JP3303614B2 - Idle speed control device for internal combustion engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an idle speed control device for an internal combustion engine.

[0002]

2. Description of the Related Art A conventional internal combustion engine idling speed control apparatus detects a rotation speed of an internal combustion engine, and according to a deviation from a target rotation speed, an air amount, a fuel amount, and an ignition timing supplied to the internal combustion engine. Is known to stabilize the rotational speed of the internal combustion engine near the target rotational speed (for example, Japanese Utility Model Application Laid-Open No. 56-165962).

[0003] This device is intended to suppress the fluctuation of the rotation of the internal combustion engine caused by disturbances (load of auxiliary equipment, variation in combustion, etc.) by making use of the features of the respective operation amounts. That is, the operation of the amount of air supplied to the internal combustion engine (generally, the operation of the opening degree of the auxiliary air valve interposed in the bypass passage that bypasses the throttle valve) or the operation of the amount of fuel supplied is
Although it has excellent ability to constantly suppress the influence of disturbance,
Because the delay until the operation is reflected as a change in the rotation speed of the internal combustion engine is large, it is used to suppress the influence of steady disturbance, while the ignition timing operation generally uses the basic ignition timing as the MBT (maximum torque). However, there is a disadvantage that the operating range is narrow because it is set near (ignition timing at which
Since the delay before the ignition timing operation appears as a change in the rotational speed of the internal combustion engine is small, the method is used to transiently suppress disturbance.

There is also known a method in which when the rotational speed of the internal combustion engine is reduced, the drop in rotation is reduced by manipulating the amount of air supplied to the internal combustion engine or temporarily increasing the amount of supplied fuel (see, for example, Japanese Patent Application Laid-Open No. HEI 4-1992). No. 31494).

[0005]

However, in such an idle speed control device for an internal combustion engine,
When the throttle valve is momentarily opened by depressing the accelerator pedal during idle speed control, and then the throttle valve is closed (hereinafter, this operation is referred to as "choice stepping"),
Drivability could be deteriorated as follows.

[0006] Generally, the idle speed control is executed when the following conditions are satisfied. [Condition 1] The throttle opening is minimum. [Condition 2] The engine speed is equal to or lower than a predetermined value. Therefore, as shown in FIG. 3, when the stepping is performed at the point A, the idle rotation speed control is executed up to the point A (idle control ON), and the idle rotation speed is temporarily set between the points A and B. Pause control (idle control OFF), point B
Thereafter, the idle speed control is restarted.

In this case, when the throttle valve is opened between the points A and B, the air flowing into the collector temporarily increases, and accordingly, the engine speed increases with a certain delay. Then, since the idle speed control is performed between the points B and C, the auxiliary air valve is operated to the closing side so that the engine speed converges to the target speed. Here, since the auxiliary air valve is generally operated so as to suppress the steady disturbance, the auxiliary air valve is operated to the closed side even at the point C where the engine rotation speed reaches the target rotation speed. Become. Therefore, after point C, the amount of air supplied to the internal combustion engine becomes insufficient, and the engine speed may drop below the target speed.

[0008] In the conventional idle speed control device, there is a fear that the driving performance may be degraded when stepping on the choi. Further, according to the method disclosed in JP-A-4-31494, since the operation amount is controlled only after the engine speed is reduced, it is not possible to prevent the engine speed from decreasing when the driver steps on the vehicle. Was. SUMMARY OF THE INVENTION The present invention has been made in view of the above-described conventional problems, and has as its object to prevent a decrease in engine speed after a stepping on idling speed control.

[0009]

Therefore, according to the first aspect of the present invention, as shown in FIG. 1, a condition for performing idle speed control so as to maintain the speed of the internal combustion engine at the target speed is determined. An idle speed control condition determining means for determining whether or not the idle speed control condition is satisfied, and a rotational speed feedback control for calculating and operating an operation amount of the internal combustion engine so that the rotational speed converges to the target speed when the idle speed control condition is determined. A throttle opening detecting means for detecting a throttle opening, and an accelerator pedal based on idle speed control conditions.
Momentarily step on the dal and the throttle valve opens momentarily
Perform the choise operation to close, and again idle speed control
Assuming that idle speed control is started after returning to control conditions
At the start of idle speed control
A target for calculating a correction amount of the target rotation speed at the start of the idle rotation speed control in accordance with past throttle opening information corresponding to the chopping operation by the throttle opening detecting means so as to increase and correct the rotation speed. A rotational speed correction amount calculating means and a target rotational speed calculating means for calculating a target rotational speed according to the correction amount by the target rotational speed correction amount calculating means are provided.

