Control device for electronic control throttle

Abstract

The present invention addresses the problem of providing a control device which is for an internal combustion engine and which reduces power consumption of an electronic control throttle device. A control device (4) for an internal combustion engine according to the present invention is for controlling a throttle opening of a throttle valve (31) against a spring reaction force of a return spring (36) by driving a drive motor (33), and is characterized in that, when the throttle valve (31) is held at a prescribed throttle opening and remains stationary, power saving control is performed for reducing the motor drive DUTY of the drive motor (33) by an amount corresponding to the friction torque which is the static friction of the throttle valve (31).

Description

Electronic throttle control device

[0001] The present invention relates to a control device for an electronically controlled throttle that drives an actuator to control a throttle valve.

[0002] Patent Document 1 proposes a technology for an electronically controlled throttle in which a throttle valve is controlled by a motor.

[0003] Japanese Patent Application Laid-Open No. 2001-90561

[0004] In conventional electronically controlled throttle control methods, the throttle valve opening is adjusted against the spring reaction force of the return spring, so power must be continuously supplied to the motor to generate a motor torque corresponding to the spring reaction force, making it difficult to reduce power consumption.The present invention has been made in view of the above points, and its object is to provide a control device for an electronically controlled throttle that reduces power consumption.

[0005] The throttle valve control device of the present invention, which solves the above problem, is a control device for an electronically controlled throttle that drives a motor to control the throttle opening of a throttle valve against the spring reaction force of a return spring, and is characterized in that when the target throttle opening of the throttle valve is fixed and the deviation between the target throttle opening and the actual throttle opening of the throttle valve is maintained at or below a predetermined value for a certain period of time, power-saving control is performed to reduce the motor drive amount of the motor by the amount of friction torque, which is the static friction of the throttle valve.

[0006] According to the present invention, it is possible to reduce the power consumption of an electronically controlled throttle by utilizing the friction torque of the throttle valve. Further features related to the present invention will become apparent from the description of the present specification and the accompanying drawings. Furthermore, problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments.

[0007] 1 is a system diagram of an electronic fuel injection type internal combustion engine control system using a control device for an electronically controlled throttle according to an embodiment of the present disclosure. FIG. 2 is a diagram illustrating the configuration of an electronically controlled throttle according to a first embodiment. FIG. 3 is a block diagram illustrating the internal functions of the control device. FIG. 4 is a functional block diagram illustrating the feedback control function of a control calculation unit. FIG. 5 is a flowchart illustrating the content of control processing by an F / B control stop determination unit. FIG. 6 is a flowchart illustrating the content of power saving control processing by a stop-time DUTY calculation unit. FIG. 7 is a diagram illustrating the relationship between spring reaction force and motor torque with and without feedback control. FIG. 8 is a diagram illustrating the relationship between motor torque immediately after the throttle valve reaches the target throttle opening and motor torque in a situation where the throttle valve is stationary at the target throttle opening for a certain period of time. FIG. 9 is a time chart illustrating an example of EBT control operation by the control device of this embodiment.

[0008] Hereinafter, an embodiment of a control device for an electronically controlled throttle according to the present disclosure will be described with reference to the drawings.

[0009] 1 is a system diagram of an electronic fuel injection type internal combustion engine control system using an electronically controlled throttle control device according to an embodiment of the present disclosure. The internal combustion engine control system according to this embodiment is a control system for a prime mover mounted on, for example, an automobile equipped with only an internal combustion engine or a hybrid automobile equipped with both an internal combustion engine and a traction motor.

[0010] In the internal combustion engine control system 1, intake air 2 is drawn in through an air cleaner 21 based on the operation of an internal combustion engine 10 having an engine cylinder 11 and an engine piston 12. The intake air 2 is guided to the combustion chamber of the engine cylinder 11 via an intake body which is a main passage 22, an electronic throttle body (hereinafter referred to as ETB) 30, and an intake manifold 24.

