JPS6210433A - Control method for idle speed in internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent a decrease of torque caused by vapor generated in a fuel pipe, by increasing a quantity of intake air when an engine is started in a high temperature thereafter decreasing the increased quantity after a predetermine time or when an engine speed increases to a predetermined value or more. CONSTITUTION:An engine, providing an intake air temperature sensor 8 detecting an intake air temperature in a surge tank 7a provided interposing in an intake manifold 7, inputs the output of said sensor 8 with the other output of operative condition detecting sensors to an electronic control circuit 20. And the electronic control circuit 20, increasing pulse duty ratio of a control signal, applied to an idle speed control valve 13 provided in a bypass line 12 detouring around a throttle valve 10, when the engine is started in a high temperature with the intake temperature in a predetermined value (for instance, 45 deg.C) or more, increases a quantity of intake air. While the electronic control circuit 20 controls said increased quantity so as to be gradually decreased after a predetermined time (for instance, 2sec) from staring the engine or after its speed rises to a predetermined value (for instance, 800rpm).

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an idle rotation speed control method for controlling the idle rotation speed by increasing or decreasing the amount of intake air, and in particular to prevent a drop or fluctuation in the idle rotation speed during high temperature startup. The present invention relates to a method for controlling the idle speed of an internal combustion engine.

[Prior Art] Conventionally, when an internal combustion engine is restarted after being operated at high speed or under a high load for a long period of time, there is a problem in that the idle speed decreases and fluctuates, and in some cases, the engine cannot be started. Ta. This is a problem that occurs when an internal combustion engine becomes high in temperature due to reasons such as stopping the cooling fan, vapor is generated in the fuel pipes, the fuel density decreases, the air-fuel ratio becomes lean, and the torque decreases. As a way to deal with this problem, the patent application No. 59-18709
As stated in No. 0, when starting at a high temperature when the engine salinity is above a predetermined temperature, the amount of intake air is increased to increase the engine torque, and after a predetermined period of time, the increased amount of intake air is gradually reduced. There is a way.

[Problems to be Solved by the Invention] However, in the above-mentioned control method, a decrease in torque at the time of high-temperature starting of the internal combustion engine is prevented by increasing the amount of fuel injection as the amount of intake air increases. Although it is possible to stably control the idle speed at startup without causing the air-fuel ratio to become too rich, causing deterioration of emissions or deterioration of fuel efficiency, the increase control of the intake air amount continues for a predetermined period of time. Therefore, depending on the cooling state of the internal combustion engine at the time of starting, there is a problem that the idle speed becomes too high.

In other words, even if the internal combustion engine is started at the same high temperature, the amount of vapor produced differs depending on the time from when the internal combustion engine stops until it starts again. [r, p, 1
．． ]More than and high <su') Too Z! 'This causes problems such as giving the driver a sense of discomfort.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for controlling the idle speed of an internal combustion engine, which can control the idle speed to an appropriate value without causing discomfort when the intake air amount is controlled to increase when the internal combustion engine is started at a high temperature as described above. It was created for this purpose and has the following structure.

[Means for Solving the Problems] That is, the idle speed control method for an internal combustion engine of the present invention, as shown in FIG.
In l), if the amount of intake air of the internal combustion engine is increased (P2), if a predetermined time has elapsed after starting the internal combustion engine (P3), or if the rotational speed of the internal combustion engine exceeds a predetermined rotational speed (
P4) is characterized in that the increase in the amount of intake air is reduced (P5).

[Operation] By configuring as described above, when the intake air amount is controlled to increase when the internal combustion engine is started at a high temperature, the idling speed of the internal combustion engine does not become too high and the driver does not feel uncomfortable.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

First, FIG. 2 is a schematic system diagram showing a four-stroke, four-cylinder internal combustion engine and its peripheral equipment in an embodiment to which the method of the present invention is applied.

