JP2008002273A - Variable valve gear - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid an engine stall by a shortage of compressive pressure when an engine speed reduces, even if operating in a delay closing mirror cycle. <P>SOLUTION: This variable valve gear has a first variable valve train 100a capable of continuously changing the opening-closing timing of an intake valve, a variable valve train control means 17 controlling the first variable valve train 100a in response to the operation state of an internal combustion engine, an engine speed variation detecting means detecting a variation in an engine speed of the internal combustion engine, and an engine speed reduction time control means controlling the first variable valve train 100a when it is determined that the engine speed reduces on the basis of a detecting value of the engine speed variation detecting means. When the engine speed reduces, the first variable valve train 100a is controlled for advancing the ignition timing so that the closing timing of the intake valve approaches the intake bottom dead center. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable valve operating apparatus for an internal combustion engine, and more particularly to a variable valve operating apparatus including a mechanism that continuously and variably controls the opening / closing timing of at least one of an intake valve and an exhaust valve.

  As a variable valve mechanism for an internal combustion engine, an external rotating body including a cam and a pulley (or sprocket) that rotate in conjunction with a crankshaft, and the internal rotating body are housed in the external rotating body and rotate integrally with the intake camshaft. An internal rotary body, and by rotating both rotary bodies relative to each other by a hydraulically driven conversion device, the phase of the valve operation center angle (center angle) relative to the crank angle, that is, the valve timing is advanced or retarded. A so-called valve timing control (VTC) mechanism is known.

  In the VTC mechanism as described above, the valve timing is set so that the valve overlap period for a low engine speed region such as the idle engine speed is zero as the initial position, and the valve overlap period is increased as the engine speed or load increases. Controlled to enlarge.

  If the throttle is suddenly closed during low-speed operation or low-load operation, such as when driving in a so-called partial state, the hydraulic control of the conversion device is set to an uncontrolled state in order to prevent deterioration of combustibility. Thus, the valve timing is returned to the initial position.

  However, since there is a delay in the operation of the VTC mechanism, there is a state in which the overlap period becomes long with a low intake air amount. For this reason, residual gas may stay in the cylinder and the combustibility may deteriorate.

As a means for solving this problem, there has been described a means for limiting the maximum value of the valve overlap period by limiting the operating range of the VTC mechanism under a predetermined operating condition such as low vehicle speed or no-load operation. .
JP-A-6-213021

  By the way, a valve timing called a so-called late-closed mirror cycle is known in which fuel efficiency is improved by an internal EGR effect and a pumping loss reduction effect.

  When executing the slow-close mirror cycle, the intake valve closing timing is set to around 90 degrees after bottom dead center in order to increase the pumping loss reduction effect during idle rotation, etc. Control is performed to provide a valve overlap period by advancing the intake valve closing timing and retarding the exhaust valve closing timing as the number and load increase.

  When the control described in Patent Document 1 is executed in such a slow closing mirror cycle, it is possible to prevent deterioration of combustibility due to the operation delay of the VTC mechanism. However, as described above, the closing timing of the intake valve at the initial position is very slow, around 90 degrees after bottom dead center, so the compression pressure is low, so the valve timing is initial when the engine speed drops rapidly during traveling. When it returns to the position, there is a risk that the combustion will deteriorate due to insufficient compression pressure and engine stall will occur.

  Therefore, an object of the present invention is to avoid an engine stall when the engine speed is suddenly decreased due to the rapid closing of the accelerator or the like even when the engine is operated in the slow closing mirror cycle.

  A variable valve apparatus according to the present invention includes a first variable valve mechanism that can continuously change the opening and closing timing of an intake valve, and a variable valve that controls the first variable valve mechanism in accordance with the operating state of an internal combustion engine. The mechanism control means, the rotation speed change amount detection means for detecting the change amount of the rotation speed of the internal combustion engine, and the case where it is determined that the rotation speed has decreased based on the detection value of the rotation speed change amount detection means And a control means for controlling the variable valve mechanism when the engine speed decreases. When the engine speed decreases, the first variable valve mechanism is advanced so that the closing timing of the intake valve approaches the intake bottom dead center. .

