JP2014105578A - Control device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sufficient control result regarding various performances required for an internal combustion engine by an improved cooperative control of a variable valve timing mechanism (VVT) and a supercharger characteristic control actuator.SOLUTION: Target suction pipe pressure is calculated on the basis of a target air amount and an actual valve timing. Then, a control variable of a supercharger characteristic control actuator is calculated on the basis of the target suction pipe pressure. A control variable of the VVT is calculated on the basis of the target air amount. Here, if an estimated air amount when a flow rate of air passing through a suction valve is maximized by controlling of the VVT is smaller than the target air amount, the VVT control variable is calculated for controlling the VVT so that the flow rate of the air passing through the VVT is maximized. Then, when the estimated air amount becomes not less than the target air amount, the VVT control variable is calculated on the basis of the target air amount and reference supercharger pressure. The reference supercharger pressure is higher than actual supercharger pressure.

Description

  The present invention relates to a control device for an internal combustion engine having a variable valve timing mechanism, a supercharger, and an actuator that changes a supercharging characteristic of the supercharger.

  Patent Document 1 below describes a control method of a variable valve timing mechanism (hereinafter referred to as VVT) that changes the valve timing of an intake valve in an internal combustion engine for a vehicle. By changing the valve timing of the intake valve by VVT, the amount of air taken into the cylinder can be controlled.

JP 2010-223097 A Japanese Patent No. 495848 JP 2009-007934 A JP 2007-262968 A JP-A-11-141375

  By the way, in an internal combustion engine with a supercharger, a supercharging characteristic control actuator that changes a supercharging characteristic such as a waste gate valve (hereinafter referred to as WGV) or a variable nozzle may be provided. Since the amount of air sucked into the cylinder changes depending on the supercharging pressure, for example, if the supercharger is provided with a WGV, the supercharging characteristic of the supercharger is changed by changing the opening of the WGV. By controlling this, the amount of air can be controlled.

  That is, the amount of air sucked into the cylinder can be controlled also by the above-described VVT, and can also be controlled by a supercharging characteristic control actuator such as WGV. However, if the cooperative operation of these two types of actuators is not performed successfully, interference occurs between the air amount control by the VVT and the air amount control by the supercharging characteristic control actuator, and the actual air amount with respect to the target air amount There is a possibility that a problem occurs in followability and convergence. In addition, when the cooperative operation of these two types of actuators is not performed well, even if the followability and convergence of the actual air amount with respect to the target air amount can be satisfied, other fuel consumption performance, exhaust gas performance, etc. There is a risk that the control result may be unsatisfactory in performance.

  The present invention has been made in view of the above-described problems, and it is possible to obtain favorable control results regarding various performances required for an internal combustion engine by improved cooperative control of a VVT and a supercharging characteristic control actuator. The purpose is to.

  The control device for an internal combustion engine according to the present invention is a control device applied to an internal combustion engine including at least a VVT, a supercharger, and a supercharging characteristic control actuator. VVT is a mechanism that can change the valve timing of the intake valve, more specifically, at least the closing timing of the intake valve. The supercharger may be a turbocharger or a mechanical supercharger. If the supercharger is a turbocharger, WGV or a variable nozzle is preferable as the supercharging characteristic control actuator.

  The control apparatus for an internal combustion engine according to the present invention includes first calculation means for calculating a target intake pipe pressure of the internal combustion engine. The first calculating means calculates the target intake pipe pressure based on the target air amount of the internal combustion engine and the valve timing realized by VVT. A certain relationship is established between the air amount and the intake pipe pressure for each valve timing value. The first calculation means uses this relationship to calculate the target intake pipe pressure.

  The control apparatus for an internal combustion engine according to the present invention includes second calculation means for calculating an actuator control variable that is a control variable of a supercharging characteristic control actuator. The second calculation means calculates an actuator control variable based on the target intake pipe pressure. There is a certain relationship between the intake pipe pressure and the supercharging pressure, and there is also a certain relationship between the supercharging pressure and the actuator control variable. The second calculation means calculates the actuator control variable using these relationships.

