JPH11324778A - Gasoline direct injection engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the deposition amount of fuel on the piston crown and cylinder bore wall of a gasoline direct injection engine while it is cold. SOLUTION: At a normal operation, an exhaust valve (EXH) and an intake valve (INT) are overlapped in opening, and a fuel injection is carried out while the intake valve opens. At a cold operation, on the other hand, the exhaust and intake valves are no longer overlapped in opening so that the exhaust valve is closed before TDC and the intake valve is opened after TDC, and a fuel injection is preformed between the exhaust valve closing and the intake valve opening. This control, which means a fuel injection into the high- temperature combustion gas that remains in the cylinder, promotes the carburetion of fuel spray, and allows a fuel injection nearer to TDC that avoids fuel deposition on the piston crown and bore wall.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct injection gasoline engine, and more particularly, to a technique for preventing oil dilution and smoke generation on a cylinder bore wall surface during a cold period.

[0002]

2. Description of the Related Art Conventionally, in a direct injection gasoline engine, when the engine temperature is lower than a set temperature (in a cold state), fuel injection is performed at an early stage of an intake stroke, and when the engine temperature is higher than the set temperature. (Normal time) there is a configuration in which fuel injection is performed at the end of the compression stroke.
-71343 gazette).

[0003]

However, when the fuel injection timing at the time of cold is set at the beginning of the intake stroke, the fuel adheres to the piston crown surface to form a liquid film, and the fuel film from the liquid film is formed. Smoke could be generated by diffusion combustion.
On the other hand, if the fuel injection timing is set in the middle to late stages of the intake stroke, the fuel adheres to the cylinder bore wall and the oil on the bore wall surface is diluted, which may reduce the lubricity. Was difficult to avoid at the same time.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and a cylinder-injection gasoline engine capable of simultaneously suppressing oil dilution and generation of smoke by suppressing fuel adhesion to a cylinder bore wall surface and a piston crown surface during a cold period. The purpose is to provide.

[0005]

SUMMARY OF THE INVENTION Therefore, the present invention is directed to a direct injection gasoline engine having a fuel injection valve for directly injecting fuel into a cylinder, after a predetermined crank angle from the closing timing of the exhaust valve. The opening timing of the intake valve is set so that the fuel injection by the fuel injection valve is performed from the closing timing of the exhaust valve to the opening timing of the intake valve.

According to this configuration, the opening period of the exhaust valve and the intake valve are not overlapped, and the intake valve is opened after a predetermined crank angle from the closing of the exhaust valve. Until the opening timing of, that is, while both the exhaust valve and the intake valve are closed, fuel injection is performed. In the invention described in claim 2, the opening timing of the intake valve is set after the piston top dead center, and the fuel injection by the fuel injection valve is performed from the piston top dead center to the opening timing of the intake valve. The configuration was adopted.

According to this configuration, the opening timing of the intake valve set after the closing timing of the exhaust valve is set after the piston top dead center (TDC), and the opening timing of the intake valve from the piston top dead center to the opening timing of the intake valve is set. Fuel injection is performed while the piston is descending. According to the third aspect of the invention, the injection timing of the fuel injection valve is set to be immediately before the opening timing of the intake valve.

According to this configuration, the fuel is injected at a position before the opening timing of the intake valve, at the time when the piston is descending, and at the lowest position. In the invention described in claim 4, the opening timing of the intake valve is configured to be changeable, and the opening timing of the intake valve is made closer to the piston top dead center as the engine rotation speed increases.

With this configuration, when the engine rotation speed is high and the piston descending speed is high, the opening timing of the intake valve approaches the piston top dead center. Conversely, when the engine rotational speed is low and the piston descending speed is low, Move the intake valve open timing away from the piston top dead center. Claim 5
In the described invention, the opening timing of the intake valve is set to a timing at which the in-cylinder pressure and the intake pipe pressure become substantially equal.

According to this configuration, the intake valve is opened after the piston top dead center and at a time when the in-cylinder pressure and the intake pipe pressure become substantially equal. In the invention according to claim 6, the closing timing of the exhaust valve is set before the piston top dead center. According to such a configuration, the exhaust valve is closed before the piston top dead center, and thereafter the intake valve is opened at every predetermined crank angle, during which fuel injection is performed.

In the invention described in claim 7, the opening timing of the intake valve is set after the piston top dead center, and the angle from the piston top dead center to the opening timing of the intake valve is set from the closing timing of the exhaust valve. The angle is set to be greater than the angle to the piston top dead center. According to this configuration, the closing timing of the exhaust valve and the opening timing of the intake valve are set before and after the piston top dead center, and the angle from the piston top dead center to the opening timing of the intake valve is determined by the closing timing of the exhaust valve. Is set to be equal to or larger than the angle from to the piston top dead center.

