JPH02241937A - Controller for engine - Google Patents

Abstract

PURPOSE:To prevent the occurrence of knocking by providing a load adding means for applying the external load to an engine under a predetermined low speed low load condition detected by a running condition detecting means. CONSTITUTION:A control unit 27 for an engine E judges the running condition from the output of an air flowmeter 12 and the rotational frequency N of the engine to set an intake-exhaust overlap amount small under a low speed low load condition and large under the other conditions for the prevention of knocking. On the other hand, under the idling condition, the idle rotational frequency is controlled to be a set value. Under a predetermined low speed low load condition, an electromagnetic clutch 25 is connected to operate a supercharger 14. When the external load is added to the engine E, the rotational frequency N of the engine tends to be reduced. However, an intake amount is correctively increased by opening an ISC valve 24 so that the idle rotational speed reaches a set value. Thus, the stability of the engine can be ensured.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is capable of reducing the variable range of an engine control device, particularly an overlap amount changing means that changes the intake and exhaust overlap amount according to the operating condition, and This invention relates to an engine improved to ensure engine stability under low load and low speed conditions.

[Prior art]

Conventionally, as an engine with a supercharger, for example, JP-A-61-1
As disclosed in Publication No. 87543, a mechanical supercharger is provided in the intake passage, and this supercharger is connected to the engine output shaft via a clutch. By connecting the engine and operating the supercharger, the engine is supercharged and its output is increased, while outside the above supercharging range, the clutch is disengaged and the engine runs naturally, reducing fuel consumption. I have to. In addition, a timing change device that is driven by a step motor and that makes the intake/exhaust timing variable is installed in the engine's valve train system, making it possible to vary the intake/exhaust overlap period. By making the effective stroke of the piston smaller and substantially lowering the compression ratio, the occurrence of knocking is suppressed.

[Problem to be solved by the invention]

In a supercharged engine having a timing change device as described above, knocking can be prevented by making the amount of overlap between intake and exhaust sufficiently large under high speed and high load conditions. By the way, there is a demand for simplifying and downsizing the timing change device and shortening the operating time by reducing the variable width of the intake/exhaust overlap amount. Since the amount of overlap between the two becomes correspondingly large, the stability of the engine cannot be ensured due to a decrease in combustibility. In particular, in a low speed, low load region such as an idle region, the stability of the engine decreases, making it difficult to maintain a predetermined idle speed. Therefore, it is necessary to set a large variable range for the amount of overlap between intake and exhaust, which causes the problem that the timing change device becomes complicated and large, and the operating time becomes longer.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine control device that can reduce the variable range of intake and exhaust overlap, shorten operating time, and ensure engine stability at low speeds and low loads.

[Means to solve the problem]

An engine control device according to a first aspect of the present invention includes an overlap amount changing means for varying an intake/exhaust overlap amount depending on the operating state, and an idle rotation speed control means for controlling a rotation speed in an idle state. The engine comprises an operating state detection means for detecting the operating state of the engine, and a load adding means for applying an external load to the engine in a predetermined low speed and low load state in response to an output from the operating state detection means. It is something that

An engine control device according to a second aspect includes: a mechanical supercharger connected to an engine output shaft via a clutch; and overlap amount changing means for varying an intake and exhaust overlap amount according to operating conditions. , an idle rotation speed control means for controlling the rotation speed in an idle state, and an engine for supercharging when an intake/exhaust overlap amount is large; and control means for operating the supercharger in a predetermined low speed and low load state in response to the output from the operating state detection means.

[Effect]

In the engine control device according to the first aspect, the overlap amount changing means sets the overlap amount small in a low speed and low load state, and also sets the overlap amount small in a state other than the above to prevent the occurrence of knocking. The wrap amount is set large.

On the other hand, when the engine is in an idle state, the engine speed is controlled by the idle speed control means so that the engine speed becomes a set value.

The operating state detecting means detects the operating state of the engine (for example, rotation speed and intake air amount), and when the detected operating state is a predetermined low speed and low load state, the load adding means applies an external load to the engine. Ru. When this external load is added, the engine speed tends to decrease, but the idle speed control means increases the intake air amount so that the engine speed reaches the set value.

In other words, if the load adding means is not provided, it is difficult to maintain a stable idle state due to a decrease in combustibility unless the intake and exhaust overlap amount during the idle state is set sufficiently small.

