KR930001769B1 - Idle revolution controller - Google Patents

Abstract

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Description

Idle speed control device of internal combustion engine

1 is a block diagram showing the configuration of an idle speed control device according to an embodiment of the present invention.

2 is an experimental result display diagram for explaining the effect of this Example apparatus.

3 is a control result display diagram of a conventional idle rotation control device.

4 is a block diagram showing the configuration of a conventional internal combustion engine speed control apparatus.

5 is a simplified block diagram showing the operation of a conventional speed control device of an internal combustion engine.

6 is a Nyquist diagram of the rotational speed control device of the internal combustion engine.

FIG. 7 is a diagram for explaining the variation of the transfer function due to the load column of the control system shown in FIG.

8 is a block diagram showing a configuration of an improvement of a conventional internal combustion engine speed control apparatus.

* Explanation of symbols for main parts of the drawings

1: Setting circuit 2: Proportional integral controller

3: actuator 4: engine

5: rotation speed detection circuit 6: detection circuit

11, 13, 14: Subtractor

345: transfer function from the actuator to the speed detection circuit

The present invention relates to an idle engine speed control apparatus for an internal combustion engine that stably and stably controls the idle engine speed of an internal combustion engine.

Recently, various accessories are installed in automobiles due to various demands, and among them, the engines are driven by engine rotation, and there are many large loads that vary the engine rotation speed, especially during idling.

For example, an air conditioner or a power steering device or a device that consumes a large amount of current (such as a defrosting device) has a drawback of increasing the load torque of an alternator and causing an engine stop by its operation.

Next, a conventional example of an engine speed control system for a vehicle equipped with such a heavy load accessory device will be described with reference to the drawings.

4 shows a block diagram of a conventional engine speed control apparatus. 1 is a setting circuit for outputting a voltage setting signal according to a desired target revolution, and a detection signal given with a voltage corresponding to the actual engine speed output from this setting signal and the speed detection circuit 5 It is input to the subtractor 11.

The subtractor 11 calculates the difference between the set signal and the detection signal and outputs the difference to the proportional integral controller 2. This proportional integral controller 2 is a parallel connection between a circuit for amplifying a deviation signal and a circuit for integrating the deviation signal. According to the output voltage of the proportional integral controller 2, the actuator 3 adjusts the ignition timing or the intake air amount of the engine 4.

In FIG. 4, the transfer function from the input end of the actuator 3 to the output end of the speed detection circuit 5 via the engine 4 is summed into one transfer function 345 and the speed control system is displayed. Becomes as shown in FIG.

Next, the operation of the conventional engine recovery control system will be described with reference to FIG. First, it is said that the setting circuit 1 outputs a target voltage signal according to a target rotational speed (typically varying by the operating point of the engine, but 800-900 rpm when operating the air conditioner in the idle).

The target voltage signal is calculated by the subtractor 11 to be a deviation signal from the difference between the voltage signal corresponding to the actual engine speed output from the rotation speed detection circuit 5. The deviation signal is proportionally amplified and integrated amplified by the proportional integral controller 2, and this voltage signal is sent to the actuator 3 as an operation amount. The actuator 3 controls the ignition timing of the engine 4 or the intake air flow rate in accordance with this voltage signal. The engine 4 generates an actual rotational speed suitable for the ignition timing or the intake air flow rate commanded from the actuator 3, and the rotational speed detection circuit 5 generates a voltage signal corresponding to the actual rotational speed. And the voltage signal according to this actual rotation speed returns to the subtractor 11 side.

Needless to say, such a feedback controller system is stabilized where the deviation signal becomes zero in a steady state.

At this time, the voltage signal according to the target speed and the voltage signal according to the actual speed are the same, and the engine speed is equal to the target speed.

That is, in the steady state, the engine speed is always controlled to be equal to the target speed.

The following describes the operation in transient state. As a representative case of the transient state, a case where a load (for example, air conditioning politics) is suddenly caught during idling will be described. When the control system shown in FIG. 4 is now in the normal state, the load suddenly falls on the engine 4 and the engine speed decreases.

