JP2591046B2 - Variable flow rate characteristic idle speed control valve - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle speed control valve for an internal combustion engine, and more particularly to an idle speed control valve whose flow rate characteristics can be switched.

[Prior Art] Conventionally, in an internal combustion engine for an automobile, a device for precisely controlling the engine speed during idling, realizing stable idling and improving fuel efficiency, so-called idle speed control (hereinafter also referred to as ISC). .) Has been implemented.

In such idle speed control, an intake air flow path bypassing a throttle valve of an internal combustion engine is provided, and an idle speed control valve (hereinafter, also referred to as ISCV) for changing an opening area in the intake air passage. The feedback control of this control valve according to the difference between the target rotation speed and the actual rotation speed adjusts the intake air flow rate to control the rotation speed of the internal combustion engine.

However, even with the same idling, stable rotation is not achieved with the same change in the ISCV opening for the same amount of feedback due to friction and the like when the engine is cold and when the engine is cold. At the time of starting, reliable starting cannot be performed unless the full opening of the ISCV is sufficiently ensured.

Therefore, the design of the ISCV takes into account both the cold state and the warm state. That is, the full opening of the ISCV is determined from the startability and the idling speed at the extremely low temperature,
Generally, the air flow rate characteristic with respect to the opening degree (ISCV driving amount) is determined from the idle stability at the time of warming and the like.

Therefore, the relationship between the opening degree and the air flow rate in the conventional ISCV is as shown in FIG. That is, in the region where the air flow rate is low, the gradient is reduced in order to realize stable air flow characteristics at the time of warm air. The gradient was increased to achieve the flow characteristics. Therefore, an irregular pattern was formed in which a bending point was formed on the way.

[Problems to be Solved by the Invention] However, in such an ISCV, when the air conditioner is turned on during a warm period, the rotation speed must be increased in response to an external load. Becomes large, and control is performed in a region where the gradient is large. In such a case, there arises a problem of deterioration of fuel economy as well as deterioration of control such as rotation blowing and hunting.

To prevent this, there is a control in which the open-loop control is specially performed in the cold state, and the opening degree of the ISCV is gradually reduced from the start of the engine on the premise of an increase in the temperature of the engine. 124047).

However, since this system does not feed back the rotation speed when it is cold, it cannot be said that a truly optimum rotation speed has been realized, and again the stability of the engine rotation is impaired and the fuel efficiency may deteriorate. Was.

The present invention has been made for the purpose of solving the above problems, and reliably realizes both of these characteristics depending on whether the vehicle is cold or warm regardless of the opening degree of the ISCV. is there.

Configuration of the Invention [Means for Solving the Problems] The present invention made to solve the above-mentioned problem is, as exemplified in FIG. 1, a suction passage M2 bypassing a throttle valve M1 of an internal combustion engine.
An idle speed control valve that adjusts an intake air amount by changing an opening area and feedback-controls a rotation speed so as to eliminate a difference between a target rotation speed and an actual rotation speed of the internal combustion engine; A valve element M4 having a characteristic for cold and a valve element M5 having a characteristic for a sense of warmness at separate positions on the valve element drive shaft M3;
Switching means M6 for switching the two valve bodies by moving the valve body drive shaft in accordance with the warm-up state of the internal combustion engine, and the valve body drive shaft during the feedback control of the rotational speed. An actuator that changes the opening area of the suction passage by moving the valve, the maximum intake air amount when the valve body drive shaft driven by the actuator moves to a position at the time of full opening, the characteristic for cold is determined. The valve element has a larger valve element than the valve element having the warm characteristic, and the cold characteristic has a larger change in the amount of intake air with respect to the movement of the valve element drive shaft than the warm characteristic. The switching means inhibits feedback control of the rotation speed when performing switching from the valve element having the cold characteristic to the valve element having the warm characteristic, and performs switching. Cold before Forcibly driving the actuator to move the valve element drive shaft to a position where the intake air flow rate by the characteristic valve element and the intake air flow rate by the warm characteristic valve element after switching are equal. The flow characteristic variable idle rotation speed control valve is characterized in that:

[Operation] Since the valve body drive shaft M3 of the idle speed control valve is provided with two valve bodies M4 having a characteristic for a cold state and a valve element M5 having a characteristic for a warm state, the switching means M6 Simply switches between the two valves M4 and M5 according to the warm-up state of the internal combustion engine, the air flow change pattern switches almost instantaneously, and the air flow characteristics according to each requirement are realized over the full opening range Is done.

