JP2009002211A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the electric power consumption of a heater while securing startability by injecting fuel heated by the heater during low temperature start of an intake port injection engine. <P>SOLUTION: First injection fuel heated by the heater is actively hit on an intake valve and the intake valve is effectively warmed up by executing the first fuel injection to each cylinder mainly during close period of the intake valve when fuel (alcohol or fuel containing alcohol) heated by the heater is injected during start in a heater ON zone (low temperature zone). Second injection fuel heated by the heater is inhibited from being cooled by the intake valve and is made flow into the cylinder without dropping temperature of the injection fuel so much by executing the second fuel injection mainly during open period of the intake valve. Consequently, startability in low temperature can be secured by burning air fuel mixture with the second fuel injection and electric power consumption of the heater can be reduced by reducing heating value of the heater as compared to former devices. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine that includes a fuel injection valve that injects fuel into an intake port of the internal combustion engine and a heating unit that heats the fuel injected by the fuel injection valve.

  As fuels for internal combustion engines mounted on vehicles, there are alcohols such as ethanol and methanol, or mixed fuels in which alcohol and gasoline are mixed. Alcohol fuels containing these alcohols, Compared to gasoline, the flash point is high and the latent heat of vaporization is large (not easily vaporized), so when alcohol fuel is used, the startability at low temperatures tends to deteriorate.

  As a countermeasure against this, as described in Patent Document 1 (Japanese Patent Laid-Open No. 5-26087), the fuel injected from the fuel injection valve at the time of low temperature start of the internal combustion engine is heated by a heater to promote fuel vaporization. There is something like that.

Alternatively, as described in Patent Document 2 (Japanese Patent Laid-Open No. 5-26130), fuel heated by a heater is injected by a fuel injection valve to promote fuel vaporization.
Japanese Patent Laid-Open No. 5-26087 (second page, etc.) Japanese Patent Laid-Open No. 5-26130 (second page, etc.)

  However, in the system in which the fuel is heated by the heater as described above, in order to quickly raise the temperature of the fuel to a temperature at which startability can be ensured when the internal combustion engine is started at a low temperature, the heat generation amount (energization amount) of the heater is set. There is a problem that the power consumption of the heater increases because it needs to be considerably increased.

  For example, in a system that injects fuel into an intake port, the injected fuel hits an intake valve that opens and closes the intake port. Therefore, even when fuel heated by a heater is injected at a low temperature start, the injected fuel hits the cooled intake valve When cooled, the temperature of the fuel flowing into the cylinder is lowered. For this reason, at the time of low temperature start, even if the injected fuel heated by the heater is cooled by the cold intake valve, the heater can be flown into the cylinder at a temperature at which the fuel can be started (for example, a temperature above the flash point). It is necessary to set the heat generation amount, which increases the heat generation amount of the heater and increases the power consumption of the heater.

  The present invention has been made in consideration of such circumstances. Accordingly, the object of the present invention is to inject the fuel heated by the heating means at the time of low-temperature start of the internal combustion engine and ensure the startability while heating means. It is an object of the present invention to provide a control device for an internal combustion engine that can reduce the power consumption of the engine and achieve both startability and low power consumption.

  In order to achieve the above object, an invention according to claim 1 is an internal combustion engine comprising: a fuel injection valve that injects fuel into an intake port of the internal combustion engine; and a heating unit that heats the fuel injected by the fuel injection valve. When the fuel heated by the heating means is injected by the fuel injection valve at the low temperature start of the internal combustion engine, the first fuel injection of each cylinder is mainly performed by the start time control means during the valve closing period of the intake valve. The second fuel injection is executed mainly during the intake valve opening period.

