JPH09209806A - Idle engine speed controller for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably perform feedback correction transition so as to provide stable starting performance and the stability of an engine speed just after starting by shifting from starting time fixing output means to feedback correcting means on the basis of starting time intake pressure judging means. SOLUTION: Air is sucked from an air cleaner 1 through a throttle chamber 2 and an intake manifold 3, and an airflow control valve 5 is mounted in a pass bypassing a throttle valve 4 in the throttle chamber 2. The airflow control valve 5 is controlled by a duty signal from a control unit 6. A driving signal in its feedback condition may not be generated from the airflow control valve 5 until pressure by which the airflow control valve 5 can be operated is developed by inlet negative pressure conditions for judgement after starting from starting. An always stable opening area can be secured regardless of the magnitude and fluctuation of the intake pressure, hereby, the starting performance of an engine and rotational stability after starting can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an idle speed control device for controlling an idle speed after starting an internal combustion engine.

[0002]

2. Description of the Related Art In an internal combustion engine in which an air flow control valve is provided in a bypass passage that bypasses a throttle valve, the air flow control valve is fixed at a predetermined duty ratio at the time of starting, and a target rotation is started when the engine operating condition becomes stable. Feedback correction is performed so that the rotation speed converges to a desired number, and the setting is made so that a desired rotation speed can be obtained (JP-A-58-158344). In this case, the transition condition from the time of starting to the time of starting is generally carried out by detecting that the number of revolutions of the engine has reached a predetermined number of revolutions.

[0003]

In the idle speed control device according to the above-mentioned prior art, generally, the air flow rate control valve to be controlled is an air flow rate control part and an electric drive part for moving it, that is, a solenoid valve. Composed of and. In such an air flow rate control valve, a desired air flow rate is obtained by structurally balancing the electric driving force of the solenoid valve and the mechanical force pressing the flow rate control unit. In other words, this state is a state where there is no electric driving force of the solenoid valve, that is, the flow control valve is fixed to either the fully closed side or the fully open side of the operating range when not energized. Become. Whether the flow control valve is fixed to the fully closed side or the fully open side when not energized is normally set to the fully closed side. This is selected because the air amount is not supplied to the internal combustion engine when the flow control valve is out of order and the rotation speed is not increased against the driver's intention. On the other hand, in addition to the above-mentioned viewpoint of safety, the problem of sticking of the flow rate control valve has recently become apparent. This is because sticky components such as gasoline, which is the fuel for the internal combustion engine, and oil, which is the lubricant for the drive system of the engine, accumulates in the flow rate control unit while deteriorating during engine operation, increasing the sticking force over time. The flow rate control unit is fixed so that the idle speed control is disabled. The phenomenon of sticking is due to the flow measuring unit being fully closed when the flow control unit is not energized.
As a countermeasure against this, an air flow rate control valve that holds the flow rate control valve in an intermediate position that is neither fully closed nor fully open when de-energized has been proposed.In particular, in order to generate a larger separation force on the control valve side with respect to the sticking force. , An air flow control valve with a flow control unit mounted via a diaphragm has been proposed (USP4,8
23,750). With such an air flow rate control valve that holds the flow rate control unit at the intermediate position when de-energized, both the above-mentioned problems of safety and sticking can be solved. However, in the case of the air flow control valve of this structure, since the position of the flow control valve is controlled by using the suction negative pressure generated by the engine, the operation at the time of starting is changed to the suction negative pressure from the electric driving force of the solenoid valve. Many depend on it. In other words, the air flow rate control valve operates only after a certain amount of negative pressure is generated at the time of start, and the control at the time of start is changed from the start time control under the engine speed condition as in the prior art to the feedback correction to converge to the target speed. Doing so deteriorated the stability of the engine speed immediately after starting. Normally, the engine speed is, for example, 4 when the engine is started and after it is started.
It is determined by whether or not it has reached 00 rpm. However, in the case of an air flow control valve that uses a diaphragm at this point, it may be possible that the suction negative pressure has not reached the operating negative pressure of the diaphragm, so operate it until the suction negative pressure at startup reaches the operating negative pressure. As a result, the amount of air as set is not obtained. Especially since the diaphragm is made of rubber,
It is unavoidable that the hardness changes with temperature, and it hardens at low temperatures and shifts to the higher pressure side with respect to normal operating pressure. This has a great influence at the time of cold start, and even if a predetermined duty is set, the air flow control valve does not operate until the suction negative pressure at start corresponding to the low temperature hardening force of the diaphragm is generated. In addition, the low temperature curing power is not constant and varies depending on the product.As a result, the operation of the air flow rate control valve becomes extremely unstable at the time of starting, causing fluctuations in the air-fuel ratio due to variations in the supply air amount, etc. It deteriorated the startability and the rotational stability after the start.