However, since the load adding means is provided as described above, even if the intake/exhaust overlap amount is larger than the required value in a predetermined low-speed, low-load state, the intake air filling amount can be controlled via the idle speed control means. By increasing the amount, engine stability can be ensured. In other words, it is possible to prevent the occurrence of knocking by ensuring a sufficient amount of overlap during high intake air flow conditions such as high-speed, high-load conditions, and at the same time, by setting the width of the variable amount to be changed by the overlap changing means to be small. can be simplified and miniaturized, and its operating time can be shortened.

Adding an external load as described above will inevitably lead to a deterioration in fuel efficiency, but when accelerating from low speed and low load conditions, part of the exhaust gas flows back into the intake passage and exhaust gas recirculation occurs. The same effect (hereinafter referred to as internal EGR)
This results in an improvement in fuel efficiency (referred to as a fuel efficiency improvement effect), so there is no disadvantage in terms of overall fuel efficiency.

In the engine control device according to the second claim, the first
Similarly to the claims, the overlap amount changing means sets the overlap amount small when the vehicle is in a low speed and low load state, and sets the overlap amount large when the vehicle is in a state other than the above. Then, when the amount of overlap is large, the supercharger is driven to perform supercharging, but since the amount of overlap is set large, the compression ratio does not substantially decrease and knocking does not occur.

Further, in a predetermined low speed and low load state, the control means connects the clutch of the supercharger and drives the supercharger. As a result, the engine load increases, so that the same effect as in the first aspect can be obtained. However, since the supercharged intake air is recirculated through the bypass passage, the engine is not substantially supercharged.

〔Effect of the invention〕

According to the engine control device according to the first claim, the above [
As explained in the section [Operations], by providing the load adding means, it is possible to secure a sufficient amount of intake and exhaust overlap at high intake air amounts and prevent the occurrence of knocking. By setting the variable width of the overlap amount small, the overlap amount changing means can be simplified and miniaturized, and its operating time can be shortened. Moreover, in a predetermined low speed and low load state, the stability of the engine can be ensured by increasing the intake air filling amount by an amount that is larger than the required overlap amount.

According to the engine control device according to the second claim, the above [
As explained in the section ``Operation'', the same effects as in the first aspect can be obtained by providing a control means for operating the supercharger at a predetermined low speed and low load.

In addition, since the supercharger, which does not need to be used at low speeds and low loads, is used as an external load, there is no need to provide a special external load (and it can be operated without any other restrictions, and the engine control system The configuration of can be simplified.

〔Example〕

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

This embodiment is an example in which the present invention is applied to a DOHC type supercharged engine of an automobile.

As shown in FIG. 1, the engine E is provided with four cylinders 1, and each cylinder 1 has an intake boat 2 that is opened and closed by an intake valve.
and an exhaust port 3 which is opened and closed by an exhaust valve.The four intake valves are driven by an intake camshaft 4, and the four exhaust valves are driven by an exhaust camshaft 5. These camshafts 4 and 5 are interlocked and connected to a crankshaft pulley 6 by a timing belt or the like, as will be described later.

The intake passage 10 of the engine E includes, in order from the upstream side, an air cleaner 11, an air flow meter 12, a throttle valve 13, a mechanical supercharger 14, an intercooler 15, and a surge tank 16.
The surge tank 16 is connected to the intake boat 2 through each branch intake pipe 17. Each branch intake pipe 17 is provided with an injector that injects fuel toward the intake boat 2. The throttle valve 13 is connected to an accelerator pedal, and the throttle valve 13 is provided with a throttle opening sensor 18 that electrically detects its opening, and an idle switch (not shown) that is closed when the throttle valve is fully closed. There is. Intake passage 1 between the throttle valve 13 and the supercharger 14
0 is provided with a bypass passage 19 that connects to the surge tank 16, a bypass valve 20 is interposed in the bypass passage 19, and the bypass valve 20 is driven by an actuator 21 into which boost negative pressure is introduced via a negative pressure introduction passage 22. be done.

The characteristic of the valve opening degree of this bypass valve 20 is the sixth
It looks like the picture.

Furthermore, as an idle rotation speed control means, an idle bypass passage 23 is provided which connects the intake passage 10 between the air flow meter 12 and the throttle valve 13 to the surge tank 16, and this bypass passage 23 has a near solenoid 2.
An ISC valve 24 that can precisely control the intake flow rate is installed at 4a. Note that ISO is an abbreviation for idle speed control.