At this time, since the level of the voltage signal output by the rotation speed detection circuit 5 decreases, the deviation signal becomes a positive voltage signal, and the control system is driven by signal processing in the proportional integral controller 2 and driving of the actuator 3. The engine operates to increase the rotational speed of the engine 4, and the engine rotational speed is restored to the original target rotational speed.

In order to return the engine speed to the original target speed as soon as possible during this process, increase the proportional gain or integral gain in the proportional integral controller 2 that receives the deviation signal and increase the integral gain. It is apparent that it is preferable to output a large voltage signal to the actuator 3 with respect to.

In other words, the reduced engine speed can be quickly returned to the original target speed by increasing the sensitivity of the control system.

In general, increasing the proportional gain or integral gain of the proportional integral controller (2) in the feedback control system to increase the sensitivity of the control system (1) quickly eliminates the influence of disturbance (2) changes in the characteristics or deviations of the control object. Regardless, the point of obtaining a predetermined control grade is extremely important.

However, in the actual rotation speed control system, it is usually very difficult to increase the sensitivity of the control system.

The reason is generally that in the case of an engine, for example, when the actuator 3 manipulates the intake air flow rate, for example, the transfer characteristic between the response of the intake air flow rate and the response of the engine speed is 180 degrees or more late. 2nd delay factor (2) If the sensitivity of the control system is increased due to the dead time factor due to administrative delay, etc. (high gain), the control system itself becomes unstable and hunting occurs. Because.

This point will be described in detail with reference to FIG. 5 using, for example, an equation. In this figure, the transfer functions of the proportional integral controller 2 and the transfer function 345 are Gc (S) and G ₃₄₅ (S) e ^-SL , ^respectively , and the voltage signal of the setting circuit 1 is r, the transfer function 345. When the output (voltage signal) of Y is Y, the closed loop transfer function y / r from the voltage signal r to the output y is given by the following equation (1).

Therefore, the characteristic equation that governs the stability of the control system is given by the following equation (2).

Where Gc (S) is the transfer function of the proportional integral controller (2). As is well known, stability analysis using the above equation (2) is performed by drawing a Nyquist diagram.

The Nyquist diagram was actually drawn below to analyze the stability of the control system.

First, Gc (S) is proportional integral, so the proportional gain is K. If the integral gain (integral time) is Ti,

Becomes

On the other hand, the transfer function G345 (S) from the actuator (3) to the engine is

It can be approximated with the second delay that is to some extent.

Where T is the time constant and depends on the engine speed, flywheel moment of inertia, volume of the surge tank, etc., but it is about 0.3 seconds at the engine balance speed No = 750rpm.

If the dead time L is set to 4 strokes, the engine balance speed No = 750 rpm and 4 × 60 / (2 × No) = 0.16 seconds.

Substituting S = jω into equations (3) and (4)

ωKTi = ωT × (KTi / T)

ωTi = ωT × (Ti / T)

ω L = ω T × (L / T)

If the Nyquist diagram is drawn using K and Ti as parameters, for example, it is sixth.

This figure is when k = 0 and Ti / T = 1.

As apparent from this figure, it can be seen that the phase is 180 degrees and the absolute value is 0.96 at the frequency f = 0.37 Hz, and the control system is in a safe system and does not actually operate stably. Similarly, the frequency at which the control system becomes unstable in each Nyquist diagram with K and Ti as parameters is in the range of 0.37 Hz to 0.7 Hz.

On the other hand, the experiment shows that the idle speed control system becomes unstable, and the actual frequency when hunting is in the range of about 0.3-0.7 Hz, and the above analysis is in good agreement with the experiment.

In this analysis, if the range of K and Ti for which the control system is stable is obtained, K = 1-2 and Ti / T is 1 or more, and this result is also in agreement with the experiment.

