JP4432746B2 - Intake control device for internal combustion engine - Google Patents

Description

  The present invention relates to an intake air control device for an internal combustion engine that controls an intake air amount by changing a valve lift characteristic of an intake valve by a variable valve operating device.

  In a gasoline engine, the intake air amount is generally controlled by controlling the opening of a throttle valve provided in the intake passage. As is well known, this type of system has a particularly small throttle valve opening. There is a problem that the pumping loss is large at low load. On the other hand, attempts have been made to control the intake air amount without depending on the throttle valve by changing the opening / closing timing of the intake valve and the lift amount.

  Patent Document 1 previously proposed by the present applicant, as a variable valve operating device for an intake valve, is a first variable valve that can simultaneously increase and decrease the lift and operating angle of the intake valve simultaneously. A mechanism (lift / operating angle variable mechanism) and a second variable valve mechanism (phase variable mechanism) that continuously delays the position of the central angle of the operating angle. An intake control device for an internal combustion engine is disclosed in which the intake air amount is controlled by changing the valve lift characteristic of the intake valve.

According to this type of intake control device, as described above, it is possible to variably control the amount of air flowing into the cylinder without depending on the opening degree control of the throttle valve, and particularly in a region with a small load. So-called throttleless operation or operation with a sufficiently large throttle valve opening can be realized, and the pumping loss can be greatly reduced.
JP 2002-256905 A

  In the intake control apparatus for an internal combustion engine having the variable valve mechanism as described above, the lift characteristic of the intake valve is not necessarily suitable for the next start when the engine is stopped. In other words, assuming that the key-off operation of the internal combustion engine is performed after the vehicle has stopped running, the internal combustion engine generally stops with a lift characteristic suitable for low speed, low load or idle. There may be a lift characteristic that cannot secure the amount of intake air required at the start (particularly at the time of cold start), and there is a concern that startability may be deteriorated.

  Therefore, before cranking the engine (for example, when the engine is stopped), it may be necessary to perform advance control of the lift characteristic, for example, the operating angle. In such a case, in a multi-cylinder internal combustion engine, If the intake valve is open even slightly in any of the cylinders, the valve spring reaction force acts on each part, so that it is generally difficult to change the lift characteristics by the actuator. In particular, in order to increase the operating angle, the intake valve in the middle of the lift is further pushed open against the valve spring reaction force, which requires a very large actuator, which is not preferable.

The present invention relates to an intake valve urged in a closing direction by a valve spring, a drive shaft common to a plurality of cylinders driven to rotate by a crankshaft, and a control shaft common to a plurality of cylinders whose rotational angle positions are controlled by an actuator And a cam interlocking mechanism for each cylinder that opens and closes each intake valve by transmitting the rotational motion of the drive shaft to the intake valve of each cylinder and expands and contracts the operating angle according to the rotational angle position of the control shaft. In the intake control device for an internal combustion engine that controls the intake angle of the internal combustion engine by controlling the operating angle according to engine operating conditions, the control shaft is controlled to the small operating angle side. Sometimes it is configured to have a period when the intake valves of all cylinders with a common drive shaft are not lifted, and the relative rotational displacement between the crankshaft and the drive shaft is allowed while the engine is stopped And, while the engine is stopped, in preparation for the next engine start, so as not to actual lift amount of one of the cylinders is increased, the period in which the intake valves of all the cylinders of the do not lift does not disappear Within the operating angle range, the actuator is moved in advance to the large operating angle side by the actuator.

  In the above configuration, for example, when the control shaft is moved to the large operating angle side by the actuator in preparation for the next engine start while the engine is stopped, the intake valve of any cylinder is in the middle of the lift. In this case, the lift of the cylinder does not increase due to the valve spring reaction force, and the drive shaft tends to rotate conversely with the rotation of the control shaft due to the actuator drive force. At this time, since the relative rotational displacement between the crankshaft and the drive shaft is allowed, the drive shaft is rotationally displaced, and the rotational angle position of the control shaft changes to a position where the operating angle becomes larger. In other words, the control position is such that the operating angle of the intake valve is potentially enlarged while the internal combustion engine is stopped. Therefore, at the start, cranking of the internal combustion engine is started, and when the drive shaft is rotationally driven together with the crankshaft, the control state immediately becomes a large operating angle.