Further, when performing switching from the valve element having the cold characteristic to the valve element having the warm characteristic, the switching means M6 inhibits the feedback control of the idle rotation speed, and performs the cold control before the switching in advance. The actuator is driven to move the valve element drive shaft to a position where the intake air flow rate by the valve element having the characteristic for use and the intake air flow rate by the valve element for the warm characteristic after switching are equal to each other, and then the idle rotation is performed. The speed feedback control will be restarted. Therefore, when the switching is performed after the warm-up is completed, it is possible to prevent a problem that the air flow rate suddenly decreases and the engine stalls.

If the feedback control of the rotation speed is continued at the time of switching the valve element characteristics, the actuator is driven in response to the change in the rotation speed. However, in the present invention, the opening of the actuator cannot be controlled by the feedback control of the actuator. By performing the open loop control at the time of switching in anticipation of the degree change, control accuracy in a system in which a control valve that feedback-controls the idling rotational speed has two opening characteristics can be further improved.

[Embodiment] Next, a preferred embodiment of the present invention will be described in detail with reference to the drawings. The present invention is not limited to these, and includes various embodiments in a range not departing from the gist thereof.

FIG. 2 is a schematic system diagram of a system configuration of the internal combustion engine 3 using the ISCV1 according to the first embodiment of the present invention.

The internal combustion engine 3 includes an intake pipe 5 for introducing intake air from an air cleaner (not shown), and a combustion chamber (not shown).
The intake air is introduced into. The intake pipe 5 is provided with a throttle valve 7 for adjusting an intake air flow rate in conjunction with an accelerator pedal, a surge tank 9 for absorbing pulsation of the intake air, a fuel injection valve 11, and the like.

The ISCV 1 is attached to the surge tank 9 and adjusts the flow rate of the intake air supplied from the intake air flow path 13 bypassing the throttle valve 7. The ISCV 1 includes a flow rate adjustment drive unit 17 that precisely adjusts the valve unit 15 based on a required intake air amount, and a valve body switching drive unit 19 that instantaneously switches the type of the valve body of the valve unit 15 as necessary. It is composed of

Electronic control circuit for idle speed control (EC
U) 21 is configured as a logical operation circuit centered on the CPU 21a, ROM 21b, RAM 21c, and backup RAM 21d, and receives signals from various external sensors via an input port 21f via a common bus 21e. The CPU 21a executes predetermined arithmetic processing based on this signal, forms an output signal according to the engine state, sends it to the drive circuit 22 from the output port 21g, and controls the ISCV1. The ROM 21b stores a relationship map between the valve opening and the flow rate corresponding to the characteristics A and B shown in FIG.

The various sensors include a vehicle speed sensor 23 for detecting a rotation speed of a wheel (not shown), an engine cooling water temperature sensor 25 for detecting a cooling water temperature of the internal combustion engine 3, and an engine provided in the distributor 26 for detecting the rotation speed of the internal combustion engine 3. A rotational speed sensor 27; an idle switch 29 for detecting a fully closed state of the throttle valve 7;

A generally known drive device is used for the flow rate adjustment drive unit 17 of the ISCV1, and for example, a mechanism that allows the valve body to move forward and backward by a stepping motor, an electromagnetic solenoid, and the like, and allows the valve opening to be precisely controlled. Used.

On the other hand, the valve body switching drive unit 19 of the ISCV1 is shown in FIG.
The configuration is as shown in FIG. That is, a rectangular parallelepiped casing 33 has a fitting hole 33a provided on one end surface of the base valve body drive shaft 31 which extends from the flow rate adjustment drive section 17 and whose stroke amount is controlled by the flow rate adjustment drive section 17.
Are fitted and integrated. A cylindrical sleeve 35 is provided in the casing 33 from the back side of the bottom surface of the fitting hole 33a.
The center of 3 is protruded inward. Sleeve 3
5, one end 37a of a valve body drive shaft 37 is slidably fitted in a liquid-tight manner. The other end portion 37b of the valve body drive shaft 37 forms a valve body fitting portion, in which a valve body member 39 having two types of valve bodies 39a and 39b is fitted and fixed by screwing a nut 41. Have been. The first valve body 39a has a suitable shape when used in a warm state, and the second valve body 39b has a suitable shape when used in a cold state.

