JPS6027745A - Fuel supply controlling method for engine - Google Patents

Abstract

PURPOSE:To reduce the amount of HC and CO contained in the exhaust gas of an engine, by proventing over-enriching of the air-fuel ratio by increasing the decreasing rate of increased fuel quantity in case that it is judged from a signal representing the altitude that the altitude is greater than a prescribed value. CONSTITUTION:Whether the altitude is greater than a prescribed value is judged by an altitude compensating value representing the percentage of deviation of the actual air-fuel ratio from the theoretical air-fuel ratio which is calculated by way of learning control. In case that the altitude is judged to be greater than the prescribed value and the water temperature detected by a water-temperature sensor 59 lies in the range of X deg.C to Y deg.C, a value B is used for the decreasing rate of increased fuel quantity. Here, the decreasing rate B is large as compared with a reference rate A. For instance, the value B is 0.5% per one rotation of an engine whereas the value A is 0.1%. Therefore, in case that the altitude is greater than the above prescribed value and the engine temperature stands within a prescribed range, increasing of fuel is interrupted within a short time, so that it is enabled to reduce the amount of HC, CO contained in the exhaust gas.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of fuel supplied to an engine.

Conventionally, the fuel injection amount in a fuel injection engine is controlled to a predetermined amount relative to the engine intake air amount when the engine temperature is lower than a predetermined control switching temperature. This is so-called open-loop control, and when the engine temperature is higher than a predetermined control switching temperature, feedback control is performed so that the air-fuel ratio becomes the stoichiometric air-fuel ratio. In other words, when the engine temperature is low, open-loop control is performed to make the air-fuel ratio slightly richer to ensure Okel engine performance when the engine is cold, and when the engine temperature is high, the air-fuel ratio is controlled to the stoichiometric air-fuel ratio. Feedback control is applied to reduce HC in the gas emitted from the engine.
, Co, etc. are kept to low values.

Also, for fuel-injected engines, at the time of starting.

A predetermined operating state such as during acceleration is detected, and in such an operating state, the amount of fuel supplied to the engine is increased by a predetermined amount to ensure engine performance during the predetermined operating state. The increased amount of fuel decreases at a predetermined rate as the engine rotates, and gradually returns to the normal state.

Engines that control the amount of fuel injection in this way are usually optimally adjusted for use on flat ground, and when such engines are used at relatively high altitudes, the first order In other words, because the air density is thinner at high altitudes, the air-fuel ratio becomes richer than at flatlands even when the amount of fuel increases, which increases the amount of HC and CO in the gases emitted from the engine. There is a problem with this.

In view of these conventional problems, it is an object of the present invention to prevent the air-fuel ratio from becoming richer than necessary by reducing the increased fuel amount more quickly during open-loop control at high altitudes. The objective is to prevent HC and CO in particular from the gas emitted from the engine.

In order to achieve this object, the present invention is characterized in that it is established whether or not the altitude is higher than a predetermined level based on a signal representing the altitude, and if the altitude is higher than a predetermined level, the reduction rate of the increased fuel amount is increased. shall be.

According to the present invention, even when the engine is operated at a relatively low altitude and at a relatively low altitude, the amount of fuel that is increased in a predetermined operating state is quickly reduced, so that the air density can be reduced. The air-fuel ratio, which tends to be on the rich side due to its thinness, can be prevented from becoming over-rich, and in particular HC and Co in the gas exhausted from the engine can be suppressed.

The invention will now be described in detail by way of example embodiments with reference to the accompanying drawings.

FIG. 1 is a schematic diagram showing a preferred embodiment of a fuel injection type engine in which the fuel supply control method according to the present invention is implemented. In the figure, 1 indicates an engine, and this engine 1 has a cylinder block 2 and a cylinder head 3, and the cylinder block 2 receives a piston 4 in a cylinder bore formed inside the cylinder block 2. A combustion chamber 5 is provided above the piston 4 in cooperation with the cylinder head.
is defined.

An intake boat 6 and an exhaust boat 7 are formed in the cylinder head 3, and these boats are opened and closed by an intake valve 8 and an exhaust valve 9, respectively. Further, a spark plug 19 is attached to the cylinder head 3. The spark plug 19 is supplied with current generated by an ignition coil (not shown) via a distributor 27, and generates a spark in the combustion chamber 5 by discharge.

The intake boat 6 has an intake manifold 11. Surge tank 12. Throttle body 13. Intake tube 14. An air flow meter 151 and an air cleaner 16 are connected in this order, and these constitute the intake system of the engine.