Preferably, as in claim 2 , the control shaft is moved to a position of an operating angle at which a period during which the intake valves of all the cylinders are not lifted disappears. If the operating angle is changed to a position where the operating angle is larger than that while the engine is stopped, the actual lift of one of the cylinders increases (that is, the valve spring reaction force increases). This is not preferable.

Further, the invention of claim 3 further includes a phase variable mechanism that is interposed between the crankshaft and the drive shaft and delays the central angle of the operating angle by relatively changing the phase of both. When the engine is stopped, the phase variable mechanism is in a non-fixed state.

  Preferably, the actuator is an electric actuator and can be driven even when the engine is stopped.

  The cam interlocking mechanism is, for example, a link arm that is fitted to the outer periphery of an eccentric cam provided on the drive shaft so as to be relatively rotatable, and is rotatably attached to an eccentric cam portion of the control shaft. A rocker arm that is rocked, and a rocking cam that is rotatably supported by the drive shaft and that is coupled to the rocker arm via a link and that rocks with the rocker arm to press the intake valve. It is prepared for. In this configuration, both the operating angle and the lift change simultaneously and continuously.

  According to this invention, in preparation for the next engine start in the engine stop state, the operating angle of the rotation angle position of the control shaft becomes larger in advance without increasing the actual lift, that is, the valve spring reaction force. Can be changed to position. Therefore, without increasing the size of the actuator, it is possible to reliably secure the intake air amount at the time of starting and improve the startability.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is an explanatory diagram showing a system configuration of an intake valve control device for an internal combustion engine according to the present invention. The internal combustion engine 1 has an intake valve 3 and an exhaust valve 4, and the operation of the intake valve 3. As a valve mechanism, the first variable valve mechanism (VEL) 5 capable of continuously expanding / reducing the lift / operation angle of the intake valve 3 and the center angle of the operation angle can be continuously delayed. The second variable valve mechanism (VTC) 6 is provided. The intake passage 7 is provided with an electronically controlled throttle valve 2 whose opening degree is controlled by an actuator such as a motor. Here, the throttle valve 2 is used only for generating a slight negative pressure (for example, −50 mmHg) necessary for processing blow-by gas in the intake passage 7 and adjusting the intake air amount. Is basically performed by changing the valve lift characteristics of the intake valve 3 by the first and second variable valve mechanisms 5 and 6. That is, a substantial throttle-less operation that does not depend on the throttle valve opening for adjusting the intake air amount is realized. The first and second variable valve mechanisms 5 and 6 and the electronic control throttle valve 2 are controlled by the control unit 10.

  A fuel injection valve 8 is disposed in the intake passage 7, and an amount of fuel corresponding to the intake air amount adjusted by the intake valve 3 as described above is injected from the fuel injection valve 8. Accordingly, the output of the internal combustion engine 1 is controlled by adjusting the intake air amount by the first and second variable valve mechanisms 5 and 6.

  The control unit 10 includes an accelerator opening signal APO from an accelerator opening sensor 11 provided on an accelerator pedal operated by a driver, an engine rotation speed signal Ne from an engine rotation speed sensor 12, and an intake air amount sensor. The control unit 10 inputs the fuel injection amount, the ignition timing, the throttle valve opening, the operating angle target value, the center angle target value, etc. based on these signals. And the fuel injection valve 8, the spark plug 9, the throttle valve 2, the first and second variable valve mechanisms 5, 6, and the like are controlled. Also, a starter motor (not shown) is provided, and when starting the engine, predetermined start-up control including cranking is executed based on an input from a starter switch (key switch) (not shown).

  FIG. 2 is an explanatory diagram showing the configuration of the first and second variable valve mechanisms 5 and 6. The mechanical structure of the first variable valve mechanism 5 and the second variable valve mechanism 6 is known, and for example, has the same structure as the device described in Patent Document 1 described above. Therefore, only the outline will be described.

