JP3962356B2 - Control device for variable cylinder internal combustion engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is operated by switching the operation mode between an all-cylinder operation mode in which all of a plurality of cylinders are operated and a partial cylinder operation mode in which some operations are suspended, and a variable that performs fuel cut during deceleration. The present invention relates to a control device for a cylinder internal combustion engine.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, a control device for an internal combustion engine mounted on a vehicle that performs fuel cut during deceleration is disclosed in Patent Document 1. In this control device, when the internal combustion engine is in a predetermined operating state, fuel cut (hereinafter referred to as “F / C”) is performed to improve fuel efficiency. It is canceled when the rotational speed of the internal combustion engine (hereinafter referred to as “engine speed”) becomes a predetermined value as the speed of the vehicle (hereinafter referred to as “vehicle speed”) decreases due to execution. Further, it is determined during F / C whether or not the reduction degree of the vehicle speed is large. If the reduction degree is large, F / C is released before the engine speed reaches the predetermined value, and the release is canceled. The timing is advanced. This is because there is a time delay until the fuel injection is executed by the drive signal from the control device with the release of F / C, so when the degree of decrease in the vehicle speed is large, this fuel injection delay causes This is to avoid the engine speed from dropping significantly and possibly causing engine stall.
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 2001-193530 [0004]
[Problems to be solved by the invention]
However, when the above-described conventional control device is applied to a variable cylinder internal combustion engine, there are the following problems. That is, in the partial cylinder operation mode, since the number of cylinders to be operated is smaller than in the full cylinder operation mode, if the fuel injection amount for each cylinder is the same, the output of the internal combustion engine is small. For this reason, in the conventional control device, as one of the conditions for releasing the fuel cut, even if the degree of decrease in the vehicle speed is determined, the operation in the partial cylinder operation mode is performed after the release of the F / C. Since the output of the internal combustion engine is not sufficient, a significant drop in the engine speed cannot be prevented, and engine stall may occur.
[0005]
Such inconvenience is caused, for example, by loosening the standard for determining the magnitude of the reduction degree of the vehicle speed, so that the release timing of F / C is advanced even when the reduction degree of the vehicle speed is relatively small. It can be resolved. However, in that case, when the operation in the all-cylinder operation mode is performed after the release of the F / C, there is a margin in the output of the internal combustion engine with respect to the reduction degree of the vehicle speed, and there is no possibility of engine stall. However, the F / C is immediately released at that time, resulting in a deterioration in fuel consumption.
[0006]
The present invention has been made in order to solve such a problem, and the fuel cut can be released at an optimal timing according to the operation mode, thereby maintaining the fuel efficiency and maintaining the fuel. An object of the present invention is to provide a control device for a variable cylinder internal combustion engine that can prevent the occurrence of engine stall after the release of cut.
[0007]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 includes a plurality of cylinders (cylinders # 1 to # 3 in the right bank and cylinders # 4 to # 6 in the left bank in the embodiment (hereinafter the same in this section)). The operation mode is switched between an all-cylinder operation mode that operates all and a partial cylinder operation mode in which a part of the operation is stopped by the cylinder deactivation mechanism 4, and fuel cut is executed in a predetermined deceleration state. 3 is a control device 1 for a variable cylinder type internal combustion engine 3, which is a deceleration rate parameter detection means (vehicle speed sensor 25, ECU 2, step of FIG. 3) for detecting a deceleration rate parameter (deceleration rate DTV) indicating the deceleration rate of the internal combustion engine 3. 2) and the deceleration rate parameter detected during fuel cut is a predetermined threshold value (threshold value VEMA for all cylinder operation mode, partial cylinder operation mode) Use threshold VEMM, when it becomes a failure threshold VEM) or for the time, fuel cut release means (ECU 2 for canceling the fuel cut, the steps 5, 7, 8) in FIG. 3, after release of the fuel cut Operation mode setting means (ECU 2, step 11 in FIG. 2) for setting the operation mode to be selected, LAF sensor 22 for detecting the oxygen concentration in the exhaust gas discharged from the internal combustion engine 3, and the detected exhaust gas The failure determination means (ECU 2, step 3 in FIG. 3) for determining whether or not the cylinder deactivation mechanism 4 has failed according to the oxygen concentration VLAF in the engine, and the determination result by the set operation mode and failure determination means Accordingly, there is provided threshold value setting means (ECU 2, steps 4 and 6 to 8 in FIG. 3) for setting a threshold value.