An electromagnetic clutch 25 is interposed on the input shaft 14a of the supercharger 14, and a pulley 26 of the input shaft 14a is interlocked with a crankshaft boot I76 by a belt or chain.

A control unit 27 is provided to control the electromagnetic clutch 25, the ISC valve 24, an overlap switching solenoid 31 of a valve timing change mechanism 30 for switching the intake/exhaust overlap amount (described later), and the like. A signal from the air flow meter 12, a signal from the throttle opening sensor 18, a signal from the idle switch, an engine speed signal N from the distributor, etc. are input.

Next, the valve timing changing mechanism 30 will be explained based on FIGS. 2 and 3.

In this engine valve train, a cylindrical spacer 32 is fixed to the end of the exhaust camshaft 5, and a drive pulley 7 is attached to the outside of the spacer 32. This pulley 7 is in sliding contact with the outer periphery of the tip of the spacer 32 at the tip of the boss portion 34, and the base end side of the boss portion 34 is fixed to a cylindrical connecting member 35 rotatably attached to the exhaust camshaft 5. . The connecting member 35 is connected to the cylinder head 36
The connecting member 3 is rotatably supported on the bearing portion 36A of the
A first gear 8 is spline-coupled to the other end of 5 and fixed by a lock nut 37.

A second gear 9 fixed to the tip of the intake camshaft 4 is meshed and connected to the first gear 8 .

An annular piston 38 is installed inside the boss portion 34 of the pulley 7 between it and the spacer 32 . piston 3
The date has a structure in which it is divided into two in the axial direction, and both divided parts are fixed to each other by a plurality of pins 39 arranged at equal intervals in the circumferential direction. Helical splines 40 and 41 are formed on the inside and outside of the piston 38 in opposite directions. A helical spline 42 is formed on the outer periphery of the spacer 32 relative to the spline 40 on the inside of the piston 38,
A helical spline 43 is formed on the inner circumference of the boss portion 34 of the pulley 7 in contrast to a helical spline 41 on the outer circumference of the piston 38 . The piston 38 is biased toward the distal end side by a spring 44 installed between the piston 38 and the end surface of the connecting member 35 .

The exhaust camshaft 5 has an oil passage 4 along its axis.
5 is formed. The cylindrical spacer 32 is the stopper member 4
The exhaust camshaft 5 is fixed by the fixing bolt 47 through the
Fixed. This fixing bolt 47 is provided with an axial through hole 48 that communicates with the oil passage 45.

A pressure chamber 49 is provided at the tip of the boss portion 34 of the pulley 7, facing the head of the piston 38, for introducing the hydraulic pressure from the oil passage 45.

The other end of the exhaust camshaft 5 is rotatably supported by a bearing 36B of the cylinder rod 36, and the end of the pivot hole 50 is closed by a plug 51.

As shown in FIGS. 2 and 3, in order to supply hydraulic pressure to the oil passage 45 and discharge the hydraulic pressure from the oil passage 45,
A switching valve 52 that is operated by an overlap switching solenoid 31 is incorporated in the cylinder head 36 on the side of the pivot hole 50, and as shown in FIG.
When is OFF, the switching valve 52 is in the discharge position, the oil passage 45 is connected to the drain passage 53, and the solenoid 3
1 is ON, the switching valve 52 is in the supply position and the oil passage 45 is connected to the hydraulic pressure supply passage 54 (oil gallery). Pressurized oil is supplied to the hydraulic pressure supply path 54 from a lubricating oil pump driven by a crankshaft.

That is, when the switching solenoid 31 is turned on and the switching valve 52 is switched to the supply position, hydraulic pressure is supplied to the pressure chamber 49 through the oil passage 45, compressing the spring 44 and moving the piston 38 in the axial direction. As a result, splines 4 in opposite directions are formed on the inner and outer circumferences of this piston 38.
One of the spacer 32 and the pulley 7 that fits into the o.41 rotates relative to the other. This changes the relative phase between the exhaust camshaft 5, which is integrated with the spacer 32, and the pulley 7.

As described later, in the large overlap area, the oil passage 4
5, the exhaust valve closing timing shifts to the delayed side as shown in FIG. 4, and the intake valve opening timing does not change, so the amount of overlap between intake and exhaust becomes large. On the other hand, in the small overlap region, the oil pressure in the oil passage 45 is discharged and the piston 38 returns to its original position due to the elastic force of the spring 44, so that the amount of overlap becomes small.

