JPS5922058B2 - electronically controlled internal combustion engine - Google Patents

Description

[Detailed Description of the Invention] The present invention aims to improve fuel efficiency, drivability, and exhaust performance by optimally controlling ignition timing and exhaust recirculation rate according to engine operating conditions in an engine with an electronically controlled carburetor. be.

Reducing harmful components in exhaust gas without reducing the operability of internal combustion engines is a very difficult problem, especially when internal combustion engines for automobiles are operated from low speed and low load ranges to high speed and high load ranges. It was thought that it would be almost impossible to satisfy the above conditions in all areas because the exhaust gas composition changes in each area in a case where the area is wide.

Conventionally, attempts have been made to realize control that responds to operating conditions, but these have been limited to negative pressure-responsive control, for example, when controlling ignition timing, exhaust recirculation amount, air-fuel ratio, etc. according to intake negative pressure and engine speed. Since negative pressure characteristics and rotation speed characteristics are directly utilized by components (diaphragms), rotation speed governors, etc., even if the required ignition timing and required reflux amount can be obtained approximately, it is not always possible to A sufficient effect cannot be expected, and particularly when the operating conditions change rapidly within the above range, the response delay of the control becomes noticeable and there is a tendency for the drivability or exhaust performance to temporarily deteriorate significantly.

The present invention was proposed to solve these technical problems, and the air-fuel ratio is accurately maintained at approximately the stoichiometric air-fuel ratio by a feedback system, and the exhaust gas recirculation rate and ignition timing are stored in advance. The purpose of the present invention is to provide an internal combustion engine equipped with an electronic control system so as to accurately match the required characteristics.

Some embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, 1 is a reciprocating internal combustion engine body, 2 is an intake passage, 3 is an exhaust passage, 4 is an air cleaner, and 5 is a carburetor.

The carburetor 5 is configured to feedback-control the air-fuel ratio to approximately the stoichiometric air-fuel ratio via a control circuit 20 based on the output of an exhaust sensor 6 (oxygen sensor) provided in the exhaust passage 3.

Air bleeds 11 and 12 are installed in the middle of fuel passages 9 and 10 that connect to the carburetor main nozzle 7 and slow nozzle 8, respectively.
are in communication with each other, and auxiliary air bleeds 13 and 14 are also in communication with each other, and on-off type solenoid valves 15 and 16 open and close these auxiliary air bleeds 13 and 14.

The electromagnetic valves 15 and 16 open and close at a constant frequency based on the pulse signal from the control circuit 20, and the amount of air bleed is made variable by changing the on/off time ratio, thereby indirectly increasing or decreasing the fuel flow rate to achieve mixing. Controls the air-fuel ratio of air.

The exhaust sensor (oxygen sensor) 6 detects the oxygen concentration in the exhaust gas, which is closely related to the air-fuel ratio, and inputs the detected value to the control circuit 20. If the air-fuel ratio matches the stoichiometric air-fuel ratio, then For example, the oxygen in the exhaust gas is zero; if the mixture is leaner than this, the oxygen concentration will increase, and if the mixture is richer than this, the oxygen concentration will be zero.

Therefore, the output of this sensor changes sharply near the stoichiometric air-fuel ratio, and by utilizing this characteristic, it is possible to control the air-fuel ratio to near the stoichiometric air-fuel ratio.

For example, when the detected air-fuel ratio is richer than the target value, the on/off opening/closing operation of the solenoid valves 15, 16 will increase the on/off time ratio so that the average opening degree of the auxiliary air bleeds 13, 14 increases. It is controlled based on a high pulse signal and corrected to reach the target air-fuel ratio.

Conversely, when the detected air-fuel ratio is lower than the target value, a corrective action is performed to reduce the average opening degree of the auxiliary air bleeds 13 and 14.

In the figure, 17 is a carburetor venturi, and 18 is a throttle valve.

An exhaust gas recirculation passage 19 communicates the exhaust passage 3 and the intake passage 2 so that a portion of the exhaust gas is recirculated downstream of the throttle valve 18.

