JPH0771280A - Control device for variable number of cylinder engine - Google Patents

Abstract

PURPOSE:To improve operational performance of a vehicle by closing a bypass valve more when the number of operating cylinders is reduced more at the time of engine braking and more opening the valve when the number of operating cylinder is more at the time of completion of the engine brake during partial cylinder operation in a variable number of cylinder engine. CONSTITUTION:In a variable number of cylinder engine, fuel supply to partial cylinders is stopped and controlled by a number of operating cylinder control means A, according to engine operating condition. The opening degree of a bypass valve E interposed in a bypass passage D for bypassing a throttle valve B is regulated by a bypass control means F so as to control an intake flow amount. In this case, the opening degree of the bypass valve E is increased more by the bypass control means F when the number of operating cylinder is reduced more, and also the bypass valve E is closing-operated by a prescribed amount which is set to be a level larger when the number of operating cylinder is reduced more when it is detected by a throttle opening detecting means C that the throttle valve B becomes fully closed condition from opening condition, so that operational performance of a vehicle is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable cylinder engine that suspends the operation of some cylinders depending on the engine operating condition.

[0002]

2. Description of the Related Art A variable cylinder engine is generally known in which the fuel consumption rate of the engine as a whole is improved by stopping the operation of some cylinders when the engine is partially loaded to reduce the number of operating cylinders. . In a normal engine, in partial load operation, the throttle valve narrows the intake passage in order to reduce the intake air amount of the entire engine, and the negative pressure in the intake pipe downstream of the throttle valve increases. For this reason, pumping loss at the time of sucking air into the engine combustion chamber increases. On the other hand, in the variable cylinder engine, operation of some cylinders is suspended during low load operation, and operation is performed only in the remaining cylinders. Under the same load condition, it is necessary to increase the intake amount according to the decrease of the operating cylinders and increase the output per operating cylinder when the cylinders are deactivated, as compared with the normal all-cylinder operation.
Therefore, in the variable cylinder engine, the throttle in the intake passage is less than that in the all-cylinder operation under the same load condition when the cylinder is inactive.
It will be operated in a state where the negative pressure of the intake pipe is small. Therefore, pumping loss at the time of partial load is reduced and the fuel consumption rate of the engine as a whole is improved.

An example of the variable cylinder engine is described in Japanese Patent Application Laid-Open No. 52-36230. The variable cylinder engine of the above publication stops the operation by stopping the fuel injection of some cylinders during the partial cylinder operation, and performs the partial cylinder operation without interrupting the supply of intake air to the idle cylinders. Further, a plurality of bypass passages that bypass the throttle valve are provided in order to increase the intake flow rate to the operating cylinders during the partial cylinder operation, and the bypass valves are opened according to the decrease in the operating cylinders.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
According to Japanese Patent Laid-Open No. 230-230, when the partial cylinder is in operation, a bypass passage that bypasses the throttle valve is opened to increase the intake flow rate, thereby lowering the intake pipe negative pressure and reducing the engine pumping loss. However, when the bypass passage is opened during the partial cylinder operation as in the variable cylinder engine disclosed in the above publication, a problem occurs when the engine is decelerated.

That is, in the variable cylinder engine disclosed in the above publication, even when the throttle valve is fully closed during engine braking during partial cylinder operation, the bypass passage is open, so that air is introduced from the bypass passage to the intake manifold. It will flow in. Therefore, since the negative pressure of the intake manifold does not rise even when the throttle valve is fully closed, a sufficient pumping loss required for braking cannot be obtained and the effect of engine braking deteriorates. In view of the above problems, it is an object of the present invention to solve the above problems during deceleration of a variable cylinder engine and improve the braking force during engine braking without impairing the fuel consumption rate reduction effect during partial cylinder operation. I am trying.

[0006]

According to the present invention, as shown in the block diagram of the present invention in FIG. 1, the fuel supply to some cylinders is stopped in accordance with the engine operating state, and the engine 1 is operated. The operating cylinder number control means A for controlling the number of cylinders, the throttle opening degree detection means C for detecting the opening degree of the throttle valve B arranged in the engine intake passage 4, and the intake air to the engine by bypassing the throttle valve B. The bypass includes a bypass passage D for supplying, a bypass valve E provided in the bypass passage D, and a bypass control means F for adjusting an opening of the bypass valve to control an intake flow rate flowing through the bypass passage. The control means F increases the opening degree of the bypass valve E as the number of operating cylinders of the engine decreases, and the throttle opening degree detecting means C changes the throttle valve B from the open state to the fully closed state. By a predetermined amount that is set larger the smaller the number of operating cylinders when the detected the bypass valve E
When the throttle opening detecting means C detects that the throttle valve B has changed from the fully closed state to the open state, the bypass valve is set to a predetermined amount that is set larger as the number of operating cylinders is smaller. A control device for a variable cylinder engine that opens E is provided.

[0007]

The bypass control means F increases the opening degree of the bypass valve E as the number of operating cylinders decreases during normal operation.
As a result, the intake flow rate to the operating cylinder is increased during the partial cylinder operation. Further, the bypass control means F is a throttle valve B
Is detected to be fully closed, the bypass valve E is closed by a larger amount as the number of operating cylinders is smaller. During normal operation, the opening of the bypass valve E increases as the number of operating cylinders decreases, but this reduces the intake air amount according to the number of operating cylinders, so the negative pressure of the engine intake manifold rises and engine braking Appropriate braking force is secured. Further, when it is detected that the throttle valve B is opened from the fully closed state, the bypass control means F opens the bypass valve E by a larger amount as the number of operating cylinders decreases. This allows
During partial cylinder operation after engine braking is completed, the bypass valve E is maintained at an opening degree according to the number of operating cylinders.