[0004]

According to the present invention, in order to solve the above-mentioned problems, a starting suction pressure judging means is set in the judgment from the starting to the starting.

According to the idle speed control device having this structure, the air amount control valve is a drive signal in a feedback state from the time of starting to a pressure at which the air flow rate control valve can operate depending on the suction negative pressure condition determined after starting. Is not generated, a stable opening area can be always secured regardless of the magnitude and fluctuation of the suction pressure, and the engine start can be stabilized.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows an electronically controlled fuel injection type internal combustion engine equipped with an idle speed control device according to the present invention, which includes an air cleaner 1, a throttle chamber 2 and an intake manifold 3.
The air flow rate control valve 5 is attached to a passage that bypasses the throttle valve 4 in the throttle chamber 2 by sucking air through the air. The air flow rate control valve 5 is controlled by a duty signal from the control unit 6. The control unit 6 inputs the outputs of a water temperature sensor 7 for detecting the cooling water temperature of the engine, a pressure sensor 8 for detecting the intake pipe pressure and calculating the intake air amount, etc., and a ROM (not shown) in the control unit 6 Various actuators such as the injector 9 and the air flow rate control valve 5 are controlled according to a control program stored in advance. Next, the structure of the air flow control valve 5 is shown in FIG. The air flow control valve 5 is composed of an electromagnetic valve 10 driven by a duty signal and a body 13 forming a valve 11 for measuring the amount of air held in the diaphragm 12. The passage 19 of the body 13 communicates with the upstream side of the throttle valve 4 in the intake passage and is on the atmospheric pressure side. The passage 20 communicates with the intake manifold 3 downstream of the throttle valve 4 and is on the negative pressure side. Further, the plunger 15 via the spring 14 of the solenoid valve 10 is controlled in the left-right direction in the figure by the electromagnetic force generated by the duty signal of the control unit 6 of the coil 16. On the other hand, the valve 11 for measuring the amount of air retained in the diaphragm 12 is the spring 1
7, the force of the solenoid valve 10 in the direction of the plunger 15 is received. Due to the above-mentioned force relationship, the position of the valve 11 when the air amount control valve 5 is not energized is held at the position where the spring 17 and the spring 14 are in balance with each other, and the valve 11 does not come into contact with the seat 18 of the body 13 and sticks to the valve. In contrast, it is in an advantageous state. The operation of the air amount control valve 5 is performed by the valve 11
Is operated in combination with the operation of the plunger 15 by the electromagnetic force of the solenoid valve 10. First, the suction negative pressure generated by the engine reaches the pressure chamber 22 formed by the diaphragm 12 from the passage 20 through the hollow passage in the valve 11. The diaphragm 12 is provided with a leak orifice 23 that communicates with the atmosphere, and the suction negative pressure is reduced. A force generated by the diaphragm 12 in the left direction in the figure is applied to the valve 11 by the suction negative pressure. On the other hand, the plunger 15 of the solenoid valve 10 is controlled to a position corresponding to the duty signal. Considering the constant duty state, the position of the plunger 15 is constant, and the operation of the valve 11 is such that the suction negative pressure of the pressure chamber 22 closes the hollow passage in the valve 11 by the plunger 15. Therefore, it is held at a fixed position. However, when a certain pressure is obtained due to the pressure reduction from the leak orifice 23 over time,
The valve 11 moves to the right in the figure because the force generated by the suction negative pressure on the surface of the valve 11 exceeds the force generated by the diaphragm 12. However, at this moment, a gap is formed between the hollow passage outlet in the valve 11 of the pressure chamber 22 which has been closed so far and the plunger 15, and the suction negative pressure is applied to the diaphragm 12 again.
Will follow the original plunger 15 position. By repeating the above operation, as a result, the valve 11
Is controlled to the plunger position set by the duty signal. This means that the position of the plunger 15 is the pressure chamber 2
This means that only the pressure of 2 is controlled, and the driving force of the electromagnetic force of the electromagnetic valve 10 does not contribute to the driving force of the valve 11. Therefore, the valve 11 is the diaphragm 1
2 is driven by the difference between the force generated by the valve 11 and the force generated by the suction negative pressure on the surface of the valve 11, and the force generated by the diaphragm 12 is much larger than the force generated by the solenoid valve, so the separation force for valve sticking is set to a large value. can do. It can be seen that the air amount control valve does not operate unless the suction negative pressure applied to the diaphragm 12 reaches a certain value. This has the greatest effect at the time of starting when suction negative pressure starts to be generated. Next, a control method at the time of starting will be described. FIG. 3 shows the relationship between the engine speed and the suction negative pressure at the time of starting. The engine speed increases from the cranking state after the start of the engine, to the initial explosion, and then to the target rotation after the complete explosion. Here, N1 in the figure is the complete explosion determination rotation speed described in the prior art, which is a determination condition from the time of starting to the time