  The control apparatus for an internal combustion engine according to the present invention includes third calculation means for calculating a reference supercharging pressure for controlling the VVT. The third calculation means calculates a boost pressure higher than the actual boost pressure as the reference boost pressure. If the reference supercharging pressure is more limited, it is preferably the maximum supercharging pressure that can be reached by the control of the supercharging characteristic control actuator. The reference supercharging pressure may be a value obtained by adding an offset amount to the supercharging pressure measured by the pressure sensor, or the supercharging pressure measured by the pressure sensor is defined as the lower limit of the rate of increase. It may be a value obtained by correcting with a lower limit guard.

  The control apparatus for an internal combustion engine according to the present invention includes fourth calculation means for calculating a VVT control variable which is a control variable of VVT. The fourth calculation means calculates the VVT control variable based on the target air amount. However, during the transient period in which the target air amount has increased, the estimated air amount realized by maximizing the flow rate of the air passing through the intake valve by controlling the VVT is calculated. While the estimated air amount is smaller than the target air amount, a value at which the flow rate of the air passing through the intake valve is maximized is calculated as a VVT control variable. If the estimated air amount is equal to or greater than the target air amount, the VVT control variable is calculated based on the target air amount and the reference supercharging pressure. There is a fixed relationship between the intake pipe pressure and the supercharging pressure, and a fixed relationship is established for each value of the VVT control variable between the air amount and the intake pipe pressure. The fourth calculation means uses these relationships to calculate the VVT control variable in the transient period. However, if the difference between the reference supercharging pressure and the supercharging pressure measured by the pressure sensor exceeds the reference value, it is preferable to limit the rate of change of the VVT control variable in the direction of decreasing the air amount. Alternatively, a limit is added to the rate of increase of the reference supercharging pressure used for calculating the VVT control variable.

  The control apparatus for an internal combustion engine according to the present invention controls the supercharging characteristic control actuator according to the actuator control variable calculated by the second calculation means, and controls the VVT according to the VVT control variable calculated by the fourth calculation means.

  According to the control apparatus for an internal combustion engine according to the present invention, no interference occurs between the air amount control by VVT and the air amount control by the supercharging characteristic control actuator. As a result, the supercharging pressure and the valve timing that can obtain good control results regarding various performances required for the internal combustion engine while ensuring the followability and convergence of the actual air amount with respect to the target air amount during acceleration operation. Can be realized.

It is a functional block diagram which shows the structure of the control apparatus of the internal combustion engine which concerns on Embodiment 1 of this invention. It is a functional block diagram which shows the structure of the control apparatus as a comparative example. It is a graph which shows the relationship between intake pipe pressure, air quantity, and valve timing. It is a time chart which shows the image of the operation | movement at the time of the target acceleration operation. It is a time chart which shows the image of the control result by the control apparatus of the structure shown in FIG. It is a time chart which shows the image of the control result by the control apparatus of the structure shown in FIG. It is a functional block diagram which shows the structure of the control apparatus of the internal combustion engine which concerns on Embodiment 2 of this invention. It is a time chart which shows the image of the control result by the control apparatus of the structure shown in FIG. It is a functional block diagram which shows the structure of the control apparatus of the internal combustion engine which concerns on Embodiment 3 of this invention. It is a time chart which shows the image of the control result by the control apparatus of the structure shown in FIG. It is a time chart for demonstrating the subject accompanying each embodiment. 12 is a time chart for explaining a countermeasure against the problem shown in FIG. 11.

Embodiment 1 FIG.
Embodiment 1 of the present invention will be described below with reference to the drawings.

  FIG. 1 is a functional block diagram showing a configuration of a control device for an internal combustion engine according to the present embodiment. The internal combustion engine 2 to which the control device according to the present embodiment is applied is a spark ignition type 4-cycle reciprocating engine including a turbocharger with a WGV4. The WGV 4 according to the present embodiment is an active control compatible WGV driven by the E-VRV, and the opening degree can be controlled by a duty supplied to the solenoid. An electronically controlled throttle (not shown) is attached to the intake passage, and a VVT 6 is attached to the intake valve. The VVT 6 according to the present embodiment is a device that changes the intake valve open timing and the close timing in conjunction with a constant operating angle. In the present specification, the valve timing controlled by the VVT 6 means an average timing of the opening timing and closing timing of the intake valve.

