Engine control device

Abstract

To provide a controller of an engine in which variation in a combustion state after starting is suppressed.SOLUTION: A controller of an engine comprises: a determination unit that determines whether an engine is in a complete combustion state; a calculation unit that calculates an integrated intake volume, which is an integrated value of an intake volume of the engine after the determination unit makes a positive determination; a setting unit that sets a target equivalence ratio of the engine according to the integrated intake volume; and a control unit that controls the intake volume and a fuel injection volume of the engine so that an equivalence ratio of a mixture becomes the target equivalence ratio.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] The target equivalence ratio of the engine is set according to the integrated intake air amount, which is the integrated value of the intake air amount of the engine, and the operating state of the engine is controlled so that the equivalence ratio of the actual air-fuel mixture becomes the target equivalence ratio (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The engine is started as follows. While intake air is introduced into the engine by cranking, fuel injection is executed. When the air-fuel mixture is ignited and the engine reaches a complete explosion state, the engine startup is completed. Here, the time from the start of cranking to the complete explosion state may vary depending on factors such as the properties of the fuel used and the environmental temperature. Therefore, when the integrated intake air amount is calculated from the start of cranking, the integrated intake air amount at the time of reaching the complete explosion state may vary. As a result, the target equivalence ratio set according to the integrated intake air amount may vary. Therefore, the combustion state of the engine after startup may vary.

[0005] Therefore, an object of the present invention is to provide an engine control device in which variations in the combustion state after startup are suppressed.

Means for Solving the Problems

[0006] The above object can be achieved by an engine control device including a determination unit that determines whether the engine has reached a complete explosion state, a calculation unit that calculates an integrated intake air amount that is an integrated value of the intake air amount of the engine after a positive determination is made by the determination unit, a setting unit that sets a target equivalence ratio of the engine according to the integrated intake air amount, and a control unit that controls the intake air amount and fuel injection amount of the engine so that the equivalence ratio of the air-fuel mixture becomes the target equivalence ratio.

[0007] The setting unit may set the target equivalence ratio from a value greater than 1 to a lower value as the integrated intake air amount increases.

[0008] The setting unit may set the target equivalence ratio to a value greater than 1 as the temperature of the engine is lower.

Advantages of the Invention

[0009] According to the present invention, it is possible to provide an engine control device in which variations in the combustion state after startup are suppressed.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] [Schematic Configuration of Engine] Figure 1 is a schematic configuration diagram of the engine 10. The engine 10 is mounted on, for example, an engine vehicle, but may also be mounted on a hybrid vehicle. The engine 10 is a gasoline engine, but may also be a diesel engine. A piston 13 is provided in each cylinder 12 of the engine 10. The piston 13 is connected to a crankshaft 15, which is the output shaft of the engine 10, via a connecting rod 14. The reciprocating motion of the piston 13 is converted into the rotational motion of the crankshaft 15 by the connecting rod 14. The crankshaft 15 is connected to a starter motor 25. The starter motor 25 is connected to the crankshaft 15. The starter motor 25 cranks the engine 10 by rotating the crankshaft 15 when the engine 10 is started.

[0012] Above the piston 13 and within each cylinder 12, a combustion chamber 16 is formed. An ignition plug 18 for igniting the air-fuel mixture is attached to the combustion chamber 16. The ignition timing of the air-fuel mixture by this ignition plug 18 is adjusted by an igniter 19 provided above the ignition plug 18.

[0013] An intake passage 20 and an exhaust passage 21 communicate with the combustion chamber 16. A throttle valve 23 for measuring the amount of air introduced into the combustion chamber 16 is provided in the intake passage 20. A catalyst 50 is provided in the exhaust passage 21.

[0014] In-cylinder injection valves 17 for injecting fuel into each combustion chamber 16 are provided in the engine 10. In addition to or instead of the in-cylinder injection valves 17, port injection valves for injecting fuel into the intake ports may be provided.