The exhaust gas recirculation passage 19 is provided with an exhaust gas recirculation control valve 21 and an exhaust gas recirculation amount sensor 22 upstream thereof. The operation of the exhaust gas recirculation control valve 21 is controlled based on the comparison with the required exhaust gas recirculation pattern corresponding to the current operating state, and the amount of exhaust gas recirculation is appropriately controlled.

In this embodiment, the operating state is detected via a throttle valve opening sensor 23 and an engine rotation speed sensor 24, as will be described later.

In the exhaust gas recirculation control valve 21, suction negative pressure is introduced to a negative pressure chamber 26 defined by a diaphragm 25 via a passage 21, and an atmosphere inlet 28 communicated with the negative chamber 26 is connected to a solenoid valve 29.
A valve body 30 is connected to a diaphragm 25 that is configured to open and close, and responds to the negative pressure adjusted in this way,
Controls the amount of exhaust gas recirculation.

The solenoid valve 29 is an on-off type solenoid valve operated by a signal from the control circuit 20.

On the other hand, the exhaust gas recirculation amount sensor 22 is an electrostatic type corona discharge sensor, and is composed of a high-voltage electrode 32 connected to a high-voltage generator 31 and an ion detection electrode 33 placed opposite thereto, which also serves as a ground electrode for detecting ions. The amount of exhaust gas recirculation is detected based on the discharge ions detected by the detection electrode 33.

When a corona discharge is caused between electrodes in a fluid flow, the ions generated at this time are carried downstream depending on the flow rate.

Therefore, as the flow rate increases, the number of ions carried downstream increases, so the ion current detected by the earth electrode decreases.

As a result, by detecting ions at the ground electrode, it is possible to indirectly measure the flow rate, and the exhaust recirculation amount sensor 22 utilizes this principle.

In addition, an electrode for collecting ions is provided downstream of the discharge electrode,
The electrode may be configured to detect ions flowing downstream.

Next, a crank angle and rotation speed sensor 24 that utilizes this corona discharge is provided, and a control circuit 20 controls the high voltage generation timing of the high voltage spark generator 34 based on this detected value.
The ignition timing of an ignition plug (not shown) is appropriately controlled via the distributor 35.

The ignition timing control pattern is stored in advance in the control circuit 20 in the same manner as the above-mentioned exhaust gas recirculation control pattern, and is set to the optimum ignition timing according to the operating state detected by the rotation speed sensor 24 and the throttle valve opening sensor 23. The timing is selected and an activation signal is output to the high voltage spark generator 34.

Therefore, the crank angle and rotational speed sensor 24 together with the throttle valve opening sensor 23 serve as elements for detecting the operating state, and at the same time,
It also has an angle detection function for crank rotation angle to control ignition timing.

This crank angle/rotation speed sensor 24 has a disk 36 that rotates in the same manner as the rotation of the crankshaft.A ring-shaped insulator 31 on the outer periphery of the disk 36 has needle electrodes 38 radially arranged corresponding to the crank disassembly angle to be detected. are arranged, and each needle electrode 38
A conductive ring 39 and a contact brush 40 are thrown so as to apply a high voltage from a high voltage generator 31 for corona discharge to the electrode, while also serving as a ground electrode for causing corona discharge between the conductive ring 39 and the needle electrode 38. An ion detection electrode 41 is arranged close to the outer periphery of the disk 36 .

The needle-like electrodes 38 rotate in synchronization with the rotation of the crankshaft, and pass one after another in accordance with the rotational speed of the stationary ion detection electrode 41. At this time, corona is generated between each needle-like electrode 38. A discharge occurs.

Therefore, each needle electrode 38 is included in the ion detection electrode 41.
The maximum ion current is detected when the distance between the two is closest, and this detected value has a pulse-like current change characteristic in which the intervals become narrower as the rotation speed increases.