[0011] A fuel injection valve 14 is provided in an intake port of the internal combustion engine 10. Fuel injected into the intake port is mixed with intake air, and the mixture of fuel and intake air is guided to a combustion chamber via an intake valve 15 and combusted to generate mechanical energy. The mixture guided to the combustion chamber is a mixture of fuel and air, and is combusted explosively by spark ignition from an ignition plug 13 to generate mechanical energy. The combusted gas is guided to an exhaust pipe via an exhaust valve 16 and is discharged from the exhaust pipe as exhaust gas 3 to the outside of the vehicle.

[0012] The flow rate of intake air 2 introduced into the combustion chamber is controlled by ETB 30. ETB 30 uses a control device 4 to determine the optimum flow rate of intake air 2 based on the position of the accelerator pedal and the operating state of the internal combustion engine 10, and controls the throttle valve 31 to an optimum throttle opening using a drive motor 33, which is an actuator. The control of the throttle opening by the control device 4 is to match the throttle opening (actual throttle opening) of the throttle valve 31 with a target throttle opening, and feedback control based on the deviation between the two is used.

[0013] Furthermore, the amount of fuel supplied is controlled based on the flow rate of intake air introduced into the combustion chamber. In the internal combustion engine control system 1, the throttle opening of the throttle valve 31 of the ETB 30 is controlled to control the flow rate of intake air introduced into the combustion chamber, thereby controlling the mechanical energy generated by the internal combustion engine 10.

[0014] The output of an opening sensor 32 that measures the opening of the throttle valve 31 is input to the control device 4, and the output of a rotation angle sensor 17 is input to the control device 4 to measure the positions and states of the engine piston 12, intake valve 15, and exhaust valve 16 of the internal combustion engine 10, as well as the rotation speed of the internal combustion engine 10. The output of an oxygen sensor 28 is input to the control device 4 to measure the mixture ratio of the fuel and air amounts from the state of the exhaust gas 3.

[0015] The control device (ECU) 4 is composed of a microcomputer having a central processing unit (CPU), memory, storage device, communication interface, etc. The control device 4 calculates the fuel injection amount and ignition timing based on the physical quantity of intake air output from the physical quantity measuring device 20 and the rotational speed of the internal combustion engine 10 measured based on the output of the rotational angle sensor 17. Based on these calculation results, the amount of fuel supplied from the fuel injection valve 14 and the ignition timing of ignition by the spark plug 13 are controlled. In reality, the fuel supply amount and ignition timing are also finely controlled based on the temperature measured by the physical quantity measuring device 20, changes in the throttle opening, changes in the engine rotational speed, and the air-fuel ratio measured by the oxygen sensor 28. The control device 4 further controls the amount of air bypassing the throttle valve 31 using an idle air control valve 27 when the internal combustion engine 10 is idling, thereby controlling the rotational speed of the internal combustion engine 10 when idling.

[0016] 2 is a diagram illustrating the configuration of the ETB according to this embodiment. The ETB 30 includes a main body 37 having a passage through which the intake air 2 passes, a butterfly-type throttle valve 31 rotatably mounted within the passage of the main body 37, a return spring 36 attached to a valve stem of the throttle valve 31, a reduction gear 35 connected to the valve stem of the throttle valve 31, and a drive motor (DC motor) 33 for rotating the reduction gear 35. The throttle valve 31 is driven by the drive motor 33 via the reduction gear 35. The throttle valve 31 is also provided with an opening sensor 32 that detects the throttle opening of the throttle valve 31 and a drive circuit 34 that drives the drive motor 33. The return spring 36 biases the throttle valve 31 to rotate around the valve stem, and is configured to return the throttle valve 31 to a constant opening (standby position) by its biasing force when the drive motor 33 is not generating torque. In order to rotate the throttle valve 31 against the spring reaction force of the return spring 36, the drive motor 33 needs to generate a motor torque that is balanced against the spring reaction force.

