JP2004076677A - Variable cylinder control for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the torque fluctuation when changing the number of operating cylinders outputting power in an internal combustion engine having a plurality of cylinders. <P>SOLUTION: The internal combustion engine has a variable valve mechanism capable of adjusting the intake quantity of each cylinder by controlling the opening period of an intake value. The range of a realizable load ratio is determined for before and after changing the number of operating cylinders by controlling the opening period in a state where the negative pressure of an intake pipe is held at a constant pressure such as atmospheric pressure. The area A where the both are overlapped is set in a changeable area of cylinder number. A control unit changes the cylinder number when the operating state of the internal combustion engine is in this area. In order to keep the output from the internal combustion engine constant, the change of intake quantity required for the change of cylinder number is realized by the control of the opening period. The intake quantity of each cylinder can be rapidly changed, and the torque fluctuation in the change of cylinder number can be suppressed. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a variable cylinder control that changes the number of working cylinders that output power in an internal combustion engine having a plurality of cylinders.
[0002]
[Prior art]
Regarding the operation of an internal combustion engine having a plurality of cylinders, variable cylinder control has been proposed in which the number of working cylinders that output power is switched according to the operating state of the internal combustion engine. In the internal combustion engine, when the load on each cylinder is low, fuel efficiency tends to deteriorate. Variable cylinder control is a technique for improving fuel efficiency by reducing the number of cylinders and increasing the load per cylinder when the required load of the internal combustion engine is relatively low.
[0003]
Regarding variable cylinder control, various control methods have been proposed for reducing torque shock when the number of cylinders is changed. For example, Japanese Patent Laying-Open No. 5-1579 discloses a technique for correcting the throttle opening when changing the number of cylinders. Japanese Patent Laying-Open No. 7-217463 discloses a technique for gradually changing the valve opening characteristic when the number of cylinders is changed in an internal combustion engine having a mechanism capable of controlling the valve opening characteristic of an intake valve for each cylinder. Further, a technique for suppressing torque shock by controlling the ignition timing when changing the number of cylinders has been proposed (for example, JP-A-5-332172, JP-A-10-103097, JP-A-6-193478). Gazette).
[0004]
[Problems to be solved by the invention]
However, in the related art, there is room for further improvement in torque shock when the number of cylinders is changed. An object of the present invention is to suppress the torque shock or the influence of the torque shock when changing the number of cylinders by a control method different from the conventional method.
[0005]
[Means for Solving the Problems and Their Functions and Effects]
In the first control of the present invention, a plurality of cylinders, a variable valve mechanism capable of controlling the opening characteristics of the intake valves for each cylinder, and an intake air amount of each cylinder regardless of the opening characteristics of the intake valves. An internal combustion engine having an intake control means capable of controlling the pressure is controlled. In such an internal combustion engine, when changing the number of working cylinders that output power among a plurality of cylinders, in order to achieve the required rotation speed and the required load of the internal combustion engine, the intake air amount of each cylinder is changed before and after the change. There is a need. In the first control, the change in the intake air amount can be realized only by changing the valve opening characteristics of the intake valve in the range of the rotational speed and the load (hereinafter, such an operation region is referred to as a “switchable region”). Execute the change in the number of working cylinders. With this configuration, the intake amount required after the change in the number of cylinders can be quickly realized by the variable valve mechanism having sufficiently high responsiveness, so that the torque shock accompanying the change in the number of cylinders can be suppressed.
[0006]
Note that the valve opening characteristics can be specified by parameters that affect the amount of intake air, such as the opening period during which the intake valve is open and the amount of opening of the intake valve, among the parameters that indicate the open state of the intake valve. . The intake control means includes, for example, a throttle valve for controlling a negative pressure in the intake pipe, a supercharger for pressurizing the intake pipe, and the like.
[0007]
The switchable area can be set, for example, by the following method. First, in a state where the number of cylinders is large, by adjusting only the valve opening characteristic without depending on the valve opening characteristic of the intake valve, a load range in which the intake air amount can be controlled while the intake pipe negative pressure is kept constant (hereinafter, referred to as “ A "multi-cylinder load range" is obtained for each rotation speed. Next, in a state where the number of cylinders is small, the load range in which the control of the intake air amount can be realized only by adjusting the valve opening characteristics while maintaining the intake pipe negative pressure equal to the load range at the time of multiple cylinders (hereinafter, referred to as the load range) "Reduced cylinder load range" is obtained for each rotation speed. Then, an overlapping portion between the multi-cylinder load range and the reduced-cylinder load range is set as a switchable region. When the intake pipe negative pressure can be controlled by the throttle valve, such a switchable region may be obtained for each of various operating conditions using the intake pipe negative pressure as a parameter.
[0008]
The switchable region can thus be determined for various intake pipe negative pressures. In this case, it is preferable to apply the region set under the condition that the inside of the intake pipe to the cylinder is at atmospheric pressure. When the inside of the intake pipe is at atmospheric pressure, the influence on the intake pipe negative pressure by the change in the number of cylinders and the change in valve opening characteristics is relatively small, and the intake air amount can be controlled stably. The switchable region only needs to be set when the inside of the intake pipe is at atmospheric pressure, and does not necessarily need to be set when the throttle valve is fully open.
[0009]
When the switchable area is set according to the negative pressure of the intake pipe, the switchable area widens and narrows according to the negative pressure. Therefore, the negative pressure of the intake pipe may be controlled first so that the required rotational speed and the required load fall within the switchable range, and after entering the switchable range, the number of cylinders may be changed. The negative pressure of the intake pipe can be controlled by, for example, the opening of the throttle valve. By properly using a plurality of switchable areas in this way, it is possible to suppress torque shock at the time of switching in a wide range of operating conditions.
