JPH04237854A - Cylinder injection type internal combustion engine - Google Patents

Abstract

PURPOSE:To provide such an internal combustion engine as preventing an amount of fuel flowing into a cylinder from sharply decreasing at time of injection starting of the fuel in an intake pipe by a second fuel injection valve, in the cylinder injection type internal combustion engine which has a first fuel injection valve being set up in the cylinder and the second fuel injection valve being set up in the intake pipe, and changes fuel injection according to the extent of engine load. CONSTITUTION:In a cylinder injection type internal combustion engine which is made so as to inject fuel for stratified combustion at a compression stroke by a first fuel injection valve 4 at the time of engine low load, and to inject the fuel for uniform combustion by a second fuel injection valve 7 at the time of high engine load, fuel injection should be started also from the first fuel injection valve 4, in an intake stroke at the time of a specified load A at the lower side than that to be started of the fuel injection by the second fuel injection valve 7.

Description

[Detailed description of the invention]

0001

[Industrial Field of Application] The present invention comprises a fuel injection valve that injects fuel directly into a cylinder and a fuel injection valve that injects fuel into an intake pipe, and these fuel injection valves are operated according to the engine load condition, This invention relates to a direct injection internal combustion engine that achieves both improved combustibility at low loads and improved air utilization at high loads.

0002

2. Description of the Related Art A first fuel injection valve that injects fuel directly into a cylinder and a second fuel injection valve that injects fuel into an intake pipe are provided. This injects fuel into the cylinder in the latter half of the compression stroke to perform so-called stratified combustion to improve combustibility, and when the engine is under high load, the second fuel injection valve injects fuel into the intake pipe during the intake stroke. However, an internal combustion engine that achieves so-called uniform combustion and improves air utilization has been proposed (Japanese Patent Laid-Open No. 60-3
(See Publication No. 0416).

0003

[Problems to be Solved by the Invention] In the above-mentioned internal combustion engine, at the start of intake pipe injection, a portion of the fuel injected into the intake pipe adheres to the wall surface of the intake pipe, and therefore flows into the cylinder. The amount of fuel decreases momentarily and the air-fuel ratio becomes over-lean, causing misfires, torque shocks, or emission spikes. The present invention provides an internal combustion engine that has two fuel injection valves and switches fuel injection according to the engine load, in which the fuel injection in the intake pipe is affected by the change in the amount of fuel flowing into the cylinder at the start of the intake pipe fuel injection as described above. It is an object of the present invention to provide an internal combustion engine that does not cause phenomena such as misfires as described above.

0004

[Means for Solving the Problems] To achieve the above object, the present invention provides a first fuel injection valve that injects fuel directly into a cylinder, a second fuel injection valve that injects fuel into an intake pipe. When the load is low, the first fuel injection valve injects fuel during the compression stroke of the engine for stratified combustion, and when the load is high, the second fuel injection valve injects fuel for uniform combustion. In the direct injection internal combustion engine, fuel injection is also started from the first fuel injection valve during the intake stroke at a predetermined load lower than the load at which fuel injection from the second fuel injection valve is started. A direct injection internal combustion engine is provided.

[0005]

[Operation] At a load lower than the load at which intake pipe fuel injection starts, the first fuel injection valve starts injecting a predetermined amount of fuel during the intake stroke in addition to the previous injection only during the compression stroke. Ru. As a result, even if fuel adheres to the intake pipe wall surface when the second fuel injection valve starts injecting fuel into the intake pipe and the accuracy of the amount of fuel flowing into the cylinder deteriorates, the fuel necessary for combustion will be transferred to the first fuel injection valve. This is covered by fuel injection from the fuel injection valve during the intake stroke.

[0006]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of an internal combustion engine according to the present invention, in which a concave combustion chamber 2 is formed at the top of a piston 1. Furthermore, a first fuel injection valve (hereinafter referred to as the first fuel injection valve) 4 that injects fuel directly into the combustion chamber 2 is installed inside the cylinder head 3.
Further, the intake pipe 5 is equipped with a second fuel injection valve (hereinafter referred to as a second fuel injection valve) 7 that injects fuel into the intake port 6.

The first fuel injection valve 4 is supplied with fuel that is pumped from a fuel tank 8 to a reservoir tank 11 via a low pressure pump 9 and a high pressure pump 10.
Further, the second fuel injection valve 7 is supplied with fuel that is branched from the low-pressure pump 9 and fed under pressure to another reservoir tank 12.