  In this configuration, the first fuel injection is executed mainly during the valve closing period of the intake valve, so that the first injected fuel heated by the heating means is positively applied to the intake valve so that the intake valve is efficiently operated. Can warm up. In this way, the second injected fuel heated by the heating means is performed by executing the second fuel injection mainly during the valve opening period of the intake valve while the intake valve is warmed by the first fuel injection. The cooling by the intake valve can be suppressed, and the temperature of the injected fuel can be made to flow into the cylinder without much lowering. Thereby, combustion of the air-fuel mixture can be enabled by the second fuel injection, and startability at a low temperature can be ensured. In this case, the heat generation amount of the heating means may be set so that the second injected fuel with a small temperature drop can flow into the cylinder at a temperature at which the fuel can be started (for example, a temperature above the flash point). It is possible to reduce the power consumption of the heating means, and to ensure both startability and low power consumption.

  The present invention may be applied to a system that uses alcohol or a fuel containing alcohol as a fuel. In this way, even if alcohol fuel (alcohol or fuel containing alcohol) has a higher flash point and higher vaporization latent heat (harder to vaporize) than gasoline, startability at low temperatures is improved. Can be secured.

  Further, as described in claim 3, the intake air amount adjusting valve (for example, a throttle valve or an idle speed control valve) is controlled to be closed during cranking when the internal combustion engine is cold started. You may make it prohibit fuel injection until the predetermined period when a pressure falls below a predetermined value passes. In this manner, the pressure in the intake passage is quickly reduced by cranking (increasing the negative pressure in the intake passage) while the opening of the intake air amount adjusting valve is controlled to the closed side, and the inside of the cylinder is increased. Fuel injection can be started in a state where the in-cylinder temperature is raised by the compression heat of air, and the vaporization of the injected fuel can be effectively promoted.

  In the present invention, ignition may be performed for the first fuel injection. However, the first fuel injection is performed mainly during the closing period of the intake valve so that the first fuel injection is performed. In order to warm the intake valve, the temperature of the fuel flowing into the cylinder is considerably lowered during the first fuel injection. For this reason, even if ignition is performed for the first fuel injection, it is unlikely that the air-fuel mixture will burn. However, if the air-fuel mixture burns in any one of the cylinders, cranking is in progress. May cause unpleasant rotational fluctuations.

  Therefore, as in claim 4, ignition for the first fuel injection may be prohibited. In this way, it is possible to reliably prevent the air-fuel mixture from combusting by the first fuel injection, and to prevent unpleasant rotational fluctuations during cranking.

Hereinafter, an embodiment embodying the best mode for carrying out the present invention will be described.
First, a schematic configuration of the entire engine control system will be described with reference to FIG.
An air cleaner 13 is provided at the most upstream portion of the intake pipe 12 of the engine 11 that is an internal combustion engine, and an air flow meter 14 that detects the intake air amount is provided downstream of the air cleaner 13. On the downstream side of the air flow meter 14, a throttle valve 16 (intake air amount adjustment valve) whose opening is adjusted by a motor 15, and a throttle opening sensor 17 that detects the opening (throttle opening) of the throttle valve 16. And are provided.

  Further, a surge tank 18 is provided on the downstream side of the throttle valve 16, and an intake manifold 20 for introducing air into each cylinder of the engine 11 is provided in the surge tank 18. A fuel injection valve 21 for injecting fuel is attached in the vicinity of the intake port of the intake manifold 20 of each cylinder. An ignition plug 22 is attached to the cylinder head of the engine 11 for each cylinder, and the air-fuel mixture in the cylinder is ignited by spark discharge of each ignition plug 22.

  On the other hand, the exhaust pipe 23 of the engine 11 is provided with an exhaust gas sensor 24 (air-fuel ratio sensor, oxygen sensor, etc.) for detecting the air-fuel ratio or rich / lean of the exhaust gas. A catalyst 25 such as a three-way catalyst for purifying gas is provided.

  A cooling water temperature sensor 26 that detects the cooling water temperature and a knock sensor 29 that detects knocking are attached to the cylinder block of the engine 11. A crank angle sensor 28 that outputs a pulse signal every time the crankshaft 27 rotates by a predetermined crank angle is attached to the outer peripheral side of the crankshaft 27. Based on the output signal of the crank angle sensor 28, the crank angle and engine The rotation speed is detected.

