Internal combustion engine control device

Abstract

In an internal combustion engine control device (50), when the ratio of an increase in the amount of torque that is output by an internal combustion engine (1) to an increase in the throttle opening degree of the internal combustion engine (1) decreases to a threshold value or less, a control unit (152) executes a throttle opening degree limiting process to limit the increase in the throttle opening degree.

Description

Internal combustion engine control device

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

[0002] BACKGROUND ART In recent years, fuel efficiency regulations for internal combustion engines, which are the power sources of vehicles such as motorcycles, have been tightened in response to global demands for reducing energy consumption and carbon dioxide gas emissions.

[0003] Under such circumstances, Patent Document 1 relates to an intake control device for an internal combustion engine, and discloses a configuration in which, in the low rotation speed range, the throttle valve opening (throttle opening) is limited so as not to open beyond a first predetermined opening A (an opening which results in an intake air flow rate that is approximately 5% less than the maximum intake air flow rate), and at high loads and in the low rotation speed range, the throttle opening is limited so as not to open beyond a predetermined opening B (B < A).

[0004] Japanese Patent Application Laid-Open No. 2000-54888

[0005] However, according to the inventor's investigations, the configuration of Patent Document 1 limits the throttle opening so that it does not open beyond a predetermined opening when the internal combustion engine is in the low rotation speed range or in the low rotation speed range under high load, but this is merely intended to reduce intake noise and does not disclose any configuration for limiting the increase in throttle opening in order to improve fuel efficiency, and there is room for improvement from the perspective of contributing to improved fuel efficiency.

[0006] The present invention was made based on the above considerations, and aims to provide an internal combustion engine control device that can limit an increase in the throttle opening so as to achieve improved fuel efficiency of the internal combustion engine.

[0007] In order to achieve the above-mentioned object, one aspect of the present invention is a control device for an internal combustion engine that includes a control unit that executes a limiting process to limit an increase in the throttle opening, which is the opening of the throttle valve of an internal combustion engine of a vehicle, and the control unit executes the limiting process when the ratio of the increase in the torque output by the internal combustion engine to the increase in the throttle opening falls below a threshold value.

[0008] According to an internal combustion engine control device of one aspect of the present invention, the control unit executes a limiting process to limit the increase in the throttle opening when the ratio of the increase in the torque output by the internal combustion engine to the increase in the throttle opening of the internal combustion engine falls below a threshold value, thereby limiting the increase in the throttle opening so as to achieve improved fuel efficiency of the internal combustion engine.

[0009] Fig. 1 is a schematic diagram showing the configuration of an internal combustion engine control device (hereinafter sometimes referred to as engine control device) according to an embodiment of the present invention, together with an internal combustion engine (hereinafter sometimes referred to as engine) to which the same is applied. Fig. 2 is a schematic diagram showing the high-load over-rich region exhibited by an engine to which the engine control device according to this embodiment is applied, in terms of the relationship between engine speed (engine rotational speed) and throttle opening. Fig. 3 is a flowchart showing an example of a process for calculating a target value for throttle opening, including a throttle opening limiting process, of the engine control device according to this embodiment. Fig. 4 is a time chart showing an example of the operation of the engine control device according to this embodiment.

[0010] Hereinafter, engine control devices according to embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[0011] <Configuration of Engine> First, with reference to FIG. 1, the configuration of an engine to which the engine control device of this embodiment is applied will be described in detail.

[0012] FIG. 1 is a schematic diagram showing the configuration of an engine control device according to this embodiment, together with an engine to which the control device is applied.

