JP2010025086A - Throttle control device of internal combustion engine - Google Patents

Abstract

In a throttle control device for an internal combustion engine that controls a throttle motor so that the opening of a throttle valve coincides with the target throttle opening, the target throttle opening and the actual opening differ, Prevents the actual flow rate from deviating.
A throttle target opening lower limit guard value is obtained based on a throttle command voltage lower limit guard value acquired when the throttle valve is fully closed, and the lower limit guard value is used to limit the lower limit of the throttle target opening. Further, an engine required flow rate lower limit guard value is obtained based on the throttle command voltage lower limit guard value (throttle target opening lower limit guard value), and the lower limit of the engine required flow rate is limited using the guard value. By such guard processing, the deviation between the target throttle opening and the actual opening and the deviation between the engine required flow rate and the actual flow rate can be resolved. Can be prevented.
[Selection] Figure 4

Description

  The present invention relates to a throttle control device for an internal combustion engine that controls an opening degree of a throttle valve for adjusting an intake air amount provided in an intake passage of the internal combustion engine.

  An internal combustion engine (hereinafter also referred to as an engine) mounted on a vehicle or the like, for example, guides an air-fuel mixture in which air flowing through an intake passage and fuel are mixed into a combustion chamber, and the air-fuel mixture burns and explodes in the combustion chamber. The crankshaft is rotated by the energy generated by.

  In such an engine, a throttle motor (for example, a DC motor) for driving a throttle valve provided in the intake passage is provided, and an electronic throttle control capable of controlling the throttle opening independently of the driver's operation of the accelerator pedal. The device is known.

  In the electronic throttle control device, the actual throttle opening of the throttle valve is detected using a throttle opening sensor or the like, and the throttle opening (throttle target opening) from which the actual throttle opening can obtain the target intake amount (engine flow rate). ), The throttle motor of the throttle valve is feedback controlled (see, for example, Patent Document 1).

  Specifically, for example, as shown in FIG. 6, the engine required flow rate (including the load correction amount and the like) calculated based on the operating state of the engine is converted into a throttle target opening, and the throttle target opening is calculated. Converted to throttle command voltage (throttle motor command voltage). Based on the throttle command voltage (target voltage) and the output voltage of the throttle opening sensor, the motor drive duty ratio of the throttle motor is controlled so that the actual throttle opening matches the throttle target opening. In such throttle control, a lower limit guard value is provided for the slot command voltage to limit the lower limit of the throttle opening. The throttle command voltage lower limit guard value is acquired when the throttle valve is brought into contact with a fully closed position (for example, a fully closed stopper).

In this type of throttle control device, the fully closed position of the throttle valve is learned as a reference position, and the opening degree of the throttle valve is controlled using the learned fully closed position as a reference (see, for example, Patent Document 2). . In the technique described in Patent Document 2, the fully closed position is learned by the throttle valve abutting control in a state where the throttle valve is abutted against the fully closed position.
JP 2002-021617 A JP 2005-188464 A

  Incidentally, in an engine mounted on a vehicle, the required engine flow rate required for control may be equal to or less than the throttle fully closed. Specifically, for example, when the variation in temperature characteristics of the throttle opening sensor is large, or when the amount of leaked air is large due to manufacturing variation (tolerance) of the throttle valve, as shown in FIG. The required flow rate during idling may be smaller than the flow rate (one-dot chain line) when closed to the closed position. In this case, even if the throttle valve is closed to the fully closed position, the engine speed becomes higher than the idle target speed, so that a request for lowering the air flow rate is generated in terms of control.

