JP5525275B2 - Scavenging control device for internal combustion engine - Google Patents

Description

  The present invention relates to a scavenging control device for an internal combustion engine, and more particularly to a scavenging control device for an internal combustion engine that rotates a crankshaft while fuel is stopped when the engine is stopped or started.

  Conventionally, there is a possibility that scavenging is performed when the engine is stopped because there is a possibility that startability at the time of restarting may deteriorate if fuel adheres to the intake pipe when the internal combustion engine is stopped. In the scavenging control device for an internal combustion engine configured to perform such scavenging control, in order to improve the scavenging performance, the throttle control as the intake control valve is stopped during scavenging, and the scavenging is performed fully open. There are some (see, for example, Patent Document 1). Also, there is an engine that motorizes an internal combustion engine immediately after the engine is stopped so that the fuel adhering to the intake passage constituting member is separated by the flow of air generated in the intake pipe (for example, Patent Document 2). . For exhaust gas purification at idle stop, the motor is rotated by a motor to send fresh air to the engine. During residual exhaust gas purification control, the throttle is fully opened and the exhaust ring flow control valve is fully closed. (For example, Patent Document 3).

JP 2000-265880 A JP 2004-144030 A JP 2002-256919 A

  As described above, in each patent document, a scavenging flow is caused in the intake pipe, and the fuel adhering to the intake pipe is removed by the scavenging flow. On the other hand, the present inventors paid attention to volatilizing the fuel adhering to the intake pipe while reducing the pressure in the intake pipe.

  On the other hand, in Patent Document 1, when the throttle is fully opened, the scavenging flow rate increases, but the pressure in the intake pipe does not decrease. Moreover, since the throttle opening is not prescribed | regulated in the thing of patent document 2, since optimal purification cannot be performed and it becomes estimation control, there exists a problem that accurate purification control cannot be performed. . Further, in Patent Document 3, the exhaust purification efficiency is aimed to be improved, but the fuel adhering to the intake pipe is not actively removed, and the adhering fuel must be sufficiently removed. Also, the exhaust purification improvement is not enough.

In order to solve such a problem and realize a scavenging control device for an internal combustion engine that can not only perform efficient scavenging control but also improve exhaust purification, the present invention provides an internal combustion engine. Fuel supply means (4) for supplying fuel to the engine (1) and crankshaft rotation means (11) for rotating the crankshaft (7), the fuel supply means when the engine is stopped or the engine is started A scavenging control device for an internal combustion engine that stops scavenging by stopping fuel supply in (4) and rotating the crankshaft (7) by the crankshaft rotating means (11). An intake control valve (3) for controlling the intake pipe internal pressure; valve control means (12b) for controlling opening and closing of the intake control valve (3); and a pressure detection means (10) for detecting the intake pipe internal pressure. The valve control means (12b) When stopping or during engine starting, the intake pipe pressure controls the intake control valve such that the subatmospheric target pressure (3) to said detected by the pressure detecting means (10), wherein the target pressure, the The predetermined value is based on the amount of fuel desorption obtained from the volatilization amount of the fuel corresponding to the intake pipe internal pressure and the scavenging amount corresponding to the intake pipe internal pressure .

  According to this, since the intake control valve is controlled so that the intake pipe pressure becomes a target pressure lower than the atmospheric pressure in the scavenging control, the intake pipe is depressurized, so the volatilization amount of the fuel adhering to the intake pipe is positively increased. Can be increased.

  In particular, the valve control means (12b) may control the intake control valve (3) to a fully closed state until the intake pipe internal pressure detected by the pressure detection means (10) reaches at least the target pressure. According to this, by making the intake control valve fully closed from the start of the scavenging control, the intake pipe internal pressure can be quickly reduced to the target pressure.

  Further, a rotation speed detection means (8) for detecting the engine rotation speed is provided, and the crankshaft rotation means (11) corresponds to the target pressure with the engine rotation speed detected by the rotation speed detection means (8). It is preferable to control the rotation of the crankshaft (7) so as to be a predetermined value. According to this, the scavenging flow rate can be controlled by rotation control of the crankshaft, and it is possible to adjust the pressure reduction effect and the flow rate securing, so that scavenging can be performed more reliably.

