JP2000352342A - Throttle control system for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a throttle valve from being damaged during learning of all-closed position of throttle valves and during normal valve-closing control. SOLUTION: When an ignition switch is off and temperature surrounding a throttle valve is at prescribed value or less (S1, S2, S3), while distortion of a throttle bore on the throttle valve due to expansion is small and thus roundness is maintained, a target opening TGTVO of the throttle valve is reduced by a set amount DTGTOV beginning with value TVOTSCL equivalent to the value at fail-safe (S4, S6). Then, when the deviation between an actual opening detection value TPS1V and a value obtained by averaging the TPS1V is within a prescribed value, the opening detection value is averaged in order to learn it as an all-closed position (S5→S7).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throttle control device which opens and closes a throttle valve provided in an intake system of an internal combustion engine by an actuator so as to attain a target opening degree, and more particularly to a throttle control device which is driven to a fully closed state or a vicinity thereof. Control when the

[0002]

2. Description of the Related Art Conventionally, based on an accelerator opening (accelerator pedal depression amount) or an engine speed, etc.
There is a throttle control device that electronically controls the opening of a throttle valve so as to obtain a target air amount (Japanese Patent Laid-Open No. 7-180).
570, etc.).

In such a throttle control device, the opening of the throttle valve is set with reference to the fully closed position of the throttle valve. Therefore, when the ignition key is turned off, the throttle valve is forcibly driven to the fully closed position, and the fully closed position is set. I am learning.

[0004] Incidentally, a small-sized throttle control device does not have a mechanical stopper for regulating the fully closed position in order to have an inexpensive structure, and the throttle valve is in contact with the inner wall (bore) of the intake passage. Becomes the fully closed position.

[0005]

However, in such a small throttle control device as described above, the throttle valve is pressed against the inner wall of the intake passage many times every time the fully closed position is learned. It causes galling. In addition, in the case where the gear for driving the throttle valve is formed of a resin material to reduce the weight of the throttle control device, durability of the gear becomes a problem due to a large load applied to the gear when the throttle valve is pressed.

At high temperatures, the roundness of the inner wall (bore) of the intake passage with which the throttle valve comes into contact changes due to temperature expansion, so that large galling is likely to occur. on the other hand,
When the throttle valve is controlled to an opening close to the fully closed state, for example, during a deceleration operation by the normal control, the throttle valve undershoots and easily collides with the inner wall of the intake passage, and this also causes galling.

SUMMARY OF THE INVENTION The present invention has been made in view of such a conventional problem. Galling between the throttle valve and the inner wall of the intake passage at the time of learning the throttle valve to be fully closed or at the time of controlling the throttle valve to be in the vicinity of the fully closed state. It is an object of the present invention to provide a throttle control device for an internal combustion engine, which can suppress the occurrence of the pressure as much as possible and can reduce the load on the driving gear at the time of the fully closed learning.

[0008]

According to the first aspect of the present invention, as shown in FIG. 1 (A), the opening of a throttle valve provided in an intake system is detected by a throttle opening sensor. A throttle control device for an internal combustion engine that controls the throttle valve by energizing and driving an actuator so that the throttle valve has a target opening degree, wherein the throttle valve is driven to a fully closed position in contact with an inner wall of the intake passage, and Fully-closed position learning means for learning the detection value of the throttle opening sensor; when the fully-closed position learning means drives the throttle valve to the fully-closed position; and when the throttle valve is driven to a position close to fully-closed during normal control. When the throttle valve is brought into contact with the inner wall of the intake passage by the valve closing speed restricting means for restricting the valve closing speed of the throttle valve to a value smaller than the other driving times, and the fully closed position learning means A drive current regulating means for regulating the drive current sufficiently less than the maximum, characterized by being configured to include.

According to the first aspect of the present invention, the fully-closed learning means drives the throttle valve to the fully-closed position in contact with the inner wall of the intake passage under predetermined learning conditions including before the start of the engine. Learning value of the throttle opening sensor at the time of learning.

In normal control, the throttle valve is driven to close to an opening close to fully closed, for example, at the time of deceleration exceeding a predetermined value. When learning the throttle valve fully closed as described above,
At the time of driving to an opening close to the fully closed state during the normal control, the closing speed restricting means restricts the valve closing speed of the throttle valve to be smaller than at the time of other driving.

