JP3239379B2 - Internal combustion engine speed control method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for controlling the rotational speed of an internal combustion engine.

[0002]

2. Description of the Related Art A cargo handling load acts on an internal combustion engine mounted on an industrial vehicle such as a forklift in addition to a running load. Therefore, in the internal combustion engine, when the running load fluctuates, not only the running is affected but also the cargo handling work is affected. Similarly, when the cargo handling load fluctuates, not only cargo handling work is affected, but also traveling is affected. Therefore, an internal combustion engine mounted on an industrial vehicle is required to have particularly high stability against load fluctuation.

In order to enhance stability against load fluctuations, a throttle, which is means for adjusting the rotation speed of the internal combustion engine, is set so that the rotation speed changed with the load fluctuations quickly returns to the original rotation speed (target rotation speed). It is necessary to adjust the valve to control the rotation speed.

For this purpose, the electronic governor device is used to determine a deviation between the current actual rotational speed changed by the load fluctuation and the target rotational speed, and a PID (proportional / integral) defining a gain value based on the deviation. PI for differential) control
D operation is being performed. Then, the target throttle valve opening which is the opening of the throttle valve for rotating at the target rotation speed is determined, and the rotation speed is controlled.

[0005] As shown in FIG. 4, the conventional electronic governor device 10 includes control parameters 11 A to 11 C, a switching control device 12, and a control operation device 13. The control operation device 13 inputs the target rotation speed stored in the memory and the actual rotation speed at the present time changed by the fluctuation of the load, and receives one of the control parameters 11A to 11C via the switching control device 12. PID calculation is performed based on a PID control calculation formula for defining a gain value in the input PID calculation, and a target throttle valve opening which is a throttle valve opening for rotating the internal combustion engine at a target rotation speed is determined. And output it.

The control parameters 11A to 11C are PI
It is composed of a memory in which D control arithmetic expressions are stored. There are three control parameters, 11A to 11C,
As will be described later, this is for correcting the non-linearity of the torque / throttle valve opening characteristic of the internal combustion engine.

[0007] The switching control device 12 inputs the current throttle valve opening changed by the load fluctuation, switches and selects control parameters 11A to 11C corresponding to the throttle valve opening, and controls the control arithmetic device 1.
3 is output.

By the way, the torque / throttle valve opening characteristic of the internal combustion engine has a non-linearity as shown by a curve α in FIG. 5 in which the torque does not increase linearly with the throttle valve opening when the rotational speed is constant. Show.

That is, the throttle valve opening Pa, P
b, the slope of the curve α greatly changes, and the throttle valve opening is smaller than the area A where the throttle valve opening is Pa or less.
In the region B equal to or more than Pb, the torque greatly changes with a slight change in the throttle valve opening. Also,
In a region C where the throttle valve opening is equal to or more than Pb and equal to or less than the maximum throttle valve opening Pc, a corresponding change in torque does not appear unless the throttle valve opening greatly changes as compared with the region A.

For this reason, for example, if a PID control calculation formula is obtained from the torque / throttle valve opening characteristics in the region A and the PID calculation is performed for all the regions A to C, the PID control is performed in the region C. Is insufficient, and in the region B, the gain becomes over-gain. In the region C where the gain is insufficient, it takes a long time to reach the target rotation speed from the current rotation speed.
Further, in the over-gain region B, the rotation speed rapidly rises to (or falls below) the target rotation speed and then converges to the target rotation speed while increasing or decreasing the rotation speed. In any case, in the areas B and C where the gain values are not optimal, the required stability against the load fluctuation cannot be obtained.

Therefore, PID control arithmetic expressions corresponding to the respective areas A to C are obtained in advance by an experiment in which the internal combustion engine is tested on an engine bench, and the respective PID control arithmetic expressions are determined by the respective control parameters 11A. ~ 11
It is stored as C. Then, the switching control device 12
Thus, the control parameters 11A to 11C corresponding to the current throttle valve opening are appropriately selected and output.
PID of the selected control parameter 11A-11C
Based on the control calculation formula, the control calculation device 13 calculates and outputs the target throttle valve opening.

