JP2016169641A - Intake/exhaust device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently utilize a scavenging effect while suppressing exhaust interference, in an intake and exhaust device of an internal combustion engine.SOLUTION: An intake/exhaust device 1 sets an overlap period on the basis of a port pressure difference ΔP being an average value of pressure differences which is obtained by subtracting an exhaust port P2 from an intake port P1 in a prescribed period ΔTa within a maximum period which can be taken as the overlap period. By this constitution, since the overlap period is set by a comparison of the pressure of the intake port and the pressure of the exhaust port in the prescribed period ΔTa in the vicinity of a top dead point in which the overlap period is actually set, the overlap period which can suppress an influence of exhaust interference can be set by sufficiently utilizing a scavenging effect.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an intake / exhaust device for an internal combustion engine including a turbocharger.

  2. Description of the Related Art Conventionally, an intake / exhaust device for an internal combustion engine having a turbocharger that rotates the turbine by the energy of exhaust gas exhausted from the internal combustion engine and rotationally drives the compressor by the rotational torque to pump intake air to the internal combustion engine. It is well known.

  By the way, in a turbocharger, generation | occurrence | production of what is called a turbo lag is regarded as a subject. Turbo lag, for example, can be considered as the time difference from when the accelerator is depressed by the occupant to when the pumping of the intake air by the turbocharger starts in earnest, and is expected from the internal combustion engine until the pumping of intake air starts in earnest. It is not possible to obtain enough torque and output.

As a method of reducing the turbo lag, there is a method of promoting a so-called scavenging effect, that is, in-cylinder scavenging in which intake air passes from the intake port to the exhaust port.
As a conventional technique, when the intake manifold pressure becomes larger than the exhaust manifold pressure after the acceleration request of the internal combustion engine is requested, the overlap period in which the valve opening period of the intake valve overlaps the valve opening period of the exhaust valve is increased. Patent Document 1 describes a technique for promoting the scavenging effect.

  By the way, in order to obtain the scavenging effect, the intake port pressure needs to be larger than the exhaust port pressure during the period when the overlap is scheduled to be performed, and the differential pressure between the intake port pressure and the exhaust port pressure is large. As the scavenging effect increases.

On the other hand, in the technique of Patent Document 1, the intake manifold pressure and the exhaust manifold pressure are compared. However, the intake manifold pressure and the exhaust manifold pressure are often calculated as average values of all cylinders. In this case, since the intake port pressure is different from the actual intake port pressure and exhaust port pressure, the intake port pressure becomes larger than the exhaust port pressure. Nevertheless, the intake manifold pressure may be detected smaller than the exhaust manifold pressure.
Moreover, in the technique of patent document 1, it is unclear in which period the intake manifold pressure and the exhaust manifold pressure are compared. There is a possibility that the comparison is made by the average value over the entire period of one cycle.

  For this reason, in the technique of Patent Document 1, in fact, it is determined that the intake manifold pressure is smaller than the exhaust manifold pressure, even though the intake port pressure is higher than the exhaust port pressure during the period when the overlap is scheduled to be performed. As a result, the overlap period increase control (scavenging effect promotion control) may not be performed.

In the technique of Patent Document 1, the period until the intake manifold pressure becomes larger than the exhaust manifold pressure after the acceleration request is made gradually overlaps with the acceleration from the overlap period when the acceleration request is made. It is thought that the period will be increased.
However, with this method, the overlap period gradually increases in a state where the intake port pressure is smaller than the exhaust port pressure, so there is a possibility that exhaust interference between cylinders may occur. When the exhaust interference occurs, the amount of intake air introduced into the intake port is reduced, and the acceleration performance is deteriorated.

JP 2005-201086 A

  The present invention has been made to solve the above-described problems, and an object of the present invention is to fully utilize the scavenging effect while suppressing exhaust interference in an intake / exhaust device of an internal combustion engine.

  An intake / exhaust device for an internal combustion engine according to the present invention includes a turbocharger, an intake valve, an exhaust valve, a variable valve mechanism, and a control device, which will be described below.

The turbocharger rotates the turbine with exhaust gas exhausted from the internal combustion engine, and rotationally drives the compressor with the rotational torque of the turbine, thereby pumping intake air to the internal combustion engine.
The intake valve opens and closes the intake port of the internal combustion engine.
The exhaust valve opens and closes the exhaust port of the internal combustion engine.
The variable valve mechanism changes the opening / closing timing of at least one of the intake valve and the exhaust valve to vary the overlap period in which the valve opening period of the intake valve and the valve opening period of the exhaust valve overlap.
The control device controls the operation of the variable valve mechanism.

  The control device includes a port differential pressure calculation unit, a port differential pressure determination unit, and an overlap period setting unit described below.

