Fuel injection control device

Abstract

A fuel injection control device (12) that has timers (84, 86) and uses the timers to control a fuel injection valve (32) that supplies a fuel (F) containing alcohol to an internal combustion engine (10) comprises a concentration determination unit (100) that determines the alcohol concentration in the fuel, and a valve control unit (106) that adjusts the valve opening interval of the fuel injection valve by controlling the opening / closing of the fuel injection valve, according to the timers, counted at count periods (P1, P2) based on the alcohol concentration, wherein the count periods become longer as the alcohol concentration becomes higher.

Description

fuel injection control device

[0001] The present invention relates to a fuel injection control device.

[0002] Japanese Patent Laid-Open Publication No. 8-21273 discloses a fuel injection control device for an internal combustion engine, which is capable of correcting the amount of fuel injection.

[0003] The fuel injection amount can be changed by adjusting the valve opening period of the fuel injector. When the fuel contains alcohol, a longer valve opening period is required than when the fuel contains only gasoline. In this case, there is a problem that the valve opening period cannot be finely adjusted.

[0004] The present invention aims to solve the above-mentioned problems.

[0005] One aspect of the present invention is a fuel injection control device that has a timer and uses the timer to control a fuel injection valve that supplies fuel containing alcohol to an internal combustion engine, and is equipped with a valve control unit that controls the opening and closing of the fuel injection valve in accordance with the timer counted at a count period based on the alcohol concentration of the alcohol in the fuel, and the higher the alcohol concentration, the longer the count period.

[0006] According to the present invention, the valve opening period can be finely adjusted.

[0007] FIG. 1 is a diagram illustrating an internal combustion engine and a fuel injection control device according to an embodiment. FIG. 2 is a diagram illustrating the relationship between a valve opening period, a fuel injection amount, and an alcohol concentration in fuel. FIGS. 3A, 3B, and 3C are diagrams for explaining an example of timer operation. FIG. 4 is a flowchart illustrating an example of a processing procedure for controlling the opening and closing of a fuel injection valve. FIG. 5 is a diagram illustrating an example of convergence of feedback control based on an oxygen concentration. FIG. 6 is a diagram illustrating an example of convergence of feedback control based on an oxygen concentration. FIG. 7 is a diagram illustrating an example of convergence of feedback control based on an oxygen concentration. FIG. 8 is a flowchart illustrating an example of a processing procedure for calculating the valve opening period of a fuel injection valve. FIG. 9 is a flowchart illustrating an example of a processing procedure for fuel injection valve control in Modification 1. FIG. 10 is a flowchart illustrating an example of a processing procedure for fuel injection valve control in Modification 2. FIG. 11 is a diagram illustrating an internal combustion engine, a fuel injection control device, and a fuel tank in Modification 3.

[0008] A fuel injection control device according to one embodiment will be described with reference to the drawings. FIG. 1 is a diagram illustrating an internal combustion engine 10 and a fuel injection control device 12 according to this embodiment. In this embodiment, the internal combustion engine 10 is an engine mounted on a saddle-ride vehicle. However, the internal combustion engine 10 may also be mounted on a moving body such as a vehicle other than a saddle-ride vehicle. The fuel F used in the internal combustion engine 10 is gasoline or a synthetic fuel containing gasoline and alcohol. Instead of gasoline, other types of petroleum, such as diesel oil, may be included in the fuel F. When the fuel F is a synthetic fuel, the alcohol included in the fuel F is, for example, ethanol.

[0009] The internal combustion engine 10 is equipped with an electronically controlled throttle 14, a fuel injector 16, an ignition device 18, and an exhaust purification device 20. The electronically controlled throttle 14 has a throttle valve 22, a throttle driver 24, and a throttle position sensor 26. The throttle valve 22 is a butterfly throttle that adjusts the amount of air supplied to an intake port 30 provided upstream of an intake valve 28. The throttle driver 24 is a motor. The throttle driver 24 drives the throttle valve 22 to open and close it. The throttle position sensor 26 detects the opening degree of the throttle valve 22.

[0010] The fuel injection device 16 has a fuel injection valve 32. The fuel injection valve 32 is provided in the intake port 30. The fuel injection valve 32 injects fuel F into the intake port 30. This generates a mixture of fuel F and air. If the internal combustion engine 10 is a direct fuel injection engine, the fuel injection valve 32 may be provided in the cylinder head 40 and may directly inject fuel F into the combustion chamber 34.

[0011] The ignition device 18 has a spark plug 36 and an ignition coil 38. The spark plug 36 and the ignition coil 38 are provided in the cylinder head 40. The spark plug 36 discharges electricity in the combustion chamber 34 to ignite the air-fuel mixture. The ignition coil 38 boosts the voltage of a battery (not shown). The spark plug 36 discharges electricity using the boosted voltage. The ignited air-fuel mixture is combusted in the combustion chamber 34, and exhaust gas is discharged from the combustion chamber 34.

[0012] The exhaust purification device 20 has a three-way catalyst 42. The three-way catalyst 42 is provided in an exhaust port 46 downstream of an exhaust valve 44. The three-way catalyst 42 removes harmful substances contained in the exhaust gas discharged from the combustion chamber 34 by means of a catalyst.

[0013] The internal combustion engine 10 is equipped with various sensors for detecting the operating state of the internal combustion engine 10. The internal combustion engine 10 is equipped with an intake air temperature sensor 48, an intake air pressure sensor 50, a crank angle sensor 52, a coolant temperature sensor 54, and an oxygen concentration sensor 56. The intake air temperature sensor 48 is provided in an intake duct 58 upstream of the throttle valve 22. The intake air temperature sensor 48 detects the temperature inside the intake duct 58. The intake air pressure sensor 50 is provided in the intake port 30. The intake air pressure sensor 50 detects the pressure inside the intake port 30.

[0014] The crank angle sensor 52 detects the rotation angle of the crankshaft 60. The crank angle sensor 52 detects the rotation angle of the crankshaft 60 based on a pulse signal generated by a protrusion of a signal rotor 62 that rotates together with the crankshaft 60. The coolant temperature sensor 54 is provided in the cylinder 64. The coolant temperature sensor 54 detects the temperature of the coolant in the coolant jacket.

[0015] The oxygen concentration sensor 56 is provided in the exhaust port 46 upstream of the three-way catalyst 42. The oxygen concentration sensor 56 detects the concentration of oxygen contained in the exhaust gas discharged from the combustion chamber 34. In this manner, the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10 is detected. Through feedback control based on the detected oxygen concentration, the fuel injection control device 12 calculates the fuel injection amount of fuel F to be injected into the intake port 30 by the fuel injection valve 32. Based on the fuel injection amount calculated in this manner, the fuel injection control device 12 also calculates the valve opening period of the fuel injection valve 32.

