JP2001207880A - Cylinder injection type spark ignition engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform stratified charge combustion in an engine operation area of a wide range. SOLUTION: This cylinder injection type spark ignition engine is provided with a fuel injection valve 16 for directly injecting fuel into a combustion chamber 15 and a spark plug 16a for igniting the fuel in the combustion chamber. Present required engine output is detected, a theoretical engine speed required in either one of engine operation modes is calculated for obtaining the detected present required engine output, and when this theoretical engine speed is a first limit value to a second limit value in the theoretical engine speed corresponding to engine torque, the engine operation mode is set to two cycles, and a combustion mode is set to the stratified charge combustion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a direct injection type spark ignition engine.

[0002]

2. Description of the Related Art A technique for stratified combustion of fuel in a combustion chamber for improving fuel efficiency of a direct injection spark ignition engine is known. The stratified combustion means combustion in which fuel is injected from the fuel injection valve into the combustion chamber so that the fuel exists only near the spark plug in the combustion chamber, and the fuel is burned by the spark plug. As described above, in the stratified charge combustion, the fuel is injected so that the fuel is present only in the vicinity of the ignition plug, so that even a small amount of fuel can be satisfactorily burned, and a sufficient engine output can be obtained. Therefore, the fuel efficiency of stratified combustion is high. An in-cylinder injection type spark ignition engine which performs stratified combustion in this way is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-79063.

[0003]

In order to effectively perform stratified combustion, it is necessary that the engine speed be relatively low. This is because, when the engine speed is relatively high, the reciprocating speed of the piston in the combustion chamber is high, and the fuel injected near the spark plug is diffused into the combustion chamber by the rapidly moving piston. Also, stratified combustion can be used only when the engine load is relatively small. This is because the torque that can be output by stratified combustion is relatively small. Thus, the engine operating range in which stratified combustion can be performed is limited according to the engine speed and the engine load. However, from the viewpoint of improving fuel efficiency, it is preferable that stratified combustion can be performed in the engine operating range as wide as possible. Therefore, an object of the present invention is to enable stratified combustion to be performed in a wide range of engine operation.

[0004]

According to a first aspect of the present invention, there is provided a fuel injection valve for injecting fuel directly into a combustion chamber, and an ignition valve for igniting fuel in the combustion chamber. A plug, means for switching the engine operation mode between four cycles and two cycles, means for switching the combustion mode in the combustion chamber between stratified combustion and uniform combustion, and detection of the current required engine output Means for calculating the theoretical engine speed required in one of the engine operation modes to obtain the detected current required engine output, and a theoretical engine speed corresponding to the engine torque. Calculating means for calculating a first limit value and a second limit value larger than the first limit value in the cylinder injection type spark ignition engine, wherein the theoretical engine speed is equal to or higher than the first limit value. A combustion mode between stratified charge combustion with a 2-cycle engine operation mode when the second limit value or less. According to this, when the theoretical engine speed is equal to or higher than the first limit value and equal to or lower than the second limit value, the engine operation mode is operated in two cycles, so that the engine speed required to output the required engine output is reduced. It becomes smaller than the engine speed required during the operation of the four-cycle engine.

According to a second aspect, in the first aspect, when the theoretical engine speed is equal to or less than the first limit value, the engine operation mode is set to four cycles and the combustion mode is set to stratified combustion. When the rotation speed is equal to or higher than the second limit value, the engine operation mode is set to four cycles and the combustion mode is set to uniform combustion. According to a third aspect, in the first aspect, when the theoretical engine speed is equal to or less than the first limit value, the engine operation mode is set to four.
When the theoretical engine speed is equal to or higher than the second limit value, the engine operation mode is set to two cycles and the combustion mode is set to uniform combustion.

According to a fourth aspect, in the first aspect, when the theoretical engine speed is equal to or less than the first limit value, the engine operation mode is set to two cycles and the combustion mode is set to stratified combustion. When the rotation speed is equal to or higher than the second limit value, the engine operation mode is set to four cycles and the combustion mode is set to uniform combustion. According to a fifth aspect, in any one of the second to fourth aspects, when both the engine operation mode and the combustion mode are switched, the combustion mode is set to uniform combustion and the engine operation mode is set to a low theoretical engine speed. Side engine operation mode.

According to a sixth aspect of the present invention, in any one of the second to fourth aspects, there is provided an engine speed changing means for changing an engine speed output from the engine, and the engine operation mode is set to four. The engine speed is decreased when the cycle is switched from two to two, and the engine speed is increased when the engine operation mode is switched from two to four.

According to a seventh aspect, in the sixth aspect, the engine speed changing means is a continuously variable transmission. According to an eighth invention, in any one of the second to fourth inventions, there is provided an engine torque increasing means for increasing the engine torque when switching the engine operation mode from two cycles to four cycles.

According to a ninth aspect, in the eighth aspect, the engine torque increasing means increases the engine torque by increasing the fuel injection amount from the fuel injector. According to a tenth aspect, in the eighth aspect, the engine torque increasing means includes an electric motor connected to an engine output shaft, and the engine increases the engine torque by rotating the engine output shaft by the electric motor.

According to a tenth aspect of the present invention, in any one of the second to fourth aspects, there is provided an engine torque reducing means for reducing the engine torque when switching the engine operation mode from four cycles to two cycles. I do. According to a twelfth aspect, in any one of the second to fourth aspects, the engine torque reducing means reduces the engine torque by reducing the fuel injection amount from the fuel injection valve.