During full-close learning, the drive current regulating means regulates the drive current for bringing the throttle valve into contact with the inner wall of the intake passage to a value sufficiently smaller than the maximum. Thereby, the closing speed when the throttle valve hits the inner wall of the intake passage at the time of the full-close learning is reduced, and the pressing force against the intake passage wall is reduced, so that galling can be suppressed, and
Even when the throttle valve is driven to an opening close to the fully closed state during the normal control, the valve closing speed is reduced to prevent undershoot and prevent galling.

Also, the load acting on the drive system of the throttle valve is reduced by reducing the pressing force of the throttle valve against the intake passage wall at the time of fully closed learning, and the throttle valve is made of a resin material for weight reduction. The durability of gears and the like can be improved.

According to a second aspect of the present invention, as shown in FIG. 1B, the throttle valve is set to a target opening while detecting the opening of the throttle valve interposed in the intake system by a throttle opening sensor. In the throttle control device for an internal combustion engine that controls the actuator by energizing the actuator so that the throttle valve is driven, the throttle valve is driven to a fully closed position that abuts an inner wall of the intake passage, and a detection value of a throttle opening sensor at the fully closed position is obtained. Fully closed position learning means for learning; throttle valve peripheral temperature detecting means for detecting a temperature around the throttle valve; and a fully closed position by the fully closed position learning means when the temperature around the throttle valve is equal to or higher than a predetermined value. Fully closed position learning prohibiting means for prohibiting learning.

According to the second aspect of the present invention, when the temperature around the throttle valve detected by the throttle valve peripheral temperature detecting means is equal to or higher than a predetermined value, the fully closed position learning prohibiting means causes the fully closed position learning means to perform the full closing position learning. Prohibit closed position learning.

With this arrangement, under conditions where the temperature around the throttle valve is high and the roundness of the inner wall (bore) of the intake passage with which the throttle valve comes into contact changes due to temperature expansion, and galling easily occurs, Since learning of the fully closed position is prohibited, galling can be effectively suppressed.

According to a third aspect of the present invention, the throttle valve peripheral temperature detecting means detects the temperature around the throttle valve based on parameters including engine coolant temperature, intake air temperature, and intake air amount. It is characterized by.

According to the third aspect of the present invention, the amount of heat received from the engine body to the vicinity of the throttle valve is obtained from the engine body temperature estimated from the engine cooling water temperature, and the amount of heat received from the throttle valve by the intake air temperature and the intake air amount. The amount of heat released into the intake air from the engine can be obtained, so that the temperature around the throttle valve can be detected based on the amount of heat received and the amount of heat released.

The invention according to claim 4 is the same as that shown in FIG.
As shown in the figure, the throttle control of the internal combustion engine is controlled by energizing the actuator so that the throttle valve reaches the target opening while detecting the opening of the throttle valve interposed in the intake system by the throttle opening sensor. In the device,
Undershoot occurrence condition detecting means for detecting a condition under which the closing operation of the throttle valve is likely to undershoot; and detecting a condition under which the valve closing operation of the throttle valve is likely to undershoot by the undershoot occurrence condition detecting means, And lower limit correction means for increasing and correcting the lower limit of the throttle valve target opening.

According to the fourth aspect of the invention, when the undershoot occurrence condition detecting means detects a condition under which the closing operation of the throttle valve tends to undershoot, the lower limit value correcting means sets the lower limit value of the throttle valve target opening. Is increased.

Accordingly, under the condition that undershoot is likely to occur, the closing speed of the throttle valve is reduced, so that the occurrence of undershoot can be prevented, and thus the occurrence of galling can be prevented.

According to a fifth aspect of the present invention, the undershoot occurrence condition detecting means includes a throttle control system peripheral temperature detecting means for detecting a temperature around the throttle control system, and the temperature around the throttle control system is a predetermined value. When the temperature is higher or lower than the temperature range, a condition that undershoot easily occurs is detected.

According to the fifth aspect of the present invention, in the electronically controlled throttle control device, the control performance is reduced at extremely low temperatures or extremely high temperatures, and the possibility of undershoot increases.