  According to the present invention, when the engine speed rapidly decreases, the intake valve closing timing approaches the bottom dead center, so that the compression pressure is recovered, and the engine speed is decreased when operating in the slow closing mirror cycle. In this case, engine stall due to insufficient compression pressure can be avoided.

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

  FIG. 1 is a system diagram of a variable valve mechanism (hereinafter referred to as VTC) 100 of an internal combustion engine to which the present embodiment is applied, and FIG. 2 is a cross-sectional view of main parts of the system according to operating states. ) Is an AA arrow view of FIG. 1, and FIG. 2B is a BB arrow view of FIG. Hereinafter, the VTC 100 as the first variable valve mechanism attached to the intake side will be described, but the same VTC 100 is attached to the exhaust side as the second variable valve mechanism.

  1 is a camshaft drive sprocket (hereinafter simply referred to as a cam sprocket), 2 is a camshaft, 3 is a housing, 4 is a vane comprising a cylindrical portion 4a and blades 4b, 12 is a flow path switching valve, 17 is a control means, A control unit 18 is a cam angle sensor as a control means when the rotational speed is reduced. Although the vane 4 is described as four blades, it is not limited to this. Further, the attachment position of the cam angle sensor 18 is not limited to the position shown in FIG.

  The housing 3 includes a vane 4 that is rotatable relative to the housing 3. An end surface 4 a of the vane 4 is connected to the end surface 2 a of the camshaft 2 by a connecting pin 6. A cam sprocket 1 is attached to the end surface 3a of the housing 3 with a bolt 5 or the like. The cam sprocket 1 rotates in synchronization with a crankshaft (not shown) when a timing chain or the like is wound around.

  The flow path switching valve 12 communicates with a retard chamber 7 and an advance chamber 8 which will be described later by an oil passage 9 on the retard chamber side and an oil passage 10 on the advance chamber side, such as a crank angle sensor and an air flow meter. It is controlled by the control unit 17 based on the detection value of each sensor. The internal structure and control of the flow path switching valve 12 will be described later.

  In the VTC 100, the vane 4 is rotated in the housing 3 by hydraulic control by the flow path switching valve 12, thereby changing the phases of the camshaft 2 and the cam sprocket 1 and opening / closing timing of an intake valve (not shown) (hereinafter referred to as a valve). Timing). That is, the valve timing of the intake valve can be changed by the relative rotation position of the vane 4 with respect to the housing 3.

  2A shows a state where the valve timing of the intake valve is the most retarded (initial state), and FIG. 2B shows a state where the valve timing change amount is maximum, that is, the most advanced angle.

  In the movement space of each vane 4b of the vane 4 in the housing 3, a retarding chamber 7 for applying hydraulic pressure in a direction to return the valve timing of the intake valve to the initial state with respect to the vane 4 with each vane 4b interposed therebetween, and the vane 4 On the other hand, an advance chamber 8 is provided in which hydraulic pressure is applied in a direction to change the valve timing of the intake valve to the advance side.

  An oil passage 9 is connected to the retard chamber 7, and this oil passage 9 passes through a cylindrical portion 4 a of the vane 4, a support body 11 that is disposed so as to be relatively rotatable therein, and the like. Port (retarding chamber port) 19.

  An oil passage 10 is connected to the advance chamber 8, and this oil passage 10 is one of the flow path switching valves 12 through a cylindrical portion 4 a of the vane 4, a support 11 that is disposed so as to be relatively rotatable therein, and the like. It is connected to a port (advance angle chamber port) 20.