1 is an engine, 2 is a piston, 3 is a spark plug, 4 is an exhaust manifold, 5 is provided in the exhaust manifold 4,
An oxygen sensor detects the residual oxygen concentration in exhaust gas, 6 is a fuel injection valve provided for each cylinder and injects fuel, 7 is an intake manifold, and 8 is provided in a surge tank 7a, which is sent to the engine body 1. An intake air temperature sensor that detects the temperature of intake air; 9 a water temperature sensor that detects the engine cooling water temperature; 10 a throttle valve; 11 that is linked to the throttle valve 10 and outputs a signal according to the opening degree of the throttle valve 10. throttle position sensor,
12 is a bypass passage which is an air passage that bypasses the throttle valve 10; 13 is an idle speed control valve (ISCV) that controls the opening area of the bypass passage 12 to control the idle rotation speed; and 14 is an air flow that measures the amount of intake air. Meters 15 each represent an air cleaner that purifies the amount of intake air. Here, above ■5CV1
3 is used in this embodiment to realize the idle speed control method of the present invention, and is driven in accordance with a control signal whose pulse duty ratio is controlled to control the opening area of the bypass path 12. Do it N! Equipped with 1 solenoid.

Further, 16 is an igniter that is equipped with an ignition coil and outputs the high voltage necessary for ignition, and 17 is a distributor that is linked to a crankshaft (not shown) and distributes the high voltage generated by the igniter 16 to the spark plugs 3 of each cylinder. , 18
is installed in the distributor 17 and rotates 24 times per revolution of the distributor 17, that is, two revolutions of the crankshaft.
19 is a cylinder discrimination sensor that outputs one pulse signal per revolution of the distributor 17, and 20 is an electronic control circuit.

Next, FIG. 3 shows a block diagram of the electronic control circuit 20. As shown in FIG.

A central processing unit (CPU) 30 inputs and calculates data output from each sensor according to a control program, and performs processing to control the operation of various devices such as the fuel injection valve 6 and the igniter 16.
1 is a read-only memory (ROM) in which data such as the control program and a map for calculating the ignition advance angle are stored.
, 32 is a random access memory (RAM) in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read and written; 33 is a random access memory (RAM) in which data input to the electronic control circuit 20 and data necessary for arithmetic control are temporarily read and written; 33 is a memory for subsequent engine operation even if a key switch (not shown) is turned off. A backup random access memory (backup R) backed up by a battery is used to retain necessary data, etc.
AM), 34 is an input port (not shown), a waveform shaping circuit provided as necessary, and an output signal from each sensor is connected to CP.
The input sections each include a multiplexer for selectively outputting to U30, an A/D converter for converting an analog signal into a digital signal, and the like. In addition, 35 is provided with an output port in addition to an input port (not shown), and is connected to a fuel injection valve 6, an igniter 16, etc. as necessary.
Input/output unit equipped with a drive circuit etc. that drives according to control signals of U30, 36 +;t CPU 30, RO
The path lines connecting each element such as M31 and the input section 34 and output section 35 and through which each data is sent are respectively shown.

The electronic control circuit 20 takes in the detection data input from each sensor, calculates the optimal fuel injection amount and ignition timing according to the operating conditions, and when idling, adjusts the rotation speed to a target rotation speed set in advance according to the operating conditions. Find the pulse duty ratio of the control signal so that the engine speed matches, and l
This control signal is output to 5CV13 to control the opening degree of 15CV13, thereby controlling the idle rotation speed.

Next, the idle rotation speed control processing routine executed by the CPU 30 will be explained with reference to the flowchart of FIG.

Note that this processing routine represents a part of the main routine that is repeatedly executed together with the fuel injection control and ignition timing control.

As shown in the figure, when the processing of this routine is started, step 101 is first executed, and the pulse signal output from the rotation angle sensor 18 is counted to calculate the engine rotation speed NE. Next, in step 102, it is determined whether the flag X5TA, which is always set when the ignition switch is turned on at the time of starting, is set.

If it is assumed that the engine has just started, flag X5
Since TA is in the set state, r
It is determined as YESJ, and the process moves to the following step 103.

In step 103, it is determined whether the engine rotation fiNE determined in step 101 is equal to or less than 500 [r, p, +n,]. If NE≦500, the process moves to the next step 104, sets the flag X5TA, and moves to step 105.