[0008]
According to this control device for a variable cylinder internal combustion engine, fuel cut is executed in a predetermined deceleration state, and the deceleration rate parameter indicating the detected deceleration rate of the internal combustion engine during the fuel cut is set to a predetermined value. When the threshold is exceeded, the fuel cut is released. This threshold value is set according to the operation mode to be selected after cancellation of the fuel cut, that is, according to the full cylinder operation mode and the partial cylinder operation mode. For this reason, for example, when the operation mode after canceling the fuel cut is the partial cylinder operation mode in which the output of the internal combustion engine is small, by setting the threshold value to a smaller value, the deceleration rate of the internal combustion engine does not become so large. In addition, since the fuel cut can be released early, it is possible to prevent a significant drop in the rotational speed of the internal combustion engine due to a delay in fuel injection, and therefore it is possible to prevent the occurrence of engine stall.
[0009]
Also, when the operation mode after canceling the fuel cut is the all-cylinder operation mode in which the output of the internal combustion engine has a margin, by setting the threshold value to a larger value, until the deceleration rate of the internal combustion engine becomes relatively large, That is, the fuel cut can be continued up to the limit where engine stall can be prevented, so that the best fuel consumption can be obtained. Further, it is determined whether or not the cylinder deactivation mechanism has failed according to the oxygen concentration in the exhaust gas detected by the LAF sensor, and a threshold value is further set according to this determination result.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a schematic configuration of a control apparatus 1 for a variable cylinder internal combustion engine according to an embodiment of the present invention and a variable cylinder internal combustion engine (hereinafter referred to as “engine”) 3 controlled thereby.
[0011]
The engine 3 is a V-type 6-cylinder DOHC gasoline engine mounted on a vehicle (not shown), and includes three cylinders # 1, # 2, and # 3 (a plurality of cylinders) in the right bank 3R and a left bank. 3L three cylinders # 4, # 5, and # 6 (multiple cylinders) are provided. The right bank 3R is provided with a cylinder deactivation mechanism 4 for executing a partial cylinder operation mode described later.
[0012]
The cylinder deactivation mechanism 4 is connected to a hydraulic pump (not shown) via oil passages 6a and 6b. Further, between the hydraulic pump and the cylinder deactivation mechanism 4, electromagnetic valves 5a and 5b for intake valves and exhaust valves are arranged. These electromagnetic valves 5a and 5b are both normally closed, and open the oil passages 6a and 6b, respectively, when turned on by a drive signal from the ECU 2. In the partial cylinder operation mode, both the solenoid valves 5a and 5b are turned on, and the oil passages 6a and 6b are opened, whereby the hydraulic pressure from the hydraulic pump is supplied to the cylinder deactivation mechanism 4. As a result, in the cylinders # 1 to # 3 of the right bank 3R, the intake valve and the intake cam and the exhaust valve and the exhaust cam (both not shown) are blocked, so that the intake valve and the exhaust valve are It is held in a resting state (closed state).
[0013]
On the other hand, in the all-cylinder operation mode, contrary to the above, both the solenoid valves 5a and 5b are turned off and the oil passages 6a and 6b are closed, whereby the supply of hydraulic pressure from the hydraulic pump to the cylinder deactivation mechanism 4 is stopped. Is done. As a result, in the cylinders # 1 to # 3 of the right bank 3R, the shutoff state between the intake valve and the intake cam and between the exhaust valve and the exhaust cam is released, so that the intake valve and the exhaust valve become movable. .
[0014]
An intake pipe 7 is connected to the six cylinders # 1 to # 6 via an intake manifold 7a. An injector 8 is attached to each branch portion 7b of the intake manifold 7a so as to face an intake port (not shown) of each cylinder. These injectors 8 are controlled by a drive signal from the ECU 2, and in the all-cylinder operation mode, fuel is injected from all the injectors 8 into the respective branch portions 7b. On the other hand, in the partial cylinder operation mode, the fuel injection from the three injectors 8 in the right bank 3R is controlled to stop.
[0015]
As described above, in the partial cylinder operation mode, the operation of the three cylinders # 1 to # 3 in the right bank 3R is suspended by the suspension of the intake valve and the exhaust valve and the suspension of fuel injection from the injector 8. . On the other hand, in the all-cylinder operation mode, all the six cylinders # 1 to # 6 are operated and are operated in the order of # 1 → # 5 → # 3 → # 6 → # 2 → # 4.
[0016]
The intake pipe 7 is provided with a throttle valve 9, and this throttle valve 9 is connected to a rotating shaft of a motor 9a. The motor 9a is constituted by, for example, a DC motor, and the opening degree (hereinafter referred to as “throttle valve opening degree”) TH of the throttle valve 9 is controlled by the ECU 2 by controlling the duty value of the drive current supplied to the motor 9a. Controlled. Further, the throttle valve opening TH is detected by a throttle valve opening sensor 21 provided in the intake pipe 7, and the detection signal is output to the ECU 2.
