JPH0694825B2 - Idle speed control device for internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention relates to an idle speed control device for an internal combustion engine, and more particularly to an idle speed control device for an internal combustion engine that performs control in relation to smoothness of rotation.

(B) Prior Art An idle speed control device for an internal combustion engine has already been described in German Patent Publication No. 3039435. According to the control device disclosed therein, the rotation speed of the internal combustion engine is detected and the rotation speed is PID controlled. The target value is controlled by the vessel. Therefore, the amount of air-fuel mixture or the air flow rate in the intake pipe is changed by changing either the position of the throttle valve or the amount of air flowing through the bypass pipe for the throttle valve.

Apart from this, so-called rotational smoothness control is known.
In this case, the smoothness of rotation means the uniformity of rotation of the crankshaft. For example, in the case of an internal combustion engine of external ignition type, if the air-fuel mixture is made extremely lean, the smoothness of rotation is reduced, and therefore the non-uniformity of rotation is increased, so that all combustion processes are not always well controlled. As a result, the torque of the internal combustion engine fluctuates, which makes the rotation more uneven, and in some cases causes sway (low-frequency vibration). If the rotation non-uniformity is based on an extremely thin mixture, it can be dealt with by thickening the mixture. Therefore, according to the conventional rotation smoothness control device, it has been attempted to control to the lean limit value by changing the composition of the air-fuel mixture, that is, rich and thin, for the reason of fuel saving. As an example of rotation smoothness control by changing the lambda value (air ratio or excess air ratio), German Laid-Open Publication No. 2434742
Issue, German publication No. 2417187, German publication No. 293
9590 and U.S. Pat. No. 3,789,816.

According to the conventional idle speed control device as described above, only the speed signal is processed, and the target value and the actual value of the speed are compared. In that case, since the target idle speed value is related to temperature, there is a high possibility that the internal combustion engine will stop if it is still cold.

For this reason, in the conventional system, the target idle speed is set to a relatively large value in order to prevent the internal combustion engine from being stopped even when the internal combustion engine is loaded in the idle state, especially when the air conditioner is operated. To be done. Therefore, a predetermined difference (margin) occurs between the target idle speed and the minimum speed at which the internal combustion engine is still smoothly rotated and is not stopped. In the conventional idle speed control device, since the target idle speed is set to a relatively large value, this predetermined difference becomes a relatively large value, which is desirable in view of fuel saving. It will not be a thing.

Further, in Japanese Laid-Open Patent Publication No. 54-91623, the idle speed is controlled so that the stability of the idle speed of the engine is within a predetermined range, and the idle speed is reduced when warming is sufficiently promoted. The possible configurations are described. However, in this device, when the engine temperature is high, a considerably low idle rotation speed is adjusted, and when the accelerator pedal is depressed at this time and the load suddenly increases, the rotation speed of the driver is increased. There is a drawback in that the transient characteristic deteriorates because it increases not only immediately upon request but only after a delay.

(C) Purpose Accordingly, the present invention has been made in order to solve such a drawback, and ensures smooth rotation of an internal combustion engine, and also lowers idle speed to reduce fuel consumption and idle rotation. An object of the present invention is to provide an idle speed control device for an internal combustion engine capable of improving the speed control characteristic.

In order to achieve such an object, the present invention provides, in an idle speed control device for an internal combustion engine in which an idle speed of the internal combustion engine is controlled, means for detecting a rotational smoothness or rotational fluctuation of the internal combustion engine; In the case of an Otto internal combustion engine, means for setting a target value of smoothness of rotation or rotational fluctuation in the idling state of the engine, comparison means for forming a difference between the target value and actual value of smoothness of rotation or rotational fluctuation, The fuel supply amount is controlled by controlling the air flow rate, and in the case of a diesel internal combustion engine, the fuel supply amount is adjusted to control the actual value to the target value, and the minimum and maximum idle speeds. Means for setting a value, and the control of the smoothness of rotation of the internal combustion engine to the set target value is performed only when the idling speed exceeds the minimum value and falls below the maximum value. In that case, the rotation speed is an idle rotation speed that is larger than the minimum value and smaller than the maximum value,
A configuration is adopted in which the rotational smoothness or the rotational fluctuation is adjusted to an idle rotational speed that reaches the set target value.

