JP4295173B2 - Control device for internal combustion engine - Google Patents

Description

  The present invention relates to a control device for an internal combustion engine, and more specifically, to improve exhaust emission when an overlap amount of an intake valve and an exhaust valve is a predetermined value or more and fuel is injected at an intake process timing. Related to technology.

Conventionally, when the intake / exhaust valve is composed of an electromagnetic valve and the target air amount (required load) is greater than or equal to a predetermined value, the amount of overlap between the intake and exhaust valves is controlled by controlling the opening and closing timing of the intake and exhaust valves. There is known a control device for an internal combustion engine that increases fuel flow and injects fuel during the intake stroke (see, for example, Patent Document 1). According to such a control device for an internal combustion engine, the target air amount can be realized using the scavenging effect.
JP 2001-159343 A

  However, conventional control devices for internal combustion engines have a configuration in which the amount of overlap between the intake valve and the exhaust valve is increased and fuel is injected at the time of the intake stroke. Decreases and the spray pattern is disturbed. As a result, the wall flow rate of the fuel spray adhering to the intake port increases, and the exhaust emission decreases due to an increase in unburned fuel (HC).

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an exhaust when fuel is injected at the intake process timing when the overlap amount between the intake valve and the exhaust valve is a predetermined value or more. An object of the present invention is to provide a control device for an internal combustion engine capable of improving emission.

  In order to achieve the above object, the control device for an internal combustion engine according to the present invention determines whether or not the fuel injection timing is the intake stroke timing, and when the fuel injection timing is the intake stroke timing, It is determined whether or not the overlap amount of the valve is equal to or greater than a predetermined value. If the overlap amount is equal to or greater than the predetermined value, the fuel injection pressure is increased. And according to such an aspect, since the influence of the blowback from the cylinder with respect to fuel spray can be reduced, the wall flow rate of fuel can be reduced and exhaust emission can be improved.

  It is desirable that the fuel injection pressure be increased in accordance with the amount of overlap. In general, the amount of blowback from the cylinder increases as the amount of overlap between the intake valve and the exhaust valve increases. Therefore, according to such an aspect, it is possible to set an optimal injection pressure in accordance with the blowback amount from the cylinder.

  Further, it is desirable to determine whether or not the internal combustion engine temperature is equal to or lower than a predetermined value, and when the internal combustion engine temperature is equal to or lower than the predetermined value, it is desirable to execute the above processing. In general, when the internal combustion engine temperature is low, the fuel is difficult to atomize, and the wall flow rate of the fuel due to blow-back from the cylinder increases. Therefore, according to such an aspect, the fuel wall flow rate can be reduced and the exhaust emission can be improved.

  The control device according to the present invention can be applied to an internal combustion engine having a hydraulically controlled variable valve mechanism as shown in FIG. Hereinafter, a configuration of an internal combustion engine and a control method thereof according to an embodiment of the present invention will be described in detail with reference to the drawings.

