JPH0559974A - Engine speed control method for internal combustion engine - Google Patents

Abstract

PURPOSE:To prevent occurrence of engine stall by recovering an engine, speed which is lowered through application of a load under an idling operation of an internal combustion engine. CONSTITUTION:Rotational direction and rate of a step motor 3 which adjust an opening of a cab valve of a caburetter 2 provided on an intake passage of an internal combustion engine 1 is controlled by means of a controller 4. The controller 4 controls the step motor 3 such that, in case that an actual engine speed is lowered compared an idling engine speed through application of a load and danger of engine stall is generated, the lowering of the actual engine speed is judged based on the fact that a frequency of an ignition signal output from an ignition device 5 at the present time is elongaged compared to the preset frequency in a danger of engine stall, and the opening of the cab valve is speedily enlarged with a specified opening.

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 rotation speed of an internal combustion engine.

[0002]

2. Description of the Related Art In addition to traveling load, cargo handling load,
In addition, a load for driving the hydraulic pump that operates the power steering, the brake, and the like acts.

Further, the torque generated by the internal combustion engine during idling is usually large enough to maintain the idling speed in a state where no load is applied to the internal combustion engine (no-load state). ..

Therefore, if an excessive load exceeding the torque is applied during idling, the load exceeds the torque and the rotational speed of the internal combustion engine drops below the idle rotational speed.
As a result, it may stall. Especially in a forklift, the power steering is often operated during idling, but the load generated when the steering is cut (the load for driving the hydraulic pump that operates the power steering) exceeds the torque during idling. Therefore, stalling was likely to occur.

In order to prevent such engine stalling, conventionally, an idle speed increasing device as shown in FIG. 8 has been used. That is, inside the carburetor 10, one end of the intake negative pressure pipeline 12 is connected to the intake valve (not shown) side of the internal combustion engine from the cab valve 11 that is rotatably provided around the cab valve shaft 11a.
The other end of the intake negative pressure pipe line 12 bent in the U shape is connected to a cab valve drive device 13.

The cab valve driving device 13 is composed of a diaphragm case 14, a diaphragm 15 stretched so as to divide the inside of the diaphragm case 14, and a cab valve driving rod 16 protruding from the diaphragm 15.
Further, a spherical cab valve pressing member 16a is attached to the tip of the cab valve driving rod 16.

Therefore, in the intake negative pressure line 12, and
The pressure in the diaphragm antechamber 17 on the intake negative pressure conduit 12 side in the diaphragm case 14 becomes equal to the intake negative pressure of the carburetor 10. The diaphragm 15 has an original shape when the pressure in the diaphragm front chamber 17 is equal to the atmospheric pressure (atmospheric pressure) around the idle speed increasing device, but when the pressure in the diaphragm front chamber 17 becomes lower than the atmospheric pressure. It is deformed to the diaphragm anterior chamber 17 side. Therefore, the diaphragm 15 takes the original shape when the intake negative pressure of the carburetor 10 is equal to the atmospheric pressure, and is deformed to the diaphragm front chamber 17 side when the intake negative pressure becomes larger than the atmospheric pressure.

The diaphragm 15 is a diaphragm front chamber 17
When it is deformed to the side, according to the degree of that deformation,
The cab valve drive rod 16 is a diaphragm case 14.
Shrink to be stored in. Also, the diaphragm 1
As the degree of bloat deformation of 5 decreases,
The cab valve drive rod 16 extends into the carburetor 10. That is, the cab valve drive rod 16 contracts toward the diaphragm front chamber 17 side when the intake negative pressure of the carburetor 10 becomes larger than the atmospheric pressure, and extends into the carburetor 10 when it approaches the atmospheric pressure.

By the way, the opening degree of the cab valve 11 at the time of idling is predetermined so that the idle speed can be maintained in a no-load state. for that reason,
When a load is applied during idling, the rotation speed falls below the idle rotation speed, but in order to increase the lowered rotation speed up to the idle rotation speed, the intake air amount may be increased. That is, the cab valve 11 corresponding to the required intake air amount
The opening may be increased.