According to the present invention, the fuel injection valve injects fuel obliquely below the cylinder, and the closing timing of the exhaust valve and the opening timing of the intake valve are determined by an exhaust stroke of the piston. It was set to be set between the latter half and the first half of the intake stroke. According to such a configuration, while the piston is located relatively upward during the second half of the exhaust stroke and the first half of the intake stroke, fuel is injected diagonally below the cylinder, that is, toward the piston crown surface.

According to a ninth aspect of the present invention, at least when the temperature of the engine is equal to or lower than a predetermined temperature, the fuel injection by the fuel injection valve is performed between the closing timing of the exhaust valve and the opening timing of the intake valve. The configuration was adopted. According to such a configuration, fuel injection is performed between the closing timing of the exhaust valve and the opening timing of the intake valve during a cold time when the fuel spray is less likely to evaporate.

According to a tenth aspect of the present invention, there is provided a valve operating device capable of changing the opening timing of the intake valve, wherein the closing timing of the exhaust valve is at least when the opening timing of the intake valve is at a predetermined retarded position. And the opening timing of the intake valve is set to the predetermined retarded position at least when the temperature of the engine is equal to or lower than the predetermined temperature. The fuel injection by the fuel injection valve is performed during the period from the closing timing to the opening timing of the intake valve.

According to this configuration, the non-overlap state in which the intake valve opens at a predetermined crank angle after the exhaust valve closes is realized by the retard control of the opening timing of the intake valve by the valve operating device. The fuel injection is performed in the non-overlapping state. The invention according to claim 11, further comprising a valve operating device capable of changing a closing timing of the exhaust valve, wherein at least when the closing timing of the exhaust valve is at a predetermined advanced position, a predetermined crank from the closing timing of the exhaust valve is provided. The opening timing of the intake valve is set after the angle, and at least when the temperature of the engine is equal to or lower than a predetermined temperature, the closing timing of the exhaust valve is set to the predetermined advanced position, and the closing timing of the exhaust valve is set. The fuel injection by the fuel injection valve is performed during the period from to the opening timing of the intake valve.

According to this configuration, the non-overlap state in which the intake valve opens at a predetermined crank angle after the exhaust valve closes is realized by the advance control of the exhaust valve close timing by the valve operating device. The fuel injection is performed in the non-overlapping state. In the invention according to claim 12, the valve train has a mechanism for changing a phase between a crankshaft and a camshaft.

According to this configuration, by changing the phase between the crankshaft and the camshaft, the valve timing is shifted while the operating angle is kept constant, and the closing timing of the exhaust valve and / or the opening timing of the intake valve is changed. Advance and retard control can be performed. In the invention according to claim 13, the valve train has a mechanism for periodically changing the angular velocity of the camshaft with respect to the angular velocity of the crankshaft.

According to this configuration, the angular velocity of the camshaft relative to the angular velocity of the crankshaft is periodically changed,
Valve timing and operating angle can be changed at the same time,
For example, it is possible to fix the closing timing of the intake valve and change only the opening timing. In the invention according to claim 14,
The valve train has a mechanism for switching a plurality of cams.

According to this configuration, the valve timing and the operating angle can be changed at the same time by selectively using a plurality of cams having different valve lift characteristics. In the invention according to claim 15, the valve train is configured to be a device that drives a valve by hydraulic pressure. According to such a configuration,
The valve is opened and closed by hydraulic pressure instead of cam drive, and the valve timing is changed by controlling the hydraulic pressure generation timing.

[0020] In the invention according to claim 16, the valve operating device is configured to drive the valve by electromagnetic force. According to this configuration, the valve is opened and closed by the electromagnetic force, not by the cam drive, and the valve timing is changed by controlling the timing at which the electromagnetic force is generated.

[0021]

According to the first aspect of the present invention, the combustion gas remains in the combustion chamber by preventing the open periods of the exhaust valve and the intake valve from overlapping, and the fuel is injected into the high-temperature combustion gas. During the spraying, the fuel from the surrounding high temperature gas receives heat during the spraying, and the vaporization of the fuel proceeds, so that the fuel adhesion to the piston crown surface and the cylinder bore wall surface is reduced, and the fuel once adhered is also removed from the surrounding high temperature gas. , Which is quickly vaporized by receiving heat from the piston, so that the generation of smoke due to the adhesion of fuel to the piston crown surface can be suppressed, and the oil dilution of the cylinder bore wall can be prevented.

When the overlap is increased,
The fuel gas can be retained in the combustion chamber by sucking the combustion gas back into the combustion chamber.In this case, fresh air is also sucked together with the combustion gas. Not very high. In contrast,
If the opening periods of the exhaust valve and the intake valve are not overlapped, no fresh air will be introduced until the intake valve is opened, so that only the residual combustion gas will be present in the combustion chamber, and the combustion The indoor gas temperature can be sufficiently increased.

According to the second aspect of the present invention, since the fuel is injected during the lowering of the piston, the fuel spray whose downward speed component is smaller than the lowering speed of the piston cannot catch up with the lowering of the piston. This has the effect that fuel adhesion to the piston crown surface can be reduced. According to the third aspect of the present invention, the fuel is injected when the piston is descending and is farthest away, so that there is an effect that the fuel adhesion to the piston crown surface can be further reduced.

