Control circuit of internal combustion engine and motor cycle

Abstract

To provide a control circuit of an internal combustion engine for stabilizing a state of exhaust gas.SOLUTION: A control circuit of an internal combustion engine of a vehicle is configured so as to determine whether a first condition that the internal combustion engine is in an idle state is satisfied, determine whether a second condition that air that bypasses the internal combustion engine is sent to an exhaust passage of the internal combustion engine is satisfied, acquire air-fuel ratio information on an air-fuel ration detected from exhaust gas of the internal combustion engine by an air-fuel ratio sensor, and execute first feedback control for increasing and decreasing a fuel supply amount to the internal combustion engine so as to correspond to an increase and a decrease in the air-fuel ratio on the basis of the air-fuel ratio information when the first condition and the second condition are satisfied.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a control circuit for an internal combustion engine and a motorcycle. [Background technology]

[0002] Patent Document 1 discloses an internal combustion engine in which secondary air is supplied to an exhaust port when the engine is operating in an idle operating range. The control device for the internal combustion engine controls the fuel injection amount so that the air-fuel ratio of the exhaust gas after the secondary air is supplied becomes lean when the engine is operating in an idle operating range. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-136970 Summary of the Invention [Problem to be solved by the invention]

[0004] In order to make the air-fuel ratio of the exhaust gas lean after the secondary air is supplied, it is necessary to increase the flow rate of the secondary air. Because the flow rate of the secondary air is unstable, the state of the exhaust gas and the behavior of the internal combustion engine may become unstable. Therefore, one aspect of the present disclosure aims to provide a control circuit for an internal combustion engine that stabilizes the state of exhaust gas. [Means for solving the problem]

[0005] A control circuit according to one embodiment of the present disclosure is a control circuit for an internal combustion engine of a vehicle, and is configured to: determine whether a first condition, that is, that the internal combustion engine is in an idle state, is satisfied; determine whether a second condition, that is, that air that has bypassed the internal combustion engine is being sent into the exhaust flow path of the internal combustion engine, is satisfied; acquire air-fuel ratio information, which is information regarding the air-fuel ratio detected from the exhaust gas of the internal combustion engine by an air-fuel ratio sensor; and, when the first condition and the second condition are satisfied, perform first feedback control, based on the air-fuel ratio information, to increase and decrease the amount of fuel supplied to the internal combustion engine in response to increases and decreases in the air-fuel ratio. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a side view showing an example of a configuration of a vehicle according to an exemplary embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of a power system of the motorcycle 1 of FIG. [Figure 3] FIG. 3 is a diagram showing an example of the behavior over time of the detection signal of the air-fuel ratio sensor, the estimated value of the air-fuel ratio, and the correction coefficient of the fuel injection amount during the second feedback control when the secondary air control valve is in a closed state. [Figure 4] FIG. 4 is a diagram showing an example of the behavior over time of the detection signal of the air-fuel ratio sensor, the estimated value of the air-fuel ratio, and the correction coefficient of the fuel injection amount during the first feedback control when the secondary air control valve is in an open state. [Figure 5] FIG. 5 is a flowchart illustrating an example of the feedback control operation of the ECU according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the drawings. The embodiments described below are all comprehensive or specific examples. Among the components in the following embodiments, components that are not recited in an independent claim showing a top concept will be described as optional components. Each figure in the accompanying drawings is a schematic diagram and is not necessarily an exact drawing. In each figure, substantially identical components are assigned the same reference numerals, and duplicated descriptions may be omitted or simplified.

[0008] A vehicle 1 according to an exemplary embodiment will be described with reference to FIG. 1. FIG. 1 is a side view showing an example of the configuration of a vehicle 1 according to an exemplary embodiment. The vehicle 1 is a moving body capable of carrying one or more people. The vehicle 1 may be any vehicle equipped with an internal combustion engine. Examples of the vehicle 1 include automobiles and motorcycles. For example, an automobile may include three or more wheels for moving the automobile. A motorcycle may include three or fewer wheels for moving the motorcycle. Examples of motorcycles include saddle-type vehicles on which a person straddles and scooter-type vehicles with footrests in front of the seat. Examples of automobiles include three-wheeled vehicles and buggies.

[0009] In the following description, a saddle-ride type motorcycle will be taken as an example of the vehicle 1. For this reason, the "vehicle 1" may also be referred to as a "motorcycle 1."

[0010] Here, in this specification and claims, the terms up, above, down, downward, forward, front, rear, left, right, lateral, and side refer to directions relative to the motorcycle 1 placed on a horizontal plane. The terms up and up refer to directions from the horizontal plane toward the motorcycle 1, and the terms down and down refer to directions from the motorcycle 1 toward the horizontal plane. The terms forward and forward refer to the direction in which the motorcycle 1 moves forward. The terms rear, left, right, lateral, and side refer to directions relative to the forward direction or forward.

[0011] The motorcycle 1 includes a front wheel 2, a rear wheel 3, a body frame 4, an internal combustion engine 5, an intake structure 6, an exhaust structure 7, a secondary air supply structure 8, and an electronic control unit 10. Hereinafter, the "electronic control unit 10" may be referred to as the "ECU 10."

[0012] Motorcycle 1 further includes handlebars 11, a steering shaft 12, a pair of left and right front forks 13, a swing arm 14, a rear suspension 15, a fuel tank 16, and a seat 17. The upper portions of front forks 13 are connected to a pair of brackets 13a spaced apart in the vertical direction, and the lower portions of front forks 13 rotatably support front wheel 2. Brackets 13a are connected to steering shaft 12 that supports handlebars 11. Steering shaft 12 is supported by a head pipe 4a, which is part of body frame 4, so as to be angularly displaceable.

[0013] The swing arm 14 supports the rear wheel 3, extends in the front-to-rear direction, and is pivotally supported by the body frame 4. A rear suspension 15 is connected to the swing arm 14 and the body frame 4.

[0014] The fuel tank 16 is disposed behind the handlebars 11, and behind the fuel tank 16 is disposed a seat 17 on which the driver sits.

[0015] The internal combustion engine 5 is disposed in a space surrounded by the body frame 4 between the front wheels 2 and the rear wheels 3, and is fixed at multiple portions to the body frame 4. The internal combustion engine 5 includes a crankcase 51 and a cylinder block 52 extending upward from the top of the crankcase 51. The cylinder block 52 includes an intake port 52a and an exhaust port 52b. In this embodiment, the intake port 52a is disposed at the rear of the cylinder block 52, and the exhaust port 52b is disposed at the front of the cylinder block 52, but the positions of the intake port 52a and the exhaust port 52b are not limited to the above.

[0016] The exhaust port 52b is connected to the exhaust structure 7. The exhaust structure 7 includes an exhaust pipe 71 connected to the exhaust port 52b at its upstream end, a silencer 72 connected to the downstream end of the exhaust pipe 71, and a catalyst 73. In this embodiment, the catalyst 73 is disposed in the silencer 72, but it may also be disposed in the exhaust pipe 71. The catalyst 73 has the ability to purify the exhaust gas by promoting an oxidation reaction of the exhaust gas.

[0017] The intake port 52a is connected to an intake structure 6. The intake structure 6 includes an intake pipe 61 extending rearward from the intake port 52a, a throttle device 62 connected to the intake pipe 61, an intake duct 63 connected to the rear of the throttle device 62, and an air cleaner 64 connected to the rear of the intake duct 63. The intake pipe 61, the intake duct 63, and the air cleaner 64 form an intake flow path 60 that introduces outside air into the internal combustion engine 5. The operation of the throttle device 62 is controlled by the ECU 10.

[0018] The air cleaner 64 has an air cleaner case 64a and a filter 64b that is housed in the air cleaner case 64a and purifies outside air supplied from outside. The filter 64b divides the internal space of the air cleaner case 64a into a dirty space 64aa and a clean space 64ab. Outside air flows into the dirty space 64aa through an opening in the air cleaner case 64a. Clean air that has passed through the filter 64b flows into the clean space 64ab. The clean space 64ab communicates with the intake duct 63.

[0019] FIG. 2 is a schematic diagram showing an example of the power system of the motorcycle 1 of FIG. 1. As shown in FIGS. 1 and 2, the air cleaner case 64a is also connected to a secondary air supply structure 8. The secondary air supply structure 8 includes a secondary air pipe 81 and a secondary air control valve 82. One end of the secondary air pipe 81 is connected to the air cleaner case 64a and communicates with the clean space 64ab. The other end of the secondary air pipe 81 is connected to the exhaust flow path 70. The secondary air pipe 81 forms a supply flow path that bypasses the internal combustion engine 5 and connects the intake flow path 60 and the exhaust flow path 70. The secondary air control valve 82 is disposed midway along the secondary air pipe 81 and opens and closes the flow path within the secondary air pipe 81. The secondary air control valve 82 is, for example, a solenoid valve, and the opening and closing operation of the secondary air control valve 82 is controlled by the ECU 10.