According to a thirteenth aspect, in the twelfth aspect, the engine torque reducing means reduces the engine torque by stopping the fuel injection from the fuel injection valve.
According to a fourteenth aspect, in the twelfth aspect, the engine torque reducing means includes a generator connected to an engine output shaft, and the engine output shaft generates the engine torque by causing the generator to generate power. Decrease.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIGS. 1 and 2 show a drive system including an internal combustion engine to which the present invention is applied. FIG. 1 is an overall view of the drive system of the present embodiment. The drive system according to the present embodiment is a so-called hybrid type drive system that is mounted on a vehicle and uses motive power obtained by combining output from an internal combustion engine and output from an electric motor. The internal combustion engine of this embodiment is a direct injection type spark ignition engine.

In FIG. 1, reference numeral 1 denotes an engine body. An engine output shaft 3 of the engine body 1 is connected to a transmission 9 and a generator 4 via a power transmission device 2. The transmission according to the present embodiment is a continuously variable transmission that can continuously change the gear ratio. Generator 4 is connected to battery 6 via inverter 5. The battery 6 is connected to an electric motor (electric motor) 7 via the inverter 5. The electric motor 7 is connected to the transmission 9. The transmission 9 is also connected to an axle 10 connected to the wheels 8.

Next, the operation of the drive system will be briefly described. When the vehicle starts or when the required output is small, the electric motor 7 is driven by the electric power stored in the battery 6, thereby driving the wheels 8. When the required output is very high, the output of the engine body 1 is transmitted to the transmission 9 and the generator 4.
To communicate with. The electric power generated by the generator 4 is directly supplied to the electric motor 7 to drive the electric motor 7. Further, electric power is also supplied from the battery 6 to the electric motor 7 to drive the electric motor 7. That is, when the required output is very high, the transmission 9 transmits the output directly transmitted from the engine body 1 and the power generated by the output from the engine body 1 to the transmission 9.
Power from battery 6 is transmitted.

When the vehicle is to be decelerated, the engine body 1
And the battery 6 does not drive the transmission 9, but drives the transmission 9 by the axle 10, thereby decelerating the vehicle. The electric motor 7 is rotated by the power transmitted to the transmission 9. At this time, the electric motor 7 works as a generator,
The electric power generated by the electric motor 7 is
Supplied and stored. In a normal operation state other than the above, the output from the engine body 1 is transmitted to the transmission 9 and the generator 4, and the output is driven by the power directly transmitted to the transmission 9 and the power generated by the generator 4. It is driven by the motive power from the electric motor 7.

Next, the internal combustion engine will be described. FIG. 2 is an overall view showing the internal combustion engine of this embodiment. Referring to FIG. 2, 1 is an engine body, 12 is a cylinder block, 13 is a cylinder head, 14 is a piston, 15 is a combustion chamber, 16 is an electrically controlled fuel injection valve, 16a is a spark plug, 17 is an intake valve, 18 is An intake port, 19 indicates an exhaust valve, and 20 indicates an exhaust port. The intake port 18 is connected to a surge tank 22 through a corresponding intake branch pipe 21, and the surge tank 22 is connected to a supercharger, for example, an outlet of a compressor 26 of an exhaust turbocharger 25 via an intake duct 23 and an intercooler 24. Be linked. The inlet of the compressor 26 is connected to an air cleaner 28 via an air suction pipe 27, and a throttle valve 30 driven by a step motor 29 is arranged in the air suction pipe 27. A mass flow detector 31 for detecting the mass flow of the intake air is disposed in the air intake pipe 27 upstream of the throttle valve 30.

The exhaust port 20 is connected via an exhaust manifold 32 to an inlet of an exhaust turbine 33 of an exhaust turbocharger 25, and the outlet of the exhaust turbine 33 is provided with a three-way catalyst 35 via an exhaust pipe 34. Converter 3
6. Exhaust pipe 3 downstream of catalytic converter 36
4 are connected to each other through an exhaust gas circulation (hereinafter, EGR) passage 50, and a stepping motor 5 is provided in the EGR passage 50.
An EGR control valve 52 driven by 1 is disposed. In the EGR passage 50, EG flowing through the EGR passage 50 is provided.
An intercooler 53 for cooling the R gas is arranged. In the embodiment shown in FIG. 2, the engine cooling water is guided into the intercooler 53, and the engine cooling water cools the EGR gas.

The fuel injection valve 16 is connected to a fuel reservoir, a so-called common rail 55, via a fuel supply pipe 54. Fuel is supplied into the common rail 55 from a fuel pump 56 that is electrically controlled and capable of discharging a quantity of fuel. The fuel supplied into the common rail 55 is supplied to the fuel injection valve 16 through each fuel supply pipe 54. A fuel pressure sensor 57 for detecting fuel pressure in the common rail 55 is attached to the common rail 55, and a fuel pump 56 is provided so that the fuel pressure in the common rail 55 becomes a target fuel pressure based on an output signal of the fuel pressure sensor 57. Is controlled.

The electronic control unit 60 is composed of a digital computer, and is connected to a ROM (read only memory) 62, a RAM (random access memory) 63, a CPU (microprocessor) 64, an input port 65, An output port 66 is provided. The output signal of the mass flow meter 31 is input to the input port 65 via the corresponding AD converter 67, and the output signals of the air-fuel ratio sensor 47 and the fuel pressure sensor 57 are also input to the input port 65 via the corresponding AD converter 67, respectively. Is input to
The accelerator pedal 70 has a depression amount L of the accelerator pedal 70.
Is connected to a load sensor 71 that generates an output voltage proportional to the A / D converter 6.
7 to the input port 65. The input port 65 is connected to a crank angle sensor 72 that generates an output pulse every time the engine output shaft 3 rotates, for example, by 30 °. On the other hand, the output port 66 is connected to the corresponding drive circuit 68
Are connected to the fuel injection valve 16, the ignition plug 16a, the step motor 29 for controlling the throttle valve, the step motor 51 for controlling the EGR control valve, and the fuel pump 56.

