JP2007297963A - Variable intake control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable intake control device for an internal combustion engine capable of suitably inhibiting engine stall during engine low speed operation by taking an effect of pulsation of intake air into account. <P>SOLUTION: The variable intake control device for the internal combustion engine 10 is provided with a variable intake mechanism 60 varying effective intake pipe length in relation to intake pulsation of the internal combustion engine 10, and drives and controls the variable intake mechanism 60 to change effective intake pipe length according to engine rotation speed. When the device detects a risk of stall of the engine 10 during idling operation, the device drives and controls the variable intake mechanism 60 to keep effective intake pipe length longer than effective intake pipe length at a time of detection only during a period until 2 cycles of the engine 10 elapse. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable intake control device for an internal combustion engine.

  In general, air taken into the air cleaner reaches the intake port through the throttle body, surge tank, and intake manifold, and is introduced into the combustion chamber of the engine when the intake valve is opened. Here, it is known that the intake air flowing through the intake manifold is a dense wave (pulsating flow) having a portion with a coarse air density and a dense portion.

  Therefore, if the dense portion of the pulsating flow of intake air can reach the intake port when the intake valve is opened, more air can be introduced into the combustion chamber. That is, the combustion efficiency in the combustion chamber can be improved, and as a result, the output characteristics of the internal combustion engine can be improved.

  Here, it is known that the above effect can be improved by lengthening the intake pipe length when the engine rotational speed is low and shortening the intake pipe length when the engine rotational speed is high. Therefore, in order to introduce more air into the combustion chamber using intake air pulsation, it is desirable to appropriately change the intake pipe length in accordance with the engine rotational speed.

  By the way, in an internal combustion engine for a vehicle, since an auxiliary machine mounted on the vehicle, for example, an air conditioner or a power steering is driven directly or indirectly by the output of the internal combustion engine, the auxiliary machine is turned on. The load on the internal combustion engine may increase and the engine speed may decrease. For this reason, in the variable intake control device as described above, the following problems cannot be ignored when the auxiliary machine of the internal combustion engine is turned on.

  That is, since the variable intake control device is driven and controlled so as to change the intake pipe length according to the engine rotational speed, immediately after the auxiliary machine is turned on and the engine rotational speed decreases, the cycle of the intake pulsating flow Is in a state having a cycle immediately before the engine speed decreases. For this reason, there is a possibility that the pulsation of the intake air cannot be used effectively immediately after the engine rotational speed decreases. Further, if the relationship between the cycle of the opening operation of the intake valve and the cycle of the pulsating flow of the intake air is such that a rough portion of the pulsating flow reaches the intake port when the intake valve is opened, Due to the negative pressure generated in the exhaust gas, the exhaust gas in the exhaust port may be sucked back into the cylinder. As a result, the combustion efficiency in the combustion chamber decreases due to an increase in the ratio of exhaust gas remaining in the combustion chamber, and therefore engine stall may occur if the engine speed is low.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an internal combustion engine capable of suitably suppressing the occurrence of engine stall during low-speed engine operation by considering the effect of pulsation of intake air. The object is to provide a variable intake control device.

In the following, means for achieving the above object and its effects are described.
According to a first aspect of the present invention, a variable intake mechanism that varies an effective intake pipe length with respect to intake air pulsation of an internal combustion engine is provided, and the variable intake mechanism is driven and controlled to change the effective intake pipe length according to the engine rotational speed. In the variable intake control device for an internal combustion engine, when it is detected that the engine may stall during low-speed operation of the engine, the effective intake pipe length when the engine is detected only during the period until several cycles elapses is detected. The gist is to drive and control the variable intake mechanism so that the effective intake pipe length is long.

