Engine control device

Abstract

To provide a control device for an engine suppressing deterioration of a combustion state while suppressing occurrence of a torque shock when returning from fuel cut.SOLUTION: A control device for an engine mounted on a vehicle, the control device including an acquisition unit configured to acquire an engine speed and an atmospheric pressure when a return from fuel cut is requested, and a return control unit configured to execute return processing from fuel cut by retarding an ignition timing at the time of return from fuel cut from an MBT ignition timing by a predetermined retard amount. A retardation amount control unit configured to increase a decrease rate as the atmospheric pressure decreases, the decrease rate being an amount of decrease in the retardation amount with respect to an increase in the engine rotation speed.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] There is a technology that suppresses the output torque of the engine when returning from a fuel cut by retarding the ignition timing by a predetermined amount from the MBT (Minimum advance for the Best Torque) ignition timing when returning from a fuel cut, thereby suppressing the occurrence of torque shock (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-162185 Summary of the Invention [Problem to be solved by the invention]

[0004] If the engine speed is high when the engine resumes from a fuel cut, a large retard amount may worsen the combustion state. In particular, when the engine speed is high and the atmospheric pressure is low, the amount of oxygen introduced into the engine's combustion chamber is small, which may further worsen the combustion state. Furthermore, even when the engine speed is low, if the atmospheric pressure is low, the engine's pumping loss decreases, which may increase the engine's output torque when the engine resumes from a fuel cut, resulting in a torque shock.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine control device that stabilizes the combustion state while suppressing the occurrence of torque shock when returning from a fuel cut. [Means for solving the problem]

[0006] The above object can be achieved by an engine control device mounted on a vehicle, the engine control device including: an acquisition unit that acquires engine speed and atmospheric pressure when there is a request to return from fuel cut; a return control unit that executes the process of returning from fuel cut by retarding the ignition timing at the time of returning from fuel cut by a predetermined retard amount relative to the MBT ignition timing; and a delay amount control unit that decreases the retard amount as the engine speed increases, increases the retard amount as the atmospheric pressure decreases, and increases the reduction rate, which is the amount by which the retard amount decreases relative to an increase in the engine speed, as the atmospheric pressure decreases.

[0007] The retard amount control unit may gradually decrease the retard amount as the engine rotation speed increases.

[0008] The retard amount control unit may gradually decrease the retard amount as the engine rotation speed increases. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an engine control device that suppresses the occurrence of torque shock when returning from a fuel cut and also suppresses deterioration of the combustion state. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a vehicle equipped with an engine. [Figure 2] FIG. 2 is a flowchart illustrating the fuel injection resumption control executed by the ECU. [Figure 3] FIG. 3A is a diagram illustrating an example of a map for controlling the amount of retardation, and FIG. 3B is a diagram illustrating a modified example of the map for controlling the amount of retardation. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Vehicle outline] FIG. 1 is a schematic diagram of a vehicle 1 equipped with an engine 10. The vehicle 1 includes the engine 10, an ECU (Electronic Control Unit) 30, and drive wheels 40. The engine 10 is a gasoline engine that is a power source for driving the vehicle 1. Therefore, the vehicle 1 may be a gasoline vehicle, or a hybrid vehicle that is equipped with a motor as a power source for driving in addition to the engine 10. The engine 10 is, for example, an in-line engine having four cylinders, but is not limited to this.

[0012] Air is drawn into a combustion chamber 11 of the engine 10 through an intake passage 12, and fuel is supplied from an in-cylinder injection valve 13. The in-cylinder injection valve 13 is a fuel injection valve that injects fuel directly into the combustion chamber 11. Instead of or in addition to the in-cylinder injection valve 13, a port injection valve that injects fuel into an intake port may be provided. When a mixture of intake air and injected fuel is ignited by a spark plug 14, the mixture burns, causing a piston 15 to reciprocate and rotate a crankshaft 16 of the engine 10. The rotational power of the crankshaft 16 is transmitted to drive wheels 40 via a transmission (not shown). The combusted mixture is sent from the combustion chamber 11 of the engine 10 to an exhaust passage 17 as exhaust gas. A catalyst 17a that purifies the exhaust gas is provided in the exhaust passage 17.