That is, a target rotation speed at the time of idling rotation speed control is generated in consideration of the influence of the past throttle operation, and then the actual rotation speed is feedback-controlled to the target rotation speed. As a result, it is possible to avoid excessive operation (excessive closing of the auxiliary air valve between points B and C in FIG. 3) caused by feedback control of the actual rotation speed to the set rotation speed after stepping on the choi. As a result, it is possible to smoothly converge the engine rotation speed to the set rotation speed without deteriorating drivability due to excessive operation (without lowering the engine rotation speed) (see FIG. 4).

[0011] In the invention according to claim 2, wherein the target rotation speed correction quantity calculation device, the idle rotational speed control before the start of the previous
The correction amount is calculated based on at least one of the throttle opening time and the throttle opening within a predetermined time corresponding to the time of the chopping operation . Thus, the correction amount can be easily calculated. In the invention according to claim 3, the target rotational speed correction amount calculating means is similar to a rotational blow-up after a chopping operation.
A first model (m1) describing characteristics from the throttle opening to the engine speed so that the input value of the first model (m1) is determined by the throttle opening detected by the throttle opening detecting means. The correction amount is calculated based on the output value of the first model (m1) at this time.

As described above, the rotational blowing after the choking operation is performed.
By using the first model (m1) describing the characteristic from the throttle opening to the engine speed in a manner similar to the rise, the engine speed rise amount (target rotation speed correction amount) due to the influence of the past throttle operation. Can be calculated with high accuracy. Accordingly, the difference between the actual rotation speed and the target rotation speed is reduced, and the operation of the auxiliary air valve and the like can be almost eliminated during the chop step operation (between points B and C in FIG. 4). It is possible to reduce fluctuations in engine speed due to operation of an air valve or the like.

[0013] In the invention according to claim 4, the target rotational speed correction amount calculating means determines that the rotational speed after the chopping operation is increased.
A target rotation speed that is set according to a first model (m1) describing characteristics from the throttle opening to the engine rotation speed in a manner similar to that of the first rotation speed and that does not fall below the set rotation speed is generated.
A second model (m2) capable of causing no overshoot and having an input value of the second model (m2) as a throttle opening detected by the throttle opening detecting means. The correction amount is calculated based on the output value of m2).

When the first model (m1) having the overshoot characteristic is used, the target rotation speed may be lower than the set rotation speed, so that the actual rotation speed may be lower than the target rotation speed due to the rotation speed feedback action. (See FIG. 11). Therefore, the second model (m) that does not cause overshoot and is designed based on the first model (m1)
By using 2), a target rotation speed that does not cause overshoot (does not fall below the set rotation speed) is generated. This makes it difficult for the engine rotation speed to fall below the set rotation speed (see FIG. 11).

[0015] In the invention according to claim 5, the target rotational speed correction amount calculating means is configured to determine that the rotational speed after the chopping operation is increased.
The lower limit of the output value of the first model (m1) describing the characteristics from the throttle opening to the engine speed in a manner similar to
0 is provided, and the output value of the third model (m3) is obtained when the input value of the third model (m3) is the throttle opening detected by the throttle opening detecting means. The correction amount is calculated based on

As described above, by using the third model (m3) in which the lower limit value 0 is provided for the output value of the first model (m1), an effect equal to or more than the case of using the second model (m2) can be obtained. It is possible to realize the correction amount calculation more reliably and more easily.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments (examples) of the present invention will be described below. FIG. 2 is a system diagram. Internal combustion engine 1
Has a combustion chamber 5 defined by a cylinder head 2, a cylinder block 3 and a piston 4. The combustion chamber 5 is connected to an intake passage 7 via an intake valve 6, and also via an exhaust valve 8. An exhaust passage 9 is connected. In this example, a four-cycle four-cylinder reciprocating engine is used.