Therefore, such a temperature state is detected as a condition that facilitates undershoot, and the lower limit of the target opening of the throttle valve is corrected to be increased to prevent the occurrence of undershoot and to prevent galling. Can be prevented.

According to a sixth aspect of the present invention, the undershoot occurrence condition detecting means includes a battery voltage detecting means for detecting a battery voltage, and undershoot occurs when the battery voltage is out of a predetermined voltage range. According to the invention according to claim 6, wherein the condition becomes easy, the electronic control type throttle control device is configured such that when the battery voltage is too high or too low,
The possibility that undershoot will occur due to a decrease in control performance increases.

Therefore, such a temperature condition is detected as a condition that facilitates undershoot, and the lower limit value of the target opening of the throttle valve is corrected to be increased to prevent the occurrence of undershoot and to prevent galling. Can be prevented.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 shows a system configuration according to an embodiment of the present invention.

The accelerator opening sensor 1 detects the amount of accelerator pedal depression (accelerator opening) depressed by the driver. The crank angle sensor 2 generates a position signal for each unit crank angle and a reference signal for each cylinder stroke phase difference, and measures the number of occurrences of the position signal per unit time, or measures the reference signal generation cycle. By doing so, the engine speed can be detected.

The air flow meter 3 detects the amount of intake air to the engine 4 (intake air amount per unit time = intake air flow rate). The water temperature sensor 5 detects a cooling water temperature of the engine.

The engine 4 has a fuel injection valve 6, which is driven by a fuel injection signal and supplies fuel directly into the combustion chamber.
An ignition plug 7 that is attached to the combustion chamber and performs ignition is provided.
By the direct injection method into the combustion chamber, leaning by stratified combustion becomes possible, and the air-fuel ratio can be variably controlled over a wide range.

A throttle valve 9 is interposed in the intake passage 8 of the engine 4. The valve opening can be electronically controlled by driving the throttle valve 9 via a lever 10 connected to the valve shaft. A simple actuator (DC motor) 11 is provided. A return spring 12 and a default spring 13 are connected to both sides of the lever 10, and when the energization of the actuator 11 is turned off, the return spring 12 and the default spring 13 are in a position where the urging forces of the return spring 12 and the default spring 13 are balanced. The throttle valve 9 is maintained at a predetermined default opening. Further, the throttle valve 9 is provided with a throttle opening sensor 14 for detecting the opening of the throttle valve 9.

The exhaust passage 15 is provided with an air-fuel ratio sensor 16 for detecting the air-fuel ratio of the combustion mixture by detecting the concentration of a specific component such as oxygen in the exhaust gas. further,
An intake air temperature sensor 17 for detecting an intake air temperature and a current sensor 18 for detecting a drive current of a DC motor constituting the actuator 11 are provided.

Signals such as the detection signals from the various sensors, the ON / OFF signal of the ignition switch 19, and the battery voltage VB are input to the control unit 20. The control unit 20 controls the opening of the throttle valve 9 by driving the actuator 11 in accordance with the operating state detected based on the various signals, and drives the fuel injection valve 6 to control the fuel injection amount ( (Fuel supply amount), an ignition timing is set, and the ignition plug 7 is set at the ignition timing.
And the learning of the fully closed position of the throttle valve 9, which will be described later, every time the operation of the engine is stopped.

Next, the learning of the fully closed position of the throttle valve will be described with reference to the flowchart of FIG. Step (referred to as S in the figure; the same applies hereinafter) In step 1, it is determined whether or not the ignition switch 19 has been turned off.

In step 1, the ignition switch 1
When it is determined that 9 has been turned OFF, the step 2
Then, the temperature around the throttle valve 9 is detected. The temperature may be detected by providing a temperature sensor in the vicinity, but it can also be obtained by estimation using an existing temperature sensor as follows. That is, the amount of heat received from the engine main body to the vicinity of the throttle valve 9 is obtained from the engine main body temperature estimated from the engine cooling water temperature detected by the water temperature sensor 5,
On the other hand, the amount of heat radiated from the vicinity of the throttle valve 9 into the intake air is obtained from the intake air temperature detected by the intake air temperature sensor 17 and the amount of intake air detected by the air flow meter 3, and the throttle amount is determined based on the amount of heat received and the amount of heat radiation. Valve 9
Estimate the ambient temperature.

