JPS63253132A - Engine controller - Google Patents

Abstract

PURPOSE:To improve engine output as well as prevent exhaust gas emission from deteriorating by controlling valve opening timing of an exhaust valve with an exhaust valve controlling device according to combustion maximum pressure generating time for an air-fuel mixture in an engine combustion chamber. CONSTITUTION:An engine control circuit 9 changes a cam of an exhaust valve controller 40 over to a high-speed cam 31 from a low-speed cam 30 when an engine is not in a lean burn driving range and more than the reference engine speed are judged, and it sets the on-off timing of an exhaust valve 14 corresponding to high speed driving. On the other hand, at a lean burn range by the low- speed cam 30 and in the state that a swirl control valve 25 normally operates, if knock occurrence is judged by a knock sensor 41, it delays control over ignition timing, while the valve opening timing of the exhaust valve 14 is retarded as much as the specified timing advance value by a magnetic actuator 33, corresponding to a drop in combustion speed of an air-fuel mixture in a combustion chamber. Thus, improvement in engine output is promoted and, what is more, the deterioration of exhaust emission is preventable in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine control device having an exhaust valve opening timing control function for controlling the opening timing of an exhaust valve.

(Prior art) In general, knob kinging in a spark ignition engine can be suppressed by retarding the ignition timing by a predetermined amount or enriching the air-fuel ratio A/F by a predetermined value in response to the occurrence of knob king. A tank configuration that reduces the combustion rate of air is used (for example, Japanese Patent Application Laid-Open No. 59-200
(See Publication No. 042).

That is, by retarding the ignition timing and making the air-fuel ratio rich as described above, knocking becomes less likely to occur.

Therefore, it functions most effectively as a means for preventing knocking.

(Problem to be Solved by the Invention) However, when the combustion speed is reduced as described above, the opening timing of the exhaust valve is still the same as when the combustion speed is normal. In this case, the expansion energy of the combustion gas in the combustion process is exhausted without being sufficiently recovered, leading to an increase in heat loss and a decrease in engine output (see Figure 6), as well as deterioration of exhaust emissions. be. Further, it is not preferable to supply the high temperature unburned air-fuel mixture to the exhaust system as it is from the viewpoint of protecting the catalytic converter as an exhaust purification treatment device.

Furthermore, similar problems occur not only in cases where combustion speed is delayed due to retardation of ignition timing or air-fuel ratio enrichment during knock suppression as described above, but also in lean-burn engines equipped with swirl control valves, for example. During lean burn operation, due to some reason (failure, etc.) the swirl control combustion speed cannot be compensated for, and the combustion speed will essentially drop significantly, so it will not be the same as in the above case. A similar problem arises.

(Means for Solving the Problems) The present invention has been made for the purpose of solving the above-mentioned problems, and includes exhaust valve control means for controlling the opening timing of the exhaust valve. The opening timing of the exhaust valve is controlled according to the timing of maximum combustion pressure generation.

(Function) According to the means of the present invention, the opening timing of the exhaust valve can be changed in accordance with the timing of the maximum combustion pressure of the air-fuel mixture in the engine combustion chamber. This makes it possible to set an appropriate opening timing for the exhaust valve.

(Embodiment) First, FIGS. 2 and 3 show an engine control device according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a control system of the embodiment device, and FIG. is a flowchart showing control operations by the engine control unit in the same control system.

First, the outline of the control system according to the embodiment of the present invention will be explained with reference to FIG. 2, and then the control of the main parts will be explained.

In FIG. 2, reference numeral I designates the engine body, and the intake air to the engine body L is drawn from the atmosphere via the air cleaner AC, and then the air flow meter 2, the throttle valve 3, the surge tank 6, and the intake boat 4. The fuel is then supplied into the combustion chamber 8 of each cylinder. Further, fuel is supplied from a fuel tank 29 to the engine side by a fuel pump 28 and injected by an air bleed type fuel injector 5. The amount of intake air into the cylinder combustion chamber 8 during engine operation is controlled by the throttle valve 3. The throttle valve 3 is operated in conjunction with the accelerator pedal, and is maintained at a minimum opening state in an idling state.

Further, reference numeral 10 indicates an exhaust pipe equipped with three photocatalytic converters II, and reference numeral 16 indicates an 02 sensor installed in the first stream of the exhaust pipe 10.