According to the fourth aspect of the present invention, since the spray speed is generally constant irrespective of the rotation speed, the higher the rotation speed of the piston is, the lower the fuel adhesion to the piston crown surface becomes. However, at high revolutions, even if the fuel injection timing is closer to the piston top dead center, the amount of fuel attached to the piston crown surface does not increase so much. There is an effect that the opening timing is advanced to improve the intake charging efficiency.

According to the fifth aspect of the present invention, the pump loss can be reduced by opening the intake valve after the in-cylinder pressure and the intake pipe pressure become substantially equal. According to the sixth aspect of the present invention, the combustion gas is confined in the combustion chamber without being discharged to the exhaust passage and remains there, so that the temperature of the residual gas can be kept high. Even if the closing timing of the exhaust valve is set after the piston top dead center, it is possible to suck back the combustion gas discharged into the exhaust passage and leave it in the combustion chamber.
Since the heat of the combustion gas is taken away by the exhaust passage wall and the like, the temperature is slightly lowered. Therefore, by setting the closing timing of the exhaust valve before the piston top dead center, the residual gas temperature can be further increased. .

According to the present invention, the compression work performed by the engine between the closing timing of the exhaust valve and the top dead center of the piston is recovered as a torque from the top dead center of the piston to the opening timing of the intake valve. As a result, there is an effect that there is no deterioration in fuel efficiency. According to the eighth aspect of the invention, when the piston is relatively upward, the fuel is injected obliquely downward, so that combustion adhesion to the cylinder bore wall surface is extremely reduced. Here, the fuel spray adheres more easily to the piston crown surface than the cylinder bore wall surface, but even if fuel adheres to the piston crown surface, it is quickly vaporized by receiving heat from the surrounding high-temperature gas. The generation of smoke due to fuel adhesion to the fuel cell can also be suppressed.

According to the ninth aspect of the present invention, it is possible to prevent the generation of smoke due to the adhesion of the fuel to the piston crown surface and the generation of oil dilution due to the adhesion of the fuel to the cylinder bore during a cold time when the fuel is difficult to vaporize. is there. Claim
According to the invention described in 10, in the cold state, it is possible to prevent the generation of smoke due to the adhesion of fuel to the piston crown surface and the generation of oil dilution due to the adhesion of fuel to the cylinder bore. There is an effect that the output can be secured by improving the intake charging efficiency.

According to the eleventh aspect of the invention, when cold, it is possible to prevent the generation of smoke due to the adhesion of fuel to the piston crown surface and the generation of oil dilution due to the adhesion of fuel to the cylinder bore. By retarding the timing, there is an effect that the escape of the residual gas is improved, the intake charging efficiency is improved, and the output can be secured. According to the invention of claim 12, by shifting the valve timing as a whole without changing the operating angle, valve timing that can avoid smoke generation and oil dilution during cold time,
There is an effect that it can be easily switched to the valve timing that can secure the output during normal operation.

According to the thirteenth aspect of the present invention, while keeping the opening timing of the exhaust valve and the closing timing of the intake valve fixed, the closing timing of the exhaust valve and / or the opening timing of the intake valve can be changed during the cold generation of smoke. In addition, there is an effect that it is possible to switch to a timing at which oil dilution can be avoided.
According to the invention described in claim 14, it is possible to independently change the opening timing and the closing timing of the valve by switching the cam, and it is possible to set the optimal valve timing in each of the cold state and the normal state. There is.

According to the present invention, the opening timing of the intake valve and / or the closing timing of the exhaust valve can be freely and continuously changed, and the optimum valve can be optimally used in a cold state and a normal state. There is an effect that the timing can be reliably set.

[0031]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a system configuration diagram of a direct injection gasoline engine for a vehicle according to an embodiment. In FIG. 1, an accelerator opening sensor 1 detects an opening of an accelerator pedal operated by a driver.

The crank angle sensor 2 generates a position signal for each unit crank angle and a reference signal for each stroke phase difference between the cylinders, and measures the number of the position signals generated per unit time, or By measuring the generation cycle of the reference signal, the engine rotation speed N (rpm) is detected. The air flow meter 3
The intake air flow rate Qa of the engine 4 is detected.

The water temperature sensor 5 detects a cooling water temperature Tw of the engine 4. In the present embodiment, the cooling water temperature Tw is used as a parameter representing the temperature of the engine 4. The engine 4 is provided with a fuel injection valve 6 for injecting fuel directly into the cylinder, and an ignition plug 7 mounted in a combustion chamber and ignited for each cylinder. The fuel injection valve 6
Is mounted so as to inject fuel obliquely downward toward substantially the center of the cylinder.