  Here, the structure and operation of the flow path switching valve 12 will be described with reference to FIG. 3 (A) and 3 (B) are cross-sectional views of the flow path switching valve 12 according to operating states, and FIG. 3 (A) is a non-energized state (duty 0%) controlled to the initial state which is the most retarded position. FIG. 3B shows an energized state (duty 100%) controlled to the most advanced position. The duty control is performed by the control unit 17.

  13 is a valve housing, 14 is a spool valve shaft that can move in the axial direction within the valve housing 13, 15 is a return spring that urges the spool valve shaft 14, and 16 is a solenoid.

  The valve housing 13 of the flow path switching valve 12 includes a retard chamber port 19 that communicates with the oil passage 9 on the retard chamber 7 side, an advance chamber port 20 that communicates with the oil passage 10 on the advance chamber 8 side, A hydraulic port 21 that communicates with the hydraulic pressure supply passage 27 and drain ports 22 and 23 that communicate with the drain passages 28 and 29 are provided, and these are arranged in the axial direction in the drain port 22, the retard chamber port 19, the hydraulic port 21, and the advance angle. The chamber port 20 and the drain port 23 are arranged in this order.

  The spool valve shaft 14 in the housing 13 is formed with three valve bodies 24, 25, and 26. The spool valve shaft 14 moves in the housing 13 by energization control to a solenoid 16 described later. Each valve body 24-26 opens and closes each port 19-23. The spool valve shaft 14 is urged by a return spring 15, and is driven in the axial direction by a solenoid 16 against the urging force. By duty-controlling energization to the solenoid 16, The axial position of the spool valve shaft 14 can be controlled.

  In the flow path switching valve 12 configured as described above, when the solenoid 16 is in a non-energized state (duty 0%), the spool valve shaft 14 is moved to the right in the drawing by the return spring 15 as shown in FIG. The hydraulic passage 27 and the hydraulic port 21 communicate with each other, and the advance chamber port 20 and the drain port 29 communicate with each other. As a result, the hydraulic pressure is supplied to the retard chamber 7 and the hydraulic pressure is drained from the advance chamber 8, so that the valve timing of the intake valve becomes the most retarded position, that is, the initial state as shown in FIG. .

  On the other hand, assuming that the duty to the solenoid 16 is 100%, for example, as shown in FIG. 3 (B), the spool valve shaft 14 is moved to the left in the figure by the electromagnetic force of the solenoid 16, and the hydraulic port 21 and the advance angle are increased. The chamber port 20 communicates with the retarded chamber port 19 and the drain port 22. As a result, the hydraulic pressure is supplied to the advance chamber 8 and the hydraulic pressure is drained from the retard chamber 7, so that the valve timing of the intake valve is at the most advanced position as shown in FIG.

  As described above, the valve timing of the intake valve can be arbitrarily controlled by variably controlling the duty to the solenoid 16.

  As described above, the VTC 100 is also provided on the exhaust side, and the intake side and exhaust side VTCs (hereinafter referred to as the intake side VTC 100a and the exhaust side VTC 100b) 100 are controlled by the control unit 17 according to the operating state of the engine. Control the valve timing. In contrast to the intake side VTC 100a, the exhaust side VTC 100b is initially in the most advanced position, and changes to the retard side by increasing the duty.

  Next, control of the valve timing of the intake / exhaust valves will be described.

  FIG. 4A shows the valve timing in the partial region such as low rotation and low load in the case of applying the slow closing mirror cycle, and FIG. 4B shows the initial state executed in the idle rotation region or the like. Represents. Note that each valve timing is an example, and the present invention is not limited to this.

  As shown in FIG. 4B, in the initial state, the intake valve closing timing is approximately 90 degrees after bottom dead center, the exhaust valve closing timing is approximately top dead center, and there is no valve overlap period. Then, the intake side VTC 100a is advanced and the exhaust side VTC 100b is retarded according to an increase in engine speed and load, and a valve overlap period is provided after top dead center as shown in FIG.

  By providing the valve overlap period in this way, a so-called internal EGR effect can be obtained in which the exhaust gas discharged from the exhaust valve is drawn into the combustion chamber.