A throttle valve 10 which opens and closes in conjunction with an accelerator pedal is interposed in the intake passage 7 to control the amount of intake air. Further, a bypass passage 11 that bypasses the throttle valve 10 is provided, and an electromagnetic auxiliary air valve 12 is interposed in the bypass passage 11.
The auxiliary air valve 12 is an engine control unit (hereinafter referred to as E).
The opening degree is adjusted by a duty signal from a CU (referred to as CU) 15 to control the amount of auxiliary air (≒ the amount of intake air during idling).

An electromagnetic fuel injection valve 13 is provided for each cylinder in the intake passage 7, specifically, a branch portion of the intake manifold.
Is provided, and injects and supplies an amount of fuel instructed at a predetermined timing synchronized with the engine rotation by a drive pulse signal from the ECU 15. An ignition plug 14 is provided to face the combustion chamber 5, and operates via an ignition coil (not shown) according to a signal from the ECU 15, and the air-fuel mixture in the combustion chamber 5 is instructed at a specified timing. Ignite.

Auxiliary air valve 12, fuel injection valve 13 and spark plug 14
For the control, signals are input to the ECU 15 from various sensors. The various sensors include an intake passage 7
Is provided with a hot wire type air flow meter 16 for detecting an intake air flow rate QA. Also,
A crank angle sensor 17 that generates a reference signal for each predetermined rotation of the crankshaft is provided, and the engine speed NE can be calculated from the cycle of the reference signal. In this example, a camshaft type crank angle sensor is used for each combustion (crank angle 180 °).
°).

The throttle valve 10 includes a potentiometer type throttle sensor 18 as a throttle opening detecting means.
Is installed, which allows the throttle opening TVO
Is detected. Further, a water temperature sensor 19 is provided facing the water jacket of the cylinder block 3,
As a result, the engine cooling water temperature TW is detected.

Further, an O ₂ sensor
20 is provided, which outputs a signal corresponding to the oxygen concentration in the exhaust gas which is closely related to the air-fuel ratio (rich / lean) of the engine intake air-fuel mixture. Here, the ECU 15
Performs control according to a control routine shown in FIG.
Note that this control routine is executed every 10 ms.

A description will be given in accordance with the control routine of FIG. In step 1 (indicated as S1 in the figure, the same applies hereinafter)
Each combustion (crank angle 1
The cycle measurement value TREF of the reference signal output every 80 °)
Based on (s), the engine speed NE is calculated from the following equation. NE = 30 / TREF In step 2, according to the past throttle opening information,
The correction amount of the target rotation speed during the idle rotation speed control is calculated. This part corresponds to a target rotation speed correction amount calculating means.

Hereinafter, the method of calculating the correction amount of the target rotation speed in step 2 will be described in detail. First, a method of calculating the correction amount of the target rotation speed according to the invention according to claim 2 is shown in FIG.
This will be described with reference to the flowchart of FIG. Based on the signal from the throttle sensor, the throttle opening TVO (t) is sequentially A / D converted and read, and the data up to Tm (s) is stored in the memory (step 11).

It is determined whether or not the condition is the idling speed control condition (step 12).
After the control condition is satisfied, it is determined whether or not it is the first time (step 13),
If it is the first time, the throttle opening TVO (t) from Tm (s) to the present time is added to calculate an added value sumTVO (step 14), and the initial correction of the target rotation speed according to the added value sumTVO is performed. The quantity y0 is determined with reference to the table of FIG. 7 (step 15).

If the elapsed time after the start of the control is T (s) during the idle rotation speed control, it is initially 1 in accordance with the T, and gradually decreases with time and finally decreases. Is set to a coefficient k which becomes 0 (step 16).
Then, from the initial correction amount y0 and the coefficient k,
The correction amount NEplus of the target rotation speed is calculated (step 1).
7).

NEplus = y0 × k More specifically, as shown in FIG. 8, when the elapsed time from the start of the idle rotation speed control is T, if T <T1, the correction amount NEplus = y0, and T ≧ T At T1, the correction amount NEplus is reduced by y0 / 3, and thereafter, every time T2 elapses, the correction amount NEplus is reduced by y0 / 3, and finally the correction amount NEplus = 0.