[0020] The exhaust flow path 70 is a flow path that guides exhaust gas from the internal combustion engine 5. The exhaust flow path 70 includes an in-engine flow path 70a in the cylinder block 52 and an out-engine flow path 70b formed by the exhaust pipe 71 and the silencer 72. The in-engine flow path 70a is a flow path that allows exhaust gas in a cylinder 52c included in the cylinder block 52 to flow out of the cylinder block 52, and includes the exhaust port 52b. In this embodiment, the secondary air pipe 81 is connected to the cylinder block 52 and communicates with the in-engine flow path 70a at a position closer to the cylinder 52c than the exhaust port 52b, but is not limited to this. For example, the secondary air pipe 81 may be connected to the exhaust pipe 71 so as to communicate with the out-engine flow path 70b. The secondary air pipe 81 may be connected to the exhaust flow path 70 at a position where outside air supplied via the secondary air pipe 81 can recombine the fuel and carbon monoxide that were not completely combusted in the cylinder 52c.

[0021] The secondary air supply structure 8 is a structure for supplying secondary air, which is air that has passed through the air cleaner 64, to an exhaust passage 70 through which exhaust gas generated by the internal combustion engine 5 flows. In this embodiment, the secondary air supply structure 8 has a suction type structure that sucks secondary air into the exhaust passage 70 by using negative pressure generated in the exhaust passage 70 while the internal combustion engine 5 is operating, but is not limited to this.

[0022] Because the negative pressure generated in the exhaust flow path 70 is unstable, the flow rate of secondary air supplied by the secondary air supply structure 8 is also unstable. For example, when the internal combustion engine 5 is in an idling state during warm-up operation, even if secondary air is supplied to the exhaust flow path 70 by the secondary air supply structure 8, the secondary air may not be able to sufficiently re-burn unburned fuel and carbon monoxide contained in the exhaust gas. On the other hand, if the air-fuel ratio is made excessively lean in order to reduce the concentrations of unburned fuel and carbon monoxide, the internal combustion engine 5 may stop or stall. As will be described later, the ECU 10 according to this embodiment performs air-fuel ratio feedback control while secondary air is being supplied, thereby preventing the above-described state from occurring in the internal combustion engine 5.

[0023] Motorcycle 1 further includes transmission 21 and clutch 22 housed within crankcase 51. Internal combustion engine 5 includes crankshaft 53 housed within crankcase 51, and one or more pistons 54 slidably disposed within one or more cylinders 52c of cylinder block 52 and connected to crankshaft 53 so as to transmit driving force.

[0024] The internal combustion engine 5 generates power by repeatedly burning and exploding a mixture of fuel and air in the cylinder 52c. The internal combustion engine 5 converts the reciprocating motion of the piston 54 caused by the combustion and explosion into the rotational motion of the crankshaft 53, and transmits the rotational power of the crankshaft 53 to the rear wheel 3, which is a drive wheel. One end of the crankshaft 53 is connected to the clutch 22, and is further connected to the input shaft of the transmission 21 via the clutch 22 so as to be able to transmit power. The output shaft of the transmission 21 transmits the rotational power of the crankshaft 53 to the rear wheel 3 via a power transmission member 23, such as a chain or a belt.

[0025] The internal combustion engine 5 may be either a four-stroke engine or a two-stroke engine. The fuel used by the internal combustion engine 5 may be any fuel, such as fuels containing hydrocarbon compounds such as gasoline, ethanol, propane gas, and methane, fuels derived from animals and plants such as biofuels, or non-carbonized fuels such as hydrogen. The number of cylinders 52c of the internal combustion engine 5 may be either a single cylinder or a multi-cylinder.

[0026] The transmission 21 includes a plurality of gears, and can change the gear ratio by changing the gear that transmits the power of the internal combustion engine 5 to the rear wheels 3. The transmission 21 may have a structure in which the gear ratio is changed by a movable operator such as a shift pedal mechanically connected to the transmission 21. The transmission 21 may also include an actuator that changes the gear ratio under the control of the ECU 10. The clutch 22 has a structure that connects and disconnects the transmission of power between the crankshaft 53 and the transmission 21. The clutch 22 may have a structure that connects and disconnects by a movable operator such as a clutch lever mechanically connected to the clutch 22. The clutch 22 may also include an actuator that connects and disconnects the clutch 22 under the control of the ECU 10.

[0027] The motorcycle 1 may include a gear position sensor 31. The gear position sensor 31 detects a command specifying the gear ratio of the transmission 21 and outputs a detection signal to the ECU 10. For example, the gear position sensor 31 detects an operation on an operator such as a shift pedal, a shift lever, or a shift button. The ECU 10 may cause an actuator of the transmission 21 to change the gear that transmits the power of the internal combustion engine 5 to the rear wheel 3 in accordance with the detection signal from the gear position sensor 31.

[0028] The motorcycle 1 may include a clutch sensor 32. The clutch sensor 32 detects whether the clutch 22 is in an engaged state or a disengaged state, and outputs a detection signal to the ECU 10. The ECU 10 may cause an actuator of the clutch 22 to drive the clutch 22 based on the detection signal from the clutch sensor 32.

[0029] The motorcycle 1 may be equipped with a throttle position sensor 33 that detects the operating position of a throttle grip 11a arranged on the handlebar 11. The throttle position sensor 33 outputs a detection signal to the ECU 10. The detection signal of the operating position of the throttle grip 11a is a signal that commands the opening degree of a throttle valve of the throttle device 62. The ECU 10 causes the throttle actuator 40a of the throttle device 62 to drive the throttle valve in accordance with the detection signal of the throttle position sensor 33.

[0030] The motorcycle 1 may include a temperature sensor 34 that detects the temperature state of the internal combustion engine 5. One or more temperature sensors 34 may be arranged to detect the temperature of the coolant that cools the internal combustion engine 5, the temperature of the lubricating oil that lubricates the inside of the internal combustion engine 5, or both. The temperature sensor 34 may be arranged in the coolant flow path or the lubricating oil flow path. The temperature sensor 34 outputs a detection signal to the ECU 10.

[0031] The motorcycle 1 is equipped with a vehicle speed sensor 35 on the rear wheel 3. The vehicle speed sensor 35 detects the rotation speed of the rear wheel 3 and outputs a detection signal to the ECU 10. The vehicle speed sensor 35 or the ECU 10 detects the vehicle speed of the motorcycle 1 from the rotation speed. An example of the vehicle speed sensor 35 may include a rotation sensor such as an encoder. The vehicle speed sensor 35 may be disposed on the front wheel 2 and detect the rotation speed of the front wheel 2. The vehicle speed sensor 35 may be realized by a GNSS (Global Navigation Satellite System) that detects the position of the motorcycle 1 on the Earth.

[0032] The motorcycle 1 is equipped with an air-fuel ratio sensor 36. The air-fuel ratio sensor 36 detects air-fuel ratio information, which is information relating to the air-fuel ratio detected from the exhaust gas of the internal combustion engine 5. The air-fuel ratio is a dimensionless quantity obtained by dividing the air mass by the fuel mass at the time of combustion and explosion in the internal combustion engine 5. For example, the stoichiometric air-fuel ratio is 14.7.

[0033] Although not limited thereto, in this embodiment, the air-fuel ratio sensor 36 is an O2 sensor and is disposed in the exhaust flow path 70. The O2 sensor may be disposed in the exhaust flow path 70 downstream in the exhaust gas flow direction of the connection between the exhaust flow path 70 and the secondary air pipe 81. For example, the O2 sensor is disposed between the exhaust port 52b and the catalyst 73. The O2 sensor detects the presence or absence of oxygen contained in the exhaust gas flowing through the exhaust flow path 70 as air-fuel ratio information and outputs a signal indicating the detection result to the ECU 10. The O2 sensor outputs a voltage signal as the detection result. When the oxygen concentration in the exhaust gas is low, the O2 sensor outputs a voltage signal with a high voltage value, for example, near a reference voltage value. This voltage signal indicates that the air-fuel ratio is lower than the stoichiometric air-fuel ratio, i.e., a rich state. When the oxygen concentration in the exhaust gas is high, the O2 sensor outputs a voltage signal with a low voltage value, for example, near a voltage value of 0. This voltage signal indicates that the air-fuel ratio is higher than the stoichiometric air-fuel ratio, i.e., a lean state.