D) Embodiments The present invention will be described in detail below with reference to embodiments shown in the drawings.

The embodiment relates to an idle speed control device for an internal combustion engine, which measures rotational smoothness and performs control to a predetermined target value of rotational smoothness. With this control device, the idle speed can be significantly reduced, which plays a major role in reducing fuel consumption. In city driving, for example, by reducing the idle speed by 100 rpm, the fuel consumption can be saved up to 2%. That is, the fuel consumption in city driving becomes the average fuel consumption in the stopped state of the vehicle (the engine is rotating) and the traveling state of the vehicle (the engine is also rotating). Since the fuel consumption when the engine is rotating increases as the rotation speed increases, the fuel consumption in city driving can be reduced by lowering the idle rotation speed as described above. On the other hand, according to the present invention, when the rotational fluctuation (non-uniformity) exceeds a predetermined value, the amount of the air-fuel mixture is increased again. In the case of a gasoline engine, this is done by opening the throttle valve or opening the bypass cross-section, while in the case of a diesel engine this is done by increasing the fuel.

Fig. 1 shows an external ignition internal combustion engine (gasoline engine) 10
Is shown with the controller. Reference numeral 11 indicates an intake pipe, and reference numeral 12 indicates an exhaust pipe. An air flow sensor 13, a throttle valve 14, and an injection valve 15 are provided in the intake pipe 11. Throttle valve
14 is bypassed by a bypass pipe 16, and a bypass cross-sectional area adjuster (hereinafter abbreviated as bypass adjuster) 17 is provided in the bypass pipe 16. Reference numeral 20 is attached to the electronic control unit. The input signals of the electronic control unit 20 are signals from the temperature (θ) sensor 21, the rotation speed (n) sensor 22 and the air flow rate sensor 13, and are also output signals of the control unit 20 as indicated by two arrows. Other signals that have an effect are input signals. The output of the electronic control unit 20 is connected to at least one injection valve and also to the bypass regulator 17. The throttle valve 14 is directly operated by the accelerator pedal 24. When electronically controlling the angle of the throttle valve 14, the bypass controller 17 may be unnecessary, and in that case, the electronic controller 20 is used.
Changes the angle of the throttle valve 14 directly via the control line 25 indicated by the dotted line. Also, ignition timing control is performed via the control line 23.

The basic structure of the internal combustion engine control shown in FIG. 1 is the same as the conventional structure. The electronic control unit 20 controls the injection amount signal for controlling the injection valve 15 on the basis of the load and the rotation speed, and the correction data such as the temperature of the cooling water, and the bypass controller.
A control signal for controlling 17 is formed.

What is important here is that a signal indicating the rotational smoothness or a rotational fluctuation (non-uniformity) signal is generated in the electronic control unit 20, and the bypass controller 17 or the throttle valve 14 is associated therewith.
Is to be controlled. When the smoothness decreases, the air flow rate in the intake pipe 11 increases due to the control described above, which is detected by the air flow rate sensor 13 and the injection amount is increased. That is, in the embodiment of the present invention, when the rotation fluctuation (nonuniformity) is too large, the fuel supply amount signal is not directly changed, but the air amount signal is first changed, and the fuel supply amount is adjusted based on the change. Therefore, the air-fuel mixture amount is changed.

Further, the control device of the present invention will be described with reference to FIGS. 2 and 3.