[0008]

FIG. 2 is an overall view showing an embodiment in which the present invention is applied to a V-type 8-cylinder variable cylinder engine. In FIG. 2, reference numeral 1 denotes an engine body. In the embodiment according to the present invention, the engine 1 has two cylinder banks 1A and 1B, and the bank A has the second, fourth, sixth, and sixth cylinders from the front end side to the rear end (output shaft end) side. Eight cylinders are arranged in the bank B, and first, third, fifth, and seventh cylinders are arranged in the bank B from the front end side to the rear end side of the engine.

The intake ports of the respective cylinders are connected to a common intake pipe 4 via an intake branch pipe 3, respectively. Further, each intake branch pipe 3 is provided with a fuel injection valve 3a for injecting fuel into the intake port of each cylinder,
Further, the intake pipe 4 has a driver's accelerator pedal (not shown).
A throttle valve 6 that opens and closes in accordance with the operation amount of the throttle valve 6, a throttle opening sensor 6a that generates an output voltage signal corresponding to the opening of the throttle valve 6, and an intake air amount of the engine in the intake pipe upstream of the throttle valve 6. Air flow meters 8 for generating output voltage signals according to the above are respectively arranged.

Reference numeral 5 in the drawing denotes a throttle bypass passage connecting the upstream and downstream intake passages of the throttle valve 6. A bypass valve 7 that is opened and closed by an actuator 71 is provided in the bypass passage 5. In the embodiment according to the present invention, a step motor is used as the actuator 71, and an electronic control unit (ECU) described later is used.
The bypass valve 7 is opened and closed by an operation amount corresponding to the drive signal from 30.

Further, in the embodiment according to the present invention,
Exhaust ports of 8, 3, and 5 cylinders are independent exhaust pipes
12, 18, 13, 15 are individually connected to the
The 4th and 6th cylinders and the 1st and 7th cylinders have a common exhaust pipe,
They are connected to 14 and 11, respectively. The structure of this exhaust pipe is
Considering the combination of operating cylinders during partial cylinder operation described later
Has been decided. Each exhaust pipe 11, 12, 13, 14,
In 15 and 18, the oxygen concentration in the exhaust gas is detected and the exhaust air-fuel ratio is detected.
0 when the ratio is on the lean side with respect to the theoretical air-fuel ratio.
A voltage (lean voltage) of about 1 volt and a rich signal
When it is on the (rich) side, the voltage (rich
Oxygen concentration sensor (O ₂Sensor) 3
1 is arranged for each exhaust pipe. Furthermore, each exhaust
O of the tube₂On the downstream side of the sensor 31, HC, CO in exhaust gas,
NO_XIs a three-way catalyst 21 that can purify the three components of
They are arranged respectively.

Further, in the embodiment according to the present invention, the engine 1
The output shaft of is connected to the automatic transmission 23, and a rotation speed sensor 32 for detecting the rotation speed of the output shaft (not shown) of the automatic transmission 23 is provided. Reference numeral 30 in the drawing denotes an electronic control unit (ECU) that controls the engine 1. ECU 30 is a ROM (Read Only Memory), RA
It is configured as a digital computer having an M (random access memory), a CPU (central processing unit), an input port, an output port, etc., and in the embodiment according to the present invention, basic control such as fuel injection amount control of the engine 1 and ignition timing control. In addition to the above, the function of the operating cylinder number control means and the bypass control means of claim 1 is performed. That is, the ECU 30 stops the fuel supply to some of the cylinders according to the engine load state and performs the partial cylinder operation. In this case, only the intake air is supplied to the idle cylinder, but no combustion occurs. Further, the ECU 30 opens and closes the bypass valve 7 in accordance with the number of operating cylinders, and controls the operation of the bypass valve 7 during engine braking and after engine braking is completed to secure braking force during engine braking and engine braking completion. The subsequent partial cylinder operation state is restored. For this purpose, signals from the air flow meter 8, the output shaft speed sensor 32 of the automatic transmission, the respective O ₂ sensors 31, and the throttle opening sensor 6a are input to the input port of the ECU 30 by an analog / digital converter (A / D) (not shown). In addition to being input via a converter, signals representing the engine cooling water temperature and the engine speed of the engine 1 are respectively input from a cooling water temperature sensor and an engine speed sensor (not shown). The output port of the ECU 30 is connected to the step motor 71 of the bypass valve, supplies a drive pulse to the step motor to control the drive of the bypass valve 7, and controls the fuel injection valve 3a of each cylinder and an ignition plug (not shown). The fuel injection control and the ignition timing control of each cylinder are performed.

Next, the control of the number of operating cylinders of the variable cylinder engine 1 according to the embodiment of the present invention will be described with reference to FIGS. 3 and 4. In the embodiment according to the present invention, the ECU 30 switches the number of operating cylinders according to the operating load of the engine 1 and the traveling speed of the vehicle. FIG. 3 is a map showing an example of the relationship between the number of operating cylinders of the engine 1 and the load state. Although FIG. 3 shows only the case of switching between three different operating cylinder numbers of four cylinders, six cylinders, and all eight cylinders in order to avoid complication, actually, in the middle five cylinders and seven cylinders, Including the number of operating cylinders, a total of five operating cylinder number operations are possible.

The vertical axis of FIG. 3 represents a value Q / N obtained by dividing the engine intake air amount Q detected by the air flow meter 8 by the engine speed N, that is, the intake air amount per engine revolution. Q / N is used as a parameter representing the engine load. The horizontal axis of FIG. 3 represents the automatic transmission output rotation speed NA detected by the sensor 32 and is used as a parameter representing the vehicle speed. As shown in FIG. 3, in the embodiment of the present invention, the number of operating cylinders is reduced as the vehicle speed NA is higher in the region where the engine load Q / N is low. As described above, in the variable cylinder engine, the output per number of operating cylinders can be increased as the number of operating cylinders is reduced. Therefore, when the load is low, the smaller the number of operating cylinders, the greater the effect of improving the fuel consumption rate. However, the pulsation of the output torque increases as the number of operating cylinders decreases, and this pulsation of torque appears as greater vibration as the vehicle speed (engine speed) is lower. It is not preferable in terms of operation to reduce the amount. Therefore, in the embodiment according to the present invention, the number of operating cylinders is increased as the vehicle traveling speed is lower during low load operation to prevent deterioration of drivability.

