JP2006144723A - Air intake control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To compatibly materialize characteristics attaching importance on fuel economy and characteristics attaching importance to torque response as setting of valve lift characteristics and to prevent torque variation at a time of change over of the characteristics. <P>SOLUTION: This device is provided with a first variable valve system capable of continuously varying operation angle VEL of an intake valve and a second variable valve system capable of continuously varying center angle VTC, and controls intake air quantity by lift characteristics of the intake valve materialized by that. The device includes a mode attaching importance to fuel economy and a mode attaching response as setting of target operating angle and target center angle in relation to target torque, and changes the mode over according to an operation condition. The target operating angle gradually changes with change speed limited during change over and the target center angle is calculated based on actual operating angle, demand torque and engine speed. Consequently, torque variation accompanying change over is reduced. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an intake air control device that controls an intake air amount sucked into a cylinder of an internal combustion engine, and more particularly to an internal combustion engine that achieves control of an intake air amount by variable control of valve lift characteristics of an intake valve. The present invention relates to an intake control 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. Similarly, it has been proposed to realize a so-called throttle-less configuration in which the intake system is not equipped with a throttle valve.

Patent Document 1 discloses a variable valve mechanism that can be continuously variably controlled by a lift amount and an operating angle of an intake valve and a central angle of the lift previously proposed by the present applicant. According to this type of variable valve mechanism, 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, particularly in a region where the load is small. In other words, so-called throttleless operation or operation with a sufficiently large opening of the throttle valve can be realized, and the pumping loss can be greatly reduced.
JP 2001-263105 A

  By the way, as described above, when two variable valve mechanisms are provided and the operating angle of the intake valve and the central angle thereof are variably controlled independently of each other according to the engine operating state, the operating angle capable of realizing the required torque There are an infinite number of combinations with the central angle, but usually the target operating angle and the target central angle are set for each target torque so that the fuel efficiency is the best. Generally, by setting the central angle of the valve lift to the advance side closer to the top dead center, the internal exhaust gas recirculation is increased and the pump loss is reduced. That is, in order to improve fuel efficiency, it is desirable to set the center angle as far as possible.

  However, if the target operating angle and the target central angle are set so that the central angle is as advanced as possible for each target torque, for example, when accelerating from a low load range to a high load range, As a tendency, the operation angle increases preferentially while keeping the central angle on the advance side, and after the operation angle becomes a certain size, the behavior is such that the center angle is retarded.

  Therefore, in an extreme case, the two variable valve mechanisms move in order one by one, and in reality, the two variable valve mechanisms are each set at the time of a transient when the operating state changes suddenly. There is a problem that the torque response becomes low because it operates with a certain delay with respect to the value.

  An intake control apparatus for an internal combustion engine according to the present invention includes a first variable valve mechanism that can continuously change the operating angle of the intake valve of the internal combustion engine, and a second variable valve that can continuously change the central angle of the operating angle. A variable valve mechanism, and variable valve control means for controlling the first variable valve mechanism and the second variable valve mechanism in accordance with a target torque, which are realized by these two variable valve mechanisms. The intake air amount is controlled by the lift characteristics of the intake valve.

  In the present invention, the variable valve control means has at least two types of setting of the target operating angle and the target center angle with respect to the target torque, and sets the characteristic selected by the switching means. Along with this, the first and second variable valve mechanisms are controlled. For example, it has two settings: setting of the target operating angle and target center angle with characteristics focusing on fuel efficiency, and setting of the target operating angle and target center angle with characteristics focusing on torque responsiveness. A suitable operation mode is discriminated from the change in the accelerator operation of the person, and two settings are switched.

  Furthermore, in the present invention, when the characteristic is switched by the switching means, the target value of the second variable valve mechanism is given from the actual operating angle and the target torque of the first variable valve mechanism. It should be noted that it is desirable to limit the changing speed of the target operating angle given to the first variable valve mechanism when switching the characteristics.