The injection start timing and injection amount (valve opening period) of the first fuel injection valve 4 and the second fuel injection valve 7 are controlled by a control circuit 13. An accelerator opening signal is input from an accelerator opening sensor 14 that detects the opening of an accelerator pedal (not shown) as a load detection means, and a crank angle sensor 15 provided in a distributor (not shown) is input. A rotation angle signal is input. In addition to the above-mentioned signals, various signals representing engine operating conditions are input to the actual control circuit 13, and various signals are outputted therefrom, but they are not directly related to the present invention and will therefore be omitted.

A plug pocket 16 is formed at the outer circumferential portion of the combustion chamber 2 formed at the top of the piston 1 and at the center of the piston 1 shown in FIG. , the tip (gap portion) of the spark plug 17 enters into this plug pocket 16. The top surface of the piston 1 excluding the combustion chamber 2 and the plug pocket 16 described above is constituted by a convex curved surface as shown in the figure, and furthermore, the outer circumference of the piston 1 has a convex curved surface, and the outer circumferential portion of the piston 1 has a convex curved surface, excluding the combustion chamber 2 and plug pocket 16. A weir 18 is formed to prevent unidirectional dispersion, and as described above, the top of the piston 1 functions as a so-called evaporation plate for vaporizing the fuel injected into the cylinder.

FIG. 2 shows an example of injection timing control for each fuel injector, which is a feature of the present invention. (top dead center to compression top dead center). Further, in the figure, the length of the hatched portion in the vertical axis direction indicates the injection period of the corresponding fuel injection valve.

As is clear from this figure, in the so-called low and medium load operating range from load 0 to load B, the fuel supply is
The fuel injection valve 4 starts to inject fuel in the intake stroke by the second fuel injection valve 7 for the first time at load B, but from 0 to load A within the range of load 0 to B. Stratified combustion in which fuel is injected from the first fuel injection valve 4 is performed only in the compression stroke. Then, the compression stroke fuel injection amount (injection period) is gradually increased up to load A.

However, at load A, the compression stroke fuel injection amount is rapidly reduced to the fuel amount Qd required for ignition, and the first fuel injection valve 4 injects fuel by the reduced amount of fuel even during the intake stroke. is started. As a result, the fuel injected during the intake stroke adheres to the top surface of the piston 1, vaporizes from the intake to the compression stroke, and creates a nearly uniform lean mixture by the ignition timing. Become. Ignition of the fuel injected in the latter half of the compression stroke is ensured by generating a rich air-fuel mixture near the tip of the spark plug 17, thereby achieving stratified combustion. The amount of fuel injected by the first fuel injection valve 4 in the first half of the intake stroke is gradually increased up to load B.

Next, in the high-load operating range starting from load B, it is necessary to increase the amount of fuel injection, so in addition to the previous injection from the first fuel injection valve 4 in the first half of the intake stroke,
Fuel is also injected from the second fuel injection valve 7 attached to the intake pipe 5 during the intake stroke. The fuel injected from the second fuel injection valve 7 is almost uniformly mixed with the fuel already injected from the first fuel injection valve 4, producing a relatively rich air-fuel mixture than between the loads AB, and compressing the fuel. Ignition is ensured by fuel injection by the first fuel injection valve 4 in the latter half of the stroke, and combustion occurs.

That is, according to this embodiment, the second fuel injection valve 7
Even at the start timing of fuel injection into the intake pipe 5 (at the time of load B), the first fuel injection valve 4 supplies enough fuel to the intake stroke to allow flame propagation. Even if insufficient fuel intake into the cylinder occurs due to adhesion of injected fuel to the intake pipe wall, misfires can be prevented and smooth combustion can be continued.

As an example of injection control, in addition to the above-mentioned pattern, for example, as shown in FIG. Either the fuel injection in the latter half of the compression stroke is stopped, or, as shown in FIG. 4, in the extremely high-load operating range where the load is D or higher, the intake pipe injection is performed using only the second fuel injection valve 7, as shown in the pattern of FIG. It is also possible to add a pattern.

Taking the injection pattern of FIG. 2 as an example, FIG. 5 shows a routine for executing such injection. Note that this routine is executed as an interrupt routine at every fixed crank angle.

Referring to FIG. 5, first, in step 51, the engine speed NE and the accelerator opening θA are read from the signals from the aforementioned crank angle sensor 15 and accelerator opening sensor 14, respectively. Next, in step 52, the required fuel injection amount Q is calculated from the read NE and θA using, for example, map 1 as shown in FIG.

[0018] In the following step 53, step 5
The engine load detected in step 1, that is, θA, is the predetermined load A (Fig. 2
Reference) It is determined whether or not the following is true. If the determination is Yes here, the routine proceeds to step 54, in which the injection amount Q is added to the compression stroke fuel injection amount Qc in order to inject the entire required fuel injection amount Q from the first fuel injection valve 4 in the latter half of the compression stroke. Stored. Then, in the subsequent step 55, the intake stroke fuel injection amount Qi is set to zero.