[Configuration of internal combustion engine]
As shown in FIG. 1, an internal combustion engine 1 according to an embodiment of the present invention transmits power from a crankshaft 2 to an exhaust side camshaft 6 and an intake side camshaft 7 via a sprocket 4, 5 by a timing chain 3. It is to be transmitted. Further, a hydraulically driven intake side variable valve timing mechanism 8 and an intake side camshaft sensor 9 for adjusting the advance amount of the intake side camshaft 7 with respect to the crankshaft 2 are attached to the intake side camshaft 7. The exhaust camshaft 6 is provided with a hydraulically driven exhaust variable valve timing mechanism 10 and an exhaust camshaft sensor 11 that adjust the advance amount of the exhaust camshaft 6 with respect to the crankshaft 2.
On the other hand, a crankshaft sensor 12 is attached to the crankshaft 2. The crankshaft sensor 12 generates N crankshaft phase detection pulse signals per revolution of the crankshaft 2, while the intake side / exhaust side camshaft sensors 9, 11 are provided with intake side / exhaust side camshafts. 2N camshaft phase detection pulse signals are generated per rotation of 7,6. Further, when the maximum advance amount / maximum retard amount of the intake side / exhaust side cam shafts 7 and 6 is θmax ° C., the crankshaft phase detection pulse signal number N is set so that N <360 / θmax. ing. As a result, the relative rotation angle between the crankshaft phase detection pulse signal from the crankshaft sensor 12 and the camshaft phase detection pulse signals from the intake side / exhaust side camshaft sensors 9 and 11 generated thereafter is determined. The actual valve timings (the actual advance amount of the intake side camshaft 7 and the actual retard amount of the exhaust side camshaft 6) of the intake valve and the exhaust valve (both not shown) are calculated.
The detection pulse signals from the crankshaft sensor 12 and the intake / exhaust-side camshaft sensors 9 and 11 are input to an engine control circuit (hereinafter referred to as “ECU”) 13, and the ECU 13 controls the intake valve and the exhaust. The actual valve timing of the valve is calculated, and the engine speed is calculated based on the detection pulse signal interval from the crankshaft sensor 12. Although not shown, the outputs of various sensors that detect engine operating conditions such as an intake pipe pressure sensor, a water temperature sensor, and a throttle sensor are also input to the ECU 13, and based on these various sensor outputs, a target exhaust residual ratio (target valve over-range) is obtained. (Lap amount) is calculated, and target valve timings of the intake valve and the exhaust valve (target advance angle amount of the intake camshaft 7 and target retard amount of the exhaust camshaft 6) are calculated.
Further, the ECU 13 controls a hydraulic control valve (not shown) of the intake side hydraulic circuit 14 so that the actual valve timing of the intake valve (actual advance angle of the intake camshaft 7) matches the target advance angle. Then, feedback control of the intake side variable valve timing mechanism 8 is performed, and the hydraulic control of the exhaust side hydraulic circuit 15 is performed so that the actual valve timing of the exhaust valve (actual retard amount of the exhaust camshaft 6) matches the target retard amount. A valve (not shown) is controlled to feedback control the exhaust side variable valve timing mechanism 10.
Further, the ECU 13 stores a fuel pressure-overlap amount map in which the relationship between the pressure (fuel pressure) of fuel injected from the fuel injection valve and the overlap amount is mapped, and the fuel pressure can be controlled with reference to this map. It is configured. In this embodiment, the fuel pressure-overlap amount map shows the characteristic that the fuel pressure increases as the overlap amount between the intake valve and the exhaust valve increases.

  And in the internal combustion engine 1 which has such a structure, ECU13 performs the fuel pressure control process shown below, and reduces the influence of the blowback from a cylinder with respect to fuel spray. Hereinafter, the operation of the ECU 13 when executing the fuel pressure control process will be described in detail with reference to the flowchart shown in FIG.

[Fuel pressure control processing]
The flowchart shown in FIG. 2 starts when the ignition switch of the vehicle is turned on, and the fuel pressure control process proceeds to the process of step S1.

  In the process of step S1, the ECU 13 reads information on the temperature of the cooling water, the load of the internal combustion engine 1, and the rotational speed of the internal combustion engine 1. Thereby, the process of step S1 is completed, and the fuel pressure control process proceeds from the process of step S1 to the process of step S2.

  In the process of step S2, the ECU 13 determines whether or not the temperature of the cooling water is equal to or higher than a predetermined value. As a result of the determination, if the temperature of the cooling water is equal to or higher than the predetermined value, the ECU 13 determines that the temperature of the internal combustion engine 1 is high (HOT state), and advances the fuel pressure control process to the process of step S7. On the other hand, when the temperature of the cooling water is equal to or lower than the predetermined value, the ECU 13 determines that the temperature of the internal combustion engine 1 is low (COLD state), and advances the fuel pressure control process to the process of step S3.

  In the process of step S3, the ECU 13 determines whether or not the injection timing of the fuel spray from the fuel injection valve is the exhaust process timing. And as a result of discrimination | determination, when injection timing is an exhaust process, ECU13 advances a fuel pressure control process to the process of step S6. On the other hand, when the injection timing is not the exhaust process but the intake process, the ECU 13 advances the fuel pressure control process to the process of step S4.

  In the process of step S4, the ECU 13 determines the overlap (O / L) amount of the intake valve and the exhaust valve according to the information on the load of the internal combustion engine 1 and the rotation speed of the internal combustion engine 1 read in the process of step S1. Then, it is determined whether or not the determined overlap amount is equal to or less than a predetermined value. If the overlap amount is equal to or smaller than the predetermined value as a result of the determination, the ECU 13 advances the fuel pressure control process to the process of step S6. On the other hand, if the overlap amount is greater than or equal to the predetermined value, the ECU 13 advances the fuel pressure control process to the process of step S5.

