JPH072996Y2 - Engine fuel controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a fuel control device for an engine which controls fuel pressure in response to changes in fuel temperature.

(Prior Art) Conventionally, for example, when the engine is stopped immediately after continuing high-speed operation, the fuel temperature in the fuel supply pipe rises due to an increase in the engine temperature and the ambient temperature, and bubbles (vapor) are generated inside. If the engine is restarted in this bubble generation state, even if combustion injection is performed with a regular fuel injection pulse, the amount of injected fuel will be reduced by the amount of the bubble, the air-fuel ratio will become lean, and hot re-heating will occur. The startability may be deteriorated, the rough idle after the start or the engine may be stopped, and the startability may be deteriorated.

Therefore, for example, as seen in Japanese Patent Laid-Open No. 59-96439, the temperature of fuel or cooling water is detected, and when the temperature is above a predetermined value and bubbles are generated, the fuel injection pressure is increased. A technique is known in which the amount of fuel discharged is increased by compressing air bubbles to improve leanness of the air-fuel ratio and improve startability.

(Problems to be solved by the invention) In the case of performing the fuel supply control associated with the generation of bubbles in the fuel as described above, for example, the type of gasoline or the mixed fuel of gasoline and alcohol is used. Different components have different volatility with respect to temperature,
The characteristics of the temperature and the degree of bubble generation change, and it is difficult to accurately determine the state of bubble generation. In addition, it is necessary to install a dedicated temperature sensor to directly detect the fuel temperature, which is disadvantageous in terms of cost, etc., but in the control that corresponds to the intake temperature, cooling water temperature, load, etc. used for other control There is a problem that the detection accuracy of the fuel temperature itself is lowered.

Then, the control corresponding to the bubble generation state cannot be performed accurately, and, for example, if the fuel pressure does not rise even though the bubble is actually generated, the startability and the idle stability are lowered as described above. On the other hand, if the fuel pressure is increased in a state where no bubbles are generated, the fuel supply amount becomes excessive and the air-fuel ratio becomes abnormally rich, which may adversely affect the exhaust emission.

In view of the above circumstances, the present invention has an object to provide a fuel control device for an engine capable of ensuring good startability even if the actual bubble generation state with respect to temperature changes due to changes in fuel components. To do.

(Means for Solving the Problems) In order to achieve the above object, the fuel control device of the present invention has a temperature equal to or higher than a first temperature preset by temperature detecting means for detecting a temperature related to the fuel temperature at the time of engine start. A first fuel pressure increasing means for increasing the fuel pressure when the temperature is detected, the temperature detected by the temperature detecting means is equal to or higher than a second temperature lower than the first temperature, and the starting period is The second fuel pressure increasing means for increasing the fuel pressure when a predetermined period of time or more has elapsed is also provided.

FIG. 1 is an overall configuration diagram for clearly showing the configuration of the present invention.

A fuel pressure adjusting device C for adjusting the fuel injection pressure by a fuel injection valve B interposed in an intake passage A of the engine E is provided, and the fuel pressure adjusting device C controls the increase of the fuel pressure corresponding to the fuel temperature at the time of engine start. First and second fuel pressure increasing means
The signals from F and G are input.

The temperature detecting means H detects a temperature related to the fuel temperature such as an intake air temperature, and the first fuel pressure increasing means F receiving the detection signal of the temperature detecting means H is a preset first
When a temperature equal to or higher than the temperature is detected and bubbles are generated in any fuel composition, a signal for increasing the fuel pressure is output to the fuel pressure adjusting device C. Further, the second fuel pressure increasing means G has a temperature detected by the temperature detecting means H that is equal to or higher than a second temperature lower than the first temperature,
In addition, when the start period detected by the start period detecting means J has passed a predetermined period or more, the bubble generation state is set, and similarly, a signal for increasing the fuel pressure is output to the fuel pressure adjusting device C.

The region between the first temperature and the second temperature is a state in which bubbles may be generated due to changes in the fuel composition and the like. In this temperature region, even if the engine is started for a predetermined period, the engine It is determined that it is difficult to start due to the generation of air bubbles in the state where is not started.