[0013] The ECU 30 executes various controls for driving the vehicle 1. The ECU 30 includes a central processing unit that executes various arithmetic processes related to the various controls, a non-volatile memory that stores programs and data required for the calculations, a volatile memory that temporarily stores the calculation results of the central processing unit, an input port and an output port for inputting and outputting signals to and from the outside, and the like.

[0014] Various sensors are connected to the ECU 30. These sensors include an accelerator position sensor 31, a throttle position sensor 32, an air flow meter 34, a crank angle sensor 35, and an atmospheric pressure sensor 36. The accelerator position sensor 31 detects the accelerator position, which is the amount of depression of the accelerator pedal 18. The throttle position sensor 32 detects the opening of the throttle valve 19 provided in the intake passage 12. The air flow meter 34 detects the amount of intake air passing through the intake passage 12. The crank angle sensor 35 detects the rotation speed of the crankshaft 16, i.e., the rotation speed of the engine 10. The atmospheric pressure sensor 36 detects the atmospheric pressure around the vehicle 1.

[0015] The ECU 30 grasps the operating conditions of the engine 10, such as the rotation speed and load, based on output signals from various sensors. The ECU 30 controls the opening of the throttle valve 19, the amount of fuel injected from the in-cylinder injection valve 13, the ignition timing of the air-fuel mixture by the spark plug 14, and the like, according to the grasped operating conditions. The ECU 30 functionally realizes an acquisition unit, a return control unit, and a retard amount control unit, which will be described in detail later. The ECU 30 is an example of an engine control device.

[0016] [Fuel injection return control] 2 is a flowchart illustrating the fuel injection restoration control executed by the ECU 30. This control is repeatedly executed while the ignition is on. The ECU 30 determines whether or not there is a restoration request to restore the engine 10 from a fuel cut state to a fuel injection state (step S1). If the answer is No in step S1, this control ends.

[0017] If the answer is Yes in step S1, the ECU 30 acquires the engine speed and the atmospheric pressure based on the crank angle sensor 35 and the atmospheric pressure sensor 36 (step S2). Step S2 is an example of a process executed by the acquisition unit.

[0018] Next, the ECU 30 controls the amount of retardation of the ignition timing when returning from the fuel cut based on the engine speed and atmospheric pressure acquired by referring to the map of Fig. 3A (step S3). Step S3 is an example of processing executed by the retardation control unit.

[0019] FIG. 3A is an example diagram of a map for controlling the retard amount. The map in FIG. 3A defines the relationship between the engine speed and the retard amount according to the atmospheric pressure. The retard amount is the amount of retard of the ignition timing based on the MBT ignition timing. FIG. 3A illustrates examples where the acquired atmospheric pressure is 100 kPa, 75 kPa, and 50 kPa. When the atmospheric pressure is 75 kPa or 50 kPa, the vehicle 1 is, for example, at high altitude.

[0020] The map in Figure 3A specifies that the retard amount gradually decreases as the engine speed increases, regardless of atmospheric pressure. Here, the higher the engine speed, the shorter the combustion interval becomes, so if the retard amount is constant, the combustion state may become unstable. Therefore, by gradually decreasing the retard amount as the engine speed increases, the combustion state becomes more stable.

[0021] 3A, the amount of retardation is set to increase as the atmospheric pressure decreases, regardless of the engine speed. As the atmospheric pressure decreases, the pumping loss decreases, which increases the output torque of the engine 10 when it returns to normal, which may cause a torque shock. Therefore, by increasing the amount of retardation as the atmospheric pressure decreases, the occurrence of a torque shock is suppressed.

