JP6870350B2 - Internal combustion engine control device - Google Patents

Description

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

Conventionally, as a combustion form of an internal combustion engine such as a gasoline engine, SI (Spark Ignition) combustion in which an air-fuel mixture is forcibly ignited by a spark discharge from a spark plug has been widely and generally used. In recent years, the development of a gasoline engine that utilizes premixed compression self-ignition combustion in which a high-temperature burned gas is introduced into a cylinder to self-ignite the air-fuel mixture as a combustion mode has been promoted. Here, the premixed compression self-ignition combustion is referred to as HCCI (Homogeneous Charge Compression Ignition) combustion.

According to Patent Document 1, when it is determined that the required torque and the engine rotation speed are within the possible range of compression self-ignition combustion, preparations for compression self-ignition combustion are started, and conditions for switching to compression self-ignition combustion are possible. It is disclosed that compression self-ignition combustion is started when is satisfied.

Further, since the engine speed and torque at which the thermal efficiency at the same output is optimal are different between SI combustion and HCCI combustion, it is necessary to have an optimum gear ratio target map for each. With such a configuration, when the driver's required output enters the HCCI operable range from outside the HCCI operable range, the gear ratio target map is switched from SI to HCCI. After that, when the gear ratio actually changed and the engine speed and the required torque entered the HCCI operable range, preparations for switching from SI operation to HCCI operation were started.

Japanese Unexamined Patent Publication No. 2007-16685

In this way, when the driver's required output falls within the HCCI operable range from outside the HCCI operable range, the target gear ratio is first changed, and then when the engine speed and required torque enter the HCCI operable range, the HCCI A preparatory operation for operation is performed. After that, when the preparation for the HCCI operation is completed, the switching to the HCCI operation is performed. Therefore, it takes time to start the HCCI operation, and the frequency of the HCCI operation is reduced, so that there is a problem that the improvement in fuel efficiency due to the HCCI operation is reduced.

Therefore, an object of the present invention is to provide a control device for an internal combustion engine capable of minimizing the switching time from SI operation to HCCI operation and increasing the frequency of HCCI operation.

In order to solve the above problems, the present invention is a control device for an internal combustion engine mounted on a vehicle equipped with an automatic transmission and a supercharger, which is configured to switch between spark ignition combustion and compression self-ignition combustion. The internal combustion engine is provided with a control unit that starts preparation for switching from the spark ignition combustion to the compression self-ignition combustion when the required output of the internal combustion engine enters a predetermined HCCI operable range, and the control unit prepares for the switching. As a result, switching from the spark ignition gear ratio map having a small gear ratio to the compression self-ignition gear ratio map having a large gear ratio in the gear ratio target map for controlling the gear ratio of the automatic transmission and the supercharger The amount of intake air is increased by the supply pressure .

As described above, according to the present invention, the switching time from SI operation to HCCI operation can be minimized, and the frequency of HCCI operation can be increased.

FIG. 1 is a schematic configuration diagram of a control device for an internal combustion engine according to an embodiment of the present invention. FIG. 2 is a diagram showing an operating region of a control device for an internal combustion engine according to an embodiment of the present invention. FIG. 3 is a diagram showing an example of a shift map of a control device for an internal combustion engine according to an embodiment of the present invention. FIG. 4 is a flowchart showing a procedure of HCCI switching processing of the control device of the internal combustion engine according to the embodiment of the present invention. FIG. 5 is a time chart showing the operation of the control device of the internal combustion engine according to the embodiment of the present invention by the HCCI switching process.

The control device for an internal combustion engine according to an embodiment of the present invention is a control device for an internal combustion engine mounted on a vehicle equipped with an automatic transmission, which is configured to switch between spark ignition combustion and compression self-ignition combustion. When the required output of the internal combustion engine falls within the predetermined HCCI operable range, the gear ratio target map that controls the gear ratio of the automatic transmission is switched from the SI gear ratio map to the HCCI gear ratio map, and compression self-ignition is performed. It is configured to include a control unit that initiates preparations for combustion. As a result, the switching time from SI operation to HCCI operation can be minimized, and the frequency of HCCI operation can be increased.