[0010]
In the first control, for example, the number of cylinders can be changed by controlling the valve opening characteristics and the fuel injection amount according to the required rotation speed and the required load while fixing the opening of the throttle valve. . According to this control, the amount of intake air is controlled by the valve opening characteristics while the intake pipe negative pressure is kept substantially constant, so that torque shock when the number of cylinders is changed can be suppressed.
[0011]
According to the second control of the present invention, first, the negative pressure of the intake pipe is controlled according to the required rotational speed and the required load so as to realize the required intake air amount of each cylinder after the number of working cylinders is changed. Then, the valve opening characteristics of the intake valves of each cylinder are controlled so as to compensate for the response delay in the control of the negative pressure. Since the valve opening characteristic has higher response than the intake pipe negative pressure, the torque shock caused by the negative pressure response delay can be suppressed by such control.
[0012]
In the second control, the ignition timing of each cylinder may be controlled so as to compensate for the response delay. In this case, for example, it is preferable to use the compensation based on the valve opening characteristic preferentially over the compensation based on the ignition timing from the viewpoints of combustion stability, control accuracy, and a compensable range.
[0013]
The third control of the present invention controls an internal combustion engine mounted on a moving body and having a plurality of cylinders. It does not matter whether a variable valve mechanism is provided. The moving object includes, for example, a vehicle, a ship, an aircraft, and the like. In such an internal combustion engine, in the third control, first, it is determined whether the operating state of the internal combustion engine satisfies a predetermined condition for changing the number of working cylinders, and whether the moving body is accelerating or decelerating. Determine whether or not. Then, the number of working cylinders is changed only during acceleration or deceleration. By changing the number of cylinders in synchronization with acceleration or deceleration in this way, even if a torque shock occurs at the time of the change, it is possible to reduce the discomfort given to the occupant of the moving body.
[0014]
In the fourth control of the present invention, for example, when the moving body is accelerating, the number of cylinders is changed, for example, at a timing when the combustion stroke of the working cylinder is continuous before and after the number of cylinders is changed. Conversely, when the moving body is decelerating, for example, the number of cylinders is changed at a timing at which the combustion stroke of the working cylinder and the combustion stroke of the stopped cylinder are continuous before and after the change in the number of cylinders. By selecting the switching timing in this way, the change in output of each cylinder that occurs at the time of switching follows the acceleration or deceleration sensation, and the discomfort of the occupant can be reduced.
[0015]
In the present invention, regardless of which of the first to fourth controls is applied, the number of cylinders is changed at the timing of starting the control for any one of the cylinders for which both the fuel injection amount and the valve opening characteristic are not set. Is preferred. For example, when the condition for switching the number of cylinders is satisfied at the time when the fuel injection amount is set for any one of the cylinders, the cylinder is operated under the condition before the change in the number of cylinders, and then the fuel injection amount or the like is changed. It is preferable to apply the changed condition from the cylinder in which is set. Since the output required for each cylinder differs before and after the change in the number of cylinders, and the intake amount, fuel injection amount, etc., differ, the conditions are changed from the start of control for cylinders for which both the fuel injection amount and intake valve are not set. By doing so, unstable combustion can be avoided.
[0016]
The present invention can be configured in various modes such as an internal combustion engine control device for realizing the above-described control, an internal combustion engine provided with such a control device, and a control method for an internal combustion engine. In addition, the above-described first to fourth controls can be appropriately combined and applied. For example, the second control and the third control may be used in an operation state in which switching by the first control cannot be performed. By applying different controls, the number of cylinders can be changed in a wide range of operating conditions.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described in the following order.
A. Device configuration:
B. Cylinder number change control:
C. Second embodiment:
D. Modification:
[0018]
A. Device configuration:
FIG. 1 is an explanatory diagram showing an engine system as an embodiment. The engine system according to the present embodiment includes a four-cylinder gasoline engine mounted on a vehicle and a control unit 100 that controls the operation of the engine. In the figure, for convenience of description, symbols # 1 to # 4 are given to each cylinder of the gasoline engine.
[0019]
The control unit 100 is configured as a microcomputer including a CPU, a RAM, and a ROM inside. The CPU controls the operation of the gasoline engine by software according to a program provided in the ROM. Various signals are input to and output from the control unit 100 to perform this control. In the figure, only representative ones are shown. The input signal includes an accelerator pedal depression amount detected by the accelerator opening sensor 21, an engine speed detected by the speed sensor 23, and the like. The output signal will be sequentially described together with the configuration of the engine.
[0020]
The structure of the engine will be described using the cylinder # 1 as an example. The engine outputs power by burning fuel in the combustion chamber. The intake pipe 17 for sucking air into the combustion chamber is provided with an intake valve 11. Air is introduced into the combustion chamber while the intake valve 11 is open. In this embodiment, the opening and closing of the intake valve 11 is controlled by the actuator 14 based on a control signal from the control unit 100.
[0021]
The intake pipe 17 is provided with an injector 16 for injecting fuel. In this embodiment, a port injection type engine that injects fuel into the intake pipe 17 is illustrated, but a so-called direct injection type engine may be used. The control unit 100 controls the injector 16 according to the intake air amount, and injects an appropriate amount of fuel so that normal combustion is performed.
[0022]
An ignition plug 13 is provided in the combustion chamber. The mixture of fuel and air is compressed by the spark plug 13 after being compressed in the combustion chamber. The control unit 100 controls the ignition timing according to the engine speed, the required load, and the like.
[0023]
The exhaust gas after the combustion is discharged from the exhaust pipe 18. The exhaust pipe 18 is provided with the exhaust valve 12. The opening and closing of the exhaust valve 12 is controlled by the actuator 15.
[0024]
Although illustration is omitted to avoid complication, the cylinders # 2 to # 4 have the same structure as # 1.