Thus, conventionally, the torque / torque of the internal combustion engine
By using a plurality of PID control arithmetic expressions corresponding to changes in the gradient of the throttle valve opening characteristic, an optimal gain value in which the non-linearity has been corrected is determined, and an arithmetic operation for PID control is performed.

As another control method, Japanese Patent Laid-Open No.
There is one disclosed in JP-A-77943. That is, since the change of the gradient in the torque / throttle valve opening characteristic is continuous, it is assumed that the gradient is virtually ignored and the gradient is constant. That is, it is assumed that the actual throttle valve opening and the torque have a linear relationship. Then, a PID calculation is performed to obtain a virtual throttle valve opening such that the actual rotation speed becomes the target rotation speed.

[0014] Thereafter, the obtained virtual throttle valve opening is corrected for a gradient change in the torque / throttle valve opening characteristic which is initially neglected according to the actual nonlinear relationship between the throttle valve opening and the torque. And convert it to the actual throttle valve opening. That is, a table showing a conversion relationship between a virtual throttle valve opening and an actual throttle valve opening such that an actual throttle valve opening corresponding to an arbitrary virtual throttle valve opening is uniquely obtained. Is obtained in advance. A plurality of such tables are prepared and stored for each actual number of revolutions, and a table corresponding to the actual number of revolutions is selected to correct for a change in gradient.

In this method, the rotational speed of the internal combustion engine is adjusted based on the actual throttle valve opening obtained by correction.

[0016]

However, according to the former method using a plurality of PID control arithmetic expressions, when the gradient of the torque / throttle valve opening characteristic varies greatly, a large number of gradients corresponding to the variations of the gradient are obtained. Must be prepared. That is, it is necessary to provide a large number of control parameters 11, and the electronic governor device 1
However, there is a problem that the number of man-hours for design increases as well as the complexity of the design.

In the latter method of determining the virtual throttle valve opening, the followability to instantaneous load fluctuation is superior to the former method. However, it is necessary to obtain a table showing a conversion relationship between a virtual throttle valve opening and an actual throttle valve opening corresponding to all throttle valve openings in the torque / throttle valve opening characteristic. Therefore, there is the same problem as the former in that the man-hour for design increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to achieve an improvement in responsiveness and stability in controlling the rotational speed of an internal combustion engine.
It is to provide a simple method using a simple device.

[0019]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention obtains a deviation between an actual rotation speed of an internal combustion engine and a target rotation speed and, based on the deviation, determines a PID (proportional / integral /
PID calculation for differential) control is performed, and the calculation result is corrected according to a correction coefficient for correcting non-linearity in torque characteristics with respect to throttle valve opening to obtain a target throttle valve opening. In the method for controlling the rotational speed of the internal combustion engine, the rotational speed of the internal combustion engine is controlled by adjusting the degree of rotation .
Linearly approximated the gradient in each area obtained by dividing I, the basis of the inclination of the put that straight line in any area of its respective straight lines, each area ratio of the slope of the line in the other region
And the reciprocal of the ratio is used as the correction coefficient.
Therefore, the PID control equation corresponding to the arbitrary area
The result of the PID calculation is corrected by the
The gist is that the target throttle valve opening in the region is determined.

[0020]

According to the above configuration, since the correction of the non-linearity in the characteristic of the torque with respect to the throttle valve opening is performed in accordance with the correction coefficient, even if a load change occurs, the load can sufficiently follow the change. Responsiveness can be realized.

Further, since only one PID control arithmetic expression is used, the number of man-hours for design can be reduced and the apparatus can be simplified. As described above, it is particularly effective when there is a large change in the gradient of the torque characteristic with respect to the throttle valve opening.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will now be described with reference to FIGS.
This will be described with reference to FIG. 3 and FIG.