[0016] The fuel injection control device 12 controls the fuel injection valve 32, which supplies fuel F containing alcohol to the internal combustion engine 10. The fuel F is stored in a fuel tank 70. The fuel F flows through a pipe 72 connected to the fuel tank 70 and is supplied from the fuel tank 70 to the fuel injection valve 32. The fuel injection valve 32 injects the supplied fuel F into the intake port 30 during a valve opening period under the control of the fuel injection control device 12.

[0017] The fuel injection control device 12 includes a calculation unit 80, a storage unit 82, a first timer 84, a second timer 86, and a drive circuit 88. The calculation unit 80 includes a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). In other words, the calculation unit 80 includes processing circuitry.

[0018] The storage unit 82 includes volatile memory such as RAM (Random Access Memory) and non-volatile memory such as ROM (Read Only Memory) or flash memory. The volatile memory is used as working memory for the processor. The non-volatile memory stores programs executed by the processor and other necessary data.

[0019] The first timer 84 receives a first clock signal obtained by dividing the frequency of the reference clock signal by a first division ratio from a frequency divider (not shown). The count period of the first timer 84 is a first period P1, which is the period of the first clock signal. That is, when the first timer 84 is activated, it counts at the first period P1. Each time it counts at the first period P1, the count value is incremented or decremented. When the number of counts by the first timer 84 reaches, for example, a value Cs, the first timer 84 expires.

[0020] The second timer 86 receives a second clock signal obtained by dividing the frequency of the reference clock signal by a second division ratio from a frequency divider (not shown). The count period of the second timer 86 is a second period P2, which is the period of the second clock signal. That is, when the second timer 86 is activated, it counts at the second period P2. Each time it counts at the second period P2, the count value is incremented or decremented. When the number of counts by the second timer 86 reaches, for example, a value Cs, the second timer 86 expires.

[0021] As will be described later, either the first timer 84 or the second timer 86 is used to control the fuel injection valve 32. A second cycle P2, which is the count cycle of the second timer 86, is longer than a first cycle P1, which is the count cycle of the first timer 84. When the valve-open period of the fuel injection valve 32 is determined, if the determined valve-open period is longer than a predetermined period, the second timer 86 is used. If the determined valve-open period is within the predetermined period, the first timer 84 is used. In other words, the longer the valve-open period, the longer the count cycle of the timer used to control the fuel injection valve 32.

[0022] The maximum count number that the second timer 86 can count is equal to or less than the maximum count number that the first timer 84 can count. If the first timer 84 has a 16-bit counter, for example, the maximum count number that the first timer 84 can count is 65,535. In this case, the maximum count number that the second timer 86 can count is equal to or less than 65,535. Since the counter of the second timer 86 can be 16 bits or less, costs can be kept down.

[0023] The fuel injection valve 32 has a coil (not shown) that opens and closes the fuel injection valve 32. The drive circuit 88 has a switch (not shown) for supplying power to the coil of the fuel injection valve 32. When the switch of the drive circuit 88 is turned on, power is supplied to the coil. When power is supplied to the coil, the fuel injection valve 32 opens. When the switch of the drive circuit 88 is turned off, the power supply to the coil is cut off. When the power supply to the coil is cut off, the fuel injection valve 32 closes.

[0024] The calculation unit 80 has a concentration determination unit 100, a valve open period determination unit 102, a timer determination unit 104, and a valve control unit 106. When the calculation unit 80 executes a program stored in the storage unit 82, the concentration determination unit 100, the valve open period determination unit 102, the timer determination unit 104, and the valve control unit 106 are realized.

[0025] At least some of the concentration determination unit 100, the valve open period determination unit 102, the timer determination unit 104, and the valve control unit 106 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field Programmable Gate Array), or an electronic circuit including discrete devices.

[0026] The concentration determination unit 100 determines the alcohol concentration of alcohol in the fuel F injected from the fuel injection valve 32 during the valve-open period. With the level value of the alcohol concentration set to a predetermined initial value, the above-described feedback control based on the oxygen concentration is performed. The level value of the alcohol concentration is updated based on the convergence result of the feedback control. By updating the level value of the alcohol concentration in this way, the concentration determination unit 100 determines the alcohol concentration to be the updated level value.

[0027] The valve opening period determination unit 102 performs the above-described feedback control based on the oxygen concentration to determine a target injection amount, which is the fuel injection amount of fuel F injected from the fuel injection valve 32. A basic injection amount, which is the fuel injection amount of fuel F injected from the fuel injection valve 32 per unit period, is determined in advance according to the alcohol concentration. The valve opening period determination unit 102 calculates the valve opening period of the fuel injection valve 32 based on the determined target injection amount and a predetermined basic injection amount. In this way, the valve opening period of the fuel injection valve 32 is determined.

[0028] That is, the valve opening period of the fuel injection valve 32 is determined based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10. A specific processing procedure for calculating the valve opening period of the fuel injection valve 32 will be described later with reference to Fig. 8. The process for calculating the valve opening period is started when the ignition switch 120 of the saddle-ride type vehicle on which the internal combustion engine 10 is mounted is turned on. The process for calculating the valve opening period is repeated until the ignition switch 120 is turned off.

[0029] The timer determination unit 104 determines, based on the calculated valve-open period of the fuel injection valve 32, either the first timer 84 or the second timer 86 as the timer to be used for controlling the fuel injection valve 32. That is, the timer that counts at a cycle based on the valve-open period of the fuel injection valve 32 is used for controlling the fuel injection valve 32.

[0030] The valve control unit 106 controls the opening and closing of the fuel injection valve 32 by switching the switch of the drive circuit 88 in accordance with the timer determined by the timer determination unit 104. The valve control unit 106 controls the opening and closing of the fuel injection valve 32 to adjust the opening period of the fuel injection valve 32. A specific procedure for the opening and closing control process of the fuel injection valve 32 will be described later with reference to FIG. 4. The opening and closing control process of the fuel injection valve 32 is started when a starter switch 122 of the saddle-ride type vehicle on which the internal combustion engine 10 is mounted is turned on. The opening and closing control process of the fuel injection valve 32 is repeated until the ignition switch 120 is turned off.

[0031] 2 is a diagram showing the relationship between the valve opening period, the fuel injection amount, and the alcohol concentration in the fuel F. The higher the alcohol concentration of the alcohol in the fuel F, the larger the fuel injection amount required. In other words, the higher the alcohol concentration in the fuel F, the longer the valve opening period of the fuel injection valve 32 needs to be. In particular, when the fuel F contains a high concentration of alcohol, the valve opening period may need to be several times longer than when the fuel F does not contain alcohol.

[0032] 3A, 3B, and 3C are diagrams illustrating an example of timer operation. Fig. 3A illustrates an example of changes in the count value of the first timer 84 when the first timer 84 is used to control the fuel injector 32. The count cycle of the first timer 84 is a first cycle P1. If the maximum number of counts that the first timer 84 can count is Cs, the first timer 84 can measure a time Tn obtained by multiplying the first cycle P1 by Cs.

