JPH08105339A - Internal combustion engine with variable cylinder mechanism - Google Patents

Abstract

PURPOSE: To secure the output torque of an internal combustion engine with a variable cylinder mechanism even if it is operated to a higher load region in a partial cylinder operation mode. CONSTITUTION: An internal combustion engine with a variable cylinder mechanism is provided with a variable cylinder mechanism 48 which can switch an all cylinder operation mode and a partial cylinder operation mode, a variable cylinder control means 70 which controls the operation of the variable cylinder mechanism 48 in such a way that according to the load conditions of the internal combustion engine, operation modes are switched, that is, where a light load acts on the internal combustion engine, the engine is operated in the partial cylinder operation mode, and where a high load acts on the engine, the engine is operated in the all cylinder operation mode, and an air-fuel ratio control means 72. The variable cylinder control means 70 switches modes at a first engine load which is higher than a reference engine load where the engine output torque when it is operated in the partial cylinder operation mode is nearly equal to the engine output torque when it is operated in the all cylinder operation mode, and the air-fuel ratio control means 72 makes the air-fuel ratio become rich more than that when it is operated in the all cylinder operation mode at a load nearly equal to the first engine load when it is operated in the partial cylinder operation mode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-cylinder mode in which all cylinders are operated, and an idle mode in which the operation of these cylinders is stopped by shutting off intake air introduction to some of the cylinders. The present invention relates to an internal combustion engine with a variable cylinder mechanism that can switch between cylinder mode.

[0002]

2. Description of the Related Art Conventionally, in a multi-cylinder internal combustion engine, when the engine load is low, intake air is cut off to some cylinders, fuel supply is stopped, and some cylinders are deactivated. Technology has been developed and put into practical use to increase the combustion efficiency of operating cylinders to suppress the generation of harmful exhaust gas and to improve the fuel efficiency by reducing pumping loss by improving the load factor of the engine. .

In this case, the point is how to smoothly switch between the mode in which all cylinders are operated (all cylinder mode) and the mode in which some cylinders are deactivated (cylinder deactivation mode). For example, in Japanese Examined Patent Publication No. 63-21811, the intake manifold pressure at which the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal to each other is set as a switching point, and the intake manifold pressure of the engine is changed. A technique is disclosed in which the cylinder deactivation mode is selected when it is smaller than this switching point, and the all cylinders mode is selected when the intake manifold pressure of the engine is equal to or higher than this switching point.

The intake manifold pressure of the engine corresponds to the load of the engine represented by the throttle valve opening. However, in a general internal combustion engine in which intake is introduced through the same throttle valve, the engine output torque is the engine. The characteristics with respect to the load (throttle valve opening) are as shown in FIG. That is, within a certain range, as the engine load increases, the output torque of the engine also increases, but at low load all cylinder operation has a greater effect of pumping loss than in cylinder deactivation operation, so under the same load Although the output torque is larger in the cylinder operation, the output torque is naturally larger in the all-cylinder operation than in the cylinder deactivation operation due to the absolute difference in combustion energy at high load.

As described above, there is an intersection point (cross point) where the output torques are equal, and by using this cross point as a switching point to switch the cylinder deactivation mode to the all cylinders mode, a shock at the time of mode switching is avoided. It is possible to switch smoothly. Further, among the conventional techniques, as disclosed in Japanese Patent Laid-Open No. 61-123735,
A technique is disclosed in which the switching control between the cylinder deactivation mode (partial cylinder mode) and the all cylinders mode and the control of the air-fuel ratio are combined to improve the fuel efficiency while suppressing the torque fluctuation. In other words, such a technology operates when the air-fuel ratio is lean in the cylinder deactivated state when the throttle opening is closed,
In the small opening range where the throttle opening is larger than this,
In the cylinder deactivated state, the air-fuel ratio is operated as stoichio, and in the medium / large opening range where the throttle opening is further open,
The air-fuel ratio is controlled to become lean or stoichiometric in all cylinder states, such that the air-fuel ratio becomes small (rich tendency) from a small throttle opening to a large throttle opening.

[0006]

By the way, in order to further improve the fuel efficiency of the engine and suppress the generation of harmful exhaust gas, the engine must be operated in the cylinder deactivation mode up to a load higher than the cross point. Can be considered. In particular, in vehicles having an automatic transmission connected to an engine through a fluid coupling, which has become widespread in automobiles, there is a torque cross due to the fluid coupling, so that the demand for improvement in fuel consumption is more remarkable.

However, in the high load region above the cross point, as shown in FIG. 9, when the cylinder deactivation mode is set, the output torque of the engine becomes smaller than that in the all cylinders mode.
There is a problem in that the output becomes insufficient and steady running may be difficult unless the engine load is increased by further depressing the accelerator during high speed steady running, for example.

Further, when the cylinder deactivation mode is switched to the all cylinders mode in the load region higher than the cross point as described above, there is a problem that the output torque sharply increases and a large switching shock is caused. Of course, since the output of the engine can be changed by controlling the air-fuel ratio, the switching control between the cylinder deactivation mode and the all-cylinder mode can be performed as disclosed in Japanese Patent Laid-Open No. 61-123735. It is conceivable to add control of the air-fuel ratio, but there is a problem how to control the air-fuel ratio.

The present invention was devised in view of the above problems, and is a boundary point (cross point) at which the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal. It is an object of the present invention to provide an internal combustion engine with a variable cylinder mechanism, which can ensure the output torque of the engine even when operating in the cylinder deactivation mode up to a higher load region.

[0010]

Therefore, an internal combustion engine with a variable cylinder mechanism of the present invention according to claim 1 is an internal combustion engine having a plurality of cylinders, and a full cylinder mode in which all the plurality of cylinders are operated. And a variable cylinder mechanism capable of switching between a cylinder deactivation mode in which the operation of some of the cylinders is stopped by cutting off the intake air intake to some of the plurality of cylinders, and a load state of the internal combustion engine. Variable cylinder control means for controlling the operation of the variable cylinder mechanism so as to operate in the cylinder deactivation mode when the engine load is small, and to operate in the full cylinder mode when the engine load is large. In an internal combustion engine with a variable cylinder mechanism having an air-fuel ratio control means for controlling a fuel ratio state, the variable cylinder control means has an engine output torque during the cylinder deactivation mode operation and an engine output torque during the all cylinder mode operation. A group in which The first engine load, which is larger than the reference engine load with respect to the engine load, is set to switch between the cylinder deactivation mode operation and the all cylinder mode operation, and the air-fuel ratio control means sets It is characterized in that it is set to become richer than the air-fuel ratio at the time of the all-cylinder mode operation in the vicinity of the first engine load during the cylinder deactivation mode operation.

In the internal combustion engine with a variable cylinder mechanism according to a second aspect of the present invention, in the configuration according to the first aspect, the air-fuel ratio control means is smaller than the first engine load during the cylinder deactivation mode operation. It is characterized in that the air-fuel ratio is set to be richer when the second engine load is equal to or more than the second engine load and is less than the second engine load with the second engine load as a boundary.