Hereinafter, the control device for the internal combustion engine according to the embodiment of the present invention will be described in detail with reference to the drawings.

In FIG. 1, a vehicle 1 equipped with an internal combustion engine control device according to an embodiment of the present invention includes an internal combustion engine type engine 2 and an ECU (Electronic Control Unit) 3 as a control unit. ..

The engine 2 includes a cylinder block 4 and a cylinder head 5 fastened to the upper portion of the cylinder block 4. A cylinder 4a is formed in the cylinder block 4, and a piston 6 capable of reciprocating up and down is housed inside the cylinder (hereinafter referred to as "inside the cylinder").

A combustion chamber 7 is provided above the cylinder 4a. The combustion chamber 7 is defined by the top surface of the piston 6 and the bottom surface of the cylinder head 5. The engine 2 is a so-called four-cycle gasoline engine that performs a series of four strokes including an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke while the piston 6 reciprocates twice in the cylinder.

The piston 6 is connected to a crankshaft (not shown) via a connecting rod 8. The connecting rod 8 converts the reciprocating motion of the piston 6 into the rotational motion of the crankshaft.

The cylinder head 5 is provided with a spark plug 50, an intake port 51, and an exhaust port 52. The spark plug 50 is arranged in the cylinder head 5 with the electrodes protruding into the combustion chamber 7, and the ignition timing is adjusted by the ECU 3.

The intake port 51 communicates the combustion chamber 7 with the intake passage 16a described later. Further, the intake port 51 is provided with an intake valve 11.

The intake valve 11 is opened and closed to communicate or shut off the intake passage 16a and the combustion chamber 7. The intake valve 11 is opened and closed by the intake side variable valve mechanism 12.

As the intake-side variable valve mechanism 12, for example, an electromagnetic variable valve mechanism that opens and closes the intake valve 11 by an electromagnetic actuator composed of an electromagnet, a spring, or the like can be used. Specifically, the intake-side variable valve mechanism 12 opens the intake valve 11 which is constantly urged in the valve closing direction by a spring by attracting a movable portion fixed to the intake valve 11 by excitation of an electromagnet. It is designed to move in the valve direction.

Further, the intake side variable valve mechanism 12 is electrically connected to the ECU 3 described later, and the excitation and non-excitation of the electromagnet are controlled by the ECU 3. Therefore, the ECU 3 can arbitrarily change the opening / closing timing of the intake valve 11, whereby the opening period of the intake valve 11 can be easily adjusted.

Further, the intake side variable valve mechanism 12 can continuously change the lift amount of the intake valve 11 with the opening / closing timing of the intake valve 11 by adjusting the exciting current for the electromagnet by the ECU 3.

As the intake side variable valve mechanism 12, a hydraulic variable valve mechanism using a hydraulic actuator may be used instead of the electromagnetic actuator.

Further, an intake manifold 13 is connected to the intake port 51 side of the cylinder head 5. An injector 10 is provided in the vicinity of the intake port 51 of the intake manifold 13.

The injector 10 is a so-called port injection type fuel injection valve that injects fuel pumped by a fuel pump from a fuel tank (not shown) into the intake port 51. The injector 10 is not limited to the port injection type, and may be a so-called direct injection type fuel injection valve that directly injects fuel into the combustion chamber 7.

The fuel injected into the intake port 51 is mixed with intake air, that is, fresh air to form an air-fuel mixture, which is introduced into the combustion chamber 7. The air-fuel mixture introduced into the combustion chamber 7 is burned and exploded by spark discharge by the spark plug 50 or self-ignition by compression in the combustion chamber. Due to the combustion and explosion of this air-fuel mixture, the piston 6 reciprocates in the cylinder 4a, and the crankshaft rotates.

A surge tank 14 is provided on the upstream side of the intake manifold 13 in the intake direction in which the intake air flows. The surge tank 14 is provided with an intake pressure sensor 15 that detects the intake pressure.

An intake pipe 16 is connected to the upstream side of the surge tank 14 in the intake direction. Inside the intake pipe 16, an intake passage 16a communicating with the intake port 51 is formed. The intake passage 16a is provided with a compressor 17 for compressing air, an intercooler 18 for cooling the compressed air, and an intake throttle 19 for adjusting the flow rate of air in this order from the upstream in the intake direction.

