JP2015209777A - Control device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a back flow of exhaust gas from an exhaust passage to an intake passage while securing the effect of decompression when an internal combustion engine is stopped.SOLUTION: A control device for an internal combustion engine includes: a decompression device 50 for communicating an in-cylinder combustion chamber 12 with an exhaust passage 8 to release an in-cylinder pressure at least during a compression stroke; a throttle valve 18; acquiring units 31, 20 for acquiring a pressure in an intake passage on the downstream side of the throttle valve, and a control unit 20 for controlling the decompression device and the throttle valve. After starting the stopping operation of the internal combustion engine, the control unit controls the throttle valve so that opening of the throttle valve becomes a predetermined opening larger than a predetermined minimum opening, and then when the acquired pressure in the intake passage becomes higher than a predetermined pressure, the control unit operates the decompression device so that the in-cylinder combustion chamber can be made to always communicate with the exhaust passage.

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly to a control device for an internal combustion engine provided with a decompression device for releasing in-cylinder compression pressure.

  An internal combustion engine having a decompression device (or a decompression device) that communicates an in-cylinder combustion chamber with an exhaust passage in order to release in-cylinder pressure at least during a compression stroke is known. Such a decompression device is used for the purpose of suppressing vibration noise and rotation fluctuation of the internal combustion engine when the internal combustion engine is stopped or started, and reduces the compression load and thus the load of the starting motor when starting the internal combustion engine, thereby reducing battery power consumption. It is used for the purpose of suppressing etc. The decompression device normally includes a valve for selectively bringing the in-cylinder combustion chamber and the exhaust passage into a communication state (open) or a non-communication state (close).

JP 2008-215224 A

  By the way, in order to suppress vibration noise and rotational fluctuation when the internal combustion engine is stopped, the decompression device may be opened to always connect the in-cylinder combustion chamber to the exhaust passage.

  However, when this is done, both the intake valve and the valve of the decompression device are open in the intake stroke. At this time, the exhaust passage is almost at atmospheric pressure, whereas the intake passage is at a pressure lower than atmospheric pressure, so the exhaust gas may flow backward from the exhaust passage to the intake passage.

  If this reverse flow occurs, the injector injection hole clogging may occur due to deposits or condensed water in the intake passage, or when the internal combustion engine is restarted, the amount of fresh air is insufficient and the start-up time is delayed due to deterioration of combustion, the start feeling is deteriorated, the start There is a problem that energy increases and fuel consumption deteriorates.

  As a technique for preventing this reverse flow, Patent Document 1 prohibits the overlap between the intake valve and the exhaust valve until the pressure difference between the intake passage pressure and the exhaust passage pressure becomes smaller than a predetermined value. It is disclosed.

  However, since the device of Patent Document 1 does not have a decompression device, the cylinder pressure during the compression stroke is not released during the overlap prohibition period, that is, decompression cannot be performed, and vibration noise and rotation fluctuation suppression when the internal combustion engine is stopped There is a drawback that the original effect of decompression cannot be obtained.

  Accordingly, the present invention has been made in view of the above circumstances, and an object of the present invention is to control an internal combustion engine that can suppress the backflow of exhaust gas from the exhaust passage to the intake passage while ensuring the decompression effect when the internal combustion engine is stopped. To provide an apparatus.

According to one aspect of the invention,
A decompression device for communicating the in-cylinder combustion chamber with the exhaust passage in order to release the in-cylinder pressure at least during the compression stroke;
A throttle valve provided in the intake passage;
An acquisition unit configured to acquire a pressure in the intake passage downstream of the throttle valve;
A control unit configured to control the decompression device and the throttle valve;
With
The control unit controls the throttle valve so that the opening degree of the throttle valve becomes a predetermined opening degree larger than a predetermined minimum opening degree after the stop operation of the internal combustion engine is started, and then acquired by the acquisition unit. When the pressure in the intake passage becomes higher than a predetermined pressure, the decompression device is operated so that the in-cylinder combustion chamber is always in communication with the exhaust passage. .