[0013] As shown in FIG. 1 , engine 1 is typically mounted on a vehicle such as a motorcycle (not shown). It is a four-stroke reciprocating internal combustion engine, and its operating state is controlled by an engine control device 50. It includes a cylinder block 2. While the engine 1 is shown in the figure as having a single cylinder 2a for ease of explanation, it may also have multiple cylinders 2a, and the cylinders 2a may be arranged in an in-line, horizontally opposed, or V-type configuration. Furthermore, engine 1 is typically water-cooled, and a coolant passage 3 provided in the side wall of cylinder block 2 is provided with a water temperature sensor 101 for detecting the temperature of the coolant flowing through the coolant passage. This water temperature sensor 101 outputs an electrical signal indicating the coolant temperature to engine control device 50. If engine 1 were air-cooled, a temperature sensor (not shown) capable of detecting the temperature of engine 1 would be provided in the cylinder block 2 or elsewhere instead of water temperature sensor 101.

[0014] A piston 4 is disposed inside the cylinder block 2. The piston 4 is connected to a crankshaft 6 via a connecting rod 5. A reluctor 7 is provided on the crankshaft 6, rotating coaxially with the crankshaft 6. A plurality of teeth 7a are provided on the outer circumferential surface of the reluctor 7, and are arranged in a predetermined pattern along the circumferential direction. A crank angle sensor 102 is provided near the plurality of teeth 7a in a lower case (not shown) or the like attached to the bottom of the cylinder block 2 to detect the rotational angle of the crankshaft 6 so that the engine control device 50 can detect the rotational speed of the engine 1. The crank angle sensor 102 outputs an electrical signal indicating the rotational angle of the crankshaft 6 to the engine control device 50.

[0015] A cylinder head 8 is attached to the top of the cylinder block 2. The inner wall surface of the cylinder block 2, the upper surface of the piston 4, and the inner wall surface of the cylinder head 8 cooperate to define an internal space which serves as a combustion chamber 9.

[0016] The cylinder block 2 and the cylinder head 8 are provided with a spark plug 10 for each cylinder 2a, which ignites an air-fuel mixture produced from fuel and air in the combustion chamber 9. The ignition operation of the spark plug 10 is controlled by the engine control device 50, which controls the supply of electricity to an ignition coil (not shown).

[0017] The cylinder head 8 is provided with an intake valve 12 that freely opens and closes communication between the combustion chamber 9 and an intake passage 11a formed in the cylinder head 8 and an intake pipe 11 attached to the cylinder head 8. The intake pipe 11 is provided with a fuel injection valve 13 that injects fuel into the intake passage 11a, and a throttle valve 14a that is located upstream of the fuel injection valve 13 and is a component of a throttle device 14. The intake pipe 11 is also provided with an intake pressure sensor 103 between the intake valve 12 and the throttle valve 14a that detects the pressure (intake pressure) of air flowing into the intake pipe 11. The intake pressure sensor 103 outputs an electric signal indicating a voltage corresponding to the intake pressure to the engine control device 50. A throttle opening sensor 104 that detects the opening degree of the throttle valve 14a is attached to the main body of the throttle device 14 or the like. The throttle opening sensor 104 outputs an electric signal indicating a voltage corresponding to the opening degree of the throttle valve 14a (throttle opening degree) to the engine control device 50. The opening and closing operations of the fuel injection valve 13 are controlled by the engine control device 50 controlling the supply of electricity to a solenoid coil (not shown). The throttle device 14 is typically an electronically controlled throttle device, and the throttle opening degree is controlled by the engine control device 50 controlling the supply of electricity to a throttle motor (not shown). Typically, a feedback control process is performed on the throttle opening degree of the throttle device 14 to bring the throttle opening degree closer to a target opening degree, which is a target value for the throttle opening degree calculated based on the accelerator opening degree, engine speed, coolant temperature, etc.

[0018] An exhaust pipe 15 is attached to the cylinder head 8 on the opposite side of the intake pipe 11, and an exhaust passage 15a communicating with the combustion chamber 9 is formed within the cylinder head 8 and the exhaust pipe 15. The cylinder head 8 is also provided with an exhaust valve 16 that freely opens and closes communication between the combustion chamber 9 and the exhaust passage 15a. A catalyst 17, typically a three-way catalyst, is provided in the exhaust pipe 15 downstream of the exhaust valve 16 to purify the exhaust gas discharged from the combustion chamber 9, and an O2 sensor 105 is provided upstream of and close to the catalyst 17 to detect the oxygen concentration in the exhaust gas. The O2 sensor 105 outputs an electrical signal indicating a voltage corresponding to the oxygen concentration in the exhaust gas upstream of the catalyst 17 to the engine control device 50.