[0025]
The power output from the engine varies depending on the amount of intake air to the combustion chamber. In this embodiment, the intake air amount is controlled by two methods. One is a negative pressure of the intake pipe 17. The intake pipes # 1 to # 4 are connected upstream to the intake manifold. A throttle valve 22 is provided in the intake manifold. When the control unit 100 controls the opening of the throttle valve 22, the negative pressure of the intake pipe fluctuates, and the intake air amount fluctuates. For example, when the throttle valve 22 is almost fully open, the pressure in the intake pipe becomes the atmospheric pressure, and the intake air is easily taken into the combustion chamber, so that the intake amount increases. When the throttle valve 22 is throttled, the pressure in the intake pipe becomes a negative pressure lower than the atmospheric pressure, so that the amount of intake air to the combustion chamber is suppressed. In the control of the engine, the term "intake pipe negative pressure" which generally means the difference between the pressure in the intake pipe and the atmospheric pressure is used. In order to avoid the misunderstanding of the control, the contents of the control will be described using "intake pipe pressure".
[0026]
In this embodiment, the amount of intake air can be controlled not only by the opening degree of the throttle valve 22 but also by the period during which the intake valve 11 is open. FIG. 2 is an explanatory diagram showing the operation of the intake valve and the exhaust valve. The period during which each valve is open is shown using the crank angle. The period from the state where the piston is at the top dead center (TDC) to the time when it rotates clockwise in the drawing and reaches the bottom dead center (BDC) corresponds to the intake stroke. A period from BDC to TDC corresponds to an exhaust stroke. The period during which the exhaust valve is open is in the range indicated by the solid arrow in the figure, and is fixed in this embodiment.
[0027]
The period during which the intake valve is open is the range indicated by the white arrow in the figure. Hereinafter, this range is referred to as a working angle. As shown by the solid line and the broken line in the figure, in the present embodiment, the magnitude of the operating angle can be changed by controlling the actuator 14. The timing at which the intake valve starts to open, that is, the phase can also be changed. When the operating angle is large, the effective intake stroke becomes substantially longer, so that the intake amount increases. When the operating angle is small, the effective intake stroke is substantially shortened, so that the intake amount is reduced.
[0028]
The control of the intake air amount by the throttle opening is characterized by relatively low response. This is because even if the throttle opening is changed, there is a time delay before the intake pipe pressure changes. On the other hand, the control of the intake air amount by the operating angle has a characteristic that the response is extremely high. The intake air amount can be controlled not only by the operating angle but also by the lift-up amount of the intake valve. Hereinafter, in the embodiment, the case where the control based on the operating angle is performed will be exemplified. However, the lift-up amount may be controlled instead of or together with the operating angle.
[0029]
In this embodiment, two operating states are switched according to the load required for the engine having the structure described above. One is an operation state in which combustion is performed in all four cylinders to output power (hereinafter, referred to as “all cylinder operation”), and the other is combustion in only two cylinders to output power. (Hereinafter, referred to as “reduced cylinder operation”). During the reduced-cylinder operation, fuel is supplied and ignited to two cylinders that output power (hereinafter, referred to as working cylinders). For the remaining two cylinders (hereinafter referred to as idle cylinders), fuel supply is stopped and ignition is not performed. In the present embodiment, reduced cylinder operation is performed with cylinders # 2 and # 3 being idle cylinders and # 1 and # 4 being working cylinders. The idle cylinder and the working cylinder may be changed according to the operating state and the like.
[0030]
B. Cylinder number change control:
The control unit 100 switches between the all-cylinder operation and the reduced-cylinder operation with reference to a map prepared in advance. FIG. 3 is an explanatory diagram illustrating a switching map. As shown in the lower part of the figure, in the present embodiment, the map defines a region to be switched in relation to the engine speed and the load factor.
[0031]
The definition of the load factor is shown at the top of the figure. As illustrated, the torque output from the engine varies according to the rotation speed. A curve UL4S indicates the maximum torque during all-cylinder operation. A curve UL2S indicates the maximum torque during the reduced cylinder operation. The load factor is a ratio to the maximum torque during all-cylinder operation. For example, in the case of the rotation speed Ne, assuming that the maximum torque during the all-cylinder operation is T4 and the maximum torque during the reduced-cylinder operation is T2, the load factor during the reduced-cylinder operation is T2 / T4. Since the maximum output is substantially proportional to the number of cylinders, the load ratio of the maximum torque during the reduced cylinder operation is about 50%. Similarly, various torques output from the engine can be converted into a load factor by dividing by the value of the curve UL4S at each rotation speed.
[0032]
Next, a method of setting a switching map will be described. Consider a case where the load ratio is reduced from the maximum torque at a constant rotation speed during all-cylinder operation. As described above, the torque can be controlled by the opening degree of the throttle valve 22 and the operating angle of the intake valve 11. At the time of output of the maximum torque, the throttle valve 22 is almost fully opened, and the operating angle is also the maximum. From this state, the load ratio can be reduced by fixing the intake pipe pressure and gradually reducing the operating angle. The load factor obtained when the operating angle reaches the minimum value is indicated by a straight line L4 in the figure. The load factor smaller than the straight line L4 is realized by reducing the opening of the throttle valve 22. That is, the straight line L4 is a boundary between a region where the load ratio can be controlled only by the operating angle and a region where the load ratio can be controlled by changing the intake pipe pressure by the opening degree of the throttle valve 22. It becomes. In other words, this boundary means a load factor obtained in a state where the operating angle is minimum under the condition that the intake pipe pressure is constant.