Here, T1, T2, and Tm are set such that the correction amount of the target rotation speed is similar to the rotation speed after the stepping on the choi. As an example, T1 = 1s, T2
= 0.2 s and Tm = 1 s. Here, an example is shown in which the correction amount of the target rotation speed is calculated in accordance with the throttle opening addition value (throttle opening time and throttle opening) before the start of the idle rotation speed control Tm (s). The correction amount of the target rotation speed may be calculated according to the throttle opening time Tm (s) before the start of the speed control or the maximum value of the throttle opening.

Next, a method of calculating the correction amount of the target rotation speed according to the third aspect of the present invention will be described (see the flowchart of FIG. 9). The ECU includes a model m1 in which the characteristic from the throttle opening of the internal combustion engine to the engine speed is approximated by the following cubic expression and dead time. Sampling time is 10ms
And q is a 10 ms advance operator.

M1 (q) = [(b0 × q ² + b1 × q + b2) /
^{(A1 × q 3 + a2 ×} q 2 + a3 × q + a4) ] × q ^-n1 where reads and sequentially A / D converts the throttle opening TVO (t) on the basis of a signal from a throttle sensor (step 21) . Then, the target rotation speed correction amount NEplus = y2
If (t) is set, the correction amount y2 (t) is calculated according to the following equation (step 22).

Y2 (t) = m1 (q) .times.TVO (t) Since m1 (q) is a commonly used time-synchronous digital filter, a detailed description of its operation and its realization is omitted. Next, a method of calculating the correction amount of the target rotation speed according to the invention according to claim 4 will be described (see the flowchart of FIG. 9).

The ECU is provided with a model m2 of the following formula having characteristics similar to those of the model m1 (especially, transfer characteristics are similar particularly in a low frequency range) and not causing overshoot (see FIGS. 10 and 11). ). The sampling time is 10 ms. q is a 10 ms advance operator. m @ 2 (q) = ^{[(d0 × q 2 + d1 ×} q + d2) / (c1 × q 3 +
c2 × q ² + c3 × q + c4)] × q ^{−n2 As} the model m2, a low-dimensional model thereof may be used instead of the above equation.

Here, the throttle opening TVO (t) is sequentially A / D converted and read based on the signal from the throttle sensor (step 21). Then, the target rotation speed correction amount N
When Eplus = y3 (t), the correction amount y is calculated according to the following equation.
3 (t) is calculated (step 22). y3 (t) = m2 (q) × TVO (t) Next, a method of calculating the correction amount of the target rotation speed according to the invention of claim 5 will be described (refer to the flowchart of FIG. 9).

The ECU includes a model m3 in which the output value of the model m1 has a lower limit value 0. Here, based on the signal from the throttle sensor, the throttle opening TVO (t)
Are sequentially A / D converted and read (step 21). And
When the target rotational speed correction amount NEplus = y4 (t), the correction amount y4 (t) is calculated according to the following equation (step 2).
2).

Y4 (t) = max (m1 (q) × TVO (t), 0) That is, by selecting and outputting the larger one of m1 (q) × TVO (t) and 0, A lower limit of 0 is provided. FIG.
Return to and continue the explanation. In step 3, it is determined whether or not an idle rotation speed control condition is satisfied. It should be noted that whether or not the condition is the idle speed control condition is determined as the idle speed control condition at least when the throttle valve is fully closed, based on the state of the throttle opening, the engine speed, the vehicle speed, and the like. This part corresponds to idle speed control condition determination means.

In the case of the idling rotational speed control condition, the routine proceeds to step 4, where the set rotational speed NEset and the correction amount NEpl
The target rotation speed NEtgt = NEset + N as the sum with us
Calculate Eplus. This part corresponds to a target rotation speed calculating means. The set rotational speed NEset at the time of idling rotational speed control is set by referring to a map according to the state of the engine cooling water temperature TW, the engine load (air conditioner signal), and the like.

