JPS6282253A - Drive circuit for idling speed control valve - Google Patents

Abstract

PURPOSE:To make it possible to prevent a flow rate from varying widely by turning electricity off at a time when the detected current value to an electromagnetic coil reaches the value of a current function which corresponds to the control value for the flow rate of supplemental air. CONSTITUTION:When an operating condition meets the requirement for an idling speed control, the value of applied current at a moment when the current, which has been integrated since in has been applied to an electromagnetic oil 11, reaches a target value corresponding to a flow rate control value controlled by an idling control valve, is set as a time function for the variation in characteristics of current while a timer contained in a microcomputer 15 is reset. And then the value is inputted into a comparator 13 as a voltage function through a D/A converter 14 with a specified frequency maintained. Current to the electromagnetic coil 11 is increased with time, on the other hand, the voltage function keeps on decreasing until its voltage drops below the terminal voltage of a current detecting resistor 16 when the output level of the comparator 13 is turned out to be a L level allowing a transistor 12 to be turned off to permit electricity to the electromagnetic coil 11 to be turned off.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to an electromagnetic idle speed control that is installed in an auxiliary air passage bypassing the throttle valve of the intake system of an internal combustion engine to control the auxiliary air flow rate. This invention relates to a valve drive circuit.

(Prior art) Conventionally, this type of idle speed control valve has a valve body that is installed in an auxiliary air passage that bypasses the throttle valve of the engine intake system and controls the passage area by the movement position of the valve body, and a valve body that moves the valve body in the closing direction. It is equipped with a return spring that energizes and an electromagnetic coil that moves the valve body in the opening direction when energized, and by duty-controlling the energization to the electromagnetic coil, the movement position of the valve body is controlled and the passage area is controlled. Controlling the idle speed by controlling the amount of auxiliary air
(See No. 3579).

<Problems to be Solved by the Invention> However, in such a conventional idle speed control valve, the flow rate control value determined based on the engine operating state is converted into a duty signal using a triangular wave generator and a comparator. Convert it to ! The desired flow rate is obtained by applying it to the magnetic coil, but due to fluctuations in the rX voltage or changes in coil resistance due to heat generation in the coil due to energization, actual There is a problem in that the flowing current changes and the flow rate changes, resulting in deterioration of control accuracy.

In view of these conventional problems, the present invention aims to reduce the variation in flow rate by driving an electromagnetic coil with a drive amount corresponding to a flow rate control value, regardless of fluctuations in power supply voltage or temperature changes in coil resistance. The purpose of the present invention is to provide a drive circuit for an idle speed control valve that can perform the following steps.

(Means for Solving the Problems) Therefore, as shown in FIG. Current function output means for outputting at a predetermined cycle an energizing current value between ll# whose value is a target value corresponding to an auxiliary air flow rate control value of an idle control valve as a function of time according to a change in energizing current characteristics; Energization control means is provided that starts energizing the electromagnetic coil at the beginning of a cycle of the current function output from the current function output means and ends energization when the detected value of the energized current becomes equal to or higher than the function output value. This constitutes the drive circuit for the idle speed control valve.

<Operation> In the above configuration, after starting the energization to the electromagnetic coil at a predetermined period, the current flowing through the current coil is detected, and the current function is output from the current function output means, and the current flowing through the electromagnetic coil is detected. Duty control is performed by terminating the energization when the detected value reaches the current function value corresponding to the control value of the auxiliary air flow rate. Therefore, even if there are fluctuations in the power supply voltage or temperature changes in the coil resistance, if the flow rate control value is constant, the integral value of the drive current will be constant and there will be no fluctuation in the flow rate.

<Example> The present invention will be explained in detail below.

An example of an idle speed control valve is shown in FIGS. 2 to 4, and this will be explained first.

A valve seat 3 having a cylindrical surface is formed in a housing 2 having a passage 1 forming a part of an auxiliary air passage that bypasses the throttle valve of the engine intake system.・Downstream is connected. A valve body 4 having a cylindrical surface is fixed to one end of a hollow rotor 5 and slides on the valve seat 3, and this rotor 5 is attached to a fixed shaft 6 with a bearing 7.
．． It is rotatably supported via 8. therefore,
The valve body 4 is rotatable around a fixed shaft 6, and as the valve body 4 rotates, the passage area of the opening 3a formed in the valve seat 3 is controlled.

A helical return spring 9 is interposed between the rotor 5, which rotates together with the valve body 4, and the housing 2, and this return spring 9 moves the valve body 4 in the closing direction (counterclockwise in FIG. 3). ) is energized.

The rotor 5 is made of a magnetic material and has a protrusion 5a.