[0034] The air-fuel ratio sensor 36 may be a full-range air-fuel ratio sensor that detects the concentration of oxygen contained in exhaust gas. Examples of full-range air-fuel ratio sensors include an A / F (Air-by-Fuel) sensor and an LAF (Linear Air-Fuel Ratio) sensor. In a full-range air-fuel ratio sensor, the value of the current flowing through the full-range air-fuel ratio sensor corresponds to the concentration of oxygen contained in the exhaust gas. The full-range air-fuel ratio sensor outputs a signal indicating a current value corresponding to the oxygen concentration. For example, the ECU 10 can detect the deviation of the air-fuel ratio from the stoichiometric air-fuel ratio based on the detection signal of the full-range air-fuel ratio sensor.

[0035] The air-fuel ratio sensor 36 may include a heater that heats the air-fuel ratio sensor 36 when energized. This prevents damage to the air-fuel ratio sensor 36 due to the heat of the exhaust gas. The motorcycle 1 may include, in addition to an O2 sensor, a full-range air-fuel ratio sensor or an O2 sensor that is arranged in the exhaust flow path 70 between the catalyst 73 and the silencer 72 as the air-fuel ratio sensor 36. The ECU 10 uses the detection results of the O2 sensor, the full-range air-fuel ratio sensor, or both as feedback information to control the amount of fuel injection supplied to the internal combustion engine 5 so as to bring the air-fuel ratio closer to the stoichiometric air-fuel ratio and reduce impurities in the exhaust gas downstream of the catalyst 73.

[0036] The motorcycle 1 is equipped with one or more internal combustion engine actuators that control the operation of the internal combustion engine 5. The one or more internal combustion engine actuators include at least a throttle actuator 40a, a fuel injection actuator 40b, and an ignition actuator 40c. The throttle actuator 40a drives a throttle valve that adjusts the flow rate of air flowing into the cylinder block 52. The fuel injection actuator 40b includes a fuel injector that injects fuel into the cylinder block 52. The ignition actuator 40c includes a spark plug that ignites the air-fuel mixture in the cylinder block 52.

[0037] The ECU 10 adjusts the torque output by the internal combustion engine 5 in response to detection signals from sensors that detect the vehicle state of the motorcycle 1. For example, the ECU 10 controls the operations of the throttle actuator 40a, the fuel injection actuator 40b, and the ignition actuator 40c so that the torque corresponds to the rotation speed of the crankshaft 53, the vehicle speed, and the throttle opening.

[0038] The ECU 10 controls various actuators and the like in response to detection signals from sensors equipped on the motorcycle 1 that detect vehicle conditions. The ECU 10 includes a control circuit. Such an ECU 10 may include a microcomputer equipped with a processor P, such as a central processing unit (CPU) or a digital signal processor (DSP), and a memory M. The ECU 10 may also include a clock for measuring time. Examples of the memory include volatile memory, such as random access memory (RAM), and non-volatile memory, such as read-only memory (ROM). Some or all of the functions of the ECU 10 may be implemented by the CPU using the RAM as working memory and executing a program stored in the ROM. Some or all of the functions of the ECU 10 may be implemented by a dedicated hardware circuit, such as an electronic circuit or an integrated circuit. Some or all of the functions of the ECU 10 may be implemented by a combination of the above software functions and hardware circuits. Communication between the ECU 10 and devices mounted on the motorcycle 1 may be via an in-vehicle network, such as a controller area network (CAN).

[0039] The ECU 10 performs feedback control to control the amount of fuel injected by the fuel injection actuator 40b, using air-fuel ratio information detected by the air-fuel ratio sensor 36 as feedback information. In the feedback control, the ECU 10 increases or decreases the amount of fuel injected into the internal combustion engine 5 in response to an increase or decrease in the air-fuel ratio based on the air-fuel ratio information. In this embodiment, the air-fuel ratio sensor 36 is an O2 sensor, so the ECU 10 performs O2 feedback control.

[0040] The ECU 10 executes first and second feedback controls as feedback controls. The first feedback control corresponds to a state in which the secondary air supply structure 8 supplies secondary air to the exhaust flow path 70, and the second feedback control corresponds to a state in which the secondary air supply structure 8 does not supply secondary air to the exhaust flow path 70.

[0041] The ECU 10 determines whether a first feedback implementation condition is satisfied. When the first feedback implementation condition is satisfied, that is, in response to determining that the first feedback implementation condition is satisfied, the ECU 10 decides to execute the first feedback control. The ECU 10 determines whether a second feedback implementation condition is satisfied. When the second feedback implementation condition is satisfied, that is, in response to determining that the second feedback implementation condition is satisfied, the ECU 10 decides to execute the second feedback control.

[0042] The first feedback implementation condition includes one or more of the first to sixth implementation conditions, and in this embodiment, includes all of the first to sixth implementation conditions. The first implementation condition relates to the operating state of the air-fuel ratio sensor 36, specifically, a condition that the air-fuel ratio sensor 36 is in an activated state. The second implementation condition relates to the state of the transmission 21, specifically, a condition that the transmission 21 is in a neutral gear state in which the gear of the transmission 21 is not connected to the internal combustion engine 5 so as to be able to transmit driving force. The third implementation condition relates to an abnormality of the air-fuel ratio sensor 36, specifically, a condition that a failure diagnosis of the air-fuel ratio sensor 36 is not established. The fourth implementation condition relates to an abnormality of the heater of the air-fuel ratio sensor 36, specifically, a condition that a failure diagnosis of the heater of the air-fuel ratio sensor 36 is not established. The fifth implementation condition relates to an abnormality of the secondary air control valve 82, specifically, a condition that a failure diagnosis of the secondary air control valve 82 is not established. The sixth implementation condition relates to the control state of the ECU 10, specifically, the second feedback control is not being executed. The first to sixth implementation conditions contribute to the second condition, the second implementation condition corresponds to the third condition, and the sixth implementation condition corresponds to the fourth condition.

[0043] The first feedback implementation condition may further include a seventh implementation condition related to the operating state of the internal combustion engine 5, and in this embodiment, includes the seventh implementation condition. Specifically, the seventh implementation condition is a condition that the internal combustion engine 5 is in an idling state. The idling state is a state in which the ECU 10 operates the internal combustion engine 5 at a predetermined rotation speed while the throttle position sensor 33 is not outputting a signal instructing the opening of the throttle valve. The seventh implementation condition corresponds to the first condition.

[0044] The first feedback implementation condition may further include an eighth implementation condition related to the operating state of the secondary air control valve 82. Specifically, the eighth implementation condition is a condition in which the secondary air control valve 82 is in an open state in which it opens the exhaust passage 70. The open state is a state in which air that has bypassed the internal combustion engine 5 is sent into the exhaust passage 70. The eighth implementation condition corresponds to the second condition.

[0045] The first feedback implementation condition may further include a ninth implementation condition related to the temperature of the internal combustion engine 5. Specifically, the ninth implementation condition is a condition that the temperature detected by the temperature sensor 34 is equal to or lower than a predetermined temperature. The predetermined temperature may be a temperature at which the internal combustion engine 5 transitions from a warm-up operation state to a normal operation state. Satisfaction of the ninth implementation condition may indicate that the internal combustion engine 5 is in a warm-up operation state.

[0046] The first feedback implementation condition may further include a tenth implementation condition related to the vehicle speed of the motorcycle 1. Specifically, the tenth implementation condition is a condition that the vehicle speed of the motorcycle 1 detected by the vehicle speed sensor 35 is "0".

[0047] The first feedback implementation condition may further include an eleventh implementation condition related to the state of the clutch 22. Specifically, the eleventh implementation condition is a condition that the state of the clutch 22 detected by the clutch sensor 32 is a disengaged state in which power transmission is interrupted.

[0048] The first feedback implementation condition being satisfied means that all of the implementation conditions included in the first feedback implementation condition are satisfied. If at least one of the implementation conditions included in the first feedback implementation condition is not satisfied, the first feedback implementation condition is not satisfied.