  That is, by controlling as described above, the internal EGR effect by providing the valve overlap period and the pumping loss reduction effect by significantly retarding the intake valve closing timing from the bottom dead center, Improvements can be made.

  Next, a description will be given of VTC control in the case of an engine to which the above-described delayed closing mirror cycle is applied, in a case where the engine speed is rapidly decreased due to accelerator off or the like during operation in the partial region. In a general VTC, the valve timing is returned to the initial state when the engine speed rapidly decreases. This is to prevent deterioration of combustibility due to residual gas in the combustion chamber and leading to engine stall. That is, it is for suppressing generation | occurrence | production of residual gas by returning to the initial state without a valve overlap period. When returning to the initial state, the duty of the solenoid 16 is set to 0% regardless of the engine speed, that is, in a so-called uncontrolled state. This is because the uncontrolled state has the fastest response speed of VTC.

  However, in the case of the delayed closing mirror cycle, if the valve timing is returned to the initial state as described above, the generation of residual gas can be suppressed by eliminating the valve overlap period, but the intake valve closing timing is at the bottom dead center. Since it is slow at about 90 degrees, the compression pressure is low and the combustibility is deteriorated, which may lead to engine stall.

  Therefore, in the present embodiment, the following control is performed. FIG. 5 is a flowchart of valve timing control executed by the control unit 17. This control is repeatedly executed at regular intervals.

  In step S100, the operating state is read. The operating state read here includes, for example, engine coolant temperature, rotational speed, load, and the like.

  In step S101, the amount of change in engine speed per hour (hereinafter referred to as the speed change amount) ΔV is calculated. Note that the amount of change is zero during the first calculation.

  In step S102, it is determined whether the rotational speed change amount ΔV is smaller than a preset change amount (hereinafter referred to as a set change amount) V1. When it determines with it being small, it progresses to step S108, and the valve timing control for the time of normal operation mentioned later is performed. If it is determined that the value is larger, the process proceeds to step S103. The set change amount V1 is set in accordance with the engine specifications, but is at least a value larger than the change amount when the rotational speed is decreased due to other than accelerator-off. When the control of the present embodiment is executed to advance the intake side VTC 100a, torque is generated. For this reason, if this control is executed in a state where the engine speed has not decreased, a torque shock may occur and the driver may feel uncomfortable. Therefore, by setting the set change amount V1 as described above, it is possible to prevent the driver from feeling uncomfortable by executing this control other than when the accelerator is off.

  In step S103, the exhaust side VTC 100b is brought into an uncontrolled state. As a result, the valve timing on the exhaust side returns to the initial state.

  In step S104, the position of the exhaust-side VTC 100b, that is, the degree of delay from the initial state, is detected from the detection value of the cam angle sensor 18.

  In step S105, the exhaust valve closing timing is calculated from the detection value in step S104, and the intake side VTC 100a is advanced within a range in which the valve overlap period does not occur.

  In step S106, the engine speed is read again, and the change amount ΔV is calculated.

  In step S107, it is determined whether or not the change amount ΔV is larger than a preset change amount (hereinafter referred to as a set change amount) V2. If the change amount ΔV is larger than the set change amount V2, the process returns as it is, and if it is smaller, the process returns to step S104.

  Here, the normal control executed in step S108 will be described. FIG. 8 shows an example of a map used for valve timing control. This map gives the amount of advance / retard according to the coolant temperature of the engine, the number of revolutions, and the load. The curve in the map shows a set of points where the advance / retard amount is a constant value. The control unit 17 includes such a map for each cooling water temperature, for example, a cooling water temperature of 10 degrees, 30 degrees, 50 degrees, and 70 degrees. Further, two types of maps for each cooling water temperature are provided, one used during steady operation and the other used during transient operation. In addition, a map that gives an upper limit value of the advance / retard amount during transient operation may be required.