  According to this configuration, when it is detected that the engine may stall during low-speed operation of the engine, the effective intake pipe length that is longer than the effective intake pipe length when the engine is detected only during the period until several cycles elapse The variable intake mechanism is driven and controlled so that For this reason, the effective intake pipe length with respect to the intake pulsation can be increased in accordance with the decrease in the engine rotational speed when the engine rotational speed decreases during engine low speed operation and the engine may be stalled. As a result, the effective intake pipe length with respect to the intake pulsation can be made suitable for the engine speed, so that more air can be introduced into the combustion chamber and the combustion state can be stabilized. Furthermore, by improving the effect of the intake pulsation in this way, it is possible to suppress the exhaust in the exhaust port from being sucked back into the cylinder by the negative pressure generated in the intake port. Therefore, the combustion state can be further stabilized by reducing the ratio of the exhaust gas remaining in the combustion chamber.

  The variable intake mechanism is driven and controlled so that the effective intake pipe length becomes the effective intake pipe length corresponding to the engine rotational speed after several cycles of the engine have been detected since the possibility of stall occurrence has been detected. For this reason, even when the effective intake pipe length for intake pulsation is temporarily increased, deterioration of the combustion state due to a decrease in the intake pulsation effect can be suppressed thereafter.

  The effective intake pipe length with respect to the intake pulsation is a substantial length of the intake pipe through which the pulsation of the intake air propagates, and is not necessarily limited to that in which the length of the intake pipe changes.

Hereinafter, an embodiment in which the present invention is embodied in a variable intake control device for an in-vehicle internal combustion engine will be described with reference to FIGS. 1 and 2.
As shown in FIG. 1, the internal combustion engine 10 to which this variable intake control device is applied includes six cylinders # 1 to # 6. Each of the cylinders # 1 to # 3 is connected to the first intake manifold 23 via an intake port 25A formed in the internal combustion engine 10. Each of the cylinders # 4 to # 6 is connected to the second intake manifold 24 via an intake port 25B. An intake pipe 20 is connected to the first intake manifold 23 and the second intake manifold 24.

  The intake pipe 20 branches into a first distribution pipe 21 and a second distribution pipe 22 downstream of the branch portion A. The first distribution pipe 21 is connected to the cylinder # 1 to the cylinder # 3 via the first intake manifold 23 and the intake port 25A. The second distribution pipe 22 is connected to the cylinders # 4 to # 6 via the second intake manifold 24 and the intake port 25B.

  The intake pipe 20 is provided with a throttle valve 50 for adjusting the intake air intake amount upstream of the branch portion A. The throttle valve 50 is provided with a throttle valve actuator 51 for rotationally driving the throttle valve 50. The intake pipe 20 is provided with an air cleaner 40 for removing dust contained in intake air upstream of the throttle valve 50.

  Each of the cylinders # 1 to # 3 of the internal combustion engine 10 is connected to an exhaust manifold 31 via an exhaust port 32 formed in the internal combustion engine 10. An exhaust pipe 30 is connected to the exhaust manifold 31.

  The intake air that has passed through the air cleaner 40 is introduced into the combustion chamber of the internal combustion engine 10 through the intake pipe 20, the first intake manifold 23, the second intake manifold 24, and the intake ports 25A and 25B. The intake air introduced into the combustion chamber is mixed with fuel injected from a fuel injection valve provided in the internal combustion engine 10 to become an air-fuel mixture. Then, after the air-fuel mixture burns in the combustion chamber, the exhaust gas generated by the combustion is discharged from the combustion chamber to the outside through the exhaust port 32, the exhaust manifold 31, and the exhaust pipe 30.

  Here, the intake pipe 20 according to the present embodiment is provided with a variable intake mechanism 60 that makes the effective intake pipe length of the intake pipe 20 variable. The effective intake pipe length is a substantial length of the intake pipe through which the pulsation of the intake air propagates. The variable intake mechanism 60 includes a first communication pipe 61, a second communication pipe 62, a first communication control valve 63, a second communication control valve 64, and a communication control valve actuator 65. .