In step 3, it is determined whether the temperature around the throttle valve 9 estimated in step 2 is lower than a predetermined value. When the temperature around the throttle valve 9 exceeds a predetermined value, the roundness of the inner wall (bore) of the intake passage portion (throttle chamber) in which the throttle valve is mounted decreases due to temperature expansion, and Since it is highly likely that galling will occur if fully closed learning is performed, this routine is terminated without performing the fully closed learning. This function of prohibiting fully closed learning constitutes fully closed learning prohibiting means.

If it is determined in step 3 that the temperature around the throttle valve 9 is equal to or lower than the predetermined value, the routine proceeds to step 4 and thereafter, where the fully closed position of the throttle valve 9 is learned. First,
In step 4, the target opening degree TGTVO of the throttle valve 9 is set.
Is set to a predetermined value TVOFCL. Here, the ignition switch 19 is turned off and the actuator 1 is turned off.
Since the throttle valve 9 is maintained at the default opening as described above at the stage when the power supply to 1 is cut off, the predetermined value TVOFCL as the initial opening is set to the default opening irrespective of the indefinite accelerator opening. The degree of opening is set near the degree.

In step 5, the difference between the actual opening TPS1V of the throttle valve 9 detected by the throttle opening sensor 14 and the opening TPS1AV obtained by averaging the opening detection values TPS1V obtained in time series is calculated. Set value ER
It is determined whether it has converged to RTV or less, and the process proceeds to step 6 at predetermined intervals until the convergence, and the target opening TGTVO is decreased by the predetermined opening DTGTVOCL.

When it is determined that the difference between TPS1V and TPS1AV has converged to the set value ERRTV or less, it is determined that the throttle valve 9 has come into contact with the intake passage wall and is fully closed, and the routine proceeds to step 7. Then, learning for averaging the throttle valve opening detection value TPS1V at that time is performed, and the learning result TPS1RN is stored in a memory (backup ram). As a result, at the time of the next learning, the value learned at this time and the detected value at the time of full closing detected next time are averaged to update the learning result.

FIG. 4 shows a state at the time of the learning of the fully closed state. In the course of the throttle valve 9 being fully closed, the opening degree TPS1 averaged with respect to the actual opening degree TPS1V of the throttle valve 9 is shown.
Since the AV has a delay, a deviation greater than a predetermined value occurs between the two. However, when the throttle valve 9 contacts the intake passage wall and is fully closed, the average opening TPS1AV is reduced to the actual opening TPS.
Since the deviation converges sufficiently close to 1 V, the fully closed state can be detected based on the value of the deviation.

In the present invention, the predetermined opening DTGT
Set VOCL to a sufficiently small value (for example, 0.021
°), whereby the closing speed of the throttle valve 9 is controlled to be small, so that the reaction force when the throttle valve 9 comes into contact with the intake passage wall is suppressed to a small extent, and galling can be suppressed.

Next, control of the drive current of the actuator 11 at the time of learning the fully closed position will be described with reference to the flowchart of FIG. In step 11, it is determined whether or not the fully-closed position learning is being performed. If the learning is being performed, the process proceeds to step 2 and thereafter to execute the drive current control.

In step 12, it is determined whether the drive current of the actuator 11 (DC motor) detected by the current sensor 18 is equal to or more than a predetermined value (for example, 3 A).

When it is determined that the drive current is equal to or more than the predetermined value, the process proceeds to step 13, where the command value ICOM of the drive current is corrected by a predetermined amount. Thus, for example, the pulse width PWM when controlling the drive current by pulse width modulation (PWM) is set by the following equation.

PWM = ICOM / IMAX · 100% where IMAX = VB (battery voltage) / MOTRE
S (motor resistance value) Since the drive current controlled in this way is limited to the predetermined value or less, the force with which the throttle valve 9 is pressed against the intake passage wall at the time of learning the fully closed position is set to a sufficiently small value. When the gear for driving the throttle valve 9 is made of a resin material to reduce the weight, the force applied to the gear can be reduced. And the durability of the gear can be improved.