As will be described later, in the embodiment of the present invention, the opening degree of the throttle bypass valve 7 is increased as the number of operating cylinders is decreased to increase the intake air amount Q of the entire engine. Therefore, for example, when Q / N is reduced in FIG. 3 and it becomes necessary to reduce the number of operating cylinders, the intake air amount is increased as the number of operating cylinders is reduced after switching. There is a possibility that N may increase and enter the operating cylinder number increase region again, and the operating cylinder number may increase. Therefore, the judgment value for switching the number of operating cylinders is provided with hysteresis as shown by the solid and dotted lines in FIG. 3 to prevent hunting in the switching operation. The solid line in FIG. 3 indicates the switching determination line on the operating cylinder number increasing side, and the dotted line indicates the switching determination line on the operating cylinder number decreasing side.

Next, FIG. 4 shows an example of combinations of operating cylinders during partial cylinder operation. FIG. 4 shows a combination of operating cylinders during partial cylinder operation of four cylinders, five cylinders, six cylinders, and seven cylinders, and the cylinder arrangement is the same as in FIG. (That is, the upper side represents the bank 1A, and the circles in the figure indicate the second, fourth, and
Represents 6 and 8 cylinders. The lower side represents the bank 1B, and the circles in the figure represent the first, third, fifth, and seventh cylinders from the left side. ) Also, in the figure, the cylinders indicated by ● are operating cylinders, and the cylinders indicated by ○ are inactive cylinders. In the embodiment according to the present invention, a plurality of combination patterns of operating cylinders are set according to the number of operating cylinders. Naturally, combinations of operating cylinders during partial cylinder operation are possible other than those shown in FIG. 4, but the embodiment according to the present invention adopts the combination pattern as shown in FIG. 4 in consideration of the following conditions. .

First, since the deactivated cylinder does not generate torque during the partial cylinder operation, the engine output torque drops at each time corresponding to the decommission stroke of the deactivated cylinder during one rotation cycle of the engine. Therefore, in order to avoid a large torque pulsation, it is preferable to consider the ignition sequence so that the torque drop due to the idle cylinders is dispersed as much as possible during one operating cycle of the engine. In the embodiment according to the present invention, engine ignition is performed as follows: 1st → 8th → 4th → 3rd →
Since the sixth cylinder, the fifth cylinder, the seventh cylinder, and the second cylinder are performed in this order, the combination of the deactivated cylinders is set so that the deactivated cylinders are dispersed as much as possible in this ignition order. FIG. 5 shows the positions of the idle cylinders in the engine ignition sequence in the operating cylinder combination pattern in the case of the 5-cylinder operation. As shown in FIG. 5, the idle cylinders in the pattern 1 (first, third, and seventh cylinders → shown in FIG. 5) and the idle cylinders in the pattern 2 (second, fourth, sixth cylinders → FIG. (Shown above) are also considered to be evenly distributed. Figure 5
Although only the case of 5-cylinder operation is shown in Fig. 4, the same consideration is given to the combination pattern in other operating cylinder numbers.

Further, in the embodiment according to the present invention, a combination pattern of a plurality of operating cylinders is provided for each operating cylinder number as shown in FIG. 4, for the reason described below. That is, in the embodiment according to the present invention, air is supplied to the idle cylinders even during the partial cylinder operation, but since combustion does not occur in the cylinders, this air is discharged to the exhaust pipe at a low temperature and the three-way catalyst 21 is discharged. Will pass through. For this reason, if the partial cylinder operation continues, the temperature of the deactivated cylinder will decrease, which may affect the durability of each part due to non-uniform engine temperature. The original catalyst 21 is cooled, and when the operation of the idle cylinder is restarted next time, the three-way catalyst is below the activation temperature, and there is a possibility that exhaust purification will not be performed on this catalyst until the temperature rises. . Therefore, in the embodiment according to the present invention, a plurality of patterns of combinations of the number of operating cylinders during the partial cylinder operation are provided, and the combination pattern of the operating cylinders is switched at predetermined time intervals during the partial cylinder operation, so that an excessive catalyst is used. It prevents cooling.

The operating cylinder combination pattern shown in FIG. 4 has the minimum required number of patterns that can evenly suspend all the catalysts and minimize the number of exhaust systems required by the above pattern switching. Has been done. That is, in the embodiment according to the present invention, as shown in FIG.
The seventh and seventh cylinders, and the second and sixth cylinders are set to operate and stop at the same time, respectively, and the operating cylinder combination pattern is set to these cylinders, as shown in FIG.
A common exhaust system is provided for each two cylinders to reduce the number of exhaust systems.

Next, the control of the bypass valve 7 during the partial cylinder operation of the embodiment according to the present invention will be described. As described above, it is necessary to increase the intake air amount supplied to the operating cylinders during the partial cylinder operation, but in the embodiment according to the present invention, it is necessary to increase the intake air amount of the entire engine in order to continue supplying the intake air to the idle cylinders. is there. In the embodiment according to the present invention, the opening amount of the throttle valve 6 is changed by increasing the opening amount of the bypass valve 7 in accordance with the decrease in the number of operating cylinders to increase the intake amount supplied through the bypass passage 7. Without increasing the intake amount.