Further, reference numeral 17 is an ignition plug provided in the cylinder head portion IA of the engine body 1, and a predetermined ignition voltage is applied to the ignition plug 17 via a distributor 18 and an igniter 19. Ori,
The application timing of this ignition voltage, that is, the ignition timing, is controlled by the engine control unit (hereinafter referred to as ECU).
20'' is controlled by the ignition timing control signal 1gc supplied to the bipedal igniter 19. Further, reference numeral 40 is a boost pressure sensor that detects an engine boost pressure B corresponding to the engine load and manually inputs it to the ECU 20. Further, the reference numeral 41 is a knock sensor installed in the cylinder block IB of the engine main body I,
The output KF of the knock sensor 41 is manually inputted to the ECU 20.

The ECU 20 includes, for example, a microcomputer (CPU) which is an arithmetic unit, and a memory (ROM and R
AM), an interface (Ilo) circuit, etc. In addition to detection signals such as the boost pressure B1 and knock output KF described above, the interface circuit of this ECU 20 also receives, for example, an engine start signal (ECUI-rigger) from a starter switch (not shown), and an engine rotation installed in the distributor 18. engine rotational speed detection signal N from the engine side water jacket, engine cooling water temperature detection signal detected by the water temperature thermistor of the engine side water jacket, throttle opening detection signal TVO detected by the throttle opening sensor 3a,
Various detection signals such as the intake air amount detection signal Q detected by the air flow meter 2 are also input.

The intake boat 4 of the engine body 1 has two upper and lower sets of primary port IA with a small passage cross-sectional area for low rotation and low load and a secondary port 4B with a large passage cross section for high rotation and high load by a partition wall I2. The primary bow) 4A is formed with its intake passage axis offset by a predetermined angle with respect to the center of the combustion chamber 8 in the cylinder of the engine main body, and the primary bow 4A is formed by offsetting the axis of the intake passage by a predetermined angle with respect to the center of the combustion chamber 8 in the cylinder of the engine main body. It has the effect of generating a swirl inside.

On the other hand, a swirl control valve 25 is installed at the upstream end of the intake port of the secondary port 4B. The opening/closing state of the swirl control valve 25 is controlled by a swirl control valve operating actuator (hereinafter simply referred to as an actuator) 26 made of, for example, a diaphragm. This actuator 26 is provided with a negative pressure chamber at one end side and an operating chamber at the other end side across the diaphragm valve, and the negative pressure chamber side of the one end side is connected to a passageway downstream of the throttle valve 3 of the engine side intake passage 7. 42, and controls the opening of the swirl control valve 25 according to the intake negative pressure on the engine side, and when the engine is in a low rotation and low load operating state, the swirl control valve 25 is controlled. By closing the valve 25 and supplying intake air through the above-mentioned primary port 4A, sufficient swirl is generated in the engine combustion chamber 8 to agitate the air-fuel mixture and promote atomization of fuel at the time of low intake air amount. The swirl actively improves the combustion speed to enable lean burn operation, thereby improving the combustion performance during lean burn operation at low rotation speeds and low loads.

On the other hand, during high-speed, high-load operation, the valve opening I is increased according to the intake negative pressure corresponding to the load 1, and the valve opening I is increased according to the intake negative pressure corresponding to the load 1, and the large diameter secondary port 4B with low intake resistance is connected to the primary port 4Δ to meet the above load. This provides sufficient intake air to improve engine speed, ensure high output, and reduce combustion noise.

On the other hand, numeral 13 is an intake valve supported and provided in the cylinder head portion IA of the engine main body I, and numeral 14 is an exhaust valve. An exhaust valve control device 40 for controlling the valve timing of the exhaust valve 14 is provided in the cylinder head portion IA of the engine main body l in which the intake valve 13 and the exhaust valve 14 are provided. This exhaust valve control device 40
A low-speed cam 30 (a cam that determines the opening/closing timing of the exhaust valve 14 in a low-speed engine operating range) and a high-speed cam (a cam that controls the exhaust valve I4 in a high-speed engine operating range) slides arbitrarily in the thrust direction on the cam shaft 24. The exhaust valve 14 is equipped with two cams, a cam 30 and a cam 31 that determines opening/closing valve timing, and these two cams 30 and 31 are arbitrarily selected by an electromagnetic actuator 33 to correspond to the rocker arm 35 of the exhaust valve 14. . and,
By appropriately controlling the operation of the electromagnetic actuator 33 by the engine control unit (ECU) 20 according to the engine operating ranges A, B, and C as shown in FIG. 4, the engine rotational speed is increased as shown in FIG. It is designed to obtain the optimum output characteristics corresponding to the

Next, the engine control operation by the ECU 9 (
In particular, the valve opening timing control operation of the exhaust valve will be described in detail with reference to the flowchart of FIG.