  The first variable valve mechanism 5 that variably controls the lift / working angle is rotatably supported by a drive shaft 22 driven by a crankshaft of the internal combustion engine 1, an eccentric cam 23 fixed to the drive shaft 22. A control shaft 32, a rocker arm 26 that is swingably supported by an eccentric cam portion 38 of the control shaft 32, and a swing cam 29 that contacts the tappet 30 of the intake valve 3. 23 and the rocker arm 26 are linked by a link arm 24, and the rocker arm 26 and the swing cam 29 are linked by a link member 28.

  The rocker arm 26 is supported at its substantially central portion by the eccentric cam portion 38 so as to be swingable, and the arm portion of the link arm 24 is linked to one end portion thereof via a connecting pin 25. The upper end portion of the link member 28 is linked to the end portion via a connecting pin 27. The eccentric cam portion 38 is eccentric from the axis of the control shaft 32, and accordingly, the rocking center of the rocker arm 26 changes according to the angular position of the control shaft 32.

  The swing cam 29 is rotatably supported by being fitted to the outer periphery of the drive shaft 22, and a lower end portion of the link member 28 is linked to an end portion extending laterally via a connecting pin 37. ing. On the lower surface of the swing cam 29, a base circle surface concentric with the drive shaft 22 and a cam surface extending in a predetermined curve from the base circle surface are continuously formed. These base circle surface and cam surface come into contact with the upper surface of the tappet 30 according to the swing position of the swing cam 29. When the cam surface presses the tappet 30, the intake valve 3 is pushed open against a valve spring reaction force (not shown). Accordingly, the valve spring reaction force is reversed from the swing cam 29. It acts on each part reaching the drive shaft 22.

  The control shaft 32 is configured to rotate within a predetermined angle range by a lift / operating angle control actuator 33 provided at one end. The lift / operating angle control actuator 33 is composed of, for example, an electric motor that drives the control shaft 32 via the worm gear 35, and is controlled by a control signal from the control unit 10. The rotation angle of the control shaft 32 is detected by a control shaft sensor 34. The control shaft 32 is urged in a direction in which the lift / operation angle is reduced as a result of repeatedly receiving the valve spring reaction force.

  According to the first variable valve mechanism 5, the lift and operating angle of the intake valve 3 are continuously expanded and reduced simultaneously according to the rotational angle position of the control shaft 32. With the change in size, the opening timing and closing timing of the intake valve 3 change substantially symmetrically. Since the magnitude of the lift / operating angle is uniquely determined by the rotation angle of the control shaft 32, the actual lift / operating angle at that time is indicated by the detected value of the control shaft sensor 34.

  Although only one cylinder is shown in the figure, the drive shaft 22 and the control shaft 32 are common to a plurality of cylinders, and the other eccentric cam 23, link arm 24, rocker arm 26, link member 28 are provided. The cam interlocking mechanism including the swing cam 29, the eccentric cam portion 38, and the like is provided for each cylinder. In a V-type internal combustion engine or the like, a drive shaft 22 and a control shaft 32 are provided for each bank.

  On the other hand, the second variable valve mechanism 6 serving as a phase variable mechanism that variably controls the central angle includes a sprocket 42 provided at a front end portion of the drive shaft 22, a sprocket 42, and the drive shaft 22. And a phase control actuator 43 that relatively rotates within the angle range. The sprocket 42 is linked to the crankshaft via a timing chain or timing belt (not shown). In the present embodiment, the phase control actuator 43 is a hydraulic rotary actuator, and is controlled by a control signal from the control unit 10 via a hydraulic control valve (not shown). The action of the phase control actuator 43 causes the sprocket 42 and the drive shaft 22 to rotate relative to each other, thereby delaying the lift center angle in the valve lift. That is, the lift characteristic curve itself does not change, and the whole advances or retards. This change can also be obtained continuously. The control state of the second variable valve mechanism 6 is detected by a drive shaft sensor 36 that responds to the rotational position of the drive shaft 22.