  In such a situation, as shown in FIG. 6, there is a difference between the target throttle opening and the actual opening. Further, since there is a discrepancy between the engine required flow rate and the actual flow rate, there is a possibility of erroneous detection of the throttle opening or erroneous learning of the engine required flow rate in the throttle control. Then, after such an erroneous learning of the engine required flow rate occurs, even if the engine required flow rate increases in control due to, for example, an air conditioner ON (load increase), the increase amount of the required flow rate is the engine required flow rate described above. There is a dead zone where the throttle valve does not open until the difference between the actual air amount and the actual air amount becomes larger, and there is a possibility that a response delay of the actual flow rate (actual intake air amount) may occur. In addition, if the throttle target opening (required opening) deviates from the actual opening, there is a possibility that an abnormality detection error occurs.

  The present invention has been made in view of such circumstances, and in a throttle control device for an internal combustion engine that controls a throttle motor so that the opening of the throttle valve matches the throttle target opening, the throttle target opening and the actual It is an object of the present invention to realize a control capable of preventing the opening degree from deviating and the engine requested flow rate from deviating from the actual flow rate.

  In order to achieve the above object, the present invention provides a throttle valve that is disposed in an intake passage of an internal combustion engine and controls an intake air amount, a throttle motor that drives the throttle valve, and a throttle opening degree of the throttle valve is a throttle target. Assuming a throttle control device that controls the throttle motor to match the opening, in such a throttle control device for an internal combustion engine, a throttle command voltage used for controlling the throttle motor when the throttle valve is fully closed. A guard value acquisition means for acquiring a lower limit guard value is provided, a throttle target opening lower limit guard value is obtained based on the throttle command voltage lower limit guard value, and the lower limit guard value is used to limit the lower limit of the throttle target opening. It is characterized by.

  Further, the present invention is arranged in an intake passage of an internal combustion engine, and controls a throttle valve that controls the amount of intake air, a throttle motor that drives the throttle valve, and a throttle opening of the throttle valve matches a throttle target opening. In such a throttle control device for an internal combustion engine, the required intake air amount lower limit guard value (hereinafter referred to as the engine required flow rate lower limit) is determined based on the throttle command voltage lower limit guard value. And a lower limit guard value is used to limit the lower limit of the required intake air amount (hereinafter also referred to as engine required flow rate).

  Further, the present invention is arranged in an intake passage of an internal combustion engine, and controls a throttle valve that controls the amount of intake air, a throttle motor that drives the throttle valve, and a throttle opening of the throttle valve matches a throttle target opening. As described above, the throttle control device for controlling the throttle motor is obtained, and in such a throttle control device for an internal combustion engine, when the throttle valve is fully closed, the throttle command voltage lower limit guard value used for controlling the throttle motor is obtained. Guard value acquisition means for obtaining a throttle target opening lower limit guard value based on the throttle command voltage lower limit guard value, limiting the lower limit of the throttle target opening using the lower limit guard value, and opening the throttle target opening From the lower limit guard value, the required intake air amount lower limit guard Calculated values, and limits the lower limit of the required intake air amount by using the lower limit guard value.

  In the present invention, the engine required flow rate lower limit guard value may be directly converted from the throttle command voltage lower limit guard value, or the throttle target opening lower limit guard value converted from the throttle command voltage lower limit guard value is used. The throttle target opening lower limit guard value may be calculated by a method of converting into an engine required flow lower limit guard value using, for example, an opening-flow rate map.

  According to the present invention, based on the throttle command voltage lower limit guard value based on the throttle fully closed position, that is, the actual throttle motor drive voltage (throttle fully closed voltage) when the throttle valve is in the fully closed position. The throttle target opening lower limit guard value is obtained, and the lower limit guard value is used to limit the lower limit of the throttle target opening for control. Therefore, the throttle target opening does not become less than or equal to the throttle fully closed. Accordingly, the difference between the throttle target opening and the actual opening as shown in FIG. 6 can be eliminated, and erroneous detection of the throttle target opening can be prevented.