  For example, in the characteristic that emphasizes fuel efficiency, the center angle is set to the advance side than the characteristic that emphasizes torque response. Therefore, the target operating angle and the target center angle may be relatively different for the same target torque between the setting for emphasizing fuel efficiency and the setting for emphasizing torque response. Here, if each target value changes stepwise at the time of switching characteristics, each variable valve mechanism operates individually with a delay, so the actually obtained torque is not necessarily a constant value. However, it can change greatly. In the present invention, at the time of switching characteristics, the target value of the second variable valve mechanism is given from the actual operating angle of the first variable valve mechanism and the target torque, so that the torque change at the time of switching becomes smaller.

  In one aspect of the present invention, when the target torque is increased within a certain range, the operating angle is preferentially increased while maintaining the center angle at the advanced angle side, and the center angle is then delayed in the characteristics that emphasize fuel efficiency. Each target value is set so as to make an angle.

  Further, in one aspect of the present invention, at the time of acceleration in which the target torque increases within a certain range, in the characteristic that emphasizes torque response, the delay of the central angle and the increase of the operating angle are the responses of each variable valve mechanism. Each target value is set so as to occur simultaneously along the speed.

  According to the present invention, the control of the operating angle and the central angle of the intake valve can be performed by selectively switching to a plurality of characteristics such as a characteristic that emphasizes fuel consumption and a characteristic that emphasizes torque response. Depending on the situation, suitable characteristics can be obtained. And the torque change resulting from the switching of this characteristic can be suppressed smaller.

  FIG. 1 is a configuration explanatory view showing the system configuration of an intake 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 valve of the intake valve 3 is operated. As a 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. A second variable valve mechanism (VTC) 6 is provided. The intake passage 7 is provided with a negative pressure control valve 2 whose opening degree is controlled by an actuator such as a motor. Here, the negative pressure control valve 2 is used to generate a slight negative pressure (for example, −50 mmHg) necessary for blowby gas processing or the like in the intake passage 7. The adjustment is basically performed by changing the lift characteristics of the intake valve 3 by the first and second variable valve mechanisms 5 and 6.

  More specifically, in the low load side region (first region), the opening degree (target opening degree tTVO) of the negative pressure control valve 2 is controlled so that the suction negative pressure is constant (for example, −50 mmHg). And in the high load side region (second region) where the required load exceeds the maximum load that can be realized by changing the lift characteristic while generating this constant negative pressure, it is fixed to the lift characteristic at the point that becomes the limit, As the load, for example, the accelerator opening APO increases, the opening of the negative pressure control valve 2 further increases. That is, the intake air amount is adjusted by changing the lift characteristic of the intake valve 3 while maintaining a relatively weak intake negative pressure up to a certain load, and in the high load side region close to the fully open region, the intake negative pressure is adjusted. The amount of intake air is adjusted by reducing.

  The first and second variable valve mechanisms 5 and 6 and the negative pressure control 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 or the negative pressure control valve 2 as described above is supplied from the fuel injection valve 8. Be injected. 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 in the first region, and the negative pressure control valve 2 in the second region. Is controlled by adjusting the intake air amount.

  The control unit 10 includes an accelerator opening signal APO from an accelerator angle sensor 11 provided on an accelerator pedal operated by a driver, an engine speed signal Ne from an engine speed sensor 12, and an intake air amount sensor. 13 is received, and based on these signals, the fuel injection amount, ignition timing, negative pressure control valve target opening (opening target value), first variable valve mechanism target angle (target) Operating angle) and second variable valve mechanism target angle (target center angle) are calculated. The fuel injection valve 8 and the spark plug 9 are controlled so as to realize the required fuel injection amount and ignition timing, and the negative pressure control valve target opening, the first variable valve mechanism target angle, and the second variable valve are controlled. Control signals for realizing the mechanism target angle are output to the actuator of the negative pressure control valve 2, the actuator of the first variable valve mechanism 5, and the actuator of the second variable valve mechanism 6, respectively. The first variable valve mechanism 5 and the second variable valve mechanism 6 have known mechanical configurations, and have, for example, the same configuration as the device described in Patent Document 1 described above. Therefore, the detailed description is abbreviate | omitted.