That is, when a load is applied during idling and the rotation speed falls below the idle rotation speed, the intake negative pressure of the carburetor 10 decreases. Then, the degree of bulging deformation of the diaphragm 15 decreases as the intake negative pressure decreases, and accordingly, the cab valve drive rod 16 extends into the carburetor 10. Then, the cab valve drive rod 16 presses and opens the cab valve 11 via the cab valve pressing member 16a. Therefore, the opening degree of the cab valve 11 increases as the intake negative pressure decreases, increasing the intake amount.

As described above, in the idle speed increasing device shown in FIG. 8, when the rotational speed falls below the idle rotational speed, the opening degree of the cab valve 11 is increased to an extent corresponding to the decrease and the intake amount is increased. Acts to increase the rotation speed. Therefore, even if an excessive load is applied during idling, engine stall can be prevented.

In addition to the idle speed increasing device, an electronic governor device for controlling the rotation speed by PID (proportional, integral, differential) control is used to cause an engine stall when an excessive load is applied during idling. There is also a way to prevent this.

That is, the actual rotational speed at the present time (actual rotational speed) that has changed due to the change in load is detected based on the ignition signal output from the ignition device. A PID for PID control in which a gain value is defined by obtaining a deviation between the detected actual rotation speed and an idle rotation speed that is a target rotation speed
The calculation is performed based on the obtained deviation. Then, the target cab valve opening, which is the opening of the cab valve for rotating at the idle speed, is determined to control the rotation speed to prevent the engine stall.

[0014]

However, in the former idle speed increasing device, the degree of opening of the cab valve 11 with respect to the decrease of the rotating speed is arbitrarily adjusted / changed depending on the use condition of the internal combustion engine. There was a problem that I could not do it. Further, the intake negative pressure does not decrease immediately in response to the decrease in the rotation speed, but decreases with a slight delay. Therefore, there is also a problem of responsiveness that the opening degree of the cab valve 11 does not increase rapidly even if a load is applied, and it cannot respond to a sudden load change.

By the way, when a load for driving the hydraulic pump for operating the power steering is applied during idling of the internal combustion engine, as shown in FIG. 8, the hydraulic pressure of the hydraulic oil discharged from the hydraulic pump ( The time displacement of the power steering oil pressure 20) corresponds to the time displacement of the load for driving the hydraulic pump.

In the latter rotational speed control using the electronic governor device, the cycle of the ignition signal 21 becomes longer as the power steering hydraulic pressure 20 increases, and the rotational speed decreases. However, the cycle of the ignition signal 21 does not become long in response to an increase in the power steering hydraulic pressure 20. That is, the decrease in the rotation speed is slightly delayed with respect to the increase in the load. And at time A, an engine stall is occurring.

Further, the intake negative pressure 22 of the carburetor decreases as the power steering hydraulic pressure 20 increases. However, the decrease in the intake negative pressure 22 does not immediately respond to the change in the cycle of the ignition signal 21. That is, the decrease in the intake negative pressure 22 is slightly delayed with respect to the decrease in the rotation speed.

In a four-cycle four-cylinder internal combustion engine, the output shaft makes one revolution each time it is ignited twice.
In the electronic governor device, every time the ignition signal 21 is input twice, the actual rotation speed is calculated from the total time of the two cycles of the ignition signal 21 to perform the PID control. Therefore, if a sudden load change occurs while the ignition signal 21 is input twice, there is a problem of responsiveness that the change cannot be detected.

If the actual rotational speed is calculated and the target cab valve opening is determined every time the ignition signal 21 is input, it is possible to cope with a sudden load change during idling and to respond. Sex improves. However, when the rotational speed is increased for traveling, the opening degree of the cab valve changes in response to a slight change in the cycle of the ignition signal 21, which causes a problem in the stability of the rotational speed. Become.

Further, as compared with the time C in which there is no load before the power steering hydraulic pressure 20 rises, the time B
Then, the cycle of the ignition signal 21 becomes longer as the power steering hydraulic pressure 20 increases. Therefore, if the cab valve opening 23 is increased at this time B to increase the intake air amount, the engine stall can be avoided. That is, the deviation between the actual rotation speed and the idle rotation speed at time B may be obtained, and the required gain value for PID control may be set based on the deviation. However, with the gain value set like that,
When the rotation speed is increased to drive the vehicle, the result of the PID calculation becomes an over-gain, which again causes a problem in the stability of the rotation speed.