The characteristics resulting from the positional relationship between the valve bodies 39a and 39b and the valve seat 43 are as shown in FIG. That is, the first valve body 39
a is like the characteristic A, and the change in the air flow rate is relatively small with respect to the change in the valve opening, that is, the change in the stroke of the base valve body drive shaft 31. The second valve element 39b has a characteristic B as shown in the figure, and the change in air flow is relatively large with respect to the change in the valve opening.

A partition wall 45 is provided at the center of the valve body drive shaft 37 in a direction perpendicular to the center axis of the valve body drive shaft 37, and its peripheral edge 45a abuts on the inner peripheral surface 33b of the casing 33. The chamber 47 is separated from the spring storage chamber 49 in a watertight manner. A stopper 51 protrudes below the partition wall 45.

Between the inner bottom 35a of the sleeve 35 and the end 37a of the valve body drive shaft 37, a coiled elastic member 53 made of a shape memory alloy is provided. Since the entire sleeve 35 belongs to the cooling water chamber 47, the elastic member 53 is immersed in the cooling water. Joint portions 55 and 57 are slidably contacted with the cooling water chamber 47 in a watertight and slidable manner. A part of the cooling water sent from a water pump of an engine cooling device (not shown) is supplied from the joint portion 55. Joint part
Cooling water that reaches 55 is introduced into an inlet 59
From the cooling water chamber 47, and further flows into the inside of the sleeve 35 in which the elastic member 53 is housed from the introduction port 61 formed in the sleeve 35. Here, the cooling water circulates around the elastic member 53 and then flows out of the cooling water chamber through an outlet 63 formed in the sleeve 35.
It flows out to 47, and further flows out from the outlet port 65 formed in the casing 33 to the other joint portion 57 and is returned to the cooling device side.

In the spring storage chamber 49, a compressed spring 67 is disposed between the partition wall 45 and the inner surface of the end of the casing 33, and applies a biasing force to the partition wall 45.

The elastic member 53 expands or contracts almost instantaneously at a predetermined temperature. This predetermined temperature is set, for example, to 70 ° C. or higher. FIG. 3 (A) shows a state in which the cooling water temperature is lower than a predetermined temperature, and the elastic member 53 whose temperature is controlled by the cooling water is shortened. Therefore, the entire valve body drive shaft 37 is lifted by the spring 67, and the partition wall 45 collides with the distal end 35b of the sleeve 35. Therefore, the valve body drive shaft 37 is stopped at the upper limit position.

At this time, of the valve body members 39, the second valve body 39b for cold use
Is located at the valve seat 43 portion. When the ISC is performed in this state, the joint portions 55 and 57 slidably hold the casing 33, so that the flow rate adjustment drive unit 17
The stroke amount of the second valve body 39b can be precisely adjusted by integrally moving the 31, the casing 33 and the valve body drive shaft 37.
Thus, the flow rate of the intake air is adjusted by changing the vertical position of the second valve body 39b. That is, the intake air flow rate is controlled by the characteristic B.

On the other hand, when the cooling water temperature exceeds a predetermined temperature, FIG.
As shown in FIG. 7, the elastic member 53 extends almost instantaneously. Since the spring constant of the elastic member 53 is sufficiently larger than the spring 67,
The spring 67 is compressed. In response to this, the valve body drive shaft 37 is lowered, the partition wall 45 is separated from the distal end 35b of the sleeve 35, and the stopper 51 collides with the bottom 33c of the casing 33. Therefore, the valve body drive shaft 37 stops at the lower limit position.

At this time, of the valve body members 39, the first valve body 39a for warm time is used.
Is located at the valve seat 43, and the flow rate of the intake air is precisely adjusted by the change in the vertical position of the first valve body 39a due to the ISC as in the case of the cold state. That is, the intake air flow rate is the characteristic A
Is to be controlled.

Since the ISCV1 is configured as described above, the characteristic B at the time of cold can be set as the characteristic B at the time of cold, and the characteristic A at the time of warm can be set at the entire region of the valve opening. For this reason, appropriate control can always be performed in accordance with the cooling water temperature, so that control deterioration such as rotation up and hunting due to a change in external load such as turning on / off the air conditioner and deterioration of fuel efficiency do not occur.