[0033]
A similar boundary L2 is obtained also during the reduced cylinder operation. During the reduced cylinder operation, as shown by the straight line UL2S, an output-capable upper-limit load factor is obtained near 50%. In the present embodiment, the area A surrounded by the boundary lines L4, L2, and UL2S thus obtained is set as the switchable area. This region is a region where the load ratio can be controlled only by the operating angle in both the full cylinder operation and the reduced cylinder operation.
[0034]
Such a region can be defined not only when the intake pipe pressure is at the atmospheric pressure. When the intake pipe pressure is lower than the atmospheric pressure, the boundary line during the all-cylinder operation shifts from L4 to L4a on the low torque side. Similarly, the boundary line during the reduced cylinder operation shifts from L2 to L2a on the low torque side. At the same time, the maximum load factor during the reduced cylinder operation also shifts to the broken line in the figure. Therefore, when the intake pipe pressure is lower than the atmospheric pressure, the area B becomes a new area in which the load factor can be controlled only by the operating angle. On the other hand, the portion above the broken line in the region A is a region that cannot be realized. Thus, the switchable region can be determined according to the intake pipe pressure. In general, it can be seen that, as the intake pipe pressure decreases, the switchable region expands toward the low torque and high rotation speed side.
[0035]
FIG. 4 is a flowchart of the cylinder control process. This is a process that the CPU of the control unit 100 repeatedly executes during the operation of the engine while referring to the map shown in FIG. This process is a process for changing the number of cylinders according to the operating state of the engine, and the control for outputting the required number of revolutions and load during the all-cylinder operation and the reduced-cylinder operation is separately performed. Done. The control of the intake amount, the fuel injection amount, the ignition timing, and the like for performing the desired output is a well-known technique, and thus the description is omitted.
[0036]
In this process, first, the control unit 100 inputs the required engine speed and load (step S10). The required rotation speed can use the output value of the rotation speed sensor 23, and the required load can be set based on the accelerator opening.
[0037]
Next, the control unit 100 determines whether the number of cylinders can be changed (step S12). The map shown in FIG. 3 is used for this determination. The map is also shown in the figure. As described above, the switchable region is set according to the intake pipe pressure. Here, three stages of the intake pipe pressures θ1, θ2, and θ3 are illustrated. At the intake pipe pressure θ1, the throttle is almost fully opened, and the inside of the intake pipe is at atmospheric pressure.
[0038]
The switchable region for the intake pipe pressure θ1 is a region A hatched in the figure. When the required rotational speed and the required load (hereinafter, both are collectively referred to as “operating points”) are present in the region A (for example, point P1 in the drawing), the control unit 100 determines that the number of cylinders should be switched. . Similarly, when the operating point corresponds to the point P2, the control unit 100 determines that the switching should be performed in a state where the intake pipe pressure is reduced to θ2. It is determined that the operation point P3 should be switched while the intake pipe pressure is reduced to θ3. On the other hand, if the requested operation state does not exist in the switchable area in the map, control unit 100 determines that the number of cylinders should not be switched.
[0039]
If the determination that the number of cylinders should be switched is made during the all-cylinder operation, the control unit 100 determines that the switching to the reduced-cylinder operation should be performed. If the determination that the all-cylinder operation should be performed is made during the reduced-cylinder operation, the control unit 100 determines that the switching to the all-cylinder operation should be performed. In order to avoid frequent switching of the number of cylinders, hysteresis may be appropriately provided for the determination of the switching. In addition, the determination may be made in consideration of another condition such as a change in the previous operation state, in addition to whether the operation state exists in the switchable region.
[0040]
In the present embodiment, a case is described in which a map is prepared for three stages of intake pipe pressures. However, only a map for the intake pipe pressure θ1, that is, a map for fully opening the throttle may be used. A map may be prepared for three or more stages of intake pipe pressure.
[0041]
When it is determined that the number of cylinders should be changed (step S14), the control unit 100 controls the intake pipe pressure based on the throttle opening and the operating angle while maintaining the number of working cylinders and the torque (step S16). ). When the switching is performed at the operating point P1, before switching the number of cylinders, the intake pipe pressure is set to θ1, the operating angle is controlled, and the state at the operating point P1 is achieved. Similarly, at the time of switching at the operating point P2, the intake pipe pressure is set to θ2, and at the time of switching at the operating point P3, the intake pipe pressure is set to θ3. Here, in order to suppress the torque shock accompanying the control of the intake pipe pressure, it is preferable that the throttle opening and the operating angle are changed sufficiently slowly. When the change of the intake pipe pressure is achieved, the control unit 100 changes the number of cylinders (step S18), and ends the cylinder number control process. When it is determined that the number of cylinders should not be changed (step S14), the control of the throttle opening and the change of the number of cylinders are skipped.
[0042]
FIG. 5 is a flowchart of the cylinder number changing process. This is processing corresponding to step S18 of the cylinder control processing (FIG. 4). When switching the number of cylinders, it is necessary to change parameters such as the intake air amount and the fuel injection amount for each cylinder before and after the switching. The control unit 100 sets a cylinder for changing these parameters (hereinafter, referred to as a switching cylinder) (step S20). As the switching cylinder, a cylinder in which both the fuel injection amount and the intake amount, that is, the operating angle is not set is selected.
[0043]
The method for selecting the switching cylinder is also shown in the figure. In the present embodiment, it is assumed that the engine is configured to perform combustion in the order of # 1, # 3, # 4, and # 2. Although not shown, the combustion stroke is performed immediately before the exhaust stroke. Fuel is injected into the intake pipe of each cylinder in synchronization with the combustion stroke and the exhaust stroke.