That is, in FIG. 8, the cab valve opening 23 does not change even if the power steering hydraulic pressure 20 rises because the gain of the PID control does not become over-gain when the rotation speed is increased. This is because the value is set.

As described above, in the latter electronic governor device,
It is superior to the former idle rotation speed increasing device in that the cab valve opening with respect to the actual rotation speed can be arbitrarily adjusted and changed by changing the gain value of the PID control. However, if the rotation speed control is set at high rotation speed, the responsiveness will decrease when an excessive load is applied during idling, and if the rotation speed control is set at idle speed, stability will decrease at high rotation speed. I had the conflicting problems of doing.

The present invention has been made to solve the above problems, and an object thereof is to improve the responsiveness and stability in the rotational speed control of an internal combustion engine, and to prevent an excessive load during idling. An object of the present invention is to provide a method for controlling the rotation speed of an internal combustion engine that does not cause engine stall even if it is applied.

[0024]

In order to solve the above-mentioned problems, the present invention has a predetermined cycle in which the ignition signal output from the ignition device at the time of idling of the internal combustion engine may cause an engine stall. The gist of the invention is to increase the opening degree of the cab valve by a predetermined opening degree in addition to the opening degree of the cab valve at that time when it becomes longer than the cycle of the ignition signal.

[0025]

[Action] When idling, a certain load (for example, a load for driving the hydraulic pump that operates the power steering, etc.) is suddenly applied, which may cause the engine speed to drop suddenly from the idle speed to cause engine stall. When it occurs, the decrease in the actual rotation speed is determined based on the fact that the current cycle of the ignition signal is longer than the predetermined cycle, and the opening degree of the cab valve is rapidly increased by a fixed opening degree. Therefore, the opening degree of the cab valve increases in response to the actual rotation speed reduced by the sudden application of the load, the intake amount of the carburetor increases, and the reduced actual rotation speed returns to the idle rotation speed, causing an engine stall. Absent.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment embodying the present invention will now be described with reference to FIGS.
It will be described with reference to FIG. FIG. 1 is a schematic diagram of a rotation speed control device for an internal combustion engine embodying the present invention.

A carburetor 2 is provided in the intake passage of a 4-cycle 4-cylinder internal combustion engine 1, and a step motor 3 is attached to the carburetor 2. The controller 4 is composed of a microcomputer, and inputs the ignition signal output from the ignition device 5 and the target rotation speed output from a target rotation speed command device (not shown).

Further, the controller 4 has a built-in memory, and selects and selects the governor control, which is a program for controlling the rotational speed of the internal combustion engine stored in the memory, and the idle-up control described later. Based on the control, the rotation direction and the rotation amount of the step motor 3 are defined, and the step motor 3 is drive-controlled.

As shown in FIG. 2, the cab valve 2 is provided inside the carburetor 2 so as to be rotatable about the cab valve shaft 2a by the step motor 3.
The opening of b is adjusted. That is, the step motor 3
A motor pulley 3b is attached to the motor shaft 3a. Also, the cab valve shaft 2a has a cab valve
The pulley 2c is attached. A drive belt 3c is wound around the motor / pulley 3b and the cab valve / pulley 2c. Therefore, when the drive belt 3c moves corresponding to the rotation amount of the motor pulley 3b that rotates according to the rotation direction and the rotation amount of the step motor 3, the cab valve and the cab valve according to the movement direction and the movement amount of the drive belt 3c. The pulley 2c rotates, which changes the opening degree of the cab valve 2b. That is, the opening degree of the cab valve 2b can be adjusted by controlling the rotation direction and the rotation amount of the step motor 3.

Now, each processing of the governor control and the idle-up control of the controller 4 will be described. Since the total time of each cycle of the two ignition signals corresponds to the time required for one rotation of the output shaft of the internal combustion engine in the governor control,
Every time the ignition signal is input twice, the actual rotation speed is calculated and the deviation between the actual rotation speed and the target rotation speed is obtained. Next, PID calculation for PID control in which the gain value is defined is performed based on the obtained deviation. Then, the target cab valve opening, which is the opening of the cab valve for rotating at the target rotation speed, is determined. The step motor 3 is drive-controlled based on the target cab valve opening.