  According to the present invention, an excellent effect is exhibited in that the backflow of exhaust gas from the exhaust passage to the intake passage can be suppressed while ensuring the decompression effect when the internal combustion engine is stopped.

1 is a schematic diagram illustrating an overall configuration of a control device for an internal combustion engine according to an embodiment of the present invention. It is the schematic which shows the structure of an internal combustion engine and its control apparatus. It is an expanded front sectional view of a decompression device. It is an expanded side sectional view of a decompression device. It is a time chart which shows the change of the lift amount of an intake valve and an exhaust valve, the intake flow rate, and the exhaust flow rate at the time of non-operation of a decompression device. It is a time chart which shows the change of the lift amount of an intake valve and an exhaust valve, the intake air flow rate, and the exhaust gas flow rate at the time of operation of a decompression device. It is a time chart for demonstrating the engine stop control of this embodiment. It is a flowchart which shows the routine of engine stop control. It is an expanded front sectional view showing a modification of a decompression device. It is an expanded side sectional view which shows the modification of a decompression apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 schematically shows an overall configuration of a control device for an internal combustion engine according to the present embodiment. An internal combustion engine (engine) 1 according to the present embodiment is mounted on a vehicle, and in particular, is mounted on a hybrid vehicle including two power sources, an engine 1 and a motor generator. The hybrid vehicle is provided with an electronic control unit (hereinafter referred to as ECU) 20 as a control unit configured to control the vehicle and the engine.

  Two motor generators including a first motor generator MG1 and a second motor generator MG2 are provided. The first motor generator MG1 is mainly used for starting the engine, and the second motor generator MG2 is mainly used as a power source for running the vehicle.

  The ECU 20 includes a power management ECU 20A for controlling the first and second motor generators MG1, MG2 and an engine ECU 20B for controlling the engine 1 so as to communicate with each other. However, the ECUs may be integrated without being separated as described above.

  The engine 1 of this embodiment is configured as a multi-cylinder (for example, in-line four-cylinder) spark ignition internal combustion engine. However, the type of engine, the number of cylinders, the cylinder arrangement type (in-line, V-type, horizontally opposed, etc.), the ignition method, etc. are not particularly limited. For example, the engine may be a compression ignition type internal combustion engine (diesel engine).

  FIG. 2 shows the configuration of the engine 1 and its control device. A piston 3 is accommodated in a cylinder (cylinder) 2 a formed in a cylinder block 2 of the engine 1 so as to be able to reciprocate. A crankshaft 4 is connected to the piston 3. The cylinder head 5 of the engine 1 is provided with two intake valves 7 for opening and closing the intake port 6 and two exhaust valves 9 for opening and closing the exhaust port 8 for each cylinder. Each intake valve 7 and each exhaust valve 9 are driven to open and close by a valve operating mechanism including camshafts 10 and 11. A spark plug 13 for igniting the air-fuel mixture in the in-cylinder combustion chamber 12 is attached to the top of the cylinder head 5 for each cylinder. A variable valve mechanism (for example, a variable valve timing mechanism) for changing the opening characteristic of at least one of the intake valve 7 and the exhaust valve 9 may be provided.

  The intake port 6 of each cylinder is connected to a surge tank 15 that is an intake manifold through an intake manifold or branch pipe 14 for each cylinder. An intake pipe 16 is connected to the upstream side of the surge tank 15, and an air cleaner (not shown) is provided at the upstream end of the intake pipe 16. An air flow meter 17 for detecting the intake air amount and an electronically controlled throttle valve 18 are incorporated in the intake pipe 16 in order from the upstream side. An intake passage is formed by the intake port 6, the branch pipe 14, the surge tank 15, and the intake pipe 16. An injector 19 for injecting fuel into the intake passage, particularly the intake port 6 is provided for each cylinder.