  Control device 110 according to the present embodiment is realized as a part of a function provided in an in-vehicle ECU (Electronic Control Unit). When the ECU functions as the control device 110 according to the present embodiment, the ECU cooperatively operates actuators related to the air amount, that is, the throttle, the WGV4, and the VVT6 according to a control program stored in the memory.

  The control device 110 according to the present embodiment includes a target air amount calculation unit 22. The target air amount calculation unit 22 calculates the air amount necessary for realizing the required torque as the target air amount. The required torque is a torque necessary for realizing the driving force required by the driver or the vehicle control device, and is determined based on the required driving force and the current engine speed. For the calculation of the target air amount, a map in which the torque and the air amount are associated with each other using various engine information such as the engine speed, ignition timing, and air-fuel ratio as arguments is used.

  The control device 110 according to the present embodiment is further a control variable of a target intake pipe pressure calculation unit 24 for calculating a target intake pipe pressure, a WGV control unit 26 for calculating a WGV duty that is a control variable of the WGV4, and a control variable of VVT6. A VVT control unit 28 for calculating the target valve timing and a maximum boost pressure calculation unit 30 are provided. The control device 110 also has a function of determining a target throttle opening, which is a throttle control variable, based on the target intake pipe pressure. During acceleration operation in which the target air volume increases, the throttle is controlled to fully open to maximize the increase speed of the intake pipe pressure. When the actual intake pipe pressure rises close to the target intake pipe pressure, the throttle is opened according to the target air volume. Closed to a degree. However, since the subject of the present invention is the cooperative control of WGV4 and VVT6, particularly the cooperative control during acceleration operation in which the target air amount increases, the details of the throttle control will be omitted.

  The target intake pipe pressure calculation unit 24 calculates the target intake pipe pressure based on the valve timing (actual VT) realized by the VVT 6 and the target air amount. In calculating the target intake pipe pressure, a map that associates the amount of air passing through the intake valve with the intake pipe pressure and the valve timing is used. According to this map, when the air amount is constant, the intake pipe pressure tends to decrease as the valve timing is advanced. When the intake pipe pressure is constant, the air amount increases as the valve timing is advanced. When the valve timing is constant, the amount of air tends to increase as the intake pipe pressure increases. However, since scavenging occurs in the supercharging region, the amount of air passing through the intake valve does not necessarily match the amount of air used for combustion. For this reason, when the target air amount is applied to the above-described map, the target air amount is corrected by the scavenging amount.

  The WGV control unit 26 calculates the target boost pressure from the target intake pipe pressure, calculates the opening of the WGV 4 that can achieve the target boost pressure with reference to the current engine speed, and the WGV opening WGV duty required to obtain The WGV duty means the duty of the solenoid that operates the WGV4. The target supercharging pressure is set to a value equal to the target intake pipe pressure or a value obtained by adding a predetermined margin to the target intake pipe pressure. At least during acceleration operation in which the throttle is fully opened, the target supercharging pressure is set to a value equal to the target intake pipe pressure.

  The VVT control unit 28 has a function of calculating a target valve timing. More specifically, the target valve timing means a target displacement angle from the reference position (initial position) of the VVT 6. The VVT control unit 28 calculates a valve timing optimum for realizing the target air amount as the base valve timing. For the calculation, a map in which the air amount and the valve timing are associated with each other using the engine speed as an argument is used. The base valve timing is a displacement angle of the VVT 6 that is optimal for achieving the target air amount based on the current engine speed. More specifically, in the steady state of the internal combustion engine 2, performance required for the internal combustion engine 2 such as fuel efficiency performance, exhaust gas performance, and combustion stability can be satisfied, and the displacement angle of the VVT 6 with respect to the engine speed and the air amount , That is, the displacement angle of the VVT 6 that can satisfy the controllability of the VVT 6. The specific value of the base valve timing is determined by adaptation for each air amount and each engine speed.