FIG. 1 is a schematic diagram of an electronic governor device 1 which is a rotation speed control device of an internal combustion engine. The electronic governor device 1
Is a control arithmetic unit 2, a read-only memory (ROM) 3,
It comprises a throttle valve opening correction device 4.

The ROM 3 has a PID for PID control.
A PID control calculation expression for defining a gain value in calculation is stored. The control arithmetic unit 2 is a current actual rotational speed (actual rotational speed) changed by a change in the target rotational speed and a load output from a target rotational speed command device (not shown).
Is input, and the PID calculation is performed based on the PID control calculation formula stored in the ROM 3 to obtain the throttle valve opening. The control arithmetic unit 2 corrects the throttle valve opening in accordance with a correction coefficient input from the throttle valve opening correction device 4 to set a target throttle which is an opening of a throttle valve for rotating the internal combustion engine at a target rotation speed. The valve opening is calculated and output.

The throttle valve opening correction device 4 inputs the current throttle valve opening (actual throttle valve opening) that has changed due to a change in load, and calculates a correction coefficient corresponding to the actual throttle valve opening in the correction table. The information is selected from among them and output to the control arithmetic unit 2.

Here, the throttle valve opening correction device 4
The correction coefficient of the throttle valve opening output from the ECU will be described. As described in the related art, the torque / throttle valve opening characteristic of the internal combustion engine is such that when the rotational speed is constant, the torque does not increase linearly with respect to the throttle valve opening, as shown by a curve α in FIG. The gradient of the curve α changes greatly at the boundaries of the throttle valve openings Pa and Pb.

Therefore, as shown in FIG. 2, a straight line β is obtained by linearly approximating the gradient of the curve α in the region A where the throttle valve opening is Pa or less. Similarly, a region B between Pa and Pb, and a maximum throttle valve P from Pb to Pb.
A straight line γ and a straight line δ are obtained by linearly approximating the gradient of the curve α in the region C below c.

Then, the slopes of the straight lines γ and δ when the slope of the straight line β is set to 1, that is, the ratio of the slopes are obtained. In that straight line β
The reciprocal of the ratio of the slopes of the straight lines γ and δ to the straight line is used as a correction coefficient for the throttle valve opening. That is, the PID obtained from the torque / throttle valve opening characteristic in the region A
If the PID calculation in the region B is performed based on the control calculation formula, the gain in the PID control will be over. The excess of the gain is calculated as the slope of the straight line γ.
Correction is performed using the reciprocal of the ratio to obtain a corrected throttle valve opening. Then, the corrected throttle valve opening is
It becomes equal to the target throttle valve opening in the region B obtained by performing the PID calculation based on the PID control calculation formula obtained from the torque / throttle valve opening characteristics in the region B.

Therefore, the reciprocal of the slope ratio of the straight line γ is used as a correction coefficient. Similarly, if the PID calculation in region C is performed based on the PID control calculation formula obtained from the torque / throttle valve opening characteristic in region A,
The gain in the PID control becomes insufficient. The shortage of the gain is corrected by the reciprocal of the ratio of the slope of the straight line δ to obtain a corrected throttle valve opening. Then, the corrected throttle valve opening becomes equal to the target throttle valve opening in the region C obtained by performing the PID calculation based on the PID control calculation formula obtained from the torque / throttle valve opening characteristics in the region C.

Therefore, the reciprocal of the ratio of the slope of the straight line δ is used as a correction coefficient. Therefore, the throttle valve opening obtained by performing the PID calculation based on the PID control equation corresponding to the area A is corrected by the correction coefficient corresponding to the actual throttle valve opening whose actual rotation speed has changed due to the load fluctuation. Thereby, the target throttle valve opening corresponding to the actual throttle valve opening can be obtained.

That is, as shown in FIG. 3, a data map is created such that a corrected throttle valve opening uniquely corrected by a correction coefficient is obtained from an actual throttle valve opening.