of starting. When this condition is satisfied, the control of the fuel, ignition, and air flow control valve shifts from the start mode to the post-start mode, and the air flow control valve shifts from the fixed output at the start to the feedback correction control. To do. N1 is usually set to a value around 400 rpm. The reason for setting a low value around 400 rpm is to end a long fuel injection pulse time for achieving a small air-fuel ratio (mixing ratio is rich) at the start as early as possible. That is, even if one engine start fails, the engine speed is set to a low value so that the engine will rotate stably in order to prevent the air-fuel mixture from becoming rich. Next, paying attention to the movement of the suction negative pressure at the time of starting, like the engine speed, it gradually reaches a high suction negative pressure from the initial explosion to the complete explosion. In the figure, P1 indicates the pressure at which the diaphragm of the air flow control valve operates. However, P1
It can be seen that the engine speed reaching N is N2 and N2> N1. This means that when switching from the start mode of the air amount control valve to the post-start mode, the desired air amount is not supplied as judged by the engine speed, which promotes variations in the air-fuel ratio, and as a result, It will cause deterioration and the alienation of stability immediately after starting. Further, FIG. 4 is a diagram showing the air flow rate with respect to the suction negative pressure of the air flow control valve 5.
The valve 11 of the air flow rate control valve 5 is held at the intermediate position when not energized. If the suction negative pressure is increased in this state, the air flow rate with respect to the suction negative pressure becomes as shown by the solid line a in FIG. Next, assuming that the duty given to the solenoid valve 10 is 70%, the air flow rate with respect to the suction negative pressure is shown in FIG.
Is indicated by a broken line b. Further, the suction negative pressure at which the diaphragm 12 of the air flow control valve 5 operates is described as P1.
It should be noted that the broken line b indicates the valve 1
1 is the air flow rate when it is forcibly fixed to the position of the duty of 70%, and it shows that the characteristic of the solid line a is shown in the suction negative pressure region below P1 where the diaphragm does not actually operate. That is, assuming that the feedback start duty is 70% from the time of starting to the time of starting, the air flow rate follows the locus of o-a-e in the figure with respect to the suction negative pressure increase after starting. Further, the operating suction negative pressure P1 of the diaphragm 12 varies from PL to PH in the figure because of the hardness change with temperature. For example, if feedback is started in the same manner as described above when the operating suction negative pressure is PL, the air flow rate follows the locus of o-a-ow in the figure with respect to the suction negative pressure increase after the start. Similarly, when the suction negative pressure is PH, the trajectory of the o-curve in the figure is followed. This phenomenon causes the amount of air at the start of feedback to vary between QL and QH (hatched portion), which results in difficulty in setting the air-fuel ratio immediately after the start.
Further, PF in the figure indicates the suction negative pressure at the complete explosion speed N1 in FIG. 3, which is lower than the operating pressure of the air flow control valve.
Therefore, even if feedback is started in this state, the desired air amount cannot be obtained. In the present invention, the feedback start condition is determined when the suction negative pressure reaches a predetermined value, that is, when it reaches Pok in FIG. Pok
In that case, since there is a margin for the PH pressure, which is the maximum variation in operating negative pressure, sufficient consideration is given to variations in products, and as a result, stable air-fuel ratio setting is possible. Therefore, it is possible to provide an idle speed control device for an internal combustion engine, which has excellent startability and rotational stability immediately after starting. Further, by starting the feedback after a lapse of a predetermined time after reaching Pok, a more stable transition to the feedback control can be realized.
Next, FIG. 5 is a flowchart of a control program from the start to the start of the idle speed control device according to the present invention.
Shown in First, in step 101, it is determined whether the engine is in the starting mode. The state of the starting mode is determined by detecting the on / off state of the ignition switch, the on / off state of the starter SW, etc., and further determining the rotational speed condition and the like.
Next, when it is determined that the engine is in the starting mode, step 10
Proceed to 2. In step 102, a rise in suction negative pressure, which is a feedback permission condition, is observed. Here, the suction negative pressure P of the engine
It is determined whether M has reached Pok, which is the pressure at which the air flow control valve can start operating. If the suction negative pressure PM has not reached Pok which is the operation startable pressure, step 1
At 03, the starting duty of the air flow rate control valve control at starting is set. Here, the output duty (DUT
Set STDUTY to the register of Y). After that, the program repeats the determination in step 102, and when it is determined that the start mode is finished, the program shifts to the post-start mode in step 104 and performs idle speed control by feedback control. If it is determined whether or not the suction negative pressure PM has reached Pok, which is the pressure at which the air flow control valve can be actuated, and if it is further determined that a predetermined time has elapsed after the condition is satisfied, step 105 is added to Pok. It is determined whether the elapsed time T after reaching T has exceeded a predetermined time TIMPOK.