[0049] During execution of the first feedback control, if ECU 10 determines that a stop condition for the first feedback control is satisfied, ECU 10 may stop the first feedback control. The stop condition for the first feedback control may include a condition that at least one of the implementation conditions included in the first feedback implementation condition is no longer satisfied. The stop condition for the first feedback control may include a condition that a seventh implementation condition related to an idle state of the internal combustion engine 5 is not satisfied. Satisfaction of the stop condition for the first feedback control may be a condition that one or more of the conditions included in the stop condition for the first feedback control are satisfied.

[0050] The second feedback implementation condition includes one or more of the first, third, fourth, and fifth implementation conditions. The second feedback implementation condition may further include a twelfth implementation condition related to the first feedback implementation condition. Specifically, the twelfth implementation condition is a condition in which the first feedback implementation condition is not satisfied. Although not limited thereto, in this embodiment, the second feedback implementation condition includes all of the first, third, fourth, fifth, and twelfth implementation conditions.

[0051] The second feedback implementation condition may further include a thirteenth implementation condition related to the temperature of the internal combustion engine 5. Specifically, the thirteenth implementation condition is a condition that the temperature detected by the temperature sensor 34 exceeds a predetermined temperature. The predetermined temperature may be a temperature at which the internal combustion engine 5 transitions from a warm-up operation state to a normal operation state. Satisfaction of the thirteenth implementation condition may indicate that the internal combustion engine 5 is in a normal operation state.

[0052] The second feedback implementation condition being satisfied means that all of the implementation conditions included in the second feedback implementation condition are satisfied. If at least one of the implementation conditions included in the second feedback implementation condition is not satisfied, the second feedback implementation condition is not satisfied.

[0053] During execution of the second feedback control, the ECU 10 may stop the second feedback control when it determines that a stop condition for the second feedback control is satisfied. The stop condition for the second feedback control may include a condition that at least one of the implementation conditions included in the second feedback implementation condition is no longer satisfied. The stop condition for the second feedback control may include a condition that a seventh implementation condition related to an idle state of the internal combustion engine 5 is satisfied. In other words, the stop condition for the second feedback control may include a condition that the operating position of the throttle grip 11a detected by the throttle position sensor 33 indicates a fully closed state of the throttle valve. Satisfaction of the stop condition for the second feedback control may be a condition that one or more of the conditions included in the stop condition for the second feedback control are satisfied.

[0054] The ECU 10 controls the operation of the secondary air control valve 82. The ECU 10 determines whether or not an open drive condition is satisfied, and, in response to determining that the open drive condition is satisfied, causes the secondary air control valve 82 to perform an opening operation to open the exhaust flow path 70. The ECU 10 determines whether or not a close drive condition is satisfied, and, in response to determining that the close drive condition is satisfied, causes the secondary air control valve 82 to perform a closing operation to close the exhaust flow path 70.

[0055] The open drive condition includes a condition that the first feedback implementation condition is satisfied. The open drive condition may include a condition that at least the first to sixth implementation conditions of the first feedback implementation condition are satisfied. The open drive condition may further include a condition that the seventh implementation condition, that is, the internal combustion engine 5 is in an idle state, is satisfied. Satisfaction of the open drive condition means that all of the implementation conditions related to the open drive condition are satisfied.

[0056] The closed drive condition includes a condition that the second feedback implementation condition is satisfied. The closed drive condition may include a condition that at least the first, third, fourth, and fifth implementation conditions of the second feedback implementation condition are satisfied. The closed drive condition may further include a condition that a twelfth implementation condition, that is, the first feedback implementation condition is not satisfied, is satisfied. The closed drive condition may further include a condition that a fourteenth implementation condition related to the control state of ECU 10 is satisfied. Specifically, the fourteenth implementation condition is a condition that the second feedback control is being executed. Satisfaction of the closed drive condition means that all of the implementation conditions related to the closed drive condition are satisfied.

[0057] The second feedback control by the ECU 10 will be described with reference to Fig. 3. Fig. 3 is a diagram showing an example of the behavior over time of the detection signal of the air-fuel ratio sensor 36, the estimated value of the air-fuel ratio, and the correction coefficient for the fuel injection amount during the second feedback control when the secondary air control valve 82 is closed.

[0058] In this embodiment, the air-fuel ratio sensor 36 is an O2 sensor, and therefore the voltage value of the air-fuel ratio sensor 36 during the second feedback control indicates a first voltage value Va1 or a second voltage value Va2 depending on whether or not oxygen is contained in the exhaust gas. The first voltage value Va1 is smaller than the second voltage value Va2 and corresponds to an air-fuel ratio that is higher than the stoichiometric air-fuel ratio and in a lean state. The second voltage value Va2 corresponds to an air-fuel ratio that is lower than the stoichiometric air-fuel ratio and in a rich state. The voltage reference value Vr corresponds to the stoichiometric air-fuel ratio. In the second feedback control, the reference value Vr is an intermediate value between the voltage values ​​Va1 and Va2, and the average value of the voltage value of the air-fuel ratio sensor 36 per predetermined time period can be the reference value Vr or a value close to it.

[0059] The ECU 10 stores a fuel map that correlates a reference target injection amount at which fuel is injected by the fuel injection actuator 40b with the rotation speed of the internal combustion engine 5 and the intake air amount of the internal combustion engine 5. Although not limited thereto, in this embodiment, the reference target injection amount is a fuel injection amount that achieves a theoretical air-fuel ratio with respect to the intake air amount. The fuel injection amount is the amount of fuel injected per unit time and is expressed, for example, using the mass or volume of fuel injected per minute. The intake air amount corresponds to a target load to be generated in the internal combustion engine 5. The fuel map is a map for determining the reference target injection amount based on the rotation speed of the internal combustion engine 5 and the intake air amount of the internal combustion engine 5. The reference target injection amount is an example of a reference fuel supply amount.

[0060] The ECU 10 determines a reference target injection amount by applying the rotation speed and intake air amount of the internal combustion engine 5 to a fuel map, and causes the fuel injection actuator 40b to inject fuel at the determined reference target injection amount. The intake air amount may be detected by a sensor such as an air flow sensor, or may be calculated by the ECU 10 based on the opening of a throttle valve, etc.

[0061] In the second feedback control, the ECU 10 determines the value of a fuel injection amount correction coefficient FA based on the detection signal of the air-fuel ratio sensor 36, and causes the fuel injection actuator 40b to inject fuel at a fuel injection amount obtained by multiplying the base target injection amount by the value of the correction coefficient FA. The correction coefficient FA indicates the rate at which the base target injection amount is increased or decreased. For example, the value of the correction coefficient FA can be "1," in which case the base target injection amount is not increased or decreased. The value of the correction coefficient FA can be "1.1," in which case the fuel injection amount is increased by 10% from the base target injection amount. The value of the correction coefficient FA can be "0.9," in which case the fuel injection amount is decreased by 10% from the base target injection amount.

[0062] In both the first feedback control and the second feedback control, the ECU 10 adjusts the fuel injection amount supplied to the internal combustion engine 5 by adjusting a correction coefficient for the reference target injection amount based on the detection signal of the air-fuel ratio sensor 36.

[0063] An upper limit value FAh and a lower limit value FAl are preset for the correction coefficient FA of the second feedback control. The value of the correction coefficient FA is determined within the range between the upper limit value FAh and the lower limit value FAl. Furthermore, a first correction coefficient FAa and a second correction coefficient FAb are set for the correction coefficient FA.

[0064] The ECU 10 corrects the base target injection amount using the first correction coefficient FAa when the voltage value of the air-fuel ratio sensor 36 is less than the reference value Vr, and corrects the base target injection amount using the second correction coefficient FAb when the voltage value of the air-fuel ratio sensor 36 exceeds the reference value Vr. When the voltage value of the air-fuel ratio sensor 36 increases from the first voltage value Va1 and reaches the reference value Vr, the ECU 10 switches the correction coefficient to be used from the first correction coefficient FAa to the second correction coefficient FAb. When the voltage value of the air-fuel ratio sensor 36 decreases from the second voltage value Va2 and reaches the reference value Vr, the ECU 10 switches the correction coefficient to be used from the second correction coefficient FAb to the first correction coefficient FAa.

[0065] The first correction coefficient FAa takes a value greater than 1. Although not limited thereto, in this embodiment, the first correction coefficient FAa can be varied within a range from its lower limit value FAa1 to its upper limit value FAa2. The second correction coefficient FAb takes a value less than 1. Although not limited thereto, in this embodiment, the second correction coefficient FAb can be varied within a range from its lower limit value FAb1 to its upper limit value FAb2. The upper limit value FAa2 of the first correction coefficient FAa is set to a value equal to or less than the upper limit value FAh. The lower limit value FAb1 of the second correction coefficient FAb is set to a value equal to or greater than the lower limit value FAl.