Next, normal control having an undershoot prevention function when the throttle valve is closed will be described with reference to the flowchart of FIG. In step 21, the throttle valve corresponding to the required output of the engine is searched by a map based on the accelerator opening detected by the accelerator opening sensor 1 and the engine rotation speed detected by the crank angle sensor 2. 9, the target opening degree TGTVO is set.

In step 22, the target opening TGTV
It is determined whether O is equal to or less than a predetermined value. When it is determined that the target opening TGTVO is larger than the predetermined value, the process proceeds to step 24 without correcting the target opening TGTVO.

If it is determined that the target opening TGTVO is equal to or less than the predetermined value, the routine proceeds to step 23, where the target opening TGTVO is determined.
GTVO last time (one cycle before the execution cycle of this routine)
The set target opening degree TGTVO _n-1 is set by changing the change amount DTGTVO limited by the change rate limiter (when the target opening degree TGTVO decreases, a negative value is added and decreased, and when the target opening degree TGTVO increases, the target opening degree TGTVO n decreases. Increase by adding a positive value).

In step 24, the throttle valve 9 is driven so as to have the target opening TGTVO set or corrected as described above. In this manner, as shown in FIG. 7, when performing control to close the throttle valve 9 to an opening close to fully closed by deceleration operation or the like in normal control, the target opening TG
After the TVO becomes equal to or less than the predetermined value, even if the target opening TGTVO set in step 21 decreases sharply due to a decrease in the accelerator opening (shown by a dashed line), the target speed TGTVO is not affected by this and the set speed is not affected. , The throttle valve 9 closes at a sufficiently small predetermined speed.

Therefore, undershoot of the throttle valve 9 can be prevented, and contact with the intake passage wall can be avoided, whereby galling can be prevented. Next, normal control according to another embodiment having an undershoot prevention function when the throttle valve is closed will be described with reference to the flowchart of FIG.

In step 31, based on the accelerator opening detected by the accelerator opening sensor 1 and the engine rotational speed detected by the crank angle sensor 2, a search from a map or the like is performed to match the required output of the engine. The target opening TGTVO of the throttle valve 9 is set.

In step 32, the temperature around the throttle control system (control unit 20, actuator 11) is detected. Normally, since the throttle control system is located near the throttle valve 9, the temperature may be estimated in the same manner as when the temperature around the throttle valve 9 is estimated. Estimate the temperature by obtaining the amount of heat received and radiated according to the installation location of the system, or install a temperature sensor near the throttle control system (or use a temperature sensor installed nearby for another purpose), etc. Detection.

In step 33, the temperature ETCT around the throttle control system is set in a predetermined range (for example, -20 ° C <ETCT <10) in which good throttle control performance can be ensured.
0 ° C.).

Then, at an extremely low temperature or at an extremely high temperature (for example, ETCT ≦ −20 ° C., E
If it is determined that TCT ≧ 100 ° C.), there is a possibility that an undershoot will occur when the throttle valve 9 is driven to close due to a decrease in throttle control performance. Therefore, the routine proceeds to step 34, where the lower limit of the target opening degree TGTVO is set. Set the value to a value larger than usual (for example, 1.5 °).

If it is determined in step 33 that the temperature ETCT around the throttle control system is within the predetermined range, the process proceeds to step 35 to determine whether the battery voltage VB is within the predetermined range in which a good throttle control performance can be ensured. It is determined whether or not it is. Here, the throttle control system is generally matched when the battery voltage VB is the reference voltage, and the correction is made according to the deviation of the battery voltage VB from the reference voltage. The lower the control performance, the lower the control performance.

If it is determined that the temperature ETCT around the throttle control system is out of the predetermined range, there is a possibility that an undershoot may occur when the throttle valve 9 is driven to close due to a decrease in control performance. Because there is
In this case also, the process proceeds to step 34, where the target opening degree TGTVO is set.
Set the lower limit of to a value larger than the normal time.

If it is determined in step 35 that the battery voltage VB is within the predetermined range, good throttle control performance is ensured, and the routine proceeds to step 36, where the lower limit value of the target opening TGTVO is set to the normal value. Value (for example,
0.5 °).