[0044]
Assume that it is determined that the number of cylinders should be switched in the section D1 until the injection amount is calculated for the cylinder # 4. At this point, as shown, the cylinder # 1 has already entered the intake stroke, and the fuel injection is being performed in the cylinder # 3. Therefore, for these cylinders, the fuel injection amount and the intake amount cannot be set under the conditions after the change in the number of cylinders. Therefore, the control unit 100 sets the # 4 cylinder in which these parameters are not set as the switching cylinder. Similarly, in the section D2 until the injection amount of # 2 is calculated, the cylinder of # 2 is set as the switching cylinder. In section D3, cylinder # 1 is set as the switching cylinder, and in section D4, cylinder # 3 is set as the switching cylinder.
[0045]
When the switching cylinder is set, the control unit 100 sets the parameters, that is, the fuel injection amount and the operating angle (Step S21). For the cylinders after the switching cylinder, parameters are set using the load required for each cylinder in the state after the change in the number of cylinders. For the cylinders before the switching cylinder number, the parameters are set using the load required for each cylinder in the state before the cylinder number change.
[0046]
For example, consider the processing in the section D1. Since the switching cylinder is # 4, for # 4, the parameters are calculated under the changed conditions. After the change, if the cylinders # 2 and # 3 are stopped and the reduced cylinder operation is performed, the load required for the cylinder # 4 becomes twice as large as that before the change. Conversely, if the operation is switched from the reduced cylinder operation to the all-cylinder operation, the load required for the cylinder # 4 becomes half that before the change. On the other hand, for # 3 which is burned before the switching cylinder, since the fuel injection amount has already been determined, the operating angle is determined under the condition before the change.
[0047]
When the parameters are set in this way, the control unit 100 controls the fuel injection amount and the operating angle of each cylinder (Step S22). As a result, the number of cylinders is changed after the operation of the switching cylinder. At the time of switching to the reduced cylinder operation, the intake cylinders # 1 and # 4, which are working cylinders, are subjected to intake and fuel injection for obtaining an output twice as large as that of the full cylinder operation, and the cylinders # 2 and # 2 which become idle cylinders. The fuel supply to 3 is stopped. At the time of switching to all-cylinder operation, fuel supply to # 2 and # 3, which have been idle cylinders, is started. Intake and fuel injection for obtaining output are performed.
[0048]
According to the embodiment described above, the number of cylinders is changed in a region where the intake air amount can be controlled only by the operating angle of the intake valve. Therefore, the intake air amount of each cylinder can be changed with good responsiveness before and after the change in the number of cylinders, so that torque shock at the time of switching can be suppressed.
[0049]
C. Second embodiment:
FIG. 6 is a flowchart of a cylinder control process according to the second embodiment. The configuration of the device to be controlled is the same as that of the first embodiment (FIGS. 1 and 2), and a description thereof will be omitted. The first embodiment exemplifies a case in which the number of cylinders is changed within a switchable region in which the intake air amount can be controlled only with a high response angle. The second embodiment exemplifies a control in which the number of cylinders is switched irrespective of the switchable range, and a torque shock accompanying the switching is compensated by the operating angle and the ignition timing.
[0050]
When the control process is started, the control unit 100 inputs a required rotation speed and a load (Step S30). Then, it is determined whether the number of cylinders needs to be changed based on a preset switching map (step S32). The map for switching is illustrated in the figure. In this embodiment, the area A1 in which the reduced cylinder operation is to be performed is set according to the rotation speed and the load factor. Unlike the first embodiment, the area A1 may be set regardless of whether the intake air amount can be controlled only by the operating angle.
[0051]
Consider a case where the operating point of the engine shifts from P1 to P2. According to the map, the reduced-cylinder operation is to be performed at the operation point P1, and the all-cylinder operation is to be performed at the operation point P2. At this point, it is determined that switching from reduced cylinder operation to all cylinder operation should be performed. Conversely, when shifting from the operating point P2 to P1, when the boundary point P is reached, it is determined that switching from all-cylinder operation to reduced-cylinder operation should be performed. Hysteresis may be provided to avoid frequent switching.
[0052]
In this way, when it is determined that the change in the number of cylinders is unnecessary (step S14), the control unit 100 performs the following process for changing the number of cylinders (step S18), and ends the cylinder number control process. If it is determined that the change in the number of cylinders is not necessary (step S14), the processing for changing the number of cylinders is skipped, and the processing for controlling the number of cylinders ends.
[0053]
FIG. 7 is a flowchart of the cylinder number changing process. This is processing corresponding to step S18 in FIG. In the present embodiment, the number of cylinders is changed while the vehicle is accelerating or decelerating, thereby suppressing a passenger from experiencing a torque shock generated at the time of the change. Therefore, the control unit 100 determines whether the vehicle is operating at a constant speed (step S40). The constant speed operation means that the change in vehicle speed is so small that it can be regarded as substantially constant speed. If it is determined that the vehicle is operating at a constant speed, the control unit 100 skips the process of step S41, but changes the number of cylinders and ends the process. Switching of the number of cylinders may be performed in any one of the cylinders.
[0054]
When the vehicle is not operating at a constant speed, that is, when the vehicle is accelerating or decelerating (step S40), the control unit 100 sets the switching cylinder (step S41). In the present embodiment, the switching cylinder is set so that the torque shock generated when the number of cylinders is switched follows the experience of acceleration or deceleration. This setting method will be described later.
[0055]
The control unit 100 also sets the throttle opening (step S42). When switching from the all-cylinder operation to the reduced-cylinder operation, the required output of each cylinder increases, so that it is necessary to increase the throttle opening. Conversely, when switching from the reduced cylinder operation to the all-cylinder operation, the required output of each cylinder is reduced, so that it is necessary to reduce the throttle opening.
[0056]
When the setting of the throttle opening is completed in this way, the number of cylinders is changed from the operation of the switching cylinder set in step S41 (step S43). Thereafter, the process shifts to a process of compensating for the torque shock generated in the transition period of the switching by controlling the operating angle and the ignition timing. In this embodiment, the operating angle is preferentially used to compensate for the torque shock.
