JPH04272448A - Catalyst activation control device of intra-cylinder direct injection type engine - Google Patents

Abstract

PURPOSE:To enhance the exhaust gas purification efficiency by activating catalyst quickly and certainly without impairing the combustion proper in the striation, etc., according to the intra-cylindrical direct injection type while the catalyst state is held with low temperature. CONSTITUTION:A control unit 50 is equipped on an intra-cylindrical direct injection type engine, in which a catalyst device 13 is mounted in its exhaust system. This control unit 50 is fitted with a means 61 to judge that the engine is in the starting process or in operation with extra-low load, a post-injection control means 62 to make post-injection of the fuel once again immediately after the normal combustion period if the judgment is in starting or in extra-low load operation, and a post-ignition control means 63 to perform post-ignition immediately after post-injection of the fuel. Post-injection is made immediately after finish of the combustion proper in the striation, etc., followed by post- ignition to produce the combustion gas, which should raise the temp. and activate the catalyst quickly without impairing the function proper of the catalyzer device. Thus purification of the exhaust gas can be made in good performance.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a catalyst activation control device installed in the exhaust system of a direct injection type engine for a vehicle to purify harmful components in exhaust gas.

0002

[Prior Art] As a two-stroke engine for a vehicle, the engine itself has no suction capacity, so a scavenging pump is installed in the air supply system to increase the scavenging capacity, and an injector injects fuel directly into the cylinder to improve the performance. The applicant has already proposed an in-cylinder direct injection engine that performs stratified combustion and prevents fuel from blowing through. This engine is expected to be effective in improving drivability, fuel efficiency, etc., and is being put into practical use.

[0003] In the above-mentioned in-cylinder direct injection engine, the combustion period is short and combustion occurs only locally in the combustion chamber, so the fresh air component in the exhaust gas increases, and for these reasons, the temperature of the exhaust gas decreases. is low overall. Therefore, immediately after the engine is started or when the engine is operated at an extremely low load, there is a problem that the catalyst is not activated and the exhaust gas purification efficiency is poor, especially because the exhaust gas is small and the temperature is low. Therefore, in this in-cylinder direct injection engine, it is necessary to take measures to actively activate the catalyst when the temperature of the catalyst is low, such as during startup.

[0004] Conventionally, as a measure for activating the catalyst, an electric heater is installed on the catalyst, and the temperature of the catalyst is increased by heating the catalyst with the electric heater. Furthermore, for example, the prior art disclosed in Japanese Unexamined Patent Publication No. 58-72632 discloses that when the temperature of the catalyst is low, the amount of fuel injected from the injector is corrected to increase.

[0005]

[Problems to be Solved by the Invention] By the way, in the case of using the electric heater of the above-mentioned prior art, the effect of activating the catalyst is large, but at the time of starting, for example,
It is necessary to heat the catalyst with an electric heater for a long time of 0 seconds, and the power consumption becomes very large, making it impractical. In addition, in-cylinder direct injection engines are configured to perform stratified combustion by setting the fuel injection timing at low load just before ignition, so if the fuel is increased as in the latter case of the prior art, stratified combustion will occur. This may cause problems such as the increased amount of fuel not burning properly.

The present invention has been made in view of this point, and is a method for quickly and reliably activating the catalyst under conditions of low catalyst temperature without impairing the original stratified combustion conditions of the in-cylinder direct injection type. The purpose is to improve exhaust gas purification efficiency.

[0007]

[Means for Solving the Problems] In order to achieve the above object, the present invention includes an injector whose fuel injection is controlled by a control unit and a spark plug whose ignition timing is controlled are attached to a combustion chamber of an engine body, and an exhaust system is provided with an injector whose fuel injection is controlled by a control unit and a spark plug whose ignition timing is controlled. In a direct injection engine equipped with a catalytic converter, the control unit has a means for determining engine start or very low load operating conditions and, in the case of start or very low load, for restarting the fuel immediately after the normal combustion period. The fuel injection apparatus includes a post-injection control means for post-injection, and a post-ignition control means for post-ignition immediately after the post-injection of fuel.