[0017]
A LAF sensor 22 is provided in an exhaust pipe (not shown) of the internal combustion engine. The LAF sensor 22 linearly detects the oxygen concentration VLAF in the exhaust gas, and a detection signal proportional to the oxygen concentration VLAF. Is output to the ECU 2.
[0018]
A detection signal indicating the engine speed (hereinafter referred to as “engine speed”) NE from the engine speed sensor 23 is transmitted to the ECU 2 from the accelerator position sensor 24 to an accelerator pedal (not shown). A detection signal representing AP (referred to as “opening degree”) is output from the vehicle speed sensor 25 (deceleration total parameter detection means), and a detection signal representing vehicle speed (hereinafter referred to as “vehicle speed”) VP. The engine speed sensor 23 outputs a TDC signal to the ECU 2 at the timing near the top dead center position before the intake stroke of pistons (not shown) in the cylinders # 1 to # 6 as the engine 3 rotates. .
[0019]
The ECU 2 is composed of a microcomputer including an I / O interface, CPU, RAM, ROM, and the like. The detection signals from the various sensors 21 to 25 described above are A / D converted by the I / O interface and then input to the CPU. In response to these detection signals, the CPU sets the operation mode of the engine 3 to the full cylinder operation mode or the partial cylinder operation mode in accordance with a control program stored in the ROM. In addition, the injection time of the injector 8 is controlled according to the set operation mode, and various controls such as a deceleration fuel cut (hereinafter referred to as “deceleration F / C”) control are executed. In the present embodiment, the ECU 2 constitutes a deceleration rate parameter detection means, a fuel cut release means, an operation mode setting means, a failure determination means, and a threshold value setting means.
[0020]
FIG. 2 shows an operation mode setting process for setting the operation mode of the engine 3. In step 11, the operation mode of the engine 3 is set as follows. That is, when the engine speed NE is within a predetermined range (for example, 1000 to 3500 rpm), or when the accelerator opening AP is below a predetermined table value set in accordance with the engine speed NE, the operation mode is partially set. The cylinder operation mode is set, and in all other cases, the all cylinder operation mode is set. Further, when the set operation mode is the partial cylinder operation mode, the partial cylinder operation mode flag F_CYLSTP is set to “1”, and when it is the all cylinder operation mode, it is set to “0”.
[0021]
Further, the deceleration F / C is executed when all of the following conditions (a) to (c) are satisfied, and fuel injection by all the injectors 8 is stopped at the deceleration F / C.
(A) The engine speed NE is equal to or higher than a predetermined F / C speed NFCA (for example, 900 rpm) for a full cylinder operation mode in the all cylinder operation mode, and in a predetermined partial cylinder operation mode in the partial cylinder operation mode. F / C rotational speed for NFCM (for example, 1100 rpm) or more.
(B) The accelerator opening AP is in a fully closed state.
[0022]
Further, the executed deceleration F / C is canceled when the engine speed NE is reduced to less than the above F / C speed NFC, whereby the fuel injection by the injector 8 is resumed. Further, during execution of the deceleration F / C, the deceleration F / C execution flag F_DECFC is set to “1”, and when the deceleration F / C is released, the deceleration F / C execution flag F_DECFC is set to “0”. Is done.
[0023]
FIG. 3 shows a process for releasing the deceleration F / C. This deceleration F / C release processing is executed every predetermined time (for example, 10 msec). First, in step 1, it is determined whether or not a deceleration F / C execution flag F_DECFC is “1”. If the answer is NO and the deceleration F / C is not executed, the program is terminated as it is.
[0024]
If the answer is YES and deceleration F / C is being executed, a value obtained by subtracting the current value VP from the previous value VP0 of the vehicle speed is calculated as a deceleration total DTV (deceleration total parameter) of the vehicle speed VP (step 2). . Next, it is determined whether or not the cylinder deactivation mechanism 4 has failed (step 3). This determination is performed in an interrupted manner in synchronization with the input of the TDC signal by a process separate from the deceleration F / C release process of FIG. 3, and the specific contents thereof are as follows, for example. That is, when the operation mode is switched from the partial cylinder operation mode to the all cylinder operation mode, the supply of hydraulic pressure to the cylinder deactivation mechanism 4 is stopped while the fuel supply to the cylinders # 1 to # 3 of the right bank 3R is stopped. Thus, the intake / exhaust valve is controlled to be movable. The oxygen concentration VLAF detected in this state is compared with a predetermined value, and it is determined whether or not the cylinder deactivation mechanism 4 has failed based on the comparison result. That is, when cylinders # 1 to # 3 in the right bank 3R are out of order, the intake / exhaust valves are held in a closed state even though the intake / exhaust valves are controlled to be movable. The oxygen concentration VLAF hardly changes, so the oxygen concentration VLAF does not reach a predetermined value. Therefore, when the oxygen concentration VLAF is smaller than the predetermined value, it can be determined that a failure of the pattern that cannot normally return from the partial cylinder operation mode to the all cylinder operation mode occurs in the cylinder deactivation mechanism 4.