Further, as described above, since the opening degree of the bypass valve is increased during the partial cylinder operation, if the engine brake state is maintained as it is, the negative pressure of the intake manifold rises even if the throttle valve 6 is fully closed. Without (the pressure of the intake manifold does not drop), the braking force of the engine brake cannot be obtained sufficiently. Therefore, in the embodiment according to the present invention, when the engine is braked during the partial cylinder operation, the opening amount of the bypass valve 7 is decreased to reduce the intake air amount as the number of operating cylinders at the start of the engine brake is reduced, so that the intake manifold has a sufficiently large negative impact. I try to generate pressure.

Further, after the engine braking is finished, it is necessary to open the bypass valve again to increase the intake flow rate.
Since the vehicle speed decreases during engine braking, the engine load condition after engine braking is different from that before engine braking, and the number of operating cylinders required may change. In the embodiment according to the present invention, after the engine braking is completed, the opening amount of the bypass valve 7 is increased as the number of operating cylinders is reduced in accordance with the number of operating cylinders required after completion of the engine braking, whereby the engine braking is performed. The partial cylinder operation according to the load state after the end can be promptly restored.

FIG. 6 is a table showing the operation amount of the bypass valve 7 (the number of driving steps of the step motor 71) at the time of switching the number of operating cylinders according to the embodiment of the present invention. In FIG. 6, the horizontal axis represents the number of operating cylinders (FX) before switching the number of operating cylinders, and the vertical axis represents the number of operating cylinders (FY) after switching. For example, if the eight-cylinder operation state (FX = 8) before the switching is changed to the five-cylinder operation state (FY = 5) after the switching, the step motor 71 causes the bypass valve to pass 3 × a steps. 7 is driven in the valve opening direction. Also, for example, before switching 6
If the cylinder operation state (FX = 6) is changed to the 7-cylinder operation state (FY = 7) after the switching, the step motor 71 causes the bypass valve 7 to close in the valve closing direction by 1 × a steps. Driven to. When the number of operating cylinders is the same before and after the switching (FX = FY), the operation amount of the step motor 71 is naturally zero, and the opening degree of the bypass valve 7 is not changed. Here, a is a constant value and is preset according to the type of engine.

As can be seen from FIG. 6, the opening degree of the bypass valve 7 is increased by a larger amount as the number of operating cylinders is decreased when the number of operating cylinders is decreased after the switching as compared with the state before the switching, and conversely. When the number of operating cylinders increases, the larger the number of operating cylinders, the greater the amount of decrease. Further, during engine braking, as described above, the smaller the number of operating cylinders at the start of engine braking, the larger the valve closing operation amount of the bypass valve 7 needs to be. However, in the embodiment according to the present invention, the step motor is closed at this time. The drive amount in the valve direction is, for example, 4 × a steps when operating with four cylinders, and 3 when operating with five cylinders.
Xa step, 2xa step during 6-cylinder operation, and 1xa step during 7-cylinder operation. That is, in the embodiment according to the present invention, the number of driving steps of the step motor 71 is set so that the opening degree of the bypass valve 7 during engine braking becomes equal to the opening degree during 8-cylinder operation (the minimum set opening degree of the bypass valve during normal operation). It is set.

7 to 15 show an example of a flowchart of the above control operation executed by the ECU 30. This routine is executed as part of the main routine of the ECU 30. 7 to 15, steps 703 to 737 (FIGS. 7 and 8) control the four-cylinder operation, and steps 903 to 937 (FIGS. 9 and 10).
Indicates the control during 5-cylinder operation, and steps 1103 to 1
137 (FIGS. 11 and 12), steps 1303 to 13
Reference numerals 37 (FIGS. 13 and 14) show controls during 6-cylinder operation and 7-cylinder operation, respectively. Also, steps 1505 to 1
Reference numeral 537 (FIG. 15) shows the control during 8-cylinder operation.

In FIG. 7, at step 701, the output speed of the automatic transmission 23, the output shaft speed NA, the air flow meter 8 of the engine intake air amount Q, and the engine speed sensor (not shown) of the engine speed N, respectively. It is read and the intake air amount Q / N per engine revolution is calculated. Next, at step 703, it is judged whether or not the current engine load condition is within the range where four-cylinder operation is performed, and if it is within the four-cylinder operation region, step 705.
The variable FY representing the number of operating cylinders after switching is set to 4, and the routine proceeds to step 706A. Here, the variable FY is the number of operating cylinders after the switching (in addition to step 703, step 903 in FIG. 9, step 1103 in FIG. 11, step 1303 in FIG. Is a variable that is set to the same number as 8 cylinders). That is, FY = 4 represents 4-cylinder operation, FY = 5 represents 5-cylinder operation, and FY = 6, 7, 8
Represents 6-cylinder, 7-cylinder, and 8-cylinder operation, respectively. Also,
The number of operating cylinders at the time of executing the previous routine (the number of operating cylinders before switching) is also set in step 725 (or steps 925, 1).
It is stored as a variable FX in any one of steps 125, 1325, and 1525).

It should be noted that the determination in step 703 as to whether or not it is in the 4-cylinder operating region is based on the operating region map of FIG.
It is judged using N and NA. Also, the relationship in FIG. 3 is Q /
It is stored in advance in the ROM of the ECU 30 as a two-dimensional map using N and NA. It should be noted that if the operation is not in the 4-cylinder operating range in step 703, the same determination is made in FIG. 9 as to the case of 5 cylinders in step 903, and if it is not applicable to the case of 5 cylinders, 6 cylinders in FIG. 11 and FIG. ,
Similar determinations are made for 7 cylinders,
If none of the above applies, it is determined to be in the 8-cylinder operating range (FIG. 15).