[0017] The control device 4 performs A / D conversion on signals from, for example, an accelerator pedal position sensor 5 and a throttle valve 31 opening sensor 32 to determine a target throttle opening (target throttle opening) of the throttle valve 31 according to the engine operating conditions. Then, based on the deviation between the target throttle opening and the measured actual throttle opening (actual throttle opening) of the throttle valve 31, it performs feedback control such as PID control to minimize the deviation and calculates a drive signal to be provided to the drive circuit 34. This drive signal is a PWM-controlled motor drive duty (PWM duty ratio) and is transmitted from the control device 4 to the drive circuit 34. The drive circuit 34 amplifies this PWM-controlled motor drive duty and supplies it as power to the drive motor 33, thereby driving the drive motor 33. The drive motor 33 rotates a reduction gear 35 to position the throttle valve 31 at an optimal throttle opening.

[0018] 3 is a block diagram illustrating the internal functions of the control device 4. As shown in FIG. 3, the control device 4 has, as its internal functions, a target throttle opening calculation unit 41, a throttle opening detection unit 42, a throttle opening deviation calculation unit 43, a control calculation unit 44, and a throttle valve drive unit 45. Each of these functions is realized by the CPU loading a program stored in a storage device of the control device 4 into memory and executing it.

[0019] A target throttle opening calculation unit 41 calculates a target throttle opening based on a signal from the accelerator pedal position sensor 5 and the operating state of the internal combustion engine 10. A throttle opening detection unit 42 detects the actual throttle opening of the throttle valve 31 based on a signal from the opening sensor 32. A throttle opening deviation calculation unit 43 calculates the deviation between the target throttle opening and the actual throttle opening. A control calculation unit 44 calculates a motor drive duty, which is a drive signal for driving a throttle valve drive unit 45, based on the deviation calculated by the throttle opening deviation calculation unit 43. A dithering signal is added to this motor drive duty to reduce friction by changing the frictional force exerted when moving the throttle valve into a kinetic friction state. Furthermore, when the change in the target throttle opening is small, the control calculation unit 44 learns the motor drive duty when the throttle valve 31 is maintained at the target throttle opening as a calculated value of the motor drive duty corresponding to the spring reaction force required to maintain the opening. The throttle valve driving section 45 outputs a motor driving duty to the driving circuit 34 .

[0020] 4 is a functional block diagram illustrating the feedback control function of the control calculation unit 44. When the calculation result of the target throttle opening calculation unit 41 is in a stationary state, the difference with the throttle valve 31 opening is equal to or less than a predetermined value, and the throttle valve 31 opening is maintained at the predetermined throttle opening and in a stationary state, the control calculation unit 44 stops dithering to change from a dynamic friction state to a static friction state, thereby performing power saving control by reducing the motor drive duty of the drive motor 33 by the amount of friction torque, which is the static friction of the ETB 30.

[0021] 4, the control calculation unit 44 has, as internal functions, a feedback control amount calculation unit 51, a stop duty calculation unit 52, a switching unit 53, a feedback control stop determination unit 54, a friction torque calculation unit 55, and a duty average value calculation unit 56. Each of these functions is also realized by the CPU loading a program stored in the storage device of the control device 4 into memory and executing it.

[0022] The F / B control amount calculation unit 51 calculates a feedback control amount that matches the actual throttle opening to the target throttle opening. The F / B control amount calculation unit 51 calculates a motor drive duty, which is the feedback control amount, based on information on the target throttle opening and information on the actual throttle opening. During feedback control, the F / B control amount calculation unit 51 also performs so-called dithering, which slightly changes the target throttle opening within a predetermined range. In dithering, control is performed to change the motor drive duty so that the actual throttle opening of the throttle valve 31 moves up and down based on the target throttle opening.

