JPS6019932A - Method of controlling rotational speed of internal-combustion engine - Google Patents

Abstract

PURPOSE:To prevent drop of an engine rotational speed at transition and smoothly decrease the rotational speed to a target rotational speed, by controlling an amount of air bypassing a throttle valve upon receiving a load to increase the amount of air over a target amount, and decreasing the amount of air to the target amount with a reduction rate increased. CONSTITUTION:A target rotational speed NF according to an operational condition and an estimated duty ratio De according to an amount of air are set. When an ISC timing is reached, an average value NE of an engine rotational speed is calculated, and a basic duty ratio Do for feedback controlling the average value NE to the target value NF is calculated. When a load is received, the estimated duty ratio De for feedforward control is added to the basic duty ratio Do to determine a control duty ratio D. An opening degree of an ISC valve is controlled by the control duty ratio D so that the average value of the engine rotational speed may become the target rotational speed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the rotational speed of an internal combustion engine, and more particularly, to a method for controlling the rotational speed of an internal combustion engine, and in particular, for controlling the amount of air flowing through a detour provided around a throttle valve to bring the engine rotational speed to a target rotational speed. The present invention relates to a method for controlling the rotational speed of an internal combustion engine.

In modern internal combustion engines, there is a trend to reduce the weight of the engine and to set the idle speed low in order to improve fuel efficiency.

For this reason, when idling, high beams are turned on, FC is activated, electric fans are driven, and automatic transmissions are biased, even a slight load caused by operating the shift lever, etc., causes a drop in the engine speed, causing a drop in idling. Sometimes the engine speed becomes unstable.

Furthermore, if deposits are deposited on the system throttle valve due to changes over time, the engine speed gradually decreases and the engine speed during idling becomes unstable.

For this reason, a detour is provided to bypass the throttle valve, and when the throttle valve is fully closed and the vehicle speed is at a predetermined value (for example, 0 to
2.5 km/h) or less, that is, when the engine is idling, a method is known in which the amount of air flowing through this detour is controlled and the engine speed is feedback-controlled to the target speed. This detour is equipped with an idle rotation speed control valve (ISO pulp) whose opening is controlled by a step motor or solenoid to control the air 'JJk' flowing into the detour, and which controls the opening of this ISC valve. As a result, the engine opening rotation speed is feedback-controlled to be close to the target rotation speed determined according to the engine load, shift position, etc. Note that when feedback control is not performed, the ISC valve is maintained at a predetermined opening degree.

However, in this method, the engine speed is controlled by feedback, so the amount of air flowing to the detour is controlled as the engine speed fluctuates, and it takes time for this control to be reflected in the engine speed. However, especially when a load is applied and the engine speed decreases, there is a problem that the engine speed decreases and the engine stops before the feedback control is reflected on the engine speed. For this reason, it has been proposed to predetermine a target air amount when a load is applied, and to perform feedforward control of the ISO valve so that the target air amount flows to a detour when the load is applied.

However, immediately after the load is applied, the load value is transiently large, and then it becomes a steady state, so there is a problem that the amount of air is insufficient during the transient period, leading to a drop in the engine speed and a stall. For example, in an internal combustion engine equipped with an automatic magic transmission, immediately after shifting the shift lever from the neutral range (N range) to the drive range (D range) or reverse range (R range), the fluid resistance of the torque converter is large, so the transient The load increases. For this reason, it is conceivable that when a load is applied, the air amount is increased from the target air amount when the load is applied, and then this air amount is decreased at a constant rate to the target air amount. However, if the amount of air is reduced at a certain rate, the amount of air will be excessive in operating conditions that are close to steady state, and unnatural problems such as the -H engine speed rising and falling when the engine speed drops will occur. The problem arises that the behavior is displayed.

The present invention has been made to solve the above-mentioned problems, and it prevents the engine speed from dropping or stalling during transient periods, and
An object of the present invention is to provide a method for controlling the rotational speed of an internal combustion engine that smoothly lowers the engine rotational speed to a target rotational speed.