The port differential pressure calculation unit is a port differential pressure that is an average value of the differential pressures obtained by subtracting the exhaust port P2 from the intake port pressure P1 within a predetermined period ΔTa within the maximum possible period of the overlap period and straddling the top dead center. ΔP is calculated.
The port differential pressure determination unit determines whether or not the port differential pressure ΔP is equal to or greater than a predetermined value.
When the port differential pressure determination unit determines that the port differential pressure ΔP is less than a predetermined value when an acceleration request for the internal combustion engine is made, the overlap period setting unit sets the overlap period to the first set value. After that, when it is determined that the port differential pressure ΔP has become equal to or greater than a predetermined value, the overlap period is set to a second set value that is greater than the first set value.

  In the present invention, the overlap period is set based on the port differential pressure ΔP that is an average value of the differential pressure obtained by pulling the exhaust port P2 from the intake port pressure P1 in the predetermined period ΔTa within the maximum possible period of the overlap period. doing. Therefore, the scavenging effect can be fully utilized because the overlap period is set not by comparing the intake manifold pressure and the exhaust manifold pressure but by comparing the intake port pressure and the exhaust port pressure.

  In the present invention, since there is a concern about exhaust interference in a period immediately after the acceleration request, in which the port differential pressure ΔP is smaller than a predetermined value (including a period in which the exhaust port pressure P2 is greater than the intake port pressure P1), exhaust interference In order to suppress this, the overlap period is set to a small value (first set value). When the port differential pressure ΔP becomes sufficiently large, a scavenging effect can be obtained instead of exhaust interference, so the overlap period is set to a larger value (second set value). As a result, the scavenging effect can be fully utilized while suppressing the exhaust interference.

1 is a configuration diagram of an intake / exhaust device for an internal combustion engine (Example 1). FIG. FIG. 6 is a diagram for explaining a maximum period, a minimum period, and a predetermined period ΔTa that can be taken as an overlap period (Example 1). (Example 1) which is an example of the map used for calculation of intake port pressure. (Example 1) which is an example of the map used for calculation of exhaust port pressure. (Example 1) which is a control flow of the variable valve mechanism by a control apparatus. FIG. 3 is a time chart showing the time transition of the output torque, the intake air amount, the port differential pressure ΔP, and the overlap period of the internal combustion engine (Example 1). FIG. (Example 1) for demonstrating the technical significance of determining with the average value of the port differential pressure | voltage in predetermined period (DELTA) Ta. (Example 2) which is a block diagram of the intake / exhaust apparatus of an internal combustion engine. It is an example of the map used for calculation of a 2nd setting value (Example 2). (Example 2) which is a control flow of the variable valve mechanism by a control apparatus. FIG. 7 is a time chart showing the time transition of the output torque, intake air amount, port differential pressure ΔP, and overlap period of the internal combustion engine (Example 2). (Example 3) which is a block diagram of the intake / exhaust apparatus of an internal combustion engine. (Example 3) which is a control flow of the variable valve mechanism and capacity | capacitance change mechanism by a control apparatus. FIG. 10 is a time chart showing the time transition of output torque, intake air amount, port differential pressure ΔP, overlap period, and turbine capacity of an internal combustion engine (Example 3).

  The mode for carrying out the present invention will be described in detail with reference to the following examples.

[Example 1]
[Configuration of Example 1]
A first embodiment will be described with reference to FIGS.
The intake / exhaust device 1 causes the internal combustion engine 2 to suck in intake air and exhaust the exhaust gas from the internal combustion engine 2.
The intake / exhaust device 1 includes an intake passage 3, an exhaust passage 4, a turbocharger 5, an intake valve 6, an exhaust valve 7, a variable valve mechanism 8, and a control device 9 described below.

  The intake passage 3 is a passage that guides intake air from the fresh air inlet 13 to the internal combustion engine 2 through the air cleaner 14, the throttle valve 15, the intake manifold 16, and the like. The internal combustion engine of the present embodiment is a four-cylinder type, and intake air is guided to the intake port 17 of each cylinder.

  The exhaust passage 4 is a passage that guides exhaust gas from the exhaust port 18 of each cylinder of the internal combustion engine 2 to the exhaust port 22 through the catalyst 20 and the muffler 21.

  The turbocharger 5 includes a turbine 27 that converts heat energy and kinetic energy of exhaust gas into rotational energy of the rotary shaft 26, and a compressor 28 that compresses intake air by the rotational torque transmitted from the rotary shaft 26 and sends the compressed air to the internal combustion engine 2. The impeller of the turbine 27 is rotated at high speed using the energy of the exhaust gas, and the impeller of the compressor 28 is rotationally driven by the rotational torque to compress the intake air and send it to the internal combustion engine 2.