Next, terms used in the following description of the engine operation control will be described. In this specification, "engine operation mode" means "operation mode of the internal combustion engine", and in this embodiment, there are a four-cycle mode and a two-cycle mode classified according to the number of strokes. In the following description, the engine operation mode is simply called an operation mode, the four-cycle mode is simply called four cycles, and the two-cycle mode is simply called two cycles. In this specification, the term "combustion mode" means "the form of combustion in the combustion chamber".
There are a uniform combustion mode and a stratified combustion mode, which are classified according to the distribution of the fuel in the fuel cell 5. In the following description, the uniform combustion mode is simply referred to as uniform combustion, and the stratified combustion mode is simply referred to as stratified combustion.

In this specification, "uniform combustion" means "combustion in which fuel is injected from a fuel injection valve into a combustion chamber so that the fuel is substantially uniformly dispersed in the combustion chamber, and the fuel is ignited by a spark plug and burned. Mode ”. On the other hand, "stratified combustion" means "a combustion mode in which fuel is injected from a fuel injection valve into a combustion chamber so that fuel is present only near the spark plug, and the fuel is ignited by the spark plug and burned". At the time of stratified combustion, even if the amount of fuel injected from the fuel injection valve 16 is smaller than that at the time of uniform combustion, the fuel is present in the vicinity of the ignition plug 16a, so that even a small amount of fuel is sufficient to operate the internal combustion engine. Provides explosive power. Therefore, the fuel efficiency during stratified combustion is higher than the fuel efficiency during uniform combustion.

In the present specification, the "engine speed ratio" means "the same predetermined engine torque and the same predetermined engine torque with respect to the engine speed which outputs a certain predetermined engine output at a certain predetermined engine torque during two-cycle operation." Ratio of the engine speed during four-cycle operation that outputs the engine output ”. The number of explosion strokes per unit engine speed during two-cycle operation is theoretically twice as large as that during four-cycle operation. In other words, if the engine torque is the same,
The engine speed during two-cycle operation required to output a certain predetermined engine output is theoretically one half of the engine speed during four-cycle operation. Therefore, the engine speed ratio is theoretically 2. In practice, this engine speed ratio is a value smaller than 2 and larger than 1. However, for convenience of explanation, the engine speed ratio is appropriately indicated by a coefficient K in the following description, and K = 2 to control the operation of the internal combustion engine. Will be described.

In this specification, "theoretical engine speed" is used.
Means "the engine speed required to output the actual engine output with the actual engine torque during the four-cycle operation in the current operation mode". Therefore, during four-cycle operation, the actual engine speed becomes the theoretical engine speed as it is.
On the other hand, in the two-cycle operation, the engine speed required to output the actual engine output in the current operation mode, that is, the two-cycle operation at the actual engine torque in the current two-cycle operation in the four-cycle operation is the theoretical engine speed. It becomes a number. That is, during two-cycle operation, the theoretical engine speed is a value obtained by multiplying the current engine speed by the engine speed ratio, that is, twice the engine speed.

In this specification, "stratified combustion limit value"
Means "engine speed at which stratified combustion cannot be effectively performed". The stratified combustion limit value is a value determined for each actual engine torque, but may be determined for each required engine torque. The reason why the stratified combustion limit value is determined for each engine torque, in other words, the stratified combustion limit value is determined according to the engine speed and the engine torque is as follows. In the stratified combustion, the fuel must be present only near the spark plug 16a because the internal combustion engine needs to be operated with a relatively small amount of fuel. Therefore, the reciprocating speed of the piston 14 must be relatively low, that is, the engine speed must be relatively low. This is because if the reciprocating speed of the piston 14 is relatively high, the time required for the fuel to evaporate is short, and the fuel does not collect near the spark plug 16a due to the violent reciprocating motion of the piston 14 and is diffused throughout the combustion chamber 15. It is because. Thus, the stratified combustion limit value is determined according to the engine speed, and stratified combustion can be performed only when the engine speed is relatively low. In addition, since the amount of fuel injected from the fuel injection valve 16 is relatively small in stratified combustion, the torque that can be output by stratified combustion is also relatively small. Therefore, if stratified charge combustion is performed when the required engine torque is relatively large, the required engine torque cannot be output. For these reasons, stratified combustion is determined according to the engine torque, and can be performed only when the engine torque is relatively small.

FIG. 3 shows this as a function of the actual engine speed and the actual engine torque. Here, stratified combustion can be performed only in a region S (hereinafter, referred to as a "stratified combustion region") surrounded by a curve C defined by a stratified combustion limit value determined for each engine torque. The other region H is a region where uniform combustion is to be performed (hereinafter, referred to as a “uniform combustion region”).

In this specification, the "first stratified combustion limit value" means "the theoretical engine speed at which stratified combustion cannot be effectively performed during four-cycle operation". In practice, this first stratified combustion limit is equal to the above-described stratified combustion limit. The “second stratified combustion limit value” means “the theoretical engine speed at which stratified combustion cannot be effectively performed during two-cycle operation”. The second stratified combustion limit value is larger than the first stratified combustion limit value, and is actually a value obtained by multiplying the stratified combustion limit value by the engine speed ratio, that is, twice the stratified combustion limit value. In the following description, the first stratified combustion limit value is referred to as a first limit value, and the second stratified combustion limit value is referred to as a second limit value.