Incidentally, the gain value of the PID control is predetermined so as to be optimum at an actual rotational speed equal to or higher than the idle rotational speed. Therefore, at the actual rotational speed equal to or higher than the idle rotational speed, the actual rotational speed can be controlled to be equal to the target rotational speed. That is, when the actual rotation speed becomes lower than the idle rotation speed, the responsiveness deteriorates.

The idle-up control is performed when the idling current cycle is longer than the predetermined ignition signal cycle that may cause engine stall during idling, that is, the actual engine speed may stall. When the rotation speed is lower than a certain value, the step motor 3 is drive-controlled so as to increase the cab valve opening by a predetermined opening E in addition to the cab valve opening at that time.

That is, as shown in FIG. 3, the ignition signal 6
If the cycle is equal to or shorter than a predetermined ignition signal cycle TX (= T1) that may cause engine stalling, idle-up control is not performed. However, when the cycle of the ignition signal 6 is longer than the cycle TX (= T2), the idle-up control is performed.

In the present embodiment, the period TX of the ignition signal that may cause an engine stall, that is, the number of revolutions that may cause an engine stall, is predetermined by experiment (TX = 50 msec in the present embodiment). ). Also,
The opening E is determined in advance so as to be able to cope with the maximum load by an experiment in which a load for driving a hydraulic pump that operates a power steering, a brake, and the like during idling, a cargo handling load, and the like are applied (this embodiment). At E = 5.4 °).

Next, according to FIG. 4 showing the time displacement of each characteristic when the internal combustion engine 1 is loaded, and FIG. 5 and FIG. 6 which are flowcharts showing the operation of the controller 4, the internal combustion engine is idling. The operation of the idle-up control and the governor control when a load is applied will be described.

When a load for driving the hydraulic pump for operating the power steering is applied to the internal combustion engine during idling, the respective characteristics are displaced with time as shown in FIG. The time displacement of the load corresponds to the time displacement of the hydraulic pressure of the hydraulic fluid discharged from the hydraulic pump (power steering hydraulic pressure 7).

In the controller 4, as shown in FIG. 5, the ignition signal output from the ignition device 5 is set to 2
Every time input is performed, in step (hereinafter referred to as S) 1, the governor control process is performed to keep the actual rotation speed at the idle rotation speed.

Then, the routine shown in FIG. 6 is performed by interrupting the routine of the governor control processing shown in FIG. That is, at the same time that the governor control process (S1) shown in FIG. 5 is performed, as shown in FIG. 6, in S2, the cycle of the input ignition signal is set every predetermined time (2 msec in this embodiment). Compare T with the period TX of the ignition signal that may cause an engine stall. Then, the cycle T is the cycle TX
When it is longer, that is, when the actual rotation speed is lower than the rotation speed that may cause engine stall, the process proceeds to S3, and the idle-up control process is performed in S3.

That is, when the cycle T of the ignition signal 6 becomes longer than the cycle TX of the ignition signal which may cause an engine stall with the increase of the power steering oil pressure 7 (= the increase of the load), that is, the actual rotational speed is At a time point (= time D) at which the engine speed is lower than the engine speed at which engine stall may occur, the governor control response becomes low and the engine does not work. Therefore, the routine of the governor control process shown in FIG. 5 is interrupted, the routine of the idle-up control process shown in FIG. 6 is performed, and in addition to the opening degree of the cab valve at that time specified by the governor control, a predetermined opening is performed. Degree E
Only the cab valve opening 8 is increased.

Then, the cycle T of the ignition signal 6 is slightly delayed from the time D when the cab valve opening 8 becomes large, and returns to the cycle before the power steering hydraulic pressure 7 increased. That is, the rotational speed that has decreased with the increase in the load returns to the idle rotational speed because the intake amount of the carburetor 2 increases as the cab valve opening 8 increases. Therefore, no stalling will occur. Further, even if the cycle T of the ignition signal 6 does not return to the cycle before the power steering oil pressure 7 increased, the cycle T of the ignition signal 6 becomes short, the actual rotation speed increases, and torque enough to avoid engine stall is generated. can do.

