JPH0514565U - Ignition control device for cylinder injection type internal combustion engine - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to eliminate waste of ignition energy and improve combustibility at low load of a cylinder injection type internal combustion engine using alcohol fuel. [Structure] The control unit 27 superimposes on the ignition energy supply of the ignition coil 24 based on the OFF operation of the power transistor 26, and the control unit 31 controls the DC-D.
Ignition energy is supplied by the C converter 30. This D
The ignition energy supply period (corresponding to the ignition period) by the C-DC converter 30 is variably set according to the injection period set based on the engine load state. As a result, the ignition period can be set in accordance with the injection period, the ignition period can be shortened when the engine load is low, and the ignition energy can be supplied at a high energy density. You can give it a mixture.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an ignition control device for a direct injection internal combustion engine, and more particularly to a ignition control technique for improving combustibility at low load in an internal combustion engine that uses alcohol fuel having a low cetane number.

[0002]

[Prior Art]

 Conventionally, there is known a cylinder injection type internal combustion engine in which fuel is directly injected into a combustion chamber in a cylinder and forcedly ignited by a spark plug (for example, Japanese Utility Model Laid-Open No. 57-127856 and Japanese Patent Application No. 2-101521). reference). FIG. 9 shows an example of a conventional cylinder injection type internal combustion engine.

In the figure, this is a two-plug type equipped with two spark plugs, and a fuel injection nozzle 4 and a fuel injection nozzle 4 are provided in a combustion chamber 3 formed on a top surface of a piston 2 in each cylinder of an engine body 1. The ignition plugs 5 and 6 are arranged to face each other, the fuel supplied from the fuel injection pump 7 is directly injected from the fuel injection nozzle 4 into the combustion chamber 3, and the injected fuel is ignited by the ignition plugs 5 and 6. It is designed to burn. The ignition timing of the ignition plugs 5 and 6 is based on the engine load signal L based on the fuel control lever position and the engine speed signal N from the rotation sensor 8 that detects the rotation of the crankshaft. Controlled by the control unit 9 to turn off the transistors 10 and 11 in response to an ignition signal from the control unit 9 at a predetermined ignition timing corresponding to the engine operating state to generate a high voltage in the secondary side coils of the ignition coils 12 and 13. The ignition plugs 5 and 6 are ignited with. In the figure, one of the two spark plugs 5 and 6 is an auxiliary one for surely performing ignition. In the figure, 14 is a battery, and 15 is an ignition switch.

[0004]

[Problems to be solved by the device]

 By the way, in the conventional ignition control device for this kind of internal combustion engine, only the ignition start timing is controlled in relation to the fuel injection timing corresponding to the engine operating state. It was uniquely fixed by. Then, the ignition period was set to be long according to the high engine load with a large amount of fuel injection. For this reason, even when the engine has a short fuel injection period and a low load, the ignition operation is continued for a while even after the fuel injection is completed and the mixture state in which ignition by the spark plug is impossible is performed, and the ignition energy is wasted. That is, the ignition is started at the time when the fuel injection is started and the rich air-fuel mixture sufficient for ignition actually starts passing through the vicinity of the spark plug, but after the fuel injection is completed, the rich air-fuel mixture has finished passing through the spark plug. Even if the vicinity of the spark plug is in a thin air-fuel mixture state that is insufficient for ignition, the ignition operation is conventionally continued, so the ignition energy during this period of the latter half of the ignition operation is wasted. Therefore, when the engine load is low, there is a problem that the combustion energy becomes unstable because the ignition energy given to the air-fuel mixture is wasted and reduced.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide an ignition control device for a cylinder injection type internal combustion engine, which can effectively give the ignition energy to the air-fuel mixture even when the engine load is low. To aim.

[0006]

[Means for Solving the Problems]

 Therefore, the present invention is an ignition control device for a cylinder injection type internal combustion engine configured to inject fuel directly into a combustion chamber from a fuel injection nozzle and ignite and burn by a spark plug. It is provided with rotational speed detection means and ignition period control means for variably controlling the ignition period of the ignition plug according to the fuel injection period set based on the engine load and the engine rotational speed detected by both detection means. did.

[0007]

[Action]

 According to this structure, the load and the rotation speed are detected by the engine load detection means and the engine rotation speed detection means. The ignition period control means sets the ignition period to be long according to the fuel injection period set by the detected load and the rotational speed, and when the injection period is long at a high engine load, the engine low period is set accordingly. If the injection period is short under load, set the ignition period accordingly.