  The intake air compressed by the compressor 28 is cooled by the intercooler 29 and then sucked into the internal combustion engine 2 through the throttle valve 15.

The turbocharger 5 has a waste gate valve 31 that opens and closes a bypass circuit 30 that bypasses the turbine 27 and flows exhaust gas from the upstream side of the turbine 27 to the downstream side of the turbine 27.
In other words, in order to avoid the situation where the intake air is pumped excessively by the turbocharger 5 or the exhaust gas flow velocity reaches the sonic speed and the exhaust amount is restricted by the turbine 27, the turbine 27 is provided in the exhaust passage 4. A bypass 30 that bypasses and a wastegate valve 31 that opens and closes the bypass 30 are provided.

The intake valve 6 is a known valve that opens and closes the intake port 17.
The exhaust valve 7 is a well-known valve that opens and closes the exhaust port 18.

The variable valve mechanism 8 changes the opening / closing timing of at least one of the intake valve 6 and the exhaust valve 7 to vary the overlap period in which the valve opening period of the intake valve 6 overlaps the valve opening period of the exhaust valve 7. It is.
The variable valve mechanism 8 of this embodiment is of a type that can change the opening / closing timing of both the intake valve 6 and the exhaust valve 7.

  The variable valve mechanism 8 includes a relative rotational phase between a crankshaft (not shown) and an intake camshaft (not shown) of the internal combustion engine 2, and a crankshaft (not shown) and an exhaust camshaft (not shown). Relative to the predetermined reference position, the phase can be changed to the advance side and the retard side. That is, the opening / closing timing of the intake valve 6 and the opening / closing timing of the exhaust valve 7 can be advanced and retarded, respectively.

  Then, the overlap period in which the valve opening period of the intake valve 6 overlaps the valve opening period of the exhaust valve 7 is variable by advancing and retarding the opening / closing timing of the intake valve 6 and the opening / closing timing of the exhaust valve 7 respectively. can do.

As shown in FIG. 2, the overlap period becomes the maximum Lmax in a state where the opening / closing timing of the intake valve 6 is most advanced and the opening / closing timing of the exhaust valve 7 is most retarded. The overlap period becomes the minimum Lmin in a state where the opening / closing timing of the intake valve 6 is most retarded and the opening / closing timing of the exhaust valve 7 is most advanced.
That is, the variable range of the overlap period is from Lmin to Lmax.
Note that the overlap period straddles the top dead center (TDC) as shown in FIG.

  The control device 9 includes a microcomputer having a well-known structure configured to include functions of a CPU that performs control processing and arithmetic processing, a storage device that stores various programs and various data, an input circuit, an output circuit, and the like. Devices such as the throttle valve 15, the waste gate valve 31, the variable valve mechanism 8 and the like are controlled in accordance with detection signals input from various sensors such as the supercharging pressure sensor 35 and the engine speed sensor 36.

[Features of Example 1]
In the intake / exhaust device 1 of the present embodiment, the control device 9 includes a port differential pressure calculation unit 40, a port differential pressure determination unit 41, and an overlap period setting unit 42 which will be described below.

The port differential pressure calculation unit 40 calculates the intake port pressure P1 from the intake port pressure P1 within a predetermined period ΔTa within the maximum possible period of the overlap period and sandwiching the top dead center (TDC) when the internal combustion engine 2 is requested to accelerate. A port differential pressure ΔP, which is an average value of the differential pressures drawn through the exhaust port P2, is calculated.
As an example of the acceleration request, when the required supercharging pressure is higher than the actual supercharging pressure, the actual supercharging pressure is output so as to approach the required supercharging pressure. The required supercharging pressure is set by an ECU (not shown) depending on the accelerator depression amount and the state of the internal combustion engine. Further, the state of the internal combustion engine 2 is determined by the crank rotational speed and load of the internal combustion engine 2, the intake air pressure, and the like. However, the acceleration request is not limited to the above.

  The maximum period that the overlap period can take is the maximum period of the variable range of the overlap period. As described above, the opening / closing timing of the intake valve 6 is advanced most, and the opening / closing timing of the exhaust valve 7 is delayed the most. It is the overlap period Lmax in the state where it is made to be horned. As shown in FIG. 2, a predetermined period within this period and sandwiching the top dead center is defined as ΔTa (hereinafter also referred to as a pressure determination period ΔTa).

The pressure determination period ΔTa is a range from α ° before top dead center to β ° after top dead center, and is determined by a crank angle range.
The port differential pressure calculation unit 40 receives an output signal from the crank angle sensor 44 and calculates a differential pressure obtained by subtracting the exhaust port pressure P2 from the intake port pressure P1 in the pressure determination period ΔTa.