  Further, it is preferable to provide means (14 · 12e) for calculating an integrated value of the scavenging amount, and to end the scavenging control when the integrated value of the scavenging amount exceeds a threshold value. Alternatively, a means (12d) for calculating the scavenging time for performing the scavenging control may be provided, and the scavenging control may be terminated when the scavenging time exceeds a threshold value. According to these, the scavenging amount necessary for scavenging is set as a threshold value, and scavenging is performed until the integrated value of the scavenging amount reaches the threshold value, so that the adhering fuel is surely removed and the startability is improved. Can do. Furthermore, it is preferable to include temperature detection means (9) for detecting the engine temperature or the outside air temperature, and threshold setting means (12a) for increasing the threshold value as the engine temperature or the outside air temperature is lower. According to this, the adhering fuel increases as the temperature is lower, and therefore, by performing the setting for increasing the scavenging amount in accordance with such increase, it is possible to perform appropriate scavenging according to the situation.

  Further, it is preferable to provide means (6a, 12a) for determining whether or not the catalyst is active, and to perform the scavenging control when it is determined that the catalyst is active when the engine is stopped. According to this, scavenging can be executed in a state that does not affect the exhaust purification. Alternatively, a means (12a) for determining failure of engine start may be provided, and scavenging control may be executed when it is determined that the start has failed at the time of engine start. According to this, it can be avoided that the fuel adhering at the time of starting failure remains and further fails at the time of restart.

  As described above, according to the present invention, it is possible to prevent the fuel from adhering to the intake pipe and prevent the startability from deteriorating when the engine is stopped or the engine is started. In particular, the engine can be idled for scavenging. Even when vibration is generated by the above, the scavenging time is shortened by the pressure reducing effect, and the idling time is shortened, so that the merchantability is improved. In addition, since the adhering fuel can be scavenged more by the reduced pressure boiling effect, the exhaust gas purification at the time of start-up is improved and the scavenging amount per hour increases, so the power consumption of the electrical equipment used for scavenging control is reduced. As a result, fuel consumption improves.

It is a schematic diagram which shows the principal part of the scavenging device of the internal combustion engine to which the present invention is applied. It is a flowchart which shows an example of the control point based on this invention. It is a time chart which shows the control point. (A) is a figure which shows the change of the volatilization amount with respect to an intake pipe internal pressure, (b) is a figure which shows the change of scavenging amount, (c) is the adhesion by combining (a) and (b). It is a figure which shows the change of the detachment | leave amount of a fuel.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing a main part of a scavenging device for an internal combustion engine to which the present invention is applied. The internal combustion engine 1 may be a known gasoline engine or diesel engine, and detailed description thereof is omitted.

  An intake pipe 2 connected to the internal combustion engine 1 is provided with an intake control valve 3 for controlling the intake pipe internal pressure, and a fuel injection valve 4 as a fuel supply means provided near the intake port of the cylinder head, for example. Yes. The intake control valve 3 is opened and closed by an electronically controlled actuator 3a. The intake control valve 3 may be of a known throttle structure, but is not limited thereto, and may be any one that can change the pressure in the intake pipe 2, such as the maximum lift amount of the intake valve. You may use the variable valve mechanism which makes variable. Moreover, you may combine them.

  An exhaust pipe 5 connected to the internal combustion engine 1 is provided with a catalyzer 6 for preventing the diffusion of harmful substances in the exhaust gas. Further, a rotation sensor 8 which is a rotation speed detecting means for detecting the rotation speed of the crankshaft 7 as the engine rotation speed, an engine temperature sensor 9 for detecting the coolant temperature or the oil temperature of the internal combustion engine 1 as the engine temperature, and the intake air A pressure sensor 10 is provided as pressure detection means for detecting the internal pressure of the pipe 2. The engine temperature sensor 9 may be provided as a part that can detect the outside air temperature and used as an outside air temperature sensor.

  The crankshaft 7 is connected to a starter 11 for starting. In the case of a hybrid car, a motor that also serves as a starter may be connected, but in the following description, it will be described as a starter used in a normal internal combustion engine.