As a result, when the engine is under a low load, the same amount of ignition energy as when the engine is under a high load is applied to the air-fuel mixture in a short period of time, so that the ignition energy can be effectively used, and combustion at a low engine load is performed. It becomes possible to stabilize the sex.

[0009]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 showing the main configuration of the first embodiment of the present invention, a fuel injection nozzle 22 is arranged at a substantially central position of the combustion chamber 21, and the inside of the combustion chamber 21 is provided from the fuel injection nozzle 22. The spark plug 23 is arranged at a predetermined position on the swirl downstream side (on the line connecting the position indicated by β in FIG. 2 and the nozzle) from the spray direction (the position indicated by α in FIG. 2) that is injected and supplied to .. One side of the secondary coil of the ignition coil 24 is connected to the spark plug 23. A battery 25 is connected to one side of the primary coil of the ignition coil 24, and a power transistor 26 for shutting off the primary current is connected to the other side. The power transistor 26 is driven and controlled by a control unit 27 containing a microcomputer. The control unit 27 inputs an engine rotation speed signal N and an engine load signal L from a rotation sensor 28 as an engine rotation speed detection means and a load sensor 29 as an engine load detection means, which are the same as those in the conventional case. Based on the above, the ignition timing corresponding to the current engine operating state is searched and set from the ignition timing map stored in advance, and the power transistor 26 is turned off at the set ignition timing. Further, on the other side of the secondary coil of the ignition coil 24, there is provided a DC-DC converter 30 which boosts a DC voltage from the battery 25 and can supply the DC voltage to the secondary coil. Are controlled by the control unit 31. Like the control unit 27, the control unit 31 has a built-in micro computer, and based on the engine speed N and the engine load L, a preset equal injection period characteristic map as shown in FIG. The ignition energy supply period by the DC-DC converter 30 is calculated according to the injection period retrieved from the map according to the detection signals from the both sensors 28, 29, and the power of the other control unit 27 is calculated. The DC-DC converter 30 is driven in synchronization with the input of the transistor OFF signal, that is, the ignition start timing. Here, the control unit 31 and the DC-DC converter 30 constitute an ignition period control means. The rotation sensor 28 is also used to detect the crank angle position.

Next, the ignition control operation of the apparatus of this embodiment will be described. First, the fuel injection period is determined according to the operating state of the engine, and the fuel is injected and supplied from the fuel injection nozzle 22 into the combustion chamber 21. On the other hand, the engine speed N and the engine load L at this time are input to the control unit 27 from the rotation sensor 28 and the load sensor 29. In the control unit 27, the ignition timing is set according to the operating state at that time based on the both detected values. The detection signals from the rotation sensor 28 and the load sensor 29 are also input to the control unit 31, and the control unit 31 determines the injection period at this time from the injection period map of FIG. 3 according to the operating state based on these input signals. Then, the ignition period corresponding to the obtained injection period is calculated. After that, at the crank angle position corresponding to the set ignition timing, the power transistor 26 is turned off by the output from the control unit 27, and the primary current of the ignition coil 24 is cut off, so that the secondary coil side is cut off. A high voltage is induced in the spark plug 23 to generate spark discharge in the spark plug 23. At the same time, the DC-DC converter 30 is also driven by the control unit 31 based on the output from the control unit 27, and is superimposed on the ignition energy induced by the OFF operation of the power transistor 26 during the injection period calculated above. The ignition energy from the DC-DC converter 30 is supplied to the spark plug 23.

The fuel injection timing and period and the ignition timing and ignition period are set as shown in FIGS. 4 (A) to 4 (D) according to the engine load state. That is, at the time of high engine load, the injection period is long and the fuel injection amount is sufficient, so that ignition is started after the injection is completed. Then, as the engine load becomes lower, the injection period becomes shorter and the injection amount becomes smaller.Therefore, the injection period is retarded and the ignition timing is advanced so that both periods overlap and ignite. It is easy to do. Then, the ignition energy supply period by the DC-DC converter 30, that is, the ignition period is variably set according to the injection period, and is set in the same manner as in the conventional case at the time of high engine load of the injection period. When the engine load is short, the injection period ends, and the rich mixture is set to end almost at the same time when it ends passing through the vicinity of the spark plug 23.