FIG. 4 shows the first limit value and the second limit value in relation to the actual engine torque and the theoretical engine speed. In FIG. 4, a curve C1 is a curve defined by a first limit value determined for each engine torque, and a curve C2 is a curve defined by a second limit value determined for each engine torque. In the following description, the engine operating state determined by the engine speed and the engine torque in FIG. 3 is referred to as the actual engine operating state, and the engine operating state determined by the theoretical engine speed and the engine torque in FIG. Called.

In this specification, the resulting “engine torque” and “actual engine torque” mean actual engine torque, but “engine torque” as a control parameter.
The “actual engine torque” is actually the required engine torque. This is because it can be assumed that the actual engine torque is substantially equal to the required engine torque. Therefore, the "actual engine output" also means the required engine output.
Of course, when a means capable of detecting the actual engine torque is provided, the "real engine torque" is the detected actual engine torque, and the "real engine output" is also the actual engine output.

Next, the operation control of the internal combustion engine according to the present embodiment will be described with reference to FIGS. In the following description, a case will be described in which the engine output of the internal combustion engine is increased in response to, for example, an acceleration request of a vehicle equipped with the internal combustion engine. In the internal combustion engine of this embodiment, the required engine output corresponding to the vehicle acceleration request is calculated according to the accelerator pedal depression amount, and the actual engine output is calculated from the actual engine torque T and the actual engine speed Ne. The actual engine torque T is controlled so that the actual engine torque T gradually approaches the required engine torque in accordance with the difference between the required engine output and the actual engine output. Actually, the actual engine torque T is controlled by controlling the amount of fuel to be injected from the fuel injection valve 16.

In this embodiment, when the theoretical engine speed RNe is equal to or less than the first limit value L1 determined for each engine torque T, that is, when the theoretical engine operating state is closer to the origin than the curve C1 in FIG. When it is at the point X1, the operation mode is four cycles and the combustion mode is stratified combustion. Since the point X1 in FIG. 4 corresponds to the point X1 in FIG. 3, when the theoretical engine operating state is at the point X1 in FIG. 4, the actual engine operating state is in the stratified combustion region S as shown in FIG. Is relatively small, and the actual engine torque T is also relatively small, so that stratified combustion is effectively performed.

Next, when acceleration of the vehicle is required and the required engine output is increased, the engine torque T is increased, and accordingly the engine speed Ne is increased, and the actual engine operation state is changed from the point X1 in FIG. It shifts gradually toward point X2. Of course, since the theoretical engine speed RNe also increases, the operating state of the theoretical engine gradually changes from the point X1 to the point X2 in FIG.

When the actual engine operating state reaches point X2 in FIG. 3, the theoretical engine operating state also reaches point X2 in FIG.
When the actual engine operation state exceeds the curve C in FIG. 3, the theoretical engine operation state also exceeds the curve C1 in FIG. That is, the theoretical engine speed RNe becomes equal to or greater than the first limit value L1. Thus, the theoretical engine speed RNe is equal to the first limit value L1.
In this embodiment, the operation mode is switched from 4 cycles to 2 cycles while maintaining the combustion mode in stratified combustion.

When the operation mode is switched from four cycles to two cycles, the number of explosion strokes per unit engine speed is doubled. Therefore, if the engine speed Ne is maintained at the engine speed Ne at the time of operation mode switching, the engine The output sharply increases to twice the required engine output when the operation mode is switched. In this case, a discontinuous portion occurs in the engine output characteristic. However, according to the normal engine operation control of the present embodiment, the actual engine operation state is set to the point shown in FIG. 3 so that the engine speed Ne becomes one half (1 / K) of the engine speed Ne when the operation mode is switched. The movement is gradually shifted from X2 to the point X3, and then gradually shifted again to the point X2 in FIG. This is because according to the normal engine operation control, the fuel injection amount is controlled so that the engine output becomes the required engine output.

However, in the present embodiment, the first auxiliary control, which will be described later, is executed at the time of operating mode switching, so that the engine speed output to the axle 10 immediately, not gradually, is halved of the engine speed at the time of operating mode switching. In addition, the engine speed Ne itself is set to one half (1 / K) of the engine speed Ne when the operation mode is switched. If the engine speed immediately output to the axle 10 at the time of operation mode switching is set to half (1 / K) of the engine speed at the time of operation mode switching, rapid acceleration of the vehicle is prevented, and the operation mode switching is performed. Sometimes, the engine speed Ne is immediately reduced by half (1/1 /
If K), the engine output immediately becomes equal to the required engine output when the operation mode is switched, so that there is no discontinuity in the engine output characteristics. Therefore, the vehicle is smoothly accelerated. While such control is being performed, the actual engine operating state immediately changes from point X2 to point X3 in FIG.

If the engine speed Ne is set to one half (1 / K) of the engine speed Ne at the time of the operation mode switching, the engine output becomes equal to the required engine output at the time of the operation mode switching. , The engine torque T is increased, and the engine speed Ne is increased. While such control is being executed, the actual engine operating state is changed to the point X3 in FIG.
Again to point X2.

While the actual engine operating state changes from point X2 to point X3 in FIG. 3, the theoretical engine operating state changes from point X2 to point X3 in FIG. Then, while the actual engine operating state shifts from the point X3 in FIG. 3 to the point X2 again, the theoretical engine operating state shifts from the point X3 to the point X2 ′ in FIG. Further, according to the acceleration demand, the engine torque T
Is increased, the actual engine operating state becomes the point X in FIG.
2 and crosses curve C1. At this time, the theoretical engine operation state reaches the point X2 'in FIG. 4 and exceeds the curve C2. That is, the theoretical engine speed RNe is equal to or greater than the second limit value L2 determined for each engine torque T. As described above, when the theoretical engine speed RNe becomes equal to or more than the second limit value L2, in this embodiment, the operation mode is switched from 2 cycles to 4 cycles, and the combustion mode is switched from stratified combustion to uniform combustion.