Next, at step 706A, it is judged if the values of the variables FX and FY are equal, and if FX = FY, the routine proceeds to step 707. If FX ≠ FY, the routine proceeds to step 706B, where it is judged whether or not the flag XDEC is reset (= “0”), and if it is reset, the routine proceeds to step 721 to bypass the normal condition. Valve actuation control is performed. On the other hand, step 706
If the flag XDEC is set (= “1”) in B, the process proceeds to step 707.

Here, XDEC is a flag indicating whether or not the bypass valve 7 is currently closed at the time of engine braking, and is set (=) in step 713 after execution of the closing operation of the bypass valve 7 described later. "1"). Step 7
Reference numerals 07 to 721 are steps showing the opening / closing operation control of the bypass valve 7. First, at step 707, it is judged from the output of the throttle opening sensor 6a whether or not the throttle valve 6 is fully closed. When the throttle valve 6 is not fully closed, the routine proceeds to step 715, where the flag XDEC is set (=
"1") is determined.

If the flag XDEC is reset (= "0") in step 715, it means that the engine is not being braked and the state immediately after the engine braking is finished.
In step 721, the operation control of the bypass valve at the normal time is performed. That is, in step 721, the driving step number ΔS of the step motor 71 is determined from the table shown in FIG. 6 using the number of operating cylinders before switching FX and the number of operating cylinders after switching FY. As a result, the opening degree of the bypass valve 7 increases as the number of operating cylinders decreases. As described above, when FX = FY, that is, when the number of operating cylinders has not changed since the last time the routine was executed, the number of drive steps ΔS of the step motor is set to zero as shown in FIG. The opening of 7 is not changed. The table of FIG. 6 is stored in the ROM of the ECU 30 as a two-dimensional map using FX and FY, and in step 721, ΔS is calculated using this map.
Is determined.

Steps 709 to 713 show the valve closing operation control of the bypass valve 7 during engine braking. When the throttle valve 6 is fully closed in step 707, it is determined in step 709 from the value of the flag XDEC whether or not the valve closing operation has already been performed, and if it has not been performed yet (XDEC = “ 0 "), the step number ∆S of driving the step motor is set to -4a (driving to the valve closing side) in step 711, and then the flag XDEC is set (=" 1 ") in step 713. That is, steps 709 to 713 are executed only once immediately after it is detected that the throttle valve 6 is fully closed, and the bypass valve 7 is closed. When the 5-cylinder operation is performed, ΔS is set to −3a at this time (FIG. 9, step 9).
11), -2a, and-when operating in 6 and 7 cylinders, respectively.
is set to a (FIG. 11, step 1111 and FIG.
3, step 1311). By performing this step,
During engine braking, the bypass valve 7 is driven to be closed more as the number of operating cylinders is smaller, so that the braking force during engine braking during partial cylinder operation is secured.

Steps 717 and 719 show the valve opening operation control of the bypass valve 7 after the end of engine braking. These steps are also executed only once when the engine brake ends and the throttle valve 6 is opened from the fully closed state. If the throttle valve 6 is not in the fully closed state in step 709 and the flag XDEC is set in step 715, the bypass valve 7 is closed until the last time and the intake air amount reduction during engine braking is executed. Since the throttle valve 6 has been opened this time, it means that it is in a state immediately after the engine braking is finished. Therefore, in this case, the process proceeds from step 715 to step 717, and the driving step number ΔS of the step motor 71 is set to 4a (driving to the valve opening side), and then step 71
At 9 the flag XDEC is reset (= "0"). In addition, when the 5-cylinder operation is performed, ΔS is 3 at this time.
a (FIG. 9, step 917), and is set to 2a and a, respectively, when operating in 6 and 7 cylinders (FIG. 11,
Step 1117 and FIG. 13, step 1317).

It should be noted here that the valve opening amount of the bypass valve 7 after the engine braking is finished is determined according to the number of operating cylinders (step 703) determined based on the operating region at the time of executing the routine this time. Should. That is, when the engine braking is started when the engine is operated with the other number of operating cylinders, and as a result, the four-cylinder operation region is entered because the load state of the engine is changed by the determination of FIG. 3, steps 703 to 705 are performed. , 706A, 706B, and 707, the routine proceeds to 715. Therefore, ΔS is 4a corresponding to the 4-cylinder operating state after the engine braking is completed.
Is set to. When the engine is braked, the bypass valve 7 is closed to the minimum set opening corresponding to 8-cylinder operation. Therefore, by opening the bypass valve 7 by ΔS = 4a, the bypass valve opening is in the 4-cylinder operating state. The opening corresponds to. The same applies to other operating cylinder numbers. (See FIG. 6) As described above, according to this routine, when the bypass valve is closed at the time of engine braking, and then the load state is changed and the number of operating cylinders is changed, the number of operating cylinders is immediately changed after the engine braking is finished. Bypass valve opening can be obtained,
Immediately after the end of engine braking, the output torque according to the load state at that time can be obtained. For this reason,
The relationship between the accelerator operation amount and the output torque before and after the engine braking is substantially the same, and there is no discomfort in driving, so the vehicle drivability during partial cylinder operation is improved.

Since the bypass valve is held at the minimum set opening during the 8-cylinder operation, the opening / closing operation of the bypass valve during engine braking is not performed during the 8-cylinder operation (FIG. 1).
5, steps 1505-1537). Next, after executing the above operation, steps 723 to 737 of FIG. 8 are executed. In FIG. 8, steps 723 to 737 are steps for changing the combination pattern of the operating cylinders described above.