[0033] 3A, the first timer 84 is started at time Ts. The count value is decremented by one each time the first period P1 elapses, until the count value reaches 0 from Cs. When a time Tn has elapsed since the start of the first timer 84, the first timer 84 expires.

[0034] When the fuel F burned in the internal combustion engine 10 does not contain alcohol, the first period P1 is determined so that the maximum valve opening period of the fuel injection valve 32 is within the time Tn. As described above, when the fuel F contains alcohol, the valve opening period of the fuel injection valve 32 becomes longer as the alcohol concentration increases. In other words, the valve opening period can be longer than the time Tn.

[0035] If the first period P1, which is the count period, is a fixed value, when the first timer 84 expires, the interrupt handler restarts the first timer 84, making it possible to measure a valve-open period longer than the time Tn. However, activating the interrupt handler increases the processing load on the calculation unit 80, and is therefore not desirable.

[0036] Furthermore, by using a timer whose maximum count number is greater than Cs to control the fuel injection valve 32, it is possible to measure a valve opening period longer than the time Tn. That is, for example, a timer having a 32-bit counter, which is larger than a 16-bit counter, can be used. However, if the fuel injection control device 12 is provided with a timer having a large counter, the manufacturing cost of the fuel injection control device 12 increases, which is not preferable.

[0037] Therefore, even when the fuel F contains alcohol, it is conceivable to set the count cycle of the timer so that the time measured from the start of the timer to its expiration is longer than the maximum valve-open period of the fuel injection valve 32. Fig. 3B illustrates an example of changes in the count value of the second timer 86 when the second timer 86, which has a longer count cycle than the first timer 84, is used to control the fuel injection valve 32. For ease of explanation, the maximum number of counts that the second timer 86 can count is assumed to be Cs, which is equal to the maximum number of counts that the first timer 84 can count.

[0038] In the example shown in Fig. 3B, the second cycle P2, which is the count cycle of the second timer 86, is longer than the first cycle P1 shown in Fig. 3A. The second timer 86 can measure a time Te obtained by multiplying the second cycle P2 by Cs. This time Te is longer than the maximum time Tn that can be measured by the first timer 84. Therefore, the second timer 86 can measure an open period of the fuel injector 32 that is longer than the time Tn when the fuel F contains alcohol.

[0039] 3B, the second timer 86 is activated at time Ts. The count value is decremented by one each time the second period P2 elapses, until the count value reaches 0 from Cs. When the time Te has elapsed since the activation of the second timer 86, the second timer 86 expires.

[0040] As described above, when the fuel F does not contain alcohol, the valve opening period of the fuel injector 32 is time Tn. Time Tn is shorter than the time Te that the second timer 86 can measure. Therefore, it appears that the second timer 86 can be used to measure the valve opening period of the fuel injector 32 when the fuel F does not contain alcohol. Figure 3C illustrates an example of changes in the count value of the second timer 86 when the second timer 86 is used to control the fuel injector 32 that injects fuel F that does not contain alcohol.

[0041] The second timer 86 can measure time Tn if it counts at least Cr times. As shown in Figure 3C, the second timer 86 starts at time Ts. The count value is counted down by one each time the second period P2 elapses, until the count value reaches 0 from Cr. When time Ta has elapsed since the start of the second timer 86, the second timer 86 expires. Time Ta is obtained by multiplying the second period P2 by Cr.

[0042] The time Ta measured by the second timer 86 is longer than the time Tn determined as the valve-open period of the fuel injection valve 32. Because the second cycle P2 is long, a difference occurs between the time Ta and the time Tn. As a result of the valve control unit 106 controlling the opening and closing of the fuel injection valve 32 in accordance with the second timer 86, the valve-open period is adjusted to the time Ta measured by the second timer 86. Therefore, fuel F is injected wastefully for a period corresponding to the difference between the time Ta and the time Tn. In other words, it is not preferable to use the second timer 86 to measure the valve-open period of the fuel injection valve 32 when the fuel F does not contain alcohol.

[0043] Therefore, in the fuel injection control device 12 according to this embodiment, when the valve opening period determined by the valve opening period determination unit 102 is within a predetermined period, the first timer 84 is used. When the valve opening period determined by the valve opening period determination unit 102 is longer than the predetermined period, the second timer 86 is used. This allows the valve opening period of the fuel injection valve 32 to be finely adjusted. Even when the valve opening period varies greatly depending on the fuel F, it is possible to suppress an increase in the calculation processing load and an increase in manufacturing costs, while also suppressing waste of the fuel F.

[0044] Alternatively, the divider that supplies the clock signal to the timer or the division ratio set in the divider may be switched instead of switching between the first timer 84 and the second timer 86. This allows the count cycle of the timer to be changed according to the valve open period determined by the valve open period determination unit 102.

[0045] 4 is a flowchart illustrating a processing procedure for controlling the opening and closing of the fuel injection valve 32. This processing procedure is performed by the calculation unit 80 of the fuel injection control device 12 by executing a program stored in the storage unit 82. This processing procedure is started when the calculation unit 80 detects a starter-on signal from the starter switch 122 after the valve-opening duration determination unit 102 determines the valve-opening duration of the fuel injection valve 32. Details of determining the valve-opening duration of the fuel injection valve 32 will be described later. This processing procedure is repeated until the ignition switch 120 is turned off.

[0046] When this processing procedure starts, in step S1, the timer determination unit 104 acquires the valve-opening period of the fuel injection valve 32 determined by the valve-opening period determination unit 102 from the valve-opening period determination unit 102. The timer determination unit 104 determines whether the valve-opening period is longer than a predetermined period. The predetermined period is, for example, the maximum time Tn that the first timer 84 can measure. If step S1 is YES, this processing procedure proceeds to step S2. If step S1 is NO, this processing procedure proceeds to step S11.

[0047] If step S1 is YES, then in step S2, the timer determination unit 104 determines whether both the first timer 84 and the second timer 86 are stopped. If step S2 is YES, the process proceeds to step S3. If step S2 is NO, the process ends. In step S3, the timer determination unit 104 determines the second timer 86 as the timer to be used for controlling the fuel injection valve 32. The timer determination unit 104 starts the second timer 86. When the process of step S3 is completed, the process proceeds to step S4.

[0048] If the result of step S1 is NO, then in step S11, the timer determination unit 104 determines the first timer 84 as the timer to be used for controlling the fuel injection valve 32. The timer determination unit 104 starts the first timer 84. When the processing of step S11 is completed, the process proceeds to step S4.

[0049] In step S4, the valve control unit 106 controls the opening and closing of the fuel injection valve 32 in accordance with the timer determined in step S3 or step S11. The valve control unit 106 controls the opening and closing of the fuel injection valve 32 to adjust the opening period of the fuel injection valve 32. When the timer starts, the fuel injection valve 32 opens. When the timer expires, the fuel injection valve 32 closes. That is, the fuel injection valve 32 opens for the opening period determined by the opening period determination unit 102. When the processing of step S4 is completed, this processing procedure ends.