An electrode at a specific position among the needle electrodes 38,
For example, if the electrodes corresponding to the top dead center and bottom dead center positions are made to have a smaller discharge gap with the detection electrode 41 than the others (that is, by making a specific needle electrode 38 longer), the discharge with this electrode can be made smaller. The detected value of one ion becomes larger than the other, making it possible to identify a specific rotation angle.

Therefore, by counting the peak pulse as a reference point, a signal such as ignition at a position before the top dead center due to a change in crank angle can be outputted accurately, and the number of rotations can also be easily detected.

By the way, along with this crank angle/rotation speed sensor 24,
The detected value from the throttle valve opening sensor 23 that detects the engine operating state is input to the control circuit 20, and a control pattern of the exhaust gas recirculation amount and ignition timing corresponding to the operating state based on these two factors is determined by the second control circuit. As shown in the figure, the control circuit 20 is set in advance (
memory).

As the exhaust gas recirculation rate is increased, the NOx reduction effect increases, but at the same time, the combustion delay gradually increases and drivability deteriorates.

In addition, depending on the operating conditions, the amount of NOx generated may be small to begin with, so it is preferable to control the exhaust gas recirculation rate so that it is basically small in the low speed and low load range and large in the high speed and high load range. The required characteristics shown in Fig. 2 are obtained by plotting the optimum exhaust gas recirculation rate at each point.

On the other hand, if the ignition timing is not properly controlled in response to combustion delays caused by increases and decreases in the exhaust gas recirculation rate, engine operability and fuel efficiency will be seriously affected.

In addition, the required ignition advance angle changes depending on the load or rotational speed regardless of the magnitude of exhaust gas recirculation, and the optimal ignition timing is selected based on both of these factors according to the rotational speed and throttle valve opening as shown in the figure. This is the required ignition characteristic.

In order to satisfy these required exhaust gas recirculation amount and required ignition timing, a control signal is outputted to the exhaust recirculation control valve 21 and the high voltage spark generator 34 via the control circuit 20 based on the detected exhaust gas recirculation amount and crank angle. It is.

Note that a three-way catalyst device 43 is installed in the exhaust passage 3, and promotes the reduction of NOx contained in the exhaust gas and the oxidation of HC9CO to render them harmless.

The three-way catalytic converter 43 operates only when the total air-fuel ratio in the exhaust gas (which corresponds to the air-fuel ratio of the intake air-fuel mixture since no secondary air is introduced in this embodiment) is approximately within an extremely narrow range of the stoichiometric air-fuel ratio. , the above-mentioned reduction and oxidation efficiencies are both close to 100%.

Therefore, the air-fuel ratio feedback control carburetor 5
Therefore, the three-way catalyst functions effectively when the air-fuel mixture is accurately controlled close to the stoichiometric air-fuel ratio.

Based on exhaust gas recirculation, NOx in the exhaust gas is significantly reduced, but depending on the driving conditions, the level of NOx emissions may increase slightly due to the relationship with fuel efficiency and drivability, and these are almost completely removed. Therefore, a three-way catalytic converter 43 is installed, and at the same time, the air-fuel ratio is feedback-controlled.

Therefore, the burden on the three-way catalyst device 43 is not so large, and it has a supplementary exhaust purification function.

Next, it will be explained in more detail, including its effect.

Depending on the opening degree of the carburetor throttle valve 18, fuel is sucked out from the main system or the slow system nozzle 7.8, and is mixed with the air sucked through the air cleaner 4 to produce an air-fuel mixture.

The air-fuel mixture supplied to the engine body 1 passes through the exhaust passage 3 after combustion.
Here, the exhaust sensor 6 detects the oxygen concentration contained in the exhaust gas and outputs the detected value to the control circuit 20.

This detected concentration is compared with the oxygen concentration at the stoichiometric air-fuel ratio, and if there is an error, a control signal is output to the electromagnetic valves 15, 16 to eliminate the error.

This control signal is a pulse signal with a constant frequency, and therefore the ratio of on-off pulse width is changed depending on the detected concentration, thereby increasing or decreasing the average opening degree of the solenoid valves 15 and 16.

