JPS6332142A - Intake air quantity control device for internal combustion engine - Google Patents

Abstract

PURPOSE:To reduce time lag, and to prevent the occurrence of hunting by obtaining the actual value of engine speed in accordance with the burning condi tion inside the cylinder of an engine, and feedback-controlling the intake air quantity so that the actural value converges on a target value. CONSTITUTION:The detected values of a water temperature sensor 25, an idle switch 27, a neutral switch 28, and a car speed switch 29 are input into a micro computer 20, and on the basis of these detected values, a target idling speed is set. At the time of idling, a mean effective pressure is obtained by integrating the detected value of a cylinder internal pressure sensor 32 fitted on the seating part of an ignition plug, and further after converting this into an engine speed, on the basis of the deviation from a target idling speed, the feedback control of an idle control valve 11 is carried out.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an intake air amount control device for stabilizing the rotation of an internal combustion engine.

<Prior art> As a conventional intake air amount control device, for example,
There is one as shown in Japanese Patent No.-160138.

This controls the amount of intake air by dividing the operating state into feedback control that makes the engine speed match the target engine speed and feedback control that is determined in each operating state.

(Problems to be solved by the invention) - However, in such conventional intake air amount control devices, the number of revolutions of the engine is detected and the intake air amount is controlled based on that value. , there were problems in that there was a large time delay and large hunting.

That is, as shown in Figure 5, the rotational speed Ne is as follows: After torque is generated by the combustion system, it is output through the entire inertial system. Therefore, in the conventional system, as shown in FIG. 6, when a load fluctuation occurs at time t0 and the target rotational speed changes, the rotational speed fluctuation occurs later than the torque fluctuation. In other words, since the rotational speed is detected with a delay, hunting occurs even if PID (proportional integral differential) control is performed.

SUMMARY OF THE INVENTION In view of these conventional problems, it is an object of the present invention to provide an intake air amount control device that can perform good control without causing time delays and hunting due to passing through an inertial system.

<Means for Solving the Problems> For this reason, the present invention, as shown in FIG. Comparison means for comparing the obtained actual parameter with a predetermined target parameter, and intake air m jlill ? for controlling the amount of intake air so as to bring about a loss in both parameters according to the comparison result. f
f11 means are provided.

In other words, by performing control based on the combustion state in the combustion system, the time delay caused by passing through the inertial system is eliminated and hunting is suppressed.

<Example) The present invention will be explained in detail below.

In Fig. 2, reference numeral 1 denotes the internal combustion engine main body, intake air is supplied from an air cleaner 2 to each cylinder through an air flow meter 3, a throttle chamber 4, and each branch of an intake manifold 5, and fuel is provided to each branch. The fuel is injected from the fuel injection valve 6. Here, the flow of intake air is controlled by a throttle valve 7 in the throttle chamber 4 whose opening degree is determined by the operation of the accelerator pedal, and the throttle valve 7 is almost closed when the engine is idling. The flow of air during idling passes through the bypass port 8 and is adjusted by the idle adjustment screw 9 installed therein. The idle control valve 11 provided ensures the appropriate amount of air.

The idle control valve 11 includes a valve body 12 interposed in a bypass passage 10, a diaphragm 13 to which the valve body 12 is connected, and a negative pressure operating chamber 15 housing a spring 14 that biases the diaphragm 13. , the amount of lift of the valve body 12 by the diaphragm 13 is changed in accordance with the negative pressure introduced into the negative pressure working chamber 15 to increase or decrease its opening degree. This negative pressure working chamber 15
communicates with the intake passage downstream of the throttle valve 7 via the constant pressure valve 17 by means of the negative pressure introduction passage, and also communicates with the air intake passage 1 downstream of the throttle valve 7.
8 communicates with the intake passage upstream of the throttle valve 7 via a pulse solenoid valve 19. Thus, pulse solenoid valve 1
By closing fjM 9, the degree of opening of the idle control valve 11 is controlled by changing the dilution ratio of the negative pressure introduced into the negative pressure working chamber 15 with the atmosphere.

The pulse solenoid valve 19 as an intake air amount control means is controlled by the microcomputer 20.

The microcomputer 20 is mainly a central processing unit (C
It is composed of a PU) 21, a memory (ROM, RAM) 22, and an interface (input/output signal processing circuit) 23.