The intake throttle 19 adjusts the intake air amount of the engine 2 by controlling the throttle opening degree in response to a command signal from the ECU 3. The intake throttle 19 is provided with a throttle opening sensor 41 for detecting the throttle opening.

On the upstream side of the intake throttle 19 in the intake direction, there are a supercharging pressure sensor 42 that detects the boost pressure by the turbocharger 9, which will be described later, and an intake temperature sensor 43 that detects the intake temperature upstream of the intake throttle 19 in the intake direction. It is provided.

On the other hand, the exhaust port 52 is provided with an exhaust valve 21. The exhaust valve 21 is opened and closed to communicate or shut off the exhaust passage 23a and the combustion chamber 7, which will be described later. The exhaust valve 21 is opened and closed by the exhaust side variable valve mechanism 22.

Since the exhaust side variable valve mechanism 22 has the same configuration as the intake side variable valve mechanism 12 described above, detailed description thereof will be omitted, but the excitation and non-excitation of the electromagnet are controlled by the ECU 3 to exhaust the gas. The opening / closing timing and lift amount of the valve 21 are arbitrarily changed. Therefore, the ECU 3 can easily adjust the valve opening period and the lift amount of the exhaust valve 21.

An exhaust pipe 23 is connected to the exhaust port 52 side of the cylinder head 5. Inside the exhaust pipe 23, an exhaust passage 23a communicating with the exhaust port 52 is formed. The exhaust passage 23a is provided with an exhaust turbine 24 driven by an exhaust flow, a catalyst (not shown) for purifying the exhaust, and a muffler (not shown) for silencing.

The exhaust turbine 24 is connected to the compressor 17. The power of the exhaust turbine 24 driven by the exhaust flow is used as the power for the compressor 17 to compress the air. The compressor 17 and the exhaust turbine 24 constitute a turbocharger 9 as a supercharger.

A bypass passage 25 is provided between the upstream side and the downstream side in the exhaust direction in which the exhaust gas of the exhaust pipe 23 flows across the exhaust turbine 24. The bypass passage 25 is provided with a wastegate valve 26 capable of adjusting the exhaust flow to the exhaust turbine 24. The wastegate valve 26 can control the supercharging pressure, which is the pressure of the intake air obtained by supercharging the turbocharger 9, by adjusting the exhaust flow to the exhaust turbine 24. The wastegate valve 26 is composed of, for example, an electromagnetic valve, and is controlled to open and close by the ECU 3. The boost pressure may be controlled by using a variable nozzle turbo whose boost pressure can be changed.

An automatic transmission 31 is connected to the engine 2. The automatic transmission 31 shifts the rotation of the crankshaft of the engine 2 at a predetermined gear ratio and transmits it to a drive shaft (not shown) via a differential gear (not shown) or the like to rotate a wheel (not shown). The automatic transmission 31 is composed of, for example, a CVT (Continuously Variable Transmission). The automatic transmission 31 can change the gear ratio under the control of the ECU 3.

The ECU 3 is composed of a computer unit including a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an input port, and an output port.

In the ROM of this computer unit, a program for making the computer unit function as an ECU 3 is stored together with various control constants, various maps, and the like. That is, when the CPU executes the program stored in the ROM, the computer unit functions as the ECU 3.

In addition to the above-mentioned intake pressure sensor 15, throttle opening sensor 41, boost pressure sensor 42, and intake temperature sensor 43, the input port of the ECU 3 includes an air flow meter 44, a crank angle sensor 45, an exhaust pressure sensor 46, and an exhaust temperature. Various sensors such as the sensor 47 and the accelerator opening sensor 48 are connected.

The air flow meter 44 detects the intake air amount. The crank angle sensor 45 outputs a rectangular crank angle signal for each predetermined crank angle as the engine 2 rotates. The ECU 3 calculates the engine speed, which is the engine speed of the engine 2, based on the crank angle signal.

The exhaust pressure sensor 46 detects the exhaust pressure. The exhaust temperature sensor 47 detects the temperature of the exhaust gas. The accelerator opening sensor 48 detects the amount of depression of the accelerator pedal (not shown) by the driver as the accelerator opening.