(Operation) In the fuel control device as described above, the temperature related to the fuel temperature is detected at the time of starting the engine, and when the temperature is equal to or higher than the preset first temperature, bubbles are generated in any fuel composition. In this case, the fuel pressure is increased at this time to obtain good startability and idleness by compressing the bubbles and increasing the injected fuel. When the detected temperature is equal to or higher than the second temperature which is lower than the first temperature, it is determined that the start failure has occurred due to the generation of bubbles when the start period exceeds a predetermined period, and the fuel pressure is similarly set. By raising the temperature, good startability is ensured even if air bubbles are generated due to changes in fuel composition, etc.
Even in such a temperature range, the occurrence of overrich due to unnecessary increase in fuel pressure is avoided when bubbles are not generated.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. FIG. 2 is an overall configuration diagram of a concrete example.

An intake port 3 and an exhaust port 4 are provided in the combustion chamber 2 of the engine 1.
Is opened, and the opening portions of both ports 3 and 4 are opened and closed by the intake valve 5 and the exhaust valve 6 at predetermined timings. An intake passage 7 that communicates with the intake port 3 and supplies intake air to the combustion chamber 2 is provided with an air cleaner 8, an intake air amount sensor 9 for measuring the intake air amount, and a throttle valve 10 for controlling the intake air amount from the upstream side. , The downstream side of the surge tank 11 is formed independently for each cylinder, and in the downstream side portion,
Fuel injection valve 12 for injecting fuel toward the intake port 3
Is provided.

Further, a fuel pressure regulator 14 is installed as a fuel pressure adjusting device C for adjusting the pressure of fuel supplied to the fuel injection valve 12, that is, the injected fuel pressure. A negative pressure passage 15 is connected to the fuel pressure regulator 14, and an intake negative pressure in the intake passage 7 downstream of the throttle valve 10 is introduced, and the fuel pressure is adjusted according to the negative pressure. That is, the fuel pressure regulator 14 adjusts the fuel pressure low so that the differential pressure from the intake negative pressure becomes constant when a high intake negative pressure is generated due to a low load or the like.

A negative pressure cut valve 16 as a fuel pressure increasing means is provided in the middle of the negative pressure passage 15.
Reference numeral 16 stops the introduction of negative pressure into the fuel pressure regulator 14 during its operation, and introduces atmospheric pressure to raise the fuel pressure adjusted by the fuel pressure regulator 14.

An operation signal is output to the negative pressure cut valve 16 from a control unit 18 as control means. In order to control the fuel pressure in accordance with the fuel temperature, the control unit 18 receives an intake air temperature signal from an intake air temperature sensor 19 arranged in the intake passage 7 and a cooling water temperature of the engine 1. A water temperature signal from a water temperature sensor 20 for detection, an engine rotation signal from a distributor 21, and a starter signal from a starter switch 22 for detecting engine start time are input.

The control unit 18 determines the bubble generation state of the fuel injected by the fuel injection valve 12 according to signals from various sensors, and controls the increase of the fuel pressure.

Next, the operation of the control unit 18 will be described with reference to the logic circuit diagram of FIG. The water temperature determination signal 30 is a “1” signal when the water temperature Tw detected by the water temperature sensor 20 is 90 ° C. or higher, and the first intake air temperature determination signal 31 is that the intake air temperature Ta detected by the intake temperature sensor 19 is 55 ° C. At the above (first temperature), the "1" signal is output, and the second intake air temperature determination signal 32 is the intake air temperature sensor 19
"1" when the intake air temperature Ta detected at 50 ℃ or more (second temperature)
A signal is output, the start timer signal 33 is a "1" signal when the operation time Cc (cranking time) of the starter switch 22 is 3 seconds or more, and the load judgment signal 34 is idle running at the gear IN. The "1" signal is output under a load condition such as when the
"1" signal is output within 3 min or less after starting.

Then, the second intake air temperature determination signal 32 and the start timer 33 signal are input to the AND circuit 36, and the output of the AND circuit 36 and the first
The intake air temperature determination signal 31 is input to the OR circuit 37. And
The output of the OR circuit 37, the inversion signal of the water temperature determination signal 30, the inverted signal of the load determination signal 34, and the after-start timer signal 35 are input to the final AND circuit 38, and the output of the final AND circuit 38 is output to the driver 3
9 (transistor), and an operation signal is output to the negative pressure cut valve 16 by the operation of the driver 39.