The port differential pressure calculation unit 40 according to the present embodiment calculates the port differential pressure ΔP based on the intake air amount, the engine speed, and the opening degree of the waste gate valve 31.
The intake air amount is the flow rate of the intake air introduced into the intake port 17 and is calculated from the pressure (surge tank pressure) in the surge tank 16 a provided in the intake manifold 16. The surge tank pressure is detected by a surge tank pressure sensor 45.
The engine speed is detected by an engine speed sensor 36.
Further, the opening degree of the waste gate valve is detected by the WGV opening degree sensor 46.
Therefore, the port differential pressure calculation unit 40 receives the output signals from the surge tank pressure sensor 45, the engine speed sensor 36, and the WGV opening sensor 46, and calculates the port differential pressure ΔP.

  Specifically, the port differential pressure calculation unit 40 has a map that shows the relationship between the intake port pressure P1, the intake air amount, the engine speed, and the opening degree of the wastegate valve 31, as shown in FIG. The intake port pressure P1 is estimated from this map.

Further, the port differential pressure calculation unit 40 has a map as shown in FIG. 4 showing the relationship between the exhaust port pressure P2, the intake air amount, the engine speed, and the opening degree of the wastegate valve 31. The exhaust port pressure P2 is estimated from this map.
Then, the port differential pressure calculation unit 40 subtracts the estimated exhaust port pressure P2 from the estimated intake port pressure P1, and calculates the average value of the value in the pressure determination period ΔTa as the port differential pressure ΔP.

The port differential pressure determination unit 41 determines whether or not the port differential pressure ΔP output from the port differential pressure calculation unit 40 is equal to or greater than a predetermined value X.
The predetermined value X is set to a minimum differential pressure value at which it can be estimated that a scavenging effect can be obtained.

  The port differential pressure calculation unit 40 and the port differential pressure determination unit 41 may calculate and determine the port differential pressure ΔP in each cylinder, or calculate and determine the port differential pressure ΔP in the representative cylinder. You may do it.

  The overlap period setting unit 42 sets the overlap period to the first when the port differential pressure determination unit 41 determines that the port differential pressure ΔP is less than the predetermined value X when the acceleration request for the internal combustion engine 2 is made. After setting to the set value L1, and then determining that the port differential pressure ΔP has become equal to or greater than the predetermined value X, the overlap period is set to a second set value L2 that is greater than the first set value L1.

  In the present embodiment, the first set value L1 is the period Lmin, and the second set value L2 is the period Lmax.

The overlap period setting unit 42 may set the overlap period in each cylinder, or set the overlap period in the representative cylinder and apply the set value to all the other cylinders. May be.
Ideally, when the acceleration request is made, the cylinder that is about to start the suction process is set as the representative cylinder, the port differential pressure ΔP is calculated and determined, and the overlap period is set based on the result, The set value is preferably applied to all the cylinders after the next cycle.

Hereinafter, a detailed description will be given using the flowchart of FIG. 5 and the time chart of FIG. The processing of this flow is performed every predetermined time (for example, every 100 milliseconds).
When there is an acceleration request, the port differential pressure calculation unit 40 calculates the port differential pressure ΔP (see steps S1 and S2).
Thereafter, the process proceeds to step S3, and the port differential pressure determination unit 41 determines whether or not the port differential pressure ΔP is equal to or greater than a predetermined value X. The port differential pressure ΔP is negative when the intake port pressure is lower than the exhaust port pressure, and is therefore determined to be smaller than the predetermined value X.

  If the determination in step S3 is NO, that is, if the port differential pressure ΔP is less than the predetermined value X, the process proceeds to step S4, and a control command is sent to the variable valve mechanism 8 to set the overlap period to the first set value L1. To finish the process. Then, after a predetermined time, the flow starts from the first step S1.

  If the overlap period at the time when the acceleration request is made is already the same as the first set value L1, the variable valve mechanism 8 maintains the overlap period as it is. However, when the overlap period at the time when the acceleration request is made is longer than the first set value L1, the variable valve mechanism 8 reduces the overlap period to the first set value L1.

In order to return to the start of the flow after setting the overlap period to the first set value L1, the processes of S1, S2, S3, and S4 are repeated until the port differential pressure ΔP becomes equal to or greater than the predetermined value X.
When the port differential pressure ΔP becomes equal to or greater than the predetermined value X, the process proceeds to step S5, and a control command is sent to the variable valve mechanism 8 so that the overlap period is set to the second set value L2. That is, the overlap period is set to the second set value L2, and the process ends. Then, after a predetermined time, the flow starts from the first step S1.