A fuel injection valve 2o is attached near the connection end of the intake manifold 11 to the intake boat 6. The fuel injection valve 20 is supplied with liquid fuel such as gasoline stored in a fuel tank 21 by a fuel pump 22 through a fuel supply pipe 23, and its opening time is controlled by a pulse signal generated by a control device 50, which will be described later. The fuel injection amount is controlled quantitatively.

The throttle body 13 has a throttle valve 24 that controls the amount of intake air.
is adapted to be driven in response to depression of the accelerator pedal 25.

Further, the intake system of the engine is provided with an air bypass passage 3o that bypasses the throttle body 13 and connects the intake tube 14 and the surge tank 12. The opening/closing and the degree of opening are controlled, and the engine's idle speed is mainly controlled.

The exhaust boat 7 has an exhaust manifold 17 and an exhaust pipe 18.
are connected in order.

The control device 50 may be a microcomputer, an example of which is shown in FIG. This microcomputer includes a central processing unit (cPU) 51, a read only memory (ROM) 52, and a random access memory (RAM) 53.

A with another random access memory (RAM) 54 that retains memory even after power is turned off, and a multiplexer.
It has a /D converter 55 and an I10 device 56 having a buffer 1 memory, which are connected to each other by a common bus 57.

The A/D converter 55 receives the intake air flow rate signal generated by the air flow meter 15 and the cooling water temperature signal generated by the water temperature sensor 59 attached to the cylinder block 2, and converts the data into A/D. The data is output to the CPU 51 and RAM 53 or 54 at a predetermined time according to instructions from the CPU 51. In addition, the I10 device 56 receives an engine rotation speed signal and a crank angle signal generated by a rotation speed sensor 29 attached to the distributor 27, and a throttle fully closed signal generated by a throttle switch 60 attached to the throttle body 13. The data is stored in the CPU at a predetermined time according to instructions from the CPU 51.
It is configured to output to the PU 51 and RAM 53 or 54.

The CPU 51 calculates the fuel injection amount based on the data detected by each sensor according to a program stored in the ROM 52, and outputs a pulse signal based on the calculated amount to the fuel injection valve 2° via the I10 device 56. There is. That is, if the cooling water temperature detected by the water temperature sensor 59 is lower than a predetermined control switching temperature (for example, 40° C.), the CPU 51 executes the predetermined open loop control, and if the cooling water temperature is higher than the control switching temperature, the CPU 51 executes the predetermined open loop control. It is designed to perform feedback control. here.

Open-loop control is based on the intake air flow rate detected by the airflow meter 15 and the engine rotation speed detected by the rotation speed sensor 29, and the fuel injection time per stroke is determined at predetermined intervals based on the intake air amount per stroke of the engine. 1. For example, the pulse signal is calculated repeatedly at every predetermined crank angle and has a pulse width corresponding to the fuel injection time.Furthermore, the feedback control is a pulse signal with a pulse width corresponding to the fuel injection time calculated by the above-mentioned open loop control. Fuel is injected according to the signal.

The air-fuel ratio at that time is calculated from the oxygen concentration contained in the exhaust gas, and the fuel injection time is corrected so that this air-fuel ratio becomes the stoichiometric air-fuel ratio.

In addition, learning control is used in conjunction with the feedback control in order to more stably maintain the air-fuel ratio at the stoichiometric air-fuel ratio. Learning control calculates the percentage deviation of the actual air-fuel ratio from the stoichiometric air-fuel ratio as an altitude compensation needle (FHA'C), and uses this altitude compensation needle to correct the fuel injection time in advance. Note that most of the causes of deviation of the air-fuel ratio from the stoichiometric air-fuel ratio are due to changes in air density due to changes in altitude. Therefore, the ratio of the difference in air-fuel ratio to the stoichiometric air-fuel ratio is called the altitude compensation needle.

Furthermore, the CPU 51 is in the starting state of the engine.

When an acceleration state or a predetermined operating state that requires an output anop of the engine other than JC is detected from a signal from a predetermined sensor, the fuel injection amount to the engine is controlled to be increased by a predetermined amount. Increased fuel amount.

It is configured to decrease at a predetermined rate (for example, 0.1% per engine rotation) as the engine rotates.

Further, the CPU 51 calculates the amount of bypass air according to the water temperature detected by the water temperature sensor 59 according to a program stored in the ROM 52.