[0050] As described above, the fuel injection amount of the fuel F injected by the fuel injection valve 32 is calculated by feedback control based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10. Specifically, a basic injection amount of the fuel injection amount is determined in advance, and a target injection amount is calculated by multiplying the basic injection amount by the correction coefficient α corresponding to the oxygen concentration described above.

[0051] The amount of change from the previous valve-opening period to the current valve-opening period is determined by feedback control, which multiplies the deviation between the target injection amount and the actual fuel injection amount by a gain. Adjusting the gain changes the correction coefficient α, thereby adjusting the fuel injection amount and valve-opening period. The larger the gain, the larger the correction coefficient α, and the larger the fuel injection amount and the longer the valve-opening period.

[0052] FIG. 5 is a diagram showing an example of convergence of feedback control based on oxygen concentration. In the example shown in FIG. 5, the correction coefficient α fluctuates over time due to feedback control based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10. The oxygen concentration is obtained from the oxygen concentration sensor signal from the oxygen concentration sensor 56. The oxygen concentration sensor signal indicates whether the mixture is fuel-rich, which corresponds to a state in which the fuel F in the mixture is higher than the stoichiometric air-fuel ratio, or fuel-lean, which corresponds to a state in which the fuel F in the mixture is lower than the stoichiometric air-fuel ratio. Fuel-rich corresponds to a low oxygen concentration, and fuel-lean corresponds to a high oxygen concentration.

[0053] In Fig. 5, when feedback control converges and the correction coefficient α fluctuates within the range of region S, it is considered that the air-fuel ratio of the mixture has reached the so-called stoichiometric air-fuel ratio, which is close to the theoretical air-fuel ratio. In the example shown in Fig. 5, the oxygen concentration sensor signal indicates a fuel-rich condition at time t1. At this point, the correction coefficient α is included in a region corresponding to a fuel-rich condition, which is higher than region S, but begins to decrease after time t1.

[0054] Time t2 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether or not the feedback control, which will be described later, has converged. The value of the correction coefficient α at time t2 is α1, which is included in a region corresponding to a fuel lean condition, lower than region S. Shortly thereafter, at time t3, the oxygen concentration sensor signal switches to a signal indicating a fuel lean condition. The correction coefficient α begins to increase after time t3.

[0055] Time t4 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether or not the feedback control, which will be described later, has converged. The value of the correction coefficient α at time t4 is α2, which is included in a region corresponding to fuel rich, higher than region S. Shortly thereafter, at time t5, the oxygen concentration sensor signal switches to a signal indicating fuel rich. The correction coefficient α begins to decrease after time t5.

[0056] Time t6 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether or not the feedback control has converged, which will be described later. The value of the correction coefficient α at time t6 is α3, which is included in a region corresponding to a fuel lean condition, lower than region S. Thereafter, the correction coefficient α repeatedly rises and falls, but the fluctuation range D of the correction coefficient α gradually becomes smaller. If the fluctuation range D is equal to or smaller than a predetermined value Dth, it is determined that the feedback control has converged.

[0057] The fluctuation range D of the correction coefficient α is calculated as the absolute value of the difference between the values ​​of the correction coefficient α at the timing when ignition occurs or at a timing close to the timing when ignition occurs during the compression stroke of the internal combustion engine 10. In the example shown in Fig. 5 , the absolute value D1 of the difference between the value α1 of the correction coefficient α at time t2 and the value α2 of the correction coefficient α at time t4 is obtained as the first value of the fluctuation range D of the correction coefficient α. Similarly, the absolute value D2 of the difference between the value α2 of the correction coefficient α at time t4 and the value α3 of the correction coefficient α at time t6 is obtained as the second value of the fluctuation range D of the correction coefficient α.

[0058] Assume that the absolute value D1, which is the first value of the fluctuation range D of the correction coefficient α, is greater than a predetermined value Dth. In this case, it is determined that the feedback control has not converged at time t4. Assume that the absolute value D2, which is the second value of the fluctuation range D of the correction coefficient α, is greater than a predetermined value Dth. In this case, it is determined that the feedback control has not converged at time t6.

[0059] Time t22 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to that timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t22 is α11, which is included in region S. Shortly thereafter, at time t23, the oxygen concentration sensor signal switches to a signal indicating fuel lean. The correction coefficient α begins to increase after time t23.

[0060] Time t24 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t24 is α12, which is included in region S. The absolute value D11 of the difference between the value α11 of the correction coefficient α at time t22 and the value α12 of the correction coefficient α at time t24 is obtained as the 11th value of the fluctuation range D of the correction coefficient α.

[0061] Assume that the absolute value D11, which is the 11th value of the fluctuation range D of the correction coefficient α, is equal to or less than the predetermined value Dth. In this case, it is determined that the feedback control has converged at time t22. In the example shown in FIG. 5, the value of the correction coefficient α is always included in region S at time t22 when the feedback control has converged and at subsequent times. This is considered to be an appropriate state in which the air-fuel ratio of the mixture is close to the stoichiometric air-fuel ratio.

[0062] In calculating the fluctuation range D of the correction coefficient α described above, the value of the adjacent correction coefficient α is used as the value of the correction coefficient α used in the process of determining whether the feedback control has converged. For example, the absolute value D1 described above, which is the first value of the fluctuation range D of the correction coefficient α, is the absolute value of the difference between the value α1 of the correction coefficient α at time t2 and the value α2 of the correction coefficient α at time t4.

[0063] However, the absolute value of the difference between the value α1 of the correction coefficient α at time t2 and the value α3 of the correction coefficient α at time t6 may be used as the initial value of the fluctuation range D of the correction coefficient α. In other words, the value of the correction coefficient α used in the process of determining whether the feedback control has converged does not necessarily have to be the value of an adjacent correction coefficient α.

[0064] Fig. 6 is a diagram showing an example of convergence of feedback control based on oxygen concentration. Fig. 6 shows an example different from Fig. 5. In the example shown in Fig. 6, the oxygen concentration sensor signal indicates a fuel-rich condition at time t1. At this point, the correction coefficient α is included in a region corresponding to a fuel-rich condition, which is higher than region S, but begins to decrease after time t1.

[0065] Time t2 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t2 is α1, which is included in region S. Shortly thereafter, at time t3, the oxygen concentration sensor signal switches to a signal indicating fuel lean. The correction coefficient α begins to increase after time t3.

[0066] Time t4 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t4 is α2, which is included in a region corresponding to fuel rich, higher than region S. Shortly thereafter, at time t5, the oxygen concentration sensor signal switches to a signal indicating fuel rich. The correction coefficient α begins to decrease after time t5.

[0067] Time t6 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t6 is α3, which is included in region S. Thereafter, the correction coefficient α repeatedly rises and falls, but the fluctuation range D of the correction coefficient α gradually becomes smaller.