On the other hand, the output port of the ECU 3 includes the above-mentioned injector 10, an intake side variable valve mechanism 12, an intake throttle 19, an exhaust side variable valve mechanism 22, a wastegate valve 26, and a spark plug 50. Various control targets are connected.

The ECU 3 switches between SI combustion and HCCI combustion according to the operating state of the engine 2. Specifically, the ECU 3 refers to a combustion region map as shown in FIG. 2 in which the engine speed and the required engine output are parameters, so that the operating region of the engine 2 is the SI operable region and the HCCI operable region. It is determined which one is in, and based on this determination, SI operation or HCCI operation is selected.

The ECU 3 calculates the required engine output based on the accelerator opening degree and the like input from the accelerator opening degree sensor 48.

In FIG. 2, the SI operable region is a region indicated by reference numerals S and H, and the HCCI operable region is a region indicated by reference numeral H. As shown in FIG. 2, the HCCI operable area H is set in a range where the required engine output is relatively low, and the SI operable area S is set in a range where the required engine output is higher than the HCCI operable area H.

In FIG. 2, the target operation line L _s is a line connecting points where combustion can be realized with optimum thermal efficiency in SI operation. The target operating line L _h is a line connecting points where combustion can be realized with optimum thermal efficiency in HCCI operation.

Normally, in an engine in which only spark ignition is performed, engine torque control and transmission speed change control are performed so that combustion is performed on the target operating line. However, in the engine 2 in which two different operable regions are set as described above, the point at which the thermal efficiency is maximized in each region is different in the same required engine output.

Specifically, as shown in FIG. 2, in a given requested engine output O, the highest point of thermal efficiency in HCCI operation can region H P _h and the highest point thermal efficiency in SI operating region S P _s And exists. As described above, since the point at which the thermal efficiency is maximized is different for the same required engine output, in this embodiment, a different gear ratio map is prepared for each combustion mode, and the gear ratio map is switched according to the required engine output. I am trying to do it.

In FIG. 2, when the required engine output is within the HCCI operation range R, the ECU 3 uses the gear ratio map for HCCI operation. The HCCI operable range R is set between _{O 1} and O _{2 of the required engine output.}

_{Further, hysteresis R h1} and hysteresis R _h2 are provided at the upper and lower ends of the HCCI operable range R. Specifically, the required engine output O ₃ slightly larger than the required engine output O ₁ is set, and the lower hysteresis R _h1 is set between the required engine output O ₃ and the required engine output O _1. It also sets the required engine output O ₂ slightly less than the required engine output O _4, is between the required engine output O ₄ and the required engine output O ₂ and upper hysteresis R _h2.

The ECU 3 has, for example, a gear ratio when the required engine output enters the HCCI operable range R, not when the required engine output enters the HCCI operable range R, but when it _{exceeds hysteresis R h1} or hysteresis R _h2. Switch the map for HCCI operation.

By doing so, it is possible to prevent the occurrence of hunting in which the combustion mode frequently switches even when the required engine output fluctuates frequently in the vicinity of the boundary of the HCCI operable range R.

In this embodiment, as shown in FIG. 3, the HCCI operation gear ratio map V _h and the SI operation gear ratio map V _s are provided.

The HCCI driving gear ratio map V _h is a map for adjusting the gear ratio of the automatic transmission 31 so that the engine 2 is operated on _{the target operating line L h} of the HCCI operable region H. The SI operation gear ratio map V _s is a map for adjusting the gear ratio of the automatic transmission 31 so that the engine 2 is operated on _{the target operating line L s} of the SI operable region S.

_{The ECU 3 selects either the HCCI operation gear ratio map V h} or the SI operation gear ratio map V _s according to whether or not the required engine output is within the HCCI operable range R, and the gear ratio thereof. The gear ratio of the automatic transmission 31 is adjusted with the target of the map.

Next, with reference to FIG. 3, the operation of switching the combustion mode of the control device of the internal combustion engine according to the present embodiment will be described. In the following, the operation when switching from the SI operable area S to the HCCI operable area H, specifically, the required engine output shifts from the point A to the point B (a to b on the gear ratio map) in the figure. The operation at the time will be explained.