When the set rotational speed is changed due to the change in the state, the set rotational speed is dynamically compensated so that the set rotational speed before the change and the set rotational speed after the change are continuously connected. It is determined. FIG. 12 shows a generation example of the target rotation speed when the change of the set rotation speed and the correction of the target rotation speed are performed simultaneously. If the condition is the idling rotational speed control condition, the process proceeds to step 5, and the idling feedback control, that is, the feedback control of the supplied air amount, the supplied fuel amount, the ignition timing, etc., is performed so that the rotational speed converges to the target rotational speed. I do. This part corresponds to the rotational speed feedback control means.

The supply air amount is controlled as follows. After setting the basic duty to the auxiliary air valve according to the engine cooling water temperature TW and the like, the actual rotation speed NE and the target rotation speed NE are set.
The duty is corrected so that the actual rotation speed NE converges to the target rotation speed NEtgt in accordance with the deviation from tgt, and the opening of the auxiliary air valve is controlled. Specifically, for example, when the actual rotation speed NE is lower than the target rotation speed NEtgt, the duty is corrected in the direction in which the opening degree of the auxiliary air valve increases.

The control of the supplied fuel amount is performed as follows. From the intake air flow rate QA detected by the air flow meter and the rotational speed NE, the basic fuel injection amount TP = K × QA / NE
(K is a constant), and a correction such as a water temperature increase correction based on the engine cooling water temperature TW and an air-fuel ratio feedback correction based on a signal from the O ₂ sensor is added thereto to calculate a final fuel injection amount TI. A drive pulse signal having a pulse width corresponding to TI is output to the fuel injection valve. The above is the same as the normal fuel injection amount control, except that the air-fuel ratio is kept constant by the amount by which the opening degree of the auxiliary air valve is increased or decreased according to the deviation between the actual rotation speed NE and the target rotation speed NEtgt. The fuel injection amount is increased or decreased. However, in order to compensate for the detection delay of the intake air flow rate by the air flow meter, the actual rotational speed NE and the target rotational speed N
If the fuel injection amount is transiently corrected according to the deviation from Etgt, the idle speed control becomes better.

The control of the ignition timing is performed as follows. After setting the basic ignition timing according to the engine rotational speed NE and the basic fuel injection amount TP, the actual rotational speed NE and the target rotational speed N
The ignition timing is corrected so that the actual rotational speed NE converges to the target rotational speed NEtgt in accordance with the deviation from Etgt. Specifically, for example, the actual rotation speed NE is changed to the target rotation speed NEtg.
If it is lower than t, the ignition timing is corrected in the advance direction (output increase direction).

If the condition is not the idle speed control,
Proceeding to step 6, non-idle control is performed. With respect to the supply air amount, a basic duty to the auxiliary air valve is set according to the engine cooling water temperature TW and the like, and is controlled based on this. For the supplied fuel amount, normal fuel injection amount control is performed.

Regarding the ignition timing, the basic ignition timing is set according to the engine speed NE and the basic fuel injection amount TP,
Control is performed based on this.

[0043]

As described above, according to the first aspect of the present invention, considering the influence of the past throttle operation,
This is caused by generating the target rotation speed during idle rotation speed control and then performing feedback control of the actual rotation speed to the target rotation speed, and then performing feedback control of the actual rotation speed to the set rotation speed after stepping on the choi. Excessive operation such as excessive closing of the auxiliary air valve can be avoided, and as a result, the engine rotational speed smoothly converges to the set rotational speed without deteriorating drivability due to excessive operation (without lowering the engine rotational speed). The effect is obtained.

According to the second aspect of the present invention, the correction amount of the target rotation speed is calculated based on at least one of the throttle opening time and the throttle opening within a predetermined time before the start of the idle rotation speed control. The effect is obtained that the correction amount can be easily calculated. According to the third aspect of the invention, by using the first model (m1) describing the characteristics from the throttle opening to the engine speed,
The engine rotational speed increase (target rotational speed correction amount) due to the influence of the past throttle operation can be calculated with high accuracy. As a result, the difference between the actual rotational speed and the target rotational speed is reduced, and assistance is provided during the chop step operation. The operation of the air valve and the like can be almost eliminated, and as a result, the effect of reducing the engine speed fluctuation due to the operation of the auxiliary air valve and the like can be obtained.