[0019] An accelerator opening sensor 106 is attached to a steering wheel or the like (not shown) of the vehicle, and an accelerator opening sensor 108 detects the amount of operation (accelerator opening) of an accelerator grip or the like, which is an accelerator operating member (not shown) of the vehicle. The accelerator opening sensor 106 outputs an electric signal indicating a voltage corresponding to the accelerator opening to the engine control device 50. A vehicle speed sensor 107 is attached to the front wheels, which are driven wheels (not shown) of the vehicle, and the vehicle speed sensor 107 detects the rotation speed of the front wheels so that the engine control device 50 can calculate the vehicle speed. The vehicle speed sensor 107 outputs an electric signal indicating a voltage corresponding to the rotation speed of the front wheels to the engine control device 50.

[0020] <Configuration of Engine Control Device> Next, with further reference to FIG. 2, the configuration of the engine control device 50 in this embodiment will be described in detail.

[0021] FIG. 2 is a schematic diagram showing the high load over-rich region of an engine to which the engine control device of this embodiment is applied, in terms of the relationship between engine speed and throttle opening.

[0022] First, as shown in FIG. 1, the engine control device 50 is configured by an ECU (Electronic Control Unit) 150, which is an electronic control device mounted on a vehicle and controls the operation of the engine 1.

[0023] The ECU 150 has a CPU (Central Processing Unit) that functions as a control unit 152, as well as a memory and a timer (not shown), and the memory stores necessary control and processing programs and control and processing data.

[0024] In addition, the ECU 150 controls the operation of various control objects such as the spark plug 10, fuel injection valve 13, and throttle device 14, based on output signals from various sensors, reads out the necessary control / processing programs and control / processing data from memory, and executes the control / processing programs to control the operating state of the engine 1.

[0025] Furthermore, when the ratio of the increase in the torque output by the engine 1 per unit time to the increase in the throttle opening of the engine 1 per unit time falls below a threshold, the ECU 150 executes throttle opening limiting processing to limit the increase in the throttle opening. At this time, the ECU 150 executes the throttle opening limiting processing so as to prevent the engine 1 from operating in the high-load over-rich region shown in FIG. 2 .

[0026] 2, the high-load over-rich region is a region in which, even if the fuel injection amount is set to a corresponding value while the throttle opening is increased at a given engine speed, the increase in the torque output by the engine 1 does not increase as much as the increase in the throttle opening. In other words, when the torque output by the engine 1 is increased by increasing the throttle opening, the increase in the torque output by the engine 1 (the increase in the torque per unit time) relative to the increase in the throttle opening (the increase in the throttle opening per unit time) is equal to or less than a predetermined threshold, and the air-fuel ratio of the engine 1 is richer than the stoichiometric air-fuel ratio. In other words, in this high-load over-rich region, the engine 1 operates in an operating state in which its fuel economy is likely to deteriorate. In the figure, the high load over-rich region and the other region, the non-over-rich region where the air-fuel ratio of the engine 1 can be maintained near the stoichiometric air-fuel ratio, are separated by a boundary line A whose positive slope gradually decreases as the engine speed increases, with the region above boundary line A being the high load over-rich region and the region below boundary line A being the non-over-rich region. In the figure, the lower limit of the engine speed is indicated by NEL (e.g., the full combustion speed), the upper limit of the engine speed by NEH (e.g., the lower limit of the red zone), the lower limit of the throttle opening by THL (e.g., the fully closed opening), and the upper limit of the throttle opening by THH (e.g., the fully open opening).