[0023] The F / B control amount calculation unit 51 calculates an initial duty value of the motor drive duty when feedback control is resumed after feedback control is stopped by the F / B control stop determination unit 54. When the F / B control stop determination unit 54 determines that feedback control is to be resumed from a stopped state, the F / B control amount calculation unit 51 sets the average value of the motor drive duty before the feedback control was stopped as the initial duty value when feedback is resumed.

[0024] The friction torque calculation unit 55 calculates a motor drive duty corresponding to the friction torque of the ETB 30. The friction torque calculation unit 55 determines, as friction torque, static friction generated in the ETB 30 by holding the throttle valve 31 at a fixed opening for a certain period of time or longer after stopping dithering. The friction torque may be a fixed value, or may be increased in accordance with the length of time during which a state in which the deviation between the target throttle opening and the actual throttle opening is held at or below a predetermined value is held. The friction torque calculation unit 55 calculates, as friction torque, the motor drive duty required to start moving from a throttle-stopped state.

[0025] The friction torque calculation unit 55 calculates the motor drive duty for the friction torque by, for example, acquiring a learned value from a friction torque learning unit that learns the friction torque. The friction torque learning unit learns the motor drive duty required when the throttle valve 31 starts moving from a stationary state without dithering. The friction torque calculation unit 55 can also calculate the friction torque based on the usage time of the ETB 30. For example, the friction torque calculation unit 55 can increase the friction torque according to the usage time of the ETB 30, or can increase the friction torque in stages each time the usage time of the ETB 30 becomes longer than a preset reference time.

[0026] The duty average value calculation unit 56 calculates a duty average value, which is the average value of the motor drive duty.

[0027] The stop duty calculation unit 52 calculates a motor drive duty that generates a minimum motor torque that can keep the throttle valve 31 stationary, taking into account the nature of static friction that increases with the passage of time after the throttle valve 31 is held at the target throttle opening and dithering is stopped, and sets this as the motor drive duty when feedback control is stopped. The stop duty calculation unit 52 calculates the motor drive duty when feedback control is stopped by subtracting the motor drive duty corresponding to the friction torque calculated by the friction torque calculation unit 55 from the average duty value (average value of motor drive duty) before feedback control is stopped calculated by the duty average value calculation unit 56. The motor drive duty when feedback control is stopped is the control drive amount that generates the minimum motor torque that can keep the throttle valve 31 stationary by utilizing static friction.

[0028] Furthermore, the stop duty calculation unit 52 calculates an opening maintenance margin that offsets torque fluctuations in the main direction of the valve stem of the throttle valve 31 to actively suppress vibration, and adds this to the motor drive duty when feedback control is stopped as a fluctuation component of the spring reaction force. The opening maintenance margin is a force that compensates for intake pulsation and VBATT (battery) voltage fluctuations and maintains the stationary state (static friction) of the throttle valve. The opening maintenance margin is calculated based on changes in the reaction force and friction of the throttle valve 31 due to changes in the temperature characteristics of the drive motor 33, negative pressure in the intake pipe, etc., and is calculated, for example, by referring to a preset calculation table.

[0029] The F / B control stop determination unit 54 determines whether to stop feedback control based on feedback control stop conditions. When the target throttle opening is fixed, the actual throttle opening reaches near the target throttle opening, and the deviation between the actual throttle opening and the target throttle opening is maintained at or below a predetermined value for a predetermined time, the F / B control stop determination unit 54 determines that the throttle valve 31 is stationary and that the feedback control stop conditions are met, and determines to stop feedback control of the throttle valve 31 and stop dithering. The F / B control stop determination unit 54 also functions as a power saving determination unit that determines whether to perform power saving control of the ETB 30.

[0030] Furthermore, the F / B control stop determination unit 54 may set the feedback control stop condition to, for example, when the required output from a higher-level system controller (not shown) becomes stable (when the required output amount becomes constant). In this case, the friction torque calculation unit 55 calculates the friction torque based on the time during which the stable state continues.