The spring storage chamber 49 is provided with contacts 69 and 71 of a changeover detection switch 68. One fixed contact 69 is the partition wall 45
The other elastic contact 71 is provided on the inner peripheral surface 33b of the casing 33 so as to be electrically insulated by the insulator 73. The voltage of the power supply 75 is applied to the elastic contact 71, and the voltage signal is input to a predetermined external device, here the electronic control circuit 21, as a switching signal. When the elastic member 53 is extended, FIG. 3 (B)
As shown in FIG. 7, both the contacts 69 and 71 are closed and the switching signal is in the ground state. Therefore, by examining the voltage of this switching signal, the expanding / contracting state of the elastic member 53, that is, the switching state of the valve member 39, can be determined.

Next, control using the above ISCV1 will be described.
FIG. 5 shows a flowchart of the ISC process executed by the electronic control circuit 21. This processing is repeatedly executed at a sufficiently short time interval.

When the process is started, first, it is determined whether or not the switch detection switch 68 is currently on (step 110).

If it is off, as shown in FIG. 3 (A), the second valve body 39b for the cold state is located at the valve seat 43, so that the characteristic B
Control of ISCV1 using the map of step 12
0). That is, the control under the situation where the intake air flow rate changes abruptly as compared with the change in the valve opening is performed in the entire valve opening range. As this control, various kinds of anticipation control based on an external load or the like in the normal feedback control are performed.

On the other hand, when it is determined that the switch detection switch 68 is on (step 110), it is determined whether the switch 68 was also on last time (step 130).

If the switch was also turned on last time, as shown in FIG. 3 (B), since the first valve element 39a for the warm state is located in the valve seat 43, the control of the ISCV1 is performed using the map of the characteristic A. Is performed (step 140). That is, the control under the situation where the intake air amount changes more slowly than the change in the valve opening is performed in the entire valve opening range.

If the valve was previously turned off and turned on this time, the valve opening is switched so that the intake air amount becomes the same (step 15).
0). This is because the characteristic of the ISCV1 is mechanically switched from B to A, and if the same valve opening V1 is maintained as shown in FIG. 4, the intake air amount drops sharply from Q1 to Q2, and the internal combustion engine 3 In addition, there is a fear that the engine may become unstable such as a stall.

In order to prevent this instability, when the switch 68 is turned on, the valve opening is increased from V1 to V2, and the same flow rate Q1 is maintained. Thereafter, the opening is adjusted to a desired degree by feedback control or the like of ISCV1 (step 140).

As described above, when the switching from the second valve body 39b of the cold characteristic B to the first valve body 39a of the warm characteristic A is performed, the feedback control of the idle rotation speed is prohibited, and The valve body drive shaft 37 reaches the valve opening V2 at which the intake air flow rate Q1 at the time and the intake air flow rate Q2 after the switching become equal.
Then, the feedback control of the idle rotation speed is restarted after driving the flow rate adjustment drive unit 17 so as to move from the opening position of V1. That is, when the switching is performed after the warm-up is completed, the stall due to the follow-up delay in the case where the feedback control of the rotation speed is continued at the time of switching the valve element characteristics is anticipated in advance so as to prevent two stalls during the characteristic switching. Open-loop control of the actuator is performed by the difference of the opening area between the valve elements to move the valve element drive shaft 37, and thereafter, the process shifts to feedback control. With the characteristics described above, it is possible to start the feedback control from the beginning with an appropriate air flow rate, and it is possible to improve the followability of the feedback control in the full opening range.

The distance between the contacts 69 and 71 of the changeover detection switch 68 is
Since it is shorter than the switching movement amount of the valve bodies 39a and 39b, it is closed before the valve bodies 39a and 39b are completely switched, and a switching signal is output. Therefore, before the air flow rate decreases, the same flow rate opening degree V2 of the characteristic A can be adjusted, which is more effective in preventing instability.

The process of step 150 may not be particularly performed in a region where the flow rate difference between the characteristics A and B is small, in a region where the valve opening is low in the drawing. Further, when the switch 68 is switched from on to off, the warming-up control is normally impossible, and if so, the air flow is increased, so there is no danger of engine stall. Therefore, it is not necessary to provide a process corresponding to step 150.

Next, a second embodiment will be described with reference to FIG. FIG. 6 schematically shows the valve body switching drive unit 200, and the other parts are the same as those of the first embodiment.