  An exhaust manifold and an exhaust pipe (not shown) are connected to the exhaust port 8 of each cylinder, and a catalyst composed of a three-way catalyst is installed in the exhaust pipe. Upstream and downstream air-fuel ratio sensors for detecting the air-fuel ratio of exhaust gas are installed upstream and downstream of the catalyst. The ECU 20 executes air-fuel ratio feedback control for controlling each air-fuel ratio to stoichiometric (theoretical air-fuel ratio) based on the outputs of these air-fuel ratio sensors.

  Regarding the sensors, in addition to the air flow meter 17 and the upstream and downstream air-fuel ratio sensors described above, a crank angle sensor 35 for detecting the crank angle of the engine 1, an accelerator opening sensor 36 for detecting the accelerator opening, A water temperature sensor 37 for detecting the coolant temperature of the engine 1 is electrically connected to the ECU 20. In addition, a power switch 39 for making engine 1 and first and second motor generators MG1, MG2 operable (ON) or stopped (OFF) is electrically connected to ECU 20. The ECU 20 controls the spark plug 13, the throttle valve 18, the injector 6, the first and second motor generators MG1, MG2 based on the detection values of these sensors. The ignition timing, fuel injection amount, fuel injection timing, throttle opening, motor generator output, and the like are controlled. As shown in FIG. 1, the accelerator opening sensor 36 is connected to the power management ECU 20A.

  Further, an intake pressure sensor 31 for detecting the pressure (intake pressure) in the intake passage on the downstream side of the throttle valve 18 is provided. In the present embodiment, the intake pressure sensor 31 is installed in the surge tank 15 so as to detect the intake pressure in the surge tank 15. However, the installation position is arbitrary as long as it is downstream of the throttle valve 18. The intake pressure sensor 31 is electrically connected to the ECU 20 and outputs a signal corresponding to the detected intake pressure value to the ECU 20.

  As described above, in the present embodiment, the intake pressure is directly detected by the intake pressure sensor 31 and the ECU 20, but this may be estimated by the ECU 20. The estimation method is arbitrary, and a known method can also be adopted. These detection and estimation are collectively called acquisition. When the intake pressure is detected, the intake pressure sensor 31 and the ECU 20 constitute an acquisition unit that acquires the intake pressure downstream of the throttle valve 18, and when the intake pressure is estimated, the ECU 20 constitutes the acquisition unit.

  In addition, in the engine 1 of the present embodiment, a decompression device (or a decompression device) 50 that communicates the in-cylinder combustion chamber 12 with the exhaust passage (exhaust port 8) in order to release the in-cylinder pressure at least during the compression stroke of the engine. Is provided.

  Hereinafter, the decompression device 50 will be described with reference to FIGS. 3 and 4. The decompression device 50 of the present embodiment is configured to release at least the in-cylinder pressure, that is, the compression pressure during the compression stroke, by lifting (opening) the exhaust valve 9 of the engine 1 by a certain amount. Therefore, the decompression device 50 according to the present embodiment includes the exhaust valve 9 as a component thereof, but a separate and dedicated decompression device may be provided without using the exhaust valve 9 in this way. The exhaust valve 9 forms a decompression valve as a component of the decompression device 50.

  As shown in the figure, the cylinder head 5 includes an exhaust camshaft 11, an exhaust valve spring 51, a rocker arm 52, and a hydraulic lash adjuster (hereinafter referred to as “HLA”) 53 as components of a valve operating mechanism for the exhaust valve 9. Provided. The exhaust valve spring 51, the rocker arm 52, and the HLA 53 are provided for each exhaust valve 9. The valve operating mechanism for the intake valve 7 is configured in the same manner. The exhaust camshaft 11 drives the exhaust valve 9 urged in the closing direction by the exhaust valve spring 51 through the rocker arm 52 to move up and down (open and close). As is well known, the HLA 53 operates to eliminate the clearance between the exhaust camshaft 11 and the rocker arm 52 at all times. The HLA 53 includes an HLA main body 53A and a plunger 53B that protrudes upward from the HLA main body 53A and can move up and down in the HLA main body 53A. A roller arm may be interposed between the exhaust camshaft 11 and the rocker arm 52. In this case, the HLA 53 operates so as to always eliminate the clearance between the roller arm and the rocker arm 52.