  The VVT control unit 28 calculates the base valve timing as the target valve timing in the steady state. However, if there is a difference between the target air amount and the actual air amount due to an increase in the target air amount during the acceleration operation, the actual air amount is increased at the maximum speed to follow the target air amount. The target valve timing is advanced to the maximum air flow valve timing at which the air flow rate through the intake valve is maximized. By maximizing the air flow rate that passes through the intake valve, the charging efficiency of in-cylinder air is improved, and the boost pressure tends to increase due to the increase in the turbine flow rate. The actual air amount can be estimated from the valve timing using a physical model of the internal combustion engine 2. When the air amount (estimated air amount) estimated from the maximum air flow valve timing becomes equal to or larger than the target air amount, the VVT control unit 28 sets the target air amount and the reference supercharging pressure for VVT control to the maximum. The target valve timing is calculated based on the supercharging pressure. This calculation uses a map that correlates valve timing, air amount, and intake pipe pressure. Since the intake pipe pressure and the supercharging pressure substantially coincide with each other during the acceleration operation, the maximum supercharging pressure is substituted for the argument of the intake pipe pressure in the map.

  The VVT control unit 28 controls the VVT 6 according to the target valve timing. However, the valve timing may be guarded from the viewpoint of operability and reliability. For example, when the cooling water temperature is lower than the threshold value, the advance amount from the reference position of the valve timing may be limited. For this reason, when the guard function is activated for the valve timing, there may be a deviation between the target valve timing and the valve timing realized by the VVT 6. That is, even in a steady state, when the guard function is active, the actual valve timing is not necessarily controlled to the most efficient base valve timing. For this reason, the target intake pipe pressure calculated by the target intake pipe pressure calculation unit 24 uses the valve timing actually realized by the VVT 6 instead of the target valve timing.

  The calculation of the maximum boost pressure is performed by the maximum boost pressure calculation unit 30. The maximum boost pressure calculation unit 30 calculates the maximum boost pressure that can be achieved by operating the WGV 4 under the current operating state of the internal combustion engine 2. Specifically, the estimated boost pressure when the WGV 4 is fully closed is calculated as the maximum boost pressure. The estimated supercharging pressure when the WGV 4 is fully closed can be calculated using a physical model of the supercharger based on the amount of air flowing into the turbine and the engine speed.

  The above is the configuration of the control device 110 according to the present embodiment. Next, in order to make it easier to understand the advantages of the control device 110 according to the present embodiment, as a comparative example for the control device 110 according to the present embodiment, the configuration of the control device first studied in the inventive process of the present invention. Also explained. FIG. 2 is a functional block diagram illustrating a configuration of the control device 100 as a comparative example. In the configuration shown in FIG. 2, elements that are the same as those of the control device 110 according to the present embodiment are given the same reference numerals.

  The control device 100 as a comparative example includes a target air amount calculation unit 22, a target intake pipe pressure calculation unit 24, a WGV control unit 26, and a VVT control unit 28. That is, the control device 100 as a comparative example does not include the maximum supercharging pressure calculation unit 30 included in the control device 110 according to the present embodiment. The actual boost pressure measured by the boost pressure sensor 8 is input to the VVT control unit 28 of the comparative example as a reference boost pressure used for calculation of the target valve timing during acceleration operation. When the target air amount increases, the VVT control unit 28 of the comparative example first advances the target valve timing to the valve timing at which the flow rate of air passing through the intake valve becomes maximum, and then the target air amount and the actual air amount are exceeded. The target valve timing is calculated based on the supply pressure.

  Here, FIG. 3 is a graph showing the relationship among the intake pipe pressure, the air amount, and the valve timing. The vertical axis represents the intake pipe pressure, the horizontal axis represents the valve timing, and a plurality of curves in the graph are contour lines connecting coordinates with equal air amounts. As can be seen from this graph, there are an infinite number of combinations of intake pipe pressure and valve timing that can achieve the target air amount, including points A and B. However, there is one combination that can satisfy the performance required for the internal combustion engine 2 such as fuel efficiency performance, exhaust gas performance, combustion stability, etc. to the maximum, and it is assumed here that the combination at point B is that. Therefore, when the target air amount increases to the air amount specified by the thick line in the graph, it is desired to cooperatively control WGV4 and VVT6 so that the intake pipe pressure and valve timing at point B, not point A, can be obtained.

  In this regard, in the configuration of the control device 100 as a comparative example, once the point A is reached, the state cannot be shifted to the point B. The control apparatus 100 as a comparative example determines the target intake pipe pressure while referring to the actual valve timing, and the actual supercharging pressure (the supercharging pressure during the acceleration operation in which the throttle is fully opened is equal to the intake pipe pressure). This is because the target valve timing is determined while referring to FIG. The actual valve timing corresponds to the output of the air amount control by VVT6, and the actual supercharging pressure corresponds to the output of the air amount control by WGV4. In the method of cross-referencing the outputs between the air amount control by WGV4 and the air amount control by VVT6 as in the control device 100 as a comparative example, the target air amount is achieved by the actual supercharging pressure and valve timing. If it is, the action of moving the operating point from the A point to the B point which is the optimal operating point does not work.