[0027] The engine control device 50 having the configuration described above executes a throttle opening limiting process to limit the increase in the throttle opening when the ratio of the increase in the torque output by the engine 1 per unit time to the increase in the throttle opening per short time falls below a threshold. Hereinafter, with further reference to Figures 3 and 4, the operation of the engine control device 50 when executing the process of calculating the target value of the throttle opening, including the throttle opening limiting process, will be described in detail.

[0028] <Operation of Engine Control Device> Fig. 3 is a flowchart showing an example of a process for calculating a target value of the throttle opening, including a throttle opening limit process, of the engine control device according to this embodiment. Fig. 4 is a time chart showing an example of an operation of the engine control device according to this embodiment.

[0029] 3 starts when an ignition switch (not shown) is turned on from an off state and the ECU 150 is started, and the process of calculating the target value of the throttle opening proceeds to the process of step S1. This process of calculating the target value of the throttle opening is typically executed for feedback control processing to bring the throttle opening closer to the target value and match it, and while the ECU 150 is in the started state, the necessary control / processing programs and control / processing data are read from the memory and executed repeatedly at predetermined control intervals.

[0030] In step S1, the control unit 152 reads the flag value from memory and determines whether the flag value is 1. A flag value of 1 indicates that a target throttle opening (target opening) has been set that limits the throttle opening so that the throttle opening does not increase. A flag value of 0 indicates that a target throttle opening that limits the throttle opening is not set, but rather that a normal required throttle opening that reflects the accelerator pedal position is set. If the flag value is 1, the control unit 152 advances the calculation of the throttle opening target value to step S2. If the flag value is 0, the control unit 152 advances the calculation of the throttle opening target value to step S3. The initial value of the flag is set to 0.

[0031] As shown in FIG. 4, the flag value is 1 during the period from time t2 to time t3, and the flag value is 0 during other periods.

[0032] In step S2, the control unit 152 calculates a required throttle opening, which is a throttle opening that reflects the accelerator opening detected by the accelerator opening sensor 106, and determines whether the required throttle opening is equal to or less than the throttle opening detected by the throttle opening sensor 104. If the determination results in the required throttle opening being equal to or less than the throttle opening, the control unit 152 temporarily resets the target throttle opening, which is maintained at a value that limits the increase in throttle opening, and proceeds to step S3 for calculating the target throttle opening. On the other hand, if the required throttle opening is greater than the throttle opening, the control unit 152 proceeds to step S7 for calculating the target throttle opening. Note that the throttle opening detected by the throttle opening sensor 104 used in this step may be replaced by a target value (target throttle opening) used in the feedback control of the throttle opening.

[0033] As shown in Figure 4, the required opening is equal to or less than the throttle opening from time t3 onwards, and is greater than the throttle opening during other periods. However, the graph shows that the throttle opening is restricted so as not to increase during the period from time t2 to time t3.

[0034] In the process of step S3, the control unit 152 determines whether the accelerator opening detected by the accelerator opening sensor 106 is equal to or greater than a predetermined value. If the result of the determination is that the accelerator opening is equal to or greater than the predetermined value, the control unit 152 advances the calculation process of the target value of the throttle opening to the process of step S4. On the other hand, if the accelerator opening is less than the predetermined value, the control unit 152 advances the calculation process of the target value of the throttle opening to the process of step S9. Note that instead of the accelerator opening used in this step, the throttle opening detected by the throttle opening sensor 104 or the target value (target opening) used in the feedback control process of the throttle opening may be applied.

[0035] As shown in FIG. 4, the accelerator opening is equal to or greater than the predetermined value only from time t1 onward, and is less than the predetermined value during other periods.

[0036] In the process of step S4, the control unit 152 calculates the torque change rate, that is, the amount of change in torque output by the engine 1 (the amount of change in the magnitude of torque per unit time) relative to the amount of change in the throttle opening (the amount of change in the magnitude of the throttle opening per unit time). At this time, the control unit 152 uses the amount of change in the throttle opening detected by the throttle opening sensor 104. Furthermore, the control unit 152 calculates the rotational angular velocity from the rotational angle of the crankshaft 6 detected by the crank angle sensor 102, and then calculates the torque output by the engine 1 based on this rotational angular velocity. This completes the process of step S4, and the process of calculating the target value of the throttle opening proceeds to the process of step S5.