[0068] The absolute value D1 of the difference between the value α1 of the correction coefficient α at time t2 and the value α2 of the correction coefficient α at time t4 is obtained as the first value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D1 is greater than a predetermined value Dth. At time t4, it is determined that the feedback control has not converged. The absolute value D2 of the difference between the value α2 of the correction coefficient α at time t4 and the value α3 of the correction coefficient α at time t6 is obtained as the second value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D2 is greater than a predetermined value Dth. At time t6, it is determined that the feedback control has not converged.

[0069] Time t22 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t22 is α11, which is higher than region S and falls within a region corresponding to a fuel-rich condition. Shortly thereafter, at time t23, the oxygen concentration sensor signal switches to a signal indicating a fuel-lean condition. The correction coefficient α begins to increase after time t23.

[0070] Time t24 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the feedback control has converged. The value of the correction coefficient α at time t24 is α12, which is higher than region S and falls within a region corresponding to a fuel-rich condition.

[0071] The absolute value D11 of the difference between the value α11 of the correction coefficient α at time t22 and the value α12 of the correction coefficient α at time t24 is obtained as the 11th value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D11 is equal to or smaller than a predetermined value Dth. At time t22, it is determined that the feedback control has converged.

[0072] 6, at time t22 when the feedback control is converged and thereafter, the value of the correction coefficient α is always included in a region corresponding to a fuel-rich condition, which is higher than the region S. This indicates that the fuel injection valve 32 is required to inject a large amount of fuel F. The reason for this is thought to be that the alcohol concentration in the fuel F is high.

[0073] 2, when the alcohol concentration in the fuel F is high, the fuel injection valve 32 needs to inject a large amount of fuel F. Therefore, the valve opening period needs to be extended. In this case, as described above, the gain of the feedback control increases, and therefore the correction coefficient α also increases, and the value of the correction coefficient α falls within the region corresponding to a fuel-rich condition.

[0074] As described above, the concentration determination unit 100 updates the alcohol concentration level value based on the convergence result of the feedback control. The valve opening period determination unit 102 adjusts the fuel injection amount and the valve opening period through feedback control based on the updated alcohol concentration. In this way, the value of the correction coefficient α after the feedback control has converged is always included in the region S, as shown in the example of FIG. 5.

[0075] FIG. 7 is a diagram showing an example of convergence of feedback control based on oxygen concentration. FIG. 7 shows an example different from FIGS. 5 and 6. In the example shown in FIG. 7, at time t1, the oxygen concentration sensor signal indicates a fuel-rich state. At this time, the correction coefficient α is included in region S. After time t1, the correction coefficient α begins to decrease.

[0076] Time t2 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t2 is α1, which is included in a region corresponding to fuel lean, lower than region S. Shortly thereafter, at time t3, the oxygen concentration sensor signal switches to a signal indicating fuel lean. The correction coefficient α begins to increase after time t3.

[0077] Time t4 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t4 is α2, which is included in region S. Shortly thereafter, at time t5, the oxygen concentration sensor signal switches to a signal indicating fuel rich. The correction coefficient α begins to decrease after time t5.

[0078] Time t6 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used in the process of determining whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t6 is α3, which is included in a region corresponding to a fuel lean condition, lower than region S. Thereafter, the correction coefficient α repeatedly rises and falls, but the fluctuation range D of the correction coefficient α gradually becomes smaller.

[0079] The absolute value D1 of the difference between the value α1 of the correction coefficient α at time t2 and the value α2 of the correction coefficient α at time t4 is obtained as the first value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D1 is greater than a predetermined value Dth. At time t4, it is determined that the feedback control has not converged. The absolute value D2 of the difference between the value α2 of the correction coefficient α at time t4 and the value α3 of the correction coefficient α at time t6 is obtained as the second value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D2 is greater than a predetermined value Dth. At time t6, it is determined that the feedback control has not converged.

[0080] Time t22 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10, or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t22 is α11, which is included in a region corresponding to fuel lean, lower than region S. Shortly thereafter, at time t23, the oxygen concentration sensor signal switches to a signal indicating fuel lean. The correction coefficient α begins to increase after time t23.

[0081] Time t24 is the timing at which ignition occurs during the compression stroke of the internal combustion engine 10 or a timing close to this timing. The value of the correction coefficient α at this timing is used to determine whether the above-mentioned feedback control has converged. The value of the correction coefficient α at time t24 is α12, which is included in a region corresponding to a fuel lean condition, lower than region S.

[0082] The absolute value D11 of the difference between the value α11 of the correction coefficient α at time t22 and the value α12 of the correction coefficient α at time t24 is obtained as the 11th value of the fluctuation range D of the correction coefficient α. Assume that the absolute value D11 is equal to or smaller than a predetermined value Dth. At time t22, it is determined that the feedback control has converged.

[0083] 7, at time t22 when the feedback control is converged and thereafter, the value of the correction coefficient α is always included in the region corresponding to the fuel lean condition, which is lower than the region S. This indicates that the fuel injection valve 32 is required to inject a small amount of fuel F. This is thought to be because the alcohol concentration in the fuel F is low.

[0084] As can be seen from Figure 2, when the alcohol concentration in the fuel F is low, it is necessary to inject a small amount of fuel F. Therefore, it is necessary to shorten the valve opening period. In this case, the gain of the feedback control becomes small, and therefore the correction coefficient α also becomes small, and the value of the correction coefficient α falls within a region corresponding to a lean fuel condition.

[0085] As described above, the concentration determination unit 100 updates the alcohol concentration level value based on the convergence result of the feedback control. The valve opening period determination unit 102 adjusts the fuel injection amount and the valve opening period through feedback control based on the updated alcohol concentration. In this way, the value of the correction coefficient α after the feedback control has converged is always included in the region S, as shown in the example of FIG. 5.

[0086] 8 is a flowchart showing an example of a processing procedure for calculating the valve opening period of the fuel injection valve 32. This processing procedure is performed by the calculation unit 80 of the fuel injection control device 12 executing a program stored in the storage unit 82. This processing procedure is started when the calculation unit 80 detects an ignition-on signal from the ignition switch 120. This processing procedure is also repeated until the ignition switch 120 is turned off.

[0087] During this processing procedure, the above-described feedback control is performed based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10. The learned value stored in the memory unit 82 is used as the initial value of the gain of this feedback control. That is, feedback control is performed using the learned value stored in the memory unit 82 as the gain.

[0088] When this processing procedure is started, in step S51, the concentration determination unit 100 obtains the alcohol concentration level of alcohol in the fuel F injected from the fuel injection valve 32 from the memory unit 82. The memory unit 82 stores a predetermined initial value for the alcohol concentration level. In this case, the initial value may be obtained. If this processing procedure has been executed in the past, the memory unit 82 stores the alcohol concentration level value updated in step S56, which will be described later. Therefore, the updated alcohol concentration level may be obtained.