[0015] The ECU (Electronic Control Unit) 30 is an electronic control unit that performs control processing related to the engine 10. The ECU 30 is mainly composed of a computer including volatile and non-volatile memories such as a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). Although details of the ECU 30 will be described later, various sensors are connected to it. The ECU 30 is an example of an engine control device and functionally realizes a determination unit, a calculation unit, a setting unit, and a control unit, which will be described in detail later.

[0016] An accelerator opening sensor 31, a water temperature sensor 32, an air flow meter 33, a crank angle sensor 34, and an air-fuel ratio sensor 35 are connected to the ECU 30. The accelerator opening sensor 31 detects the accelerator opening. The water temperature sensor 32 detects the temperature of the cooling water that cools the engine 10. The air flow meter 33 detects the intake air amount. The crank angle sensor 34 detects the rotational speed of the engine 10. The air-fuel ratio sensor 35 is provided in the exhaust passage 21 upstream of the catalyst 50. The air-fuel ratio sensor 35 detects the air-fuel ratio of the exhaust gas flowing into the catalyst 50.

[0017] The ECU 30 sets a target equivalence ratio by the method described later. The ECU 30 controls the intake air amount and the fuel injection amount so that the equivalence ratio of the air-fuel mixture becomes the target equivalence ratio. The air-fuel ratio of the air-fuel mixture is calculated by the ECU 30 based on the detected value of the air-fuel ratio sensor 35. Here, the equivalence ratio is an index value representing the fuel concentration in the air-fuel mixture and is the value obtained by dividing the fuel amount that results in the stoichiometric air-fuel ratio by the actual fuel amount. When the air-fuel ratio of the air-fuel mixture is the stoichiometric air-fuel ratio, the equivalence ratio is "1". When the air-fuel ratio of the air-fuel mixture is richer than the stoichiometric air-fuel ratio, the equivalence ratio is a value greater than "1". When the air-fuel ratio of the air-fuel mixture is leaner than the stoichiometric air-fuel ratio, the equivalence ratio is a value smaller than "1". The intake air amount is controlled according to the opening degree of the throttle valve 23. The fuel injection amount is controlled according to the energization time of the in-cylinder injection valve 17. The intake air amount and the fuel injection amount are adjusted based on the target torque set according to the accelerator opening, vehicle speed, etc.

[0018] [Equivalence Ratio Control] Figure 2 is a flowchart illustrating an example of the equivalence ratio control executed by the ECU 30. This control is repeatedly executed in the ignition-on state. The ECU 30 determines whether the engine 10 has reached the complete explosion state (step S1). The complete explosion state means a state where the start of the engine 10 is completed and it can operate independently. In other words, the complete explosion state means a state where the assistance by the starter motor 25 is not required during the operation of the engine 10. In this embodiment, the ECU 30 determines whether the engine 10 is in the complete explosion state by using the rotational speed of the engine 10. More specifically, when the rotational speed of the engine 10 becomes equal to or higher than a predetermined rotational speed for a predetermined time or more, it is determined that the engine 10 is in the complete explosion state. Step S1 is an example of the process executed by the determination unit. If the result in step S1 is No, this control ends.

[0019] If the result in step S1 is Yes, the ECU 30 calculates the integrated intake air amount based on the detected value of the air flow meter 33 (step S2). That is, the ECU 30 calculates the integrated intake air amount, which is the integrated value of the intake air amount after being determined to be in the complete explosion state in step S1. Step S2 is an example of the process executed by the calculation unit.

[0020] Next, the ECU 30 sets the target equivalence ratio (step S3). Figure 3 is an example of a map defining the target equivalence ratio. This map is stored in the memory of the ECU 30. The horizontal axis represents the integrated intake air amount, and the vertical axis represents the target equivalence ratio. In the map of Figure 3, the target equivalence ratios corresponding to the temperatures T1 to T3 of the cooling water at the start of cranking of the engine 10 are defined. Among the temperatures T1 to T3, the temperature T1 is the lowest and the temperature T3 is the highest. For example, the temperatures T1 and T2 are less than 0°C, and the temperature T3 is 0°C or higher. The ECU 30 uses the temperature of the cooling water as the temperature of the engine 1. Therefore, the ECU 30 refers to the map of Figure 3 to set the target equivalence ratio based on the temperature of the cooling water detected by the water temperature sensor 32 at the start of cranking and the integrated intake air amount. Step S3 is an example of the process executed by the setting unit.