  As the fuel for the engine 11, alcohol such as ethanol or methanol, or a mixed fuel obtained by mixing alcohol and gasoline can be used, and alcohol fuel containing these alcohols is supplied to the engine 11. Yes. A fuel pump 31 for pumping fuel is provided in the fuel tank 30 for storing fuel, and a fuel pipe 32 is connected to the fuel pump 31 via a filter 34. The fuel discharged from the fuel pump 31 is sent to the delivery pipe 33 through the fuel pipe 32, and is distributed from the delivery pipe 33 to the fuel injection valves 21 of the respective cylinders through a small capacity heating delivery 36 (see FIG. 2). The

  As shown in FIG. 3, the heating delivery 36 (sub-delivery) is provided with a heater 37 (heating means) for heating the internal fuel. The heater 37 is composed of, for example, a PTC heater (self-temperature adjusting heater). Since this PTC heater has a positive resistance temperature characteristic and a resistance value is small in a low temperature region, a relatively large heater current flows after the start of energization, the heater temperature quickly rises, and when a predetermined temperature (Curie temperature) is exceeded, The resistance value is rapidly increased and the heater current (heat generation amount) is rapidly decreased, so that the heater temperature is prevented from rising and automatically adjusted to a predetermined temperature (Curie temperature). In the present embodiment, the heater 37 is disposed so as to sandwich the heating delivery 36 from both the upper and lower sides, and the fuel in the heating delivery 36 is indirectly heated from the outside of the heating delivery 36. It should be noted that the position and type of the heater may be changed as appropriate, for example, a heater may be disposed inside the heating delivery 36 and the fuel in the heating delivery 36 may be directly heated.

  As shown in FIG. 1, the outputs of the various sensors described above are input to a control circuit (hereinafter referred to as “ECU”) 38. The ECU 38 is mainly composed of a microcomputer, and executes various engine control programs stored in a built-in ROM (storage medium), so that the fuel injection amount of the fuel injection valve 21 according to the engine operating state and the like. The ignition timing of the spark plug 22 is controlled.

  At this time, the ECU 38 sets the air-fuel ratio F so that the air-fuel ratio of the exhaust gas matches the target air-fuel ratio based on the output of the exhaust gas sensor 24 when a predetermined air-fuel ratio F / B (feedback) control execution condition is satisfied. / B correction amount is calculated, and air-fuel ratio F / B control for correcting the fuel injection amount of the fuel injection valve 21 using this air-fuel ratio F / B correction amount is executed.

  Further, the ECU 38 executes respective heater control routines shown in FIGS. 8 and 9 to be described later, so that the door of the driver's seat is opened and the door sensor 39 is turned on or the IG switch 40 (ignition switch) is turned on. Depending on whether or not the cooling water temperature is lower than a predetermined value and the alcohol concentration of the fuel is higher than a predetermined value, the heater ON region (the low temperature region where starting without the fuel is heated by the heater 37 is difficult). ).

  Here, the alcohol concentration of the fuel is based on, for example, at least one of an air-fuel ratio F / B correction amount, an air-fuel ratio deviation amount, combustion stability (engine rotation fluctuation), engine torque, etc. during the previous engine operation. The value calculated in the above may be used. In the case of a system including an alcohol concentration sensor for detecting the alcohol concentration of the fuel, the alcohol concentration of the fuel may be detected by the alcohol concentration sensor.

  And when it determines with it being a heater ON area | region, electricity supply of the heater 37 is turned ON and the fuel (fuel injected by the fuel injection valve 21) in the heating delivery 36 is heated. Thereafter, the heater 37 is turned off when the ON time of the heater 37 exceeds a predetermined time.

  Furthermore, the ECU 38 performs the following startup control by executing a startup control routine of FIG. When it is not in the heater ON region, normal start-up control is executed. In this normal start-up control, as shown in FIG. 4, the fuel injection of each cylinder is executed mainly during the valve opening period of the intake valve 41. In this case, both the injection start timing and the injection end timing may be set within the valve opening period of the intake valve 41, but the injection start timing is slightly earlier (advanced side) than the valve opening timing of the intake valve 41. May be set.