A signal corresponding to this is outputted to the bypass flow rate control valve 31 via the I10 device 56.

The opening/closing and opening degree of the bypass flow control valve 31 are controlled in accordance with the bypass air amount signal given by the I10 device 56, and mainly controls the idle speed of the engine.

A feature of the present invention is that the rate of decrease in the amount of fuel increased in a predetermined operating state is changed depending on the altitude, and a program for setting the rate of decrease in the amount of increased fuel for this purpose is shown in a flowchart in FIG. ing. This program is included in the main routine for engine control stored in the ROM 52, and well-known engine control programs exist before and after this program.

As the program processing progresses and reaches step 51 in FIG. 3, the altitude compensation needle (FHA) in the learning control is
C) is loaded from the RAM 54.

As mentioned above, since the altitude can be known from the size of the altitude compensation needle, in step S4, which will be described later, it is determined from the altitude compensation value whether or not the altitude is higher than a predetermined value. In steps S2 and S3, it is determined whether the water temperature detected by the water temperature sensor 59 is between x°C (for example, 10°C) and yb (for example, 30°C). When the engine water temperature is lower than X℃ or higher than Y'C, the
A negative determination is made in step S2 or S3, and the reduction rate of the increased fuel amount is set to A in step S5. Engine water temperature is
If the temperature is higher than or equal to Y°C, an affirmative determination is made in steps S2 and S3, and the process proceeds to step S4. In step S4, it is determined whether or not the area is at a high altitude as described above.
As a result of the determination, if it is not a highland, a negative determination is made in step S4 and the reduction rate of the increased fuel amount is set to A, and if it is a highland, an affirmative determination is made in step S4 and the reduction rate is set to B.

Here, the reduction rate B is larger than A by 2. For example, B
is 0.5% per engine revolution, whereas A is 0.1% per engine revolution.

Figure 4 shows the decreasing characteristic of the increased fuel amount, and when the decreasing rate is set to A, assuming that there is no fluctuation in the engine rotation, the increased fuel amount will decrease over the course of one hour, but at high altitudes It can be seen that when the reduction rate is set to B, the increased fuel amount is reduced faster than when the reduction rate is A.

Therefore, when the engine is in a given temperature range and at high altitude, the additional fuel is exhausted in a single time period;
In particular, HC and Co in the gas exhausted from the engine can be suppressed to low values.

One embodiment of the present invention has been described above.

The present invention is not limited to this example.

Various embodiments are included within the scope of the claims. For example, high altitude determination may be performed by detecting atmospheric pressure.

[Brief explanation of the drawing]

Fig. 1 is a schematic configuration diagram of an engine for carrying out the method of the present invention, Fig. 2 is a block diagram of the control device shown in Fig. 1, and Fig. 3 shows a part of the program of the computer forming the control device. Flowchart 1-1 shown in FIG. 4 is a characteristic diagram showing the decreasing characteristic of the increased fuel amount. 1... Engine 2... Cylinder block 3... Cylinder head 4... Piston 5... Combustion chamber 6.
・Intake port 7...Exhaust port 8...Intake valve 9...Exhaust valve 11...Intake manifold 12
...Surge tank 13...Throttle valve 14.
... Intake tube 15 ... Air flow meter 16 ... Air cleaner 17 ... Exhaust manifold 18 ... Exhaust pipe 20 ... Fuel injection valve 21 ... Fuel tank 22 ...
... Fuel pump 23 ... Fuel supply pipe 24 ... Throttle valve 25 ... Accelerator pedal 27 ... Distributor 29 ... Rotation speed sensor 30 ... Air bypass passage 31 ... Bypass flow control valve 50 ...control device 5
1... Central processing unit (CPU) 52... Read only memory (ROM) 53, 54... Random access memory (RAM) 55... A/D converter 56.
...I10 device 57...Common bus 59...Water temperature sensor 60...Surono Torsuinochi

Claims (1)

[Claims] (1) The amount of fuel supplied to the engine is set to a predetermined amount relative to the amount of intake air of the engine, and it is detected whether the engine is being operated in a predetermined operating state. When this occurs, the amount of fuel supplied to the engine is increased by a predetermined amount, and thereafter. A fuel supply control method for an engine in which an increased amount of fuel is decreased at a predetermined rate as the engine rotates. It is established whether or not the altitude is higher than a specified level by a signal representing the altitude, and if the altitude is higher than a specified level. A method for controlling fuel supply to an engine, comprising increasing a reduction rate of an increased fuel amount.