[0037] In the process of step S5, the control unit 152 determines whether the torque is decreasing, that is, whether the torque output by the engine 1 calculated by the control unit 152 is decreasing. If the result of the determination is that the torque output by the engine 1 is decreasing, the control unit 152 advances the calculation process of the target value of the throttle opening to the process of step S9. On the other hand, if the torque output by the engine 1 is not decreasing, the control unit 152 advances the calculation process of the target value of the throttle opening to the process of step S6.

[0038] 4, the torque output by the engine 1 is decreasing from time t3 onwards, and the requested opening is greater than the throttle opening during other periods. However, the graph shows that the throttle opening is restricted so as not to increase during the period from time t2 to time t3.

[0039] In the process of step S6, the control unit 152 determines whether the torque change rate calculated in the process of step S4, i.e., the torque increase rate (which for convenience includes the case where the same torque value is maintained) is equal to or less than a predetermined threshold value because it has been determined in the process of step S5 that the torque output by the engine 1 is not decreasing. If the result of the determination is that the torque increase rate is equal to or less than the predetermined threshold value, the control unit 152 proceeds to the process of step S7 for calculating the target value of the throttle opening. On the other hand, if the torque increase rate is greater than the predetermined threshold value, the control unit 152 proceeds to the process of step S9 for calculating the target value of the throttle opening.

[0040] 4, the torque increase rate becomes equal to or less than the predetermined threshold at time t2, and is greater than the predetermined threshold at other times. However, because the throttle opening is restricted from increasing between time t2 and time t3, the torque increase rate increases to exceed the predetermined threshold as shown by the phantom line, and then decreases toward the predetermined threshold after time t3.

[0041] In the process of step S7, the control unit 152 sets the target value of the throttle opening calculated in the process of calculating the target value of the throttle opening last time (previous value: previously calculated target opening) as the target value of the throttle opening for the feedback control process. In other words, this process is a throttle opening limiting process that limits the increase in the throttle opening. This completes the process of step S7, and the process of calculating the target value of the throttle opening proceeds to the process of step S8. The initial value of the previous value is typically set to the value of the fully closed opening.

[0042] In the process of step S8, the control unit 152 sets the value of the flag to 1 and stores it in memory, thereby completing the current series of processes for calculating the target value of the throttle opening.

[0043] As shown in FIG. 4, the flag value is set to 1 during the period from time t2 to time t3.

[0044] In step S9, the control unit 152 sets the required opening calculated in step S2 as the target value (target opening) of the throttle opening for feedback control. In other words, in this process, throttle opening limiting processing that limits the increase in the throttle opening is not performed. This completes step S9, and the process of calculating the target value of the throttle opening proceeds to step S10.

[0045] In the process of step S10, the control unit 152 sets the value of the flag to 0 and stores it in memory, thereby completing the current series of processes for calculating the target value of the throttle opening.

[0046] As shown in FIG. 4, the flag value is set to 0 until time t2 or from time t3 onwards.

[0047] In the first aspect of the internal combustion engine control device 50 in this embodiment described above, the control unit 152 executes a throttle opening limiting process that limits the increase in the throttle opening when the ratio of the increase in the torque output by the internal combustion engine 1 to the increase in the throttle opening of the internal combustion engine 1 falls below a threshold value, thereby making it possible to limit the increase in the throttle opening so as to achieve improved fuel efficiency of the internal combustion engine 1.

[0048] Furthermore, in the second aspect of the internal combustion engine control device 50 of this embodiment, in addition to the first aspect, the control unit 152 executes a throttle opening limiting process when the accelerator operation amount is equal to or greater than a predetermined value, thereby more appropriately limiting the increase in the throttle opening.

