Start control method of spark ignition type internal combustion engine and device

Abstract

To enable a large ignition timing retard without deteriorating startability at a cold start, and to early raise a temperature of a catalyst.SOLUTION: When a cold start which requires a retard operation is determined, a tumble control valve is brought into a closed position before a start of cranking, and a tumble flow in a cylinder is reinforced. In an initial start, startability is secured by setting single injection without performing an ignition timing retard. After the completion of explosion, injection is switched to two-stage injection in a stage that a speed reaches an idle rotational speed, and at the substantially same time, the ignition timing retard is started. By fuel atomization by the two-stage injection in a state that a tumble flow is reinforced, fundamental combustion stability can be highly obtained. Therefore, a large ignition timing retard becomes possible.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to start control of a spark ignition internal combustion engine that performs retarded operation with ignition timing retardation in order to warm up a catalyst during cold start. [Background technology]

[0002] It is known that, during a cold start of an internal combustion engine, the exhaust temperature is increased by retarding the ignition timing, thereby quickly raising the temperature of a catalyst provided in the exhaust system.

[0003] Patent Document 1 discloses that in a direct injection internal combustion engine equipped with a tumble control valve in an intake port, in order to suppress adhesion of injected fuel to the cylinder wall surface and thus oil dilution when the engine is cold, fuel is injected in multiple divided injections during the intake stroke while the fuel pressure is controlled to be high, and further, the tumble control valve is closed to strengthen the tumble flow in the cylinder. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-2176 A Summary of the Invention [Problem to be solved by the invention]

[0005] Patent Document 1 describes a technique for preventing the injected fuel from adhering to the cylinder wall surface when the engine is cold, but makes no mention of retard operation immediately after a cold start. [Means for solving the problem]

[0006] A method for controlling a start of a spark ignition internal combustion engine according to the present invention comprises: In a cylinder direct injection type spark ignition internal combustion engine equipped with a tumble control valve in an intake port, Determines whether a cold start requires retard operation to warm up the catalyst at start-up, and if retard operation is required, Close the tumble control valve before cranking begins. Fuel injection is performed as single-stage injection from the first cycle until the engine speed increases, and then as multi-stage injection after the engine speed increases; Ignition timing retardation begins at approximately the same time as the transition to multi-stage injection.

[0007] With the tumble control valve closed, the strength of the tumble flow inside the cylinder increases. Immediately after cranking begins, the ignition timing is not retarded and single-stage injection is used to ensure reliable ignition and combustion. Then, when the engine speed increases, the system switches to multi-stage injection and ignition timing retard begins. The strengthening of the tumble flow and multi-stage injection stabilizes combustion, making it possible to significantly retard the ignition timing. Effect of the Invention

[0008] According to the present invention, it is possible to realize a large amount of ignition timing retard without deteriorating startability, and to achieve an early temperature rise of the catalyst. [Brief description of the drawings]

[0009] [Figure 1] 1 is a configuration explanatory diagram showing a system configuration of an internal combustion engine according to the present invention; [Diagram 2] 4 is a time chart showing the operation of the tumble control valve and the like during cold start. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an internal combustion engine 1 of an embodiment to which the present invention is applied. The internal combustion engine 1 of the embodiment is a four-stroke cycle spark ignition internal combustion engine (so-called gasoline engine), and each cylinder is provided with an intake valve 2, an exhaust valve 3, and an ignition plug 4. As an in-cylinder direct injection type internal combustion engine, a fuel injection valve 5 that injects fuel into the cylinder is disposed at an appropriate position in the cylinder. Fuel adjusted to a predetermined fuel pressure by a pressure regulator (not shown) is supplied to the fuel injection valve 5, and the fuel injection valve 5 opens in response to a drive pulse signal from an engine controller 9, thereby injecting an amount of fuel corresponding to the pulse width.

[0011] An electronically controlled throttle valve 10, the opening of which is controlled by a control signal from an engine controller 9, is disposed upstream of a collector section 8 in an intake passage 7 connected to an intake port 6 of each cylinder. An air flow meter 11 that detects the amount of intake air is disposed upstream of the throttle valve 10, and an air cleaner (not shown) is disposed further upstream.