According to a third aspect of the present invention, in the internal combustion engine with a variable cylinder mechanism according to the first aspect, the air-fuel ratio control means is larger than the reference engine load during the cylinder deactivation mode operation. A second engine load smaller than the first engine load is set as a boundary, and when the second engine load is equal to or more than the second engine load, the air-fuel ratio is set to be richer than when the second engine load is less than the second engine load. There is.

In the internal combustion engine with a variable cylinder mechanism according to a fourth aspect of the present invention, in the configuration according to any one of the first to third aspects, the throttle opening is used as a parameter indicating the engine load of the internal combustion engine, The variable cylinder control means performs switching between the cylinder deactivation mode operation and the all cylinder mode operation so that the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal to each other. The air-fuel ratio control means is set to perform a first throttle opening larger than the throttle opening, and the air-fuel ratio control means performs the second cylinder opening smaller than the first throttle opening during the cylinder deactivation mode operation. It is characterized in that the air-fuel ratio is set to be richer when the second throttle opening is equal to or larger than the second throttle opening with the degree being a boundary than when the second throttle opening is smaller than the second throttle opening.

In the internal combustion engine with a variable cylinder mechanism according to a fifth aspect of the present invention, in the configuration according to any one of the first to third aspects, the throttle opening is used as a parameter indicating the engine load of the internal combustion engine, The variable cylinder control means performs switching between the cylinder deactivation mode operation and the all cylinder mode operation so that the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal to each other. The air-fuel ratio control means is set to operate at a first throttle opening that is larger than the throttle opening, and the air-fuel ratio control means sets the first throttle opening larger than the reference throttle opening for the cylinder deactivation mode operation. When the second throttle opening is smaller than the second throttle opening, the air-fuel ratio is set to be richer than when the second throttle opening is smaller than the second throttle opening. It is characterized in.

According to a sixth aspect of the present invention, in the internal combustion engine with a variable cylinder mechanism according to the fourth or fifth aspect, the second throttle opening is set according to the rotational speed of the internal combustion engine. It is characterized by that. An internal combustion engine with a variable cylinder mechanism according to a seventh aspect of the present invention is the internal combustion engine according to any one of the first to third aspects, wherein the air-fuel ratio control means has a larger engine load than the first engine load. Even in the all-cylinder mode operation, the air-fuel ratio is set to be richer than when the engine load is less than the third load state when the engine load is equal to or higher than the third engine load which is larger than the first engine load. It is characterized by being.

An internal combustion engine with a variable cylinder mechanism according to an eighth aspect of the present invention is the internal combustion engine according to any one of the first to seventh aspects, further comprising oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas. The fuel ratio control means is set to feedback-correct the air-fuel ratio based on the oxygen concentration information from the oxygen concentration detection means in a region where the air-fuel ratio is not enriched.

[0017]

In the internal combustion engine with a variable cylinder mechanism according to the first aspect of the present invention, the variable cylinder control means causes the engine output torque during the cylinder deactivation mode operation to be substantially equal to the engine output torque during the all cylinder mode operation. The switching between the cylinder deactivation mode operation and the all cylinder mode operation is performed with a first engine load larger than the reference engine load with respect to the reference engine load. The air-fuel ratio control means sets the air-fuel ratio during the cylinder deactivation mode operation to the first
In the vicinity of the engine load, the air-fuel ratio becomes richer than the air-fuel ratio during the all cylinder mode operation. As a result, when the engine is operated in the cylinder deactivation mode in the vicinity of the first engine load, the output torque of the engine increases. Especially, in the vicinity of the first engine load,
If the air-fuel ratios are equal, the output torque of the engine in the cylinder deactivation mode operation becomes smaller than that in the all-cylinder mode operation, but due to the enrichment of the air-fuel ratio, the output torque of the engine in the cylinder deactivation mode operation becomes The output torque during the cylinder mode operation is approached.

In the internal combustion engine with a variable cylinder mechanism according to the present invention as set forth in claim 2, the air-fuel ratio control means applies the second engine load smaller than the first engine load during the cylinder deactivation mode operation. As a boundary, if the second engine load is exceeded, the second
The air-fuel ratio is made richer than when the engine load is less than. As a result, the output torque of the engine is increased during the cylinder deactivation mode operation in the engine load region equal to or higher than the second engine load.

In the internal combustion engine with a variable cylinder mechanism according to the third aspect of the present invention, the air-fuel ratio control means is larger than the reference engine load and higher than the first engine load during the cylinder deactivation mode operation. This second with a small second engine load as the boundary
When the engine load is equal to or more than the second engine load, the air-fuel ratio is made richer than when the second engine load is less than the second engine load. As a result, the output torque of the engine is increased during the cylinder deactivation mode operation in the engine load region equal to or higher than the second engine load. In particular, at least in the vicinity of the second engine load or more, if the air-fuel ratio is equal, the output torque of the engine becomes smaller in the cylinder deactivation mode operation than in the all-cylinder mode operation. The output torque of the engine during the cylinder deactivation mode operation approaches the output torque during the all cylinder mode operation.

In the internal combustion engine with a variable cylinder mechanism according to the present invention as set forth in claim 4, the variable cylinder control means switches between the cylinder deactivation mode operation and the all cylinder mode operation during the cylinder deactivation mode operation. Of the engine output torque and the engine output torque during the all cylinder mode operation are substantially equal to each other at the first throttle opening larger than the reference throttle opening. In the cylinder deactivation mode operation, the air-fuel ratio control means has a second throttle opening smaller than the first throttle opening as a boundary, and becomes smaller than the second throttle opening when the second throttle opening is equal to or larger than the second throttle opening. The air-fuel ratio is made richer than in the case of. This allows
The output torque of the engine increases during the cylinder deactivation mode operation in the throttle opening range that is equal to or larger than the second throttle opening.

In the internal combustion engine with a variable cylinder mechanism according to the fifth aspect of the present invention, the variable cylinder control means switches between the cylinder deactivation mode operation and the all cylinder mode operation during the cylinder deactivation mode operation. Of the engine output torque and the engine output torque during the all cylinder mode operation are substantially equal to each other at the first throttle opening larger than the reference throttle opening. In the cylinder deactivation mode operation, the air-fuel ratio control means has a second throttle opening degree larger than the reference throttle opening degree and smaller than the first throttle opening degree as a boundary and is equal to or more than the second throttle opening degree. Then, the air-fuel ratio is made richer than when the throttle opening is less than the second throttle opening. As a result, the output torque of the engine increases during the cylinder deactivation mode operation in the throttle opening range that is equal to or larger than the second throttle opening. Particularly, at least in the vicinity of the second throttle opening or more, if the air-fuel ratio is equal, the output torque of the engine becomes smaller in the cylinder deactivation mode operation than in the all-cylinder mode operation, but due to the enrichment of the air-fuel ratio, The output torque of the engine during the cylinder deactivation mode operation approaches the output torque during the all cylinder mode operation.