  Control device 110 according to the present embodiment employs improved cooperative control of VVT 6 and WGV 4 in order to solve the above-described problem of control device 100 as a comparative example. The improved cooperative control means that, instead of the actual supercharging pressure measured by the supercharging pressure sensor 8, the maximum supercharging pressure calculated by the maximum supercharging pressure calculation unit 30 is used for the target valve timing during acceleration operation. It is used for calculation. According to this, the actual valve timing is referred to in the air amount control by WGV4, but the actual supercharging pressure is not referred to in the air amount control by VVT6. Therefore, the air amount control by VVT6 and the air amount control by WGV4 are not used. No interference occurs. Furthermore, since the maximum supercharging pressure is higher than the actual supercharging pressure, referring to the maximum supercharging pressure acts to retard the valve timing without waiting for the actual supercharging pressure to rise. . Therefore, according to the improved cooperative control by the control device 110 according to the present embodiment, the operating point on the contour line of the target air amount is directed toward the maximum supercharging pressure, that is, the point B which is the optimal operating point. You can move towards.

  Next, regarding the advantages of the control device 110 according to the present embodiment, the control result during acceleration operation by the control device 110 according to the present embodiment is compared with the control result during acceleration operation by the control device 100 as a comparative example. To clarify. First, the target operation during acceleration operation will be described with reference to the time chart of FIG. In the target operation, when the target air amount increases, the valve timing is advanced to a value at which the air flow rate passing through the intake valve becomes maximum, and the target intake pipe pressure is increased corresponding to the target air amount, The supercharging pressure rises quickly toward the increased target intake pipe pressure. Then, after the actual air amount rises until the difference between the target air amount and the actual air amount falls below the threshold, the valve timing returns to the base valve timing, which is the most efficient value (in this example, however, the valve timing Is not guarded). If such an operation is achieved as intended, good control results regarding various performances required for the internal combustion engine 2 while ensuring followability and convergence of the actual air amount with respect to the target air amount during acceleration operation. Can be obtained.

  However, in the case of the control device 100 as a comparative example, the control result during the acceleration operation is as shown in the time chart of FIG. According to the control device 100 as a comparative example, the valve timing is advanced to a value that maximizes the flow rate of air passing through the intake valve as intended. However, since the target intake pipe pressure is determined from the target air amount and the actual valve timing, the target intake pipe pressure is temporarily increased as the target air amount increases, as indicated by the dotted line in the lower graph. Later, it is lowered as the valve timing advances. Since WGV4 is controlled based on the target intake pipe pressure, as shown by the solid line in the lower graph, if the target intake pipe pressure decreases, the supercharging pressure realized by the control of WGV4 is kept low. Become. And the valve timing controlled based on the target air amount and the actual boost pressure remains advanced by suppressing the actual boost pressure low. That is, the control device 100 as the comparative example can achieve the target air amount, but cannot return the valve timing to the most efficient base valve timing while increasing the supercharging pressure.

  On the other hand, in the case of the control device 110 according to the present embodiment, it is possible to obtain a control result during acceleration operation as shown in the time chart of FIG. According to the control device 110 according to the present embodiment, first, the valve timing is advanced from the base valve timing to a value at which the flow rate of air passing through the intake valve becomes maximum as the target air amount increases. Thereafter, by referring to the maximum boost pressure in the calculation of the target valve timing, the valve timing is retarded again toward an efficient base valve timing. As a result of the valve timing being controlled in this way, as indicated by the dotted line in the lower graph, the target intake pipe pressure that has been increased in accordance with the increase in the target air amount is once lowered as the valve timing advances, The target intake pipe pressure rises again as the valve timing is retarded. Since the WGV 4 is controlled based on the target intake pipe pressure, the boost pressure realized by the control of the WGV 4 increases as the target intake pipe pressure increases. As indicated by the solid line and the alternate long and short dash line in the lower graph, the actual boost pressure rises so as to follow the maximum boost pressure.