In order to achieve the above object, the present invention increases the amount of air flowing through the detour when a load is applied, compared to the target amount of air when the load is applied, and then flows the detour while increasing the rate of decrease. It is configured to reduce the amount of flowing air to the target amount of air. The rate of decrease is changed depending on the engine speed, the time since the start of decrease, the number of times of decrease, the amount of air after decrease, etc., and the rate of decrease is increased in the latter half of the decrease. Note that the reduction rate may be changed continuously or in steps.

According to the above configuration of the present invention, the optimal amount of air is supplied to the transient peak and is reduced by changing the reduction rate, so that the engine speed can be smoothly lowered to the target speed. can get.

Next, an example of an internal combustion engine to which the present invention is applied will be explained with reference to Figure 1. This engine is equipped with an automatic transmission and is controlled by an electronic control circuit such as a microcomputer, and is equipped with an air flow meter 2 downstream of an air cleaner (not shown) for detecting the amount of intake air. The air flow meter 2 includes a convention plate rotatably provided in a damping chamber, a measuring plate connected to the convention plate, and a potentiometer 4 that detects the opening degree of the convention plate. Therefore, the intake air amount can be determined from the intake air amount signal output from the potentiometer as a voltage value. Also, there is a suction valve near the air flow meter 2. ! An intake air temperature sensor 6 is provided which detects air temperature 17 and outputs an intake air temperature signal.

A throttle valve 8 is arranged downstream of the air flow meter 2, and the throttle valve 8 is in a fully closed state (
An idle switch 10 that is turned on at idle position) is added, and a surge tank 12 is provided downstream of the throttle valve 8. A bypass path 14 is provided to bypass the throttle valve 8 and communicate the upstream side of the throttle valve with the surge tank 12 on the downstream side of the throttle valve.

An ISC pulp 16 whose opening degree is adjusted by controlling the excitation current of a solenoid is attached to this detour 14. The surge tank 12 is connected to the engine 20 via an intake manifold 18 and an intake boat 22.
It communicates with the combustion chamber. A fuel injection valve 24 is attached to each cylinder so as to protrude into the intake manifold 18.

The combustion chamber of the engine 20 is connected via an exhaust port 26 and an exhaust manifold 28 to a catalytic converter (not shown) filled with a three-way catalyst. An 02 sensor 30 is attached to the exhaust manifold 28 to detect the residual oxygen concentration in the exhaust gas and output an air-fuel ratio signal. An engine coolant temperature sensor 34 is attached to the engine block 32 so as to penetrate through the block 32 and protrude into the water jacket. This cooling water temperature sensor 34 detects the engine cooling water temperature and outputs a water temperature signal.

A false spark plug 38 is attached to each cylinder so as to penetrate the cylinder head 36 of the engine 20 and protrude into the combustion chamber. The spark plug 38 is connected via a distributor 40 and an igniter 42 to an electronic control circuit 44 composed of a microcomputer or the like. A cylinder discrimination sensor 46 and a crank angle sensor 48 are installed inside the distributor 40, each of which includes a signal rotor fixed to the distributor shaft and a pickup fixed to the distributor housing. In the case of a six-cylinder engine, the cylinder discrimination sensor 46 outputs a cylinder discrimination signal, for example, every 7200 CA, and the crank angle sensor 48 outputs an engine rotation speed signal, for example, every 30 CA.

The electronic control circuit 44 also includes a key switch 50, a neutral start switch 52, and an air conditioner switch 54.
, a vehicle speed sensor 56, and a battery 58 are connected. The key switch 50 outputs a starter signal when starting the engine, the neutral start switch 52 outputs a neutral signal only when the transmission is in the neutral position, and the air conditioner switch 54 outputs an air conditioner signal when the air conditioner nano compressor is activated. . The vehicle speed sensor 56 is composed of a magnet fixed to the speedometer cable, a reed switch, and a magnetically sensitive element, and outputs a vehicle speed signal in accordance with the rotation of the speedometer cable.