In the internal combustion engine with a variable cylinder mechanism according to the sixth aspect of the present invention, since the second throttle opening is set according to the rotation speed of the internal combustion engine, the cylinder deactivation mode operation and the cylinder deactivation mode operation are performed. Switching to the all-cylinder mode operation is appropriately executed according to the engine speed. In the internal combustion engine with a variable cylinder mechanism according to the present invention described in claim 7, the air-fuel ratio control means comprises:
Even in the all-cylinder mode operation in which the engine load is larger than the first engine load, when the engine load is equal to or larger than the third engine load larger than the first engine load, the state is less than the third load state. The air-fuel ratio is made richer than in the case of. Therefore, even in the all cylinder mode operation, when the engine load becomes equal to or higher than the third engine load, the engine output increases.

In the internal combustion engine with a variable cylinder mechanism according to the present invention described in claim 8, the air-fuel ratio control means is based on the oxygen concentration information from the oxygen concentration detection means in a region where the air-fuel ratio is not enriched. Feedback correction of the air-fuel ratio. As a result, the air-fuel ratio is controlled to the desired air-fuel ratio state.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. First, an internal combustion engine with a variable cylinder mechanism as a first embodiment of the present invention will be described with reference to FIGS. Now, as shown in FIG. 2, the internal combustion engine with a variable cylinder mechanism of the present embodiment is a fuel injection engine (hereinafter, the internal combustion engine is referred to as an engine) 1 that uses DOHC in-line 4-cylinder gasoline fuel.

In the cylinder head 2 of this engine 1,
One end of an intake manifold IM capable of communicating with each cylinder is attached, and a surge tank 37 is attached to the other end of the intake manifold IM to form an intake passage IR, and the intake passage IR is further connected to the surge tank 37. It has an intake pipe and an air cleaner 38 which communicate with each other. An exhaust manifold EM capable of communicating with each cylinder is attached to the other side of the cylinder head 2, and an exhaust passage ER including an exhaust pipe and the like is connected to the exhaust manifold EM.

A throttle valve 40 is provided downstream of the air cleaner 38 in the intake passage IR, and a rotary shaft 41 of the throttle valve 40 is rotated by a valve drive actuator 42 having a stepper motor. It is configured. The valve drive actuator 42 is connected to an engine control unit (ECU) 32, which will be described later, and is configured to perform desired rotation by a predetermined control signal.

Further, the throttle valve 40 outputs a throttle opening signal θs corresponding to the throttle opening to the EC
A throttle opening sensor 36 for outputting to U32 is attached. Further, a negative pressure sensor 35 that outputs a negative pressure signal Pb corresponding to the negative pressure of the intake pipe is attached to the surge tank 37 of the intake passage IR.

An intake port (not shown) of each cylinder is opened and closed by an intake valve (not shown), and an exhaust port (not shown) is opened / closed by an exhaust port (not shown). Each intake / exhaust valve is a well-known DOHC valve operating valve. It is driven by the system 4. The valve train 4 includes intake / exhaust cam shafts 5, 6 attached to the cylinder head 2 and intake / exhaust rocker shafts 7, 8.

Timing gears 9 and 10 are fixed to one ends of the intake and exhaust cam shafts 5 and 6, respectively.
0 is connected to the crankshaft side (not shown) via a timing belt 11 and is driven at a rotational speed of 1/2 of the engine speed. The intake / exhaust rocker shafts 7 and 8 are separately provided for each cylinder.

The intake and exhaust valves of each cylinder are constructed so as to be opened and closed by a known valve operating system, one example of which is as follows:
It is disclosed in the specification and drawings of Japanese Patent Application No. 4-232322 filed by the present applicant. The valve train is equipped with low / high switching means (mode switching mechanisms) ML and MH having a cylinder deactivation / all cylinder switching mechanism 50 which is a main part of the variable cylinder mechanism 48. The mode switching mechanisms ML and MH have low electromagnetic valves 26 for the 1 and 4 cylinders and low electromagnetic valves 30 for the 2 and 3 cylinders, which connect the switching oil passage 23 to the hydraulic pump 25 in an intermittent manner. Further, the mode switching mechanisms ML and MH connect the switching oil passage 24 to the hydraulic pump 25 in a discontinuous manner.
It has a high solenoid valve 27 for four cylinders and a high solenoid valve 31 for two and three cylinders. The hydraulic pump 25 is communicatively connected to the oil tank as shown.

Each of the low and high solenoid valves 26, 30, 27, 31 is composed of a three-way valve, and when they are turned on, pressure oil for driving a hydraulic piston, which will be described later, is supplied, and when turned off, the hydraulic actuator is connected to the drain. It is designed to connect. In this way, the solenoid valves 26, 30, 27, 31 are valves (= Oil Control Valve) that control the hydraulic pressure for driving the hydraulic piston.
Since it is ve), it is hereinafter also referred to as OCV.

These low and high solenoid valves 26, 30, 27, 3
1 is connected to the ECU 32, and is configured so that a desired switching operation is performed by a control signal from the ECU 32. Furthermore, the mode switching mechanism ML, MH
When the low electromagnetic valves 26, 30 and the high electromagnetic valves 27, 31 are both off, the intake / exhaust valve (not shown) is driven in the low speed mode. On the other hand, low and high solenoid valves 26, 30, 2
When both 7 and 31 are on, an intake / exhaust valve (not shown) is driven in the high speed mode.

Further, when only the low solenoid valve 26 is turned on, the first cylinder (# 1) and the fourth cylinder (#
The cylinder deactivation mode in which the intake / exhaust valve (not shown) is idled in 4) is achieved. With reference to FIG. 3, the mode switching mechanisms ML and MH in the first cylinder (# 1) and the fourth cylinder (# 4) that can be in the cylinder deactivated state (this corresponds to the cylinder deactivated / all cylinder switching mechanism 50) will be described. However, the rocker arms 51, 5 for opening and closing the intake valve and the exhaust valve are connected to the first and fourth cylinders.
2, the rocker arm 51 is driven by a high speed cam (not shown), and the rocker arm 52 is driven by a low speed cam (not shown).

These rocker arms 51 and 52 can be interlocked with a T-lever 55 that can contact and drive an intake valve or an exhaust valve via hydraulic pistons 53 and 54, respectively. The hydraulic pistons 53 and 54 have fitting holes 51A and 52 formed in the rocker arms 51 and 52, respectively.
When the head is inserted into A, the rocker arms 51 and 52 and the T lever 55 are connected so as to operate integrally, and the insertion hole 51
When the head is removed from A, 52A, the rocker arm 51,
The connection between 52 and the T lever 55 is released.

The hydraulic piston 53 is the return spring 5
6 is urged to separate the head from the fitting hole 51A, and when the hydraulic pressure is supplied to the oil chamber 53A, the fitting hole 5A is inserted.
Insert the head into 1A. The hydraulic piston 54 is urged by a return spring 57 so that the head portion is fitted into the fitting hole 52A, and when the hydraulic pressure is supplied to the oil chamber 54A, the head portion is separated from the fitting hole 52A.

As a result, when hydraulic pressure is supplied to the hydraulic piston 53, the rocker arm 51 and the T lever 55 are connected,
When the hydraulic pressure of the hydraulic piston 53 is removed, the rocker arm 51
And the T lever 55 is disconnected. When the hydraulic pressure is supplied to the hydraulic piston 54, the connection between the rocker arm 52 and the T lever 55 is released, and when the hydraulic pressure of the hydraulic piston 54 is removed, the rocker arm 52 and the T lever 55 are connected.