Next, in step 56, the compression stroke fuel injection period Tc for achieving fuel injection of the set fuel injection amount Qc is calculated using map 2 as shown in FIG. The fuel injection period Ti is set to zero.

In step 58 following step 57, the compression stroke fuel injection start timing TSc is calculated from the compression stroke fuel injection amount Qc (or load θA) and the engine speed NE using a map as shown in FIG. 8, for example. This routine is then completed as described above. In addition, in FIG. 8, TSc is shown as the injection advance angle from compression top dead center, and Qc or θ
As A increases, the ignition timing is advanced as well.

On the other hand, in step 53, No, that is, θA>A
In this case, the routine proceeds to step 59, where it is determined whether or not the second predetermined load B (see FIG. 2) is lower than or equal to the second predetermined load B (see FIG. 2). If the determination is Yes here, the process proceeds to step 60 and subsequent steps, and the required fuel injection amount Q is divided and injected into an intake stroke and a compression stroke by the first fuel injection valve 4.

In step 60, the compression stroke fuel injection amount Qc
Qd (see FIG. 2) is stored in . This injection amount Qd is an amount that can reliably achieve fuel ignition from the spark plug, and is a constant value that can be determined experimentally. and,
In step 61, Q-Qd is stored in the intake stroke fuel injection amount Qi. That is, in this load range (A<θA≦B), the sum of the intake stroke fuel injection amount Qi and the compression stroke fuel injection amount Qc is set to be the required fuel injection amount Q calculated in step 52.

[0023] In the next step 62, the previous map 2
(Fig. 7), the compression stroke fuel injection period Tc is based on Qc.
is calculated, and in the subsequent step 63, the intake stroke fuel injection period Ti is calculated based on Qi.

Next, in step 64, the compression stroke fuel injection start timing TSc is calculated from the map 4 in FIG. 9 based on the required fuel injection amount Q and the engine speed NE. In subsequent step 65, the intake stroke fuel injection start timing TSi is calculated based on the intake stroke fuel injection amount Qi and the engine speed NE using the map 5 shown in FIG. As is clear from Map 5, TSi is normally set to advance as NE increases, but since intake stroke injection allows sufficient time for mixture generation, the compression stroke fuel injection amount It does not change depending on Qi.

[0025] Once the intake and compression strokes, their respective fuel injection periods, and injection start timings have been determined in the manner described above, this routine is terminated. Finally, if the determination in step 59 is No, that is, in the case of a high-load operating range where θA>B, the routine proceeds to step 66 and subsequent steps, and the previous fuel injection from the first fuel injection valve 4 is continued. In addition, fuel injection from the second fuel injection valve 7 is started. i.e. step 5
The required fuel injection amount Q calculated in step 2 is calculated by the first fuel injection valve 4.
The injection is divided into a total of three injections: intake/compression stroke injection by the second fuel injection valve 7 and intake stroke injection by the second fuel injection valve 7.

In step 66, Qd (see FIG. 2) is subsequently stored in the compression stroke fuel injection amount Qc. Then, in step 67, a constant value Qa when the load is equal to or higher than a preset load B is stored as the intake stroke fuel injection amount Q1i by the first fuel injection valve 4. In the subsequent step 68, the intake stroke fuel injection amount Q2i by the second fuel injection valve 7 is changed to Q-(Qd
+Qa) is stored. That is, this load range (θA>B)
Then, the sum of the intake stroke fuel injection amount Q1i+Q2i by the first fuel injection valve 4 and the second fuel injection valve 7 and the compression stroke fuel injection amount Qc by the first fuel injection valve 4 is the required fuel injection amount calculated in step 52. It is set to be Q.

[0027] In the next step 69, the previous map 2
(FIG. 7), the compression stroke fuel injection period Tc (same as between load ranges A and B) is calculated based on Qc (=Qd), and in the following step 70, based on Q1i (=Qa), The intake stroke fuel injection period T1i is calculated using map 2. Further, in step 71, similarly to map 2 in FIG. 7, the injection period T2i is determined using the fuel injection amount Q2i set for the second fuel injection valve 7 and the map 6 (see FIG. 11) of the intake stroke fuel injection period. Calculate.