In the case of an Otto engine, fluctuations in energy conversion during idling operation are very closely related to ambient conditions such as engine temperature, air temperature, air flow rate and the like. As the rotation speed decreases, this fluctuation value, that is, the fluctuation of the engine rotation increases non-linearly as shown in FIG. In FIG. 2, as an example, the cooling water temperature θ1,
The rotation smoothness (LU) when θ2 and θ3 (note that the temperatures are in the relationship of θ1 <θ2 <θ3) is different is shown.
Note that the rotational smoothness means “the degree that the engine rotational fluctuation is within a predetermined range and the engine is rotating smoothly, that is, uniform without fluctuation”, and when the rotational fluctuation becomes large (small), It can be seen that the rotation smoothness is inversely related to the rotation fluctuation because the rotation smoothness becomes smaller (greater). In Fig. 2, the smoothness is small in the upper part, and as a result, in particular, the formation and distribution of the air-fuel mixture is deteriorated and the ignition conditions are deteriorated. As a result, the rotational fluctuation increases as the temperature decreases, and the rotational smoothness is increased. You can see that it will be smaller.

The idle speed control in the case of the configuration of FIG. 1 is performed as follows with reference to FIG. The temperature dependence of the rotational smoothness on the rotational speed shown in FIG. 2 is obtained by physical characteristics and is experimentally obtained.

Its actual value is measured to control the rotational smoothness,
When the rotational smoothness (rotational fluctuation) is equal to or more than (or less than) the target value LUsoll compared with the target value LUsoll (for example, point a in FIG. 2), the air supplied to the internal combustion engine in order to eliminate the deviation. The amount is reduced and vice versa. As a result, the idle speed is determined according to the engine temperature at that time according to the characteristics shown in FIG. In the present invention, the maximum idle speed (nLmax) and the minimum idle speed (nLm)
control of the smoothness of rotation becomes effective in the range of (in), but when the rotation speed falls within this range at the point a, the fluctuation of rotation becomes smaller than the target value (the smoothness of rotation becomes larger than the target value), and the fluctuation of rotation becomes Since the amount is small (the rotation smoothness is sufficient), the air supply amount is reduced and the rotation smoothness is adjusted to the target value LUsoll. In this case, assuming that the engine temperatures are the same, the idle speed nL1 determined by the point b is obtained, while when the engine temperature increases (θ1 to θ2), the smoothness of rotation is still insufficient. As such, the air supply is further reduced. In this case, the engine speed further decreases from nL1 to the idle speed nL2 along the characteristic of θ2 so that the target value of the same rotational smoothness is obtained (point c).

When the learning function is used in the electronic control unit 20,
At the time of each idling control, it is not always necessary to start from the point a, and the rotation speed obtained in the preceding idling state is stored, and this value is used as the data of the new starting point in the subsequent idling control.

When the engine speed is low, for example, when the accelerator pedal is depressed and a load is applied, the load suddenly increases, so the engine speed decreases, but if the speed before the load is too low, the speed will decrease. There is a delay in increasing. In a special case, for example, after running for a long time at full load, if the air supply amount is reduced too much to adjust the rotational smoothness to the target value, the engine speed becomes too low, and the engine becomes Inhalation becomes impossible, and the above-described problem occurs, that is, the rotational speed increases not only immediately but at a delay in response to the driver's request, and the transient characteristic deteriorates. This problem can be solved by introducing the minimum idle speed nLmin. This minimum idle speed is set to a speed value required to increase the engine speed without noticeable delay even when the load suddenly increases, and the value is determined based on experimental results. This means that the idle speed is controlled in a region between its minimum and maximum values, in which case a predetermined target value of the rotational smoothness is taken into consideration.

FIG. 3 shows a modification of the operating method of the idle speed control shown in FIG. This control is a combination of control of the air-fuel mixture amount or air-fuel mixture concentration and the number of revolutions, and is extremely preferable because it can reduce the emission of harmful substances such as carbon monoxide (CO) during the warm-up operation of the engine. FIG. 3 shows two different cooling water temperatures θ.
1, θ2 and two different concentrations of carbon monoxide (CO) in the exhaust gas of 0.5% and 2% (this concentration is determined by the mixture composition of fuel and air), idle speed nL and rotational smoothness The LU relationships are shown. Points a to d indicate points where the idle speed control is performed. In the idle speed control, first, a relatively rich mixture composition (for example, the carbon monoxide concentration becomes 2%) is used. At this time, if the cooling water temperature is θ1, the idle speed control starts at point a. In this state, the rotation smoothness is sufficient, and the rotation speed may be decreased, so that the rotation speed is reduced to the point b along the central curve shown in the figure by adjusting the air flow rate or the fuel supply amount. Therefore, the target value LUsoll of the predetermined idle speed and the smoothness of rotation is reached. Then, the air-fuel mixture composition is diluted (for example, the carbon monoxide concentration becomes 0.5%), and the idle speed is changed while maintaining the target value of the rotational smoothness. At this time, when the cooling water temperature is the same θ1, the rotation speed becomes the point c, while the cooling water temperature is θ2.
When it changes to, the rotation speed at the point d is controlled.