First, in step S1, among the various inputs into the flAM of the engine control unit (ECU) 9,
Read engine boost pressure P1, engine speed N, and knock sensor output KF, respectively. Next, step S on top of that,
Next, it is determined whether or not the value of the engine boost pressure P and the value of the engine speed N read in step S1 above exceed the predetermined set values I]1 and Nl, respectively, that is, the current value is determined from the above two parameters. It is determined whether the engine operating range is in the lean burn operating range A shown in FIG. FIG. 4 shows an engine map in which the operating range of the engine is specified by the engine boost pressure P and engine speed N, and in the first range A, the opening timing of the exhaust valve 14 is determined by the low-speed cam 30. The second region B is a normal low-speed operation region in which the opening timing of the exhaust valve 14 is determined by the low-speed cam 30 outside the lean-burn operation region, and the third region
Area C indicates a high-speed operation area in which 1υ1 is determined by the high-speed cam 31 when the exhaust valve 14 is opened.

If YES in step S2, that is, if it is determined that the operation is not in the lean burn operation region, the process proceeds to step S3, where the current engine speed N divides the second region I3. It is determined whether the cam of the two-legged exhaust valve control device 40 is switched from the low-speed cam 30 to the high-speed cam 31 and is in the operating range. do.

If the result is YES, the process proceeds to step S to change the cam of the exhaust valve control device 40 from the low speed cam 30 to the high speed force 1.
．． 31 to set the opening timing of the exhaust valve 4 corresponding to high-speed operation, and achieve sufficient output characteristics (FIG. 5 (a)) corresponding to the increase in engine speed N. Then, the process proceeds to steps S1 to 5i11, which are ignition timing control operations aimed at suppressing knocking (this ignition timing control operation will be described in detail later). Also,
If NO in step S, the current engine operating range is neither the first range (lean-burn operating range) A nor the third range (high-speed operating range) C, but the normal low-speed cam operation. 2 area B, so jump to step S4 above and proceed to step S13.
~Proceed to S+9. The second low-speed cam 30 is selected.
In region B, as shown in the characteristics of FIG.
As the valve overlap amount of the intake valve 14 becomes smaller, the ink close angle of the intake valve 14 becomes smaller, and the closing timing of the exhaust valve I4 is delayed in accordance with the reduction in the combustion speed of the air-fuel mixture in the engine combustion chamber, thereby increasing the engine torque. .

On the other hand, if NO in step S2, that is, if it is determined that the lean burn operation region (first region) A is present, then step S, ~SI! Let us move on to the ignition timing control operation during lean burn operation.

That is, first, when moving to step S, the valve opening degree 0 of the swirl control valve 25, which largely influences the combustion speed of the air-fuel mixture in the engine combustion chamber during the lean burn operation, is read at that point, and then in step S8, the valve opening degree 0 of the swirl control valve 25 is read. Determine whether the swirl control valve 25 is normal.

As a result, if it is determined that the swirl control valve 25 is abnormal (NO), the process first proceeds to step S7 to control the bipedal fuel injector 5 (the duty ratio of the fuel injection amount control signal G is set to a predetermined value). ) and engine air-fuel ratio A
/F is made slightly lean (intermediate value A/F = +7), and first the ignition timing is advanced by a predetermined advance (A/F = +7).
F=20) to maintain appropriate combustion performance as much as possible according to the intermediate lean-burn operating conditions. On the other hand, the process further proceeds to step S8, in which the air-fuel ratio is made lean and the output is reduced (combustion In order to prevent loss of gas expansion energy, the exhaust valve 14 is
The valve opening timing is retarded by a predetermined crank angle. As a result, it becomes possible to effectively recover the loss of combustion gas expansion energy caused by the reduction in combustion speed caused by the lack of swirl formation even though the air-fuel ratio is lean, and the loss of combustion gas expansion energy is effectively recovered. It becomes possible to compensate for the decrease in engine output. As a result, even in a failure state of the swirl control valve 25, stable lean burn operation can be performed, contributing to improved fuel efficiency.

Then, the execution fact of the exhaust valve retard control in step S8 is stored by setting FLAG Fl (F, = 1) in the next step S8, and then the process proceeds to steps S13 to S+9.