Once the injection period of each fuel injection valve has been determined as described above, the routine proceeds to step 72, where the injection period is determined based on the required fuel injection amount Q and engine speed NE from map 4 in FIG. The compression stroke fuel injection start timing TSc is calculated. Then, in the subsequent step 73, the intake stroke fuel injection start timing TS1i by the first fuel injection valve 4 is calculated based on the intake stroke fuel injection amount Q1i and the engine speed NE, using the map 5 shown in FIG. 10, and the following step 7
4, the fuel injection timing TS2i by the second fuel injection valve 7 is determined using a map 7 of the fuel injection amount Q2i and the intake stroke fuel injection start timing TS2i based on the engine speed NE as shown in FIG.

[0029] As described above, the intake/compression stroke,
Once each fuel injection period and injection start timing are determined, this routine ends. Further, actual fuel injection based on the injection characteristics determined in this way will be executed by another fuel injection execution routine (not shown), but the operation control of each of these fuel injection valves is the same as that of the conventional one. The explanation will be omitted.

An example of the operation of the control circuit for determining the fuel injection period and fuel injection start timing in this case has been explained using the injection pattern shown in FIG. 2 as an example, but the injection pattern shown in FIGS. 3 and 4 is executed. In this case, it is natural to add a new load determination process and a calculation routine for the fuel injection period and injection start timing corresponding to each load range to the routine shown in FIG. Furthermore, as is clear from the injection patterns shown in FIGS. 2 to 4, the present invention provides the first and second
Since fuel is injected from both fuel injection valves, the amount of fuel injected from the first fuel injection valve is lower than that in the case where, for example, the intake stroke injection from the first fuel injection valve alone covers the fuel injection amount from the second fuel injection valve in the same operating range. The amount of fuel injected by the injection valve is small, and the accuracy of the amount of fuel injected can be improved. Further, along with this, it becomes possible to downsize the first fuel injection valve and the high pressure pump. In addition, in the case of fuel supply from only the first fuel injector as described above, in a load operation range where the intake stroke injection amount is large, the time between the intake stroke injection end time and the compression stroke injection start time becomes short. This imposes a fairly high response on the injection valve itself, which may make it impossible to control with a normal electromagnetic valve type fuel injection valve.

[0031]

As described above, according to the present invention, at a load lower than the load at which intake pipe fuel injection starts, the first fuel injection valve performs injection only during the compression stroke, and Since a predetermined amount of fuel injection also starts during the intake stroke,
Even if fuel adheres to the wall of the intake pipe when the second fuel injection valve starts injecting fuel into the intake pipe, the fuel necessary for combustion is secured from the first fuel injection valve, so the sudden supply of fuel This will prevent the occurrence of misfires, torque differences, emission spikes, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing an embodiment of an internal combustion engine of the present invention.

FIG. 2 is a diagram showing an example of a fuel injection control pattern of the present invention.

FIG. 3 is a diagram showing an example of a fuel injection control pattern different from that in FIG. 2;

4 is a diagram showing an example of a pattern in which fuel is injected only from the second fuel injection valve in an extremely high load range, unlike the pattern in FIG. 3; FIG.

FIG. 5 is a flowchart illustrating the operation of the control circuit corresponding to the fuel injection control pattern shown in FIG. 2;

FIG. 6 is a diagram showing the relationship between accelerator opening and required fuel injection amount.

FIG. 7 is a diagram showing the relationship between the fuel injection amount of the first fuel injection valve and the fuel injection period.

FIG. 8 is a diagram showing the relationship between the compression stroke fuel injection amount and the compression stroke fuel injection start timing of the first fuel injection valve.

FIG. 9 is a diagram showing the relationship between the required fuel injection amount and the compression stroke fuel injection start timing of the first fuel injection valve.

FIG. 10 is a diagram showing the relationship between the intake stroke fuel injection amount and the intake stroke fuel injection start timing of the first fuel injection valve.

FIG. 11 is a diagram showing the relationship between the fuel injection amount of the second fuel injection valve and the fuel injection period.

FIG. 12 is a diagram showing the relationship between the intake stroke fuel injection amount and the intake stroke fuel injection start timing of the second fuel injection valve.

[Explanation of symbols]

4...First fuel injection valve 5...Intake pipe 7...Second fuel injection valve 13...Control circuit

Claims (1)

[Claims] Claim 1: A first fuel injection valve that injects fuel directly into a cylinder, and a second fuel injection valve that injects fuel into an intake pipe, and when the load is low, the first fuel injection valve In a direct injection internal combustion engine, in which fuel is injected during the compression stroke of the engine to perform stratified combustion, and when the load is high, fuel is injected by the second fuel injection valve to achieve uniform combustion. A direct injection internal combustion engine characterized in that fuel injection is started from a first fuel injection valve during an intake stroke at a predetermined load lower than a load at which fuel injection is started.