  As can be seen from the control results described above, the control device 110 according to the present embodiment can achieve targeted operations with respect to valve timing and supercharging pressure. As a result, various performances required for the internal combustion engine 2 such as fuel efficiency, exhaust gas performance, and combustion stability are satisfied while ensuring followability and convergence of the actual air amount with respect to the target air amount during acceleration operation. be able to.

  In the present embodiment, the target intake pipe pressure calculation unit 24 corresponds to the “first calculation means” in the present invention. The WGV control unit 26 corresponds to “second calculation means” in the present invention, and the WGV duty corresponds to “actuator control variable”. The maximum boost pressure calculation unit 30 corresponds to “third calculation means” in the present invention. The VVT control unit 28 corresponds to “fourth calculation means” in the present invention, and the target valve timing corresponds to “VVT control variable”. In the present embodiment, VVT 6 is controlled according to the target valve timing. More specifically, the duty of the solenoid that drives the oil control valve (OCV) of VVT 6 is calculated from the target valve timing. Therefore, the duty of the solenoid that drives the OCV can be interpreted as a “VVT control variable”.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a functional block diagram showing the configuration of the control device for the internal combustion engine according to the present embodiment. In the configuration shown in FIG. 7, elements that are the same as those of the control device 110 according to Embodiment 1 are given the same reference numerals.

  The control device 120 according to the present embodiment includes a target air amount calculation unit 22, a target intake pipe pressure calculation unit 24, a WGV control unit 26, a VVT control unit 28, and an offset amount addition unit 32. That is, the control device 120 according to the present embodiment includes an offset amount addition unit 32 instead of the maximum supercharging pressure calculation unit 30 provided in the control device 110 according to the first embodiment.

  The offset amount adding unit 32 performs a calculation for adding a predetermined offset amount to the actual boost pressure measured by the boost pressure sensor 8, and calculates the calculated value as a reference boost pressure for VVT control. . That is, in the control device 120 according to the present embodiment, as the reference boost pressure used for calculating the target valve timing during acceleration operation, the boost pressure calculated by the offset amount adding unit 32, that is, the actual boost pressure is used. Also, a boost pressure higher by the offset amount is input to the VVT control unit 28.

  FIG. 8 is a time chart showing an image of a control result during acceleration operation by control device 120 according to the present embodiment. According to the control device 120 according to the present embodiment, first, the valve timing is advanced from the base valve timing to a value at which the flow rate of air passing through the intake valve becomes maximum as the target air amount increases. Thereafter, by referring to the boost pressure higher than the actual boost pressure in the calculation of the target valve timing, the valve timing starts to return to the retarded side first without waiting for the boost pressure to rise. As a result of the valve timing starting to return to the retarded side first, as indicated by the dotted line in the lower graph, the target intake pipe pressure increased in accordance with the increase in the target air amount is the valve timing at the start of acceleration. Although it is once lowered with advance, the target intake pipe pressure rises again as the valve timing is retarded. If the target intake pipe pressure increases, the supercharging pressure realized by the control of the WGV 4 also increases. As indicated by the solid line and the alternate long and short dash line in the lower graph, the actual boost pressure rises so as to follow the added value of the offset amount. Prior to that, the valve timing is the most efficient base valve. Go back to timing.

  As can be seen from the above control results, according to the control device 120 according to the present embodiment, similar to the control device 110 according to the embodiment, it is possible to realize a targeted operation regarding the valve timing and the supercharging pressure. Can do. As a result, various performances required for the internal combustion engine 2 such as fuel efficiency, exhaust gas performance, and combustion stability are satisfied while ensuring followability and convergence of the actual air amount with respect to the target air amount during acceleration operation. be able to.

  In the present embodiment, the offset amount addition unit 32 corresponds to the “third calculation means” in the present invention.

Embodiment 3 FIG.
Next, Embodiment 3 of the present invention will be described with reference to the drawings.

  FIG. 9 is a functional block diagram showing the configuration of the control device for the internal combustion engine according to the present embodiment. In the configuration shown in FIG. 9, elements common to the elements included in control device 110 according to Embodiment 1 are denoted by the same reference numerals.