[0049] Furthermore, in a third aspect of the internal combustion engine control device 50 of this embodiment, in addition to the first aspect, the control processing includes feedback control that controls the throttle opening so that the throttle opening approaches a target value, and the control unit 152 executes throttle opening limiting processing when the throttle opening or the target value is equal to or greater than a predetermined value, so that the increase in the throttle opening can be more appropriately limited.

[0050] Furthermore, in a fourth aspect of the internal combustion engine control device 50 of this embodiment, in addition to any one of the first to third aspects, the control processing includes feedback control that controls the throttle opening so that the throttle opening approaches a target value, and the control unit 152 terminates the execution of the throttle opening limiting processing when the requested opening, which is the throttle opening that reflects the amount of accelerator operation, becomes equal to or less than the throttle opening or the target value, so that the throttle opening limiting processing can be terminated appropriately.

[0051] Furthermore, in a fifth aspect of the internal combustion engine control device 50 of this embodiment, in addition to any one of the first to fourth aspects, the control processing includes feedback control that controls the throttle opening so that the throttle opening approaches a target value, and the control unit 152 executes the throttle opening limiting processing by maintaining the target value, so that the increase in the throttle opening can be more appropriately limited.

[0052] It should be noted that the present invention is not limited to the above-described embodiment in terms of the type, shape, arrangement, number, etc. of the components, and it goes without saying that such modifications can be made as appropriate within the scope of the gist of the invention, such as by appropriately replacing the components with components that achieve equivalent effects.

[0053] As described above, the present invention provides an internal combustion engine control device that can limit the throttle opening so as to improve the fuel efficiency of the internal combustion engine, and due to its versatile and universal nature, it is expected to be widely applicable to internal combustion engine control devices for motorcycles.

[0054] DESCRIPTION OF SYMBOLS 1...Engine (internal combustion engine) 2...Cylinder block 2a...Cylinder 3...Cooling water passage 4...Piston 5...Connecting rod 6...Crankshaft 7...Reluctor 7a...Tooth portion 8...Cylinder head 9...Combustion chamber 10...Spark plug 11...Intake pipe 11a...Intake passage 12...Intake valve 13...Fuel injection valve 14...Throttle device 14a...Throttle valve 15...Exhaust pipe 15a...Exhaust passage 16...Exhaust valve 17...Catalyst 50...Engine control device (internal combustion engine control device) 101...Water temperature sensor 102...Crank angle sensor 103...Intake pressure sensor 104...Throttle opening sensor 105...O2 sensor 106...Accelerator opening sensor 107...Vehicle speed sensor 150...ECU 152...Control unit

Claims

1. A control device for an internal combustion engine that includes a control unit that executes control processing including a limiting process to limit an increase in throttle opening, which is the opening of a throttle valve of an internal combustion engine of a vehicle, wherein the control unit executes the limiting process when a torque increase rate, which is the ratio of an increase in the torque output by the internal combustion engine per unit time to an increase in the throttle opening per unit time, falls below a threshold value.

2. The internal combustion engine control device according to claim 1, wherein the control unit executes the limiting process when the amount of operation of the accelerator of the vehicle is equal to or greater than a predetermined value.

3. An internal combustion engine control device as described in claim 1, characterized in that the control processing includes feedback control that controls the throttle opening so that the throttle opening approaches a target value, and the control unit executes the limiting processing when the throttle opening or the target value is equal to or greater than a predetermined value.

4. An internal combustion engine control device as described in any one of claims 1 to 3, characterized in that the control processing includes feedback control that controls the throttle opening so that the throttle opening approaches a target value, and the control unit terminates execution of the restriction processing when the requested throttle opening, which is the throttle opening that reflects the amount of accelerator operation of the vehicle, becomes equal to or less than the throttle opening or the target value.

5. An internal combustion engine control device according to any one of claims 1 to 3, characterized in that the control process includes feedback control for controlling the throttle opening so that the throttle opening approaches a target value, and the control unit executes the limiting process by maintaining the target value.

Images