Next, in step 105, a counter C3TA that counts the elapsed time after the engine is started is cleared, and the process moves to step 106. In step 106, it is determined whether the surge tank internal temperature THCA detected by the intake air temperature sensor 8 is equal to or higher than a predetermined temperature a (for example, 45° C.). If THCA≧a, the process moves to the next step 107, where the duty ratio DHO is set to increase the amount of intake air at high temperature startup.
Set the initial value α (for example, 20%) to the king, and proceed to the next step 1.
08, and conversely, if THCA<a, the process directly proceeds to step 108.

Next, in step 103, the engine speed NE is set to 50.
If it is determined that the value exceeds 0 [r, p, m, ], the process moves to step 109 and the flag X5TA is reset.
The process directly advances to step 108.

If it is determined in step 102 that the flag
+n, ], and if NE≦300, proceed to step 104; conversely, if NE>300
If so, the process moves to step 109.

Note that in steps 103, 104, 109, and 110, even if the flag X5TA is set, the engine speed NE is 500 [r,p
, m, ], it is assumed that the engine has been completely started and the flag X5TA is reset; conversely, the flag
The engine rotates even when 5TA is in the reset state! It!
When NE is as low as 300 [r, I), nl,],
If the engine speed has decreased after starting, the flag X5TA is set again and processing is performed to start the engine. This makes it possible to increase the amount of intake air at startup even when the amount of intake air has decreased.

Next, in step 108, it is determined whether the value of the duty ratio DHOT for increasing the amount of intake air at the time of high temperature startup is "0". If it is determined in step 108 that DHOT≠0, the process moves to step 111, and DHOT
If it is determined that the value is -0, control to increase the amount of intake air at the time of high-temperature startup is unnecessary, so the process moves to step 121, which will be described later.

Next, in step 111, the engine speed NE is 800.
Determine whether it is greater than or equal to [r, p, m,], and determine whether NE≧8
If it is 00, a flag XN is set in the next step 112.

On the other hand, if it is determined in step 111 that it is a day when NE<800, or in step 112, the flag
If N is set, the process proceeds to step 113, where it is determined whether the value of the counter C3TA is less than a predetermined time A (for example, 2 seconds), that is, whether a predetermined time A has elapsed after the engine was started.

If it is determined in step 113 that C3TA<A, the process moves to the next step 114, and the process proceeds to step 112.
It is determined whether the flag XN, which is set when the engine rotational speed NE is 800 [r, p, m, ] or more, is in the sera [.] state.

If it is determined in step 114 that flag XN is set, or in step 113,
If it is determined that 3TA≧A, the subsequent step 115 is executed, and it is determined whether the flag XTDC, which is set every 180'CA rotation of the engine (for example, every TDC of each cylinder), is set. to decide. If it is determined in step 115 that the flag XTDC is set, the process proceeds to the next step 116, where the duty ratio D HOT is decreased by β (for example, O74%), and the process proceeds to the next step 117.

In step 117, it is determined whether the duty ratio DHOT reduced in step 116 is less than 05. If it is determined that DHOT<O, then in step 118 DHOT is set to f'OJ, and in step 119 flag XN is reset. Next, if it is determined in step 117 that DHOT<O, or if the flag
Reset C.

If the flag XTDC is reset in step 120, and if it is determined in step 114 that the flag XN is in the reset state, then in step 115 the flag
If it is determined that TDC is in the reset state, or if it is determined in step 108 that TDHOTffiO%, step 121 is executed to calculate the basic duty ratio DO of the intake air amount. Note that the process in step 121 is similar to the conventional idle speed control, and is a basic duty for controlling the idle speed to a predetermined speed using the cooling water temperature and engine speed as parameters. The purpose is to find the ratio DO. Then, in this step 121, the basic duty ratio DO
Once obtained, the process moves to the next step 122, where the duty ratio DHOT, which is an increase i correction term at high temperature start, is added to this basic duty ratio DO, the final pulse duty ratio is calculated, and the processing of this routine is started. end once.

