JP2940126B2 - Fuel control device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel control device, and more particularly, to a fuel control device that stabilizes an operating state of an engine in a two-stroke engine in response to a change in feedback control of an air-fuel ratio. Related to the device.

2. Description of the Related Art In an engine, various controls that match the operating state of the engine are performed by control means including a microcomputer.

In a two-stroke engine such as an outboard motor, the control means controls ignition timing and fuel injection.

Further, in a four-cycle engine, the air-fuel ratio is feedback-controlled based on a detection signal from an O2 sensor provided in an exhaust system.

In the above-described two-cycle engine, in order to stabilize the operating state of the engine, the engine speed (rotation speed) is sampled (detected) by a certain amount under predetermined conditions, that is, sampling is performed. A system for controlling the fuel amount and performing feedback control of the air-fuel ratio has been considered.

In this system, the standard deviation σi of the sampled engine speed is used to determine the stability of the engine speed. It is calculated by

As a fuel control device for a two-stroke engine
For example, it is disclosed in JP-A-2-33439. In this publication, an exhaust-side target air-fuel ratio and an exhaust-side actual air-fuel ratio set in advance under each operating condition are compared, and the air-fuel ratio is feedback-controlled by the comparison.

Furthermore, in a marine engine such as an outboard motor, a relatively constant speed and a constant load (there is no sloping road during running) are relatively high (referred to as a cruising state). Is possible. However, if the standard deviation σi can be calculated even during the acceleration / deceleration operation, the feedback mode determination can be made satisfactorily, and the feedback operation time occupied in the actual running can be extended. In particular,
Conventionally, the condition that α (throttle opening) is constant is indispensable as one of the feedback mode determinations. However, if the throttle opening α is changed within a certain range, the feedback mode is maintained even if it is changed.

[Problems to be Solved by the Invention] However, in the method of performing feedback control of the air-fuel ratio based on the distribution of changes in the engine speed in a two-cycle engine, when the air-fuel ratio changes due to feedback control, the next sampling is performed. The average engine speed changes as shown in FIGS.

That is, in FIG. 11, the standard deviation σ and the average engine speed have independent characteristics with respect to the air-fuel ratio, but when the air-fuel ratio is feedback-controlled so as to further reduce σi obtained by the previous sampling. As shown in FIG. 10, the current average engine speed changes following this change.

Therefore, the standard deviation σi becomes larger as the average engine speed becomes larger, even if the engine speed is the same, so that σi + 1 obtained from the changed new current sampling can be directly compared with the previous standard deviation σi. I can no longer do it.

Also, consciously (for example, by operating the throttle)
A similar inconvenience occurred when changing the average engine speed.

[Object of the Invention] Accordingly, an object of the present invention is to precisely control the air-fuel ratio by directly comparing the detected values in the two-stroke engine between the previous and current times with the feedback control in order to eliminate the above-mentioned disadvantages. Accordingly, a fuel control device capable of stabilizing the operating state of the engine is realized.

Means for Solving the Problems In order to achieve this object, the present invention relates to a fuel control device for controlling the amount of fuel supplied to the two-stroke engine to feedback-control the air-fuel ratio of the engine. Is calculated to calculate the distribution state of the change in the engine speed, and the standard deviation of the distribution is divided by the average engine speed to calculate the standard deviation per engine speed. Control means for controlling the amount of fuel supplied to the engine so as to provide feedback control of the air-fuel ratio.

[Operation] According to the configuration of the present invention, the control means detects the state of the engine speed, calculates the distribution state of the change in the engine speed, and divides the standard deviation of this distribution by the average engine speed. By calculating the standard deviation per rotation speed and controlling the fuel amount to the engine so that the standard deviation per rotation speed is minimized, the air-fuel ratio is feedback-controlled, so that a new detected change in the two-cycle engine is obtained. The value can be directly compared with the previous detected value, and the air-fuel ratio control can be performed with high accuracy, and the operating state of the engine can be stabilized.

Embodiment An embodiment of the present invention will be described below in detail and specifically with reference to the drawings.

1 to 6 show an embodiment of the present invention.
In the figure, reference numeral 2 denotes control means for controlling the operation state of a two-cycle engine (not shown) (hereinafter simply referred to as "engine"). The control means 2 includes a throttle opening sensor 4 for detecting a throttle opening α and an engine speed N.
, An intake air temperature sensor 8 for detecting the intake air temperature TA, an atmospheric pressure sensor 10 for detecting the atmospheric pressure P, a cooling water temperature sensor 12 for detecting the cooling water temperature Tw, and the like. ing.

The control means 2 operates the fuel injection valve 10 of the fuel injection device 8 based on signals from the throttle opening sensor 4 and the engine speed sensor 6 to supply a basic fuel amount to the engine, , 10, 12, etc., to correct the reference fuel amount.

Further, the control means 2 detects, for example, a change state of the engine speed N, that is, a distribution state, for each input of the ignition signal, and calculates a standard deviation σi of the engine speed. Then, in order to make the engine rotational speed dimensionless, the standard deviation σi ′ is calculated by dividing the standard deviation σi by the average engine rotational speed j.

That is, the dimensionless standard deviation σi ′ is Is calculated by

In the above equation, It is possible to make the engine speed non-order, and even if the average engine speed j differs between the previous and current times, the sampled value obtained by the previous sampling and the sampled value obtained by Can be directly compared.

Further, as shown in FIGS. 9 (a) and 9 (b), for example, in an acceleration state, a trend which is a change gradient of the engine speed occurs, and the apparent σi ′ increases.

Here, the trend refers to a certain frequency component having a cycle longer than the sampling period.

Therefore, in this method, the data in this state cannot be directly compared with the data in the steady state as shown in FIGS. 7 (a) and 7 (b).