[0031] The switching unit 53 selects either the motor drive duty with feedback control calculated by the F / B control amount calculation unit 51 or the motor drive duty when feedback control is stopped (without feedback control) calculated by the stop-time duty calculation unit 52, depending on the determination result of the F / B control stop determination unit 54, and outputs this to the ETB 30. If it is determined that feedback control is to be stopped, the switching unit 53 outputs the motor drive duty calculated by the stop-time duty calculation unit 52 to the drive circuit 34 of the ETB 30. If it is determined that feedback control is not to be stopped, the switching unit 53 outputs the motor drive duty and dithering control value calculated by the F / B control amount calculation unit 51 to the drive circuit 34 of the ETB 30.

[0032] 5 is a flowchart illustrating the control process performed by the F / B control stop determination unit 54. The F / B control stop determination unit 54 determines whether the target throttle opening is maintained at a steady state (S101). If the target throttle opening is maintained at a steady state (Yes in S101), the unit determines whether the difference between the target throttle opening and the actual throttle opening is within a predetermined range and the actual throttle opening has been maintained at a constant opening for a certain period of time (S102). If the difference between the target throttle opening and the actual throttle opening is within a predetermined range and the actual throttle opening has been maintained at a constant opening for a certain period of time (Yes in S102), the unit determines to stop feedback control (S103). On the other hand, if the target throttle opening is not maintained at a steady state (No in S101) or if the difference between the target throttle opening and the actual throttle opening is within a predetermined range and the actual throttle opening has not been maintained at a constant opening for a certain period of time (No in S102), the unit determines to continue feedback control (S104).

[0033] 6 is a flowchart illustrating the power-saving control process performed by the stop duty calculation unit 52. The stop duty calculation unit 52 calculates the spring reaction force of the return spring 36 based on the actual throttle opening detected by the opening sensor 32 (S111). Then, it calculates the friction torque, which is static friction that holds the throttle valve 31 stationary at that opening (S112). It also calculates an opening maintenance margin (S113).

[0034] The stop duty calculation unit 52 uses the calculated spring reaction force, friction torque, and opening degree maintenance margin to calculate a minimum drive force, which is the minimum motor torque of the drive motor 33 that can maintain the throttle valve 31 in a stationary state (S114). The minimum drive force can be calculated using the following equation (1): Minimum drive force = spring reaction force - friction torque + opening degree maintenance margin (1) Then, the stop duty calculation unit 52 calculates a motor drive duty for causing the drive motor 33 to output the minimum drive force (S115). Note that dithering is not performed at this time.

[0035] FIG. 7 is a diagram showing the relationship between spring reaction force and motor torque with and without feedback control.

[0036] For example, when feedback control is in effect and the actual throttle opening of the throttle valve 31 is maintained at a constant opening, the motor drive duty when feedback control is in effect, calculated by the F / B control amount calculation unit 51, is output to the drive circuit 34 of the ETB 30. The motor drive duty when feedback control is in effect is a value that allows the throttle valve 31 to move against the spring reaction force of the return spring 36. Therefore, as shown in Figure 7 (1), a motor torque equal to the spring reaction force of the return spring 36 is output from the drive motor 33 (motor torque = spring reaction force).

[0037] On the other hand, when there is no feedback control, the target throttle opening is fixed and the actual throttle opening of the throttle valve 31 is held at a constant opening for a certain period of time, so the motor drive duty when there is no feedback calculated by the stop duty calculation unit 52 is output to the drive circuit 34 of the ETB 30. The motor drive duty when there is no feedback control is a value that generates the minimum drive force that can maintain the stationary state of the throttle valve 31 by utilizing static friction, and is calculated by subtracting the motor drive duty corresponding to the friction torque from the motor drive duty before feedback control was stopped.

[0038] Therefore, as shown in Figure 7 (2), the drive motor 33 outputs a motor torque that is lower by the amount of friction torque than the motor torque when dithering control and feedback control are enabled. In other words, the power supplied to the drive motor 33 can be reduced by the amount of friction torque, and power consumption when the throttle valve 31 is stationary can be reduced. At the same time, radio noise radiated from the electronically controlled throttle and wiring can also be reduced.