That is, in the region A, the correction coefficient becomes 1 because the inclination of the straight line β is 1, and the corrected throttle valve opening P1 becomes equal to the actual throttle valve opening Pa. In the region B, as shown in FIG. 2, since the slope of the straight line γ is larger than the slope of the straight line β, the correction coefficient becomes 1 or less, and the actual throttle valve opening Pb is multiplied by the correction coefficient to obtain a corrected throttle. The valve opening P2 is determined. Further, in the region C, as shown in FIG. 2, since the slope of the straight line δ is smaller than the slope of the straight line β, the correction coefficient becomes 1 or more, and the correction throttle coefficient is obtained by multiplying the actual throttle valve opening Pc by the correction coefficient. The valve opening P3 is determined. Corrected throttle valve opening degrees P1 to P
When 3 is connected by a straight line, a data map showing the corrected throttle valve opening / actual throttle valve opening characteristic is completed.

The data map shown in FIG. 3 is tabulated to form a correction table. Next, the operation of the electronic governor device 1 configured as described above will be described. It is assumed that a traveling load or a cargo handling load fluctuates during a work operation of an industrial vehicle equipped with an internal combustion engine.

Then, the rotational speed of the internal combustion engine changes with the load fluctuation. The changed actual rotation speed is detected by a rotation sensor (not shown) for detecting the rotation speed of the flywheel fixed to the output shaft of the internal combustion engine (= the rotation speed of the internal combustion engine) or the like, and is input to the control arithmetic unit 2. I do.

A target rotation speed output from a target rotation speed command device (not shown) is input to the control arithmetic unit 2. At the same time, the actual throttle valve opening is detected by a potentiometer (not shown) provided on the throttle valve of the internal combustion engine and input to the throttle valve opening correction device 4.

The throttle valve opening correction device 4 determines which of the areas A to C shown in FIG. 2 the actual throttle valve opening belongs to. In accordance with the determination, a correction coefficient is selected from a throttle valve opening correction table corresponding to each of the predetermined areas A to C, and is output to the control arithmetic unit 2.

The ROM 3 has been obtained in advance by an experiment in which the internal combustion engine is tested on an engine bench.
A PID control operation expression corresponding to the area A shown in FIG. 2 is stored.

The control operation unit 2 performs a PID operation based on the PID control operation expression input from the ROM 3.
That is, a deviation between the target rotational speed and the actual rotational speed is obtained, and based on the deviation, PID calculation for PID control is performed with the gain value determined by the PID control calculation formula being constant, and the throttle valve before correction is opened. Ask for degrees.

The pre-correction throttle valve opening is corrected according to a correction coefficient selected from a correction table on the basis of the actual throttle valve opening at that time input from the throttle valve opening correction device 4 to set the internal combustion engine at the target. The target throttle valve opening, which is the opening of the throttle valve for rotating at the rotational speed, is calculated and output.

As described above, in this embodiment, the torque / throttle valve opening characteristics obtained by experiments are divided into predetermined regions of the throttle valve opening, and the gradient change in each of the divided regions A to C. the linear approximation, based on the slope of the line obtained by linear approximation in the region a, the region B, obtains the ratio of the slope of a straight line linearly approximated in C, that the regions B, the inverse of the ratio of the slope of the line in the C Is a correction coefficient in each of the regions B and C, and a data map of the corrected throttle valve opening with respect to the actual throttle valve opening is created from each correction coefficient and is tabulated.

Therefore, in this embodiment, one PID
Only the control calculation formula is used, and it is not necessary to prepare a plurality of PID control calculation formulas corresponding to changes in the gradient in the torque / throttle valve opening characteristics of the internal combustion engine. However,
A correction table must be prepared. However, obtaining the data map corresponding to the change in the gradient and creating the correction table is performed by using a large number of Ps corresponding to the change in the gradient.
It is much easier than creating an ID control arithmetic expression, and the man-hour for design is much less.

Further, the provision of the correction table in the throttle valve opening correction device simplifies the device compared to the prior art method of providing a large number of control parameters 11A to 11C storing PID control calculation formulas. Can be.

