JPH03151543A - Idle revolution controller of engine - Google Patents

Abstract

PURPOSE:To increase bypass air quantity according to increase in target revolutions and prevent generation of idle roughness and engine stall by providing a detection means which detects volatility of fuel, and setting high target revolutions as the volatility of fuel is low. CONSTITUTION:The number of revolutions of an engine is calculated from output of a crank angle sensor 34. A map for setting target revolutions and basic bypass air quantity according to a volatile judging flag which is different when it is started and finished. The selected map is used and the target revolutions and basic bypass air quantity are calculated by water temperature. At the idle operation time, increase in feedback(F/B) compensation is calculated by difference between the target and engine revolutions so as to calculate the F/B compensation. Volatility of fuel is judged by a judged result that water temperature is less than a specified temperature or not, and that the F/B compensation is less than a specified value. Target revolutions are set high as the volatility of fuel is lower.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an engine idle speed control device, and in particular, to an engine idle speed control device that improves idle stability by setting a higher target engine speed as fuel has lower volatility. related to what was done.

[Prior Art] In recent automobile engines, an ISC valve (idle speed control valve) having a duty solenoid is generally installed in a bypass passage that bypasses a throttle valve in the intake passage. An idle speed control device is provided that precisely adjusts the amount of bypass air and performs feedback control so that the engine speed becomes the target speed (Japanese Patent Laid-Open No. 55-10
(See Publication No. 7034).

Normally, the above target rotation speed is set based on a map with cooling water temperature as a parameter, because when the temperature inside the combustion chamber is low, fuel volatility is low and idle roughness and engine stall are likely to occur. Its own lightness/
There are no differences in characteristics due to fuel properties such as heavy weight, and the characteristics are set based on a map of characteristics based on ordinary standard gasoline fuel with high volatility.

[Problems to be Solved by the Invention] In conventional idle speed control devices, the target speed is set to a relatively low value based on highly volatile standard gasoline fuel and the cooling water temperature as a parameter. The amount is also relatively small (set according to the target rotation speed), so if heavy fuel with poor volatility is used, the amount of bypass air is small, the filling efficiency is low, and the fuel itself vaporizes. Since the atomization property is poor and the air-fuel mixture becomes lean, there is a problem that combustibility deteriorates and idle roughness and engine stall occur.

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine idle speed control device that can improve idle stability by setting a target engine speed higher as the volatility of fuel is lower.

[Means to solve the problem]

An engine idle speed control device according to the present invention is an engine idle speed control device including a feedback control means for performing feedback control so that the engine speed becomes a target speed. A detecting means for directly or indirectly detecting the fuel temperature is provided, and a target rotation speed setting means is provided for receiving the output of the detecting means and setting the target rotation speed higher as the volatility of the fuel is lower.

[Operation] In the engine idle speed control device according to the present invention, the volatility of the fuel supplied to the engine is detected by the detection means, and the target rotation speed setting means receives the output of the detection means and adjusts the volatility of the fuel. Since the target engine speed is set higher as the engine speed is lower, the amount of bypass air is also increased in accordance with the increase in the target engine speed, making idle roughness and engine stall less likely to occur.

[Effects of the Invention] According to the engine idle speed control device according to the present invention, as described in detail in the [Operation] section above, the detection means for detecting the continuity of fuel and the low volatility of the fuel are provided. Since a target rotation speed adjustment means is provided to set the target rotation speed as high as possible,
Idle stability can be ensured when fuel volatility is low.

〔Example〕

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

Figure 1 shows the overall configuration of a four-cylinder automobile engine E, including a cylinder block 1, cylinder head 2, piston 3, connecting rod 4, crankshaft 5, intake port 6 and intake valve 7, exhaust port 8 and exhaust. valve 9, valve mechanism 10,
The intake passage 11, the exhaust passage 12, the spark plug 13, etc. are the same as normal ones, so a detailed explanation will be omitted.

In the intake passage 11, an air cleaner 2 is installed in order from the upstream side.
0, an air flow meter 21, a throttle valve 22, and an injector 23 are installed, and the throttle valve 22 is equipped with a throttle opening sensor 33 that detects the opening of the throttle valve 22, and an idle switch that is turned ON when the throttle valve 22 is fully closed. , a bypass passage 25 that bypasses the throttle valve 22
ISC valve (idle speed control valve) 26
is installed in the cylinder block 1, and a water temperature sensor 35 is installed in the cylinder block 1 to detect the temperature of the cooling water in the water jacket la.
A crank angle sensor 34 for detecting the crank angle of the crankshaft 5 is provided in conjunction with the crankshaft 5.

