve 14 and the exhaust valve 15 and functions as means for changing the overlap width.

[2-2. Valve lift control unit]
The valve lift amount control unit 2 (valve lift amount control means) outputs a control signal to the variable valve lift mechanism 6a according to the engine speed Ne and the engine load, and controls the valve lift amounts of the intake valve 14 and the exhaust valve 15. To do. Here, for example, the engine load is determined based on the accelerator pedal depression operation amount θ _AC . The specific control content of the valve lift amount is arbitrary.

Further, the valve lift amount control unit 2 performs pause control for stopping the operation of the intake valve 14 and the exhaust valve 15 based on the target value of valve overlap set by the valve timing control unit 1. Since the target value of the valve overlap is set based on the engine speed Ne, the intake pressure P ₁ and the exhaust pressure P ₂ , the conditions for executing the stop control are the engine speed Ne, the intake pressure P ₁ and the exhaust pressure. it may be determined based on P _2.

In the present embodiment, as indicated by a thick broken line in FIG. 4, the intake pressure P ₁ is higher than the exhaust pressure P ₂ (the state where the intake port 11 side of the cylinder 19 is higher than the exhaust port 12 side). and, when the valve overlap is the engine speed Ne within a predetermined range of a predetermined value OL ₇ above, pause control is performed. Further, even if the valve overlap is less than the predetermined value OL ₇ , if the intake pressure P ₁ is higher than the exhaust pressure P ₂ and the engine speed Ne is within the predetermined range, the engine is stopped. Control is to be implemented.

  In the stop control, as shown in FIG. 3, the operation of the intake valve 14B and the exhaust valve 15A not opposed thereto is prohibited, and the variable valve lift mechanism 6a is set so that the valve lift amounts of the intake valve 14B and the exhaust valve 15A become zero. Is controlled. As a result, only the first intake port opening 11A and the second exhaust port opening 12B of the cylinder 19 are opened.

  At this time, the intake air that should originally pass through the second intake port opening portion 11B continues to be pushed into the cylinder 19 through the first intake port opening portion 11A. Accordingly, the flow rate of the intake air that passes through the first intake port opening 11A is increased as compared to when the pause control is not performed. When the stop control is performed, the charging efficiency is lower than when the stop control is not performed, but the amount of decrease is small.

  On the other hand, as indicated by white arrows in FIG. 3, the intake flow containing a large amount of the HC component injected from the injector 18 forms a swirl flow along the outer peripheral surface of the cylinder 19. Thereby, the moving distance of the intake air which tries to blow through from the first intake port opening portion 11A to the second exhaust port opening portion 12B is increased. That is, unless the intake air in the cylinder 19 goes around, it cannot escape from the second exhaust port opening 12B, and the amount of HC component blow-through decreases.

[2-3. Throttle opening control unit]
The throttle opening control unit 3 (throttle opening control means) outputs a control signal to the throttle valve 24 in accordance with the engine speed Ne and the engine load to control the throttle opening. Here, for example, the engine load is determined based on the accelerator pedal depression operation amount θ _AC . Specific control details of the throttle opening are arbitrary.

Further, the throttle opening degree control unit 3 performs throttle opening degree correction control for controlling the throttle opening degree in the opening direction when the engine output becomes insufficient during the suspension control by the valve lift amount control unit 2. The lack of engine output is determined based on, for example, the accelerator pedal depression operation amount θ _AC . In the present embodiment, when the state where the operation amount θ _AC is equal to or greater than a predetermined amount continues for a predetermined time, control for increasing the throttle opening by a predetermined amount is performed. In addition, when the engine speed Ne gradually increases and the conditions for executing the pause control are not satisfied, the throttle opening degree control unit 3 stops the throttle opening degree correction control.

[3. flowchart]
FIG. 5 is a flowchart illustrating a control procedure executed by the engine control device 5. This flow is repeatedly performed in a predetermined cycle inside the engine control device 5.
In step A10, the engine speed Ne, the intake pressure P ₁ , the exhaust pressure P ₂ and the accelerator operation amount θ _AC are input to the engine control device 5. In subsequent step A20, the valve lift amount control unit 2 determines the execution condition of the pause control. For example, when the engine speed Ne and the intake / exhaust pressure difference P ₂ -P ₁ are within the execution range of the pause control indicated by the broken line in FIG. 4, the process proceeds to Step A30 and the pause control is performed. That is, a control signal is output from the valve lift amount control unit 2 to the variable valve lift mechanism 6a, and the valve lift amounts of the intake valve 14B and the exhaust valve 15A are controlled to zero.

Thereby, as shown in FIG. 3, only the first intake port opening 11A and the second exhaust port opening 12B are opened, in other words, the openings of the cylinders 19 are opened in a staggered manner. The intake air flow introduced into the cylinder 19 during the valve overlap period moves in an arc along the outer peripheral surface of the cylinder 19. Thereby, since the moving distance of the intake air from the first intake port opening 11A to the second exhaust port opening 12B increases, the amount of HC component blow-through decreases. Incidentally, the process proceeds to step A40 if the engine speed Ne and the intake pressure P ₁ is outside Scope pause control is determined in step A20. In this case, the suspension control is not performed, and this flow is finished as it is.

In step A50 following step A30, the throttle opening degree control unit 3 determines the conditions for performing the throttle opening degree correction control. For example, when the state where the accelerator pedal depression operation amount θ _AC is equal to or greater than a predetermined amount continues for a predetermined time, the routine proceeds to step A60 and throttle opening correction control is performed. That is, a control signal is output from the throttle opening control unit 3 to the throttle valve 24, and the throttle opening is controlled in the opening direction. As a result, the amount of intake air introduced into the cylinder 19 increases, and the engine speed Ne gradually increases. If it is determined in step A50 that the throttle opening correction control execution condition is not satisfied, the process proceeds to step A70. In this case, the throttle opening correction control is not performed, and this flow is finished as it is.

[4. effect]
In the control device for the engine 10 described above, the valve lift amounts of the intake valve 14B and the exhaust valve 15A are controlled to zero according to the valve overlap. Here, when attention is paid to a pair of the four intake valves 14 and the exhaust valves 15 that are opposed to each other, the engine 10 has two pairs. The first pair is a pair of an intake valve 14A and an exhaust valve 15A facing the intake valve 14A, and the second pair is a pair of an intake valve 14B and an exhaust valve 15B facing the intake valve 14B.

  In the stop control described above, the valve lift amount of the exhaust valve 15A that is one of the first pairs is controlled to zero, and the valve lift amount of the intake valve 14B that is one of the second pairs is zero. Controlled. As described above, by reducing the valve lift amount of at least one of the pair of valves opposed to the flow direction of the intake air in the cylinder 19, the direct flow amount of the intake air through the opposed openings is reduced. To do. Therefore, it is possible to prevent the intake air containing the HC component from being blown into the exhaust passage 39 side. Thereby, the fuel consumption and exhaust performance of the engine 10 can be improved. Further, since the amount of HC component discharged from the engine 10 itself is reduced, there is an advantage that the load on the exhaust catalyst 32 can be reduced.

  Further, in a four-valve engine in which a pair of intake valves 14 and exhaust valves 15 are provided, the intake air flowing in from the first intake port opening 11A is opened by opening the openings of the cylinders 19 in a staggered manner as described above. Can earn a distance until it flows out from the second exhaust port opening 12B. As a result, the effect of preventing the blow-through of the HC component can be enhanced, and the fuel consumption and exhaust performance of the engine 10 can be further improved.

  Further, in the control device for the engine 10 described above, the intake valve 14B and the exhaust valve 15A are deactivated when the valve overlap is a predetermined value or more. Thus, by stopping the operation of the valve in a state where the intake air in the cylinder 19 is easy to blow through, the effect of preventing blow-through of the HC component can be enhanced.

Further, in the control device for the engine 10 described above, the valve lift amount is controlled with reference to the intake / exhaust pressure difference P ₂ -P ₁ as well as the valve overlap. Thereby, it is possible to reduce the valve lift amount in a pressure state in which intake air is likely to blow through (a state where intake pressure P ₁ > exhaust pressure P ₂ ).
In the control device for the engine 10 described above, the valve lift amount is controlled with reference to the engine speed Ne. Such a configuration is also advantageous in grasping the operating state of the engine 10 in which intake air is easy to blow through, and it is possible to appropriately reduce the valve lift amount, thereby enhancing the effect of preventing blow-through of HC components.

Further, the control device for the engine 10 requires that the intake pressure P ₁ is higher than the exhaust pressure P ₂ as an execution condition of the stop control. The reason why the pause control is not performed when the intake pressure P ₁ is lower than the exhaust pressure P ₂ is that intake air does not blow through. In this way, it is possible to appropriately reduce the valve lift amount in the operating state of the engine 10 in which intake air is easy to blow through, and it is possible to enhance the effect of preventing blow-through of HC components.

  Further, in the control device for the engine 10 described above, as shown in FIG. 3, the injection direction of the fuel injected from the injector 18 is on the outer peripheral side of the cylinder 19 relative to the valve stem 50 of the intake valve 14 that is opened during the stop control. Therefore, it is possible to make it easy to circulate along the outer peripheral surface of the cylinder 19 through a portion having a high HC concentration in the intake air. Thereby, compared with the case where fuel is injected toward the center of the cylinder 19, the amount of HC flowing out to the exhaust passage 39 side due to the blow-in of intake air can be more effectively suppressed, and the fuel consumption of the engine 10 can be reduced. In addition, the exhaust performance can be further improved.

  Further, in the control device for the engine 10 described above, when the engine output is insufficient during the pause control, the throttle opening correction control is performed. Therefore, the intake amount is increased by increasing the throttle opening. The engine speed Ne can be increased. Thereby, it is possible to easily escape from the operation region from the control region in which the valve lift amount is decreased, and early recovery from a state in which the output is reduced is possible. Further, the intake air amount reduced by the control of the valve lift amount can be compensated by the control of the throttle opening, and an excessive decrease in the output can be prevented.

  In the control device for the engine 10 described above, control for changing the valve lift amount is performed using the valve overlap as a control condition, and the target value of the valve overlap itself is not changed. Therefore, even in an operation state in which a change in valve overlap is not preferable in terms of control in a port injection type engine, it is possible to improve the effect of preventing blow-through of HC components and improve exhaust emission performance and fuel consumption. effective.

[5. Modified example]
Regardless of the embodiment described above, various modifications can be made without departing from the spirit of the invention. Each structure of this embodiment can be selected as needed, or may be combined appropriately.
In the above-described embodiment, the operation of stopping the operation of the intake valve 14B and the exhaust valve 15A at the time of the stop control is exemplified, but at least if the valve lift amount is reduced, the intake exhaust passage 39 including the HC component is included. The blow-through to the side can be suppressed. Therefore, the valve lift amounts of the intake valve 14B and the exhaust valve 15A may be controlled in a decreasing direction according to the operating state of the engine 10. In this case, as the valve overlap is larger, the reduction amount of the valve lift amount is increased, so that the effect of suppressing blow-through can be enhanced.

In the above-described embodiment, the example in which the stop control is performed when the intake / exhaust pressure difference P ₂ -P ₁ and the engine speed Ne are within the stop control execution range shown in FIG. The execution condition of the pause control is not limited to this. For example, the stop control may be performed based only on the valve lift amount, and not only the valve lift amount, the intake pressure P ₁ and the engine speed Ne, but also the accelerator pedal depression operation amount θ _AC , the engine coolant temperature, the oil The implementation conditions may be determined taking into account temperature, outside air temperature, and the like.

In the above-described embodiment, the exhaust pressure sensor 46 is used to detect the exhaust pressure P _2. However, instead of or in addition to such a configuration, it is estimated from the operating state of the engine 10 (that is, The engine control device 5 may calculate the pressure value corresponding to the exhaust pressure P ₂ ). For example, in the engine 10 provided with the turbocharger 31, the intake / exhaust pressure difference P ₂ -P ₁ generally becomes positive by performing supercharging. Therefore, the sign of the exhaust pressure P ₂ can be estimated without using the exhaust pressure sensor 46. Further, even in an engine that does not include the turbocharger 31, the intake pressure may be larger than the exhaust pressure in an operation region where the intake throttle is small (when the throttle opening is almost fully open). Therefore, the exhaust pressure P ₂ and the intake / exhaust pressure difference P ₂ -P ₁ can be estimated based on the engine speed Ne and the throttle opening.