5b. A yoke (yoke) 1 has protrusions 10a and 10b surrounding the protrusions 5a and 5b.
0 is fixedly placed. Further, an electromagnetic coil 11 for exciting the yoke 10 is also fixedly arranged. Here, when the electromagnetic coil 11 is energized, an attractive force acts between the protrusions 10a and 10b of the yoke 10 and the protrusions 5a and 5b of the rotor 5, and the rotor 5 and therefore the valve body 4 are opened in the opening direction (third direction).
It can be rotated in the clockwise direction (in the figures and FIG. 4).

Therefore, by duty-controlling the energization to the electromagnetic coil 11, the torque in the valve opening direction is controlled, and the valve body 4 is brought to a position where this torque and the biasing force of the return spring 9 are balanced.
Control? ffl L controls the passage area of the opening 3a,
This allows the engine's idle speed to be controlled by controlling the auxiliary air flow rate.

Next, a first embodiment of the drive circuit for the idle speed control valve will be described with reference to the circuit diagram of FIG. 5 and the flowchart of FIG. 6.

Referring to FIG. 5, one end of the electromagnetic coil 11 of the idle speed control valve is connected to a power source VB, and a transistor 12 is connected in series to the ground side of the other end.

] - The transistor 12 is controlled on/off by the output of a comparator 13 as a current control means,
A function voltage E ft is applied to the child terminal of the comparator 13 from the microcomputer 15 via the D/A converter 14.
) is input.

Further, a current detection resistor 16 as a current detection means is connected in series to the ground side of the transistor 12, and the terminal voltage of this resistor is inputted to one terminal of the comparator 13. 17 is a diode connected in parallel to the electromagnetic coil 11 to prevent generation of back electromotive voltage.

The microcomputer 15 determines the auxiliary air flow rate control value by the idle speed control valve based on the engine operating state detected by various sensors (not shown), and also determines the function voltage E (tl is output to the D/A converter 14 during the period.

Explaining along the flowchart of FIG. 6, in step 1 (denoted as Sl in the figure, the same applies hereinafter), it is determined whether or not the operating conditions are such that idle speed control is to be performed.

If the determination is YES, proceed to step 2 and reset the timer built into the microcomputer 15 (1=0).
do.

In step 3, the current value at the moment when the integral value of the current to the electromagnetic coil 11 after the start of the current flow reaches a certain value is determined as i1.
! Outputs changes in current characteristics as a function of time.

As mentioned above, the characteristics of the current flowing to the electromagnetic coil 11 are as follows:
The resistance changes due to changes in the resistance of the electromagnetic coil 11 due to heat generation.

Due to this change in characteristics, the value and timing of the current flowing at the moment when the integral value of the flowing current reaches a constant value differs.

That is, the energizing current function is output as a energizing current value having a characteristic such that the integral value becomes a constant value at that time point with respect to the elapsed time t after the start of energization.

Specifically, the energizing current function Io(t) is determined by the following equation.

< t e −L / T ) (where T is the time constant of the electromagnetic coil) Next, in step 4, the integral value of the energizing current after the start of energization to the electromagnetic coil 11 is determined as the flow rate control value by the idle speed control valve. The instantaneous energizing current value that becomes the target value corresponding to is set as a function of time according to the change in energizing current characteristics as in step 3, and the energizing current function is set as a voltage function for comparison with the energizing current detection value. After converting to E (t), it is output.

That is, the energizing current function [(1) corresponding to the target value is
Since the flow rate control value and the integral value of the energizing current are proportional, it is set by the following formula.

10(t) = K −i o(t) (where K is a set value proportional to the flow rate control value) and the actual energizing current i (t) is the terminal voltage e (t) of the current detection resistor r. −r −i (t), so in order to compare the above 1() and the detected current i (t), the function voltage E(t)=I ft) also multiplied by the resistance r
Output as r·I (t)−r−K Io(t).

In step 5, the set lap after resetting the timer in step 2! It is determined whether or not tJI (for example, 20m5) has elapsed, and if the time has not passed, the process returns to step 3. After the time has elapsed, the process returns to step 2 and a new voltage function E(1) is determined.
Set and output.

In this way, in step 4, when the function voltage E (tl) is output at a predetermined period, this digital signal is converted into an analog value by the D/A converter 14, and then output to the comparator 13, Initially, the current flowing to the electromagnetic coil 11 is O, so the output of the comparator I3 becomes H level, the transistor 12 is turned on, and the electricity flowing to the electromagnetic coil 11 is started.

Then, the current i (t) flowing to the electromagnetic coil 11 increases as time passes, while the function voltage E (t) decreases, and at the time when E (t)≦r − i (tl). The output level of the comparator 13 changes to the L level, the transistor 12 is turned off, and the energization of the electromagnetic coil 11 is terminated.

Thereafter, the power to the electromagnetic coil 11 is cut off until the determination in step 5 becomes YES.