If the port differential pressure ΔP is already equal to or greater than the predetermined value X at the time of the acceleration request, the process does not proceed to S4, but proceeds to S5 from the beginning, and the overlap period is set to the second set value L2. To do.
If there is no acceleration request in step S1, this process is terminated. In this case, the control device 9 sets the opening / closing timing of the intake valve 6 and / or the exhaust valve 7 according to normal control logic, and controls the variable valve mechanism 8 at the opening / closing timing.
On the other hand, when step S4 or step S5 is executed, the control device 9 does not execute normal control logic for setting the opening / closing timing of the intake valve 6 and / or the exhaust valve 7. Alternatively, the control device 9 includes the first predetermined value L1 and the second predetermined value L2 in normal control logic for setting the opening / closing timing of the intake valve 6 and / or the exhaust valve 7.

[Effects of Example 1]
The effect of Example 1 is demonstrated using FIG.6 and FIG.7.
In the intake / exhaust device 1 of the first embodiment, based on the port differential pressure ΔP, which is an average value of the differential pressure obtained by subtracting the exhaust port P2 from the intake port pressure P1, in a predetermined period ΔTa within the maximum possible period of overlap. Set the overlap period.
Therefore, instead of comparing the intake manifold pressure and the exhaust manifold pressure, the overlap period is determined by comparing the intake port pressure and the exhaust port pressure in the predetermined period ΔTa near the top dead center where the overlap period is actually set. Therefore, the scavenging effect can be fully utilized and the influence of exhaust interference can be suppressed.

FIG. 7 shows changes in the exhaust port pressure and the intake port pressure when the overlap period is set. At this time, the average value P2a of the exhaust port pressure P2 is higher than the average value P1a of the intake port pressure P1 in terms of the average value over the entire period of one cycle.
Therefore, if it is determined whether or not the scavenging effect can be obtained with the average values P1a and P2a (that is, whether or not the intake port pressure is higher than the exhaust port pressure), the scavenging effect is obtained. Therefore, it is determined that the control for increasing the overlap period is not performed.

However, when looking at the predetermined period ΔTa near the top dead center where the overlap period is actually set, it is determined that the region where the intake port pressure is higher than the exhaust port pressure is dominant, and a scavenging effect can be obtained. it can.
In this embodiment, the overlap period is determined based on the port differential pressure ΔP, which is the average value of the differential pressure obtained by pulling the exhaust port P2 from the intake port pressure P1 in a predetermined period ΔTa within the maximum possible period of the overlap period. Therefore, the scavenging effect can be fully utilized even in an area where it has been determined that the scavenging effect cannot be obtained with the average value over the entire period of one cycle.

  According to this embodiment, immediately after the acceleration request, in the period in which the port differential pressure ΔP is smaller than a predetermined value (including the period in which the exhaust port pressure P2 is greater than the intake port pressure P1), the overlap period is made smaller (first setting). Set to value L1). Thereby, exhaust interference can be suppressed. In particular, the influence of exhaust interference can be minimized by setting the first set value L1 to the minimum period Lmin of the overlap period as in this embodiment.

  When the port differential pressure ΔP becomes sufficiently large, not the exhaust interference but the scavenging effect can be obtained, so the overlap period is set to a larger value (second set value L2). Thereby, the scavenging effect can be fully utilized.

  In this embodiment, since the scavenging effect can be fully utilized, as shown in FIG. 6, the increase rate of the output torque and the intake air amount of the internal combustion engine immediately after the acceleration request is larger as compared with the conventional example. Become. For this reason, turbo lag can be reduced.

In this embodiment, the port differential pressure ΔP is calculated from the intake air amount, the engine speed, and the opening degree of the waste gate valve.
Since the port differential pressure ΔP can be calculated from the output from the sensor provided in the conventional intake / exhaust device 1 without providing a pressure sensor in each of the intake port 17 and the exhaust port 18, the cost can be reduced. .

[Example 2]
[Configuration of Example 2]
A second embodiment will be described with reference to FIGS. In the second embodiment, the same reference numerals as those in the first embodiment denote the same functional objects.
The control device 9 of the intake / exhaust device 1 according to the second embodiment includes a second set value calculation unit 50 described below.
The second set value calculation unit 50 grasps the intake air amount or intake port pressure P1 and the exhaust port pressure P2 introduced into the intake port 17, and the intake air amount or intake port pressure P1 and the exhaust port pressure P2. From the relationship, the second set value L2 is calculated.

For example, the second set value calculation unit 50 has a map as shown in FIG. 9 that shows the relationship between the second set value L2, the intake port pressure P1, and the exhaust port pressure P2.
Then, the input of the intake port pressure P1 and the exhaust port pressure P2 calculated by the port differential pressure calculation unit 40 is received, and the second set value L2 is calculated according to the intake port pressure P1 and the exhaust port pressure P2.