On the other hand, a throttle valve 9 is interposed in an intake passage 8 of the engine 4, and the throttle valve 9 is opened and closed by a throttle actuator 10 such as a DC motor. Detection signals from the various sensors are input to a control unit 11 including a CPU, a RAM, a ROM, an input / output interface, and the like. The control unit 11 is detected based on signals from the sensors. In accordance with the operating state, the opening degree of the throttle valve 9 is controlled, the fuel injection amount and the injection timing by the fuel injection valve 6 are controlled, and the ignition timing by the ignition plug 7 is controlled.

The intake valve 12 (IN) of the engine 4
T) and the exhaust valve 13 (EXH) driven by cams are provided with variable valve mechanisms 14a and 14b for variably controlling the valve opening / closing timing (valve timing). Here, a first embodiment of the valve timing control and the fuel injection control by the control unit 11 will be described with reference to the flowchart of FIG.

In the flowchart of FIG. 2, first, S
In step 1, the cooling water temperature Tw detected by the water temperature sensor 5 is read. In S2, it is determined whether or not the engine is cold by comparing the cooling water temperature Tw with a preset reference temperature. When the cooling water temperature Tw is higher than the reference temperature and is in a state after normal warm-up (normal time), the process proceeds to S3,
As shown in FIGS. 3 and 4, the exhaust valve 13 (EXH) closes after the intake TDC and the exhaust valve 12 (INT)
Is opened before the intake TDC, the variable valve mechanisms 14a and 14b are controlled so that the open period between the exhaust valve 13 and the intake valve 12 becomes a normal valve timing that overlaps before and after the intake TDC. In FIG. 3, the opening timing of the intake valve 12 is indicated by IVO, the closing timing is indicated by IVC, the opening timing of the exhaust valve 13 is indicated by EVO, and the closing timing is indicated by EVC.

In the next step S4, the injection timing for normal operation is determined with reference to a table corresponding to the engine speed. As shown in FIGS. 3 and 4, homogeneous combustion is performed when the intake valve 12 is opened to form a homogeneous mixture in the combustion chamber, and the ignition plug 7 is injected during the compression stroke.
When it is possible to switch to stratified combustion in which the combustible air-fuel mixture is unevenly distributed around the fuel cell, an injection timing table is set for each combustion method.

On the other hand, if it is determined in S2 that the engine is in the cold state in which the cooling water temperature Tw is equal to or lower than the reference temperature, the process proceeds to S5, and the exhaust valve 13 is opened from the normal state shown in FIGS.・ Adjusts the closing timing and opens the intake valve 12.
The closing timing is switched to a retarded angle, and as shown in FIGS. 5 and 6, the exhaust valve 13 is closed before the intake TDC and the intake valve 12 is opened after the intake TDC, so that the exhaust valve 13 is opened.
The opening timing of the intake valve 12 is set after a predetermined crank angle from the closing timing.

That is, in the valve timing control in S5, the opening / closing timing of the intake valve 12 is shifted entirely in the retard direction while the operating angle is kept constant, and the opening / closing timing of the exhaust valve 13 is shifted in the overall advance direction. Variable valve mechanisms 14a and 14b for performing the switching.
A known mechanism that switches the phase of the camshaft with respect to the crankshaft can be used.

In the next step S6, the injection timing for the cold period for performing the fuel injection between the closing timing of the exhaust valve 13 and the opening timing of the intake valve 12 is determined by referring to a table corresponding to the engine speed. Set. Here, as the injection timing for the cold time, it is preferable that the fuel injection be performed immediately before the opening timing of the intake valve 12, and furthermore, as shown in FIGS. More preferably, it coincides with the opening timing of the intake valve 12. Therefore, instead of setting the injection timing (start timing or end timing) with reference to a table corresponding to the engine rotation speed, the injection start timing is varied so that the end timing of fuel injection matches the opening timing of the intake valve 12. It is more preferable to adopt a configuration in which control is performed at

As described above, in the first embodiment, as shown in FIG. 6, the intake valve 12 and the exhaust valve
The fuel injection is performed during the opening or compression stroke of the intake valve 12 while the opening period of the exhaust valve 13 is overlapped with the opening period of the exhaust valve 13. After the crank angle, the opening timing of the intake valve 12 is set (non-overlap state), and the fuel injection is performed when both valves are closed between the closing timing of the exhaust valve 13 and the opening timing of the intake valve 12. Is performed.

If the intake valve 12 is opened at a predetermined crank angle after the exhaust valve 13 is closed, a relatively high temperature combustion gas remains in the combustion chamber, and fuel is injected into the residual gas. By doing so, the vaporization of the fuel is promoted, and the adhesion of the fuel to the piston crown surface is suppressed. Also,
Since the in-cylinder pressure is relatively high at the injection timing, the reach of the fuel spray is shortened, which also suppresses the adhesion of fuel to the piston crown surface. Therefore, even if the fuel is injected relatively near the top dead center, the adhesion of fuel to the piston crown is suppressed, and the generation of smoke due to the diffusion and combustion of the fuel attached to the piston crown can be prevented.