In the case of idle speed control of a diesel internal combustion engine, control of smoothness of rotation is performed in association with a control circuit that adjusts a member that controls a fuel supply amount. Since the diesel engine is usually driven by excess air, changing the air-fuel mixture amount in the case of a gasoline engine corresponds to the characteristic by changing the injection amount in the case of a diesel engine.

The method for detecting the rotation fluctuation is, for example, the measurement of the rotation time T of the crankshaft, the fluctuation of the rotation time or the differential coefficient, and the like.
That is, the smoothness of rotation is detected.

It is of course also possible to realize the invention by corresponding programming of a computer, ie purely in software, in connection with the computer control commonly used today in connection with motor vehicles. FIG. 4 is a block circuit diagram showing the configuration for realizing the functions of the present invention.

Reference numeral 30 indicates a rotation fluctuation detection circuit, and reference numerals 31 and 32 indicate signal generators that give the maximum value nLmax and the minimum value nLmin of the idle speed, respectively. 33 is a target value (LU) of smoothness that can be changed by an external input (for example, temperature θ).
The target value generator 34 generates a target value λsoll of the lambda value (excess air ratio). The target value and the actual value of the rotational smoothness are compared by the comparator 36, and the comparison result is finally guided to the bypass controller 17 via a plurality of circuits. Among the plurality of circuits described above, the maximum value selection circuit 38 allows the rotation smoothness control to be performed only in the rotation speed region larger than the minimum idle rotation speed, and the minimum value selection circuit 39 limits the upper limit of the idle rotation speed. It Still another maximum value selection circuit 40
This enables the lambda control to change the lambda value corresponding to that shown in FIG.

In FIG. 4, the rotation fluctuation detection circuit 30 outputs the actual value of the smoothness of rotation or the fluctuation of rotation by the method described above, while
A target value LUsoll of the rotational smoothness is generated by the target value generator 33, and this target value is compared with the actual value of the rotational smoothness detected by the rotation fluctuation detection circuit 30 by the comparator 36,
An output signal that drives the bypass regulator 17 is formed. With these devices 30, 33, 36, a configuration for controlling the rotational smoothness to a set target value can be obtained. In order to limit the control of the smoothness of rotation according to the number of revolutions, the signal generators 31, 32, 32,
A maximum value selection circuit 38 and a minimum value selection circuit 39 are used.

First, in FIG. 2, when the temperature is θ1 and the idle speed is at the point a, the rotation smoothness detected by the rotation fluctuation detection circuit 30 is larger than the target value LUsoll,
By the output of the comparator 36, the bypass controller 17 is driven, the air flow rate is reduced, and the rotation speed nL1 at the point b is adjusted. When the temperature becomes high (from θ1 to θ2), since the rotation smoothness is still sufficient, similarly, the bypass controller 17 is driven by the output signal from the comparator 36, and the rotation speed is further reduced to nL2 (point c). In that case, the idle speed is limited between the minimum value nLmin and the maximum value nLmax by the maximum value selection circuit 38 and the minimum value selection circuit 39, respectively. In this case, the switches 41 and 42 are opened and the switch 43 is closed, so that the maximum value selection circuit 40 does not function.