[0057]
Accordingly, the control unit 100 first controls the operating angle so as to suppress the torque shock, and controls the amount of intake air to the cylinder (step S44). In this control, for example, a torque shock, an intake air amount, a change in the number of revolutions of the engine, and the like are detected by a sensor, and feedback control can be performed to compensate for this. According to the intake pipe pressure before and after the change in the number of cylinders, a predicted value related to the torque shock generated in each cylinder may be held in the form of a map, a function, or the like, and the operating angle may be controlled based on the predicted value.
[0058]
When it is determined that the torque shock is large and cannot be compensated only by the operating angle (step S45), the control unit 100 controls the ignition timing to compensate for the torque shock (step S46). For example, if the output torque is excessive, compensation can be made by retarding the ignition timing. If the torque shock can be compensated only by the operating angle (step S45), the compensation by the ignition timing is skipped. The control unit 100 repeatedly executes the compensation based on the operating angle and the ignition timing until the torque shock in the transition period is suppressed and the operation is started stably (step S47).
[0059]
FIG. 8 is an explanatory diagram showing a setting method of the switching cylinder in the second embodiment. This corresponds to the process performed in the cylinder number changing process (Step S41 in FIG. 7). As described above, in the present embodiment, the switching cylinder is set such that the torque shock generated at the time of switching the number of cylinders follows the feeling of acceleration or deceleration.
[0060]
As shown in the upper left column, when switching from all-cylinder operation to reduced-cylinder operation during acceleration, the switching cylinder is set so that the working cylinders are continuous. For example, when the # 1 and # 4 cylinders become the working cylinders during the reduced cylinder operation, either # 1 or # 4 becomes the switching cylinder. Although the case where # 1 is the switching cylinder is illustrated in the drawing, # 4 may be the switching cylinder. By doing so, a feeling of acceleration can be obtained immediately after the switching, and a sense of discomfort at the time of switching can be reduced.
[0061]
As shown in the lower left column, the switching cylinder is set so that the working cylinders are continuous even when switching from the reduced cylinder operation to the all-cylinder operation during acceleration. If the cylinders # 1 and # 4 are operating cylinders during the reduced cylinder operation, the cylinder in which the combustion stroke is performed subsequent to any of these, that is, # 2 or # 3 is set as the switching cylinder. With such a setting, it can be said that the cylinder that has been in the idle operation during the reduced cylinder operation is set as the switching cylinder. By doing so, a sufficient feeling of acceleration is obtained immediately before switching, so that even if the torque of each cylinder is reduced in all-cylinder operation, the feeling of strangeness can be reduced.
[0062]
As shown in the upper right column, when switching from all-cylinder operation to reduced-cylinder operation during deceleration, the switching cylinder is set so that the deactivated cylinder comes immediately after the switching. In other words, the idle cylinder is set as the switching cylinder. Although the case where # 3 is the switching cylinder is illustrated in the drawing, # 2 may be the switching cylinder. By doing so, a sense of deceleration is generated immediately after the switching, and a sense of discomfort at the time of the switching can be reduced.
[0063]
As shown in the lower right column, when switching from the reduced cylinder operation to the all-cylinder operation during deceleration, the switching cylinder is set so that the switching is performed after the idle cylinder. If the cylinders # 2 and # 3 are idle cylinders during the reduced-cylinder operation, the cylinder in which the combustion stroke is performed subsequent to either of them, that is, # 1 or # 4 is set as the switching cylinder. With such a setting, it can be said that the working cylinder during the reduced cylinder operation is the switching cylinder. By doing so, switching is performed after a feeling of deceleration occurs immediately before switching, and a sense of discomfort at the time of switching can be reduced.
[0064]
According to the control processing of the second embodiment described above, by switching the number of cylinders during acceleration or deceleration, it is possible to suppress the perceived torque shock during switching. Further, by setting the switching cylinder by the method described with reference to FIG. 8, the sense of discomfort can be further reduced. However, in the control processing of the second embodiment, the setting method of the switching cylinder is not limited to the method of FIG.
[0065]
According to the control processing of the second embodiment, in addition to the above-described effects, the torque shock at the time of switching can be compensated by controlling the operating angle and the ignition timing with high responsiveness. The torque shock compensation has an advantage that the combustion in each cylinder can be relatively stabilized by using the control of the operating angle prior to the control of the ignition timing.
[0066]
FIG. 9 is an explanatory diagram showing a torque compensation effect. The time change of the throttle opening, the intake pipe pressure, and the torque is shown by taking an example of switching from the reduced cylinder operation to the all-cylinder operation at the time t1. When the operation mode is switched to the all-cylinder operation, the required output of each cylinder decreases, so that the throttle opening is reduced. Since the response of the change in the intake pipe pressure is delayed, the time becomes stable at time t2 after the throttle opening is changed. In the period until the intake pipe pressure stabilizes (the period from time t1 to t2), excessive intake is performed to each cylinder, and the torque becomes excessive. As a result, a torque shock shown by a curve C1 occurs. In the present embodiment, the torque shock is suppressed as shown by the curve C2 by controlling the operating angle of each cylinder to suppress the intake air amount. If the torque shock cannot be completely compensated, the torque is further suppressed by controlling the ignition timing.
[0067]
When switching from the all-cylinder operation to the reduced-cylinder operation, a phenomenon opposite to the change shown in FIG. 9 occurs. Therefore, torque shock can be suppressed by increasing the operating angle and increasing the intake air amount. Further, torque shock can be suppressed by advancing the ignition timing.