From these things we can see:

(1) The proportional gain K of the idling speed control system is at most 2 and the integration system Ti becomes unstable unless the integration time Ti is greater than 0.3 seconds (and thus the integration gain is small).

(2) Therefore, the sensitivity of the control system cannot be increased (high gain), and the response to disturbance (dominantity) is deteriorated, and the engine is stopped when a large load is suddenly added.

In addition, the response to the disturbance of the idle rotation speed control system is poor and the engine is stopped when a large load is suddenly added.Also, the load disturbance to the engine changes the transmission characteristics of the engine to be controlled. The idle speed control system has no reasonable and effective countermeasure against load disturbance.

This will be described in detail with reference to FIG.

In FIG. 7, Gc (S) denotes a controller, Ge (S) denotes a transfer function of a control target, and D ₁ and D ₂ denote disturbances. R represents a target value, Y represents a control amount to be controlled, and U represents an operation amount.

The formula below holds true as in the formula (1).

In the equations (6) and (7), if the gain of the controller Gc (S) is very large, Y / D ₁ and Y / D ₂ are all zero, and the control amount Y is not affected by the disturbance D ₁ and D ₂ . have.

The importance of increasing the above sensitivity is right here, but another important implicit assumption is that the transfer function Ge (s) of the control target is not converted by the disturbances D ₁ and D ₂ in the above formulation. .

That is, in the design of a normal feedback control system, the disturbance D ₁ and D ₂ are designed to be as high gain as possible as long as it does not impair stability, assuming that the transfer function Ge (s) to be controlled does not change. To eliminate the effects of disturbances D ₁ and D ₂ . For example, first, the disturbance D ₁ , D ₂ = 0 is designed so that the gain of the controller can be as high as possible based on the closed loop transfer characteristic (Eq. (6)) from the target value R to the control amount Y. In this case, when the gain of the controller of equation (6) is high, Y / D ₁ and Y / D ₂ are both zero, and the control amount Y is not affected by the disturbances D ₁ and D ₂ .

But what makes this design possible

(1) The gain of the controller should be high.

(2) The disturbance D ₁ and D ₂ should not change the transfer function Ge (s) of the control target.

Only when this is corrected.

In the idle rotation speed control system, however, the gain of the original controller cannot be increased because of the aforementioned reasons, and the transfer function of the control target is converted by disturbance as described later.

Therefore, in the current idle speed control system, the engine speed is significantly reduced by the torque disturbance due to the disturbance, and in some cases, even engine stall may occur.

Various methods have been considered to improve this phenomenon even a little. For example, a method of driving the actuator 3 by inputting a switch signal such as an air conditioner (hereinafter referred to as an air conditioner) to the computer and recognizing that the air conditioner is operated before the load of the air conditioner is actually applied to the engine is often used. It is adopted.

However, in this method, when there is a significant time difference between the input time of the switch signal and the time when the air conditioner load is actually added to the engine, the speed may be lowered once the speed is increased, which often gives an unpleasant impression to the driver. As another example of improvement, Japanese Unexamined Patent Application Publication No. 61-43535 proposes a feedback control system shown in FIG.

That is, the parts indicated by reference numerals (1)-(5) and (11) in FIG. 8 are the same as those in FIG. 4, and the parts indicated by (6) and (12) are added to the configuration of FIG. 4, and (6) It is a detection circuit which outputs a detection signal of a voltage corresponding to the reduction of the engine speed detected and output by the rotation speed detection circuit 5. The detection signal output from this detection circuit 6 and the detection signal output from the rotation speed detection circuit 5 are added by the adder 12 so that the addition result is output by the subtractor 11. Next, the operation of FIG. 8 will be described.

Like FIG. 4, when the control system of FIG. 8 is in a steady state, load disturbance is suddenly added, and the engine speed is rapidly reduced. In this case, the setting circuit 1 to the rotation speed detection circuit 5 operate in the same manner as in FIG. 4, but in FIG. 8, the rotation is caused by the detection circuit 6 which outputs an output signal at a voltage proportional to the deceleration of the rotation speed. The voltage proportional to the deceleration of the number is fed back redundantly so that the deviation signal becomes larger than in the operation of FIG. 4 and returns to the original target speed more quickly than in FIG.