  The exhaust camshaft 11, the exhaust valve spring 51, the rocker arm 52, and the HLA 53 constitute constituent elements of the decompression device 50. In addition to these, the decompression device 50 is inserted into the plurality of bottomed cylindrical HLA holders 54 that are fixed to the cylinder head 5 and accommodate the HLA 52 so as to be able to be moved up and down, and all the HLA holders 54 are located at the bottom of each HLA 53. A single slider 55 extended in the cylinder row direction (that is, the crankshaft axial direction), a plurality of HLA lifters 56 disposed in the gap between the cam surface 55A of the slider 55 and the HLA 53, and the slider 55 in the cylinder row direction And an electric decompression actuator 57 for slidably moving. The decompression actuator 57 is electrically connected to the ECU 20 (in particular, the engine ECU 20B, see FIG. 1) and is controlled by the ECU 20. An on / off signal and a signal indicating the target displacement amount of the decompression actuator 57 are sent from the ECU 20 to the decompression actuator 57, and a signal showing the actual displacement amount of the decompression actuator 57 is sent from the decompression actuator 57 to the ECU 20.

  When the decompression device 50 is operated, the decompression actuator 57 is turned on, and the decompression actuator 57 is displaced by an amount equal to the target displacement amount, so that the slider 55 is moved to the left side from the stop position shown in FIG. Slide to. Then, the cam surface 55 </ b> A of the slider 55 lifts the HLA 53 upward via the HLA lifter 56. As a result, the rocker arm 52 rotates and lifts the exhaust valve 9 in the opening direction (downward). Such an operation is performed simultaneously for each exhaust valve 9. As a result, the same effect as the enlargement of the base circle of the exhaust camshaft 11 can be obtained, and each exhaust valve 9 is not fully closed, but is lifted at least by a minute amount much smaller than the lift amount when fully opened.

  The HLA 53 is extended to eliminate the clearance between the exhaust camshaft 11 and the rocker arm 52 when hydraulic pressure is supplied from the oil pump during engine operation, but is contracted when hydraulic pressure is not supplied when the engine is stopped. become. For example, it is assumed that the amount of contraction from the extended state to the contracted state is about 1.5 mm. For example, if the lift amount of the cam surface 55A (equal to the lift amount of the HLA lifter 56) when the slider 55 is moved from the stop position to the operating position is set to 2.3 mm, the decompression device 50 is operated when the engine is stopped. Then, the HLA 53 subtracts the contraction and lifts 0.8 mm (2.3-1.5 = 0.8). For example, when the lever ratio of the rocker arm 52 is about 1.5: 1, the lift amount Ld of the exhaust valve 9 due to the operation of the decompression device 50 is about 0.5 mm. Hereinafter, this lift amount Ld is referred to as a decompression lift amount.

  Here, when the engine is stopped etc., the hydraulic pressure supply from the oil pump is insufficient or not at all, and the engine speed is also low, so the decompression actuator 57 is not hydraulic, considering the certainty of operation. Electric type is used. In addition, the decompression device 50 of the present embodiment is configured using the components of the exhaust valve and the valve operating mechanism, which is very advantageous for cost reduction.

  5 and 6 show changes in the lift amount ((A) diagram) of the intake valve 7 and the exhaust valve 9 and the intake flow rate and exhaust flow rate ((B) diagram) in a specific cylinder. FIG. 5 shows when the decompression device 50 is not in operation, and FIG. 6 shows when the decompression device 50 is in operation. In FIG. 5B, the intake flow rate is positive in the direction flowing into the in-cylinder combustion chamber 12, and the exhaust flow rate is positive in the direction flowing out from the in-cylinder combustion chamber 12. 5 and 6 show data when the engine is motored at 1000 rpm.