[0089] In step S52, the valve opening period determination unit 102 determines whether the oxygen concentration sensor 56 has been activated. If the oxygen concentration sensor 56 has been activated, the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10 can be detected. If the answer is YES in step S52, the process proceeds to step S53. If the answer is NO in step S52, the process proceeds to step S57.

[0090] In step S53, the valve opening duration determination unit 102 acquires the rotation speed of the internal combustion engine 10 and the opening degree of the throttle valve 22. The rotation speed of the internal combustion engine 10 is obtained based on the rotation angle of the crankshaft 60 detected by the crank angle sensor 52. The opening degree of the throttle valve 22 is detected by the throttle position sensor 26. The valve opening duration determination unit 102 determines whether the rotation speed of the internal combustion engine 10 is less than a predetermined rotation speed, and whether the opening degree of the throttle valve 22 is less than the predetermined opening degree.

[0091] If the rotation speed of the internal combustion engine 10 is equal to or greater than a predetermined rotation speed, or if the opening of the throttle valve 22 is equal to or greater than a predetermined opening, it is considered that the vehicle equipped with this internal combustion engine 10 has just started traveling. In this state, the load on the internal combustion engine 10 may be high. In this case, a NO determination is made in step S53. If a YES determination is made in step S53, the process proceeds to step S54. If a NO determination is made in step S53, the process proceeds to step S71.

[0092] If step S53 is YES, then in step S54, the valve opening period determination unit 102 determines whether the feedback control has converged. If step S54 is YES, the valve opening period determination unit 102 stores the gain in the state in which the feedback control has converged as the learned value in the storage unit 82, and the process proceeds to step S55. If step S54 is NO, the process proceeds to step S57.

[0093] In step S55, the valve opening period determination unit 102 determines whether the correction coefficient α is within a region higher or lower than region S while the feedback control is converging. A region higher or lower than region S is a region outside region S that corresponds to a fuel-rich or fuel-lean condition. If step S55 returns YES, the process proceeds to step S56. If step S55 returns NO, the process proceeds to step S57.

[0094] In step S56, the concentration determination unit 100 updates the alcohol concentration level of alcohol in the fuel F injected from the fuel injection valve 32. When the correction coefficient α is included in the region corresponding to fuel rich while the feedback control is converging, it is considered that the alcohol concentration in the fuel F is high, as described above. Therefore, the concentration determination unit 100 increases the alcohol concentration level by one step.

[0095] When the correction coefficient α is within the region corresponding to the lean fuel while the feedback control is converging, it is considered that the alcohol concentration in the fuel F is low, as described above. Therefore, the concentration determination unit 100 reduces the alcohol concentration level by one level. The concentration determination unit 100 stores the updated alcohol concentration level in the memory unit 82.

[0096] If the result in step S53 is NO, then in step S71, the valve opening duration determination unit 102 determines whether the oxygen concentration sensor signal from the oxygen concentration sensor 56 indicates a fuel lean condition. If the result in step S71 is YES, the process proceeds to step S56. If the result in step S71 is NO, the process proceeds to step S57.

[0097] As described above, if the determination in step S53 is NO, there is a possibility that the load on the internal combustion engine 10 is high. If the oxygen concentration sensor signal indicates a fuel lean state in step S71 despite this condition, it is considered that this is due to a high alcohol concentration. Therefore, if the determination in step S71 is YES, the alcohol concentration level is raised by one level by the concentration determination unit 100 in step S56. However, if the oxygen concentration sensor signal does not indicate a fuel lean state in step S71, there is no need to change the alcohol concentration level, and the processing procedure proceeds to step S57.

[0098] In step S57, the valve opening period determination unit 102 calculates the fuel injection amount and the valve opening period of the fuel injection valve 32 based on the alcohol concentration level stored in the storage unit 82. When the processing of step S57 is completed, this processing procedure ends.

[0099] [Modifications] The above-described embodiment may be modified as follows.

[0100] (Variation 1) In the above-described embodiment, the timer determination unit 104 determines the timer to be used for controlling the fuel injector 32 based on the calculated valve-open period of the fuel injector 32. As described above, the higher the alcohol concentration in the fuel F, the longer the valve-open period of the fuel injector 32. Therefore, the timer determination unit 104 may determine the timer to be used for controlling the fuel injector 32 based on the alcohol concentration determined by the concentration determination unit 100. In other words, a timer that counts at a cycle based on the alcohol concentration is used for controlling the fuel injector 32.

[0101] 9 is a flowchart illustrating a processing procedure for fuel injection valve control in Modification 1. This processing procedure is performed by the calculation unit 80 of the fuel injection control device 12 by executing a program stored in the storage unit 82. This processing procedure is started when the calculation unit 80 detects a starter-on signal from the starter switch 122 after the valve-opening duration determination unit 102 determines the valve-opening duration of the fuel injection valve 32. This processing procedure is repeated until the ignition switch 120 is turned off. In FIG. 9, steps that are the same as those described above with reference to FIG. 4 are assigned the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0102] When this processing procedure starts, in step S101, the timer determination unit 104 determines whether the alcohol concentration level of alcohol in the fuel F acquired by the concentration determination unit 100 is equal to or higher than a predetermined level. As described with reference to FIG. 2 , when the alcohol concentration of the fuel F is high, the fuel injection valve 32 needs to inject a large amount of fuel F. Therefore, when the alcohol concentration level is equal to or higher than the predetermined level, a relatively large amount of fuel injection is required, and the opening period of the fuel injection valve 32 may become long.

[0103] If the answer is YES in step S101, the process proceeds to step S102, whereas if the answer is NO in step S101, the process proceeds to step S11.

[0104] In step S102, the timer determination unit 104 acquires the rotation speed of the internal combustion engine 10. The rotation speed of the internal combustion engine 10 is obtained based on the rotation angle of the crankshaft 60 detected by the crank angle sensor 52. The timer determination unit 104 determines whether the rotation speed of the internal combustion engine 10 is less than a predetermined rotation speed. Immediately after the start of the internal combustion engine 10, the rotation speed of the internal combustion engine 10 is less than the predetermined rotation speed. Because a relatively large amount of fuel injection is required until the start of the internal combustion engine 10 is completed, the opening period of the fuel injection valve 32 may become long.

[0105] If step S102 is YES, the process proceeds to step S2. If step S102 is NO, the process proceeds to step S11. The processes performed in step S2 and step S11 and subsequent steps have been described using FIG. 4, so their description will be omitted. In step S3 or step S11, a timer used to control the fuel injection valve 32 is determined. The count cycle of the timer is based on the alcohol concentration in the fuel F and the rotation speed of the internal combustion engine 10. In particular, the lower the rotation speed of the internal combustion engine 10, the longer the count cycle of the timer.

[0106] The alcohol concentration level used in step S101 in Fig. 9 is obtained by the concentration determination unit 100 in step S51 in Fig. 8. The alcohol concentration in the fuel F approaches the actual alcohol concentration by repeating the process of calculating the valve opening period of the fuel injection valve 32 shown in Fig. 8. Therefore, after a value close to the actual alcohol concentration is stored in the memory unit 82, the alcohol concentration determination by the concentration determination unit 100 does not necessarily have to be performed.