[0066] The ECU 10 switches the correction coefficient used from the second correction coefficient FAb to the first correction coefficient FAa immediately after the voltage value of the air-fuel ratio sensor 36 decreases and reaches the reference value Vr. The ECU 10 then applies the lower limit value FAa1 to correct the base target injection amount, and increases the value of the first correction coefficient FAa applied to the base target injection amount to the upper limit value FAa2 over time. In this embodiment, the ECU 10 increases the value of the first correction coefficient FAa linearly with respect to the elapsed time, but it may increase the value according to other functions. As a result, the increasing air-fuel ratio reaches a maximum value, then decreases, and reaches the stoichiometric air-fuel ratio. The decreasing voltage value of the air-fuel ratio sensor 36 reaches the first voltage value Va1, then increases, and reaches the reference value Vr. For example, a period TAa is required from the time when the second correction coefficient FAb is switched to the first correction coefficient FAa until the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. The upper limit value FAa2 of the first correction coefficient FAa is a limit value that limits the upper limit of the correction coefficient FA that shifts the air-fuel ratio to rich, and is an example of a third limit value.

[0067] The ECU 10 switches the correction coefficient used from the first correction coefficient FAa to the second correction coefficient FAb immediately after the voltage value of the air-fuel ratio sensor 36 increases and reaches the reference value Vr. The ECU 10 then applies the upper limit value FAb2 to correct the base target injection amount, and decreases the value of the second correction coefficient FAb applied to the base target injection amount to the lower limit value FAb1 over time. In this embodiment, the ECU 10 decreases the value of the second correction coefficient FAb linearly with respect to the elapsed time, but it may decrease according to other functions. As a result, the decreasing air-fuel ratio reaches a minimum value, then increases, and reaches the stoichiometric air-fuel ratio. The increasing voltage value of the air-fuel ratio sensor 36 reaches the second voltage value Va2, then decreases, and reaches the reference value Vr. For example, a period TAb is required from the time when the first correction coefficient FAa is switched to the second correction coefficient FAb until the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. In this example, the period TAb is equal to the period TAa. The lower limit value FAb1 of the second correction coefficient FAb is a limit value that limits the lower limit of the correction coefficient FA that shifts the air-fuel ratio to the lean side, and is an example of a fourth limit value.

[0068] Because the internal combustion engine 5 is not idling and secondary air is not supplied to the exhaust passage 70 of the internal combustion engine 5, the ECU 10 corrects the base target injection amount by alternately switching between the first correction coefficient FAa and the second correction coefficient FAb so that the air-fuel ratio approaches the stoichiometric air-fuel ratio. Furthermore, because the period TAa during which the first correction coefficient FAa is applied to the base target injection amount is equal to the period TAb during which the second correction coefficient FAb is applied to the base target injection amount, the voltage value of the air-fuel ratio sensor 36 exhibits an oscillating behavior, fluctuating alternately between the first voltage value Va1 and the second voltage value Va2. Furthermore, the average value of the voltage value of the air-fuel ratio sensor 36 per predetermined time period may be equal to or near the reference value Vr. Furthermore, because the value of the correction coefficient FA is within the range between the upper limit value FAh and the lower limit value FAl, the upper and lower limits of the air-fuel ratio are limited.

[0069] The first feedback control by the ECU 10 will be described with reference to Fig. 4. Fig. 4 is a diagram showing an example of the behavior over time of the detection signal of the air-fuel ratio sensor 36, the estimated value of the air-fuel ratio, and the correction coefficient for the fuel injection amount during the first feedback control when the secondary air control valve 82 is in an open state.

[0070] In the first feedback control, the ECU 10 determines the value of a correction coefficient FB of the fuel injection amount based on the detection signal of the air-fuel ratio sensor 36, and causes the fuel injection actuator 40b to inject fuel at a fuel injection amount obtained by multiplying the standard target injection amount by the value of the correction coefficient FB.

[0071] The voltage value of the air-fuel ratio sensor 36 during the first feedback control exhibits a first voltage value Vb1 or a second voltage value Vb2 depending on whether oxygen is present in the exhaust gas. The first voltage value Vb1 is smaller than the second voltage value Vb2 and corresponds to an air-fuel ratio higher than the stoichiometric air-fuel ratio, i.e., a lean state. The second voltage value Vb2 corresponds to an air-fuel ratio lower than the stoichiometric air-fuel ratio, i.e., a rich state. During the first feedback control, the reference value Vr is an intermediate value between the voltage values ​​Vb1 and Vb2, and the average voltage value of the air-fuel ratio sensor 36 is smaller than the reference value Vr. The average voltage value of the air-fuel ratio sensor 36 per predetermined time period is 50% or less of the reference value Vr, and can be, for example, within a range of 40% to 50% of the reference value Vr. As a result, during the first feedback control, the air-fuel ratio exhibits a behavior biased toward a lean state.

[0072] In the first feedback control, the ECU 10 determines the value of a fuel injection amount correction coefficient FB based on the detection signal of the air-fuel ratio sensor 36, and causes the fuel injection actuator 40b to inject fuel at a fuel injection amount obtained by multiplying the reference target injection amount by the value of the correction coefficient FB. An upper limit value FBh and a lower limit value FBl are set in advance for the correction coefficient FB of the first feedback control. The upper limit value FBh is smaller than the upper limit value FAh of the second feedback control. The lower limit value FBl is larger than the lower limit value FAl of the second feedback control. The value of the correction coefficient FB is determined within the range between the upper limit value FBh and the lower limit value FBl.

[0073] As a result, the air-fuel ratio in the first feedback control is controlled so that the maximum value of the air-fuel ratio in the first feedback control is smaller than the maximum value of the air-fuel ratio in the second feedback control and the minimum value of the air-fuel ratio in the first feedback control is larger than the minimum value of the air-fuel ratio in the second feedback control. Since the air-fuel ratio is biased toward the lean state while preventing the air-fuel ratio from transitioning to an excessively lean state, the concentrations of unburned fuel and carbon monoxide in the exhaust gas are reduced without causing the internal combustion engine 5 to stop or stall, even when the internal combustion engine 5 is in an idling state.

[0074] The correction coefficient FB is set to a first correction coefficient FBa and a second correction coefficient FBb. The ECU 10 corrects the base target injection amount using the first correction coefficient FBa when the voltage value of the air-fuel ratio sensor 36 is less than the reference value Vr. In such a case, the air-fuel ratio sensor 36 displays a detection result similar to that when the air-fuel ratio is lean, which means that the concentrations of unburned fuel and carbon monoxide in the exhaust gas to which secondary air is supplied are low. The ECU 10 corrects the base target injection amount using the second correction coefficient FBb when the voltage value of the air-fuel ratio sensor 36 exceeds the reference value Vr. In such a case, the air-fuel ratio sensor 36 displays a detection result similar to that when the air-fuel ratio is rich, which means that the concentrations of unburned fuel and carbon monoxide in the exhaust gas to which secondary air is supplied are high. In other words, the flow rate of secondary air is insufficient.

[0075] When the voltage value of the air-fuel ratio sensor 36 increases from the first voltage value Vb1 and reaches the reference value Vr, the ECU 10 switches the correction coefficient to be used from the first correction coefficient FBa to the second correction coefficient FBb. When the voltage value of the air-fuel ratio sensor 36 decreases from the second voltage value Vb2 and reaches the reference value Vr, the ECU 10 switches the correction coefficient to be used from the second correction coefficient FBb to the first correction coefficient FBa.

[0076] In this embodiment, the first correction coefficient FBa is set to 1 or a value close to 1, but is not limited to this. The first correction coefficient FBa may be greater than 1 or less than 1. In this embodiment, the first correction coefficient FBa is constant or approximately constant over time. The first correction coefficient FBa does not cause the fuel injection amount to shift from the base target injection amount toward the rich side. The second correction coefficient FBb takes a value in a range less than 1 that is smaller than the first correction coefficient FBa. Although not limited to this, in this embodiment, the second correction coefficient FBb can be varied within a range from its upper limit value FBb2 to its lower limit value FBb1. The value of the first correction coefficient FBa is equal to or smaller than the upper limit value FBh. The lower limit value FBb1 of the second correction coefficient FBb is set to a value equal to or larger than the lower limit value FBl.