  A control device 12 is provided for performing drive control of the actuator 3a and starter 11 and scavenging control. The control device 12 includes a CPU 12a programmed to perform overall control including start / stop in the scavenging control, and is configured by a known I / O circuit, a control IC, a driver circuit using a transistor, and the like. It's okay.

  The control device 12 includes a throttle control unit 12b for performing drive control of the actuator 3a, a start control unit 12c for calculating engine rotational speed based on a signal from the rotation sensor 8 and controlling drive of the starter 11, and throttle control. A timer 12d connected to the unit 12b is provided. Further, the control device 12 receives as input signals from the outside the engine temperature from the engine temperature sensor 9, the intake pipe internal pressure from the pressure sensor 10, and the catalyzer from the catalyzer temperature sensor 6 a provided in the catalyzer 6. The temperature and the engine operation signal from the ignition switch 13 are input.

  The throttle control unit 12b controls the opening degree of the intake control valve 3 via the actuator 3a. For example, the throttle control unit 12b receives a signal from an angle sensor (not shown) built in the actuator 3a and opens the intake control valve 3. For example, feedback control is performed so that the opening degree target value from the CPU 12a is obtained. The start control unit 12 c outputs a drive control signal for starting the engine to the starter 11 when a start signal is input from the ignition switch 13.

  The control point in the scavenging apparatus configured as described above will be described below with reference to the flowchart of FIG. 2 and the time chart of FIG. First, in step ST1, it is determined whether or not scavenging control is started. As a start condition for the scavenging control, one is when the normal engine is stopped and the catalyzer 6 is in an active state when the engine is stopped, and the other is when the start fails. The active state of the catalyzer 6 can be determined by the CPU 12a based on the catalyzer temperature detected by the catalyzer temperature sensor 6a provided in the catalyzer 6, but may be estimated from the operation (operation) time of the internal combustion engine 1. The reason why the catalyzer active state is used is that it is possible to avoid deterioration of exhaust purification by scavenging in the catalyzer active state.

  When the engine is stopped, it may include an idle stop state such as waiting for a signal while driving, and when starting fails, when the engine temperature is extremely low and the starting fails, such as when starting in a cold district or winter As good. As an example of detection of the start failure, there is a fuel injection signal or an ignition signal, and the engine speed is lower than a predetermined value (e.g., equivalent to idling) for a predetermined time or a predetermined number of rotations (rotated integrated value). As good. Alternatively, the ignition switch 13 is turned off in a state where there is a fuel injection signal or an ignition signal and the engine rotational speed is less than a predetermined value (e.g., equivalent to idling), and a predetermined time (a time during which the attached fuel does not spontaneously evaporate). ) Shows the case where the ignition switch 13 is turned on. The CPU 12a can be applied as a means for determining whether the engine has stopped or started.

  If it is determined in step ST1 that the scavenging is not started, step ST1 is repeated. If it is determined that the scavenging is started, the process proceeds to step ST2 to start scavenging (T1 in FIG. 3). In step ST2, a drive signal is output from the start controller 12c to the starter 11 to rotate the crankshaft 7 at a specified rotational speed. The specified rotational speed may be such that intake and exhaust are performed to the extent necessary for scavenging, and feedback control may be performed as the rotational speed control. Further, for example, PID control is preferably performed in order to quickly start up to the specified rotational speed without overshooting or hunting. Further, the rotation speed may not be a predetermined constant rotation speed. For example, the rotation speed control may be changed according to a rotation speed pattern with respect to an elapsed time according to a preset map.

  In the next step ST3, the timer 12d starts counting (T1 in FIG. 3). The threshold value TM (see FIG. 3), which is the set time of the timer 12d, is a time until reaching the integrated flow rate necessary for scavenging. The threshold value TM may be set so as to increase as the engine temperature or the outside air temperature decreases, and the threshold value setting means may be the CPU 12a.

  In the next step ST4, a fully closed signal is output from the throttle control unit 12b to the actuator 3a to bring the intake control valve 3 into a fully closed state (T1 in FIG. 3). Thereby, the downstream side of the intake control valve 3 in the intake pipe 2 is depressurized with respect to the atmospheric pressure Pa (see FIG. 3), and the volatilization of the fuel adhering to the intake pipe 2 is promoted by the reduced pressure state. In the next step ST5, it is determined whether or not the intake pipe internal pressure P has reached the specified pressure Pd as the target pressure. If not reached (P> Pd), step ST5 is repeated and reached (P ≦ Pd). ), The process proceeds to step ST6. By performing the control in steps ST4 and ST5, it is possible to quickly obtain a predetermined reduced pressure state at the start of scavenging, whereby the volatilization effect can be maximized and the time required for scavenging can be shortened.