In step 37, the throttle valve 9 is driven so as to attain the target opening TGTVO with the lower limit set as described above. As described above, when there is a possibility that an undershoot may occur when the throttle valve 9 is driven to close due to a decrease in control performance due to the influence of the temperature around the throttle control system and the battery voltage, the lower limit value of the target opening degree TGTVO is set to the normal value. By setting the value to a larger value, the valve closing speed near the end of the valve closing operation is reduced, so that the occurrence of undershoot can be prevented, and the occurrence of galling can be prevented.

The control for increasing the lower limit of the target opening degree TGTVO and the control for decreasing the valve closing speed shown in FIG. 6 may be used together (after step 24 in FIG. 6 and FIG. 8). Steps 32 to 35 are inserted), so that undershoot can be more effectively prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration and functions of the present invention.

FIG. 2 is a diagram showing a system configuration according to an embodiment of the present invention.

FIG. 3 is a flowchart showing a control routine for learning a fully closed position of a throttle valve according to the embodiment;

FIG. 4 is a time chart showing how the throttle opening and its detection value change when learning the fully closed position.

FIG. 5 is a flowchart showing a drive current control routine during learning of the fully closed position according to the first embodiment;

FIG. 6 is a flowchart showing a normal control routine of the throttle valve according to the embodiment;

FIG. 7 is a time chart showing a state of a change in a throttle valve target opening in the valve closing control in the normal state.

FIG. 8 is a flowchart showing a normal control routine of a throttle valve according to another embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Accelerator opening sensor 4 Engine 5 Water temperature sensor 9 Throttle valve 11 Actuator 17 Intake air temperature sensor 18 Current sensor 19 Ignition switch 20 Control unit

Claims (6)

[Claims] 1. A throttle control system for an internal combustion engine, comprising: detecting an opening of a throttle valve interposed in an intake system by a throttle opening sensor and energizing and controlling an actuator to control the throttle valve to a target opening. In the device, the throttle valve is driven to a fully closed position in contact with an inner wall of the intake passage, and a fully closed position learning unit that learns a detection value of a throttle opening sensor at the fully closed position; and a fully closed position learning unit. Valve closing speed regulating means for regulating the valve closing speed when the throttle valve is driven to the fully closed position and when the throttle valve is driven to a position close to the fully closed position in the normal control as compared with other driving times; Drive current regulating means for regulating the drive current when the throttle valve is brought into contact with the inner wall of the intake passage by the closed position learning means to a value sufficiently smaller than the maximum. And a throttle control device for an internal combustion engine. 2. A throttle control system for an internal combustion engine, wherein an opening of a throttle valve interposed in an intake system is detected by a throttle opening sensor and an actuator is energized to control the throttle valve to a target opening. In the device, the throttle valve is driven to a fully closed position abutting on an inner wall of the intake passage, and a fully closed position learning means for learning a detection value of a throttle opening sensor at the fully closed position; and detecting a temperature around the throttle valve. And a fully closed position learning prohibiting unit for prohibiting the fully closed position learning by the fully closed position learning unit when the temperature around the throttle valve is equal to or higher than a predetermined value. A throttle control device for an internal combustion engine. 3. The throttle valve peripheral temperature detecting means detects the temperature around the throttle valve based on parameters including engine coolant temperature, intake air temperature, and intake air amount. A throttle control device for an internal combustion engine according to claim 1. 4. A throttle control of an internal combustion engine, wherein an opening of a throttle valve interposed in an intake system is detected by a throttle opening sensor and an actuator is energized to control the throttle valve to a target opening. In the apparatus, undershoot occurrence condition detecting means for detecting a condition under which the throttle valve closing operation is likely to undershoot, and conditions under which the throttle valve closing operation easily undershoots are detected by the undershoot occurrence condition detecting means. And a lower limit value correcting means for increasing and correcting the lower limit value of the throttle valve target opening when the throttle control is performed. 5. The undershoot occurrence condition detecting means includes a throttle control system peripheral temperature detecting means for detecting a temperature around the throttle control system, and when the temperature around the throttle control system is higher or lower than a predetermined temperature range. 5. The throttle control device for an internal combustion engine according to claim 4, wherein the condition is detected as a condition under which the vehicle easily undershoots. 6. The undershoot occurrence condition detecting means includes a battery voltage detecting means for detecting a battery voltage, and detects undershoot occurrence condition when the battery voltage is out of a predetermined voltage range. The throttle control device for an internal combustion engine according to claim 4, wherein: