JPH04143433A - Fuel control method after starting engine - Google Patents

Abstract

PURPOSE:To prevent generation of engine stall and stabilize engine rotational speed just after restarting an engine by increasingly compensating a basic injection quantity transiently in response to cooling water temperature or intake air temperature in the case when the cooling water temperature is more than a specified value. CONSTITUTION:A water temperature signal (d) from a water temperature sensor 12 and an intake air temperature signal (e) from an intake air temperature sensor 13 are respectively inputted to an electronic control unit 4. A basic injection quantity just after starting an engine is increasingly compensated transiently by an increasing value after the first start in response to cooling water temperature of engine thereat, an increasing value after the second start varying its value in complience with an intake air temperature is set. In the case, when the cooling water temperature of the engine is more than a specified value, the basic injection quantity is increasingly compensated transiently, by the increasing value at least just after the first start or second start. Consequently, generation of engine stall just after restarting the engine can be prevented without complexity of its structure, and engine rotational speed just after restarting the engine can be effectively stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel control method after starting an engine, which is applied to an automobile or the like equipped with an electronically controlled fuel injection device.

[Prior Art] In an engine equipped with an electronically controlled fuel injection device, the basic injection amount during warm-up immediately after startup is temporarily increased by a first post-start increase value that corresponds to at least the engine cooling water temperature. , to deal with combustion instability during cold conditions. Specifically, based on the engine cooling water temperature at the time of engine startup, an initial value of a first post-start increase value that is approximately inversely proportional to the cooling water temperature is determined. As a prior art of the present invention, for example, as shown in Japanese Unexamined Patent Publication No. 157246/1982, the initial value is attenuated by a substantially constant value as warm-up progresses, and the amount is finally increased. I am trying to set the minutes to 0.

[Problems to be Solved by the Invention] However, when the engine is stopped and enters a dead soak state after climbing or driving at high speed, the injectors, delivery pipes, etc. become heated due to the high ambient temperature in the engine room and heat received from the engine body. It becomes a difficult situation. Therefore, the fuel temperature in the injector and delivery pipe increases, vapor is generated, and the density of the fuel decreases. This tendency is particularly likely to occur in cab-over type vehicles. On the other hand, the engine cooling water temperature is approximately constant or increases once and then gradually decreases. Therefore, if the engine is restarted within about 20 to 30 minutes after the engine has stopped, the fuel supply amount cannot be appropriately corrected with the first post-start increase value determined by the engine cooling water temperature, and the air-fuel ratio becomes lean temporarily. As a result, it is not uncommon for the engine speed to drop immediately after restarting, resulting in engine stall or unstable idling.

Although it is possible to avoid the above-mentioned problems by temporarily increasing the set pressure of the regulator for adjusting the fuel pressure, this method does not increase the set pressure of the regulator. Since a change means is required, the structure becomes complicated.

The present invention aims to eliminate the above-mentioned problems all at once.

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, the fuel control method after engine startup according to the present invention is applicable to an engine configured to temporarily increase the basic injection amount after engine startup using a first post-startup increase value that corresponds to the engine cooling water temperature. In the post-start fuel control method, a second post-start increase value whose value changes in accordance with the intake air temperature is set, and if the engine cooling water temperature exceeds a predetermined value, at least the first post-start increase value is set. The present invention is characterized in that the basic injection amount is transiently increased and corrected using an increase value or the second post-start increase value.

In addition, since the fuel temperature during dead sorting changes almost in the same way as the intake temperature, if the second post-start increase value is set in accordance with this intake temperature, it will be possible to specifically detect the fuel temperature. There is no need to add additional mechanisms.

[Operation] According to this configuration, when the engine is restarted before the engine cooling water temperature has reached the predetermined value,
The basic injection amount is temporarily increased by the first post-start increase value.

When the engine is stopped after climbing a hill or driving at high speed, and then restarted, the first post-start increase value becomes an initial value corresponding to the engine cooling water temperature that has already decreased. . In addition, in this case, the intake air temperature is rising along with the fuel temperature due to the high atmospheric temperature in the engine room during dead soak and heat received from the engine body, so the second post-start increase value will vary depending on the intake air temperature. Set. Since the basic injection amount is temporarily increased by at least the second post-start increase value and the first post-start increase value, it is possible to compensate for a fuel shortage due to a decrease in fuel density.

[Example code] Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

The engine shown in FIG. 1 is for an automobile and is equipped with an electronically controlled fuel injection device 1. The engine shown in FIG. This electronically controlled fuel injection device M1 includes an injector 3 attached to an intake pipe 2 and an electronic control device 4 that controls the operation of the injector 3, and controls the amount of fuel supplied from the injector 3 to the combustion chamber 5. It is configured to be adjusted by the electronic control device 4 according to the engine condition.

The injector 3 has a built-in electromagnetic coil, and when a fuel injection signal a is applied to the electromagnetic coil from the electronic control device 4, the injector 3 injects fuel in an amount corresponding to the application time into the vicinity of the intake boat. It has become.

The electronic control device 4 includes a central processing unit 6 and a memory 7.
, an input interface 8 , and an output interface 9 . The input interface 8 includes at least an intake pressure signal from a pressure sensor 10, an engine rotation signal C from a crank angle sensor 11, and a water temperature sensor 12.
A water temperature signal d from the intake air temperature sensor 13 and an intake air temperature signal e from the intake air temperature sensor 13 are respectively input.

A fuel injection signal a is output from the output interface 9 to the injector 3.

The pressure sensor 10 has, for example, a function in which the output voltage changes depending on the pressure difference acting above and below the diaphragm, and the intake pressure from inside the surge tank 14 can be detected based on the output voltage. Crank angle sensor 1
1 is configured to generate a pulse signal proportional to engine rotation, and is built into the distributor 15.