[0107] However, before the ignition switch 120 is turned on, the fuel tank 70 may be newly refilled with fuel F. In this case, the alcohol concentration of the fuel F may change. After the ignition switch 120 is turned on, the fuel injection control device 12 is started. Therefore, at least when the fuel injection control device 12 is started, it is preferable to perform the processing procedure for calculating the valve opening period of the fuel injection valve 32 shown in FIG. 8 and the subsequent processing procedure for controlling the opening and closing of the fuel injection valve 32 shown in FIG. 4.

[0108] Therefore, it is preferable that the concentration determination unit 100 determines the alcohol concentration of the fuel F when the fuel injection control device 12 is started up. The timer determination unit 104 determines the timer to be used for controlling the fuel injection valve 32 based on the alcohol concentration determined by the concentration determination unit 100. In other words, the count cycle of the timer is based on the alcohol concentration determined when the fuel injection control device 12 is started up. This makes it possible to appropriately control the opening and closing of the fuel injection valve 32 in response to changes in the alcohol concentration of the fuel F.

[0109] (Variation 2) In the above-described variation 1, the timer determination unit 104 determines the timer to be used for controlling the fuel injection valve 32 based on the alcohol concentration determined by the concentration determination unit 100. As described above, the higher the alcohol concentration in the fuel F, the greater the fuel injection amount by the fuel injection valve 32. In this case, the oxygen concentration sensor signal from the oxygen concentration sensor 56 indicates a fuel lean state. A fuel lean state corresponds to a case where the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10 is high.

[0110] Therefore, the timer determination unit 104 may determine the timer to be used for controlling the fuel injection valve 32 based on the oxygen concentration detected by the oxygen concentration sensor 56. That is, the timer that counts at a cycle based on the oxygen concentration is used for controlling the fuel injection valve 32.

[0111] 10 is a flowchart illustrating a processing procedure for fuel injection valve control in Modification 2. This processing procedure is performed by the calculation unit 80 of the fuel injection control device 12 by executing a program stored in the storage unit 82. This processing procedure is started when the calculation unit 80 detects a starter-on signal from the starter switch 122 after the valve-opening duration determination unit 102 determines the valve-opening duration of the fuel injection valve 32. This processing procedure is repeated until the ignition switch 120 is turned off. In FIG. 10, steps that are the same as those described above with reference to FIG. 4 or FIG. 9 are denoted by the same reference numerals, and descriptions thereof will be omitted where appropriate.

[0112] When this process procedure starts, in step S121, the timer determination unit 104 determines whether the oxygen concentration detected by the oxygen concentration sensor 56 is a concentration corresponding to a fuel lean condition. If the oxygen concentration is a concentration corresponding to a fuel lean condition, the fuel injection valve 32 needs to inject a large amount of fuel F. Therefore, the opening period of the fuel injection valve 32 may become long.

[0113] If step S121 returns YES, the process proceeds to step S102. If step S121 returns NO, the process proceeds to step S11. The processes performed in step S102 and step S11 and subsequent steps have been described using FIG. 4 or FIG. 9, and therefore will not be described here.

[0114] (Variation 3) In the above-described embodiment and variations, the concentration determination unit 100 determines the alcohol concentration in the fuel F based on the convergence result of feedback control based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine 10, and stores the determined alcohol concentration in the memory unit 82. However, the concentration determination unit 100 may determine the alcohol concentration based on the measurement result of the alcohol concentration in the fuel F stored in the fuel tank 70.

[0115] 11 is a diagram illustrating an internal combustion engine 10, a fuel injection control device 12, and a fuel tank 70 in Modification 3. An alcohol concentration sensor 150 is disposed at the bottom of the fuel tank 70. The alcohol concentration sensor 150 is immersed in the fuel F stored in the fuel tank 70 and measures the alcohol concentration of alcohol contained in the fuel F. The concentration determination unit 100 determines the alcohol concentration by acquiring the alcohol concentration measured from the alcohol concentration sensor 150.

[0116] The alcohol concentration sensor 150 may be disposed inside a pipe 72 connected to the fuel tank 70. In this case, the alcohol concentration sensor 150 measures the alcohol concentration of the alcohol contained in the fuel F flowing through the pipe 72. The concentration determination unit 100 determines the alcohol concentration by acquiring the measured alcohol concentration from the alcohol concentration sensor 150.

[0117] (Modification 4) The above-described embodiment and modifications may be combined as appropriate within a range that does not cause contradiction.

[0118] The following additional notes are provided regarding the above-described embodiment.

[0119] (Note 1) A fuel injection control device (12) has a timer (84, 86) and controls a fuel injection valve (32) that supplies an alcohol-containing fuel (F) to an internal combustion engine (10) using the timer. The fuel injection control device (12) includes: a concentration determination unit (100) that determines the alcohol concentration of the alcohol in the fuel; and a valve control unit (106) that controls opening and closing of the fuel injection valve in accordance with the timer counted at count cycles (P1, P2) based on the alcohol concentration, thereby adjusting a valve opening period of the fuel injection valve. The higher the alcohol concentration, the longer the count cycle. With this configuration, the valve opening period of the fuel injection valve can be finely adjusted.

[0120] (Supplementary Note 2) The fuel injection control device according to Supplementary Note 1 may further include a valve opening period determination unit (102) that determines the valve opening period by feedback control based on an oxygen concentration of oxygen in exhaust gas from the internal combustion engine, wherein the valve opening period determined by the valve opening period determination unit is longer as a gain of the feedback control increases, and the gain of the feedback control is larger as the alcohol concentration increases, and the valve control unit may control opening and closing of the fuel injection valve according to the timer counted at a period based on the valve opening period. With this configuration, the valve opening period of the fuel injection valve can be appropriately adjusted.

[0121] The fuel injection control device according to claim 2 may further include a memory unit (82) that stores the gain of the feedback control as a learned value, and the valve opening period determination unit may determine the valve opening period by the feedback control using the learned value as the gain. With this configuration, the valve opening period of the fuel injection valve can be quickly adjusted.

[0122] (Supplementary Note 4) In the fuel injection control device according to Supplementary Note 3, the learned value stored in the storage unit may be the gain in a state where the feedback control has converged. With this configuration, the opening period of the fuel injection valve can be quickly adjusted.

[0123] In the fuel injection control device according to any one of Supplementary Notes 1 to 4, the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine may be increased as the alcohol concentration is increased, and the valve control unit may control the opening and closing of the fuel injection valve in accordance with the timer counted at a period based on the oxygen concentration. With this configuration, the opening period of the fuel injection valve can be appropriately adjusted.