  The first communication pipe 61 communicates the first distribution pipe 21 and the second distribution pipe 22 in the first communication section B downstream of the branch section A. Further, the second communication pipe 62 communicates the first distribution pipe 21 and the second distribution pipe 22 in the second communication section C downstream of the first communication section B. The first communication pipe 61 is provided with a first communication control valve 63 for opening and closing the communication pipe 61. Similarly, the second communication pipe 62 is provided with a second communication control valve 64 for opening and closing the communication pipe 62. The first communication control valve 63 is drivingly connected to the communication control valve actuator 65, and the first communication control valve 63 is rotationally driven by the communication control valve actuator 65 to switch between opening and closing of the first communication pipe 61. It is done. The second communication control valve 64 is also drivingly connected to the communication control valve actuator 65, and the second communication control valve 64 is rotationally driven by the communication control valve actuator 65 to open and close the second communication pipe 62. Is switched.

  A rotation speed sensor 80 is provided on the output shaft of the internal combustion engine 10, and the rotation speed sensor 80 detects the rotation speed of the output shaft, that is, the engine rotation speed NE. Further, an accelerator sensor 81 is provided in the accelerator pedal of the vehicle, and the accelerator sensor 81 detects an accelerator pedal depression amount ACCP that is a depression amount.

  The detection signals of these sensors 80 and 81 are all taken into the electronic control unit 70 of the internal combustion engine. The electronic control device 70 includes a memory for storing and holding various control programs, calculation maps, data calculated when the control is executed, and the like. Further, the electronic control unit 70 controls various devices such as the throttle valve actuator 51 and the communication control valve actuator 65 based on detection signals from the sensors 80 and 81 and the like.

  Here, in the variable intake mechanism 60 in the present embodiment, the first communication control valve 63 and the second communication control valve 64 are brought into the following three states (a) to (c) by the communication control valve actuator 65. Driven.

(A) A state in which the first communication control valve 63 closes the first communication pipe 61 and a second communication control valve 64 also closes the second communication pipe 62. (b) The first communication control valve 63. Opens the first communication pipe 61, and the second communication control valve 64 closes the second communication pipe 62. (c) The first communication control valve 63 opens the first communication pipe 61. The second communication control valve 64 also opens the second communication pipe 62. The effective intake pipe length of the intake pipe 20 in the states (a) to (c) is as follows.

In the case of (a), the effective intake pipe length of the intake pipe 20 is the longest because it extends from the branch portion A to each cylinder # 1 to cylinder # 6.
In the case of (b), the effective intake pipe length of the intake pipe 20 is from the first communication part B to each cylinder # 1 to cylinder # 6, and therefore has an intermediate length.

In the case of (c), the effective intake pipe length of the intake pipe 20 is from the second communication portion C to each cylinder # 1 to cylinder # 6, and therefore becomes the shortest.
As described above, the effective intake pipe length of the intake pipe 20 can be changed in three ways by the variable intake mechanism 60 according to the present embodiment.

  Hereinafter, the variable intake control of the intake pipe 20 performed in such a variable intake control apparatus for an on-vehicle internal combustion engine will be described with reference to FIG. The series of processing shown in the flowchart of FIG. 2 is repeatedly executed by the electronic control device 70 with a predetermined period. Further, as an initial process of this flowchart, the count value CINIT is set to “0”.

As shown in FIG. 2, in this series of processing, first, the engine speed NE and the accelerator pedal depression amount ACCP are read based on the detection signals of the sensors 80 and 81 (S100).
Subsequent to S100, it is determined whether or not the internal combustion engine is in an idle operation state (S101). Specifically, it is determined that the engine is in the idling state based on the fact that the engine rotational speed NE is equal to or lower than the predetermined rotational speed NE1 and the accelerator pedal depression amount ACCP is equal to or smaller than the predetermined depression amount ACCP1.

  If it is determined through this determination process that the engine is in the idling state (S101: YES), an engine speed change amount ΔNE is calculated (S102). Specifically, the engine rotational speed change amount ΔNE is calculated from the deviation between the previous engine rotational speed value NEF and the engine rotational speed NE.