  In this type of known phase variable mechanism, generally, the relative position between the sprocket 42 and the drive shaft 22 is fixedly held in the phase control actuator 43 at a reference position such as the most retarded position of the center angle. However, the second variable valve mechanism 6 of this embodiment does not have such a holding mechanism. The phase control actuator 43 is driven in the rotational direction by the hydraulic oil flowing into and out of the two hydraulic chambers. A hydraulic control valve (not shown) for controlling the flow of the hydraulic oil is used when the engine is stopped, that is, the power source. Each hydraulic chamber is configured to open to the drain port when turned off. Therefore, when the engine is stopped, the sprocket 42 and the drive shaft 22 are not relatively fixed, and can be relatively rotationally displaced within a certain angle range.

  FIG. 3 shows the valve lift characteristics of the intake valve 3 under typical operating conditions. As shown in the figure, in an extremely low load range such as an idle, the lift / operating angle is minimum and the central angle is The phase is the most retarded position. As a result, the closing time becomes the position immediately before the bottom dead center.

  In a low load region where the load is larger than an extremely low load region such as an idle (including an idle state where an auxiliary machine load is applied), the lift / operation angle is large and the center angle is an advanced position. At this time, the intake amount is controlled to a relatively small amount by advancing the intake valve closing timing.

  In the middle load range where the load further increases and the combustion becomes stable, the phase of the central angle is advanced while further increasing the lift / operation angle. The phase of the central angle is the most advanced state at a certain point in the middle load region.

  Further, at the maximum load, the second variable valve mechanism 6 is controlled so that the lift / operation angle is further expanded and the optimum valve timing is obtained. As shown in the figure, the optimum valve lift characteristic varies depending on the engine speed.

  Next, the intake valve lift characteristics when the internal combustion engine is stopped and restarted, which is a feature of the present invention, will be described.

  FIG. 4 shows the lift characteristics of the entire internal combustion engine when the lift / operating angle is controlled to be sufficiently small, taking an in-line four-cylinder internal combustion engine as an example. When the internal combustion engine is stopped through the idle state, the internal combustion engine is basically stopped with the lift / operating angle being small as shown in FIG. At this time, there is a period (zero lift period) during which the intake valves 3 of all the cylinders are not lifted between the operating angles (lift periods) of the cylinders. In the case of an in-line four-cylinder engine, this zero lift period occurs when each operating angle is controlled to be less than 180 ° CA. When the rotation of the internal combustion engine is completely stopped, the crankshaft stops at a certain crank angle position, but may stop at the timing when the intake valve 3 of any cylinder is lifted, or It may stop at the timing of the above-described zero lift period.

  In this embodiment, immediately after the internal combustion engine is stopped, the electric lift / operation angle control actuator 33 is driven in preparation for the next start, and the control shaft 32 has a size suitable for the start. Rotate in that enlargement direction. However, until the operating angle reaches 180 ° CA at the maximum, in other words, the operating angle is expanded within the range in which the zero lift period is not lost.

  When the lift / operating angle control actuator 33 is driven in this way, if the engine rotation stop timing (crank angle position) is within the above-described zero lift period, the intake valve 3 of any cylinder is lifted. The valve spring reaction force does not act on each swing cam 29. Therefore, when the lift / operating angle control actuator 33 is driven, the control shaft 32 can be easily rotationally displaced in the same manner as during normal operation, and can reach a rotational angle position where the lift / operating angle becomes larger.

  As will be described later, when the control shaft 32 reaches the rotational angle position where the operating angle is 180 ° CA or more in the case of a four-cylinder engine, the actual lift of the intake valve 3 of any cylinder is further increased. Therefore, an excessive load is applied to the lift / operating angle control actuator 33, which is not preferable. Therefore, it is necessary to output a control command so that the operating angle is 180 ° CA at the maximum. While it is possible to increase the lift and the operating angle while the engine is stopped, the valve clearance becomes larger due to thermal expansion immediately after the stop when each part of the internal combustion engine is warmed. This is preferable because it is easier to change the lift and operating angle. FIG. 5 shows an example in which the rotation stop timing is positioned during the zero lift period before the lift start of the intake valve 3 of a certain cylinder. Without requiring a large driving force of the actuator 33 for operating angle control, the lift / operating angle can be increased as in the characteristic L2.