[0124] (Supplementary Note 6) The fuel injection control device according to any one of Supplementary Notes 1 to 4 may further include a valve opening period determination unit (102) that determines the valve opening period based on an oxygen concentration of oxygen in exhaust gas from the internal combustion engine, the valve opening period determined by the valve opening period determination unit may be longer as the alcohol concentration is higher, and the valve control unit may control the opening and closing of the fuel injection valve according to the timer counted at a period based on the valve opening period. With this configuration, the valve opening period of the fuel injection valve can be appropriately adjusted.

[0125] In the fuel injection control device according to any one of Supplementary Notes 1 to 6, the concentration determination unit may determine the alcohol concentration at the time of startup of the fuel injection control device, and the counting period may be based on the alcohol concentration determined at the time of startup of the fuel injection control device. With this configuration, it is possible to appropriately adjust the opening period of the fuel injection valve.

[0126] In the fuel injection control device according to any one of Supplementary Notes 1 to 7, the concentration determination unit may determine the alcohol concentration by acquiring the alcohol concentration of the alcohol contained in the fuel stored in a fuel tank (70) of a vehicle equipped with the internal combustion engine or the alcohol contained in the fuel flowing through a pipe (72) connected to the fuel tank. With this configuration, the opening period of the fuel injection valve can be easily adjusted.

[0127] (Supplementary Note 9) The fuel injection control device according to any one of Supplementary Notes 1 to 8 further includes a first timer (84) having a count period of a first period (P1), a second timer (86) having a count period of a second period (P2) longer than the first period, and a timer determination unit (104) that determines one of the first timer and the second timer as the timer to be used for controlling the fuel injection valve, wherein a maximum count number that the second timer can count is equal to or less than a maximum count number that the first timer can count, and the timer determination unit determines the first timer as the timer to be used for controlling the fuel injection valve, so that the count period based on the alcohol concentration becomes the first period, and the timer determination unit determines the second timer as the timer to be used for controlling the fuel injection valve, so that the count period based on the alcohol concentration becomes the second period. With this configuration, it is possible to appropriately adjust the valve opening period of the fuel injection valve.

[0128] (Supplementary Note 10) In the fuel injection control device according to any one of Supplementary Notes 1 to 9, the count period may be based on the alcohol concentration and the rotation speed of the internal combustion engine. With this configuration, it is possible to appropriately adjust the opening period of the fuel injection valve.

[0129] (Supplementary Note 11) In the fuel injection control device according to Supplementary Note 10, the count period may be longer as the rotation speed of the internal combustion engine decreases. With this configuration, the opening period of the fuel injection valve can be appropriately adjusted.

[0130] Although the present disclosure has been described in detail, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0131] 10...Internal combustion engine 12...Fuel injection control device 14...Electronically controlled throttle 16...Fuel injection device 18...Ignition device 20...Exhaust gas purification device 22...Throttle valve 24...Throttle drive unit 26...Throttle position sensor 28...Intake valve 30...Intake port 32...Fuel injection valve 34...Combustion chamber 36...Spark plug 38...Ignition coil 40...Cylinder head 42...Three-way catalyst 44...Exhaust valve 46...Exhaust port 48...Intake air temperature sensor 50...Intake pressure sensor 52...Crank angle sensor 54...Cooling water temperature sensor 56...Oxygen concentration sensor 58...Intake duct 60...Crankshaft 62...Signal rotor 64...Cylinder 70...Fuel tank 72...Pipe 80...Calculation unit 82...Storage unit 84...First timer 86...Second timer 88...Drive circuit 100...Concentration determination unit 102: Valve opening period determination unit 104: Timer determination unit 106: Valve control unit 120: Ignition switch 122: Starter switch 150: Alcohol concentration sensor

Claims

1. A fuel injection control device (12) having a timer (84, 86) and using the timer to control a fuel injection valve (32) that supplies fuel (F) containing alcohol to an internal combustion engine (10), comprising: a concentration determination unit (100) that determines the alcohol concentration of the alcohol in the fuel; and a valve control unit (106) that controls the opening and closing of the fuel injection valve in accordance with the timer counted at count periods (P1, P2) based on the alcohol concentration, thereby adjusting the opening period of the fuel injection valve, wherein the higher the alcohol concentration, the longer the count period.

2. A fuel injection control device as set forth in claim 1, further comprising a valve opening period determination unit (102) that determines the valve opening period by feedback control based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine, wherein the valve opening period determined by the valve opening period determination unit is longer as the gain of the feedback control increases, and the gain of the feedback control is larger as the alcohol concentration is higher, and the valve control unit controls the opening and closing of the fuel injection valve according to the timer counted at a period based on the valve opening period.

3. A fuel injection control device according to claim 2, further comprising a memory unit (82) that stores the gain of the feedback control as a learned value, and the valve opening period determination unit determines the valve opening period by the feedback control using the learned value as the gain.

4. A fuel injection control device according to claim 3, wherein the learned value stored in the storage unit is the gain in a state where the feedback control has converged.

5. A fuel injection control device as claimed in claim 1, wherein the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine is higher as the alcohol concentration is higher, and the valve control unit controls the opening and closing of the fuel injection valve in accordance with the timer counted at a period based on the oxygen concentration.

6. A fuel injection control device as set forth in claim 1, further comprising a valve opening period determination unit (102) that determines the valve opening period based on the oxygen concentration of oxygen in the exhaust gas from the internal combustion engine, wherein the valve opening period determined by the valve opening period determination unit is longer the higher the alcohol concentration, and the valve control unit controls the opening and closing of the fuel injection valve in accordance with the timer counted at a period based on the valve opening period.

7. A fuel injection control device according to claim 1, wherein the concentration determination unit determines the alcohol concentration when the fuel injection control device is started up, and the counting period is based on the alcohol concentration determined when the fuel injection control device is started up.

8. A fuel injection control device according to claim 1, wherein the concentration determination unit determines the alcohol concentration by obtaining the alcohol concentration of the alcohol contained in the fuel stored in a fuel tank (70) of a vehicle equipped with the internal combustion engine, or the alcohol concentration of the alcohol contained in the fuel flowing through a pipe (72) connected to the fuel tank.

9. A fuel injection control device according to claim 1, further comprising: a first timer (84) whose count period is a first period (P1); a second timer (86) whose count period is a second period (P2) longer than the first period; and a timer determination unit (104) that determines either the first timer or the second timer as the timer to be used for controlling the fuel injection valve, wherein the maximum number of counts that the second timer can count is equal to or less than the maximum number of counts that the first timer can count; when the timer determination unit determines the first timer as the timer to be used for controlling the fuel injection valve, the count period based on the alcohol concentration becomes the first period; and when the timer determination unit determines the second timer as the timer to be used for controlling the fuel injection valve, the count period based on the alcohol concentration becomes the second period.

10. A fuel injection control device according to claim 1, wherein the counting period is based on the alcohol concentration and the rotation speed of the internal combustion engine.

11. A fuel injection control device according to claim 10, wherein the count period is longer as the rotation speed of the internal combustion engine is lower.

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