[0008]

According to the present invention, the feedback correction transition from the start to the start is stably performed, the air-fuel ratio can be set to an appropriate value, and stable startability and stability of the engine speed immediately after the start are achieved. can get.

[Brief description of drawings]

FIG. 1 is a systematic diagram of a system showing an embodiment of the present invention.

FIG. 2 is a sectional view showing an embodiment of an air flow control valve of the present invention.

FIG. 3 is a characteristic diagram showing a situation at the time of starting the engine of the present invention.

FIG. 4 is a flow rate characteristic diagram of the air amount control valve of the present invention.

FIG. 5 is a flowchart of air amount control valve control at the time of starting according to an embodiment of the present invention.

[Explanation of symbols]

5 ... Air flow control valve, 6 ... Control unit, 8 ...
Pressure sensor.

Claims (3)

[Claims] 1. An air flow control valve controlled by a signal having a predetermined duty ratio in a bypass passage bypassing a throttle valve interposed in an intake passage of the internal combustion engine, and a duty ratio when the internal combustion engine is started. Fixed start-time output means for fixing to a predetermined value, means for setting a target speed in accordance with the cooling water temperature of the internal combustion engine or operating conditions, means for setting the target speed, and a deviation between the actual speed In an idle speed control device for an internal combustion engine, which includes a means and a feedback correction means for converging an actual speed to a target speed according to the deviation, it is determined that the suction pressure at the start has reached a predetermined pressure. A start-up suction pressure determination means, and based on the start-up suction pressure determination means, shifts from the start-time fixed output means to the feedback correction means. Idle speed control apparatus for an internal combustion engine that. 2. An air flow control valve controlled by a signal having a predetermined duty ratio in a bypass passage bypassing a throttle valve provided in an intake passage of the internal combustion engine, and a duty ratio when starting the internal combustion engine. Fixed start-time output means for fixing to a predetermined value, means for setting a target speed in accordance with the cooling water temperature of the internal combustion engine or operating conditions, means for setting the target speed, and a deviation between the actual speed In an idle speed control device for an internal combustion engine, which includes a means and a feedback correction means for converging an actual speed to a target speed according to the deviation, it is determined that the suction pressure at the start has reached a predetermined pressure. Starting suction pressure determination means,
The idle speed control device for an internal combustion engine, wherein the starting fixed output means shifts to the feedback correcting means after a lapse of a predetermined time after the starting suction pressure determining means operates. 3. The air flow control valve according to claim 1 or 2, wherein the air flow rate control valve controls an air amount in accordance with an electric signal input to the solenoid valve, and a driving negative pressure acting on a diaphragm is input to the solenoid valve. An idle speed control device for an internal combustion engine having a drive negative pressure control means for controlling according to an electric signal.