  Similarly, an engine required flow rate lower limit guard value is obtained based on a throttle command voltage lower limit guard value (throttle target opening lower limit guard value) based on the throttle fully closed position, and the lower limit guard value is used for control. Since the lower limit of the engine required flow rate is limited, the engine required flow rate does not become less than or equal to the throttle fully closed. Accordingly, the difference between the engine required flow rate and the actual flow rate as shown in FIG. 6 can be eliminated, and erroneous learning of the engine required flow rate can be prevented.

  As a specific configuration of the present invention, when the condition that the motor drive duty ratio of the throttle motor in the throttle closing direction is equal to or greater than the determination threshold and the state beyond the determination threshold continues for a predetermined time or longer is satisfied, The throttle command voltage lower limit guard value can be obtained by determining that it is at the time of full closing.

  In this case, it is preferable to determine whether the throttle valve is fully closed during idle speed control. When such a configuration is adopted, the detection accuracy of the fully closed position can be increased. This point will be described.

  First, in the conventional electronic throttle system, the output signal of the throttle opening sensor is read immediately after the ignition switch is turned on (immediately before the engine is started), and the reference position (fully closed position) of the throttle opening is learned from the output signal. However, the output change (temperature characteristic) due to the temperature rise of the throttle opening sensor after the engine start causes a detection error of the throttle opening, and the fully closed position during engine operation and the learned reference position (fully closed position) There may be a gap between On the other hand, in the present invention, since the determination of the fully closed contact of the throttle valve is performed during the idle speed control during engine operation, the fully closed position can be detected with high accuracy.

  According to the present invention, the throttle target opening lower limit guard value is obtained based on the throttle command voltage lower limit guard value acquired when the throttle valve is fully closed, and the lower limit guard value is used to limit the lower limit of the throttle target opening. Therefore, the deviation between the throttle target opening and the actual opening can be eliminated, and erroneous learning of the throttle target opening can be prevented. Similarly, the engine request flow rate lower limit guard value is obtained based on the throttle command voltage lower limit guard value (throttle target opening lower limit guard value), and the lower limit of the engine request flow rate is limited using the guard value. Deviation between the flow rate and the actual flow rate can be eliminated, and erroneous learning of the engine required flow rate can be prevented.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, an engine to which the throttle control device of the present invention is applied will be described.

-Engine-
FIG. 1 is a diagram showing a schematic configuration of an engine to which the present invention is applied. FIG. 1 shows only the configuration of one cylinder of the engine.

  The engine 1 is a multi-cylinder gasoline engine, and includes a piston 1b that forms a combustion chamber 1a and a crankshaft 15 that is an output shaft. The piston 1b is connected to the crankshaft 15 via the connecting rod 16, and the reciprocating motion of the piston 1b is converted into rotation of the crankshaft 15 by the connecting rod 16.

  A signal rotor 17 having a plurality of protrusions (teeth) 17 a... 17 a on the outer peripheral surface is attached to the crankshaft 15. An engine speed sensor (crank position sensor) 25 is disposed near the side of the signal rotor 17. The engine speed sensor 25 is, for example, an electromagnetic pickup, and generates a pulsed signal (output pulse) corresponding to the protrusion 17a of the signal rotor 17 when the crankshaft 15 rotates.

  The cylinder block 1c of the engine 1 is provided with a water temperature sensor 21 that detects the engine water temperature (cooling water temperature). An oil pan 18 for storing engine oil is provided below the cylinder block 1c.

  The engine oil stored in the oil pan 18 is pumped up by an oil pump through an oil strainer that removes foreign matters during the operation of the engine 1 and further purified by an oil filter, and then the piston 1b, the crankshaft 15, the connecting rod. 16 is used for lubrication and cooling of each part. The engine oil supplied in this way is used for lubrication and cooling of each part of the engine 1 and then returned to the oil pan 18 and stored in the oil pan 18 until it is pumped up again by the oil pump. Is done.

  A spark plug 3 is disposed in the combustion chamber 1 a of the engine 1. The ignition timing of the spark plug 3 is adjusted by the igniter 4. The igniter 4 is controlled by an ECU (Electronic Control Unit) 100 described later.

  An intake passage 11 and an exhaust passage 12 are connected to the combustion chamber 1 a of the engine 1. An intake valve 13 is provided between the intake passage 11 and the combustion chamber 1a. By opening and closing the intake valve 13, the intake passage 11 and the combustion chamber 1a are communicated or blocked. Further, an exhaust valve 14 is provided between the exhaust passage 12 and the combustion chamber 1a. By opening and closing the exhaust valve 14, the exhaust passage 12 and the combustion chamber 1a are communicated or blocked. The opening / closing drive of the intake valve 13 and the exhaust valve 14 is performed by each rotation of the intake camshaft and the exhaust camshaft to which the rotation of the crankshaft 15 is transmitted.

  An air cleaner 7, a hot-wire air flow meter 22, an intake air temperature sensor 23 (built in the air flow meter 22), and an electronically controlled throttle valve 5 for adjusting the intake air amount of the engine 1 are arranged in the intake passage 11. Has been. The throttle valve 5 is driven by a throttle motor (for example, a DC motor) 6. The opening degree of the throttle valve 5 is detected by a throttle opening degree sensor 26.

  The drive shaft of the throttle motor 6 is connected to the rotation shaft of the throttle valve 5 via a reduction gear unit (not shown). In this example, a fully closed stopper is provided for the final stage resin throttle gear of the reduction gear unit. When the throttle valve 5 is rotated to the closed side by the throttle motor 6, the resin throttle gear is fully closed. The stopper comes into contact, and the rotation of the throttle valve 5 stops. The position where the resin throttle gear comes into contact with the fully closed stopper is defined as the fully closed position of the throttle valve 5.

On the other hand, the exhaust passage 12 of the engine 1 is provided with an O ₂ sensor 24 for detecting the oxygen concentration in the exhaust gas, the three-way catalyst 8 and the like.

  A fuel injection injector (fuel injection valve) 2 is arranged in the intake passage 11. Fuel of a predetermined pressure is supplied from the fuel tank to the injector 2 by a fuel pump, and the fuel is injected into the intake passage 11. This injected fuel is mixed with intake air to form an air-fuel mixture and introduced into the combustion chamber 1a of the engine 1. The air-fuel mixture (fuel + air) introduced into the combustion chamber 1a is ignited by the spark plug 3 and burns and explodes. The piston 1b reciprocates due to combustion / explosion of the air-fuel mixture in the combustion chamber 1a, and the crankshaft 15 rotates. The operating state of the engine 1 is controlled by the ECU 100. And the throttle control apparatus of the internal combustion engine of this invention is implement | achieved by the program run by this ECU100.

-ECU-
As shown in FIG. 2, the ECU 100 includes a CPU 101, a ROM 102, a RAM 103, a backup RAM 104, and the like.

  The ROM 102 stores various control programs, maps that are referred to when the various control programs are executed, and the like. The CPU 101 executes arithmetic processing based on various control programs and maps stored in the ROM 102. The RAM 103 is a memory that temporarily stores calculation results of the CPU 101, data input from each sensor, and the like. The backup RAM 104 is a non-volatile memory that stores data to be saved when the engine 1 is stopped. is there.

  The CPU 101, ROM 102, RAM 103, and backup RAM 104 are connected to each other via a bus 107, and are connected to an input interface 105 and an output interface 106.

The input interface 105 outputs a water temperature sensor 21, an air flow meter 22, an intake air temperature sensor 23, an O ₂ sensor 24, an engine speed sensor 25, a throttle opening sensor 26, and a detection signal corresponding to the depression amount of the accelerator pedal. Various sensors such as an accelerator opening sensor 27 and a vehicle speed sensor 28 are connected.

  The output interface 106 is connected to the injector 2, the igniter 4 of the spark plug 3, the throttle motor 6 of the throttle valve 5, and the like.