  As can be seen from FIG. 6, even when the exhaust valve 9 is always open when the decompression device 50 is in operation and closed when the decompression device 50 is not in operation (see FIG. 5), the exhaust valve 9 has a predetermined decompression lift. Lifted by an amount Ld. Thus, the in-cylinder combustion chamber 12 is always in communication with the exhaust passage (particularly the exhaust port 8). The decompression amount Ld defines the minimum lift amount of the exhaust valve 9 when the decompression device 50 is operated.

  By the way, the decompression device 50 of this embodiment is operated in order to suppress vibration noise and rotational fluctuation when the engine is stopped.

  However, when the decompression device 50 is operated, the pressure in the exhaust passage is almost atmospheric pressure, whereas the pressure in the intake passage on the downstream side of the throttle valve is lower than atmospheric pressure (that is, negative pressure). During the open period, exhaust gas may pass through the in-cylinder combustion chamber 12 from the exhaust passage and backflow into the intake passage.

  If this reverse flow occurs, the injector injection hole clogging may occur due to deposits or condensed water in the intake passage, or when the engine is restarted, the amount of fresh air is insufficient and the start-up time is delayed due to combustion deterioration, start-up feeling deterioration, start-up energy There is a problem that the fuel consumption increases and the fuel consumption deteriorates.

  On the other hand, Patent Document 1 discloses a device that prohibits the overlap between the intake valve and the exhaust valve until the pressure difference between the pressure in the intake passage and the pressure in the exhaust passage becomes smaller than a predetermined value. However, since this device does not have a decompression device, the in-cylinder pressure during the compression stroke is released during the overlap prohibition period, that is, decompression cannot be performed, and the decompression effect of suppressing vibration noise and rotation fluctuation when the engine is stopped is obtained. There are disadvantages that cannot be achieved.

  Thus, in the present embodiment, the ECU 20 executes engine stop control as described below in order to suppress the backflow of exhaust gas from the exhaust passage to the intake passage while ensuring the decompression effect when the engine is stopped.

  In FIG. 7, the time chart for demonstrating the basic example of the engine stop control of this embodiment is shown. (A) is the accelerator opening (detected value of the accelerator opening sensor 36), (B) is the state of the first stop flag that is an engine stop flag in the power management ECU (power management ECU) 20A, and (C) is in the engine ECU 20B. The state of the second stop flag that is an engine stop flag, (D) is the detected value of the engine speed (rpm) calculated based on the output of the crank angle sensor 35, and (E) is the state of the engine stop end flag in the engine ECU 20B. , (F) is the state of the fuel injection prohibition flag in the engine ECU 20B, (G) is the throttle opening (the detected value of the throttle opening sensor provided in the throttle valve 18), which is the opening of the throttle valve 18, and (H). Is the intake pressure (indicated by the detected value of the intake pressure sensor 31, absolute pressure), and (I) is the engine ECU 20 Decompression execution flag state, the (J) is the displacement amount of the decompression actuator 57 in, respectively.

  The illustrated example shows an example in which control (idle stop control) for automatically stopping the engine when the vehicle is temporarily stopped is executed. However, the present invention is not limited to this example, and the engine stop control of the present embodiment can be applied, for example, when the engine is stopped normally (for example, when the engine is stopped when the power switch 39 is turned off) or when the engine is stopped when the deceleration fuel cut is executed. is there. When the engine is automatically stopped by executing the idle stop control, a control for automatically starting the engine at the time of starting or accelerating the vehicle is also executed.

  Here, “the engine is stopped” refers to a state in which fuel supply to the engine and ignition are stopped, the crankshaft is not rotationally driven by fuel combustion, and the engine is not generating power. It has nothing to do with whether the crankshaft is rotating. On the other hand, “the engine is operating” refers to a state in which fuel is supplied to the engine and ignition is performed, the crankshaft is rotationally driven by the combustion of the fuel, and the engine is generating power.

  In the illustrated example, the first stop flag in the power management ECU 20A is turned on at time t1 when the accelerator opening is reduced to zero (fully closed state). Substantially simultaneously with this flag on, the second stop flag and the fuel injection prohibition flag in the engine ECU 20B are turned on.