Base valve body drive shaft extending from the flow rate adjustment drive unit 17
A rectangular parallelepiped casing 203 substantially similar to that of the first embodiment is fitted and integrated with 201. In the casing 203,
Similarly, a cylindrical sleeve 205 protrudes from the center of the casing 203. One end of the valve body drive shaft 207 is attached to the sleeve 205
207a is slidably fitted in an airtight manner. The first spring 21 is provided in the sleeve 205 above the end 207a of the valve drive shaft 207.
5 is stored in a compressed state. Further, a peripheral portion 209a of the partition wall 209 at the center of the valve body drive shaft 207 is
3b, the sleeve chamber 211 and the spring storage chamber 213 are hermetically isolated from each other.

A through hole 217 is formed in the first spring 215 housing portion of the sleeve 205, and the sleeve chamber 211 and the inside of the sleeve 205 are communicated. Further, a through hole 219 is also formed in the casing 203 on the side of the sleeve chamber 211 to communicate the outside with the sleeve chamber 211.

In the spring storage chamber 213, a second spring 221 in a compressed state is disposed between the partition 209 and the inner surface of the end of the casing 203.
09 is giving the urging force. A through-hole 223 is also formed in the casing 203 on the side of the spring storage chamber 213, and a joint 225 is abutted on the casing 203 in an airtight and slidable manner. The atmospheric pressure or the pressure in the intake pipe 5 of the internal combustion engine 3 is switched and introduced into the joint 225 by the pressure switching valve 227. This switching is performed by the electronic control circuit 21 in accordance with the condition of cold or warm.

The valve switching drive unit 200 having the above configuration by the electronic control circuit 21
The control of the ISCV1 having the above is shown in the flowchart of FIG. This processing is repeatedly executed at a sufficiently short time interval.

First, it is determined whether the coolant temperature detected by the engine coolant temperature sensor 25 is equal to or higher than a predetermined switching temperature (step 31).
0).

If a negative determination is made here, the various controls of the ISCV1 are controlled based on the characteristic B (step 320).

In the initial setting, the pressure switching valve 227 introduces the atmospheric pressure to the joint 225. Therefore, the atmospheric pressure is introduced into the spring storage chamber 213 through the through hole 223. The first spring 2
The spring constant of the second spring 221 is larger than that of the second spring 221. Therefore, when atmospheric pressure is introduced into the spring storage chamber 213,
Since the sleeve chamber 211 side is always at atmospheric pressure, the spring 21
The valve body drive shaft 207 is pushed up by the balance of the urging forces of 5,221. As a result, the partition wall 209 collides with the tip 205b of the sleeve 205. Therefore, the valve body drive shaft 2
07 is to stop at the upper limit position. At this time, of the valve body members 39, the second valve body 39b for cold use is located at the valve seat 43 portion. Therefore, even if the various controls of the ISCV1 are controlled based on the characteristic B as in step 320, appropriate control is realized.

On the other hand, when the cooling water temperature exceeds the switching temperature, the pressure switching valve 22
7 is switched to introduce the pressure in the intake pipe 5 to the joint 225 (step 330). Idle intake pipe 5
Since the inside is sufficiently lower than the atmospheric pressure, the spring storage chamber
The pressure inside 213 drops significantly. Since the difference between the urging forces of the springs 215 and 221 is designed to be sufficiently small with respect to the difference between the atmospheric pressure and the pressure in the intake pipe 5, the valve body drive shaft 207 is pushed down. As a result, the partition wall 209 is positioned at the tip 205b of the sleeve 205.
The stopper 229 stops against the bottom 203c of the casing 203. Therefore, the valve body drive shaft 207 stops at the lower limit position. At this time, of the valve body members 39, the first valve body 39a for warm time is located at the valve seat 43 portion.

Next, the same processing as in step 150 is performed (step 340), and various controls of ISCV1 are appropriately controlled based on the characteristic A (step 350).

As described above, according to the present embodiment, as in the first embodiment, it is possible to obtain the characteristic B at the time of cold at the time of cold and the characteristic A at the time of warm at the time of cold in the entire region of the valve opening. It can be. For this reason, appropriate control can always be performed in accordance with the cooling water temperature, so that the engine rotation is stabilized, and deterioration of control such as rotation up and hunting and deterioration of fuel efficiency can be prevented.