  Following this S102, it is determined whether there is a possibility of engine stall (S103). Specifically, it is determined that there is a possibility of engine stall when the engine rotational speed NE is equal to or lower than a predetermined rotational speed NE2 and the engine rotational speed change amount ΔNE is equal to or greater than a predetermined change amount ΔNE1. This determination result is maintained until the count value CINIT is set to “0” in S111. The predetermined rotational speed NE2 and the predetermined change amount ΔNE1 are set to appropriate values that can be used to determine whether there is a possibility of engine stall.

  If it is determined through this determination processing that there is a possibility of engine stall (S103: YES), it is determined whether or not the count value CINIT is smaller than the predetermined count value CINITK (S104). Here, the electronic control unit 70 stores a function map that defines the relationship between the predetermined count value CINITK and the engine speed NE. The electronic control unit 70 refers to the function map and sets the predetermined count value CINITK. calculate. More specifically, the predetermined count value CINITK is executed during this period T when the period until the engine passes two cycles when the internal combustion engine is at the engine rotational speed NE is defined as the period T. This is the number of times expected to be done. One cycle of the engine refers to a period in which the intake stroke, the compression stroke, the combustion stroke, and the exhaust stroke are completed.

  When it is determined that the count value CINIT is equal to or smaller than the predetermined count value CINITK through this determination process (S104: YES), the effective intake pipe length of the intake pipe 20 is set to be the longest (S105). Specifically, the first communication control valve 63 is driven by the communication control valve actuator 65 so as to close the first communication pipe 61 and the second communication pipe 62 is closed so as to close the second communication pipe 62. The control valve 64 is driven.

Following S105, the count value CINIT is incremented (S106).
On the other hand, when it is determined that the engine is not idling (S101: NO) and when it is determined that there is no possibility of engine stall (S103: NO), it is determined whether the engine is operating at high speed. (S108). Further, when it is determined that the count value CINIT exceeds the predetermined count value CINITK (S104: NO), it is also determined whether or not the engine is operating at high speed (S108). Specifically, it is determined that the engine is operating at high speed based on the engine speed NE being greater than or equal to a predetermined speed NE3. The predetermined rotational speed NE3 is set to an appropriate value that can be determined when it is determined whether or not the engine is in a high speed operation state.

  If it is determined through this determination processing that the engine is in a high speed operation state (S108: YES), the effective intake pipe length of the intake pipe 20 is set to the shortest (S109). Specifically, the first communication control valve 63 is driven so as to open the first communication pipe 61 and the second communication pipe 62 is opened so as to open the second communication pipe 62 by the communication control valve actuator 65. The control valve 64 is driven.

  When it is determined that the engine is not in a high speed operation state (S108: NO), that is, when the engine is in a low speed operation state or a medium speed operation state, the effective intake pipe length of the intake pipe 20 is set to a medium length. (S110). Specifically, the first communication control valve 63 is driven by the communication control valve actuator 65 so as to open the first communication pipe 61, and the second communication pipe 62 is closed so as to close the second communication pipe 62. The communication control valve 64 is driven. Note that the effective intake pipe length of the intake pipe 20 is set to a medium length even when the engine is in an idle operation state and there is no fear of engine stall.

  Subsequent to S109 and S110, the count value CINIT is set to “0” (S111). Further, when it is determined that the count value CINIT exceeds the predetermined count value CINITK (S104: NO), the count value CINIT is set to “0” (S111).

Subsequently to S106 and S111, the current engine speed NE is stored as the previous value NEF in preparation for the next process (S107), and this series of processes is temporarily terminated.
As described above in detail, according to the present embodiment, the following effects can be obtained.

 (1) When it is detected that the engine 10 may stall during idle operation, the effective intake pipe length becomes longer than the effective intake pipe length when the engine 10 is detected only for a period until two cycles elapse. Thus, the variable intake mechanism 60 is driven and controlled. For this reason, when there is a possibility that the engine rotation speed NE decreases and the engine 10 stalls during idling, the effective intake pipe length for the intake pulsation can be increased as the engine rotation speed NE decreases. As a result, the effective intake pipe length with respect to the intake pulsation can be made suitable for the engine rotational speed NE, so that more air is introduced into the combustion chambers of the cylinders # 1 to # 6 to change the combustion state. It can be stabilized. Further, by improving the effect of the intake pulsation in this way, the exhaust in the exhaust port 32 is sucked back into the cylinders # 1 to # 6 by the negative pressure generated in the intake ports 25A and 25B. Can be suppressed. Accordingly, the combustion state can be further stabilized by reducing the ratio of the exhaust gas remaining in the combustion chambers of the cylinders # 1 to # 6.