  In this map, at the same exhaust port pressure P2, the second set value L2 is gradually increased until the intake port pressure P1 reaches a certain value, and when it exceeds a certain value, the second set value L2 is gradually decreased. .

In the control flow by the control device 9 in this embodiment, as shown in FIG. 10, step S5a for calculating the second set value L2 is added before step S5 in the flow of the first embodiment.
For this reason, as shown in FIG. 11, after the port differential pressure ΔP becomes larger than a predetermined value, the second set value L2 varies as the intake air pressure increases and the intake port pressure P1 rises. That is, the overlap amount is changed. According to the map shown in FIG. 9, when the intake port pressure P1 rises to some extent, the second set value L2 is reduced.

[Effects of Example 2]
According to the present embodiment, it is possible to control so that the amount of intake air through which intake air passes from the intake port 17 to the exhaust port 18 does not become excessive.
If the amount of intake air through which intake air passes from the intake port 17 to the exhaust port 18 becomes excessive, the air-fuel ratio of the exhaust gas flowing into the catalyst 20 may greatly deviate from the stoichiometry, which may deteriorate emissions.
In this embodiment, it is possible to control the amount of intake air from which intake air passes through the intake port 17 to the exhaust port 18 so that the amount of intake air does not become excessive.
Note that, as the exhaust port pressure P2 is higher, the amount of intake air that escapes to the exhaust port 18 is less likely to be excessive. Therefore, the necessity for reducing the second set value L2 when the intake port pressure is high is reduced. Therefore, in the map shown in FIG. 9 of the present embodiment, the intake port pressure P1 at which the second set value starts to decrease increases as the exhaust port pressure P2 increases.

Example 3
[Configuration of Example 3]
A third embodiment will be described with reference to FIGS. In the third embodiment, the same reference numerals as those in the first embodiment denote the same functional objects.
The turbocharger 5 of the intake / exhaust device 1 according to the third embodiment is a variable capacity turbocharger having a capacity changing mechanism 52 that changes the capacity of the turbine 27.

  The capacity of the turbine 27 (hereinafter referred to as turbine capacity) is the magnitude of the flow rate of the exhaust gas flowing into the turbine 27 when the turbine drive pressure is constant when the upstream and downstream pressure difference is referred to as the turbine drive pressure. The smaller the turbine capacity, the larger the turbine output (the work amount of the turbine 27).

  The capacity changing mechanism 52 has various modes. For example, in this embodiment, there are two scroll chambers into which exhaust gas for impinging on the impeller of the turbine 27 flows, and the exhaust gas flowing into the two scroll chambers. The turbine capacity is changed into two stages, large and small, by switching the state in which the impeller is rotated using gas and the state in which the impeller is rotated using exhaust gas flowing into one scroll chamber by the variable displacement valve 53. The mode is adopted.

In this case, when the turbine driving pressure is constant, the state in which the impeller is rotated using exhaust gas flowing into both scroll chambers is more than the state in which the impeller is rotated using exhaust gas flowing into one scroll chamber. The flow rate of the exhaust gas flowing into the turbine 27 is large.
That is, a state in which the impeller is rotated using exhaust gas flowing into both scroll chambers is a state where the turbine capacity is large, and a state where the impeller is rotated using exhaust gas flowing into one scroll chamber is a state where the turbine capacity is small. State.

  The variable capacity valve 53 is a valve that opens and closes an inflow passage of exhaust gas to one of the two scroll chambers. When the valve is opened, the impeller is rotated using the exhaust gas flowing into the two scroll chambers (turbine When the valve is closed, the impeller is rotated using the exhaust gas flowing into one scroll chamber (the turbine capacity is small).

  The variable capacity valve 53 is connected to the waste gate valve 31 by a link mechanism 55 and is driven by one actuator 56. Therefore, the opening degree of the waste gate valve 31 and the open / closed state of the variable capacity valve 53 can be grasped by the output of the sensor 57 that detects the position information of the actuator 56.

The intake / exhaust device 1 includes a capacity control device that controls driving of the capacity changing mechanism 52.
In the present embodiment, the capacity control device is provided as a capacity control unit 60 provided in the control device 9. The capacity control device may be provided separately from the control device 9.

  When there is a request for acceleration of the internal combustion engine 2, the capacity control unit 60 controls the capacity of the turbine 27 to the first predetermined capacity value V1, and then the overlap amount is set to the second set value L2, and When the difference between the supercharging pressure detected by the supercharging pressure sensor 35 and the target supercharging pressure falls within a predetermined differential pressure, it increases to a second predetermined capacity value V2 larger than the first predetermined capacity value V1. The driving of the capacity changing mechanism 52 is controlled so as to be performed.

