JP3544741B2 - Engine idle speed control method - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to an idle speed control method for an engine that prevents a decrease in engine speed and instability due to an alternator power generation load that increases when power is supplied to an electric load such as a fog lamp or a wiper during idling operation.
[0002]
[Prior art]
In recent idle speed control, there is a tendency to improve the fuel efficiency and quietness by keeping the engine speed low, but if the idle speed is kept low, the engine will not rotate even under the influence of a slight load. Easy to stabilize.
[0003]
The most prominent factor of the engine rotation instability is an increase in alternator power generation load. When power is supplied to the electric load during the idling operation, the voltage of the battery drops, and the alternator power generation load increases. Then, this becomes the engine load, which causes a decrease in idling rotation or instability.
[0004]
The electric loads driven by the battery power supply include continuous electric loads required to drive the engine such as an ignition coil, an injector coil, and a control device, and situations such as a headlamp, a rear defogger, a wiper motor, and an air conditioner. There is a situational electrical load that is consumed accordingly. The instability of the idle speed is caused by the fact that when power is supplied to the situational electric load, the feedback control cannot follow the load fluctuation.
[0005]
Conventionally, in order to prevent a decrease in idling speed or instability under such a transient situation, for example, in Japanese Unexamined Patent Publication No. Hei 3-237241, when power is supplied to a situational electric load, By detecting an operation signal and increasing the amount of air passing through an idle speed control (hereinafter, “ISC”) valve in a stepwise manner, the engine output is increased in a stepwise manner, thereby preventing the idle speed from decreasing. . In Japanese Patent Publication No. 4-32216, the change amount (ΔV) of the alternator generated voltage (or battery voltage) within a predetermined time is compared with a predetermined determination value (β), and the change amount (ΔV) is determined. When it is larger than the determination value (β), it is determined that power has been supplied to the situational electric load, and when this variation (ΔV) has increased from the previous variation, the passage of the ISC valve Control is performed to increase the amount of air in a stepwise manner.
[0006]
[Problems to be solved by the invention]
However, in addition to headlights and rear defoggers, there are many situational electrical loads, such as brake lamps and radiator fans. Poor feasibility.
[0007]
In this regard, in the latter idle speed control, the change in only the voltage of the battery is detected to detect whether the power is supplied to the situational electric load, so the configuration is relatively simple. Since the battery voltage fluctuates even under normal conditions due to continuous electric loads such as ignition coils and injectors, it is extremely difficult to judge from the fluctuations in the battery voltage that power has been supplied to the situational electric load. difficult.
[0008]
That is, when the battery voltage VB changes as shown in FIG. 6A, the change (variation ΔV) of the battery voltage VB is measured at a relatively long cycle as shown in FIG. Since the fluctuation of voltage VB is large, the determination value (β) can be set to a relatively large value that allows the continuous fluctuation of the electric load, but the response becomes poor and the battery voltage VB becomes low. In the case where the voltage drop occurs in the same pattern, the variation (ΔV) may differ depending on the detection timing as shown in FIGS. There is. Conversely, if the detection cycle is shortened as shown in FIG. 4D, the response is improved, but the fluctuation amount (ΔV) is reduced, and the voltage fluctuation due to the general electric load can be clearly distinguished. , And erroneous detection is likely to occur.
[0009]
As described above, in the conventional control method, it is difficult to detect the situational operation of the electric load with high accuracy from the temporal change (ΔV) of the battery voltage VB.
[0010]
The present invention has been made in view of the above circumstances, without detecting the operation of each situational electric load one by one, at a low cost, a reduction in idle speed caused by alternator power generation load at the time of battery voltage drop, It is an object of the present invention to provide an idle speed control method for an engine that can appropriately prevent instability.
[0011]
[Means for Solving the Problems]
The engine idle speed control method according to the present invention, the battery voltage during idle weighted average of every predetermined time to calculate the average battery voltage, the difference between the average battery voltage and the latest battery voltage, preset In addition, when the fluctuation of the continuous electric load exceeds a permissible determination value, it is determined that the power is turned on to the situational electric load, and the amount of passing air by the idle speed control valve is increased and corrected.
[0012]
[Operation]
In the present invention, an average battery voltage of a predetermined first order delay the weighted average by monitoring the battery voltage during idling at predetermined time intervals, the difference between the average battery voltage and the latest battery voltage, preset and continued When the variation of the dynamic electric load exceeds an allowable determination value, it is determined that the power is turned on to the circumstance electric load, and the amount of passing air by the idle speed control valve is increased and the engine output is increased.