  FIG. 2 shows a process of calculating the target operating angle tVEL of the first variable valve mechanism 5, the target center angle tVTC of the second variable valve mechanism 6, and the negative pressure control valve target opening tTVO in the configuration of the above embodiment. It is a schematic flowchart. First, the accelerator opening APO and the engine speed Ne are read (step 11), and the negative pressure control valve target opening tTVO, the target operating angle tVEL, and the target center angle tVTC are determined in accordance with the required torque determined from them. It calculates with ~ 14, respectively.

  In this embodiment, the control mode of the intake valve lift characteristic includes a fuel efficiency priority mode with a focus on fuel efficiency and a response sensitivity priority mode with a focus on torque response.

  FIG. 3 schematically shows the characteristics of the fuel efficiency mode. In the low to medium load region, the center angle is set close to top dead center (VTC setting value: large) to improve fuel efficiency, and the internal While promoting exhaust gas recirculation, the operating angle is gradually set to the large operating angle (VEL set value: large) side according to the torque demand. In the first region described above, the negative pressure control valve opening TVO is set to a normal engine (not a variable valve mechanism, but a throttle valve opening to control the intake air amount so as to keep the intake negative pressure (Boost) at a predetermined value. Compared to the characteristics of the item to be controlled (shown as Std-Eng in the figure), the characteristics are slightly open. In the middle to high load range, in order to ensure torque, the center angle is set to be close to the bottom dead center (VTC set value: small), the internal exhaust gas recirculation is reduced, and the operating angle is set to a large operating angle (VEL set value: Constant on the large side. When reaching the second region, that is, the high load region where the air amount does not increase by the operation of the valve lift characteristic, the valve lift characteristic is fixed in that state, and the negative intake pressure (Boost) is decreased to generate torque. In addition, the negative pressure control valve opening TVO opens in the same manner as the normal engine.

  As a result, the valve lift characteristic changes roughly as shown by the arrow in FIG. 4 as the accelerator opening APO increases. That is, the operating angle (lift / operating angle) increases in the initial stage, and after the operating angle has become sufficiently large, the angle is gradually retarded.

  FIG. 5 schematically shows an example of characteristics of the responsiveness emphasis mode. In this case, when the accelerator opening APO is increased from the low load side, the center angle is set to the retarded side, that is, near the bottom dead center (VTC). At the same time, the operating angle is gradually changed to a large operating angle (VEL setting value: large).

  Thereby, the valve lift characteristic changes roughly as shown by the arrow in FIG. 6 with respect to the increase in the accelerator opening APO. That is, the operating angle (lift / operating angle) increases while the central angle is retarded.

  7 and 8 are explanatory diagrams showing the transition (change trajectory) of the maximum lift point of the intake valve (in other words, the lift at the central angle) during transition (acceleration) in each mode, together with the generated torque. In the drawing, the horizontal axis indicates the center angle VTC, the vertical axis indicates the operating angle (in other words, lift) VEL, and the maximum lift point is determined as a combination of both. This maximum lift point correlates with volumetric efficiency and thus torque. The generated torque is shown as contour lines, but in the illustrated range, the upper right side of the figure is the high load side, that is, the torque is large.

  In the setting of the fuel efficiency emphasis mode described with reference to FIGS. 3 and 4, the maximum lift point changes like an L-shaped broken line indicated by reference numeral M1 in FIGS. That is, while the maximum lift point is kept as close to the advance side as possible, the lift / operation angle first increases mainly, and then gradually moves toward the retard side. As a result, the internal exhaust gas recirculation becomes large, and the fuel efficiency can be improved by reducing the pumping loss. On the other hand, in the response-oriented mode described with reference to FIGS. 5 and 6, the maximum lift point changes like a straight line indicated by reference numeral M2 in FIGS. That is, in this case, the first variable valve mechanism 5 and the second variable valve mechanism 6 are driven at the same time, and the operating angle and the central angle change at the same time. The increase in the operating angle is set in consideration of the response speeds of the variable valve mechanisms 5 and 6. The characteristic M2 in FIG. 7 is an example suitable when the response speed of the first variable valve mechanism 5 is relatively fast and the response speed of the second variable valve mechanism 6 is relatively slow. Since the target value of the two variable valve mechanism 6 does not change much, high torque responsiveness can be obtained. On the contrary, the characteristic M2 in FIG. 8 is a suitable example when the response speed of the first variable valve mechanism 5 is relatively slow and the response speed of the second variable valve mechanism 6 is relatively fast. As described above, the target value of the second variable valve mechanism 6 changes more greatly than in FIG. 7, but since the actual change in the center angle corresponds to the change in the actual operating angle, a high torque response is obtained. .