  A change in valve timing when the above control is performed will be described with reference to FIGS. FIG. 6 shows the change over time in the duty of the intake side VTC 100a and the exhaust side VTC 100b when the accelerator is turned off during traveling at a constant engine speed and the engine speed decreases to idle rotation. ) To (e) show examples of valve timings at the respective time points in FIG. 6.

  At t0, the accelerator is turned off and the engine speed starts to decrease. When it is determined that the change amount ΔV is smaller than the set change amount V1 at t1, the duty of the exhaust side VTC 100b is set to 0%, the angle is advanced in an uncontrolled state, and the initial state is restored (FIG. 7B). Between t1 and t2, the position of the exhaust side VTC 100b that advances in an uncontrolled state is detected, and based on this detection value, the duty is set so that the intake side VTC 100a is advanced within a range in which the valve overlap period does not occur. Increase (FIG. 7C). Assuming that the time when the exhaust side VTC 100b is advanced to the initial state is t2, since the intake side VTC 100a cannot be advanced after t2, the duty is made constant (FIG. 7 (d)). If it is determined that the change amount ΔV is larger than the set change amount V2 at t3, the duty of the intake side VTC 100a is set to 0% (FIG. 7 (e)). If the accelerator is turned on while the rotational speed is decreasing, the state shown in FIG. 7D is shifted to the state shown in FIG.

  Further, whether or not the engine speed is drastically decreased is detected using a change amount ΔV of the engine speed between t0 and t1, but it is detected that the accelerator pedal is turned on or off instead. An idle switch may be provided as the accelerator opening detection means, and when it is detected that the accelerator is turned off by the idle switch, the control in steps S103 to S107 may be executed immediately. Furthermore, instead of steps S106 and S107, which are determinations as to whether to continue or stop the control of steps S103 to S105, the control of steps S103 to S105 is stopped as soon as it is detected that the accelerator is turned on. You may do it.

By performing the control as described above, the following effects can be obtained in the present embodiment.
(1) The intake side VTC 100a capable of continuously changing the valve timing of the intake valve is provided, and when it is determined that the engine speed has decreased, the control unit 17 sets the intake valve closing timing to the intake bottom dead center. Since the intake side VTC 100a is advanced so as to approach, the residual gas in the combustion chamber can be reduced and the compression pressure can be secured. That is, the engine stall can be avoided by preventing deterioration of combustibility. In addition, by improving the engine stall resistance when the engine speed drops sharply, it is possible to retard the intake valve closing timing and increase the EGR amount in the partial state, thereby improving fuel efficiency. Can be planned.
(2) Since the intake-side VTC 100a operates in a delayed mirror cycle during the normal operation with the most retarded state in which the intake valve closing timing is a predetermined timing after bottom dead center, and in the normal operation, the pump loss is reduced. It is possible to improve fuel efficiency.
(3) An exhaust side VTC 100b is provided, which can control the exhaust valve closing timing as an initial state where the exhaust valve closing timing is close to top dead center and can continuously change the opening / closing timing of the exhaust valve according to the operating state of the engine. The unit 17 controls the intake side VTC 100a and the exhaust side VTC 100b according to the operating state to adjust the internal EGR amount by changing the valve overlap period, so that the internal EGR effect can be obtained. In addition, when it is determined that the engine speed has decreased, the exhaust side VTC 100b is returned to the initial state and the internal EGR amount is controlled to be reduced, so that the residual gas in the combustion chamber can be reduced, thereby reducing the combustion. It is possible to prevent the deterioration of the property and ensure the engine stall resistance.
(4) When the control unit 17 determines that the engine speed has decreased, the control unit 17 advances the intake side VTC 100a according to the retard amount of the exhaust side VTC 100b so that the valve overlap period does not occur. Residual gas can be reduced more reliably, and the engine stall resistance can be improved.
(5) When the amount of change ΔV of the engine speed per hour becomes smaller than the set change amount V1, it is determined that the engine speed has decreased. Therefore, the intake side VTC 100a advances at the time of deceleration with no fear of engine stall. No corner control is performed. As a result, it is possible to prevent the driver from feeling uncomfortable with the torque generated when the intake side VTC 100a is advanced.
(6) When accelerator-off is detected by an idle switch that detects whether the accelerator pedal is on or off, it is possible to start the control described above immediately after starting deceleration by determining that the engine speed has decreased. The engine stall can be prevented more reliably.
(7) After determining that the engine speed has decreased, when the change amount ΔV is equal to or greater than the set change amount V2, the control is switched to the control during normal operation, so that the time during which the intake side VTC 100a is advanced Can be prevented from becoming unnecessarily long, and a decrease in fuel efficiency can be suppressed.
(8) Since the control is switched to the normal operation when the accelerator on is detected by the idle switch, the intake side VTC 100a can be returned to the normal control earlier to suppress the deterioration of the fuel consumption performance.