  At time t1 when the second stop flag is turned on, the engine stop operation is started. The second stop flag is turned on when a predetermined stop condition is satisfied. The stop condition is, for example, the vehicle speed is zero, the first stop flag is on (that is, the accelerator opening is zero), the engine speed is equal to or lower than a predetermined speed, and the engine coolant temperature is equal to or higher than a predetermined temperature. This is established when all the conditions that the catalyst temperature is equal to or higher than the predetermined temperature and the remaining battery level is equal to or higher than the predetermined value are satisfied. The vehicle speed is detected by a vehicle speed sensor (not shown), the engine speed is calculated based on the detected value of the crank angle sensor 35, the engine cooling water temperature is detected by the water temperature sensor 37, and the catalyst temperature and the remaining battery level are estimated by the ECU 20. Or detected by a sensor or the like.

  When the fuel injection prohibition flag is turned on, fuel injection by the injector 19 is prohibited or stopped, and ignition by the spark plug 13 is also prohibited or stopped. Thereafter, the engine speed gradually decreases and becomes zero at time t3. When the engine speed reaches zero, the engine stop end flag is turned on. It should be noted that the engine speed at the start of the stop operation (time t1) and immediately before in the illustrated example is approximately the idle speed Ni (for example, 1000 rpm).

  The throttle opening is decreased in conjunction with the accelerator opening in a period before time t1, and reaches the opening during idling, that is, the idle opening TH2 at time t1. On the other hand, when the stop operation is started at time t1, the throttle opening becomes a predetermined opening larger than the idle opening TH2, that is, a predetermined decompression opening TH3, as indicated by a solid line a in (G). Will be increased. The throttle opening is maintained at the decompression opening TH3 until the engine speed becomes zero.

  The decompression opening TH3 is larger than the idle opening TH2 and larger than a predetermined minimum opening TH1. The minimum opening TH1 has a character as a guard value that ensures the minimum passage of intake air. The idle opening TH2 is slightly larger than the minimum opening TH1 (TH1 <TH2 <TH3). For example, the minimum opening TH1 is about 5 °, the idle opening TH2 is about 6 °, and the decompression opening TH3 is about 10 °.

  When the throttle opening is controlled to the decompression opening TH3 in this way, inflow of fresh air into the surge tank 15 through the throttle valve 18 is promoted compared to a comparative example described later. As indicated by a solid line b in (H), the intake pressure rises from the intake pressure Pi during idle (for example, 40 kPa) toward the atmospheric pressure Pa (for example, 100 kPa) at a relatively high speed. In other words, the negative pressure in the surge tank 15 decreases at a relatively fast rate.

  Then, when the intake pressure becomes higher than a predetermined pressure, that is, a predetermined decompression start pressure Ps (for example, 70 kPa) during the increase process (t2), the decompression execution flag is turned on and the decompression device 50 is activated. Along with this, the displacement amount of the decompression actuator 57 is increased in the direction of lifting (opening) the exhaust valve 9.

  Thereafter, when the engine stop end flag is turned on (t3), the engine stop operation is ended. The throttle opening is reduced to the minimum opening TH1, the decompression execution flag is turned off, and the decompression device 50 is stopped. Accordingly, the displacement amount of the decompression actuator 57 is gradually returned toward zero.

  The engine stop control of this embodiment will be described in comparison with a comparative example. In the comparative example, as indicated by a broken line c in (G), the throttle opening is maintained at the minimum opening TH1 during the stop operation (t1 to t3). The reason is that the amount of air flowing into the in-cylinder combustion chamber 12 is reduced as much as possible, and the in-cylinder pressure is reduced to suppress vibration when the engine is stopped.

  Then, as indicated by a broken line d in (H), the rate of increase of the intake pressure is significantly reduced, and the negative pressure in the intake passage on the downstream side of the throttle valve does not readily decrease. In the comparative example, the negative pressure in the intake passage tends to be larger than in the present embodiment.

  Under such circumstances, if the decompression device is operated, for example, at the same timing t2 as in the present embodiment, a larger amount of exhaust gas than in the present embodiment flows backward into the intake passage, resulting in the above-described backflow of exhaust gas. Various problems become noticeable.