  Next, FIG. 9 shows the contents of intake air amount control by the control unit 10 as a functional block diagram, and the fuel efficiency emphasis mode target value calculation unit B2 has the above-described characteristics emphasizing fuel efficiency. Based on the required load and the engine speed Ne, the negative pressure control valve target opening tTVO that is the target value of the negative pressure control valve 2 and the target operating angle tVEL that is the target value of the first variable valve mechanism 5 Then, a target center angle tVTC that is a target value of the second variable valve mechanism 6 is calculated. Specifically, as shown in FIG. 10, the target opening calculation unit B11 and the target operating angle calculation unit B12 are made up of maps in which corresponding values are assigned with the required load and the rotational speed Ne as parameters. The target center angle calculation unit B13. As a parameter indicating the load or torque, “volume flow rate ratio QH0” defined as “a value obtained by dividing the intake air amount by the maximum intake air amount at the engine rotation speed when the intake air amount is obtained” is used. Alternatively, publicly known parameters indicating the load or torque such as the accelerator opening APO and the intake air amount can be used instead. FIG. 11 shows an example of the TVO map of the target opening degree calculation unit B11, FIG. 12 shows an example of the operation angle map of the target operation angle calculation unit B12, and FIG. 13 shows the center angle of the target center angle calculation unit B13. An example of a map is shown.

  Further, the responsiveness-oriented mode target value calculation unit B3 has a characteristic that emphasizes torque responsiveness as described above, and based on the required load and the engine speed Ne, the negative pressure control valve target opening tTVO, the target An operating angle tVEL and a target center angle tVTC are calculated. This is composed of a target opening degree calculation unit, a target operating angle calculation unit, and a target center angle calculation unit, which are composed of three maps similar to those described in FIG. Then, in the target value selection unit B4, based on the mode selection command from the driving state determination unit B1, one of the target values of the fuel efficiency-oriented mode target value calculation unit B2 or the responsiveness-oriented mode target value calculation unit B3 is selected. And it outputs to the actuators of the negative pressure control valve 2 and the first and second variable valve mechanisms 5 and 6, respectively. The driving state determination unit B1 is suitable for the fuel efficiency mode or the responsiveness mode based on the mode of change of the accelerator opening APO operated by the driver (absolute value, speed of change, amount of change, etc.). A mode selection command is output according to this determination. Note that frequent switching between the above two modes is not preferable in terms of drivability, so it is desirable to provide appropriate hysteresis. Further, the present invention is not limited to such automatic switching of the operation mode, and may be configured to include a mode selection switch that is switched by the driver, for example.

  As a matter of course, the three maps included in the responsiveness emphasis mode target value calculation unit B3 are set to characteristics emphasizing torque responsiveness. FIG. 14 shows an example of the TVO map of the target opening degree calculation unit, FIG. 15 shows an example of the operation angle map of the target operation angle calculation unit, and FIG. 16 shows an example of the center angle map of the target center angle calculation unit. Indicates. These correspond to the setting of the responsiveness importance mode described with reference to FIGS.

  On the other hand, the VEL target value calculation unit B5 at the time of switching in FIG. 9 calculates the target operating angle tVEL in the transient period of operation mode, that is, the period during switching. As shown in FIG. 17, the switching unit B21 selects either the target operating angle in the fuel intensive mode or the target operating angle in the responsiveness mode based on the mode selection command from the driving state determination unit B1. And an operating angle change rate limiting unit B22 that limits the changing speed of the target operating angle tVEL input through the switching unit B21. The operating angle change rate limiting unit B22 limits the change of the target operating angle tVEL at the time of switching so as to be a gradual change taking into account the responsiveness of the second variable valve mechanism 6, and in this example In this case, the change rate limiter is used, but instead of this, a first-order lag process or the like considering the response speed may be added. By limiting the change speed in this way, the target operating angle tVEL does not change suddenly step by step, but gradually changes as illustrated in FIG. 18 when the operation mode is switched.