The control unit 27 has a general configuration including an A/D converter, a waveform shaping circuit, a human output interface, a micro combinator, and a plurality of drive circuits.
A program PA that controls the electromagnetic clutch 25 according to the operating state, a program PB that controls the idle rotation speed via the tSC valve 24 during the idle state and the low speed low load state in the vicinity, and a switching solenoid that controls the electromagnetic clutch 25 according to the operating state. 31, an intake/exhaust overlap control program PC1 for switching the intake/exhaust overlap amount to a larger or smaller amount, and other programs for ignition timing control, fuel injection control, etc. are input and stored in advance.

FIG. 5 is an explanatory diagram of various areas included in the table and map in the program PA-PB-PC, and shows the curve a
A region A inside the curve is an idle speed feedback region in which feedback control is performed so that the engine speed N becomes a predetermined idle speed (for example, 800 rpm) in the idle state, and a region B between the curve a and the curve is I
The region where the SC valve 24 is held at a predetermined opening degree, the low speed and low load regions A and B are the first electromagnetic clutch ONM region where the supercharger 14 is operated as an external load to ensure engine stability, and the inside of the curve C. Areas A, B, and C are switching solenoids 31
The small overlap area where the oil pressure in the oil passage 45 is kept at OFF and the intake/exhaust overlap amount is kept small, the area outside curve C and E is when the switching solenoid 31 is turned OFF.
N and supplies hydraulic pressure to the oil passage 45 to maintain the intake/exhaust overlap amount at "large", and the supercharger 14 is not operated in the regions C and D between the curved line d. The electromagnetic clutch OFF region, the region E outside the broken line d, is the second electromagnetic clutch ON which operates the supercharger 14 to supercharge.
area (supercharging area).

By the way, the bypass pulp 20 is fully opened in the region on the low load side from the straight line e, and as the load shifts from the straight line e to the high load side, the opening degree of the bypass pulp 20 decreases, and when the load exceeds a predetermined high load, the bypass pulp 20 is fully opened. Closed (see Figure 6).

Next, an outline of the routine of the control program PA-PB-PC will be explained based on FIGS. 7 to 9. In the figure, Si (i=1.2.3...) indicates each step, and these routines are executed by interrupt processing at predetermined time intervals or by output from a crank angle sensor (not shown) every time the crankshaft rotates once. This is executed by interrupt processing every time a crank angle signal is input.

FIG. 7 shows the electromagnetic clutch ON/OFF control routine. After the start of control, the engine speed N and the intake air ilQ from the air flow meter 12 are read (S 1 ),
Next, the operating state corresponding to these engine speed N and intake air IQ is the electromagnetic clutch ON region (first electromagnetic clutch O
N region and second electromagnetic clutch 0N91 region) (S 2 ), and is ON? When it is in the ill range, a drive current is output to the electromagnetic clutch 25 to turn it ON (connection).S3
), when it is not in the 0Nei range, the drive current is cut off and the O
FF (separate) (S4) and return to the main routine. In this way, the electromagnetic clutch 25 is maintained in the connected state when the operating state is in regions A, B, and E in FIG. 5, and is maintained in the disengaged state when the operating state is in regions C and D.

However, in areas A and B, the bypass pulp 20 is fully open, so even if the supercharger 14 operates, a portion of the intake air will flow into the surge tank 1.
Bypass from 6! 19, the engine E is not substantially supercharged.

Figure 8 shows the idle speed control routine. After the start of control, the engine speed N, intake air area Q, and idle switch signal are read (310), and the operating state is determined to be in the ISC control area (area A in Figure 5). B) It is determined whether or not (Sll)
, when the result is Yes, it is determined whether the idle switch is ON or not (S12), and when the throttle valve 18 is fully closed and the idle switch is ON (at area A in FIG. 5), the IS
Idle rotation speed control is executed via the C valve 24 so that the idle rotation speed becomes the target idle rotation speed No (S13/514). This idle rotation speed control is similar to existing well-known control, so a detailed explanation will be omitted.

On the other hand, when the idle switch is not ON in S12 (at the time of region B in FIG. 5), the ■SC pulp 24 is maintained at a constant opening degree (S15/516). On the other hand, S11
As a result of the determination, if the operating state is not in the ■SC valve control region, the ISC valve 24 is controlled to be fully closed (S1
7.318).

After executing the above routine, return to the main routine.