On the other hand, if the swirl control valve 25 for which the determination in step S6 is YES is normal (not malfunctioning) and normal swirl flow can be expected to be formed, the process first proceeds to step S1G and the previous It is determined whether or not the set value of FLAGF+ is F,=1, that is, whether or not the retard control of the exhaust valve 14 is being performed in the previous control cycle, and if YES (retard control is present), step S1; The exhaust valve has been retarded above! 4
After returning the valve opening timing to the regular valve opening timing and resetting the value of FLAG F to r',=o, the air-fuel ratio A of the engine is set in step SI.
/P is feedback-controlled to a normal lean value (for example, A/P=20).''2, the process proceeds to steps 813 to S19.

Next, the above steps S, -S4. S,,S2. S5～
S9.51 After going through each routine of St, Ss, Ss, S, o-S, and t and proceeding to step S+3, the step S
+3, it is first determined from the output value KF of the knock sensor 41 whether or not knocking has occurred.

If the result is YES that knocking is occurring, the process proceeds to step S14, where the predetermined advanced ignition timing is retarded according to the intensity of the knocking to suppress knocking, and the process further proceeds to step SI5, where the above-mentioned The opening timing of the exhaust valve 14 is advanced by a predetermined value in response to the amount of retardation of the ignition timing (in other words, in response to the decrease in the combustion speed of the air-fuel mixture in the engine combustion chamber that occurs in response to the amount of retardation of the ignition timing). Retard the angle. Then, the fact that the retard control has been executed is displayed as FLAG F,=1 (step s, . . . ), and the process returns to step S1 described above. As a result, the loss of combustion gas expansion energy due to the reduction in the mixture combustion speed caused by the retardation of the ignition timing for suppressing knocking is reduced by the exhaust gas in the same way as when the swirl control valve 25 fails during the lean burn operation. By delaying the opening timing of the valve 14, the RL-effect is recovered and can contribute to preventing a decrease in engine output.

On the other hand, in the case of No in the judgment in step S+3 above, where knocking does not occur, the process moves to step Sl'1, and the fact of execution of exhaust valve retard control for the turn is determined based on the value of FLAGPg, and F2=I. In the case of (YES), the process proceeds to step S+8, where the ignition timing and the opening timing of the exhaust valve 14 are restored to their normal values, and then the process proceeds to step S+.
At step 9, the first shift of the PLAGF2 is reset to P, -0, and the process returns to step S1. Also, in step S17
If it is determined to be o, that is, if retard control with exhaust valve 1=1 was not performed last time, the process directly returns to step S1.

(Effects of the Invention) As described above, the present invention is provided with an exhaust valve control means for controlling the opening timing of the exhaust valve, and the exhaust valve is opened in accordance with the timing at which the maximum combustion pressure of the air-fuel mixture in the engine combustion chamber is generated. This is done by controlling the valve opening timing.

That is, according to the present invention, the opening timing of the exhaust valve can be changed in accordance with the timing at which the maximum combustion pressure of the air-fuel mixture in the engine combustion chamber is generated. It becomes possible to set the valve opening timing.

As a result, when the combustion speed of the air-fuel mixture becomes slower, the opening timing of the exhaust valve is delayed accordingly to effectively recover the expansion energy of the combustion gas, which contributes to engine output. In this case, deterioration of exhaust emissions can be prevented and there is no fear of damage to the catalytic converter.

[Brief explanation of the drawing]

FIG. 1 is a claim correspondence diagram of the present invention, and FIG. 2 is a control system diagram of an Ennon control device according to an embodiment of the present invention.
Fig. 3 is a flowchart showing the control operation of the engine control unit in the control system, Fig. 4 is an engine map showing the control area in the control system, and Fig. 5 shows the output characteristics of the engine in the control system. The graph in FIG. 6 is a graph showing the relationship between engine combustion pressure and crank angle. l...Engine body 2...Air flow meter 3...Throttle valve 4...Intake bow) 4A...Primary port 4B...Secondary port 5. ... Fuel intake valve 13 ... Intake valve 14 ... Exhaust valve 17 ... Spark plug 18 ... Distributor 20 ... Engine control unit (ECU) 25 ...・Swirl control valve 30...Low speed cam 31...High speed cam Engine rotation speed Figure 4 Figure 5 Knocking '1 Hour Llr iIJ+ Figure 6

Claims (1)

[Claims] 1. An engine control device comprising an exhaust valve control means for controlling the opening timing of the exhaust valve, and controlling the opening timing of the exhaust valve according to the timing of the maximum combustion pressure of the air-fuel mixture in the combustion chamber of the engine. .