  Further, the switching time VTC target value calculation unit B6 in FIG. 9 includes the actual operating angle rVEL of the first variable valve mechanism 5 that gradually changes along the target operating angle tVEL by the switching time VEL target value calculation unit B5. Based on the required load at that time and the engine speed Ne, the target center angle tVTC during the switching period is calculated. That is, since the generated torque is determined by the operating angle VEL, the central angle VTC, and the engine speed Ne, the actual operating angle rVEL, the required load, and the engine speed Ne are referenced with reference to a multidimensional map in which these four relationships are assigned. The target center angle tVTC corresponding to can be obtained. The actual operating angle rVEL can be obtained from the position of the actuator of the first variable valve mechanism 5, for example. FIG. 19 is an explanatory view similar to FIGS. 7 and 8 and shows an isotorque line and an operating angle (actual operating angle rVEL) corresponding to a required load under a certain engine speed Ne as illustrated. In addition, a necessary center angle (target center angle tVTC) is uniquely determined. In addition, since the search from the map is a multidimensional map, it may be obtained by calculation using each parameter.

  9 receives a mode selection command from the operation state determination unit B1, and outputs a signal indicating that the operation mode is being switched, that is, a transition period, to the second target value selection unit B8. To do. For example, ON / OFF switching of a flag indicating that switching is in progress is performed. In the second target value selection unit B8, while the flag indicating that the switching is in progress is ON, the switching period target output from the switching time VEL target value calculation unit B5 and the switching time VTC target value calculation unit B6. The values are output as the final target operating angle tVEL and target center angle tVTC. The state switching determination unit B7 turns on the flag for a certain time after the operation mode is switched. However, if there is a change in the accelerator opening that exceeds a predetermined level during that period, the flag is turned OFF in order to immediately respond to the change in the required load.

  Next, FIG. 20 and FIG. 21 are explanatory diagrams showing the operation at the time of acceleration of the intake control device of the above embodiment (however, the engine speed is constant), and the accelerator opening APO increases stepwise. The change of the operating angle VEL and the center angle VTC in the case of having performed is shown with the change of the engine torque Te. FIG. 20 shows an example in the case of the fuel efficiency emphasis mode, and FIG. 21 shows an example in the case of the responsiveness emphasis mode, in particular, an example in which the operating angle VEL and the center angle VTC change simultaneously. In either case, the target values of the operating angle VEL and the central angle VTC change as shown by solid lines, whereas the actual values change with a delay as shown by broken lines depending on the response speed of each mechanism. In FIG. 21, the actual value characteristic in the fuel efficiency mode is shown by a one-dot chain line for comparison. As is apparent from FIG. 21, in the response-oriented mode, the initial center angle VTC is on the retard side, so that the torque sensitivity to the amount of change in the same operating angle VEL increases, and the center angle Since the amount of change in VTC is smaller than that in the fuel economy priority mode, the torque converges faster, and therefore torque response is higher than in the fuel efficiency priority mode.