  In step ST6, control for appropriately opening and closing the intake control valve 3 is performed in order to maintain the intake pipe internal pressure P at the specified pressure Pd. In this throttle control, feedback control of the detected value (P) with respect to the specified pressure Pd is preferably performed. Further, when the opening degree of the intake control valve 3 is changed as shown in FIG. 3, for example, PID control is preferably performed in order to open and close the target opening degree quickly and without overshoot or hunting.

  Note that it is not always necessary to perform both the full-closed control and the feedback control, and it is only necessary to perform the control as shown in the flowchart. For example, either one or both may not be performed. In that case, for example, the closing amount of the intake control valve 3 is set to such an extent that at least the intake pipe 2 can be depressurized with respect to the atmospheric pressure Pa, and the opening / closing control is performed by the opening / closing pattern with respect to the elapsed time according to a preset map. Can do.

  In this way, by controlling both the decompression in the intake pipe 2 and the opening / closing control to the specified pressure Pd, the attached fuel by an appropriate combination of the volatilization amount by the decompression effect and the scavenging flow rate by the size of the opening degree. Scavenging can be performed.

  In FIG. 4, the horizontal axis represents the intake pipe pressure P, FIG. 4 (a) shows the change in the volatilization amount of the adhered fuel, FIG. 4 (b) shows the change in the scavenging flow rate, and FIG. 4 (c) shows the volatilization amount. The change in the amount of attached fuel released when combined with the scavenging flow rate is shown. In this embodiment, the description is made on the assumption that the engine has a fixed maximum lift amount of the intake valve. In this case, the intake pipe internal pressure depends on the throttle opening and the engine speed, and FIG. Shows the change in a state where the engine rotation speed is fixed to a predetermined rotation speed. Therefore, the horizontal axis of FIG. 4 also represents the throttle opening.

  As shown in FIG. 4, the volatilization amount increases as the intake pipe internal pressure P decreases, but the scavenging flow rate increases as the intake pipe internal pressure P increases because the scavenging flow rate is proportional to the opening degree of the intake control valve 3. When the both are combined, the amount of adhering fuel detached from the tube wall peaks at a certain value (Pd) as shown in FIG. 4C, and this value is used as the specified pressure Pd as the target pressure. As a result, the attached fuel can be scavenged with maximum efficiency. According to the present invention, this effect can be utilized, and as a result, the time required for the scavenging time can be shortened, and an improvement in merchantability can be achieved by shortening the idling time. The specified pressure Pd may be changed depending on the state of the engine, and parameters such as the engine temperature and atmospheric pressure may be considered. The prescribed rotational speed set in step ST2 corresponds to the engine rotational speed (predetermined rotational speed) at which the prescribed pressure Pd is set.

  In the next step S7, it is determined whether or not the time measured by the timer 12d is up (END in FIG. 3), and steps ST6 and 7 are repeated until the time is up. If it is determined in step ST7 that the time is up, the process proceeds to step ST8, where the rotational drive of the crankshaft 7 is stopped and this control is terminated.

  After scavenging, when the engine is stopped, the engine is continuously stopped until the ignition switch 13 is turned on or the idle stop is released. When the engine fails, start start control is performed after scavenging (the starter 11 performs crankshaft control). 7 is rotated to inject fuel and ignite).

  In the flow in FIG. 2 described above, the scavenging start time (T1) is set as the rotation start time of the crankshaft 7. However, for example, it may be from the time when the intake pipe internal pressure P reaches the specified pressure Pd (T2 in FIG. 3). . In addition, although the timer 12d starts counting from T1 in FIG. 3, the timing is not limited to this, and may be started from T2 in FIG. The start time T2 can be a time when it is detected that the intake pipe internal pressure P has reached the specified pressure Pd.