The control unit 30 that controls the engine E includes an air flow meter 21 and a throttle opening sensor 33.
Detection signals from sensors and switches such as the idle switch, crank angle sensor 34, and water temperature sensor 35 are input, and control signals are output from the control unit 30 to the injector 23, ignition unit 24, ISC valve 26, etc., respectively. Ru.

The control unit 30 has a general configuration mainly consisting of a microcomputer, including an A/D converter for A/D converting detection signals from sensors, and a waveform for shaping the detection signal from the crank angle sensor 34. Shaping circuit, input/output interface, injector 23 and ISC valve 2
A plurality of drive circuits for 6 are also provided. The ROM of the microcomputer of the control unit 30 (
A control program for idle rotation speed control, which will be described later, various maps necessary for this control, and other control programs and maps necessary for controlling the engine E are stored in advance in the read-only memory (read-only memory).

By the way, when the fuel supplied to the engine E contains heavy components with low volatility and the temperature of the cooling water is below a predetermined temperature (for example, 50°C), the volatility of the fuel is low. becomes very low.

Therefore, in this idle speed control, when the volatility of the fuel is low and the cooling water temperature is below a predetermined temperature,
The target rotation speed and basic bypass air amount are set large to ensure idle stability.

Next, the idle rotation speed control routine performed by the control unit 30 will be explained based on the flowchart of FIG. 2. In addition, 5 (i=1.2.3,・
) indicates each step.

When this control is started when the engine is started, necessary initial settings are performed, and then various signals are read from sensors and switches (Sl).

Next, the engine rotation speed N5 is calculated using the crank angle signal from the crank angle sensor 34 (S2), and then a volatility determination flag F for determining whether the volatility of the fuel is good or bad is set. It is determined whether (S3). Note that this volatility determination flag F is initially set to F=O at startup, but after startup, it is set to 0 in the volatility determination routine described later.
or set to l.

When F=O, that is, when the volatility of the fuel is high, map A1 shown by the solid line in FIG. 3 is selected in order to set the target rotational speed N0 small (S4), and then the basic bypass air amount G is selected. In order to set the map to be small, map B1 shown by a solid line in FIG. 4 is selected (S5). On the other hand, in the case of F=1, that is, when the volatility of the fuel is low, the target rotation speed N0 is increased (
In order to set the basic bypass air amount G, map A2 shown by a broken line in FIG. 3 is selected (S6), and then map B2 shown by a broken line in FIG.
7).

Next, the water temperature T is determined using the map selected from the maps A1 and A2. The target rotation speed No. is calculated from (S8
), then basic bypass air IG is calculated from water/l1To using the map selected from maps B1-82 (S9).

Next, it is determined whether or not it is idling based on the signals from the idle switch and the neutral position switch of the transmission (SIO), and if it is idling, the engine rotation speed N and the target rotation speed N0 are determined. Deviation ΔN is ΔN=
N, -N0 (Sll), and then an increase ΔGFm in the feedback correction amount (hereinafter referred to as F/B correction amount) is calculated from the rotational speed deviation ΔN using the map shown in FIG. 5 (S12). ), then the increase in the F/B correction amount ΔGFB is added to the previous F/B correction amount G F s calculated last time and stored in the RAM memory to obtain the current F/B correction I.
G r ll is calculated (313). When not in idle, F/B correction I G Fa is GFI=O
(314).

Next, in order to determine whether the volatility of the fuel is good or bad, it is first determined whether the water temperature T is 50°C or less (S15), and Y
If es, go to S16; if No, go to 519; if T8≦50"C, F/B correction fit
G r m is the upper limit value GF□□ for which feedback can be corrected
If it is less than a smaller predetermined value α, the upper limit value GFB of the F/B correction correction IC is set to increase the engine rotation speed N2.
It is determined whether the amount has been increased to near Hmx (3
16).

That is, at the time of initial setting, flag F is set to F=0 and map A1 and map B1 are selected, so when heavy fuel with low volatility is used and the water temperature T8 is low, the engine rotation speed Ne will rise. The F/B correction correction IC becomes weaker and GFff>α. Therefore, in the case of GFfi>α, it is determined that the volatility of the fuel is low, and from S16 to 31
7, it is determined whether the volatility determination flag F is F=1 or not, and if F=0, the target rotation speed N is determined as that the volatility of the fuel is low. In order to recalculate the basic bypass air amount GB, the volatility determination flag F is set to F=1 (318
) to move to 33. If F=1, the fuel is calculated to have low volatility, so the process directly proceeds to S22.

When the F/B correction 1 cm is less than the predetermined value α and the volatility of the fuel itself is sufficiently high, the F/B correction I G y s is the lower limit value GFl+++ that allows feedback correction! Whether the F/B correction amount GFI is equal to or greater than a predetermined value β larger than □, that is, the engine rotation speed N, is determined by its lower limit value G□+
It is determined whether or not Ml has been applied to near mi++ (
31B).