  As can be seen from the above description, in the present embodiment, after starting the engine stop operation, the ECU 20 first sets the throttle valve opening to the decompression opening TH3 larger than the minimum opening TH1 and the idle opening TH2. After the throttle valve is controlled, when the intake pressure detected by the intake pressure sensor 31 becomes higher than the decompression start pressure Ps, the decompression device 50 is operated so that the in-cylinder combustion chamber 12 is always in communication with the exhaust passage.

  Before the operation of the decompression device 50, the intake pressure is increased in advance at a relatively fast speed, and the decompression device 50 is actuated when the intake pressure is sufficiently increased. Therefore, the pressure difference between the intake passage internal pressure and the exhaust passage internal pressure is reduced. The decompression device 50 can be operated after it is sufficiently reduced. Therefore, the backflow of the exhaust gas due to the operation of the decompression device 50 can be effectively suppressed, and various problems resulting from the backflow can also be suppressed.

  Moreover, since the decompression device 50 is activated when the intake pressure becomes higher than the decompression start pressure Ps, it is possible to ensure the decompression effect of suppressing vibration noise and rotational fluctuation when the engine is stopped.

  As can be seen from the above description, the decompression opening TH3 is set to the minimum opening without sacrificing the vibration suppression effect when the engine is stopped, which is obtained when the throttle opening is set to the minimum opening TH1. The optimum value is set so that the rate of increase of the intake pressure can be increased more than when the degree TH1 is set.

  Incidentally, with respect to the basic example shown in FIG.

  As a first modification, it is conceivable that the throttle opening is controlled to the minimum opening TH1 within a predetermined time from the engine stop operation start time t1, and the throttle opening is controlled to the decompression opening TH3 after the predetermined time has elapsed. . That is, the throttle opening is controlled to the decompression opening TH3 after the engine stop operation start t1. However, the predetermined time is set to a relatively short time so that the intake pressure becomes higher than the decompression start pressure Ps after the throttle opening is controlled to the decompression opening TH3.

  According to this, during the period from the start of the engine stop operation until the intake pressure becomes higher than the decompression start pressure Ps, and while the throttle opening is initially controlled to the minimum opening TH1, the in-cylinder combustion chamber 12 It is possible to obtain an effect of suppressing vibration by reducing the amount of air flowing into the. Further, while the throttle opening is controlled to the decompression opening TH3 in the latter period, an effect of suppressing the backflow of the exhaust gas by increasing the rising speed of the intake pressure can be obtained.

  As a second modification, it is conceivable to change the condition for turning on the decompression execution flag, that is, the operating condition of the decompression device 50 as follows. In the basic example, the operating condition of the decompression device 50 is that the intake pressure is higher than the decompression start pressure Ps. On the other hand, in the second modified example, the decompression device 50 is configured such that the intake pressure is higher than the decompression start pressure Ps and the engine speed is lower than a predetermined speed, that is, a predetermined decompression start speed Ns (see FIG. 7). The operating condition is assumed. Preferably, the decompression start rotational speed Ns is set lower than the idle rotational speed Ni, for example, 800 rpm. In this way, the operation of the decompression device 50 when the engine speed is still higher than the decompression start speed Ns immediately after the engine stop operation is started is prohibited, and the backflow of exhaust gas into the intake passage can be effectively suppressed. .

  The second modification can be combined with the first modification.

  Incidentally, the fact that the intake pressure is higher than the predetermined pressure is equivalent to the fact that the pressure difference between the intake passage internal pressure and the exhaust passage internal pressure (atmospheric pressure) is smaller than a predetermined value. Therefore, the latter is included in the former, and a third modified example in which the latter is an operating condition of the decompression device 50 is also possible. This third modification can also be combined with the first and second modifications.

  Next, an engine stop control routine will be described with reference to FIG. The routine is executed by the ECU 20 (particularly, the engine ECU 20B) according to the procedure shown in FIG. The routine corresponds to the second modification described above, but it will be understood that the routine can be easily modified to correspond to the basic example, the first modification, or the third modification.

  First, in step S101, it is determined whether or not the second stop flag is on. When it is not on (when it is off), it enters a standby state, and when it is on, it proceeds to step S102.

  In step S102, the fuel injection prohibition flag is turned on. This prohibits or stops fuel injection and ignition.

  Next, in step S103, the throttle opening is controlled to the decompression opening TH3.

  In step S104, it is determined whether or not the intake pressure is higher than the decompression start pressure Ps and the engine speed is lower than the decompression start speed Ns. If no, the process enters a standby state. If yes, the process proceeds to step S105. The timing when the answer is yes is indicated by t2 'in FIG.

  In step S105, the decompression execution flag is turned on. As a result, the decompression device 50 is operated, and the exhaust valve 9 is always lifted at least by the decompression lift amount Ld.

  Next, in step S106, it is determined whether an engine stop end flag is on. If it is not on (if it is off), it enters a standby state. If it is on, the process proceeds to step S107.

  In step S107, the decompression execution flag is turned off. Thereby, the decompression device 50 is stopped. In step S108, the throttle opening is controlled to the minimum opening TH1, and the routine is terminated.

  Although the basic example of the present embodiment has been described above, the present embodiment can be modified as follows.

  (1) The configuration of the decompression device 50 can be changed as shown in FIGS. In this modified embodiment, the HLA 53 is lifted using an HLA lifter cam shaft 59 instead of the slider 55. The HLA lifter cam shaft 59 is rotatably inserted into and supported by a cam shaft insertion hole 60 formed in the cylinder head 5 so as to face the bottom of each HLA 53, and is driven to rotate by an electric decompression actuator 57 '. The HLA holder 54 is omitted, and instead, the HLA 53 is supported by an HLA support hole 61 formed in the cylinder head 5 so as to be movable up and down.

  During operation of the decompression device 50, the decompression actuator 57 'is turned on, and the decompression actuator 57' rotates the HLA lifter cam shaft 59 to an operating position (indicated by phantom lines) that is 180 ° different from the stop position shown in FIG. Then, the cam surface 59A of the HLA lifter cam shaft 59 directly pushes up the HLA 53 and lifts it upward. The rest is the same as in the basic embodiment.

  (2) Various configurations of the decompression device other than those described above are possible. For example, when an electromagnetically driven exhaust valve that drives the exhaust valve with an electromagnetic actuator is employed, the decompression device may be configured by this electromagnetically driven exhaust valve. As described above, a dedicated decompression device that does not use the exhaust valve may be provided.

  (3) The use of the engine is arbitrary and may not be for vehicles. The type of vehicle is also arbitrary, and it may be a normal vehicle that is not a hybrid vehicle, that is, a vehicle that uses an engine as a sole power source. In the case of a normal vehicle, for example, when the ignition switch is turned off, a predetermined stop condition is established, and the engine stop operation is started.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable. Each of the above-described embodiments, examples, and configurations can be arbitrarily combined as long as no contradiction occurs. The embodiments of the present invention include all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention.

1 Internal combustion engine
12 In-cylinder combustion chamber 18 Throttle valve 20 Electronic control unit (ECU)
31 Intake pressure sensor 50 Decompression device

Claims (1)

A decompression device for communicating the in-cylinder combustion chamber with the exhaust passage in order to release the in-cylinder pressure at least during the compression stroke;
A throttle valve provided in the intake passage;
An acquisition unit configured to acquire a pressure in the intake passage downstream of the throttle valve;
A control unit configured to control the decompression device and the throttle valve;
With
The control unit controls the throttle valve so that the opening degree of the throttle valve becomes a predetermined opening degree larger than a predetermined minimum opening degree after the stop operation of the internal combustion engine is started, and then acquired by the acquisition unit. The internal combustion engine control device, wherein when the pressure in the intake passage becomes higher than a predetermined pressure, the decompression device is operated so that the in-cylinder combustion chamber is always in communication with the exhaust passage.

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