First, at step 723, the above-mentioned variable FX
And FY are equal to each other is determined. If FX = FY, the 4-cylinder operation has been performed since the previous time, so the routine proceeds to step 727, where the counter CT representing the operation continuation time in the same operating cylinder combination pattern has a predetermined time T _0.
It is determined whether or not the above. The counter CT is counted up by an interrupt routine executed at regular time intervals shown in FIG. Where Δ in FIG.
T is the execution interval of the routine of FIG. Further, the predetermined time T ₀ of step 727 is the operation continuation allowable time in the same operating cylinder combination pattern for preventing the catalyst of the idle cylinder from being excessively cooled to below the activation temperature. T ₀ is generally set to about 5 to 20 seconds, but since this time varies depending on the type of catalyst and engine, it is preferable to determine it in advance by experiments or the like in detail.

If CT ≧ T ₀ in step 727, the operation duration time in the same operating cylinder combination pattern is longer than the allowable time, and the operating cylinder combination pattern needs to be changed, so that steps 729 to 73 are executed.
5 is executed. In steps 729 to 735, the variable X4 representing the working cylinder combination pattern in the four-cylinder operation is changed. Here, X4 = 1 is the pattern 1 at the time of 4-cylinder operation.
And X4 = 2 represents pattern 2 (see FIG. 4).
Further, in step 735, the counter CT is cleared,
The routine of FIG. 16 starts counting the operation duration time in the newly set working cylinder combination pattern.

Next, at step 737, the values of the flags J1 to J8 are set according to the operating cylinder combination pattern X4 set as described above. Here, the flags J1 to J8 are the fuel injection permission flags corresponding to the first cylinder to the eighth cylinder, respectively.
If 1X4 = 1 in 37, the flags J4, J6,
J1 and J7 are set (= "1"), and flags J2 and J are set.
8, J3 and J5 are reset (= "0"), and in the fuel injection time calculation routine separately executed by this,
The fuel injection time is calculated in the fourth, sixth, first, and seventh cylinders of the engine 1, and the fuel injection time is zero in the second, eighth, third, and fifth cylinders.
Since the fuel injection is stopped (fuel injection is stopped), the operating cylinder combination pattern 1 shown in FIG. Therefore, by executing steps 727 to 737, the working cylinder combination pattern is changed at regular intervals.

On the other hand, if FX ≠ FY in step 723, it means that the number of operating cylinders has been switched between when the previous routine was executed and when this routine was executed. It is necessary to set again based on the number of operating cylinders. Therefore, in this case, after the variable FX is set to the number of operating cylinders after switching (here, four cylinders) in step 725, step 727 is bypassed and steps 729 and thereafter are directly executed. As a result, the number of operating cylinders is switched.

Although the above description is for the case of four-cylinder operation, the same switching operation and pattern changing operation are also performed for 5, 6, 7-cylinder operation. Further, during the 8-cylinder operation, the flags J1 to J8 are all set (=
It is fixed to "1") (FIG. 15, step 1537).
The bypass valve actuation control during the four-cylinder operation and the switching control of the number of operating cylinders and the combination pattern of operating cylinders have been described above, but according to this routine, as shown in FIG. 9 to FIG. The same operation is performed during driving. Since each step of FIGS. 9 to 15 is substantially the same as that of FIGS. 7 and 8, detailed description thereof will be omitted here.

After the above operation corresponding to the number of operating cylinders is completed, in step 739, the step motor drive step number of the bypass valve 7 is output to a drive circuit (not shown) to drive the bypass valve. In the embodiment according to the present invention, the smaller the number of operating cylinders, the larger the step motor operating amount during engine braking. Therefore, the smaller the number of operating cylinders, the higher the driving speed of the step motor. Can be improved.

Next, the fuel injection control of the embodiment according to the present invention will be described. In the embodiment of the present invention, each exhaust pipe is provided with a three-way catalyst 21. As is well known, the three-way catalyst is an exhaust air-fuel ratio of the engine (here, the ratio of the air and the fuel supplied to the exhaust passage on the upstream side of the engine and the three-way catalyst is referred to as the exhaust air-fuel ratio. When secondary air or the like is not supplied, the exhaust air-fuel ratio is the ratio of the amount of intake air supplied to each cylinder of the engine to the fuel injection amount.) It is possible to simultaneously purify the three components of HC, CO, and NO _x . Therefore, in the case of a variable cylinder engine, it is necessary to accurately control the exhaust air-fuel ratio of the operating cylinders to near the stoichiometric air-fuel ratio even during partial cylinder operation. In an embodiment according to the invention,
By performing feedback control of the fuel injection amount to each cylinder based on the output signal of the O ₂ sensor 31 arranged in each exhaust pipe, accurate air-fuel ratio control is performed even during partial cylinder operation.

The feedback control of the air-fuel ratio performed based on the output signal of the O ₂ sensor 31 according to the embodiment of the present invention will be described with reference to FIGS. 17 to 19. In the embodiment according to the present invention, the air-fuel ratio control of each cylinder is independently performed by a similar method based on the output signal of each O ₂ sensor 31 arranged in the exhaust pipe connected to the cylinder. (However, since the fourth and sixth cylinders and the first and seventh cylinders have common exhaust pipes, the air-fuel ratio control of each of the two cylinders is performed based on the output signal of one O ₂ sensor 31). Therefore, in the following description, only the air-fuel ratio control of one cylinder (second cylinder) will be described, but in reality, similar air-fuel ratio control is individually performed for each cylinder. In addition,
In the following embodiments, the basic fuel injection time TAUP described later is corrected by the air-fuel ratio correction coefficient FAF so that the air-fuel ratio becomes the stoichiometric air-fuel ratio.

17 and 18 show an air-fuel ratio feedback control routine for calculating the air-fuel ratio correction coefficient FAF based on the output of the O ₂ sensor 31. This routine is executed by the ECU 30 at a predetermined time, for example, every 4 ms. It In step 1701, it is judged whether or not the closed loop (feedback) condition of the air-fuel ratio by the O ₂ sensor 31 arranged in the exhaust pipe 12 of the second cylinder is satisfied. For example, the closed loop condition is not satisfied when the cooling water temperature is equal to or lower than a predetermined value or during the engine start, and in other cases, the closed loop condition is satisfied. When the closed loop condition is not satisfied, the processing cycle is completed, and when the closed loop condition is satisfied, the process proceeds to step 1702.