[0025]
On the other hand, when the cylinders # 1 to # 3 in the right bank 3R are normal, the oxygen concentration VLAF increases immediately after the exhaust valves of the cylinders # 1 to # 3 are opened with a greater degree of change than before. Therefore, when the oxygen concentration VLAF is equal to or higher than the predetermined value, it can be determined that the cylinder deactivation mechanism 4 is normal.
[0026]
Similarly, when switching the operation mode from the full cylinder operation mode to the partial cylinder operation mode, control is performed so that the intake / exhaust valves are in a paused state while the fuel supply to the cylinders # 1 to # 3 in the right bank 3R is stopped. To do. When the oxygen concentration VLAF detected in this state is larger than a predetermined value, it is assumed that the intake / exhaust valve remains in an operating state even though the intake / exhaust valve is controlled to be in a resting state. It can be determined that the cylinder deactivation mechanism 4 has a pattern failure that cannot be switched from the mode to the partial cylinder operation mode.
[0027]
Returning to FIG. 3, when the answer to step 3 is YES and the cylinder deactivation mechanism 4 has failed, the deceleration total DTV calculated in step 2 is a predetermined failure threshold value VEM (for example, 0.02 km). / S ² ) or more (step 4). If the answer is NO and DTV <VEM, the program is terminated as it is. If the answer is YES and DTV ≧ VEM, the deceleration F / C being executed is canceled (step 5), and the program is executed. finish.
[0028]
On the other hand, if the answer to step 3 is NO and the cylinder deactivation mechanism 4 is normal, it is determined whether or not the partial cylinder operation mode flag F_CYLSTP is “1” (step 6). If the answer is YES and the operation mode is the partial cylinder operation mode, it is determined whether or not the deceleration total DTV is equal to or greater than a predetermined partial cylinder operation mode threshold value VEMM (threshold value) (step 7). . When the answer is NO and DTV <VEMM, the program is terminated as it is. When the answer is YES and DTV ≧ VEMM, the step 5 is executed and the program is terminated. This partial cylinder operation mode threshold value VEMM is set to a value (for example, 0.08 km / s ² ) larger than the above-mentioned failure threshold value VEM (VEMM> VEM).
[0029]
On the other hand, if the answer to step 6 is NO and the operation mode is the all-cylinder operation mode, it is determined whether or not the deceleration DTV is equal to or greater than a predetermined all-cylinder operation mode threshold value VEMA (threshold value). (Step 8). If the answer is NO and DTV <VEMA, the program is terminated as it is, while if the answer is YES and DTV ≧ VEMA, the step 5 is executed and the program is terminated. The threshold value VEMA for all cylinder operation mode is set to a value (for example, 0.14 km / s ² ) greater than the threshold value VEM for partial cylinder operation mode (VEMA> VEMM).
[0030]
As described above, according to the present embodiment, during the deceleration F / C, it is determined whether or not the set operation mode and the cylinder deactivation mechanism 4 are out of order, and according to the determination results, The deceleration F / C is canceled when the deceleration DTV is equal to or higher than the threshold values VEMA, VEMM, and VEM for the predetermined full cylinder operation mode, partial cylinder operation mode, and failure. Further, since the partial cylinder operation mode threshold value VEMM is set to a value smaller than the all cylinder operation mode threshold value VEMA, the deceleration F / C can be increased as soon as the deceleration DTV does not increase. Can be released. As a result, the engine speed NE can be prevented from dropping significantly due to the delay in fuel injection, so that the engine stall can be prevented. Further, since the threshold value VEMA for all-cylinder operation mode is set to a larger value, the deceleration F / C is continued until the deceleration rate DTV becomes relatively large, that is, until the engine stall can be prevented. Therefore, the best fuel consumption can be obtained.