As shown in FIG. 2, the electronic control circuit 44 includes a central processing unit (CPU) 60, a read-only memory IJ (RoM
)62. Ramdam access memory (RAM) 64,
It is composed of a backup RAM (BU-RAM) 66, an input/output converter 8, an analog/digital converter (ADC) 70, and buses and components such as a data bus and a control bus that connect these. In the entry and exit capotro 8,
A vehicle speed signal, a cylinder discrimination signal, an engine speed signal, a throttle fully closed signal from the idle switch 10, an air-fuel ratio signal, a starter signal, a neutral signal, and an air conditioner signal are input. In addition, the input/output capotro 8 outputs to the drive circuit an SC pulp control signal for controlling the opening degree of the ISC valve, a fuel injection signal for opening and closing the fuel injection valve, and an ignition signal for turning on and off the igniter. The drive circuit operates the ISO valve, fuel injection valve,
Control each igniter. Further, an intake air amount signal, an intake air temperature signal, a battery voltage, and a water temperature signal are input to the ADC 70, and the ADC sequentially converts these signals into digital signals according to instructions from the CPU. ROM62 contains information such as engine cooling water temperature, intake temperature, load condition, and shift lever.
The target rotation speed determined according to the range position, etc., the estimated amount for feedforward control when a load is applied, data on the amount of increase and rate of decrease in air amount during transient periods, and other control programs, etc. It is stored in advance.

Next, an embodiment in which the present invention is applied to the engine as described above will be described in detail. In the following, an embodiment will be described in which the shift lever of the automatic transmission is shifted from the N range to the D or N range and the duty ratio of the ISO pulp is controlled.

FIG. 3 shows the middle of the main routine of the first embodiment of the present invention. In step 100, the engine operating state is determined based on the air conditioner signal, the neutral signal, etc., and the target rotation is determined according to this operating state. Number NF'
Then, the expected duty ratio De corresponding to the expected air amount according to this operating state is set in a predetermined area of the RAM. In the next step 102, it is determined whether the idle speed control (rsC) timing has come, by determining whether it is every 120° CA, for example. IS
When the C timing is reached, the average value i of the engine speed is calculated based on the engine speed signal in step 104, and it is determined in step 106 whether the feedback control condition is satisfied. This feedback control condition is, for example, when the throttle valve is fully closed and the vehicle speed is at a predetermined value (
(for example, 2.5 h/h) or less, and the engine cooling water temperature is a predetermined temperature (for example, 70° C. or more).

If the feedback control condition is satisfied, in step 110, a basic duty ratio Do for feedback control of the average value of the engine rotation speed to the target rotation speed is calculated, and feedforward control is performed when a load is applied. The control duty ratio is determined by adding the expected duty ratio De to the basic duty ratio.

In the next step 112, it is determined whether the learning control condition is satisfied, and if it is, the learning control is performed in step 114, and then in step 116, the control duty ratio is stored in the register as the output duty ratio Dout. set. An example of this learning control is as follows. One is that after a predetermined period of time has elapsed after feedback control, the average value of the engine speed changes to the target engine speed NF constant value (for example,
25r, p, 11! , ) When the deviation between the output duty ratio Dout and the learned value stored in the BU-RAM is greater than or equal to a predetermined value, the learned value is gradually increased or decreased to bring the learned value closer to Dout. It's a method. Another method is to constantly compare the average engine speed and the target engine speed, and set the learned value based on the magnitude relationship.
If it is determined that the method of increasing or decreasing the learned value to bring it closer to is not established, the control duty ratio is set as the output duty ratio Dout in step 108.

FIG. 4 shows an interrupt routine executed every predetermined time (for example, 4.m8ec) to control the ISC valve. In step 118, an NSC pulp control signal is output to excite the solenoid of the SC valve, in step 120, TSCSC pulp off is calculated to demagnetize the solenoid from the output duty ratio D out, and in the next step 122, the off time is set for the conveyor. Set in register. As a result, the ISC pulp solenoid is demagnetized at the off time.

As explained above, when the feedback control condition is satisfied, the basic duty ratio Do is changed so that the average value of the engine speed is equal to the target speed, and when there is an expected duty ratio De, the expected duty ratio The opening degree of the ISO pulp is controlled by the added value. Note that during open loop control, the control duty ratio becomes a predetermined value, so the ISC valve opening degree is kept constant.