As shown in FIG. 3, A point, since it is HCCI operation range R out, ECU 3 selects the SI operation for gear ratio map _{V s} as the gear ratio map.

For example, when the required engine output by the driver of the accelerator operation from the point A is lowered, ECU 3 is adjusted so that the gear ratio of the automatic transmission 31 is reduced based on the SI operation for gear ratio map V _s. Thus, it is shown in FIG. 2, along the target operating line L _s of SI operating region S engine rotational speed is lowered. The engine torque is controlled according to the required engine torque obtained by dividing the required engine output by the actual engine speed.

Gradually decrease the required engine output and the engine speed, the required engine output is reduced to O ₄ of the lower end of the hysteresis R _h2, ECU 3 switches the gear ratio map in HCCI operation for gear ratio map V _h. Further, the ECU 3 mainly increases the intake air amount in preparation for switching from the SI operation to the HCCI operation. In addition to increasing the intake amount, the fuel injection timing is changed for stratified combustion when lean combustion is performed, the ignition timing is retarded when maintaining the stoichiometric air-fuel ratio, continuously variable valve timing and continuously variable lift. When the mechanism is provided, the control value may be brought close to the value of the HCCI condition (increase of internal EGR (Exhaust Gas Recirculation) gas) or the like.

ECU3, when switching the transmission gear ratio map to HCCI operation for gear ratio map V _h, as shown in FIG. 3 is adjusted to the gear ratio increases. As shown in FIG. 3, even if abruptly change the transmission ratio, from the response of the relationship of the automatic transmission 31, the actual transmission ratio, for example, varies along the curve V _r.

Further the required engine output decreases, ECU 3 along the HCCI operation for gear ratio map V _h, adjusted to the gear ratio becomes smaller. Then, the engine speed and the required engine output enter the HCCI operable region H in the vicinity of point B where the actual gear ratio becomes the same as the gear ratio of the HCCI driving gear ratio map V _h along the curve V _r. Then, the ECU 3 determines whether or not the state quantity such as the intake pressure has reached the target of HCCI operation switching. When it is determined that the state quantity such as the intake pressure has reached the target of HCCI operation switching, the ECU 3 switches each control value such as the valve operating valve for HCCI operation and starts the HCCI operation.

The HCCI switching process by the control device of the internal combustion engine according to the present embodiment configured as described above will be described with reference to FIG. The HCCI switching process described below is started when the process of the ECU 3 is started, and is executed for each cycle of each cylinder (in the case of four cylinders, every crank angle of 180 deg.).

In step S1, the ECU 3 determines whether or not SI operation is in progress. If it is determined that the SI operation is not in progress, the ECU 3 ends the process.

When it is determined that the SI operation is in progress, in step S2, the ECU 3 determines whether or not the required engine output is within the above-mentioned HCCI operable range. If the required engine output is determined not to HCCI operable range, in step S8, ECU 3 selects the SI operation for gear ratio map V _s as the speed ratio target map, the process ends.

If the required engine output is determined to be in the HCCI operable range, in step S3, ECU 3 selects the HCCI operation for gear ratio map _{V h} as the speed ratio target map. Then, the ECU 3 starts changing the gear ratio (change in engine speed and target torque) toward the target gear ratio. HCCI operation for gear ratio map V _h is essentially in HCCI operation is set so as to achieve the engine speed and the torque thermal efficiency is the highest.

In step S4, the ECU 3 mainly increases the intake air amount in preparation for switching from the SI operation to the HCCI operation. In addition to increasing the intake amount, the fuel injection timing is changed for stratified combustion when lean combustion is performed, the ignition timing is retarded when maintaining the stoichiometric air-fuel ratio, continuously variable valve timing and continuously variable lift. When the mechanism is provided, the control value may be kept close to the value of the HCCI condition (increase of the internal EGR gas) or the like.

In step S5, the ECU 3 determines whether or not the engine speed and the required engine output are within the above-mentioned HCCI operable region H. This speed ratio that approaches the target value of the HCCI operation for gear ratio map V _h, judges whether the required engine output with the engine rotational speed enters the HCCI operable region H. When it is determined that the engine speed and the required engine output are not within the HCCI operable area H, the ECU 3 ends the process.