  On the other hand, FIG. 6 shows a case where the rotation stop timing is positioned during the lift period (particularly during the first half lift increase period) of the intake valve 3 of a certain cylinder in the lift / operating angle characteristic L1 at the time of stop. In this case, since the valve spring reaction force of the intake valve 3 during the lift period acts on the swing cam 29, even if the lift / working angle control actuator 33 is driven in the lift / working angle expansion direction, The cylinder swing cam 29 cannot swing further in the direction in which the lift increases. On the other hand, the drive shaft 22 is not fixed to the crankshaft while the engine is stopped, and relative rotational displacement is allowed in the phase control actuator 43. Accordingly, the drive shaft 22 is rotationally displaced by the drive force of the lift / operating angle control actuator 33 via the cam interlocking mechanism. That is, as indicated by the characteristic L2 in FIG. 6, the phase of the drive shaft 22 is relatively shifted to the retard side while the actual lift of the intake valve 3 of the cylinder remains unchanged, and the rotational angle position of the control shaft 32 is The rotation angle position corresponding to the lift / operation angle indicated as the characteristic L2.

  If the control shaft 32 reaches the rotational angle position where the operating angle is 180 ° CA or more in the case of a four-cylinder engine, the intake stroke is accompanied by the actual lift of the intake valve 3 of the adjacent cylinder. This is not preferable because an excessive load is applied to the lift / operating angle control actuator 33. Therefore, it is necessary to output a control command so that the operating angle is 180 ° CA at the maximum.

  In the example of FIG. 5 in which the rotation is stopped during the zero lift period, the lift of the actual intake valve 3 at the stop timing (crank angle position) is maintained at zero, so that the lift / operating angle is expanded to a certain stage. If the intake valve 3 of any cylinder starts to lift, the phase of the drive shaft 22 is relatively displaced as in the case of FIG. Strictly speaking, the characteristic L2 in FIG. 5 illustrates a state in which the phase of the drive shaft 22 is slightly shifted to the retard side in this way.

  FIG. 7 shows the case where the rotation stop timing is located during the lift period of the intake valve of a certain cylinder in the lift / operating angle characteristic L1 at the time of stop, as in FIG. The case where the rotation stop timing is located during the lift reduction period is shown. Also in this case, even if the valve spring reaction force of the intake valve 3 during the lift period acts on the swing cam 29 and the lift / working angle control actuator 33 is driven in the lift / working angle expansion direction, the cylinder Further, the swing cam 29 cannot swing in the direction in which the lift increases. Since the drive shaft 22 is not fixed to the crankshaft when the engine is stopped, the drive shaft 22 is rotationally displaced via the cam interlocking mechanism by the driving force of the lift / operation angle control actuator 33. To do. However, in this case, as indicated by the characteristic L2 in FIG. 7, the actual lift of the intake valve 3 of the cylinder remains unchanged, and the phase of the drive shaft 22 is relatively shifted to the advance side. Thereby, the rotation angle position of the control shaft 32 becomes a rotation angle position corresponding to the lift / operation angle indicated as the characteristic L2.

  6 or 7, when the engine is subsequently started, the phase control actuator 43 returns to the state in which the crankshaft and the drive shaft 22 are connected, and the lift / operation angle is sufficient from the beginning. Therefore, cranking is started in the control state that has become large, so that even when the intake air amount is required to be relatively large as in cold start, good startability can be ensured.

  As a method of allowing relative rotational displacement between the crankshaft and the drive shaft 22 when the lift / operating angle is widened while the engine is stopped, the phase control actuator 43 is not fixed as in the above embodiment. In addition to the method described above, it is sufficient to allow the deviation of both at an appropriate position of the transmission mechanism from the crankshaft to the drive shaft 22, and various configurations are possible. For example, a tensioner that applies tension to the timing chain or timing belt between the two can be switched by a solenoid, etc., and when applying a lift or operating angle, tension is stopped and the timing chain or timing belt is By giving looseness, the same phase change of the drive shaft 22 can be realized.