Also, different from the first embodiment, the valve 39 on the electronic control circuit 21 side.
Since a and 39b are switched, the switching timing can be set freely. For example, the ISCV1 may prohibit switching in the high opening range and permit switching only in the low opening range. In this case, the processing in step 340 can be omitted.

In the first embodiment, the valve body switching drive section 19 corresponds to the switching means M6, and in the second embodiment, the valve body switching drive section 200 and the idle speed control electronic control circuit 21 correspond to the switching means M6.

When the valve bodies 39a and 39b are switched, the flow rate passes through the minimum state, but since it is very short, there is almost no effect on the operating state of the internal combustion engine 3. In particular, as described above, ISCV1
Or in the low opening range of the vehicle, or at the time of racing, after the start of running of the vehicle, or at the time of fuel cut due to the deceleration operation of the vehicle, since the influence on the internal combustion engine is further reduced, the switching is performed at such a timing. Is also good.

In the above-described embodiment, the valve body is switched using a shape memory alloy or air pressure. Alternatively, the valve body may be switched using a hydraulic pressure or may be switched using an electromagnetic actuator.

Effect of the Invention According to the present invention, when switching from the valve element having the cold characteristic to the valve element having the warm characteristic is performed, the feedback control of the idle rotation speed is prohibited, and the cooling before the switching is performed in advance. The actuator is driven to move the valve element drive shaft to a position where the intake air flow rate of the intermediate characteristic valve element and the intake air flow rate of the warm characteristic valve element after switching are equal to each other. The feedback control of the rotation speed will be restarted. That is, when the switching is performed after the warm-up is completed, the stall due to the follow-up delay in the case where the feedback control of the rotation speed is continued at the time of switching the valve element characteristics is anticipated in advance so as to prevent two stalls during the characteristic switching. Open-loop control of the actuator is performed by the difference in the opening area between the valve bodies to move the valve body drive shaft, and then the control is shifted to feedback control. With the characteristics, it is possible to start feedback control from the beginning with an appropriate air flow rate,
The followability of the feedback control can be improved in the full opening range.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram conceptually illustrating the contents of the present invention, FIG. 2 is a schematic system configuration diagram utilizing a first embodiment of the present invention, and FIGS. FIG. 4 is a graph showing the characteristics of each valve element, FIG. 5 is a flowchart of the control process, and FIGS. 6 (A) and 6 (B) are the end views for explaining the configuration and operation of the main part. FIG. 7 is an end view for explaining the configuration and operation of the main part of the second embodiment, FIG. 7 is a flowchart of the control process, and FIG. 8 is a graph showing the characteristics of a conventional ISCV. M1,7… Throttle valve M2,13 …… Intake air flow path M3,31,37,201,207 …… Valve drive shaft M4,39b …… Valve M5,39a that has cold-time characteristics M5,39a… Warm-time Valve element M6 having characteristics: switching means 19: valve switching drive section 21 electronic control circuit for controlling idle speed

Claims (1)

(57) [Claims] An internal combustion engine is provided in an intake passage which bypasses a throttle valve, and an opening area is changed to adjust an intake air amount so as to eliminate a difference between a target rotational speed and an actual rotational speed of the internal combustion engine. An idle speed control valve for feedback control of a valve body having two characteristics: a valve body having a characteristic for cold and a valve body having a characteristic for a sense of warmness at distant positions on the same valve body drive shaft. Switching means for switching between the two valve elements by moving the valve element drive shaft in accordance with a warm-up state of the internal combustion engine; and moving the valve element drive axis during the feedback control of the rotational speed to perform the suction. An actuator for changing the opening area of the passage, wherein the maximum intake air amount when the valve body drive shaft driven by the actuator moves to a position at the time of full opening is the cold characteristic. The valve element has a larger valve element than the valve element having the warm characteristic, and the cold characteristic has a larger change in the amount of intake air with respect to the movement of the valve element drive shaft than the warm characteristic. The switching means inhibits feedback control of the rotation speed when performing switching from the valve element having the cold characteristic to the valve element having the warm characteristic, and performs switching. The actuator is forced to move the valve element drive shaft to a position where the intake air flow rate by the cold characteristic valve element before becomes equal to the intake air flow rate by the warm characteristic valve element after switching. Variable flow rate characteristic idle speed control valve characterized by being driven in a dynamic manner.