Therefore, the above-mentioned trend is removed by the average distribution method or the least squares method. That is, for the sampling period, the trend due to acceleration / deceleration can be considered to be a very large cycle, so that the trend can be linear in first order.

Here, when the trend to be removed is obtained by the least square method, u (j) = b ₀ + bl (j) k: Sampling time.

Therefore, by using the de-trended data N'j = Ni-u (j), even when the average engine speed changes, the trend is removed and the distribution state of the engine speed can be easily changed. Can be calculated.

As a result, the control means 2 sums up the above equations, The air-fuel ratio is controlled by operating the fuel injection valve 10 to change the amount of fuel so that is minimized, that is, so that the variation in the number of revolutions is reduced.

At this time, as shown in FIG. 2, the judgment mode can extend the feedback operation range to the acceleration / deceleration state, so that the operation is performed in four stages of start, warm-up, feedback, and high speed. Is done.

On the other hand, if fuel efficiency is regarded as important, as shown in FIG. TP = q (TP (σ = min), TP (j · / TP = max)) And

Next, the operation of this embodiment will be described.

The control means 2 inputs the throttle opening α from the throttle opening sensor 4 and inputs the engine speed N from the engine speed sensor 6 to determine the basic fuel injection amount. Based on the detection signal from 12, the basic fuel injection amount is corrected to determine the actual fuel amount, and the operation of the fuel injection valve 10 is controlled.

Further, as shown in FIG. 10, the control means 2 performs feedback control of the air-fuel ratio after sampling the engine speed, and again samples the engine speed after this feedback control.

Then, the control means 2 calculates the distribution state of the sampled engine speed as shown in FIG.

The standard deviation of this engine speed distribution is Is required.

Then, in order to make the engine speed non-dimensional, the standard deviation (variation coefficient) σi is gradually reduced by the average engine speed Nj, Is calculated by

Therefore, the engine speed is made dimensionless, and the sampled value of the engine speed obtained by the previous sampling can be compared with the sampled value of the engine speed obtained by the current sampling, and the average engine speed changes for each sampling. Even so, the fuel amount can be properly corrected, and the accuracy of the air-fuel ratio feedback control can be improved.

Further, as shown in FIG. 4, the control means 2 calculates the trend at the time of acceleration / deceleration of the engine by the average gradient method or the minimum 2
Remove by multiplication.

That is, assuming that the trend is linear in the first order and the trend to be removed is determined by the least square method, u (j) = b ₀ + bl (j) Here, k: sampling time. Therefore, if the data subjected to detrending processing, N'j = Ni-u (j), is used, feedback control can be performed even during acceleration and deceleration. Even when the average engine speed is changed, the feedback operation range can be extended to the acceleration / deceleration state, and the operation state can be stabilized.

As a result It is preferable to change the fuel injection amount so as to minimize.

That is, as shown in FIG. 6, it is possible to cope with a change in the engine speed accompanying a change in output with respect to a change in air-fueling.

In addition, since acceleration / deceleration is included in the feedback area, as shown in FIG. 2, a stable operation is obtained in a reduced and more expanded state.

When the engine speed Ni is obtained from the time interval Δti of the ignition signal, when the ignition timing control system using the microcomputer is used, the results may interfere with each other and the values may not converge. Instead, a signal synchronized with another crank rotation may be used.

In consideration of the balance between the response speed of the engine and the rotational stability (smoothness), the sampling number n may be changed according to the situation.

Furthermore, considering the convergence speed and stability, the fuel injection amount
The modifiers α and β of the TP may be changed according to the state.

[Effects of the Invention] As is apparent from the detailed description above, according to the present invention, in a two-cycle engine, the state of the engine speed is detected, the distribution of the change in the engine speed is calculated, and the standard of this distribution is calculated. Control means for calculating a standard deviation per revolution by dividing the deviation by an average engine speed, and controlling an amount of fuel supplied to the engine so as to minimize the standard deviation per revolution; Is provided, the accuracy of the control of the air-fuel ratio can be increased by directly comparing the detection values of the previous time and the present time with the feedback control therebetween, and the operating state of the two-stroke engine can be stabilized.

[Brief description of the drawings]

1 to 6 show an embodiment of the present invention, FIG. 1 is a block diagram of a fuel control device for an engine, FIG. 2 is an explanatory diagram of mode determination, and FIGS. FIG. 5 is a diagram of the standard deviation and the engine speed for the fuel injection amount (σ = min), and FIG. 6 is a diagram of the standard deviation and the engine speed for the fuel injection amount (N = max). . FIGS. 7 (a), (b), and FIGS. 8 (a), (b) are diagrams showing how the engine speed changes during steady operation. FIGS. 9 (a) and 9 (b) are diagrams showing how the engine speed changes during acceleration operation. FIG. 10 is a diagram showing a change state of the average engine speed in the previous sampling and the current sampling. FIG. 11 is a diagram of a standard deviation with respect to an air-fuel ratio and an average engine speed. In the figure, 2 is an engine control means, 4 is a throttle opening sensor, 6 is an engine speed sensor, 8 is a fuel injection device, 10 is a fuel injection valve, 12 is an intake air temperature sensor, 14 is an atmospheric pressure sensor, and 16 Is a cooling water temperature sensor.

Claims (1)

(57) [Claims] 1. A fuel control system for controlling the amount of fuel supplied to a two-stroke engine to feedback-control an air-fuel ratio of a two-stroke engine, detecting a state of an engine speed and calculating a distribution state of a change in the engine speed. The standard deviation per revolution is calculated by dividing the standard deviation of this distribution by the average engine speed, and the amount of fuel supplied to the engine is controlled so that the standard deviation per speed is minimized. And a control unit for performing feedback control of the fuel supply.