At step 1702, O₂Of the sensor 31
Output V₁Are A / D converted and captured, then step
1703 is V₁Is the comparison voltage V_R1Below, for example, 0.45
Determines whether V or less, that is, whether the air-fuel ratio is lean
To be done. Air-fuel ratio is lean (V ₁≤V_R1) Then
Go to step 1704 to see if the delay counter CDLY is negative.
It is determined whether or not, and if CDLY> 0, step 170
After setting CDLY to 0 in step 5, to step 1706
move on. In step 1706, the delay counter CDL
Y is decremented by 1, and in steps 1707 and 1708
The delay counter CDLY is guarded by the minimum value TDL
It In this case, the delay counter CDLY has the minimum value TD.
When L is reached, in step 1709 the air-fuel ratio
The flag F1 is set to "0" (lean). The minimum value
TDL is a negative value.

On the other hand, if rich (V ₁ > V _R1 ), in step 1710 the delay counter CDL
Whether or not Y is positive is determined. If CDLY <0, then in step 1711 CDLY is set to 0, and then step 1
Proceed to 712. In step 1712, the delay counter CDLY is incremented by 1, and in steps 1713 and 1714, the delay counter CDLY is guarded by the maximum value TDR. In this case, when the delay counter CDLY reaches the maximum value TDR, the air-fuel ratio flag F1 is set to "1" (rich) in step 1715. In addition,
The maximum value TDR is a positive value.

Next, at step 1716 in FIG. 18, the air-fuel ratio flag F1 is inverted ("0" → "1" or "1" →
It is determined whether or not it has changed to "0". When the air-fuel ratio flag F1 is reversed, it is determined in step 1717 whether the air-fuel ratio is changed from rich to lean or lean to rich depending on the value of the air-fuel ratio flag F1. If it is the reversion from rich to lean, FAF is increased in a skip manner to FAF + RSR in step 1718, and conversely, if the reversion is from lean to rich, then step 17
At 19, FAF and FAF-RSL are reduced in a skip manner. That is, skip processing is performed.

When the sign of the air-fuel ratio club F1 is not reversed, integration processing is performed in steps 1720, 1721 and 1722. That is, in step 1720, it is determined whether or not F1 = "0". If F1 = "0" (lean), FAF is FAF in step 1721.
+ KIR is set, and if F1 = "1" (rich), FAF is set to FAF-KIL in step 1722. Here, the integration constants KIR and KIL are skip amounts RS
It is set sufficiently smaller than R and RSL.

Steps 1718, 1719, 1721,
The air-fuel ratio correction coefficient FAF calculated in 1722 is the minimum value in steps 1723 and 1724, for example, 0.
8 and at steps 1725 and 1726 at the maximum value, eg 1.2. This prevents the air-fuel ratio correction coefficient FAF from becoming too large or too small for some reason.

FIG. 19 is a timing chart for explaining the operation according to the flowcharts of FIGS. 17 and 18.
When the rich / lean air-fuel ratio signal A / F is obtained from the output of the O ₂ sensor 31 as shown in FIG. 19 (A), the delay counter CDLY is
It counts up in the rich state and counts down in the lean state. As a result, as shown in FIG. 19C, the delayed air-fuel ratio signal A / F ′ (corresponding to the flag F1) is formed. For example, even if the air-fuel ratio signal A / F changes from lean to rich at time t ₁ , the delayed air-fuel ratio signal A / F ′ is held lean for the rich delay time TDR and then at time t ₂ . Change to rich. Even the air-fuel ratio signal A / F at time t ₃ is changed from rich to lean, the delayed air-fuel-fuel ratio signal A / F 'is the time after being held rich only equivalent lean delay time (-TDL) t Change to lean at ₄ . However, if the air-fuel ratio signal A / F 'is inverted during the rich delay time TDR at times t ₅ , t ₆ , and t ₇ , the delay counter CDLY
Takes a long time to reach the maximum value TDR, and as a result, the delayed air-fuel ratio signal A / F ′ is inverted at time t ₈ . Therefore, the air-fuel ratio signal A / F 'after the delay processing is more stable than the air-fuel ratio signal A / F before the delay processing. In this way, the air-fuel ratio correction coefficient FAF shown in FIG. 19D is obtained based on the stable air-fuel ratio signal A / F 'after the delay processing.

FIG. 20 shows a fuel injection time calculation routine using the FAF value calculated as described above. This routine is executed by the ECU 30 at every predetermined crankshaft rotation angle (for example, every 360 degrees). Referring to FIG. 20, first, in step 2000, the value of the fuel injection permission flag set in FIGS. 7 to 15 is determined for the cylinder for which the calculation is performed. (Since FIG. 20 shows the calculation of the fuel injection time of the second cylinder, the value of the flag J2 is determined, but the values of the corresponding fuel injection permission flags are similarly determined for the other cylinders). If the fuel injection permission flag is reset (= "0"), this cylinder corresponds to a deactivated cylinder, and the following calculation is not performed, and step 2
The routine proceeds to step 005, where the fuel injection time TAU is set to zero, and the routine is immediately terminated. As a result, fuel injection in this cylinder is stopped. If the permission flag is set (= “1”) in step 2000, step 200
Calculations of 1 or less are performed. In step 2001, the basic fuel injection amount TAU is calculated from the intake air amount Q and the engine speed N.
P (= α · Q / N) is calculated (α is a constant). Here, the basic fuel injection time TAUP is the fuel injection time (amount) required to obtain the stoichiometric air-fuel ratio.