[0013]
【Example】
Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 5 shows an overall schematic diagram of the engine.
In FIG. 5, reference numeral 1 denotes an engine, and an injector 3 faces a downstream end of an intake pipe 2 communicating with an intake port of the engine 1. A collector chamber 4 is interposed in the middle of the upstream side of the intake pipe 2, a throttle valve 5 is interposed upstream of the collector chamber 4, and an air cleaner 6 is interposed at an air intake port upstream of the collector chamber 4.
[0014]
An air bypass passage 7 is connected to the intake pipe 2 so as to bypass the throttle valve 5 and communicate upstream and downstream of the throttle valve 5. An ISC valve 8 for controlling the amount is interposed. On the other hand, the collector chamber 4 is provided with an intake air temperature sensor 9 for detecting an intake air temperature, and is connected to a pressure sensor 10 for detecting an intake pipe pressure downstream of the throttle valve 5.
[0015]
A coolant temperature sensor 11 for detecting a coolant temperature is provided in a coolant passage 1 a formed in the engine 1. Further, a cam angle sensor 13 that detects a protrusion or a slit formed on the cam rotor 12 and outputs a cam pulse to an electronic control unit 21 described later is provided opposite to the cam rotor 12 connected to a cam shaft (not shown). Further, a 02 sensor 15 faces the exhaust pipe 14 communicating with the exhaust port of the engine 1 upstream of a catalytic converter (not shown). The electronic control unit 21 calculates the engine speed NE from the interval time between the cam pulses, and calculates the air-fuel ratio feedback correction coefficient as a correction term when setting the fuel injection amount from the output signal of the 02 sensor 15. I do.
[0016]
Reference numeral 16 denotes an alternator, which is connected via a belt 18 to a crank pulley 17 mounted on a crankshaft (not shown). The electric current generated by the alternator 16 is charged in the battery 19 shown in FIG. 20 is energized.
[0017]
The electronic control unit 21 performs various controls such as fuel injection control, ignition timing control, and idle speed control based on output signals of various sensors and switches. As shown in FIG. 4, the electronic control device 21 mainly includes a microcomputer in which a ROM 22, a RAM 23, a CPU 24, and an I / O interface 25 are connected to each other via a bus line. A control program and various data are stored, and a calculation result obtained by the CPU 24 and the like are temporarily stored in the RAM 23.
[0018]
A pressure sensor 10, a cam angle sensor 13, and an O2 sensor 15 are connected to the input side of the I / O interface 25, and a water temperature sensor 11 and an intake air temperature sensor 9 are connected via an A / D converter 26. Further, the battery 19 is connected, and the battery voltage VB is monitored. The output side is connected to respective drive coils of the ISC valve 8 and the injector 3 via a drive circuit 27.
[0019]
Further, the electronic control unit 21 has a built-in constant voltage circuit 31. The constant voltage circuit 31 is connected to the battery 19 via a relay contact of an ECU relay 32. The battery 19 is connected via an ignition switch 33. When the ignition switch 33 is turned on and the contact point of the ECU relay 32 is closed, the constant voltage circuit 31 stabilizes the voltage of the battery 19 and supplies the voltage to each section of the electronic control device 21.
[0020]
In the fuel injection control, the fuel injection amount is obtained based on the output signals of the sensors, and a pulse width corresponding to the fuel injection amount is output to the injector 3 via the drive circuit 27 at a predetermined timing, and the fuel injection amount is determined by the injector 3 to a predetermined value. Inject the metered fuel. In the idle speed control, the control amount for the ISC valve 8 is calculated based on the difference between the engine speed during idling and the target speed, and the valve opening of the ISC valve 8 is controlled. The amount of bypass air passing through is adjusted, and feedback control is performed so that the engine speed matches the target speed. Further, the voltage of the battery 19 is monitored, and it is determined whether or not the power is supplied to the situational electric load 20. When it is determined that the power is supplied, the valve opening of the ISC valve 8 is increased and corrected, and Prevents reduction in rotation speed or instability.
[0021]
Next, the procedure for controlling the idle speed by the electronic control unit 21 will be described with reference to the flowcharts shown in FIGS.
[0022]
When it is determined that the engine operation state is idling, in a routine started every 40 ms shown in FIG. 2, the battery voltage VB is weighted and averaged to calculate the average battery voltage VBAVE. That is, first, in step S1, the difference between the A / D-converted battery voltage VB and the average battery voltage VBAVE calculated by the weighted average at the time of execution of the previous routine is obtained, and in step S2, this difference (VB-VBAVE) is calculated. 1/16 times.