The engine rotation speed is input to the interface 23 as a digital signal detected by a telephone pick-up type rotation speed sensor 24 . In addition, the engine cooling water temperature is detected as an analog signal by the water temperature sensor 25 of the thermos valve 2,
The signal is input as a digital signal via the /D converter 26. Additionally, an idle switch 27 detects that the throttle valve 7 is in the fully open position, a neutral switch 28 detects that the transmission is in the neutral position, and a neutral switch 28 detects that the vehicle speed is below a predetermined value (for example, 3 km/h). from the vehicle speed switch 29, respectively.
An N/OFF signal is input. In addition, although not shown, signals from an air conditioner switch and the like are also input.

Further, a signal is input to the ink fence 23 from a cylinder pressure sensor 32 attached to a washer of the spark plug 31. This in-cylinder pressure sensor 32 is used as a combustion state detection means, is made of a piezoelectric element, and is designed to generate an electric charge depending on the combustion pressure in the cylinder. Then, by integrating the output signal of the cylinder pressure sensor 32 over one combustion cycle, the indicated mean effective pressure during that combustion can be obtained.

The central processing unit 21 includes an idle switch 27, a neutral switch 28 . Depending on the state of the vehicle speed switch 29, it is determined whether the vehicle is in an idling state, that is, whether or not feedback control is to be performed.Only when it is determined that feedback control is to be performed, the pulse solenoid valve 19 as an intake air amount control means is Feedback control is performed by changing the duty of the pulse signal.

FIG. 3 is a control block diagram showing one embodiment of the present invention. In this example, the engine rotation speed is predicted based on the indicated average effective pressure, the predicted rotation speed (actual parameter) is compared with a predetermined target rotation speed (target parameter), and the engine speed is determined based on the comparison result. Pulse solenoid valve 1 to match
9 now to control the amount of intake air.

The intake air-fuel mixture is combusted within the cylinders of the engine to generate combustion pressure. The cylinder pressure sensor 3 measures the cylinder pressure according to the combustion.
2 and integrated over one combustion cycle, the indicated mean effective pressure Pi is obtained.

Assuming that the fuel injection amount is always controlled to be optimal according to the intake air amount (that is, the mixture ratio is around 14.7), as the intake air amount increases, the in-cylinder pressure increases. The indicated average effective pressure Pi also increases. That is,
There is a very close relationship between the intake air amount and the indicated mean effective pressure.

If the indicated average effective pressure Pi is multiplied by a constant by 1, the engine output torque Tr' is obtained, and from this output torque Tr', the friction component k is determined according to the engine rotation speed Ne.

The actual output torque Tr can be obtained by subtracting Ne (k is a constant) and torque disturbance due to external factors. This output torque Tr is converted into the engine rotational speed Ne through an inertial system (constant 2).

Here, torque disturbances caused by external factors include, for example, the load on the alternator that is applied when the air conditioner switch is turned on, or torque fluctuations when the clutch starts to engage from a disengaged state, but these torque fluctuations are Since a switch or the like is provided to detect this, the timing can be known in advance, and the magnitude of the torque fluctuation can be determined in advance through experiments.

From these facts, the equation within the broken line in FIG. 3 is as follows.

However, kl. kt, is a constant, P i, Tr',
T r.

Ne and D are functions of time.

(When formula 11 is rearranged, shir = kTr- + P i -D... (2 digits, k = - 2 ·k).

In equation (2), the second term on the right side is known by measuring the indicated mean effective pressure Pi, and the third term is also known for the reason described above.

Therefore, by solving the first-order differential equation, equation (2) is actually solved by converting it into a first-order difference equation to be solved by a microcomputer, and the solution T r = T r [tl・(3 ) is found, and from the third equation of +11 equations, N e
−N e (tl=·(41) can be obtained.

From the above, the predicted rotational speed Ne' can be determined from the indicated mean effective pressure Pi using the model within the broken line in FIG.

Then, a comparator 50 serving as a comparison means calculates the difference between this predicted rotation speed Ne' and a target rotation speed Ne5et predetermined for each operating state, and performs PID (proportional integral derivative) control to control the pulse solenoid valve. If the intake air fiQ is corrected through 19, the predicted rotational speed Ne determined by the model
' can be made to match the target rotational speed Ne5et.

Here, the target rotational speed Ne5et is predetermined based on the cooling water temperature, the state of the air conditioner switch, etc.

This method, which predicts the engine speed through a model from the indicated mean effective pressure and performs feedbank control, can feed back a value that does not pass through the inertial frame, compared to the conventional method of feeding back the actual speed. There is little time delay and stable engine rotation can be obtained.