Since the rocker arm 51 is driven by a high speed cam having a cam profile including a low speed cam, the movement of the rocker arm 51 is caused by the rocker arm 51.
Includes 2 movements. Therefore, the rocker arm 51 is T
When the locker arm 52 is connected to the lever 55,
The T-lever 55 is driven by the high speed cam regardless of non-connection.

Since the rocker arm 51 is driven by a high speed cam having a cam profile including a low speed cam, the movement of the rocker arm 51 is caused by the rocker arm 5 movement.
Includes 2 movements. Therefore, the rocker arm 51 is T
When the locker arm 52 is connected to the lever 55,
Regardless of non-connection, the T-lever 55 is driven by the high speed cam, and the intake valve and the exhaust valve are driven in the all cylinder high speed mode.

When the rocker arm 51 is disconnected from the T-lever 55, when the rocker arm 52 is connected to the T-lever 55, the T-lever 55 is driven by the low speed cam, and the intake valve and the exhaust valve are all cylinder low speed. Driven in mode.
Further, when the connection between the rocker arm 51 and the T lever 55 is released and the connection between the rocker arm 52 and the T lever 55 is also released, the T lever 55 is not driven, so that the intake valve and the exhaust valve are not opened. Will be realized.

The oil pressure in the oil chamber 53A is controlled by a high electromagnetic valve (OCV for high speed) 27, and the oil pressure in the oil chamber 54A is controlled by a low electromagnetic valve (OCV for low speed / cylinder deactivation) 26.
That is, when the high solenoid valve 27 is turned on (hydraulic pressure supply), the all cylinder high speed mode is set, and when both the high solenoid valve 27 and the low solenoid valve 26 are turned off (hydraulic pressure removed), the all cylinder low speed mode is set and the high solenoid valve 27 is turned off. When the low electromagnetic valve 26 is turned off (hydraulic pressure supply) as (hydraulic pressure removal), the cylinder is deactivated in the cylinder deactivation mode.

These low solenoid valve 26 and high solenoid valve 27
Are controlled by the ECU 32 together with the low electromagnetic valve 30 and the high electromagnetic valve 31, as described above. The oil chamber 53A
Is supplied with a high pressure oil pressure from an upstream side of an oil passage from an engine pump (not shown) on the engine side so that a high response hydraulic piston 53 can be driven through a high electromagnetic valve 27. It's becoming. The oil pressure in the downstream of the oil passage from the engine pump (not shown) on the engine side is supplied to the oil chamber 54A while being pressurized by the pump 60 and accumulated in the accumulator 61, and supplied through the low solenoid valve 26. The hydraulic piston 54 can be driven with a stable hydraulic pressure.

Referring again to FIG. 2, the cylinder head 2 of the engine 1 is equipped with fuel supply means FS, and the fuel supply means FS injects fuel into intake ports (not shown) of each cylinder. The injector 28 and the fuel pressure adjusting means 29 are provided. The fuel pressure adjusting means 29 is configured to supply the fuel from the fuel supply source 44 to each injector 28 after adjusting the pressure to a constant pressure, and these injectors 28 serve as fuel control means for performing injection drive control. It is connected to the ECU 32.

The engine control by the ECU 32 will now be described. The ECU 32 has a microcomputer as its main part, and the low solenoid valves 26, 30 and the high solenoid valves are operated according to the operation mode set in accordance with the operation information. Two
It is configured to perform injector drive control, ignition control, and the like together with Nos. 7 and 31. Focusing on engine operation mode control including variable cylinder control, the ECU 32 is provided with a function (hereinafter, referred to as mode control means) 70 for controlling the engine operation mode.
Since it also performs variable cylinder control, it also functions as variable cylinder control means. That is, as described above, the operation modes of the present engine include the cylinder deactivation mode in which the first cylinder and the fourth cylinder are deactivated by turning on / off each of the solenoid valves 26, 30, 27, 31 and the intake air of all cylinders. The all-cylinder low-speed mode in which the valves and exhaust valves are operated in the low-speed mode and the all-cylinder high-speed mode in which the intake and exhaust valves of all the cylinders are operated in the high-speed mode can be selected.
At 0, one of these modes is selected to perform the operation of the intake valve / exhaust valve, the fuel supply state, the idle speed control through the idle speed controller (ISC) 66, and the like.

These modes are selected by the engine load and the engine speed (hereinafter referred to as engine speed).
It is designed to be performed according to Ne. Here, the throttle opening TPS is used as an amount corresponding to the engine load. Therefore, the throttle opening sensor 36 and the engine speed sensor 33 are connected to the ECU 32.

When the engine load is small, the cylinder deactivation mode is selected. When the engine load is large, the all cylinders low speed mode is selected. When the engine load is even larger, the all cylinders high speed mode is selected. There is. When switching between the cylinder deactivation mode and the all-cylinder mode (all-cylinder low-speed mode) and the switching between the all-cylinder low-speed mode and the all-cylinder low-speed mode in the all-cylinder mode, the load (switching load) serving as a switching reference is set, respectively. Then, the detected engine load can be compared with this switching load.

By the way, in the variable cylinder mechanism of the present engine, the switching throttle opening TPS1 corresponding to the load for deactivating cylinders / all cylinders (first engine load) is given as follows. That is, the output torque of the engine (here, indicated by the average effective pressure Pe corresponding to the output torque) increases the engine load (throttle valve opening TPS) within a certain range, as described in the section of the related art. And the characteristics become as shown in FIGS. 4 and 5. FIG. 5 shows FIG. 4 in more detail. Although the intake pressure itself is different between the cylinder deactivated state and the full cylinder state as shown in FIG. 5A, the average effective pressure Pe corresponding to the output torque of the engine. In the low load, the output torque is larger in the in-cylinder operation than in the all-cylinder operation, but the output torque is larger in the all-cylinder operation than in the in-cylinder operation, and there is an intersection (cross point) where the output torque becomes equal. Conventionally, the cross point is used as a switching point, and if it is less than this, switching is made to the cylinder deactivation mode, and if it is more than this, switching is made to the all cylinder mode.

On the other hand, in this engine, the switching point is changed to a region where the engine load (throttle valve opening TPS) is larger than this cross point, and the engine load (throttle valve opening TPS) is increased to a large region. The cylinder deactivation mode is maintained to perform the cylinder deactivation mode in a wider operating region, and the fuel consumption is further improved by expanding the range of the cylinder deactivation mode operation.

Specifically, the switching throttle opening (first engine load) TPS1 is set in a load region larger than the load (reference load) corresponding to the cross point, and the engine load, that is, the throttle opening TPS is set to this. The cylinder deactivation mode is selected in a region less than the switching throttle opening TPS1, and the all cylinders mode is selected in a region in which the throttle opening TPS is greater than the switching throttle opening TPS1.

Since the optimum value of the switching load changes depending on the engine speed, the switching load (switching throttle opening TPS1) is set according to the engine speed. Therefore, based on the switching throttle opening TPS1, for example, the engine speed Ne and the engine load (throttle opening)
Select the cylinder deactivation mode and all cylinders mode for TPS 2
A dimension map is provided, and the optimum mode can be selected from the detected engine speed Ne and engine load (throttle opening) TPS based on this map.