  The control device 130 according to the present embodiment includes a target air amount calculation unit 22, a target intake pipe pressure calculation unit 24, a WGV control unit 26, a VVT control unit 28, and an inclination lower limit guard unit 34. That is, the control device 130 according to the present embodiment includes an inclination lower limit guard unit 34 instead of the maximum supercharging pressure calculation unit 30 provided in the control device 110 according to the first embodiment.

  The inclination lower limit guard unit 34 performs a calculation for correcting the supercharging pressure measured by the supercharging pressure sensor 8 with a lower limit guard that defines the lower limit of the rate of increase, and calculates the calculated value as a reference supercharging pressure for VVT control. To do. That is, in the control device 130 according to the present embodiment, the reference boost pressure used for calculating the target valve timing during acceleration operation is defined by the boost pressure calculated by the slope lower limit guard unit 34, that is, the lower limit guard. The supercharging pressure that monotonously increases at a rate of increase equal to or greater than the value is input to the VVT control unit 28.

  FIG. 10 is a time chart showing an image of a control result during acceleration operation by control device 130 according to the present embodiment. According to the control device 130 according to the present embodiment, first, the valve timing is advanced from the base valve timing to a value at which the flow rate of air passing through the intake valve becomes maximum as the target air amount increases. Thereafter, by referring to the boost pressure that monotonously increases in the calculation of the target valve timing, the valve timing is retarded according to the increase in the reference boost pressure. As indicated by the dotted line in the lower graph, the target intake pipe pressure that has been increased in accordance with the increase in the target air amount is once lowered with the advance of the valve timing at the start of acceleration, but the valve timing is delayed. As the angle is increased, the target intake pipe pressure increases again. If the target intake pipe pressure increases, the supercharging pressure realized by the control of the WGV 4 also increases. As indicated by the solid line and the alternate long and short dash line in the lower graph, the actual boost pressure increases so as to follow the boost pressure calculated by the slope lower limit guard unit 34 (actual boost pressure after the slope guard process). Prior to that, the valve timing returns to the most efficient base valve timing.

  As can be seen from the above control results, according to the control device 130 according to the present embodiment, similar to the control device 110 according to the embodiment, it is possible to realize a targeted operation regarding the valve timing and the supercharging pressure. Can do. As a result, various performances required for the internal combustion engine 2 such as fuel efficiency, exhaust gas performance, and combustion stability are satisfied while ensuring followability and convergence of the actual air amount with respect to the target air amount during acceleration operation. be able to.

  In the present embodiment, the inclination lower limit guard unit 34 corresponds to the “third calculation means” in the present invention.

Others.
As described above, the control devices 110, 120, and 130 according to the embodiments of the present invention are common in that the boost pressure higher than the actual boost pressure is calculated as the reference boost pressure for VVT control. It has characteristics. However, as shown in the time chart of FIG. 11, when the deviation between the actual supercharging pressure and the reference supercharging pressure for VVT control is large, the actual air amount deviates from the target air amount by the difference. As a result, the air amount varies. The cause of such a problem is the operation of VVT 6 shown in the middle graph. In any of the above-described embodiments, after the VVT 6 is operated once to adjust the actual air amount to the target air amount, the actual air amount is deviated from the target air amount when returning to the efficient base valve timing again. Operated on the side. For this reason, if the increase in the supercharging pressure is insufficient compared to the target, the decrease in the air amount due to the retardation of the valve timing cannot be compensated by the increase in the supercharging pressure. The situation where the value deviates from the target air amount occurs.

  The following two plans can be considered as countermeasures against such problems.

  The first countermeasure proposal is that when the difference between the reference boost pressure for VVT control and the actual boost pressure measured by the boost pressure sensor 8 exceeds the reference value, the valve timing changes in the retard direction. To limit the rate. Specifically, in the VVT control unit 28, an upper limit guard may be applied to the rate of change when the target valve timing is returned to the base valve timing. By taking such measures, the actual supercharging pressure can easily follow the reference supercharging pressure for VVT control, and the range of fluctuation of the air amount is reduced. In addition, since the frequency of fluctuation of the air amount is lowered, there is an advantage that it is difficult for the driver to feel uncomfortable.