When it is determined that the engine speed and the required engine output are within the HCCI operable region H, in step S6, the ECU 3 determines whether or not the preparation for switching from the SI operation to the HCCI operation is completed. If stable HCCI operation is possible by a method such as predicting whether stable operation is possible when switching to HCCI operation based on each sensor value and various state quantities calculated from them. It is determined that the preparation for switching to the HCCI operation is completed. When it is determined that the preparation for switching from the SI operation to the HCCI operation is not completed, the ECU 3 ends the process.

When it is determined that the preparation for switching from the SI operation to the HCCI operation is completed, in step S7, the ECU 3 switches each control value such as the valve for the HCCI operation and starts the HCCI operation.

The operation by such HCCI switching processing will be described with reference to FIG.
When the accelerator opening is reduced, the required engine output is reduced, and the HCCI operation range is reached at timing t1, the gear ratio target map is _{switched to the HCCI driving gear ratio map V h} , and the gear ratio is toward the target gear ratio. The engine speed changes.

In addition, preparations for switching from SI operation to HCCI operation have started, the wastegate valve 26 is fully closed toward the target intake pressure, the intake amount is increased, the closing time of the exhaust valve 21 is advanced, and the internal EGR The amount is increased.

When the engine speed and the required engine output enter the HCCI operable region H at the timing t2, it is determined whether the preparation for switching from the SI operation to the HCCI operation is completed. In the conventional switching process, preparations for switching from SI operation to HCCI operation are started from this timing when the engine speed and the required engine output enter the HCCI operable area H. In this embodiment, preparations for switching from SI operation to HCCI operation are started at an earlier stage than the conventional switching process.

At timing t3, when it is determined that the preparation for switching from SI operation to HCCI operation is completed because the intake pressure reaches the target intake pressure, the control of the exhaust valve 21 and the like is switched to HCCI operation, and HCCI operation starts. Will be done.

In this way, since the preparation for switching from the SI operation to the HCCI operation is started at an earlier stage than the conventional switching process, the HCCI operation can be started at an earlier stage than the conventional switching process, and the SI operation to the HCCI operation can be started. The switching time to is minimized, and the frequency of HCCI operation can be increased.

In this embodiment, the HCCI driving range is determined by the required engine output, but the required engine output may be determined by the driver's required driving force divided by the current vehicle speed. In this case, in the map of FIG. 2, the vertical axis represents the driving force required by the driver and the horizontal axis represents the vehicle speed.

Although the embodiments of the present invention have been disclosed, it is clear that some skilled in the art can make changes without departing from the scope of the present invention. All such modifications and equivalents are intended to be included in the following claims.

1 Vehicle 2 Engine (internal combustion engine)
3 ECU (control unit)
9 Turbocharger (supercharger)
11 Intake valve 12 Intake side variable valve mechanism 15 Intake pressure sensor 19 Intake throttle 26 Westgate valve 31 Automatic transmission 42 Supercharging pressure sensor 45 Crank angle sensor 48 Accelerator opening sensor

Claims (3)

It is a control device for an internal combustion engine mounted on a vehicle equipped with an automatic transmission and a supercharger, which is configured to switch between spark ignition combustion and compression self-ignition combustion.
A control unit for starting preparation for switching from the spark ignition combustion to the compression self-ignition combustion when the required output of the internal combustion engine falls within a predetermined HCCI operable range is provided.
In preparation for the switching, the control unit switches from the gear ratio map for spark ignition , which has a small gear ratio, to the gear ratio map for compression self-ignition, which has a large gear ratio, in the gear ratio target map that controls the gear ratio of the automatic transmission. And an internal combustion engine control device that increases the intake amount by the boost pressure of the supercharger. The control device for an internal combustion engine according to claim 1, wherein the control unit increases the amount of the internal EGR in preparation for the switching. Wherein the control unit, after starting the switching preparation, when the required output and the engine speed of the internal combustion engine has entered a predetermined HCCI operation region, claim 1 or determining whether the switching preparation is complete The control device for an internal combustion engine according to claim 2.

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