The optimum switching load (switching throttle opening TPS1) tends to be set to a smaller value as the engine speed increases. In the mode control means 70, the mode determination unit 70A determines between the cylinder deactivation mode and the all-cylinder mode (in the case of the all-cylinder mode, the all-cylinder low-speed mode and the all-cylinder high-speed mode). The mode setting unit 70B sets a selection mode, and the intake valve / exhaust valve operation, fuel supply control, idle speed control, and the like are performed according to the setting mode.

The operation control of the intake valve / exhaust valve is performed by switching the mode switching mechanisms ML, MH through the low electromagnetic valves 26, 30 and the high electromagnetic valves 27, 31 described above. FIG.
In the figure, the function of the cylinder / all cylinder switching mechanism 50 in the mode switching mechanisms ML and MH is focused and shown, and the cylinder / all cylinder switching control is performed by the low solenoid valve (low speed / OCV for cylinder deactivation) 26 and Through the high solenoid valve (OCV for high speed) 27, the cylinder / all cylinder switching mechanism 5
It is performed while switching 0.

In this engine, different air-fuel ratio control is performed depending on the load condition in both the cylinder deactivation mode and the all cylinders mode. That is, the fuel supply control means 7 that controls the fuel injection amount of the injector 28.
2 includes an air-fuel ratio control means 72A and an injector 28 based on the air-fuel ratio set by the air-fuel ratio control means 72A.
Injector drive time setting means 7 for setting the drive time of
2B are provided, and in the air-fuel ratio control means 72A,
At the time of low load to control the air-fuel ratio by O ₂ feedback so that stoichiometric state or desired lean conditions, at the time of high load to release the O ₂ feedback, rich than when the air-fuel ratio by open-loop O ₂ feedback control It is designed to control the state. Therefore, E
An O ₂ sensor 46 is connected to the CU 32.

Similar to the mode switching, such switching of the air-fuel ratio control is also performed based on the engine speed Ne and the engine load (that is, the throttle opening) TPS. Of course, the switching point for this air-fuel ratio control is different from the switching point for mode switching. For example, in the cylinder deactivation mode, the switching throttle opening (second engine load) TPS2 that is larger than the switching throttle opening (reference load) corresponding to the cross point and smaller than the switching throttle opening (first engine load) TPS1. Is set, the O ₂ feedback control is performed if it is less than the switching throttle opening TPS2, and the O ₂ feedback control is released if it is more than the switching throttle opening TPS2 to enrich the air-fuel ratio.

In the all-cylinder mode, the switching throttle opening (third engine load) is naturally larger than the switching throttle opening (first engine load) TPS1.
When TPS3 is set, if the switching throttle opening TPS3 is less than this, O ₂ feedback control is performed. If it is more than the switching throttle opening TPS3, O ₂ feedback control is canceled to enrich the air-fuel ratio.

In the rich region of the air-fuel ratio in the cylinder deactivation mode (TPS2≤TPS≤TPS1), an air-fuel ratio richer than the air-fuel ratio by the O ₂ feedback control in the all-cylinder mode close to this region is set. It should be noted that such air-fuel ratio switching control is also performed by, for example, the engine speed Ne.
And engine load (throttle opening) TPS O ₂
A two-dimensional map for selecting the feedback control mode and the enrichment mode is provided, and the optimum air-fuel ratio control mode is selected from the detected engine speed Ne and engine load (throttle opening) TPS based on this map. You can

The optimum switching load (switching throttle opening TPS2) for such air-fuel ratio switching control also tends to be set to a smaller value as the engine speed increases. The specific air-fuel ratio control is performed by the fuel supply means F.
This is performed by controlling the fuel injection amount of the injector 28 that constitutes S. Specifically, the air-fuel ratio is controlled by the control of the injector driver 28A that drives the injector 28.

Since the internal combustion engine with the variable cylinder mechanism as the first embodiment of the present invention is constructed as described above, the switching control between the cylinder deactivation mode and the all cylinders mode is shown in FIGS. As described above, the switching is performed at the switching point in the load area larger than the load (reference load) corresponding to the cross point. Therefore, the cylinder deactivation mode is activated in a load region that is larger than the cross point.In this region, the deceleration mode of the engine tends to slow down the output torque of the engine and cause insufficient output. Since the fuel ratio enrichment control is performed, sufficient engine output torque can be obtained while performing the cylinder deactivation mode operation in the load region larger than the cross point.

That is, in this engine, the air-fuel ratio control according to the switching control between the cylinder deactivation mode and the all cylinders mode is performed as shown in FIG. 6, for example. That is, first, EC
At U32, the detected values TPS from the throttle opening sensor 36, the engine speed sensor 33, and the O ₂ sensor 46,
Ne, O ₂ is read (step A10), and the detected throttle opening TPS is switched to the engine operation mode at the detected engine speed Ne.
It is determined whether or not it is in the cylinder deactivation mode by comparing with 1 (step A
12).

When the detected throttle opening TPS is less than the switching throttle opening TPS1, the cylinder is in the cylinder deactivation mode, the solenoid valves 27 and 26 are set to the cylinder deactivation mode, and the idle speed control and the like are also set to the cylinder deactivation mode. In the cylinder deactivation mode, the routine proceeds to step A14, where the detected throttle opening TPS is compared with the switching throttle opening TPS2 for air-fuel ratio control at the detected engine speed Ne to determine whether it is an O ₂ feedback zone or a rich zone. To do.

If the detected throttle opening TPS is less than the switching throttle opening TPS2, it means the O ₂ feedback zone, and the routine proceeds to step A16, where the O ₂ feedback control is executed. If the detected throttle opening TPS is equal to or larger than the switching throttle opening TPS2, it means the enrichment zone, and the routine proceeds to step A18, the O ₂ feedback control is canceled, and the routine proceeds to step A20 to perform the enrichment control.

In this way, when the throttle opening TPS is greater than or equal to the switching throttle opening TPS2, the air-fuel ratio is made rich, so the output torque of the engine in this engine load region is shown by the chain line in FIG. 5 (B). It will increase as shown. As a result, it is possible to obtain an effect of improving fuel consumption by the cylinder deactivation mode operation while sufficiently securing the output torque of the engine up to a throttle opening area larger than the switching throttle opening (reference load) corresponding to the cross point.

Further, as described above, the switching throttle opening T
When PS2 is less than PS2, the air-fuel ratio is rich although the cylinder deactivation mode operation is performed. When the switching throttle opening TPS2 is greater than or equal to all cylinder mode operation, the air-fuel ratio is not rich. The difference in engine output torque between the front and rear is reduced, and a sharp increase in engine output torque due to switching from the cylinder deactivation mode to the all cylinders mode is also avoided.
The effect that the switching shock is reduced is also obtained concomitantly.

By the way, such control according to the present invention may be performed in combination with various other controls of the engine. Here, as a second embodiment, an example in which the control according to the present invention is combined with other control of the engine will be described. FIG. 7 is a schematic diagram showing the configuration of the control system according to the second embodiment. As shown in FIG. 7, the ECU 32 includes a throttle opening sensor (throttle position sensor) 36, an engine speed sensor 33, and an oxygen sensor. From the concentration sensor 46 and the automatic transmission control means 74, information such as the throttle opening TPS, the engine speed Ne, the oxygen concentration O ₂ and whether or not the automatic transmission is shifting is taken in.