According to the fourth aspect of the present invention, by using the second model (m2) having no overshoot designed based on the first model (m1), no overshoot occurs (set rotation). It is possible to generate the target rotation speed (which does not fall below the speed), and it is possible to obtain the effect that the engine rotation speed does not easily fall below the set rotation speed. According to the invention according to claim 5, by using the third model (m3) in which the lower limit value is provided for the output value of the first model (m1), the output value is equal to or greater than the case where the second model (m2) is used. The effect is obtained that the effect can be realized more reliably and the correction amount can be calculated more easily.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing a basic configuration of the present invention.

FIG. 2 is a system diagram showing an embodiment of the present invention.

FIG. 3 is a diagram illustrating a problem of the related art.

FIG. 4 is a diagram illustrating the operation of the present invention.

FIG. 5 is a flowchart showing a control routine in the ECU.

FIG. 6 is a flowchart illustrating an example of a target rotation speed correction amount calculation method;

FIG. 7 is a diagram showing an initial correction amount setting table;

FIG. 8 is a diagram illustrating an example of generating a target rotation speed correction amount.

FIG. 9 is a flowchart showing another example of the target rotation speed correction amount calculation method.

FIG. 10 shows a model characteristic.

FIG. 11 is a diagram showing control characteristics based on a model.

FIG. 12 is a diagram illustrating an example of generating a target rotation speed when the set rotation speed is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 10 Throttle valve 12 Auxiliary air valve 13 Fuel injection valve 14 Spark plug 15 ECU 16 Air flow meter 17 Crank angle sensor 18 Throttle sensor 19 Water temperature sensor 20 O ₂ sensor

Claims (5)

(57) [Claims] An idle speed control condition determining means for determining whether or not idle speed control is performed so as to maintain the internal speed of the internal combustion engine at a target speed, and an idle speed control condition is determined. A rotation speed feedback control means for calculating and operating an operation amount of the internal combustion engine so that the rotation speed converges to the target rotation speed. An idle speed control device for an internal combustion engine comprising: a throttle for detecting a throttle opening degree From the opening detection means and idle speed control conditions,
The throttle valve opens momentarily and then closes
Perform the depressing operation and return to the idle speed control condition again.
Assuming that idle speed control has started
Target rotation speed at the start of idle speed control
A target rotation speed correction for calculating a correction amount of the target rotation speed at the start of the idle rotation speed control according to the past throttle opening information corresponding to the time of the chopping operation by the throttle opening detecting means so as to increase the correction. An idle rotation speed control device for an internal combustion engine, comprising: an amount calculation unit; and a target rotation speed calculation unit that calculates a target rotation speed according to a correction amount by the target rotation speed correction amount calculation unit. 2. The method according to claim 1, wherein the target rotation speed correction amount calculating means calculates the target rotation speed correction amount during a time of the chopping operation before starting the idle rotation speed control.
2. The idle speed control device for an internal combustion engine according to claim 1, wherein a correction amount is calculated based on at least one of a throttle opening time and a throttle opening within a corresponding predetermined time. Wherein said target rotational speed correction quantity calculation device, Cho
A first model describing characteristics from the throttle opening to the engine rotation speed in a manner similar to the rotation up after the stepping operation , and inputting the input value of the first model to the throttle opening detection 2. The idle speed control device for an internal combustion engine according to claim 1, wherein a correction amount is calculated based on an output value of the first model when the throttle opening is detected by the means. Wherein said target rotational speed correction quantity calculation device, Cho
A target rotation which is set in accordance with the first model describing characteristics from the throttle opening to the engine rotation speed so as to be similar to the rotation up after the stepping operation, and does not fall below the set rotation speed
Can generate overspeed and overshoot
And a correction amount is calculated based on an output value of the second model when an input value of the second model is a throttle opening detected by the throttle opening detecting means. 2. The idle speed control device for an internal combustion engine according to claim 1, wherein: Wherein said target rotational speed correction quantity calculation device, Cho
A third model in which a lower limit value 0 is provided in an output value of the first model in which characteristics from the throttle opening to the engine rotation speed are described in a manner similar to the rotation up after the stepping operation ; The correction amount is calculated based on an output value of the third model when an input value of the third model is a throttle opening detected by the throttle opening detecting means. An idle speed control device for an internal combustion engine according to claim 1.