  The ECU 100 executes various controls of the engine 1 including the injection timing control of the injector 2 and the ignition timing control of the spark plug 3 based on the detection signals of the various sensors described above. Further, the ECU 100 executes the following [throttle control], [fully closed position determination / fully closed voltage sampling process], and [guard process].

-Throttle control-
In this example, the engine 1 is operated such as the engine speed Ne read from the output signal of the engine speed sensor 25 and the accelerator pedal depression amount (accelerator opening Acc read from the output signal of the accelerator opening sensor 27). The throttle opening is feedback controlled so that the optimum intake air amount (engine target flow rate) corresponding to the state is obtained.

  Specifically, for example, the engine required flow rate (including the load correction amount and the like) is calculated with reference to a map or the like based on the engine speed Ne and the accelerator opening degree Acc. The engine required flow rate is converted into a throttle target opening ([flow rate → opening]), and the throttle target opening is converted into a throttle command voltage ([opening → voltage]). Based on the throttle command voltage (target voltage) and the output voltage of the throttle opening sensor 26, the motor drive duty ratio of the throttle motor 6 is controlled so that the actual throttle opening matches the throttle target opening. In this example, the lower limit of the throttle command voltage is limited by a throttle command voltage lower limit guard value httppgd described later. Further, the lower limits of the engine required flow rate and the throttle target opening are also limited by a guard process described later.

  In addition, the ECU 100 executes idle speed control (ISC: Idle Speed Control). The ISC control is executed when the engine 1 is idling, and the opening of the throttle valve 5 is adjusted so that the actual idling speed during idling matches the target idling speed. Feedback control of intake air volume. Specifically, the target idle speed is calculated with reference to a map or the like based on the operating state of the engine 1, and the actual idle speed (engine speed ne) is read from the output signal of the engine speed sensor 25. The intake air amount to the engine 1 is adjusted by feedback control of the opening degree of the throttle valve 5 so that the actual idle speed matches the idle target speed.

-Fully closed position judgment and fully closed voltage sampling process-
Next, the fully closed position determination process executed in this example will be described with reference to the flowchart of FIG. The control routine shown in FIG. 3 is repeatedly executed by the ECU 100 every predetermined time (for example, about several milliseconds to several tens of milliseconds).

  First, in step ST101, it is determined whether or not ISC control is being performed. If the determination result is affirmative, the process proceeds to step ST102. If the determination result in step ST101 is negative, the process returns.

  Here, during the ISC control, the throttle valve 5 is controlled to be closed when the throttle target opening (engine required flow rate) for control is smaller than the actual opening (actual flow rate). If the resin throttle gear of the speed reduction gear unit hits the fully closed stopper during the execution of the throttle closing side control, the load on the throttle motor 6 increases and the motor drive duty ratio increases. The fully closed position of the throttle valve 5 can be detected from the magnitude of the motor drive duty ratio.

  Therefore, in this example, in step ST102, it is determined whether or not the motor drive duty ratio of the throttle motor 6 in the throttle closing direction is equal to or greater than a predetermined determination threshold value, and whether or not a state equal to or greater than the determination threshold value has continued for a predetermined time. If the determination result is affirmative, it is determined that the end of the fully closed stopper is reached (step ST103). If the determination result in step ST102 is negative, the process returns.

  When it is determined in this way that the throttle valve 5 is in contact with the fully closed stopper, the ECU 100 collects the drive voltage (throttle fully closed voltage) of the throttle motor 6.

  For the determination threshold value and the predetermined time used in the determination process of step ST102, a value that can be determined that the resin throttle gear is surely hitting the fully closed stopper is empirically obtained in advance through experiments and calculations. Can be set.