  Further, FIG. 8 is similar to FIG. 6, assuming that the timing of the rotation stop is located during the lift period of the intake valve of a certain cylinder (for example, during the lift increase period of the first half). An example of the behavior when corner enlargement is performed is shown. In this example, as described above, the phase of the drive shaft 22 is displaced to the retard side by the drive of the lift / operating angle control actuator 33, but the swing cam that is being lifted by the lift / operating angle control actuator 33. The phase of the drive shaft 22 is displaced in such a direction that the valve spring reaction force decreases, that is, the actual lift contracts, triggered by the movement of 29.

  In the above embodiment, an in-line four-cylinder internal combustion engine has been described as an example, but the present invention is not limited to this, and can be applied to various internal combustion engines. For example, in a V-type 6-cylinder internal combustion engine, one bank has three cylinders, and the interval between intake strokes in the same bank becomes larger, which is more advantageous.

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows one Example of the intake control device which concerns on this invention. Structure explanatory drawing which shows a variable valve apparatus. The characteristic view which shows the valve lift characteristic in a typical driving | running condition. The characteristic view which shows the lift characteristic of the whole engine at the time of the small lift and working angle in the case of an in-line 4 cylinder internal combustion engine. Explanatory drawing which shows the example of the enlargement of the lift and operating angle when the engine is stopped. Explanatory drawing which similarly shows the example of the enlargement of the lift and operating angle when the engine is stopped. Explanatory drawing which similarly shows the example of the enlargement of the lift and operating angle when the engine is stopped. Explanatory drawing which similarly shows the example of the enlargement of the lift and operating angle when the engine is stopped.

Explanation of symbols

3 ... Intake valve 5 ... First variable valve mechanism 6 ... Second variable valve mechanism

Claims (5)

An intake valve urged in the closing direction by a valve spring, a drive shaft common to a plurality of cylinders driven to rotate by a crankshaft, a control shaft common to a plurality of cylinders whose rotational angle positions are controlled by an actuator, and the above drive And a cam-linked mechanism for each cylinder whose operating angle expands and contracts according to the rotational angle position of the control shaft. In the intake control device for an internal combustion engine that controls the intake air amount of the internal combustion engine by controlling the operating angle according to the engine operating conditions,
When the control shaft is controlled to the small operating angle side, the drive shaft is configured to have a period in which the intake valves of all the common cylinders are not lifted, and when the engine is stopped, the crankshaft and the drive shaft Relative rotation displacement with
In order to prevent the actual lift amount of any cylinder from increasing in preparation for the next engine start while the engine is stopped, the operating angle at which the intake valves of all the cylinders are not lifted is not lost. An intake control apparatus for an internal combustion engine, wherein the control shaft is moved in advance to a large operating angle side by the actuator within a range . 2. The intake control apparatus for an internal combustion engine according to claim 1, wherein the control shaft is moved to a position of an operating angle at which a period in which the intake valves of all the cylinders are not lifted disappears. It is further provided with a phase variable mechanism that is interposed between the crankshaft and the drive shaft and delays the central angle of the operating angle by relatively changing the phase of the two. The intake control device for an internal combustion engine according to claim 1 or 2 , wherein the variable mechanism is in a non-fixed state. The intake control apparatus for an internal combustion engine according to any one of claims 1 to 3 , wherein the actuator is an electric actuator. The cam interlocking mechanism is rotatably attached to an eccentric cam portion of the control shaft and is linked to an outer periphery of an eccentric cam provided on the drive shaft, and is swingable by the link arm. A rocker arm that is rotatably supported by the drive shaft, and is connected to the rocker arm via a link, and swings along with the rocker arm to press the intake valve. The intake control device for an internal combustion engine according to any one of claims 1 to 4 , wherein the intake control device is configured.

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