[0008]

[Operation] Based on the above configuration, when the engine is operating, fuel is directly injected into the cylinder by the injector and ignited by the spark plug to cause stratified or uniform combustion, and the exhaust gas after this combustion is guided to the catalyst device and purified. Ru. Under conditions such as starting or extremely low load, where the exhaust gas temperature is low and the catalyst is not fully activated, the control unit will cause post-injection and post-ignition to produce combustion gas immediately after the original combustion ends. By being controlled in such a manner, the temperature of the catalytic device quickly rises and becomes activated without impairing its original function, making it possible to effectively purify exhaust gas even under such operating conditions.

[0009]

Embodiments Hereinafter, embodiments of the present invention will be explained based on the drawings. In FIG. 2, the overall structure of a two-cycle direct injection engine is described. Reference numeral 1 is an engine main body, in which a piston 3 is inserted into a cylinder 2 so as to be able to reciprocate, and connecting rod 6
is connected to the piston 3, and a balancer 7 is provided on the crankshaft 5 so as to offset the reciprocating inertia of the piston 3. Further, a spark plug 9 and an in-cylinder direct injection type injector 10 are attached to the top of the combustion chamber 8. An exhaust port 11 opened and closed by a piston 3 is opened in the middle of the cylinder 2, and a catalyst device 13 and a muffler 14 are disposed in an exhaust pipe 12 communicating with the exhaust port 11. Further, an exhaust rotary valve 15 is attached to the exhaust port 11, and the exhaust rotary valve 15 is connected to the crankshaft 5 via a drive means 16 to exhaust the air at a predetermined timing. A scavenging port 17 is provided at a position below the exhaust port 11 of the cylinder 2 and shifted approximately 90 to 180 degrees in the circumferential direction, and similarly opens and closes with the piston 3 .

The injector 10 is of a high-pressure fluid type, for example, and includes a filter 31 communicating with a fuel tank 30;
Fuel pump 32, accumulator 34 for absorbing pressure fluctuations
A fuel passage 35 with a fuel passage 35 communicates with the injector 10. The pump discharge side of the fuel passage 35 communicates with a fuel pressure regulator 33, which allows the fuel pump 32 to constantly adjust the fuel pressure of the fuel supplied to the injector 10 and to control the fuel injection amount by the pulse width of the fuel pulse. ing.

Next, the air supply system of the scavenging port 17 will be explained. A displacement type scavenging pump 21 is connected to the air supply pipe 18 communicating with the scavenging port 17, and a displacement type scavenging pump 21 is connected to the air cleaner 19 upstream of the scavenging pump 21. , a throttle valve 20 for controlling load is provided. The scavenging pump 21 is connected to the crankshaft 5 via a drive means 22, and is set to perform scavenging by driving the pump with engine power even in a low rotation range. Further, a bypass passage 23 is connected to the scavenging pump 21, and a control valve 24 of this bypass passage 23 is opened and closed according to each operating condition to keep the volumetric flow rate of air from the scavenging pump 21 constant at all times, and to cycle This is designed to minimize air supply fluctuations. Further, various signals are input to and processed by the control unit 50, and the control unit 50 outputs an injection signal to the injector 10, an ignition signal to the spark plug 9, and a fuel pressure signal to the fuel pressure regulator 33. ing.

Referring to FIG. 1, the fuel injection and ignition timing control system of the control unit 50 will be described. First, it has a crank angle sensor 40, a cylinder discrimination sensor 41, an accelerator opening sensor 42, etc., and signals from these sensors are input to a control unit 50. The control unit 50 has an engine rotation speed detection section 51 to which the signal from the crank angle sensor 40 is input, and detects the engine rotation speed Ne. Crank angle sensor 4
0 and the signal of the cylinder discrimination sensor 41 are detected by the crank position detection section 5.
2 to detect the reference position before top dead center in each cylinder. It also has a fuel injection pulse width calculation unit 53 which inputs the engine speed Ne and the accelerator opening degree α, searches for the fuel injection amount Gf according to each operating condition, and furthermore, searches for the fuel injection amount Gf according to the fuel pressure.
, the fuel injection pulse width Ti is calculated by taking into account the voltage correction amount Ts. The engine rotation speed Ne and the fuel injection amount Gf are input to the fuel injection timing determining section 54, the ignition timing determining section 55, and the combustion method determining section 56. The combustion method determination unit 56 has a preset value Gs for switching between the stratified combustion method and the uniform combustion method, and at low and medium loads where the fuel injection amount Gf is less than this preset value Gs, stratified combustion is performed, and when the fuel injection amount Gf is less than this preset value Gs, stratified combustion is performed, and when the fuel injection amount Gf is less than this preset value Gs, stratified combustion is performed. At high loads, uniform combustion is determined, and this determination signal is output to the fuel injection timing determining section 54 and the ignition timing determining section 55.