  In the above-described embodiment, the vane variable valve mechanism that changes the valve timing by rotating the vane 4 by hydraulic pressure has been described. However, the applicable variable valve mechanism is limited to this. Instead, for example, even if the spline shaft is rotated by electromagnetic drive as described in JP-A-2002-97908, the same applies.

  A second embodiment will be described.

  In this embodiment, the variable valve mechanism is provided only on the intake side VTC 100a, and the valve timing of the exhaust valve is fixed. That is, the valve timing is as shown in FIG. 9B for the initial state and FIG. 9A for the partial state.

  Then, an EGR pipe as an external EGR device that communicates the exhaust passage and the intake passage, and an EGR valve as an EGR amount adjusting means for adjusting the flow passage cross-sectional area of the EGR pipe are provided, and a part of the exhaust gas is taken in. A so-called external EGR is made to return to the passage.

  With reference to FIGS. 10 and 11, control of the valve timing when the engine speed rapidly decreases due to the accelerator being off in such a configuration will be described.

  FIG. 10 shows a flowchart of the valve timing control executed by the control unit 17 as in FIG. FIG. 11 shows changes over time in the duty of the intake side VTC 100a and the opening of the EGR valve when the accelerator is turned off during traveling at a constant engine speed and the engine speed decreases to idle rotation.

  Steps S200 to S202 are the same control as steps S100 to S102 in FIG.

  In step S203, the EGR valve is closed. This is to prevent deterioration of combustibility by stopping the supply of EGR gas.

  In step S204, the intake side VTC 100a is advanced. In this embodiment, since the exhaust valve closing timing is fixed near the top dead center, the exhaust valve closing timing is advanced so as not to cause a valve overlap period.

  Steps S205 to S206 and S207 are the same controls as steps S106 to S107 and S108 in FIG.

  When the control as described above is executed, the time change of the opening degree of the EGR valve and the duty of the intake side VTC 100a is as shown in FIG. That is, when the accelerator is turned off at t0 and the change amount ΔV is determined to be smaller than the set change amount V1 as the first determination value at t1, the EGR valve is fully closed and the duty of the intake side VTC 100a is increased. When the intake side VTC 100a reaches the most advanced position within a range where the valve overlap period does not occur at t2, the state is maintained. If it is determined that the change amount ΔV is larger than the set change amount V2 as the second determination value at t3, the intake side VTC 100a is returned to the initial state in the uncontrolled state.

  As described above, the EGR pipe and the EGR valve as the external EGR device are provided, and when it is determined that the engine speed has decreased, the EGR gas amount is reduced, so that the engine stall is avoided as in the first embodiment. In addition, fuel efficiency can be improved.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims.