  Next, FIG. 22 is an explanatory diagram showing an operation (when the engine speed is constant and the required load does not change) at the time of switching the operation mode of the intake control device. When the performance priority mode is switched to the fuel efficiency priority mode, a flag indicating that switching is in progress is ON for a certain time. As the operation mode is switched, the target value of the operating angle VEL changes from the target value of the relatively small responsiveness priority mode to the target value of the relatively large fuel consumption priority mode, but the above flag is ON. Since the rate of change is limited during switching, the final target operating angle tVEL gradually changes as shown by the dotted line. And with respect to this target operating angle tVEL, the actual operating angle rVEL changes with a slight response delay as shown by a thick solid line. On the other hand, the target value of the center angle VTC changes from the target value of the relatively small responsiveness priority mode to the target value of the relatively large fuel consumption priority mode, but during the switching in which the above flag is ON, A target center angle tVTC at which the required torque is generated based on the operating angle rVEL is determined as indicated by a dotted line. The actual center angle VTC follows the target center angle tVTC with a slight response delay as shown by a thick solid line. Therefore, the actually generated torque is almost constant, although it is affected by a slight response delay of the second variable valve mechanism 6, that is, the torque is not changed due to the switching of the operation mode. Torque characteristics along.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. The flowchart of basic control. The characteristic view which showed roughly the change of each parameter by the fuel consumption priority mode when the accelerator opening was increased. Explanatory drawing which shows the change of the valve lift characteristic in the case of FIG. The characteristic view which showed schematically the change of each parameter by the response priority mode when the accelerator opening was increased. Explanatory drawing which shows the change of the valve lift characteristic in the case of FIG. Explanatory drawing which shows the transition of the maximum lift point at the time of a transition in the fuel consumption priority mode and the response priority mode. Explanatory drawing similar to FIG. 7 which shows the example in case the response speed of a variable valve mechanism is different. The functional block diagram which shows the content of the control of mode switching. The functional block diagram which shows the detail of fuel consumption priority mode target value calculating part B2. The characteristic view of the TVO map of block B11. The characteristic view of the operating angle map of block B12. The characteristic view of the center angle map of block B13. The characteristic figure of the TVO map in the responsiveness importance mode target value calculating part B3. The characteristic diagram of the operating angle map in the responsiveness importance mode target value calculating part B3. The characteristic figure of the center angle map in the responsiveness importance mode target value calculating part B3. The functional block diagram which shows the detail of the VEL target value calculating part B5 at the time of switching. The time chart which shows the change of the target operating angle tVEL at the time of mode switching. FIG. 9 is an explanatory view similar to FIG. 7 showing a target value calculation method of the switching VTC target value calculation unit B6. The time chart which shows the operation | movement at the time of the transition in fuel consumption priority mode. The time chart which shows the operation | movement at the time of the transition in responsiveness importance mode. The time chart which shows the operation | movement at the time of mode switching.

Explanation of symbols

2 ... Negative pressure control valve 5 ... First variable valve mechanism 6 ... Second variable valve mechanism 10 ... Control unit 11 ... Accelerator opening sensor

Claims (7)

A first variable valve mechanism capable of continuously changing the operating angle of the intake valve of the internal combustion engine;
A second variable valve mechanism capable of continuously changing the central angle of the operating angle;
Variable valve control means for controlling the first variable valve mechanism and the second variable valve mechanism according to a target torque;
An intake control device for an internal combustion engine comprising:
The variable valve control means has at least two types of target operating angle and target center angle settings for the target torque, and the first and first characteristics are set in accordance with the characteristic settings selected by the switching means. 2 Controlling the variable valve mechanism,
An intake air control apparatus for an internal combustion engine, wherein a target value of a second variable valve mechanism is given from an actual operating angle of the first variable valve mechanism and a target torque when the characteristic is switched by the switching means.   2. The intake control apparatus for an internal combustion engine according to claim 1, wherein a change speed of a target operating angle given to the first variable valve mechanism is limited when the characteristic is switched.   As the setting of the target operating angle and target center angle for the target torque, the setting of the target operating angle and target center angle with characteristics that emphasize fuel efficiency, the setting of the target operating angle and target center angle with characteristics that emphasize torque response, and The intake control device for an internal combustion engine according to claim 1 or 2, wherein the two settings are provided.   4. The intake control device for an internal combustion engine according to claim 3, wherein the center angle is set to an advance side in the characteristic that emphasizes fuel consumption, compared to the characteristic that emphasizes torque response.   In acceleration characteristics where the target torque increases within a certain range, the characteristics that place importance on torque response are such that the delay of the central angle and the increase of the operating angle occur simultaneously along the response speed of each variable valve mechanism. The intake air control apparatus for an internal combustion engine according to claim 3 or 4, wherein the target value is set.   In acceleration characteristics where the target torque increases within a certain range, with the characteristics that emphasize fuel efficiency, each target is set so that the operating angle preferentially increases while the central angle is kept on the advanced side, and then the central angle is retarded. The intake control device for an internal combustion engine according to any one of claims 3 to 5, wherein a value is set. The intake control device for an internal combustion engine according to any one of claims 1 to 6, wherein the switching means discriminates a suitable operation mode from a change in a driver's accelerator operation.

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