The solenoid valves 15, 16 open and close the auxiliary air bleeds 13, 14, control the flow rate of air mixed into the fuel, and control the air-fuel ratio. The fuel ratio shifts to the lean side.

Therefore, the detection result of the exhaust sensor 6 does not indicate that the air-fuel ratio is lower than the stoichiometric air-fuel ratio.

If so, the output signal from the control circuit 20 is transmitted to the solenoid valve 15.1.
6, the average opening degree of the auxiliary air bleeds 13, 14 is controlled to decrease, and based on this, the emulsion air in the fuel is reduced, and the air-fuel ratio approaches the stoichiometric air-fuel ratio.

In this way, the air-fuel ratio is maintained at approximately the stoichiometric air-fuel ratio, but depending on the operating conditions, a mixture richer than the stoichiometric air-fuel ratio may be required.

Therefore, when starting the engine cold, etc., the set value of the air-fuel ratio is shifted to the rich side based on the detected value from the cooling water temperature sensor 45. Specifically, the feedback system is stopped, and the auxiliary air Bleeds 13 and 14 may be fully closed) to improve engine stability when cold.

If the air-fuel mixture is accurately controlled to approximately the stoichiometric air-fuel ratio, both fuel efficiency and driving performance will be in the best condition, and HC and CO contained in the exhaust gas will also be significantly reduced.

On the other hand, a part of the exhaust gas is recirculated into the intake air through the exhaust gas recirculation passage 19, thereby relatively lowering the maximum temperature of combustion so as to reduce the generation of NOx.

In general, as the exhaust gas recirculation rate increases, the NOx generation rate decreases, but exhaust gas recirculation also has a very large effect on engine operating performance.
The amount of exhaust gas recirculation must be accurately controlled to a target value depending on the operating conditions.

In the present invention, an optimal exhaust recirculation control pattern is set in advance in accordance with the operating state, and this pattern is set by the throttle valve opening sensor 23.
and the signal from the rotation speed sensor 24,
The selected control target value and the actual exhaust gas recirculation amount are compared, and the exhaust gas recirculation control valve 21 is feedback-controlled.

Therefore, in order to detect the actual exhaust gas recirculation amount, an exhaust gas recirculation amount sensor 22 is provided. This sensor 23 is a corona ion detection type sensor that uses corona discharge, and the high voltage electrode 32 is connected to the ion detection electrode 33. A corona discharge occurs between the two.

Ions generated by corona discharge are carried downstream according to the amount of exhaust gas recirculation, so the ion current reaching the detection electrode 33 decreases as the amount of recirculation increases.

Therefore, the control circuit 20 converts this detected value into a flow rate and compares it with the selected target value as a signal.

Based on this comparison, the solenoid valve 29 of the exhaust recirculation control valve 21
A control signal is output that activates the .

This control signal is an on/off pulse signal, and operates the electromagnetic valve 29 to increase or decrease the average opening degree of the atmospheric inlet 28 of the negative pressure chamber 260.

If this average opening increases, the dilution rate of the atmosphere with respect to the suction negative pressure introduced into the negative pressure chamber 26 increases, and the control negative pressure weakens, so the control valve opening decreases, and conversely, the average opening increases. If it decreases, the control valve opening will increase based on the completely opposite operation, and the amount of exhaust gas recirculation will increase.

In this way, the exhaust gas recirculation amount is controlled so as to match the target value selected depending on the operating state.

In operating ranges where NOx generation is naturally low, such as when the engine is operating at low speeds and low loads, or during deceleration, the exhaust gas recirculation amount (rate) can be reduced to improve the stability of operating performance, while at high loads, when NOx generation increases. etc., requires control to increase the amount of exhaust recirculation.As mentioned above, these operating conditions are detected using the throttle valve opening and rotation speed as elements, and the optimal exhaust recirculation control pattern is selected. This allows the actual control flow rate to match the target value with high accuracy.