Further, the ECU 32 has a mode setting means 80 for setting the operation mode of the engine to either the cylinder deactivation mode or the all cylinder mode, and the solenoid valve (OCV) 91 depending on the setting by the mode setting means 80. Solenoid valve control means 81 for controlling the operation of the bypass type idle speed controller (ISC) 92, ISC control means 82 for controlling the operation of the bypass type idle speed controller (ISC) 92, fuel injection control means 83 for controlling the fuel injection means 93, and ignition means (ignition means). The ignition timing control means 84 for controlling the ignition timing of the plug 94 and the power generation control means 85 for controlling the operation of the generator 95 driven by the engine 1 are provided.

The mode setting means 80 uses the throttle opening TPS and the engine speed Ne as the switching point, based on the throttle opening TPS and the engine speed Ne, with the throttle opening TPS1 in the higher load range than the cross point as the switching point or the cylinder deactivation mode or the whole cylinder. Set the tube mode. However, when it is necessary to switch from the all cylinders mode to the cylinder deactivation mode by this setting, if the automatic transmission is in the gear shifting operation, it does not switch to the cylinder deactivation mode and waits until the shifting operation is completed. After the shifting operation is completed, switching to the cylinder deactivation mode is performed.

The solenoid valve control means 81 controls the operation of each solenoid valve (OCV) 91 in a state corresponding to the mode set by the mode setting means 80, and sets the cylinder deactivation / all cylinder switching mechanism to the corresponding mode state. To The ISC control means 82 controls the opening position of the valve interposed in the bypass of the ISC 92 to a cylinder deactivation position so that the idle rotation is relatively low in the cylinder deactivation mode, so that the idle rotation is higher in the all cylinder mode. The opening position of the valve installed in the bypass is controlled to the full cylinder position. In the all cylinder mode, the valve opening position may be changed between the all cylinder low speed mode and the all cylinder high speed mode.

The fuel injection control means 83 performs air-fuel ratio control in addition to the control as to whether or not fuel injection is performed.
Of course, in principle, fuel is injected into all the cylinders in the all cylinder mode, but in the cylinder deactivation mode, fuel injection is not performed in the cylinders that are in the cylinder deactivation mode. Then, at the time of switching from the cylinder deactivation mode to the all cylinders mode, fuel injection into the cylinder that newly starts intake is started after a predetermined period T1 has passed after the mode switching.
In this case as well, the fuel injection is not started at the same time for all of the cylinders for which the intake has been newly started, but the fuel injection is started while providing a time difference one by one.

For example, taking a 4-cylinder engine as an example,
The cylinders that are deactivated are, for example, two cylinders, a first cylinder and a fourth cylinder, and when switching from the deactivated cylinder mode to the all cylinders mode,
The introduction of intake air into these first cylinder and fourth cylinder is started. In the fuel injection control means 83, the first cylinder and the fourth cylinder
Even if the introduction of intake air into the cylinders is started, fuel injection is not started at the same time. For example, after a predetermined period T1 has passed after the mode switching, fuel injection into the first cylinder is first started to set the three-cylinder fuel injection state. After the lapse of the predetermined period T3, the fuel injection into the first cylinder is started to bring the fuel injection into all cylinders. Further, the periods T1 and T3 in this case are set based on the crank angle of the normal engine. The output torque of the engine is being increased stepwise by such stepwise fuel injection. As another procedure of performing the fuel injection stepwise, the three-cylinder fuel injection state may be set immediately after the mode switching, and the all-cylinder fuel injection state may be set after the subsequent period.

In the air-fuel ratio control by the fuel injection control means 83, the air-fuel ratio is stoichiometric or desired by O ₂ feedback based on the detection information of the O ₂ sensor 46 at the time of low load in both the cylinder deactivation mode and the all cylinders mode. Is controlled to be in a lean state, the O ₂ feedback is released at the time of high load, and the air-fuel ratio is controlled to be richer than that at the time of O ₂ feedback control by the open loop.

The switching load (switching throttle opening TPS) in the air-fuel ratio control mode changes depending on the engine speed, but the switching throttle opening TP in the cylinder deactivation mode.
S2 is larger than the cross point and smaller than the switching throttle opening TPS1 in the operation mode during the period. The switching throttle opening TPS3 in the all cylinder mode is naturally larger than the switching throttle opening TPS1.

The ignition timing control means 84 is an ignition timing for suppressing an increase in the output torque of the engine that occurs when fuel injection into a new cylinder is started at the time of switching from the cylinder deactivation mode to the all cylinders mode. It is designed to perform retard control. This suppression of the ignition timing is intended to allow the output torque of the engine to increase more gradually when switching from the cylinder deactivation mode to the all cylinders mode. When fuel injection is started from the cylinder deactivated state to the activated state, the output torque rapidly increases stepwise in response to this,
At this time, if the ignition timing is temporarily retarded, the output torque is suppressed from increasing, and gradually increases to reduce the mode switching shock. The retard of the ignition timing is slightly delayed from the start of fuel injection to the cylinder that has started the operation (waiting only for the periods T2 and T4), and the timing at which the output torque actually increases after the start of fuel injection is estimated. To be executed.

The power generation control means 85 carries out control (power generation cut control) to stop the power generation by the power generator 95 when the engine is rotating at high speed in the cylinder deactivation mode. Of course, under conditions other than that, the power generation cut control is canceled and the generator 9
Power generation by 5 is executed. As a result, the switching shock, which is a problem when switching from the cylinder deactivation mode to the all cylinders mode when the engine is rotating at a high speed, is intended to be suppressed.

Since the control system of the internal combustion engine with a variable cylinder mechanism of the second embodiment of the present invention is configured as described above,
For example, each control is performed as shown in FIG. That is, as shown in FIG. 8, in step S10, the throttle opening TPS, the engine speed Ne, the oxygen concentration O ₂ and the information as to whether or not the automatic transmission is shifting are read, and the process proceeds to step S12. First, it is determined from the flag information in the ECU 32 whether or not the current mode is the all cylinder mode. In other words,
If the all-cylinder flag F is 1, it is currently in the all-cylinder mode, and if the flag F is 0, it is currently in the cylinder-off mode.

If the all cylinder mode is currently selected, the operation proceeds to step S14, where the throttle opening TPS is set to the switching point value TPS1.
And whether to switch to the cylinder deactivation mode or not. If TPS is less than TPS1, it is necessary to switch to the cylinder deactivation mode, but at this time, the routine proceeds to step S16, where it is determined whether or not the automatic transmission (AT) is in a switching operation. If the automatic transmission is in the switching operation, the operation waits until the switching operation is completed (step S16), and the switching to the cylinder deactivation mode is executed.
As a result, the switching to the cylinder deactivation mode is not performed during the switching operation of the transmission. Accordingly, if the all cylinder mode is switched to the cylinder deactivation mode during the switching operation of the transmission, a large switching shock will occur, but this can be avoided.