Next, at step 2002, the warm-up increasing coefficient FWL is calculated based on the engine cooling water temperature Tw.
Note that the relationship between the engine cooling water temperature Tw and the warm-up increase coefficient FWL shown in step 2002 is stored in advance in the ROM of the ECU 30.
It is stored in. Next, at step 2003, the fuel injection time TAU is calculated based on the following equation. TAU = TAUP * FAF * (FWL + [beta]) + [gamma] where [beta] and [gamma] are correction coefficients determined by the operating condition. Next, at step 2004, the fuel injection time TAU
Is output to the output port, and fuel is injected from each fuel injection valve 3a based on this fuel injection time TAU.

As described above, in the embodiment according to the present invention, the basic fuel injection time TAUP is determined based on the intake air amount Q and the engine speed N of the entire engine regardless of the number of operating cylinders. In the embodiment according to the present invention, since the intake air is supplied to the idle cylinder even during the partial cylinder operation, if the intake air amount supplied to the operating cylinder during the partial cylinder operation is increased, the intake air amount supplied to the idle cylinder also increases accordingly. To do. Therefore, the intake air amount of the entire engine becomes an amount proportional to the intake air amount of the operating cylinder even during the partial load operation. Therefore, as described above, regardless of the number of operating cylinders, by determining TAUP based on the intake air amount of the entire engine, it is possible to set the basic fuel injection time TAUP that accurately corresponds to the intake air amount of the operating cylinders.

Further, in reality, between the idle cylinder and the operating cylinder,
May cause slight inhomogeneity in intake distribution
In this case, the intake air amount of the operating cylinder is
Since it is not exactly proportional to the intake air amount Q of the whole
The basic fuel injection time TAUP is set as described above.
And there is a possibility that an accurate stoichiometric air-fuel ratio cannot be obtained. Shi
However, in the embodiment according to the present invention, as shown in FIGS.
As you can see, the exhaust pipe O ₂Based on the output signal of the sensor 31
The actual fuel injection amount using the air-fuel ratio correction coefficient determined by
Since TAU is calculated, it is between the active cylinder and the idle cylinder.
Even if the intake distribution is uneven,
The amount is O of the exhaust pipe₂Corrected according to the output signal of the sensor
The air-fuel ratio is always kept near the stoichiometric air-fuel ratio. Therefore,
The three-way catalyst in the exhaust passage functions normally even during partial cylinder operation.
Therefore, it is necessary to maintain good exhaust characteristics during partial cylinder operation.
You can

[0054]

As described above, according to the present invention, the opening degree of the bypass valve is closed to a greater extent as the number of operating cylinders is reduced during engine braking during the partial cylinder operation of the variable cylinder engine.
When the engine brake is finished, the valve opening operation is made larger as the number of operating cylinders is smaller, so that the braking force at the time of engine braking can be secured and the engine output torque according to the load state can be obtained after the engine brake is finished. The effect of improving vehicle drivability during partial cylinder operation can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of the present invention.

FIG. 2 is an overall view of an embodiment of a variable cylinder engine to which the present invention is applied.

FIG. 3 is a diagram showing a relationship between a load state and the number of operating cylinders.

FIG. 4 is a diagram illustrating a combination pattern of operating cylinders during partial cylinder operation.

FIG. 5 is a diagram showing positions in an ignition sequence of idle cylinders during a 5-cylinder operation.

FIG. 6 is a diagram showing a drive amount of a step motor when switching the number of operating cylinders.

FIG. 7 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 8 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 9 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 10 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 11 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 12 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 13 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 14 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 15 is a part of a flowchart showing a routine for bypass valve operation control and operating cylinder number control.

FIG. 16 is a flowchart showing a time interruption routine.

FIG. 17 is a part of a flowchart showing an air-fuel ratio feedback control routine.

FIG. 18 is a part of a flowchart showing an air-fuel ratio feedback control routine.

FIG. 19 is a time chart for supplementary explanation of the control of FIGS. 17 and 18.

FIG. 20 is a flowchart showing a fuel injection time calculation routine.

[Explanation of symbols]

1 ... Engine 3a ... Fuel injection valve 4 ... Intake pipe 5 ... Throttle bypass passage 6 ... Throttle valve 6a ... Throttle opening sensor 7 ... Bypass valve 11, 14 ... Exhaust pipe 12, 13, 15, 18 ... Exhaust pipe 21 ... Three Source catalyst 30 ... ECU 31 ... O ₂ sensor 71 ... Step motor

Continuation of front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical indication location F02D 41/02 315 8011-3G (72) Inventor Toyokazu Umebana 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Corporation Stock In-house (72) Inventor Toshiaki Asada 1 Toyota-cho, Toyota-shi, Aichi Toyota Motor Co., Ltd.

Claims (1)

[Claims] 1. A number-of-operating-cylinders control means for controlling the number of operating cylinders of the engine by stopping fuel supply to some of the cylinders according to an engine operating state, and an opening of a throttle valve arranged in an engine intake passage. A throttle opening detecting means for detecting the bypass valve, a bypass passage for bypassing the throttle valve to supply intake air to the engine, a bypass valve provided in the bypass passage, and an opening of the bypass valve for adjusting the bypass opening. A bypass control means for controlling the amount of intake air flowing through the passage, wherein the bypass control means increases the opening degree of the bypass valve as the number of operating cylinders of the engine decreases,
When it is detected by the throttle opening detection means that the throttle valve has changed from the opened state to the fully closed state,
When the number of operating cylinders is smaller, the bypass valve is closed by a predetermined amount that is set larger, and when the throttle opening detection means detects that the throttle valve has changed from the fully closed state to the open state, the operation is performed. A control device for a variable cylinder engine that opens the bypass valve by a predetermined amount that is set larger as the number of cylinders is smaller.