[0031]
Further, the failure threshold value VEM is set to the smallest value. This is because when the cylinder deactivation mechanism 4 is out of order, the operation of the engine 3 cannot be ensured and its reliability is low, and the failure determination method described above can determine whether or not the cylinder deactivation mechanism 4 has failed. This is because the actual number of operating cylinders cannot be determined. Therefore, by setting the failure threshold value VEM as described above, the deceleration F / C is canceled at an early stage, so that a significant drop in the engine speed NE is surely prevented in preference to fuel consumption. be able to.
[0032]
In addition, this invention can be implemented in various aspects, without being limited to embodiment described. For example, in the present embodiment, the number of deactivated cylinders in the partial cylinder operation mode is three examples with respect to the all-cylinder operation mode in which the number of activated cylinders is 6, but the number of deactivated cylinders may be other numbers. Moreover, it may be variably controlled to an arbitrary number of 1 to 5. In this case, the threshold value VEMM for partial cylinder operation mode is preferably set so as to become larger as it increases in accordance with the number of operating cylinders in the partial cylinder operation mode. C can be released more finely and appropriately.
[0033]
In the present embodiment, when the cylinder deactivation mechanism 4 fails, the failure threshold value VEM is uniformly set to a small value. However, the failure is determined for each cylinder, and the determination result is determined according to the determination result. A threshold value may be set for each actual number of operating cylinders. The determination of the failure for each cylinder can be performed, for example, as follows. That is, in the above-described method for determining the failure of the pattern that cannot be normally returned from the partial cylinder operation mode to the all cylinder operation mode, the control for making the intake / exhaust valve movable in a state where fuel injection is not performed is It is possible to determine the failure of the cylinder by performing only one cylinder. Thereafter, the failure determination can be performed for each cylinder by performing the same operation every time the other cylinders are switched to the all-cylinder operation mode. it can.
[0034]
Further, although the vehicle speed reduction rate DTV is used as the deceleration rate parameter, other parameters may be used as long as they represent the deceleration rate of the internal combustion engine, for example, the reduction rate of the engine speed NE may be used. Good. The control device of the present invention is not limited to the variable cylinder internal combustion engine mounted on the vehicle in the present embodiment, and includes a marine vessel propulsion engine such as an outboard motor having a crankshaft arranged in the vertical direction. The present invention can be applied to various industrial variable cylinder internal combustion engines. In addition, it is possible to appropriately change the detailed configuration within the scope of the gist of the present invention.
[0035]
【The invention's effect】
As described above, according to the control device for a variable cylinder internal combustion engine of the present invention, the release of the fuel cut can be performed at an optimal timing according to the operation mode, thereby maintaining good fuel economy, It has the effect of preventing the engine stall from occurring after canceling the fuel cut.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a control device of the present invention and a variable cylinder internal combustion engine controlled by the control device.
FIG. 2 is a flowchart showing an operation mode setting process.
FIG. 3 is a flowchart showing a deceleration F / C release process.
[Explanation of symbols]
1 control device 2 ECU (deceleration parameter detection means,
Fuel cut release means, operation mode setting means,
(Failure judging means, threshold setting means)
3 Engine
4- cylinder deactivation mechanism # 1 to # 3 Right bank cylinder (multiple cylinders)
# 4 to # 6 Left bank cylinders (multiple cylinders)
22 LAF sensor 25 Vehicle speed sensor (deceleration total parameter detection means)
DTV deceleration rate (deceleration rate parameter)
VEMA Threshold for all cylinder operation mode (threshold)
VEMM Threshold value for partial cylinder operation mode (threshold value)
VEM failure threshold (threshold)
Oxygen concentration in VLAF exhaust gas

Claims (1)

The operation mode is switched between an all-cylinder operation mode in which all of a plurality of cylinders are operated and a partial cylinder operation mode in which some operations are suspended by a cylinder deactivation mechanism, and the fuel is operated in a predetermined deceleration state. A control device for a variable cylinder internal combustion engine that performs cutting,
Deceleration rate parameter detecting means for detecting a deceleration rate parameter indicating the deceleration rate of the internal combustion engine;
During the fuel cut, a fuel cut release means for releasing the fuel cut when the detected deceleration rate parameter is equal to or greater than a predetermined threshold value;
Operation mode setting means for setting the operation mode to be selected after cancellation of the fuel cut;
A LAF sensor for detecting the oxygen concentration in the exhaust gas discharged from the internal combustion engine;
Failure determination means for determining whether or not the cylinder deactivation mechanism has failed according to the detected oxygen concentration in the exhaust gas;
Depending on the result of determination by the failure determination means and the set operation mode, and threshold setting means for setting the threshold value,
A control apparatus for a variable cylinder internal combustion engine, comprising:

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