  In this embodiment, the first predetermined capacity value V1 is the turbine capacity when the variable capacity valve 53 is closed, and the second predetermined capacity value V1 is the turbine capacity when the variable capacity valve 53 is opened. It is. In the turbocharger 5 of the present embodiment, the first predetermined capacity value V1 is the turbine capacity that maximizes the turbine output.

This will be described in detail below with reference to the flowchart of FIG. 13 and the time chart of FIG.
First, if there is an acceleration request in step S11, the process proceeds to S12, and the capacity control unit 60 controls the turbine capacity to the first predetermined capacity value V1. Thereafter, the process proceeds to step S13, where the port differential pressure calculation unit 40 calculates the port differential pressure ΔP.
Note that the order of step S12 and step S13 may be reversed.

  Thereafter, the process proceeds to step S14, where the port differential pressure determination unit 41 determines whether or not the port differential pressure ΔP is equal to or greater than a predetermined value X.

  If the determination in step S14 is NO, that is, if the port differential pressure ΔP is less than the predetermined value X, the process proceeds to step S15, and a control command is sent to the variable valve mechanism 8 to set the overlap period to the first set value L1. To finish the process. Then, after a predetermined time, the flow starts from the first step S11.

In order to return to the start of the flow after setting the overlap period to the first set value L1, the processes of S11, S12, S13, S14, and S15 are repeated until the port differential pressure ΔP becomes equal to or greater than the predetermined value X.
When the port differential pressure ΔP becomes equal to or greater than the predetermined value X, the process proceeds to step S16, and a control command is sent to the variable valve mechanism 8 so that the overlap period is set to the second set value L2.

In step S17, it is determined whether or not the difference between the supercharging pressure detected by the supercharging pressure sensor 35 and the target supercharging pressure is within a predetermined differential pressure.
When the determination result is YES, the process proceeds to step S18, and the turbine capacity is increased to a second predetermined capacity value V2 that is larger than the first predetermined capacity value V1.

Note that the port differential pressure calculation unit 40 of the present embodiment calculates the port differential pressure ΔP from the intake air amount, the engine speed, the opening degree of the waste gate valve, and the turbine capacity.
The turbine capacity can be calculated from the open / closed state of the variable capacity valve 53. The port differential pressure calculation unit 40 grasps the open / close state of the variable capacity valve 53 and the opening degree of the waste gate valve from the output signal of the sensor 57 that detects the position information of the actuator 56.

[Effects of Example 3]
According to the third embodiment, the variable capacity turbocharger 5 can achieve the same effects as the first embodiment.

  In the variable capacity type turbocharger 5, when acceleration is requested, by reducing the turbine capacity, the pressure on the upstream side of the turbine 27 can be increased, and the increase in the turbine speed can be accelerated.

However, if the turbine capacity is reduced, there is a problem that the influence of exhaust interference increases.
For this reason, when controlling the turbine capacity, it is necessary to control the overlap period with higher accuracy.
Therefore, it is particularly effective for the variable capacity turbocharger 5 to perform the overlap period control using the port differential pressure ΔP.

Further, in this embodiment, control is performed to increase the turbine capacity when the difference between the supercharging pressure detected by the supercharging pressure sensor 35 and the target supercharging pressure is within a predetermined differential pressure.
According to this, it is possible to prevent overshoot by suppressing the boost pressure increasing speed.

[Modification]
In the first to third embodiments, the port differential pressure ΔP is calculated from the intake air amount or the like. However, a pressure sensor is provided in each of the intake port 17 and the exhaust port 18, and the port differential pressure ΔP is calculated from the output signal of the pressure sensor. You may ask for it.

  In the first to third embodiments, the intake manifold pressure may be used instead of using the intake air amount to calculate the port differential pressure ΔP. The intake manifold pressure may be, for example, a surge tank pressure or a pressure before branching to each cylinder downstream of the surge tank.

  In the second embodiment, the intake air amount introduced into the intake port 17 may be used instead of using the intake port pressure P1 to calculate the second set value L2.

  The capacity changing mechanism 52 of the third embodiment is not limited to the one described in the third embodiment, and is, for example, a mechanism that switches the angle and area of the intake air blown to the impeller of the turbine 27 with a variable nozzle (so-called variable nozzle turbo). May be.