In the case of the embodiment shown in FIG. 3, since the air-fuel mixture is rich at point a and the rotation smoothness is present, the same control as in FIG. 2 is performed, and the rotational speed decreases to reach point b. After that, the switch 43 is opened (the switches 41 and 42 are still open) in order to make the air-fuel mixture lean (the carbon monoxide concentration is changed from 2% to 0.5%). At this time, the lambda target value generator 34
A signal is generated that represents the air flow rate required to produce a lean mixture, which causes the mixture to become lean (eg, shift to the curve of θ1, CO = 0.5% or θ2, CO = 0.5% in Fig. 3). To). When the curve shifts to θ1 and CO = 0.5%, the rotation smoothness decreases, so the rotation speed is increased, but the minimum value selection circuit 39 limits it to nLmax and the idle rotation speed is adjusted to nLmax. (Point c). On the other hand, the temperature θ
In the case of 2, since the rotation smoothness is large, the rotation speed is reduced until it reaches the rotation speed nL2 (point d).

Each minimum and maximum selection circuit can be shorted by switches 41-43 as shown by the dotted line,
As a result, it can be selectively used according to the needs of each selection circuit.

The rotation fluctuation detection circuit 30 of FIG. 4 is substantially composed of a differentiator, and as described above, detects the fluctuation of the crankshaft rotation time to detect the rotation smoothness. The maximum value (minimum value) selection circuit is configured by a circuit that compares the magnitudes of the input signals with a comparator and switches the switch to select the large (small) value of the input signals. For other circuit blocks, if the principle of the present invention is understood, there is no problem for those skilled in the control circuit field to realize the other circuit blocks, and therefore detailed description thereof will be omitted.

(E) Effect As described above, in the present invention, the idling speed can be further reduced by controlling the rotational smoothness of the internal combustion engine when the rotational smoothness is large (the rotational fluctuation is small). Therefore, it becomes possible to reduce the combustion consumption. Further, since this rotation smoothness control is performed when the idle speed exceeds the minimum value, the idle speed is prevented from decreasing below the minimum value, and the accelerator pedal is depressed to suddenly increase the load. Even in such a case, the rotation speed can be increased without delay and the transient characteristics can be improved. Further, since the maximum value of the idle speed for performing the smoothness control is set, it is possible to prevent the idle speed control from being delayed without deteriorating the control characteristics even when returning to the idle speed region again. .

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram for explaining the configuration of an internal combustion engine and a control device to which the present invention is applied, and FIGS. 2 and 3 are each for explaining the control operation according to the present invention. FIG. 4 is a block circuit diagram showing an example of a circuit configuration for realizing the function of the present invention. 10 …… Internal combustion engine, 11 …… Intake pipe 13 …… Air flow sensor, 14 …… Throttle valve 15 …… Injection valve, 16 …… Bypass pipe 17 …… Bypass cross-sectional area regulator 20 …… Electronic control unit, 21 Temperature sensor 22 Rotation speed sensor 30 Rotation fluctuation detection circuit, 31, 32 Signal generator 33 Target value generator 34 Lambda target value generator 38, 40 Maximum value selection Circuit, 39 ... Minimum value selection circuit

Claims (2)

[Claims] 1. An idle speed control device for an internal combustion engine in which the idle speed of the internal combustion engine is controlled, a means for detecting a smoothness of rotation or a fluctuation of the rotation of the internal combustion engine, and a smoothness of rotation for the idling state of the internal combustion engine. Fuel supply by means of setting the target value of rotational fluctuation, comparison means for forming the difference between the target value and actual value of rotational smoothness or rotational fluctuation, and in the case of an Otto type internal combustion engine, controlling the air flow rate The amount of fuel, and in the case of a diesel internal combustion engine, means for controlling the actual value to the target value by adjusting the amount of fuel supply, and means for setting the minimum and maximum idle speeds. , The control of the rotational smoothness of the internal combustion engine to the set target value is performed only when the idle speed exceeds the minimum value and falls below the maximum value, and in that case, the rotation speed is the minimum value. Ri large with a small idle speed than the maximum value,
An idle speed control device for an internal combustion engine, wherein the smoothness of rotation or fluctuation of rotation is adjusted to an idle speed that reaches the set target value. 2. The idle speed of an internal combustion engine according to claim 1, wherein the control of the air flow rate is performed by adjusting a throttle valve or a bypass section that bypasses the throttle valve. Control device.