[0077] The ECU 10 switches the correction coefficient used from the second correction coefficient FBb to the first correction coefficient FBa when the voltage value of the air-fuel ratio sensor 36 drops and reaches the reference value Vr, and corrects the reference target injection amount by applying the set value of the first correction coefficient FBa. As a result, the increasing air-fuel ratio reaches a maximum value, then drops and reaches the stoichiometric air-fuel ratio. The decreasing voltage value of the air-fuel ratio sensor 36 reaches the first voltage value Vb1, then rises and reaches the reference value Vr. For example, a period TBa is required from the time when the second correction coefficient FBb is switched to the first correction coefficient FBa until the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. Because the first correction coefficient FBa does not correct the reference target injection amount toward the rich side, the period TBa is significantly longer than the period TAa in the second feedback control. The set value of the first correction coefficient FBa is a limit value that limits the upper limit of the correction coefficient FB, which transitions the air-fuel ratio toward the rich side, and is an example of a first limit value.

[0078] The ECU 10 corrects the base target injection amount by applying the upper limit value FBb2 immediately after switching the correction coefficient used from the first correction coefficient FBa to the second correction coefficient FBb when the voltage value of the air-fuel ratio sensor 36 increases and reaches the reference value Vr. Over time, the ECU 10 then decreases the value of the second correction coefficient FBb applied to the base target injection amount to the lower limit value FBb1. In this embodiment, the ECU 10 decreases the value of the second correction coefficient FBb linearly with respect to the elapsed time, but it may decrease according to other functions. As a result, the increasing voltage value of the air-fuel ratio sensor 36 reaches the second voltage value Vb2, then decreases to the reference value Vr. The decreasing air-fuel ratio then reaches a minimum value, then increases to the stoichiometric air-fuel ratio. For example, a period TBb is required from the time when the first correction coefficient FBa is switched to the second correction coefficient FBb until the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. The lower limit value FBb1 of the first correction coefficient FBa is a limit value that limits the lower limit of the correction coefficient FB that shifts the air-fuel ratio to the lean side, and is an example of a second limit value.

[0079] Since the first correction coefficient FBa does not correct the base target injection amount to the rich side, the behavior of the air-fuel ratio is biased toward the lean state. Therefore, the period TBb may be significantly shorter than the period TBa and may be shorter than the period TAb in the second feedback control.

[0080] The ECU 10 corrects the base target injection amount so as not to shift toward a richer state while alternately switching between the first correction coefficient FBa and the second correction coefficient FBb so as to bring the air-fuel ratio closer to the stoichiometric air-fuel ratio. Because the period TBa during which the first correction coefficient FBa is applied to the base target injection amount is significantly longer than the period TBb during which the second correction coefficient FBb is applied to the base target injection amount, the period during which the voltage value of the air-fuel ratio sensor 36 indicates the first voltage value Vb1 is longer. Therefore, the average value of the voltage value of the air-fuel ratio sensor 36 per predetermined time period becomes 50% or less of the reference value Vr, and the behavior of the air-fuel ratio is biased toward a leaner state. Therefore, even when the internal combustion engine 5 is idling and secondary air is supplied to the exhaust passage 70 of the internal combustion engine 5, the exhaust gas is purified and stopping and stalling of the internal combustion engine 5 are suppressed.

[0081] Also, immediately after the internal combustion engine 5 is started, as shown at time t1 in Fig. 4, the ECU 10 applies the second correction coefficient FBb to the reference target injection amount. Since the fuel injection amount at the start of the internal combustion engine 5 is larger than the reference target injection amount and the air-fuel ratio is in a rich state, the ECU 10 may set the second correction coefficient FBb to a lower limit value FBb1 so that it remains constant or approximately constant over time.

[0082] An example of the operation of the ECU 10 that executes the first feedback control and the second feedback control will be described below. Fig. 5 is a flowchart showing an example of the operation of the feedback control of the ECU 10 according to the embodiment.

[0083] First, in step S101, the ECU 10 determines whether the first feedback execution condition is satisfied. If the first feedback execution condition is satisfied (Yes in step S101), the ECU 10 proceeds to step S102, and if the first feedback execution condition is not satisfied (No in step S101), the ECU 10 proceeds to step S103. The ECU 10 determines that the first feedback execution condition is satisfied when all of the execution conditions included in the first feedback execution condition are satisfied, and determines that the first feedback execution condition is not satisfied when one or more of the execution conditions are not satisfied.

[0084] In step S102, the ECU 10 executes the first feedback control, ie, controls the driving of the fuel injection actuator 40b based on the detection signal received from the air-fuel ratio sensor .

[0085] Next, in step S104, the ECU 10 operates the secondary air control valve 82 to open it. If the secondary air control valve 82 is already open, this step is omitted.

[0086] Next, in step S105, ECU 10 determines whether or not the stop condition of the first feedback control is satisfied. If the stop condition is satisfied (Yes in step S105), ECU 10 proceeds to step S106, and if the stop condition is not satisfied (No in step S105), ECU 10 repeats step S105. If one or more conditions included in the stop condition of the first feedback control are satisfied, ECU 10 determines that the stop condition is satisfied, and if all of the conditions included in the stop condition are not satisfied, ECU 10 determines that the stop condition is not satisfied.

[0087] In step S106, the ECU 10 stops the feedback control that is being executed, and controls the internal combustion engine 5 without using the feedback control. For example, the ECU 10 determines the amount of fuel injection into the internal combustion engine 5 according to a fuel map. The ECU 10 makes the determination of step S101 while executing step S106.

[0088] In step S103, ECU 10 determines whether the second feedback execution condition is satisfied. If the second feedback execution condition is satisfied (Yes in step S103), ECU 10 proceeds to step S107, and if the second feedback execution condition is not satisfied (No in step S103), ECU 10 proceeds to step S106.

[0089] ECU10 determines that the second feedback implementation condition is satisfied when all of the implementation conditions included in the second feedback implementation condition are satisfied, and determines that the second feedback implementation condition is not satisfied when one or more of the implementation conditions are not satisfied.

[0090] In step S107, the ECU 10 executes the second feedback control, ie, controls the driving of the fuel injection actuator 40b based on the detection signal received from the air-fuel ratio sensor .

[0091] Next, in step S108, the ECU 10 operates the secondary air control valve 82 to close it. If the secondary air control valve 82 is already closed, this step is omitted.

[0092] Next, in step S109, ECU 10 determines whether or not the stop condition of the second feedback control is satisfied. If the stop condition is satisfied (Yes in step S109), ECU 10 proceeds to step S106, and if the stop condition is not satisfied (No in step S109), ECU 10 repeats step S109. If one or more conditions included in the stop condition of the second feedback control are satisfied, ECU 10 determines that the stop condition is satisfied, and if all of the conditions included in the stop condition are not satisfied, ECU 10 determines that the stop condition is not satisfied.

[0093] Through steps S101 to S109, the ECU 10 selects and executes the first feedback control or the second feedback control according to the vehicle state of the motorcycle 1. Note that the ECU 10 executes the determination in step S103 after the determination in step S101, but the determinations may be executed in the reverse order. The ECU 10 may execute step S102 after step S104. The ECU 10 may execute step S107 after step S108.

[0094] [others] Although exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments. In other words, various modifications and improvements are possible within the scope of the present disclosure. For example, various modifications made to the embodiments and embodiments constructed by combining components of different embodiments are also included within the scope of the present disclosure.

[0095] For example, in the embodiment, ECU 10 operates the secondary air control valve 82 to the open state after starting the first feedback control, and operates the secondary air control valve 82 to the closed state after starting the second feedback control, but this is not limited to this. For example, ECU 10 may operate the secondary air control valve 82 to the open state before starting the first feedback control. ECU 10 may operate the secondary air control valve 82 to the closed state before starting the second feedback control. In such a case, the first feedback implementation condition may include a condition that the secondary air control valve 82 is in the open state. The second feedback implementation condition may include a condition that the secondary air control valve 82 is in the closed state.

[0096] In the embodiment, the open drive condition for the secondary air control valve 82 includes a condition that the first feedback implementation condition is satisfied, and the close drive condition for the secondary air control valve 82 includes a condition that the second feedback implementation condition is satisfied, but is not limited to this. The implementation conditions included in the open drive condition may be different from the implementation conditions included in the first feedback implementation condition. For example, the implementation conditions included in the open drive condition may be more or fewer than the implementation conditions included in the first feedback implementation condition. The implementation conditions included in the close drive condition may be different from the implementation conditions included in the second feedback implementation condition. For example, the implementation conditions included in the close drive condition may be more or fewer than the implementation conditions included in the second feedback implementation condition.