Next, a routine for calculating the output duty ratio Dout of this embodiment will be explained with reference to FIG. In the routine of Jin, the increased duty ratio DI at the time of shifting is set to a predetermined value and reduced by changing the damping ratio, based on the control duty ratio determined in steps 108 and 110.
The output duty ratio Dout is determined by adding D. This routine is executed at predetermined intervals, and in step 124, the shift position # is determined based on the neutral signal.
It is determined whether or not the range is in the N range, and if it is in the N range, a flag FN is set in step 126.

If it is not the N range, that is, if it is the D or N range, it is determined in step 128 whether or not 72gF is set. If flag FN is set,
That is, when shifted from the N range, the increased duty ratio DID at the time of shifting is set to a predetermined value in step 132, the flag FN k is reset in step 134, and the process proceeds to step 146. Note that the predetermined value in step 132 is given by a constant value or a function whose absolute value increases as the engine speed increases, using the engine speed as a parameter. The optimal value for each engine is determined through experiments as this constant value.

Note that since it normally takes approximately 0 to 1 sec from the time of shift until the torque converter operates, the increased duty ratio DND may be set after this time has elapsed.

On the other hand, after setting the flag FN k in step 126 or when it is determined in step 128 that the flag FN has been reset, that is, when a state other than the N range continues, the duty ratio DND is set to 0 in step 136. Determine whether or not. When the duty ratio DID is 0, the process directly proceeds to step 146, and when the duty ratio DND is other than 0, the attenuation amount α is calculated in step 130 based on the engine speed. This attenuation amount α is the 6th
As shown in Figure (1), it is determined to decrease as the engine speed increases. Incidentally, the broken line is the attenuation lid when one change is made in two stages. Further, as shown in FIGS. 6(2) and 6(3), the damping lid α may be set to a value proportional to the elapsed time T, and may be set to a value that increases as the residual value of the increased duty ratio DND decreases. And step 1
At step 38, the attenuation amount α is subtracted from the increased duty ratio DND to attenuate the duty ratio I)un. Next step 140
Then, it is determined whether or not the reduced duty ratio DND is a negative value, and if it is a negative value, the value of the duty ratio DND is set to 0 in step 142 to prevent the adder 70-.
shall be.

Then, in step 146, a value obtained by adding the increased duty ratio DND to the control duty ratio is set as the output duty ratio.

Increased duty ratio DID when controlling as above
Figure 7 shows the changes in engine speed and engine speed. The duty ratio DND changes as shown by a solid line when the damping lid α is changed continuously, and changes as shown by a broken line when changing the damping lid α in two stages. Further, the engine speed when the duty ratio DND is not used changes as shown by the broken line L3, and the engine speed when the duty ratio DID is attenuated to a constant value changes as shown by the solid line.

On the other hand, on the flow side, it changes smoothly as shown by the dashed line L2.

In addition, in the control when the feedback control condition is satisfied on the flow side, when DND is not 0, it is preferable to keep the basic duty ratio Do constant and stop the feedback control.

By the way, during feedback control, the engine speed is controlled to be a predetermined idle speed.

Therefore, if the amount of air is increased under such conditions, there is a risk that the engine speed will increase because the amount of air is already small. Therefore, the second embodiment of the present invention, which will be described below, prevents such an increase in engine speed.

This second embodiment sets the duty ratio DNDk to a predetermined value when the engine speed is above a predetermined value during a shift, and also sets the duty ratio DNDk to a predetermined value when the engine speed is less than a predetermined value and when the throttle valve opens slightly. The duty ratio D11D is set to a predetermined value within a predetermined time after fully closing. In addition, on the main rush side, the duty ratio D
YC may be set to a predetermined value. Furthermore, in explaining the main fire flow side processing routine, the main routine and ISO valve control routine are the same as those shown in FIGS. 3 and 4, so their explanation will be omitted.