  On the other hand, in the heater ON region (region where the coolant temperature is lower than the predetermined value and the alcohol concentration of the fuel is higher than the predetermined value), the start-up control in the heater ON region is executed. In the start-up control in the heater ON region, as shown in FIG. 5, when the fuel heated by the heater 37 is injected by the fuel injection valve 21, the first fuel injection of each cylinder is mainly performed by the intake valve 41. The second and subsequent fuel injections are executed mainly during the valve opening period of the intake valve 41. In this case, in the first fuel injection, both the injection start timing and the injection end timing may be set within the valve closing period of the intake valve 41, but the injection end timing is set to be higher than the valve opening timing of the intake valve 41. It may be set slightly later (retarded side). In the second and subsequent fuel injections, both the injection start timing and the injection end timing may be set within the valve opening period of the intake valve 41, but the injection start timing is set to be higher than the valve opening timing of the intake valve 41. It may be set slightly forward (advance side).

  As shown in FIG. 6, by executing the first fuel injection mainly during the valve closing period of the intake valve 41, the first injected fuel heated by the heater 37 is positively applied to the intake valve 41. The intake valve 41 can be efficiently warmed. As described above, the second fuel injection is executed mainly during the valve opening period of the intake valve 41 in the state where the intake valve 41 is warmed by the first fuel injection, so that the second time heated by the heater 37 is performed. Cooling of the injected fuel by the intake valve 41 can be suppressed, and the temperature of the injected fuel can be made to flow into the cylinder without being lowered so much that the air-fuel mixture can be combusted in the second fuel injection. it can.

  In the start-up control in the heater ON region, as shown in FIG. 7, the throttle opening is controlled to be close to the fully closed position (fully closed position or its vicinity) during cranking by the starter ON (intake air). Fuel injection is prohibited until the time required for the pipe pressure to drop below a predetermined value). As a result, the intake pipe pressure is quickly reduced by cranking while the throttle opening is controlled near the fully closed position (intake pipe negative pressure is increased), and the in-cylinder temperature is increased by the compression heat of the air in the cylinder. In this state, fuel injection is started to effectively promote vaporization of the injected fuel.

  By the way, in the start-up control in the heater ON region, the first fuel injection is executed mainly during the valve closing period of the intake valve 41 to warm up the intake valve 41 with the first injected fuel. At the first fuel injection, the temperature of the fuel flowing into the cylinder is considerably lowered. For this reason, even if ignition is performed for the first fuel injection, it is unlikely that the air-fuel mixture will burn. However, if the air-fuel mixture burns in any one of the cylinders, cranking is in progress. May cause unpleasant rotational fluctuations.

  Therefore, in the start-up control in the heater ON region, ignition for the first fuel injection is prohibited, and ignition is executed for the second and subsequent fuel injections. This reliably prevents the air-fuel mixture from combusting due to the first fuel injection, and prevents unpleasant rotational fluctuations during cranking.

  The processing contents of the routines shown in FIGS. 8 to 10 executed by the ECU 38 will be described below. In this embodiment, power supply to the ECU 38 is started when the door of the driver's seat is opened and the door sensor 39 is turned on or when the IG switch 40 is turned on.

  The heater-on control routine shown in FIG. 8 is executed at a predetermined cycle while the ECU 38 is powered on (after the driver's seat door is opened or the IG switch 40 is turned on). When this routine is started, first, in step 101, depending on whether the coolant temperature is lower than a predetermined value and the alcohol concentration of the fuel is higher than a predetermined value, the heater ON region (if the fuel is not heated by the heater 37). It is determined whether or not the low temperature region is difficult to start. If it is determined in step 101 that the heater is in the ON region, the process proceeds to step 102 where the heater 37 is turned on to heat the fuel in the heating delivery 36 (fuel injected by the fuel injection valve 21). .

  The heater-off control routine shown in FIG. 9 is executed at a predetermined cycle while the ECU 38 is powered on. When this routine is started, first, in step 201, it is determined whether or not the heater ON time (heater ON duration) exceeds a predetermined time. Here, the predetermined time is a value set by a map or a mathematical formula according to the cooling water temperature and the alcohol concentration of the fuel. When it is determined in step 201 that the heater ON time has exceeded a predetermined time, the process proceeds to step 202 and the heater is turned off.