[0097] In the embodiment, in the second feedback control, the ECU 10 increases the value of the first correction coefficient FAa over time and decreases the value of the second correction coefficient FAb over time, but is not limited to this. For example, the ECU 10 may decrease the value of the first correction coefficient FAa over time or maintain it constant or approximately constant. The ECU 10 may increase the value of the second correction coefficient FAb over time or maintain it constant or approximately constant. The ECU 10 may control the value of the first correction coefficient FAa so that the integral of the value of the first correction coefficient FAa for each period TAa becomes a constant value. The ECU 10 may control the value of the second correction coefficient FAb so that the integral of the value of the second correction coefficient FAb for each period TAb becomes a constant value.

[0098] In the embodiment, in the first feedback control, the ECU 10 maintains the value of the first correction coefficient FBa constant or approximately constant over time and decreases the value of the second correction coefficient FBb over time, but is not limited to this. For example, the ECU 10 may increase or decrease the value of the first correction coefficient FBa over time. The ECU 10 may increase the value of the second correction coefficient FBb over time or maintain it constant or approximately constant. The ECU 10 may control the value of the first correction coefficient FBa so that the integral of the value of the first correction coefficient FBa for each period TBa becomes a constant value. The ECU 10 may control the value of the second correction coefficient FBb so that the integral of the value of the second correction coefficient FBb for each period TBb becomes a constant value.

[0099] In the embodiment, the ECU 10 switches between the first correction coefficient FAa and the second correction coefficient FAb during the second feedback control at the timing when the voltage value of the air-fuel ratio sensor 36 rises or falls and reaches the reference value Vr, but this is not limiting. The timing for switching between the first correction coefficient FAa and the second correction coefficient FAb may be a timing before the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. For example, the switching timing may be any timing between the timing when the voltage value of the air-fuel ratio sensor 36 transitions from rising to falling and the timing when the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. The switching timing may be any timing between the timing when the voltage value of the air-fuel ratio sensor 36 transitions from falling to rising and the timing when the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr.

[0100] In the embodiment, the ECU 10 switches between the first correction coefficient FBa and the second correction coefficient FBb during the first feedback control at the timing when the voltage value of the air-fuel ratio sensor 36 rises or falls and reaches the reference value Vr, but this is not limiting. The timing for switching between the first correction coefficient FBa and the second correction coefficient FBb may be a timing before the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. For example, the switching timing may be any timing between the timing when the voltage value of the air-fuel ratio sensor 36 transitions from rising to falling and the timing when the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr. The switching timing may be any timing between the timing when the voltage value of the air-fuel ratio sensor 36 transitions from falling to rising and the timing when the voltage value of the air-fuel ratio sensor 36 reaches the reference value Vr.

[0101] In the embodiment, the first feedback control and the second feedback control of the ECU 10 are described for a case where the air-fuel ratio sensor 36 is an O2 sensor. However, the ECU 10 can similarly perform the first feedback control and the second feedback control even when the air-fuel ratio sensor 36 is a sensor other than an O2 sensor. In the embodiment, the ECU 10 determines a correction coefficient to be used depending on whether the air-fuel ratio corresponding to the voltage value of the O2 sensor is in a state of going from a lean state to the stoichiometric air-fuel ratio, a state of going from a rich state to the stoichiometric air-fuel ratio, a state of transitioning from an increasing state to a decreasing state, or a state of transitioning from a decreasing state to an increasing state, and adjusts and uses the determined correction coefficient. The ECU 10 may also determine a correction coefficient to be used for an air-fuel ratio sensor other than an O2 sensor depending on whether the air-fuel ratio corresponding to the detection signal of the air-fuel ratio sensor is in a state of going from a lean state to the stoichiometric air-fuel ratio, a state of going from a rich state to the stoichiometric air-fuel ratio, a state of transitioning from an increasing state to a decreasing state, or a state of transitioning from a decreasing state to an increasing state, and adjusts and uses the determined correction coefficient.

[0102] Examples of each aspect of the technology of the present disclosure are as follows: A control circuit according to a first aspect of the present disclosure is a control circuit for an internal combustion engine of a vehicle, and is configured to determine whether a first condition is satisfied that the internal combustion engine is in an idle state, determine whether a second condition is satisfied that air that has bypassed the internal combustion engine is being sent into an exhaust flow path of the internal combustion engine, acquire air-fuel ratio information that is information related to the air-fuel ratio detected from exhaust gas of the internal combustion engine by an air-fuel ratio sensor, and, when the first condition and the second condition are satisfied, execute first feedback control that increases and decreases the amount of fuel supplied to the internal combustion engine in response to increases and decreases in the air-fuel ratio based on the air-fuel ratio information.

[0103] According to the first aspect, the control circuit executes the first feedback control when the first condition and the second condition are satisfied, i.e., in response to determining that the first condition and the second condition are satisfied. Therefore, the internal combustion engine undergoes the first feedback control when secondary air is supplied and the engine is idling. In the first feedback control, the control circuit adjusts the amount of fuel supplied to the internal combustion engine in response to an increase or decrease in the air-fuel ratio of the exhaust gas containing secondary air. Therefore, the control circuit can stabilize the state of the exhaust gas emitted from the internal combustion engine.

[0104] In the above-mentioned first aspect, the control circuit according to the second aspect of the present disclosure may be further configured to determine whether a third condition is satisfied, in which the transmission provided in the vehicle is in a neutral gear state in which the gear of the transmission is not connected to the internal combustion engine so as to be able to transmit driving force, and the control circuit may execute the first feedback control when the third condition is satisfied in addition to the first condition and the second condition.

[0105] According to the second aspect, the control circuit executes the first feedback control when the third condition is satisfied in addition to the first and second conditions, i.e., when it is determined that the third condition is satisfied in addition to the first and second conditions. This limits the vehicle state for executing the first feedback control to a state where the load on the internal combustion engine is low. In such a state, the control circuit can stabilize the state of exhaust gas emitted from the internal combustion engine.

[0106] In the above-described first or second aspect, a control circuit according to a third aspect of the present disclosure may be further configured to, when the second condition is not satisfied, execute a second feedback control that increases and decreases the amount of fuel supplied to the internal combustion engine in accordance with an increase and decrease in the air-fuel ratio based on the air-fuel ratio information, the second feedback control being in accordance with an air-fuel ratio restriction different from that of the first feedback control, and to determine whether a fourth condition is satisfied that the second feedback control is not being executed, and the control circuit may execute the first feedback control when the fourth condition is satisfied in addition to the first condition and the second condition.

[0107] According to the third aspect, the control circuit executes the second feedback control when the second condition is not satisfied, i.e., in response to determining that the second condition is not satisfied. The control circuit executes the first feedback control when the fourth condition is satisfied in addition to the first and second conditions, i.e., in response to determining that the fourth condition is satisfied in addition to the first and second conditions. Therefore, execution of the first feedback control is limited to when the second feedback control is not being executed. Therefore, the first feedback control corresponds to an internal combustion engine in a state where secondary air is supplied and in an idle state, and is executed as control separate from the second feedback control.

[0108] In any of the above first to third aspects, a control circuit according to a fourth aspect of the present disclosure is further configured to execute, when the second condition is not satisfied, a second feedback control that increases and decreases the amount of fuel supplied to the internal combustion engine in response to an increase and a decrease in the air-fuel ratio based on the air-fuel ratio information, and adjusts the amount of fuel supplied to the internal combustion engine so that it falls within a range between a third limit value that limits an upper limit of the amount of fuel supplied that causes the air-fuel ratio to transition rich and a fourth limit value that limits a lower limit of the amount of fuel supplied that causes the air-fuel ratio to transition lean, and the control circuit may, in the first feedback control, adjust the amount of fuel supplied to the internal combustion engine so that it falls within a range between a first limit value that limits an upper limit of the amount of fuel supplied that causes the air-fuel ratio to transition rich and a second limit value that limits a lower limit of the amount of fuel supplied that causes the air-fuel ratio to transition lean, and the first limit value may be smaller than the third limit value or the second limit value may be larger than the fourth limit value.

[0109] According to the fourth aspect, when the second condition is not satisfied, that is, in response to determining that the second condition is not satisfied, the control circuit executes second feedback control to adjust the amount of fuel supplied to the internal combustion engine so that it falls within a range between the third limit value and the fourth limit value. In the first feedback control, the control circuit adjusts the amount of fuel supplied to the internal combustion engine so that it falls within a range between the first limit value, which is smaller than the third limit value, and the second limit value, which is larger than the fourth limit value. This makes the difference between the first feedback control and the second feedback control clear. The first feedback control can prevent the air-fuel ratio from shifting richer than the second feedback control, thereby reducing the concentrations of unburned fuel and carbon monoxide in the exhaust gas. The first feedback control can prevent the air-fuel ratio from shifting leaner than the second feedback control, thereby preventing unstable behavior of the internal combustion engine, such as stalling during idle.