Further, by causing fuel injection near the top dead center by the fuel injection valve 6 for injecting fuel obliquely downward substantially toward the center of the cylinder, fuel adhesion to the cylinder bore can be avoided, and Oil dilution due to fuel adhesion can also be prevented. Also, if the injection timing is set immediately before the opening timing of the intake valve 12, the fuel can be injected while the piston is descending and at the position where the piston is most lowered, thereby reducing fuel adhesion to the piston crown surface. it can.

Further, as shown in FIGS. 5 and 6, the angle from the closing timing of the exhaust valve 13 to the intake TDC and the intake TD
If the angle from C to the opening timing of the intake valve 12 is substantially matched, as shown in FIG. 7, the compression work from the closing timing of the exhaust valve to the piston top dead center, Since it is collected before the opening timing, the pump loss can be reduced as compared with the pump loss (see FIG. 8) at the normal valve timing that causes the overlap.

However, as shown in FIGS. 9 and 10, the angle from the closing timing of the exhaust valve 13 to the intake TDC and the intake TD
It is not always necessary to make the angle from C to the opening timing of the intake valve 12 coincide, and even if the valve timing is as shown in FIGS. 9 and 10, from the closing timing of the exhaust valve 13 to the opening timing of the intake valve 12 By performing the fuel injection during this time, generation of smoke and generation of oil dilution on the cylinder bore wall surface can be prevented.

As shown in FIGS. 11 and 12, the valve timing is not switched, and the intake valve 12 is always opened at a predetermined crank angle after the exhaust valve 13 is closed. Although it is possible to prevent the generation of smoke and the dilution of oil on the bore wall surface during the cold period even if the switching is performed based on whether or not By switching to the generated valve timing, the output during normal operation can be ensured.

Further, a configuration may be adopted in which only one of the valve timings of the intake valve 12 and the exhaust valve 13 is switched to switch from the overlap state to the non-overlap state. It should be noted that when both valve timings are switched, if the angle from the closing timing of the exhaust valve 13 to the intake TDC and the angle from the intake TDC to the opening timing of the intake valve 12 are set to be the same, a single It is easy to configure so that both valve timings are switched by the valve timing changing mechanism.

FIG. 13 is a flow chart showing a second embodiment of the valve timing control and the fuel injection control by the control unit 11. In the cold state at S12 based on the cooling water temperature Tw read at S11. If it is determined that there is, the process proceeds to S15, in which the closing timing of the exhaust valve 13 is advanced and the opening timing of the intake valve 12 is advanced, whereby the normal overshoot shown in FIGS. From the wrapped state, as shown in FIG.
Is switched to a non-overlapping state in which the intake valve 12 is opened after a predetermined crank angle from the closing timing of.

That is, the closing timing of the exhaust valve 13 is advanced and the opening timing of the intake valve 12 is retarded without changing the opening timing of the exhaust valve 13 and the closing timing of the intake valve 12 from the normal time. In the non-overlapping state, the variable valve mechanisms 14a, 14
As b, a mechanism capable of variably controlling the valve timing and the operating angle by periodically changing the angular speed of the camshaft with respect to the angular speed of the crankshaft can be used.

In step S16, similarly to step S6, the injection timing for cold operation is set. On the other hand, if it is determined in S12 that the warm-up has been completed, the process proceeds to S13, where the exhaust valve 13 closes after the intake TDC and the intake valve 12 closes the intake TDC as shown in FIGS. By opening in front, the exhaust valve 13
The closing timing of the exhaust valve 13 is retarded and the opening timing of the intake valve 12 is advanced with respect to the cold state so that the normal valve timing at which the opening states of the intake valve 12 and the intake valve 12 overlap is provided.

In the next step S14, a normal injection timing is set as in step S4. In the above-described second embodiment, smoke generation and oil dilution on the bore wall surface during cold can be avoided while securing the output during normal operation. On the other hand, smoke generation and oil dilution on the bore wall surface during cold operation can be avoided. Switching to non-overlapping state to avoid
This can be performed only by advancing the closing timing of the exhaust valve 13 and retarding the opening timing of the intake valve 12.

FIG. 15 is a flow chart showing a third embodiment of the valve timing control and the fuel injection control by the control unit 11. The variable valve mechanism 14a, 14b includes a cam for normal use and a cold control. It is assumed that a configuration that switches between the cams for the interim time is used. Fig. 15
When it is determined in S22 that the warm-up has been completed in S22 based on the cooling water temperature Tw read in S21, the process proceeds to S23, where the cam is switched to the normal cam, and FIG.
Then, the valve timing is controlled so as to cause overlap as shown in FIG. 4, and in the next S24, the injection timing at the normal time is set as in S4.