[0023]
Then, in step S3, the calculation result of step S2 is added to the average battery voltage VBAVE calculated in the previous execution of the routine, the value is stored in the RAM 23 as a new average battery voltage VBAVE, and the routine exits.
[0024]
As a result, the battery voltage VB undergoes a primary delay process of 16 × 40 ms by the weighted averaging process. For example, the battery voltage VB temporarily drops suddenly at the moment when the power is turned on to the situational electric load 20. Even in such a state, the average battery voltage VBVE hardly changes. In the process of gradually increasing the battery voltage VB by charging the battery 19, the average battery voltage VBAVE also gradually increases with a time constant of 16 × 40 ms.
[0025]
In the routine started every 5 ms shown in FIG. 1, it is determined whether or not the amount of bypass air passing through the air bypass passage 7 should be increased from conditions such as the battery voltage VB. When the amount is increased, the valve of the ISC valve 8 is opened. The ON (valve opening) duty for controlling the degree is skip-controlled. The ON duty for the ISC valve 8 during normal idle operation is set for each control mode in an idle speed control routine (not shown). In this control mode, open-loop control or closed-loop control is selected according to the cooling water temperature, the engine speed, and the like.
[0026]
Hereinafter, description will be made with reference to a time chart shown in FIG.
First, in step S11, a difference (difference voltage) DVB between the latest average battery voltage VBAVE and the latest battery voltage VB is determined. In step S12, the battery voltage VB is set to a voltage relative to the average battery voltage VBAVE. Determine if it is descending. If DVB <0, it is determined that no voltage drop has occurred, and the flow branches to step S14 to set the skippable flag F, and then exits from the routine to shift to normal idle speed control.
[0027]
Further, when the power is supplied to the status electric load 20 such as the headlight, the rear defogger, the brake lamp, and the radiator fan, the battery voltage VB drops. When it is determined that DVB ≧ 0 in the above step S12, Proceeding to step S13, the difference voltage DVB is compared with a skip determination voltage KDVBH as a preset determination value, and it is determined whether the difference voltage DVB is higher than the skip determination voltage KDVBH. At the initial stage of the voltage drop, as shown in FIG. 3, the difference voltage DVB has not yet sufficiently increased, so that DVB <KDVBH, and the flow branches to step S15. It is determined whether DVB is lower than skippability determination voltage KDVBL. When DVB <KDVBL, the routine proceeds to step S14, and when DVB ≧ KDVBL, the routine exits from the routine and shifts to normal idle speed control. Immediately after the power is turned on to the situational electric load 20, since DVB <KDVBL, the process proceeds to step S14, sets the skip enable flag F, exits the routine, and shifts to the normal idle speed control. .
[0028]
Therefore, in step S13, even if a voltage drop occurs in the battery 19, during DVB <KDVBH, the process directly shifts to the normal idle speed control. In such a case, control hunting is prevented without increasing the bypass air amount by this routine.
[0029]
Then, when the power supply to the situational electric load 20 is turned on, the difference voltage DVB gradually increases. When DVB ≧ KDVBH, the process proceeds from step S13 to step S16, and the value of the skippable flag F is referred to. In the first routine after DVB ≧ KDVBH, the skippable flag F has already been set in step S14. Thus, in step S17, the skippable flag F is cleared, and the process proceeds to step S18. In steps S18 to S20, the engine operating conditions are determined.
[0030]
First, in step S18, the engine speed NE is compared with a preset skip determination speed KNESK. In step S19, it is determined whether at least KTAFSTA seconds have elapsed since the engine was started, and in step S20, the idle speed was determined. It is determined whether the control mode of the control is a closed loop. Then, when NE <KNESK, KTAFSTA seconds have elapsed after the start, and in the closed loop control state, it is determined that the skip increasing condition is satisfied, and the routine proceeds to step S21, where the opening of the ISC valve 8 is skip-controlled.
[0031]
On the other hand, if NE ≧ KNESK, or less than KTAFSTA seconds after starting, or if the control mode is an open loop, the process directly exits the routine and shifts to normal idle speed control. The above-described skip determination rotational speed KNESK is appropriately set according to the engine to be adopted, for example, when the idling rotational speed is 850 rpm and the margin for increasing the rotational speed is 50 rpm, the rotational speed is set to 900 rpm.