Although not shown in FIG. 4, the cycle T of the ignition signal 6 is equal to or less than the cycle TX of the ignition signal 6 that may cause an engine stall, that is, the actual rotational speed is equal to or greater than the rotational speed that may cause an engine stall. Then, governor control comes to work. Therefore, the interrupt of the routine of the idle-up control process shown in FIG. 6 is stopped, the routine of the governor control process shown in FIG. 5 is performed, and the actual rotation speed is kept at the idle rotation speed.

The intake negative pressure 9 of the carburetor decreases slightly later than the rise of the power steering oil pressure 7. Then, after a slight delay from the time D when the cab valve opening 8 becomes large, the value returns to the value of the intake negative pressure before the power steering hydraulic pressure 7 increased. That is, the intake negative pressure that has decreased with the increase in load returns to the value before the load was applied due to the increase in the cab valve opening 8.

As described above, in this embodiment, the fact that the actual rotation speed is lower than the rotation speed at which the governor control response becomes low and does not work is that the current ignition signal cycle becomes longer than the predetermined cycle. High responsiveness and stability are achieved at any speed by performing idle-up control instead of governor control.

Furthermore, when some kind of load (for example, a load for driving a hydraulic pump for operating a power steering, etc.) is suddenly applied during idling,
Even if there is a risk that the engine speed will suddenly drop from the idle speed and cause engine stall, the decrease in the actual engine speed is determined based on the fact that the current ignition signal cycle is longer than the predetermined cycle. Then, the opening degree of the cab valve is rapidly increased by a fixed opening degree. Therefore, the opening degree of the cab valve increases in response to the actual rotation speed reduced by the sudden application of the load, the intake amount of the carburetor increases, and the reduced actual rotation speed returns to the idle rotation speed, causing an engine stall. Absent.

The present invention is not limited to the above embodiment, but may be carried out in an internal combustion engine other than a 4-cycle 4-cylinder engine, for example. In that case, in the governor control, the actual rotation speed may be calculated every time the ignition signal is input an appropriate number of times.

Alternatively, only the idle-up control may be performed independently without performing the governor control. Further, the opening degree E may be arbitrarily set and implemented regardless of the load.

In addition, the adjustment of the opening degree of the cab valve is not limited to the configuration using the step motor, but may be performed by any configuration.

[0048]

As described in detail above, according to the present invention, the responsiveness and stability of the rotational speed control of the internal combustion engine are improved, and the engine does not stall even when an excessive load is applied during idling. There is an excellent effect that it is possible to provide a method for controlling the rotation speed of an internal combustion engine.

[Brief description of drawings]

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

FIG. 2 is a schematic diagram for explaining the configurations of a carburetor and a step motor in one embodiment embodying the present invention.

FIG. 3 is an explanatory diagram for explaining a cycle of an ignition signal in one embodiment embodying the present invention.

FIG. 4 is a characteristic diagram showing the time displacement of each characteristic in one example embodying the present invention.

FIG. 5 is a flowchart showing the operation of the rotation speed control device in one embodiment of the present invention.

FIG. 6 is a flowchart showing the operation of the rotation speed control device in one embodiment of the present invention.

FIG. 7 is a schematic diagram for explaining an idle speed increasing device that is a conventional speed control device.

FIG. 8 is a characteristic diagram showing a time displacement of each characteristic in an electronic governor device which is a conventional rotation speed control device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine, 2 ... Carburetor, 3 ... Step motor for adjusting the opening degree of a cuff valve in the carburetor, 5 ...
Ignition device

Claims (1)

[Claims] 1. When the internal combustion engine is idling and the cycle of the ignition signal output from the ignition device at that time is longer than the cycle of a predetermined ignition signal that may cause engine stalling, the cab valve at that time is A method for controlling the rotation speed of an internal combustion engine in which, in addition to the opening degree, the opening degree of the cab valve is increased by a predetermined opening degree.