1 intake / exhaust device, 2 internal combustion engine, 5 turbocharger, 6 intake valve, 7 exhaust valve, 8 variable valve mechanism, 9 control device, 17 intake port, 18 exhaust port, 27 turbine, 28 compressor, 40 port differential pressure calculation Part, 41 port differential pressure judgment part, 42 overlap period setting part

Claims (7)

The turbine (27) is rotated by the exhaust gas exhausted from the internal combustion engine (2), and the compressor (28) is rotationally driven by the rotational torque of the turbine (27), whereby the intake air is supplied to the internal combustion engine (2). Turbocharger (5),
An intake valve (6) for opening and closing the intake port (17) of the internal combustion engine;
An exhaust valve (7) for opening and closing the exhaust port (18) of the internal combustion engine;
The opening / closing timing of at least one of the intake valve (6) and the exhaust valve (7) is changed to overlap the opening period of the intake valve (6) and the opening period of the exhaust valve (7). A variable valve mechanism (8) for varying the period;
An intake / exhaust device for an internal combustion engine comprising a control device (9) for controlling the operation of the variable valve mechanism,
When the pressure of the intake port (17) is the intake port pressure P1, and the pressure of the exhaust port (18) is the exhaust port pressure P2,
The control device (9)
A port differential pressure ΔP, which is an average value of the differential pressure obtained by subtracting the exhaust port P2 from the intake port pressure P1, within a predetermined period ΔTa within the maximum possible period of the overlap period and straddling top dead center is calculated. A port differential pressure calculator (40);
A port differential pressure determination unit (41) for determining whether or not the port differential pressure ΔP is equal to or greater than a predetermined value;
When the port differential pressure determination unit (41) determines that the port differential pressure ΔP is less than the predetermined value when there is a request for acceleration of the internal combustion engine (2), the overlap period is set to An overlap period setting unit that sets the overlap period to a second set value that is larger than the first set value when it is determined that the port differential pressure ΔP is equal to or greater than the predetermined value. (42) and an intake / exhaust device for an internal combustion engine. The intake / exhaust device for an internal combustion engine according to claim 1,
The intake / exhaust device for an internal combustion engine, wherein the first set value is a minimum period that the overlap period can take. The intake / exhaust device for an internal combustion engine according to claim 1 or 2,
The control device (9)
The intake air amount introduced into the intake port (17) or the intake port pressure P1 and the exhaust port pressure P2 are grasped, and the intake air amount or the intake port pressure P1 and the exhaust port pressure P2 are determined. Therefore, the intake / exhaust device for an internal combustion engine has a second set value calculation unit (50) for calculating the second set value. The intake / exhaust device for an internal combustion engine according to any one of claims 1 to 3,
The turbocharger (5) opens and closes a bypass circuit (30) that bypasses the turbine (27) and flows exhaust gas from the upstream side of the turbine (27) to the downstream side of the turbine (27). (31)
The port differential pressure calculation unit (40) grasps the intake air amount or intake manifold pressure introduced into the intake port (17), the engine speed, and the opening degree of the waste gate valve (31). An intake / exhaust device for an internal combustion engine, wherein the port differential pressure ΔP is calculated from the relationship between the intake air amount or the intake manifold pressure, the engine speed, and the opening degree of the waste gate valve (31). . The intake / exhaust device for an internal combustion engine according to any one of claims 1 to 3,
The turbocharger (5) is a variable capacity turbocharger having a capacity changing mechanism (52) for changing the capacity of the turbine (27),
An intake / exhaust device for an internal combustion engine is
A supercharging pressure detecting means (35) for detecting the supercharging pressure;
Capacity control means (60) for controlling the drive of the capacity changing mechanism (52),
The capacity control means (60)
When there is a request for acceleration of the internal combustion engine (2), the capacity of the turbine is controlled to a predetermined capacity value, and then the overlap amount is set to the second set value, and the supercharging pressure When the difference between the supercharging pressure detected by the detecting means (35) and the target supercharging pressure is within a predetermined differential pressure, the capacity changing mechanism (in order to increase the capacity of the turbine above the predetermined capacity value) 52) controlling the driving of the internal combustion engine. The intake / exhaust device for an internal combustion engine according to claim 5,
The turbocharger (5) opens and closes a bypass circuit (30) that bypasses the turbine (27) and flows exhaust gas from the upstream side of the turbine (27) to the downstream side of the turbine (27). (31)
The port differential pressure calculation unit (40) includes an intake air amount or intake manifold pressure introduced into the intake port (17), an engine speed, an opening degree of the waste gate valve (31), and a capacity of the turbine. And the port differential pressure ΔP from the relationship between the grasped intake air amount or the intake manifold pressure, the engine speed, the opening of the wastegate valve (31), and the turbine capacity. An intake / exhaust device for an internal combustion engine, wherein The intake / exhaust device for an internal combustion engine according to claim 5 or 6,
The intake / exhaust device for an internal combustion engine, wherein the predetermined capacity value is a capacity at which a turbine output is maximized.

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