  In the process of step S5, the ECU 13 reads the fuel pressure corresponding to the overlap amount detected in the process of step S4 with reference to the fuel pressure-overlap amount map, and reads the pressure of the fuel injected by the fuel injection valve. Set the fuel pressure value. Thereby, the process of step S5 is completed, and the fuel pressure control process proceeds from the process of step S5 to the process of step S7.

  In step S6, the ECU 13 sets the pressure of the fuel injected by the fuel injection valve to a fixed value. Thereby, the process of step S6 is completed, and the fuel pressure control process proceeds from the process of step S6 to the process of step S7.

  In the process of step S7, the ECU 13 controls the opening timing of the intake valve and the exhaust valve so that the overlap amount determined by the process of step S4 is achieved, and the fuel pressure set by the process of step S5 or step S6. The fuel injection valve is controlled so as to inject fuel. Thereby, the process of step S7 is completed, and the fuel pressure control process returns to the process of step S1.

  As is clear from the above description, according to the internal combustion engine 1 according to the embodiment of the present invention, the ECU 13 determines whether the fuel injection timing is the intake process timing, and the fuel injection timing is the intake process timing. In some cases, it is determined whether or not the overlap amount between the intake valve and the exhaust valve is equal to or greater than a predetermined value. If the overlap amount is equal to or greater than a predetermined value, the pressure of the fuel injected from the fuel injection valve is increased. And according to such a structure, since the influence of the blowback from a cylinder with respect to fuel spray can be reduced, the wall flow rate of a fuel can be reduced and exhaust emission can be improved.

  Further, according to the internal combustion engine 1 according to the embodiment of the present invention, the ECU 13 increases the pressure of the fuel injected from the fuel injection valve in accordance with the size of the overlap amount according to the fuel pressure-overlap amount map. Generally, the amount of blowback from the cylinder increases as the amount of overlap between the intake valve and the exhaust valve increases. With such a configuration, the optimum fuel pressure is set in accordance with the amount of blowback from the cylinder. Can do.

  Furthermore, according to the internal combustion engine 1 according to the embodiment of the present invention, the ECU 13 determines whether or not the temperature of the cooling water is equal to or lower than a predetermined value. It is determined that the temperature is low, and the above processing is executed. In general, when the temperature of the cooling water is low and the temperature of the internal combustion engine 1 is low, the fuel is difficult to be atomized, and the flow rate of the fuel wall is increased by blowing back from the cylinder. The flow rate can be reduced and exhaust emission can be improved.

  In this embodiment, the control device according to the present invention is applied to an internal combustion engine having a hydraulically controlled variable valve mechanism. However, the control device according to the present invention changes the valve lift amount and the operating angle. The present invention can also be applied to an internal combustion engine having a variable valve mechanism of this type or an internal combustion engine in which the valve overlap amount is changed by an electromagnetic valve.

  The present invention can be applied to an internal combustion engine that can variably control the amount of overlap between an intake valve and an exhaust valve.

It is a mimetic diagram showing composition of an internal-combustion engine used as an embodiment of the present invention. It is a flowchart figure which shows the flow of the fuel pressure control process used as embodiment of this invention.

Explanation of symbols

1: internal combustion engine 2: crankshaft 3: timing chain 4, 5: sprocket 6: exhaust side camshaft 7: intake side camshaft 8: intake side variable valve timing mechanism 9: exhaust side camshaft sensor 10: exhaust side variable valve Timing mechanism 11: exhaust camshaft sensor 12: crankshaft sensor 13: engine control circuit (ECU)
14: Intake side hydraulic circuit 15: Exhaust side hydraulic circuit

Claims (3)

A control device for an internal combustion engine having a variable valve mechanism capable of variably controlling the amount of overlap between the intake valve and the exhaust valve by controlling the opening and closing timing of the intake valve and the exhaust valve,
It is determined whether or not the fuel injection timing is the intake process timing. If the fuel injection timing is the intake process timing, it is determined whether or not the overlap amount is a predetermined value or more, and the overlap amount is a predetermined value. When it is above, the control apparatus of the internal combustion engine characterized by including the control part which raises the injection pressure of fuel.   2. The control device for an internal combustion engine according to claim 1, wherein the control unit increases the fuel injection pressure in accordance with the size of the overlap amount.   The control unit determines whether or not the internal combustion engine temperature is equal to or lower than a predetermined value, and executes the processing when the internal combustion engine temperature is equal to or lower than a predetermined value. The internal combustion engine control device described.

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