FIG. 9 shows a routine for controlling the intake and exhaust overlap amount via the valve timing change mechanism 30 including the switching solenoid 31. After the start of control, the engine speed N and the intake air amount Q are read (320), and the operating state is It is determined whether or not is a large overlapping area (area RI and E in FIG. 5) (S21).
, when Yes, the switching solenoid 31 is controlled to be ON (322), hydraulic pressure is supplied to the oil passage 45, and the valve timing change mechanism 30 increases the amount of intake/exhaust overlap (as shown by the dotted line in FIG. 4). Can be switched.

On the other hand, when there is no large overlap area, the switching solenoid 31 is controlled to be OFF (S23), and the oil passage 4
5 of the oil pressure is discharged, and the timing change mechanism 30 switches the intake/exhaust overlap amount to "small". After executing the above routine, return to the main routine.

In the engine control device described above, when the operating state of the engine E is in a predetermined low speed and low load region shown by regions A and B in FIG. 5, the electromagnetic clutch 25 is connected and the supercharger
4, thereby applying a predetermined load to the engine.

The reason for this is that when the operating stroke of the piston 38 in the valve timing change mechanism 30 is set small to simplify and downsize the change mechanism 30, the variable width of the intake/exhaust overlap amount is relatively small. Become. As a result, it is not possible to set the intake and exhaust overlap amounts to a sufficiently small value in regions A and B in Fig. 5, and when the area is in an extremely low speed and low load region like region A, the combustibility due to the increase in the amount of residual gas increases. However, by operating the supercharger 14 and adding a load as described above, the intake air filling amount is corrected to the increasing side via the idle speed control means. Therefore, the stability of the engine E is improved and the target idle speed N0 can be maintained.

Incidentally, it is not necessary to operate the supercharger 14 in the region B of FIG. 5, and the supercharger 14 may be operated only in the region A in order to achieve the above objective.

Furthermore, instead of the supercharger 14, a load such as a compressor of an air conditioner may be operated.

Furthermore, since the intake and exhaust overlap amount is maintained at r large in the supercharging region (region E in Figure 5), the compression ratio is substantially lowered and the amount of residual gas is reduced, thereby preventing the occurrence of knocking. You can.

As mentioned above, operating the supercharger 14 in areas A and B slightly deteriorates fuel efficiency, but since the internal ECR effect improves fuel efficiency during acceleration from low speed and low load conditions, the total fuel consumption improves. It doesn't get worse.

In the above embodiment, the valve timing changing mechanism 30 is incorporated into the exhaust camshaft 5, but this mechanism is incorporated into the intake camshaft 4, and by fixing the exhaust valve timing and changing the intake valve timing, it is possible to The amount of wrap may be changed.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of a supercharged engine, FIG. 2 is a sectional view of a valve timing changing mechanism, FIG. 3 is a sectional view of a switching valve, and FIG. 4 is a sectional view of a switching valve. The figure is an explanatory diagram of valve timing, Figure 5 is an explanatory diagram of supercharging area, etc.
Figure 6 is an opening characteristic diagram of the bypass valve, Figure 7 is a flowchart of the electromagnetic clutch ON/OFF control routine,
FIG. 8 is a flowchart of the idle rotation speed control routine, and FIG. 9 is a flowchart of the intake/exhaust overlap amount control routine. E...Engine, 4.Intake camshaft, 5.
・Exhaust camshaft, 12. Air flow meter, 14. Supercharger, 23. Idle bypass passage, 24. ISC valve, 25. Electromagnetic clutch, 27. Control unit, 30. Valve timing. Changing mechanism, 31... switching solenoid.

Claims (2)

[Claims] (1) In an engine equipped with an overlap amount changing means that changes the amount of intake and exhaust overlap according to the operating state, and an idle speed control means that controls the number of revolutions in an idling state, An engine control device comprising: an operating state detecting means for detecting the operating state; and a load adding means for receiving an output from the operating state detecting means and applying an external load to the engine when the engine is in a predetermined low speed and low load state. . (2) A mechanical supercharger connected to the engine output shaft via a clutch, an overlap amount changing means that changes the intake and exhaust overlap amount depending on the operating state, and a In the engine, the engine is equipped with an idle rotation speed control means for controlling, and supercharging is performed when an intake/exhaust overlap amount is large, an operating state detecting means for detecting the operating state of the engine, and an output from the operating state detecting means. and control means for operating the supercharger in a predetermined low speed and low load state.