-Guard processing-
First, in the engine 1 mounted on the vehicle, as described above, the engine required flow rate required for control may be less than or equal to the throttle fully closed. Specifically, for example, when the variation in temperature characteristics of the throttle opening sensor 26 is large, or when the amount of leaked air is large due to manufacturing variation (tolerance) of the throttle valve 5, as shown in FIG. The required flow rate during idling may be smaller than the flow rate (one-dot chain line) when 5 is closed to the fully closed position. In this case, even if the throttle valve 5 is closed to the fully closed position, the engine speed Ne becomes higher than the target idling speed, so that a request for lowering the air flow rate is generated in terms of control.

  In such a situation, as shown in FIG. 6, there is a difference between the target throttle opening and the actual opening. Further, since there is a discrepancy between the engine required flow rate and the actual flow rate, there is a possibility of erroneous detection of the throttle opening or erroneous learning of the engine required flow rate in the throttle control. After such mislearning occurs, even if the engine required flow rate increases in control due to, for example, air conditioner ON (load increase), the required increase amount is the difference between the engine required flow rate and the actual air amount described above. There is a dead zone where the throttle valve 5 does not open until it becomes larger than the deviation amount, which may cause a response delay of the actual flow rate (actual intake air amount). In addition, if the throttle target opening (required opening) deviates from the actual opening, there is a possibility that an abnormality detection error occurs.

  In order to solve such a problem, in this example, a guard process of the throttle target opening and the engine required flow rate is executed. An example of the guard process is shown in FIG. The guard process of FIG. 4 is executed in the ECU 100.

  First, the ECU 100 acquires the throttle full-closed voltage collected at the time of the above-mentioned full-closed stopper hitting as the throttle command voltage lower limit guard value httppgd [V].

  Next, ECU 100 converts throttle command voltage lower limit guard value httppgd [V] into throttle target opening lower limit guard value htaiscmn [deg], for example, by unit conversion by a bit shift calculation. Further, using the converted throttle target opening lower limit guard value htaiscmn [deg], the engine required flow lower limit guard value hqgd (the throttle full close flow lower limit guard value with reference to the opening-flow rate map shown in FIG. 5). ) [L / s] is calculated. Note that the opening-flow rate map of FIG. 5 obtains the relationship between the throttle opening of the throttle valve 5 and the air flow rate through experiments and calculations, etc., and converts the throttle opening into the engine required flow rate based on the result. The conversion value to be obtained is obtained and mapped, and stored in the ROM 102 of the ECU 100.

  In this example, the throttle target opening lower limit guard value htaiscmn [deg] calculated as described above, that is, the throttle target converted from the throttle command voltage lower limit guard value htpgd [V] based on the throttle fully closed position. The lower limit of the throttle target opening for control is limited using the opening lower limit guard value htaiscmn [deg]. By such a guard process, the throttle target opening does not become less than or equal to the throttle fully closed, thereby eliminating the difference between the target throttle opening and the actual opening as shown in FIG. It is possible to prevent erroneous detection of the target opening.

  Further, the engine required flow rate lower limit guard value hqgd [L / s] is calculated using the throttle target opening lower limit guard value htaiscmn [deg] converted from the throttle command voltage lower limit guard value httppgd [V] with the throttle fully closed position as a reference. The lower limit guard value hqgd [L / s] is calculated, and the lower limit of the engine required flow rate for control is limited. By such a guard process, the engine required flow rate does not become less than or equal to the throttle fully closed, thereby eliminating the difference between the engine required flow rate and the actual flow rate as shown in FIG. Incorrect learning can be prevented.

  The engine required flow rate lower limit guard value hqgd [L / s] may be directly converted from the throttle command voltage lower limit guard value httppgd [V].

-Other embodiments-
In the above example, the air flow rate (intake air amount) is read from the output signal of the air flow meter 22 when it is determined by the processing of FIG. 3 that the throttle valve 5 reaches the fully closed stopper, and the air flow rate in the fully closed state. Based on these values, limit values on the closing side during throttle control (the engine required flow rate lower limit guard value and the throttle target opening guard value) may be set.