  In the above-described embodiment, the engine 10 including four supply / exhaust valves has been described as an example, but the number of valves is not limited thereto. As shown in FIG. 6, in the case of a five-valve engine 40 having three intake valves 41, 42, 43 and two exhaust valves 44, 45, the intake air disposed opposite to one exhaust valve 44. By paying attention to the pair of valves 41 and the pair of intake valves 43 arranged to face the other exhaust valve 45, it is possible to perform the same control as in the above-described embodiment.

  For example, it can be considered that the intake valve 43 and the exhaust valve 44 are valves that are stopped (or the valve lift amount is decreased) during the stop control. In such control as well, as indicated by the white arrow in FIG. 6, the intake flow containing a lot of HC components flows along the outer peripheral surface of the cylinder 19, so that the blow-through amount toward the exhaust passage 39 is reduced. . Therefore, the same effects as those of the above-described embodiment are achieved.

  The operation of the central intake valve 42 sandwiched between the two intake valves 41 and 43 is arbitrary, and may not be controlled, or may be completely stopped. In order to further improve the effect of preventing the blow-in of the intake air, it is preferable to increase the closing amount of the intake valve 42, and in order to suppress a decrease in charging efficiency, the closing amount of the intake valve 42 is reduced (opened). It is considered preferable.

1 Valve timing controller (detection means)
2 Valve lift control unit (lift control means)
3 Throttle opening control unit (throttle opening control means)
5 Engine control device 10 Engine 14 Intake valve 15 Exhaust valve 18 Injector (fuel injection means)
20 Intake manifold (intake manifold)
22 In manifold pressure sensor (intake pressure detection means)
30 Exhaust manifold (Exhaust manifold)
31 Turbocharger (supercharger)
33 Crank angle sensor (rotational speed detection means)
46 Exhaust pressure sensor (exhaust pressure detection means)

Claims (7)

Detecting means for detecting the overlap width of the opening periods of the intake valve and the exhaust valve of the engine;
Fuel injection means for injecting fuel into the intake passage of the engine;
In accordance with the overlap width detected by the detection means, a valve lift amount for at least one of the pair of the intake valve and the exhaust valve opposed to the flow direction of the intake air in the cylinder into which the fuel is injected. An engine control device comprising: a valve lift amount control means for reducing the valve lift amount. Intake pressure detection means for detecting the intake pressure of the engine,
The valve lift amount control means, the overlap width and in accordance with the intake pressure and decreases the valve lift control device according to claim 1, wherein the engine. The engine control device according to claim 2 , wherein the valve lift amount control means decreases the valve lift amount when the intake pressure is higher than an exhaust pressure. A rotation speed detecting means for detecting the engine speed of the engine;
The engine control device according to any one of claims 1 to 3 , wherein the valve lift amount control means decreases the valve lift amount according to the overlap width and the engine speed. A plurality of the intake valves and the exhaust valves, respectively,
5. The valve lift amount control unit according to claim 1, wherein when the overlap width is equal to or greater than a predetermined width, the valve lift amount control unit stops the operation of at least one of the pair of intake valves and exhaust valves . The engine control device according to any one of the preceding claims . The engine control according to any one of claims 1 to 5, wherein the fuel injection means injects the fuel between a stem of the intake valve and an outer peripheral surface of the cylinder. apparatus. The engine is a multi-valve engine having a pair of intake valves and a pair of exhaust valves that operate in synchronization with each other,
The valve lift amount control means pauses one of the pair of the intake valve and the exhaust valve that faces the one intake valve that introduces intake air into the cylinder, and supplies air to the exhaust passage. The engine control device according to any one of claims 1 to 6, wherein the other intake valve facing the other exhaust valve that is discharging is deactivated.

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