The required ignition timing inevitably changes based on such exhaust gas recirculation, but these required characteristics are also set in advance in the control circuit 20 in the same way as above, and the exhaust gas recirculation and The high voltage generation timing of the high voltage spark generator 34 is controlled by the signal from the control circuit 20 so that appropriate ignition timing can be obtained by taking into consideration the balance between the following.

The ignition timing control pattern depending on the operating state is selected based on the signals from the throttle valve opening sensor 23 and the rotation speed sensor 24, similarly to the selection of the exhaust gas recirculation control pattern.

The rotation speed sensor 24 is a sensor that uses corona discharge, and as described above, it has needle-like electrodes 38 whose number corresponds to the resolution angle of the crank rotation angle, so it outputs a pulse signal for each minute angle. It functions as a highly accurate crank angle detection sensor.

By using this sensor output, it is possible to accurately control the ignition timing, and in order to match the ignition timing of the selected control pattern, the detected crank angle signal can be used, for example, at top dead center. When the count reaches a predetermined angle, an ignition signal is output to the high voltage spark generator 34,
Ignition energy is supplied to the ignition plug via a distributor (power distribution section) 35 while controlling the high voltage generation timing.

In this way, by controlling the ignition timing to match the required characteristics, even if exhaust gas recirculation is performed as described above, instability of combustion characteristics (combustion delay) is avoided, and deterioration of fuel efficiency and driving performance is avoided. I can do it.

As described above, the characteristics of exhaust gas recirculation and ignition timing can be optimally feedback-controlled according to the operating conditions.
Since the air-fuel ratio of the air-fuel mixture is accurately controlled to the stoichiometric air-fuel ratio, which is the target value, these factors work together to reduce NOx without deteriorating fuel efficiency or drivability.

CO and HC can be significantly reduced as required.

Next, FIG. 3 shows a case where a suction negative pressure sensor 46 is provided in place of the throttle valve opening sensor 23 as an element for detecting the operating state.

Since the suction negative pressure varies depending on the engine load, the load condition can be determined by detecting the suction negative pressure, and at the same time, the operating condition can be accurately detected by knowing the engine speed.

A control pattern for exhaust gas recirculation and ignition timing using the suction negative pressure and rotational speed as parameters is shown in FIG.

Of course, these control patterns are essentially the same as those shown in FIG. 2, and were created by plotting optimal exhaust gas recirculation and ignition timing based on suction negative pressure and rotational speed.

Further, in the embodiment shown in FIG. 5, the operating state is detected using the intake air amount and the engine speed as elements, and the control pattern of the control circuit 200 is selected based on this.

For this reason, an intake air amount sensor 47 is provided in the intake duct 4a of the air cleaner 4.

This sensor 41 is constructed in the same manner as the above-mentioned corona discharge type sensor, but a high voltage electrode 48 and a ground electrode 49 are arranged facing each other, and an ion collecting electrode 50 is installed downstream thereof.

The high voltage electrode 48 is connected to the high voltage generator 31 for corona discharge, and inputs the ion current detected by the collection electrode 50 to the control circuit 20.

Ions generated by the corona discharge are carried downstream in accordance with the amount of intake air, and therefore the detection ion current of the collection electrode 50 increases in proportion to the increase in flow rate.

Based on the intake air amount and engine speed detected in this way, FIG. 6 shows an optimal control pattern for exhaust gas recirculation and ignition timing.

Of course, in this case, the exhaust gas recirculation amount and the ignition timing are feedback-controlled by the same operation as in each of the embodiments described above.

Furthermore, in the embodiment shown in FIG. 7, the exhaust flow rate is used as a detection element instead of the intake air amount in FIG.

The exhaust flow rate basically has the same tendency as the intake air amount, so by detecting the exhaust flow rate, it is possible to grasp the operating state.

Therefore, an exhaust flow rate sensor 51 using corona discharge was installed in the exhaust passage 3.