When the operation mode is switched from two cycles to four cycles, the number of explosion strokes per unit engine speed is reduced by half, so that the engine speed Ne is maintained at the engine speed Ne at the time of operation mode switching. The engine output sharply decreases to one half of the required engine output when the operation mode is switched. In this case, a discontinuous portion occurs in the engine output characteristic. However, according to the normal engine operation control of the present embodiment, the actual engine operation state is changed from the point X2 in FIG. 3 so that the engine speed Ne becomes twice (K times) the engine speed Ne when the operation mode is switched. It is gradually shifted to the point X2 '. This is because according to the normal engine operation control, the fuel injection amount is controlled so that the engine output becomes the required engine output.

However, in the present embodiment, the first auxiliary control, which will be described later, is executed when the operation mode is switched, so that the engine speed output to the axle 10 immediately, not gradually, is twice the engine speed when the operation mode is switched. (K times) and the engine speed Ne itself is twice (K times) the engine speed Ne when the operation mode is switched. As described above, if the engine speed immediately output to the axle 10 at the time of operating mode switching is set to twice (K times) the engine speed at the time of operating mode switching, deceleration of the vehicle during acceleration is prevented, and the operating mode switching is performed. Sometimes, if the engine speed Ne is doubled (K times) immediately, the engine output immediately becomes equal to the required engine output when the operation mode is switched, so that there is no discontinuity in the engine output characteristics. Therefore, the vehicle is smoothly accelerated. While such control is being performed, the actual engine operating state immediately changes from point X2 to point X2 'in FIG.

If the engine speed Ne is set to one half (1 / K) of the engine speed Ne at the time of switching the operation mode, the engine output becomes equal to the required engine output at the time of switching the operation mode. , The engine torque T is increased, and the engine speed Ne is increased. Note that while the actual engine operation state changes from the point X2 to the point X2 'in FIG. 3, the theoretical engine operation state changes from the point X2 to the point X2' in FIG.

To summarize the above engine operation control, in this embodiment, when the theoretical engine speed RNe is equal to or less than the first limit value L1, the operation mode is set to four cycles and the combustion mode is set to stratified combustion. When the theoretical engine speed RNe is equal to or more than the first limit value L1 and equal to or less than the second limit value L2, the operation mode is set to two cycles and the combustion mode is set to stratified combustion. Further, when the theoretical engine speed RNe is equal to or more than the second limit value L2, the operation mode is set to 4 cycles and the combustion mode is set to uniform combustion.

In the engine operation control described above, the first auxiliary control is executed when the operation mode is switched. This first auxiliary control will be described in detail below. In the first auxiliary control, when the cycle is switched from four cycles to two cycles, the engine speed transmitted to the axle 10 is reduced to one half (1/1 /
K). Further, when switching from four cycles to two cycles, the fuel injection amount is reduced in a stepwise manner, and in some cases, fuel injection is stopped, and the engine speed N
e is reduced to one half (1 / K). On the other hand, when switching from two cycles to four cycles, the number of revolutions transmitted to the axle 10 is increased by the continuously variable transmission 9 to twice (K times). Further, when switching from two cycles to four cycles, the fuel injection amount is increased stepwise, and the engine speed is increased to twice (K times).

As another control having the same function as that of the first auxiliary control, the electric motor 7 is operated by the engine output when the cycle is switched from 4 cycles to 2 cycles, so that the electric motor 7 functions as a generator. , The engine speed is reduced by half (1 / K),
On the other hand, when switching from two cycles to four cycles, the engine output shaft is driven to rotate by the electric motor to assist the operation of the internal combustion engine, and the control is adopted to increase the engine speed twice (K times). Can also.

As described above, the theoretical engine speed R
When Ne crosses the second limit value L2, both the operation mode and the combustion mode are simultaneously switched. This is not preferable from the viewpoint of smoothly accelerating or decelerating the internal combustion engine. This is because when the operation mode is switched, the engine speed is forcibly increased or decreased as described above, so that the engine operation state greatly changes and becomes unstable, and when the combustion mode is switched, the combustion state of the fuel in the combustion chamber becomes inadequate. This is because the operation becomes stable and the operation of the internal combustion engine becomes unstable as a whole. In addition, since both the operation mode switching and the combustion mode switching are accompanied by fluctuations in the engine output, the engine output characteristics greatly fluctuate when both modes are switched.

Therefore, in this embodiment, when both the operation mode and the combustion mode are simultaneously switched, the second auxiliary control is executed. That is, when both the operation mode and the combustion mode are simultaneously switched, the combustion mode is set to the uniform combustion, and the operation mode is set to the operation mode on the side where the theoretical engine speed RNe is lower. According to this, in the present embodiment, when the theoretical engine speed RNe becomes equal to or more than the second limit value L2, the combustion mode is switched from stratified combustion to uniform combustion first while the operation mode is maintained at two cycles, and then the operation is performed. The mode is switched from 2 cycles to 4 cycles. On the other hand, when the theoretical engine speed RNe becomes equal to or less than the second limit value L2, the operation mode is first switched from four cycles to two cycles while maintaining the combustion mode at uniform combustion. As described above, by executing one mode switching first and then executing the other mode switching, the engine output characteristics become smooth. Also, when the theoretical engine speed RNe is equal to or greater than the second limit value L2 or less, the operation mode is switched in a state where the combustion mode is uniform combustion. Since uniform combustion is more stable than stratified combustion, switching the operation mode in a state where such stable combustion is being performed is preferable from the viewpoint of stabilizing the operation of the internal combustion engine. Next, the mode switching control of this embodiment will be described with reference to the flowcharts of FIGS.
First, in step 10 of FIG.
The engine speed Ne and the engine torque T are detected by the load sensor 2 and the load sensor 71, and then in step 11, the theoretical engine speed RNe is calculated. The theoretical engine speed RNe is a value equal to the engine speed Ne if the operation mode is four cycles, and twice (K times) the engine speed Ne if the operation mode is two cycles. Next, at step 12, the theoretical engine speed RNe is smaller than the first limit value L1 (RNe <
L1) is determined. RN in step 11
When it is determined that e <L1, the process proceeds to step S13. On the other hand, when it is determined in step 11 that RNe ≧ L1, the process proceeds to step 19 in FIG.