[0039] FIG. 8 is a diagram showing the relationship between the motor torque immediately after the throttle valve reaches the target throttle opening and the motor torque when the throttle valve remains stationary at the target throttle opening for a certain period of time.

[0040] While the throttle opening is fluctuating, dynamic friction acts on the ETB 30, so the motor torque for moving the throttle valve 31 to the target throttle opening is the spring reaction force minus the dynamic friction. This dynamic friction also acts on the ETB 30 immediately after the throttle valve 31 reaches the target throttle opening. Therefore, in this state, a motor drive duty is supplied to the drive motor 33 that outputs a motor torque equal to the spring reaction force minus the dynamic friction.

[0041] On the other hand, when the throttle valve 31 is held at a fixed opening for a certain period of time or longer in a stationary state, static friction acts on the ETB 30. Therefore, the motor torque required to maintain the throttle valve 31 at the target throttle opening is the spring reaction force minus the static friction. Because static friction is greater than dynamic friction (static friction < dynamic friction), even if the motor torque is lowered compared to when dynamic friction is present, the force resisting the spring reaction force is equal to the motor torque when feedback control is present, allowing the ETB 30 to maintain the throttle valve 31 at the desired throttle opening and maintain the stationary state. In other words, even if the motor torque is reduced by the amount of static friction, the throttle valve 31 does not fluctuate. Therefore, the motor drive duty can be reduced compared to when dynamic friction is present, enabling power savings by reducing the power supply. This also reduces radio noise emitted from the electronically controlled throttle and wiring.

[0042] Furthermore, the throttle valve 31 is affected by fluctuations caused by the spring reaction force and the force of fluctuations in intake pulsation and battery voltage. By compensating for these fluctuations and taking them into account as an "opening compensation margin" for maintaining the throttle stationary state (static friction) when calculating the motor drive duty, a more accurate motor drive duty can be determined. The power supplied to the drive motor 33 is calculated using the following equation (2): Power supply (PWM duty ratio) = Spring reaction force - Static friction force + Opening maintenance margin ... (2)

[0043] FIG. 9 is a time chart illustrating an example of the control operation of the EBT by the control device of this embodiment.

[0044] For example, from time t0 to time t2, the deviation between the target throttle opening and the actual throttle opening is large, and the control calculation unit 44 executes feedback control to bring the actual throttle opening closer to the target throttle opening.

[0045] At time t1, it is determined that the target throttle opening has been fixed (point a), and at time t2, it is determined that the actual throttle opening has reached the target throttle opening (point b), at which point the switching unit 53 switches from feedback control to no feedback control. At time t2, the stop duty calculation unit 52 performs calculation processing to reduce the dithering control amount of the motor drive duty near the target throttle opening (point d).

[0046] When it is determined at time t3 that the throttle valve 31 is stationary (point c), the system switches to power saving mode, the motor drive duty of the throttle valve is calculated taking into account the friction torque due to static friction, and minimum output control is initiated to output the minimum drive force from the drive motor 33 that keeps the throttle opening of the throttle valve 31 stationary (point e).

[0047] The motor drive duty is reduced by the amount of friction torque between time t4 and time t5, thereby reducing power consumption accordingly. At time t5, when the deviation between the actual throttle opening and the target throttle opening exceeds a predetermined value (point g), it is determined that the feedback control stop condition is not met, and the feedback control is switched on.

[0048] Here, a motor torque equal to the spring reaction force is calculated to make the actual throttle opening of the throttle valve 31 coincide with the target throttle opening, and a motor drive duty for outputting this motor torque is output (point i). Then, feedback control accompanied by dithering control is resumed (point j).