[0032]
In step S21, the duty ratio KDSKVB corresponding to the increased air amount is added to the ON duty DISC set in the normal idle speed control routine. In step S22, the added value becomes 100% (fully open). It is determined whether or not it exceeds, and if DISC + KDSKVB ≧ 100%, the process proceeds to step S24, where the ON duty DISC is set to 100%, and the routine exits. If DISC + KDSKVB <100%, the routine proceeds to step S23, where the value added in step S21 is set as the ON duty DISC for the new ISC valve 8, and the routine exits. The duty ratio KDSKVB is a fixed value, and is set in advance by an experiment or the like corresponding to the voltage peak value of the situational electric load 20.
[0033]
When the difference voltage DVB is higher than the skip determination voltage KDVBH at the next startup of the routine, the process proceeds from step S13 to step S16. At this time, since the skip enable flag F has been cleared in step S17, The process directly exits the routine and shifts to normal idle speed control. As a result, the idle speed is feedback-controlled. Therefore, the control for skipping the opening of the ISC valve 8 is performed only once when the difference voltage DVB indicates a value equal to or higher than the skip determination voltage KDVBH. As a result, it is possible to prevent a sudden increase in the idle speed due to the skip control.
[0034]
When the ON duty DISC set in step S23 is output to the ISC valve 8 at a predetermined timing, the bypass air amount is increased by the duty ratio KDSKVB by the ISC valve 8, the engine output rises, and the engine output increases due to the power generation load of the alternator 16. The reduction or instability of the rotation speed is suppressed, and then this idle speed control is returned to a constant state by normal feedback control. At that time, the battery voltage VB also gradually recovers, and when DVB <KDVBL soon (see FIG. 3), the process proceeds from step S13 to step S14 via step S15, sets the skip enable flag F, and exits the routine. Shift to idle speed control.
[0035]
As described above, since it is determined whether or not power has been supplied to the contextual electric load 20 based on a change in the battery voltage VB with respect to the weighted average battery voltage VBAVE, it is necessary to detect output signals of all electric loads. Cost can be reduced. Further, since it is determined whether or not the power is supplied to the situational electric load 20 based on the difference voltage DVB between the weighted average value of the battery voltage VB and the latest battery voltage VB, Even if the ratio of the voltage fluctuation when the electric load 20 is turned on is set to a large value, no erroneous determination occurs. In addition, since the upper limit of the idle speed is limited by the skip determination speed KNESK, even when the electric load repeats ON / OFF at a relatively fast cycle such as an intermittent operation of a blinker or a wiper motor, the engine speed is not changed. Will not rise unnecessarily.
[0036]
【The invention's effect】
As described above, according to the present invention, it is determined whether or not power has been supplied to the situational electric load based on the difference between the weighted average of the battery voltage and the latest battery voltage. And can be realized without erroneous determination even if a relatively large determination value for determining whether power is supplied to the situational electric load is set. Therefore, it is possible to accurately predict and prevent the reduction and instability of the idle speed caused by the alternator power generation load when the battery voltage drops.
[0037]
Further, since it is determined whether or not power is supplied to the situational electric load based on the voltage fluctuation of the battery, it is not necessary to detect the output signals of all the electric loads one by one, and the cost can be reduced. .
[Brief description of the drawings]
FIG. 1 is a flowchart showing an ON duty setting routine at the time of voltage drop. FIG. 2 is a flowchart showing a routine for calculating an average battery voltage. FIG. 3 is a battery voltage and an average battery voltage when power is turned on to a situational electric load. , Difference voltage, and time chart showing values of skippable flags. FIG. 4 is a circuit diagram of an electronic control system. FIG. 5 is a schematic diagram of an engine. FIG. 6 is a time chart showing a state of detection of occurrence of a voltage drop in a conventional example. [Explanation of symbols]
5 Throttle valve 8 Idle speed control valve 20 Situational electric load DISC ON duty DVB Difference voltage KDVBH Skip judgment voltage (predetermined judgment value)
VB Battery voltage VBAVE Average battery voltage

Claims (1)

An average battery voltage is calculated by performing a weighted average of the battery voltage at the time of idling at predetermined time intervals , and a difference between the average battery voltage and the latest battery voltage is set in advance and a determination is made that a continuous change in the electric load is allowable. An idle speed control method for an engine, characterized in that it is determined that power has been supplied to a situational electric load when the value exceeds the value, and the amount of air passing through the idle speed control valve is increased and corrected.

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