In step 13, it is determined whether or not the first flag F1 is set (F1 = 1). The first flag F1 is set when the theoretical engine speed RNe becomes smaller than the first limit value L1, and is reset when the theoretical engine speed RNe becomes equal to or more than the first limit value L1. In step 13, F1
When it is determined that = 1, since the internal combustion engine is currently operated with four cycles and stratified combustion, the routine directly proceeds to step 14, sets the first flag F1, resets the second flag F2, and executes the processing. To end. The second flag F2 is set when the theoretical engine speed RNe becomes larger than the second limit value L2, and is reset when the theoretical engine speed RNe becomes equal to or less than the second limit value L2.

When it is determined in step 13 that F1 = 0, the routine proceeds to step 15, where the second flag F2
Is set (F2 = 1).
When it is determined in step 15 that F2 = 1, the first combustion mode switching control is executed in step 16 to change the uniform combustion to stratified combustion because the internal combustion engine is currently operated with four cycles and uniform combustion. Switch. On the other hand, when it is determined in step 15 that F2 = 0, the first cam switching control is executed in step 17 since the internal combustion engine is currently operated in two cycles and stratified combustion, and the Is switched from the second cam for two cycles to the first cam for four cycles, and then proceeds to step 18 to execute the first auxiliary control described above.

In step 19 of FIG. 6, the theoretical engine speed R
It is determined whether Ne is larger than the second limit value L2 (RNe> L2). When it is determined in step 19 that RNe> L2, the process proceeds to step 20. on the other hand,
When it is determined in step 19 that RNe ≦ L2, the process proceeds to step 27 in FIG. In step 20, it is determined whether or not the first flag F1 is set (F1 = 1). When it is determined in step 20 that F1 = 1, the internal combustion engine is currently operated in four cycles and stratified charge combustion, so the second combustion mode switching control is executed in step 21 to convert stratified charge combustion to uniform combustion. Switch to step 22 to proceed to the first flag F1.
Is reset, the second flag F2 is set, and the process ends.

In step 23, it is determined whether or not the second flag F2 is set (F2 = 1). When it is determined in step 23 that F2 = 1, the process proceeds directly to step 22 because the internal combustion engine is currently operated with four cycles and uniform combustion. On the other hand, when it is determined in step 23 that F2 = 0, the internal combustion engine is currently operated in two cycles and stratified charge combustion. Therefore, in step 24, the second combustion mode switching control is executed to make stratified charge combustion uniform. The combustion is switched to combustion, and then the first cam switching control is executed in step 25 to switch the cam from the second cam for two cycles to the first cam for four cycles, as will be described later. Execute control. Steps 24 and 25 here correspond to the second auxiliary control described above.

In step 27 of FIG. 7, it is determined whether or not the first flag F1 is set (F1 = 1). If it is determined in step 27 that F1 = 1, the internal combustion engine is currently operated in four cycles and stratified charge combustion, so the second cam switching control is executed in step 28 to change the cam to four as described later. The first cam for the cycle is switched to the second cam for two cycles, and then the first auxiliary control described above is executed in step 29,
Next, in step 30, the first flag F1 is reset, the second flag F2 is reset, and the process ends. On the other hand, when it is determined in step 27 that F1 = 0, the process proceeds to step 31.

At step 31, it is determined whether or not the second flag F2 is set (F2 = 1). If it is determined in step 31 that F2 = 1, the internal combustion engine is currently operated for four cycles and with uniform combustion. Therefore, in step 32, the second cam switching control is executed to change the cam to four as described later. The first cam for the cycle is switched to the second cam for the two cycles, then the first auxiliary control described above is executed in step 33, and then the first combustion mode switching control is executed in step 34 to achieve uniform combustion and stratified combustion. Switch to. Here, Steps 32 to 34 correspond to the above-described second auxiliary control.

On the other hand, when it is determined in step 31 that F2 = 0, the process proceeds directly to step 30 because the internal combustion engine is currently operated in two cycles and stratified combustion. An example of the operation control of the internal combustion engine of the present embodiment described above will be described with reference to a time chart of FIG. In FIG. 8, (A) is the required engine output, (B) is the engine torque T, (C) is the engine speed Ne, (D) is the theoretical engine speed RNe, (E) is the operation mode, and (F) is The combustion mode and (G) indicate time. Before time t1, the required engine output is the first required value RT1, and the theoretical engine speed RNe is equal to or less than the first limit value L1, so the operation mode is four cycles, and the combustion mode is stratified combustion.

When the required engine output increases from the first required value RT1 to the second required value RT2 at time t1, the engine torque T is gradually increased, and the engine speed N is accordingly increased.
e gradually increases, and accordingly, the theoretical engine speed RNe also gradually increases. At time t2, the theoretical engine speed RN
When e reaches the first limit value L1, the operation mode is switched from four cycles to two cycles while the stratified combustion mode is maintained. At this time, the engine torque T is reduced stepwise by the first auxiliary control, and therefore the engine speed Ne sharply decreases. At this time, similarly, the engine speed Ne transmitted to the wheel shaft by the first auxiliary control is immediately reduced to one half (1 / K) by the continuously variable transmission 9, so that the vehicle is smoothly accelerated. I have.