The fuel injection timing determination unit 54 determines the injection end timing θie in the case of the stratified combustion method, and the injection start timing θis in the case of the uniform combustion method, under each operating condition depending on the engine speed Ne and the fuel injection amount Gf. decide. The ignition timing determination unit 55 also determines the ignition timing θ under each operating condition for each combustion method.
Determine g. Fuel injection pulse width Ti and fuel injection timing θ
The ie or θis signal is sent to the fuel injection timing setting section 5.
7 and input the injection timing θi relative to the crank angle reference position.
e or θis, an injection signal with a predetermined pulse width Ti is output to the injector 10 via the drive unit 58. Also,
The signal of the ignition timing θg is input to the ignition timing setting unit 59, and the ignition signal of the ignition timing θg with respect to the crank angle reference position is output to the spark plug 9 via the drive unit 60.

Next, the control system for catalyst activation will be explained. The engine rotation speed Ne, the accelerator opening α, and the signals from the ignition switch 43 are input to the starting etc. determination unit 6.
1, and these signals are used to determine starting and extremely low loads. This determination signal for starting, etc. is input to the after-injection control unit 62 and the after-ignition control unit 63, and the after-injection control unit 62 is operated at the end of the original combustion period after top dead center TDC or immediately after the end, as shown in FIG. A predetermined post-injection amount Ga is set, and a signal of this injection pulse width is output to the fuel injection timing setting section 57. The post-ignition control unit 63 sets the post-ignition timing θga with the exhaust port 11 open immediately after post-injection, and outputs it to the ignition timing setting unit 59.

Next, the operation of this embodiment will be explained. When the engine is operating, the scavenging pump 21 is constantly driven by the power generated by the engine, and fresh air is pressurized according to the opening degree of the throttle valve 20 and introduced into the scavenging port 17. Therefore, when the piston 3 of the engine body 1 descends to the bottom dead center side and opens the exhaust port, and when the piston descends and opens both the scavenging port 17 and the exhaust port 11, fresh air from the scavenging pump 21 is pumped into the cylinder 2. It flows into the interior and pushes out residual gas, providing effective scavenging in a short period of time. Then, when the piston 3 rises, the exhaust rotary valve 15 closes the exhaust side at an early timing, making it possible to inject fuel without causing fuel blow-through, and then the scavenging port 17 closes, completing the scavenging and entering the compression stroke. Transition.

At this time, the control unit 50 determines the combustion method based on the engine rotational speed Ne and the fuel injection amount Gf based on the accelerator opening α. At low and medium loads, the injection end timing θie is determined as the fuel injection timing using the stratified combustion map, and an injection signal based on the fuel injection timing θie and the fuel injection pulse width Ti is output to the injector 10, thereby controlling the compression stroke. A relatively small amount of fuel is injected in the latter half of , and immediately after that, an ignition signal at ignition timing θg is output to the spark plug 9 . Therefore, the rear end of the fuel spray is ignited before it diffuses, and stable and good stratified combustion is achieved using the spark of this rich mixture. In addition, at high load, the injection start timing θis is determined as the fuel injection timing using the uniform combustion map, and the injection signal based on this fuel injection timing θis and the fuel injection pulse width Ti injects a large amount of fuel during the long injection period from the initial stage of compression. The fuel and air are injected into the cylinder 2 and are thoroughly premixed during compression. Then, this uniform air-fuel mixture is ignited by the spark plug 9 to achieve uniform combustion with high air utilization. In this way, after the engine is driven through stratified or uniform combustion, the exhaust port 11 opens due to the descent of the piston 3, and the exhaust stroke begins, and the exhaust gas is led to the catalyst device 13 through the exhaust pipe 12, purifying harmful components in the exhaust gas. It is then discharged.