Next, in step S20, the operating state in the cylinder deactivation mode is set. When the cylinder deactivation mode is set, the map for cylinder deactivation is selected as the O ₂ feedback zone determination map (step S22) and step S3.
The cylinder deactivation air-fuel ratio control by 0 to S36 is executed. Also,
The solenoid valve (OCV) 81 is set to the cylinder deactivation mode (step S2
4), the ISC 92 is controlled to the cylinder deactivation position, and various control targets to be linked to the cylinder deactivation are controlled to the cylinder deactivation side (step S26). Further, in the cylinder deactivation mode, in the high engine speed region where the engine speed Ne is equal to or higher than the predetermined engine speed Ne ₁ , the process proceeds from the determination of step S28 to step S40 to perform the power generation cut control. The engine speed Ne is the predetermined speed N
If it is not in the high rotation region of e ₁ or more, the process proceeds from step S28 to step S42 to cancel the power generation cut control and execute power generation.

[0076] air-fuel ratio control for cylinder deactivation in step S30~S38 from first, at step S30, by using the O ₂ feedback zone determination map for cylinder deactivation, the detected engine speed Ne and the throttle opening TPS, O ₂ Determine if it is in the feedback zone. Throttle opening TP
If S is less than the switching throttle opening TPS2 corresponding to the engine speed Ne at this time, it is the O ₂ feedback zone, and the process proceeds to step S32 to carry out the O ₂ feedback control. If the detected throttle opening TPS is equal to or greater than the switching throttle opening TPS2, it means the enrichment zone, the process proceeds to step S34, the O ₂ feedback control is canceled, and the enrichment control is performed in step S36. Thereafter, the process proceeds to step S38, and the cylinder deactivation / all cylinder flag F is set to 0.
(Cylinder suspension mode).

On the other hand, if the flag F is 0, the cylinder is currently in the cylinder deactivation mode, and the program proceeds from step S12 to step S44 to compare the throttle opening TPS with the switching point value TPS1 to determine whether or not to switch to the all cylinders mode. To do. TP
If S is TPS1 or more, it is necessary to switch to the all cylinder mode.
At this time, the process proceeds to step S46 to set the operating state in the all-cylinder mode.

When the all cylinder mode is set, the solenoid valve (OC
V) 81 is set to full cylinder mode (step S48), ISC
Various control targets that should be linked to all cylinders, such as controlling 92 to all cylinder positions, are controlled to all cylinders (step S50). Further, the process proceeds to step S52 to cancel the power generation cut control and execute power generation. Immediately after switching to the all cylinders mode, the flag F is 0, the process proceeds to step S56 in the determination of step S54, and after waiting for a predetermined period T1,
In step S58, the map for all cylinders is selected as the O ₂ feedback zone determination map, fuel injection is started only in one of the cylinders that have been switched from the cylinder deactivated operation to the three-cylinder fuel injection state. Yes (step S60). Further, after waiting for a predetermined period T2 in step S62, the ignition timing is retarded (step S64). Then, after the three-cylinder fuel injection state is set in step S66, the fuel injection is started for the predetermined period T3, and the fuel injection to the remaining cylinders is started to set the all-cylinder fuel injection state (step S6).
8). Furthermore, after waiting for a predetermined period T4 in step S70, the ignition timing is retarded again (step S70).
72).

In this way, when the all-cylinder fuel injection state is reached, the all-cylinder air-fuel ratio control in steps S74 to S80 is executed. That is, first, in step S74, O for all cylinders
_{2 Based} on the detected engine speed Ne and throttle opening TPS using the feedback zone determination map,
₂ Determine if it is in the feedback zone. If the throttle opening TPS is less than the switching throttle opening TPS2 corresponding to the engine speed Ne at this time, it is in the O ₂ feedback zone, and the routine proceeds to step S76 to execute the O ₂ feedback control. If the detected throttle opening TPS is equal to or greater than the switching throttle opening TPS2, it means the enrichment zone, the process proceeds to step S78, the O ₂ feedback control is released, and the enrichment control is performed in step S80. After that, the process proceeds to step S82, and the cylinder deactivation all cylinder flag F is set to 1 (all cylinder mode).

In each of the above-mentioned embodiments, the four-cylinder engine is explained, but the engine (internal combustion engine) to which the present invention can be applied is not limited to the number of cylinders, the in-line type or the V-type. .

[0081]

As described in detail above, the present invention is defined in claims 1, 2, and 3.
According to the described internal combustion engine with a variable cylinder mechanism of the present invention, a load higher than a boundary point (cross point) at which the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal to each other It becomes possible to secure the output torque of the engine while operating in the cylinder deactivation mode, and it is possible to achieve a significant improvement in fuel efficiency by expanding the cylinder deactivation mode operation range while securing the output performance of the engine. Further, in this case, it is possible to contribute to reduction of shift shock from the cylinder deactivation mode to the all cylinders mode.

According to the internal combustion engine with a variable cylinder mechanism of the present invention as defined in claims 4 and 5, the engine operation mode can be switched reliably and easily while using the throttle opening as a parameter indicating the engine load of the internal combustion engine. Control and air-fuel ratio control, it becomes possible to secure the output torque of the engine while operating in the cylinder deactivation mode up to a higher load range than before, and by expanding the cylinder deactivation mode operating range while ensuring the output performance of the engine. A significant improvement in fuel efficiency can be realized, and in this case, it can also contribute to a reduction in shift shock from the cylinder deactivation mode to the all cylinders mode.

According to the internal combustion engine with a variable cylinder mechanism of the present invention described in claim 6, in the configuration of claim 4 or 5, the second throttle opening is set in accordance with the rotational speed of the internal combustion engine. With this configuration, the air-fuel ratio can be controlled appropriately. According to the internal combustion engine with a variable cylinder mechanism of the present invention according to claim 7, in the configuration according to any one of claims 1 to 3, the air-fuel ratio control means is configured such that the engine load is lower than the first engine load. Even in the all-cylinder mode operation, which is also large, when the engine load is equal to or higher than the third engine load which is larger than the first engine load, the air-fuel ratio is made richer than that under the third load state. With this configuration, the output can be increased by air fuel consumption control according to the output demand even in the all-cylinder mode operation, which contributes to the improvement of engine performance.

According to the eighth aspect of the present invention, there is provided the variable cylinder mechanism-equipped internal combustion engine according to the first aspect, further comprising oxygen concentration detecting means for detecting the oxygen concentration in the exhaust gas. Due to the configuration in which the air-fuel ratio control means is set so as to perform feedback correction of the air-fuel ratio based on the oxygen concentration information from the oxygen concentration detection means in a region where the air-fuel ratio is not enriched, the output demand is not significant. In this case, it is possible to balance the improvement of fuel consumption and the securing of the required engine output.

[Brief description of drawings]

FIG. 1 is a schematic block diagram showing a control system of an internal combustion engine with a variable cylinder mechanism as a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an internal combustion engine with a variable cylinder mechanism as a first embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a variable cylinder mechanism of an internal combustion engine with a variable cylinder mechanism as a first embodiment of the present invention.

FIG. 4 is a characteristic diagram of the output torque of the engine for explaining the control and effect of the internal combustion engine with the variable cylinder mechanism as the first embodiment of the present invention.