Further, when the engine torque T is gradually increased, the engine speed Ne also gradually increases, and the theoretical engine speed RNe reaches the second limit value L2 at time t3. At this time, since the second auxiliary control is executed, the combustion mode is switched from the stratified combustion to the uniform combustion, and the subsequent time t
At 4, the operation mode is switched from 2 cycles to 4 cycles. Further, at this time, the engine torque T is increased stepwise by the first auxiliary control, so that the engine speed Ne sharply increases. At this time, similarly, the engine speed Ne transmitted to the wheel shaft by the first auxiliary control is immediately doubled (K times) by the continuously variable transmission 9, so that the vehicle is smoothly accelerated.

When the required engine output decreases from the second required value RT2 to the first required value RT1 at time t5, the engine torque T is gradually reduced, and the engine speed N is accordingly reduced.
e gradually decreases, and accordingly, the theoretical engine speed RNe also gradually decreases. At time t6, the theoretical engine speed RN
When e reaches the second limit value L2, the operation mode is switched from four cycles to two cycles, and the combustion mode is switched from uniform combustion to stratified combustion. At this time, the engine torque T is reduced stepwise by the first auxiliary control, and therefore the engine speed Ne sharply decreases. At this time, similarly, the engine speed Ne transmitted to the wheel shaft by the first auxiliary control is immediately reduced to one half (1 / K) by the continuously variable transmission 9, so that the vehicle is smoothly accelerated. I have.

Further, when the engine torque T is gradually decreased, the engine speed Ne also gradually decreases, and the theoretical engine speed RNe reaches the first limit value L1 at time t7. At this time, the operation mode is switched from 2 cycles to 4 cycles while the combustion mode is kept uniform by the second auxiliary control. Further, at this time, the engine torque T is increased stepwise by the first auxiliary control, so that the engine speed Ne sharply increases. At this time, similarly, the engine speed Ne transmitted to the wheel shaft by the first auxiliary control is immediately doubled (K times) by the continuously variable transmission 9, so that the vehicle is smoothly accelerated.

In the above description, the present invention has been described using a typical example among the examples in which the engine output is increased in response to the acceleration request, but various examples are conceivable. For example, the present invention can be applied to a case where the theoretical engine speed directly increases from a region where the theoretical engine speed is equal to or lower than the first limit value to equal to or higher than the second limit value. Further, instead of the continuously variable transmission, a transmission having a plurality of gears that can change the transmission ratio from half (1 / K) to twice (K times) may be adopted.

As another embodiment, an embodiment as shown in FIG. 9 may be employed. In this embodiment, when the theoretical engine speed RNe is equal to or less than the first limit value L1, the operation mode is set to four cycles and the combustion mode is set to stratified combustion. When the theoretical engine speed RNe is equal to or more than the first limit value L1 and equal to or less than the second limit value L2, the operation mode is set to two cycles and the combustion mode is set to stratified combustion.
Further, when the theoretical engine speed RNe is equal to or more than the second limit value L2, the operation mode is set to two cycles and the combustion mode is set to uniform combustion. According to this, the theoretical engine speed R
When Ne exceeds the second limit value L2, the operation mode is not switched. That is, the operation mode is not switched when the internal combustion engine is accelerated from when it is operated at a relatively moderate engine torque T and a relatively moderate engine speed Ne. Characteristics become smoother. Note that the first auxiliary control and the second auxiliary control are also applied to this embodiment. The components and control of the drive system other than those described above are the same as in the first embodiment.

As another embodiment, an embodiment as shown in FIG. 10 may be employed. In this embodiment, when the theoretical engine speed RNe is equal to or less than the first limit value L1, the operation mode is set to two cycles and the combustion mode is set to stratified combustion. When the theoretical engine speed RNe is equal to or more than the first limit value L1 and equal to or less than the second limit value L2, the operation mode is set to two cycles and the combustion mode is set to stratified combustion.
Further, when the theoretical engine speed RNe is equal to or more than the second limit value L2, the operation mode is set to 4 cycles and the combustion mode is set to uniform combustion. According to this, the operation mode is not switched in the region where the stratified combustion is performed. Since stratified combustion is more unstable than homogeneous combustion, according to the present embodiment, stratified combustion can be favorably performed in all stratified combustion regions. Note that the first auxiliary control and the second auxiliary control are also applied to this embodiment. The components and control of the drive system other than those described above are the same as in the first embodiment.

Finally, specific means for switching the operation mode between four cycles and two cycles in this embodiment will be described. As shown in FIG. 11, the internal combustion engine of this embodiment has a first cam 80 for performing four cycles and a second cam 81 for performing two cycles. The first cam 80 and the second cam 81 share a common shaft 82.
Can be attached with a gap above. Both ends of the shaft 82 are rotatably supported by the cylinder block 12. The shaft 82 is provided with an electromagnetic solenoid 83, and the shaft 82 can be moved back and forth in the axial direction by the electromagnetic solenoid 83. When the shaft 82 is moved by the electromagnetic solenoid 83 and positioned at the first position, the first cam 80 contacts the head of the intake valve 17. At this time, the internal combustion engine is operated in four cycles. When the shaft 82 is moved by the electromagnetic solenoid 83 and positioned at the second position, the second cam 81 comes into contact with the head of the intake valve 17. At this time, the internal combustion engine is operated in two cycles.