With this kind of feedforward, the engine speed surely returns to the original target speed faster than in the case of FIG. 4, but it is generally extremely limited that such a feedforward compensation achieves its initial purpose (e.g., control target There are many cases where the change in the characteristics of is very small), and therefore it is not always possible to always obtain the effect.

For example, when the target speed is 600 rpm, it works without problem, but when it is 1000 rpm, it is often harmful. Specifically, when the feed forward compensation parameter is set for a certain target speed (600 rpm), the relative speed (1000 rpm) in which the target speed is largely changed does not feed forward compensation for the rotational speed variation, but rather encourages variation. There is damage. Moreover, according to Japanese Unexamined Patent Application Publication No. 61-53544, it is proposed to control the ignition timing by the actuator 3 of FIG.

In general, when controlling the engine speed, it can be considered to control one of the intake air flow rate and the ignition timing, but since the response of the ignition timing is faster, the ignition timing is controlled to some extent to quickly affect the effect of the speed reduction due to disturbance. Can be removed. However, the width of the number of revolutions that can be controlled by the ignition timing is limited and there is no effect when the load exceeding the width is too far.

The various conventional engine speed control apparatuses of FIGS. 4 and 8 described above have an effect of quickly controlling the influence of load disturbance added to the engine and returning to the original target speed, but essentially the proportional integral controller 2 The effect was limited because the proportional gain or the integral gain was not increased to increase the sensitivity of the control system.

The present invention has been made to solve this problem, and can increase the sensitivity of the control system and at the same time control the air flow reasonably, thereby quickly eliminating the influence of load disturbance and quickly returning the idle speed to the original target speed. An object is to obtain an idle speed control device of an internal combustion engine.

The idle speed control device according to the present invention provides a torque disturbance detection means for directly detecting a torque disturbance and converting the magnitude of the torque disturbance into an electrical signal, and simultaneously adjusting the air flow rate or the ignition timing in proportion to the magnitude of the disturbance load and the derivative of the time. The control means for controlling is installed.

In the present invention, the load disturbance is detected directly and the air flow rate or the ignition timing is controlled in proportion to the magnitude of the disturbance load and the derivative of the time, so that the variation of the transfer function of the rotational speed control system due to the load disturbance can be compensated. It is possible to stabilize the rotation speed of the engine caused by the feedback control quickly. Next, an embodiment of this invention will be described with reference to the drawings.

1 is a block diagram showing the configuration of an engine speed control apparatus according to an embodiment of the present invention. In the figure, the same reference numerals as in FIG. 4 denote the same, 13 is an adder, 14 is a subtractor, 110 is a subfeedback transfer function, and 111 is a subfeedback control system.

In addition, the part shown with the broken line in FIG. 1 shows the function of the engine 4 of the conventional example of FIG. 4, namely the change of intake air flow rate. Change of Ga intake pipe pressure Change of rotation speed through Pb The function of converting to N is shown in a block diagram. The essence of this invention is the torque disturbance Intake air flow at Td G · a / G · ao (hereafter The sub-feedback 110 is installed on the (G + a ^* ) axis through (1 + Sτa) / Kp so that the transmission characteristics of the engine's idle speed control system can be changed by disturbance, thereby changing the rotational speed of the engine caused by the disturbance. To stabilize quickly. Therefore, the explanation will be explained in detail using the formula, focusing on the advantages.

Intake pressure ΔPb / Pbo (hereinafter referred to as error signal ΔE / Eo of normalized air flow rate in FIG. 1) The transfer characteristic G _N (S) to Pb ^{* is} also given by the following first delay. Here, for simplicity, tau n of FIG. 1 is assumed.