That is, when using a heavy fuel with low volatility, when warm-up progresses from the state where MAP A2 and MAP B2 are selected and the volatility of the fuel becomes sufficiently high, the engine rotation speed N becomes the target. Since the engine rotation speed N is too high than the engine rotation speed N0, in order to lower the engine rotation speed N, GFB<β.

Therefore, when GFll<β, it is determined in S20 whether the flag F=0 or not, and if F=1, the target rotation speed N0 and the basic bypass air amount G are recalculated assuming that the fuel is highly volatile. Therefore, the volatility determination flag F is set to F=O (S21) and the process moves to 83. In the case of F=O, it is calculated that the fuel is highly volatile, so
The process directly advances to S22.

In S22, it is determined whether or not these external loads are operating based on the switch signals of the power steering, air conditioner, etc., and if they are operating, the load correction amount G corresponding to the external load is displayed on a map or table. It is calculated based on (S
23), if it is not operating, the load correction amount GL is
L=0 is set (S24).

Next, it is determined whether the vehicle is decelerating or not based on the signal from the throttle opening sensor 33 (S25), and if the vehicle is in 1st gear, the dashpot air correction amount G , , are calculated (S26), and if the J series is not present, the dump spot air correction amount G is calculated. , is Go
r=0 is set (327).

Next, the final bypass air amount GA is G^=G8+G Fl
+ G L + G op (S28)
, the drive pulse corresponding to the final bypass air amount GA is ■S
It is output to the C valve (S29) and then returns to S1.

Next, the operation of the idle speed control will be explained with reference to the time chart of FIG. 6.

In the idling state after starting engine E, water temperature T
There is no problem with standard gasoline fuel with high volatility when w is not high enough, but if heavy fuel with low volatility is supplied to the engine, the flag F = 0 is set in the initial setting. Then, map A1 and map B1 are selected, and the target rotation speed N is set assuming normal gasoline fuel. I
and basic bypass air IG are set, so the air-fuel mixture becomes over-lean and the engine speed N becomes the target speed N. It becomes lower than 1. As a result, the feedback correction amount GFll increases to become GFll>α, and it is determined that the volatility of the fuel is low and MAP A2 and MAP B2 are selected via the flag F, so that the target rotation speed N. I is the target rotational speed N higher than that. 2 and the basic bypass air Ic is also switched to a large value. the result,
Engine speed N. Feedback control is performed so that the number of revolutions increases and becomes the target rotational speed No.2.

As the water temperature Tw increases, the volatility within the combustion chamber increases and the combustibility improves, so the target rotational speed N02 and the basic bypass air amount Gg are gradually changed to lower values.

When the water temperature T, , becomes higher than 50°C, the volatility of even heavy fuel becomes sufficiently high, so the engine speed N8 starts to increase more than the target speed N02, and the feedback correction amount GFB becomes negative. CF increases to ! 1 <
.beta., so it is determined that the volatility of the fuel is not low, and map At and map B1 are selected via flag F. Therefore, the target rotational speed N02 is switched to the original target rotational speed NO+, and the basic bypass air Ic is also switched to the original small value.

As described above, the lower the volatility of the fuel, the higher the target rotational speed N0 is set and the basic bypass air amount G.

By setting a large value, it is possible to improve idle stability.

In this embodiment, volatility was detected from the F/B correction amount GF[l, but for example, as shown in FIG. A U-bent optical fiber sensor 53 including a light emitting element 51 arranged to face each other and a light receiving element 52 arranged to face the other end of the optical fiber 50 is attached to the fuel tank 5.
It may be provided on the side wall portion of No. 4. In this case, the fuel tank 54
The heavier the fuel with lower volatility, the greater the attenuation of light and the smaller the output from the light-receiving element 52. Since the output from the element 52 increases, the volatility of the fuel is detected based on the output from the light receiving element 52.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an engine and its control system, FIG. 2 is a flowchart of idle rotation speed control, FIG. 3 is a characteristic diagram of target rotation speed, and FIG. The figure is a characteristic diagram of the basic bypass air amount, Figure 5 is a characteristic diagram of the increase in F/B correction amount, Figure 6 is a time chart of engine rotation speed, etc., and Figure 7 is a fuel tank and U vent optical fiber sensor. FIG. E...Engine, 26...■SC valve, 34...Water temperature sensor, 53 Sensor.

Claims (1)

[Claims] (1) In an engine idle speed control device equipped with a feedback control means for performing feedback control so that the engine speed becomes a target speed, the volatility of the fuel supplied to the engine is directly or indirectly detected. An engine idle speed control device comprising a detection means, and a target rotation speed setting means for receiving an output from the detection means and setting a target rotation speed higher as the volatility of the fuel is lower.