On the other hand, if it is determined in S22 that the engine is in the cold state, the process proceeds to S25, in which the control for switching to the cam for the cold state is performed, and as shown in FIGS. Is switched to a non-overlap state in which the intake valve 12 is opened after a predetermined crank angle. Then, in S26, similarly to S6, the injection timing for cold operation is set. The characteristics of the cold cam shown in FIGS. 16 and 17 are as follows.
By advancing the closing timing of the exhaust valve 13 and retarding the opening timing of the intake valve 12, it is configured to switch to the non-overlapping state, and the valve lift is smaller than the normal cam, and The opening timing of the exhaust valve 13 is slightly retarded, and the closing timing of the intake valve 12 is slightly advanced. That is, the exhaust valve 13 is advanced to the non-overlap state by performing the advance timing of the closing timing and the retarding of the opening timing, and the intake valve 12 by the retarding of the opening timing and the advance of the closing timing.

As described above, if the cam for normal use and the cam for cold use can be selectively used, the intake / exhaust valve 1 can be set at the most suitable valve timing and lift amount during cold use.
2, 13 can be operated. The flowchart of FIG. 18 shows a fourth embodiment of the valve timing control and the fuel injection control by the control unit 11, and the flow chart of FIG. 18 is based on the cooling water temperature Tw read in S31.
If it is determined in 32 that the engine is in the cold state, the process proceeds to S36, and the retard amount of the opening timing of the intake valve 12 is calculated. Here, the retard amount indicates a retard amount of the opening timing in the cold state with respect to the opening timing in the normal state.

In the fourth embodiment, similarly to the second embodiment, the closing timing of the exhaust valve 13 is advanced without changing the opening timing of the exhaust valve 13 and the closing timing of the intake valve 12 from the normal time. And, by delaying the opening timing of the intake valve 12,
It switches to a non-overlapping state. However,
Although the advance amount of the closing timing of the exhaust valve 13 is fixed, the angle from the intake TDC to the opening timing of the intake valve 12 is made larger than the angle from the closing timing of the exhaust valve 13 to the intake TDC, so that The opening angle of the intake valve 12 is variably set in accordance with the condition at that time so that the intake valve 12 is opened at a time when the pressure in the cylinder coincides with the pressure in the cylinder (FIG. 19). reference).

Therefore, in S36, the retard amount of the opening timing of the intake valve 12 is calculated so that the intake valve 12 is opened at the time when the pressure in the intake pipe and the pressure in the cylinder coincide. Specifically, the advance amount can be calculated as follows. That is, if P is the in-cylinder pressure, V is the combustion chamber volume, θ is the crank angle, and n is the polytropic index, generally, the following equation is established between the in-cylinder pressure P and the combustion chamber volume V of a reciprocating engine. The relationship holds.

PVⁿ= Const. If the crank radius, connecting rod length, etc. are known,
The combustion chamber volume V is determined as a function of the crank angle θ.
You. V = f (θ) Here, intake pipe pressure Pintake = opening timing I of intake valve 12
In-cylinder pressure P in VO _IVOOpening timing of intake valve 12
θ_IVOIn order to determine the in-cylinder pressure P when the exhaust valve 13 is closed,_EV ⁰¹= 1 atm. Combustion chamber volume V when exhaust valve 13 is closed_EV ⁰¹= F
(Θ_EV ⁰¹Intake pipe pressure Pintake = value measured by sensor or operating condition
Assuming that the above three values are known as
I just need to unravel.

[0058] For _{^{P EV 01 · V EV 01n =}} Pintake · V IVO n V IVO = f (θ IVO) polytropic exponent n, but the usual 1.2 to 1.4 degree value, here, the working gas is burned gas Therefore, the calculation may be performed with n = about 1.25. Note that, for simplicity, as shown in FIG. 20, the retard amount may be set smaller as the intake pipe pressure is closer to the atmospheric pressure.

When the retard amount of the opening timing of the intake valve 12 (open timing during cold) is calculated in S36, the opening timing of the intake valve 12 is retarded from the normal timing by the computed retard amount in S37. At the same time, the closing timing of the exhaust valve 13 is advanced from a normal time by a preset angle. In S38, the injection timing for cold operation is set with reference to a table corresponding to the engine speed. In the next S39, the injection timing obtained in S37 is compared with the opening timing of the intake valve 12. The injection timing is appropriately corrected so that the injection ends before the intake valve 12 opens.

However, when the injection start timing is set to end the injection at the opening timing of the intake valve 12, the above-described S
The processing in 39 becomes unnecessary. On the other hand, if it is determined in S32 that the warm-up has been completed, the process proceeds to S33, in which the retard amount obtained in S36 is referred to, and the setting is advanced by the retard amount to return to normal. Then, in S34, control is performed to return the closing timing of the exhaust valve 13 and the opening timing of the intake valve 12 to normal,
In S35, the injection timing for normal operation is set.

In the fourth embodiment, after the exhaust valve 13 is closed and the compression work is performed up to the intake TDC,
Intake valve 12 until piston lowers by the same angle
Is closed, the compression work is recovered, and then, when the pressure in the intake pipe and the pressure in the cylinder match, the intake valve 12 is opened. And the angle from the intake TDC to the opening timing of the intake valve 12 is substantially the same, the pump loss can be further reduced, and the fuel efficiency can be improved (FIG.
21).