On the other hand, when the two-stroke engine is started or operated at an extremely low load, the above-mentioned control system performs stratified combustion using a particularly small amount of fuel, and a large amount of fresh air is contained in the exhaust gas, causing the exhaust gas temperature to rise. As a result, the catalyst in the catalyst device 13 cannot be activated by itself. In this case, the starting etc. determination section 61 of the control unit 50 determines this operating condition, and the after-injection control section 62 injects fuel again immediately after the original stratified combustion ends. Immediately after this, the after-ignition control section 63 outputs an ignition signal to perform the second ignition combustion, and the combustion gas in this case is discharged while being after-burned and similarly guided to the catalyst device 13. Therefore, the catalyst device 13 is heated in a short time by this after-burning combustion gas, the temperature rises, and the catalyst device 13 is quickly activated, thus purifying the exhaust gas quickly and well even under such operating conditions. It turns out.

According to another embodiment of the invention in FIG. 4, the catalytic device 13 is fitted with a temperature sensor 44. The signal from this temperature sensor 44 is input to the post-injection control section 62 and the post-ignition control section 63, and post-injection and post-ignition are performed as described above only when the catalyst temperature is below a set value. Therefore, in this embodiment, when the catalyst temperature is low and inactive, the catalytic device 13 is effectively activated regardless of the operating conditions.

Although the embodiments of the present invention have been described above, the second ignition can be omitted if the self-ignition conditions are met. Moreover, it is applicable not only to the case of 2 cycles as in the embodiment but also to the case of 4 cycles.

[0020]

[Effects of the Invention] As explained above, according to the present invention,
In a cylinder direct injection engine with a catalyst device in the exhaust system, under operating conditions such as engine startup, extremely low load, or when the catalyst temperature is actually low, fuel is injected again and combusted, and this exhaust gas is transferred to the catalyst. Since the catalyst is additionally supplied, the catalyst can be activated quickly and reliably, and the exhaust gas purification efficiency is improved. After the original combustion period, the fuel is post-injected and post-ignited and combusted separately, so the stratified combustion during low load of the direct injection engine is not impaired, and the second combustion control can be performed easily. A configuration in which after-combustion is performed automatically according to operating conditions such as startup, is preferable in terms of exhaust gas purification because the catalyst can be activated in advance, whereas a configuration in which after-combustion is performed in accordance with catalyst temperature reduces fuel consumption. etc. can be kept to a minimum.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a catalyst activation control device for a direct injection engine according to the present invention.

FIG. 2 is an overall configuration diagram of a two-cycle direct injection type engine to which the present invention is applied.

FIG. 3 is a time chart showing the states of post-injection and post-ignition.

FIG. 4 is a block diagram of main parts of another embodiment of the present invention.

[Explanation of symbols]

1 Engine body 8 Combustion chamber 9 Spark plug 10 Injector 13 Catalyst device 50 Control unit 53 Fuel injection pulse width calculation unit 54 Fuel injection timing determination section 55 Ignition timing determination section 56 Combustion method determination section 57 Fuel injection timing setting section 59 Ignition timing setting section 61 Starting determination section 62 After injection control section 63 Post-ignition control section

Claims (2)

[Claims] 1. In a direct injection engine in which an injector whose fuel injection is controlled by a control unit and a spark plug whose ignition timing is controlled are attached to a combustion chamber of an engine body, and a catalyst device is attached to an exhaust system, the above-mentioned control is provided. The unit includes a means for determining engine starting or very low load operating conditions, a post-injection control means for after-injecting fuel again immediately after the normal combustion period in the case of starting or very low load, and a post-injection control means for again post-injecting fuel immediately after the normal combustion period in case of starting or very low load. 1. A catalyst activation control device for an in-cylinder direct injection engine, comprising a post-ignition control means for post-ignition. 2. The cylinder interior according to claim 1, wherein a temperature sensor is installed in the catalyst device, and the after-injection control means and the after-ignition control means are operated according to the catalyst temperature detected by the temperature sensor. Catalyst activation control device for direct injection engines.