JP4534705B2 - Intake control device for internal combustion engine - Google Patents

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 is configured to set a target operating angle and a target center angle with a focus on fuel efficiency and a target operating angle and a target center with a focus on torque response with respect to the target torque. At least two settings including a corner setting are provided, and the first and second variable valve mechanisms are controlled in accordance with the setting of the characteristic selected by the switching means.

  In general, in the fuel efficiency-oriented characteristic, that is, the fuel efficiency-oriented mode, the central angle is set to be more advanced with respect to the same target torque than in the characteristic that emphasizes torque response, that is, the responsiveness-oriented mode. Thereby, internal exhaust gas recirculation increases and a pump loss reduces.

  The switching means includes, for example, a mode selection switch operated by the driver.

  Alternatively, the switching means can be configured to automatically switch modes by determining a suitable driving mode from a change in the driver's accelerator operation. For example, when the accelerator operation is repeated relatively slowly, the fuel consumption priority mode is selected, and when the accelerator operation is performed rapidly, the responsiveness priority mode is selected.

  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.

  Also, in one aspect of the present invention, during acceleration in which the target torque increases within a certain range, the characteristic that emphasizes torque responsiveness mainly operates while keeping the center angle on the retard side than the characteristic that emphasizes fuel efficiency. Each target value is set so that the angle increases.

  Further, in another aspect, in acceleration characteristics in which the target torque increases within a certain range, in the characteristics in which torque response is emphasized, the delay of the central angle and the increase of the operating angle follow the response speed of each variable valve mechanism. Each target value is set to occur simultaneously.

  According to the present invention, the control of the operating angle and the central angle of the intake valve can be selectively switched between a characteristic that emphasizes fuel consumption and a characteristic that emphasizes torque response, and according to the situation, An improvement in torque response can be achieved.

  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 (actuation) Angle target value) and second variable valve mechanism target angle (center angle target value) 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 is a schematic flowchart of processing for calculating the first variable valve mechanism target angle tVEL, the second variable valve mechanism target angle tVTC, and the negative pressure control valve target opening tTVO in the configuration of the above embodiment. . First, the accelerator opening APO and the engine speed Ne are read (step 11), and the negative pressure control valve target opening tTVO, the first variable valve mechanism target angle tVEL, and the second variable movement are determined according to the required torque determined from them. The valve mechanism target angle tVTC is calculated in steps 12 to 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 the characteristic of the responsiveness emphasis mode. In this case, the center angle is relatively retarded, that is, near the bottom dead center (VTC setting value: small) even on the low load side. When the accelerator opening APO increases from this state, the central angle is not changed, and only the operating angle is gradually increased to a large operating angle (VEL set 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 remains constant.

  FIG. 7 schematically shows an example of different 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 ( At the same time, the operating angle is gradually changed to a large operating angle (VEL set value: large).

  As a result, the valve lift characteristic changes roughly as shown by the arrow in FIG. 8 as the accelerator opening APO increases. That is, the operating angle (lift / operating angle) increases while the central angle is retarded.

  FIGS. 9 to 11 are explanatory diagrams showing the transition (change locus) of the maximum lift point (in other words, lift at the central angle) of the intake valve at the time of transition (acceleration) in each of the above modes, along 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 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 first example of the responsiveness-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 FIG. 9 during acceleration traveling. In this case, only the second variable valve mechanism 6 is driven, and the operating angle increases at a portion where the gradient of the isotorque line is steep, so that high torque response is obtained.

  In the second example of the responsiveness-oriented mode described with reference to FIGS. 7 and 8, the maximum lift point changes like the straight lines indicated by reference numerals M2 and M3 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 of the operating angle target value is set in consideration of the response speeds of the variable valve mechanisms 5 and 6. The characteristic M2 in FIG. 10 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 M3 in FIG. 11 is an example suitable for the case where 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. 10, but since the actual change in the central angle corresponds to the change in the actual operating angle, high torque response is obtained. .

  Next, FIG. 12 shows the content 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 accelerator opening APO 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 that is the target value of the first variable valve mechanism 5 tVEL and a target center angle tVTC that is a target value of the second variable valve mechanism 6 are calculated. Specifically, as shown in FIG. 13, each of the target opening calculation unit B11 and the target operating angle calculation includes a map in which corresponding values are assigned with the accelerator opening APO and the rotational speed Ne as parameters. Part B12 and target center angle calculation part B13. FIG. 14 shows an example of the TVO map of the target opening calculation unit B11, FIG. 15 shows an example of the operation angle map of the target operation angle calculation unit B12, and FIG. 16 shows the center angle of the target center angle calculation unit B13. An example of a map is shown.