The water temperature sensor 12 has, for example, a built-in thermistor, and outputs an electric signal depending on the engine cooling water temperature. The intake temperature sensor 13 is the water temperature sensor 1
It has the same configuration as No. 2, and outputs an electric signal depending on the intake air temperature inside the saji tank 14.

Further, a program as schematically shown in FIG. 2 is set in the electronic control device 4. First, step 51
Based on the water temperature signal d, the engine cooling water temperature T at the time of startup is determined based on the water temperature signal d.
HW is read, and the intake air temperature THA at the time of startup is read based on the intake air temperature signal e, and the process proceeds to Stella 752. In step 52, it is determined whether the engine coolant temperature THW exceeds a predetermined value Tl. If it is above, the process proceeds to step 53; if it is not, the process proceeds to step 54. In step 53, the second post-start increase value F
The initial value of SEHOT is determined and the process proceeds to step 55.

As shown in Fig. 3, the initial value of the second post-start increase value PSEHOT becomes a large value when the intake air temperature THA becomes high, and becomes a small value when the intake air temperature THA becomes low. The settings are as follows. In step 54, the second post-start increase value PSEHOT is set to 0, and in step 5
Proceed to step 5. In step 55, the engine coolant temperature THW
Based on this, the initial values of two types of post-start increase values FSE1 and PSE2, which are the first post-start increase values, are determined, and the process proceeds to step 56. As shown in FIG. 4, one post-start increase value PSEI has a small attenuation rate, and the other post-start increase value FSE2 has a large attenuation rate. In step 56, these post-start increase values PSEI
, PSE2, and PSEHOT, and select the largest value among them, and proceed to step 57. In step 57, the selected maximum value is determined as the post-start increase value during fuel injection, and the process proceeds to step 58. In step 58, fuel injection time (fuel injection teeth) is determined based on a predetermined procedure.

That is, the basic injection amount is determined according to the intake air amount calculated from the intake pressure signal S, the engine rotation signal C, etc., and the basic injection amount is increased by the increase value after starting, etc., and the injector 3 is opened. After determining the time, proceed to step 59. In step 59, as shown in FIG. 4, the post-start increase values PSEi, PSE2, and PSEHOT are each attenuated by a fixed percentage every time fuel is supplied or every fixed time from immediately after the engine starts, and the process returns to step 56.

According to the above configuration, when the engine is restarted before the engine coolant temperature THW has reached the set value Tl, the second post-start quantity PSE)IOT is set to 0 and ( In step 54), the first post-start increase values FSE1 and FSE2 are set to values in the middle of decay. In that case, the basic injection amount is corrected to increase with the first post-start increase values PSEI and PSE2 (steps 52-54 to 58), so that the amount of fuel that matches the required amount during cold is injected into the combustion chamber. 5.

On the other hand, when the engine is stopped after climbing a hill or driving at high speed, the engine cooling water temperature rises once and then gradually decreases, as shown schematically in Figure 5. The temperature of the fuel inside the tank gradually rises and then drops after about 20 to 30 minutes. In this case, the intake air temperature and the fuel temperature change in substantially the same way. Therefore, if the engine is restarted within about 20 to 30 minutes after the engine has been stopped, the first post-start increase values FSEI and PSE2, which are determined by the engine coolant temperature, will become values corresponding to the already lowered engine coolant temperature. , second post-start increase value PSEHOT
will be set to a value greater than 0.

In this case, the second post-start increase value FSEH
Since the basic injection amount is increased by the larger value of OT and the first post-start increase value PSEI, PSE2, the fuel shortage due to the decrease in fuel density is compensated for.

Therefore, according to the above configuration, the air-fuel ratio lean state caused by insufficient fuel supply after a restart after climbing a hill or after a high-speed run can be corrected without causing irregularities in engine rotation after a cold restart. It can be effectively prevented.

As a result, it is possible to stabilize the idle rotation after restarting after dead soak, and it is also possible to effectively avoid the occurrence of engine stall.

Moreover, according to such a configuration, it is possible to temporarily change the set pressure of the regulator for adjusting the fuel pressure,
Since the existing intake air temperature sensor 13 can be effectively used without specifically detecting the fuel temperature and correcting the fuel supply amount, the structure is not complicated, which is advantageous.

In addition, when increasing the basic injection amount with the post-start increase value, all post-start increase values may be added to the basic injection amount.
Alternatively, the basic injection amount may be corrected by multiplying all post-start increase values.

Furthermore, it goes without saying that the second post-start increase value is not limited to being set in the manner shown in the drawings.

[Effects of the Invention] Since the present invention has the above-described configuration, it is possible to prevent the engine from stalling immediately after restarting without complicating the structure, and to reduce the engine speed immediately after restarting. It is possible to provide a fuel control method after the engine U that can effectively stabilize the fuel and has excellent control accuracy.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, in which Fig. 1 is a schematic overall configuration diagram, Fig. 2 is a flowchart schematically showing a control procedure, and Figs. 3 and 4 each show control setting conditions. FIG. 5 is an explanatory view of the operation. 1...Electronically controlled fuel injection device 3...Injector 4...Electronic control device 12...Water temperature sensor 13...Intake temperature sensor

Claims (1)

[Claims] In a fuel control method after an engine start, which is configured to temporarily increase the basic injection amount after the engine starts with a first post-start increase value that corresponds to the engine cooling water temperature, the value increases as the intake air temperature increases. A variable second post-start increase value is set, and if the engine cooling water temperature is higher than a predetermined value, the basic injection is performed at least at the first post-start increase value or the second post-start increase value. A fuel control method after starting an engine, characterized in that the fuel amount is temporarily increased.