[0012] Here, a tumble control valve 12 is provided in the intake port 6 of each cylinder so as to cover, for example, the lower half of the passage cross section. The tumble control valve 12 is configured to rotate about a rotation axis that crosses the center of the passage cross section of the intake port 6, and the opening degree is controlled by a control signal from the engine controller 9. When the tumble control valve 12 is in a closed state, the intake air flowing into the cylinder through the intake valve 2 flows in one direction at a high speed, so that the strength of the tumble flow in the cylinder increases. The tumble control valve 12 in one embodiment is of a so-called normally closed type configuration, and is in a closed position as shown in the figure when an actuator (not shown) is not driven by the engine controller 9.

[0013] The exhaust ports 13 of the cylinders are gathered together as a single exhaust passage 14, and a three-way catalyst 15 for purifying exhaust gas is provided in this exhaust passage 14. The three-way catalyst 15 is, for example, a so-called monolith ceramic catalyst in which a catalyst layer containing a catalytic metal is coated on the surface of a monolith ceramic body in which fine passages are formed. The three-way catalyst 15 may be configured to include multiple catalysts (for example, a manifold catalyst and an underfloor catalyst) arranged in series.

[0014] An air-fuel ratio sensor 19 for detecting the exhaust air-fuel ratio is disposed on the inlet side of the three-way catalyst 15 in the exhaust passage 14, that is, on the upstream side of the three-way catalyst 15.

[0015] Detection signals from the air-fuel ratio sensor 19 and the air flow meter 11 are input to the engine controller 9. Detection signals from a number of sensors, such as a crank angle sensor 21 for detecting the engine speed, a water temperature sensor 22 for detecting the coolant temperature, an outside air temperature sensor 23 for detecting the outside air temperature, and an accelerator position sensor 24 for detecting the amount of depression of the accelerator pedal operated by the driver, are also input to the engine controller 9. Based on these input signals, the engine controller 9 optimally controls the amount and timing of fuel injection by the fuel injection valve 5, the ignition timing by the spark plug 4, the opening of the throttle valve 10, the opening of the tumble control valve 12, etc.

[0016] As one of various controls of the internal combustion engine 1, the engine controller 9 performs retard operation with ignition timing retard to warm up the catalyst during cold start. That is, when the main switch (ignition switch) of the vehicle is turned on, the engine controller 9 judges whether the cold start requires retard operation to warm up the catalyst based on the cooling water temperature, the outside air temperature, etc. Then, when it is judged that the conditions require retard operation, the engine controller 9 transitions from start to retard operation according to the sequence shown in the time chart of FIG. 2.

[0017] The time chart in FIG. 2 shows the changes in (a) vehicle speed, (b) engine speed, (c) ignition timing retard amount, (d) number of injections, (e) tumble control valve opening / closing position, (f) fuel pressure, and (g) exhaust gas temperature at the inlet of the three-way catalyst 15 from a cold start to retard operation while the engine is left idling.

[0018] In the case of cold start requiring retard operation, as shown in (e), the tumble control valve 12 is controlled to the closed position before cranking starts. In this state, cranking is started by a starter motor (not shown). Fuel injection is performed as a single-stage injection during the intake stroke from the first cycle until the engine speed increases, as shown in (d). In addition, the ignition timing is controlled to a normal ignition timing without intentional retarding for increasing the exhaust temperature at the beginning of starting. In this way, by performing single-stage injection at the beginning of starting and not retarding the ignition timing, reliable ignition and combustion are ensured when the engine is cold. In other words, there is no concern about poor starting due to cranking. During single-stage injection, the fuel pressure is controlled to a relatively low fuel pressure, as shown in (f).

[0019] As shown in (b), the engine speed rises from cranking to complete combustion and then to the idle speed. Although not shown in the figure, in more detail, the engine speed momentarily rises to a speed exceeding the idle speed, then drops to the idle speed and is maintained at the idle speed by so-called idle speed control. The idle speed during this retard operation is set to a level higher than the idle speed after the warm-up is complete.