[0060]

According to the present invention, when the theoretical engine speed is equal to or higher than the first limit value and equal to or lower than the second limit value, the engine operation mode is operated in two cycles. The required engine speed is smaller than the engine speed required during four-cycle engine operation. Therefore, the speed of movement of the piston in the combustion chamber is reduced, so that stratified combustion can be effectively performed. Therefore, stratified combustion can be performed in a wide range.

[Brief description of the drawings]

FIG. 1 is an overall view of a drive system according to the present invention.

FIG. 2 is an overall view of an internal combustion engine of the present invention.

FIG. 3 is a diagram showing a relationship between an engine speed and an engine torque.

FIG. 4 is a diagram showing a relationship between a theoretical engine speed and an engine torque.

FIG. 5 is a part of a flowchart of operation control of the internal combustion engine of the present invention.

FIG. 6 is a part of a flowchart of operation control of the internal combustion engine of the present invention.

FIG. 7 is a part of a flowchart of operation control of the internal combustion engine of the present invention.

FIG. 8 is a time chart for explaining the operation control of the internal combustion engine of the present invention.

FIG. 9 is a diagram showing a relationship between a theoretical engine speed and an engine torque in another embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between a theoretical engine speed and an engine torque in still another embodiment of the present invention.

FIG. 11 is an overall view of a cam switching system of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 3 ... Engine output shaft 4 ... Generator 7 ... Electric motor 9 ... Stepless reduction gear 15 ... Combustion chamber 16 ... Fuel injection valve 16a ... Spark plug

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (reference) // F02B 69/06 F02B 69/06 F term (reference) 3G092 AA01 AA03 AA06 AA09 AB02 BB06 DB04 DE03S EA11 GA18 HC09X HE01X HF01X 3G093 AA16 AB04 CA11 DA01 EA05 EA13 EB08 FA10 3G301 HA01 HA03 HA04 HA16 HA27 KA25 LB04 MA11 MA18 MA26 PB05A PE01A PE06A PE09A PF12A

Claims (14)

[Claims] 1. A fuel injection valve for injecting fuel directly into a combustion chamber, an ignition plug for igniting fuel in the combustion chamber, and an engine operating mode for switching an engine operation mode between four and two cycles. Means for switching the combustion mode in the combustion chamber between stratified combustion and homogeneous combustion, means for detecting the current required engine output, and obtaining the detected current required engine output. Means for calculating a theoretical engine speed required in one of the engine operation modes, and a first limit value and a second limit value larger than the first limit value in the theoretical engine speed corresponding to the engine torque. Calculating means, the engine operation mode is set to two cycles when the theoretical engine speed is equal to or more than the first limit value and equal to or less than the second limit value. A direct injection type spark ignition engine characterized in that the combustion mode is stratified combustion. 2. When the theoretical engine speed is equal to or lower than the first limit value, the engine operation mode is set to four cycles and the combustion mode is stratified combustion, and the theoretical engine speed is equal to or higher than the second limit value. Sometimes the engine operation mode is set to 4
The in-cylinder injection type spark ignition engine according to claim 1, wherein the combustion mode is a uniform combustion mode. 3. When the theoretical engine speed is equal to or lower than the first limit value, the engine operation mode is set to four cycles, the combustion mode is set to stratified combustion, and the theoretical engine speed is equal to or higher than the second limit value. Sometimes the engine operation mode is set to 2
The in-cylinder injection type spark ignition engine according to claim 1, wherein the combustion mode is a uniform combustion mode. 4. When the theoretical engine speed is equal to or lower than the first limit value, the engine operation mode is set to two cycles, the combustion mode is set to stratified combustion, and the theoretical engine speed is equal to or higher than the second limit value. Sometimes the engine operation mode is set to 4
The in-cylinder injection type spark ignition engine according to claim 1, wherein the combustion mode is a uniform combustion mode. 5. When both the engine operation mode and the combustion mode are switched, the combustion mode is set to uniform combustion, and the engine operation mode is set to an engine operation mode in which the theoretical engine speed is lower. The in-cylinder injection spark ignition engine according to any one of claims 1 to 4. 6. An engine speed changing means for changing an engine speed output from the engine, wherein the engine speed is reduced when the engine operation mode is switched from four cycles to two cycles, and the engine speed is reduced. The in-cylinder injection spark ignition engine according to any one of claims 2 to 4, wherein the engine speed is increased when the mode is switched from two cycles to four cycles. 7. An in-cylinder injection spark ignition engine according to claim 6, wherein said engine speed changing means is a continuously variable transmission. 8. An engine torque increasing means for increasing engine torque when switching the engine operation mode from two cycles to four cycles.
The in-cylinder injection spark ignition engine according to any one of claims 1 to 4. 9. The in-cylinder injection spark ignition engine according to claim 8, wherein said engine torque increasing means increases the engine torque by increasing a fuel injection amount from a fuel injection valve. 10. The engine according to claim 8, wherein the engine torque increasing means includes an electric motor connected to an engine output shaft, and the electric motor rotates the engine output shaft to increase the engine torque. In-cylinder injection spark ignition engine. 11. The apparatus according to claim 2, further comprising an engine torque reducing means for reducing the engine torque when switching the engine operation mode from four cycles to two cycles. In-cylinder injection spark ignition engine. 12. The in-cylinder injection according to claim 2, wherein the engine torque reducing means reduces the engine torque by reducing a fuel injection amount from a fuel injection valve. -Type spark ignition engine. 13. The in-cylinder injection spark ignition engine according to claim 12, wherein said engine torque reducing means reduces the engine torque by stopping fuel injection from a fuel injection valve. 14. The engine torque reducing means includes a generator connected to an engine output shaft, and reduces the engine torque by causing the generator to generate power using the engine output shaft. 2. The in-cylinder injection spark ignition engine according to claim 1.