Where tau a is a time constant given by

ηvo is the volumetric efficiency at equilibrium, No is the engine speed at equilibrium,

Vm is the intake manifold volume from the throttle valve to the intake valve,

Vh is usually No = 750rpm ηvo = 0.6

When Vm = Vh, the value of τa = 0.27sec is obtained.

In addition, the rotational speed feedback before G _N (S) relates to a mechanical mechanism in which the intake pressure increases or falls when the rotational speed decreases or rises in the idle state. Gc (S) is a transmission characteristic that depends on the air metering method of fuel control, and when the fuel is injected in proportion to the intake pressure, that is, the speed tensioner method (D Jettro (trade name of West German Bushsch) ((speed Desity, D-jetro) ) Is 1 if the administrative delay is not taken into consideration.In case of injecting fuel in proportion to the action of the unit rotational speed by re-injecting the intake air flow rate with the intake meter, that is, L-jetro (West Germany ) Is given by 1 + Sτa.

For simplicity, the description is referred to as Gc (S). Gλ (S) is the injection pulse width Pw / Pwo and air ratio λ / Fuel transport characteristics in the so-called intake pipe relating to? o are shown. In this case, it is also referred to as 1 for the sake of simplicity. Another engine torque Tb and N / No (less than N ^* as described), Pb / Pbo, λ / Gb (S) is related to the transfer characteristic relating λ o as follows.

Where Kn, Kp and Kλ are integers and are experimentally determined at the equilibrium operating points (No, Pbo, λo).

Physical constants of these integers and their measurement methods are described in the Society of automotive engineering article 860411 (SAE paper 860411). Constant Kn is the rotational speed Change of net torque by N / No, constant Kp is intake pressure The net torque change by Pb / Pbo, and the constant Kλ is the air ratio Changes in maintenance torque due to λ / λo are shown, respectively.

For simplicity, there is no change in the air ratio. Tb is the intake pressure fluctuation Pb ^* ( Pb / Pbo) changes only, and the size is as follows.

Engine Torque Tb and load disturbance Td's car turns again as indicated by the well-known Euler's equation of motion. It is converted to N / No.

Where J is the moment of inertia of the flywheel.

Finally, the intake air flow rate G a / G ao and E / Eo, rpm The relationship between N / No is defined by the formula of the conservation of mass in the intake manifold, the equation of state and the volumetric efficiency.

It becomes

Intake air flow rate by combining equations (8)-(13) above Ga and rotation speed N and load disturbance The relationship between Td is obtained from the following equation. However, dead time is excluded in administrative delay.

From Eq. (14), the following can be seen.

If load disturbance Rotational speed change even when Td is applied N ^* ( N / No) to zero

Air flow rate displayed in You can see that Ga ^* can be sent to the engine through the actuator. Load disturbance The amount of Td detected and multiplied by 1 / Kp (proportional constant) (the first term in (15)) and the load disturbance What is necessary is just to send an air flow rate corresponding to the sum of the derivative of Td multiplied by (tau a / Kp (proportional constant) (the right item 2 of (15)).

Feedback 110 in FIG. 1 shows this.

Appearance of load disturbance in Eq. The influence of Td can be eliminated and the transfer characteristic from the air flow rate to the rotational speed of the engine The inventor has found that it is possible to be independent of Td.

If this is explained in more detail as follows.

That is, dividing the air flow into two parts

By If G · as ^* is given by (15), (14) is expressed as Td is erased.

In other words, the shear characteristics of the engine except dead time

Secondary delay and load disturbance It has nothing to do with Td.

The physical meaning of airflow separation as shown in (16) is as follows.

That is, the air flow rate passing through the first passage bypassing the throttle by the right paragraph 1 of the formula Air flow through the second passage that bypasses the throttle with G · ap ^* G · as ^{* *} (in reality, it is not necessary to make such a distinction, and the air flow rate shown in paragraph 2 is added to the air flow rate flowing through the first passage). Equation (18) is the air flow rate flowing through the first passage. G · ap ^* and engine speed It indicates that the transmission characteristic is established between N ^* .