  Then, after two cycles have elapsed since the possibility of the occurrence of a stall has been detected, the variable intake mechanism 60 is driven and controlled so that the effective intake pipe length becomes an effective intake pipe length corresponding to the engine rotational speed NE. For this reason, even when the effective intake pipe length for intake pulsation is temporarily increased, deterioration of the combustion state due to a decrease in the intake pulsation effect can be suppressed thereafter.

In addition, the said embodiment can also be implemented with the following forms which changed this suitably.
In the above embodiment, the control for driving the variable intake mechanism 60 is executed only for a period until two cycles of the engine so that the effective intake pipe length of the intake pipe 20 is the longest, but such control is performed. You may perform only the period until about 1 to 5 cycles elapses.

  In the above embodiment, whether or not there is a possibility of engine stall is determined based on the engine rotational speed NE and the engine rotational speed change amount ΔNE, but it is determined based only on the engine rotational speed NE. May be.

  In the above embodiment, the variable intake control for preventing the engine stall is performed when the engine is in the idling operation state. However, the variable intake control may be performed when the engine is in the engine low speed operation state. Specifically, in S101 of FIG. 2, the predetermined rotational speed NE1 is set to a value larger than the idle rotational speed, and the condition that the accelerator pedal depression amount ACCP is equal to or smaller than the predetermined depression amount ACCP1 may be omitted.

  In the above embodiment, the effective intake pipe length of the intake pipe 20 is changed to the shortest effective intake pipe length that can be set by the variable intake mechanism 60 when it is detected that the engine may stall during idle operation. It was. The target effective intake pipe length of the intake pipe 20 at the time of detection may be changed to an effective intake pipe length longer than the effective intake pipe length at the time of detection, and the variable intake mechanism 60 needs to be set to the shortest. Absent. Further, as the variable intake mechanism, a variable intake mechanism that can change the effective intake pipe length of the intake pipe 20 in two stages or four or more stages may be adopted.

  The configuration of the variable intake mechanism may be a configuration other than the variable intake mechanism 60, for example, a configuration in which the effective intake pipe length is changed by providing a bypass in the intake pipe or the intake manifold.

The schematic diagram which shows the outline about one Embodiment of the variable intake control apparatus concerning this invention. The flowchart which shows the process sequence at the time of performing the variable intake control in the control apparatus of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 20 ... Intake pipe, 21 ... 1st distribution pipe, 22 ... 2nd distribution pipe, 23 ... 1st intake manifold, 24 ... 2nd intake manifold, 25A, 25B ... Intake port, 30 DESCRIPTION OF SYMBOLS ... Exhaust pipe, 31 ... Exhaust manifold, 32 ... Exhaust port, 40 ... Air cleaner, 50 ... Throttle valve, 51 ... Throttle valve actuator, 60 ... Variable intake mechanism, 61 ... First communication pipe, 62 ... Second communication pipe , 63: first communication control valve, 64: second communication control valve, 65: communication control valve actuator, 70: electronic control device, 80: rotational speed sensor, 81: accelerator sensor.

Claims (1)

In a variable intake control device for an internal combustion engine that includes a variable intake mechanism that varies an effective intake pipe length with respect to intake air pulsation of the internal combustion engine, and that drives and controls the variable intake mechanism to change the effective intake pipe length in accordance with the engine rotation speed,
When it is detected that the engine may stall during low-speed operation of the engine, the effective intake pipe length is longer than the effective intake pipe length when the engine is detected only during the period until several cycles elapse. A variable intake control device for an internal combustion engine, wherein the variable intake mechanism is driven and controlled.

Images