  As shown in the time chart of FIG. 12, when the difference between the reference boost pressure for VVT control and the actual boost pressure measured by the boost pressure sensor 8 exceeds the reference value, the second countermeasure plan is as follows. To limit the rate of increase of the reference supercharging pressure. By limiting the rate of increase of the reference boost pressure, the actual boost pressure can easily catch up with the reference boost pressure, and the difference between the actual boost pressure and the reference boost pressure is reduced. As a result, the deviation of the actual air amount from the target air amount is also reduced, and fluctuations in the air amount are suppressed.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the throttle is fully open during acceleration operation, but it is not essential that the throttle is fully open, and the throttle opening may always be controlled according to the target intake pipe pressure. Alternatively, the throttle may be controlled to be fully open in the supercharging region. That is, the target to which the present invention is applied may be a control device that performs cooperative control of VVT and WGV.

  Further, the control device according to the present invention can be applied not only to an internal combustion engine having a turbocharger with WGV but also to an internal combustion engine having a variable displacement turbocharger having a variable nozzle. If the supercharging characteristics can be changed by an actuator such as an electric motor, the control device according to the present invention is applied not only to the turbocharger but also to an internal combustion engine having a mechanical supercharger. Can do.

2 Internal combustion engine 4 Wastegate valve (WGV)
6 Variable valve timing mechanism (VVT)
8 Supercharging pressure sensor 22 Target air amount calculation unit 24 Target intake pipe pressure calculation unit 26 WGV control unit 28 VVT control unit 30 Maximum supercharging pressure calculation unit 32 Offset amount addition unit 34 Inclination lower limit guard unit 100 Control device as a comparative example 110 Control Device 120 According to Embodiment 1 Control Device 130 According to Embodiment 2 Control Device According to Embodiment 3

Claims (6)

In a control device for an internal combustion engine having a variable valve timing mechanism, a supercharger, and a supercharging characteristic control actuator that changes a supercharging characteristic of the supercharger,
First calculating means for calculating a target intake pipe pressure of the internal combustion engine based on a target air amount of the internal combustion engine and a valve timing realized by the variable valve timing mechanism;
Second calculating means for calculating an actuator control variable that is a control variable of the supercharging characteristic control actuator based on the target intake pipe pressure;
Third calculation means for calculating a supercharging pressure higher than an actual supercharging pressure as a reference supercharging pressure for controlling the variable valve timing mechanism;
Calculate the estimated air amount when the flow rate of air passing through the intake valve is maximized by the control of the variable valve timing mechanism, and if the estimated air amount is smaller than the target air amount, pass through the intake valve VVT control variable, which is a control variable of the variable valve timing mechanism, is calculated so that the flow rate of air to be maximized. If the estimated air amount is equal to or greater than the target air amount, the target air amount and the reference excess amount are calculated. And a fourth calculation means for calculating the VVT control variable based on the supply pressure,
The control device of the internal combustion engine, wherein the control device controls the variable valve timing mechanism according to the VVT control variable and controls the supercharging characteristic control actuator according to the actuator control variable.   2. The control device for an internal combustion engine according to claim 1, wherein the third calculation means calculates, as the reference supercharging pressure, a maximum supercharging pressure that can be reached by control of the supercharging characteristic control actuator. 3.   2. The internal combustion engine according to claim 1, wherein the third calculation unit calculates a value obtained by adding an offset amount to a boost pressure measured by a pressure sensor as the reference boost pressure. Control device.   The third calculation means calculates, as the reference supercharging pressure, a value obtained by correcting the supercharging pressure measured by a pressure sensor with a lower limit guard that defines a lower limit of an increase rate. The control apparatus for an internal combustion engine according to claim 1.   The fourth calculating means calculates a difference between the reference boost pressure and a boost pressure measured by a pressure sensor when calculating the VVT control variable based on the target air amount and the reference boost pressure. 5. The control of the internal combustion engine according to claim 1, wherein when the value exceeds a reference value, the rate of change of the VVT control variable in the direction of decreasing the air amount is limited. apparatus.   The fourth calculating means calculates a difference between the reference boost pressure and a boost pressure measured by a pressure sensor when calculating the VVT control variable based on the target air amount and the reference boost pressure. The internal combustion engine according to any one of claims 1 to 4, wherein when the engine pressure exceeds a reference value, a limit is imposed on an increase rate of the reference supercharging pressure used for calculation of the VVT control variable. Control device.

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