FIG. 8 shows a routine executed at predetermined time intervals similar to FIG. to judge. If shifted, the engine speed NE (or average value) is set to a predetermined value (for example, 1000 to 1.500r) in step 150.
, p, m, ), and if it is greater than a predetermined value, the duty ratio DND is set to a predetermined value in step 158. On the other hand, if the engine speed is less than the predetermined value, step 15
In step 2, it is determined whether the idle switch is off, that is, whether the throttle valve is open. If the idle switch is turned off, the process proceeds to step 158, and if the idle switch is turned on, it is determined in step 154 whether or not a predetermined period of time (for example, 1 to 5 seconds) has elapsed since the idle switch was turned on. If the predetermined time has elapsed since the idle switch was turned on, the process proceeds to step 158, and if the predetermined time has elapsed, the process proceeds to step 156, described in step 130.1.
The attenuation amount α is changed in the same manner as in steps 36 to 142, and the entire attenuation process for the duty ratio DND is performed. Next, step 16
0, the control duty ratio and the duty ratio DND are added to obtain the output duty ratio Dout.

As a result of the above, when shifting from the N range, when the engine speed is above a predetermined value, the idle switch is turned on when the engine speed is less than the predetermined value, and within a predetermined time after the idle switch is turned on, and when the engine speed is less than the predetermined value, the idle switch is turned on. is off, the duty ratio DND is set to a predetermined value.

Here, when the engine speed is less than a predetermined value, the duty ratio D
The reason why ND is set to a predetermined value is because the inertia of a lightweight engine is small, so after racing, the engine speed drops and undershoot occurs, and if the torque converter load is added at this time, the engine stalls. This is because there are certain things. For this reason, after the end of racing, that is, within a predetermined time after turning on the idle switch, the increased duty ratio DNrl is set to a predetermined value to increase the air amount. In addition, the throttle lever is equipped with a dashpot that temporarily delays closing the throttle valve to the idle position, so the idle switch may remain off even though racing has ended.
This is because if a load is applied at this time, the same aK engine stall as described above may occur. For this reason, the amount of air is increased when the engine speed is below a predetermined value, that is, when the idle switch is turned off after racing ends.

As can be understood from the above, in this embodiment, as a king, the output duty is calculated by adding the increased duty ratio DND to the control duty ratio D set in step 108 of the open loop control (for example, the output duty ratio at the end of the feedback control). controlled by the ratio.

As explained above, according to this embodiment, the effect that smooth engine rotational behavior can be obtained during shifting under any driving conditions can be obtained.

In each of the embodiments described above, the increased duty ratio DNne may be attenuated at a predetermined rotation period. Also,
The present invention can also be applied to cases where various loads such as electrical loads and cooler compressors are applied. is detected. Furthermore, the present invention provides an engine equipped with an ISC valve k 4jN equipped with a step motor that controls the opening of the pulp by the number of pulses instead of the duty ratio, an engine equipped with a manual transmission, and an intake pipe downstream of the throttle valve instead of the air flow meter. It is also possible to apply the present invention to an engine equipped with a pressure sensor for detecting pressure.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of an engine to which the present invention is applied, FIG. 2 is a block diagram showing the electronic control circuit of FIG. 1,
FIG. 3 is a flowchart showing the main routine according to the embodiment of the invention, FIG. 4 is a flowchart showing the 4m5ec interrupt routine according to the embodiment of the invention, and FIG. 5 is the output duty ratio in the first embodiment of the invention. FIG. 6 is a diagram showing changes in the attenuation rate α, FIG. 7 is a diagram showing changes in the increased duty ratio, etc. of the first embodiment,
FIG. 8 is a flowchart showing a routine for calculating the output duty ratio in the second embodiment of the present invention. 10... Idle switch, 14... Detour, 16
...ISC valve, 44...Electronic control circuit, 52.
...Neutral start switch. Agent Tatsuyuki Unuma (and 1 other person) @Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Renzo ゛□ B Pi □ Time

Claims (1)

[Claims] (1) A rotational speed control method for an internal combustion engine that controls the engine rotational speed to a target rotational speed by controlling air it flowing through a detour that bypasses the throttle valve and communicates the upstream side of the throttle valve with the downstream side of the throttle valve. In. An internal combustion engine characterized in that when a load is applied, the air amount is increased from a target air amount when a load is applied, and the increased air amount is reduced to the target air amount while increasing the rate of decrease. rotation speed control method.