  Further, regardless of whether or not the heater ON time has exceeded a predetermined time, it is determined in the next step 203 whether or not a predetermined time after the start (a predetermined time since the start or completion of the start) has elapsed. When the time has elapsed, the routine proceeds to step 204 where the heater 37 is turned off.

  The start time control routine shown in FIG. 10 is executed at a predetermined cycle while the ECU 38 is turned on, and serves as a start time control means in the claims. When this routine is started, first, at step 301, it is determined whether or not the IG switch 40 is ON. If it is determined that the IG switch 40 is ON, the routine proceeds to step 302 and the heater ON region ( It is determined whether or not the cooling water temperature at the start is lower than a predetermined value and the alcohol concentration of the fuel is higher than a predetermined value.

  If it is determined in step 302 that the heater is not in the ON region, the process proceeds to step 303 and normal start-up control is executed. In this normal start-up control, fuel injection for each cylinder is executed mainly during the valve opening period of the intake valve 41.

  On the other hand, when it is determined in step 302 that the heater is in the ON region, the start-up control in the heater ON region is executed as follows. First, in step 304, it is determined whether the intake pipe pressure has dropped below a predetermined pressure based on whether the starter ON time (cranking time) has exceeded a predetermined time. Here, the predetermined time is set to a time necessary for the intake pipe pressure to drop to a predetermined value or less by cranking in a state where the throttle opening is controlled in the vicinity of the fully closed state.

  If it is determined in step 304 that the starter ON time does not exceed the predetermined time, the process proceeds to step 305, in which fuel injection is prohibited and the throttle opening is set to the fully closed position (fully closed position or the vicinity thereof). Keep in control. Thus, fuel injection is prohibited until a predetermined time elapses while the throttle opening is controlled to be fully closed during cranking.

  Thereafter, when it is determined in step 304 that the starter ON time has exceeded a predetermined time, the intake pipe pressure is reduced by cranking in a state where the throttle opening is controlled to be close to the fully closed position (the intake pipe negative pressure is increased). At the same time, it is determined that the in-cylinder temperature has risen due to the compression heat of the air, fuel injection is permitted, and processing relating to fuel injection after step 306 is executed as follows.

  First, at step 306, it is determined whether or not it is the first fuel injection of each cylinder. If it is the first fuel injection, the routine proceeds to step 307, where the first fuel injection timing is mainly taken as the intake air. The first fuel injection is executed mainly during the valve opening period of the intake valve 41 by setting the valve 41 during the valve closing period, and the ignition for the first fuel injection is prohibited in the next step 308.

  Thereafter, the process proceeds to step 309, where it is determined whether or not the second and subsequent fuel injections of each cylinder. If it is the second and subsequent fuel injections, the process proceeds to step 310 and the second and subsequent fuel injections. The timing is mainly set in the valve opening period of the intake valve 41, and the second and subsequent fuel injections are executed mainly in the valve opening period of the intake valve 41, and in the next step 311, the second and subsequent fuel injections are performed. Allow ignition.

  In the present embodiment described above, when the fuel heated by the heater 37 is injected by the fuel injection valve 21 at the start in the heater ON region (low temperature region), the first fuel injection of each cylinder is mainly performed as the intake valve 41. Therefore, the first injection fuel heated by the heater 37 can be positively applied to the intake valve 41 to efficiently warm the intake valve 41, and thus the first time Since the second fuel injection is executed mainly during the valve opening period of the intake valve 41 in a state where the intake valve 41 is warmed by the fuel injection, the intake air of the second injected fuel heated by the heater 37 is used. Cooling by the valve 41 can be suppressed, and the temperature of the injected fuel can be caused to flow into the cylinder without much lowering. Thereby, combustion of the air-fuel mixture can be enabled by the second fuel injection, and startability at a low temperature can be ensured. In addition, the amount of heat generated by the heater 37 may be set so that the second injected fuel with a small temperature drop can flow into the cylinder at a temperature at which the fuel can be started (for example, a temperature higher than the flash point). The heat generation amount of the heater 37 can be reduced to reduce the power consumption of the heater 37, and both startability and low power consumption can be achieved.