It is the schematic of the variable valve mechanism (VTC) to which this embodiment is applied. It is the schematic of the principal part of a variable valve mechanism. (A), (B) is the schematic of the flow-path switching valve of a variable valve mechanism. (A) is a figure showing an example of the valve timing in a partial state and (B) in an initial state. It is a flowchart of control of a 1st embodiment. It is a time chart of an engine speed and the duty of a variable valve mechanism. (A)-(e) is a figure showing the valve timing at the time of performing control of this embodiment. It is a figure showing an example of the control map of a variable valve mechanism. (A) is a figure showing an example of the valve timing in a partial state and (B) in an initial state. It is a flowchart of control of a 2nd embodiment. It is a time chart of an engine speed and the duty of a variable valve mechanism.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Camshaft drive sprocket 2 Camshaft 3 Housing 4 Vane 5 Bolt 6 Connection pin 7 Retarded chamber 8 Advance chamber 9 Oil passage 10 Oil passage 11 Support body 12 Flow path switching valve 13 Housing 14 Spool valve shaft 15 Return spring 16 Solenoid 17 Control unit 18 Cam angle sensor 19 Retarded chamber port 20 Advanced chamber port 21 Hydraulic port 22 Drain port 23 Drain port

Claims (9)

A first variable valve mechanism capable of continuously changing the opening and closing timing of the intake valve of the internal combustion engine;
Variable valve mechanism control means for controlling the first variable valve mechanism according to the operating state of the internal combustion engine;
A rotational speed variation detecting means for detecting a rotational speed variation of the internal combustion engine;
If it is determined that the rotational speed has decreased based on the detection value of the rotational speed change amount detection means, the first variable valve mechanism is advanced so that the closing timing of the intake valve approaches the intake bottom dead center. A rotation speed control means for angle control;
A variable valve operating apparatus comprising:   The first variable valve mechanism is configured to operate in the initial delay state where the intake valve closing timing is a predetermined timing after bottom dead center, and to operate in a delayed closing mirror cycle during normal operation. Item 2. The variable valve operating device according to Item 1.   The control means for reducing the number of revolutions decreases the amount of EGR gas recirculated from the exhaust passage of the internal combustion engine to the intake passage when it is determined that the number of revolutions has decreased. The variable valve operating device described. A second variable valve mechanism capable of continuously changing the opening / closing timing of the exhaust valve according to the operating state of the internal combustion engine, with the state of the most advanced angle at which the exhaust valve closing timing is near top dead center as an initial state ,
The variable valve mechanism control means adjusts the internal EGR amount by changing the valve overlap period by controlling the first variable valve mechanism and the second variable valve mechanism according to the operating state of the internal combustion engine. And
4. The control device according to claim 1, wherein when the rotational speed is reduced, the control means reduces the internal EGR amount by returning the second variable valve mechanism to an initial state when it is determined that the rotational speed has decreased. The variable valve operating apparatus according to any one of the above.   When the rotational speed decrease control means determines that the rotational speed has decreased, the first variable valve operating mechanism according to a retard amount of the second variable valve operating mechanism so that a valve overlap period does not occur. The variable valve operating apparatus according to claim 4, wherein the mechanism is advanced.   6. The control unit according to claim 1, wherein the rotation speed reduction control unit determines that the rotation speed has decreased when a change amount of the rotation speed per time becomes equal to or less than a first determination value. The variable valve operating apparatus according to any one of the above. Accelerator opening detection means to detect on / off of the accelerator pedal,
6. The control unit according to claim 1, wherein the control unit at the time of a decrease in the rotational speed determines that the rotational speed has decreased when the accelerator opening detection unit detects that the accelerator pedal is turned off. The variable valve operating device according to claim 1.   When the rotational speed decrease control means determines that the rotational speed has decreased and the amount of change in the rotational speed per time becomes equal to or greater than a second determination value, the control means switches to control during normal operation. The variable valve operating apparatus according to any one of claims 1 to 7, wherein:   When the engine speed detecting means detects that the accelerator pedal is turned on after determining that the engine speed has decreased, the control means at the time of reduction in the engine speed is switched to control during normal operation. The variable valve operating apparatus according to claim 7.