[0068]
In the second embodiment, the case of performing both the process of switching the number of cylinders in synchronization with the acceleration or deceleration and the compensation of the torque shock by the operating angle and the ignition timing is performed, but one of these is omitted. Is also good. As for the compensation of the torque shock, the ignition timing may be used preferentially over the operating angle.
[0069]
D. Modification:
FIG. 10 is a flowchart of a cylinder number changing process as a modification. The second embodiment has exemplified the case where the number of cylinders is switched in synchronization with acceleration or deceleration. In the modification, torque shock is suppressed by gradually changing the operating angle of each cylinder.
[0070]
When the process is started, the control unit 100 gradually changes the operating angle of each cylinder (Step S50). The manner in which the operating angle is changed is illustrated in the figure. When decreasing the number of cylinders, the operating angle θ is increased by Δθ for each cylinder that should become the working cylinder after switching. For the cylinder that is to be the idle cylinder after the switching, the operating angle θ is reduced by Δθ. Thus, the output of each cylinder changes in the order of Cy1, Cy2, Cy3, and Cy4 in the figure. The output of the working cylinder is indicated by a hatched band, and the output of the stopped cylinder is indicated by a white band. As for the working cylinder, the operating angle increases each time the process of step S50 is repeated as in the sections Cy1, Cy2,. Conversely, the output of the idle cylinder gradually decreases.
[0071]
On the other hand, when increasing the number of cylinders, the operating angle θ is reduced by Δθ for the working cylinder before switching. For idle cylinders, that is, cylinders to be reactivated after switching, the operating angle θ is increased by Δθ. Thus, the output of each cylinder changes in the order of Cy4 → Cy3 → Cy2 → Cy1 in the figure. Regarding the working cylinder, the output angle gradually decreases because the operating angle becomes smaller each time the process of step S50 is repeated as in the sections Cy4, Cy3,.... Conversely, the output of the reactivated cylinder gradually increases.
[0072]
The control unit 100 controls the operating angle in this way, and also controls the fuel injection amount and the throttle opening together (step S51). In the modified example, since cylinders having different operating angles coexist, it is preferable to calculate the fuel injection amount for each cylinder in accordance with the operating angle. As in the second embodiment, the throttle opening may be controlled so as to achieve a desired intake pipe pressure after the number of cylinders is changed.
[0073]
The above processing is repeatedly executed until the operating angle of each cylinder reaches the limit (step S52). When the operating angle reaches the limit, the control unit 100 changes the number of cylinders, and shifts to compensation of torque shock by operating angle and ignition timing (step S44 in FIG. 7). When switching from the all-cylinder operation to the reduced-cylinder operation, the torque is output from the deactivated cylinder even when the operating angle is minimized, so that a relatively small torque shock may occur at the time of complete deactivation. In a modified example, this torque shock can be compensated by controlling the operating angle and the ignition timing of the working cylinder. If the torque shock is sufficiently small, the processing after step S44 may be omitted.
[0074]
When switching from the reduced-cylinder operation to the all-cylinder operation, the output of all the cylinders may become equal before the operating angle reaches the limit. Therefore, in step S52, it is determined whether or not the operating angles of all the cylinders are equal, and when the operating angles are equal, the gradual change of the operating angle may be completed. When switching from the reduced cylinder operation to the all-cylinder operation, there is a possibility that a torque shock may occur at the time of restarting the deactivated cylinder. Compensation (steps S44 to S47 in FIG. 7) may be performed. That is, the torque shock may be compensated in a state where the operating angle of the cylinder to be restarted is minimized, and the gradual change of the operating angle may be started when the torque shock accompanying the restart is stabilized.
[0075]
According to the processing of the modified example, the torque shock accompanying the switching of the number of cylinders can be suppressed by gradually changing the operating angle in advance.
[0076]
Although various embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and it goes without saying that various configurations can be adopted without departing from the spirit of the present invention. For example, the above-described control processing may be realized by software or by hardware. The processes of the first embodiment, the second embodiment, and the modified example described above may be appropriately executed in combination, or may be properly used depending on the operation state. For example, when the operating state of the engine is outside the switchable range shown in the first embodiment, the number of cylinders may be changed by the processing of the second embodiment or the modification.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an engine system as an embodiment.
FIG. 2 is an explanatory diagram showing operations of an intake valve and an exhaust valve.
FIG. 3 is an explanatory diagram illustrating a switching map;
FIG. 4 is a flowchart of a cylinder control process.
FIG. 5 is a flowchart of a cylinder number changing process.
FIG. 6 is a flowchart of a cylinder control process as a second embodiment.
FIG. 7 is a flowchart of a cylinder number changing process.
FIG. 8 is an explanatory diagram showing a setting method of a switching cylinder in a second embodiment.
FIG. 9 is an explanatory diagram showing a torque compensation effect.
FIG. 10 is a flowchart of a cylinder number changing process as a modified example.