Specifically, as shown in FIG. 6, it is assumed that a load fluctuation occurs at time t0, and the target rotational speed Ne5et changes as shown in the figure. At that time, the actual rotation speed Ne and the predicted rotation speed Ne'' obtained from the model are as shown in the same figure.Next, if the timing to read the rotation speed comes at time t1, the actual rotation speed Ne passes through the inertial frame. The signal is detected with a delay because of the rotation speed Ne when excluding the inertial frame.
' is detected earlier than Ne. Therefore, highly accurate control can be performed with less time delay.

Expressed in block diagrams, Figure 5 shows the conventional method, and Figure 5 ■ shows the block diagram of the present method.It requires an order of several hundred m5 to pass through an inertial frame, but the number of rotations can be calculated using a microcomputer. Since prediction is possible within about 100 μS, the time delay when performing feedback control can be almost ignored. Therefore, more accurate feedback control than the conventional method can be performed, and a stable rotational speed can be obtained.

FIG. 4 is a control block diagram showing another embodiment of the present invention. In this example, the indicated mean effective pressure Pi is used as an actual parameter, and is compared with a target value (target parameter), and the pulse solenoid valve 1 is set to match the two according to the comparison result.
9 for controlling the amount of intake air.

The indicated average effective pressure pi is determined in advance by the operating conditions (engine speed,
The comparator 60 as a comparison means calculates the difference from the target indicated mean effective pressure P1set determined by the intake air amount, cooling water temperature, idle switch, neutral switch, etc.), and based on the difference, PID (proportional integral The actual indicated mean effective pressure is corrected via the pulse solenoid valve 19 so that the actual indicated mean effective pressure Pi matches the target indicated mean effective pressure P1set by controlling the differential). One purpose of making the pressure Pi match the target indicated average effective pressure P 1set is to stabilize the engine rotation speed in the idle state, and the target indicated average effective pressure P 1set is calculated from the target rotation speed N ese t in the idle state. and the actual indicated mean effective pressure Pi
By controlling the intake air amount Q so that P1set corresponds to the target indicated mean effective pressure P1set, the actual rotational speed Ne can be made to correspond to the target rotational speed Ne5et.

Specifically, as shown in Fig. 6 (C1), it is assumed that a load change occurs at time L0 and the target rotational speed Ne5et changes from No to N1.Next, sampling of the rotational speed Ne is performed at time 1. At this time, the rotational speed Ne has passed through the inertial system and is rising slowly, so the proportional amount should be reduced, but the target rotational speed Ne5e
Since the difference with t is large, the proportional portion becomes large.

Therefore, a large amount of hunting remains.

However, when Piset is controlled as the target value as shown in the lower part of FIG. 6(C), the actual Pi approaches the target Pi quickly, so better control can be achieved than when using rotational speed feedback.

Comparing this method with the conventional method (Fig. 5), the feedback parameter in the conventional method is the engine rotational speed Ne that has passed through the inertial frame, but in this method, the parameter fed back is the engine rotation speed Ne as shown in Fig. 5 (C
), and since feedback control is performed on the indicated mean effective pressure Pi before passing through the inertial system, the state of the engine can be known quickly and better feedback control can be performed. That is, the stability of the engine speed can be improved.

Here, since the engine output torque Tr' is the indicated mean effective pressure Pi multiplied by a constant 1, Tr' is used instead of Pi, and Tr'set (-P tset) is used instead of PisetO. May be controlled.

Note that although the above embodiment is limited to the idle state, the control can be performed in a similar manner even in a general driving state (for example, during acceleration).

<Effects of the Invention> As explained above, according to the present invention, the combustion state of the engine such as the indicated mean effective pressure is detected, and the parameters determined thereby are fed back to control the intake air amount. Compared to the case where control is performed by feedback of numbers, the time delay can be reduced and better control can be achieved without causing hunting.

[Brief explanation of the drawing]

Fig. 1 is a functional block diagram showing the configuration of the present invention, Fig. 2 is a system diagram showing an embodiment of the invention, Fig. 3 is a control block diagram showing an embodiment of the invention, and Fig. 4 is a functional block diagram showing the configuration of the present invention. A control block diagram showing another embodiment of the invention, FIGS. 5-5C are schematic diagrams for explaining the differences between the conventional example and each embodiment, and FIGS. It is a control characteristic diagram at the time of load fluctuation of an example. 1... Internal combustion engine body 11... Idle control valve 1
9... Pulse 'HiLfP 20... Microcomputer 32... Cylinder pressure sensor

Claims (1)

[Claims] a combustion state detection means for detecting a state quantity corresponding to the combustion state in the cylinders of the engine; a comparison means for comparing an actual parameter obtained from the state quantity with a predetermined target parameter; An intake air amount control device for an internal combustion engine, comprising an intake air amount control means for controlling the intake air amount so that both parameters match.