In this way, by controlling the on-time of the duty control so that the integral value of the current flowing to the electromagnetic coil 11 becomes the target integral value corresponding to the flow rate control value, fluctuations in the power supply voltage and temperature changes in the coil resistance can be prevented. However, if the flow rate control value is constant, the integral value of the drive current will be constant and there will be no flow rate fluctuation.

Incidentally, as is clear from the above explanation, the current detection resistor 16
constitutes current detection means, microcomputer 15 constitutes current function output means, and D/A converter 14 and comparator 13 constitute energization control means.

Next, a second embodiment of the drive circuit for the idle speed control valve will be described with reference to FIG.

In this embodiment, the current detection resistor 16 and the comparator I
3 is provided in the same manner as in the first embodiment, but the current function signal (function voltage) input to the child terminal of the comparator 13 is generated by a differentiating circuit.

In other words, the input terminal ■ is input with a control voltage corresponding to the control value of the auxiliary air flow rate. , two resistors R1゜R2 and a capacitor C are connected in series, and a capacitor C and a resistor R2 are connected in series.
The connection point between the two terminals is connected to the + terminal of the comparator 13.

A diode 21 for speeding up the discharge time of a capacitor C, which will be described later, is connected in parallel to the resistor R2.

On the other hand, the connection point between the resistor R and the capacitor C is grounded through the collector and emitter terminals of the transistor 22, and the heath terminal of the transistor 22 is connected to the timer 23 which is generated at a predetermined frequency M (for example, 20 m5). A pulse signal is input.

In this configuration, when a pulse is generated from the timer 23, the transistor 22 is turned on, and the capacitor C is discharged in a short time by a circuit connected to the transistor 22 and the diode 21, and the input to the child terminal of the conhalator 13 is Reset the terminal to Ov.

When the pulse signal from the timer 23 becomes L level and the transistor 22 is turned off, the control voltage applied to the terminal I0 causes the capacitor C to connect its capacitance and the two resistors R1.
, R2, and is gradually charged with a time constant determined by R2. Therefore, the voltage applied to the child terminal of the comparator 13 is equal to the control voltage at the start of charging, but decreases as the capacitor C is charged. That is, a voltage having a characteristic obtained by differentiating the charging current to the capacitor C is input.

The voltage with such characteristics is very similar to the function voltage E ftl shown in the first embodiment, except for the part near the start of energization and the part near the end of the cycle, and moreover, the characteristic of the energizing current is Even if it changes, the energization end time remains within this similar range.

Therefore, by substituting the voltage having the above characteristics for the function voltage E (t) of the first embodiment and manually applying it to the child terminal of the comparator 13, the same function as that of the first embodiment can be obtained.

In this embodiment, resistors R, , R, capacitor C, diode 21, transistor 22, and timer 23 constitute current function output means.

<Effects of the Invention> As explained above, according to the present invention, the integral value of the drive current of the idle speed control valve corresponds to the flow rate control value by the current function that is set according to the control value of the auxiliary air flow rate. Since the on-time of duty control is controlled to reach the target value, there is no flow fluctuation even if there are fluctuations in the power supply voltage or temperature changes in the coil resistance.The effect is that the flow rate variation is reduced and the control accuracy is improved. is obtained.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a front cross-sectional view showing an example of an idle speed control valve, Fig. 3 is a side cross-sectional view of the valve body of the same control valve, and Fig. 4 is the same as above. 5 is a circuit diagram of a drive circuit showing the first embodiment of the present invention, FIG. 6 is a flowchart of the same embodiment, and FIG. 7 is a second embodiment. FIG. 2 is a circuit diagram of a drive circuit showing an example. 4... Valve body 9... Return spring 11
... Electromagnetic coil 12 ... Transistor 13
...Comparator 14...D/A converter 1
5... Microcomputer 16... Current detection resistor 21... Diode 22... Transistor 23... Timer R,, R,... Resistor
C... Capacitor patent applicant Nippon Electronics Co., Ltd. Agent Patent attorney Fujio Sasashima Seirei 1st shift 2nd Figure 3 Figure 5B Figure 7

Claims (1)

[Claims] A valve body that is provided in an auxiliary air passage that bypasses a throttle valve of an engine intake system and controls the passage area by its movement position, and a return spring that biases the valve body in a closing direction.
An idle speed control valve for an internal combustion engine, which includes a duty-controlled electromagnetic coil that moves a valve body in an opening direction when energized, includes current detection means for detecting a current flowing through the electromagnetic coil, and energization after energization of the electromagnetic coil starts. current function output means for outputting a current value at a moment when an integral value of the current becomes a target value corresponding to an auxiliary air flow rate control value of an idle control valve as a function of time in accordance with a change in a current characteristic; , energization control means that starts energizing the electromagnetic coil at the beginning of a cycle of the current function output from the current function output means, and ends energization when the detected value of the energized current becomes equal to or higher than the function output value. A drive circuit for the idle speed control valve.