The operating condition of the negative pressure cut valve 16 by the above logic circuit, that is, the condition for increasing the fuel pressure is basically that the water temperature Tw is 90
Within 3 minutes from when the engine is started when the engine is hot above ℃ and when there is no load, two intake temperature conditions are added to this condition to increase the fuel pressure. The first is when the intake air temperature Ta is 55 ° C or higher and the ambient temperature is high. In this situation, the fuel injection valve 12, the fuel supply pipe, etc. are in a high temperature state, and bubbles are generated even in gasoline with low volatility. Is what
Operates to increase fuel pressure.

The second is the case where the intake air temperature Ta is 50 ° C. or higher (less than 55 ° C.) and the starting period is 3 seconds or more, and the starting condition is poor. In this temperature range, bubbles are not generated in gasoline with low volatility, for example, alcohol Bubbles are likely to be generated in highly volatile gasoline that has been mixed in, and the state of bubble generation is judged by a start failure.If bubbles are generated, the startability is improved by increasing the fuel pressure. However, when no bubbles are generated, the fuel pressure is not increased and the engine is started as it is to avoid overrich.

In the above control, the reason why the fuel pressure is raised under no-load condition is usually the start-up failure and the unstable idle that cause the problem of the bubble generation. The stable state is difficult to detect in combination with the vehicle body vibration, so unnecessary fuel increase is avoided. Further, after the lapse of a predetermined time (3 minutes) after the start, the fuel pressure does not increase even if the detected temperature is high, because the fuel of low temperature is supplied with the operation of the engine 1 and bubbles are less likely to be generated. is there.

According to the above-described embodiment, the fuel pressure increase as a countermeasure against the occurrence of bubbles is determined based on the water temperature determination, the two-stage intake air temperature determination, the start period determination, the load determination, and the elapsed time after startup determination. By performing the operation, even if the fuel component changes, it is possible to accurately control the generation of bubbles without detecting the fuel component, and to maintain a certain range without directly detecting the fuel temperature. With such control, it is possible to accurately improve the startability when a bubble is generated and rough idle. Further, it is possible to avoid an unnecessary increase in the fuel pressure when there is a load or after a lapse of a predetermined time after the start, and to reduce the influence of exhaust gas on exhaust emission.

(Effect of the Invention) According to the present invention as described above, the temperature related to the fuel temperature is detected at the time of engine start, and when the temperature is equal to or higher than the preset first temperature, any fuel composition is obtained. In the case where bubbles are generated, the fuel pressure is raised by the fuel pressure raising means in this state, and when the detected temperature is equal to or higher than the second temperature lower than the first temperature, the starting period elapses for a predetermined period or longer. At this time, it is determined that the start-up is defective due to the generation of bubbles, and the fuel pressure is similarly increased by the fuel pressure increasing means. Even if the generation condition of bubbles is changed and the fuel pressure is adjusted based on this information and the composition of the bubbles changes due to the change in the fuel composition due to the use of alcohol-blended fuel, the actual generation of bubbles does not occur. The fuel pressure can be controlled according to the bubbles that are generated, and the startability, idleness, etc. can be improved satisfactorily without supplying excessive fuel more than necessary.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram for clarifying the configuration of the present invention, FIG. 2 is an overall configuration diagram of an engine of a specific example, and FIG. 3 is a logic circuit diagram for explaining the operation of a control unit. 1, E …… Engine, 12, B …… Fuel injection valve, 14 …… Fuel pressure regulator, 15 …… Negative pressure passage, 16 …… Negative pressure cut valve, 18 …… Control unit, 19 …… Intake temperature sensor, 22 …… Starter switch, C …… Fuel pressure adjusting device, F
...... First fuel pressure increasing means, G ...... Second fuel pressure increasing means, H ...
... Temperature detection means.

Claims (1)

[Scope of utility model registration request] 1. A first fuel pressure increasing means for increasing a fuel pressure when a temperature equal to or higher than a preset first temperature is detected by a temperature detecting means for detecting a temperature related to a fuel temperature when the engine is started. In the fuel control device for the engine, the temperature detected by the temperature detecting means is the first
A second temperature that is higher than the second temperature and lower than the second temperature, and the fuel pressure is similarly increased when the starting engine has passed a predetermined period or more.
A combustion control device for an engine, comprising a fuel pressure increasing means.