[0110] In the control circuit according to a fifth aspect of the present disclosure, in the fourth aspect described above, the first limit value may be a limit value of the fuel supply amount corresponding to a stoichiometric air-fuel ratio or an air-fuel ratio leaner than the stoichiometric air-fuel ratio.

[0111] According to the fifth aspect, the first feedback control can suppress the air-fuel ratio from shifting to the rich side.

[0112] In any of the first to fifth aspects described above, a control circuit according to a sixth aspect of the present disclosure may, in the first feedback control, reduce the amount of fuel supplied to the internal combustion engine when a first state in which the air-fuel ratio transitions to rich is detected based on the air-fuel ratio information, and increase the amount of fuel supplied to the internal combustion engine when a second state in which the air-fuel ratio transitions to lean is detected based on the air-fuel ratio information.

[0113] According to the sixth aspect, the first feedback control increases and decreases the fuel supply amount in response to the air-fuel ratio shifting to a lean state and a rich state, thereby improving the robustness of the air-fuel ratio for exhaust gas containing secondary air.

[0114] In the sixth aspect above, the control circuit according to a seventh aspect of the present disclosure may, in the first feedback control, adjust the amount of fuel supplied to the internal combustion engine so as to maintain a constant amount of fuel supplied in the first state.

[0115] According to the seventh aspect, the first feedback control can effectively prevent the air-fuel ratio from becoming rich.

[0116] In any of the first to seventh aspects described above, in the control circuit according to an eighth aspect of the present disclosure, increasing, decreasing, or maintaining constant the fuel supply amount may be increasing, decreasing, or maintaining constant a correction coefficient, which is a rate at which a reference fuel supply amount corresponding to the stoichiometric air-fuel ratio is increased or decreased.

[0117] According to the eighth aspect, the control circuit can perform feedback control in response to changes in the state of the internal combustion engine, such as changes in the rotation speed.

[0118] A motorcycle according to a ninth aspect of the present disclosure comprises a control circuit according to any one of the first to eighth aspects described above, the internal combustion engine, a supply passage connecting an intake passage that introduces air into the internal combustion engine and an exhaust passage that discharges exhaust gas from the internal combustion engine, a secondary air supply structure including a valve that opens and closes the supply passage, and the air-fuel ratio sensor that is positioned in the exhaust passage downstream of the supply passage in the flow direction of the exhaust gas, and the control circuit determines whether the second condition is satisfied based on the open / closed state of the valve.

[0119] According to the ninth aspect, the same effects as those of the control circuits according to the aspects of the present disclosure can be obtained.

[0120] The functions of the elements disclosed herein can be performed using circuits or processing circuitry, including general-purpose processors, special-purpose processors, integrated circuits, ASICs, conventional circuits, and / or combinations thereof, configured or programmed to perform the disclosed functions. A processor is considered a processing circuit or circuitry because it includes transistors and other circuitry. In this disclosure, a circuit, unit, or means is hardware that performs the recited functions or hardware that is programmed to perform the recited functions. The hardware may be hardware disclosed herein or other known hardware that is programmed or configured to perform the recited functions. Where the hardware is a processor, which is considered a type of circuit, the circuit, means, or unit is a combination of hardware and software, and the software is used to configure the hardware and / or processor.

[0121] All numbers such as ordinal numbers and quantities used in this specification are provided as examples to specifically explain the technology of the present disclosure, and the present disclosure is not limited to the illustrated numbers. The connection relationships between components are provided as examples to specifically explain the technology of the present disclosure, and the connection relationships that realize the functions of the present disclosure are not limited to these.

[0122] Because the present disclosure may be embodied in various forms without departing from the scope of its essential characteristics, the scope of the present disclosure is defined by the appended claims rather than the description in the specification, and therefore the exemplary embodiments and modifications are intended to be illustrative and not limiting. All modifications within the scope of the claims and their equivalents are intended to be embraced by the claims. [Explanation of symbols]

[0123] 1. Vehicles, motorcycles 5. Internal combustion engine 8 Secondary air supply structure 10 Electronic control unit, ECU (control circuit) 70 Exhaust flow path 60 Intake passage 81 Secondary air pipe (supply line) 82 Secondary air control valve

Claims

1. A control circuit for an internal combustion engine of a vehicle, determining whether a first condition is satisfied that the internal combustion engine is in an idle state; determining whether a second condition is satisfied, that is, air that has bypassed the internal combustion engine is being sent into an exhaust flow path of the internal combustion engine; acquiring air-fuel ratio information that is information about the air-fuel ratio detected from exhaust gas of the internal combustion engine by an air-fuel ratio sensor; and when the first condition and the second condition are satisfied, executing a first feedback control that increases and decreases the amount of fuel supplied to the internal combustion engine based on the air-fuel ratio information so as to correspond to an increase and a decrease in the air-fuel ratio. Control circuit.

2. a transmission included in the vehicle is further configured to determine whether a third condition is satisfied, in which a gear of the transmission is in a neutral gear state in which the gear is not connected to the internal combustion engine so as to be able to transmit driving force; The control circuit executes the first feedback control when the third condition is satisfied in addition to the first and second conditions. The control circuit of claim 1 .

3. When the second condition is not satisfied, a second feedback control is executed to increase and decrease the amount of fuel supplied to the internal combustion engine in accordance with an increase and a decrease in the air-fuel ratio based on the air-fuel ratio information, the second feedback control being in accordance with a different air-fuel ratio limitation than that of the first feedback control; and determining whether a fourth condition is satisfied, the fourth condition being that the second feedback control is not being executed; The control circuit executes the first feedback control when the fourth condition is satisfied in addition to the first and second conditions. The control circuit of claim 1 .

4. when the second condition is not satisfied, a second feedback control is executed to increase and decrease the amount of fuel supplied to the internal combustion engine in accordance with an increase and a decrease in the air-fuel ratio based on the air-fuel ratio information, and the second feedback control is executed to adjust the amount of fuel supplied to the internal combustion engine so as to fall within a range between a third limit value that limits an upper limit of the amount of fuel supplied at which the air-fuel ratio shifts to rich and a fourth limit value that limits a lower limit of the amount of fuel supplied at which the air-fuel ratio shifts to lean, the control circuit, in the first feedback control, adjusts the amount of fuel supplied to the internal combustion engine so that the amount of fuel supplied falls within a range between a first limit value that limits an upper limit of the amount of fuel supplied at which the air-fuel ratio shifts to rich and a second limit value that limits a lower limit of the amount of fuel supplied at which the air-fuel ratio shifts to lean; The first limit value is smaller than the third limit value, or the second limit value is larger than the fourth limit value. The control circuit of claim 1 .

5. The first limit value is a limit value of the fuel supply amount corresponding to the stoichiometric air-fuel ratio or an air-fuel ratio leaner than the stoichiometric air-fuel ratio.

5. The control circuit of claim 4.

6. In the first feedback control, When a first state in which the air-fuel ratio transitions to a rich state is detected based on the air-fuel ratio information, the amount of fuel supplied to the internal combustion engine is reduced; When a second state in which the air-fuel ratio transitions to a lean state is detected based on the air-fuel ratio information, the amount of fuel supplied to the internal combustion engine is increased. The control circuit of claim 1 .

7. The first feedback control adjusts the amount of fuel supplied to the internal combustion engine so as to maintain a constant amount of fuel supplied in the first state.

7. The control circuit of claim 6.

8. Increasing, decreasing, or maintaining constant the fuel supply amount means increasing, decreasing, or maintaining constant the correction coefficient, which is the rate at which the reference fuel supply amount corresponding to the stoichiometric air-fuel ratio is increased or decreased. A control circuit according to any one of claims 1 to 7.

9. a control circuit according to claim 1; the internal combustion engine; a secondary air supply structure including a supply passage connecting an intake passage that introduces air into the internal combustion engine and an exhaust passage that discharges exhaust gas from the internal combustion engine, and a valve that opens and closes the supply passage; the air-fuel ratio sensor is disposed in the exhaust flow path downstream of the supply flow path in the flow direction of the exhaust gas, The control circuit determines whether the second condition is satisfied based on the open / closed state of the valve. Motorcycle.

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