  Further, in the responsiveness-oriented mode target value calculation unit B3, the negative pressure control valve target opening tTVO is determined based on the accelerator opening APO and the engine speed Ne with the characteristics that emphasize torque responsiveness as described above. The target operating angle tVEL and the 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 input of the mode selection switch B1 operated by the driver, one of the target values of the fuel efficiency priority mode target value calculation unit B2 or the responsiveness priority mode target value calculation unit B3 is selected. And output to the negative pressure control valve 2 and the actuators of the first and second variable valve mechanisms 5 and 6, respectively.

  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. 17 shows an example of the TVO map of the target opening calculation unit, FIG. 18 shows an example of the operation angle map of the target operation angle calculation unit, and FIG. 19 shows an example of the center angle map of the target center angle calculation unit. Indicates. These are those of the first example of the responsiveness importance mode described with reference to FIGS. 20 to 22 show a TVO map, an operation angle map, and a center angle map in the case of the second example of the responsiveness importance mode described with reference to FIGS.

  Next, FIG. 23 and FIG. 24 are explanatory views 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. 23 shows an example in the case of the fuel efficiency emphasis mode, and FIG. 24 shows an example in the case of the responsiveness emphasis mode, particularly 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. 24, the characteristics of the actual values in the fuel consumption priority mode are shown with a one-dot chain line for comparison. As is apparent from FIG. 24, in the response-oriented mode, the initial center angle VTC is on the retard side, so that the torque sensitivity to the change amount of the same operating angle VEL is increased, 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. 25 is a functional block diagram showing the contents of the second embodiment in which the mode is automatically switched. The fuel efficiency emphasis mode target value calculation unit B2, the responsiveness emphasis mode target. The value calculation unit B3 is not particularly different from that in FIG. In other words, the fuel efficiency-oriented mode target value calculation unit B2 has characteristics that place importance on fuel efficiency, and based on the accelerator opening APO and the engine speed Ne, the negative pressure control valve target opening tTVO, the target operating angle tVEL, and the target center The angle tVTC is calculated, and the responsiveness-oriented mode target value calculation unit B3 similarly calculates the negative pressure control valve target opening tTVO, the target operating angle tVEL, and the target central angle tVTC with characteristics that emphasize responsiveness. calculate. In the present embodiment, the driving state determination unit B21 determines whether the fuel efficiency priority mode is appropriate or the responsiveness priority mode is appropriate based on the change mode (absolute value, change speed, change amount, etc.) of the accelerator opening APO. In accordance with this determination, the target value selection unit B4 selects the target value of either the fuel efficiency-oriented mode target value calculation unit B2 or the responsiveness-oriented mode target value calculation unit B3. Note that frequent switching between the above two modes is not preferable in terms of drivability, so it is desirable to provide appropriate hysteresis.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a configuration explanatory view showing a system configuration of an intake control device according to the present invention. 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 roughly the change of each parameter by the 1st example of the responsiveness importance mode when increasing the accelerator opening. Explanatory drawing which shows the change of the valve lift characteristic in the case of FIG. The characteristic view which showed roughly the change of each parameter by the 2nd example of the responsiveness importance mode when increasing the accelerator opening. 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 in the case of the 2nd example of responsiveness importance mode similarly. Explanatory drawing similar to FIG. 10 which shows an example in case the response speed of a variable valve mechanism is different. The functional block diagram which shows the 1st Example 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 characteristic diagram of the TVO map in the case of the 2nd example of responsiveness importance mode. The characteristic diagram of the operating angle map in the case of the 2nd example of responsiveness importance mode. The characteristic figure of the center angle map in the case of the 2nd example of responsiveness importance mode. 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 functional block diagram which shows the 2nd Example 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 (6)

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 is configured to set a target operating angle and a target central angle with characteristics focusing on fuel efficiency and a target operating angle and a target central angle with characteristics focusing on torque responsiveness. Comprising at least two settings including, and configured to control the first and second variable valve mechanisms in accordance with the setting of the characteristic selected by the switching means,
During acceleration of the target torque is increased from a low load region, a characteristic that emphasizes fuel efficiency, increased central angle advance side to the operating angle is preferentially while keeping, then, as the center angle is retarded, respectively An intake control device for an internal combustion engine, characterized in that a target value is set.   2. The intake control apparatus for an internal combustion engine according to claim 1, wherein the switching means comprises a mode selection switch operated by a driver.   2. The intake control apparatus for an internal combustion engine according to claim 1, wherein the switching means determines a suitable operation mode from a change in a driver's accelerator operation.   The intake control device for an internal combustion engine according to any one of claims 1 to 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. During acceleration target torque from the low load region is increased, as a characteristic that emphasizes torque response, while maintaining the retard side of the characteristics of the central angle emphasizes the fuel economy mainly operating angle increases, respectively The intake air control apparatus for an internal combustion engine according to any one of claims 1 to 4, wherein the target value is set. During acceleration target torque from the low load region is increased, the characteristic that emphasizes torque response, as the increase in the retard and operating angle of the center angle, occurs simultaneously along the response speed of the variable valve operating mechanism 5. The intake control device for an internal combustion engine according to claim 1, wherein each target value is set.

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