The flowchart of FIG. 22 shows a fifth embodiment of the valve timing control and the fuel injection control by the control unit 11. In the fifth embodiment, similarly to the second embodiment, the opening timing of the exhaust valve 13 and the closing timing of the intake valve 12 are not changed from the normal time.
The non-overlap state is switched by advancing the closing timing of the exhaust valve 13 and retarding the opening timing of the intake valve 12, and the exhaust valve 13 is set at the same angle before and after the intake TDC. And the opening timing of the intake valve 12 are basically set.

In the flowchart of FIG. 22, if it is determined in S42 that the engine is in a cold state based on the cooling water temperature Tw read in S41, the process proceeds to S46, where the engine speed is determined based on a signal from the crank angle sensor 2. To calculate. Next S
In FIG. 47, as shown in FIG. 23, based on a characteristic preset so that the angle from the closing timing of the exhaust valve 13 to the opening timing of the intake valve 12 becomes shorter as the engine rotation speed becomes higher, The amount of advance of the closing timing of the exhaust valve 13 and the amount of retardation of the opening of the intake valve 12 corresponding to the engine speed are set.

When the engine rotational speed is high, the speed at which the piston moves away from the top dead center is large. Therefore, even if the fuel is injected at a position closer to the top dead center, the amount of fuel adhering to the piston crown surface can be sufficiently suppressed. . Therefore, the angle from the closing timing of the exhaust valve 13 to the opening timing of the intake valve 12 becomes shorter as the engine speed increases (see FIG.
24), while suppressing fuel adhesion to the piston crown surface, and minimizing a decrease in output due to a decrease in charging efficiency due to a non-overlapping state in a cold state.

In S48, the closing timing of the exhaust valve 13 is advanced and the opening timing of the intake valve 12 is retarded based on the setting in S47. In S49, the injection timing is set with reference to the cold time table. In S50, the injection timing set in S49 is compared with the opening timing of the intake valve 12, and the injection timing is set before the opening timing of the intake valve 12. The injection timing is appropriately corrected so that the injection is performed. Here, if the injection opening timing is variably controlled so as to end the injection at the opening timing of the intake valve 12, the processing of S50 can be omitted.

On the other hand, when it is determined in S42 that the warm-up has been completed, in S43, the advance amount of the closing timing of the exhaust valve 13 and the opening timing of the intake valve 12 according to the engine speed during the cold state are determined. The amount of retard of the closing timing of the exhaust valve 13 and the amount of advance of the opening timing of the intake valve 12 for returning to the normal overlapping state are set with reference to the retarding amount of the intake valve 12. And S
At 44, the closing timing of the exhaust valve 13 is retarded based on the setting, and the opening timing of the intake valve 12 is advanced to return to the normal overlapping state.

In step S45, a normal injection timing is set.
In the above embodiment, the intake valve 12 and the exhaust valve 13
Although a device that opens and closes a valve by a cam is used as the valve operating device, a valve operating device that drives the valve by hydraulic pressure or electromagnetic force may be used. In this case, the timing of generation of hydraulic pressure or electromagnetic force With the above control, the valve timing in any of the above-described embodiments can be realized, and the degree of freedom in setting the valve timing is higher, and the optimum valve timing can be easily set.

[Brief description of the drawings]

FIG. 1 is a system diagram showing a direct injection gasoline engine according to an embodiment.

FIG. 2 is a flowchart showing a first embodiment of valve timing and injection control.

FIG. 3 is a diagram showing valve timing and injection timing in a normal state.

FIG. 4 is a view showing valve timing and injection timing in a normal state.

FIG. 5 is a view showing valve timing and injection timing in a cold state according to the first embodiment.

FIG. 6 is a diagram showing differences in valve timing and injection timing between a cold state and a normal state in the first embodiment.

FIG. 7 is a pressure diagram at the time of cold of the first embodiment.

FIG. 8 is a pressure diagram in a normal state in which the opening timings of an intake valve and an exhaust valve overlap.

FIG. 9 is a diagram showing another example of the non-overlapping state at the time of cold.

FIG. 10 is a diagram showing another example of the non-overlapping state at the time of cold.

FIG. 11 is a diagram showing an example in which only the injection timing is switched while the valve timing is fixed.

FIG. 12 is a diagram showing an example in which only the injection timing is switched while the valve timing is fixed.

FIG. 13 is a flowchart illustrating a second embodiment of valve timing and injection control.

FIG. 14 is a diagram illustrating differences in valve timing and injection timing between a cold state and a normal state in the second embodiment.

FIG. 15 is a flowchart illustrating a third embodiment of valve timing and injection control.

FIG. 16 is a view showing valve timing and injection timing at the time of cold in the third embodiment.

FIG. 17 is a diagram illustrating differences in valve timing and injection timing between a cold state and a normal state in the third embodiment.

FIG. 18 is a flowchart illustrating a fourth embodiment of valve timing and injection control.

FIG. 19 is a diagram illustrating differences in valve timing and injection timing between a cold state and a normal state in the fourth embodiment.