[0022] The map in FIG. 3A specifies that the rate of decrease in the retard amount relative to an increase in engine speed (hereinafter referred to as the retard amount decrease rate) increases as the atmospheric pressure decreases. In the example in FIG. 3A, the retard amount decrease rate corresponds to the slope. The retard amount decrease rate is smallest when the atmospheric pressure is 100 kPa and largest when the atmospheric pressure is 50 kPa. As mentioned above, the higher the engine speed, the shorter the combustion interval. Furthermore, the lower the atmospheric pressure, the less oxygen is introduced into the combustion chamber 11. This makes the combustion state more unstable, and there is a risk of afterfire, for example. Therefore, by increasing the retard amount decrease rate as the atmospheric pressure decreases, the combustion state is stabilized.

[0023] 3A, the retard amount with respect to the engine speed is defined linearly, but it may be defined as a curve. In this case, the reduction rate of the retard amount is, for example, the average value of the reduction rate of the retard amount when the engine speed changes from the minimum value to the maximum value. Furthermore, the retard amount may be calculated by a calculation using the engine speed and atmospheric pressure as arguments, without using such a map.

[0024] Next, the ECU 30 executes a return process to resume fuel injection from the fuel cut by the set delay amount (step 4). The return process is a process in which fuel injection is started and the ignition timing is retarded by the above-mentioned delay amount, gradually advancing the ignition timing to the MBT ignition timing. By controlling the delay amount as described above, the occurrence of torque shock when returning from the fuel cut is suppressed and the combustion state is stabilized. Step S4 is an example of a process executed by the return control unit. After the return process is completed, the ECU 30 increases the output torque of the engine 10 to the required torque by controlling the intake air amount and the fuel injection amount.

[0025] FIG. 3B shows a modified map for controlling the retard amount. In the example of FIG. 3B, the retard amount is gradually reduced as the engine speed increases. Specifically, the retard amount is reduced when the engine speed is equal to or greater than a predetermined engine speed R. The predetermined engine speed R is the minimum engine speed at which a large retard amount can cause unstable combustion. By reducing the retard amount when the engine speed is equal to or greater than the predetermined engine speed R, the combustion state is stabilized. Also, in the map of FIG. 3B, the retard amount increases as the atmospheric pressure decreases, regardless of the engine speed, and the rate of decrease in the retard amount increases as the atmospheric pressure decreases. This suppresses torque shock and stabilizes the combustion state. The rate of decrease in the retard amount in the map of FIG. 3B is the average rate of decrease in the retard amount as the engine speed changes from minimum to maximum. In other words, the rate of decrease in the retard amount can be calculated by dividing the difference between the maximum and minimum retard amounts by the difference between the minimum and maximum engine speeds.

[0026] In the example of Fig. 3B, the retard amount decreases by one step as the engine speed increases, but the retard amount may also decrease in multiple steps. Also, the retard amount may be calculated by a calculation using the engine speed and atmospheric pressure as arguments without using such a map.

[0027] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0028] 1 vehicle 10 Engine 14 Spark plug 30 ECU (engine control unit, acquisition unit, recovery control unit, retard amount control unit)

Claims

1. A control device for an engine mounted on a vehicle, an acquisition unit that acquires an engine speed and an atmospheric pressure when a request to resume from a fuel cut is received; a recovery control unit that executes a recovery process from a fuel cut by retarding the ignition timing at the time of recovery from a fuel cut by a predetermined retard amount compared to the MBT ignition timing; a delay amount control unit that decreases the delay amount as the engine rotation speed increases, increases the delay amount as the atmospheric pressure decreases, and increases a reduction rate of the delay amount relative to an increase in the engine rotation speed as the atmospheric pressure decreases; An engine control device comprising:

2. 2. The engine control device according to claim 1, wherein the retard amount control section gradually decreases the retard amount as the engine speed increases.

3. 2. The engine control device according to claim 1, wherein the retard amount control section reduces the retard amount in stages as the engine speed increases.

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