And the pulse duty ratio calculated as above is
It is set in the counter of the input/output section 35, and rscvi3
It is added as a control amount to the control signal (pulse signal) output to. Then, in l5CV13, the opening degree is controlled according to this pulse duty ratio, the amount of intake air at the time of high temperature startup is increased, and the rotation of the engine is controlled to a favorable idle rotation speed.

In this embodiment configured as described above, when the temperature inside the surge tank exceeds a predetermined value a°C and the engine is started under high temperature conditions, the amount of intake air is increased, as shown in Fig. 5 or 6. , after a predetermined time A (here, 2 seconds) has elapsed after the engine has started, or when the engine speed is 800 [r, p, m
, ], the increased amount (DHOT) will be gradually reduced. Therefore, even when the engine is started under high temperature, the engine torque will decrease due to the generation of vapor, and the idle speed will not drop or fluctuate, and the idle speed will not increase too much and cause the driver to feel uncomfortable. The idle speed can be well controlled without any problems.

The characteristics indicated by the broken line in FIG. 6 are due to the conventional idle speed control method, and are caused by the engine speed N.
This indicates that even if E exceeds 800 [r, I], L], the same state continues for a predetermined period of time. Furthermore, even if the process of step 119 in FIG. 4 is configured to be executed between step 116 and step 117, it is possible to prevent the idle rotation speed from becoming too high as 800 [r, p, m, ] or more. It is possible to do so.

Here, in the above embodiment, the intake air temperature sensor 8 provided in the surge tank 7a is used to detect the engine temperature, and a high temperature start of the internal combustion engine is detected based on the temperature inside the surge tank. Alternatively, a high temperature start of the internal combustion engine may be detected by providing a sensor that directly detects the fuel temperature on the fuel injection valve, or it may be detected based on the cooling water temperature.

Furthermore, in the above embodiment, when a high temperature start of the engine is detected,
The duty ratio DHOT, which is a correction term for increasing the amount of intake air, is set to a predetermined value α, but in this case, if it is set according to the surge tank internal temperature THCA, that is, the engine temperature, it will be more precise. Idle speed control can be executed.

Furthermore, in the above embodiment, the opening degree of the electromagnetic solenoid-type ISC■ is controlled by the pulse duty ratio of the control signal, but in the case of 15CV using a step motor, the number of steps is calculated and the opening degree of the rscv is controlled according to the number of steps. The amount of intake air is controlled in a similar manner.

[Effects of the Invention] As detailed above, in the method of the present invention, when the internal combustion engine is started at a high temperature above a predetermined temperature, the amount of intake air is increased, and then when a predetermined period of time has elapsed, or the engine speed is increased. When the internal combustion engine reaches a predetermined rotation speed or higher, the increase in the amount of intake air is reduced, which prevents the engine from stalling by preventing a drop in torque during idling caused by vapor generated in the fuel piping when the internal combustion engine is started at a high temperature. This makes it possible to prevent an abnormal drop in the idle speed and maintain a stable idle speed without increasing the idle speed pointlessly.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the present invention, FIGS. 2 to 6 show embodiments of the present invention, FIG. 2 is a schematic block diagram including a control system of an internal combustion engine to which the method of the present invention is applied, and FIG. The figure is a block diagram of the electronic control circuit, FIG. 4 is a flowchart showing the idle rotation speed control process executed by the electronic control circuit, and FIGS. 5 and 6 are graphs explaining the operation. 8... Intake temperature sensor 12... Bypass path 1 3-I S CV 18... Rotation angle sensor 20... Electronic control circuit 30... CPU

Claims (1)

[Claims] If the temperature of the internal combustion engine is equal to or higher than a predetermined temperature at the time of starting, the intake air amount of the internal combustion engine is increased, and if a predetermined time has elapsed after the internal combustion engine has been started, or the rotation speed of the internal combustion engine is lower than the predetermined rotation speed. 1. A method for controlling the idle speed of an internal combustion engine, comprising: reducing the increase in the amount of intake air when the amount exceeds the amount of intake air.