FIG. 20 is a diagram illustrating a correlation between an intake valve opening timing and an intake pipe pressure in a cold state according to the fourth embodiment.

FIG. 21 is a pressure diagram at the time of cold of the fourth embodiment.

FIG. 22 is a flowchart showing a fifth embodiment of valve timing and injection control.

FIG. 23 is an EVC at the time of cold in the fifth embodiment.
FIG. 4 is a diagram illustrating a correlation between the length of an IVO period and the engine speed.

FIG. 24 is a diagram showing differences in valve timing and injection timing between a cold state and a normal state in the fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accelerator opening sensor 2 Crank angle sensor 3 Air flow meter 4 Engine 5 Water temperature sensor 6 Fuel injection valve 7 Spark plug 8 Intake passage 9 Throttle valve 10 Throttle actuator 11 Control unit 12 Intake valve 13 Exhaust valve 14a, 14b Variable valve mechanism

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI F02D 43/00 301 F02D 43/00 301Z

Claims (16)

[Claims] 1. An in-cylinder injection gasoline engine having a fuel injection valve for injecting fuel directly into a cylinder, wherein the intake valve is opened at a predetermined crank angle after the exhaust valve is closed. A direct injection gasoline engine wherein fuel injection is performed by the fuel injection valve during a period between a closing time of the fuel injection valve and an opening timing of the intake valve. 2. The method according to claim 1, wherein the opening timing of the intake valve is set after the piston top dead center, and fuel is injected by the fuel injection valve from the piston top dead center to the opening timing of the intake valve. The direct injection gasoline engine according to claim 1, wherein: 3. The direct injection gasoline engine according to claim 2, wherein the injection timing of the fuel injection valve is set immediately before the opening timing of the intake valve. 4. The intake valve according to claim 2, wherein the opening timing of the intake valve is changeable, and the opening timing of the intake valve is made closer to the piston top dead center as the engine speed increases. In-cylinder injection gasoline engine. 5. An in-cylinder injection gasoline engine according to claim 2, wherein the opening timing of the intake valve is set to a timing at which the in-cylinder pressure and the intake pipe pressure become substantially equal. 6. The direct injection gasoline engine according to claim 1, wherein the closing timing of the exhaust valve is set before the top dead center of the piston. 7. An opening timing of said intake valve is set after a piston top dead center, and an angle from a piston top dead center to an opening timing of said intake valve is set between a closing timing of said exhaust valve and a piston top dead center. 7. The direct injection gasoline engine according to claim 6, wherein the angle is set to be equal to or larger than the angle. 8. The fuel injection valve according to claim 1, wherein the fuel injection valve injects fuel obliquely below the cylinder, wherein the closing timing of the exhaust valve and the opening timing of the intake valve are set in the second half of the exhaust stroke of the piston and the first half of the intake stroke. The cylinder-injected gasoline engine according to any one of claims 1 to 7, wherein the gasoline engine is set between the two. 9. The fuel injection valve according to claim 1, wherein the fuel injection is performed by the fuel injection valve during a period from the closing timing of the exhaust valve to the opening timing of the intake valve at least when the temperature of the engine is equal to or lower than a predetermined temperature. Item 9. A direct injection gasoline engine according to any one of Items 1 to 8. 10. A valve operating device capable of changing an opening timing of the intake valve, wherein at least when the opening timing of the intake valve is at a predetermined retarded position, after a predetermined crank angle from the closing timing of the exhaust valve. The intake valve is configured to be opened at a timing, and at least when the temperature of the engine is equal to or lower than a predetermined temperature, the opening timing of the intake valve is set to the predetermined retarded position. The direct injection gasoline engine according to any one of claims 1 to 8, wherein the fuel injection by the fuel injection valve is performed before the valve is opened. 11. A valve operating device capable of changing a closing timing of the exhaust valve, wherein at least when the closing timing of the exhaust valve is at a predetermined advanced position, after a predetermined crank angle from the closing timing of the exhaust valve. The intake valve is configured to be opened, and at least when the temperature of the engine is equal to or lower than a predetermined temperature, the closing timing of the exhaust valve is set to the predetermined advanced position, and the intake valve is closed from the closing timing of the exhaust valve. The direct injection gasoline engine according to any one of claims 1 to 8, wherein the fuel injection by the fuel injection valve is performed before the valve is opened. 12. The valve operating device according to claim 1, further comprising a mechanism for changing a phase between a crankshaft and a camshaft.
12. The in-cylinder injection gasoline engine according to 10 or 11. 13. The direct injection gasoline engine according to claim 10, wherein the valve train has a mechanism for periodically changing an angular speed of a camshaft with respect to an angular speed of a crankshaft. 14. The direct injection gasoline engine according to claim 10, wherein the valve train has a mechanism for switching a plurality of cams. 15. The direct injection gasoline engine according to claim 10, wherein the valve operating device is a device that drives a valve by hydraulic pressure. 16. The direct injection gasoline engine according to claim 10, wherein the valve train is a device that drives a valve by electromagnetic force.