[0021] In a state where the integrated intake air amount is small until it reaches a predetermined value, the target equivalence ratio at temperature T1 among temperatures T1 to T3 is the largest, and the target equivalence ratio at temperature T3 is the smallest. That is, the lower the temperature of the engine 10, the larger the target equivalence ratio is set. The lower the temperature of the engine 10, the lower the wall temperature of the combustion chamber of the engine 10. The lower this wall temperature, the larger the amount of uncontributed fuel that adheres to this wall and does not contribute to combustion in the fuel injection amount. In order to compensate for this amount of uncontributed fuel, the lower the temperature of the engine 10, the higher the target equivalence ratio is set. Also, at temperature T3, the target equivalence ratio is "1" regardless of the integrated intake air amount. This is because the amount of uncontributed fuel adhering to the wall of the combustion chamber is small at temperature T3.

[0022] At temperatures T1 and T2, as the integrated intake air amount increases until it reaches a predetermined value, the target equivalence ratio decreases toward "1". As the integrated intake air amount increases after the complete combustion state, the wall temperature of the combustion chamber of the engine 10 rises. As a result, the amount of uncontributed fuel that adheres to this wall in the fuel injection amount decreases.

[0023] In the case of temperatures T1 and T2 in FIG. 3, as the integrated intake air amount increases until it reaches a predetermined value, the target equivalence ratio decreases linearly. However, the target equivalence ratio may decrease curvilinearly or stepwise. Also, the target equivalence ratio may be calculated by an arithmetic expression taking the integrated intake air amount and the temperature of the cooling water as arguments.

[0024] Next, the ECU 30 controls the intake air amount and the fuel injection amount so that the equivalence ratio of the actual air-fuel mixture becomes the target equivalence ratio (step S4). Specifically, as described above, the ECU 30 controls the opening degree of the throttle valve 23 and the energization time of the in-cylinder injection valve 17 to control the intake air amount and the fuel injection amount. Step S4 is an example of a process executed by the control unit.

[0025] As described above, the target equivalence ratio is set based on the integrated intake air amount calculated after the complete explosion state is reached. Therefore, even if there is variation in the time from the start of cranking to the complete explosion state, the variation in the target equivalence ratio at the time of reaching the complete explosion state is suppressed. As a result, the variation in the combustion state after the engine 10 is started is suppressed.

[0026] The ECU 30 may use the temperature of the lubricating oil that lubricates the engine 10 as the temperature of the engine 10. The content of the above embodiment may be applied to, for example, a control device for an engine mounted on a motorcycle or the like, or a control device for an engine mounted on something other than a vehicle such as a ship or a construction machine.

[0027] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Signs

[0028] 1 Engine 30 ECU (Engine control device, determination unit, calculation unit, setting unit, control unit)

Claims

【Claim 1】 A determination unit that determines whether the engine has reached a complete explosion state; A calculation unit that calculates an integrated intake air amount, which is an integrated value of the intake air amount of the engine after a positive determination is made by the determination unit; A setting unit that sets a target equivalence ratio of the engine according to the integrated intake air amount after a positive determination is made by the determination unit; A control unit that controls the intake air amount and fuel injection amount of the engine so that the equivalence ratio of the air-fuel mixture becomes the target equivalence ratio, The setting unit sets the target equivalence ratio from a value greater than 1 to a lower value as the integrated intake air amount increases; The setting unit sets the target equivalence ratio to a value greater than 1 as the temperature of the engine is lower; The temperature of the engine is the temperature of the cooling water of the engine at the start of cranking of the engine before the engine reaches a complete explosion state; The temperature of the cooling water is detected by a water temperature sensor; The setting unit sets the target equivalence ratio to decrease as the integrated intake air amount increases until the integrated intake air amount reaches a predetermined value when the temperature of the cooling water is less than 0°C, and sets the target equivalence ratio to 1 regardless of the integrated intake air amount when the temperature of the cooling water is 0°C or higher. An engine control device.

Images