FIG. 5 is a characteristic diagram of the output torque of the engine for explaining the control and the effect of the internal combustion engine with the variable cylinder mechanism as the first embodiment of the present invention.

FIG. 6 is a flowchart showing a control procedure of an internal combustion engine with a variable cylinder mechanism as a first embodiment of the present invention.

FIG. 7 is a schematic block diagram showing a control system of an internal combustion engine with a variable cylinder mechanism as a second embodiment of the present invention.

FIG. 8 is a flowchart showing a control procedure of an internal combustion engine with a variable cylinder mechanism as a second embodiment of the present invention.

FIG. 9 is a characteristic diagram of the output torque of the engine for explaining the problems of the conventional example and the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 engine (internal combustion engine with variable cylinder mechanism) 2 cylinder head 4 DOHC type valve system 5,6 intake / exhaust cam shaft 7,8 intake / exhaust rocker shaft 9,10 timing gear 11 timing belt 23 switching oil passage 23 hydraulic pump 26 low electromagnetic valve (OCV for low speed and cylinder deactivation) 27 High solenoid valve (OCV for high speed) 28 Injector 28A Injector driver 29 Fuel pressure adjusting means 30 Low solenoid valve (OCV for low speed) 31 High solenoid valve (OCV for high speed) 32 Electronic control unit 35 Negative Pressure sensor 36 Throttle opening sensor 37 Surge tank 38 Air cleaner 40 Throttle valve 41 Throttle valve 40 rotation shaft 42 Valve drive actuator 44 Fuel supply source 46 O ₂ sensor 48 Variable cylinder mechanism 50 Cylinder / all cylinder switching mechanism 51, 52 Rocker arm 51A, 52A Fitting hole 5 , 54 hydraulic piston 53A, 54A oil chamber 55 T lever 56, 57 return spring 60 hydraulic pump 61 accumulator 66 idle speed controller (ISC) 70 mode control means (variable cylinder control means) 70A mode determination section 70B mode setting section 72 fuel supply Control means 72A Air-fuel ratio control means 72B Injector drive time setting means 80 Mode setting means 81 Electromagnetic valve control means 82 ISC control means 83 Fuel injection control means 84 Ignition timing control means 85 Power generation control means 91 Electromagnetic valve (OCV) 92 Bypass idle Speed controller (IS
C) 93 fuel injection means 94 ignition means (ignition plug) 95 generator EM exhaust manifold ER exhaust path FS fuel supply means IM intake manifold IR intake path ML, MH low / high switching means (mode switching mechanism)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hideo Nakai 5-3-8 Shiba, Minato-ku, Tokyo Mitsubishi Motors Corporation (72) Inventor Atsushi Isomoto 5-33-8 Shiba, Minato-ku, Tokyo Automobile Industry Co., Ltd. (72) Inventor Shinichi Murata 5-3-8, Shiba, Minato-ku, Tokyo Mitsubishi Motors Industry Co., Ltd.

Claims (8)

[Claims] 1. An internal combustion engine having a plurality of cylinders, wherein the all-cylinder mode in which all of the plurality of cylinders are operated and the introduction of intake air to a part of the plurality of cylinders is cut off. A variable cylinder mechanism capable of switching between a cylinder deactivation mode for stopping the operation of the cylinders of the other section, and a case where the engine load is small when the engine load is small based on the load state of the internal combustion engine and the engine load is large In the internal combustion engine with a variable cylinder mechanism, which includes variable cylinder control means for controlling the operation of the variable cylinder mechanism so as to operate in the all cylinder mode, and air-fuel ratio control means for controlling the air-fuel ratio state, The cylinder control means uses a first engine load larger than the reference engine load with respect to the reference engine load at which the engine output torque during the cylinder deactivation mode operation and the engine output torque during the all cylinder mode operation are substantially equal. , The rest cylinder The air-fuel ratio control means is set so as to switch between the normal operation and the all-cylinder mode operation, and the air-fuel ratio control means controls the air-fuel ratio in the all-cylinder mode operation in the vicinity of the first engine load during the cylinder deactivation mode operation. An internal combustion engine with a variable cylinder mechanism, characterized in that it is set to be richer than a fuel ratio. 2. The second engine load when the air-fuel ratio control means exceeds the second engine load with a second engine load smaller than the first engine load as a boundary during the cylinder deactivation mode operation. The internal combustion engine with a variable cylinder mechanism according to claim 1, wherein the air-fuel ratio is set to be richer than that of the case of less than. 3. The air-fuel ratio control means has a second engine load greater than the reference engine load and smaller than the first engine load as a boundary during the cylinder cutoff mode operation, and the second engine load or more. 2. The internal combustion engine with a variable cylinder mechanism according to claim 1, wherein the air-fuel ratio is set to be richer than when the load is less than the second engine load. 4. The throttle opening is used as a parameter indicating the engine load of the internal combustion engine, and the variable cylinder control means switches between the cylinder cutoff mode operation and the all cylinder mode operation. Is set to be performed at a first throttle opening that is larger than a reference throttle opening at which the engine output torque during operation and the engine output torque when operating in the all cylinder mode are substantially equal, and the air-fuel ratio control means In the cylinder deactivation mode operation, when the second throttle opening which is smaller than the first throttle opening is set as a boundary, when the second throttle opening is equal to or larger than the second throttle opening, the air-fuel ratio becomes higher than that when the second throttle opening is smaller than the second throttle opening. The internal combustion engine with a variable cylinder mechanism according to claim 1, wherein the internal combustion engine is set to be rich. 5. A throttle opening is used as a parameter indicating an engine load of the internal combustion engine, and the variable cylinder control means switches between the cylinder deactivation mode operation and the all cylinder mode operation. Is set to be performed at a first throttle opening that is larger than a reference throttle opening at which the engine output torque during operation and the engine output torque when operating in the all cylinder mode are substantially equal, and the air-fuel ratio control means In the cylinder deactivation mode operation, when the second throttle opening is larger than the reference throttle opening and smaller than the first throttle opening as a boundary, the second throttle opening is exceeded. The variable cylinder mechanism-equipped internal combustion engine according to any one of claims 1 to 3, wherein the air-fuel ratio is set to be richer than the case of less than. 6. The internal combustion engine with a variable cylinder mechanism according to claim 4, wherein the second throttle opening is set according to the rotational speed of the internal combustion engine. 7. The air-fuel ratio control means according to the third aspect, wherein the engine load is larger than the first engine load even in the all cylinder mode operation in which the engine load is larger than the first engine load. The internal combustion engine with variable cylinder mechanism according to any one of claims 1 to 3, wherein the air-fuel ratio is set to be richer when the engine load is equal to or higher than the third load condition. organ. 8. An oxygen concentration detecting means for detecting an oxygen concentration in exhaust gas is provided, wherein the air-fuel ratio control means is based on the oxygen concentration information from the oxygen concentration detecting means in a region where the air-fuel ratio is not enriched. The internal combustion engine with a variable cylinder mechanism according to any one of claims 1 to 7, wherein the internal combustion engine is set to perform feedback correction of an air-fuel ratio.