  Further, in this embodiment, during the cranking at the start in the heater ON region (low temperature region), the throttle opening is controlled in the vicinity of the fully closed state for a predetermined time (when the intake pipe pressure drops below the predetermined value). Fuel injection is prohibited until the required time) has elapsed, so the intake pipe pressure is quickly reduced by cranking while the throttle opening is controlled to be close to full close (intake pipe negative pressure is increased). At the same time, fuel injection can be started in a state where the in-cylinder temperature is raised by the compression heat of the air in the cylinder, and the vaporization of the injected fuel can be effectively promoted.

  In the case of a system equipped with an ISC valve (idle control valve), fuel injection may be prohibited until a predetermined time elapses while the opening of the ISC valve is controlled near the fully closed position. In the case of a system equipped with an intake pipe pressure sensor, the intake pipe pressure detected by the intake pipe pressure sensor in a state in which the opening of the intake air amount adjustment valve (throttle valve or ISC valve) is controlled to be fully closed is You may make it prohibit fuel injection until it falls below a predetermined value. However, the present invention is not limited to a configuration in which fuel injection is prohibited until a predetermined period elapses during cranking at low temperature start, and fuel injection is started promptly at low temperature start as long as startability can be ensured. You may do it.

  Further, in this embodiment, since the ignition for the first fuel injection is prohibited, the air-fuel mixture is surely prevented from burning by the first fuel injection, and uncomfortable rotation during cranking. It is possible to prevent fluctuations from occurring. However, in the present invention, ignition may be performed for the first fuel injection.

  In the above embodiment, the present invention is applied to a system that uses alcohol fuel (alcohol or a fuel containing alcohol) as the fuel. However, the present invention may be applied to a system that uses gasoline as the fuel.

It is a schematic block diagram of the whole engine control system in one Example of this invention. It is a front view of a heating delivery and its peripheral part. It is sectional drawing of a heat delivery. It is a figure explaining normal starting time control. It is a figure explaining the starting control in a heater ON area | region. It is a time chart which shows the action of intake valve temperature at the time of performing control at the time of starting in a heater ON field. It is a time chart which shows behavior, such as intake pipe pressure and in-cylinder temperature, when starting-time control is performed in the heater ON region. It is a flowchart explaining the flow of a process of a heater ON control routine. It is a flowchart explaining the flow of a process of a heater off control routine. It is a flowchart explaining the flow of a process of the control routine at the time of starting.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 11 ... Engine (internal combustion engine), 12 ... Intake pipe, 16 ... Throttle valve (intake air amount adjustment valve), 21 ... Fuel injection valve, 22 ... Spark plug, 23 ... Exhaust pipe, 26 ... Cooling water temperature sensor, 33 ... Delivery Pipe, 36 ... Heating delivery, 37 ... Heater (heating means), 38 ... ECU (startup control means), 41 ... Intake valve

Claims (4)

In a control device for an internal combustion engine, comprising: a fuel injection valve that injects fuel into an intake port of the internal combustion engine; and a heating unit that heats the fuel injected by the fuel injection valve.
When the fuel heated by the heating means is injected by the fuel injection valve when the internal combustion engine is started at a low temperature, the first fuel injection of each cylinder is executed mainly during the valve closing period of the intake valve. A control apparatus for an internal combustion engine, comprising start-up control means for executing fuel injection mainly during a valve opening period of an intake valve.   The control device for an internal combustion engine according to claim 1, wherein the fuel is alcohol or fuel containing alcohol.   The start-up control means passes a predetermined period during which the pressure in the intake passage drops below a predetermined value while the opening of the intake air amount adjustment valve is controlled to the closed side during cranking at the time of low-temperature start of the internal combustion engine 3. The control device for an internal combustion engine according to claim 1 or 2, wherein fuel injection is prohibited until the engine is stopped.   The internal combustion engine control device according to any one of claims 1 to 3, wherein the start-up control means prohibits ignition of the first fuel injection.

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