FIG. 5 shows the states of the secondary current, the secondary voltage, the ignition period, and the injection period in the ignition operation at the time of low engine load of the present embodiment. That is, after the start of injection, a predetermined delay period (the period from the start of injection until the rich air-fuel mixture begins to pass near the ignition plug 23) elapses, and at the same time the power transistor 26 is turned off, the DC-DC converter 30 is driven and ignition is performed. After the injection period ends, the ignition ends almost at the same time when the rich air-fuel mixture finishes passing near the ignition plug 23. The period from the start of ignition to t is the normal ignition period due to the supply of ignition energy generated by the interruption of the primary current of the ignition coil 24, and thereafter the ignition due to the supply of energy from the DC-DC converter 30. The ignition period is controlled by the energy supply period from the DC-DC converter 30. More specifically, during the OFF operation of the power transistor 26 and the ignition energy supply period by the DC-DC converter 30, as shown in FIGS. 6A to 6C, the position of α of the combustion chamber 21 from the fuel injection nozzle 22. After the fuel was injected into (shown in FIG. 2), the swirl spreads the fuel spray and the spray reaches the position of β in the combustion chamber 21 (shown in FIG. 2), that is, the position where the spark plug 23 exists. Sometimes, ignition energy is supplied to the spark plug 23 to start ignition, and further, when the fuel spray is carried by the swirl and the end of the spray passes the position of the spark plug 23, the ignition operation is terminated. Is set. As described above, when the engine load is low, the oscillation frequency of energy generation of the DC-DC converter 30 is increased so that high energy can be supplied to the spray in a short time, and ignition energy is effectively supplied to the spray. I have to.

According to this structure, the energy supplied from the DC-DC converter 30 is superimposed on the ignition energy generated in the normal ignition coil 24, and the energy supply time is variable according to the length of the injection period. In addition, the frequency of the energy oscillation of the DC-DC converter 30 is controlled to control the energy density to the optimum state for ignition. Since no energy is supplied, waste of ignition energy can be eliminated. Further, since the ignition energy supply from the DC-DC converter 30 is superposed on the ignition energy of the ignition coil 24 and the energy supply density of the DC-DC converter 30 is increased, the unit energy supplied per unit time is increased as compared with the conventional case. Since the energy density of the engine can be increased and the ignition energy can be effectively given to the mixture at low load, the fuel can be stably burned at low engine load. Furthermore, the unnecessary discharge period is eliminated, the electrode wear of the spark plug 24 is reduced, and the durability is improved.

Next, FIG. 7 shows a second embodiment. In this device, a large-capacity capacitor C is provided in parallel with the ignition coil 24, and the energy stored in the capacitor C is dividedly discharged by intermittently turning off the power transistor 26 by the control unit 41, as shown in FIG. Thus, the spark plug 23 is intermittently discharged. Then, by determining the discharge start timing and the number of discharges in correspondence with the ignition period set according to the injection period set based on the engine speed signal N and the engine load signal L, the ignition period is set. It is variably controlled.

The second embodiment has the same effect as that of the first embodiment.

[0016]

[Effect of the device]

 As described above, according to the present invention, the ignition period is variably controlled according to the fuel injection period, so that the ignition energy is effectively supplied to the air-fuel mixture without wasting the ignition energy when the engine load is low. It is possible to stabilize combustion at low engine load. Therefore, it is particularly effective for internal combustion engines that use alcohol fuel that is difficult to burn. Moreover, since the unnecessary discharge period can be eliminated, the wear of the electrodes of the spark plug can be reduced and the durability of the ignition plug can be improved.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a main part showing a first embodiment of the present invention.

FIG. 2 is a simplified diagram showing a combustion chamber of the above embodiment.

FIG. 3 is an injection period characteristic diagram of the internal combustion engine of the present embodiment.

FIG. 4 is a diagram showing a relationship between an injection period and a timing and an ignition period and a timing according to the embodiment.

FIG. 5 is a diagram for explaining an ignition operation when the engine has a low load according to the embodiment.

FIG. 6 is a diagram showing the relationship between the spray state in the combustion chamber and the ignition start and end timing when the engine load is low.

FIG. 7 is a configuration diagram of essential parts showing a second embodiment of the present invention.

FIG. 8 is a diagram showing an ignition operation at a low engine load according to the embodiment.

FIG. 9 is a configuration diagram showing a conventional example.

[Explanation of symbols]

 21 Combustion chamber 22 Fuel injection nozzle 23 Spark plug 24 Ignition coil 26 Power transistor 27, 31 Control unit 28 Rotation sensor 29 Load sensor 30 DC-DC converter

Claims (1)

[Scope of utility model registration request] 1. An ignition control device for a cylinder injection type internal combustion engine having a structure in which fuel is directly injected from a fuel injection nozzle into a combustion chamber and is ignited and burned by an ignition plug, in an engine load detection means and an engine rotation speed detection means. And a ignition period control means for variably controlling the ignition period of the spark plug according to a fuel injection period set based on the engine load and the engine speed detected by both detection means. Ignition control device for internal injection type internal combustion engine.