[Explanation of symbols]
11 ... intake valve
12. Exhaust valve
13. Spark plug
14. Actuator
15 Actuator
16 ... Injector
17 ... intake pipe
18. Exhaust pipe
21 ... Accelerator opening sensor
22 ... Throttle valve
23 ... Rotation speed sensor
100 ... control unit

Claims (13)

A plurality of cylinders, a variable valve mechanism capable of controlling the valve opening characteristics of the intake valves that are open for each cylinder, and intake control means capable of controlling the intake amount of each cylinder regardless of the valve opening characteristics of the intake valves. A control device for controlling the operation of an internal combustion engine comprising:
An input unit for inputting a required rotational speed and a required load of the internal combustion engine,
A cylinder number control unit that changes the number of working cylinders that output power among the plurality of cylinders,
The number-of-cylinder control unit is configured to set the required rotational speed within a predetermined switchable region in which a change in the intake air amount of each cylinder required before and after the change in the number of the working cylinders can be realized by changing only the valve opening characteristic. A control device for changing the number of the working cylinders when the number and the required load exist. The control device for an internal combustion engine according to claim 1,
The control device, wherein the switchable region is set under a condition in which the inside of an intake pipe to the cylinder is at atmospheric pressure. The control device for an internal combustion engine according to claim 1,
The switchable region is set according to a negative pressure of an intake pipe to the cylinder,
A control device comprising: a negative pressure control unit that controls a negative pressure of the intake pipe so that the required rotation speed and the required load fall within the switchable region before the number of cylinders is changed. The control device for an internal combustion engine according to any one of claims 1 to 3,
The intake control means is a throttle valve for controlling a negative pressure of an intake pipe to the cylinder,
When changing the number of cylinders, the cylinder number control unit controls the valve opening characteristics and the fuel injection amount of each cylinder according to the required rotation speed and the required load while fixing the opening of the throttle valve. apparatus. A plurality of cylinders, a variable valve mechanism that can control the valve opening characteristics of the intake valves that are open for each cylinder, and a negative pressure of the intake pipe to each cylinder that is controlled by the valve opening characteristics of the intake valves. A control device for controlling the operation of the internal combustion engine, comprising: intake control means capable of controlling the intake amount of each cylinder,
An input unit for inputting a required rotational speed and a required load of the internal combustion engine,
A cylinder number control unit that changes the number of working cylinders that output power among the plurality of cylinders,
The cylinder number control unit includes:
A negative pressure control unit that controls a negative pressure of an intake pipe to the cylinder so as to realize an intake amount of each cylinder required after a change in the number of the working cylinders according to the required rotation speed and the required load;
A valve opening characteristic control unit that controls the valve opening characteristic so as to compensate for a response delay in the control of the negative pressure. The control device for an internal combustion engine according to claim 5, wherein
The cylinder number control unit includes:
An ignition timing control unit that controls the ignition timing of each cylinder to compensate for the response delay;
A compensation control unit that compensates for the response delay by using the valve opening characteristic control unit with priority over the ignition timing control unit. A control device mounted on a moving body and controlling operation of an internal combustion engine including a plurality of cylinders,
An operating state of the internal combustion engine, a cylinder number switching determination unit that determines whether or not a predetermined condition to change the number of working cylinders that output power among the plurality of cylinders is satisfied;
An acceleration / deceleration determination unit that determines whether the moving body is accelerating or decelerating,
A control unit that changes the number of working cylinders only when the predetermined condition is satisfied during the acceleration or deceleration. A control device mounted on a moving body and controlling operation of an internal combustion engine including a plurality of cylinders,
An operating state of the internal combustion engine, a cylinder number switching determination unit that determines whether or not a predetermined condition to change the number of working cylinders that output power among the plurality of cylinders is satisfied;
An acceleration / deceleration determination unit that determines whether the moving body is accelerating,
A control device that, when the moving body satisfies the predetermined condition during acceleration, changes the number of working cylinders at a timing when the combustion stroke of the working cylinder is continuous before and after changing the number of cylinders. . A control device mounted on a moving body and controlling operation of an internal combustion engine including a plurality of cylinders,
An operating state of the internal combustion engine, a cylinder number switching determination unit that determines whether or not a predetermined condition to change the number of working cylinders that output power among the plurality of cylinders is satisfied;
An acceleration / deceleration determination unit that determines whether the moving body is decelerating,
The cylinder number control unit is configured to perform the operation at a timing in which the combustion stroke of the working cylinder and the combustion stroke of the deactivated cylinder are continuous before and after the change in the number of cylinders when the moving body satisfies the predetermined condition during deceleration. A control device that changes the number of cylinders. A control device for an internal combustion engine according to any one of claims 1 to 9,
A control device for changing the number of cylinders at a timing at which control of one of the cylinders for which both the fuel injection amount and the valve opening characteristic of the intake valve are not set is started. A plurality of cylinders, a variable valve mechanism capable of controlling the valve opening characteristics of the intake valves that are open for each cylinder, and intake control means capable of controlling the intake amount of each cylinder regardless of the valve opening characteristics of the intake valves. A control method for controlling the operation of an internal combustion engine comprising:
Inputting a required rotational speed and a required load of the internal combustion engine;
When changing the number of working cylinders that output power among the plurality of cylinders, the change in the intake amount of each cylinder required before and after the change is performed only by changing the valve opening characteristic. Determining whether the required rotational speed and the required load satisfy the feasible condition;
Changing the number of the working cylinders when the condition is satisfied. A plurality of cylinders, a variable valve mechanism that can control the valve opening characteristics of the intake valves that are open for each cylinder, and a negative pressure of the intake pipe to each cylinder that is controlled by the valve opening characteristics of the intake valves. A control method for controlling the operation of the internal combustion engine, comprising: intake control means capable of controlling the intake amount of each cylinder,
(A) inputting a required rotational speed and a required load of the internal combustion engine;
(B) changing the number of working cylinders that output power among the plurality of cylinders,
The step (b) comprises:
(B1) controlling a negative pressure of an intake pipe to each of the cylinders according to the required rotation speed and the required load so as to realize an intake amount of each cylinder required after the number of the working cylinders is changed;
(B2) controlling the valve opening characteristic so as to compensate for a response delay in the control of the negative pressure. A control method for controlling operation of an internal combustion engine mounted on a moving body and including a plurality of cylinders,
A step of determining whether or not the operating state of the internal combustion engine satisfies a predetermined condition to change the number of working cylinders that output power among the plurality of cylinders;
A step of determining whether the moving body is accelerating or decelerating,
Changing the number of working cylinders only when the predetermined condition is satisfied during the acceleration or deceleration.

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