2 shows experimental results confirming the above effects. In the figure, the broken line shows the air flow rate, the solid line shows the engine speed, and the dashed-dotted line shows the load current (load disturbance) of the generator.

In the figure, load disturbance is applied at the time of ON and load disturbance is canceled at the time of OFF. This load is considered to be a step disturbance, in which a rush current flows. In this case, the air flow to be supplied is given by the inverse of the equation (15). In other words,

It can be seen that the air flow rate in this case is given by the sum of the unit step function u (t) and the model function δ (t).

By the way, it can be seen that the broken line representing the air flow rate in FIG. 2 shows a change very close to the change given by equation (19). On the other hand, the rotation speed (solid line) at this time fluctuates slightly due to disturbance (set rotation speed 750rpm, load on 715rpm, load off 790rpm), and compared with the conventional case of FIG. It turns out that the fall of the rotation speed at the time of load ON and the increase of the rotation speed at the time of load OFF are remarkably decreasing.

Load disturbance The coefficients 1 / Kp and τa / Kp for each of Tb and its derivatives are natural because they depend on the operating point of the engine and the manifold volume Vm, engine exhaust volume Vh, and volumetric efficiency ηVo shown in Eq. (9). It goes without saying that must be changed corresponding to the operating point of the engine.

As a result, even if there is a change in the operating point, the effect of the present invention can be sufficiently exhibited. As a parameter for indicating the operating point of the engine, in general, the torque-revolution is easily thought of, but in addition, the intake pipe pressure = rotational speed, the city average effective pressure-revolution, and the effective calorific value Q-revolution per cycle defined by the following equation. And the like can be considered.

Where K is the specific heat ratio, p (θ) is the cylinder pressure for each crank angle θ, and v (θ) is the cylinder volume for each crank angle θ.

As an electric load detection method, in the case of an electric load, the method of detecting the load current of a generator by a magnetic field detection element, such as a hool element and a flux gate element, can be considered. In the case of a mechanical load (for example, a power steering, an electric control window, 4ws, etc.), it is conceivable to detect the hydraulic pressure by a pressure sensor.

In this embodiment, the load disturbance is directly detected, and the magnitude thereof is multiplied by (1 + Sτa) / Kp, that is, the detection amount of the load disturbance. Tw times 1 / Kp (proportional constant) multiplied by the right term (1) of the amount (15) and load disturbance In response to the sum of the derivative τa / Kp (proportional constant) multiplied by Td (right part 2 of the equation (15)), the airflow is fed back to the airflow rate. Load disturbance Since it can be independent of Td, the result is that the influence of load disturbance can be eliminated quickly, and it can be quickly returned to the original target speed.

In the above embodiment, the electronic fuel injection device is mainly described, but this may be a carburettor or an electronic control carburettor, and in this case, it has the same remarkable effect as the above embodiment.

In the above embodiment, the case of the load torque disturbance on the step has been described. However, even when a load torque disturbance other than the above is received, the air flow Ga * given in the above formula (15) is supplied to the engine through the actuator. do. In addition, in the above embodiment, the case where the air flow is mainly considered as the operation amount has been described, but this may be the ignition timing, and in this case, the same effect is obtained.

Claims (1)

Intake passage for bypassing the throttle valve of the heat-resistant engine, actuator for controlling the air flow flowing through the passage, rotation speed detection circuit for detecting idle rotation speed of the internal combustion engine, and corresponding set signal of the predetermined target rotation speed of the internal combustion engine And a proportional integral controller for amplifying and integrating a deviation between the detected signal of the rotational speed detection circuit and the deviation of the set signal, wherein the feedback device controls the idle rotational speed of the internal combustion engine. Disturbance detection means for detecting the applied torque disturbance and converting the magnitude into an electrical signal, and control means for controlling the air flow rate or the ignition timing in proportion to the electrical signal and the time derivative Idle speed control device of an internal combustion engine.