The torque / throttle valve opening characteristic is divided into predetermined throttle valve opening regions, correction coefficients are obtained for each of the divided regions A to C, and the actual throttle valve opening is determined from each correction coefficient. A data map of the corrected throttle valve opening with respect to degree is created and tabulated. That is, determine a correction factor may be performed only manually for each region A~C obtained by dividing.

For this reason, Japanese Unexamined Patent Application Publication No.
As in the method disclosed in JP 77943, "virtual throttle valve opening" (corresponding to the pre-correction throttle valve opening shown in FIG. 3 in this embodiment) for all throttle valve openings. The number of man-hours for design is reduced as compared with obtaining a table indicating a conversion relationship with "the actual throttle valve opening" (corresponding to the target throttle valve opening in the present embodiment).

However, since the gradient change is linearly approximated for each of the regions A to C, an error accompanying the linear approximation is included between the throttle valve opening before correction and the target throttle valve opening. . However, if attention is paid to the setting of each of the regions A to C, no practical problem occurs due to the error.

That is, the present embodiment is particularly effective when the gradient of the torque / throttle valve opening characteristic changes greatly. The present invention is not limited to the above-described embodiment. For example, a PID control calculation formula corresponding to an arbitrary region where the gradient in the torque / throttle valve opening characteristic does not change may be determined in advance. That is, in the above embodiment, the PI
Although the D control calculation formula is determined in advance, the PID control calculation formula corresponding to the area B or the area C may be determined and implemented.

The slope of a straight line approximating a straight line in an arbitrary area may be set to an appropriate coefficient without being set to 1. Further, the present invention is effective not only for an internal combustion engine mounted on an industrial vehicle but also for an internal combustion engine mounted on an automobile or an internal combustion engine used as a power source such as a generator.

In addition, the present invention may be applied not only to the electronic governor device for stabilizing the load fluctuation but also to appropriate control of the rotational speed of the internal combustion engine.

[0049]

As described above in detail, according to the present invention, it is possible to provide a simple method using a simple device for realizing an improvement in responsiveness and stability in controlling the rotational speed of an internal combustion engine. There is an excellent effect that it can be done.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining a rotation speed control device of an internal combustion engine according to an embodiment of the present invention.

FIG. 2 is a characteristic diagram showing torque / throttle valve opening of an internal combustion engine according to an embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a correction table according to an embodiment of the present invention.

FIG. 4 is a schematic diagram for explaining a conventional rotation speed control device for an internal combustion engine.

FIG. 5 is a characteristic diagram showing torque / throttle valve opening of a conventional internal combustion engine.

[Explanation of symbols]

1 .... an electronic governor device for controlling the rotation speed of an internal combustion engine, 2 ....
A control operation device for performing PID operation for PID control, 3
... ROM for storing a predetermined PID control operation formula,
4. Throttle valve opening correction device that outputs a correction table corresponding to the actual throttle valve opening to the control arithmetic device

Claims (1)

(57) [Claims] A PID calculation for PID (proportional / integral / differential) control is performed based on a deviation between an actual rotational speed of an internal combustion engine and a target rotational speed. An internal combustion engine in which the target throttle valve opening is corrected according to a correction coefficient for correcting the non-linearity of the torque characteristic with respect to the valve opening, and the rotation speed of the internal combustion engine is controlled by adjusting the throttle valve opening. in speed control method of the engine, said in the characteristic of torque with respect to the throttle valve opening, its within each region was divided by the difference of the gradient
Gradient linearly approximated, and the reference tilt your <br/> only that straight lines in an arbitrary area of the respective straight lines, the lines in the other region of the
The slope ratio is obtained for each region, and the reciprocal of the ratio is calculated as a correction coefficient.
Then, according to the correction coefficient, it corresponds to the arbitrary area.
Complements the calculation result of PID calculation by the PID control calculation expression.
A method for controlling the rotational speed of an internal combustion engine , wherein the target throttle valve opening in the other region is determined.