[0049] According to the control device 4 of the ETB 30 of this embodiment, when the target throttle opening is fixed and the actual throttle opening is maintained at a constant opening for a certain period of time, the control device 4 switches between with and without feedback control of the throttle valve 31. Without feedback control, a motor drive duty is calculated to generate the minimum motor torque that can keep the throttle valve 31 stationary using static friction, and this motor drive duty is supplied to the drive motor 33.

[0050] The motor drive duty that generates this minimum motor torque is calculated by subtracting the motor drive duty for the friction torque from the motor drive duty before feedback control was stopped.

[0051] As a result, the drive motor 33 outputs motor torque that is lower by the amount of friction torque than the motor torque when feedback control is enabled. Therefore, when feedback control is disabled, the power supplied to the drive motor 33 can be reduced by the amount of friction torque, thereby reducing the power consumption of the drive motor 33 accordingly. In other words, power saving control can be performed by utilizing the friction torque of the throttle valve 31 to reduce the power consumption of the electronically controlled throttle.

[0052] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various design modifications can be made without departing from the spirit of the present invention as defined in the claims. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0053] 1... internal combustion engine control system, 4... control device (ECU), 30... electronically controlled throttle (ETB), 31... throttle valve, 33... drive motor (DC motor), 36... return spring, 51... F / B control amount calculation unit (feedback control amount calculation unit), 52... stop-time DUTY calculation unit, 53... switching unit, 54... F / B control stop determination unit, 55... friction torque calculation unit, 56... DUTY average value calculation unit 56

Claims

1. A control device for an electronically controlled throttle which drives a motor to control the throttle opening of a throttle valve against the spring reaction force of a return spring, characterized in that when the throttle valve is held at a specified throttle opening and in a stationary state, power saving control is performed to reduce the motor drive duty of the motor by an amount equivalent to the friction torque, which is the static friction of the throttle valve.

2. A control device for an electronically controlled throttle as described in claim 1, characterized in having a feedback control stop judgment unit which judges that the throttle valve is in the stationary state when a target throttle opening of the throttle valve is fixed and a deviation between the target throttle opening and the actual throttle opening of the throttle valve is maintained at or below a predetermined value for a predetermined time, and judges to stop feedback control for matching the actual throttle opening to the target throttle opening, and a stop time DUTY calculation unit which, when it is judged by the feedback control stop judgment unit to stop the feedback control, calculates a motor drive DUTY at the time of feedback control being stopped by subtracting a motor drive DUTY equivalent to the friction torque from an average value of the motor drive DUTY before the feedback control was stopped.

3. A control device for an electronically controlled throttle as described in claim 2, further comprising a feedback control amount calculation unit which calculates a feedback control amount for matching the actual throttle opening with the target throttle opening, wherein when the feedback control stop determination unit determines that the feedback control should be resumed from a stopped state, the feedback control amount calculation unit sets the average value of the motor drive DUTY before the feedback control was stopped as the initial DUTY value when feedback is resumed.

4. A control device for an electronically controlled throttle as described in claim 3, characterized in that the feedback control amount calculation unit changes the motor drive duty so that the actual throttle opening of the throttle valve moves up and down based on the target throttle opening.

5. The control device for an electronically controlled throttle as described in claim 4, characterized in that the stop-time DUTY calculation unit calculates an opening maintenance margin that offsets rotational torque fluctuations in the main direction of the valve shaft of the throttle valve and actively suppresses vibrations, and adds this to the motor drive DUTY when feedback control is stopped as a fluctuation component of the spring reaction force.

6. The control device for an electronically controlled throttle as described in claim 5, characterized in that the stop time duty calculation unit calculates a motor drive duty that generates a minimum motor torque that can hold the throttle valve in a stationary state, taking into account the nature of static friction that increases with the passage of time since the throttle valve is held at the target throttle opening, and sets this as the motor drive duty when the feedback control is stopped.

7. A control device for an electronically controlled throttle as described in claim 1, characterized in that when the output demand from the host system controller becomes constant, it is determined that the throttle valve is maintained at a predetermined throttle opening and is in a stationary state.

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