  Further, although the time for performing the scavenging control is set to the time set by the timer 12d (threshold value TM), the integrated flow rate Q calculated by integrating the flow rate during scavenging is set instead of the threshold value TM based on the timer timing time. May be. As for calculation of the integrated flow rate Q, it is preferable to provide the air flow meter 14 in the intake pipe 2 as shown in FIG. 1 and provide the flow rate integrating unit 12e in the control device 12 to detect and integrate the flow rate.

On the other hand, it can be obtained by using the pressure sensor 10 and the number of top dead centers passing through each cylinder. The formula in that case is as follows.
Q = Σ (CL) * P * Pa
Here, Σ (CL) is the integrated value of the stroke volume (π * (bore diameter / 2) ^ 2 * stroke), P is the intake pipe internal pressure detected by the pressure sensor 10, and Pa is the atmospheric pressure sensor. 15 is the atmospheric pressure detected. The intake pipe internal pressure P is a value detected every time the top dead center is passed, and the atmospheric pressure Pa is a value detected when the integrated flow rate Q is determined.

1 Internal combustion engine 3 Intake control valve 4 Fuel injection valve (fuel supply means)
6a Catalyzer temperature sensor (catalyst activity discrimination means)
7 Crankshaft 8 Rotation sensor (Rotation speed detection means)
9 Engine temperature sensor (temperature detection means)
10 Pressure sensor (pressure detection means)
11 Starter (Crankshaft rotating means)
12a CPU (threshold setting means / catalyst activity judging means / engine starting failure judging means)
12b Throttle control unit (valve control means)
12e Flow rate integration unit (means for calculating the integrated value of scavenging amount)
14 Air flow meter (means for calculating integrated value of scavenging amount)

Claims (8)

Fuel supply means for supplying fuel to the internal combustion engine, and crankshaft rotation means for rotating the crankshaft,
A scavenging control apparatus for an internal combustion engine that performs scavenging by stopping the supply of fuel by the fuel supply means and rotating the crankshaft by the crankshaft rotating means when the engine is stopped or started.
An intake control valve that controls the intake pipe internal pressure of the internal combustion engine, valve control means that controls opening and closing of the intake control valve, and pressure detection means that detects the intake pipe internal pressure,
The valve control means controls the intake control valve so that the intake pipe internal pressure detected by the pressure detection means becomes a target pressure lower than atmospheric pressure when the engine is stopped or the engine is started .
The internal combustion engine, wherein the target pressure is a predetermined value based on a fuel removal amount determined from a fuel volatilization amount corresponding to the intake pipe internal pressure and a scavenging amount corresponding to the intake pipe internal pressure. Scavenging control device.   2. The internal combustion engine according to claim 1, wherein the valve control unit controls the intake control valve to a fully closed state until the intake pipe internal pressure detected by the pressure detection unit reaches at least the target pressure. Scavenging control device. A rotation speed detecting means for detecting the engine rotation speed;
The crankshaft rotating means controls the rotation of the crankshaft so that the engine rotational speed detected by the rotational speed detecting means becomes a predetermined value corresponding to the target pressure. Item 3. A scavenging control device for an internal combustion engine according to Item 2. Means for calculating the integrated value of the scavenging amount,
4. The scavenging control device for an internal combustion engine according to claim 1, wherein the scavenging control is terminated when the integrated value of the scavenging amount exceeds a threshold value. A means for calculating a scavenging time for performing scavenging control is provided.
The scavenging control device for an internal combustion engine according to any one of claims 1 to 3, wherein the scavenging control is terminated when the scavenging time exceeds a threshold value.   6. The internal combustion engine according to claim 4, further comprising a temperature detection unit that detects an engine temperature or an outside air temperature, and a threshold setting unit that increases the threshold value as the engine temperature or the outside air temperature is lower. Engine scavenging control device. Means for determining the presence or absence of catalyst activity,
The scavenging control device for an internal combustion engine according to any one of claims 1 to 6, wherein scavenging control is executed when it is determined that the catalyst is active when the engine is stopped. Equipped with means for determining engine start failure,
The scavenging control device for an internal combustion engine according to any one of claims 1 to 6, wherein scavenging control is executed when it is determined that the starting has failed at the time of starting the engine.

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