This sensor 51 is also composed of a high voltage electrode 52 connected to the high voltage generator 31 and an ion detection electrode 53 that also serves as a ground electrode, and the flow rate is determined based on the value detected by the detection electrode 53 of the ionic current generated based on corona discharge. Measure.

In addition, since the characteristics of intake air amount and exhaust flow rate are almost the same,
The control pattern for the exhaust gas recirculation amount and the ignition timing can be determined by replacing the intake air amount with the exhaust flow amount in FIG. 6.

As explained above, according to the present invention, the operating state of the engine is detected, the exhaust gas recirculation amount and the ignition timing are accurately feedback-controlled to match the target values selected at each time, and the air-fuel mixture is Feedback control is performed so that the air-fuel ratio of the engine is almost the stoichiometric air-fuel ratio, so while maintaining good driving performance such as engine fuel efficiency and drivability, it significantly reduces NOx and reduces HC and CO2.
Comprehensive exhaust countermeasures can be taken to prevent the occurrence of

Furthermore, since a corona discharge type sensor is used in common as the operating state detection means, exhaust gas recirculation amount sensor, etc., measurement accuracy is significantly improved, and input signals to the control circuit are unified, simplifying the input system. On the other hand, the power source for corona discharge, etc. can be used effectively, and the overall cost of the device can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a schematic sectional view of the first embodiment of the present invention, FIG. 2 is a control characteristic diagram of exhaust gas recirculation and ignition timing, FIG. 3 is a schematic sectional view of the second embodiment, and FIG. Similarly, FIG. 5 is a schematic sectional view of the third embodiment, FIG. 6 is a control characteristic diagram of exhaust gas recirculation and ignition timing, and FIG. 7 is a diagram of the fourth embodiment. FIG. 1... Engine body, 2... Intake passage, 3... Exhaust passage, 5... Carburetor, 6... Exhaust sensor, 1, 8...
・Fuel nozzle, 13.14... Auxiliary air bleed, 1
5, 16... Solenoid valve, 18... Throttle valve, 19... Exhaust recirculation passage, 20... Control circuit, 21... Exhaust recirculation control valve, 22... Exhaust recirculation amount sensor, 23 ... Throttle valve opening sensor, 24 ... Crank angle/rotation speed sensor, 2
5...Diaphragm, 31...High voltage generator, 3
2... High voltage electrode, 33... Detection electrode, 34... High voltage spark generator, 35... Distributor, 3
8... Consolidated electrode, 41... Detection electrode, 43... Three-way catalyst device.

Claims (1)

[Claims] 1. A carburetor equipped with a sensor that detects exhaust components that have a correlation with the air-fuel ratio of an intake air-fuel mixture, and that has a solenoid valve that feedback controls the fuel flow rate via a control circuit according to the output of the sensor. On the other hand, an exhaust recirculation control valve and a corona discharge type recirculation amount sensor are installed in the passage where part of the exhaust gas is recirculated into the intake air, and a high-voltage spark generator is installed to control the ignition timing, which is set in advance in the control circuit. A control pattern for the exhaust gas recirculation amount and the ignition timing is selected in accordance with the operating state detected through the operating state detection means including at least a corona discharge type engine speed sensor, and is set to match the selected target value. An electronically controlled internal combustion engine configured to feedback-control the operation of the exhaust gas recirculation control valve and the high-voltage spark generator via a control circuit. 2. The electronically controlled internal combustion engine according to claim 1, wherein the operating state detection means comprises a throttle valve opening sensor and the rotation speed sensor. 3. The electronically controlled internal combustion engine according to claim 1, wherein the operating state detection means comprises an intake negative pressure sensor and the rotation speed sensor. 4. The electronically controlled internal combustion engine according to claim 1, wherein the operating state detection means comprises a corona discharge type intake air amount sensor and the rotation speed sensor. 5. Claim 1, wherein the operating state detection means comprises a corona discharge type exhaust flow rate sensor and the rotation speed sensor.
The electronically controlled internal combustion engine described in .