[0020] When the engine speed reaches the idle speed, the fuel injection is switched from single-stage injection to multi-stage injection. In one embodiment, the multi-stage injection is a two-stage injection including a first injection during the intake stroke and a second injection at the beginning of the compression stroke. Two injections may be performed during the intake stroke. Note that the multi-stage injection in one embodiment is not intended for stratification, but is basically intended for homogeneous combustion. With the transition to multi-stage injection, the fuel pressure is controlled to a relatively high fuel pressure, as shown in column (f). Such two-stage injection is advantageous in terms of fuel atomization and therefore vaporization under cold engine conditions.

[0021] Almost simultaneously with the transition to multi-stage injection, ignition timing retardation for increasing the exhaust gas temperature is started. In detail, it is necessary that the switch to multi-stage injection precedes the start of ignition timing retardation so that a cycle in which ignition timing retardation is performed under single-stage injection does not occur. The ignition timing retard is performed gradually so that the ignition timing does not change stepwise to the target retard amount, as shown in (c). In this way, the gas flow in the cylinder, i.e., the tumble flow, is strengthened by closing the tumble control valve 12, and the fuel can be atomized by performing two-stage injection with a relatively high fuel pressure, so that the basic combustion stability is improved. Therefore, compared with the case of single-stage injection without strengthening the tumble flow, the retard limit of the ignition timing restricted by combustion stability can be obtained further to the retard side, and a larger ignition timing retard is possible. Since the tumble control valve 12 is in a closed state before the start of cranking, when the ignition timing retard starts, the strengthening of the gas flow in the cylinder is reliably obtained without being affected by the delay in the transport of the intake air. Therefore, combustion does not become unstable in the cycle immediately after the start of the ignition timing retard.

[0022] As shown in (g), a large ignition timing retardation provides a high exhaust temperature, accelerating the warm-up of the three-way catalyst 15. When it is determined that the temperature of the three-way catalyst 15 has reached a sufficient level, the retard operation ends. The tumble control valve 12 remains closed until the end of this retard operation.

[0023] Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications are possible. For example, in the above embodiment, the switch to multi-stage injection and the start of ignition timing retard are performed at the stage where the engine speed reaches the idle speed after complete explosion, but the switch to multi-stage injection and the start of ignition timing retard may be performed at the stage where a predetermined time (or a predetermined cycle) has elapsed after complete explosion. [Explanation of symbols]

[0024] 1. Internal combustion engine 2...Intake valve 5...Fuel injection valve 6…Intake port 9. Controller 12...Tumble control valve 15...Three-way catalyst

Claims

1. In a cylinder direct injection type spark ignition internal combustion engine equipped with a tumble control valve in an intake port, Determines whether a cold start requires retard operation to warm up the catalyst at start-up, and if retard operation is required, Close the tumble control valve before cranking begins. Fuel injection is performed as single-stage injection from the first cycle until the engine speed increases, and then as multi-stage injection after the engine speed increases; The ignition timing retard begins at approximately the same time as the transition to multi-stage injection. A method for controlling the starting of a spark ignition internal combustion engine.

2. The tumble control valve is maintained in a closed state until the end of the retard operation.

2. A method for controlling a start of a spark ignition internal combustion engine according to claim 1.

3. The multi-stage injection is a two-stage injection including a first injection during the intake stroke and a second injection at the beginning of the compression stroke.

2. A method for controlling a start of a spark ignition internal combustion engine according to claim 1.

4. Initiating multi-stage injection and ignition retard after reaching idle speed, 2. A method for controlling a start of a spark ignition internal combustion engine according to claim 1.

5. During single-stage injection, the fuel pressure is controlled to be relatively low, and during multi-stage injection, the fuel pressure is controlled to be relatively high.

2. A method for controlling a start of a spark ignition internal combustion engine according to claim 1.

6. A normally closed tumble control valve is used as the tumble control valve.

2. A method for controlling a start of a spark ignition internal combustion engine according to claim 1.

7. A direct injection type spark ignition internal combustion engine having a tumble control valve in an intake port; A controller; Equipped with The above controller is Determines whether a cold start requires retard operation to warm up the catalyst at start-up, and if retard operation is required, Close the tumble control valve before cranking begins. Fuel injection is performed as single-stage injection from the first cycle until the engine speed increases, and then as multi-stage injection after the engine speed increases; The ignition timing retard begins at approximately the same time as the transition to multi-stage injection. A starting control device for a spark ignition internal combustion engine.

Images