  In the above example, the present invention is applied to a throttle control device for a gasoline engine. However, the present invention is not limited to this, and other examples such as LPG (liquefied petroleum gas) and LNG (liquefied natural gas) are available. The present invention can be applied to a throttle control device for an ignition-type engine using the above-described fuel, and is not limited to a port injection type engine, but can also be applied to a throttle control device for an in-cylinder direct injection type engine. The engine is not limited to an ignition type engine, and may be a diesel engine.

It is a schematic block diagram which shows an example of the engine to which the throttle control apparatus of this invention is applied. It is a block diagram which shows the structure of control systems, such as ECU. It is a flowchart which shows an example of the control routine of the fully closed position determination process performed in ECU. It is a figure which shows the content of the calculation process of a throttle target opening lower limit guard value and an engine request | requirement flow volume lower limit guard value. It is a figure which shows the opening-flow rate map used for converting throttle opening into engine request | requirement flow volume. It is a figure explaining the reason why the erroneous detection of the throttle target opening and the erroneous learning of the engine required flow rate occur. It is a figure which shows the relationship between a throttle opening and an air flow rate.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Injector 3 Spark plug 5 Throttle valve 6 Throttle motor 11 Intake passage 12 Exhaust passage 13 Intake valve 14 Exhaust valve 22 Air flow meter 25 Engine speed sensor 26 Throttle opening sensor 27 Accelerator opening sensor 100 ECU

Claims (5)

A throttle valve that is disposed in the intake passage of the internal combustion engine and controls the amount of intake air; a throttle motor that drives the throttle valve; and the throttle motor so that the throttle opening of the throttle valve matches the throttle target opening In the throttle control device to control,
Guard value acquisition means for acquiring a throttle command voltage lower limit guard value used for control of the throttle motor when the throttle valve is fully closed is provided, and based on the throttle command voltage lower limit guard value, the throttle target opening lower limit guard value is A throttle control device for an internal combustion engine, wherein the lower limit guard value is obtained and the lower limit of the target throttle opening is limited. A throttle valve that is disposed in the intake passage of the internal combustion engine and controls the amount of intake air; a throttle motor that drives the throttle valve; and the throttle motor so that the throttle opening of the throttle valve matches the throttle target opening In the throttle control device to control,
A throttle control device for an internal combustion engine, wherein a required intake air amount lower limit guard value is obtained based on the throttle command voltage lower limit guard value, and a lower limit of the required intake air amount is limited using the lower limit guard value. A throttle valve that is disposed in the intake passage of the internal combustion engine and controls the amount of intake air; a throttle motor that drives the throttle valve; and the throttle motor so that the throttle opening of the throttle valve matches the throttle target opening In the throttle control device to control,
Guard value acquisition means for acquiring a throttle command voltage lower limit guard value used for control of the throttle motor when the throttle valve is fully closed is provided, and based on the throttle command voltage lower limit guard value, the throttle target opening lower limit guard value is The lower limit guard value is used to limit the lower limit of the throttle target opening, and the required intake air amount lower limit guard value is obtained from the throttle target opening lower limit guard value, and the required intake air amount is calculated using the lower limit guard value. A throttle control device for an internal combustion engine characterized by limiting the lower limit of the engine. The throttle control device for an internal combustion engine according to any one of claims 1 to 3,
When the motor drive duty ratio in the throttle closing direction of the throttle motor is equal to or greater than a determination threshold and the state equal to or greater than the determination threshold continues for a predetermined time or more, it is determined that the throttle valve is at the fully closed end, A throttle control device for an internal combustion engine, wherein a throttle command voltage lower limit guard value is acquired. The throttle control device for an internal combustion engine according to claim 4,
Idle rotation speed control means for feedback controlling the intake air amount of the internal combustion engine so that the actual idle rotation speed of the internal combustion engine matches the target idle rotation speed, and during the idle rotation speed control, A throttle control device for an internal combustion engine, which performs a determination of a fully closed end.

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